[Effect of CO2 laser on prostheses used in middle ear surgery].

PubMed

Szymański, Marcin

2005-01-01

The use of CO2 laser is advocated in primary and revision stapes surgery. The aim of the study was to assess the effect of CO2 laser on stapes prostheses. CO2 laser was applied on several types of stapes prostheses and PORPs, with power settings suggested by the manufacturer (continuous wave, 2 W and 6 W; 0,05 s). Application of the laser on stainless steel or titanium prosthesis did not exert any effect on the structure of the prosthesis. The use of the laser on the Teflon piston caused superficial burning with power 2 W, and melting and holes in the piston with power settings at 6W. Similar plastipore prostheses were melting. Hydroxyapatite PORP shattered after application of the laser energy. Teflon and hydroxyapatite prostheses are easily damaged by the laser energy, therefore applying a laser on them should be avoided. CO2 laser can be used on stainless steel and titanium prostheses without risk of damaging them. However the possibility of transmission of heat to the vestibule has to be taken into consideration.

Miniaturized Laser Heterodyne Radiometer for Measurements of CO2 in the Atmospheric Column

NASA Technical Reports Server (NTRS)

Wilson, E. L.; Mclinden, M. L.; Miller, J. H.; Allan, G. R.; Lott, L. E.; Melroy, H. R.; Clarke, G. B.

2013-01-01

We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H2O) and nitrous oxide (N2O).

Experimental Investigation of Laser-sustained Plasma in Supersonic Argon Flow

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

Sperber, David; Eckel, Hans-Albert; Moessinger, Peter

Laser-induced energy deposition is widely discussed as a flow control technique in supersonic transportation. In case of thermal laser-plasma upstream of a blunt body, a substantial adaptation of shock wave geometry and magnitude of wave drag is predicted. Related to the research on laser supported detonation, the paper describes the implementation of laser-sustained plasma in a supersonic Argon jet. The stable plasma state is generated by the intersection of a Q-switched Nd:YAG-laser and a continuous wave CO{sub 2}-laser beams, for ignition and maintenance of the plasma respectively. A miniature supersonic Ludwieg tube test facility generates a supersonic jet at velocitiesmore » of Mach 2.1. Modifications of the flow and plasma conditions are investigated and characterized by Schlieren flow visualisation, laser energy transmission and plasma radiation measurements. The results include the discussions of the flow field as well as the required laser and gas parameters.« less

Solar pumped continuous wave carbon dioxide laser

NASA Technical Reports Server (NTRS)

Yesil, O.; Christiansen, W. H.

1978-01-01

In an effort to demonstrate the feasibility of a solar pumped laser concept, gain has been measured in a CO2-He laser medium optically pumped by blackbody radiation. Various gas mixtures of CO2 and He have been pumped by blackbody radiation emitted from an electrically heated oven. Using a CO2 laser as a probe, an optical gain coefficient of 1.8 x 10 to the -3rd/cm has been measured at 10.6 microns for a 9:1 CO2-He mixture at an oven temperature of about 1500 K, a gas temperature of about 400 K and a pressure of about 1 torr. This corresponds to a small signal gain coefficient when allowance is made for saturation effects due to the probe beam, in reasonable agreement with a theoretical value.

Closed cycle electric discharge laser design investigation

NASA Technical Reports Server (NTRS)

Baily, P. K.; Smith, R. C.

1978-01-01

Closed cycle CO2 and CO electric discharge lasers were studied. An analytical investigation assessed scale-up parameters and design features for CO2, closed cycle, continuous wave, unstable resonator, electric discharge lasing systems operating in space and airborne environments. A space based CO system was also examined. The program objectives were the conceptual designs of six CO2 systems and one CO system. Three airborne CO2 designs, with one, five, and ten megawatt outputs, were produced. These designs were based upon five minute run times. Three space based CO2 designs, with the same output levels, were also produced, but based upon one year run times. In addition, a conceptual design for a one megawatt space based CO laser system was also produced. These designs include the flow loop, compressor, and heat exchanger, as well as the laser cavity itself. The designs resulted in a laser loop weight for the space based five megawatt system that is within the space shuttle capacity. For the one megawatt systems, the estimated weight of the entire system including laser loop, solar power generator, and heat radiator is less than the shuttle capacity.

Thermal damage produced by high-irradiance continuous wave CO2 laser cutting of tissue.

PubMed

Schomacker, K T; Walsh, J T; Flotte, T J; Deutsch, T F

1990-01-01

Thermal damage produced by continuous wave (cw) CO2 laser ablation of tissue in vitro was measured for irradiances ranging from 360 W/cm2 to 740 kW/cm2 in order to investigate the extent to which ablative cooling can limit tissue damage. Damage zones thinner than 100 microns were readily produced using single pulses to cut guinea pig skin as well as bovine cornea, aorta, and myocardium. Multiple pulses can lead to increased damage. However, a systematic decrease in damage with irradiance, predicted theoretically by an evaporation model of ablation, was not observed. The damage-zone thickness was approximately constant around the periphery of the cut, consistent with the existence of a liquid layer which stores heat and leads to tissue damage, and with a model of damage and ablation recently proposed by Zweig et al.

Carbon dioxide laser polishing of fused silica surfaces for increased laser-damage resistance at 1064 nm.

PubMed

Temple, P A; Lowdermilk, W H; Milam, D

1982-09-15

Mechanically polished fused silica surfaces were heated with continuous-wave CO(2) laser radiation. Laser-damage thresholds of the surfaces were measured with 1064-nm 9-nsec pulses focused to small spots and with large-spot, 1064-nm, 1-nsec irradiation. A sharp transition from laser-damage-prone to highly laser-damage-resistant took place over a small range in CO(2) laser power. The transition to high damage resistance occurred at a silica surface temperature where material softening began to take place as evidenced by the onset of residual strain in the CO(2) laser-processed part. The small-spot damage measurements show that some CO(2) laser-treated surfaces have a local damage threshold as high as the bulk damage threshold of SiO(2). On some CO(2) laser-treated surfaces, large-spot damage thresholds were increased by a factor of 3-4 over thresholds of the original mechanically polished surface. These treated parts show no obvious change in surface appearance as seen in bright-field, Nomarski, or total internal reflection microscopy. They also show little change in transmissive figure. Further, antireflection films deposited on CO(2) laser-treated surfaces have thresholds greater than the thresholds of antireflection films on mechanically polished surfaces.

Atmospheric CO2 Column Measurements with an Airborne Intensity-Modulated Continuous-Wave 1.57-micron Fiber Laser Lidar

NASA Technical Reports Server (NTRS)

Dobler, Jeremy T.; Harrison, F. Wallace; Browell, Edward V.; Lin, Bing; McGregor, Doug; Kooi, Susan; Choi, Yonghoon; Ismail, Syed

2013-01-01

The 2007 National Research Council (NRC) Decadal Survey on Earth Science and Applications from Space recommended Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as a mid-term, Tier II, NASA space mission. ITT Exelis, formerly ITT Corp., and NASA Langley Research Center have been working together since 2004 to develop and demonstrate a prototype Laser Absorption Spectrometer for making high-precision, column CO2 mixing ratio measurements needed for the ASCENDS mission. This instrument, called the Multifunctional Fiber Laser Lidar (MFLL), operates in an intensity-modulated, continuous-wave mode in the 1.57- micron CO2 absorption band. Flight experiments have been conducted with the MFLL on a Lear-25, UC-12, and DC-8 aircraft over a variety of different surfaces and under a wide range of atmospheric conditions. Very high-precision CO2 column measurements resulting from high signal-to-noise (great than 1300) column optical depth measurements for a 10-s (approximately 1 km) averaging interval have been achieved. In situ measurements of atmospheric CO2 profiles were used to derive the expected CO2 column values, and when compared to the MFLL measurements over desert and vegetated surfaces, the MFLL measurements were found to agree with the in situ-derived CO2 columns to within an average of 0.17% or approximately 0.65 ppmv with a standard deviation of 0.44% or approximately 1.7 ppmv. Initial results demonstrating ranging capability using a swept modulation technique are also presented.

Fractional Ablative Laser Followed by Transdermal Acoustic Pressure Wave Device to Enhance the Drug Delivery of Aminolevulinic Acid: In Vivo Fluorescence Microscopy Study.

PubMed

Waibel, Jill S; Rudnick, Ashley; Nousari, Carlos; Bhanusali, Dhaval G

2016-01-01

Topical drug delivery is the foundation of all dermatological therapy. Laser-assisted drug delivery (LAD) using fractional ablative laser is an evolving modality that may allow for a greater precise depth of penetration by existing topical medications, as well as more efficient transcutaneous delivery of large drug molecules. Additional studies need to be performed using energy-driven methods that may enhance drug delivery in a synergistic manner. Processes such as iontophoresis, electroporation, sonophoresis, and the use of photomechanical waves aid in penetration. This study evaluated in vivo if there is increased efficacy of fractional CO2 ablative laser with immediate acoustic pressure wave device. Five patients were treated and biopsied at 4 treatment sites: 1) topically applied aminolevulinic acid (ALA) alone; 2) fractional ablative CO2 laser and topical ALA alone; 3) fractional ablative CO2 laser and transdermal acoustic pressure wave device delivery system; and 4) topical ALA with transdermal delivery system. The comparison of the difference in the magnitude of diffusion with both lateral spread of ALA and depth diffusion of ALA was measured by fluorescence microscopy. For fractional ablative CO2 laser, ALA, and transdermal acoustic pressure wave device, the protoporphyrin IX lateral fluorescence was 0.024 mm on average vs 0.0084 mm for fractional ablative CO2 laser and ALA alone. The diffusion for the acoustic pressure wave device was an order of magnitude greater. We found that our combined approach of fractional ablative CO2 laser paired with the transdermal acoustic pressure wave device increased the depth of penetration of ALA.

Ultraviolet absorption cross-sections of hot carbon dioxide

NASA Astrophysics Data System (ADS)

Oehlschlaeger, Matthew A.; Davidson, David F.; Jeffries, Jay B.; Hanson, Ronald K.

2004-12-01

The temperature-dependent ultraviolet absorption cross-section for CO 2 has been measured in shock-heated gases between 1500 and 4500 K at 216.5, 244, 266, and 306 nm. Continuous-wave lasers provide the spectral brightness to enable precise time-resolved measurements with the microsecond time-response needed to monitor thermal decomposition of CO 2 at temperatures above 3000 K. The photophysics of the highly temperature dependent cross-section is discussed. The new data allows the extension of CO 2 absorption-based temperature sensing methods to higher temperatures, such as those found in behind detonation waves.

[Examination of laser-treated tooth surfaces after exposure to acid].

PubMed

Beeking, P O; Herrmann, C; Zuhrt, R

1990-12-01

In principle it is possible to homogenize the enamel surface by melting structural elements with the continuous wave CO2 laser. An experimental caries model was used for testing the acid resistance of the laser exposed tooth surfaces. Laser-treatment and measured exposure to acid produced zones of homogeneous smelting with microcracks and disintegration symptoms. Underneath the melted region the heat leakage obviously causes photo-thermic++ effects determined by increased resistance to acid.

Wavelength Locking to CO2 Absorption Line-Center for 2-Micron Pulsed IPDA Lidar Application

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Petros, Mulugeta; Antill, Charles W.; Singh, Upendra N.; Yu, Jirong

2016-01-01

An airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is currently under development at NASA Langley Research Center (LaRC). This IPDA lidar system targets both atmospheric carbon dioxide (CO2) and water vapor (H2O) column measurements. Independent wavelength control of each of the transmitted laser pulses is a key feature for the success of this instrument. The wavelength control unit provides switching, tuning and locking for each pulse in reference to a 2-micron CW (Continuous Wave) laser source locked to CO2 line-center. Targeting the CO2 R30 line center, at 2050.967 nanometers, a wavelength locking unit has been integrated using semiconductor laser diode. The CO2 center-line locking unit includes a laser diode current driver, temperature controller, center-line locking controller and CO2 absorption cell. This paper presents the CO2 center-line locking unit architecture, characterization procedure and results. Assessment of wavelength jitter on the IPDA measurement error will also be addressed by comparison to the system design.

CO2 and diode laser for excisional biopsies of oral mucosal lesions. A pilot study evaluating clinical and histopathological parameters.

PubMed

Suter, Valérie G A; Altermatt, Hans Jörg; Sendi, Pedram; Mettraux, Gérald; Bornstein, Michael M

2010-01-01

The present pilot study evaluates the histopathological characteristics and suitability of CO2 and diode lasers for performing excisional biopsies in the buccal mucosa with special emphasis on the extent of the thermal damage zone created. 15 patients agreed to undergo surgical removal of their fibrous hyperplasias with a laser. These patients were randomly assigned to one diode or two CO2 laser groups. The CO2 laser was used in a continuous wave mode (cw) with a power of 5 W (Watts), and in a pulsed char-free mode (cf). Power settings for the diode laser were 5.12 W in a pulsed mode. The thermal damage zone of the three lasers and intraoperative and postoperative complications were assessed and compared. The collateral thermal damage zone on the borders of the excisional biopsies was significantly smaller with the CO, laser for both settings tested compared to the diode laser regarding values in pm or histopathological index scores. The only intraoperative complication encountered was bleeding, which had to be controlled with electrocauterization. No postoperative complications occurred in any of the three groups. The CO2 laser seems to be appropriate for excisional biopsies of benign oral mucosal lesions. The CO2 laser offers clear advantages in terms of smaller thermal damage zones over the diode laser. More study participants are needed to demonstrate potential differences between the two different CO2 laser settings tested.

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

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.

Research on radiation induced laser plasmas

NASA Technical Reports Server (NTRS)

Schneider, R. T.; Rowe, M. J.; Carter, B. D.; Walters, R. A.; Cox, J. D.; Liang, R.; Roxey, T.; Zapata, L.

1979-01-01

The development of high power nuclear pumped lasers is discussed. The excitation mechanism of continuous wave (CW) HeNe nuclear pumped lasers is studied and a CO2 nuclear pumped laser is used to demonstrate the CW output in the order of watts. The assumption that high power densities are only achievable by volume fission fragment sources is used to identify laser gases which are compatible with UF6 by excited states lifetime measurements. The examination of Xe2, XeF, and KrF under nuclear irradiation to determine if they are good candidates for nuclear-pumped lasers is described.

Imaging Fourier transform spectroscopy of the boundary layer plume from laser irradiated polymers and carbon materials

NASA Astrophysics Data System (ADS)

Acosta, Roberto I.

The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.

Spectral Analysis of Vibrational Harmonic Motion by use of a Continuous-Wave CO2 Doppler Lidar

NASA Technical Reports Server (NTRS)

Jarzembski, Maurice A.; Srivastava, Vandana

1999-01-01

Vibrational motion of a harmonic oscillator was investigated using a focused continuous wave CO2 Doppler lidar at 9.1 microns wavelength. A continuum of frequencies along with many discrete, equally spaced, resonant frequency modes was observed. The frequency modes are similar in structure to the oscillatory longitudinal modes of a laser cavity and arise because of interference of the natural resonant frequency of the oscillator with specific frequencies within the continuum. The spectra revealed departures from linear motion for vigorous vibrations of the oscillator. Each consecutive resonant frequency mode occurred for a movement of the oscillator much less than the wavelength of incident lidar radiation.

Fluid mechanics of fusion lasers. Final report, September 11, 1978-June 5, 1980

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

Shwartz, J; Kulkarny, V A; Ausherman, D A

1980-01-01

Flow loop components required to operate continuous-flow, repetitively-pulsed CO/sub 2/ and KrF laser drivers for ICF were identified and their performance requirements were specified. It was found that the laser flow loops can have a major effect on the laser beam quality and overall efficiency. The pressure wave suppressor was identified as the most critical flow loop component. The performance of vented side-wall suppressors was evaluated both analytically and experimentally and found capable of meeting the performance requirements of the CO/sub 2/ and KrF fusion lasers. All other laser flow loop components are essentially similar to those used in conventional,more » low speed wind tunnels and are therefore well characterized and can be readily incorporated into fusion laser flow systems designs.« less

Latest developments for low-power infrared laser-based trace gas sensors for sensor networks

NASA Astrophysics Data System (ADS)

So, Stephen; Thomazy, David; Wang, Wen; Marchat, Oscar; Wysocki, Gerard

2011-09-01

Academic and industrial researchers require ultra-low power, compact laser based trace-gas sensor systems for the most demanding environmental and space-borne applications. Here the latest results from research projects addressing these applications will be discussed: 1) an ultra-compact CO2 sensor based on a continuous wave quantum cascade laser, 2) an ultra-sensitive Faraday rotation spectrometer for O2 detection, 3) a fully ruggedized compact and low-power laser spectrometer, and 4) a novel non-paraxial nonthin multipass cell. Preliminary tests and projection for performance of future sensors based on this technology is presented.

Generation conditions of CW Diode Laser Sustained Plasma

NASA Astrophysics Data System (ADS)

Nishimoto, Koji; Matsui, Makoto; Ono, Takahiro

2016-09-01

Laser sustained plasma was generated using 1 kW class continuous wave diode laser. The laser beam was focused on the seed plasma generated by arc discharge in 1 MPa xenon lamp. The diode laser has advantages of high energy conversion efficiency of 80%, ease of maintenance, compact size and availability of conventional quartz based optics. Therefore, it has a prospect of further development compared with conventional CO2 laser. In this study, variation of the plasma shape caused by laser power is observed and also temperature distribution in the direction of plasma radius is measured by optical emission spectroscopy.

CO2 laser annealing of 50-microns-thick silicon solar cells

NASA Technical Reports Server (NTRS)

Walker, F. E.

1979-01-01

A test program is conducted to determine thin solar cell annealing effects using a laser energy source. A CO2 continuous-wave laser was used in annealing experiments on 50 micrometers-thick silicon solar cells after proton irradiation. Test cells were irradiated to a fluence of 1.0 x 10 to the 12th power protons/sq cm with 1.9 MeV protons. After irradiation, those cells receiving full proton dosage were degraded by an average of 30% in output power. In annealing tests laser beam exposure times on the solar cell varied from 2 seconds to 16 seconds reaching cell temperatures of from 400 C to 500 C. Under those conditions annealing test results showed recovery in cell output power of from 33% to 90%.

Cw hyper-Raman laser and four-wave mixing in atomic sodium

NASA Astrophysics Data System (ADS)

Klug, M.; Kablukov, S. I.; Wellegehausen, B.

2005-01-01

Continuous wave hyper-Raman (HR) generation in a ring cavity on the 6s → 4p transition at 1640 nm in sodium is realized for the first time by two-photon excitation of atomic sodium on the 3s → 6s transition with a continuous wave (cw) dye laser at 590 nm and a single frequency argon ion laser at 514 nm. It is shown, that the direction and efficiency of HR lasing depends on the propagation direction of the pump waves and their frequencies. More than 30% HR gain is measured at 250 mW of pump laser powers for counter-propagating pump waves and a medium length of 90 mm. For much shorter interaction lengths and corresponding focussing of the pump waves a dramatic increase of the gain is predicted. For co-propagating pump waves, in addition, generation of 330 nm radiation on the 4p → 3s transition by a four-wave mixing (FWM) process is observed. Dependencies of HR and parametric four-wave generation have been investigated and will be discussed.

[Experimental study of brain lesions after combined coaxial exposure to high-peaked pulse wave form CO2 and Nd: YAG lasers on the brain].

PubMed

Tsuyumu, M; Verasques, G; Yamazaki, S; Kuroiwa, T; Suzuki, R; Takei, H; Suzuki, K; Inaba, Y

1985-04-01

The CO2 laser is useful for cutting and vaporization but not for coagulation and hemostasis. On the contrary, YAG laser is effective for coagulation and hemostasis but not for cutting. The purpose of this study is to examine the effect of the exposure of combined, coaxial CO2 and YAG laser on the animal brain to supplement the advantages and draw-backs of each other. To compare these results, each of non-combined pulse wave form CO2 and YAG lasers was employed separately. The lasers in this study were pulse wave form CO2 and YAG lasers, employed separately or simultaneously using 130 YZ of Nihon Infrared Industries Company. Japanese white rabbits were anesthetized with pentobarbital. Fronto-parietal burr holes were made, the dura was removed and then Evans blue solution was injected intravenously. The lasers were employed to the cerebral cortex without great vessels using a micromanipulator attached to the operative microscope with a distance of 30 cm. The spot size was 700 mu for CO2 laser and 1200 mu for YAG laser. The first experiment was to see the effect of nine combinations of simultaneous coaxial CO2 of 2, 4 and 8 watts and YAG lasers of 10, 20 and 40 watts, 1 sec on the brain. In the second experiment, also combining two lasers, the exposure time of YAG laser was elongated from 1 or 2 seconds into 2 or 4 seconds and the arrangement of powers was the same as that of the first experiment. The lesions were thus made in 18 different conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

ARTICLES: Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

NASA Astrophysics Data System (ADS)

Berger, N. K.; Zhukov, E. A.; Novokhatskiĭ, V. V.

1984-04-01

The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO2 laser radiation at a phase transition in VO2. A three-wave interaction on a VO2 surface was achieved using low-power cw and pulsed CO2 lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm2 and in the second case, it was 42% for a threshold reference wave energy density of 0.6-0.8 mJ/cm2.

Investigation of SOI Raman Lasers for Mid-Infrared Gas Sensing

PubMed Central

Passaro, Vittorio M.N.; De Leonardis, Francesco

2009-01-01

In this paper, the investigation and detailed modeling of a cascaded Raman laser, operating in the midwave infrared region, is described. The device is based on silicon-on-insulator optical waveguides and a coupled resonant microcavity. Theoretical results are compared with recent experiments, demonstrating a very good agreement. Design criteria are derived for cascaded Raman lasers working as continuous wave light sources to simultaneously sense two types of gases, namely C2H6 and CO2, at a moderate power level of 130 mW. PMID:22408481

Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO 2

DOE PAGES

Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; ...

2013-01-01

Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO 2 and H 2 reactants to CH 4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au–ZnO from 30 to ~600 °C and simultaneously tune the CH 4 : CO product ratio. The laser induced heating and resulting CH 4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction ismore » a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO 2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO 2 reduction is low ( ~2.5 x 10 5 W m -2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO 2 utilization and other practical thermal catalytic applications.« less

Development of Sesquioxide Ceramic for High Energy Lasers

DTIC Science & Technology

2015-05-25

CSJ308 , Mutsuno, Atsuta- ku Nagoya 456-0023 Japan 8. PERFORMING ORGANIZATION REPORT NUMBER N/A 9. SPONSORING/MONITORING AGENCY NAME...Labo Co., Ltd.,1-2-19-CSJ308 , Mutsuno, Atsuta- ku ,Nagoya 456-0023,Japan,NA,NA 8. PERFORMING ORGANIZATION REPORT NUMBER N/A 9. SPONSORING/MONITORING...Huang, D. Shen , J. Zhang, H. Chen, Y. Wang, X. Liu, D. Tang, “Room Temperature Continuous-wave Laser Performance of LD Pumped Er:Lu2O3 and Er:Y2O3

Development of a cw-laser-based cavity-ringdown sensor aboard a spacecraft for trace air constituents

NASA Technical Reports Server (NTRS)

Awtry, A. R.; Miller, J. H.

2002-01-01

The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous-wave (cw), external-cavity tunable diode laser centered at 1.55 micrometers is used to pump an optical cavity absorption cell in cw-cavity ringdown spectroscopy (cw-CRDS). Preliminary results are presented that demonstrate the sensitivity, selectivity and reproducibility of this method. Detection limits of 2.0 ppm for CO, 2.5 ppm for CO2, 1.8 ppm for H2O, 19.4 ppb for NH3, 7.9 ppb for HCN and 4.0 ppb for C2H2 are calculated.

High-damage-threshold antireflection coatings on diamond for CW and pulsed CO2 lasers

NASA Astrophysics Data System (ADS)

Komlenok, M. S.; Pivovarov, P. A.; Volodkin, B. O.; Pavelyev, V. S.; Anisimov, V. I.; Butuzov, V. V.; Sorochenko, V. R.; Nefedov, S. M.; Mineev, A. P.; Soifer, V. A.; Konov, V. I.

2018-03-01

A multilayer antireflection coating for diamond optics that allows work in the infrared spectral range of 8 -12 µm with minimal optical losses is developed. The optical transmittance of a chemical vapour deposition diamond plate coated with this film on both sides exceeds 94% over the whole specified wavelength range. The coatings deposited on the diamond plate were damage-tested by coherent-wave and pulsed (τ  =  90 ns) CO2 lasers. Results of the tests demonstrated that the coating can withstand prolonged radiation loads with intensity above 3 MW cm-2 in a continuous-mode laser exposure. In the case of a nanosecond pulsed action, destruction of the coating begins at intensities greater than 50 MW cm-2.

Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities, January 1976 to December 1977

NASA Technical Reports Server (NTRS)

Javan, A.

1979-01-01

A tunable multiatmospheric pulsed CO2 laser with emphasis on experimental features and supporting theoretical analyses important to differential absorption lidar and Doppler lidar measurement of pollutants and wind velocities is reported. The energy deposition and the means to produce the uniform high density plasma in the multiatmospheric medium, through UV preionization of an organic seed gas is discussed. Design features of the pulsed CO2 laser are presented. The radiative processes which are operative and prevent the laser from breaking into oscillations in a large number of modes over its broad amplification bandwidth are described. The mode competition for the transient pulsed laser oscillation in a standing wave and traveling wave ring laser configuration is discussed and contrasted with the approach to steady state oscillations. The latter findings are important to transient injection locking for production of a highly stable pulsed CO2 laser output.

In situ laser annealing system for real-time surface kinetic analysis

NASA Astrophysics Data System (ADS)

Wang, Q.; Sun, Y.-M.; Zhao, W.; Campagna, J.; White, J. M.

2002-11-01

For real-time analysis during thermal annealing, a continuous wave CO2 infrared laser was coupled to a surface analysis system equipped for x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). The laser beam was directed into the vacuum chamber through a ZnSe window to the back side of the sample. With 10 W laser output, the sample temperature reached 563 K. The chamber remained below 10-8 Torr during annealing and allowed XPS and ISS data to be gathered as a function of time at selected temperatures. As a test example, real time Cu2O reduction at 563 K was investigated.

Simultaneous multi-laser, multi-species trace-level sensing of gas mixtures by rapidly swept continuous-wave cavity-ringdown spectroscopy.

PubMed

He, Yabai; Kan, Ruifeng; Englich, Florian V; Liu, Wenqing; Orr, Brian J

2010-09-13

The greenhouse-gas molecules CO(2), CH(4), and H(2)O are detected in air within a few ms by a novel cavity-ringdown laser-absorption spectroscopy technique using a rapidly swept optical cavity and multi-wavelength coherent radiation from a set of pre-tuned near-infrared diode lasers. The performance of various types of tunable diode laser, on which this technique depends, is evaluated. Our instrument is both sensitive and compact, as needed for reliable environmental monitoring with high absolute accuracy to detect trace concentrations of greenhouse gases in outdoor air.

Application of a flexible CO(2) laser fiber for neurosurgery: laser-tissue interactions.

PubMed

Ryan, Robert W; Wolf, Tamir; Spetzler, Robert F; Coons, Stephen W; Fink, Yoel; Preul, Mark C

2010-02-01

The CO(2) laser has an excellent profile for use in neurosurgery. Its high absorption in water results in low thermal spread, sparing adjacent tissue. Use of this laser has been limited to line-of-sight applications because no solid fiber optic cables could transmit its wavelength. Flexible photonic bandgap fiber technology enables delivery of CO(2) laser energy through a flexible fiber easily manipulated in a handheld device. The authors examined and compared the first use of this CO(2) laser fiber to conventional methods for incising neural tissue. Carbon dioxide laser energy was delivered in pulsed or continuous wave settings for different power settings, exposure times, and distances to cortical tissue of 6 anesthetized swine. Effects of CO(2) energy on the tissue were compared with bipolar cautery using a standard pial incision technique, and with scalpel incisions without cautery. Tissue was processed for histological analysis (using H & E, silver staining, and glial fibrillary acidic protein immunohistochemistry) and scanning electron microscopy, and lesion measurements were made. Light microscopy and scanning electron microscopy revealed laser incisions of consistent shape, with central craters surrounded by limited zones of desiccated and edematous tissue. Increased laser power resulted in deeper but not significantly wider incisions. Bipolar cautery lesions showed desiccated and edematous zones but did not incise the pia, and width increased more than depth with higher power. Incisions made without using cautery produced hemorrhage but minimal adjacent tissue damage. The photonic bandgap fiber CO(2) laser produced reliable cortical incisions, adjustable over a range of settings, with minimal adjacent thermal tissue damage. Ease of application under the microscope suggests this laser system has reached true practicality for neurosurgery.

Efficient continuous-wave and passively Q-switched pulse laser operations in a diffusion-bonded sapphire/Er:Yb:YAl3(BO3)4/sapphire composite crystal around 1.55 μm.

PubMed

Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

2018-01-08

A composite crystal consisting of a 1.5-mm-thick Er:Yb:YAl 3 (BO 3 ) 4 crystal between two 1.2-mm-thick sapphire crystals was fabricated by the thermal diffusion bonding technique. Compared with a lone Er:Yb:YAl 3 (BO 3 ) 4 crystal measured under the identical experimental conditions, higher laser performances were demonstrated in the sapphire/Er:Yb:YAl 3 (BO 3 ) 4 /sapphire composite crystal due to the reduction of the thermal effects. End-pumped by a 976 nm laser diode in a hemispherical cavity, a 1.55 μm continuous-wave laser with a maximum output power of 1.75 W and a slope efficiency of 36% was obtained in the composite crystal when the incident pump power was 6.54 W. Passively Q-switched by a Co 2+ :MgAl 2 O 4 crystal, a 1.52 μm pulse laser with energy of 10 μJ and repetition frequency of 105 kHz was also realized in the composite crystal. Pulse width was 315 ns. The results show that the sapphire/Er:Yb:YAl 3 (BO 3 ) 4 /sapphire composite crystal is an excellent active element for 1.55 μm laser.

Quantum cascade laser based sensor for open path measurement of atmospheric trace gases

NASA Astrophysics Data System (ADS)

Deng, Hao; Sun, Juan; Liu, Ningwu; Ding, Junya; Chao, Zhou; Zhang, Lei; Li, Jingsong

2017-02-01

A sensitive open-path gas sensor employing a continuous-wave (CW) distributed feedback (DFB) quantum cascade laser (QCL) and direct absorption spectroscopy (DAS) was demonstrated for simultaneously measurements of atmospheric CO and N2O. Two interference free absorption lines located at 2190.0175 cm-1 and 2190.3498 cm-1 were selected for CO and N2O concentration measurements, respectively. The Allan variance analysis technique was performed to investigate the long-term performance of the QCL sensor system. The results indicate that a detection limit of 9.92 ppb for CO and 7.7 ppb for N2O with 1-s integration time were achieved, which can be further improved to 1.5 ppb and 1.1 ppb by increasing the average time up to 80 s.

Room Temperature Erbium-Doped Yttrium Vanadate (Er:YVO4) Laser and Amplifier

DTIC Science & Technology

2016-09-01

perpendicular to the laser cavity axis, was pumped in σ-polarization and lased in π-polarization. The laser operated in a quasi -continuous wave regime...laser, amplifier, quasi -continuous wave 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF...distribution unlimited. iii Contents List of Figures iv 1. Introduction 1 2. Laser Experimental Setup and Results 2 3. Laser Amplifier Setup 6 4

CO2 Laser Excision of a Pyogenic Granuloma Associated with Dental Implants: A Case Report and Review of the Literature.

PubMed

Truschnegg, Astrid; Acham, Stephan; Kqiku, Lumnije; Beham, Alfred; Jakse, Norbert

2016-09-01

This article reports the CO2 laser excision of a pyogenic granuloma related to dental implants and reviews the current literature on this pathology in association with dental implants. Five publications describe pyogenic granulomas related to dental implants, and a further one describes the removal of such a lesion with an Er:YAG laser; removal with a CO2 laser is not reported. A 67-year-old male patient presented with a hyperplastic gingival lesion around two implants in the left lower jaw. The hyperplastic tissue was removed with a CO2 laser (Lasram; model OPAL 25, 25 W continuous wave, 10.600 nm, gas laser), and a vestibuloplasty was performed. The excised tissue was examined histopathologically. The patient was followed up after 4 weeks, 6 weeks, 6 months, and 1 year, and a panoramic X-ray was also made. There were no complications during surgery or follow-up. The panoramic X-ray taken 1 year after excision showed neither vertical bone loss nor impaired osseointegration of the implant. Histopathology reported a pyogenic granuloma. After vestibuloplasty, the height of the fixed mucosa was satisfactory. The CO2 laser seems to be a safe and appropriate tool for removal of a pyogenic granuloma in close proximity to dental implants. The laser parameters must, however, be chosen carefully and any additional irritants should be excluded to prevent a recurrence.

Continuous multispectral imaging of surface phonon polaritons on silicon carbide with an external cavity quantum cascade laser

NASA Astrophysics Data System (ADS)

Dougakiuchi, Tatsuo; Kawada, Yoichi; Takebe, Gen

2018-03-01

We demonstrate the continuous multispectral imaging of surface phonon polaritons (SPhPs) on silicon carbide excited by an external cavity quantum cascade laser using scattering-type scanning near-field optical microscopy. The launched SPhPs were well characterized via the confirmation that the theoretical dispersion relation and measured in-plane wave vectors are in excellent agreement in the entire measurement range. The proposed scheme, which can excite and observe SPhPs with an arbitrary wavelength that effectively covers the spectral gap of CO2 lasers, is expected to be applicable for studies of near-field optics and for various applications based on SPhPs.

Mid-infrared trace gas detection using continuous-wave difference frequency generation in periodically poled RbTiOAsO4

NASA Technical Reports Server (NTRS)

Chen, W.; Mouret, G.; Boucher, D.; Tittel, F. K.

2001-01-01

A tunable mid-infrared continuous-wave (cw) spectroscopic source in the 3.4-4.5 micrometers region is reported, based on difference frequency generation (DFG) in a quasi-phase-matched periodically poled RbTiOAsO4 (PPRTA) crystal. DFG power levels of 10 microW were generated at approximately 4 micrometers in a 20-mm long PPRTA crystal by mixing two cw single-frequency Ti:Al2O3 lasers operating near 713 nm and 871 nm, respectively, using a laser pump power of 300 mW. A quasi-phase-matched infrared wavelength-tuning bandwidth (FWHM) of 12 cm-1 and a temperature tuning rate of 1.02 cm-1/degree C were achieved. Experimental details regarding the feasibility of trace gas detection based on absorption spectroscopy of CO2 in ambient air using this DFG radiation source are also described.

Skin graft take and healing following 193-nm excimer, continuous-wave carbon dioxide (CO2), pulsed CO2, or pulsed holmium: YAG laser ablation of the graft bed.

PubMed

Green, H A; Burd, E E; Nishioka, N S; Compton, C C

1993-08-01

Ablative lasers have been used for cutaneous surgery for greater than two decades since they can remove skin and skin lesions bloodlessly and efficiently. Because full-thickness skin wounds created after thermal laser ablation may require skin grafting in order to heal, we have examined the effect of the residual laser-induced thermal damage in the wound bed on subsequent skin graft take and healing. In a pig model, four different pulsed and continuous-wave lasers with varying wavelengths and radiant energy exposures were used to create uniform fascial graft bed thermal damage of approximately 25, 160, 470, and 1100 microns. Meshed split-thickness skin graft take and healing on the thermally damaged fascial graft beds were examined on a gross and microscopic level on days 3 and 7, and then weekly up to 42 days. Laser-induced thermal damage on the graft bed measuring greater than 160 +/- 60 microns in depth significantly decreased skin graft take. Other deleterious effects included delayed graft revascularization, increased inflammatory cell infiltrate at the graft-wound bed interface, and accelerated formation of hypertrophied fibrous tissue within the graft bed and underlying muscle. Ablative lasers developed for cutaneous surgery should create less than 160 +/- 60 microns of residual thermal damage to permit optimal skin graft take and healing. Pulsed carbon dioxide and 193-nm excimer lasers may be valuable instruments for the removal of full-thickness skin, skin lesions, and necrotic tissue, since they create wound beds with minimal thermal damage permitting graft take comparable to that achieved with standard surgical techniques.

DAWN Coherent Wind Profiling Lidar Flights on NASA's DC-8 During GRIP

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Beyon, Jeffrey Y.; Creary, Garfield A.; Koch, Grady J.; Petros, Mulugeta; Petzar, Paul J.; Singh, Upendra N.; Trieu, Bo C.; Yu, Jirong

2011-01-01

Almost from their invention, lasers have been used to measure the velocity of wind and objects; over distances of cm to 10s of km. Long distance (remote) sensing of wind has been accomplished with continuous-wave (CW), focused pulsed, and collimated pulsed lasers; with direct and coherent (heterodyne) optical detection; and with a multitude of laser wavelengths. Airborne measurement of wind with pulsed, coherent-detection lidar was first performed in 1971 with a CW CO2 laser1, in 1972 with a pulsed CO2 laser2, in 1993 with a pulsed 2-micron laser3, and in 1999 with a pulsed CO2 laser and nadir-centered conical scanning4. Of course there were many other firsts and many other groups doing lidar wind remote sensing with coherent and direct detection. A very large FOM coherent wind lidar has been built by LaRC and flown on a DC-8. However a burn on the telescope secondary mirror prevented the full demonstration of high FOM. Both the GRIP science product and the technology and technique demonstration from aircraft are important to NASA. The technology and technique demonstrations contribute to our readiness for the 3D Winds space mission. The data analysis is beginning and we hope to present results at the conference.

Portable Laser Spectrometer for Airborne and Ground-Based Remote Sensing of Geological CO2 Emissions

NASA Technical Reports Server (NTRS)

Queisser, Manuel; Burton, Mike; Allan, Graham R.; Chiarugi, Antonio

2017-01-01

A 24 kilogram, suitcase-sized, CW (Continuous Wave) Laser Remote Sensing Spectrometer (LARSS) with an approximately 2-kilometer range has been developed. It has demonstrated its flexibility in measuring both atmospheric CO2 from an airborne platform and terrestrial emission of CO2 from a remote mud volcano, Bledug Kuwu, Indonesia, from a ground-based sight. This system scans the CO2 absorption line with 20 discrete wavelengths, as opposed to the typical two-wavelength online-offline instrument. This multi-wavelength approach offers an effective quality control, bias control, and confidence estimate of measured CO2 concentrations via spectral fitting. The simplicity, ruggedness, and flexibility in the design allow for easy transportation and use on different platforms with a quick setup in some of the most challenging climatic conditions. While more refinement is needed, the results represent a stepping stone towards widespread use of active one-sided gas remote sensing in the earth sciences.

[Measuring microhardness of laser exposed tooth surface].

PubMed

Florin, R; Herrmann, C; Bernhardt, W

1990-02-01

In principle it is possible to homogenize the enamel surface by melting structural elements with the continuous wave CO2 laser. Using the precision instrument NEOPHOT 2 (Carl Zeiss JENA) the microhardness of extracted laserexposed premolares were tested so as to clarify the functional strain capasity and the mechanical characteristics of laserexposed regions of enamel surfaces. The proven higher hardness in the centre of the laserinduced fusing zones (in comparison with adjacent enamel) objectify an attainable refining of the enamel surface that probably causes an increase in the caries-preventive resistance.

2-micrometer continuous wave laser treatment for multiple non-muscle-invasive bladder cancer with intravesical instillation of epirubicin.

PubMed

Liu, Haitao; Xue, Song; Ruan, Yuan; Sun, Xiaowen; Han, Bangmin; Xia, Shujie

2011-01-01

We have reported the efficacy and safety of 2-micrometer continuous wave laser resection of non-muscle-invasive bladder tumor (NMIVBC) (World J Urology 2010;28:157-161). In this study, we evaluated the use of 2-micrometer continuous wave laser resection in combination with intravesical instillation of epirubicin for the treatment of multiple NMIVBC. From September 2007 to April 2008, sixty patients with multiple NMIVBC were included in this study (44 cases of low grade papillary urothelial carcinoma, 10 cases of high grade papillary urothelial carcinoma, and six cases of papillary urothelial neoplasm with low malignant potential). Imaging examinations including pelvic computer tomography (CT) and intravenous urography showed no extravesical extension, lymphatic metastasis or any lesions of upper urinary tract. All patients received 2-micrometer continuous wave laser therapy under continuous epidural anesthesia, and intravesical chemotherapy with epirubicin 1 week later (intravesical instillation weekly for 8 weeks, followed by monthly maintenance to 12 months). Totally 211 tumors in 60 patients were successfully removed with 2-micrometer continuous wave laser. The mean operation time was 48 minutes per patient (ranged 20-90 minutes) and 13.6 minutes per tumor (range 5-25 minutes). No obturator nerve reflection or bladder perforation occurred during the procedure. All patients finished 12 months of intravesical chemotherapy without severe complications. The mean followed-up time was 23 months. Tumor recurrences were found in 13 patients (22%). The combination of 2-micrometer continuous wave laser and intravesical chemotherapy is feasible, safe, and efficacious for the treatment of multiple NMIVBC. Copyright © 2011 Wiley-Liss, Inc.

Laser beam-plasma plume interaction during laser welding

NASA Astrophysics Data System (ADS)

Hoffman, Jacek; Moscicki, Tomasz; Szymanski, Zygmunt

2003-10-01

Laser welding process is unstable because the keyhole wall performs oscillations which results in the oscillations of plasma plume over the keyhole mouth. The characteristic frequencies are equal to 0.5-4 kHz. Since plasma plume absorbs and refracts laser radiation, plasma oscillations modulate the laser beam before it reaches the workpiece. In this work temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, being not diluted by the shielding gas. As expected the values of electron density are about two times higher in peaks than their time-averaged values. Since the plasma absorption coefficient scales as ~N2e/T3/2 (for CO2 laser radiation) the results show that the power of the laser beam reaching the metal surface is modulated by the plasma plume oscillations. The attenuation factor equals 4-6% of the laser power but it is expected that it is doubled by the refraction effect. The results, together with the analysis of the colour pictures from streak camera, allow also interpretation of the dynamics of the plasma plume.

2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Bai, Yingxin; Yu, Jirong

2009-01-01

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam size is suitable for high efficiency. For Q-switched operation, the optimal energy extraction relies on the pump intensity, pump volume, and pump duration which is inversely proportion to the repetition rate. CW and Q-switched Ho:YLF lasers with different linear cavity configurations have been designed and demonstrated for a 30 W Tm:fiber pump laser. The CW Ho laser slope efficiency and optical-to-optical efficiencies reach 65% and 55%, respectively. The pulsed laser efficiency depends on the repetition rate. For 1 kHz operation, the optical-to-optical efficiency is 39% when the pump power is 14.5W. Currently, the injection seeding success rate is between 99.4% and 99.95%. After a ten thousand pulses, the standard deviation of the laser frequency jitter is about 3 MHz. It meets the requirements of highly precise CO2 concentration measurement. In conclusion, an injection seeded, high repetition rate, Q-switched Ho:YLF laser has been developed for a coherent CO2 differential absorption lidar. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. It can potentially meet the requirements of the coherent detection of CO2 concentration by a differential absorption lidar technique.

High-Power DFB Diode Laser-Based CO-QEPAS Sensor: Optimization and Performance.

PubMed

Ma, Yufei; Tong, Yao; He, Ying; Yu, Xin; Tittel, Frank K

2018-01-04

A highly sensitive carbon monoxide (CO) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was demonstrated. A high-power distributed feedback (DFB), continuous wave (CW) 2.33 μm diode laser with an 8.8 mW output power was used as the QEPAS excitation source. By optimizing the modulation depth and adding an optimum micro-resonator, compared to a bare quartz tuning fork (QTF), a 10-fold enhancement of the CO-QEPAS signal amplitude was achieved. When water vapor acting as a vibrational transfer catalyst was added to the target gas, the signal was further increased by a factor of ~7. A minimum detection limit (MDL) of 11.2 ppm and a calculated normalized noise equivalent absorption (NNEA) coefficient of 1.8 × 10 -5 cm -1 W/√Hz were obtained for the reported CO-QEPAS sensor.

High-Power DFB Diode Laser-Based CO-QEPAS Sensor: Optimization and Performance

PubMed Central

Ma, Yufei; Tong, Yao; He, Ying; Yu, Xin

2018-01-01

A highly sensitive carbon monoxide (CO) trace gas sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was demonstrated. A high-power distributed feedback (DFB), continuous wave (CW) 2.33 μm diode laser with an 8.8 mW output power was used as the QEPAS excitation source. By optimizing the modulation depth and adding an optimum micro-resonator, compared to a bare quartz tuning fork (QTF), a 10-fold enhancement of the CO-QEPAS signal amplitude was achieved. When water vapor acting as a vibrational transfer catalyst was added to the target gas, the signal was further increased by a factor of ~7. A minimum detection limit (MDL) of 11.2 ppm and a calculated normalized noise equivalent absorption (NNEA) coefficient of 1.8 × 10−5 cm−1W/√Hz were obtained for the reported CO-QEPAS sensor. PMID:29300310

Absorption coefficients and frequency shifts measurement in the spectral range of 1071.88-1084.62 cm-1 vs. pressure for chlorodifluoromethane (CHClF2) using tunable CW CO2 laser

NASA Astrophysics Data System (ADS)

Al-Hawat, Sharif

2013-02-01

Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.

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.

Novel method to sample very high power CO2 lasers: II Continuing Studies

NASA Astrophysics Data System (ADS)

Eric, John; Seibert, Daniel B., II; Green, Lawrence I.

2005-04-01

For the past 28 years, the Laser Hardened Materials Evaluation Laboratory (LHMEL) at the Wright-Patterson Air Force Base, OH, has worked with CO2 lasers capable of producing continuous energy up to 150 kW. These lasers are used in a number of advanced materials processing applications that require accurate spatial energy measurements of the laser. Conventional non-electronic methods are not satisfactory for determining the spatial energy profile. This paper describes continuing efforts in qualifying the new method in which a continuous, real-time electronic spatial energy profile can be obtained for very high power, (VHP) CO2 lasers.

Diode-pumped continuous wave and passively Q-switched Tm, Mg: LiTaO₃ lasers.

PubMed

Feng, T; Li, T; Zhao, S; Li, Q; Yang, K; Zhao, J; Qiao, W; Hang, Y; Zhang, P; Wang, Y; Xu, J

2014-02-24

We have demonstrated the continuous wave and passively Q-switched Tm, Mg: LiTaO3 lasers for the first time. In continuous wave (CW) regime, a maximum CW output power of 1.03 W at 1952 nm was obtained, giving a slope efficiency of 9.5% and a beam quality M2 = 2.2. In passive Q-switching regime, a single walled carbon nanotube (SWCNT) was employed as saturable absorber (SA). The Tm,Mg:LiTaO3 laser has yielded a pulse of 560 ns under repetition rate of 34.2 kHz at 1926 nm, corresponding to a single pulse energy of 10.1 μJ. The results indicate a promising potential of nonlinear crystals in the applications for laser host materials.

Soft tissue molding technique in cleft lip and palate patient using laser surgery in combination with orthodontic appliance: A case report.

PubMed

Theerasopon, Pornpat; Wangsrimongkol, Tasanee; Sattayut, Sajee

2017-03-31

Although surgical treatment protocols for cleft lip and palate patients have been established, many patients still have some soft tissue defects after complete healing from surgical interventions. These are excess soft tissue, high attached fraena and firmed tethering scares. These soft tissue defects resulted shallowing of vestibule, restricted tooth movement, compromised periodontal health and trended to limit the maxillary growth. The aim of this case report was to present a method of correcting soft tissue defects after conventional surgery in cleft lip and palate patient by using combined laser surgery and orthodontic appliance. A bilateral cleft lip and palate patient with a clinical problem of shallow upper anterior vestibule after alveolar bone graft received a vestibular extension by using CO 2 laser with ablation and vaporization techniques at 4 W and continuous wave. A customized orthodontic appliance, called a buccal shield, was placed immediately after surgery and retained for 1 month to 3 months until complete soft tissue healing. The procedures were performed 2 episodes. Both interventions used the same CO 2 laser procedure. The first treatment resulted in partial re-attachment of soft tissue at surgical area. The second laser operation with the proper design of buccal shield providing passive contact with more extended flange resulting in a favorable outcome from 1 year follow up. Then the corrective orthodontic treatment could be continued effectively. The CO 2 laser surgery was a proper treatment for correcting soft tissue defects and the design of buccal shield was a key for success in molding surgical soft tissue.

In vitro study of root fracture treated by CO2 laser and DP-bioactive glass paste.

PubMed

Wang, Yin-Lin; Lee, Bor-Shiunn; Tseng, Ching-Li; Lin, Feng-Huei; Lin, Chun-Pin

2008-01-01

An ideal material has yet to be discovered that can successfully treat vertical root fracture. Therefore, the purpose of this study was to use a continuous-wave CO2 laser of medium-energy density to fuse DP-bioactive glass paste (DPGP) to vertical root fracture. The DP-bioglass powder was based on a Na2O-CaO-SiO2-P2O5 system and it was mixed with phosphoric acid (65% concentration) with a powder/liquid ratio of 2 g/4 mL to form DPGP. The interaction of DPGP and dentin was analyzed by means of X-ray diffractometer (XRD) and differential thermal analysis/thermogravimetric analysis (DTA/TGA). Root fracture line was filled with DPGP followed by CO2 laser irradiation and the result was examined by scanning electron microscopy (SEM). The main crystal phase of DPGP was monocalcium phosphate monohydrate (Ca(H2PO4)2.H2O) and the phase transformed to dicalcium phosphate dihydrate (CaHPO4.2H2O) after mixing DPGP with dentin powder (DPG-D). Additionally, gamma-Ca2P2O7 and beta-Ca2P2O7 were identified when DPG-D was lased by CO2 laser. The reaction temperature was between 500 degrees C and 1100 degrees C. SEM results demonstrated that the fracture line was effectively sealed by DPGP. The chemical reaction of DPGP and dentin indicated that DPGP combined with CO2 laser is a potential regimen for the treatment of vertical root fracture.

Pseudorandom Noise Code-Based Technique for Thin Cloud Discrimination with CO2 and O2 Absorption Measurements

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudo noise (PN) code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

The use of laser CO2 in salivary gland diseases

NASA Astrophysics Data System (ADS)

Ciolfi, C.; Rocchetti, F.; Fioravanti, M.; Tenore, G.; Palaia, G.; Romeo, U.

