Simultaneous generation of sub-5-femtosecond 400  nm and 800  nm pulses for attosecond extreme ultraviolet pump-probe spectroscopy.

PubMed

Chang, Hung-Tzu; Zürch, Michael; Kraus, Peter M; Borja, Lauren J; Neumark, Daniel M; Leone, Stephen R

2016-11-15

Few-cycle laser pulses with wavelengths centered at 400 nm and 800 nm are simultaneously obtained through wavelength separation of ultrashort, spectrally broadened Vis-NIR laser pulses spanning 350-1100 nm wavelengths. The 400 nm and 800 nm pulses are separately compressed, yielding pulses with 4.4 fs and 3.8 fs duration, respectively. The pulse energy exceeds 5 μJ for the 400 nm pulses and 750 μJ for the 800 nm pulses. Intense 400 nm few-cycle pulses have a broad range of applications in nonlinear optical spectroscopy, which include the study of photochemical dynamics, semiconductors, and photovoltaic materials on few-femtosecond to attosecond time scales. The ultrashort 400 nm few-cycle pulses generated here not only extend the spectral range of the optical pulse for NIR-XUV attosecond pump-probe spectroscopy but also pave the way for two-color, three-pulse, multidimensional optical-XUV spectroscopy experiments.

Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

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

Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun, E-mail: wenjunwang@mail.xjtu.edu.cn

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloymore » were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.« less

High-energy directly diode-pumped Q-switched 1617 nm Er:YAG laser at room temperature.

PubMed

Wang, Mingjian; Zhu, Liang; Chen, Weibiao; Fan, Dianyuan

2012-09-01

We describe high-energy Erbium-doped yttrium aluminum garnet (Er:YAG) lasers operating at 1617 nm, resonantly pumped using 1532 nm fiber-coupled laser diodes. A maximum continuous wave output power of 4.3 W at 1617 nm was achieved with an output coupler of 20% transmission under incident pump power of 29.7 W, resulting in an optical conversion of 14% with respect to the incident pump power. In Q-switched operation, the pulse energy of 11.8 mJ at 100 Hz pulse repetition frequency and 81 ns pulse duration was obtained. This energy is the highest pulse energy reported for a directly diode-pumped Q-switched Er:YAG laser operating at 1617 nm.

Short-wavelength infrared laser activates the auditory neurons: comparing the effect of 980 vs. 810 nm wavelength.

PubMed

Tian, Lan; Wang, Jingxuan; Wei, Ying; Lu, Jianren; Xu, Anting; Xia, Ming

2017-02-01

Research on auditory neural triggering by optical stimulus has been developed as an emerging technique to elicit the auditory neural response, which may provide an alternative method to the cochlear implants. However, most previous studies have been focused on using longer-wavelength near-infrared (>1800 nm) laser. The effect comparison of different laser wavelengths in short-wavelength infrared (SWIR) range on the auditory neural stimulation has not been previously explored. In this study, the pulsed 980- and 810-nm SWIR lasers were applied as optical stimuli to irradiate the auditory neurons in the cochlea of five deafened guinea pigs and the neural response under the two laser wavelengths was compared by recording the evoked optical auditory brainstem responses (OABRs). In addition, the effect of radiant exposure, laser pulse width, and threshold with the two laser wavelengths was further investigated and compared. The one-way analysis of variance (ANOVA) was used to analyze those data. Results showed that the OABR amplitude with the 980-nm laser is higher than the amplitude with the 810-nm laser under the same radiant exposure from 10 to 102 mJ/cm 2 . And the laser stimulation of 980 nm wavelength has lower threshold radiant exposure than the 810 nm wavelength at varied pulse duration in 20-500 μs range. Moreover, the 810-nm laser has a wider optimized pulse duration range than the 980-nm laser for the auditory neural stimulation.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

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

Furukawa, Yuki; Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502; Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011

By pairing femtosecond laser pulses (duration ∼40 fs and central wavelength ∼810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm{sup 2} and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm{sup 2}, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

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.

Comparison of a novel high-power blue diode laser (λ=442 nm) with Ho:YAG (λ=2100 nm), Tm fiber (λ=1940 nm), and KTP (λ=532 nm) lasers for soft tissue ablation

NASA Astrophysics Data System (ADS)

Vinnichenko, Victoriya; Kovalenko, Anastasiya; Arkhipova, Valeriya; Yaroslavsky, Ilya; Altshuler, Gregory; Gapontsev, Valentin

2018-02-01

Three lasers were directly compared, including the Ho:YAG laser (λ = 2100 nm), Tm fiber laser (λ = 1940 nm) operating in 3 different modes (CW, regular pulse, and super pulse), and blue diode laser (λ = 442 nm) for vaporization and coagulation efficiency for treating blood-rich soft tissues, ex vivo, in a porcine kidney model at quasi-contact cutting in water. In addition, experimental results were compared with published data on performance of KTP laser (λ = 532 nm) at similar experimental settings (Power = 60 W and cutting speed = 2 mm/s). Tm fiber laser in pulsed mode and blue laser produced highest vaporization rates of 3.7 and 3.4 mm3/s, respectively. Tm fiber laser (in both CW and pulsed modes) also produced the largest coagulation zone among the laser sources tested. A carbonization zone was observed for Tm fiber laser in CW and pulsed modes, as well as for the blue diode laser. Tm fiber laser in super-pulse mode and Ho:YAG laser both resulted in irregular coagulation zones without carbonization. Comparison with known data for KTP laser revealed that tissue effects of the blue laser are similar to that of the KTP laser. These results suggest that the combination of the two lasers (Tm fiber and blue diode) in one system may achieve high cutting efficiency and optimal coagulation for hemostasis during surgical treatment. Ex vivo testing of the combined system revealed feasibility of this approach. The combination of the CW Tm fiber laser (120W) and the blue diode laser (60W) emitting through a combination tip were compared with CW 120 W Tm fiber laser alone and 120 W Ho:YAG laser. Vaporization rates measured 34, 28, and 6 mm3/s, and coagulation zones measured 0.6, 1.3, and 1.7 mm, respectively. A carbonization zone was only observed with CW Tm fiber laser. The vaporization rate of combined CW Tm fiber laser / blue diode laser was comparable to published data for KTP laser for equivalent total power. Thus, high-power blue diode laser, Tm fiber laser, and their combination may provide an alternative to conventional Ho:YAG and KTP lasers for applications in urology and other surgical fields.

Direct micromachining of quartz glass plates using pulsed laser plasma soft x-rays

NASA Astrophysics Data System (ADS)

Makimura, Tetsuya; Miyamoto, Hisao; Kenmotsu, Youichi; Murakami, Kouichi; Niino, Hiroyuki

2005-03-01

We have investigated direct micromachining of quartz glass, using pulsed laser plasma soft x-rays (LPSXs) having a potential capability of nanomachining because the diffraction limit is ˜10nm. The LPSX's were generated by irradiation of a Ta target with 532nm laser light from a conventional Q switched Nd :YAG laser at 700mJ/pulse. In order to achieve a sufficient power density of LPSX's beyond the ablation threshold, we developed an ellipsoidal mirror to obtain efficient focusing of LPSXs at around 10nm. It was found that quartz glass plates are smoothly ablated at 45nm/shot using the focused and pulsed LPSX's.

Histologic evaluation of laser lipolysis comparing continuous wave vs pulsed lasers in an in vivo pig model.

PubMed

Levi, Jessica R; Veerappan, Anna; Chen, Bo; Mirkov, Mirko; Sierra, Ray; Spiegel, Jeffrey H

2011-01-01

To evaluate acute and delayed laser effects of subdermal lipolysis and collagen deposition using an in vivo pig model and to compare histologic findings in fatty tissue after continuous wave diode (CW) vs pulsed laser treatment. Three CW lasers (980, 1370, and 1470 nm) and 3 pulsed lasers (1064, 1320, and 1440 nm) were used to treat 4 Göttingen minipigs. Following administration of Klein tumescent solution, a laser cannula was inserted at the top of a 10 × 2.5-cm rectangle and was passed subdermally to create separate laser "tunnels." Temperatures at the surface and at intervals of 4-mm to 20-mm depths were recorded immediately after exposure and were correlated with skin injury. Full-thickness cutaneous biopsy specimens were obtained at 1 day, 1 week, and 1 month after exposure and were stained with hematoxylin-eosin and trichrome stain. Qualitative and semiquantitative histopathologic evaluations were performed with attention to vascular damage, lipolysis, and collagen deposition. Skin surface damage occurred at temperatures exceeding 46°C. Histologic examination at 1 day after exposure showed hemorrhage, fibrous collagen fiber coagulation, and adipocyte damage. Adipocytes surrounded by histiocytes, a marker of lipolysis, were present at 1 week and 1 month after exposure. Collagen deposition in subdermal fatty tissue and in reticular dermis of some specimens was noted at 1 week and had increased at 1 month. Tissue treated with CW laser at 1470 nm demonstrated greater hemorrhage and more histiocytes at damage sites than tissue treated with pulsed laser at 1440 nm. There was a trend toward more collagen deposition with pulsed lasers than with CW lasers, but this was not statistically significant. Histopathologic comparison between results of CW laser at 980 nm vs pulsed laser at 1064 nm showed the same trend. Hemorrhage differences may result from pulse duration variations. A theoretical calculation estimating temperature rise in vessels supported this hypothesis. Pulsed lasers with higher peak powers provided better hemostatic effects than CW lasers. The degree of lipolysis depended on wavelength, laser power, and energy density. Subdermal laser irradiation can stimulate collagen deposition in subdermal tissue and reticular dermis.

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.

Effect of shorter pulse duration in cochlear neural activation with an 810-nm near-infrared laser.

PubMed

Wang, Jingxuan; Tian, Lan; Lu, Jianren; Xia, Ming; Wei, Ying

2017-02-01

Optical neural stimulation in the cochlea has been presented as an alternative technique to the electrical stimulation due to its potential in spatially selectivity enhancement. So far, few studies have selected the near-infrared (NIR) laser in cochlear neural stimulation and limited optical parameter space has been examined. This paper focused on investigating the optical parameter effect on NIR stimulation of auditory neurons, especially under shorter pulse durations. The spiral ganglion neurons in the cochlea of deafened guinea pigs were stimulated with a pulsed 810-nm NIR laser in vivo. The laser radiation was delivered by an optical fiber and irradiated towards the modiolus. Optically evoked auditory brainstem responses (OABRs) with various optical parameters were recorded and investigated. The OABRs could be elicited with the cochlear deafened animals by using the 810-nm laser in a wide pulse duration ranged from 20 to 1000 μs. Results showed that the OABR intensity increased along with the increasing laser radiant exposure of limited range at each specific pulse duration. In addition, for the pulse durations from 20 to 300 μs, the OABR intensity increased monotonically along with the pulse duration broadening. While for pulse durations above 300 μs, the OABR intensity basically kept stable with the increasing pulse duration. The 810-nm NIR laser could be an effective stimulus in evoking the cochlear neuron response. Our experimental data provided evidence to optimize the pulse duration range, and the results suggested that the pulse durations from 20 to 300 μs could be the optimized range in cochlear neural activation with the 810-nm-wavelength laser.

High power high repetition rate VCSEL array side-pumped pulsed blue laser

NASA Astrophysics Data System (ADS)

van Leeuwen, Robert; Zhao, Pu; Chen, Tong; Xu, Bing; Watkins, Laurence; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

2013-03-01

High power, kW-class, 808 nm pump modules based on the vertical-cavity surface-emitting laser (VCSEL) technology were developed for side-pumping of solid-state lasers. Two 1.2 kW VCSEL pump modules were implemented in a dual side-pumped Q-switched Nd:YAG laser operating at 946 nm. The laser output was frequency doubled in a BBO crystal to produce pulsed blue light. With 125 μs pump pulses at a 300 Hz repetition rate 6.1 W QCW 946 nm laser power was produced. The laser power was limited by thermal lensing in the Nd:YAG rod.

Laser diode and pumped Cr:Yag passively Q-switched yellow-green laser at 543 nm

NASA Astrophysics Data System (ADS)

Yao, Y.; Ling, Zhao; Li, B.; Qu, D. P.; Zhou, K.; Zhang, Y. B.; Zhao, Y.; Zheng, Q.

2013-03-01

Efficient and compact yellow green pulsed laser output at 543 nm is generated by frequency doubling of a passively Q-switched end diode-pumped Nd:YVO4 laser at 1086 nm under the condition of sup-pressing the higher gain transition near 1064 nm. With 15 W of diode pump power and the frequency doubling crystal LBO, as high as 1.58 W output power at 543 nm is achieved. The optical to optical conversion efficiency from the corresponding Q-switched fundamental output to the yellow green output is 49%. The peak power of the Q-switched yellow green pulse laser is up to 30 kW with 5 ns pulse duration. The output power stability over 8 hours is better than 2.56% at the maximum output power. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by frequency doubling of a passively Q-switched end diode pumped Nd:YVO4 laser at 1086 nm.

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

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

Holmium:YAG (lambda = 2,120 nm) versus thulium fiber (lambda = 1,908 nm) laser lithotripsy.

PubMed

Blackmon, Richard L; Irby, Pierce B; Fried, Nathaniel M

2010-03-01

The holmium:YAG laser is currently the most common laser lithotripter. However, recent experimental studies have demonstrated that the thulium fiber laser is also capable of vaporizing urinary stones. The high-temperature water absorption coefficient for the thulium wavelength (mu(a) = 160 cm(-1) at lambda = 1,908 nm) is significantly higher than for the holmium wavelength (mu(a) = 28 cm(-1) at lambda = 2,120 nm). We hypothesize that this should translate into more efficient laser lithotripsy using the thulium fiber laser. This study directly compares stone vaporization rates for holmium and thulium fiber lasers. Holmium laser radiation pulsed at 3 Hz with 70 mJ pulse energy and 220 microseconds pulse duration was delivered through a 100-microm-core silica fiber to human uric acid (UA) and calcium oxalate monohydrate (COM) stones, ex vivo (n = 10 each). Thulium fiber laser radiation pulsed at 10 Hz with 70 mJ pulse energy and 1-millisecond pulse duration was also delivered through a 100-microm fiber for the same sets of 10 stones each. For the same number of pulses and total energy (126 J) delivered to each stone, the mass loss averaged 2.4+/-0.6 mg (UA) and 0.7+/-0.2 mg (COM) for the holmium laser and 12.6+/-2.5 mg (UA) and 6.8+/-1.7 (COM) for the thulium fiber laser. UA and COM stone vaporization rates for the thulium fiber laser averaged 5-10 times higher than for the holmium laser at 70 mJ pulse energies. With further development, the thulium fiber laser may represent an alternative to the conventional holmium laser for more efficient laser lithotripsy.

Germanium Sub-Microspheres Synthesized by Picosecond Pulsed Laser Melting in Liquids: Educt Size Effects

PubMed Central

Zhang, Dongshi; Lau, Marcus; Lu, Suwei; Barcikowski, Stephan; Gökce, Bilal

2017-01-01

Pulsed laser melting in liquid (PLML) has emerged as a facile approach to synthesize submicron spheres (SMSs) for various applications. Typically lasers with long pulse durations in the nanosecond regime are used. However, recent findings show that during melting the energy absorbed by the particle will be dissipated promptly after laser-matter interaction following the temperature decrease within tens of nanoseconds and hence limiting the efficiency of longer pulse widths. Here, the feasibility to utilize a picosecond laser to synthesize Ge SMSs (200~1000 nm in diameter) is demonstrated by irradiating polydisperse Ge powders in water and isopropanol. Through analyzing the educt size dependent SMSs formation mechanism, we find that Ge powders (200~1000 nm) are directly transformed into SMSs during PLML via reshaping, while comparatively larger powders (1000~2000 nm) are split into daughter SMSs via liquid droplet bisection. Furthermore, the contribution of powders larger than 2000 nm and smaller than 200 nm to form SMSs is discussed. This work shows that compared to nanosecond lasers, picosecond lasers are also suitable to produce SMSs if the pulse duration is longer than the material electron-phonon coupling period to allow thermal relaxation. PMID:28084408

Compact high-pulse-energy ultraviolet laser source for ozone lidar measurements.

PubMed

Elsayed, Khaled A; DeYoung, Russell J; Petway, Larry B; Edwards, William C; Barnes, James C; Elsayed-Ali, Hani E

2003-11-20

An all solid-state Ti:sapphire laser differential absorption lidar transmitter was developed. This all-solid-state laser provides a compact, robust, and highly reliable laser transmitter for potential application in differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy-pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 and 900 nm, with M2 of 1.3, have been experimentally demonstrated and their properties compared with model results. The output pulse energy was 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively. At these energies, the beam quality was good enough so that we were able to achieve 30 mJ of ultraviolet laser output at 289 and 300 nm after frequency tripling with two lithium triborate nonlinear crystals.

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

PubMed

Schulze, Philipp; Ludwig, Martin; Belder, Detlev

2008-12-01

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

A pulsed single-frequency Nd:GGG/BaWO4 Raman laser

NASA Astrophysics Data System (ADS)

Liu, Zhaojun; Men, Shaojie; Cong, Zhenhua; Qin, Zengguang; Zhang, Xingyu; Zhang, Huaijin

2018-04-01

A single-frequency pulsed laser at 1178.3 nm was demonstrated in a crystalline Raman laser. A crystal combination of Nd:GGG and BaWO4 was selected to realize Raman conversion from a 1062.5 nm fundamental wave to a 1178.3 nm Stokes wave. An entangled cavity was specially designed to form an intracavity Raman configuration. Single-longitudinal-mode operation was realized by introducing two Fabry-Perot etalons into the Raman laser cavity. This laser operated at a pulse repetition rate of 50 Hz with 2 ms long envelopes containing micro pulses at a 30 kHz repetition rate. The highest output power was 41 mW with the micro pulse duration of 15 ns. The linewidth was measured to be less than 130 MHz.

Two-color short-pulse laser altimeter measurements of ocean surface backscatter

NASA Technical Reports Server (NTRS)

Abshire, James B.; Mcgarry, Jan F.

1987-01-01

The timing and correlation properties of pulsed laser backscatter from the ocean surface have been measured with a two-color short-pulse laser altimeter. The Nd:YAG laser transmitted 70- and 35-ps wide pulses simultaneously at 532 and 355 nm at nadir, and the time-resolved returns were recorded by a receiver with 800-ps response time. The time-resolved backscatter measured at both 330-m and 1291-m altitudes showed little pulse broadening due to the submeter laser spot size. The differential delay of the 355-nm and 532-nm backscattered waveforms were measured with a rms error of about 75 ps. The change in aircraft altitudes also permitted the change in atmospheric pressure to be estimated by using the two-color technique.

Saturable absorber Q- and gain-switched all-Yb3+ all-fiber laser at 976 and 1064 nm.

PubMed

Tsai, Tzong-Yow; Fang, Yen-Cheng; Huang, Huai-Min; Tsao, Hong-Xi; Lin, Shih-Ting

2010-11-08

We demonstrate a novel passively pulsed all-Yb3+ all-fiber laser pumped by a continuous-wave 915-nm pump laser diode. The laser was saturable absorber Q-switched at 976 nm and gain-switched at 1064 nm, using the method of mode-field-area mismatch. With a pump power of 
105 mW, the laser iteratively produced a 976-nm pulse with an energy of 2.8 μJ and a duration of 280 ns, followed by a 1064-nm pulse with 1.1 μJ and a 430-ns duration at a repetition rate of 9 kHz. A set of rate equations was established to simulate the self-balancing mechanism and the correlation between the Q- and gain-switched photon numbers and the populations of the gain and absorber fibers.

Frequency-doubled passively Q-switched microchip laser producing 225  ps pulses at 671  nm.

PubMed

Nikkinen, Jari; Korpijärvi, Ville-Markus; Leino, Iiro; Härkönen, Antti; Guina, Mircea

2016-11-15

We report a 671 nm laser source emitting 225 ps pulses with an average power of 55 mW and a repetition rate of 444 kHz. The system consists of a 1342 nm SESAM Q-switched Nd:YVO₄ microchip master oscillator and a dual-stage Nd:YVO₄ power amplifier. The 1342 nm signal was frequency-doubled to 671 nm using a periodically poled lithium niobate crystal. This laser source provides a practical alternative for applications requiring high energy picosecond pulses, such as time-gated Raman spectroscopy.

Visible and near infrared resonance plasmonic enhanced nanosecond laser optoporation of cancer cells

PubMed Central

St-Louis Lalonde, Bastien; Boulais, Étienne; Lebrun, Jean-Jacques; Meunier, Michel

2013-01-01

In this paper, we report a light driven, non-invasive cell membrane perforation technique based on the localized field amplification by a nanosecond pulsed laser near gold nanoparticles (AuNPs). The optoporation phenomena is investigated with pulses generated by a Nd:YAG laser for two wavelengths that are either in the visible (532 nm) or near infrared (NIR) (1064 nm). Here, the main objective is to compare on and off localized surface plasmonic resonance (LSPR) to introduce foreign material through the cell membrane using nanosecond laser pulses. The membrane permeability of human melanoma cells (MW278) has been successfully increased as shown by the intake of a fluorescent dye upon irradiation. The viability of this laser driven perforation method is evaluated by propidium iodide exclusion as well as MTT assay. Our results show that up to 25% of the cells are perforated with 532 nm pulses at 50 mJ/cm2 and around 30% of the cells are perforated with 1064 nm pulses at 1 J/cm2. With 532 nm pulses, the viability 2 h after treatment is 64% but it increases to 88% 72 h later. On the other hand, the irradiation with 1064 nm pulses leads to an improved 2 h viability of 81% and reaches 98% after 72 h. Scanning electron microscopy images show that the 5 pulses delivered during treatment induce changes in the AuNPs size distribution when irradiated by a 532 nm beam, while this distribution is barely affected when 1064 nm is used. PMID:23577284

Nanoparticles based laser-induced surface structures formation on mesoporous silicon by picosecond laser beam interaction

NASA Astrophysics Data System (ADS)

Talbi, A.; Petit, A.; Melhem, A.; Stolz, A.; Boulmer-Leborgne, C.; Gautier, G.; Defforge, T.; Semmar, N.

2016-06-01

In this study, laser induced periodic surface structures were formed on mesoporous silicon by irradiation of Nd:YAG picosecond pulsed laser beam at 266 nm wavelength at 1 Hz repetition rate and with 42 ps pulse duration. The effects of laser processing parameters as laser beam fluence and laser pulse number on the formation of ripples were investigated. Scanning electron microscopy and atomic force microscopy were used to image the surface morphologies and the cross section of samples after laser irradiation. At relatively low fluence ∼20 mJ/cm2, ripples with period close to the laser beam wavelength (266 nm) and with an always controlled orientation (perpendicular to the polarization of ps laser beam) appeared after a large laser pulse number of 12,000. It has been found that an initial random distribution of SiOx nanoparticles is periodically structured with an increase of the laser pulse number. Finally, it is experimentally demonstrated that we formed a 100 nm liquid phase under the protusion zones including the pores in the picosecond regime.

Tunable femtosecond laser based on the Nd3+:BaLaGa 3O 7 disordered crystal

NASA Astrophysics Data System (ADS)

Agnesi, A.; Pirzio, F.; Tartara, L.; Ugolotti, E.; Zhang, H.; Wang, J.; Yu, H.; Petrov, V.

2014-03-01

We demonstrate clear inhomogeneous linewidth broadening for the disordered laser crystal Nd:BaLaGa3O7 (Nd:BLG), which is very promising for the replacement of Nd:glass for ultrafast sources in multiwatt power applications. A Nd:BLG laser oscillator passively mode-locked and pumped by a Ti:sapphire laser generated pulses of 316-fs duration at 1060 nm, whose spectrum completely fills the fluorescence peak at such wavelength. More interestingly, sub-picosecond pulses were smoothly tunable in a 20-nm range, from 1070 to 1090 nm. The shortest pulses achieved were 290 fs long, centered at 1075 nm.

Influence of laser wavelength on two-dimensional carbon nanosheet formation from laser-induced exfoliation of naphthalene

NASA Astrophysics Data System (ADS)

Qian, Min; Niu, Yue Ping; Gong, Shang Qing

2018-01-01

Pulsed Nd:YAG (532 nm) and Excimer (248 nm) lasers were employed to produce freestanding, two-dimensional (2D), carbon nanosheets (CNSs) from naphthalene, through laser-induced exfoliation. The polymer-to-carbon transition was investigated in terms of laser wavelengths, fluences, as well as target preparations. Continuous and porous CNSs of several nanometers in thickness and micrometers in size were obtained from 532 and 248 nm pulsed laser exfoliation of spin-coated naphthalene films, respectively. The porous morphology is ascribed to the photon-induced dissociation of chemical bonds dominated in 248 nm laser interaction with ablated naphthalene. With the increase of laser fluences from 1 to 5 J cm-2, amorphous carbon and ultrathin CNS structures were obtained in sequence. This work revealed a general mechanism of producing 2D structured carbon materials from pulsed laser exfoliation.

Enhanced 5-aminolevulinic acid-gold nanoparticle conjugate-based photodynamic therapy using pulse laser

NASA Astrophysics Data System (ADS)

Xu, Hao; Yao, Cuiping; Wang, Jing; Chang, Zhennan; Zhang, Zhenxi

2016-02-01

The low bioavailability is a crucial limitation for the application of 5-aminolevulinic acid (ALA) in theranostics. In this research, 5-aminolevulinic acid and gold nanoparticle conjugates (ALA-GNPs) were synthesized to improve the bioavailability of ALA and to investigate the impact of ALA photodynamic therapy (ALA-PDT) in Hela cells. A 532 nm pulse laser and light-emitting diode (central wavelengths 502 nm) were jointly used as light sources in PDT research. The results show a 532 nm pulse laser can control ALA release from ALA-GNPs by adjusting the pulse laser dose. This laser control release may be attributed to the heat generation from GNPs under pulse laser irradiation, which indicates accurately adjusting the pulse laser dose to control the drug release in the cell interior can be considered as a new cellular surgery modality. Furthermore, the PDT results in Hela cells indicate the enhancement of ALA release by pulse laser before PDT can promote the efficacy of cell eradication in the light-emitting diode PDT (LED-PDT). This laser mediated drug release system can provide a new online therapy approach in PDT and it can be utilized in the optical monitor technologies based individual theranostics.

Generation of broadband laser by high-frequency bulk phase modulator with multipass configuration.

PubMed

Zhang, Peng; Jiang, Youen; Zhou, Shenlei; Fan, Wei; Li, Xuechun

2014-12-10

A new technique is presented for obtaining a large broadband nanosecond-laser pulse. This technique is based on multipass phase modulation of a single-frequency nanosecond-laser pulse from the integrated front-end source, and it is able to shape the temporal profile of the pulse arbitrarily, making this approach attractive for high-energy-density physical experiments in current laser fusion facilities. Two kinds of cavity configuration for multipass modulation are proposed, and the performances of both of them are discussed theoretically in detail for the first time to our knowledge. Simulation results show that the bandwidth of the generated laser pulse by this approach can achieve more than 100 nm in principle if adjustment accuracy of the time interval between contiguous passes is controlled within 0.1% of a microwave period. In our preliminary experiment, a 2 ns laser pulse with 1.35-nm bandwidth in 1053 nm is produced via this technique, which agrees well with the theoretical result. Owing to an all-solid-state structure, the energy of the pulse achieves 25 μJ. In the future, with energy compensation and spectrum filtering, this technique is expected to generate a nanosecond-laser pulse of 3 nm or above bandwidth with energy of about 100 μJ.

Nonlinear excitation fluorescence microscopy: source considerations for biological applications

NASA Astrophysics Data System (ADS)

Wokosin, David L.

2008-02-01

Ultra-short-pulse solid-state laser sources have improved contrast within fluorescence imaging and also opened new windows of investigation in biological imaging applications. Additionally, the pulsed illumination enables harmonic scattering microscopy which yields intrinsic structure, symmetry and contrast from viable embryos, cells and tissues. Numerous human diseases are being investigated by the combination of (more) intact dynamic tissue imaging of cellular function with gene-targeted specificity and electrophysiology context. The major limitation to more widespread use of multi-photon microscopy has been the complete system cost and added complexity above and beyond commercial camera and confocal systems. The current status of all-solid-state ultrafast lasers as excitation sources will be reviewed since these lasers offer tremendous potential for affordable, reliable, "turnkey" multiphoton imaging systems. This effort highlights the single box laser systems currently commercially available, with defined suggestions for the ranges for individual laser parameters as derived from a biological and fluorophore limited perspective. The standard two-photon dose is defined by 800nm, 10mW, 200fs, and 80Mhz - at the sample plane for tissue culture cells, i.e. after the full scanning microscope system. Selected application-derived excitation wavelengths are well represented by 700nm, 780nm, ~830nm, ~960nm, 1050nm, and 1250nm. Many of the one-box lasers have fixed or very limited excitation wavelengths available, so the lasers will be lumped near 780nm, 800nm, 900nm, 1050nm, and 1250nm. The following laser parameter ranges are discussed: average power from 200mW to 2W, pulse duration from 70fs to 700fs, pulse repetition rate from 20MHz to 200MHz, with the laser output linearly polarized with an extinction ratio at least 100:1.

Combination of 595-nm pulsed dye laser, long-pulsed 755-nm alexandrite laser, and microdermabrasion treatment for keratosis pilaris: retrospective analysis of 26 Korean patients.

PubMed

Lee, Sang Ju; Choi, Min Ju; Zheng, Zhenlong; Chung, Won Soon; Kim, Young Koo; Cho, Sung Bin

2013-06-01

Keratosis pilaris (KP) has beenpresented as small keratotic follicular papules with or without surrounding erythema. Various treatments with laser or light therapy have been used for the management of KP with various clinical outcomes. In the present study, we investigated the efficacy and safety of a combination therapy for KP. A total of 29 anatomical sites with KP in 26 patients were treated using a 595-nm pulsed dye laser (PDL) with nonpurpuragenic fluences, a long-pulsed 755-nm alexandrite laser, and microdermabrasion. Clinical improvement was assessed by comparing preand posttreatment clinical photographs and patient satisfaction rates. Evaluation of the clinical results three months after the treatments showed that 12 of the 29 anatomical sites (41.4%) demonstrated Grade 3 clinical improvement, ten (34.5%) had Grade 2 clinical improvement, four (13.8%) showed Grade 1 improvement, and three (10.3%) showed Grade 4 improvement. We observed that KP lesions improved not only in erythema and skin texture, but also in brownish dyschromias. Potential adverse events were not observed, except prolonged posttherapy scaling. Our observations demonstrate that combination therapy using a 595-nm PDL, a long-pulsed 755-nm alexandrite laser, and microdermabrasion can have a positive therapeutic effect on KP.

High-efficency stable 213-nm generation for LASIK application

NASA Astrophysics Data System (ADS)

Wang, Zhenglin; Alameh, Kamal; Zheng, Rong

2005-01-01

213nm Solid-state laser technology provides an alternative method to replace toxic excimer laser in LASIK system. In this paper, we report a compact fifth harmonic generation system to generate high pulse energy 213nm laser from Q-switched Nd:YAG laser for LASIK application based on three stages harmonic generation procedures. A novel crystal housing was specifically designed to hold the three crystals with each crystal has independent, precise angular adjustment structure and automatic tuning control. The crystal temperature is well maintained at ~130°C to improve harmonic generation stability and crystal operation lifetime. An output pulse energy 35mJ is obtained at 213nm, corresponding to total conversion efficiency ~10% from 1064nm pump laser. In system verification tests, the 213nm output power drops less than 5% after 5 millions pulse shots and no significant damage appears in the crystals.

Comparison of a long-pulse Nd:YAG laser and a combined 585/1,064-nm laser for the treatment of acne scars: a randomized split-face clinical study.

PubMed

Min, Seong U K; Choi, Yu Sung; Lee, Dong Hun; Yoon, Mi Young; Suh, Dae Hun

2009-11-01

Nonablative laser is gaining popularity because of the low risk of complications, especially in patients with darker skin. To compare the efficacy and safety of a long-pulse neodymium-doped yttrium aluminium garnet (Nd:YAG) laser and a combined 585/1,064-nm laser for the treatment of acne scars. Nineteen patients with mild to moderate atrophic acne scars received four long-pulse Nd:YAG laser or combined 585/1,064-nm laser treatment sessions at fortnightly intervals. Treatments were administered randomly in a split-face manner. Acne scars showed mild to moderate improvement, with significant Echelle d'évaluation clinique des cicatrices d'acné (ECCA) score reductions, after both treatments. Although intermodality differences were not significant, combined 585/1,064-nm laser was more effective for deep boxcar scars. In patients with combined 585/1,064-nm laser-treated sides that improved more than long-pulse Nd:YAG laser-treated sides, ECCA scores were significantly lower for combined 585/1,064-nm laser treatment. Histologic evaluations revealed significantly greater collagen deposition, although there was no significant difference between the two modalities. Patient satisfaction scores concurred with physicians' evaluations. Both lasers ameliorated acne scarring with minimal downtime. In light of this finding, optimal outcomes might be achieved when laser treatment types are chosen after considering individual scar type and response.

High average power, widely tunable femtosecond laser source from red to mid-infrared based on an Yb-fiber-laser-pumped optical parametric oscillator.

PubMed

Gu, Chenglin; Hu, Minglie; Zhang, Limeng; Fan, Jintao; Song, Youjian; Wang, Chingyue; Reid, Derryck T

2013-06-01

We report on the highly efficient generation of widely tunable femtosecond pulses based on intracavity second harmonic generation (SHG) and sum frequency generation (SFG) in a MgO-doped periodically poled LiNbO(3) optical parametric oscillator (OPO), which is pumped by a Yb-doped large-mode-area photonics crystal fiber femtosecond laser. Red and near infrared from intracavity SHG and SFG and infrared signals were directly obtained from the OPO. A 2 mm β-BaB(2)O(4) is applied for Type I (oo → e) intracavity SHG and SFG, and then femtosecond laser pulses over 610 nm ~ 668 nm from SFG and 716 nm ~ 970 nm from SHG are obtained with high efficiency. In addition, the oscillator simultaneously generates signal and idler femtosecond pulses over 1450 nm ~ 2200 nm and 2250 nm ~ 4000 nm, respectively.

Nanosurgery with near-infrared 12-femtosecond and picosecond laser pulses

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada; Zhang, Huijing; Lemke, Cornelius; König, Karsten

2011-03-01

Laser-assisted surgery based on multiphoton absorption of NIR laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. Here we apply femtosecond laser scanning microscopes for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) with an in situ pulse duration at the target ranging from 12 femtoseconds up to 3 picoseconds was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy (AFM) and electron microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery.

Nanosurgery of cells and chromosomes using near-infrared twelve-femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada; Lessel, Matthias; Nietzsche, Sander; Zeitz, Christian; Jacobs, Karin; Lemke, Cornelius; König, Karsten

2012-10-01

Laser-assisted surgery based on multiphoton absorption of near-infrared laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. In this paper we describe usage of an ultrashort femtosecond laser scanning microscope for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) and an in situ pulse duration at the target ranging from 12 fs up to 3 ps was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery of cells and cellular organelles.

Effect of frequency-doubling pulse Nd:YAG laser on microbial mutation

NASA Astrophysics Data System (ADS)

Zhao, Yansheng; Wang, Luyan; Zheng, Heng; Yin, Hongping; Chen, Xiangdong; Tan, Zheng; Wu, Wutong

1999-09-01

We are going to report the mutagenic effect of frequency-doubling pulse Nd:YAG laser (532 nm) on microbe. After irradiation with pulse laser, mutants of abscisic acid producing strains and erythromycin producing strains were obtained, one of which could produce 62.1% and 57% more products than control, respectively. In the study of mutagenization of Spirulina platensis caused by pulse laser, we selected a high photosynthetic strains, with improved productivity of protein and exocellular ploysaccharides of 12% and 246%, respectively. The experimental results indicate that frequency-doubling pulse laser (532 nm) is a potential new type of physical mutagenic factor.

Passive, active, and hybrid mode-locking in a self-optimized ultrafast diode laser

NASA Astrophysics Data System (ADS)

Alloush, M. Ali; Pilny, Rouven H.; Brenner, Carsten; Klehr, Andreas; Knigge, Andrea; Tränkle, Günther; Hofmann, Martin R.

2018-02-01

Semiconductor lasers are promising sources for generating ultrashort pulses. They are directly electrically pumped, allow for a compact design, and therefore they are cost-effective alternatives to established solid-state systems. Additionally, their emission wavelength depends on the bandgap which can be tuned by changing the semiconductor materials. Theoretically, the obtained pulse width can be few tens of femtoseconds. However, the generated pulses are typically in the range of several hundred femtoseconds only. Recently, it was shown that by implementing a spatial light modulator (SLM) for phase and amplitude control inside the resonator the optical bandwidth can be optimized. Consequently, by using an external pulse compressor shorter pulses can be obtained. We present a Fourier-Transform-External-Cavity setup which utilizes an ultrafast edge-emitting diode laser. The used InGaAsP diode is 1 mm long and emits at a center wavelength of 850 nm. We investigate the best conditions for passive, active and hybrid mode-locking operation using the method of self-adaptive pulse shaping. For passive mode-locking, the bandwidth is increased from 2.34 nm to 7.2 nm and ultrashort pulses with a pulse width of 216 fs are achieved after external pulse compression. For active and hybrid mode-locking, we also increased the bandwidth. It is increased from 0.26 nm to 5.06 nm for active mode-locking and from 3.21 nm to 8.7 nm for hybrid mode-locking. As the pulse width is strongly correlated with the bandwidth of the laser, we expect further reduction in the pulse duration by increasing the bandwidth.

Comparison of pulsed dye laser versus combined pulsed dye laser and Nd:YAG laser in the treatment of inflammatory acne vulgaris.

PubMed

Salah El Din, Manal Mohamed; Samy, Nevien Ahmed; Salem, Amira Eid

2017-06-01

Both pulsed dye laser and combined 585/1064-nm (sequential dual-wavelength PDL and Nd:YAG) laser improves inflammatory skin disorders including acne vulgaris. To compare the efficacy of 585-nm pulsed dye laser versus sequential dual-wavelength PDL and Nd:YAG in treatment of acne vulgaris. Thirty patients with acne vulgaris were treated by PDL alone on half of the face while contra lateral half was treated by combined 585/1064 nm laser. The study showed that inflammatory acne lesions count was significantly reduced by 82.5% (p 0.0001) on PDL sides and by 83.5% (p 0.00001) on combined 585/1064-nm side after 8 weeks, while reduction of non-inflammatory acne lesions was observed at 8 weeks by 58.4% and 71.5% respectively. However, difference between the two modalities was not statistically significant. PDL and combined PDL/Nd:YAG laser treatment were found to be an effective, safe and well-tolerated treatment option for inflammatory and non-inflammatory acne vulgaris.

Pulse length of ultracold electron bunches extracted from a laser cooled gas

PubMed Central

Franssen, J. G. H.; Frankort, T. L. I.; Vredenbregt, E. J. D.; Luiten, O. J.

2017-01-01

We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps) but hot (∼104 K) electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K) and ultrafast (∼25 ps) electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales. PMID:28396879

Advances in generation of high-repetition-rate burst mode laser output.

PubMed

Jiang, Naibo; Webster, Matthew C; Lempert, Walter R

2009-02-01

It is demonstrated that the incorporation of variable pulse duration flashlamp power supplies into an Nd:YAG burst mode laser system results in very substantial increases in the realizable energy per pulse, the total pulse train length, and uniformity of the intensity envelope. As an example, trains of 20 pulses at burst frequencies of 50 and 20 kHz are demonstrated with individual pulse energy at 1064 nm of 220 and 400 mJ, respectively. Conversion efficiency to the second- (532 nm) and third- (355 nm) harmonic wavelengths of approximately 50% and 35-40%, respectively, is also achieved. Use of the third-harmonic output of the burst mode laser as a pump source for a simple, home built optical parametric oscillator (OPO) produces pulse trains of broadly wavelength tunable output. Sum-frequency mixing of OPO signal output at 622 nm with residual output from the 355 nm pump beam is shown to produce uniform bursts of tunable output at approximately 226 nm, with individual pulse energy of approximately 0.5 mJ. Time-correlated NO planar laser induced fluorescence (PLIF) image sequences are obtained in a Mach 3 wind tunnel at 500 kHz, representing, to our knowledge, the first demonstration of NO PLIF imaging at repetition rates exceeding tens of hertz.

Surface nanotexturing of tantalum by laser ablation in water

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

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

2009-01-31

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

Vortex operation in Er:LuYAG crystal laser at ∼1.6 μm

NASA Astrophysics Data System (ADS)

Liu, Qiyao; Zhao, Yongguang; Zhou, Wei; Shen, Deyuan

2017-09-01

An Er3+-doped Lu1.5Y1.5Al5O12 (Er:LuYAG) solid-state laser with direct generation of optical vortex is reported. The vortex laser operation was realized through being pumped by an annular beam at 1532 nm, which was reformatted by a specially fabricated optical mirror. With two different laser output couplers of 10% and 20% transmissions, pure LG01 mode lasers with right-handedness at 1647.7 nm and 1619.5 nm were yielded from a simple two-mirror cavity, respectively, without any helicity control optical element. Furthermore, stable pulse trains at 1647.7 nm have been achieved via employing an acousto-optic Q-switch, and ∼0.66 mJ pulsed energy and ∼65 ns pulse duration were finally obtained at 1 kHz repetition rate, corresponding to a peak power of ∼10.2 kW. The generated pulse vortex maintained LG01 mode with well-determined right-handedness, as in the case of cw laser operation.

High-power actively Q-switched single-mode 1342 nm Nd:YVO₄ ring laser, injection-locked by a cw single-frequency microchip laser.

PubMed

Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

2015-11-30

In this paper we report on the realization of a single-mode Q-switched Nd:YVO₄ ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO₄ microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M² < 1.05). By frequency doubling of the fundamental 1342 nm laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M² < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.

1.6 μm microchip laser

NASA Astrophysics Data System (ADS)

Šulc, J.; Jelínková, H.; Ryba-Romanowski, W.; Lukasiewicz, T.

2009-03-01

Properties of new pulsed-diode-pumped Er:YVO4 and Er:YVO4+CaO microchip lasers working in an ``eye-safe'' spectral region were investigated. As a pumping source, a fiber coupled (core diameter-200 μm) laser diode emitting radiation at wavelength 976 nm was used. The laser diode was operating in pulsed regime with 3 ms pulse width, and 20 Hz repetition rate. The result obtained was 175 mW and 152 mW output peak power for the Er:YVO4 and Er:YVO4+CaO lasers, respectively. The maximal efficiency with respect to the absorbed power was ~ 5%. The laser emission for Er:YVO4 microchip was observed in detail in the range 1593 nm to 1604 nm with respect to pumping. However, for Er:YVO4+CaO crystal only 1604 nm was generated.

New stable tunable solid-state dye laser in the red

NASA Astrophysics Data System (ADS)

Gvishi, Raz; Reisfeld, Renata; Burshtein, Zeev; Miron, Eli

1993-08-01

A red perylene derivative was impregnated into a composite silica-gel glass, and characterized as a dye laser material. The absorption spectrum in the range 480 - 600 nm belongs to the S0 - S1 electronic transition, with a structure reflecting the perylene skeletal vibrations, of typical energy 1100 - 1200 cm-1. An additional peak between 400 and 460 nm belongs to the S0 - S2 transition. The fluorescence exhibits a mirror image relative to the S0 - S1 absorption, with a Stokes shift of about 40 nm for the 0 - 0 transition. Laser tunability was obtained in the range 605 - 630 nm using a frequency-doubled Nd:YAG laser for pumping ((lambda) equals 532 nm). This wavelength range is important for medical applications, such as photodynamic therapy of some cancer tumors. Maximum laser efficiency of approximately 2.5% was obtained at 617 nm. Maximum output was approximately 0.36 mJ/pulse at a repetition rate of 10 Hz. Minimum laser threshold obtained was 0.45 mJ/pulse. The medium losses are attributed to an excited-state singlet-singlet absorption, with an upper limit cross-section of approximately 2.5 X 10-16 cm2. The laser output was stable over more than approximately 500,000 pulses, under excitation with the green line of a copper vapor laser (510 nm), of energy density approximately 40 mJ/cm2 per pulse. Good prospects exist for a considerable enhancement in laser output efficiency.

Influence of Temperature on Nanosecond Pulse Amplification in Thulium Doped Fiber Lasers

NASA Astrophysics Data System (ADS)

Abdulfattah, Ali; Gausmann, Stefan; Sincore, Alex; Bradford, Joshua; Bodnar, Nathan; Cook, Justin; Shah, Lawrence; Richardson, Martin

2018-05-01

Thulium silica doped fiber (TDF) lasers are becoming important laser sources in both research and applications in industry. A key element of all high-power lasers is thermal management and its impact on laser performance. This is particularly important in TDF lasers, which utilize an unusual cross-relation pumping scheme, and are optically less efficient than other types of fiber lasers. The present work describes an experimental investigation of thermal management in a high power, high repetition-rate, pulsed Thulium (Tm) fiber laser. A tunable nanosecond TDF laser system across the 1838 nm – 1948 nm wavelength range, has been built to propagate 2μm signal seed pulses into a TDF amplifier, comprising a polarized large mode area (PLMA) thulium fiber (TDF) with a 793nm laser diode pump source. The PLMA TDF amplifier is thermally managed by a separately controlled cooling system with a temperature varied from 12°C to 36°C. The maximum output energy (∼400 μJ), of the system is achieved at 12°C at 1947 nm wavelength with ∼32 W of absorbed pump power at 20 kHz with a pulse duration of ∼ 74 ns.

Laser-driven hydrothermal process studied with excimer laser pulses

NASA Astrophysics Data System (ADS)

Mariella, Raymond; Rubenchik, Alexander; Fong, Erika; Norton, Mary; Hollingsworth, William; Clarkson, James; Johnsen, Howard; Osborn, David L.

2017-08-01

Previously, we discovered [Mariella et al., J. Appl. Phys. 114, 014904 (2013)] that modest-fluence/modest-intensity 351-nm laser pulses, with insufficient fluence/intensity to ablate rock, mineral, or concrete samples via surface vaporization, still removed the surface material from water-submerged target samples with confinement of the removed material, and then dispersed at least some of the removed material into the water as a long-lived suspension of nanoparticles. We called this new process, which appears to include the generation of larger colorless particles, "laser-driven hydrothermal processing" (LDHP) [Mariella et al., J. Appl. Phys. 114, 014904 (2013)]. We, now, report that we have studied this process using 248-nm and 193-nm laser light on submerged concrete, quartzite, and obsidian, and, even though light at these wavelengths is more strongly absorbed than at 351 nm, we found that the overall efficiency of LDHP, in terms of the mass of the target removed per Joule of laser-pulse energy, is lower with 248-nm and 193-nm laser pulses than with 351-nm laser pulses. Given that stronger absorption creates higher peak surface temperatures for comparable laser fluence and intensity, it was surprising to observe reduced efficiencies for material removal. We also measured the nascent particle-size distributions that LDHP creates in the submerging water and found that they do not display the long tail towards larger particle sizes that we had observed when there had been a multi-week delay between experiments and the date of measuring the size distributions. This is consistent with transient dissolution of the solid surface, followed by diffusion-limited kinetics of nucleation and growth of particles from the resulting thin layer of supersaturated solution at the sample surface.

Picosecond transient backward stimulated Raman scattering and pumping of femtosecond dye lasers

NASA Astrophysics Data System (ADS)

Arrivo, Steven M.; Spears, Kenneth G.; Sipior, Jeffrey

1995-02-01

We report studies of transient, backward stimulated, Raman scattering (TBSRS) in solvents with a 10 Hz, 27 ps, 532 nm pump laser. The TBSRS effect was used to create pulses at 545 nm and 630 nm with durations of 2-3 ps and 5-10 μJ of energy. The duration, energy and fluctuations of the Raman pulse were studied as a function of pump energy and focal parameters. A 5 μJ Raman pulse was amplified in either a Raman amplifier or two stage dye amplifier to 1 mJ levels. A 545 nm pulse of 3 ps duration was generated in CCl 4 and was then used to pump a short cavity dye laser (SCDL). The SCDL oscillator and a 5 stage dye amplifier provided a pulse of 700 fs and 400 μJ that was tunable near 590 nm.

Generation of spectrally-stable continuous-wave emission and ns pulses at 800 nm and 975 nm with a peak power of 4 W using a distributed Bragg reflector laser and a ridge-waveguide power amplifier

NASA Astrophysics Data System (ADS)

Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Liero, A.; Hoffmann, Th.; Erbert, G.; Tränkle, G.

2015-03-01

Semiconductor based sources which emit high-power spectrally stable nearly diffraction-limited optical pulses in the nanosecond range are ideally suited for a lot of applications, such as free-space communications, metrology, material processing, seed lasers for fiber or solid state lasers, spectroscopy, LIDAR and frequency doubling. Detailed experimental investigations of 975 nm and 800 nm diode lasers based on master oscillator power amplifier (MOPA) light sources are presented. The MOPA systems consist of distributed Bragg reflector lasers (DBR) as master oscillators driven by a constant current and ridge waveguide power amplifiers which can be driven DC and by current pulses. In pulse regime the amplifiers modulated with rectangular current pulses of about 5 ns width and a repetition frequency of 200 kHz act as optical gates, converting the continuous wave (CW) input beam emitted by the DBR lasers into a train of short optical pulses which are amplified. With these experimental MOPA arrangements no relaxation oscillations in the pulse power occur. With a seed power of about 5 mW at a wavelength of 973 nm output powers behind the amplifier of about 1 W under DC injection and 4 W under pulsed operation, corresponding to amplification factors of 200 (amplifier gain 23 dB) and 800 (gain 29 dB) respectively, are reached. At 800 nm a CW power of 1 W is obtained for a seed power of 40 mW. The optical spectra of the emission of the amplifiers exhibit a single peak at a constant wavelength with a line width < 10 pm in the whole investigated current ranges. The ratios between laser and ASE levels were > 50 dB. The output beams are nearly diffraction limited with beam propagation ratios M2lat ~ 1.1 and M2ver ~ 1.2 up to 4 W pulse power.

Picosecond pulsed micro-module emitting near 560 nm using a frequency doubled gain-switched DBR ridge waveguide semiconductor laser

NASA Astrophysics Data System (ADS)

Kaltenbach, André; Hofmann, Julian; Seidel, Dirk; Lauritsen, Kristian; Bugge, Frank; Fricke, Jörg; Paschke, Katrin; Erdmann, Rainer; Tränkle, Günther

2017-02-01

A miniaturized picosecond pulsed semiconductor laser source in the spectral range around 560nm is realized by integrating a frequency doubled distributed Bragg reflector ridge waveguide laser (DBR-RWL) into a micromodule. Such compact laser sources are suitable for mobile application, e.g. in microscopes. The picosecond optical pulses are generated by gain-switching which allows for arbitrary pulse repetition frequencies. For frequency conversion a periodically poled magnesium doped lithium niobate ridge waveguide crystal (PPLN) is used to provide high conversion efficiency with single-pass second harmonic generation (SHG). The coupling of the pulsed radiation into the PPLN crystal is realized by a GRIN-lens. Such types of lenses collect the divergent laser radiation and focus it into the crystal waveguide providing high coupling efficiency at a minimum of space compared to the usage of fast axis collimator(FAC)/slow axis collimator (SAC) lens combinations. The frequency doubled output pulses show a pulse width of about 60 ps FWHM and a spectral width around 0.06nm FWHM at a central wavelength of 557nm at 15Å. The pulse peak power could be determined to be more than 300mW at a repetition frequency of 40 MHz.

Broadband pulsed difference frequency generation laser source centered 3326 nm based on ring fiber lasers

NASA Astrophysics Data System (ADS)

Chen, Guangwei; Li, Wenlei

2018-03-01

A broadband pulsed mid-infrared difference frequency generation (DFG) laser source based on MgO-doped congruent LiNbO3 bulk is experimentally demonstrated, which employs a homemade pulsed ytterbium-doped ring fiber laser and a continuous wave erbium-doped ring fiber laser to act as seed sources. The experimental results indicate that the perfect phase match crystal temperature is about 74.5∘C. The maximum spectrum bandwidth of idler is about 60 nm with suitable polarization states of fundamental lights. The central wavelength of idlers varies from 3293 nm to 3333 nm over the crystal temperature ranges of 70.4-76∘C. A jump of central wavelength exists around crystal temperature of 72∘C with variation of about 30 nm. The conversion efficiency of DFG can be tuned with the crystal temperature and polarization states of fundamental lights.

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

NASA Astrophysics Data System (ADS)

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

2011-03-01

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

Experimental investigation on a diode-pumped cesium-vapor laser stably operated at continuous-wave and pulse regime.

PubMed

Chen, Fei; Xu, Dongdong; Gao, Fei; Zheng, Changbin; Zhang, Kuo; He, Yang; Wang, Chunrui; Guo, Jin

2015-05-04

Employing a fiber-coupled diode-laser with a center wavelength of 852.25 nm and a line width of 0.17 nm, experimental investigation on diode-end-pumped cesium (Cs) vapor laser stably operated at continuous-wave (CW) and pulse regime is carried out. A 5 mm long cesium vapor cell filled with 60 kPa helium and 20 kPa ethane is used as laser medium. Using an output coupler with reflectivity of 48.79%, 1.26 W 894.57 nm CW laser is obtained at an incident pump power of 4.76 W, corresponding an optical-optical efficiency of 26.8% and a slope-efficiency of 28.8%, respectively. The threshold temperature is 67.5 °C. Stable pulsed cesium laser with a maximum average output power of 2.6 W is obtained at a repetition rate of 76 Hz, and the pulse repetition rate can be extend to 1 kHz with a pulse width of 18 μs.

10 kHz ps 1342 nm laser generation by an electro-optically cavity-dumped mode-locked Nd:YVO4 laser

NASA Astrophysics Data System (ADS)

Chen, Ying; Liu, Ke; He, Li-jiao; Yang, Jing; Zong, Nan; Yang, Feng; Gao, Hong-wei; Liu, Zhao; Yuan, Lei; Lan, Ying-jie; Bo, Yong; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2017-01-01

We have demonstrated an electro-optically cavity-dumped mode-locked (CDML) picosecond Nd:YVO4 laser at 1342 nm with 880 nm diode-laser direct pumping. At a repetition rate of 10 kHz, an average output power of 0.119 W was achieved, corresponding to a pulse energy of 11.9 μJ. Compared with the continuous wave mode-locking pulse energy of 17.5 nJ, the CDML pulse energy was 680 times higher. The pulse width was measured to be 33.4 ps, resulting in the peak power of 356 kW. Meanwhile, the beam quality was nearly diffraction limited with an average beam quality factor M2 of 1.29.

Regular subwavelength surface structures induced by femtosecond laser pulses on stainless steel.

PubMed

Qi, Litao; Nishii, Kazuhiro; Namba, Yoshiharu

2009-06-15

In this research, we studied the formation of laser-induced periodic surface structures on the stainless steel surface using femtosecond laser pulses. A 780 nm wavelength femtosecond laser, through a 0.2 mm pinhole aperture for truncating fluence distribution, was focused onto the stainless steel surface. Under different experimental condition, low-spatial-frequency laser-induced periodic surface structures with a period of 526 nm and high-spatial-frequency laser-induced periodic surface structures with a period of 310 nm were obtained. The mechanism of the formation of laser-induced periodic surface structures on the stainless steel surface is discussed.

Studies on nanosecond 532nm and 355nm and ultrafast 515nm and 532nm laser cutting super-hard materials

NASA Astrophysics Data System (ADS)

Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

2017-02-01

In this paper, micro-processing of three kinds of super-hard materials of poly-crystal diamond (PCD)/tungsten-carbide (WC), CVD-diamond and cubic boron nitride (CNB) has been systematically studied using nanosecond laser (532nm and 355nm), and ultrafast laser (532nm and 515nm). Our purpose is to investigate a full laser micro-cutting solution to achieve a ready-to-use cutting tool insert (CTI). The results show a clean cut with little burns and recasting at edge. The cutting speed of 2-10mm/min depending on thickness was obtained. The laser ablation process was also studied by varying laser parameters (wavelength, pulse width, pulse energy, repetition rate) and tool path to improve cutting speed. Also, studies on material removal efficiency (MRE) of PCD/WC with 355nm-ns and 515nm-fs laser as a function of laser fluence show that 355nm-ns laser is able to achieve higher MRE for PCD and WC. Thus, ultrafast laser is not necessarily used for superhard material cutting. Instead, post-polishing with ultrafast laser can be used to clean cutting surface and improve smoothness.

Room-temperature operation of a Co:MgF2 laser

NASA Technical Reports Server (NTRS)

Welford, D.; Moulton, P. F.

1988-01-01

A normal-mode, pulsed Co:MgF2 laser has been operated at room temperature for the first time. Continuous tuning from 1750 to 2500 nm with pulse energies up to 70 mJ and 46-percent slope efficiency was obtained with a 1338-nm Nd:YAG pump laser.

