Electronic sideband locking of a broadly tunable 318.6 nm ultraviolet laser to an ultra-stable optical cavity

NASA Astrophysics Data System (ADS)

Bai, Jiandong; Wang, Jieying; He, Jun; Wang, Junmin

2017-04-01

We demonstrate frequency stabilization of a tunable 318.6 nm ultraviolet (UV) laser system using electronic sideband locking. By indirectly changing the frequency of a broadband electro-optic phase modulator, the laser can be continuously tuned over 4 GHz, while a 637.2 nm laser is directly stabilized to a high-finesse ultra-stable optical cavity. The doubling cavity also remains locked to the 637.2 nm light. We show that the tuning range depends mainly on the gain-flattening region of the modulator and the piezo-tunable range of the seed laser. The frequency-stabilized tunable UV laser system is able to compensate for the offset between reference and target frequencies, and has potential applications in precision spectroscopy of cold atoms.

Low cost, patterning of human hNT brain cells on parylene-C with UV & IR laser machining.

PubMed

Raos, Brad J; Unsworth, C P; Costa, J L; Rohde, C A; Doyle, C S; Delivopoulos, E; Murray, A F; Dickinson, M E; Simpson, M C; Graham, E S; Bunting, A S

2013-01-01

This paper describes the use of 800nm femtosecond infrared (IR) and 248nm nanosecond ultraviolet (UV) laser radiation in performing ablative micromachining of parylene-C on SiO2 substrates for the patterning of human hNT astrocytes. Results are presented that support the validity of using IR laser ablative micromachining for patterning human hNT astrocytes cells while UV laser radiation produces photo-oxidation of the parylene-C and destroys cell patterning. The findings demonstrate how IR laser ablative micromachining of parylene-C on SiO2 substrates can offer a low cost, accessible alternative for rapid prototyping, high yield cell patterning.

Compact Ozone Differential Absorption Lidar (DIAL) Transmitter Using Solid-State Dye Polymers

NASA Technical Reports Server (NTRS)

Jones, Alton L., Jr.; DeYoung, Russell J.; Elsayid-Ele, Hani

2001-01-01

A new potential DIAL laser transmitter is described that uses solid-state dye laser materials to make a simpler, more compact, lower mass laser system. Two solid-state dye laser materials were tested to evaluate their performance in a laser oscillator cavity end pumped by a pulsed Nd:YAG laser at 532 nm. The polymer host polymethyl-methacrylate was injected with a pyrromethene laser dye, PM 580, or PM 597. A narrowband laser oscillator cavity was constructed to produce visible wavelengths of 578 and 600 nm which were frequency doubled into the UV region (299 or 300 nm) by using a BBO crystal, resulting in a maximum energy of 11 mJ at a wavelength of 578 nm when pumped by the Nd:YAG laser at an energy of 100 mJ (532 nm). A maximum output energy of 378 microJ was achieved in the UV region at a wavelength of 289 nm but lasted only 2000 laser shots at a repetition rate of 10 Hz. The results are promising and show that a solid-state dye laser based ozone DIAL system is possible with improvements in the design of the laser transmitter.

High-power 266 nm ultraviolet generation in yttrium aluminum borate.

PubMed

Liu, Qiang; Yan, Xingpeng; Gong, Mali; Liu, Hua; Zhang, Ge; Ye, Ning

2011-07-15

A yttrium aluminum borate [YAl(3)(BO(3))(4)] (YAB) crystal with UV cutoff wavelength of 165 nm is used as the nonlinear optical crystal for fourth harmonic generation. The fundamental frequency laser at 1064 nm from an Nd:YVO(4) master oscillator power amplifier laser was frequency doubled to 532 nm. Using the type I phase-matching YAB crystal, a 5.05 W average power 266 nm UV laser was obtained at the pulse repetition frequency of 65 kHz, corresponding to the conversion efficiency of 12.3% from 532 to 266 nm. The experimental results show great potential for the application of using YAB as a nonlinear optical crystal to get high-power fourth harmonic generation. © 2011 Optical Society of America

A six-color four-laser mobile platform for multi-spectral fluorescence imaging endoscopy

NASA Astrophysics Data System (ADS)

Black, John F.; Tate, Tyler; Keenan, Molly; Swan, Elizabeth; Utzinger, Urs; Barton, Jennifer

2015-03-01

The properties of multi-spectral fluorescence imaging using deep-UV-illumination have recently been explored using a fiber-coupled thermal source at 280 nm. The resulting images show a remarkable level of contrast thought to result from the signal being overwhelmingly generated in the uppermost few cell layers of tissue, making this approach valuable for the study of diseases that originate in the endothelial tissues of the body. With a view to extending the technique with new wavelengths, and improving beam quality for efficient small core fiber coupling we have developed a mobile self-contained tunable solid-state laser source of deep UV light. An alexandrite laser, lasing at around 750 nm is frequency doubled to produce 375 nm and then tripled to produce 250 nm light. An optical deck added to the system allows other laser sources to be incorporated into the UV beam-line and a lens system has been designed to couple these sources into a single delivery fiber with core diameters down to 50 microns. Our system incorporates five wavelengths [250 nm, 375 nm, 442 nm (HeCd), 543 nm (HeNe) and 638 nm (diode laser)] as the illumination source for a small diameter falloposcope designed for the study of the distal Fallopian tube origins of high grade serous ovarian cancer. The tunability of alexandrite offers the potential to generate other wavelengths in the 720-800, 360-400 and 240-265 nm ranges, plus other non-linear optical conversion techniques taking advantage of the high peak powers of the laser.

Investigation of optical fibers for gas-phase, ultraviolet laser-induced-fluorescence (UV-LIF) spectroscopy.

PubMed

Hsu, Paul S; Kulatilaka, Waruna D; Jiang, Naibo; Gord, James R; Roy, Sukesh

2012-06-20

We investigate the feasibility of transmitting high-power, ultraviolet (UV) laser pulses through long optical fibers for laser-induced-fluorescence (LIF) spectroscopy of the hydroxyl radical (OH) and nitric oxide (NO) in reacting and non-reacting flows. The fundamental transmission characteristics of nanosecond (ns)-duration laser pulses are studied at wavelengths of 283 nm (OH excitation) and 226 nm (NO excitation) for state-of-the-art, commercial UV-grade fibers. It is verified experimentally that selected fibers are capable of transmitting sufficient UV pulse energy for single-laser-shot LIF measurements. The homogeneous output-beam profile resulting from propagation through a long multimode fiber is ideal for two-dimensional planar-LIF (PLIF) imaging. A fiber-coupled UV-LIF system employing a 6 m long launch fiber is developed for probing OH and NO. Single-laser-shot OH- and NO-PLIF images are obtained in a premixed flame and in a room-temperature NO-seeded N(2) jet, respectively. Effects on LIF excitation lineshapes resulting from delivering intense UV laser pulses through long fibers are also investigated. Proof-of-concept measurements demonstrated in the current work show significant promise for fiber-coupled UV-LIF spectroscopy in harsh diagnostic environments such as gas-turbine test beds.

Kinetics of UV laser radiation defects in high performance glasses

NASA Astrophysics Data System (ADS)

Natura, U.; Feurer, T.; Ehrt, D.

2000-05-01

High purity fluoride phosphate glasses are attractive candidates as UV transmitting materials. The calculated values for the ultraviolet resonance wavelength are comparable with those of pure silica glass or fluoride single crystal CaF2. The formation of radiation-induced defect centers leads to additional absorption bands in the VUV-UV-vis range. The damage and the healing behavior by lamps and lasers are investigated in dependence on phosphate content and the content of impurities, mainly transition metals. Experiments were carried out using pulsed lasers with a duration of femto- and nanoseconds at a wavelength of 248 nm. The initial slope of the induced absorption shows a nonlinear dependence on the pulse energy density. Resonant and non-resonant two-photon mechanisms were observed. Two-photon-absorption coefficients at 248 nm for samples with different phosphate contents were measured. Models of the kinetics of the radiation-induced defects were developed. The inclusion of energy transfer was necessary to explain the difference in the damage behavior for nanosecond (248 nm, 193 nm) and femtosecond (248 nm) laser pulses.

Deep UV laser-induced fluorescence detection of unlabeled drugs and proteins in microchip electrophoresis.

PubMed

Schulze, Philipp; Ludwig, Martin; Kohler, Frank; Belder, Detlev

2005-03-01

Deep UV fluorescence detection at 266-nm excitation wavelength has been realized for sensitive detection in microchip electrophoresis. For this purpose, an epifluorescence setup was developed enabling the coupling of a deep UV laser into a commercial fluorescence microscope. Deep UV laser excitation utilizing a frequency quadrupled pulsed laser operating at 266 nm shows an impressive performance for native fluorescence detection of various compounds in fused-silica microfluidic devices. Aromatic low molecular weight compounds such as serotonin, propranolol, a diol, and tryptophan could be detected at low-micromolar concentrations. Deep UV fluorescence detection was also successfully employed for the detection of unlabeled basic proteins. For this purpose, fused-silica chips dynamically coated with hydroxypropylmethyl cellulose were employed to suppress analyte adsorption. Utilizing fused-silica chips permanently coated with poly(vinyl alcohol), it was also possible to separate and detect egg white chicken proteins. These data show that deep UV fluorescence detection significantly widens the application range of fluorescence detection in chip-based analysis techniques.

Choice of the laser wavelength for a herpetic keratitis treatment

NASA Astrophysics Data System (ADS)

Razhev, Alexander M.; Bagayev, Sergei N.; Chernikh, Valery V.; Kargapoltsev, Evgeny S.; Trunov, Alexander; Zhupikov, Andrey A.

2002-06-01

For the first time the effect of the UV laser radiation to human eye cornea with herpetic keratitis was experimentally investigated. In experiments the UV radiation of ArF (193 nm), KrCl (223 nm), KrF (248 nm) excimer lasers were used. Optimal laser radiation parameters for the treatment of the herpetic keratitis were determined. The immuno-biochemical investigations were carried out and the results of clinical trials are presented. The maximum ablation rate was obtained for the 248 nm radiation wavelength. The process of healing was successful but in some cases the haze on the surface of the cornea was observed. When used the 193 nm radiation wavelength the corneal surface was clear without any hazes but the epithelization process was slower than for 248 nm wavelength and in some cases the relapse was occurred. The best results for herpetic keratitis treatment have been achieved by utilizing the 223 nm radiation wavelength of the KrCl excimer laser. The use of the 223 nm radiation wavelength allows treating the herpetic keratitis with low traumatic process of ablation and provides high quality of corneal surface.

Pulsed UV laser light on Escherichia coli and Saccharomyces cerevisiae suspended in non-alcoholic beer

PubMed Central

Hosseini, SM; Azar-Daryany, MK; Massudi, R; Elikaei, A

2011-01-01

Background The aim of this study was to investigate the effect of pulsed ultra-violet (UV) irradiation on inactivation of beer spoilage microorganisms. UV irradiation is nowadays cost effective enough to compete with traditional biological, physical, and chemical treatment technologies and has become an alternative to such methods. Material and Methods Photoinactivation effects of pulsed UV laser with the wavelengths of 355 and 266 nm, which inactivate typical prokaryotic (Escherichia coli) and eukaryotic (Saccharomyces cerevisiae) microorganisms, were examined with different doses and exposure times. Results A dose of 100 J/cm2 of the 355 nm pulsed UV laser was able to reduce about 1 to 2 log (88.75%) of E.coli with the population of 1.6×108 colony-forming units (CFU/ml), and 97% of 3.2×107, 3×106, 5.5×105, and 9×104 CFU/ml. In the case of 266 nm, more than 99% reduction in E. coli serial dilutions was inactivated, using 10 J/cm2 with exception of 7×104 CFU/ml which was not detected any bacterial growth using 5 J/cm2. In addition, 50, 40, and 20 J/cm2 energy were used successfully to inactivate S. cerevisiae at the populations of 5.4×106, 7×105, 5×104 and 4×103 CFU/ml, respectively. As a result, pulsed UV Laser with 266 nm was strong enough to inactivate a high titer of bacterial and yeast indicator standards suspended in non-alcoholic beer in comparison with 355nm doses. Conclusion Results indicate that pulsed UV technology, in principle, is an attractive alternative to conventional methods for the inactivation of indicator microorganisms and has potential in irradiation of unpasteurized beer. PMID:22347580

Fabrication of Ta nanoparticles induced by nanosecond laser ablation in ethanol: the study of laser fluence effects

NASA Astrophysics Data System (ADS)

Azadi Kenari, Fariba; Moniri, Samira; Hantehzadeh, Mohammad Reza; Dorranian, Davoud; Ghoranneviss, Mahmood

2018-05-01

Tantalum nanoparticles (Ta NPs) were synthesized in ethanol solution by ablation with a 1064 nm Nd:YAG laser. Prepared NPs were investigated by UV-visible absorption spectroscopy, Transmission electron microscopy, X-ray diffraction and Photoluminescence measurement. The average sizes of NPs were calculated to be in the range of 12-18 nm. From the UV-visible studies, the plasmon peak position of Ta NPs was observed in the spectral range of 206-208 nm. The XRD spectra clearly showed the crystalline structure of NPs and various peaks of Ta and Ta2O5. Moreover, the UV region in the PL spectrum included the free exciton and the bound exciton emission correlated with the defect concentration. In fact, the laser ablation in the organic and inorganic solvents is a strong technique to obtain some NPs with particular structures, which are impossible to produce by conventional methods.

Tuneable powerful UV laser system with UV noise eater

NASA Astrophysics Data System (ADS)

Kobtsev, Sergey; Radnatarov, Daba; Khripunov, Sergey; Zarudnev, Yurii

2018-02-01

The present work for the first time presents the study of a laser system delivering into the fibre up to 250 mW of CW radiation tuneable across the 275-310-nm range with the output line width less than 5 GHz and stability of UV output power within 1%. This system can automatically set the output radiation wavelength within the range of 275-310 nm to the precision of 2 pm. UV output power stabilisation is provided by a newly proposed by the authors noise eating technology. This paper discusses details of the developed technology and the results of its application.

Factors affecting color strength of printing on film-coated tablets by UV laser irradiation: TiO2 particle size, crystal structure, or concentration in the film, and the irradiated UV laser power.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2011-08-01

The purpose of this article is to study factors affecting color strength of printing on film-coated tablets by ultraviolet (UV) laser irradiation: particle size, crystal structure, or concentration of titanium dioxide (TiO2) in film, and irradiated UV laser power. Hydroxypropylmethylcellulose films containing 4.0% of TiO2, of which BET particle sizes were ranging from 126.1 to 219.8 nm, were irradiated 3.14W of UV laser at a wavelength 355 nm to study effects of TiO2 particle size and crystal structure on the printing. The films containing TiO2 concentration ranging from 1.0 to 7.7% were irradiated 3.14 or 5.39W of the UV laser to study effect of TiO2 concentration on the printing. The film containing 4.0% of TiO2, was irradiated the UV laser up to 6.42W to study effect of the UV laser power on the printing. The color strength of the printed films was estimated by a spectrophotometer as total color difference (dE). Particle size, crystal structure, and concentration of TiO2 in the films did not affect the printing. In the relationship between the irradiated UV laser power and dE, there found an inflection point (1.6W). When the UV laser power was below 1.6W, the films were not printed. When it was beyond the point, total color difference increased linearly in proportion with the irradiated laser power. The color strength of the printing on film was not changed by TiO2 particle size, crystal structure, and concentration, but could be controlled by regulating the irradiated UV laser power beyond the inflection point.

Coumarin-BODIPY hybrids by heteroatom linkage: versatile, tunable and photostable dye lasers for UV irradiation.

PubMed

Esnal, I; Duran-Sampedro, G; Agarrabeitia, A R; Bañuelos, J; García-Moreno, I; Macías, M A; Peña-Cabrera, E; López-Arbeloa, I; de la Moya, S; Ortiz, M J

2015-03-28

Linking amino and hydroxycoumarins to BODIPYs through the amino or hydroxyl group lets the easy construction of unprecedented photostable coumarin-BODIPY hybrids with broadened and enhanced absorption in the UV spectral region, and outstanding wavelength-tunable laser action within the green-to-red spectral region (∼520-680 nm). These laser dyes allow the generation of a valuable tunable UV (∼260-350 nm) laser source by frequency doubling, which is essential to study accurately the photochemistry of biological molecules under solar irradiation. The tunability is achieved by selecting the substitution pattern of the hybrid. Key factors are the linking heteroatom (nitrogen vs. oxygen), the number of coumarin units joined to the BODIPY framework and the involved linking positions.

UV lifetime demonstrator for space-based applications

NASA Astrophysics Data System (ADS)

Albert, Michael; Puffenburger, Kent; Schum, Tom; Fitzpatrick, Fran; Litvinovitch, Slava; Jones, Darrell; Rudd, Joseph; Hovis, Floyd

2016-05-01

A long-lived UV laser is an enabling technology for a number of high-priority, space-based lidar instruments. These include next generation cloud and aerosol lidars that incorporates a UV channel, direct detection 3-D wind lidars, and ozone DIAL (differential absorption lidar) systems. In previous SBIR funded work we developed techniques for increasing the survivability of components in high power UV lasers and demonstrated improved operational lifetimes. In this Phase III ESTO funded effort we are designing and building a TRL (Technology Readiness Level) 6 demonstrator that will have increased output power and a space-qualifiable package that is mechanically robust and thermally-stable. For full space compatibility, thermal control will be through pure conductive cooling. Contamination control processes and optical coatings will be chosen that are compatible with lifetimes in excess of 1 billion shots. The 1064nm output will be frequency tripled to provide greater than 100 mJ pulses of 355 nm light at 150 Hz. The laser module build was completed in the third quarter of 2015 at which time a series of life tests were initiated. The first phase of the lifetime testing is a 532 nm only test that is expected to complete in April 2016. The 532 nm lifetest will be followed by a 4 month half power UV life test and then a four month full power UV life test. The lifetime tests will be followed by thermal/vacuum (TVAC) and vibration testing to demonstrate that the laser optics module design is at TRL 6.

Measurements of Raman scattering in the middle ultraviolet band from persistent chemical warfare agents

NASA Astrophysics Data System (ADS)

Kullander, Fredrik; Landström, Lars; Lundén, Hampus; Mohammed, Abdesalam; Olofsson, Göran; Wästerby, Pär.

2014-05-01

The very low Raman scattering cross section and the fluorescence background limit the measuring range of Raman based instruments operating in the visible or infrared band. We are exploring if laser excitation in the middle ultraviolet (UV) band between 200 and 300 nm is useful and advantageous for detection of persistent chemical warfare agents (CWA) on various kinds of surfaces. The UV Raman scattering from tabun, mustard gas, VX and relevant simulants in the form of liquid surface contaminations has been measured using a laboratory experimental setup with a short standoff distance around 1 meter. Droplets having a volume of 1 μl were irradiated with a tunable pulsed laser swept within the middle UV band. A general trend is that the signal strength moves through an optimum when the laser excitation wavelength is swept between 240 and 300 nm. The signal from tabun reaches a maximum around 265 nm, the signal from mustard gas around 275 nm. The Raman signal from VX is comparably weak. Raman imaging by the use of a narrow bandpass UV filter is also demonstrated.

The optical effect of a semiconductor laser on protecting wheat from UV-B radiation damage.

PubMed

Qiu, Zong-Bo; Zhu, Xin-Jun; Li, Fang-Min; Liu, Xiao; Yue, Ming

2007-07-01

Lasers have been widely used in the field of biology along with the development of laser technology, but the mechanism of the bio-effect of lasers is not explicit. The objective of this paper was to test the optical effect of a laser on protecting wheat from UV-B damage. A patent instrument was employed to emit semiconductor laser (wavelength 650 nm) and incoherent red light, which was transformed from the semiconductor laser. The wavelength, power and lightfleck diameter of the incoherent red light are the same as those of the semiconductor laser. The semiconductor laser (wavelength 650 nm, power density 3.97 mW mm(-2)) and incoherent red light (wavelength 650 nm, power density 3.97 mW mm(-2)) directly irradiated the embryo of wheat seeds for 3 min respectively, and when the seedlings were 12-day-old they were irradiated by UV-B radiation (10.08 kJ m(-2)) for 12 h in the dark. Changes in the concentration of malondialdehyde (MDA), hydrogen peroxide (H(2)O(2)), glutathione (GSH), ascorbate (AsA), carotenoids (CAR), the production rate of superoxide radical (O(2)(-)), the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD) and the growth parameters of seedlings (plant height, leaf area and fresh weight) were measured to test the optical effect of the laser. The results showed that the incoherent red light treatment could not enhance the activities of SOD, POD and CAT and the concentration of AsA and CAR. When the plant cells were irradiated by UV-B, the incoherent red light treatment could not eliminate active oxygen and prevent lipid peroxidation in wheat. The results also clearly demonstrate that the plant DNA was damaged by UV-B radiation and semiconductor laser irradiance had the capability to protect plants from UV-B-induced DNA damage, while the incoherent red light could not. This is the first investigation reporting the optical effect of a semiconductor laser on protecting wheat from UV-B radiation damage.

Compact lasing system at 13.5-nm to ground state of LiIII at 2Hz

NASA Astrophysics Data System (ADS)

Goltsov, A. Y.; Korobkin, D.; Nam, C. H.; Suckewer, Szymon

1997-11-01

The recent results of the demonstration of the lasing action at 13.5 nm in transition to ground state of LiIII at 2 Hz repetition rate using two lasers is being presented in this paper. A gain length of GL approximately equals 5.5 was measured in the 5 mm long, 0.3 mm diameter, LiF microcapillary using a 50 mJ, 250 fsec UV laser beam. The initial plasma was created in the microcapillary by a low power, relatively long pulse Nd/YAG laser. In order to shed light on observed unusually high efficiency of the ionization of the atoms in microcapillaries, the subpicosecond UV laser beam transmissions through the plasma in microcapillaries were measured. Strong dependence of the beam transmission on the delay time between inial plasma formation with the Nd/YAG laser and the sub-picosecond UV laser was recorded. The final part of the paper discusses some necessary conditions for an extension of the present results towards the shorter wavelength lasers with an emphasis on the presently conducted experiments at Princeton University for the generation gain at 4.8 nm in BV.

Studies on activated cytostatic fluorouracil as photosensitizer: to use in eye tumor treatment

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Carstocea, Benone D.; Brezeanu, Mihail; Voicu, Letitia; Staicu, Angela; Gazdaru, Doina M.; Pascu, Ruxandra A.

2004-09-01

Hydroxypyrimidine 5-fluorouracil (5-FU) belongs to the cytostatics group known as antimetabolites. The effect of UV irradiation on 5-FU was investigated by absorption and fluorescence spectroscopy. The study of the photosensitizer properties of 5-FU was made since their effects could be enhanced by exposure to UV radiation at different doses. Solutions 2.5x10-4M in natural saline water (0.8% NaCl), irradiated with optical beams emitted by N2 laser and UV Hg classic lamp, were used. The 5-FU was chosen due to its strong absorption along a large spectral range which makes possible the fluorescence excitation in UV. The absorption spectra exhibit bands between 250 - 450 nm. The emission fluorescence was measured in the 400-550 nm spectral range, with λex=320 and 350 nm for samples irradiated with Hg lamp and with λex=360 nm for samples irradiated with N2 laser. The excitation fluorescence was measured in the spectral range 200-400 nm, with λem=440 nm for samples irradiated with N2 laser. The spectra reveal a fluorescence enhancement with the exposure time, with a maximum at 3 min due to the transformation of 5-FU molecule into a fluorescent tautomeric form. The destruction more rapid than usual of the neovascularisation was observed for conjunctive of rabbit eyes, when they are impregnated with 5-FU solution and exposed to incoherent UV and visible light.

UV laser radiation alters the embryonic protein profile of adrenal-kidney-gonadal complex and gonadal differentiation in the lizard, Calotes Versicolor.

PubMed

Khodnapur, Bharati S; Inamdar, Laxmi S; Nindi, Robertraj S; Math, Shivkumar A; Mulimani, B G; Inamdar, Sanjeev R

2015-02-01

To examine the impact of ultraviolet (UV) laser radiation on the embryos of Calotes versicolor in terms of its effects on the protein profile of the adrenal-kidney-gonadal complex (AKG), sex determination and differentiation, embryonic development and hatching synchrony. The eggs of C. versicolor, during thermo-sensitive period (TSP), were exposed to third harmonic laser pulses at 355 nm from a Q-switched Nd:YAG laser for 180 sec. Subsequent to the exposure they were incubated at the male-producing temperature (MPT) of 25.5 ± 0.5°C. The AKG of hatchlings was subjected to protein analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and to histology. The UV laser radiation altered the expression of the protein banding pattern in the AKG complex of hatchlings and it also affected the gonadal sex differentiation. SDS-PAGE of AKG of one-day-old hatchlings revealed a total of nine protein bands in the control group whereas UV laser irradiated hatchlings expressed a total of seven protein bands only one of which had the same Rf as a control band. The UV laser treated hatchlings have an ovotestes kind of gonad exhibiting a tendency towards femaleness instead of the typical testes. It is inferred that 355 nm UV laser radiation during TSP induces changes in the expression of proteins as well as their secretions. UV laser radiation had an impact on the gonadal differentiation pathway but no morphological anomalies were noticed.

The modification of spectral characteristics of cytostatics by optical beams

NASA Astrophysics Data System (ADS)

Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

2004-10-01

Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

All-Solid-State UV Transmitter Development for Ozone Sensing Applications

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Armstrong, Darrell Jr.

2009-01-01

In this paper, recent progress made in the development of an all-solid-state UV transmitter suitable for ozone sensing applications from space based platforms is discussed. A nonlinear optics based UV setup based on Rotated Image Singly Resonant Twisted Rectangle (RISTRA) optical parametric oscillator (OPO) module was effectively coupled to a diode pumped, single longitudinal mode, conductively cooled, short-pulsed, high-energy Nd:YAG laser operating at 1064 nm with 50 Hz PRF. An estimated 10 mJ/pulse with 10% conversion efficiency at 320 nm has been demonstrated limited only by the pump pulse spatial profile. The current arrangement has the potential for obtaining greater than 200 mJ/pulse. Previously, using a flash-lamp pumped Nd:YAG laser with round, top-hat profile, up to 24% IR-UV conversion efficiency was achieved with the same UV module. Efforts are underway to increase the IR-UV conversion efficiency of the all solid-state setup by modifying the pump laser spatial profile along with incorporating improved OPO crystals.

Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.

2018-05-01

Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.

Analysis of UV-excited fluorochromes by flow cytometry using near-ultraviolet laser diodes.

PubMed

Telford, William G

2004-09-01

Violet laser diodes have become common and reliable laser sources for benchtop flow cytometers. While these lasers are very useful for a variety of violet and some ultraviolet-excited fluorochromes (e.g., DAPI), they do not efficiently excite most UV-stimulated probes. In this study, the next generation of InGaN near-UV laser diodes (NUVLDs) emitting in the 370-375-nm range have been evaluated as laser sources for cuvette-based flow cytometers. Several NUVLDs, ranging in wavelength from 370 to 374 nm and in power level from 1.5 to 10 mW, were mounted on a BD Biosciences LSR II and evaluated for their ability to excite cells labeled with the UV DNA binding dye DAPI, several UV phenotyping fluorochromes (including Alexa Fluor 350, Marina Blue, and quantum dots), and the fluorescent calcium chelator indo-1. NUVLDs at the 8-10-mW power range gave detection sensitivity levels comparable to more powerful solid-state and ion laser sources, using low-fluorescence microsphere beads as measurement standards. NUVLDs at all tested power levels allowed extremely high-resolution DAPI cell cycle analysis, and sources in the 8-10-mW power range excited Alexa Fluor 350, Marina Blue, and a variety of quantum dots at virtually the same signal-to-noise ratios as more powerful UV sources. These evaluations indicate that near-UV laser diodes installed on a cuvette-based flow cytometer performed nearly as well as more powerful solid-state UV lasers on the same instrumentation, and comparably to more powerful ion lasers on a jet-in-air system, and. Despite their limited power, integration of these small and inexpensive lasers into benchtop flow cytometers should allow the use of flow cytometric applications requiring UV excitation on a wide variety of instruments. Copyright 2004 Wiley-Liss, Inc.

Raman spectroscopy of white wines.

PubMed

Martin, Coralie; Bruneel, Jean-Luc; Guyon, François; Médina, Bernard; Jourdes, Michael; Teissedre, Pierre-Louis; Guillaume, François

2015-08-15

The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 different wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV-visible range of two wine samples as well as their laser induced fluorescence have also been investigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic resonance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm(-1). This feasibility study demonstrates the potential of the Raman spectroscopic technique for the analysis of white wines. Copyright © 2015 Elsevier Ltd. All rights reserved.

A new nanosecond UV laser at 355 nm: early results of corneal flap cutting in a rabbit model.

PubMed

Trost, Andrea; Schrödl, Falk; Strohmaier, Clemens; Bogner, Barbara; Runge, Christian; Kaser-Eichberger, Alexandra; Krefft, Karolina; Vogel, Alfred; Linz, Norbert; Freidank, Sebastian; Hilpert, Andrea; Zimmermann, Inge; Grabner, Günther; Reitsamer, Herbert A

2013-12-03

A new 355 nm UV laser was used for corneal flap cutting in an animal model and tested for clinical and morphologic alterations. Corneal flaps were created (Chinchilla Bastards; n = 25) with an UV nanosecond laser at 355 nm (150 kHz, pulse duration 850 ps, spot-size 1 μm, spot spacing 6 × 6 μm, side cut Δz 1 μm; cutting depth 130 μm) and pulse energies of 2.2 or 2.5 μJ, respectively. Following slit-lamp examination, animals were killed at 6, 12, and 24 hours after treatment. Corneas were prepared for histology (hematoxylin and eosin [HE], TUNEL-assay) and evaluated statistically, followed by ultrastructural investigations. Laser treatment was tolerated well, flap lift was easier at 2.5 μJ compared with 2.2 μJ. Standard HE at 24 hours revealed intact epithelium in the horizontal cut, with similar increase in corneal thickness at both energies. Irrespective of energy levels, TUNEL assay revealed comparable numbers of apoptotic cells in the horizontal and vertical cut at 6, 12, and 24 hours, becoming detectable in the horizontal cut as an acellular stromal band at 24 hours. Ultrastructural analysis revealed regular morphology in the epi- and endothelium, while in the stroma, disorganized collagen lamellae were detectable representing the horizontal cut, again irrespective of energy levels applied. This new UV laser revealed no epi- nor endothelial damage at energies feasible for corneal flap cutting. Observed corneal swelling was lower compared with existing UV laser studies, albeit total energy applied here was much higher. Observed loss of stromal keratinocytes is comparable with available laser systems. Therefore, this new laser is suitable for refractive surgery, awaiting its test in a chronic environment.

Near-IR, blue, and UV generation by frequency conversion of a Tm:YAP laser

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew; Chinn, Steve

2018-02-01

We describe generation of near-infrared (944nm, 970nm), blue (472nm, 485nm), and UV (236 nm) light by frequency up-conversion of 2 μm output of a compact and efficient passively Q-switched Tm:YAP laser. The Tm:YAP laser source was near diffraction limited with maximum Q-switched pulse peak power of 190 kW. For second harmonic generation (SHG) of NIR, both periodically poled lithium niobate (PPLN) and lithium tri-borate (LBO) were evaluated, with 58% conversion efficiency and 3.1 W of 970 nm power achieved with PPLN. The PPLN 970nm emission was frequency doubled in 20mm long type I LBO, generating 1.1 W at 485nm with a conversion efficiency of 34%. With LBO used for frequency doubling of 2.3 W of 1888 nm Tm:YAP output to 944nm, 860mW was generated, with 37% conversion efficiency. Using a second LBO crystal to generate the 4th harmonic, 545mW of 472nm power was generated, corresponding to 64% conversion efficiency. To generate the 8th harmonic of Tm:YAP laser emission, the 472nm output of the second LBO was frequency doubled in a 7mm long BBO crystal, generating 110 mW at 236nm, corresponding to 21% conversion efficiency.

Fabrication of optical waveguides using laser direct writing method

NASA Astrophysics Data System (ADS)

Cho, Sung H.; Kim, Jung Min; Kim, Jae G.; Chang, Won S.; Lee, Eung S.

2004-09-01

Laser direct writing (LDW) process is developed using 3-rd harmonic Diode Pumped Solid State Laser (DPSSL) with the near UV wavelength of 355 nm. Photo-sensitive curable polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D patterns. We performed basic experiments for the various process conditions such as laser power, writing speed, laser focus, and optical polymer property to get the optimal conditions. This process could be applied to fabricate a single-mode waveguide without expensive mask projection method. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8.4μm width and 7.5μm height. Propagation loss of planar waveguide was 1.42 dB/cm at wavelength of 1,550 nm.

Laser effect on the 248 nm KrF transition using heavy ion beam pumping

NASA Astrophysics Data System (ADS)

Adonin, A.; Jacoby, J.; Turtikov, V.; Fertman, A.; Golubev, A.; Hoffmann, D. H. H.; Ulrich, A.; Varentsov, D.; Wieser, J.

2007-07-01

In December 2005 the first successful operation of a UV excimer laser pumped with a heavy ion beam was demonstrated at GSI. It was the first experiment in which the specific power deposition was sufficient to overcome laser threshold for a UV excimer scheme. The well known KrF* excimer laser line at λ=248 nm has been chosen for this experiment, because the wavelength is short, but still in the range of usual optical diagnostic tools and the emitted light can propagate in air without attenuation. A bunch compressed U+73238 beam with a particle energy of 250 MeV/u and about 110 ns pulse duration (FWHM) was used for this experiment. Single pulses of a beam intensity up to 2.5×109 particles per bunch were focused into the laser cell along the cavity axis. Compact spectrometers, high speed UV-photodiodes and gated CCD-cameras were used for diagnostics of the spontaneous and stimulated emission. As a main result of the experiment laser effect on the 248 nm KrF* excimer laser line has been obtained and verified by temporal and spectral narrowing of the laser line as well as the threshold behaviour and exponential growth of intensity with increasing pumping power. In summary it could be shown that the pumping power of the heavy ion beam at GSI is now sufficient to pump short wavelength lasers. It is planned to extend laser experiments in near future to the VUV range of the spectrum (λ<200 nm).

Coupled optical resonance laser locking.

PubMed

Burd, S C; du Toit, P J W; Uys, H

2014-10-20

We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to coupled transitions of ions in the same spectroscopic sample, by detecting only the absorption of the UV laser. Separate signals for locking the different lasers are obtained by modulating each laser at a different frequency and using lock-in detection of a single photodiode signal. Experimentally, we simultaneously lock a 369 nm and a 935 nm laser to the (2)S(1/2) → (2)(P(1/2) and (2)D(3/2) → (3)D([3/2]1/2) transitions, respectively, of Yb(+) ions generated in a hollow cathode discharge lamp. Stabilized lasers at these frequencies are required for cooling and trapping Yb(+) ions, used in quantum information and in high precision metrology experiments. This technique should be readily applicable to other ion and neutral atom systems requiring multiple stabilized lasers.

Transient Fluorescence Spectroscopy and laser induced fluorescence lifetimes of terbium doped dipicolinic acid

NASA Astrophysics Data System (ADS)

Makoui, Anali

We have investigated the use of deep UV laser induced fluorescence for the sensitive detection and spectroscopic lifetime studies of terbium doped dipicolinic acid (DPA-Tb) and used this to study the optical characteristics of DPA which is a chemical surrounding most bacterial spores. Background absorption spectra, fluorescence spectra, and Excitation Emission Matrix (EEM) spectra were made of the DPA-Tb complex, using both fixed 266 nm wavelength and tunable (220 nm--280 nm) UV laser excitations. Of importance, the fluorescence lifetimes of the four main fluorescence peaks (488 nm, 543 nm, 581 nm, and 618 nm) of the DPA-Tb complex have been measured for the first time to our knowledge. The lifetimes of all the fluorescing lines have been measured as a function of DPA-Tb concentration, solvent pH, and solvent composition, including that for the weakest fluorescing line of DPA-Tb at 618 nm. In addition, a new spectroscopic lifetime measurement technique, which we call "Transient Fluorescence Spectroscopy", was developed. In this technique, a weak, quasi-CW, amplitude modulated UV laser (8.5 kHz) was used to measure the lifetimes of the fluorescence lines, and yields insight into energy transfer and excitation lifetimes within the system. This technique is especially useful when a high power laser is not either available or not suitable. In the latter case, this would be when a high power pulsed deep-UV laser could produce bleaching or destruction of the biological specimen. In addition, this technique simulated the excitation and fluorescence emission of the DPA-Tb using a 4-level energy model, and solved the dynamic transient rate equations to predict the temporal behavior of the DPA-Tb emitted fluorescence. Excellent agreement between the experiments and the simulation were found. This technique has the potential to provide a more accurate value for the fluorescence lifetime values. In addition, with the use of asymmetric excitation waveforms, the dynamic transient rate equation analysis may allow for detailed studies of selected transfer mechanisms in a wide range of other spectroscopic applications including rare-earth solid-state lasing materials and biological samples.

Generation of 369.4 nm Radiation by Efficient Doubling of a Diode Laser

NASA Technical Reports Server (NTRS)

Williams, A.; Seidel, D. J.; Maleki, J.

1993-01-01

A resonant cavity second harmonic generation system has been developed to produce 369.4 nm radiation from a 738.8 nm diode laser with 10 mW nominal output power. This system utilizes a polarization technique to lock the cavity to the laser frequency. In this paper we report on an evaluation of the system using a Titanium:Sapphire laser as the input source, and preliminary results with a diode laser source. To our knowledge, this is the deepest uv light ever produced by frequency-doubling a diode laser.

Determination of UV-visible-NIR absorption coefficient of graphite bulk using direct and indirect methods

NASA Astrophysics Data System (ADS)

Smausz, T.; Kondász, B.; Gera, T.; Ajtai, T.; Utry, N.; Pintér, M.; Kiss-Albert, G.; Budai, J.; Bozóki, Z.; Szabó, G.; Hopp, B.

2017-10-01

Absorption coefficient of graphite bulk pressed from 1 to 5 μm-sized crystalline grains was measured in UV-Vis-NIR range with three different methods: (i) determination of pulsed laser ablation rate as the function of laser fluence for different wavelengths (248, 337, 532, and 1064 nm, respectively); (ii) production of aerosol particles by UV laser ablation of the bulk graphite in inert atmosphere and determination of the mass-specific absorption coefficient with a four-wavelength (266, 355, 532, and 1064 nm, respectively) photoacoustic spectrometer, and (iii) spectroscopic ellipsometry in 250-1000 nm range. Taking into account the wide range of the absorption coefficients of different carbon structures, an overall relatively good agreement was observed for the three methods. The ellipsometric results fit well with the ablation rate measurement, and the data obtained with photoacoustic method are also similar in the UV and NIR region; however, the values were somewhat higher in visible and near-UV range. Taking into account the limitations of the methods, they can be promising candidates for the determination of absorption coefficient when the samples are strongly scattering and there is no possibility to perform transmissivity measurements.

Effect of laser UV radiation on the eye scleral tissue in patients with open-angle glaucoma

NASA Astrophysics Data System (ADS)

Razhev, A. M.; Iskakov, I. A.; Churkin, D. S.; Orishich, A. M.; Maslov, N. A.; Tsibul'skaya, E. O.; Lomzov, A. A.; Ermakova, O. V.; Trunov, A. N.; Chernykh, V. V.

2018-05-01

We report the results of an experimental study of the effect of short-pulse laser UV radiation on the eye scleral tissue. As samples, we used isolated flaps of the eye scleral tissue from the patients with open-angle glaucoma of the second and third stages. The impact was implemented using the radiation of an excimer XeCl laser with a wavelength of 308 nm and a laser with a wavelength tunable within from 210 to 355 nm. Depending on the problem to be solved, the energy density on the surface of the irradiated tissue varied from a fraction of mJ cm-2 to 15 J cm-2. For the first time we studied the optical properties of the intraocular fluid in the UV and blue spectral range. The study of the ablation process under the action of radiation with a wavelength of 308 nm showed that the rate of material evaporation can vary within 24%–30% at an energy density above 7 J cm-2, depending on the glaucoma stage and the individual features of a patient. The excitation–emission matrices of laser-induced fluorescence (LIF) of the eye scleral tissue were studied experimentally using a laser with a wavelength tuned in the range 210–355 nm. We found the differences in the LIF spectra caused by the excitation wavelength and the openangle glaucoma stage.

Corneal reshaping using a pulsed UV solid-state laser

NASA Astrophysics Data System (ADS)

Ren, Qiushi; Simon, Gabriel; Parel, Jean-Marie A.; Shen, Jin-Hui; Takesue, Yoshiko

1993-06-01

Replacing the gas ArF (193 nm) excimer laser with a solid state laser source in the far-UV spectrum region would eliminate the hazards of a gas laser and would reduce its size which is desirable for photo-refractive keratectomy (PRK). In this study, we investigated corneal reshaping using a frequency-quintupled (213 nm) pulsed (10 ns) Nd:YAG laser coupled to a computer-controlled optical scanning delivery system. Corneal topographic measurements showed myopic corrections ranging from 2.3 to 6.1 diopters. Post-operative examination with the slit-lamp and operating microscope demonstrated a smoothly ablated surface without corneal haze. Histological results showed a smoothly sloping surface without recognizable steps. The surface quality and cellular effects were similar to that of previously described excimer PRK. Our study demonstrated that a UV solid state laser coupled to an optical scanning delivery system is capable of reshaping the corneal surface with the advantage of producing customized, aspheric corrections without corneal haze which may improve the quality of vision following PRK.

UV waveguides light fabricated in fluoropolymer CYTOP by femtosecond laser direct writing.

PubMed

Hanada, Yasutaka; Sugioka, Koji; Midorikawa, Katsumi

2010-01-18

We have fabricated optical waveguides inside the UV-transparent polymer, CYTOP, by femtosecond laser direct writing for propagating UV light in biochip applications. Femtosecond laser irradiation is estimated to increase the refractive index of CYTOP by 1.7 x 10(-3) due to partial bond breaking in CYTOP. The waveguide in CYTOP has propagation losses of 0.49, 0.77, and 0.91 dB/cm at wavelengths of 632.8, 355, and 266 nm, respectively.

Laser-induced bulk damage of silica glass at 355nm and 266nm

NASA Astrophysics Data System (ADS)

Kashiwagi, R.; Aramomi, S.

2016-12-01

Laser processing machines using Nd:YAG 3rd harmonic wave (355 nm) and 4th harmonic wave (266 nm) have been developed and put into practical use lately. Due to this, optical elements with high laser durability to 355 nm and 266 nm are required. Silica glass is the optical element which has high UV transmission and high laser durability. Laser-induced surface damage of the silica glass has been studied in detail, but we hardly have the significant knowledge of laserinduced bulk damage. This knowledge is required in order to evaluate the silica glass itself. That is because cracks and scratches on the surface give rise to a higher possibility of damage. Therefore, we studied the laser durability of a variety of the silica glass samples by 1-on-1 and S-on-1 laser-induced bulk damage threshold (LIDT) at 355 nm and 266 nm. In this study, we gained knowledge in three areas about bulk damage to the silica glass. First, the LIDT became lower as shot counts increased. Second, the LIDT decreased as the hydroxyl content in the silica glass increased. Last, the LIDT became higher as the hydrogen concentration in the silica glass increased. Under the UV irradiation, impurities are generated and the silica glass absorbs more light. Therefore, the LIDT decreased as shot counts increased. Also, the hydroxyl in particular generates more impurities, so damage easily occurs. On the other hand, the hydrogen reacts with impurities and absorption is suppressed. Based on these results, we can improve laser durability at 355 nm and 266 nm by reducing the hydroxyl content and increasing the hydrogen concentration in the silica glass.

New 223-nm excimer laser surgical system for photorefractive keratectomy

NASA Astrophysics Data System (ADS)

Bagaev, Sergei N.; Razhev, Alexander M.; Zhupikov, Andrey A.

1999-02-01

The using of KrCl (223 nm) excimer laser in ophthalmic devices for Photorefractive Keratectomy (PRK) and phototherapeutic Keratectomy (PTK) is offered. The structure and functions of a new surgical UV ophthalmic laser systems Medilex using ArF (193 nm) or KrCl (223 nm) excimer laser for corneal surgery are presented. The systems Medilex with the new optical delivery system is used for photoablative reprofiling of the cornea to correct refraction errors (myopia, hyperopia and astigmatism) and to treat a corneal pathologies. The use of the 223 nanometer laser is proposed to have advantages over the 193 nanometer laser. The results of application of the ophthalmic excimer laser systems Medilex for treatment of myopia are presented.

UV Lidar Receiver Analysis for Tropospheric Sensing of Ozone

NASA Technical Reports Server (NTRS)

Pliutau, Denis; DeYoung, Russell J.

2013-01-01

A simulation of a ground based Ultra-Violet Differential Absorption Lidar (UV-DIAL) receiver system was performed under realistic daytime conditions to understand how range and lidar performance can be improved for a given UV pulse laser energy. Calculations were also performed for an aerosol channel transmitting at 3 W. The lidar receiver simulation studies were optimized for the purpose of tropospheric ozone measurements. The transmitted lidar UV measurements were from 285 to 295 nm and the aerosol channel was 527-nm. The calculations are based on atmospheric transmission given by the HITRAN database and the Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological data. The aerosol attenuation is estimated using both the BACKSCAT 4.0 code as well as data collected during the CALIPSO mission. The lidar performance is estimated for both diffuseirradiance free cases corresponding to nighttime operation as well as the daytime diffuse scattered radiation component based on previously reported experimental data. This analysis presets calculations of the UV-DIAL receiver ozone and aerosol measurement range as a function of sky irradiance, filter bandwidth and laser transmitted UV and 527-nm energy

Pulsed UV laser-induced modifications in optical and structural characteristics of alpha-irradiated PM-355 SSNTD.

PubMed

Alghamdi, S S; Farooq, W A; Baig, M R; Algarawi, M S; Alrashidi, Talal Mohammed; Ali, Syed Mansoor; Alfaramawi, K

2017-10-01

Pre- and postalpha-exposed PM-355 detectors were irradiated using UV laser with different number of pulses (100, 150, 200, 300, and 400). UV laser beam energy of 20mJ per pulse with a pulse width of 9ns was incident on an area of 19.6mm 2 of the samples. XRD spectra indicated that for both reference and UV-irradiated samples, the structure is amorphous, but the crystallite size increases upon UV irradiation. The same results were obtained from SEM analysis. Optical properties of PM-355 polymeric solid-state nuclear track detectors were also investigated. Absorbance measurements for all PM-355 samples in the range of 200-400nm showed that the absorption edge had a blue shift up to a certain value, and then, it had an oscillating behavior. Photoluminescence spectra of PM-355 at 250nm revealed a decrease in the broadband peak intensity as a function of the number of UV pulses, while the wavelengths corresponding to the peaks had random shifts. Copyright © 2017 Elsevier Ltd. All rights reserved.

Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths.

PubMed

Wang, Jenny; Schuele, Georg; Palanker, Daniel

2015-01-01

Transparent ocular tissues, such as the cornea and crystalline lens, can be ablated or dissected using short-pulse lasers. In refractive and cataract surgeries, the cornea, lens, and lens capsule can be cut by producing dielectric breakdown in the focus of a near-infrared (IR) femtosecond laser, which results in explosive vaporization of the interstitial water, causing mechanical rupture of the surrounding tissue. Here, we compare the texture of edges of lens capsule cut by femtosecond lasers with IR and ultraviolet (UV) wavelengths and explore differences in interactions of these lasers with biological molecules. Scanning electron microscopy indicates that a 400-nm laser is capable of producing very smooth cut edges compared to 800 or 1030 nm at a similar focusing angle. Using gel electrophoresis and liquid chromatography/mass spectrometry, we observe laser-induced nonlinear breakdown of proteins and polypeptides by 400-nm femtosecond pulses above and below the dielectric breakdown threshold. On the other hand, 800-nm femtosecond lasers do not produce significant dissociation even above the threshold of dielectric breakdown. However, despite this additional interaction of UV femtosecond laser with proteins, we determine that efficient cutting requires plasma-mediated bubble formation and that remarkably smooth edges are the result of reduced thresholds and smaller focal volume.

Fiber optic systems in the UV region

NASA Astrophysics Data System (ADS)

Huebner, Michael; Meyer, H.; Klein, Karl-Friedrich; Hillrichs, G.; Ruetting, Martin; Veidemanis, M.; Spangenberg, Bernd; Clarkin, James P.; Nelson, Gary W.

2000-05-01

Mainly due to the unexpected progress in manufacturing of solarization-reduced all-silica fibers, new fiber-optic applications in the UV-region are feasible. However, the other components like the UV-sources and the detector- systems have to be improved, too. Especially, the miniaturization is very important fitting to the small-sized fiber-optic assemblies leading to compact and mobile UV- analytical systems. Based on independent improvements in the preform and fiber processing, UV-improved fibers with different properties have been developed. The best UV-fiber for the prosed applications is selectable by its short and long-term spectral behavior, especially in the region from 190 to 350 nm. The spectrum of the UV-source and the power density in the fiber have an influence on the nonlinear transmission and the damaging level; however, hydrogen can reduce the UV-defect concentration. After determining the diffusion processes in the fiber, the UV-lifetime in commercially available all-silica fibers can be predicted. Newest results with light from deuterium-lamps, excimer- lasers and 5th harmonics of Nd:YAG laser will be shown. Many activities are in the field of UV-sources. In addition to new UV-lasers like the Nd:YAG laser at 213 nm, a new low- power deuterium-lamp with smaller dimensions has been introduced last year. Properties of this lamp will be discussed, taking into account some of the application requirements. Finally, some new applications with UV-fiber optics will be shown; especially the TLC-method can be improved significantly, combining a 2-row fiber-array with a diode-array spectrometer optimized for fiber-optics.

Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates

DOE PAGES

Crawford, Mary H.; Allerman, Andrew A.; Armstrong, Andrew M.; ...

2015-10-30

We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al 0.32Ga 0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 10 8 cm –2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm 2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm 2. Furthermore, reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodesmore » into the deep UV.« less

Aequorea green fluorescent protein analysis by flow cytometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ropp, J.D.; Cuthbertson, R.A.; Donahue, C.J.

The isolation and expression of the cDNA for the green fluorescent protein (GFP) from the bioluminescent jellyfish Aequorea victoria has highlighted its potential use as a marker for gene expression in a variety of cell types. The longer wavelength peak (470 nm) of GFP`s bimodal absorption spectrum better matches standard fluorescein filter sets; however, it has a considerably lower amplitude than the major absorption peak at 395. In an effort to increase the sensitivity of GFP with routinely available instrumentation, Heim et al. have generated a GFP mutant (serine-65 to threonine; S65T-GFP) which possesses a single absorption peak centered atmore » 490 nm. We have constructed this mutant in order to determine whether it or wild-type GFP (wt-GFP) afforded greater sensitivity when excited near their respective absorption maxima. Using the conventionally available 488 nm and ultraviolet (UV) laser lines from the argon ion laser as well as the 407 nm line from a krypton ion laser with enhanced violet emission, we were able to closely match the absorption maxima of both the S65T and wild-type forms of Aequorea GFP and analyze differences in fluorescence intensity of transiently transfected 293 cells with flow cytometry. The highest fluorescence signal was observed with 488 nm excitation of S65T-GFP relative to all other laser line/GFP pairs. The wt-GFP fluorescence intensity, in contrast, was significantly higher at 407 nm relative to either 488 nm or UV. These results were consistent with parallel spectrofluorometric analysis of the emission spectrum for wt-GFP and S65T- GFP. The relative contribution of cellular autofluorescence at each wavelength was also investigated and shown to be significantly reduced at 407 nm relative to either UV or 488 nm. 29 refs., 5 figs.« less

A Novel High Efficient Laser Transmitter Design for a Space-borne Ozone Differential Lidar (DIAL)

NASA Technical Reports Server (NTRS)

Edwards, W. C.; Chen, S.; Petway, L. B.; Marsh, W. D.; Storm, M. E.; Barnes, J. C.

2000-01-01

Development of a UV laser transmitter capable of operating from a space platform is a critical step in enabling global earth observations of aerosols and ozone at resolutions greater than current passive instrument capabilities. Tropospheric chemistry is well recognized as the next frontier for global atmospheric measurement. NASA Langley Research Center (LaRC) and the Canadian Space Agency (CSA) have jointly studied the requirements for a satellite based, global ozone monitoring instrument. The study, called Ozone Research using Advanced Cooperative Lidar Experiment (ORACLE) has defined the Differential Absorption Lidar (DIAL) instrument performance, weight and power, and configuration requirements for a space based measurement. In order to achieve the measurement resolution and acceptable signal-to-noise from lidar returns, 500mJ/pulse (5 Watts average power) is required at both 305-308nm and 315-320nm wavelengths. These are consecutive pulses, in a 10 Hz, double-pulsed format. The two wavelengths are used as the on- and off-lines for the ozone DIAL measurement. NASA Langley is currently developing technology for a UV laser transmitter capable of meeting the ORACLE requirements. Experimental efforts to date have shown that the UV generation scheme is viable, and that energies greater than l00mJ/pulse are possible. In this paper, we will briefly discuss the down select process for the proposed laser design, the study effort to date and the laser system design, including both primary and alternate approaches. We will describe UV laser technology that minimizes the total number of optical components (for enhanced reliability) as well as the number of UV coated optics required to transmit the light from the laser (for enhanced optical damage resistance). While the goal is to develop a laser that will produce 500 mJ of energy, we will describe an optional design that will produce output energies between 100 - 200 mJ/unit and techniques for combining multiple laser modules in order to transmit a minimum of 500mJ of UV energy in each pulse of the on- and off-line pulse pairs. This modular laser approach provides redundancy and significantly reduces development time, risk and cost when compared to the development of a single, 500mJ double-pulsed laser subsystem. Finally, we will summarize the laser development effort to date, including results that include the highest known UV energy ( 130 mJ at 320nm) ever produced by a solid-state laser operating in this wavelength region.

303 nm continuous wave ultraviolet laser generated by intracavity frequency-doubling of diode-pumped Pr3+:LiYF4 laser

NASA Astrophysics Data System (ADS)

Zhu, Pengfei; Zhang, Chaomin; Zhu, Kun; Ping, Yunxia; Song, Pei; Sun, Xiaohui; Wang, Fuxin; Yao, Yi

2018-03-01

We demonstrate an efficient and compact ultraviolet laser at 303 nm generated by intracavity frequency doubling of a continuous wave (CW) laser diode-pumped Pr3+:YLiF4 laser at 607 nm. A cesium lithium borate (CLBO) crystal, cut for critical type I phase matching at room temperature, is used for second-harmonic generation (SHG) of the fundamental laser. By using an InGaN laser diode array emitting at 444.3 nm with a maximum incident power of 10 W, as high as 68 mW of CW output power at 303 nm is achieved. The output power stability in 4 h is better than 2.85%. To the best of our knowledge, this is high efficient UV laser generated by frequency doubling of an InGaN laser diode array pumped Pr3+:YLiF4 laser.

Multi-photon excited coherent random laser emission in ZnO powders

NASA Astrophysics Data System (ADS)

Tolentino Dominguez, Christian; Gomes, Maria De A.; Macedo, Zélia S.; de Araújo, Cid B.; Gomes, Anderson S. L.

2014-11-01

We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

UV Raman detection of 2,4-DNT in contact with sand particles

NASA Astrophysics Data System (ADS)

Blanco, Alejandro; Pacheco-Londoño, Leonardo C.; Peña-Quevedo, Alvaro J.; Hernández-Rivera, Samuel P.

2006-05-01

Deep Ultra Violet Raman Spectroscopy (DUV-RS) is an emerging tool for vibrational spectroscopy analysis and can be used in Point Detection mode to detect explosive components of landmines and Improvised Explosive Devices (IED). Interactions of explosives with different substrates can be measured by using quantitative vibrational signal shift information of scattered Raman light associated with these interactions. In this research, grounds were laid for detection of explosives using UV-Raman Spectroscopy equipped with 244 nm laser excitation line from a 488 nm frequency doubled Coherent FreD laser. In other experiments, samples of 2,4-DNT were allowed to interact with Ottawa Sand and were studied using DUV-RS. Characteristic vibrational signals of energetic compounds were analyzed in the ranges: 400-1200 cm -1, 1200-1800 cm -1, and 2800-3500 cm -1. In addition these Raman spectra were compared with dispersive spectra that were acquired using Raman Microscopy equipped with 514.5 nm (VIS) 785 nm (NIR) and 1064 nm (NIR) excitation lasers.

Response of antioxidant defense system to laser radiation apical meristem of Isatis indigotica seedlings exposed to UV-B.

PubMed

Chen, Yi-Ping

2009-07-01

To determine the response of antioxidant defense system to laser radiation apical meristem of Isatis indigotica seedlings, Isatis indigotica seedlings were subjected to UV-B radiation (10.08 kJ m(-2)) for 8 h day(-1) for 8 days (PAR, 220 micromol m(-2) s(-1)) and then exposed to He-Ne laser radiation (633 nm; 5.23 mW mm(-2); beam diameter: 1.5 mm) for 5 min each day without ambient light radiation. Changes in free radical elimination systems were measured, the results indicate that: (1) UV-B radiation enhanced the concentration of Malondialdahyde (MDA) and decreased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in seedlings compared with the control. The concentration of MDA was decreased and the activities of SOD, CAT and POD were increased when seedlings were subjected to elevated UV-B damage followed by laser; (2) the concentration of UV absorbing compounds and proline were increased progressively with UV-B irradiation, laser irradiation and He-Ne laser irradiation plus UV-B irradiation compared with the control. These results suggest that laser radiation has an active function in repairing UV-B-induced lesions in seedlings.

Development of a pulsed UV laser system for laser-desorption mass spectrometry on Mars

NASA Astrophysics Data System (ADS)

Kolleck, C.; Büttner, A.; Ernst, M.; Hülsenbusch, T.; Lang, T.; Marwah, R.; Mebben, S.; Priehs, M.; Kracht, D.; Neumann, J.

2017-11-01

A near-flight prototype of a pulsed UV laser has been developed for the Mars Organic Molecule Analyzer (MOMA) of the ExoMars mission. The laser head is based on a Nd:YAG oscillator with subsequent frequency quadrupling and emits nanosecond pulses with an energy of > 300 μJ at a wavelength of 266 nm. The design is compact and lightweight. Tests in relevant environment regarding temperature, vibration, and radiation have been performed.

Bulk damage and absorption in fused silica due to high-power laser applications

NASA Astrophysics Data System (ADS)

Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

2015-11-01

Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and consists of three different absorption bands centered at 165 nm (peroxy radicals), 215 nm (E'-center), and 265 nm (non-bridging oxygen hole center (NBOH)), which change the transmission behavior of material.

Sm 3+-doped polymer optical waveguide amplifiers

NASA Astrophysics Data System (ADS)

Huang, Lihui; Tsang, Kwokchu; Pun, Edwin Yue-Bun; Xu, Shiqing

2010-04-01

Trivalent samarium ion (Sm 3+) doped SU8 polymer materials were synthesized and characterized. Intense red emission at 645 nm was observed under UV laser light excitation. Spectroscopic investigations show that the doped materials are suitable for realizing planar optical waveguide amplifiers. About 100 μm wide multimode Sm 3+-doped SU8 channel waveguides were fabricated using a simple UV exposure process. At 250 mW, 351 nm UV pump power, a signal enhancement of ˜7.4 dB at 645 nm was obtained for a 15 mm long channel waveguide.

Colour centre recovery in yttria-stabilised zirconia: photo-induced versus thermal processes

NASA Astrophysics Data System (ADS)

Costantini, Jean-Marc; Touati, Nadia; Binet, Laurent; Lelong, Gérald; Guillaumet, Maxime; Beuneu, François

2018-05-01

The photo-annealing of colour centres in yttria-stabilised zirconia (YSZ) was studied by electron paramagnetic resonance spectroscopy upon UV-ray or laser light illumination, and compared to thermal annealing. Stable hole centres (HCs) were produced in as-grown YSZ single crystals by UV-ray irradiation at room temperature (RT). The HCs produced by 200-MeV Au ion irradiation, as well as the F+-type centres (? centres involving oxygen vacancies) were left unchanged upon UV illumination. In contrast, a significant photo-annealing of the latter point defects was achieved in 1.4-MeV electron-irradiated YSZ by 553-nm laser light irradiation at RT. Almost complete photo-bleaching was achieved by laser irradiation inside the absorption band of ? centres centred at a wavelength 550 nm. Thermal annealing of these colour centres was also followed by UV-visible absorption spectroscopy showing full bleaching at 523 K. Colour-centre evolutions by photo-induced and thermally activated processes are discussed on the basis of charge exchange processes between point defects.

Biomodulation of light on cells in laser surgery

NASA Astrophysics Data System (ADS)

Liu, Timon C.; Li, Yan; Duan, Rui; Cai, Xiongwei

2002-04-01

In laser surgery, it has been observed pulsed 532-nm laser can avoid postoperative purpura, but pulsed 585-nm, 595-nm or 600-nm lasers nonetheless cause purpura when they were used to treat port-wine stains; the XeCl excimer laser (308 nm) can safely and effectively clear psoriasis; both XeCl excimer laser and Ho:YAG laser were used in coronary interventions, but only former was approved by the FDA; open channels after ultraviolet (UV) laser treatment and closed channels with infrared (IR) lasers for transmyocardial laser revascularization; and so on. In this paper, the biological information model of low intensity laser (BIML) is extended to include UVA biomodulation and is used to understand these phenomena. Although the central intensity of the laser beam is so intense that it destroys the tissue, the edge intensity is so low that it can induce biomodulation. Our investigation showed that biomodulation of light on cells might play an important role in the long-term effects of laser surgery.

Solid-state-based laser system as a replacement for Ar⁺ lasers.

PubMed

Beck, Tobias; Rein, Benjamin; Sörensen, Fabian; Walther, Thomas

2016-09-15

We report on a solid-state-based laser system at 1028 nm. The light is generated by a diode laser seeded ytterbium fiber amplifier. In two build-up cavities, its frequency is doubled and quadrupled to 514 nm and 257 nm, respectively. At 514 nm, the system delivers up to 4.7 W of optical power. In the fourth harmonic, up to 173 mW are available limited by the nonlinear crystal. The frequency of the laser is mode-hop-free tunable by 16 GHz in 10 ms in the UV. Therefore, the system is suitable as a low maintenance, efficient, and tunable narrowband replacement for frequency doubled Ar⁺ laser systems.

Investigation of holmium-doped zirconium oxide ceramic phosphor as an ultraviolet wavelength-discriminating laser beam viewer

NASA Astrophysics Data System (ADS)

Yamanoi, Kohei; Hori, Tatsuhiro; Minami, Yuki; Empizo, Melvin John F.; Luong, Mui Viet; Shiro, Atsushi; Watanabe, Jun; Iwano, Keisuke; Iwasa, Yuki; Cadatal-Raduban, Marilou; Gabayno, Jacque Lynn; Shimizu, Toshihiko; Sarukura, Nobuhiko; Norimatsu, Takayoshi

2018-01-01

We report the fluorescence spectra of ZrO2 and trivalent Ho-doped ZrO2 ceramics under ultraviolet (UV) excitation at 213, 266, and 355 nm wavelengths. The Ho3+-doped ZrO2 ceramics exhibited varying fluorescence color tones depending on the excitation wavelength used. The different color tones match the fluorescence spectrum characteristics at each excitation wavelength. Our results demonstrate that Ho3+-doped ZrO2 ceramics can discriminate between UV light, specifically the third, fourth, and fifth harmonics of a Nd:YAG laser. It can potentially be used for developing UV laser beam viewers to aid laser alignment.

Fine-pitched microgratings encoded by interference of UV femtosecond laser pulses.

PubMed

Kamioka, Hayato; Miura, Taisuke; Kawamura, Ken-ichi; Hirano, Masahiro; Hosono, Hideo

2002-01-01

Fine-pitched microgratings are encoded on fused silica surfaces by a two-beam laser interference technique employing UV femtosecond pulses from the third harmonics of a Ti:sapphire laser. A pump and prove method utilizing a laser-induced optical Kerr effect or transient optical absorption change has been developed to achieve the time coincidence of the two pulses. Use of the UV pulses makes it possible to narrow the grating pitches to an opening as small as 290 nm, and the groove width of the gratings is of nanoscale size. The present technique provides a novel opportunity for the fabrication of periodic nanoscale structures in various materials.

Enhanced optical absorbance and fabrication of periodic arrays on nickel surface using nanosecond laser

NASA Astrophysics Data System (ADS)

Fu, Jinxiang; Liang, Hao; Zhang, Jingyuan; Wang, Yibo; Liu, Yannan; Zhang, Zhiyan; Lin, Xuechun

2017-04-01

A hundred-nanosecond pulsed laser was employed to structure the nickel surface. The effects of laser spatial filling interval and laser scanning speed on the optical absorbance capacity and morphologies on the nickel surface were experimentally investigated. The black nickel surface covered with dense micro/nanostructured broccoli-like clusters with strong light trapping capacity ranging from the UV to the near IR was produced at a high laser scanning speed up to v=100 mm/s. The absorbance of the black nickel is as high as 98% in the UV range of 200-400 nm, more than 97% in the visible spectrum, ranging from 400 to 800 nm, and over 90% in the IR between 800 and 2000 nm. In addition, when the nickel surface was irradiated in two-dimensional crossing scans by laser with different processing parameters, self-organized and shape-controllable structures of three-dimensional (3D) periodic arrays can be fabricated. Compared with ultrafast laser systems previously used for such processing, the nanosecond fiber laser used in this work is more cost-effective, compact and allows higher processing rates. This nickel surface structured technique may be applicable in optoelectronics, batteries industry, solar/wave absorbers, and wettability materials.

Effect of particle size on the UV pulsed-laser scribing in computational fluid dynamics-based simulations

NASA Astrophysics Data System (ADS)

Park, Kwan-Woo; Na, Suck-Joo

2010-06-01

A computational model for UV pulsed-laser scribing of silicon target is presented and compared with experimental results. The experiments were performed with a high-power Q-switched diode-pumped solid state laser which was operated at 355 nm. They were conducted on n-type 500 μm thick silicon wafers. The scribing width and depth were measured using scanning electron microscopy. The model takes into account major physics, such as heat transfer, evaporation, multiple reflections, and Rayleigh scattering. It also considers the attenuation and redistribution of laser energy due to Rayleigh scattering. Especially, the influence of the average particle sizes in the model is mainly investigated. Finally, it is shown that the computational model describing the laser scribing of silicon is valid at an average particle size of about 10 nm.

AlGaInN laser diode technology for free-space telecom applications

NASA Astrophysics Data System (ADS)

Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Boćkowski, M.; Leszczyński, M.; Wisniewski, P.; Czernecki, R.; Kucharski, R.; Targowski, G.; Watson, S.; Kelly, A. E.; Watson, M. A.; Blanchard, P.; White, H.

2015-03-01

The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. We consider the suitability of AlGaInN laser diode technology for free space laser communication, both airborne links and underwater telecom applications, mainly for defense and oil and gas industries.

Single-photon cesium Rydberg excitation spectroscopy using 318.6-nm UV laser and room-temperature vapor cell.

PubMed

Wang, Jieying; Bai, Jiandong; He, Jun; Wang, Junmin

2017-09-18

We demonstrate a single-photon Rydberg excitation spectroscopy of cesium (Cs) atoms in a room-temperature vapor cell. Cs atoms are excited directly from 6S 1/2 ground state to nP 3/2 (n = 70 - 100) Rydberg states with a 318.6 nm ultraviolet (UV) laser, and Rydberg excitation spectra are obtained by transmission enhancement of a probe beam resonant to Cs 6S 1/2 , F = 4 - 6P 3/2 , F' = 5 transition as partial population on F = 4 ground state are transferred to Rydberg state. Analysis reveals that the observed spectra are velocity-selective spectroscopy of Rydberg state, from which the amplitude and linewidth influenced by lasers' Rabi frequency have been investigated. Fitting to energies of Cs nP 3/2 (n = 70 -100) states, the determined quantum defect is 3.56671(42). The demodulated spectra can also be employed as frequency references to stabilize the UV laser frequency to specific Cs Rydberg transition.