2016-03-01

Salivary gland diseases can include reactive lesions, obstructive lesions, and benign tumors. All these clinical entities are slow growing. Salivary glands reactive lesions, such as mucoceles, can result from extravasation of saliva into the surrounding soft tissue or from retention of saliva within the duct. Sialolithiasis, one of the most common obstructive lesions, is generally due to calculi, which are attributed to retention of saliva. Monomorphic adenoma is a salivary gland benign tumor, which is exclusively resulted from proliferation of epithelial cells, with no alterations interesting the connective tissue. The elective therapy of these lesions is surgical excision because sometimes they can be accompained by difficulties during chewing and phonation and can interfere with prosthesis's stability. The aim of the study is to evaluate the efficacy of CO2 laser in the treatment of patients with salivary gland diseases. Three different cases - a mucocele, a scialolithiasis and a monomorphic adenoma - were treated with CO2 laser excision (CW and 4W), under local anesthesia. Two different techniques were used: circumferential incision for the adenoma, and mucosa preservation technique for mucocele and sialolithiasis. In each case final haemostasis was obtained by thermocoagulation, but suture was applied to guarantee good healing by sewing up the flaps. The patients were checked after twenty days and the healing was good. The carbon dioxide laser (CO2 laser) was one of the earliest gas laser to be developed, and is still the highest-power continuous wave laser that is currently available. In dentistry the CO2 laser produces a beam of infrared light with the principal wavelength bands centering around 9.4 and 10.6 micrometers. Laser excision can be very useful in oral surgery. In the cases presented CO2 laser offered, differently from traditional surgery, simplified surgical technique, shorter duration of operation, minimal postoperative pain, minimal scarring, bloodless field and the possibility to realize minimally invasive surgery. These advantages made the operation tolerable for the patients, that became more compliant. Optimum functional results can be expected.

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.

TEA CO2 laser machining of CFRP composite

NASA Astrophysics Data System (ADS)

Salama, A.; Li, L.; Mativenga, P.; Whitehead, D.

2016-05-01

Carbon fibre-reinforced polymer (CFRP) composites have found wide applications in the aerospace, marine, sports and automotive industries owing to their lightweight and acceptable mechanical properties compared to the commonly used metallic materials. Machining of CFRP composites using lasers can be challenging due to inhomogeneity in the material properties and structures, which can lead to thermal damages during laser processing. In the previous studies, Nd:YAG, diode-pumped solid-state, CO2 (continuous wave), disc and fibre lasers were used in cutting CFRP composites and the control of damages such as the size of heat-affected zones (HAZs) remains a challenge. In this paper, a short-pulsed (8 μs) transversely excited atmospheric pressure CO2 laser was used, for the first time, to machine CFRP composites. The laser has high peak powers (up to 250 kW) and excellent absorption by both the carbon fibre and the epoxy binder. Design of experiment and statistical modelling, based on response surface methodology, was used to understand the interactions between the process parameters such as laser fluence, repetition rate and cutting speed and their effects on the cut quality characteristics including size of HAZ, machining depth and material removal rate (MRR). Based on this study, process parameter optimization was carried out to minimize the HAZ and maximize the MRR. A discussion is given on the potential applications and comparisons to other lasers in machining CFRP.

Highlights of Thirty-Year Experience of CO2 Laser Use at the Florence (Italy) Department of Dermatology

PubMed Central

Campolmi, Piero; Bonan, Paolo; Cannarozzo, Giovanni; Bassi, Andrea; Bruscino, Nicola; Arunachalam, Meena; Troiano, Michela; Lotti, Torello; Moretti, Silvia

2012-01-01

The CO2 laser has been used extensively in dermatological surgery over the past 30 years and is now recognised as the gold standard for soft tissue vaporization. Considering that the continuous wave CO2 laser delivery system and the newer “superpulsed” and scanned CO2 systems have progressively changed our practice and patient satisfaction, a long range documentation can be useful. Our experience has demonstrated that the use of CO2 laser involves a reduced healing time, an infrequent need for anaesthesia, reduced thermal damage, less bleeding, less inflammation, the possibility of intra-operative histologic and/or cytologic examination, and easy access to anatomically difficult areas. Immediate side effects have been pain, erythema, edema, typically see with older methods, using higher power. The percentage of after-treatment keloids and hypertrophic scars observed was very low (~1%) especially upon the usage of lower parameters. The recurrence of viral lesions (condylomas and warts) have been not more frequent than those due to other techniques. Tumor recurrence is minor compared with radiotherapy or surgery. This method is a valid alternative to surgery and/or diathermocoagulation for microsurgery of soft tissues. Our results are at times not consistent with those published in the literature, stressing the concept that multicentric studies that harmonization methodology and the patient selection are vital. PMID:22593693

Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work

NASA Astrophysics Data System (ADS)

Muniz, German; Alum, Jorge

1996-02-01

In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.

Fundamental Properties of Non-equilibrium Laser-Supported Detonation Wave

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

Shiraishi, Hiroyuki

For developing laser propulsion, it is very important to analyze the mechanism of Laser-Supported Detonation (LSD), because it can generate high pressure and high temperature to be used by laser propulsion can be categorized as one type of hypersonic reacting flows, where exothermicity is supplied not by chemical reaction but by radiation absorption. I have numerically simulated the 1-D and Quasi-1-D LSD waves propagating through an inert gas, which absorbs CO2 gasdynamic laser, using a 2-temperature model. Calculated results show the fundamental properties of the non-equilibrium LSD Waves.

Treatment of tooth fracture by medium-energy CO2 laser and DP-bioactive glass paste: the interaction of enamel and DP-bioactive glass paste during irradiation by CO2 laser.

PubMed

Lin, C P; Tseng, Y C; Lin, F H; Liao, J D; Lan, W H

2001-03-01

Acute trauma or trauma associated with occlusal disturbance can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible, it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. We have tried to use a continuous-wave CO2 laser and a newly developed DP-bioactive glass paste (DPGP) to fuse or bridge tooth crack or fracture lines. Both the DP-bioactive glass paste and tooth enamel have strong absorption bands at the wavelength of 10.6 microm. Therefore, under CO2 laser, DPGP and enamel should have an effective absorption and melt together. The interface between DPGP and enamel could be regarded as a mixture of DPGP and enamel (DPG-E). The study focused on the phase transformation, microstructure, functional group and thermal behavior of DPG-E with or without CO2 laser irradiation, by the analytical techniques of XRD, FTIR, DTA/TGA, and SEM. The results of XRD showed that the main crystal phase in the DPG-E was dicalcium phosphate dihydrate (CaHPO4.2H2O). It changed into CaHPO4, gamma-Ca2P2O7, beta-Ca2P2O7 and finally alpha-Ca2P2O7 with increasing temperature. In the FTIR analysis, the 720 cm(-1) absorption band ascribed to the P-O-P linkage in pyrophosphate rose up and the intensities of the OH- bands reduced after laser irradiation. In regard to the results of DTA/TGA after irradiation, the weight loss decreased due to the removal of part of absorption water and crystallization water by the CO2 laser. SEM micrographs revealed that the melted masses and the plate-like crystals formed a tight chemical bond between the enamel and DPGP. We expect that DPGP with the help of CO2 laser can be an alternative to the treatment of tooth crack or fracture.

Study into penetration speed during laser cutting of brain tissues.

PubMed

Yilbas, Z; Sami, M; Patiroglu, T

1998-01-01

The applications of CO2 continuous-wave lasers in neurosurgery have become important in recent years. Theoretical considerations of laser applicability in medicine are subsequently confirmed experimentally. To obtain precision operation in the laser cutting process, further theoretical developments and experimental studies need to be conducted. Consequently, in the present study, the heat transfer mechanism taking place during laser-tissue interaction is introduced using Fourier theory. The results obtained from the theoretical model are compared with the experimental results. In connection with this, an experiment is designed to measure the penetration speed during the laser cutting process. The measurement is carried out using an optical method. It is found that both results for the penetration speed obtained from the theory and experiment are in a good agreement.

Optical discharge with absorption of repetitive CO{sub 2} laser pulses in supersonic air flow: wave structure and condition of a quasi-steady state

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

Bobarykina, T A; Malov, A N; Orishich, A M

We report a study of the wave structure formed by an optical discharge plasma upon the absorption of repetitively pulsed CO{sub 2} laser radiation in a supersonic (M = 1.36) air flow. Experimental data are presented on the configuration of the head shock wave and the geometry and characteristic dimensions of breakdown regions behind a laser plasma pulsating in the flow at a frequency of up to 150 kHz. The data are compared to calculation in a point explosion model with allowance for counterpressure, which makes it possible to identify the relationship between laser radiation and supersonic flow parameters thatmore » ensures quasisteady- state energy delivery and is necessary for extending the possibilities of controlling the structure of supersonic flows. (interaction of laser radiation with matter)« less

Multi-species trace gas sensing with dual-wavelength QCLs

NASA Astrophysics Data System (ADS)

Hundt, P. Morten; Tuzson, Béla; Aseev, Oleg; Liu, Chang; Scheidegger, Philipp; Looser, Herbert; Kapsalidis, Filippos; Shahmohammadi, Mehran; Faist, Jérôme; Emmenegger, Lukas

2018-06-01

Instrumentation for environmental monitoring of gaseous pollutants and greenhouse gases tends to be complex, expensive, and energy demanding, because every compound measured relies on a specific analytical technique. This work demonstrates an alternative approach based on mid-infrared laser absorption spectroscopy with dual-wavelength quantum cascade lasers (QCLs). The combination of two dual- and one single-DFB QCL yields high-precision measurements of CO (0.08 ppb), CO2 (100 ppb), NH3 (0.02 ppb), NO (0.4 ppb), NO2 (0.1 ppb), N2O (0.045 ppb), and O3 (0.11 ppb) simultaneously in a compact setup (45 × 45 cm2). The lasers are driven time-multiplexed in intermittent continuous wave mode with a repetition rate of 1 kHz. The individual spectra are real-time averaged (1 s) by an FPGA-based data acquisition system. The instrument was assessed for environmental monitoring and benchmarked with reference instrumentation to demonstrate its potential for compact multi-species trace gas sensing.

Comparative morphological investigation on the rabbit's auricle after exposure to CO2- and Nd:YAG-laser radiation.

PubMed

Wandhöfer, A; Bally, G; Kauffmann, G; Karduck, A

1977-10-31

By comparing the effects of CO2- and Nd:YAG-laser radiation (mainly differing in wave-length by a factor of 10), a surgical instrument suitable for Otorhinolaryngology had to be found. The studies were performed on the rabbit's auricle in order to examine the effect of the laser irradiation mainly on the cartilage. The CO2-laser was found to be more efficient in cutting and caused less extended tissue damage than the Nd:YAG-laser. The latter seems to be more suitable for soft tissue surgery.

Surface Modification of Thermal Barrier Coatings by Single-Shot Defocused Laser Treatments

NASA Astrophysics Data System (ADS)

Akdoğan, Vakur; Dokur, Mehmet M.; Göller, Gültekin; Keleş, Özgül

2013-09-01

Thermal barrier coatings (TBC) consisting of atmospheric plasma-sprayed ZrO2-8 wt.% Y2O3 and a high velocity oxygen fuel-sprayed metallic bond coat were subjected to CO2 continuous wave laser treatments. The effects of laser power on TBCs were investigated as was the thermally grown oxide (TGO) layer development of all as-sprayed and laser-treated coatings after thermal oxidation tests in air environment for 50, 100, and 200 h at 1100 °C. The effects of laser power on TBCs were investigated. TGO layer development was examined on all as-sprayed and laser-treated coatings after thermal oxidation tests in air environment for 50, 100, and 200 h at 1100 °C. Melted and heat-affected zone regions were observed in all the laser-treated samples. Oxidation tests showed a stable alumina layer and mixed spinel oxides in the TGO layers of the as-sprayed and laser-treated TBCs.

Continuous-wave and Q-switched microchip laser performance of Yb:Y3Sc2Al3O12 crystals.

PubMed

Dong, Jun; Ueda, Ken-ichi; Kaminskii, Alexander A

2008-04-14

Optical properties of Yb:Y(3)Sc(2)Al(3)O(12) crystal were investigated and compared with those from Yb:YAG crystals. The broad absorption and emission spectra of Yb:Y(3)Sc(2)Al(3)O(12) show that this crystal is very suitable for laser-diode pumping and ultrafast laser pulse generation. Laser-diode pumped continuous-wave and passively Q-switched Yb:Y(3)Sc(2)Al(3)O(12) lasers with Cr(4+):YAG crystals as saturable absorber have been demonstrated for the first time. Continuous-wave output power of 1.12 W around 1032 nm (multi-longitudinal modes) was measured with an optical-to-optical efficiency of 30%. Laser pulses with pulse energy of over 31 microJ and pulse width of 2.5 ns were measured at repetition rate of over 12.7 kHz; a corresponding peak power of over 12 kW was obtained. The longitudinal mode selection by a thin plate of Cr(4+):YAG as an intracavity etalon was also observed in passively Q-switched Yb:Y(3)Sc(2)Al(2)O(12) microchip lasers.

High temperature infrared absorption cross sections of methane near 3.4 µm in Ar and CO 2 mixtures

DOE PAGES

Koroglu, Batikan; Neupane, Sneha; Pryor, Owen; ...

2017-11-04

In this study, the absorption cross-sections of CH 4 at two wavelengths in the mid-IR region: λ peak = 3403.4 nm and λ valley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH 4/Ar/CO 2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the linemore » shapes in various bath gasses (Ar, CO 2, and N 2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO 2, O 2, and Ar. Lastly, current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.« less

High temperature infrared absorption cross sections of methane near 3.4 µm in Ar and CO 2 mixtures

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

Koroglu, Batikan; Neupane, Sneha; Pryor, Owen

In this study, the absorption cross-sections of CH 4 at two wavelengths in the mid-IR region: λ peak = 3403.4 nm and λ valley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH 4/Ar/CO 2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the linemore » shapes in various bath gasses (Ar, CO 2, and N 2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO 2, O 2, and Ar. Lastly, current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.« less

High temperature infrared absorption cross sections of methane near 3.4 μm in Ar and CO2 mixtures

NASA Astrophysics Data System (ADS)

Koroglu, Batikan; Neupane, Sneha; Pryor, Owen; Peale, Robert E.; Vasu, Subith S.

2018-02-01

The absorption cross-sections of CH4 at two wavelengths in the mid-IR region: λpeak = 3403.4 nm and λvalley = 3403.7 nm were measured. Data were taken using three different compositions of non-reactive gas mixtures comprising CH4/Ar/CO2 between 700 < T < 2000 K and 0.1 < P < 1.5 atm in a shock tube utilizing a continuous-wave distributed-feedback quantum cascade laser. Also, broadband room temperature methane cross section measurements were performed using a Fourier transform infrared spectrometer and the cascade laser to gain a better insight into the changes of the line shapes in various bath gasses (Ar, CO2, and N2). An application of the high-temperature cross-section data was demonstrated to determine the concentration of methane during oxy-methane combustion in a mixture of CO2, O2, and Ar. Current measurements will be valuable addition to the spectroscopy database for methane- an important fuel used for power generation and heating around the world.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Phase locking of the radiation of ring waveguide CO2 lasers

NASA Astrophysics Data System (ADS)

Glova, A. F.; Lebedev, E. A.; Lysikov, A. Yu; Shchetnikov, S. B.

1999-12-01

Phase locking of the radiation of two ring waveguide CO2 lasers with a common cavity and unidirectional lasing was achieved for an output power of about 20 W. Measurements of the fringe visibility of the radiation intensity distributions in the far-field zone agreed qualitatively with the calculations for plane waves.

Cavity-Enhanced Quantum-Cascade Laser-Based Instrument for Trace gas Measurements

NASA Astrophysics Data System (ADS)

Provencal, R.; Gupta, M.; Owano, T.; Baer, D.; Ricci, K.; O'Keefe, A.

2005-12-01

An autonomous instrument based on Off-Axis Integrated Cavity Output Spectroscopy has been successfully deployed for measurements of CO in the troposphere and tropopause onboard a NASA DC-8 aircraft. The instrument consists of a measurement cell comprised of two high reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data acquisition electronics, and data analysis software. The instrument reports CO mixing ratio at a 1-Hz rate based on measured absorption, gas temperature and pressure using Beer's Law. During several flights in May-June 2004 and January 2005 that reached altitudes of 41000 ft, the instrument recorded CO values with a precision of 0.2 ppbv (1-s averaging time). Despite moderate turbulence and measurements of particulate-laden airflows, the instrument operated consistently and did not require any maintenance, mirror cleaning, or optical realignment during the flights. We will also present recent development efforts to extend the instrument's capabilities for the measurements of CH4, N2O and CO in real time.

Real-time breath gas analysis of CO and CO2 using an EC-QCL

NASA Astrophysics Data System (ADS)

Ghorbani, Ramin; Schmidt, Florian M.

2017-05-01

Real-time breath gas analysis is a promising, non-invasive tool in medical diagnostics, and well-suited to investigate the physiology of carbon monoxide (CO), a potential biomarker for oxidative stress and respiratory diseases. A sensor for precise, breath-cycle resolved, simultaneous detection of exhaled CO (eCO) and carbon dioxide (eCO2) was developed based on a continuous wave, external-cavity quantum cascade laser (EC-QCL), a low-volume multi-pass cell and wavelength modulation spectroscopy. The system achieves a noise-equivalent (1σ) sensitivity of 8.5 × 10-8 cm-1 Hz-1/2 and (2σ) detection limits of 9 ± 2 ppbv and 650 ± 7 ppmv at 0.14 s spectrum acquisition time for CO and CO2, respectively. Integration over 15 s yields a precision of 0.6 ppbv for CO. The fact that the eCO2 expirograms measured by capnography and laser spectroscopy have essentially identical shape confirms true real-time detection. It is found that the individual eCO exhalation profiles from healthy non-smokers have a slightly different shape than the eCO2 profiles and exhibit a clear dependence on exhalation flow rate and breath-holding time. Detection of indoor air CO and broadband breath profiling across the 93 cm-1 mode-hop-free tuning range of the EC-QCL are also demonstrated.

Study of plasma formation in CW CO2 laser beam-metal surface interaction

NASA Astrophysics Data System (ADS)

Azharonok, V. V.; Vasilchenko, Zh V.; Golubev, Vladimir S.; Gresev, A. N.; Zabelin, Alexandre M.; Chubrik, N. I.; Shimanovich, V. D.

1994-04-01

An interaction of the cw CO2 laser beam and a moving metal surface has been studied. The pulsed and thermodynamical parameters of the surface plasma were investigated by optical and spectroscopical methods. The subsonic radiation wave propagation in the erosion plasma torch has been studied.

Excimer lasers

NASA Technical Reports Server (NTRS)

Palmer, A. J.; Hess, L. D.; Stephens, R. R.; Pepper, D. M.

1977-01-01

The results of a two-year investigation into the possibility of developing continuous wave excimer lasers are reported. The program included the evaluation and selection of candidate molecular systems and discharge pumping techniques. The K Ar/K2 excimer dimer molecules and the xenon fluoride excimer molecule were selected for study; each used a transverse and capillary discharges pumping technique. Experimental and theoretical studies of each of the two discharge techniques applied to each of the two molecular systems are reported. Discharge stability and fluorine consumption were found to be the principle impediments to extending the XeF excimer laser into the continuous wave regime. Potassium vapor handling problems were the principal difficulty in achieving laser action on the K Ar/K2 system. Of the four molecular systems and pumping techniques explored, the capillary discharge pumped K Ar/K2 system appears to be the most likely candidate for demonstrating continuous wave excimer laser action primarily because of its predicted lower pumping threshold and a demonstrated discharge stability advantage.

Co removal and phase transformations during high power diode laser irradiation of cemented carbide

NASA Astrophysics Data System (ADS)

Barletta, M.; Rubino, G.; Gisario, A.

2011-02-01

The use of a continuous wave-high power diode laser for removing surface Co-binder from Co-cemented tungsten carbide (WC-Co (5.8 wt%.)) hardmetal slabs was investigated. Combined scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses were performed in order to study the phase transformations and micro-structural modifications of the WC-Co substrates occurring during and after laser irradiation. The micro-structure of the WC-Co progressively transforms as energy density increased, exhibiting stronger removal of Co and WC grain growth. At very high energy density, local melting of the WC grains with the formation of big agglomerates of interlaced grains is observed, and the crystalline structure of the irradiated substrate shows the presence of a brittle ternary eutectic phase of W, Co and C (often referred to as the η-phase). The latter can be detrimental to the mechanical properties of WC-Co. Therefore, the proper adjustment of the laser processing parameters plays a crucial role in surface treatments of WC-Co substrates prior to post-processing like diamond deposition.

Pseudorandom Noise Code-Based Technique for Cloud and Aerosol Discrimination Applications

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.; Harrison, Fenton Wallace

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a PN code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths. Keywords: ASCENDS, CO2 sensing, O2 sensing, PN codes, CW lidar

Dynamics of Laser-Driven Shock Waves in Solid Targets

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J.; Schmitt, A. J.; Obenschain, S. P.; Grun, J.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

2009-11-01

Accurate shock timing is a key issue of both indirect- and direct-drive laser fusions. The experiments on the Nike laser at NRL presented here were made possible by improvements in the imaging capability of our monochromatic x-ray diagnostics based on Bragg reflection from spherically curved crystals. Side-on imaging implemented on Nike makes it possible to observe dynamics of the shock wave and ablation front in laser-driven solid targets. We can choose to observe a sequence of 2D images or a continuous time evolution of an image resolved in one spatial dimension. A sequence of 300 ps snapshots taken using vanadium backlighter at 5.2 keV reveals propagation of a shock wave in a solid plastic target. The shape of the shock wave reflects the intensity distribution in the Nike beam. The streak records with continuous time resolution show the x-t trajectory of a laser-driven shock wave in a 10% solid density DVB foam.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases

NASA Astrophysics Data System (ADS)

Kanevskiĭ, M. F.; Stepanova, M. A.

1990-06-01

An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

Ambient-temperature co-oxidation catalysts

NASA Technical Reports Server (NTRS)

Upchurch, Billy T.; Schryer, David R.; Brown, Kenneth G.; Kielin, Erik J.

1991-01-01

Oxidation catalysts which operate at ambient temperature were developed for the recombination of carbon monoxide (CO) and oxygen (O2) dissociation products which are formed during carbon dioxide (CO2) laser operation. Recombination of these products to regenerate CO2 allows continuous operation of CO2 lasers in a closed cycle mode. Development of these catalyst materials provides enabling technology for the operation of such lasers from space platforms or in ground based facilities without constant gas consumption required for continuous open cycle operation. Such catalysts also have other applications in various areas outside the laser community for removal of CO from other closed environments such as indoor air and as an ambient temperature catalytic converter for control of auto emissions.

Laser plasmatron for diamond coating deposition

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

Glova, A. F., E-mail: afglova@triniti.ru; Lysikov, A. Yu.; Malyuta, D. D.

2016-12-15

An experimental installation with a laser plasmatron based on a continuous wave CO{sub 2} laser with a radiation power of up to 3.5 kW has been created. The plasmatron design makes it possible to bring out the plasma jet into atmospheric air both along and across the laser beam direction. The spatial temperature distributions on the metal substrate surface heated by the plasma jet are measured. The threshold power for optical discharge maintenance as a function of the gas flow rate and the focal length of the focusing lens are obtained for an Ar and Ar/CH{sub 4}/H{sub 2} gas mixturemore » under atmospheric pressure; the radiation spectrum of the discharge plasma is measured. A one-dimensional model of the discharge for estimation of its geometrical parameters in a convergent laser beam with consideration of radiation refraction on the discharge is given.« less

Diode-pumped 1.5-1.6 μm laser operation in Er³⁺ doped YbAl₃(BO₃)₄ microchip.

PubMed

Chen, Yujin; Lin, Yanfu; Zou, Yuqi; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

2014-06-02

Er3+ doped YbAl3(BO3)4 crystal with large absorption coefficient of 184 cm(-1) at pump wavelength of 976 nm is a promising microchip gain medium of 1.5-1.6 μm laser. End-pumped by a 976 nm diode laser, 1.5-1.6 μm continuous-wave laser with maximum output power of 220 mW and slope efficiency of 8.1% was obtained at incident pump power of 4.54 W in a c-cut 200-μm-thick Er:YbAl3(BO3)4 microchip. When a Co2+:Mg0.4Al2.4O4 crystal was used as the saturable absorber, 1521 nm passively Q-switched pulse laser with about 0.19 μJ energy, 265 ns duration, and 96 kHz repetition rate was realized.

Continuous-wave broadly tunable Cr 2+:ZnSe laser pumped by a thulium fiber laser

NASA Astrophysics Data System (ADS)

Sennaroglu, Alphan; Demirbas, Umit; Vermeulen, Nathalie; Ottevaere, Heidi; Thienpont, Hugo

2006-12-01

We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+:ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 × 10 18 cm -3 was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF 2 prism and a single set of optics.

Reactivation of a Tin-Oxide-Containing Catalyst

NASA Technical Reports Server (NTRS)

Hess, Robert; Sidney, Barry; Schryer, David; Miller, Irvin; Miller, George; Upchurch, Bill; Davis, Patricia; Brown, Kenneth

2010-01-01

The electrons in electric-discharge CO2 lasers cause dissociation of some CO2 into O2 and CO, and attach themselves to electronegative molecules such as O2, forming negative O2 ions, as well as larger negative ion clusters by collisions with CO or other molecules. The decrease in CO2 concentration due to dissociation into CO and O2 will reduce the average repetitively pulsed or continuous wave laser power, even if no disruptive negative ion instabilities occur. Accordingly, it is the primary object of this invention to extend the lifetime of a catalyst used to combine the CO and O2 products formed in a laser discharge. A promising low-temperature catalyst for combining CO and O2 is platinum on tin oxide (Pt/SnO2). First, the catalyst is pretreated by a standard procedure. The pretreatment is considered complete when no measurable quantity of CO2 is given off by the catalyst. After this standard pretreatment, the catalyst is ready for its low-temperature use in the sealed, high-energy, pulsed CO2 laser. However, after about 3,000 minutes of operation, the activity of the catalyst begins to slowly diminish. When the catalyst experiences diminished activity during exposure to the circulating gas stream inside or external to the laser, the heated zone surrounding the catalyst is raised to a temperature between 100 and 400 C. A temperature of 225 C was experimentally found to provide an adequate temperature for reactivation. During this period, the catalyst is still exposed to the circulating gas inside or external to the laser. This constant heating and exposing the catalyst to the laser gas mixture is maintained for an hour. After heating and exposing for an appropriate amount of time, the heated zone around the catalyst is allowed to return to the nominal operating temperature of the CO2 laser. This temperature normally resides in the range of 23 to 100 C. Catalyst activity can be measured as the percentage conversion of CO to CO2. In the specific embodiment described above, the initial steady-state conversion percentage was 70 percent. After four days, this conversion percentage decreased to 67 percent. No decrease in activity is acceptable because the catalyst must maintain its activity for long periods of time. After being subjected to the reactivation process of the present invention, the conversion percentage rose to 77 percent. Such a reactivation not only returned the catalyst to its initial steady state but resulted in a 10-percent improvement over the initial steady state value.

Geophysical Signatures to Monitor Fluids and Mineralization for CO2 Sequestration in Basalts

NASA Astrophysics Data System (ADS)

Otheim, L. T.; Adam, L.; Van Wijk, K.; Batzle, M. L.; Mcling, T. L.; Podgorney, R. K.

2011-12-01

Carbon dioxide sequestration in large reservoirs can reduce emissions of this green house gas into the atmosphere. Basalts are promising host rocks due to their volumetric extend, worldwide distribution, and recent observations that CO2-water mixtures react with basalt minerals to precipitate as carbonate minerals, trapping the CO2. The chemical reaction between carbonic acid and minerals rich in calcium, magnesium and iron precipitates carbonates in the pore space. This process would increase the elastic modulus and velocity of the rock. At the same time, the higher compressibility of CO2 over water changes the elastic properties of the rock, decreasing the saturated rock bulk modulus and the P-wave velocity. Reservoirs where the rock properties change as a result of fluid or pressure changes are commonly monitored with seismic methods. Here we present experiments to study the feasibility of monitoring CO2 migration in a reservoir and CO2-rock reactions for a sequestration scenario in basalts. Our goal is to measure the rock's elastic response to mineralization with non-contacting ultrasonic lasers, and the effect of fluid substitution at reservoir conditions at seismic and ultrasonic frequencies. For the fluid substitution experiment we observe changes in the P- and S-wave velocities when saturating the sample with super-critical (sc) CO2, CO2-water mixtures and water alone for different pore and confining pressures. The bulk modulus of the rock is significantly dependent on frequency in the 2~to 106~Hz range, for CO2-water mixtures and pure water saturations. Dry and pure CO2 (sc or gas) do not show a frequency dependence on the modulus. Moreover, the shear wave modulus is not dispersive for either fluid. The frequency dependence of the elastic parameters is related to the attenuation (1/Q) of the rock. We will show the correlation between frequency dependent moduli and attenuation data for the different elastic moduli of the rocks. Three other basalt samples were stored in a pressure chamber with a sc CO2-water solution to study the effect of mineralization on the elastic properties of the rock. The rock elastic properties are recorded with non-contacting ultrasonic lasers at room conditions. After 15 weeks the first post-mineralization scan showed differences in the rock velocities with respect to the pre-mineralization scan. The analysis is done through coda wave interferometry and direct arrivals. The samples were inserted back into the pressure vessel for continuing mineralization and subsequent scans. Finally, we will discuss the applicability of Gassmann's equation and how the combination of mineralization together with CO2-water mixture affects the velocity of waves in basalt rocks.

Theoretical study of the characteristics of a continuous wave iron-doped ZnSe laser

NASA Astrophysics Data System (ADS)

Pan, Qikun; Chen, Fei; Xie, Jijiang; Wang, Chunrui; He, Yang; Yu, Deyang; Zhang, Kuo

2018-03-01

A theoretical model describing the dynamic process of a continuous-wave Fe2+:ZnSe laser is presented. The influence of some of the operating parameters on the output characteristics of an Fe2+:ZnSe laser is studied in detail. The results indicate that the temperature rise of the Fe2+:ZnSe crystal is significant with the use of a high power pump laser, especially for a high doped concentration of crystal. The optimal crystal length increases with decreasing the doped concentration of crystal, so an Fe2+:ZnSe crystal with simultaneous doping during growth is an attractive choice, which usually has a low doped concentration and long length. The laser pumping threshold is almost stable at low temperatures, but increases exponentially with a working temperature in the range of 180 K to room temperature. The main reason for this phenomenon is the short upper level lifetime and serious thermal temperature rise when the working temperature is higher than 180 K. The calculated optimum output mirror transmittance is about 35% and the performance of a continuous-wave Fe2+:ZnSe laser is more efficient at a lower operating temperature.

Light-induced generation of singlet oxygen by naked gold nanoparticles and its implications to cancer cell phototherapy.

PubMed

Pasparakis, George

2013-12-20

Generation of singlet oxygen by direct irradiation of naked gold nanoparticles is observed using either continuous wave or pulsed laser sources. The underlying mechanism involves plasmon- and hot-electron-mediated reaction pathways and (1) O2 seems to significantly amplify the overall death rates during photothermal treatment of cancer cell lines in vitro. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High repetition ration solid state switched CO2 TEA laser employed in industrial ultrasonic testing of aircraft parts

NASA Astrophysics Data System (ADS)

von Bergmann, Hubertus; Morkel, Francois; Stehmann, Timo

2015-02-01

Laser Ultrasonic Testing (UT) is an important technique for the non-destructive inspection of composite parts in the aerospace industry. In laser UT a high power, short pulse probe laser is scanned across the material surface, generating ultrasound waves which can be detected by a second low power laser system and are used to draw a defect map of the part. We report on the design and testing of a transversely excited atmospheric pressure (TEA) CO2 laser system specifically optimised for laser UT. The laser is excited by a novel solid-state switched pulsing system and utilises either spark or corona preionisation. It provides short output pulses of less than 100 ns at repetition rates of up to 1 kHz, optimised for efficient ultrasonic wave generation. The system has been designed for highly reliable operation under industrial conditions and a long term test with total pulse counts in excess of 5 billion laser pulses is reported.

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.

Clinical application of CO2 laser in periodontal treatment

NASA Astrophysics Data System (ADS)

Hayase, Yasuhiro

1994-09-01

CO2 lasers in particular are expected to have many dental applications because the CO2 laser beam exhibits strong tissue transpirative actions, such as instant coagulation, carbonization, and vaporization, and because its wavelength at 10.6 micrometers is fully absorbed by water so that the ability to make precise incisions with a high degree of safety is excellent, without damaging the deep tissues. However, clinical application of the CO2 laser has been slowed since a fiber which can conduct the laser beam to the oral cavity has only recently developed. This new fiber is an extremely flexible fiber with a minimum bending radius of 20 mm and utilizes pulse wave modes that have improved the handling characteristics in the mouth, and this has enabled us to apply the CO2 laser to a variety of periodontal conditions. The aim of this study was to evaluate the effectiveness of CO2 lasers for the early treatment of inflammation and pain relief of acute periodontitis, curettage of periodontal pockets, healing after excision of gingiva, and early improvement of gingivitis.

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers

PubMed Central

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-01-01

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. PMID:27009375

Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers.

PubMed

Lu, Quanyong; Wu, Donghai; Sengupta, Saumya; Slivken, Steven; Razeghi, Manijeh

2016-03-24

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06-4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

Resonantly enhanced four-wave mixing

DOEpatents

Begley, Richard F.; Kurnit, Norman A.

1978-01-01

A method and apparatus for achieving large susceptibilities and long interaction lengths in the generation of new wavelengths in the infrared spectral region. A process of resonantly enhanced four-wave mixing is employed, utilizing existing laser sources, such as the CO.sub.2 laser, to irradiate a gaseous media. The gaseous media, comprising NH.sub.3, CH.sub.3 F, D.sub.2, HCl, HF, CO, and H.sub.2 or some combination thereof, are of particular interest since they are capable of providing high repetition rate operation at high flux densities where crystal damage problems become a limitation.

Measurements of Forest-Atmosphere Isotopic CO2 Exchange by Eddy Covariance

NASA Astrophysics Data System (ADS)

Wehr, R. A.; Munger, J. W.; Nelson, D. D.; McManus, J. B.; Zahniser, M. S.; Saleska, S. R.

2010-12-01

Isotopic CO2 flux measurements are a promising means for partitioning the net ecosystem exchange of CO2 into photosynthetic and respiratory components. This approach to partitioning is possible in principle because of the distinct isotopic signatures of respired and photosynthesized CO2, but has been infeasible in practice—especially in forests—because of the difficulty of measuring isotopic ratios with sufficient precision and time response for use in eddy covariance (EC) flux calculations. Recent advances in laser spectroscopic instrumentation have changed that. We report measurements of isotopic (13C and 18O) CO2 exchange made by eddy covariance at Harvard Forest between April and December, 2010. The measurements were made using a continuous-wave quantum cascade laser spectrometer (Aerodyne Research Inc.) sampling at 4 Hz and are, to our knowledge, the first EC isotopic flux measurements at a forest site. The spectrometer can measure δ13C and δ18O with internal precisions (standard deviation of 1-minute averages) of 0.03 ‰, and [CO2] with an internal precision of 15 ppb; the instrumental accuracy, calibration, and long-term stability are discussed in detail. The isotopic data are considered in relation to environmental variables (PAR, temperature, humidity, soil temperature and moisture), and a first attempt at flux partitioning using the isotopic fluxes is presented.

Cavity-enhanced quantum-cascade laser-based instrument for carbon monoxide measurements.

PubMed

Provencal, Robert; Gupta, Manish; Owano, Thomas G; Baer, Douglas S; Ricci, Kenneth N; O'Keefe, Anthony; Podolske, James R

2005-11-01

An autonomous instrument based on off-axis integrated cavity output spectroscopy has been developed and successfully deployed for measurements of carbon monoxide in the troposphere and tropopause onboard a NASA DC-8 aircraft. The instrument (Carbon Monoxide Gas Analyzer) consists of a measurement cell comprised of two high-reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data-acquisition electronics, and data-analysis software. CO measurements were determined from high-resolution CO absorption line shapes obtained by tuning the laser wavelength over the R(7) transition of the fundamental vibration band near 2172.8 cm(-1). The instrument reports CO mixing ratio (mole fraction) at a 1-Hz rate based on measured absorption, gas temperature, and pressure using Beer's Law. During several flights in May-June 2004 and January 2005 that reached altitudes of 41,000 ft (12.5 km), the instrument recorded CO values with a precision of 0.2 ppbv (1-s averaging time) and an accuracy limited by the reference CO gas cylinder (uncertainty < 1.0%). Despite moderate turbulence and measurements of particulate-laden airflows, the instrument operated consistently and did not require any maintenance, mirror cleaning, or optical realignment during the flights.

Nonlinear optical properties of Nd3+-Li+ co-doped ZnS-PVP thin films

NASA Astrophysics Data System (ADS)

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

2018-04-01

The nonlinear optical properties of Nd3+-Li+ co-doped ZnS-PVP nanocomposite were studied using a continuous wave (CW) He-Ne laser (λ = 632.8 nm)by z-scan technique. The nonlinear refractive index (n2), absorption coefficient (β) and third order nonlinear susceptibility (χ(3)) of PVP thin films embedded with Nd3+-Li+ co-doped ZnS NPs was found in the order of 10-7 cm2/W, 10-6 cm/W and 10-7 esu respectively. The nonlinearity found increasing with Nd3+-Li+ co-dopant concentration. Based on the results, it is proposed that this material is a new class of luminescent material suitable in optoelectronics devices application, especially in light-emitting devices, electroluminescent devices, display devices, etc.

Mode transition of plasma expansion for laser induced breakdown in Air

NASA Astrophysics Data System (ADS)

Shimamura, Kohei; Matsui, Kohei; Ofosu, Joseph A.; Yokota, Ippei; Komurasaki, Kimiya

2017-03-01

High-speed shadowgraph visualization experiments conducted using a 10 J pulse transversely excited atmospheric (TEA) CO2 laser in ambient air provided a state transition from overdriven to Chapman-Jouguet in the laser-supported detonation regime. At the state transition, the propagation velocity of the laser-supported detonation wave and the threshold laser intensity were 10 km/s and 1011 W/m2, respectively. State transition information, such as the photoionization caused by plasma UV radiation, of the avalanche ionization ahead of the ionization wave front can be elucidated from examination of the source seed electrons.

Characteristics of the evolution of a plasma generated by radiation from CW and repetitively pulsed CO2 lasers in different gases

NASA Astrophysics Data System (ADS)

Kanevskii, M. F.; Stepanova, M. A.

1990-06-01

The interaction between high-power CW and repetitively pulsed CO2 laser radiation and a low-threshold optical-breakdown plasma near a metal surface is investigated. The characteristics of the breakdown plasma are examined as functions of the experimental conditions. A qualitative analysis of the results obtained was performed using a simple one-dimensional model for laser combustion waves.

Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

NASA Astrophysics Data System (ADS)

Wu, Shikai; Xiao, Rongshi

2015-04-01

The effects of laser radiation on the characteristics of the DC tungsten inert gas (TIG) arc were investigated by applying a high power slab CO2 laser and a Yb:YAG disc laser. Experiment results reveal that the arc voltage-current curve shifts downwards, the arc column expands, and the arc temperature rises while the high power CO2 laser beam vertically interacts with the TIG arc in argon. With the increase of the laser power, the voltage-current curve of the arc shifts downwards more significantly, and the closer the laser beam impingement on the arc to the cathode, the more the decrease in arc voltage. Moreover, the arc column expansion and the arc temperature rise occur mainly in the region between the laser beam incident position and the anode. However, the arc characteristics hardly change in the cases of the CO2 laser-helium arc and YAG laser-arc interactions. The reason is that the inverse Bremsstrahlung absorption coefficients are greatly different due to the different electron densities of the argon and helium arcs and the different wave lengths of CO2 and YAG lasers.

Flexible CO2 laser waveguide: a comparison of tracheal resection dosimetry and histology with the rigid waveguide

NASA Astrophysics Data System (ADS)

Slack, Christopher L.; Pankratov, Michail M.; Perrault, Donald F., Jr.; Shapshay, Stanley M.; Aretz, H. Thomas

1993-07-01

The CO2 laser has been limited in its application within the tracheobronchial tree by its lack of a fiber delivery system. Recently a new product has been marketed, Luxar's flexible CO2 laser waveguide or FlexiguideTM, a spin-off of the presently used rigid waveguide or MicroguideTM. The study was undertaken so as to delineate the properties and thus the usefulness of this new product which promised an increased ease of delivery of the CO2 laser wavelength. We compared the flexiguide with its rigid counterpart along two parameters. Specifically, we determined the total energy necessary to endoscopically resect bovine tracheal rings with each guide and then examined the histologic crater characteristics of each guide at a given energy setting. In so doing we endeavored to see if the experience of the surgeon with the microguide could be translated to the use of the flexiguide. We found the flexiguide to require a greater total energy than the microguide in the continuous wave (cw) and chopped pulse (cp) operational modes p < 0.01. There was, however, no demonstrated difference in required energy in the superpulse (sp) operational mode. Preliminary histologic evidence when measuring such indices as crater depth, crater width, and shoulder width thermal damage seem to suggest that the flexiguide is less efficient at tissue ablation than its rigid counterpart at the same given energy. It also appears to cause a greater degree of associated thermal injury.

Research on industrial 10kW CO2 laser achieves major breakthrough

NASA Astrophysics Data System (ADS)

1991-01-01

The industrial 10kW CO2 laser is one of the items which the industrially developed nations are competing to develop. This laser is capable of continuous output power of over 10kW and can operate continuously for more than 6 hours. The 10kW CO2 laser developed as a key task of China's 7th Five-Year Plan and all its technological targets such as output power, electrooptical conversion efficiency and primary charging continuous operating time, have reached the level of world advancement, allowing China to enter the ranks of international advancement in the area of laser technology. The industrial 10kW CO2 laser can have wide application in such areas of industry as heat treating, machining, welding and surface treatment in industries such as steel, automobiles, ship building and aircraft manufacturing. For instance, using the high-efficiency laser beams of this 10kW laser to treat rollers, fan blades and automotive cylinder blocks can increase the life of these parts and produce large economic benefits. At present, industrial tests of gear welding is already being done on this 10kW laser.

Laser absorption waves in metallic capillaries

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Kanevskii, M. F.; Kondrashov, V. V.

1987-07-01

The propagation of laser absorption waves in metallic capillaries was studied experimentally and numerically during pulsed exposure to CO2 laser radiation. The dependence of the plasma front propagation rate on the initial air pressure in the capillary is determined. In a broad range of parameters, the formation time of the optically opaque plasma layer is governed by the total laser pulse energy from the beginning of the exposure to the instant screening appears, and is weakly dependent on the pulse shape and gas pressure.

Heterodyne frequency measurements on N2O at 5.3 and 9.0 microns

NASA Technical Reports Server (NTRS)

Wells, J. S.; Jennings, D. A.; Hinz, A.; Murray, J. S.; Maki, A. G.

1985-01-01

Heterodyne frequency measurements on the 01(1)1-00(0)0 band of N2O have been made with the use of a tunable-diode laser, CO laser transfer oscillator, and a CO2 laser frequency synthesizer. A beat frequency was measured between a CO laser and tunable-diode laser whose frequency was locked to the peak of N2O absorption features. The frequency of the CO laser was simultaneously determined by neasuring the beat frequency with respect to a reference synthesized from two CO2 lasers. New rovibrational constants are given for the 01(1)1 state of N2O, which are in excellent agreement with previous results, although the band center is 4 MHz higher than in the previous measurements. A table for the line frequencies and their absolute uncertainties is given for the N2O absorption lines in the wave-number region from 1830 to 1920 kaysers. Some additional frequency measurements near the lower-frequency end of the 02(0)0-00(0)0 band have also been made with respect to a C-12)(0-18)2 laser.

High-sensitivity detection of TNT

PubMed Central

Pushkarsky, Michael B.; Dunayevskiy, Ilya G.; Prasanna, Manu; Tsekoun, Alexei G.; Go, Rowel; Patel, C. Kumar N.

2006-01-01

We report high-sensitivity detection of 2,4,6-trinitrotoluene (TNT) by using laser photoacoustic spectroscopy where the laser radiation is obtained from a continuous-wave room temperature high-power quantum cascade laser in an external grating cavity geometry. The external grating cavity quantum cascade laser is continuously tunable over ≈400 nm around 7.3 μm and produces a maximum continuous-wave power of ≈200 mW. The IR spectroscopic signature of TNT is sufficiently different from that of nitroglycerine so that unambiguous detection of TNT without false positives from traces of nitroglycerine is possible. We also report the results of spectroscopy of acetylene in the 7.3-μm region to demonstrate continuous tunability of the IR source. PMID:17164325

Extinction of CO2 Laser Radiation Under Adverse Weather Conditions

DTIC Science & Technology

1982-06-01

System Design 60 a, Gaussian Optics 60 b, Laser Transmissometer 61 4. Measurement Errors 68 VI DISCUSSION OF RESULTS 69 1, Introduction...water soluble aerosols (a 1 106 AFWAL-TR-81 -.1280 TABLE 17 EXTINCTION OF CO2 LASER LINES FOR A CONSTANI RAIN RATE OF 1.82 mm/HR, 22 APRIL, 1935 HOURS...number) Laser Propagation Rain Laser Extinction CO2 Lasers Adverse Weather Aerosol s - 20 RACT (Continue on reverse side If necessary

Spectroscopic detection of biological NO with a quantum cascade laser

NASA Technical Reports Server (NTRS)

Menzel, L.; Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.;

A Capillary Absorption Spectrometer for Stable Carbon Isotope Ratio (13C/12C) Analysis in Very Small Samples

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

Kelly, James F.; Sams, Robert L.; Blake, Thomas A.

2012-02-06

A capillary absorption spectrometer (CAS) suitable for IR laser isotope analysis of small CO{sub 2} samples is presented. The system employs a continuous-wave (cw) quantum cascade laser to study nearly adjacent rovibrational transitions of different isotopologues of CO{sub 2} near 2307 cm{sup -1} (4.34 {mu}m). This initial CAS system can achieve relative isotopic precision of about 10 ppm {sup 13}C, or {approx}1{per_thousand} (per mil in delta notation relative to Vienna Pee Dee Belemnite) with 20-100 picomoles of entrained sample within the hollow waveguide for CO{sub 2} concentrations {approx}400 to 750 ppm. Isotopic analyses of such gas fills in a 1-mmmore » ID hollow waveguide of 0.8 m overall physical path length can be carried out down to {approx}2 Torr. Overall {sup 13}C/{sup 12}C ratios can be calibrated to {approx}2{per_thousand} accuracy with diluted CO{sub 2} standards. A novel, low-cost method to reduce cw-fringing noise resulting from multipath distortions in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level (peak-to-rms) after 1,000 scans are co-added in {approx}10 sec. The CAS is meant to work directly with converted CO{sub 2} samples from a Laser Ablation-Catalytic-Combustion (LA CC) micro-sampler to provide {sup 13}C/{sup 12}C ratios of small biological isolates with spatial resolutions {approx}50 {mu}m.« less

Energy modulation of nonrelativistic electrons with a CO2 laser using a metal microslit

NASA Astrophysics Data System (ADS)

Bae, Jongsuck; Ishikawa, Ryo; Okuyama, Sumio; Miyajima, Takashi; Akizuki, Taiji; Okamoto, Tatsuya; Mizuno, Koji

2000-04-01

A metal microslit has been used as an interaction circuit between a CO2 laser beam and nonrelativistic free electrons. Evanescent waves which are induced on the slit by illumination of the laser light modulate the energy of electrons passing close to the surface of the slit. The electron-energy change of more than ±5 eV for the 80 keV electron beam has been observed using the 7 kW laser beam at the wavelength of 10.6 μm.

High-performance continuous-wave room temperature 4.0-μm quantum cascade lasers with single-facet optical emission exceeding 2 W

PubMed Central

Lyakh, A.; Maulini, R.; Tsekoun, A.; Go, R.; Von der Porten, S.; Pflügl, C.; Diehl, L.; Capasso, Federico; Patel, C. Kumar N.

2010-01-01

A strain-balanced, AlInAs/InGaAs/InP quantum cascade laser structure, designed for light emission at 4.0 μm using nonresonant extraction design approach, was grown by molecular beam epitaxy. Laser devices were processed in buried heterostructure geometry. An air-cooled laser system incorporating a 10-mm × 11.5-μm laser with antireflection-coated front facet and high-reflection-coated back facet delivered over 2 W of single-ended optical power in a collimated beam. Maximum continuous-wave room temperature wall plug efficiency of 5.0% was demonstrated for a high-reflection-coated 3.65-mm × 8.7-μm laser mounted on an aluminum nitride submount.

A 2-microm continuous-wave laser system for safe and high-precision dissection during NOTES procedures.

PubMed

Dray, Xavier; Donatelli, Gianfranco; Krishnamurty, Devi Mukkai; Dubcenco, Elena; Wroblewski, Ronald J; Assumpcao, Lia; Giday, Samuel A; Buscaglia, Jonathan M; Shin, Eun J; Magno, Priscilla; Pipitone, Laurie J; Marohn, Michael R; Kantsevoy, Sergey V; Kalloo, Anthony N

2010-09-01

Lasers 2-microm in wavelength offer efficient tissue cutting with limited thermal damage in biological tissue. To evaluate the dissection capabilities of a 2-microm continuous-wave laser for NOTES procedures. We conducted 18 acute animal experiments. Group 1 (three animals): transcolonic access to the peritoneal cavity (15-W transcolonic laser puncture, balloon dilation over the laser probe). Group 2 (six animals): transcolonic access with needle-knife puncture and balloon dilation. Group 3 (three animals): transgastric access to the peritoneal cavity (similar technique as group 1) followed by laser-assisted dissection of the kidney. In one animal of group 3, a therapeutic target (hematoma) was created by percutaneous puncture of the kidney. Group 4 (six animals): transgastric access (similar to the technique of group 2). Translumenal access to the peritoneal cavity was achieved in 2-3 min in group 1 (significantly shorter than with the needle-knife-assisted technique, 4-5 min, p=0.02) and in 7-10 min in group 3 (compared to 6-17 min in group 4, p=0.88). In group 3, laser dissection of the parietal peritoneum and of perinephric connective tissue allowed access to the retroperitoneum with complete removal of a blood collection in the animal with puncture trauma. Laser dissection demonstrated good maneuverability, clean and rapid cutting, and excellent hemostasis. Peritoneoscopy and necropsy showed no damage of targeted tissue and surrounding organs. The 2-microm continuous-wave laser system showed promising capabilities for highly precise and safe dissection during NOTES procedures.

Laser shocking of 2024 and 7075 aluminum alloys

NASA Technical Reports Server (NTRS)

Clauer, A. H.; Fairand, B. P.; Slater, J. E.