Experimental investigation into generation of bursts of linearly-polarized, dissipative soliton pulses from a figure-eight fiber laser at 1.03 µm

NASA Astrophysics Data System (ADS)

Ko, Seunghwan; Lee, Junsu; Koo, Joonhoi; Lee, Ju Han

2018-03-01

We experimentally demonstrate a simple and stable all-polarization maintaining fiber (PMF) nonlinear amplifying loop mirror (NALM)-based burst pulse fiber laser with a pulse number tuning capability, which can readily generate bursts of linearly-polarized femtosecond pulses at 1030 nm. The laser was based on an NALM that was operated to produce burst-mode, dissipative soliton pulses at a wavelength of 1030 nm, and these were then compressed into 400 fs Gaussian pulses using a grating pair-based compressor. The laser was constructed with the figure-eight configuration incorporating ytterbium-doped fiber as gain medium. It was shown that the number of burst pulses was readily tunable through the adjustment of the pump power. Further, the output-pulse characteristics were quantitatively investigated and the laser stability was checked by observing the temporal characteristic variation of the output pulses for one hour.

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.

Optimizing laser crater enhanced Raman scattering spectroscopy

NASA Astrophysics Data System (ADS)

Lednev, V. N.; Sdvizhenskii, P. A.; Grishin, M. Ya.; Fedorov, A. N.; Khokhlova, O. V.; Oshurko, V. B.; Pershin, S. M.

2018-05-01

The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1-1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for L-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes.

PubMed

Li, Diao; Jussila, Henri; Wang, Yadong; Hu, Guohua; Albrow-Owen, Tom; C T Howe, Richard; Ren, Zhaoyu; Bai, Jintao; Hasan, Tawfique; Sun, Zhipei

2018-02-09

Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration.

Compact high-pulse-energy passively Q-switched Nd:YLF laser with an ultra-low-magnification unstable resonator: application for efficient optical parametric oscillator.

PubMed

Cho, C Y; Huang, Y P; Huang, Y J; Chen, Y C; Su, K W; Chen, Y F

2013-01-28

We exploit an ultra-low-magnification unstable resonator to develop a high-pulse-energy side-pumped passively Q-switched Nd:YLF/Cr⁴⁺:YAG laser with improving beam quality. A wedged laser crystal is employed in the cavity to control the emissions at 1047 nm and 1053 nm independently through the cavity alignment. The pulse energies at 1047 nm and 1053 nm are found to be 19 mJ and 23 mJ, respectively. The peak powers for both wavelengths are higher than 2 MW. Furthermore, the developed Nd:YLF lasers are employed to pump a monolithic optical parametric oscillator for confirming the applicability in nonlinear wavelength conversions.

Widely wavelength tunable gain-switched Er³⁺-doped ZBLAN fiber laser around 2.8 μm.

PubMed

Wei, Chen; Luo, Hongyu; Shi, Hongxia; Lyu, YanJia; Zhang, Han; Liu, Yong

2017-04-17

In this paper, we demonstrate a wavelength widely tunable gain-switched Er³⁺-doped ZBLAN fiber laser around 2.8 μm. The laser can be tuned over 170 nm (2699 nm~2869.9 nm) for various pump power levels, while maintaining stable μs-level single-pulse gain-switched operation with controllable output pulse duration at a selectable repetition rate. To the best of our knowledge, this is the first wavelength tunable gain-switched fiber laser in the 3 μm spectral region with the broadest tuning range (doubling the record tuning range) of the pulsed fiber lasers around 3 μm. Influences of pump energy and power on the output gain-switched laser performances are investigated in detail. This robust, simple, and versatile mid-infrared pulsed fiber laser source is highly suitable for many applications including laser surgery, material processing, sensing, spectroscopy, as well as serving as a practical seed source in master oscillator power amplifiers.

Single-beam Denisyuk holograms recording with pulsed 30Hz RGB laser

NASA Astrophysics Data System (ADS)

Zacharovas, Stanislovas; Bakanas, Ramūnas; Stankauskas, Algimantas

2016-03-01

It is well known fact that holograms can be recorded either by continuous wave (CW) laser, or by single pulse coming from pulsed laser. However, multi-pulse or multiple-exposure holograms were used only in interferometry as well as for information storage. We have used Geola's single longitudinal mode pulsed RGB laser to record Denisyuk type holograms. We successfully recorded objects situated at the distance of more than 30cm, employing the multi-pulse working regime of the laser. To record Denisyuk hologram we have used 50 ns duration 440, 660nm wavelength and 35ns duration 532nm wavelength laser pulses at the repetition rate of 30Hz. As photosensitive medium we have used Slavich-Geola PFG-03C glass photoplate. Radiations with different wavelengths were mixed into "white" beam, collimated and directed onto the photoplate. For further objects illumination an additional flat silver coated mirror was used.

Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: influence of laser-induced plasma.

PubMed

Ogura, Makoto; Sato, Shunichi; Ishihara, Miya; Kawauchi, Satoko; Arai, Tunenori; Matsui, Takemi; Kurita, Akira; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

2002-01-01

We investigated the mechanism and characteristics of porcine myocardium tissue ablation in vitro with nanosecond 1,064- and 532-nm pulsed lasers at laser intensities up to approximately 5.0 GW/cm(2). Particular attention was paid to study the influence of the laser-induced plasma on the ablation characteristics. The applicability of these two lasers to transmyocardial laser revascularization (TMLR) was discussed. Porcine myocardium tissue samples were irradiated with 1,064- and 532-nm, Q-switched Nd:YAG laser pulses, and the ablation depths were measured. The temporal profiles of the laser-induced optical emissions were measured with a biplanar phototube. For the ablated tissue samples, histological analysis was performed with an optical microscope and a polarization microscope. The ablation efficiency at 1,064 nm was higher than that at 532 nm. The ablation threshold at 1,064 nm (approximately 0.8 GW/cm(2)) was lower than that at 532 nm (approximately 1.6 GW/cm(2)), in spite of the lower absorption coefficient being expected at 1,064 nm. For the 1,064-nm laser-ablated tissues, thermal damage was very limited, while damage presumably caused by the mechanical effect was observed in most of the cases. For the 1,064-nm laser ablation, the ablation threshold was equal to the threshold of the laser-induced optical emission (approximately 0.8 GW/cm(2)), while for the 532-nm laser ablation, the optical emission threshold ( approximately 2.4 GW/cm(2)) was higher than the ablation threshold. We considered that for the 1,064-nm laser ablation, the tissue removal was achieved through a photodisruption process at laser intensities of > approximately 0.8 GW/cm(2). At laser intensities of > 3.0 GW/cm(2), however, the ablation efficiency decreased; this can be attributed to the absorption of incoming laser pulses by the plasma. For the 532-nm laser ablation, the tissue removal was achieved through a photothermal process at laser intensities of > approximately 1.6 GW/cm(2). At laser intensities of > 2.4 GW/cm(2), a photodisruption process may also contribute to the tissue removal, in addition to a photothermal process. With regard to the ablation rates, the 1,064-nm laser was more suitable for TMLR than the 532-nm laser. We concluded that the 1,064-nm Q-switched Nd:YAG laser would be a potential candidate for a laser source for TMLR because of possible fiber-based beam delivery, its compact structure, cost effectiveness, and easy maintenance. Animal trials, however, have to be carried out to evaluate the influence of the tissue damage. Copyright 2002 Wiley-Liss, Inc.

Laser-assisted hair removal for facial hirsutism in women: A review of evidence.

PubMed

Lee, Chun-Man

2018-06-01

Poly cystic ovarian syndrome (PCOS) has been described as the common diagnosis for hirsutism in women. Facial hirsutism is by far the most distressing symptom of hyperandrogenism in women with PCOS. A statistically significant improvement in psychological well-being has been reported in patients with PCOS allocated for laser-assisted hair removal. The theory of selective photothermolysis has revolutionized laser hair removal in that it is effective and safe, when operated by sufficiently trained and experienced professionals. Long-pulsed ruby (694 nm), long-pulsed alexandrite (755 nm), diode (800-980 nm), and long-pulsed Nd:YAG (1064 nm) are commercially available laser devices for hair removal most widely studied. This article will introduce the fundamentals and mechanism of action of lasers in hair removal, in a contemporary literature review looking at medium to long term efficacy and safety profiles of various laser hair removal modalities most widely commercially available to date.

Inactivation of Viruses by Coherent Excitations with a Low Power Visible Femtosecond Laser

DTIC Science & Technology

2007-06-05

visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density...was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width...visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power

36 W Q-switched Ho:YAG laser at 2097 nm pumped by a Tm fiber laser: evaluation of different Ho3+ doping concentrations

NASA Astrophysics Data System (ADS)

Antipov, O. L.; Eranov, I. D.; Kositsyn, R. I.

2017-01-01

A laser oscillator based on Ho:YAG crystal pumped by a Tm fiber laser with an acousto-optical Q-switch was optimized for maximum output power and pulse-to-pulse stability. Stable operation at 2097 nm in Q-switched mode is demonstrated, with pulse repetition rates from 10 to 30 kHz, and output power of 36 W (at 55 W of pump power at 1908 nm) in the good quality beam. The influence of Ho ion up-conversion and thermal lensing on the oscillation efficiency is discussed.

Nanosurgery of cells and chromosomes using near-infrared twelve-femtosecond laser pulses.

PubMed

Uchugonova, Aisada; Lessel, Matthias; Nietzsche, Sander; Zeitz, Christian; Jacobs, Karin; Lemke, Cornelius; König, Karsten

2012-10-01

ABSTRACT. Laser-assisted surgery based on multiphoton absorption of near-infrared laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. In this paper we describe usage of an ultrashort femtosecond laser scanning microscope for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770  nm/830  nm) and an in situ pulse duration at the target ranging from 12 fs up to 3 ps was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery of cells and cellular organelles.

Histologic evaluation of laser lipolysis: pulsed 1064-nm Nd:YAG laser versus cw 980-nm diode laser.

PubMed

Mordon, Serge; Eymard-Maurin, Anne Françoise; Wassmer, Benjamin; Ringot, Jean

2007-01-01

The use of the laser as an auxiliary tool has refined the traditional technique for lipoplasty. During laser lipolysis, the interaction between the laser and the fat produced direct cellular destruction before the suction, reduced bleeding, and promoted skin tightening. This study sought to perform a comparative histologic evaluation of laser lipolysis with the pulsed 1064-nm Nd:YAG laser versus a continuous 980-nm diode laser. A pulsed 1064-nm Nd:YAG (Smart-Lipo; Deka, Italy) and a CW 980-nm diode laser (Pharaon, Osyris, France) were evaluated at different energy settings for lipolysis on the thighs of a fresh cadaver. The lasers were coupled to a 600-microm optical fiber inserted in a 1-mm diameter cannula. Biopsy specimens were taken on irradiated and non-irradiated areas. Hematoxylin-erythrosin-safran staining and immunostaining (anti-PS100 polyclonal antibody) were performed to identify fat tissue damage. In the absence of laser exposures (control specimens), cavities created by cannulation were seen; adipocytes were round in appearance and not deflated. At low energy settings, tumescent adipocytes were observed. At higher energy settings, cytoplasmic retraction, disruption of membranes, and heat-coagulated collagen fibers were noted; coagulated blood cells were also present. For the highest energy settings, carbonization of fat tissue involving fibers and membranes was clearly seen. For equivalent energy settings, 1064-nm and 980-nm wavelengths gave similar histologic results. Laser lipolysis is a relatively new technique that is still under development. Our histologic findings suggest several positive benefits of the laser, including skin retraction and a reduction in intraoperative bleeding. The interaction of the laser with the tissue is similar at 980 nm and 1064 nm with the same energy settings. Because higher volumes of fat are removed with higher total energy, a high-power 980-nm diode laser could offer an interesting alternative to the 1064-nm Nd:YAG laser.

Ablation characteristics of carbon-doped glycerol irradiated by a 1064 nm nanosecond pulse laser

NASA Astrophysics Data System (ADS)

Jing, QI; Siqi, ZHANG; Tian, LIANG; Ke, XIAO; Weichong, TANG; Zhiyuan, ZHENG

2018-03-01

The ablation characteristics of carbon-doped glycerol were investigated in laser plasma propulsion using a pulse laser with 10 ns pulse width and 1064 nm wavelength. The results showed that with the incident laser intensity increasing, the target momentum decreased. Results still indicated that the strong plasma shielded the consumption loss and resulted in a low coupling coefficient. Furthermore, the carbon-doping gave rise to variations in the laser focal position and laser intensity, which in turn reduced the glycerol splashing. Based on the glycerol viscosity and the carbon doping, a high specific impulse is anticipated.

Periodic structures on germanium induced by high repetition rate femtosecond laser

NASA Astrophysics Data System (ADS)

Lin, Xiaoming; Li, Xiaohong; Zhang, Yanbin; Xie, Changxin; Liu, Kaijun; Zhou, Qiang

2018-05-01

Laser-induced periodic surface structures (LIPSS) are studied on germanium surface in air by the femtosecond pulsed laser with repetition frequency of 76 MHz and wavelength λ of 800 nm. Three types of LIPSS were found and they are low-spatial-frequency LIPSS (LSFL), high-spatial-frequency LIPSS (HSFL), and LSFL superimposed with HSFL. The period ΛLSFL of LSFL shrinks quickly from approximately 650 nm to 400 nm (∼λ/2) when lowering the scanning speed. Comparatively, the period ΛHSFL of HSFL keeps almost constant between 90 and 100 nm (∼λ/8) when the scanning speed and the laser pulse energy vary. LSFL and HSFL coexist when the laser pulse energy is around 3.3 nJ/pulse and the scanning speed ranges between 3 and 8 mm/s. The surface plasmon polariton waves make a contribution to the formation of LIPSS and the fourth harmonic generation (FHG) might be involved in the formation of HSFL.

Mode-locked Nd:YAG laser with output at 1052, 1061, 1064, and 1074 nm

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

Badalian, A.A.; Sapondzhian, S.O.; Sarkisian, D.G.

The picosecond Nd:YAG laser with an output radiation at 1064 nm is currently widely used. However, in connection with many applications, picosecond pulses at other wavelengths are also needed. The present study is, therefore, concerned with the development of a picosecond laser which provides pulses at 1052, 1061.5, and 1073.7 nm. Lasing at 1052, 1061.5, 1064, and 1073.7 nm was achieved by varying the angle between the resonator axis and the normal to the etalon by four degrees. Attention is given to the measurement of the lengths of the ultrashort pulses, and the transverse distribution of the energy in themore » second harmonic for the wavelength 1052 nm. The discretely tunable picosecond Nd:YAG laser described appears to be a promising tool for many research applications. 9 references.« less

Histologic analyses on the response of the skin to 1,927-nm fractional thulium fiber laser treatment.

PubMed

Kwon, In Ho; Bae, Youin; Yeo, Un-Cheol; Lee, Jin Yong; Kwon, Hyuck Hoon; Choi, Young Hee; Park, Gyeong-Hun

2018-02-01

The histologic responses to varied parameters of 1,927-nm fractional thulium fiber laser treatment have not yet been sufficiently elucidated. This study sought to evaluate histologic changes immediately after 1,927-nm fractional thulium fiber laser session at various parameters. The dorsal skin of Yucatan mini-pig was treated with 1,927-nm fractional thulium fiber laser at varied parameters, with or without skin drying. The immediate histologic changes were evaluated to determine the effects of varying laser parameters on the width and the depth of treated zones. The increase in the level of pulse energy widened the area of epidermal changes in the low power level, but increased the dermal penetration depth in the high power level. As the pulse energy level increased, the increase in the power level under the given pulse energy level more evidently made dermal penetration deeper and the treatment area smaller. Skin drying did not show significant effects on epidermal changes, but evidently increased the depth of dermal denaturation under both high and low levels of pulse energy. These results may provide important information to establish treatment parameters of the 1,927-nm fractional thulium fiber laser for various skin conditions.

Spectroscopic study of carbon plasma produced by the first (1064 nm) and second (532 nm) harmonics of Nd:YAG laser

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

Hanif, M., E-mail: drhanif-mcs@nust.edu.pk; Salik, M.; Arif, F.

2015-03-15

In this research work, spectroscopic studies of carbon (C) plasma by using laser-induced breakdown spectroscopy (LIBS) are presented. The plasma was produced by the first (1064 nm) and second (532 nm) harmonics of a Q-switched Nd:YAG (Quantel Brilliant) pulsed laser having a pulse duration of 5 ns and 10-Hz repetition rate, which is capable of delivering 400 mJ at 1064 nm and 200 mJ at 532 nm. The laser beam was focused on the target material (100% carbon) by placing it in air at atmospheric pressure. The experimentally observed line profiles of five neutral carbon (C I) lines at 247.85,more » 394.22, 396.14, 588.95, and 591.25 nm were used to extract the electron temperature T{sub e} by using the Boltzmann plot method and determine its value, 9880 and 9400 K, respectively, for the fundamental and second harmonics of the laser, whereas the electron density N{sub e} was determined from the Stark broadening profile of neutral carbon line at 247.85 nm. The values of N{sub e} at a distance of 0.05 mm from the target surface for the fundamental-harmonic laser with a pulse energy of 130 mJ and the second-harmonic laser with a pulse energy of 72 mJ are 4.68 × 10{sup 17} and 5.98 × 10{sup 17} cm{sup −3}, respectively. This extracted information on T{sub e} and N{sub e} is useful for the deposition of carbon thin films by using the pulsed laser deposition technique. Moreover, both plasma parameters (T{sub e} and N{sub e}) were also calculated by varying the distance from the target surface along the line of propagation of the plasma plume and also by varying the laser irradiance.« less

Laser processing of sapphire with picosecond and sub-picosecond pulses

NASA Astrophysics Data System (ADS)

Ashkenasi, D.; Rosenfeld, A.; Varel, H.; Wähmer, M.; Campbell, E. E. B.

1997-11-01

Laser processing of sapphire using a Ti:sapphire laser at 790 and 395 nm and pulse widths varying between 0.2 and 5 ps is reported. A clear improvement in quality is demonstrated for multi-shot processing with sub-ps laser pulses. For fluences between 3 and 12 J/cm 2 two ablation phases were observed, in agreement with previous work from Tam et al. using 30 ps, 266 nm laser pulses [A.C. Tam, J.L. Brand, D.C. Cheng, W. Zapka, Appl. Phys. Lett. 55 (20) (1994) 2045]. During the `gentle ablation' phase periodic wavelike structures, i.e. ripples, were observed on the Al 2O 3 surface, perpendicular to the laser polarisation and with a spacing almost equalling the laser wavelength, indicating metallic-like behaviour. The ripple modulation depth was in the order of a few tens of nm. For fluences between 1 and 2.5 J/cm 2, below the single-shot surface damage threshold and at a pulse width above 200 fs, microstructures could be produced at the rear side of a 1 mm thick sapphire substrate without affecting the front surface.

Bidirectional current triggering in planar devices based on serially connected VO₂ thin films using 965 nm laser diode.

PubMed

Kim, Jihoon; Park, Kyongsoo; Kim, Bong-Jun; Lee, Yong Wook

2016-08-08

By incorporating a 965 nm laser diode, the bidirectional current triggering of up to 30 mA was demonstrated in a two-terminal planar device based on serially connected vanadium dioxide (VO₂) thin films grown by pulsed laser deposition. The bidirectional current triggering was realized by using the focused beams of laser pulses through the photo-thermally induced phase transition of VO₂. The transient responses of laser-triggered currents were also investigated when laser pulses excited the device at a variety of pulse widths and repetition rates of up to 4.0 Hz. A switching contrast between off- and on-state currents was obtained as ~8333, and rising and falling times were measured as ~39 and ~29 ms, respectively, for 50 ms laser pulses.

Optically pumped quantum-dot Cd(Zn)Se/ZnSe laser and microchip converter for yellow-green spectral region

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

Lutsenko, E V; Voinilovich, A G; Rzheutskii, N V

2013-05-31

The room temperature laser generation in the yellow-green ({lambda} = 558.5-566.7 nm) spectral range has been demonstrated under optical pumping by a pulsed nitrogen laser of Cd(Zn)Se/ZnSe quantum dot heterostructures. The maximum achieved laser wavelength was as high as {lambda} = 566.7 nm at a laser cavity length of 945 {mu}m. High values of both the output pulsed power (up to 50 W) and the external differential quantum efficiency ({approx}60%) were obtained at a cavity length of 435 {mu}m. Both a high quality of the laser heterostructure and a low lasing threshold ({approx}2 kW cm{sup -2}) make it possible tomore » use a pulsed InGaN laser diode as a pump source. A laser microchip converter based on this heterostructure has demonstrated a maximum output pulse power of {approx}90 mW at {lambda} = 560 nm. The microchip converter was placed in a standard TO-18 (5.6 mm in diameter) laser diode package. (semiconductor lasers. physics and technology)« less

Picosecond 1064-nm fiber laser with tunable pulse width and low timing jitter

NASA Astrophysics Data System (ADS)

Tian, Wenyan; Zhang, Shukui

2018-02-01

We report an all-fiber, linearly polarized, 1.1-W, 1064-nm fiber laser based on a two-stage Ytterbium-doped fiber amplifier seeded by a gain-switched diode laser with tunable pulse width from 21 to 200 ps at repetition rates of 0.5-1.5 GHz. Timing jitter of our 1064-nm fiber laser was measured to be 0.60 ps over 10 Hz-40 MHz when the gain-switched diode laser was operated at a repetition rate of 0.5, 1, and 1.5 GHz. The fiber laser offers an excellent long term power stability of +/- 0.3% and wavelength stability of +/- 0.01 nm over 8 hours

Laser antisepsis of Phorphyromonas gingivalis in vitro with dental lasers

NASA Astrophysics Data System (ADS)

Harris, David M.

2004-05-01

It has been shown that both pulsed Nd:YAG (1064nm) and continuous diode (810nm) dental lasers kill pathogenic bacteria (laser antisepsis), but a quantitative method for determining clinical dosimetry does not exist. The purpose of this study was to develop a method to quantify the efficacy of ablation of Porphyromonas gingivalis (Pg) in vitro for two different lasers. The ablation thresholds for the two lasers were compared in the following manner. The energy density was measured as a function of distance from the output of the fiber-optic delivery system. Pg cultures were grown on blood agar plates under standard anaerobic conditions. Blood agar provides an approximation of gingival tissue for the wavelengths tested in having hemoglobin as a primary absorber. Single pulses (Nd:YAG: 100- Œs diode: 100-msec) of laser energy were delivered to Pg colonies and the energy density was increased until the appearance of a small plume was observed coincident with a laser pulse. The energy density at this point defines the ablation threshold. Ablation thresholds to a single pulse were determined for both Pg and for blood agar alone. The large difference in ablation thresholds between the pigmented pathogen and the host matrix for pulsed-Nd:YAG represented a significant therapeutic ratio and Pg was ablated without visible effect on the blood agar. Near threshold the 810-nm diode laser destroyed both the pathogen and the gel. Clinically, the pulsed Nd:YAG may selectively destroy pigmented pathogens leaving the surrounding tissue intact. The 810-nm diode laser may not demonstrate this selectivity due to its longer pulse length and greater absorption by hemoglobin.

Comparison of three pulsed infrared lasers for optical stimulation of the rat prostate cavernous nerves

NASA Astrophysics Data System (ADS)

Stahl, Charlotte S. D.; Tozburun, Serhat; Hutchens, Thomas C.; Lagoda, Gwen A.; Burnett, Arthur L.; Keller, Matthew D.; Fried, Nathaniel M.

2013-03-01

Optical nerve stimulation (ONS) is being explored for identification and preservation of the cavernous nerves (CN), responsible for erectile function, during prostate cancer surgery. This study compares three pulsed infrared lasers to determine whether differences in spectral linewidth and/or temporal pulse profile influence successful ONS of CN. Infrared laser radiation from the Capella diode laser (1873 nm, 5 ms, 10 Hz), Thulium fiber laser (TFL) (1873 nm, 5 ms, 10 Hz), and solid-state Holmium:YAG laser (2120 nm, 200 μs, 5 Hz) were transmitted through 400-μm-corediameter optical fibers, producing a 1-mm-diameter-spot on the nerve surface. Successful ONS was judged by an intracavernous pressure (ICP) response in the penis (n =10 rats) during a total stimulation time of 30 s. The narrow linewidth TFL (Δλ 0.5 nm) and broad linewidth Capella laser (Δλ 12 nm) performed similarly, producing ICP responses with a threshold radiant exposure of 0.45 J/cm2, and ICP response times of 12-17 s, while the Holmium laser stimulated at 0.59 J/cm2, and ICP response times of about 14-28 s. All three lasers demonstrated successful ONS of CN. ICP response time was dependent on the rate of energy deposition into the CN, rather than linewidth or temporal pulse profile.

Q-switched Nd:YAG/V:YAG microchip 1338 nm laser for laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

2017-12-01

Q-switched microchip laser emitting radiation at wavelength 1338nm was tested as a radiation source for laser induced breakdown spectroscopy (LIBS). This laser used sandwich crystal which combined in one piece the cooling part (undoped YAG crystal 4mm long), the active laser part (Nd:YAG crystal 12mm long), and the saturable absorber (V:YAG crystal 0.7mm long). The diameter of this crystal was 5 mm. The microchip resonator consisted of dielectric mirrors directly deposited on the monolith crystal surfaces. The pump mirror (HT @ 808 nm, HR @ 1.3 ¹m) was placed on the undoped YAG part. The output coupler (R = 90% @ 1338 nm) was placed on the V:YAG part. The fibre-coupled 808nm pumping laser diode was operating in pulsed regime (rep. rate 250 Hz, pulse width 300 ¹s, pulse energy 6 mJ). Using this pumping, stable and high reproducible Q-switched pulses were generated at wavelength 1338 nm. Pulse length was 6.2 ns (FWHM) and the mean output power was 33mW. The single pulse energy and peak power was 0.13mJ and 21kW, respectively. Laser was operating in fundamental TEM00 mode. The laser radiation was focused on a tested sample using single plano-convex lens (focal length 75 mm). The focal spot radius was 40 ¹m. The corresponding peak-power density was 0.83GW/cm2. The laser induced break-down was successfully reached and corresponding laser-induced plasma spectra were recorded for set of metallic elements (Cu, Ag, Au, In, Zn, Al, Fe, Ni, Cr) and alloys (Sn-Pb solder, duralumin, stainless-steel, brass). To record the spectra, StellarNet BLACK-Comet concave grating CCD-based spectrometer was used without any special collimation optics. Thanks to used laser wavelength far from the detector sensitivity, no special filtering was needed to overcome the CCD dazzling. The constructed laser could significantly improve repletion-rate of up-to-date LIBS devices.

Synchronization of 1064 and 1319 nm Pulses Emitted from Actively Mode-Locked Nd:YAG Lasers and Its Application to 589 nm Sum-Frequency Generation

NASA Astrophysics Data System (ADS)

Saito, Norihito; Akagawa, Kazuyuki; Hayano, Yutaka; Saito, Yoshihiko; Takami, Hideki; Iye, Masanori; Wada, Satoshi

2005-11-01

Sum-frequency generation was carried out by mixing 1064 and 1319 nm pulses emitted from actively mode-locked neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers for efficient 589 nm light generation. A radio frequency of approximately 75 MHz was split into two and fed to acousto-optic mode lockers of two lasers for mode-locked operation. The synchronization of the pulses was achieved by controlling the phase difference between the radio frequencies. The maximum output power at 589 nm reached 260 mW, which corresponded to an energy conversion efficiency of more than 13%. The output power was 3.8-fold that in continuous-wave operation.

Design of a patterned nanostructure array using a nanosecond pulsed laser

NASA Astrophysics Data System (ADS)

Yoshida, Yutaka; Ohnishi, Ko; Matsuo, Yasutaka; Watanabe, Seiichi

2018-04-01

For design the patterned nanostructure array (PNSA) on material surface using a nanosecond pulsed laser, we investigated the influence of phase shift between scattered lights on silicon (Si) substrate using 30-nm-wide gold lines (GLs) spacings. At a spacing of 5,871 nm, ten nanodot (ND) arrays were formed at intervals of 533 nm by nanosecond pulsed laser. The results show that the formation of the PNSA was affected by the resonance of scattered light. We conclude that ND arrays were formed with a spacing of Λ = nλ. And we have designed PNSA comprising two ND arrays on the substrate. The PNSA with dimensions of 1,600 nm × 1,600 nm was prepared using GLs.

Orthogonally superimposed laser-induced periodic surface structures (LIPSS) upon nanosecond laser pulse irradiation of SiO2/Si layered systems

NASA Astrophysics Data System (ADS)

Nürnberger, Philipp; Reinhardt, Hendrik M.; Kim, Hee-Cheol; Pfeifer, Erik; Kroll, Moritz; Müller, Sandra; Yang, Fang; Hampp, Norbert A.

2017-12-01

In this study we examined the formation of laser-induced periodic surface structures (LIPSS) on silicon (Si) in dependence on the thickness of silicon-dioxide (SiO2) on top. LIPSS were generated in air by linearly polarized ≈8 nanosecond laser pulses with a fluence per pulse of 2.41 J cm-2 at a repetition rate of 100 kHz. For SiO2 layers <80 nm, LIPSS oriented perpendicular to the laser polarization were obtained, but for SiO2 layers >120 nm parallel oriented LIPSS were observed. In both cases the periodicity was about 80-90% of the applied laser wavelength (λ0 = 532 nm). By variation of the SiO2 layer thickness in the range between 80 nm-120 nm, the dominating orientation changes. Even orthogonally superimposed LIPSS with a periodicity of only 60% of the laser wavelength were found. We show that the transition of the orientation direction of LIPSS is related to the penetration depth of surface plasmon polariton (SPP) fields into the oxide layer.

Er:YAG laser technology for remote sensing applications

NASA Astrophysics Data System (ADS)

Chen, Moran; Burns, Patrick M.; Litvinovitch, Viatcheslav; Storm, Mark; Sawruk, Nicholas W.

2016-10-01

Fibertek has developed an injection locked, resonantly pumped Er:YAG solid-state laser operating at 1.6 μm capable of pulse repetition rates of 1 kHz to 10 kHz for airborne methane and water differential absorption lidars. The laser is resonantly pumped with a fiber-coupled 1532 nm diode laser minimizing the quantum defect and thermal loading generating tunable single-frequency output of 1645-1646 nm with a linewidth of < 100 MHz. The frequency-doubled 1.6 μm Er:YAG laser emits wavelengths in the 822-823 nm spectrum, coincident with water vapor lines. Various cavity designs were studied and optimized for compactness and performance, with the optimal design being an injection seeded and locked five-mirror ring cavity. The laser generated 4 W of average power at pulse repetition frequencies (PRFs) of 1 kHz and 10 kHz, corresponding to 4 mJ and 400 μJ pulse energies, respectively. The 1645 nm was subsequently frequency doubled to 822.5 nm with a 600 pm tuning range covering multiple water absorption lines, with a pulse energy of 1 mJ and a pulse repetition frequency of 1 kHz. The resonator cavity was locked to the seed wavelength via a Pound Drever Hall (PDH) technique and an analog Proportional Integral Derivative (PID) Controller driving a high-bandwidth piezoelectric (PZT)-mounted cavity mirror. Two seed sources lasing on and off the methane absorption line were optically switched to tune the resonator wavelength on and off the methane absorption line between each sequential output pulse. The cavity locking servo maintained the cavity resonance for each pulse.

Generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser

NASA Astrophysics Data System (ADS)

Bu, Xiangbao; Shi, Yuhang; Xu, Jia; Li, Huijuan; Wang, Pu

2018-06-01

We report on the generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser around 2415 nm. A thulium-doped double-clad fiber laser at 1908 nm was used as the pump source. Bound states with various pulse separations at different dispersion regimes were obtained. Especially, in the anomalous dispersion regime, vibrating bound state of solitons exhibiting an evolving phase was obtained.

In situ probing of pulsed laser melting and laser-induced periodic surface structures formation by dynamic reflectivity

NASA Astrophysics Data System (ADS)

Huynh, T. T. D.; Semmar, N.

2017-09-01

The melting process and nanostructure formation induced by nanosecond and picosecond laser pulses on bulk silicon and copper thin film were studied by ex situ analysis and in situ real time reflectivity. Three different probing wavelengths (633, 473 and 326 nm) were used during the pump laser processing and were correlated to the beam parameters (pulse duration, laser fluence and number of laser shots) and copper thin film thickness. On a silicon surface using a KrF laser beam (27 ns, 1 Hz, 248 nm), the melting threshold was determined close to 700 mJ cm-2 and the melting duration increased from 10 to 130 ns as the fluence increased from 700 to 1750 mJ cm-2. Nanostructures with a spatial period close to the laser wavelength were formed on both copper thin film and silicon substrate after nanosecond Nd:YAG laser (10 ns, 266 nm, 1 Hz) irradiation. In the picosecond regime, using an Nd:YAG laser (40 ps, 266 nm, 1 Hz), different nanostructures, from spikes to laser-induced periodic surface structures, were formed on 500 nm copper thin film and were analyzed with respect to the drop in dynamic reflectivity changes versus the number of laser shots.

Compact diode-pumped continuous-wave and passively Q-switched Nd:GYSO laser at 1.07 μm

NASA Astrophysics Data System (ADS)

Lin, Zhi; Huang, Xiaoxu; Lan, Jinglong; Cui, Shengwei; Wang, Yi; Xu, Bin; Luo, Zhengqian; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Zhang, Xiaoyan; Wang, Jun; Xu, Jun

2016-08-01

We report diode-pumped continuous-wave (CW) and Q-switched Nd:GYSO lasers using a compact two-mirror linear laser cavity. Single-wavelength laser emissions at 1074.11 nm with 4.1-W power and at 1058.27 nm with 1.47-W power have been obtained in CW mode. The slope efficiencies with respect to the absorbed pump powers are 48.5% and 22.9%, respectively. Wavelength tunability is also demonstrated with range of about 8 nm. Using a MoS2 saturable absorber, maximum average output power up to 410 mW at 1074 nm can be yielded with absorbed pump power 6.41 W and the maximum pulse energy reaches 1.20 μJ with pulse repetition rate of 342.5 kHz and shortest pulse width of 810 ns. The CW laser results represent the best laser performance and the Q-switching also present the highest output power for Q-switched Nd3+ lasers with MoS2 as saturable absorber.

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.

300-mW narrow-linewidth deep-ultraviolet light generation at 193 nm by frequency mixing between Yb-hybrid and Er-fiber lasers.

PubMed

Xuan, Hongwen; Zhao, Zhigang; Igarashi, Hironori; Ito, Shinji; Kakizaki, Kouji; Kobayashi, Yohei

2015-04-20

A narrow-linewidth, high average power deep-ultraviolet (DUV) coherent laser emitting at 193 nm is demonstrated by frequency mixing a Yb-hybrid laser with an Er-fiber laser. The Yb-hybrid laser consists of Yb-fiber lasers and an Yb:YAG amplifier. The average output power of the 193 nm laser is 310 mW at 6 kHz, which corresponds to a pulse energy of 51 μJ. To the best of our knowledge, this is the highest average power and pulse energy ever reported for a narrow-linewidth 193 nm light generated by a combination of solid-state and fiber lasers with frequency mixing. We believe this laser will be beneficial for the application of interference lithography by seeding an injection-locking ArF eximer laser.

Microchip laser based on Yb:YAG/V:YAG monolith crystal

NASA Astrophysics Data System (ADS)

Nejezchleb, Karel; Šulc, Jan; Jelínková, Helena; Škoda, Václav

2016-03-01

V:YAG crystal was investigated as a passive Q-switch of longitudinally diode-pumped microchip laser, emitting radiation at wavelength 1030.5 nm. This laser was based on diffusion bonded monolith crystal (diameter 3 mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3 mm long) and saturable absorber (V:YAG crystal, 2 mm long, initial transmission 86 % @ 1031 nm). The microchip resonator consisted of dielectric mirrors directly deposited on the monolith surfaces (pump mirror HT @ 968 nm and HR @ 1031 nm on Yb:YAG part, output coupler with reflection 55 % @ 1031 nm on the V:YAG part). For longitudinal CW pumping of Yb:YAG part, a fibre coupled (core diameter 100 μm, NA = 0.22, emission @ 968 nm) laser diode was used. The laser threshold was 3.8W. The laser slope efficiency for output mean in respect to incident pumping was 16 %. The linearly polarized generated transversal intensity beam profile was close to the fundamental Gaussian mode. The generated pulse length, stable and mostly independent on pumping power, was equal to 1.3 ns (FWHM). The single pulse energy was increasing with the pumping power and for the maximum pumping 9.7W it was 78 μJ which corresponds to the pulse peak-power 56 kW. The maximum Yb:YAG/V:YAG microchip laser mean output power of 1W was reached without observable thermal roll-over. The corresponding Q-switched pulses repetition rate was 13.1 kHz.

Mixed garnet laser for a water vapour DIAL

NASA Astrophysics Data System (ADS)

Treichel, Rainer; Strohmaier, Stephan; Nikolov, Susanne; Eichler, Hans-Joachim; Murphy, Eamonn

2017-11-01

For the water vapour DIAL "WALES" the wavelength regions around 935 nm, 942 nm and 944 nm have been identified as the most suitable wavelength ranges. These wavelengths can be obtained using opticalparametric-oscillators (OPOs), stimulated Raman shifters and the Ti-Sapphire laser but none of these systems could deliver all the needed parameters like beam quality, efficiency, pulse length and energy yet. Also these systems are comparably big and heavy making them less suitable for a satellite based application. A fourth possibility to achieve these wavelength ranges is to shift the quasi-3-level laser lines (938 nm and 946 nm) of the Nd:YAG laser by replacing aluminium and yttrium by other rare earth elements. Changes of the host lattice characteristics lead to a shift of the upper and lower laser levels. These modified crystals are summarized under the name of "Mixed Garnet" crystals. Only the Mixed Garnet lasers can be pumped directly with diode laser and use a direct approach to generate the required laser pulses without frequency conversion. Therefore no additional non-linear crystals or special pump lasers are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons. In a first phase such mixed garnet crystals had been grown and characterised. The outcome was the selection of the gadolinium-scandium garnet for the most suitable laser crystal. During a second phase the complete laser system with output energy about 18 mJ in single 20 ns pulses and up to 8 mJ in free running mode with a combined pulse width of 250 μs at 942 nm have been demonstrated. The results of the first laser operation and the achieved performance parameter are reported.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

NASA Astrophysics Data System (ADS)

Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

2016-11-01

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber.

PubMed

Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

2016-11-02

Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm 3+ :ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

PubMed

Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

2006-05-29

We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

A diode-pumped Tm:CaYAlO4 laser at 1851 nm

NASA Astrophysics Data System (ADS)

Lan, Jinglong; Guan, Xiaofeng; Xu, Bin; Moncorgé, Richard; Xu, Huiying; Cai, Zhiping

2017-07-01

Laser emission at ~1850 nm is of great interest for neural stimulation applications. In this letter, we report on the diode-pumped continuous-wave (CW) and Q-switched (QS) laser operation of Tm:CaYAlO4 at 1851 nm, for the first time to our knowledge. In the CW regime, a maximum output power up to 0.62 W is obtained with a laser slope efficiency of about 18.0%. Using a Cr:ZnSe saturable absorber, QS laser operation is achieved with a maximum average output power of 0.25 W, the narrowest pulse width of 107 ns and the highest repetition rate of 5.85 kHz. The corresponding pulse peak power and pulse energy are about 388 W and 42.8 µJ, respectively. In this Q-switched mode, wavelength tuning is also realized over about 3 nm by slightly tilting the saturable absorber.

Electro-optically Q-switched dual-wavelength Nd:YLF laser emitting at 1047 nm and 1053 nm

NASA Astrophysics Data System (ADS)

Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Li, Yongfu; Zhang, Xingyu

2015-05-01

A flash-lamp pumped electro-optically Q-switched dual-wavelength Nd:YLF laser is demonstrated. Two Nd:YLF crystals placed in two cavities are employed to generate orthogonally polarized 1047 nm and 1053 nm radiations, respectively. The two cavities are jointed together by a polarizer and share the same electro-optical Q-switch. Two narrow-band pass filters are used to block unexpected oscillations at the hold-off state of the electro-optical Q-switch. In this case, electro-optical Q-switching is able to operate successfully. With pulse synchronization realized, the maximum output energy of 66.2 mJ and 83.9 mJ are obtained for 1047 nm and 1053 nm lasers, respectively. Correspondingly, the minimum pulse width is both 17 ns for 1047 nm and 1053 nm lasers. Sum frequency generation is realized. This demonstrates the potential of this laser in difference-frequency generations to obtain terahertz wave.

Ti:sapphire-pumped diamond Raman laser with sub-100-fs pulse duration.

PubMed

Murtagh, Michelle; Lin, Jipeng; Mildren, Richard P; Spence, David J

2014-05-15

We report a synchronously pumped femtosecond diamond Raman laser operating at 895 nm with a 33% slope efficiency. Pumped using a mode-locked Ti:sapphire laser at 800 nm with a duration of 170 fs, the bandwidth of the Stokes output is broadened and chirped to enable subsequent pulse compression to 95 fs using a prism pair. Modeling results indicate that self-phase modulation drives the broadening of the Stokes spectrum in this highly transient laser. Our results demonstrate the potential for Raman conversion to extend the wavelength coverage and pulse shorten Ti:sapphire lasers.

Extended-area nanostructuring of TiO2 with femtosecond laser pulses at 400 nm using a line focus.

PubMed

Das, Susanta Kumar; Dasari, Kiran; Rosenfeld, Arkadi; Grunwald, Ruediger

2010-04-16

An efficient way to generate nanoscale laser-induced periodic surface structures (LIPSS) in rutile-type TiO(2) with frequency-converted femtosecond laser pulses at wavelengths around 400 nm is reported. Extended-area structuring on fixed and moving substrates was obtained by exploiting the line focus of a cylindrical lens. Under defined conditions with respect to pulse number, pulse energy and scanning velocity, two types of ripple-like LIPSS with high and low spatial frequencies (HSFL, LSFL) with periods in the range of 90 nm and 340 nm, respectively, were formed. In particular, lower numbers of high energetic pulses favour the generation of LSFL whereas higher numbers of lower energetic pulses enable the preferential creation of HSFL. Theoretical calculations on the basis of the Drude model support the assumption that refractive index changes by photo-excited carriers are a major mechanism responsible for LSFL. Furthermore, the appearance of random substructures as small as 30 nm superimposing low spatial frequency ripples is demonstrated and their possible origin is discussed.

Picosecond laser with 11 W output power at 1342 nm based on composite multiple doping level Nd:YVO4 crystal

NASA Astrophysics Data System (ADS)

Rodin, Aleksej M.; Grishin, Mikhail; Michailovas, Andrejus

2016-01-01

We report results of design and optimization of high average output power picosecond and nanosecond laser operating at 1342 nm wavelength. Developed for selective micromachining, this DPSS laser is comprised of master oscillator, regenerative amplifier and output pulse control module. Passively mode-locked by means of semiconductor saturable absorber mirror and pumped with 808 nm wavelength Nd:YVO4 master oscillator emits 12.5 ps pulses at repetition rate of 55 MHz with average output power of ∼100 mW. The four-pass confocal delay line forms a longest part of the oscillator cavity in order to suppress thermo-mechanical misalignment. Picked from the train seed pulses were injected to the cavity of regenerative amplifier based on composite Nd:YVO4 crystal with diffusion-bonded segments of multiple Nd doping concentration end-pumped at 880 nm wavelength. Laser produces pulses of ∼13 ps duration at 300 kHz repetition rate with average output power of 11 W and nearly diffraction limited beam quality of M2∼1.03. Attained high peak power ∼2.8 MW facilitates conversion to the 2nd, 3rd and 6th harmonics at 671 nm, 447 nm and 224 nm wavelengths with 80%, 50% and 15% efficiency respectively. Without seeding the regenerative amplifier transforms to electro-optically cavity-dumped Q-switched laser providing 10 ns output pulses at high repetition rates with beam propagation factor of M2∼1.06.

Dye laser traveling wave amplifier

NASA Technical Reports Server (NTRS)

Davidson, F.; Hohman, J.

1985-01-01

Injection locking was applied to a cavity-dumped coaxial flashlamp pumped dye laser in an effort to obtain nanosecond duration pulses which have both high energy and narrow-linewidth. In the absence of an injected laser pulse, the cavity-dumped dye laser was capable of generating high energy (approx. 60mJ) nanosecond duration output pulses. These pulses, however, had a fixed center wavelength and were extremely broadband (approx. 6nm FWHM). Experimental investigations were performed to determine if the spectral properties of these outputs could be improved through the use of injection-locking techniques. A parametric study to determine the specific conditions under which the laser could be injection-locked was also carried out. Significant linewidth reduction to 0.0015nm) of the outputs was obtained through injection-locking but only at wavelengths near the peak lasing wavelength of the dye. It was found, however; that by inserting weakly dispersive tuning elements in the laser cavity, these narrow-linewidth outputs could be obtained over a wide (24nm) tuning range. Since the tuning elements had low insertion losses, the tunability of the output was obtained without sacrificing output pulse energy.

Single Frequency, Pulsed Laser Diode Transmitter for Dial Water Vapor Measurements at 935nm

NASA Technical Reports Server (NTRS)

Switzer, Gregg W.; Cornwell, Donald M., Jr.; Krainak, Michael A.; Abshire, James B.; Rall, Johnathan A. R.

1998-01-01

We report a tunable, single frequency, narrow linewidth, pulsed laser diode transmitter at 935.68nm for remote sensing of atmospheric water vapor. The transmitter consists of a CW, tunable, external cavity diode laser whose output is amplified 2OdB using a tapered diode amplifier. The output is pulsed for range resolved DIAL lidar by pulsing the drive current to the diode amplifier at 4kHz with a .5% duty cycle. The output from the transmitter is 36OnJ/pulse and is single spatial mode. It maintains a linewidth of less than 25MHz as its wavelength is tuned across the water vapor absorption line at 935.68nm. The transmitter design and its use in a water vapor measurement will be discussed.

Comparison of epidermal/dermal damage between the long-pulsed 1064 nm Nd:YAG and 755 nm alexandrite lasers under relatively high fluence conditions: quantitative and histological assessments.

PubMed

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon; Kim, Sung Min

2014-07-01

The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser.

Multispectral photoacoustic microscopy of lipids using a pulsed supercontinuum laser.

PubMed

Buma, Takashi; Conley, Nicole C; Choi, Sang Won

2018-01-01

We demonstrate optical resolution photoacoustic microscopy (OR-PAM) of lipid-rich tissue between 1050-1714 nm using a pulsed supercontinuum laser based on a large-mode-area photonic crystal fiber. OR-PAM experiments of lipid-rich samples show the expected optical absorption peaks near 1210 and 1720 nm. These results show that pulsed supercontinuum lasers are promising for OR-PAM applications such as label-free histology of lipid-rich tissue and imaging small animal models of disease.

Power and Efficiency Scaling of Fiber OPO Around 700 to 850 nm and Power-scaling of High Coherence Fiber Raman Amplifiers

DTIC Science & Technology

2013-10-01

sources and on a fiber OPO at red wavelengths. The fiber Raman laser reached 20 W of output power at 1019 nm, pulsed operation at 835 nm, and M2 = 2 at...1019 nm from a double-clad fiber Raman laser . These three results are all world records or world firsts. It was also found that the fiber OPO suffers...power multimode diode sources and on a fiber OPO at red wavelengths. With the fiber Raman laser we reach 20 W of output power at 1019 nm, pulsed

Tunable KTA Stokes laser based on stimulated polariton scattering and its intracavity frequency doubling.

PubMed

Zang, Jie; Cong, Zhenhua; Chen, Xiaohan; Zhang, Xingyu; Qin, Zengguang; Liu, Zhaojun; Lu, Jianren; Wu, Dong; Fu, Qiang; Jiang, Shiqi; Zhang, Shaojun

2016-04-04

This paper presents the tunable Stokes laser characteristics of KTiOAsO₄ (KTA) crystal based on stimulated polariton scattering (SPS). When the pumping laser wavelength is 1064.2 nm, the KTA Stokes wave can be discontinuously tuned from 1077.9 to 1088.4 nm with four gaps from 1079.0 to 1080.1 nm, from 1080.8 to 1082.8 nm, from 1083.6 to 1085.5 nm, and from 1085.8 to 1086.8 nm. When a frequency doubling crystal LiB₃O₅ (LBO) is inserted into the Stokes laser cavity, the frequency-doubled wave can be discontinuously tuned from 539.0 to 539.5 nm, from 540.1 to 540.4 nm, from 541.3 to 541.8 nm, from 542.7 to 542.9 nm and from 543.4 to 544.2 nm. With a pumping pulse energy of 130.0 mJ and an output coupler reflectivity of about 30%, the obtained maximum Stokes laser pulse energy at 1078.6 nm is 33.9 mJ and the obtained maximum frequency-doubled laser pulse energy at 543.8 nm is 15.7 mJ. By using the most probably coupled transverse optical modes obtained from the literature, the polariton refractive indexes, and the simplified polariton Sellmeier equations, the polariton dispersion curve is obtained. The formation of the Stokes frequency gaps is explained.

XUV generation from the interaction of pico- and nanosecond laser pulses with nanostructured targets

NASA Astrophysics Data System (ADS)

Barte, Ellie Floyd; Lokasani, Ragava; Proska, Jan; Stolcova, Lucie; Maguire, Oisin; Kos, Domagoj; Sheridan, Paul; O'Reilly, Fergal; Sokell, Emma; McCormack, Tom; O'Sullivan, Gerry; Dunne, Padraig; Limpouch, Jiri

2017-05-01

Laser-produced plasmas are intense sources of XUV radiation that can be suitable for different applications such as extreme ultraviolet lithography, beyond extreme ultraviolet lithography and water window imaging. In particular, much work has focused on the use of tin plasmas for extreme ultraviolet lithography at 13.5 nm. We have investigated the spectral behavior of the laser produced plasmas formed on closely packed polystyrene microspheres and porous alumina targets covered by a thin tin layer in the spectral region from 2.5 to 16 nm. Nd:YAG lasers delivering pulses of 170 ps (Ekspla SL312P )and 7 ns (Continuum Surelite) duration were focused onto the nanostructured targets coated with tin. The intensity dependence of the recorded spectra was studied; the conversion efficiency (CE) of laser energy into the emission in the 13.5 nm spectral region was estimated. We have observed an increase in CE using high intensity 170 ps Nd:YAG laser pulses as compared with a 7 ns pulse.

Laser-drilled micro-hole arrays on polyurethane synthetic leather for improvement of water vapor permeability

NASA Astrophysics Data System (ADS)

Wu, Y.; Wang, A. H.; Zheng, R. R.; Tang, H. Q.; Qi, X. Y.; Ye, B.

2014-06-01

Three kinds of lasers at 1064, 532 and 355 nm wavelengths respectively were adopted to construct micro-hole arrays on polyurethane (PU) synthetic leather with an aim to improve water vapor permeability (WVP) of PU synthetic leather. The morphology of the laser-drilled micro-holes was observed to optimize laser parameters. The WVP and slit tear resistance of the laser-drilled leather were measured. Results show that the optimized pulse energy for the 1064, 532 and 355 nm lasers are 0.8, 1.1 and 0.26 mJ, respectively. The diameters of the micro-holes drilled with the optimized laser pulse energy were about 20, 15 and 10 μm, respectively. The depths of the micro-holes drilled with the optimized pulse energy were about 21, 60 and 69 μm, respectively. Compared with the untreated samples, the highest WVP growth ratio was 38.4%, 46.8% and 53.5% achieved by the 1064, 532 and 355 nm lasers, respectively. And the highest decreasing ratio of slit tear resistance was 11.1%, 14.8%, and 22.5% treated by the 1064, 532 and 355 nm lasers, respectively. Analysis of the interaction mechanism between laser beams at three kinds of laser wavelengths and the PU synthetic leather revealed that laser micro-drilling at 355 nm wavelength displayed both photochemical ablation and photothermal ablation, while laser micro-drilling at 1064 and 532 nm wavelengths leaded to photothermal ablation only.

Optical field ionization of atoms and ions using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fittinghoff, D. N.

1993-12-01

This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He(+2), Ne(+2), and Ar(+2). The ion yields for He(+1), Ne(sup +1) and Ar(sup +1) agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved the following: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

[Quantitative analysis of Cu in water by collinear DP-LIBS].

PubMed

Zheng, Mei-Lan; Yao, Ming-Yin; Chen, Tian-Bing; Lin, Yong-Zeng; Li, Wen-Bing; Liu, Mu-Hua

2014-07-01

The purpose of this research is to study the influence of double pulse laser induced breakdown spectroscopy (DP-LIBS) on the sensitivity of Cu in water. The water solution of Cu was tested by collinear DP-LIBS in this article. The results show that spectral intensity of Cu can be enhanced obviously by DP-LIBS, compared with single pulse laser induced breakdown spectroscopy (SP-LIBS). Besides, the experimental results were significantly impacted by delay time between laser pulse and spectrometer acquisition, delay time of double laser pulse and energy of laser pulse and so on. The paper determined the best conditions for DP-LIBS detecting Cu in water. The optimal acquisition delay time was 1 380 ns. The best laser pulse delay time was 25 ns. The most appropriate energy of double laser pulse was 100 mJ. Characteristic analysis of spectra of Cu at 324.7 and 327.4 nm was done for quantitative analysis. The detection limit was 3.5 microg x mL(-1) at 324.7 nm, and the detection limit was 4.84 microg x mL(-1) at 327.4 nm. The relative standard deviation of the two characteristic spectral lines was within 10%. The calibration curve of characteristic spectral line, established by 327.4 nm, was verified with 500 microg x mL(-1) sample. Concentration of the sample was 446 microg x mL(-1) calculated by the calibration curve. This research shows that the detection sensitivity of Cu in water can be improved by DP-LIBS. At the same time, it had high stability.

300-MHz-repetition-rate, all-fiber, femtosecond laser mode-locked by planar lightwave circuit-based saturable absorber.

PubMed

Kim, Chur; Kim, Dohyun; Cheong, YeonJoon; Kwon, Dohyeon; Choi, Sun Young; Jeong, Hwanseong; Cha, Sang Jun; Lee, Jeong-Woo; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jungwon

2015-10-05

We show the implementation of fiber-pigtailed, evanescent-field-interacting, single-walled carbon nanotube (CNT)-based saturable absorbers (SAs) using standard planar lightwave circuit (PLC) fabrication processes. The implemented PLC-CNT-SA device is employed to realize self-starting, high-repetition-rate, all-fiber ring oscillators at telecommunication wavelength. We demonstrate all-fiber Er ring lasers operating at 303-MHz (soliton regime) and 274-MHz (stretched-pulse regime) repetition-rates. The 303-MHz (274-MHz) laser centered at 1555 nm (1550 nm) provides 7.5 nm (19 nm) spectral bandwidth. After extra-cavity amplilfication, the amplified pulse train of the 303-MHz (274-MHz) laser delivers 209 fs (178 fs) pulses. To our knowledge, this corresponds to the highest repetition-rates achieved for femtosecond lasers employing evanescent-field-interacting SAs. The demonstrated SA fabrication method, which is based on well-established PLC processes, also shows a potential way for mass-producible and lower-cost waveguide-type SA devices suitable for all-fiber and waveguide lasers.

Tm:GdVO4 microchip laser Q-switched by a Sb2Te3 topological insulator

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Bogusławski, Jakub; Serres, Josep Maria; Kifle, Esrom; Kowalczyk, Maciej; Mateos, Xavier; Sotor, Jarosław; Zybała, Rafał; Mars, Krzysztof; Mikuła, Andrzej; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin

2018-02-01

We report on the first application of a topological insulator based on antimony telluride (Sb2Te3) as a saturable absorber (SA) in a bulk microchip laser. The transmission-type SA consisted of a thin film of Sb2Te3 (thickness: 3 nm) deposited on a glass substrate by pulsed magnetron sputtering. The saturable absorption of the Sb2Te3 film was confirmed for ns-long pulses. The microchip laser was based on a Tm:GdVO4 crystal diode-pumped at 802 nm. In the continuous-wave regime, this laser generated 3.54 W at 1905-1921 nm with a slope efficiency η of 37%. The Q-switched laser generated a maximum average output power of 0.70 W at 1913 nm. The pulse energy and duration were 3.5 μJ and 223 ns, respectively, at a repetition rate of 200 kHz. The Sb2Te3 SAs are promising for passively Q-switched waveguide lasers at 2 μm.