Two-photon absorption measurements of deep UV transmissible materials at 213 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patankar, S.; Yang, S. T.; Moody, J. D.

We report on two photon absorption measurements at 213nm of deep UV transmissible media including LiF, MgF 2, CaF 2, BaF 2, Sapphire (Al 2O 3) and high purity grades of fused-silica (SiO 2). A high stability 24ps Nd:YAG laser operating at the 5th harmonic (213nm) was used to generate a high intensity, long Rayleigh length Gaussian focus inside the samples. The measurements of the Fluoride crystals and Sapphire indicate two photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two photon absorption, however, there are differences in linearmore » losses associated with purity. A low two photon absorption cross section is measured for MgF 2 making it an ideal material for the propagation of high intensity deep UV lasers.« less

Two-photon absorption measurements of deep UV transmissible materials at 213 nm

DOE PAGES

Patankar, S.; Yang, S. T.; Moody, J. D.; ...

2017-09-19

We report on two photon absorption measurements at 213nm of deep UV transmissible media including LiF, MgF 2, CaF 2, BaF 2, Sapphire (Al 2O 3) and high purity grades of fused-silica (SiO 2). A high stability 24ps Nd:YAG laser operating at the 5th harmonic (213nm) was used to generate a high intensity, long Rayleigh length Gaussian focus inside the samples. The measurements of the Fluoride crystals and Sapphire indicate two photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two photon absorption, however, there are differences in linearmore » losses associated with purity. A low two photon absorption cross section is measured for MgF 2 making it an ideal material for the propagation of high intensity deep UV lasers.« less

Two-photon absorption measurements of deep UV transmissible materials at 213  nm.

PubMed

Patankar, S; Yang, S T; Moody, J D; Swadling, G F; Erlandson, A C; Bayramian, A J; Barker, D; Datte, P; Acree, R L; Pepmeier, B; Madden, R E; Borden, M R; Ross, J S

2017-10-20

We report on two-photon absorption measurements at 213 nm of deep UV transmissible media, including LiF, MgF 2 , CaF 2 , BaF 2 , sapphire (Al 2 O 3 ), and high-purity grades of fused-silica (SiO 2 ). A high-stability 24 ps Nd:YAG laser operating at the 5th harmonic (213 nm) was used to generate a high-intensity, long-Rayleigh-length Gaussian focus inside the samples. The measurements of the fluoride crystals and sapphire indicate two-photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two-photon absorption; however, there are differences in linear losses associated with purity. A low two-photon absorption cross section is measured for MgF 2 , making it an ideal material for the propagation of high-intensity deep UV lasers.

Direct on-strip analysis of size- and time-resolved aerosol impactor samples using laser induced fluorescence spectra excited at 263 and 351 nm.

PubMed

Wang, Chuji; Pan, Yong-Le; James, Deryck; Wetmore, Alan E; Redding, Brandon

2014-04-11

We report a novel atmospheric aerosol characterization technique, in which dual wavelength UV laser induced fluorescence (LIF) spectrometry marries an eight-stage rotating drum impactor (RDI), namely UV-LIF-RDI, to achieve size- and time-resolved analysis of aerosol particles on-strip. The UV-LIF-RDI technique measured LIF spectra via direct laser beam illumination onto the particles that were impacted on a RDI strip with a spatial resolution of 1.2mm, equivalent to an averaged time resolution in the aerosol sampling of 3.6 h. Excited by a 263 nm or 351 nm laser, more than 2000 LIF spectra within a 3-week aerosol collection time period were obtained from the eight individual RDI strips that collected particles in eight different sizes ranging from 0.09 to 10 μm in Djibouti. Based on the known fluorescence database from atmospheric aerosols in the US, the LIF spectra obtained from the Djibouti aerosol samples were found to be dominated by fluorescence clusters 2, 5, and 8 (peaked at 330, 370, and 475 nm) when excited at 263 nm and by fluorescence clusters 1, 2, 5, and 6 (peaked at 390 and 460 nm) when excited at 351 nm. Size- and time-dependent variations of the fluorescence spectra revealed some size and time evolution behavior of organic and biological aerosols from the atmosphere in Djibouti. Moreover, this analytical technique could locate the possible sources and chemical compositions contributing to these fluorescence clusters. Advantages, limitations, and future developments of this new aerosol analysis technique are also discussed. Published by Elsevier B.V.

Pulsed UV laser technologies for ophthalmic surgery

NASA Astrophysics Data System (ADS)

Razhev, A. M.; Chernykh, V. V.; Bagayev, S. N.; Churkin, D. S.; Kargapol'tsev, E. S.; Iskakov, I. A.; Ermakova, O. V.

2017-01-01

The paper provides an overview of the results of multiyear joint researches of team of collaborators of Institute of Laser Physics SB RAS together with NF IRTC “Eye Microsurgery” for the period from 1988 to the present, in which were first proposed and experimentally realized laser medical technologies for correction of refractive errors of known today as LASIK, the treatment of ophthalmic herpes and open-angle glaucoma. It is proposed to carry out operations for the correction of refractive errors the use of UV excimer KrCl laser with a wavelength of 222 nm. The same laser emission is the most suitable for the treatment of ophthalmic herpes, because it has a high clinical effect, combined with many years of absence of recrudescence. A minimally invasive technique of glaucoma operations using excimer XeCl laser (λ=308 nm) is developed. Its wavelength allows perform all stages of glaucoma operations, while the laser head itself has high stability and lifetime, will significantly reduce operating costs, compared with other types of lasers.

Organization of the Topical Meeting on Tunable Solid State Lasers Held in North Falmouth, Massachusetts on 1-3 May 1989

DTIC Science & Technology

1989-08-30

nm to produce blue light at 455 nm (Figure 1). A 20 Hz doubled Nd:YAG pump laser emitting up to 150 mJ at 532 nm 147 WA4-2 was used to resonantly...pumped by a diode laser, then in addition to the processes of Fig. 1, excited state absorption of the pump light from both 4I13,/z and 4I3112 may be...are visible and UV systems pumped at wavelengths that are available from semiconductor diode lasers and infrared emitting systems having high slope

Pulsed lasers versus continuous light sources in capillary electrophoresis and fluorescence detection studies: Photodegradation pathways and models.

PubMed

Boutonnet, Audrey; Morin, Arnaud; Petit, Pierre; Vicendo, Patricia; Poinsot, Véréna; Couderc, François

2016-03-17

Pulsed lasers are widely used in capillary electrophoresis (CE) studies to provide laser induced fluorescence (LIF) detection. Unfortunately pulsed lasers do not give linear calibration curves over a wide range of concentrations. While this does not prevent their use in CE/LIF studies, the non-linear behavior must be understood. Using 7-hydroxycoumarin (7-HC) (10-5000 nM), Tamra (10-5000 nM) and tryptophan (1-200 μM) as dyes, we observe that continuous lasers and LEDs result in linear calibration curves, while pulsed lasers give polynomial ones. The effect is seen with both visible light (530 nm) and with UV light (355 nm, 266 nm). In this work we point out the formation of byproducts induced by pulsed laser upon irradiation of 7-HC. Their separation by CE using two Zeta LIF detectors clearly shows that this process is related to the first laser detection. All of these photodegradation products can be identified by an ESI-/MS investigation and correspond to at least two 7HC dimers. By using the photodegradation model proposed by Heywood and Farnsworth (2010) and by taking into account the 7-HC results and the fact that in our system we do not have a constant concentration of fluorophore, it is possible to propose a new photochemical model of fluorescence in LIF detection. The model, like the experiment, shows that it is difficult to obtain linear quantitation curves with pulsed lasers while UV-LEDs used in continuous mode have this advantage. They are a good alternative to UV pulsed lasers. An application involving the separation and linear quantification of oligosaccharides labeled with 2-aminobezoic acid is presented using HILIC and LED (365 nm) induced fluorescence. Copyright © 2016 Elsevier B.V. All rights reserved.

UV lifetime laser demonstrator for space-based applications

NASA Astrophysics Data System (ADS)

Albert, Michael; Puffenburger, Kent; Schum, Tom; Fitzpatrick, Fran; Litvinovitch, Slava; Jones, Darrell; Rudd, Joseph; Hovis, Floyd

2015-09-01

A long-lived UV laser is an enabling technology for a number of high-priority, space-based lidar instruments. These include next generation cloud and aerosol lidars that incorporates a UV channel, direct detection 3-D wind lidars, and ozone DIAL (differential absorption lidar) system. In previous SBIR funded work we developed techniques for increasing the survivability of components in high power UV lasers and demonstrated improved operational lifetimes. In this Phase III ESTO funded effort we are designing and building a TRL (Technology Readiness Level) 6 demonstrator that will have increased output power and a space-qualifiable package that is mechanically robust and thermally-stable. For full space compatibility, thermal control will be through pure conductive cooling. Contamination control processes and optical coatings will be chosen that are compatible with lifetimes in excess of 1 billion shots. The 1064nm output will be frequency tripled to provide greater than 100mJ pulses of 355nm light at 150 Hz. After completing the laser module build in the third quarter of 2015 we will initiate lifetime testing, followed by thermal/vacuum (TVAC) and vibration testing to demonstrate that the design is at TRL 6.

Microchip Lasers

DTIC Science & Technology

2016-10-31

microchip laser : (top) schematic and (bottom) photograph of working device mounted on 12.7-mm- dia. post. switch 17 (355-nm UV ), 1.5 µJ of fourth......USA E-mail: zayhowski@ll.mit.edu Abstract Microchip lasers are a rich family of solid-state lasers defined by their small size, robust integration

[Cleavage of DNA fragments induced by UV nanosecond laser excitation at 193 nm].

PubMed

Vtiurina, N N; Grokhovskiĭ, S L; Filimonov, I V; Medvedkov, O I; Nechipurenko, D Iu; Vasil'ev, S A; Nechipurenko, Iu D

2011-01-01

The cleavage of dsDNA fragments in aqueous solution after irradiation with UV laser pulses at 193 nm has been studied. Samples were investigated using polyacrylamide gel electrophoresis. The intensity of damage of particular phosphodiester bond after hot alkali treatment was shown to depend on the base pair sequence. It was established that the probability of cleavage is twice higher for sites of DNA containing two or more successively running guanine residues. A possible mechanism of damage to the DNA molecule connected with the migration of holes along the helix is discussed.

Induction of lambda prophage by 213 nm laser radiation: a quantitative comparison with 193 nm excimer radiation using image analysis.

PubMed

Matchette, L S; Grossman, L W; Hahn, D W; Cooney, C

1996-03-01

We compared the DNA damage produced by radiation from two UV laser wavelengths, 213 nm and 193 nm, with that produced by noncoherent 254 nm radiation. Following irradiation of Escherichia coli BR339, a bacteriophage lambda lysogen containing the lacZ gene, pro-phage induction was measured by assaying for beta-galactosidase. Because of the limited penetration by UV laser wavelengths an agar overlay of the lysogen was used as the irradiation target. Irradiation of 254 nm was performed in buffer suspension followed by transfer of 5 microL spots onto assay plants. Computer image analysis was used to monitor the rate of product formation, observed as an increase in optical density of the irradiated zones on assay plates. We found that the rate of product formation was a more reproducible unit of comparison than the optical density present at the end of the reaction. Although the rate of product formation was not linearly related to enzyme concentration, the data could be fit to a simple logarithmic function. Using this method, we concluded that the DNA damaging ability of 213 nm radiation was 10 times more efficient than 193 nm radiation and about 100 times less efficient than 254 nm noncoherent radiation.

Cascade generation in Al laser induced plasma

NASA Astrophysics Data System (ADS)

Nagli, Lev; Gaft, Michael; Raichlin, Yosef; Gornushkin, Igor

2018-05-01

We found cascade IR generation in Al laser induced plasma. This generation includes doublet transitions 3s 25s 2S1/2 → 3s24p 2P1/2,3/2 → 3s24s 2S1/2; corresponding to strong lines at 2110 and 2117 nm, and much weaker lines at 1312-1315 nm. The 3s25s2S 1/2 starting IR generation level is directly pumped from the 3s23p 2P3/2 ground level. The starting level for UV generation at 396.2 nm (transitions 3s24s 2S1/2 → 4p 2P3/2) is populated due to the fast collisional processes in the plasma plume. These differences led to different time and special dependences on the lasing in the IR and UV spectral range within the aluminum laser induced plasma.

Sensitive detection of chlorine in iron oxide by single pulse and dual pulse laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Pedarnig, J. D.; Haslinger, M. J.; Bodea, M. A.; Huber, N.; Wolfmeir, H.; Heitz, J.

2014-11-01

The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe2O3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe2O3 pellets and Fe3O4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λL). The UV pulses (λL = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λL = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of td ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

DURIP: Fast Oscilloscope and Detectors for Air Laser Research

DTIC Science & Technology

2015-01-01

TEKTRONIX DPO73304D, 33 GHz Digital Phosphor Oscilloscope; 4 analog channels DPO70604C, 6 GHz Digital Phosphor Oscilloscope; 4 analog channels...when we focus in air intense UV pulses resonantly with two-photon transitions in atomic oxygen or nitrogen. The UV pump pulse (or an...two-­‐photon   UV  pumping  at  226nm  for  oxygen,  and  at  207  or  211nm  for   nitrogen   is   followed   by

Advances in single mode and high power AlGaInN laser diode technology for systems applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lujca; Boćkowski, Michal; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Smalc-Koziorowska, Julita; Stanczyk, Szymon; Watson, Scott; Kelly, Antony E.

2015-03-01

The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries.

Responses of He-Ne laser on agronomic traits and the crosstalk between UVR8 signaling and phytochrome B signaling pathway in Arabidopsis thaliana subjected to supplementary ultraviolet-B (UV-B) stress.

PubMed

Gao, Limei; Li, Yongfeng; Shen, Zhihua; Han, Rong

2018-05-01

UV-B acclimation effects and UV-B damage repair induced by a 632.8-nm He-Ne laser were investigated in Arabidopsis thaliana plants in response to supplementary UV-B stress. There was an increasing trend in growth parameters in the combination-treated plants with He-Ne laser and UV-B light compared to those stressed with enhanced UV-B light alone during different developmental stages of plants. The photosynthetic efficiency (Pn) and survival rates of seedlings were significantly higher in the combination treatments than UV-B stress alone. The expression of UVR8, phytochrome B (PhyB), and their mediated signal responsive genes such as COP1, HY5, and CHS were also significantly upregulated in plants with the laser irradiation compared with other groups without the laser. Levels of flavonol accumulation in leaves and capsule yield of He-Ne laser-treated plants were increased. The phyB-9 mutants were more sensitive to enhanced UV-B stress and had no obvious improvements in plant phenotypic development and physiological damage caused by enhanced UV-B stress after He-Ne laser irradiation. Our results suggested that UVR8 and its mediated signaling pathway via interaction with COP1 can be induced by He-Ne laser, and these processes were dependent on cytoplasmic PhyB levels in plant cells, which might be one of the most important mechanisms of He-Ne laser on UV-B protection and UV-B damage repair. These current data have also elucidated that the biostimulatory effects of He-Ne laser on Arabidopsis thaliana plants would happen not only during the early growth stage but also during the entire late developmental stage.

Comparison and characterization of efficient frequency doubling at 397.5 nm with PPKTP, LBO and BiBO crystals

NASA Astrophysics Data System (ADS)

Wen, Xin; Han, Yashuai; Wang, Junmin

2016-04-01

A continuous-wave Ti:sapphire laser at 795 nm is frequency doubled in a bow-tie type enhancement four-mirror ring cavity with LiB3O5 (LBO), BiB3O6 (BiBO), and periodically polled KTiOPO4 (PPKTP) crystals, respectively. The properties of 397.5 nm ultra-violet (UV) output power, beam quality, stability for these different nonlinear crystals are investigated and compared. For PPKTP crystal, the highest doubling efficiency of 58.1% is achieved from 191 mW of 795 nm mode-matched fundamental power to 111 mW of 397.5 nm UV output. For LBO crystal, with 1.34 W of mode-matched 795 nm power, 770 mW of 397.5 nm UV output is achieved, implying a doubling efficiency of 57.4%. For BiBO crystal, with 323 mW of mode-matched 795 nm power, 116 mW of 397.5 nm UV output is achieved, leading to a doubling efficiency of 35.9%. The generated UV radiation has potential applications in the fields of quantum physics.

Radiation damage of all-silica fibers in the UV region

NASA Astrophysics Data System (ADS)

Gombert, Joerg; Ziegler, M.; Assmus, J.; Klein, Karl-Friedrich; Nelson, Gary W.; Clarkin, James P.; Pross, H.; Kiefer, J.

1999-04-01

Since several years, UVI-fibers having higher solarization- resistance are well known stimulating new fiber-optic applications in the UV-region below 250 nm. Besides the description of the improved transmission properties of UV- light from different UV-sources, the mechanisms of improvement have been discussed in detail. The UV-defects, mainly the E'- center with the UV-absorption band around 215 nm, were passivated by using hydrogen-doping. Besides DUV-light, ionizing radiation like Gamma-radiation or X-rays can create similar defects in the UV-region. In the past, the radiation- damage in the UV-region was studied on silica bulk samples: again, E'-centers were generated. Up to now, no UV- transmission through a 1 m long fiber during or after Gamma- radiation had been observed. However, the hydrogen in the UVI- fibers behaves the same for Gamma-irradiation, leading to a passivation of the radiation-induced defects and an improved transmission in the UV-C region below 250 nm. On this report, the influence of total dose and fiber diameter on the UV- damage after irradiation will be described and discussed. In addition, we will include annealing studies, with and without UV-light. Based on our results, the standard process of Gamma- sterilization with a total dose of approx. 2 Mrad can be used for UVI-fibers resulting in a good UV-transmission below 320 nm. Excimer-laser light at 308 nm (XeCl) and 248 nm (KrF) and deuterium-lamp light with the full spectrum starting at 200 nm can also be transmitted.

Persistent Flagellate Hyperpigmentation

DTIC Science & Technology

2017-04-28

hydroquinone), laser modalities such as Q-switched 755/1064 nm lasers , and ablative C02 resurfacing lasers . In addition, patients should be counseled on...the importance of UV protection. The patient was treated with each of these treatment modal ities with minimal improvement. Resources: 1. Lee HY

Nd:YAG laser double wavelength ablation of pollution encrustation on marble and bonding glues on duplicated painting canvas

NASA Astrophysics Data System (ADS)

Batishche, Sergei; Englezis, Apostolis; Gorovets, Tatiana; Kouzmouk, Andrei; Pilipenka, Uladzimir; Pouli, Paraskevi; Tatur, Hennady; Totou, Garyfallia; Ukhau, Viktar

2005-07-01

In the present study, a newly developed one-beam IR-UV laser cleaning system is presented. This system may be used for different applications in diverse fields, such as outdoors stonework conservation and canvas paintings restoration. The simultaneous use of the fundamental radiation of a Q-switched Nd:YAG laser at 1064 nm and its third harmonic at 355 nm was found appropriate to clean pollution crusts, while ensuring that no discoloration ("yellowing") would occur. The optimum ratio of UV to IR wavelengths in the final cleaning beam was investigated. In parallel, the same system was tested in diverse applications, such as the removal of bonding glues from duplicated canvases. The optimum laser parameters were investigated both on technical samples as well as on original paintings.

Study of noninvasive detection of latent fingerprints using UV laser

NASA Astrophysics Data System (ADS)

Li, Hong-xia; Cao, Jing; Niu, Jie-qing; Huang, Yun-gang; Mao, Lin-jie; Chen, Jing-rong

2011-06-01

Latent fingerprints present a considerable challenge in forensics, and noninvasive procedure that captures a digital image of the latent fingerprints is significant in the field of criminal investigation. The capability of photography technologies using 266nm UV Nd:YAG solid state laser as excitation light source to provide detailed images of unprocessed latent fingerprints is demonstrated. Unprocessed latent fingerprints were developed on various non-absorbent and absorbing substrates. According to the special absorption, reflection, scattering and fluorescence characterization of the various residues in fingerprints (fatty acid ester, protein, and carbosylic acid salts etc) to the UV light to weaken or eliminate the background disturbance and increase the brightness contrast of fingerprints with the background, and using 266nm UV laser as excitation light source, fresh and old latent fingerprints on the surface of four types of non-absorbent objects as magazine cover, glass, back of cellphone, wood desktop paintwork and two types of absorbing objects as manila envelope, notebook paper were noninvasive detected and appeared through reflection photography and fluorescence photography technologies, and the results meet the fingerprint identification requirements in forensic science.

Nanotechnology in lithium niobate for integrated optic frequency conversion in the UV

NASA Astrophysics Data System (ADS)

Busacca, Alessandro C.; Santini, Claudia; Oliveri, Luigi; Riva-Sanseverino, Stefano; Parisi, Antonino; Cino, Alfonso C.; Assanto, Gaetano

2017-11-01

In the domain of Earth Explorer satellites nanoengineered nonlinear crystals can optimize UV tunable solid-state laser converters. Lightweight sources can be based on Lithium Niobate (LN) domain engineering by electric field poling and guided wave interactions. In this Communication we report the preliminary experimental results and the very first demonstration of UltraViolet second-harmonic generation by first-order quasi-phase-matching in a surface-periodically-poled proton-exchanged LN waveguide. The pump source was a Ti-Sapphire laser with a tunability range of 700- 980 nm and a 40 GHz linewidth. We have measured UV continuous-wave light at 390 nm by means of a lock-in amplifier and of a photodiode with enhanced response in the UV. Measured conversion efficiency was about 1%W-1cm-2. QPM experiments show good agreement with theory and pave the way for a future implementation of the technique in materials less prone to photorefractive damage and wider transparency in the UV, such as Lithium Tantalate.

UV fatigue investigations with non-destructive tools in silica

NASA Astrophysics Data System (ADS)

Natoli, Jean-Yves; Beaudier, Alexandre; Wagner, Frank R.

2017-08-01

A fatigue effect is often observed under multiple laser irradiations, overall in UV. This decrease of LIDT, is a critical parameter for laser sources with high repetition rates and with a need of long-term life, as in spatial applications at 355nm. A challenge is also to replace excimer lasers by solid laser sources, this challenge requires to improve drastically the lifetime of optical materials at 266nm. Main applications of these sources are devoted to material surface nanostructuration, spectroscopy and medical surgeries. In this work we focus on the understanding of the laser matter interaction at 266nm in silica in order to predict the lifetime of components and study parameters links to these lifetimes to give keys of improvement for material suppliers. In order to study the mechanism involved in the case of multiple irradiations, an interesting approach is to involve the evolution of fluorescence, in order to observe the first stages of material changes just before breakdown. We will show that it is sometime possible to estimate the lifetime of component only with the fluorescence measurement, saving time and materials. Moreover, the data from the diagnostics give relevant informations to highlight "defects" induced by multiple laser irradiations.

Time-dependent preparation of gelatin-stabilized silver nanoparticles by pulsed Nd:YAG laser

NASA Astrophysics Data System (ADS)

Darroudi, Majid; Ahmad, M. B.; Zamiri, Reza; Abdullah, A. H.; Ibrahim, N. A.; Sadrolhosseini, A. R.

2011-03-01

Colloidal silver nanoparticles (Ag-NPs) were successfully prepared using a nanosecond pulsed Nd:YAG laser, λ = 1064 nm, with laser fluence of approximately about 360 mJ/pulse, in an aqueous gelatin solution. In this work, gelatin was used as a stabilizer, and the size and optical absorption properties of samples were studied as a function of the laser ablation times. The results from the UV-vis spectroscopy demonstrated that the mean diameter of Ag-NPs decrease as the laser ablation time increases. The Ag-NPs have mean diameters ranging from approximately 10 nm to 16 nm. Compared with other preparation methods, this work is clean, rapid, and simple to use.

Atomic force microscopy analysis of human cornea surface after UV (λ=266 nm) laser irradiation

NASA Astrophysics Data System (ADS)

Spyratou, E.; Makropoulou, M.; Moutsouris, K.; Bacharis, C.; Serafetinides, A. A.

2009-07-01

Efficient cornea reshaping by laser irradiation for correcting refractive errors is still a major issue of interest and study. Although the excimer laser wavelength of 193 nm is generally recognized as successful in ablating corneal tissue for myopia correction, complications in excimer refractive surgery leads to alternative laser sources and methods for efficient cornea treatment. In this work, ablation experiments of human donor cornea flaps were conducted with the 4th harmonic of an Nd:YAG laser, with different laser pulses. AFM analysis was performed for examination of the ablated cornea flap morphology and surface roughness.

Lasers, extreme UV and soft X-ray

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nilsen, Joseph

2015-09-20

Three decades ago, large ICF lasers that occupied entire buildings were used as the energy sources to drive the first X-ray lasers. Today X-ray lasers are tabletop, spatially coherent, high-repetition rate lasers that enable many of the standard optical techniques such as interferometry to be extended to the soft X-ray regime between wavelengths of 10 and 50 nm. Over the last decade X-ray laser performance has been improved by the use of the grazing incidence geometry, diode-pumped solid-state lasers, and seeding techniques. The dominant X-ray laser schemes are the monopole collisional excitation lasers either driven by chirped pulse amplification (CPA)more » laser systems or capillary discharge. The CPA systems drive lasing in neon-like or nickel-like ions, typically in the 10 – 30 nm range, while the capillary system works best for neon-like argon at 46.9 nm. Most researchers use nickel-like ion lasers near 14 nm because they are well matched to the Mo:Si multilayer mirrors that have peak reflectivity near 13 nm and are used in many applications. As a result, the last decade has seen the birth of the X-ray free electron laser (XFEL) that can reach wavelengths down to 0.15 nm and the inner-shell Ne laser at 1.46 nm.« less

GaN thin films growth and their application in photocatalytic removal of sulforhodamine B from aqueous solution under UV pulsed laser irradiation.

PubMed

Gondal, Mohammed A; Chang, Xiao F; Yamani, Zain H; Yang, Guo F; Ji, Guang B

2011-01-01

Single-crystalline Gallium Nitride (GaN) thin films were fabricated and grown by metal organic chemical vapor deposition (MOCVD) method on c-plane sapphire substrates and then characterized by high resolution-X-ray diffraction (HR-XRD) and photoluminescence (PL) measurements. The photocatalytic decomposition of Sulforhodamine B (SRB) molecules on GaN thin films was investigated under 355 nm pulsed UV laser irradiation. The results demonstrate that as-grown GaN thin films exhibited efficient degradation of SRB molecules and exhibited an excellent photocatalytic-activity-stability under UV pulsed laser exposure.

Classifying the Basic Parameters of Ultraviolet Copper Bromide Laser

NASA Astrophysics Data System (ADS)

Gocheva-Ilieva, S. G.; Iliev, I. P.; Temelkov, K. A.; Vuchkov, N. K.; Sabotinov, N. V.

2009-10-01

The performance of deep ultraviolet copper bromide lasers is of great importance because of their applications in medicine, microbiology, high-precision processing of new materials, high-resolution laser lithography in microelectronics, high-density optical recording of information, laser-induced fluorescence in plasma and wide-gap semiconductors and more. In this paper we present a statistical study on the classification of 12 basic lasing parameters, by using different agglomerative methods of cluster analysis. The results are based on a big amount of experimental data for UV Cu+ Ne-CuBr laser with wavelengths 248.6 nm, 252.9 nm, 260.0 nm and 270.3 nm, obtained in Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences. The relevant influence of parameters on laser generation is also evaluated. The results are applicable in computer modeling and planning the experiments and further laser development with improved output characteristics.

Ultraviolet emission in Tm3+-doped fluoride fiber pumped with two infrared wavelengths

NASA Astrophysics Data System (ADS)

Mejía, E. B.

2006-12-01

An infrared, two-wavelength pumping scheme for generating UV in Tm3+-doped fibers is investigated and proposed as an alternative because the pump wavelengths are accessible from laser diodes. Spectral characterizations of fiber samples with different concentrations revealed that moderate concentrations are best suitable to produce UV (348-362nm) emission when single—or double-line pumping with 1117 and 725nm. Detailed spectroscopic measurements realized to the fiber with the best performance, the 2000ppmwt, allowed to obtain the copumping wavelengths (in the ˜725nm region) that enhanced the UV emission. For example, when applying tens of milliwatts at 725nm, which represented a 28% increase of total pump power, the UV emission increased in an avalanchelike fashion up to three orders of magnitude. Then, a high-power 1117nm source that currently exists in the market and a moderate power 725nm source under development are possible to be used as pumps for this scheme.

The influence of UV laser radiation on the absorption and luminescence of photothermorefractive glasses containing silver ions

NASA Astrophysics Data System (ADS)

Ignat'ev, A. I.; Ignat'ev, D. A.; Nikonorov, N. V.; Sidorov, A. I.

2015-08-01

It is experimentally shown that irradiation of silver-containing glasses by nanosecond laser pulses with a wavelength of 248 nm leads to the formation of unstable point defects (having absorption bands in the UV and visible spectral ranges) in the irradiated region and causes the transition of ions and charged molecular silver clusters to the neutral state, which is accompanied by an increase in the luminescence intensity in the visible spectral range. The influence of pulsed laser irradiation is compared with the effect of exposure to cw UV light of a mercury lamp. Some models are proposed to explain the influence of the laser effect on the optical properties of glasses.

UV solid state laser ablation of intraocular lenses

NASA Astrophysics Data System (ADS)

Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

2013-06-01

Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a smooth optical surface on the intraocular lens with no irregularities, observed with other wavelengths.

International Symposium on Special Topics in Chemical Propulsion (3rd): Non-Intrusive Combustion Diagnostics Held in Scheveningen, Netherlands on 10-14 May 93

DTIC Science & Technology

1993-05-14

Saima, and H. Watanabe 67 11:00 Vacuum- UV cw-Resonance Fluorescence Studies on Laser Photodissoclation of Hydrazine Fuels, G. L. Vaghjani 78 11:30...Transfer In Disc-Stabiluzed ames, P. Ferrdo and M. V. Heitor 116 3:30 Coffee Break 3:50 UV Raman Measurements of Temperature and Concentrations with 308...in remote or hostile environments, including flight instrumentation. LOSA results to be presented include uv ring dye laser measurements of OH (306 nm

Quantitative absorption data from thermally induced wavefront distortions on UV, Vis, and NIR optics

NASA Astrophysics Data System (ADS)

Mann, Klaus; Schäfer, Bernd; Leinhos, Uwe; Lübbecke, Maik

2017-11-01

A photothermal absorption measurement system was set up, deploying a Hartmann-Shack wavefront sensor with extreme sensitivity to accomplish spatially resolved monitoring of thermally induced wavefront distortions. Photothermal absorption measurements in the near-infrared and deep ultra-violet spectral range are performed for the characterization of optical materials, utilizing a Yb fiber laser (λ = 1070 nm) and an excimer laser (193nm, 248nm) to induce thermal load. Wavefront deformations as low as 50pm (rms) can be registered, allowing for a rapid assessment of material quality. Absolute calibration of the absorption data is achieved by comparison with a thermal calculation. The method accomplishes not only to measure absorptances of plane optical elements, but also wavefront deformations and focal shifts in lenses as well as in complex optical systems, such as e.g. F-Theta objectives used in industrial high power laser applications. Along with a description of the technique we present results from absorption measurements on coated and uncoated optics at various laser wavelengths ranging from deep UV to near IR.

AlGaInN laser diode technology and systems for defence and security applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Boćkowski, Mike; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Scott; Kelly, Antony E.

2015-05-01

The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications such as underwater communications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries.

All Fiber-Coupled OH Planar Laser-Induced-Fluorescence (OH-PLIF)-Based Two-Dimensional Thermometry.

PubMed

Hsu, Paul S; Jiang, Naibo; Patnaik, Anil K; Katta, Vish; Roy, Sukesh; Gord, James R

2018-04-01

Two-color, planar laser-induced fluorescence (PLIF)-based two-dimensional (2D) thermometry techniques for reacting flows, which are typically developed in the laboratory conditions, face a stiff challenge in their practical implementation in harsh environments such as combustion rigs. In addition to limited optical access, the critical experimental conditions (i.e., uncontrolled humidity, vibration, and large thermal gradients) often restrict sensitive laser system operation and cause difficulties maintaining beam-overlap. Thus, an all fiber-coupled, two-color OH-PLIF system has been developed, employing two long optical fibers allowing isolation of the laser and signal-collection systems. Two OH-excitation laser beams (∼283 nm and ∼286 nm) are delivered through a common 6 m long, 400 µm core, deep ultraviolet (UV)-enhanced multimode fiber. The fluorescence signal (∼310 nm) is collected by a 3 m long, UV-grade imaging fiber. Proof-of-principle temperature measurements are demonstrated in atmospheric pressure, near adiabatic, CH 4 /O 2 /N 2 jet flames. The effects of the excitation pulse interval on fiber transmission are investigated. The proof-of-principle measurements show significant promise for thermometry in harsh environments such as gas turbine engine tests.

A dense plasma ultraviolet source

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.

1978-01-01

The intense ultraviolet emission from the NASA Hypocycloidal-Pinch (HCP) plasma is investigated. The HCP consists of three disk electrodes whose cross section has a configuration similar to the cross section of a Mather-type plasma focus. Plasma foci were produced in deuterium, helium, xenon, and krypton gases in order to compare their emission characteristics. Time-integrated spectra in the wavelength range from 200 nm to 350 nm and temporal variations of the uv emission were obtained with a uv spectrometer and a photomultiplier system. Modifications to enhance uv emission in the iodine-laser pump band (250 to 290 nm) and preliminary results produced by these modifications are presented. Finally, the advantages of the HCP as a uv over use of conventional xenon lamps with respect to power output limit, spectral range, and lifetime are discussed.

Photonic structures in diamond based on femtosecond UV laser induced periodic surface structuring (LIPSS).

PubMed

Granados, Eduardo; Martinez-Calderon, Miguel; Gomez, Mikel; Rodriguez, Ainara; Olaizola, Santiago M

2017-06-26

We study the fabrication of photonic surface structures in single crystal diamond by means of highly controllable direct femtosecond UV laser induced periodic surface structuring. By appropriately selecting the excitation wavelength, intensity, number of impinging pulses and their polarization state, we demonstrate emerging high quality and fidelity diamond grating structures with surface roughness below 1.4 nm. We characterize their optical properties and study their potential for the fabrication of photonic structure anti-reflection coatings for diamond Raman lasers in the near-IR.

The variation in surface morphology and hardness of human deciduous teeth samples after laser irradiation

NASA Astrophysics Data System (ADS)

Khalid, Arooj; Bashir, Shazia; Akram, Mahreen; Salman Ahmed, Qazi

2017-11-01

The variation in surface morphology and hardness of human deciduous teeth samples has been investigated after laser irradiation at different wavelengths and energies. Nd:YAG was employed as a source of irradiation for IR (1064 nm) and visible (532 nm) radiation, whereas an excimer laser was used as the source of UV (248 nm) radiation. Scanning electron microscope (SEM) analysis was carried out to reveal the surface morphological evolution of teeth samples. Vickers microhardness tester was employed to investigate the modifications in the hardness of the laser-treated samples. It is observed from SEM analysis that IR wavelength is responsible for ablation of collagen matrix and intertubular dentine. For visible radiation, the ablation of collagen along with hydroxypatite is observed. With UV radiation, the ablation of peritubular dentine is dominant and is responsible for the sealing of tubules. The decrease in hardness at lower energy for both wavelengths is due to the evaporation of carbon content. With increasing energy, evaporation of water along with carbon content, and resolidification and re-organization of inorganic content causes the increase in hardness of the treated dentine. SEM as well as microhardness analyses reveal that laser wavelengths and energy of laser radiation significantly influence the surface morphology and hardness of samples.

The near-UV absorber OSSO and its isomers.

PubMed

Wu, Zhuang; Wan, Huabin; Xu, Jian; Lu, Bo; Lu, Yan; Eckhardt, André K; Schreiner, Peter R; Xie, Changjian; Guo, Hua; Zeng, Xiaoqing

2018-05-01

Disulfur dioxide, OSSO, has been proposed as the enigmatic "near-UV absorber" in the yellowish atmosphere of Venus. However, the fundamentally important spectroscopic properties and photochemistry of OSSO are scarcely documented. By either condensing gaseous SO or 266 laser photolysis of an S2O2 complex in Ar or N2 at 15 K, syn-OSSO, anti-OSSO, and cyclic OS([double bond, length as m-dash]O)S were identified by IR and UV/Vis spectroscopy for the first time. The observed absorptions (λmax) for OSSO at 517 and 390 nm coincide with the near-UV absorption (320-400 nm) found in the Venus clouds by photometric measurements with the Pioneer Venus orbiter. Subsequent UV light irradiation (365 nm) depletes syn-OSSO and anti-OSSO and yields a fourth isomer, syn-OSOS, with concomitant dissociation into SO2 and elemental sulfur.

Nanosecond laser-induced back side wet etching of fused silica with a copper-based absorber liquid

NASA Astrophysics Data System (ADS)

Lorenz, Pierre; Zehnder, Sarah; Ehrhardt, Martin; Frost, Frank; Zimmer, Klaus; Schwaller, Patrick

2014-03-01

Cost-efficient machining of dielectric surfaces with high-precision and low-roughness for industrial applications is still challenging if using laser-patterning processes. Laser induced back side wet etching (LIBWE) using UV laser pulses with liquid heavy metals or aromatic hydrocarbons as absorber allows the fabrication of well-defined, nm precise, free-form surfaces with low surface roughness, e.g., needed for optical applications. The copper-sulphatebased absorber CuSO4/K-Na-Tartrate/NaOH/formaldehyde in water is used for laser-induced deposition of copper. If this absorber can also be used as precursor for laser-induced ablation, promising industrial applications combining surface structuring and deposition within the same setup could be possible. The etching results applying a KrF excimer (248 nm, 25 ns) and a Nd:YAG (1064 nm, 20 ns) laser are compared. The topography of the etched surfaces were analyzed by scanning electron microscopy (SEM), white light interferometry (WLI) as well as laser scanning microscopy (LSM). The chemical composition of the irradiated surface was studied by energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR). For the discussion of the etching mechanism the laser-induced heating was simulated with finite element method (FEM). The results indicate that the UV and IR radiation allows micro structuring of fused silica with the copper-based absorber where the etching process can be explained by the laser-induced formation of a copper-based absorber layer.

Studies on the mechanism of printing film-coated tablets containing titanium dioxide in the film by using UV laser irradiation.

PubMed

Kato, Yoshiteru; Nakashima, Yasuhiko; Shino, Naoki; Sasaki, Koichi; Hosokawa, Akihiro; Ishihara, Hiroshi

2010-04-01

The purpose of this article is to study a detailed mechanism of printing when film-coated tablets were irradiated by UV laser at a wavelength of 355 nm. Hydroxypropylmethylcellulose (HPMC) film containing titanium dioxide (TiO(2)) and the film not containing TiO(2) and TiO(2) powder were lirradiated by the UV laser and estimated by the morphological observation by zoom stereo microscope, thermogravimetric analysis (TGA), total color difference (dE), X-ray powder diffraction (XRD), and dispersive Raman microscopy. In the case of the film containing TiO(2), the film showed a visible change in its color from white to gray by the UV laser irradiation. By zoom stereo microscope, it was found that the entire UV laser-irradiated area was not grayed uniformly, but many black particles, whose diameter was about 2 microm, were observed on the film. When TiO(2) powder was irradiated by the UV laser, a visible change in its color from white to gray was observed similar to the case of the film containing TiO(2). There were many black particles locally in the UV laser-treated TiO(2) powder by the morphological observation, and these black particles, agglomerates of the grayed oxygen-defected TiO(2), were associated with the visible change of the TiO(2). It was found that the film-coated tablets were printed utilizing the formation of the black particles by the agglomeration of the grayed oxygen-defected TiO(2) by the UV laser irradiation.

Power enhancement of burst-mode UV pulses using a doubly-resonant optical cavity

DOE PAGES

Rahkman, Abdurahim; Notcutt, Mark; Liu, Yun

2015-11-24

We report a doubly-resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (IR, 1064 nm) and its frequency tripled ultraviolet (UV, 355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber optic frequency shifter. The DREC technique opens a new paradigm in the applications of optical cavities to power enhancement of burst-mode lasers with arbitrarymore » macropulse width and repetition rate.« less

Trace element analysis of synthetic mono- and poly-crystalline CaF 2 by ultraviolet laser ablation inductively coupled plasma mass spectrometry at 266 and 193 nm

NASA Astrophysics Data System (ADS)

Koch, J.; Feldmann, I.; Hattendorf, B.; Günther, D.; Engel, U.; Jakubowski, N.; Bolshov, M.; Niemax, K.; Hergenröder, R.

2002-06-01

The analytical figures of merit for ultraviolet laser ablation-inductively coupled plasma mass spectrometry (UV-LA-ICP-MS) at 266 nm with respect to the trace element analysis of high-purity, UV-transmitting alkaline earth halides are investigated and discussed. Ablation threshold energy density values and ablation rates for mono- and poly-crystalline CaF 2 samples were determined. Furthermore, Pb-, Rb-, Sr-, Ba- and Yb-specific analysis was performed. For these purposes, a pulsed Nd:YAG laser operated at the fourth harmonic of the fundamental wavelength (λ=266 nm) and a double-focusing sector field ICP-MS detector were employed. Depending on the background noise and isotope-specific sensitivity, the detection limits typically varied from 0.7 ng/g for Sr to 7 ng/g in the case of Pb. The concentrations were determined using a glass standard reference material (SRM NIST612). In order to demonstrate the sensitivity of the arrangement described, comparative measurements by means of a commercial ablation system consisting of an ArF excimer laser (λ=193 nm) and a quadrupole-type ICP-MS (ICP-QMS) instrument were carried out. The accuracy of both analyses was in good agreement, whereas ablation at 266 nm and detection using sector-field ICP-MS led to a sensitivity that was one order of magnitude above that obtained at 193 nm with ICP-QMS.

Real-time investigations of structural and optical changes in photochromic Ag/TiO2 nanocomposite thin films under laser irradiation

NASA Astrophysics Data System (ADS)

Babonneau, D.; Diop, D. K.; Simonot, L.; Lamongie, B.; Blanc, N.; Boudet, N.; Vocanson, F.; Destouches, N.

2018-03-01

Photochromic reaction dynamics in silver nanoparticles embedded in mesoporous titanium dioxide thin films is investigated by combining real-time grazing incidence small-angle x-ray scattering (GISAXS) and optical transmission measurements during UV-visible laser exposure cycles. While GISAXS probes changes in the particle size distribution, transmittance measurements are sensitive to spectral changes induced by photo-activated processes. Our results reveal a repeatable photochromic behavior with a good correlation in terms of kinetics between the morphological and optical fluctuations. Visible laser irradiation at 532 nm induces a preferential photo-dissolution of small silver particles, which in turn causes an increase in transmittance near the excitation wavelength. Furthermore, the photo-dissolution process can be significantly accelerated and amplified by associating visible laser with x-ray irradiation. Under UV laser irradiation at 360 nm, the bleaching process can be reverted by photocatalytic reduction with the mesopores in the TiO2 film acting as molds, which have the ability to confine the nanoparticle growth. However, in the irradiation conditions used in the present study, it appears that the photocatalytic growth of silver nanoparticles is slower than the photo-dissolution process, whereas its efficiency gradually degrades throughout the exposures to UV light.

A Compact Ti:Sapphire Laser With its Third Harmonic Generation (THG) for an Airborne Ozone Differential Absorption Lidar (DIAL) Transmitter

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Storm, Mark E.; Marsh, Waverly D.; Petway, Larry B.; Edwards, William C.; Barnes, James C.

2000-01-01

A compact and high-pulse-energy Ti:Sapphire laser with its Third Harmonic Generation (THG) has been developed for an airborne ozone differential absorption lidar (DIAL) to study the distributions and concentrations of the ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a frequency-doubled Nd:YAG laser and seeded by a single mode diode laser, is operated either at 867 nm or at 900 nm with a pulse repetition frequency of 20 Hz. High energy laser pulses (more than 110 mJ/pulse) at 867 nm or 900 nm with a desired beam quality have been achieved and utilized to generate its third harmonic at 289nm or 300nm, which are on-line and off-line wavelengths of an airborne ozone DIAL. After being experimentally compared with Beta-Barium Borate (beta - BaB2O4 or BBO) nonlinear crystals, two Lithium Triborate (LBO) crystals (5 x 5 x 20 cu mm) are selected for the Third Harmonic Generation (THG). In this paper, we report the Ti:Sapphire laser at 900 nm and its third harmonic at 300 nm. The desired high ultraviolet (UV) output pulse energy is more than 30 mJ at 300 nm and the energy conversion efficiency from 900 nm to 300 nm is 30%.

Effectiveness of low level laser therapy for treating male infertility

PubMed Central

Vladimirovich Moskvin, Sergey; Ivanovich Apolikhin, Oleg

2018-01-01

In half of the cases, the infertility of the couple is due to the disorder of the male fertility. The leading factors that cause male infertility are urogenital infections, disorders of the immune system, testicular and prostate pathology, as well as endocrine disorders. Low level laser therapy (LLLT) is a very effective physical therapy method, used in many areas of medicine, including obstetrics and gynaecology, andrology and urology; and it is recommended as an integral part of the complex treatment of infertility. The literature review showed that LLLT is beneficial in treating male infertility. Laser can significantly improve the survival, motility and speed of movement of spermatozoa. Laser therapy of patients with prostatitis and vesiculitis can eliminate infiltrative-exudative changes, improve reproductive and copulatory functions. Local illumination of red (635 nm) and infrared (904 nm) spectra should be combined with intravenous laser blood illumination (ILBI) of red (635 nm) and ultraviolet (UV) (365 nm) spectra. PMID:29806585

Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH.

PubMed

Hsu, Paul S; Kulatilaka, Waruna D; Roy, Sukesh; Gord, James R

2013-05-01

We investigate the fundamental transmission characteristics of nanosecond-duration, 10 kHz repetition rate, ultraviolet (UV) laser pulses through state-of-the-art, UV-grade fused-silica fibers being used for hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) imaging. Studied in particular are laser-induced damage thresholds (LIDTs), nonlinear absorption, and optical transmission stability during long-term UV irradiation. Solarization (photodegradation) effects are significantly enhanced when the fiber is exposed to high-repetition-rate, 283 nm UV irradiation. For 10 kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10 Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10 kHz. The nearly spatially uniform output beam that exits a long multimode fiber becomes ideal for PLIF measurements. The proof-of-concept measurements show significant promise for extending the application of a fiber-coupled, high-speed OH-PLIF system to harsh environments such as combustor test beds, and potential system improvements are suggested.

A comparative study of the effects of different low-level lasers on the proliferation, viability, and migration of human melanocytes in vitro.

PubMed

AlGhamdi, Khalid M; Kumar, Ashok; Ashour, Abdelkader E; AlGhamdi, Attieh A

2015-07-01

The aim of this study was to investigate the effects of different low-level laser therapies (LLLTs) of various wavelengths and energies on normal cultured human melanocytes. Various studies have shown the effects of LLLs on various types of cultured cells. Presently, little is known about the biological effects of LLLTs on melanocytes. Melanocytes were exposed to LLLT at 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 J/cm(2) using a blue (457 nm), red (635 nm), or ultraviolet (UV) (355 nm) laser. Melanocyte viability, proliferation, and migration were monitored at 72 h after irradiation. The blue (P < 0.001) and red (P < 0.001 and P < 0.01) lasers significantly enhanced viability at 0.5 to 2.0 J/cm(2), whereas the UV laser (P < 0.001) could significantly enhance viability only at 0.5 and 1.0 J/cm(2) compared with controls. The blue and red lasers also significantly enhanced the proliferation of the melanocytes at 0.5 to 2.0 J/cm(2) (P < 0.001), and the UV laser significantly enhanced proliferation at 0.5 to 1.5 J/cm(2) (P < 0.001 and P < 0.01) compared with controls. The blue laser significantly enhanced melanocyte migration at 0.5 to 4.0 J/cm(2) (P < 0.001 to P < 0.05), but the red (P < 0.001 and P < 0.01) and UV (P < 0.001 to P < 0.05) lasers could significantly enhance such migration at 0.5 to 1.0 J/cm(2) and 0.5 to 2.0 J/cm(2), respectively, compared with controls. LLLT at low energy densities is able to significantly increase melanocyte viability, proliferation, and migration in vitro, and at higher energy densities, it gives non-stimulatory results. Additionally, the blue laser was the best among the three lasers. These findings might have potential application in vitiligo treatment in future.

Effect of nanosecond UV laser irradiation on luminescence and absorption in silver- and copper-containing phosphate glasses

NASA Astrophysics Data System (ADS)

Murashov, A. A.; Sidorov, A. I.; Stoliarchuk, M. V.

2018-03-01

Experimental evidence is presented that nanosecond UV laser irradiation of silver- and copper-containing barium phosphate glasses leads to luminescence quenching in the visible range. Subsequent heat treatment induces an absorption in the range 350–500 nm. These effects are due to the ionisation and fragmentation of subnanometre molecular clusters by laser radiation and subsequent (heat treatment-induced) formation of nanoparticles possessing plasmon resonance. Our numerical modelling results demonstrate the feasibility of producing stable AgnCum hybrid molecular clusters in glass. Local modification of the optical properties of glass by laser light can be used for optical information recording.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-06-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-04-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

Physicochemical modifications accompanying UV laser induced surface structures on poly(ethylene terephthalate) and their effect on adhesion of mesenchymal cells.

PubMed

Rebollar, Esther; Pérez, Susana; Hernández, Margarita; Domingo, Concepción; Martín, Margarita; Ezquerra, Tiberio A; García-Ruiz, Josefa P; Castillejo, Marta

2014-09-07

This work reports on the formation of different types of structures on the surface of polymer films upon UV laser irradiation. Poly(ethylene terephthalate) was irradiated with nanosecond UV pulses at 193 and 266 nm. The polarization of the laser beam and the irradiation angle of incidence were varied, giving rise to laser induced surface structures with different shapes and periodicities. The irradiated surfaces were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via micro-Raman and fluorescence spectroscopies. Contact angle measurements were performed with different liquids, and the results evaluated in terms of surface free energy components. Finally, in order to test the influence of surface properties for a potential application, the modified surfaces were used for mesenchymal stem cell culture assays and the effect of nanostructure and surface chemistry on cell adhesion was evaluated.

Asbestos as 'toxic short-circuit' optic-fibre for UV within the cell-net: — Likely roles and hazards for secret UV and IR metabolism

NASA Astrophysics Data System (ADS)

Traill, Robert R.

2011-12-01

The most toxic asbestos fibres have widths 250nm-10nm, and this toxicity is "physical", which could mean either mechanical or optical: Tangling with chromosomes is a •mechanical hazard occasionally reported, and fibres <100nm wide would probably be most knife-like. Our other concern here is •optical: Calculations for fibres <=300nm reveal such a transmission possibility, but only when the amphibole fibres (brown and blue asbestos) are >100nm wide — or chrysotile (white asbestos) is >150nm. In both cases, UVA/UVB -transmission would then predominate. (Chrysotile 150nm might be benign — escaping both mechanical and optical!). But what would generate such UV, and why would its transmission be toxic? Thar and Kühl (J.Theor.Biol.:2004) explain that the long mitochondria on microtubules may be able to act as UV-lasers, (and many observers since Gurwitsch 1923 have reported ultraweak UV emissions escaping from all types of living bio-tissue). That all suggests some universal secret role for UV, apparently related to mitosis. Insertion of fibre "short-circuits" could then cause upsets in mitosis-control, and hence DNA irregularities. Such UV-control could parallel similar lower-powered Infra-Red control-systems (as considered elsewhere for coaxial myelin; or as portrayed by G.Albrecht-Buehler's online animations etc.); and the traditional short mitochondria seem better suited for this IR task.

Impact of laser excitation intensity on deep UV fluorescence detection in microchip electrophoresis.

PubMed

Schulze, Philipp; Ludwig, Martin; Belder, Detlev

2008-12-01

A high intensity 266 nm continuous wave (cw-) laser developed for material processing was utilised as an excitation source for sensitive native fluorescence detection of unlabelled compounds in MCE. This 120 mW laser was attached via an optical fibre into a commercial epifluorescence microscope. With this MCE set-up we evaluated the impact of laser power on the S/N of aromatic compounds as well as of proteins. Compared with a previous work which used a 4 mW pulsed laser for excitation, improved S/N for small aromatics and to a lesser extent for proteins could be attained. The LOD of the system was determined down to 24 ng/mL for serotonin (113 nM), 24 ng/mL for propranolol (81 nM), 80 ng/mL for tryptophan (392 nM) and 80 ng/mL for an aromatic diol (475 nM). Sensitive protein detection was obtained at concentrations of 5 microg/mL for lysocyme, trypsinogen and chymotrypsinogen (340, 208 and 195 nM, respectively). Finally, a comparison of the cw- with a pulsed 266 nm laser, operating at the same average power, showed a higher attainable sensitivity of the cw-laser. This can be attributed to fluorescence saturation and photobleaching effects of the pulsed laser at high pulse energies.

Laser micromachining of optical devices

NASA Astrophysics Data System (ADS)

Kopitkovas, Giedrius; Lippert, Thomas; David, Christian; Sulcas, Rokas; Hobley, Jonathan; Wokaun, Alexander J.; Gobrecht, Jens

2004-10-01

The combination of a gray tone phase mask with a laser assisted wet etching process was applied to fabricate complex microstructures in UV transparent dielectric materials. This one-step method allows the generation of arrays of plano-convex and Fresnel micro-lenses using a conventional XeCl excimer laser and an absorbing liquid, which is in contact with the UV transparent material. An array of plano-convex micro-lenses was tested as beam homogenizer for a high power XeCl excimer and ps Nd:YAG laser. The roughness of the etched features varies from several μm to 10 nm, depending on the laser fluence and concentration of the dye in the organic liquid. The etching process can be divided into several etching mechanisms which vary with laser fluence.

Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser.

PubMed

Hammer, Christian M; Petsch, Corinna; Klenke, Jörg; Skerl, Katrin; Paulsen, Friedrich; Kruse, Friedrich E; Seiler, Theo; Menzel-Severing, Johannes

2015-06-01

To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery. Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. Experimental study. Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium. Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable. The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty. Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Ultraviolet /UV/ sensitive phosphors for silicon imaging detectors

NASA Technical Reports Server (NTRS)

Viehmann, W.; Cowens, M. W.; Butner, C. L.

1981-01-01

The fluorescence properties of UV sensitive organic phosphors and the radiometric properties of phosphor coated silicon detectors in the VUV, UV, and visible wavelengths are described. With evaporated films of coronene and liumogen, effective quantum efficiencies of up to 20% have been achieved on silicon photodiodes in the vacuum UV. With thin films of methylmethacrylate (acrylic), which are doped with organic laser dyes and deposited from solution, detector quantum efficiencies of the order of 15% for wavelengths of 120-165 nm and of 40% for wavelengths above 190 nm have been obtained. The phosphor coatings also act as antireflection coatings and thereby enhance the response of coated devices throughout the visible and near IR.

Simple Ultraviolet Short-Pulse Intensity Diagnostic Method Using Atmosphere

NASA Astrophysics Data System (ADS)

Aota, Tatsuya; Takahashi, Eiichi; Losev, Leonid L.; Tabuchi, Takeyuki; Kato, Susumu; Matsumoto, Yuji; Okuda, Isao; Owadano, Yoshiro

2005-05-01

An ultraviolet (UV) short-pulse intensity diagnostic method using atmosphere as a nonlinear medium was developed. This diagnostic method is based on evaluating the ion charge of the two-photon ionization of atmospheric oxygen upon irradiation with a UV (238-299 nm) short-pulse laser. The observed ion signal increased proportionally to the input intensity to the power of ˜2.2, during the two-photon ionization of atmospheric oxygen. An autocorrelator was constructed and used to successfully measure a UV laser pulse of ˜400 fs duration. Since this diagnostic system is used in the open-air under windowless conditions, it can be set along the beam path and used as a UV intensity monitor.

Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal

PubMed Central

Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun

2013-01-01

In current inertial confinement fusion (ICF) facilities, KDP and DKDP crystals are the second harmonic generation (SHG) and third harmonic generation (THG) materials for the Nd:glass laser (1053 nm). Based on the trend for the development of short wavelengths for ICF driving lasers, technical solutions for fourth harmonic generation (FHG) will undoubtedly attract more and more attention. In this paper, the rapid growth of an ADP crystal and non-critical phase-matching (NCPM) FHG of a 1053-nm laser using an ADP crystal are reported. The NCPM temperature is 33.7°C. The conversion efficiency from 526 to 263 nm is 70%, and the angular acceptance range is 55.4 mrad; these results are superior to those for the DKDP crystals. This research has shown that ADP crystals will be a competitive candidate in future ICF facilities when the utilisation of high-energy, high-efficiency UV lasers at wavelengths shorter than the present 351 nm is of interest. PMID:23549389

Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal.

PubMed

Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun

2013-01-01

In current inertial confinement fusion (ICF) facilities, KDP and DKDP crystals are the second harmonic generation (SHG) and third harmonic generation (THG) materials for the Nd:glass laser (1053 nm). Based on the trend for the development of short wavelengths for ICF driving lasers, technical solutions for fourth harmonic generation (FHG) will undoubtedly attract more and more attention. In this paper, the rapid growth of an ADP crystal and non-critical phase-matching (NCPM) FHG of a 1053-nm laser using an ADP crystal are reported. The NCPM temperature is 33.7°C. The conversion efficiency from 526 to 263 nm is 70%, and the angular acceptance range is 55.4 mrad; these results are superior to those for the DKDP crystals. This research has shown that ADP crystals will be a competitive candidate in future ICF facilities when the utilisation of high-energy, high-efficiency UV lasers at wavelengths shorter than the present 351 nm is of interest.

Pulsed Laser Synthesized Magnetic Cobalt Oxide Nanoparticles for Biomedical Applications

NASA Astrophysics Data System (ADS)

Bhatta, Hari; Gupta, Ram; Ghosh, Kartik; Kahol, Pawan; Delong, Robert; Wanekawa, Adam

2011-03-01

Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Biocompatible and chemically stable magnetic metal oxide nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication of magnetic cobalt oxide nanoparticles using a safe, cost effective, and easy to handle technique that is capable of producing nanoparticles free of any contamination. Cobalt oxide nanoparticles have been synthesized at room temperature using cobalt foil by pulsed laser ablation technique. These cobalt oxide nanoparticles were characterized using UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and dynamic laser light scattering (DLLS). The magnetic cobalt oxides nanoparticles were stabilized in glucose solutions of various concentrations in deionized water. The presence of UV-Vis absorption peak at 270 nm validates the nature of cobalt oxide nanoparticles. The DLLS size distributions of nanoparticles are in the range of 110 to 300 nm, which further confirms the presence nanoparticles. This work is partially supported by National Science Foundation (DMR- 0907037).

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, K. S.

1985-10-01

An intense and efficient excitation source for blue-green lasers useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, hypocycloidal pinch plasma (HCP), and a newly designed dense-plasma focus (DPF) can produce intense UV photons (200 to 300 nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400 nm). During the current project period, the successful enhancement of blue-green laser output of both Coumarin 503 and LD490 dye through the spectral conversion of the HCP pumping light has been achieved with a converter dye BBQ. The factor of enhancement in the blue-green laser output energy of both Coumarin 503 and LD490 is almost 73%. This enhancement will definitely be helpful in achieving the direct high power blue-green laser (> 1 MW) with the existing blue green dye laser. On the other hand the dense-plasma focus (DPF) with new optical coupling has been designed and constructed. For the optimization of the DPF device as the UV pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as function of argon or argon-deuterium fill gas pressure. Finally, the blue-green dye laser (LD490) has been pumped with the DPF device for preliminary tests. Experimental results with the DPF device show that the velocity of the current sheath follows the inverse relation of sq st. of pressure as expected. The blue-green dye (LD490) laser output exceeded 3.1 m at the best cavity tuning of laser system. This corresponds to 3J/1 cu cm laser energy extraction.

Laser induced fluorescence of biochemical for UV LIDAR application.

PubMed

Gupta, L; Sharma, R C; Razdan, A K; Maini, A K

2014-05-01

Laser induced fluorescence spectroscopy in the ultraviolet regime has been used for the detection of biochemical through a fiber coupled CCD detector from a distance of 2 m. The effect of concentration and laser excitation energy on the fluorescence spectra of nicotinamide adenine dinucleotide (NADH) has been investigated. The signature fluorescence peak of NADH was centred about 460 nm. At lower concentration Raman peak centred at 405 nm was also observed. The origin of this peak has been discussed. Detection limit with the proposed set up is found to be 1 ppm.

Autofluorescence of pigmented skin lesions using a pulsed UV laser with synchronized detection: clinical results

NASA Astrophysics Data System (ADS)

Cheng, Haynes P. H.; Svenmarker, Pontus; Xie, Haiyan; Tidemand-Lichtenberg, Peter; Jensen, Ole B.; Bendsoe, Niels; Svanberg, Katarina; Petersen, Paul Michael; Pedersen, Christian; Andersson-Engels, Stefan; Andersen, Peter E.

2010-04-01

We report preliminary clinical results of autofluorescence imaging of malignant and benign skin lesions, using pulsed 355 nm laser excitation with synchronized detection. The novel synchronized detection system allows high signal-tonoise ratio to be achieved in the resulting autofluorescence signal, which may in turn produce high contrast images that improve diagnosis, even in the presence of ambient room light. The synchronized set-up utilizes a compact, diode pumped, pulsed UV laser at 355 nm which is coupled to a CCD camera and a liquid crystal tunable filter. The excitation and image capture is sampled at 5 kHz and the resulting autofluorescence is captured with the liquid crystal filter cycling through seven wavelengths between 420 nm and 580 nm. The clinical study targets pigmented skin lesions and evaluates the prospects of using autofluorescence as a possible means in differentiating malignant and benign skin tumors. Up to now, sixteen patients have participated in the clinical study. The autofluorescence images, averaged over the exposure time of one second, will be presented along with histopathological results. Initial survey of the images show good contrast and diagnostic results show promising agreement based on the histopathological results.

Laser synthesis and spectroscopy of acetonitrile/silver nanoparticles

NASA Astrophysics Data System (ADS)

Akin, S. T.; Liu, X.; Duncan, M. A.

2015-11-01

Silver nanoparticles with acetonitrile ligands are produced in a laser ablation flow reactor. Excimer laser ablation produces gas phase metal clusters which are thermalized with helium or argon collisions in the flowtube, and reactions with acetonitrile vapor coordinate this ligand to the particle surface. The gaseous mixture is captured in a cryogenic trap; warming produces a solution of excess ligand and coated particles. TEM images reveal particle sizes of 10-30 nm diameter. UV-vis absorption and fluorescence spectra are compared to those of standard silver nanoparticles with surfactant coatings. Deep-UV ligand absorption is strongly enhanced by nanoparticle adsorption.

Effects of laser fluence and liquid media on preparation of small Ag nanoparticles by laser ablation in liquid

NASA Astrophysics Data System (ADS)

Moura, Caroline Gomes; Pereira, Rafael Santiago Floriani; Andritschky, Martin; Lopes, Augusto Luís Barros; Grilo, João Paulo de Freitas; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel

2017-12-01

This study aims to assess a method for preparation of small and highly stable Ag nanoparticles by nanosecond laser ablation in liquid. Effect of liquid medium and laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Nd:YAG laser of 1064 nm wavelength at 35 ns pulse width at different fluences were employed to irradiate the silver target in different environments (water, ethanol and acetone). The UV-Visible absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. STEM and TEM micrographs were used to evaluate the size and shape of nanoparticles. The stability of silver colloids in terms of oxidation at different liquid media was analyzed by SAED patterns. The results showed that characteristics of Ag nanoparticles and their production rate were strongly influenced by varying laser fluence and liquid medium. Particles from 2 to 80 nm of diameter were produced using different conditions and no oxidation was found in ethanol and acetone media. This work puts in evidence a promising approach to produce small nanoparticles by using high laser fluence energy.

Ultraviolet Radiation in Wound Care: Sterilization and Stimulation

PubMed Central

Gupta, Asheesh; Avci, Pinar; Dai, Tianhong; Huang, Ying-Ying; Hamblin, Michael R.

2013-01-01

Significance Wound care is an important area of medicine considering the increasing age of the population who may have diverse comorbidities. Light-based technology comprises a varied set of modalities of increasing relevance to wound care. While low-level laser (or light) therapy and photodynamic therapy both have wide applications in wound care, this review will concentrate on the use of ultraviolet (UV) radiation. Recent Advances UVC (200–280 nm) is highly antimicrobial and can be directly applied to acute wound infections to kill pathogens without unacceptable damage to host tissue. UVC is already widely applied for sterilization of inanimate objects. UVB (280–315 nm) has been directly applied to the wounded tissue to stimulate wound healing, and has been widely used as extracorporeal UV radiation of blood to stimulate the immune system. UVA (315–400 nm) has distinct effects on cell signaling, but has not yet been widely applied to wound care. Critical Issues Penetration of UV light into tissue is limited and optical technology may be employed to extend this limit. UVC and UVB can damage DNA in host cells and this risk must be balanced against beneficial effects. Chronic exposure to UV can be carcinogenic and this must be considered in planning treatments. Future Directions New high-technology UV sources, such as light-emitting diodes, lasers, and microwave-generated UV plasma are becoming available for biomedical applications. Further study of cellular signaling that occurs after UV exposure of tissue will allow the benefits in wound healing to be better defined. PMID:24527357

Interaction of UV laser pulses with reactive dusty plasmas

NASA Astrophysics Data System (ADS)

van de Wetering, Ferdi; Beckers, Job; Nijdam, Sander; Oosterbeek, Wouter; Kovacevic, Eva; Berndt, Johannes

2016-09-01

This contribution deals with the effects of UV photons on the synthesis and transport of nanoparticles in reactive complex plasmas (capacitively coupled RF discharge). First measurements showed that the irradiation of a reactive acetylene-argon plasma with high-energy, ns UV laser pulses (355 nm, 75 mJ pulse energy, repetition frequency 10Hz) can have a large effect on the global discharge characteristics. One particular example concerns the formation of a dust void in the center of the discharge. At sufficiently high pulse energies, this formation of a dust free region - which occurs without laser irradiation-is totally suppressed. Moreover the experiments indicate that the laser pulses influence the early stages of the particle formation. Although the interaction between the laser and the plasma is not yet fully understood, it is remarkable that these localized nanosecond laser pulses can influence the plasma on a global scale. Besides new insights into fundamental problems, this phenomenon opens also new possibilities for the controlled manipulation of particle growth and particle transport in reactive plasmas.

In situ FBG inscription during fiber laser operation.

PubMed

Leich, Martin; Fiebrandt, Julia; Jetschke, Sylvia; Rothhardt, Manfred; Jäger, Matthias

2013-03-01

We demonstrate the inscription of a 266 nm UV femtosecond pulse-induced fiber Bragg grating (FBG) in an Yb-doped fiber during optical pumping at 976 nm and the initiation of lasing with increasing grating reflectivity. Output spectra show the emission of the pumped fiber changing from the broad-ranged amplified spontaneous emission in the nonlasing case to the narrow-range laser operation due to the enhancement of FBG reflectivity during inscription. The proposed technique enables the direct characterization and control of FBG performance in fiber lasers. After FBG fabrication, we investigate the spectral characteristics of the fiber laser for different laser powers and study the influence of a thermal treatment of the FBG.