1977-01-01

The effect of laser generated stress waves on the microstructure, hardness, strength and stress corrosion resistance of 2024 and 7075 aluminum alloys was investigated. Pulsed CO2 and neodymium-glass lasers were used to determine the effect of wavelength and pulse duration on pressure generation and material property changes. No changes in material properties were observed with CO2 laser. The strength and hardness of 2024-T351 and the strength of 7075-T73 aluminum alloys were substantially improved by the stress wave environments generated with the neodymium-glass laser. The mechanical properties of 2024-T851 and 7075-T651 were unchanged by the laser treatment. The correlation of the laser shock data with published results of flyer plate experiments demonstrated that a threshold pressure needed to be exceeded before strengthening and hardening could occur. Peak pressures generated by the pulsed laser source were less than 7.0 GPa which was below the threshold pressure required to change the mechanical properties of 2024-T851 and 7075-T651. Corrosion studies indicated that laser shocking increased the resistance to local attack in 2024-T351 and 7075-T651.

High-power terahertz quantum cascade lasers with ∼0.23 W in continuous wave mode

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

Wang, Xuemin; Shen, Changle; Jiang, Tao

2016-07-15

Terahertz quantum cascade lasers with a record output power up to ∼0.23 W in continuous wave mode were obtained. We show that the optimal 2.9-mm-long device operating at 3.11 THz has a low threshold current density of 270 A/cm{sup 2} at ∼15 K. The maximum operating temperature arrived at ∼65 K in continuous wave mode and the internal quantum efficiencies decreased from 0.53 to 0.19 for the devices with different cavity lengths. By using one convex lens with the effective focal length of 13 mm, the beam profile was collimated to be a quasi Gaussian distribution.

Intra-puff CO and CO 2 measurements of cigarettes with iron oxide cigarette paper using quantum cascade laser spectroscopy

NASA Astrophysics Data System (ADS)

Crawford, Danielle R.; Parrish, Milton E.; Gee, Diane L.; Harward, Charles N.

2007-05-01

The objective of this research was to apply Fourier transform infrared spectroscopy (FTIR) and tunable infrared laser differential absorption spectroscopy (TILDAS) for measuring selected gaseous constituents in mainstream (MS) and sidestream (SS) smoke for experimental cigarettes designed to reduce MS CO using iron oxide cigarette papers. These two complimentary analytical techniques are well suited for providing per puff smoke deliveries and intra-puff evolution profiles in cigarette smoke respectively. The quad quantum cascade (QC) laser high resolution infrared spectroscopy system has the necessary temporal and spectral resolution and whole smoke analysis capabilities to provide detailed information for CO and CO 2 as they are being formed in both MS and SS smoke. The QC laser system has an optimal data rate of 20 Hz and a unique puffing system, with a square wave shaped puff, that allows whole smoke to enter an 18 m, 0.3 L multi-pass gas cell in real time (0.1 s cell response time) requiring no syringe or Cambridge filter pad. Another similar multi-pass gas cell with a 36 m pathlength simultaneously monitors the sidestream cigarette smoke. The smoke from experimental cigarettes manufactured with two types of iron oxide papers were compared to the smoke from cigarettes manufactured similarly without iron oxide in the paper using both instrument systems. The delivery per puff determined by the QC laser method agreed with FTIR results. MS CO intra-puff evolution profiles for iron oxide prototype cigarettes demonstrated CO reduction when compared to cigarettes without iron oxide paper. Additionally, both CO and CO 2 intra-puff evolution profiles of the cigarettes with iron oxide paper showed a significant reduction at the initial portion of the 2 s puff not observed in the non-iron oxide prototype cigarettes. This effect also was observed for ammonia and ethylene, suggesting that physical parameters such as paper porosity and burn rate are important. The SS CO and CO 2 deliveries for the experimental cigarettes evaluated remained unaffected. The iron oxide paper technology remains under development and continues to be evaluated.

Intra-puff CO and CO2 measurements of cigarettes with iron oxide cigarette paper using quantum cascade laser spectroscopy.

PubMed

Crawford, Danielle R; Parrish, Milton E; Gee, Diane L; Harward, Charles N

2007-05-01

The objective of this research was to apply Fourier transform infrared spectroscopy (FTIR) and tunable infrared laser differential absorption spectroscopy (TILDAS) for measuring selected gaseous constituents in mainstream (MS) and sidestream (SS) smoke for experimental cigarettes designed to reduce MS CO using iron oxide cigarette papers. These two complimentary analytical techniques are well suited for providing per puff smoke deliveries and intra-puff evolution profiles in cigarette smoke respectively. The quad quantum cascade (QC) laser high resolution infrared spectroscopy system has the necessary temporal and spectral resolution and whole smoke analysis capabilities to provide detailed information for CO and CO(2) as they are being formed in both MS and SS smoke. The QC laser system has an optimal data rate of 20 Hz and a unique puffing system, with a square wave shaped puff, that allows whole smoke to enter an 18 m, 0.3 L multi-pass gas cell in real time (0.1s cell response time) requiring no syringe or Cambridge filter pad. Another similar multi-pass gas cell with a 36 m pathlength simultaneously monitors the sidestream cigarette smoke. The smoke from experimental cigarettes manufactured with two types of iron oxide papers were compared to the smoke from cigarettes manufactured similarly without iron oxide in the paper using both instrument systems. The delivery per puff determined by the QC laser method agreed with FTIR results. MS CO intra-puff evolution profiles for iron oxide prototype cigarettes demonstrated CO reduction when compared to cigarettes without iron oxide paper. Additionally, both CO and CO(2) intra-puff evolution profiles of the cigarettes with iron oxide paper showed a significant reduction at the initial portion of the 2 s puff not observed in the non-iron oxide prototype cigarettes. This effect also was observed for ammonia and ethylene, suggesting that physical parameters such as paper porosity and burn rate are important. The SS CO and CO(2) deliveries for the experimental cigarettes evaluated remained unaffected. The iron oxide paper technology remains under development and continues to be evaluated.

Prevention of CO2 laser-induced endotracheal tube fires with the laser-guard protective coating.

PubMed

Sosis, M B; Dillon, F

1992-01-01

To determine how well Laser-Guard protects polyvinyl chloride (PVC) endotracheal tubes from the carbon dioxide (CO2) laser. Bare and Laser-Guard-protected PVC endotracheal tubes were tested with 5 L/min of oxygen (O2) passing through them. Research laboratory of a university-affiliated metropolitan medical center. After moistening the Laser-Guard-protected endotracheal tubes, we subjected the tubes to CO2 laser radiation at 10 and 70 watts until combustion occurred or 60 seconds had elapsed. The bare PVC tube ignited and a "blowtorch" fire occurred after 3 seconds of CO2 laser use at 70 watts. The moistened Laser-Guard-protected PVC endotracheal tubes were not significantly damaged by 1 minute of laser use at 70 watts. Laser-Guard protects the shafts of combustible PVC endotracheal tubes from direct, high-power, continuous CO2 laser radiation.

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

NASA Astrophysics Data System (ADS)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Continuous-wave and quasi-continuous wave thulium-doped all-fiber laser: implementation on kidney stone fragmentations.

PubMed

Pal, Debasis; Ghosh, Aditi; Sen, Ranjan; Pal, Atasi

2016-08-10

A continuous-wave (CW) as well as quasi-continuous wave (QCW) thulium-doped all-fiber laser at 1.94 μm has been designed for targeting applications in urology. The thulium-doped active fiber with an octagonal-shaped inner cladding is pumped at 793 nm to achieve stable CW laser power of 10 W with 32% lasing efficiency (against launched pump power). The linear variation of laser power with pump offers a scope of further power scaling. A QCW operation with variation of duty cycle from 0.5% to 90%, repetition rate from 0.1 Hz to 1 kHz, and pulse width from 40 μs to 2 s has been presented. Laser power of 9.5 W in CW mode of operation and average power of 5.2 W with energy range of 10.4-104 mJ in QCW mode of operation has been employed to fragment calcium oxalate monohydrate kidney stones (size of 1.5-4 cm) having different colors and composition. Dependence of ablation threshold, ablation rate, and average fragmented particle size on the average power and energy has been studied. One minute of laser exposure results in fragmentation of a stone surface with ablation rate of 8  mg/min having minimum particle size of 6.54 μm with an average size of 20-100 μm ensuring the natural removal of fragmented parts through the urethra.

Formation of surface nanolayers in chalcogenide crystals using coherent laser beams

NASA Astrophysics Data System (ADS)

Ozga, K.; Fedorchuk, A. O.; El-Naggar, A. M.; Albassam, A. A.; Kityk, V.

2018-03-01

We have shown a possibility to form laser modified surface nanolayers with thickness up to 60 nm in some ternary chalcogenide crystals (Ag3AsS3, Ag3SbS3, Tl3SbS3) The laser treatment was performed by two coherent laser beams split in a space. As the inducing lasers we have applied continuous wave (cw) Hesbnd Cd laser at wavelength 441 nm and doubled frequency cw Nd: YAG laser at 532 nm. The spectral energies of these lasers were higher with respect to the energy gaps of the studied crystals. The optical anisotropy was appeared and defected by monitoring of birefringence at probing wavelength of cw Hesbnd Ne laser at λ = 3390 nm. The changes of the laser stimulated near the surface layer morphology was monitored by TEM and AFM methods as well as by the reflected optical second harmonic generation at fundamental wavelength of microsecond CO2 laser generating at wavelength 10600 nm. This technique may open a new approach for the formation of the near the surface nanolayers in chalcogenides using external cw laser illumination.

Power- or frequency-driven hysteresis for continuous-wave optically injected distributed-feedback semiconductor lasers.

PubMed

Blin, Stéphane; Vaudel, Olivier; Besnard, Pascal; Gabet, Renaud

2009-05-25

Bistabilities between a steady (or pulsating, chaotic) and different pulsating regimes are investigated for an optically injected semi-conductor laser. Both numerical and experimental studies are reported for continuous-wave single-mode semiconductor distributed-feedback lasers emitting at 1.55 microm. Hysteresis are driven by either changing the optically injected power or the frequency difference between both lasers. The effect of the injected laser pumping rate is also examined. Systematic mappings of the possible laser outputs (injection locking, bimodal, wave mixing, chaos or relaxation oscillations) are carried out. At small pumping rates (1.2 times threshold), only locking and bimodal regimes are observed. The extent of the bistable area is either 11 dB or 35 GHz, depending on the varying parameters. At high pumping rates (4 times threshold), numerous injection regimes are observed. Injection locking and its bistabilities are also reported for secondary longitudinal modes.

The spectrum of laser skin resurfacing: nonablative, fractional, and ablative laser resurfacing.

PubMed

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2008-05-01

The drive to attain cosmetic facial enhancement with minimal risk and rapid recovery has inspired the field of nonsurgical skin rejuvenation. Laser resurfacing was introduced in the 1980s with continuous wave carbon dioxide (CO(2)) lasers; however, because of a high rate of side effects, including scarring, short-pulse, high-peak power, and rapidly scanned, focused-beam CO(2) lasers and normal-mode erbium-doped yttrium aluminium garnet lasers were developed, which remove skin in a precisely controlled manner. The prolonged 2-week recovery time and small but significant complication risk prompted the development of non-ablative and, more recently, fractional resurfacing in order to minimize risk and shorten recovery times. Nonablative resurfacing produces dermal thermal injury to improve rhytides and photodamage while preserving the epidermis. Fractional resurfacing thermally ablates microscopic columns of epidermal and dermal tissue in regularly spaced arrays over a fraction of the skin surface. This intermediate approach increases efficacy as compared to nonablative resurfacing, but with faster recovery as compared to ablative resurfacing. Neither nonablative nor fractional resurfacing produces results comparable to ablative laser skin resurfacing, but both have become much more popular than the latter because the risks of treatment are limited in the face of acceptable improvement. At the completion of this learning activity, participants should be familiar with the spectrum of lasers and light technologies available for skin resurfacing, published studies of safety and efficacy, indications, methodologies, side effects, complications, and management.

A CO trace gas detection system based on continuous wave DFB-QCL

NASA Astrophysics Data System (ADS)

Dang, Jingmin; Yu, Haiye; Sun, Yujing; Wang, Yiding

2017-05-01

A compact and mobile system was demonstrated for the detection of carbon monoxide (CO) at trace level. This system adopted a high-power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at ∼22 °C as excitation source. Wavelength modulation spectroscopy (WMS) as well as second harmonic detection was used to isolate complex, overlapping spectral absorption features typical of ambient pressures and to achieve excellent specificity and high detection sensitivity. For the selected P(11) absorption line of CO molecule, located at 2099.083 cm-1, a limit of detection (LoD) of 26 ppb by volume (ppbv) at atmospheric pressure was achieved with a 1 s acquisition time. Allan deviation analysis was performed to investigate the long term performance of the CO detection system, and a measurement precision of 3.4 ppbv was observed with an optimal integration time of approximate 114 s, which verified the reliable and robust operation of the developed system.

A computational study of laser-supported detonation waves propagating up an oblique incident beam

NASA Astrophysics Data System (ADS)

Bohn, C. L.; Crawford, M. L.

1987-01-01

A series of numerical experiments was conducted to study the propagation of laser-supported detonation waves (LSDWs) in the case that a CO2 laser beam strikes an aluminum surface obliquely in air. A reflected shock formed at the aluminum surface was more prominent at higher angles of incidence theta of the beam, but otherwise the hydrodynamics of the plasma and the LSDW were insensitive to theta. Furthermore, the total impulse delivered to the aluminum varied approximately as 1/cos theta, a result that can be modeled with elementary blast-wave theory.

Continuous-wave Nd:YVO4/KTiOPO4 green laser at 542 nm under diode pumping into the emitting level

NASA Astrophysics Data System (ADS)

Liu, J. H.

2012-10-01

We report a green laser at 542 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1086 nm Nd:YVO4 laser under 880 nm diode pumping into the emitting level 4 F 3/2. A KTiOPO4 (KTP) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 14.5 W, as high as 1.33 W of CW output power at 542 nm is achieved. The optical-to-optical conversion efficiency is up to 9.2%, and the fluctuation of the green output power was better than 3.8% in the given 30 min.

Single-crystal Brillouin spectroscopy with CO{sub 2} laser heating and variable q

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

Zhang, Jin S.; Bass, Jay D.; Zhu, Gaohua

2015-06-15

We describe a Brillouin spectroscopy system integrated with CO{sub 2} laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ∼13 GPa, 1300 ± 200 K. The pressure as measured by rubymore » fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (∼141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm)« less

Estimates of Rayleigh-to-Love wave ratio in microseisms by co-located Ring Laser and STS-2

NASA Astrophysics Data System (ADS)

Tanimoto, Toshiro; Hadziioannou, Céline; Igel, Heiner; Wassermann, Joachim; Schreiber, Ulrich; Gebauer, André

2015-04-01

In older studies of microseisms (seismic noise), it was often assumed that microseisms, especially the secondary microseisms (0.1-0.3 Hz), mainly consist of Rayleigh waves. However, it has become clear that there exists a large amount of Love-wave energy mixed in it (e.g., Nishida et al., 2008). However, its confirmation is not necessarily straightforward and often required an array of seismographs. In this study, we take advantage of two co-located instruments, a Ring Laser and an STS-2 type seismograph, at Wettzell (WET), Germany (Schreiber et al., 2009). The Ring Laser records rotation (its vertical component) and is thus only sensitive to Love waves. The vertical component of STS-2 seismograph is only sensitive to Rayleigh waves. Therefore, a combination of the two instruments provides a unique opportunity to separate Rayleigh waves and Love waves in microseisms. The question we address in this paper is the ratio of Rayleigh waves to Love waves in microseisms. For both instruments, we analyze data from 2009 to 2014. Our basic approach is to create stacked vertical acceleration spectra for Rayleigh waves from STS-2 and stacked transverse acceleration spectra for Love waves from Ring Laser. The two spectra at Earth's surface can then be compared directly by their amplitudes. The first step in our analysis is a selection of time portions (each six-hour long) that are least affected by earthquakes. We do this by examining the GCMT (Global Centroid Moment Tensor) catalogue and also checking the PSDs for various frequency ranges. The second step is to create stacked (averaged) Fourier spectra from those selected time portions. The key is to use the same time portions for the STS-2 and the Ring Laser data so that the two can be directly compared. The vertical spectra from STS-2 are converted to acceleration spectra. The Ring Laser rotation spectra are first obtained in the unit of radians/sec (rotation rate). But as the Ring Laser spectra are dominated by fundamental-mode Love waves, the rotation spectra can be converted to transverse (SH) acceleration by multiplying them by the factor 2xCp where Cp is the Love-wave phase velocity. We used a seismic model by Fichtner et al. (2013) at WET to estimate Love-wave phase velocity. This conversion from rotation to transverse acceleration was first extensively used by Igel et al. (2005) for the analysis of lower frequency Love waves and the same relation holds for our spectral data. The two spectra provide the ratio of surface amplitudes. In the frequency range of secondary microseisms (0.10-0.35 Hz), they are comparable; near the spectral peak (~0.20 Hz), Rayleigh waves are about 20 percent larger in amplitudes but outside this peak region, Love waves have comparable or slightly larger amplitudes than Rayleigh waves. Therefore, the secondary microseisms at WET consist of similar contributions from Rayleigh waves and Love waves.

Activities report in quantum optics

NASA Astrophysics Data System (ADS)

1985-03-01

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

Distributed feedback laser diode integrated with distributed Bragg reflector for continuous-wave terahertz generation.

PubMed

Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Ko, Hyunsung; Park, Jeong-Woo; Lee, Donghun; Jeon, Min Yong; Park, Kyung Hyun

2012-07-30

A widely tunable dual mode laser diode with a single cavity structure is demonstrated. This novel device consists of a distributed feedback (DFB) laser diode and distributed Bragg reflector (DBR). Micro-heaters are integrated on the top of each section for continuous and independent wavelength tuning of each mode. By using a single gain medium in the DFB section, an effective common optical cavity and common modes are realized. The laser diode shows a wide tunability of the optical beat frequency, from 0.48 THz to over 2.36 THz. Continuous wave THz radiation is also successfully generated with low-temperature grown InGaAs photomixers from 0.48 GHz to 1.5 THz.

Numerical Analysis on Thermal Non-Equilibrium Process of Laser-Supported Detonation Wave in Axisymmetric Nozzle

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

Shiraishi, Hiroyuki

Numerical Analyses on Laser-Supported Plasma (LSP) have been performed for researching the mechanism of laser absorption occurring in the laser propulsion system. Above all, Laser-Supported Detonation (LSD), categorized as one type of LSP, is considered as one of the most important phenomena because it can generate high pressure and high temperature for performing highly effective propulsion. For simulating generation and propagation of LSD wave, I have performed thermal non-equilibrium analyses by Navier-stokes equations, using a CO{sub 2} gasdynamic laser into an inert gas, where the most important laser absorption mechanism for LSD propagation is Inverse Bremsstrahlung. As a numerical method,more » TVD scheme taken into account of real gas effects and thermal non-equilibrium effects by using a 2-temperature model, is applied. In this study, I analyze a LSD wave propagating through a conical nozzle, where an inner space of an actual laser propulsion system is simplified.« less

Long range coherence in free electron lasers

NASA Technical Reports Server (NTRS)

Colson, W. B.

1984-01-01

The simple free electron laser (FEL) design uses a static, periodic, transverse magnetic field to undulate relativistic electrons traveling along its axis. This allows coupling to a co-propagating optical wave and results in bunching to produce coherent radiation. The advantages of the FEL are continuous tunability, operation at wavelengths ranging from centimeters to angstroms, and high efficiency resulting from the fact that the interaction region only contains light, relativistic electrons, and a magnetic field. Theoretical concepts and operational principles are discussed.

Subsurface plasma in beam of continuous CO2-laser

NASA Astrophysics Data System (ADS)

Danytsikov, Y. V.; Dymshakov, V. A.; Lebedev, F. V.; Pismennyy, V. D.; Ryazanov, A. V.

1986-03-01

Experiments performed at the Institute of Atomic Energy established the conditions for formation of subsurface plasma in substances by laser radiation and its characteristics. A quasi-continuous CO2 laser emitting square pulses of 0.1 to 1.0 ms duration and 1 to 10 kW power as well as a continuous CO2 laser served as radiation sources. Radiation was focused on spots 0.1 to 0.5 mm in diameter and maintained at levels ensuring constant power density during the interaction time, while the temperature of the target surface was measured continuously. Metals, graphite and dielectric materials were tested with laser action taking place in air N2 + O2 mixtures, Ar or He atmosphere under pressures of 0.01 to 1.0 atm. Data on radiation intensity thresholds for evaporation and plasma formation were obtained. On the basis of these thresholds, combined with data on energy balance and the temperature profile in plasma layers, a universal state diagram was constructed for subsurface plasma with nonquantified surface temperature and radiation intensity coordinates.

Pulsed-laser excitation of acoustic modes in open high-Q photoacoustic resonators for trace gas monitoring: results for C2H4

NASA Astrophysics Data System (ADS)

Brand, Christian; Winkler, Andreas; Hess, Peter; Miklós, András; Bozóki, Zoltán; Sneider, János

1995-06-01

The pulsed excitation of acoustic resonances was studied with a continuously monitoring photoacoustic detector system. Acoustic waves were generated in C2H4/N 2 gas mixtures by light absorption of the pulses from a transversely excited atmospheric CO2 laser. The photoacoustic part consisted of high-Q cylindrical resonators (Q factor 820 for the first radial mode in N2) and two adjoining variable acoustic filter systems. The time-resolved signal was Fourier transformed to a frequency spectrum of high resolution. For the first radial mode a Lorentzian profile was fitted to the measured data. The outside noise suppression and the signal-to-noise ratio were investigated in a normal laboratory environment in the flow-through mode. The acoustic and electric filter system combined with the

Stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor

NASA Astrophysics Data System (ADS)

Ferdous, T.; Salahuddin, M.; Amin, M. R.; Salimullah, M.

1995-09-01

In the present paper we have studied the stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor. The nonlinearity in the low-frequency ion-acoustic wave arises through the ponderomotive force on both electrons and holes. The high-frequency nonlinearity arises through the nonlinear current density. For typical plasma parameters in compensated Ge, ɛL=16, T0=77 K, n00=1017 cm-3, Bs=60 kG, θ=30°, laser power density corresponding to a CO2 laser ~=0.1 MW cm-2, the growth rate of the low-frequency ion-acoustic wave turns out to be ~=107 rad sec-1.

Continuous-wave Nd:GYSGG laser at 1.1 μm

NASA Astrophysics Data System (ADS)

Lin, Hongyi; Liu, Hong; Huang, Xiaohua; Copner, Nigel; Sun, Dong

2018-02-01

We demonstrated a compact and simple continuous-wave (CW) Nd:GYSGG laser with triple-wavelength lines at 1105, 1107 and 1110 nm based on R2 → Y6, R1 → Y5 and R1 → Y6 of the 4F3/2 → 4I11/2 transition. The total output power of the triple-wavelength lines was 480 mW. Moreover, we obtained an efficient CW Nd:GYSGG laser at 1110 nm with the output power of 1560 mW at the pump power of 11.05 W. Those lines at 1058 and 1062 nm were suppressed completely by the simple output mirror of high transmission at 1.06 μm.

Efficient Q-switched Tm:YAG ceramic slab laser.

PubMed

Zhang, Shuaiyi; Wang, Mingjian; Xu, Lin; Wang, Yan; Tang, Yulong; Cheng, Xiaojin; Chen, Weibiao; Xu, Jianqiu; Jiang, Benxue; Pan, Yubai

2011-01-17

Characteristics of Tm:YAG ceramic for high efficient 2-μm lasers are analyzed. Efficient diode end-pumped continuous-wave and Q-switched Tm:YAG ceramic lasers are demonstrated. At the absorbed pump power of 53.2W, the maximum continuous wave (cw) output power of 17.2 W around 2016 nm was obtained with the output transmission of 5%. The optical conversion efficiency is 32.3%, corresponding to a slope efficiency of 36.5%. For Q-switched operation, the shortest width of 69 ns was achieved with the pulse repetition frequency of 500 Hz and single pulse energy of 20.4 mJ, which indicates excellent energy storage capability of the Tm:YAG ceramic.

Calibration of phase contrast imaging on HL-2A Tokamak

NASA Astrophysics Data System (ADS)

Yu, Y.; Gong, S. B.; Xu, M.; Xiao, C. J.; Jiang, W.; Zhong, W. L.; Shi, Z. B.; Wang, H. J.; Wu, Y. F.; Yuan, B. D.; Lan, T.; Ye, M. Y.; Duan, X. R.; HL-2A Team

2017-10-01

Phase contrast imaging (PCI) has recently been developed on HL-2A tokamak. In this article we present the calibration of this diagnostic. This system is to diagnose chord integral density fluctuations by measuring the phase shift of a CO2 laser beam with a wavelength of 10.6 μm when the laser beam passes through plasma. Sound waves are used to calibrate PCI diagnostic. The signal series in different PCI channels show a pronounced modulation of incident laser beam by the sound wave. Frequency-wavenumber spectrum is achieved. Calibrations by sound waves with different frequencies exhibit a maximal wavenumber response of 12 cm-1. The conversion relationship between the chord integral plasma density fluctuation and the signal intensity is 2.3 × 1013 m-2/mV, indicating a high sensitivity.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

NASA Astrophysics Data System (ADS)

Richter, A.; Pavel, N.; Heumann, E.; Huber, G.; Parisi, D.; Toncelli, A.; Tonelli, M.; Diening, A.; Seelert, W.

2006-04-01

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF4 and Pr:BaY2F8 was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB3O5 as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF4 and Pr:BaY2F8, respectively.

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)

Comparing mechanical effects and sound production of KTP, thulium, and CO2 laser in stapedotomy.

PubMed

Kamalski, Digna M A; Verdaasdonk, Rudolf M; de Boorder, Tjeerd; Vincent, Robert; Versnel, Huib; Grolman, Wilko

2014-08-01

The mechanical and acoustic effects that occur during laser-assisted stapedotomy differ among KTP, CO2, and thulium lasers. Making a fenestration in stapedotomy with a laser minimizes the risk of a floating footplate caused by mechanical forces. Theoretically, the lasers used in stapedotomy could inflict mechanical trauma because of absorption in the perilymph, causing vaporization bubbles. These bubbles can generate a shock wave, when imploding. In an inner ear model, we made a fenestration in a fresh human stapes with KTP, CO2, and thulium laser. During the fenestration, we performed high-speed imaging from different angles to capture mechanical effects. The sounds produced by the fenestration were recorded simultaneously with a hydrophone; these recordings were compared with acoustics produced by a conventional microburr fenestration. KTP laser fenestration showed little mechanical effects, with minimal sound production. With CO2 laser, miniscule bubbles arose in the vestibule; imploding of these bubbles corresponded to the acoustics. Thulium laser fenestration showed large bubbles in the vestibule, with a larger sound production than the other two lasers. Each type of laser generated significantly less noise than the microburr. The microburr maximally reached 95 ± 7 dB(A), compared with 49 ± 8 dB(A) for KTP, 68 ± 4 dB(A) for CO2, and 83 ± 6 dB(A) for thulium. Mechanical and acoustic effects differ among lasers used for stapedotomy. Based on their relatively small effects, KTP and CO2 lasers are preferable to thulium laser.

Feasibility of a Novel Optoacoustic Device to Precisely Localize Endotracheal Tube Positioning in a Cadaver Model

DTIC Science & Technology

2016-11-02

million per year to U.S. hospitals [1,2]. Current methods of assessing ETT position include chest radiography, end- tidal carbon dioxide (EtCO2...lasers to generate sound waves to determine the position of “labeled” ETTs within millimeters of accuracy. Laser optoacoustic imaging combines the merits...of optical tomography (high optical contrast) and ultrasound imaging (minimal scattering of acoustic waves ) to yield high contrast, sensitivity, and

The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology

PubMed Central

Omi, Tokuya; Numano, Kayoko

2014-01-01

Background: Tremendous advances have been made in the medical application of the laser in the past few decades. Many diseases in the dermatological field are now indications for laser treatment that qualify for reimbursement by many national health insurance systems. Among laser types, the carbon dioxide (CO2) laser remains an important system for the dermatologist. Rationale: The lasers used in photosurgery have wavelengths that differ according to their intended use and are of various types, but the CO2 laser is one of the most widely used lasers in the dermatology field. With its wavelength in the mid-infrared at 10,600 nm, CO2 laser energy is wellabsorbed in water. As skin contains a very high water percentage, this makes the CO2 laser ideal for precise, safe ablation with good hemostasis. In addition to its efficacy in ablating benign raised lesions, the CO2 laser has been reported to be effective in the field of esthetic dermatology in the revision of acne scars as well as in photorejuvenation. With the addition of fractionation of the beam of energy into myriad microbeams, the fractional CO2 laser has offered a bridge between the frankly full ablative indications and the nonablative skin rejuvenation systems of the 2000s in the rejuvenation of photoaged skin on and off the face. Conclusions: The CO2 laser remains an efficient, precise and safe system for the dermatologist. Technological advances in CO2 laser construction have meant smaller spot sizes and greater precision for laser surgery, and more flexibility in tip sizes and protocols for fractional CO2 laser treatment. The range of dermatological applications of the CO2 laser is expected to continue to increase in the future. PMID:24771971

The Role of the CO2 Laser and Fractional CO2 Laser in Dermatology.

PubMed

Omi, Tokuya; Numano, Kayoko

2014-03-27

Tremendous advances have been made in the medical application of the laser in the past few decades. Many diseases in the dermatological field are now indications for laser treatment that qualify for reimbursement by many national health insurance systems. Among laser types, the carbon dioxide (CO2) laser remains an important system for the dermatologist. The lasers used in photosurgery have wavelengths that differ according to their intended use and are of various types, but the CO2 laser is one of the most widely used lasers in the dermatology field. With its wavelength in the mid-infrared at 10,600 nm, CO2 laser energy is wellabsorbed in water. As skin contains a very high water percentage, this makes the CO2 laser ideal for precise, safe ablation with good hemostasis. In addition to its efficacy in ablating benign raised lesions, the CO2 laser has been reported to be effective in the field of esthetic dermatology in the revision of acne scars as well as in photorejuvenation. With the addition of fractionation of the beam of energy into myriad microbeams, the fractional CO2 laser has offered a bridge between the frankly full ablative indications and the nonablative skin rejuvenation systems of the 2000s in the rejuvenation of photoaged skin on and off the face. The CO2 laser remains an efficient, precise and safe system for the dermatologist. Technological advances in CO2 laser construction have meant smaller spot sizes and greater precision for laser surgery, and more flexibility in tip sizes and protocols for fractional CO2 laser treatment. The range of dermatological applications of the CO2 laser is expected to continue to increase in the future.

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.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Experimental study of CO/sub 2/-laser-induced histological effects on human fallopian tube: determination of CO/sub 2/ laser parameters to be used in microsurgery

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

Foulot, H.; Lefebvre, G.; Jagueux, M.

This experiment investigates CO/sub 2/-laser-induced histological effects on fallopian tubes obtained during hysterectomies in women. Tubal transversal sections were performed at isthmic and ampullar sites. Forty strips were available for histological study of the cut section area. The role of different parameters such as radiation power and beam fractionation (continuous versus pulsed) on tissue lesions was assessed. In tubal microsurgery, the CO/sub 2/ laser can be used as a scalpel with the predominant advantage of minimal tissular alterations. As a result of this study, our recommended parameters are the following: radiation power, 7-10 W; beam focalization zone, 0.2 mm; energymore » density, 20,000-35,000 W/cm2; continuous operation; moving speed, 1 cm/s.« less

Studies on third-order optical nonlinearity and power limiting of conducting polymers using the z-scan technique for nonlinear optical applications

NASA Astrophysics Data System (ADS)

Pramodini, S.; Sudhakar, Y. N.; SelvaKumar, M.; Poornesh, P.

2014-04-01

We present the synthesis and characterization of third-order optical nonlinearity and optical limiting of the conducting polymers poly (aniline-co-o-anisidine) and poly (aniline-co-pyrrole). Nonlinear optical studies were carried out by employing the z-scan technique using a He-Ne laser operating in continuous wave mode at 633 nm. The copolymers exhibited a reverse saturable absorption process and self-defocusing properties under the experimental conditions. The estimated values of βeff, n2 and χ(3) were found to be of the order of 10-2 cm W-1, 10-5 esu and 10-7 esu respectively. Self-diffraction rings were observed due to refractive index change when exposed to the laser beam. The copolymers possess a lower limiting threshold and clamping level, which is essential to a great extent for power limiting devices. Therefore, copolymers of aniline emerge as a potential candidate for nonlinear optical device applications.

Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell

DOE PAGES

Dong, Lei; Yu, Yajun; Li, Chunguang; ...

2015-07-27

A ppb-level formaldehyde (H 2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H 2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variancemore » analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. Finally, a side-by-side comparison between two measurement schemes is also discussed in detail.« less

Laser excitation dynamics of argon metastables generated in atmospheric pressure flows by microwave frequency microplasma arrays

NASA Astrophysics Data System (ADS)

Rawlins, W. T.; Galbally-Kinney, K. L.; Davis, S. J.; Hoskinson, A. R.; Hopwood, J. A.

2014-03-01

The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkali-exciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at atmospheric pressure. This paper describes initial investigations of the use of linear microwave micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure in optical pump-and-probe experiments for laser development. Power requirements to ignite and sustain the plasma at 1 atm are low, <30 W. We report on the laser excitation dynamics of argon metastables, Ar (4s, 1s5) (Paschen notation), generated in flowing mixtures of Ar and He at 1 atm. Tunable diode laser absorption measurements indicate Ar(1s5) concentrations near 3 × 1012 cm-3 at 1 atm. The metastables are optically pumped by absorption of a focused beam from a continuous-wave Ti:S laser, and spectrally selected fluorescence is observed with an InGaAs camera and an InGaAs array spectrometer. We observe the optical excitation of the 1s5-->2p9 transition at 811.5 nm and the corresponding laser-induced fluorescence on the 2p10-->1s5 transition at 912.3 nm; the 2p10 state is efficiently populated by collisional energy transfer from 2p9. Using tunable diode laser absorption/gain spectroscopy, we observe small-signal gains of ~1 cm-1 over a 1.9 cm path. We also observe stable, continuous-wave laser oscillation at 912.3 nm, with preliminary optical efficiency ~55%. These results are consistent with efficient collisional coupling within the Ar(4s) manifold.

The generation of a continuous-wave Nd:YVO4/LBO laser at 543 nm by direct in-band diode pumping at 888 nm

NASA Astrophysics Data System (ADS)

Fu, S. C.; Wang, X.; Chu, H.

2013-02-01

We report the generation of a green laser at 543 nm by intracavity frequency doubling of the continuous-wave (cw) laser operation of a 1086 nm Nd:YVO4 laser under 888 nm diode pumping into the emitting level 4F3/2. An LiB3O5 (LBO) crystal, cut for critical type I phase matching at room temperature, is used for the laser second-harmonic generation. At an incident pump power of 17.8 W, as high as 4.53 W cw output power at 543 nm is achieved. The optical-to-optical conversion efficiency is up to 25.4%, and the fluctuation of the green output power is better than 2.3% in a 30 min period.

Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

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

Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measuredmore » properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.« less

Electron Beam Transport in Advanced Plasma Wave Accelerators

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

Williams, Ronald L

2013-01-31

The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams weremore » generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.« less

Spin wave propagation detected over 100 μm in half-metallic Heusler alloy Co2MnSi

NASA Astrophysics Data System (ADS)

Stückler, Tobias; Liu, Chuanpu; Yu, Haiming; Heimbach, Florian; Chen, Jilei; Hu, Junfeng; Tu, Sa; Alam, Md. Shah; Zhang, Jianyu; Zhang, Youguang; Farrell, Ian L.; Emeny, Chrissy; Granville, Simon; Liao, Zhi-Min; Yu, Dapeng; Zhao, Weisheng

2018-03-01

The field of magnon spintronics offers a charge current free way of information transportation by using spin waves (SWs). Compared to forward volume spin waves for example, Damon-Eshbach (DE) SWs need a relatively weak external magnetic field which is suitable for small spintronic devices. In this work we study DE SWs in Co2MnSi, a half-metallic Heusler alloy with significant potential for magnonics. Thin films have been produced by pulsed laser deposition. Integrated coplanar waveguide (CPW) antennas with different distances between emitter and detection antenna have been prepared on a Co2MnSi film. We used a vector network analyzer to measure spin wave reflection and transmission. We observe spin wave propagation up to 100 μm, a new record for half-metallic Heusler thin films.

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.

Continuous wave room temperature external ring cavity quantum cascade laser

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

Revin, D. G., E-mail: d.revin@sheffield.ac.uk; Hemingway, M.; Vaitiekus, D.

2015-06-29

An external ring cavity quantum cascade laser operating at ∼5.2 μm wavelength in a continuous-wave regime at the temperature of 15 °C is demonstrated. Out-coupled continuous-wave optical powers of up to 23 mW are observed for light of one propagation direction with an estimated total intra-cavity optical power flux in excess of 340 mW. The uni-directional regime characterized by the intensity ratio of more than 60 for the light propagating in the opposite directions was achieved. A single emission peak wavelength tuning range of 90 cm{sup −1} is realized by the incorporation of a diffraction grating into the cavity.

Time-synchronized continuous wave laser-induced fluorescence on an oscillatory xenon discharge.

PubMed

MacDonald, N A; Cappelli, M A; Hargus, W A

2012-11-01

A novel approach to time-synchronizing laser-induced fluorescence measurements to an oscillating current in a 60 Hz xenon discharge lamp using a continuous wave laser is presented. A sample-hold circuit is implemented to separate out signals at different phases along a current cycle, and is followed by a lock-in amplifier to pull out the resulting time-synchronized fluorescence trace from the large background signal. The time evolution of lower state population is derived from the changes in intensity of the fluorescence excitation line shape resulting from laser-induced fluorescence measurements of the 6s(')[1/2](1)(0)-6p(')[3/2](2) xenon atomic transition at λ = 834.68 nm. Results show that the lower state population oscillates at twice the frequency of the discharge current, 120 Hz.

Advancements for Active Remote Sensing of Carbon Dioxide from Space using the ASCENDS CarbonHawk Experiment Simulator: First Results

NASA Astrophysics Data System (ADS)

Obland, M. D.; Nehrir, A. R.; Lin, B.; Harrison, F. W.; Kooi, S. A.; Choi, Y.; Plant, J.; Yang, M. M.; Antill, C.; Campbell, J. F.; Ismail, S.; Browell, E. V.; Meadows, B.; Dobler, J. T.; Zaccheo, T. S.; Moore, B., III; Crowell, S.

2014-12-01

The ASCENDS CarbonHawk Experiment Simulator (ACES) is an Intensity-Modulated Continuous-Wave lidar system recently developed at NASA Langley Research Center that seeks to advance technologies and techniques critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. These advancements include: (1) increasing the power-aperture product to approach ASCENDS mission requirements by implementing multi-aperture telescopes and multiple co-aligned laser transmitters; (2) incorporating high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) developing and incorporating a high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration operation on Global Hawk aircraft, and (4) advancing algorithms for cloud and aerosol discrimination. The ACES instrument architecture is being developed for operation on high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. ACES simultaneously transmits five laser beams: three from commercial EDFAs operating near 1571 nm, and two from the Exelis oxygen (O2) Raman fiber laser amplifier system operating near 1260 nm. The Integrated-Path Differential Absorption (IPDA) lidar approach is used at both wavelengths to independently measure the CO2 and O2 column number densities and retrieve the average column CO2 mixing ratio. The outgoing laser beams are aligned to the field of view of ACES' three fiber-coupled 17.8-cm diameter athermal telescopes. The backscattered light collected by the three telescopes is sent to the detector/TIA subsystem, which has a bandwidth of 4.7 MHz and operates service-free using a tactical dewar and cryocooler. Two key laser modulation approaches are being tested to significantly mitigate the effects of thin clouds on the retrieved CO2 column amounts. Full instrument development concluded in the spring of 2014. After ground range tests of the instrument, ACES successfully completed six test flights on the Langley Hu-25 aircraft in July, 2014, and recorded data at multiple altitudes over land and ocean surfaces with and without intervening clouds. Preliminary results from these flights will be presented in this paper.

Toward continuous-wave operation of organic semiconductor lasers

PubMed Central

Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-01-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

Toward continuous-wave operation of organic semiconductor lasers.

PubMed

Sandanayaka, Atula S D; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-04-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.

Continuous Wave Potassium Titanyl Phosphate Laser Treatment is Safe and Effective for Xanthelasma Palpebrarum.

PubMed

Greijmans, Ellen; Luiting-Welkenhuyzen, Hedwig; Luijks, Harriet; Bovenschen, H Jorn

2016-07-01

Although not an accepted standard treatment, the 532-nm continuous wave potassium titanyl phosphate (CW-KTP) laser might be a powerful device to treat xanthelasma palpebrarum (XP). To determine the safety and efficacy of CW-KTP laser treatment for XP. Between January 2013 and January 2015, 30 consecutive patients with XP were treated with a 532-nm CW-KTP laser (spot size: 0.9 mm, power: 5.0 W, fluence: 36-38 J/cm, pulse width: 46 milliseconds, frequency: 2.0 Hz, passes per session: 3). In a retrospective study design, safety and efficacy data were collected and analyzed. Overall, 29/30 (97%) of patients had an excellent cosmetical result. Downtime was 1 week with crusted lesions. Although slight hypopigmentation was common, only 1/30 (3%) patients had hypopigmentation that was more than expected. Recurrences (13/30; 43%) were frequent, so that yearly maintenance therapy was warranted. No major side effects were noticed. Continuous wave KTP laser therapy is safe and highly effective for XP, although regular follow-up treatments are often necessary to maintain the achieved cosmetic results.

End-pumped continuous-wave intracavity yellow Raman laser at 590 nm with SrWO4 Raman crystal

NASA Astrophysics Data System (ADS)

Yang, F. G.; You, Z. Y.; Zhu, Z. J.; Wang, Y.; Li, J. F.; Tu, C. Y.

2010-01-01

We present an end-pumped continuous-wave intra-cavity yellow Raman laser at 590 nm with a 60 mm long pure crystal SrWO4 and an intra-cavity LiB3O5 frequency doubling crystal. The highest output power of yellow laser at 590 nm was 230 mW and the output power and threshold were found to be correlative with the polarized directions of pure single crystal SrWO4 deeply. Along different directions, the minimum and maximum thresholds of yellow Raman laser at 590 nm were measured to be 2.8 W and 14.3 W with respect to 808 nm LD pump power, respectively.

1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

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

Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.

2014-10-13

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{supmore » −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.« less

Resonantly cladding-pumped Yb-free Er-doped LMA fiber laser with record high power and efficiency.

PubMed

Zhang, Jun; Fromzel, Viktor; Dubinskii, Mark

2011-03-14

We report the results of our power scaling experiments with resonantly cladding-pumped Er-doped eye-safe large mode area (LMA) fiber laser. While using commercial off-the-shelf LMA fiber we achieved over 88 W of continuous-wave (CW) single transverse mode power at ~1590 nm while pumping at 1532.5 nm. Maximum observed optical-to-optical efficiency was 69%. This result presents, to the best of our knowledge, the highest power reported from resonantly-pumped Yb-free Er-doped LMA fiber laser, as well as the highest efficiency ever reported for any cladding-pumped Er-doped laser, either Yb-co-doped or Yb-free.

Characterization of the surfaces of platinum/tin oxide based catalysts by Fourier transform spectroscopy (FTIR)

NASA Technical Reports Server (NTRS)

Keiser, Joseph T.

1989-01-01

The Laser Atmospheric Wind Sounder (LAWS) Program has as one of its goals the development of a satellite based carbon dioxide laser for making wind velocity measurements. The specifications for this laser include the requirement that the laser operate at a repetition rate of 10 Hertz continuously for three years. Earth-based carbon dioxide lasers can operate for only a short time on a single charge of gas because the lasing action causes the CO2 to break down into CO and O2. Therefore, earth-based CO2 lasers are generally operated in a flow through mode in which the spent gas is continually exhausted and fresh gas is continually added. For a satellite based system, however, a recirculation system is desired because it is not practical to send up extra tanks of CO2. A catalyst which could enable a recirculating CO2 laser to function continuously for three years needs to be developed. In the development of a catalyst system there are many variables. Obviously, not all possible formulations can be tested for three years, therefore, an accurate model which is based on the reaction mechanism is needed. The construction of a multistep reaction mechanism is similar to the construction of a jigsaw puzzle. Different techniques each supply a piece of the puzzle and the researcher must put the pieces together. Transmission infrared spectroscopy was shown to be very useful in supplying some of the information needed to elucidate reaction mechanisms. The purpose was to see what kind of information might be obtained about the NASA catalyst using infrared absorption spectroscopy. Approximately 200 infrared spectra of the prototype Pt/tin oxide catalyst and its precursor components are observed under a variety of different conditions. The most significant observations are summarized.

An investigation of laser cutting quality of 22MnB5 ultra high strength steel using response surface methodology

NASA Astrophysics Data System (ADS)

Tahir, Abdul Fattah Mohd; Aqida, Syarifah Nur

2017-07-01

In hot press forming, changes of mechanical properties in boron steel blanks have been a setback in trimming the final shape components. This paper presents investigation of kerf width and heat affected zone (HAZ) of ultra high strength 22MnB5 steel cutting. Sample cutting was conducted using a 4 kW Carbon Dioxide (CO2) laser machine with 10.6 μm wavelength with the laser spot size of 0.2 mm. A response surface methodology (RSM) using three level Box-Behnken design of experiment was developed with three factors of peak power, cutting speed and duty cycle. The parameters were optimised for minimum kerf width and HAZ formation. Optical evaluation using MITUTOYO TM 505 were conducted to measure the kerf width and HAZ region. From the findings, laser duty cycle was crucial to determine cutting quality of ultra-high strength steel; followed by cutting speed and laser power. Meanwhile, low power intensity with continuous wave contributes the narrowest kerf width formation and least HAZ region.

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

Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

We use a two-dimensional laser-induced fluorescence spectroscopy technique to measure the coupled absorption and emission properties of atomic species in plasmas produced via laser ablation of solid aluminum targets at atmospheric pressure. Emission spectra from the Al I 394.4 nm and Al I 396.15 nm transitions are measured while a frequency-doubled, continuous-wave, Ti:Sapphire laser is tuned across the Al I 396.15 nm transition. The resulting two-dimensional spectra show the energy coupling between the two transitions via increased emission intensity for both transitions during resonant absorption of the continuous-wave laser at one transition. Time-delayed and gated detection of the emission spectrummore » is used to isolate the resonantly-excited fluorescence emission from the thermally-excited emission from the plasma. In addition, the tunable continuous-wave laser measures the absorption spectrum of the Al transition with ultra-high resolution after the plasma has cooled, resulting in narrower spectral linewidths than observed in emission spectra. Our results highlight that fluorescence spectroscopy employing continuous-wave laser re-excitation after pulsed laser ablation combines benefits of both traditional emission and absorption spectroscopic methods.« less

Active optical CO2 sensing for Ground-based, Airborne, and from Space platform

NASA Astrophysics Data System (ADS)

Sakaizawa, D.; Kawakami, S.; Nakajima, M.; Tanaka, T.; Miyamoto, Y.; Inoue, M.; Morino, I.; Uchino, O.; Sawa, Y.; Matsueda, H.

2011-12-01

Accurate measurements of lower tropospheric CO2 from space are strongly needed to quantify processes that identify the CO2 flux by the lands and oceans. The Greenhouse gases Observing SATellite (GOSAT) is the first space mission focused on lower tropospheric CO2 measurements by detecting the near-infrared spectral absorption in reflected sunlight. The GOSAT mission is a key first step, and will increase knowledge about atmospheric CO2 distributions. However there are unavoidable limitations imposed by its measurements approach, 1) the best performance of CO2 total column measurements can only be performed under the clear-sky atmosphere, 2) seasonal dependence reduces its global coverage, such as the case of the northern hemisphere in winter, and 3) unknowns and variations in cloud and aerosol contamination is also sensitive for CO2 measurements. The laser-based CO2 remote sensing is advantage of those un-met needs. We have developed and improved a compact differential laser absorption sensor (LAS) for measuring the weighted column-averaged dry CO2 mixing ratio (Wq) as a candidate for space mission. Our instrument employs two continuous-wave lasers and a fiber amplifier, which are available of simultaneous measurements of CO2 differential absorption optical depth and range to the target. The amplitude-modulated laser outputs are amplified by a fiber-amplifier. The receiver uses a compact telescope and photodiodes, and measures the laser powers reflected from the target. The gas absorption and column-averaged mixing ratio for the CO2 are evaluated from the ratio of the on- and off-line signals. We have performed ground-based and airborne measurement to evaluate uncertainty of Wq measurements. In these measurements R(12) line in the (30012<-00001) absorption bands of 12C16O2 was used. The precision of the ground-based measurements of horizontal Wq was 0.49% for a horizontal range of 2.1 km. The first airborne measurements were also made during August 2009. These measurements were made over grasslands from 0.5-7 km altitude. There results were compared with airborne flask sampling data and confirmed same trends along height. In February 2010 and February 2011 we made a total of 6 flights and also measured the vertical Wq over the urban area. A high correlation coefficient of 0.99 was obtained between Wq observed by LAS and that calculated by airborne in-situ measurement. More details about measurements and analysis will be presented in the meeting.

Dye system for dye laser applications

DOEpatents

Hammond, Peter R.

1991-01-01

A dye of the DCM family, [2-methyl-6-[2-(1,2,3,4-tetrahydro-1-methyl-6-quinolinyl)ethenyl]-4H-pyran -4-ylidene]-propanedinitrile, dissolved in 2-phenoxyethanol, is non-mutagenic, stable and efficient, particularly in a pumped continuous wave laser system.

Laser probe for measuring 2-D wave slope spectra of ocean capillary waves

NASA Technical Reports Server (NTRS)

Palm, C. S.; Anderson, R. C.; Reece, A. M.

1977-01-01

A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.

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.

Life problems of dc and RF-excited low-power CW CO2 waveguide lasers

NASA Technical Reports Server (NTRS)

Hochuli, U. E.; Haldemann, P. R.

1986-01-01

A number of different, RF-excited 3-W CW CO2 waveguide lasers have been built. Four of these lasers, after continuously working for 15,000-30,000 h, still yield about 70 percent of their original power output. The design variations cover N2and CO-bearing gas mixtures, as well as internal- and external-capacitively coupled excitation electrodes. A similar laser survived 50,000 5-min-ON/5-min-OFF cycles without significant mirror damage. It was not possible to find suitable cold cathodes that allow the building of longitudinally dc-excited CW CO2 waveguide lasers that work for such extended periods of time.

