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.

Excimer Laser Curing Of Polymer Coatings

NASA Astrophysics Data System (ADS)

Klick, David; Akerman, M. Alfred; Paul, George L.; Supurovic, Darko; Tsuda, Haruki

1988-12-01

The use of the excimer laser as a source of energy for photo-assisted curing of industrial polymeric coatings was investigated. Presently, UV lamps are sometimes used to excite a photoinitiating molecule mixed with the starting monomers and oligomers of a coating. The resulting polymeric chain reaction multiplies the effect of the initial photons, making economical use of the light source. The high cost of laser photons may thus be justifiable if lasers provide advantages over lamps. A series of visibly transparent 7 μm coatings (a typical thickness for 'slick' magazine coatings) with various photoinitiators, monomers, and oligomers was illuminated with excimer laser light of various wavelengths, fluences, and pulse repetition rates. For the optimum parameters, it was found that the laser had large advantages in curing speed over existing UV lamp processes, due to its monochromaticity. Pigmented coatings (20 μm TiO2 mixtures typical of appliance or automotive finishes) are not easily cured with UV lamps due to the inability of light to penetrate the absorbing and scattering pigmented layer. However, economically-viable cure rates were achieved with certain photoinitiators using a tunable excimer-pumped dye laser. A prototype of such a laser suitable for factory use was built and used to cure these coatings. Results are scaled to a factory situation, and costs are calculated to show the advantages of the laser method over currently used processes.

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.

Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

NASA Technical Reports Server (NTRS)

Harris, S. E.; Siegman, A. E.; Kuizenga, D. J.; Kung, A. H.; Young, J. F.; Bekkers, G. W.; Bloom, D. M.; Newton, J. H.; Phillion, D. W.

1975-01-01

The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources.

Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

DOE PAGES

Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; ...

2014-01-01

A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parametermore » dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.« less

UV-Enhanced IR Raman System for Identifying Biohazards

NASA Technical Reports Server (NTRS)

Stirbl, Robert; Moynihan, Philip; Lane, Arthur

2003-01-01

An instrumentation system that would include an ultraviolet (UV) laser or light-emitting diode, an infrared (IR) laser, and the equivalent of an IR Raman spectrometer has been proposed to enable noncontact identification of hazardous biological agents and chemicals. In prior research, IR Raman scattering had shown promise as a means of such identification, except that the Raman-scattered light was often found to be too weak to be detected or to enable unambiguous identification in practical applications. The proposed system would utilize UV illumination as part of a two-level optical-pumping scheme to intensify the Raman signal sufficiently to enable positive identification.

Production of organic compounds in plasmas - A comparison among electric sparks, laser-induced plasmas, and UV light

NASA Technical Reports Server (NTRS)

Scattergood, Thomas W.; Mckay, Christopher P.; Borucki, William J.; Giver, Lawrence P.; Van Ghyseghem, Hilde

1989-01-01

In order to ascertain the features of organic compound-production in planetary atmospheres under the effects of plasmas and shocks, various mixtures of N2, CH4, and H2 modeling the atmosphere of Titan were subjected to discrete sparks, laser-induced plasmas, and UV radiation. The experimental results obtained suggest that UV photolysis from the plasma is an important organic compound synthesis process, as confirmed by the photolysis of gas samples that were exposed to the light but not to the shock waves emitted by the sparks. The thermodynamic equilibrium theory is therefore incomplete in the absence of photolysis.

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.

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.

QCL seeded, ns-pulse, multi-line, CO2 laser oscillator for laser-produced-plasma extreme-UV source

NASA Astrophysics Data System (ADS)

Nowak, Krzysztof Michał; Suganuma, Takashi; Kurosawa, Yoshiaki; Ohta, Takeshi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saitou, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru; Sumitani, Akira; Endo, Akira

2017-01-01

Successful merger of state-of-the-art, semiconductor quantum-cascade lasers (QCL), with the mature CO2 laser technology, resulted in a delivery of highly-desired qualities of CO2 laser output that were not available previously without much effort. These qualities, such as multi-line operation, excellent spectro-temporal stability and pulse waveform control, became available from a single device of moderate complexity. This paper describes the operation principle and the unique properties of the solid{state seeded CO2 laser, invented for an application in laser-produced-plasma (LPP), extreme-UV (EUV) light source.

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.

Electronic-beam analysis of excimer lasers used for photorefractive keratotomy

NASA Astrophysics Data System (ADS)

Roundy, Carlos B.

1998-07-01

Excimer lasers are an excellent instrument for performing photorefractive keratotomy, PRK. The UV light from the laser causes an ablation of the cornea in proportion to the intensity of the light. The primary characteristic essential to successful PRK is the uniformity of the Top Hat, or working portion of the laser beam. In order for this intensity profile to be sufficiently uniform for PRK, it is essential to periodically measure the equality of the laser beam profile. This ensures that the laser continues to operate properly and provide the expected performance.

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.

Laterally injected light-emitting diode and laser diode

DOEpatents

Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

2015-06-16

A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

Monolithic translucent BaMgAl 10O 17:Eu 2+ phosphors for laser-driven solid state lighting

DOE PAGES

Cozzan, Clayton; Brady, Michael J.; O’Dea, Nicholas; ...

2016-10-11

With high power light emitting diodes and laser diodes being explored for white light generation and visible light communication, thermally robust encapsulation schemes for color-converting inorganic phosphors are essential. In the current work, the canonical blue-emitting phosphor, high purity Eu-doped BaMgAl 10O 17, has been prepared using microwave-assisted heating (25 min) and densified into translucent ceramic phosphor monoliths using spark plasma sintering (30 min). Lastly, the resulting translucent ceramic monoliths convert UV laser light to blue light with the same efficiency as the starting powder and provide superior thermal management in comparison with silicone encapsulation.

UV laser-induced cross-linking in peptides

PubMed Central

Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

2013-01-01

RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

Laser-ultraviolet-A-induced ultraweak photon emission in mammalian cells.

PubMed

Niggli, Hugo J; Tudisco, Salvatore; Privitera, Giuseppe; Applegate, Lee Ann; Scordino, Agata; Musumeci, Franco

2005-01-01

Photobiological research in the last 30 yr has shown the existence of ultraweak photon emission in biological tissue, which can be detected with sophisticated photomultiplier systems. Although the emission of this ultraweak radiation, often termed biophotons, is extremely low in mammalian cells, it can be efficiently increased by ultraviolet light. Most recently it was shown that UV-A (330 to 380 nm) releases such very weak cell radiation in differentiated human skin fibroblasts. Based on these findings, a new and powerful tool in the form of UV-A-laser-induced biophotonic emission of cultured cells was developed with the intention to detect biophysical changes between carcinogenic and normal cells. With suspension densities ranging from 1 to 8 x 10(6) cells/mL, it was evident that an increase of the UV-A-laser-light induced photon emission intensity could be observed in normal as well as melanoma cells. Using this new detection procedure of ultraweak light emission, photons in cell suspensions as low as 100 microL could be determined, which is a factor of 100 lower compared to previous procedures. Moreover, the detection procedure has been further refined by turning off the photomultiplier system electronically during irradiation leading to the first measurements of induced light emission in the cells after less than 10 micros instead of 150 ms, as reported in previous procedures. This improvement leads to measurements of light bursts up 10(7) photons/s instead of several hundred as found with classical designs. Overall, we find decreasing induction ratings between normal and melanoma cells as well as cancer-prone and melanoma cells. Therefore, it turns out that this highly sensitive and noninvasive device enables us to detect high levels of ultraweak photon emission following UV-A-laser-induced light stimulation within the cells, which enables future development of new biophysical strategies in cell research. Copyright 2005 Society of Photo-Optical Instrumentation Engineers.

Radiation-damage-induced phasing: a case study using UV irradiation with light-emitting diodes.

PubMed

de Sanctis, Daniele; Zubieta, Chloe; Felisaz, Franck; Caserotto, Hugo; Nanao, Max H

2016-03-01

Exposure to X-rays, high-intensity visible light or ultraviolet radiation results in alterations to protein structure such as the breakage of disulfide bonds, the loss of electron density at electron-rich centres and the movement of side chains. These specific changes can be exploited in order to obtain phase information. Here, a case study using insulin to illustrate each step of the radiation-damage-induced phasing (RIP) method is presented. Unlike a traditional X-ray-induced damage step, specific damage is introduced via ultraviolet light-emitting diodes (UV-LEDs). In contrast to UV lasers, UV-LEDs have the advantages of small size, low cost and relative ease of use.

Quantum Phenomena in High Energy Density Plasmas

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

Murnane, Margaret; Kapteyn, Henry

The possibility of implementing efficient (phase matched) HHG upconversion of deep- UV lasers in multiply-ionized plasmas, with potentially unprecedented conversion efficiency is a fascinating prospect. HHG results from the extreme nonlinear response of matter to intense laser light:high harmonics are radiated as a result of a quantum coherent electron recollision process that occurs during laser field ionization of an atom. Under current support from this grant in work published in Science in 2015, we discovered a new regime of bright HHG in highly-ionized plasmas driven by intense UV lasers, that generates bright harmonics to photon energies >280eV

Generation of radicals in hard biological tissues under the action of laser radiation

NASA Astrophysics Data System (ADS)

Sviridov, Alexander P.; Bagratashvili, Victor N.; Sobol, Emil N.; Omelchenko, Alexander I.; Lunina, Elena V.; Zhitnev, Yurii N.; Markaryan, Galina L.; Lunin, Valerii V.

2002-07-01

The formation of radicals upon UV and IR laser irradiation of some biological tissues and their components was studied by the EPR technique. The radical decay kinetics in body tissue specimens after their irradiation with UV light were described by various models. By the spin trapping technique, it was shown that radicals were not produced during IR laser irradiation of cartilaginous tissue. A change in optical absorption spectra and the dynamics of optical density of cartilaginous tissue, fish scale, and a collagen film under exposure to laser radiation in an air, oxygen, and nitrogen atmosphere was studied.

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.

Laser-Stimulated Fluorescence in Paleontology

PubMed Central

Kaye, Thomas G.; Falk, Amanda R.; Pittman, Michael; Sereno, Paul C.; Burnham, David A.; Gong, Enpu; Xu, Xing; Wang, Yinan

2015-01-01

Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser’s ability to concentrate very high flux rates both at the macroscopic and microscopic levels results in specimens fluorescing in ways a standard UV bulb cannot induce. Presented here are five paleontological case histories that illustrate the technique across a broad range of specimens and scales. Novel uses such as back-lighting opaque specimens to reveal detail and detection of specimens completely obscured by matrix are highlighted in these examples. The recent cost reductions in medium-power short wavelength lasers and use of standard photographic filters has now made this technique widely accessible to researchers. This technology has the potential to automate multiple aspects of paleontology, including preparation and sorting of microfossils. This represents a highly cost-effective way to address paleontology's preparatory bottleneck. PMID:26016843

Photoelectrolysis of water at high current density - Use of laser light excitation of semiconductor-based photoelectrochemical cells

NASA Technical Reports Server (NTRS)

Wrighton, M. S.; Bocarsley, A. B.; Bolts, J. M.

1978-01-01

In the present paper, some results are given for UV laser light irradiation of the photoanode (SnO2, SrTiO3, or TiO2) in a cell for the light-driven electrolysis of H2O, at radiation intensities of up to 380 W/sq cm. The properties of the anode material are found to be independent of light intensity. Conversion of UV light to stored chemical energy in the form of 2H2/O2 from H2O was driven at a rate of up to 30 W/sq cm. High O2 evolution rates at the irradiated anodes without changes in the current-voltage curves are attributed to the excess oxidizing power associated with photogenerated holes. A test for this sort of hypothesis for H2 evolution at p-type materials is proposed.

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

People with Increased Risk of Eye Damage from UV Light

MedlinePlus

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Laser discrimination by stimulated emission of a phosphor

NASA Technical Reports Server (NTRS)

Mathur, V. K.; Chakrabarti, K.

1991-01-01

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

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.

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.

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.

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.

Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

NASA Astrophysics Data System (ADS)

Xiong, Zhongmin; Kushner, Mark J.

2011-10-01

Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

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 reflection from oxide-coated aluminum

NASA Technical Reports Server (NTRS)

Williams, M. D.

1982-01-01

The theory of reflection from an oxide-coated metal is combined with experimentally measured parameters of aluminum to produce useful amplitude and phase shift information applicable to the concentration and direction of laser light. Amplitude and phase are plotted vs angle of incidence for several important laser wavelengths in the near UV, visible, and IR spectral regions.

Photoactive energetic materials

DOEpatents

Chavez, David E.; Hanson, Susan Kloek; Scharff, Robert Jason; Veauthier, Jacqueline Marie; Myers, Thomas Winfield

2018-02-27

Energetic materials that are photoactive or believed to be photoactive may include a conventional explosive (e.g. PETN, nitroglycerine) derivatized with an energetic UV-absorbing and/or VIS-absorbing chromophore such as 1,2,4,5-tetrazine or 1,3,5-triazine. Absorption of laser light having a suitably chosen wavelength may result in photodissociation, decomposition, and explosive release of energy. These materials may be used as ligands to form complexes. Coordination compounds include such complexes with counterions. Some having the formula M(L).sub.n.sup.2+ were synthesized, wherein M is a transition metal and L is a ligand and n is 2 or 3. These may be photoactive upon exposure to a laser light beam having an appropriate wavelength of UV light, near-IR and/or visible light. Photoactive materials also include coordination compounds bearing non-energetic ligands; in this case, the counterion may be an oxidant such as perchlorate.

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.

UV response on dielectric properties of nano nematic liquid crystal

NASA Astrophysics Data System (ADS)

Pandey, Kamal Kumar; Tripathi, Pankaj Kumar; Misra, Abhishek Kumar; Manohar, Rajiv

2018-03-01

In this work, we investigate the effect of UV light irradiation on the dielectric parameters of nematic liquid crystal (5CB) and ZnO nanoparticles dispersed liquid crystal. With addition of nanoparticles in nematic LC are promising new materials for a variety of application in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however we optimize the properties of liquid crystal and understand how the UV light irradiation interact the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor have discussed the pure nematic LC and dispersed/doped system after, during and before UV light exposure. The dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz-10 MHz in the nematic mesophase range.

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.

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.

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.

Controlled UV-C light-induced fusion of thiol-passivated gold nanoparticles.

PubMed

Pocoví-Martínez, Salvador; Parreño-Romero, Miriam; Agouram, Said; Pérez-Prieto, Julia

2011-05-03

Thiol-passivated gold nanoparticles (AuNPs) of a relatively small size, either decorated with chromophoric groups, such as a phthalimide (Au@PH) and benzophenone (Au@BP), or capped with octadecanethiol (Au@ODCN) have been synthesized and characterized by NMR and UV-vis spectroscopy as well as transmission electron microscopy (TEM). These NPs were irradiated in chloroform at different UV-wavelengths using either a nanosecond laser (266 and 355 nm, ca. 12 mJ/pulse, 10 ns pulse) or conventional lamps (300 nm < λ < 400 nm and ca. 240 nm < λ < 280 nm) and the new AuNPs were characterized by X-ray and UV-vis spectroscopy, as well as by TEM. Laser irradiation at 355 nm led to NP aggregation and precipitation, while the NPs were photostable under UV-A lamp illumination. Remarkably, laser excitation at 266 nm induced a fast (minutes time-scale) increase in the size of the NPs, producing huge spherical nanocrystals, while lamp-irradiation at UV-C wavelengths brought about nanonetworks of partially fused NPs with a larger diameter than the native NPs.

Designs for optimizing depth of focus and spot size for UV laser ablation

NASA Astrophysics Data System (ADS)

Wei, An-Chi; Sze, Jyh-Rou; Chern, Jyh-Long

2010-11-01

The proposed optical systems are designed for extending the depths of foci (DOF) of UV lasers, which can be exploited in the laser-ablation technologies, such as laser machining and lithography. The designed systems are commonly constructed by an optical module that has at least one aspherical surface. Two configurations of optical module, lens-only and lens-reflector, are presented with the designs of 2-lens and 1-lens-1-reflector demonstrated by commercially optical software. Compared with conventional DOF-enhanced systems, which required the chromatic aberration lenses and the light sources with multiple wavelengths, the proposed designs are adapted to the single-wavelength systems, leading to more economical and efficient systems.

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

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.

Meeting Future C3I (Command-Control-Communications-Intelligence) Needs with Fiber Optics,

DTIC Science & Technology

1985-05-01

Frequency dependence of the sensitivity of fibers with hard coatings is relatively small. Nylon gives the weakest dependence, while the soft UV -cured...elastomer gives the strongest. Maximum sensitivity is obtained with Teflon TFE, while the minimum is achieved with the soft UV coating. With the latter...fiber-optics systems: the LED (Light Emitting Diode) and ILD (Injection Laser Diode). These devices emit light when an electric current is applied. The

Apparatus to collect, classify, concentrate, and characterize gas-borne particles

DOEpatents

Rader, Daniel J.; Torczynski, John R.; Wally, Karl; Brockmann, John E.

2003-12-16

An aerosol lab-on-a-chip (ALOC) integrates one or more of a variety of particle collection, classification, concentration (enrichment), an characterization processes onto a single substrate or layered stack of such substrates. By mounting a UV laser diode laser light source on the substrate, or substrates tack, so that it is located down-stream of the sample inlet port and at right angle the sample particle stream, the UV light source can illuminate individual particles in the stream to induce a fluorescence response in those particles having a fluorescent signature such as biological particles, some of said particles. An illuminated particle having a fluorescent signal above a threshold signal would trigger a sorter module that would separate that particle from the particle stream.

[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.

[Physical treatment methods for acne. Light, laser, photodynamic therapy and peeling].

PubMed

Borelli, C; Korting, H C

2010-02-01

The medical treatment of acne is generally sufficient to meet the expectations of acne patients. However, in a number of situations additional therapeutic approaches may be advisable. There are a wide variety of useful physical methods. They range from electromagnetic waves, usually light, to peeling and manual therapy. Phototherapy of acne includes not just visible light but also laser and flash lamp therapy. The present review provides an overview on the evidence. Visible light, in particular blue light, provides an effective option for treatment of inflammatory acne. Photodynamic therapy also is efficacious; however, it should not be used because of an unfavorable risk-benefit ratio. UV treatment of acne is obsolete. Newer studies on the use of a variety of laser systems and flash lamps have demonstrated in part rewarding results.

Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance.

PubMed

Chang, Nai-Yuan N; Jew, Jamison M; Simon, Jacob C; Chen, Kenneth H; Lee, Robert C; Fried, William A; Cho, Jinny; Darling, Cynthia L; Fried, Daniel

2017-12-01

Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO 2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO 2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO 2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

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.

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.

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.

Modulation of voltage-gated conductances of retinal horizontal cells by UV-excited TiO2 nanoparticles.

PubMed

Meshik, Xenia; Choi, Min; Baker, Adam; Malchow, R Paul; Covnot, Leigha; Doan, Samuel; Mukherjee, Souvik; Farid, Sidra; Dutta, Mitra; Stroscio, Michael A

2017-04-01

This study examines the ability of optically-excited titanium dioxide nanoparticles to influence voltage-gated ion channels in retinal horizontal cells. Voltage clamp recordings were obtained in the presence and absence of TiO 2 and ultraviolet laser excitation. Significant current changes were observed in response to UV light, particularly in the -40 mV to +40 mV region where voltage-gated Na + and K + channels have the highest conductance. Cells in proximity to UV-excited TiO 2 exhibited a left-shift in the current-voltage relation of around 10 mV in the activation of Na + currents. These trends were not observed in control experiments where cells were excited with UV light without being exposed to TiO 2 . Electrostatic force microscopy confirmed that electric fields can be induced in TiO 2 with UV light. Simulations using the Hodgkin-Huxley model yielded results which agreed with the experimental data and showed the I-V characteristics of individual ion channels in the presence of UV-excited TiO 2 . Copyright © 2016 Elsevier Inc. All rights reserved.

Physical properties of organic particulate UV-absorbers used in sunscreens. I. Determination of particle size with fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry.

PubMed

Herzog, Bernd; Katzenstein, Armin; Quass, Katja; Stehlin, Albert; Luther, Helmut

2004-03-01

In this study microparticles consisting of a benzotriazole derivative, which are used as absorbers for UV radiation in cosmetic sunscreens, were investigated. The particles were micronized in presence of a dispersing agent by means of a ball milling process. According to the energy input different particle sizes were produced in the range of 0.16 to 4 microm. The particle sizes obtained after different stages of the micronization process were measured using fiber-optic quasi-elastic light scattering (FOQELS), disc centrifugation, and laser diffractometry. All methods showed satisfactory agreement over the whole range of sizes. With the FOQELS technique the particle size distribution could be resolved to sizes well below 0.1 microm.

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.

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.

A picosecond beam-timing system for the OMEGA laser

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

Donaldson, W. R.; Katz, J.; Huff, R.

Here, a timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the UV light from each beam into a single photodetector.

A picosecond beam-timing system for the OMEGA laser

DOE PAGES

Donaldson, W. R.; Katz, J.; Huff, R.; ...

2016-05-27

Here, a timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the UV light from each beam into a single photodetector.

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

Liu, Rui; Su, Rongxin, E-mail: surx@tju.edu.cn; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072

Highlights: {yields} We compare the structures of insulin upon heating with or without laser irradiation. {yields} Laser irradiation inhibits insulin fibrillation and may be of insert for mechanistic disease studies. {yields} Online laser measurements should be carefully used in the study of amyloid proteins. -- Abstract: Protein aggregation and amyloid fibrillation can lead to several serious diseases and protein drugs ineffectiveness; thus, the detection and inhibition of these processes have been of great interest. In the present study, the inhibition of insulin amyloid fibrillation by laser irradiation was investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), far-UV circularmore » dichroism (far-UV CD), and thioflavin T (ThT) fluorescence. During heat-induced aggregation, the size distribution of two insulin solutions obtained by online and offline dynamic light scattering were different. The laser-on insulin in the presence of 0.1 M NaCl exhibited fewer fibrils than the laser-off insulin, whereas no insulin fibril under laser irradiation was observed in the absence of 0.1 M NaCl for 45 h incubation. Moreover, our CD results showed that the laser-irradiated insulin solution maintained mainly an {alpha}-helical conformation, but the laser-off insulin solution formed bulk fibrils followed by a significant increase in {beta}-sheet content for 106 h incubation. These findings provide an inhibition method for insulin amyloid fibrillation using the laser irradiation and demonstrate that the online long-time laser measurements should be carefully used in the study of amyloid proteins because they may change the original results.« less

Circular dichroism measurements at an x-ray free-electron laser with polarization control

NASA Astrophysics Data System (ADS)

Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

2016-08-01

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

GaN-based photon-recycling green light-emitting diodes with vertical-conduction structure.

PubMed

Sheu, Jinn-Kong; Chen, Fu-Bang; Yen, Wei-Yu; Wang, Yen-Chin; Liu, Chun-Nan; Yeh, Yu-Hsiang; Lee, Ming-Lun

2015-04-06

A p-i-n structure with near-UV(n-UV) emitting InGaN/GaN multiple quantum well(MQW) structure stacked on a green unipolar InGaN/GaN MQW was epitaxially grown at the same sapphire substrate. Photon recycling green light-emitting diodes(LEDs) with vertical-conduction feature on silicon substrates were then fabricated by wafer bonding and laser lift-off techniques. The green InGaN/GaN QWs were pumped with n-UV light to reemit low-energy photons when the LEDs were electrically driven with a forward current. Efficiency droop is potentially insignificant compared with the direct green LEDs due to the increase of effective volume of active layer in the optically pumped green LEDs, i.e., light emitting no longer limited in the QWs nearest to the p-type region to cause severe Auger recombination and carrier overflow losses.

Ultrafast Pulse Sequencing for Fast Projective Measurements of Atomic Hyperfine Qubits

NASA Astrophysics Data System (ADS)

Ip, Michael; Ransford, Anthony; Campbell, Wesley

2015-05-01

Projective readout of quantum information stored in atomic hyperfine structure typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also discuss methods of Doppler cooling with mode-locked lasers for trapped ions, where the creation of the necessary UV light is often difficult with CW lasers.

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.

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.

Dynamic evolution of the spectrum of long-period fiber Bragg gratings fabricated from hydrogen-loaded optical fiber by ultraviolet laser irradiation.

PubMed

Fujita, Keio; Masuda, Yuji; Nakayama, Keisuke; Ando, Maki; Sakamoto, Kenji; Mohri, Jun-pei; Yamauchi, Makoto; Kimura, Masanori; Mizutani, Yasuo; Kimura, Susumu; Yokouchi, Takashi; Suzaki, Yoshifumi; Ejima, Seiki

2005-11-20

Long-period fiber Bragg gratings fabricated by exposure of hydrogen-loaded fiber to UV laser light exhibit large-scale dynamic evolution for approximately two weeks at room temperature. During this time two distinct features show up in their spectrum: a large upswing in wavelength and a substantial deepening of the transmission minimum. The dynamic evolution of the transmission spectrum is explained quantitatively by use of Malo's theory of UV-induced quenching [Electron. Lett. 30, 442 (1994)] followed by refilling of hydrogen in the fiber core and the theory of hydrogen diffusion in the fiber material. The amount of hydrogen quenched by the UV irradiation is 6% of the loaded hydrogen.

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns

PubMed Central

Jeong, Hyun; Salas-Montiel, Rafael; Lerondel, Gilles; Jeong, Mun Seok

2017-01-01

In this study, we investigated the improvement in the light output power of indium gallium nitride (InGaN)-based ultraviolet (UV), blue, and green light-emitting diodes (LEDs) by fabricating shallow periodic hole patterns (PHPs) on the LED surface through laser interference lithography and inductively coupled plasma etching. Noticeably, different enhancements were observed in the light output powers of the UV, blue, and green LEDs with negligible changes in the electrical properties in the light output power versus current and current versus voltage curves. In addition, confocal scanning electroluminescence microscopy is employed to verify the correlation between the enhancement in the light output power of the LEDs with PHPs and carrier localization of InGaN/GaN multiple quantum wells. Light propagation through the PHPs on the UV, blue, and green LEDs is simulated using a three-dimensional finite-difference time-domain method to confirm the experimental results. Finally, we suggest optimal conditions of PHPs for improving the light output power of InGaN LEDs based on the experimental and theoretical results. PMID:28374856

Indium gallium nitride-based ultraviolet, blue, and green light-emitting diodes functionalized with shallow periodic hole patterns.

PubMed

Jeong, Hyun; Salas-Montiel, Rafael; Lerondel, Gilles; Jeong, Mun Seok

2017-04-04

In this study, we investigated the improvement in the light output power of indium gallium nitride (InGaN)-based ultraviolet (UV), blue, and green light-emitting diodes (LEDs) by fabricating shallow periodic hole patterns (PHPs) on the LED surface through laser interference lithography and inductively coupled plasma etching. Noticeably, different enhancements were observed in the light output powers of the UV, blue, and green LEDs with negligible changes in the electrical properties in the light output power versus current and current versus voltage curves. In addition, confocal scanning electroluminescence microscopy is employed to verify the correlation between the enhancement in the light output power of the LEDs with PHPs and carrier localization of InGaN/GaN multiple quantum wells. Light propagation through the PHPs on the UV, blue, and green LEDs is simulated using a three-dimensional finite-difference time-domain method to confirm the experimental results. Finally, we suggest optimal conditions of PHPs for improving the light output power of InGaN LEDs based on the experimental and theoretical results.

Using Stars to Align a Steered Laser System for Cosmic Ray Simulation

NASA Astrophysics Data System (ADS)

Krantz, Harry; Wiencke, Lawrence

2016-03-01

Ultra high energy cosmic rays (UHECRs) are the highest energy cosmic particles with kinetic energy above 1018eV . UHECRs are detected from the air shower of secondary particles and UV florescence that results from interaction with the atmosphere. A high power UV laser beam can be used to simulate the optical signature of a UHCER air shower. The Global Light System (GLS) is a planned network of ground-based light sources including lasers to support the planned space-based Extreme Universe Space Observatory (EUSO). A portable prototype GLS laser station has been constructed at the Colorado School of Mines. Currently the laser system uses reference targets on the ground but stars can be used to better align the beam by providing a complete hemisphere of targets. In this work, a CCD camera is used to capture images of known stars through the steering head optics. The images are analyzed to find the steering head coordinates of the target star. The true coordinates of the star are calculated from the location and time of observation. A universal adjustment for the steering head is determined from the differences between the two pairs of coordinates across multiple stars. This laser system prototype will also be used for preflight tests of the ESUO Super Pressure Balloon mission.

Lifetime testing UV LEDs for use in the LISA charge management system

NASA Astrophysics Data System (ADS)

Hollington, D.; Baird, J. T.; Sumner, T. J.; Wass, P. J.

2017-10-01

As a future charge management light source, UV light-emitting diodes (UV LEDs) offer far superior performance in a range of metrics compared to the mercury lamps used in the past. As part of a qualification program a number of short wavelength UV LEDs have been subjected to a series of lifetime tests for potential use on the laser interferometer space antenna (LISA) mission. These tests were performed at realistic output levels for both fast and continuous discharging in either a DC or pulsed mode of operation and included a DC fast discharge test spanning 50 days, a temperature dependent pulsed fast discharge test spanning 21 days and a pulsed continuous discharge test spanning 507 days. Two types of UV LED have demonstrated lifetimes equivalent to over 25 years of realistic mission usage with one type providing a baseline for LISA and the other offering a backup solution.

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.

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.

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.

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.

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.

Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light.

PubMed

Hadjichristov, Georgi B; Marinov, Yordan G; Petrov, Alexander G

2011-06-01

The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25 μm and droplet size up to 50 μm exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (λ=633 nm), an electrically commanded phase shift as large as π/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light.

Construction, alignment, and implementation of an acousto-optical deflector-based system for patterned uncaging with ultraviolet light.

PubMed

Civillico, Eugene F; Shoham, Shy; O'Connor, Daniel H; Sarkisov, Dmitry V; Wang, Samuel S-H

2012-08-01

The method of patterned photoactivation is a natural fit for the study of neuronal dendritic integration. Photoactivatable molecules that influence a wide range of extracellular and intracellular neurophysiological functions are available. The choice of photosensitive molecules depends on the research question and will influence the design of the experimental apparatus. An acousto-optical deflector (AOD)-based system can be used for rapid ultraviolet (UV) photolysis in arbitrary spatial and temporal patterns. Photolysis-activated "caged" diffusible molecules or newer light-sensitive membrane proteins can be used in this system. This protocol describes the addition of a UV beam for uncaging to a homebuilt two-photon microscope. The goal is to get UV light from the light source (laser) to the approximate center of the objective's back aperture, passing through a pair of perpendicularly oriented AODs along the way. The protocol also describes the fine alignment of the UV beam and the implementation of AOD-based beam steering. Performing the final alignment with the beam passing through the AODs will ensure that the system is optimized for the idiosyncrasies of the crystals.

A switchable digital microfluidic droplet dye-laser.

PubMed

Kuehne, Alexander J C; Gather, Malte C; Eydelnant, Irwin A; Yun, Seok-Hyun; Weitz, David A; Wheeler, Aaron R

2011-11-07

Digital microfluidic devices allow the manipulation of droplets between two parallel electrodes. These electrodes can act as mirrors generating a micro-cavity, which can be exploited for a droplet dye-laser. Three representative laser-dyes with emission wavelengths spanning the whole visible spectrum are chosen to show the applicability of this concept. Sub-microlitre droplets of laser-dye solution are moved in and out of a lasing site on-chip to down-convert the UV-excitation light into blue, green and red laser-pulses. This journal is © The Royal Society of Chemistry 2011

Multifunctional Polymer Nanofibers: UV Emission, Optical Gain, Anisotropic Wetting, and High Hydrophobicity for Next Flexible Excitation Sources

PubMed Central

2015-01-01

The use of UV light sources is highly relevant in many fields of science, being directly related to all those detection and diagnosis procedures that are based on fluorescence spectroscopy. Depending on the specific application, UV light-emitting materials are desired to feature a number of opto-mechanical properties, including brightness, optical gain for being used in laser devices, flexibility to conform with different lab-on-chip architectures, and tailorable wettability to control and minimize their interaction with ambient humidity and fluids. In this work, we introduce multifunctional, UV-emitting electrospun fibers with both optical gain and greatly enhanced anisotropic hydrophobicity compared to films. Fibers are described by the onset of a composite wetting state, and their arrangement in uniaxial arrays further favors liquid directional control. The low gain threshold, optical losses, plastic nature, flexibility, and stability of these UV-emitting fibers make them interesting for building light-emitting devices and microlasers. Furthermore, the anisotropic hydrophobicity found is strongly synergic with optical properties, reducing interfacial interactions with liquids and enabling smart functional surfaces for droplet microfluidic and wearable applications. PMID:26401889

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.

Detection of Biochemical Pathogens, Laser Stand-off Spectroscopy, Quantum Coherence, and Many Body Quantum Optics

DTIC Science & Technology

2012-02-24

AND SUBTITLE Detection of Biochemical Pathogens, Laser Stand-off Spectroscopy, Quantum Coherence, and Many Body Quantum Optics 6. AUTHORS Marian O...Maximum 200 words) Results of our earlier research in the realm of quantum optics were extended in order to solve the challenging technical problems of...efficient methods of generating UV light via quantum coherence. 14. SUBJECT TERMS Quantum coherence, quantum optics, lasers 15. NUMBER OF PAGES 15

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.

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

Hartmann, G.; Shevchuk, I.; Walter, P.

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. Anmore » also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.« less

Side- and end-illumination of polymer optical fibers in the UV region

NASA Astrophysics Data System (ADS)

Eckhardt, Hanns-S.; Jungling, B.; Klein, Karl-Friedrich; Poisel, Hans

2003-07-01

Since more than 2 decades, the polymer optical fiber (POF) based on PMMA is well known. A lot of applications were studied and initiated: in addition to data transmission, the automotive, lighting and sensor applications are of main interest. Due to the spectral attenuation and applications, light-sources like broadband metal-halide lamps and halogen lamps, or LEDs and laser-diodes are mainly used. Due to improvement in manufacturing of the standard step-index POF, the variations of the spectral attenuation in the blue region have been reduced. Therefore, the losses are acceptable for short-length applications in the UV-A region. Using different light-sources like high-power Xenon-lamp, deuterium-lamp or UV-LEDs, the UV-damage is an important factor. In addition to the basic attenuation, the UV-induced losses will be determined by experiment, in the interesting UV-A region. The higher flexibilty of the thick-core POF is superior in comparison to silica or glass fibers with the same outer diameter. Therefore, the bending losses in the UV-region are important, too. For special applications in the medical field, side-illuminating fibers are highly accepted. The axial and spectral dependence on the lateral radiation pattern will be described, using a very thick fiber.

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.

Study of resonance light scattering for remote optical probing

NASA Technical Reports Server (NTRS)

Penney, C. M.; Morey, W. W.; St. Peters, R. L.; Silverstein, S. D.; Lapp, M.; White, D. R.

1973-01-01

Enhanced scattering and fluorescence processes in the visible and UV were investigated which will enable improved remote measurements of gas properties. The theoretical relationship between scattering and fluorescence from an isolated molecule in the approach to resonance is examined through analysis of the time dependence of re-emitted light following excitation of pulsed incident light. Quantitative estimates are developed for the relative and absolute intensities of fluorescence and resonance scattering. New results are obtained for depolarization of scattering excited by light at wavelengths within a dissociative continuum. The experimental work was performed in two separate facilities. One of these utilizes argon and krypton lasers, single moded by a tilted etalon, and a 3/4 meter double monochromator. This facility was used to determine properties of the re-emission from NO2, I2 and O3 excited by visible light. The second facility involves a narrow-line dye laser, and a 3/4 meter single monochromator. The dye laser produces pulsed light with 5 nsec pulse duration and 0.005 nm spectral width.

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.

First observations of speed of light tracks by a fluorescence detector looking down on the atmosphere

NASA Astrophysics Data System (ADS)

Abdellaoui, G.; Abe, S.; Adams, J. H., Jr.; Ahriche, A.; Allard, D.; Allen, L.; Alonso, G.; Anchordoqui, L.; Anzalone, A.; Arai, Y.; Asano, K.; Attallah, R.; Attoui, H.; Ave Pernas, M.; Bacholle, S.; Bakiri, M.; Baragatti, P.; Barrillon, P.; Bartocci, S.; Bayer, J.; Beldjilali, B.; Belenguer, T.; Belkhalfa, N.; Bellotti, R.; Belov, A.; Belov, K.; Benmessai, K.; Bertaina, M.; Biermann, P. L.; Biktemerova, S.; Bisconti, F.; Blanc, N.; Błȩcki, J.; Blin-Bondil, S.; Bobik, P.; Bogomilov, M.; Bozzo, E.; Bruno, A.; Caballero, K. S.; Cafagna, F.; Campana, D.; Capdevielle, J.-N.; Capel, F.; Caramete, A.; Caramete, L.; Carlson, P.; Caruso, R.; Casolino, M.; Cassardo, C.; Castellina, A.; Catalano, C.; Catalano, O.; Cellino, A.; Chikawa, M.; Chiritoi, G.; Christl, M. J.; Connaughton, V.; Conti, L.; Cordero, G.; Cotto, G.; Crawford, H. J.; Cremonini, R.; Csorna, S.; Cummings, A.; Dagoret-Campagne, S.; De Donato, C.; de la Taille, C.; De Santis, C.; del Peral, L.; Di Martino, M.; Diaz Damian, A.; Djemil, T.; Dutan, I.; Ebersoldt, A.; Ebisuzaki, T.; Engel, R.; Eser, J.; Fenu, F.; Fernández-González, S.; Fernández-Soriano, J.; Ferrarese, S.; Flamini, M.; Fornaro, C.; Fouka, M.; Franceschi, A.; Franchini, S.; Fuglesang, C.; Fujii, T.; Fujimoto, J.; Fukushima, M.; Galeotti, P.; García-Ortega, E.; Garipov, G.; Gascón, E.; Genci, J.; Giraudo, G.; González Alvarado, C.; Gorodetzky, P.; Greg, R.; Guarino, F.; Guzmán, A.; Hachisu, Y.; Haiduc, M.; Harlov, B.; Haungs, A.; Hernández Carretero, J.; Hidber Cruz, W.; Ikeda, D.; Inoue, N.; Inoue, S.; Isgrò, F.; Itow, Y.; Jammer, T.; Jeong, S.; Joven, E.; Judd, E. G.; Jung, A.; Jochum, J.; Kajino, F.; Kajino, T.; Kalli, S.; Kaneko, I.; Karadzhov, Y.; Karczmarczyk, J.; Katahira, K.; Kawai, K.; Kawasaki, Y.; Kedadra, A.; Khales, H.; Khrenov, B. A.; Kim, Jeong-Sook; Kim, Soon-Wook; Kleifges, M.; Klimov, P. A.; Kolev, D.; Krantz, H.; Kreykenbohm, I.; Kudela, K.; Kurihara, Y.; Kusenko, A.; Kuznetsov, E.; La Barbera, A.; Lachaud, C.; Lahmar, H.; Lakhdari, F.; Larson, R.; Larsson, O.; Lee, J.; Licandro, J.; López Campano, L.; Maccarone, M. C.; Mackovjak, S.; Mahdi, M.; Maravilla, D.; Marcelli, L.; Marcos, J. L.; Marini, A.; Marszał, W.; Martens, K.; Martín, Y.; Martinez, O.; Martucci, M.; Masciantonio, G.; Mase, K.; Mastafa, M.; Matev, R.; Matthews, J. N.; Mebarki, N.; Medina-Tanco, G.; Mendoza, M. A.; Menshikov, A.; Merino, A.; Meseguer, J.; Meyer, S. S.; Mimouni, J.; Miyamoto, H.; Mizumoto, Y.; Monaco, A.; Morales de los Ríos, J. A.; Moretto, C.; Nagataki, S.; Naitamor, S.; Napolitano, T.; Naslund, W.; Nava, R.; Neronov, A.; Nomoto, K.; Nonaka, T.; Ogawa, T.; Ogio, S.; Ohmori, H.; Olinto, A. V.; Orleański, P.; Osteria, G.; Pagliaro, A.; Painter, W.; Panasyuk, M. I.; Panico, B.; Pasqualino, G.; Parizot, E.; Park, I. H.; Pastircak, B.; Patzak, T.; Paul, T.; Pérez-Grande, I.; Perfetto, F.; Peter, T.; Picozza, P.; Pindado, S.; Piotrowski, L. W.; Piraino, S.; Placidi, L.; Plebaniak, Z.; Pliego, S.; Pollini, A.; Polonski, Z.; Popescu, E. M.; Prat, P.; Prévôt, G.; Prieto, H.; Puehlhofer, G.; Putis, M.; Rabanal, J.; Radu, A. A.; Reyes, M.; Rezazadeh, M.; Ricci, M.; Rodríguez Frías, M. D.; Rodencal, M.; Ronga, F.; Roudil, G.; Rusinov, I.; Rybczyński, M.; Sabau, M. D.; Sáez Cano, G.; Sagawa, H.; Sahnoune, Z.; Saito, A.; Sakaki, N.; Salazar, H.; Sanchez Balanzar, J. C.; Sánchez, J. L.; Santangelo, A.; Sanz-Andrés, A.; Sanz Palomino, M.; Saprykin, O.; Sarazin, F.; Sato, M.; Schanz, T.; Schieler, H.; Scotti, V.; Selmane, S.; Semikoz, D.; Serra, M.; Sharakin, S.; Shimizu, H. M.; Shinozaki, K.; Shirahama, T.; Spataro, B.; Stan, I.; Sugiyama, T.; Supanitsky, D.; Suzuki, M.; Szabelska, B.; Szabelski, J.; Tajima, N.; Tajima, T.; Takahashi, Y.; Takami, H.; Takeda, M.; Takizawa, Y.; Talai, M. C.; Tenzer, C.; Thomas, S. B.; Tibolla, O.; Tkachev, L.; Tokuno, H.; Tomida, T.; Tone, N.; Toscano, S.; Traïche, M.; Tsenov, R.; Tsunesada, Y.; Tsuno, K.; Tubbs, J.; Turriziani, S.; Uchihori, Y.; Vaduvescu, O.; Valdés-Galicia, J. F.; Vallania, P.; Vankova, G.; Vigorito, C.; Villaseñor, L.; Vlcek, B.; von Ballmoos, P.; Vrabel, M.; Wada, S.; Watanabe, J.; Watts, J., Jr.; Weber, M.; Weigand Muñoz, R.; Weindl, A.; Wiencke, L.; Wille, M.; Wilms, J.; Włodarczyk, Z.; Yamamoto, T.; Yang, J.; Yano, H.; Yashin, I. V.; Yonetoku, D.; Yoshida, S.; Young, R.; Zgura, I. S.; Zotov, M. Yu.; Zuccaro Marchi, A.

2018-05-01

EUSO-Balloon is a pathfinder mission for the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). It was launched on the moonless night of the 25th of August 2014 from Timmins, Canada. The flight ended successfully after maintaining the target altitude of 38 km for five hours. One part of the mission was a 2.5 hour underflight using a helicopter equipped with three UV light sources (LED, xenon flasher and laser) to perform an inflight calibration and examine the detectors capability to measure tracks moving at the speed of light. We describe the helicopter laser system and details of the underflight as well as how the laser tracks were recorded and found in the data. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. Finally, we present a first reconstruction of the direction of the laser tracks relative to the detector.

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

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.

AlGaInN laser diode technology for free-space and plastic optical fibre telecom applications

NASA Astrophysics Data System (ADS)

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

2016-03-01

Gallium Nitride laser diodes fabricated from the AlGaInN material system is an emerging technology for laser sources from the UV to visible and is a potential key enabler for new system applications such as free-space (underwater & air bourne links) and plastic optical fibre telecommunications. We measure visible light (free-space and underwater) communications at high frequency (up to 2.5 Gbit/s) and in plastic optical fibre (POF) using a directly modulated GaN laser diode.

Dynamics of defects in Ce³⁺ doped silica affecting its performance as protective filter in ultraviolet high-power lasers.