Evaluation of the performance of small diode pumped UV solid state (DPSS) Nd:YAG lasers as new radiation sources for atmospheric pressure laser ionization mass spectrometry (APLI-MS).

PubMed

Kersten, Hendrik; Lorenz, Matthias; Brockmann, Klaus J; Benter, Thorsten

2011-06-01

The performance of a KrF* bench top excimer laser and a compact diode pumped UV solid state (DPSS) Nd:YAG laser as photo-ionizing source in LC-APLI MS is compared. The commonly applied bench-top excimer laser, operating at 248 nm, provides power densities of the order of low MW/cm(2) on an illuminated area of 0.5 cm(2) (8 mJ/pulse, 5 ns pulse duration, beam waist area 0.5 cm(2), 3 MW/cm(2)). The DPSS laser, operating at 266 nm, provides higher power densities, however, on a two orders of magnitude smaller illuminated area (60 μJ/pulse, 1 ns pulse duration, beam waist area 2 × 10(-3) cm(2), 30 MW/cm(2)). In a common LC-APLI MS setup with direct infusion of a 10 nM pyrene solution, the DPSS laser yields a significantly smaller ion signal (0.9%) and signal to noise ratio (1.4%) compared with the excimer laser. With respect to the determined low detection limits (LODs) for PAHs of 0.1 fmol using an excimer laser, LODs in DPSS laser LC-APLI MS in the low pmol regime are expected. The advantages of the DPSS laser with respect to applicability (size, cost, simplicity) may render this light source the preferred one for APLI applications not focusing on ultimately high sensitivities. Furthermore, the impact of adjustable ion source parameters on the performance of both laser systems is discussed in terms of the spatial sensitivity distribution described by the distribution of ion acceptance (DIA) measurements. Perspectives concerning the impact on future APLI-MS applications are given.

Enhancement of the design of a pulsed UV laser system for a laser-desorption mass spectrometer on Mars

NASA Astrophysics Data System (ADS)

Kolleck, C.; Büttner, A.; Ernst, M.; Hunnekuhl, M.; Hülsenbusch, T.; Moalem, A.; Priehs, M.; Kracht, D.; Neumann, J.

2017-11-01

A laser-desorption mass spectrometer will be part of the ESA-led ExoMars mission with the objective of identifying organic molecules on planet Mars. A UV laser source emitting nanosecond pulses with pulse energy of about 250 μJ at a wavelength of 266 nm is required for the ionization of nonvolatile soil constituents. A passively q-switched, diode-pumped Nd∶YAG laser oscillator with external frequency quadrupling has been developed. The basic optical concept and a previously developed flight-near prototype are redesigned for the engineering qualification model of the laser, mainly due to requirements updated during the development process and necessary system adaptations. Performance issues like pulse energy stability, pulse energy adjustment, and burst mode operation are presented in this paper.

Time-resolved photoelectron spectroscopy of polyatomic molecules using 42-nm vacuum ultraviolet laser based on high harmonics generation

NASA Astrophysics Data System (ADS)

Nishitani, Junichi; West, Christopher W.; Higashimura, Chika; Suzuki, Toshinori

2017-09-01

Time-resolved photoelectron spectroscopy (TRPES) of gaseous polyatomic molecules using 266-nm (4.7 eV) pump and 42-nm (29.5 eV) probe pulses is presented. A 1-kHz Ti:sapphire laser with a 35 fs pulse duration is employed to generate high harmonics in Kr gas, and the 19th harmonic (42-nm) was selected using two SiC/Mg mirrors. Clear observation of the ultrafast electronic dephasing in pyrazine and photoisomerization of 1,3-cyclohexadiene demonstrates the feasibility of TRPES with the UV pump and VUV probe pulses under weak excitation conditions in the perturbation regime.

Optical Trapping-Cavity Ringdown Spectroscopy System for Single Aerosol Particle Measurements

DTIC Science & Technology

2015-02-17

ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Final Report REPORT DOCUMENTATION PAGE 11. SPONSOR...focused 532 nm laser ( Bermuda grass smut spores, horizontal illumination at power of 4.5 mW, focus length = 10 mm, UV quartz cuvette is from Starna...Cells, Inc.) (b) Single bioaerosol particles trapped using a focused 405 nm laser ( Bermuda grass smut spores, upward illumination at power of 2.0

Single Frequency Monolithic Solid State Green Laser as a Potential Source for Vibrometry Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sotor, Jaroslaw Z.; Antonczak, Arkadiusz J.; Abramski, Krzysztof M.

2010-05-28

In this paper miniature, monolithic single frequency solid state laser operating at 532 nm is presented. Developed Nd:GdVO{sub 4}/YVO{sub 4}/KTP consist of three crystal bonded together with a UV adhesive. The single frequency operation was obtained in wide temperature range from 17 deg. C to 27 deg. C. The laser operated with output power up to 90 mW at 532 nm. The total optical efficiency (808 nm to 532 nm) was 9.5%. Power stability was at the level of +-0.8% and the long term frequency stability was approximately 3centre dot10{sup -8}. The beam has a Gaussian profile and the M2more » parameter was below 1.1.« less

Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2015-06-27

Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

Combined Advanced Finishing and UV-Laser Conditioning for Producing UV-Damage-Resistant Fused Silica Optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menapace, J A; Penetrante, B; Golini, D

2001-11-01

Laser induced damage initiation on fused silica optics can limit the lifetime of the components when used in high power UV laser environments. Foe example in inertial confinement fusion research applications, the optics can be exposed to temporal laser pulses of about 3-nsec with average fluences of 8 J/cm{sup 2} and peak fluences between 12 and 15 J/cm{sup 2}. During the past year, we have focused on optimizing the damage performance at a wavelength of 355-nm (3{omega}), 3-nsec pulse length, for optics in this category by examining a variety of finishing technologies with a challenge to improve the laser damagemore » initiation density by at least two orders of magnitude. In this paper, we describe recent advances in improving the 3{omega} damage initiation performance of laboratory-scale zirconium oxide and cerium oxide conventionally finished fused silica optics via application of processes incorporating magnetorheological finishing (MRF), wet chemical etching, and UV laser conditioning. Details of the advanced finishing procedures are described and comparisons are made between the procedures based upon large area 3{omega} damage performance, polishing layer contamination, and optical subsurface damage.« less

Ultrafast disk technology enables next generation micromachining laser sources

NASA Astrophysics Data System (ADS)

Heckl, Oliver H.; Weiler, Sascha; Luzius, Severin; Zawischa, Ivo; Sutter, Dirk

2013-02-01

Ultrashort pulsed lasers based on thin disk technology have entered the 100 W regime and deliver several tens of MW peak power without chirped pulse amplification. Highest uptime and insensitivity to back reflections make them ideal tools for efficient and cost effective industrial micromachining. Frequency converted versions allow the processing of a large variety of materials. On one hand, thin disk oscillators deliver more than 30 MW peak power directly out of the resonator in laboratory setups. These peak power levels are made possible by recent progress in the scaling of the pulse energy in excess of 40 μJ. At the corresponding high peak intensity, thin disk technology profits from the limited amount of material and hence the manageable nonlinearity within the resonator. Using new broadband host materials like for example the sesquioxides will eventually reduce the pulse duration during high power operation and further increase the peak power. On the other hand industry grade amplifier systems deliver even higher peak power levels. At closed-loop controlled 100W, the TruMicro Series 5000 currently offers the highest average ultrafast power in an industry proven product, and enables efficient micromachining of almost any material, in particular of glasses, ceramics or sapphire. Conventional laser cutting of these materials often requires UV laser sources with pulse durations of several nanoseconds and an average power in the 10 W range. Material processing based on high peak power laser sources makes use of multi-photon absorption processes. This highly nonlinear absorption enables micromachining driven by the fundamental (1030 nm) or frequency doubled (515 nm) wavelength of Yb:YAG. Operation in the IR or green spectral range reduces the complexity and running costs of industrial systems initially based on UV light sources. Where UV wavelength is required, the TruMicro 5360 with a specified UV crystal life-time of more than 10 thousand hours of continues operation at 15W is an excellent choice. Currently this is the world's most powerful industrial sub-10 ps UV laser.

UV-laser-based longitudinal illuminated diffuser (LID) incorporating diffractive and Lambertian reflectance for the disinfection of beverages

NASA Astrophysics Data System (ADS)

Lizotte, Todd

2010-08-01

A novel laser beam shaping system was designed to demonstrate the potential of using high power UV laser sources for large scale disinfection of liquids used in the production of food products, such as juices, beer, milk and other beverage types. The design incorporates a patented assembly of optical components including a diffractive beam splitting/shaping element and a faceted pyramidal or conically shaped Lambertian diffuser made from a compression molded PTFE compounds. When properly sintered to an appropriate density, as an example between 1.10 and 1.40 grams per cubic centimeter, the compressed PTFE compounds show a ~99% reflectance at wavelengths ranging from 300 nm to 1500 nm, and a ~98.5% refection of wavelengths from 250 nm to 2000 nm [1]. The unique diffuser configuration also benefits from the fact that the PTFE compounds do not degrade when exposed to ultraviolet radiation as do barium sulfate materials and silver or aluminized mirror coatings [2]. These components are contained within a hermetically sealed quartz tube. Once assembled a laser beam is directed through one end of the tube. This window takes the form of a computer generated diffractive splitter or other diffractive shaper element to split the laser beam into a series of spot beamlets, circular rings or other geometric shapes. As each of the split beamlets or rings cascade downward, they illuminate various points along the tapered PTFE cone or faceted pyramidal form. As they strike the surface they each diffuse in a Lambertian reflectance pattern creating a pseudo-uniform circumferential illuminator along the length of the quartz tube enclosing the assembly. The compact tubular structure termed Longitudinal Illuminated Diffuser (LID) provides a unique UV disinfection source that can be placed within a centrifugal reactor or a pipe based reactor chamber. This paper will review the overall design principle, key component design parameters, preliminary analytic and bench operational testing results.

High-Speed Digital-Image Data Acquisition, Processing, and Visualization System for Turbulent Mixing and Combustion

DTIC Science & Technology

2007-05-25

of-the-art optical filters. Specifically, a FF01 -510/84 Semrock green band-pass filter (transmission >95% with 1% standard deviation between 467nm...used to reject the UV laser light (-390nm) exciting the CH radicals, and a NF0I-532U Semrock notch filter (transmission ə 04 % at 527nm, and >95

Particle-fluorescence spectrometer for real-time single-particle measurements of atmospheric organic carbon and biological aerosol.

PubMed

Pan, Yong-Le; Pinnick, Ronald G; Hill, Steven C; Chang, Richard K

2009-01-15

A particle-fluorescence spectrometer (PFS) for real-time measurements of single-particle UV-laser-induced fluorescence (UV-LIF) excited with a pulsed (263-nm) laser is reported. The dispersed UV-LIF spectra are measured by a 32-anode PMT detector with spectral coverage from 280-600 nm. The PFS represents a significant improvement over our previous apparatus [Pinnick et al., Atmos. Environ. 2004, 38, 1657] and can (1) measure fluorescence spectra of bacterial particles having light-scattering sizes as small as 1 microm (previously limited to about 3 microm) and so can measure particles with size in the range of 1-10 microm, (2) measure each particle's elastic scattering which can be used to estimate particle size (not available previously), (3) measure single-particle fluorescence spectra with a laser and detector that can record spectra as fast as 90,000/s, although the highest rates we have found experimentally in atmospheric measurements is only several hundred per second (previously limited by detectors to only 25/s), and (4) provide a time stamp for a data block of spectra with time resolution from 10 ms to 10 min. In addition, the PFS has been modified to be more robust, transportable, and smaller. The use of an aerodynamic-focusing sheath inlet nozzle assembly has improved the sample rate. The PFS has been employed to measure UV-LIF spectra from individual atmospheric particles during October-December 2006 and January-May 2008 in New Haven, CT, and during January-May 2007 in Las Cruces, NM.

Visualization of corona discharge induced by UV (248 nm) pulses of a KrF excimer laser

NASA Astrophysics Data System (ADS)

Mizeraczyk, Jerzy; Ohkubo, Toshikazu; Kanazawa, Seiji; Nomoto, Yukiharu; Kawasaki, Toshiyuki; Kocik, Marek

2000-11-01

A KrF excimer laser (248 nm) was used to induce DC corona discharge streamers in air between the electrodes of a needle-to-plane geometry. The UV laser beam pulses were transformed into the form of a laser sheet (1.5 mm thick and 20 mm-wide) that was positioned along the axis directed from the needle electrode to the plane electrode. The laser pulses were time-synchronized with the exposure of an ICCD camera that record images of the corona streamers induced by the laser sheet. The laser pulse energy flux (75 MW/cm2) crossing the gap was high enough to induce corona streamers with a reliability of 100% even at relatively low operating voltages (e.g., 15 kV) at which self-sustained streamers could not occur. Due to the full synchronization of the corona streamer onset, induced by the laser pulse and the exposure of the ICCD camera, 2-D visualization of the corona streamer evolution with a time resolution of 10 ns was possible. The recorded images made possible determining such features of the corona discharge streamer as its velocity (2.5 105 m/s) and the diameters of the leader channel (200 micrometers ) and the leader streamers (100 micrometers ).

Nonlinear absorption enhancement of AuNPs based polymer nanocomposites

NASA Astrophysics Data System (ADS)

Zulina, Natalia A.; Baranov, Mikhail A.; Kniazev, Kirill I.; Kaliabin, Viacheslav O.; Denisyuk, Igor Yu.; Achor, Susan U.; Sitnikova, Vera E.

2018-07-01

Au nanoparticles (AuNPs) based polymer nanocomposites with high nonlinear absorption coefficient were synthesized by UV-photocuring. AuNPs were synthesized by laser ablation method in liquid monomer isodecyl acrylate (IDA). In this research, two colloids with 70 nm and 20 nm nanoparticles average sizes were studied. Size control was performed with SEM and STEM. Prepared nanomaterials exhibit strong third-order nonlinear optical responses under CW laser irradiation at 532 nm, which was estimated by using z-scan technique performed with open aperture. It was found experimentally that nonlinear absorption β is almost twice higher for nanocomposites with smaller AuNPs.

Distribution and avoidance of debris on epoxy resin during UV ns-laser scanning processes

NASA Astrophysics Data System (ADS)

Veltrup, Markus; Lukasczyk, Thomas; Ihde, Jörg; Mayer, Bernd

2018-05-01

In this paper the distribution of debris generated by a nanosecond UV laser (248 nm) on epoxy resin and the prevention of the corresponding re-deposition effects by parameter selection for a ns-laser scanning process were investigated. In order to understand the mechanisms behind the debris generation, in-situ particle measurements were performed during laser treatment. These measurements enabled the determination of the ablation threshold of the epoxy resin as well as the particle density and size distribution in relation to the applied laser parameters. The experiments showed that it is possible to reduce debris on the surface with an adapted selection of pulse overlap with respect to laser fluence. A theoretical model for the parameter selection was developed and tested. Based on this model, the correct choice of laser parameters with reduced laser fluence resulted in a surface without any re-deposited micro-particles.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser-induced extreme UV radiation sources for manufacturing next-generation integrated circuits

NASA Astrophysics Data System (ADS)

Borisov, V. M.; Vinokhodov, A. Yu; Ivanov, A. S.; Kiryukhin, Yu B.; Mishchenko, V. A.; Prokof'ev, A. V.; Khristoforov, O. B.

2009-10-01

The development of high-power discharge sources emitting in the 13.5±0.135-nm spectral band is of current interest because they are promising for applications in industrial EUV (extreme ultraviolet) lithography for manufacturing integrated circuits according to technological precision standards of 22 nm and smaller. The parameters of EUV sources based on a laser-induced discharge in tin vapours between rotating disc electrodes are investigated. The properties of the discharge initiation by laser radiation at different wavelengths are established and the laser pulse parameters providing the maximum energy characteristics of the EUV source are determined. The EUV source developed in the study emits an average power of 276 W in the 13.5±0.135-nm spectral band on conversion to the solid angle 2π sr in the stationary regime at a pulse repetition rate of 3000 Hz.

Critical dimensional linewidth calibration using UV microscope and laser interferometry

NASA Astrophysics Data System (ADS)

Li, Qi; Gao, Si-tian; Li, Wei; Lu, Ming-zhen; Zhang, Ming-kai

2013-10-01

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two dimensional metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The microscope mainly consists of UV light receiving components, piezoelectric ceramics (PZT) driven stage and interferometer calibration framework. In UV light receiving components they include all optical elements on optical path. The UV light originates from Köhler high aperture transmit/reflect illumination sources; then goes through objective lens to UV splitting optical elements; after that, one part of light attains UV camera for large range calibration, the other part of light passes through a three dimensional adjusted pinhole and is collected by PMT for nanoscale scanning. In PZT driven stage, PZT stick actuators with closed loop control are equipped to push/pull a flexural hinge based platform. The platform has a novel designed compound flexural hinges which nest separate X, Y direction moving mechanisms within one layer but avoiding from mutual cross talk, besides this, the hinges also contain leverage structures to amplify moving distance. With these designs, the platform can attain 100 μm displacement ranges as well as 1 nm resolution. In interferometer framework a heterodyne multi-pass interferometer is mounted on the platform, which measures X-Y plane movement and Z axis rotation, through reference mirror mounted on objective lens tube and Zerodur mirror mounted on PZT platform, the displacement is traced back to laser wavelength. When development is finished, the apparatus can offer the capability to calibrate one dimensional linewidths and two dimensional pitches ranging from 200nm to 50μm with expanded uncertainty below 20nm.

Application of the UV laser printing technique to soft gelatin capsules containing titanium dioxide in the shells.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2012-03-01

The purpose of this study was to examine application of ultraviolet (UV) laser irradiation to printing soft gelatin capsules containing titanium dioxide (TiO(2)) in the shells and to study effect of UV laser power on the color strength of printing on the soft gelatin capsules. Size 6 Oval type soft gelatin capsules of which shells contained 0.685% TiO(2) and 0.005% ferric dioxide were used in this study. The capsules were irradiated pulsed UV laser at a wavelength 355 nm. The color strength of the printed capsules was determined by a spectrophotometer as total color difference (dE). The soft gelatin capsules which contained TiO(2) in the shells could be printed gray by the laser. Many black particles, which were associated with the printing, were formed at the colored parts of the shells. It was found that there were two inflection points in relationship between output laser energy of a pulse and dE. Below the lower point, the capsules were not printed. From the lower point to the upper point, the capsules were printed gray and total color difference of the printing increased linearly in proportion with the output laser energy. Beyond the upper point, total color difference showed saturation because of micro-bubbles formation at the laser irradiated spot. Soft gelatin capsules containing TiO(2) in the shells could be performed stable printing using the UV laser printing technique. Color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Modeling Photochemical Dynamics in Optically Active Energetic Materials

NASA Astrophysics Data System (ADS)

Nelson, Tammie; Bjorgaard, Josiah; Greenfield, Margo; Bolme, Cindy; Brown, Katie; McGrane, Shawn; Scharff, R. Jason; Tretiak, Sergei

Most high explosives (HEs) absorb in the UV range, making it difficult to develop HEs that can be excited with standard lasers. The conventional optical initiation mechanisms require high laser intensity and occur via indirect thermal or shock processes. A photochemical initiation mechanism could allow control over the chemistry contributing to decomposition leading to initiation. We combine UV femtosecond transient absorption (TA) spectroscopy and excited state femtosecond stimulated Raman spectroscopy (FSRS) with Nonadiabatic Excited State Molecular Dynamics (NA-ESMD) to model the photochemical pathways in nitromethane (NM), a low sensitivity HE known to undergo UV photolysis. We investigate the ultrafast photodecomposition of NM from the nπ* state excited at 266 nm. The FSRS photoproduct spectrum points to methyl nitrite formation as the dominant photoproduct. A total photolysis quantum yield of 0.27 and an nπ* state lifetime of 20 fs were predicted from simulations. Predicted time scales reveal that NO2 dissociation occurs in 81 +/-4 fs and methyl nitrite formation is much slower at 452 +/-9 fs corresponding to the absorption feature in the TA spectrum. The relative time scales are consistent with isomerization by NO2 dissociation and ONO rebinding.

High-resolution setup for measuring wavelength sensitivity of photoyellowing of translucent materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaskuri, Anna, E-mail: anna.vaskuri@aalto.fi; Kärhä, Petri; Heikkilä, Anu

2015-10-15

Polystyrene and many other materials turn yellow when exposed to ultraviolet (UV) radiation. All photodegradation mechanisms including photoyellowing are functions of the exposure wavelength, which can be described with an action spectrum. In this work, a new high-resolution transmittance measurement setup based on lasers has been developed for measuring color changes, such as the photoyellowing of translucent materials aged with a spectrograph. The measurement setup includes 14 power-stabilized laser lines between 325 nm and 933 nm wavelengths, of which one at a time is directed on to the aged sample. The power transmitted through the sample is measured with amore » silicon detector utilizing an integrating sphere. The sample is mounted on a high-resolution XY translation stage. Measurement at various locations aged with different wavelengths of exposure radiation gives the transmittance data required for acquiring the action spectrum. The combination of a UV spectrograph and the new high-resolution transmittance measurement setup enables a novel method for studying the UV-induced ageing of translucent materials with a spectral resolution of 3–8 nm, limited by the adjustable spectral bandwidth range of the spectrograph. These achievements form a significant improvement over earlier methods.« less

Transient lateral photovoltaic effect in synthetic single crystal diamond

NASA Astrophysics Data System (ADS)

Prestopino, G.; Marinelli, M.; Milani, E.; Verona, C.; Verona-Rinati, G.

2017-10-01

A transient lateral photovoltaic effect (LPE) is reported for a metal-semiconductor structure of synthetic single crystal diamond (SCD). A SCD Schottky photodiode was specifically designed to measure a LPE under collimated irradiation from a tunable pulsed laser. A transient lateral photovoltage parallel to the Schottky junction was indeed detected. LPE on the p-type doped SCD side showed a non-linearity of 2% and a fast response time, with a rise time of 2 μs and a decay time of 12 μs. The position sensitivity (up to 30 mV/mm at a laser wavelength of 220 nm and a pulse energy density of 2.9 μJ/mm2) was measured as a function of laser wavelength, and an ultraviolet (UV)-to-visible contrast ratio of about four orders of magnitude with a sharp cutoff at 225 nm was observed. Our results demonstrate that a large LPE at UV wavelengths is achievable in synthetic single crystal diamond, potentially opening opportunities for the study and application of LPE in diamond and for the fabrication of high performance visible blind UV position sensitive detectors with high sensitivity and microsecond scale response time.

Passive optical limiting studies of nanostructured Cu doped ZnO-PVA composite thin films

NASA Astrophysics Data System (ADS)

Tamgadge, Y. S.; Sunatkari, A. L.; Talwatkar, S. S.; Pahurkar, V. G.; Muley, G. G.

2016-01-01

We prepared undoped and Cu doped ZnO semiconducting nanoparticles (NPs) by chemical co-precipitation method and obtained Cu doped ZnO-polyvinyl alcohol (PVA) nanocomposite thin films by spin coating to investigate third order nonlinear optical and optical limiting properties under cw laser excitation. Powder samples of NPs were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy, transmission electron microscopy, ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy. XRD pattern and FE-SEM micrograph revealed the presence of hexagonal wurtzite phase ZnO NPs having uniform morphology with average particle size of 20 nm. The presence of excitons and absorption peaks in the range 343-360 nm, revealed by UV-vis study, were attributed to excitons in n = 1 quantum state. Third order NLO properties of all composite thin films were investigated by He-Ne continuous wave (cw) laser of wavelength 632.8 nm using Z-scan technique. Thermally stimulated enhanced values of nonlinear refraction and absorption coefficients were obtained which may be attributed to self-defocusing effect, reverse saturable absorption, weak free carrier absorption and surface states properties originated from thermo optic effect. Optical limiting properties have been studied using cw diode laser of wavelength 808 nm and results are presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atanasov, Petar A., E-mail: paatanas@ie.bas.bg; Nedyalkov, Nikolay N.; Valova, Eugenia I.

We present an experimental analysis on surface structuring of polydimethylsiloxane films with UV (263 nm) femtosecond laser pulses, in air. Laser processed areas are analyzed by optical microscopy, SEM, and μ-Raman spectroscopy. The laser-treated sample shows the formation of a randomly nanostructured surface morphology. μ-Raman spectra, carried out at both 514 and 785 nm excitation wavelengths, prior and after laser treatment allow evidencing the changes in the sample structure. The influence of the laser fluence on the surface morphology is studied. Finally, successful electro-less metallization of the laser-processed sample is achieved, even after several months from the laser-treatment contrary to previous observationmore » with nanosecond pulses. Our findings address the effectiveness of fs-laser treatment and chemical metallization of polydimethylsiloxane films with perspective technological interest in micro-fabrication devices for MEMS and nano-electromechanical systems.« less

Bandgap engineering of InGaAsP/InP laser structure by photo-absorption-induced point defects

NASA Astrophysics Data System (ADS)

Kaleem, Mohammad; Nazir, Sajid; Saqib, Nazar Abbas

2016-03-01

Integration of photonic components on the same photonic wafer permits future optical communication systems to be dense and advanced performance. This enables very fast information handling between photonic active components interconnected through passive optical low loss channels. We demonstrate the UV-Laser based Quantum Well Intermixing (QWI) procedure to engineer the band-gap of compressively strained InGaAsP/InP Quantum Well (QW) laser material. We achieved around 135nm of blue-shift by simply applying excimer laser (λ= 248nm). The under observation laser processed material also exhibits higher photoluminescence (PL) intensity. Encouraging experimental results indicate that this simple technique has the potential to produce photonic integrated devices and circuits.

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru; Terada, Katsuhide

2014-08-01

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

355-nm, nanosecond laser mirror thin film damage competition

NASA Astrophysics Data System (ADS)

Negres, Raluca A.; Stolz, Christopher J.; Thomas, Michael D.; Caputo, Mark

2017-11-01

This competition aimed to survey state-of-the-art UV high reflectors. The requirements of the coatings are a minimum reflection of 99.5% at 45 degrees incidence angle for P-polarized light at 355-nm. The choice of coating materials, design, and deposition method were left to the participants. Laser damage testing was performed at a single testing facility using the raster scan method with a 5-ns pulse length laser system operating at 10 Hz in a single longitudinal mode. A double blind test assured sample and submitter anonymity. In addition to the laser damage resistance results, details of the deposition processes, cleaning method, coating materials and layer count are also shared.

Dye Foils With Increased Durability For Passive Q-Switching In A 1064 Nm Laser.

NASA Astrophysics Data System (ADS)

Mierczyk, Z.; Kwasny, M.; Czeszko, J.

1987-10-01

The results of spectral (IR, UV-VIS, H NMR) , gel permeation chromatography and differential thermal analysis investigations of structures of dye foils consisting of bis-(4-dimethyl-amino-dithio-benzil)-nickel dye suspended in polymethylmethacrylate matrix, to be used for passive Q-switching in a 1064 nm laser, are reported. Results of experimental measurements and of numerical calculations of thermal and generating properties, and of the endurance of passive foil type Q-switches in the resona-tor of YAG:Nd3+ laser are also presented. Optimization of polymerization conditions has enabled the production of dye foils with high thermal and photochemical resistance, which give stable operation of a giant pulsed laser.

[The commonest therapeutic methods for laser irradiation of blood].

PubMed

Moskvin, S V; Konchugova, T V; Khadartsev, A А

2017-12-05

One of the most widely employed methods of laser therapy is laser irradiation of blood (LIB). There are two modifications of this technique, one being intravenous low-intensity laser irradiation of blood (ILIB), the other non-invasive blood irradiation(NLIB). The two methods have been developing independently since either has its advantages and disadvantages. The present article was designed to review the main currently available techniques for laser irradiation of blood which are presented in the form of tables (charts). Replacing the UV irradiation of blood with UV lamps by laser ultraviolet irradiation of blood (LUVIB®) has made it possible to significantly simplify the technique and enhanced its efficiency. The most effective options for ILIB are the combined techniques: ILIB-635 + LUVIB® and ILIB-525 + LUVIB. The most effective technique for ELIB is believed to be the use of low-intensity pulsed laser light with a wavelength of 635 nm and output power up to 40 W.

Extended plasma channels created by UV laser in air and their application to control electric discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zvorykin, V. D., E-mail: zvorykin@sci.lebedev.ru; Ionin, A. A.; Levchenko, A. O.

2015-02-15

Results are presented from a series of experimental and theoretical studies on creating weakly ionized extended plasma channels in atmospheric air by 248-nm UV laser radiation and their application to control long high-voltage discharges. The main mechanisms of air ionization by UV laser pulses with durations from 100 fs to 25 ns and intensities in the ranges of 3×10{sup 11}–1.5×10{sup 13} and 3×10{sup 6}–3×10{sup 11} W/cm{sup 2}, respectively, which are below the threshold for optical gas breakdown, as well as the main relaxation processes in plasma with a density of 10{sup 9}–10{sup 17} cm{sup −3}, are considered. It is shownmore » that plasma channels in air can be efficiently created by amplitude-modulated UV pulses consisting of a train of subpicosecond pulses producing primary photoelectrons and a long UV pulse suppressing electron attachment and sustaining the density of free electrons in plasma. Different modes of the generation and amplification of trains of subterawatt subpicosecond pulses and amplitude-modulated UV pulses with an energy of several tens of joules were implemented on the GARPUN-MTW hybrid Ti:sapphire-KrF laser facility. The filamentation of such UV laser beams during their propagation in air over distances of up to 100 m and the parameters of the corresponding plasma channels were studied experimentally and theoretically. Laser initiation of high-voltage electric discharges and control of their trajectories by means of amplitude-modulated UV pulses, as well as the spatiotemporal structure of breakdowns in air gaps with length of up to 80 cm, were studied.« less

A study of the composition of the products of laser-induced breakdown of hexogen, octogen, pentrite and trinitrotoluene using selected ion flow tube mass spectrometry and UV-Vis spectrometry.

PubMed

Sovová, Kristýna; Dryahina, Kseniya; Spanel, Patrik; Kyncl, Martin; Civis, Svatopluk

2010-05-01

Four types of explosives were studied using a combination of Laser Induced Breakdown Spectroscopy (LIBS) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (ArF excimer laser) as the energy source to convert small amounts samples into plasma and to produce the emission from their molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three precursor ions, with the capability to determine concentrations of trace gases and vapours of volatile organic compounds in real time. This is the first time that SIFT-MS has been used to study the release of NO, NO(2), HCN, HNO(3), HONO, HCHO and C(2)H(2) after a laser-induced breakdown of pure explosive compounds HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclo-octane), RDX (1,3,5-trinitro-2-oxo-1,3,5-triazacyclo-hexane), PETN (pentaerithrityl-tetranitrate) and TNT (2,4,6-trinitrotoluene) in solid form. The radiation emitted after excitation was analysed using a time resolving UV-Vis spectrometer with a ICCD detector. Electronic bands of the CN radical (388 nm), the Swan system of the C(2) radical (512 nm), the NH radical (336 nm), the OH radical (308.4 nm) and atomic lines of oxygen, nitrogen and hydrogen were identified. Vibrational and excitation temperatures were determined from the intensity distributions and a scheme of chemical reactions responsible for the formation of the observed species was proposed.

Towards excimer-laser-based stereolithography: a rapid process to fabricate rigid biodegradable photopolymer scaffolds

PubMed Central

Beke, S.; Anjum, F.; Tsushima, H.; Ceseracciu, L.; Chieregatti, E.; Diaspro, A.; Athanassiou, A.; Brandi, F.

2012-01-01

We demonstrate high-resolution photocross-linking of biodegradable poly(propylene fumarate) (PPF) and diethyl fumarate (DEF) using UV excimer laser photocuring at 308 nm. The curing depth can be tuned in a micrometre range by adjusting the total energy dose (total fluence). Young's moduli of the scaffolds are found to be a few gigapascal, high enough to support bone formation. The results presented here demonstrate that the proposed technique is an excellent tool for the fabrication of stiff and biocompatible structures on a micrometre scale with defined patterns of high resolution in all three spatial dimensions. Using UV laser photocuring at 308 nm will significantly improve the speed of rapid prototyping of biocompatible and biodegradable polymer scaffolds and enables its production in a few seconds, providing high lateral and horizontal resolution. This short timescale is indeed a tremendous asset that will enable a more efficient translation of technology to clinical applications. Preliminary cell tests proved that PPF : DEF scaffolds produced by excimer laser photocuring are biocompatible and, therefore, are promising candidates to be applied in tissue engineering and regenerative medicine. PMID:22696484

Electrically driven deep ultraviolet MgZnO lasers at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit

Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

Electrically driven deep ultraviolet MgZnO lasers at room temperature

DOE PAGES

Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit; ...

2017-06-01

Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

Synthesis and Characterization of Nano-Structure Metal Oxides and Peroxides Prepared by Laser Ablation in Liquids

NASA Astrophysics Data System (ADS)

Drmosh, Qasem Ahmed Qasem

Pulsed laser ablation technique was applied for synthesize of ZnO, ZnO 2 and SnO2 nanostructure using metallic target in different liquids. For this purpose, a laser emitting pulsed UV radiations generated by the third harmonic of Nd:YAG (λ= 355 nm) was applied. For the synthesis of ZnO nanoparticles (NPs), a high-purity metallic plate of Zn was fixed at the bottom of a glass cell in the presence of deionized water and was irradiated at different laser energies (80- 100- 120) mJ per pulse. The average sizes and lattice parameters of ZnO produced by this method were estimated by X-ray diffraction (XRD). ZnO nanoparticles were also produced by ablation of zinc target in the presence of deionized water mixed with two types of surfactants: cetyltrimethyl ammonium bromide (CTAB) and octaethylene glycol monododecyl (OGM). The results showed that the average grain sizes decreased from 38 nm in the case of deionized water to 27 nm and 19 nm in CTAB and OGM respectively. The PL emission in CTAB and OGM showed two peaks: the sharp UV emission at 380 nm and a broad visible peak ranging from 450 nm to 600 nm. Zinc peroxide (ZnO2) nanoparticles having grain size less than 5 nm were also synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3 % hydrogen peroxide H2O2 for the first time. The effect of surfactants on the optical and structure of ZnO2 was studied by applying different spectroscopic techniques. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7 nm, 3.7 nm, 3.3 nm and 2.8 nm in pure H2O2; and H2O 2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO2 nanoparticles prepared with and without surfactants showed characteristic peaks of ZnO2 absorption at 435-445 cm-1. FTIR spectrum also revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. Both FTIR and UV-Vis spectra showed a red shift in the presence of SDS and blue shift in presence of CTAB and OGM. The effect of post annealing temperature on dry ZnO2 nanoparticles prepared by PLA technique of solid zinc target in 3% H2O2 was studied by variation of the annealing temperatures from 100 to 600 °C for 8 hours under 1 atmospheric pressure. The XRD showed the phase transition from ZnO2 to ZnO at 200 °C. Based on XRD data, both the average grain size and lattice parameters of ZnO increased by post annealing of ZnO2 higher than 200 °C. In contrast, the band gap of ZnO nanoparticles decreased when the annealing temperature increased. The average sizes were 5, 6, 9, 15 and 19 nm at 200, 300, 400, 500 and 600 °C respectively. The PL emission spectra for ZnO showed strong UV emission peaks in all samples. In addition, the UV emission peaks were shifted to longer wavelength (red shifting) as the annealing temperature increase from 200 to 600 °C. From the above findings, we concluded that the grain size, lattice parameters, PL and band gap were size dependent as predicted by theoretical studies. (Abstract shortened by UMI.).

Non-destructive evaluation of UV pulse laser-induced damage performance of fused silica optics.

PubMed

Huang, Jin; Wang, Fengrui; Liu, Hongjie; Geng, Feng; Jiang, Xiaodong; Sun, Laixi; Ye, Xin; Li, Qingzhi; Wu, Weidong; Zheng, Wanguo; Sun, Dunlu

2017-11-24

The surface laser damage performance of fused silica optics is related to the distribution of surface defects. In this study, we used chemical etching assisted by ultrasound and magnetorheological finishing to modify defect distribution in a fused silica surface, resulting in fused silica samples with different laser damage performance. Non-destructive test methods such as UV laser-induced fluorescence imaging and photo-thermal deflection were used to characterize the surface defects that contribute to the absorption of UV laser radiation. Our results indicate that the two methods can quantitatively distinguish differences in the distribution of absorptive defects in fused silica samples subjected to different post-processing steps. The percentage of fluorescence defects and the weak absorption coefficient were strongly related to the damage threshold and damage density of fused silica optics, as confirmed by the correlation curves built from statistical analysis of experimental data. The results show that non-destructive evaluation methods such as laser-induced fluorescence and photo-thermal absorption can be effectively applied to estimate the damage performance of fused silica optics at 351 nm pulse laser radiation. This indirect evaluation method is effective for laser damage performance assessment of fused silica optics prior to utilization.

Structural-modification mechanism for polyimide-doped poly(tetrafluoroethylene)at subthreshold fluences using 248 nm radiation

NASA Astrophysics Data System (ADS)

Davis, C. R.; Snyder, R. W.; Egitto, F. D.; D'Couto, G. C.; Babu, S. V.

1994-09-01

Single-photon excimer laser ablation of neat poly(tetrafluoroethylene) (PTFE) is not observed at emissions in the 'quartz' UV, i.e., from about 190-380 nm. However, it has been successfully demonstrated that, when the fluoropolymer is doped with small quantities of polyimide (PI), ablation in the quartz UV, e.g., at 248 and 308 nm and pulse widths of about 25 ns, is readily achieved. When PI-PTFE blends are exposed to subthreshold fluences, considerable changes in surface topography occur although clearly defined structures, e.g., pits, are not formed. Using photoacoustic infrared spectroscopy to evaluate surface and bulk chemical changes to blends exposed to subthreshold excimer laser fluences, is less than 100 mJ/sq cm, it is shown that PI (1) is distributed throughout the bulk and resides at the surface and (2) is selectively absorbing the high-energy photons and as a result being preferentially removed from the surface.

Resonance-enhanced two-photon excitation of CaI

NASA Astrophysics Data System (ADS)

Casero-Junquera, Elena; Lawruszczuk, Rafal; Rostas, Joëlle; Taieb, Guy

1994-07-01

Induced fluorescence following visible (620-655 nm) laser excitation of the CaI radical has been detected not only in the same region (B, A-X transitions), but also in the UV (315-330 nm). The UV two-photon excitation spectrum consists of narrow bands appearing at laser frequencies located within certain bands of the Δ v = 1, 0 sequences of the B 2Σ +-X 2Σ + and A 2Π 1/2-X 2Σ + systems. The main peaks are tentatively assigned to resonance-enhanced excitation of a single vibrational level of the lowest Rydberg D 2Σ + state from successive vibrational levels of the ground state. The excitation process is a one-color two-photon optical—optical-double-resonance via B 2Σ + and A 2Π 1/2 intermediate levels. This analysis is supported by the absorption spectrum observed long ago by Walters and Barratt. The absorption and laser excitation complementary data have been used to derive approximate molecular constants for the D state.

A multi-wavelength (u.v. to visible) laser system for early detection of oral cancer

NASA Astrophysics Data System (ADS)

Najda, S. P.; Perlin, P.; Leszczyński, M.; Slight, T. J.; Meredith, W.; Schemmann, M.; Moseley, H.; Woods, J. A.; Valentine, R.; Kalra, S.; Mossey, P.; Theaker, E.; Macluskey, M.; Mimnagh, G.; Mimnagh, W.

2015-03-01

A multi-wavelength (360nm - 440nm), real-time Photonic Cancer Detector (PCD) optical system based on GaN semiconductor laser technology is outlined. A proof of concept using blue laser technology for early detection of cancer has already been tested and proven for esophageal cancer. This concept is expanded to consider a wider range of wavelengths and the PCD will initially be used for early diagnosis of oral cancers. The PCD creates an image of the oral cavity (broad field white light detection) and maps within the oral cavity any suspicious lesions with high sensitivity using a narrow field tunable detector.

[The 308 nm Excimer laser for the treatment of psoriasis and inflammatory skin diseases].

PubMed

Fritz, K; Salavastru, C

2018-01-01

Overall, the 308 nm Excimer laser enables not only a more effective and safer UVB therapy than classical UV phototherapy, but also targeted irradiation in higher doses with a lower cumulative load, which results in faster healing of mainly circumscribed skin changes. This also applies to therapy-resistant residual lesions which, despite systemic therapy, did not diminish. Combination therapies usually improve the result and enable the dose of UVB and systemic medication to be reduced. Excimer laser therapy can be used for an increasing number of skin diseases, especially those that respond to phototherapy or photochemotherapy.

The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

1995-01-01

We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

Langley Mobile Ozone Lidar: Ozone and Aerosol Atmospheric Profiling for Air Quality Research

NASA Technical Reports Server (NTRS)

De Young, Russell; Carrion, William; Ganoe, Rene; Pliutau, Denis; Gronoff, Guillaume; Berkoff, Timothy; Kuang, Shi

2017-01-01

The Langley mobile ozone lidar (LMOL) is a mobile ground-based ozone lidar system that consists of a pulsed UV laser producing two UV wavelengths of 286 and 291 nm with energy of approximately 0.2 mJ/pulse 0.2 mJ/pulse and repetition rate of 1 kHz. The 527 nm pump laser is also transmitted for aerosol measurements. The receiver consists of a 40 cm parabolic telescope, which is used for both backscattered analog and photon counting. The lidar is very compact and highly mobile. This demonstrates the utility of very small lidar systems eventually leading to space-based ozone lidars. The lidar has been validated by numerous ozonesonde launches and has provided ozone curtain profiles from ground to approximately 4 km in support of air quality field missions.

Comparative study of pulsed laser cleaning applied to weathered marble surfaces

NASA Astrophysics Data System (ADS)

Ortiz, P.; Antúnez, V.; Ortiz, R.; Martín, J. M.; Gómez, M. A.; Hortal, A. R.; Martínez-Haya, B.

2013-10-01

The removal of unwanted matter from surface stones is a demanding task in the conservation of cultural heritage. This paper investigates the effectiveness of near-infrared (IR) and ultraviolet (UV) laser pulses for the cleaning of surface deposits, iron oxide stains and different types of graffiti (black, red and green sprays and markers, and black cutting-edge ink) on dolomitic white marble. The performance of the laser techniques is compared to common cleaning methods on the same samples, namely pressurized water and chemical treatments. The degree of cleaning achieved with each technique is assessed by means of colorimetric measurements and X-ray microfluorescence. Eventual morphological changes induced on the marble substrate are monitored with optical and electronic microscopy. It is found that UV pulsed laser ablation at 266 nm manages to clean all the stains except the cutting-edge ink, although some degree of surface erosion is produced. The IR laser pulses at 1064 nm can remove surface deposits and black spray acceptably, but a yellowing is observed on the stone surface after treatment. An economic evaluation shows that pulsed laser cleaning techniques are advantageous for the rapid cleaning of small or inaccessible surface areas, although their extensive application becomes expensive due to the long operating times required.

Modification of the amorphous carbon films by the ns-laser irradiation

NASA Astrophysics Data System (ADS)

Grigonis, Alfonsas; Marcinauskas, Liutauras; Vinciunaite, Vinga; Raciukaitis, Gediminas

2011-10-01

The effect of a nanosecond laser irradiation of thin (60 and 145 nm) amorphous, diamond-like carbon films deposited on Si substrate by an ion beam deposition (IBD) from pure acetylene and acetylene/hydrogen (1:2) gas mixture was analyzed in this work. The films were irradiated with the infrared (IR) and ultraviolet (UV) radiation of the nanosecond Nd:YAG lasers working at the first (1.16 eV) and the third (3.48 eV) harmonics, using a multi-shot regime. The IR laser irradiation stimulated a minor increase in the fraction of sp2 bonds, causing a slight decrease in the hardness of the films and initiated SiC formation. Irradiation with the UV laser caused the formation of carbides and increased hydrogenization of the Si substrate and the fraction of sp2 sites. Spalliation and ablation were observed at a higher energy density and with a large number of laser pulses per spot.

Solid-state laser source of narrowband ultraviolet B light for skin disease care

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong

2013-03-01

We report about the development of all-solid-state laser source of narrowband UV-B light for medical applications. The device is based on a gain-switched Ti: Sapphire laser with volume Bragg grating, pumped at 532 nm and operating at 931.8 nm, followed by a third harmonic generator and a fiber optic beam homogenizer. The maximum available pulse energy exceeded 5 mJ at 310.6 nm, with a pulse repetition rates of 50 Hz. The output characteristics satisfy the medical requirements for psoriasis and vitiligo treatment. A new optical scheme for third harmonic generation enhancement at moderate levels of input intensities is proposed and investigated. As a result, 40% harmonic efficiency was obtained, when input pulse power was only 300 kW.

UV laser deposition of metal films by photogenerated free radicals

NASA Technical Reports Server (NTRS)

Montgomery, R. K.; Mantei, T. D.

1986-01-01

A novel photochemical method for liquid-phase deposition of metal films is described. In the liquid phase deposition scheme, a metal containing compound and a metal-metal bonded carbonyl complex are dissolved together in a polar solvent and the mixture is irradiated using a UV laser. The optical arrangement consists of a HeCd laser which provides 7 mW of power at a wavelength of 325 nm in the TEM(OO) mode. The beam is attenuated and may be expanded to a diameter of 5-20 mm. Experiments with photochemical deposition of silver films onto glass and quartz substrates are described in detail. Mass spectrometric analysis of deposited silver films indicated a deposition rate of about 1 A/s at incident power levels of 0.01 W/sq cm. UV laser-induced copper and palladium films have also been obtained. A black and white photograph showing the silver Van Der Pauw pattern of a solution-deposited film is provided.

In Vitro UV-Visible Spectroscopy Study of Yellow Laser Irradiation on Human Blood

NASA Astrophysics Data System (ADS)

Fuad, Siti Sakinah Mohd; Suardi, N.; Mustafa, I. S.

2018-04-01

This experimental study was performed to investigate the effect of low level yellow laser of 589nm wavelength with various laser irradiation time. Human blood samples with random diseases are irradiated with yellow laser of power density of 450mW/cm2 from 10 minutes to 60 minutes at 10 minutes intervals. The morphology of the red blood cell were also observed for different irradiation time. The result shows that there is a significant different in the absorption of light with varying laser irradiation time (p<0.01). The maximum absorption recorded at 40 minutes of irradiation at 340nm peak. Blood smear of the samples reveals that there are observable changes in the morphology of the red blood cell at 40 minutes and 60 minutes of irradiation.

Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

NASA Astrophysics Data System (ADS)

Trautner, Stefan; Jasik, Juraj; Parigger, Christian G.; Pedarnig, Johannes D.; Spendelhofer, Wolfgang; Lackner, Johannes; Veis, Pavel; Heitz, Johannes

2017-03-01

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157 nm F2 laser and 532 nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925 nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1 wt% feasible.

Direct nanopatterning of 100 nm metal oxide periodic structures by Deep-UV immersion lithography.

PubMed

Stehlin, Fabrice; Bourgin, Yannick; Spangenberg, Arnaud; Jourlin, Yves; Parriaux, Olivier; Reynaud, Stéphanie; Wieder, Fernand; Soppera, Olivier

2012-11-15

Deep-UV lithography using high-efficiency phase mask has been developed to print 100 nm period grating on sol-gel based thin layer. High efficiency phase mask has been designed to produce a high-contrast interferogram (periodic fringes) under water immersion conditions for 244 nm laser. The demonstration has been applied to a new developed immersion-compatible sol-gel layer. A sol-gel photoresist prepared from zirconium alkoxides caped with methacrylic acids was developed to achieve 50 nm resolution in a single step exposure. The nanostructures can be thermally annealed into ZrO(2). Such route considerably simplifies the process for elaborating nanopatterned surfaces of transition metal oxides, and opens new routes for integrating materials of interest for applications in the field of photocatalysis, photovoltaic, optics, photonics or microelectronics.

Preparation of CuO nanoparticles by laser ablation in liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdulateef, Sinan A., E-mail: sinan1974@yahoo.com; MatJafri, M. Z.; Omar, A. F., E-mail: thinker-academy@yahoo.com

2016-07-06

Colloidal Cu nanoparticles (NPs) were synthesized by pulsed Nd:YAG laser ablation in acetone. Cu NPs were converted into CuO. The size and optical properties of these NPs were characterized using an UV/Vis spectrophotometer, transmission electron microscopy, and X-ray diffraction. Cu NPs were spherical, and their mean diameter in acetone was 8 nm–10 nm. Optical extinction immediately after the ablation showed surface Plasmon resonance peaks at 602 nm. The color of Cu NPs in acetone was green and stable even after a long time.

AlGaInN laser diode technology for defence, security and sensing applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Boćkowski, Mike; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Scott; Kelly, Antony E.

2014-10-01

The latest developments in AlGaInN laser diode technology are reviewed for defence, security and sensing applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., i.e, 380nm, to the visible, i.e., 530nm, by tuning the indium content of the laser GaInN quantum well. Advantages of using Plasma assisted MBE (PAMBE) compared to more conventional MOCVD epitaxy to grow AlGaInN laser structures are highlighted. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of <100mW in the 400-420nm wavelength range that are suitable for telecom applications. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Gallium-nitride (GaN) blue laser diode is reported. High power operation of AlGaInN laser diodes is demonstrated with a single chip, AlGaInN laser diode `mini-array' with a common p-contact configuration at powers up to 2.5W cw at 410nm. Low defectivity and highly uniform GaN substrates allow arrays and bars of nitride lasers to be fabricated. GaN laser bars of up to 5mm with 20 emitters, mounted in a CS mount package, give optical powers up to 4W cw at ~410nm with a common contact configuration. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space and/or fibre optic system integration within a very small form-factor.or.

A comparison of the DPSS UV laser ablation characteristic of 1024 and H10F WC-Co

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-07-01

An investigation on ablation characteristics of 1024 and H10F cobalt cemented tungsten carbide (WC-Co) with a DPSS nanosecond UV laser (50 ns pulse width, 355 nm wavelength, 90 W average power and 10 kHz repetition rate) is presented. The ablation characteristic parameters such as ablation threshold, incubation effect and optical penetration depth were evaluated based on the spot ablation diameter and depth. It was observed that the ablation threshold is significantly influenced by the number of pulses (NOP) and it decreases with increase NOP which is attributed to the incubation effect. Only one ablation region is observed at low laser fluence and an additional molten ablation region is observed at high laser fluence accompanied with cracks. The cracks formation is due to the thermal induced stress and changes in WC microstructure during laser beam irradiation. The crack depth is proportional to the thickness of the molten WC region. The ablation threshold of 1024 WC-Co and H10F WC-Co were found to be Fth1 =4.32 J/cm2 and Fth1 =4.26 J/cm2 respectively. The difference in chemical composition has insignificant effect on the ablation threshold value of the material. The incubation factor and optical penetration depth values of 1024 WC-Co and H10F WC-Co were found to be ξ=0.73, α-1 =411 nm and ξ=0.75, α-1 =397 nm respectively.

Production of High Intracavity UV Power From a CW Laser Source

NASA Technical Reports Server (NTRS)

David, R. T.; Chyba, T. H.; Keppel, C. E.; Gaskell, D.; Ent, R.

1998-01-01

The goal of this research project is to create a prototype high power CW source of ultraviolet (UV) photons for photon-electron scattering at the Thomas Jefferson National Accelerator Facility (TJNAF), Hall B. The facility will use optical resonant cavities to produce a high photon flux. The technical approach will be to frequency-double the 514.5 mn light from an Argon-Ion Laser to create 0.1 to 1.0 watt in the UV. The produced UV power will be stored in a resonant cavity to generate an high intracavity UV power of 102 to 103 watts. The specific aim of this project is to first design and construct the low-Q doubling cavity and lock it to the Argon-Ion wavelength. Secondly, the existing 514.5 nm high-Q build-up cavity and its locking electronics will be modified to create high intracavity UV power. The entire system will then be characterized and evaluated for possible beam line use.

355-nm, nanosecond laser mirror thin film damage competition

DOE PAGES

Negres, Raluca A.; Stolz, Christopher J.; Thomas, Michael D.; ...

2017-11-23

Here, this competition aimed to survey state-of-the-art UV high reflectors. The requirements of the coatings are a minimum reflection of 99.5% at 45 degrees incidence angle for P-polarized light at 355-nm. The choice of coating materials, design, and deposition method were left to the participants. Laser damage testing was performed at a single testing facility using the raster scan method with a 5-ns pulse length laser system operating at 10 Hz in a single longitudinal mode. A double blind test assured sample and submitter anonymity. Finally, in addition to the laser damage resistance results, details of the deposition processes, cleaningmore » method, coating materials and layer count are also shared.« less

Tunable Molecular Lasers.

DTIC Science & Technology

1986-09-01

689 (1983). ~~ +. 10. H . Helvajian and C. Wittig, "Vibration quenching of HgBrx 2 E 1 2 ) " Appl. Phys. Lett. 38, 731-733 (1981). 11. N. H . Cheung...aSE (the UV- band stimulated-emission cross section) - 5 X 10- 16 cm 2 and 5 -0 h =uv 5.8 X I0- 19 J. Therefore the stimulated-emission rate 0 at 342...nm is aSEIuv( h ) - ’ - 1.7 X 109 sec - ’ for an intensity - 4 - of 2 MW cm- 2 (no injected green-laser energy). Next, quenching of the 12 D’ state is

Detection of tropospheric OH and HO2 by laser-induced fluorescence at low pressure using the 308nm excitation of OH

NASA Technical Reports Server (NTRS)

Hofzumahaus, Andreas; Holland, Frank

1994-01-01

Laser-induced fluorescence (LIF) spectroscopy is a highly sensitive method for the direct in situ measurement of hydroxyl concentrations in the atmosphere. Its sensitivity and selectivity relies on the intense discrete UV-absorption lines of OH which are strongest around 282nm and 308nm. We have developed a LIF-instrument based on the low-pressure experiment (FAGE). However, we use 308nm instead of 282nm as excitation wavelength for OH, a concept that is also pursued by other groups. One advantage of the longer excitation wavelength is the higher detection sensitivity due to the about 6 times larger effective OH-fluorescence cross-section. Moreover, the O3/H2O-interference (OH self-generation by the laser) is about a factor of 200 smaller at 308nm than at 282nm. This keeps the interference level well below the projected detection limit of 10(exp 5) OH/cm(exp 3). Atmospheric HO2-radicals are detected by chemical conversion of HO2 into OH with NO.

Surface nanotexturing of tantalum by laser ablation in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barmina, E V; Simakin, Aleksandr V; Shafeev, Georgii A

2009-01-31

Surface nanotexturing of tantalum by ablation with short laser pulses in water has been studied experimentally using three ablation sources: a neodymium laser with a pulse duration of 350 ps, an excimer laser (248 nm) with a pulse duration of 5 ps and a Ti:sapphire laser with a pulse duration of 180 fs. The morphology of the nanotextured surfaces has been examined using a nanoprofilometer and field emission scanning electron microscope. The results demonstrate that the average size of the hillocks produced on the target surface depends on the laser energy density and is {approx}200 nm at an energy densitymore » approaching the laser-melting threshold of tantalum and a pulse duration of 350 ps. Their surface density reaches 10{sup 6} cm{sup -2}. At a pulse duration of 5 ps, the average hillock size is 60-70 nm. Nanotexturing is accompanied by changes in the absorption spectrum of the tantalum surface in the UV and visible spectral regions. The possible mechanisms of surface nanotexturing and potential applications of this effect are discussed. (nanostructures)« less

Photoluminescence of Copper-Doped Lithium Niobate Crystals

NASA Astrophysics Data System (ADS)

Gorelik, V. S.; Pyatyshev, A. Yu.; Sidorov, N. V.

2018-05-01

The photoluminescence (PL) of copper-doped lithium niobate single crystals is studied using different UV-Vis light-emitting diodes and a pulse-periodic laser with a wavelength of 266 nm as excitation radiation sources. With the resonance excitation from a 527-nm light-emitting diode, the intensity of PL increases sharply (by two orders of magnitude). When using a 467-nm light-emitting diode for excitation, the PL spectrum is characterized by the presence of multiphonon lines in the range of 520-620 nm.

PRK by Er:YAG laser: in-vitro studies and first in-vivo experiences

NASA Astrophysics Data System (ADS)

Steiner, Rudolf W.; Leiacker, Richard; Russ, Detlef; Seiler, Theo

1996-01-01

Photorefractive keratectomy (PRK) is usually performed by an excimer laser at 193 nm wavelength. Ablatio of corneal tissue is, however, not only possible in the UV region of the optical spectrum but also in the IR where water is an excellent absorber. Therefore, an Er:YAG laser was used at 2.94 micrometer wavelength as an alternative laser light source to perform in vitro studies of corneal ablation and also first clinical experiments to correct myopia of patients with blind eyes.

Megawatt level UV output from [110] Cr⁴⁺:YAG passively Q-switched microchip laser.

PubMed

Bhandari, Rakesh; Taira, Takunori

2011-11-07

Recent development of megawatt peak power, giant pulse microchip lasers has opened new opportunities for efficient wavelength conversion, provided the output of the microchip laser is linearly polarized. We obtain > 2 MW peak power, 260 ps, 100 Hz pulses at 266 nm by fourth harmonic conversion of a linearly polarized Nd:YAG microchip laser that is passively Q-switched with [110] cut Cr⁴⁺:YAG. The SHG and FHG conversion efficiencies are 85% and 51%, respectively.

Temporal, thermal, and light stability of continuously tunable cholesteric liquid crystal laser array.

PubMed

Jeong, Mi-Yun; Chung, Ki Soo; Wu, Jeong Weon

2014-11-01

Fine-structured polymerized cholesteric liquid crystal (PCLC) wedge laser devices have been realized, with high fine spatial tunability of the lasing wavelength. With resolution less than 0.3 nm in a broad spectral range, more than one hundred laser lines could be obtained in a PCLC cell without extra devices. For practical device application, we studied the stability of the device in detail over time, and in response to strong external light sources, and thermal perturbation. The PCLC wedge cells had good temporal stability for 1 year and showed good stability for strong perturbations, with the lasing wavelength shifting less than 1 nm, while the laser peak intensities decreased by up to 34%, and the high energy band edge of the photonic band gap (PBG) was red shifted 3 nm by temperature perturbation. However, when we consider the entire lasing spectrum for the PCLC cell, the 1-nm wavelength shift may not matter. Although the laser peak intensities were decreased by up to 34% in total for all of the perturbation cases, the remaining 34% laser peak intensity is considerable extent to make use. This good stability of the PCLC laser device is due to the polymerization of the CLC by UV curing. This study will be helpful for practical CLC laser device development.

Optical properties of Eu2+ ions in BaY2F8 for completely-solid-state cw UV laser emission

NASA Astrophysics Data System (ADS)

Toncelli, Alessandra; Moglia, Francesca; Tonelli, Mauro

2010-11-01

Eu-doped BaYF single crystals have been grown with two different Eu ion concentrations: 0.5%, 1% Eu doping levels. It was found that part of the Eu ions added in the melt were reduced during the growth process and the ratio between the Eu and Eu content in the crystal depends on the duration of the growth process. A complete room-temperature polarized spectroscopic characterization of the divalent Eu ions in this host crystal is presented with particular insights in the laser potentialities of the compound in the UV region. Polarized absorption, emission and excitation spectra are presented together with the lifetime measurement of the emitting level. It was found that due to the weak nephelauxetic effect the 4f7→4f65d1 band is located at higher energy than the 4f→4f(8S→6P) transition. As a result, when pumped in the 200- 300 nm range, this crystal shows an interesting emission that extends from 351 to 366 nm and has a decay-time as long as τ=(1.5±0.1) ms. This opens the possibility to obtain completely-solid-state laser emission in the UV region with potentialities for cw or mode-locked emission.

A simple resonance enhanced laser ionization scheme for CO via the A1Π state

NASA Astrophysics Data System (ADS)

Sun, Z. F.; von Zastrow, A. D.; Parker, D. H.

2017-07-01

We investigate the laser ionization process taking place when the CO molecule is exposed to vacuum ultraviolet (VUV) radiation resonant with the CO A1Π (v = 0) ← X1Σ+ (v = 0) transition around 154 nm, along with the ultraviolet (UV) and visible (Red) radiation used to generate VUV by four-wave difference-frequency mixing. By measuring the CO+ ion recoil and a room temperature gas spectrum, it is possible to assign the ionization process as 1 + 1' + 1'' REMPI where the one-photon steps refer to the VUV, UV, and Red radiation, respectively. Resonance enhanced ionization of rotational states around J = 12 arise due to the overlap of the fixed wavelength UV (˜250 nm) with the R band-head of a transition assigned to CO E1Π (v = 6) ← A1Π (v = 0) with a term value of 104 787.5 cm-1. The REMPI process is efficient and polarization sensitive and should be useful in a wide range of studies involving nascent CO.

Influence of wavelength on the laser removal of lichens colonizing heritage stone

NASA Astrophysics Data System (ADS)

Sanz, M.; Oujja, M.; Ascaso, C.; Pérez-Ortega, S.; Souza-Egipsy, V.; Fort, R.; de los Rios, A.; Wierzchos, J.; Cañamares, M. V.; Castillejo, M.

2017-03-01

Laser irradiation of lichen thalli on heritage stones serves for the control of epilithic and endolithic biological colonizations. In this work we investigate rock samples from two quarries traditionally used as source of monumental stone, sandstone from Valonsadero (Soria, Spain) and granite from Alpedrete (Madrid, Spain), in order to find conditions for efficient laser removal of lichen thalli that ensure preservation of the lithic substrate. The samples presented superficial areas colonized by different types of crustose lichens, i.e. Candelariella vitellina, Aspicilia viridescens, Rhizocarpon disporum and Protoparmeliopsis muralis in Valonsadero samples and P. cf. bolcana and A. cf. contorta in Alpedrete samples. A comparative laser cleaning study was carried out on the mentioned samples with ns Q-switched Nd:YAG laser pulses of 1064 nm (fundamental radiation), 355 nm (3rd harmonic) and 266 nm (4th harmonic) and sequences of IR-UV pulses. A number of techniques such as UV-Vis absorption spectroscopy, stereomicroscopy, scanning electron microscopy (SEM) at low vacuum, SEM with backscattered electron imaging (SEM-BSE), electron dispersive spectroscopy (EDS) and FT-Raman spectroscopy were employed to determine the best laser irradiation conditions and to detect possible structural, morphological and chemical changes on the irradiated surfaces. The results show that the laser treatment does not lead to the complete removal of the studied lichen thalli, although clearly induces substantial damage, in the form of loss of the lichen upper cortex and damage to the algal layer. In the medium term these alterations could result in the destruction of the lichen thalli, thus providing a degree of control of the biodeterioration processes of the lithic substrate and reducing the chances of subsequent lichen recolonization.

Free-space and underwater GHz data transmission using AlGaInN laser diode technology

NASA Astrophysics Data System (ADS)

Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Boćkowski, M.; Leszczyński, M.; Wisniewski, P.; Czernecki, R.; Kucharski, R.; Targowski, G.; Watson, S.; Kelly, A. E.

2016-05-01

Laser diodes fabricated from the AlGaInN material system is an emerging technology for defence and security applications; in particular for free space laser communication. Conventional underwater communication is done acoustically with very slow data rates, short reach, and vulnurable for interception. AlGaInN blue-green laser diode technology allows the possibility of both airbourne links and underwater telecom that operate at very fast data rates (GHz), long reach (100's of metres underwater) and can also be quantum encrypted. The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with optical powers of <100mW. Visible light communications at high frequency (up to 2.5 Gbit/s) using a directly modulated 422nm Galliumnitride (GaN) blue laser diode is reported in free-space and underwater.

UV-laser photochemistry of isoxazole isolated in a low-temperature matrix.

PubMed

Nunes, Cláudio M; Reva, Igor; Pinho e Melo, Teresa M V D; Fausto, Rui

2012-10-05

The photochemistry of matrix-isolated isoxazole, induced by narrowband tunable UV-light, was investigated by infrared spectroscopy, with the aid of MP2/6-311++G(d,p) calculations. The isoxazole photoreaction starts to occur upon irradiation at λ = 240 nm, with the dominant pathway involving decomposition to ketene and hydrogen cyanide. However, upon irradiation at λ = 221 nm, in addition to this decomposition, isoxazole was also found to isomerize into several products: 2-formyl-2H-azirine, 3-formylketenimine, 3-hydroxypropenenitrile, imidoylketene, and 3-oxopropanenitrile. The structural and spectroscopic assignment of the different photoisomerization products was achieved by additional irradiation of the λ = 221 nm photolyzed matrix, using UV-light with λ ≥ 240 nm: (i) irradiation in the 330 ≤ λ ≤ 340 nm range induced direct transformation of 2-formyl-2H-azirine into 3-formylketenimine; (ii) irradiation with 310 ≤ λ ≤ 318 nm light induced the hitherto unobserved transformation of 3-formylketenimine into 3-hydroxypropenenitrile and imidoylketene; (iii) irradiation with λ = 280 nm light permits direct identification of 3-oxopropanenitrile; (iv) under λ = 240 nm irradiation, tautomerization of 3-hydroxypropenenitrile to 3-oxopropanenitrile is observed. On the basis of these findings, a detailed mechanistic proposal for isoxazole photochemistry is presented.

Changing of optical absorption and scattering coefficients in nonlinear-optical crystal lithium triborate before and after interaction with UV-radiation

NASA Astrophysics Data System (ADS)

Demkin, Artem S.; Nikitin, Dmitriy G.; Ryabushkin, Oleg A.

2016-04-01

In current work optical properties of LiB3O5 (LBO) crystal with ultraviolet (UV) (λ= 266 nm) induced volume macroscopic defect (track) are investigated using novel piezoelectric resonance laser calorimetry technique. Pulsed laser radiation of 10 W average power at 532 nm wavelength, is consecutively focused into spatial regions with and without optical defect. For these cases exponential fitting of crystal temperature kinetics measured during its irradiation gives different optical absorption coefficients α1 = 8.1 • 10-4 cm-1 (region with defect) and α =3.9ṡ10-4 cm-1 (non-defected region). Optical scattering coefficient is determined as the difference between optical absorption coefficients measured for opaque and transparent lateral facets of the crystal respectively. Measurements reveal that scattering coefficient of LBO in the region with defect is three times higher than the optical absorption coefficient.

Laser wavelength selection for Raman spectroscopy of microbial pigments in situ in Antarctic desert ecosystem analogues of former habitats on Mars

NASA Astrophysics Data System (ADS)

Edwards, Howell G. M.; Newton, Emma M.; Wynn-Williams, David D.; Dickensheets, David; Schoen, Chris; Crowder, Chelle

2002-10-01

The vital ultraviolet- (UV-) protective and photosynthetic pigments of cyanobacteria and lichens (microbial symbioses) that dominate primary production in Antarctic desert ecosystems auto-fluoresce at short wavelengths. We therefore use a long-wavelength (1064 nm) infrared laser for non-intrusive in situ Raman spectrometry of their ecologically significant compounds (especially pigments). To confirm that the power loss at this longer wavelength is justified to avoid swamping by background fluorescence, we compared Raman spectra obtained with excitation at 1064, 852, 830, 785, 633 and 515 nm. These are typical of lasers used for Raman spectroscopy. We analysed communities of the cyanobacterium Nostoc commune and the highly pigmented lichens Acarospora chlorophana and Caloplaca saxicola. These require screening compounds (e.g. pigments such as scytonemin in cyanobacteria and rhizocarpic acid in the fungal symbiont of lichens). They are augmented by quenching pigments (e.g. carotenoids) to dissipate the energy of free radicals generated by penetrating UV. We also analysed organisms having avoidance strategies (e.g. endolithic communities within translucent rocks, including the common cyanobacterium Chroococcidiopsis). These require accessory pigments for photosynthesis at very low light intensities. Although some organisms gave useable Raman spectra with short-wavelength lasers, 1064 nm was the only excitation that was consistently excellent for all organisms. We conclude that a 1064 nm Raman spectrometer, miniaturized using an InGaAs detector, is the optimal instrument for in situ studies of pigmented microbial communities at the limits of life on Earth. This has practical potential for the quest for biomolecules residual from any former surface life on Mars.