Laser lithotripsy of gallstones: alexandrite and rhodamine-6G versus coumarin dye laser: fragmentation and fiber burn-off in vitro

NASA Astrophysics Data System (ADS)

Hochberger, Juergen; Bredt, Marion; Mueller, Gudrun; Hahn, Eckhart G.; Ell, Christian

1993-05-01

In the following study three different pulsed laser lithotripsy systems were compared for the fine fragmentation of identical sets of natural and synthetic gallstones `in vitro.' Using a pulsed coumarin dye laser (504 nm), a pulsed rhodamine 6G dye laser (595 nm), and a pulsed Alexandrite laser (755 nm) a total of 184 concrements of known chemical composition, size, and weight were disintegrated to a fragment size of

Tailoring Ion Charge State Distribution in Tetramethyltin Clusters under Influence of Moderate Intensity Picosecond Laser Pulse: Role of Laser Wavelength and Rate of Energy Deposition

NASA Astrophysics Data System (ADS)

Sharma, Pramod; Das, Soumitra; Vatsa, Rajesh K.

2017-07-01

Systematic manipulation of ionic-outcome in laser-cluster interaction process has been realized for studies carried out on tetramethyltin (TMT) clusters under picosecond laser conditions, determined by choice of laser wavelength and intensity. As a function of laser intensity, TMT clusters exhibit gradual enhancement in overall ionization of its cluster constituents, up to a saturation level of ionization, which was distinct for different wavelengths (266, 355, and 532 nm). Simultaneously, systematic appearance of higher multiply charged atomic ions and shift in relative abundance of multiply charged atomic ions towards higher charge state was observed, using time-of-flight mass spectrometer. At saturation level, multiply charged atomic ions up to (C2+, Sn2+) at 266 nm, (C4+, Sn4+) at 355 nm, and (C4+, Sn6+) at 532 nm were detected. In addition, at 355 nm intra-cluster ion chemistry within the ionized cluster leads to generation of molecular hydrogen ion (H2 +) and triatomic molecular hydrogen ion (H3 +). Generation of multiply charged atomic ions is ascribed to efficient coupling of laser pulse with the cluster media, facilitated by inner-ionized electrons produced within the cluster, at the leading edge of laser pulse. Role of inner-ionized electrons is authenticated by measuring kinetic energy distribution of electrons liberated upon disintegration of excessively ionized cluster, under the influence of picosecond laser pulse.

Combined pulsed dye laser and fiberoptic Nd-YAG laser for the treatment of hypertrophic port wine stain.

PubMed

Radmanesh, Mohammed; Radmanesh, Ramin

2017-10-01

The hypertrophic Port Wine Stain (PWS) is only partially and superficially treated with the Pulsed dye laser (PDL) because of its limited depth of penetration. We used combined PDL and fiberoptic 1444-nm Nd-YAG laser to treat a case with hypertrophic PWS. After tumescent anesthesia, few holes were made by a 16-gauge needle on different sides of the lesion. The fiberoptic tip of 1444-nm Nd-YAG laser was inserted within the holes and was pushed forward while triggering. In a fan pattern and by a back and forth movement, the subcutaneous and deep dermal areas were coagulated. The skin and outer mucosal surfaces were then treated by PDL. The fiberoptic system used was Accusculpt 1444-nm Nd-YAG laser (Lutronic lasers, South Korea), and the PDL used was 585 nm Nlite system (Chromogenex UK). The parameters used for PDL were fluence = 9 Joules/cm 2 and the spot size was 5 mm. The parameters used for fiberoptic 1444-nm Nd-YAG laser were: Pulse rate = 30 Hz, pulse energy = 300 mJ, power = 6 W, and the total energy = 4000 J for the whole face and mucosa. Little sign of regression and moderate purpura were detected immediately after combined fiberoptic Nd-YAG and PDL therapy. The lesion gradually regressed within 4 months with satisfactory color and volume change. Combined fiberoptic Nd-YAG laser and PDL can be used for the treatment of deeper and superficial layers of hypertrophic PWS.

The effects of 595- and 1,064-nm lasers on rooster comb blood vessels using dual-wavelength and multipulse techniques.

PubMed

Li, Guang; Sun, Jianfang; Shao, Xuebao; Sang, Honggui; Zhou, Zhanchao

2011-10-01

After laser irradiation, hemoglobin can transform into methemoglobin and coagulum, which have high absorptivity of near-infrared light. Sequential irradiation with 595 nm and 1,064 nm may be more effective than single wavelength to decrease residual vessel number in rooster combs. Six protocols (single pulse with 595 nm, double pulse with 595 nm, single pulse with 1,064 nm, double pulse with 1,064 nm, sequential irradiation with 595 nm and 1,064 nm (multiplex), and a blank control group) were used to compare the effects of sequential and single-wavelength irradiation on reducing residual vessel number, as well as the epidermal side effects, in the rooster comb. Different treatment techniques were applied to the same comb, at the same time. The treated areas of the epidermis and the residual vessels were observed using an optical microscope. All five techniques were effective in decreasing the number of residual vessels in the comb, and the side effects on the epidermis were similar for all. Considering the selectivity of the 595-nm laser and the rich melanin in the human epidermis, the dual-wavelength laser has a distinct advantage in treating vascular lesions. The authors have indicated no significant interest with commercial supporters. © 2011 by the American Society for Dermatologic Surgery, Inc.

Pulsed multiwavelength laser ranging system. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Abshire, J. B.

1982-01-01

A pulsed multiwavelength laser ranging system for measuring atmospheric delay was built and tested, and its theoretical performance limits were calculated. The system uses a dye modelocked ND:YAG laser, which transmits 70 psec wide pulses simultaneously at 1064, 532, and 355 nm. The differential delay of the 1064 and 355 nm pulses is measured by a specially calibrated waveform digitizer to estimate the dry atmospheric delay. The delay time of the 532 nm pulse is used to measure the target distance. Static crossed field photomultipliers are used as detectors for all wavelengths. Theoretical analysis shows that path curvature and atmospheric turbulence are fundamental limits to the ranging accuracy of both single and multicolor systems operating over horizontal paths. For two color systems, an additional error is caused by the uncertainty in the path averaged water vapor. The standard deviation of the multicolor instrument's timing measurements is directly proportional to the laser pulse width plus photomultiplier jitter divided by the square root of the received photoelectron number. The prototype system's maximum range is km, which is limited by atmospheric and system transmission losses at 355 nm. System signal detection and false alarm calculations are also presented.

Highly stable self-pulsed operation of an Er:Lu2O3 ceramic laser at 2.7 µm

NASA Astrophysics Data System (ADS)

Wang, Li; Huang, Haitao; Shen, Deyuan; Zhang, Jian; Chen, Hao; Tang, Dingyuan

2017-04-01

We report on the highly stable self-pulsed operation of a 2.74 µm Er:Lu2O3 ceramic laser pumped by a wavelength locked narrow bandwidth 976 nm laser diode. The operating pulse repetition rate is continuously tunable from 126 kHz to 270 kHz depending on the pump power level. For 12.3 W of absorbed diode pump power, the Er:Lu2O3 ceramic laser generates 820 mW of average output power at a 270 kHz repetition rate and with a pulse duration of 183 ns. The corresponding pulse-to-pulse amplitude fluctuation is estimated to be less than 0.7%. In the continues-wave (CW) mode of operation, the laser yields over 1.3 W of output power with a slope efficiency of 11.9% with respect to the 976 nm pump power.

Compact high-power optical source for resonant infrared pulsed laser ablation and deposition of polymer materials

NASA Astrophysics Data System (ADS)

Kolev, V. Z.; Duering, M. W.; Luther-Davies, B.; Rode, A. V.

2006-12-01

We propose a novel tuneable table-top optical source as an alternative to the free electron laser currently used for resonant infrared pulsed laser deposition of polymers. It is based on two-stage pulsed optical parametric amplification using MgO doped periodically poled lithium niobate crystals. Gain in excess of 106 in the first stage and pump depletion of 58% in the second stage were achieved when the system was pumped by a high-power Nd:YVO4 picosecond laser source at 1064 nm and seeded by a CW tuneable diode laser at 1530 nm. An average power of 2 W was generated at 3.5 µm corresponding to 1.3 µJ pulse energy.

Two-photon photoemission from a copper cathode in an Χ-band photoinjector

DOE PAGES

Li, H.; Limborg-Deprey, C.; Adolphsen, C.; ...

2016-02-24

This study presents two-photon photoemission from a copper cathode in an X-band photoinjector. We experimentally verified that the electron bunch charge from photoemission out of a copper cathode scales with laser intensity (I) square for 400 nm wavelength photons. We compare this two-photon photoemission process with the single photon process at 266 nm. Despite the high reflectivity (R) of the copper surface for 400 nm photons (R=0.48) and higher thermal energy of photoelectrons (two-photon at 200 nm) compared to 266 nm photoelectrons, the quantum efficiency of the two-photon photoemission process (400 nm) exceeds the single-photon process (266 nm) when themore » incident laser intensity is above 300 GW/cm 2. At the same laser pulse energy (E) and other experimental conditions, emitted charge scales inversely with the laser pulse duration. A thermal emittance of 2.7 mm-mrad per mm root mean square (rms) was measured on our cathode which exceeds by sixty percent larger compared to the theoretical predictions, but this discrepancy is similar to previous experimental thermal emittance on copper cathodes with 266 nm photons. The damage of the cathode surface of our first-generation X-band gun from both rf breakdowns and laser impacts mostly explains this result. Using a 400 nm laser can substantially simplify the photoinjector system, and make it an alternative solution for compact pulsed electron sources.« less

Laser Applications in Microelectronic and Optoelectronic Manufacturing IV

DTIC Science & Technology

1999-07-15

laser irradiation of the clusters with 6000 laser pulses of X...insulating ma- terials during and after irradiation by tunable, ultrashort pulses from a mid-infrared laser . The three salient examples we con- sider...with ultrashort pulses re- sembles the rear-side ablation seen in irradiation of calcite by Nd:YAG lasers (1064 nm), while the off-resonance FEL

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, Kwang S.

1986-10-01

An intense and efficient source for blue green laser useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, the hypocycloidal pinch plasma (HCP), and the dense plasma focus (DPF) can produce intense uv photons (200 to 400nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400nm). As a result of optimization of the DPF light at 355nm, the blue green dye (LD490) laser output exceeding 4mJ was obtained at the best cavity tunning of the laser system. With the HCP pumped system a significant enhancement of the blue green laser outputs with dye LD490 and coumarin 503 has been achieved through the spectrum conversion of the pumping light by mixing a converter dye BBQ. The maximum increase of laser output with the dye mixture of LD490+BBQ and coumarin 503+BBQ was greater than 80%. In addition, the untunned near UV lasers were also obtained. The near UV laser output energy of P-terphenyl dye was 0.5mJ at lambda sub C=337nm with the bandwidth of 3n m for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2microsec.

Differential Gene Expression in Explanted Human Retinal Pigment Epithelial Cells 24-Hours Post-Exposure to 532 nm, 3.0 ns Pulsed Laser Light and 1064 nm, 170 ps Pulsed Laser Light 12-Hours Post-Exposure: Results Compendium

DTIC Science & Technology

2004-06-01

Additionally, we offer 3 conceptual cartoons outlining our vision for the future progres of laser bioeffects research, metabonomic risk assessment...future progress of laser bioeffects research, metabonomic risk assessment modeling and knowledge building from laser bioeffects data. BACKGROUND In the...our concepts of future laser bioeffects research directions (Figure 5), a metabonomic risk assessment model of laser tissue interaction (Figure 6

Passive mode locking of a Tm,Ho:KY(WO4)2 laser around 2 microm.

PubMed

Lagatsky, A A; Fusari, F; Calvez, S; Gupta, J A; Kisel, V E; Kuleshov, N V; Brown, C T A; Dawson, M D; Sibbett, W

2009-09-01

We report the first demonstration, to our knowledge, of passive mode locking in a Tm(3+), Ho(3+)-codoped KY(WO(4))(2) laser operating in the 2000-2060 nm spectral region. An InGaAsSb-based quantum well semiconductor saturable absorber mirror is used for the initiation and stabilization of the ultrashort pulse generation. Pulses as short as 3.3 ps were generated at 2057 nm with average output powers up to 315 mW at a pulse repetition frequency of 132 MHz for 1.15 W of absorbed pump power at 802 nm from a Ti:sapphire laser.

Simulation of laser-tattoo pigment interaction in a tissue-mimicking phantom using Q-switched and long-pulsed lasers.

PubMed

Ahn, K J; Kim, B J; Cho, S B

2017-08-01

Laser therapy is the treatment of choice in tattoo removal. However, the precise mechanisms of laser-tattoo pigment interactions remain to be evaluated. We evaluated the geometric patterns of laser-tattoo pigment particle interactions using a tattoo pigment-embedded tissue-mimicking (TM) phantom. A Q-switched (QS) neodymium-doped yttrium aluminum garnet laser was used at settings of 532-, 660-, and 1064-nm wavelengths, single-pulse and quick pulse-to-pulse treatment modes, and spot sizes of 4 and 7 mm. Most of the laser-tattoo interactions in the experimental conditions formed cocoon-shaped or oval photothermal and photoacoustic injury zones, which contained fragmented tattoo particles in various sizes depending on the conditions. In addition, a long-pulsed 755-nm alexandrite laser was used at a spot size of 6 mm and pulse widths of 3, 5, and 10 ms. The finer granular pattern of tattoo destruction was observed in TM phantoms treated with 3- and 5-ms pulse durations compared to those treated with a 10-ms pulse. We outlined various patterns of laser-tattoo pigment interactions in a tattoo-embedded TM phantom to predict macroscopic tattoo and surrounding tissue reactions after laser treatment for tattoo removal. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Design of micro-second pulsed laser mode for ophthalmological CW self-raman laser

NASA Astrophysics Data System (ADS)

Mota, Alessandro D.; Rossi, Giuliano; Ortega, Tiago A.; Costal, Glauco Z.; Fontes, Yuri C.; Yasuoka, Fatima M. M.; Stefani, Mario A.; de Castro N., Jarbas C.; Paiva, Maria S. V.

2011-02-01

This work presents the mechanisms adopted for the design of micro-second pulsed laser mode for a CW Self-Raman laser cavity in 586nm and 4W output power. The new technique for retina disease treatment discharges laser pulses on the retina tissue, in laser sequences of 200 μs pulse duration at each 2ms. This operation mode requires the laser to discharge fast electric pulses, making the system control velocity of the electronic system cavity vital. The control procedures to keep the laser output power stable and the laser head behavior in micro-second pulse mode are presented.

High-efficiency generation of pulsed Lyman-α radiation by resonant laser wave mixing in low pressure Kr-Ar mixture.

PubMed

Saito, Norihito; Oishi, Yu; Miyazaki, Koji; Okamura, Kotaro; Nakamura, Jumpei; Louchev, Oleg A; Iwasaki, Masahiko; Wada, Satoshi

2016-04-04

We report an experimental generation of ns pulsed 121.568 nm Lyman-α radiation by the resonant nonlinear four-wave mixing of 212.556 nm and 845.015 nm radiation pulses providing a high conversion efficiency 1.7x10^-3 with the output pulse energy 3.6 μJ achieved using a low pressure Kr-Ar mixture. Theoretical analysis shows that this efficiency is achieved due to the advantage of using (i) the high input laser intensities in combination with (ii) the low gas pressure allowing us to avoid the onset of full-scale discharge in the laser focus. In particular, under our experimental conditions the main mechanism of photoionization caused by the resonant 2-photon 212.556 nm radiation excitation of Kr atoms followed by the 1-photon ionization leads to ≈17% loss of Kr atoms and efficiency loss only by the end of the pulse. The energy of free electrons, generated by 212.556 nm radiation via (2 + 1)-photon ionization and accelerated mainly by 845.015 nm radiation, remains during the pulse below the level sufficient for the onset of full-scale discharge by the electron avalanche. Our analysis also suggests that ≈30-fold increase of 845.015 nm pulse energy can allow one to scale up the L-α radiation pulse energy towards the level of ≈100 μJ.

Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source

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

Gibson, D J; Barty, C J; Betts, S M

2005-04-21

The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3-5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 {micro}J, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, anmore » optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a pump beam in pump-probe diffraction experiments using the ultrashort tunable x-rays generated as the probe.« less

Investigation of a Pulsed 1550 nm Fiber Laser System

DTIC Science & Technology

2015-12-15

SPONSOR/MONITOR’S ACRONYM(S) Air Force Research Laboratory AFRL /RDLT 3550 Aberdeen Ave SE Kirtland AFB, NM 87117-5776 11. SPONSOR/MONITOR’S REPORT...6218 1 cy AFRL /RVIL Kirtland AFB, NM 87117-5776 1 cy Leanne Henry Official Record Copy AFRL /RDLT 1 cy ... AFRL -RD-PS- TP-2016-0006 AFRL -RD-PS- TP-2016-0006 INVESTIGATION OF A PULSED 1550 NM FIBER LASER SYSTEM Leanne Henry, et al. 15 December 2015

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

Razhev, A M; Kargapol'tsev, E S; Churkin, D S

Results of an experimental study of the influence of a gas mixture (laser active medium) composition on an output energy and total efficiency of gas-discharge excimer lasers on ArF* (193 nm), KrCl* (222 nm), KrF* (248 nm) and XeCl* (308 nm) molecules operating without a buffer gas are presented. The optimal ratios of gas components (from the viewpoint of a maximum output energy) of an active medium are found, which provide an efficient operation of laser sources. It is experimentally confirmed that for gas-discharge excimer lasers on halogenides of inert gases the presence of a buffer gas in an activemore » medium is not a necessary condition for efficient operation. For the first time, in two-component gas mixtures of repetitively pulsed gas-discharge excimer lasers on electron transitions of excimer molecules ArF*, KrCl*, KrF* and XeCl*, the pulsed energy of laser radiation obtained under pumping by a transverse volume electric discharge in a low-pressure gas mixture without a buffer gas reached up to 170 mJ and a high pulsed output power (of up to 24 MW) was obtained at a FWHM duration of the KrF-laser pulse of 7 ns. The maximal total efficiency obtained in the experiment with two-component gas mixtures of KrF and XeCl lasers was 0.8%. (lasers)« less

High-power pulsed and CW diode-pumped mode-locked Nd:YAG lasers

NASA Technical Reports Server (NTRS)

Marshall, Larry R.; Hays, A. D.; Kaz, Alex; Kasinski, Jeff; Burnham, R. L.

1991-01-01

The operation of both pulsed and CW diode-pumped mode-locked Nd:YAG lasers are presented. The pulsed laser produced 1.0 mJ with pulsewidths of 90 psec at 20 Hz. The CW pumped laser produced 6 W output at 1.064 microns and 3 W output at 532 nm.

Subnanosecond Tm:KLuW microchip laser Q-switched by a Cr:ZnS saturable absorber.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Yumashev, Konstantin; Yasukevich, Anatoly; Petrov, Valentin; Griebner, Uwe; Aguiló, Magdalena; Díaz, Francesc

2015-11-15

Passive Q-switching of a compact Tm:KLu(WO(4))(2) microchip laser diode pumped at 805 nm is demonstrated with a polycrystalline Cr(2+):ZnS saturable absorber. This laser generates subnanosecond (780 ps) pulses with a pulse repetition frequency of 5.6 kHz at 1846.6 nm, the shortest pulse duration ever achieved by Q-switching of ~2 μm lasers. The maximum average output power is 146 mW with a slope efficiency of 21% with respect to the absorbed power. This corresponds to a pulse energy of 25.6 μJ and a peak power of 32.8 kW.

Wavelength dependence on the forensic analysis of glass by nanosecond 266 nm and 1064 nm laser induced breakdown spectroscopy

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

Cahoon, Erica M.; Almirall, Jose R.

Laser induced breakdown spectroscopy can be used for the chemical characterization of glass to provide evidence of an association between a fragment found at a crime scene to a source of glass of known origin. Two different laser irradiances, 266 nm and 1064 nm, were used to conduct qualitative and quantitative analysis of glass standards. Single-pulse and double-pulse configurations and lens-to-sample-distance settings were optimized to yield the best laser-glass coupling. Laser energy and acquisition timing delays were also optimized to result in the highest signal-to-noise ratio corresponding to the highest precision and accuracy. The crater morphology was examined and themore » mass removed was calculated for both the 266 nm and 1064 nm irradiations. The analytical figures of merit suggest that the 266 nm and 1064 nm wavelengths are capable of good performance for the forensic chemical characterization of glass. The results presented here suggest that the 266 nm laser produces a better laser-glass matrix coupling, resulting in a better stoichiometric representation of the glass sample. The 266 nm irradiance is therefore recommended for the forensic analysis and comparison of glass samples.« less

Surface microstructure and chemistry of polyimide by single pulse ablation of picosecond laser

NASA Astrophysics Data System (ADS)

Du, Qifeng; Chen, Ting; Liu, Jianguo; Zeng, Xiaoyan

2018-03-01

Polyimide (PI) surface was ablated by the single pulse of picosecond laser, and the effects of laser wavelength (λ= 355 nm and 1064 nm) and fluence on surface microstructure and chemistry were explored. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the concave of concentric ring and the convex of porous circular disk, were generated by 355 nm and 1064 nm picosecond laser ablation, respectively. X-ray photoelectron spectroscopy (XPS) characterization indicated that due to the high peak energy density of picosecond laser, oxygen and nitrogen from the ambient were incorporated into the PI surface mainly in the form of Cdbnd O and Csbnd Nsbnd C groups. Thus, both of the O/C and N/C atomic content ratios increased, but the increase caused by 1064 nm wavelength laser was larger. It inferred that the differences of PI surface microstructures and chemistry resulted from different laser parameters were related to different laser-matter interaction effects. For 355 nm picosecond laser, no obvious thermal features were observed and the probable ablation process of PI was mainly governed by photochemical effect; while for 1064 nm picosecond laser, obvious thermal feature appeared and photothermal effect was thought to be dominant.

Comparison of Epidermal/Dermal Damage Between the Long-Pulsed 1064 nm Nd:YAG and 755 nm Alexandrite Lasers Under Relatively High Fluence Conditions: Quantitative and Histological Assessments

PubMed Central

Lee, Ju Hwan; Park, So Ra; Jo, Jeong Ho; Park, Sung Yun; Seo, Young Kwon

2014-01-01

Abstract Objective: The purpose of this study was to compare degrees of epidermal/dermal tissue damage quantitatively and histologically after laser irradiation, to find ideal treatment conditions with relatively high fluence for skin rejuvenation. Background data: A number of recent studies have evaluated the clinical efficacy and safety of therapeutic lasers under relatively low fluence conditions. Methods: We transmitted the long-pulsed 1064 nm Nd:YAG and 755 nm Alexandrite lasers into pig skin according to different fluences and spot diameters, and estimated epidermal/dermal temperatures. Pig skin specimens were stained with hematoxylin and eosin for histological assessments. The fluence conditions comprised 26, 30, and 36 J/cm2, and the spot diameter conditions were 5, 8, and 10 mm. Pulse duration was 30 ms for all experiments. Results: Both lasers produced reliable thermal damage on the dermis without any serious epidermal injuries, under relatively high fluence conditions. The 1064 nm laser provided more active fibrous formations than the 755 nm laser, while higher risks for tissue damages simultaneously occurred. Conclusions: The ideal treatment conditions for skin rejuvenation were 8 mm diameter with 30 J/cm2 and 10 mm diameter with 26 J/cm2 for the 1064 nm laser, and 8 mm diameter with 36 J/cm2 and 10 mm diameter with 26 J/cm2 for the 755 nm laser. PMID:24992273

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.

Silver-free solar cell interconnection by laser spot welding of thin aluminum layers: analysis of process limits for ns- and μs-lasers

NASA Astrophysics Data System (ADS)

Schulte-Huxel, H.; Blankemeyer, S.; Kajari-Schröder, S.; Brendel, R.

2014-03-01

We investigate a laser welding process for contacting aluminum metallized crystalline silicon solar cells to a 10-μm-thick aluminum layers on a glass substrate. The reduction of the solar cell metallization thickness is analyzed with respect to laser induced damage using SiNx passivated silicon wafers. Additionally, we measure the mechanical stress of the laser welds by perpendicular tear-off as well as the electrical contact resistance. We apply two types of laser processes; one uses one to eight 20-ns-laser pulses at 355 nm with fluences between 12 and 40 J/cm2 and the other single 1.2-μs-laser pulses at 1064 nm with 33 to 73 J/cm2. Ns laser pulses can contact down to 1-μm-thick aluminum layers on silicon without inducing laser damage to the silicon and lead to sufficient strong mechanical contact. In case of μs laser pulses the limiting thickness is 2 μm.

Efficient extreme ultraviolet plasma source generated by a CO2 laser and a liquid xenon microjet target

NASA Astrophysics Data System (ADS)

Ueno, Yoshifumi; Ariga, Tatsuya; Soumagne, George; Higashiguchi, Takeshi; Kubodera, Shoichi; Pogorelsky, Igor; Pavlishin, Igor; Stolyarov, Daniil; Babzien, Marcus; Kusche, Karl; Yakimenko, Vitaly

2007-05-01

We demonstrated efficacy of a CO2-laser-produced xenon plasma in the extreme ultraviolet (EUV) spectral region at 13.5nm at variable laser pulse widths between 200ps and 25ns. The plasma target was a 30μm liquid xenon microjet. To ensure the optimum coupling of CO2 laser energy with the plasma, they applied a prepulse yttrium aluminum garnet laser. The authors measured the conversion efficiency (CE) of the 13.5nm EUV emission for different pulse widths of the CO2 laser. A maximum CE of 0.6% was obtained for a CO2 laser pulse width of 25ns at an intensity of 5×1010W/cm2.

2-μm Cr2+: CdSe passively Q-switched laser

NASA Astrophysics Data System (ADS)

Ji, E. C.; Liu, Q.; Yao, Y.; Lu, S.; Lue, Q. T.

2018-02-01

We demonstrate the bleaching characteristics of Cr2+: CdSe (Cr: CdSe) crystal around 2 μm and prove that Cr: CdSe crystal is an effective saturable absorber to obtain Q-switched pulsed output in Tm3+-doped fiber laser pumped Ho: YAG system. The saturable absorption property of Cr: CdSe is investigated with a pulsed source at 2090 nm. The laserinduced damage threshold of uncoated Cr: CdSe is estimated around 9.92 J/cm2 at 2090 nm with the pulse duration of 30 ns. With the measured bleaching curve, the estimated pulse saturation fluence is around 1.06 J/cm2, and the estimated ground-state absorption cross section is 8.97×10-20 cm2, which is very close to the experimental value. The preliminary laser experiments are all finished with an antireflection coated Cr: CdSe crystal to reduce the insertion loss. The maximum output pulse energy is about 1.8 mJ with repetition frequency of 685 Hz, pulse duration of 15.4 ns, and pulse peak power of 115 kW. The pulsed laser wavelength is measured to be 2090.2 nm.

Improving the efficiency of x-ray lasers

NASA Astrophysics Data System (ADS)

Tallents, Gregory J.; Zeitoun, Philippe; Behjat, A.; Demir, A.; Holden, M.; Krishnan, J.; Lewis, Ciaran L. S.; MacPhee, Andrew G.; Warwick, P. J.; Nantel, Marc; Jamelot, Gerard; Rus, Bedrich; Jaegle, Pierre; Klisnick, Annie; Goedtkindt, P.; Carillon, Antoine; Fill, Ernst E.; Li, Yuelin; Pretzler, Georg; Schloegl, Dieter; Steingruber, Juergen; Neely, David; Norreys, Peter A.; Key, Michael H.; Zhang, Jie; Pert, Geoffrey J.; Healy, S. B.; Plowes, J. A.

1995-09-01

Current successful approaches for achieving soft x-ray lasing typically require pumping laser pulses of duration approximately ns and energy approximately kJ (collisionally pumped schemes) or approximately ps pulses and powers of approximately several TW (recombination-pumped schemes). For applications, it is important to improve the efficiency of soft x-ray lasers and so reduce the required power of pumping lasers. The effect of pre- pulse on neon-like collisionally pumped lasers has been investigated using the LULI laser (Ecole Polytechnique, France). A small pre-pulse level approximately 10-3 of the main pulse energy was found to increase the J equals 0 minus 1 neon-like zinc laser output at 21 nm by an order-of-magnitude with a comparable increase in efficiency. A double pumping laser pulse on neon-like yttrium lasing output at 15 nm obtained with the VULCAN laser (Rutherford Appleton Laboratory, England) was also found to increase the x-ray lasing efficiency. With adiabatically cooled recombination lasing, it is shown that approximately 2 ps pulses are optimum for achieving the desired ionization balance for lasing output. The possibility of achieving recombination lasing at short wavelengths on lithium-like ions with longer pulse lasers has been investigated using the ASTERIX laser (Max-Planck Quantenoptik, Germany). These results are presented and interpreted to provide possible directions for improving the efficiency of x-ray lasers.

Diamond Raman laser emitting at 1194, 1419, and 597 nm

NASA Astrophysics Data System (ADS)

Pashinin, V. P.; Ralchenko, V. G.; Bolshakov, A. P.; Ashkinazi, E. E.; Konov, V. I.

2018-03-01

A Raman laser based on a synthetic diamond crystal pumped by nanosecond pulses of a 1030-nm Yb : YAG laser and emitting in the IR region at the first and second Stokes wavelengths of 1194 and 1419 nm, respectively, was developed. The conversion efficiency was 34% with a slope efficiency of 50% and an average power of 1.1 W at a wavelength of 1194 nm; the average power at 1419 nm was 0.52 W. Frequency doubling of the first Stokes component in a nonlinear BBO crystal resulted in orange (597.3 nm) radiation with a pulse energy of 0.15 mJ, an average power of 0.22 W, and a maximum efficiency of 20%.

All-fiber tunable laser based on an acousto-optic tunable filter and a tapered fiber.

PubMed

Huang, Ligang; Song, Xiaobo; Chang, Pengfa; Peng, Weihua; Zhang, Wending; Gao, Feng; Bo, Fang; Zhang, Guoquan; Xu, Jingjun

2016-04-04

An all-fiber tunable laser was fabricated based on an acousto-optic tunable filter and a tapered fiber. The structure was of a high signal-to-noise ratio, therefore, no extra gain flattening was needed in the laser. In the experiment, the wavelength of the laser could be tuned from 1532.1 nm to 1570.4 nm with a 3-dB bandwidth of about 0.2 nm. Given enough nonlinearity in the laser cavity, it could also generate a sliding-frequency pulse train. The laser gains advantages of fast tuning and agility in pulse generation, and its simple structure is low cost for practical applications.

Development of lasers optimized for pumping Ti:Al2O3 lasers

NASA Technical Reports Server (NTRS)

Rines, Glen A.; Schwarz, Richard A.

1994-01-01

Laboratory demonstrations that were completed included: (1) an all-solid-state, broadly tunable, single-frequency, Ti:Al2O3 master oscillator, and (2) a technique for obtaining 'long' (nominally 100- to 200-ns FWHM) laser pulses from a Q-switched, Nd oscillator at energy levels commensurate with straightforward amplification to the joule level. A diode-laser-pumped, Nd:YLF laser with intracavity SHG was designed, constructed, and evaluated. With this laser greater than 0.9 W of CW, output power at 523.5 nm with 10 W of diode-laser pump power delivered to the Nd:YLF crystal was obtained. With this laser as a pump source, for the first time, to our knowledge, an all solid-state, single frequency, Ti:Al203 laser with sufficient output power to injection seed a high-energy oscillator over a 20-nm bandwidth was demonstrated. The pulsed laser work succeeded in demonstrating pulse-stretching in a Q-switched Nd:YAG oscillator. Pulse energies greater than 50-mJ were obtained in pulses with 100- to 200-ns pulsewidths (FWHM).

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

DOE PAGES

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.; ...

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

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

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M.

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution ofmore » the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.« less

Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition.

PubMed

Dumitrache, Ciprian; VanOsdol, Rachel; Limbach, Christopher M; Yalin, Azer P

2017-08-31

The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We perform a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution of the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.

Passively mode-locked pulse generation in a c-cut Nd:LuVO4 laser at 1086 nm with a semiconductor saturable-absorber mirror

NASA Astrophysics Data System (ADS)

Lin, Ja-Hon; Yang, Pao-Keng; Lin, Wei-Cheng

2012-04-01

We demonstrate a diode-pumped passively mode-locked (ML) c-cut Nd:LuVO4 laser with central wavelength at 1086 nm by shifting the reflectance band of the SESAM into a longer wavelength to result in larger loss around 1068 nm. At 15 W absorbed pump power, the highest output power of the ML pulse was about 2.6 W that corresponded to the 17.3% optical-to-optical conversion efficiency and the slope efficiency of laser was about 22.9%. Using our ML laser as the light source, we have also successfully measured the saturation fluence of the SESAM at 1086 nm.

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

NASA Astrophysics Data System (ADS)

Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

2004-07-01

Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.

Comparative study of dual-pulsed 1064 nm Q-switched Nd:YAG laser and single-pulsed 1064 nm Q-switched Nd:YAG laser by using zebrafish model and prospective split-face analysis of facial melasma.

PubMed

Jang, Hee Won; Chun, Seung Hyun; Park, Hae Chul; Ryu, Hwa Jung; Kim, Il-Hwan

2017-04-01

Recently dual-pulsed low-fluence 1064-nm Q-switched Nd:YAG (QSNY) laser has been developed for reducing complication during melasma treatment. Comparison of the efficacy and safety between dual-pulsed mode and single-pulsed mode for the treatment of melasma. In preclinical study, adult zebrafish were irradiated with dual-pulsed and single-pulsed mode. Changes of melanophore and cell death were assessed. In split-face clinical study, dual-pulsed and single-pulsed mode were irradiated on the left and right side of the face, respectively. L* value, clinical digital photos, modified Melasma Area and Severity Index (MASI) scores, and side effects were measured. As compared to single-pulsed mode and dual-pulsed mode with longer intervals, zebrafish melanophore was cleared quickly at dual-pulsed mode with 80-μsec interval and 0.3 J/cm 2 fluence. Dual-pulsed mode showed the least regeneration of melanophore at 4 weeks after irradiation and no cell death was observed with 80-μsec interval. Both pulse modes improved melasma significantly but modified MASI score and L* value were not significantly different between each other. Lesser pain and shorter duration of post-laser erythema were observed with dual-pulsed mode. Dual-pulsed mode was as effective as single-pulsed mode for the treatment of melasma and revealed less side effects.

Waveform agile high-power fiber laser illuminators for directed-energy weapon systems

NASA Astrophysics Data System (ADS)

Engin, Doruk; Lu, Wei; Kimpel, Frank; Gupta, Shantanu

2012-06-01

A kW-class fiber-amplifier based laser illuminator system at 1030nm is demonstrated. At 125 kHz pulse repetition rate, 1.9mJ energy per pulse (235W average power) is achieved for 100nsec pulses with >72% optical conversion efficiency, and at 250kHz repetition, >350W average power is demonstrated, limited by the available pumps. Excellent agreement is established between the experimental results and dynamic fiber amplifier simulation, for predicting the pulse shape, spectrum and ASE accumulation throughout the fiber-amplifier chain. High pulse-energy, high power fiber-amplifier operation requires careful engineering - minimize ASE content throughout the pre-amplifier stages, use of large mode area gain fiber in the final power stage for effective pulse energy extraction, and pulse pre-shaping to compensate for the laser gain-saturation induced intra-pulse and pulse-pattern dependent distortion. Such optimization using commercially available (VLMA) fibers with core size in the 30-40μm range is estimated to lead to >4mJ pulse energy for 100nsec pulse at 50kHz repetition rate. Such waveform agile high-power, high-energy pulsed fiber laser illuminators at λ=1030nm satisfies requirements for active-tracking/ranging in high-energy laser (HEL) weapon systems, and in uplink laser beacon for deep space communication.

PCF based high power narrow line width pulsed fiber laser

NASA Astrophysics Data System (ADS)

Chen, H.; Yan, P.; Xiao, Q.; Wang, Y.; Gong, M.

2012-09-01

Based on semiconductor diode seeded multi-stage cascaded fiber amplifiers, we have obtained 88-W average power of a 1063-nm laser with high repetition rate of up to 1.5 MHz and a constant 2-ns pulse duration. No stimulated Brillouin scattering pulse or optical damage occurred although the maximum pulse peak power has exceeded 112 kW. The output laser exhibits excellent beam quality (M2x = 1.24 and M2y = 1.18), associated with a spectral line width as narrow as 0.065 nm (FWHM). Additionally, we demonstrate high polarization extinction ratio of 18.4 dB and good pulse stabilities superior to 1.6 % (RMS).

Determination of pulse energy dependence for skin denaturation from 585nm fibre laser

NASA Astrophysics Data System (ADS)

Mujica-Ascencio, S.; Velazquez-Gonzalez, J. S.; Mujica-Ascencio, C.; Alvarez-Chavez, J. A.

2014-05-01

In this paper, simulation and mathematical analysis for the determination of pulse energy from a Q-switched Yb3+-doped fibre laser is required in Port Wine Stain (PWS) treatment. The pulse energy depends on average power, gain, volume, repetition rate and pulse duration. In some treatments such as Selective Photothermolysis (SP), the peak power at the end of the optical fibre and pulse duration can be obtained and modified via a cavity design. For that purpose, a 585nm optical fibre laser full design which considers all of the above besides the average losses through the optical devices proposed for the design and the Ytterbium optical fibre overall gain will be presented.

Cavitation bubble dynamics during thulium fiber laser lithotripsy

NASA Astrophysics Data System (ADS)

Hardy, Luke A.; Kennedy, Joshua D.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

2016-02-01

The Thulium fiber laser (TFL) is being explored for lithotripsy. TFL parameters differ from standard Holmium:YAG laser in several ways, including smaller fiber delivery, more strongly absorbed wavelength, low pulse energy/high pulse rate operation, and more uniform temporal pulse structure. High speed imaging of cavitation bubbles was performed at 105,000 fps and 10 μm spatial resolution to determine influence of these laser parameters on bubble formation. TFL was operated at 1908 nm with pulse energies of 5-75 mJ, and pulse durations of 200-1000 μs, delivered through 100-μm-core fiber. Cavitation bubble dynamics using Holmium laser at 2100 nm with pulse energies of 200-1000 mJ and pulse duration of 350 μs was studied, for comparison. A single, 500 μs TFL pulse produced a bubble stream extending 1090 +/- 110 μm from fiber tip, and maximum bubble diameters averaged 590 +/- 20 μm (n=4). These observations are consistent with previous studies which reported TFL ablation stallout at working distances < 1.0 mm. TFL bubble dimensions were five times smaller than for Holmium laser due to lower pulse energy, higher water absorption coefficient, and smaller fiber diameter used.

Tunable all-fiber dissipative-soliton laser with a multimode interference filter.

PubMed

Zhang, Lei; Hu, Jinmeng; Wang, Jianhua; Feng, Yan

2012-09-15

We report on a tunable all-fiber dissipative-soliton laser with a multimode interference filter that consists of a multimode fiber spliced between two single-mode fibers. By carefully selecting the fiber parameters, a filter with a central wavelength at 1032 nm and a bandwidth of 7.6 nm is constructed and used for spectral filtering in an all-normal-dispersion mode-locked ytterbium-doped fiber laser based on nonlinear polarization evolution. The laser delivers 31 mW of average output power with positively chirped 7 ps pulses. The repetition rate of the pulses is 15.3 MHz, and pulse energy is 2.1 nJ. Tunable dissipative-soliton over 12 nm is achieved by applying tension to the single-mode-multimode-single-mode filter.

All-fiber pulse shortening of passively Q-switched microchip laser pulses down to sub-200 fs.

PubMed

Lehneis, R; Steinmetz, A; Limpert, J; Tünnermann, A

2014-10-15

We present an all-fiber concept that generates ultrashort pulses using a passively Q-switched microchip seed laser. A proof-of-principle configuration combines nonlinear pulse compression applying a chirped fiber-Bragg-grating, dispersion-free pulse shortening by means of a fiber-integrated spectral filtering, and a final hollow-core-fiber compression to reach the sub-200-fs pulse-duration region. In a compact all-fiber pulse-shortening unit, initial 100 ps long microchip pulses at 1064 nm wavelength have been shortened to 174 fs and shifted to 1034 nm while preserving a high temporal quality.

Nano- and micro-structuring of fused silica using time-delay adjustable double flash ns-laser radiation

NASA Astrophysics Data System (ADS)

Lorenz, Pierre; Zhao, Xiongtao; Ehrhardt, Martin; Zagoranskiy, Igor; Zimmer, Klaus; Han, Bing

2018-02-01

Large area, high speed, nanopatterning of surfaces by laser ablation is challenging due to the required high accuracy of the optical and mechanical systems fulfilling the precision of nanopatterning process. Utilization of self-organization approaches can provide an alternative decoupling spot precision and field of machining. The laser-induced front side etching (LIFE) and laser-induced back side dry etching (LIBDE) of fused silica were studied using single and double flash nanosecond laser pulses with a wavelength of 532 nm where the time delay Δτ of the double flash laser pulses was adjusted from 50 ns to 10 μs. The fused silica can be etched at both processes assisted by a 10 nm chromium layer where the etching depth Δz at single flash laser pulses is linear to the laser fluence and independent on the number of laser pulses, from 2 to 12 J/cm2, it is Δz = δLIFE/LIBDE . Φ with δLIFE 16 nm/(J/cm2) and δLIBDE 5.2 nm/(J/cm2) 3 . δLIFE. At double flash laser pulses, the Δz is dependent on the time delay Δτ of the laser pulses and the Δz slightly increased at decreasing Δτ. Furthermore, the surface nanostructuring of fused silica using IPSM-LIFE (LIFE using in-situ pre-structured metal layer) method with a single double flash laser pulse was tested. The first pulse of the double flash results in a melting of the metal layer. The surface tension of the liquid metal layer tends in a droplet formation process and dewetting process, respectively. If the liquid phase life time ΔtLF is smaller than the droplet formation time the metal can be "frozen" in an intermediated state like metal bare structures. The second laser treatment results in a evaporation of the metal and in a partial evaporation and melting of the fused silica surface, where the resultant structures in the fused silica surface are dependent on the lateral geometry of the pre-structured metal layer. A successful IPSM-LIFE structuring could be achieved assisted by a 20 nm molybdenum layer at Δτ >= 174 ns. That path the way for the high speed ultra-fast nanostructuring of dielectric surfaces by self-organizing processes. The different surface structures were analyzed by scanning electron microscopy (SEM) and white light interferometry (WLI).

Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

DOE PAGES

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; ...

2014-11-05

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less

Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

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

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less

Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery in vivo

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

Hutson, M. Shane; Ma Xiaoyan

We compare the plasma and cavitation dynamics underlying pulsed laser microsurgery in water and in fruit fly embryos (in vivo)--specifically for nanosecond pulses at 355 and 532 nm. We find two key differences. First, the plasma-formation thresholds are lower in vivo --especially at 355 nm--due to the presence of endogenous chromophores that serve as additional sources for plasma seed electrons. Second, the biological matrix constrains the growth of laser-induced cavitation bubbles. Both effects reduce the disrupted region in vivo when compared to extrapolations from measurements in water.

Orthogonal control of the frequency comb dynamics of a mode-locked laser diode.

PubMed

Holman, Kevin W; Jones, David J; Ye, Jun; Ippen, Erich P

2003-12-01

We have performed detailed studies on the dynamics of a frequency comb produced by a mode-locked laser diode (MLLD). Orthogonal control of the pulse repetition rate and the pulse-to-pulse carrier-envelope phase slippage is achieved by appropriate combinations of the respective error signals to actuate the diode injection current and the saturable absorber bias voltage. Phase coherence is established between the MLLD at 1550 nm and a 775-nm mode-locked Ti:sapphire laser working as part of an optical atomic clock.

Two-photon fluorescence bioimaging with an all-semiconductor laser picosecond pulse source.

PubMed

Kuramoto, Masaru; Kitajima, Nobuyoshi; Guo, Hengchang; Furushima, Yuji; Ikeda, Masao; Yokoyama, Hiroyuki

2007-09-15

We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.

Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

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

Danilov, P A; Zayarnyi, D A; Ionin, A A

The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fieldsmore » and their applications)« less

Visible lesion thresholds and model predictions for Q-switched 1318-nm and 1540-nm laser exposures to porcine skin

NASA Astrophysics Data System (ADS)

Zohner, Justin J.; Schuster, Kurt J.; Chavey, Lucas J.; Stolarski, David J.; Kumru, Semih S.; Rockwell, Benjamin A.; Thomas, Robert J.; Cain, Clarence P.

2006-02-01

Skin damage thresholds were measured and compared with theoretical predictions using a skin thermal model for near-IR laser pulses at 1318 nm and 1540 nm. For the 1318-nm data, a Q-switched, 50-ns pulse with a spot size of 5 mm was applied to porcine skin and the damage thresholds were determined at 1 hour and 24 hours postexposure using Probit analysis. The same analysis was conducted for a Q-switched, 30-ns pulse at 1540 nm with a spot size of 5 mm. The Yucatan mini-pig was used as the skin model for human skin due to its similarity to pigmented human skin. The ED 50 for these skin exposures at 24 hours postexposure was 10.5 J/cm2 for the 1318-nm exposures, and 6.1 J/cm2 for the 1540-nm exposures. These results were compared to thermal model predictions. We show that the thermal model fails to account for the ED 50 values observed. A brief discussion of the possible causes of this discrepancy is presented. These thresholds are also compared with previously published skin minimum visible lesion (MVL) thresholds and with the ANSI Standard's MPE for 1318-nm lasers at 50 ns and 1540-nm lasers at 30 ns.

Enhanced laser conditioning using temporally shaped pulses

DOE PAGES

Kafka, K. R. P.; Papernov, S.; Demos, S. G.

2018-03-06

Laser conditioning was investigated as a function of the temporal shape and duration of 351-nm, nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. Here, the aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.

Enhanced laser conditioning using temporally shaped pulses.

PubMed

Kafka, K R P; Papernov, S; Demos, S G

2018-03-15

Laser conditioning was investigated as a function of the temporal shape and duration of 351 nm nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. The aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.

Enhanced laser conditioning using temporally shaped pulses

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

Kafka, K. R. P.; Papernov, S.; Demos, S. G.

Laser conditioning was investigated as a function of the temporal shape and duration of 351-nm, nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. Here, the aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.

Porcine dermal lesions produced by 1540-nm laser radiation pulses

NASA Astrophysics Data System (ADS)

Roach, William P.; Johnson, Thomas E.

2001-07-01

Completion of recent studies within our group indicates a breed-based difference in dermal response to 1540 nm 0.8 millisecond laser pulses. Laser exposure to Yucatan Mini- Pigs (highly pigmented skin) and Yorkshire pigs (lightly pigmented skin) demonstrate statistical differences between the ED50's of the two breeds. Laser delivery is accomplished using an Er:Glass system producing 1540 nm of light at millisecond exposure times and in the range of 5 to 95 J/cm2. Dermal lesion development was evaluated for acute, 1 hour, and 24-hour post exposure presentation. Our data contradicts the theory that water absorption is the sole mechanism of dermal tissue damage observed from 1540 nm laser exposures, as skin chromophores appear to play a role in lesion development.

Pulse Width Dependence Of Pigment Cell Damage At 694 nm In Guinea Pig Skin

NASA Astrophysics Data System (ADS)

Dover, Jeffrey S.; Polla, Luigi L.; Margolis, Randall J.; Whitaker, Diana; Watanabe, Schinichi; Murphy, George F.; Parrish, John A.; Anderson, R. R.

1987-03-01

351 nm, 20-nsec XeF excimer laser irradiation has previously been shown to selectively target and damage melanosomes in human skin. In the following studies selective targeting with melanosomal photodisruption has been demonstrated in pigmented guinea pig skin with a Q-switched 40-nsec ruby laser, and a 750-nsec pulsed dye laser but not with a 400-usec pulsed dye laser. The pulse width dependence of melanosomal disruption, occurring only at pulsewidths shorter than the thermal relaxation time of the melanosome (0.5 - 1.0 usec), is in accordance with the theory of selective photothermolysis. Possible mechanisms of melanosomal photodisruption include development of sudden thermal gradients leading to cavitation or shock wave production.

Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

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

Liu, Chunyang, E-mail: chunyangliu@126.com; Sui, Xin; Yang, Fang

2014-03-15

A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of themore » microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.« less

Bright broadband coherent fiber sources emitting strongly blue-shifted resonant dispersive wave pulses

PubMed Central

Tu, Haohua; Lægsgaard, Jesper; Zhang, Rui; Tong, Shi; Liu, Yuan; Boppart, Stephen A.

2013-01-01

We predict and realize the targeted wavelength conversion from the 1550-nm band of a fs Er:fiber laser to an isolated band inside 370-850 nm, corresponding to a blue-shift of 700-1180 nm. The conversion utilizes resonant dispersive wave generation in widely available optical fibers with good efficiency (~7%). The converted band has a large pulse energy (~1 nJ), high spectral brightness (~1 mW/nm), and broad Gaussian-like spectrum compressible to clean transform-limited ~17 fs pulses. The corresponding coherent fiber sources open up portable applications of optical parametric oscillators and dual-output synchronized ultrafast lasers. PMID:24104233

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

NASA Astrophysics Data System (ADS)

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

2017-09-01

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

Continuous-wave and actively Q-switched resonantly dual-end-pumped Er : YAG ceramic laser emitting at 1.6 μm

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

Dai, T Y; Deng, Yu; Ju, Y-L

2015-12-31

We demonstrate a continuous-wave (cw) and actively Q-switched Er : YAG ceramic laser resonantly dual-end-pumped by a 1532 nm fibre-coupled laser diode. A maximum cw output power of 1.48 W at 1645.3 nm is obtained at an absorbed pump power of 12.72 W, corresponding to a slope efficiency of 19.2%. In the Q-switched regime the maximum pulse energy of 0.84 mJ is reached at a pulse repetition rate of 100 Hz, pulse duration of 48.03 ns and absorbed pump power of 10.51 W. (lasers)

Laser annealing and in situ absorption measurement of float glass implanted with Ag ions

NASA Astrophysics Data System (ADS)

Okur, I.; Townsend, P. D.

2004-08-01

In this paper in situ pulsed laser annealing and absorption measurements results of Ag-implanted float glass are reported. A Nd:YAG laser harmonic at 266 nm was used to anneal the target area by coupling energy to the glass host, whilst an argon laser at 488 nm was used as a probe beam of changes in nanoparticle size. The equilibrium conditions show a third order power dependence on the laser pulse energy, which is attributed to the volume in which ion migration can occur during excitation.

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials

NASA Astrophysics Data System (ADS)

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R.; Hao, Xiaotao; Chen, Feng

2017-04-01

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS2) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO2 as low-cost saturable absorber for subnanosecond laser generation.

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials.

PubMed

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R; Hao, Xiaotao; Chen, Feng

2017-04-06

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO 4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO 2 ). The unique feature of VO 2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO 4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO 2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS 2 ) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO 2 as low-cost saturable absorber for subnanosecond laser generation.

Efficient laser emission from cladding waveguide inscribed in Nd:GdVO(4) crystal by direct femtosecond laser writing.

PubMed

Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

2014-08-01

We report on the fabrication of depressed cladding waveguides in Nd:GdVO(4) laser crystal by using femtosecond laser inscription. The cross section of the structure is a circular shape with a diameter of 150 μm. Under the optical pump at 808 nm, the continuous wave (cw) as well as pulsed (Q-switched by graphene saturable absorber) waveguide lasing at 1064 nm has been realized, supporting guidance of both TE and TM polarizations. The maximum output power of 0.57 W was obtained in the cw regime, while the maximum pulse energy of the pulsed laser emissions was up to 19 nJ (corresponding to a maximum average output power of 0.33 W, at a resonant frequency of 18 MHz). The slope efficiencies achieved for the cw and pulsed Nd:GdVO(4) waveguide lasers were as high as 68% and 52%, respectively.

Dynamics of femtosecond laser-induced periodic surface structures on silicon by high spatial and temporal resolution imaging

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

Jia, X., E-mail: jiaxin@sdju.edu.cn; Department of Mathematics and Physics, Shanghai Dianji University, Shanghai 201306; Jia, T. Q., E-mail: tqjia@phy.ecnu.edu.cn

2014-04-14

The formation dynamics of periodic ripples induced by femtosecond laser pulses (pulse duration τ = 50 fs and central wavelength λ = 800 nm) are studied by a collinear pump-probe imaging technique with a temporal resolution of 1 ps and a spatial resolution of 440 nm. The ripples with periods close to the laser wavelength begin to appear upon irradiation of two pump pulses at surface defects produced by the prior one. The rudiments of periodic ripples emerge in the initial tens of picoseconds after fs laser irradiation, and the ripple positions keep unmoved until the formation processes complete mainly in a temporal span of 1500 ps. Themore » results suggest that the periodic deposition of laser energy during the interaction between femtosecond laser pulses and sample surface plays a dominant role in the formation of periodic ripples.« less

Nearly penalty-free, less than 4 ps supercontinuum Gbit/s pulse generation over 1535-1560 nm

NASA Astrophysics Data System (ADS)

Morioka, T.; Kawanishi, S.; Mori, K.; Saruwatari, M.

1994-05-01

Nearly penalty-free less than 4ps supercontinuum WDM pulses are generated at 6.3 Gbit/s over 1535-1560 nm for the first time using a 200 nm superbroadened supercontinuum in an optical fibre pumped by 1.7 W, 3.3 ps, 1542 nm short pulses from an Er(3+)-doped fibre ring laser.

Two-Color Laser High-Harmonic Generation in Cavitated Plasma Wakefields

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

Schroeder, Carl; Benedetti, Carlo; Esarey, Eric

2016-10-03

A method is proposed for producing coherent x-rays via high-harmonic generation using a laser interacting with highly-stripped ions in cavitated plasma wakefields. Two laser pulses of different colors are employed: a long-wavelength pulse for cavitation and a short-wavelength pulse for harmonic generation. This method enables efficient laser harmonic generation in the sub-nm wavelength regime.

Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate

DOE PAGES

Begishev, I. A.; Bromage, J.; Yang, S. T.; ...

2018-05-16

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Furthermore, energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.

Record fifth-harmonic-generation efficiency producing 211  nm, joule-level pulses using cesium lithium borate

DOE PAGES

Begishev, I. A.; Bromage, J.; Yang, S. T.; ...

2018-01-01

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.

Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate

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

Begishev, I. A.; Bromage, J.; Yang, S. T.

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Furthermore, energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.

Generation of UV light by intense ultrashort laser pulses in air

NASA Astrophysics Data System (ADS)

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

2004-11-01

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

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

PubMed

Huang, Chunning; Deibele, Craig; Liu, Yun

2013-04-08

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

Self-phase modulation of submicrojoule femtosecond pulses in a hollow-core photonic-crystal fiber

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

Konorov, S.O.; Sidorov-Biryukov, D.A.; Zheltikov, A.M.

Hollow-core photonic-crystal fibers (PCFs) capable of transporting sub-100-fs pulses of Ti:sapphire laser radiation in one of their transmission peaks centered around 800 nm have been designed and demonstrated. These fibers are shown to enhance self-phase modulation of submicrojoule 100-fs Ti:sapphire laser pulses, allowing a spectral bandwidth of 35 nm to be achieved with an 8-cm PCF sample.

Generation of high-power subpicosecond pulses at 155 nm.

PubMed

Mossavi, K; Fricke, L; Liu, P; Wellegehausen, B

1995-06-15

Subpicosecond vacuum-ultraviolet radiation at 155 nm with pulse energies above 0.2 mJ has been obtained by near-resonant four-wave difference-frequency mixing in a Xe gas jet. Laser fields for the mixing process have been generated by a short-pulse KrF dye excimer laser system and a Raman converter. The process permits tuning in a broad vacuum-ultraviolet range and can be scaled up to higher output energies.

Diode end-pumped passively Q-switched Tm:YAP laser with 1.85-mJ pulse energy.

PubMed

Sebbag, Daniel; Korenfeld, Arik; Ben-Ami, Udi; Elooz, David; Shalom, Eran; Noach, Salman

2015-04-01

Passive Q switching of a Tm:YAP solid-state laser at 1935 nm with Cr:ZnSe and Cr:ZnS polycrystalline saturable absorbers is demonstrated for the first time, to the best of our knowledge. With Cr:ZnS, a maximum pulse energy of 1.85 mJ is obtained for a pulse duration of 35.8 ns, resulting in a peak power of 51.7 kW. With Cr:ZnSe, the achieved pulse energy of 1.55 mJ with a pulse duration of 42.2 ns leads to 36.7-kW peak power. These high pulse energies, together with the unique lasing wavelength at 1935 nm, make this laser a promising tool for biomedical and microsurgery applications.

Acousto-optic replication of ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Yushkov, Konstantin B.; Molchanov, Vladimir Ya.; Ovchinnikov, Andrey V.; Chefonov, Oleg V.

2017-10-01

Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pulses is generated from a single femtosecond laser pulse by means of applying a piecewise linear phase modulation over the whole emission spectrum. Analysis demonstrates that the main factor which limits maximum delay between the pulse replicas is spectral resolution of the acousto-optic dispersive delay line used for pulse shaping. In experiments with a Cr:forsterite laser system, we obtained delays from 0.3 to 3.5 ps between two replicas of 190 fs transform-limited pulses at the central wavelength of laser emission, 1230 nm.

Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation.

PubMed

Takeshita, Tatsuya; Hara, Michihiro

2018-03-15

Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υ t→c ) by 27%. It was concluded that the increase in Υ t→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S n ), which was reached by S 1 →S n transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools. Copyright © 2018 Elsevier B.V. All rights reserved.

Nearly fully compressed 1053 nm pulses directly obtained from 800 nm laser-seeded photonic crystal fiber below zero dispersion point

NASA Astrophysics Data System (ADS)

Refaeli, Zaharit; Shamir, Yariv; Ofir, Atara; Marcus, Gilad

2018-02-01

We report a simple robust and broadly spectral-adjustable source generating near fully compressed 1053 nm 62 fs pulses directly out of a highly-nonlinear photonic crystal fiber. A dispersion-nonlinearity balance of 800 nm Ti:Sa 20 fs pulses was obtained initially by negative pre-chirping and then launching the pulses into the fibers' normal dispersion regime. Following a self-phase modulation spectral broadening, some energy that leaked below the zero dispersion point formed a soliton whose central wavelength could be tuned by Self-Frequency-Raman-Shift effect. Contrary to a common approach of power, or, fiber-length control over the shift, here we continuously varied the state of polarization, exploiting the Raman and Kerr nonlinearities responsivity for state of polarization. We obtained soliton pulses with central wavelength tuned over 150 nm, spanning from well below 1000 to over 1150 nm, of which we could select stable pulses around the 1 μm vicinity. With linewidth of > 20 nm FWHM Gaussian-like temporal-shape pulses with 62 fs duration and near flat phase structure we confirmed high quality pulse source. We believe such scheme can be used for high energy or high power glass lasers systems, such as Nd or Yb ion-doped amplifiers and systems.

Femtosecond laser processing of NiPd single and 5x(Ni/Pd) multilayer thin films

NASA Astrophysics Data System (ADS)

Petrović, S.; Gaković, B.; Zamfirescu, M.; Radu, C.; Peruško, D.; Radak, B.; Ristoscu, C.; Zdravković, S.; Luculescu, C. L.; Mihailescu, I. N.

2017-09-01

Modification of single and complex nickel-palladium samples by laser processing in the femtosecond time domain was studied. The samples were processed by focused Ti:Sapphire laser beam (Clark CPA-2101) with 775 nm laser wavelength, 2 kHz repetition rate, 200 fs pulse duration. The laser-induced morphological modifications have shown dependence on the applied fluences and number of laser pulses. The formed surface nanostructures on the single NiPd/Si and multilayer 5x(Ni/Pd)/Si systems are compared with individual Ni and Pd thin films. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. At low number of pulses (less than 10 pulses) and low pulse energies range (not over 1.7 μJ), the two types of laser-induced periodic surface structure (LIPSS) can be observed: low and high spatial frequency LIPSS (HSFL and LSFL). For all samples, the measured LSFL periods were 720 nm for the ripples created solely on thin film surfaces during the single pulse action. In the case of the multi-pulse irradiation, the periodicities of created LSFLs on the all investigated thin films have shown tendency to reduction with increasing of pulse energies.

Synchronization of pairs of nanosecond pulses from a laser with two gain crystals pumped with two different sources.

PubMed

Staufert, Daniel; Cudney, Roger S

2018-05-10

We report a laser that emits two Q-switched pulses, one at 1.047 μm and the other at 1.064 μm, generated by a Nd:YLF and a Nd:YVO 4 , respectively. The crystals are pumped by two fiber-coupled diode lasers (808 nm and 880 nm); the delay between the pulses can be controlled by adjusting the power of the pumps. Two kinds of Q-switching techniques are reported, passive (Cr:YAG saturable absorber) and active (electro-optic modulator). We model both the active and passive Q switching and make a comparison between numerical simulations and experiments. We show experimentally and theoretically that in both cases the pulses can be synchronized; however, the stability of the synchronization (sensitivity to pump power fluctuations) is better for active than for passive Q switching. We also report that under certain experimental conditions a third wavelength is obtained, 1156 nm, which corresponds to the first Stokes shift of the 1047 nm pulse produced by stimulated Raman scattering from the Nd:YVO 4 crystal.

Divided-pulse nonlinear amplification and simultaneous compression

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

Hao, Qiang; Zhang, Qingshan; Sun, Tingting

2015-03-09

We report on a fiber laser system delivering 122 fs pulse duration and 600 mW average power at 1560 nm by the interplay between divided pulse amplification and nonlinear pulse compression. A small-core double-clad erbium-doped fiber with anomalous dispersion carries out the pulse amplification and simultaneously compresses the laser pulses such that a separate compressor is no longer necessary. A numeric simulation reveals the existence of an optimum fiber length for producing transform-limited pulses. Furthermore, frequency doubling to 780 nm with 240 mW average power and 98 fs pulse duration is achieved by using a periodically poled lithium niobate crystal at roommore » temperature.« less

Transcutaneous laser treatment of leg veins.

PubMed

Meesters, Arne A; Pitassi, Luiza H U; Campos, Valeria; Wolkerstorfer, Albert; Dierickx, Christine C

2014-03-01

Leg telangiectasias and reticular veins are a common complaint affecting more than 80% of the population to some extent. To date, the gold standard remains sclerotherapy for most patients. However, there may be some specific situations, where sclerotherapy is contraindicated such as needle phobia, allergy to certain sclerosing agents, and the presence of vessels smaller than the diameter of a 30-gauge needle (including telangiectatic matting). In these cases, transcutaneous laser therapy is a valuable alternative. Currently, different laser modalities have been proposed for the management of leg veins. The aim of this article is to present an overview of the basic principles of transcutaneous laser therapy of leg veins and to review the existing literature on this subject, including the most recent developments. The 532-nm potassium titanyl phosphate (KTP) laser, the 585-600-nm pulsed dye laser, the 755-nm alexandrite laser, various 800-983-nm diode lasers, and the 1,064-nm neodymium yttrium-aluminum-garnet (Nd:YAG) laser and various intense pulsed light sources have been investigated for this indication. The KTP and pulsed dye laser are an effective treatment option for small vessels (<1 mm). The side effect profile is usually favorable to that of longer wavelength modalities. For larger veins, the use of a longer wavelength is required. According to the scarce evidence available, the Nd:YAG laser produces better clinical results than the alexandrite and diode laser. Penetration depth is high, whereas absorption by melanin is low, making the Nd:YAG laser suitable for the treatment of larger and deeply located veins and for the treatment of patients with dark skin types. Clinical outcome of Nd:YAG laser therapy approximates that of sclerotherapy, although the latter is associated with less pain. New developments include (1) the use of a nonuniform pulse sequence or a dual-wavelength modality, inducing methemoglobin formation and enhancing the optical absorption properties of the target structure, (2) pulse stacking and multiple pass laser treatment, (3) combination of laser therapy with sclerotherapy or radiofrequency, and (4) indocyanin green enhanced laser therapy. Future studies will have to confirm the role of these developments in the treatment of leg veins. The literature still lacks double-blind controlled clinical trials comparing the different laser modalities with each other and with sclerotherapy. Such trials should be the focus of future research.

Effects of pulse durations and environments on femtosecond laser ablation of stainless steel

NASA Astrophysics Data System (ADS)

Xu, Shizhen; Ding, Renjie; Yao, Caizhen; Liu, Hao; Wan, Yi; Wang, Jingxuan; Ye, Yayun; Yuan, Xiaodong

2018-04-01

The influence of pulse durations (35fs and 260 fs) and environments (air and vacuum) on the laser-induced damage thresholds (LIDTs) and ablation rates of 304 stainless steel were studied. Two distinct ablation regimes were obtained from the ablation rate curves. At low fluence regime, the ablation rates were similar in spite of the differences of pulse durations and experiment environments. At high fluence regime, the ablation rates of 35 fs pulse duration in vacuum were obviously higher than others. The ablation craters showed smooth edges, moth-eye such as structures, and laser-induced periodic surface structures (LIPSSs). At a fixed fluence, the periods of LIPSSs decreased monotonously in their mean spatial period between 700 nm (5 pulses) and 540 nm (200 pulses) with the increase of pulse numbers in air with 35 fs pulse duration. The formation mechanisms of moth-eye like structures and LIPSSs were also discussed.

High-pulse energy supercontinuum laser for high-resolution spectroscopic photoacoustic imaging of lipids in the 1650-1850 nm region.

PubMed

Dasa, Manoj Kumar; Markos, Christos; Maria, Michael; Petersen, Christian R; Moselund, Peter M; Bang, Ole

2018-04-01

We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ~25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC source ever used in this wavelength range). We demonstrate how such an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm). We show the successful discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source for spectroscopic photoacoustic imaging.

On the physics of laser-induced selective photothermolysis of hair follicles: Influence of wavelength, pulse duration, and epidermal cooling.

PubMed

Svaasand, Lars O; Nelson, J Stuart

2004-01-01

The physical basis for optimization of wavelength, pulse duration, and cooling for laser-induced selective photothermolysis of hair follicles in human skin is discussed. The results indicate that the most important optimization parameter is the cooling efficiency of the technique utilized for epidermal protection. The optical penetration is approximately the same for lasers at 694, 755, and 800 nm. The penetration of radiation from Nd:yttrium-aluminum-garnet lasers at 1064 nm is, however, somewhat larger. Photothermal damage to the follicle is shown to be almost independent of laser pulse duration up to 100 ms. The results reveal that epidermal cooling by a 30-80-ms-long cryogen spurt immediately before laser exposure is the only efficient technique for laser pulse durations less than 10 ms. For longer pulse durations in the 30-100 ms range, protection can be done efficiently by skin cooling during laser exposure. For laser pulses of 100 ms, an extended precooling period, e.g., by bringing a cold object into good thermal contact with the skin for about 1 s, can be of value. Thermal quenching of laser induced epidermal temperature rise after pulsed exposure can most efficiently be done with a 20 ms cryogen spurt applied immediately after irradiation. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Bubble formation during pulsed laser ablation: mechanism and implications

NASA Astrophysics Data System (ADS)

van Leeuwen, Ton G. J. M.; Jansen, E. Duco; Motamedi, Massoud; Welch, Ashley J.; Borst, Cornelius

1993-07-01

Holmium ((lambda) equals 2.09 micrometers ) and excimer ((lambda) equals 308 nm) lasers are used for ablation of tissue. In a previous study it was demonstrated that both excimer and holmium laser pulses produce fast expanding and collapsing vapor bubbles. To investigate whether the excimer induced bubble is caused by vaporization of water, the threshold fluence for bubble formation at a bare fiber tip in water was compared between the excimer laser (pulse length 115 ns) and the Q-switched and free-running holmium lasers (pulse length 1 microsecond(s) to 250 microsecond(s) , respectively). To induce bubble formation by excimer laser light in water, the absorber oxybuprocaine-hydrochloride (OBP-HCl) was added to the water. Fast flash photography was used to measure the threshold fluence as a function of the water temperature (6 - 90 degree(s)C) at environmental pressure. The ultraviolet excimer laser light is strongly absorbed by blood. Therefore, to document the implications of bubble formation at fluences above the tissue ablation threshold, excimer laser pulses were delivered in vitro in hemoglobin solution and in vivo in the femoral artery of the rabbit. We conclude that the principal content of the fast bubble induced by a 308 nm excimer laser pulse is water vapor. Therefore, delivery of excimer laser pulses in a water or blood environment will cause fast expanding water vapor bubbles, which may induce mechanical damage to adjacent tissue.

The formation of periodic micro/nano structured on stainless steel by femtosecond laser irradiation

NASA Astrophysics Data System (ADS)

Yao, Caizhen; Gao, Wei; Ye, Yayun; Jiang, Yong; Xu, Shizhen; Yuan, Xiaodong

2017-07-01

Stainless steel surface was irradiated by linear polarized laser (800 nm, 35 fs, 4 Hz and 0.7 J/cm2) with different pulse numbers. Environmental scanning electron microscope (ESEM/EDS) was used for detailed morphology, microstructure and composition studies. The wettability of irradiated steel surface was tested by Interface Tensiometer JC-2000X and compared with untreated stainless steel. Results showed that micro/nanostripes with different periods were formed. The period increased with the increasing pulse numbers from 450 nm for 90 pulses to 500 nm for 180 pulses. The orientation of those stripes was parallel with the laser beam polarization. Nanoparticles were observed on those periodic structures. EDS indicated that the atomic ratio of Cr increased and the atomic ratios of Fe and Ni decreased after laser irradiation, which may enhance the corrosion resistance due to the Cr-rich layer. The prepared structure exhibited hydrophobic property without further treatment. The formation mechanism of micro/nanoperiodic structures was also explored.

Pulsed laser ablation of dental calculus in the near ultraviolet.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2014-02-01

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ≤8  J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5  J/cm2 but has not been observed above this fluence.

High single-spatial-mode pulsed power from 980 nm emitting diode lasers

NASA Astrophysics Data System (ADS)

Hempel, Martin; Tomm, Jens W.; Elsaesser, Thomas; Bettiati, Mauro

2012-11-01

Single-spatial-mode pulsed powers as high as 13 W and 20 W in 150 and 50 ns pulses, respectively, are reported for 980 nm emitting lasers. In terms of energy, single-spatial-mode values of up to 2 μJ within 150 ns pulses are shown. In this high-power pulsed operation, the devices shield themselves from facet degradation, being the main degradation source in continuous wave (cw) operation. Our results pave the way towards additional applications while employing available standard devices, which have originally been designed as very reliable cw fiber pumps.

Holmium:YAG (lambda=2120nm) vs. Thulium fiber (lambda=1908nm) laser for high-power vaporization of canine prostate tissue

NASA Astrophysics Data System (ADS)

Casperson, Andrew L.; Barton, Robert A.; Scott, Nicholas J.; Fried, Nathaniel M.

2008-02-01

Direct studies comparing different lasers for treatment of BPH are lacking. This preliminary study compares continuous-wave (CW) vs. pulsed prostate tissue vaporization for the Thulium fiber laser and Holmium:YAG laser, both operating near the 1940 nm water absorption peak in tissue. A 50-W Thulium fiber laser (λ= 1908 nm) delivered CW laser radiation through a 600-μm silica fiber in non-contact mode with a 5-mm-diameter spot at the tissue surface. A Holmium:YAG laser (λ= 2120 nm) operated with an energy of 2 J, pulse rate of 25 Hz, and average power of 50 W, and delivered pulsed laser radiation through a 600-μm silica fiber with a 5-mm-diameter laser spot to achieve similar irradiances at the tissue surface. Tissue vaporization was performed in air with the prostate kept hydrated in saline. Tissue vaporization efficiency of both lasers was compared (n = 10 canine prostates for each laser group). Mean vaporization efficiency measured 5.30 +/- 0.48 kJ/g vs. 4.13 +/- 0.46 kJ/g for Thulium fiber and Holmium lasers (P < 0.05). Tissue vaporization rates measured 0.57 +/- 0.05 g/min vs. 0.73 +/- 0.07 g/min (P < 0.05). The Holmium:YAG laser vaporizes prostate tissue at a higher rate than the Thulium fiber laser, for the same average power delivered to the tissue. Both the Thulium fiber laser and Holmium:YAG lasers are capable of vaporizing prostate tissue at a rate > 1 g/min if operated at the high powers (100-W) typically used in the clinic.

The Dual Wavelength UV Transmitter Development for Space Based Ozone DIAL Measurements

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.

2008-01-01

The objective of this research is to develop efficient 1-micron to UV wavelength conversion technology to generate tunable, single mode, pulsed UV wavelengths of 320 nm and 308 nm. The 532 nm wavelength radiation is generated by a 1064 nm Nd:YAG laser through second harmonic generation. The 532 nm pumps an optical parametric oscillator (OPO) to generate 803 nm. The 320 nm is generated by sum frequency generation (SFG) of 532 nm and 803 nm wavelengths The hardware consists of a conductively cooled, 1 J/pulse, single mode Nd:YAG pump laser coupled to an efficient RISTRA OPO and SFG assembly-Both intra and extra-cavity approaches are examined for efficiency.

Micro and Nano Laser Pulses for Melting and Surface Alloying of Aluminum with Copper

NASA Astrophysics Data System (ADS)

Hamoudi, Walid K.; Ismail, Raid A.; Sultan, Fatima I.; Jaleel, Summayah

2017-03-01

In the present work, the use of microsecond and nanosecond laser pulses to alloy copper in aluminum is presented. In the first run, high purity (99.999%) copper thin film was thermally evaporated over (99.9%) purity, 300 μm aluminum sheet. Thereafter, surface alloying was performed using (1-3) 500 μs, (0.1-1.5) Joule Nd: YAG laser pulses; operating at 1060 nm wavelength. Hard homogeneous alloyed zone was obtained at depths between 60 and 110 μm below the surface. In the second run, 9 ns laser pulses from Q-switched Nd: YAG laser operating at 1060 nm was employed to melt/alloy Al-Cu sheets. The resulted alloyed depth, after using 20 laser pulses, was 199.22 μm for Al over Cu samples and 419.61 μm for Cu over Al samples. X-ray diffraction and fluorescence analysis revealed the formation of Cu2Al2, CuAl2 and δ- Al4Cu9 phases with percentage depended on laser energy and copper layer thicknesses.

Sub-wavelength ripples in fused silica after irradiation of the solid/liquid interface with ultrashort laser pulses.

PubMed

Böhme, R; Vass, C; Hopp, B; Zimmer, K

2008-12-10

Laser-induced backside wet etching (LIBWE) is performed using ultrashort 248 nm laser pulses with a pulse duration of 600 fs to obtain sub-wavelength laser-induced periodic surface structures (LIPSS) on the back surface of fused silica which is in contact with a 0.5 mol l(-1) solution of pyrene in toluene. The LIPSS are strictly one-dimensional patterns, oriented parallel to the polarization of the laser radiation, and have a constant period of about 140 nm at all applied laser fluences (0.33-0.84 J cm(-2)) and pulse numbers (50-1000 pulses). The LIPSS amplitude varies due to the inhomogeneous fluence in the laser spot. The LIPSS are examined with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their power spectral density (PSD) distribution is analysed at a measured area of 10 µm × 10 µm. The good agreement of the measured and calculated LIPSS periods strongly supports a mechanism based on the interference of surface-scattered and incident waves.

Generation of 70 fs broadband pulses in a hybrid nonlinear amplification system with mode-locked Yb:YAG ceramic oscillator

NASA Astrophysics Data System (ADS)

Liu, Yang; Wang, Chao; Luo, Daping; Yang, Chao; Li, Jiang; Ge, Lin; Pan, Yubai; Li, Wenxue

2017-12-01

We demonstrate the passively mode-locked laser performances of bulk Yb:YAG ceramic prepared by non-aqueous tape casting, which generates initial pulses in temporal width of 3 ps and spectrum width of 3 nm without intra-cavity dispersion management. The ceramic laser is further used as seeding oscillator in a fiber nonlinear amplification system, where ultrashort pulses in maximum output power of ˜100 W and pulse duration of 70 fs are achieved. Moreover, the laser spectrum is broadened to be ˜41 nm due to self-phase modulation effects in the gain fiber, overcoming the narrow spectrum limitations of ceramic materials. Our approach opens a new avenue for power-scaling and spectrum-expanding of femtosecond ceramic lasers.

Broadly tunable femtosecond mode-locking in a Tm:KYW laser near 2 μm.

PubMed

Lagatsky, A A; Calvez, S; Gupta, J A; Kisel, V E; Kuleshov, N V; Brown, C T A; Dawson, M D; Sibbett, W

2011-05-09

Efficient mode-locking in a Tm:KY(WO(4))(2) laser is demonstrated by using InGaAsSb quantum-well SESAMs. Self-starting ultrashort pulse generation was realized in the 1979-2074 nm spectral region. Maximum average output power up to 411 mW was produced around 1986 nm with the corresponding pulse duration and repetition rate of 549 fs and 105 MHz respectively. Optimised pulse durations of 386 fs were produced with an average power of 235 mW at 2029 nm. © 2011 Optical Society of America

Kinetics of UV laser radiation defects in high performance glasses

NASA Astrophysics Data System (ADS)

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

2000-05-01

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

Tunable, stable source of femtosecond pulses near 2 μm via supercontinuum of an Erbium mode-locked laser.

PubMed

Klose, Andrew; Ycas, Gabriel; Maser, Daniel L; Diddams, Scott A

2014-11-17

A source of ultrashort pulses of light in the 2 μm region was constructed using supercontinuum broadening from an erbium mode-locked laser. The output spectrum spanned 1000 nm to 2200 nm with an average power of 250 mW. A pulse width of 39 fs for part of the spectrum in the 2000 nm region, corresponding to less than six optical cycles, was achieved. A heterodyne measurement of the free-running mode-locked laser with a narrow-linewidth continuous wave laser resulted in a near shot noise-limited beat note with a signal-to-noise ratio of 45 dB in a 10 kHz resolution bandwidth. The relative intensity noise of the broadband system was investigated over the entire supercontinuum, and the integrated relative intensity noise of the 2000 nm portion of the spectrum was 1.7 × 10(-3). The long-term stability of the system was characterized, and intensity fluctuations in the spectrum were found to be highly correlated throughout the supercontinuum. Spectroscopic limitations due to the laser noise characteristics are discussed.

Spectroscopy and laser action of the "red perylimide dye" in various solvents

NASA Astrophysics Data System (ADS)

Gvishi, R.; Reisfeld, R.; Burshtein, Z.

1993-10-01

Optical properties of the red perylimide laser dye in various solvents are studied. The absorption spectrum exhibits two main bands, in the ranges 480-600 and 400-460 nm, due to the S 0-S 1 and S 0-S 2 transition. The fluorescence spectrum is a mirror image of the S 0-S 1 absorption (shift of ˜ 30-50 nm). The Stokes shift increases with solvent polarity. Such dye-solvent interactions are compared to theoretical predictions. The fluorescence quantum yields approaches unity in all the solvents studied. Laser tunability around 30 nm was obtained each time, covering the spectral range 580-640 nm. This interval is important for medical applications in photodynamic therapy and fluorescence diagnostics. The laser threshold energy varied from 0.35 mJ/pulse in cyclohexane to 1.87 mJ/pulse in methanol, and the slope efficiency from about 6.6% in methanol to 14% in xylenes. The laser output was stable for several hours of operation under an average pump energy of about 20 mJ/pulse at 1 Hz repetition rate, without flow.

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

PubMed

Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

2013-01-01

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

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.

New 445 nm blue laser for laryngeal surgery combines photoangiolytic and cutting properties.

PubMed

Hess, Markus M; Fleischer, Susanne; Ernstberger, Marcel

2018-06-01

Photoangiolytic lasers have broadened the surgical armamentarium for many phonosurgical interventions. However, the pulse dye laser and potassium titanyl phosphate (KTP) laser have technical drawbacks and a smaller spectrum of indications. The new 445 nm wavelength laser, the so-called 'blue laser', proves to show tissue effects comparable to the KTP laser and is also capable of treating subepithelial vessels due to its photoangiolytic properties, it can coagulate and carbonize at higher energy levels, and can be used via glass fibers in non-contact and contact mode for in-office procedures. In contrast to the KTP, the new 445 nm laser can also be used as a cutting laser, thus combining very much wanted properties of diode or CO2 lasers with photoangiolytic lasers. Further advantages of the new laser are the; (1) portability of the shoe box sized, shock-proof laser machine for in-office and operating room usage, (2) the selection of pulse rates from continuous wave (cw) to less than a millisecond, (3) stronger tissue effects compared to KTP with similar energy and pulse settings, (4) far better cutting properties than the KTP, and thus (5) more possibilities for usage in laryngology as well as in other fields or surgery. We demonstrate the feasibility of the 445 nm laser in several laboratory experiments and show clinical cases where photoangiolysis and cutting was possible. However, this is a preliminary report and further systematic studies in greater numbers are warranted.

Stimulation of the cochlea using green laser light

NASA Astrophysics Data System (ADS)

Wenzel, G. I.; Balster, S.; Lim, H. H.; Zhang, K.; Reich, U.; Lubatschowski, H.; Ertmer, W.; Lenarz, T.; Reuter, G.

2009-02-01

The success of conventional hearing aids and electrical cochlear implants have generally been limited to hearing in quiet situations, in part due to a lack of localized (i.e., frequency specificity) sensorineural activation and subsequent impaired speech discrimination in noise. Laser light is a source of energy that can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. Compound action potentials have been elicited using 2.12 µm laser pulses through activation of auditory nerve fibers (Izzo et al. 2006). Laser stimulation (813 nm) of the cochlea has shown to induce basilar membrane motion and cochlear microphonic potentials (Fridberger et al. 2006). We sought to assess if visible light (green, 532 nm, 10 ns pulses) could be used to consistently activate the cochlea. The laser parameters were selected based on our initial attempt to induce an optoacoustic effect as the energy transfer mechanism to the cochlea. Click evoked auditory brainstem responses (AABRs) were recorded preoperatively in ketamine-anesthetized guinea pigs to confirm normal hearing. The bulla and then the cochlea were exposed. Optically evoked ABRs (OABR) were recorded in response to laser stimulation with a 50 µm optical fiber (532 nm, 10 ns pulses, 500 repetitions, 10 pulses/s; Nd:YAG laser) at the round window (RW) directed towards the basilar membrane (BM). OABRs similar in morphology to acoustically evoked ABRs, except for shorter latencies, were obtained for stimulation through the RW with energy levels between 1.7-30 µJ/pulse. The OABRs increased with increasing energy level reaching a saturation level around 13-15 µJ/pulse. Furthermore the responses remained consistent across stimulation over time, including stimulation at 13 µJ/pulse for over 30 minutes, indicating minimal or no damage within the cochlea with this type of laser stimulation. Overall we have demonstrated that laser light stimulation with 532 nm has potential for a new type of auditory prosthesis that can activate the cochlea without any apparent functional damage. Further studies are needed to determine the optimal laser parameters and fiber placement locations for localized and tonotopic activation.

Dual sub-picosecond and sub-nanosecond laser system

NASA Astrophysics Data System (ADS)

Xie, Xinglong; Liu, Fengqiao; Yang, Jingxin; Yang, Xin; Li, Meirong; Xue, Zhiling; Gao, Qi; Guan, Fuyi; Zhang, Weiqing; Huang, Guanlong; Zhuang, Yifei; Han, Aimei; Lin, Zunqi

2003-11-01

A high power laser system delivering a 20-TW, 0.5 - 0.8 ps ultra-short laser pulse and a 20-J, 500-ps long pulse simultaneously in one shot is completed. This two-beam laser operates at the wavelength of 1053 nm and uses Nd doped glass as the gain media of the main amplification chain. The chirped-pulse amplification (CPA) technology is used to compress the stretched laser pulse. After compression, the ultrashort laser pulse is measured: energy above 16.0 J, S/N contrast ratio ~ 10^(5) : 1, filling factor ~>52.7%. Another long pulse beam is a non-compressed chirped laser pulse, which is measured: energy ~ 20 J, pulse duration 500 ps. The two beams are directed onto the target surface at an angle of 15°.

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2017-02-01

In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

Q-switched Erbium-doped fiber laser at 1600 nm for photoacoustic imaging application

PubMed Central

Zeng, Lvming; Chen, Zhongping; Kim, Chang-Seok

2016-01-01

We present a nanosecond Q-switched Erbium-doped fiber (EDF) laser system operating at 1600 nm with a tunable repetition rate from 100 kHz to 1 MHz. A compact fiber coupled, acousto-optic modulator-based EDF ring cavity was used to generate a nanosecond seed laser at 1600 nm, and a double-cladding EDF based power amplifier was applied to achieve the maximum average power of 250 mW. In addition, 12 ns laser pulses with the maximum pulse energy of 2.4 μJ were obtained at 100 kHz. Furthermore, the Stokes shift by Raman scattering over a 25 km long fiber was measured, indicating that the laser can be potentially used to generate the high repetition rate pulses at the 1.7 μm region. Finally, we detected the photoacoustic signal from a human hair at 200 kHz repetition rate with a pulse energy of 1.2 μJ, which demonstrates that a Q-switched Er-doped fiber laser can be a promising light source for the high speed functional photoacoustic imaging. PMID:27110032

Q-switched Erbium-doped fiber laser at 1600 nm for photoacoustic imaging application

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

Piao, Zhonglie; Beckman Laser Institute, Department of Biomedical Engineering, University of California, Irvine, California 92612; Zeng, Lvming

We present a nanosecond Q-switched Erbium-doped fiber (EDF) laser system operating at 1600 nm with a tunable repetition rate from 100 kHz to 1 MHz. A compact fiber coupled, acousto-optic modulator-based EDF ring cavity was used to generate a nanosecond seed laser at 1600 nm, and a double-cladding EDF based power amplifier was applied to achieve the maximum average power of 250 mW. In addition, 12 ns laser pulses with the maximum pulse energy of 2.4 μJ were obtained at 100 kHz. Furthermore, the Stokes shift by Raman scattering over a 25 km long fiber was measured, indicating that the laser can be potentially used to generate the highmore » repetition rate pulses at the 1.7 μm region. Finally, we detected the photoacoustic signal from a human hair at 200 kHz repetition rate with a pulse energy of 1.2 μJ, which demonstrates that a Q-switched Er-doped fiber laser can be a promising light source for the high speed functional photoacoustic imaging.« less

Photo-ionization and modification of nanoparticles on transparent substrates by ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Komolov, Vladimir; Li, Hao; Yu, Qingsong; Przhibel'skii, Sergey; Smirnov, Dmitry

2011-02-01

The objective of this combined experimental and theoretical research is to study the dynamics and mechanisms of nanoparticle interaction with ultrashort laser pulses and related modifications of substrate surface. For the experimental effort, metal (gold), dielectric (SiO2) and dielectric with metal coating (about 30 nm thick) spherical nanoparticles deposited on glass substrate are utilized. Size of the particles varies from 20 to 200 nm. Density of the particles varies from low (mean inter-particle distance 100 nm) to high (mean inter-particle distance less than 1 nm). The nanoparticle assemblies and the corresponding empty substrate surfaces are irradiated with single 130-fs laser pulses at wavelength 775 nm and different levels of laser fluence. Large diameter of laser spot (0.5-2 mm) provides gradient variations of laser intensity over the spot and allows observing different laser-nanoparticle interactions. The interactions vary from total removal of the nanoparticles in the center of laser spot to gentle modification of their size and shape and totally non-destructive interaction. The removed particles frequently form specific sub-micrometer-size pits on the substrate surface at their locations. The experimental effort is supported by simulations of the nanoparticle interactions with high-intensity ultrashort laser pulse. The simulation employs specific modification of the molecular dynamics approach applied to model the processes of non-thermal particle ablation following laser-induced electron emission. This technique delivers various characteristics of the ablation plume from a single nanoparticle including energy and speed distribution of emitted ions, variations of particle size and overall dynamics of its ablation. The considered geometry includes single isolated particle as well a single particle on a flat substrate that corresponds to the experimental conditions. The simulations confirm existence of the different regimes of laser-nanoparticle interactions depending on laser intensity and wavelength. In particular, implantation of ions departing from the nanoparticles towards the substrate is predicted.

Injection-seeded tunable mid-infrared pulses generated by difference frequency mixing

NASA Astrophysics Data System (ADS)

Miyamoto, Yuki; Hara, Hideaki; Masuda, Takahiko; Hiraki, Takahiro; Sasao, Noboru; Uetake, Satoshi

2017-03-01

We report on the generation of nanosecond mid-infrared pulses having frequency tunability, a narrow linewidth, and a high pulse energy. These pulses are obtained by frequency mixing between injection-seeded near-infrared pulses in potassium titanyl arsenate crystals. A continuous-wave external cavity laser diode or a Ti:sapphire ring laser is used as a tunable seeding source for the near-infrared pulses. The typical energy of the generated mid-infrared pulses is in the range of 0.4-1 mJ/pulse. The tuning wavelength ranges from 3142 to 4806 nm. A narrow linewidth of 1.4 GHz and good frequency reproducibility of the mid-infrared pulses are confirmed by observing a rovibrational absorption line of gaseous carbon monoxide at 4587 nm.

Room-temperature Q-switched Tm:BaY2F8 laser pumped by CW diode laser

NASA Astrophysics Data System (ADS)

Coluccelli, Nicola; Galzerano, Gianluca; Laporta, Paolo; Parisi, Daniela; Toncelli, Alessandra; Tonelli, Mauro

2006-02-01

We report on the realization of CW diode-pumped Tm:BaY2F8 Q-switched laser at 1.93 µm. Active Q-switching was obtained by means of an intracavity Pockels cell. A functional characterization of the laser performance is presented with particular attention to output energy, pulse duration, pulse stability, and wavelength tunability. Pulses with time duration as short as 170 ns were demonstrated at the minimum repetition rate of 5 Hz with an energy of 3.2 mJ (corresponding to a peak power of 19 kW). A wavelength tunability range from 1905 nm to 1990 nm has been observed.

A high power diode-side-pumped Nd:YAG/BaWO4 Raman laser at 1103 nm

NASA Astrophysics Data System (ADS)

Li, Lei; Zhang, Xingyu; Liu, Zhaojun; Wang, Qingpu; Cong, Zhenhua; Zhang, Yuangeng; Wang, Weitao; Wu, Zhenguo; Zhang, Huaijin

2013-04-01

Pulsed operation at 1103 nm of a diode-side-pumped Nd:YAG laser with intracavity Raman shifting in BaWO4 is reported. The first Stokes wavelength at 1103 nm was generated by a Raman shift of 332 cm-1 from the fundamental wave (1064 nm). A maximum power at 1103 nm of 9.4 W was obtained for a diode pump power of 115 W at a pulse repetition rate of 15 kHz. The pump-to-Stokes conversion efficiency was up to 8.2%. When the output power at 1103 nm was over 7 W, a second Stokes line at 1145 nm was also observed in the experiment. Our research indicates that efficient Raman conversion can be realized by a Raman frequency shift at 332 cm-1 in BaWO4 Raman lasers.

Short infrared laser pulses block action potentials in neurons

NASA Astrophysics Data System (ADS)

Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.

2017-02-01

Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

Diode-pumped continuous-wave and femtosecond Cr:LiCAF lasers with high average power in the near infrared, visible and near ultraviolet.

PubMed

Demirbas, Umit; Baali, Ilyes; Acar, Durmus Alp Emre; Leitenstorfer, Alfred

2015-04-06

We demonstrate continuous-wave (cw), cw frequency-doubled, cw mode-locked and Q-switched mode-locked operation of multimode diode-pumped Cr:LiCAF lasers with record average powers. Up to 2.54 W of cw output is obtained around 805 nm at an absorbed pump power of 5.5 W. Using intracavity frequency doubling with a BBO crystal, 0.9 W are generated around 402 nm, corresponding to an optical-to-optical conversion efficiency of 12%. With an intracavity birefringent tuning plate, the fundamental and frequency-doubled laser output is tuned continuously in a broad wavelength range from 745 nm to 885 nm and from 375 to 440 nm, respectively. A saturable Bragg reflector is used to initiate and sustain mode locking. In the cw mode-locked regime, the Cr:LiCAF laser produces 105-fs long pulses near 810 nm with an average power of 0.75 W. The repetition rate is 96.4 MHz, resulting in pulse energies of 7.7 nJ and peak powers of 65 kW. In Q-switched mode-locked operation, pulses with energies above 150 nJ are generated.

Influence of Laser Radiation Power Density on the Intensity of Spectral Lines for Main Components in a Clay Laser-Induced Plasma

NASA Astrophysics Data System (ADS)

Anufrik, S. S.; Kurian, N. N.; Znosko, K. F.; Belkov, M. V.

2018-05-01

We have studied the intensity of the spectral lines for the main components in clay: Al I 309.4 nm, Al II 358.7 nm, Mg II 279.6 nm, Ti II 323.6 nm vs. the position of the object relative to the focus of the optical system when the samples are exposed to single laser pulses from a YAG:Nd3+ laser. We have determined the permissible ranges for positioning the object relative to the focus of the optical system (positive and negative defocusing) for which there is practically no change in the reproducibility of the intensity for the spectral lines for red and white clay samples. We show that the position of the object relative to the focus of the optical system should be within the range ΔZ ±1.5 mm for optimal laser pulse energies for the analyte spectral lines. We have calculated the radiation flux density for different laser pulse energies and different distances from the focus to the object. We have shown experimentally that reducing the radiation flux density leads to a decrease in the intensity of the analyte spectral lines.

Compact gain saturated plasma based X-ray lasers down to 6.9nm

NASA Astrophysics Data System (ADS)

Rocca, Jorge; Wang, Y.; Wang, S.; Rockwood, A.; Berrill, M.; Shlyaptsev, V.

2017-10-01

Plasma based soft x-ray amplifiers allow many experiments requiring bright, high energy soft x-ray laser pulses to be conducted in compact facilities. We have extended the wavelength of compact gain saturated x-ray lasers to 6.89 nm in a Ni-like Gd plasma generated by a Ti:Sa laser. Gain saturated laser operation was also obtained at 7.36 nm in Ni-like Sm. Isolectronic scaling and optimization of laser pre-pulse duration allowed us to also observe strong lasing at 6.6 nm and 6.1 nm in Ni-like Tb, and amplification at 6.4 nm and 5.89 nm in Ni-like Dy. The results were obtained by transient laser heating of solid targets with traveling wave excitation at progressively increased gracing incidence angles. We show that the optimum pump angle of incidence for collisional Ni-like lasers increases linearly with atomic number from Z =42 to Z =66, reaching 43 degrees for Ni-like Dy, in good agreement with hydrodynamic/atomic physics simulations. These results will enable single-shot nano-scale imaging and other application of sub-7 nm lasers to be performed at compact facilities. Work supported by Grant DE-FG02-4ER15592 of the Department of Energy, Office of Science, and by the National Science Foundation Grant ECCS 1509925.

Development of high repetition rate nitric oxide planar laser induced fluorescence imaging

NASA Astrophysics Data System (ADS)

Jiang, Naibo

This thesis has documented the development of a MHz repitition rate pulse burst laser system. Second harmonic and third harmonic efficiencies are improved by adding a Phase Conjugate Mirror to the system. Some high energy fundamental, second harmonic, and third harmonic burst sequences consisting of 1--12 pulses separated in time by between 4 and 12 microseconds are now routinely obtained. The reported burst envelopes are quite uniform. We have also demonstrated the ability to generate ultra-high frequency sequences of broadly wavelength tunable, high intensity laser pulses using a home built injection seeded Optical Parametric Oscillator (OPO), pumped by the second and third harmonic output of the pulse burst laser. Typical OPO output burst sequences consist of 6--10 pulses, separated in time by between 6 and 10 microseconds. With third harmonic pumping of the OPO system, we studied four conditions, two-crystal Singly Resonant OPO (SRO) cavity, three-crystal OPO cavity, single pass two-crystal Doubly Resonant OPO (DRO) cavity and double pass two-crystal OPO cavity. The double pass two-crystal OPO cavity gives the best operation in burst mode. For single pass OPO, the average total OPO conversion efficiency is approximately 25%. For double pass OPO, the average total OPO conversion efficiency is approximately 35%. As a preliminary work, we studied 532nm pumping of a single crystal OPO cavity. With single pulse pumping, the conversion efficiency can reach 30%. For both 355nm and 532nm pumping OPO, we have demonstrated injection seeding. The OPO output light linewidth is significantly narrowed. Some preliminary etalon traces are also reported. By mixing the OPO signal output at 622nm with residual third harmonic at 355nm, we obtained 226nm burst sequences with average pulse energy of ˜0.2 mJ. Injection seeding of the OPO increases the energy achieved by a factor of ˜2. 226nm burst sequences with reasonably uniform burst envelopes are reported. Using the system we have obtained, for the first time by any known optical method, Planar Laser Induced Fluorescence (PLIF) image sequences at ultrahigh (≥100kHz) frame rates, in particular NO PLIF image sequences, have been obtained in a Mach 2 jet. We also studied the possibility of utilizing a 250 kHz pulsed Nd:YVO 4 laser as the master oscillator. 10-pulse-10-mus spacing burst sequences with reasonably uniform burst envelope have been obtained. The total energy of the burst sequence is ˜2.5J.

Selective ablation of dental calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1996-01-01

The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.

Modulated Pulsed Laser Sources for Imaging Lidars

DTIC Science & Technology

2007-10-01

doped PM fiber . The ytterbium ions in the fiber are cladding-pumped to their excited states using four, 6-Watt multimode lasers at 976 nm. Yh-dop...next amplified using a fiber amplifier to an average power of 10-15 Watts. A highly efficient, periodically poled nonlinear optical material will be...establish the feasibility of both pulsing a 1064 nm laser to produce enough average power to successfully seed a Yb- doped fiber amplifier so it will

Several hundred kHz repetition rate nanosecond pulses amplification in Er-Yb co-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Yang, Weiqiang; Yin, Ke; Zhang, Bin; Xue, Guanghui; Hou, Jing

2014-07-01

We have experimentally investigated several hundred kHz repetition rate 1,550-nm nanosecond pulses amplification in Er-Yb co-doped fiber amplifier (EYDFA). The experimental setup has three stage fiber amplifiers. At the output of the second stage EYDFA, Yb3+ ions induced amplified spontaneous emission (Yb-ASE) is not observed owing to the low pump power. In the third stage EYDFA, a simultaneously seeded 1,064-nm continuous-wave laser is used to control Yb-ASE. Without any additional 1,064-nm signal, significantly backward Yb-ASE which caused loss-induced heat accumulation at the input port of the pump combiner can be observed. The monitored temperature at the input port of the pump combiner rapidly grows from 30 to 80 °C when the pump power is turned from 20 to 32 W. When a 196-mW forward 1,064-nm laser is added, the monitored backward Yb-ASE power is significantly declined, and the monitored temperature is kept below 35 °C. But, the additional signal caused a large power fraction at 1,064 nm in the output laser. In our experiment at the maximum pump power of 48.5 W, the total output power is 20 W with ~6.4-W 1,550-nm pulsed laser and ~13-W 1,064-nm continuous-wave laser.

Passively Q-switched Nd:YAG/Cr(4+):YAG bonded crystal microchip laser operating at 1112  nm and its application for second-harmonic generation.

PubMed

Fu, S G; Ouyang, X Y; Liu, X J

2015-10-10

A passively Q-switched Nd:YAG/Cr⁴⁺:YAG microchip laser operating at 1112 nm is demonstrated. Under a pump power of 5.5 W, a maximum average output power of 623 mW was obtained with T=6% output coupler, corresponding to an optical-to-optical conversion efficiency of 11.3% and a slope efficiency of 19.5%. The minimum pulse width was 2.8 ns, the pulse energy and peak power were 39.3 μJ and 14 kW, respectively. Additionally, based on the 1112 nm laser, a 230 mW 556 nm green-yellow laser was achieved within an LBO crystal.

Investigation of a Pulsed 1550 nm Fiber Laser System (Briefing Charts)

DTIC Science & Technology

2016-02-14

AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) Air Force Research Laboratory AFRL /RDLT 3550 Aberdeen Ave SE Kirtland AFB, NM 87117-5776 11...LIST DTIC/OCP 8725 John J. Kingman Rd, Suite 0944 Ft Belvoir, VA 22060-6218 1 cy AFRL /RVIL Kirtland AFB, NM 87117-5776 1 cy Leanne Henry Official Record Copy AFRL /RDLT 1 cy ... AFRL -RD-PS- TP-2016-0007 AFRL -RD-PS- TP-2016-0007 INVESTIGATION OF A PULSED 1550 NM FIBER LASER SYSTEM Leanne Henry, et al. 14 February 2016

Fiber-optic manipulation of urinary stone phantoms using holmium:YAG and thulium fiber lasers.

PubMed

Blackmon, Richard L; Case, Jason R; Trammell, Susan R; Irby, Pierce B; Fried, Nathaniel M

2013-02-01

Fiber-optic attraction of urinary stones during laser lithotripsy may be exploited to manipulate stone fragments inside the urinary tract without mechanical grasping tools, saving the urologist time and space in the ureteroscope working channel. We compare thulium fiber laser (TFL) high pulse rate/low pulse energy operation to conventional holmium:YAG low pulse rate/high pulse energy operation for fiber-optic suctioning of plaster-of-paris (PoP) stone phantoms. A TFL (wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10 to 350 Hz) and a holmium laser (wavelength of 2120 nm, pulse energy of 35 to 360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz) were tested using 270-μm-core optical fibers. A peak drag speed of ~2.5 mm/s was measured for both TFL (35 mJ and 150 to 250 Hz) and holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber-optic suctioning of urinary stone phantoms is feasible. TFL operation at high pulse rates/low pulse energies is preferable to holmium operation at low pulse rates/high pulse energies for rapid and smooth stone pulling. With further development, this novel technique may be useful for manipulating stone fragments in the urinary tract.

Diode injection - seeded, 940 nanometer (nm), titanium - sapphire laser for H2O DIAL (differential absorption lidar), measurements

NASA Technical Reports Server (NTRS)

Miller, George E.

1992-01-01

Differential absorption of laser radiation by various molecular species represents both a selective and a sensitive method of measuring specific atmospheric constituents. DIAL measurements can be carried out via two different means. Both involve using two laser pulses with slightly different wavelengths (lambda), (one lambda at a strong absorption line of the molecule of interest, the other detuned into the wing of the line), and comparing the attenuation of the pulses. One approach relies on scattering of the radiation from some conveniently located topographical target. In the other technique elastic scattering from atmospheric aerosols and particulates is used to return the radiation to the lidar receiver system. This case is referred to as the differential absorption and scattering technique, and is the technique we are interested in to measure water vapor at 940 nm. The 940 nm wavelength is extremely desirable to atmospheric scientist interested in accurate DIAL measurements of H2O in the upper and lower troposphere. Simulated measurements using approximately 940 nm and 815 nm lasers at a range of altitudes and experimental conditions are shown. By offering access to larger absorption cross-sections, injected seeded, 940 nm DIAL laser transmitters would allow for more accurate water profile measurements at altitudes from 6 to 16 km than is currently possible with 730 nm and 815 nm DIAL laser transmitters. We have demonstrated the operation of an injected seeded titanium-sapphire (TS) laser operating at approximately 940 nm with an energy of more than 90 mJ per pulse. The TS laser is pumped by a commercial, 600 mJ, 532 nm, 10 Hz Nd:YAG laser. The slope efficiency of the laser using a flat 50 percent R output coupler and a 10 m end-mirror is shown. The laser was injected seeded with a CW, AlGaAs, semiconductor diode laser which had an output of 83 mW. The CW diode seed beam was introduced into the TS laser cavity through a HR end-mirror. When the diode beam is aligned to the TS resonator, it controls the TS laser output wavelength and its spectral line width with the required resolution for DIAL applications. This work supports the need for the development of 940 nm, titanium-sapphire DIAL transmitters.

Femtosecond pulses generated from a synchronously pumped chromium-doped forsterite laser

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1993-01-01

Kerr lens mode-locking (KLM) has become a standard method to produce femtosecond pulses from tunable solid state lasers. High power inside the laser resonator propagating through the laser-medium with nonlinear index of refraction, coupled with the stability conditions of the laser modes in the resonator, result in a passive amplitude modulation which explains the mechanism for pulse shortening. Recently, chromium doped forsterite was shown to exhibit similar pulse behavior. A successful attempt to generate femtosecond pulses from a synchronously pumped chromium-doped forsterite laser with intracavity dispersion compensation is reported. Stable, transform limited pulses with duration of 105 fs were routinely generated, tunable between 1240 to 1270 nm.

High-efficiency diode-pumped actively Q-switched ceramic Nd:YAG/BaWO₄ Raman laser operating at 1666 nm.

PubMed

Zhang, H N; Chen, X H; Wang, Q P; Zhang, X Y; Chang, J; Gao, L; Shen, H B; Cong, Z H; Liu, Z J; Tao, X T; Li, P

2014-05-01

A diode-pumped actively Q-switched Raman laser employing BaWO4 as the Raman active medium and a ceramic Nd:YAG laser operating at 1444 nm as the pump source is demonstrated. The first-Stokes-Raman generation at 1666 nm is achieved. With a pump power of 20.3 W and pulse repetition frequency rate of 5 kHz, a maximum output power of 1.21 W is obtained, which is the highest output power for a 1.6 μm Raman laser. The corresponding optical-to-optical conversion efficiency is 6%; the pulse energy and peak power are 242 μJ and 8.96 kW, respectively.

CW and passively Q-switched laser performance of Nd:Lu2SiO5 crystal

NASA Astrophysics Data System (ADS)

Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

2016-01-01

We demonstrated an efficient and controllable dual-wavelength continuous-wave (CW) laser of Nd:Lu2SiO5 (Nd:LSO) crystal. The maximum output power was 3.02 W at wavelength of 1075 nm and 1079 nm, and with increasing of absorbed pump power, the ratio of 1079 nm laser rose. The slope efficiency of 65.6% and optical-to-optical conversion efficiency of 63.3% were obtained. The passively Q-switched laser properties of Nd:LSO were investigated for the first time. The shortest pulse, maximum pulse energy and peak power were 11.58 ns, 29.05 μJ and 2.34 kW, respectively.

LIBS spectra of multi-component Al, Fe, Cu alloys and composite materials used for selected elements of armament and munition

NASA Astrophysics Data System (ADS)

Ostrowski, R.; Skrzeczanowski, W.; Rycyk, A.; CzyŻ, K.; Sarzyński, A.; Strzelec, M.; Jach, K.; Świerczyński, R.

2017-10-01

Spectral investigations in the UV-VIS range of selected Al, Cu, and Fe alloys and composite materials were performed using LIBS technique. The investigated objects were typical rifle cartridges, mortars, rocket launchers and samples of different type steel, Cu and Al alloys, as well as composite materials of special chemical composition. Two Nd:YAG lasers were applied: a short 4 ns, 60 mJ Brio Quantel/BigSky laser (1064 nm) and a long pulse 200/400 (up to 1000) µs ({ 2/4 up to 10 J) laser (1064 nm) constructed at the Institute of Optoelectronics MUT. This spectrochemical analysis was possible for Al, Cu, and Fe alloys objects for both lasers, and in case of composites only if the samples were irradiated by short laser pulse since in the experiment with the long pulse, all composite materials spectra, in general, were very similar to each other - they imitated a grey/black body spectra. For metal alloys in experiments with a short laser pulse only atomic spectra were observed while for long microsecond laser pulses molecular transitions have been registered for Al alloys. Electron temperatures of plasma created on different materials for short and long laser pulses were found on the base of Boltzmann plots. Temperatures are clearly higher for plasmas generated with a short laser pulse which results from much higher laser power density on the sample surface for short pulse and not from fluence which is 20-40 times larger for long pulse.

Experimental study of fs-laser induced sub-100-nm periodic surface structures on titanium.

PubMed

Nathala, Chandra S R; Ajami, Ali; Ionin, Andrey A; Kudryashov, Sergey I; Makarov, Sergey V; Ganz, Thomas; Assion, Andreas; Husinsky, Wolfgang

2015-03-09

In this work the formation of laser-induced periodic surface structures (LIPSS) on a titanium surface upon irradiation by linearly polarized femtosecond (fs) laser pulses with a repetition rate of 1 kHz in air environment was studied experimentally. In particular, the dependence of high-spatial-frequency-LIPSS (HSFL) characteristics on various laser parameters: fluence, pulse number, wavelength (800 nm and 400 nm), pulse duration (10 fs - 550 fs), and polarization was studied in detail. In comparison with low-spatial-frequency-LIPSS (LSFL), the HSFL emerge at a much lower fluence with orientation perpendicular to the ridges of the LSFL. It was observed that these two types of LIPSS demonstrate different fluence, shot number and wavelength dependencies, which suggest their origin is different. Therefore, the HSFL formation mechanism cannot be described by the widely accepted interference model developed for describing LSFL formation.

Room-temperature subnanosecond waveguide lasers in Nd:YVO4 Q-switched by phase-change VO2: A comparison with 2D materials

PubMed Central

Nie, Weijie; Li, Rang; Cheng, Chen; Chen, Yanxue; Lu, Qingming; Romero, Carolina; Vázquez de Aldana, Javier R.; Hao, Xiaotao; Chen, Feng

2017-01-01

We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66.7 mW. To compare the Q-switched laser performances by VO2 saturable absorber with those based on two-dimensional materials, the 1064-nm laser pulses have been realized in the same waveguide platform with either graphene or transition metal dichalcogenide (in this work, WS2) coated mirror. The results on 2D material Q-switched waveguide lasers have shown that the shortest pulses are with 22-ns duration, whilst the maximum output average powers reach ~161.9 mW. This work shows the obvious difference on the lasing properties based on phase-change material and 2D materials, and suggests potential applications of VO2 as low-cost saturable absorber for subnanosecond laser generation. PMID:28383017

Investigation of continuous wave and pulsed laser performance based on Nd3+:Gd0.6Y1.4SiO5 crystal

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Zhaojun; Cong, Zhenhua; Shen, Hongbin; Li, Yongfu; Wang, Qingpu; Fang, Jiaxiong; Xu, Xiaodong; Xu, Jun; Zhang, Xingyu

2015-12-01

We systematically investigated a laser diode (LD) pumped Nd:GYSO (Nd3+:Gd0.6Y1.4SiO5) laser. The output power of the continuous wave laser was as high as 3.5 W with a slope efficiency of 31.8%. In the Q-switched operation; the laser exhibited dual-wavelengths output (1073.6 nm and 1074.7 nm) synchronously with a Cr4+:YAG as the saturable absorber (SA). Additionally, a passively mode-locked laser was demonstrated using a semiconductor SA mirror with a maximum average output power of 510 mW at a central wavelength of 1074 nm, while the pulse width of the laser was as short as 5 ps. Our experiment proved that the Nd:GYSO mixed crystal was a promising material for a solid-state laser.

Tuning the frequency of ultrashort laser pulses by a cross-phase-modulation-induced shift in a photonic crystal fiber.

PubMed

Konorov, S O; Akimov, D A; Zheltikov, A M; Ivanov, A A; Alfimov, M V; Scalora, M

2005-06-15

Femtosecond pulses of fundamental Cr:forsterite laser radiation are used as a pump field to tune the frequency of copropagating second-harmonic pulses of the same laser through cross-phase modulation in a photonic crystal fiber. Sub-100-kW femtosecond pump pulses coupled into a photonic crystal fiber with an appropriate dispersion profile can shift the central frequency of the probe field by more than 100 nm, suggesting a convenient way to control propagation and spectral transformations of ultrashort laser pulses.

Formation of laser-induced periodic surface structures on fused silica upon two-color double-pulse irradiation

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

Höhm, S.; Herzlieb, M.; Rosenfeld, A.

2013-12-16

The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of laser pulse pairs (50 fs single-pulse duration) of two different wavelengths (400 and 800 nm) is studied experimentally. Parallel polarized double-pulse sequences with a variable delay Δt between −10 and +10 ps and between the individual fs-laser pulses were used to investigate the LIPSS periods versus Δt. These two-color experiments reveal the importance of the ultrafast energy deposition to the silica surface by the first laser pulse for LIPSS formation. The second laser pulse subsequently reinforces the previously seeded spatial LIPSSmore » frequencies.« less

Fiber optic suctioning of urinary stone phantoms during laser lithotripsy

NASA Astrophysics Data System (ADS)

Blackmon, Richard L.; Case, Jason R.; Trammell, Susan R.; Irby, Pierce B.; Fried, Nathaniel M.

2013-03-01

Fiber optic attraction of urinary stones during laser lithotripsy has been previously observed, and this phenomenon may potentially be exploited to pull stones inside the urinary tract without mechanical grasping tools, thus saving the urologist valuable time and space in the ureteroscope's single working channel. In this study, Thulium fiber laser (TFL) high-pulse-rate/low-pulse-energy operation and Holmium:YAG low-pulse-rate/high-pulse-energy operation are compared for fiber optic "suctioning" of Plaster-of-Paris stone phantoms. A TFL with wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10-350 Hz, and Holmium laser with wavelength of 2120 nm, pulse energy of 35-360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz were tested using 270-μm-core fibers. A peak "pull" speed of 2.5 mm/s was measured for both TFL (35 mJ and 150-250 Hz) and Holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber optic suctioning of urinary stone phantoms is feasible for both lasers. However, TFL operation at high-pulse-rates/low-pulse-energies provides faster, smoother stone pulling than Holmium operation at low-pulserates/ high-pulse-energies. After further study, this method may be used to manipulate urinary stones in the clinic.

A single-frequency Ho:YLF pulsed laser with frequency stability better than 500 kHz

NASA Astrophysics Data System (ADS)

Kucirek, P.; Meissner, A.; Nyga, S.; Mertin, J.; Höfer, M.; Hoffmann, H.-D.