PubMed

Demos, Stavros G; Ehrmann, Paul R; Qiu, S Roger; Schaffers, Kathleen I; Suratwala, Tayyab I

2014-11-17

We investigate defects forming in Ce³⁺-doped fused silica samples following exposure to nanosecond ultraviolet laser pulses and their relaxation as a function of time and exposure to low intensity light at different wavelengths. A subset of these defects are responsible for inducing absorption in the visible and near infrared spectral range, which is of critical importance for the use of this material as ultraviolet light absorbing filter in high power laser systems. The dependence of the induced absorption as a function of laser fluence and methods to most efficiently mitigate this effect are presented. Experiments simulating the operation of the material as a UV protection filter for high power laser systems were performed in order to determine limitations and practical operational conditions.

Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

NASA Technical Reports Server (NTRS)

Harris, S. E.

1974-01-01

Projects aimed at the generation of tunable visible, infrared, and ultraviolet light, and on the control of this light by means of novel mode-locking and modulation techniques are discussed. During this period the following projects have been active: (1) studies of transient mode-locking of the Nd:YAG laser and the application of short optical pulses; (2) experimental investigations of the Na-Xe excimer laser system; (3) further development of techniques for vacuum ultraviolet holography; and (4) theoretical and initial experimental studies of a new device which should prove very useful for both infrared up-conversion and generation of tunable UV radiation - a two-photon resonantly pumped frequency converter.

Activities report in quantum optics

NASA Astrophysics Data System (ADS)

1985-03-01

Soft X-ray radiation from laser plasmas, intense Planck radiation, X-ray spectroscopy with transmission gratings, simulation of laser-produced shock waves, self-similar expansion in vacuum, radiation hydrodynamics, electronic structure of highly compressed matter, and heavy-ion beams for inertial confinement were investigated, and a high power iodine laser was developed. Laser-spectroscopy experiments, as well as a gravitational wave experiments were conducted. The fundamentals of light-matter interaction and nonlinear dynamics were studied. Many-photon ionization of molecules; spectroscopy of shock pairs; interaction of excited molecules with surfaces; IR laser applications; organic photochemistry with UV lasers; theoretical chemistry; and a ClF laser were investigated. Thin layers, and a high-pressure CO2 laser were studied.

Optical and laser spectroscopic diagnostics for energy applications

NASA Astrophysics Data System (ADS)

Tripathi, Markandey Mani

The continuing need for greater energy security and energy independence has motivated researchers to develop new energy technologies for better energy resource management and efficient energy usage. The focus of this dissertation is the development of optical (spectroscopic) sensing methodologies for various fuels, and energy applications. A fiber-optic NIR sensing methodology was developed for predicting water content in bio-oil. The feasibility of using the designed near infrared (NIR) system for estimating water content in bio-oil was tested by applying multivariate analysis to NIR spectral data. The calibration results demonstrated that the spectral information can successfully predict the bio-oil water content (from 16% to 36%). The effect of ultraviolet (UV) light on the chemical stability of bio-oil was studied by employing laser-induced fluorescence (LIF) spectroscopy. To simulate the UV light exposure, a laser in the UV region (325 nm) was employed for bio-oil excitation. The LIF, as a signature of chemical change, was recorded from bio-oil. From this study, it was concluded that phenols present in the bio-oil show chemical instability, when exposed to UV light. A laser-induced breakdown spectroscopy (LIBS)-based optical sensor was designed, developed, and tested for detection of four important trace impurities in rocket fuel (hydrogen). The sensor can simultaneously measure the concentrations of nitrogen, argon, oxygen, and helium in hydrogen from storage tanks and supply lines. The sensor had estimated lower detection limits of 80 ppm for nitrogen, 97 ppm for argon, 10 ppm for oxygen, and 25 ppm for helium. A chemiluminescence-based spectroscopic diagnostics were performed to measure equivalence ratios in methane-air premixed flames. A partial least-squares regression (PLS-R)-based multivariate sensing methodology was investigated. It was found that the equivalence ratios predicted with the PLS-R-based multivariate calibration model matched with the experimentally measured equivalence ratios within 7 %. A comparative study was performed for equivalence ratios measurement in atmospheric premixed methane-air flames with ungated LIBS and chemiluminescence spectroscopy. It was reported that LIBS-based calibration, which carries spectroscopic information from a "point-like-volume," provides better predictions of equivalence ratios compared to chemiluminescence-based calibration, which is essentially a "line-of-sight" measurement.

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.

Matrix Optical Absorption in UV-MALDI MS

NASA Astrophysics Data System (ADS)

Robinson, Kenneth N.; Steven, Rory T.; Bunch, Josephine

2018-03-01

In ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI MS) matrix compound optical absorption governs the uptake of laser energy, which in turn has a strong influence on experimental results. Despite this, quantitative absorption measurements are lacking for most matrix compounds. Furthermore, despite the use of UV-MALDI MS to detect a vast range of compounds, investigations into the effects of laser energy have been primarily restricted to single classes of analytes. We report the absolute solid state absorption spectra of the matrix compounds α-cyano-4-hydroxycinnamic acid (CHCA), para-nitroaniline (PNA), 2-mercaptobenzothiazole (MBT), 2,5-dihydroxybenzoic acid (2,5-DHB), and 2,4,6-trihydroxyacetophenone (THAP). The desorption/ionization characteristics of these matrix compounds with respect to laser fluence was investigated using mixed systems of matrix with either angiotensin II, PC(34:1) lipid standard, or haloperidol, acting as representatives for typical classes of analyte encountered in UV-MALDI MS. The first absolute solid phase spectra for PNA, MBT, and THAP are reported; additionally, inconsistencies between previously published spectra for CHCA are resolved. In light of these findings, suggestions are made for experimental optimization with regards to matrix and laser wavelength selection. The relationship between matrix optical cross-section and wavelength-dependant threshold fluence, fluence of maximum ion yield, and R, a new descriptor for the change in ion intensity with fluence, are described. A matrix cross-section of 1.3 × 10-17 cm-2 was identified as a potential minimum for desorption/ionization of analytes.

Matrix Optical Absorption in UV-MALDI MS.

PubMed

Robinson, Kenneth N; Steven, Rory T; Bunch, Josephine

2018-03-01

In ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI MS) matrix compound optical absorption governs the uptake of laser energy, which in turn has a strong influence on experimental results. Despite this, quantitative absorption measurements are lacking for most matrix compounds. Furthermore, despite the use of UV-MALDI MS to detect a vast range of compounds, investigations into the effects of laser energy have been primarily restricted to single classes of analytes. We report the absolute solid state absorption spectra of the matrix compounds α-cyano-4-hydroxycinnamic acid (CHCA), para-nitroaniline (PNA), 2-mercaptobenzothiazole (MBT), 2,5-dihydroxybenzoic acid (2,5-DHB), and 2,4,6-trihydroxyacetophenone (THAP). The desorption/ionization characteristics of these matrix compounds with respect to laser fluence was investigated using mixed systems of matrix with either angiotensin II, PC(34:1) lipid standard, or haloperidol, acting as representatives for typical classes of analyte encountered in UV-MALDI MS. The first absolute solid phase spectra for PNA, MBT, and THAP are reported; additionally, inconsistencies between previously published spectra for CHCA are resolved. In light of these findings, suggestions are made for experimental optimization with regards to matrix and laser wavelength selection. The relationship between matrix optical cross-section and wavelength-dependant threshold fluence, fluence of maximum ion yield, and R, a new descriptor for the change in ion intensity with fluence, are described. A matrix cross-section of 1.3 × 10 -17 cm -2 was identified as a potential minimum for desorption/ionization of analytes. Graphical Abstract ᅟ.

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).

New Dimensions for Manufacturing: A UK Strategy for Nanotechnology

DTIC Science & Technology

2002-06-01

market sun-block creams based on nanoparticles that absorb UV light lasers, modulators and amplifiers for telecommunications computer...the spectrum in sunlight. Which is why these particles could appeal to people who make sunscreen or cosmetics. Nanoparticles can absorb much more UV ...company has its sights on one of today’s hot subjects, counterfeiting , which costs the UK more than £6 billion a year. NanoCo is working with a major

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.

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.

Complete fluorescent fingerprints of extremophilic and photosynthetic microbes

NASA Astrophysics Data System (ADS)

Dartnell, Lewis R.; Storrie-Lombardi, Michael C.; Ward, John M.

2010-10-01

The work reported here represents a study into the total fluorescence exhibited by a broad selection of model, extremophilic and photosynthetic bacterial strains, over a great range of excitation and emission wavelengths from ultraviolet (UV) through visible to near infrared. The aim is to identify distinctive fluorescent features that may serve as detectable biosignatures of remnant microbial life on the Martian surface. A lab-bench fluorescence spectrometer was used to generate an excitation-emission matrix (EEM) for the unpigmented Escherichia coli, radiation-resistant Deinococcus radiodurans, Antarctic Dry Valley isolates Brevundimonas sp. MV.7 and Rhodococcus sp. MV.10, and the cyanobacterium Synechocystis sp. PCC 6803. Detailed EEMs, representing the fluorescence signature of each organism, are presented, and the most significant features suitable for biosignature surveys are identified, including small-molecule cellular metabolites, light-harvesting photosynthetic pigments and extracellular UV-screening compounds. E. coli exhibits the most intense emission from tryptophan, presumably due to the absence of UV-screening pigments that would shield the organism from short-wavelength light-exciting intracellular fluorescence. The efficacy of commonly available laser diodes for exciting cellular fluorescence is treated, along with the most appropriate filter wavelengths for imaging systems. The best combination of available laser diodes and PanCam filters aboard the ExoMars probe is proposed. The possibility of detecting fluorescence excited by solar UV radiation in freshly exposed surface samples by imaging when both sunlit and shadowed, perhaps by the body of the rover itself, is discussed. We also study how these biological fluorophore molecules may be degraded, and thus the potential biosignatures erased, by the high flux of far-ultraviolet light on Mars.

Use of ZnO:Tb down-conversion phosphor for Ag nanoparticle plasmon absorption using a He-Cd ultraviolet laser.

PubMed

Abbass, A E; Swart, H C; Kroon, R E

2016-09-01

Although noble metal nanoparticles (NPs) have attracted some attention for potentially enhancing the luminescence of rare earth ions for phosphor lighting applications, the absorption of energy by NPs can also be beneficial in biological and polymer applications where local heating is desired, e.g. photothermal applications. Strong interaction between incident laser light and NPs occurs only when the laser wavelength matches the NP plasmon resonance. Although lasers with different wavelengths are available and the NP plasmon resonance can be tuned by changing its size and shape or the dielectric medium (host material), in this work, we consider exciting the plasmon resonance of Ag NPs indirectly with a He-Cd UV laser using the down-conversion properties of Tb(3+) ions in ZnO. The formation of Ag NPs was confirmed by X-ray diffraction, transmission electron microscopy and UV-vis diffuse reflectance measurements. Radiative energy transfer from the Tb(3+) ions to the Ag NPs resulted in quenching of the green luminescence of ZnO:Tb and was studied by means of spectral overlap and lifetime measurements. The use of a down-converting phosphor, possibly with other rare earth ions, to indirectly couple a laser to the plasmon resonance wavelength of metal NPs is therefore successfully demonstrated and adds to the flexibility of such systems. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

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.

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.

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.

Electron beam induced light emission

NASA Astrophysics Data System (ADS)

Ulrich, A.; Heindl, T.; Krücken, R.; Morozov, A.; Skrobol, C.; Wieser, J.

2009-08-01

Electron beams with a particle energy of typically 12keV are used for collisional excitation of dense gases. The electrons are sent through ceramic membranes of only 300nm thickness into gas targets. Excimer light emission from the pure rare gases and from gas mixtures are studied for the development of brilliant VUV and UV light sources. The application of the technology for gas kinetic studies is described and its potential for building very small electron beam pumped lasers is discussed.

The JLab high power ERL light source

NASA Astrophysics Data System (ADS)

Neil, G. R.; Behre, C.; Benson, S. V.; Bevins, M.; Biallas, G.; Boyce, J.; Coleman, J.; Dillon-Townes, L. A.; Douglas, D.; Dylla, H. F.; Evans, R.; Grippo, A.; Gruber, D.; Gubeli, J.; Hardy, D.; Hernandez-Garcia, C.; Jordan, K.; Kelley, M. J.; Merminga, L.; Mammosser, J.; Moore, W.; Nishimori, N.; Pozdeyev, E.; Preble, J.; Rimmer, R.; Shinn, M.; Siggins, T.; Tennant, C.; Walker, R.; Williams, G. P.; Zhang, S.

2006-02-01

A new THz/IR/UV photon source at Jefferson Lab is the first of a new generation of light sources based on an Energy-Recovered, (superconducting) Linac (ERL). The machine has a 160 MeV electron beam and an average current of 10 mA in 75 MHz repetition rate hundred femtosecond bunches. These electron bunches pass through a magnetic chicane and therefore emit synchrotron radiation. For wavelengths longer than the electron bunch the electrons radiate coherently a broadband THz ˜ half cycle pulse whose average brightness is >5 orders of magnitude higher than synchrotron IR sources. Previous measurements showed 20 W of average power extracted [Carr, et al., Nature 420 (2002) 153]. The new facility offers simultaneous synchrotron light from the visible through the FIR along with broadband THz production of 100 fs pulses with >200 W of average power. The FELs also provide record-breaking laser power [Neil, et al., Phys. Rev. Lett. 84 (2000) 662]: up to 10 kW of average power in the IR from 1 to 14 μm in 400 fs pulses at up to 74.85 MHz repetition rates and soon will produce similar pulses of 300-1000 nm light at up to 3 kW of average power from the UV FEL. These ultrashort pulses are ideal for maximizing the interaction with material surfaces. The optical beams are Gaussian with nearly perfect beam quality. See www.jlab.org/FEL for details of the operating characteristics; a wide variety of pulse train configurations are feasible from 10 ms long at high repetition rates to continuous operation. The THz and IR system has been commissioned. The UV system is to follow in 2005. The light is transported to user laboratories for basic and applied research. Additional lasers synchronized to the FEL are also available. Past activities have included production of carbon nanotubes, studies of vibrational relaxation of interstitial hydrogen in silicon, pulsed laser deposition and ablation, nitriding of metals, and energy flow in proteins. This paper will present the status of the system and discuss some of the discoveries we have made concerning the physics performance, design optimization, and operational limitations of such a first generation high power ERL light source.

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.

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).

The analysis of colored acrylic, cotton, and wool textile fibers using micro-Raman spectroscopy. Part 2: comparison with the traditional methods of fiber examination.

PubMed

Buzzini, Patrick; Massonnet, Genevieve

2015-05-01

In the second part of this survey, the ability of micro-Raman spectroscopy to discriminate 180 fiber samples of blue, black, and red cottons, wools, and acrylics was compared to that gathered with the traditional methods for the examination of textile fibers in a forensic context (including light microscopy methods, UV-vis microspectrophotometry and thin-layer chromatography). This study shows that the Raman technique plays a complementary and useful role to obtain further discriminations after the application of light microscopy methods and UV-vis microspectrophotometry and assure the nondestructive nature of the analytical sequence. These additional discriminations were observed despite the lower discriminating powers of Raman data considered individually, compared to those of light microscopy and UV-vis MSP. This study also confirms that an instrument equipped with several laser lines is necessary for an efficient use as applied to the examination of textile fibers in a forensic setting. © 2015 American Academy of Forensic Sciences.

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.

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.

Laser induced disruption of bacterial spores on a microchip.

PubMed

Hofmann, Oliver; Murray, Kirk; Wilkinson, Alan-Shaun; Cox, Timothy; Manz, Andreas

2005-04-01

We report on the development of a laser based spore disruption method. Bacillus globigii spores were mixed with a laser light absorbing matrix and co-crystallized into 200-microm-wide and 20-microm-deep nanovials formed in a polydimethylsiloxane (PDMS) target plate. Surface tension effects were exploited to effect up to 125-fold spore enrichment. When the target zones were illuminated at atmospheric pressure with pulsed UV-laser light at fluences below 20 mJ cm(-2) a change in spore morphology was observed within seconds. Post illumination PCR analysis suggests the release of endogenous DNA indicative of spore disruption. For laser fluences above 20 mJ cm(-2), desorption of spores and fragments was also observed even without a matrix being employed. Desorbed material was collected in a PDMS flowcell attached to the target plate during laser illumination. This opens up a route towards the direct extraction of released DNA in an integrated spore disruption-PCR amplification microchip device.

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

Electrically Injected UV-Visible Nanowire Lasers

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

Wang, George T.; Li, Changyi; Li, Qiming

2015-09-01

There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasersmore » emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.« 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.

Nonlinear Optical Interactions in Plasmas at JILA

NASA Astrophysics Data System (ADS)

Dollar, F.; Hickstein, D. D.; Popmintchev, D.; Becker, A.; Ellis, J.; Hernandez-Garcia, C.; Jaron-Becker, A.; Popmintchev, T.; Xiong, W.; Murnane, M. M.; Kapteyn, H. C.; Dukovic, G.; Jimenez, J.; Palm, B.; Schnitzenbaumer, K.; Perez-Hernandez, J.; Gaeta, A.; Gao, X.; Shim, B.; Plaja, L.; Levis, R.; Tarazkar, M.; Foord, M. E.; Gaffney, J. A.; Libby, S. B.

2014-10-01

We present data from two recent experiments. First, we demonstrate direct observations of localized light absorption in a single nanoparticle irradiated by a strong femtosecond laser field. By imaging the photoion momentum distribution resulting from plasma formation in a laser-irradiated nanostructure, we map the spatial location of the highly localized plasma and thereby image the nanoscale light absorption. Secondly, we show the high linear and nonlinear UV refractive indices of both neutral atoms and ions compensate for plasma dispersion, even in multiply-ionized gases. The experimental work was primarily funded by DOE Grant Number: DE-SC0008803, the DARPA PULSE program, and ARO W911NF-12-1-0436.

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.

HUBBLE DISCOVERS POWERFUL LASER BEAMED FROM CHAOTIC STAR

NASA Technical Reports Server (NTRS)

2002-01-01

This is an artist's concept of a gas cloud (left) that acts as a natural ultraviolet laser, near the huge, unstable star Eta Carinae (right) -- one of most massive and energetic stars in our Milky Way Galaxy. The super-laser was identified by a team led by Kris Davidson of the University of Minnesota, and including nine other collaborators in the U.S. and Sweden during spectroscpic observations made with the Goddard High Resolution spectrograph aboard NASA's Hubble Space Telescope. Since it's unlikely that a single beam from the cloud would happen to be precisely aimed in earth's driection, the astronomers conclude that numerous beams must be radiating from the cloud in all directions - beams from a dance hall mirror-ball. The interstellar laser may result from Eta Carinae's violently chaotic eruptions, illustrated here as a reddish (due to light scattering by dust) outflow from the bright star. A laser, (an acronym for Light Amplification by Stimulated Emission of Radiation) creates an intense coherent beam of light when atoms or molecules in a gas, liquid or solid medium, force an incoming mix of wavelengths (or colors) of light to work in phase, or, at the same wavelength. Though a natural infrared laser was identified in space in 1995, lasers are very rare in space and nothing like the UV laser has ever been seen before. Eta Carinae is several million times brighter than the Sun, and one hundred times as massive. The superstar, located 8,000 light-years away in the souther constellation Carina, underwent a colossal outburst 150 years ago. Illustration courtesy James Gitlin/STScI

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.

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler.

PubMed

Kardaś, Tomasz M; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-22

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

NASA Astrophysics Data System (ADS)

Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-01

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Femtosecond Laser Filamentation for Atmospheric Sensing

PubMed Central

Xu, Huai Liang; Chin, See Leang

2011-01-01

Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints) from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation. PMID:22346566

Laser measurements of bacterial endospore destruction from shock waves

NASA Astrophysics Data System (ADS)

Lappas, Petros P.; McCartt, A. Daniel; Gates, Sean D.; Jeffries, Jay B.; Hanson, Ronald K.

2013-12-01

The effects of shock waves on bioaerosols containing endospores were measured by combined laser absorption and scattering. Experiments were conducted in the Stanford aerosol shock tube for post-shock temperatures ranging from 400 K to 1100 K. Laser intensity measurements through the test section of the shock tube at wavelengths of 266 and 665 nm provided real-time monitoring of the morphological changes (includes changes in shape, structure and optical properties) in the endospores. Scatter of the visible light measured the integrity of endospore structure, while absorption of the UV light provided a measure of biochemicals released when endospores ruptured. For post-shock temperatures above 750 K the structural breakdown of Bacillus atrophaeus (BA) endospores was observed. A simple theoretical model using laser extinction is presented for determining the fraction of endospores that are ruptured by the shock waves. In addition, mechanisms of endospore mortality preceding their disintegration due to shock waves are discussed.

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.

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.

A clinical review of phototherapy for psoriasis.

PubMed

Zhang, Ping; Wu, Mei X

2018-01-01

Psoriasis is an autoimmune inflammatory skin disease. In the past several decades, phototherapy has been widely used to treat stable psoriatic lesions, including trunk, scalp, arms and legs, and partial nail psoriasis. A variety of light/lasers with different mechanisms of action have been developed for psoriasis including ultraviolet B (UVB), psoralen ultraviolet A (PUVA), pulsed dye laser (PDL), photodynamic therapy (PDT), intense pulsed light (IPL), light-emitting diodes (LED), and so on. Because light/laser each has specific therapeutic and adverse effects, it is important to adequately choose the sources and parameters in management of psoriasis with different pathogenic sites, severities, and duration of the disorder. This review aims at providing most updated clinic information to physicians about how to select light/laser sources and individual therapeutic regimens. To date, UV light is primarily for stable plaque psoriasis and PDL for topical psoriatic lesions with small area, both of which are safe and effective. On the other hand, PUVA has better curative effects than UVB for managing refractory psoriasis plaques, if its side effects can be better controlled. PDL provides optimal outcomes on nail psoriasis compared with other lasers. Although the trails of low-level light/laser therapy (LLLT) are still small, the near infrared (NIR) and visible red light with low energy show promise for treating psoriasis due to its strong penetration and encouraging photobiomodulation. IPL is rarely reported for psoriasis treatment, but PDT-IPL has been found to offer a moderate effect on nail psoriasis. In brief, various phototherapies have been used either in different combinations or as monotherapy. The modality has become a mainstay in the treatment of mild-to-moderate psoriasis without systemic adverse events in today's clinical practice.

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.

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.

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).

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.

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

NASA Astrophysics Data System (ADS)

Ahn, Minwoo; Nguyen, Trung Hau; Nguyen, Van Phuc; Oh, Junghwan; Kang, Hyun Wook

2015-02-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of 44.2+/-0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser treatment for BPH with low power application.

Blue light emitting diesel soot for photonic applications

NASA Astrophysics Data System (ADS)

Swapna, M. S.; Sankararaman, S.

2018-01-01

The present work is the first report of producing blue light emission from phosphor free and low-cost material—the diesel soot from the internal combustion engines (ICEs). The structural morphology is analyzed by field emission scanning electron microscopy and high-resolution transmission electron microscopy. The optical characterization is done by recording UV-visible spectrum and photoluminescent Spectrum. The CIE plot and the power spectrum for the sample show blue emission. This is further verified by collecting diesel soot from the ICE of different year of make. A visual confirmation of blue emission is obtained by exciting the sample with UV laser. The presence of various allotropic forms of carbon in the sample is identified by x-ray diffraction, Fourier transform infrared and Raman spectroscopic analysis.

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

Nonlinear side effects of fs pulses inside corneal tissue during photodisruption

NASA Astrophysics Data System (ADS)

Heisterkamp, A.; Ripken, T.; Mamom, T.; Drommer, W.; Welling, H.; Ertmer, W.; Lubatschowski, H.

In order to evaluate the potential for refractive surgery, fs laser pulses of 150-fs pulse duration were used to process corneal tissue of dead and living animal eyes. By focusing the laser radiation down to spot sizes of several microns, very precise cuts could be achieved inside the treated cornea, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. During histo-pathological analysis by light and transmission electron microscopy considerable side effects of fs photodisruption were found. Due to the high intensities at the focal region several nonlinear effects occurred. Self-focusing, photodissociation, UV-light production were observed, leading to streak formation inside the cornea.

In situ optical measurements of bacterial endospore breakdown in a shock tube

NASA Astrophysics Data System (ADS)

McCartt, A. D.; Gates, S.; Lappas, P.; Jeffries, J. B.; Hanson, R. K.

2012-03-01

The interaction of endospore-laden bioaerosols and shock waves is monitored with a combination of laser absorption and scattering. Tests are performed in the Stanford aerosol shock tube for post-shock temperatures ranging from 400-1100 K. In situ laser measurements at 266 and 665 nm provide a real-time monitor of endospore morphology. Scatter of visible light measures the integrity of endospore structure, while absorption of UV light provides a monitor of biochemicals released by endospore rupture. For post-shock temperatures greater than 750 K endospore morphological breakdown is observed. A simple theoretical model is employed to quantify the optical measurements, and mechanisms leading to the observed data are discussed.

High-energy krypton fluoride lasers for inertial fusion.

PubMed

Obenschain, Stephen; Lehmberg, Robert; Kehne, David; Hegeler, Frank; Wolford, Matthew; Sethian, John; Weaver, James; Karasik, Max

2015-11-01

Laser fusion researchers have realized since the 1970s that the deep UV light from excimer lasers would be an advantage as a driver for robust high-performance capsule implosions for inertial confinement fusion (ICF). Most of this research has centered on the krypton-fluoride (KrF) laser. In this article we review the advantages of the KrF laser for direct-drive ICF, the history of high-energy KrF laser development, and the present state of the art and describe a development path to the performance needed for laser fusion and its energy application. We include descriptions of the architecture and performance of the multi-kilojoule Nike KrF laser-target facility and the 700 J Electra high-repetition-rate KrF laser that were developed at the U.S. Naval Research Laboratory. Nike and Electra are the most advanced KrF lasers for inertial fusion research and energy applications.

Developing Photoacoustic Tomography Devices for Translational Medicine and Basic Science Research

NASA Astrophysics Data System (ADS)

Wong, Terence Tsz Wai

Photoacoustic (PA) tomography (PAT) provides volumetric images of biological tissue with scalable spatial resolutions and imaging depths, while preserving the same imaging contrast--optical absorption. Taking the advantage of its 100% sensitivity to optical absorption, PAT has been widely applied in structural, functional, and molecular imaging, with both endogenous and exogenous contrasts, at superior depths than pure optical methods. Intuitively, hemoglobin has been the most commonly studied biomolecule in PAT due to its strong absorption in the visible wavelength regime. One of the main focuses of this dissertation is to investigate an underexplored wavelength regime--ultraviolet (UV), which allows us to image cell nuclei without labels and generate histology-like images naturally from unprocessed biological tissue. These preparation-free and easy-to-interpret characteristics open up new possibilities for PAT to become readily applicable to other important biomedical problems (e.g., surgical margin analysis, Chapter 2) or basic science studies (e.g., whole-organ imaging, Chapter 3). For instance, we developed and optimized a PA microscopy system with UV laser illumination (UV-PAM) to achieve fast, label-free, multilayered, and histology-like imaging of human breast cancer in Chapter 2. These imaging abilities are essential to intraoperative surgical margin analysis, which enables promptly directed re-excision and reduces the number of repeat surgeries. We have incorporated the Gruneisen relaxation (GR) effect with UV-PAM to improve the performance of our UV-PAM system (e.g., the axial resolution), thus providing more accurate three-dimensional (3D) information (Chapter 4). The nonlinear PA signals caused by the GR effect enable optical sectioning capability, revealing important 3D cell nuclear distributions and internal structures for cancer diagnosis. In the final focus of this dissertation, we have implemented a low-cost PA computed tomography (PACT) system with a single xenon flash lamp as the illumination source (Chapter 5). Lasers have been commonly used as illumination light sources in PACT. However, lasers are usually expensive and bulky, limiting their applicability in many clinical usages. Therefore, the use of a single xenon flash lamp as an alternative light source was explored. We found that PACT images acquired with flash lamp illumination were comparable to those acquired with laser illumination. This low-cost and portable PACT system opens up new potentials, such as low-cost skin melanoma imaging in undeveloped countries.

Laccase-Catalyzed Synthesis of Low-Molecular-Weight Lignin-Like Oligomers and their Application as UV-Blocking Materials.

PubMed

Lim, Jieyan; Sana, Barindra; Krishnan, Ranganathan; Seayad, Jayasree; Ghadessy, Farid J; Jana, Satyasankar; Ramalingam, Balamurugan

2018-02-02

The laccase-catalyzed oxidative polymerization of monomeric and dimeric lignin model compounds was carried out with oxygen as the oxidant in aqueous medium. The oligomers were characterized by using gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis. Oxidative polymerization led to the formation of oligomeric species with a number-average molecular weight (M n ) that ranged from 700 to 2300 Da with a low polydispersity index. Spectroscopic analysis provided insight into the possible modes of linkages present in the oligomers, and the oligomerization is likely to proceed through the formation of C-C linkages between phenolic aromatic rings. The oligomers were found to show good UV light absorption characteristics with high molar extinction coefficient (5000-38 000 m -1  cm -1 ) in the UV spectral region. The oligomers were blended independently with polyvinyl chloride (PVC) by using solution blending to evaluate the compatibility and UV protection ability of the oligomers. The UV/Vis transmittance spectra of the oligomer-embedded PVC films indicated that these lignin-like oligomers possessed a notable ability to block UV light. In particular, oligomers obtained from vanillyl alcohol and the dimeric lignin model were found to show good photostability in accelerated UV weathering experiments. The UV-blocking characteristics and photostability were finally compared with the commercial low-molecular-weight UV stabilizer 2,4-dihydroxybenzophenone. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial Control of Photoemitted Electron Beams using a Micro-Lens-Array Transverse-Shaping Technique

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

Halavanau, A.; Qiang, G.; Ha, G.

2017-07-24

A common issue encountered in photoemission electron sources used in electron accelerators is the transverse inhomogeneity of the laser distribution resulting from the laser-amplification process and often use of frequency up conversion in nonlinear crystals. A inhomogeneous laser distribution on the photocathode produces charged beams with lower beam quality. In this paper, we explore the possible use of microlens arrays (fly-eye light condensers) to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes. We also demonstrate the use of such microlens arrays to generate transversely-modulated electron beams and present a possible application to diagnose the propertiesmore » of a magnetized beam.« less

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.

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.

The laser and optical system for the RIBF-PALIS experiment

NASA Astrophysics Data System (ADS)

Sonoda, T.; Iimura, H.; Reponen, M.; Wada, M.; Katayama, I.; Sonnenschein, V.; Takamatsu, T.; Tomita, H.; Kojima, T. M.

2018-01-01

This paper describes the laser and optical system for the Parasitic radioactive isotope (RI) beam production by Laser Ion-Source (PALIS) in the RIKEN fragment separator facility. This system requires an optical path length of 70 m for transporting the laser beam from the laser light source to the place for resonance ionization. To accomplish this, we designed and implemented a simple optical system consisting of several mirrors equipped with compact stepping motor actuators, lenses, beam spot screens and network cameras. The system enables multi-step laser resonance ionization in the gas cell and gas jet via overlap with a diameter of a few millimeters, between the laser photons and atomic beam. Despite such a long transport distance, we achieved a transport efficiency for the UV laser beam of about 50%. We also confirmed that the position stability of the laser beam stays within a permissible range for dedicated resonance ionization experiments.

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.

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.

Ultraviolet/visible photodiode of nanostructure Sn-doped ZnO/Si heterojunction

NASA Astrophysics Data System (ADS)

Kheirandish, N.; Mortezaali, A.

2013-05-01

Sn doped ZnO nanostructures deposited on Si substrate with (100) orientation by spray pyrolysis method at temperature 450 °C. Sn/Zn atomic ratio varies from 0% to 5%. The scanning electron microscope measurements showed that size of particles reduce with increasing the doping concentration. The X-ray diffraction analysis revealed formation of the wurtzite phase of ZnO. I-V curves of Sn doped ZnO/Si were investigated in dark and shows diode-like rectifying behavior. Among doped ZnO/Si, sample with atomic ratio of Sn/Zn = 5% is a good candidate to study photodiode properties in UV/visible range. Photoelectric effects have been observed under illumination monochromatic laser light with a wavelength of 325 nm and halogen lamp. Measurements demonstrate that the photodiode has high sensitivity and reproducibility to halogen light respect to laser light.

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.

The potential for optical beam shaping of UV laser sources for mass scale quarantine disinfection applications

NASA Astrophysics Data System (ADS)

Lizotte, Todd

2010-08-01

Recent events concerning H1N1 "swine flu", have demonstrated to the world the significant potential of rapid increases in death and illness among all age groups and even among the healthy population [1] when a highly infectious influenza virus is introduced. In terms of mass casualties due to a pandemic, preparedness and response planning must be done. One course of action to prevent a pandemic outbreak or reduce the impact of a bioterrorist event is the use of isolation or quarantine facilities. The first level of isolation or quarantine is within the personal residence of the person exposed or infected. In the case where, the specific virus is extremely contagious and its onset of symptoms is rapid and severe, there will be a need for the deployment and setup of larger self contained quarantine facilities. Such facilities are used to house infectious individuals to minimize the exposure of susceptible individuals to contagious individuals, especially when specialized care or treatment is required and during the viral shedding period (5 to 7 days). These types of facilities require non-shared air conditioning, heating and ventilating systems where 100% of air is vented to the outside through a series of disinfection systems and staged filters. Although chemical disinfection is possible, there is a desire to incorporate intense UV radiation as a means to deactivate and disinfect airborne virus within hospital settings and isolated mass scale quarantine facilities. UV radiation is also being considered for disinfection of contaminated surfaces, such as table tops, walls and floors in hospitals and temporary quarantine facilities. In such applications the use of UV bulb technology can create many problems, for instance bulb technology requires numerous bulbs to treat a large volume of air, generates significant heat, uses significant power and does not produce large fluxes of UV light efficiently. This paper provides several methods of creating quarantine level disinfection systems using high intensity UV laser sources instead of UV bulb techniques by using laser beam shaping optics in conjunction with traditional optical laser beam delivery techniques.

A Compact, Tunable Near-UV Source for Quantitative Microgravity Combustion Diagnostics

NASA Technical Reports Server (NTRS)

Peterson, K. A.; Oh, D. B.

1999-01-01

There is a need for improved optical diagnostic methods for use in microgravity combustion research. Spectroscopic methods with fast time response that can provide absolute concentrations and concentration profiles of important chemical species in flames are needed to facilitate the understanding of combustion kinetics in microgravity. Although a variety of sophisticated laser-based diagnostics (such as planar laser induced fluorescence, degenerate four wave mixing and coherent Raman methods) have been applied to the study of combustion in laboratory flames, the instrumentation associated with these methods is not well suited to microgravity drop tower or space station platforms. Important attributes of diagnostic systems for such applications include compact size, low power consumption, ruggedness, and reliability. We describe a diode laser-based near-UV source designed with the constraints of microgravity research in mind. Coherent light near 420 nm is generated by frequency doubling in a nonlinear crystal. This light source is single mode with a very narrow bandwidth suitable for gas phase diagnostics, can be tuned over several 1/cm and can be wavelength modulated at up to MHz frequencies. We demonstrate the usefulness of this source for combustion diagnostics by measuring CH radical concentration profiles in an atmospheric pressure laboratory flame. The radical concentrations are measured using wavelength modulation spectroscopy (WMS) to obtain the line-of-sight integrated absorption for different paths through the flame. Laser induced fluorescence (LIF) measurements are also demonstrated with this instrument, showing the feasibility of simultaneous WMS absorption and LIF measurements with the same light source. LIF detection perpendicular to the laser beam can be used to map relative species densities along the line-of-sight while the integrated absorption available through WMS provides a mathematical constraint on the extraction of quantitative information from the LIF data. Combining absorption with LIF - especially if the measurements are made simultaneously with the same excitation beam - may allow elimination of geometrical factors and effects of intensity fluctuations (common difficulties with the analysis of LIF data) from the analysis.

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.

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.

High-power LED light sources for optical measurement systems operated in continuous and overdriven pulsed modes

NASA Astrophysics Data System (ADS)

Stasicki, Bolesław; Schröder, Andreas; Boden, Fritz; Ludwikowski, Krzysztof

2017-06-01

The rapid progress of light emitting diode (LED) technology has recently resulted in the availability of high power devices with unprecedented light emission intensities comparable to those of visible laser light sources. On this basis two versatile devices have been developed, constructed and tested. The first one is a high-power, single-LED illuminator equipped with exchangeable projection lenses providing a homogenous light spot of defined diameter. The second device is a multi-LED illuminator array consisting of a number of high-power LEDs, each integrated with a separate collimating lens. These devices can emit R, G, CG, B, UV or white light and can be operated in pulsed or continuous wave (CW) mode. Using an external trigger signal they can be easily synchronized with cameras or other devices. The mode of operation and all parameters can be controlled by software. Various experiments have shown that these devices have become a versatile and competitive alternative to laser and xenon lamp based light sources. The principle, design, achieved performances and application examples are given in this paper.

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.

Growth of new borate crystals with fiber shape by the micro-pulling down technique

NASA Astrophysics Data System (ADS)

Assi, Farah; Ferriol, Michel; Aillerie, Michel; Cochez, Marianne

2017-07-01

Borate-based materials are of high interest to generate an UV laser light from a crystal. Fiber-shaped crystals combining the advantages of fiber lasers and crystalline lasers, we have investigated the growing conditions required to obtain usable fibers of Bi2ZnB2O7 (BZBO) and LaBGeO5 (LBGO). For BZBO, the major drawback was the pronounced color of the fibers and for LBGO, it was the high viscosity of its melt leading to use a flux. This paper presents our state of the art to obtain good quality BZBO and LBGO crystal fibers.

Photoresponsive Polymer Surfaces

NASA Astrophysics Data System (ADS)

Anastasiadis, Spiros H.; Lygeraki, M. I.; Lakiotaki, K.; Varda, M.; Athanassiou, A.; Farsari, M.; Fotakis, C.

2007-03-01

Photochromic spiropyran molecules are utilized as additives for the development of polymer surfaces whose wetting characteristics can reversibly respond to irradiation with laser beams of properly chosen photon energy. The hydrophilicity is enhanced upon UV laser irradiation since the embedded non-polar spiropyran molecules convert to their polar merocyanine isomers, which is reversed upon green laser irradiation. Micropatterning of the photochromic-polymer films using soft lithography or photo-polymerization techniques affects their wettability towards a more hydrophobic or more hydrophilic behavior depending on the dimensions of the patterned features and on the hydrophilicity-hydrophobicity of the flat surface. The light-induced wettability variations of the structured surfaces are enhanced by up to a factor of three as compared to those on the flat surfaces. This enhancement is attributed to the photoinduced reversible volume changes to the imprinted gratings, which additionally contribute to the wettability changes due to the light-induced photochromic interconversions.

Electrical Activation Studies of Silicon Implanted Aluminum Gallium Nitride with High Aluminum Mole Fraction

DTIC Science & Technology

2007-12-01

realized with silicon due to its indirect band gap that results in poor quantum efficiency . The first LEDs and laser diodes were developed with...deep UV (λ < 340 nm) still face many challenges and have low internal quantum efficiency . Jong Kyu Kim et al. have developed a light emitting triode...LET) to try to overcome some of the challenges and 16 have produced a lighting device with increased quantum efficiency (16). AlxGa1-xN has been

Design and Analysis of an Optical Interface Message Processor

DTIC Science & Technology

1993-03-01

Device 16 2.2.15 Microchannel Spatial Light Modulator (MSLM) 16 2.2.16 Si/PLST Modulator 16 2.2.17 Deformable Mirror Device ( DMD ) 17 2.2.18 Charged...wavelength of UV light, ’n this process, is the minimum image which can be developed. X-Ray lithography wil’ reduce the image size to the 1000 Angstrom...resonance of laser wavelength. This is due to a change in the index of refraction which results in an optical path allowing constructive interference

Electronically conducting polymers with silver grains

NASA Technical Reports Server (NTRS)

Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor); Hodko, Dolibor (Inventor)

1999-01-01

The present invention provides electronically conducting polymer films formed from photosensitive formulations of pyrrole and an electron acceptor that have been selectively exposed to UV light, laser light, or electron beams. The formulations may include photoinitiators, flexibilizers, solvents and the like. These solutions can be used in applications including printed circuit boards and through-hole plating and enable direct metallization processes on non-conducting substrates. After forming the conductive polymer patterns, a printed wiring board can be formed by sensitizing the polymer with palladium and electrolytically depositing copper.

Capillary electrophoresis hyphenated with UV-native-laser induced fluorescence detection (CE/UV-native-LIF).

PubMed

Couderc, François; Ong-Meang, Varravaddheay; Poinsot, Véréna

2017-01-01

Native laser-induced fluorescence using UV lasers associated to CE offers now a large related literature, for now 30 years. The main works have been performed using very expensive Ar-ion lasers emitting at 257 and 275 nm. They are not affordable for routine analyses, but have numerous applications such as protein, catecholamine, and indolamine analysis. Some other lasers such as HeCd 325 nm have been used but only for few applications. Diode lasers, emitting at 266 nm, cheaper, are extensively used for the same topics, even if the obtained sensitivity is lower than the one observed using the costly UV-Ar-ion lasers. This review presents various CE or microchips applications and different UV lasers used for the excitation of native fluorescence. We showed that CE/Native UV laser induced fluorescence detection is very sensitive for detection as well as small aromatic biomolecules than proteins containing Trp and Tyr amino acids. Moreover, it is a simple way to analyze biomolecules without derivatization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Use of the CEBAF Accelerator for IR and UV Free Electron Lasers

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

Yunn, Byung; Sinclair, Charles; Leemann, Christoph

1992-08-01

The CEBAF superconducting linac is capable of accelerating electron beams suitable for driving high-power free-electron lasers. The 45 MeV injector linac with a 6 cm period wiggler can produce kilowatt output powers of infrared light (3.6-17 micrometer), while the 400 MeV north linac can produce ultraviolet light (~200 nm) at similar powers. The FELs require the addition of a high-peak intensity electron source (~ 60 A peak current) and extraction beam lines to wigglers with appropriate electron and photon optics. FEL operation is compatible with simultaneous baseline CEBAF nuclear physics operation. A design for a CEBAF-based FEL facility has beenmore » developed. The current status of the FEL project is reported.« less

High-power multi-megahertz source of waveform-stabilized few-cycle light

PubMed Central

Pronin, O.; Seidel, M.; Lücking, F.; Brons, J.; Fedulova, E.; Trubetskov, M.; Pervak, V.; Apolonski, A.; Udem, Th.; Krausz, F.

2015-01-01

Waveform-stabilized laser pulses have revolutionized the exploration of the electronic structure and dynamics of matter by serving as the technological basis for frequency-comb and attosecond spectroscopy. Their primary sources, mode-locked titanium-doped sapphire lasers and erbium/ytterbium-doped fibre lasers, deliver pulses with several nanojoules energy, which is insufficient for many important applications. Here we present the waveform-stabilized light source that is scalable to microjoule energy levels at the full (megahertz) repetition rate of the laser oscillator. A diode-pumped Kerr-lens-mode-locked Yb:YAG thin-disk laser combined with extracavity pulse compression yields waveform-stabilized few-cycle pulses (7.7 fs, 2.2 cycles) with a pulse energy of 0.15 μJ and an average power of 6 W. The demonstrated concept is scalable to pulse energies of several microjoules and near-gigawatt peak powers. The generation of attosecond pulses at the full repetition rate of the oscillator comes into reach. The presented system could serve as a primary source for frequency combs in the mid infrared and vacuum UV with unprecedented high power levels. PMID:25939968

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.

Topical treatment and combination approaches for vitiligo: new insights, new developments.

PubMed

Hossani-Madani, A R; Halder, R M

2010-02-01

Despite much research done involving elucidation of the pathogenesis of vitiligo, a precise cause is still not known. Prevalent hypotheses include the autoimmune, genetic, neural, self-destruction, growth factor deficiency, viral, and convergence theories, which have served as the basis for treatment formulation. Topical therapies have been a mainstay of vitiligo treatment, with or without phototherapy. Topical treatments used in the treatment of vitiligo include steroids, calcineurin inhibitors, vitamin D analogues, pseudocatalase, and depigmenting agents. Combination therapies are used to improve the success rate of repigmentation. In this article, we have examined randomized controlled trials utilizing topical treatments used as monotherapy or combination therapy. Although psoralen and khellin can be used as topical agents, used in conjunction with UV radiation, we have not included them in the review due to their inability to be used as monotherapy. We have also excluded less used or ineffective topical agents, such as melagenina, topical phenylalanine, topical L-DOPA, coal tar, anacarcin forte oil and topical minoxidil. According to current guidelines, a less than two month trial of potent or very potent topical corticosteroids or topical calcineurin inhibitors may be used for therapy of localized vitiligo (<20% skin surface area). Combinations of topical corticosteroids with excimer laser and UVA seem to be more effective than steroids alone. Pseudocatalase plus NB-UVB does not seem to be more effective than placebo with NB-UVB. Combinations of vitamin D analogues have varied efficacy based on which type is used and the type of UV light. Efficacy of calcineurin inhibitor combinations also vary based on the type used and UV light combined, with tacrolimus being more effective with excimer laser. Pimecrolimus has been effective with NB-UVB and excimer laser on facial lesions, and microdermabrasion on localized areas.