SO2 Spectroscopy with A Tunable UV Laser

NASA Technical Reports Server (NTRS)

Morey, W. W.; Penney, C. M.; Lapp, M.

1973-01-01

A portion of the fluorescence spectrum of SO2 has been studied using a narrow wavelength doubled dye laser as the exciting source. One purpose of this study is to evaluate the use of SO2 resonance re-emission as a probe of SO2 in the atmosphere. When the SO2 is excited by light at 300.2 nm, for example, a strong reemission peak is observed which is Stokes-shifted from the incident light wavelength by the usual Raman shift (the VI symmetric vibration frequency 1150.5/cm ). The intensity of this peak is sensitive to small changes (.01 nm) in the incident wavelength. Measurements of the N2 quenching and self quenching of this re-emission have been obtained. Preliminary analysis of this data indicates that the quenching is weak but not negligible. The dye laser in our system is pumped by a pulsed N2 laser. Tuning 'and spectral narrowing are accomplished using a telescope-echelle grating combination. In a high power configuration the resulting pulses have a spectral width of about 5 x 10(exp -3) nm and a time duration of about 6 nsec. The echelle grating is rotated by a digital stepping motor, such that each step shifts the wavelength by 6 x 10(exp -4) nm. In addition to the tunable, narrow wavelength uv source and spectral analysis of the consequent re-emission, the system also provides time resolution of the re-emitted light to 6 nsec resolution. This capability is being used to study the lifetime of low pressure S02 fluorescence at different wavelengths and pressures.

Laser-Induced Fluorescence Emission (L.I.F.E.): searching for Mars organics with a UV-enhanced PanCam.

PubMed

Storrie-Lombardi, Michael C; Muller, Jan-Peter; Fisk, Martin R; Cousins, Claire; Sattler, Birgit; Griffiths, Andrew D; Coates, Andrew J

2009-12-01

The European Space Agency will launch the ExoMars mission in 2016 with a primary goal of surveying the martian subsurface for evidence of organic material. We have recently investigated the utility of including either a 365 nm light-emitting diode or a 375 nm laser light source in the ExoMars rover panoramic camera (PanCam). Such a modification would make it feasible to monitor rover drill cuttings optically for the fluorescence signatures of aromatic organic molecules and map the distribution of polycyclic aromatic hydrocarbons (PAHs) as a function of depth to the 2 m limit of the ExoMars drill. The technique described requires no sample preparation, does not consume irreplaceable resources, and would allow mission control to prioritize deployment of organic detection experiments that require sample destruction, expenditure of non-replaceable consumables, or both. We report here for the first time laser-induced fluorescence emission (L.I.F.E.) imaging detection limits for anthracene, pyrene, and perylene targets doped onto a Mars analog granular peridotite with a 375 nm Nichia laser diode in optically uncorrected wide-angle mode. Data were collected via the Beagle 2 PanCam backup filter wheel fitted with original blue (440 nm), green (530 nm), and red (670 nm) filters. All three PAH species can be detected with the PanCam green (530 nm) filter. Detection limits in the green band for signal-to-noise ratios (S/N) > 10 are 49 parts per million (ppm) for anthracene, 145 ppm for pyrene, and 20 ppm for perylene. The anthracene detection limit improves to 7 ppm with use of the PanCam blue filter. We discuss soil-dependent detection limit constraints; use of UV excitation with other rover cameras, which provides higher spatial resolution; and the advantages of focused and wide-angle laser modes. Finally, we discuss application of L.I.F.E. techniques at multiple wavelengths for exploration of Mars analog extreme environments on Earth, including Icelandic hydrothermally altered basalts and the ice-covered lakes and glaciers of Dronning Maud Land, Antarctica.

Enhancing Protein Disulfide Bond Cleavage by UV Excitation and Electron Capture Dissociation for Top-Down Mass Spectrometry.

PubMed

Wongkongkathep, Piriya; Li, Huilin; Zhang, Xing; Loo, Rachel R Ogorzalek; Julian, Ryan R; Loo, Joseph A

2015-11-15

The application of ion pre-activation with 266 nm ultraviolet (UV) laser irradiation combined with electron capture dissociation (ECD) is demonstrated to enhance top-down mass spectrometry sequence coverage of disulfide bond containing proteins. UV-based activation can homolytically cleave a disulfide bond to yield two separated thiol radicals. Activated ECD experiments of insulin and ribonuclease A containing three and four disulfide bonds, respectively, were performed. UV-activation in combination with ECD allowed the three disulfide bonds of insulin to be cleaved and the overall sequence coverage to be increased. For the larger sized ribonuclease A with four disulfide bonds, irradiation from an infrared laser (10.6 µm) to disrupt non-covalent interactions was combined with UV-activation to facilitate the cleavage of up to three disulfide bonds. Preferences for disulfide bond cleavage are dependent on protein structure and sequence. Disulfide bonds can reform if the generated radicals remain in close proximity. By varying the time delay between the UV-activation and the ECD events, it was determined that disulfide bonds reform within 10-100 msec after their UV-homolytic cleavage.

Compact 2100 nm laser diode module for next-generation DIRCM

NASA Astrophysics Data System (ADS)

Dvinelis, Edgaras; Greibus, Mindaugas; TrinkÅ«nas, Augustinas; NaujokaitÄ--, Greta; Vizbaras, Augustinas; Vizbaras, Dominykas; Vizbaras, Kristijonas

2017-10-01

Compact high-power 2100 nm laser diode module for next-generation directional infrared countermeasure (DIRCM) systems is presented. Next-generation DIRCM systems require compact, light-weight and robust laser modules which could provide intense IR light emission capable of disrupting the tracking sensor of heat-seeking missile. Currently used solid-state and fiber laser solutions for mid-IR band are bulky and heavy making them difficult to implement in smaller form-factor DIRCM systems. Recent development of GaSb laser diode technology greatly improved optical output powers and efficiencies of laser diodes working in 1900 - 2450 nm band [1] while also maintaining very attractive size, weight, power consumption and cost characteristics. 2100 nm laser diode module presented in this work performance is based on high-efficiency broad emitting area GaSb laser diode technology. Each laser diode emitter is able to provide 1 W of CW output optical power with working point efficiency up to 20% at temperature of 20 °C. For output beam collimation custom designed fast-axis collimator and slow-axis collimator lenses were used. These lenses were actively aligned and attached using UV epoxy curing. Total 2 emitters stacked vertically were used in 2100 nm laser diode module. Final optical output power of the module goes up to 2 W at temperature of 20 °C. Total dimensions of the laser diode module are 35 x 25 x 16 mm (L x W x H) with a weight of 28 grams. Finally output beam is bore-sighted to mechanical axes of the module housing allowing for easy integration into next-generation DIRCM systems.

Toward a comprehensive UV laser ablation modeling of multicomponent materials—A non-equilibrium investigation on titanium carbide

NASA Astrophysics Data System (ADS)

Ait Oumeziane, Amina; Parisse, Jean-Denis

2018-05-01

Titanium carbide (TiC) coatings of great quality can be produced using nanosecond pulsed laser deposition (PLD). Because the deposition rate and the transfer of the target stoichiometry depend strongly on the laser-target/laser-plasma interaction as well as the composition of the laser induced plume, investigating the ruling fundamental mechanisms behind the material ablation and the plasma evolution in the background environment under PLD conditions is essential. This work, which extends previous investigations dedicated to the study of nanosecond laser ablation of pure target materials, is a first step toward a comprehensive non-equilibrium model of multicomponent ones. A laser-material interaction model coupled to a laser-plasma interaction one is presented. A UV 20 ns KrF (248 nm) laser pulse is considered. Ablation depths, plasma ignition thresholds, and shielding rates have been calculated for a wide range of laser beam fluences. A comparison of TiC behavior with pure titanium material under the same conditions is made. Plasma characteristics such as temperature and composition have been investigated. An overall correlation between the various results is presented.

UV-fibers: two decades of improvements for new applications

NASA Astrophysics Data System (ADS)

Klein, Karl-Friedrich; Khalilov, Valery K.

2015-03-01

Multimode UV-fibers with high-OH synthetic silica core and F-doped silica cladding have been available for over 40 years. At the beginning, the spectral UV-range above 250 nm wavelength was commonly used, because the generation of UV-absorbing defect centers prevented reliable light transfer below 250 nm; even light from a low-power broadband deuterium-lamp was sufficient to damage these UV-fibers of the 1st generation. However, even then, applications in the field of spectroscopy, laser light delivery, sensors and process control were discussed and improvements of fiber quality in this very interesting UVC range required by researchers and industrial end-users. Starting in 1993 with hydrogen-loaded fibers, further modification in preform and fiber manufacturing including additional fiber treatments lead to currently available hydrogen-free UV-fiber (4th generation) with significantly improved stability in the UVC, enabling routine use of optical fibers in this field. In addition to the UV-fiber improvements, some selected UV fiber-optic applications using broadband deuterium-lamps will be discussed. Finally, there is still room for further improvements, especially in combination with newly available pulsed UV light sources, which are low-cost, small sized and highly reliable.

Modeling of a UV laser beam—silicon nitride interaction

NASA Astrophysics Data System (ADS)

Dgheim, J. A.

2016-11-01

A numerical model is developed to study heat and radiation transfers during the interaction between a UV laser beam and silicon nitride. The laser beam has temporal Gaussian or Gate shapes of a wavelength of 247 nm, with pulse duration of 27 ns. The mathematical model is based on the heat equation coupled to Lambert-Beer relationship by taking into account the conduction, convection and radiation phenomena. The resulting equations are schemed by the finite element method. Comparison with the literature shows qualitative and quantitative agreements. The investigated parameters are the temperature, the timing of the melting process and the melting phase thickness. The effects of the laser fluences, ranging from 500 to 16 000 J.m-2, the Gaussian and Gate shapes on the heat transfer, and the melting phenomenon are studied.

Pulsed Gas Lasers Pumped by a Runaway Electron Initiated Discharge

NASA Astrophysics Data System (ADS)

Panchenko, A. N.; Tarasenko, V. F.; Panchenko, N. A.

2017-12-01

The generation parameters are investigated in a runaway electron preionized diffuse discharge (REP DD). Laser generation is produced in different spectral bands from the IR to VUV range. New modes of the nitrogen laser operation are obtained. Ultimate efficiencies of N2- and nonchain HF(DF)-lasers are achieved. A possibility of increasing the pulse durations of XeF-, KrF-, ArF- and VUV F2- lasers (157 nm) in an oscillating REP DD is shown. The efficiencies of VUV- and UV-generation comparable with that of a laser pumped by a self-sustained volume discharge with preionization are gained.

A novel multiplex absorption spectrometer for time-resolved studies

NASA Astrophysics Data System (ADS)

Lewis, Thomas; Heard, Dwayne E.; Blitz, Mark A.

2018-02-01

A Time-Resolved Ultraviolet/Visible (UV/Vis) Absorption Spectrometer (TRUVAS) has been developed that can simultaneously monitor absorption at all wavelengths between 200 and 800 nm with millisecond time resolution. A pulsed photolysis laser (KrF 248 nm) is used to initiate chemical reactions that create the target species. The absorption signals from these species evolve as the composition of the gas in the photolysis region changes over time. The instrument can operate at pressures over the range ˜10-800 Torr and can measure time-resolved absorbances <10-4 in the UV (300 nm) and even lower in the visible (580 nm) 2.3 × 10-5, with the peak of sensitivity at ˜500 nm. The novelty of this setup lies in the arrangement of the multipass optics. Although appearing similar to other multipass optical systems (in particular the Herriott cell), there are fundamental differences, most notably the ability to adjust each mirror to maximise the overlap between the probe beam and the photolysis laser. Another feature which aids the sensitivity and versatility of the system is the use of 2 high-throughput spectrographs coupled with sensitive line-array CCDs, which can measure absorbance from ˜200 to 800 nm simultaneously. The capability of the instrument is demonstrated via measurements of the absorption spectrum of the peroxy radical, HOCH2CH2O2, and its self-reaction kinetics.

UV lidar measurements of the stratospheric aerosol layer and comparison with other optical data

NASA Technical Reports Server (NTRS)

Uchino, O.

1985-01-01

After the violent volcanic eruptions of El Chichon in Mexico (17.33 deg. N, 93.20 deg. W) in late March and early April 1982, enhanced stratospheric aerosols have been monitored by ruby (lasing wavelength lambda=694.3 nm) or Nd:YAG lidars (lambda=1064 or 532 nm). By these lidars, visible or near-infrared optical informations of stratospheric aerosols and their space-time variations can be obtained. It is usually difficult to measure the background level of stratospheric aerosols by an ultraviolet (UV) lidar, since Rayleigh scattering prevails over Mie scattering in the stratosphere. However, after the large volcanic eruptions, UV lidar measurements of stratospheric aerosols are possible. In order to obtain UV optical properties of stratospheric aerosols, measurements have been made at Fukuoka (33.65 deg. N, 130.35 deg. E) by a p-terphenyl dye laser at a wavelength of 340.5 nm. Observational results during October 1982, through May 1983, are shown and are compared with the results obtained by a ruby lidar at Tsukuba (36.05 deg. N, 140.13 deg. E).

Properties of Al- and Ga-doped thin zinc oxide films treated with UV laser radiation

NASA Astrophysics Data System (ADS)

Al-Asedy, Hayder J.; Al-Khafaji, Shuruq A.; Bakhtiar, Hazri; Bidin, Noriah

2018-03-01

This paper reports the Nd:YAG laser irradiation treated modified properties of aluminum (Al) and gallium (Ga) co-doped zinc oxide (ZnO) (AGZO) films prepared on Si-substrate via combined sol-gel and spin-coating method. The impact of varying laser energy (150-200 mJ) on the structure, morphology, electrical and optical properties of such AGZO films were determined. Laser-treated samples were characterized using various analytical tools. Present techniques could achieve a high-quality polycrystalline films compared with those produced via conventional high temperature processing. AGZO films irradiated with third harmonics UV radiation (355 nm) from Nd:YAG laser source revealed very low resistivity of 4.02 × 10- 3 Ω cm. The structural properties grain size was calculated firm the X-ray diffraction spectra using the Scherrer equation that increased from 12.7 to 22.5 nm as the annealing laser energy increased from (150-200) mJ. The differences in crystallinity and orientation are explained in terms of the thermal effect caused by laser irradiation. (FESEM) images have been demonstrated that Nd:YAG laser annealing can significantly improve the crystallinity level, densification, and surface flatness of sol-gel derived AGZO thin films that occurred as a result of laser processing. Synthesized AGZO films displayed favorable growth orientation along (101) lattice direction. AGZO films with energy band gap of 3.37-3.41 eV were obtained. Results on the crystallinity, surface morphology, roughness, bonding vibration, absorption, photoluminescence, and resistivity of the laser-irradiated films were analyzed and discussed.

Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation.

PubMed

Abd El-Kader, F H; Hakeem, N A; Elashmawi, I S; Menazea, A A

2015-03-05

Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ=38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40min and short laser wavelength 532nm together with high laser power 570mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect. Copyright © 2014 Elsevier B.V. All rights reserved.

An airborne laser fluorosensor for the detection of oil on water

NASA Technical Reports Server (NTRS)

Kim, H. H.; Hickman, G. D.

1975-01-01

An airborne laser fluorosensor for the detection of oil derivatives on water has been tested. The system transmits 337 nm UV radiation at the rate of 100 pulses per second and monitors fluorescent emission at 540 nm. Daylight flight tests were made over the areas of controlled oil spills and additional reconnaissance flights were made over a 50 km stretch of the Delaware River to establish ambient oil baseline in the river. The results show that the device is capable of monitoring and mapping out extremely low level oil on water which cannot be identified by ordinary photographic method.

Pulse Q-switched Nd:YAG laser ablation grown cinnamon nanomorphologies: Influence of different liquid medium

NASA Astrophysics Data System (ADS)

Salim, Ali Aqeel; Bidin, Noriah

2017-12-01

Broad range of biomedical applications demands accurate synthesis and characterization of various nanoparticles. We report the characterization of cinnamon nanoparticles (CNPs) grown via simple pulsed laser ablation in liquid (PLAL). The influence of different liquid media (olive oil, ethanol, and citric acid each of volume 4 ml) on the growth morphology, structure and optical properties of CNPs is determined. Q-switched 1064-Nd: YAG laser of 10 ns pulse duration, 1 Hz repetition rate, 532 nm s harmonic generation and laser fluence of 6.37 J/cm2 is used to irradiate the cinnamon targets immersed in those liquids. Samples are characterized using TEM, HRTEM, SAED, FTIR, UV-Vis and Photoluminescence measurements. TEM images revealed the nucleation of CNPs of average size 18.36 nm (in olive oil), 21.48 nm (in ethanol), and 29.56 nm (in citric acid). Morphology of CNPs is demonstrated to be sensitive to the liquid medium. Our simple and innovative method may constitute a basis to produce CNPs of desired size distribution potential for the development of nanobiomedicine.

Laser microprocessing and nanoengineering of large-area functional micro/nanostructures

NASA Astrophysics Data System (ADS)

Tang, M.; Xie, X. Z.; Yang, J.; Chen, Z. C.; Xu, L.; Choo, Y. S.; Hong, M. H.

2011-12-01

Laser microprocessing and nanoengineering are of great interest to both scientists and engineers, since the inspired properties of functional micro/nanostructures over large areas can lead to numerous unique applications. Currently laser processing systems combined with high speed automation ensure the focused laser beam to process various materials at a high throughput and a high accuracy over large working areas. UV lasers are widely used in both laser microprocessing and nanoengineering. However by improving the processing methods, green pulsed laser is capable of replacing UV lasers to make high aspect ratio micro-grooves on fragile and transparent sapphire substrates. Laser micro-texturing can also tune the wetting property of metal surfaces from hydrophilic to super-hydrophobic at a contact angle of 161° without chemical coating. Laser microlens array (MLA) can split a laser beam into multiple laser beams and reduce the laser spot size down to sub-microns. It can be applied to fabricate split ring resonator (SRR) meta-materials for THz sensing, surface plasmonic resonance (SPR) structures for NIR and molding tools for soft lithography. Furthermore, laser interference lithography combined with thermal annealing can obtain a large area of sub-50nm nano-dot clusters used for SPR applications.

Generation of UV light by intense ultrashort laser pulses in air

NASA Astrophysics Data System (ADS)

Alexeev, Ilya; Ting, Antonio; Gordon, Daniel; Briscoe, Eldridge; Penano, Joe; Sprangle, Phillip

2004-11-01

The propagation of collimated high-peak-power ultrashort laser pulses in air has attracted considerable attention, which may have a variety of important applications including remote sensing and chemical-biological aerosols standoff detection. Sub-millimeter diameter laser filaments can develop without any focusing optics and instead solely from laser self-focusing and plasma formation in air. These filaments can produce ultraviolet radiations in the form of the 3rd harmonic of the fundamental frequency and also through spectral broadening due to self-phase modulation of the laser pulse. Using femtosecond laser pulses produced by a high power Ti:Sapphire laser (0.8 TW, 50 fs, 800 nm) we observed generation of the third harmonic radiation light in air (centered around 267 nm) by the laser filaments. Characterization of the 3rd harmonic generation with respect to the major gas components of the air will be reported. Supported by the ONR and RDECOM. I. Alexeev is NRC/NRL Post-Doc.

Narrow linewidth picosecond UV pulsed laser with mega-watt peak power.

PubMed

Huang, Chunning; Deibele, Craig; Liu, Yun

2013-04-08

We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth < 5 KHz), a high bandwidth electro-optic modulator (EOM), a picosecond pulse generator, and a fiber based preamplifier. A very high extinction ratio (45 dB) has been achieved by using an adaptive bias control of the EOM. The multi-stage Nd:YAG amplifier system allows a uniformly temporal shaping of the macropulse with a tunable pulse duration. The light output from the amplifier is converted to 355 nm, and over 1 MW peak power is obtained when the laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).

Design and manufacture of optical system for use in ultraviolet lithography with the free-electron laser

NASA Astrophysics Data System (ADS)

Byrd, Donald A.; Viswanathan, Vriddhachalam K.; Woodfin, Gregg L.; Horn, William W.; Lazazzera, Vito J.; Schmell, Rodney A.

1993-08-01

At Los Alamos National Laboratory, we are preparing to image submicrometer-size features using the Free Electron Laser (FEL) operating at 248 nm. This article describes the optical transfer systems that were designed to relay the ultraviolet (UV) optical output of the FEL, resulting in expected imaged feature sizes in the range 0.3 - 0.5 micrometers . Nearly all optical subsystems are reflective, and once the coatings were optimized any optical wavelength could be used. All refractive optics were UV-grade fused silica. The optical design, engineering, and manufacture of the various component systems are described along with some experimental results.

Compact, integrable, and long life time Raman multiline UV-Vis source based on hypocycloid core Kagome HC-PCF

NASA Astrophysics Data System (ADS)

Chafer, M.; Lekiefs, Q.; Gorse, A.; Beaudou, B.; Debord, B.; Gérôme, F.; Benabid, F.

2017-02-01

Raman-gas filled HC-PCF has proved to be an outstanding Raman-convertor, as illustrated by the generation of more than 5 octaves wide Raman comb using a hydrogen-filled Kagome HC-PCF pumped with high power picosecond-laser, or the generation of multiline Raman-source in the UV-Vis using a very compact system pumped with micro-chip laser. Whilst these demonstrations are promising, a principal challenge for the industrialization of such a Raman source is its lifetime as the H2 diffusion through silica is high enough to leak out from the fiber within only a few months. Here, we report on a HC-PCF based Raman multiline source with a very long life-span. The system consists of hydrogen filled ultra-low loss HC-PCF contained in highly sealed box, coined CombBox, and pumped with a 532 nm micro-chip laser. This combination is a turnkey multiline Raman-source with a "shoe box" size. The CombBox is a robust and compact component that can be integrated and pumped with any common pulsed laser. When pumped with a 32 mW average power and 1 ns frequency-doubled Nd:Yag microchip laser, this Raman-source generates 24 lines spanning from 355 to 745 nm, and a peak power density per line of 260 mW/nm for the strongest lines. Both the output power and the spectrum remained constant over its monitoring duration of more than six months. The spectrum of this multiline laser superimposes with no less than 17 absorption peaks of fluorescent dyes from the Alexa Fluor family used as biological markers.

Flame Characterization Using a Tunable Solid-State Laser with Direct UV Pumping

NASA Technical Reports Server (NTRS)

Kamal, Mohammed M.; Dubinskii, Mark A.; Misra, Prabhakar

1996-01-01

Tunable solid-state lasers with direct UV pumping, based on d-f transitions of rare earth ions incorporated in wide band-gap dielectric crystals, are reliable sources of laser radiation that are suitable for excitation of combustion-related free radicals. We have employed such a laser for analytical flame characterization utilizing Laser-Induced Fluorescence (LIF) techniques. LIF spectra of alkane-air flames (used for studying combustion processes under normal and microgravity conditions) excited in the region of the A-X (0,0) OH-absorption band have been recorded and found to be both temperature-sensitive and positionally-sensitive. In addition, also clearly noticeable was the sensitivity of the spectra to the specific wavelength used for data registration. The LiCAF:Ce laser shows good prospects for being able to cover the spectral region between 280 and 340 nm and therefore be used excitation of combustion-intermediates such as the hydroxyl OH, methoxy CH30 and methylthio CH3S radicals.

Characterization of absorption and degradation on optical components for high power excimer lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, K.; Eva, E.; Granitza, B.

1996-12-31

At Laser-Laboratorium Goettingen, the performance of UV optical components for high power excimer lasers is characterized, aiming to employ testing procedures that meet industrial conditions, i.e. very high pulse numbers and repetition rates. Measurements include determination of single and multiple pulse damage thresholds, absorption loss and degradation of optical properties under long-term irradiation. Absorption of excimer laser pulses is investigated by a calorimetric technique which provides greatly enhanced sensitivity compared to transmissive measurements. Thus, it allows determining both single and two photon absorption coefficients at intensities of standard excimer lasers. Results of absorption measurements at 248nm are presented for baremore » substrates (CaF{sub 2}, BaF{sub 2}, z-cut quartz and fused silica). UV calorimetry is also employed to investigate laser induced aging phenomena, e.g. color center formation in fused silica. A separation of transient and cumulative effects as a function of intensity is achieved, giving insight into various loss mechanisms.« less

Initiation precursors and initiators in laser-induced copolymerization of styrene and maleic anhydride in acetone

NASA Technical Reports Server (NTRS)

Miner, Gilda A.; Meador, Willard E.; Chang, C. Ken

1990-01-01

The initiation step of photopolymerized styrene/maleic anhydride copolymer was investigated at 365 nm. UV absorption measurements provide decisive evidence that the styrene/maleic anhydride charge transfer complex is the sole absorbing species; however, key laser experiments suggest intermediate reactions lead to a monoradical initiating species. A mechanism for the photoinitiation step of the copolymer is proposed.

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

NASA Astrophysics Data System (ADS)

Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

2017-08-01

Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

Wavelength-dependent photoresponse of biological and aqueous model systems using the photodynamic plant pigment hypericin.

PubMed

Kubin, A; Alth, G; Jindra, R; Jessner, G; Ebermann, R

1996-11-01

Photodynamic eradication of tumour cells in vivo depends on the presence of a photosensitizer, light delivery to the cells, and an oxygen supply. Hypericin, a polycyclic quinone with absorption maxima in the ultraviolet and visible ranges, was prepared for clinical use as a photosensitizer. Due to antitumoral and antineoplastic activities as well as the generation of singlet oxygen after photoexcitation, hypericin was applied in clinical oncology and photodynamic therapy. Hypericin was administered subcutaneously (20 micrograms hypericin in 200 microliters Nacl/pyridine solution) into the ante brachium (forearm) of two volunteers. After the diffusion and equilibration of 120 min phototesting was carried out using outdoor light exposure, halogen lamp, laser 514 nm (argon), laser 632 nm (argon dye) and laser 670 nm (diode laser), from 60 to 120 J cm-2. Positive phototests to outdoor light exposure, halogen lamp and laser 514 nm were characterized by rubescence, oozing, vesiculation and darting pain. Phototests with laser 632 nm and 670 nm showed no effects after irradiation. When hypericin was administered topically on skin, erythema and flaring could not be induced by any irradiation. These results suggest that hypericin is a potent photosensitizer only within the UV and green light ranges. This characteristic photoresponse could also be obtained in guinea pig papillary muscle (GPPM) bioassay, which may be established as a model for photosensitizer testing. Irradiation of hypericin-incubated GPPM with 514 nm (20 J cm-2) led to a decrease of the contractile force of about 31%. However, excitation with 632 nm and 670 nm did not cause inotropic effects on GPPM. In addition, hypericin and Photosan 3 were shown to be capable of sensitizing the photo-oxidation of sodium linoleate. This assay should be established for testing interactions between photosensitizers and light sources in vitro.

Plasmonic enhancement of ultraviolet fluorescence

NASA Astrophysics Data System (ADS)

Jiao, Xiaojin

Plasmonics relates to the interaction between electromagnetic radiation and conduction electrons at metallic interfaces or in metallic nanostructures. Surface plasmons are collective electron oscillations at a metal surface, which can be manipulated by shape, texture and material composition. Plasmonic applications cover a broad spectrum from visible to near infrared, including biosensing, nanolithography, spectroscopy, optoelectronics, photovoltaics and so on. However, there remains a gap in this activity in the ultraviolet (UV, < 400 nm), where significant opportunity exists for both fundamental and application research. Motivating factors in the study of UV Plasmonics are the direct access to biomolecular resonances and native fluorescence, resonant Raman scattering interactions, and the potential for exerting control over photochemical reactions. This dissertation aims to fill in the gap of Plasmonics in the UV with efforts of design, fabrication and characterization of aluminium (Al) and magnesium (Mg) nanostructures for the application of label-free bimolecular detection via native UV fluorescence. The first contribution of this dissertation addresses the design of Al nanostructures in the context of UV fluorescence enhancement. A design method that combines analytical analysis with numerical simulation has been developed. Performance of three canonical plasmonic structures---the dipole antenna, bullseye nanoaperture and nanoaperture array---has been compared. The optimal geometrical parameters have been determined. A novel design of a compound bullseye structure has been proposed and numerically analyzed for the purpose of compensating for the large Stokes shift typical of UV fluorescence. Second, UV lifetime modification of diffusing molecules by Al nanoapertures has been experimentally demonstrated for the first time. Lifetime reductions of ~3.5x have been observed for the high quantum yield (QY) laser dye p-terphenyl in a 60 nm diameter aperture with 50 nm undercut. Furthermore, quantum-yield-dependence of lifetime reduction has been experimentally demonstrated for the first time. Lifetime reduction as a function of aperture size and native quantum yield has been accurately predicted by simulation. Simulation further predicts greater net fluorescence enhancement for tryptophan compared to p-terphenyl. In order to increase fluorescence enhancement, the "poor" molecules and structures with proper undercuts are required. Third, UV lifetime modification by Mg nanoapertures has been experimentally demonstrated for the fisrt time. Lifetime reductions of ~13x have been observed for the laser dye p-terphenyl with high QY in a 50 nm diameter aperture with 125 nm undercut. In addition, extraordinary optical transmission of Mg nanohole arrays in the UV has been measured for the first time. By using Al as a reference, the feasibility of applying Mg in the UV plasmonic applications has been evaluated both numerically and experimentally. Finally, this work has established a methodology for the study of plasmonic enhancement of UV fluorescence, including design method, thin-film characterization, nanofabrication with focus ion beam milling, and fluorescence measurement. It has paved the way for more extensive research on UV fluorescence enhancement.

A novel polishing technology for epoxy resin based on 355 nm UV laser

NASA Astrophysics Data System (ADS)

Meng, Xinling; Tao, Luqi; Liu, Zhaolin; Yang, Yi; Ren, Tianling

2017-06-01

The electromagnetic shielding film has drawn much attention due to its wide applications in the integrated circuit package, which demands a high surface quality of epoxy resin. However, gaseous Cu will splash and adhere to epoxy resin surface when the Cu layer in PCB receives enough energy in the process of laser cutting, which has a negative effect on the quality of the shielding film. Laser polishing technology can solve this problem and it can effectively improve the quality of epoxy resin surface. The paper studies the mechanism of Cu powder spraying on the compound surface by 355 nm ultraviolet (UV) laser, including the parameters of laser polishing process and the remains of Cu content on compound surface. The results show that minimal Cu content can be realized with a scanning speed of 700 mm/s, a laser frequency of 50 kHz and the distance between laser focus and product top surface of -1.3 mm. This result is important to obtain an epoxy resin surface with high quality. Project supported by the National Natural Science Foundation of China (Nos. 61574083, 61434001), the National Basic Research Program (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002), the Special Fund for Agroscientic Research in the Public Interest of China (No 201303107), the support of the Independent Research Program of Tsinghua University (No. 2014Z01006), and Advanced Sensor and Integrated System Lab of Tsinghua University Graduate School at Shenzhen (No. ZDSYS20140509172959969).

Laser Ablated Carbon Nanodots for Light Emission.

PubMed

Reyes, Delfino; Camacho, Marco; Camacho, Miguel; Mayorga, Miguel; Weathers, Duncan; Salamo, Greg; Wang, Zhiming; Neogi, Arup

2016-12-01

The synthesis of fluorescent carbon dots-like nanostructures (CNDs) obtained through the laser ablation of a carbon solid target in liquid environment is reported. The ablation process was induced in acetone with laser pulses of 1064, 532, and 355 nm under different irradiation times. Close-spherical amorphous CNDs with sizes between 5 and 20 nm, whose abundance strongly depends on the ablation parameters were investigated using electron microscopy and was confirmed using absorption and emission spectroscopies. The π- π* electronic transition at 3.76 eV dominates the absorption for all the CNDs species synthesized under different irradiation conditions. The light emission is most efficient due to excitation at 3.54 eV with the photoluminescence intensity centered at 3.23 eV. The light emission from the CNDs is most efficient due to ablation at 355 nm. The emission wavelength of the CNDs can be tuned from the near-UV to the green wavelength region by controlling the ablation time and modifying the ablation and excitation laser wavelength.

How safe is gamete micromanipulation by laser tweezers?

NASA Astrophysics Data System (ADS)

Koenig, Karsten; Tromberg, Bruce J.; Tadir, Yona; Berns, Michael W.

1998-04-01

Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.

AlGaInN laser diode technology and systems for defence and security applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lujca; Boćkowski, Mike; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Scott; Kelly, Antony E.

2015-10-01

AlGaInN laser diodes is an emerging technology for defence and security applications such as underwater communications and sensing, atomic clocks and quantum information. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries. Ridge waveguide laser diodes are fabricated to achieve single mode operation with optical powers up to 100mW with the 400-440nm wavelength range with high reliability. Visible free-space and underwater communication at frequencies up to 2.5GHz is reported using a directly modulated 422nm GaN laser diode. Low defectivity and highly uniform GaN substrates allow arrays and bars to be fabricated. High power operation operation of AlGaInN laser bars with up to 20 emitters have been demonstrated at optical powers up to 4W in a CS package with common contact configuration. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space or optical fibre system integration with a very small form-factor.

TE modes of UV-laser generated waveguides in a planar polymer chip of parabolic refractive index profile

NASA Astrophysics Data System (ADS)

Shams El-Din, M. A.

2018-04-01

The UV-laser lithographic method is used for the preparation of Polymeric integrated-optical waveguides in a planar polymer chip. The waveguide samples are irradiated by an excimer laser of wavelength 248 nm with different doses and with the same fluencies. The refractive index depth profile for the waveguides, in the first zone is found to have a parabolic shape and Gaussian shape in the second one that can be determined by Mach-Zehnder interferometer. Both the mode field distribution and the effective mode indices for the first zone only are determined by making use of the theoretical mode and the experimental data. It is found that the model field distribution is strongly dependent on the refractive indices for each zone.

Additive-free size-controlled synthesis of gold square nanoplates using photochemical reaction in dynamic phase-separating media.

PubMed

Kajimoto, Shinji; Shirasawa, Daisuke; Horimoto, Noriko Nishizawa; Fukumura, Hiroshi

2013-05-14

Ultrafast phase separation of water and 2-butoxyethanol mixture was induced by nanosecond IR laser pulse irradiation. After a certain delay time, a UV laser pulse was introduced to induce photoreduction of aurate ions, which led to the formation of gold nanoparticles in dynamic phase-separating media. The structure and size of the nanoparticles varied depending on the delay time between the IR and UV pulses. For a delay time of 5 and 6 μs, gold square plates having edge lengths of 150 and 100 nm were selectively obtained, respectively. With a delay time of 3 μs, on the other hand, the size of the square plates varied widely from 100 nm to a few micrometers. The size of the gold square plates was also varied by varying the total irradiation time of the IR and UV pulses. The size distribution of the square plates obtained under different conditions suggests that the growth process of the square plates was affected by the size of the nanophases during phase separation. Electron diffraction patterns of the synthesized square plates showed that the square plates were highly crystalline with a Au(100) surface. These results showed that the nanophases formed during laser-induced phase separation can provide detergent-free reaction fields for size-controlled nanomaterial synthesis.

Observation of sum-frequency-generation-induced cascaded four-wave mixing using two crossing femtosecond laser pulses in a 0.1 mm beta-barium-borate crystal.

PubMed

Liu, Weimin; Zhu, Liangdong; Fang, Chong

2012-09-15

We demonstrate the simultaneous generation of multicolor femtosecond laser pulses spanning the wavelength range from UV to near IR in a 0.1 mm Type I beta-barium borate crystal from 800 nm fundamental and weak IR super-continuum white light (SCWL) pulses. The multicolor broadband laser pulses observed are attributed to two concomitant cascaded four-wave mixing (CFWM) processes as corroborated by calculation: (1) directly from the two incident laser pulses; (2) by the sum-frequency generation (SFG) induced CFWM process (SFGFWM). The latter signal arises from the interaction between the frequency-doubled fundamental pulse (400 nm) and the SFG pulse generated in between the fundamental and IR-SCWL pulses. The versatility and simplicity of this spatially dispersed multicolor self-compressed laser pulse generation offer compact and attractive methods to conduct femtosecond stimulated Raman spectroscopy and time-resolved multicolor spectroscopy.

Evaluation results for the positive deep-UV resist AZ DX 46

NASA Astrophysics Data System (ADS)

Spiess, Walter; Lynch, Thomas J.; Le Cornec, Charles; Escher, Gary C.; Kinoshita, Yoshiaki; Kochan, John; Kudo, Takanori; Masuda, Seiya; Mourier, Thierry; Nozaki, Yuko; Olson, Setha G.; Okazaki, Hiroshi; Padmanaban, Munirathna; Pawlowski, Georg; Przybilla, Klaus J.; Roeschert, Horst; Suehiro, Natusmi; Vinet, Francoise; Wengenroth, Horst

1994-05-01

This contribution emphasizes resist application site by communicating lithographic results for AZ DX 46, obtained using the GCA XLS 7800/31 stepper, NA equals 0.53, equipped with krypton fluoride excimer laser ((lambda) equals 248 nm), model 4500 D, as exposure source, delivered by Cymer Laser Technologies. As far as delay time experiments are concerned ASM-L PAS 5500/70 stepper, NA equals 0.42, was used in combination with Lambda Physik excimer laser, model 248 L.

Gain measurements of the Ca-Xe charge exchange system. [for UV lasers

NASA Technical Reports Server (NTRS)

Michels, C. J.; Chubb, D. L.

1978-01-01

Charge-exchange-pumped Ca(+) was studied for possible positive laser gain at 370.6 and 315.9 nm using an Xe MPD arc as the Xe(+) source. The present paper describes the MPD arc, the calcium injection system, the diagnostics for gain, and spontaneous emission measurements and results. No positive gain measurements were observed. A small Xe-Ca charge exchange cross section compared to He-metal laser systems charge exchange cross sections is the most probable reason why the result was negative.

Carbon dioxide UV laser-induced fluorescence in high-pressure flames

NASA Astrophysics Data System (ADS)

Bessler, W. G.; Schulz, C.; Lee, T.; Jeffries, J. B.; Hanson, R. K.

2003-07-01

Laser-induced fluorescence (LIF) of carbon dioxide is investigated with excitation between 215 and 255 nm with spectrally resolved detection in 5-40 bar premixed CH 4/O 2/Ar and CH 4/air flat-flames at fuel/air ratios between 0.8 and 1.9. The LIF signal consists of a broad (200-450 nm) continuum with a faint superimposed structure, and this signal is absent in similar H 2/O 2/Ar flames. There is strong evidence this signal arises from CO 2, as the signal variations with excitation wavelength, equivalence ratio and flame temperature all correlate with CO 2 absorption cross-sections. The signal is linear with pressure and laser fluence within the investigated ranges.

Lidar stratospheric ozone measurements at the observatoire de Haute Provence (France)

NASA Technical Reports Server (NTRS)

Godin, S.; Pelon, J.; Megie, G.

1986-01-01

Strastospheric ozone monitoring is of particular importance to confirm present day theories predicting a maximal ozone depletion, due to chlorofluorocarbon emission, in the 35 to 45 km altitude range. Measurements presently rely on both ground based and satellite-borne passive experiments. Such systems have been recently shown to have intrinsic limitations mainly due to atmospheric aerosol presence and calibration problems. During the last few years, active lidar profiling of the ozone vertical distribution by the Differential Absorption Laser technique (DIAL) in the UV wavelength range has been developed using two different laser sources: a Nd-YAG pumped dye laser which enables a large tuning range of the UV emitted wavelengths; and exciplex laser sources using xenon chloride as an active medium and emitting at 308 nm, the off wavelength being usually generated by Raman shifting techniques. Advantages and limitations of using both of these systems are briefly discussed.

Modeling of UV laser-induced patterning of ultrathin Co films on bulk SiO2: verification of short- and long-range ordering mechanisms

NASA Astrophysics Data System (ADS)

Trice, Justin; Favazza, Christopher; Kalyanaraman, Ramki; Sureshkumar, R.

2006-03-01

Irradiating ultrathin Co films (1 to 10 nm) by a short-pulsed UV laser leads to pattern formation with both short- and long-range order (SRO, LRO). Single beam irradiation produces SRO, while two-beam interference irradiation produces a quasi-2D arrangement of nanoparticles with LRO and SRO. The pattern formation primarily occurs in the molten phase. An estimate of the thermal behavior of the film/substrate composite following a laser pulse is presented. The thermal behavior includes the lifetime of the liquid phase and the thermal gradient during interference heating. Based on this evidence, the SRO is attributed to spinodal dewetting of the film while surface tension gradients induced by the laser interference pattern appear to influence LRO [1]. [1] C.Favazza, J.Trice, H.Krishna, R.Sureshkumar, and R.Kalyanaraman, unpublished.

Cutaneous porphyrins exhibit anti-stokes fluorescence that is detectable in sebum (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tian, Giselle; Zeng, Haishan; Zhao, Jianhua; Wu, Zhenguo; Al Jasser, Mohammed; Lui, Harvey; Mclean, David I.

2016-02-01

Porphyrins produced by Propionibacterium acnes represent the principal fluorophore associated with acne, and appear as orange-red luminescence under the Wood's lamp. Assessment of acne based on Wood's lamp (UV) or visible light illumination is limited by photon penetration depth and has limited sensitivity for earlier stage lesions. Inducing fluorescence with near infrared (NIR) excitation may provide an alternative way to assess porphyrin-related skin disorders. We discovered that under 785 nm CW laser excitation PpIX powder exhibits fluorescence emission in the shorter wavelength range of 600-715 nm with an intensity that is linearly dependent on the excitation power. We attribute this shorter wavelength emission to anti-Stokes fluorescence. Similar anti-Stokes fluorescence was also detected focally in all skin-derived samples containing porphyrins. Regular (Stokes) fluorescence was present under UV and visible light excitation on ex vivo nasal skin and sebum from uninflamed acne, but not on nose surface smears or sebum from inflamed acne. Co-registered CW laser-excited anti-Stokes fluorescence and fs laser-excited multi-photon fluorescence images of PpIX powder showed similar features. In the skin samples because of the anti-Stokes effect, the NIR-induced fluorescence was presumably specific for porphyrins since there appeared to be no anti-Stokes emission signals from other typical skin fluorophores such as lipids, keratins and collagen. Anti-Stokes fluorescence under NIR CW excitation is more sensitive and specific for porphyrin detection than UV- or visible light-excited regular fluorescence and fs laser-excited multi-photon fluorescence. This approach also has higher image contrast compared to NIR fs laser-based multi-photon fluorescence imaging. The anti-Stokes fluorescence of porphyrins within sebum could potentially be applied to detecting and targeting acne lesions for treatment via fluorescence image guidance.

Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy.

PubMed

Shkolyar, Svetlana; Eshelman, Evan J; Farmer, Jack D; Hamilton, David; Daly, Michael G; Youngbull, Cody

2018-04-01

The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples. Key Words: Raman spectroscopy-Laser-induced fluorescence spectroscopy-Mars Sample Return-Mars 2020 mission-Kerogen-Biosignatures. Astrobiology 18, 431-453.

Universal liquid-phase laser fabrication of various nano-metals encapsulated by ultrathin carbon shells for deep-UV plasmonics.

PubMed

Yu, Miao; Yang, Chao; Li, Xiao-Ming; Lei, Tian-Yu; Sun, Hao-Xuan; Dai, Li-Ping; Gu, Yu; Ning, Xue; Zhou, Ting; Wang, Chao; Zeng, Hai-Bo; Xiong, Jie

2017-06-29

The exploration of localized surface plasmon resonance (LSPR) beyond the usual visible waveband, for example within the ultraviolet (UV) or deep-ultraviolet (D-UV) regions, is of great significance due to its unique applications in secret communications and optics. However, it is still challenging to universally synthesize the corresponding metal nanostructures due to their high activity. Herein, we report a universal, eco-friendly, facile and rapid synthesis of various nano-metals encapsulated by ultrathin carbon shells, significantly with a remarkable deep-UV LSPR characteristic, via a liquid-phase laser fabrication method. Firstly, a new generation of the laser ablation in liquid (LAL) method has been developed with an emphasis on the elaborate selection of solvents to generate ultrathin carbon shells, and hence to stabilize the formed metal nanocrystals. As a result, a series of metal@carbon nanoparticles (NPs), including Cr@C, Ti@C, Fe@C, V@C, Al@C, Sn@C, Mn@C and Pd@C, can be fabricated by this modified LAL method. Interestingly, these NPs exhibit LSPR peaks in the range of 200-330 nm, which are very rare for localized surface plasmon resonance. Consequently, the UV plasmonic effects of these metal@carbon NPs were demonstrated both by the observed enhancement in UV photoluminescence (PL) from the carbon nanoshells and by the improvement of the photo-responsivity of UV GaN photodetectors. This work could provide a universal method for carbon shelled metal NPs and expand plasmonics into the D-UV waveband.

Laser-induced nonlinear crystalline waveguide on glass fiber format and diode-pumped second harmonic generation

NASA Astrophysics Data System (ADS)

Shi, Jindan; Feng, Xian

2018-03-01

We report a diode pumped self-frequency-doubled nonlinear crystalline waveguide on glass fiber. A ribbon fiber has been drawn on the glass composition of 50GeO2-25B2O3-25(La,Yb)2O3. Surface channel waveguides have been written on the surface of the ribbon fiber, using space-selective laser heating method with the assistance of a 244 nm CW UV laser. The Raman spectrum of the written area indicates that the waveguide is composed of structure-deformed nonlinear (La,Yb)BGeO5 crystal. The laser-induced surface wavy cracks have also been observed and the forming mechanism of the wavy cracks has been discussed. Efficient second harmonic generation has been observed from the laser-induced crystalline waveguide, using a 976 nm diode pump. 13 μW of 488 nm output has been observed from a 17 mm long waveguide with 26.0 mW of launched diode pump power, corresponding to a normalized conversion efficiency of 4.4%W-1.

Third-harmonic generation and scattering in combustion flames using a femtosecond laser filament.

PubMed

Zang, Hong-Wei; Li, He-Long; Su, Yue; Fu, Yao; Hou, Meng-Yao; Baltuška, Andrius; Yamanouchi, Kaoru; Xu, Huailiang

2018-02-01

Coherent radiation in the ultraviolent (UV) range has high potential applicability to the diagnosis of the formation processes of soot in combustion because of the high scattering efficiency in the UV wavelength region, even though the UV light is lost largely by the absorption within the combustion flames. We show that the third harmonic (TH) of a Ti:sapphire 800 nm femtosecond laser is generated in a laser-induced filament in a combustion flame and that the conversion efficiency of the TH varies sensitively by the ellipticity of the driver laser pulse but does not vary so much by the choice of alkanol species introduced as fuel for the combustion flames. We also find that the TH recorded from the side direction of the filament is the Rayleigh scattering of the TH by soot nanoparticles within the flame and that the intensity of the TH varies depending on the fuel species as well as on the position of the laser filament within the flame. Our results show that a remote and in situ measurement of distributions of soot nanoparticles in a combustion flame can be achieved by Rayleigh scattering spectroscopy of the TH generated by a femtosecond-laser-induced filament in the combustion flame.

Ion yields in UV-MALDI mass spectrometry as a function of excitation laser wavelength and optical and physico-chemical properties of classical and halogen-substituted MALDI matrixes.

PubMed

Soltwisch, Jens; Jaskolla, Thorsten W; Hillenkamp, Franz; Karas, Michael; Dreisewerd, Klaus

2012-08-07

The laser wavelength constitutes a key parameter in ultraviolet-matrix-assisted laser desorption ionization-mass spectrometry (UV-MALDI-MS). Optimal analytical results are only achieved at laser wavelengths that correspond to a high optical absorption of the matrix. In the presented work, the wavelength dependence and the contribution of matrix proton affinity to the MALDI process were investigated. A tunable dye laser was used to examine the wavelength range between 280 and 355 nm. The peptide and matrix ion signals recorded as a function of these irradiation parameters are displayed in the form of heat maps, a data representation that furnishes multidimensional data interpretation. Matrixes with a range of proton affinities from 809 to 866 kJ/mol were investigated. Among those selected are the standard matrixes 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (HCCA) as well as five halogen-substituted cinnamic acid derivatives, including the recently introduced 4-chloro-α-cyanocinnamic acid (ClCCA) and α-cyano-2,4-difluorocinnamic acid (DiFCCA) matrixes. With the exception of DHB, the highest analyte ion signals were obtained toward the red side of the peak optical absorption in the solid state. A stronger decline of the molecular analyte ion signals generated from the matrixes was consistently observed at the low wavelength side of the peak absorption. This effect is mainly the result of increased fragmentation of both analyte and matrix ions. Optimal use of multiply halogenated matrixes requires adjustment of the excitation wavelength to values below that of the standard MALDI lasers emitting at 355 (Nd:YAG) or 337 nm (N(2) laser). The combined data provide new insights into the UV-MALDI desorption/ionization processes and indicate ways to improve the analytical sensitivity.

Remote Detection of Biological Particles and Chemical Plumes Using UV Fluorescence Lidar

NASA Technical Reports Server (NTRS)

Tiee, J. J.; Hof, D. E.; Karl, R. R.; Martinez, R. J.; Quick, C. R.; Cooper, D. I.; Eichinger, W. E.; Holtkamp, D. B.

1992-01-01

A lidar system based on ultraviolet (UV) laser induced fluorescence (LIF) was developed for the remote detection of atmospherically dispersed biological particles and chemical vapors. This UV fluorescence lidar has many potential applications for monitoring environmental pollution, industrial waste emission, agricultural insect control, illicit chemical processing, and military defense operations. The general goal of this work is to investigate the research issues associated with the long range detection and identification of chemicals, e.g. aromatic solvents and chemical precursors, and biological materials, e.g. bacillus thuringiensis (BT) and bacillus globiggi (BG). In the detection of biological particulates, we are particularly interested in extending the detection range of an existing solar-blind 248-nm lidar system. We are investigating the use of longer excitation laser wavelengths (i.e. lambda greater than 280-nm to have more favorable atmospheric light transmission characteristics) for improving detection range to better than 10 km. In the detection of chemical plumes, our main research objectives are to determine how accurately and sensitively a chemical plume can be located at range, and how well spectrally the chemical species can be measured to allow their identification.

Visible emission in Sm3+ and Tb3+ doped phosphate glass excited by UV radiation

NASA Astrophysics Data System (ADS)

Zmojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Czajkowski, Karol; Ragin, Tomasz

2013-10-01

In the article analysis of UV absorption and visible fluorescence of Sm3+ and Tb3+ ions doped phosphate glass with molar composition: 65P2O5 + 8Al2O3 + 10BaO + 17(Na2O + MgO + ZnO) have been investigated. As a result of optical pumping fabricated glass with radiation from a deuterium lamp four luminescence bands were observed near to the wavelength of 600 nm for Sm3+ ions and 550 nm for Tb3+ ions. It was found that larger energy gap between laser and ground levels leads to the strongest emission in the visible range in terbium doped glasses than in glasses doped with samarium ions. Both fabricated glasses are characterized by the ability to selectively detect the radiation in the UV range.

Nano- and femtosecond UV laser pulses to immobilize biomolecules onto surfaces with preferential orientation

NASA Astrophysics Data System (ADS)

Lettieri, S.; Avitabile, A.; Della Ventura, B.; Funari, R.; Ambrosio, A.; Maddalena, P.; Valadan, M.; Velotta, R.; Altucci, C.

2014-10-01

By relying on the photonic immobilization technique of antibodies onto surfaces, we realized portable biosensors for light molecules based on the use of quartz crystal microbalances, given the linear dependence of the method on the laser pulse intensity. Here, we compare the quality of the anchoring method when using nanosecond (260 nm, 25 mJ/pulse, 5 ns, 10 Hz rep. rate) and femtosecond (258 nm, 25 μJ/pulse, 150 fs, 10 kHz rep. rate) laser source, delivering the same energy to the sample with the same average power. As a reference, we also tethered untreated antibodies by means of the passive adsorption. The results are striking: When the antibodies are irradiated with the femtosecond pulses, the deposition on the gold plate is much more ordered than in the other two cases. The effects of UV pulses irradiation onto the antibodies are also analyzed by measuring absorption and fluorescence and suggest the occurrence of remarkable degradation when nanosecond pulses are used likely induced by a larger thermal coupling. In view of the high average power required to activate the antibodies for the achievement of the photonic immobilization technique, we conclude that femtosecond rather than nanosecond laser pulses have to be used.

An effective approach to reduce inflammation and stenosis in carotid artery: polypyrrole nanoparticle-based photothermal therapy

NASA Astrophysics Data System (ADS)

Peng, Zhiyou; Qin, Jinbao; Li, Bo; Ye, Kaichuang; Zhang, Yuxin; Yang, Xinrui; Yuan, Fukang; Huang, Lijia; Hu, Junqing; Lu, Xinwu

2015-04-01

Photothermal therapy (PTT), as a promising treatment for tumours, has rarely been reported for application in artery restenosis, which is a common complication of endovascular management due to enduring chronic inflammation and abnormal cell proliferation. In our study, biodegradable polypyrrole nanoparticles (PPy-NPs) were synthesized and characterized, including their size distribution, UV-vis-NIR absorbance, molar extinction coefficients, and photothermal properties. We then verified that PPy-NP incubation followed by 915 nm near-infrared (NIR) laser irradiation could effectively ablate inflammatory macrophages in vitro, leading to significant cell apoptosis and cell death. Further, it was found that a combination of local PPy-NP injection with 915 nm NIR laser irradiation could significantly alleviate arterial inflammation by eliminating infiltrating macrophages and further ameliorating artery stenosis in an ApoE-/- mouse model, without showing any obvious toxic side effects. Thus, we propose that PTT based on PPy-NPs as photothermal agents and a 915 nm NIR laser as a power source can serve as a new effective treatment for reducing inflammation and stenosis formation in inflamed arteries after endovascular management.Photothermal therapy (PTT), as a promising treatment for tumours, has rarely been reported for application in artery restenosis, which is a common complication of endovascular management due to enduring chronic inflammation and abnormal cell proliferation. In our study, biodegradable polypyrrole nanoparticles (PPy-NPs) were synthesized and characterized, including their size distribution, UV-vis-NIR absorbance, molar extinction coefficients, and photothermal properties. We then verified that PPy-NP incubation followed by 915 nm near-infrared (NIR) laser irradiation could effectively ablate inflammatory macrophages in vitro, leading to significant cell apoptosis and cell death. Further, it was found that a combination of local PPy-NP injection with 915 nm NIR laser irradiation could significantly alleviate arterial inflammation by eliminating infiltrating macrophages and further ameliorating artery stenosis in an ApoE-/- mouse model, without showing any obvious toxic side effects. Thus, we propose that PTT based on PPy-NPs as photothermal agents and a 915 nm NIR laser as a power source can serve as a new effective treatment for reducing inflammation and stenosis formation in inflamed arteries after endovascular management. Electronic supplementary information (ESI) available: Figures. See DOI: 10.1039/c5nr00542f

Application of LIF technique for the space- and time-resolved monitoring of pollutant gas decomposition in nonthermal plasma reactors

NASA Astrophysics Data System (ADS)

Mizeraczyk, Jerzy; Ohkubo, Toshikazu; Kanazawa, Seiji; Kocik, Marek

2003-10-01

Laser-induced fluorescence (LIF) technique aided by intensified CCD light signal detection and fast digital image processing is demonstrated to be a useful diagnostic method for in-situ observation of the discharge-induced plasma-chemistry processes responsible for NOx(NO + NO2) decomposition occurring in non-thermal plasma reactors. In this paper a method and results of the LIF measurement of two-dimensional distribution of the ground-state NO molecule density inside a DC positive streamer corona reactor during NO removal from a flue gas simulator [air/NO(up to 300 ppm)] are presented. Either a needle-to-plate or nozzle-to-plate electrode system, having an electrode gap of 30-50 mm was used for generating the corona discharge in the reactor. The LIF monitoring of NO molecules was carried out under the steady-state DC corona discharge condition. The laser-induced fluorescence on the transition NO X2Π(v"=0)<--A2Σ+(v'=0) at λ=226nm was chosen for monitoring ground-state NO molecules in the reactor. This transition was induced by irradiation of the NO molecules with UV laser pulses generated by a laser system consisted of a XeF excimer laser, dye laser and BBO crystal. The laser pulses from the XeF excimer laser (Lambda Physik, Complex 150, λ=351 nm) pumped the dye laser (Lambda Physik, Scanmate) with Coumarin 47 as a dye, which generated the laser beam of a wavelength turned around λ=450 nm. Then, the tuned dye laser beam pumped the BBO crystal in which the second harmonic radiation of a wavelength correspondingly tuned around λ=226 nm was generated. The 226-nm UV laser pulses of energy of 0.8-2 mJ and duration of about 20 ns were transformed into the form of the so-called laser sheet (width of 1 mm, height of 30-50 mm) which passed between the electrodes through the operating gas. The obtained results, presented in the form of images, which illustrated the two-dimensional distributions of NO molecule concentration in the non-thermal reactor, showed that the corona discharge-induced removal of NO molecules occurred not only in the vicinity of the plasma region formed by the corona discharge-induced removal of NO molecules occurred not only in the vicinity of the plasma region formed by the corona streamers and in the downstream region of the reactor but also in the upstream region of the reactor, i.e. before the flue gas simulator has entered the plasma region. This information obtained owing to the LIF technique, is important for the understanding of the plasma-chemistry processes responsible for NOx decomposition in non-thermal plasma reactors and for optimising their performance.

Fabrication and characterization of homogeneous surface-enhanced Raman scattering substrates by single pulse UV-laser treatment of gold and silver films.

PubMed

Christou, Konstantin; Knorr, Inga; Ihlemann, Jürgen; Wackerbarth, Hainer; Beushausen, Volker

2010-12-07

The fabrication of SERS-active substrates, which offer high enhancement factors as well as spatially homogeneous distribution of the enhancement, plays an important role in the expansion of surface-enhanced Raman scattering (SERS) spectroscopy to a powerful, quantitative, and noninvasive measurement technique for analytical applications. In this paper, a novel method for the fabrication of SERS-active substrates by laser treatment of 20, 40, and 60 nm thick gold and of 40 nm thick silver films supported on quartz glass is presented. Single 308 nm UV-laser pulses were applied to melt the thin gold and silver films. During the cooling process of the noble metal, particles were formed. The particle size and density were imaged by atomic force microscopy. By varying the fluence, the size of the particles can be controlled. The enhancement factors of the nanostructures were determined by recording self-assembled monolayers of benzenethiol. The intensity of the SERS signal from benzenethiol is correlated to the mean particle size and thus to the fluence. Enhancement factors up to 10(6) with a high reproducibility were reached. Finally we have analyzed the temperature dependence of the SERS effect by recording the intensity of benzenethiol vibrations from 300 to 120 K. The temperature dependence of the SERS effect is discussed with regard to the metal properties.

Effects of optical dopants and laser wavelength on atom probe tomography analyses of borosilicate glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xiaonan; Schreiber, Daniel K.; Neeway, James J.

Atom probe tomography (APT) is a novel analytical microscopy method that provides three dimensional elemental mapping with sub-nanometer spatial resolution and has only recently been applied to insulating glass and ceramic samples. In this paper, we have studied the influence of the optical absorption in glass samples on APT characterization by introducing different transition metal optical dopants to a model borosilicate nuclear waste glass (international simple glass). A systematic comparison is presented of the glass optical properties and the resulting APT data quality in terms of compositional accuracy and the mass spectra quality for two APT systems: one with amore » green laser (532 nm, LEAP 3000X HR) and one with a UV laser (355 nm, LEAP 4000X HR). These data were also compared to the study of a more complex borosilicate glass (SON68). The results show that the analysis data quality such as compositional accuracy and total ions collected, was clearly linked to optical absorption when using a green laser, while for the UV laser optical doping aided in improving data yield but did not have a significant effect on compositional accuracy. Comparisons of data between the LEAP systems suggest that the smaller laser spot size of the LEAP 4000X HR played a more critical role for optimum performance than the optical dopants themselves. The smaller spot size resulted in more accurate composition measurements due to a reduced background level independent of the material’s optical properties.« less

Integration of Optical Manipulation and Electrophysiological Tools to Modulate and Record Activity in Neural Networks

NASA Astrophysics Data System (ADS)

Difato, F.; Schibalsky, L.; Benfenati, F.; Blau, A.

2011-07-01

We present an optical system that combines IR (1064 nm) holographic optical tweezers with a sub-nanosecond-pulsed UV (355 nm) laser microdissector for the optical manipulation of single neurons and entire networks both on transparent and non-transparent substrates in vitro. The phase-modulated laser beam can illuminate the sample concurrently or independently from above or below assuring compatibility with different types of microelectrode array and patch-clamp electrophysiology. By combining electrophysiological and optical tools, neural activity in response to localized stimuli or injury can be studied and quantified at sub-cellular, cellular, and network level.

Towards eye-safe standoff Raman imaging systems

NASA Astrophysics Data System (ADS)

Glimtoft, Martin; Bââth, Petra; Saari, Heikki; Mäkynen, Jussi; Näsilä, Antti; Östmark, Henric

2014-05-01

Standoff Raman imaging systems have shown the ability to detect single explosives particles. However, in many cases, the laser intensities needed restrict the applications where they can be safely used. A new generation imaging Raman system has been developed based on a 355 nm UV laser that, in addition to eye safety, allows discrete and invisible measurements. Non-dangerous exposure levels for the eye are several orders of magnitude higher in UVA than in the visible range that previously has been used. The UV Raman system has been built based on an UV Fabry-Perot Interferometer (UV-FPI) developed by VTT. The design allows for precise selection of Raman shifts in combination with high out-of-band blocking. The stable operation of the UV-FPI module under varying environmental conditions is arranged by controlling the temperature of the module and using a closed loop control of the FPI air gap based on capacitive measurement. The system presented consists of a 3rd harmonics Nd:YAG laser with 1.5 W average output at 1000 Hz, a 200 mm Schmidt-Cassegrain telescope, UV-FPI filter and an ICCD camera for signal gating and detection. The design principal leads to a Raman spectrum in each image pixel. The system is designed for field use and easy manoeuvring. Preliminary results show that in measurements of <60 s on 10 m distance, single AN particles of <300 μm diameter can be identified.

Single-Shot Spectrally Resolved UV Rayleigh Scattering Measurements in High Speed Flow

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1996-01-01

A single-shot UV molecular Rayleigh scattering technique to measure velocity in high speed flow is described. The beam from an injection-seeded, frequency quadrupled Nd:YAG laser (266 nm) is focused to a line in a free air jet with velocities up to Mach 1.3. Rayleigh scattered light is imaged through a planar mirror Fabry-Perot interferometer onto a Charged Coupled Device (CCD) array detector. Some laser light is also simultaneously imaged through the Fabry-Perot to provide a frequency reference. Two velocity measurements are obtained from each image. Multiple-pulse data are also given. The Rayleigh scattering velocity data show good agreement with velocities calculated from isentropic flow relations.

Sacrificial-layer free transfer of mammalian cells using near infrared femtosecond laser pulses

PubMed Central

Zhang, Jun; Hartmann, Bastian; Siegel, Julian; Marchi, Gabriele; Clausen-Schaumann, Hauke; Sudhop, Stefanie; Huber, Heinz P.

2018-01-01

Laser-induced cell transfer has been developed in recent years for the flexible and gentle printing of cells. Because of the high transfer rates and the superior cell survival rates, this technique has great potential for tissue engineering applications. However, the fact that material from an inorganic sacrificial layer, which is required for laser energy absorption, is usually transferred to the printed target structure, constitutes a major drawback of laser based cell printing. Therefore alternative approaches using deep UV laser sources and protein based acceptor films for energy absorption, have been introduced. Nevertheless, deep UV radiation can introduce DNA double strand breaks, thereby imposing the risk of carcinogenesis. Here we present a method for the laser-induced transfer of hydrogels and mammalian cells, which neither requires any sacrificial material for energy absorption, nor the use of UV lasers. Instead, we focus a near infrared femtosecond (fs) laser pulse (λ = 1030 nm, 450 fs) directly underneath a thin cell layer, suspended on top of a hydrogel reservoir, to induce a rapidly expanding cavitation bubble in the gel, which generates a jet of material, transferring cells and hydrogel from the gel/cell reservoir to an acceptor stage. By controlling laser pulse energy, well-defined cell-laden droplets can be transferred with high spatial resolution. The transferred human (SCP1) and murine (B16F1) cells show high survival rates, and good cell viability. Time laps microscopy reveals unaffected cell behavior including normal cell proliferation. PMID:29718923

Raman shifting of KrF laser radiation for tropospheric ozone measurements

NASA Technical Reports Server (NTRS)

Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Ismail, Syed

1991-01-01

The differential absorption lidar (DIAL) measurement of tropospheric ozone requires use of high average power UV lasers operating at two appropriate DIAL wavelengths. Laboratory experiments have demonstrated that a KrF excimer laser can be used to generate several wavelengths with good energy conversion efficiencies by stimulated Raman shifting using hydrogen (H2) and deuterium (D2). Computer simulations for an airborne lidar have shown that these laser emissions can be used for the less than 5 percent random error, high resolution measuremment of ozone across the troposphere using the DIAL technique. In the region of strong ozone absorption, laser wavelengths of 277.0 and 291.7 nm were generated using H2 and D2, respectively. In addition, a laser wavelength at 302.0 nm was generated using two cells in series, with the first containing D2 and the second containing H2. The energy conversion efficiency for each wavelength was between 14 and 27 percent.

Fundamental Scaling of Microplasmas and Tunable UV Light Generation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manginell, Ronald P.; Sillerud, Colin Halliday; Hopkins, Matthew M.

2016-11-01

The temporal evolution of spectral lines from microplasma devices (MD) was studied, including impurity transitions. Long-wavelength emission diminishes more rapidly than deep UV with decreasing pulse width and RF operation. Thus, switching from DC to short pulsed or RF operation, UV emissions can be suppressed, allowing for real-time tuning of the ionization energy of a microplasma photo-ionization source, which is useful for chemical and atomic physics. Scaling allows MD to operate near atmospheric pressure where excimer states are efficiently created and emit down to 65 nm; laser emissions fall off below 200 nm, making MD light sources attractive for deepmore » UV use. A first fully-kinetic three-dimensional model was developed that explicitly calculates electron-energy distribution function. This, and non-continuum effects, were studied with the model and how they are impacted by geometry and transient or DC operation. Finally, a global non-dimensional model was developed to help explain general trends MD physics.« less

Mechanistic study of fulvic acid assisted propranolol photodegradation in aqueous solution.

PubMed

Makunina, Maria P; Pozdnyakov, Ivan P; Chen, Yong; Grivin, Vyacheslav P; Bazhin, Nikolay M; Plyusnin, Victor F

2015-01-01

Laser flash (355 nm) and stationary (365 nm) photolysis were used to study the mechanisms of propranolol photolysis in the presence of fulvic acid in aqueous solutions. The FA-assisted photodegradation of propranolol was observed using UV-A irradiation (where propranolol is stable). Direct evidence indicated that the photodegradation resulted from the static quenching of the FA triplet state by propranolol via the electron transfer mechanism. The triplet state yield (ϕT≈0.6%) and the T-T absorption coefficient (ɛT(620 nm)≈5×10(4) M(-1) cm(-1)) were estimated for the first time by modeling the yields of the FA triplet state in the presence of propranolol. Thus, fulvic acid is a promising agent for accelerating propranolol photodegradation in aqueous solutions under UV-A light irradiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Structure and luminescence of nanocrystalline gallium nitride synthesized by a novel polymer pyrolysis route

NASA Astrophysics Data System (ADS)

Garcia, Rafael; Hirata, Gustavo A.; Thomas, Alan C.; Ponce, Fernando A.