Technology Advancements for Active Remote Sensing of Carbon Dioxide from Space using the ASCENDS CarbonHawk Experiment Simulator

NASA Astrophysics Data System (ADS)

Obland, M. D.; Nehrir, A. R.; Liu, Z.; Chen, S.; Campbell, J. F.; Lin, B.; Kooi, S. A.; Fan, T. F.; Choi, Y.; Plant, J.; Yang, M. M.; Browell, E. V.; Harrison, F. W.; Meadows, B.; Dobler, J. T.; Zaccheo, T. S.

2015-12-01

This work describes advances in critical lidar technologies and techniques developed as part of the ASCENDS CarbonHawk Experiment Simulator (ACES) system for measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The ACES design demonstrates advancements in: (1) enhanced power-aperture product through the use and operation of multiple co-aligned laser transmitters and a multi-aperture telescope design; (2) high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration operation; and (4) advanced algorithms for cloud and aerosol discrimination. The ACES instrument, an Intensity-Modulated Continuous-Wave (IM-CW) lidar, was designed for high-altitude aircraft operations and can be directly applied to space instrumentation to meet the ASCENDS mission requirements. Specifically, the lidar simultaneously transmits three IM-CW laser beams from the high power EDFAs operating near 1571 nm. The outgoing laser beams are aligned to the field of view of three fiber-coupled 17.8-cm diameter telescopes, and the backscattered light collected by the same three telescopes is sent to the detector/TIA subsystem, which has a bandwidth of 4.9 MHz and operates service-free with a tactical Dewar and cryocooler. The electronic bandwidth is only slightly higher than 1 MHz, effectively limiting the noise level. Two key laser modulation approaches are being tested to significantly mitigate the effects of thin clouds on the retrieved CO2 column amounts. This work provides an over view of these technologies, the modulation approaches, and results from recent test flights.

Technology Advancements for Active Remote Sensing of Carbon Dioxide From Space using the ASCENDS CarbonHawk Experiment Simulator

NASA Astrophysics Data System (ADS)

Obland, M. D.; Liu, Z.; Campbell, J. F.; Lin, B.; Kooi, S. A.; Carrion, W.; Hicks, J.; Fan, T. F.; Nehrir, A. R.; Browell, E. V.; Meadows, B.; Davis, K. J.

2016-12-01

This work describes advances in critical lidar technologies and techniques developed as part of the ASCENDS CarbonHawk Experiment Simulator (ACES) system for measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The ACES design demonstrates advancements in: (1) enhanced power-aperture product through the use and operation of multiple co-aligned laser transmitters and a multi-aperture telescope design; (2) high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration operation; and (4) advanced algorithms for cloud and aerosol discrimination. The ACES instrument, an Intensity-Modulated Continuous-Wave (IM-CW) lidar, was designed for high-altitude aircraft operations and can be directly applied to space instrumentation to meet the ASCENDS mission requirements. Specifically, the lidar simultaneously transmits three IM-CW laser beams from the high power EDFAs operating near 1571 nm. The outgoing laser beams are aligned to the field of view of three fiber-coupled 17.8-cm diameter telescopes, and the backscattered light collected by the same three telescopes is sent to the detector/TIA subsystem, which has a bandwidth of 4.9 MHz and operates service-free with a tactical Dewar and cryocooler. The electronic bandwidth is only slightly higher than 1 MHz, effectively limiting the noise level. Two key laser modulation approaches are being tested to significantly mitigate the effects of thin clouds on the retrieved CO2 column amounts. This work provides an over view of these technologies, the modulation approaches, and results from recent test flights during the Atmospheric Carbon and Transport - America (ACT-America) Earth Venture Suborbital flight campaign.

Modeling of intensity-modulated continuous-wave laser absorption spectrometer systems for atmospheric CO(2) column measurements.

PubMed

Lin, Bing; Ismail, Syed; Wallace Harrison, F; Browell, Edward V; Nehrir, Amin R; Dobler, Jeremy; Moore, Berrien; Refaat, Tamer; Kooi, Susan A

2013-10-10

The focus of this study is to model and validate the performance of intensity-modulated continuous-wave (IM-CW) CO(2) laser absorption spectrometer (LAS) systems and their CO(2) column measurements from airborne and satellite platforms. The model accounts for all fundamental physics of the instruments and their related CO(2) measurement environments, and the modeling results are presented statistically from simulation ensembles that include noise sources and uncertainties related to the LAS instruments and the measurement environments. The characteristics of simulated LAS systems are based on existing technologies and their implementation in existing systems. The modeled instruments are specifically assumed to be IM-CW LAS systems such as the Exelis' airborne multifunctional fiber laser lidar (MFLL) operating in the 1.57 μm CO(2) absorption band. Atmospheric effects due to variations in CO(2), solar radiation, and thin clouds, are also included in the model. Model results are shown to agree well with LAS atmospheric CO(2) measurement performance. For example, the relative bias errors of both MFLL simulated and measured CO(2) differential optical depths were found to agree to within a few tenths of a percent when compared to the in situ observations from the flight of 3 August 2011 over Railroad Valley (RRV), Nevada, during the summer 2011 flight campaign. In addition, the horizontal variations in the model CO(2) differential optical depths were also found to be consistent with those from MFLL measurements. In general, the modeled and measured signal-to-noise ratios (SNRs) of the CO(2) column differential optical depths (τd) agreed to within about 30%. Model simulations of a spaceborne IM-CW LAS system in a 390 km dawn/dusk orbit for CO(2) column measurements showed that with a total of 42 W of transmitted power for one offline and two different sideline channels (placed at different locations on the side of the CO(2) absorption line), the accuracy of the τd measurements for surfaces similar to the playa of RRV, Nevada, will be better than 0.1% for 10 s averages. For other types of surfaces such as low-reflectivity snow and ice surfaces, the precision and bias errors will be within 0.23% and 0.1%, respectively. Including thin clouds with optical depths up to 1, the SNR of the τd measurements with 0.1 s integration period for surfaces similar to the playa of RRV, Nevada, will be greater than 94 and 65 for sideline positions placed +3 and +10  pm, respectively, from the CO(2) line center at 1571.112 nm. The CO(2) column bias errors introduced by the thin clouds are ≤0.1% for cloud optical depth ≤0.4, but they could reach ∼0.5% for more optically thick clouds with optical depths up to 1. When the cloud and surface altitudes and scattering amplitudes are obtained from matched filter analysis, the cloud bias errors can be further reduced. These results indicate that the IM-CW LAS instrument approach when implemented in a dawn/dusk orbit can make accurate CO(2) column measurements from space with preferential weighting across the mid to lower troposphere in support of a future ASCENDS mission.

Infrared laser dissociation of single megadalton polymer ions in a gated electrostatic ion trap: the added value of statistical analysis of individual events.

PubMed

Halim, Mohammad A; Clavier, Christian; Dagany, Xavier; Kerleroux, Michel; Dugourd, Philippe; Dunbar, Robert C; Antoine, Rodolphe

2018-05-07

In this study, we report the unimolecular dissociation mechanism of megadalton SO 3 -containing poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) polymer cations and anions with the aid of infrared multiphoton dissociation coupled to charge detection ion trap mass spectrometry. A gated electrostatic ion trap ("Benner trap") is used to store and detect single gaseous polymer ions generated by positive and negative polarity in an electrospray ionization source. The trapped ions are then fragmented due to the sequential absorption of multiple infrared photons produced from a continuous-wave CO 2 laser. Several fragmentation pathways having distinct signatures are observed. Highly charged parent ions characteristically adopt a distinctive "stair-case" pattern (assigned to the "fission" process) whereas low charge species take on a "funnel like" shape (assigned to the "evaporation" process). Also, the log-log plot of the dissociation rate constants as a function of laser intensity between PAMPS positive and negative ions is significantly different.

An overview of optical diagnostics developed for the Lockheed Martin compact fusion reactor

NASA Astrophysics Data System (ADS)

Sommers, Bradley; Raymond, Anthony; Gucker, Sarah; Lockheed Martin Compact Fusion Reactor Team

2017-10-01

The T4B experiment is a linear, encapsulated ring cusp confinement device, designed to develop a physics and technology basis for a follow-on high beta machine as part of the compact fusion reactor program. Toward this end, a collection of non-invasive optical diagnostics have been developed to investigate confinement, neutral beam heating, and source behavior on the T4B device. These diagnostics include: (1) a multipoint Thomson scattering system employing a 532 nm Nd:YAG laser and high throughput spectrometer to measure 1D profiles of electron density and temperature, (2) a dispersion interferometer utilizing a continuous-wave CO2 laser (10.6 μm) to measure time resolved, line-integrated electron density, and (3) a bolometer suite utilizing four AXUV photodiodes with 64 lines of sight to generate 2D reconstructions of total radiative power and soft x-ray emission (via beryllium filters). An overview of design methods, including laser systems, detection schemes, and data analysis techniques is presented as well as results to date.

2.05-μm Holmium-doped all-fiber continuous-wave laser at in-core diode-pumping at 1.125 μm

NASA Astrophysics Data System (ADS)

Kir'yanov, Alexander V.; Barmenkov, Yuri O.

2017-08-01

We report a Holmium-doped all-fiber laser oscillating in continuous-wave at 2.05 μm, at in-core pumping by a 1.125-μm laser diode. The active fibers employed are alumino-germano-silicate fibers doped with Ho3+ at concentrations of 1.2×1019 and 1.8×1019 cm-3. The laser is implemented in non-optimized Fabry-Perot cavity's geometry, composed of a couple of fiber Bragg gratings with reflectivity of 99 and 90%. When using the lower doped Holmium-doped fiber of proper length (1.4 m), low threshold ( 370 mW) and moderate slope efficiency ( 13%) of 2.05-μm lasing were obtained. High-brightness (laser line's width is 60 pm) and good noise-to-signal ratio (<0.006) are the laser's attractivities. In case of the heavier doped fiber of optimal length (1.2 m), the laser output (threshold of 430 mW, slope efficiency of 9%, output power of 9 mW, laser line's width of 110 pm, noise-to-signal ratio of <0.009) is worse, with a probable reason being deteriorating Ho3+ concentration effects.

Continuous-wave single-frequency laser with dual wavelength at 1064 and 532 nm.

PubMed

Zhang, Chenwei; Lu, Huadong; Yin, Qiwei; Su, Jing

2014-10-01

A continuous-wave high-power single-frequency laser with dual-wavelength output at 1064 and 532 nm is presented. The dependencies of the output power on the transmission of the output coupler and the phase-matching temperature of the LiB(3)O(5) (LBO) crystal are studied. An output coupler with transmission of 19% is used, and the temperature of LBO is controlled to the optimal phase-matching temperature of 422 K; measured maximal output powers of 33.7 W at 1064 nm and of 1.13 W at 532 nm are obtained with optical-optical conversion efficiency of 45.6%. The laser can be single-frequency operated stably and mode-hop-free, and the measured frequency drift is less than 15 MHz in 1 min. The measured Mx2 and My2 for the 1064 nm laser are 1.06 and 1.09, respectively. The measured Mx2 and My2 for the 532 nm laser are 1.12 and 1.11, respectively.

Mode selection and frequency tuning by injection in pulsed TEA-CO2 lasers

NASA Technical Reports Server (NTRS)

Flamant, P. H.; Menzies, R. T.

1983-01-01

An analytical model characterizing pulsed-TEA-CO2-laser injection locking by tunable CW-laser radiation is presented and used to explore the requirements for SLM pulse generation. Photon-density-rate equations describing the laser mechanism are analyzed in terms of the mode competition between photon densities emitted at two frequencies. The expression derived for pulsed dye lasers is extended to homogeneously broadened CO2 lasers, and locking time is defined as a function of laser parameters. The extent to which injected radiation can be detuned from the CO2 line center and continue to produce SLM pulses is investigated experimentally in terms of the analytical framework. The dependence of locking time on the detuning/pressure-broadened-halfwidth ratio is seen as important for spectroscopic applications requiring tuning within the TEA-laser line-gain bandwidth.

Room temperature continuous wave operation of quantum cascade laser at λ ~ 9.4 μm

NASA Astrophysics Data System (ADS)

Hou, Chuncai; Zhao, Yue; Zhang, Jinchuan; Zhai, Shenqiang; Zhuo, Ning; Liu, Junqi; Wang, Lijun; Liu, Shuman; Liu, Fengqi; Wang, Zhanguo

2018-03-01

Continuous wave (CW) operation of long wave infrared (LWIR) quantum cascade lasers (QCLs) is achieved up to a temperature of 303 K. For room temperature CW operation, the wafer with 35 stages was processed into buried heterostructure lasers. For a 2-mm-long and 10-μm-wide laser with high-reflectivity (HR) coating on the rear facet, CW output power of 45 mW at 283 K and 9 mW at 303 K is obtained. The lasing wavelength is around 9.4 μm locating in the LWIR spectrum range. Project supported by the National Key Research And Development Program (No. 2016YFB0402303), the National Natural Science Foundation of China (Nos. 61435014, 61627822, 61574136, 61774146, 61674144, 61404131), the Key Projects of Chinese Academy of Sciences (Nos. ZDRW-XH-2016-4, QYZDJ-SSW-JSC027), and the Beijing Natural Science Foundation (No. 4162060, 4172060).

Effect of scanning speed on continuous wave laser scribing of metal thin films: theory and experiment

NASA Astrophysics Data System (ADS)

Shahbazi, AmirHossein; Koohian, Ata; Madanipour, Khosro

2017-01-01

In this paper continuous wave laser scribing of the metal thin films have been investigated theoretically and experimentally. A formulation is presented based on parameters like beam power, spot size, scanning speed and fluence thresholds. The role of speed on the transient temperature and tracks width is studied numerically. By using two frameworks of pulsed laser ablation of thin films and laser printing on paper, the relation between ablation width and scanning speed has been derived. Furthermore, various speeds of the focused 450 nm continuous laser diode with an elliptical beam spot applied to a 290 nm copper thin film coated on glass, experimentally. The beam power was 150 mW after spatial filtering. By fitting the theoretical formulation to the experimental data, the threshold fluence and energy were obtained to be 13.2 J mm-2 and 414~μ J respectively. An anticipated theoretical parameter named equilibrium~border was verified experimentally. It shows that in the scribing of the 290 nm copper thin film, at a distance where the intensity reaches about 1/e of its maximum value, the absorbed fluence on the surface is equal to zero. Therefore the application of continuous laser in metal thin film ablation has different mechanism from pulsed laser drilling and beam scanning in printers.

Non-uniform temperature and species concentration measurements in a laminar flame using multi-band infrared absorption spectroscopy

NASA Astrophysics Data System (ADS)

Ma, Liu Hao; Lau, Lok Yin; Ren, Wei

2017-03-01

We report in situ measurements of non-uniform temperature, H2O and CO2 concentration distributions in a premixed methane-air laminar flame using tunable diode laser absorption spectroscopy (TDLAS). A mid-infrared, continuous-wave, room-temperature interband cascade laser (ICL) at 4183 nm was used for the sensitive detection of CO2 at high temperature.The H2O absorption lines were exploited by one distributed feedback (DFB) diode laser at 1343 nm and one ICL at 2482 nm to achieve multi-band absorption measurements with high species concentration sensitivity, high temperature sensitivity, and immunity to variations in ambient conditions. A novel profile-fitting function was proposed to characterize the non-uniform temperature and species concentrations along the line-of-sight in the flame by detecting six absorption lines of CO2 and H2O simultaneously. The flame temperature distribution was measured at different heights above the burner (5-20 mm), and compared with the thermocouple measurement with heat-transfer correction. Our TDLAS measured temperature of the central flame was in excellent agreement (<1.5% difference) with the thermocouple data.The TDLAS results were also compared with the CFD simulations using a detailed chemical kinetics mechanism (GRI 3.0) and considering the heat loss to the surroundings.The current CFD simulation overpredicted the flame temperature in the gradient region, but was in excellent agreement with the measured temperature and species concentration in the core of the flame.

Continuous-wave laser operation at 743 and 753 nm based on a diode-pumped c-cut Pr:YAlO3 crystal

NASA Astrophysics Data System (ADS)

Lin, Xiuji; Huang, Xiaoxu; Liu, Bin; Xu, Bin; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Li, Dongzhen; Liu, Jian; Xu, Jun

2018-02-01

We report on blue-diode-pumped continuous-wave Pr:YAlO3 (YAP) crystal lasers. Using a b-cut sample, a maximum output power of 181 mW is achieved at ∼747 nm with slope efficiency of 12.7% with respect to the absorbed power. Using a c-cut sample, a dual-wavelength laser at ∼743 and ∼753 nm is obtained with a total maximum output power of 72 mW by using the blue diode pumping, for the first time to our knowledge. These laser emissions are all linearly polarized and M2 factors of these output laser beams are also measured. YAP is experimentally verified to be one of effective oxide hosts for Pr-doped visible laser operation besides its fluoride counterparts.

Measurements of CO, CO2, OH, and H2O in room-temperature and combustion gases by use of a broadly current-tuned multisection InGaAsP diode laser.

PubMed

Upschulte, B L; Sonnenfroh, D M; Allen, M G

1999-03-20

A new laser technology that achieves nearly 100-nm quasi-continuous tuning with only injection-current control in a four-section grating-coupler sampled-reflector laser was used to detect CO and CO(2) simultaneously in room-temperature gas mixtures. The same grating-coupler sampled-reflector laser was used to perform in situ measurements of CO, H(2)O, and OH in the exhaust gases of a CH(4)-air flame. This laser is being evaluated for inclusion in a multispecies combustion-emissions exhaust-analysis sensor, and its operational characteristics as they have an impact on gas sensing are described. Preliminary results suggest that this single laser can be used to replace multilaser sensor configurations for some combustion-emissions monitoring applications.

Millimeter-wave generation and characterization of a GaAs FET by optical mixing

NASA Technical Reports Server (NTRS)

Ni, David C.; Fetterman, Harold R.; Chew, Wilbert

1990-01-01

Coherent mixing of optical radiation from a tunable continuous-wave dye laser and a stabilized He-Ne laser was used to generate millimeter-wave signals in GaAs FETs attached to printed-circuit millimeter-wave antennas. The generated signal was further down-converted to a 2-GHz IF by an antenna-coupled millimeter-wave local oscillator at 62 GHz. Detailed characterizations of power and S/N under different bias conditions have been performed. This technique is expected to allow signal generation and frequency-response evaluation of millimeter-wave devices at frequencies as high as 100 GHz.

Diode-pumped continuous-wave Nd:Gd3Ga5O12 lasers at 1406, 1415 and 1423 nm

NASA Astrophysics Data System (ADS)

Lin, Haifeng; Zhu, Wenzhang; Xiong, Feibing; Ruan, Jianjian

2018-05-01

We report a diode-pumped continuous-wave Nd:Gd3Ga5O12 (GGG) laser operating at 1.4 μm spectral region. A dual-wavelength laser at 1423 and 1406 nm is achieved with output power of about 2.59 W at absorbed pump power of 13.4 W. Further increasing the pump power, simultaneous tri-wavelength laser at 1423, 1415 and 1406 nm is also obtained with a maximum output power of 3.96 W at absorbed pump power of 18.9 W. Single-wavelength lasing is also realized at the three emission lines using an intracavity etalon. The laser result is believed to be the highest output power achieved in Nd:GGG crystal, at present, to the best of our knowledge.

The 2014 ASCENDS Field Campaign - a Carbon Dioxide Laser Absorption Spectrometer Perspective

NASA Astrophysics Data System (ADS)

Spiers, G. D.; Menzies, R. T.; Jacob, J. C.; Geier, S.; Fregoso, S. F.

2014-12-01

NASA's ASCENDS mission has been flying several candidate lidar instruments on board the NASA DC-8 aircraft to obtain column integrated measurements of Carbon Dioxide. Each instrument uses a different approach to making the measurement and combined they have allowed for the informed development of the ASCENDS mission measurement requirements(1). The JPL developed Carbon Dioxide Laser Absorption Spectrometer, CO2LAS is one of these instruments. The CO2LAS measures the weighted, column averaged carbon dioxide between the aircraft and the ground using a continuous-wave heterodyne technique. The instrument operates at a 2.05 micron wavelength optimized for enhancing sensitivity to boundary layer carbon dioxide. Since the 2013 field campaign the instrument has undergone significant upgrades that improve the data collection efficiency and instrument stability and has recently been re-integrated onto the NASA DC-8 for the August 2014 ASCENDS field campaign. This presentation will summarize the instrument and algorithm improvements and review the 2014 field campaign flights and preliminary results. (1) Abshire, J.B. et al., "An overview of NASA's ASCENDS Mission lidar measurement requirements", submitted to 2014 Fall AGU Conference.

Absolute calibration of Phase Contrast Imaging on HL-2A tokamak

NASA Astrophysics Data System (ADS)

Yu, Yi; Gong, Shaobo; Xu, Min; Wu, Yifan; Yuan, Boda; Ye, Minyou; Duan, Xuru; HL-2A Team Team

2017-10-01

Phase contrast imaging (PCI) has recently been developed on HL-2A tokamak. In this article we present the calibration of this diagnostic. This system is to diagnose chord integral density fluctuations by measuring the phase shift of a CO2 laser beam with a wavelength of 10.6 μm when the laser beam passes through plasma. Sound waves are used to calibrate PCI diagnostic. The signal series in different PCI channels show a pronounced modulation of incident laser beam by the sound wave. Frequency-wavenumber spectrum is achieved. Calibrations by sound waves with different frequencies exhibit a maximal wavenumber response of 12 cm-1. The conversion relationship between the chord integral plasma density fluctuation and the signal intensity is 2.3-1013 m-2/mV, indicating a high sensitivity. Supported by the National Magnetic Confinement Fusion Energy Research Project (Grant No.2015GB120002, 2013GB107001).

LASER PLASMA AND LASER APPLICATIONS: Plasma transparency in laser absorption waves in metal capillaries

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Kozolupenko, A. P.; Sebrant, A. Yu

1988-12-01

An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO2 laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1-100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.

Simultaneous three-wavelength continuous wave laser at 946 nm, 1319 nm and 1064 nm in Nd:YAG

NASA Astrophysics Data System (ADS)

Lü, Yanfei; Zhao, Lianshui; Zhai, Pei; Xia, Jing; Fu, Xihong; Li, Shutao

2013-01-01

A continuous-wave (cw) diode-end-pumped Nd:YAG laser that generates simultaneous laser at the wavelengths 946 nm, 1319 nm and 1064 nm is demonstrated. The optimum oscillation condition for the simultaneous three-wavelength operation has been derived. Using the separation of the three output couplers, we obtained the maximum output powers of 0.24 W at 946 nm, 1.07 W at 1319 nm and 1.88 W at 1064 nm at the absorbed pump power of 11.2 W. A total output power of 3.19 W for the three-wavelength was achieved at the absorbed pump power of 11.2 W with optical conversion efficiency of 28.5%.

Application of CO laser for laser balloon angioplasty

NASA Astrophysics Data System (ADS)

Miyamoto, Akira; Sakurada, Masami; Mizuno, Kyoichi; Kurita, Akira; Nakamura, Haruo; Suda, Akira; Arai, Tsunenori; Kikuchi, Makoto

1990-07-01

CO laser may be efficient for thermal fusion of intima of arterial wall without adventitial tissue damage because of high tissue absorption. To investigate the efficacy of CO laser as a laser bam for laser balloon angioplasty (LBA). CO laser was irradiated to aortic tissue through 3Oim polyethylene membrane and tissue temperature was measured by a thermistor. At 2Owatt/cm2 200joules/cm2 continuous laser exposure (CE), tissue temperature was above 100°C within a depth of 1mm and rapidly decreased to 60 °C or below between 2 and 3mm in depth. Moreover, adventitial temperature could be decreased by changing duty ratio (exposure duration/interval) of intermittent laser exposure (IE) despite of the same laser energy. Light microscopy showed high degree of medial coagulation necrosis in CE, however thermal coagulation was observed only at the surface of intima of aortic tissue in IE at duty ratio 1 / 2. These findings suggested CO laser could coagulate intimal layer with less deep thermal damage compared to Nd- YAG laser and that IE was better for superficial welding than CE at the same energy. We concluded that CO laser might be more efficient as a laser beam for LBA than Nd-YAG laser.

Molecular dynamics study of lubricant depletion by pulsed laser heating

NASA Astrophysics Data System (ADS)

Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

2018-05-01

In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

Ceramic planar waveguide laser of non-aqueous tape casting fabricated YAG/Yb:YAG/YAG

PubMed Central

Wang, Chao; Li, Wenxue; Yang, Chao; Bai, Dongbi; Li, Jiang; Ge, Lin; Pan, Yubai; Zeng, Heping

2016-01-01

Ceramic YAG/Yb:YAG/YAG planar waveguide lasers were realized on continuous-wave and mode-locked operations. The straight waveguide, fabricated by non-aqueous tape casting and solid state reactive sintering, enabled highly efficient diode-pumped waveguide continuous-wave laser with the slope efficiency of 66% and average output power of more than 3 W. The influence of the waveguide structure on the wavelength tunability was also experimentally investiccgated with a dispersive prism. Passively mode-locked operation of the ceramic waveguide laser was achieved by using a semiconductor saturable absorber mirror (SESAM), output 2.95 ps pulses with maximum power of 385 mW at the central wavelength of 1030 nm. PMID:27535577

Continuous-wave yellow-green laser at 0.56  μm based on frequency doubling of a diode-end-pumped ceramic Nd:YAG laser.

PubMed

Yao, Wenming; Gao, Jing; Zhang, Long; Li, Jiang; Tian, Yubing; Ma, Yufei; Wu, Xiaodong; Ma, Gangfei; Yang, Jianming; Pan, Yubai; Dai, Xianjin

2015-06-20

We present what is, to the best of our knowledge, the first report on yellow-green laser generation based on the frequency doubling of the 1.1 μm transitions in Nd:YAG ceramics. By employing an 885 nm diode laser as the end-pumping source and a lithium triborate crystal as the frequency doubler, the highest continuous wave output powers of 1.4, 0.5, and 1.1 W at 556, 558, and 561 nm are achieved, respectively. These result in optical-to-optical efficiencies of 6.9%, 2.5%, and 5.4% with respect to the absorbed pump power, respectively.

Efficient Tm:Fiber Pumped Solid-State Ho:YLF 2-micrometer Laser for Remote Sensing Applications

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta

2012-01-01

An efficient 19 W, TEM(sub 00) mode, Ho:YLF laser pumped by continuous wave Tm:fiber laser has been demonstrated at the room temperature. The slope efficiency and optical-to-optical efficiency are 65% and 55%, respectively.

Focusers of obliquely incident laser radiation

NASA Astrophysics Data System (ADS)

Goncharskiy, A. V.; Danilov, V. A.; Popov, V. V.; Prokhorov, A. M.; Sisakyan, I. N.; Sayfer, V. A.; Stepanov, V. V.

1984-08-01

Focusing obliquely incident laser radiation along a given line in space with a given intensity distribution is treated as a problem of synthesizing a mirror surface. The intricate shape of such a surface, characterized by a function z= z (u,v) in the approximation of geometrical optics, is determined from the equation phi (u,v,z) - phi O(u,v,z)=O, which expresses that the incident field and the reflected field have identical eikonals. Further calculations are facilitated by replacing continuous mirror with a more easily manufactured piecewise continuous one. The problem is solved for the simple case of a plane incident wave with a typical iconal phi O(u,v,z)= -z cos0 at a large angle to a focus mirror in the z-plane region. Mirrors constructed on the basis of the theoretical solution were tested in an experiment with a CO2 laser. A light beam with Gaussian intensity distribution was, upon incidence at a 45 deg angle, focused into a circle or into an ellipse with uniform intensity distribution. Improvements in amplitudinal masking and selective tanning technology should reduce energy losses at the surface which results in efficient laser focusing mirrors.

Corona Preionization Technique for Carbon Dioxide TEA Lasers.

DTIC Science & Technology

1982-11-30

34’" " " " "- -. .. " "I~ 82R8O701-02 CORONA PREIONIZATION TECHNIQUE FOR CARBON DIOXIDE TEA LASERS W after R. Kamnki SUnited Technologiles Research Center C...TITLE (and Subtitle) S. TYPE OF REPORT a PERIOD COVERED CORONA PREIONIZATION TECHNIQUE FOR CARBON Final Report DIOXIDE TEA LASERS May 5, 1981...Preionization Laser UV Preionization Pulsed CO2 Laser Corona Preionization CO2 TEA Laser 10. ABSTRACT (Continue on reverse side If neceeeiny md Identify

Supporting Structure of the LSD Wave in an Energy Absorption Perspective

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

Fukui, Akihiro; Hatai, Keigo; Cho, Shinatora

In Repetitively Pulsed (RP) Laser Propulsion, laser energy irradiated to a vehicle is converted to blast wave enthalpy during the Laser Supported Detonation (LSD) regime. Based on the measured post-LSD electron number density profiles by two-wavelength Mach Zehnder interferometer in a line-focusing optics, electron temperature and absorption coefficient were estimated assuming Local Thermal Equilibrium. A 10J/pulse CO{sub 2} laser was used. As a result, laser absorption was found completed in the layer between the shock wave and the electron density peak. Although the LSD-termination timing was not clear from the shock-front/ionization-front separation in the shadowgraph images, there observed drastic changesmore » in the absorption layer thickness from 0.2 mm to 0.5 mm and in the peak heating rate from 12-17x10{sup 13} kW/m{sup 3} to 5x10{sup 13} kW/m{sup 3} at the termination.« less

Intercomparison of six fast-response sensors for the eddy-covariance flux measurement of nitrous oxide over agricultural grassland

NASA Astrophysics Data System (ADS)

Nemitz, Eiko; Famulari, Daniela; Ibrom, Andreas; Vermeulen, Alex; Hensen, Arjan; van den Bulk, Pim; Loubet, Benjamin; Laville, Patricia; Mammarella, Ivan; Haapanala, Sami; Lohila, Annalea; Laurila, Tuomas; Eva, Rabot; Laborde, Marie; Cowan, Nicholas; Anderson, Margaret; Helfter, Carole

2015-04-01

Nitrous oxide (N2O) is the third most important greenhouse gas and its terrestrial budget remains poorly constraint, with bottom up and top down estimates of country emissions often disagreeing by more than a factor of two. Whilst the measurements of the biosphere / atmosphere exchange of CO2 with micrometeorological methods is commonplace, emissions of CH4 and N2O are more commonly measured with enclosure techniques due to limitations in fast-response sensors with good signal-to-noise characteristics. Recent years have seen the development of a range of instruments based on optical spectroscopy. This started in the early 1990s with instruments based on lead salt lasers, which had temperamental long-term characteristics. More recent developments in quantum cascade lasers has lead to increasingly stable instruments, initially based on pulsed, later on continuous wave lasers. Within the context of the European FP7 Infrastructure Project InGOS ('Integrated non-CO2 Greenhouse gas Observing System'), we conducted an intercomparison of six fast response sensors for N2O: three more or less identical instruments based on off-axis Integrated Cavity Optical Spectrocopy (ICOS) (Los Gatos Research Inc.) and three instruments based on quantum cascade laser absorption spectrometry (Aerodyne Research Inc.): one older generation pulsed instrument (p-QCL) and two of the latest generation of compact continuous wave instruments (cw-QCL), operating at two different wavelengths. One of the ICOS instruments was operated with an inlet drier. In addition, the campaign was joined by a relaxed eddy-accumulation system linked to a FTIR spectrometer (Ecotech), a gradient system based on a home-built slower QCL (INRA Orleans) and a fast chamber system. Here we present the results of the study and a detailed examination of the various corrections and errors of the different instruments. Overall, with the exception of the older generation QCL, the average fluxes based on the different fast-response instruments agreed within +/- 7.4%, although fluxes were moderate. The cw-QCL systems showed somewhat better signal-to-noise characteristics and a lower flux detection limit than the ICOS analysers. Intriguingly, there seemed to be some minor differences between the ICOS instruments which showed cross sensitivities to CO to varying degree. Overall the study demonstrates, that, while not cheap, both the ICOS-based instruments and the cw-QCLs are suitable for the measurement of even moderate N2O fluxes.

History of Laser Weapon Research

DTIC Science & Technology

2012-01-01

designed to damage, disable, or destroy targets with little or no collateral damage. Airborne Laser (ABL) (CO2) Chemical Oxygen The ABL C-130H aircraft ...mirrors. Weapons systems based on lasers and “ray guns,” long a staple of science fiction, have captured the imagination of people everywhere. But...waves (millimeters to centimeters), with wavelengths 10,000 times longer than lasers. Diffraction of any electromagnetic radia- tion beam is based

Watt-Level Continuous-Wave Emission from a Bi-Functional Quantum Cascade Laser/Detector

DTIC Science & Technology

2017-04-18

facet continuous wave emission at 15◦C. Apart from the general performance benets, this enables sensing techiques which rely on continuous wave...record achieved with strained material at this wavelength. Keywords quantum cascade laser, quantum cascade detector, lab- on -a-chip, monolithic integrated...materials, which makes their integration on Si particularly dicult. Heterogeneous integration using transfer techniques allows both single device and wafer

First staging of two laser accelerators.

PubMed

Kimura, W D; van Steenbergen, A; Babzien, M; Ben-Zvi, I; Campbell, L P; Cline, D B; Dilley, C E; Gallardo, J C; Gottschalk, S C; He, P; Kusche, K P; Liu, Y; Pantell, R H; Pogorelsky, I V; Quimby, D C; Skaritka, J; Steinhauer, L C; Yakimenko, V

2001-04-30

Staging of two laser-driven, relativistic electron accelerators has been demonstrated for the first time in a proof-of-principle experiment, whereby two distinct and serial laser accelerators acted on an electron beam in a coherently cumulative manner. Output from a CO2 laser was split into two beams to drive two inverse free electron lasers (IFEL) separated by 2.3 m. The first IFEL served to bunch the electrons into approximately 3 fs microbunches, which were rephased with the laser wave in the second IFEL. This represents a crucial step towards the development of practical laser-driven electron accelerators.

Integrated injection-locked semiconductor diode laser

DOEpatents

Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

1991-01-01

A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet.

A model for a continuous-wave iodine laser

NASA Technical Reports Server (NTRS)

Hwang, In H.; Tabibi, Bagher M.

1990-01-01

A model for a continuous-wave (CW) iodine laser has been developed and compared with the experimental results obtained from a solar-simulator-pumped CW iodine laser. The agreement between the calculated laser power output and the experimental results is generally good for various laser parameters even when the model includes only prominent rate coefficients. The flow velocity dependence of the output power shows that the CW iodine laser cannot be achieved with a flow velocity below 1 m/s for the present solar-simulator-pumped CW iodine laser system.

Laser production and heating of plasma for MHD application

NASA Technical Reports Server (NTRS)

Jalufka, N. W.

1988-01-01

Experiments have been made on the production and heating of plasmas by the absorption of laser radiation. These experiments were performed to ascertain the feasibility of using laser-produced or laser-heated plasmas as the input for a magnetohydrodynamic (MHD) generator. Such a system would have a broad application as a laser-to-electricity energy converter for space power transmission. Experiments with a 100-J-pulsed CO2 laser were conducted to investigate the breakdown of argon gas by a high-intensity laser beam, the parameters (electron density and temperature) of the plasma produced, and the formation and propagation of laser-supported detonation (LSD) waves. Experiments were also carried out using a 1-J-pulsed CO2 laser to heat the plasma produced in a shock tube. The shock-tube hydrogen plasma reached electron densities of approximately 10 to the 17th/cu cm and electron temperatures of approximately 1 eV. Absorption of the CO2 laser beam by the plasma was measured, and up to approximately 100 percent absorption was observed. Measurements with a small MHD generator showed that the energy extraction efficiency could be very large with values up to 56 percent being measured.

Fast continuous tuning of terahertz quantum-cascade lasers by rear-facet illumination

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

Hempel, Martin, E-mail: hempel@pdi-berlin.de; Röben, Benjamin; Schrottke, Lutz

2016-05-09

GaAs-based terahertz quantum-cascade lasers (QCLs) are continuously tuned in their emission frequency by illuminating the rear facet with a near-infrared, high-power diode laser. For QCLs emitting around 3.1 THz, the maximum tuning range amounts to 2.8 GHz for continuous-wave operation at a heat sink temperature of 55 K, while in pulsed mode 9.1 and 8.0 GHz are achieved at 35 and 55 K, respectively.

Laser-assisted solar-cell metallization processing

NASA Technical Reports Server (NTRS)

Dutta, S.

1984-01-01

A photolytic metal deposition system using a focused continuous wave ultraviolet laser, a photolytic metal deposition system using a mask and ultraviolet flood illumination, and a pyrolytic metal deposition system using a focused continuous wave laser were studied. Fabrication of solar cells, as well as characterization to determine the effects of transient heat on solar cell junctions were investigated.

Intracavity-pumped Raman laser action in a mid IR, continuous-wave (cw) MgO:PPLN optical parametric oscillator

NASA Astrophysics Data System (ADS)

Okishev, Andrey V.; Zuegel, Jonathan D.

2006-12-01

Intracavity-pumped Raman laser action in a fiber-laser pumped, single-resonant, continuous-wave (cw) MgO:PPLN optical parametric oscillator with a high-Q linear resonator has been observed for the first time to our knowledge. Experimental results of this phenomenon investigation will be discussed.

Direct inscription of Bragg gratings into coated fluoride fibers for widely tunable and robust mid-infrared lasers.

PubMed

Bharathan, Gayathri; Woodward, Robert I; Ams, Martin; Hudson, Darren D; Jackson, Stuart D; Fuerbach, Alex

2017-11-27

We report the development of a widely tunable all-fiber mid-infrared laser system based on a mechanically robust fiber Bragg grating (FBG) which was inscribed through the polymer coating of a Ho 3+ -Pr 3+ co-doped double clad ZBLAN fluoride fiber by focusing femtosecond laser pulses into the core of the fiber without the use of a phase mask. By applying mechanical tension and compression to the FBG while pumping the fiber with an 1150 nm laser diode, a continuous wave (CW) all-fiber laser with a tuning range of 37 nm, centered at 2870 nm, was demonstrated with up to 0.29 W output power. These results pave the way for the realization of compact and robust mid-infrared fiber laser systems for real-world applications in spectroscopy and medicine.

Investigation of mechanical dissipation in CO2 laser-drawn fused silica fibres and welds

NASA Astrophysics Data System (ADS)

Heptonstall, Alastair; Barton, Mark; Cantley, Caroline; Cumming, Alan; Cagnoli, Geppo; Hough, James; Jones, Russell; Kumar, Rahul; Martin, Iain; Rowan, Sheila; Torrie, Calum; Zech, Steven

2010-02-01

The planned upgrades to the LIGO gravitational wave detectors include monolithic mirror suspensions to reduce thermal noise. The mirrors will be suspended using CO2 laser-drawn fused silica fibres. We present here measurements of mechanical dissipation in synthetic fused silica fibres drawn using a CO2 laser. The level of dissipation in the surface layer is investigated and is found to be at a similar level to fibres produced using a gas flame. Also presented is a method for examining dissipation at welded interfaces, showing clear evidence of the existence of this loss mechanism which forms an additional component of the total detector thermal noise. Modelling of a typical detector suspension configuration shows that the thermal noise contribution from this loss source will be negligible.

Generation of silicon nanocrystals by damage free continuous wave laser annealing of substrate-bound SiO{sub x} films

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

Fricke-Begemann, T., E-mail: fricke-begemann@llg-ev.de; Ihlemann, J.; Wang, N.

2015-09-28

Silicon nanocrystals have been generated by laser induced phase separation in SiO{sub x} films. A continuous wave laser emitting at 405 nm is focused to a 6 μm diameter spot on 530 nm thick SiO{sub x} films deposited on fused silica substrates. Irradiation of lines is accomplished by focus scanning. The samples are investigated by atomic force microscopy, TEM, Raman spectroscopy, and photoluminescence measurements. At a laser power of 35 mW corresponding to an irradiance of about 1.2 × 10{sup 5 }W/cm{sup 2}, the formation of Si-nanocrystals in the film without any deterioration of the surface is observed. At higher laser power, the centralmore » irradiated region is oxidized to SiO{sub 2} and exhibits some porous character, while the surface remains optically smooth, and nanocrystals are observed beside and beneath this oxidized region. Amorphous Si-nanoclusters are formed at lower laser power and around the lines written at high power.« less

A radiatively pumped CW CO2 laser

NASA Technical Reports Server (NTRS)

Insuik, R. J.; Christiansen, W. H.

1984-01-01

A proof of principle experiment to demonstrate the physics of a radiatively pumped laser has been carried out. For the first time, a blackbody cavity has optically pumped a CW CO2 laser. Results are presented from a series of experiments using mixtures of CO2, He, and Ar in which maximum output power was obtained with a 20 percent CO2-15 percent He-65 percent Ar mixture. The dependence of the output power on the blackbody temperature and the cooling gas flow rate is also discussed. By appropriately varying these parameters, continuous output powers of 8-10 mW have been achieved.

Lidar Observations of Atmospheric CO2 Column During 2014 Summer Flight Campaigns

NASA Technical Reports Server (NTRS)

Lin, Bing; Harrison, F. Wallace; Fan, Tai-Fang

2015-01-01

Advanced knowledge in atmospheric CO2 is critical in reducing large uncertainties in predictions of the Earth' future climate. Thus, Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) from space was recommended by the U.S. National Research Council to NASA. As part of the preparation for the ASCENDS mission, NASA Langley Research Center (LaRC) and Exelis, Inc. have been collaborating in development and demonstration of the Intensity-Modulated Continuous-Wave (IM-CW) lidar approach for measuring atmospheric CO2 column from space. Airborne laser absorption lidars such as the Multi-Functional Fiber Laser Lidar (MFLL) and ASCENDS CarbonHawk Experiment Simulator (ACES) operating in the 1.57 micron CO2 absorption band have been developed and tested to obtain precise atmospheric CO2 column measurements using integrated path differential absorption technique and to evaluate the potential of the space ASCENDS mission. This presentation reports the results of our lidar atmospheric CO2 column measurements from 2014 summer flight campaign. Analysis shows that for the 27 Aug OCO-2 under flight over northern California forest regions, significant variations of CO2 column approximately 2 ppm) in the lower troposphere have been observed, which may be a challenge for space measurements owing to complicated topographic condition, heterogeneity of surface reflection and difference in vegetation evapotranspiration. Compared to the observed 2011 summer CO2 drawdown (about 8 ppm) over mid-west, 2014 summer drawdown in the same region measured was much weak (approximately 3 ppm). The observed drawdown difference could be the results of the changes in both meteorological states and the phases of growing seasons. Individual lidar CO2 column measurements of 0.1-s integration were within 1-2 ppm of the CO2 estimates obtained from on-board in-situ sensors. For weak surface reflection conditions such as ocean surfaces, the 1- s integrated signal-to-noise ratio (SNR) of lidar measurements at 11 km altitude reached 376, which was equivalent to a 10-s CO2 error 0.33 ppm. For the entire processed 2014 summer flight campaign data, the mean differences between lidar remote sensed and in-situ estimated CO2 values were about -0.013 ppm. These results indicate that current laser absorption lidar approach could meet space measurement requirements for CO2 science goals.

High Power OPO Laser and wavelength-controlled system for 1.6μm CO2-DIAL

NASA Astrophysics Data System (ADS)

Abo, M.; Nagasawa, C.; Shibata, Y.

2009-12-01

Unlike the existing 2.0μm CO2-DIAL, a high-energy pulse laser operating in the 1.6μm absorption band of CO2 has not been realized. Quasi phase matching (QPM) devices have high conversion efficiency and high beam quality due to their higher nonlinear optical coefficient. We adapt the PPMgLT crystal as the QPM device. The PPMgLT crystal had 3mm × 3mm apertures, and the periodically poled period was 30.9 μm, with the duty ratio close to the ideal value of 0.5. The beam quality of the pumping laser was exceed M2 ≥1.2. The repetition rate was 400 Hz and the energy was 35 mJ. The pumping laser pulse was injection-seeded by the continuous-wave (CW) fiber laser, which had a narrow spectrum. The pulse pumped the PPMgLT crystal in the ring cavity with a single pass through the dielectric mirror. The PPMgLT crystal was mounted on a copper holder, and the temperature was maintained at 40 °C using a Peltier module. The holder’s temperature was stabilized to within 0.01 °C when the copper holder was covered with a plastic case. The OPO ring cavity was a singly resonant oscillator optimized for the signal wave. Single-frequency oscillation of the PPMgLT OPO was achieved by injection seeding, as described in the following. The injection seeder was a DFB laser having a power of 30mW with a 1MHz oscillation spectrum. Their oscillation wavelength was coarse tuned by temperature and fine tuned by adjusting injection currents. The partial power of the online wavelength was split in the wavelength control unit. We locked the DFB laser as an injection seeder of the online wavelength onto the line center by referencing the fiber coupled multipath gas cell (path length 800mm) containing pure CO2 at a pressure of 700 Torr. Stabilization was estimated to within 1.8MHz rms of the line center of the CO2 absorption line by monitoring the feedback signal of a wavelength-controlled unit. Injection seeding of the PPMgLT OPO was performed by matching the cavity length to the seeder wavelength for each oscillation pulse. The on-line and off-line wavelengths were injected into the OPO cavity through its output mirror. The injection seeder could be automatically switched by applying the TTL trigger to an optical fiber switch. A typical power of 8mW was injected into the cavity. The OPO cavity length was controlled as follows. A slope voltage was applied to the piezoelectric element mounted on the cavity mirror. If the longitudinal mode of the cavity was closed at the wavelength of the injection seeder, the electrical signal monitored by the photodiode would be maximized. The CW laser beam was injected from the output coupler to control the oscillation wavelength. The maximum output energy of 12mJ at 400 Hz was observed at 35mJ of pumping laser energy. The slope efficiency was 43.7%. This output energy and this repetition rate were the highest achieved so far. No damage was observed even after 1 h of operation. Therefore higher-energy operations can be expected with this device if the beam quality of the pumping laser is improved. This work was financially supported by the System Development Program for Advanced Measurement and Analysis by the JST.

Generation of ultrasound in materials using continuous-wave lasers.

PubMed

Caron, James N; DiComo, Gregory P; Nikitin, Sergei

2012-03-01

Generating and detecting ultrasound is a standard method of nondestructive evaluation of materials. Pulsed lasers are used to generate ultrasound remotely in situations that prohibit the use of contact transducers. The scanning rate is limited by the repetition rates of the pulsed lasers, ranging between 10 and 100 Hz for lasers with sufficient pulse widths and energies. Alternately, a high-power continuous-wave laser can be scanned across the surface, creating an ultrasonic wavefront. Since generation is continuous, the scanning rate can be as much as 4 orders of magnitude higher than with pulsed lasers. This paper introduces the concept, comparing the theoretical scanning speed with generation by pulsed laser. © 2012 Optical Society of America

The Tea-Carbon Dioxide Laser as a Means of Generating Ultrasound in Solids

NASA Astrophysics Data System (ADS)

Taylor, Gregory Stuart

1990-01-01

Available from UMI in association with The British Library. Requires signed TDF. The aim of this thesis is to characterise the interaction between pulsed, high power, 10.6 mu m radiation and solids. The work is considered both in the general context of laser generation of ultrasound and specifically to gain a deeper understanding of the interaction between a laser supported plasma and a solid. The predominant experimental tools used are the homodyne Michelson interferometer and a range of electromagnetic acoustic transducers. To complement the ultrasonic data, various plasma inspection techniques, such as high speed, streak camera photography and reflection photometry, have been used to correlate the plasma properties with those of the ultrasonic transients. The work involving the characterisation of a laser supported plasma with a solid, which is based on previous experimental and theoretical analysis, gives an increased understanding of the plasma's ultrasonic generation mechanism. The ability to record the entire plasma-sample interaction, time history yields information of the internal dynamics of the plasma growth and shock wave generation. The interaction of the radiation with a solid is characterised in both the plasma breakdown and non-breakdown regimes by a wide ultrasonic source. The variation in source diameter enables the transition from a point to a near planar ultrasonic source to be studied. The resultant ultrasonic modifications are examined in terms of the wave structure and the directivity pattern. The wave structure is analysed in terms of existing wide source, bulk wave theories and extended to consider the effects on surface and Lamb waves. The directivity patterns of the longitudinal and shear waves are analysed in terms of top-hat and non -uniform source profiles, giving additional information into the radiation-solid interaction. The wide, one dimensional source analysis is continued to a two dimensional, extended ultrasonic source, generated on non-metals by the optical penetration of radiation within the target. The generation of ultrasound in both metals and non-metals, using the CO_2 laser, is shown to be an efficient process and may be employed almost totally non-destructively. Such a laser may therefore be used effectively on a greatly enhanced range of materials than those tested to-date via laser generation, resulting in the increased suitability of the laser technique within the field of Non Destructive Testing.

Pulpotomies with CO2 laser in dogs

NASA Astrophysics Data System (ADS)

Figueiredo, Jose A. P.; Chavantes, Maria C.; Gioso, Marco A.; Pesce, Hildeberto F.; Jatene, Adib D.

1995-05-01

The aim of this study was to evaluate the clinical aspects of dental pulps submitted to shallow pulpotomy followed by CO2 laser radiation at five different procedures. For this purpose, initially 66 dogs' teeth were opened and about 2 or 3 mm of coronal dental pulp was removed. Continuous irrigation with saline solution was implemented. The teeth were randomly divided into 6 groups of 11 each. After cessation of bleeding, in group I, CO2 laser (Xanar-20, USA) was irradiated for 1 second at a power of 5 watts; in group II, 2 seconds at 3 watts; in Group III, 2 seconds at 5 watts; in Group IV, 1 second at 3 watts; in Group V, a continuous mode at 3 watts; Group VI served as a control, with no laser irradiation. The results showed no clinical differences between the 3 W and 5 W powers. Time period of irradiation exposition influenced definitively the clinical appearance of the dental pulps. Groups I and IV (1 second) were unable to stop the bleeding, which persisted over 15 minutes for all teeth. This may be due to the intense heat generated by CO2 laser, causing vasodilatation. Groups II and III displayed a similar appearance, but bleeding stopped in about 10 minutes. Group V (continuous mode) had no bleeding after irradiation, but a plasma-like liquid would come out for almost 2 minutes. When comparing to the control (Group VI), all the pulps would assume a jelly-like aspect, with black granulated tissue on the surface, covering totally the pulps of Group V and partially the other groups. The histological results will be discussed in a further study. From the data obtained, it seems that CO2 laser irradiation for pulpotomies should be done in a continuous mode, for clinical convenience in terms of time taken and effective irradiation.