Projection lenses for high-resolution ablation with excimer lasers: high-performance, wide-field and high-UV laser power

NASA Astrophysics Data System (ADS)

Schlichting, Johannes; Winkler, Kerstin; Koerner, Lienhard; Schletterer, Thomas; Burghardt, Berthold; Kahlert, Hans-Juergen

2000-10-01

The productive and accurate ablation of microstructures demands the precise imaging of a mask pattern onto the substrate under work. The job can be done with high performance wide field lenses as a key component of ablation equipment. The image field has dimensions of 20 to 30 mm. Typical dimensions and accuracy of the microstructures are in the order of some microns. On the other hand, the working depth of focus (DOF) has to be in the order of some 10 microns to be successful on drilling through 20 to 50 μm substrates. All these features have to be reached under the conditions of high power laser UV light. Some design principles for such systems are applied, such as optimum number of elements, minimum tolerance sensitivity, material restrictions for the lens elements as well as mechanical parts (mounting), restrictions of possible power densities on lens surfaces (including ghosts), matched quality for the manufactures system. The special applications require appropriate performance criteria for theoretical calculation and measurements, which allow to conclude the performance of the application. The base is wave front calculation and measurement (using Shack- Hartmann sensor) in UV. Derived criteria are calculated and compared with application results.

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.

Ultraviolet 320 nm laser excitation for flow cytometry.

PubMed

Telford, William; Stickland, Lynn; Koschorreck, Marco

2017-04-01

Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry. © 2017 International Society for Advancement of Cytometry.

Dynamic high-resolution patterning for biomedical, materials, and semiconductor research

NASA Astrophysics Data System (ADS)

Garner, Harold R.; Joshi, Amruta; Mitnala, Sandhya N.; Huebschman, Michael L.; Shandy, Surya; Wallek, Brandi; Wong, Season

2009-02-01

By combining unique light sources, a Texas Instruments DLP system and a microscope, a submicron dynamic patterning system has been created. This system has a resolution of 0.5 microns, and can illuminate with rapidly changing patterns of visible, UV or pulsed laser light. This system has been used to create digital masks for the production of micron scale electronic test circuits and has been used in biological applications. Specifically we have directed light on a sub-organelle scale to cells to control their morphology and motility with applications to tissue engineering, cell biology, drug discovery and neurology.

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

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.

Ultrafast pre-breakdown dynamics in Al₂O₃SiO₂ reflector by femtosecond UV laser spectroscopy.

PubMed

Du, Juan; Li, Zehan; Xue, Bing; Kobayashi, Takayoshi; Han, Dongjia; Zhao, Yuanan; Leng, Yuxin

2015-06-29

Ultrafast carrier dynamics in Al2O3/SiO2 high reflectors has been investigated by UV femtosecond laser. It is identified by laser spectroscopy that, the carrier dynamics contributed from the front few layers of Al2O3 play a dominating role in the initial laser-induced damage of the UV reflector. Time-resolved reflection decrease after the UV excitation is observed, and conduction electrons is found to relaxed to a mid-gap defect state locating about one photon below the conduction band . To interpret the laser induced carrier dynamics further, a theoretical model including electrons relaxation to a mid-gap state is built, and agrees very well with the experimental results.. To the best of our knowledge, this is the first study on the pre-damage dynamics in UV high reflector induced by femtosecond UV laser.

Delivery of vincristine sulfate-conjugated gold nanoparticles using liposomes: a light-responsive nanocarrier with enhanced antitumor efficiency

PubMed Central

Liu, Ying; He, Man; Niu, Mengmeng; Zhao, Yiqing; Zhu, Yuanzhang; Li, Zhenhua; Feng, Nianping

2015-01-01

Rapid drug release at the specific site of action is still a challenge for antitumor therapy. Development of stimuli-responsive hybrid nanocarriers provides a promising strategy to enhance therapeutic effects by combining the unique features of each component. The present study explored the use of drug–gold nanoparticle conjugates incorporated into liposomes to enhance antitumor efficiency. A model drug, vincristine sulfate, was physically conjugated with gold nanoparticles and verified by UV-visible and fourier transform infrared spectroscopy, and differential scanning calorimetry. The conjugates were incorporated into liposomes by film dispersion to yield nanoparticles (113.4 nm) with light-responsive release properties, as shown by in vitro release studies. Intracellular uptake and distribution was studied in HeLa cells using transmission electron microscopy and confocal laser scanning microscopy. This demonstrated liposome internalization and localization in endosomal–lysosomal vesicles. Fluorescence intensity increased in cells exposed to UV light, indicating that this stimulated intracellular drug release; this finding was confirmed by quantitative analyses using flow cytometry. Antitumor efficacy was evaluated in HeLa cells, both in culture and in implants in vivo in nude mice. HeLa cell viability assays showed that light exposure enhanced liposome cytotoxicity and induction of apoptosis. Furthermore, treatment with the prepared liposomes coupled with UV light exposure produced greater antitumor effects in nude mice and reduced side effects, as compared with free vincristine sulfate. PMID:25960649

Precision Control Module For UV Laser 3D Micromachining

NASA Astrophysics Data System (ADS)

Wu, Wen-Hong; Hung, Min-Wei; Chang, Chun-Li

2011-01-01

UV laser has been widely used in various micromachining such as micro-scribing or patterning processing. At present, most of the semiconductors, LEDs, photovoltaic solar panels and touch panels industries need the UV laser processing system. However, most of the UV laser processing applications in the industries utilize two dimensional (2D) plane processing. And there are tremendous business opportunities that can be developed, such as three dimensional (3D) structures of micro-electromechanical (MEMS) sensor or the precision depth control of indium tin oxide (ITO) thin films edge insulation in touch panels. This research aims to develop a UV laser 3D micromachining module that can create the novel applications for industries. By special designed beam expender in optical system, the focal point of UV laser can be adjusted quickly and accurately through the optical path control lens of laser beam expender optical system. Furthermore, the integrated software for galvanometric scanner and focal point adjustment mechanism is developed as well, so as to carry out the precise 3D microstructure machining.

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.

Demonstration of miniaturized 20mW CW 280nm and 266nm solid-state UV laser sources

NASA Astrophysics Data System (ADS)

Landru, Nicolas; Georges, Thierry; Beaurepaire, Julien; Le Guen, Bruno; Le Bail, Guy

2015-02-01

Visible 561 nm and 532 nm laser emissions from 14-mm long DPSS monolithic cavities are frequency converted to deep UV 280 nm and 266 nm in 16-mm long monolithic external cavities. Wavelength conversion is fully insensitive to mechanical vibrations and the whole UV laser sources fit in a miniaturized housing. More than 20 mW deep UV laser emission is demonstrated with high power stability, low noise and good beam quality. Aging tests are in progress but long lifetimes are expected thanks to the cavity design. Protein detection and deep UV resonant Raman spectroscopy are applications that could benefit from these laser sources.

Near-ultraviolet laser diodes for brilliant ultraviolet fluorophore excitation.

PubMed

Telford, William G

2015-12-01

Although multiple lasers are now standard equipment on most modern flow cytometers, ultraviolet (UV) lasers (325-365 nm) remain an uncommon excitation source for cytometry. Nd:YVO4 frequency-tripled diode pumped solid-state lasers emitting at 355 nm are now the primary means of providing UV excitation on multilaser flow cytometers. Although a number of UV excited fluorochromes are available for flow cytometry, the cost of solid-state UV lasers remains prohibitively high, limiting their use to all but the most sophisticated multilaser instruments. The recent introduction of the brilliant ultraviolet (BUV) series of fluorochromes for cell surface marker detection and their importance in increasing the number of simultaneous parameters for high-dimensional analysis has increased the urgency of including UV sources in cytometer designs; however, these lasers remain expensive. Near-UV laser diodes (NUVLDs), a direct diode laser source emitting in the 370-380 nm range, have been previously validated for flow cytometric analysis of most UV-excited probes, including quantum nanocrystals, the Hoechst dyes, and 4',6-diamidino-2-phenylindole. However, they remain a little-used laser source for cytometry, despite their significantly lower cost. In this study, the ability of NUVLDs to excite the BUV dyes was assessed, along with their compatibility with simultaneous brilliant violet (BV) labeling. A NUVLD emitting at 375 nm was found to excite most of the available BUV dyes at least as well as a UV 355 nm source. This slightly longer wavelength did produce some unwanted excitation of BV dyes, but at sufficiently low levels to require minimal additional compensation. NUVLDs are compact, relatively inexpensive lasers that have higher power levels than the newest generation of small 355 nm lasers. They can, therefore, make a useful, cost-effective substitute for traditional UV lasers in multicolor analysis involving the BUV and BV dyes. Published 2015 Wiley Periodicals Inc. on behalf of ISAC.

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.

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.

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

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.

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.

In-situ tomographic observation of tissue surface during laser ablation

NASA Astrophysics Data System (ADS)

Haruna, Masamitsu; Konoshita, Ryuh; Ohmi, Masato; Kunizawa, Naomi; Miyachi, Mayumi

2001-07-01

In laser ablation of tissues, tomography of the tissue surface is necessary for measurement of the crater depth and observation of damage of the surrounding tissue. We demonstrate here OCT images of craters made by UV laser ablation of different tissues. The maximum depth of a crater is found among several OCT images, and then the ablation rate is determined. The conventional OCT of the spatial resolution of 15 μm was used in our experiment, but OCT of the resolution of the order of 1 μm is required because the ablation rate is usually a few microns per pulse. Such a high-resolution OCT is also demonstrated in this paper, where the light source is a halogen lamp. Combination of laser ablation and OCT will lead to in situ tomographic observation of tissue surface during laser ablation, which should allow us to develop new laser surgeries.

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.

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.

Probing electron delays in above-threshold ionization

DOE PAGES

Zipp, Lucas J.; Natan, Adi; Bucksbaum, Philip H.

2014-11-21

Recent experiments have revealed attosecond delays in the emission of electrons from atoms ionized by extreme UV light, offering a glimpse into the ultrafast nature of light-induced electron dynamics. In this work, we extend these measurements to the strong-field above-threshold ionization (ATI) regime, by measuring delays in the photoemission of electrons from argon in the presence of an intense laser field. We probe the ATI process with a weak coherent reference, at half the laser frequency. The interfering ionization signal reveals the relative spectral phase of adjacent ATI channels, with an equivalent resolution of a few attoseconds. These relative delaysmore » depend on the strong field, and approach zero at higher intensity. Our phase measurements of ATI electrons show how strong fields alter ionization dynamics in atoms.« less

Integrated ultraviolet and tunable mid-infrared laser source for analyses of proteins

NASA Astrophysics Data System (ADS)

Hazama, Hisanao; Takatani, Yoshiaki; Awazu, Kunio

2007-02-01

Mass spectrometry using matrix-assisted laser desorption/ionization (MALDI) technique is one of the most widely used method to analyze proteins in biological research fields. However, it is difficult to analyze insoluble proteins which have important roles in researches on disease mechanisms or in developments of drugs by using ultraviolet (UV) lasers which have commonly been used for MALDI. Recently, a significant improvement in MALDI process of insoluble proteins using a combination of a UV nitrogen laser and a tunable mid-infrared (MIR) free electron laser (FEL) was reported. Since the FEL is a very large and expensive equipment, we have developed a tabletop laser source which can generate both UV and tunable MIR lasers. A tunable MIR laser (5.5-10 μm) was obtained by difference frequency generation (DFG) between a Nd:YAG and a tunable Cr:forsterite lasers using two AgGaS II crystals. The MIR laser can generate pulses with an energy of up to 1.4 mJ at a repetition rate of 10 Hz. A UV laser was obtained by third harmonic generation of a Nd:YAG laser splitted from that used for DFG. A time interval between the UV and the MIR laser pulses can be adjusted with a variable optical delay.

Polymer-Coated Hollow Mesoporous Silica Nanoparticles for Triple-Responsive Drug Delivery.

PubMed

Zhang, Yuanyuan; Ang, Chung Yen; Li, Menghuan; Tan, Si Yu; Qu, Qiuyu; Luo, Zhong; Zhao, Yanli

2015-08-19

In this study, pH, reduction and light triple-responsive nanocarriers based on hollow mesoporous silica nanoparticles (HMSNs) modified with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) were developed via surface-initiated atom transfer radical polymerization. Both reduction-cleavable disulfide bond and light-cleavable o-nitrobenzyl ester were used as the linkages between HMSNs and pH-sensitive PDEAEMA polymer caps. A series of characterization techniques were applied to characterize and confirm the structures of the intermediates and final nanocarriers. Doxorubicin (DOX) was easily encapsulated into the nanocarriers with a high loading capacity, and quickly released in response to the stimuli of reducing agent, acid environment or UV light irradiation. In addition, flow cytometry analysis, confocal laser scanning microscopy observations and cytotoxicity studies indicated that the nanocarriers were efficiently internalized by HeLa cancer cells, exhibiting (i) enhanced release of DOX into the cytoplasm under external UV light irradiation, (ii) better cytotoxicity against HeLa cells, and (iii) superior control over drug delivery and release. Thus, the triple-responsive nanocarriers present highly promising potentials as a drug delivery platform for cancer therapy.

Accelerating CR-39 Track Detector Processing by Utilizing UV

NASA Astrophysics Data System (ADS)

Sparling, Jonathan; Padalino, Stephen; McLean, James; Sangster, Craig; Regan, Sean

2017-10-01

The use of CR-39 plastic as a Solid State Nuclear Track Detector is an effective technique for obtaining data in high energy particle experiments including inertial confinement fusion. To reveal particle tracks after irradiation, CR-39 is chemically etched in NaOH at 80°C, producing micron-scale signal pits at the nuclear track sites. It has been shown that illuminating CR-39 with UV light prior to etching increases bulk and track etch rates, especially when combined with elevated temperature. Spectroscopic analysis for amorphous solids has helped identify which UV wavelengths are most effective at enhancing etch rates. Absorption peaks found in the near infrared range provide for efficient sample heating, and may allow targeting cooperative IR-UV chemistry. Avoiding UV induced noise can be achieved through variations in absorption depths with wavelength. Vacuum drying and water absorption tests allow measurement of the resulting variation of bulk etch rate with depth. Funded in part by the NSF and an Department of Energy Grant through the Lab of Laser Energetics.

Method of forming electronically conducting polymers on conducting and nonconducting substrates

NASA Technical Reports Server (NTRS)

Hodko, Dalibor (Inventor); Clarke, Eric T. (Inventor); Miller, David L. (Inventor); Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor); Parker, Donald L. (Inventor)

2001-01-01

The present invention provides electronically conducting polymer films formed from photosensitive formulations of pyrrole and an electron acceptor that have been selectively exposed to UV light, laser light, or electron beams. The formulations may include photoinitiators, flexibilizers, solvents and the like. These solutions can be used in applications including printed circuit boards and through-hole plating and enable direct metallization processes on non-conducting substrates. After forming the conductive polymer patterns, a printed wiring board can be formed by sensitizing the polymer with palladium and electrolytically depositing copper.

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.

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.

Differentiation of tissue and kidney stones for laser lithotripsy using different spectroscopic approaches

NASA Astrophysics Data System (ADS)

Lange, Birgit; Cordes, Jens; Brinkmann, Ralf

2015-07-01

Holmium lasers are nowadays the gold standard for endoscopic laser lithotripsy. However, there is a risk of damaging or perforating the ureter or kidney tissue when the vision is poor. An automatic tissue/stone differentiation would improve the handling and safety of the procedure. To achieve this objective, an easy and robust real-time discrimination method has to be found which can be used to realize a feedback loop to control the laser system. Two possible approaches have been evaluated: White light reflectance and fluorescence spectroscopy. In both cases, we use the treatment fiber for detection and evaluate the possibility to decide whether the fiber is placed in front of tissue or calculus by the signal that is delivered by the surface in front of it. White light reflectance spectroscopy uses the standard light source for endourologic surgeries: Radiation of a Xenon light source is coupled to the ureteroscope via a liquid light guide. The part of the white light that is reflected back into the fiber is spectroscopically analyzed. In a clinical proof of concept study reflection signals were measured in vivo in 8 patients. For differentiation of stone and tissue via autofluorescence, excitation as well as detection was done via the treatment fiber. A suitable excitation wavelength was chosen with in vitro measurements (UV / visible) on several human renal calculi and porcine tissues. For verification of the positive results with green excitation in a clinical proof of concept study, a measurement set-up was realized which allows the recording of fluorescence signals during an endourological intervention.

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.

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).

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.

Nonpolar InGaN/GaN Core-Shell Single Nanowire Lasers.

PubMed

Li, Changyi; Wright, Jeremy B; Liu, Sheng; Lu, Ping; Figiel, Jeffrey J; Leung, Benjamin; Chow, Weng W; Brener, Igal; Koleske, Daniel D; Luk, Ting-Shan; Feezell, Daniel F; Brueck, S R J; Wang, George T

2017-02-08

We report lasing from nonpolar p-i-n InGaN/GaN multi-quantum well core-shell single-nanowire lasers by optical pumping at room temperature. The nanowire lasers were fabricated using a hybrid approach consisting of a top-down two-step etch process followed by a bottom-up regrowth process, enabling precise geometrical control and high material gain and optical confinement. The modal gain spectra and the gain curves of the core-shell nanowire lasers were measured using micro-photoluminescence and analyzed using the Hakki-Paoli method. Significantly lower lasing thresholds due to high optical gain were measured compared to previously reported semipolar InGaN/GaN core-shell nanowires, despite significantly shorter cavity lengths and reduced active region volume. Mode simulations show that due to the core-shell architecture, annular-shaped modes have higher optical confinement than solid transverse modes. The results show the viability of this p-i-n nonpolar core-shell nanowire architecture, previously investigated for next-generation light-emitting diodes, as low-threshold, coherent UV-visible nanoscale light emitters, and open a route toward monolithic, integrable, electrically injected single-nanowire lasers operating at room temperature.

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.

Quantitative NO-LIF imaging in high-pressure flames

NASA Astrophysics Data System (ADS)

Bessler, W. G.; Schulz, C.; Lee, T.; Shin, D.-I.; Hofmann, M.; Jeffries, J. B.; Wolfrum, J.; Hanson, R. K.

2002-07-01

Planar laser-induced fluorescence (PLIF) images of NO concentration are reported in premixed laminar flames from 1-60 bar exciting the A-X(0,0) band. The influence of O2 interference and gas composition, the variation with local temperature, and the effect of laser and signal attenuation by UV light absorption are investigated. Despite choosing a NO excitation and detection scheme with minimum O2-LIF contribution, this interference produces errors of up to 25% in a slightly lean 60 bar flame. The overall dependence of the inferred NO number density with temperature in the relevant (1200-2500 K) range is low (<±15%) because different effects cancel. The attenuation of laser and signal light by combustion products CO2 and H2O is frequently neglected, yet such absorption yields errors of up to 40% in our experiment despite the small scale (8 mm flame diameter). Understanding the dynamic range for each of these corrections provides guidance to minimize errors in single shot imaging experiments at high pressure.

Femtosecond UV-laser pulses to unveil protein-protein interactions in living cells.

PubMed

Itri, Francesco; Monti, Daria M; Della Ventura, Bartolomeo; Vinciguerra, Roberto; Chino, Marco; Gesuele, Felice; Lombardi, Angelina; Velotta, Raffaele; Altucci, Carlo; Birolo, Leila; Piccoli, Renata; Arciello, Angela

2016-02-01

A hallmark to decipher bioprocesses is to characterize protein-protein interactions in living cells. To do this, the development of innovative methodologies, which do not alter proteins and their natural environment, is particularly needed. Here, we report a method (LUCK, Laser UV Cross-linKing) to in vivo cross-link proteins by UV-laser irradiation of living cells. Upon irradiation of HeLa cells under controlled conditions, cross-linked products of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were detected, whose yield was found to be a linear function of the total irradiation energy. We demonstrated that stable dimers of GAPDH were formed through intersubunit cross-linking, as also observed when the pure protein was irradiated by UV-laser in vitro. We proposed a defined patch of aromatic residues located at the enzyme subunit interface as the cross-linking sites involved in dimer formation. Hence, by this technique, UV-laser is able to photofix protein surfaces that come in direct contact. Due to the ultra-short time scale of UV-laser-induced cross-linking, this technique could be extended to weld even transient protein interactions in their native context.

Photocrosslinking and Photodamage in Protein-Nucleic Acid Systems Resulting from UV and IR Radiation.

NASA Astrophysics Data System (ADS)

Kozub, John Andrew

1995-01-01

Photocrosslinking of protein-nucleic acid complexes with low intensity UV has frequently been used to study biological systems. We have investigated the photochemistry of protein-nucleic acid systems using nanosecond UV pulses from a Nd:YAG-pumped dye laser system, low-intensity continuous UV from a typical germicidal lamp, and high-intensity mid -IR pulses from the Vanderbilt Free Electron Laser. Quantum yields for UV-induced nucleic acid damage from laser pulses and the germicidal lamp were found to be nearly equivalent. We have demonstrated the general applicability of the laser to this technique by successfully crosslinking hnRNP protein to RNA, yeast TATA-binding protein to dsDNA, and gene 32 protein to ssDNA with UV laser pulses. Our results indicate that UV-crosslinking has an intrinsic specificity for nucleic acid sites containing thymidine (or uridine), forcing a distinction between preferred binding sites and favorable crosslinking sites. We have found in each system that protein and nucleic acid photodamage competes with crosslinking, limits the yield, and may interfere with subsequent analysis. The distribution of photoproducts in the gene 32 protein-ssDNA system was investigated as a function of the total dose of UV radiation and the intensity of UV laser pulses. It was found that laser pulses providing up to 50 photons per nucleic acid base induce a linear response from the system; the absolute and relative yields of photoproducts depend only on the total dose of UV and not on the rate of delivery. At higher intensities, the yield of crosslinks per incident photon was reduced. A single pulse at the optimum intensity (about 100-200 photons per nucleic acid base) induced roughly 80% of the maximum attainable yield of crosslinks in this system. The early results of our search for photochemistry induced by Free Electron Laser pulses indicate the potential to induce a unique photoreaction in the gene 32 protein -ssDNA system. The yield is apparently enhanced by simultaneous exposure to UV pulses. Future experiments will test the potential of IR and UV irradiations to increase the specificity for photocrosslinks.

Dictating photoreactivity through restricted bond rotations: cross-photoaddition of atropisomeric acrylimide derivatives under UV/visible-light irradiation.

PubMed

Iyer, Akila; Jockusch, Steffen; Sivaguru, J

2014-11-13

Nonbiaryl atropisomeric acrylimides underwent facile [2 + 2] photocycloaddition leading to cross-cyclobutane adducts with very high stereospecificity (enantiomeric excess (ee): 99% and diastereomeric excess (de): 99%). The photoreactions proceeded smoothly in isotropic media for both direct and triplet sensitized irradiations. The reactions were also found to be very efficient in the solid state where the same cross-cyclobutane adduct was observed. Photophysical studies enabled us to understand the excited-state photochemistry of acrylimides. The triplet energy was found to be ∼63 kcal/mol. The reactions proceeded predominantly via a singlet excited state upon direct irradiation with very poor intersystem crossing that was ascertained by quantification of the generated singlet oxygen. The reactions progressed smoothly with triplet sensitization with UV or visible-light irradiations. Laser flash photolysis experiments established the triplet transient of atropisomeric acrylimides with a triplet lifetime at room temperature of ∼40 ns.

Laser processing of ceramics for microelectronics manufacturing

NASA Astrophysics Data System (ADS)

Sposili, Robert S.; Bovatsek, James; Patel, Rajesh

2017-03-01

Ceramic materials are used extensively in the microelectronics, semiconductor, and LED lighting industries because of their electrically insulating and thermally conductive properties, as well as for their high-temperature-service capabilities. However, their brittleness presents significant challenges for conventional machining processes. In this paper we report on a series of experiments that demonstrate and characterize the efficacy of pulsed nanosecond UV and green lasers in machining ceramics commonly used in microelectronics manufacturing, such as aluminum oxide (alumina) and aluminum nitride. With a series of laser pocket milling experiments, fundamental volume ablation rate and ablation efficiency data were generated. In addition, techniques for various industrial machining processes, such as shallow scribing and deep scribing, were developed and demonstrated. We demonstrate that lasers with higher average powers offer higher processing rates with the one exception of deep scribes in aluminum nitride, where a lower average power but higher pulse energy source outperformed a higher average power laser.

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.

Transfer of ultraviolet photon energy into fluorescent light in the visible path represents a new and efficient protection mechanism of sunscreens

NASA Astrophysics Data System (ADS)

Vergou, Theognosia; Patzelt, Alexa; Richter, Heike; Schanzer, Sabine; Zastrow, Leonhard; Golz, Karin; Doucet, Olivier; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

2011-10-01

The development of sunscreens with high sun protection factor (SPF) values but low filter concentrations is the ultimate goal. The purpose of the present study was to investigate why a sunscreen spray and cream with different concentrations of the same UV-filters provided the same SPF. Therefore, the homogeneity of the distribution of both sunscreens was investigated by laser scanning microscopy (LSM) and tape stripping (TS). Additionally, the energy transfer mechanisms of the sunscreens on the skin were analyzed. The TS and LSM showed a better homogeneity of the distribution of the spray. With Wood's light, a total absorption of the irradiation was detected in the spray area. In contrast, after cream treatment, an intensive fluorescent signal was observed. It was demonstrated that this fluorescent signal was caused by nonthermal energy transferred from the UV-filters to one compound of the cream releasing its excitation energy by fluorescence. This nonthermal energy transfer seemed to be the reason for the high efficiency of the cream, which is subjected to thermal relaxation. The transfer of UV photon energy into fluorescent light represents a new approach to increase the efficiency of sunscreens and could form the basis for a new generation of sunscreens.

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.

High Energy, Single-Mode, All-Solid-State and Tunable UV Laser Transmitter

NASA Technical Reports Server (NTRS)

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

2007-01-01

A high energy, single mode, all solid-state Nd:YAG laser primarily for pumping an UV converter is developed. Greater than 1 J/pulse at 50 HZ PRF and pulse widths around 22 ns have been demonstrated. Higher energy, greater efficiency may be possible. Refinements are known and practical to implement. Technology Demonstration of a highly efficient, high-pulse-energy, single mode UV wavelength generation using flash lamp pumped laser has been achieved. Greater than 90% pump depletion is observed. 190 mJ extra-cavity SFG; IR to UV efficiency > 21% (> 27% for 1 mJ seed). 160 mJ intra-cavity SFG; IR to UV efficiency up to 24% Fluence < 1 J/sq cm for most beams. The pump beam quality of the Nd:YAG pump laser is being refined to match or exceed the above UV converter results. Currently the Nd:YAG pump laser development is a technology demonstration. System can be engineered for compact packaging.

Recent Progress Made in the Development of High-Energy UV Transmitter

NASA Technical Reports Server (NTRS)

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

2007-01-01

In this paper, the status of an all-solid-state UV converter development for ozone sensing applications is discussed. A high energy Nd:YAG laser for pumping the UV converter arrangement was recently reported. The pump is an all-solid-state, single longitudinal mode, and conductively cooled Nd:YAG laser operating at 1064 nm wavelength. Currently, this pump laser provides an output pulse energy of greater than 1J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of approx. 2. The spatial profile of the output beam is a rectangular super Gaussian. This Nd:YAG pump laser has been developed to pump the nonlinear optics based UV converter arrangement to generate 320 nm and 308 nm wavelengths by means of 532 nm wavelength. Previously, this UV converter arrangement has demonstrated IR-to-UV conversion efficiency of 24% using a flash lamp pumped laser providing a round, flat top spatial profile. Recently, the UV converter was assembled and tested at NASA LaRC for pumping with the diode pumped Nd:YAG laser. With current spatial profile, the UV converter was made operational. Current efforts to maximize the nonlinear conversion efficiency by refining its spatial profile to match RISTRA OPO requirements are progressing.

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.

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.

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.

Stray light correction on array spectroradiometers for optical radiation risk assessment in the workplace.

PubMed

Barlier-Salsi, A

2014-12-01

The European directive 2006/25/EC requires the employer to assess and, if necessary, measure the levels of exposure to optical radiation in the workplace. Array spectroradiometers can measure optical radiation from various types of sources; however poor stray light rejection affects their accuracy. A stray light correction matrix, using a tunable laser, was developed at the National Institute of Standards and Technology (NIST). As tunable lasers are very expensive, the purpose of this study was to implement this method using only nine low power lasers; other elements of the correction matrix being completed by interpolation and extrapolation. The correction efficiency was evaluated by comparing CCD spectroradiometers with and without correction and a scanning double monochromator device as reference. Similar to findings recorded by NIST, these experiments show that it is possible to reduce the spectral stray light by one or two orders of magnitude. In terms of workplace risk assessment, this spectral stray light correction method helps determine exposure levels, with an acceptable degree of uncertainty, for the majority of workplace situations. The level of uncertainty depends upon the model of spectroradiometers used; the best results are obtained with CCD detectors having an enhanced spectral sensitivity in the UV range. Thus corrected spectroradiometers require a validation against a scanning double monochromator spectroradiometer before using them for risk assessment in the workplace.

UV diode-pumped solid state laser for medical applications

NASA Astrophysics Data System (ADS)

Apollonov, Victor V.; Konstantinov, K. V.; Sirotkin, A. A.

1999-07-01

A compact, solid-state, high-efficiency, and safe UV laser medical system with optical fiber output was created for treatment of destructive forms of pulmonary tuberculosis. A frequency-quadruped quasi-CW Nd:YVO4 laser system pumped by laser-diode array is investigated with various resonator configurations. A longitudinal end-pumping scheme was used in a compact acousto-optical Q-switched laser for producing stable pulses of UV radiation at the repetition frequency 10-20 kHz and the duration 7-10 ns with the fiber-guide output power exceeding 10 mW.

Near-infrared continuous-wave light driving a two-photon photochromic reaction with the assistance of localized surface plasmon.

PubMed

Tsuboi, Yasuyuki; Shimizu, Ryosuke; Shoji, Tatsuya; Kitamura, Noboru

2009-09-09

We demonstrate that a photochromic reaction can be driven by irradiation from a weak, near-infrared continuous-wave (NIR-CW) laser light. A two-photon ring-opening photochromic reaction of a diarylethene (DE) derivative can be induced by irradiation with a NIR-CW laser light (lambda = 808 nm). An ultrathin polymer film doped with DE in its closed form was coated onto a gold-nanoparticle-integrated glass substrate. Upon irradiation of the sample with a CW laser at low fluence (0.1-4.0 W/cm(2)), we could clearly observe bleaching of the DE (ring-opening reaction). Following the IR irradiation, the bleached absorption could be reversibly recovered by applying UV irradiation (ring-closing reaction). We verified that the yield of the photochromic ring-opening reaction of the DE was proportional to the square of the irradiation fluence. The origin of this NIR-CW-induced two-photon photochromic reaction is an "enhancing effect" that acts on the electromagnetic field (localized surface plasmon) of the gold nanoparticles. The DE interacts with the surface plasmon and receives energy from two photons, which excites it to a state from which the ring-opening reaction can be initiated.

Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring.

PubMed

Avci, Pinar; Gupta, Asheesh; Sadasivam, Magesh; Vecchio, Daniela; Pam, Zeev; Pam, Nadav; Hamblin, Michael R

2013-03-01

Low-level laser (light) therapy (LLLT) is a fast-growing technology used to treat a multitude of conditions that require stimulation of healing, relief of pain and inflammation, and restoration of function. Although skin is naturally exposed to light more than any other organ, it still responds well to red and near-infrared wavelengths. The photons are absorbed by mitochondrial chromophores in skin cells. Consequently, electron transport, adenosine triphosphate nitric oxide release, blood flow, reactive oxygen species increase, and diverse signaling pathways are activated. Stem cells can be activated, allowing increased tissue repair and healing. In dermatology, LLLT has beneficial effects on wrinkles, acne scars, hypertrophic scars, and healing of burns. LLLT can reduce UV damage both as a treatment and as a prophylactic measure. In pigmentary disorders such as vitiligo, LLLT can increase pigmentation by stimulating melanocyte proliferation and reduce depigmentation by inhibiting autoimmunity. Inflammatory diseases such as psoriasis and acne can also be managed. The noninvasive nature and almost complete absence of side effects encourage further testing in dermatology.

Coherent Spectroscopy of Ultra-Cold Mercury for the UV to VUV

DTIC Science & Technology

2015-11-20

clock. During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin...During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin. This...able  to  slowly  scan  the   UV   laser  system  to  locate  the  clock  transition   (using  the  standard  technique

Application of Time-Resolved Spectroscopies to the Study of Energetic Materials - 1982

DTIC Science & Technology

1983-05-24

fluores- cence intensity as a function of UV pulse energy, for individual laser shots. The lower curve shows the UV + probe induced fluorescence... intensity as a function of UV pulse energy, for individual laser shots. The lower curve shows the UV + probe Induced fluorescence, at 1 ns delay...locked Nd:YAG Laser Pulse ", Appl. Phys. Lett 26, 501-503 (1975). 97 43. A. J. Campillo, V. H. Kollman and S. L. Shapiro, " Intensity Dependence of

CITIUS: An infrared-extreme ultraviolet light source for fundamental and applied ultrafast science

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

Grazioli, C.; Gauthier, D.; Ivanov, R.

2014-02-15

We present the main features of CITIUS, a new light source for ultrafast science, generating tunable, intense, femtosecond pulses in the spectral range from infrared to extreme ultraviolet (XUV). The XUV pulses (about 10{sup 5}-10{sup 8} photons/pulse in the range 14-80 eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized by a time-preserving monochromator, also allowing one to work with high-resolution bandwidth selection. The tunable IR-UV pulses (10{sup 12}-10{sup 15} photons/pulse in the range 0.4-5.6 eV) are generated by an optical parametric amplifier, which is driven by a fraction of the same laser pulse thatmore » generates high order harmonics. The IR-UV and XUV pulses follow different optical paths and are eventually recombined on the sample for pump-probe experiments. We also present the results of two pump-probe experiments: with the first one, we fully characterized the temporal duration of harmonic pulses in the time-preserving configuration; with the second one, we demonstrated the possibility of using CITIUS for selective investigation of the ultra-fast dynamics of different elements in a magnetic compound.« less

Material Processing Opportunites Utilizing a Free Electron Laser

NASA Astrophysics Data System (ADS)

Todd, Alan

1996-11-01

Many properties of photocathode-driven Free Electron Lasers (FEL) are extremely attractive for material processing applications. These include: 1) broad-band tunability across the IR and UV spectra which permits wavelength optimization, depth deposition control and utilization of resonance phenomena; 2) picosecond pulse structure with continuous nanosecond spacing for optimum deposition efficiency and minimal collateral damage; 3) high peak and average radiated power for economic processing in quantity; and 4) high brightness for spatially defined energy deposition and intense energy density in small spots. We discuss five areas: polymer, metal and electronic material processing, micromachining and defense applications; where IR or UV material processing will find application if the economics is favorable. Specific examples in the IR and UV, such as surface texturing of polymers for improved look and feel, and anti-microbial food packaging films, which have been demonstrated using UV excimer lamps and lasers, will be given. Unfortunately, although the process utility is readily proven, the power levels and costs of lamps and lasers do not scale to production margins. However, from these examples, application specific cost targets ranging from 0.1=A2/kJ to 10=A2/kJ of delivered radiation at power levels from 10 kW to 500 kW, have been developed and are used to define strawman FEL processing systems. Since =46EL radiation energy extraction from the generating electron beam is typically a few percent, at these high average power levels, economic considerations dictate the use of a superconducting RF accelerator with energy recovery to minimize cavity and beam dump power loss. Such a 1 kW IR FEL, funded by the US Navy, is presently under construction at the Thomas Jefferson National Accelerator Facility. This dual-use device, scheduled to generate first light in late 1997, will test both the viability of high-power FELs for shipboard self-defense against cruise missiles, and for the first time, provide an industrial testbed capable of processing various materials in market evaluation quantities.

Quantitative Detection of Combustion Species using Ultra-Violet Diode Lasers

NASA Technical Reports Server (NTRS)

Pilgrim, J. S.; Peterson, K. A.

2001-01-01

Southwest Sciences is developing a new microgravity combustion diagnostic based on UV diode lasers. The instrument will allow absolute concentration measurements of combustion species on a variety of microgravity combustion platforms including the Space Station. Our approach uses newly available room temperature UV diode lasers, thereby keeping the instrument compact, rugged and energy efficient. The feasibility of the technique was demonstrated by measurement of CH radicals in laboratory flames. Further progress in fabrication technology of UV diode lasers at shorter wavelengths and higher power will result in detection of transient species in the deeper UV. High sensitivity detection of combustion radicals is provided with wavelength modulation absorption spectroscopy.

Ultraviolet light-absorbing and emitting diodes consisting of a p-type transparent-semiconducting NiO film deposited on an n-type GaN homoepitaxial layer

NASA Astrophysics Data System (ADS)

Nakai, Hiroshi; Sugiyama, Mutsumi; Chichibu, Shigefusa F.

2017-05-01

Gallium nitride (GaN) and related (Al,Ga,In)N alloys provide practical benefits in the production of light-emitting diodes (LEDs) and laser diodes operating in ultraviolet (UV) to green wavelength regions. However, obtaining low resistivity p-type AlN or AlGaN of large bandgap energies (Eg) is a critical issue in fabricating UV and deep UV-LEDs. NiO is a promising candidate for useful p-type transparent-semiconducting films because its Eg is 4.0 eV and it can be doped into p-type conductivity of sufficiently low resistivity. By using these technologies, heterogeneous junction diodes consisting of a p-type transparent-semiconducting polycrystalline NiO film on an n-type single crystalline GaN epilayer on a low threading-dislocation density, free-standing GaN substrate were fabricated. The NiO film was deposited by using the conventional RF-sputtering method, and the GaN homoepitaxial layer was grown by metalorganic vapor phase epitaxy. They exhibited a significant photovoltaic effect under UV light and also exhibited an electroluminescence peak at 3.26 eV under forward-biased conditions. From the conduction and valence band (EV) discontinuities, the NiO/GaN heterointerface is assigned to form a staggered-type (TYPE-II) band alignment with the EV of NiO higher by 2.0 eV than that of GaN. A rectifying property that is consistent with the proposed band diagram was observed in the current-voltage characteristics. These results indicate that polycrystalline NiO functions as a hole-extracting and injecting layer of UV optoelectronic devices.

Development of deep-ultraviolet metal vapor lasers

NASA Astrophysics Data System (ADS)

Sabotinov, Nikola V.

2004-06-01

Deep ultraviolet laser generation is of great interest in connection with both the development of new industrial technologies and applications in medicine, biology, chemistry, etc. The development of metal vapor UV lasers oscillating in the pulsed mode with high pulse repetition frequencies and producing high average output powers is of particular interest for microprocessing of polymers, photolithography and fluorescence applications. At present, metal vapor lasers generate deep-UV radiation on the base of two methods. The first method is non-linear conversion of powerful laser generation from the visible region into the deep ultraviolet region. The second method is direct UV laser action on ion and atomic transitions of different metals.

Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

NASA Astrophysics Data System (ADS)

Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

1997-12-01

The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

Elucidation of Free Radical and Optogalvanic Spectroscopy Associated with Microgravity Combustion via Conventional and Novel Laser Platforms

NASA Technical Reports Server (NTRS)

Misra, Prabhakar; She, Yong-Bo; Zhu, Xin-Ming; King, Michael

1997-01-01

Combustion studies under both normal gravity and microgravity conditions depend a great deal on the availability and quality of the diagnostic systems used for such investigations. Microgravity phenomena are specially susceptible to even small perturbations and therefore non-intrusive diagnostic techniques are of paramount importance for successful understanding of reduced-gravity combustion phenomena. Several non-intrusive diagnostic techniques are available for probing and delineating normal as well as reduced gravity combustion processes, such as Rayleigh scattering, Raman scattering, Mie scattering, velocimetry, interferometric and Schlieren techniques, emission and laser-induced fluorescence (LIF) spectroscopy. Our approach is to use the LIF technique as a non-intrusive diagnostic tool for the study of combustion-associated free radicals and use the concomitant optogalvanic transitions to accomplish precise calibration of the laser wavelengths used for recording the excitation spectra of transient molecular species. In attempting to perform spectroscopic measurements on chemical intermediates, we have used conventional laser sources as well as new and novel platforms employing rare-earth doped solid-state lasers. Conventional (commercially available) sources of tunable UV laser radiation are extremely cumbersome and energy-consuming devices that are not very suitable for either in-space or in-flight (or microgravity drop tower) experiments. Traditional LIF sources of tunable UV laser radiation involve in addition to a pump laser (usually a Nd:YAG laser with an attached frequency-doubling stage), a tunable dye laser. In turn, the dye laser has to be provided with a dye circulation system and a subsequent stage for frequency-doubling of the dye laser radiation, together with a servo-tuning system (termed the 'Autotracker') to follow the wavelength changes and also an optical system (called the 'Frequency Separator') for separation of the emanating visible and UV beams. In contrast to this approach, we have devised an alternate arrangement for recording LIF excitation spectra of free radicals (following appropriate precursor fragmentation) that utilizes a tunable rare-earth doped solid state laser system with direct UV pumping. We have designed a compact and portable tunable UV laser system incorporating features necessary for both in-space and in-flight spectroscopy experiments. For the purpose of LIF excitation, we have developed an all-solid-state tunable UV laser that employs direct pumping of the solid-state UV-active medium employing UV harmonics from a Nd:YAG laser. An optical scheme with counterpropagating photolysis and excitation beams focused by suitable lenses into a reaction vacuum chamber was employed.

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.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers.

PubMed

Arbabi, Amir; Briggs, Ryan M; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

2015-12-28

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. Here we report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventional UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M2=1.02.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers

DOE PAGES

Arbabi, Amir; Briggs, Ryan M.; Horie, Yu; ...

2015-01-01

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. We report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventionalmore » UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M² =1.02.« less

Vibrational spectra and structures of neutral Si(m)C(n) clusters (m + n = 6): sequential doping of silicon clusters with carbon atoms.

PubMed

Savoca, Marco; Lagutschenkov, Anita; Langer, Judith; Harding, Dan J; Fielicke, André; Dopfer, Otto

2013-02-14

Vibrational spectra of mixed silicon carbide clusters Si(m)C(n) with m + n = 6 in the gas phase are obtained by resonant infrared-vacuum-ultraviolet two-color ionization (IR-UV2CI for n ≤ 2) and density functional theory (DFT) calculations. Si(m)C(n) clusters are produced in a laser vaporization source, in which the silicon plasma reacts with methane. Subsequently, they are irradiated with tunable IR light from an IR free electron laser before they are ionized with UV photons from an F(2) laser. Resonant absorption of one or more IR photons leads to an enhanced ionization efficiency for Si(m)C(n) and provides the size-specific IR spectra. IR spectra measured for Si(6), Si(5)C, and Si(4)C(2) are assigned to their most stable isomers by comparison with calculated linear absorption spectra. The preferred Si(m)C(n) structures with m + n = 6 illustrate the systematic transition from chain-like geometries for bare C(6) to three-dimensional structures for bare Si(6). In contrast to bulk SiC, carbon atom segregation is observed already for the smallest n (n = 2).

An imaging system for PLIF/Mie measurements for a combusting flow

NASA Technical Reports Server (NTRS)

Wey, C. C.; Ghorashi, B.; Marek, C. J.; Wey, C.