2017-03-01

The spectral stability of a previously reported Ho:YLF single frequency pulsed laser oscillator emitting at 2051 nm is drastically improved by utilizing a narrow linewidth Optically Pumped Semiconductor Laser (OPSL) as a seed for the oscillator. The oscillator is pumped by a dedicated gain-switched Tm:YLF laser at 1890 nm. The ramp-and-fire method is employed for generating single frequency emission. The heterodyne technique is used to analyze the spectral properties. The laser is designed to meet a part of the specifications for future airborne or space borne LIDAR detection of CO2. Seeding with a DFB diode and with an OPSL are compared. With OPSL seeding an Allan deviation of the centroid of the spectral distribution of 38 kHz and 517 kHz over 10 seconds and 60 milliseconds of sampling time for single pulses is achieved. The spectral width is approximately 30 MHz. The oscillator emits 2 mJ pulse energy with 50 Hz pulse repetition frequency (PRF) and 20 ns pulse duration. The optical to optical efficiency of the Ho:YLF oscillator is 10 % and the beam quality is diffraction limited. To our knowledge this is the best spectral stability demonstrated to date for a Ho:YLF laser with millijoule pulse energy and nanosecond pulse duration.

Effects of ion and nanosecond-pulsed laser co-irradiation on the surface nanostructure of Au thin films on SiO{sub 2} glass substrates

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

Yu, Ruixuan; Meng, Xuan; Takayanagi, Shinya

2014-04-14

Ion irradiation and short-pulsed laser irradiation can be used to form nanostructures on the surfaces of substrates. This work investigates the synergistic effects of ion and nanosecond-pulsed laser co-irradiation on surface nanostructuring of Au thin films deposited under vacuum on SiO{sub 2} glass substrates. Gold nanoparticles are randomly formed on the surface of the substrate after nanosecond-pulsed laser irradiation under vacuum at a wavelength of 532 nm with a repetition rate of 10 Hz and laser energy density of 0.124 kJ/m{sup 2}. Gold nanoparticles are also randomly formed on the substrate after 100-keV Ar{sup +} ion irradiation at doses of upmore » to 3.8 × 10{sup 15} ions/cm{sup 2}, and nearly all of these nanoparticles are fully embedded in the substrate. With increasing ion irradiation dose (number of incident laser pulses), the mean diameter of the Au nanoparticles decreases (increases). However, Au nanoparticles are only formed in a periodic surface arrangement after co-irradiation with 6000 laser pulses and 3.8 × 10{sup 15} ions/cm{sup 2}. The periodic distance is ∼540 nm, which is close to the wavelength of the nanosecond-pulsed laser, and the mean diameter of the Au nanoparticles remains at ∼20 nm with a relatively narrow distribution. The photoabsorption peaks of the ion- or nanosecond-pulsed laser-irradiated samples clearly correspond to the mean diameter of Au nanoparticles. Conversely, the photoabsorption peaks for the co-irradiated samples do not depend on the mean nanoparticle diameter. This lack of dependence is likely caused by the periodic nanostructure formed on the surface by the synergistic effects of co-irradiation.« less

Q-switched pulse laser generation from double-cladding Nd:YAG ceramics waveguides.

PubMed

Tan, Yang; Luan, Qingfang; Liu, Fengqin; Chen, Feng; Vázquez de Aldana, Javier Rodríguez

2013-08-12

This work reports on the Q-switched pulsed laser generation from double-cladding Nd:YAG ceramic waveguides. Double-cladding waveguides with different combination of diameters were inscribed into a sample of Nd:YAG ceramic. With an additional semiconductor saturable absorber, stable pulsed laser emission at the wavelength of 1064 nm was achieved with pulses of 21 ns temporal duration and ~14 μJ pulse energy at a repetition rate of 3.65 MHz.

LASERS: Excimer XeCl laser excited by microsecond megawatt microwave pulses from a commercial 3.07-GHz microwave oscillator

NASA Astrophysics Data System (ADS)

Vaulin, V. A.; Slinko, V. N.; Sulakshin, S. S.

1990-12-01

An excimer laser (λ approx 308 nm) utilizing an Ne-Xe-HCl mixture was excited by microwave (ν0 = 3.07 GHz) pulses of 2.8-μs duration and ~ 0.9 MW power delivered by a commercial microwave oscillator. A peak laser radiation power of 130 W was obtained in pulses of 280 ns duration. Laser radiation from along the center of a laser tube was recorded in addition to that from the skin layer.

Pulsed and cw laser oscillations in LiF:F-2 color center crystal under laser diode pumping.

PubMed

Basiev, Tasoltan T; Vassiliev, Sergey V; Konjushkin, Vasily A; Gapontsev, Valentin P

2006-07-15

Continuous-wave laser oscillations in LiF:F-2 crystal optically pumped by a laser diode at 970 nm were demonstrated for what is believed to be the first time. The slope efficiency of 14% and conversion efficiency of 5.5% were achieved for 80 micros pump pulse duration and 5 Hz pulse repetition rate. An efficiency twice as low was measured at a 6.25 kHz pulse repetition rate (50% off-duty factor) and in cw mode of laser operation.

Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

NASA Astrophysics Data System (ADS)

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon.

PubMed

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.

Interaction of gold nanoparticles with nanosecond laser pulses: Nanoparticle heating

NASA Astrophysics Data System (ADS)

Nedyalkov, N. N.; Imamova, S. E.; Atanasov, P. A.; Toshkova, R. A.; Gardeva, E. G.; Yossifova, L. S.; Alexandrov, M. T.; Obara, M.

2011-04-01

Theoretical and experimental results on the heating process of gold nanoparticles irradiated by nanosecond laser pulses are presented. The efficiency of particle heating is demonstrated by in-vitro photothermal therapy of human tumor cells. Gold nanoparticles with diameters of 40 and 100 nm are added as colloid in the cell culture and the samples are irradiated by nanosecond pulses at wavelength of 532 nm delivered by Nd:YAG laser system. The results indicate clear cytotoxic effect of application of nanoparticle as more efficient is the case of using particles with diameter of 100 nm. The theoretical analysis of the heating process of nanoparticle interacting with laser radiation is based on the Mie scattering theory, which is used for calculation of the particle absorption coefficient, and two-dimensional heat diffusion model, which describes the particle and the surrounding medium temperature evolution. Using this model the dependence of the achieved maximal temperature in the particles on the applied laser fluence and time evolution of the particle temperature is obtained.

Efficient continuous-wave, broadly tunable and passive Q-switching lasers based on a Tm3+:CaF2 crystal

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Zhang, Cheng; Zu, Yuqian; Fan, Xiuwei; Liu, Jie; Guo, Xinsheng; Qian, Xiaobo; Su, Liangbi

2018-04-01

Laser operations in the continuous-wave as well as in the pulsed regime of a 4 at.% Tm3+:CaF2 crystal are reported. For the continuous-wave operation, a maximum average output power of 1.15 W was achieved, and the corresponding slope efficiency was more than 64%. A continuous tuning range of about 160 nm from 1877-2036 nm was achieved using a birefringent filter. Using Argentum nanorods as a saturable absorber, the significant pulsed operation of a passively Q-switched Tm3+:CaF2 laser was observed at 1935.4 nm for the first time, to the best of our knowledge. A maximum output power of 385 mW with 41.4 µJ pulse energy was obtained under an absorbed pump power of 2.04 W. The present results indicate that the Tm3+:CaF2 lasers could be promising laser sources to operate in the eye-safe spectral region.

Laser-induced periodic surface structures of thin, complex multi-component films

NASA Astrophysics Data System (ADS)

Reif, Juergen; Varlamova, Olga; Ratzke, Markus; Uhlig, Sebastian

2016-04-01

Femtosecond laser-induced regular nanostructures are generated on a complex multilayer target, namely a piece of a commercial, used hard disk memory. It is shown that after single-shot 800-nm irradiation at 0.26 J/cm2 only the polymer cover layer and—in the center—a portion of the magnetic multilayer are ablated. A regular array of linearly aligned spherical 450-nm features at the uncovered interface between cover and magnetic layers appears not to be produced by the irradiation. Only after about 10 pulses on one spot, classical ripples perpendicular to the laser polarization with a period of ≈700 nm are observed, with a modulation between 40 nm above and 40 nm below the pristine surface and an ablation depth only slightly larger than the thickness of the multilayer magnetic film. Further increase of the pulse number does not result in deeper ablation. However, 770-nm ripples become parallel to the polarization and are swelling to more than 120 nm above zero, much more than the full multilayer film thickness. In the spot periphery, much shallower 300-nm ripples are perpendicular to the strong modulation and the laser polarization. Irradiation with 0.49-J/cm2 pulses from an ultrafast white-light continuum results—in the spot periphery—in the formation of 200-nm ripples, only swelling above zero after removal of the polymer cover, without digging into the magnetic film.

Laser damage of HR, AR-coatings, monolayers and bare surfaces at 1064 nm

NASA Technical Reports Server (NTRS)

Garnov, S. V.; Klimentov, S. M.; Said, A. A.; Soileau, M. J.

1993-01-01

Laser induced damage thresholds and morphologies were investigated in a variety of uncoated and coated surfaces, including monolayers and multi-layers of different chemical compositions. Both antireflective (AR) and highly reflective (HR) were tested. Testing was done at 1064 nm with 25 picosecond and 8 nanosecond YAG/Nd laser single pulses. Spot diameter in the experiments varied from 0.09 to 0.22 mm. The laser damage measurement procedure consisted of 1-on-1 (single laser pulse in the selected site) and N-on-1 experiments including repeated irradiation by pulses of the same fluence and subsequently raised from pulse to pulse fluence until damage occurred. The highest picosecond damage thresholds of commercially available coatings averaged 12 - 14 J/sq cm, 50 percent less than thresholds obtained in bare fused silica. Some coatings and bare surfaces revealed a palpable preconditioning effect (an increase in threshold of 1.2 to 1.8 times). Picosecond and nanosecond data were compared to draw conclusions about pulse width dependence. An attempt was made to classify damage morphologies according to the type of coating, class of irradiating, and damage level.

A Comparison of Microvascular Responses to Visible and Near-Infrared Lasers

PubMed Central

Li, D.; Farshidi, D.; Wang, G.X.; He, Y.L.; Kelly, K.M.; Wu, W.J.; Chen, B.; Ying, Z.X.

2015-01-01

Background and Objective Pulsed dye laser (PDL) is a commonly used treatment for Port Wine Stain birthmarks (PWS). However, deeper components of PWS are often resistant to PDL. Deeper penetrating lasers, including the long pulsed Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser have been used, but carry greater risk. This study evaluates the distinct blood vessel thermal responses to visible (595 nm) and near infrared (1,064 nm) lasers using animal and numerical models. Study Design/Materials and Methods Blood vessels in the rodent dorsal skin chamber (DSC) were irradiated by a 595 nm PDL and a long-pulsed 1,064 nm Nd:YAG laser. Laser-induced immediate and 1-hour post-structural and functional changes in the vessels were documented. Numerical simulations were conducted using a 1,000 μm depth SD mouse skin fold to simulate experimental conditions. Results PDL irradiation produced immediate blood vessel hemorrhage. Modeling indicated this occurs due to preferential heating of the superior parts of large blood vessels. Nd:YAG irradiation resulted in blood vessel constriction; modeling indicated more uniform heating of vessel walls. Conclusion PDL and Nd:YAG lasers result in distinct tissue responses. This supports different observable clinical treatment end points when using these devices. Vessel constriction associated with the Nd:YAG may be more difficult to observe and is one reason this device may carry greater risk. Lasers Surg. Med. 46:479–487, 2014. PMID:24974953

Long-pulsed Nd: YAG Laser and Intense Pulse Light-755 nm for Idiopathic Facial Hirsutism: A Comparative Study.

PubMed

Shrimal, Arpit; Sardar, Souvik; Roychoudhury, Soumyajit; Sarkar, Somenath

2017-01-01

Hirsutism means excessive terminal hair growth in a female in male pattern distribution. Perception of hirsutism is subjective. Permanent laser hair reduction is a slow process taking many sessions and tracking of improvement parameters is tedious. Hence, a lot of confusion still exists regarding the type of laser most beneficial for treatment. The aim of this study was to compare the effectiveness and safety profile of long-pulsed Nd: YAG laser (1064 nm) and intense pulse light (IPL)-755 nm in management of idiopathic facial hirsutism. Open-labelled, randomly allocated experimental study. The study included 33 cases of idiopathic facial hirsutism. Patients were randomly divided into Group A, treated with long-pulsed Nd: YAG laser and Group B, treated with IPL-755 for a total of six sessions at 1 month interval. Chi-square test was used in Medcalc ® version 9.0 and the test of significance was taken to be P < 0.05. Average percentage of improvement in Group A, according to patients at each sessions were 46.33%, 70.66%, 81.66%, 84.67%, 85.33%, 87.33% and that in Group B were 28.06%, 39.72%, 52.22%, 64.72%, 67.78%, 71.11%, respectively. Excellent response (>75% reduction in hair) after six sessions in Group A was seen in fourteen (93.33%) out of fifteen patients, whereas in Group B, it was seen only in three (16.66%) out of eighteen patients. In Group A, erythema was seen in 26.67%, perifollicular edema and hyperpigmentation in 13.33% each. In Group B, erythema was seen in 50% patients, perifollicular edema in 16.67% and hyperpigmentation in 38.89% patients. Long-pulsed Nd: YAG Laser (1064 nm) is better than IPL-755 nm in terms of safety and effectiveness in the management of idiopathic facial hirsutism.

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.

All-fiber mode-locked laser oscillator with pulse energy of 34 nJ using a single-walled carbon nanotube saturable absorber.

PubMed

Jeong, Hwanseong; Choi, Sun Young; Rotermund, Fabian; Cha, Yong-Ho; Jeong, Do-Young; Yeom, Dong-Il

2014-09-22

We demonstrate a dissipative soliton fiber laser with high pulse energy (>30 nJ) based on a single-walled carbon nanotube saturable absorber (SWCNT-SA). In-line SA that evanescently interacts with the high quality SWCNT/polymer composite film was fabricated under optimized conditions, increasing the damage threshold of the saturation fluence of the SA to 97 mJ/cm(2). An Er-doped mode-locked all-fiber laser operating at net normal intra-cavity dispersion was built including the fabricated in-line SA. The laser stably delivers linearly chirped pulses with a pulse duration of 12.7 ps, and exhibits a spectral bandwidth of 12.1 nm at the central wavelength of 1563 nm. Average power of the laser output is measured as 335 mW at an applied pump power of 1.27 W. The corresponding pulse energy is estimated to be 34 nJ at the fundamental repetition rate of 9.80 MHz; this is the highest value, to our knowledge, reported in all-fiber Er-doped mode-locked laser using an SWCNT-SA.

High efficiency, linearly polarized, directly diode-pumped Er:YAG laser at 1617  nm.

PubMed

Yu, Zhenzhen; Wang, Mingjian; Hou, Xia; Chen, Weibiao

2014-12-01

An efficient, directly diode-pumped Er:YAG laser at 1617 nm was demonstrated. A folding mirror with high reflectivity for the s-polarized light at the laser wavelength was used to achieve a linearly polarized laser. A maximum continuous-wave output power of 7.73 W was yielded under incident pump power of 50.57 W, and the optical conversion efficiency with respect to incident pump power was ∼15.28%, which was the highest optical conversion efficiency with directly diode-pumped Er:YAG lasers up to now; in Q-switched operation, the maximum pulse energy of 7.82 mJ was generated with pulse duration of about 80 ns at a pulse repetition frequency of 500 Hz.

Successful Treatment of Congenital Lymphangioma Circumscriptum of the Vulva with CO2 and Long-Pulsed Nd:YAG Lasers.

PubMed

Sasaki, Ryosuke; Negishi, Kei; Akita, Hirotaka; Suzuki, Kayoko; Matsunaga, Kayoko

2014-01-01

A 16-year-old girl presented with a 9-year history of vesicles on the vulva. She had initially taken a wait-and-see approach, but required treatment because of bleeding. Histological examination of a biopsied vesicle revealed dilated lymph channels in the upper dermis, suggesting lymphangioma circumscriptum (LC). The challenge for this pathology has been to find a conservative treatment with low morbidity and better results than those reported for surgical excision, which has been the mainstay of therapy. In this case, LC of the vulva was successfully treated using a 10,600-nm CO2 laser and long-pulsed Nd:YAG laser. Use of the 10,600-nm CO2 laser and long-pulsed Nd:YAG laser appeared effective for treating LC.

Enhancement of EUV emission from a liquid microjet target by use of dual laser pulses

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Rajyaguru, Chirag; Koga, Masato; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi; Kikuchi, Takashi; Yugami, Noboru; Kawata, Shigeo; Andreev, Alexander A.

2005-03-01

Extreme ultraviolet (EUV) radiation at the wavelength of around 13nm waws observed from a laser-produced plasma using continuous water-jet. Strong dependence of the conversion efficiency (CE) on the laser focal spot size and jet diameter was observed. The EUV CE at a given laser spot size and jet diameter was further enhanced using double laser pulses, where a pre-pulse was used for initial heating of the plasma.

Graphene Oxide saturable absorber for generating eye-safe Q-switched fiber laser

NASA Astrophysics Data System (ADS)

Rosol, A. H. A.; Jusoh, Z.; Rahman, H. A.; Rusdi, M. F. M.; Harun, S. W.; Latiff, A. A.

2017-06-01

This paper reports the generation of Q-switched fiber laser using thulium doped fiber (TDF) as a gain medium and graphene oxide (GO) as a saturable absorber (SA). The GO powder is embedded into polyvinyl alcohol (PVA) to form an SA film based on a drop-casting technique. GO-SA film is sandwiched between two fiber connectors and tighten by FC adapter before it is incorporated into an TDF laser cavity for Q-switching pulse generation. At 344 mW pump level, a stable Q-switching regime presence at 1943 nm with a 3-dB spectral bandwidth of 9 nm. The maximum repetition rate, pulse width, and pulse energy are at 25 kHz, 4.2 µs, and 0.68 µJ, respectively. All finding results are comparable with other reported pulse fiber lasers.

Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse

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

Xu Junjie; Zeng Bin; Yu Yongli

2010-11-15

We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecondmore » pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about 11 as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an 800-nm fundamental pulse and a 1600-nm subharmonic pulse is investigated.« less

Single mode wavelength control of modulated AlGaAs lasers with external and internal etalon feedback

NASA Technical Reports Server (NTRS)

Maynard, William L.

1989-01-01

Single mode lasing without mode hops has been obtained for VSIS and CSP laser diodes with an external etalon attached to the laser's front facet for up to an 8 C range CW and a 4 C range pulsed, with .07 nm/C tuning. Tests of thin tapered-thickness (TTT) laser diodes show CW and pulsed single mode lasing over 10 C and 2 C ranges, respectively, with .08 nm/C tuning. An analysis of the TTT structure reveals the equivalent of an internal etalon. The time-resolved pulsed behavior for both types of lasers show single mode lasing within the proper temperature ranges with minor modes present only early in the optical pulse, if at all. The external etalon produces noticeable interference fringes in the farfield pattern, while those of the TTT lasers are smooth. Ongoing CW lifetest results indicate stability to within one longitudinal mode after a few hundred hours of operation, along with at least several thousand hours lifetime.

Precision resection of intestine using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Beck, Rainer J.; Gora, Wojciech S.; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

2016-03-01

Endoscopic resection of early colorectal neoplasms typically employs electrocautery tools, which lack precision and run the risk of full thickness thermal injury to the bowel wall with subsequent perforation. We present a means of endoluminal colonic ablation using picosecond laser pulses as a potential alternative to mitigate these limitations. High intensity ultrashort laser pulses enable nonlinear absorption processes, plasma generation, and as a consequence a predominantly non-thermal ablation regimen. Robust process parameters for the laser resection are demonstrated using fresh ex vivo pig intestine samples. Square cavities with comparable thickness to early colorectal neoplasms are removed for a wavelength of 1030 nm and 515 nm using a picosecond laser system. The corresponding histology sections exhibit in both cases only minimal collateral damage to the surrounding tissue. The ablation depth can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers for the resection of intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional electrocautery.

Wide-band fanned-out supercontinuum source covering O-, E-, S-, C-, L- and U-bands

NASA Astrophysics Data System (ADS)

Ahmad, H.; Latif, A. A.; Awang, N. A.; Zulkifli, M. Z.; Thambiratnam, K.; Ghani, Z. A.; Harun, S. W.

2012-10-01

A wide-band supercontinuum source generated by mode-locked pulses injected into a Highly Non-Linear Fiber (HNLF) is proposed and demonstrated. A 49 cm long Bismuth-Erbium Doped Fiber (Bi-EDF) pumped by two 1480 nm laser diodes acts as the active gain medium for a ring fiber laser, from which mode-locked pulses are obtained using the Non-Polarization Rotation (NPR) technique. The mode-locked pulses are then injected into a 100 m long HLNF with a dispersion of 0.15 ps/nm km at 1550 nm to generate a supercontinuum spectrum spanning from 1340 nm to more than 1680 nm with a pulse width of 0.08 ps and an average power of -17 dBm. The supercontinuum spectrum is sliced using a 24 channel Arrayed Waveguide Grating (AWG) with a channel spacing of 100 GHz to obtain a fanned-out laser output covering the O-, E-, S-, C-, L- and U-bands. The lasing wavelengths obtained have an average pulse width of 9 ps with only minor fluctuations and a mode-locked repetition rate of 40 MHz, and is sufficiently stable to be used in a variety of sensing and communication applications, most notably as cost-effective sources for Fiber-to-the-Home (FTTH) networks.

Wavelength-tunable, sub-picosecond pulses from a passively Q-switched microchip laser system.

PubMed

Lehneis, R; Steinmetz, A; Limpert, J; Tünnermann, A

2013-07-15

We present a novel concept to generate sub-picosecond pulses from a passively Q-switched Nd:YVO4 microchip laser system with an adjustable wavelength shift up to a few tens of nanometers around the original emission wavelength of 1064 nm. This concept comprises two stages: one that carries out a nonlinear compression of fiber-amplified microchip pulses and a subsequent stage in which the compressed pulses are coupled into a further waveguide structure followed by a bandpass filter. In a proof-of-principle experiment, pedestal-free 0.62 ps long pulses have been demonstrated with a wavelength shift to 1045 nm.

Clean sub-8-fs pulses at 400 nm generated by a hollow fiber compressor for ultraviolet ultrafast pump-probe spectroscopy.

PubMed

Liu, Jun; Okamura, Kotaro; Kida, Yuichiro; Teramoto, Takahiro; Kobayashi, Takayoshi

2010-09-27

Clean 7.5 fs pulses at 400 nm with less than 3% energy in tiny satellite pulses were obtained by spectral broadening in a hollow fiber and dispersive compensating using a prism pair together with a deformable mirror system. As an example, this stable and clean pulse was used to study the ultrafast pump-probe spectroscopy of photoactive yellow protein. Moreover, the self-diffraction signal shows a smoothed and broadened laser spectrum and is expected to have a further clean laser pulse, which makes it more useful in the ultrafast pump-probe spectroscopy in the future.

Comprehensive description of the Orion laser facility

NASA Astrophysics Data System (ADS)

Hopps, Nicholas; Oades, Kevin; Andrew, Jim; Brown, Colin; Cooper, Graham; Danson, Colin; Daykin, Simon; Duffield, Stuart; Edwards, Ray; Egan, David; Elsmere, Stephen; Gales, Steve; Girling, Mark; Gumbrell, Edward; Harvey, Ewan; Hillier, David; Hoarty, David; Horsfield, Colin; James, Steven; Leatherland, Alex; Masoero, Stephen; Meadowcroft, Anthony; Norman, Michael; Parker, Stefan; Rothman, Stephen; Rubery, Michael; Treadwell, Paul; Winter, David; Bett, Thomas

2015-06-01

The Orion laser facility at the atomic weapons establishment (AWE) in the UK has been operational since April 2013, fielding experiments that require both its long and short pulse capability. This paper provides a full description of the facility in terms of laser performance, target systems and diagnostics currently available. Inevitably, this is a snapshot of current capability—the available diagnostics and the laser capability are evolving continuously. The laser systems consist of ten beams, optimised around 1 ns pulse duration, which each provide a nominal 500 J at a wavelength of 351 nm. There are also two short pulse beams, which each provide 500 J in 0.5 ps at 1054 nm. There are options for frequency doubling one short pulse beam to enhance the pulse temporal contrast. More recently, further contrast enhancement, based on optical parametric amplification (OPA) in the front end with a pump pulse duration of a few ps, has been installed. An extensive suite of diagnostics are available for users, probing the optical emission, x-rays and particles produced in laser-target interactions. Optical probe diagnostics are also available. A description of the diagnostics is provided.

Sodium temperature/wind lidar based on laser-diode-pumped Nd:YAG lasers deployed at Tromsø, Norway (69.6°N, 19.2°E).

PubMed

Kawahara, T D; Nozawa, S; Saito, N; Kawabata, T; Tsuda, T T; Wada, S

2017-06-12

An Nd:YAG laser-based sodium temperature/wind lidar was developed for the measurement of the northern polar mesosphere and lower thermosphere at Tromsø (69.6N, 19.2E), Norway. Coherent light at 589 nm is produced by sum frequency generation of 1064 nm and 1319 nm from two diode laser end-pumped pulsed Nd:YAG lasers. The output power is as high as 4W, with 4 mJ/pulse at 1000 Hz repetition rate. Five tilting Cassegrain telescopes enable us to make five-direction (zenith, north, south, east, west) observation for temperature and wind simultaneously. This highly stable laser system is first of its kind to operate virtually maintenance-free during the observation season (from late September to March) since 2010.

Generation of energetic femtosecond green pulses based on an OPCPA-SFG scheme.

PubMed

Mero, M; Sipos, A; Kurdi, G; Osvay, K

2011-05-09

Femtosecond green pulses were generated from broadband pulses centered at 800 nm and quasi-monochromatic pulses centered at 532 nm using noncollinear optical parametric chirped pulse amplification (NOPCPA) followed by sum frequency mixing. In addition to amplifying the 800-nm pulses, the NOPCPA stage pumped by a Q-switched, injection seeded Nd:YAG laser also provided broadband idler pulses at 1590 nm. The signal and idler pulses were sum frequency mixed using achromatic and chirp assisted phase matching yielding pulses near 530 nm with a bandwidth of 12 nm and an energy in excess of 200 μJ. The generated pulses were recompressed with a grating compressor to a duration of 150 fs. The technique is scalable to high energies, broader bandwidths, and shorter pulse durations with compensation for higher order chirps and dedicated engineering of the interacting beams. © 2011 Optical Society of America

Pulse-burst laser systems for fast Thomson scattering (invited)

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

Den Hartog, D. J.; Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706; Ambuel, J. R.

2010-10-15

Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinchmore » to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.« less

MoS2-based passively Q-switched diode-pumped Nd:YAG laser at 946 nm

NASA Astrophysics Data System (ADS)

Lin, Haifeng; Zhu, Wenzhang.; Xiong, Feibing; Cai, Lie

2017-06-01

We demonstrate a passively Q-switched Nd: YAG quasi-three-level laser operating at 946 nm using MoS2 as saturable absorber. A maximum average output power of 210 mW is achieved at an absorbed pump power of 6.67 W with a slope efficiency of about 5.8%. The shortest pulse width and maximum pulse repetition frequency are measured to be 280 ns and 609 kHz, respectively. The maximum pulse energy and maximum pulse peak power are therefore estimated to be about 0.35 μJ and 1.23 W, respectively. This work represents the first MoS2-based Q-switched laser operating at 0.9 μm spectral region.

Broadly wavelength tunable acousto-optically Q-switched Tm:Lu2SiO5 laser.

PubMed

Feng, T; Yang, K; Zhao, S; Zhao, J; Qiao, W; Li, T; Zheng, L; Xu, J

2014-09-20

A broadly wavelength tunable acousto-optically Q-switched Tm:Lu2SiO5 (Tm:LSO) laser is presented for the first time, to our best knowledge. The emission wavelength was tuned in a broad spectral region over 111 nm ranging from 1959 to 2070 nm. A shortest pulse duration of 345 ns with beam quality of M(2)≤1.65 was obtained at pulse repetition frequency (PRF) of 1 kHz, corresponding to a maximum single pulse energy of 0.26 mJ and peak power of 0.75 kW. The experimental results indicated that Tm:LSO crystal has outstanding potential for obtaining broadly wavelength tunable and low-PRF laser pulses at 2 μm.

Comparison between laser-induced photoemissions and phototransmission of hard tissues using fibre-coupled Nd:YAG and Er(3+)-doped fibre lasers.

PubMed

El-Sherif, Ashraf Fathy

2012-07-01

During pulsed laser irradiation of dental enamel, laser-induced photoemissions result from the laser-tissue interaction through mechanisms including fluorescence and plasma formation. Fluorescence induced by non-ablative laser light interaction has been used in tissue diagnosis, but the photoemission signal accompanying higher power ablative processes may also be used to provide real-time monitoring of the laser-tissue interaction. The spectral characteristics of the photoemission signals from normal and carious tooth enamel induced by two different pulsed lasers were examined. The radiation sources compared were a high-power extra-long Q-switched Nd:YAG laser operating at a wavelength of 1,066 nm giving pulses (with pulse durations in the range 200-250 μs) in the near infrared and a free-running Er(3+)-doped ZBLAN fibre laser operating at a wavelength near 3 μm with similar pulse durations in the mid-infrared region. The photoemission spectra produced during pulsed laser irradiation of enamel samples were recorded using a high-resolution spectrometer with a CCD array detector that enabled an optical resolution as high as 0.02 nm (FWHM). The spectral and time-dependence of the laser-induced photoemission due to thermal emission and plasma formation were detected during pulsed laser irradiation of hard tissues and were used to distinguish between normal and carious teeth. The use of these effects to distinguish between hard and soft biological tissues during photothermal ablation with a pulsed Nd:YAG laser or an Er fibre laser appears feasible. The real-time spectrally resolved phototransmission spectrum produced during pulsed Nd:YAG laser irradiation of human tooth enamel samples was recorded, with a (normalized) relative transmission coefficient of 1 (100%) for normal teeth and 0.6 (60%) for the carious teeth. The photoemission signal accompanying ablative events may also be used to provide real-time monitoring of the laser-tissue interaction.

Laser radiation at various wavelengths for decompression of intervertebral disk. Experimental observations on human autopsy specimens.

PubMed

Choy, D S; Altman, P A; Case, R B; Trokel, S L

1991-06-01

The interaction of laser radiation with the nucleus pulposus from autopsy specimens of human intervertebral disks was evaluated at different wavelengths (193 nm, 488 nm & 514 nm, 1064 nm, 1318 nm, 2150 nm, 2940 nm, and 10600 nm). A significant correlation of linear least squares fit of the mass ablated as a function of incident energy was found for all lasers used except the Excimer at 193 nm. The 2940-nm Erbium:YAG laser was most efficient in terms of mass of disk ablated per joule in the limited lower range where this wavelength was observed. At higher energy levels, the CO2 laser in the pulsed mode was most efficient. However, the Nd:YAG 1064-nm and 1318-nm lasers are currently best suited for percutaneous laser disk decompression because of the availability of usable waveguides. Carbonization of tissue with the more penetrating Nd:YAG 1064-nm laser increases the efficiency of tissue ablation and makes it comparable to the Nd:YAG 1318-nm laser.

The DUV Stability of Superlattice-Doped CMOS Detector Arrays

NASA Technical Reports Server (NTRS)

Hoenk, M. E.; Carver, A. G.; Jones, T.; Dickie, M.; Cheng, P.; Greer, H. F.; Nikzad, S.; Sgro, J.; Tsur, S.

2013-01-01

JPL and Alacron have recently developed a high performance, DUV camera with a superlattice doped CMOS imaging detector. Supperlattice doped detectors achieve nearly 100% internal quantum efficiency in the deep and far ultraviolet, and a single layer, Al2O3 antireflection coating enables 64% external quantum efficiency at 263nm. In lifetime tests performed at Applied Materials using 263 nm pulsed, solid state and 193 nm pulsed excimer laser, the quantum efficiency and dark current of the JPL/Alacron camera remained stable to better than 1% precision during long-term exposure to several billion laser pulses, with no measurable degradation, no blooming and no image memory at 1000 fps.

The OH + HBr reaction revisited

NASA Technical Reports Server (NTRS)

Ravishankara, A. R.; Wine, P. H.; Wells, J. R.

1985-01-01

Variable-temperature measurements of the rate coefficient /k(1)/ for the reaction OH + HBr yield Br + H2O are presented. The measurements are verified by two techniques: one involved a 266-nm pulsed-laser photolysis of O3/H2O/HBr/He mixtures in conjunction with time-resolved resonance fluorescence detection of OH, the second comprised pulsed laser-induced fluorescence detection of OH following 248-nm pulsed-laser photolysis of H2O2/HBr/Ar mixtures. It is reported that k(1) = (11.9 + or -1.4 x 10 to the -12th (cu cm)/(molecule)(s) independent of temperature. The measurements are compared with other available results.

Environmentally stable seed source for high power ultrafast laser

NASA Astrophysics Data System (ADS)

Samartsev, Igor; Bordenyuk, Andrey; Gapontsev, Valentin

2017-02-01

We present an environmentally stable Yb ultrafast ring oscillator utilizing a new method of passive mode-locking. The laser is using all-fiber architecture which makes it insensitive to environmental factors, like temperature, humidity, vibrations, and shocks. The new method of mode-locking is utilizing crossed bandpass transmittance filters in ring architecture to discriminate against CW lasing. Broadband pulse evolves from cavity noise under amplification, after passing each filter, causing strong spectral broadening. The laser is self-starting. It generates transform limited spectrally flat pulses of 1 - 50 nm width at 6 - 15 MHz repetition rate and pulse energy 0.2 - 15 nJ at 1010 - 1080 nm CWL.

Office-based 532-nm pulsed KTP laser treatment of glottal papillomatosis and dysplasia.

PubMed

Zeitels, Steven M; Akst, Lee M; Burns, James A; Hillman, Robert E; Broadhurst, Matthew S; Anderson, R Rox

2006-09-01

Treatment of glottal papillomatosis and dysplasia was mirror-guided and done in surgeons' offices in the 19th century. It migrated to the operating room in the 20th century to accommodate direct laryngoscopic surgery, which required assistants to administer anesthesia and procedural support. The primary treatment goals, which are disease regression and voice restoration and/or maintenance, are tempered by the morbidity of general anesthesia and potential treatment-induced vocal deterioration. To obviate general anesthesia, office-based laser laryngeal surgery was first done in 2001 with the 585-nm pulsed dye laser (PDL), because it employs a fiber delivery system and its energy is selectively absorbed by oxyhemoglobin. Since then, this new angiolytic laser treatment paradigm has become a mainstay of management for many surgeons; however, there are a number of shortcomings of the PDL. To further develop this concept and address the limitations of the PDL, we used a 532-nm pulsed potassium titanyl phosphate (KTP) laser. A prospective assessment was performed on 48 patients in 72 cases of recurrent glottal dysplasia (36) or papillomatosis (36). All individuals had previously undergone microlaryngoscopic management with histopathologic evaluation. Two dysplasia patients did not tolerate the procedure. Of the treatable dysplasia cases, there was follow-up in 29 of 34. Disease regression was at least 75% in 18 of 29 cases (62%), 50% to 75% in 7 of 29 (24%), and 25% to 50% in the remaining 4 of 29 (14%). Papilloma patients returned for treatment when symptoms recurred, so disease regression could not be assessed accurately. Similar to data obtained with the PDL, these data confirmed that dysplastic mucosa could normalize without resection. Our observations revealed that the 532-nm pulsed KTP laser provided enhanced performance over the PDL laser in a number of ways. The ability to use smaller glass fibers precluded mechanical trauma to the channels of the flexible laryngoscopes and allowed for improved suctioning of secretions. Oxyhemoglobin absorbs energy better at 532 nm than at 585 nm, and the KTP laser can be delivered through a longer pulse width. These factors provide enhanced hemostasis and improved intralesional energy absorbance. Finally, unlike the PDL, the KTP laser is a solid-state laser and is not prone to mechanical failure.

Femtosecond (191 fs) NaY(WO4)2 Tm,Ho-codoped laser at 2060 nm.

PubMed

Lagatsky, A A; Han, X; Serrano, M D; Cascales, C; Zaldo, C; Calvez, S; Dawson, M D; Gupta, J A; Brown, C T A; Sibbett, W

2010-09-15

We report, for the first time to our knowledge, femtosecond-pulse operation of a Tm,Ho:NaY(WO(4))(2) laser at around 2060 nm. Transform-limited 191 fs pulses are produced with an average output power of 82 mW at a 144 MHz pulse repetition frequency. Maximum output power of up to 155 mW is generated with a corresponding pulse duration of 258 fs. An ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror is used for passive mode-locking maintenance.

Energy transport in short-pulse-laser-heated targets measured using extreme ultraviolet laser backlighting.

PubMed

Wilson, L A; Tallents, G J; Pasley, J; Whittaker, D S; Rose, S J; Guilbaud, O; Cassou, K; Kazamias, S; Daboussi, S; Pittman, M; Delmas, O; Demailly, J; Neveu, O; Ros, D

2012-08-01

The accurate characterization of thermal electron transport and the determination of heating by suprathermal electrons in laser driven solid targets are both issues of great importance to the current experiments being performed at the National Ignition Facility, which aims to achieve thermonuclear fusion ignition using lasers. Ionization, induced by electronic heat conduction, can cause the opacity of a material to drop significantly once bound-free photoionization is no longer energetically possible. We show that this drop in opacity enables measurements of the transmission of extreme ultraviolet (EUV) laser pulses at 13.9 nm to act as a signature of the heating of thin (50 nm) iron layers with a 50-nm thick parylene-N (CH) overlay irradiated by 35-fs pulses at irradiance 3×10(16) Wcm(-2). Comparing EUV transmission measurements at different times after irradiation to fluid code simulations shows that the target is instantaneously heated by hot electrons (with approximately 10% of the laser energy), followed by thermal conduction with a flux limiter of ≈0.05.

Electronically tunable femtosecond all-fiber optical parametric oscillator for multi-photon microscopy

NASA Astrophysics Data System (ADS)

Hellwig, Tim; Brinkmann, Maximilian; Fallnich, Carsten

2018-02-01

We present a femtosecond fiber-based optical parametric oscillator (FOPO) for multiphoton microscopy with wavelength tuning by electronic repetition rate tuning in combination with a dispersive filter in the FOPO cavity. The all-spliced, all-fiber FOPO cavity is based on polarization-maintaining fibers and a broadband output coupler, allowing to get access to the resonant signal pulses as well as the idler pulses simultaneously. The system was pumped by a gain-switched fiber-coupled laser diode emitting pulses at a central wavelength of 1030 nm and an electronically tunable repetition frequency of about 2 MHz. The pump pulses were amplified in an Ytterbium fiber amplifier system with a pulse duration after amplification of 13 ps. Tuning of the idler (1140 nm - 1300 nm) and signal wavelengths (850 nm - 940 nm) was achieved by changing the repetition frequency of the pump laser by about 4 kHz. The generated signal pulses reached a pulse energy of up to 9.2 nJ at 920 nm and were spectrally broadened to about 6 nm in the FOPO by a combination of self-phase and cross-phase modulation. We showed external compression of the idler pulses at 920 nm to about 430 fs and appleid them to two-photon excitation microscopy with green fluorescent dyes. The presented system constitutes an important step towards a fully fiber-integrated all-electronically tunable and, thereby, programmable light source and already embodies a versatile and flexible light source for applications, e.g., for smart microscopy.

Micro-scale patterning of indium tin oxide film by spatially modulated pulsed Nd:YAG laser beam

NASA Astrophysics Data System (ADS)

Lee, Jinsoo; Kim, Seongsu; Lee, Myeongkyu

2012-09-01

Here we demonstrate that indium tin oxide (ITO) films deposited on glass can be directly patterned by a spatially -modulated pulsed Nd-YAG laser beam (wavelength = 1064 nm, pulse width = 6 ns) incident onto the film. This method utilizes a pulsed laser-induced thermo-elastic force exerting on the film which plays a role to detach it from the substrate. Sharp-edged clean patterns with feature size as small as 4 μm could be obtained. The threshold pulse energy density for patterning was estimated to be ˜0.8 J/cm2 for 150 nm-thick ITO film, making it possible to pattern over one square centimeter by a single pulse with energy of 850 mJ. Not only being free from photoresist and chemical etching steps, the presented method can also provide much higher throughput than the tradition photoablation process utilizing a tightly focused beam.

Cleaning of copper traces on circuit boards with excimer laser radiation

NASA Astrophysics Data System (ADS)

Wesner, D. A.; Mertin, M.; Lupp, F.; Kreutz, E. W.

1996-04-01

Cleaning of Cu traces on circuit boards is studied using pulsed excimer laser radiation (pulse width ˜ 20 ns, wavelength 248 nm), with the goal of improving the properties of the Cu surface for soldering and bonding. Traces with well-defined oxide overlayers are cleaned by irradiation in air using ≤ 10 3 laser pulses at fluences per pulse of ≤ 2 J cm -2. After treatment the surface morphology is analyzed using optical microscopy, optical profilometry, and scanning electron microscopy, while the chemical state of the surface is investigated with X-ray photoelectron (XPS) spectroscopy. Ellipsometry is used to determine the oxide overlayer thickness. Prior to cleaning samples exhibit a contamination overlayer about 15-25 nm in thickness containing Cu 2O and C. Cleaning reduces the overlayer thickness to ≤ 10 nm by material removal. The process tends to be self-limiting, since the optical reflectivity of the oxidized Cu surface for laser radiation is smaller than that of the cleaned surface. Additionally, the interaction with the laser radiation results in surface segregation of a minor alloy component out of the bulk (e.g. Zn), which may help to passivate the surface for further chemical reactions.

Femtosecond optical parametric amplification in BBO and KTA driven by a Ti:sapphire laser for LIDT testing and diagnostic development

NASA Astrophysics Data System (ADS)

Meadows, Alexander R.; Cupal, Josef; Hříbek, Petr; Durák, Michal; Kramer, Daniel; Rus, Bedřich

2017-05-01

We present the design of a collinear femtosecond optical parametric amplification (OPA) system producing a tunable output at wavelengths between 1030 nm and 1080 nm from a Ti:Sapphire pump laser at a wavelength of 795 nm. Generation of a supercontinuum seed pulse is followed by one stage of amplification in Beta Barium Borate (BBO) and two stages of amplification in Potassium Titanyle Arsenate (KTA), resulting in a 225 μJ output pulse with a duration of 90 fs. The output of the system has been measured by self-referenced spectral interferometry to yield the complete spectrum and spectral phase of the pulse. When compared to KTP, the greater transparency of KTA in the spectral range from 3 - 4 μm allows for reduced idler absorption and enhanced gain from the OPA process when it is pumped by the fundamental frequency of a Ti:sapphire laser. In turn, the use of the Ti:sapphire fundamental at 795 nm as a pump improves the efficiency with which light can be converted to wavelengths between 1030 nm and 1080 nm and subsequently used to test components for Nd-based laser systems. This OPA system is operated at 1 kHz for diagnostic development and laser-induced damage threshold testing of optical components for the ELI-Beamlines project.

Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

NASA Astrophysics Data System (ADS)

Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

Stable room-temperature LiF:F2+* tunable color-center laser for the 830-1060-nm spectral range pumped by second-harmonic radiation from a neodymium laser

NASA Astrophysics Data System (ADS)

Ter-Mikirtychev, V. V.

1995-09-01

Simultaneous photostability and thermostability of a room-temperature LiF:F2+ * tunable color-center laser, with an operating range over 830-1060 nm, pumped by second-harmonic radiation of a YAG:Nd3+ laser with a 532-nm wavelength has been achieved. The main lasing characteristics of the obtained LiF:F2+* laser have been measured. Twenty-five percent real efficiency in a nonselective resonator cavity and 15% real efficiency in a selective resonator cavity have been obtained. The stable LiF:F2 +* laser operates at a 1-100-Hz pulse-repetition rate with a 15-ns pulse duration, a 1-1.5-cm-1 narrow-band oscillation bandwidth, and divergency of better than 6 \\times 10-4. Doubling the fundamental frequencies of F2+ * oscillation made it possible to obtain stable blue-green tunable radiation over the 415-530-nm range.

Laser-diode pumped self-mode-locked praseodymium visible lasers with multi-gigahertz repetition rate.

PubMed

Zhang, Yuxia; Yu, Haohai; Zhang, Huaijin; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

2016-06-15

We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr³⁺) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr³⁺-doped GdLiF₄ crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range.

Magnetic field effects on ultrafast lattice compression dynamics of Si(111) crystal when excited by linearly-polarized femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Hatanaka, Koji; Odaka, Hideho; Ono, Kimitoshi; Fukumura, Hiroshi

2007-03-01

Time-resolved X-ray diffraction measurements of Si (111) single crystal are performed when excited by linearly-polarized femtosecond laser pulses (780 nm, 260 fs, negatively-chirped, 1 kHz) under a magnetic field (0.47 T). Laser fluence on the sample surface is 40 mJ/cm^2, which is enough lower than the ablation threshold at 200 mJ/cm^2. Probing X-ray pulses of iron characteristic X-ray lines at 0.193604 and 0.193998 nm are generated by focusing femtosecond laser pulses onto audio-cassette tapes in air. Linearly-polarized femtosecond laser pulse irradiation onto Si(111) crystal surface induces transient lattice compression in the picosecond time range, which is confirmed by transient angle shift of X-ray diffraction to higher angles. Little difference of compression dynamics is observed when the laser polarization is changed from p to s-pol. without a magnetic field. On the other hand, under a magnetic field, the lattice compression dynamics changes when the laser is p-polarized which is vertical to the magnetic field vector. These results may be assigned to photo-carrier formation and energy-band distortion.

DiPOLE: a 10 J, 10 Hz cryogenic gas cooled multi-slab nanosecond Yb:YAG laser.

PubMed

Banerjee, Saumyabrata; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; De Vido, Mariastefania; Smith, Jodie M; Butcher, Thomas J; Hernandez-Gomez, Cristina; Greenhalgh, R Justin S; Collier, John L

2015-07-27

The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.

Pulse generation without gain-bandwidth limitation in a laser with self-similar evolution.

PubMed

Chong, A; Liu, H; Nie, B; Bale, B G; Wabnitz, S; Renninger, W H; Dantus, M; Wise, F W

2012-06-18

With existing techniques for mode-locking, the bandwidth of ultrashort pulses from a laser is determined primarily by the spectrum of the gain medium. Lasers with self-similar evolution of the pulse in the gain medium can tolerate strong spectral breathing, which is stabilized by nonlinear attraction to the parabolic self-similar pulse. Here we show that this property can be exploited in a fiber laser to eliminate the gain-bandwidth limitation to the pulse duration. Broad (∼200 nm) spectra are generated through passive nonlinear propagation in a normal-dispersion laser, and these can be dechirped to ∼20-fs duration.

Pulsed lasers in dentistry: sense or nonsense?

NASA Astrophysics Data System (ADS)

Koort, Hans J.; Frentzen, Matthias

1991-05-01

The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C02-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser radiation the Er:YAG-laser radiation could also only be delivered via mirror systems, while the radiation of the Ho:YAG-Laser can be well transmitted through quartz fibers. The energy of the well known and in other medical disciplines often used Nd:YAG - laser (1,064 μm, pulse duration 150 us) laser can be transmitted through fiber systems without problems, but this laser has not the effectivity to work sufficient on healthy hard dental tissues due to the high transmission in mineralized dental tissues. The thermal injuries of this laser type are not tolerable. The short pulsed TEA-C02-laser (9,6 and 10,6 μm, pulse duration 200-300 ns), which has an excellent coupling not only to the hydrogeneous tissues but also to the mineralized tissues could be an alternative system to prepare dental tissues. The greatest disadvantage of this system is the noneffective delivery of the light energy through flexible fiber systems, which are still in development. Another good chance perhaps will have the q-switched Neodym, Erbium and Holmium:- YAG lasers with pulse durations of about some hundred ns. Both, possible thermal influences and possible disruptive effects should be small enough to let the adjacent tissues undamaged.

Lasers Induced Damage in Optical Materials: 1985. Proceedings of the Symposium on Optical Materials for High-Power Lasers (17th) Held in Boulder, Colorado on October 28-30, 1985

DTIC Science & Technology

1988-07-01

optical coatings.[lj In * single and multilayer anatase TiO 2 coatings, sufficiently intense pulsed laser irradiation at 532 nm led to observation of...temperatures of pulsed laser - irradiated anatase coatings have been computed from Stokes/anti-Stokes band intensity ratios at zero time delay as a function of...Adar Time-Resolved Temperature Determinations from Raman Scattering of TiO𔃼 Coatings During Pulsed Laser Irradiation

Nanoshell-mediated targeted photothermal therapy of HER2 human breast cancer cells using pulsed and continuous wave lasers: an in vitro study.

PubMed

Khosroshahi, Mohammad E; Hassannejad, Zahra; Firouzi, Masoumeh; Arshi, Ahmad R

2015-09-01

In this study, we report the apoptosis induction in HER2 overexpressed breast cancer cells using pulsed, continuous wave lasers and polyvinylpyrrolidone (PVP)-stabilized magneto-plasmonic nanoshells (PVP-MPNS) delivered by immunoliposomes. The immunoliposomes containing PVP-MPNS were fabricated and characterized. Heating efficiency of the synthesized nanostructures was calculated. The effect of functionalization on cellular uptake of nanoparticles was assessed using two cell lines of BT-474 and Calu-6. The best uptake result was achieved by functionalized liposome (MPNS-LAb) and BT-474. Also, the interaction of 514 nm argon (Ar) and Nd/YAG second harmonic 532-nm lasers with nanoparticles was investigated based on the temperature rise of the nanoshell suspension and the release value of 5(6)-carboxyfluorescein (CF) from CF/MPNS-loaded liposomes. The temperature increase of the suspensions after ten consecutive pulses of 532 nm and 5 min of irradiation by Ar laser were measured approximately 2 and 12 °C, respectively. The irradiation of CF/MPNS-loaded liposomes by Ar laser for 3 min resulted in 24.3 % release of CF, and in the case of 532 nm laser, the release was laser energy dependent. Furthermore, the comparison of CF release showed a higher efficiency for the Ar laser than by direct heating of nanoshell suspension using circulating water. The percentage of cell apoptosis after irradiation by Ar and 532 nm lasers were 44.6 and 42.6 %, respectively. The obtained results suggest that controlling the NP-laser interaction using optical properties of nanoshells and the laser parameters can be used to develop a new cancer therapy modality via targeted nanoshell and drug delivery.

Emulsions for pulsed holography: new and improved processing schemes

NASA Astrophysics Data System (ADS)

Rodin, Alexey M.; Taylor, Rob

2003-05-01

Recent improvements in the processing of commercially available holographic recording materials for pulsed holography are reviewed. Harmonics of pulsed Nd:YLF/Nd:Phosphate Glass, Nd:YLF, Nd:YAG laser's, and the fundamental wavelength of a pulsed Ruby laser were used as radiation sources for the recording of transmission and reflection holography gratings. It is shown that ultra-fine grain size materials such as PFG-03C and Ultimate-15 can be successfully applied for small and medium format pulsed holography applications. These small grain size emulsions are especially important in the areas of artistic archival portraiture and contact Denisyuk micro-holography of living objects, where noiseless image reconstruction is of a primary concern. It suggests that HOE's, such as full-color image projection screens, may be successfully recorded on PFG-03C holographic emulsions using a pulsed RGB laser. A range of commercial RGB pulsed lasers suitable for these applications are introduced. Visible wavelengths currently produced from these lasers covers the spectrum of 440 - 660nm. Latest developments of a full range of pulsed holographic camera systems manufactured by GEOLA that are suitable for medium and large format portraiture, medical imaging, museum artifact archival recording, and other types of holography are also reviewed with particular reference to new integrated digital mastering features. Finally, the initial commercial production of a new photopolymer film with a sensitivity range of 625-680nm is introduced. Initial CW exposure energies at 633nm were 30 - 50mJ/cm2; with diffraction efficiencies of 75 - 80% observed with this new material.

Superior local conductivity in self-organized nanodots on indium-tin-oxide films induced by femtosecond laser pulses.

PubMed

Wang, Chih; Wang, Hsuan-I; Tang, Wei-Tsung; Luo, Chih-Wei; Kobayashi, Takayoshi; Leu, Jihperng

2011-11-21

Large-area surface ripple structures of indium-tin-oxide films, composed of self-organized nanodots, were induced by femtosecond laser pulses, without scanning. The multi-periodic spacing (~800 nm, ~400 nm and ~200 nm) was observed in the laser-induced ripple of ITO films. The local conductivity of ITO films is significantly higher, by approximately 30 times, than that of the as-deposited ITO films, due to the formation of these nanodots. Such a significant change can be ascribed to the formation of indium metal-like clusters, which appear as budges of ~5 nm height, due to an effective volume increase after breaking the In-O to form In-In bonding. © 2011 Optical Society of America

Pulsed laser deposition to synthesize the bridge structure of artificial nacre: Comparison of nano- and femtosecond lasers

NASA Astrophysics Data System (ADS)

Melaibari, Ammar A.; Molian, Pal

2012-11-01

Nature offers inspiration to new adaptive technologies that allow us to build amazing shapes and structures such as nacre using synthetic materials. Consequently, we have designed a pulsed laser ablation manufacturing process involving thin film deposition and micro-machining to create hard/soft layered "brick-bridge-mortar" nacre of AlMgB14 (hard phase) with Ti (soft phase). In this paper, we report pulsed laser deposition (PLD) to mimic brick and bridge structures of natural nacre in AlMgB14. Particulate formation inherent in PLD is exploited to develop the bridge structure. Mechanical behavior analysis of the AlMgB14/Ti system revealed that the brick is to be 250 nm thick, 9 μm lateral dimensions while the bridge (particle) is to have a diameter of 500 nm for a performance equivalent to natural nacre. Both nanosecond (ns) and femtosecond (fs) pulsed lasers were employed for PLD in an iterative approach that involves varying pulse energy, pulse repetition rate, and target-to-substrate distance to achieve the desired brick and bridge characteristics. Scanning electron microscopy, x-ray photoelectron spectroscopy, and optical profilometer were used to evaluate the film thickness, particle size and density, stoichiometry, and surface roughness of thin films. Results indicated that both ns-pulsed and fs-pulsed lasers produce the desired nacre features. However, each laser may be chosen for different reasons: fs-pulsed laser is preferred for much shorter deposition time, better stoichiometry, uniform-sized particles, and uniform film thickness, while ns-pulsed laser is favored for industrial acceptance, reliability, ease of handling, and low cost.

Laser at 532 nm by intracavity frequency-doubling in BBO

NASA Astrophysics Data System (ADS)

Yuan, Xiandan; Wang, Jinsong; Chen, Yongqi; Wu, Yulong; Qi, Yunfei; Sun, Meijiao; Wang, Qi

2017-06-01

A simple and compact linear resonator green laser at 532 nm is generated by intracavity frequency-doubling of a diode-side-pumped acousto-optically (AO) Q-switched Nd:YAG laser at 1064 nm. Two acousto-optic Q-switches were placed orthogonally with each other to improve the hold-off capacity. As high as 214 W of continuous-wave (CW) and 154 W of quasi-continuous-wave (QCW) output power at 1064 nm were obtained when the pumping power was 1598 W. The type I phase-matched BBO crystal was used as the nonlinear medium in the second harmonic generation. A green laser with an average output power of 37 W was obtained at a repetition rate of 20 kHz and a pulse width of 54 ns, which corresponds to pulse energy of 1.85 mJ per pulse and a peak power 34.26 kW, respectively. Project supported by the Beijing Engineering Technology Research Center of All-Solid-State Lasers Advanced Manufacturing, the National High Technology Research and Development Program of China (No. 2014AA032607), and the National Natural Science Foundation of China (Nos. 61404135, 61405186, 61308032, 61308033).

Graphene-PVA saturable absorber for generation of a wavelength-tunable passively Q-switched thulium-doped fiber laser in 2.0 µm

NASA Astrophysics Data System (ADS)

Ahmad, H.; Samion, M. Z.; Sharbirin, A. S.; Norizan, S. F.; Aidit, S. N.; Ismail, M. F.

2018-05-01

Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding.

An expanded study of long-pulsed 1064 nm Nd:YAG laser treatment of basal cell carcinoma.