High power tapered lasers with optimized photonic crystal structure for low divergence and high efficiency

NASA Astrophysics Data System (ADS)

Ma, Xiaolong; Qu, Hongwei; Qi, Aiyi; Zhou, Xuyan; Ma, Pijie; Liu, Anjin; Zheng, Wanhua

2018-04-01

High power tapered lasers are designed and fabricated. A one-dimensional photonic crystal structure in the vertical direction is adopted to narrow the far field divergence. The thickness of the defect layer and the photonic crystal layers are optimized by analyzing the optical field theoretically. For tapered lasers, the continuous-wave power is 7.3 W and the pulsed power is 17 W. A maximum wall-plug efficiency of 46% under continuous-wave operation and 49.3% in pulsed mode are obtained. The beam divergences are around 11° and 6° for the vertical and lateral directions, respectively. High beam qualities are also obtained with a vertical M2 value of 1.78 and a lateral M2 value of 1.62. As the current increases, the lateral M2 value increases gradually while the vertical M2 value remains around 2.

Theoretical evaluation of a continues-wave Ho3+:BaY2F8 laser with mid-infrared emission

NASA Astrophysics Data System (ADS)

Rong, Kepeng; Cai, He; An, Guofei; Han, Juhong; Yu, Hang; Wang, Shunyan; Yu, Qiang; Wu, Peng; Zhang, Wei; Wang, Hongyuan; Wang, You

2018-01-01

In this paper, we build a theoretical model to study a continues-wave (CW) Ho3+:BaY2F8 laser by considering both energy transfer up-conversion (ETU) and cross relaxation (CR) processes. The influences of the pump power, reflectance of an output coupler (OC), and crystal length on the output features are systematically analyzed for an end-pumped configuration, respectively. We also investigate how the processes of ETU and CR in the energy-level system affect the output of a Ho3+:BaY2F8 laser by use of the kinetic evaluation. The simulation results show that the optical-to-optical efficiency can be promoted by adjusting the parameters such as the reflectance of an output coupler, crystal length, and pump power. It has been theoretically demonstrated that the threshold of a Ho3+:BaY2F8 laser is very high for the lasing operation in a CW mode.

High repetition-rate Q-switched and intracavity doubled diode-pumped Nd:YAG laser

NASA Technical Reports Server (NTRS)

Hemmati, Hamid; Lesh, James R.

1992-01-01

A Nd:YAG laser was end pumped with 2.2 W of continuous-wave (CW) diode laser output. Efficient operation of the laser at high repetition rates was emphasized. This laser provides 890 mW of TEM00 CW output at 1064 nm, and 340 mW of 532 nm average power at a Q-switched repetition rate of 25 kHz. Experimental data are compared with analysis.

Single-shot measurement of ultrafast time-varying phase modulation induced by femtosecond laser pulses with arbitrary polarization

NASA Astrophysics Data System (ADS)

Hartinger, Klaus; Bartels, Randy A.

2008-01-01

We demonstrate a single-shot measurement of the transient phase modulation due to field free molecular alignment at the revival times of a rotational wave packet. The wave packet is excited by an arbitrarily polarized ultrashort laser pulse in CO2 at room temperature. With this technique the time dependence along the eigenpolarization directions of the linear susceptibility tensor, i.e., the time dependence of its principle components, can be directly observed with high sensitivity.

Continuous Wave Stimulated Raman Spectroscopy Inside a Hollow Core Photonic Crystal Fiber

NASA Astrophysics Data System (ADS)

Domenech, Jose L.; Cueto, Maite

2013-06-01

Hollow-core photonic crystal fibers (HCPCF) have raised new opportunities to study light-matter interaction. Dielectric or metallic capillaries are intrinsically lossy, making poor light guides. In contrast, HCPCFs can guide light quite efficiently, due to the band-gap effect produced by an array of smaller channels which surrounds a central hollow core with a few μm diameter. The tight confinement of light inside the core, that can be filled with gases, as well as a long interaction length, enhance multiple nonlinear phenomena, making it possible to devise new ways to do low signal level spectroscopy, as is the case of high resolution stimulated Raman spectroscopy (SRS). A. Owyoung demonstrated high resolution continuous wave SRS in 1978. Shortly afterwards, seeking higher sensitivity, he developed the quasi-continuous SRS technique (a high peak power pump laser, interacting with a low power cw probe laser). That variant remains today the best compromise between resolution and sensitivity for gas-phase Raman spectroscopy. In this work, we show the possibility of fully cw stimulated Raman spectroscopy, using a gas cell built around a HCPCF to overcome the limitations posed by the weakness of the stimulated Raman effect when not using pulsed sources. The interaction length (1.2 m), longer than that of a multiple pass refocusing cell, and the narrow diameter of the core (4.8 μm), can compensate for the much lower laser powers used in the cw set-up. The experimental complexity is considerably reduced and the instrumental resolution is at the 10's of MHz level, limited, with our fiber, by transit time effects. At present, we have demonstrated the feasibility of the experiment, a sensitivity enhancement of ˜ 6000 over the single focus regime, and a spectral resolution better than 0.005 wn in the unresolved Q-branch of the ν_1 component of the Fermi dyad of CO_2 at 1388 wn. Other examples of rotationally resolved spectra will be shown: the Q branch of O_2 at 1555 wn, and the 2ν_2 component of the Fermi dyad of CO_2 at 1285 wn. P. St. Russell, Science {299}, 358, 2003. A.Owyoung, C. W. Patterson, R S. McDowell, Chem. Phys. Lett. {59}, 156, 1978

Continuous wave channel waveguide lasers in Nd:LuVO4 fabricated by direct femtosecond laser writing.

PubMed

Ren, Yingying; Dong, Ningning; Macdonald, John; Chen, Feng; Zhang, Huaijin; Kar, Ajoy K

2012-01-30

Buried channel waveguides in Nd:LuVO<4 were fabricated by femtosecond laser writing with the double-line technique. The photoluminescence properties of the bulk materials were found to be well preserved within the waveguide core region. Continuous-wave laser oscillation at 1066.4 nm was observed from the waveguide under ~809 nm optical excitation, with the absorbed pump power at threshold and laser slope efficiency of 98 mW and 14%, respectively.

Progress Toward Measuring CO2 Isotopologue Fluxes in situ with the LLNL Miniature, Laser-based CO2 Sensor

NASA Astrophysics Data System (ADS)

Osuna, J. L.; Bora, M.; Bond, T.

2015-12-01

One method to constrain photosynthesis and respiration independently at the ecosystem scale is to measure the fluxes of CO2­ isotopologues. Instrumentation is currently available to makes these measurements but they are generally costly, large, bench-top instruments. Here, we present progress toward developing a laser-based sensor that can be deployed directly to a canopy to passively measure CO2 isotopologue fluxes. In this study, we perform initial proof-of-concept and sensor characterization tests in the laboratory and in the field to demonstrate performance of the Lawrence Livermore National Laboratory (LLNL) tunable diode laser flux sensor. The results shown herein demonstrate measurement of bulk CO2 as a first step toward achieving flux measurements of CO2 isotopologues. The sensor uses a Vertical Cavity Surface Emitting Laser (VCSEL) in the 2012 nm range. The laser is mounted in a multi-pass White Cell. In order to amplify the absorption signal of CO2 in this range we employ wave modulation spectroscopy, introducing an alternating current (AC) bias component where f is the frequency of modulation on the laser drive current in addition to the direct current (DC) emission scanning component. We observed a strong linear relationship (r2 = 0.998 and r2 = 0.978 at all and low CO2 concentrations, respectively) between the 2f signal and the CO2 concentration in the cell across the range of CO2 concentrations relevant for flux measurements. We use this calibration to interpret CO2 concentration of a gas flowing through the White cell in the laboratory and deployed over a grassy field. We will discuss sensor performance in the lab and in situ as well as address steps toward achieving canopy-deployed, passive measurements of CO2 isotopologue fluxes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675788

Plasma optical modulators for intense lasers

PubMed Central

Yu, Lu-Le; Zhao, Yao; Qian, Lie-Jia; Chen, Min; Weng, Su-Ming; Sheng, Zheng-Ming; Jaroszynski, D. A.; Mori, W. B.; Zhang, Jie

2016-01-01

Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 1016 W cm−2 to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations. PMID:27283369

Enhancing the antibacterial performance of orthopaedic implant materials by fibre laser surface engineering

NASA Astrophysics Data System (ADS)

Chan, Chi-Wai; Carson, Louise; Smith, Graham C.; Morelli, Alessio; Lee, Seunghwan

2017-05-01

Implant failure caused by bacterial infection is extremely difficult to treat and usually requires the removal of the infected components. Despite the severe consequence of bacterial infection, research into bacterial infection of orthopaedic implants is still at an early stage compared to the effort on enhancing osseointegration, wear and corrosion resistance of implant materials. In this study, the effects of laser surface treatment on enhancing the antibacterial properties of commercially pure (CP) Ti (Grade 2), Ti6Al4V (Grade 5) and CoCrMo alloy implant materials were studied and compared for the first time. Laser surface treatment was performed by a continuous wave (CW) fibre laser with a near-infrared wavelength of 1064 nm in a nitrogen-containing environment. Staphylococcus aureus, commonly implicated in infection associated with orthopaedic implants, was used to investigate the antibacterial properties of the laser-treated surfaces. The surface roughness and topography of the laser-treated materials were analysed by a 2D roughness testing and by AFM. The surface morphologies before and after 24 h of bacterial cell culture were captured by SEM, and bacterial viability was determined using live/dead staining. Surface chemistry was analysed by XPS and surface wettability was measured using the sessile drop method. The findings of this study indicated that the laser-treated CP Ti and Ti6Al4V surfaces exhibited a noticeable reduction in bacterial adhesion and possessed a bactericidal effect. Such properties were attributable to the combined effects of reduced hydrophobicity, thicker and stable oxide films and presence of laser-induced nano-features. No similar antibacterial effect was observed in the laser-treated CoCrMo.

Matched Template Signal Processing for Continuous Wave Laser Tracking of Space Debris

NASA Astrophysics Data System (ADS)

Raj, S.; Ward, R.; Roberts, L.; Fleddermann, R.; Francis, S.; McClellend, D.; Shaddock, D.; Smith, C.

2016-09-01

The build up of space junk in Earth's orbit space is a growing concern as it shares the same orbit as many currently active satellites. As the number of objects increase in these orbits, the likelihood of collisions between satellites and debris will increase [1]. The eventual goal is to be able to maneuver space debris to avoid such collisions. We at SERC aim to accomplish this by using ground based laser facilities that are already being used to track space debris orbit. One potential method to maneuver space debris is using continuous wave lasers and applying photon pressure on the debris and attempt to change the orbit. However most current laser ranging facilities operates using pulsed lasers where a pulse of light is sent out and the time taken for the pulse to return back to the telescope is measured after being reflected by the target. If space debris maneuvering is carried out with a continuous wave laser then two laser sources need to be used for ranging and maneuvering. The aim of this research is to develop a laser ranging system that is compatible with the continuous wave laser; using the same laser source to simultaneously track and maneuver space debris. We aim to accomplish this by modulating the outgoing laser light with pseudo random noise (PRN) codes, time tagging the outgoing light, and utilising a matched filter at the receiver end to extract the various orbital information of the debris.

940  mW 1564  nm multi-longitudinal-mode and 440  mW 1537  nm single-longitudinal-mode continuous-wave Er:Yb:Lu2Si2O7 microchip lasers.

PubMed

Huang, Jianhua; Chen, Yujin; Lin, Yanfu; Gong, Xinghong; Luo, Zundu; Huang, Yidong

2018-04-15

An Er:Yb:Lu 2 Si 2 O 7 microchip laser was constructed by placing a 1.2 mm thick, Y-cut Er:Yb:Lu 2 Si 2 O 7 microchip between two 1.2 mm thick sapphire crystals, in which input and output mirrors were directly deposited onto one face of each crystal. End-pumped by a continuous-wave 975.4 nm diode laser, a 1564 nm multi-longitudinal-mode laser with a maximum output power of 940 mW and slope efficiency of 20% was realized at an absorbed pump power of 5.5 W when the transmission of output mirror was 2.2%. When the transmission of the output mirror was increased to 6%, a 1537 nm single-longitudinal-mode laser with a maximum output power of 440 mW and slope efficiency of 12% was realized at an absorbed pump power of 4.3 W. The results indicate that the Er:Yb:Lu 2 Si 2 O 7 crystal is a promising microchip gain medium to realize a single-longitudinal-mode laser.

Femtosecond laser excitation of multiple spin waves and composition dependence of Gilbert damping in full-Heusler Co{sub 2}Fe{sub 1−x}Mn{sub x}Al films

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

Cheng, Chuyuan; Li, Shufa; Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn, E-mail: jhzhao@red.semi.ac.cn

2013-12-02

Spin-wave dynamics in 30 nm thick Co{sub 2}Fe{sub 1−x}Mn{sub x}Al full-Heusler films is investigated using time-resolved magneto-optical polar Kerr spectroscopy under an external field perpendicular to films. Damon-Eshbach (DE) and the first-order perpendicular standing spin-wave (PSSW) modes are observed simultaneously in four samples with x = 0, 0.3, 0.7, and 1. The frequency of DE and PSSW modes does not apparently depend on composition x, but damping of DE mode significantly on x and reaches the minimum as x = 0.7. The efficient coherent excitation of DE spin wave exhibits the promising application of Co{sub 2}Fe{sub 0.3}Mn{sub 0.7}Al films in magnonic devices.

Room-temperature continuous-wave operation in the telecom wavelength range of GaSb-based lasers monolithically grown on Si

NASA Astrophysics Data System (ADS)

Castellano, A.; Cerutti, L.; Rodriguez, J. B.; Narcy, G.; Garreau, A.; Lelarge, F.; Tournié, E.

2017-06-01

We report on electrically pumped GaSb-based laser diodes monolithically grown on Si and operating in a continuous wave (cw) in the telecom wavelength range. The laser structures were grown by molecular-beam epitaxy on 6°-off (001) substrates. The devices were processed in coplanar contact geometry. 100 μm × 1 mm laser diodes exhibited a threshold current density of 1 kA/cm-2 measured under pulsed operation at 20 °C. CW operation was achieved up to 35 °C with 10 μm × 1 mm diodes. The output power at 20 °C was around 3 mW/uncoated facet, and the cw emission wavelength 1.59 μm, in the C/L-band of telecom systems.

Dual-wavelength and efficient continuous-wave operation of a Yb:CaGd0.1Y0.9AlO4 laser

NASA Astrophysics Data System (ADS)

Di, J. Q.; Sai, Q. L.; Sun, X. H.; Xu, X. D.; Kong, L. C.; Xie, G. Q.; Liu, Y. L.; Teng, F.; Zhu, L.

2018-05-01

The spectra and laser properties of single crystalline Yb:CaGd0.1Y0.9AlO4 were investigated for the first time. The peak absorption cross-sections of 4.01 cm2 and 1.39  ×  10‑20 cm2 with full width at half maximum of 17 and 32 nm, and the maximum emission cross-sections of 2.11 and 1.53  ×  10‑20 cm2 were obtained for π and σ polarizations, respectively. The fluorescence decay time was 638 µs. The maximum continuous-wave laser achieved was 1.60 W with a slope efficiency of 23.4% for an a-cut Yb:CaGd0.1Y0.9AlO4 crystal. Dual-wavelength lasers at 1041.7 and 1044.9 nm were also demonstrated. The results show that Yb:CaGd0.1Y0.9AlO4 crystal is a promising ultra-short and dual-wavelength laser medium.

An external-cavity quantum cascade laser operating near 5.2 µm combined with cavity ring-down spectroscopy for multi-component chemical sensing

NASA Astrophysics Data System (ADS)

Dutta Banik, Gourab; Maity, Abhijit; Som, Suman; Pal, Mithun; Pradhan, Manik

2018-04-01

We report on the performance of a widely tunable continuous wave mode-hop-free external-cavity quantum cascade laser operating at λ ~ 5.2 µm combined with cavity ring-down spectroscopy (CRDS) technique for high-resolution molecular spectroscopy. The CRDS system has been utilized for simultaneous and molecule-specific detection of several environmentally and bio-medically important trace molecular species such as nitric oxide, nitrous oxide, carbonyl sulphide and acetylene (C2H2) at ultra-low concentrations by probing numerous rotationally resolved ro-vibrational transitions in the mid-IR spectral region within a relatively small spectral range of ~0.035 cm-1. This continuous wave external-cavity quantum cascade laser-based multi-component CRDS sensor with high sensitivity and molecular specificity promises applications in environmental sensing as well as non-invasive medical diagnosis through human breath analysis.

Laser-based sensor for detection of hazardous gases in the air using waveguide CO2 laser.

PubMed

Gondal, Mohammed A; Bakhtiari, Imran A; Dastageer, Abdul K

2007-06-01

A spectrometer based on the principle of photoacoustic spectroscopy has been developed recently at our laboratory for the detection of hazardous gases such as O3, C2H4, SO2, NO2 and SF6. In most of our earlier works, we employed a mechanical chopper to modulate the laser beam and this chopper modulation has the crucial disadvantage of instability in the chopper frequency. Even a minor shift of about 1 Hz in the modulation frequency could significantly reduce the photoacoustic signal by an order of magnitude at the acoustic resonant mode of the photoacoustic cell. To overcome this problem, we developed a photoacoustic spectrometer where a wave guided CW CO2 laser beam is modulated electronically with the external frequency generator. Our preliminary results show that the electronic modulation of CO2 laser beam improved the sensitivity of our spectrometer by a factor of 6. The parametric dependence of photoacoustic signal on laser power, modulation frequency and trace gas concentration, was investigated and the comparison between the two modulation techniques is presented in this paper for detection of trace gases such as C2H4.

High output power of differently cut Nd:MgO:LiTaO3 CW lasers

NASA Astrophysics Data System (ADS)

Sun, D. H.; Liu, S. D.; Wang, D. Z.; Sang, Y. H.; Kang, X. L.; Liu, H.; Bi, Y.; Yan, B. X.; He, J. L.; Wang, J. Y.

2013-04-01

A high-quality Nd3+ and Mg2+ co-doped LiTaO3 (Nd:MgO:LT) crystal was grown by the Czochralski method. The polarized absorption spectra and fluorescence spectra were studied, and the absorption cross section was calculated by Judd-Ofelt (J-O) theory. The laser performance with different sample cuts of the crystal was investigated for the first time, and it was found that Nd:MgO:LT crystal with different cutting directions (a and c) exhibits different laser properties. By optimizing a partial reflectivity mirror in the laser experimental setting, a high continuous wave output power of 3.58 W was obtained at 1092 and 1076 nm with an optical-to-optical conversion efficiency of 22.78% and slope efficiency of 26.06%. The results indicate that Nd:MgO:LT crystal is a promising candidate for the manufacture of Nd3+ doped periodically poled MgO:LiTaO3 crystal (Nd:PPMgOLT), which should have considerable applications in self-frequency doubling and optical parametric oscillation laser devices.

Numerical simulation of temperature at drilling micro-hole on moving CO2 laser irradiated sticking plaster

NASA Astrophysics Data System (ADS)

Rao, Zhiming; He, Zhifang; Du, Jianqiang; Zhang, Xinyou; Ai, Guoping; Zhang, Chunqiang; Wu, Tao

2012-03-01

This paper applied numerical simulation of temperature by using finite element analysis software Ansys to study a model of drilling on sticking plaster. The continuous CO2 laser doing uniform linear motion and doing uniform circular motion irradiated sticking plaster to vaporize. The sticking plaster material was chosen as the thermal conductivity, the heat capacity and the density. For temperatures above 450 °C, sticking plaster would be vaporized. Based on the mathematical model of heat transfer, the process of drilling sticking plaster by laser beams could be simulated by Ansys. The simulation results showed the distribution of the temperature at the surface of the sticking plaster with the time of vaporizing at CO2 laser to do uniform linear motion and to do uniform circular motion. The temperature of sticking plaster CO2 laser to do uniform linear motion was higher than CO2 laser to do uniform circular motion in the same condition.

Integrated injection-locked semiconductor diode laser

DOEpatents

Hadley, G.R.; Hohimer, J.P.; Owyoung, A.

1991-02-19

A continuous wave integrated injection-locked high-power diode laser array is provided with an on-chip independently-controlled master laser. The integrated injection locked high-power diode laser array is capable of continuous wave lasing in a single near-diffraction limited output beam at single-facet power levels up to 125 mW (250 mW total). Electronic steering of the array emission over an angle of 0.5 degrees is obtained by varying current to the master laser. The master laser injects a laser beam into the slave array by reflection of a rear facet. 18 figures.

Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

NASA Astrophysics Data System (ADS)

Berger, N. K.; Zhukov, E. A.; Novokhatskii, V. V.

1984-04-01

Nonlinear interactions (including wavefront reversal) of light from CW or pulsed 10.6-micron CO2 lasers at the semiconductor-metal phase transition in a VO2 film are investigated experimentally. The results are presented in graphs and characterized in detail. The intensity reflection coefficients of the three-wave interactions are found to be 0.5 percent for a CW reference wave of intensity 900 mW/sq cm and 42 percent for a pulsed reference wave of threshold density 600-800 microjoule/sq cm.

BRIEF COMMUNICATIONS: Dynamics of lasing of two TEA CO2 lasers coupled by a nonlinear SF6 cell

NASA Astrophysics Data System (ADS)

Baranov, V. Yu; Dyad'kin, A. P.; Shpilyun, O. V.

1991-10-01

A study was made of the kinetics of stimulated emission from two TEA CO2 lasers in a system with frequency locking by phase conjugation as a result of a four-wave interaction of light [V. Yu. Baranov, A. P. Dyad'kin, V. V. Likhanskiĭ et al., Sov. J. Quantum Electron. 18, 1462 (1988)]. A simple method for ensuring two-pulse lasing with a variable time delay between the pulses in one gas-discharge chamber was proposed.

Sensitive detection of formaldehyde using an interband cascade laser near 3.6 μm

DOE PAGES

Ren, Wei; Luo, Longqiang; Tittel, Frank K.

2015-12-31

Here, we report the development of a formaldehyde (H 2CO) trace gas sensor using a continuous wave (CW), thermoelectrically-cooled (TEC), distributed-feedback interband cascade laser (DFB-ICL) at 3.6 μm. Wavelength modulation spectroscopy was used to detect the second harmonic spectra of a strong H 2CO absorption feature centered at 2778.5 cm -1 (3599 nm) in its ν 1 fundamental vibrational band. A compact and novel multipass cell (7.6-cm physical length and 32-ml sampling volume) was implemented to achieve an effective optical path length of 3.75 m. A minimum detection limit of 6 parts per billion (ppb) at an optimum gas pressuremore » of 200 Torr was achieved with a 1-s data acquisition time. An Allan-Werle deviation analysis was performed to investigate the long-term stability of the sensor system and a 1.5 ppb minimum detectable concentration could be achieved by averaging up to 140 s. Absorption interference eeffects from atmospheric H 2O (2%) and CH 4(5 ppm) were also analyzed in this work and proved to be insignificant for the current sensor configuration.« less

Sensitive detection of formaldehyde using an interband cascade laser near 3.6 μm

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

Ren, Wei; Luo, Longqiang; Tittel, Frank K.

Here, we report the development of a formaldehyde (H 2CO) trace gas sensor using a continuous wave (CW), thermoelectrically-cooled (TEC), distributed-feedback interband cascade laser (DFB-ICL) at 3.6 μm. Wavelength modulation spectroscopy was used to detect the second harmonic spectra of a strong H 2CO absorption feature centered at 2778.5 cm -1 (3599 nm) in its ν 1 fundamental vibrational band. A compact and novel multipass cell (7.6-cm physical length and 32-ml sampling volume) was implemented to achieve an effective optical path length of 3.75 m. A minimum detection limit of 6 parts per billion (ppb) at an optimum gas pressuremore » of 200 Torr was achieved with a 1-s data acquisition time. An Allan-Werle deviation analysis was performed to investigate the long-term stability of the sensor system and a 1.5 ppb minimum detectable concentration could be achieved by averaging up to 140 s. Absorption interference eeffects from atmospheric H 2O (2%) and CH 4(5 ppm) were also analyzed in this work and proved to be insignificant for the current sensor configuration.« less

Laser welding aluminum without filler metal using continuous wave and pulsed Nd:YAG lasers

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

Bransch, H.N.

1994-12-31

A problem with automotive aluminum tubing applications, particularly for air conditioning heat exchanger assemblies, is terminating the tube reliably and inexpensively. An alternative to upsetting and mchining threads to the tube end is welding a nut (made from a stronger, easily machinable alloy such as Al 5456 or Al 6061) to lengths of tubing (made from a softer alloy such as Al 3003). Laser welding was investigated in order to reduce heat input and increase process speeds copared to brazing or gas metal arc welding (GMAW). Nd:YAG lasers were selected as beam source because of better absorptivity of the wavelengthmore » compared to CO{sub 2} lasers and simplified tooling with fiber optic beam delivery. It wa determined that a pulsed Nd:YAG laser produced 1.0 mm penetration at 0.3 m/min with 400 W average power, and 1.0 mm penetration at 0.75 m/min with 1000 W average power, however, an Al 4047 filler metal was required to eliminate solidification cracking. A 1900 W CW laser could weld the Al 3003 tube to the Al 5456 nut without filler metal, however, there was insufficient penetration (0.25 mm) to meet the mechanical and hermeticity requirements. To enhance penetration, but still reduce the tendency for hot cracking, the 1900 W average power beam was sine wave modulated from 400 W to 3600 W at 250 Hz and usd to weld the Al 3003 directly to the Al 5456. These parameters produced 1.2 mm penetration at 1.2 m/min without significant cracking and without using a filler metal. In addition, the welds passed all hermeticity and tensile strength tests. This combination of materials, joint design, and laser parameters produced tube assemblies that passed a leak check (300 psi nitrogen in 60{degrees}C water for 1 min) and tensile (tube breakage 100 mm from the joint, 5.2 kN tensile strength).« less

Extending laser plasma accelerators into the mid-IR spectral domain with a next-generation ultra-fast CO 2 laser

DOE PAGES

Pogorelsky, I. V.; Babzien, M.; Ben-Zvi, I.; ...

2016-01-20

Here we discuss how expanding the scope of relativistic plasma research to wavelengths longer than λ/≈0.8₋1.1μm covered by conventional mode-locked solid-state lasers would offer attractive opportunities due to the quadratic scaling of the ponderomotive electron energy and critical plasma density with λ. Answering this quest, a next-generation mid-IR laser project is being advanced at the BNL ATF as a part of the user facility upgrade. We discuss the technical approach to this conceptually new 100 TW, 100 fs, λ=9₋11 μm CO 2 laser BESTIA (Brookhaven Experimental Supra-Terawatt Infrared at ATF) that encompasses several innovations applied for the first time tomore » molecular gas lasers. BESTIA will enable new regimes of laser plasma accelerators. One for example is shock-wave ion acceleration from gas jets. We review ongoing efforts to achieve stable, monoenergetic proton acceleration by dynamically shaping the plasma density profile from a hydrogen gas target with laser-produced blast waves. At its full power, 100 TW BESTIA promises to achieve proton beams at energy exceeding 200 MeV. In addition to ion acceleration in over-critical plasma, the ultra-intense mid-IR laser BESTIA will open new opportunities in driving wakefields in tenuous plasmas, expanding the landscape of Laser Wake Field Accelerator (LWFA) studies into unexplored long-wavelength spectral domain. Simple wavelength scaling suggests that a 100-TW CO2 laser beam will be capable to efficiently generate plasma “bubbles” thousand times bigger in volume compared to a near-IR solid state laser of an equivalent power. Combined with a femtosecond electron linac available at the ATF, this wavelength scaling will facilitate study of external seeding and staging of LWFA.« less

QEPAS based ppb-level detection of CO and N2O using a high power CW DFB-QCL.

PubMed

Ma, Yufei; Lewicki, Rafał; Razeghi, Manijeh; Tittel, Frank K

2013-01-14

An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor platform was demonstrated for detection of carbon monoxide (CO) and nitrous oxide (N2O). This sensor used a state-of-the art 4.61 μm high power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at 10°C as the excitation source. For the R(6) CO absorption line, located at 2169.2 cm(-1), a minimum detection limit (MDL) of 1.5 parts per billion by volume (ppbv) at atmospheric pressure was achieved with a 1 sec acquisition time and the addition of 2.6% water vapor concentration in the analyzed gas mixture. For the N2O detection, a MDL of 23 ppbv was obtained at an optimum gas pressure of 100 Torr and with the same water vapor content of 2.6%. In both cases the presence of water vapor increases the detected CO and N2O QEPAS signal levels as a result of enhancing the vibrational-translational relaxation rate of both target gases. Allan deviation analyses were performed to investigate the long term performance of the CO and N2O QEPAS sensor systems. For the optimum data acquisition time of 500 sec a MDL of 340 pptv and 4 ppbv was obtained for CO and N2O detection, respectively. To demonstrate reliable and robust operation of the QEPAS sensor a continuous monitoring of atmospheric CO and N2O concentration levels for a period of 5 hours were performed.

Biological applications and effects of optical masers

NASA Astrophysics Data System (ADS)

Ham, William T., Jr.; Mueller, Harold A.; Williams, Ray C.; Geeraets, Walter J.; Ruffolo, John J., Jr.

1988-02-01

Research experiments and projects pertaining to the ocular hazards of lasers and other optical sources are reviewed and discussed in some detail. Early studies to determine threshold retinal damage in the rabbit from ruby and neodymium lasers are described and followed by more elaborate experiments with monkeys using the He;Ne laser. A comparison between threshold retinal lesions in human volunteers, monkeys and rabbits is given. Retinal damage in the rhesus monkey is evaluated in terms of visual acuity. Quantitative data on solar retinitis as determined in the rhesus monkey are provided and the effects of wavelength on light toxicity are evaluated for eight monochromatic laser lines. Experiments performed at Los Alamos to evaluate the ocular effects and hazards of picosecond and nanosecond pulses of radiation from CO2 and HF lasers are described. A list of published papers describing the above research is included. The HF laser effects on the rabbit cornea were very similar to those caused by exposure to the CO2 laser. The energy from the CO2 and HF lasers is completely absorbed in the superficial layers of the cornea, creating a sharp sonic or shock wave which can disrupt the epithelial cells but does not penetrate to the stroma.

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.

Ablation behaviors of carbon reinforced polymer composites by laser of different operation modes

NASA Astrophysics Data System (ADS)

Wu, Chen-Wu; Wu, Xian-Qian; Huang, Chen-Guang

2015-10-01

Laser ablation mechanism of Carbon Fiber Reinforced Polymer (CFRP) composite is of critical meaning for the laser machining process. The ablation behaviors are investigated on the CFRP laminates subject to continuous wave, long duration pulsed wave and short duration pulsed wave lasers. Distinctive ablation phenomena have been observed and the effects of laser operation modes are discussed. The typical temperature patterns resulted from laser irradiation are computed by finite element analysis and thereby the different ablation mechanisms are interpreted.

Interband cascade lasers with >40% continuous-wave wallplug efficiency at cryogenic temperatures

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

Canedy, C. L.; Kim, C. S.; Merritt, C. D.

2015-09-21

Broad-area 10-stage interband cascade lasers (ICLs) emitting at λ = 3.0–3.2 μm are shown to maintain continuous-wave (cw) wallplug efficiencies exceeding 40% at temperatures up to 125 K, despite having a design optimized for operation at ambient and above. The cw threshold current density at 80 K is only 11 A/cm{sup 2} for a 2 mm cavity with anti-reflection/high-reflection coatings on the two facets. The external differential quantum efficiency for a 1-mm-long cavity with the same coatings is 70% per stage at 80 K, and still above 65% at 150 K. The results demonstrate that at cryogenic temperatures, where free carrier absorption losses are minimized, ICLs can convert electricalmore » to optical energy nearly as efficiently as the best specially designed intersubband-based quantum cascade lasers.« less

Continuous-wave operation of a room-temperature, diode-laser-pumped, 946-nm Nd:YAG laser

NASA Technical Reports Server (NTRS)

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

1987-01-01

Single-stripe diode-laser-pumped operation of a continuous-wave 946-nm Nd:YAG laser with less than 10-mW threshold has been demonstrated. A slope efficiency of 16 percent near threshold was shown with a projected slope efficiency well above a threshold of 34 percent based on results under Rhodamine 6G dye-laser pumping. Nonlinear crystals for second-harmonic generation of this source were evaluated. KNbO3 and periodically poled LiNbO3 appear to be the most promising.

Removal of dogs' gingival pigmentation with CO2 laser

NASA Astrophysics Data System (ADS)

Figueiredo, Jose A. P.; Chavantes, Maria C.; Gioso, Marco A.; Pesce, Hildeberto F.; Jatene, Adib D.

1995-05-01

The aim of this study was to analyze the ability of CO2 laser to remove physiologic pigmentation of gingiva. Dogs were chosen for this study because of their intense black pigmentation on the gingiva, similar to what can be found in human negroes and other dark- skinned races. Three specimens were irradiated at the left side of the buccal aspect of the gingiva, while for comparison the right side was used as a control. CO2 laser in a continuous mode applying 3 watt power was used (Xanar-20, USA). The portion to be irradiated was continuously irrigated with saline solution, to prevent tissue damage from the excessive heat generated. The handpiece device irradiated the target easily and fast, with no bleeding. All the pigmentation could be removed from the portion exposed to the laser beam. A 45th day follow up showed very little repigmentation just in one of the specimens. It could be concluded that CO2 laser irradiation can be an alternative to remove pigmentation of the gingiva for cosmetic purposes. The risk of repigmentation exists, so the patients should be aware of this inconvenience, sometimes demanding further irradiation.

Ambient Seismic Noise Monitoring of Time-lapse Velocity Changes During CO2 Injection at Otway, South Australia

NASA Astrophysics Data System (ADS)

Saygin, E.; Lumley, D. E.

2017-12-01

We use continuous seismic data recorded with an array of 909 buried geophones at Otway, South Australia, to investigate the potential of using ambient seismic noise for time-lapse monitoring of the subsurface. The array was installed prior to a 15,000 ton CO2 injection in 2016-17, in order to detect and monitor the evolution of the injected CO2 plume, and any associated microseismic activity. Continuously recorded data from the vertical components of the geophone array were cross-correlated to retrieve the inter-station Green's functions. The dense collection of Green's functions contains diving body waves and surface Rayleigh waves. Green's Functions were then compared with each other at different time frames including the pre-injection period to track subtle changes in the travel times due to the CO2 injection. Our results show a clear change in the velocities of Green's functions at the start of injection for both body waves and surface waves for wave paths traversing the injection area, whereas the observed changes are much smaller for areas which are far from the injection well.

Slow waves in microchannel metal waveguides and application to particle acceleration

NASA Astrophysics Data System (ADS)

Steinhauer, L. C.; Kimura, W. D.

2003-06-01

Conventional metal-wall waveguides support waveguide modes with phase velocities exceeding the speed of light. However, for infrared frequencies and guide dimensions of a fraction of a millimeter, one of the waveguide modes can have a phase velocity equal to or less than the speed of light. Such a metal microchannel then acts as a slow-wave structure. Furthermore, if it is a transverse magnetic mode, the electric field has a component along the direction of propagation. Therefore, a strong exchange of energy can occur between a beam of charged particles and this slow-waveguide mode. Moreover, the energy exchange can be sustained over a distance limited only by the natural damping of the wave. This makes the microchannel metal waveguide an attractive possibility for high-gradient electron laser acceleration because the wave can be directly energized by a long-wavelength laser. Indeed the frequency of CO2 lasers lies at a fortuitous wavelength that produces a strong laser-particle interaction in a channel of reasonable macroscopic size (e.g., ˜0.6 mm). The dispersion properties including phase velocity and damping for the slow wave are developed. The performance and other issues related to laser accelerator applications are discussed.

Benchtop Energetics Progress

DTIC Science & Technology

2011-07-01

sensitivity. We employ direct laser irradiation, and indirect laser-driven shock, techniques to initiate thin-film explosive samples contained in a...energetic events in a few minutes. 14. ABSTRACT A detonation wave passing through an organic explosive , such as pentaerythritol tetranitrate (PETN...C5H4N4O12), is remarkably efficient in converting the solid explosive into final thermodynamically-stable gaseous products (e.g. N2, CO2, H2O

Theoretical peak performance and optical constraints for the deflection of an S-type asteroid with a continuous wave laser

NASA Astrophysics Data System (ADS)

Thiry, Nicolas; Vasile, Massimiliano

2017-03-01

This paper presents a theoretical model to evaluate the thrust generated by a continuous wave (CW) laser, operating at moderate intensity (<100 GW/m2), ablating an S-type asteroid made of Forsterite. The key metric to assess the performance of the laser system is the thrust coupling coefficient which is given by the ratio between thrust and associated optical power. Three different models are developed in the paper: a one dimensional steady state model, a full 3D steady state model and a one dimensional model accounting for transient effects resulting from the tumbling motion of the asteroid. The results obtained with these models are used to derive key requirements and constraints on the laser system that allow approaching the ideal performance in a realistic case.

High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

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

Centeno, R.; Marchenko, D.; Mandon, J.

We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm{sup −1} (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup −8 }cm{sup −1 }Hz{sup −1/2} was obtained.

Backward-propagating MeV electrons in ultra-intense laser interactions: Standing wave acceleration and coupling to the reflected laser pulse

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

Orban, Chris, E-mail: orban@physics.osu.edu; Feister, Scott; Innovative Scientific Solutions, Inc., Dayton, Ohio 45459

Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense (∼10{sup 18 }W/cm{sup 2}), ∼40 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-in-Cell simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave can “inject” electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standingmore » wave acceleration: a highly relativistic case (a{sub 0} ≥ 1), and a moderately relativistic case (a{sub 0} ∼ 0.5) which operates over a larger fraction of the laser period. In previous studies, other groups have investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this by investigating electron acceleration in the specular (back reflection) direction and over a wide range of intensities (10{sup 17}–10{sup 19 }W cm{sup −2})« less

Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation

NASA Astrophysics Data System (ADS)

Jaschek, Rainer; Konrad, Peter E.; Mayerhofer, Roland; Bergmann, Hans W.; Bickel, Peter G.; Kowalewicz, Roland; Kuttenberger, Alfred; Christiansen, Jens

1995-03-01

The TEA-CO2-laser (transversely excited atmospheric pressure) is a tool for the pulsed processing of materials with peak power densities up to 1010 W/cm2 and a FWHM of 70 ns. The interaction between the laser beam, the surface of the work piece and the surrounding atmosphere as well as gas pressure and the formation of an induced plasma influences the response of the target. It was found that depending on the power density and the atmosphere the response can take two forms. (1) No target modification due to optical break through of the atmosphere and therefore shielding of the target (air pressure above 10 mbar, depending on the material). (2) Processing of materials (air pressure below 10 mbar, depending on the material) with melting of metallic surfaces (power density above 0.5 109 W/cm2), hole formation (power density of 5 109 W/cm2) and shock hardening (power density of 3.5 1010 W/cm2). All those phenomena are usually linked with the occurrence of laser supported combustion waves and laser supported detonation waves, respectively for which the mechanism is still not completely understood. The present paper shows how short time photography and spatial and temporal resolved spectroscopy can be used to better understand the various processes that occur during laser beam interaction. The spectra of titanium and aluminum are observed and correlated with the modification of the target. If the power density is high enough and the gas pressure above a material and gas composition specific threshold, the plasma radiation shows only spectral lines of the background atmosphere. If the gas pressure is below this threshold, a modification of the target surface (melting, evaporation and solid state transformation) with TEA-CO2- laser pulses is possible and the material specific spectra is observed. In some cases spatial and temporal resolved spectroscopy of a plasma allows the calculation of electron temperatures by comparison of two spectral lines.

Fusion welding studies using laser on Ti-SS dissimilar combination

NASA Astrophysics Data System (ADS)

Shanmugarajan, B.; Padmanabham, G.

2012-11-01

Laser welding investigations were carried out on dissimilar Ti-SS combination. The study is aimed to improve the weld strength and ductility by minimizing harmful intermetallics and taking advantage of high cooling rates in laser welding. Results of continuous wave 3.5 kW CO2 laser welding of totally dissimilar combination of Titanium and stainless steel (304) have been discussed. Bead on plate welding experiments were conducted to identify the laser welding parameters using depth of penetration as criteria. The welding of dissimilar combination has been attempted both autogenously and with interlayers such as Vanadium (V) and Tantalum (Ta) in the form of laser cladding as well as strip. Autogenous welds were carried out by varying the laser power, welding speed and position of the laser beam with respect to the joint centre. The resultant welds are characterized by macrostructure analysis, SEM/EDAX and XRD and as welded tensile test in UTM. The autogenous welds have exhibited extensive cracking even when welded at high speeds or by manipulating the beam position with respect to the joint. Similarly Vandaium as interlayer could not achieve crack free joint. A joint with 40 MPa strength could be made with Ta as interlayer. Results and analysis of these variants of laser welded joints are reported and discussed.

Coherent cavity-enhanced dual-comb spectroscopy

PubMed Central

Fleisher, Adam J.; Long, David A.; Reed, Zachary D.; Hodges, Joseph T.; Plusquellic, David F.

2016-01-01

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO2, CO, HDO, and H2O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors. PMID:27409866

High sensitivity detection of NO2 employing cavity ringdown spectroscopy and an external cavity continuously tunable quantum cascade laser.

PubMed

Rao, Gottipaty N; Karpf, Andreas

2010-09-10

A trace gas sensor for the detection of nitrogen dioxide based on cavity ringdown spectroscopy (CRDS) and a continuous wave external cavity tunable quantum cascade laser operating at room temperature has been designed, and its features and performance characteristics are reported. By measuring the ringdown times of the cavity at different concentrations of NO(2), we report a sensitivity of 1.2 ppb for the detection of NO(2) in Zero Air.

2  μm laser oscillation of Ho3+:Tm3+-codoped silica microspheres.

PubMed

Peng, Longxiang; Huang, Yantang; Duan, Yafan; Zhuang, Shijian; Liao, Tingdi; Xu, Canhua

2017-09-10

2 μm laser oscillation with a low threshold has been achieved in Ho 3+ :Tm 3+ -codoped silica microspheres (HTCSMs). Ho 3+ :Tm 3+ -codoped solgel functionalization film is applied to the surface of a silica microsphere, and an optical tapered fiber is adopted to couple an 808 nm continuous-wave laser to serve as the pump light source. Multimode and single-mode laser oscillations around 2 μm within the eye-safe wave band are observed due to the I 7 5→I 8 5 transitions of Ho 3+ ions sensitized by Tm 3+ . The morphology characteristics of microspheres determine the multimode laser oscillation spectrum. The free spectral range is in good accordance with the calculated value based on Mie scattering theory. The HTCSM laser oscillation shows characteristics of good capability, simple process, high flexibility, and low cost.

Catalytic recombination of dissociation products with Pt/SnO2 for rare and common isotope long-life, closed-cycle CO2 lasers

NASA Technical Reports Server (NTRS)

Brown, Kenneth G.; Sidney, B. D.; Schryer, D. R.; Upchurch, B. T.; Miller, I. M.

1986-01-01

This paper reports results on recombination of pulsed CO2 laser dissociation products with Pt/SnO2 catalysts, and supporting studies in a surrogate laboratory catalyst reactor. The closed-cycle, pulsed CO2 laser has been continuously operated for one million pulses with an overall power degradation of less than 5 percent by flowing the laser gas mixture through a 2-percent Pt/SnO2 catalyst bed. In the surrogate laboratory reactor, experiments have been conducted to determine isotopic exchange with the catalyst when using rare-isotope gases. The effects of catalyst pretreatment, sample weight, composition, and temperature on catalyst efficiency have also been determined.

Generation of continuous-wave 194 nm laser for mercury ion optical frequency standard

NASA Astrophysics Data System (ADS)

Zou, Hongxin; Wu, Yue; Chen, Guozhu; Shen, Yong; Liu, Qu; Precision measurement; atomic clock Team

2015-05-01

194 nm continuous-wave (CW) laser is an essential part in mercury ion optical frequency standard. The continuous-wave tunable radiation sources in the deep ultraviolet (DUV) region of the spectrum is also serviceable in high-resolution spectroscopy with many atomic and molecular lines. We introduce a scheme to generate continuous-wave 194 nm radiation with SFM in a Beta Barium Borate (BBO) crystal here. The two source beams are at 718 nm and 266 nm, respectively. Due to the property of BBO, critical phase matching (CPM) is implemented. One bow-tie cavity is used to resonantly enhance the 718 nm beam while the 266 nm makes a single pass, which makes the configuration easy to implement. Considering the walk-off effect in CPM, the cavity mode is designed to be elliptical so that the conversion efficiency can be promoted. Since the 266 nm radiation is generated by a 532 nm laser through SHG in a BBO crystal with a large walk-off angle, the output mode is quite non-Gaussian. To improve mode matching, we shaped the 266 nm beam into Gaussian modes with a cylindrical lens and iris diaphragm. As a result, 2.05 mW 194 nm radiation can be generated. As we know, this is the highest power for 194 nm CW laser using SFM in BBO with just single resonance. The work is supported by the National Natural Science Foundation of China (Grant No. 91436103 and No. 11204374).

Characterization of a Continuous Wave Laser for Resonance Ionization Mass Spectroscopy Analysis in Nuclear Forensics

DTIC Science & Technology

2015-06-01

OF A CONTINUOUS WAVE LASER FOR RESONANCE IONIZATION MASS SPECTROSCOPY ANALYSIS IN NUCLEAR FORENSICS by Sunny G. Lau June 2015 Thesis...IONIZATION MASS SPECTROSCOPY ANALYSIS IN NUCLEAR FORENSICS 5. FUNDING NUMBERS 6. AUTHOR(S) Sunny G. Lau 7. PERFORMING ORGANIZATION NAME(S) AND...200 words) The application of resonance ionization mass spectroscopy (RIMS) to nuclear forensics involves the use of lasers to selectively ionize

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.

Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation.

PubMed

Kim, Namje; Shin, Jaeheon; Sim, Eundeok; Lee, Chul Wook; Yee, Dae-Su; Jeon, Min Yong; Jang, Yudong; Park, Kyung Hyun

2009-08-03

We report on a monolithic dual-mode semiconductor laser operating in the 1550-nm range as a compact optical beat source for tunable continuous-wave (CW) terahertz (THz) generation. It consists of two distributed feedback (DFB) laser sections and one phase section between them. Each wavelength of the two modes can be independently tuned by adjusting currents in micro-heaters which are fabricated on the top of the each DFB section. The continuous tuning of the CW THz emission from Fe(+)-implanted InGaAs photomixers is successfully demonstrated using our dual-mode laser as the excitation source. The CW THz frequency is continuously tuned from 0.17 to 0.49 THz.

Analysis of the Microstructure and Thermal Shock Resistance of Laser Glazed Nanostructured Zirconia TBCs

NASA Astrophysics Data System (ADS)

Chen, Hui; Hao, Yunfei; Wang, Hongying; Tang, Weijie

2010-03-01

Nanostructured zirconia thermal barrier coatings (TBCs) have been prepared by atmospheric plasma spraying using the reconstituted nanosized yttria partially stabilized zirconia powder. Field emission scanning electron microscope was applied to examine the microstructure of the resulting TBCs. The results showed that the TBCs exhibited a unique, complex structure including nonmelted or partially melted nanosized particles and columnar grains. A CO2 continuous wave laser beam has been applied to laser glaze the nanostructured zirconia TBCs. The effect of laser energy density on the microstructure and thermal shock resistance of the as-glazed coatings has been systematically investigated. SEM observation indicated that the microstructure of the as-glazed coatings was very different from the microstructure of the as-sprayed nanostructured TBCs. It changed from single columnar grain to a combination of columnar grains in the fracture surface and equiaxed grains on the surface with increasing laser energy density. Thermal shock resistance tests have showed that laser glazing can double the lifetime of TBCs. The failure of the as-glazed coatings was mainly due to the thermal stress caused by the thermal expansion coefficient mismatch between the ceramic coat and metallic substrate.

Long-term frequency and amplitude stability of a solid-nitrogen-cooled, continuous wave THz quantum cascade laser

NASA Astrophysics Data System (ADS)

Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.

2012-02-01

Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.

Microwave tunable laser source: A stable, precision tunable heterodyne local oscillator

NASA Technical Reports Server (NTRS)

Sachse, G. W.

1980-01-01

The development and capabilities of a tunable laser source utilizing a wideband electro-optic modulator and a CO2 laser are described. The precision tunability and high stability of the device are demonstrated with examples of laboratory spectroscopy. Heterodyne measurements are also presented to demonstrate the performance of the laser source as a heterodyne local oscillator. With the use of five CO2 isotope lasers and the 8 to 18 GHz sideband offset tunability of the modulator, calculations indicate that 50 percent spectral coverage in the 9 to 12 micron region is achievable. The wavelength accuracy and stability of this laser source is limited by the CO2 laser and is more than adequate for the measurement of narrow Doppler-broadened line profiles. The room-temperature operating capability and the programmability of the microwave tunable laser source are attractive features for its in-the-field implementation. Although heterodyne measurements indicated some S/N degradation when using the device as a local oscillator, there does not appear to be any fundamental limitation to the heterodyne efficiency of this laser source. Through the use of a lower noise-figure traveling wave tube amplifier and optical matching of the output beam with the photomixer, a substantial increase in the heterodyne S/N is expected.

Optical trapping of nanoparticles by ultrashort laser pulses.

PubMed

Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

2013-01-01

Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field.

Wavelength modulation spectroscopy near 5 μm for carbon monoxide sensing in a high-pressure kerosene-fueled liquid rocket combustor

NASA Astrophysics Data System (ADS)

Lee, Daniel D.; Bendana, Fabio A.; Schumaker, S. Alexander; Spearrin, R. Mitchell

2018-05-01

A laser absorption sensor was developed for carbon monoxide (CO) sensing in high-pressure, fuel-rich combustion gases associated with the internal conditions of hydrocarbon-fueled liquid bipropellant rockets. An absorption feature near 4.98 μm, comprised primarily of two rovibrational lines from the P-branch of the fundamental band, was selected to minimize temperature sensitivity and spectral interference with other combustion gas species at the extreme temperatures (> 3000 K) and pressures (> 50 atm) in the combustion chamber environment. A scanned wavelength modulation spectroscopy technique (1 f-normalized 2 f detection) is utilized to infer species concentration from CO absorption, and mitigate the influence of non-absorption transmission losses and noise associated with the harsh sooting combustor environment. To implement the sensing strategy, a continuous-wave distributed-feedback (DFB) quantum cascade laser (QCL) was coupled to a hollow-core optical fiber for remote mid-infrared light delivery to the test article, with high-bandwidth light detection by a direct-mounted photovoltaic detector. The method was demonstrated to measure time-resolved CO mole fraction over a range of oxidizer-to-fuel ratios and pressures (20-70 atm) in a single-element-injector RP-2-GOx rocket combustor.