1990-01-01

The equipment required to establish an imaging system can be divided into four parts: (1) the light source and beam shaping optics; (2) camera and recording; (3) image acquisition and processing; and (4) computer and output systems. A pulsed, Nd:YAG-pummped, frequency-doubled dye laser which can freeze motion in the flowfield is used for an illumination source. A set of lenses is used to form the laser beam into a sheet. The induced fluorescence is collected by an UV-enhanced lens and passes through an UV-enhanced microchannel plate intensifier which is optically coupled to a gated solid state CCD camera. The output of the camera is simultaneously displayed on a monitor and recorded on either a laser videodisc set of a Super VHS VCR. This videodisc set is controlled by a minicomputer via a connection to the RS-232C interface terminals. The imaging system is connected to the host computer by a bus repeater and can be multiplexed between four video input sources. Sample images from a planar shear layer experiment are presented to show the processing capability of the imaging system with the host computer.

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.

Ultraviolet Free Electron Laser Facility preliminary design report

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

Ben-Zvi, I.

1993-02-01

This document, the Preliminary Design Report (PDR) for the Brookhaven Ultraviolet Free Electron Laser (UV FEL) facility, describes all the elements of a facility proposed to meet the needs of a research community which requires ultraviolet sources not currently available as laboratory based lasers. Further, for these experiments, the requisite properties are not extant in either the existing second or upcoming third generation synchrotron light sources. This document is the result of our effort at BNL to identify potential users, determine the requirements of their experiments, and to design a facility which can not only satisfy the existing need, butmore » have adequate flexibility for possible future extensions as need dictates and as evolving technology allows. The PDR is comprised of three volumes. In this, the first volume, background for the development of the proposal is given, including descriptions of the UV FEL facility, and representative examples of the science it was designed to perform. Discussion of the limitations and potential directions for growth are also included. A detailed description of the facility design is then provided, which addresses the accelerator, optical, and experimental systems. Information regarding the conventional construction for the facility is contained in an addendum to volume one (IA).« less

A Solid State Ultraviolet Lasers Based on Cerium-Doped LiCaAIF(sub 6) Crystal Resonator

NASA Technical Reports Server (NTRS)

Yu, Nan; Le, Thanh; Schowalter, Steven J.; Rellergert, Wade; Jeet, Justin; Lin, Guoping; Hudson, Eric

2012-01-01

We report the first demonstration of a UV laser using a high-Q whispering gallery mode (WGM) resonator of Ce+: LiCaAlF6. We show that WGM resonators from LiCaAlF6 can achieve a Q of 2.6 x 10(sup 7) at UV. We demonstrated a UV laser at 290 nm with a pulsed pump laser at 266 nm. The experiments showed the low pump threshold intensity of 7.5 x 10(sup 9) W/m(sup 2) and slope efficiency of 25%. We have also observed lasing delay dynamics. These results are consistent with our modeling and theoretical estimates, and pave the way for a low threshold cw UV laser using WGM resonator cavity.

Daily light integral and day light quality: Potentials and pitfalls of nighttime UV treatments on cucumber powdery mildew.

PubMed

Suthaparan, Aruppillai; Solhaug, Knut Asbjørn; Stensvand, Arne; Gislerød, Hans Ragnar

2017-10-01

Nighttime ultraviolet (UV) radiation, if applied properly, has a significant potential for management of powdery mildews in many crop species. In this study, the role of growth light duration, irradiance, a combination of both (daily light integral) and light spectral quality (blue or red) on the efficacy of UV treatments against powdery mildew caused by Podosphaera xanthii and the growth performance of cucumber plants was studied in growth chambers. Increasing daily light integral provided by high-pressure sodium lamps (HPS) decreased efficacy of nighttime UV treatments against P. xanthii, but it increased plant growth. Furthermore, the efficacy of nighttime UV decreased when day length was increased from 16 to 20h at a constant daily light integral. The efficacy of nighttime UV increased if red light was applied after UV treatment, showing the possibility of day length extension without reducing the effect of UV. Increasing the dose of blue light during daytime reduced the efficacy of nighttime UV in controlling the disease, whereas blue deficient growth light (<6% of blue) caused UV mediated curling of young leaves. Furthermore, application of blue light after nighttime UV reduced its disease control efficacy. This showed the importance of maintaining a minimum of blue light in the growth light before nighttime UV treatment. Findings from this study showed that optimization of nighttime UV for management of powdery mildew is dependent on the spectral composition of the photosynthetically active radiation. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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.

Contamination and UV lasers: lessons learned

NASA Astrophysics Data System (ADS)

Daly, John G.

2015-09-01

Laser induced damage to optical elements has been a subject of significant research, development, and improvement, since the first lasers were built over the last 50 years. Better materials, with less absorption, impurities, and defects are available, as well as surface coatings with higher laser damage resistance. However, the presence of contamination (particles, surface deposition films, or airborne) can reduce the threshold for damage by several orders of magnitude. A brief review of the anticipated laser energy levels for damage free operation is presented as a lead into the problems associated with contamination for ultraviolet (UV) laser systems. As UV lasers become more common in applications especially in areas such as lithography, these problems have limited reliability and added to costs. This has been characterized as Airborne Molecular Contamination (AMC) in many published reports. Normal engineering guidelines such as screening materials within the optical compartment for low outgassing levels is the first step. The use of the NASA outgassing database (or similar test methods) with low Total Mass Loss (TML) and Condensed Collected Volatiles Collected Mass (CVCM) is a good baseline. Energetic UV photons are capable of chemical bond scission and interaction with surface contaminant or airborne materials results in deposition of obscuring film laser footprints that continue to degrade laser system performance. Laser systems with average powers less than 5 mW have been shown to exhibit aggressive degradation. Lessons learned over the past 15 years with UV laser contamination and steps to reduce risk will be presented.

Optofluidic FRET Lasers Using Aqueous Quantum Dots as Donors

PubMed Central

Chen, Qiushu; Kiraz, Alper; Fan, Xudong

2015-01-01

An optofluidic FRET (fluorescence resonance energy transfer) laser is formed by putting FRET pairs inside a microcavity acting as gain medium. This integration of optofluidic laser and FRET mechanism provides novel research frontiers, including sensitive biochemical analysis and novel photonic devices, such as on-chip coherent light sources and bio-tunable lasers. Here we investigated an optofluidic FRET laser using quantum dots (QDs) as FRET donors. We achieved lasing from Cy5 as the acceptor in the QD-Cy5 pair when excited at 450 nm where Cy5 has negligible absorption by itself. The threshold was approximately 14 µJ/mm2. The demonstrated capability of QDs as the donor in a FRET laser greatly improves the versatility of optofluidic laser operation due to the broad and large absorption cross section of QDs in the blue and UV spectral region. The excitation efficiency of the acceptor molecules through FRET channel was also analyzed, showing that the energy transfer rate and the non-radiative Auger recombination rate of QDs plays a significant role in FRET laser performance. PMID:26659274

Optofluidic FRET lasers using aqueous quantum dots as donors.

PubMed

Chen, Qiushu; Kiraz, Alper; Fan, Xudong

2016-01-21

An optofluidic FRET (fluorescence resonance energy transfer) laser is formed by putting FRET pairs inside a microcavity acting as a gain medium. This integration of an optofluidic laser and the FRET mechanism provides novel research frontiers, including sensitive biochemical analysis and novel photonic devices, such as on-chip coherent light sources and bio-tunable lasers. Here, we investigated an optofluidic FRET laser using quantum dots (QDs) as FRET donors. We achieved lasing from Cy5 as the acceptor in a QD-Cy5 pair upon excitation at 450 nm, where Cy5 has negligible absorption by itself. The threshold was approximately 14 μJ mm(-2). The demonstrated capability of QDs as donors in the FRET laser greatly improves the versatility of optofluidic laser operation due to the broad and large absorption cross section of the QDs in the blue and UV spectral regions. The excitation efficiency of the acceptor molecules through a FRET channel was also analyzed, showing that the energy transfer rate and the non-radiative Auger recombination rate of QDs play a significant role in FRET laser performance.

Molecular characterization of multivalent bioconjugates by size-exclusion chromatography with multiangle laser light scattering.

PubMed

Pollock, Jacob F; Ashton, Randolph S; Rode, Nikhil A; Schaffer, David V; Healy, Kevin E

2012-09-19

The degree of substitution and valency of bioconjugate reaction products are often poorly judged or require multiple time- and product-consuming chemical characterization methods. These aspects become critical when analyzing and optimizing the potency of costly polyvalent bioactive conjugates. In this study, size-exclusion chromatography with multiangle laser light scattering was paired with refractive index detection and ultraviolet spectroscopy (SEC-MALS-RI-UV) to characterize the reaction efficiency, degree of substitution, and valency of the products of conjugation of either peptides or proteins to a biopolymer scaffold, i.e., hyaluronic acid (HyA). Molecular characterization was more complete compared to estimates from a protein quantification assay, and exploitation of this method led to more accurate deduction of the molecular structures of polymer bioconjugates. Information obtained using this technique can improve macromolecular engineering design principles and help to better understand multivalent macromolecular interactions in biological systems.

Molecular characterization of multivalent bioconjugates by size-exclusion chromatography (SEC) with multi-angle laser light scattering (MALS)

PubMed Central

Pollock, Jacob F.; Ashton, Randolph S.; Rode, Nikhil A.; Schaffer, David V.; Healy, Kevin E.

2013-01-01

The degree of substitution and valency of bioconjugate reaction products are often poorly judged or require multiple time- and product- consuming chemical characterization methods. These aspects become critical when analyzing and optimizing the potency of costly polyvalent bioactive conjugates. In this study, size-exclusion chromatography with multi-angle laser light scattering was paired with refractive index detection and ultraviolet spectroscopy (SEC-MALS-RI-UV) to characterize the reaction efficiency, degree of substitution, and valency of the products of conjugation of either peptides or proteins to a biopolymer scaffold, i.e., hyaluronic acid (HyA). Molecular characterization was more complete compared to estimates from a protein quantification assay, and exploitation of this method led to more accurate deduction of the molecular structures of polymer bioconjugates. Information obtained using this technique can improve macromolecular engineering design principles and better understand multivalent macromolecular interactions in biological systems. PMID:22794081

Influence of the frequency of laser toning for melasma on occurrence of leukoderma and its early detection by ultraviolet imaging.

PubMed

Sugawara, Jun; Kou, Seiko; Kou, Sousei; Yasumura, Kazunori; Satake, Toshihiko; Maegawa, Jiro

2015-02-01

Laser "toning" with a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has recently been described to be effective for the treatment of melasma. Leukoderma is a refractory complication of laser toning for melasma, but it can be detected early with ultraviolet (UV) imaging. We assessed the relationship between leukoderma and the frequency or total number of laser toning sessions, as well as the effectiveness of UV imaging for detecting leukoderma. The subjects included 147 patients who received at least five laser toning sessions. Subjects were classified into three groups according to the frequency of treatment (weekly for Group A1, fortnightly for Group A2, and monthly for Group B), and the incidence of leukoderma was compared among the three groups. In patients who developed leukoderma, the interval between clinical diagnosis and leukoderma detection on UV images (obtained with a Visia Evolution during every laser toning session) was determined to evaluate the effectiveness of UV imaging for the early detection of leukoderma. The overall incidence of leukoderma was 2% (3/147 patients): 3.8% (1/26 patients) in Group A1, 4% (2/49 patients) in Group A2, and 0% (0/72 patients) in Group B. There were no significant differences in the incidence of leukoderma relative to the frequency of laser toning. In two of the three patients who developed leukoderma, it was diagnosed clinically at the 20th and 21st laser toning session, whereas it was diagnosed by UV imaging at the 12th and 13th session. In the remaining 1 patient, leukoderma was detected clinically and by UV imaging at the 7th session. There was no significant difference in the incidence of leukoderma related to the frequency of laser toning. This study showed that there are two types of leukoderma associated with laser toning. UV imaging was effective for the early detection of type 1 leukoderma, which seems to be related to the cumulative laser energy delivered, but not for detecting type 2 leukoderma, which may be due to direct phototoxicity. © 2015 Wiley Periodicals, Inc.

A combination of He-Ne laser irradiation and exogenous NO application efficiently protect wheat seedling from oxidative stress caused by elevated UV-B stress.

PubMed

Li, Yongfeng; Gao, Limei; Han, Rong

2016-12-01

The elevated ultraviolet-B (UV-B) stress induces the accumulation of a variety of intracellular reactive oxygen species (ROS), which seems to cause oxidative stress for plants. To date, very little work has been done to evaluate the biological effects of a combined treatment with He-Ne laser irradiation and exogenous nitric oxide (NO) application on oxidative stress resulting from UV-B radiation. Thus, our study investigated the effects of a combination with He-Ne laser irradiation and exogenous NO treatment on oxidative damages in wheat seedlings under elevated UV-B stress. Our data showed that the reductions in ROS levels, membrane damage parameters, while the increments in antioxidant contents and antioxidant enzyme activity caused by a combination with He-Ne laser and exogenous NO treatment were greater than those of each individual treatment. Furthermore, these treatments had a similar effect on transcriptional activities of plant antioxidant enzymes. This implied that the protective effects of a combination with He-Ne laser irradiation and exogenous NO treatment on oxidative stress resulting from UV-B radiation was more efficient than each individual treatment with He-Ne laser or NO molecule. Our findings might provide beneficial theoretical references for identifying some effective new pathways for plant UV-B protection.

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.

Hybrid 2D patterning using UV laser direct writing and aerosol jet printing of UV curable polydimethylsiloxane

NASA Astrophysics Data System (ADS)

Obata, Kotaro; Schonewille, Adam; Slobin, Shayna; Hohnholz, Arndt; Unger, Claudia; Koch, Jürgen; Suttmann, Oliver; Overmeyer, Ludger

2017-09-01

The hybrid technique of aerosol jet printing and ultraviolet (UV) laser direct writing was developed for 2D patterning of thin film UV curable polydimethylsiloxane (PDMS). A dual atomizer module in an aerosol jet printing system generated aerosol jet streams from material components of the UV curable PDMS individually and enables the mixing in a controlled ratio. Precise control of the aerosol jet printing achieved the layer thickness of UV curable PDMS as thin as 1.6 μm. This aerosol jet printing system is advantageous because of its ability to print uniform thin-film coatings of UV curable PDMS on planar surfaces as well as free-form surfaces without the use of solvents. In addition, the hybrid 2D patterning using the combination of UV laser direct writing and aerosol jet printing achieved selective photo-initiated polymerization of the UV curable PDMS layer with an X-Y resolution of 17.5 μm.

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.

Rectified photocurrent in a planar ITO/graphene/ITO photodetector on SiC by local irradiation of ultraviolet light

NASA Astrophysics Data System (ADS)

Yang, Junwei; Guo, Liwei; Huang, Jiao; Mao, Qi; Guo, Yunlong; Jia, Yuping; Peng, Tonghua; Chen, Xiaolong

2017-10-01

A rectified photocurrent behaviour is demonstrated in a simple planar structure of ITO-graphene-ITO formed on a SiC substrate when an ultraviolet (UV) light is locally incident on one of the edges between the graphene and ITO electrode. The photocurrent has similar characteristics as those of a vertical structure graphene/semiconductor junction photodiode, but is clearly different from those found in a planar structure metal-graphene-metal device. Furthermore, the device behaves multi-functionally as a photodiode with sensitive UV photodetection capability (responsivity of 11.7 mA W-1 at 0.3 V) and a self-powered UV photodetector (responsivity of 4.4 mA W-1 at zero bias). Both features are operative in a wide dynamic range and with a fast speed of response in about gigahertz. The linear I-V behaviour with laser power at forward bias and cutoff at reverse bias leads to a conceptual photodiode, which is compatible with modern semiconductor planar device architecture. This paves a potential way to realize ultrafast graphene planar photodiodes for monolithic integration of graphene-based devices on the same SiC substrate.

Ultrahigh-Speed Electrically Injected 1.55 micrometer Quantum Dot Microtube and Nanowire Lasers on Si

DTIC Science & Technology

2015-08-30

Ultrahigh-Speed Electrically Injected 1.55 um Quantum Dot Microtube and Nanowire Lasers on Si In this report, we describe the progress made in rolled...up InP-based tube lasers and in the growth and characterization of III-nitride nanowire structures on Si. We report on the demonstration of...injected AlGaN nanowire lasers that can operate in the UV-AII (315-340 nm), UV-B (280-315nm), and UV-C (200-280 nm). The views, opinions and/or findings

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.

Fast and slow UV-photoresponse in n-type GaN

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

Rocha, R.; Koynov, S.; Brogueira, P.

1999-07-01

The photocurrent decay in n-type GaN films prepared by low-pressure chemical vapor deposition (LPCVD) was measured in the ms-to-s time range using steady-state UV light and in the {micro}s time regime using short high-power pulses from higher harmonics of a Nd:YAG laser. A power law time dependence is observed with exponents ranging from {minus}0.1 to {minus}0.3, which is an indication of a broad distribution of trapping states inside the band gap. Combining Hall effect results and the magnitude of the initial slope of the photocurrent decay they estimate a mobility-lifetime product of 2.1 x 10{sup {minus}4} cm{sup 2}/V for photogeneratedmore » electrons at times below a few {micro}s. Slow transients might be a handicap for applications of GaN in UV detectors.« less

Improvement of UV electroluminescence of n-ZnO/p-GaN heterojunction LED by ZnS interlayer.

PubMed

Zhang, Lichun; Li, Qingshan; Shang, Liang; Wang, Feifei; Qu, Chong; Zhao, Fengzhou

2013-07-15

n-ZnO/p-GaN heterojunction light emitting diodes with different interfacial layers were fabricated by pulsed laser deposition. The electroluminescence (EL) spectra of the n-ZnO/p-GaN diodes display a broad blue-violet emission centered at 430 nm, whereas the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN devices exhibit ultraviolet (UV) emission. Compared with the AlN interlayer, which is blocking both electron and hole at hetero-interface, the utilization of ZnS as intermediate layer can lower the barrier height for holes and keep an effective blocking for electron. Thus, an improved UV EL intensity and a low turn-on voltage (~5V) were obtained. The results were studied by peak-deconvolution with Gaussian functions and were discussed using the band diagram of heterojunctions.

Contributions of visible and ultraviolet parts of sunlight to photoinhibition.

PubMed

Hakala-Yatkin, Marja; Mäntysaari, Mika; Mattila, Heta; Tyystjärvi, Esa

2010-10-01

Photoinhibition is light-induced inactivation of PSII, and action spectrum measurements have shown that UV light causes photoinhibition much more efficiently than visible light. In the present study, we quantified the contribution of the UV part of sunlight in photoinhibition of PSII in leaves. Greenhouse-grown pumpkin leaves were pretreated with lincomycin to block the repair of photoinhibited PSII, and exposed to sunlight behind a UV-permeable or UV-blocking filter. Oxygen evolution and Chl fluorescence measurements showed that photoinhibition proceeds 35% more slowly under the UV-blocking than under the UV-permeable filter. Experiments with a filter that blocks UV-B but transmits UV-A and visible light revealed that UV-A light is almost fully responsible for the UV effect. The difference between leaves illuminated through a UV-blocking and UV-transparent filter disappeared when leaves of field-grown pumpkin plants were used. Thylakoids isolated from field-grown and greenhouse-grown plants were equally sensitive to UV light, and measurements of UV-induced fluorescence from leaves indicated that the protection of the field-grown plants was caused by substances that block the passage of UV light to the chloroplasts. Thus, the UV part of sunlight, especially the UV-A part, is potentially highly important in photoinhibition of PSII but the UV-screening compounds of plant leaves may offer almost complete protection against UV-induced photoinhibition.

Comparison of UV-C and Pulsed UV Light Treatments for Reduction of Salmonella, Listeria monocytogenes, and Enterohemorrhagic Escherichia coli on Eggs.

PubMed

Holck, Askild L; Liland, Kristian H; Drømtorp, Signe M; Carlehög, Mats; McLEOD, Anette

2018-01-01

Ten percent of all strong-evidence foodborne outbreaks in the European Union are caused by Salmonella related to eggs and egg products. UV light may be used to decontaminate egg surfaces and reduce the risk of human salmonellosis infections. The efficiency of continuous UV-C (254 nm) and pulsed UV light for reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, and enterohemorrhagic Escherichia coli on eggs was thoroughly compared. Bacterial cells were exposed to UV-C light at fluences from 0.05 to 3.0 J/cm 2 (10 mW/cm 2 , for 5 to 300 s) and pulsed UV light at fluences from 1.25 to 18.0 J/cm 2 , resulting in reductions ranging from 1.6 to 3.8 log, depending on conditions used. Using UV-C light, it was possible to achieve higher reductions at lower fluences compared with pulsed UV light. When Salmonella was stacked on a small area or shielded in feces, the pulsed UV light seemed to have a higher penetration capacity and gave higher bacterial reductions. Microscopy imaging and attempts to contaminate the interior of the eggs with Salmonella through the eggshell demonstrated that the integrity of the eggshell was maintained after UV light treatments. Only minor sensory changes were reported by panelists when the highest UV doses were used. UV-C and pulsed UV light treatments appear to be useful decontamination technologies that can be implemented in continuous processing.

Effect of UV irradiation on the apoptosis and necrosis of Jurkat cells using UV LEDs

NASA Astrophysics Data System (ADS)

Inada, Shunko A.; Amano, Hiroshi; Akasaki, Isamu; Morita, Akimichi; Kobayashi, Keiko

2009-02-01

Phototherapy is a very effective method for treating most of the incurable skin diseases. A fluorescent light bulb is used as a conventional UV light source for this type of therapy. However, infrared radiation from the light source sometimes causes serious problems on patient's health. In addition, the normal part of the skin is irradiated when a large fluorescent light bulb is used. Moreover, a conventional UV irradiation system is heavy and has a short lifetime and a high electrical power consumption. Therefore, a new UV light source for solving the problems of phototherapy is required. To realize low-power-consumption, lightweight and long-lifetime systems, group III nitride-based UV-A1 light-emitting diodes (LEDs) were investigated. We examined the UV LED irradiation of Jurkat cell, which is a tumor cell and more sensitive to UV light than a healthy cell. The numbers of apoptotic and necrotic cells were confirmed to be the same using a UV LED and a conventional lamp system. The UV LED showed the possibility of realizing a new UV light source for phototherapy.

Two-Step Processes and IR Recording in Photorefractive Crystals

NASA Astrophysics Data System (ADS)

Kraetzig, Eckhard; Buse, Karsten

Two-step excitation processes have been used for hologram storage in photorefractive crystals. By this means the interference pattern can be formed with red or near-IR light and nondestructive readout of information is possible. Often shallow levels are involved in the holographic recording process in photorefractive crystals. The shallow levels can be populated by illumination with visible or UV pulses forming states with relatively long lifetimes, thus sensitizing the crystals for holographic recording with IR pulses. In LiNbO3 and LiTaO3 the most important shallow levels have been identified. They result from NbLi^5+ and TaLi^5+ antisite defects (Nb5+ or Ta5+ on Li+ site). The crystals can also be pre-illuminated with visible light from a cw argon laser or a xenon lamp and holograms can be recorded with red light from a laser diode. The sensitization process is possible for other photorefractive crystals, too. The holograms can be read nondestructively with IR light and can be erased with green light. The hologram lifetime is limited by electron tunneling or by an ionic conductivity. Lifetimes up to years can be achieved. Recording of components for telecommunication applications with IR light allows one to create reconfigurable and thus more versatile devices.

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.

Thermal distribution in biological tissue at laser induced fluorescence and photodynamic therapy

NASA Astrophysics Data System (ADS)

Krasnikov, I. V.; Seteikin, A. Yu.; Drakaki, E.; Makropoulou, M.

2012-03-01

Laser induced fluorescence spectroscopy and photodynamic therapy (PDT) are techniques currently introduced in clinical applications for visualization and local destruction of malignant tumours as well as premalignant lesions. During the laser irradiation of tissues for the diagnostic and therapeutic purposes, the absorbed optical energy generates heat, although the power density of the treatment light for surface illumination is normally low enough not to cause any significantly increased tissue temperature. In this work we tried to evaluate the utility of Monte Carlo modeling for simulating the temperature fields and the dynamics of heat conduction into the skin tissue under several laser irradiation conditions with both a pulsed UV laser and a continuous wave visible laser beam. The analysis of the results showed that heat is not localized on the surface, but it is collected inside the tissue. By varying the boundary conditions on the surface and the type of the laser radiation (continuous or pulsed) we can reach higher than normal temperature inside the tissue without simultaneous formation of thermally damaged tissue (e.g. coagulation or necrosis zone).

Optical system for UV-laser technological equipment

NASA Astrophysics Data System (ADS)

Fedosov, Yuri V.; Romanova, Galina E.; Afanasev, Maxim Ya.

2017-09-01

Recently there has been an intensive development of intelligent industrial equipment that is highly automated and can be rapidly adjusted for certain details. This equipment can be robotics systems, automatic wrappers and markers, CNC machines and 3D printers. The work equipment considered is the system for selective curing of photopolymers using a UV-laser and UV-radiation in such equipment that leads to additional technical difficulties. In many cases for transporting the radiation from the laser to the point processed, a multi-mirror system is used: however, such systems are usually difficult to adjust. Additionally, such multi-mirror systems are usually used as a part of the equipment for laser cutting of metals using high-power IR-lasers. For the UV-lasers, using many mirrors leads to crucial radiation losses because of many reflections. Therefore, during the development of the optical system for technological equipment using UV-laser we need to solve two main problems: to transfer the radiation for the working point with minimum losses and to include the system for controlling/handling the radiation spot position. We introduce a system for working with UV-lasers with 450mW of power and a wavelength of 0.45 μm based on a fiber system. In our modelling and design, we achieve spot sizes of about 300 μm, and the designed optical and mechanical systems (prototypes) were manufactured and assembled. In this paper, we present the layout of the technological unit, the results of the theoretical modelling of some parts of the system and some experimental results.

UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry in the diagnostics of alopecia

NASA Astrophysics Data System (ADS)

Skomorokha, Diana P.; Pigoreva, Yulia N.; Salmin, Vladimir V.

2016-04-01

Development of optical biopsy methods has a great interest for medical diagnostics. In clinical and experimental studies it is very important to analyze blood circulation quickly and accurately, thereby laser Doppler flowmetry (LDF) is widely used. UV laser-induced fluorescence spectroscopy (UV LIFS) is express highly sensitive and widely-spread method with no destructive impact, high excitation selectivity and the possibility to use in highly scattering media. The goal of this work was to assess a correlation of UV laser-induced fluorescence spectroscopy and laser Doppler flowmetry parameters, and a possibility to identify or to differentiate various types of pathological changes in tissues according to their autofluorescence spectra. Three groups of patients with diffuse (symptomatic) alopecia, androgenic alopecia, and focal alopecia have been tested. Each groups consisted of not less than 20 persons. The measurements have been done in the parietal and occipital regions of the sculls. We used the original automated spectrofluorimeter to record autofluorescence spectra, and standard laser Doppler flowmeter BLF-21 (Transonic Systems, Inc., USA) to analyze the basal levels of blood circulation. Our results show that UV LIFS accurately distinguishes the zones with different types of alopecia. We found high correlation of the basal levels of blood circulation and the integrated intensity of autofluorescence in the affected tissue.

Use of near infrared femtosecond lasers as sub-micron radiation microbeam for cell DNA damage and repair studies.

PubMed

Botchway, S W; Reynolds, P; Parker, A W; O'Neill, P

2010-01-01

Laser induced radiation microbeam technology for radiobiology research is undergoing rapid growth because of the increased availability and ease of use of femtosecond laser sources. The main processes involved are multiphoton absorption and/or plasma formation. The high peak powers these lasers generate make them ideal tools for depositing sub-micrometer size radiant energy within a region of a living cell nucleus to activate ionising and/or photochemically driven processes. The technique allows questions relating to the effects of low doses of radiation, the propagation and treatment of deoxyribonucleic acid (DNA) damage and repair in individual live cells as well as non-targeted cell to cell effects to be addressed. This mini-review focuses on the use of near infrared (NIR) ca. 800nm radiation to induce damage that is radically different from the early and subsequent ultraviolet microbeam techniques. Ultrafast pulsed NIR instrumentation has many benefits including the ability to eliminate issues of unspecific UV absorption by the many materials prevalent within cells. The multiphoton interaction volume also permits energy deposition beyond the diffraction limit. Work has established that the fundamental process of the damage induced by the ultrashort laser pulses is different to those induced from continuous wave light sources. Pioneering work has demonstrated that NIR laser microbeam radiation can mimic ionising radiation via multiphoton absorption within the 3D femtolitre volume of the highly focused Gaussian beam. This light-matter interaction phenomenon provides a novel optical microbeam probe for mimicking both complex ionising and UV radiation-type cell damage including double strand breaks (DSBs) and base damage. A further advantage of the pulsed laser technique is that it provides further scope for time-resolved experiments. Recently the NIR laser microbeam technique has been used to investigate the recruitment of repair proteins to the sub-micrometre size area of damage in viable cells using both immuno-fluorescent staining of gamma-H2AX (a marker for DSBs) and real-time imaging of GFP-labelled repair proteins including ATM, p53 binding protein 1 (53BP1), RAD51 and Ku 70/80 to elucidate the interaction of the two DNA DSB repair pathways, homologous recombination and the non-homologous end joining pathway. 2010 Elsevier B.V. All rights reserved.

DNA Damage in Bone Marrow Cells Induced by Femtosecond and Nanosecond Ultraviolet Laser Pulses.

PubMed

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

2015-12-01

The purpose of this study was to investigate the possible genotoxic impact of new generation 205 nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro, and to compare the DNA damage caused by both femtosecond and nanosecond UV laser pulses. Recent experiments of corneal stromal ablation in vitro and in vivo applying femtosecond UV pulses showed results comparable with or superior to those obtained using nanosecond UV lasers. However, the possible genotoxic effect of ultrashort laser pulses was not investigated. Mouse bone marrow cells were exposed to different doses of 205 nm femtosecond, 213 and 266 nm nanosecond lasers, and 254 nm UV lamp irradiation. The comet assay was used for the evaluation of DNA damage. All types of irradiation demonstrated intensity-dependent genotoxic impact. The DNA damage induced depended mainly upon wavelength rather than on other parameters such as pulse duration, repetition rate, or beam delivery to a target. Both 205 nm femtosecond and clinically applied 213 nm nanosecond lasers' pulses induced a comparable amount of DNA breakage in cells exposed to the same irradiation dose. To further evaluate the suitability of femtosecond UV laser sources for microsurgery, a separate investigation of the genotoxic and mutagenic effects on corneal cells in vitro and, particularly, in vivo is needed.

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.

Green synthesis of chondroitin sulfate-capped silver nanoparticles: characterization and surface modification.

PubMed

Cheng, Kuang-ming; Hung, Yao-wen; Chen, Cheng-cheung; Liu, Cheng-che; Young, Jenn-jong

2014-09-22

A one-step route for the green synthesis of highly stable and nanosized silver metal particles with narrow distribution is reported. In this environmentally friendly synthetic method, silver nitrate was used as silver precursor and biocompatible chondroitin sulfate (ChS) was used as both reducing agent and stabilizing agent. The reaction was carried out in a stirring aqueous medium at the room temperature without any assisted by microwave, autoclave, laser irradiation, γ-ray irradiation or UV irradiation. The transparent colorless solution was converted to the characteristics light red then deep red-brown color as the reaction proceeds, indicating the formation of silver nanoparticles (Ag NPs). The Ag NPs were characterized by UV-visible spectroscopy (UV-vis), photon correlation spectroscopy, laser Doppler anemometry, transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that the obtained metallic nanoparticles were Ag NPs capped with ChS. In this report, dynamic light scattering (DLS) was used as a routinely analytical tool for measuring size and distribution in a liquid environment. The effects of the reaction time, reaction temperature, concentration and the weight ratio of ChS/Ag+ on the particle size and zeta potential were investigated. The TEM image clearly shows the morphology of the well-dispersed ChS-capped Ag NPs are spherical in shape, and the average size (<20 nm) is much smaller than the Z-average value (76.7 nm) measured by DLS. Meanwhile, the ChS-capped Ag NPs coated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) were prepared by an ionic gelation method and the surface charge of Ag NPs was switched from negative to positive. Copyright © 2014 Elsevier Ltd. All rights reserved.

Performance Assessment of a Plate Beam Splitter for Deep-Ultraviolet Raman Measurements with a Spatial Heterodyne Raman Spectrometer.

PubMed

Lamsal, Nirmal; Angel, S Michael

2017-06-01

In earlier works, we demonstrated a high-resolution spatial heterodyne Raman spectrometer (SHRS) for deep-ultraviolet (UV) Raman measurements, and showed its ability to measure UV light-sensitive compounds using a large laser spot size. We recently modified the SHRS by replacing the cube beam splitter (BS) with a custom plate beam splitter with higher light transmission, an optimized reflectance/transmission ratio, higher surface flatness, and better refractive index homogeneity than the cube beam splitter. Ultraviolet Raman measurements were performed using a SHRS modified to use the plate beam splitter and a matching compensator plate and compared to the previously described cube beam splitter setup. Raman spectra obtained using the modified SHRS exhibit much higher signals and signal-to-noise (S/N) ratio and show fewer spectral artifacts. In this paper, we discuss the plate beam splitter SHRS design features, the advantages over previous designs, and discuss some general SHRS issues such as spectral bandwidth, S/N ratio characteristics, and optical efficiency.

Emerging Endoscopic Imaging Technologies for Bladder Cancer Detection

PubMed Central

Lopez, Aristeo; Liao, Joseph C.

2014-01-01

Modern urologic endoscopy is the result of continuous innovations since early 19th century. White light cystoscopy is the primary strategy for identification, resection, and local staging of bladder cancer. While highly effective, white light cystoscopy has several well-recognized shortcomings. Recent advances in optical imaging technologies and device miniaturization hold the potential to improve bladder cancer diagnosis and resection. Photodynamic diagnosis and narrow band imaging are the first to enter the clinical arena. Confocal laser endomicroscopy, optical coherence tomography, Raman spectroscopy, UV autofluorescence, and others have shown promising clinical and pre-clinical feasibility. We review their mechanisms of action, highlight their respective advantages, and propose future directions. PMID:24658832

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

Plasma ignition thresholds in UV laser ablation plumes

NASA Astrophysics Data System (ADS)

Clarke, P.; Dyer, P. E.; Key, P. H.; Snelling, H. V.

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of 10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.

A SYNCHRONIZED FIR/VUV LIGHT SOURCE AT JEFFERSON LAB

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

Stephen Benson, David Douglas, George Neil, Michelle D. Shinn, Gwyn Williams

We describe a dual free-electron laser (FEL) configuration on the UV Demo FEL at Jefferson Lab that allows simultaneous lasing at FIR/THz and UV wavelengths. The FIR/THz source would be an FEL oscillator with a short wiggler providing nearly diffraction-limited pulses with pulse energy exceeding 50 microJoules. The FIR source would use the exhaust beam from a UVFEL. The coherent harmonics in the VUV from the UVFEL are out-coupled through a hole. The FIR source uses a shorter resonator with either hole or edge coupling to provide very high power FIR pulses. Simulations indicate excel-lent spectral brightness in the FIRmore » region with over 100 W/cm-1 output.« less

Photon-induced formation of CdS nanocrystals in selected areas of polymer matrices

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

Athanassiou, Athanassia; Cingolani, Roberto; Tsiranidou, Elsa

2007-10-08

We demonstrate light-induced formation of semiconductor quantum dots in TOPAS registered polymer matrix with very high control of their size and their spatial localization. Irradiation with UV laser pulses of polymer films embedding Cd thiolate precursors results in the formation of cadmium sulfide nanocrystals well confined in the irradiation area, through a macroscopically nondestructive procedure for the host matrix. With increasing number of laser pulses, we accomplish the formation of nanoparticles with gradually increasing dimensions, resulting in the dynamic change of the spectra emitted by the formed nanocomposite areas. The findings are supported by x-ray diffraction and transmission electron microscopymore » measurements.« less

The spectroscopy of singlets and triplets excites electronic states, spatial and electronic structure of hydrocarbons and quantum classifications in chemmotology

NASA Astrophysics Data System (ADS)

Obukhov, A. E.

2017-01-01

In this work we demonstrate the physical foundations of the spectroscopy of the grounds states: E- and X-ray, (RR) Raman scattering the NMR 1H and 13C and IR-, EPR- absorption and the singlets and triplets electronic excited states in the multinuclear hydrocarbons in chemmotology. The parameters of UV-absorption, RR-Raman scattering of light, the fluorescence and the phosphorescence and day-lasers at the pumping laser and lamp, OLEDs and OTETs- are measurements. The spectral-energy properties are briefly studied. The quantum-chemical LCAO-MO SCF expanded-CI PPP/S and INDO/S methods in the electronic and spatial structure hidrocarbons are considered.

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.

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.

Reliability, Durability and Packaging of Fibre Bragg Gratings for Large-Scale Structural Health Monitoring of Defence Platforms

DTIC Science & Technology

2013-08-01

thermoset system designed to achieve good wetting , high-strength and low-creep adhesion. Many commercially-available adhesives were sourced and...Bragg grating: 1. Removal of the fibre coating. 2. Photosensitization of the fibre. 3. Exposure of the grating to UV laser light. 4. Annealing and...molecular hydrogen loading (H2 loading) in a heated pressure vessel . Photosensitisation results in a stronger refractive index contrast for a given

Significance of Retinal Lesions Potentially Caused by Dazzling Lasers

DTIC Science & Technology

2015-12-01

Refractive eye surgery (e.g., LASIK and PRK ) exploit this property of UV light to reshape the cornea with great precision (Barkana and Belkin 2000). 39...response, perimetry tests document the boundaries between seeing vs . not seeing the target to produce a drawing of the visual field (Broadway 2012). Figure...8 shows an example of the perimetry test results. The curves drawn are known as “isopters” and represent boundaries between seeing vs . not seeing

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.

Production of organic compounds in plasmas: A comparison among electric sparks, laser-induced plasmas and UV light

NASA Technical Reports Server (NTRS)

Scattergood, T. W.; Mckay, C. P.; Borucki, W. J.; Giver, L. P.; Vanghyseghem, H.; Parris, J. E.; Miller, S. L.

1991-01-01

In order to study the production of organic compounds in plasmas (and shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple hydrocarbons were measured and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the yields of C2H6 and other hydrocarbons were much higher than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The results of these experiments demonstrate that, in addition to the well-known efficient synthesis of organic compounds in plasmas, the yields of saturated species, e.g., ethane, may be higher than predicted by theory and that LIP provide a convenient and clean way of simulating planetary lightning and impact plasmas in the laboratory.

Penetration of UV-A, UV-B, blue, and red light into leaf tissues of pecan measured by a fiber optic microprobe system

NASA Astrophysics Data System (ADS)

Qi, Yadong; Bai, Shuju; Vogelmann, Thomas C.; Heisler, Gordon M.

2003-11-01

The depth of light penetration from the adaxial surfaces of the mature leaves of pecan (Carya illinoensis) was measured using a fiber optic microprobe system at four wavelengths: UV-B (310nm), UV-A (360 nm), blue light (430nm), and red light (680nm). The average thickness of the leaf adaxial epidermal layer was 15um and the total leaf thickness was 219um. The patterns of the light attenuation by the leaf tissues exhibited strong wavelength dependence. The leaf adaxial epidermal layer was chiefly responsible for absorbing the UV-A UV-B radiation. About 98% of 310 nm light was steeply attenuated within the first 5 um of the adaxial epidermis; thus, very little UV-B radiation was transmitted to the mesophyll tissues where contain photosynthetically sensitive sites. The adaxial epidermis also attenuated 96% of the UV-A radiation. In contrast, the blue and red light penetrated much deeper and was gradually attenutated by the leaves. The mesophyll tissues attenuated 17% of the blue light and 42% of the red light, which were available for photosynthesis use. Since the epidermal layer absorbed nearly all UV-B light, it acted as an effective filter screening out the harmful radiation and protecting photosynthetically sensitive tissues from the UV-B damage. Therefore, the epidermal function of the UV-B screening effectiveness can be regarded as one of the UV-B protection mechanisms in pecan.

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.

Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring

PubMed Central

Avci, Pinar; Gupta, Asheesh; Sadasivam, Magesh; Vecchio, Daniela; Pam, Zeev; Pam, Nadav; Hamblin, Michael R

2013-01-01

Low-level laser (light) therapy (LLLT) is a fast-growing technology used to treat a multitude of conditions that require stimulation of healing, relief of pain and inflammation, and restoration of function. Although the skin is the organ that is naturally exposed to light more than any other organ, it still responds well to red and near-infrared wavelengths. The photons are absorbed by mitochondrial chromophores in skin cells. Consequently electron transport, adenosine triphosphate (ATP) nitric oxide release, blood flow, reactive oxygen species increase and diverse signaling pathways get activated. Stem cells can be activated allowing increased tissue repair and healing. In dermatology, LLLT has beneficial effects on wrinkles, acne scars, hypertrophic scars, and healing of burns. LLLT can reduce UV damage both as a treatment and as a prophylaxis. In pigmentary disorders such as vitiligo, LLLT can increase pigmentation by stimulating melanocyte proliferation and reduce depigmentation by inhibiting autoimmunity. Inflammatory diseases such as psoriasis and acne can also benefit. The non-invasive nature and almost complete absence of side-effects encourages further testing in dermatology. PMID:24049929

Non-Destructive and Discriminating Identification of Illegal Drugs by Transient Absorption Spectroscopy in the Visible and Near-IR Wavelength Range

NASA Astrophysics Data System (ADS)

Sato, Chie; Furube, Akihiro; Katoh, Ryuzi; Nonaka, Hidehiko; Inoue, Hiroyuki

2008-11-01

We have tested the possibility of identifying illegal drugs by means of nanosecond transient absorption spectroscopy with a 10-ns UV-laser pulse for the excitation light and visible-to-near-IR light for the probe light. We measured the transient absorption spectra of acetonitrile solutions of d-methamphetamine, dl-3,4-methylenedioxymethamphetamine hydrochloride (MDMA), and dl-N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine hydrochloride (MBDB), which are illegal drugs widely consumed in Japan. Transient absorption signals of these drugs were observed between 400 and 950 nm, a range in which they are transparent in the ground state. By analyzing the spectra in terms of exponential and Gaussian functions, we could identify the drugs and discriminate them from chemical substances having similar structures. We propose that transient absorption spectroscopy will be a useful, non-destructive method of inspecting for illegal drugs, especially when they are dissolved in liquids. Such a method may even be used for drugs packed in opaque materials if it is further extended to utilize intense femtosecond laser pulses.

An estimation methode for measurement of ultraviolet radiation during nondestructive testing

NASA Astrophysics Data System (ADS)

Hosseinipanah, M.; Movafeghi, A.; Farvadin, D.

2018-04-01

Dye penetrant testing and magnetic particle testing are among conventional NDT methods. For increased sensitivity, fluorescence dyes and particles can be used with ultraviolet (black) lights. UV flaw detection lights have different spectra. With the help of photo-filters, the output lights are transferred to UV-A and visible zones. UV-A light can be harmful to human eyes in some conditions. In this research, UV intensity and spectrum were obtained by a Radio-spectrometer for two different UV flaw detector lighting systems. According to the standards such as ASTM E709, UV intensity must be at least 10 W/m2 at a distance of 30 cm. Based on our measurements; these features not achieved in some lamps. On the other hand, intensity and effective intensity of UV lights must be below the some limits for prevention of unprotected eye damage. NDT centers are usually using some type of UV measuring devices. A method for the estimation of effective intensity of UV light has been proposed in this research.

New down-converter for UV-stable perovskite solar cells: Phosphor-in-glass

NASA Astrophysics Data System (ADS)

Roh, Hee-Suk; Han, Gill Sang; Lee, Seongha; Kim, Sanghyun; Choi, Sungwoo; Yoon, Chulsoo; Lee, Jung-Kun

2018-06-01

Degradation of hybrid lead halide perovskite by UV light is a crucial issue that limits the commercialization of lead halide perovskite solar cells (PSCs). To address this problem, phosphor-in-glass (PiG) is used to convert UV to visible light. Down-conversion of UV light by PiG dramatically increases UV-stability of PSCs and enables PSCs to harvest UV light that is currently wasted. Performance of PSCs with PiG layer does not change significantly during 100 h-long UV-irradiation, while conventional PSCs degrade quickly by 1 h-long UV-irradiation. After 100 h long UV-irradiation, power conversion efficiency of PSCs with PiG is 440% larger than that of conventional PSCs. This result points a direction toward PSCs which are very stable and highly efficient under UV light.