2006-10-01

Thermal decomposition in a horizontal quartz tube reactor of a polymer [-(CH 6N 4O) 3Ga(NO 3) 3-] in a nitrogen atmosphere, yield directly nano-structured gallium nitride (GaN) powder. The polymer was obtained by the reaction between high purity gallium nitrate (Ga(NO 3) 3) dissolved in toluene and carbohydrazide as an azotic ligand. The powder synthesized by this method showed a yellow color and elemental analysis suggested that the color is due to some carbon and oxygen impurities in the as-synthesized powder. Electron microscopy showed that the as-synthesized powders consist of a mixture of various porous particles containing nanowires and nano-sized platelets. The size of the crystallites can be controlled by annealing processes under ammonia. Photoluminescence analysis at 10 K on as-synthesized powders showed a broad red luminescence around 668 nm under UV laser excitation (He-Cd laser, 325 nm). However after annealing process the red luminescence disappears and the typical band edge emission of GaN around 357 nm (3.47 eV) and the UV band were the dominant emissions in the PL spectra.

A Compact, Solid-State UV (266 nm) Laser System Capable of Burst-Mode Operation for Laser Ablation Desorption Processing

NASA Technical Reports Server (NTRS)

Arevalo, Ricardo, Jr.; Coyle, Barry; Paulios, Demetrios; Stysley, Paul; Feng, Steve; Getty, Stephanie; Binkerhoff, William

2015-01-01

Compared to wet chemistry and pyrolysis techniques, in situ laser-based methods of chemical analysis provide an ideal way to characterize precious planetary materials without requiring extensive sample processing. In particular, laser desorption and ablation techniques allow for rapid, reproducible and robust data acquisition over a wide mass range, plus: Quantitative, spatially-resolved measurements of elemental and molecular (organic and inorganic) abundances; Low analytical blanks and limits-of-detection ( ng g-1); and, the destruction of minimal quantities of sample ( g) compared to traditional solution and/or pyrolysis analyses (mg).

Laser-induced fusion of human embryonic stem cells with optical tweezers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Shuxun; Wang Xiaolin; Sun Dong

2013-07-15

We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

Nanosecond laser photolysis studies of vitamin K 3 in aqueous solution

NASA Astrophysics Data System (ADS)

Chen, J. F.; Ge, X. W.; Chu, G. S.; Zhang, Z. C.; Zhang, M. W.; Yao, S. D.; Lin, N. Y.

1999-06-01

Vitamin K 3 in aqueous solution was investigated by 248 nm laser flash photolysis. Laser-induced transient species were characterized according to kinetic analysis and quenching experiments by Mn 2+ and O 2. In neutral solutions, the intermediates recorded were assigned to excited triplet states and dehydrogenated radicals of vitamin K 3. In comparison with the results of pulse radiolytical experiment, vitamin K 3 not only has strong electron affinity but could also could be photoionized by UV laser light. All this shows that vitamin K 3 acts as an effective electron carrier and electron transfer agent.

300 mW of coherent light at 488 nm using a generic approach

NASA Astrophysics Data System (ADS)

Karamehmedović, Emir; Pedersen, Christian; Andersen, Martin T.; Tidemand-Lichtenberg, Peter

2008-02-01

We present a generic approach for efficient generation of CW light with a predetermined wavelength within the visible or UV spectrum. Based on sum-frequency generation (SFG), the circulating intra-cavity field of a high-finesse diode pumped CW solid-state laser (DPSSL) and the output from a tapered, single-frequency external cavity diode laser (ECDL) are mixed inside a 10 mm periodically poled KTP crstal (pp-KTP). The pp-KTP is situated inside the DPSSL cavity to enhance conversion efficiency of the nonlinear mixing process. This approach combines different solid state technologies; the tuneability of ECDLs, the high intra-cavity filed of DPSSLs and flexible quasi phase matching in pp-tapered ECDL with a center wavelength of 766 nm in combination with a high finesse Nd:YVo4 laser at 1342 nm. Up to 308 mW of light at 488nm was measured in our experiments. The conversion of te ECDL beam was up to 47% after it was transmitted through a PM fiber, and up to 32% without fiber coupling. Replacing the seed laser and the nonlinear crystal makes it possible to generate light at virtually any desired wavelength withing the visible spectrum.

Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobkov, K K; Rybaltovsky, A A; Vel'miskin, V V

2014-12-31

We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb{sup 2+} ions in the glass network under IR laser pumping at a wavelength λ = 915 nm and under UV irradiation with an excimer laser (λ = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb{sup 2+} ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicatemore » glass, has been identified: photoinduced Yb{sup 3+} charge-transfer state excitation. (optical fibres)« less

Two-step excitation and blue fluorescence under continuous-wave pumping in Nd:YLF

NASA Technical Reports Server (NTRS)

Fan, T. Y.; Byer, Robert L.

1986-01-01

Near-UV and blue fluorescence from the 4D3/2 and 4D5/2 manifolds in Nd:YLF has been observed at room temperature under CW pumping by a rhodamine 590 dye laser. Excitation to these manifolds is attributed to two-step excitation involving excited-state absorption from the 4F3/2 metastable level. A similar phenomenon has also been observed in Nd:YAG and Nd:glass. The effective excited-state absorption cross section is measured to be (2 + or - 1) x 10 to the -20th sq cm at 587.4 nm in the pi polarization, and the peak effective stimulated emission cross section is measured to be 5 x 10 to the -20th sq cm at 411.7 nm, also in the pi polarization. Estimated laser threshold at 411.7 nm for two-step pumping at 587.4 nm is 70 mW.

Bandwidth Dependence of Laser Plasma Instabilities Driven by the Nike KrF Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Phillips, L.; Lehmberg, R. H.; McLean, E.; Manka, C.; Feldman, U.

2011-10-01

The Nike krypton-fluoride (KrF) laser at the Naval Research Laboratory operates in the deep UV (248 nm) and employs beam smoothing by induced spatial incoherence (ISI). In the first ISI studies at longer wavelengths (1054 nm and 527 nm) [Obenschain, PRL 62, 768(1989);Mostovych, PRL, 59, 1193(1987); Peyser, Phys. Fluids B 3, 1479(1991)], stimulated Raman scattering, stimulated Brillouin scattering, and the two plasmon decay instability were reduced when wide bandwidth ISI (δν / ν ~ 0.03-0.19%) pulses irradiated targets at moderate to high intensities (1014-1015W/cm2) . Recent Nike work showed that the threshold for quarter critical instabilities increased with the expected wavelength scaling, without accounting for the large bandwidth (δν ~ 1-3 THz). New experiments will compare laser plasma instabilities (LPI) driven by narrower bandwidth pulses to those observed with the standard operation. The bandwidth of KrF lasers can be reduced by adding narrow filters (etalons or gratings) in the initial stages of the laser. This talk will discuss the method used to narrow the output spectrum of Nike, the laser performance for this new operating mode, and target observations of LPI in planar CH targets. Work supported by DoE/NNSA.

High-speed photorefractive keratectomy with femtosecond ultraviolet pulses

NASA Astrophysics Data System (ADS)

Danieliene, Egle; Gabryte, Egle; Vengris, Mikas; Ruksenas, Osvaldas; Gutauskas, Algimantas; Morkunas, Vaidotas; Danielius, Romualdas

2015-05-01

Femtosecond near-infrared lasers are widely used for a number of ophthalmic procedures, with flap cutting in the laser-assisted in situ keratomileusis (LASIK) surgery being the most frequent one. At the same time, lasers of this type, equipped with harmonic generators, have been shown to deliver enough ultraviolet (UV) power for the second stage of the LASIK procedure, the stromal ablation. However, the speed of the ablation reported so far was well below the currently accepted standards. Our purpose was to perform high-speed photorefractive keratectomy (PRK) with femtosecond UV pulses in rabbits and to evaluate its predictability, reproducibility and healing response. The laser source delivered femtosecond 206 nm pulses with a repetition rate of 50 kHz and an average power of 400 mW. Transepithelial PRK was performed using two different ablation protocols, to a total depth of 110 and 150 μm. The surface temperature was monitored during ablation; haze dynamics and histological samples were evaluated to assess outcomes of the PRK procedure. For comparison, analogous excimer ablation was performed. Increase of the ablation speed up to 1.6 s/diopter for a 6 mm optical zone using femtosecond UV pulses did not significantly impact the healing process.

Visualizing different uranium oxidation states during the surface alteration of uraninite and uranium tetrachloride.

PubMed

Grossmann, Kay; Arnold, Thuro; Steudtner, Robin; Weiss, Stefan; Bernhard, Gert

2009-08-01

Low-temperature alteration reactions on uranium phases may lead to the mobilization of uranium and thereby poses a potential threat to humans living close to uranium-contaminated sites. In this study, the surface alteration of uraninite (UO(2)) and uranium tetrachloride (UCl(4)) in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy using an excitation wavelength of 408 nm. It was found that within minutes the oxidation state on the surface of the uraninite and the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride surface became stepwise oxidized by a one-electron step at first to U(V) and then further to U(VI). These observed changes in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on the basis of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415-475 nm was indicative for metastable uranium(V), and a fluorescence signal in the range of 480-560 nm was identified as uranium(VI). In addition, the oxidation process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically identified. The combination of microscopy and fluorescence spectroscopy provided a very convincing visualization of the brief presence of U(V) as a metastable reaction intermediate and of the simultaneous coexistence of the three states U(IV), U(V), and U(VI). These results have a significant importance for fundamental uranium redox chemistry and should contribute to a better understanding of the geochemical behavior of uranium in nature.

Photoaggregation of crystallins (main proteins of eye lens) under the effect of XeCl laser radiation

NASA Astrophysics Data System (ADS)

Soustov, Lev V.; Chelnokov, Evgeny V.; Bityurin, Nikita M.; Kiselev, A. L.; Nemov, V. V.; Sergeev, Yu. V.; Ostrovsky, Michail A.

2004-07-01

UV light is one of primary factors associated with cataract formation in the eye lens. α-, β-, γ-Crystallins maintain lens transparency, and damage to these proteins plays a major role in cataract formation. The effect of XeCl laser radiation (308 nm) on βL-crystallin solution is studied. The strong dependence of protein aggregation kinetics on both laser fluence (w) and repetition rate (F) is investigated. The kinetics features are similar to those of carbonic anhydrase photoaggregation studied previously.

Femtosecond laser microfabrication in polymers towards memory devices and microfluidic applications

NASA Astrophysics Data System (ADS)

Deepak, K. L. N.; Venugopal Rao, S.; Narayana Rao, D.

2011-12-01

We have investigated femtosecond laser induced microstructures, gratings, and craters in four different polymers: poly methyl methacrylate (PMMA), poly dimethyl siloxane (PDMS), polystyrene (PS) and poly vinyl alcohol (PVA) using Ti:sapphire laser delivering 800 nm, 100 femtosecond (fs) pulses at 1 kHz repetition rate with a maximum pulse energy of 1 mJ. Local chemical modifications leading to the formation of optical centers and peroxide radicals which were studied using UV-Visible absorption and emission, confocal micro-Raman and Electron Spin Resonance (ESR) spectroscopic techniques.

Two-dimensional imaging of molecular hydrogen in H2-air diffusion flames using two-photon laser-induced fluorescence

NASA Technical Reports Server (NTRS)

Lempert, W.; Kumar, V.; Glesk, I.; Miles, R.; Diskin, G.

1991-01-01

The use of a tunable ArF laser at 193.26 nm to record simultaneous single-laser-shot, planar images of molecular hydrogen and hot oxygen in a turbulent H2-air diffusion flame. Excitation spectra of fuel and oxidant-rich flame zones confirm a partial overlap of the two-photon H2 and single-photon O2 Schumann-Runge absorption bands. UV Rayleigh scattering images of flame structure and estimated detection limits for the H2 two-photon imaging are also presented.

Rapid, controllable, one-pot and room-temperature aqueous synthesis of ZnO:Cu nanoparticles by pulsed UV laser and its application for photocatalytic degradation of methyl orange.

PubMed

Arabi, Mozhgan; Baizaee, Seyyed Mahdy; Bahador, Alireza; Otaqsara, Seyed Mohammad Taheri

2018-05-01

Zinc oxide (ZnO) and ZnO:Cu nanoparticles (NPs) were synthesized using a rapid, controllable, one-pot and room-temperature pulsed UV-laser assisted method. UV-laser irradiation was used as an effective energy source in order to gain better control over the NPs size and morphology in aqueous media. Parameters effective in laser assisted synthesis of NPs such as irradiation time and laser shot repetition rate were optimized. Photoluminescence (PL) spectra of ZnO NPs showed a broad emission with two trap state peaks located at 442 and 485 nm related to electronic transition from zinc interstitial level (I Zn ) to zinc vacancy level (V Zn ) and electronic transition from conduction band to the oxygen vacancy level (V O ), respectively. For ZnO:Cu NPs, trap state emissions disappeared completely and a copper (Cu)-related emission appeared. PL intensity of Cu-related emission increased with the increase in concentration of Cu 2+ , so that for molar ratio of Cu:Zn 2%, optimal value of PL intensity was obtained. The photocatalytic activity of Cu-doped ZnO revealed 50 and 100% increasement than that of undoped NPs under UV and visible irradiation, respectively. The enhanced photocatalytic activity could be attributed to smaller crystal size, as well as creation of impurity acceptor levels (T 2 ) inside the ZnO energy band gap. Copyright © 2017 John Wiley & Sons, Ltd.

Dynamics of Re(2,2'-bipyridine)(CO)3Cl MLCT formation and decay after picosecond pulsed X-ray excitation and femtosecond UV excitation.

PubMed

Zhao, Liyan; Odaka, Hideho; Ono, Hiroshi; Kajimoto, Shinji; Hatanaka, Koji; Hobley, Jonathan; Fukumura, Hiroshi

2005-01-01

The dynamics of Re(2,2'-bipyridine)(CO)3Cl MLCT state formation and decay were determined after femtosecond UV laser excitation and picosecond pulsed X-ray excitation, in an N,N-dimethylformamide (DMF) solution as well as in its solid form. At room temperature, after UV excitation, this MLCT excited state emits both in DMF solution and in the solid form. Transient absorption spectra were measured in solution at various delay times following excitation by a 160 fs, 390 nm laser pulse. There was a prompt absorption increase at around 460 nm occurring within the pump probe convolution (<1 ps), which was assigned to the formation of the 3MLCT state. This transient absorbance was constant over 100 ps. In contrast to the solution state, in the solid state, the emission maximum slightly red-shifts with increasing time after laser excitation. In both solid and solution the emission rises within the system response time. The solid sample exhibited a 1.4 ns emission decay that was not observed for the solution sample. The emission rise from a solid sample after 20 ps pulsed X-ray excitation was significantly slower than the system's time resolution. It is proposed that kinetically energetic electrons are ejected following X-ray induced ionisation, creating ionised tracks in which energetic cations and electrons take time to recombine yielding delayed 3MLCT states that emit.

Ultrafast laser induced periodic sub-wavelength aluminum surface structures and nanoparticles in air and liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuladeep, Rajamudili; Dar, Mudasir H.; Rao, D. Narayana, E-mail: dnrsp@uohyd.ac.in, E-mail: dnr-laserlab@yahoo.com

2014-09-21

In this communication, we demonstrate the generation of laser-induced periodic sub-wavelength surface structures (LIPSS) or ripples on a bulk aluminum (Al) and Al nanoparticles (NPs) by femtosecond (fs) laser direct writing technique. Laser irradiation was performed on Al surface at normal incidence in air and by immersing in ethanol (C₂H₅OH) and water (H₂O) using linearly polarized Ti:sapphire fs laser pulses of ~110 fs pulse duration and ~800 nm wavelength. Field emission scanning electron microscope is utilized for imaging surface morphology of laser written structures and it reveals that the spatial periodicity as well as the surface morphology of the LIPSSmore » depends on the surrounding dielectric medium and also on the various laser irradiation parameters. The observed LIPSS have been classified as low spatial frequency LIPSS which are perpendicularly oriented to the laser polarization with a periodicity from 460 to 620 nm and high spatial frequency LIPSS which spectacles a periodicity less than 100 nm with the orientation parallel to the polarization of the incident laser beam. Fabricated colloidal solutions, which contain the Al NPs, were characterized by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). TEM results reveal the formation of internal cavities in Al NPs both in ethanol and water. Formation mechanism of LIPSS and cavities inside the nanoparticles are discussed in detail.« less

Laser ablation of a silicon target in chloroform: formation of multilayer graphite nanostructures

NASA Astrophysics Data System (ADS)

Abderrafi, Kamal; García-Calzada, Raúl; Sanchez-Royo, Juan F.; Chirvony, Vladimir S.; Agouram, Saïd; Abargues, Rafael; Ibáñez, Rafael; Martínez-Pastor, Juan P.

2013-04-01

With the use of high-resolution transmission electron microscopy, selected area electron diffraction and x-ray photoelectron spectroscopy methods of analysis we show that the laser ablation of a Si target in chloroform (CHCl3) by nanosecond UV pulses (40 ns, 355 nm) results in the formation of about 50-80 nm core-shell nanoparticles with a polycrystalline core composed of small (5-10 nm) Si and SiC mono-crystallites, the core being coated by several layers of carbon with the structure of graphite (the shell). In addition, free carbon multilayer nanostructures (carbon nano-onions) are also found in the suspension. On the basis of a comparison with similar laser ablation experiments implemented in carbon tetrachloride (CCl4), where only bare (uncoated) Si nanoparticles are produced, we suggest that a chemical (solvent decomposition giving rise to highly reactive CH-containing radicals) rather than a physical (solvent atomization followed by carbon nanostructure formation) mechanism is responsible for the formation of graphitic shells. The silicon carbonization process found for the case of laser ablation in chloroform may be promising for silicon surface protection and functionalization.

Selective removal of composite sealants with near-UV laser pulses

NASA Astrophysics Data System (ADS)

Louie, Tiffany M.; Jones, Robert S.; Sarma, Anupama V.; Fried, Daniel

2004-05-01

It is often necessary to replace pit and fissure sealants and composite restorations. This task is complicated by the necessity for complete removal of the remaining composite to enable suitable adhesion of new composite. Previous studies have shown that lasers pulses from a frequency-tripled Nd:YAG laser (355-nm) can selectively remove residual composite after orthodontic bracket removal on enamel surfaces. UV laser light is preferentially absorbed by polymeric resins and the organic content of the tooth enamel. The objective of this study was to determine if such laser pulses are suitable for selective removal of the old composite from pit and fissure sealants and restorations without damaging surrounding sound tissues. Optical coherence tomography was used to acquire optical cross sections of the occlusal topography and peripheral tooth structure non-destructively before application of the sealants, after sealant application, and after sealant removal with 355-nm laser pulses with intensities ranging from 0-10 J/cm2. Thermocouples were used to monitor the temperature in the pulp chamber during composite removal under clinically relevant ablation rates, i.e., 30 Hz and 30 mJ per laser pulse. At an irradiation intensity of 1.3 J/cm2 pit and fissure sealants were completely removed without visible damage to the underlying enamel. At intensities above 1.5 J/cm2, the laser removes the resin layer while at the same time preferentially etching the surface of the enamel. Temperature excursions in the pulp chamber of extracted teeth was limited to less than 5°C if air-cooling was used during the rapid removal (1-2 min) of sealants, water-cooling was not needed. This is the first presentation of a method for the selective removal of composite restorative materials without damage to the underlying sound tooth structure.

Lead extraction by selective operation of a nanosecond-pulsed 355nm laser

NASA Astrophysics Data System (ADS)

Herzog, Amir; Bogdan, Stefan; Glikson, Michael; Ishaaya, Amiel A.; Love, Charles

2016-03-01

Lead extraction (LE) is necessary for patients who are suffering from a related infection, or in opening venous occlusions that prevent the insertion of additional lead. In severe cases of fibrous encapsulation of the lead within a vein, laser-based cardiac LE has become one of the foremost methods of removal. In cases where the laser radiation (typically at 308 nm wavelength) interacts with the vein wall rather than with the fibrotic lesion, severe injury and subsequent bleeding may occur. Selective tissue ablation was previously demonstrated by a laser operating in the UV regime; however, it requires the use of sensitizers (e.g.: tetracycline). In this study, we present a preliminary examination of efficacy and safety aspects in the use of a nanosecond-pulsed solid-state laser radiation, at 355 nm wavelength, guided in a catheter consisting of optical fibers, in LE. Specifically, we demonstrate a correlation between the tissue elasticity and the catheter advancement rate, in ex-vivo experiments. Our results indicate a selectivity property for specific parameters of the laser radiation and catheter design. The selectivity is attributed to differences in the mechanical properties of the fibrotic tissue and a normal vein wall, leading to a different photomechanical response of the tissue's extracellular matrix. Furthermore, we performed successful in-vivo animal trials, providing a basic proof of concept for using the suggested scheme in LE. Selective operation using a 355 nm laser may reduce the risk of blood vessel perforation as well as the incidence of major adverse events.

Study of UV imaging technology for noninvasive detection of latent fingerprints

NASA Astrophysics Data System (ADS)

Li, Hong-xia; Cao, Jing; Niu, Jie-qing; Huang, Yun-gang

2013-09-01

Using UV imaging technology, according to the special absorption 、reflection 、scattering and fluorescence characterization of the various residues in fingerprints (fatty acid ester, protein, and carboxylic acid salts etc) to the UV light, weaken or eliminate the background disturbance to increase the brightness contrast of fingerprints with the background, and design、setup the illumination optical system and UV imaging system, the noninvasive detection of latent fingerprints remaining on various object surface are studied. In the illumination optical system, using the 266nm UV Nd:YAG solid state laser as illumination light source, by calculating the best coupling conditions of the laser beam with UV liquid core fiber and analyzing the beam transforming characterizations, we designed and setup the optical system to realize the UV imaging uniform illumination. In the UV imaging system, the UV lens is selected as the fingerprint imaging element, and the UV intensified CCD (ICCD) which consists of a second-generation UV image intensifier and a CCD coupled by fiber plate and taper directly are used as the imaging sensing element. The best imaging conditions of the UV lens with ICCD were analyzed and the imaging system was designed and setup. In this study, by analyzing the factors which influence the detection effect, optimal design and setup the illumination system and imaging system, latent fingerprints on the surface of the paint tin box、plastic、smooth paper、notebook paper and print paper were noninvasive detected and appeared, and the result meet the fingerprint identification requirements in forensic science.

Possible mechanisms of vascular relaxation induced by pulsed-UV laser.

PubMed

Morimoto, Y; Arai, T; Matsuo, H; Kikuchi, M

1998-09-01

This study was designed to examine the mechanism of vasorelaxation induced by pulsed-UV laser. Luminal diameters of rat femoral arteries were measured prior to and following krypton-fluoride excimer laser irradiation of 248 nm in wavelength. The diameter was enlarged to 1.3 times the preirradiated size at 1 or 10 Hz irradiation when the fluence was over 2.0 mJ/pulse/mm2, while the diameter reached 1.8 times at 100 Hz with a fluence of 0.8 mJ/pulse/mm2. Vasorelaxation by the 100 Hz irradiation was inhibited when the artery was pretreated with methylene blue but was enhanced with superoxide dismutase. Pathological analysis revealed an ablation crater and vacuole formation in the vessel at 1 or 10 Hz irradiation, but these changes were not remarkable in the 100 Hz-exposed sample. These findings suggest that vasorelaxation induced by the pulsed UV irradiation at 1 or 10 Hz results from structural alteration of vascular smooth muscle by the ablation crater or vacuolization. On the other hand, a possible mechanism of vasorelaxation at the 100 Hz irradiation is partially related to nitric oxide.

Influence of plasmon coupling on the photoluminescence of ZnS/Ag nanoparticles obtained by laser irradiation in liquid

NASA Astrophysics Data System (ADS)

Moos, Rafaela; Graff, Ismael L.; de Oliveira, Vinicius S.; Schreiner, Wido H.; Bezerra, Arandi G.

2017-10-01

We investigate the photoluminescence, optical absorption and structural properties of ZnS submitted to laser irradiation in water and isopropyl alcohol. Nanoparticles were produced by irradiating micro-sized ZnS particles dispersed in both liquids, with and without the addition of Ag nanoparticles, taking advantage of the laser-assisted fragmentation effect. When ZnS microparticles are irradiated either in pure water or isopropyl alcohol a considerable size reduction is achieved (from micra to few nanometers). The photoluminescence of these nanoparticles mainly occurs in the UV, centered at 350 nm, and with smaller intensity in the visible, centered at 600 nm. Irradiation of ZnS microparticles dispersed in colloidal silver triggers a reaction between both materials, modifying its optical absorption and photoluminescent properties. After irradiation of ZnS in alcohol containing Ag nanoparticles, a giant increase of the UV photoluminescence is observed. Interestingly, when the irradiation is performed in aqueous Ag nanoparticles colloids, the photoluminescence suffers a red-shift towards the violet-blue. The data show that core-shell (Ag-ZnO) nanostructures are formed after irradiation and the visible emission likely originates from the ZnO shell grown around silver nanoparticles. The presence of Ag nanoparticles in the liquid medium promotes a stronger absorption of the laser beam during irradiation due to the coupling with the surface plasmon resonance, fostering intense reactions among ZnS, Ag nanoparticles, and the liquid medium. Our study shows that with a simple change of the liquid medium wherein the irradiation is conducted the photoluminescence can be tuned from UV to visible and core-shell nanostructures can be obtained.

Design, assembly, and testing of a high-resolution relay lens used for holography with operation at both doubled and tripled Nd:YAG laser wavelengths

NASA Astrophysics Data System (ADS)

Malone, Robert M.; Capelle, Gene A.; Cox, Brian C.; Frogget, Brent C.; Grover, Mike; Kaufman, Morris I.; Pazuchanics, Peter; Sorenson, Danny S.; Stevens, Gerald D.; Tibbitts, Aric; Turley, William D.

2009-08-01

The design and assembly of a nine-element lens that achieves >2000 lp/mm resolution at a 355-nm wavelength (ultraviolet) has been completed. By adding a doublet to this lens system, operation at a 532-nm wavelength (green) with >1100 lp/mm resolution is achieved. This lens is used with high-power laser light to record holograms of fast-moving ejecta particles from a shocked metal surface located inside a test package. Part of the lens and the entire test package are under vacuum with a 1-cm air gap separation. Holograms have been recorded with both doubled and tripled Nd:YAG laser light. The UV operation is very sensitive to the package window's tilt. If this window is tilted by more than 0.1 degrees, the green operation performs with better resolution than that of the UV operation. The setup and alignment are performed with green light, but the dynamic recording can be done with either UV light or green light. A resolution plate can be temporarily placed inside the test package so that a television microscope located beyond the hologram position can archive images of resolution patterns that prove that the calibration wires, interference filter, holographic plate, and relay lenses are in their correct positions. Part of this lens is under vacuum, at the point where the laser illumination passes through a focus. Alignment and tolerancing of this high-resolution lens are presented. Resolution variation across the 12-mm field of view and throughout the 5-mm depth of field is discussed for both wavelengths.

Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Cohen, R. C.; Hazen, N. L.; Lapson, L. B.; Allen, N. T.; Hanisco, T. F.; Oliver, J. F.; Lanham, N. W.; Demusz, J. N.; Anderson, J. G.

1994-01-01

The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10(exp 14) in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electric state near 282 nm. the laser light is produced by a high-repetition rate pulsed dye-laser powered with all solid-state pump lasers. HO2 is measured as OH after gas-phase titration with nitric oxide. Measurements aboard a NASA ER-2 aircraft demonstrate the capability of this instrument to perform reliably with very high signal-to-noise ratios (greater than 30) achieved in short integration times (less than 20 sec).

Absorption spectra of localized surface plasmon resonance observed in an inline/picoliter spectrometer cell fabricated by a near ultraviolet femtosecond laser

NASA Astrophysics Data System (ADS)

Shiraishi, Masahiko; Nishiyama, Michiko; Watanabe, Kazuhiro; Kubodera, Shoichi

2018-03-01

Absorption spectra based on localized surface plasmon resonance (LSPR) were obtained with an inline/picoliter spectrometer cell. The spectrometer cell was fabricated into an optical glass fiber by focusing a near UV (NUV) femtosecond laser pulses at a wavelength of 400 nm with an energy of 30 μJ. The laser beam was focused from two directions opposite to each other to fabricate a through-hole spectrometer cell. A diameter of the cell was approximately 3 μm, and the length was approximately 62.5 μm, which was nearly equal to the core diameter of the optical fiber. Liquid solution of gold nanoparticles (GNPs) with a diameter of 5-10 nm was injected into the spectrometer cell with its volume of 0.4 pL. The absorption peak centered at 518 nm was observed. An increase of absorption associated with the increase of the number of nanoparticles was in agreement with the numerical calculation based on the Lambert-Beer law.

Using a micro-molding process to fabricate polymeric wavelength filters

NASA Astrophysics Data System (ADS)

Chuang, Wei-Ching; Lee, An-Chen; Ho, Chi-Ting

2008-08-01

A procedure for fabricating a high aspect ratio periodic structure on a UV polymer at submicron order using holographic interferometry and molding processes is described. First, holographic interferometry using a He-Cd (325 nm) laser was used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 20 nm nickel thin film was then sputtered on the photoresist. The final line pattern on a UV polymer was obtained from casting against the master mold. Finally, a SU8 polymer was spun on the polymer grating to form a planar waveguide or a channel waveguide. The measurement results show that the waveguide length could be reduced for the waveguide having gratings with a high aspect ratio.

Optoelectronic and photoacoustic studies of an organic dye synthesized through green route

NASA Astrophysics Data System (ADS)

Vijayakumar, S.; Sreelatha, S.; Hatamimoslehabadi, M.; Yelleswarappu, C. S.

2017-10-01

An azo dye was prepared through an environmentally benign and economically feasible synthesis route with cardanol as a starting material. Cardanol is a cost-effective and renewable natural source obtained from Cashew Nut Shell Liquid, a by-product of the cashew industry. The dye was spectrally characterized by IR, UV-Vis, NMR and fluorescence studies. UV-Vis absorption showed a bathochromic shift between solvents of lower and higher polarities. Nonlinear optical and photoacoustic properties were studied using a frequency doubled Nd:YAG laser producing 532 nm laser pulses of 3 ns pulse width. Results show that the nonlinear absorption coefficient decreases with the increase of on-axis intensity, suggesting excited state absorption as the principal mechanism. The observed nonlinearity has applications in optoelectronics.

Cryogenic radiometers and intensity-stabilized lasers for Eos radiometric calibrations

NASA Technical Reports Server (NTRS)

Foukal, P.; Hoyt, C.; Jauniskis, L.

1991-01-01

Liquid helium-cooled electrical substitution radiometers (ESRs) provide irradiance standards with demonstrated absolute accuracy at the 0.01 percent level, spectrally flat response between the UV and IR, and sensitivity down to 0.1 nW/sq cm. We describe an automated system developed for NASA - Goddard Space Flight Center, consisting of a cryogenic ESR illuminated by servocontrolled laser beams. This system is designed to provide calibration of single-element and array detectors over the spectral range between 257nm in the UV to 10.6 microns in the IR. We also describe a cryogenic ESR optimized for black body calibrations that has been installed at NIST, and another that is under construction for calibrations of the CERES scanners planned for Eos.

Facile and fast synthesis of SnS2 nanoparticles by pulsed laser ablation in liquid

NASA Astrophysics Data System (ADS)

Johny, J.; Sepulveda-Guzman, S.; Krishnan, B.; Avellaneda, D.; Shaji, S.

2018-03-01

Nanoparticles (NPs) of tin disulfide (SnS2) were synthesized using pulsed laser ablation in liquid (PLAL) technique. Effects of different liquid media and ablation wavelengths on the morphology and optical properties of the nanoparticles were studied. Nd: YAG laser wavelengths of 532 nm and 1064 nm (frequency 10 Hz and pulse width 10 ns) were used to irradiate SnS2 target immersed in liquid for the synthesis of SnS2 nanoparticles. Here PLAL was a fast synthesis technique, the ablation was only for 30 s. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis absorption spectroscopy and photoluminescence spectroscopy were used to characterize the SnS2 NPs. TEM images showed that the liquid medium and laser wavelength influence the morphology of the NPs. SAED patterns and high resolution TEM (HRTEM) images confirmed the crystallinity of the particles. XRD and XPS analyses confirmed that SnS2 NPs were having exact crystalline structure and chemical states as that of the target. Raman analysis also supported the results obtained by XRD and XPS. Optical band gaps of the nanocolloids evaluated from their UV-vis absorption spectra were 2.4-3.05 eV. SnS2 NPs were having luminescence spectra in the blue-green region irrespective of the liquid media and ablation wavelength.

Test measurements on a secco white-lead containing model samples to assess the effects of exposure to low-fluence UV laser radiation

NASA Astrophysics Data System (ADS)

Raimondi, Valentina; Andreotti, Alessia; Colombini, Maria Perla; Cucci, Costanza; Cuzman, Oana; Galeotti, Monica; Lognoli, David; Palombi, Lorenzo; Picollo, Marcello; Tiano, Piero

2015-05-01

Laser-induced fluorescence technique is widely used for diagnostic purposes in several applications and its use could be of advantage for non-invasive on-site characterisation of pigments or other compounds in wall paintings. However, it is well known that long-time exposure to UV and VIS radiation can cause damage to wall paintings. Several studies have investigated the effects of lighting, e.g., in museums: however, the effects of low-fluence laser radiation have not been studied much so far. This paper investigates the effects of UV laser radiation using fluences in the range of 0.1 mJ/cm2-1 mJ/cm2 on a set of a secco model samples prepared with lead white and different type of binders (animal glue and whole egg, whole egg, skimmed milk, egg-oil tempera). The samples were irradiated using a Nd:YAG laser (emission wavelength at 355 nm; pulse width: 5 ns) by applying laser fluences between 0.1 mJ/cm2 and 1 mJ/cm2 and a number of laser pulses between 1 and 500. The samples were characterised before and after laser irradiation by using several techniques (colorimetry, optical microscopy, fibre optical reflectance spectroscopy, FT-IR spectroscopy Attenuated Total Reflectance microscopy and gas chromatography/mass spectrometry), to detect variations in the morphological and physico-chemical properties. The results did not point out significant changes in the sample properties after irradiation in the proposed range of laser fluences.

Constraints on the Early Terrestrial Surface UV Environment Relevant to Prebiotic Chemistry.

PubMed

Ranjan, Sukrit; Sasselov, Dimitar D

2017-03-01

The UV environment is a key boundary condition to abiogenesis. However, considerable uncertainty exists as to planetary conditions and hence surface UV at abiogenesis. Here, we present two-stream multilayer clear-sky calculations of the UV surface radiance on Earth at 3.9 Ga to constrain the UV surface fluence as a function of albedo, solar zenith angle (SZA), and atmospheric composition. Variation in albedo and latitude (through SZA) can affect maximum photoreaction rates by a factor of >10.4; for the same atmosphere, photoreactions can proceed an order of magnitude faster at the equator of a snowball Earth than at the poles of a warmer world. Hence, surface conditions are important considerations when computing prebiotic UV fluences. For climatically reasonable levels of CO 2 , fluence shortward of 189 nm is screened out, meaning that prebiotic chemistry is robustly shielded from variations in UV fluence due to solar flares or variability. Strong shielding from CO 2 also means that the UV surface fluence is insensitive to plausible levels of CH 4 , O 2 , and O 3 . At scattering wavelengths, UV fluence drops off comparatively slowly with increasing CO 2 levels. However, if SO 2 and/or H 2 S can build up to the ≥1-100 ppm level as hypothesized by some workers, then they can dramatically suppress surface fluence and hence prebiotic photoprocesses. H 2 O is a robust UV shield for λ < 198 nm. This means that regardless of the levels of other atmospheric gases, fluence ≲198 nm is only available for cold, dry atmospheres, meaning sources with emission ≲198 (e.g., ArF excimer lasers) can only be used in simulations of cold environments with low abundance of volcanogenic gases. On the other hand, fluence at 254 nm is unshielded by H 2 O and is available across a broad range of [Formula: see text], meaning that mercury lamps are suitable for initial studies regardless of the uncertainty in primordial H 2 O and CO 2 levels. Key Words: Radiative transfer-Origin of life-Planetary environments-UV radiation-Prebiotic chemistry. Astrobiology 17, 169-204.

High speed printing with polygon scan heads

NASA Astrophysics Data System (ADS)

Stutz, Glenn

2016-03-01

To reduce and in many cases eliminate the costs associated with high volume printing of consumer and industrial products, this paper investigates and validates the use of the new generation of high speed pulse on demand (POD) lasers in concert with high speed (HS) polygon scan heads (PSH). Associated costs include consumables such as printing ink and nozzles, provisioning labor, maintenance and repair expense as well as reduction of printing lines due to high through put. Targets that are applicable and investigated include direct printing on plastics, printing on paper/cardboard as well as printing on labels. Market segments would include consumer products (CPG), medical and pharmaceutical products, universal ID (UID), and industrial products. In regards to the POD lasers employed, the wavelengths include UV(355nm), Green (532nm) and IR (1064nm) operating within the repetition range of 180 to 250 KHz.

Laser-induced ferroelectric domain engineering in LiNbO3 crystals using an amorphous silicon overlayer

NASA Astrophysics Data System (ADS)

Zisis, G.; Martinez-Jimenez, G.; Franz, Y.; Healy, N.; Masaud, T. M.; Chong, H. M. H.; Soergel, E.; Peacock, A. C.; Mailis, S.

2017-08-01

We report laser-induced poling inhibition and direct poling in lithium niobate crystals (LiNbO3), covered with an amorphous silicon (a-Si) light-absorbing layer, using a visible (488 nm) continuous wave laser source. Our results show that the use of the a-Si overlayer produces deeper poling inhibited domains with minimum surface damage, as compared to previously reported UV laser writing experiments on uncoated crystals, thus increasing the applicability of this method in the production of ferroelectric domain engineered structures for nonlinear optical applications. The characteristics of the poling inhibited domains were investigated using differential etching and piezoresponse force microscopy.

Effect of ultraviolet light on fatigue of lead zirconate titanate thin-film capacitors

NASA Astrophysics Data System (ADS)

Lee, J.; Esayan, S.; Safari, A.; Ramesh, R.

1994-07-01

Fatigue of Pb(Zr0.52Ti0.48)O3 (PZT) thin-film capacitors was studied under UV light (He-Cd laser, λ=325 nm). The remanent polarization of the PZT film capacitors increased upon light illumination. Fatigue resistance was also improved under UV light. During fatigue test, the change in polarization of PZT films upon UV light illumination increased gradually with cycling. These results were examined within the framework of the polarization screening model, which is suggested as an essential process for fatigue. This leads to a conclusion that more charged defects are involved in the fatigue process through internal screening of polarization.

Photon synthesis of iron oxide thin films for thermo-photo-chemical sensors

NASA Astrophysics Data System (ADS)

Mulenko, S. A.; Petrov, Yu. N.; Gorbachuk, N. T.

2012-09-01

Ultraviolet photons of KrF-laser (248 nm) and of photodiode (360 nm) were used for the synthesis of iron oxide thin films with variable thickness, stoichiometry and electrical properties. The reactive pulsed laser deposition (RPLD) method was based on KrF-laser and photon-induced chemical vapor deposition (PCVD) was based on a photodiode. Deposited films demonstrated semiconductor properties with variable band gap (Eg). The film thickness (50-140 nm) and Eg depended on the laser pulse number, oxygen and iron carbonyl vapor pressure in the deposition chamber, and exposure time to the substrate surface with ultraviolet (UV) radiation. Sensing characteristics strongly depended on electrical and structural properties of such thin films. Iron oxide films were deposited on <1 0 0> Si substrate and had large thermo electromotive force (e.m.f.) coefficient (S) and high photosensitivity (F). The largest value of the S coefficient obtained by RPLD was about 1.65 mV/K in the range 270-290 K and by PCVD was about 1.5 mV/K in the range 280-322 K. The largest value F obtained by RPLD and PCVD was about 44 Vc/W and 40 Vc/W, accordingly, for white light at power density (I ≅ 0.006 W/cm2). It was shown that the S coefficient and F strongly depended on Eg. Moreover, these films were tested as chemical sensors: the largest sensitivity of NO molecules was at the level of 3 × 1012 cm-3. Our results showed that RPLD and PCVD were used to synthesize semiconductor iron oxide thin films with different sensing properties. So iron oxide thin films synthesized by UV photons are up-to-date materials for multi-parameter sensors: thermo-photo-chemical sensors operating at moderate temperature.

Films of brookite TiO2 nanorods/nanoparticles deposited by matrix-assisted pulsed laser evaporation as NO2 gas-sensing layers

NASA Astrophysics Data System (ADS)

Caricato, A. P.; Buonsanti, R.; Catalano, M.; Cesaria, M.; Cozzoli, P. D.; Luches, A.; Manera, M. G.; Martino, M.; Taurino, A.; Rella, R.

2011-09-01

Titanium dioxide (TiO2) nanorods in the brookite phase, with average dimensions of 3-4 nm × 20-50 nm, were synthesized by a wet-chemical aminolysis route and used as precursors for thin films that were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. A nanorod solution in toluene (0.016 wt% TiO2) was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser at a fluence of 350 mJ/cm2 and repetition rate of 10 Hz. Single-crystal Si wafers, silica slides, carbon-coated Cu grids and alumina interdigitated slabs were used as substrates to allow performing different characterizations. Films fabricated with 6000 laser pulses had an average thickness of ˜150 nm, and a complete coverage of the selected substrate as achieved. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO2 nanorods and crystalline spherical nanoparticles with an average diameter of ˜13 nm. Spectrophotometric analysis showed high transparency through the UV-Vis spectral range. Promising resistive sensing responses to 1 ppm of NO2 mixed in dry air were obtained.

Examination of the laser-induced variations in the chemical etch rate of a photosensitive glass ceramic

NASA Astrophysics Data System (ADS)

Voges, Melanie; Beversdorff, Manfred; Willert, Chris; Krain, Hartmut

2007-10-01

Previous studies in our laboratory have reported that the chemical etch rate of a commercial photosensitive glass ceramic (FoturanTM, Schott Corp., Germany) in dilute hydrofluoric acid is strongly dependent on the incident laser irradiance during patterning at λ=266 nm and λ=355 nm. To help elucidate the underlying chemical and physical processes associated with the laser-induced variations in the chemical etch rate, several complimentary techniques were employed at various stages of the UV laser exposure and thermal treatment. X-ray diffraction (XRD) was used to identify the crystalline phases that are formed in Foturan following laser irradiation and annealing, and monitor the crystalline content as a function of laser irradiance at λ=266 nm and λ=355 nm. The XRD results indicate the nucleation of lithium metasilicate (Li2SiO3) crystals as the exclusive phase following laser irradiation and thermal treatment at temperatures not exceeding 605 °C. The XRD studies also show that the Li2SiO3 density increases with increasing laser irradiance and saturates at high laser irradiance. For our thermal treatment protocol, the average Li2SiO3 crystal diameters are 117.0±10.0 nm and 91.2±5.8 nm for λ=266 nm and λ=355 nm, respectively. Transmission electron microscopy (TEM) was utilized to examine the microscopic structural features of the lithium metasilicate crystals. The TEM results reveal that the growth of lithium metasilicate crystals proceeds dendritically, and produces Li2SiO3 crystals that are ˜700 1000 nm in length for saturation exposures. Optical transmission spectroscopy (OTS) was used to study the growth of metallic silver clusters that act as nucleation sites for the Li2SiO3 crystalline phase. The OTS results show that the (Ag0)x cluster concentration has a dependence on incident laser irradiance that is similar to the etch rate ratios and Li2SiO3 concentration. A comparison between the XRD and optical transmission results and our prior etch rate results show that the etch rate contrast and absolute etch rates are dictated by the Li2SiO3 concentration, which is in turn governed by the (Ag0)x cluster concentration. These results characterize the relationship between the laser exposure and chemical etch rate for Foturan, and permit a more detailed understanding of the photophysical processes that occur in the general class of photostructurable glass ceramic materials. Consequently, these results may also influence the laser processing of other photoactive materials.

Constraints on the Early Terrestrial Surface UV Environment Relevant to Prebiotic Chemistry

NASA Astrophysics Data System (ADS)

Ranjan, Sukrit; Sasselov, Dimitar D.

2017-03-01

The UV environment is a key boundary condition to abiogenesis. However, considerable uncertainty exists as to planetary conditions and hence surface UV at abiogenesis. Here, we present two-stream multilayer clear-sky calculations of the UV surface radiance on Earth at 3.9 Ga to constrain the UV surface fluence as a function of albedo, solar zenith angle (SZA), and atmospheric composition. Variation in albedo and latitude (through SZA) can affect maximum photoreaction rates by a factor of >10.4; for the same atmosphere, photoreactions can proceed an order of magnitude faster at the equator of a snowball Earth than at the poles of a warmer world. Hence, surface conditions are important considerations when computing prebiotic UV fluences. For climatically reasonable levels of CO2, fluence shortward of 189 nm is screened out, meaning that prebiotic chemistry is robustly shielded from variations in UV fluence due to solar flares or variability. Strong shielding from CO2 also means that the UV surface fluence is insensitive to plausible levels of CH4, O2, and O3. At scattering wavelengths, UV fluence drops off comparatively slowly with increasing CO2 levels. However, if SO2 and/or H2S can build up to the ≥1-100 ppm level as hypothesized by some workers, then they can dramatically suppress surface fluence and hence prebiotic photoprocesses. H2O is a robust UV shield for λ < 198 nm. This means that regardless of the levels of other atmospheric gases, fluence ≲198 nm is only available for cold, dry atmospheres, meaning sources with emission ≲198 (e.g., ArF excimer lasers) can only be used in simulations of cold environments with low abundance of volcanogenic gases. On the other hand, fluence at 254 nm is unshielded by H2O and is available across a broad range of NCO2, meaning that mercury lamps are suitable for initial studies regardless of the uncertainty in primordial H2O and CO2 levels.

LIBS analysis of artificial calcified tissues matrices.

PubMed

Kasem, M A; Gonzalez, J J; Russo, R E; Harith, M A

2013-04-15

In most laser-based analytical methods, the reproducibility of quantitative measurements strongly depends on maintaining uniform and stable experimental conditions. For LIBS analysis this means that for accurate estimation of elemental concentration, using the calibration curves obtained from reference samples, the plasma parameters have to be kept as constant as possible. In addition, calcified tissues such as bone are normally less "tough" in their texture than many samples, especially metals. Thus, the ablation process could change the sample morphological features rapidly, and result in poor reproducibility statistics. In the present work, three artificial reference sample sets have been fabricated. These samples represent three different calcium based matrices, CaCO3 matrix, bone ash matrix and Ca hydroxyapatite matrix. A comparative study of UV (266 nm) and IR (1064 nm) LIBS for these three sets of samples has been performed under similar experimental conditions for the two systems (laser energy, spot size, repetition rate, irradiance, etc.) to examine the wavelength effect. The analytical results demonstrated that UV-LIBS has improved reproducibility, precision, stable plasma conditions, better linear fitting, and the reduction of matrix effects. Bone ash could be used as a suitable standard reference material for calcified tissue calibration using LIBS with a 266 nm excitation wavelength. Copyright © 2013 Elsevier B.V. All rights reserved.

Optimization strategies for a fluorescent dye with bimodal excitation spectra: application to semiautomated proteomics

NASA Astrophysics Data System (ADS)

Patton, Wayne F.; Berggren, Kiera N.; Lopez, Mary F.

2001-04-01

Facilities engaged in proteome analysis differ significantly in the degree that they implement automated systems for high-throughput protein characterization. Though automated workstation environments are becoming more routine in the biotechnology and pharmaceutical sectors of industry, university-based laboratories often perform these tasks manually, submitting protein spots excised from polyacrylamide gels to institutional core facilities for identification. For broad compatibility with imaging platforms, an optimized fluorescent dye developed for proteomics applications should be designed taking into account that laser scanners use visible light excitation and that charge-coupled device camera systems and gas discharge transilluminators rely upon UV excitation. The luminescent ruthenium metal complex, SYPRO Ruby protein gel stain, is compatible with a variety of excitation sources since it displays intense UV (280 nm) and visible (470 nm) absorption maxima. Localization is achieved by noncovalent, electrostatic and hydrophobic binding of dye to proteins, with signal being detected at 610 nm. Since proteins are not covalently modified by the dye, compatibility with downstream microchemical characterization techniques such as matrix-assisted laser desorption/ionization-mass spectrometry is assured. Protocols have been devised for optimizing fluorophore intensity. SYPRO Ruby dye outperforms alternatives such as silver staining in terms of quantitative capabilities, compatibility with mass spectrometry and ease of integration into automated work environments.

High Energy, Single-Mode, All-Solid-State Nd:YAG Laser

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Hovis, Floyd

2006-01-01

In this paper, recent progress made in the design and development of an all-solid-state, single longitudinal mode, conductively cooled Nd:YAG laser operating at 1064 nm wavelength for UV lidar for ozone sensing applications is presented. Currently, this pump laser provides an output pulse energy of greater than 1.1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns. The spatial profile of the output beam is a rectangular super Gaussian. Electrical-to-optical system efficiency of greater than 7% and a minimum M(sup 2) value of less than 2 have been achieved.

Raman spectroscopy measurement of CH4 gas and CH4 dissolved in water for laser remote sensing in water

NASA Astrophysics Data System (ADS)

Somekawa, Toshihiro; Fujita, Masayuki

2018-04-01

We examined the applicability of Raman spectroscopy as a laser remote sensing tool for monitoring CH4 in water. The Raman technique has already been used successfully for measurements of CO2 gas in water. In this paper, considering the spectral transmittance of water, third harmonics of Q-switched Nd:YAG laser at 355 nm (UV region) was used for detection of CH4 Raman signals. The Raman signal at 2892 cm-1 from CH4 dissolved in water was detected at a tail of water Raman signal.

Direct Observations of Reaction Zone Structure in Propagating Detonations

DTIC Science & Technology

2003-02-08

with sufficient spatial resolution and signal-to-noise ratio were achieved by using a tunable KrF laser with a pulse energy of 450 mJ exciting the OH...self-sustaining waves within the test section. The detonation reaction zone has been visualized by exciting OH fluorescence at about 284 nm with a...in some tests. The UV light for excitation of the OH molecules is produced by frequency dou- bling the output of an excimer-pumped dye laser. The

A review of visible, near-IR, and mid-IR transitions in rare-earth doped glass waveguides for remote sensing and LIDAR

NASA Astrophysics Data System (ADS)

Jha, Animesh

2006-12-01

In the review article we explain the recent investigations on rare-earth doped glass and optical fibres for designing lasers which may be suitable for remote sensing and LIDAR applications. The paper explains the importance of engineering efficient lasing transitions in visible (480-650 nm) for generating UV lasers via one-stage harmonic generation. Besides visible transitions, we also demonstrate the transitions in near- and mid-IR via near-IR pumping scheme.

Advances in deep-UV processing using cluster tools

NASA Astrophysics Data System (ADS)

Escher, Gary C.; Tepolt, Gary; Mohondro, Robert D.

1993-09-01

Deep-UV laser lithography has shown the capability of supporting the manufacture of multiple generations of integrated circuits (ICs) due to its wide process latitude and depth of focus (DOF) for 0.2 micrometers to 0.5 micrometers feature sizes. This capability has been attained through improvements in deep-UV wide field lens technology, excimer lasers, steppers and chemically amplified, positive deep-UV resists. Chemically amplified deep-UV resists are required for 248 nm lithography due to the poor absorption and sensitivity of conventional novolac resists. The acid catalyzation processes of the new resists requires control of the thermal history and environmental conditions of the lithographic process. Work is currently underway at several resist vendors to reduce the need for these controls, but practical manufacturing solutions exist today. One of these solutions is the integration of steppers and resist tracks into a `cluster tool' or `Lithocell' to insure a consistent thermal profile for the resist process and reduce the time the resist is exposed to atmospheric contamination. The work here reports processing and system integration results with a Machine Technology, Inc (MTI) post-exposure bake (PEB) track interfaced with an advanced GCA XLS 7800 deep-UV stepper [31 mm diameter, variable NA (0.35 - 0.53) and variable sigma (0.3 - 0.74)].

UV irradiation-induced Raman spectra changes in lead silicate glasses

NASA Astrophysics Data System (ADS)

Jia, Hongzhi; Chen, Guanghui; Wang, Wencheng

2006-12-01

The Raman spectra for a series of lead silicate glasses with different PbO content before and after irradiation with different energy density by the frequency-quadrupled output of a Q-switched YAG laser (266 nm, 10 Hz repetition rate) were measured. The intensity of Pb-O band near 140 cm -1 in the Raman spectra decreases after UV irradiation and no new band appears in the Raman spectra. Exposed to the UV beam with high energy density (150 mJ/cm 2), although the total dose is smaller than the dose with low energy density (50 mJ/cm 2), the intensity of the 140 cm -1 band drops heavilier than exposed to the UV beam with low energy density. This shows that the UV irradiation can cause the broken of Pb-O bond in lead silicate glasses and the broken of Pb-O bond is related to the energy density of UV beam.

WATSON: Detecting organic material in subsurface ice using deep-UV fluorescence and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Eshelman, E.; Wanger, G.; Manatt, K.; Malaska, M.; Willis, M.; Abbey, W.; Doloboff, I.; Beegle, L. W.; DeFlores, L. P.; Priscu, J. C.; Lane, A. L.; Carrier, B. L.; Mellerowicz, B.; Kim, D.; Paulsen, G.; Zacny, K.; Bhartia, R.

2017-12-01

Future astrobiological missions to Europa and other ocean worlds may benefit from next-generation instrumentation capable of in situ organic and life detection in subsurface ice environments. WATSON (Wireline Analysis Tool for in Situ Observation of Northern ice sheets) is an instrument under development at NASA's Jet Propulsion Laboratory. WATSON contains high-TRL instrumentation developed for SHERLOC, the Mars 2020 deep-UV fluorescence and Raman spectrometer, including a 248.6 nm NeCu hollow cathode laser as an excitation source. In WATSON, these technologies provide spectroscopic capabilities highly sensitive to many organic compounds, including microbes, in an instrument package approximately 1.2 m long with a 101.6 mm diameter, designed to accommodate a 108 mm ice borehole. Interrogation into the ice wall with a laser allows for a non-destructive in situ measurement that preserves the spatial distribution of material within the ice. We report on a successful deployment of WATSON to Kangerlussuaq, Greenland, where the instrument was lowered to a 4.5 m depth in a hand-cored hole on the Kangerlussuaq sector of the Greenland ice sheet. Motorized stages within the instrument were used to raster a laser across cm-scale regions of the interior surface of the borehole, obtaining fluorescence spectral maps with a 200 µm spatial resolution and a spectral range from 265 nm to 440 nm. This region includes the UV emission bands of many aromatic compounds and microbes, and includes the water and ice Raman O-H stretching modes. We additionally report on experiments designed to inform an early-2018 deployment to Kangerlussuaq where WATSON will be incorporated into a Honeybee Robotics planetary deep drill, with a goal of drilling to a depth of 100 m and investigating the distribution of organic material within the ice sheet. These experiments include laboratory calibrations to determine the sensitivity to organic compounds embedded in ice at various depths, as well as analysis of ice cores obtained during the deployment and returned for subsequent study.

Local residual stress monitoring of aluminum nitride MEMS using UV micro-Raman spectroscopy

DOE PAGES

Choi, Sukwon; Griffin, Benjamin A.

2016-01-06

Localized stress variation in aluminum nitride (AlN) sputtered on patterned metallization has been monitored through the use of UV micro-Raman spectroscopy. This technique utilizing 325 nm laser excitation allows detection of the AlN E2(high) phonon mode in the presence of metal electrodes beneath the AlN layer with a high spatial resolution of less than 400 nm. The AlN film stress shifted 400 MPa from regions where AlN was deposited over a bottom metal electrode versus silicon dioxide. Thus, across wafer stress variations were also investigated showing that wafer level stress metrology, for example using wafer curvature measurements, introduces large uncertaintiesmore » for predicting the impact of AlN residual stress on the device performance.« less

Effects of γ-ray irradiation on optical absorption and laser damage performance of KDP crystals containing arsenic impurities.

PubMed

Guo, D C; Jiang, X D; Huang, J; Wang, F R; Liu, H J; Xiang, X; Yang, G X; Zheng, W G; Zu, X T

2014-11-17

The effects of γ-irradiation on potassium dihydrogen phosphate crystals containing arsenic impurities are investigated with different optical diagnostics, including UV-VIS absorption spectroscopy, photo-thermal common-path interferometer and photoluminescence spectroscopy. The optical absorption spectra indicate that a new broad absorption band near 260 nm appears after γ-irradiation. It is found that the intensity of absorption band increases with the increasing irradiation dose and arsenic impurity concentration. The simulation of radiation defects show that this absorption is assigned to the formation of AsO₄⁴⁻ centers due to arsenic ions substituting for phosphorus ions. Laser-induced damage threshold test is conducted by using 355 nm nanosecond laser pulses. The correlations between arsenic impurity concentration and laser induced damage threshold are presented. The results indicate that the damage performance of the material decreases with the increasing arsenic impurity concentration. Possible mechanisms of the irradiation-induced defects formation under γ-irradiation of KDP crystals are discussed.

Effect of ablation time on femtosecond laser synthesis of Au- Ag colloidal nanoalloys

NASA Astrophysics Data System (ADS)

Hidayah, A. N.; Triyono, D.; Herbani, Y.; Isnaeni; Suliyanti, M. M.

2018-03-01

Au-Ag nanoalloys have been synthesized by laser irradiation technique. First, Au and Ag nanoparticles were prepared from Au and Ag pure metal (99.9%) ablated using an 800 nm femtosecond laser in distilled water. Using the same laser, Au and Ag nanoparticle with 1:1 ratio were subsequently mixed and irradiated with various irradiation time, i.e. 0, 5, 20, and 35 minutes. We varied the ablation time for each metal nanoparticles, i.e. 25 minutes and 1 hour to see its effect on the production of nanoalloys in the subsequent irradiation. Au-Ag nanoalloys were characterized and analyzed using transmission electron microscope and UV-Vis spectrophotometry. The result shows that Au-Ag nanoalloys were already formed in 20 minutes irradiation, either for the sample ablated for 25 minutes or 1 hour. The result of TEM shows that the size of Au-Ag nanoalloys prepared from 1 hour ablation was around 15.03 nm.

Elicitation of trans-resveratrol by laser resonant irradiation of table grapes

NASA Astrophysics Data System (ADS)

Jiménez Sánchez, J. B.; Crespo Corral, E.; Orea, J. M.; Santos Delgado, M. J.; González Ureña, A.

2007-05-01

Table grapes were irradiated with UV nanosecond laser pulses in searching for resonant photo-elicitation of trans-resveratrol, a known antioxidant compound naturally produced by grapevines and other plants. To this end, the irradiation time as well as the wavelength dependence of the induced trans-resveratrol content was investigated by comparing the elicitation level of this compound at two laser wavelengths. One wavelength was selected right at the maximum of the absorption band (302.1 nm, the resonant wavelength for this compound) while the second was selected (300 nm, a non-resonant wavelength) such that trans-resveratrol absorption is negligible. It was found that the resonant irradiation enhances the resveratrol content in grapes by up to six times more than that of non-resonant irradiation, the rest of the conditions being the same. This work demonstrates how selective laser excitation of fruits can open new possibilities for the development of functional foods with enhanced nutritional and beneficial properties.

Laser fluorescence spectrometers for medical diagnosis

NASA Astrophysics Data System (ADS)

Kwasny, Miroslaw; Mierczyk, Zygmunt

2000-11-01

The paper presents fibre fluorescence analysers for in vivo examined biological tissues. The systems devoted to clinical investigations are equipped with laser excitation sources; He-Cd (442 nm), Nd:YAG (II and III harmonic: 532 and 355 nm, respectively) and He-Ne (632.8 nm). They allow non-invasive determination of endogenous fluorophones level in any organs as well as monitoring of external sensitisers level when photodynamic method of diagnosis and treatment of tumors is used. Selection of various wavelengths within the range of porphyrines, excitation depends on different light penetration in various tissues. For the tumors localised under mucous membrane, UV, violet, and blue radiation was used for excitation and for deeply localised tumors, a radiation of longer wavelengths (green and red) was used. The carried out clinical examinations showed usefulness of fluorometric systems for diagnostics of skin diseases, gynaecological spheres, and pneumopathies. These analysers can be also applied for environmental protection, food control, and industrial processes monitoring.

Imaging charge transfer in a cation-π system: velocity-map imaging of Ag(+)(benzene) photodissociation.

PubMed

Maner, Jonathon A; Mauney, Daniel T; Duncan, Michael A

2015-11-19

Ag(+)(benzene) complexes are generated in the gas phase by laser vaporization and mass selected in a time-of-flight spectrometer. UV laser excitation at either 355 or 266 nm results in dissociative charge transfer (DCT), leading to neutral silver atom and benzene cation products. Kinetic energy release in translationally hot benzene cations is detected using a new instrument designed for photofragment imaging of mass-selected ions. Velocity-map imaging and slice imaging techniques are employed. In addition to the expected translational energy release, DCT of Ag(+)(benzene) produces a distribution of internally hot benzene cations. Compared with experiments at 355 nm, 266 nm excitation produces only slightly higher translational excitation and a much greater fraction of internally hot benzene ions. The maximum kinetic energy release in the photodissociation sets an upper limit on the Ag(+)(benzene) dissociation energy of 32.8 (+1.4/-1.5) kcal/mol.

Pulse laser ablation of Au, Ag, and Cu metal targets in liquid for nanoparticle production

NASA Astrophysics Data System (ADS)

Herbani, Y.; Irmaniar; Nasution, R. S.; Mujtahid, F.; Masse, S.

2018-03-01

We have fabricated metal and oxide nanoparticles using pulse laser ablation of Au, Ag, and Cu metal targets immersed in water. While laser ablation of Au and Ag targets in water produced metal nanoparticles which were stable for a month even without any dispersant, we found CuO nanoparticles for Cu target due to rapid oxidation of Cu in water resulted in its poor stability. Au, Ag, and CuO nanoparticles production were barely identified by naked eyes for their distinctive colour of red, yellow, and dark green colloidal suspensions, respectively. It was also verified using UV-Vis spectrometer that Au, Ag, and CuO colloidal nanoparticles have their respective surface plasmon resonance at 520, 400, and 620 nm. TEM observation showed that particle sizes for all the fabricated nanoparticles were in the range of 20 – 40 nm with crystalline structures.

Antireflection effect of femtosecond laser-induced periodic surface structures on silicon.

PubMed

Vorobyev, A Y; Guo, Chunlei

2011-09-12

Following direct femtosecond laser pulse irradiation, we produce a unique grating structure over a large area superimposed by finer nanostructures on a silicon wafer. We study, for the first time, the antireflection effect of this femtosecond laser-induced periodic surface structures (FLIPSSs) in the wavelength range of 250 - 2500 nm. Our study shows that the FLIPSSs suppress both the total hemispherical and specular polarized reflectance of silicon surface significantly over the entire studied wavelength range. The total polarized reflectance of the processed surface is reduced by a factor of about 3.5 in the visible and 7 in the UV compared to an untreated sample. The antireflection effect of the FLIPSS surface is broadband and the suppression stays to the longest wavelength (2500 nm) studied here although the antireflection effect in the infrared is weaker than in the visible. Our FLIPSS structures are free of chemical contamination, highly durable, and easily controllable in size.

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

NASA Astrophysics Data System (ADS)

Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

2018-03-01

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

Minimal invasive control of paintings cleaning by LIBS

NASA Astrophysics Data System (ADS)

Staicu, A.; Apostol, I.; Pascu, A.; Urzica, I.; Pascu, M. L.; Damian, V.

2016-03-01

In cultural heritage restoration and conservation, it has been proved that LIBS is an appropriate technique for pigments identification, analysis of multilayered paintings, and quantitative analysis of ancient materials. Generally, experiments involving the use of laser for paint cleaning and LIBS in order to identify the composition of the removed material are made. Here, we report LIBS studies on mastic and dammar varnishes removal using visible (532 nm) and UV (266 nm) laser pulses (5 ns) with fluences in the range 0.6-4.4 J/cm2. The studied varnish layers were on-purpose painted on glass supports or were part of several mock-up samples having dammar or mastic as final layer - gold foil, yellow ochre or cobalt blue egg tempera as painting layer - chalk or acrylic ground as link to an wooden support. LIBS was used to monitor the laser induced stepwise selective removal of the layers and to analyze their composition.

Deep Ultraviolet Light Emitters Based on (Al,Ga)N/GaN Semiconductor Heterostructures

NASA Astrophysics Data System (ADS)

Liang, Yu-Han

Deep ultraviolet (UV) light sources are useful in a number of applications that include sterilization, medical diagnostics, as well as chemical and biological identification. However, state-of-the-art deep UV light-emitting diodes and lasers made from semiconductors still suffer from low external quantum efficiency and low output powers. These limitations make them costly and ineffective in a wide range of applications. Deep UV sources such as lasers that currently exist are prohibitively bulky, complicated, and expensive. This is typically because they are constituted of an assemblage of two to three other lasers in tandem to facilitate sequential harmonic generation that ultimately results in the desired deep UV wavelength. For semiconductor-based deep UV sources, the most challenging difficulty has been finding ways to optimally dope the (Al,Ga)N/GaN heterostructures essential for UV-C light sources. It has proven to be very difficult to achieve high free carrier concentrations and low resistivities in high-aluminum-containing III-nitrides. As a result, p-type doped aluminum-free III-nitrides are employed as the p-type contact layers in UV light-emitting diode structures. However, because of impedance-mismatch issues, light extraction from the device and consequently the overall external quantum efficiency is drastically reduced. This problem is compounded with high losses and low gain when one tries to make UV nitride lasers. In this thesis, we provide a robust and reproducible approach to resolving most of these challenges. By using a liquid-metal-enabled growth mode in a plasma-assisted molecular beam epitaxy process, we show that highly-doped aluminum containing III-nitride films can be achieved. This growth mode is driven by kinetics. Using this approach, we have been able to achieve extremely high p-type and n-type doping in (Al,Ga)N films with high aluminum content. By incorporating a very high density of Mg atoms in (Al,Ga)N films, we have been able to show, by temperature-dependent photoluminescence, that the activation energy of the acceptors is substantially lower, thus allowing a higher hole concentration than usual to be available for conduction. It is believed that the lower activation energy is a result of an impurity band tail induced by the high Mg concentration. The successful p-type doping of high aluminum-content (Al,Ga)N has allowed us to demonstrate operation of deep ultraviolet LEDs emitting at 274 nm. This achievement paves the way for making lasers that emit in the UV-C region of the spectrum. In this thesis, we performed preliminary work on using our structures to make UV-C lasers based on photonic crystal nanocavity structures. The nanocavity laser structures show that the threshold optical pumping power necessary to reach lasing is much lower than in conventional edge-emitting lasers. Furthermore, the photonic crystal nanocavity structure has a small mode volume and does not need mirrors for optical feedback. These advantages significantly reduce material loss and eliminate mirror loss. This structure therefore potentially opens the door to achieving efficient and compact lasers in the UV-C region of the spectrum.

Laser photolysis of caged compounds at 405 nm: photochemical advantages, localisation, phototoxicity and methods for calibration.