315mJ, 2-micrometers Double-Pulsed Coherent Differential Absorption Lidar Transmitter for Atmospheric CO2 Sensing

NASA Technical Reports Server (NTRS)

Yu, Jirong; Trieu, Bo; Bai, Yingxin; Koch, Grady; Chen, Songsheng; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

The design of a double pulsed, injection seeded, 2-micrometer compact coherent Differential absorption Lidar (DIAL) transmitter for CO2 sensing is presented. This system is hardened for ground and airborne applications. The design architecture includes three continuous wave lasers which provide controlled on and off line seeding, injection seeded power oscillator and a single amplifier operating in double pass configuration. As the derivative a coherent Doppler wind lidar, this instrument has the added benefit of providing wind information. The active laser material used for this application is a Ho: Tm:YLF crystal operates at the eye-safe wavelength. The 3-meter long folded ring resonator produces energy of 130-mJ (90/40) with a temporal pulse length around 220 nanoseconds and 530 nanosecond pulses for on and off lines respectively. The separation between the two pulses is on the order of 200 microseconds. The line width is in the order of 2.5MHz and the beam quality has an M(sup 2) of 1.1 times diffraction limited beam. A final output energy for a pair of both on and off pulses as high as 315 mJ (190/125) at a repetition rate of 10 Hz is achieved. The operating temperature is set around 20 C for the pump diode lasers and 10 C for the rod. Since the laser design has to meet high-energy as well as high beam quality requirements, close attention is paid to the laser head design to avoid thermal distortion in the rod. A side-pumped configuration is used and heat is removed uniformly by passing coolant through a tube slightly larger than the rod to reduce thermal gradient. This paper also discusses the advantage of using a long upper laser level life time laser crystal for DIAL application. In addition issues related to injection seeding with two different frequencies to achieve a transform limited line width will be presented.

Progress in high-power continuous-wave quantum cascade lasers [Invited].

PubMed

Figueiredo, Pedro; Suttinger, Matthew; Go, Rowel; Tsvid, Eugene; Patel, C Kumar N; Lyakh, Arkadiy

2017-11-01

Multi-watt continuous-wave room temperature operation with efficiency exceeding 10% has been demonstrated for quantum cascade lasers essentially in the entire mid-wave and long-wave infrared spectral regions. Along with interband cascade lasers, these devices are the only room-temperature lasers that directly convert electrical power into mid- and long-infrared optical power. In this paper, we review the progress in high-power quantum cascade lasers made over the last 10 years. Specifically, an overview of the most important active region, waveguide, and thermal design techniques is presented, and various aspects of die packaging for high-power applications are discussed. Prospects of power scaling with lateral device dimensions for reaching optical power level in the range from 10 W to 20 W are also analyzed. Finally, coherent and spectral beam-combining techniques for very high-power infrared platforms are discussed.

Contact diode laser: high power application through fiberoptic cutting tips.

PubMed

Wafapoor, H; Peyman, G A; Moritera, T

1994-01-01

Diode laser energy has been applied through a fiberoptic probe using a power setting of 2.5 watts (W) in the continuous mode. In this study we employed high-power diode laser energy (4 to 12 W, continuous wave) to incise ocular tissue through a fiberoptic probe using 100 microns and 300 microns tips. The retina was photocoagulated with a 300 microns orb tip. No bleeding occurred at the incision sites. Histologic evaluation revealed coagulation into the healthy tissue ranging from 10 to 50 microns.

Continuous-wave operation of InAsSb/InP quantum - dot lasers near 2 (mu)m at room temperature

NASA Technical Reports Server (NTRS)

Qiu, Yueming; Uhl, David; Keo, Sam

2004-01-01

InAsSb quantum-dot lasers near 2 pm were demonstrated in cw operation at room temperature with a threshold current density of below 1 kA/cm, output power of 3 mW/facet and a differential quantum efficiency of 13%.

First field determination of the 13C/12C isotope ratio in volcanic CO2 by diode-laser.

PubMed

Castrillo, A; Casa, G; van Burgel, M; Tedesco, D; Gianfrani, L

2004-12-27

Carbon isotope ratio analysis using a laser-based technique has been performed in the field, on the gaseous emissions from an active volcano. We here describe that 13CO2/12CO2 determinations can be carried out in a quasi-continuous regime using a compact, selective and sensitive diode laser spectrometer at a wavelength of 2 mum. Within the Solfatara crater (near Naples, Italy), in a very harsh environment, we were able to determine relative 13CO2/12CO2 values, on the highest flux fumarole, with an accuracy of 0.5 per thousand. Regular and frequent observations of the carbon isotopes in volcanic gases, which become possible with our methodology, are of the utmost importance for geochemical surveillance of volcanoes.

Ignition characteristics of the nickel-based alloy UNS N07001 in pressurized oxygen

NASA Technical Reports Server (NTRS)

Bransford, J. W.; Billiard, P. A.

1990-01-01

The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel-based alloy UNS N07001. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to combustion from temperatures below the solidus temperature. In addition, the alloy had a tendency to develop combustion zones (hot spots) at high oxygen pressures when the incremental (step) heating test mode was used. Unique points on the temperature-time curves that describe certain events are defined and the temperatures at which these events occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

Mass Spectrometry of the CO2 Laser Plasma.

DTIC Science & Technology

1981-06-01

Lasers Plasma Chemistry Discharge Electrochemistry 20. ABSTRACT (Continue on reverse side If necessary end identify by block number) ... The neutral and...Reference 3). The evidence indicates that valuable information concerning the plasma chemistry of the discharge can be obtained with the aid of a mass...gives very reliable results as will be shown later. The ultimate goal of this project was to investigate the plasma chemistry of the CO2 laser discharge

CO2 laser laparoscopic surgery. Adhesiolysis, salpingostomy, laser uterine nerve ablation and tubal pregnancy.

PubMed

Donnez, J; Nisolle, M

1989-09-01

Used endoscopically, the CO2 laser offers some advantages over other operative techniques for endometriosis and adhesions but, in spite of the continuing development of new instrumentation there are still problems with the system. The technique needs specialized equipment requiring ongoing biomedical maintenance and specialized technical care in the operating room. Some problems such as the intraperitoneal accumulation of smoke, gas leakage, and difficulty with maintenance of proper beam alignment still occur. In spite of these problems the advantages are numerous: the system allows precise bloodless destruction of diseased tissue and eliminates the risks of cautery. In the hands of an experienced laparoscopist, it appears safe and effective in vaporization of endometriotic lesions, utero-sacral neurectomy, adhesiolysis and salpingostomy. The judicious use of these techniques, combined with carefully planned further investigations by well-trained and experienced laparoscopists and continuing improvements in the delivery systems, will soon reveal the true efficacy of the CO2 laser laparoscope. If studies continue to show pregnancy rates and pain relief to be equivalent to those patients treated by laparotomy, CO2 laser laparoscopy will become the preferred procedure for the management of pelvic endometriosis and its associated adhesions, distal tubal occlusion, pelvic pain and tubal pregnancy. With the exception of using the argon laser to treat endometriosis, the selective absorption characteristic of lasers has not been greatly utilized. While the CO2 laser is heavily absorbed by water and hence vaporizes most cells in a rather indiscriminate fashion, this is not true for other wavelengths, such as argon, Nd-YAG, KTP, krypton, xenon, copper and gold vapour lasers. The energy form of each of these lasers has different properties of penetration, absorption, reflection and heat dissipation. Many of these lasers have not yet been evaluated in human subjects. An exciting, although not new, area of possible laser application involves the use of photosensitizers and fluorescing agents (Dougherty et al, 1978). Some recent experimental studies (Schellhas and Schneider, 1986; Schneider et al, 1988) may lead to new therapeutic possibilities. The surgical laser is not, however, a panacea. Only controlled trials carried out carefully over the next few years will clearly define its potential. In the meantime it is incumbent upon all of us to investigate the clinical, gynaecological and surgical applications in a careful, methodical and scientific manner.

Research on influence of parasitic resistance of InGaAs solar cells under continuous wave laser irradiation

NASA Astrophysics Data System (ADS)

Li, Guangji; Zhang, Hongchao; Zhou, Guanglong; Lu, Jian; Zhou, Dayong

2017-06-01

InGaAs solar cells were irradiated by 1060-1080nm continuous wave (CW) laser, and studied the laser-electrical conversion and damage experiment with the power density as 97mW/cm2 and 507W/cm2 respectively. The result indicated that there is no obvious damage phenomenon but air layer appeared in the damaged region, and there is no direct relationship between the area and the extent of damage. Moreover, the p-n junction in the damage zone was destroyed, lost the ability of photoelectric conversion. The region acts as a resistance between the two electrodes, resulting in an increase in the leakage current of the solar cells and a decrease in the parallel resistance, which is the main reason leading to the decline of open circuit voltage, short circuit current and conversion efficiency. This paper would provide a reference for wireless energy transmission and the subsequent laser damage of solar cells.

Continuous-wave lasing in an organic-inorganic lead halide perovskite semiconductor

NASA Astrophysics Data System (ADS)

Jia, Yufei; Kerner, Ross A.; Grede, Alex J.; Rand, Barry P.; Giebink, Noel C.

2017-12-01

Hybrid organic-inorganic perovskites have emerged as promising gain media for tunable, solution-processed semiconductor lasers. However, continuous-wave operation has not been achieved so far1-3. Here, we demonstrate that optically pumped continuous-wave lasing can be sustained above threshold excitation intensities of 17 kW cm-2 for over an hour in methylammonium lead iodide (MAPbI3) distributed feedback lasers that are maintained below the MAPbI3 tetragonal-to-orthorhombic phase transition temperature of T ≈ 160 K. In contrast with the lasing death phenomenon that occurs for pure tetragonal-phase MAPbI3 at T > 160 K (ref. 4), we find that continuous-wave gain becomes possible at T ≈ 100 K from tetragonal-phase inclusions that are photogenerated by the pump within the normally existing, larger-bandgap orthorhombic host matrix. In this mixed-phase system, the tetragonal inclusions function as carrier recombination sinks that reduce the transparency threshold, in loose analogy to inorganic semiconductor quantum wells, and may serve as a model for engineering improved perovskite gain media.

Continuous wave power scaling in high power broad area quantum cascade lasers

NASA Astrophysics Data System (ADS)

Suttinger, M.; Leshin, J.; Go, R.; Figueiredo, P.; Shu, H.; Lyakh, A.

2018-02-01

Experimental and model results for high power broad area quantum cascade lasers are presented. Continuous wave power scaling from 1.62 W to 2.34 W has been experimentally demonstrated for 3.15 mm-long, high reflection-coated 5.6 μm quantum cascade lasers with 15 stage active region for active region width increased from 10 μm to 20 μm. A semi-empirical model for broad area devices operating in continuous wave mode is presented. The model uses measured pulsed transparency current, injection efficiency, waveguide losses, and differential gain as input parameters. It also takes into account active region self-heating and sub-linearity of pulsed power vs current laser characteristic. The model predicts that an 11% improvement in maximum CW power and increased wall plug efficiency can be achieved from 3.15 mm x 25 μm devices with 21 stages of the same design but half doping in the active region. For a 16-stage design with a reduced stage thickness of 300Å, pulsed roll-over current density of 6 kA/cm2 , and InGaAs waveguide layers; optical power increase of 41% is projected. Finally, the model projects that power level can be increased to 4.5 W from 3.15 mm × 31 μm devices with the baseline configuration with T0 increased from 140 K for the present design to 250 K.

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

Dong, Lei; Yu, Yajun; Li, Chunguang

A ppb-level formaldehyde (H 2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H 2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variancemore » analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. Finally, a side-by-side comparison between two measurement schemes is also discussed in detail.« less

Thermal Mechanical Stability of Single-Crystal-Oxide Refractive Concentrators Evaluated for High-Temperature Solar-Thermal Propulsion

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Recently, refractive secondary solar concentrator systems were developed for solar thermal power and propulsion (ref. 1). Single-crystal oxides-such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO), and sapphire (Al2O3)-are candidate refractive secondary concentrator materials. However, the refractive concentrator system will experience high-temperature thermal cycling in the solar thermal engine during the sun/shade transition of a space mission. The thermal mechanical reliability of these components in severe thermal environments is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions. In this research at the NASA Lewis Research Center, a controlled heat flux test approach was developed for investigating the thermal mechanical stability of the candidate oxide. This approach used a 3.0-kW continuous-wave (wavelength, 10.6 mm) carbon dioxide (CO2) laser (ref. 2). The CO2 laser is especially well-suited for single-crystal thermal shock tests because it can directly deliver well-characterized heat energy to the oxide surfaces. Since the oxides are opaque at the 10.6-mm wavelength of the laser beam, the light energy is absorbed at the surfaces rather than transmitting into the crystals, and thus generates the required temperature gradients within the specimens. The following figure is a schematic diagram of the test rig.

GreenLITE: a new laser-based tool for near-real-time monitoring and mapping of CO2 and CH4 concentrations on scales from 0.04-25 km2

NASA Astrophysics Data System (ADS)

Dobler, Jeremy T.; Pernini, Timothy G.; Blume, Nathan; Zaccheo, T. Scott; Braun, Michael

2017-08-01

In 2013, Harris and Atmospheric and Environmental Research developed the greenhouse gas laser imaging tomography experiment (GreenLITE™) under a cooperative agreement with the National Energy Technology Laboratory of the Department of Energy. The system uses a pair of high-precision, intensity-modulated, continuous-wave (IMCW) transceivers and a series of retroreflectors to generate overlapping atmospheric density measurements from absorption of a particular greenhouse gas (e.g. CO2 or CH4), to provide an estimate of the two-dimensional spatial distribution of the gas within the area of interest. The system can take measurements over areas ranging from approximately 0.04 square kilometers (km2) to 25 km2 ( 200 meters (m) × 200 m, up to 5 km × 5 km). Multiple GreenLITE™ CO2 demonstrations have been carried out to date, including a full year, November 04, 2015 through November 14, 2016, deployment over a 25 km2 area of downtown Paris, France. In late 2016, the GreenLITE™ system was converted to provide similar measurements for CH4. Recent experiments showed that GreenLITE™ CH4 concentration readings correlated with an insitu instrument, calibrated with World Meteorological Organization traceable gas purchased from the NOAA Earth Systems Research Laboratory, to within approximately 0.5% of CH4 background or 10-15 parts per billion. Several experiments are planned in 2017 to further evaluate the accuracy of the CH4 and CO2 retrieved concentration values compared to the calibrated in situ instrument and to demonstrate the feasibility of GreenLITE™ for environmental and safety monitoring of CO2 and CH4 in industrial applications.

Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

PubMed Central

Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

2016-01-01

Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency. PMID:27194181

Oxidation-Based Continuous Laser Writing in Vertical Nano-Crystalline Graphite Thin Films

NASA Astrophysics Data System (ADS)

Loisel, Loïc; Florea, Ileana; Cojocaru, Costel-Sorin; Tay, Beng Kang; Lebental, Bérengère

2016-05-01

Nano and femtosecond laser writing are becoming very popular techniques for patterning carbon-based materials, as they are single-step processes enabling the drawing of complex shapes without photoresist. However, pulsed laser writing requires costly laser sources and is known to cause damages to the surrounding material. By comparison, continuous-wave lasers are cheap, stable and provide energy at a more moderate rate. Here, we show that a continuous-wave laser may be used to pattern vertical nano-crystalline graphite thin films with very few macroscale defects. Moreover, a spatially resolved study of the impact of the annealing to the crystalline structure and to the oxygen ingress in the film is provided: amorphization, matter removal and high oxygen content at the center of the beam; sp2 clustering and low oxygen content at its periphery. These data strongly suggest that amorphization and matter removal are controlled by carbon oxidation. The simultaneous occurrence of oxidation and amorphization results in a unique evolution of the Raman spectra as a function of annealing time, with a decrease of the I(D)/I(G) values but an upshift of the G peak frequency.

Compact and efficient CW 473nm blue laser with LBO intracavity frequency doubling

NASA Astrophysics Data System (ADS)

Qi, Yan; Wang, Yu; Wang, Yanwei; Zhang, Jing; Yan, Boxia

2016-10-01

With diode end pumped Nd:YAG directly and LBO intracavity frequency doubling, a compact, high efficient continuous wave blue laser at 473nm is realized. When the incident pump power reach 6.2W, 630mW maximum output power of blue laser at 473nm is achieved with 15mm long LBO, the optical-to-optical conversion efficiency is as high as 10.2%.

CW lasing of Ho in KLu(WO4)2 in-band pumped by a diode-pumped Tm:KLu(WO4)2 laser.

PubMed

Mateos, Xavier; Jambunathan, Venkatesan; Pujol, Maria Cinta; Carvajal, Joan Josep; Díaz, Francesc; Aguiló, Magdalena; Griebner, Uwe; Petrov, Valentin

2010-09-27

We demonstrate continuous wave (CW) room temperature laser operation of the monoclinic Ho(3+)-doped KLu(WO(4))(2) crystal using a diode-pumped Tm(3+):KLu(WO(4))(2) laser for in-band pumping. The slope efficiency achieved amounts to ~55% with respect to the absorbed power and the maximum output power of 648 mW is generated at 2078 nm.

Microstructures and properties of ceramic particle-reinforced metal matrix composite layers produced by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Qingmao; He, Jingjiang; Liu, Wenjin; Zhong, Minlin

2005-01-01

Different weight ratio of titanium, zirconium, WC and Fe-based alloy powders were mixed, and cladded onto a medium carbon steel substrate using a 3kW continuous wave CO2 laser, aiming at producing Ceramic particles- reinforced metal matrix composites (MMCs) layers. The microstructures of the layers are typical hypoeutectic, and the major phases are Ni3Si2, TiSi2, Fe3C, FeNi, MC, Fe7Mo3, Fe3B, γ(residual austenite) and M(martensite). The microstructure morphologies of MMCs layers are dendrites/cells. The MC-type reinforcements are in situ synthesis Carbides which main compositions consist of transition elements Zr, Ti, W. The MC-type particles distributed within dendrite and interdendritic regions with different volume fractions for single and overlapping clad layers. The MMCs layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The addition ratio of WC in the mixtures has the remarkable effect on the microhardness of clad layers.

Multipass pumped Nd-based thin-disk lasers: continuous-wave laser operation at 1.06 and 0.9 {mu}m with intracavity frequency doubling

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

Pavel, Nicolaie; Luenstedt, Kai; Petermann, Klaus

2007-12-01

The laser performances of the 1.06 {mu}m 4F3/2 --> 4I11/2 four-level transition and of the 0.9 {mu}m 4F3/2 --> I9/24 quasi-three-level transition were investigated using multipass pumped Nd-based media in thin-disk geometry. When pumping at 0.81 {mu}m into the 4F5/2 level, continuous-wave laser operation was obtained with powers in excess of 10 W at 1.06 {mu}m, in the multiwatt region at 0.91 {mu}m in Nd:YVO4 and Nd:GdVO4, and at 0.95 {mu}m in Nd:YAG. Intracavity frequency-doubled Nd:YVO4 thin-disk lasers with output powers of 6.4 W at 532 nm and of 1.6 W at 457 nm were realized at this pumping wavelength.more » The pumping at 0.88 {mu}m, which is directed into the 4F3/2 emitting level, was also employed, and Nd:YVO4 and Nd:GdVO4 thin-disk lasers with {approx}9 W output power at 1.06 {mu}m and visible laser radiation at 0.53 {mu}m with output power in excess of 4 W were realized. Frequency-doubled Nd:vanadate thin-disk lasers with deep blue emission at 0.46 {mu}m were obtained under pumping directly into the 4F3/2 emitting level.« less

Rapid fibrin plug formation within cutaneous ablative fractional CO2 laser lesions.

PubMed

Kositratna, Garuna; Evers, Michael; Sajjadi, Amir; Manstein, Dieter

2016-02-01

Ablative fractional laser procedures have been shown to facilitate topical drug delivery into the skin. Past studies have mainly used ex vivo models to demonstrate enhanced drug delivery and in vivo studies have investigated laser created channels over a time course of days and weeks rather than within the first few minutes and hours after exposures. We have noticed rapid in vivo fibrin plug formation within ablative fractional laser lesions impairing passage through the laser created channels. In vivo laser exposures were performed in a porcine model. A fractional CO2 laser (AcuPulse™ system, AcuScan 120™ handpiece, Lumenis, Inc., Yokneam, Israel) was programmed in quasi-continuous wave (QCW) mode, at 40W, 50 mJ per pulse, 5% coverage, nominal 120 µm spot size, 8 × 8 mm square pattern, 169 MTZs per scan. Six millimeters punch biopsies were procured at 0, 2, 5, 10, 15, 30, 60, 90 minutes after completion of each scan, then fixed in 10% formalin. 12 repeats were performed of each time point. Skin samples were processed for serial vertically cut paraffin sections (5 μm collected every 25 μm) then H&E and special immunohistochemistry staining for fibrin and platelet. Dimensions of Microscopic Treatment Zones (MTZs) and extent of fibrin plug were assessed and quantified histologically. Ex vivo laser exposures of the identical laser parameter were performed on porcine and human skin at different storage conditions. Histology procured at various predetermined time intervals after in vivo fractional CO2 laser exposures revealed a rapidly forming fibrin plug initiating at the bottom of the MTZ lesions. At longer time intervals, the fibrin plug was extending towards the superficial sections. Within the first 5 minutes, more than 25% length of the entire laser-ablated channel was filled with a fibrin plug. With increased time intervals, the cavity was progressively filled with a fibrin plug. At 90 minutes, more than 90% length of the entire laser-ablated channel was occluded. Ex vivo exposures failed to produce any significant fibrin plug formation. The current study has demonstrated rapid fibrin plug formation after ablative fractional laser procedures. It was shown that the passage through laser created pathways is critically time dependent for in vivo exposures. In contrast, ex vivo exposures do not exhibit such time dependent passage capacity. In particular, drug, substance, and cell delivery studies for ablative fractional laser treatments should take early fibrin plug formation into consideration and further investigate the impact on transdermal delivery. © 2015 Wiley Periodicals, Inc.

Shock wave loading of a magnetic guide

NASA Astrophysics Data System (ADS)

Kindt, L.

2011-10-01

The atom laser has long been a holy grail within atom physics and with the creation of an atom laser we hope to bring a similar revolution in to the field of atom optics. With the creation of the Bose-Einstein Condensate (BEC) in 1995 the path to an atom laser was initiated. An atom laser is continues source of BEC. In a Bose condensate all the atoms occupy the same quantum state and can be described by the same wave function and phase. With an atom laser the De Broglie wavelength of atoms can be much smaller than the wavelength of light. Due to the ultimate control over the atoms the atom laser is very interesting for atom optics, lithography, metrology, etching and deposition of atoms on a surface. All previous atom lasers have been created from atoms coupled out from an existing Bose-Einstein Condensate. There are different approaches but common to them all is that the duration of the output of the atom laser is limited by the size of the initial BEC and they all have a low flux. This leaves the quest to build a continuous high flux atom laser. An alternative approach to a continuous BEC beam is to channel a continuous ultra cold atomic beam into a magnetic guide and then cool this beam down to degeneracy. Cooling down a continuous beam of atoms faces three large problems: The collision rate has to be large enough for effective rethermalization, since evaporative cooling in 2D is not as effective as in 3D and a large thermal conductivity due to atoms with a high angular momentum causes heating downstream in the guide. We have built a 4 meter magnetic guide that is placed on a downward slope with a magnetic barrier in the end. In the guide we load packets of ultra cold rubidium atoms with a frequency rate large enough for the packets to merge together to form a continuous atomic beam. The atomic beam is supersonic and when the beam reaches the end barrier it will return and collide with itself. The collisions lowers the velocity of the beam into subsonic velocities and a shock wave is created between the two velocity regions. In order to conserve number of particle, momentum and enthalpy the density of the atomic beam passing through the shock wave must increase. We have build such a shock wave in an atomic beam and observed the density increase due to this. As an extra feature having a subsonic beam on a downward slope adds an extra density increase due to gravitational compression. Loading ultra cold atoms into a 3D trap from the dense subsonic beam overcomes the problem with 2D cooling and thermal conductivity. This was done and evaporative cooling was applied creating an unprecedented large number rubidium BEC.

Continuous two-wave lasing in microchip Nd : YAG lasers

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

Ievlev, Ivan V; Koryukin, Igor' V; Lebedeva, Yu S

2011-08-31

Simultaneous two-wave lasing was obtained in microchip end-pumped Nd:YAG lasers at the wavelengths of 1061.5 and 1064.17 nm at room temperature. Laser wave intensities were studied as functions of crystal temperature and pump power. The ranges of parameters were determined in which the two-wave lasing occurs and the reasons for such lasing were established. A model is suggested, which adequately describes the experimental results obtained. (control of radiation parameters)

Continuous-wave to pulse regimes for a family of passively mode-locked lasers with saturable nonlinearity

NASA Astrophysics Data System (ADS)

Dikandé, Alain M.; Voma Titafan, J.; Essimbi, B. Z.

2017-10-01

The transition dynamics from continuous-wave to pulse regimes of operation for a generic model of passively mode-locked lasers with saturable absorbers, characterized by an active medium with non-Kerr nonlinearity, are investigated analytically and numerically. The system is described by a complex Ginzburg-Landau equation with a general m:n saturable nonlinearity (i.e {I}m/{(1+{{Γ }}I)}n, where I is the field intensity and m and n are two positive numbers), coupled to a two-level gain equation. An analysis of stability of continuous waves, following the modulational instability approach, provides a global picture of the self-starting dynamics in the system. The analysis reveals two distinct routes depending on values of the couple (m, n), and on the dispersion regime: in the normal dispersion regime, when m = 2 and n is arbitrary, the self-starting requires positive values of the fast saturable absorber and nonlinearity coefficients, but negative values of these two parameters for the family with m = 0. However, when the spectral filter is negative, the laser can self-start for certain values of the input field and the nonlinearity saturation coefficient Γ. The present work provides a general map for the self-starting mechanisms of rare-earth doped figure-eight fiber lasers, as well as Kerr-lens mode-locked solid-state lasers.

Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

NASA Technical Reports Server (NTRS)

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

1992-01-01

Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

Surface treatment of dental porcelain: CO2 laser as an alternative to oven glaze.

PubMed

Sgura, Ricardo; Reis, Mariana Cavalcante; Hernandes, Antonio Carlos; de Abreu Fantini, Márcia Carvalho; Andreeta, Marcello Rubens Barsi; Medeiros, Igor Studart

2015-02-01

This work tested continuous CO2 laser as a surface treatment to dental porcelain and compared it to oven glaze (auto-glaze) by means of roughness and color parameters. Three commercial veneering porcelains with different crystalline content were tested: VM7, VM9, and VM13. Porcelain discs (3.5 × 2.0 mm, diameter × height) were sintered and had one side ground by a diamond bur (45 μm) simulating a chairside adjustment in a clinical office. Specimens (n = 7) were divided into the following groups: C--control (no treatment), G--auto-glaze (oven), and L--surface continuous irradiation with CO2 laser (Gem Laser, Coherent; λ = 10.6 μm). Laser was tested in three exposure times (3, 4, or 5 min) and two irradiances (45 and 50 W/cm(2)). Roughness parameters (Ra, Rz, and Rpm/Rz) were measured using a rugosimeter (Surftest 301, Mitutoyo). Color differences (ΔE) between the G and L groups were calculated (VITA Easyshade); ΔE values up to 3.3 were considered as not perceivable. A surface analysis was conducted by stereomicroscopy (Olympus SZ61) and SEM (Stereoscan 440, LEO). Crystalline content of specimens from groups C and L (50 W/cm(2), 5 min) was assessed by X-ray diffraction and then compared. Surface roughness (Ra and Rz) observed for laser-irradiated groups was similar to G for all studied porcelains. Rpm/Rz ratios were near 1.0 for all groups that indicated a sharp ridge profile for all specimens. Only one laser condition studied (50 W/cm(2), 3 min) from VM7 porcelain resulted in color difference (ΔE = 3.5) to G. Specimens irradiated with 50 W/cm(2) for 5 min presented the smoother surface observed by SEM, comparable to G. X-ray diffraction data revealed an increase in leucite crystallite size for VM9 and VM13 porcelains after laser treatment. Regarding roughness, continuous CO2 laser applied on porcelain surface was as effective as conventional oven auto-glaze.

Real-time, in situ, continuous monitoring of CO in a pulverized-coal-fired power plant with a 2.3 μm laser absorption sensor

NASA Astrophysics Data System (ADS)

Chao, Xing; Jeffries, Jay B.; Hanson, Ronald K.

2013-03-01

A real-time, in situ CO sensor using 2.3 μm DFB diode laser absorption, with calibration-free wavelength-modulation-spectroscopy, was demonstrated for continuous monitoring in the boiler exhaust of a pulverized-coal-fired power plant up to temperatures of 700 K. The sensor was similar to a design demonstrated earlier in laboratory conditions, now refined to accommodate the harsh conditions of utility boilers. Measurements were performed across a 3 m path in the particulate-laden economizer exhaust of the coal-fired boiler. A 0.6 ppm detection limit with 1 s averaging was estimated from the results of a continuous 7-h-long measurement with varied excess air levels. The measured CO concentration exhibited expected inverse trends with the excess O2 concentration, which was varied between 1 and 3 %. Measured CO concentrations ranged between 6 and 200 ppm; evaluation of the data suggested a dynamic range from 6 to 10,000 ppm based on a minimum signal-to-noise ratio of ten and maximum absorbance of one. This field demonstration of a 2.3 μm laser absorption sensor for CO showed great potential for real-time combustion exhaust monitoring and control of practical combustion systems.

Dual-wavelength mid-infrared CW and Q-switched laser in diode end-pumped Tm,Ho:GdYTaO4 crystal

NASA Astrophysics Data System (ADS)

Wang, Beibei; Gao, Congcong; Dou, Renqin; Nie, Hongkun; Sun, Guihua; Liu, Wenpeng; Yu, Haijuan; Wang, Guoju; Zhang, Qingli; Lin, Xuechun; He, Jingliang; Wang, Wenjun; Zhang, Bingyuan

2018-02-01

Dual-wavelength continuous-wave and Q-switched lasers are demonstrated in a Tm,Ho:GdYTaO4 crystal under 790 nm laser diode end pumping for the first time to the best of our knowledge. The laser operates with a dual wavelength at 1949.677 nm and 2070 nm for continuous-wave with a spacing of about 120 nm. The maximum output power is 0.332 W with a pump power of 3 W. By using graphene as the saturable absorber, a passively Q-switched operation is performed with a dual-wavelength at 1950.323 nm and 2068.064 nm with a wavelength interval of about 118 nm. The maximum average output power of the Q-switched laser goes up to 200 mW with a minimum pulse duration of 1.2 µs and a maximum repetition rate of 34.72 kHz.

Infrared skin damage thresholds from 1319-nm continuous-wave laser exposures

NASA Astrophysics Data System (ADS)

Oliver, Jeffrey W.; Vincelette, Rebecca; Noojin, Gary D.; Clark, Clifton D.; Harbert, Corey A.; Schuster, Kurt J.; Shingledecker, Aurora D.; Kumru, Semih S.; Maughan, Justin; Kitzis, Naomi; Buffington, Gavin D.; Stolarski, David J.; Thomas, Robert J.

2013-12-01

A series of experiments were conducted in vivo using Yucatan miniature pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1319-nm continuous-wave Nd:YAG laser irradiation. Experiments employed exposure durations of 0.25, 1.0, 2.5, and 10 s and beam diameters of ˜0.6 and 1 cm. Thermal imagery data provided a time-dependent surface temperature response from the laser. A damage endpoint of fifty percent probability of a minimally visible effect was used to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Resultant trends with respect to exposure duration and beam diameter are compared with current standardized exposure limits for laser safety. Mathematical modeling agreed well with experimental data, predicting that though laser safety standards are sufficient for exposures <10 s, they may become less safe for very long exposures.

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.

Four-Wave Mixing of Gigawatt Power, Long-Wave Infrared Radiation in Gases and Semiconductors

NASA Astrophysics Data System (ADS)

Pigeon, Jeremy James

The nonlinear optics of gigawatt power, 10 microm, 3 and 200 ps long pulses propagating in gases and semiconductors has been studied experimentally and numerically. In this work, the development of a high-repetition rate, picosecond, CO2 laser system has enabled experiments using peak intensities in the range of 1-10 GW/cm2, approximately one thousand times greater than previous nonlinear optics experiments in the long-wave infrared (LWIR) spectral region. The first measurements of the nonlinear refractive index of the atomic and molecular gases Kr, Xe, N2, O2 and the air at a wavelength near 10 microm were accomplished by studying the four-wave mixing (FWM) of dual-wavelength, 200 ps CO2 laser pulses. These measurements indicate that the nonlinearities of the diatomic molecules N2, O2 and the air are dominated by the molecular contribution to the nonlinear refractive index. Supercontinuum (SC) generation covering the infrared spectral range, from 2-20 microm, was realized by propagating 3 ps, 10 microm pulses in an approximately 7 cm long, Cr-doped GaAs crystal. Temporal measurements of the SC radiation show that pulse splitting accompanies the generation of such broadband light in GaAs. The propagation of 3 ps, 10 microm pulses in GaAs was studied numerically by solving the Generalized Nonlinear Schrodinger Equation (GNLSE). These simulations, combined with analytic estimates, were used to determine that stimulated Raman scattering combined with a modulational instability caused by the propagation of intense LWIR radiation in the negative group velocity dispersion region of GaAs are responsible for the SC generation process. The multiple FWM of a 106 GHz, 200 ps CO2 laser beat-wave propagating in GaAs was used to generate a broadband FWM spectrum that was compressed by the negative group velocity dispersion of GaAs and NaCl crystals to form trains of high-power, picosecond pulses at a wavelength near 10 microm. Experimental FWM spectra obtained using 165 and 882 GHz beat-waves revealed an unexpected and rapid decrease in the FWM yield that was not predicted by the GNLSE model that accounts for third-order nonlinearities alone. These results suggest that the effective nonlinear refractive index of GaAs, having formidable second- and third-order susceptibilities, may be altered by quadratic nonlinearities.

Suppression of thermal transients in advanced LIGO interferometers using CO2 laser preheating

NASA Astrophysics Data System (ADS)

Jaberian Hamedan, V.; Zhao, C.; Ju, L.; Blair, C.; Blair, D. G.

2018-06-01

In high optical power interferometric gravitational wave detectors, such as Advanced LIGO, the thermal effects due to optical absorption in the mirror coatings and the slow thermal response of fused silica substrate cause time dependent changes in the mirror profile. After locking, high optical power builds up in the arm cavities. Absorption induced heating causes optical cavity transverse mode frequencies to drift over a period of hours, relative to the fundamental mode. At high optical power this can cause time dependent transient parametric instability, which can lead to interferometer disfunction. In this paper, we model the use of CO2 laser heating designed to enable the interferometer to be maintained in a thermal condition such that transient changes in the mirrors are greatly reduced. This can minimize transient parametric instability and compensate dark port power fluctuations. Modeling results are presented for both single compensation where a CO2 laser acting on one test mass per cavity, and double compensation using one CO2 laser for each test mass. Using parameters of the LIGO Hanford Observatory X-arm as an example, single compensation allows the maximum mode frequency shift to be limited to 6% of its uncompensated value. However, single compensation causes transient degradation of the contrast defect. Double compensation minimise contrast defect degradation and reduces transients to less than 1% if the CO2 laser spot is positioned within 2 mm of the cavity beam position.

CO2-laser-assisted processing of glass fiber-reinforced thermoplastic composites

NASA Astrophysics Data System (ADS)

Brecher, Christian; Emonts, Michael; Schares, Richard Ludwig; Stimpfl, Joffrey

2013-02-01

To fully exploit the potential of fiber-reinforced thermoplastic composites (FRTC) and to achieve a broad industrial application, automated manufacturing systems are crucial. Investigations at Fraunhofer IPT have proven that the use of laser system technology in processing FRTC allows to achieve high throughput, quality, flexibility, reproducibility and out-of-autoclave processing simultaneously. As 90% of the FRP in Europe1 are glass fiber-reinforced a high impact can be achieved by introducing laser-assisted processing with all its benefits to glass fiber-reinforced thermoplastics (GFRTC). Fraunhofer IPT has developed the diode laser-assisted tape placement (laying and winding) to process carbon fiber-reinforced thermoplastic composites (CFRTC) for years. However, this technology cannot be transferred unchanged to process milky transparent GFRTC prepregs (preimpregnated fibers). Due to the short wavelength (approx. 980 nm) and therefore high transmission less than 20% of the diode laser energy is absorbed as heat into non-colored GFRTC prepregs. Hence, the use of a different wave length, e.g. CO2-laser (10.6 μm) with more than 90% laser absorption, is required to allow the full potential of laser-assisted processing of GFRTC. Also the absorption of CO2-laser radiation at the surface compared to volume absorption of diode laser radiation is beneficial for the interlaminar joining of GFRTC. Fraunhofer IPT is currently developing and investigating the CO2-laser-assisted tape placement including new system, beam guiding, process and monitoring technology to enable a resource and energy efficient mass production of GFRP composites, e.g. pipes, tanks, masts. The successful processing of non-colored glass fiber-reinforced Polypropylene (PP) and Polyphenylene Sulfide (PPS) has already been proven.

[Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].

PubMed

He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

2009-01-01

With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology.

Modeling and Simulation of a Laser Deposition Process

DTIC Science & Technology

2007-09-04

LAMP system, the diode laser is used. Material of both powder and substrates is Ti - 6Al - 4V , which is widely used in the aerospace industry. Melt Pool...The laser emits at 808 nm and operates in the continuous wave (CW) mode. The substrates have dimensions of 2.5×2.5×0.4 in. The Ti - 6Al - 4V samples were...irradiated using a laser beam with a beam spot diameter of 2.5 mm. Table 1. Material properties for Ti - 6Al - 4V and main process parameters

Visualization of transient phenomena during the interaction of pulsed CO2 laser radiation with matter

NASA Astrophysics Data System (ADS)

Schmitt, R.; Hugenschmidt, Manfred

1996-05-01

Carbon-dioxide-lasers operating in the pulsed mode with energy densities up to several tens of J/cm2 and peak power densities in the multi-MW/cm2-range may cause fast heating and melting. Eventually quasi-explosive ejection, decomposition or vaporization of material can be observed. Surface plasmas are strongly influencing the energy transfer from the laser radiation field to any target. For optically transparent plastics, such as PMMA for example, only slowly expanding plasmas (LSC-waves) are ignited at fluences around 20 J/cm2, with a low level of self-luminosity. High brightness, supersonically expanding plasma jets (LSD-waves) are generated at the same fluences on glasses. Similar conditions were found for metals as well. From recordings with a high speed CCD-camera, interesting features concerning the initial plasma phases and temporal evolution were deduced. Additionally, information was obtained concerning the quasi explosive ejection of material for PMMA.

Self-organized micro-holes on titania based sol-gel films under continuous direct writing with a continuous wave ultraviolet laser

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

Bakhti, S.; Destouches, N.; Gamet, E.

The microstructuring of titania based sol-gel films is investigated by direct writing with a continuous wave ultraviolet laser beam emitting at 244 nm. Depending on the exposure conditions, the films exhibit a volume expansion, a volume shrinkage, a self-shaped delamination, or are damaged. This paper is mainly focused on the regime where spontaneous local delamination occurs, which corresponds to a narrow range of laser irradiances and writing speeds. In this regime, self-organized round-shape micro-holes opened on the substrate are generated.

Comparison of lasers used in stapedotomy using specialized visualization techniques for mechanical and thermal effects in an inner ear model

NASA Astrophysics Data System (ADS)

Kamalski, Digna M. A.; Verdaasdonk, Rudolf M.; de Boorder, Tjeerd; Grolman, Wilko

2011-03-01

The outcome of stapedotomy depends on several surgical steps. Using laser light, the ossicular chain can be handled and the oval window can be punctured with a non-touch method. Various lasers are being used or considered, however, it is not clear which settings and characteristics will contribute to optimal or adverse effects (vestibule damage and loss hearing frequencies). Using a unique high speed thermal imaging setup based on Schlieren techniques, the mechanical and thermal effects during laser stapedotomy were studied in an inner ear model consisting of human, fresh frozen stapes positioned on a liquid filled cavity in a gel cast. The cw KTP (532 nm), cw CO2 (10.6 μm), cw Thulium (2.0 μm), pulsed Er,Cr;YSGG (2.78 μm) coupled to special fiber delivery systems were applied at typical clinical settings for comparison. The imaging techniques provided a good insight in the extent of heat conduction beneath the footplate and (explosive) vapour formation on both sides. For the pulsed laser modes, explosive vapour expansion can to be controlled with optimized pulse energies while for continuous wave lasers the thermal effects can be controlled with the pulse length and repetition rate. The fluence at the tip of the delivery system and the distance to the footplate has a major impact on the ablation effect. The pulsed IR lasers with fiber delivery show to be promising for a controlled stapedotomy.

Nd:(Gd0.3Y0.7)2SiO5 crystal: A novel efficient dual-wavelength continuous-wave medium

NASA Astrophysics Data System (ADS)

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

2016-05-01

Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd0.3Y0.7)2SiO5 crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr4+:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

CO{sub 2} Laser Ablation Propulsion Area Scaling With Polyoxymethylene Propellant

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

Sinko, John E.; Ichihashi, Katsuhiro; Ogita, Naoya

The topic of area scaling is of great importance in the laser propulsion field, including applications to removal of space debris and to selection of size ranges for laser propulsion craft in air or vacuum conditions. To address this issue experimentally, a CO{sub 2} laser operating at up to 10 J was used to irradiate targets. Experiments were conducted in air and vacuum conditions over a range of areas from about 0.05-5 cm{sup 2} to ablate flat polyoxymethylene targets at several fluences. Theoretical effects affecting area scaling, such as rarefaction waves, thermal diffusion, and diffraction, are discussed in terms ofmore » the experimental results. Surface profilometry was used to characterize the ablation samples. A CFD model is used to facilitate analysis, and key results are compared between experimental and model considerations. The dependence of key laser propulsion parameters, including the momentum coupling coefficient and specific impulse, are calculated based on experimental data, and results are compared to existing literature data.« less

Shock-wave proton acceleration from a hydrogen gas jet

NASA Astrophysics Data System (ADS)

Cook, Nathan; Pogorelsky, Igor; Polyanskiy, Mikhail; Babzien, Marcus; Tresca, Olivier; Maharjan, Chakra; Shkolnikov, Peter; Yakimenko, Vitaly

2013-04-01

Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.

Dissipative Structures At Laser-Solid Interactions

NASA Astrophysics Data System (ADS)

Nanai, Laszlo

1989-05-01

The questions which are discussed in this lecture refer to one of sections of laser-solid interactions, namely: to formation of different dissipative structures on the surface of metals and semiconductors when they are irradiated by intensive laser light in chemically active media (f.e.air). Some particular examples of the development at different spatial and time instabilities, periodic and stochastic structures, auto-wave processes are present-ed using testing materials vanadium metal and semiconducting V205 single crystals and light sources: cw and pulsed CO2 and YAG lasers.

Effect of the three-dimensional structure of laser emission on the dynamics of low-threshold optical breakdown plasmas

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Derkach, O. N.; Kanevskii, M. F.

1989-03-01

The effect of the transverse structure of pulsed CO2 laser emission on the dynamics of laser-induced detonation waves propagating from a metal surface and on plasma transparency recovery is investigated theoretically and experimentally. Particular attention is given to breakdown initiation near the surface. It is suggested that the inclusion of refraction in the plasma into a self-consistent numerical mode is essential for the adequate quantitative description of experimental data on the interaction of laser emission with low-threshold optical breakdown plasmas.

Organization of the Topical Meeting on Short Wavelength Coherent Radiation: Generation and Applications (4th) Held in North Falmouth, Massachusetts

DTIC Science & Technology

1989-03-01

00 PM oleton Laboratory, U K. Stripe. foil. and fiber targets were ir- TuC, SESSION 7: POSTER SESSION radiated ,vith high intensity line-focused laser...Interference in Four-Wave TuC28 Gain Measurement on a 18.2-nm Carbon Recombin- Mixing, K. G. H. Baldwin. Australian National U. Constructive ation Laser...mixing in sodium vapor. (p. 76) cylindrical wall confined carbon recombination laser produc- ed by a high power CO laser are presented. A maximum gain

Simultaneous atmospheric nitrous oxide, methane and water vapor detection with a single continuous wave quantum cascade laser.

PubMed

Cao, Yingchun; Sanchez, Nancy P; Jiang, Wenzhe; Griffin, Robert J; Xie, Feng; Hughes, Lawrence C; Zah, Chung-en; Tittel, Frank K

2015-02-09

A continuous wave (CW) quantum cascade laser (QCL) based absorption sensor system was demonstrated and developed for simultaneous detection of atmospheric nitrous oxide (N(2)O), methane (CH(4)), and water vapor (H(2)O). A 7.73-µm CW QCL with its wavelength scanned over a spectral range of 1296.9-1297.6 cm(-1) was used to simultaneously target three neighboring strong absorption lines, N(2)O at 1297.05 cm(-1), CH(4) at 1297.486 cm(-1), and H(2)O at 1297.184 cm(-1). An astigmatic multipass Herriott cell with a 76-m path length was utilized for laser based gas absorption spectroscopy at an optimum pressure of 100 Torr. Wavelength modulation and second harmonic detection was employed for data processing. Minimum detection limits (MDLs) of 1.7 ppb for N(2)O, 8.5 ppb for CH(4), and 11 ppm for H(2)O were achieved with a 2-s integration time for individual gas detection. This single QCL based multi-gas detection system possesses applications in environmental monitoring and breath analysis.

Spectroscopic, luminescent and laser properties of nanostructured CaF2:Tm materials

NASA Astrophysics Data System (ADS)

Lyapin, A. A.; Fedorov, P. P.; Garibin, E. A.; Malov, A. V.; Osiko, V. V.; Ryabochkina, P. A.; Ushakov, S. N.

2013-08-01

The laser quality transparent СаF2:Tm fluoride ceramics has been prepared by hot forming. Comparative study of absorption and emission spectra of СаF2:Tm (4 mol.% TmF3) ceramic and single crystal samples demonstrated that these materials possess almost identical spectroscopic properties. Laser oscillations of СаF2:Tm ceramics were obtained at 1898 nm under diode pumping, with the slope efficiency of 5.5%. Also, the continuous-wave (CW) laser have been obtained for СаF2:Tm single crystal at 1890 nm pumped by a diode laser was demonstrated.

Sensitive detection of temperature behind reflected shock waves using wavelength modulation spectroscopy of CO2 near 2.7 μm

NASA Astrophysics Data System (ADS)

Farooq, A.; Jeffries, J. B.; Hanson, R. K.

2009-07-01

Tunable diode-laser absorption of CO2 near 2.7 μm incorporating wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) is used to provide a new sensor for sensitive and accurate measurement of the temperature behind reflected shock waves in a shock-tube. The temperature is inferred from the ratio of 2f signals for two selected absorption transitions, at 3633.08 and 3645.56 cm-1, belonging to the ν 1+ ν 3 combination vibrational band of CO2 near 2.7 μm. The modulation depths of 0.078 and 0.063 cm-1 are optimized for the target conditions of the shock-heated gases ( P˜1-2 atm, T˜800-1600 K). The sensor is designed to achieve a high sensitivity to the temperature and a low sensitivity to cold boundary-layer effects and any changes in gas pressure or composition. The fixed-wavelength WMS-2f sensor is tested for temperature and CO2 concentration measurements in a heated static cell (600-1200 K) and in non-reactive shock-tube experiments (900-1700 K) using CO2-Ar mixtures. The relatively large CO2 absorption strength near 2.7 μm and the use of a WMS-2f strategy minimizes noise and enables measurements with lower concentration, higher accuracy, better sensitivity and improved signal-to-noise ratio (SNR) relative to earlier work, using transitions in the 1.5 and 2.0 μm CO2 combination bands. The standard deviation of the measured temperature histories behind reflected shock waves is less than 0.5%. The temperature sensor is also demonstrated in reactive shock-tube experiments of n-heptane oxidation. Seeding of relatively inert CO2 in the initial fuel-oxidizer mixture is utilized to enable measurements of the pre-ignition temperature profiles. To our knowledge, this work represents the first application of wavelength modulation spectroscopy to this new class of diode lasers near 2.7 μm.

Field-based stable isotope analysis of carbon dioxide by mid-infrared laser spectroscopy for carbon capture and storage monitoring.

PubMed

van Geldern, Robert; Nowak, Martin E; Zimmer, Martin; Szizybalski, Alexandra; Myrttinen, Anssi; Barth, Johannes A C; Jost, Hans-Jürg

2014-12-16

A newly developed isotope ratio laser spectrometer for CO2 analyses has been tested during a tracer experiment at the Ketzin pilot site (northern Germany) for CO2 storage. For the experiment, 500 tons of CO2 from a natural CO2 reservoir was injected in supercritical state into the reservoir. The carbon stable isotope value (δ(13)C) of injected CO2 was significantly different from background values. In order to observe the breakthrough of the isotope tracer continuously, the new instruments were connected to a stainless steel riser tube that was installed in an observation well. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10 day carbon stable isotope data set with 30 min resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within analytical precision. This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time stable isotope data directly in the field. The laser spectroscopy data revealed for the first time a prior to this experiment unknown, intensive dynamic with fast changing δ(13)C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The short-term variances as observed in this study might have been missed during previous works that applied laboratory-based IRMS analysis. The new technique could contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long-term integrity of the reservoir.

The second-order interference of two independent single-mode He-Ne lasers

NASA Astrophysics Data System (ADS)

Liu, Jianbin; Le, Mingnan; Bai, Bin; Wang, Wentao; Chen, Hui; Zhou, Yu; Li, Fu-li; Xu, Zhuo

2015-09-01

The second-order spatial and temporal interference patterns with two independent single-mode continuous-wave He-Ne lasers are observed when these two lasers are incident to two adjacent input ports of a 1:1 non-polarizing beam splitter, respectively. Two-photon interference based on the superposition principle in Feynman's path integral theory is employed to interpret the experimental results. The conditions to observe the second-order interference pattern with two independent single-mode continuous-wave lasers are discussed. It is concluded that frequency stability is important to observe the second-order interference pattern with two independent light beams.

Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser.

PubMed

Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

2010-03-20

We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input coupler's reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser.

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.

Precision improvement of frequency-modulated continuous-wave laser ranging system with two auxiliary interferometers

NASA Astrophysics Data System (ADS)

Shi, Guang; Wang, Wen; Zhang, Fumin

2018-03-01

The measurement precision of frequency-modulated continuous-wave (FMCW) laser distance measurement should be proportional to the scanning range of the tunable laser. However, the commercial external cavity diode laser (ECDL) is not an ideal tunable laser source in practical applications. Due to the unavoidable mode hopping and scanning nonlinearity of the ECDL, the measurement precision of FMCW laser distance measurements can be substantially affected. Therefore, an FMCW laser ranging system with two auxiliary interferometers is proposed in this paper. Moreover, to eliminate the effects of ECDL, the frequency-sampling method and mode hopping influence suppression method are employed. Compared with a fringe counting interferometer, this FMCW laser ranging system has a measuring error of ± 20 μm at the distance of 5.8 m.