Carcinogenic damage to deoxyribonucleic acid is induced by near-infrared laser pulses in multiphoton microscopy via combination of two- and three-photon absorption

NASA Astrophysics Data System (ADS)

Nadiarnykh, Oleg; Thomas, Giju; Van Voskuilen, Johan; Sterenborg, Henricus J. C. M.; Gerritsen, Hans C.

2012-11-01

Nonlinear optical imaging modalities (multiphoton excited fluorescence, second and third harmonic generation) applied in vivo are increasingly promising for clinical diagnostics and the monitoring of cancer and other disorders, as they can probe tissue with high diffraction-limited resolution at near-infrared (IR) wavelengths. However, high peak intensity of femtosecond laser pulses required for two-photon processes causes formation of cyclobutane-pyrimidine-dimers (CPDs) in cellular deoxyribonucleic acid (DNA) similar to damage from exposure to solar ultraviolet (UV) light. Inaccurate repair of subsequent mutations increases the risk of carcinogenesis. In this study, we investigate CPD damage that results in Chinese hamster ovary cells in vitro from imaging them with two-photon excited autofluorescence. The CPD levels are quantified by immunofluorescent staining. We further evaluate the extent of CPD damage with respect to varied wavelength, pulse width at focal plane, and pixel dwell time as compared with more pronounced damage from UV sources. While CPD damage has been expected to result from three-photon absorption, our results reveal that CPDs are induced by competing two- and three-photon absorption processes, where the former accesses UVA absorption band. This finding is independently confirmed by nonlinear dependencies of damage on laser power, wavelength, and pulse width.

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

Excimer laser beam delivery systems for medical applications

NASA Astrophysics Data System (ADS)

Kubo, Uichi; Hashishin, Yuichi; Okada, Kazuyuki; Tanaka, Hiroyuki

1993-05-01

We have been doing the basic experiments of UV laser beams and biotissue interaction with both KrF and XeCl lasers. However, the conventional optical fiber can not be available for power UV beams. So we have been investigating about UV power beam delivery systems. These experiments carry on with the same elements doped quartz fibers and the hollow tube. The doped elements are OH ion, chlorine and fluorine. In our latest work, we have tried ArF excimer laser and biotissue interactions, and the beam delivery experiments. From our experimental results, we found that the ArF laser beam has high incision ability for hard biotissue. For example, in the case of the cow's bone incision, the incision depth by ArF laser was ca.15 times of KrF laser. Therefore, ArF laser would be expected to harden biotissue therapy as non-thermal method. However, its beam delivery is difficult to work in this time. We will develop ArF laser beam delivery systems.

Spectroscopic investigations of novel pharmaceuticals: Stability and resonant interaction with laser beam

NASA Astrophysics Data System (ADS)

Smarandache, Adriana; Boni, Mihai; Andrei, Ionut Relu; Handzlik, Jadwiga; Kiec-Kononowicz, Katarzyna; Staicu, Angela; Pascu, Mihail-Lucian

2017-09-01

This paper presents data about photophysics of two novel thio-hydantoins that exhibit promising pharmaceutical properties in multidrug resistance control. Time stability studies are necessary to establish the proper use of these compounds in different applications. As for their administration as drugs, it is imperative to know their shelf life, as well as storage conditions. At the same time, laser induced modified properties of the two new compounds are valuable to further investigate their specific interactions with other materials, including biological targets. The two new thio-hydantoins under generic names SZ-2 and SZ-7 were prepared as solutions in dimethyl sulfoxide at different concentrations, as well as in deionised water. For the stability assay they were kept in various light/temperature conditions up to 60 days. The stability was estimates based on UV-vis absorption measurements. The samples in bulk shape were exposed different time intervals to laser radiation emitted at 266 nm as the fourth harmonic of a Nd:YAG laser. The resonant interaction of the studied compounds with laser beams was analysed through spectroscopic methods UV-vis and FTIR absorption, as well as laser induced fluorescence spectroscopy. As for stability assay, only solutions kept in dark at 4 °C have preserved the absorption characteristics, considering the cumulated measuring errors, less than one week. The vibrational changes that occur in their FTIR and modified fluorescence spectra upon laser beam exposure are also discussed. A result of the experimental analysis is that modifications are induced in molecular structures of the investigated compounds by resonant interaction with laser radiation. This fact evidences that the molecules are photoreactive and their characteristics might be shaped through controlled laser radiation exposure using appropriate protocols. This conclusion opens many opportunities both in the biomedical field, but also in other industrial activities involving the use of hydantoins.

Fungal Gene Mutation Analysis Elucidating Photoselective Enhancement of UV-C Disinfection Efficiency Toward Spoilage Agents on Fruit Surface.

PubMed

Zhu, Pinkuan; Li, Qianwen; Azad, Sepideh M; Qi, Yu; Wang, Yiwen; Jiang, Yina; Xu, Ling

2018-01-01

Short-wave ultraviolet (UV-C) treatment represents a potent, clean and safe substitute to chemical sanitizers for fresh fruit preservation. However, the dosage requirement for microbial disinfection may have negative effects on fruit quality. In this study, UV-C was found to be more efficient in killing spores of Botrytis cinerea in dark and red light conditions when compared to white and blue light. Loss of the blue light receptor gene Bcwcl1 , a homolog of wc-1 in Neurospora crassa , led to hypersensitivity to UV-C in all light conditions tested. The expression of Bcuve1 and Bcphr1 , which encode UV-damage endonuclease and photolyase, respectively, were strongly induced by white and blue light in a Bcwcl1 -dependent manner. Gene mutation analyses of Bcuve1 and Bcphr1 indicated that they synergistically contribute to survival after UV-C treatment. In vivo assays showed that UV-C (1.0 kJ/m 2 ) abolished decay in drop-inoculated fruit only if the UV-C treatment was followed by a dark period or red light, while in contrast, typical decay appeared on UV-C irradiated fruits exposed to white or blue light. In summary, blue light enhances UV-C resistance in B. cinerea by inducing expression of the UV damage repair-related enzymes, while the efficiency of UV-C application for fruit surface disinfection can be enhanced in dark or red light conditions; these principles seem to be well conserved among postharvest fungal pathogens.

Fabrication et applications des reseaux de Bragg ultra-longs

NASA Astrophysics Data System (ADS)

Gagne, Mathieu

This thesis presents the principal accomplishments realized during the PhD project. The thesis is presented by publication format and is a collection of four published articles having fiber Bragg gratings as a central theme. First achieved in 1978, UV writing of fiber Bragg gratings is nowadays a common and mature technology being present in both industry and academia. The property of reflecting light guided by optical fibers lead to diverse applications in telecommunication, lasers as well as several types of sensors. The conventional fabrication technique is generally based on the use of generally expensive phase masks which determine the obtained characteristics of the fiber Bragg grating. The fiber being photosensitive at those wavelengths, a periodic pattern can be written into it. The maximal length, the period, the chirp, the index contrast and the apodisation are all characteristics that depend on the phase mask. The first objective of the research project is to be able to go beyond this strong dependance on the phase mask without deteriorating grating quality. This is what really sets apart the technique presented in this thesis from other long fiber Bragg grating fabrication techniques available in the literature. The fundamental approach to obtain ultra long fiber Bragg gratings of arbitrary profile is to replace the scheme of scanning a UV beam across a phase mask to expose a fixed fiber by a scheme where the UV beam and phase mask are fixed and where the fiber is moving instead. To obtain a periodic index variation, the interference pattern itself must be synchronized with the moving fiber. Two variations of this scheme were implanted: the first one using electro-optical phase modulator placed in each arm of a Talbot interferometer and the second one using a phase mask mounted on a piezo electric actuator. A new scheme that imparts fine movements of the interferometer is also implemented for the first time and showed to be essential to achieve high quality ultra long fiber Bragg gratings. High quality theory matching ultra long fiber Bragg gratings up to 1 meter long are obtained for the first time. The possibility of fabricating high quality ultra long fiber Bragg grating of more than 10 cm (approximately the maximal phase mask length) opens a variety of new applications otherwise impossible with short fiber Bragg grating technology. Ultra long fiber Bragg gratings have unique characteristics such as high reflectivity, high dispersion and ultra narrow bandwidth. Those characteristics can be used to do advanced signal processing, non linear propagation experiments, distributed feedback fiber lasers and dispersion compensator for telecommunication or optical tomography. The second objective of this project is to use these ultra-long fiber Bragg gratings as an optical cavity for fiber lasers. Alot of research in the past years have been concentrated on those lasers, particularly on distributed feedback fiber lasers where the gratings spans all the gain media. A new random fiber laser configuration is presented. It is based on passive or active insertion of phase shifts along the Bragg grating to obtained a phenomenon called light localization which is the optical equivalent of Anderson localization. This complex wave phenomenon has the unique property to mimic the reflection of a uniform photonic crystal with the random diffusion of light among the elements of a random media. Being commonly obtained in fine powders which must respect a certain set of rules, the realization of 1D structures is vastly simplified in optical fibers. Two random fiber laser schemes based on light localization, one using erbium dopant and the other one Raman scattering, are demonstrated for the first time and compared to traditional distributed feedback fiber lasers.

Photoactive dye-enhanced tissue ablation for endoscopic laser prostatectomy.

PubMed

Ahn, Minwoo; Hau, Nguyen Trung; Van Phuc, Nguyen; Oh, Junghwan; Kang, Hyun Wook

2014-11-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH) over 20 years. Recently, application of high laser power up to 200 W was often reported to swiftly remove a large amount of prostatic tissue. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue vaporization with low laser power. Chicken breast tissue was selected as a target tissue due to minimal optical absorption at the visible wavelength. Four biocompatible photoactive dyes, including amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532 nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm(2) . Light absorbance and ablation threshold were measured with UV-Vis spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with radiant exposure, dye concentration, and number of injection. Among the dyes, AR created the highest ablation rate of 44.2 ± 0.2 µm/pulse due to higher absorbance and lower ablation threshold. High aspect ratios up to 7.1 ± 0.4 entailed saturation behavior in the tissue ablation injected with AR and BD, possibly resulting from plume shielding and increased scattering due to coagulation. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33% reduced laser power with almost equivalent performance. Due to efficient coupling of optical energy, pre-injection of photoactive dyes promoted the degree of tissue removal during laser irradiation. Further studies will investigate spatial distribution of dyes and optimal injecting pressure to govern the extent of dye-assisted ablation in a predictable manner. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser vaporization for BPH with low power application. © 2014 Wiley Periodicals, Inc.

Exploration of dynamical regimes of irradiated small protonated water clusters

NASA Astrophysics Data System (ADS)

Ndongmouo Taffoti, U. F.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.; Wang, Z. P.

2010-05-01

We explore from a theoretical perspective the dynamical response of small water clusters, (H2O)nH3O+ with n=1,2,3, to a short laser pulse for various frequencies, from infrared (IR) to ultra-violet (UV) and intensities (from 6×10^{13} W/cm^2 to 5×10^{14} W/cm^2). To that end, we use time-dependent local-density approximation for the electrons, coupled to molecular dynamics for the atomic cores (TDLDA-MD). The local-density approximation is augmented by a self-interaction correction (SIC) to allow for a correct description of electron emission. For IR frequencies, we see a direct coupling of the laser field to the very light H+ ions in the clusters. Resonant coupling (in the UV) and/or higher intensities lead to fast ionization with subsequent Coulomb explosion. The stability against Coulomb pressure increases with system size. Excitation to lower ionization stages induced strong ionic vibrations. The latter maintain a rather harmonic pattern in spite of the sizeable amplitudes (often 10% of the bond length).

Investigation of room temperature UV emission of ZnO films with different defect densities induced by laser irradiation.

PubMed

Zhao, Yan; Jiang, Yijian

2010-08-01

We studied the room temperature UV emission of ZnO films with different defect densities which is fabricated by KrF laser irradiation process. It is shown room temperature UV photoluminescence of ZnO film is composed of contribution from free-exciton (FX) recombination and its longitudinal-optical phonon replica (FX-LO) (1LO, 2LO). With increase of the defect density, the FX emission decreased and FX-LO emission increased dramatically; and the relative strengths of FX to FX-LO emission intensities determine the peak position and intensity of UV emission. What is more, laser irradiation with moderate energy density could induce the crystalline ZnO film with very flat and smooth surface. This investigation indicates that KrF laser irradiation could effectively modulate the exciton emission and surface morphology, which is important for the application of high performance of UV emitting optoelectronic devices. Copyright 2010 Elsevier B.V. All rights reserved.

UV-induced hydrogen-atom transfer in 3,6-dithiopyridazine and in model compounds 2-thiopyridine and 3-thiopyridazine.

PubMed

Rostkowska, Hanna; Lapinski, Leszek; Reva, Igor; Almeida, Bruno J A N; Nowak, Maciej J; Fausto, Rui

2011-11-10

Monomeric 3,6-dithiopyridazine (3-mercapto- 6(1H)-pyridazinethione) was studied using the matrix-isolation method combined with quantum chemical calculations. The monomers of 3,6-dithiopyridazine, trapped from the gas phase into a low-temperature Ar matrix, were found to adopt the thione-thiol structure. In agreement with this experimental observation, the thione-thiol form was predicted (at the QCISD level) to be more stable by 13.5 kJ mol(-1) and by 39.6 kJ mol(-1) than the dithiol and the dithione tautomers, respectively. Monomers of 3,6-dithiopyridazine isolated in Ar matrixes were then irradiated with broadband UV (λ > 335 nm) light. Upon such irradiation, the thione-thiol form of the compound converted into the dithiol tautomer. The same phototransformation was observed when monochromatic λ = 385 nm laser light was used for irradiation. This allowed a first observation and spectral characterization of the dithiol form of 3,6-dithiopyridazine. Subsequent irradiation of the UV-generated dithiol tautomer with shorter-wavelength UV (λ > 275 nm) light led to partial repopulation of the thione-thiol form. Spectral signatures of the analogous photoreversibility were also found for the phototautomeric transformation in the model compound 3-thiopyridazine. The reliability of the QCISD predictions of relative energies of thiol and thione tautomeric forms was tested on the archetype example of 2-thiopyridine. For this compound, the comparison of the computed relative energy 10.9 kJ mol(-1) with the experimental estimate 10.0 ± 1.5 kJ mol(-1) (both in favor of the thiol form) was more than satisfactory.

Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Armstrong, Darrell, J.; Edwards, William C.; Singh, Upendra N.

2008-01-01

In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of <2. The single frequency UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.

Plume characteristics and dynamics of UV and IR laser-desorbed oligonucleotides.

PubMed

Merrigan, Tony L; Timson, David J; Hunniford, C Adam; Catney, Martin; McCullough, Robert W

2012-05-01

Laser desorption of dye-tagged oligonucleotides was studied using laser-induced fluorescence imaging. Desorption with ultra violet (UV) and infra-red (IR) lasers resulted in forward directed plumes of molecules. In the case of UV desorption, the initial shot desorbed approximately seven-fold more material than subsequent shots. In contrast, the initial shot in IR desorption resulted in the ejection of less material compared to subsequent shots and these plumes had a component directed along the path of the laser. Thermal equilibrium of the molecules in the plume was achieved after approximately 25 μs with a spread in molecular temperature which was described by a modified Maxwell-Boltzmann equation. Copyright © 2012 Elsevier B.V. All rights reserved.

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.

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.

Novel Designs and Coupling Schemes for Affordable High Energy Laser Modules

DTIC Science & Technology

2007-09-28

possibility of single polarization operation of phase- locked multicore fiber lasers and amplifiers. 5.5. UV...transverse direction (propagation and polarization vectors shown as solid arrows and dashed lines, respectively) having a dipole-like wave front from an...31 5.4. Phase Locking in Monolithic Multicore Fiber Laser..................................................... 38 5.5. UV

Kinetic Studies on Photodeposition of Polydiacetylene Thin Film from Solution: Preliminary Determination of the Rate Law

NASA Technical Reports Server (NTRS)

Paley, M. S.; Armstrong, S.; Witherow, W. K.; Frazier, D. O.

1996-01-01

Preliminary kinetic studies were undertaken on the photodeposition of thin films of a polydiacetylene derivative of 2-methyl-4-nitroaniline from monomer solutions onto quartz substrates. Solutions of the monomer, DAMNA, in 1,2-dichloroethane at various concentrations were irradiated at 364 nm using an argon-ion laser at several intensities. It was found that the rate of polydiacetylene (PDAMNA) film photodeposition varies linearly with UV light intensity and as the square root of monomer concentration.

The EUSO-Balloon pathfinder

NASA Astrophysics Data System (ADS)

Adams, J. H.; Ahmad, S.; Albert, J.-N.; Allard, D.; Anchordoqui, L.; Andreev, V.; Anzalone, A.; Arai, Y.; Asano, K.; Ave Pernas, M.; Baragatti, P.; Barrillon, P.; Batsch, T.; Bayer, J.; Bechini, R.; Belenguer, T.; Bellotti, R.; Belov, K.; Berlind, A. A.; Bertaina, M.; Biermann, P. L.; Biktemerova, S.; Blaksley, C.; Blanc, N.; Błȩcki, J.; Blin-Bondil, S.; Blümer, J.; Bobik, P.; Bogomilov, M.; Bonamente, M.; Briggs, M. S.; Briz, S.; Bruno, A.; Cafagna, F.; Campana, D.; Capdevielle, J.-N.; Caruso, R.; Casolino, M.; Cassardo, C.; Castellinic, G.; Catalano, C.; Catalano, G.; Cellino, A.; Chikawa, M.; Christl, M. J.; Cline, D.; Connaughton, V.; Conti, L.; Cordero, G.; Crawford, H. J.; Cremonini, R.; Csorna, S.; Dagoret-Campagne, S.; de Castro, A. J.; De Donato, C.; de la Taille, C.; De Santis, C.; del Peral, L.; Dell'Oro, A.; De Simone, N.; Di Martino, M.; Distratis, G.; Dulucq, F.; Dupieux, M.; Ebersoldt, A.; Ebisuzaki, T.; Engel, R.; Falk, S.; Fang, K.; Fenu, F.; Fernández-Gómez, I.; Ferrarese, S.; Finco, D.; Flamini, M.; Fornaro, C.; Franceschi, A.; Fujimoto, J.; Fukushima, M.; Galeotti, P.; Garipov, G.; Geary, J.; Gelmini, G.; Giraudo, G.; Gonchar, M.; González Alvarado, C.; Gorodetzky, P.; Guarino, F.; Guzmán, A.; Hachisu, Y.; Harlov, B.; Haungs, A.; Hernández Carretero, J.; Higashide, K.; Ikeda, D.; Ikeda, H.; Inoue, N.; Inoue, S.; Insolia, A.; Isgrò, F.; Itow, Y.; Joven, E.; Judd, E. G.; Jung, A.; Kajino, F.; Kajino, T.; Kaneko, I.; Karadzhov, Y.; Karczmarczyk, J.; Karus, M.; Katahira, K.; Kawai, K.; Kawasaki, Y.; Keilhauer, B.; Khrenov, B. A.; Kim, J.-S.; Kim, S.-W.; Kim, S.-W.; Kleifges, M.; Klimov, P. A.; Kolev, D.; Kreykenbohm, I.; Kudela, K.; Kurihara, Y.; Kusenko, A.; Kuznetsov, E.; Lacombe, M.; Lachaud, C.; Lee, J.; Licandro, J.; Lim, H.; López, F.; Maccarone, M. C.; Mannheim, K.; Maravilla, D.; Marcelli, L.; Marini, A.; Martinez, O.; Masciantonio, G.; Mase, K.; Matev, R.; Medina-Tanco, G.; Mernik, T.; Miyamoto, H.; Miyazaki, Y.; Mizumoto, Y.; Modestino, G.; Monaco, A.; Monnier-Ragaigne, D.; Morales de los Ríos, J. A.; Moretto, C.; Morozenko, V. S.; Mot, B.; Murakami, T.; Murakami, M. Nagano; Nagata, M.; Nagataki, S.; Nakamura, T.; Napolitano, T.; Naumov, D.; Nava, R.; Neronov, A.; Nomoto, K.; Nonaka, T.; Ogawa, T.; Ogio, S.; Ohmori, H.; Olinto, A. V.; Orleański, P.; Osteria, G.; Panasyuk, M. I.; Parizot, E.; Park, I. H.; Park, H. W.; Pastircak, B.; Patzak, T.; Paul, T.; Pennypacker, C.; Perez Cano, S.; Peter, T.; Picozza, P.; Pierog, T.; Piotrowski, L. W.; Piraino, S.; Plebaniak, Z.; Pollini, A.; Prat, P.; Prévôt, G.; Prieto, H.; Putis, M.; Reardon, P.; Reyes, M.; Ricci, M.; Rodríguez, I.; Rodríguez Frías, M. D.; Ronga, F.; Roth, M.; Rothkaehl, H.; Roudil, G.; Rusinov, I.; Rybczyński, M.; Sabau, M. D.; Sáez-Cano, G.; Sagawa, H.; Saito, A.; Sakaki, N.; Sakata, M.; Salazar, H.; Sánchez, S.; Santangelo, A.; Santiago Crúz, L.; Sanz Palomino, M.; Saprykin, O.; Sarazin, F.; Sato, H.; Sato, M.; Schanz, T.; Schieler, H.; Scotti, V.; Segreto, A.; Selmane, S.; Semikoz, D.; Serra, M.; Sharakin, S.; Shibata, T.; Shimizu, H. M.; Shinozaki, K.; Shirahama, T.; Siemieniec-Oziȩbło, G.; Silva López, H. H.; Sledd, J.; Słomińska, K.; Sobey, A.; Sugiyama, T.; Supanitsky, D.; Suzuki, M.; Szabelska, B.; Szabelski, J.; Tajima, F.; Tajima, N.; Tajima, T.; Takahashi, Y.; Takami, H.; Takeda, M.; Takizawa, Y.; Tenzer, C.; Tibolla, O.; Tkachev, L.; Tokuno, H.; Tomida, T.; Tone, N.; Toscano, S.; Trillaud, F.; Tsenov, R.; Tsunesada, Y.; Tsuno, K.; Tymieniecka, T.; Uchihori, Y.; Unger, M.; Vaduvescu, O.; Valdés-Galicia, J. F.; Vallania, P.; Valore, L.; Vankova, G.; Vigorito, C.; Villaseñor, L.; von Ballmoos, P.; Wada, S.; Watanabe, J.; Watanabe, S.; Watts, J.; Weber, M.; Weiler, T. J.; Wibig, T.; Wiencke, L.; Wille, M.; Wilms, J.; Włodarczyk, Z.; Yamamoto, T.; Yamamoto, Y.; Yang, J.; Yano, H.; Yashin, I. V.; Yonetoku, D.; Yoshida, K.; Yoshida, S.; Young, R.; Zotov, M. Yu.; Zuccaro Marchi, A.

2015-11-01

EUSO-Balloon is a pathfinder for JEM-EUSO, the Extreme Universe Space Observatory which is to be hosted on-board the International Space Station. As JEM-EUSO is designed to observe Ultra-High Energy Cosmic Rays (UHECR)-induced Extensive Air Showers (EAS) by detecting their ultraviolet light tracks "from above", EUSO-Balloon is a nadir-pointing UV telescope too. With its Fresnel Optics and Photo-Detector Module, the instrument monitors a 50 km2 ground surface area in a wavelength band of 290-430 nm, collecting series of images at a rate of 400,000 frames/sec. The objectives of the balloon demonstrator are threefold: a) perform a full end-to-end test of a JEM-EUSO prototype consisting of all the main subsystems of the space experiment, b) measure the effective terrestrial UV background, with a spatial and temporal resolution relevant for JEM-EUSO. c) detect tracks of ultraviolet light from near space for the first time. The latter is a milestone in the development of UHECR science, paving the way for any future space-based UHECR observatory. On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. From a float altitude of 38 km, the instrument operated during the entire astronomical night, observing UV-light from a variety of ground-covers and from hundreds of simulated EASs, produced by flashers and a laser during a two-hour helicopter under-flight.

Effect of ultraviolet light on water- and fat-soluble vitamins in cow and goat milk.

PubMed

Guneser, O; Karagul Yuceer, Y

2012-11-01

The objective of this study was to investigate and compare the effects of UV light and heat treatment on vitamins A, B(2), C, and E in cow and goat milk. Vitamins were analyzed by reverse-phase high-pressure liquid chromatography. Ultraviolet and pasteurization treatments caused loss in vitamin C in milk. Pasteurization did not have any significant effect on vitamin B(2). However, UV light treatment decreased the amount of vitamin B(2) after several passes of milk through the UV system. In addition, UV light treatment decreased the amount of vitamins A and E. Vitamins C and E are more sensitive to UV light. UV light sensitivities of vitamins were C>E>A>B(2). These results show that UV light treatment decreases the vitamin content in milk. Also, the number of passes through the UV system and the initial amount of vitamins in milk are important factors affecting vitamin levels. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Melanin may promote photooxidation of linoleic acid

NASA Astrophysics Data System (ADS)

Glickman, Randolph D.; Lam, Kwok-Wai

1995-05-01

We have previously shown that laser-exposed melanin granules isolated from the retinal pigment epithelium (RPE) are capable of oxidizing ascorbic acid. We are now characterizing the reactions of light- activated melanin with other cellular components such as linoleic acid, a polyunsaturated fatty acid. Commercial linoleic acid, and melanin granules isolated from bovine RPE cells, are mixed and exposed to the broad band output of a 150 W Xenon arc lamp or the CW output of an Argon laser. Native linoleic acid is separated from its hydroperoxides by HPLC, and the relative amounts of each are detected by UV absorbance at 210 and 232 nm, respectively. Exposure of the linoleic acid alone to the xenon arc source results in production of linoleic hydroperoxides (LHP) in an intensity-dependent reaction that doubles in extent over the temperature range of 0° to 80°C. Addition of melanin granules at a density of 108 granules/ml reduces the production of LHP, probably because of light absorption and self-screening by the melanin. At or below a density of 107 granules/ml, however, the light-driven production of LHP is enhanced, especially during exposure to the blue- green output of the Argon laser. Physiological antioxidants (Vit. C,E protect the linoleic acid from photo-oxidation in the presence or absence of melanin. These observations support the hypothesis that light-activated melanin can react with some cellular components and thereby contribute to photochemical damage, especially if endogenous antioxidants are depleted.

Average power scaling of UV excimer lasers drives flat panel display and lidar applications

NASA Astrophysics Data System (ADS)

Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

2012-03-01

Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.

Plume Image Profiling of UV Laser Desorbed Biomolecules

NASA Astrophysics Data System (ADS)

Merrigan, T. L.; Hunniford, C. A.; Timson, D. J.; Catney, M.; McCullough, R. W.

2008-12-01

An experimental system, based upon the techniques of UV and IR laser desorption with time of flight mass spectrometry, has been constructed to enable the production and characterization of neutral biomolecular targets. The feasibility of the laser desorption technique for the purpose of radiation interaction experiments is investigated here. Fluorescent dye tagging and laser induced fluorescence imaging has been used to help characterize the laser produced plumes of biomolecules revealing their spatial density profiles and temporal evolution. Peak target thicknesses of 2×1012 molecules cm-2 were obtained 30 μs after laser desorption.

Development of high power UV irradiance meter calibration device

NASA Astrophysics Data System (ADS)

Xia, Ming; Gao, Jianqiang; Yin, Dejin; Li, Tiecheng

2016-09-01

With the rapid development of China's economy, many industries have more requirements for UV light applications, such as machinery manufacturing, aircraft manufacturing using high power UV light for detection, IT industry using high power UV light for curing component assembly, building materials, ink, paint and other industries using high power UV light for material aging test etc. In these industries, there are many measuring instruments for high power UV irradiance which are need to traceability. But these instruments are mostly imported instruments, these imported UV radiation meter are large range, wide wavelength range and high accuracy. They have exceeded our existing calibration capability. Expand the measuring range and improve the measurement accuracy of UV irradiance calibration device is a pressing matter of the moment. The newly developed high power UV irradiance calibration device is mainly composed of high power UV light, UV filter, condenser, UV light guide, optical alignment system, standard cavity absolute radiometer. The calibration device is using optical alignment system to form uniform light radiation field. The standard is standard cavity absolute radiometer, which can through the electrical substitution method, by means of adjusting and measuring the applied DC electric power at the receiver on a heating wire, which is equivalent to the thermo-electromotive force generated by the light radiation power, to achieve absolute optical radiation measurement. This method is the commonly used effective method for accurate measurement of light irradiation. The measuring range of calibration device is (0.2 200) mW/cm2, and the uncertainty of measurement results can reached 2.5% (k=2).

The role of laser wavelength on plasma generation and expansion of ablation plumes in air

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

Hussein, A. E.; Department of Physics, McGill University, Montreal, Quebec H3A 0G4; Diwakar, P. K.

2013-04-14

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photographymore » and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.« less

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

DOE PAGES

Liu, Y.; Rakhman, A.; Menshov, A.; ...

2016-12-01

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

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

Liu, Y.; Rakhman, A.; Menshov, A.

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Long-term effects of UV light on contractility of rat arteries in vivo.

PubMed

Morimoto, Yuji; Kohyama, Shinya; Nakai, Kanji; Matsuo, Hirotaka; Karasawa, Fujio; Kikuchi, Makoto

2003-10-01

Several studies have shown that UV irradiation may be effective for preventing vascular restenosis or vasopasm. However, the long-term effects of UV light on the physiological properties of vessels such as arterial tension have not been elucidated. We therefore studied the long-term effects of UV using rat carotid arteries treated with UV-B light (wavelength = 313 nm, total energy = 14 mJ/mm2). The animals were sacrificed at 1, 7 and 14 days after UV light exposure, and the carotid arteries were studied by light microscopy and the contractile responses of isolated arterial rings were recorded under isometric tension. UV treatment had induced a substantial loss of smooth muscle cells (SMC) along the entire circumference of the media on days 7 and 14, whereas loss of SMC on day 1 was negligible. Contractile responses of arteries that had been exposed to UV light were significantly reduced on days, 1, 7 and 14. The susceptibility of UV-treated arteries to phenylephrine and prostaglandin F2 alpha was significantly decreased on days 1 and 7, but decreased susceptibility was not seen on day 14. Acetylcholine-induced relaxations were not altered by UV treatment. These results suggest that the long-term effect of UV light is an attenuation of smooth muscle contractility without impairment of endothelial function.

Efficacy of UV-Pit-light traps for discerning micro-habitat-specific beetle and ant species related with different oil palm age stands and tropical annual seasons for accurate ecology and diversity interpretations

NASA Astrophysics Data System (ADS)

Ahmad Bukhary, A. K.; Ruslan, M. Y.; Mohd. Fauzi, M. M.; Nicholas, S.; Muhamad Fahmi, M. H.; Izfa Riza, H.; Idris, A. B.

2015-09-01

A newly innovated and efficient UV-Pit-light Trap is described and the results of the experiments on its efficacy that were carried out within different oil palm age stands of the year 2013 were evaluated and compared with previous study year of 2010, with out the implementation of the UV-Pit-light Trap. In 2013 the UV-Pit-light Traps, the Malaise Traps, and the Pit-fall Traps were employed, while in 2010, the conventional canopy-height UV-Light Traps, Malaise Traps, and the Pit-fall Traps were employed. The UV-Pit-light traps caught more beetle and ant families, morpho-species, and individuals per species compared with the passive Pit-fall traps. The UV-Pit-light Trap targets different subsets of the oil palm beetles and ants' communities, specifying on epigaeic-related micro-habitats, with different oil palm age stands have different compositions of micro-habitats. The UV-Pit-light Traps have the dual quality for satisfying both the biological and statistical data requirements and evaluations. There were no significant difference between the UV-Pit-light Traps and the passive Pit-fall Traps, while the trapping difference with the Malaise traps for different seasons of the year 2013. The UV-Pit-light Traps and the Malaise Traps were complementary to each other, detecting the activities of beetles and ants around the epigaeic-related micro-habitats or having active flight activities respectively according to annual seasons. The UV-Pit-light Trap is an oil-palm specific type of passive trapping system, focusing on the insect species dwelling the upper-ground/epigaeic micro-habitats.

Characterization of diffraction gratings scattering in uv and ir for space applications

NASA Astrophysics Data System (ADS)

Achour, Sakina; Kuperman-Le Bihan, Quentin; Etcheto, Pierre

2017-09-01

The use of Bidirectional Scatter Distribution Function (BSDF) in space industry and especially when designing telescopes is a key feature. Indeed when speaking about space industry, one can immediately think about stray light issues. Those important phenomena are directly linked to light scattering. Standard BSDF measurement goniophotometers often have a resolution of about 0.1° and are mainly working in or close to the visible spectrum. This resolution is far too loose to characterize ultra-polished surfaces. Besides, wavelength range of BSDF measurements for space projects needs to be done far from visible range. How can we measure BSDF of ultra-polished surfaces and diffraction gratings in the UV and IR range with high resolution? We worked on developing a new goniophometer bench in order to be able to characterize scattering of ultra-polished surfaces and diffraction gratings used in everyday space applications. This ten meters long bench was developed using a collimated beam approach as opposed to goniophotometer using focused beam. Sources used for IR characterization were CO2 (10.6?m) and Helium Neon (3.39?m) lasers. Regarding UV sources, a collimated and spatially filtered UV LED was used. The detection was ensure by a photomultiplier coupled with synchronous detection as well as a MCT InSb detector. The so-built BSDF measurement instrument allowed us to measure BSDF of ultra-polished surfaces as well as diffraction gratings with an angular resolution of 0.02° and a dynamic of 1013 in the visible range. In IR as well as in UV we manage to get 109 with same angular resolution of 0.02°. The 1m arm and translation stages allows us to measure samples up to 200mm. Thanks to such a device allowing ultra-polished materials as well as diffraction gratings scattering characterization, it is possible to implement those BSDF measurements into simulation software and predict stray light issues. This is a big help for space industry engineers to apprehend stray light due to surface finishes and to delete those effects before the whole project is done. We are now thinking of possible improvement on our optical bench to try to get dynamic in IR and UV similar to what we have in visible range (e.g. 1013).

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.

Perspectives of using the 223-nm wavelength of the KrCl excimer laser for refractive surgery and for the treatment of some eye diseases

NASA Astrophysics Data System (ADS)

Bagayev, Sergei N.; Chernikh, Valery V.; Razhev, Alexander M.; Zhupikov, Andrey A.

2000-06-01

The new surgical UV ophthalmic laser system Medilex based on the KrCl (223 nm) excimer laser for refractive surgery was created. The comparative analysis of using the UV ophthalmic laser systems Medilex based on the ArF (193 nm) and the KrCl (223 nm) excimer lasers for the correction of refractive errors was performed. The system with the radiation wavelength of 223 nanometer of the KrCl excimer laser for refractive surgery was shown to have several medical and technical advantages over the system with the traditionally used radiation wavelength of 193 nanometer of the ArF excimer laser. In addition the use of the wavelength of 223 nanometer extends functional features of the system, allowing to make not only standard for this type systems surgical and therapeutic procedures but also to treat such ocular diseases as the glaucoma and herpetic keratities. For the UV ophthalmic laser systems Medilex three variations of the beam delivery system including special rotating masks and different beam homogenize systems were developed. All created beam delivery systems are able to make the correction of myopia, hyperopia, astigmatism and myopic or hyperopic astigmatism and may be used for therapeutic procedures. The results of the initial treatments of refractive error corrections using the UV ophthalmic laser systems Medilex for both photorefractive keratectomy (PRK) and LASIK procedures are presented.

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

NASA Astrophysics Data System (ADS)

Oh, Jaechul; Weaver, J. L.; Karasik, M.; Chan, L. Y.

2015-08-01

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (˜1 ns FWHM) with the intensity of 1.1 × 1015 W/cm2. The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 1021 cm-3 with the density scale length of 120 μm along the plasma symmetry axis. The resulting ne and Te profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

Multiphoton tomography to detect chemo- and biohazards

NASA Astrophysics Data System (ADS)

König, Karsten

2015-03-01

In vivo high-resolution multiphoton/CARS tomography provides optical biopsies with 300 nm lateral resolution with chemical fingerprints. Thousands of volunteers and patients have been investigated for early cancer diagnosis, evaluation of anti-ageing cosmetic products, and changes of cellular metabolism by UV exposure and decreased oxygen supply. The skin as the outermost and largest organ is also the major target of CB agents. Current UV-based sensors are useful for bio-aerosol sensing but not for evaluating exposed in vivo skin. Here we evaluate the use of 4D multiphoton/CARS tomographs based on near infrared femtosecond laser radiation, time-correlated single photon counting (FLIM) and white light generation by photonic crystal fibers to detect bio- and chemohazards in human in vivo skin using twophoton fluorescence, SHG, and Raman signals.

Silica Integrated Optical Circuits Based on Glass Photosensitivity

NASA Technical Reports Server (NTRS)

Abushagur, Mustafa A. G.

1999-01-01

Integrated optical circuits play a major rule in the new photonics technology both in communication and sensing due to their small size and compatibility with integrated circuits. Currently integrated optical circuits (IOCs) are fabricated using similar manufacturing to those used in the semiconductor industry. In this study we are considering a new technique to fabricate IOCs which does not require layers of photolithography, depositing and etching. This method is based on the photosensitivity of germanosilicate glasses. Waveguides and other IOC devises can be patterned in these glasses by exposing them using UV lasers. This exposure by UV light changes the index of refraction of the germanosilicate glass. This technique enjoys both the simplicity and flexibility of design and fabrication with also the potential of being fast and low cost.

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility.

PubMed

Ross, J S; Datte, P; Divol, L; Galbraith, J; Froula, D H; Glenzer, S H; Hatch, B; Katz, J; Kilkenny, J; Landen, O; Manuel, A M; Molander, W; Montgomery, D S; Moody, J D; Swadling, G; Weaver, J

2016-11-01

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ 0 = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10 20 cm -3 while a 3ω probe will be used for plasma densities of ∼1 × 10 19 cm -3 . The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).

Solid State Mobile Lidar for Ozone Atmospheric Profiling

NASA Technical Reports Server (NTRS)

De Young, Russell; Carrion, William; Pliutau, Denis; Ganoe, Rene

2014-01-01

A tunable Ce:LiCAF laser is pumped by a CLBO crystal pumped by a doubled Nd:YLF laser running at 1 kilohertz. The UV tunable Ce:LiCAF laser produces two UV pulses between 280 to 295 nanometers. These pulses are transmitted into the atmosphere to profile the concentration of ozone as a function of altitude.

Identification of novel direct protein-protein interactions by irradiating living cells with femtosecond UV laser pulses.

PubMed

Itri, Francesco; Monti, Daria Maria; Chino, Marco; Vinciguerra, Roberto; Altucci, Carlo; Lombardi, Angela; Piccoli, Renata; Birolo, Leila; Arciello, Angela

2017-10-07

The identification of protein-protein interaction networks in living cells is becoming increasingly fundamental to elucidate main biological processes and to understand disease molecular bases on a system-wide level. We recently described a method (LUCK, Laser UV Cross-linKing) to cross-link interacting protein surfaces in living cells by UV laser irradiation. By using this innovative methodology, that does not require any protein modification or cell engineering, here we demonstrate that, upon UV laser irradiation of HeLa cells, a direct interaction between GAPDH and alpha-enolase was "frozen" by a cross-linking event. We validated the occurrence of this direct interaction by co-immunoprecipitation and Immuno-FRET analyses. This represents a proof of principle of the LUCK capability to reveal direct protein interactions in their physiological environment. Copyright © 2017 Elsevier Inc. All rights reserved.

X-ray photoelectron spectroscopy investigations of band offsets in Ga0.02Zn0.98O/ZnO heterojunction for UV photodetectors

NASA Astrophysics Data System (ADS)

Singh, Karmvir; Rawal, Ishpal; Punia, Rajesh; Dhar, Rakesh

2017-10-01

Here, we report the valence and conduction band offset measurements in pure ZnO and the Ga0.02Zn0.98O/ZnO heterojunction by X-Ray photoelectron spectroscopy studies for UV photodetector applications. For detailed investigations on the band offsets and UV photodetection behavior of Ga0.02Zn0.98O/ZnO heterostructures, thin films of pristine ZnO, Ga-doped ZnO (Ga0.02Zn0.98O), and heterostructures of Ga-doped ZnO with ZnO (Ga0.02Zn0.98O/ZnO) were deposited using a pulsed laser deposition technique. The deposited thin films were characterized by X-ray diffraction, atomic force microscopy, and UV-Vis spectroscopy. X-ray photoelectron spectroscopy studies were carried out on all the thin films for the investigation of valence and conduction band offsets. The valence band was found to be shifted by 0.28 eV, while the conduction band has a shifting of -0.272 eV in the Ga0.02Zn0.98O/ZnO heterojunction as compared to pristine ZnO thin films. All the three samples were analyzed for photoconduction behavior under UVA light of the intensity of 3.3 mW/cm2, and it was observed that the photoresponse of pristine ZnO (19.75%) was found to increase with 2 wt. % doping of Ga (22.62%) and heterostructured thin films (29.10%). The mechanism of UV photodetection in the deposited samples has been discussed in detail, and the interaction of chemisorbed oxygen on the ZnO surface with holes generated by UV light exposure has been the observed mechanism for the change in electrical conductivity responsible for UV photoresponse on the present deposited ZnO films.

A method of atmospheric density measurements during Shuttle entry using UV laser Rayleigh scattering

NASA Technical Reports Server (NTRS)

Mckenzie, Robert L.

1987-01-01

A detailed study is described of the performance capabilities and the hardware requirements for a method in which ambient density is measured along the Space Shuttle flight path using on-board optical instrumentation. The technique relies on Rayleigh scattering of light from a pulsed, ultraviolet, ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing direct measurements of ambient density with an uncertainty of less than 1 percent and with a spatial resolution of 1 km, over an altitude range from 50 to 90 km. In addition, extensions of this concept are discussed that allow measurements of the shock wave location and the density profile within the shock layer. Two approaches are identified that appear to be feasible, in which the same laser system is used for the extended measurements as that required for the ambient density measurements.

Mid-Ir Cavity Ring-Down Spectrometer for Biological Trace Nitric Oxide Detection

NASA Astrophysics Data System (ADS)

Kan, Vincent; Ragab, Ahemd; Stsiapura, Vitali; Lehmann, Kevin K.; Gaston, Benjamin M.

2011-06-01

S-nitrosothiols have received much attention in biochemistry and medicine as donors of nitrosonium ion (NO^+) and nitric oxide (NO) - physiologically active molecules involved in vasodilation and signal transduction. Determination of S-nitrosothiols content in cells and tissues is of great importance for fundamental research and medical applications. We will report on our ongoing development of a instrument to measure trace levels of nitric oxide gas (NO), released from S-nitrosothiols after exposure to UV light (340 nm) or reaction with L-Cysteine+CuCl mixture. The instrument uses the method of cavity ring-down spectroscopy, probing rotationally resolved lines in the vibrational fundamental transition near 5.2 μm. The laser source is a continuous-wave, room temperature external cavity quantum cascade laser. An acousto-optic modulator is used to abruptly turn off the optical power incident on the cavity when the laser and cavity pass through resonance.

Molybdenum oxide nanocolloids prepared by an external field-assisted laser ablation in water

NASA Astrophysics Data System (ADS)

Spadaro, Salvatore; Bonsignore, Martina; Fazio, Enza; Cimino, Francesco; Speciale, Antonio; Trombetta, Domenico; Barreca, Francesco; Saija, Antonina; Neri, Fortunato

2018-01-01

he synthesis of extremely stable molybdenum oxide nanocolloids by pulsed laser ablation was studied. This green technique ensures the formation of contaminant-free nanostructures and the absence of by-products. A focused picosecond pulsed laser beam was used to ablate a solid molybdenum target immersed in deionized water. Molybdenum oxide nearly spherical nanoparticles with dimensions within few nanometers (20-100 nm) are synthesized when the ablation processes were carried out, in water, at room temperature and 80°C. The application of an external electric field during the ablation process induces a nanostructures reorganization, as indicated by Scanning-Transmission Electron Microscopy images analysis. The ablation products were also characterized by some spectroscopic techniques: conventional UV-vis optical absorption, atomic absorption, dynamic light scattering, micro-Raman and X-ray photoelectron spectroscopies. Finally, NIH/3T3 mouse fibroblasts were used to evaluate cell viability by the sulforhodamine B assay

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.