PubMed

Ortiz, Arisa E; Anderson, R Rox; DiGiorgio, Catherine; Jiang, Shang I Brian; Shafiq, Faiza; Avram, Mathew M

2018-02-13

Basal cell carcinoma (BCC) is an indolent form of skin cancer that is rarely life threatening, but can cause significant cosmetic and functional morbidity. Surgical treatments often result in disfiguring scars, while topical therapies frequently result in recurrence. The need for a more effective nonsurgical alternative has led to the investigation of laser treatment of BCC. We have previously conducted a pilot study which showed 100% histologic clearance at high fluences. Treatments were well tolerated with no significant adverse events. The objective of this larger study was to confirm preliminary results that the 1064 nm Nd:YAG laser is a safe and effective method for treating non-facial BCC. This is an IRB-approved, prospective, multi-center study evaluating the safety and efficacy of the 1064 nm Nd:YAG laser for the treatment of BCC on the trunk and extremities. Thirty-three subjects seeking treatment for biopsy-proven BCC that did not meet the criteria for Mohs surgery were recruited. Subjects on current anticoagulation therapy, or with a history of immunosuppression were excluded. Subjects received one treatment with the 1064 nm Nd:YAG laser as follows: 5-6 mm spot, fluence of 125-140 J/cm 2 and a pulse duration of 7-10 ms. Standard excision with 5 mm clinical margins was performed at 30 days after laser treatment to evaluate clinical and histologic clearance of BCC. Standardized photographs and adverse assessments were taken at the baseline visit, immediately after laser treatment and on the day of excision. Thirty-one subjects completed the study. BCC tumors had a 90% (28 of 31 BCC tumors) histologic clearance rate after one treatment with the long-pulsed 1064 nm Nd:YAG laser. Treatments were generally well tolerated without any anesthesia. Immediate side effects included edema and erythema. At 1-month follow-up, some patients had residual crusting. No significant adverse events occurred. The 1064 nm long-pulsed Nd:YAG laser is an alternative for treating non-facial BCC for those that are poor surgical candidates. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

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

NASA Astrophysics Data System (ADS)

Salim, Ali Aqeel; Bidin, Noriah

2017-12-01

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

Fiber-optic manipulation of urinary stone phantoms using holmium:YAG and thulium fiber lasers

NASA Astrophysics Data System (ADS)

Blackmon, Richard L.; Case, Jason R.; Trammell, Susan R.; Irby, Pierce B.; Fried, Nathaniel M.

2013-02-01

Fiber-optic attraction of urinary stones during laser lithotripsy may be exploited to manipulate stone fragments inside the urinary tract without mechanical grasping tools, saving the urologist time and space in the ureteroscope working channel. We compare thulium fiber laser (TFL) high pulse rate/low pulse energy operation to conventional holmium:YAG low pulse rate/high pulse energy operation for fiber-optic suctioning of plaster-of-paris (PoP) stone phantoms. A TFL (wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10 to 350 Hz) and a holmium laser (wavelength of 2120 nm, pulse energy of 35 to 360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz) were tested using 270-μm-core optical fibers. A peak drag speed of ˜2.5 mm/s was measured for both TFL (35 mJ and 150 to 250 Hz) and holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber-optic suctioning of urinary stone phantoms is feasible. TFL operation at high pulse rates/low pulse energies is preferable to holmium operation at low pulse rates/high pulse energies for rapid and smooth stone pulling. With further development, this novel technique may be useful for manipulating stone fragments in the urinary tract.

Pulsed laser-induced damage of metals at 492 nm.

PubMed

Marrs, C D; Faith, W N; Dancy, J H; Porteus, J O

1982-11-15

A triaxial flashlamp-pumped dye laser has been used to perform laser damage testing of metal surfaces in the blue-green spectral region. Using LD490 laser dye, the laser produces 0.18-J, 0.5-microsec pulses at 492 nm. The spatial profile of the focused beam is measured in orthogonal directions in the plane of the sample surface. The orthogonal profiles are flat-topped Gaussians with 1/e(2) widths of 270 microm. Multithreshold laser damage test results are presented for polished Mo, diamond-turned high-purity Al alloy, diamond-turned bulk Cu, and diamond-turned electrodeposits of Ag and Au on Cu. Comparisons are made between calculated and experimentally measured slip and melt thresholds.

Optimizing laser crater enhanced Raman spectroscopy.

PubMed

Lednev, V N; Sdvizhenskii, P A; Grishin, M Ya; Filichkina, V A; Shchegolikhin, A N; Pershin, S M

2018-03-20

Raman signal enhancement by laser crater production was systematically studied for 785 nm continuous wave laser pumping. Laser craters were produced in L-aspartic acid powder by a nanosecond pulsed solid state neodymium-doped yttrium aluminum garnet laser (532 nm, 8 ns, 1 mJ/pulse), while Raman spectra were then acquired by using a commercial spectrometer with 785 nm laser beam pumping. The Raman signal enhancement effect was studied in terms of the number of ablating pulses used, the lens-to-sample distance, and the crater-center-laser-spot offset. The influence of the experiment parameters on Raman signal enhancement was studied for different powder materials. Maximum Raman signal enhancement reached 11 fold for loose powders but decreased twice for pressed tablets. Raman signal enhancement was demonstrated for several diverse powder materials like gypsum or ammonium nitrate with better results achieved for the samples tending to give narrow and deep craters upon the laser ablation stage. Alternative ways of cavity production (steel needle tapping and hole drilling) were compared with the laser cratering technique in terms of Raman signal enhancement. Drilling was found to give the poorest enhancement of the Raman signal, while both laser ablation and steel needle tapping provided comparable results. Here, we have demonstrated for the first time, to the best of our knowledge, that a Raman signal can be enhanced 10 fold with the aid of simple cavity production by steel needle tapping in rough highly reflective materials. Though laser crater enhancement Raman spectroscopy requires an additional pulsed laser, this technique is more appropriate for automatization compared to the needle tapping approach.

Self-induced laser line sweeping and self-pulsing in double-clad fiber lasers in Fabry-Perot and unidirectional ring cavities

NASA Astrophysics Data System (ADS)

Peterka, Pavel; Navrátil, Petr; Dussardier, Bernard; Slavík, Radan; Honzátko, Pavel; Kubecek, Václav

2012-06-01

Rare-earth doped fiber lasers are subject to instabilities and various self-pulsed regimes that can lead to catastrophic damage of their components. An interesting self-pulsing regime accompanied with laser wavelength drift with time is the so called self-induced laser line sweeping (SLLS). Despite the early observations of the SLLS in solid-state ruby lasers, in fiber lasers it was first time mentioned in literature only in 2009 where such a laser wavelength drift with time was observed in a relatively broad range of about 1076 -1084 nm in ring ytterbium-doped fiber laser (YDFL). The main characteristic of the SLLS is the scanning of the laser wavelength from shorter to longer wavelength, spanning over large interval of several nanometers, and instantaneous bounce backward. The period of this sweeping is usually quite long, of the order of seconds. This spectacular effect was attributed to spatial-hole burning caused by standing-wave in the laser cavity. In this paper we present experimental investigation of the SLLS in YDFLs in Fabry-Perot cavity and ring cavities. The SLLS was observed also in erbium-doped fiber laser around 1560 nm. We present for the first time observation of the laser wavelength sweep in reverse direction, i.e., from longer towards shorter wavelengths. It was observed in YDFL around 1080 nm.

Limiting of microjoule femtosecond pulses in air-guided modes of a hollow photonic-crystal fiber

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

Konorov, S.O.; Serebryannikov, E.E.; Sidorov-Biryukov, D.A.

Self-phase-modulation-induced spectral broadening of laser pulses in air-guided modes of hollow photonic-crystal fibers (PCFs) is shown to allow the creation of fiber-optic limiters for high-intensity ultrashort laser pulses. The performance of PCF limiters is analyzed in terms of elementary theory of self-phase modulation. Experiments performed with 100 fs microjoule pulses of 800 nm Ti:sapphire laser radiation demonstrate the potential of hollow PCFs as limiters for 10 MW ultrashort laser pulses and show the possibility to switch the limiting level of output radiation energy by guiding femtosecond pulses in different PCF modes.

Studies on the optogalvanic effect and isotope-selective excitation of ytterbium in a hollow cathode discharge lamp using a pulsed dye laser.

PubMed

Kumar, Pankaj; Kumar, Jitendra; Prakash, Om; Saini, Vinod K; Dixit, Sudhir K; Nakhe, Shankar V

2013-09-01

This paper presents studies on the pulsed optogalvanic effect and isotope-selective excitation of Yb 555.648 nm (0 cm(-1) → 17 992.007 cm(-1)) and 581.067 nm (17 992.007 cm(-1) → 35 196.98 cm(-1)) transitions, in a Yb/Ne hollow cathode lamp. The Yb atoms were excited by narrow linewidth (500-1000 MHz) Rh110 and Rh6G dye based pulsed lasers. Optogalvanic signal inversion for ground state transition at 555.648 nm was observed beyond a hollow cathode discharge current of 8.5 mA, in contrast to normal optogalvanic signal at 581.067 nm up to maximum current of 14 mA. The isotope-selective excitation studies of Yb were carried out by recording Doppler limited optogalvanic signals as a function of dye laser wavelength. For the 581.067 nm transition, three even isotopes, (172)Yb, (174)Yb, and (176)Yb, and one odd isotope, (171)Yb, were clearly resolved. These data were compared with selective isotope excitation by 10 MHz linewidth continuous-wave dye laser. For 555.648 nm transition, isotopes were not clearly resolved, although isotope peaks of low modulation were observed.

Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

PubMed

Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

2001-09-15

We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long.

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

Bierbach, Jana; Yeung, Mark; Eckner, Erich

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·1019 W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generationmore » becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.« less

Comparison of holmium:YAG and thulium fiber laser lithotripsy: ablation thresholds, ablation rates, and retropulsion effects.

PubMed

Blackmon, Richard L; Irby, Pierce B; Fried, Nathaniel M

2011-07-01

The holmium:YAG (Ho:YAG) laser lithotriptor is capable of operating at high pulse energies, but efficient operation is limited to low pulse rates (∼10 Hz) during lithotripsy. On the contrary, the thulium fiber laser (TFL) is limited to low pulse energies, but can operate efficiently at high pulse rates (up to 1000 Hz). This study compares stone ablation threshold, ablation rate, and retropulsion for the two different Ho:YAG and TFL operation modes. The TFL (λ = 1908 nm) was operated with pulse energies of 5 to 35 mJ, 500-μs pulse duration, and pulse rates of 10 to 400 Hz. The Ho:YAG laser (λ = 2120 nm) was operated with pulse energies of 30 to 550 mJ, 350-μs pulse duration, and a pulse rate of 10 Hz. Laser energy was delivered through 200- and 270-μm-core optical fibers in contact mode with human calcium oxalate monohydrate (COM) stones for ablation studies and plaster-of-Paris stone phantoms for retropulsion studies. The COM stone ablation threshold for Ho:YAG and TFL measured 82.6 and 20.8 J∕cm(2), respectively. Stone retropulsion with the Ho:YAG laser linearly increased with pulse energy. Retropulsion with TFL was minimal at pulse rates less than 150 Hz, then rapidly increased at higher pulse rates. For minimal stone retropulsion, Ho:YAG operation at pulse energies less than 175 mJ at 10 Hz and TFL operation at 35 mJ at 100 Hz is recommended, with both lasers producing comparable ablation rates. Further development of a TFL operating with both high pulse energies of 100 to 200 mJ and high pulse rates of 100 to 150 Hz may also provide an alternative to the Ho:YAG laser for higher ablation rates, when retropulsion is not a primary concern.

Q-switched and mode-locked Er{sup 3+}-doped fibre laser using a single-multi-single fibre filter and piezoelectric

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

Ji Wang; Yunjun Zhang; Aotuo Dong

2014-04-28

The active Q-switched and passive mode-locked Er{sup 3+}-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energymore » is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64–68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses. (lasers)« less

Comparison of the antimicrobial efficacy of photodynamic therapy with two mediators against Lactobacillus acidophilus in vitro.

PubMed

Azizi, Arash; Mousavian, Shiva; Taheri, Soudabeh; Lawaf, Shirin; Gonoudi, Elnaz; Rahimi, Arash

2018-03-01

Lactobacillus is a cariogenic microorganism. Different therapeutic approaches including photodynamic therapy (PDT) have been suggested for treatment of bacterial infection. The purpose of the current study was to compare the effects of PDT with Indocyanine green (ICG) and Methylene blue (MB) photosensitizers (PSs) on Lactobacillus acidophilus (L. acidophilus). In this in-vitro experimental study, 84 samples of L. acidophilus (1 McFarland standard) were compared in 14 experimental groups including: MB, ICG, 660-nm laser, 808-nm laser (pulsed, 74s/continuous-wave, 37s), different combinations of lasers and PSs, Chlorhexidine (CHX) 0.2%, sodium hypochlorite (NaOCl) 2.5%, penicillin 6.3.3 and control groups. The samples were cultured in microplates containing blood agar culture medium. After incubation at 37 °C for 48 h, the colony forming units (CFUs) of L. acidophilus were counted and compared before and after therapeutic interventions. Data were analyzed using SPSS19 software program according to one-way ANOVA test. This study showed that the separate use of ICG, 660- and 808-nm lasers (pulsed, 74s/continuous-wave, 37s), and the combined use of 808-nm laser (pulsed, 74s/continuous-wave, 37s) and ICG have no significant inhibitory effect on L. acidophilus colonies (P > 0.05), whereas the separate use of MB and the combined use of 660-nm laser (continuous-wave, 37s/pulsed, 74s) and MB significantly inhibited the growth of L. acidophilus in comparison with the control group (p < 0.05). Likewise, CHX 0.2%, NaOCl 2.5% and penicillin 6.3.3 significantly inhibited the bacterial growth (p < 0.05). The results showed that separate use of MB and combined use of 660-nm laser and MB have a significant inhibitory effect on L. acidophilus growth. Copyright © 2018 Elsevier B.V. All rights reserved.

Rapid vaporization of kidney stones, ex vivo, using a Thulium fiber laser at pulse rates up to 500 Hz with a stone basket

NASA Astrophysics Data System (ADS)

Hardy, Luke A.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

2014-03-01

The Holmium:YAG laser (λ = 2120 nm) is currently the preferred laser for fragmenting kidney stones in the clinic. However, this laser has some limitations, including operation at low pulse rates and a multimode spatial beam profile which prohibits its use with smaller, more flexible optical fibers. Our laboratory is studying the Thulium fiber laser (λ = 1908 nm) as an alternative lithotripter. The TFL has several advantages, including lower stone ablation thresholds, use with smaller and more flexible fibers, and operation at arbitrary pulse lengths and pulse rates. Previous studies have reported increased stone ablation rates with TFL operation at higher pulse rates, however, stone retropulsion remains an obstacle to even more efficient stone ablation. This study explores TFL operation at high pulse rates in combination with a stone stabilization device (e.g. stone basket) for improved efficiency. A TFL beam with pulse energy of 35 mJ, pulse duration of 500-μs, and pulse rates of 10-500 Hz was coupled into 100-μm-core, low-OH, silica fibers, in contact mode with uric acid and calcium oxalate monohydrate stones, ex vivo. TFL operation at 500 Hz produced UA and COM stone ablation rates up to 5.0 mg/s and 1.3 mg/s, respectively. High TFL pulse rates produced increased stone ablation rates sufficient for use in the clinic.

Single-treatment skin tightening by radiofrequency and long-pulsed, 1064-nm Nd: YAG laser compared.

PubMed

Key, Douglas J

2007-02-01

To compare single-treatment facial skin tightening achieved with the current radiofrequency (RF) protocol with single-treatment tightening achieved with the long-pulsed, 1064-nm Nd:YAG laser. A total of 12 patients were treated with RF energy on one side of the face and laser energy on the other. Results were evaluated on a numerical scale (0-12 with 12 = greatest enhancement) from pre- and posttreatment photographs by a blinded panel. Upper face improvement (posttreatment score minus pretreatment score) was essentially the same on both sides (30.2 and 31.3% improvement for laser and RF, respectively, P=0.89). Lower face improvement was greater in the laser-treated side (35.7 and 23.8% improvement for laser and RF, respectively), but the difference was not significant (P=0.074). Overall face improvement was significantly greater on the laser-treated side (47.5 and 29.8% improvement for laser and RF, respectively, P=0.028). A single high-fluence treatment with the long-pulse 1064-nm Nd:YAG laser may improve skin laxity more than a single treatment with the RF device. Further controlled split-face or very large non-self controlled studies are needed to conclusively determine the relative efficacies of the two technologies. (c) 2007 Wiley-Liss, Inc.

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

1.44-μm giant pulse generation

NASA Astrophysics Data System (ADS)

Šulc, Jan; Arátor, Pavel; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

2007-02-01

We have compared two solid-state saturable absorbers for Q-switching of longitudinally diode-pumped Nd:YAG laser operating at wavelength 1444 nm: vanadium doped garnet (V 3+:Y 3Al IIO 5, V:YAG), and cobalt doped spinel (Co 2+:MgAl IIO 4, Co:MALO). V:YAG crystal with initial transmission 91% was 2.2mm thick. Co:MALO crystal with initial transmission 91% was 2.0mm thick. Q-switched laser consisted of the Nd:YAG composite rod (8mm long Nd-doped part, 4mm long undoped YAG part) and the saturable absorber placed in 80mm long hemispheric cavity. As an output coupler was used concave mirror (r = 150mm) with reflectivity 98% on lasing wavelength. Giant pulses were obtained with both passive Q-switches. When V:YAG saturable absorber was used, 55 ns long (FWHM) pulses were generated with peak power 0.47kW (pulse energy 26 μJ). Using Co:MALO, more powerful pulses were obtained (40 ns long, 1.0kW peak power, 45 μJ energy). Advantage of less efficient V:YAG consist in possibility of diffusion bonding between Q-switch and laser active medium which allows to prepare miniature compact laser device. This concept was demonstrated by using of Nd:YAG/V:YAG monolith crystal (4mm long undoped YAG part, 8mm long Nd:YAG part, 0.5mm long V:YAG part - initial transmission 97% @ 1444 nm). This monolithic crystal, originally designed for 1338nm lasing, was placed into 23mm long cavity resonating at wavelength 1444 nm. For output coupler reflectivity 96% pulses 39 ns long with peak power 0.64kW were generated at wavelength 1444 nm.

Sub-200 femtosecond dispersion-managed soliton ytterbium-doped fiber laser based on carbon nanotubes saturable absorber.

PubMed

Hou, Lei; Guo, Hongyu; Wang, Yonggang; Sun, Jiang; Lin, Qimeng; Bai, Yang; Bai, Jintao

2018-04-02

Ultrafast fiber laser light sources attract enormous interest due to the booming applications they are enabling, including long-distance communication, optical metrology, detecting technology of infra-biophotons, and novel material processing. In this paper, we demonstrate 175 fs dispersion-managed soliton (DMS) mode-locked ytterbium-doped fiber (YDF) laser based on single-walled carbon nanotubes (SWCNTs) saturable absorber (SA). The output DMSs have been achieved with repetition rate of 21.2 MHz, center wavelength of 1025.5 nm, and a spectral width of 32.7 nm. The operation directly pulse duration of 300 fs for generated pulse is the reported shortest pulse width for broadband SA based YDF lasers. By using an external grating-based compressor, the pulse duration could be compressed down to 175 fs. To the best of our knowledge, it is the shortest pulse duration obtained directly from YDF laser based on broadband SAs. In this paper, SWCNTs-SA has been utilized as the key optical component (mode locker) and the grating pair providing negative dispersion acts as the dispersion controller.

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.

Quadrupole distribution generated by a laser induced plasma (LIP) in air in earliest instants using pulses of 532 or 355 nm

NASA Astrophysics Data System (ADS)

Paulin-Fuentes, J. Mauricio; Sánchez-Aké, C.; Bredice, Fausto O.; Villagrán-Muniz, Mayo

2015-07-01

The self-generated electric and magnetic fields in laser induced plasmas (LIPs) in air during the first 40 ns are experimentally investigated using different electric, magnetic and optical techniques. To produce LIPs we used the second and third harmonics (532 and 355 nm) of a Nd:YAG nanosecond pulsed laser with a range of irradiance from {{10}11} to {{10}12} W \\text{c}{{\\text{m}}-2} . The variation in time of the electric field was detected using the tip of a coaxial cable, and the spontaneous magnetic field (SMF) was measured using a \\dot{B} probe. The spatial and temporal evolution of the plasma was studied using shadowgraphy and fast photography. It was observed that produced LIPs using pulses of 532 and 355 nm, generate plasmas of double core over the laser axis, while we observed that produced LIPs by pulses of 1064 nm are composed of a single core plasma. We found that the double-core plasmas have a quadrupole distribution of the charge, consisting of two oppositely directed dipoles which in turn correspond to each plasma core. The magnetic diagnostic showed an oscillating magnetic field azimuthal to the main axis of the double-plasma.

Green and ultraviolet pulse generation with a compact, fiber laser, chirped-pulse amplification system for aerosol fluorescence measurements.

PubMed

Lou, Janet W; Currie, Marc; Sivaprakasam, Vasanthi; Eversole, Jay D

2010-10-01

We use a compact chirped-pulse amplified system to harmonically generate ultrashort pulses for aerosol fluorescence measurements. The seed laser is a compact, all-normal dispersion, mode-locked Yb-doped fiber laser with a 1050 nm center wavelength operating at 41 MHz. Average powers of more than 1.2 W at 525 nm and 350 mW at 262 nm are generated with <500 fs pulse durations. The pulses are time-stretched with high-dispersion fiber, amplified by a high-power, large-mode-area fiber amplifier, and recompressed using a chirped volume holographic Bragg grating. The resulting high-peak-power pulses allow for highly efficient harmonic generation. We also demonstrate for the first time to our knowledge, the use of a mode-locked ultraviolet source to excite individual biological particles and other calibration particles in an inlet air flow as they pass through an optical chamber. The repetition rate is ideal for biofluorescence measurements as it allows faster sampling rates as well as the higher peak powers as compared to previously demonstrated Q-switched systems while maintaining a pulse period that is longer than the typical fluorescence lifetimes. Thus, the fluorescence excitation can be considered to be quasicontinuous and requires no external synchronization and triggering.

1W frequency-doubled VCSEL-pumped blue laser with high pulse energy

NASA Astrophysics Data System (ADS)

Van Leeuwen, Robert; Chen, Tong; Watkins, Laurence; Xu, Guoyang; Seurin, Jean-Francois; Wang, Qing; Zhou, Delai; Ghosh, Chuni

2015-02-01

We report on a Q-switched VCSEL side-pumped 946 nm Nd:YAG laser that produces high average power blue light with high pulse energy after frequency doubling in BBO. The gain medium was water cooled and symmetrically pumped by three 1 kW 808 nm VCSEL pump modules. More than 1 W blue output was achieved at 210 Hz with 4.9 mJ pulse energy and at 340 Hz with 3.2 mJ pulse energy, with 42% and 36% second harmonic conversion efficiency respectively. Higher pulse energy was obtained at lower repetition frequencies, up to 9.3 mJ at 70 Hz with 52% conversion efficiency.

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

NASA Astrophysics Data System (ADS)

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

2000-11-01

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

Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

PubMed

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

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

Pan, A.; Dias, A.; Gomez-Aranzadi, M.

2014-05-07

The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observedmore » with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.« less

Use of 1070 nm fiber lasers in oral surgery: preliminary ex vivo study with FBG temperature monitoring.

PubMed

Fornaini, Carlo; Merigo, Elisabetta; Poli, Federica; Cavatorta, Chiara; Rocca, Jean-Paul; Selleri, Stefano; Cucinotta, Annamaria

2017-12-31

The aim of this ex vivo study was to demonstrate the performances of 1070 nm fiber lasers for the ablation of oral tissues through the evaluation of the histological modifications made by a blind pathologist and the measurement of the thermal elevation during laser irradiation by a sensor based on a fiber Bragg grating. The source used was a pulsed fiber laser emitting at 1070 nm, with 20 W maximum average output power and 100 ns fixed pulse duration. Different tests were performed by changing the laser parameters, particularly the peak power of the pulses and the repetition rate. The tissue of the measurements demonstrated that the best properties in term of cutting capability and, at the same time, the lower thermal damages to the tissues can be obtained with a peak power of 3 kW, a repetition rate of 50 kHz and a speed of 5 mm/s. This ex vivo study showed that 1070 nm fiber lasers can be very useful in oral surgery, since they provide a reduced thermal elevation in the irradiated tissues, thus consequently respecting their biological structures. Moreover, this work demonstrates that FBG sensors, based on the optical fiber technology as the laser source considered for the tests, may be good instruments to record thermal elevation when applied to the ex vivo studies on animal models.

Optical damage testing at the Z-Backlighter facility at Sandia National Laboratories

NASA Astrophysics Data System (ADS)

Kimmel, Mark; Rambo, Patrick; Broyles, Robin; Geissel, Matthias; Schwarz, Jens; Bellum, John; Atherton, Briggs

2009-10-01

To enable laser-based radiography of high energy density physics events on the Z-Accelerator[4,5] at Sandia National Laboratories, a facility known as the Z-Backlighter has been developed. Two Nd:Phosphate glass lasers are used to create x-rays and/or proton beams capable of this radiographic diagnosis: Z-Beamlet (a multi-kilojoule laser operating at 527nm in a few nanoseconds) and Z-Petawatt (a several hundred joule laser operating at 1054nm in the subpicosecond regime) [1,2]. At the energy densities used in these systems, it is necessary to use high damage threshold optical materials, some of which are poorly characterized (especially for the sub-picosecond pulse). For example, Sandia has developed a meter-class dielectric coating capability for system optics. Damage testing can be performed by external facilities for nanosecond 532nm pulses, measuring high reflector coating damage thresholds >80J/cm2 and antireflection coating damage thresholds >20J/cm2 [3]. However, available external testing capabilities do not use femtosecond/picosecond scale laser pulses. To this end, we have constructed a sub-picoseond-laser-based optical damage test system. The damage tester system also allows for testing in a vacuum vessel, which is relevant since many optics in the Z-Backlighter system are used in vacuum. This paper will present the results of laser induced damage testing performed in both atmosphere and in vacuum, with 1054nm sub-picosecond laser pulses. Optical materials/coatings discussed are: bare fused silica and protected gold used for benchmarking; BK7; Zerodur; protected silver; and dielectric optical coatings (halfnia/silica layer pairs) produced by Sandia's in-house meter-class coating capability.

Wavelength dependence of laser-induced retinal injury

NASA Astrophysics Data System (ADS)

Lund, David J.; Edsall, Peter; Stuck, Bruce E.

2005-04-01

The threshold for laser-induced retinal damage is dependent primarily upon the laser wavelength and the exposure duration. The study of the wavelength dependence of the retinal damage threshold has been greatly enhanced by the availability of tunable lasers. The Optical Parametric Oscillator (OPO), capable of providing useful pulse energy throughout a tuning range from 400 nm to 2200 nm, made it possible to determine the wavelength dependence of laser-induced retinal damage thresholds for q-switched pulses throughout the visible and NIR spectrum. Studies using the a tunable TI:Saph laser and several fixed-wavelength lasers yielded threshold values for 0.1 s exposures from 440 nm to 1060 nm. Laser-induced retinal damage for these exposure durations results from thermal conversion of the incident laser irradiation and an action spectrum for thermal retinal damage was developed based on the wavelength dependent transmission and absorption of ocular tissue and chromatic aberration of the eye optics. Long (1-1000s) duration exposures to visible laser demonstrated the existence of non-thermal laser-induced retinal damage mechanisms having a different action spectrum. This paper will present the available data for the wavelength dependence of laser-induced thermal retinal damage and compare this data to the maximum permissible exposure levels (MPEs) provided by the current guidelines for the safe use of lasers.

In-band pumped Q-switched fiber laser based on monolayer graphene

NASA Astrophysics Data System (ADS)

Wu, Hanshuo; Wu, Jian; Xiao, Hu; Leng, Jinyong; Xu, Jiangming; Zhou, Pu

2017-06-01

We propose and demonstrate an in-band pumped all-fiberized passively Q-switched laser emitting at 1080 nm. A single mode 1030 nm fiber laser is used as the pump source, while a 2D material, CVD-grown monolayer graphene, is adopted as a saturable absorber inside the ring cavity. The repetition rate of the output pulses can be varied from 12.74 to 24.6 kHz with the pulse duration around 12 µs. The maximum average output power is 34.25 mW, with the pulse energy of 1.392 µJ. This work proves the practicability of achieving passively Q-switched operation via in-band pump.

175 fs-long pulses from a high-power single-mode Er-doped fiber laser at 1550 nm

NASA Astrophysics Data System (ADS)

Elahi, Parviz; Kalaycıoğlu, Hamit; Li, Huihui; Akçaalan, Önder; Ilday, F. Ömer

2017-11-01

Development of Er-doped ultrafast lasers have lagged behind the corresponding developments in Yb- and Tm-doped lasers, in particular, fiber lasers. Various applications benefit from operation at a central wavelength of 1.5 μm and its second harmonic, including emerging applications such as 3D processing of silicon and 3D printing based on two-photon polymerization. We report a simple, robust fiber master oscillator power amplifier operating at 1.55 μm, implementing chirp pulse amplification using single-mode fibers for diffraction-limited beam quality. The laser generates 80 nJ pulses at a repetition rate of 43 MHz, corresponding to an average power of 3.5 W, which can be compressed down to 175 fs. The generation of short pulses was achieved using a design which is guided by numerical simulations of pulse propagation and amplification and manages to overturn gain narrowing with self-phase modulation, without invoking excessive Raman scattering processes. The seed source for the two-stage amplifier is a dispersion-managed passively mode-locked oscillator, which generates a ∼40 nm-wide spectrum and 1.7-ps linearly chirped pulses.

Fabrication of oxidation-resistant Ge colloidal nanoparticles by pulsed laser ablation in aqueous HCl

NASA Astrophysics Data System (ADS)

Hamanaka, Yasushi; Iwata, Masahiro; Katsuno, Junichi

2017-06-01

Spherical Ge nanoparticles with diameters of 20-80 nm were fabricated by laser ablation of a Ge single crystal in water and in aqueous HCl using sub-picosecond laser pulses (1040 nm, 700 fs, 100 kHz, and a pulse energy of 10 µJ). We found that the as-synthesized nanoparticles suffered rapid oxidization followed by dissolution when laser ablation was conducted in pure water. In contrast, oxidation of Ge nanoparticles produced in dilute HCl and stored intact was minimal, and colloidal dispersions of the Ge nanoparticles remained stable up to 7 days. It was elucidated that dangling bonds on the surfaces of the Ge nanoparticles were terminated by Cl, which inhibited oxidation, and that such hydrophilic surfaces might improve the dispersibility of nanoparticles in aqueous solvent.

Cell optoporation with a sub-15 fs and a 250-fs laser

NASA Astrophysics Data System (ADS)

Breunig, Hans Georg; Batista, Ana; Uchugonova, Aisada; König, Karsten

2016-06-01

We employed two commercially available femtosecond lasers, a Ti:sapphire and a ytterbium-based oscillator, to directly compare from a user's practical point-of-view in one common experimental setup the efficiencies of transient laser-induced cell membrane permeabilization, i.e., of so-called optoporation. The experimental setup consisted of a modified multiphoton laser-scanning microscope employing high-NA focusing optics. An automatic cell irradiation procedure was realized with custom-made software that identified cell positions and controlled relevant hardware components. The Ti:sapphire and ytterbium-based oscillators generated broadband sub-15-fs pulses around 800 nm and 250-fs pulses at 1044 nm, respectively. A higher optoporation rate and posttreatment viability were observed for the shorter fs pulses, confirming the importance of multiphoton effects for efficient optoporation.

Laser induced fluorescence in algae: A new technique for remote detection

NASA Technical Reports Server (NTRS)

Friedman, E. J.; Hickman, G. D.

1972-01-01

Measurements of the absorption and fluorescence spectra were obtained for four various types of marine and fresh water algae using a pulsed N2/Ne dye laser as the source of excitation. The absorption maxima for the algae ranged from 420 to 675 nm, while their fluorescent spectra ranged from 580 to 685 nm. It appears feasible that various algal species can be identified by detection of their fluorescent signatures using a tunable laser as the excitation source. However, if one is concerned only with detection of chlorophyll a, the optimum excitation is approximately 600 + 50 nm while detection is at 685 nm. An analysis of both calculations and laboratory results indicates that it should be feasible to measure chlorophyll a in concentrations as low as 1.0 mg/m3 using a 100 kW peak pulsed laser from an altitude of 500 meters.

Sub-nanosecond lasers for cosmetics and dermatology

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong

2018-02-01

We report about the development of two new subnanosecond solid-state laser models for application in dermatology and cosmetics. One model uses subnanosecond Nd: YAG microchip laser as a master oscillator and includes Nd: YAG double- and single-pass amplifiers. At 10 Hz this laser produces more than 600 mJ pulse energy with duration 500 +/- 5 ps. Another model (under development) is gain-switched Ti: Sapphire laser with short cavity. This laser produces 200 mJ, 560 ps pulses at 790 nm and uses standard Q-Switched Nd: YAG laser with nanosecond pulse duration as a pumping sourse.

Diode-pumped Alexandrite laser with passive SESAM Q-switching and wavelength tunability

NASA Astrophysics Data System (ADS)

Parali, Ufuk; Sheng, Xin; Minassian, Ara; Tawy, Goronwy; Sathian, Juna; Thomas, Gabrielle M.; Damzen, Michael J.

2018-03-01

We report the first experimental demonstration of a wavelength tunable passively Q-switched red-diode-end pumped Alexandrite laser using a semiconductor saturable absorber mirror (SESAM). We present the results of the study of passive SESAM Q-switching and wavelength-tuning in continuous diode-pumped Alexandrite lasers in both linear cavity and X-cavity configurations. In the linear cavity configuration, pulsed operation up to 27 kHz repetition rate in fundamental TEM00 mode was achieved and maximum average power was 41 mW. The shortest pulse generated was 550 ns (FWHM) and the Q-switched wavelength tuning band spanned was between 740 nm and 755 nm. In the X-cavity configuration, a higher average power up to 73 mW, and obtained with higher pulse energy 6 . 5 μJ at 11.2 kHz repetition rate, in fundamental TEM00 mode with excellent spatial quality M2 < 1 . 1. The Q-switched wavelength tuning band spanned was between 775 nm and 781 nm.

Pulsed laser-assisted removal of powder coating from galvanised steel surface: a characterisation study

NASA Astrophysics Data System (ADS)

Kumar, Aniruddha; Prasad, Manisha; Shail, Shailini; Bhatt, R. B.; Behere, P. G.; Afzal, Md.; Kumar, Arun; Kar, Rajib; Nilaya, J. P.; Biswas, D. J.

2015-06-01

Removal of pure polyester powder coating from galvanised steel surface is studied using the fundamental, second and third harmonic radiations obtained from a Q-switched Nd-YAG laser capable of delivering pulses of duration 10 ns. Removal of the coating was found to be most effective for 1064 nm radiation followed by 532 and 355 nm radiations. Measurement of absorption of the incident radiation by the paint layer carried out with an integrating sphere has helped to gain insight into the removal mechanisms operative at these wavelengths. Single shot removal of the entire thickness of the powder coating was successfully achieved using 1064 nm radiation. Characterisation study of the laser-treated surface revealed that the coating removal was achieved leaving the underneath zinc layer as before. Usage of pulsed emission at 1064 nm of fluence 0.7 J/cm2 and repetition rate 5 Hz allowed stripping of 60-micron-thick coating at the rate of ~35 cm2 per minute.

Research on laser-removal of a deuterium deposit from a graphite sample

NASA Astrophysics Data System (ADS)

Kubkowska, M.; Skladnik-Sadowska, E.; Malinowski, K.; Sadowski, M. J.; Rosinski, M.; Gasior, P.

2014-04-01

The paper presents experimental results of investigation of a removal of deuterium deposits from a graphite target by means of pulsed laser beams. The sample was a part of the TEXTOR limiter with a deuterium-deposited layer. That target was located in the vacuum chamber, pumped out to 5×10-5 Torr, and it was irradiated with a Nd:YAG laser, which generated 3.5-ns pulses of energy of 0.5 J at λ1 = 1063 nm, or 0.1 J at λ3 = 355 nm.

Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses.

PubMed

Grivas, Christos; Corbari, Costantino; Brambilla, Gilberto; Lagoudakis, Pavlos G

2012-11-15

Fabrication and cw lasing at 798.25 nm is reported for femtosecond (fs) and picosecond (ps) laser-inscribed channel waveguides in Ti:sapphire crystals. Lasing in channels written by fs (ps) pulses was obtained above a threshold of 84 mW (189 mW) with a maximum output power and a slope efficiency of 143 mW (45 mW) and 23.5% (7.1%), respectively. The emission wavelength was tuned over a 170 nm range by using a birefringent filter in an external cavity.

> 6 MW peak power at 532 nm from passively Q-switched Nd:YAG/Cr4+:YAG microchip laser.

PubMed

Bhandari, Rakesh; Taira, Takunori

2011-09-26

Megawatt peak power, giant pulse microchip lasers are attractive for wavelength conversion, provided their output is linearly polarized. We use a [110] cut Cr(4+):YAG for passively Q-switched Nd:YAG microchip laser to obtain a stable, linearly polarized output. Further, we optimize the conditions for second harmonic generation at 532 nm wavelength to achieve > 6 MW peak power, 1.7 mJ, 265 ps, 100 Hz pulses with a conversion efficiency of 85%. © 2011 Optical Society of America

High-pulse-energy passively Q-switched quasi-monolithic microchip lasers operating in the sub-100-ps pulse regime.

PubMed

Nodop, D; Limpert, J; Hohmuth, R; Richter, W; Guina, M; Tünnermann, A

2007-08-01

We present passively Q-switched microchip lasers with items bonded by spin-on-glass glue. Passive Q-switching is obtained by a semiconductor saturable absorber mirror. The laser medium is a Nd:YVO(4) crystal. These lasers generate pulse peak powers up to 20 kW at a pulse duration as short as 50 ps and pulse repetition rates of 166 kHz. At 1064 nm, a linear polarized transversal and longitudinal single-mode beam is emitted. To the best of our knowledge, these are the shortest pulses in the 1 microJ energy range ever obtained with passively Q-switched microchip lasers. The quasi-monolithic setup ensures stable and reliable performance.

All fiber passively mode locked zirconium-based erbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Ahmad, H.; Awang, N. A.; Paul, M. C.; Pal, M.; Latif, A. A.; Harun, S. W.

2012-04-01

All passively mode locked erbium-doped fiber laser with a zirconium host is demonstrated. The fiber laser utilizes the Non-Linear Polarization Rotation (NPR) technique with an inexpensive fiber-based Polarization Beam Splitter (PBS) as the mode-locking element. A 2 m crystalline Zirconia-Yttria-Alumino-silicate fiber doped with erbium ions (Zr-Y-Al-EDF) acts as the gain medium and generates an Amplified Spontaneous Emission (ASE) spectrum from 1500 nm to 1650 nm. The generated mode-locked pulses have a spectrum ranging from 1548 nm to more than 1605 nm, as well as a 3-dB bandwidth of 12 nm. The mode-locked pulse train has an average output power level of 17 mW with a calculated peak power of 1.24 kW and energy per pulse of approximately 730 pJ. The spectrum also exhibits a Signal-to-Noise Ratio (SNR) of 50 dB as well as a repetition rate of 23.2 MHz. The system is very stable and shows little power fluctuation, in addition to being repeatable.

Kilohertz Cr:forsterite regenerative amplifier.

PubMed

Evans, J M; Petri Evi, V; Alfano, R R; Fu, Q

1998-11-01

We report on a tunable regenerative amplifier that is operational in the near-infrared spectral region from 1230 to 1280 nm based on the vibronic laser material Cr:forsterite. Utilizing the technique of chirped-pulse amplification, we generated pulses as short as 150 fs at 1255 nm at a repetition rate of 1 kHz. Pulse amplification of more than 5 x 10(5) times was observed, with recorded output pulse energies of 34 muJ . Implementation of a second-harmonic generator yielded 110-fs-duration pulses of 7-muJ energy at 625 nm.

Fiber laser driven dual photonic crystal fiber femtosecond mid-infrared source tunable in the range of 4.2 to 9 μm

NASA Astrophysics Data System (ADS)

Yao, Yuhong; Knox, Wayne H.

2014-02-01

We report a fiber based approach to broadly tunable femtosecond mid-IR source based on difference frequency mixing of the outputs from dual photonic crystal fibers (PCF) pumped by a femtosecond fiber laser, which is a custom-built Yb-doped fiber chirped pulse amplifier (CPA) delivering 1.35 W, 300 fs, 40 MHz pulses centered at 1035 nm. The CPA output is split into two arms to pump two different types of PCFs for generation of the spectrally separated pulses. The shorter wavelength pulses are generated in one PCF with its single zero dispersion wavelength (ZDW) at 1040 nm. Low normal dispersion around the pumping wavelength enables spectral broadening dominated by self-phase modulation (SPM), which extends from 970 to 1092 nm with up to 340 mW of average power. The longer wavelength pulses are generated in a second PCF which has two closely spaced ZDWs around the laser wavelength. Facilitated by its special dispersion profile, the laser wavelength is converted to the normal dispersion region of the fiber, leading to the generation of the narrow-band intense Stokes pulses with 1 to 1.25 nJ of pulse energy at a conversion efficiency of ~30% from the laser pulses. By difference mixing the outputs from both PCFs in a type-II AgGaS2 crystal, mid-IR pulses tunable from 4.2 to 9 μm are readily generated with its average power ranging from 135 - 640 μW, corresponding to 3 - 16 pJ of pulse energy which is comparable to the reported fiber based mid-IR sources enabled by the solitons self-frequency shift (for example, 3 - 10 μm with 10 pJ of maximum pulse energy in [10]). The reported approach provides a power-scalable route to the generation of broadly tunable femtosecond mid-IR pulses, which we believe to be a promising solution for developing compact, economic and high performance mid-IR sources.

1997 Technical Digest Series. Volume 7: Applications of High Field and Short Wavelength Sources VII

DTIC Science & Technology

1997-03-01

clusters irradiated with ultrashort , high intensity laser pulses can exhibit "ionization ig- nition" which leads...8, 9]. 25-atom Ne clusters and 25-atom Ar clusters are modelled as irradiated by a 800 nm, 15 fs (fwhm) laser pulse with peak intensities ranging...Measurements of the spatial and spectral properties of ultrashort , intense laser pulses propagating in underdense plasmas demonstrate

Generation of sub-100-fs pulses from a CW mode-locked chromium-doped forsterite laser

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1992-01-01

Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite laser is reported. The forsterite laser was actively mode locked by using an acoustooptic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intracavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses measured had a 60-fs pulse width.

Controlled assembly of high-order nanoarray metal structures on bulk copper surface by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Qin, Wanwan; Yang, Jianjun

2017-07-01

We report a new one-step maskless method to fabricate high-order nanoarray metal structures comprising periodic grooves and particle chains on a single-crystal Cu surface using femtosecond laser pulses at the central wavelength of 400 nm. Remarkably, when a circularly polarized infrared femtosecond laser pulse (spectrally centered at 800 nm) pre-irradiates the sample surface, the geometric dimensions of the composite structure can be well controlled. With increasing the energy fluence of the infrared laser pulse, both the groove width and particle diameter are observed to reduce, while the measured spacing-to-diameter ratio of the nanoparticles tends to present an increasing tendency. A physical scenario is proposed to elucidate the underlying mechanisms: as the infrared femtosecond laser pulse pre-irradiates the target, the copper surface is triggered to display anomalous transient physical properties, on which the subsequently incident Gaussian blue laser pulse is spatially modulated into fringe-like energy depositions via the excitation of ultrafast surface plasmon. During the following relaxation processes, the periodically heated thin-layer regions can be transferred into the metastable liquid rivulets and then they break up into nanodroplet arrays owing to the modified Rayleigh-like instability. This investigation indicates a simple integrated approach for active designing and large-scale assembly of complexed functional nanostructures on bulk materials.

Laser nitriding of iron: Nitrogen profiles and phases

NASA Astrophysics Data System (ADS)

Illgner, C.; Schaaf, P.; Lieb, K. P.; Schubert, E.; Queitsch, R.; Bergmann, H.-W.

1995-07-01

Armco iron samples were surface nitrided by irradiating them with pulses of an excimer laser in a nitrogen atmosphere. The resulting nitrogen depth profiles measured by Resonant Nuclear Reaction Analysis (RNRA) and the phase formation determined by Conversion Electron Mössbauer Spectroscopy (CEMS) were investigated as functions of energy density and the number of pulses. The nitrogen content of the samples was found to be independent of the number of pulses in a layer of 50 nm from the surface and to increase in depths exceeding 150 nm. The phase composition did not change with the number of pulses. The nitrogen content can be related to an enhanced nitrogen solubility based on high temperatures and high pressures due to the laser-induced plasma above the sample. With increasing pulse energy density, the phase composition changes towards phases with higher nitrogen contents. Nitrogen diffusion seems to be the limiting factor for the nitriding process.

Theoretical exploration of control factors for the high-order harmonic generation (HHG) spectrum in two-color field.

PubMed

Huang, Xinting; Yang, Dapeng; Yao, Li

2014-09-15

In this work, the laser-parameter effects on the high-order harmonic generation (HHG) spectrum and attosecond trains by mixing two-color laser field, a visible light field of 800 nm and a mid-infrared (mid-IR) laser pulses of 2400 nm, are theoretically demonstrated for the first time. Different schemes are applied to discuss the function of intensity, carrier-envelope phase (CEP) and pulse duration on the generation of an isolated attosecond pulse. As a consequence, an isolated 16as pulse is obtained by Fourier transforming an ultrabroad XUV continuum of 208 eV with the fundamental field of duration of 6 fs, 9×10(14)W/cm2 of intensity, the duration of 12 fs, the CEPs of the two driving pulses of -π and the relative strength ratio √R=0.2. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective Photothermolysis to target Sebaceous Glands: Theoretical Estimation of Parameters and Preliminary Results Using a Free Electron Laser

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

Fernanda Sakamoto, Apostolos Doukas, William Farinelli, Zeina Tannous, Michelle D. Shinn, Stephen Benson, Gwyn P. Williams, H. Dylla, Richard Anderson

2011-12-01

The success of permanent laser hair removal suggests that selective photothermolysis (SP) of sebaceous glands, another part of hair follicles, may also have merit. About 30% of sebum consists of fats with copious CH2 bond content. SP was studied in vitro, using free electron laser (FEL) pulses at an infrared CH2 vibrational absorption wavelength band. Absorption spectra of natural and artificially prepared sebum were measured from 200 nm to 3000 nm, to determine wavelengths potentially able to target sebaceous glands. The Jefferson National Accelerator superconducting FEL was used to measure photothermal excitation of aqueous gels, artificial sebum, pig skin, humanmore » scalp and forehead skin (sebaceous sites). In vitro skin samples were exposed to FEL pulses from 1620 to 1720 nm, spot diameter 7-9.5 mm with exposure through a cold 4C sapphire window in contact with the skin. Exposed and control tissue samples were stained using H and E, and nitroblue tetrazolium chloride staining (NBTC) was used to detect thermal denaturation. Natural and artificial sebum both had absorption peaks near 1210, 1728, 1760, 2306 and 2346 nm. Laser-induced heating of artificial sebum was approximately twice that of water at 1710 and 1720 nm, and about 1.5x higher in human sebaceous glands than in water. Thermal camera imaging showed transient focal heating near sebaceous hair follicles. Histologically, skin samples exposed to {approx}1700 nm, {approx}100-125 ms pulses showed evidence of selective thermal damage to sebaceous glands. Sebaceous glands were positive for NBTC staining, without evidence of selective loss in samples exposed to the laser. Epidermis was undamaged in all samples. Conclusions: SP of sebaceous glands appears to be feasible. Potentially, optical pulses at {approx}1720 nm or {approx}1210 nm delivered with large beam diameter and appropriate skin cooling in approximately 0.1 s may provide an alternative treatment for acne.« less

Machining of glass and quartz using nanosecond and picosecond laser pulses

NASA Astrophysics Data System (ADS)

Ashkenasi, David; Kaszemeikat, Tristan; Mueller, Norbert; Lemke, Andreas; Eichler, Hans Joachim

2012-03-01

New laser processing strategies in micro processing of glass, quartz and other optically transparent materials are being developed with increasing effort. Utilizing diode-pumped solid-state laser generating nanosecond pulsed green (532 nm) laser light in conjunction with either scanners or special trepanning systems can provide for reliable glass machining at excellent efficiency. Micro ablation can be induced either from the front or rear side of the glass sample. Ablation rates of over 100 μm per pulse can be achieved in rear side processing. In comparison, picosecond laser processing of glass and quartz (at a wavelength of 1064 or 532 nm) yield smaller feed rates at however much better surface and bore wall quality. This is of great importance for small sized features, e.g. through-hole diameters smaller 50 μm in thin glass. Critical for applications with minimum micro cracks and maximum performance is an appropriate distribution of laser pulses over the work piece along with optimum laser parameters. Laser machining tasks are long aspect micro drilling, slanted through holes, internal contour cuts, micro pockets and more complex geometries in e.g. soda-lime glass, B33, B270, D236T, AF45 and BK7 glass, quartz, and Zerodur.

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE PAGES

Laurence, T. A.; Negres, R. A.; Ly, S.; ...

2017-06-22

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

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

Laurence, T. A.; Negres, R. A.; Ly, S.

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less

LD-pumped actively Q-switched c-cut Nd:GdVO4 self-Raman laser operating at 1166 and 1176 nm

NASA Astrophysics Data System (ADS)

Sun, Xinzhi; Zhang, Xihe; Li, Shutao; Dong, Yuan

2017-12-01

A laser diode pumped actively Q-switched c-cut Nd:GdVO4 self-Raman laser is experimentally investigated. Simultaneous pulse outputs at 1166 nm and 1176 nm corresponding to the Raman shifts of 807 and 882 cm-1 are acquired. At the pulse repetition frequency (PRF) of 20 kHz, the maximum output power is 103 mW at 1166 nm with the incident pump power of 2.31 W, while 1176 nm output power reaches 530 mW with the incident pump power of 4.11 W. The maximum output power of Raman laser is 570 mW with the incident pump power of 4.11 W and the PRF of 30 kHz. With the incident pump power of 3.67 W and the PRF of 30 kHz, the highest diode-to-Stokes optical conversion efficiency of 14.9% is obtained with the corresponding average output power of 547 mW.

Low-cost, single-mode diode-pumped Cr:Colquiriite lasers.

PubMed

Demirbas, Umit; Li, Duo; Birge, Jonathan R; Sennaroglu, Alphan; Petrich, Gale S; Kolodziejski, Leslie A; Kaertner, Franz X; Fujimoto, James G

2009-08-03

We present three Cr3+:Colquiriite lasers as low-cost alternatives to Ti:Sapphire laser technology. Single-mode laser diodes, which cost only $150 each, were used as pump sources. In cw operation, with approximately 520 mW of absorbed pump power, up to 257, 269 and 266 mW of output power and slope efficiencies of 53%, 62% and 54% were demonstrated for Cr:LiSAF, Cr:LiSGaF and Cr:LiCAF, respectively. Record cw tuning ranges from 782 to 1042 nm for Cr:LiSAF, 777 to 977 nm for Cr:LiSGaF, and 754 to 871 nm for Cr:LiCAF were demonstrated. In cw mode-locking experiments using semiconductor saturable absorber mirrors at 800 and 850 nm, Cr:Colquiriite lasers produced approximately 50-100 fs pulses with approximately 1-2.5 nJ pulse energies at approximately 100 MHz repetition rate. Electrical-to-optical conversion efficiencies of 8% in mode-locked operation and 12% in cw operation were achieved.

Evolution of size distribution and structure of Si and SiO2 nanoparticles: laser-assisted formation and fragmentation

NASA Astrophysics Data System (ADS)

Eidelman, K.; Gudkov, D.; Segbefia, O.; Ageev, E.; Krivonosov, A.; Matuhina, A.

2017-11-01

In this work, Si and SiO2, nanoparticles (NPs) was prepared by pulsed laser ablation (PLA) in distilled water. The radiation of a ytterbium fiber laser (repetition rate f = 50 kHz, wavelength λ = 1064 nm and pulse duration τ = 8 ns and 100 ns) at different laser intensities was utilized to ablate the Si target (99.999%, cubic, 7×7 mm2) under liquid layer to synthesize and to fragment the silicon colloidal NPs. Studies of morphology and size distribution of silica NPs were conducted using Transmission Electron Microscopy (TEM). The NPs of crystalline and amorphous phases were founded. Most of the NPs in the nano colloids were found to have dimensions less than 100 nm, and a few of them were between 100 nm and 700 nm. Dependence of average NP size on the number of laser passes was revealed. The average size of the nanoparticles obtained by TEM was confirmed by dynamic light scattering (DLS) measurements.

Development of a solid-state sodium Doppler lidar using an all-fiber-coupled injection seeding unit for simultaneous temperature and wind measurements in the mesopause region.

PubMed

Xia, Yuan; Du, LiFang; Cheng, XueWu; Li, FaQuan; Wang, JiHong; Wang, ZeLong; Yang, Yong; Lin, Xin; Xun, YuChang; Gong, ShunSheng; Yang, GuoTao

2017-03-06

A solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) aiming to simultaneous wind and temperature measurement of mesopause region was reported. The 589 nm pulse laser was produced by two injection seeded 1064 nm and 1319 nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. A fiber amplifier is implemented to boost the seed power at 1064 nm, enabling a robust, all-fiber-coupled design for seeding laser unit, absolute laser frequency locking, and cyclic three-frequency switching necessary for simultaneous temperature and wind measurements. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation. A preliminary observational result obtained with this solid-state sodium Doppler lidar was also reported in this paper.

Characteristics of indium-gallium-nitride multiple-quantum-well blue laser diodes grown by MOCVD

NASA Astrophysics Data System (ADS)

Mack, M. P.; Abare, A. C.; Hansen, M.; Kozodoy, P.; Keller, S.; Mishra, U.; Coldren, L. A.; DenBaars, S. P.

1998-06-01

Room temperature (RT) pulsed operation of blue (420 nm) nitride-based multi-quantum well (MQW) laser diodes grown on c-plane sapphire substrates has been demonstrated. Atmospheric pressure MOCVD was used to grow the active region of the device which consisted of a 10 pair In 0.21Ga 0.79N (2.5 nm)/In 0.07Ga 0.93N (5 nm) InGaN MQW. Threshold current densities as low as 12.6 kA/cm 2 were observed for 10×1200 μm lasers with uncoated reactive ion etched (RIE) facets. The emission is strongly TE polarized and has a sharp transition in the far-field pattern above threshold. Laser diodes were tested under pulsed conditions lasted up to 6 h at room temperature.

Mars 1064-nm Spectral Radiance Measurements from the Receiver Noise Response of the Mars Orbiter Laser Altimeter

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Neumann, Gregory A.; Abshire, James B.; Zuber, Maria T.

2005-01-01

The Mars Orbiter Laser Altimeter not only provides surface topography from the laser pulse time-of-flight, but also two radiometric measurements, the active measurement of transmitted and reflected laser pulse energy, and the passive measurement of reflected solar illumination. The passive radiometry measurement is accomplished in a novel fashion by monitoring the noise density at the output of the photodetector and solving for the amount of background light. The passive radiometry measurements provide images of Mars at 1064-nm wavelength over a 2 nm bandwidth with sub-km spatial resolution and with 2% or better precision under full illumination. We describe in this paper the principle of operation, the receiver mathematical model, its calibration, and performance assessment from sample measurement data.

Porcine Skin Visible Lesion Thresholds for Near-Infrared Lasers Including Modeling at Two Pulse Durations and Spot Sizes

DTIC Science & Technology

2006-08-01

injuries, including corneal, lenticular , and retinal lesions as a function of pulse duration. American National Standards Institute (ANSI) laser...little for skin effects. Unlike most other laser wavelengths, 1315-nm irradiation has been shown to cause damage at corneal, lenticular , and retinal

Excitation of H+2 with one-cycle laser pulses: shaped post-laser-field electronic oscillations, generation of higher- and lower-order harmonics

NASA Astrophysics Data System (ADS)

Paramonov, Guennaddi K.; Kühn, Oliver; Bandrauk, André D.

2017-08-01

Non-Born-Oppenheimer quantum dynamics of H+2 excited by shaped one-cycle laser pulses linearly polarised along the molecular axis have been studied by the numerical solution of the time-dependent Schrödinger equation within a three-dimensional model, including the internuclear separation, R, and the electron coordinates z and ρ. Laser carrier frequencies corresponding to the wavelengths λl = 25 nm through λl = 400 nm were used and the amplitudes of the pulses were chosen such that the energy of H+2 was close to its dissociation threshold at the end of any laser pulse applied. It is shown that there exists a characteristic oscillation frequency ωosc ≃ 0.2265 au (corresponding to the period of τosc ≃ 0.671 fs and the wavelength of λosc ≃ 201 nm) that manifests itself as a 'carrier' frequency of temporally shaped oscillations of the time-dependent expectation values ⟨z ⟩ and ⟨∂V/∂z ⟩ that emerge at the ends of the laser pulses and exist on a timescale of at least 50 fs. Time-dependent expectation values ⟨ρ⟩ and ⟨∂V /∂ρ⟩ of the optically passive degree of freedom, ρ, demonstrate post-laser-field oscillations at two basic frequencies ωρ1 ≈ ωosc and ωρ2 ≈ 2ωosc. Power spectra associated with the electronic motion show higher- and lower-order harmonics with respect to the driving field.