Phase-locking and coherent power combining of broadband linearly chirped optical waves.

PubMed

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-05

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves.

Observations on Bubble Dynamics at High Pressures and Bubble Dynamics in Stagnation Flow.

DTIC Science & Technology

1982-11-30

reverse side It nocooeuAn aifdentifly by block mt..bet) S 1 Cavitation, High Speed Photography, Ruby Laser . 20. AFSTAACT Co.nflno on revere side Of...AT NIGH ASIE3r.T PRESSUrES A.T. Ellis and J.E. Starrect University of California, San Diego Recent developsent by the authors of a unique ruby laser ...1,000,300 frames per second with exposure clue of approximately 2vl0- seconds. The coherent nature of the laser illuminacion revealed shock waves

Investigation of terahertz waves propagating through far infrared/CO2 laser stealth-compatible coating based on one-dimensional photonic crystal

NASA Astrophysics Data System (ADS)

Wang, Qichao; Wang, Jiachun; Zhao, Dapeng; Zhang, Jikui; Li, Zhigang; Chen, Zongsheng; Zeng, Jie; Miao, Lei; Shi, Jiaming

2016-11-01

We propose a new method to disclose the camouflaged targets coated with far infrared/CO2 laser stealth-compatible coating by utilizing terahertz (THz) radar. A coating based on one-dimensional photonic crystal (1DPC) with a defect mode is specially designed and successfully prepared, which possesses a high reflectivity in 8-14 μm waveband and a low reflectivity at 10.6 μm, by alternating thin films of Ge, ZnSe and Si. The propagation characteristic of 0.3-2 THz wave at incident angle from 0° to 80° in such PC coating is investigated theoretically based on characteristic matrix method. The maximal transmittance is up to 92%, and the absorptivity keeps lower than 0.5% over the whole band. The results are verified by experiments, which demonstrate the feasibility of using THz radar to detect the targets covered with such stealth-compatible coatings.

Coherent cavity-enhanced dual-comb spectroscopy.

PubMed

Fleisher, Adam J; Long, David A; Reed, Zachary D; Hodges, Joseph T; Plusquellic, David F

2016-05-16

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO₂, CO, HDO, and H₂O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors.

Ppbv-Level Ethane Detection Using Quartz-Enhanced Photoacoustic Spectroscopy with a Continuous-Wave, Room Temperature Interband Cascade Laser

PubMed Central

Li, Chunguang; Dong, Lei; Zheng, Chuantao; Lin, Jun; Wang, Yiding

2018-01-01

A ppbv-level quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane (C2H6) sensor was demonstrated by using a 3.3 μm continuous-wave (CW), distributed feedback (DFB) interband cascade laser (ICL). The ICL was employed for targeting a strong C2H6 absorption line located at 2996.88 cm−1 in its fundamental absorption band. Wavelength modulation spectroscopy (WMS) combined with the second harmonic (2f) detection technique was utilized to increase the signal-to-noise ratio (SNR) and simplify data acquisition and processing. Gas pressure and laser frequency modulation depth were optimized to be 100 Torr and 0.106 cm−1, respectively, for maximizing the 2f signal amplitude. Performance of the QEPAS sensor was evaluated using specially prepared C2H6 samples. A detection limit of 11 parts per billion in volume (ppbv) was obtained with a 1-s integration time based on an Allan-Werle variance analysis, and the detection precision can be further improved to ~1.5 ppbv by increasing the integration time up to 230 s. PMID:29495610

Investigation of effective line intensities of trans-HONO near 1255 cm-1 using continuous-wave quantum cascade laser spectrometers

NASA Astrophysics Data System (ADS)

Cui, Xiaojuan; Dong, Fengzhong; Sigrist, Markus W.; Zhang, Zhirong; Wu, Bian; Xia, Hua; Pang, Tao; Sun, Pengshuai; Fertein, Eric; Chen, Weidong

2016-10-01

Effective line intensities of P branch transitions of trans-nitrous acid (HONO) in the ν3 H-O-N bending mode near 1255 cm-1 have been determined by scaling measured HONO absorption intensities by continuous-wave quantum cascade laser absorption spectroscopy to reference values. Gaseous HONO samples were synthetized in the laboratory using the reaction of H2SO4 and NaNO2 solutions and the heterogeneous formation on surfaces in the presence of ambient water vapor and NO2 gas in a sealed gas sampling bag. The quantification of HONO was performed using a denuder associated with a NOx analyzer. Observed absorption line strengths for the trans conformer are found to be by a factor of approximately 1.17 higher than previously reported line strengths.

Dual-Beam Atom Laser Driven by Spinor Dynamics

NASA Technical Reports Server (NTRS)

Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Aveline, David

2007-01-01

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated Rb-87 atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry. In this atom-laser apparatus, a Bose-Einstein condensate of about 2 x 10(exp 6) Rb-87 atoms at a temperature of about 120 micro-K is first formed through all-optical means in a relatively weak singlebeam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultrahigh-vacuum magnetooptical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped from an adjoining vacuum chamber, wherein are performed scientific observations of the beams ultimately generated by the atom laser.

Catalysts for long-life closed-cycle CO2 lasers

NASA Technical Reports Server (NTRS)

Schryer, David R.; Sidney, Barry D.; Miller, Irvin M.; Hess, Robert V.; Wood, George M.; Batten, Carmen E.; Burney, Lewis G.; Hoyt, Ronald F.; Paulin, Patricia A.; Brown, Kenneth G.

1987-01-01

Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin (IV) oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-LaRC on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) achievement of 98% to 100% conversion of a stoichiometric mixture of CO and O2 to CO2 for 318 hours (greater than 1 x 10 to the 6th power seconds), continuous, at a catalyst temperature of 60 C, and (2) development of a technique verified in a 30-hour test, to prevent isotopic scrambling when CO-18 and O-18(2) are reacted in the presence of a common-isotope Pt/Sn O-16(2) catalyst.

Wavelength switchable high-power diode-side-pumped rod Tm:YAG Laser around 2µm.

PubMed

Wang, Caili; Du, Shifeng; Niu, Yanxiong; Wang, Zhichao; Zhang, Chao; Bian, Qi; Guo, Chuan; Xu, Jialin; Bo, Yong; Peng, Qinjun; Cui, Dafu; Zhang, Jingyuan; Lei, Wenqiang; Xu, Zuyan

2013-03-25

We report a high-power diode-side-pumped rod Tm:YAG laser operated at either 2.07 or 2.02 µm depending on the transmission of pumped output coupler. The laser yields 115W of continuous-wave output power at 2.07 µm with 5% output coupling, which is the highest output power for all solid-state 2.07 μm cw rod Tm:YAG laser reported so far. With an output coupler of 10% transmission, the center wavelength of the laser is switched to 2.02 μm with an output power of 77.1 W. This is the first observation of high-power wavelength switchable diode-side-pumped rod Tm:YAG laser around 2 µm.

A scenario for magnonic spin-wave traps

PubMed Central

Busse, Frederik; Mansurova, Maria; Lenk, Benjamin; von der Ehe, Marvin; Münzenberg, Markus

2015-01-01

Spatially resolved measurements of the magnetization dynamics on a thin CoFeB film induced by an intense laser pump-pulse reveal that the frequencies of resulting spin-wave modes depend strongly on the distance to the pump center. This can be attributed to a laser generated temperature profile. We determine a shift of 0.5 GHz in the spin-wave frequency due to the spatial thermal profile induced by the femtosecond pump pulse that persists for up to one nanosecond. Similar experiments are presented for a magnonic crystal composed of a CoFeB-film based antidot lattice with a Damon Eshbach mode at the Brillouin zone boundary and its consequences are discussed. PMID:26279466

Stable continuous-wave single-frequency Nd:YAG blue laser at 473 nm considering the influence of the energy-transfer upconversion.

PubMed

Wang, Yaoting; Liu, Jianli; Liu, Qin; Li, Yuanji; Zhang, Kuanshou

2010-06-07

We report a continuous-wave (cw) single frequency Nd:YAG blue laser at 473 nm end-pumped by a laser diode. A ring laser resonator was designed, the frequency doubling efficiency and the length of nonlinear crystal were optimized based on the investigation of the influence of the frequency doubling efficiency on the thermal lensing effect induced by energy-transfer upconversion. By intracavity frequency doubling with PPKTP crystal, an output power of 1 W all-solid-state cw blue laser of single-frequency operation was achieved. The stability of the blue output power was better than +/- 1.8% in the given four hours.

Laser dye DCM: CW, synchronously pumped, cavity pumped and single-frequency performance

NASA Astrophysics Data System (ADS)

Marason, E. G.

1981-04-01

Laser dye DCM exhibits a tuning range of 605 to 725 nm with a lasing efficiency as high as 34% when pumped by the 488 nm line of the argon ion laser, placing it among the most efficient and broadly tunable dyes known. Performance of the dye is characterized for four laser systems: 1) continuous wave, 2) synchronously pumped (SP), 3) cavity dumped synchrompously pumped (SPCD) and 4) single-frequency ring dye laser. Pulse peak powers were as high as 520 W and 2.8 kW for SP and SPCD systems respectively.

Multi-wavelength Yb:YAG/Nd³⁺:YVO₄ continuous-wave microchip Raman laser.

PubMed

Wang, Xiao-Lei; Dong, Jun; Wang, Xiao-Jie; Xu, Jie; Ueda, Ken-Ichi; Kaminskii, Alexander A

2016-08-01

Multi-wavelength continuous-wave (CW) Raman lasers in a laser diode pumped Yb:YAG/Nd³⁺:YVO₄ microchip Raman laser have been demonstrated for the first time to our best knowledge. The multi-wavelength laser of the first Stokes radiation around 1.08 μm has been achieved with a Raman shift of 261  cm^-1 for a-cut Nd:YVO₄ crystal corresponding to the fundamental wavelength at 1.05 μm. Multi-wavelength laser operation simultaneously around 1.05 and 1.08 μm has been achieved under the incident pump power between 1.5 and 1.7 W. Multi-wavelength Raman laser with frequency separation of 1 THz around 1.08 μm has been obtained when the incident pump power is higher than 1.7 W. The maximum Raman laser output power of 260 mW at 1.08 μm is obtained and the corresponding optical-to-optical conversion efficiency is 4.2%. Elliptically polarized fundamental laser and linearly polarized Raman laser were observed in an Yb:YAG/Nd:YVO₄ CW microchip Raman laser. The experimental results of linearly polarized, multi-wavelength Yb:YAG/Nd:YVO₄ CW microchip Raman laser with adjustable frequency separation provide a novel approach for developing potential compact laser sources for Terahertz generation.

A Q-switched Ho:YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm:YLF laser

NASA Astrophysics Data System (ADS)

Wang, Y. P.; Dai, T. Y.; Wu, J.; Ju, Y. L.; Yao, B. Q.

2018-06-01

We report the acousto-optically Q-switched Ho:YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm:YLF laser. In the continuous-wave operation of Ho:YAG laser, the maximum s-polarized output power of 3.2 W at 2090.3 nm was obtained under the absorbed pump power of 12.9 W by rotating the fast axis of quarter-wave plate to change the output transmission of laser cavity. The corresponding optical-to-optical conversion efficiency was 24.8% and the slope efficiency was 55.7%. When one of the corner cubes was rotated to 11.8° around vertical direction or 6.7° around horizontal direction, the laser could still operate stably. For the Q-switched operation, the pulse energy of Ho:YAG laser was 9.9 mJ with a pulse width of 53 ns at the repetition rate of 100 Hz, resulting in a peak power of 186.8 kW. The beam quality factor M2 of Ho:YAG laser was 1.3.

Remote sensing of atmospheric NO2 by employing the continuous-wave differential absorption lidar technique.

PubMed

Mei, Liang; Guan, Peng; Kong, Zheng

2017-10-02

Differential absorption lidar (DIAL) technique employed for remote sensing has been so far based on the sophisticated narrow-band pulsed laser sources, which require intensive maintenance during operation. In this work, a continuous-wave (CW) NO 2 DIAL system based on the Scheimpflug principle has been developed by employing a compact high-power CW multimode 450 nm laser diode as the light source. Laser emissions at the on-line and off-line wavelengths of the NO 2 absorption spectrum are implemented by tuning the injection current of the laser diode. Lidar signals are detected by a 45° tilted area CCD image sensor satisfying the Scheimpflug principle. Range-resolved NO 2 concentrations on a near-horizontal path are obtained by the NO 2 DIAL system in the range of 0.3-3 km and show good agreement with those measured by a conventional air pollution monitoring station. A detection sensitivity of ± 0.9 ppbv at 95% confidence level in the region of 0.3-1 km is achieved with 15-minute averaging and 700 m range resolution during hours of darkness, which allows accurate concentration measurement of ambient NO 2 . The low-cost and robust DIAL system demonstrated in this work opens up many possibilities for field NO 2 remote sensing applications.

Wave-Modulated CO2 Condensation in Mars' Polar Atmosphere From MGS/TES & MOLA and MRO/MCS.

NASA Astrophysics Data System (ADS)

Banfield, D. J.

2016-12-01

In Mars' polar night, atmospheric temperatures fall low enough to cause CO2 condensation. This has been empirically demonstrated by Mars Global Surveyor's (MGS) Mars Orbiter Laser Altimeter (MOLA), which identified reflections from above the surface, and MGS Radio Science (RS) and Thermal Emission Spectrometer (TES) and Mars Reconnaissance Orbiter's (MRO) Mars Climate Sounder (MCS), all of which showed polar night temperature profiles that were super-saturated. Detailed analysis of TES temperature profiles as well as numerical modeling both suggest that the stationary and traveling waves on the polar vortices are strong enough to significantly modulate the CO2 cloud condensation. However the extent to which this is actually occurring has not been quantified. The polar night CO2 condensation represents a significant amount of energy deposition, even if it were uniformly distributed. If instead it is concentrated in the cold sectors of the various waves, this can be a tremendous perturbation not only to the wave amplitudes (clipping them from going much below the CO2 condensation temperature), but also impacting their ability to transport heat and momentum poleward and upward, and thus it may also impact the maintenance and shape of the polar vortex itself. Mars' polar vortices remain barotropically unstable throughout the winter in spite of large amplitude waves in their vicinity. We have identified when and where the various waves (with their specific amplitudes and phases) in the vicinity of the polar vortex should modulate the CO2 condensation (see Figure of a meridional cross-section showing where no clouds are expected (blue), clouds should be ubiquitous (green) and waves should be required to form clouds (red)). We have also correlated this with the distribution of the actual observed cloud identifications from MGS MOLA and MRO MCS. We find only poor correlations between the MGS/TES identified wave modulated condensation predictions and actual simultaneous cloud identifications from MGS/MOLA. We will discuss the results of a similar study using only MRO/MCS to analyze the mean atmospheric temperature, the stationary and traveling waves along the polar vortex, and the actual locations where CO2 condensation is evident.

Efficient frequency doubler of 1560 nm laser based on a semi-monolithic resonant cavity with a PPKTP crystal

NASA Astrophysics Data System (ADS)

Wang, Junmin; Zhang, Kong; Ge, Yulong; Guo, Shanlong

2016-06-01

We have demonstrated 1.61 W of 780 nm single-frequency continuous-wave laser output with a semi-monolithic periodically poled potassium titanyl phosphate (PPKTP) crystal doubler pumped by a 2-W erbium-doped fiber amplifier boosted 1560 nm diode laser. The measured maximum doubling efficiency is 77%, and the practical value should be 80% when taking into account the fundamental-wave mode matching efficiency. The measured beam quality factor of 780 nm output, M2, is better than 1.04. Typical root-mean-square fluctuation of 780 nm output is less than 0.5% in 30 minutes. This compact frequency doubler has good mechanical stability, and can be employed for many applications, such as laser cooling and trapping, atomic coherent control, atomic interferometer, and quantum frequency standard with rubidium atoms.

The effect of CO2 and Nd:YAP lasers on CAD/CAM Ceramics: SEM, EDS and thermal studies.

PubMed

El Gamal, Ahmed; Fornaini, Carlo; Rocca, Jean Paul; Muhammad, Omid H; Medioni, Etienne; Cucinotta, Annamaria; Brulat-Bouchard, Nathalie

2016-03-31

The objective of this study was to investigate the interaction of infrared laser light on Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) ceramic surfaces. Sixty CAD/CAM ceramic discs were prepared and divided into two different groups: lithiumdisilicate ceramic (IPSe.maxCADs) and Zirconia ceramic (IPSe.maxZirCADs). The laser irradiation was performed on graphite and non-graphite surfaces with a Carbon Dioxide laser at 5W and 10W power in continuous mode (CW mode) and with Neodymium Yttrium Aluminum Perovskite (Nd:YAP) laser at 10W. Surface textures and compositions were examined using Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Thermal elevation was measured by thermocouple during laser irradiation. The SEM observation showed a rough surface plus cracks and fissures on CO2 10W samples and melting areas in Nd:YAP samples; moreover, with CO2 5W smooth and shallow surfaces were observed. EDS analysis revealed that laser irradiation does not result in modifications of the chemical composition even if minor changes in the atomic mass percentage of the components were registered. Thermocouple showed several thermal changes during laser irradiation. CO2 and Nd:YAP lasers modify CAD/CAM ceramic surface without chemical composition modifications.

Laser acoustic emission thermal technique (LAETT): a technique for generating acoustic emission in dental composites.

PubMed

Duray, S J; Lee, S Y; Menis, D L; Gilbert, J L; Lautenschlager, E P; Greener, E H

1996-01-01

This study was designed to investigate a new method for generating interfacial debonding between the resin matrix and filler particles of dental composites. A pilot study was conducted to evaluate laser-induced acoustic emission in dental resins filled with varying quantities of particles. Model systems of 50/50 BisGMA/TEGDMA resin reinforced with 0, 25, and 75 wt% 5-10 micrometers silanated BaSiO(6) were analyzed. The sample size was 3.5 mm diameter x 0.25-0.28 mm thick. A continuous wave CO2 laser (Synrad Infrared Gas Laser Model 48-1) was used to heat the composite samples. Acoustic events were detected, recorded and processed by a model 4610 Smart Acoustic Monitor (SAM) with a 1220A preamp (Physical Acoustic Corp.) as a function of laser power. Initially, the acoustic signal from the model composites produced a burst pattern characteristic of fracturing, about 3.7 watts laser power. Acoustic emission increased with laser power up to about 6 watts. At laser powers above 6 watts, the acoustic emission remained constant. The amount of acoustic emission followed the trend: unfilled resin > composite with 25 wt% BaSiO(6) > composite with 75 wt% BaSiO(6). Acoustic emission generated by laser thermal heating is dependent on the weight percent of filler particles in the composite and the amount of laser power. For this reason, laser thermal acoustic emission might be useful as a nondestructive form of analysis of dental composites.

Effects of a capping oxide layer on polycrystalline-silicon thin-film transistors fabricated by continuous-wave laser crystallization

NASA Astrophysics Data System (ADS)

Li, Yi-Shao; Wu, Chun-Yi; Chou, Chia-Hsin; Liao, Chan-Yu; Chuang, Kai-Chi; Luo, Jun-Dao; Li, Wei-Shuo; Cheng, Huang-Chung

2018-06-01

A tetraethyl-orthosilicate (TEOS) capping oxide was deposited by low-pressure chemical vapor deposition (LPCVD) on a 200-nm-thick amorphous Si (a-Si) film as a heat reservoir to improve the crystallinity and surface roughness of polycrystalline silicon (poly-Si) formed by continuous-wave laser crystallization (CLC). The effects of four thicknesses of the capping oxide layer to satisfy an antireflection condition, namely, 90, 270, 450, and 630 nm, were investigated. The largest poly-Si grain size of 2.5 × 20 µm2 could be achieved using a capping oxide layer with an optimal thickness of 450 nm. Moreover, poly-Si nanorod (NR) thin-film transistors (TFTs) fabricated using the aforementioned technique exhibited a superior electron field-effect mobility of 1093.3 cm2 V‑1 s‑1 and an on/off current ratio of 2.53 × 109.

Catalyst for Carbon Monoxide Oxidation

NASA Technical Reports Server (NTRS)

Davis, Patricia; Brown, Kenneth; VanNorman, John; Brown, David; Upchurch, Billy; Schryer, David; Miller, Irvin

2010-01-01

In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly. The primary object of this invention is to provide a catalyst that, by composition of matter alone, contains chemisorbed water within and upon its structure. Such bound moisture renders the catalyst highly active and very long-lived, such that only a small quantity of it needs to be used with a CO2 laser under ambient operating conditions. This object is achieved by a catalyst that consists essentially of about 1 to 40 percent by weight of one or more platinum group metals (Pt, Pd, Rh, Ir, Ru, Os, Pt being preferred); about 1 to 90 percent by weight of one or more oxides of reducible metals having multiple valence states (such as Sn, Ti, Mn, Cu, and Ce, with SnO2 being preferred); and about 1 to 90 percent by weight of a compound that can bind water to its structure (such as silica gel, calcium chloride, magnesium sulfate, hydrated alumina, and magnesium perchlorate, with silica gel being preferred). Especially beneficial results are obtained when platinum is present in the catalyst composition in an amount of about 5 to 25 (especially 7) percent by weight, SnO2 is present in an amount of about 30 to 40 (especially 40) percent by weight, and silica gel is present in an amount of 45 to 55 (especially 50) percent by weight. The composition of this catalyst was suggested by preliminary experiments in which a Pt/SnO2 catalyst was needed for bound water to enhance its activity. These experimental results suggested that if the water were bound to the surface, this water would enhance and prolong catalyst activity for long time periods. Because the catalyst is to be exposed to a laser gas mixture, and because a CO2 laser can tolerate only a very small amount of moisture, a hygroscopic support for the catalyst would provide the needed H2O into the gas. Silica gel is considered to be superior because of its property to chemisorb water on its surface over a wide range of moisture content.

The use of the fractional CO2 laser resurfacing in the treatment of photoaging in Asians: five years long-term results.

PubMed

Tan, Jun; Lei, Ying; Ouyang, Hua-Wei; Gold, Michael H

2014-12-01

The purpose of this clinical paper is to explore the therapeutic effects, healing times, adverse effects, and maintenance periods of using a CO2 fractional laser in the treatment of photoaging in Asian skin. One fractional CO2 laser procedure was performed on the full face in 56 patients with photoaging. Based on the Dover scoring system, we evaluated the degree of skin aging before treatment and at one-month post laser and at five years post laser therapy in 30 of the patients. Statistical analysis was performed by the Wilcoxon's method. Thirty of the treated patients have had follow-up for 5 years at this time. The photoaging scores in these thirty patients were significantly changed (P < 0.01) at one month, one year, and five years after the fractional laser treatment, as compared with their baseline. Adverse events seen during this analysis were found to be minimal and not of clinical significance. Fractional CO2 laser resurfacing in the treatment of photoaging in Asians is a useful modality with results, for the first time, being shown to have continued efficacy for up to 5 years. © 2014 Wiley Periodicals, Inc.

Modulated and continuous-wave operations of low-power thulium (Tm:YAP) laser in tissue welding

NASA Astrophysics Data System (ADS)

Bilici, Temel; Tabakoğlu, Haşim Özgür; Topaloğlu, Nermin; Kalaycıoğlu, Hamit; Kurt, Adnan; Sennaroglu, Alphan; Gülsoy, Murat

2010-05-01

Our aim is to explore the welding capabilities of a thulium (Tm:YAP) laser in modulated and continuous-wave (CW) modes of operation. The Tm:YAP laser system developed for this study includes a Tm:YAP laser resonator, diode laser driver, water chiller, modulation controller unit, and acquisition/control software. Full-thickness incisions on Wistar rat skin were welded by the Tm:YAP laser system at 100 mW and 5 s in both modulated and CW modes of operation (34.66 W/cm2). The skin samples were examined during a 21-day healing period by histology and tensile tests. The results were compared with the samples closed by conventional suture technique. For the laser groups, immediate closure at the surface layers of the incisions was observed. Full closures were observed for both modulated and CW modes of operation at day 4. The tensile forces for both modulated and CW modes of operation were found to be significantly higher than the values found by conventional suture technique. The 1980-nm Tm:YAP laser system operating in both modulated and CW modes maximizes the therapeutic effect while minimizing undesired side effects of laser tissue welding. Hence, it is a potentially important alternative tool to the conventional suturing technique.

Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode.

PubMed

Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

2015-11-16

Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

NASA Astrophysics Data System (ADS)

Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

2015-11-01

Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator

PubMed Central

Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

2015-01-01

The frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called “fringe-side locking” method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm. PMID:26548900

Long wavelength vertical cavity surface emitting laser

DOEpatents

Choquette, Kent D.; Klem, John F.

2005-08-16

Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, at and above room temperature. The lasers employ two n-type Al.sub.0.94 Ga.sub.0.06 As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the active region, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55.degree. C.

Diode-pumped continuous-wave eye-safe Nd:YAG laser at 1415 nm.

PubMed

Lee, Hee Chul; Byeon, Sung Ug; Lukashev, Alexei

2012-04-01

We describe the output performance of the 1415 nm emission in Nd:YAG in a plane-concave cavity under traditional pumping into the 4F5/2 level (808 nm) and direct in-band pumping into the 4F3/2 level (885 nm). An end-pumped Nd:YAG laser yielded maximum cw output power of 6.3 W and 4.2 W at 885 nm and 808 nm laser diode (LD) pumping, respectively. To the best of our knowledge, this is the highest output power of a LD-pumped 1415 nm laser.

Diode-pumped continuous-wave and passively Q-switched 1066 nm Nd:GYNbO4 laser

NASA Astrophysics Data System (ADS)

Ma, Yufei; Peng, Zhenfang; He, Ying; Li, Xudong; Yan, Renpeng; Yu, Xin; Zhang, Qingli; Ding, Shoujun; Sun, Dunlu

2017-08-01

A diode-pumped passively Q-switched 1066 nm laser with a novel Nd:Gd0.69Y0.3NbO4 mixed crystal was demonstrated for the first time to the best of our knowledge. In the continuous-wave (CW) operation, optimization selection of output couplers was carried out, and a maximum output power of 2.13 W was obtained when the plane mirror with transmission of 25% was chosen and the absorbed pump power was 10.5 W. The Cr4+:YAG passively Q-switched Nd:Gd0.69Y0.3NbO4 laser performance was investigated. At an absorbed pump power of 10.5 W, using Cr4+:YAG with initial transmission of 80%, the obtained minimum pulse width was 7.2 ns with the pulse repetition rate of 19 kHz. The single pulse energy and peak power were estimated to be 26.7 µJ and 3.7 kW, respectively.

Growth of micro-crystals in solution by in-situ heating via continuous wave infrared laser light and an absorber

NASA Astrophysics Data System (ADS)

Pathak, Shashank; Dharmadhikari, Jayashree A.; Thamizhavel, A.; Mathur, Deepak; Dharmadhikari, Aditya K.

2016-01-01

We report on growth of micro-crystals such as sodium chloride (NaCl), copper sulphate (CuSO4), potassium di-hydrogen phosphate (KDP) and glycine (NH2CH2COOH) in solution by in-situ heating using continuous wave Nd:YVO4 laser light. Crystals are grown by adding single walled carbon nanotubes (SWNT). The SWNTs absorb 1064 nm light and act as an in-situ heat source that vaporizes the solvent producing microcrystals. The temporal dynamics of micro-crystal growth is investigated by varying experimental parameters such as SWNT bundle size and incident laser power. We also report crystal growth without SWNT in an absorbing medium: copper sulphate in water. Even though the growth dynamics with SWNT and copper sulphate are significantly different, our results indicate that bubble formation is necessary for nucleation. Our simple method may open up new vistas for rapid growth of seed crystals especially for examining the crystallizability of inorganic and organic materials.

Comb-Resolved Dual-Comb Spectroscopy Stabilized by Free-Running Continuous-Wave Lasers

NASA Astrophysics Data System (ADS)

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2012-11-01

We demonstrate dual-comb spectroscopy with relatively phase-locked two frequency combs, instead of frequency combs firmly fixed to the absolute frequency references. By stabilizing two beat frequencies between two mode-locked lasers at different wavelengths observed via free-running continuous-wave (CW) lasers, two combs are tightly phase locked to each other. The frequency noise of the CW lasers barely affects the performance of dual-comb spectroscopy because of the extremely fast common-mode noise rejection. Transform-limited comb-resolved dual-comb spectroscopy with a 6 Hz radio frequency linewidth is demonstrated by the use of Yb-fiber oscillators.

Highly efficient single-pass frequency doubling of a continuous-wave distributed feedback laser diode using a PPLN waveguide crystal at 488 nm.

PubMed

Jechow, Andreas; Schedel, Marco; Stry, Sandra; Sacher, Joachim; Menzel, Ralf

2007-10-15

A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.

Nd:YAG and CO2 laser therapy of oral mucosal lesions.

PubMed

White, J M; Chaudhry, S I; Kudler, J J; Sekandari, N; Schoelch, M L; Silverman, S

1998-12-01

Experiences gained in the management of oral mucosal lesions by CO2 and Nd:YAG laser therapy in an outpatient clinic treated over an 80-year period are described. Lasers have indications for use in dentistry for incision, excision, and coagulation of intraoral soft tissue. Advances in laser technology have provided delivery systems for site-specific delivery of laser energy with short interaction items on tissue to be ablated. This study retrospectively evaluates a series of clinical case studies. Sixty-four patients with a variety of benign oral soft tissue lesions were treated by laser excision. Thirty-five patients were treated by a pulsed fiberoptic delivered Nd:YAG contact laser, and 29 by a continuous free-beam CO2 non-contact laser. The largest group of lesions treated were leukoplakia (39 cases). Other lesions excised and biopsied were lichen planus, squamous papilloma, pyogenic granuloma, focal melanosis, nonhealing traumatic ulceration, hemangioma, and lymphangioma. All patients were followed postoperatively (mean 6.8 months, range 1-36 months). Laser excision was well tolerated by patients with no intraoperative or postoperative adverse effects. All patients healed postsurgically with no loss of function. CO2 and Nd:YAG lasers are successful surgical options when performing excision of benign intraoral lesions. Advantages of laser therapy include minimal postoperative pain, conservative site-specific minimally invasive surgeries, and elimination of need for sutures.

Control system of an excitation power supply for fast axial flow CO2 lasersupda

NASA Astrophysics Data System (ADS)

Li, Bo; Jia, Xinting; Yuan, Hao; Gao, Yuhu; Wang, Youqing

2009-08-01

A switching power control system of fast axial flow CO2 lasers based on DSP is presented. The key techniques are described in detail, include the control principle, realization method and program design. The experiment showed that the system make the laser discharge stably and work in multi-mode. The discharge current can be adjusted from 3mA to 85mA continuously. 20-2000Hz frequency, 0-100% duty cycle laser pulse is achieved. The power supply can improve the processing efficiency and quality.

Monitoring and analysis of thermal deformation waves with a high-speed phase measurement system.

PubMed

Taylor, Lucas; Talghader, Joseph

2015-10-20

Thermal effects in optical substrates are vitally important in determining laser damage resistance in long-pulse and continuous-wave laser systems. Thermal deformation waves in a soda-lime-silica glass substrate have been measured using high-speed interferometry during a series of laser pulses incident on the surface. Two-dimensional images of the thermal waves were captured at a rate of up to six frames per thermal event using a quantitative phase measurement method. The system comprised a Mach-Zehnder interferometer, along with a high-speed camera capable of up to 20,000 frames-per-second. The sample was placed in the interferometer and irradiated with 100 ns, 2 kHz Q-switched pulses from a high-power Nd:YAG laser operating at 1064 nm. Phase measurements were converted to temperature using known values of thermal expansion and temperature-dependent refractive index for glass. The thermal decay at the center of the thermal wave was fit to a function derived from first principles with excellent agreement. Additionally, the spread of the thermal distribution over time was fit to the same function. Both the temporal decay fit and the spatial fit produced a thermal diffusivity of 5×10^-7  m²/s.

Experimental investigation of a diode-pumped powerful continuous-wave dual-wavelength Nd:YAG laser at 946 and 938.6 nm

NASA Astrophysics Data System (ADS)

Chen, F.; Yu, X.; Yan, R. P.; Li, X. D.; Li, D. J.; Yang, G. L.; Xie, J. J.; Guo, J.

2013-05-01

In this paper, a diode-pumped high-power continuous-wave (cw) dual-wavelength Nd:YAG laser at 946 and 938.6 nm is reported. By using an end-pumped structure, comparative experiments indicate that a 5 mm-length Nd:YAG crystal with a Nd3+-doping concentration of 0.3 at.% is favorable for high-power laser operation, and the optimal transmissivity of the output coupler is 9%. As a result, a maximum output power of 17.2 W for a dual-wavelength laser at 946 and 938.6 nm is obtained at an incident pump power of 75.9 W, corresponding to a slope efficiency of 26.5%. To the best of our knowledge, this is the highest output power of a quasi-three-level dual-wavelength laser using a conventional Nd:YAG crystal achieved to date. By using a traveling knife-edge method, the beam quality factor and far-field divergence angle at 17 W power level are estimated to be 4.0 and 6.13 mrad, respectively.

Pump and probe spectroscopy with continuous wave quantum cascade lasers.

PubMed

Kirkbride, James M R; Causier, Sarah K; Dalton, Andrew R; Weidmann, Damien; Ritchie, Grant A D

2014-02-07

This paper details infra-red pump and probe studies on nitric oxide conducted with two continuous wave quantum cascade lasers both operating around 5 μm. The pump laser prepares a velocity selected population in a chosen rotational quantum state of the v = 1 level which is subsequently probed using a second laser tuned to a rotational transition within the v = 2 ← v = 1 hot band. The rapid frequency scan of the probe (with respect to the molecular collision rate) in combination with the velocity selective pumping allows observation of marked rapid passage signatures in the transient absorption profiles from the polarized vibrationally excited sample. These coherent transient signals are influenced by the underlying hyperfine structure of the pump and probe transitions, the sample pressure, and the coherent properties of the lasers. Pulsed pump and probe studies show that the transient absorption signals decay within 1 μs at 50 mTorr total pressure, reflecting both the polarization and population dephasing times of the vibrationally excited sample. The experimental observations are supported by simulation based upon solving the optical Bloch equations for a two level system.

Photothermal heating and cooling of nanostructures.

PubMed

Crane, Matthew Joseph; Zhou, Xuezhe; Davis, E James; Pauzauskie, Peter

2018-06-11

A vast range of insulating, semiconducting, and metallic nanomaterials have been studied over the past several decades with the aim of understanding how continuous-wave or pulsed laser radiation can influence their chemical functionality and local environment. Many fascinating observations have been made during laser irradiation including, but not limited to, the superheating of solvents, mass-transport-mediated morphology evolution, photodynamic therapy, morphology dependent resonances, and a range of phase transformations. In addition to laser heating, recent experiments have demonstrated the laser cooling of nanoscale materials through the emission of upconverted, anti-Stokes photons by trivalent rare-earth ions. This focus review outlines the analytical modeling of photothermal heat transport with an emphasis on the experimental validation of anti-Stokes laser cooling. This general methodology can be applied to a wide range of photothermal applications, including nanomedicine, photocatalysis, and the synthesis of new materials. The review concludes with an overview of recent advances and future directions for anti-Stokes cooling. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CdS thin films prepared by continuous wave Nd:YAG laser

NASA Astrophysics Data System (ADS)

Wang, H.; Tenpas, Eric W.; Vuong, Khanh D.; Williams, James A.; Schuesselbauer, E.; Bernstein, R.; Fagan, J. G.; Wang, Xing W.

1995-08-01

We report new results on continuous wave Nd:YAG laser deposition of cadmium sulfide thin films. Substrates were soda-lime silicate glass, silica glass, silicon, and copper coated formvar sheets. As deposited films were mixtures of cubic and hexagonal phases, with two different grain sizes. As revealed by SEM micrographs, films had smooth surface morphology. As revealed by TEM analysis, grain sizes were extremely small.

Laser Sounder for Global Measurement of CO2 Concentrations in the Troposphere from Space

NASA Technical Reports Server (NTRS)

Abshire, James B.; Riris, Haris; Kawa, S. Randy; Sun, Xiaoli; Chen, Jeffrey; Stephen, Mark A.; Collatz, G. James; Mao, Jianping; Allan, Graham

2007-01-01

Measurements of tropospheric CO2 abundance with global-coverage, a few hundred km spatial and monthly temporal resolution are needed to quantify processes that regulate CO2 storage by the land and oceans. The Orbiting Carbon Observatory (OCO) is the first space mission focused on atmospheric CO2 for measuring total column CO, and O2 by detecting the spectral absorption in reflected sunlight. The OCO mission is an essential step, and will yield important new information about atmospheric CO2 distributions. However there are unavoidable limitations imposed by its measurement approach. These include best accuracy only during daytime at moderate to high sun angles, interference by cloud and aerosol scattering, and limited signal from CO2 variability in the lower tropospheric CO2 column. We have been developing a new laser-based technique for the remote measurement of the tropospheric CO2 concentrations from orbit. Our initial goal is to demonstrate a lidar technique and instrument technology that will permit measurements of the CO2 column abundance in the lower troposphere from aircraft. Our final goal is to develop a space instrument and mission approach for active measurements of the CO2 mixing ratio at the 1-2 ppmv level. Our technique is much less sensitive to cloud and atmospheric scattering conditions and would allow continuous measurements of CO2 mixing ratio in the lower troposphere from orbit over land and ocean surfaces during day and night. Our approach is to use the 1570nm CO2 band and a 3-channel laser absorption spectrometer (i.e. lidar used an altimeter mode), which continuously measures at nadir from a near polar circular orbit. The approach directs the narrow co-aligned laser beams from the instrument's lasers toward nadir, and measures the energy of the laser echoes reflected from land and water surfaces. It uses several tunable fiber laser transmitters which allowing measurement of the extinction from a single selected CO2 absorption line in the 1570 nm band. This band is free from interference from other gases and has temperature insensitive absorption lines. During the measurement the lasers are tuned on- and off- a selected CO2 line near 1572 nm and a selected O2 line near 768 nm in the Oxygen A band at kHz rates. The lasers use tunable diode seed lasers followed by fiber amplifiers, and have spectral widths much narrower than the gas absorption lines. The receiver uses a 1-m diameter telescope and photon counting detectors and measures the background light and energies of the laser echoes from the surface. The extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on and offline surface echo via the differential optical absorption technique. Our technique rapidly alternates between several on-line wavelengths set to the sides of the selected gas absorption lines. It exploits the atmospheric pressure broadening of the lines to weight the measurement sensitivity to the atmospheric column below 5 km. This maximizes sensitivity to CO2 in the boundary layer, where variations caused by surface sources and sinks are largest. Simultaneous measurements of O2 column will use an identical approach with an O2 line. Thee laser frequencies are tunable and have narrow (MHz) line widths. In combination with sensitive photon counting detectors these enables much higher spectral resolution and precision than is possible with passive spectrometer. 1aser backscatter profiles are also measured, which permits identifying measurements made to cloud tops and through aerosol layers. The measurement approach using lasers in common-nadir-zenith path allows retrieving CO2 column mixing ratios in the lower troposphere irrespective of sun angle. Pulsed laser signals, time gated receiver and a narrow receiver field-of-view are used to isolate the surface laser echo signals and to exclude photons scattered from clouds and aerosols. Nonetheless, the optical absorption change due to a change of a few ppO2 is small, <1 % which makes achieving the needed measurement sensitivities and stabilities quite challenging. Measurement SNRs and stabilities of >600:1 are needed to estimate CO2 mixing ratio at the 1-2 ppm level. We have calculated characteristics of the technique and have demonstrated aspects of the laser, detector and receiver approaches in th e laboratory We have also measured O2 in an absorption cell, and made C02 measurements over a 400 m long (one way) horizontal path using a sensor breadboard. We will describe these and more details of our approach in the paper.

High-efficiency cavity-dumped micro-chip Yb:YAG laser

NASA Astrophysics Data System (ADS)

Nishio, M.; Maruko, A.; Inoue, M.; Takama, M.; Matsubara, S.; Okunishi, H.; Kato, K.; Kyomoto, K.; Yoshida, T.; Shimabayashi, K.; Morioka, M.; Inayoshi, S.; Yamagata, S.; Kawato, S.

2014-09-01

High-efficiency cavity-dumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser was developed. Although the high quantum efficiency of ytterbium-doped laser materials is appropriate for high-efficiency laser oscillation, the efficiency is decreased by their quasi-three/four laser natures. High gain operation by high intensity pumping is suitable for high efficiency oscillation on the quasi-three/four lasers without extremely low temperature cooling. In our group, highest efficiency oscillations for continuous wave, nanosecond to picosecond pulse lasers were achieved at room temperature by the high gain operation in which pump intensities were beyond 100 kW/cm2.

Airborne Laser CO2 Column Measurements: Evaluation of Precision and Accuracy Under a Wide Range of Surface and Atmospheric Conditions

NASA Astrophysics Data System (ADS)

Browell, E. V.; Dobler, J. T.; Kooi, S. A.; Fenn, M. A.; Choi, Y.; Vay, S. A.; Harrison, F. W.; Moore, B.

2011-12-01

This paper discusses the latest flight test results of a multi-frequency intensity-modulated (IM) continuous-wave (CW) laser absorption spectrometer (LAS) that operates near 1.57 μm for remote CO2 column measurements. This IM-LAS system is under development for a future space-based mission to determine the global distribution of regional-scale CO2 sources and sinks, which is the objective of the NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. A prototype of the ASCENDS system, called the Multi-frequency Fiber Laser Lidar (MFLL), has been flight tested in eleven airborne campaigns since May 2005. This paper compares the most recent results obtained during the 2010 and 2011 UC-12 and DC-8 flight tests, where MFLL remote CO2 column measurements were evaluated against airborne in situ CO2 profile measurements traceable to World Meteorological Organization standards. The major change to the MFLL system in 2011 was the implementation of several different IM modes, which could be quickly changed in flight, to directly compare the precision and accuracy of MFLL CO2 measurements in each mode. The different IM modes that were evaluated included "fixed" IM frequencies near 50, 200, and 500 kHz; frequencies changed in short time steps (Stepped); continuously swept frequencies (Swept); and a pseudo noise (PN) code. The Stepped, Swept, and PN modes were generated to evaluate the ability of these IM modes to desensitize MFLL CO2 column measurements to intervening optically thin aerosols/clouds. MFLL was flown on the NASA Langley UC-12 aircraft in May 2011 to evaluate the newly implemented IM modes and their impact on CO2 measurement precision and accuracy, and to determine which IM mode provided the greatest thin cloud rejection (TCR) for the CO2 column measurements. Within the current hardware limitations of the MFLL system, the "fixed" 50 kHz results produced similar SNR values to those found previously. The SNR decreased as expected with increasing IM frequency with the SNR(500 kHz) equal to 31% of SNR(50 kHz). The absolute accuracy of the 50 kHz CO2 measurement showed a previously observed altitude-dependent trend that was greatly reduced at 200 kHz. Laboratory experiments have duplicated this effect which results mainly from IM frequency cross talk between LAS wavelengths in the erbium-doped fiber amplifier (EDFA) and which is reduced when operating at higher IM frequencies. Performance of the Stepped, Swept, and PN modes were evaluated in close time proximity to each other, and these results will be discussed in this paper. A second series of ASCENDS flight tests were conducted on the NASA DC-8 from 25 July to 12 August 2011 over similar local land and ocean targets as in 2010 and with additional long-range flights planned over the corn fields of Iowa, forests in northern Wisconsin, and ice fields of southeastern Alaska. MFLL CO2 measurement results from this field campaign will also be presented.

Development, Modeling and Test of Optical Coatings with Novel Thermal and Stress Management for High Energy Laser Applications

DTIC Science & Technology

2017-01-11

and to mitigate the defects in the coating that lead to damage under laser irradiation . In this final 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND...understand and to mitigate the defects in the coating that lead to damage under laser irradiation . In this final report we list the accomplishments of this...Luke A. Emmert, Wolfgang Rudolph. Time-dependent absorption of TiO_2 optical thin films under pulsed and continuous wave 790??nm laser irradiation

Ion acceleration by laser hole-boring into plasmas

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

Pogorelsky, I. V.; Dover, N. P.; Babzien, M.

By experiment and simulations, we study the interaction of an intense CO{sub 2} laser pulse with slightly overcritical plasmas of fully ionized helium gas. Transverse optical probing is used to show a recession of the front plasma surface with an initial velocity >10{sup 6} m/s driven by hole-boring by the laser pulse and the resulting radiation pressure driven electrostatic shocks. The collisionless shock propagates through the plasma, dissipates into an ion-acoustic solitary wave, and eventually becomes collisional as it slows further. These observations are supported by PIC simulations which prove the conclusion that monoenergetic protons observed in our earlier reportedmore » experiment with a hydrogen jet result from ion trapping and reflection from a shock wave driven through the plasma.« less

Tunable femtosecond lasers with low pump thresholds

NASA Astrophysics Data System (ADS)

Oppo, Karen

The work in this thesis is concerned with the development of tunable, femtosecond laser systems, exhibiting low pump threshold powers. The main motive for this work was the development of a low threshold, self-modelocked Ti:Al2O3 laser in order to replace the conventional large-frame argon-ion pump laser with a more compact and efficient all-solid-state alternative. Results are also presented for an all-solid-state, self-modelocked Cr:LiSAF laser, however most of this work is concerned with self-modelocked Ti:Al2O3 laser systems. In chapter 2, the operation of a regeneratively-initiated, and a hard-aperture self- modelocked Ti:Al2O3 laser, pumped by an argon-ion laser, is discussed. Continuous- wave oscillation thresholds as low as 160mW have been demonstrated, along with self-modelocked threshold powers as low as 500mW. The measurement and suppression of phase noise on modelocked lasers is discussed in chapter 3. This is followed by a comparison of the phase noise characteristics of the regeneratively-initiated, and hard-aperture self-modelocked Ti:Al2O3 lasers. The use of a synchronously-operating, high resolution electron-optical streak camera in the evaluation of timing jitter is also presented. In chapter 4, the construction and self-modelocked operation of an all-solid-state Ti:Al2O3 laser is described. The all-solid-state alternative to the conventional argon-ion pump laser was a continuous-wave, intracavity-frequency doubled, diode-laser pumped Nd:YLF ring laser. At a total diode-laser pump power of 10W, this minilaser was capable of producing a single frequency output of 1W, at 523.5nm in a TEM00 beam. The remainder of this thesis looks at the operation of a self-modelocked Ti:Al2O3 laser generating ultrashort pulses at wavelengths as long as 1053nm. The motive for this work was the development of an all-solid-state, self- modelocked Ti:Al2O3 laser operating at 1053nm, for use as a master oscillator in a Nd:glass power chain.

Influences of misalignment of control mirror of axisymmetric-structural CO2 laser on phase locking.

PubMed

Xu, Yonggen; Li, Yude; Qiu, Yi; Feng, Ting; Fu, Fuxing; Guo, Wei

2008-11-20

Based on the principle of phase locking of an axisymmetric-fold combination CO2 laser under the normal state condition, the mechanisms of phase locking are analyzed when the control mirror is misaligned. Then the overlapping rate (OR) of the mode volume is introduced: the main influences on phase locking are the OR, the average life of the light wave, the root mean square phase error, and the mode coupling coefficient; these influences on phase locking are studied. The distribution of the light intensity reflects the effect of phase locking. It is shown that the misaligned angle has little influence on the phase locking if it is within tolerance.

Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.

PubMed

Zhuang, Fengjiang; Jungbluth, Bernd; Gronloh, Bastian; Hoffmann, Hans-Dieter; Zhang, Ge

2013-07-20

We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment.

A continuous-wave and passively Q-switched Nd:LaGGG laser at 937 nm

NASA Astrophysics Data System (ADS)

Li, Z.-Y.; Ying, H.-Y.; Yang, H.; He, J.-L.

2013-10-01

A diode-end-pumped continuous-wave (CW) and passively Q-switched Nd:LaGGG (GGG: gadolinium gallium garnet) laser at about 937 nm was demonstrated for the first time. The maximum CW output power of 540 mW was obtained with the optical-optical conversion efficiency of 3.2% and the slope efficiency of 4.4%. A V3+:YAG (yttrium aluminum garnet) saturable absorber with the initial transmission of 97% was used for the passive Q-switching regime. The shortest pulse width was achieved as 500 ns with the pulse repetition rate of 96 kHz. The corresponding single-pulse energy and pulse peak power were determined as 1.56 μJ and 3.12 W, respectively.

Undercuts by Laser Shock Forming

NASA Astrophysics Data System (ADS)

Wielage, Hanna; Vollertsen, Frank

2011-05-01

In laser shock forming TEA-CO2-laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 μm were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.

High performance, low dissipation quantum cascade lasers across the mid-IR range.

PubMed

Bismuto, Alfredo; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Muller, Antoine

2015-03-09

In this work, we present the development of low consumption quantum cascade lasers across the mid-IR range. In particular, short cavity single-mode lasers with optimised facet reflectivities have been fabricated from 4.5 to 9.2 μm. Threshold dissipated powers as low as 0.5 W were obtained in continuous wave operation at room temperature. In addition, the beneficial impact of reducing chip length on laser mounting yield is discussed. High power single-mode lasers from the same processed wafers are also presented.

Performance of a 967 nm CW diode end-pumped Er:GSGG laser at 2.79 μm

NASA Astrophysics Data System (ADS)

Wu, Z. H.; Sun, D. L.; Wang, S. Z.; Luo, J. Q.; Li, X. L.; Huang, L.; Hu, A. L.; Tang, Y. Q.; Guo, Q.

2013-05-01

We demonstrated a 967 nm diode end-pumped Er:GSGG laser operated at 2.794 μm with spectral width 3.6 nm in the continuous wave (CW) mode. A maximum output power of 440 mW is obtained at an incident pumping power of 3.4 W, which corresponds to an optical-to-optical efficiency of 13% and slope efficiency of 13.2%. The results suggest that a short cavity and efficient cooling setup for the crystal help to improve laser performance.

Continuous-wave dual-wavelength operation of a distributed feedback laser diode with an external cavity using a volume Bragg grating

NASA Astrophysics Data System (ADS)

Zheng, Yujin; Sekine, Takashi; Kurita, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki

2018-03-01

We demonstrate continuous-wave dual-wavelength operation of a broad-area distributed feedback (DFB) laser diode with a single external-cavity configuration. This high-power DFB laser has a narrow bandwidth (<0.29 nm) and was used as a single-wavelength source. A volume Bragg grating was used as an output coupler for the external-cavity DFB laser to output another stable wavelength beam with a narrow bandwidth of 0.27 nm. A frequency difference for dual-wavelength operation of 0.88 THz was achieved and an output power of up to 415 mW was obtained. The external-cavity DFB laser showed a stable dual-wavelength operation over the practical current and temperature ranges.