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

NASA Astrophysics Data System (ADS)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; Turnbull, D.; Collins, T. J. B.; Radha, P. B.; McKenty, P. W.; Zuegel, J. D.; Marshall, F. J.; Regan, S. P.; Sangster, T. C.; Seka, W.; Campbell, E. M.; Goncharov, V. N.; Bowers, M. W.; Di Nicola, J.-M. G.; Erbert, G.; MacGowan, B. J.; Pelz, L. J.; Moody, J.; Yang, S. T.

2018-05-01

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light-changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.

The structure feature of layered M1/3TiNbO5 (M=Fe, Ce) and their photocatalytic oxidization performance for ethyl mercaptan

NASA Astrophysics Data System (ADS)

Dong, Rui; Wang, Yuan; Wang, Ningning; Xu, Lei; He, Jie; Wu, Shanshan; Lan, Yunxiang; Hu, Jinsong

2016-09-01

Layered photocatalytic materials M1/3TiNbO5 (M = Fe, Ce) were prepared by ion-exchange of KTiNbO5 with M(NO3)3. The parent KTiNbO5 was synthesized with titanium (IV) isopropoxide and niobium oxalate by a novel polymerized complex (PC) method. The micro-structures and spectral response features of the as-prepared samples were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), laser Raman spectroscopy (LRS) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The results revealed that there was a significant interaction between the interlayer cation and the terminal Nbdbnd O (Tidbnd O) bond in the NbO6 (TiO6) unit of the laminates. Photocatalytic performance was evaluated in oxidation of ethyl mercaptan under natural and UV light irradiation. It can be deduced that the photocatalytic oxidization performance can be directly affected by the characteristics of the interlayer cations.

An extended sequence specificity for UV-induced DNA damage.

PubMed

Chung, Long H; Murray, Vincent

2018-01-01

The sequence specificity of UV-induced DNA damage was determined with a higher precision and accuracy than previously reported. UV light induces two major damage adducts: cyclobutane pyrimidine dimers (CPDs) and pyrimidine(6-4)pyrimidone photoproducts (6-4PPs). Employing capillary electrophoresis with laser-induced fluorescence and taking advantages of the distinct properties of the CPDs and 6-4PPs, we studied the sequence specificity of UV-induced DNA damage in a purified DNA sequence using two approaches: end-labelling and a polymerase stop/linear amplification assay. A mitochondrial DNA sequence that contained a random nucleotide composition was employed as the target DNA sequence. With previous methodology, the UV sequence specificity was determined at a dinucleotide or trinucleotide level; however, in this paper, we have extended the UV sequence specificity to a hexanucleotide level. With the end-labelling technique (for 6-4PPs), the consensus sequence was found to be 5'-GCTC*AC (where C* is the breakage site); while with the linear amplification procedure, it was 5'-TCTT*AC. With end-labelling, the dinucleotide frequency of occurrence was highest for 5'-TC*, 5'-TT* and 5'-CC*; whereas it was 5'-TT* for linear amplification. The influence of neighbouring nucleotides on the degree of UV-induced DNA damage was also examined. The core sequences consisted of pyrimidine nucleotides 5'-CTC* and 5'-CTT* while an A at position "1" and C at position "2" enhanced UV-induced DNA damage. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Light driven optofluidic switch developed in a ZnO-overlaid microstructured optical fiber.

PubMed

Konidakis, Ioannis; Konstantaki, Maria; Tsibidis, George D; Pissadakis, Stavros

2015-11-30

A great challenge of Optofluidics remains the control of the fluidic properties of a photonic circuit by solely utilizing light. In this study, the development of a ZnO nanolayered microstructured optical fiber (MOF) Fabry-Perot interferometer is demonstrated, along with its fully reversible optofluidic switching behaviour. The actuation and switching principle is entirely based on the employment of light sources, i.e. UV 248 nm and green 532 nm lasers, while using modest irradiation doses. The synthesized ZnO within the MOF capillaries acts as a light triggered wettability transducer, allowing the controlled water filling and draining of the MOF Fabry-Perot cavity. The progression of the optofluidic cycle is monitored in situ with optical microscopy, while Fabry-Perot reflection spectra are monitored in real time to probe temporal infiltration behaviour. Finally, a first insight on the light triggered switching mechanism, employing photoluminescence and spectrophotometric measurements is presented. Results appear highly promising towards the design of smart in-fiber optofluidic light switching devices, suitable for actuating and sensing applications.

Photoswitchable non-fluorescent thermochromic dye-nanoparticle hybrid probes.

PubMed

Harrington, Walter N; Haji, Mwafaq R; Galanzha, Ekaterina I; Nedosekin, Dmitry A; Nima, Zeid A; Watanabe, Fumiya; Ghosh, Anindya; Biris, Alexandru S; Zharov, Vladimir P

2016-11-08

Photoswitchable fluorescent proteins with controllable light-dark states and spectral shifts in emission in response to light have led to breakthroughs in the study of cell biology. Nevertheless, conventional photoswitching is not applicable for weakly fluorescent proteins and requires UV light with low depth penetration in bio-tissue. Here we introduce a novel concept of photoswitchable hybrid probes consisting of thermochromic dye and absorbing nanoparticles, in which temperature-sensitive light-dark states and spectral shifts in absorption can be switched through controllable photothermal heating of doped nanoparticles. The proof-of-concept is demonstrated through the use of two different types of temperature-sensitive dyes doped with magnetic nanoparticles and reversibly photoswitched by a near-infrared laser. Photoacoustic imaging revealed the high contrast of these probes, which is sufficient for their visualization in cells and deep tissue. Our results suggest that these new photoswitchable multicolour probes can be used for multimodal cellular diagnostics and potentially for magnetic and photothermal therapy.

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.

Photoswitchable non-fluorescent thermochromic dye-nanoparticle hybrid probes

NASA Astrophysics Data System (ADS)

Harrington, Walter N.; Haji, Mwafaq R.; Galanzha, Ekaterina I.; Nedosekin, Dmitry A.; Nima, Zeid A.; Watanabe, Fumiya; Ghosh, Anindya; Biris, Alexandru S.; Zharov, Vladimir P.

2016-11-01

Photoswitchable fluorescent proteins with controllable light-dark states and spectral shifts in emission in response to light have led to breakthroughs in the study of cell biology. Nevertheless, conventional photoswitching is not applicable for weakly fluorescent proteins and requires UV light with low depth penetration in bio-tissue. Here we introduce a novel concept of photoswitchable hybrid probes consisting of thermochromic dye and absorbing nanoparticles, in which temperature-sensitive light-dark states and spectral shifts in absorption can be switched through controllable photothermal heating of doped nanoparticles. The proof-of-concept is demonstrated through the use of two different types of temperature-sensitive dyes doped with magnetic nanoparticles and reversibly photoswitched by a near-infrared laser. Photoacoustic imaging revealed the high contrast of these probes, which is sufficient for their visualization in cells and deep tissue. Our results suggest that these new photoswitchable multicolour probes can be used for multimodal cellular diagnostics and potentially for magnetic and photothermal therapy.

III-V arsenide-nitride semiconductor

NASA Technical Reports Server (NTRS)

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

III-V arsenide-nitride semiconductor are disclosed. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V materials varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V material can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Methods for forming group III-arsenide-nitride semiconductor materials

NASA Technical Reports Server (NTRS)

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2002-01-01

Methods are disclosed for forming Group III-arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Methods for forming group III-V arsenide-nitride semiconductor materials

NASA Technical Reports Server (NTRS)

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

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.

Linear self-focusing of continuous UV laser beam in photo-thermo-refractive glasses.

PubMed

Sidorov, Alexander I; Gorbyak, Veronika V; Nikonorov, Nikolay V

2018-03-19

The experimental and theoretical study of continuous UV laser beam propagation through thick silver-containing photo-thermo-refractive glass is presented. It is shown for the first time that self-action of UV Gaussian beam in glass results in its self-focusing. The observed linear effect is non-reversible and is caused by the transformation of subnanosized charged silver molecular clusters to neutral state under UV laser radiation. Such transformation is accompanied by the increase of molecular clusters polarizability and the refractive index increase in irradiated area. As a result, an extended positive lens is formed in glass bulk. In a theoretical study of linear self-focusing effect, the "aberration-free" approximation was used, taking into account spatial distribution of induced absorption.

Improvement of optical damage in specialty fiber at 266 nm wavelength

NASA Astrophysics Data System (ADS)

Tobisch, T.; Ohlmeyer, H.; Zimmermann, H.; Prein, S.; Kirchhof, J.; Unger, S.; Belz, M.; Klein, K.-F.

2014-02-01

Improved multimode UV-fibers with core diameters ranging from 70 to 600 μm diameter have been manufactured based on novel preform modifications and fiber processing techniques. Only E'-centers at 214 nm and NBOHC at 260 nm are generated in these fibers. A new generation of inexpensive laser-systems have entered the market and generated a multitude of new and attractive applications in the bio-life science, chemical and material processing field. However, for example pulsed 355 nm Nd:YAG lasers generate significant UV-damages in commercially available fibers. For lower wavelengths, no results on suitable multi-mode or low-mode fibers with high UV resistance at 266 nm wavelength (pulsed 4th harmonic Nd:YAG laser) have been published. In this report, double-clad fibers with 70 μm or 100 μm core diameter and a large claddingto- core ratio will be recommended. Laser-induced UV-damages will be compared between these new fiber type and traditional UV fibers with similar core sizes. Finally, experimental results will be cross compared against broadband cw deuterium lamp damage standards.

Scattered UV irradiation during VISX excimer laser keratorefractive surgery.

PubMed

Hope, R J; Weber, E D; Bower, K S; Pasternak, J P; Sliney, D H

2008-04-01

To evaluate the potential occupational health hazards associated with scattered ultraviolet (UV) radiation during photorefractive keratectomy (PRK) using the VISX Star S3 excimer laser. The Laser Vision Center, National Naval Medical Center, Bethesda, Maryland, USA. Intraoperative radiometric measurements were made with the Ophir Power/Energy Meter (LaserStar Model PD-10 with silicon detector) during PRK treatments as well as during required calibration procedures at a distance of 20.3 cm from the left cornea. These measurements were evaluated using a worst-case scenario for exposure, and then compared with the American Conference of Governmental Industrial Hygeinists (ACGIH) Threshold Value Limits (TVL) to perform a risk/hazard analysis. During the PRK procedures, the highest measured value was 248.4 nJ/pulse. During the calibration procedures, the highest measured UV scattered radiation level was 149.6 nJ/pulse. The maximum treatment time was 52 seconds. Using a worst-case scenario in which all treatments used the maximum power and time, the total energy per eye treated was 0.132 mJ/cm2 and the total UV radiation at close range (80 cm from the treated eye) was 0.0085 mJ/cm2. With a workload of 20 patients, the total occupational exposure at 80 cm to actinic UV radiation in an 8-hour period would be 0.425 mJ/cm2. The scattered actinic UV laser radiation from the VISX Star S3 excimer laser did not exceed occupational exposure limits during a busy 8-hour workday, provided that operating room personnel were at least 80 cm from the treated eye. While the use of protective eyewear is always prudent, this study demonstrates that the trace amounts of scattered laser emissions produced by this laser do not pose a serious health risk even without the use of protective eyewear.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion

NASA Astrophysics Data System (ADS)

Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

2016-07-01

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area. Electronic supplementary information (ESI) available: XRD patterns of the fs laser structured Cu surface as produced and after the photothermal conversion test, directly measured temperature values on Cu surfaces, temperature rise on Cu surfaces at varied solar irradiation angles, comparison of the white light and IR images of the structured Cu surface with the polished Cu surface, temperature rise on the peripheral zones of the blue coating surface. See DOI: 10.1039/c6nr03662g

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

Comparative studies on the lethal, mutagenic, and recombinogenic effects of ultraviolet -A, -B, -C, and visible light with and without 8-methoxypsoralen in Saccharomyces cerevisiae.

PubMed

Mondon, P; Shahin, M M

1992-05-01

Genetic effects of UV-A, UV-B, UV-C, and the combination of 8-methoxypsoralen (8-MOP) with UV-A or visible light were studied in the haploid strain XV185-14C and diploid strain D5 of Saccharomyces cerevisiae. The induction of his+, lys+, and hom+ reverse mutations was measured in strain XV185-14C. In strain D5 we measured the induction of genetically altered colonies, particularly twin spot colonies arising from a mitotic crossing-over. UV-C and UV-B induced point mutations at the three loci in the haploid strain and mitotic crossing-over and other genetic alterations in the diploid strain. UV-C was more mutagenic and recombinogenic than UV-B. UV-A or visible light alone did not induce genotoxic effects at the doses tested. However, UV-A plus 8-MOP produced lethal and mutagenic effects in the haploid strain XV185-14C, although mutagenic activity was less than that of UV-B. Visible light plus 8-MOP also induced genotoxic effects in strain XV185-14C. In the diploid strain D5, UV-A plus 8-MOP induced a higher frequency of genetic alterations than UV-B at comparative doses. Visible light plus 8-MOP was also genetically active in strain D5. The haploid strain was more sensitive to the lethal effects of UV-C, UV-B, UV-A, and impure visible light plus 8-MOP than the diploid strain.

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.

Novel approach to real-time flash photolysis and confocal [Ca2+] imaging

PubMed Central

Sobie, Eric A.; Kao, Joseph P.Y.; Lederer, W. J.

2008-01-01

Flash photolysis of “caged” compounds using ultraviolet light is a powerful experimental technique for producing rapid changes in concentrations of bioactive signaling molecules. Studies that employ this technique have used diverse strategies for controlling the spatial and temporal application of light to the specimen. Here we describe a new system for flash photolysis that delivers light from a pulsed, adjustable intensity laser through an optical fiber coupled into the epifluorescence port of a commercial confocal microscope. Photolysis is achieved with extremely brief (5 ns) pulses of ultraviolet light (355 nm) that can be synchronized with respect to confocal laser scanning. The system described also localizes the UV intensity spatially so that uncaging only occurs in defined sub-cellular regions; moreover, since the microscope optics are used in localization, the photolysis volume can be easily adjusted. Experiments performed on rat ventricular myocytes loaded with the Ca2+ indicator fluo-3 and the Ca2+ cage NP-EGTA demonstrate the system's capabilities. Localized intracellular increases in [Ca2+] can trigger sarcoplasmic reticular Ca2+ release events such as Ca2+ sparks and, under certain conditions, regenerative Ca2+ waves. This relatively simple and inexpensive system is therefore a useful tool for examining local signaling in heart and other tissues. PMID:17323075

UV Raman scattering measurements in a Mach 2 H2-air flame for assessment of CFD models

NASA Technical Reports Server (NTRS)

Cheng, T. S.; Wehrmeyer, J. A.; Pitz, R. W.; Jarrett, O., Jr.; Northam, G. B.

1991-01-01

An UV narrowband tunable excimer laser is used for spontaneous Raman scattering measurements in hydrogen diffusion flames. The UV Raman system is characterized by a repetition rate of about 100 Hz, a temporal resolution of about 20 ns, and a spatial resolution of about 0.4 mm. It is concluded that a single KrF excimer laser based on spontaneous Raman scattering in conjunction with laser-induced predissociative fluorescence is capable of measuring instantaneously and simultaneously major species (H2, O2, N2, H2O), minor species (OH), and temperature.

The effect of UV light on the inactivation of Giardia lamblia and Giardia muris cysts as determined by animal infectivity assay (P-2951-01).

PubMed

Mofidi, Alexander A; Meyer, Ernest A; Wallis, Peter M; Chou, Connie I; Meyer, Barbara P; Ramalingam, Shivaji; Coffey, Bradley M

2002-04-01

This study measured the effect of germicidal ultraviolet (UV) light on Giardia lamblia and Giardia muris cysts, as determined by their infectivity in Mongolian gerbils and CD-1 mice, respectively. Reduction of cyst infectivity due to UV exposure was quantified by applying most probable number techniques. Controlled bench-scale, collimated-beam tests exposed cysts suspended in filtered natural water to light from a low-pressure UV lamp. Both G. lamblia and G. muris cysts showed similar sensitivity to UV light. At 3 mJ/cm2, a dose 10-fold lower than what large-scale UV reactors may be designed to provide, > 2-log10 (99 percent) inactivation was observed. These results, combined with previously published data showing other protozoa and bacteria have similar, high sensitivity to UV light, establish that UV disinfection of drinking water is controlled by viruses which may require over 10-fold more UV dose for the same level of control.

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.

Recent developments in optical detection methods for microchip separations.

PubMed

Götz, Sebastian; Karst, Uwe

2007-01-01

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

CO2 splitting by H2O to CO and O2 under UV light in TiMCM-41silicate sieve

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

Lin, Wenyong; Han, Hongxian; Frei, Heinz

2004-04-06

The 266 nm light-induced reaction of CO{sub 2} and H{sub 2}O gas mixtures (including isotopic modifications {sup 13}CO{sub 2}, C{sup 18}O{sub 2}, and D{sub 2}O) in framework TiMCM-41 silicate sieve was monitored by in-situ FT-IR spectroscopy at room temperature. Carbon monoxide gas was observed as the sole product by infrared, and the growth was found to depend linearly on the photolysis laser power. H{sub 2}O was confirmed as stoichiometric electron donor. The work establishes CO as the single photon, 2-electron transfer product of CO{sub 2} photoreduction by H{sub 2}O at framework Ti centers for the first time. O{sub 2} wasmore » detected as co-product by mass spectrometric analysis of the photolysis gas mixture. These results are explained by single UV photon-induced splitting of CO{sub 2} by H{sub 2}O to CO and surface OH radical.« less

Multifunctional magneto-plasmonic nanotransducers for advanced theranostics: synthesis, modeling and experiment

NASA Astrophysics Data System (ADS)

Masoumi, Masoud; Wang, Ya; Liu, Mingzhao; Tewolde, Mahder; Longtin, Jon

2015-04-01

In this work, nano-transducers with a superparamagnetic iron oxide (SPIO) core have been synthesized by preparation of precursor gold nanoseeds loaded on SPIO-embedded silica to form a gold nanoshell. The goal is for such nanotansducers to be used in theranostics to detect brain tumors by using MRI imaging and then assist in their treatment by using photothermal ablation. The iron oxide core provides for the use of a magnetic-field to guide the particles to the target (tumor) site. The gold nanoshell can be then readily heated using incident light and/or an alternating magneticfield. After synthesis of nano-transducer samples, Transmission Electron Microscopy was employed to analyze the formation of each layer. Then UV spectroscopy experiments were conducted to examine the light absorbance of the synthesized samples. The UV-visible absorption spectra shows a clear surface plasmon resonance (SPR) band around 530 nm, verifying the presence of gold coating nanoshells. Finally photothermal experiments using a high-power laser beam with a wavelength of 527 nm were performed to heat the samples. It was found that the temperature reaches 45° C in 12 minutes.

Demonstration of UV LED versatility when paired with molded UV transmitting glass optics to produce unique irradiance patterns

NASA Astrophysics Data System (ADS)

Jasenak, Brian

2017-02-01

Ultraviolet light-emitting diode (UV LED) adoption is accelerating; they are being used in new applications such as UV curing, germicidal irradiation, nondestructive testing, and forensic analysis. In many of these applications, it is critically important to produce a uniform light distribution and consistent surface irradiance. Flat panes of fused quartz, silica, or glass are commonly used to cover and protect UV LED arrays. However, they don't offer the advantages of an optical lens design. An investigation was conducted to determine the effect of a secondary glass optic on the uniformity of the light distribution and irradiance. Glass optics capable of transmitting UV-A, UV-B, and UV-C wavelengths can improve light distribution, uniformity, and intensity. In this work, two simulation studies were created to illustrate distinct irradiance patterns desirable for potential real world applications. The first study investigates the use of a multi-UV LED array and optic to create a uniform irradiance pattern on the flat two dimensional (2D) target surface. The uniformity was improved by designing both the LED array and molded optic to produce a homogenous pattern. The second study investigated the use of an LED light source and molded optic to improve the light uniformity on the inside of a canister. The case study illustrates the requirements for careful selection of LED based on light distribution and subsequent design of optics. The optic utilizes total internal reflection to create optimized light distribution. The combination of the LED and molded optic showed significant improvement in uniformity on the inner surface of the canister. The simulations illustrate how the application of optics can significantly improve UV light distribution which can be critical in applications such as UV curing and sterilization.

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.

UV Generation of 25 mJ/pulse at 289 nm for Ozone Lidar

NASA Technical Reports Server (NTRS)

Storm, Mark E.; Marsh, Waverly; Barnes, James C.

1998-01-01

Our paper describes a technique for generating tunable UV laser radiation between 250-300 nm capable of energies up to 30-5O mJ/pulse. The tunability of this source is attractive for selecting ozone absorption cross sections which are optimal for ozone DIAL detection throughout the troposphere. A Nd:YAG laser is used to pump a pulsed titanium sapphire laser which is then frequency tripled into the UV. Titanium sapphire (TiS) lases robustly between 750-900 nm. In initial experiments we have converted 110 mJ of 867 nm from a TiS laser into 28 mJ at 289 nm. The energy conversion efficiency was 62% for doubling into 433 nm and 25% into 289 nm.

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.

Airborne megawatt class free-electron laser for defense and security

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

Roy Whitney; David Douglas; George Neil

2005-03-01

An airborne megawatt (MW) average power Free-Electron Laser (FEL) is now a possibility. In the process of shrinking the FEL parameters to fit on ship, a surprisingly lightweight and compact design has been achieved. There are multiple motivations for using a FEL for a high-power airborne system for Defense and Security: Diverse mission requirements can be met by a single system. The MW of light can be made available with any time structure for time periods from microseconds to hours, i.e. there is a nearly unlimited magazine. The wavelength of the light can be chosen to be from the farmore » infrared (IR) to the near ultraviolet (UV) thereby best meeting mission requirements. The FEL light can be modulated for detecting the same pattern in the small fraction of light reflected from the target resulting in greatly enhanced targeting control. The entire MW class FEL including all of its subsystems can be carried by large commercial size airplanes or on an airship. Adequate electrical power can be generated on the plane or airship to run the FEL as long as the plane or airship has fuel to fly. The light from the FEL will work well with relay mirror systems. The required R&D to achieve the MW level is well understood. The coupling of the capabilities of an airborne FEL to diverse mission requirements provides unique opportunities.« less

Epidermal UV-A absorbance and whole-leaf flavonoid composition in pea respond more to solar blue light than to solar UV radiation.

PubMed

Siipola, Sari M; Kotilainen, Titta; Sipari, Nina; Morales, Luis O; Lindfors, Anders V; Robson, T Matthew; Aphalo, Pedro J

2015-05-01

Plants synthesize phenolic compounds in response to certain environmental signals or stresses. One large group of phenolics, flavonoids, is considered particularly responsive to ultraviolet (UV) radiation. However, here we demonstrate that solar blue light stimulates flavonoid biosynthesis in the absence of UV-A and UV-B radiation. We grew pea plants (Pisum sativum cv. Meteor) outdoors, in Finland during the summer, under five types of filters differing in their spectral transmittance. These filters were used to (1) attenuate UV-B; (2) attenuate UV-B and UV-A < 370 nm; (3) attenuate UV-B and UV-A; (4) attenuate UV-B, UV-A and blue light; and (5) as a control not attenuating these wavebands. Attenuation of blue light significantly reduced the flavonoid content in leaf adaxial epidermis and reduced the whole-leaf concentrations of quercetin derivatives relative to kaempferol derivatives. In contrast, UV-B responses were not significant. These results show that pea plants regulate epidermal UV-A absorbance and accumulation of individual flavonoids by perceiving complex radiation signals that extend into the visible region of the solar spectrum. Furthermore, solar blue light instead of solar UV-B radiation can be the main regulator of phenolic compound accumulation in plants that germinate and develop outdoors. © 2014 John Wiley & Sons Ltd.

Physiological limit of the daily endogenous cholecalciferol synthesis from UV light in cattle.

PubMed

Hymøller, L; Jensen, S K; Kaas, P; Jakobsen, J

2017-04-01

The link between UV light (sunlight) and endogenous cholecalciferol (vitamin D 3 ) synthesis in the skin of humans has been known for more than a 100 years, since doctors for the first time successfully used UV light to cure rickets in children. Years later, it was shown that UV light also had a significant effect on the cholecalciferol status in the body of cattle. The cholecalciferol status in the body is measured as the plasma concentration of 25-hydroxycholecalciferol, which in cattle and humans is the major circulating metabolite of cholecalciferol. Very little is, however, known about the quantitative efficiency of UV light as a source of cholecalciferol in cattle nutrition and physiology. Hence, the aim of this study was to determine the efficiency of using UV light for increasing the plasma 25-hydroxycholecalciferol concentration in cholecalciferol-deprived cattle. Twelve cows deprived of cholecalciferol for 6 months were divided into three treatment groups and exposed to UV light for 30, 90 or 120 min/day during 28 days. UV-light wavelengths ranged from 280 to 415 nm and 30-min exposure to the UV light was equivalent to 60-min average summer-sunlight exposure at 56 °N. Blood samples were collected every 3-4 days and analysed for 25-hydroxycholecalciferol and cholecalciferol. Results showed that increasing the exposure time from 90-120 min/day did not change the slope of the daily increase in plasma 25-hydroxycholecalciferol. Hence, it appears that cholecalciferol-deprived dairy cattle are able to increase their plasma 25-hydroxycholecalciferol concentration by a maximum of 1 ng/ml/day from UV-light exposure. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

Diode-pumped UV refractive surgery laser

NASA Astrophysics Data System (ADS)

Lin, Jui T.; Hwang, Ming-Yi; Huang, C. H.

1993-07-01

Ophthalmic applications of medical lasers have been extensively explored recently because of their market potential. Refractive surgical lasers represent one of the major development efforts due to the large population of eye disorders: about 160 million people in the USA and more than 2 billion worldwide. The first refractive laser developed was the ArF excimer laser at 193 nm in 1987 - 88 for a procedure called photorefractive keratectomy (PRK). More recently, solid state refractive lasers have also been explored for preliminary clinical trials. These lasers include Nd:YLF (picosecond at 1054 nm), doubled-Nd:YAG (nanosecond at 532 nm), Ho:YAG (microsecond at 2100 nm) and ultraviolet (UV) lasers generated from the harmonic of Ti:sapphire-laser (205 - 220 nm) and Nd:YAG (at 213 nm).

Emission spectra of photoionized plasmas induced by intense EUV pulses: Experimental and theoretical investigations

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemysław; Jarocki, Roman; Fiedorowicz, Henryk

2017-03-01

Experimental measurements and numerical modeling of emission spectra in photoionized plasma in the ultraviolet and visible light (UV/Vis) range for noble gases have been investigated. The photoionized plasmas were created using laser-produced plasma (LPP) extreme ultraviolet (EUV) source. The source was based on a gas puff target; irradiated with 10ns/10J/10Hz Nd:YAG laser. The EUV radiation pulses were collected and focused using grazing incidence multifoil EUV collector. The laser pulses were focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in a formation of low temperature photoionized plasmas emitting radiation in the UV/Vis spectral range. Atomic photoionized plasmas produced this way consisted of atomic and ionic with various ionization states. The most dominated observed spectral lines originated from radiative transitions in singly charged ions. To assist in a theoretical interpretation of the measured spectra, an atomic code based on Cowan's programs and a collisional-radiative PrismSPECT code have been used to calculate the theoretical spectra. A comparison of the calculated spectral lines with experimentally obtained results is presented. Electron temperature in plasma is estimated using the Boltzmann plot method, by an assumption that a local thermodynamic equilibrium (LTE) condition in the plasma is validated in the first few ionization states. A brief discussion for the measured and computed spectra is given.

Comparison of femtosecond laser and continuous wave UV sources for protein-nucleic acid crosslinking.

PubMed

Fecko, Christopher J; Munson, Katherine M; Saunders, Abbie; Sun, Guangxing; Begley, Tadhg P; Lis, John T; Webb, Watt W

2007-01-01

Crosslinking proteins to the nucleic acids they bind affords stable access to otherwise transient regulatory interactions. Photochemical crosslinking provides an attractive alternative to formaldehyde-based protocols, but irradiation with conventional UV sources typically yields inadequate product amounts. Crosslinking with pulsed UV lasers has been heralded as a revolutionary technique to increase photochemical yield, but this method had only been tested on a few protein-nucleic acid complexes. To test the generality of the yield enhancement, we have investigated the benefits of using approximately 150 fs UV pulses to crosslink TATA-binding protein, glucocorticoid receptor and heat shock factor to oligonucleotides in vitro. For these proteins, we find that the quantum yields (and saturating yields) for forming crosslinks using the high-peak intensity femtosecond laser do not improve on those obtained with low-intensity continuous wave (CW) UV sources. The photodamage to the oligonucleotides and proteins also has comparable quantum yields. Measurements of the photochemical reaction yields of several small molecules selected to model the crosslinking reactions also exhibit nearly linear dependences on UV intensity instead of the previously predicted quadratic dependence. Unfortunately, these results disprove earlier assertions that femtosecond pulsed laser sources provide significant advantages over CW radiation for protein-nucleic acid crosslinking.

Biocompatible silver nanoparticles embedded in a PEG-PLA polymeric matrix for stimulated laser light drug release

NASA Astrophysics Data System (ADS)

Neri, F.; Scala, A.; Grimato, S.; Santoro, M.; Spadaro, S.; Barreca, F.; Cimino, F.; Speciale, A.; Saija, A.; Grassi, G.; Fazio, E.

2016-06-01

The laser-induced release of a well-known hepatoprotective drug (silibinin, SLB) from a temperature-sensitive polymeric composite loaded with silver nanoparticles (Ag NPs) was investigated. The surface chemistry tuning and the specific design of Ag NPs are fundamental in view of the engineering of specific stimuli-responsive systems, able to control drug release in response to external stimuli. The release profiles of SLB from the newly synthesized PEG-PLA@Ag composite show strong dependences on laser wavelength and Ag NPs' Surface Plasmon Resonance (SPR). The resonant laser light excites the SPR of the NPs and the absorbed energy is converted into heat due to electron-photon collisions. The heat generated from the nanometer-sized metal particles embedded within the polymer is efficient and strongly localized. The nanovector, irradiated by a relatively low-intensity laser but tuned specifically to the metal NPs' SPR, releases the encapsulated drug with a higher efficiency than that not irradiated or irradiated with a laser wavelength far from the metal SPR. A combination of analytical techniques including UV-Vis, NMR, and FT-IR spectroscopy and scanning/transmission electron microscopy has been used to study the structural and morphological properties of the composite. The controllable specificity of this approach and the possibility of the SPR-mediated localized photothermal effect to be usefully applied in aqueous environments are the relevant advances of the proposed system for photothermal therapies that make use of visible optical radiation or for the drug delivery in proximity of the tumor cells.

Light and the circadian clock mediate time-specific changes in sensitivity to UV-B stress under light/dark cycles

PubMed Central

Takeuchi, Tomomi; Newton, Linsey; Burkhardt, Alyssa; Mason, Saundra; Farré, Eva M.

2014-01-01

In Arabidopsis, the circadian clock regulates UV-B-mediated changes in gene expression. Here it is shown that circadian clock components are able to inhibit UV-B-induced gene expression in a gene-by-gene-specific manner and act downstream of the initial UV-B sensing by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) and UVR8 (UV RESISTANCE LOCUS 8). For example, the UV-B induction of ELIP1 (EARLY LIGHT INDUCIBLE PROTEIN 1) and PRR9 (PSEUDO-RESPONSE REGULATOR 9) is directly regulated by LUX (LUX ARRYTHMO), ELF4 (EARLY FLOWERING 4), and ELF3. Moreover, time-dependent changes in plant sensitivity to UV-B damage were observed. Wild-type Arabidopsis plants, but not circadian clock mutants, were more sensitive to UV-B treatment during the night periods than during the light periods under diel cycles. Experiments performed under short cycles of 6h light and 6h darkness showed that the increased stress sensitivity of plants to UV-B in the dark only occurred during the subjective night and not during the subjective day in wild-type seedlings. In contrast, the stress sensitivity of Arabidopsis mutants with a compromised circadian clock was still influenced by the light condition during the subjective day. Taken together, the results show that the clock and light modulate plant sensitivity to UV-B stress at different times of the day. PMID:25147271

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.

Responsive copolymers for enhanced petroleum recovery. Quarterly technical progress report, June 23--September 21, 1994

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

McCormick, C.; Hester, R.

Summaries are given on the technical progress on three tasks of this project. Monomer and polymer synthesis discusses the preparation of 1(7-aminoheptyloxymethyl)naphthalene and poly(maleic anhydride-alt-ethyl vinyl ether). Task 2, Characterization of molecular structure, discusses terpolymer solution preparation, UV analysis, fluorescence analysis, low angle laser light scattering, and viscometry. The paper discusses the effects of hydrophobic groups, the effect of pH, the effect of electrolyte addition, and photophysical studies. Task 3, Solution properties, describes the factorial experimental design for characterizing polymer solutions by light scattering, the light scattering test model, orthogonal factorial test design, linear regression in coded space, confidence levelmore » for coded space test mode coefficients, coefficients of the real space test model, and surface analysis of the model equations.« less

Remote Sensing of Turbine Engine Gases.

DTIC Science & Technology

1981-09-30

Institute by lasers operating in the infrared compared to the visible and of Technology. Lexington, M A 0217 3. UV region. 00l8.9197/81/0900-1917S00.75 0...mini-TEA lasers used in both single- and dual- laser consists of a UV -preionized discharge between Rogowski laser DIAL systems, and a study has been...described previously [10]. The discharge is thyratron system. This research has led to a better understanding of triggered and may operate at a pulse

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.

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

All-femtosecond laser-assisted in situ keratomileusis

NASA Astrophysics Data System (ADS)

Gabryte, Egle; Danieliene, Egle; Vaiceliunaite, Agne; Ruksenas, Osvaldas; Vengris, Mikas; Danielius, Romualdas

2013-03-01

We present a femtosecond solid-state Yb:KGW laser system capable of performing the complete laser-assisted in situ keratomileusis (LASIK) ophthalmic procedure. The fundamental infrared radiation (IR) is used to create the corneal flap, and subsequently the corneal stromal ablation is performed using the ultraviolet (UV) pulses of the fifth harmonic. The heating of cornea, ablated surface quality, and healing outcomes of the surgeries performed using the femtosecond laser system are investigated by both ex vivo and in vivo experiments and compared to the results of conventional clinical ArF excimer laser application. The results of this research indicate the feasibility of clinical application of femtosecond UV lasers for LASIK procedure.

Integrated oxide graphene based device for laser inactivation of pathogenic microorganisms

NASA Astrophysics Data System (ADS)

Grishkanich, Alexsandr; Ruzankina, Julia; Afanasyev, Mikhail; Paklinov, Nikita; Hafizov, Nail

2018-02-01

We develop device for virus disinfection of pathogenic microorganisms. Viral decontamination can be carried out due to hard ultraviolet irradiation and singlet oxygen destroying the genetic material of a virus capsid. UV rays can destroy DNA, leading to the formation of dimers of nucleic acids. This practically does not occur in tissues, tk. UV rays penetrate badly through them, however, the viral particles are small and UV can destroy their genetic material, RNA / DNA and the virus can not replicate. It is with the construction of the ultraviolet laser water disinfection system (UFLOV) based on the continuous and periodic pulsed ultraviolet laser sources (pump) binds to solve sterility and depyrogenation of water. It has been established that small doses of UV irradiation stimulate reproduction, and large doses cause the death of pathogenic microorganisms. The effect of a dose of ultraviolet is the result of photochemical action on the substance of a living bacterial cell or virion. Also complex photodynamic laser inactivation on graphene oxide is realized.

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.

Comparison of the effect of UV laser radiation and of a radiomimetic substance on chromatin

NASA Astrophysics Data System (ADS)

Radulescu, Irina; Radu, Liliana; Serbanescu, Ruxandra; Nelea, V. D.; Martin, C.; Mihailescu, Ion N.

1998-07-01

The damages of the complex of deoxyribonucleic acid (DNA) and proteins from chromatin, produced by the UV laser radiation and/or by treatment with a radiomimetic substance, bleomycin, were compared. The laser radiation and bleomycin effects on chromatin structure were determined by the static and dynamic fluorimetry of chromatin complexes with the DNA specific ligand-- proflavine and by the analysis of tryptophan chromatin intrinsic fluorescence. Time resolved spectroscopy is a sensitive technique which allows to determine the excited state lifetimes of chromatin--proflavine complexes. Also, the percentage contributions to the fluorescence of proflavine, bound and unbound to chromatin DNA, were evaluated. The damages produced by the UV laser radiation on chromatin are similar with those of radiomimetic substance action and consists in DNA and proteins destruction. The DNA damage degree has been determined. The obtained results may constitute some indications in the laser utilization in radiochimiotherapy.

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.

Photoluminescence and reflectivity studies of high energy light ions irradiated polymethyl methacrylate films

NASA Astrophysics Data System (ADS)

Bharti, Madhu Lata; Singh, Fouran; Ramola, R. C.; Joshi, Veena

2017-11-01

The self-standing films of non-conducting polymethyl methacrylate (PMMA) were irradiated in vacuum using high energy light ions (HELIs) of 50 MeV Lithium (Li+3) and 80 MeV Carbon (C+5) at various ion dose to induce the optical changes in the films. Upon HELI irradiation, films exhibit a significant enhancement in optical reflectivity at the highest dose. Interestingly, the photoluminescence (PL) emission band with green light at (514.5 nm) shows a noticeable increase in the intensity with increasing ion dose for both ions. However, the rate of increase in PL intensity is different for both HELI and can be correlated with the linear energy transfer by these ions in the films. Origin of PL is attributed to the formation of carbon cluster and hydrogenated amorphous carbon in the polymer films. HAC clusters act as PL active centres with optical reflectivity. Most of the harmful radiation like UV are absorbed by the material and is becoming opaque after irradiation and this PL active material are useful in fabrication of optoelectronic devices, UV-filter, back-lit components in liquid crystal display systems, micro-components for integrate optical circuits, diffractive elements, advanced materials and are also applicable to the post irradiation laser treatment by means of ion irradiation.

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.

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.

Research on the calibration of ultraviolet energy meters

NASA Astrophysics Data System (ADS)

Lin, Fangsheng; Yin, Dejin; Li, Tiecheng; Lai, Lei; Xia, Ming

2016-10-01

Ultraviolet (UV) radiation is a kind of non-lighting radiation with the wavelength range from 100nm to 400nm. Ultraviolet irradiance meters are now widely used in many areas. However, as the development of science and technology, especially in the field of light-curing industry, there are more and more UV energy meters or UV-integrators need to be measured. Because the structure, wavelength band and measured power intensity of UV energy meters are different from traditional UV irradiance meters, it is important for us to take research on the calibration. With reference to JJG879-2002, we SIMT have independently developed the UV energy calibration device and the standard of operation and experimental methods for UV energy calibration in detail. In the calibration process of UV energy meter, many influencing factors will affect the final results, including different UVA-band UV light sources, different spectral response for different brands of UV energy meters, instability and no uniformity of UV light source and temperature. Therefore we need to take all of these factors into consideration to improve accuracy in UV energy calibration.

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.

Do UV-A radiation and blue light during growth prime leaves to cope with acute high-light in photoreceptor mutants of Arabidopsis thaliana?

PubMed

Brelsford, Craig C; Morales, Luis O; Nezval, Jakub; Kotilainen, Titta K; Hartikainen, Saara M; Aphalo, Pedro J; Robson, T Matthew

2018-04-28

We studied how plants acclimated to growing conditions that included combinations of blue light and ultraviolet-A (UV-A) radiation, and whether their growing environment affected their photosynthetic capacity during and after a brief period of acute high light (as might happen during an under-canopy sunfleck). Arabidopsis thaliana Landsberg erecta wild-type were compared with mutants lacking functional blue-light-and-UV photoreceptors: phototropin 1PHOT1, cryptochromes (CRY1 and CRY2) and UV RESISTANT LOCUS 8 (uvr8). This was achieved using LED lamps in a controlled environment to create treatments with or without blue light, in a split-plot design with or without UV-A radiation. We compared the accumulation of phenolic compounds under growth conditions and after exposure to 30 minutes of high light at the end of the experiment (46 days), and likewise measured the operational efficiency of photosystem II (φPSII a proxy for photosynthetic performance) and dark-adapted maximum quantum yield (F v /F m to assess PSII damage). Our results indicate that cryptochromes are the main photoreceptors regulating phenolic-compound accumulation in response to blue light and UV-A radiation, and a lack of functional cryptochromes impairs photosynthetic performance under high light. Our findings also reveal a role for UVR8 in accumulating flavonoids in response to a low UV-A dose. Interestingly, phototropin 1 partially-mediated constitutive accumulation of phenolic compounds in the absence of blue light. Low irradiance blue light and UV-A did not improve φPSII and F v /F m upon our acute high light treatment, however CRYs played an important role in ameliorating high-light stress. This article is protected by copyright. All rights reserved.

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.

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.

The supercontinuum laser as a flexible source for quasi-steady state and time resolved fluorescence studies

NASA Astrophysics Data System (ADS)

Fenske, Roger; Näther, Dirk U.; Dennis, Richard B.; Smith, S. Desmond

2010-02-01

Commercial Fluorescence Lifetime Spectrometers have long suffered from the lack of a simple, compact and relatively inexpensive broad spectral band light source that can be flexibly employed for both quasi-steady state and time resolved measurements (using Time Correlated Single Photon Counting [TCSPC]). This paper reports the integration of an optically pumped photonic crystal fibre, supercontinuum source1 (Fianium model SC400PP) as a light source in Fluorescence Lifetime Spectrometers (Edinburgh Instruments FLS920 and Lifespec II), with single photon counting detectors (micro-channel plate photomultiplier and a near-infrared photomultiplier) covering the UV to NIR range. An innovative method of spectral selection of the supercontinuum source involving wedge interference filters is also discussed.

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.

Spatially selective Au nanoparticle growth in laser-quality glass controlled by UV-induced phosphate-chain cross-linkage

NASA Astrophysics Data System (ADS)

Sigaev, Vladimir N.; Savinkov, Vitaly I.; Lotarev, Sergey V.; Shakhgildyan, Georgiy Yu; Lorenzi, Roberto; Paleari, Alberto

2013-06-01

Herein we describe how UV excitation of localized electronic states in phosphate glasses can activate structural rearrangements that influence the kinetics of Au nanoparticle (NP) thermal growth in Au-doped glass. The results suggest a novel strategy to address the problem of controlling nano-assembly processes of metal NP patterns in fully inorganic and chemically stable hard materials, such as laser-quality glasses. We show that the mechanism is promoted by opening and subsequent cross-linkage of phosphate chains under UV excitation of non-bridging groups in the amorphous network of the glass, with a consequent modification of Au diffusion and metal NP growth. Importantly, the micro-Raman mapping of the UV-induced modifications demonstrates that the process is restricted within the beam waist region of the focused UV laser beam. This fact is consistent with the need for more than one excitation event, close in time and in space, in order to promote structural cross-linkage and Au diffusion confinement. The stability of the photo-induced modifications makes it possible to design new metal patterning approaches for the fabrication of three-dimensional metal structures in laser-quality materials for high-power nonlinear applications.

Spatially selective Au nanoparticle growth in laser-quality glass controlled by UV-induced phosphate-chain cross-linkage.

PubMed

Sigaev, Vladimir N; Savinkov, Vitaly I; Lotarev, Sergey V; Shakhgildyan, Georgiy Yu; Lorenzi, Roberto; Paleari, Alberto

2013-06-07

Herein we describe how UV excitation of localized electronic states in phosphate glasses can activate structural rearrangements that influence the kinetics of Au nanoparticle (NP) thermal growth in Au-doped glass. The results suggest a novel strategy to address the problem of controlling nano-assembly processes of metal NP patterns in fully inorganic and chemically stable hard materials, such as laser-quality glasses. We show that the mechanism is promoted by opening and subsequent cross-linkage of phosphate chains under UV excitation of non-bridging groups in the amorphous network of the glass, with a consequent modification of Au diffusion and metal NP growth. Importantly, the micro-Raman mapping of the UV-induced modifications demonstrates that the process is restricted within the beam waist region of the focused UV laser beam. This fact is consistent with the need for more than one excitation event, close in time and in space, in order to promote structural cross-linkage and Au diffusion confinement. The stability of the photo-induced modifications makes it possible to design new metal patterning approaches for the fabrication of three-dimensional metal structures in laser-quality materials for high-power nonlinear applications.