Very high repetition-rate electro-optical cavity-dumped Nd: YVO4 laser with optics and dynamics stabilities

NASA Astrophysics Data System (ADS)

Liu, Xuesong; Shi, Zhaohui; Huang, Yutao; Fan, Zhongwei; Yu, Jin; Zhang, Jing; Hou, Liqun

2015-02-01

In this paper, a very high repetition-rate, short-pulse, electro-optical cavity-dumped Nd: YVO4 laser is experimentally and theoretically investigated. The laser performance is optimized from two aspects. Firstly, the laser resonator is designed for a good thermal stability under large pump power fluctuation through optics methods. Secondly, dynamics simulation as well as experiments verifies that cavity dumping at very high repetition rate has better stability than medium/high repetition rate. At 30 W, 880 nm pump power, up to 500 kHz, constant 5 ns, stable 1064 nm fundamental-mode laser pulses can be obtained with 10 W average output power.

Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

NASA Astrophysics Data System (ADS)

Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

2014-03-01

By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

Craters and nanostructures on BaF2 sample induced by a focused 46.9nm laser

NASA Astrophysics Data System (ADS)

Cui, Huaiyu; Zhang, Shuqing; Li, Jingjun; Lu, Haiqiang; Zhao, Yongpeng

2017-08-01

We successfully damaged BaF2 samples by a 46.9nm capillary discharge laser of 100μJ focused by a toroidal mirror at a grazing incidence. Ablation craters with clear boundaries were detected by optical microscope and atomic force microscope (AFM). Laser-induced nanostructures with a period of ˜1μm were observed in the ablation area under single pulse irradiation and multiple pulses irradiation. The surface behavior was compared and analyzed with that induced by the laser of 50μJ. The nanostructures were supposed to be attributed to the thermoelastic effect and the period of the structures was effected by the energy of the laser.

Biodegradability of poly(lactic-co-glycolic acid) after femtosecond laser irradiation

PubMed Central

Shibata, Akimichi; Yada, Shuhei; Terakawa, Mitsuhiro

2016-01-01

Biodegradation is a key property for biodegradable polymer-based tissue scaffolds because it can provide suitable space for cell growth as well as tailored sustainability depending on their role. Ultrashort pulsed lasers have been widely used for the precise processing of optically transparent materials, including biodegradable polymers. Here, we demonstrated the change in the biodegradation of a poly(lactic-co-glycolic acid) (PLGA) following irradiation with femtosecond laser pulses at different wavelengths. Microscopic observation as well as water absorption and mass change measurement revealed that the biodegradation of the PLGA varied significantly depending on the laser wavelength. There was a significant acceleration of the degradation rate upon 400 nm-laser irradiation, whereas 800 nm-laser irradiation did not induce a comparable degree of change. The X-ray photoelectron spectroscopy analysis indicated that laser pulses at the shorter wavelength dissociated the chemical bonds effectively, resulting in a higher degradation rate at an early stage of degradation. PMID:27301578

Cluster formation in laser-induced ablation and evaporation of solids observed by laser ionization time-of-flight mass spectrometry and scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Tench, R. J.; Balooch, M.; Bernardez, L.; Allen, Mike J.; Siekhaus, W. J.; Olander, D. R.; Wang, W.

1990-04-01

Laser ionization time-of-flight mass analysis (LIMA) used pulses (5ns) of a frequency-quadrupled Nd-YAG laser (266 nm) focused onto spots of 4 to 100 microns diameter to ablate material, and a reflectron time of flight tube to mass-analyze the plume. The observed mass spectra for Si, Pt, SiC, and UO 2 varied in the distribution of ablation products among atoms, molecules and clusters, depending on laser power density and target material. Cleaved surfaces of highly oriented pyrolytic graphite (HOPG) positioned at room temperature either 10 cm away from materials ablated at 10(exp -5) Torr by 1 to 3 excimer laser (308 nm) pulses of 20 ns duration or 1 m away from materials vaporized at 10(exp -8) Torr by 10 Nd-Glass laser pulses of 1 ms duration were analyzed by Scanning Tunneling Microscopy (STM) in air with angstrom resolution. Clusters up to 30 A in diameter were observed.

Formation of nanoparticles from thin silver films irradiated by laser pulses in air

NASA Astrophysics Data System (ADS)

Nastulyavichus, A. A.; Smirnov, N. A.; Kudryashov, S. I.; Ionin, A. A.; Saraeva, I. N.; Busleev, N. I.; Rudenko, A. A.; Khmel'nitskii, R. A.; Zayarnyi, D. A.

2018-03-01

Some specific features of the transport of silver nanoparticles onto a SiO2 substrate under focused nanosecond IR laser pulses is experimentally investigated. A possibility of obtaining silver coatings is demonstrated. The formation of silver nanostructures as a result of pulsed laser ablation in air is studied. Nanoparticles are formed by exposing a silver film to radiation of an HTF MARK (Bulat) laser marker (λ = 1064 nm). The thus prepared nanoparticles are analysed using scanning electron microscopy and optical spectroscopy.

Aerospace Sponsored Research Summary Report for 1 October 1989 Through 30 September 1990. Scientific and Engineering Research

DTIC Science & Technology

1990-12-01

3,4]. This work allowed us to view the ultrashort ( - 100 fs) pulses . While this laser was being temporal characteristics of the absorption spectrum...regions of high intensity in single water drop- lets (a = 60 Ant) following excita- tion by a single 7-ns, 532-nn laser pulse . Resonant 532-nm laser ...electronic properties of cluster ions of ion beam and the laser pulse , any desired mass range for simple metals (alkali metals). Our earlier efforts

Frequency Stabilization of DFB Laser Diodes at 1572 nm for Spaceborne Lidar Measurements of CO2

NASA Technical Reports Server (NTRS)

Numata, Kenji; Chen, Jeffrey R.; Wu, Stewart T.; Abshire, James B.; Krainak, Michael A.

2010-01-01

We report a fiber-based, pulsed laser seeder system that rapidly switches among 6 wavelengths across atmospheric carbon dioxide (CO2) absorption line near 1572.3 nm for measurements of global CO2 mixing ratios to 1-ppmv precision. One master DFB laser diode has been frequency-locked to the CO2 line center using a frequency modulation technique, suppressing its peak-to-peak frequency drifts to 0.3 MHz at 0.8 sec averaging time over 72 hours. Four online DFB laser diodes have been offset-locked to the master laser using phase locked loops, with virtually the same sub-MHz absolute accuracy. The 6 lasers were externally modulated and then combined to produce the measurement pulse train.

Inhibited-coupling HC-PCF based beam-delivery-system for high power green industrial lasers

NASA Astrophysics Data System (ADS)

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

2018-02-01

We report on an ultra-low loss Hollow-Core Photonic Crystal Fiber (HC-PCF) beam delivery system (GLO-GreenBDS) for high power ultra-short pulse lasers operating in the green spectral range (including 515 nm and 532 nm). The GLOBDS- Green combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. It comprises a pre-aligned laser-injection head, a sheath-cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. A 5 m long GLO-BDS were demonstrated for a green short pulse laser with a transmission coefficient larger than 80%, and a laser output profile close to single-mode (M2 <1.3).

Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

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

Tian, Yong; Song, Xiaolin; Xie, Zhuo

For effective use of a laser-produced-plasma (LPP) light source, an LPP is desired to emit a narrow spectral peak because the reflection spectrum of multilayer mirrors for guiding emission from the source is very narrow. While a Gd plasma has been studied extensively as an extreme ultraviolet (EUV) light source at around 6.8 nm, where La/B{sub 4}C multilayer is reported to have a high reflectivity with a bandwidth of about 0.6 %, all previous works using an Nd:YAG laser reported very broad spectra. This paper reports the first narrowing of the 6.8 nm peak in the case of using anmore » Nd:YAG laser to generate a Gd plasma by using a pre-pulse. The best peak narrowing is observed when a pre-formed plasma is heated by a 1064 nm main laser pulse with a duration of 10 ns at the irradiation density of 4x 10{sup 11} W/cm{sup 2} at a delay time of 50 ns after the pre-pulse irradiation. The observed spectral width of about 0.3 nm is about one fifth of the value for no pre-formed plasma. The peak wavelength of the 6.8 nm band shifted to a longer wavelength side and the peak was broadened both for lower and higher laser irradiation density. It is discussed that this robustness of the peak position of the 6.8 nm Gd peak against temperature change is suitable to achieve a narrow bandwidth from an LPP generated on solid. The observed spectra are compared with those previously reported in various conditions.« less

Modelling of graphene Q-switched Tm lasers

NASA Astrophysics Data System (ADS)

Yasukevich, A. S.; Loiko, P.; Gusakova, N. V.; Serres, J. M.; Mateos, X.; Yumashev, K. V.; Kuleshov, N. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

2017-04-01

We report on a model of diode-pumped Thulium lasers passively Q-switched by a graphene saturable absorber applicable also for any other "fast" saturable absorber. It reasonably predicts the dependence of the pulse duration, pulse energy and pulse repetition frequency on the absorbed power. The model is applied in the present work for a Tm: KLuW microchip laser passively Q-switched with a multi-layer graphene saturable absorber. The laser generates 1 W at 1926 nm with a slope efficiency of 39%. Stable 190 ns /4.1 μJ pulses are achieved at a pulse repetition frequency of 260 kHz. The potential of graphene for the generation of few-ns pulses at 2 μm is discussed.

Characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering

NASA Astrophysics Data System (ADS)

Gu, Bo; Chen, Yubin; Wang, Zefeng

2016-11-01

We report here the detailed characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering. A 6.5 m hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak power, narrow linewidth, liner polarized subnanosecond pulsed 1064 nm microchip laser, generating pulsed 1908.5 nm vibrational Stokes wave. The linewidth of the pump laser and the vibrational Stokes wave is about 1 GHz and 2 GHz respectively. And the maximum Raman conversion quantum efficiency is about 48%. We also studied the pulse shapes of the pump laser and the vibrational Stokes wave. The polarization dependence of the vibrational and the rotational stimulated Raman scattering is also investigated. In addition, the beam profile of vibrational Stokes wave shows good quality, which may be taken advantage of in many applications.

Recycling of pneumatic scrap tyre into nano-crumb rubber by pulsed laser ablation in different pH media

NASA Astrophysics Data System (ADS)

Ezaan Khamsan, Nur; Bidin, Noriah; Islam, Shumaila; Daud, Suzairi; Krishnan, Ganesan; Bakar, Mohamad Aizat A.; Naqiuddin Razali, Muhamad; Khamis, Jamil

2018-05-01

Nano crumb rubber from scrap tyre is synthesized via 1064 nm pulsed Nd:YAG laser ablation in three different pH media i.e. DI-water (pH∼6.45), D-limonene (pH∼3.47) and NaOH solution (pH∼13.41). Field Emission Scanning Electron Microscope (FESEM) results show spherical morphology of crumb rubber with high degree of aggregation in DI-water and in D-limonene. However, dispersion of crumb rubbers is observed in NaOH solution. The smallest particles size is obtained in NaOH solution within the range of 10.9 nm – 74.3 nm. Energy-dispersive X-ray spectroscopy (EDX) and FTIR analysis confirmed the elements distribution and chemical bonding of rubber with DI-water, D-limonene and NaOH solution. The experimental findings shows that pulsed Nd:YAG laser ablation has potential for fabricating nano-crumb rubber in liquid media.

On 1064 nm and 350 nm laser damage thresholds of high index oxide films deposited from organic solutions and sols

NASA Astrophysics Data System (ADS)

Thomas, I.; Wilder, J.; Gonzales, R.; George, D.

1987-06-01

High index oxide coatings TiO2, Ta2O5, ZrO2 and HfO2 have been prepared from organic solutions of metal organic precursors or from colloidal oxide suspensions. Room temperature processing gives porous coatings of comparatively low index (1.8 to 1.9). Heat treatments can, in some cases, increase the index. Laser damage threshold levels at 1064 nm with a single 1 ns pulse are in the range 6 to 10 J/sq cm. Lower figures are obtained at 350 nm with a 25 ns pulse under multishot (25 Hz) conditions.

Diode-pumped passively Q-switched Nd:GdTaO4 laser based on tungsten disulfide nanosheets saturable absorber at 1066 nm

NASA Astrophysics Data System (ADS)

Li, M. X.; Jin, G. Y.; Li, Y.

2018-05-01

In this paper, we investigated the passively Q-switched Nd:GdTaO4 laser based on tungsten disulfide (WS2) saturable absorber (SA). The preparation method of WS2 SA was to attach the WS2-alcohol dispersion onto the quartz substrates. The diode-pumped passively Q-switched Nd:GdTaO4 laser operated at a central wavelength of 1066 nm. The stable pulse output could be obtained at the single pulse width of 560 ns. In a word, WS2 seems to be a suitable saturable absorber for solid state lasers.

Airborne Polarimetric, Two-Color Laser Altimeter Measurements of Lake Ice Cover: A Pathfinder for NASA's ICESat-2 Spaceflight Mission

NASA Technical Reports Server (NTRS)

Harding, David; Dabney, Philip; Valett, Susan; Yu, Anthony; Vasilyev, Aleksey; Kelly, April

2011-01-01

The ICESat-2 mission will continue NASA's spaceflight laser altimeter measurements of ice sheets, sea ice and vegetation using a new measurement approach: micropulse, single photon ranging at 532 nm. Differential penetration of green laser energy into snow, ice and water could introduce errors in sea ice freeboard determination used for estimation of ice thickness. Laser pulse scattering from these surface types, and resulting range biasing due to pulse broadening, is assessed using SIMPL airborne data acquired over icecovered Lake Erie. SIMPL acquires polarimetric lidar measurements at 1064 and 532 nm using the micropulse, single photon ranging measurement approach.

Long-Pulsed 532-Nm Neodymium-Doped Yttrium Aluminium Garnet Laser for Treatment of Facial Plane Warts in 160 Yemeni Patients.

PubMed

Alshami, Mohammad Ali; Mohana, Mona Jameel; Alshami, Ahlam Mohammad

2016-11-01

Warts in general and plane warts in particular pose a therapeutic challenge for dermatologists. Many treatment modalities exist, with variable success rates, side effect profiles, and precautions. The long-pulsed 532-nm neodymium-doped yttrium aluminium garnet (LP Nd:YAG) laser has not been previously used for this indication. This study was conducted to assess the efficacy and safety of the LP Nd:YAG laser for treating facial plane warts. A total of 160 Yemeni patients (62 women, 98 men; age range, 5-55 years) were exposed to 1 laser treatment session with the following parameters: wavelength, 532 nm; pulse duration, 20 millisecond; spot size, 2 to 3 mm; and fluence, 25 J/cm. The end point was graying or whitening of the lesion. Color photographs were taken before and immediately after treatment and at follow-up visits 1, 4, and 16 weeks after the laser session. An overall clearance rate of 92% after only one session was achieved, with minimal and transient side effects. The LP Nd:YAG laser is safe and effective for treating facial plane warts, with a success rate of 92% after only one session.

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.

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

Shlapakovski, A.; Gorev, S.; Krasik, Ya. E.

The influence of laser beam parameters on the output pulses of a resonant microwave compressor with a laser-triggered plasma switch was investigated. The S-band compressor, consisting of a rectangular waveguide-based cavity and H-plane waveguide tee with a shorted side arm, was filled with pressurized dry air and pumped by 1.8-μs-long microwave pulses of up to 450 kW power. A Nd:YAG laser was used to ignite the gas discharge in the tee side arm for output pulse extraction. The laser beam (at 213 nm or 532 nm) was directed along the RF electric field lines. It was found that the compressor operated most effectivelymore » when the laser beam was focused at the center of the switch waveguide cross-section. In this case, the power extraction efficiency reached ∼47% at an output power of ∼14 MW, while when the laser beam was not focused the maximal extraction efficiency was only ∼20% at ∼6 MW output power. Focusing the laser beam resulted also in a dramatic decrease (down to <1 ns) in the delay of the output pulses' appearance with respect to the time of the beam's entrance into the switch, and the jitter of the output pulses' appearance was minimized. In addition, the quality of the output pulses' waveform was significantly improved.« less

A novel fiber laser development for photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Yavas, Seydi; Aytac-Kipergil, Esra; Arabul, Mustafa U.; Erkol, Hakan; Akcaalan, Onder; Eldeniz, Y. Burak; Ilday, F. Omer; Unlu, Mehmet B.

2013-03-01

Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components.

5-fs, Multi-mJ, CEP-locked parametric chirped-pulse amplifier pumped by a 450-nm source at 1 kHz.

PubMed

Adachi, S; Ishii, N; Kanai, T; Kosuge, A; Itatani, J; Kobayashi, Y; Yoshitomi, D; Torizuka, K; Watanabe, S

2008-09-15

We report on the development of an optical parametric chirpedpulse amplifier at a 1-kHz repetition rate with a 5.5-fs pulse duration, a 2.7-mJ pulse energy and carrier-envelope phase-control. The amplifier is pumped by a 450-nm pulse from a frequency-doubled Ti:sapphire laser.

Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses

PubMed Central

Pérez-Gutiérrez, Francisco G.; Camacho-López, Santiago; Evans, Rodger; Guillén, Gabriel; Goldschmidt, Benjamin S.; Viator, John A.

2010-01-01

Circulating tumor cells (CTCs) photoacoustic detection systems can aid clinical decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond laser pulses generates photoacoustic waves that make its detection possible. This study aims at: (1) determining melanoma cell survival after laser pulses of 6 ns at λ = 355 and 532 nm; (2) comparing the potential enhancement in the photoacoustic signal using λ = 355 nm in contrast with λ = 532 nm; (3) determining the critical laser fluence at which melanin begins to leak out from melanoma cells; and (4) developing a time-resolved imaging (TRI) system to study the intracellular interactions and their effect on the plasma membrane integrity. Monolayers of melanoma cells were grown on tissue culture-treated clusters and irradiated with up to 1.0 J/cm2. Surviving cells were stained with trypan blue and counted using a hemacytometer. The phosphate buffered saline absorbance was measured with a nanodrop spectrophotometer to detect melanin leakage from the melanoma cells post-laser irradiation. Photoacoustic signal magnitude was studied at both wavelengths using piezoelectric sensors. TRI with 6 ns resolution was used to image plasma membrane damage. Cell survival decreased proportionally with increasing laser fluence for both wavelengths, although the decrease is more pronounced for 355 nm radiation than for 532 nm. It was found that melanin leaks from cells equally for both wavelengths. No significant difference in photoacoustic signal was found between wavelengths. TRI showed clear damage to plasma membrane due to laser-induced bubble formation. PMID:20589533

The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled plasma mass spectrometry

PubMed Central

LaHaye, N. L.; Harilal, S. S.; Diwakar, P. K.; Hassanein, A.; Kulkarni, P.

2015-01-01

We investigated the role of femtosecond (fs) laser wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle distribution, inductively coupled plasma-mass spectrometry (ICP-MS) signal intensity, detection limits, and elemental fractionation. Four different NIST standard reference materials (610, 613, 615, and 616) were ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate, accuracy, precision, and fractionation. Our results show that the detection limits are lower for 400 nm laser excitation than 800 nm laser excitation at lower laser energies but approximately equal at higher energies. Ablation threshold was also found to be lower for 400 nm than 800 nm laser excitation. Particle size distributions are very similar for 400 nm and 800 nm wavelengths; however, they differ significantly in counts at similar laser fluence levels. This study concludes that 400 nm LA is more beneficial for sample introduction in ICP-MS, particularly when lower laser energies are to be used for ablation. PMID:26640294

Optical and electrical properties of indium tin oxide films near their laser damage threshold [Electrical and optical properties of indium tin oxide films under multi-pulse laser irradiation at 1064 nm

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

Yoo, Jae -Hyuck; Lange, Andrew; Bude, Jeff

In this paper, we investigated whether the optical and electrical properties of indium tin oxide (ITO) films are degraded under laser irradiation below their laser ablation threshold. While performing multi-pulse laser damage experiments on a single ITO film (4.7 ns, 1064 nm, 10 Hz), we examined the optical and electrical properties in situ. A decrease in reflectance was observed prior to laser damage initiation. However, under sub-damage threshold irradiation, conductivity and reflectance of the film were maintained without measurable degradation. This indicates that ITO films in optoelectronic devices may be operated below their lifetime laser damage threshold without noticeable performancemore » degradation.« less

Optical and electrical properties of indium tin oxide films near their laser damage threshold [Electrical and optical properties of indium tin oxide films under multi-pulse laser irradiation at 1064 nm

DOE PAGES

Yoo, Jae -Hyuck; Lange, Andrew; Bude, Jeff; ...

2017-02-10

In this paper, we investigated whether the optical and electrical properties of indium tin oxide (ITO) films are degraded under laser irradiation below their laser ablation threshold. While performing multi-pulse laser damage experiments on a single ITO film (4.7 ns, 1064 nm, 10 Hz), we examined the optical and electrical properties in situ. A decrease in reflectance was observed prior to laser damage initiation. However, under sub-damage threshold irradiation, conductivity and reflectance of the film were maintained without measurable degradation. This indicates that ITO films in optoelectronic devices may be operated below their lifetime laser damage threshold without noticeable performancemore » degradation.« less

Improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam

NASA Astrophysics Data System (ADS)

Sramek, Christopher; Leung, Loh-Shan; Leng, Theodore; Brown, Jefferson; Paulus, Yannis M.; Schuele, Georg; Palanker, Daniel

2011-02-01

Decreasing the pulse duration helps confine damage, shorten treatment time, and minimize pain during retinal photocoagulation. However, the safe therapeutic window (TW), the ratio of threshold powers for thermomechanical rupture of Bruch's membrane and mild coagulation, also decreases with shorter exposures. Two potential approaches toward increasing TW are investigated: (a) decreasing the central irradiance of the laser beam and (b) temporally modulating the pulse. An annular beam with adjustable central irradiance was created by coupling a 532-nm laser into a 200-μm core multimode optical fiber at a 4-7 deg angle to normal incidence. Pulse shapes were optimized using a computational model, and a waveform generator was used to drive a PASCAL photocoagulator (532 nm), producing modulated laser pulses. Acute thresholds for mild coagulation and rupture were measured in Dutch-Belted rabbit in vivo with an annular beam (154-163 μm retinal diameter) and modulated pulse (132 μm, uniform irradiance ``flat-top'' beam) with 2-50 ms pulse durations. Thresholds with conventional constant-power pulse and a flat-top beam were also determined. Both annular beam and modulated pulse provided a 28% increase in TW at 10-ms duration, affording the same TW as 20-ms pulses with conventional parameters.

Optical effects of exposing intact human lenses to ultraviolet radiation and visible light.

PubMed

Kessel, Line; Eskildsen, Lars; Lundeman, Jesper Holm; Jensen, Ole Bjarlin; Larsen, Michael

2011-12-30

The human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation. Naturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm) lasers. The effect of irradiation was evaluated qualitatively by photography and quantitatively by measuring the direct transmission before and after irradiation. Furthermore, the effect of pulsed and continuous laser systems was compared as was the effect of short, intermediate and prolonged exposures. Irradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after irradiation with visible light. Irradiation with visible light does not seem to be harmful to the human lens except if the lens is exposed to laser irradiances that are high enough to warrant thermal protein denaturation that is more readily seen using pulsed laser systems.

Intravital autofluorescence 2-photon microscopy of murine intestinal mucosa with ultra-broadband femtosecond laser pulse excitation: image quality, photodamage, and inflammation

NASA Astrophysics Data System (ADS)

Klinger, Antje; Krapf, Lisa; Orzekowsky-Schroeder, Regina; Koop, Norbert; Vogel, Alfred; Hüttmann, Gereon

2015-11-01

Ultra-broadband excitation with ultrashort pulses may enable simultaneous excitation of multiple endogenous fluorophores in vital tissue. Imaging living gut mucosa by autofluorescence 2-photon microscopy with more than 150 nm broad excitation at an 800-nm central wavelength from a sub-10 fs titanium-sapphire (Ti:sapphire) laser with a dielectric mirror based prechirp was compared to the excitation with 220 fs pulses of a tunable Ti:sapphire laser at 730 and 800 nm wavelengths. Excitation efficiency, image quality, and photochemical damage were evaluated. At similar excitation fluxes, the same image brightness was achieved with both lasers. As expected, with ultra-broadband pulses, fluorescence from NAD(P)H, flavines, and lipoproteins was observed simultaneously. However, nonlinear photodamage apparent as hyperfluorescence with functional and structural alterations of the tissue occurred earlier when the laser power was adjusted to the same image brightness. After only a few minutes, the immigration of polymorphonuclear leucocytes into the epithelium and degranulation of these cells, a sign of inflammation, was observed. Photodamage is promoted by the higher peak irradiances and/or by nonoptimal excitation of autofluorescence at the longer wavelength. We conclude that excitation with a tunable narrow bandwidth laser is preferable to ultra-broadband excitation for autofluorescence-based 2-photon microscopy, unless the spectral phase can be controlled to optimize excitation conditions.

Effect of wavelength on cutaneous pigment using pulsed irradiation

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

Sherwood, K.A.; Murray, S.; Kurban, A.K.

Several reports have been published over the last two decades describing the successful removal of benign cutaneous pigmented lesions such as lentigines, cafe au lait macules' nevi, nevus of Ota, and lentigo maligna by a variety of lasers such as the excimer (351 nm), argon (488,514 nm), ruby (694 nm), Nd:YAG (1060 nm), and CO/sub 2/ (10,600 nm). Laser treatment has been applied to lesions with a range of pigment depths from superficial lentigines in the epidermis to the nevus of Ota in the reticular dermis. Widely divergent laser parameters of wavelength, pulse duration, energy density, and spotsizes have beenmore » used, but the laser parameters used to treat this range of lesions have been arbitrary, with little effort focused on defining optimal laser parameters for removal of each type. In this study, miniature black pig skin was exposed to five wavelengths (504, 590, 694, 720, and 750 nm) covering the absorption spectrum of melanin. At each wavelength, a range of energy densities was examined. Skin biopsies taken from laser-exposed sites were examined histologically in an attempt to establish whether optimal laser parameters exist for destroying pigment cells in skin. Of the five wavelengths examined, 504 nm produced the most pigment specific injury; this specificity being maintained even at the highest energy density of 7.0 J/cm2. Thus, for the destruction of melanin-containing cells in the epidermal compartment, 504 nm wavelength appears optimal.« less

Cladding-pumped passively mode-locked fiber laser generating femtosecond and picosecond pulses

NASA Astrophysics Data System (ADS)

Fermann, M. E.; Harter, D.; Minelly, J. D.; Vienne, G. G.

1996-07-01

Passively mode-locked fiber lasers cladding pumped by broad-area diode-laser arrays are described. With a dispersion-compenstated erbium-ytterbium fiber oscillator, 200-fs pulses with pulse energies up to 100 pJ are generated at a wavelength of 1560 nm. In a highly dispersive cavity, pulse widths of 3 ps with pulse energies up to 1 nJ are obtained. A saturable absorber is used for pulse startup, whereas nonlinear polarization evolution is exploited for steady-state pulse shaping. An environmentally stable design is ensured by use of a compensation scheme for linear polarization drifts in the cavity.

Cladding-pumped passively mode-locked fiber laser generating femtosecond and picosecond pulses.

PubMed

Fermann, M E; Harter, D; Minelly, J D; Vienne, G G

1996-07-01

Passively mode-locked fiber lasers cladding pumped by broad-area diode-laser arrays are described. With a dispersion-compenstated erbium-ytterbium fiber oscillator, 200-fs pulses with pulse energies up to 100 pJ are generated at a wavelength of 1560 nm. In a highly dispersive cavity, pulse widths of 3 ps with pulse energies up to 1 nJ are obtained. A saturable absorber is used for pulse startup, whereas nonlinear polarization evolution is exploited for steady-state pulse shaping. An environmentally stable design is ensured by use of a compensation scheme for linear polarization drifts in the cavity.

High-power parametric amplification of 11.8-fs laser pulses with carrier-envelope phase control.

PubMed

Zinkstok, R Th; Witte, S; Hogervorst, W; Eikema, K S E

2005-01-01

Phase-stable parametric chirped-pulse amplification of ultrashort pulses from a carrier-envelope phase-stabilized mode-locked Ti:sapphire oscillator (11.0 fs) to 0.25 mJ/pulse at 1 kHz is demonstrated. Compression with a grating compressor and a LCD shaper yields near-Fourier-limited 11.8-fs pulses with an energy of 0.12 mJ. The amplifier is pumped by 532-nm pulses from a synchronized mode-locked laser, Nd:YAG amplifier system. This approach is shown to be promising for the next generation of ultrafast amplifiers aimed at producing terawatt-level phase-controlled few-cycle laser pulses.

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

NASA Astrophysics Data System (ADS)

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

2009-10-01

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

CNT-based saturable absorbers with scalable modulation depth for Thulium-doped fiber lasers operating at 1.9 μm

PubMed Central

Sobon, Grzegorz; Duzynska, Anna; Świniarski, Michał; Judek, Jarosław; Sotor, Jarosław; Zdrojek, Mariusz

2017-01-01

In this work, we demonstrate a comprehensive study on the nonlinear parameters of carbon nanotube (CNT) saturable absorbers (SA) as a function of the nanotube film thickness. We have fabricated a set of four saturable absorbers with different CNT thickness, ranging from 50 to 200 nm. The CNTs were fabricated via a vacuum filtration technique and deposited on fiber connector end facets. Each SA was characterized in terms of nonlinear transmittance (i.e. optical modulation depth) and tested in a Thulium-doped fiber laser. We show, that increasing the thickness of the CNT layer significantly increases the modulation depth (up to 17.3% with 200 nm thick layer), which strongly influences the central wavelength of the laser, but moderately affects the pulse duration. It means, that choosing the SA with defined CNT thickness might be an efficient method for wavelength-tuning of the laser, without degrading the pulse duration. In our setup, the best performance in terms of bandwidth and pulse duration (8.5 nm and 501 fs, respectively) were obtained with 100 nm thick CNT layer. This is also, to our knowledge, the first demonstration of a fully polarization-maintaining mode-locked Tm-doped laser based on CNT saturable absorber. PMID:28368014

Laser Induced Hydrogen Generation from Coal in Water

NASA Astrophysics Data System (ADS)

Seyitliyev, Dovletgeldi; Kholikov, Khomidkhodzha; Er, Ali

We report an alternative way of obtaining hydrogen using nanosecond laser pulses and various ranks of coal and coke. SEM-EDS analysis shows the atomic concentrations of elements on each of the powders which also is in good agreement with calorimeter analysis. Coal and coke powders were irradiated with 1064nm IR and 532 nm green Nd:YAG pulsed laser beam for 45 minutes. The volume of the total gas generated after irradiation of each rank was measured using the water displacement method. The amount of gas generated increased when using 532 nm compared to 1064 nm. Post-irradiation SEM images show structural differences with samples before irradiation. The amount of gas generation with respect to laser energy density shows nonlinear correlation. Generated gas concentrations were then analyzed using gas chromatography (GC). Hydrogen and carbon monoxide were the two most highly generated gases, and the efficiency of each rank of coal was determined by analyzing the hydrogen to carbon monoxide ratio. The highest efficiency rank was anthracite, with hydrogen to carbon monoxide ratio of 1.4. GC analysis also showed that the maximum hydrogen generation occurs at 100 mJ/pulse laser energy. The efficiency of each rank of coal was observed to correlate with carbon content. American Chemical Society Petroleum Research Fund.

Resonantly diode-pumped continuous-wave and Q-switched Er:YAG laser at 1645 nm.

PubMed

Chang, N W H; Simakov, N; Hosken, D J; Munch, J; Ottaway, D J; Veitch, P J

2010-06-21

We describe an efficient Er:YAG laser that is resonantly pumped using continuous-wave (CW) laser diodes at 1470 nm. For CW lasing, it emits 6.1 W at 1645 nm with a slope efficiency of 36%, the highest efficiency reported for an Er:YAG laser that is pumped in this manner. In Q-switched operation, the laser produces diffraction-limited pulses with an average power of 2.5 W at 2 kHz PRF. To our knowledge this is the first Q-switched Er:YAG laser resonantly pumped by CW laser diodes.

Femtosecond laser-induced periodic surface structure on the Ti-based nanolayered thin films

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

Petrović, Suzana M.; Gaković, B.; Peruško, D.

2013-12-21

Laser-induced periodic surface structures (LIPSSs) and chemical composition changes of Ti-based nanolayered thin films (Al/Ti, Ni/Ti) after femtosecond (fs) laser pulses action were studied. Irradiation is performed using linearly polarized Ti:Sapphire fs laser pulses of 40 fs pulse duration and 800 nm wavelength. The low spatial frequency LIPSS (LSFL), oriented perpendicular to the laser polarization with periods slightly lower than the irradiation wavelength, was typically formed at elevated laser fluences. On the contrary, high spatial frequency LIPSS (HSFL) with uniform period of 155 nm, parallel to the laser light polarization, appeared at low laser fluences, as well as in themore » wings of the Gaussian laser beam distribution for higher used fluence. LSFL formation was associated with the material ablation process and accompanied by the intense formation of nanoparticles, especially in the Ni/Ti system. The composition changes at the surface of both multilayer systems in the LSFL area indicated the intermixing between layers and the substrate. Concentration and distribution of all constitutive elements in the irradiated area with formed HSFLs were almost unchanged.« less

355 nm and 1064 nm-pulse mixing to identify the laser-induced damage mechanisms in KDP

NASA Astrophysics Data System (ADS)

Reyné, Stéphane; Duchateau, Guillaume; Natoli, Jean-Yves; Lamaignère, Laurent

2011-02-01

Nanosecond laser-induced damage (LID) in potassium dihydrogen phosphate (KH2PO4 or KDP) remains an issue for light-frequency converters in large-aperture lasers such as NIF (National Ignition Facility, in USA) LMJ (Laser MegaJoule, in France). In the final optic assembly, converters are simultaneously illuminated by multiple wavelengths during the frequency conversion. In this configuration, the damage resistance of the KDP crystals becomes a crucial problem and has to be improved. In this study, we propose a refined investigation about the LID mechanisms involved in the case of a multiple wavelengths combination. Experiments based on an original pump-pump set-up have been carried out in the nanosecond regime on a KDP crystal. In particular, the impact of a simultaneous mixing of 355 nm and 1064 nm pulses has been experimentally studied and compared to a model based on heat transfer, the Mie theory and a Drude model. This study sheds light on the physical processes implied in the KDP laser damage. In particular, a three-photon ionization mechanism is shown to be responsible for laser damage in KDP.

Method to reduce damage to backing plate

DOEpatents

Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

2001-01-01

The present invention is a method for penetrating a workpiece using an ultra-short pulse laser beam without causing damage to subsequent surfaces facing the laser. Several embodiments are shown which place holes in fuel injectors without damaging the back surface of the sack in which the fuel is ejected. In one embodiment, pulses from an ultra short pulse laser remove about 10 nm to 1000 nm of material per pulse. In one embodiment, a plasma source is attached to the fuel injector and initiated by common methods such as microwave energy. In another embodiment of the invention, the sack void is filled with a solid. In one other embodiment, a high viscosity liquid is placed within the sack. In general, high-viscosity liquids preferably used in this invention should have a high damage threshold and have a diffusing property.

LASER APPLICATIONS IN MEDICINE: Effect of glucose concentration in a model light-scattering suspension on propagation of ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Popov, A. P.; Priezzhev, A. V.; Myllylä, Risto

2005-11-01

The propagation of laser pulses in the 2% aqueous solution of intralipid — a suspension of lipid particles with optical properties close to those of the human skin, is numerically simulated at different glucose concentrations. The temporal profiles of 820-nm laser pulses diffusely backscattered from a flat, 2-mm thick solution layer are simulated. The laser pulse profiles are detected by fibreoptic detectors of diameter 0.3 mm with the numerical apertures 0.19, 0.29, and 0.39. It is shown that this method can be used to detect changes in the glucose level in the physiological concentration range (100-500 mg dL-1) by monitoring variations in the peak intensity and area of the laser pulse temporal profile (pulse energy).

Phosphorus-free mode-locked semiconductor laser with emission wavelength 1550 nm

NASA Astrophysics Data System (ADS)

Kolodeznyi, E. S.; Novikov, I. I.; Babichev, A. V.; Kurochkin, A. S.; Gladyshev, A. G.; Karachinsky, L. Ya; Gadzhiev, I. M.; Buyalo, M. S.; Usikova, A. A.; Ilynskaya, N. D.; Bougrov, V. E.; Egorov, A. Yu

2017-11-01

We have fabricated passive mode-locked laser diodes based on strained InGaAlAs/InGaAs/InP heterostructures with crystal lattice mismatch parameter of +1.0 % between quantum well and barrier. The laser with temperature stabilization at 18 °C was demonstrated 10.027 GHz optical pulse repetition rate with 6 ps pulse duration time. Timing jitter of optical pulses in mode-locked regime was 0.145 ps.

LD-pumped erbium and neodymium lasers with high energy and output beam quality

NASA Astrophysics Data System (ADS)

Kabanov, Vladimir V.; Bezyazychnaya, Tatiana V.; Bogdanovich, Maxim V.; Grigor'ev, Alexandr V.; Lebiadok, Yahor V.; Lepchenkov, Kirill V.; Ryabtsev, Andrew G.; Ryabtsev, Gennadii I.; Shchemelev, Maxim A.

2013-05-01

Physical and fabrication peculiarities which provide the high output energy and beam quality for the diode pumped erbium glass and Nd:YAG lasers are considered. Developed design approach allow to make passively Q-switched erbium glass eye-safe portable laser sources with output energy 8 - 12 mJ (output pulse duration is less than 25 ns, pulse repetition rate up to 5 Hz) and beam quality M2 less than 1.3. To reach these values the erbium laser pump unit parameters were optimized also. Namely, for the powerful laser diode arrays the optimal near-field fill-factor, output mirror reflectivity and heterostructure properties were determined. Construction of advanced diode and solid-state lasers as well as the optical properties of the active element and the pump unit make possible the lasing within a rather wide temperature interval (e.g. from minus forty till plus sixty Celsius degree) without application of water-based chillers. The transversally pumped Nd:YAG laser output beam uniformity was investigated depending on the active element (AE) pump conditions. In particular, to enhance the pump uniformity within AE volume, a special layer which practically doesn't absorb the pump radiation but effectively scatters the pump and lasing beams, was used. Application of such layer results in amplified spontaneous emission suppression and improvement of the laser output beam uniformity. The carried out investigations allow us to fabricate the solid-state Nd:YAG lasers (1064 nm) with the output energy up to 420 mJ at the pulse repetition rate up to 30 Hz and the output energy up to 100 mJ at the pulse repetition rate of of 100 Hz. Also the laser sources with following characteristics: 35 mJ, 30 Hz (266 nm); 60 mJ, 30 Hz (355 nm); 100 mJ, 30 Hz (532 nm) were manufactured on the base of the developed Nd:YAG quantrons.

Temporal femtosecond pulse shaping dependence of laser-induced periodic surface structures in fused silica

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

Shi, Xuesong; Jiang, Lan; Li, Xin, E-mail: lixin02@bit.edu.cn

2014-07-21

The dependence of periodic structures and ablated areas on temporal pulse shaping is studied upon irradiation of fused silica by femtosecond laser triple-pulse trains. Three types of periodic structures can be obtained by using pulse trains with designed pulse delays, in which the three-dimensional nanopillar arrays with ∼100–150 nm diameters and ∼200 nm heights are first fabricated in one step. These nanopillars arise from the break of the ridges of ripples in the upper portion, which is caused by the split of orthogonal ripples in the bottom part. The localized transient electron dynamics and corresponding material properties are considered for the morphologicalmore » observations.« less

Laser ablation efficiency during the production of Ag nanoparticles in ethanol at a low pulse repetition rate (1-10 Hz)

NASA Astrophysics Data System (ADS)

Valverde-Alva, M. A.; García-Fernández, T.; Esparza-Alegría, E.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; de la Mora, M. B.; Márquez-Herrera, C. E.; Sánchez Llamazares, J. L.

2016-10-01

We studied the effect of the repetition rate of laser pulses (RRLP) in the range from 1-10 Hz in the production of silver nanoparticles (Ag-NPs) by laser ablation in ethanol. Laser pulses with a duration of 7 ns, a wavelength of 1064 nm and an energy of 60 mJ were used to ablate a 99.99% pure silver target immersed in 10 ml of ethanol. Transmittance analysis and atomic absorption spectroscopy were used to study the silver concentration in the colloidal solutions. The ablation process was studied by measuring the transmission of the laser pulses through the colloid. It is shown that for a fixed number of laser pulses (NLP) the ablation efficiency, in terms of the ablated silver mass per laser pulse, increases with the RRLP. This result contradicts what had previously been established in the literature.

Monolithic hybrid optics for focusing ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Fuchs, U.

2014-03-01

Almost any application of ultrashort laser pulses involves focusing them in order to reach high intensities and/or small spot sizes as needed for micro-machining or Femto-LASIK. Hence, it is indispensable to be able to understand pulse front distortion caused by real world optics. Focusing causes pulse front distortion due to aberrations, dispersion and diffraction. Thus, the spatio-temporal profile of ultrashort laser is altered, which increases automatically the pulse duration and the focusing spot. Consequently, the main advantage of having ultrashort laser pulses - pulse durations way below 100 fs - can be lost in that one last step of the experimental set-up by focusing them unfavorable. Since compensating for dispersion, aberration and diffraction effects is quite complicated and not always possible, we pursue a different approach. We present a specially designed monolithic hybrid optics comprising refraction and diffraction effects for tight spatial and temporal focusing of ultrashort laser pulses. Both aims can be put into practice by having a high numerical aperture (NA = 0.35) and low internal dispersion at the same time. The focusing properties are very promising, due to a design, which provides diffraction limited focusing for 100 nm bandwidth at 780 nm center wavelength. Thus, pulses with durations as short as 10 fs can be focused without pulse front distortion. The outstanding performance of this optics is shown in theory and experimentally. Above that, such focusing optics are easily adapted to their special purpose - changing the center wavelength, achromatic bandwidth or even correcting for focusing into material is possible.

Direct analysis of intact biological macromolecules by low-energy, fiber-based femtosecond laser vaporization at 1042 nm wavelength with nanospray postionization mass spectrometry.

PubMed

Shi, Fengjian; Flanigan, Paul M; Archer, Jieutonne J; Levis, Robert J

2015-03-17

A fiber-based laser with a pulse duration of 435 fs and a wavelength of 1042 nm was used to vaporize biological macromolecules intact from the condensed phase into the gas phase for nanospray postionization and mass analysis. Laser vaporization of dried standard protein samples from a glass substrate by 10 Hz bursts of 20 pulses having 10 μs pulse separation and <50 μJ pulse energy resulted in signal comparable to a metal substrate. The protein signal observed from an aqueous droplet on a glass substrate was negligible compared to either a droplet on metal or a thin film on glass. The mass spectra generated from dried and aqueous protein samples by the low-energy, fiber laser were similar to the results from high-energy (500 μJ), 45-fs, 800-nm Ti:sapphire-based femtosecond laser electrospray mass spectrometry (LEMS) experiments, suggesting that the fiber-based femtosecond laser desorption mechanism involves a nonresonant, multiphoton process, rather than thermal- or photoacoustic-induced desorption. Direct analysis of whole blood performed without any pretreatment resulted in features corresponding to hemoglobin subunit-heme complex ions. The observation of intact molecular ions with low charge states from protein, and the tentatively assigned hemoglobin α subunit-heme complex from blood suggests that fiber-based femtosecond laser vaporization is a "soft" desorption source at a laser intensity of 2.39 × 10(12) W/cm(2). The low-energy, turnkey fiber laser demonstrates the potential of a more robust and affordable laser for femtosecond laser vaporization to deliver biological macromolecules into the gas phase for mass analysis.

Passive Q-switching of microchip lasers based on Ho:YAG ceramics.

PubMed

Lan, R; Loiko, P; Mateos, X; Wang, Y; Li, J; Pan, Y; Choi, S Y; Kim, M H; Rotermund, F; Yasukevich, A; Yumashev, K; Griebner, U; Petrov, V

2016-06-20

A Ho:YAG ceramic microchip laser pumped by a Tm fiber laser at 1910 nm is passively Q-switched by single- and multi-layer graphene, single-walled carbon nanotubes (SWCNTs), and Cr²⁺:ZnSe saturable absorbers (SAs). Employing SWCNTs, this laser generated an average power of 810 mW at 2090 nm with a slope efficiency of 68% and continuous wave to Q-switching conversion efficiency of 70%. The shortest pulse duration was 85 ns at a repetition rate of 165 kHz, and the pulse energy reached 4.9 μJ. The laser performance and pulse stability were superior compared to graphene SAs even for a different number of graphene layers (n=1 to 4). A model for the description of the Ho:YAG laser Q-switched by carbon nanostructures is presented. This modeling allowed us to estimate the saturation intensity for multi-layered graphene and SWCNT SAs to be 1.2±0.2 and 7±1  MW/cm², respectively. When using Cr²⁺:ZnSe, the Ho:YAG microchip laser generated 11 ns/25 μJ pulses at a repetition rate of 14.8 kHz.

Broad-spectrum neodymium-doped laser glasses for high-energy chirped-pulse amplification.

PubMed

Hays, Greg R; Gaul, Erhard W; Martinez, Mikael D; Ditmire, Todd

2007-07-20

We have investigated two novel laser glasses in an effort to generate high-energy, broad-spectrum pulses from a chirped-pulse amplification Nd:glass laser. Both glasses have significantly broader spectra (>38 nm FWHM) than currently available Nd:phosphate and Nd:silicate glasses. We present calculations for small signal pulse amplification to simulate spectral gain narrowing. The technique of spectral shaping using mixed-glass architecture with an optical parametric chirped-pulse amplification front end is evaluated. Our modeling shows that amplified pulses with energies exceeding 10 kJ with sufficient bandwidth to achieve 120 fs pulsewidths are achievable with the use of the new laser glasses. With further development of current technologies, a laser system could be scaled to generate one exawatt in peak power.

Theoretical and experimental investigations on high peak power Q-switched Nd:YAG laser at 1112 nm

NASA Astrophysics Data System (ADS)

He, Miao; Yang, Feng; Wang, Zhi-Chao; Gao, Hong-Wei; Yuan, Lei; Li, Chen-Long; Zong, Nan; Shen, Yu; Bo, Yong; Peng, Qin-Jun; Cui, Da-Fu; Xu, Zu-Yan

2018-07-01

We report on the experimental measurement and theoretical analysis on a Q-switched high peak power laser diode (LD) side-pumped 1112 nm Nd:YAG laser by means of special mirrors coating design in cavity. In theory, a numerical model, based on four-wavelength rate equations, is performed to analyze the competition process of different gain lines and the output characteristics of the Q-switched Nd:YAG laser. In the experiment, a maximum output power of 25.2 W with beam quality factor M2 of 1.46 is obtained at the pulse repetition rate of 2 kHz and 210 ns of pulse width, corresponding to a pulse energy and peak power of 12.6 mJ and 60 kW, respectively. The experimental data agree well with the theoretical simulation results.

Influence of temperature on Yb:YAG/Cr:YAG microchip laser operation

NASA Astrophysics Data System (ADS)

Šulc, Jan; Eisenschreiber, Jan; Jelínková, Helena; Nejezchleb, Karel; Å koda, Václav

2017-02-01

The goal of this work was an investigation of the temperature influence (in range from 80 up to 320 K) on the laser properties of Yb:YAG/Cr:YAG Q-switched diode-pumped microchip laser. This laser was based on monolith crystal (diameter 3mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3mm long) and saturable absorber (Cr:YAG crystal, 1.36mm long, initial transmission 90% @ 1031 nm). The laser resonator pump mirror (HT for pump radiation, HR for generated radiation) was directly deposited on the Yb:YAG monolith part. The output coupler with reflection 55% for the generated wavelength was placed on the Cr:YAG part. The microchip laser was placed in the temperature controlled cupreous holder inside vacuum chamber of the liquid nitrogen cryostat. For Yb:YAG part longitudinal pulsed pumping (pumping pulse length 2.5 ms, rep-rate 20 Hz, power amplitude 21W) a fibre coupled (core diameter 400 μm, NA= 0:22) laser diode, operating at wavelength 933 nm, was used. The microchip laser mean output power, pulse duration, repetition rate, emission wavelength, and laser beam profile were measured in dependence on temperature. The generated pulse length was in range from 2.2 ns to 1.1 ns (FWHM) with the minimum at 230 K. The single pulse energy was peaking (0.4 mJ) at 180 K. The highest peak power (325 kW) was obtained at 220 K. The highest pulse repetition rate (38 kHz) and output mean power (370mW) was reached for temperature 80 K.

Influence of different approaches for dynamical performance optimization of monolithic passive colliding-pulse mode-locked laser diodes emitting around 850 nm

NASA Astrophysics Data System (ADS)

Prziwarka, T.; Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Weyers, M.; Knigge, A.; Tränkle, G.

2018-02-01

Monolithic laser diodes which generate short infrared pulses in the picosecond and sub-picosecond ranges with high peak power are ideal sources for many applications like e.g. THz-time-domain spectroscopy (TDS) scanning systems. The achievable THz bandwidth is limited by the length of the optical pulses. Due to the fact that colliding-pulse mode locking (CPM) leads to the shortest pulses which could reached by passive mode locking, we experimentally investigated in detail the dynamical and electro optical performance of InGaAsP based quantum well CPM laser diodes with well-established vertical layer structures. Simple design modifications whose implementation is technically easy were realized. Improvements of the device performance in terms of pulse duration, output power, and noise properties are presented in dependence on the different adaptions. From the results we extract an optimized configuration with which we have reached pulses with durations of ≍1.5 ps, a peak power of > 1 W and a pulse-to-pulse timing jitter < 200 fs. The laser diodes emit pulses at a wavelength around 850 nm with a repetition frequency of ≍ 12.4 GHz and could be used as pump source for GaAs antennas to generate THz-radiation. Approaches for reducing pulse width, increasing output power, and improving noise performance are described.

Effect of absorption recovery in bismuth-doped silica glass at 1450 nm on soliton grouping in fiber laser

PubMed Central

Gumenyuk, R.; Melkumov, M. A.; Khopin, V. F.; Dianov, E. M.; Okhotnikov, O. G.

2014-01-01

Saturable absorption in bismuth-doped glasses was found to have a noticeable influence on soliton interaction and group formation. This phenomenon, observed in 1450 nm mode-locked bismuth-doped fiber laser, shows the distinct feature of the multiple pulse regime, which appears as a stationary pulse group whose length can be spread over the whole cavity length by variation of the pump power and polarization. Pulse positioning within the ensemble depends on the saturation fluence and the relatively fast recovery dynamics of bismuth fiber. PMID:25391808

Tapered photonic crystal fiber for simplified Yb:fiber laser frequency comb with low pulse energy and robust f ceo singals.

PubMed

Jiang, Tongxiao; Wang, Aimin; Wang, Guizhong; Zhang, Wei; Niu, Fuzeng; Li, Chen; Zhang, Zhigang

2014-01-27

A tapered silica photonic crystal fiber was designed and fabricated to generate more than one octave spanning supercontinuum (from 550 nm to 1400 nm at -30 dB level), by an input pulse of 40 fs 200 pJ directly from an Yb:fiber ring laser. The low pulse energy spectrum broadening are favorable to generate the high contrast f ceo signals with low noise. The f ceo signal with 40 dB signal-to-noise ratio was detected, which helps to build a compact real-world frequency comb.

Sampling modulation technique in radio-frequency helium glow discharge emission source by use of pulsed laser ablation.

PubMed

Naeem, Tariq Mahmood; Matsuta, Hideyuki; Wagatsuma, Kazuaki

2004-05-01

An emission excitation source comprising a high-frequency diode-pumped Q-switched Nd:YAG laser and a radio-frequency powered glow discharge lamp is proposed. In this system sample atoms ablated by the laser irradiation are introduced into the lamp chamber and subsequently excited by the helium glow discharge plasma. The pulsed operation of the laser can produce a cyclic variation in the emission intensities of the sample atoms whereas the plasma gas species emit the radiation continuously. The salient feature of the proposed technique is the selective detection of the laser modulation signal from the rest of the continuous background emissions, which can be achieved with the phase sensitive detection of the lock-in amplifier. The arrangement may be used to estimate the emission intensity of the laser ablated atom, free from the interference of other species present in the plasma. The experiments were conducted with a 13.56 MHz radio-frequency (rf) generator operated at 80 W power to produce plasma and the laser at a wavelength of 1064 nm (pulse duration:34 ns, repetition rate:7 kHz and average pulse energy of about 0.36 mJ) was employed for sample ablation. The measurements resulted in almost complete removal of nitrogen molecular bands (N(2)(+) 391.44 nm). Considerable reduction (about 75%) in the emission intensity of a carbon atomic line (C I 193.03 nm) was also observed.

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

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

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

Surface modification of titanium nitride film by a picosecond Nd:YAG laser

NASA Astrophysics Data System (ADS)

Gakovic, B.; Trtica, M.; Batani, D.; Desai, T.; Panjan, P.; Vasiljevic-Radovic, D.

2007-06-01

The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a polycrystalline titanium nitride (TiN) film was studied. The TiN thin film was deposited by physical vapour deposition on a silicon substrate. The titanium nitride/silicon system was modified with an energy fluence from 0.2 to 5.9 J cm-2. Multi-pulse irradiation was performed in air by a focused laser beam. Surface modifications were analysed after 1 100 successive laser pulses. Depending on the laser pulse energy and pulse count, the following phenomena were observed: (i) increased surface roughness, (ii) titanium nitride film cracking, (iii) silicon substrate modification, (iv) film exfoliation and (v) laser-induced periodical surface structures on nano- (NPSS) and micro-dimensions (MPSS).

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

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Core-pumped mode-locked ytterbium-doped fiber laser operating around 980 nm

NASA Astrophysics Data System (ADS)

Zhou, Yue; Dai, Yitang; Li, Jianqiang; Yin, Feifei; Dai, Jian; Zhang, Tian; Xu, Kun

2018-07-01

In this letter, we first demonstrate a core-pumped passively mode-locked all-normal-dispersion ytterbium-doped fiber oscillator based on nonlinear polarization evolution operating around 980 nm. The dissipative soliton fiber laser pulse can be compressed down to 250 fs with 1 nJ pulse energy, and the slope efficiency of the oscillator can be as high as 19%. To improve the dissipative soliton laser output spectrum smoothness, we replace the birefringent plate based intracavity filter with a diffraction-grating based filter. The output pulse duration can then be further compressed down to 180 fs with improved spectral-smoothness. These schemes have potential applications in seeding cryogenic Yb:YLF amplifiers and underwater exploration of marine resources.

Practical application of pulsed "eye-safe" microchip laser to laser rangefinders

NASA Astrophysics Data System (ADS)

Młyńczak, J.; Kopczyński, K.; Mierczyk, Z.; Zygmunt, M.; Natkański, S.; Muzal, M.; Wojtanowski, J.; Kirwil, P.; Jakubaszek, M.; Knysak, P.; Piotrowski, W.; Zarzycka, A.; Gawlikowski, A.

2013-09-01

The paper describes practical application of pulsed microchip laser generating at 1535-nm wavelength to a laser rangefinder. The complete prototype of a laser rangefinder was built and investigated in real environmental conditions. The measured performance of the device is discussed. To build the prototype of a laser rangefinder at a reasonable price and shape a number of basic considerations had to be done. These include the mechanical and optical design of a microchip laser and the opto-mechanical construction of the rangefinder.

Above threshold spectral dependence of linewidth enhancement factor, optical duration and linear chirp of quantum dot lasers.

PubMed

Kim, Jimyung; Delfyett, Peter J

2009-12-07

The spectral dependence of the linewidth enhancement factor above threshold is experimentally observed from a quantum dot Fabry-Pérot semiconductor laser. The linewidth enhancement factor is found to be reduced when the quantum dot laser operates approximately 10 nm offset to either side of the gain peak. It becomes significantly reduced on the anti-Stokes side as compared to the Stokes side. It is also found that the temporal duration of the optical pulses generated from quantum dot mode-locked lasers is shorter when the laser operates away from the gain peak. In addition, less linear chirp is impressed on the pulse train generated from the anti-Stokes side whereas the pulses generated from the gain peak and Stokes side possess a large linear chirp. These experimental results imply that enhanced performance characteristics of quantum dot lasers can be achieved by operating on the anti-Stokes side, approximately 10 nm away from the gain peak.

Spectral and power characteristics of a 5% Tm : KLu(WO4)2 Nm-cut minislab laser passively Q-switched by a Cr2+ : ZnSe crystal

NASA Astrophysics Data System (ADS)

Vatnik, S. M.; Vedin, I. A.; Kurbatov, P. F.; Smolina, E. A.; Pavlyuk, A. A.; Korostelin, Yu. V.; Skasyrsky, Ya. K.