PubMed

Trigo, Federico F; Corrie, John E T; Ogden, David

2009-05-30

Rapid, localised photolytic release of neurotransmitters from caged precursors at synaptic regions in the extracellular space is greatly hampered at irradiation wavelengths in the near-UV, close to the wavelength of maximum absorption of the caged precursor, because of inner-filtering by strong absorption of light in the cage solution between the objective and cell. For this reason two-photon excitation is commonly used for photolysis, particularly at multiple points distributed over large fields; or, with near-UV, if combined with local perfusion of the cage. These methods each have problems: the small cross-sections of common cages with two-photon excitation require high cage concentrations and light intensities near the phototoxic limit, while local perfusion gives non-uniform cage concentrations over the field of view. Single-photon photolysis at 405 nm, although less efficient than at 330-350 nm, with present cages is more efficient than two-photon photolysis. The reduced light absorption in the bulk cage solution permits efficient wide-field uncaging at non-toxic intensities with uniform cage concentration. Full photolysis of MNI-glutamate with 100 micros pulses required intensities of 2 mW microm(-2) at the preparation, shown to be non-toxic with repeated exposures. Light scattering at 405 nm was estimated as 50% at 18 microm depth in 21-day rat cerebellum. Methods are described for: (1) varying the laser spot size; (2) photolysis calibration in the microscope with the caged fluorophore NPE-HPTS over the wavelength range 347-405 nm; and (3) determining the point-spread function of excitation. Furthermore, DM-Nitrophen photolysis at 405 nm was efficient for intracellular investigations of Ca2+-dependent processes.

Efficient Third Harmonic Generation for Wind Lidar Applications

NASA Technical Reports Server (NTRS)

Mordaunt, David W.; Cheung, Eric C.; Ho, James G.; Palese, Stephen P.

1998-01-01

The characterization of atmospheric winds on a global basis is a key parameter required for accurate weather prediction. The use of a space based lidar system for remote measurement of wind speed would provide detailed and highly accurate data for future weather prediction models. This paper reports the demonstration of efficient third harmonic conversion of a 1 micrometer laser to provide an ultraviolet (UV) source suitable for a wind lidar system based on atmospheric molecular scattering. Although infrared based lidars using aerosol scattering have been demonstrated to provide accurate wind measurement, a UV based system using molecular or Rayleigh scattering will provide accurate global wind measurements, even in those areas of the atmosphere where the aerosol density is too low to yield good infrared backscatter signals. The overall objective of this work is to demonstrate the maturity of the laser technology and its suitability for a near term flight aboard the space shuttle. The laser source is based on diode-pumped solid-state laser technology which has been extensively demonstrated at TRW in a variety of programs and internal development efforts. The pump laser used for the third harmonic demonstration is a breadboard system, designated the Laser for Risk Reduction Experiments (LARRE), which has been operating regularly for over 5 years. The laser technology has been further refined in an engineering model designated as the Compact Advanced Pulsed Solid-State Laser (CAPSSL), in which the laser head was packaged into an 8 x 8 x 18 inch volume with a weight of approximately 61 pounds. The CAPSSL system is a ruggedized configuration suitable for typical military applications. The LARRE and CAPSSL systems are based on Nd:YAG with an output wavelength of 1064 nm. The current work proves the viability of converting the Nd:YAG fundamental to the third harmonic wavelength at 355 nm for use in a direct detection wind lidar based on atmospheric Rayleigh scattering.

Growth behavior of laser-induced damage on fused silica optics under UV, ns laser irradiation.

PubMed

Negres, Raluca A; Norton, Mary A; Cross, David A; Carr, Christopher W

2010-09-13

The growth behavior of laser-induced damage sites is affected by a large number of laser parameters as well as site morphology. Here we investigate the effects of pulse duration on the growth rate of damage sites located on the exit surface of fused silica optics. Results demonstrate a significant dependence of the growth parameters on laser pulse duration at 351 nm from 1 ns to 15 ns, including the observation of a dominant exponential versus linear, multiple-shot growth behavior for long and short pulses, respectively. These salient behaviors are tied to the damage morphology and suggest a shift in the fundamental growth mechanisms for pulses in the 1-5 ns range.

Laser direct writing of thin-film copper structures as a modification of lithographic processes

NASA Astrophysics Data System (ADS)

Meyer, F.; Ostendorf, A.; Stute, U.

2007-04-01

This paper presents a flexible, mask-free and efficient technique for UV-laser micropatterning of photosensitive resist by laser direct writing (LDW). Photo resist spun on gold sputtered silicon wafers has been laser structured by a scanner guided 266nm DPSSL and electroplated. Ablation behaviour and optimum seed layer preparation in relation to parameters like pulse energy, scanning speed and number of scanned cycles and the electroplating results are discussed. The resulting adhesive strength was measured by a µ-sear device and the gold seed layer-plated copper interface investigated by SEM and EDX to explain correlation to identified bonding behaviour. Improved adhesive strength was observed with higher laser pulse energy and reduced number of cycle.

Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

NASA Astrophysics Data System (ADS)

Farrokhi, H.; Gruzdev, V.; Zheng, H. Y.; Rawat, R. S.; Zhou, W.

2016-06-01

A constant magnetic field can significantly improve the quality and speed of ablation by nanosecond laser pulses. These improvements are usually attributed to the confinement of laser-produced plasma by the magnetic field and specific propagation effects in the magnetized plasma. Here we report a strong influence of constant axial magnetic field on the ablation of silicon by 20-ns laser pulses at wavelength 355 nm, which results in an increase of ablation depth by a factor of 1.3 to 69 depending on laser parameters and magnitude of the magnetic field. The traditional plasma effects do not explain this result, and magneto-absorption of silicon is proposed as one of the major mechanisms of the significant enhancement of ablation.

Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures

NASA Astrophysics Data System (ADS)

D'Urso, Luisa; Spadaro, Salvatore; Bonsignore, Martina; Santangelo, Saveria; Compagnini, Giuseppe; Neri, Fortunato; Fazio, Enza

2018-01-01

Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10-50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.

High speed fabrication of absorbance-enhanced micro-nanostructures on nickel surface using hundred-nanosecond pulsed laser

NASA Astrophysics Data System (ADS)

Fu, Jinxiang; Zhang, Jingyuan; Liang, Hao; Wang, Yibo; Zhang, Zhiyan; Liu, Yannan; Lin, Xuechun

2017-01-01

We report the generation of micro-nanostructures on nickel surface using a pulsed laser with pulse duration of 100/200 ns. The blacken nickel, which is covered with dense broccoli-like clusters having strong light trapping capacity covering broad spectrum (200-2000 nm), can be produced at a high laser scanning speed up to 100 mm/s. The absorbance of the blacken nickel can be over 98% in the UV, more than 97% in the visible, and over 90% in the near IR. In addition, by treating the nickel surface with two crossing scans of the laser, highly organized and shape-controllable periodic arrays of hump-craters can be fabricated.

UV- Vis- NIR and luminescent characterization of PZCdO:Tm laser oxide glasses

NASA Astrophysics Data System (ADS)

Al-Assiri, M. S.; Algarni, H.; Reben, M.; Yousef, E.; Hegazy, H. H.; AbouDeif, Y. M.; Umar, Ahmad

2017-11-01

The luminescent oxide glasses with composition 50P2O5- 30ZnO- 20CdO (PZCdO pure) and 50P2O5- 30ZnO- 20CdO- 30000 ppm Tm2O3 (PZCdO:Tm) were synthesized by using melt- quenching technique. The optical energy gap and Urbach energy of these glasses were calculated by using UV-Vis-NIR spectroscopy. Judd- Ofelt parameters Ω2, Ω4 and Ω6, branching ratio, βR, and radiative lifetimes, τR, of Tm3+ ions doped PZCdO glasses were estimated. The spectroscopic results showed that the present glasses has the effective emission cross section bandwidth (Δλeff = 90 nm) and high stimulated emission cross-section (σem = 1.5 × 10-21 cm2). The blue up conversion emissions sharp band at 458 nm corresponding to transition 1D2 → 3F6 and weak emission band in NIR region assigned to 1G4→3H4 for the glasses PZCdO:Tm with UV- excited at 354 nm region were obtained. From result we can suggest that the present glasses can be used for blue light emitting diodes BLED chip.

[Two-photon up-conversion fluorescence of a neodymium organic framework Nd(BTC)].

PubMed

Xu, Hui; Jin, Run-zhi; Wu, Chun-yang; Yang, Yu; Qian, Guo-dong

2008-08-01

In the present work, a neodymium organic framework Nd(BTC) was synthesized by the solvothermal reaction of Nd(NO3)3 x 5H2O and H3BTC (BTC = 1,3,5-benzenetricarboxylate) in mixed solvents of DMF, ethanol and water, and was identified by elemental analysis. This MOF complex was characterized using X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TGA-DSC) analysis, UV-visible absorption spectra and fluorescence spectra. This polycrystalline powder lost DMF and H2O when heated to 120 degrees C, then remained stable till the temperature reached 500 degrees C. Near infrared fluorescence at 1064 nm due to the 4 F3/2--> 4 I11/2 transition of Nd3+ ions was exhibited when excited by 808 nm laser beam. It was also been found that up-conversion fluorescence of Nd(BTC) peaked at about 450 nm due to 2 D5/2 -->4 I11/2 transition of Nd3+ ions can be observed under the excitation of a 580 nm laser line. The mechanism of the up-conversion fluorescence of Nd(BTC) at around 450 nm under the excitation of 580 nm laser can be ascribed to both excited-state absorption and energy transfer up-conversion. This result indicated that such MOF can be employed as an up-conversion luminescence material in many potential application areas such as bio-labeling and fluorescence image.

Laser-assisted biosynthesis for noble nanoparticles production

NASA Astrophysics Data System (ADS)

Kukhtarev, Tatiana; Edwards, Vernessa; Kukhtareva, Nickolai; Moses, Sherita

2014-08-01

Extracellular Biosynthesis technique (EBS) for nanoparticles production has attracted a lot of attention as an environmentally friendly and an inexpensive methodology. Our recent research was focused on the rapid approach of the green synthesis method and the reduction of the homogeneous size distribution of nanoparticles using pulse laser application. Noble nanoparticles (NNPs) were produced using various ethanol and water plant extracts. The plants were chosen based on their biomedical applications. The plants we used were Magnolia grandiflora, Geranium, Aloe `tingtinkie', Aloe barbadensis (Aloe Vera), Eucalyptus angophoroides, Sansevieria trifasciata, Impatiens scapiflora. Water and ethanol extract, were used as reducing agents to produce the nanoparticles. The reaction process was monitored using a UV-Visible spectroscopy. NNPs were characterized by Fourier Transfer Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and the Dynamic Light Scattering technique (DLS). During the pulse laser Nd-YAG illumination (λ=1064nm, 532nm, PE= 450mJ, 200mJ, 10 min) the blue shift of the surface plasmon resonance absorption peak was observed from ~424nm to 403nm for silver NP; and from ~530nm to 520 nm for gold NPs. In addition, NNPs solution after Nd-YAG illumination was characterized by the narrowing of the surface plasmon absorption resonance band, which corresponds to monodispersed NNPS distribution. FTIR, TEM, DLS, Zeta potential results demonstrated that NNPs were surrounded by biological molecules, which naturally stabilized nanosolutions for months. Cytotoxicity investigation of biosynthesized NNPs is in progress.

Efficiency of magnetorheological fluid finishing on the elimination of defects in fused silica optics

NASA Astrophysics Data System (ADS)

Catrin, R.; Taroux, D.; Cormont, P.; Maunier, C.; Corbineau, T.; Razé, G.; Néauport, J.

2013-09-01

The MegaJoule laser being constructed at the CEA near Bordeaux (France) is designed to focus more than 1 MJ of energy of UV light, on a millimeter scale target in the centre of an experiment chamber. After amplification and transport at the wavelength of 1053 nm, frequency conversion at 351 nm is done with KH2PO4 crystals. The final optic assembly of this system is made up of large fused silica optics, working in transmission, that are used to convey, focus or shape the laser beam. When exposed to fluences of some joules per square centimeter at 351 nm within nanosecond pulse duration, fused silica optics can exhibit localized damage. Damage sites grow exponentially after further laser exposition and therefore dramatically limit the optic lifetime. The nature of the surface finishing process has been established to determine the lifetime of these components under high UV fluences (i.e. more than 5 J/cm2 for 3 ns pulses). Being able to reduce or eliminate the damage initiators such as subsurface cracks present in subsurface damage (SSD) layer of conventionally polished optical components aims this study. Magneto-rheological fluid finishing (MRF) is chosen as a final polishing tool to remove layers of material without inducing further damages. MRF enables to process optics with very small normal stresses applied to the surface during material removal and thus permits the elimination of the residual subsurface cracks. This study offers a better understanding of the efficiency of MRF polishing on the elimination of subsurface cracks in SSD layers.

High performance organic distributed Bragg reflector lasers fabricated by dot matrix holography.

PubMed

Wan, Wenqiang; Huang, Wenbin; Pu, Donglin; Qiao, Wen; Ye, Yan; Wei, Guojun; Fang, Zongbao; Zhou, Xiaohong; Chen, Linsen

2015-12-14

We report distributed Bragg reflector (DBR) polymer lasers fabricated using dot matrix holography. Pairs of distributed Bragg reflector mirrors with variable mirror separations are fabricated and a novel energy transfer blend consisting of a blue-emitting conjugated polymer and a red-emitting one is spin-coated onto the patterned substrate to complete the device. Under optical pumping, the device emits sing-mode lasing around 622 nm with a bandwidth of 0.41 nm. The working threshold is as low as 13.5 μJ/cm² (~1.68 kW/cm²) and the measured slope efficiency reaches 5.2%. The distributed feedback (DFB) cavity and the DBR cavity resonate at the same lasing wavelength while the DFB laser shows a much higher threshold. We further show that flexible DBR lasers can be conveniently fabricated through the UV-imprinting technique by using the patterned silica substrate as the mold. Dot matrix holography represents a versatile approach to control the number, the size, the location and the orientation of DBR mirrors, thus providing great flexibility in designing DBR lasers.

Calibration of a tunable excimer laser using the optogalvanic effect

NASA Technical Reports Server (NTRS)

Abbitt, John D.

1991-01-01

A device for the calibration of a tunable excimer laser is currently under development. The laser provides UV radiation at three principal wavelengths, 193, 248, and 308 nm and is tunable over a range of 1 nm at each of these wavelengths. The laser is used as a non-intrusive optical probe to excite electronic transitions, and thereby induce fluorescence, of the principle molecules or atoms of interest in supersonic flowfields, both reacting and nonreacting. The fluorescence resulting from the excitation is observed with an intensified camera. Over the range of tunability at the three wavelengths are a number of transitions that can be observed. The intensity of the fluorescence depends in part on the local temperature and density. The nature of this thermodynamic dependence is variable among transitions; thus, identification of the transition under observation is required. The specific transition excited corresponds directly to the wavelength of the radiation. The present technique used for transition identification consists of scanning the laser across the range of tunability and observing the fluorescence resulting from various molecular transitions.

Analysis of Biomolecules by Atmospheric Pressure Visible-Wavelength MALDI-Ion Trap-MS in Transmission Geometry

NASA Astrophysics Data System (ADS)

West, Raymond E.; Findsen, Eric W.; Isailovic, Dragan

2013-10-01

We report the development of a new AP visible-wavelength MALDI-ion trap-MS instrument with significantly improved performance over our previously reported system ( Int. J. Mass Spectrom. 315, 66-73 (2012)). A Nd:YAG pulsed laser emitting light at 532 nm was used to desorb and ionize oligosaccharides and peptides in transmission geometry through a glass slide. Limits of detection (LODs) achieved in MS mode correspond to picomole quantities of oligosaccharides and femtomole quantities of peptides. Tandem MS (MS/MS) experiments enabled identification of enzymatically digested proteins and oligosaccharides by comparison of MS/MS spectra with data found in protein and glycan databases. Moreover, the softness of ionization, LODs, and fragmentation spectra of biomolecules by AP visible-wavelength MALDI-MS were compared to those obtained by AP UV MALDI-MS using a Nd:YAG laser emitting light at 355 nm. AP visible-wavelength MALDI appears to be a softer ionization technique then AP UV MALDI for the analysis of sulfated peptides, while visible-wavelength MALDI-MS, MS/MS, and MS/MS/MS spectra of other biomolecules analyzed were mostly similar to those obtained by AP UV MALDI-MS. Therefore, the methodology presented will be useful for MS and MSn analyses of biomolecules at atmospheric pressure. Additionally, the AP visible-wavelength MALDI developed can be readily used for soft ionization of analytes on various mass spectrometers.

Optical and structure characterization of cinnamon nanoparticles synthesized by pulse laser ablation in liquid (PLAL)

NASA Astrophysics Data System (ADS)

Aqeel Salim, Ali; Bidin, Noriah; Bakhtiar, Hazri; Krishna Ghoshal, Sib; Azawi, Mohammed Al; Krishnan, Ganesan

2018-05-01

Organic nanoparticles development is under exploration due to its beneficial applications in nanobiomedical and research interests. PLAL technique of Q-switched 1064-Nd: YAG (10 ns pulse duration, repetition rate 1 Hz and laser energy 20-100 mJ) has inherent advantages and rapid growth of nanoparticles when compared to conventional methods because of the controlled fabricated nanoparticles, stability, and purity. Cinnamon sticks as a target are immersed in 5 ml ethanol medium and irradiated by a laser beam for the growth process. The morphology, optical characteristic, and bonding structure of cinnamon nanoparticles (CNPs) are determined and evaluated by transmission electron microscope (TEM), UV-Visible spectroscopy and Fourier transform infrared spectroscopy (FTIR). Spherical, homogenous and high crystallinity CNPs was revealed within the particle size range of 2 - 28 nm. The absorption band was found in the ultraviolent region around 259 nm and 319 nm. The present of FTIR spectra confirmed that the nanoparticles were covered by plant secondary metabolites. The experimental findings revealed that the synthesize CNPs in ethanol has a potential for nanomedicine applications.

UV photodissociation of proline-containing peptide ions: insights from molecular dynamics.

PubMed

Girod, Marion; Sanader, Zeljka; Vojkovic, Marin; Antoine, Rodolphe; MacAleese, Luke; Lemoine, Jérôme; Bonacic-Koutecky, Vlasta; Dugourd, Philippe

2015-03-01

UV photodissociation of proline-containing peptide ions leads to unusual product ions. In this paper, we report laser-induced dissociation of a series of proline-containing peptides at 213 nm. We observe specific fragmentation pathways corresponding to the formation of (y-2), (a + 2) and (b + 2) fragment ions. This was not observed at 266 nm or for peptides which do not contain proline residues. In order to obtain insights into the fragmentation dynamics at 213 nm, a small peptide (RPK for arginine-proline-lysine) was studied both theoretically and experimentally. Calculations of absorption spectra and non-adiabatic molecular dynamics (MD) were made. Second and third excited singlet states, S(2) and S(3), lie close to 213 nm. Non-adiabatic MD simulation starting from S(2) and S(3) shows that these transitions are followed by C-C and C-N bond activation close to the proline residue. After this first relaxation step, consecutive rearrangements and proton transfers are required to produce unusual (y-2), (a + 2) and (b + 2) fragment ions. These fragmentation mechanisms were confirmed by H/D exchange experiments.

UV Photodissociation of Proline-containing Peptide Ions: Insights from Molecular Dynamics

NASA Astrophysics Data System (ADS)

Girod, Marion; Sanader, Zeljka; Vojkovic, Marin; Antoine, Rodolphe; MacAleese, Luke; Lemoine, Jérôme; Bonacic-Koutecky, Vlasta; Dugourd, Philippe

2015-03-01

UV photodissociation of proline-containing peptide ions leads to unusual product ions. In this paper, we report laser-induced dissociation of a series of proline-containing peptides at 213 nm. We observe specific fragmentation pathways corresponding to the formation of (y-2), (a + 2) and (b + 2) fragment ions. This was not observed at 266 nm or for peptides which do not contain proline residues. In order to obtain insights into the fragmentation dynamics at 213 nm, a small peptide (RPK for arginine-proline-lysine) was studied both theoretically and experimentally. Calculations of absorption spectra and non-adiabatic molecular dynamics (MD) were made. Second and third excited singlet states, S2 and S3, lie close to 213 nm. Non-adiabatic MD simulation starting from S2 and S3 shows that these transitions are followed by C-C and C-N bond activation close to the proline residue. After this first relaxation step, consecutive rearrangements and proton transfers are required to produce unusual (y-2), (a + 2) and (b + 2) fragment ions. These fragmentation mechanisms were confirmed by H/D exchange experiments.

Dominant transverse-electric polarized emission from 298 nm MBE-grown AlN-delta-GaN quantum well ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Liu, Cheng; Ooi, Yu Kee; Islam, S. M.; Xing, Huili Grace; Jena, Debdeep; Zhang, Jing

2017-02-01

III-nitride based ultraviolet (UV) light emitting diodes (LEDs) are of considerable interest in replacing gas lasers and mercury lamps for numerous applications. Specifically, AlGaN quantum well (QW) based LEDs have been developed extensively but the external quantum efficiencies of which remain less than 10% for wavelengths <300 nm due to high dislocation density, difficult p-type doping and most importantly, the physics and band structure from the three degeneration valence subbands. One solution to address this issue at deep UV wavelengths is by the use of the AlGaN-delta-GaN QW where the insertion of the delta-GaN layer can ensure the dominant conduction band (C) - heavyhole (HH) transition, leading to large transverse-electric (TE) optical output. Here, we proposed and investigated the physics and polarization-dependent optical characterizations of AlN-delta- GaN QW UV LED at 300 nm. The LED structure is grown by Molecular Beam Epitaxy (MBE) where the delta-GaN layer is 3-4 monolayer (QW-like) sandwiched by 2.5-nm AlN sub-QW layers. The physics analysis shows that the use of AlN-delta-GaN QW ensures a larger separation between the top HH subband and lower-energy bands, and strongly localizes the electron and HH wave functions toward the QW center and hence resulting in 30-time enhancement in TEpolarized spontaneous emission rate, compared to that of a conventional Al0.35Ga0.65N QW. The polarization-dependent electroluminescence measurements confirm our theoretical analysis; a dominant TE-polarized emission was obtained at 298 nm with a minimum transverse-magnetic (TM) polarized emission, indicating the feasibility of high-efficiency TEpolarized UV emitters based on our proposed QW structure.

Utilizing Laser-Induced Breakdown Spectroscopy Method to recognize chemical composition of low-carbon steel in NH3(NO)4 material

NASA Astrophysics Data System (ADS)

Saud Oraibi, Nissan

2018-05-01

A standoff laser Induced Break down Spectroscopy (L.I.B.S) technique has been used to characterization the organic material such as NH3(NO)4, a Q-switched Nd:YAG laser (1064 nm wavelength, 9 ns pulse width and 1 Hz repetition rate, 300 mJ is focused to the targets to generate plasma. HR 4000 CG-UV-NIR spectrum analyzer was used to collect the generated plasma emissions, specific signature of each targets material can be obtained by analysis the plasma emission spectrum Peak ratio analysis technique is used for the identification of energetic materials.

Efficient second to ninth harmonic generation using megawatt peak power microchip laser.

PubMed

Bhandari, R; Tsuji, N; Suzuki, T; Nishifuji, M; Taira, T

2013-11-18

We report the design and use of a megawatt peak power Nd:YAG/Cr4+:YAG microchip laser for efficient second to ninth harmonic generation. We show that the sub-nanosecond pulse width region, between 100 ps and 1 ns, is ideally suited for efficient wavelength conversion. Using this feature, we report 85% second harmonic generation efficiency using lithium triborate (LBO), 60% fourth harmonic generation efficiency usingß-barium borate, and 44% IR to UV third harmonic generation efficiency using Type I and Type II LBO. Finally, we report the first demonstration of 118 nm VUV generation in xenon gas using a microchip laser.

Efficient visible and UV generation by frequency conversion of a mode-filtered fiber amplifier

NASA Astrophysics Data System (ADS)

Kliner, Dahv A. V.; Di Teodoro, Fabio; Koplow, Jeffrey P.; Moore, Sean W.; Smith, Arlee V.

2003-07-01

We have generated the second, third, fourth, and fifth harmonics of the output of a Yb-doped fiber amplifier seeded by a passively Q-switched Nd:YAG microchip laser. The fiber amplifier employed multimode fiber (25 μm core diameter, V ~ 7.4) to provide high-peak-power pulses, but diffraction-limited beam quality was obtained by use of bend-loss-induced mode filtering. The amplifier output had a pulse duration of 0.97 ns and smooth, transform-limited temporal and spectral profiles (~500 MHz linewidth). We obtained high nonlinear conversion efficiencies using a simple optical arrangement and critically phase-matched crystals. Starting with 320 mW of average power at 1064 nm (86 ´J per pulse at a 3.7 kHz repetition rate), we generated 160 mW at 532 nm, 38 mW at 355 nm, 69 mW at 266 nm, and 18 mW at 213 nm. The experimental results are in excellent agreement with calculations. Significantly higher visible and UV powers will be possible by operating the fiber amplifier at higher repetition rates and pulse energies and by further optimizing the nonlinear conversion scheme.

Laser-based measurements of OH in high pressure CH4/air flames

NASA Technical Reports Server (NTRS)

Battles, B. E.; Hanson, R. K.

1991-01-01

Narrow-linewidth laser absorption measurements are reported from which mole fraction and temperature of OH are determined in high-pressure (1-10 atm), lean CH4/air flames. These measurements were made in a new high pressure combustion facility which incorporates a traversable flat flame burner, providing spatially and temporally uniform combustion gases at pressures up to 10 am. A commercially avialable CW ring dye laser was used with an intracavity doubling crystal to provide near-UV single mode output at approximately 306 nm. The UV beam was rapidly scanned over 120 GHz (0.1 sec scan duration) to resolve the absorption lineshape of the A-X (0,0) R1(7)/R1(11) doublet of the OH radical. From the doublet's absorption lineshape, the temperature was determined; and from peak absorption, Beer's Law was employed to find the mole fraction of OH. These data were obtained as a function of height above the flame at various pressures.

Demonstration of high-responsivity epitaxial β-Ga2O3/GaN metal–heterojunction-metal broadband UV-A/UV-C detector

NASA Astrophysics Data System (ADS)

Kalra, Anisha; Vura, Sandeep; Rathkanthiwar, Shashwat; Muralidharan, Rangarajan; Raghavan, Srinivasan; Nath, Digbijoy N.

2018-06-01

We demonstrate epitaxial β-Ga2O3/GaN-based vertical metal–heterojunction-metal (MHM) broadband UV-A/UV-C photodetectors with high responsivity (3.7 A/W) at 256 and 365 nm, UV-to-visible rejection >103, and a photo-to-dark current ratio of ∼100. A small (large) conduction (valence) band offset at the heterojunction of pulsed laser deposition (PLD)-grown β-Ga2O3 on metal organic chemical vapor deposition (MOCVD)-grown GaN-on-silicon with epitaxial registry, as confirmed by X-ray diffraction (XRD) azimuthal scanning, is exploited to realize detectors with an asymmetric photoresponse and is explained with one-dimensional (1D) band diagram simulations. The demonstrated novel vertical MHM detectors on silicon are fully scalable and promising for enabling focal plane arrays for broadband ultraviolet sensing.

Investigation of the excited state iodine lifetime in the photodissociation of perfluoroalkyl iodides

NASA Technical Reports Server (NTRS)

Cobb, Stephen H.

1991-01-01

An evaluation of prospective laser materials for a space-based solar pumped laser system over the past decade has resulted in the identification of the iodine photodissociation laser as that system best suited to solar-pumped high energy operation. The active medium for the solar-pumped iodine photodissociation laser is from the family of perfluoroalkyl iodides. These lasants have the general form C(n)F(2n + 1)I, often abbreviated as RI. These iodides are known to exhibit photodissociaiton of the C-I bond when irradiated by near UV photons. The focus was on the experimental determination of the lifetime of the excited iodine atom following photodissociation of C4F9I, and also to monitor fluorescence from the iodine molecule at 500 nm to determine if I2 is being produced in the process. Photodissociation is achieved using an XeCl excimer laser with an output wavelength of 308 nm. The XeCl beam is focused into the middle of a cylindrical quartz cell containing the lasant. The laser pulse is detected with a fast risetime photomultiplier tube as it exits the cell. Other aspects of the investigation are discussed.

Fiber Bragg grating fabrication for the implementation of sensors in the electronics and optoelectronics laboratory at BUAP

NASA Astrophysics Data System (ADS)

Bracamontes Rodríguez, Y. E.; Beltrán Pérez, G.; Castillo Mixcóatl, J.; Muñoz Aguirre, S.

2011-09-01

Fiber Bragg gratings (FBG) are important optical devices since they have been quite successful not only in the field of communications but also in sensor systems and optical fiber lasers. In the sensors area they are generally used as detection elements for different physical parameters such as temperature, strain, flow, etc. In the electronics and optoelectronics laboratory at Benemérita Universidad Autónoma de Puebla (LEyO-BUAP), there are already experimental setups of sensors as well as laser systems, where FBGs are fundamental elements for their adequate performance. However, these FBGs are commercial devices and they present limited characteristics in their transmission profiles, bandwidth and reflectivity. On the other hand, in some occasions, the delivery time from the fabricant to the customer is quite long. Therefore, it is important for LEyO to implement a system to fabricate this kind of devices, which would mean LEyO independence in the technological development. In this work, results of FBGs fabrication based on the phase mask technique are presented. Such mask is optimized for UV and it has a period of 1060 nm. A Nd:YAG pulsed laser with a 5 ns pulse length and an energy of 40 mJ was used as the UV source employing the 4th harmonic generation to obtain a 266 nm wavelength. Ge-doped fiber was used to fabricate the devices.

Influence of RF excitation during pulsed laser deposition in oxygen atmosphere on the structural properties and luminescence of nanocrystalline ZnO:Al thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meljanac, Daniel, E-mail: dmeljan@irb.hr; Plodinec, Milivoj; Siketić, Zdravko

2016-03-15

Thin ZnO:Al layers were deposited by pulsed laser deposition in vacuum and in oxygen atmosphere at gas pressures between 10 and 70 Pa and by applying radio-frequency (RF) plasma. Grazing incidence small angle x-ray scattering and grazing incidence x-ray diffraction (GIXRD) data showed that an increase in the oxygen pressure leads to an increase in the roughness, a decrease in the sample density, and changes in the size distribution of nanovoids. The nanocrystal sizes estimated from GIXRD were around 20 nm, while the sizes of the nanovoids increased from 1 to 2 nm with the oxygen pressure. The RF plasma mainly influenced themore » nanostructural properties and point defects dynamics. The photoluminescence consisted of three contributions, ultraviolet (UV), blue emission due to Zn vacancies, and red emission, which are related to an excess of oxygen. The RF excitation lowered the defect level related to blue emission and narrowed the UV luminescence peak, which indicates an improvement of the structural ordering. The observed influence of the deposition conditions on the film properties is discussed as a consequence of two main effects: the variation of the energy transfer from the laser plume to the growing film and changes in the growth chemistry.« less

HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

NASA Astrophysics Data System (ADS)

Schubert, Elise; Rastegari, Ali; Feng, Chengyong; Mongin, Denis; Kamer, Brian; Kasparian, Jérôme; Wolf, Jean-Pierre; Arissian, Ladan; Diels, Jean-Claude

2017-12-01

We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV m–1. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 and at 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

Q-switched all-solid-state lasers and application in processing of thin-film solar cell

NASA Astrophysics Data System (ADS)

Liu, Liangqing; Wang, Feng

2009-08-01

Societal pressure to renewable clean energy is increasing which is expected to be used as part of an overall strategy to address global warming and oil crisis. Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by government, of which the costs and prices lower continuously. The next generation thin-film devices are considered to be more efficiency and greatly reduced silicon consumption, resulting in dramatically lower per unit fabrication costs. A key aspect of these devices is patterning large panels to create a monolithic array of series-interconnected cells to form a low current, high voltage module. This patterning is accomplished in three critical scribing processes called P1, P2, and P3. All-solid-state Q-switched lasers are the technology of choice for these processes, due to their advantages of compact configuration, high peak-value power, high repeat rate, excellent beam quality and stability, delivering the desired combination of high throughput and narrow, clean scribes. The end pumped all-solid-state lasers could achieve 1064nm IR resources with pulse width of nanoseconds adopting acoustic-optics Q-switch, shorter than 20ns. The repeat rate is up to 100kHz and the beam quality is close to diffraction limit. Based on this, 532nm green lasers, 355nm UV lasers and 266nm DUV lasers could be carried out through nonlinear frequency conversion. Different wave length lasers are chose to process selective materials. For example, 8-15 W IR lasers are used to scribe the TCO film (P1); 1-5 W green lasers are suitable for scribing the active semiconductor layers (P2) and the back contact layers (P3). Our company, Wuhan Lingyun Photo-electronic System Co. Ltd, has developed 20W IR and 5W green end-pumped Q-switched all-solid-state lasers for thin-film solar industry. Operating in high repeat rates, the speed of processing is up to 2.0 m/s.

Characterization of ultraviolet light cured polydimethylsiloxane films for low-voltage, dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Wohlfender, Fabian; Weiss, Florian; Osmani, Bekim; Müller, Bert

2016-04-01

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO2 surface with corresponding elastic modulus of (2.29 +/- 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 +/- 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 +/- 30) nm with an UV-irradiation density of 7.2 10-4 J cm-2 nm-1 at a wavelength of 190 nm.

Escape of carbon element in surface ablation of cobalt cemented tungsten carbide with pulsed UV laser

NASA Astrophysics Data System (ADS)

Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

2001-03-01

Surface ablation of cobalt cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 30 ns XeCl excimer laser. The surface phase transformation on different pulse number of laser shots has been investigated by means of XRD and microphotography as well as AES at laser fluence of 2.5 J/cm 2. The experimental results showed that the phase structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. It is suggested that the formation of non-stoichiometric tungsten carbide should result from the escaping of carbon element due to accumulated heating of surface by pulsed laser irradiation.

Pulsed laser-induced formation of silica nanogrids

PubMed Central

2014-01-01

Silica grids with micron to sub-micron mesh sizes and wire diameters of 50 nm are fabricated on fused silica substrates. They are formed by single-pulse structured excimer laser irradiation of a UV-absorbing silicon suboxide (SiO x ) coating through the transparent substrate. A polydimethylsiloxane (PDMS) superstrate (cover layer) coated on top of the SiO x film prior to laser exposure serves as confinement for controlled laser-induced structure formation. At sufficiently high laser fluence, this process leads to grids consisting of a periodic loop network connected to the substrate at regular positions. By an additional high-temperature annealing, the residual SiO x is oxidized, and a pure SiO2 grid is obtained. PACS 81.07.-b; 81.07.Gf; 81.65.Cf PMID:24581305

UV-tunable laser induced phototransformations of matrix isolated anethole.

PubMed

Krupa, Justyna; Wierzejewska, Maria; Nunes, Cláudio M; Fausto, Rui

2014-03-14

A matrix isolation study of the infrared spectra and structure of anethole (1-methoxy-4-(1-propenyl)benzene) has been carried out, showing the presence of two E conformers (AE1, AE2) of the molecule in the as-deposited matrices. Irradiation using ultraviolet-tunable laser light at 308-307 nm induced conformationally selective phototransformations of these forms into two less stable Z conformers (AZ1, AZ2). The back reactions were also detected upon irradiation at 301 nm. On the whole, the obtained results allow for full assignment of the infrared spectra of all the four experimentally observed anethole isomers and showed that the narrowband UV-induced E-Z photoisomerization is an efficient and selective way to interconvert the two isomers of anethole into each other, with conformational discrimination. Photolysis of anethole was observed as well, with initial methoxyl O-C bond cleavage and formation of CH3 and p-propenylphenoxy (AR) radicals, followed by radical recombination to form 2-methyl-4-propenyl-2,4-cyclohexadienone, which subsequently undergoes ring-opening generating several conformers of long-chain conjugated ketenes. Interpretation of the experimental observations was supported by density functional theory (B3LYP and B2PLYD) calculations.

High-power, high-repetition-rate performance characteristics of β-BaB₂O₄ for single-pass picosecond ultraviolet generation at 266 nm.

PubMed

Kumar, S Chaitanya; Casals, J Canals; Wei, Junxiong; Ebrahim-Zadeh, M

2015-10-19

We report a systematic study on the performance characteristics of a high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 266 nm based on β-BaB2O4 (BBO). The source, based on single-pass fourth harmonic generation (FHG) of a compact Yb-fiber laser in a two-crystal spatial walk-off compensation scheme, generates up to 2.9 W of average power at 266 nm at a pulse repetition rate of ~80 MHz with a single-pass FHG efficiency of 35% from the green to UV. Detrimental issues such as thermal effects have been studied and confirmed by performing relevant measurements. Angular and temperature acceptance bandwidths in BBO for FHG to 266 nm are experimentally determined, indicating that the effective interaction length is limited by spatial walk-off and thermal gradients under high-power operation. The origin of dynamic color center formation due to two-photon absorption in BBO is investigated by measurements of intensity-dependent transmission at 266 nm. Using a suitable theoretical model, two-photon absorption coefficients as well as the color center densities have been estimated at different temperatures. The measurements show that the two-photon absorption coefficient in BBO at 266 nm is ~3.5 times lower at 200°C compared to that at room temperature. The long-term power stability as well as beam pointing stability is analyzed at different output power levels and focusing conditions. Using cylindrical optics, we have circularized the generated elliptic UV beam to a circularity of >90%. To our knowledge, this is the first time such high average powers and temperature-dependent two-photon absorption measurements at 266 nm are reported at repetition rates as high as ~80 MHz.

Highly efficient color filter array using resonant Si3N4 gratings.

PubMed

Uddin, Mohammad Jalal; Magnusson, Robert

2013-05-20

We demonstrate the design and fabrication of a highly efficient guided-mode resonant color filter array. The device is designed using numerical methods based on rigorous coupled-wave analysis and is patterned using UV-laser interferometric lithography. It consists of a 60-nm-thick subwavelength silicon nitride grating along with a 105-nm-thick homogeneous silicon nitride waveguide on a glass substrate. The fabricated device exhibits blue, green, and red color response for grating periods of 274, 327, and 369 nm, respectively. The pixels have a spectral bandwidth of ~12 nm with efficiencies of 94%, 96%, and 99% at the center wavelength of blue, green, and red color filter, respectively. These are higher efficiencies than reported in the literature previously.

Interpreting atom probe data from chromium oxide scales.

PubMed

La Fontaine, Alexandre; Gault, Baptiste; Breen, Andrew; Stephenson, Leigh; Ceguerra, Anna V; Yang, Limei; Nguyen, Thuan Dinh; Zhang, Jianqiang; Young, David J; Cairney, Julie M

2015-12-01

Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed "laser sensitivity factor" is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite samples. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia. Copyright © 2015 Elsevier B.V. All rights reserved.

Remote sensing of the earth's surface with an airborne polarized laser

NASA Technical Reports Server (NTRS)

Kalshoven, James E.; Dabney, Philip W.

1993-01-01

Attention is given to the Airborne Laser Polarization Sensor (ALPS), which makes multispectral radiometric and polarization measurements of the earth's surface using a polarized laser light source. Results from data flights taken over boreal forests in Maine at two wavelengths (1060 and 532 nm) using an Nd:YAG laser source show distinct depolarization signatures for three broadleaf and five coniferous tree species. A statistically significant increase in depolarization is found to correlate with increasing leaf surface roughness for the broadleaf species in the near-IR. The ALPS system 3 employs 12 photomultiplier tube detectors configurable to measure desired parameters such as the total backscatter and the polarization state, including the azimuthal angle and ellipticity, at different UV to near-IR wavelengths simultaneously.

Microbial UV fluence-response assessment using a novel UV-LED collimated beam system.

PubMed

Bowker, Colleen; Sain, Amanda; Shatalov, Max; Ducoste, Joel

2011-02-01

A research study has been performed to determine the ultraviolet (UV) fluence-response of several target non-pathogenic microorganisms to UV light emitting diodes (UV-LEDs) by performing collimated beam tests. UV-LEDs do not contain toxic mercury, offer design flexibility due to their small size, and have a longer operational life than mercury lamps. Comsol Multiphysics was utilized to create an optimal UV-LED collimated beam design based on number and spacing of UV-LEDs and distance of the sample from the light source while minimizing the overall cost. The optimized UV-LED collimated beam apparatus and a low-pressure mercury lamp collimated beam apparatus were used to determine the UV fluence-response of three surrogate microorganisms (Escherichia coli, MS-2, T7) to 255 nm UV-LEDs, 275 nm UV-LEDs, and 254 nm low-pressure mercury lamps. Irradiation by low-pressure mercury lamps produced greater E. coli and MS-2 inactivation than 255 nm and 275 nm UV-LEDs and similar T7 inactivation to irradiation by 275 nm UV-LEDs. The 275 nm UV-LEDs produced more efficient T7 and E. coli inactivation than 255 nm UV-LEDs while both 255 nm and 275 nm UV-LEDs produced comparable microbial inactivation for MS-2. Differences may have been caused by a departure from the time-dose reciprocity law due to microbial repair mechanisms. Copyright © 2010 Elsevier Ltd. All rights reserved.

Laser capture microdissection: Arcturus(XT) infrared capture and UV cutting methods.

PubMed

Gallagher, Rosa I; Blakely, Steven R; Liotta, Lance A; Espina, Virginia

2012-01-01

Laser capture microdissection (LCM) is a technique that allows the precise procurement of enriched cell populations from a heterogeneous tissue under direct microscopic visualization. LCM can be used to harvest the cells of interest directly or can be used to isolate specific cells by ablating the unwanted cells, resulting in histologically enriched cell populations. The fundamental components of laser microdissection technology are (a) visualization of the cells of interest via microscopy, (b) transfer of laser energy to a thermolabile polymer with either the formation of a polymer-cell composite (capture method) or transfer of laser energy via an ultraviolet laser to photovolatize a region of tissue (cutting method), and (c) removal of cells of interest from the heterogeneous tissue section. Laser energy supplied by LCM instruments can be infrared (810 nm) or ultraviolet (355 nm). Infrared lasers melt thermolabile polymers for cell capture, whereas ultraviolet lasers ablate cells for either removal of unwanted cells or excision of a defined area of cells. LCM technology is applicable to an array of applications including mass spectrometry, DNA genotyping and loss-of-heterozygosity analysis, RNA transcript profiling, cDNA library generation, proteomics discovery, and signal kinase pathway profiling. This chapter describes the unique features of the Arcturus(XT) laser capture microdissection instrument, which incorporates both infrared capture and ultraviolet cutting technology in one instrument, using a proteomic downstream assay as a model.

Biological applications and effects of optical masers

NASA Astrophysics Data System (ADS)

Ham, William T., Jr.; Mueller, Harold A.; Guerry, R. K.; Guerry, Dupont, III; Cleary, Stephan F.

1988-09-01

Threshold radiant exposures for retinal damage in 3 macaque monkeys are given for exposures of 0.5, 0.125 and 0.016 seconds duration to laser wavelengths 514.5 and 488 nm. Intravitreal injections of 5 x .00005 gm of Cu-Zn SOD were toxic to cornea, lens and retina of the rhesus monkey after a radiant exposure of 33 j/sq cm of 440 nm light. No further experiments with SOD are contemplated. Similar experiments with catalase will be tried during the first quarter of the second contract year. The effect of oxygen on retinal toxicity during exposure to wave-lengths 540, 640 and 840 nm were delayed by the untimely death of Dr. Millen, our consultant on anesthesiology and oxygen administration. Arrangements have been made to activate this program during the second contract year. Threshold data on 40 microsecond pulse trains cannot be obtained until the acoustic modulator can be incorporated into the Ar-Kr laser which was used during the contract year to produce exposures less than 1 second to 514.5 and 488 nm laser lines. Data on PRF's of 10 and 100 KHz and 1, 10 and 20 MHz will be obtained during the second contract year. The long-term experiment on cataractogenesis on 2 rhesus monkeys exposed to a near UV spectrum (330 to 420 nm) has been completed.

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

DOE PAGES

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.; ...

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition.

PubMed

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M; Yalin, Azer P

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We perform a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution of the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.

Combined fluorescence-Raman spectroscopy measurements with an optical fiber probe for the diagnosis of melanocytic lesions

NASA Astrophysics Data System (ADS)

Cosci, Alessandro; Cicchi, Riccardo; Rossari, Susanna; De Giorgi, Vincenzo; Massi, Daniela; Pavone, Francesco S.

2012-02-01

We have designed and developed an optical fiber-probe for spectroscopic measurements on human tissues. The experimental setup combines fluorescence spectroscopy and Raman spectroscopy in a multidimensional approach. Concerning fluorescence spectroscopy, the excitation is provided by two laser diodes, one emitting in the UV (378 nm) and the other emitting in the visible (445 nm). These two lasers are used to selectively excite fluorescence from NADH and FAD, which are among the brightest endogenous fluorophores in human tissues. For Raman and NIR spectroscopy, the excitation is provided by a third laser diode with 785 nm excitation wavelength. Laser light is delivered to the tissue through the central optical fiber of a fiber bundle. The surrounding 48 fibers of the bundle are used for collecting fluorescence and Raman and for delivering light to the spectrograph. Fluorescence and Raman spectra are acquired on a cooled CCD camera. The instrument has been tested on fresh human skin biopsies clinically diagnosed as malignant melanoma, melanocytic nevus, or healthy skin, finding an optimal correlation with the subsequent histological exam. In some cases our examination was not in agreement with the clinical observation, but it was with the histological exam, demonstrating that the system can potentially contribute to improve clinical diagnostic capabilities and hence reduce the number of unnecessary biopsies.

Double optical fibre-probe device for the diagnosis of melanocytic lesions

NASA Astrophysics Data System (ADS)

Cicchi, Riccardo; Cosci, Alessandro; Rossari, Susanna; De Giorgi, Vincenzo; Kapsokalyvas, Dimitrios; Massi, Daniela; Pavone, Francesco S.

2012-06-01

We have designed and developed an optical fiber-probe for spectroscopic measurements on human tissues. The experimental setup combines fluorescence spectroscopy and Raman spectroscopy in a multidimensional approach. Concerning fluorescence spectroscopy, the excitation is provided by two laser diodes, one emitting in the UV (378 nm) and the other emitting in the visible (445 nm). These two lasers are used to selectively excite fluorescence from NADH and FAD, which are among the brightest endogenous fluorophores in human tissues. For Raman and NIR spectroscopy, the excitation is provided by a third laser diode with 785 nm excitation wavelength. Laser light is delivered to the tissue through the central optical fiber of a fiber bundle. The surrounding 48 fibers of the bundle are used for collecting fluorescence and Raman and for delivering light to the spectrograph. Fluorescence and Raman spectra are acquired on a cooled CCD camera. The instrument has been tested on fresh human skin biopsies clinically diagnosed as malignant melanoma, melanocytic nevus, or healthy skin, finding an optimal correlation with the subsequent histological exam. In some cases our examination was not in agreement with the clinical observation, but it was with the histological exam, demonstrating that the system can potentially contribute to improve clinical diagnostic capabilities and hence reduce the number of unnecessary biopsies.

Compact Two-step Laser Time-of-Flight Mass Spectrometer for in Situ Analyses of Aromatic Organics on Planetary Missions

NASA Technical Reports Server (NTRS)

Getty, Stephanie; Brickerhoff, William; Cornish, Timothy; Ecelberger, Scott; Floyd, Melissa

2012-01-01

RATIONALE A miniature time-of-flight mass spectrometer has been adapted to demonstrate two-step laser desorption-ionization (LOI) in a compact instrument package for enhanced organics detection. Two-step LDI decouples the desorption and ionization processes, relative to traditional laser ionization-desorption, in order to produce low-fragmentation conditions for complex organic analytes. Tuning UV ionization laser energy allowed control ofthe degree of fragmentation, which may enable better identification of constituent species. METHODS A reflectron time-of-flight mass spectrometer prototype measuring 20 cm in length was adapted to a two-laser configuration, with IR (1064 nm) desorption followed by UV (266 nm) postionization. A relatively low ion extraction voltage of 5 kV was applied at the sample inlet. Instrument capabilities and performance were demonstrated with analysis of a model polycyclic aromatic hydrocarbon, representing a class of compounds important to the fields of Earth and planetary science. RESULTS L2MS analysis of a model PAH standard, pyrene, has been demonstrated, including parent mass identification and the onset o(tunable fragmentation as a function of ionizing laser energy. Mass resolution m/llm = 380 at full width at half-maximum was achieved which is notable for gas-phase ionization of desorbed neutrals in a highly-compact mass analyzer. CONCLUSIONS Achieving two-step laser mass spectrometry (L2MS) in a highly-miniature instrument enables a powerful approach to the detection and characterization of aromatic organics in remote terrestrial and planetary applications. Tunable detection of parent and fragment ions with high mass resolution, diagnostic of molecular structure, is possible on such a compact L2MS instrument. Selectivity of L2MS against low-mass inorganic salt interferences is a key advantage when working with unprocessed, natural samples, and a mechanism for the observed selectivity is presented.

Laser-induced periodic surface structures formation on mesoporous silicon from nanoparticles produced by picosecond and femtosecond laser shots

NASA Astrophysics Data System (ADS)

Talbi, Abderazek; Kaya-Boussougou, Sostaine; Sauldubois, Audrey; Stolz, Arnaud; Boulmer-Leborgne, Chantal; Semmar, Nadjib

2017-07-01

This paper deals with the formation of laser-induced periodic surface structures (LIPSS) on mesoporous silicon thin films induced by two laser regimes in the UV range: picosecond and femtosecond. Different LIPSS formation mechanisms from nanoparticles, mainly coalescence and agglomeration, have been evidenced by scanning electron microscopy analysis. The apparition of a liquid phase during both laser interaction at low fluence (20 mJ/cm2) and after a large number of laser pulses (up to 12,000) has been also shown with 100 nm size through incubation effect. Transmission electron microscopy analyses have been conducted to investigate the molten phase structures below and inside LIPSS. Finally, it has shown that LIPSS are composed of amorphous silicon when mesoporous silicon is irradiated by laser beam in both regimes. Nevertheless, mesoporous silicon located between LIPSS stays crystallized.

Studies on cytostatics used as photosensitizing material in photodynamic therapy

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Danaila, Leon; Carstocea, Benone D.; Staicu, Angela; Truica, Sorina; Gazdaru, Doina M.

2002-10-01

Introduction of the photosensitizer properties of cytostatics drus was made, pointing out that the fact that besides the biochemical action of the cytostatics their effects could be enhanced by the exposure to light at different doses. A spectroscopical characterisation of methotrexate and fluorouracil, cytostatic drugs used frequently in cancer therpy was performed. The absorption, emission and excitation spectra were measured for methotrexate solutions in natural saline and sodium hydroxide at concentration in the range 10-5 -10-6M and pH 8.4. The absorption, emission and excitation spectra were measured for fluorouracil solutions in natural saline at concentration in the range 10-4 -10-5M. The absorption spectrum exhibits spectral bands in the range 250nm -450nm for both drugs. The fluorescence excitatioan for methotrexate was made at 340nm and 370nm, the fluorescence emission was detected in the spectral range 400nm - 500nm with a maximum at 470nm. The fluorescence excitation was measured in teh range 200nm-500nm with the emission centred on 530nm, for Xe lamp irradiation, and 300nm for Hg lamp and laser irradiation. The fluorescence emission spectra was monitored in the spectral range 400nm - 600nm. The effects of irradiation on spectroscopic characteristics of methrotrexate and fluorouracil were investigated. The irraditaion was made using a UV classic lamp with Xe, for the first experimental part and for the second one it was used both a class Hg lamp and a nytorgen pulsed laser.

The nature of unusual luminescence in natural calcite, CaCO3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaft, M.; Nagli, L.; Panczer, G.

2008-11-01

The unusual luminescence of particular varieties of natural pink calcite (CaCO{sub 3}) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under short-wave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under long wave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: a narrow violet band, with {lambda}{sub max} = 412 nm, {Delta} = 45 nm, two decay components of {tau}{sub 1} = 5 ns and {tau}{sub 2} = 7.2 ms,more » accompanied by very long afterglow, and an orange emission band with {lambda}{sub max} = 595 nm, {Delta} = 90 nm and {tau} = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 C, and the orange emission disappearing after heating at different temperatures starting from 230 C, although sometimes it is stable up to 500 C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations, prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence.« less

Recent Progress in the Development of Neodymium Doped Ceramic Yttria

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Edwards, Chris; Trivedi, Sudhir B.; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra; Kear, Bernard

2007-01-01

Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium doped yttria (Nd:Y2O3) is considered to be an attractive material due to its possible lasing wavelengths of aprrox.914 nm and approx.946 nm for ozone profiling. These wavelengths when frequency tripled can generate UV light at approx.305 nm and approx.315 nm, which is particularly useful for ozone sensing using differential absorption lidar technique. For practical realization of space based UV transmitter technology, ceramic Nd:Y2O3 material is considered to possess great potential. A plasma melting and quenching method has been developed to produce Nd3+ doped powders for consolidation into Nd:Y2O3 ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises of two main steps: (a) plasma melting and quenching to generate dense, and homogeneous doped metastable powders, (b) pressure assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several 1" x 1" ceramic cylinders have been produced. The infrared transmission of undoped Y2O3 ceramics was as high as approx.75% without anti-reflection coating. In the case of Nd:Y2O3 ceramics infrared transmission values of approx.50% were achieved. Furthermore, Nd:Y2O3 samples with dopant concentrations of up to approx.2 at. % were prepared without significant emission quenching.

Role of HfO 2/SiO 2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

DOE PAGES

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; ...

2016-07-15

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

Dechlorination and Decolorization of Organics in Bleach Plant E-1 Effluent by Photochemical Processes

NASA Astrophysics Data System (ADS)

Xie, Tianyan

1994-01-01

Photochemical study of the dechlorination of four model compounds, 4,5-dichloroguaiacol, 2,4,6-trichlorophenol, 2,3,4,5-tetrachlorophenol, and tetrachloroguaiacol in aqueous solutions under UV radiation was conducted using ArF (193 nm) and KrF (248 nm) excimer laser to explore the response of chlorinated phenolics present in the E_1 effluent from conventional chlorine bleaching of softwood kraft pulp towards photo-oxidation processes. Kinetic study show that the overall dechlorination reaction follow the first order rate law. The factors affecting the dechlorination were investigated. The quantum yield of chloride ion formation was found to be dependent on pH of the reaction mixture, and orignal chlorine content of the compounds. The effect of the substituents on the aromatic ring on the reactivity of the compounds was studied. The mechanism for the dechlorination was proposed involving homolytic photo-dissociation, heterolytic cleavage of carbon-chlorine bonds and substitution reactions of hydroxyl radicals. It was found that the dechlorination under formation to chloride is influenced by the amount of organically bound chlorine in the starting material. Dechlorination reaction favors high pH. Guaiacols more easily undergo dechlorination than phenols. Four fractions of high relative molecular-mass chloro-organics or polychlorinated oxylignin (PCOL) were isolated from an E_1 effluent by combination of ultrafiltration, and purified by repeated precipitation. The fractions were analysed by classical functional group analysis and spectrophotometric methods. The analytical data indicated that the major structural differences between PCOL fractions and kraft lignin preparations are with regard to the content of founctional groups such as carboxyl content, methoxyl and hydroxyl contents. In addition, IR, ^1H and ^{13 }C NMR spectral analyses revealed an almost complete absence of absorption attributable to aromatic structures in PCOLs. These results and others led to the conclusion that the PCOL fractions are comprised mainly of non-aromatic lignin oxidation products containing a considerable amount of organically bound chlorine as well as unsaturated aliphatic carbon bonded to either oxygen or chlorine. The PCOL fractions were subjected to 193 nm UV -Excimer laser photolysis in presence and absence of oxygen with and without hydrogen peroxide. Kinetic study showed that they readily undergo dechlorination and decolorization on UV ArF-excimer laser (193 nm) photolysis under both oxygen and nitrogen atmosphere. About 60% dechlorination could be achieved by 3 hours irradiation. However, the relative molecular-mass of the PCOL fractions were not changed during the photolysis. Addition of small amount (2-8% w/w) of hydrogen peroxide lead to a signifiant reduction of color and relative molecular-mass. Thus, hydrogen peroxide play very important role in degradation and decolorization of PCOLs. The possible reaction mechanism for the UV-Excimer laser photolysis of PCOLs are discussed on the basis of the observed results.

Novel Galvanic Nanostructures of Ag and Pd for Efficient Laser Desorption/Ionization of Low Molecular Weight Compounds

NASA Astrophysics Data System (ADS)

Silina, Yuliya E.; Meier, Florian; Nebolsin, Valeriy A.; Koch, Marcus; Volmer, Dietrich A.

2014-05-01

A simple approach for synthesis of palladium and silver nanostructures with readily adjustable morphologies was developed using galvanic electrochemical deposition, for application to surface-assisted laser desorption/ionization (SALDI) of small biological molecules. A range of fatty acids, triglycerides, carbohydrates, and antibiotics were investigated to assess the performance of the new materials. Intense analyte cations were generated from the galvanic surfaces upon UV laser irradiation such as potassium adducts for a film thickness <100 nm (originating from impurities of the electrolyte solution) and Pd and Ag cluster ions for films with a thickness >120 nm. Possible laser desorption/ionization mechanisms of these galvanic structures are discussed. The films exhibited self-organizing abilities and adjustable morphologies by changing electrochemical parameters. They did not require any stabilizing agents and were inexpensive and very easy to produce. SALDI analysis showed that the materials were stable under ambient conditions and analytical results with excellent measurement reproducibility and detection sensitivity similar to MALDI were obtained. Finally, we applied the galvanic surfaces to fast screening of natural oils with minimum sample preparation.

UV laser interaction with a fluorescent dye solution studied using pulsed digital holography.

PubMed

Amer, Eynas; Gren, Per; Sjödahl, Mikael

2013-10-21

A frequency tripled Q-switched Nd-YAG laser (wavelength 355 nm, pulse duration 12 ns) has been used to pump Coumarin 153 dye solved in ethanol. Simultaneously, a frequency doubled pulse (532 nm) from the same laser is used to probe the solvent perpendicularly resulting in a gain through stimulated laser induced fluorescence (LIF) emission. The resulting gain of the probe beam is recorded using digital holography by blending it with a reference beam on the detector. Two digital holograms without and with the pump beam were recorded. Intensity maps were calculated from the recorded digital holograms and used to calculate the gain of the probe beam due to the stimulated LIF. In addition numerical data of the local temperature rise was calculated from the corresponding phase maps using Radon inversion. It was concluded that about 15% of the pump beam energy is transferred to the dye solution as heat while the rest is consumed in the radiative process. The results show that pulsed digital holography is a promising technique for quantitative study of fluorescent species.

Spectroscopic Chemical Analysis Methods and Apparatus

NASA Technical Reports Server (NTRS)

Hug, William F.; Reid, Ray D.

2012-01-01

This invention relates to non-contact spectroscopic methods and apparatus for performing chemical analysis and the ideal wavelengths and sources needed for this analysis. It employs deep ultraviolet (200- to 300-nm spectral range) electron-beam-pumped wide bandgap semiconductor lasers, incoherent wide bandgap semiconductor lightemitting devices, and hollow cathode metal ion lasers. Three achieved goals for this innovation are to reduce the size (under 20 L), reduce the weight [under 100 lb (.45 kg)], and reduce the power consumption (under 100 W). This method can be used in microscope or macroscope to provide measurement of Raman and/or native fluorescence emission spectra either by point-by-point measurement, or by global imaging of emissions within specific ultraviolet spectral bands. In other embodiments, the method can be used in analytical instruments such as capillary electrophoresis, capillary electro-chromatography, high-performance liquid chromatography, flow cytometry, and related instruments for detection and identification of unknown analytes using a combination of native fluorescence and/or Raman spectroscopic methods. This design provides an electron-beampumped semiconductor radiation-producing method, or source, that can emit at a wavelength (or wavelengths) below 300 nm, e.g. in the deep ultraviolet between about 200 and 300 nm, and more preferably less than 260 nm. In some variations, the method is to produce incoherent radiation, while in other implementations it produces laser radiation. In some variations, this object is achieved by using an AlGaN emission medium, while in other implementations a diamond emission medium may be used. This instrument irradiates a sample with deep UV radiation, and then uses an improved filter for separating wavelengths to be detected. This provides a multi-stage analysis of the sample. To avoid the difficulties related to producing deep UV semiconductor sources, a pumping approach has been developed that uses ballistic electron beam injection directly into the active region of a wide bandgap semiconductor material.

Effect of temperature on the structural, linear, and nonlinear optical properties of MgO-doped graphene oxide nanocomposites

NASA Astrophysics Data System (ADS)

Kimiagar, Salimeh; Abrinaei, Fahimeh

2018-01-01

Magnesium oxide (MgO)-graphene oxide (GO) nanocomposites were prepared by the hydrothermal method at different temperatures. The effect of growth temperature on the structural, linear, and nonlinear optical (NLO) parameters was investigated. The decoration of MgO on GO sheets was confirmed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and UV-visible (UV-vis) spectroscopy analyses. The energy band-gaps of MgO-GO nanocomposites were calculated from UV-vis spectrum using Tauc plot. The NLO parameters of MgO-GO nanocomposites were calculated for the first time by the simple Z-scan technique with nanosecond Nd:YAG laser at 532 nm. The nonlinear absorption coefficient β and nonlinear refractive index n2 for MgO-GO nanocomposites at the laser intensity of 1.1×108 W/cm2 were measured to be in the order of 10-7 cm/W and 10-12 cm2/W, respectively. The third-order NLO susceptibility of MgO-GO nanocomposites was measured in the order of 10-9 esu. The results showed that MgO-GO structures have negative nonlinearity as well as good nonlinear two-photon absorption at 532 nm. Furthermore, the NLO parameters increased by the enhancement of the growth temperature. As the investigation of new materials plays an important role in the advancement of optoelectronics, MgO-GO nanocomposites possess potential applications in NLO devices.

Improved intact soil-core carbon determination applying regression shrinkage and variable selection techniques to complete spectrum laser-induced breakdown spectroscopy (LIBS).

PubMed

Bricklemyer, Ross S; Brown, David J; Turk, Philip J; Clegg, Sam M

2013-10-01

Laser-induced breakdown spectroscopy (LIBS) provides a potential method for rapid, in situ soil C measurement. In previous research on the application of LIBS to intact soil cores, we hypothesized that ultraviolet (UV) spectrum LIBS (200-300 nm) might not provide sufficient elemental information to reliably discriminate between soil organic C (SOC) and inorganic C (IC). In this study, using a custom complete spectrum (245-925 nm) core-scanning LIBS instrument, we analyzed 60 intact soil cores from six wheat fields. Predictive multi-response partial least squares (PLS2) models using full and reduced spectrum LIBS were compared for directly determining soil total C (TC), IC, and SOC. Two regression shrinkage and variable selection approaches, the least absolute shrinkage and selection operator (LASSO) and sparse multivariate regression with covariance estimation (MRCE), were tested for soil C predictions and the identification of wavelengths important for soil C prediction. Using complete spectrum LIBS for PLS2 modeling reduced the calibration standard error of prediction (SEP) 15 and 19% for TC and IC, respectively, compared to UV spectrum LIBS. The LASSO and MRCE approaches provided significantly improved calibration accuracy and reduced SEP 32-55% over UV spectrum PLS2 models. We conclude that (1) complete spectrum LIBS is superior to UV spectrum LIBS for predicting soil C for intact soil cores without pretreatment; (2) LASSO and MRCE approaches provide improved calibration prediction accuracy over PLS2 but require additional testing with increased soil and target analyte diversity; and (3) measurement errors associated with analyzing intact cores (e.g., sample density and surface roughness) require further study and quantification.

Separation of porphyrin-based photosensitizer isomers by laser-induced fluorescence capillary electrophoresis.

PubMed

Peng, Xuejun; Sternberg, Ethan; Dolphin, David

2005-10-01

Methods for the separation of photosensitizer isomers, such as benzoporphyrin derivative monoacid, benzoporphyrin ethyl monoacid, 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a, diethyleneglycol diester benzoporphyrin derivative, tin ethyl etiopurpurin, and phthalocyanine tetrasulfonate, have been systematically developed by CE. Detection was accomplished by UV absorption at 214 nm or by LIF with excitation at 442/488 nm and emission at 690 nm. The effects of three major experimental parameters of buffer types, organic solvents, and surfactant additives are described. The optimized separation conditions were determined so as to provide satisfactory separation efficiency and analysis time. The methods are shown to be suitable for the separation and determination of porphyrin and phthalocyanines regioisomers, diastereoisomers, and enantiomers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Negres, Raluca A.; Stolz, Christopher J.; Thomas, Michael D.

Here, this competition aimed to survey state-of-the-art UV high reflectors. The requirements of the coatings are a minimum reflection of 99.5% at 45 degrees incidence angle for P-polarized light at 355-nm. The choice of coating materials, design, and deposition method were left to the participants. Laser damage testing was performed at a single testing facility using the raster scan method with a 5-ns pulse length laser system operating at 10 Hz in a single longitudinal mode. A double blind test assured sample and submitter anonymity. Finally, in addition to the laser damage resistance results, details of the deposition processes, cleaningmore » method, coating materials and layer count are also shared.« less

Invisible two-dimensional barcode fabrication inside a synthetic fused silica by femtosecond laser processing using a computer-generated hologram

NASA Astrophysics Data System (ADS)

Kawashima, Hayato; Yamaji, Masahiro; Suzuki, Jun'ichi; Tanaka, Shuhei

2011-03-01

We report an invisible two-dimensional (2D) barcode embedded into a synthetic fused silica by femtosecond laser processing using a computer-generated hologram (CGH) that generates a spatially extended femtosecond pulse beam in the depth direction. When we illuminate the irradiated 2D barcode pattern with a 254 nm ultraviolet (UV) light, a strong red photoluminescence (PL) is observed, and we can read it by using a complementary metal oxide semiconductor (CMOS) camera and image processing technology. This work provides a novel barcode fabrication method by femtosecond laser processing using a CGH and a barcode reading method by a red PL.

Generation of spectral clusters in a mixture of noble and Raman-active gases.

PubMed

Hosseini, Pooria; Abdolvand, Amir; St J Russell, Philip

2016-12-01

We report a novel scheme for the generation of dense clusters of Raman sidebands. The scheme uses a broadband-guiding hollow-core photonic crystal fiber (HC-PCF) filled with a mixture of H₂, D₂, and Xe for efficient interaction between the gas mixture and a green laser pump pulse (532 nm, 1 ns) of only 5 μJ of energy. This results in the generation from noise of more than 135 rovibrational Raman sidebands covering the visible spectral region with an average spacing of only 2.2 THz. Such a spectrally dense and compact fiber-based source is ideal for applications where closely spaced narrow-band laser lines with high spectral power density are required, such as in spectroscopy and sensing. When the HC-PCF is filled with a H₂-D₂ mixture, the Raman comb spans the spectral region from the deep UV (280 nm) to the near infrared (1000 nm).

Continuous and dynamic spectral tuning of single nanowire lasers with subnanometer resolution using hydrostatic pressure

DOE PAGES

Liu, Sheng; Li, Changyi; Figiel, Jeffrey J.; ...