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.

Footprints of the sun: memory of UV and light stress in plants

PubMed Central

Müller-Xing, Ralf; Xing, Qian; Goodrich, Justin

2014-01-01

Sunlight provides the necessary energy for plant growth via photosynthesis but high light and particular its integral ultraviolet (UV) part causes stress potentially leading to serious damage to DNA, proteins, and other cellular components. Plants show adaptation to environmental stresses, sometimes referred to as “plant memory.” There is growing evidence that plants memorize exposure to biotic or abiotic stresses through epigenetic mechanisms at the cellular level. UV target genes such as CHALCONE SYNTHASE (CHS) respond immediately to UV treatment and studies of the recently identified UV-B receptor UV RESISTANCE LOCUS 8 (UVR8) confirm the expedite nature of UV signaling. Considering these findings, an UV memory seems redundant. However, several lines of evidence suggest that plants may develop an epigenetic memory of UV and light stress, but in comparison to other abiotic stresses there has been relatively little investigation. Here we summarize the state of knowledge about acclimation and adaptation of plants to UV light and discuss the possibility of chromatin based epigenetic memory. PMID:25278950

Compact and portable multiline UV and visible Raman lasers in hydrogen-filled HC-PCF.

PubMed

Wang, Y Y; Couny, F; Light, P S; Mangan, B J; Benabid, F

2010-04-15

We report on the realization of compact UV visible multiline Raman lasers based on two types of hydrogen-filled hollow-core photonic crystal fiber. The first, with a large pitch Kagome lattice structure, offers a broad spectral coverage from near IR through to the much sought after yellow, deep-blue and UV, whereas the other, based on photonic bandgap guidance, presents a pump conversion concentrated in the visible region. The high Raman efficiency achieved through these fibers allows for compact, portable diode-pumped solid-state lasers to be used as pumps. Each discrete component of this laser system exhibits a spectral density several orders of magnitude larger than what is achieved with supercontinuum sources and a narrow linewidth, making it an ideal candidate for forensics and biomedical applications.

Modification of insulating diamond-like films by pulsed UV laser emission

NASA Astrophysics Data System (ADS)

Ageev, V. P.; Glushko, T. N.; Dorfman, V. F.; Kuzmichev, A. V.; Pypkin, B. N.

1991-07-01

The basic regimes of the modification of diamond-like a-C/Si/O:H films by the emission of the KrF laser are investigated. In particular, attention is given to the effect of the graphitization process on the spatial resolution of the dimensional treament. The possibility of the submicron cross-linking of the films using the methods of ablative UV laser lithography is demonstrated.

Synthesis and photonic property study of ZnO nanowires for a real time photodynamic therapy monitoring probe

NASA Astrophysics Data System (ADS)

Sridhar, D.; Xie, Jining; Abraham, Jose K.; Varadan, Vijay K.

2007-04-01

In this paper, we present how the photonic properties of zinc oxide (ZnO) nanowires can be used to potentially advance the effectiveness of Photodynamic therapy (PDT), one of the most recent and promising approaches among cancer therapies. Presently, PDT employs laser light to activate intravenously or topically administered photosensitizers to give rise to highly reactive singlet oxygen which has a very short lifetime and is capable of biochemical damage to cell membranes of the tumor. A probe that can monitor in real time the penetration depth of the laser in the tumor and also the evolution of the singlet oxygen, which is critical for tumor eradication, is capable of improving the efficacy of PDT quite significantly. Such a probe, by providing real time feedback, can help us determine whether to increase or decrease the light exposure dose and also if further local administration of photosensitizers is required or not. ZnO nanowires are known to be photoconductive and recent research also demonstrated the temperature dependence of the photocurrent in the nanowires. They are also sensitive to blue and other near UV spectra which is same range of activation wavelengths of most photosensitizers, and hence making them a good candidate for a potential PDT monitoring probe. ZnO nanowires were fabricated on silicon substrates by vapor phase deposition using e-beam evaporated gold as a catalyst. Control of the dimensions of the nanowires could be achieved by varying the dimensions of the catalyst by means of e-beam evaporation process. Photoluminescence properties of ZnO nanowires were investigated at UV and near UV wavelengths. Further, ZnO is also known for its antimicrobial properties, thereby ruling out any possibility of bacterial infection because of the implanted probe. This study was done to compliment the existing expertise of our research group in the design and fabrication of several nanowire based probes and microsensors specifically for neuroelectronic and nanomedicine applications.

Investigation of Ultraviolet Light Curable Polysilsesquioxane Gate Dielectric Layers for Pentacene Thin Film Transistors.

PubMed

Shibao, Hideto; Nakahara, Yoshio; Uno, Kazuyuki; Tanaka, Ichiro

2016-04-01

Polysilsesquioxane (PSQ) comprising 3-methacryloxypropyl groups was investigated as an ultraviolet (UV)-light curable gate dielectric-material for pentacene thin film transistors (TFTs). The surface of UV-light cured PSQ films was smoother than that of thermally cured ones, and the pentacene layers deposited on the UV-Iight cured PSQ films consisted of larger grains. However, carrier mobility of the TFTs using the UV-light cured PSQ films was lower than that of the TFTs using the thermally cured ones. It was shown that the cross-linker molecules, which were only added to the UV-light cured PSQ films, worked as a major mobility-limiting factor for the TFTs.

Effect of Ultraviolet Light Irradiation Combined with Riboflavin on Different Bacterial Pathogens from Ocular Surface Infection.

PubMed

Shen, Jing; Liang, Qingfeng; Su, Guanyu; Zhang, Yang; Wang, Zhiqun; Liang, Hong; Baudouin, Christophe; Labbé, Antoine

2017-01-01

In order to study Staphylococcus epidermis and Staphylococcus aureus in vitro viability after the exposure to ultraviolet (UV) light and riboflavin, twelve strains of Staphylococcus epidermis and twelve strains of Staphylococcus aureus were isolated from patients with bacterial keratitis. The growth situation of Staphylococcus epidermidis and Staphylococcus aureus under different experimental conditions was qualitatively observed. The number of colonies surviving bacteria was counted under different UV light power and different exposure time. The experiment showed that there was no inhibition effect on the growth of bacteria using riboflavin alone. In UV alone group and UV-riboflavin group, inhibition effect on the bacteria growth was found. The UV-riboflavin combination had better inhibition effect on bacteria than UV irradiation alone. The amount of bacteria in the UV-riboflavin group was decreased by 99.1%~99.5% and 54.8%~64.6% in the UV alone group, when the UV light power was 10.052 mW/cm 2 and the irradiation time was 30 min. Moreover, with the increase of the UV power or irradiation time, the survival rates of bacteria were rapidly reduced. Compared with Staphylococcus aureus , Staphylococcus epidermis was more easily to be killed under the action of UV light combined with riboflavin.

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.

Evaluation of UV-fs-LA-MC-ICP-MS for precise in situ copper isotopic microanalysis of cubanite.

PubMed

Ikehata, Kei; Hirata, Takafumi

2013-01-01

We evaluated the capabilities of an in situ method for measuring copper isotopes of cubanite using UV-fs-LA-MC-ICP-MS. A comparison of the UV-fs laser results with those obtained from the NIR-fs laser system shows that there is obviously an improvement in the precision (<0.10‰, 2SE) when using the UV-fs laser. In both wavelength modes, matrix-matched standards are required for reliable in situ copper isotope analysis of cubanite. This method was applied to determinations for copper isotopes of minute cubanite grains in a skarn ore. Copper isotopic ratios of cubanite grains near a weathered surface of the sample are lower than those of intact cubanite grains within the sample, suggesting that selective leaching of heavier copper isotope in primary minerals occurred during weathering.

Simulations of a FIR Oscillator with Large Slippage parameter at Jefferson Lab for FIR/UV pump-probe experiments

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

Benson, Stephen V.; Campbell, L. T.; McNeil, B.W.T.

We previously proposed a dual FEL configuration on the UV Demo FEL at Jefferson Lab that would allow simultaneous lasing at FIR and UV wavelengths. The FIR source would be an FEL oscillator with a short wiggler providing diffraction-limited pulses with pulse energy exceeding 50 microJoules, using the exhaust beam from a UVFEL as the input electron beam. Since the UV FEL requires very short pulses, the input to the FIR FEL is extremely short compared to a slippage length and the usual Slowly Varying Envelope Approximation (SVEA) does not apply. We use a non-SVEA code to simulate this systemmore » both with a small energy spread (UV laser off) and with large energy spread (UV laser on).« less

A solid oxide photoelectrochemical cell with UV light-driven oxygen storage in mixed conducting electrodes

PubMed Central

Walch, Gregor; Rotter, Bernhard; Brunauer, Georg Christoph; Esmaeili, Esmaeil; Opitz, Alexander Karl; Kubicek, Markus; Summhammer, Johann; Ponweiser, Karl

2017-01-01

A single crystalline SrTiO3 working electrode in a zirconia-based solid oxide electrochemical cell is illuminated by UV light at temperatures of 360–460 °C. In addition to photovoltaic effects, this leads to the build-up of a battery-type voltage up to more than 300 mV. After switching off UV light, this voltage only slowly decays. It is caused by UV-induced oxygen incorporation into the mixed conducting working electrode and thus by changes of the oxygen stoichiometry δ in SrTiO3–δ under UV illumination. These changes of the oxygen content could be followed in time-dependent voltage measurements and also manifest themselves in time-dependent resistance changes during and after UV illumination. Discharge currents measured after UV illumination reveal that a large fraction of the existing oxygen vacancies in SrTiO3 become filled under UV light. Additional measurements on cells with TiO2 thin film electrodes show the broader applicability of this novel approach for transforming light into chemical energy and thus the feasibility of solid oxide photoelectrochemical cells (SOPECs) in general and of a “light-charged oxygen battery” in particular. PMID:28261480

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.

UV laser long-path absorption spectroscopy

NASA Technical Reports Server (NTRS)

Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

1994-01-01

Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive absorption measurements some specific problems of those detectors have to be solved experimentally (i.e. fixed pattern noise, dark signal noise, nonuniform efficiency of individual elements, spatial sensitivity variations). In order to improve the low spatial resolution we performed laboratory studies using a multiple reflection cell to convert the long path technique to a real in situ point measurement. Under the conditions of field experiments in Julich residual absorbance signals at present are about 1.5x10(exp -4) corresponding to an OH detection sensitivity of 2x10(exp 6) OH/cm(exp 3) using a light path of 5.8 km. Total integration times for one measurement point vary between a few minutes and an hour.

Responses of Crepis japonica induced by supplemental blue light and UV-A radiation.

PubMed

Constantino, L F da S; Nascimento, L B Dos S; Casanova, L M; Moreira, N Dos S; Menezes, E A; Esteves, R L; Costa, S S; Tavares, E S

2017-02-15

Crepis japonica (L.) D.C. (Asteraceae), a weed with antioxidant, antiallergenic, antiviral and antitumor properties displays both medicinal properties and nutritional value. This study aims to assess the effects of a supplementation of blue light and UV-A radiation on the growth, leaf anatomical structure and phenolic profile of the aerial parts of Crepis japonica. Plants were grown under two light treatments: W (control - white light), W + B (white light supplemented with blue light) and W + UV-A (white light supplemented with UV-A radiation). We recorded the length, width, and weight of fresh and dry leaves, the thickness of the epidermis and mesophyll, and stomata density. The phenolic profiles of the aqueous extracts of the aerial parts were analyzed by HPLC-DAD. There was an increase in the leaf size, stomatal density, and phenolic production, and a thickening of the mesophyll and epidermis. UV-A radiation increased the phenolic production more than blue light. Blue light and UV-A radiation both improved the production of caffeic acid by about 6 and 3 times, respectively, in comparison to control. This compound was first reported as a constituent of the extract from the aerial parts together with caftaric acid. UV-A also promoted the production of chlorogenic acid (about 1.5 times in comparison to the control). We observed that the morphological and chemical parameters of C. japonica are modified in response to blue light and UV-A radiation, which can be used as tools in the cultivation of this species in order to improve its medicinal properties and nutritional value.

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

REVIEW: Optics of globular photonic crystals

NASA Astrophysics Data System (ADS)

Gorelik, V. S.

2007-05-01

The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter ~200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported.

Optical fiber-based setup for in vivo measurement of the delayed fluorescence lifetime of oxygen sensors

NASA Astrophysics Data System (ADS)

Piffaretti, Filippo M.; Santhakumar, Kanappan; Forte, Eddy; van den Bergh, Hubert E.; Wagnières, Georges A.

2011-03-01

A new optical-fiber-based spectrofluorometer for in vivo or in vitro detection of delayed fluorescence is presented and characterized. This compact setup is designed so that it can be readily adapted for future clinical use. Optical excitation is done with a nitrogen laser-pumped, tunable dye laser, emitting in the UV-vis part of the spectrum. Excitation and luminescence signals are carried to and from the biological tissues under investigation, located out of the setup enclosure, by a single optical fiber. These measurements, as well as measurements performed without a fiber on in vitro samples in a thermostable quartz cell, in a controlled-atmosphere enclosure, are possible due to the efficient collection of the laser-induced luminescence light which is collected and focused on the detector with a high aperture parabolic mirror. The detection is based on a gated photomultiplier which allows for time-resolved measurements of the delayed fluorescence intensity. Thus, relevant luminescence lifetimes, typically in the sub-microsecond-to-millisecond range, can be measured with near total rejection of the sample's prompt fluorescence. The instrument spectral and temporal resolution, as well as its sensitivity, is characterized and measurement examples are presented. The primary application foreseen for this setup is the monitoring and adjustment of the light dose delivered during photodynamic therapy.

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research.

PubMed

Oh, Jaechul; Weaver, J L; Karasik, M; Chan, L Y

2015-08-01

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10(15) W/cm(2). The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10(21) cm(-3) with the density scale length of 120 μm along the plasma symmetry axis. The resulting n(e) and T(e) profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

Pulsed laser facilities operating from UV to IR at the Gas Laser Lab of the Lebedev Institute

NASA Astrophysics Data System (ADS)

Ionin, Andrei; Kholin, Igor; Vasil'Ev, Boris; Zvorykin, Vladimir

2003-05-01

Pulsed laser facilities developed at the Gas Lasers Lab of the Lebedev Physics Institute and their applications for different laser-matter interactions are discussed. The lasers operating from UV to mid-IR spectral region are as follows: e-beam pumped KrF laser (λ= 0.248 μm) with output energy 100 J; e-beam sustained discharge CO2(10.6 μm) and fundamental band CO (5-6 μm) lasers with output energy up to ~1 kJ; overtone CO laser (2.5-4.2 μm) with output energy ~ 50 J and N2O laser (10.9 μm) with output energy of 100 J; optically pumped NH3 laser (11-14 μm). Special attention is paid to an e-beam sustained discharge Ar-Xe laser (1.73 μm ~ 100 J) as a potential candidate for a laser-propulsion facility. The high energy laser facilities are used for interaction of laser radiation with polymer materials, metals, graphite, rocks, etc.

Replication of adeno-associated virus in cells irradiated with UV light at 254 nm

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

Yakobson, B.; Hrynko, T.A.; Peak, M.J.

1989-03-01

Irradiation of simian virus 40 (ori mutant)-transformed Chinese hamster embryo cells (OD4 line) with UV light induced a cellular capacity which supported a full cycle of helper-independent adeno-associated virus replication. Monochromatic UV light at 254 nm was about 1,000-fold more effective than UV light at 313 nm, indicating that cellular nucleic acid is the primary chromophore in the UV-induced process leading to permissiveness for adeno-associated virus replication. The UV irradiation and the infection could be separated for up to 12 h without substantial loss of permissiveness. During this time interval, the induction process was partly sensitive to cycloheximide, suggesting amore » requirement for de novo protein synthesis.« less

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.

Ultraviolet micro-Raman spectrograph for the detection of small numbers of bacterial cells

NASA Astrophysics Data System (ADS)

Chadha, S.; Nelson, W. H.; Sperry, J. F.

1993-11-01

The construction of a practical UV micro-Raman spectrograph capable of selective excitation of bacterial cells and other microscopic samples has been described. A reflective objective is used to focus cw laser light on a sample and at the same time collect the scattered light at 180°. With the aid of a quartz lens the image produced is focused on the slits of a spectrograph equipped with a single 2400 grooves/mm grating optimized for 250 nm. Spectra were detected by means of a blue-intensified diode array detector. Resonance Raman spectra of Bacillus subtilis and Flavobacterium capsulatum excited by the 257.2 nm output of a cw laser were recorded in the 900-1800 cm-1 region. Bacterial cells were immobilized on a quartz plate by means of polylysine and were counted visually. Cooling was required to retard sample degradation. Sample sizes ranged from 1 to 50 cells with excitation times varying from 15 to 180 s. Excellent spectra have been obtained from 20 cells in 15 s using a spectrograph having only 3% throughput.

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility

DOE PAGES

Ross, J. S.; Datte, P.; Divol, L.; ...

2016-07-28

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. Here, we report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ 0 = 210 nm) will be used to Thomson scatter from electron plasma densities of ~5 × 10 20more » cm -3 while a 3ω probe will be used for plasma densities of ~1 × 10 19 cm -3. The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).« less

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility

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

Ross, J. S., E-mail: ross36@llnl.gov; Datte, P.; Divol, L.

2016-11-15

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ{sub 0} = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10{sup 20} cm{supmore » −3} while a 3ω probe will be used for plasma densities of ∼1 × 10{sup 19} cm{sup −3}. The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).« less

Light propagation in gas-filled kagomé hollow core photonic crystal fibres

NASA Astrophysics Data System (ADS)

Rodrigues, Sílvia M. G.; Facão, Margarida; Ferreira, Mário F. S.

2018-04-01

We study the propagation of light in kagomé hollow core photonic crystal fibres (HC-PCFs) filled with three different noble gases, namely, helium, xenon and argon. Various properties, including the guided modes, the group-velocity dispersion, and the nonlinear parameter were determined. The zero dispersion wavelength and the nonlinear parameter vary with the gas pressure which may be used to tune the generation of new frequencies using the same pump laser and the same fibre. In the case of the kagomé HC-PCF filled with xenon, the zero dispersion wavelength shifts from 693 to 1973 nm when the pressure is increased from 1 to 150bar, while the effective Kerr nonlinearity becomes comparable to that of silica. We have simulated the propagation of femtosecond pulses launched at 790 nm in order to study the generation of supercontinuum and UV light in kagomé HC-PCFs filled with the noble gases.

Solar UV light regulates flavonoid metabolism in apple (Malus x domestica).

PubMed

Henry-Kirk, Rebecca A; Plunkett, Blue; Hall, Miriam; McGhie, Tony; Allan, Andrew C; Wargent, Jason J; Espley, Richard V

2018-03-01

Ultraviolet-B light (UV-B) is one environmental signal perceived by plants that affects the flavonoid pathway and influences the levels of anthocyanins, flavonols, and proanthocyanidins. To understand the mechanisms underlying UV exposure, apple trees were grown under spectral filters that altered transmission of solar UV light. Fruit analysis showed that UV induced changes in physiology, metabolism, and gene expression levels during development over a season. These changes were sustained after storage. Under low UV, ripening was delayed, fruit size decreased, and anthocyanin and flavonols were reduced. Expression analysis showed changes in response to UV light levels for genes in the regulation and biosynthesis of anthocyanin and flavonols. Transcription of flavonol synthase (FLS), ELONGATED HYPOCOTYL 5 (HY5), MYB10, and MYB22 were down-regulated throughout fruit development under reduced UV. Functional testing showed that the FLS promoter was activated by HY5, and this response was enhanced by the presence of MYB22. The MYB22 promoter can also be activated by the anthocyanin regulator, MYB10. As ambient levels of UV light vary around the globe, this study has implications for future crop production, the quality of which can be determined by the response to UV. © 2018 John Wiley & Sons Ltd.

Inactivation of Salmonella enterica by UV-C Light Alone and in Combination with Mild Temperatures

PubMed Central

Gayán, E.; Serrano, M. J.; Raso, J.; Álvarez, I.

2012-01-01

The aim of this investigation was to study the efficacy of the combined processes of UV light and mild temperatures for the inactivation of Salmonella enterica subsp. enterica and to explore the mechanism of inactivation. The doses to inactivate the 99.99% (4D) of the initial population ranged from 18.03 (Salmonella enterica serovar Typhimurium STCC 878) to 12.75 J ml−1 (Salmonella enterica serovar Enteritidis ATCC 13076). The pH and water activity of the treatment medium did not change the UV tolerance, but it decreased exponentially by increasing the absorption coefficient. An inactivating synergistic effect was observed by applying simultaneous UV light and heat treatment (UV-H). A less synergistic effect was observed by applying UV light first and heat subsequently. UV did not damage cell envelopes, but the number of injured cells was higher after a UV-H treatment than after heating. The synergistic effect observed by combining simultaneous UV and heat treatment opens the possibility to design combined treatments for pasteurization of liquid food with high UV absorptivity, such as fruit juices. PMID:23001665

Surface disinfection by exposure to germicidal UV light.

PubMed

Katara, G; Hemvani, N; Chitnis, S; Chitnis, V; Chitnis, D S

2008-01-01

The present study was aimed to design a simple model to check efficacy of germicidal UV tube, to standardise the position, distance and time for UV light and also to find out its efficacy against medically important bacteria, the bacterial spores and fungi. The microbial cultures tested included gram positive and gram negative bacteria, bacterial spores and fungal spores. The microbes streaked on solid media were exposed to UV light. The inactivation of the order of four logs was observed for bacteria. UV light can have efficient inactivation of bacteria up to a distance of eight feet on either side and exposure time of 30 minutes is adequate.

Long-duration planar direct-drive hydrodynamics experiments on the NIF

NASA Astrophysics Data System (ADS)

Casner, A.; Mailliet, C.; Khan, S. F.; Martinez, D.; Izumi, N.; Kalantar, D.; Di Nicola, P.; Di Nicola, J. M.; Le Bel, E.; Igumenshchev, I.; Tikhonchuk, V. T.; Remington, B. A.; Masse, L.; Smalyuk, V. A.

2018-01-01

The advent of high-power lasers facilities such as the National Ignition Facility (NIF) and the laser megajoule provide unique platforms to study the physics of turbulent mixing flows in high energy density plasmas. We report here on the commissioning of a novel planar direct-drive platform on the NIF, which allows the acceleration of targets during 30 ns. Planar plastic samples were directly irradiated by 300-450 kJ of UV laser light (351 nm) and a very good planarity of the laser drive is demonstrated. No detrimental effect of imprint is observed in the case of these thick plastic targets (300 μm), which is beneficial for future academic experiments requesting similar irradiation conditions. The long-duration direct-drive (DD) platform is thereafter harnessed to study the ablative Rayleigh-Taylor instability (RTI) in DD. The growth of two-dimensional pre-imposed perturbations is quantified through time-resolved face-on x-ray radiography and used as a benchmark for radiative hydrocode simulations. The ablative RTI is then quantified in its highly nonlinear stage starting from intentionally large 3D imprinted broadband modulations. Two generations of bubble mergers is observed for the first time in DD, as a result of the unprecedented long laser acceleration.

Ink-jet printed fluorescent materials as light sources for planar optical waveguides on polymer foils

NASA Astrophysics Data System (ADS)

Bollgruen, Patrick; Gleissner, Uwe; Wolfer, Tim; Megnin, Christof; Mager, Dario; Overmeyer, Ludger; Korvink, Jan G.; Hanemann, Thomas

2016-10-01

Polymer-based optical sensor networks on foils (planar optronic systems) are a promising research field, but it can be challenging to supply them with light. We present a solvent-free, ink-jet printable material system with optically active substances to create planar light sources for these networks. The ink is based on a UV-curable monomer, the fluorescent agents are EuDBMPhen or 9,10-diphenylantracene, which fluoresce at 612 or 430 nm, respectively. We demonstrate the application as light source by printing a small area of fluorescent material on an optical waveguide fabricated by flexographic printing on PMMA foil, resulting in a simple polymer-optical device fabricated entirely by additive deposition techniques. When excited by a 405-nm laser of 10 mW, the emitted light couples into the waveguide and appears at the end of the waveguide. In comparison to conventional light sources, the intensity is weak but could be detected with a photodiode power sensor. In return, the concept has the advantage of being completely independent of any electrical elements or external cable connections.

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation

NASA Astrophysics Data System (ADS)

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-01

The metal-oxide semiconductor TiO2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO2, but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W-1) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO2.

Significantly enhanced visible light response in single TiO2 nanowire by nitrogen ion implantation.

PubMed

Wu, Pengcheng; Song, Xianyin; Si, Shuyao; Ke, Zunjian; Cheng, Li; Li, Wenqing; Xiao, Xiangheng; Jiang, Changzhong

2018-05-04

The metal-oxide semiconductor TiO 2 shows enormous potential in the field of photoelectric detection; however, UV-light absorption only restricts its widespread application. It is considered that nitrogen doping can improve the visible light absorption of TiO 2 , but the effect of traditional chemical doping is far from being used for visible light detection. Herein, we dramatically broadened the absorption spectrum of the TiO 2 nanowire (NW) by nitrogen ion implantation and apply the N-doped single TiO 2 NW to visible light detection for the first time. Moreover, this novel strategy effectively modifies the surface states and thus regulates the height of Schottky barriers at the metal/semiconductor interface, which is crucial to realizing high responsivity and a fast response rate. Under the illumination of a laser with a wavelength of 457 nm, our fabricated photodetector exhibits favorable responsivity (8 A W -1 ) and a short response time (0.5 s). These results indicate that ion implantation is a promising method in exploring the visible light detection of TiO 2 .

An enhancing effect of visible light and UV radiation on phenolic compounds and various antioxidants in broad bean seedlings.

PubMed

Younis, Mahmoud El-Baz; Hasaneen, Mohammed Naguib Abdel-Ghany; Abdel-Aziz, Heba Mahmoud Mohammed

2010-10-01

Exposure of dark- or ambient visible light-grown broad bean seedlings to low (LL) and high (HL) visible light intensities, UV-A or UV-C, either alone or in combination, induced significant increases in total phenolic compounds as well as in anthocyanins content, throughout the germination period, as compared with the respective levels in control seedlings. In general, as compared with control levels, exposure of both dark- or light-grown broad bean seedlings to LL, HL, UV-A or UV-C, induced significant increases in the contents of non-enzymatic antioxidants (total ascorbate; ASA-DASA and total glutathione; GSSG-GSH) and enzymatic antioxidant activities (superoxide dismutase; SOD, catalase; CAT, ascorbate peroxidase; APO and glutathione reductase; GR). The obtained results are discussed in relation to induced mechanisms of protection and repair from the inevitable exposure to damaging visible light and UV-radiation. © 2010 Landes Bioscience

An enhancing effect of visible light and UV radiation on phenolic compounds and various antioxidants in broad bean seedlings

PubMed Central

Hasaneen, Mohammed Naguib Abdel-Ghany; Abdel-Aziz, Heba Mahmoud Mohammed

2010-01-01

Exposure of dark- or ambient visible light-grown broad bean seedlings to low (LL) and high (HL) visible light intensities, UV-A or UV-C, either alone or in combination, induced significant increases in total phenolic compounds as well as in anthocyanins content, throughout the germination period, as compared with the respective levels in control seedlings. In general, as compared with control levels, exposure of both dark- or light-grown broad bean seedlings to LL, HL, UV-A or UV-C, induced significant increases in the contents of non-enzymatic antioxidants (total ascorbate; ASA-DASA and total glutathione; GSSG-GSH) and enzymatic antioxidant activities (superoxide dismutase; SOD, catalase; CAT, ascorbate peroxidase; APO and glutathione reductase; GR). The obtained results are discussed in relation to induced mechanisms of protection and repair from the inevitable exposure to damaging visible light and UV radiation. PMID:20505357

Investigation of Highly Unsteady Aerodynamics of Flapping Wings With/Without a Flexible Training Edge Using High Resolution MTV Measurements

DTIC Science & Technology

2013-10-14

Aerodynamics Laboratory (TMUAL) at MSU. This modification , which was completed successfully, included two parts: (I) the addition of two large...quartz inserts and the 3 DOF motion system. The sketch also depicts a typical UV laser beam path for Molecular Tagging Velocimetry measurements UV laser ... beam UV mirror 3 IV.2. Airfoil Fabrication Using 3D Printing Methods For the parts of the investigation focused on studying the effect of

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.

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.

Using UVC Light-Emitting Diodes at Wavelengths of 266 to 279 Nanometers To Inactivate Foodborne Pathogens and Pasteurize Sliced Cheese

PubMed Central

Kim, Soo-Ji; Kim, Do-Kyun

2015-01-01

UVC light is a widely used sterilization technology. However, UV lamps have several limitations, including low activity at refrigeration temperatures, a long warm-up time, and risk of mercury exposure. UV-type lamps only emit light at 254 nm, so as an alternative, UV light-emitting diodes (UV-LEDs) which can produce the desired wavelengths have been developed. In this study, we validated the inactivation efficacy of UV-LEDs by wavelength and compared the results to those of conventional UV lamps. Selective media inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated using UV-LEDs at 266, 270, 275, and 279 nm in the UVC spectrum at 0.1, 0.2, 0.5, and 0.7 mJ/cm2, respectively. The radiation intensity of the UV-LEDs was about 4 μW/cm2, and UV lamps were covered with polypropylene films to adjust the light intensity similar to those of UV-LEDs. In addition, we applied UV-LED to sliced cheese at doses of 1, 2, and 3 mJ/cm2. Our results showed that inactivation rates after UV-LED treatment were significantly different (P < 0.05) from those of UV lamps at a similar intensity. On microbiological media, UV-LED treatments at 266 and 270 nm showed significantly different (P < 0.05) inactivation effects than other wavelength modules. For sliced cheeses, 4- to 5-log reductions occurred after treatment at 3 mJ/cm2 for all three pathogens, with negligible generation of injured cells. PMID:26386061

Fluoride glass fibers: applications and prospects

NASA Astrophysics Data System (ADS)

Poulain, Marcel

1998-09-01

Fluoride glass fibers have been intensively developed for the last 20 years. A major effort was devoted to the fabrication of low loss fibers for repeaterless long haul telecommunications. This step which ended in the late eighties provided the basic technology for the manufacturing of multimode and single mode fibers with minimum losses below 10 dB/km. Such fibers area now used for various passive applications requiring the handling of IR signal. In this respect, fluoride fibers are complementary to silica fibers when wavelength exceeds 2 micrometers . Some practical set ups are operating for IR imaging, remote spectroscopy and thermometry. Special fibers such as polarization maintaining fibers have been developed for interferometric astronomy, which could also apply to sensors. UV transmission has still to be developed. Laser power delivery is another field of application for these fibers. YAG:Er laser at 2.9 micrometers attracts a growing interest for medical applications, ophthalmology and dentistry, while prospects for CO laser are positive. Active fibers are based on rare earth doped single mode fibers. They lead to the definition of numerous new laser lines and emphasized the potential of up conversion for the generation of visible light using IR pumping laser diodes. High power output has been achieved in the blue and the red light, which open prospects for compact and all solid state fiber lasers for a wide range of applications, from displays to medical uses. Optical amplification makes another field of R and D centered on telecommunication needs. Pr3+ doped fluoride fibers have been used for the 1.3 micrometers band, and Er based fluoride fiber amplifiers exhibit wider and flatter gain than those made from silica. Optical amplification may be implemented at other wavelengths for more general purposes.

Influence of UV illumination on the cold temperature operation of a LiNbO(3) Q-switched Nd:YAG laser.

PubMed

Cole, Brian; Goldberg, Lew; King, Vernon; Leach, Jeff

2010-04-26

UV illumination of a lithium niobate Q-switch was demonstrated as an effective means to eliminate a loss in hold-off and associated prelasing that occurs under cold temperature operation of Q-switched lasers. This degradation occurs due to the pyroelectric effect, where an accumulation of charge on crystal faces results in a reduction in the Q-switch hold-off and a spatially variable loss of the Q-switch in its high-transmission state, both resulting in lowering of the maximum Q-switched pulse energy. With UV illumination, the resulting creation of photo-generated carriers was shown to be effective in eliminating both of these effects. A Q-switched Nd:YAG laser utilizing UV-illuminated LiNbO(3) was shown to operate under cold temperatures without prelasing or spatially variable loss.

Investigation of the oxidation mechanisms of limonene photosensitized by imidazole-2-carboxaldehyde

NASA Astrophysics Data System (ADS)

Rossignol, Stéphanie; Tinel, Liselotte; Aregahegn, Kifle; George, Christian

2013-04-01

Recent studies have revealed the significant formation of light absorbing materials, including imidazole and imidazole derivatives, in aqueous aerosol mimics in the presence of both ammonium sulphate and glyoxal (Galloway et al. 2009; Yu et al. 2011; Kampf et al. 2012). Besides the potential impact on radiative properties of secondary organic aerosols, our team has shown that imidazole-2-carboxaldehyde (IC) acts as a photosensitizer, initiating aerosols growth in the presence of gaseous limonene and UV/visible light (Aregahegn et al., abstract submitted). This work focuses on the characterisation of the chemical mechanisms leading to this aerosols growth, and on the major products identification. The molecular composition of organic/aqueous solutions exposed to UV/visible light and containing IC and limonene is followed in time by HR-ESI-MS/MS in positive and negative modes. Limonene consumption is followed by HPLC-UV. HR-ESI-MS/MS analyses are performed in parallel on IC/ammonium sulphate aerosols exposed to gaseous limonene and UV/visible light, in particular to assess the relevance of in solution experiments. Besides, the lifetime of the triplet state of IC in aqueous/organic solutions in the presence of different terpenes is monitored by laser photolysis experiments and compared in order to explain the first steps of the photosensitized reaction. First HR-ESI-MS/MS results show the formation of the major "traditional" limonene oxidation products (e.g., coming from gas phase limonene ozonolysis) during the irradiation of organic solutions containing IC and limonene: limononaldehyde, keto-limononaldehyde, limonic acid, limononic acid ... Hundreds of other oxygenated species are however detected, typically with a number of carbon atoms ranging from 4 to 20 and with O/C ratios ranging from 0.2 to 0.7. Monomers and dimers of limonene oxidation products are observed but species with lower carbon numbers than monomeric compounds are predominant. Moreover, and surprisingly, the production rates of all products tend to increase with reaction time and the limonene consumption presents an apparent linearity. These preliminary findings would suggest, in our experimental conditions, an oxidation mechanism initiated by a relatively slow photosensitized process e.g., electron transfer from limonene to the triplet state of IC (which formation is confirmed by laser photolysis experiments), followed by an increase of radicals in the solution leading to an extended limonene oxidation. The UV radiation, and/or the low concentration of reactants, are susceptible in our context to limit the formation of oligomers (Bateman et al. 2011) and promote fragmentation pathways. If these hypothesis need to be confirmed, this study appears to be a pertinent way to investigate the mechanisms and to assess the importance of photosensitized reactions in secondary organic aerosols growth and, possibly, in other air/condensed phase surfaces present in the environment, such as air/sea interface. Bateman, A. P., et al. (2011). Physical Chemistry Chemical Physics 13(26) 12199-12212. Galloway, M. M., et al. (2009). Atmospheric Chemistry and Physics 9(10) 3331-3345. Kampf, C. J., et al. (2012). Atmospheric Chemistry and Physics 12(14) 6323-6333. Yu, G., et al. (2011). Environmental Science & Technology 45(15) 6336-6342.

The imprints of the high light and UV-B stresses in Oryza sativa L. 'Kanchana' seedlings are differentially modulated.

PubMed

Faseela, Parammal; Puthur, Jos T

2018-01-01

High light and ultraviolet-B radiation (UV-B) are generally considered to have negative impact on photosynthesis and plant growth. The present study evaluates the tolerance potential of three cultivars of Oryza sativa L. (Kanchana, Mattatriveni and Harsha) seedlings towards high light and UV-B stress on the basis of photosynthetic pigment degradation, chlorophyll a fluorescence parameters and rate of lipid peroxidation, expressed by malondialdehyde content. Surprisingly, it was revealed that Kanchana was the most sensitive cultivar towards high light and at the same time it was the most tolerant cultivar towards UV-B stress. This contrasting feature of Kanchana towards high light and UV-B tolerance was further studied by analyzing photosystem (PS) I and II activity, mitochondrial activity, chlorophyll a fluorescence transient, enzymatic and non-enzymatic antioxidant defense system. Due to the occurrence of more PS I and PSII damages, the inhibition of photochemical efficiency and emission of dissipated energy as heat or fluorescence per PSII reaction center was higher upon high light exposure than UV-B treatments in rice seedlings of Kanchana. The mitochondrial activity was also found to be drastically altered upon high light as compared to UV-B treatments. The UV-B induced accumulation of non-enzymatic antioxidants (proline, total phenolics, sugar and ascorbate) and enzymatic antioxidants (ascorbate peroxidase, guaiacol peroxidase, superoxide dismutase and glutathione reductase) in rice seedlings than those subjected to high light exposure afforded more efficient protection against UV-B radiation in rice seedlings. Our results proved that high tolerance of Kanchana towards UV-B than high light treatments, correlated linearly with the protected photosynthetic and mitochondrial machinery which was provided by upregulation of antioxidants particularly by total phenolics, ascorbate and ascorbate peroxidase in rice seedlings. Data presented in this study conclusively proved that rice cultivar Kanchana respond to different environmental signals independently and tolerance mechanisms to individual stress factors was also varied. Copyright © 2017 Elsevier B.V. All rights reserved.

Suppression of cucumber powdery mildew by UV-B is affected by background light quality

USDA-ARS?s Scientific Manuscript database

Brief (5-10 min) exposure to UV-B radiation (280-300 nm) suppressed powdery mildew (Podosphaera xanthii) on Cucumis sativus. The effect was enhanced by red light (600-660 nm), but offset by blue light (420-500 nm) and UV-A (300-420 nm). Compared to untreated controls, 2 h red light from specific lig...

Development of injector/amplifier XUV lasers and initial studies of ultrashort pulse UV multiphoton ionization

NASA Astrophysics Data System (ADS)

Key, Michael H.; Blyth, W. J.; Cairns, Gerald F.; Damerell, A. R.; Dangor, A. E.; Danson, Colin N.; Evans, J. M.; Hirst, Graeme J.; Holden, M.; Hooker, Chris J.; Houliston, J. R.; Krishnan, J.; Lewis, Ciaran L. S.; Lister, J. M. D.; MacPhee, Andrew G.; Najmudin, Z.; Neely, David; Norreys, Peter A.; Offenberger, Allen A.; Osvay, Karoly; Pert, Geoffrey J.; Preston, S. G.; Ramsden, Stuart A.; Ross, Ian N.; Sibbett, Wilson; Tallents, Gregory J.; Smith, C.; Wark, Justin S.; Zhang, Jie

1994-02-01

An injector-amplifier architecture for XUV lasers has been developed and demonstrated using the Ge XXIII collisional laser. Results are described for injection into single and double plasma amplifiers. Prismatic lens-like and higher order aberrations in the amplifier are considered. Limitations on ultimate brightness are discussed and also scaling to operation at shorter wavelengths. A preliminary study has been made of UV multiphoton ionization using 300 fs pulses at high intensity.

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

The Influence of Geometrical Structure of AlInGaN Double Quantum Well (DQWs) UV Diode Laser on Its Performance and Operating Parameters

NASA Astrophysics Data System (ADS)

Ghazai, A. J.; Thahab, S. M.; Hassan, H. Abu; Hassan, Z.

2010-07-01

The development of efficient MQWs active regions of quaternary InAlGaN in the ultraviolet (UV) region is an engaging challenge by itself. Demonstrating lasers at such low wavelength will require resolving a number of materials, growth and device design issues. However, the quaternary AlInGaN represents a more versatile material since the bandgap and lattice constant can be independently varied. We report a quaternary AlInGaN double-quantum wells (DQWs) UV laser diode (LDs) study by using the simulation program of Integrated System Engineering-Technical Computer Aided Design (ISE TCAD). Advanced physical models of semiconductor properties were used. In this paper, the enhancement in the performance of AlInGaN laser diode can be achieved by optimizing the laser structure geometry design. The AlInGaN laser diodes operating parameters such as internal quantum efficiency ηi, internal loss αi and transparency threshold current density show effective improvements that contribute to a better performance.

Acclimation to UV-B radiation and visible light in Lactuca sativa involves up-regulation of photosynthetic performance and orchestration of metabolome-wide responses.

PubMed

Wargent, J J; Nelson, B C W; McGhie, T K; Barnes, P W

2015-05-01

UV-B radiation is often viewed as a source of stress for higher plants. In particular, photosynthetic function has been described as a common target for UV-B impairment; yet as our understanding of UV-B photomorphogenesis increases, there are opportunities to expand the emerging paradigm of regulatory UV response. Lactuca sativa is an important dietary crop species and is often subjected to rapid sunlight exposure at field transfer. Acclimation to UV-B and visible light conditions in L. sativa was dissected using gas exchange and chlorophyll fluorescence measurements, in addition to non-destructive assessments of UV epidermal shielding (SUV ). After UV-B treatment, seedlings were subjected to wide-range metabolomic analysis using liquid chromatography hybrid quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS). During the acclimation period, net photosynthetic rate increased in UV-treated plants, epidermal UV shielding increased in both subsets of plants transferred to the acclimatory conditions (UV+/UV- plants) and Fv /Fm declined slightly in UV+/UV- plants. Metabolomic analysis revealed that a key group of secondary compounds was up-regulated by higher light conditions, yet several of these compounds were elevated further by UV-B radiation. In conclusion, acclimation to UV-B radiation involves co-protection from the effects of visible light, and responses to UV-B radiation at a photosynthetic level may not be consistently viewed as damaging to plant development. © 2014 John Wiley & Sons Ltd.

Inferred UV Fluence Focal-Spot Profiles from Soft X-Ray Pinhole Camera Measurements on OMEGA

NASA Astrophysics Data System (ADS)

Theobald, W.; Sorce, C.; Epstein, R.; Keck, R. L.; Kellogg, C.; Kessler, T. J.; Kwiatkowski, J.; Marshall, F. J.; Seka, W.; Shvydky, A.; Stoeckl, C.

2017-10-01

The drive uniformity of OMEGA cryogenic implosions is affected by UV beamfluence variations on target, which require careful monitoring at full laser power. This is routinely performed with multiple pinhole cameras equipped with charge-injection devices (CID's) that record the x-ray emission in the 3- to 7-keV photon energy range from an Au-coated target. The technique relies on the knowledge of the relation between x-ray fluence Fx and UV fluence FUV ,Fx FUVγ , with a measured γ = 3.42 for the CID-based diagnostic and 1-ns laser pulse. It is demonstrated here that using a back-thinned charge-coupled-device camera with softer filtration for x-rays with photon energies <2 keV and well calibrated pinhole provides a lower γ 2 and a larger dynamic range in the measured UV fluence. Inferred UV fluence profiles were measured for 100-ps and 1-ns laser pulses and were compared to directly measured profiles from a UV equivalent-target-plane diagnostic. Good agreement between both techniques is reported for selected beams. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Isolation and characterization of ultraviolet light-sensitive mutants of the blue-green alga Anacystis nidulans.

NASA Technical Reports Server (NTRS)

Asato, Y.

1972-01-01

Three independently isolated ultraviolet light sensitive (uvs) mutants of Anacystis nidulans were characterized. Strain uvs-1 showed the highest sensitivity to UV by its greatly reduced photoreactivation capacity following irradiation. Pretreatment with caffeine suppressed the dark-survival curve of strain uvs-1, thus indicating the presence of excision enzymes involved in dark repair. Under 'black' and 'white' illumination, strain uvs-1 shows photorecovery properties comparable with wild-type cultures. Results indicate that strains uvs-1, uvs-35, and uvs-88 are probably genetically distinct UV-sensitive mutants.

Mass spectrometry of flavonoid vicenin-2, based sunlight barriers in Lychnophora species.