2017-12-01

Laser characteristics of a 5%Tm : KLu(WO4)2 Nm-cut minislab laser passively Q-switched by a Cr2+ : ZnSe saturable absorber are presented. At a pump power of 21 W, the average laser power at a wavelength of 1.91 μm was 3.2 W (pulse duration 35 ns, pulse energy 0.3 mJ). The maximum slope efficiency of the laser in the Q-switched regime was 31%; the loss in power with respect to the cw regime did not exceed 17%. At pump powers above 15 W, the dependence of the output power in the Q-switched regime on the pump power considerably differed from linear, which was explained by the formation of a thermal lens in the saturable absorber volume. The experimental energies and durations of laser pulses well agree with the values calculated from rate equations.

Narrow titanium oxide nanowires induced by femtosecond laser pulses on a titanium surface

NASA Astrophysics Data System (ADS)

Li, Hui; Li, Xian-Feng; Zhang, Cheng-Yun; Tie, Shao-Long; Lan, Sheng

2017-02-01

The evolution of the nanostructure induced on a titanium (Ti) surface with increasing irradiation pulse number by using a 400-nm femtosecond laser was examined by using scanning electron microscopy. High spatial frequency periodic structures of TiO2 parallel to the laser polarization were initially observed because of the laser-induced oxidation of the Ti surface and the larger efficacy factor of TiO2 in this direction. Periodically aligned TiO2 nanowires with featured width as small as 20 nm were obtained. With increasing pulse number, however, low spatial frequency periodic structures of Ti perpendicular to the laser polarization became dominant because Ti possesses a larger efficacy factor in this direction. The competition between the high- and low-spatial frequency periodic structures is in good agreement with the prediction of the efficacy factor theory and it should also be observed in the femtosecond laser ablation of other metals which are easily oxidized in air.

Laser action in chromium-activated forsterite for near infrared excitation

NASA Technical Reports Server (NTRS)

Petricevic, V.; Gayen, S. K.; Alfano, R. R.

1988-01-01

This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

Pulse-analysis-pulse investigation of femtosecond laser-induced periodic surface structures on silicon in air.

PubMed

Oboňa, J Vincenc; Skolski, J Z P; Römer, G R B E; in t Veld, A J Huis

2014-04-21

A new approach to experimentally investigate laser-induced periodic surface structures (LIPSSs) is introduced. Silicon was iteratively exposed to femtosecond laser pulses at λ = 800 nm and normal incidence in ambient air and at a fluence slightly over the single-pulse modification threshold. After each laser pulse, the topography of the surface was inspected by confocal microscopy. Subsequently, the sample was reproducibly repositioned in the laser setup, to be exposed to the next laser pulse. By this approach, the initiation and spatial evolution ("growth") of the LIPSSs were analyzed as function of the number of pulses applied. It was found that, after the first laser pulses, the ridges of the LIPSSs elevate, and valleys between the ridges deepen, by a few tens of nanometers relative to the initial surface. An electromagnetic model, discussed in earlier works, predicted that the spatial periodicity of LIPSSs decreases with the number of laser pulses applied. This implies material transport and reorganization of the irradiated material on the surface, due to each laser pulse. However, our experiments show a negligible shift of the lateral positions of the LIPSSs on the surface.

Simulation study of the sub-terawatt laser wakefield acceleration operated in self-modulated regime

NASA Astrophysics Data System (ADS)

Hsieh, C.-Y.; Lin, M.-W.; Chen, S.-H.

2018-02-01

Laser wakefield acceleration (LWFA) can be accomplished by introducing a sub-terawatt (TW) laser pulse into a thin, high-density gas target. In this way, the self-focusing effect and the self-modulation that happened on the laser pulse produce a greatly enhanced laser peak intensity that can drive a nonlinear plasma wave to accelerate electrons. A particle-in-cell model is developed to study sub-TW LWFA when a 0.6-TW laser pulse interacts with a dense hydrogen plasma. Gas targets having a Gaussian density profile or a flat-top distribution are defined for investigating the properties of sub-TW LWFA when conducting with a gas jet or a gas cell. In addition to using 800-nm laser pulses, simulations are performed with 1030-nm laser pulses, as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems. The peak density which allows the laser peak power PL˜2 Pc r of self-focusing critical power is favourable for conducting sub-TW LWFA. Otherwise, an excessively high peak density can induce an undesired filament effect which rapidly disintegrates the laser field envelope and violates the process of plasma wave excitation. The plateau region of a flat-top density distribution allows the self-focusing and the self-modulation of the laser pulse to develop, from which well-established plasma bubbles can be produced to accelerate electrons. The process of electron injection is complicated in such high-density plasma conditions; however, increasing the length of the plateau region represents a straightforward method to realize the injection and acceleration of electrons within the first bubble, such that an improved LWFA performance can be accomplished.

Multi-watt passively Q-switched Yb:YAB/Cr:YAG microchip lasers

NASA Astrophysics Data System (ADS)

Serres, Josep Maria; Loiko, Pavel; Mateos, Xavier; Liu, Junhai; Zhang, Huaijing; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc

2017-02-01

A trigonal 5.6 at.% Yb:YAl3(BO3)4 (Yb:YAB) crystal is employed in continuous-wave (CW) and passively Q-switched microchip lasers pumped by a diode at 978 nm. Using a 3 mm-thick, c-cut Yb:YAB crystal, which has a higher pump absorption efficiency, efficient CW microchip laser operation is demonstrated. This laser generated a maximum output power of 7.18 W at 1041-1044 nm with a slope efficiency η of 67% (with respect to the absorbed pump power) and an almost diffraction-limited beam, M2 x,y < 1.1. Inserting a Cr:YAG saturable absorber, stable passive Q-switching of the Yb:YAB microchip laser was obtained. The maximum average output power from the Yb:YAB/Cr:YAG laser reached 2.82 W at 1042 nm with η = 53% and a conversion efficiency with respect to the CW mode of 65% (when using a 0.7 mm-thick Cr:YAG). The latter corresponded to a pulse duration and energy of 7.1 ns / 47 μJ at a pulse repetition rate (PRR) of 60 kHz. Using a 1.3 mm-thick Cr:YAG, 2.02 W were achieved at 1041 nm corresponding to η = 38%. The pulse characteristics were 4.9 ns / 83 μJ at PRR = 24.3 kHz and the maximum peak power reached 17 kW. Yb:YAB crystals are very promising for compact sub-ns power-scalable microchip lasers.

Ultra-flat and ultra-broadband supercontinuum generation in photonic crystal fiber pumped by noise-like pulses

NASA Astrophysics Data System (ADS)

Chen, Yewang; Ruan, Shuangchen; Wu, Xu; Guo, Chunyu; Liu, Weiqi; Yu, Jun; Luo, Ruoheng; Ren, Xikui; Zhu, Yihuai

2017-02-01

An ultra-flat and ultra-broadband supercontinuum (SC) is demonstrated in a 4-m photonic crystal fiber (PCF) pumped by an Yb-doped all-fiber noise-like pulses (NLP) laser. The Yb-doped fiber laser is seeded by a SESAM mode-locked fiber laser, and amplified by cascaded fiber amplifiers, with its center wavelength, repetition frequency and the average noise-like bunch duration of 1064.52 nm, 50.18 MHz, 9.14 ps, respectively. Pumped by this NLP laser, the SC source has a 3 dB bandwidth and a 7 dB bandwidth (ignore the pump residue) of 1440 nm and 1790 nm at the maximum average output power of 6.94 W. To the best of our knowledge, this flatness is significantly prominent for the performance of PCF-based SC sources.

Comparative study of excimer and erbium:YAG lasers for ablation of structural components of the knee

NASA Astrophysics Data System (ADS)

Vari, Sandor G.; Shi, Wei-Qiang; van der Veen, Maurits J.; Fishbein, Michael C.; Miller, J. M.; Papaioannou, Thanassis; Grundfest, Warren S.

1991-05-01

This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm2 for the XeCl excimer and from 33 to 120 J/cm2 for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm2 and 110 J/cm2 radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

Diode-pumped passively Q-switched Nd:YAG ceramic laser with a gold nanotriangles saturable absorber at 1 µm

NASA Astrophysics Data System (ADS)

Bai, Jinxi; Li, Ping; Chen, Xiaohan; Guo, Lei; Wang, Lili; Liu, Binghai

2017-08-01

Passively Q-switched Nd:YAG ceramic lasers at 1064 and 1123 nm are demonstrated based on a gold nanotriangles saturable absorber (GNTs-SA) for the first time. The maximum average output power reaches 226 mW at 1064 nm and 172 mW at 1123 nm with corresponding shortest pulse widths and maximum pulse repetition rates of (179 ns, 320 kHz) and (231 ns, 457 kHz), respectively. Our results prove that the GNTs-SA is a promising saturable absorber around the 1-µm region.

Quasi-CW diode-pumped self-starting adaptive laser with self-Q-switched output.

PubMed

Smith, G; Damzen, M J

2007-05-14

An investigation is made into a quasi-CW (QCW) diode-pumped holographic adaptive laser utilising an ultra high gain (approximately 10(4)) Nd:YVO(4) bounce amplifier. The laser produces pulses at 1064 nm with energy approximately 0.6 mJ, duration <3 ns and peak power approximately 200 kW, with high stability, via self-Q-switching effects due to the transient dynamics of the writing and replay of the gain hologram for each pump pulse. The system produces a near-diffraction-limited output with M(2)<1.3 and operates with a single longitudinal mode. In a further adaptive laser configuration, the output was amplified to obtain pulses of approximately 5.6 mJ energy, approximately 7 ns duration and approximately 1 MW peak power. The output spatial quality is also M(2)<1.3 with SLM operation. Up to 2.9 mJ pulse energy of frequency doubled green (532 nm) radiation is obtained, using an LBO crystal, representing approximately 61% conversion efficiency. This work shows that QCW diode-pumped self-adaptive holographic lasers can provide a useful source of high peak power, short duration pulses with excellent spatial quality and narrow linewidth spectrum.

Silicon structuring by etching with liquid chlorine and fluorine precursors using femtosecond laser pulses

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

Radu, C.; Simion, S.; Zamfirescu, M.

2011-08-01

The aim of this study is to investigate the micrometer and submicrometer scale structuring of silicon by liquid chlorine and fluorine precursors with 200 fs laser pulses working at both fundamental (775 nm) and frequency doubled (387 nm) wavelengths. The silicon surface was irradiated at normal incidence by immersing the Si (111) substrates in a glass container filled with liquid chlorine (CCl{sub 4}) and fluorine (C{sub 2}Cl{sub 3}F{sub 3}) precursors. We report that silicon surfaces develop an array of spikes with single step irradiation processes at 775 nm and equally at 387 nm. When irradiating the Si surface with 400more » pulses at 330 mJ/cm{sup 2} laser fluence and a 775 nm wavelength, the average height of the formed Si spikes in the case of fluorine precursors is 4.2 {mu}m, with a full width at half maximum of 890 nm. At the same irradiation wavelength chlorine precursors develop Si spikes 4 {mu}m in height and with a full width at half maximum of 2.3 {mu}m with irradiation of 700 pulses at 560 mJ/cm{sup 2} laser fluence. Well ordered areas of submicrometer spikes with an average height of about 500 nm and a width of 300 nm have been created by irradiation at 387 nm by chlorine precursors, whereas the fluorine precursors fabricate spikes with an average height of 700 nm and a width of about 200 nm. Atomic force microscopy and scanning electron microscopy of the surface show that the formation of the micrometer and sub-micrometer spikes involves a combination of capillary waves on the molten silicon surface and laser-induced etching of silicon, at both 775 nm and 387 nm wavelength irradiation. The energy-dispersive x-ray measurements indicate the presence of chlorine and fluorine precursors on the structured surface. The fluorine precursors create a more ordered area of Si spikes at both micrometer and sub-micrometer scales. The potential use of patterned Si substrates with gradient topography as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth is envisaged.« less

Onset and evolution of laser induced periodic surface structures on indium tin oxide thin films for clean ablation using a repetitively pulsed picosecond laser at low fluence

NASA Astrophysics Data System (ADS)

Farid, N.; Dasgupta, P.; O’Connor, G. M.

2018-04-01

The onset and evolution of laser induced periodic surface structures (LIPSS) is of key importance to obtain clean ablated features on indium tin oxide (ITO) thin films at low fluences. The evolution of subwavelength periodic nanostructures on a 175 nm thick ITO film, using 10 ps laser pulses at a wavelength of 1032 nm, operating at 400 kHz, is investigated. Initially nanoblisters are observed when a single pulse is applied below the damage threshold fluence (0.45 J cm‑2) the size and distribution of nanoblisters are found to depend on fluence. Finite difference time domain (FDTD) simulations support the hypothesis that conductive nanoblisters can enhance the local intensity of the applied electromagnetic field. The LIPSS are observed to evolve from regions where the electric field enhancement has occurred; LIPSS has a perpendicular orientation relative to the laser polarization for a small number (<5) of applied pulses. The LIPSS periodicity depends on nanoblister size and distribution; a periodicity down to 100 nm is observed at the lower fluence periphery of the Gaussian irradiated area where nanoblisters are smallest and more closely arranged. Upon irradiation with successive (>5) pulses, the orientation of the periodic structures appears to rotate and evolve to become aligned in parallel with the laser polarization at approximately the same periodicity. These orientation effects are not observed at higher fluence—due to the absence of the nanoblister-like structures; this apparent rotation is interpreted to be due to stress-induced fragmentation of the LIPSS structure. The application of subsequent pulses leads to clean ablation. LIPSS are further modified into features of a shorter period when laser scanning is used. Results provide evidence that the formation of conductive nanoblisters leads to the enhancement of the applied electromagnetic field and thereby can be used to precisely control laser ablation on ITO thin films.

High-Power Single- and Dual-Wavelength Nd:GdVO4 Lasers with Potential Application for the Treatment of Telangiectasia

NASA Astrophysics Data System (ADS)

Chen, Lijuan; Wang, Zhengping; Yu, Haohai; Zhuang, Shidong; Han, Shuo; Zhao, Yongguang; Xu, Xinguang

2012-11-01

Diode-end-pumped high-power Nd:GdVO4 lasers at 1083 nm are presented. The maximum continuous-wave output power was 10.1 W with an optical conversion efficiency of 31.3%. For acoustooptic (AO) Q-switched operation, the largest pulse energy, shortest pulse width, and highest peak power were 111 µJ, 77 ns, and 1.44 kW, respectively. By decreasing the 1063 nm transmission of the output coupler, we also achieved efficient CW dual-wavelength operation at 1083 and 1063 nm. Their total output power reached 6.7 W, and the optical conversion efficiency reached 31.6%. These lasers have special requirements in the treatment of facial telangiectasia.

Au nanocage/SiO2 saturable absorber for passive Q-switching Yb-doped fiber laser

NASA Astrophysics Data System (ADS)

Bai, Jinxi; Li, Ping; Guo, Lei; Zhang, Baitao; Hu, Qiongyu; Wang, Lili; Liu, Binghai; Chen, Xiaohan

2018-05-01

Au nanocages/SiO2 (Au-NCs/SiO2) with the surface plasmon resonance peak at 1060 nm were fabricated and experimentally exploited as the saturable absorber in an all-fiber passively Q-switched ytterbium-doped fiber laser for the first time. Under a pump power of 440 mW, the average output power of 10.6 mW was obtained with the pulse duration 1.4 µs and the repetition rate of 126.9 kHz at 1060.5 nm with the 3 dB spectral width of 0.131 nm. The results indicate that Au-NCs/SiO2 exhibits the potential for applications in the field of pulse lasers.

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.

Portable double-sided pulsed laser heating system for time-resolved geoscience and materials science applications.

PubMed

Aprilis, G; Strohm, C; Kupenko, I; Linhardt, S; Laskin, A; Vasiukov, D M; Cerantola, V; Koemets, E G; McCammon, C; Kurnosov, A; Chumakov, A I; Rüffer, R; Dubrovinskaia, N; Dubrovinsky, L

2017-08-01

A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique. The system can be easily coupled with equipment at synchrotron facilities, particularly for nuclear resonance spectroscopy experiments. Examples of applications include investigations of high-pressure high-temperature behavior of iron oxides, both in house and at the European Synchrotron Radiation Facility using the synchrotron Mössbauer source and nuclear inelastic scattering.

Long-term operation of surface high-harmonic generation from relativistic oscillating mirrors using a spooling tape

DOE PAGES

Bierbach, Jana; Yeung, Mark; Eckner, Erich; ...

2015-05-01

Surface high-harmonic generation in the relativistic regime is demonstrated as a source of extreme ultra-violet (XUV) pulses with extended operation time. Relativistic high-harmonic generation is driven by a frequency-doubled high-power Ti:Sapphire laser focused to a peak intensity of 3·1019 W/cm2 onto spooling tapes. We demonstrate continuous operation over up to one hour runtime at a repetition rate of 1 Hz. Harmonic spectra ranging from 20 eV to 70 eV (62 nm to 18 nm) were consecutively recorded by an XUV spectrometer. An average XUV pulse energy in the µJ range is measured. With the presented setup, relativistic surface high-harmonic generationmore » becomes a powerful source of coherent XUV pulses that might enable applications in, e.g. attosecond laser physics and the seeding of free-electron lasers, when the laser issues causing 80-% pulse energy fluctuations are overcome.« less

Nanosecond-pulsed Q-switched Nd:YAG laser at 1064 nm with a gold nanotriangle saturable absorber

NASA Astrophysics Data System (ADS)

Chen, Xiaohan; Li, Ping; Dun, Yangyang; Song, Teng; Ma, Baomin

2018-06-01

Gold nanotriangles (GNTs) were successfully employed as a saturable absorber (SA) to achieve passively Q-switched lasers for the first time. The performance of the Q-switched Nd:YAG laser at 1064 nm has been systematically investigated. The corresponding shortest pulsewidth, the threshold pump power and the maximum Q-switched average output power were 275.5 ns, 1.37 W, and 171 mW, respectively. To our knowledge, this is the shortest pulsewidth and the lowest threshold in a passively Q-switched laser at approximately 1.1 µm based on a gold nanoparticle SA (GNPs-SA). Our experimental results proved that the GNTs-SA can be used as a promising saturable absorber for nanosecond-pulsed lasers.

Passively Q-switched Nd3+ solid-state lasers with antimonene as saturable absorber.

PubMed

Wang, Mengixa; Zhang, Fang; Wang, Zhengping; Wu, Zhixin; Xu, Xinguang

2018-02-19

Based on the saturable absorption feature of a two-dimensional (2D) nano-material, antimonene, the passively Q-switched operation for solid-state laser was realized for the first time. For the 946 and 1064 nm laser emissions of the Nd:YAG crystal, the Q-switched pulse widths were 209 and 129 ns, and the peak powers were 1.48, 1.77 W, respectively. For the 1342 nm laser emission of the Nd:YVO 4 crystal, the Q-switched pulse width was 48 ns, giving a peak power of 28.17 W. Our research shows that antimonene can be used as a stable, broadband optical modulating device for a solid-state laser, which will be particularly effective for long wavelength operation.

Review of Laser Ablation Process for Single Wall Carbon Nanotube Production

NASA Technical Reports Server (NTRS)

Arepalli, Sivaram

2003-01-01

Different types of lasers are now routinely used to prepare single wall carbon nanotubes (SWCNTs). The original method developed by researchers at Rice University utilized a "double pulse laser oven" process. A graphite target containing about 1 atomic percent of metal catalysts is ablated inside a 1473K oven using laser pulses (10 ns pulse width) in slow flowing argon. Two YAG lasers with a green pulse (532 nm) followed by an IR pulse (1064 nm) with a 50 ns delay are used for ablation. This set up produced single wall carbon nanotube material with about 70% purity having a diameter distribution peaked around 1.4 nm. The impurities consist of fullerenes, metal catalyst clusters (10 to 100 nm diameter) and amorphous carbon. The rate of production with the initial set up was about 60 mg per hour with 10Hz laser systems. Several researchers have used variations of the lasers to improve the rate, consistency and study effects of different process parameters on the quality and quantity of SWCNTs. These variations include one to three YAG laser systems (Green, Green and IR), different pulse widths (nano to microseconds as well as continuous) and different laser wavelengths (Alexandrite, CO, CO2, free electron lasers in the near to far infrared). It is noted that yield from the single laser (Green or IR) systems is only a fraction of the two laser systems. The yield seemed to scale up with the repetition rate of the laser systems (10 to 60 Hz) and depended on the beam uniformity and quality of the laser pulses. The shift to longer wavelength lasers (free electron, CO and CO2) did not improve the quality, but increased the rate of production because these lasers are either continuous (CW) or high repetition rate pulses (kHz to MHz). The average power and the peak power of the lasers seem to influence the yields. Very high peak powers (MegaWatts per square centimeter) are noted to increase ablation of bigger particles with reduced yields of SWCNTs. Increased average powers seem to help the conversion of the carbon from target into vapor phase to improve formation of nanotubes. The use of CW far infrared lasers reduced the need for the oven, at the expense of controlled ablation. Some of these variations are tried with different combinations and concentrations of metal catalysts (Nickel with Cobalt, Iron, Palladium and Platinum) different buffer gases (e.g. Helium); with different oven temperatures (Room temperature to 1473K); under different flow conditions (1 to 1000 kPa) and even different porosities of the graphite targets. It is to be noted that the original Cobalt and Nickel combination worked best, possibly because of improved carbonization with stable crystalline phases. The mean diameter and yield seemed to increase with increasing oven temperatures. Thermal conductivity of the buffer gas and flow conditions dictate the quality as well as quantity of the SWCNTs. Faster flows, lower pressures and heavier gases seem to increase the yields. This review will attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

Laser action in chromium-doped forsterite

NASA Technical Reports Server (NTRS)

Petricevic, V.; Gayen, S. K.; Alfano, R. R.; Yamagishi, Kiyoshi; Anzai, H.

1988-01-01

This paper reports on pulsed laser operation obtained in chromium-activated forsterite Cr(3+):Mg2SiO4 at room temperature. The spectrum of the free-running laser peaks at 1235 nm and a bandwidth of about 22 nm. The spectral range of the laser emission is expected to extend from 850 to 1300, provided the parasitic impurity absorption may be minimized by improved crystal growth techique.

Modulation of frequency doubled DFB-tapered diode lasers for medical treatment

NASA Astrophysics Data System (ADS)

Christensen, Mathias; Hansen, Anders K.; Noordegraaf, Danny; Jensen, Ole B.; Skovgaard, Peter M. W.

2017-02-01

The use of visible lasers for medical treatments is on the rise, and together with this comes higher expectations for the laser systems. For many medical treatments, such as ophthalmology, doctors require pulse on demand operation together with a complete extinction of the light between pulses. We have demonstrated power modulation from 0.1 Hz to 10 kHz at 532 nm with a modulation depth above 97% by wavelength detuning of the laser diode. The laser diode is a 1064 nm monolithic device with a distributed feedback (DFB) laser as the master oscillator (MO), and a tapered power amplifier (PA). The MO and PA have separate electrical contacts and the modulation is achieved with wavelength tuning by adjusting the current through the MO 40 mA.

Dual wavelength laser diode excitation source for 2D photoacoustic imaging.

NASA Astrophysics Data System (ADS)

Allen, Thomas J.; Beard, Paul C.

2007-02-01

Photoacoustic methods can be used to make spatially resolved spectroscopic measurements of blood oxygenation when using a multiwavelength excitation source, such as an OPO system. Since these excitation sources are usually expensive and bulky, an alternative is to use laser diodes. A fibre coupled laser diode excitation system has been developed, providing two wavelengths, 850 and 905nm, each composed of 6 high peak power pulsed laser diodes. The system provided variable pulse durations (65-500ns) and repetition rates of up to 5KHz. The pulse energies delivered by the excitation system at 905nm and 850nm were measured to be 120μJ and 80μJ respectively for a 200ns pulse duration. To demonstrate the utility of the system, the excitation source was combined with an ultrasound detector to form a probe for in vivo single point measurements of superficial blood vessels. Changes in blood oxygenation and volume in the finger tip were monitored while making venous and arterial occlusions. To demonstrate the imaging capability of the excitation system, 2D photoacoustic images of a physiologically realistic phantom were obtained for a range of pulse durations using a cylindrical scanning system. The phantom was composed of cylindrical absorbing elements (μa=1mm^{-1}) of 2.7mm diameter, immersed in a 1% intralipid solution (μs=1mm^{-1}). This study demonstrated the potential use of laser diodes as an excitation source for photoacoustic imaging of superficial vascular structures.

Comparative study of pulsed laser cleaning applied to weathered marble surfaces

NASA Astrophysics Data System (ADS)

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

2013-10-01

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

30-W Yb3+-pulsed fiber laser with wavelength tuning

NASA Astrophysics Data System (ADS)

Davydov, B. L.; Krylov, A. A.

2007-12-01

We have investigated various pulsed operation regimes of a diode-pumped Yb3+-doped fiber laser with both an acoustooptic filter and a shutter inside the resonator. To imbed the polarization-sensitive acoustooptic-tunable spectral filter into the polarization-nonmaintaining resonator, based on an “isotropic” single-mode fiber without “polarization’ losses, we have used a CaCO3 single-crystal nondispersive thermostable polarization splitter. Stable smooth bell-shaped laser pulses were obtained in the Q-switch generation regime across the entire wavelength tuning band. Their duration depended on the resonator travel time and their repetition rate was determined exclusively by the outer high-frequency generator controlling the acoustooptic shutter. A pulsed laser radiation tuning bandwidth of more than 20-nm at a repetition rate band of 10-100 kHz was observed in the amplification band of the Yb3+-doped fiber. A stable average power of 30 W of the pulsed 70-ns 100-kHz laser radiation in a near Gaussian beam was reached by means of the two-stage amplifier based on Yb3+-doped fibers with an enlarged mode field diameter (14 μm). The amplifier was pumped by λ = 975 nm CW multimode laser diodes with a maximum average power of 42 W.

Analysis of laser damage tests on coatings designed for broad bandwidth high reflection of femtosecond pulses

DOE PAGES

Bellum, John Curtis; Winstone, Trevor; Lamaignere, Laurent; ...

2016-08-25

We designed an optical coating based on TiO 2/SiO 2 layer pairs for broad bandwidth high reflection (BBHR) at 45-deg angle of incidence (AOI), P polarization of femtosecond (fs) laser pulses of 900-nm center wavelength, and produced the coatings in Sandia’s large optics coater by reactive, ion-assisted e-beam evaporation. This paper reports on laser-induced damage threshold (LIDT) tests of these coatings. The broad HR bands of BBHR coatings pose challenges to LIDT tests. An ideal test would be in a vacuum environment appropriate to a high energy, fs-pulse, petawatt-class laser, with pulses identical to its fs pulses. Short of thismore » would be tests over portions of the HR band using nanosecond or sub-picosecond pulses produced by tunable lasers. Such tests could, e.g., sample 10-nm-wide wavelength intervals with center wavelengths tunable over the broad HR band. Alternatively, the coating’s HR band could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to the coating absorbing moisture under ambient conditions. In conclusion, we had LIDT tests performed on the BBHR coatings at selected AOIs to gain insight into their laser damage properties and analyze how the results of the different LIDT tests compare.« less

Analysis of laser damage tests on coatings designed for broad bandwidth high reflection of femtosecond pulses

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

Bellum, John Curtis; Winstone, Trevor; Lamaignere, Laurent

We designed an optical coating based on TiO 2/SiO 2 layer pairs for broad bandwidth high reflection (BBHR) at 45-deg angle of incidence (AOI), P polarization of femtosecond (fs) laser pulses of 900-nm center wavelength, and produced the coatings in Sandia’s large optics coater by reactive, ion-assisted e-beam evaporation. This paper reports on laser-induced damage threshold (LIDT) tests of these coatings. The broad HR bands of BBHR coatings pose challenges to LIDT tests. An ideal test would be in a vacuum environment appropriate to a high energy, fs-pulse, petawatt-class laser, with pulses identical to its fs pulses. Short of thismore » would be tests over portions of the HR band using nanosecond or sub-picosecond pulses produced by tunable lasers. Such tests could, e.g., sample 10-nm-wide wavelength intervals with center wavelengths tunable over the broad HR band. Alternatively, the coating’s HR band could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to the coating absorbing moisture under ambient conditions. In conclusion, we had LIDT tests performed on the BBHR coatings at selected AOIs to gain insight into their laser damage properties and analyze how the results of the different LIDT tests compare.« less

Comparative evaluation of antimicrobial effects of Er:YAG, diode, and CO₂ lasers on titanium discs: an experimental study.

PubMed

Tosun, Emre; Tasar, Ferda; Strauss, Robert; Kıvanc, Dolunay Gulmez; Ungor, Cem

2012-05-01

This study examined carbon dioxide (CO(2); 10,600 nm), diode (808 nm), and erbium (Er):yttrium-aluminum-garnet (YAG; 2,940 nm) laser applications on Staphylococcus aureus contaminated, sandblasted, large-grit, acid-etched surface titanium discs and performed a comparative evaluation of the obtained bactericidal effects and the applicability of these effects in clinical practice. This study was carried out in 5 main groups: Er:YAG laser in very short pulse (VSP) emission mode, Er:YAG laser in short pulse (SP) emission mode, diode laser with a 320-nm fiber optic diode laser with an R24-B handpiece, and CO(2) laser. After laser irradiation, dilutions were spread on sheep blood agar plates and, after an incubation period of 24 hours, colony-forming units were counted and compared with the control group, and the bactericidal activity was assessed in relation to the colony counts. The CO(2) laser eliminated 100% of the bacteria at 6 W, 20 Hz, and a 10-ms exposure time/pulse with a 10-second application period (0.8-mm spot size). The continuous-wave diode laser eliminated 97% of the bacteria at 1 W using a 10-second application with a 320-μm optic fiber, 100% of the bacteria were killed with a 1-W, 10-second continuous-wave application with an R14-B handpiece. The Er:YAG laser eliminated 100% of the bacteria at 90 mJ and 10 Hz using a 10-second application in a superpulse mode (300-ms exposure time/pulse). The Er:YAG laser also eliminated 99% to 100% of the bacteria in VSP mode at 90 mJ and 10 Hz with a 10-second application. The results of this study show that a complete, or near complete, elimination of surface bacteria on titanium surfaces can be accomplished in vitro using a CO(2), diode, or Er:YAG laser as long as appropriate parameters are used. Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. All rights reserved.

High peak power actively Q-switched mid-infrared fiber lasers at 3 μm

NASA Astrophysics Data System (ADS)

Shen, Yanlong; Wang, Yishan; Luan, Kunpeng; Chen, Hongwei; Tao, Mengmeng; Si, Jinhai

2017-04-01

Diode-pumped pulsed Er3+-doped ZBLAN fiber lasers at 2.8 μm actively Q-switched by using an mechanical Q-switch with feedbacks of a protected gold mirror and a blazing grating were investigated, respectively. A pulse energy of 0.13 mJ and repetition rate of 10 kHz with a pulse width of 127.3 ns at 2.78 μm was obtained when using a protected gold mirror as the feedback. By replacing the mirror with a blazing grating in Littrow configuration, the wavelength of the Q-switched pulse train was tunable with over 100 nm tuning range from 2.71 to 2.82 μm and a linewidth of 1.5 nm. A maxinmum pulse energy of up to 0.15 mJ and repetition rate of 10 kHz with a pulse width of 92.6 ns was achieved, yielding the maximum peak power of exceeding 1.6 kW. The pulse energy and peak power, to our knowledge, are the highest ever reported in the mid-infrared Q-switched fiber lasers.

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

PubMed

Wang, Jenny; Schuele, Georg; Palanker, Daniel

2015-01-01

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

Self-mode-locked chromium-doped forsterite laser generates 50-fs pulses

NASA Technical Reports Server (NTRS)

Seas, A.; Petricevic, V.; Alfano, R. R.

1993-01-01

Stable transform-limited (delta nu-delta tau = 0.32) femtosecond pulses with a FWHM of 50 fs were generated from a self-mode-locked chromium-doped forsterite laser. The forsterite laser was synchronously pumped by a CW mode-locked Nd:YAG (82 MHz) laser that generated picosecond pulses (200-300 ps) and provided the starting mechanism for self-mode-locked operation. Maximum output power was 45 mW for 3.9 W of absorbed pumped power with the use of an output coupler with 1 percent transmission. The self-mode-locked forsterite laser was tuned from 1240 to 1270 nm.

A novel dual-wavelength laser stimulator to elicit transient and tonic nociceptive stimulation.

PubMed

Dong, Xiaoxi; Liu, Tianjun; Wang, Han; Yang, Jichun; Chen, Zhuying; Hu, Yong; Li, Yingxin

2017-07-01

This study aimed to develop a new laser stimulator to elicit both transient and sustained heat stimulation with a dual-wavelength laser system as a tool for the investigation of both transient and tonic experimental models of pain. The laser stimulator used a 980-nm pulsed laser to generate transient heat stimulation and a 1940-nm continuous-wave (CW) laser to provide sustained heat stimulation. The laser with 980-nm wavelength can elicit transient pain with less thermal injury, while the 1940-nm CW laser can effectively stimulate both superficial and deep nociceptors to elicit tonic pain. A proportional integral-derivative (PID) temperature feedback control system was implemented to ensure constancy of temperature during heat stimulation. The performance of this stimulator was evaluated by in vitro and in vivo animal experiments. In vitro experiments on totally 120 specimens fresh pig skin included transient heat stimulation by 980-nm laser (1.5 J, 10 ms), sustained heat stimulation by 1940-nm laser (50-55 °C temperature control mode or 1.5 W, 5 min continuous power supply), and the combination of transient/sustained heat stimulation by dual lasers (1.5 J, 10 ms, 980-nm pulse laser, and 1940-nm laser with 50-55 °C temperature control mode). Hemoglobin brushing and wind-cooling methods were tested to find better stimulation model. A classic tail-flick latency (TFL) experiment with 20 Wistar rats was used to evaluate the in vivo efficacy of transient and tonic pain stimulation with 15 J, 100 ms 980-nm single laser pulse, and 1.5 W constant 1940-nm laser power. Ideal stimulation parameters to generate transient pain were found to be a 26.6 °C peak temperature rise and 0.67 s pain duration. In our model of tonic pain, 5 min of tonic stimulation produced a temperature change of 53.7 ± 1.3 °C with 1.6 ± 0.2% variation. When the transient and tonic stimulation protocols were combined, no significant difference was observed depending on the order of stimuli. Obvious tail-flick movements were observed. The TFL value of transient pain was 3.0 ± 0.8 s, and it was 4.4 ± 1.8 s for tonic pain stimulation. This study shows that our novel design can provide effective stimulation of transient pain and stable tonic pain. Furthermore, it can also provide a reliable combination of transient and consistent stimulations for basic studies of pain perception.

Ultrashort laser pulse driven inverse free electron laser accelerator experiment

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

Moody, J. T.; Anderson, S. G.; Anderson, G.

In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

Ultrashort laser pulse driven inverse free electron laser accelerator experiment

DOE PAGES

Moody, J. T.; Anderson, S. G.; Anderson, G.; ...

2016-02-29

In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

1540-nm single frequency single-mode pulsed all fiber laser for coherent Doppler lidar

NASA Astrophysics Data System (ADS)

Zhang, Xin; Diao, Weifeng; Liu, Yuan; Liu, Jiqiao; Hou, Xia; Chen, Weibiao

2015-02-01

A single-mode single frequency eye-safe pulsed all fiber laser based on master oscillator power amplification structure is presented. This laser is composed of a narrow linewidth distributed laser diode seed laser and two-stage cascade amplifiers. 0.8 m longitudinally gradient strained erbium/ytterbium co-doped polarization-maintaining fiber with a core diameter of 10 μm is used as the gain fiber and two acoustic-optics modulators are adopted to enhance pulse extinction ratio. A peak power of 160 W and a pulse width of 200 ns at 10 kHz repetition rate are achieved with transform-limited linewidth and diffraction-limited beam quality. This laser will be employed in a compact short range coherent Doppler wind lidar.

Formation of small gold clusters in solution by laser excitation of interband transition

NASA Astrophysics Data System (ADS)

Mafuné, Fumitaka; Kondow, Tamotsu

2003-04-01

Gold nanoparticles with ˜10 nm in average diameter were prepared by laser ablation of a gold metal plate in an aqueous solution of sodium dodecyl sulfate (SDS) and were fragmented by excitation of an interband transition of gold nanoparticles under irradiation of an intense 355-nm pulsed laser. Fragmentation dynamics was investigated by comparing the fragmentation by excitation of a surface plasmon band of gold nanoparticles by a 532-nm laser. It is found that gold nanoparticles with 1.5-nm average diameter are produced together with small gold clusters by properly optimizing the surfactant concentration.

Diode-pumped continuous wave tunable and graphene Q-switched Tm:LSO lasers.

PubMed

Feng, T L; Zhao, S Z; Yang, K J; Li, G Q; Li, D C; Zhao, J; Qiao, W C; Hou, J; Yang, Y; He, J L; Zheng, L H; Wang, Q G; Xu, X D; Su, L B; Xu, J

2013-10-21

We have investigated the lasing characteristics of Tm:LSO crystal in three operation regimes: continuous wave (CW), wavelength tunable and passive Q-switching based on graphene. In CW regime, a maximum output power of 0.65 W at 2054.9 nm with a slope efficiency of 21% was achieved. With a quartz plate, a broad wavelength tunable range of 145 nm was obtained, corresponding to a FWHM of 100 nm. By using a graphene saturable absorber mirror, the passively Q-switched Tm:LSO laser produced pulses with duration of 7.8 μs at 2030.8 nm under a repetition rate of 7.6 kHz, corresponding to pulse energy of 14.0 μJ.

Effect of pulse temporal shape on optical trapping and impulse transfer using ultrashort pulsed lasers.

PubMed

Shane, Janelle C; Mazilu, Michael; Lee, Woei Ming; Dholakia, Kishan

2010-03-29

We investigate the effects of pulse duration on optical trapping with high repetition rate ultrashort pulsed lasers, through Lorentz-Mie theory, numerical simulation, and experiment. Optical trapping experiments use a 12 femtosecond duration infrared pulsed laser, with the trapping microscope's temporal dispersive effects measured and corrected using the Multiphoton Intrapulse Interference Phase Scan method. We apply pulse shaping to reproducibly stretch pulse duration by 1.5 orders of magnitude and find no material-independent effects of pulse temporal profile on optical trapping of 780nm silica particles, in agreement with our theory and simulation. Using pulse shaping, we control two-photon fluorescence in trapped fluorescent particles, opening the door to other coherent control applications with trapped particles.

Treatment of burn scars in Fitzpatrick phototype III patients with a combination of pulsed dye laser and non-ablative fractional resurfacing 1550 nm erbium:glass/1927 nm thulium laser devices.

PubMed

Tao, Joy; Champlain, Amanda; Weddington, Charles; Moy, Lauren; Tung, Rebecca

2018-01-01

Burn scars cause cosmetic disfigurement and psychosocial distress. We present two Fitzpatrick phototype (FP) III patients with burn scars successfully treated with combination pulsed dye laser (PDL) and non-ablative fractional lasers (NAFL). A 30-year-old, FP III woman with a history of a second-degree burn injury to the bilateral arms and legs affecting 30% body surface area (BSA) presented for cosmetic treatment. The patient received three treatments with 595 nm PDL (7 mm, 8 J, 6 ms), six with the 1550 nm erbium:glass laser (30 mJ, 14% density, 4-8 passes) and five with the 1927 nm thulium laser (10 mJ, 30% density, 4-8 passes). Treated burn scars improved significantly in thickness, texture and colour. A 33-year-old, FP III man with a history of a second-degree burn injury of the left neck and arm affecting 7% BSA presented for cosmetic treatment. The patient received two treatments with 595 nm PDL (5 mm, 7.5 J, 6 ms), four with the 1550 nm erbium:glass laser (30 mJ, 14% density, 4-8 passes) and two with the 1927 nm thulium laser (10 mJ, 30% density, 4-8 passes). The burn scars became thinner, smoother and more normal in pigmentation and appearance. Our patients' burn scars were treated with a combination of PDL and NAFL (two wavelengths). The PDL targets scar hypervascularity, the 1550 nm erbium:glass stimulates collagen remodelling and the 1927 nm thulium targets epidermal processes, particularly hyperpigmentation. This combination addresses scar thickness, texture and colour with a low side effect profile and is particularly advantageous in patients at higher risk of post-procedure hyperpigmentation. Our cases suggest the combination of 595nm PDL plus NAFL 1550 nm erbium:glass/1927 nm thulium device is effective and well-tolerated for burn scar treatment in skin of colour.

Laser direct writing (LDW) of magnetic structures

NASA Astrophysics Data System (ADS)

Alasadi, Alaa; Claeyssens, F.; Allwood, D. A.

2018-05-01

Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repetition rate allowed wire arrays across an area of 4 mm x 0.18 mm to be patterned in 85 s.

Organic semiconductor rubrene thin films deposited by pulsed laser evaporation of solidified solutions

NASA Astrophysics Data System (ADS)

Majewska, N.; Gazda, M.; Jendrzejewski, R.; Majumdar, S.; Sawczak, M.; Śliwiński, G.

2017-08-01

Organic semiconductor rubrene (C42H28) belongs to most preferred spintronic materials because of the high charge carrier mobility up to 40 cm2(V·s)-1. However, the fabrication of a defect-free, polycrystalline rubrene for spintronic applications represents a difficult task. We report preparation and properties of rubrene thin films deposited by pulsed laser evaporation of solidified solutions. Samples of rubrene dissolved in aromatic solvents toluene, xylene, dichloromethane and 1,1-dichloroethane (0.23-1% wt) were cooled to temperatures in the range of 16.5-163 K and served as targets. The target ablation was provided by a pulsed 1064 nm or 266 nm laser. For films of thickness up to 100 nm deposited on Si, glass and ITO glass substrates, the Raman and AFM data show presence of the mixed crystalline and amorphous rubrene phases. Agglomerates of rubrene crystals are revealed by SEM observation too, and presence of oxide/peroxide (C42H28O2) in the films is concluded from matrix-assisted laser desorption/ionization time-of-flight spectroscopic analysis.

Widely-tunable, passively Q-switched erbium-doped fiber laser with few-layer MoS2 saturable absorber.

PubMed

Huang, Yizhong; Luo, Zhengqian; Li, Yingyue; Zhong, Min; Xu, Bin; Che, Kaijun; Xu, Huiying; Cai, Zhiping; Peng, Jian; Weng, Jian

2014-10-20

We propose and demonstrate a MoS2-based passively Q-switched Er-doped fiber laser with a wide tuning range of 1519.6-1567.7 nm. The few-layer MoS2 nano-platelets are prepared by the liquid-phase exfoliation method, and are then made into polymer-composite film to construct the fiber-compatible MoS2 saturable absorber (SA). It is measured at 1560 nm wavelength, that such MoS2 SA has the modulation depth of ∼ 2% and the saturable optical intensity of ∼ 10 MW/cm(2). By further inserting the filmy MoS2-SA into an Er-doped fiber laser, stable Q-switching operation with a 48.1 nm continuous tuning from S- to C-waveband is successfully achieved. The shortest pulse duration and the maximum pulse energy are 3.3 μs and 160 nJ, respectively. The repetition rate and the pulse duration under different operation conditions have been also characterized. To the best of our knowledge, it is the first demonstration of MoS2 Q-switched, widely-tunable fiber laser.

Generation of multiple spectral bands in a diode-pumped self-mode-locked Nd:YAP laser

NASA Astrophysics Data System (ADS)

Huang, Y. J.; Tzeng, Y. S.; Cho, H. H.; Chen, Y. F.; Chen, W. D.; Zhang, G.; Chen, T. C.

2016-02-01

A single- and multispectral-band diode end-pumped self-mode-locked Nd:YAP laser is originally demonstrated with an intracavity etalon to properly control the gain-to-loss ratios among the intermanifold lines on the 4F3/2  →  4I11/2 transition level. With a pulse repetition rate of 5.07 GHz, the shortest pulse durations under the single-spectral-band operation are achieved to be 11.1 ps at 1073 nm, 10.9 ps at 1080 nm, and 15.1 ps at 1084 nm, respectively. Moreover, the temporal overlapping of the multispectral-band pulses is experimentally found to lead to the generation of an intensity fringe pattern in the autocorrelation trace with the optical-beat frequency reaching several terahertz. A simple mathematical model is developed to elucidate the formation of a train of optical-beat pulses.

Nanosecond laser pulse stimulation of spiral ganglion neurons and model cells.

PubMed

Rettenmaier, Alexander; Lenarz, Thomas; Reuter, Günter

2014-04-01

Optical stimulation of the inner ear has recently attracted attention, suggesting a higher frequency resolution compared to electrical cochlear implants due to its high spatial stimulation selectivity. Although the feasibility of the effect is shown in multiple in vivo experiments, the stimulation mechanism remains open to discussion. Here we investigate in single-cell measurements the reaction of spiral ganglion neurons and model cells to irradiation with a nanosecond-pulsed laser beam over a broad wavelength range from 420 nm up to 1950 nm using the patch clamp technique. Cell reactions were wavelength- and pulse-energy-dependent but too small to elicit action potentials in the investigated spiral ganglion neurons. As the applied radiant exposure was much higher than the reported threshold for in vivo experiments in the same laser regime, we conclude that in a stimulation paradigm with nanosecond-pulses, direct neuronal stimulation is not the main cause of optical cochlea stimulation.

Analysis of hybrid mode-locking of two-section quantum dot lasers operating at 1.5 microm.

PubMed

Heck, Martijn J R; Salumbides, Edcel J; Renault, Amandine; Bente, Erwin A J M; Oei, Yok-Siang; Smit, Meint K; van Veldhoven, René; Nötzel, Richard; Eikema, Kjeld S E; Ubachs, Wim

2009-09-28

For the first time a detailed study of hybrid mode-locking in two-section InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material.

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 fiber-MOPA-based high power blue laser

NASA Astrophysics Data System (ADS)

Engin, Doruk; Fouron, Jean-Luc; Chen, Youming; Huffman, Andromeda; Fitzpatrick, Fran; Burnham, Ralph; Gupta, Shantanu

2012-06-01

5W peak power at 911 nm is demonstrated with a pulsed Neodymium (Nd) doped fiber master oscillator power amplifier (MOPA). This result is the first reported high gain (16dB) fiber amplifier operation at 911nm. Pulse repetition frequency (PRF) and duty-cycle dependence of the all fiber system is characterized. Negligible performance degreadation is observed down to 1% duty cycle and 10 kHz PRF, where 2.5μJ of pulse energy is achieved. Continuous wave (CW) MOPA experiments achieved 55mW average power and 9dB gain with 15% optical to optical (o-o) efficiency. Excellent agreement is established between dynammic fiber MOPA simulation tool and experimental results in predicting output amplified spontaneous emission (ase) and signal pulse shapes. Using the simulation tool robust Stimulated Brillion Scattering (SBS) free operation is predicted out of a two stage all fiber system that generates over 10W's of peak power with 500 MHz line-width. An all fiber 911 nm pulsed laser source with >10W of peak power is expected to increase reliability and reduce complexity of high energy 455 nm laser system based on optical parametric amplification for udnerwater applications. The views expressed are thos of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government.

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.

An investigation on 800 nm femtosecond laser ablation of K9 glass in air and vacuum

NASA Astrophysics Data System (ADS)

Xu, Shi-zhen; Yao, Cai-zhen; Dou, Hong-qiang; Liao, Wei; Li, Xiao-yang; Ding, Ren-jie; Zhang, Li-juan; Liu, Hao; Yuan, Xiao-dong; Zu, Xiao-tao

2017-06-01

Ablation rates of K9 glass were studied as a function of femtosecond laser fluences. The central wavelength was 800 nm, and pulse durations of 35 fs and 500 fs in air and vacuum were employed. Ablation thresholds of 0.42 J/cm2 and 2.1 J/cm2 were obtained at 35 fs and 500 fs, respectively, which were independent with the ambient conditions and depend on the incident pulse numbers due to incubation effects. The ablation rate of 35 fs pulse laser increased with the increasing of laser fluence in vacuum, while in air condition, it slowly increased to a plateau at high fluence. The ablation rate of 500 fs pulse laser showed an increase at low fluence and a slow drop of ablation rate was observed at high fluence in air and vacuum, which may due to the strong defocusing effects associated with the non-equilibrium ionization of air, and/or the shielding effects of conduction band electrons (CBEs) produced by multi-photon ionization and impact ionization in K9 glass surface. The typical ablation morphologies, e.g. smooth zone and laser-induced periodic surface structures (LIPSS) were also presented and illustrated.

Extracting the distribution of laser damage precursors on fused silica surfaces for 351 nm, 3 ns laser pulses at high fluences (20-150 J/cm2).

PubMed

Laurence, Ted A; Bude, Jeff D; Ly, Sonny; Shen, Nan; Feit, Michael D

2012-05-07

Surface laser damage limits the lifetime of optics for systems guiding high fluence pulses, particularly damage in silica optics used for inertial confinement fusion-class lasers (nanosecond-scale high energy pulses at 355 nm/3.5 eV). The density of damage precursors at low fluence has been measured using large beams (1-3 cm); higher fluences cannot be measured easily since the high density of resulting damage initiation sites results in clustering. We developed automated experiments and analysis that allow us to damage test thousands of sites with small beams (10-30 µm), and automatically image the test sites to determine if laser damage occurred. We developed an analysis method that provides a rigorous connection between these small beam damage test results of damage probability versus laser pulse energy and the large beam damage results of damage precursor densities versus fluence. We find that for uncoated and coated fused silica samples, the distribution of precursors nearly flattens at very high fluences, up to 150 J/cm2, providing important constraints on the physical distribution and nature of these precursors.

Single- and multi-pulse formation of surface structures under static femtosecond irradiation

NASA Astrophysics Data System (ADS)

Guillermin, M.; Garrelie, F.; Sanner, N.; Audouard, E.; Soder, H.

2007-07-01

Femtosecond surface structure modifications are investigated under irradiation with laser pulses of 150 fs at 800 nm, on copper and silicon. We report sub-wavelength periodic structures formation (ripples) with a periodicity of 500 nm for both materials. These ripples are perpendicular to the laser polarization and can be obtained with only one pulse. The formation of these ripples corresponds to a fluence threshold of 1 J/cm 2 for copper and 0.15 J/cm 2 for silicon. We find several morphologies when more pulses are applied: larger ripples parallel to the polarization are formed with a periodicity of 1 μm and degenerate into a worm-like morphology with a higher number of pulses. In addition, walls of deep holes also show sub-wavelength and large ripples.

A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

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

Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.

2015-05-18

Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation timesmore » (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.« less

Diode pumped tunable lasers based on Tm:CaF2 and Tm:Ho:CaF2 ceramics

NASA Astrophysics Data System (ADS)

Šulc, Jan; Němec, Michal; Jelinková, Helena; Doroshenko, Maxim E.; Fedorov, Pavel P.; Osiko, Vyacheslav V.

2014-02-01

The Tm:CaF2 (4% of TmF3) and Tm:Ho:CaF2 (2% of TmF3, 0.3% of HoF3) ceramics, prepared using hot pressing, and hot formation technique had been used as an active medium of diode pumped mid-infrared tunable laser. A fibre (core diameter 400 μm, NA = 0.22) coupled laser diode (LIMO, HLU30F400-790) was used to longitudinal pumping. The laser diode was operating in the pulsed regime (6 ms pulse length, 10 Hz repetition rate). The duty-cycle 6% ensures a low thermal load even under the maximum diode pumping power amplitude 25W (ceramics samples were only air-cooled). The laser diode emission wavelength was 786 nm. The 80mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.85 - 2.15 μm, HT @ 0.78 μm) and a curved (r = 150mm) output coupler with a reflectivity of ˜ 98% @ 1.85 - 2.0 μm for Tm:CaF2 laser or ˜ 99.5% @ 2.0 - 2.15 μm for Ho:Tm:CaF2. Tuning of the laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle. Both samples offered broad and smooth tuning possibilities in mid-IR spectral range and the lasers were continuously tunable over ˜ 100 nm. The obtained Tm:CaF2 tunability ranged from 1892 to 1992nm (the maximum output energy 1.8mJ was reached at 1952nm for absorbed pumping energy 78 mJ). In case of Tm:Ho:CaF2 laser tunability from 2016 to 2111nm was reached (the maximum output energy 1.5mJ was reached at 2083nm for absorbed pumping energy 53 mJ). Both these material are good candidates for a future investigation of high energy, ultra-short, laser pulse generation.

Analysis of Indium Tin Oxide Film Using Argon Fluroide (ArF) Laser-Excited Atomic Fluorescence of Ablated Plumes.

PubMed

Ho, Sut Kam; Garcia, Dario Machado

2017-04-01

A two-pulse laser-excited atomic fluorescence (LEAF) technique at 193 nm wavelength was applied to the analysis of indium tin oxide (ITO) layer on polyethylene terephthalate (PET) film. Fluorescence emissions from analytes were induced from plumes generated by first laser pulse. Using this approach, non-selective LEAF can be accomplished for simultaneous multi-element analysis and it overcomes the handicap of strict requirement for laser excitation wavelength. In this study, experimental conditions including laser fluences, times for gating and time delay between pulses were optimized to reveal high sensitivity with minimal sample destruction and penetration. With weak laser fluences of 100 and 125 mJ/cm 2 for 355 and 193 nm pulses, detection limits were estimated to be 0.10% and 0.43% for Sn and In, respectively. In addition, the relation between fluorescence emissions and number of laser shots was investigated; reproducible results were obtained for Sn and In. It shows the feasibility of depth profiling by this technique. Morphologies of samples were characterized at various laser fluences and number of shots to examine the accurate penetration. Images of craters were also investigated using scanning electron microscopy (SEM). The results demonstrate the imperceptible destructiveness of film after laser shot. With such weak laser fluences and minimal destructiveness, this LEAF technique is suitable for thin-film analysis.

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.

Removal of Verrucaria nigrescens from Carrara marble artefacts using Nd:YAG lasers: comparison among different pulse durations and wavelengths

NASA Astrophysics Data System (ADS)

Osticioli, I.; Mascalchi, M.; Pinna, D.; Siano, S.

2015-03-01

The periodical removal of biodeteriogens is a fundamental need for the preservation of outdoor stone cultural heritage, which is stimulating significant efforts toward the development of low-impact conservation strategies. In the present work, the potential of laser removal of Verrucaria nigrescens Pers. from Carrara marble and the evaluation of the associated biocide effect on the organism residues embedded in the surface texture and through the outer porosities of the stone substrate were investigated. The fundamental wavelength of Nd:YAG laser (1,064 nm), commonly used in stone cleaning, and its second harmonic (532 nm) were comparatively tested. The phenomenology of laser treatments carried out in different irradiation conditions was characterized using optical, epifluorescence, and electron microscopes along with chlorophyll fluorescence with pulsed amplitude-modulated imaging. The results achieved show that 532 nm can provide significant advantages with respect to 1,064 nm. The potential of the latter against the biodeteriogens appears rather limited because of the low optical absorption, whereas the former can allow effective and practicable laser treatments, which disclose a significant application perspective.

Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration

NASA Astrophysics Data System (ADS)

Liu, Wenjun; Liu, Mengli; OuYang, Yuyi; Hou, Huanran; Ma, Guoli; Lei, Ming; Wei, Zhiyi

2018-04-01

In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.

Determination of chlorine, sulfur and carbon in reinforced concrete structures by double-pulse laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Labutin, Timur A.; Popov, Andrey M.; Zaytsev, Sergey M.; Zorov, Nikita B.; Belkov, Mikhail V.; Kiris, Vasilii V.; Raikov, Sergey N.

2014-09-01

Accurate and reliable quantitative determination of non-metal corrosion agents in concrete is still an actual task of analytical use of LIBS. Two double-pulse LIBS systems were tested as a tool for the determination of chlorine, sulfur and carbon in concretes. Both systems had collinear configuration; a laboratory setup was equipped with an ICCD and two lasers (355/532 nm + 540 nm), but a CCD was a detector for a mobile system with one laser (1064 nm). Analytical lines of Cl I at 837.59 nm, S I at 921 nm and C I at 247.86 nm were used to plot calibration curves. Optimal interpulse delays for the laboratory setup were 4 μs for chlorine and 2.8 μs for carbon, while an interpulse delay of 2 μs was optimal for chlorine and sulfur determination with the mobile system. We suggested the normalization of the Cl I line at 837.59 nm to the Mg II line at 279.08 nm (visible at 837.23 nm in the third order) to compensate for pulse-to-pulse fluctuations of chlorine lines. It provided the decrease of the detection limit of chlorine from 400 ppm to 50 ppm. Therefore, we reported that LIBS can be used to determine main corrosive active substances under ambient conditions in concrete below critical threshold values. Moreover, the application of the mobile system for in-situ qualitative assessment of corrosion way of a steel cage of a swimming pool dome was also demonstrated. It was found that chloride corrosion due to the disinfection of water was the main way for corrosion of the open part steel and the steel rebar inside the concrete.