2015-04-27

In this paper, we report continuous, dynamic, reversible, and widely tunable lasing from 367 to 337 nm from single GaN nanowires (NWs) by applying hydrostatic pressure up to ~7 GPa. The GaN NW lasers, with heights of 4–5 μm and diameters ~140 nm, are fabricated using a lithographically defined two-step top-down technique. The wavelength tuning is caused by an increasing Γ direct bandgap of GaN with increasing pressure and is precisely controllable to subnanometer resolution. The observed pressure coefficients of the NWs are ~40% larger compared with GaN microstructures fabricated from the same material or from reported bulk GaN values,more » revealing a nanoscale-related effect that significantly enhances the tuning range using this approach. Finally, this approach can be generally applied to other semiconductor NW lasers to potentially achieve full spectral coverage from the UV to IR.« less

Study of acoustic fingerprinting of nitromethane and some triazole derivatives using UV 266 nm pulsed photoacoustic pyrolysis technique

NASA Astrophysics Data System (ADS)

Rao, K. S.; Chaudhary, A. K.; Yehya, F.; Kumar, A. Sudheer

2015-08-01

We report a comparative study of acoustic fingerprints of nitromethane, nitrobenzene and some nitro rich triazole derivatives using pulsed photoacoustic technique. UV 266 nm wavelength i.e. Fourth harmonic of Q-switched Nd: YAG laser having pulse duration 7 ns and 10 Hz repetition rate is employed to record the time resolved PA spectrum. The PA fingerprint is produced due to absorption of incident UV light by molecule itself and photo dissociation of nitromethane and nitrobenzene at room temperature while in case of triazole it is attributed to the combination of thermal and photo-dissociation process. The entire dissociation process follows the root of cleavage of C-NO2 bond to produce free NO, NO2 and other by product gases due to π∗ ← n excitation. In addition, we have studied the thermal stability criteria of nitro rich triazoles based on the quality factor of acoustic resonance frequencies of the PA cavity. We have also studied the effect of data acquisition time to ascertain the decay behavior of HEMs samples.

Study of acoustic fingerprinting of nitromethane and some triazole derivatives using UV 266 nm pulsed photoacoustic pyrolysis technique.

PubMed

Rao, K S; Chaudhary, A K; Yehya, F; Kumar, A Sudheer

2015-08-05

We report a comparative study of acoustic fingerprints of nitromethane, nitrobenzene and some nitro rich triazole derivatives using pulsed photoacoustic technique. UV 266 nm wavelength i.e. Fourth harmonic of Q-switched Nd: YAG laser having pulse duration 7 ns and 10 Hz repetition rate is employed to record the time resolved PA spectrum. The PA fingerprint is produced due to absorption of incident UV light by molecule itself and photo dissociation of nitromethane and nitrobenzene at room temperature while in case of triazole it is attributed to the combination of thermal and photo-dissociation process. The entire dissociation process follows the root of cleavage of C-NO₂ bond to produce free NO, NO₂ and other by product gases due to π(∗)←n excitation. In addition, we have studied the thermal stability criteria of nitro rich triazoles based on the quality factor of acoustic resonance frequencies of the PA cavity. We have also studied the effect of data acquisition time to ascertain the decay behavior of HEMs samples. Copyright © 2015 Elsevier B.V. All rights reserved.

UV action spectroscopy of protonated PAH derivatives. Methyl substituted quinolines

NASA Astrophysics Data System (ADS)

Klærke, B.; Holm, A. I. S.; Andersen, L. H.

2011-08-01

Aims: We investigate the production of molecular photofragments upon UV excitation of PAH derivatives, relevant for the interstellar medium. Methods: The action absorption spectra of protonated gas-phase methyl-substituted quinolines (CH3 - C9H7NH+) have been recorded in the 215-338 nm spectral range using the electrostatic storage ring ELISA, an electrospray ion source and 3 ns UV laser pulses. Results: It is shown that the absorption profile is both redshifted and broadened when moving the methyl group from the heterocycle containing nitrogen to the homoatomic ring. The absorption profiles are explained by TD-DFT calculations. The dissociation time of the studied molecules is found to be of several milliseconds at 230 nm and it is shown that after redistribution of the absorbed energy the molecules dissociate in several channels. The dissociation time found is an order of magnitude faster than the estimated IR relaxation time. Photophysical properties of both nitrogen containing and methyl-substituted PAHs are interesting in an astrophysical context in connection with identifying the aromatic component of the interstellar medium.

Fabrication of a high-density nano-porous structure on polyimide by using ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Ma, Yong-Won; Jeong, Myung Yung; Lee, Sang-Mae; Shin, Bo Sung

2016-03-01

A new approach for fabricating a high-density nano-porous structure on polyimide (PI) by using a 355-nm UV laser is presented here. When PI was irradiated by using a laser, debris that had electrical conductivity was generated. Accordingly, that debris caused electrical defects in the field of electronics. Thus, many researchers have tried to focus on a clean processing without debris. However, this study focused on forming a high density of debris so as to fabricate a nano-porous structure consisting of nanofibers on the PI film. A PI film with closed pores and open pores was successfully formed by using a chemical blowing agent (azodicarbonamide, CBA) in an oven. Samples were precured at 130 °C and cured at 205 °C in sequence so that the closed pores might not coalesce in the film. When the laser irradiated the PI film with closed pores, nanofibers were generated because polyimide was not completely decomposed by photochemical ablation. Our results indicated that a film with micro-closed pores, in conjunction with a 355-nm pulsed laser, can facilitate the fabrication of a high-density nano-porous structure.

Modified polyhydroxystyrenes as matrix resins for dissolution inhibition type photoresists

NASA Astrophysics Data System (ADS)

Pawlowski, Georg; Sauer, Thomas P.; Dammel, Ralph R.; Gordon, Douglas J.; Hinsberg, William D.; McKean, Dennis R.; Lindley, Charlet R.; Merrem, Hans-Joachim; Roeschert, Heinz; Vicari, Richard; Willson, C. Grant

1990-06-01

It is generally accepted that the production of shrink versions of the 16 MB DRAM and the 64 MB DRAM generations will be patterned using deep UV radiation. This provides a new challenge to the photoresist suppliers, as the standard photoresist formulations are not suitable for this technology, mainly because the presently used novolak resins are highly opaque in the 200 - 300 nm region. This is especially true for the 248 nm wavelength of KrF eximer lasers. Poly 4- hydroxystyrene [PHS] has several advantages in transmission and thermal stability; however, its dissolution rate in commercial grade developers is unacceptably high. We report some recent results on modified, alkyl-substituted PHS derivatives. These polymers combine reduced alkaline solubiity with adequate optical and thermal properties, making them acceptable for future deep UV based production processes. Selected data of these new (co)polymers are discussed.

Relative quantum yield of I-asterisk(2P1/2) in the tunable laser UV photodissociation of i-C3F7I and n-C3F7I - Effect of temperature and exciplex emission

NASA Technical Reports Server (NTRS)

Smedley, J. E.; Leone, S. R.

1983-01-01

Wavelength-specific relative quantum yields of metastable I from pulsed laser photodissociation of i-C3F7I and n-C3F7I in the range 265-336 nm are determined by measuring the time-resolved infrared emission from the atomic I(P-2(1/2) P-2(3/2) transition. It is shown that although this yield appears to be unity from 265 to 298 nm, it decreases dramatically at longer wavelengths. Values are also reported for the enhancement of emission from metastable I due to exciplex formation at several temperatures. The exciplex formation emission increases linearly with parent gas pressure, but decreases with increasing temperature. Absorption spectra of i- and n-C3F7I between 303 and 497 K are presented, and the effect of temperature on the quantum yields at selected wavelengths greater than 300 nm, where increasing the temperature enhances the absorption considerably, are given. The results are discussed in regard to the development of solar-pumped iodine lasers.

Surface damage of thin AlN films with increased oxygen content by nanosecond and femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Salakhutdinov, Ildar; Chen, J. K.; Danylyuk, Yuriy; McCullen, Erik; Auner, Gregory

2009-10-01

AlN films deposited on sapphire substrates were damaged by single UV nanosecond (at 248 nm) and IR femtosecond (at 775 nm) laser pulses in air at normal pressure. The films had high (27-35 atomic %) concentration of oxygen introduced into thin surface layer (5-10 nm thickness). We measured damage threshold and studied morphology of the damage sites with atomic force and Nomarski optical microscopes with the objective to determine a correlation between damage processes and oxygen content. The damage produced by nanosecond pulses was accompanied by significant thermal effects with evident signatures of melting, chemical modification of the film surface, and specific redistribution of micro-defect rings around the damage spots. The nanosecond-damage threshold exhibited pronounced increase with increase of the oxygen content. In contrast to that, the femtosecond pulses produced damage without any signs of thermal, thermo-mechanical or chemical effects. No correlation between femtosecond-damage threshold and oxygen content as well as presence of defects within the laser-damage spot was found. We discuss the influence of the oxygen contamination on film properties and related mechanisms responsible for the specific damage effects and morphology of the damage sites observed in the experiments.

The Excimer Laser: Its Impact on Science and Industry

NASA Astrophysics Data System (ADS)

Basting, Dirk

2010-03-01

After the laser was demonstrated in 1960, 15 years were required to develop a practical method for extending laser emission into the UV: the Excimer laser. This historical review will describe the challenges with the new medium and provide an insight into the technological achievements. In the transition from Science to Industry it will be shown how start-ups successfully commercialized laboratory prototypes. The pioneers in this rapidly expanding field will be identified and the influence of government-funded research as well as the role of venture capital will be discussed. In scientific applications, the fields of photochemistry and material research were particularly stimulated by the advent of a reliable UV light source. Numerous industrial applications and worldwide research in novel applications were fueled In the early and mid 80's by progress in excimer laser performance and technology. The discovery of ablative photocomposition of polymer materials by Srinivasan at IBM opened the door to a multitude of important excimer applications. Micromachining with extreme precision with an excimer laser enabled the success of the inkjet printer business. Biological materials such as the human cornea can also be ``machined'' at 193nm, as proposed in 1983 by Trokel and Srinivasan. This provided the foundation of a new medical technology and an industry relying on the excimer laser to perform refractive surgery to correct vision Today, by far the largest use of the excimer laser is in photolithography to manufacture semiconductor chips, an application discovered by Jain at IBM in the early 80's. Moore's law of shrinking the size of the structure to multiply the number of transistors on a chip could not have held true for so long without the deep UV excimer laser as a light source. The presentation will conclude with comments on the most recent applications and latest market trends.

Highly sensitive and selective cartap nanosensor based on luminescence resonance energy transfer between NaYF4:Yb,Ho nanocrystals and gold nanoparticles.

PubMed

Wang, Zhijiang; Wu, Lina; Shen, Baozhong; Jiang, Zhaohua

2013-09-30

Fluorescent detection is an attractive method for the detection of toxic chemicals. However, most chemosensors that are currently utilized in fluorescent detection are based on organic dyes or quantum dots, which suffer from instability, high background noise and interference from organic impurities in solution, which can also be excited by UV radiation. In the present research, we developed a novel NaYF4:Yb,Ho/Au nanocomposite-based chemosensor with high sensitivity (10 ppb) and selectivity over competing analytes for the detection of the insecticide cartap. This nanosensor is excited with a 970-nm laser instead of UV radiation to give an emission peak at 541 nm. In the presence of cartap, the nanocomposites aggregate, resulting in enhanced luminescence resonance energy transfer between the NaYF4:Yb,Ho nanocrystals and the gold nanoparticles, which decreases the emission intensity at 541 nm. The relative luminescence intensity at 541 nm has a linear relationship with the concentration of cartap in the solution. Based on this behavior, the developed nanosensor successfully detected cartap in farm produce and water samples with satisfactory results. Copyright © 2013 Elsevier B.V. All rights reserved.

Microdrilling of PCB substrate using DPSS 3rd harmonic laser

NASA Astrophysics Data System (ADS)

Kim, J. G.; Chang, Won Seok; Yoon, Kyung Ku; Jeong, Sungho; Shin, Bo Sung; Whang, Kyung Hyun

2003-02-01

Micromachining using the DPSS 3rd Harmonic Laser (355nm) has outstanding advantages as a UV source in comparison with Excimer lasers in various aspects such as maintenance cost, maskless machining, high repetition rate and so on. It also has the greater absorptivity of many materials in contrast to other IR sources. In this paper, the process for micro-drilling of through and blind hope in Cu/PI/Cu substrate with the UV DPSSL and a scanning device is investigated by both experimental and numerical methods. It is known that there is a large gap between the ablation threshold of copper and that of PI. We use the multi path for through hole with high energy density and we use Archimedes spiral path for blind hole with different energy densities to ablate different material. Furthermore, Matlab simulations considering the energy threshold of material is performed to anticipate the ablation shape according to the duplication of pulse, and FEM thermal analysis is used to predict the ablation depth of copper. This study would be widely applicable to various laser micromachining applications including through and blind hole micro-drilling of PCB, and micromachining of semiconductor components, medical parts and printer nozzles amongst others.

Exposure of Chlorpromazine to 266 nm Laser Beam Generates New Species with Antibacterial Properties: Contributions to Development of a New Process for Drug Discovery

PubMed Central

Pascu, Mihail Lucian; Danko, Balazs; Martins, Ana; Jedlinszki, Nikoletta; Alexandru, Tatiana; Nastasa, Viorel; Boni, Mihai; Militaru, Andra; Andrei, Ionut Relu; Staicu, Angela; Hunyadi, Attila; Fanning, Seamus; Amaral, Leonard

2013-01-01

Introduction Phenothiazines when exposed to white light or to UV radiation undergo a variety of reactions that result in degradation of parental compound and formation of new species. This process is slow and may be sped up with exposure to high energy light such as that produced by a laser. Methods Varying concentrations of Chlorpromazine Hydrochloride (CPZ) (2–20 mg/mL in distilled water) were exposed to 266 nm laser beam (time intervals: 1–24 hrs). At distinct intervals the irradiation products were evaluated by spectrophotometry between 200–1500 nm, Thin Layer Chromatography, High Pressure Liquid Chromatography (HPLC) - Diode Array Detection, HPLC tandem mass spectrometry, and for activity against the CPZ sensitive test organism Staphylococcus aureus ATCC 25923. Results CPZ exposure to 266 nm laser beam of given energy levels yielded species, whose number increased with duration of exposure. Although the major species produced were Promazine (PZ), hydroxypromazine or PZ sulfoxide, and CPZ sulfoxide, over 200 compounds were generated with exposure of 20 mg/mL of CPZ for 24 hrs. Evaluation of the irradiation products indicated that the bioactivity against the test organism increased despite the total disappearance of CPZ, that is due, most probably, to one or more new species that remain yet unidentified. Conclusions Exposure of CPZ to a high energy (6.5 mJ) 266 nm laser beam yields rapidly a large number of new and stable species. For biological grade phenothiazines (in other words knowing the impurities in the samples: solvent and solute) this process may be reproducible because one can control within reasonably low experimental errors: the concentration of the parent compound, the laser beam wavelength and average energy, as well as the duration of the exposure time. Because the process is “clean” and rapid, it may offer advantages over the pyrogenically based methods for the production of derivatives. PMID:23405212

Solid-state laser source of narrowband ultraviolet B light for skin disease care with advanced performance

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong; Buchwald, Kristian

2015-02-01

Two years ago we reported about the development of solid state laser source for medical skin treatment with wavelength 310.6 nm and average power 200 mW. Here we describe the results of investigation of the advanced version of the laser, which is a more compact device with increased output power and flat top beam profile. Ti: Sapphire laser, the main module of our source, was modified and optimized such, that UV average power of the device was increased 1.7 times. Fiber optic homogenizer was replaced by articulated arm with diffraction diffuser, providing round spot with flat profile at the skin. We investigated and compare characteristics of Ti: Sapphire lasers with volume Bragg grating and with fused silica transmission grating, which was used first time for Ti: Sapphire laser spectral selection and tuning. Promising performance of last gratings is demonstrated.

UV-sensitive scientific CCD image sensors

NASA Astrophysics Data System (ADS)

Vishnevsky, Grigory I.; Kossov, Vladimir G.; Iblyaminova, A. F.; Lazovsky, Leonid Y.; Vydrevitch, Michail G.

1997-06-01

An investigation of probe laser irradiation interaction with substances containing in an environment has long since become a recognized technique for contamination detection and identification. For this purpose, a near and midrange-IR laser irradiation is traditionally used. However, as many works presented on last ecology monitoring conferences show, in addition to traditional systems, rapidly growing are systems with laser irradiation from near-UV range (250 - 500 nm). Use of CCD imagers is one of the prerequisites for this allowing the development of a multi-channel computer-based spectral research system. To identify and analyze contaminating impurities on an environment, such methods as laser fluorescence analysis, UV absorption and differential spectroscopy, Raman scattering are commonly used. These methods are used to identify a large number of impurities (petrol, toluene, Xylene isomers, SO2, acetone, methanol), to detect and identify food pathogens in real time, to measure a concentration of NH3, SO2 and NO in combustion outbursts, to detect oil products in a water, to analyze contaminations in ground waters, to define ozone distribution in the atmosphere profile, to monitor various chemical processes including radioactive materials manufacturing, heterogeneous catalytic reactions, polymers production etc. Multi-element image sensor with enhanced UV sensitivity, low optical non-uniformity, low intrinsic noise and high dynamic range is a key element of all above systems. Thus, so called Virtual Phase (VP) CCDs possessing all these features, seems promising for ecology monitoring spectral measuring systems. Presently, a family of VP CCDs with different architecture and number of pixels is developed and being manufactured. All CCDs from this family are supported with a precise slow-scan digital image acquisition system that can be used in various image processing systems in astronomy, biology, medicine, ecology etc. An image is displayed directly on a PC monitor through a software support.

Ultraviolet photosensitivity of sulfur-doped micro- and nano-crystalline diamond

DOE PAGES

Mendoza, Frank; Makarov, Vladimir; Hidalgo, Arturo; ...

2011-06-06

The room-temperature photosensitivity of sulfur-doped micro- (MCD), submicro- (SMCD) and nano- (NCD) crystalline diamond films synthesized by hot-filament chemical vapor deposition was studied. The structure and composition of these diamond materials were characterized by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The UV sensitivity and response time were studied for the three types of diamond materials using a steady state broad UV excitation source and two pulsed UV laser radiations. It was found that they have high sensitivity in the UV region, as high as 10 9 sec -1mV -1 range, linear response in a broad spectral range belowmore » 320 nm, photocurrents around ~10 -5 A, and short response time better than 100 ns, which is independent of fluency intensity. A phenomenological model was applied to help understand the role of defects and dopant concentration on the materials’ photosensitivity.« less

Note: Deep UV-pump THz-probe spectroscopy of the excess electron in water.

PubMed

Berger, Arian; Savolainen, Janne; Shalit, Andrey; Hamm, Peter

2017-06-28

In the work of Savolainen et al. [Nat. Chem. 6, 697 (2014)], we studied the excess (hydrated) electron in water with the help of transient THz spectroscopy, which is a sensitive probe of its delocalization length. In that work, we used laser pulses at 800 nm, 400 nm, and 267 nm for photoionization. While the detachment mechanism for 400 nm and 267 nm is complicated and requires a concerted nuclear rearrangement, we provided evidence that 800 nm pumping excites the excess electron directly and vertically into the conduction band, despite a highly nonlinear field-ionization process. In the present note, we extend that work to 200 nm pumping, which provides a much cleaner way to reach the conduction band. We show that the detachment pathways upon 200 nm and 800 nm pumping are in essence the same, as indicated by the same initial size of the electron wavefunction and the same time scales for the collapse of the wavefunction and geminate recombination.

The microstructure and photoluminescence of ZnO-MoS2 core shell nano-materials

NASA Astrophysics Data System (ADS)

Yu, H.; Liu, C. M.; Huang, X. Y.; Lei, M. Y.

2017-01-01

In this paper, ZnO-MoS2-FT (FT is the fabrication temperature of MoS2) core shell nano-material samples (with ZnO as a core and MoS2 as a shell material) were fabricated on ITO substrate using hydrothermal method. The crystal structure, morphology, optical absorption and photoluminescence (PL) of samples were investigated. Compared with that of pure ZnO nanorods, ZnO-MoS2-FT samples show an enhanced light absorption. In addition, ultraviolet (UV) and visible (Vis) PL intensity of ZnO-MoS2-FT samples excited by 325 nm laser are greatly weakened. The UV PL peak position is not changed obviously. However, the Vis PL peak position is changed visibly. The Vis PL of ZnO-MoS2-FT samples under UV excitation indicates that the ratio of oxygen interstitial to oxygen vacancy is decreased. The suppression of UV PL of ZnO-MoS2-FT samples may be related to the weakening of crystal quality of ZnO, easier separation of electron-hole pairs, enhancement of light absorption, and newly introduced defects in the interface between ZnO and MoS2. Under 514 nm laser excitation, the PL peak position of ZnO-MoS2-FT samples has a red shift with FT being increased from 80 to 160 °C. The influence of excitation power (EP) on the PL of ZnO-MoS2-FT samples was also investigated. The PL of ZnO-MoS2-FT samples have a red shift with EP being increased. This may be due to the sample temperature is increased with EP, resulting an enhancement of electron-phonon interaction. A schematic diagram of charge generation and transfer is presented to understand the mechanism of PL of ZnO-MoS2 under UV and Vis excitation.

Enhanced UV photoresponse of KrF-laser-synthesized single-wall carbon nanotubes/n-silicon hybrid photovoltaic devices.

PubMed

Le Borgne, V; Gautier, L A; Castrucci, P; Del Gobbo, S; De Crescenzi, M; El Khakani, M A

2012-06-01

We report on the KrF-laser ablation synthesis, purification and photocurrent generation properties of single-wall carbon nanotubes (SWCNTs). The thermally purified SWCNTs are integrated into hybrid photovoltaic (PV) devices by spin-coating them onto n-Si substrates. These novel SWCNTs/n-Si hybrid devices are shown to generate significant photocurrent (PC) over the entire 250-1050 nm light spectrum with external quantum efficiencies (EQE) reaching up to ~23%. Our SWCNTs/n-Si hybrid devices are not only photoactive in the traditional spectral range of Si solar cells, but generate also significant PC in the UV domain (below 400 nm). This wider spectral response is believed to be the result of PC generation from both the SWCNTs themselves and the tremendous number of local p-n junctions created at the nanotubes/Si interface. To assess the prevalence of these two contributions, the EQE spectra and J-V characteristics of these hybrid devices were investigated in both planar and top-down configurations, as a function of SWCNTs' film thickness. A sizable increase in EQE in the near UV with respect to the silicon is observed in both configurations, with a more pronounced UV photoresponse in the planar mode, confirming thereby the role of SWCNTs in the photogeneration process. The PC generation is found to reach its maximum for an optimal the SWCNT film thickness, which is shown to correspond to the best trade-off between lowest electrical resistance and highest optical transparency. Finally, by analyzing the J-V characteristics of our SWCNTs/n-Si devices with an equivalent circuit model, we were able to point out the contribution of the various electrical components involved in the photogeneration process. The SWCNTs-based devices demonstrated here open up the prospect for their use in highly effective photovoltaics and/or UV-light sensors.

UV laser-assisted wire stripping and micro-machining

NASA Astrophysics Data System (ADS)

Martyniuk, Jerry

1994-02-01

Results are reported for the use of a 266 nm frequency quadrupled Nd:YAG ultraviolet laser in the areas of wire stripping of small coaxial type transmission lines and for micro-machining of various materials including copper, glass, polyimide and DuPont TEFLONTM. This new laser is typically run with a 2 KHz repetition rate, 40 ns FWHM pulse and a fluence of about 50 joules/cm2 which makes it possible to micro-machine metals, polymers, glasses and ceramics. The high fluence of this laser allows shielding structures such as Al-MylarTM, Al-KaptonTM or the plated copper used in small coaxial cables to be precisely cut. Cut rates are reported for the above materials as well as results and photos of wire stripping and micro- machining.

Reduction of damage initiation density in fused silica optics via UV laser conditioning

DOEpatents

Peterson, John E.; Maricle, Stephen M.; Brusasco, Raymond M.; Penetrante, Bernardino M.

2004-03-16

The present invention provides a method for reducing the density of sites on the surface of fused silica optics that are prone to the initiation of laser-induced damage, resulting in optics which have far fewer catastrophic defects and are better capable of resisting optical deterioration upon exposure for a long period of time to a high-power laser beam having a wavelength of about 360 nm or less. The initiation of laser-induced damage is reduced by conditioning the optic at low fluences below levels that normally lead to catastrophic growth of damage. When the optic is then irradiated at its high fluence design limit, the concentration of catastrophic damage sites that form on the surface of the optic is greatly reduced.

Periodic surface structure creation by UV femtosecond pulses on silicon

NASA Astrophysics Data System (ADS)

Gilicze, Barnabás; Moczok, Márió; Madarász, Dániel; Juhász, Nóra; Racskó, Bence; Nánai, László

2017-01-01

Laser-induced periodic surface structures are created on Si (100) and Si (111) wafers by 500 fs laser pulses at 248 nm. The periodic structure is concentric and highly regular. The spatial period is consistently varying between 1.1 µm and 3.3 µm in the radial direction. It is shown that the fluence of the irradiation at the same pulse number determines the size of the area where the periodic structure is created and for the same fluence the pulse number determines the regularity of the created grooves by melting processes. The origin of this structure is identified as the inhomogeneity of the laser beam profile caused by Fresnel diffraction close to the focal plane. Further improvement of the formation of periodic structure with femtosecond laser pulses is suggested.

Multi-Wavelength Laser Transmitter for the Two-Step Laser Time-of-Flight Mass Spectrometer

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Li, Steven X.; Fahey, Molly E.; Grubisic, Andrej; Farcy, Benjamin J.; Uckert, Kyle; Li, Xiang; Getty, Stephanie

2017-01-01

Missions to diverse Outer Solar System bodies will require investigations that can detect a wide range of organics in complex mixtures, determine the structure of selected molecules, and provide powerful insights into their origin and evolution. Previous studies from remote spectroscopy of the Outer Solar System showed a diverse population of macromolecular species that are likely to include aromatic and conjugated hydrocarbons with varying degrees of methylation and nitrile incorporation. In situ exploration of Titan's upper atmosphere via mass and plasma spectrometry has revealed a complex mixture of organics. Similar material is expected on the Ice Giants, their moons, and other Outer Solar System bodies, where it may subsequently be deposited onto surface ices. It is evident that the detection of organics on other planetary surfaces provides insight into the chemical and geological evolution of a Solar System body of interest and can inform our understanding of its potential habitability. We have developed a prototype two-step laser desorption/ionization time-of-flight mass spectrometer (L2MS) instrument by exploiting the resonance-enhanced desorption of analyte. We have successfully demonstrated the ability of the L2MS to detect hydrocarbons in organically-doped analog minerals, including cryogenic Ocean World-relevant ices and mixtures. The L2MS instrument operates by generating a neutral plume of desorbed analyte with an IR desorption laser pulse, followed at a delay by a ultraviolet (UV) laser pulse, ionizing the plume. Desorption of the analyte, including trace organic species, may be enhanced by selecting the wavelength of the IR desorption laser to coincide with IR absorption features associated with vibration transitions of minerals or organic functional groups. In this effort, a preliminary laser developed for the instrument uses a breadboard mid-infrared (MIR) desorption laser operating at a discrete 3.475 µm wavelength, and a breadboard UV ionization laser operating at a wavelength of 266 nm. The MIR wavelength was selected to overlap the C-H stretch vibrational transition of certain aromatic hydrocarbons, and the UV wavelength provides additional selectivity to aromatic species via UV resonance-enhanced multiphoton ionization effects. The use of distinct laser wavelengths allows efficient coupling to the vibrational and electronic spectra of the analyte in independent desorption and ionization steps, mitigating excess energy that can lead to fragmentation during the ionization process and leading to selectivity that can aid in data interpretation.

Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Vladimir V.

Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics,more » magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated plasma will be studied to estimate its contribution to the Doppler broadening of x-ray lines. Development of “necks” and “hot spots” will be studied with high-resolution UV diagnostics, an x-ray streak camera, and x-ray spectroscopy. Laser initiation of hot spots in Z pinches will be tested. A Faraday rotation diagnostic at 266 nm will be applied to 1-10 MG magnetic fields. For magnetic fields B>20 MG, suggested in micropinches, Cotton-Mouton and cutoff diagnostics will be applied. A picosecond optical Kerr shutter will be tested to increase a sensitivity of UV methods for application at multi-MA Z pinches. The proposal is based on the experimental capability of NTF. The Zebra generator produces 1-1.7 MA Z-pinches with electron plasma density of 10 20-10 21cm -3, electron temperature of 0.5-1 keV, and magnetic fields >10 MG. The Leopard laser was upgraded to energy of 90-J at 0.8 ns. This regime will be used for laser initiation of hot spots. A further upgrade to energy of 250-J is suggested for laser-Z-pinch interaction. A picosecond regime will be used for optical gating. A 10-TW Tomcat laser at NTF is available for the high energy UV laser probing of the Z-pinch. Two graduate students will develop new optical and x-ray diagnostics, carry out experiments, and process experimental data. Other students will be involved in the design and fabrication of loads, supporting regular optical and x-ray diagnostics, and data processing. The new plasma diagnostics may be applied to HEDP experiments at NTF and other multi-MA generators. The feasibility of the research plan is based on the experience of the scientific team in Z-pinch plasma physics, laser physics, development of new plasma diagnostics, and the experimental capability of NTF. The experimental group of Dr. V. V. Ivanov (UNR) collaborates with a group for Z pinch MHD modeling of Dr. J. P. Chittenden (Imperial College, London), and theoretical group of Dr. D. D. Ryutov (LLNL). The suggested research ideas are supported by preliminary experiments.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

The laser-induced discoloration of stonework; a comparative study on its origins and remedies.

PubMed

Pouli, P; Fotakis, C; Hermosin, B; Saiz-Jimenez, C; Domingo, C; Oujja, M; Castillejo, M

2008-12-01

For understanding the phenomena associated with the discoloration observed in some cases of infrared laser cleaned stonework surfaces, a comparative study of three different types and morphologies of pollution encrustation and stone substrates was undertaken. Fragments originating from monuments with historic and/or artistic value, bearing homogeneous thin soiling on Pentelic marble (Athens, Greece), thick encrustation on Hontoria limestone (Burgos, Spain) and compact thin crust on gypsum decorations (Athens, Greece), have been studied on the basis of their composition and origin, together with the conditions that may induce yellowing effects upon their laser cleaning with IR wavelengths. While irradiation in the UV (i.e. at 355 nm) could not effectively remove the encrustations studied, irradiation at 1,064 nm was found efficient to remove all the studied pollution accumulations. Discoloration towards yellow was evident in all cases and at different levels, including the samples with intentional patination layer. To the limit of Raman detection no chemical alterations were detected on the irradiated areas while the presence of yellow polar compounds in all the pollution crusts studied supports the argument that the discoloration of the stone surfaces upon their IR irradiation may be due to the uncovering of existing yellow layers as result of the migration of these compounds inwards to the original stone surface. To correct and/or prevent such undesired coloration the use of IR and UV radiation both in sequential and synchronous mode was considered, with positive results.

The laser-induced discoloration of stonework; a comparative study on its origins and remedies

NASA Astrophysics Data System (ADS)

Pouli, P.; Fotakis, C.; Hermosin, B.; Saiz-Jimenez, C.; Domingo, C.; Oujja, M.; Castillejo, M.

2008-12-01

For understanding the phenomena associated with the discoloration observed in some cases of infrared laser cleaned stonework surfaces, a comparative study of three different types and morphologies of pollution encrustation and stone substrates was undertaken. Fragments originating from monuments with historic and/or artistic value, bearing homogeneous thin soiling on Pentelic marble (Athens, Greece), thick encrustation on Hontoria limestone (Burgos, Spain) and compact thin crust on gypsum decorations (Athens, Greece), have been studied on the basis of their composition and origin, together with the conditions that may induce yellowing effects upon their laser cleaning with IR wavelengths. While irradiation in the UV (i.e. at 355 nm) could not effectively remove the encrustations studied, irradiation at 1064 nm was found efficient to remove all the studied pollution accumulations. Discoloration towards yellow was evident in all cases and at different levels, including the samples with intentional patination layer. To the limit of Raman detection no chemical alterations were detected on the irradiated areas while the presence of yellow polar compounds in all the pollution crusts studied supports the argument that the discoloration of the stone surfaces upon their IR irradiation may be due to the uncovering of existing yellow layers as result of the migration of these compounds inwards to the original stone surface. To correct and/or prevent such undesired coloration the use of IR and UV radiation both in sequential and synchronous mode was considered, with positive results.

Fabrication and structural properties of AlN submicron periodic lateral polar structures and waveguides for UV-C applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alden, D.; Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin; Guo, W.

Periodically poled AlN thin films with submicron domain widths were fabricated for nonlinear applications in the UV-VIS region. A procedure utilizing metalorganic chemical vapor deposition growth of AlN in combination with laser interference lithography was developed for making a nanoscale lateral polarity structure (LPS) with domain size down to 600 nm. The Al-polar and N-polar domains were identified by wet etching the periodic LPS in a potassium hydroxide solution and subsequent scanning electron microscopy (SEM) characterization. Fully coalesced and well-defined vertical interfaces between the adjacent domains were established by cross-sectional SEM. AlN LPSs were mechanically polished and surface roughness with amore » root mean square value of ∼10 nm over a 90 μm × 90 μm area was achieved. 3.8 μm wide and 650 nm thick AlN LPS waveguides were fabricated. The achieved domain sizes, surface roughness, and waveguides are suitable for second harmonic generation in the UVC spectrum.« less

Ultraviolet Thomson Scattering from Direct-Drive Coronal Plasmas

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Goncharov, V. N.; Michel, D. T.; Follett, R. K.; Katz, J.; Froula, D. H.

2013-10-01

Ultraviolet (λ4 ω = 263 nm) Thomson scattering (TS) was used to probe ion-acoustic waves (IAW's) and electron plasma waves (EPW's) from direct-drive coronal plasmas. Fifty-nine drive beams (λ3 ω = 351 nm) illuminate a spherical target with a radius of ~860 μm. Advances in the ultraviolet (UV) TS diagnostic at the Omega Laser Facility provide the ability to detect deep UV photons (~190 nm) and allow access to scattered light from EPW's propagating near the 3 ω quarter-critical surface (~2.5 × 1021 cm-3) . A series of experiments studied the effects of ablator materials on coronal plasma conditions. Electron temperatures and densities were measured from 150 μm to 400 μm from the initial target surface. Standard CH shells were compared to three-layered shells consisting of Si doped CH, Si, and Be. Early analysis indicates that these multilayered targets have less hot-electron energy as a result of higher electron temperature in the coronal plasma. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Planar excilamp on rare gas chlorides pumped by a transverse self-sustained discharge

NASA Astrophysics Data System (ADS)

Panchenko, Aleksei N.; Tarasenko, Viktor F.

2006-02-01

The design and parameters of a UV—VUV spontaneous radiation source — an excilamp operating on chlorides of rare gases ArCl*, KrCl* and XeCl* in the wavelength range 175—308 nm are presented. The Ne—Xe(Kr, Ar)—HCl mixtures were excited by a high-pressure self-sustained discharge with spark preionisation. It is shown that upon pumping mixtures of rare gases and halogens by a transverse discharge, the intensities of the B—X emission band of molecules ArCl*, KrCl* and XeCl* are comparable and up to 90% of the emission energy of excilamps can be concentrated in the UV region. The peak UV power density at 222 and 308 nm on the output window of the excilamp was ~2 kW cm-2 for the pulse energy up to ~ 3 mJ. The output emission energy of the excilamp at 175 nm achieved ~0.6 mJ and the peak power density was ~0.4 kW cm-2.

Applicability of UV laser-induced solid-state fluorescence spectroscopy for characterization of solid dosage forms.

PubMed

Woltmann, Eva; Meyer, Hans; Weigel, Diana; Pritzke, Heinz; Posch, Tjorben N; Kler, Pablo A; Schürmann, Klaus; Roscher, Jörg; Huhn, Carolin

2014-10-01

High production output of solid pharmaceutical formulations requires fast methods to ensure their quality. Likewise, fast analytical procedures are required in forensic sciences, for example at customs, to substantiate an initial suspicion. We here present the design and the optimization of an instrumental setup for rapid and non-invasive characterization of tablets by laser-induced fluorescence spectroscopy (with a UV-laser (λ ex = 266 nm) as excitation source) in reflection geometry. The setup was first validated with regard to repeatability, bleaching phenomena, and sensitivity. The effect on the spectra by the physical and chemical properties of the samples, e.g. their hardness, homogeneity, chemical composition, and granule grain size of the uncompressed material, using a series of tablets, manufactured in accordance with design of experiments, was investigated. Investigation of tablets with regard to homogeneity, especially, is extremely important in pharmaceutical production processes. We demonstrate that multiplicative scatter correction is an appropriate tool for data preprocessing of fluorescence spectra. Tablets with different physical and chemical characteristics can be discriminated well from their fluorescence spectra by subjecting the results to principal component analysis.

STREAK CAMERA MEASUREMENTS OF THE APS PC GUN DRIVE LASER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dooling, J. C.; Lumpkin, A. H.

We report recent pulse-duration measurements of the APS PC Gun drive laser at both second harmonic and fourth harmonic wavelengths. The drive laser is a Nd:Glass-based chirped pulsed amplifier (CPA) operating at an IR wavelength of 1053 nm, twice frequency-doubled to obtain UV output for the gun. A Hamamatsu C5680 streak camera and an M5675 synchroscan unit are used for these measurements; the synchroscan unit is tuned to 119 MHz, the 24th subharmonic of the linac s-band operating frequency. Calibration is accomplished both electronically and optically. Electronic calibration utilizes a programmable delay line in the 119 MHz rf path. Themore » optical delay uses an etalon with known spacing between reflecting surfaces and is coated for the visible, SH wavelength. IR pulse duration is monitored with an autocorrelator. Fitting the streak camera image projected profiles with Gaussians, UV rms pulse durations are found to vary from 2.1 ps to 3.5 ps as the IR varies from 2.2 ps to 5.2 ps.« less

Experimental investigation of the effects of different liquid environments on the graphene oxide produced by laser ablation method

NASA Astrophysics Data System (ADS)

Ghavidel, Elham; Sari, Amir Hossein; Dorranian, Davoud

2018-07-01

In this work, the effects of liquid environments on the characteristics and optical properties of carbon nanostructures - in particular, Graphene Oxide (GO) - prepared by pulsed laser ablation were studied experimentally. The second harmonic beam of a Q-switched Nd:YAG laser of 532 nm wavelength at 6 ns pulse width and 0.7 J/cm2 fluence was employed to irradiate the graphite target in liquid nitrogen, deionized water, and 0.01 M CTAB solution under the same initial experimental conditions. Produced nanostructures were characterized by Raman scattering spectrum, FE-SEM and TEM images, Photoluminescence, and UV-Vis-NIR spectrum. TEM and FE-SEM images show sheet-like morphology with few square micrometer area graphenes in all samples. Raman and UV-Vis-NIR analyses show that graphene is oxidized due to the presence of oxygen molecules in ablation environment. Results demonstrate that the graphene nanosheets produced in deionized water are multilayer, contains the largest sp2 domain size, the least defects and the lowest possibility of aggregation.

Design, characterization and applications of new ionic liquid matrices for multifunctional analysis of biomolecules: a novel strategy for pathogenic bacteria biosensing.

PubMed

Abdelhamid, Hani Nasser; Khan, M Shahnawaz; Wu, Hui-Fen

2014-05-01

The design, preparation and performance for novel UV-light absorbing (room-temperature) ionic liquid matrices (UV-RTILMs) for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) were reported. A series of UV-RTILMs was prepared by ultrasonication of equimolar of acid (mefenamic acid) and bases (aniline (ANI), pyridine (Pyr), dimethyl aniline (DMANI) and 2-methyl picoline (2-P)). The UV-RTILMs have not only significant absorbance at the desired wavelength (337 nm of the N2 Laser), but also have available protons that can easily undergo proton transfer reactions to ionize the target molecules. The novel UV-RTILMs have the ability to ionize different and wide classes of compounds such as drugs, carbohydrate, and amino acids. The new UV-RTILMs series have been successfully and selectively applied for biosensing the lysates of pathogenic bacteria in the presence of the cell macromolecules. A new strategy for biosensing pathogens was presented via sensing the pathogens lysate in the cell suspension. The new materials can effectively detect the bacterial toxins without separation or any pretreatment. They offered excellent ionization of labile oligosaccharides with protonated peaks. They could significantly enhance the analyte signals, produce homogeneous spotting, reducing spot-to-spot variation, excellent vacuum stability, higher ion peak intensity, and wide application possibility. The physical parameters such as molar refractivity, molar volume, parachor, surface tension, density and polarizability were calculated and tabulated. The new UV-RTILMs could offer excellent reproducibility and great repeatability and they are promising matrices for wide applications on MALDI-MS. Copyright © 2014. Published by Elsevier B.V.

UV absorption spectrum of the ClO dimer (Cl2O2) between 200 and 420 nm.

PubMed

Papanastasiou, Dimitrios K; Papadimitriou, Vassileios C; Fahey, David W; Burkholder, James B

2009-12-10

The UV photolysis of Cl(2)O(2) (dichlorine peroxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV absorption spectrum of Cl(2)O(2) was measured using diode array spectroscopy and absolute cross sections, sigma, are reported for the wavelength range 200-420 nm. Pulsed laser photolysis of Cl(2)O at 248 nm or Cl(2)/Cl(2)O mixtures at 351 nm at low temperature (200-228 K) and high pressure (approximately 700 Torr, He) was used to produce ClO radicals and subsequently Cl(2)O(2) via the termolecular ClO self-reaction. The Cl(2)O(2) spectrum was obtained from spectra recorded following the completion of the gas-phase ClO radical chemistry. The spectral analysis used observed isosbestic points at 271, 312.9, and 408.5 nm combined with reaction stoichiometry and chlorine mass balance to determine the Cl(2)O(2) spectrum. The Cl(2)O(2) UV absorption spectrum peaks at 244.5 nm with a cross section of 7.6(-0.5)(+0.8) x 10(-18) cm(2) molecule(-1) where the quoted error limits are 2sigma and include estimated systematic errors. The Cl(2)O(2) absorption cross sections obtained for wavelengths in the range 300-420 nm are in good agreement with the Cl(2)O(2) spectrum reported previously by Burkholder et al. (J. Phys. Chem. A 1990, 94, 687) and significantly higher than the values reported by Pope et al. (J. Phys. Chem. A 2007, 111, 4322). A possible explanation for the discrepancy in the Cl(2)O(2) cross section values with the Pope et al. study is discussed. Representative, atmospheric photolysis rate coefficients are calculated and a range of uncertainty estimated based on the determination of sigma(Cl(2)O(2))(lambda) in this work. Although improvements in our fundamental understanding of the photochemistry of Cl(2)O(2) are still desired, this work indicates that major revisions in current atmospheric chemical mechanisms are not required to simulate observed polar ozone depletion.

UV Absorption Spectrum of the ClO Dimer (Cl2O2) between 200 and 420 nm

NASA Astrophysics Data System (ADS)

Papanastasiou, Dimitrios K.; Papadimitriou, Vassileios C.; Fahey, David W.; Burkholder, James B.

2009-11-01

The UV photolysis of Cl2O2 (dichlorine peroxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV absorption spectrum of Cl2O2 was measured using diode array spectroscopy and absolute cross sections, σ, are reported for the wavelength range 200-420 nm. Pulsed laser photolysis of Cl2O at 248 nm or Cl2/Cl2O mixtures at 351 nm at low temperature (200-228 K) and high pressure (˜700 Torr, He) was used to produce ClO radicals and subsequently Cl2O2 via the termolecular ClO self-reaction. The Cl2O2 spectrum was obtained from spectra recorded following the completion of the gas-phase ClO radical chemistry. The spectral analysis used observed isosbestic points at 271, 312.9, and 408.5 nm combined with reaction stoichiometry and chlorine mass balance to determine the Cl2O2 spectrum. The Cl2O2 UV absorption spectrum peaks at 244.5 nm with a cross section of 7.6-0.5+0.8 × 10-18 cm2 molecule-1 where the quoted error limits are 2σ and include estimated systematic errors. The Cl2O2 absorption cross sections obtained for wavelengths in the range 300-420 nm are in good agreement with the Cl2O2 spectrum reported previously by Burkholder et al. (J. Phys. Chem. A 1990, 94, 687) and significantly higher than the values reported by Pope et al. (J. Phys. Chem. A 2007, 111, 4322). A possible explanation for the discrepancy in the Cl2O2 cross section values with the Pope et al. study is discussed. Representative, atmospheric photolysis rate coefficients are calculated and a range of uncertainty estimated based on the determination of σCl2O2(λ) in this work. Although improvements in our fundamental understanding of the photochemistry of Cl2O2 are still desired, this work indicates that major revisions in current atmospheric chemical mechanisms are not required to simulate observed polar ozone depletion.

Influence of the laser pulse repetition rate and scanning speed on the morphology of Ag nanostructures fabricated by pulsed laser ablation of solid target in water

NASA Astrophysics Data System (ADS)

Nikolov, A. S.; Balchev, I. I.; Nedyalkov, N. N.; Kostadinov, I. K.; Karashanova, D. B.; Atanasova, G. B.

2017-11-01

Nanostructures of noble metal were produced by pulsed laser ablation in liquid. A solid Ag target was immersed in double distilled water and a CuBr laser in a master oscillator—power amplifier configuration oscillating at 511 nm and emitting pulses with duration of 30 ns at a repetition rate of up to 20 kHz was employed to produce different colloids. The impact was studied of the laser pulse repetition rate and the beam scanning speed on the morphology of the nanostructures formed. Further, the optical extinction spectra of the colloids in the UV/VIS range were measured and used to make an indirect assessment of the changes in the shape and size distribution of the nanostructures. The transmission values in the near UV range were used to estimate the efficiency of the ablation process under the different experimental conditions implemented. A visualization of the nanostructures was made possible by transmission electron microscopy (TEM). The structure and phase composition of the nanoparticles were studied by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), while the alteration of the target surface caused by the impact of the high-repetition-rate laser illumination was investigated by X-ray photoelectron spectroscopy (XPS). The optimal conditions were determined yielding the highest efficiency in terms of amount of ablated material.

Is energy pooling necessary in ultraviolet matrix-assisted laser desorption/ionization?

PubMed

Lin, Hou-Yu; Song, Botao; Lu, I-Chung; Hsu, Kuo-Tung; Liao, Chih-Yu; Lee, Yin-Yu; Tseng, Chien-Ming; Lee, Yuan-Tseh; Ni, Chi-Kung

2014-01-15

Energy pooling has been suggested as the key process for generating the primary ions during ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). In previous studies, decreases in fluorescence quantum yields as laser fluence increased for 2-aminobenzoic acid, 2,5-dihydroxybenzoic acid (2,5-DHB), and 3-hydroxypicolinic acid were used as evidence of energy pooling. This work extends the research to other matrices and addresses whether energy pooling is a universal property in UV-MALDI. Energy pooling was investigated in a time-resolved fluorescence experiment by using a short laser pulse (355 nm, 20 ps pulse width) for excitation and a streak camera (1 ps time resolution) for fluorescence detection. The excited-state lifetime of 2,5-DHB decreased with increases in laser fluence. This suggests that a reaction occurs between two excited molecules, and that energy pooling may be one of the possible reactions. However, the excited-state lifetime of 2,4,6-trihydroxyacetophenone (THAP) did not change with increases in laser fluence. The upper limit of the energy pooling rate constant for THAP is estimated to be approximately 100-500 times smaller than that of 2,5-DHB. The small energy pooling rate constant for THAP indicates that the potential contribution of the energy pooling mechanism to the generation of THAP matrix primary ions should be reconsidered. Copyright © 2013 John Wiley & Sons, Ltd.

Removal of sulfur compounds from diesel using ArF laser and oxygen.

PubMed

Gondal, M A; Siddiqui, M N; Al-Hooshani, K

2013-01-01

A laser-based technique for deep desulfurization of diesel and other hydrocarbon fuels by removal of dimethyldibenzothiophene (DMDBT), a persistent sulfur contaminant in fuel oils has been developed. We report a selective laser excitation of DMDBT in diesel and model compounds such as n-hexane in a reaction chamber under oxygen environment where oxidative reactions can take place. ArF laser emitting at 193 nm was employed for excitation of oxygen and DMDBT, while for process optimization, the laser energy was varied from 50 to 200 mJ/cm(2). The laser-irradiated DMDBT solution under continuous oxygen flow was analyzed by UV absorption spectrometer to determine the photochemical oxidative degradation of DMDBT. In just 5 min of laser irradiation time, almost 95% DMDBT was depleted in a diesel containing 200 ppm of DMDBT. This article provides a new method for the removal of sulfur compounds from diesel by laser based photochemical process.

100J Pulsed Laser Shock Driver for Dynamic Compression Research

NASA Astrophysics Data System (ADS)

Wang, X.; Sethian, J.; Bromage, J.; Fochs, S.; Broege, D.; Zuegel, J.; Roides, R.; Cuffney, R.; Brent, G.; Zweiback, J.; Currier, Z.; D'Amico, K.; Hawreliak, J.; Zhang, J.; Rigg, P. A.; Gupta, Y. M.

2017-06-01

Logos Technologies and the Laboratory for Laser Energetics (LLE, University of Rochester) - in partnership with Washington State University - have designed, built and deployed a one of a kind 100J pulsed UV (351 nm) laser system to perform real-time, x-ray diffraction and imaging experiments in laser-driven compression experiments at the Dynamic Compression Sector (DCS) at the Advanced Photon Source, Argonne National Laboratory. The laser complements the other dynamic compression drivers at DCS. The laser system features beam smoothing for 2-d spatially uniform loading of samples and four, highly reproducible, temporal profiles (total pulse duration: 5-15 ns) to accommodate a wide variety of scientific needs. Other pulse shapes can be achieved as the experimental needs evolve. Timing of the laser pulse is highly precise (<200 ps) to allow accurate synchronization of the x-rays with the dynamic compression event. Details of the laser system, its operating parameters, and representative results will be presented. Work supported by DOE/NNSA.

Melanogenesis inhibition in mice using a low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser: a pilot study.

PubMed

Nam, Jae-Hui; Min, Joon Hong; Kim, Wang-Kyun; Yim, Sunmin; Kim, Won-Serk

2017-07-01

A low-fluence 1064-nm Q-switched neodymium-doped yttrium aluminum garnet laser, or laser toning, has yielded favorable outcomes in various benign pigmented disorders. However, the exact mechanism of action of laser toning has not been fully elucidated. We sought to determine the inhibitory effect of laser toning on melanogenesis and to assess how laser passes influence the outcomes. To produce perceptible pigmentation, nine HRM-2 melanin-possessing hairless mice were treated with ultraviolet (UV) B radiation on the dorsal skin. This was followed by zero, two, four, or six passes of laser toning twice in 2 weeks on each designated quadrant. The spectrophotometric values and pigmentation-related protein expressions were measured. Pigment changes were found in the mice skin using the Fontana-Masson stain for histopathological analysis. Four- and six-pass laser toning significantly improved the lightness compared to that in the unirradiated control (p < 0.002). The Fontana-Masson stain showed that melanin was considerably decreased in laser-irradiated skin. As the number of laser passes increased, the expression of tyrosinase decreased (p < 0.008). The following parameters also decreased in proportion to the number of laser passes: MITF, TRP-1, TRP-2, p-ERK, and p-Akt. In contrast, TGF-β increased in proportion to the number of laser passes. However, the changes in these six proteins were not statistically significant. Our study demonstrates that laser toning improves skin pigmentation with increased number of passes in a dose-dependent manner. This effect is mediated by tyrosinase inhibition.

Biochemical Detection and Identification False Alarm Rate Dependence on Wavelength Using Laser Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bhartia, R.; Hug, W. F.; Sala, E. C.; Sijapati, K.; Lane, A. L.; Reid, R. D.; Conrad, P. G.

2006-01-01

Most organic and many inorganic materials absorb strongly in specific wavelength ranges in the deep UV between about 220nm and 300nm. Excitation within these absorption bands results in native fluorescence emission. Each compound or composite material, such as a bacterial spore, has a unique excitation-emission fingerprint that can be used to provide information about the material. The sensitivity and specificity with which these materials can be detected and identified depends on the excitation wavelength and the number and location of observation wavelengths.We will present data on our deep ultraviolet Targeted Ultraviolet Chemical Sensors that demonstrate the sensitivity and specificity of the sensors. In particular, we will demonstrate the ability to quantitatively differentiate a wide range of biochemical agent targets against a wide range of background materials. We will describe the relationship between spectral resolution and specificity in target identification, as well as simple, fast, algorithms to identify materials.Hand-held, battery operated instruments using a deep UV laser and multi-band detection have been developed and deployed on missions to the Antarctic, the Arctic, and the deep ocean with the capability of detecting a single bacterial spore and to differentiate a wide range of organic and biological compounds.

The influence of femtosecond laser pulse wavelength on embryonic stem cell differentiation

NASA Astrophysics Data System (ADS)

Mthunzi, Patience

2012-10-01

Stem cells are rich in proteins, carbohydrates, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and various other cellular components which are responsible for a diversity of functions. Mostly the building blocks of these intracellular entities play an active role in absorbing ultra-violet (UV) and visible light sources. Light-matter interactions in biomaterials are a complex situation and subsequent damage may not always amount only from wavelength dependent effects but may also be driven by a wealth of other optical parameters which may lead to a variety photochemical reactions. Previously, literature has reported efficient photo-transfection and differentiation of pluripotent stem cells via near infrared (NIR) femtosecond (fs) laser pulses with minimum compromise to their viability. Therefore, in this study the influence of using different fs laser wavelengths on optical stem cell transfection and differentiation is investigated. A potassium titanyl phosphate (KTP) crystal was employed in frequency doubling a 1064 nm fs laser beam. The newly generated 532 nm fs pulsed beam was then utilized for the first time in transient photo-transfection of ES-E14TG2a mouse embryonic stem (mES) cells. Compared to using 1064 nm fs pulses which non-invasively introduce plasmid DNA and other macromolecules into mES cells, our results showed a significant decline in the photo-transfection efficiency following transfecting with a pulsed fs visible green beam.

Nanoparticle Over Mirror plasmonic structures prepared with use of Au colloid produced by laser ablation in water

NASA Astrophysics Data System (ADS)

Sawczak, Mirosław; Zyskowski, Marcin; Karczewski, Jakub; Atanasov, Petar A.; Nedyalkov, Nikolay N.; Nikov, Rumen G.; Stankova, Nadya A.; Śliwiński, Gerard

2016-01-01

Recently, an intensive research is carried out on plasmonic structures due to their potential application in many areas such as sensing, light harvesting and energy conversion and storage. In particular, a growing interest is observed in the Nanoparticle Over Mirror (NOM) structures for which the lithography and surface chemical functionalization represent the most popular production routes1. However, the application of those techniques is limited by the low efficacy, process complexity and chemical contamination of nanoparticles (NP). In this work, we report the contamination-free and low cost fabrication method of NOMs based on wet coating and ultrasonic-assisted nanocolloid drying process. The glass plates covered with magnetron sputtered 100 nm thick Au film and subsequently with Al2O3 layers (6 - 36 nm) by means of pulsed laser deposition are used as substrates. Au NPs are produced in the form of colloidal suspension by means of laser ablation in water using the 1064 nm, 6 ns Nd:YAG laser. The NOM synthesis is finalized by imposing of the Au NP suspension onto the as prepared Au-Al2O3/glass substrates and dried. To avoid NP agglomeration, the wet coated substrates are sonicated using 20W, 20 kHz ultrasound generator. SEM inspection of the obtained NOM structures confirms the positive sonication effect, i.e. the presence of agglomerate-free, homogenous layers. These consist of NPs (36 nm average diameter) which are characterized by the resonance absorption band at 528 nm. For NOM structures the UV-vis spectra reveal increased infrared activity and peak shift in agreement with theoretical modeling2. The NOM structure characterization is completed by analysis of the SEM and profilometry measurement results.

Near-UV laser treatment of extrinsic dental enamel stains.

PubMed

Schoenly, J E; Seka, W; Featherstone, J D B; Rechmann, P

2012-04-01

The selective ablation of extrinsic dental enamel stains using a 400-nm laser is evaluated at several fluences for completely removing stains with minimal damage to the underlying enamel. A frequency-doubled Ti:sapphire laser (400-nm wavelength, 60-nanosecond pulse duration, 10-Hz repetition rate) was used to treat 10 extracted human teeth with extrinsic enamel staining. Each tooth was irradiated perpendicular to the surface in a back-and-forth motion over a 1-mm length using an ∼300-µm-diam 10th-order super-Gaussian beam with fluences ranging from 0.8 to 6.4 J/cm(2) . Laser triangulation determined stain depth and volume removed by measuring 3D surface images before and after irradiation. Scanning electron microscopy evaluated the surface roughness of enamel following stain removal. Fluorescence spectroscopy measured spectra of unbleached and photobleached stains in the spectral range of 600-800 nm. Extrinsic enamel stains are removed with laser fluences between 0.8 and 6.4 J/cm(2) . Stains removed on sound enamel leave behind a smooth enamel surface. Stain removal in areas with signs of earlier cariogenic acid attacks resulted in isolated and randomly located laser-induced, 50-µm-diam enamel pits. These pits contain 0.5-µm diam, smooth craters indicative of heat transfer from the stain to the enamel and subsequent melting and water droplet ejection. Ablation stalling of enamel stains is typically observed at low fluences (<3 J/cm(2) ) and is accompanied by a drastic reduction in porphyrin fluorescence from the Soret band. Laser ablation of extrinsic enamel stains at 400 nm is observed to be most efficient above 3 J/cm(2) with minimal damage to the underlying enamel. Unsound underlying enamel is also observed to be selectively removed after irradiation. Copyright © 2012 Wiley Periodicals, Inc.

Multicascade X-Ray Free-Electron Laser with Harmonic Multiplier and Two-Frequency Undulator

NASA Astrophysics Data System (ADS)

Zhukovsky, K. V.

2018-06-01

The feasibility of generation of powerful x-ray radiation by a cascade free-electron laser (FEL) with amplification of higher harmonics using a two-frequency undulator is studied. To analyze the FEL operation, a complex phenomenological single-pass FEL model is developed and used. It describes linear and nonlinear generation of harmonics in the FEL with seed laser that takes into account initial electron beam noise and describes all main losses of each harmonic in each FEL cascade. The model is also calibrated against and approved by the experimental FEL data and available results of three-dimensional numerical simulation. The electron beam in the undulator is assumed to be matched and focused, and the dynamics of power in the singlepass FEL with cascade harmonic multipliers is investigated to obtain x-ray laser radiation in the FEL having the shortest length, beam energy, and frequency of the seed laser as low as possible. In this context, the advantages of the two-frequency undulator used for generation of harmonics are demonstrated. The evolution of harmonics in a multicascade FEL with multiplication of harmonics is investigated. The operation of the cascade FEL at the wavelength λ = 1.14 nm, generating 30 MW already on 38 m with the seed laser operating at a wavelength of 11.43 nm corresponding to the maximal reflectivity of the multilayered mirror MoRu/Be coating is investigated. In addition, the operation of the multicascade FEL with accessible seed UVlaser operating at a wavelength of 157 nm (F2 excimer UV-laser) and electron beam with energy of 0.5 GeV is investigated. X-ray radiation simulated in it at the wavelength λ 3.9 nm reaches power of 50 MW already at 27 m, which is by two orders of magnitude shorter than 3.4 km of the x-ray FEL recently put into operation in Europe.

Effectiveness of laser sources for contactless sampling of explosives

NASA Astrophysics Data System (ADS)

Akmalov, Artem E.; Chistyakov, Alexander A.; Kotkovskii, Gennadii E.

2016-05-01

A mass-spectrometric study of photo processes initiated by ultraviolet (UV) laser radiation in explosives adsorbed on metal and dielectric substrates has been performed. A calibrated quadrupole mass spectrometer was used to determine a value of activation energy of desorption and a quantity of explosives desorbed by laser radiation. A special vacuumoptical module was elaborated and integrated into a vacuum mass-spectrometric system to focus the laser beam on a sample. It has been shown that the action of nanosecond laser radiation set at q= 107 - 108 W/cm2, λ=266 nm on adsorbed layers of molecules of trinitrotoluene (TNT ) and pentaerytritoltetranitrate (PETN) leads not only to an effective desorption, but also to the non-equilibrium dissociation of molecules with the formation of nitrogen oxide NO. The cyclotrimethylenetrinitramine (RDX) dissociation products are observed only at high laser intensities (q> 109 W/cm2) thus indicating the thermal nature of dissociation, whereas desorption of RDX is observed even at q> 107 W/cm2 from all substrates. Desorption is not observed for cyclotetramethylenetetranitramine (HMX) under single pulse action: the dissociation products NO and NO2 are registered only, whereas irradiation at 10Hz is quite effective for HMX desorption. The results clearly demonstrate a high efficiency of nanosecond laser radiation with λ = 266 nm, q ~ 107 - 108 W/cm2, Epulse= 1mJ for desorption of molecules of explosives from various surfaces.

One-step synthesis of hybrid inorganic-organic nanocomposite coatings by novel laser adaptive ablation deposition technique

NASA Astrophysics Data System (ADS)

Serbezov, Valery; Sotirov, Sotir

2013-03-01

A novel approach for one-step synthesis of hybrid inorganic-organic nanocomposite coatings by new modification of Pulsed Laser Deposition technology called Laser Adaptive Ablation Deposition (LAAD) is presented. Hybrid nanocomposite coatings including Mg- Rapamycin and Mg- Desoximetasone were produced by UV TEA N2 laser under low vacuum (0.1 Pa) and room temperature onto substrates from SS 316L, KCl and NaCl. The laser fluence for Mg alloy was 1, 8 J/cm2 and for Desoximetasone 0,176 J/cm2 and for Rapamycin 0,118 J/cm2 were respectively. The threedimensional two-segmented single target was used to adapt the interaction of focused laser beam with inorganic and organic material. Magnesium alloy nanoparticles with sizes from 50 nm to 250 nm were obtained in organic matrices. The morphology of nanocomposites films were studied by Bright field / Fluorescence optical microscope and Scanning Electron Microscope (SEM). Fourier Transform Infrared (FTIR) spectroscopy measurements were applied in order to study the functional properties of organic component before and after the LAAD process. Energy Dispersive X-ray Spectroscopy (EDX) was used for identification of Mg alloy presence in hybrid nanocomposites coatings. The precise control of process parameters and particularly of the laser fluence adjustment enables transfer on materials with different physical chemical properties and one-step synthesis of complex inorganic- organic nanocomposites coatings.

Efficient and robust photo-ionization loading of beryllium ions

NASA Astrophysics Data System (ADS)

Wolf, Sebastian; Studer, Dominik; Wendt, Klaus; Schmidt-Kaler, Ferdinand

2018-02-01

We demonstrate the efficient generation of Be^+ ions with a 60 ns and 150 nJ laser pulse near 235 nm for two-step photo-ionization, proven by subsequent counting of the number of ions loaded into a linear Paul trap. The bandwidth and power of the laser pulse are chosen in such a way that a first, resonant step fully saturates the entire velocity distribution of beryllium atoms effusing from a thermal oven. The second excitation step is driven by the same light field causing efficient non-resonant ionization. Our ion-loading scheme has a similar efficiency as compared to former pathways using two-photon continuous wave laser excitation, but with an order of magnitude lower than average UV light power.

Structural and optical investigation in Er3+ doped Y2MoO6 phosphors

NASA Astrophysics Data System (ADS)

Mondal, Manisha; Rai, Vineet Kumar

2018-05-01

The Er3+ doped Y2MoO6 phosphors have been structurally and optically characterized by X-ray Diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis absorption spectroscopy and frequency upconversion (UC) emission studies. The crystal and the particles size are found to be ˜ 85 nm and ˜ 200 nm from XRD and FESEM analysis. The intense peak at ˜ 206 nm in the UV-Vis absorption spectroscopy is attributed due to the charge transfer transition between the Mo6+ and the O2- ions in the MoO4 group in the host molybdate. The frequency UC emission studies of the prepared phosphors under 980 nm diode laser excitation shows the intense UC emission in the 0.3 mol% concentrations for the Er3+ ions. In the UC emission spectra, the emission peaks at green (˜ 525 nm and ˜ 546 nm) and red (˜ 656 nm) bands are corresponding to the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions. The mechanisms involved in the UC process have been explored with the help of energy level diagram. Moreover, the CIE point (0.31, 0.60) lie in the green colour region which indicates that the developed phosphor have suitable applications in NIR to visible upconverter and in making green light display devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu Changle; Qiao Xueliang; Luo Langli

Flower-like ZnO nano/microstructures have been synthesized by thermal treatment of Zn(NH{sub 3}){sub 4}{sup 2+} precursor in aqueous solvent, using ammonia as the structure directing agent. A number of techniques, including X-ray diffraction (XRD), field emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), thermal analysis, and photoluminescence (PL) were used to characterize the obtained ZnO structures. The photoluminescence (PL) measurements indicated that the as-synthesized ZnO structures showed UV ({approx}375 nm), blue ({approx}465 nm), and yellow ({approx}585 nm) emission bands when they were excited by a He-Gd laser using 320 nm as the excitation source. Furthermore, it has been interestingly foundmore » that the intensity of light emission at {approx}585 nm remarkably decreased when the obtained ZnO nanocrystals were annealed at 600 deg. C for 3 h in air. The reason might be the possible oxygen vacancies and interstitials in the sample decreased at high temperature.« less

Femtosecond laser generated gold nanoparticles and their plasmonic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Rupali, E-mail: phz148121@iitd.ac.in; Navas, M. P.; Soni, R. K.

The pulsed laser ablation in liquid medium is now commonly used to generate stable colloidal nanoparticles (NPs) in absence of any chemical additives or stabilizer with diverse applications. In this paper, we report generation of gold NPs (Au NPs) by ultra-short laser pulses. Femtosecond (fs) laser radiation (λ = 800 nm) has been used to ablate a gold target in pure de-ionized water to produce gold colloids with smallsize distribution. The average size of the particles can be further controlled by subjecting to laser-induced post-irradiation providing a versatile physical method of size-selected gold nanoparticles. The optical extinction and morphological dimensions weremore » investigated with UV-Vis spectroscopy and Transmission Electron Microscopy measurements, respectively. Finite difference time domain (FDTD) method is employed to calculate localized surface plasmon (LSPR) wavelength and the near-field generated by Au NPs and their hybrids.« less

Multiphoton photoemission from a copper cathode illuminated by ultrashort laser pulses in an RF photoinjector.

PubMed

Musumeci, P; Cultrera, L; Ferrario, M; Filippetto, D; Gatti, G; Gutierrez, M S; Moody, J T; Moore, N; Rosenzweig, J B; Scoby, C M; Travish, G; Vicario, C

2010-02-26

In this Letter we report on the use of ultrashort infrared laser pulses to generate a copious amount of electrons by a copper cathode in an rf photoinjector. The charge yield verifies the generalized Fowler-Dubridge theory for multiphoton photoemission. The emission is verified to be prompt using a two pulse autocorrelation technique. The thermal emittance associated with the excess kinetic energy from the emission process is comparable with the one measured using frequency tripled uv laser pulses. In the high field of the rf gun, up to 50 pC of charge can be extracted from the cathode using a 80 fs long, 2 microJ, 800 nm pulse focused to a 140 mum rms spot size. Taking into account the efficiency of harmonic conversion, illuminating a cathode directly with ir laser pulses can be the most efficient way to employ the available laser power.

Micro sculpting technology using DPSSL

NASA Astrophysics Data System (ADS)

Chang, Won-Seok; Shin, Bosung; Kim, Jae-gu; Whang, Kyung-Hyun

2003-11-01

Multiple pulse laser ablation of polymer is performed with DPSS (Diode Pumped Solid State) 3rd harmonic Nd:YVO4 laser (355 nm) in order to fabricate three-dimensional micro components. Here we considered mechanistic aspects of the interaction between UV laser and polymer to obtain optimum process conditions for maskless photomachining using DPSSL. The photo-physical and photochemical parameters such as laser wavelength and optical characteristics of polymers are investigated by experiments to reduce plume effect, which induce the re-deposited debris on the surface of substrate. In this study, LDST (laser direct sculpting technique) are developed to gain various three-dimensional shape with size less than 500 micrometer. Main process sequences are from rapid prototyping technology such as CAD/CAM modeling of products, machining path generation, layer-by-layer machining, and so on. This method can be applied to manufacture the prototype of micro device and the polymer mould for mass production without expensive mask fabrication.