PubMed

Silva, Denise Brentan; Turatti, Izabel Cristina Casanova; Gouveia, Dayana Rubio; Ernst, Madeleine; Teixeira, Simone Pádua; Lopes, Norberto Peporine

2014-03-07

Lychnophora salicifolia plants collected from four different places in Brazil (three states: Goias, Minas Gerais and Bahia) revealed a conserved accumulation of vicenin-2, a di-C-glycosyl flavonoid. Quantitative studies by UPLC-MS/MS showed high concentration of vicenin-2 in leaves from sixty specimens of six Lychnophora species. So the tissue distributions of vicenin-2 were evaluated in wild Lychnophora leaves (Asteraceae) by laser based imaging mass spectrometry (IMS) to propose its distributions and possible functions for the species analyzed. Mass spectrometric imaging revealed that vicenin-2, unlike other flavonoids, was produced at the top of the leaves. The combination of localization and UV absorption properties of vicenin-2 suggests that it could act as a UV light barrier to protect the plants, since plants are sessile organisms that have to protect themselves from harsh external conditions such as intense sunlight.

Quantitative inactivation-mechanisms of P. digitatum and A. niger spores based on atomic oxygen dose

NASA Astrophysics Data System (ADS)

Ito, Masafumi; Hashizume, Hiroshi; Ohta, Takayuki; Hori, Masaru

2014-10-01

We have investigated inactivation mechanisms of Penicillium digitatum and Asperguills niger spores using atmospheric-pressure radical source quantitatively. The radical source was specially developed for supplying only neutral radicals without charged species and UV-light emissions. Reactive oxygen radical densities such as grand-state oxygen atoms, excited-state oxygen molecules and ozone were measured using VUV and UV absorption spectroscopies. The measurements and the treatments of spores were carried out in an Ar-purged chamber for eliminating the influences of OH, NOx and so on. The results revealed that the inactivation of spores can be explained by atomic-oxygen dose under the conditions employing neutral ROS irradiations. On the basis of the dose, we have observed the changes of intracellular organelles and membrane functions using TEM, SEM and confocal- laser fluorescent microscopy. From these results, we discuss the detail inactivation-mechanisms quantitatively based on atomic-oxygen dose.

Mass Spectrometry of Flavonoid Vicenin-2, Based Sunlight Barriers in Lychnophora species

PubMed Central

Silva, Denise Brentan; Turatti, Izabel Cristina Casanova; Gouveia, Dayana Rubio; Ernst, Madeleine; Teixeira, Simone Pádua; Lopes, Norberto Peporine

2014-01-01

Lychnophora salicifolia plants collected from four different places in Brazil (three states: Goias, Minas Gerais and Bahia) revealed a conserved accumulation of vicenin-2, a di-C-glycosyl flavonoid. Quantitative studies by UPLC-MS/MS showed high concentration of vicenin-2 in leaves from sixty specimens of six Lychnophora species. So the tissue distributions of vicenin-2 were evaluated in wild Lychnophora leaves (Asteraceae) by laser based imaging mass spectrometry (IMS) to propose its distributions and possible functions for the species analyzed. Mass spectrometric imaging revealed that vicenin-2, unlike other flavonoids, was produced at the top of the leaves. The combination of localization and UV absorption properties of vicenin-2 suggests that it could act as a UV light barrier to protect the plants, since plants are sessile organisms that have to protect themselves from harsh external conditions such as intense sunlight. PMID:24603617

Mass Spectrometry of Flavonoid Vicenin-2, Based Sunlight Barriers in Lychnophora species

NASA Astrophysics Data System (ADS)

Silva, Denise Brentan; Turatti, Izabel Cristina Casanova; Gouveia, Dayana Rubio; Ernst, Madeleine; Teixeira, Simone Pádua; Lopes, Norberto Peporine

2014-03-01

Lychnophora salicifolia plants collected from four different places in Brazil (three states: Goias, Minas Gerais and Bahia) revealed a conserved accumulation of vicenin-2, a di-C-glycosyl flavonoid. Quantitative studies by UPLC-MS/MS showed high concentration of vicenin-2 in leaves from sixty specimens of six Lychnophora species. So the tissue distributions of vicenin-2 were evaluated in wild Lychnophora leaves (Asteraceae) by laser based imaging mass spectrometry (IMS) to propose its distributions and possible functions for the species analyzed. Mass spectrometric imaging revealed that vicenin-2, unlike other flavonoids, was produced at the top of the leaves. The combination of localization and UV absorption properties of vicenin-2 suggests that it could act as a UV light barrier to protect the plants, since plants are sessile organisms that have to protect themselves from harsh external conditions such as intense sunlight.

Organic light-emitting devices using spin-dependent processes

DOEpatents

Vardeny, Z. Valy; Wohlgenannt, Markus

2010-03-23

The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.

III-V aresenide-nitride semiconductor materials and devices

NASA Technical Reports Server (NTRS)

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

1997-01-01

III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

High speed micromachining with high power UV laser

NASA Astrophysics Data System (ADS)

Patel, Rajesh S.; Bovatsek, James M.

2013-03-01

Increasing demand for creating fine features with high accuracy in manufacturing of electronic mobile devices has fueled growth for lasers in manufacturing. High power, high repetition rate ultraviolet (UV) lasers provide an opportunity to implement a cost effective high quality, high throughput micromachining process in a 24/7 manufacturing environment. The energy available per pulse and the pulse repetition frequency (PRF) of diode pumped solid state (DPSS) nanosecond UV lasers have increased steadily over the years. Efficient use of the available energy from a laser is important to generate accurate fine features at a high speed with high quality. To achieve maximum material removal and minimal thermal damage for any laser micromachining application, use of the optimal process parameters including energy density or fluence (J/cm2), pulse width, and repetition rate is important. In this study we present a new high power, high PRF QuasarR 355-40 laser from Spectra-Physics with TimeShiftTM technology for unique software adjustable pulse width, pulse splitting, and pulse shaping capabilities. The benefits of these features for micromachining include improved throughput and quality. Specific example and results of silicon scribing are described to demonstrate the processing benefits of the Quasar's available power, PRF, and TimeShift technology.

The vitamin D hypothesis revisited: race-based disparities in birth outcomes in the United States and ultraviolet light availability.

PubMed

Thayer, Zaneta M

2014-04-15

Skin color has been proposed to contribute to race-based health disparities in the United States because of differences in ultraviolet (UV) light-induced vitamin D synthesis. The prediction of this hypothesis, herein named the UVD hypothesis, is that racial disparities in health outcomes are correlated with UV light availability. This paper investigates whether UV light availability is associated with disparities in the rates of low birth weight (LBW) and preterm birth (PTB) between whites and blacks, because these outcomes are thought to be influenced by vitamin D status and to shape disease risk in later life. Data on LBW and PTB from 2007 (n = 2,825,620 births) were compared with data on UV light exposure across the United States. Contrary to the predictions of the UVD hypothesis, LBW and PTB rate disparities were greatest in states with the highest UV light exposure. Notably, income inequality was positively and significantly related to LBW and PTB disparities, even after controlling for UV light availability. The results of this analysis demonstrate that there is a significant environmental gradient in racial disparities in birth outcomes in the United States, but other social or environmental factors associated with living in the southern United States are likely stronger contributors to disparities in birth outcomes than UV light-induced vitamin D status.

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.

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.

Visible light induced electropolymerization of suspended hydrogel bioscaffolds in a microfluidic chip.

PubMed

Li, Pan; Yu, Haibo; Liu, Na; Wang, Feifei; Lee, Gwo-Bin; Wang, Yuechao; Liu, Lianqing; Li, Wen Jung

2018-05-23

The development of microengineered hydrogels co-cultured with cells in vitro could advance in vivo bio-systems in both structural complexity and functional hierarchy, which holds great promise for applications in regenerative tissues or organs, drug discovery and screening, and bio-sensors or bio-actuators. Traditional hydrogel microfabrication technologies such as ultraviolet (UV) laser or multiphoton laser stereolithography and three-dimensional (3D) printing systems have advanced the development of 3D hydrogel micro-structures but need either expensive and complex equipment, or harsh material selection with limited photoinitiators. Herein, we propose a simple and flexible hydrogel microfabrication method based on a ubiquitous visible-light projection system combined with a custom-designed photosensitive microfluidic chip, to rapidly (typically several to tens of seconds) fabricate various two-dimensional (2D) hydrogel patterns and 3D hydrogel constructs. A theoretical layer-by-layer model that involves continuous polymerizing-delaminating-polymerizing cycles is presented to explain the polymerization and structural formation mechanism of hydrogels. A large area of hydrogel patterns was efficiently fabricated without the usage of costly laser systems or photoinitiators, i.e., a stereoscopic mesh-like hydrogel network with intersecting hydrogel micro-belts was fabricated via a series of dynamic-changing digital light projections. The pores and gaps of the hydrogel network are tunable, which facilitates the supply of nutrients and discharge of waste in the construction of 3D thick bio-models. Cell co-culture experiments showed the effective regulation of cell spreading by hydrogel scaffolds fabricated by the new method presented here. This visible light enabled hydrogel microfabrication method may provide new prospects for designing cell-based units for advanced biomedical studies, e.g., for 3D bio-models or bio-actuators in the future.

UV light-induced survival response in a highly radiation-resistant isolate of the Moraxella-acinetobacter group

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

Keller, L.C.; Thompson, T.L.; Maxcy, R.B.

1982-02-01

A highly radiation-resistant member of the Moraxella-Acinetobacter group, isolate 4, obtained from meat, was studied to determine the effect of preexposure to UV radiation on subsequent UV light resistance. Cultures that were preexposed to UV light and incubated for a short time in plate count broth exhibited increased survival of a UV light challenge dose. This response was inhibited in the presence of chloramphenicol. Frequencies of mutation to streptomycin, trimethoprim, and sulfanilamide resistance remained the same after the induction of this survival response and were not altered by treatment with mutagens, with the exception of mutation to streptomycin resistance aftermore » ..gamma..-irradiation or nitrosoguanidine or methyl methane sulfonate treatment. The results indicated that isolate 4 has a UV light-inducible UV light resistance mechanism which is not associated with increased mutagenesis. The characteristics of the radiation resistance response in this organism are similar to those of certain other common food contaminants. Therefore, considered as part of the total microflora of meat, isolate 4 and the other radiation-resistant Moraxella-Acinetobacter isolates should not pose unique problems in a proposed radappertizaton process.« less

UV-B light contributes directly to the synthesis of chiloglottone floral volatiles

PubMed Central

Amarasinghe, Ranamalie; Poldy, Jacqueline; Matsuba, Yuki; Barrow, Russell A.; Hemmi, Jan M.; Pichersky, Eran; Peakall, Rod

2015-01-01

Background and Aims Australian sexually deceptive Chiloglottis orchids attract their specific male wasp pollinators by means of 2,5-dialkylcyclohexane-1,3-diones or ‘chiloglottones’, representing a newly discovered class of volatiles with unique structures. This study investigated the hypothesis that UV-B light at low intensities is directly required for chiloglottone biosynthesis in Chiloglottis trapeziformis. Methods Chiloglottone production occurs only in specific tissue (the callus) of the labellum. Cut buds and flowers, and whole plants with buds and flowers, sourced from the field, were kept in a growth chamber and interactions between growth stage of the flowers and duration and intensity of UV-B exposure on chiloglottone production were studied. The effects of the protein synthesis inhibitor cycloheximide were also examined. Key Results Chiloglottone was not present in buds, but was detected in buds that were manually opened and then exposed to sunlight, or artificial UV-B light for ≥5 min. Spectrophotometry revealed that the sepals and petals blocked UV-B light from reaching the labellum inside the bud. Rates of chiloglottone production increased with developmental stage, increasing exposure time and increasing UV-B irradiance intensity. Cycloheximide did not inhibit the initial production of chiloglottone within 5 min of UV-B exposure. However, inhibition of chiloglottone production by cycloheximide occurred over 2 h of UV-B exposure, indicating a requirement for de novo protein synthesis to sustain chiloglottone production under UV-B. Conclusions The sepals and petals of Chiloglottis orchids strongly block UV-B wavelengths of light, preventing chiloglottone production inside the bud. While initiation of chiloglottone biosynthesis requires only UV-B light, sustained chiloglottone biosynthesis requires both UV-B and de novo protein biosynthesis. The internal amounts of chiloglottone in a flower reflect the interplay between developmental stage, duration and intensity of UV-B exposure, de novo protein synthesis, and feedback loops linked to the starting amount of chiloglottone. It is concluded that UV-B light contributes directly to chiloglottone biosynthesis. These findings suggest an entirely new and unexpected biochemical reaction that might also occur in taxa other than these orchids. PMID:25649114

CRYPTOCHROME mediates behavioral executive choice in response to UV light

PubMed Central

Baik, Lisa S.; Fogle, Keri J.; Roberts, Logan; Galschiodt, Alexis M.; Chevez, Joshua A.; Recinos, Yocelyn; Nguy, Vinh; Holmes, Todd C.

2017-01-01

Drosophila melanogaster CRYPTOCHROME (CRY) mediates behavioral and electrophysiological responses to blue light coded by circadian and arousal neurons. However, spectroscopic and biochemical assays of heterologously expressed CRY suggest that CRY may mediate functional responses to UV-A (ultraviolet A) light as well. To determine the relative contributions of distinct phototransduction systems, we tested mutants lacking CRY and mutants with disrupted opsin-based phototransduction for behavioral and electrophysiological responses to UV light. CRY and opsin-based external photoreceptor systems cooperate for UV light-evoked acute responses. CRY mediates behavioral avoidance responses related to executive choice, consistent with its expression in central brain neurons. PMID:28062690

Detection of elemental mercury by multimode diode laser correlation spectroscopy.

PubMed

Lou, Xiutao; Somesfalean, Gabriel; Svanberg, Sune; Zhang, Zhiguo; Wu, Shaohua

2012-02-27

We demonstrate a method for elemental mercury detection based on correlation spectroscopy employing UV laser radiation generated by sum-frequency mixing of two visible multimode diode lasers. Resonance matching of the multimode UV laser is achieved in a wide wavelength range and with good tolerance for various operating conditions. Large mode-hops provide an off-resonance baseline, eliminating interferences from other gas species with broadband absorption. A sensitivity of 1 μg/m3 is obtained for a 1-m path length and 30-s integration time. The performance of the system shows promise for mercury monitoring in industrial applications.

Bile Salt Micelles and Phospholipid Vesicles Present in Simulated and Human Intestinal Fluids: Structural Analysis by Flow Field-Flow Fractionation/Multiangle Laser Light Scattering.

PubMed

Elvang, Philipp A; Hinna, Askell H; Brouwers, Joachim; Hens, Bart; Augustijns, Patrick; Brandl, Martin

2016-09-01

Knowledge about colloidal assemblies present in human intestinal fluids (HIFs), such as bile salt micelles and phospholipid vesicles, is regarded of importance for a better understanding of the in vivo dissolution and absorption behavior of poorly soluble drugs (Biopharmaceutics Classification System class II/IV drugs) because of their drug-solubilizing ability. The characterization of these potential drug-solubilizing compartments is a prerequisite for further studies of the mechanistic interplays between drug molecules and colloidal structures within HIFs. The aim of the present study was to apply asymmetrical flow field-flow fractionation (AF4) in combination with multiangle laser light scattering in an attempt to reveal coexistence of colloidal particles in both artificial and aspirated HIFs and to determine their sizes. Asymmetrical flow field-flow fractionation/multiangle laser light scattering analysis of the colloidal phase of intestinal fluids allowed for a detailed insight into the whole spectrum of submicron- to micrometer-sized particles. With respect to the simulated intestinal fluids mimicking fasted and fed state (FaSSIF-V1 and FeSSIF-V1, respectively), FaSSIF contained one distinct size fraction of colloidal assemblies, whereas FeSSIF contained 2 fractions of colloidal species with significantly different sizes. These size fractions likely represent (1) mixed taurocholate-phospholipid-micelles, as indicated by a size range up to 70 nm (in diameter) and a strong UV absorption and (2) small phospholipid vesicles of 90-210 nm diameter. In contrast, within the colloidal phase of the fasted state aspirate of a human volunteer, 4 different size fractions were separated from each other in a consistent and reproducible manner. The 2 fractions containing large particles showed mean sizes of approximately 50 and 200 nm, respectively (intensity-weighted mean diameter, Dz), likely representing mixed cholate/phospholipid micelles and phospholipid vesicles, respectively. The sizes of the smaller 2 fractions being below the size range of multiangle laser light scattering analysis (<20 nm) and their strong UV absorption indicates that they represent either pure cholate micelles or small mixed micelles. Within the colloidal fraction of the fed-state human aspirate, similar colloidal assemblies were detected as in the fasted state human aspirates. The observed differences between SIF and HIF indicate that the simulated intestinal fluids (FaSSIF-V1 and FeSSIF-V1) represent rather simplified models of the real human intestinal environment in terms of coexisting colloidal particles. It is hypothesized that the different supramolecular assemblies detected differ in their lipid composition, which may affect their affinity toward drug compounds and thus the drug-solubilizing capabilities. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Compact probing system using remote imaging for industrial plant maintenance

NASA Astrophysics Data System (ADS)

Ito, F.; Nishimura, A.

2014-03-01

Laser induced breakdown spectroscopy (LIBS) and endoscope observation were combined to design a remote probing device. We use this probing device to inspect a crack of the inner wall of the heat exchanger. Crack inspection requires speed at first, and then it requires accuracy. Once Eddy Current Testing (ECT) finds a crack with a certain signal level, another method should confirm it visually. We are proposing Magnetic particle Testing (MT) using specially fabricated the Magnetic Particle Micro Capsule (MPMC). For LIBS, a multichannel spectrometer and a Q-switch YAG laser were used. Irradiation area is 270 μm, and the pulse energy was 2 mJ. This pulse energy corresponds to 5-2.2 MW/cm2. A composite-type optical fiber was used to deliver both laser energy and optical image. Samples were prepared to heat a zirconium alloy plate by underwater arc welding in order to demonstrate severe accidents of nuclear power plants. A black oxide layer covered the weld surface and white particles floated on water surface. Laser induced breakdown plasma emission was taken into the spectroscope using this optical fiber combined with telescopic optics. As a result, we were able to simultaneously perform spectroscopic measurement and observation. For MT, the MPMC which gathered in the defective area is observed with this fiber. The MPMC emits light by the illumination of UV light from this optical fiber. The size of a defect is estimated with this amount of emission. Such technology will be useful for inspection repair of reactor pipe.

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.

UV laser-ablated surface textures as potential regulator of cellular response.

PubMed

Chandra, Prafulla; Lai, Karen; Sung, Hak-Joon; Murthy, N Sanjeeva; Kohn, Joachim

2010-06-01

Textured surfaces obtained by UV laser ablation of poly(ethylene terephthalate) films were used to study the effect of shape and spacing of surface features on cellular response. Two distinct patterns, cones and ripples with spacing from 2 to 25 μm, were produced. Surface features with different shapes and spacings were produced by varying pulse repetition rate, laser fluence, and exposure time. The effects of the surface texture parameters, i.e., shape and spacing, on cell attachment, proliferation, and morphology of neonatal human dermal fibroblasts and mouse fibroblasts were studied. Cell attachment was the highest in the regions with cones at ∼4 μm spacing. As feature spacing increased, cell spreading decreased, and the fibroblasts became more circular, indicating a stress-mediated cell shrinkage. This study shows that UV laser ablation is a useful alternative to lithographic techniques to produce surface patterns for controlling cell attachment and growth on biomaterial surfaces.

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.

Toxic effects of combined effects of anthracene and UV radiation on Brachionus plicatilis

NASA Astrophysics Data System (ADS)

Gao, Ceng; Zhang, Xinxin; Xu, Ningning; Tang, Xuexi

2017-05-01

Anthracene is a typical polycyclic aromatic hydrocarbon, with photo activity, can absorb ultraviolet light a series of chemical reactions, aquatic organisms in the ecosystem has a potential light induced toxicity. In this paper, the effects of anthracene and UV radiation on the light-induced toxicity of Brachionus plicatilis were studied. The main methods and experimental results were as follows: (1) The semi-lethal concentration of anthracene in UV light was much lower than that in normal light, The rotifers have significant light-induced acute toxicity. (2) Under UV irradiation, anthracene could induce the increase of ROS and MDA content in B. plicatilis, and the activity of antioxidant enzymes in B. plicatilis significantly changed, Where SOD, GPx activity was induced within 24 hours of the beginning of the experiment. And the content of GPX and CAT was inhibited after 48 hours. Therefore, the anthracite stress induced by UV radiation could more strongly interfere with the ant oxidative metabolism of B. plicatilis, and more seriously cause oxidative damage, significant light-induced toxicity.

Using UVC Light-Emitting Diodes at Wavelengths of 266 to 279 Nanometers To Inactivate Foodborne Pathogens and Pasteurize Sliced Cheese.

PubMed

Kim, Soo-Ji; Kim, Do-Kyun; Kang, Dong-Hyun

2016-01-01

UVC light is a widely used sterilization technology. However, UV lamps have several limitations, including low activity at refrigeration temperatures, a long warm-up time, and risk of mercury exposure. UV-type lamps only emit light at 254 nm, so as an alternative, UV light-emitting diodes (UV-LEDs) which can produce the desired wavelengths have been developed. In this study, we validated the inactivation efficacy of UV-LEDs by wavelength and compared the results to those of conventional UV lamps. Selective media inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated using UV-LEDs at 266, 270, 275, and 279 nm in the UVC spectrum at 0.1, 0.2, 0.5, and 0.7 mJ/cm(2), respectively. The radiation intensity of the UV-LEDs was about 4 μW/cm(2), and UV lamps were covered with polypropylene films to adjust the light intensity similar to those of UV-LEDs. In addition, we applied UV-LED to sliced cheese at doses of 1, 2, and 3 mJ/cm(2). Our results showed that inactivation rates after UV-LED treatment were significantly different (P < 0.05) from those of UV lamps at a similar intensity. On microbiological media, UV-LED treatments at 266 and 270 nm showed significantly different (P < 0.05) inactivation effects than other wavelength modules. For sliced cheeses, 4- to 5-log reductions occurred after treatment at 3 mJ/cm(2) for all three pathogens, with negligible generation of injured cells. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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.

Ultraviolet Light-Assisted Copper Oxide Nanowires Hydrogen Gas Sensor

NASA Astrophysics Data System (ADS)

Sihar, Nabihah; Tiong, Teck Yaw; Dee, Chang Fu; Ooi, Poh Choon; Hamzah, Azrul Azlan; Mohamed, Mohd Ambri; Majlis, Burhanuddin Yeop

2018-05-01

We fabricated copper oxide nanowires (CuO NWs) ultraviolet (UV) light-assisted hydrogen gas sensor. The fabricated sensor shows promising sensor response behavior towards 100 ppm of H2 at room temperature and elevated temperature at 100 °C when exposed to UV light (3.0 mW/cm2). One hundred-cycle device stability test has been performed, and it is found that for sample elevated at 100 °C, the UV-activated sample achieved stability in the first cycle as compared to the sample without UV irradiation which needed about 10 cycles to achieve stability at the initial stage, whereas the sample tested at room temperature was able to stabilize with the aid of UV irradiation. This indicates that with the aid of UV light, after some "warming up" time, it is possible for the conventional CuO NW sensor which normally work at elevated temperature to function at room temperature because UV source is speculated to play a dominant role to increase the interaction of the surface of CuO NWs and hydrogen gas molecules absorbed after the light exposure.

Ultraviolet Light-Assisted Copper Oxide Nanowires Hydrogen Gas Sensor.

PubMed

Sihar, Nabihah; Tiong, Teck Yaw; Dee, Chang Fu; Ooi, Poh Choon; Hamzah, Azrul Azlan; Mohamed, Mohd Ambri; Majlis, Burhanuddin Yeop

2018-05-15

We fabricated copper oxide nanowires (CuO NWs) ultraviolet (UV) light-assisted hydrogen gas sensor. The fabricated sensor shows promising sensor response behavior towards 100 ppm of H 2 at room temperature and elevated temperature at 100 °C when exposed to UV light (3.0 mW/cm 2 ). One hundred-cycle device stability test has been performed, and it is found that for sample elevated at 100 °C, the UV-activated sample achieved stability in the first cycle as compared to the sample without UV irradiation which needed about 10 cycles to achieve stability at the initial stage, whereas the sample tested at room temperature was able to stabilize with the aid of UV irradiation. This indicates that with the aid of UV light, after some "warming up" time, it is possible for the conventional CuO NW sensor which normally work at elevated temperature to function at room temperature because UV source is speculated to play a dominant role to increase the interaction of the surface of CuO NWs and hydrogen gas molecules absorbed after the light exposure.

Tolerance of the eriophyid mite Aceria salsolae to UV-A light and implications for biological control of Russian thistle.

PubMed

Moran, Patrick J; Wibawa, M Irene; Smith, Lincoln

2017-12-01

Aceria salsolae (Acari: Eriophyidae) is being evaluated as a candidate biological control agent of Russian thistle (Salsola tragus, Chenopodiaceae), a major invasive weed of rangelands and dryland crops in the western USA. Prior laboratory host range testing under artificial lighting indicated reproduction on non-native Bassia hyssopifolia and on a native plant, Suaeda calceoliformis. However, in field tests in the native range, mite populations released on these 'nontarget' plants remained low. We hypothesized that UV-A light, which can affect behavior of tetranychid mites, would affect populations of the eriophyid A. salsolae differently on the target and nontarget plant species, decreasing the mite's realized host range. Plants were infested with A. salsolae under lamps that emitted UV-A, along with broad-spectrum lighting, and the size of mite populations and plant growth was compared to infested plants exposed only to broad-spectrum light. Russian thistle supported 3- to 55-fold larger mite populations than nontarget plants regardless of UV-A treatment. UV-A exposure did not affect mite populations on Russian thistle or S. calceoliformis, whereas it increased populations 7-fold on B. hyssopifolia. Main stems on nontarget plants grew 2- to 6-fold faster than did Russian thistle under either light treatment. The two nontarget plants attained greater volume under the control light regime than UV-A, but Russian thistle was unaffected. Although Russian thistle was always the superior host, addition of UV-A light to the artificial lighting regime did not reduce the ability of A. salsolae to reproduce on the two nontarget species, suggesting that UV-B or other environmental factors may be more important in limiting mite populations in the field.

Homogenization optics to improve detectability of a fluorescence response to a single laser pulse: Detection of feces on apples

USDA-ARS?s Scientific Manuscript database

Fecal contamination of produce is a known food safety risk. Measuring fluorescence responses to UV excitation is an established method for detecting such contamination. One measurement system utilizes a pulsed UV laser to induce a fluorescence response from fecal material and a gated intensified cam...

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.

Chemical storage of hydrogen in few-layer graphene

PubMed Central

Subrahmanyam, K. S.; Kumar, Prashant; Maitra, Urmimala; Govindaraj, A.; Hembram, K. P. S. S.; Waghmare, Umesh V.; Rao, C. N. R.

2011-01-01

Birch reduction of few-layer graphene samples gives rise to hydrogenated samples containing up to 5 wt % of hydrogen. Spectroscopic studies reveal the presence of sp3 C-H bonds in the hydrogenated graphenes. They, however, decompose readily on heating to 500 °C or on irradiation with UV or laser radiation releasing all the hydrogen, thereby demonstrating the possible use of few-layer graphene for chemical storage of hydrogen. First-principles calculations throw light on the mechanism of dehydrogenation that appears to involve a significant reconstruction and relaxation of the lattice. PMID:21282617

Improving the color of bulgur: new industrial applications of tempering and UV/sun-light treatments.

PubMed

Balci, Fatih; Bayram, Mustafa

2015-09-01

Color (CIE b*; yellowness) is an important parameter for bulgur quality. Color of bulgur is mainly due to natural pigments (carotenoids) that are present at different levels in wheat. In order to increase the customer acceptability, the producers try to obtain yellowish color in bulgur. In this study, two different tempering methods (spray and steam) were used before sun and UV- light polishing applications. Sun and UV-light were applied to tempered bulgur for 12, 24, 36, 48, 60 and 72 h. Moisture content (%, d.b.), ash content (%, d.b.), protein content (%, d.b.), total carotenoid content in terms of lutein equivalent (TCC) and color values (CIE L*; lightness, CIE b*; yellowness, CIE a*; redness and CIE YI; yellowness index) were determined. It was found that UV-light was more effective (P < 0.05) on the CIE L* and CIE b* values compared to sunlight. Both tempering methods were significantly (P < 0.05) increased the CIE L*, CIE b* and CIE YI values. Steam tempering has a significant effect (P < 0.05) on the CIE b* values as well as UV and time of UV exposure. The highest value of TCC i.e. 6.31 μg/g was obtained by using spray tempering and UV-light exposure. As a conclusion, as proposed methods steam tempering and UV-light have an obvious positive effect on the color of bulgur.

Light stabilizers added to the shell of co-extruded wood/high-density polyethylene composites to improve mechanical and anti-UV ageing properties

PubMed Central

Mei, Changtong; Xu, Bing; Chen, Weimin; Yong, Cheng; Wang, Ke; Wu, Qinglin

2018-01-01

Weathering of wood--plastic composites (WPCs) leads to discoloration and cracks, which greatly limits their outdoor application. In this study, light stabilizers (including UV-327, HS-944 and nano-SiO2) were added to the shell of a co-extruded high-density polyethylene-based WPC to improve its anti-ultraviolet (UV) ageing properties and simultaneously to maintain its good mechanical properties. The results showed that UV-327 was the most effective light stabilizer for improving the mechanical and anti-UV ageing properties of the composites among the three stabilizers used. WPC samples combined with 2% UV-327 had the highest retention rates in flexural strength and also had the smoothest surface after 2500 h of UV ageing. The samples with 2% UV-327 added had the best protection for discoloration, showing the lowest values of ΔE* (colour difference) and ΔL* (luminescence) in all samples after 2500 h of UV ageing. WPC samples with 2% UV-327 were also oxidized the least after 2500 h of UV ageing. The results reported herein serve to enhance our understanding of the efficiency of light stabilizers in preventing UV degradation of WPCs, with a view to developing co-extruded WPCs with low cost, high anti-UV ageing properties and good mechanical properties for outdoor applications. PMID:29892445

Light-extraction enhancement of GaN-based 395  nm flip-chip light-emitting diodes by an Al-doped ITO transparent conductive electrode.

PubMed

Xu, Jin; Zhang, Wei; Peng, Meng; Dai, Jiangnan; Chen, Changqing

2018-06-01

The distinct ultraviolet (UV) light absorption of indium tin oxide (ITO) limits the performance of GaN-based near-UV light-emitting diodes (LEDs). Herein, we report an Al-doped ITO with enhanced UV transmittance and low sheet resistance as the transparent conductive electrode for GaN-based 395 nm flip-chip near-UV LEDs. The thickness dependence of optical and electrical properties of Al-doped ITO films is investigated. The optimal Al-doped ITO film exhibited a transmittance of 93.2% at 395 nm and an average sheet resistance of 30.1  Ω/sq. Meanwhile, at an injection current of 300 mA, the forward voltage decreased from 3.14 to 3.11 V, and the light output power increased by 13% for the 395 nm near-UV flip-chip LEDs with the optimal Al-doped ITO over those with pure ITO. This Letter provides a simple and repeatable approach to further improve the light extraction efficiency of GaN-based near-UV LEDs.

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography

PubMed Central

2016-01-01

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition and p-type doping of gallium nitride have recently permitted the manufacture of UV LEDs capable of replacing mercury arc lamps also in these applications. These UV LEDs exceed the spectral radiance of mercury lamps even at the intense I-line at 365 nm. Here we present the successful exchange of a high-pressure mercury arc lamp for a new generation UV LED as a light source in photolithographic chemistry and its use in the fabrication of high-density DNA microarrays. We show that the improved light radiance and efficiency of these LEDs offer substantial practical, economic and ecological advantages, including faster synthesis, lower hardware costs, very long lifetime, an >85-fold reduction in electricity consumption and the elimination of mercury waste and contamination. PMID:28066690

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography.

PubMed

Hölz, K; Lietard, J; Somoza, M M

2017-01-03

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition and p -type doping of gallium nitride have recently permitted the manufacture of UV LEDs capable of replacing mercury arc lamps also in these applications. These UV LEDs exceed the spectral radiance of mercury lamps even at the intense I-line at 365 nm. Here we present the successful exchange of a high-pressure mercury arc lamp for a new generation UV LED as a light source in photolithographic chemistry and its use in the fabrication of high-density DNA microarrays. We show that the improved light radiance and efficiency of these LEDs offer substantial practical, economic and ecological advantages, including faster synthesis, lower hardware costs, very long lifetime, an >85-fold reduction in electricity consumption and the elimination of mercury waste and contamination.

Chlorophyll degradation in aqueous mediums induced by light and UV-B irradiation: An UHPLC-ESI-MS study

NASA Astrophysics Data System (ADS)

Petrović, Sanja; Zvezdanović, Jelena; Marković, Dejan

2017-12-01

Irreversible chlorophyll degradation induced by continuous white light illumination and UV-B irradiation in the aqueous mediums (with 10%, 30% and 50% of methanol) was investigated using the ultrahigh liquid chromatography coupled with diode array and electrospray ionization mass spectrometry detectors (UHPLC-DAD-ESIMS). The degradation was governed by energy input of photons: higher energy of UV-B irradiation induced faster chlorophyll degradation and accordingly faster products formation in comparison to the white light treatment. Main light- or/and UV-B-induced products of chlorophyll in the aqueous mediums were hydroxy-pheophytin a, pheophytin a and hydroxy-lactone-pheophytin a, accompanied with the corresponding epimers. Chlorophylls aggregation dominant in the aqueous medium with the highest methanol content (50%) play a protective role against the UV-B radiation and white light illumination.

Photocatalytic properties of Au-deposited mesoporous SiO{sub 2}–TiO{sub 2} photocatalyst under simultaneous irradiation of UV and visible light

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

Okuno, T., E-mail: t093507@edu.imc.tut.ac.jp; Kawamura, G., E-mail: gokawamura@ee.tut.ac.jp; Muto, H., E-mail: muto@ee.tut.ac.jp

Mesoporous SiO{sub 2} templates deposited TiO{sub 2} nanocrystals are synthesized via a sol–gel route, and Au nanoparticles (NPs) are deposited in the tubular mesopores of the templates by a photodeposition method (Au/SiO{sub 2}–TiO{sub 2}). The photocatalytic characteristics of Au/SiO{sub 2}–TiO{sub 2} are discussed with the action spectra of photoreactions of 2-propanol and methylene blue. Photocatalytic activities of SiO{sub 2}–TiO{sub 2} under individual ultraviolet (UV) and visible (Vis) light illumination are enhanced by deposition of Au NPs. Furthermore, Au/SiO{sub 2}–TiO{sub 2} shows higher photocatalytic activities under simultaneous irradiation of UV and Vis light compared to the activity under individual UV andmore » Vis light irradiation. Since the photocatalytic activity under simultaneous irradiation is almost the same as the total activities under individual UV and Vis light irradiation, it is concluded that the electrons and the holes generated by lights of different wavelengths are efficiently used for photocatalysis without carrier recombination. - Graphical abstract: This graphic shows the possible charge behavior in Au/SiO{sub 2}–TiO{sub 2} under independent light irradiation of ultraviolet and visible light irradiation. Both reactions under independent UV and Vis light irradiation occurred in parallel when Au/SiO{sub 2}–TiO{sub 2} photocatalyst was illuminated UV and Vis light simultaneously, and then photocatalytic activity is improved by simultaneous irradiation. - Highlights: • Au nanoparticles were deposited in mesoporous SiO{sub 2}–TiO{sub 2} by a photodeposition method. • Photocatalytic activity under UV and Vis light was enhanced by deposition of Au. • Photocatalytic activity of Au/SiO{sub 2}–TiO{sub 2} was improved by simultaneous irradiation.« less

Fluorescent minerals - A potential source of UV protection and visible light for the growth of green algae and cyanobacteria in extreme cosmic environments

NASA Astrophysics Data System (ADS)

Omairi, Tareq; Wainwright, Milton

2015-07-01

We propose that green algae (Chlorella variabilis and Dunaliella tertiolecta) and cyanobacteria (Synechococcus elongatus and Nostoc commune) can grow inside fluorescent rock minerals which convert damaging UV light to visible light, thereby allowing these organisms to survive and thrive in UV-rich environments without (or with limited) visible light, which would otherwise be inimical to them. The four microorganisms were incubated inside fluorescent rocks composed of fluorite, calcite and pyrite. The resultant growth was then measured following exposure to UV radiation, with the use of optical density and measurement of chlorophyll concentration. Results show that the microorganisms were shielded from harmful UV in these semi-transparent rocks, while at the same time benefiting from the fact that the minerals converted UV to visible light; this have been shown by a statistically significant increase in their growth, which although lower than when the cells were incubated in sunlight, was significantly higher than in controls incubated in the dark.

UV Degradation and Recovery of Perovskite Solar Cells

PubMed Central

Lee, Sang-Won; Kim, Seongtak; Bae, Soohyun; Cho, Kyungjin; Chung, Taewon; Mundt, Laura E.; Lee, Seunghun; Park, Sungeun; Park, Hyomin; Schubert, Martin C.; Glunz, Stefan W.; Ko, Yohan; Jun, Yongseok; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2016-01-01

Although the power conversion efficiency of perovskite solar cells has increased from 3.81% to 22.1% in just 7 years, they still suffer from stability issues, as they degrade upon exposure to moisture, UV light, heat, and bias voltage. We herein examined the degradation of perovskite solar cells in the presence of UV light alone. The cells were exposed to 365 nm UV light for over 1,000 h under inert gas at <0.5 ppm humidity without encapsulation. 1-sun illumination after UV degradation resulted in recovery of the fill factor and power conversion efficiency. Furthermore, during exposure to consecutive UV light, the diminished short circuit current density (Jsc) and EQE continuously restored. 1-sun light soaking induced recovery is considered to be caused by resolving of stacked charges and defect state neutralization. The Jsc and EQE bounce-back phenomenon is attributed to the beneficial effects of PbI2 which is generated by the decomposition of perovskite material. PMID:27909338

Enhancing the Photovoltaic Performance of Perovskite Solar Cells with a Down-Conversion Eu-Complex.

PubMed

Jiang, Ling; Chen, Wangchao; Zheng, Jiawei; Zhu, Liangzheng; Mo, Li'e; Li, Zhaoqian; Hu, Linhua; Hayat, Tasawar; Alsaedi, Ahmed; Zhang, Changneng; Dai, Songyuan

2017-08-16

Organometal halide perovskite solar cells (PSCs) have shown high photovoltaic performance but poor utilization of ultraviolet (UV) irradiation. Lanthanide complexes have a wide absorption range in the UV region and they can down-convert the absorbed UV light into visible light, which provides a possibility for PSCs to utilize UV light for higher photocurrent, efficiency, and stability. In this study, we use a transparent luminescent down-converting layer (LDL) of Eu-4,7-diphenyl-1,10-phenanthroline (Eu-complex) to improve the light utilization efficiency of PSCs. Compared with the uncoated PSC, the PSC coated with Eu-complex LDL on the reverse of the fluorine-doped tin oxide glass displayed an enhancement of 11.8% in short-circuit current density (J sc ) and 15.3% in efficiency due to the Eu-complex LDL re-emitting UV light (300-380 nm) in the visible range. It is indicated that the Eu-complex LDL plays the role of enhancing the power conversion efficiency as well as reducing UV degradation for PSCs.

UV Degradation and Recovery of Perovskite Solar Cells.

PubMed

Lee, Sang-Won; Kim, Seongtak; Bae, Soohyun; Cho, Kyungjin; Chung, Taewon; Mundt, Laura E; Lee, Seunghun; Park, Sungeun; Park, Hyomin; Schubert, Martin C; Glunz, Stefan W; Ko, Yohan; Jun, Yongseok; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2016-12-02

Although the power conversion efficiency of perovskite solar cells has increased from 3.81% to 22.1% in just 7 years, they still suffer from stability issues, as they degrade upon exposure to moisture, UV light, heat, and bias voltage. We herein examined the degradation of perovskite solar cells in the presence of UV light alone. The cells were exposed to 365 nm UV light for over 1,000 h under inert gas at <0.5 ppm humidity without encapsulation. 1-sun illumination after UV degradation resulted in recovery of the fill factor and power conversion efficiency. Furthermore, during exposure to consecutive UV light, the diminished short circuit current density (J sc ) and EQE continuously restored. 1-sun light soaking induced recovery is considered to be caused by resolving of stacked charges and defect state neutralization. The J sc and EQE bounce-back phenomenon is attributed to the beneficial effects of PbI 2 which is generated by the decomposition of perovskite material.

UV-Light Exposure of Insulin: Pharmaceutical Implications upon Covalent Insulin Dityrosine Dimerization and Disulphide Bond Photolysis

PubMed Central

Correia, Manuel; Neves-Petersen, Maria Teresa; Jeppesen, Per Bendix; Gregersen, Søren; Petersen, Steffen B.

2012-01-01

In this work we report the effects of continuous UV-light (276 nm, ∼2.20 W.m−2) excitation of human insulin on its absorption and fluorescence properties, structure and functionality. Continuous UV-excitation of the peptide hormone in solution leads to the progressive formation of tyrosine photo-product dityrosine, formed upon tyrosine radical cross-linkage. Absorbance, fluorescence emission and excitation data confirm dityrosine formation, leading to covalent insulin dimerization. Furthermore, UV-excitation of insulin induces disulphide bridge breakage. Near- and far-UV-CD spectroscopy shows that UV-excitation of insulin induces secondary and tertiary structure losses. In native insulin, the A and B chains are held together by two disulphide bridges. Disruption of either of these bonds is likely to affect insulin’s structure. The UV-light induced structural changes impair its antibody binding capability and in vitro hormonal function. After 1.5 and 3.5 h of 276 nm excitation there is a 33.7% and 62.1% decrease in concentration of insulin recognized by guinea pig anti-insulin antibodies, respectively. Glucose uptake by human skeletal muscle cells decreases 61.7% when the cells are incubated with pre UV-illuminated insulin during 1.5 h. The observations presented in this work highlight the importance of protecting insulin and other drugs from UV-light exposure, which is of outmost relevance to the pharmaceutical industry. Several drug formulations containing insulin in hexameric, dimeric and monomeric forms can be exposed to natural and artificial UV-light during their production, packaging, storage or administration phases. We can estimate that direct long-term exposure of insulin to sunlight and common light sources for indoors lighting and UV-sterilization in industries can be sufficient to induce irreversible changes to human insulin structure. Routine fluorescence and absorption measurements in laboratory experiments may also induce changes in protein structure. Structural damage includes insulin dimerization via dityrosine cross-linking or disulphide bond disruption, which affects the hormone’s structure and bioactivity. PMID:23227203

UV-light exposure of insulin: pharmaceutical implications upon covalent insulin dityrosine dimerization and disulphide bond photolysis.

PubMed

Correia, Manuel; Neves-Petersen, Maria Teresa; Jeppesen, Per Bendix; Gregersen, Søren; Petersen, Steffen B

2012-01-01

In this work we report the effects of continuous UV-light (276 nm, ~2.20 W.m(-2)) excitation of human insulin on its absorption and fluorescence properties, structure and functionality. Continuous UV-excitation of the peptide hormone in solution leads to the progressive formation of tyrosine photo-product dityrosine, formed upon tyrosine radical cross-linkage. Absorbance, fluorescence emission and excitation data confirm dityrosine formation, leading to covalent insulin dimerization. Furthermore, UV-excitation of insulin induces disulphide bridge breakage. Near- and far-UV-CD spectroscopy shows that UV-excitation of insulin induces secondary and tertiary structure losses. In native insulin, the A and B chains are held together by two disulphide bridges. Disruption of either of these bonds is likely to affect insulin's structure. The UV-light induced structural changes impair its antibody binding capability and in vitro hormonal function. After 1.5 and 3.5 h of 276 nm excitation there is a 33.7% and 62.1% decrease in concentration of insulin recognized by guinea pig anti-insulin antibodies, respectively. Glucose uptake by human skeletal muscle cells decreases 61.7% when the cells are incubated with pre UV-illuminated insulin during 1.5 h. The observations presented in this work highlight the importance of protecting insulin and other drugs from UV-light exposure, which is of outmost relevance to the pharmaceutical industry. Several drug formulations containing insulin in hexameric, dimeric and monomeric forms can be exposed to natural and artificial UV-light during their production, packaging, storage or administration phases. We can estimate that direct long-term exposure of insulin to sunlight and common light sources for indoors lighting and UV-sterilization in industries can be sufficient to induce irreversible changes to human insulin structure. Routine fluorescence and absorption measurements in laboratory experiments may also induce changes in protein structure. Structural damage includes insulin dimerization via dityrosine cross-linking or disulphide bond disruption, which affects the hormone's structure and bioactivity.