Direct Quantification of Carotenoids in Low Fat Baby Foods Via Laser Photoacoustics and Colorimetric Index *

NASA Astrophysics Data System (ADS)

Dóka, O.; Ajtony, Zs.; Bicanic, D.; Valinger, D.; Végvári, Gy.

2014-12-01

Carotenoids are important antioxidants found in various foods including those for nutrition of infants. In this investigation, the total carotenoid content (TCC) of nine different commercially available baby foods was quantified using colorimetric index * obtained via reflectance colorimetry (RC) and by laser photoacoustic spectroscopy (LPAS) at 473 nm. The latter requires a minimum of sample preparation and only a one time calibration step which enables practically direct quantification of TCC. Results were verified versus UV-Vis spectrophotometry (SP) as the reference technique. It was shown that RC and LPAS (at 473 nm) provide satisfactory results for *, = 0.9925 and = 0.9972, respectively. Other color indices do not show a correlation with TCC. When determining the TCC in baby foods containing tomatoes, it is necessary to select a different analytical wavelength to compensate for the effect of lycopene's presence in the test samples.

Growth and characterization of a novel nonlinear optical borate crystal - Yttrium calcium borate (YCB)

NASA Astrophysics Data System (ADS)

Arun Kumar, R.; Arivanandhan, M.; Dhanasekaran, R.; Hayakawa, Y.

2013-06-01

A new nonlinear optical single crystal yttrium calcium borate Y2CaB10O19 (YCB) was grown for the first time from its melt. The starting materials were prepared by the solid-state reaction method. The melting point of the synthesized material was identified to be 967 °C. YCB crystal exhibits monoclinic crystal structure with the space group C2. The crystalline perfection of the grown YCB crystal was found to be good. From the UV-VIS-NIR studies, the lower cutoff wavelength of the crystal occurs below 200 nm. The functional groups of the grown crystal were assigned using the FTIR data. The second harmonic generation (SHG) of the YCB crystal was observed using a Nd:YAG laser with a fundamental wavelength of 1064 nm. The laser damage threshold value of the YCB crystal was found to be very high - 10.5 GW/cm2.

Sensitive measurement of nonlinear absorption and optical limiting in undoped and Fe-doped ZnO quantum dots using pulsed laser

NASA Astrophysics Data System (ADS)

Sharma, D.; Malik, B. P.; Gaur, A.

2016-11-01

Zinc oxide quantum dots (QDs) with Fe-doping at different concentrations were prepared by chemical co-precipitation method. The prepared QDs were characterized by UV-Vis spectroscopy, X-ray diffraction and Z-scan technique. The sizes of QDs were found to be within 4.6-6.6 nm range. The nonlinear parameters viz. two-photon absorption coefficient (βTPA) and two-photon absorption cross-section (σTPA) were extracted with the help of open aperture Z-scan technique using nanosecond Nd:YAG laser operating at wavelength 532 nm. Higher values of βTPA and σTPA for Fe doped ZnO implied that they were potential materials for development of photonics devices and sensor protection applications. Fe doped sample (3 % by wt) was found to be the best optical limiter with limiting threshold intensity of 0.64 TW/cm2.

Crystal growth, thermal and optical studies of semiorganic nonlinear optical material: L-lysine hydrochloride dihydrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalaiselvi, D.; Mohan Kumar, R.; Jayavel, R.

2008-07-01

Single crystals of L-lysine hydrochloride dihydrate (LLHCD), a nonlinear optical material, have been grown by slow cooling technique from its aqueous solution. LLHCD was found to be highly soluble in water. The grown crystals have been subjected to single crystal X-ray diffraction to confirm the structure and to estimate the lattice parameters. The vibrational structure of the molecule is elucidated from FTIR spectra. Thermal analysis revealed the thermal stability of the grown crystals. The optical transmittance spectrum shows that the material possesses good optical transparency in the entire visible region with a UV cut-off wavelength at 228 nm. The mechanicalmore » properties of the grown crystal have been studied using Vicker's microhardness test. The laser damage threshold of 52.25 MW/cm{sup 2} has been measured by irradiating Q-switched Nd:YAG laser (1064 nm)« less

Background-free, high sensitivity staining of proteins in one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gels using a luminescent ruthenium complex.

PubMed

Berggren, K; Chernokalskaya, E; Steinberg, T H; Kemper, C; Lopez, M F; Diwu, Z; Haugland, R P; Patton, W F

2000-07-01

SYPRO Ruby dye is a permanent stain comprised of ruthenium as part of an organic complex that interacts noncovalently with proteins. SYPRO Ruby Protein Gel Stain provides a sensitive, gentle, fluorescence-based method for detecting proteins in one-dimensional and two-dimensional sodium dodecyl sulfate-polyacrylamide gels. Proteins are fixed, stained from 3h to overnight and then rinsed in deionized water or dilute methanol/acetic acid solution for 30 min. The stain can be visualized using a wide range of excitation sources commonly used in image analysis systems including a 302 nm UV-B transilluminator, 473 nm second harmonic generation (SHG) laser, 488 nm argon-ion laser, 532 nm yttrium-aluminum-garnet (YAG) laser, xenon arc lamp, blue fluorescent light bulb or blue light-emitting diode (LED). The sensitivity of SYPRO Ruby Protein Gel Stain is superior to colloidal Coomassie Brilliant Blue (CBB) stain or monobromobimane labeling and comparable with the highest sensitivity silver or zinc-imidazole staining procedures available. The linear dynamic range of SYPRO Ruby Protein Gel stain extends over three orders of magnitude, which is vastly superior to silver, zinc-imidazole, monobromobimane and CBB stain. The fluorescent stain does not contain superfluous chemicals (formaldehyde, glutaraldehyde, Tween-20) that frequently interfere with peptide identification in mass spectrometry. While peptide mass profiles are severely altered in protein samples prelabeled with monobromobimane, successful identification of proteins by peptide mass profiling using matrix-assisted laser desorption/ionization mass spectrometry was easily performed after protein detection with SYPRO Ruby Protein Gel stain.

Ozone Measurements with the US EPA UV-DIAL: Preliminary Results

NASA Technical Reports Server (NTRS)

Moosmueller, H.; Diebel, D.; Bundy, D. H.; Bristow, M. P.; Alvarez, R. J., II; Kovalev, V. A.; Edmonds, C. M.; Turner, R. M.; Mcelroy, J. L.

1992-01-01

A compact airborne down-looking lidar system was developed at the Environmental Protection Agency in Las Vegas. This differential absorption lidar (DIAL) was designed to simultaneously measure range-resolved concentrations of ozone (O3) and sulfur dioxide (SO2) in the lower troposphere, together with an indication of the aerosol distribution. The five laser wavelengths (i.e., lambda(sub 1) = 277 nm, lambda(sub 2) = 292 nm, lambda(sub 3) = 313 nm, lambda(sub4) = 319 nm, lambda(sub 5) = 369 nm) were generated via Raman conversion of a focused KrF excimer laser. The system is currently installed in a truck-based mobile laboratory. For the ground testing, an opening in the truck floor together with a folding mirror under the truck makes a horizontal, or upwardly inclined direction of measurement possible. Initial ground testing has been performed in the vicinity of a Desert Research Institute (DRI) ambient air monitoring site, located at Cottonwood Cove approximately 85 km south east of Las Vegas, Nevada. At this site O3 and SO2 concentrations are continuously monitored with an average accuracy better than +/- 10 percent. A temporary ozone measurement station with identical accuracy was set up at a distance to get a second point of comparison for the range-resolved DIAL measurements.

Removal of sulfamethoxazole, ibuprofen and nitrobenzene by UV and UV/chlorine processes: A comparative evaluation of 275 nm LED-UV and 254 nm LP-UV.

PubMed

Kwon, Minhwan; Yoon, Yeojoon; Kim, Seonbaek; Jung, Youmi; Hwang, Tae-Mun; Kang, Joon-Wun

2018-10-01

The aim of this study is to evaluate the micropollutant removal capacity of a 275 nm light-emitting diode (LED)-UV/chlorine system. The sulfamethoxazole, ibuprofen, and nitrobenzene removal efficiencies of this system were compared with those of a conventional 254 nm low-pressure (LP)-UV system as a function of the UV dose. In a direct photolysis system, the photon reactivity of sulfamethoxazole is higher than that of nitrobenzene and ibuprofen at both wavelengths. The molar absorption coefficients and quantum yields of each micropollutant were as follows: sulfamethoxazole (ε SMX, 275 nm protonated  = 17,527 M -1  cm -1 , Φ SMX, 275 nm protonated  = 0.239, ε SMX, 275 nm deprotonated  = 8430 M -1  cm -1 , and Φ SMX, 275 nm deprotonated  = 0.026), nitrobenzene (ε NB, 275 nm  = 7176 M -1  cm -1 and Φ NB, 275 nm  = 0.057), and ibuprofen (ε NB, 275 nm  = 200 M -1  cm -1 and Φ IBF, 275 nm  = 0.067). The photon reactivity of chlorine species, i.e., HOCl and OCl-, were determined at 275 nm (ε HOCl, 275 nm  = 28 M -1  cm -1 , Φ HOCl, 275 nm  = 1.97, ε OCl-, 275 nm  = 245 M -1  cm -1 , and Φ OCl-, 275 nm  = 0.8), which indicate that the decomposition rate of OCl - is higher and that of HOCl is lower by 275 nm photolysis than that by 254 nm photolysis (ε HOCl, 254 nm  = 60 M -1  cm -1 , Φ HOCl, 254 nm  = 1.46, ε OCl-, 254 nm  = 58 M -1  cm -1 , and Φ OCl-, 254 nm  = 1.11). In the UV/chlorine system, the removal rates of ibuprofen and nitrobenzene were increased by the formation of OH and reactive chlorine species. The 275-nm LED-UV/chlorine system has higher radical yields at pH 7 and 8 than the 254 nm LP-UV/chlorine system. Copyright © 2018 Elsevier B.V. All rights reserved.

High-accuracy deep-UV Ramsey-comb spectroscopy in krypton

NASA Astrophysics Data System (ADS)

Galtier, Sandrine; Altmann, Robert K.; Dreissen, Laura S.; Eikema, Kjeld S. E.

2017-01-01

In this paper, we present a detailed account of the first precision Ramsey-comb spectroscopy in the deep UV. We excite krypton in an atomic beam using pairs of frequency-comb laser pulses that have been amplified to the millijoule level and upconverted through frequency doubling in BBO crystals. The resulting phase-coherent deep-UV pulses at 212.55 nm are used in the Ramsey-comb method to excite the two-photon 4p^6 → 4p^5 5p [1/2 ]_0 transition. For the {}^{84}Kr isotope, we find a transition frequency of 2829833101679(103) kHz. The fractional accuracy of 3.7 × 10^{-11} is 34 times better than previous measurements, and also the isotope shifts are measured with improved accuracy. This demonstration shows the potential of Ramsey-comb excitation for precision spectroscopy at short wavelengths.

Characterizing the absorption and aging behavior of DUV optical material by high-resolution excimer laser calorimetry

NASA Astrophysics Data System (ADS)

Mann, Klaus R.; Eva, Eric

1998-06-01

Absorption loss in DUV optics during 193 nm irradiation is investigated by employing a high-resolution calorimetric technique which allows determining both single and two photon absorption coefficients at energy densities of several 10 mJ/cm2, avoiding a significant thermal load on the samples. UV calorimetry is also employed to investigate laser induced aging phenomena, e.g. color center formation in fused silica or CaF2. A separation of transient and cumulative effects as a function of intensity can be achieved, giving insight into various loss mechanisms. Moreover, the influence of dielectric coatings on the absorption characteristics is discussed.

A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

NASA Technical Reports Server (NTRS)

Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

1981-01-01

Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

The laser-diode-excited 5 d-4 f luminescence of Ce3+ and Pr3+ ions embedded into a BaR2F8 matrix

NASA Astrophysics Data System (ADS)

Pushkar', A. A.; Uvarova, T. V.; Kozlova, N. S.; Kuznetsov, S. Yu.; Uvarova, A. G.

2013-06-01

We show the possibility of obtaining UV luminescence from 5 d-4 f transitions of rare-earth ions in the BaY2F8: (Yb3+, Pr3+, Ce3+) crystal under upconversion excitation by standard laser diodes with lasing wavelengths of 960, 808, and 840 nm. Various upconversion mechanisms of pumping for populating the higher-lying energy levels of the active ions, as well as methods of adaptation of the active medium BaY2F8: (Yb3+, Pr3+, Ce3+) to these mechanisms, are considered.

207-nm UV light - a promising tool for safe low-cost reduction of surgical site infections. I: in vitro studies.

PubMed

Buonanno, Manuela; Randers-Pehrson, Gerhard; Bigelow, Alan W; Trivedi, Sheetal; Lowy, Franklin D; Spotnitz, Henry M; Hammer, Scott M; Brenner, David J

2013-01-01

0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ~200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure. The aim of this work was to test the biophysically-based hypothesis that ~200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues. A Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue. We found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp. As predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin.

Comparison of UV-LED and low pressure UV for water disinfection: Photoreactivation and dark repair of Escherichia coli.

PubMed

Li, Guo-Qiang; Wang, Wen-Long; Huo, Zheng-Yang; Lu, Yun; Hu, Hong-Ying

2017-12-01

Studies on ultraviolet light-emitting diode (UV-LED) water disinfection have shown advantages, such as safety, flexible design, and lower starting voltages. However, information about reactivation after UV-LED disinfection is limited, which is an important issue of UV light-based technology. In this study, the photoreactivation and dark repair of Escherichia coli after UV-LEDs and low pressure (LP) UV disinfection were compared. Four UV-LED units, 265 nm, 280 nm, the combination of 265 + 280 (50%), and 265 + 280 (75%) were tested. 265 nm LEDs was more effective than 280 nm LEDs and LP UV lamps for E. coli inactivation. No synergic effect for disinfection was observed from the combination of 265 and 280 nm LEDs. 265 nm LEDs had no different reactivation performances with that of LP UV, while 280 nm LEDs could significantly repress photoreactivation and dark repair at a low irradiation intensity of 6.9 mJ/cm 2 . Furthermore, the UV-induced damage of 280 nm LEDs was less repaired which was determined by endonuclease sensitive site (ESS) assay. The impaired protein activities by 280 nm LEDs might be one of the reasons that inhibited reactivation. A new reactivation rate constant, K max , was introduced into the logistic model to simulate the reactivation data, which showed positive relationship with the maximum survival ratio and was more reasonable to interpret the results of photoreactivation and dark repair. This study revealed the distinct roles of different UV lights in disinfection and reactivation, which is helpful for the future design of UV-LED equipment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Photocleavable Hydrogel-Coated Upconverting Nanoparticles: A Multifunctional Theranostic Platform for NIR Imaging and On-Demand Macromolecular Delivery.

PubMed

Jalani, Ghulam; Naccache, Rafik; Rosenzweig, Derek H; Haglund, Lisbet; Vetrone, Fiorenzo; Cerruti, Marta

2016-01-27

Lanthanide-doped upconverting nanoparticles (UCNPs) have emerged as excellent nanotransducers for converting longer wavelength near-infrared (NIR) light to shorter wavelengths spanning the ultraviolet (UV) to the visible (Vis) regions of the spectrum via a multiphoton absorption process, known as upconversion. Here, we report the development of NIR to UV-Vis-NIR UCNPs consisting of LiYF4:Yb(3+)/Tm(3+)@SiO2 individually coated with a 10 ± 2 nm layer of chitosan (CH) hydrogel cross-linked with a photocleavable cross-linker (PhL). We encapsulated fluorescent-bovine serum albumin (FITC-BSA) inside the gel. Under 980 nm excitation, the upconverted UV emission cleaves the PhL cross-links and instantaneously liberates the FITC-BSA under 2 cm thick tissue. The release is immediately arrested if the excitation source is switched off. The upconverted NIR light allows for the tracking of particles under the tissue. Nucleus pulposus (NP) cells cultured with UCNPs are viable both in the presence and in the absence of laser irradiation. Controlled drug delivery of large biomolecules and deep tissue imaging make this system an excellent theranostic platform for tissue engineering, biomapping, and cellular imaging applications.

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

PubMed Central

Buonanno, Manuela; Ponnaiya, Brian; Welch, David; Stanislauskas, Milda; Randers-Pehrson, Gerhard; Smilenov, Lubomir; Lowy, Franklin D.; Owens, David M.; Brenner, David J.

2017-01-01

We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200–222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence; 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro; 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200–222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure. PMID:28225654

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light.

PubMed

Buonanno, Manuela; Ponnaiya, Brian; Welch, David; Stanislauskas, Milda; Randers-Pehrson, Gerhard; Smilenov, Lubomir; Lowy, Franklin D; Owens, David M; Brenner, David J

2017-04-01

We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200-222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence; 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro; 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200-222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure.

Substrate-Mediated Laser Ablation under Ambient Conditions for Spatially-Resolved Tissue Proteomics

PubMed Central

Fatou, Benoit; Wisztorski, Maxence; Focsa, Cristian; Salzet, Michel; Ziskind, Michael; Fournier, Isabelle

2015-01-01

Numerous applications of ambient Mass Spectrometry (MS) have been demonstrated over the past decade. They promoted the emergence of various micro-sampling techniques such as Laser Ablation/Droplet Capture (LADC). LADC consists in the ablation of analytes from a surface and their subsequent capture in a solvent droplet which can then be analyzed by MS. LADC is thus generally performed in the UV or IR range, using a wavelength at which analytes or the matrix absorb. In this work, we explore the potential of visible range LADC (532 nm) as a micro-sampling technology for large-scale proteomics analyses. We demonstrate that biomolecule analyses using 532 nm LADC are possible, despite the low absorbance of biomolecules at this wavelength. This is due to the preponderance of an indirect substrate-mediated ablation mechanism at low laser energy which contrasts with the conventional direct ablation driven by sample absorption. Using our custom LADC system and taking advantage of this substrate-mediated ablation mechanism, we were able to perform large-scale proteomic analyses of micro-sampled tissue sections and demonstrated the possible identification of proteins with relevant biological functions. Consequently, the 532 nm LADC technique offers a new tool for biological and clinical applications. PMID:26674367

Crystal growth, structural, optical, mechanical and thermal properties of a new nonlinear optical single crystal: L-Ornithine monohydrochloride.

PubMed

Balakrishnan, T; Ramamurthi, K

2009-03-01

Amino acid family crystals exhibit excellent nonlinear optical and electro optical properties. l-Ornithine monohydrochloride single crystal, belongs to the amino acid group, was grown by the slow evaporation solution growth technique at room temperature. The grown crystals were characterized by single crystal and powder X-ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, TGA, DTA and DSC analyses. UV-vis-NIR spectrum shows excellent transmission in the UV, visible and NIR region (300-1600nm). The mechanical properties of grown crystals were studied using Vickers microhardness tester. Its second harmonic generation efficiency was tested using Nd:YAG laser and is 1.25 times that of KDP.

Dielectric, optical and mechanical studies of phenolic polyene OH1 organic electrooptic crystal

NASA Astrophysics Data System (ADS)

Bharath, D.; Kalainathan, S.

2014-11-01

2-{3-[2-(4-Hydroxyphenyl) vinyl]-5, 5-dimethylcyclo-hex-2-en-1-ylidene}malononitrile (OH1) phenolic locked polyene organic material has been synthesized by the Knoevenagel condensation method. OH1 single crystals were grown in methanol by a slow evaporation method. In order to avoid the multinucleation and reduce the metastable zone width, phosphoric acid is added in different concentrations. The linear optical property of OH1 crystal has been studied using UV-vis-NIR spectroscopy in the wavelength range 190-1100 nm and optical constants are calculated theoretically. The magnitude of nonlinear refractive index (10-12 m2/W), nonlinear absorption (10-6 m/W) and third order nonlinear susceptibility (10-6 esu) has been studied using a Z-scan technique. Dielectric property of OH1 crystal has been studied in frequency range 50 Hz-5 MHz. Photoluminescence spectrum was recorded using a xenon lamp in the range of 450-700 nm. Laser optical damage threshold of OH1 crystal was obtained (0.62 GW/cm2) using a pulsed Nd-YAG laser (1064 nm) of repetition rate 10 ns.

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold

PubMed Central

Makhotkin, Igor A.; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W. E.; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han-Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface. PMID:29271755

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold.

PubMed

Makhotkin, Igor A; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W E; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Nittler, Laurent; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Vozda, Vojtěch; Burian, Tomáš; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Schreiber, Siegfried; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface.

Direct spectral analysis and determination of high content of carcinogenic bromine in bread using UV pulsed laser induced breakdown spectroscopy.

PubMed

Mehder, A O; Gondal, Mohammed A; Dastageer, Mohamed A; Habibullah, Yusuf B; Iqbal, Mohammed A; Oloore, Luqman E; Gondal, Bilal

2016-01-01

Laser induced breakdown spectroscopy (LIBS) was applied for the detection of carcinogenic elements like bromine in four representative brands of loaf bread samples and the measured bromine concentrations were 352, 157, 451, and 311 ppm, using Br I (827.2 nm) atomic transition line as the finger print atomic transition. Our LIBS system is equipped with a pulsed laser of wavelength 266 nm with energy 25 mJ pulse(-1), 8 ns pulse duration, 20 Hz repetition rate, and a gated ICCD camera. The LIBS system was calibrated with the standards of known concentrations in the sample (bread) matrix and such plot is linear in 20-500 ppm range. The capability of our system in terms of limit of detection and relative accuracy with respect to the standard inductively coupled plasma mass spectrometry (ICPMS) technique was evaluated and these values were 5.09 ppm and 0.01-0.05, respectively, which ensures the applicability of our system for Br trace level detection, and LIBS results are in excellent agreement with that of ICPMS results.

Soft x ray optics by pulsed laser deposition

NASA Technical Reports Server (NTRS)

Fernandez, Felix E.

1994-01-01

A series of molybdenum thin film depositions by PLD (Pulsed Laser Deposition) have been carried out, seeking appropriate conditions for multilayer fabrication. Green (532 nm) and UV (355 nm) light pulses, in a wide range of fluences, were used. Relatively large fluences (in comparison with Si) are required to cause evaporation of molybdenum. The optical penetration depths and reflectivities for Mo at these two wavelengths are comparable, which means that results should be, and do appear to be similar for equal fluences. For all fluences above threshold used, a large number of incandescent particles is ejected by the target (either a standard Mo sputtering target or a Mo sheet were tried), together with the plasma plume. Most of these particles are clearly seen to bounce off the substrate. The films were observed with light microscopy using Nomarski and darkfield techniques. There is no evidence of large debris. Smooth films plus micron-sized droplets are usually seen. The concentration of these droplets embedded in the film appears not to vary strongly with the laser fluence employed. Additional characterization with SEM and XRD is under way.

Laboratory studies of stratospheric bromine chemistry: Kinetics of the reactions of bromine monoxide with nitrogen dioxide and atomic oxygen

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton

A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k(sub 16)) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k(sub 16)(P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k(sub 16)(P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k(sub 14)) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k(sub 14)(T) is k(sub 14)(T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k(sub 14)(T) at any temperature within the range studied is estimated to be +/- 25%. Possible kinetic interferences from production of vibrationally or electronically excited O2 are discussed. The effect of the faster reaction rate coefficients that are reported for the BrO + NO2 + M and BrO + O(P-3) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Laboratory Studies of Stratospheric Bromine Chemistry: Kinetics of the Reactions of Bromine Monoxide with Nitrogen Dioxide and Atomic Oxygen.

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton, Jr.

A laser flash photolysis - long path absorption technique has been employed to study the kinetics of the reaction rm BrO + NO_2 + M{k _{16}atopto} products as a function of temperature (248-346 K), pressure (16 -800 Torr), and buffer gas identity (rm N _2,CF_4). 351 nm photolysis of rm NO_2/Br_2/N_2 mixtures generated BrO. The BrO decay in the presence of excess NO_2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k_{16} (P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k_{16}(P,T) for use in modeling stratospheric BrO_{rm x} chemistry. The kinetics of the important stratospheric reaction rm BrO+O(^3P)_sp{to }{k_{14}}Br+O_2 in N_2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25 -150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of rm Br_2/O _3/N_2 mixtures produces O atoms in excess over Br_2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolyses a small fraction of the O_3 to generate O(^3P). The decay of O(^3P) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resolved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k_{14}(T) is given below.rm k_{14 }(T) = 1.64times 10^{-11} exp (263/T) cm^3 molecule ^{-1} s^{-1} The absolute accuracy of k_{14 }(T) at any temperature within the range studied is estimated to be +/-25%. Possible kinetic interferences from production of vibrationally or electronically excited O_2 are discussed. The effect of the faster reaction rate coefficients that are reported for the rm BrO + NO_2 + M and BrO + O(^3P) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Applications of LIBS for determination of ionic species (NaCl) in electrical cables for investigation of electrical breakdown

NASA Astrophysics Data System (ADS)

Gondal, M. A.; Shwehdi, M. H.; Khalil, A. A. I.

2011-12-01

The formation of water trees in high-voltage cables can wreak havoc to power systems. The water tree is produced within the high voltage cable insulator when impurities like sodium and magnesium present in the insulating material react with moist soil to form chlorides. This water tree causes electrical breakdown by short circuiting the metallic conductor and the earth. In this paper we use laser-induced breakdown spectroscopy (LIBS) to detect the potentially dangerous elements that form the water tree in the insulating cable. The LIBS system used for this work consists of the fundamental (1064 nm) of a Nd:YAG laser, four spectrometer modules that cover the visible and near-UV spectral ranges and an ICCD camera with proper delay and gating sequence. With this arrangement we were able to measure the elemental concentrations of trace metals present in the insulating cable. The concentrations measured with our LIBS system were counter checked by a standard technique like inductively coupled plasma (ICP) emission spectrometry. The maximum concentrations for ionic species such as Ba (455.40 nm), Ca (393.36 nm), Cr (267.71 nm), Fe (259.94 nm), Cl (542.3 nm), Mg (516.7 nm), Mn (257.61 nm), Na (589.59 nm) and Ti (334.18 nm) are 20.6, 43.2, 1.6, 148.4, 24.2, 22.1, 4.2, 39.56 and 4.35 ppm, respectively. The relative accuracy of our LIBS system for various elements as compared with the ICP method is in the range of 0.03-0.6 at 2.5% error confidence.

LIBS spectra of multi-component Al, Fe, Cu alloys and composite materials used for selected elements of armament and munition

NASA Astrophysics Data System (ADS)

Ostrowski, R.; Skrzeczanowski, W.; Rycyk, A.; CzyŻ, K.; Sarzyński, A.; Strzelec, M.; Jach, K.; Świerczyński, R.

2017-10-01

Spectral investigations in the UV-VIS range of selected Al, Cu, and Fe alloys and composite materials were performed using LIBS technique. The investigated objects were typical rifle cartridges, mortars, rocket launchers and samples of different type steel, Cu and Al alloys, as well as composite materials of special chemical composition. Two Nd:YAG lasers were applied: a short 4 ns, 60 mJ Brio Quantel/BigSky laser (1064 nm) and a long pulse 200/400 (up to 1000) µs ({ 2/4 up to 10 J) laser (1064 nm) constructed at the Institute of Optoelectronics MUT. This spectrochemical analysis was possible for Al, Cu, and Fe alloys objects for both lasers, and in case of composites only if the samples were irradiated by short laser pulse since in the experiment with the long pulse, all composite materials spectra, in general, were very similar to each other - they imitated a grey/black body spectra. For metal alloys in experiments with a short laser pulse only atomic spectra were observed while for long microsecond laser pulses molecular transitions have been registered for Al alloys. Electron temperatures of plasma created on different materials for short and long laser pulses were found on the base of Boltzmann plots. Temperatures are clearly higher for plasmas generated with a short laser pulse which results from much higher laser power density on the sample surface for short pulse and not from fluence which is 20-40 times larger for long pulse.

Laser ablation of Au-CuO core-shell nanocomposite in water for optoelectronic devices

NASA Astrophysics Data System (ADS)

Ismail, Raid A.; Abdul-Hamed, Ryam S.

2017-12-01

Core-shell gold-copper oxide Au-CuO nanocomposites were synthesized using laser ablation of CuO target in colloidal solution of Au nanoparticles (NPs). The effect of laser fluence on the structural, morphological, electrical, and optical properties of Au-CuO nanocomposites was investigated using x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), photoluminescence (PL), Fourier transformed infrared spectroscopy (FTIR), Hall measurement, and UV-vis spectroscopy. X-ray diffraction results confirm the formation of polycrystalline Au-CuO NPs with monoclinic structure. The optical energy gap for CuO was 4 eV and for the Au-CuO core-shell nanocomposites was found to be in the range of 3.4-3.7 eV. SEM and TEM investigations revealed that the structure and morphology of Au-CuO core-shell nanocomposites were strongly depending on the laser fluence. A formation of Au-CuO nanospheres and platelets structures was observed. The photoluminescence data showed an emission of broad visible peaks between 407 and 420 nm. The effect of laser fluence on the dark and illuminated I-V characteristics of Au-CuO/n-Si heterojunction photodetectors was investigated and analyzed. The experimental data demonstrated that the photodetector prepared at optimum laser fluence exhibited photosensitivity of 0.6 AW-1 at 800 nm.

Compact Solid-State 213 nm Laser Enables Standoff Deep Ultraviolet Raman Spectrometer: Measurements of Nitrate Photochemistry.

PubMed

Bykov, Sergei V; Mao, Michael; Gares, Katie L; Asher, Sanford A

2015-08-01

We describe a new compact acousto-optically Q-switched diode-pumped solid-state (DPSS) intracavity frequency-tripled neodymium-doped yttrium vanadate laser capable of producing ~100 mW of 213 nm power quasi-continuous wave as 15 ns pulses at a 30 kHz repetition rate. We use this new laser in a prototype of a deep ultraviolet (UV) Raman standoff spectrometer. We use a novel high-throughput, high-resolution Echelle Raman spectrograph. We measure the deep UV resonance Raman (UVRR) spectra of solid and solution sodium nitrate (NaNO3) and ammonium nitrate (NH4NO3) at a standoff distance of ~2.2 m. For this 2.2 m standoff distance and a 1 min spectral accumulation time, where we only monitor the symmetric stretching band, we find a solid state NaNO3 detection limit of ~100 μg/cm(2). We easily detect ~20 μM nitrate water solutions in 1 cm path length cells. As expected, the aqueous solutions UVRR spectra of NaNO3 and NH4NO3 are similar, showing selective resonance enhancement of the nitrate (NO3(-)) vibrations. The aqueous solution photochemistry is also similar, showing facile conversion of NO3(-) to nitrite (NO2(-)). In contrast, the observed UVRR spectra of NaNO3 and NH4NO3 powders significantly differ, because their solid-state photochemistries differ. Whereas solid NaNO3 photoconverts with a very low quantum yield to NaNO2, the NH4NO3 degrades with an apparent quantum yield of ~0.2 to gaseous species.

Further characterization of photothermal breakdown products of uric acid stones following holmium:YAG laser lithotripsy

NASA Astrophysics Data System (ADS)

Glickman, Randolph D.; Weintraub, Susan T.; Kumar, Neeru; Corbin, Nicole S.; Lesani, Omid; Teichman, Joel M. H.

2000-06-01

Previously we found that Ho:YAG laser (2120 nm) lithotripsy of uric acid stones produced cyanide, a known thermal breakdown product of uric acid. We now report that alloxan, another thermal breakdown product, is also likely produced. Uric acid stones (approximately 98% pure) of human origin were placed in distilled water and subjected to one of the following experimental treatments: unexposed control, exposed to Ho:YAG laser, Nd:YAG laser, or mechanically crushed. Samples were then processed for HPLC analysis with UV detection. Peaks were identified by comparison to authentic standards. All samples contained uric acid, with retention time (RT) about 6 min. All of the laser-exposed samples contained a peak that eluted at 2.5 min, identical to the RT of authentic alloxan. Ho:YAG laser irradiation, however, produced a larger presumed alloxan peak than did the Nd:YAG laser. The peak at 2.5 min, as well as unidentified later-eluting peaks, were present in the laser-exposed, but not the unexposed or mechanically crushed, samples. These results confirm the thermal nature of lithotripsy performed with long-pulse IR lasers.

Nanocomplexes of Photolabile Polyelectrolyte and Upconversion Nanoparticles for Near-Infrared Light-Triggered Payload Release.

PubMed

Xiang, Jun; Ge, Feijie; Yu, Bing; Yan, Qiang; Shi, Feng; Zhao, Yue

2018-06-07

A new approach to encapsulating charged cargo molecules into a nanovector and subsequently using near-infrared (NIR) light to trigger the release is demonstrated. NIR light-responsive nanovector was prepared through electrostatic interaction-driven complexation between negatively charged silica-coated upconversion nanoparticles (UCNP@silica, 87 nm hydrodynamic diameter, polydispersity index ∼0.05) and a positively charged UV-labile polyelectrolyte bearing pendants of poly(ethylene glycol) and o-nitrobenzyl side groups; whereas charged fluorescein (FLU) was loaded through a co-complexation process. By controlling the amount of polyelectrolyte, UCNP@silica can be covered by the polymer, whereas remaining dispersed in aqueous solution. Under 980 nm laser excitation, UV light emitted by UCNP is absorbed by photolytic side groups within polyelectrolyte, which results in cleavage of o-nitrobenzyl groups and formation of carboxylic acid groups. Such NIR light-induced partial reversal of positive charge to negative charge on the polyelectrolyte layer disrupts the equilibrium among UCNP@silica, polyelectrolyte, and FLU and, consequently, leads to release of FLU molecules.

Luminescence of phosphorus containing oxide materials: Crystalline SiO{sub 2}‐P and 3P{sub 2}O{sub 5}⋅7SiO{sub 2}; CaO⋅P{sub 2}O{sub 5}; SrO⋅P{sub 2}O{sub 5} glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trukhin, A. N., E-mail: truhins@cfi.lu.lv; Smits, K., E-mail: truhins@cfi.lu.lv; Jansons, J., E-mail: truhins@cfi.lu.lv

2014-10-21

Luminescence of phosphate glasses such as CaO⋅P{sub 2}O{sub 5} and SrO⋅P{sub 2}O{sub 5} is compared with that of phosphorus doped crystalline α-quartz and phosphosilicate glass with content 3P{sub 2}O{sub 5}⋅7SiO{sub 2}. Water and OH groups are found by IR spectra in these materials. The spectrum of luminescence contains many bands in the range 1.5 - 5.5 eV. The luminescence bands in UV range at 4.5-5 eV are similar in those materials. Decay duration in exponential approximation manifests a time constant about 37 ns. Also a component in μs range was detected. PL band of μs component is shifted to lowmore » energy with respect to that of ∼37 ns component. This shift is about 0.6 eV. It is explained as singlet-triplet splitting of excited state. Below 14 K increase of luminescence kinetics duration in μs range was observed and it was ascribed to zero magnetic field splitting of triplet excited state of the center. Yellow-red luminescence was induced by irradiation in phosphorus doped crystalline α-quartz, phosphosilicate glasses. The yellowl uminescence contains two bands at 600 and 740 nm. Their decay is similar under 193 nm laser and may be fitted with the first order fractal kinetics or stretched exponent. Thermally stimulated luminescence contains only band at 600 nm. The 248 nm laser excites luminescence at 740 nm according to intra center process with decay time constant about 4 ms at 9 K. Both type of luminescence UV and yellow were ascribed to different defects containing phosphorus. P-doped α-quartz sample heated to 550 co become opalescent. Ir spectra related to water and OH groups are changed. Photoluminescence intensity of all three bands, UV (250 nm), yellow (600 nm) and red (740 nm) strongly diminished and disappeared after heating to 660 C°. Radiation induced red luminescence of non-bridging oxygen luminescence center (NBO) appeared in crystal after heat treatment. We had observed a crystalline version of this center (l. Skuja et al, Nuclear Instruments and Methods in Physics Research B 286,159-168 (2012)). Effect of heat treatment explained as sedimentation of phosphorus in some state. Keeping of treated sample at 450-500 C° leads to partial revival of ability to create yellow luminescence center under irradiation.« less

Mitigation of laser damage on National Ignition Facility optics in volume production

NASA Astrophysics Data System (ADS)

Folta, James; Nostrand, Mike; Honig, John; Wong, Nan; Ravizza, Frank; Geraghty, Paul; Taranowski, Mike; Johnson, Gary; Larkin, Glenn; Ravizza, Doug; Peterson, John; Welday, Brian; Wegner, Paul

2013-12-01

The National Ignition Facility has recently achieved the milestone of delivering over 1.8 MJ and 500 TW of 351 nm laser energy and power on target, which required average fluences up to 9 J/cm2 (3 ns equivalent) in the final optics system. Commercial fused silica laser-grade UV optics typically have a maximum operating threshold of 5 J/cm2. We have developed an optics recycling process which enables NIF to operate above the laser damage initiation and growth thresholds. We previously reported a method to mitigate laser damage with laser ablation of the damage site to leave benign cone shaped pits. We have since developed a production facility with four mitigation systems capable of performing the mitigation protocols on full-sized (430 mm) optics in volume production. We have successfully repaired over 700 NIF optics (unique serial numbers), some of which have been recycled as many as 11 times. We describe the mitigation systems, the optics recycle loop process, and optics recycle production data.

Rapid disinfection of E-Coliform contaminated water using WO3 semiconductor catalyst by laser-induced photo-catalytic process.

PubMed

Gondal, Mohammed A; Khalil, Amjad

2008-04-01

Laser-induced photo-catalysis process using WO(3) semiconductor catalyst was applied for the study of disinfection effectiveness of E-coliform-contaminated water. For this purpose, wastewater polluted with E-coliform bacteria was exposed to 355 nm UV radiations generated by third harmonic of Nd: YAG laser in special glass cell with and without WO(3) catalyst. E-Coliform quantification was performed by direct plating method to obtain the efficiency of each disinfection treatment. The dependence of disinfection process on laser irradiation energy, amount of catalyst and duration of laser irradiation was also investigated. The disinfection with WO(3) was quite efficient inactivating E-coliforms. For inactivation of E-coliforms, less than 8 minutes' laser irradiation was required, so that, the treated water complies with the microbial standards for drinking water. This study opens the possibility of application of this simple method in rural areas of developing countries using solar radiation.

UV lasers for drilling and marking applications.

PubMed

Hannon, T

1999-10-01

Lasers emitting ultraviolet (UV) light have unique capabilities for precision micromachining and marking plastic medical devices. This review of the benefits offered by laser technology includes a look at recently developed UV diode-pumped solid-state lasers and their key features.

Effects of ultraviolet light emitting diodes (LEDs) on microbial and enzyme inactivation of apple juice.

PubMed

Akgün, Merve Pelvan; Ünlütürk, Sevcan

2017-11-02

In this study, the effects of Ultraviolet light-emitting diodes (UV-LEDs) on the inactivation of E. coli K12 (ATCC 25253), an indicator organism of E. coli O157:H7, and polyphneoloxidase (PPO) in cloudy apple juice (CAJ) were investigated. The clear (AJ) and cloudy apple juice were exposed to UV rays for 40min by using a UV device composed of four UV-LEDs with peak emissions at 254 and 280nm and coupled emissions as follows: 254/365, 254/405, 280/365, 280/405 and 254/280/365/405nm. UV-LEDs at 254nm achieved 1.6±0.1 log 10 CFU/mL inactivation of E. coli K12 at UV dose of 707.2mJ/cm 2 . The highest inactivation of E. coli K12 (2.0±0.1log 10 CFU/mL and 2.0±0.4log 10 CFU/mL) was achieved when the cloudy apple juice was treated with both 280nm and 280/365nm UV-LEDs. For clear apple juice the highest inactivation 4.4log 10 CFU/mL obtained for E. coli K12 was achieved using 4 lamps emitting light at 280nm for 40min exposure time. For the same treatment time, the experiments using a combination of lamps emitting light at 280 and 365nm (2lamp/2lamp) were resulted in 3.9±0.2log 10 CFU/mL reductions. UV-A and UV-C rays in combination showed a better inactivation effect on PPO than UV-C rays used separately. Residual activity of PPO in CAJ was reduced to 32.58% when treated with UV-LED in combination of UV-C (280nm) and UV-A (365nm) rays. Additionally, the total color change (ΔE) of CAJ subjected to combined UV-LED irradiation at 280/365nm was the lowest compared to other studied processing conditions. This study provides key implications for the future application of UV-LEDs to fruit juice pasteurization. Copyright © 2017 Elsevier B.V. All rights reserved.

SHERLOC on Mars 2020

NASA Astrophysics Data System (ADS)

Beegle, L. W.; Bhartia, R.; DeFlores, L. P.; Abbey, W.; Asher, S. A.; Burton, A. S.; Fries, M.; Conrad, P. G.; Clegg, S. M.; Wiens, R. C.; Edgett, K. S.; Ehlmann, B. L.; Nealson, K. H.; Minitti, M. E.; Popp, J.; Langenhorst, F.; Sobron, P.; Steele, A.; Williford, K. H.; Yingst, R. A.

2017-12-01

The Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) investigation is part of the Mars 2020 integrated payload. SHERLOC enables non-contact, spatially resolved, and highly sensitivity detection and characterization of organics and minerals in the Martian surface and near subsurface. SHERLOC is an arm-mounted, Deep UV (DUV) resonance Raman and fluorescence spectrometer utilizing a 248.6-nm DUV laser. Deep UV induced native fluorescence is very sensitive to condensed carbon and aromatic organics, enabling detection at or below 10-6 w/w (1 ppm) at <100 µm spatial scales. SHERLOC's deep UV resonance Raman enables detection and classification of aromatic and aliphatic organics with sensitivities of 10-2 to below 10-4 w/w. In addition to organics, the deep UV Raman enables detection and classification of minerals relevant to aqueous chemistry with grain sizes below 20 µm. SHERLOC will be able to map the distribution of organic material with respect to visible features and minerals that are identifiable with the Raman spectrometer. These maps will enable analysis of the distribution of organics with minerals.

Localized Plasmon resonance in metal nanoparticles using Mie theory

NASA Astrophysics Data System (ADS)

Duque, J. S.; Blandón, J. S.; Riascos, H.

2017-06-01

In this work, scattering light by colloidal metal nanoparticles with spherical shape was studied. Optical properties such as diffusion efficiencies of extinction and absorption Q ext and Q abs were calculated using Mie theory. We employed a MATLAB program to calculate the Mie efficiencies and the radial dependence of electric field intensities emitted for colloidal metal nanoparticles (MNPs). By UV-Vis spectroscopy we have determined the LSPR for Cu nanoparticles (CuNPs), Ni nanoparticles (NiNPs) and Co nanoparticles (CoNPs) grown by laser ablation technique. The peaks of resonances appear in 590nm, 384nm and 350nm for CuNPs, NiNPs and CoNPs respectively suspended in water. Changing the medium to acetone and ethanol we observed a shift of the resonance peaks, these values agreed with our simulations results.

Protection of Nomex from Ultraviolet Degradation

DTIC Science & Technology

1977-03-01

absorbs UV radiation beginning at approximately 390 nano- meters (nm) and extending into the near UV with a peak at approximately 360 nm. This absorption is...the region near 290 nm [ 5 ]. Sunlight is much richer in radiation at 360 nm than at 290 nm and this fact undoubt- edly accounts for the much greater...function as UV screening agents. The absorption spectrum of Nomex in the near UV and visible region which is responsible for Nomex photodegra- dation is

Direct spectral analysis of tea samples using 266 nm UV pulsed laser-induced breakdown spectroscopy and cross validation of LIBS results with ICP-MS.

PubMed

Gondal, M A; Habibullah, Y B; Baig, Umair; Oloore, L E

2016-05-15

Tea is one of the most common and popular beverages spanning vast array of cultures all over the world. The main nutritional benefits of drinking tea are its anti-oxidant properties, presumed protection against certain cancers, inhibition of inflammation and possible protective effects against diabetes. Laser induced breakdown spectrometer (LIBS) was assembled as a powerful tool for qualitative and quantitative analysis of various brands of tea samples using 266 nm pulsed UV laser. LIBS spectra for six brands of tea samples in the wavelength range of 200-900 nm was recorded and all elements present in our tea samples were identified. The major toxic elements detected in several brands of tea samples were bromine, chromium and minerals like iron, calcium, potassium and silicon. The spectral assignment was conducted prior to the determination of concentration of each element. For quantitative analysis, calibration curves were drawn for each element using standard samples prepared in known concentration in the tea matrix. The plasma parameters (electron temperature and electron density) were also determined prior to the tea samples spectroscopic analysis. The concentration of iron, chromium, potassium, bromine, copper, silicon and calcium detected in all tea samples was between 378-656, 96-124, 1421-6785, 99-1476, 17-36, 2-11 and 92-130 mg L(-1) respectively. The limits of detection estimated for Fe, Cr, K, Br, Cu, Si, Ca in tea samples were 22, 12, 14, 11, 6, 1 and 12 mg L(-1) respectively. To further confirm the accuracy of our LIBS results, we determined the concentration of each element present in tea samples by using standard analytical technique like ICP-MS. The concentrations detected with our LIBS system are in excellent agreement with ICP-MS results. The system assembled for spectral analysis in this work could be highly applicable for testing the quality and purity of food and also pharmaceuticals products. Copyright © 2016 Elsevier B.V. All rights reserved.

Deep UV Native Fluorescence Imaging of Antarctic Cryptoendolithic Communities

NASA Technical Reports Server (NTRS)

Storrie-Lombardi, M. C.; Douglas, S.; Sun, H.; McDonald, G. D.; Bhartia, R.; Nealson, K. H.; Hug, W. F.

2001-01-01

An interdisciplinary team at the Jet Propulsion Laboratory Center for Life Detection has embarked on a project to provide in situ chemical and morphological characterization of Antarctic cryptoendolithic microbial communities. We present here in situ deep ultraviolet (UV) native fluorescence and environmental scanning electron microscopy images transiting 8.5 mm into a sandstone sample from the Antarctic Dry Valleys. The deep ultraviolet imaging system employs 224.3, 248.6, and 325 nm lasers to elicit differential fluorescence and resonance Raman responses from biomolecules and minerals. The 224.3 and 248.6 nm lasers elicit a fluorescence response from the aromatic amino and nucleic acids. Excitation at 325 nm may elicit activity from a variety of biomolecules, but is more likely to elicit mineral fluorescence. The resultant fluorescence images provide in situ chemical and morphological maps of microorganisms and the associated organic matrix. Visible broadband reflectance images provide orientation against the mineral background. Environmental scanning electron micrographs provided detailed morphological information. The technique has made possible the construction of detailed fluorescent maps extending from the surface of an Antarctic sandstone sample to a depth of 8.5 mm. The images detect no evidence of microbial life in the superficial 0.2 mm crustal layer. The black lichen component between 0.3 and 0.5 mm deep absorbs all wavelengths of both laser and broadband illumination. Filamentous deep ultraviolet native fluorescent activity dominates in the white layer between 0.6 mm and 5.0 mm from the surface. These filamentous forms are fungi that continue into the red (iron-rich) region of the sample extending from 5.0 to 8.5 mm. Using differential image subtraction techniques it is possible to identify fungal nuclei. The ultraviolet response is markedly attenuated in this region, apparently from the absorption of ultraviolet light by iron-rich particles coating the filaments. Below 8.5 mm the filamentous morphology of the upper layers gives way to punctate 1-2 micron particles evidencing fluorescent activity following excitation at both deep ultraviolet wavelengths.

Growth, structural, optical, thermal and laser damage threshold studies of an organic single crystal: 1,3,5 – triphenylbenzene (TPB)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raja, R. Subramaniyan; Babu, G. Anandha; Ramasamy, P., E-mail: E-mail-ramasamyp@ssn.edu.in

2016-05-23

Good quality single crystals of pure hydrocarbon 1,3,5-Triphenylbenzene (TPB) have been successfully grown using toluene as a solvent using controlled slow cooling solution growth technique. TPB crystallizes in orthorhombic structure with the space group Pna2{sub 1}. The structural perfection of the grown crystal has been analysed by high resolution X-ray diffraction measurements. The range and percentage of the optical transmission are ascertained by recording the UV-vis spectrum. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation studies were carried out to explore its NLO properties. Laser damage threshold valuemore » has been determined using Nd:YAG laser operating at 1064 nm.« less

Application Of The Excimer Laser To Area Recontouring Of The Cornea

NASA Astrophysics Data System (ADS)

Yoder, Paul R.; Telfair, William B.; Warner, John W.; Martin, Clifford A.; L'Esperance, Francis A.

1989-04-01

Excimer lasers operating at 193 nm are being used experimentally in a special type of materials processing wherein the central portion of the anterior surface of the human cornea is selectively ablated so as to change its refractive power and, hopefully, improve impaired vision. Research to date has demonstrated recontouring as a potential means for reducing myopia and hyperopia of cadaver eyes while studies of ablations on the corneas of living monkeys and of blind human volunteers show promise of prompt and successful healing. The procedure has also shown merit in removing superficial scars from the corneal surface. In this paper, we describe the electro-optical system used to deliver the UV laser beam in these experiments and report some preliminary results of the ablation studies.

Antimony sulfide thin films prepared by laser assisted chemical bath deposition

NASA Astrophysics Data System (ADS)

Shaji, S.; Garcia, L. V.; Loredo, S. L.; Krishnan, B.; Aguilar Martinez, J. A.; Das Roy, T. K.; Avellaneda, D. A.

2017-01-01

Antimony sulfide (Sb2S3) thin films were prepared by laser assisted chemical bath deposition (LACBD) technique. These thin films were deposited on glass substrates from a chemical bath containing antimony chloride, acetone and sodium thiosulfate under various conditions of normal chemical bath deposition (CBD) as well as in-situ irradiation of the chemical bath using a continuous laser of 532 nm wavelength. Structure, composition, morphology, optical and electrical properties of the Sb2S3 thin films produced by normal CBD and LACBD were analyzed by X-Ray diffraction (XRD), Raman Spectroscopy, Atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and Photoconductivity. The results showed that LACBD is an effective synthesis technique to obtain Sb2S3 thin films for optoelectronic applications.

Spectroscopic identification of rare earth elements in phosphate glass

NASA Astrophysics Data System (ADS)

Devangad, Praveen; Tamboli, Maktum; Muhammed Shameem, K. M.; Nayak, Rajesh; Patil, Ajeetkumar; Unnikrishnan, V. K.; Santhosh, C.; Kumar, G. A.

2018-01-01

In this work, rare earth-doped phosphate glasses were synthesized and characterized using three different spectroscopic techniques. The absorption spectra of the prepared praseodymium (Pr) and samarium (Sm) doped glasses, recorded by a UV-VIS-NIR spectrophotometer, show the characteristic absorption bands of these elements. To confirm this inference, laser-induced fluorescence spectra of Pr and Sm were obtained at a laser excitation of 442 nm. Their emission bands are reported here. The elemental analysis of these samples was carried out using a laser-induced breakdown spectroscopy (LIBS) system. Characteristic emission lines of Pr and Sm have been identified and reported by the recorded LIBS spectra of glass samples. Results prove that using these three complimentary spectroscopic techniques (absorption, fluorescence and LIBS), we can meaningfully characterize rare earth-doped glass samples.

Difluorophosphoryl nitrene F2P(O)N: matrix isolation and unexpected rearrangement to F2PNO.

PubMed

Zeng, Xiaoqing; Beckers, Helmut; Willner, Helge; Neuhaus, Patrik; Grote, Dirk; Sander, Wolfram

2009-12-14

Triplet difluorophosphoryl nitrene F(2)P(O)N (X(3)A'') was generated on ArF excimer laser irradiation (lambda=193 nm) of F(2)P(O)N(3) in solid argon matrix at 16 K, and characterized by its matrix IR, UV/Vis, and EPR spectra, in combination with DFT and CBS-QB3 calculations. On visible light irradiation (lambda>420 nm) at 16 K F(2)P(O)N reacts with molecular nitrogen and some of the azide is regenerated. UV irradiation (lambda=255 nm) of F(2)P(O)N (X(3)A'') induced a Curtius-type rearrangement, but instead of a 1,3-fluorine shift, nitrogen migration to give F(2)PON is proposed to be the first step of the photoisomerization of F(2)P(O)N into F(2)PNO (difluoronitrosophosphine). Formation of novel F(2)PNO was confirmed with (15)N- and (18)O-enriched isotopomers by IR spectroscopy and DFT calculations. Theoretical calculations predict a rather long P-N bond of 1.922 A [B3LYP/6-311+G(3df)] and low bond-dissociation energy of 76.3 kJ mol(-1) (CBS-QB3) for F(2)PNO.

Rational design of a comprehensive cancer therapy platform using temperature-sensitive polymer grafted hollow gold nanospheres: simultaneous chemo/photothermal/photodynamic therapy triggered by a 650 nm laser with enhanced anti-tumor efficacy

NASA Astrophysics Data System (ADS)

Deng, Xiaoran; Chen, Yinyin; Cheng, Ziyong; Deng, Kerong; Ma, Ping'an; Hou, Zhiyao; Liu, Bei; Huang, Shanshan; Jin, Dayong; Lin, Jun

2016-03-01

Combining multi-model treatments within one single system has attracted great interest for the purpose of synergistic therapy. In this paper, hollow gold nanospheres (HAuNs) coated with a temperature-sensitive polymer, poly(oligo(ethylene oxide) methacrylate-co-2-(2-methoxyethoxy)ethyl methacrylate) (p(OEGMA-co-MEMA)), co-loaded with DOX and a photosensitizer Chlorin e6 (Ce6) were successfully synthesized. As high as 58% DOX and 6% Ce6 by weight could be loaded onto the HAuNs-p(OEGMA-co-MEMA) nanocomposites. The grafting polymer brushes outside the HAuNs play the role of ``gate molecules'' for controlled drug release by 650 nm laser radiation owing to the temperature-sensitive property of the polymer and the photothermal effect of HAuNs. The HAuNs-p(OEGMA-co-MEMA)-Ce6-DOX nanocomposites with 650 nm laser radiation show effective inhibition of cancer cells in vitro and enhanced anti-tumor efficacy in vivo. In contrast, control groups without laser radiation show little cytotoxicity. The nanocomposite demonstrates a way of ``killing three birds with one stone'', that is, chemotherapy, photothermal and photodynamic therapy are triggered simultaneously by the 650 nm laser stimulation. Therefore, the nanocomposites show the great advantages of multi-modal synergistic effects for cancer therapy by a remote-controlled laser stimulus.Combining multi-model treatments within one single system has attracted great interest for the purpose of synergistic therapy. In this paper, hollow gold nanospheres (HAuNs) coated with a temperature-sensitive polymer, poly(oligo(ethylene oxide) methacrylate-co-2-(2-methoxyethoxy)ethyl methacrylate) (p(OEGMA-co-MEMA)), co-loaded with DOX and a photosensitizer Chlorin e6 (Ce6) were successfully synthesized. As high as 58% DOX and 6% Ce6 by weight could be loaded onto the HAuNs-p(OEGMA-co-MEMA) nanocomposites. The grafting polymer brushes outside the HAuNs play the role of ``gate molecules'' for controlled drug release by 650 nm laser radiation owing to the temperature-sensitive property of the polymer and the photothermal effect of HAuNs. The HAuNs-p(OEGMA-co-MEMA)-Ce6-DOX nanocomposites with 650 nm laser radiation show effective inhibition of cancer cells in vitro and enhanced anti-tumor efficacy in vivo. In contrast, control groups without laser radiation show little cytotoxicity. The nanocomposite demonstrates a way of ``killing three birds with one stone'', that is, chemotherapy, photothermal and photodynamic therapy are triggered simultaneously by the 650 nm laser stimulation. Therefore, the nanocomposites show the great advantages of multi-modal synergistic effects for cancer therapy by a remote-controlled laser stimulus. Electronic supplementary information (ESI) available: The relevant XRD, NMR, IR, UV and photograph. See DOI: 10.1039/c5nr08253f

Improved native UV laser induced fluorescence detection for single cell analysis in poly(dimethylsiloxane) microfluidic devices.

PubMed

Hellmich, Wibke; Greif, Dominik; Pelargus, Christoph; Anselmetti, Dario; Ros, Alexandra

2006-10-20

Single cell analytics is a key method in the framework of proteom research allowing analyses, which are not subjected to ensemble-averaging, cell-cycle or heterogeneous cell-population effects. Our previous studies on single cell analysis in poly(dimethylsiloxane) microfluidic devices with native label-free laser induced fluorescence detection [W. Hellmich, C. Pelargus, K. Leffhalm, A. Ros, D. Anselmetti, Electrophoresis 26 (2005) 3689] were extended in order to improve separation efficiency and detection sensitivity. Here, we particularly focus on the influence of poly(oxyethylene) based coatings on the separation performance. In addition, the influence on background fluorescence is studied by the variation of the incident laser power as well as the adaptation of the confocal volume to the microfluidic channel dimensions. Last but not least, the use of carbon black particles further enhanced the detection limit to 25 nM, thereby reaching the relevant concentration ranges necessary for the label-free detection of low abundant proteins in single cells. On the basis of these results, we demonstrate the first electropherogram from an individual Spodoptera frugiperda (Sf9) cell with native label-free UV-LIF detection in a microfluidic chip.

Matching the laser wavelength to the absorption properties of matrices increases the ion yield in UV-MALDI mass spectrometry.

PubMed

Wiegelmann, Marcel; Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus

2013-09-01

A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities "per laser shot" and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel.

Synthesis of SiC nanoparticles by SHG 532 nm Nd:YAG laser ablation of silicon in ethanol

NASA Astrophysics Data System (ADS)

Khashan, Khawla S.; Ismail, Raid A.; Mahdi, Rana O.

2018-06-01

In this work, colloidal spherical nanoparticles NPs of silicon carbide SiC have been synthesized using second harmonic generation 532 nm Nd:YAG laser ablation of silicon target dipped in ethanol solution at various laser fluences (1.5-5) J/cm2. X-Ray diffraction XRD, scanning electron microscopy SEM, transmission electron microscope TEM, Fourier transformed infrared spectroscopy FT-IR, Raman spectroscopy, photoluminescence PL spectroscopy, and UV-Vis absorption were employed to examine the structural, chemical and optical properties of SiC NPs. XRD results showed that all synthesised SiC nanoparticles are crystalline in nature and have hexagonal structure with preferred orientation along (103) plane. Raman investigation showed three characteristic peaks 764,786 and 954 cm-1, which are indexing to transverse optic TO phonon mode and longitudinal optic LO phonon mode of 4H-SiC structure. The optical absorption data showed that the values of optical energy gap of SiC nanoparticles prepared at 1.5 J/cm2 was 3.6 eV and was 3.85 eV for SiC synthesised at 5 J/cm2. SEM investigations confirmed that the nanoparticles synthesised at 5 J/cm2 are agglomerated to form larger particles. TEM measurements showed that SiC particles prepared at 1.5 J/cm2 have spherical shape with average size of 25 nm, while the particles prepared at 5 J/cm2 have an average size of 55 nm.

Evolution of size distribution, optical properties, and structure of Si nanoparticles obtained by laser-assisted fragmentation

NASA Astrophysics Data System (ADS)

Plautz, G. L.; Graff, I. L.; Schreiner, W. H.; Bezerra, A. G.

2017-05-01

We investigate the physical properties of Si-based nanoparticles produced by an environment-friendly three-step method relying on: (1) laser ablation of a solid target immersed in water, (2) centrifugation and separation, and (3) laser-assisted fragmentation. The evolution of size distribution is followed after each step by means of dynamic light scattering (DLS) measurements and crosschecked by transmission electron microscopy (TEM). The as-ablated colloidal suspension of Si nanoparticles presents a large size distribution, ranging from a few to hundreds of nanometers. Centrifugation drives the very large particles to the bottom eliminating them from the remaining suspension. Subsequent irradiation of height-separated suspensions with a second high-fluence (40 mJ/pulse) Nd:YAG laser operating at the fourth harmonic (λ =266 nm) leads to size reduction and ultra-small nanoparticles are obtainable depending on the starting size. Si nanoparticles as small as 1.5 nm with low dispersion (± 0.7 nm) are observed for the uppermost part after irradiation. These nanoparticles present a strong blue photoluminescence that remains stable for at least 8 weeks. Optical absorption (UV-Vis) measurements demonstrate an optical gap widening as a consequence of size decrease. Raman spectra present features related to pure silicon and silicon oxides for the irradiated sample. Interestingly, a defect band associated with silicon oxide is also identified, indicating the possible formation of defect states, which, in turn, supports the idea that the blue photoluminescence has its origin in defects.

207-nm UV Light-A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. II: In-Vivo Safety Studies.

PubMed

Buonanno, Manuela; Stanislauskas, Milda; Ponnaiya, Brian; Bigelow, Alan W; Randers-Pehrson, Gerhard; Xu, Yanping; Shuryak, Igor; Smilenov, Lubomir; Owens, David M; Brenner, David J

2016-01-01

UVC light generated by conventional germicidal lamps is a well-established anti-microbial modality, effective against both bacteria and viruses. However, it is a human health hazard, being both carcinogenic and cataractogenic. Earlier studies showed that single-wavelength far-UVC light (207 nm) generated by excimer lamps kills bacteria without apparent harm to human skin tissue in vitro. The biophysical explanation is that, due to its extremely short range in biological material, 207 nm UV light cannot penetrate the human stratum corneum (the outer dead-cell skin layer, thickness 5-20 μm) nor even the cytoplasm of individual human cells. By contrast, 207 nm UV light can penetrate bacteria and viruses because these cells are physically much smaller. To test the biophysically-based hypothesis that 207 nm UV light is not cytotoxic to exposed mammalian skin in vivo. Hairless mice were exposed to a bactericidal UV fluence of 157 mJ/cm2 delivered by a filtered Kr-Br excimer lamp producing monoenergetic 207-nm UV light, or delivered by a conventional 254-nm UV germicidal lamp. Sham irradiations constituted the negative control. Eight relevant cellular and molecular damage endpoints including epidermal hyperplasia, pre-mutagenic UV-associated DNA lesions, skin inflammation, and normal cell proliferation and differentiation were evaluated in mice dorsal skin harvested 48 h after UV exposure. While conventional germicidal UV (254 nm) exposure produced significant effects for all the studied skin damage endpoints, the same fluence of 207 nm UV light produced results that were not statistically distinguishable from the zero exposure controls. As predicted by biophysical considerations and in agreement with earlier in vitro studies, 207-nm light does not appear to be significantly cytotoxic to mouse skin. These results suggest that excimer-based far-UVC light could potentially be used for its anti-microbial properties, but without the associated hazards to skin of conventional germicidal UV lamps.

207-nm UV Light—A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. II: In-Vivo Safety Studies

PubMed Central

Buonanno, Manuela; Stanislauskas, Milda; Ponnaiya, Brian; Bigelow, Alan W.; Randers-Pehrson, Gerhard; Xu, Yanping; Shuryak, Igor; Smilenov, Lubomir; Owens, David M.; Brenner, David J.

2016-01-01

Background UVC light generated by conventional germicidal lamps is a well-established anti-microbial modality, effective against both bacteria and viruses. However, it is a human health hazard, being both carcinogenic and cataractogenic. Earlier studies showed that single-wavelength far-UVC light (207 nm) generated by excimer lamps kills bacteria without apparent harm to human skin tissue in vitro. The biophysical explanation is that, due to its extremely short range in biological material, 207 nm UV light cannot penetrate the human stratum corneum (the outer dead-cell skin layer, thickness 5–20 μm) nor even the cytoplasm of individual human cells. By contrast, 207 nm UV light can penetrate bacteria and viruses because these cells are physically much smaller. Aims To test the biophysically-based hypothesis that 207 nm UV light is not cytotoxic to exposed mammalian skin in vivo. Methods Hairless mice were exposed to a bactericidal UV fluence of 157 mJ/cm2 delivered by a filtered Kr-Br excimer lamp producing monoenergetic 207-nm UV light, or delivered by a conventional 254-nm UV germicidal lamp. Sham irradiations constituted the negative control. Eight relevant cellular and molecular damage endpoints including epidermal hyperplasia, pre-mutagenic UV-associated DNA lesions, skin inflammation, and normal cell proliferation and differentiation were evaluated in mice dorsal skin harvested 48 h after UV exposure. Results While conventional germicidal UV (254 nm) exposure produced significant effects for all the studied skin damage endpoints, the same fluence of 207 nm UV light produced results that were not statistically distinguishable from the zero exposure controls. Conclusions As predicted by biophysical considerations and in agreement with earlier in vitro studies, 207-nm light does not appear to be significantly cytotoxic to mouse skin. These results suggest that excimer-based far-UVC light could potentially be used for its anti-microbial properties, but without the associated hazards to skin of conventional germicidal UV lamps. PMID:27275949

Mask technology for EUV lithography

NASA Astrophysics Data System (ADS)

Bujak, M.; Burkhart, Scott C.; Cerjan, Charles J.; Kearney, Patrick A.; Moore, Craig E.; Prisbrey, Shon T.; Sweeney, Donald W.; Tong, William M.; Vernon, Stephen P.; Walton, Christopher C.; Warrick, Abbie L.; Weber, Frank J.; Wedowski, Marco; Wilhelmsen, Karl C.; Bokor, Jeffrey; Jeong, Sungho; Cardinale, Gregory F.; Ray-Chaudhuri, Avijit K.; Stivers, Alan R.; Tejnil, Edita; Yan, Pei-yang; Hector, Scott D.; Nguyen, Khanh B.

1999-04-01

Extreme UV Lithography (EUVL) is one of the leading candidates for the next generation lithography, which will decrease critical feature size to below 100 nm within 5 years. EUVL uses 10-14 nm light as envisioned by the EUV Limited Liability Company, a consortium formed by Intel and supported by Motorola and AMD to perform R and D work at three national laboratories. Much work has already taken place, with the first prototypical cameras operational at 13.4 nm using low energy laser plasma EUV light sources to investigate issues including the source, camera, electro- mechanical and system issues, photoresists, and of course the masks. EUV lithograph masks are fundamentally different than conventional photolithographic masks as they are reflective instead of transmissive. EUV light at 13.4 nm is rapidly absorbed by most materials, thus all light transmission within the EUVL system from source to silicon wafer, including EUV reflected from the mask, is performed by multilayer mirrors in vacuum.

Effect of various SnO2 pH on ZnO/SnO2-composite film via immersion technique

NASA Astrophysics Data System (ADS)

Malek, M. F.; Mohamed, R.; Mamat, M. H.; Ismail, A. S.; Yusoff, M. M.; Rusop, M.

2018-05-01

ZnO/SnO2-composite film has been synthesized via immersion technique with various pH of SnO2. The pH of SnO2 were varied between 4.5 and 6.5. The optical measurements of the samples were carried out using Varian Cary 5000 UV-Vis spectrophotometer within the range from 350 nm to 800 nm at room temperature in air with a data interval of 1 nm. On the other hand, the optical photoluminescence properties were measured by a photoluminescence spectrometer (PL, model: Horiba Jobin Yvon - 79 DU420A-OE-325) using a He-Cd laser as the excitation source at 325 nm. These highly oriented ZnO/SnO2-composite film are potential for the creation of functional materials, such as the sensors, solar cells and etc.

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

PubMed Central

Buonanno, Manuela; Randers-Pehrson, Gerhard; Bigelow, Alan W.; Trivedi, Sheetal; Lowy, Franklin D.; Spotnitz, Henry M.; Hammer, Scott M.; Brenner, David J.

2013-01-01

Background 0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ∼200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure. Aims The aim of this work was to test the biophysically-based hypothesis that ∼200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues. Methods A Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue. Results We found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp. Conclusions As predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin. PMID:24146947