Thrust Generation with Low-Power Continuous-Wave Laser and Aluminum Foil Interaction

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

Horisawa, Hideyuki; Sumida, Sota; Funaki, Ikkoh

2010-05-06

The micro-newton thrust generation was observed through low-power continuous-wave laser and aluminum foil interaction without any remarkable ablation of the target surface. To evaluate the thrust characteristics, a torsion-balance thrust stand capable for the measurement of the thrust level down to micro-Newton ranges was developed. In the case of an aluminum foil target with 12.5 micrometer thickness, the maximum thrust level was 15 micro-newtons when the laser power was 20 W, or about 0.75 N/MW. It was also found that the laser intensity, or laser power per unit area, irradiated on the target was significantly important on the control ofmore » the thrust even under the low-intensity level.« less

Continuous-wave supercontinuum laser based on an erbium-doped fiber ring cavity incorporating a highly nonlinear optical fiber.

PubMed

Lee, Ju Han; Takushima, Yuichi; Kikuchi, Kazuro

2005-10-01

We experimentally demonstrate a novel erbium-doped fiber based continuous-wave (cw) supercontinuum laser. The laser has a simple ring-cavity structure incorporating an erbium-doped fiber and a highly nonlinear dispersion-shifted fiber (HNL-DSF). Differently from previously demonstrated cw supercontinuum sources based on single propagation of a strong Raman pump laser beam through a highly nonlinear fiber, erbium gain inside the cavity generates a seed light oscillation, and the oscillated light subsequently evolves into a supercontinuum by nonlinear effects such as modulation instability and stimulated Raman scattering in the HNL-DSF. High quality of the depolarized supercontinuum laser output with a spectral bandwidth larger than 250 nm is readily achieved.

Highly-efficient mid-infrared CW laser operation in a lightly-doped 3 at.% Er:SrF2 single crystal.

PubMed

Su, Liangbi; Guo, Xinsheng; Jiang, Dapeng; Wu, Qinghui; Qin, Zhipeng; Xie, Guoqiang

2018-03-05

3 at.% Er:SrF 2 laser crystals with high optical quality were successfully grown using the temperature gradient technique (TGT). The intense mid-infrared emission was observed around 2.7 μm with excitation by a 970 nm LD. Based on the Judd-Ofelt theory, the emission cross-sections of the 4 I 13/2 - 4 I 11/2 transition were calculated by using the Fuchtbauer-Ladenburg (FL) method. Efficient continuous-wave laser operation at 2.8 µm was achieved with the lightly-doped 3 at.% Er:SrF 2 crystal pumped by a 970 nm laser diode. The laser output power reached up to 1.06 W with a maximum slope efficiency of 26%.

Tunable multicolor and enhanced red emission of monodisperse CaF2:Yb3+/Ho3+ microspheres via Mn2+ doping

NASA Astrophysics Data System (ADS)

Wang, Rui; Yuan, Maohui; Zhang, Chaofan; Wang, Hongyan; Xu, Xiaojun

2018-05-01

Transition metal ions (e.g. Mn2+) and lanthanide co-doped upconversion (UC) materials have attracted wide attention in recent years due to their promising application in multicolor display. Here, we report the hydrothermal synthesis and characterization of Mn2+ doped monodisperse CaF2:Yb3+/Ho3+ microspheres. The results of X-ray diffraction (XRD) revealed that Mn2+ doping does not change the cubic phase of CaF2 material but will lead to diffraction peaks shifting slightly towards higher angle due to the substitution of larger Ca2+ by the relatively smaller Mn2+. Under the excitation of 980 nm continuous wave (CW) laser, these microspheres exhibit green-yellow-red tuning colors and remarkable enhancement of both red to green ratio (R/G) and red to blue ratio (R/B) when increasing Mn2+ concentration from 0 to 30 mol%. The energy migration process between Ho3+ and Mn2+ was proposed and supported by time-decay and power dependence measurements of Ho3+ UC emission. These upconversion materials may have potential applications in optical devices, color display, nanoscale lasers and biomedical imaging.

High-power, single-frequency, continuous-wave second-harmonic-generation of ytterbium fiber laser in PPKTP and MgO:sPPLT.

PubMed

Kumar, S Chaitanya; Samanta, G K; Ebrahim-Zadeh, M

2009-08-03

Characteristics of high-power, narrow-linewidth, continuous-wave (cw) green radiation obtained by simple single-pass second-harmonic-generation (SHG) of a cw ytterbium fiber laser at 1064 nm in the nonlinear crystals of PPKTP and MgO:sPPLT are studied and compared. Temperature tuning and SHG power scaling up to nearly 10 W for input fundamental power levels up to 30 W are performed. Various contributions to thermal effects in both crystals, limiting the SHG conversion efficiency, are studied. Optimal focusing conditions and thermal management schemes are investigated to maximize SHG performance in MgO:sPPLT. Stable green output power and high spatial beam quality with M(2)<1.33 and M(2)<1.34 is achieved in MgO:sPPLT and PPKTP, respectively.

Measurement of absolute frequency of continuous-wave terahertz radiation in real time using a free-running, dual-wavelength mode-locked, erbium-doped fibre laser

PubMed Central

Hu, Guoqing; Mizuguchi, Tatsuya; Zhao, Xin; Minamikawa, Takeo; Mizuno, Takahiko; Yang, Yuli; Li, Cui; Bai, Ming; Zheng, Zheng; Yasui, Takeshi

2017-01-01

A single, free-running, dual-wavelength mode-locked, erbium-doped fibre laser was exploited to measure the absolute frequency of continuous-wave terahertz (CW-THz) radiation in real time using dual THz combs of photo-carriers (dual PC-THz combs). Two independent mode-locked laser beams with different wavelengths and different repetition frequencies were generated from this laser and were used to generate dual PC-THz combs having different frequency spacings in photoconductive antennae. Based on the dual PC-THz combs, the absolute frequency of CW-THz radiation was determined with a relative precision of 1.2 × 10−9 and a relative accuracy of 1.4 × 10−9 at a sampling rate of 100 Hz. Real-time determination of the absolute frequency of CW-THz radiation varying over a few tens of GHz was also demonstrated. Use of a single dual-wavelength mode-locked fibre laser, in place of dual mode-locked lasers, greatly reduced the size, complexity, and cost of the measurement system while maintaining the real-time capability and high measurement precision. PMID:28186148

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.

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.

Development of MBE grown Pb-salt semiconductor lasers for the 8.0 to 15.0 micrometer spectral region

NASA Technical Reports Server (NTRS)

Miller, M. D.

1981-01-01

Diodes lasers are fabricated using multiple source molecular beam expitaxial growth of (PbSn)Te on BaF2 substrates. Methods for crystal growth, crystal transfer, and device fabrication by photolithographic techniques were developed. The lasers operate in the spectra range from 10 microns to 14 microns and at temperatures from 12K to 60K continuous wave and to 95 K pulsed.

Mechanistic investigation of doxycycline photosensitization by picosecond-pulsed and continuous wave laser irradiation of cells in culture

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

Shea, C.R.; Hefetz, Y.; Gillies, R.

1990-04-15

In order to elucidate the photophysical mechanisms of cellular phototoxicity sensitized by doxycycline, MGH-U1 human bladder carcinoma cells in vitro were treated with 20.7 microM doxycycline and irradiated with either a pulsed (lambda = 355 nm, pulse duration = 24 ps) or a continuous wave (lambda = 351 nm) laser. Cumulative radiant exposure and irradiance were systematically varied in experiments with both lasers. Phototoxicity was assessed by epifluorescence microscopy of unfixed cells using rhodamine 123 labeling of mitochondria. With the continuous wave source, the cumulative radiant exposure required for induction of phototoxic injury was independent of irradiance. With the 24-ps-pulsedmore » source, a significantly lower cumulative radiant exposure was required to induce the phototoxicity when the peak irradiance was 5.8 x 10(7) or 1.3 x 10(8) watts cm-2 compared with when peak irradiance was either lower (6.0 x 10(6) watts cm-2) or higher (7.6 x 10(8) watts cm-2). The measured fluorescence lifetimes of doxycycline in buffered saline solution were longer than the laser pulse duration of 24 ps. The increased efficiency of photosensitization at the optimal peak irradiance in the ps domain appears to result from sequential multiphoton absorption involving higher excited states of the singlet manifold. At the highest irradiance studied, on the other hand, reduced efficiency of photosensitization is attributed to increased photodegradation of doxycycline from higher excited states by processes such as photoionization. A model consistent with these observations is presented along with calculations, based on simple rate equations, that fit the essentials of the proposed model.« less

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.

High-speed digital holography for neutral gas and electron density imaging

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

Granstedt, E. M., E-mail: egranstedt@gmail.com; Thomas, C. E.; Kaita, R.

2016-05-15

An instrument was developed using digital holographic reconstruction of the wavefront from a CO{sub 2} laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO{sub 2} laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfullymore » reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.« less

Large energy laser pulses with high repetition rate by graphene Q-switched solid-state laser.

PubMed

Li, Xian-lei; Xu, Jin-long; Wu, Yong-zhong; He, Jing-liang; Hao, Xiao-peng

2011-05-09

We demonstrated that the graphene could be used as an effective saturable absorber for Q-switched solid-state lasers. A graphene saturable absorber mirror was fabricated with large and high-quality graphene sheets deprived from the liquid phase exfoliation. Using this mirror, 105-ns pulses and 2.3-W average output power are obtained from a passively Q-switched Nd:GdVO(4) laser. The maximum pulse energy is 3.2 μJ. The slope efficiency is as high as 37% approximating to 40% of the continue-wave laser, indicating a low intrinsic loss of the graphene. © 2011 Optical Society of America

Laser emission from diode-pumped Nd:YAG ceramic waveguide lasers realized by direct femtosecond-laser writing technique.

PubMed

Salamu, Gabriela; Jipa, Florin; Zamfirescu, Marian; Pavel, Nicolaie

2014-03-10

We report on realization of buried waveguides in Nd:YAG ceramic media by direct femtosecond-laser writing technique and investigate the waveguides laser emission characteristics under the pump with fiber-coupled diode lasers. Laser pulses at 1.06 μm with energy of 2.8 mJ for the pump with pulses of 13.1-mJ energy and continuous-wave output power of 0.49 W with overall optical efficiency of 0.13 were obtained from a 100-μm diameter circular cladding waveguide realized in a 0.7-at.% Nd:YAG ceramic. A circular waveguide of 50-μm diameter yielded laser pulses at 1.3 μm with 1.2-mJ energy.

Thulium fiber laser for the use in low-invasive endoscopic and robotic surgery of soft biological tissues

NASA Astrophysics Data System (ADS)

Michalska, M.; Brojek, W.; Rybak, Z.; Sznelewski, P.; Mamajek, M.; Gogler, S.; Swiderski, J.

2016-12-01

An all-fiber, diode-pumped, continuous-wave Tm3+-doped fiber laser operated at a wavelength of 1.94 μm was developed. 37.4 W of output power with a slope efficiency as high as 57% with respect to absorbed pump power at 790 nm was demonstrated. The laser output beam quality factor M2 was measured to be 1.2. The output beam was very stable with power fluctuations <1% measured over 1 hour. The laser system is to be implemented as a scalpel for surgery of soft biological tissues.

Versatile monolithic 2-micron laser systems

NASA Astrophysics Data System (ADS)

Wysmolek, M.; Steinke, M.; Neumann, J.; Kracht, D.

2018-02-01

To answer a growing demand in development of high power pulsed and continuous wave sources at 2 micron spectral range we have participated in several projects, which resulted in a delivery of versatile monolithic sources providing picosecond, nanosecond and CW laser signal. As an example of pulsed sources we developed all-fiber monolithic devices based on a directly modulated laser diode and gain-switched laser diode to generate nanosecond and picosecond pulses, respectively, which are amplified in the same fiber amplifier chain up to 50 µJ with 96 ps and more than 1 mJ with pulses longer than 35 ns.

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

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

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

DOE PAGES

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer; ...

2017-02-14

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Design investigation of solar-powered lasers for space applications

NASA Technical Reports Server (NTRS)

1982-01-01

The feasibility of using solar powered continuous wave (CW) lasers for space power transmission was investigated. Competing conceptual designs are considered. Optical pumping is summarized. Solar pumped Lasant type lasers are outlined. Indirect solar pumped lasers are considered.

The effect of CO2 and Nd:YAP lasers on CAD/CAM Ceramics: SEM, EDS and thermal studies

PubMed Central

Fornaini, Carlo; Rocca, Jean Paul; Muhammad, Omid H; Medioni, Etienne; Cucinotta, Annamaria; Brulat-Bouchard, Nathalie

2016-01-01

Background and aims: The objective of this study was to investigate the interaction of infrared laser light on Computer Aided Design and Computer Aided Manufacturing (CAD/CAM) ceramic surfaces. Material and Methods: Sixty CAD/CAM ceramic discs were prepared and divided into two different groups: lithiumdisilicate ceramic (IPSe.maxCADs) and Zirconia ceramic (IPSe.maxZirCADs). The laser irradiation was performed on graphite and non-graphite surfaces with a Carbon Dioxide laser at 5W and 10W power in continuous mode (CW mode) and with Neodymium Yttrium Aluminum Perovskite (Nd:YAP) laser at 10W. Surface textures and compositions were examined using Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Thermal elevation was measured by thermocouple during laser irradiation. Results: The SEM observation showed a rough surface plus cracks and fissures on CO2 10W samples and melting areas in Nd:YAP samples; moreover, with CO2 5W smooth and shallow surfaces were observed. EDS analysis revealed that laser irradiation does not result in modifications of the chemical composition even if minor changes in the atomic mass percentage of the components were registered. Thermocouple showed several thermal changes during laser irradiation. Conclusion: CO2 and Nd:YAP lasers modify CAD/CAM ceramic surface without chemical composition modifications. PMID:27141152

The Detection of Gravitational Waves

NASA Astrophysics Data System (ADS)

Blair, David G.

2005-10-01

Part I. An Introduction to Gravitational Waves and Methods for their Detection: 1. Gravitational waves in general relativity D. G. Blair; 2. Sources of gravitational waves D. G. Blair; 3. Gravitational wave detectors D. G. Blair; Part II. Gravitational Wave Detectors: 4. Resonant-bar detectors D. G. Blair; 5. Gravity wave dewars W. O. Hamilton; 6. Internal friction in high Q materials J. Ferreirinko; 7. Motion amplifiers and passive transducers J. P. Richard; 8. Parametric transducers P. J. Veitch; 9. Detection of continuous waves K. Tsubono; 10. Data analysis and algorithms for gravitational wave-antennas G. V. Paalottino; Part III. Laser Interferometer Antennas: 11. A Michelson interferometer using delay lines W. Winkler; 12. Fabry-Perot cavity gravity-wave detectors R. W. P. Drever; 13. The stabilisation of lasers for interferometric gravitational wave detectors J. Hough; 14. Vibration isolation for the test masses in interferometric gravitational wave detectors N. A. Robertson; 15. Advanced techniques A. Brillet; 16. Data processing, analysis and storage for interferometric antennas B. F. Schutz; 17. Gravitational wave detection at low and very low frequencies R. W. Hellings.

Comparison of fiber delivered CO2 laser and electrocautery in transoral robot assisted tongue base surgery.

PubMed

Karaman, Murat; Gün, Taylan; Temelkuran, Burak; Aynacı, Engin; Kaya, Cem; Tekin, Ahmet Mahmut

2017-05-01

To compare intra-operative and post-operative effectiveness of fiber delivered CO 2 laser to monopolar electrocautery in robot assisted tongue base surgery. Prospective non-randomized clinical study. Twenty moderate to severe obstructive sleep apnea (OSA) patients, non-compliant with Continuous Positive Airway Pressure (CPAP), underwent Transoral Robotic Surgery (TORS) using the Da Vinci surgical robot in our University Hospital. OSA was treated with monopolar electrocautery in 10 patients, and with flexible CO 2 laser fiber in another 10 patients. The following parameters in the two sets are analyzed: Intraoperative bleeding that required cauterization, robot operating time, need for tracheotomy, postoperative self-limiting bleeding, length of hospitalization, duration until start of oral intake, pre-operative and post-operative minimum arterial oxygen saturation, pre-operative and post-operative Epworth Sleepiness Scale score, postoperative airway complication and postoperative pain. Mean follow-up was 12 months. None of the patients required tracheotomy and there were no intraoperative complications related to the use of the robot or the CO 2 laser. The use of CO 2 laser in TORS-assisted tongue base surgery resulted in less intraoperative bleeding that required cauterization, shorter robot operating time, shorter length of hospitalization, shorter duration until start of oral intake and less postoperative pain, when compared to electrocautery. Postoperative apnea-hypopnea index scores showed better efficacy of CO 2 laser than electrocautery. Comparison of postoperative airway complication rates and Epworth sleepiness scale scores were found to be statistically insignificant between the two groups. The use of CO 2 laser in robot assisted tongue base surgery has various intraoperative and post-operative advantages when compared to monopolar electrocautery.

Thermal affected zone obtained in machining steel XC42 by high-power continuous CO 2 laser

NASA Astrophysics Data System (ADS)

Jebbari, Neila; Jebari, Mohamed Mondher; Saadallah, Faycal; Tarrats-Saugnac, Annie; Bennaceur, Raouf; Longuemard, Jean Paul

2008-09-01

A high-power continuous CO 2 laser (4 kW) can provide energy capable of causing melting or even, with a special treatment of the surface, vaporization of an XC42-steel sample. The laser-metal interaction causes an energetic machining mechanism, which takes place according to the assumption that the melting front precedes the laser beam, such that the laser beam interacts with a preheated surface whose temperature is near the melting point. The proposed model, obtained from the energy balance during the interaction time, concerns the case of machining with an inert gas jet and permits the calculation of the characteristic parameters of the groove according to the characteristic laser parameters (absorbed laser energy and impact diameter of the laser beam) and allows the estimation of the quantity of the energy causing the thermal affected zone (TAZ). This energy is equivalent to the heat quantity that must be injected in the heat propagation equation. In the case of a semi-infinite medium with fusion temperature at the surface, the resolution of the heat propagation equation gives access to the width of the TAZ.

Fiber laser at 2 μm for soft tissue surgery

NASA Astrophysics Data System (ADS)

Ghosh, Aditi; Pal, Debasis; Sen, Ranjan; Pal, Atasi

2014-11-01

Strong water absorption at 2 μm generated recent interest in lasers at this wavelength for soft tissue surgery. A fiber Bragg grating-based, all-fiber, continuous-wave, cladding pumped, thulium-doped fiber laser at 1.95 μm is configured. The thulium-doped active fiber with octagonal-shaped inner cladding is pumped at 808 nm (total power of 17 W) with six laser diodes through a combiner. The laser power of 3.3 W (after elimination of unabsorbed pump power through a passive fiber) with slope efficiency of 23% (against launched pump power) is achieved. The linear variation of laser power with pump offers scope of further power scaling.

Continuous wave operation of quantum cascade lasers with frequency-shifted feedback

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

Lyakh, A., E-mail: arkadiy.lyakh@ucf.edu; NanoScience Technology Center, University of Central Florida, 12424 Research Pkwy, Orlando, FL 32826; College of Optics and Photonics, University of Central Florida, 304 Scorpius St, Orlando, FL 32826

2016-01-15

Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm{sup −1} for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep times, consistent with sound wave grating period variation across the illuminated area on the acousto-optic modulator. Standoff detection capability of the AOM-based QCL setup was demonstrated for several solid materials.

Efficient Ho:LuLiF4 laser diode-pumped at 1.15 μm.

PubMed

Wang, Sheng-Li; Huang, Chong-Yuan; Zhao, Cheng-Chun; Li, Hong-Qiang; Tang, Yu-Long; Yang, Nan; Zhang, Shuai-Yi; Hang, Yin; Xu, Jian-Qiu

2013-07-15

We report the first laser operation based on Ho(3+)-doped LuLiF(4) single crystal, which is directly pumped with 1.15-μm laser diode (LD). Based on the numerical model, it is found that the "two-for-one" effect induced by the cross-relaxation plays an important role for the laser efficiency. The maximum continuous wave (CW) output power of 1.4 W is produced with a beam propagation factor of M(2) ~2 at the lasing wavelength of 2.066 μm. The slope efficiency of 29% with respect to absorbed power is obtained.

Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation.

PubMed

Chen, Charlton J; Zheng, Jiangjun; Gu, Tingyi; McMillan, James F; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee; Wong, Chee Wei

2011-06-20

We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

Pulsed 2-micron Laser Transmitter For Carbon Dioxide Sensing From Space

NASA Astrophysics Data System (ADS)

Singh, U. N.; Yu, J.; Bai, Y.; Petros, M.

2011-12-01

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. Studies of the carbon cycle are limited by the tools available to precisely measure CO2 concentrations by remote sensing. Active sensing, using the Integrated Path Differential Absorption (IPDA) approach, permits measurements day and night, at all latitudes and seasons. The development of a high pulse energy 2-μm laser transmitter for high-precision CO2 measurements from space leverages years of NASA investment in solid-state laser technology. Under NASA Laser Risk Reduction Program, funded by Earth Science Technology Office, researchers at NASA Langley Research Center developed an injection seeded, high repetition rate, Q-switched Ho:YLF laser transmitter for CO2 Differential Absorption Lidar/IPDA (profile/column) measurements from ground and airborne platforms. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. NASA LaRC's 2-micron pulsed laser transmitter possesses advantages over current passive and CW active sensors. First, the pulsed format provides a built-in means for determining range to the scattering target and effectively filtering out the scattering from thin clouds and aerosols, thus eliminating a source of measurement bias. Second, by concentrating the laser energy into a pulse, sufficient backscatter signal strength can be obtained from aerosol scattering rather than relying on a hard target at a known distance. Third, the absorption line at the 2.05 μm band is ideally suited for the CO2 concentration measurement. In particular, the weighting function of 2 μm is optimum for measurement in the lower troposphere where the sources and sinks of CO2 are located. The planned laser transmitter development will lead to a Tm:Fiber pumped Ho:YLF laser transmitter capable of delivering 65 mJ at 50 Hz at on-line wavelength and 50 mJ at 50 Hz at off-line wavelength. The planned laser technology development and performance capabilities are a major step forward in the laser transmitter requirements called out in recent comprehensive system studies, e.g., the European Space Agency (ESA) exploration mission studies, A-SCOPE, for future CO2 column density measurements from space. The planned laser technology development is relevant to NASA's earth science priorities, such as NASA ASCENDS mission for space-based CO2 column density measurements. This presentation will provide an overview of the current status of laser transmitter development and describe future technology development to meet the transmitter requirement for a space-based column averaged measurement of CO2 concentration.

Self-focusing Distance of Very High Power Laser Pulses

NASA Astrophysics Data System (ADS)

Fibich, Gadi; Eisenmann, Shmuel; Ilan, Boaz; Erlich, Yossi; Fraenkel, Moshe; Henis, Zohar; Gaeta, Alexander L.; Zigler, Arie

2005-07-01

We show numerically for continuous-wave beams and experimentally for femtosecond pulses propagating in air, that the collapse distance of intense laser beams in a bulk Kerr medium scales as 1/P^1/2 for input powers P that are moderately above the critical power for self focusing, but that at higher powers the collapse distance scales as 1/P.

Development of an automated diode-laser-based multicomponent gas sensor

NASA Technical Reports Server (NTRS)

Richter, D.; Lancaster, D. G.; Tittel, F. K.

2000-01-01

The implementation and application of a portable fiber-coupled trace-gas sensor for the detection of several trace gases, including CO2, CH4, and H2CO, are reported. This particular sensor is based on a cw fiber-amplified near-infrared (distributed Bragg reflector) diode laser and an external cavity diode laser that are frequency converted in a periodically poled lithium niobate crystal to the mid-IR spectroscopic fingerprint region (3.3-4.4 micrometers). A continuous absorption spectrum of CH4 and H2CO from 3.37 to 3.10 micrometers with a spectral resolution of 40 MHz (approximately 0.0013 cm-1) demonstrated the spectral performance that can be achieved by means of automated wavelength tuning and phase matching with stepper motor control. Autonomous long-term detection of ambient CO2 and CH4 over a 3- and 7-day period was also demonstrated.

Cooling rates and intensity limitations for laser-cooled ions at relativistic energies

NASA Astrophysics Data System (ADS)

Eidam, Lewin; Boine-Frankenheim, Oliver; Winters, Danyal

2018-04-01

The ability of laser cooling for relativistic ion beams is investigated. For this purpose, the excitation of relativistic ions with a continuous wave and a pulsed laser is analyzed, utilizing the optical Bloch equations. The laser cooling force is derived in detail and its scaling with the relativistic factor γ is discussed. The cooling processes with a continuous wave and a pulsed laser system are investigated. Optimized cooling scenarios and times are obtained in order to determine the required properties of the laser and the ion beam for the planed experiments. The impact of beam intensity effects, like intrabeam scattering and space charge are analyzed. Predictions from simplified models are compared to particle-in-cell simulations and are found to be in good agreement. Finally two realistic example cases of Carbon ions in the ESR and relativistic Titanium ions in SIS100 are compared in order to discuss prospects for future laser cooling experiments.

Colloid-Interface-Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities.

PubMed

Huang, Liu; Wan, Xiaodong; Rong, Hongpan; Yao, Yuan; Xu, Meng; Liu, Jia; Ji, Muwei; Liu, Jiajia; Jiang, Lan; Zhang, Jiatao

2018-04-01

High-efficient charge and energy transfer between nanocrystals (NCs) in a bottom-up assembly are hard to achieve, resulting in an obstacle in application. Instead of the ligands exchange strategies, the advantage of a continuous laser is taken with optimal wavelength and power to irradiate the film-scale NCs superlattices at solid-liquid interfaces. Owing to the Au-based NCs' surface plasmon resonance (SPR) effect, the gentle laser irradiation leads the Au NCs or Au@CdS core/shell NCs to attach each other with controlled pattern at the interfaces between solid NCs phase and liquid ethanol/ethylene glycol. A continuous wave 532 nm laser (6.68-13.37 W cm -2 ), to control Au-based superlattices, is used to form the monolayer with uniformly reduced interparticle distance followed by welded superstructures. Considering the size effect to Au NCs' melting, when decreasing the Au NCs size to ≈5 nm, stronger welding nanostructures are obtained with diverse unprecedented shapes which cannot be achieved by normal colloidal synthesis. With the help of facile scale-up and formation at solid-liquid interfaces, and a good connection of crystalline between NCs, the obtained plasmonic superstructured films that could be facilely transferred onto different substrates exhibit broad SPR absorption in the visible and near-infrared regime, enhanced electric conductivities, and wide applications as surface enhanced Raman scattering (SERS)-active substrates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructure and Mechanical Properties of Laser Clad and Post-cladding Tempered AISI H13 Tool Steel

NASA Astrophysics Data System (ADS)

Telasang, Gururaj; Dutta Majumdar, Jyotsna; Wasekar, Nitin; Padmanabham, G.; Manna, Indranil

2015-05-01

This study reports a detailed investigation of the microstructure and mechanical properties (wear resistance and tensile strength) of hardened and tempered AISI H13 tool steel substrate following laser cladding with AISI H13 tool steel powder in as-clad and after post-cladding conventional bulk isothermal tempering [at 823 K (550 °C) for 2 hours] heat treatment. Laser cladding was carried out on AISI H13 tool steel substrate using a 6 kW continuous wave diode laser coupled with fiber delivering an energy density of 133 J/mm2 and equipped with a co-axial powder feeding nozzle capable of feeding powder at the rate of 13.3 × 10-3 g/mm2. Laser clad zone comprises martensite, retained austenite, and carbides, and measures an average hardness of 600 to 650 VHN. Subsequent isothermal tempering converted the microstructure into one with tempered martensite and uniform dispersion of carbides with a hardness of 550 to 650 VHN. Interestingly, laser cladding introduced residual compressive stress of 670 ± 15 MPa, which reduces to 580 ± 20 MPa following isothermal tempering. Micro-tensile testing with specimens machined from the clad zone across or transverse to cladding direction showed high strength but failure in brittle mode. On the other hand, similar testing with samples sectioned from the clad zone parallel or longitudinal to the direction of laser cladding prior to and after post-cladding tempering recorded lower strength but ductile failure with 4.7 and 8 pct elongation, respectively. Wear resistance of the laser surface clad and post-cladding tempered samples (evaluated by fretting wear testing) registered superior performance as compared to that of conventional hardened and tempered AISI H13 tool steel.

Grating tuned unstable resonator laser cavity

DOEpatents

Johnson, Larry C.

1982-01-01

An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

Compact near-IR and mid-IR cavity ring down spectroscopy device

NASA Technical Reports Server (NTRS)

Miller, J. Houston (Inventor)

2011-01-01

This invention relates to a compact cavity ring down spectrometer for detection and measurement of trace species in a sample gas using a tunable solid-state continuous-wave mid-infrared PPLN OPO laser or a tunable low-power solid-state continuous wave near-infrared diode laser with an algorithm for reducing the periodic noise in the voltage decay signal which subjects the data to cluster analysis or by averaging of the interquartile range of the data.

Atmospheric remote sensing of water vapor, HCl and CH4 using a continuously tunable Co:MgF2 laser

NASA Technical Reports Server (NTRS)

Menyuk, Norman; Killinger, Dennis K.

1987-01-01

A differential-absorption lidar system has been developed which uses a continuously tunable (1.5-2.3 micron) cobalt-doped magnesium fluoride laser as the radiation source. Preliminary atmospheric measurements of water vapor, HCl, and CH4 have been made with this system, including both path-averaged and ranged-resolved DIAL measurements at ranges up to 6 and 3 km, respectively.

Recent advances in CO2 laser catalysts

NASA Technical Reports Server (NTRS)

Upchurch, B. T.; Schryer, D. R.; Brown, K. G.; Kielin, E. J.; Hoflund, G. B.; Gardner, S. D.

1991-01-01

This paper discusses several recent advances in CO2 laser catalysts including comparisons of the activity of Au/MnO2 to Pt/SnO2 catalysts with possible explanations for observed differences. The catalysts are compared for the effect of test gas composition, pretreatment temperature, isotopic integrity, long term activity, and gold loading effects on the Au/MnO2 catalyst activity. Tests conducted to date include both long-term tests of up to six months continuous operation and short-term tests of one week or more that include isotopic integrity testing.

Theory of CW lidar aerosol backscatter measurements and development of a 2.1 microns solid-state pulsed laser radar for aerosol backscatter profiling

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Henderson, Sammy W.; Frehlich, R. G.

1991-01-01

The performance and calibration of a focused, continuous wave, coherent detection CO2 lidar operated for the measurement of atmospheric backscatter coefficient, B(m), was examined. This instrument functions by transmitting infrared (10 micron) light into the atmosphere and collecting the light which is scattered in the rearward direction. Two distinct modes of operation were considered. In volume mode, the scattered light energy from many aerosols is detected simultaneously, whereas in the single particle mode (SPM), the scattered light energy from a single aerosol is detected. The analysis considered possible sources of error for each of these two cases, and also considered the conditions where each technique would have superior performance. The analysis showed that, within reasonable assumptions, the value of B(m) could be accurately measured by either the VM or the SPM method. The understanding of the theory developed during the analysis was also applied to a pulsed CO2 lidar. Preliminary results of field testing of a solid state 2 micron lidar using a CW oscillator is included.

Nd:GdVO4 ring laser pumped by laser diodes

NASA Astrophysics Data System (ADS)

Hao, E. J.; Li, T.; Wang, Z. D.; Zhang, Y.

2013-02-01

The design and operation of a laser diode-pumped Nd:GdVO4 ring laser is described. A composite crystal (Nd:GdVO4/YVO4) with undoped ends is single-end pumped by a fiber-coupled laser diode (LD) at 808 nm. A four-mirror ring cavity is designed to keep the laser operating unidirectionally, which eliminates spatial hole burning in the standing-wave cavity. This laser can operate either as continuous wave (CW) or Q-switched. The single-frequency power obtained was 9.1 W at 1063 nm. Q-switched operation produced 0.23 mJ/pulse at 20 kHz in the fundamental laser.

Love waves trains observed after the MW 8.1 Tehuantepec earthquake by an underground ring laser gyroscope

NASA Astrophysics Data System (ADS)

Simonelli, A.; Belfi, J.; Beverini, N.; Di Virgilio, A.; Giacomelli, U.; De Luca, G.; Igel, H.

2017-12-01

We report the observation and analysis of the MW 8.1 Tehuantepec earthquake-induced rotational ground motion as observed by the Gingerino ring laser gyroscope (RLG).This instrument is located inside the National laboratory of the "Istituto Nazionale di Fisica Nucleare" in Gran Sasso (Italy) in a deep underground environment.We compare the vertical rotation rate with the horizontal acceleration measured by a co-located broadband seismometer. This analysis, performed by means of a wavelet-based correlation method, permits to identify the G1,G2,G3,G4 onsets of the surface Love waves in the 120 to 280 seconds period range.

Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy).

PubMed

De Rosa, Maurizio; Gagliardi, Gianluca; Rocco, Alessandra; Somma, Renato; De Natale, Paolo; De Natale, Giuseppe

2007-04-20

We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-microm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater - FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (+/- 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS - Baia Levante beach) obtaid during the 1977-1993 heating phase of the crater fumaroles. In this work much more homogeneous values are found in different points of the three sites investigated. The field work, although carried out in a limited time window (25th-28th August 2004), pointed out the new apparatus is suitable for continuous gas monitoring of the two species and their ratios, which are important geochemical indicators of volcanic activity, for which other reliable continuous monitoring systems are not yet available.

Photobiomodulation with Pulsed and Continuous Wave Near-Infrared Laser (810 nm, Al-Ga-As) Augments Dermal Wound Healing in Immunosuppressed Rats

PubMed Central

Keshri, Gaurav K.; Gupta, Asheesh; Yadav, Anju; Sharma, Sanjeev K.; Singh, Shashi Bala

2016-01-01

Chronic non-healing cutaneous wounds are often vulnerable in one or more repair phases that prevent normal healing and pose challenges to the use of conventional wound care modalities. In immunosuppressed subject, the sequential stages of healing get hampered, which may be the consequences of dysregulated or stagnant wound inflammation. Photobiomodulation (PBM) or low-level laser (light) therapy (LLLT) emerges as a promising drug-free, non-invasive biophysical approach for promoting wound healing, reduction of inflammation, pain and restoration of functions. The present study was therefore undertaken to evaluate the photobiomodulatory effects of 810 nm diode laser (40 mW/cm2; 22.6 J/cm2) with pulsed (10 and 100 Hz, 50% duty cycle) and continuous wave on full-thickness excision-type dermal wound healing in hydrocortisone-induced immunosuppressed rats. Results clearly delineated that 810 nm PBM at 10 Hz was more effective over continuous and 100 Hz frequency in accelerating wound healing by attenuating the pro-inflammatory markers (NF-kB, TNF-α), augmenting wound contraction (α-SM actin), enhancing cellular proliferation, ECM deposition, neovascularization (HIF-1α, VEGF), re-epithelialization along with up-regulated protein expression of FGFR-1, Fibronectin, HSP-90 and TGF-β2 as compared to the non-irradiated controls. Additionally, 810 nm laser irradiation significantly increased CCO activity and cellular ATP contents. Overall, the findings from this study might broaden the current biological mechanism that could be responsible for photobiomodulatory effect mediated through pulsed NIR 810 nm laser (10 Hz) for promoting dermal wound healing in immunosuppressed subjects. PMID:27861614

75 FR 9868 - University of Arkansas; Notice of Decision on Applications for Duty-Free Entry of Scientific...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

..., 2010. Reasons: The instrument must be able to perform using lasers with both continuous wave (CW) and pulsed mode. The use of picoseconds pulsed lasers is necessary to measure fluorescence lifetime. The use of CW lasers, so that the fluorophores will be continuously excited, is necessary to measure...

absorption sensor for sensitive temperature and species measurements in high-temperature gases

NASA Astrophysics Data System (ADS)

Spearrin, R. M.; Ren, W.; Jeffries, J. B.; Hanson, R. K.

2014-09-01

A continuous-wave laser absorption diagnostic, based on the infrared CO2 bands near 4.2 and 2.7 μm, was developed for sensitive temperature and concentration measurements in high-temperature gas systems using fixed-wavelength methods. Transitions in the respective R-branches of both the fundamental υ 3 band (~2,350 cm-1) and combination υ 1 + υ 3 band (~3,610 cm-1) were chosen based on absorption line-strength, spectral isolation, and temperature sensitivity. The R(76) line near 2,390.52 cm-1 was selected for sensitive CO2 concentration measurements, and a detection limit of <5 ppm was achieved in shock tube kinetics experiments (~1,300 K). A cross-band, two-line thermometry technique was also established utilizing the R(96) line near 2,395.14 cm-1, paired with the R(28) line near 3,633.08 cm-1. This combination yields high temperature sensitivity (ΔE" = 3,305 cm-1) and expanded range compared with previous intra-band CO2 sensors. Thermometry performance was validated in a shock tube over a range of temperatures (600-1,800 K) important for combustion. Measured temperature accuracy was demonstrated to be better than 1 % over the entire range of conditions, with a standard error of ~0.5 % and µs temporal resolution.

Terahertz wave electro-optic measurements with optical spectral filtering

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

Ilyakov, I. E., E-mail: igor-ilyakov@mail.ru; Shishkin, B. V.; Kitaeva, G. Kh.

We propose electro-optic detection techniques based on variations of the laser pulse spectrum induced during pulse co-propagation with terahertz wave radiation in a nonlinear crystal. Quantitative comparison with two other detection methods is made. Substantial improvement of the sensitivity compared to the standard electro-optic detection technique (at high frequencies) and to the previously shown technique based on laser pulse energy changes is demonstrated in experiment.

Microhardness evaluations of CAD/CAM ceramics irradiated with CO2 or Nd:YAP laser

PubMed Central

Rocca, Jean Paul; Fornaini, Carlo; Medioni, Etienne; Brulat-Bouchard, Nathalie

2017-01-01

Background and aims The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment. Materials and Methods Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgf for lithium disilicate and 1 kgf for zirconia. Results Emax CAD irradiated with CO2 at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa. Conclusion CO2 laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD). PMID:28740324

25  W/m² collection efficiency solar-pumped Nd:YAG laser by a heliostat-parabolic mirror system.

PubMed

Liang, D; Almeida, J; Vistas, C R

2016-09-20

A large aspheric fused silica lens was used to couple efficiently the concentrated solar radiation from the focal zone of a 1.5-m-diameter primary concentrator into a 4-mm-diameter, 35-mm-long Nd:YAG single-crystal rod within a conical pump cavity. Continuous-wave laser power of 29.3 W was measured, attaining 25.0  W/m² solar laser collection efficiency, corresponding to a 19% increase over the previous record. Its laser beam figure of merit-the ratio between laser power and the product of Mx2, My2 beam quality factors-of 0.01 W is 1.6 times higher than that of a direct tracking solar laser with 30  W/m² collection efficiency. A strong dependency of solar laser power on laser resonator cavity length was found.

Research of centroiding algorithms for extended and elongated spot of sodium laser guide star

NASA Astrophysics Data System (ADS)

Shao, Yayun; Zhang, Yudong; Wei, Kai

2016-10-01

Laser guide stars (LGSs) increase the sky coverage of astronomical adaptive optics systems. But spot array obtained by Shack-Hartmann wave front sensors (WFSs) turns extended and elongated, due to the thickness and size limitation of sodium LGS, which affects the accuracy of the wave front reconstruction algorithm. In this paper, we compared three different centroiding algorithms , the Center-of-Gravity (CoG), weighted CoG (WCoG) and Intensity Weighted Centroid (IWC), as well as those accuracies for various extended and elongated spots. In addition, we compared the reconstructed image data from those three algorithms with theoretical results, and proved that WCoG and IWC are the best wave front reconstruction algorithms for extended and elongated spot among all the algorithms.

High power tunable mid-infrared optical parametric oscillator enabled by random fiber laser.

PubMed

Wu, Hanshuo; Wang, Peng; Song, Jiaxin; Ye, Jun; Xu, Jiangming; Li, Xiao; Zhou, Pu

2018-03-05

Random fiber laser, as a kind of novel fiber laser that utilizes random distributed feedback as well as Raman gain, has become a research focus owing to its advantages of wavelength flexibility, modeless property and output stability. Herein, a tunable optical parametric oscillator (OPO) enabled by a random fiber laser is reported for the first time. By exploiting a tunable random fiber laser to pump the OPO, the central wavelength of idler light can be continuously tuned from 3977.34 to 4059.65 nm with stable temporal average output power. The maximal output power achieved is 2.07 W. So far as we know, this is the first demonstration of a continuous-wave tunable OPO pumped by a tunable random fiber laser, which could not only provide a new approach for achieving tunable mid-infrared (MIR) emission, but also extend the application scenarios of random fiber lasers.

Very compact and high-power CW self-Raman laser for ophthalmological applications

NASA Astrophysics Data System (ADS)

Ortega, Tiago A.; Mota, Alessandro D.; Rossi, Giuliano; C. de Castro, Guilherme; Fontes, Yuri C.; Costal, Glauco Z.; Yasuoka, Fatima M. M.; Stefani, Mario A.; Lee, Andrew; Pask, Helen; C. de Castro N., Jarbas

2010-02-01

In this work, we present a continuous-wave yellow laser operating at 586.5nm based on self-Raman conversion in Nd:GdVO4. We report more than 4.2W CW and 5.5W instantaneous output at a 50% duty cycle regime. This is the highest CW power of a self-Raman laser to be reported so far. We also demonstrate the integration of this laser cavity into a console for applications in ophthalmology, and more specifically for retinal photocoagulation therapies.

Room-temperature continuous-wave electrically injected InGaN-based laser directly grown on Si

NASA Astrophysics Data System (ADS)

Sun, Yi; Zhou, Kun; Sun, Qian; Liu, Jianping; Feng, Meixin; Li, Zengcheng; Zhou, Yu; Zhang, Liqun; Li, Deyao; Zhang, Shuming; Ikeda, Masao; Liu, Sheng; Yang, Hui

2016-09-01

Silicon photonics would greatly benefit from efficient, visible on-chip light sources that are electrically driven at room temperature. To fully utilize the benefits of large-scale, low-cost manufacturing foundries, it is highly desirable to grow direct bandgap III-V semiconductor lasers directly on Si. Here, we report the demonstration of a blue-violet (413 nm) InGaN-based laser diode grown directly on Si that operates under continuous-wave current injection at room temperature, with a threshold current density of 4.7 kA cm-2. The heteroepitaxial growth of GaN on Si is confronted with a large mismatch in both the lattice constant and the coefficient of thermal expansion, often resulting in a high density of defects and even microcrack networks. By inserting an Al-composition step-graded AlN/AlGaN multilayer buffer between the Si and GaN, we have not only successfully eliminated crack formation, but also effectively reduced the dislocation density. The result is the realization of a blue-violet InGaN-based laser on Si.

Continuous-wave optical stimulation of the rat prostate nerves using an all-single-mode 1455 nm diode laser and fiber system

NASA Astrophysics Data System (ADS)

Tozburun, Serhat; Lagoda, Gwen A.; Burnett, Arthur L.; Fried, Nathaniel M.

2011-03-01

Optical nerve stimulation (ONS) has recently been reported as a potential alternative to electrical nerve stimulation. Continuous-wave (CW) laser stimulation of the prostate cavernous nerves (CN) in a rat model, in vivo, has also been demonstrated in our previous studies. The objective of this study is to present a new all-single-mode-fiber configuration for ONS with the laser operating in CW mode for potential diagnostic applications. An infrared pigtailed single-mode diode laser (λ = 1455 nm) was used in this study for noncontact ONS. This new all-fiber approach introduces several advantages including: (1) a less expensive and more compact ONS system, (2) elimination of alignment of optical components, and (3) an improved spatial beam profile. Successful optical stimulation of the rat CN using this new design was observed after the CN reached a threshold temperature of ~ 41 °C with response times as short as 3 s. Upon further study, this configuration may be useful for identification and preservation of the cavernous nerves during prostate cancer surgery.

Tunable continuous-wave terahertz generation/detection with compact 1.55 μm detuned dual-mode laser diode and InGaAs based photomixer.

PubMed

Kim, Namje; Han, Sang-Pil; Ko, Hyunsung; Leem, Young Ahn; Ryu, Han-Cheol; Lee, Chul Wook; Lee, Donghun; Jeon, Min Yong; Noh, Sam Kyu; Park, Kyung Hyun

2011-08-01

We demonstrate a tunable continuous-wave (CW) terahertz (THz) homodyne system with a novel detuned dual-mode laser diode (DML) and low-temperature-grown (LTG) InGaAs photomixers. The optical beat source with the detuned DML showed a beat frequency tuning range of 0.26 to over 1.07 THz. Log-spiral antenna integrated LTG InGaAs photomixers are used as THz wave generators and detectors. The CW THz radiation frequency was continuously tuned to over 1 THz. Our results clearly show the feasibility of a compact and fast scanning CW THz spectrometer consisting of a fiber-coupled detuned DML and photomixers operating in the 1.55-μm range.

Room-temperature continuous operation of InAsSb quantum-dot lasers near 2 mu m based on (100) InP substrate

NASA Technical Reports Server (NTRS)

Qui, Y.; Uhl, D.; Keo, S.

2003-01-01

Single-stack InAsSb self-assembled quantum-dot lasers based on (001) InP substrate have been grown by metalorganic vapor-phase epitaxy. The narrow ridge waveguide lasers lased at wavelengths near 2 mu m up to 25 degrees C in continuous-wave operation. At room temperature, a differential quantum efficiency of 13 percent is obtained and the maximum output optical power reaches 3 mW per facet with a threshold current density of 730 A/cm(sup 2). With increasing temperature the emission wavelength is extremely temperature stable, and a very low wavelength temperature sensitivity of 0.05 nm/degrees C is measured, which is even lower than that caused by the refractive index change.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Measurements of laser-induced shock waves in aluminium

NASA Astrophysics Data System (ADS)

Werdiger, M.; Arad, B.; Moshe, E.; Eliezer, S.

1995-02-01

A simple optical method for measurements of high-irradiance (3×1013 W cm-2) laser-induced shock waves is described. The shock wave velocity (~13 km s-1) was measured with an error not exceeding 5%. The laser-induced one-to-two-dimensional (1D-to-2D) shock wave transition was studied.

Fiber lasers and their applications [Invited].

PubMed

Shi, Wei; Fang, Qiang; Zhu, Xiushan; Norwood, R A; Peyghambarian, N

2014-10-01

Fiber lasers have seen progressive developments in terms of spectral coverage and linewidth, output power, pulse energy, and ultrashort pulse width since the first demonstration of a glass fiber laser in 1964. Their applications have extended into a variety of fields accordingly. In this paper, the milestones of glass fiber laser development are briefly reviewed and recent advances of high-power continuous wave, Q-switched, mode-locked, and single-frequency fiber lasers in the 1, 1.5, 2, and 3 μm regions and their applications in such areas as industry, medicine, research, defense, and security are addressed in detail.

Improved Sensitivity of Spectroscopic Quantification of Stable Isotope Content Using Capillary Absorption Spectroscopy

NASA Astrophysics Data System (ADS)

Moran, J.; Wilcox Freeburg, E.; Kriesel, J.; Linley, T. J.; Kelly, J.; Coleman, M. L.; Christensen, L. E.; Vance, S.

2016-12-01

Spectroscopy-based platforms have recently risen to the forefront for making stable isotope measurements of methane, carbon dioxide, water, or other analytes. These spectroscopy systems can be relatively straightforward to operate (versus a mass spectrometry platform), largely relieve the analyst of mass interference artifacts, and many can be used in the field. Despite these significant advantages, however, existing spectroscopy techniques suffer from a lack of measurement sensitivity that can ultimately limit select applications including spatially resolved and compound-specific measurements. Here we present a capillary absorption spectroscopy (CAS) system that is designed to mitigate sensitivity issues in spectroscopy-based stable isotope evaluation. The system uses mid-wave infrared excitation generated from a continuous wave quantum cascade laser. Importantly, the sample `chamber' is a flexible capillary with a total volume of less than one cc. Proprietary coatings on the internal surface of the fiber improve optical performance, guiding the light to a detector and facilitating high levels of interaction between the laser beam and gaseous analytes. We present data demonstrating that a tapered hollow fiber cell, with an internal diameter that broadens toward the detector, reduces optical feedback to further improve measurement sensitivity. Sensitivity of current hollow fiber / CAS systems enable measurements of only 10's of picomoles CO2 while theoretical improvements should enable measurements of as little as 10's of femtomoles. Continued optimization of sample introduction and improvements to optical feedback are being explored. Software is being designed to provide rapid integration of data and generation of processed isotope measurements using a graphical user interface. Taken together, the sensitivity improvements of the CAS system under development could, when coupled to a laser ablation sampling device, enable up to 2 µm spatial resolution (roughly the size of a eukaryotic cell or multiple prokaryotic cells) or provide a basis for compounds specific stable isotope analysis of trace biomarkers. The small size and low weight of the system holds future potential for field and / or remote deployment.

Continuous-wave and passively Q-switched laser performance of Nd:(LaxGd1-x)3Ga5O12 crystal at 1062 nm CW and PQS laser performance of Nd:LaGGG crystal at 1062 nm

NASA Astrophysics Data System (ADS)

Yang, H.; Fu, X.-W.; Jia, Z.-T.; He, J.-L.; Yang, X.-Q.; Zhang, B.-T.; Wang, R.-H.; Liu, X.-M.; Hou, J.; Lou, F.; Wang, Z.-W.; Yang, Y.

2012-10-01

The performance of diode-pumped continuous-wave (CW) and passively Q-switched (PQS) Nd:(LaxGd1-x)3Ga5O12 lasers at 1062 nm were demonstrated for the first time to our knowledge. The highest CW output power of 9.9 W was obtained, corresponding to an optical-to-optical efficiency of 42.9%. For the passive Q-switching operation, when the output coupler of Toc = 27% was adopted, the maximum output power of 3.97 W was obtained by a Cr4+:YAG saturable absorber with the initial transmission of T0 = 89.9%.While at T0 = 81.4% and Toc = 27%, the output power of 2.83 W, with pulse width of 7.4 ns and the repetition rate of 13.87 kHz, was obtained, corresponding to the maximum peak power of 27.6 kW and single pulse energy of 0.2 mJ, respectively.

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

21 CFR 884.4550 - Gynecologic surgical laser.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gynecologic surgical laser. 884.4550 Section 884....4550 Gynecologic surgical laser. (a) Identification. A gynecologic surgical laser is a continuous wave carbon dioxide laser designed to destroy tissue thermally or to remove tissue by radiant light energy...

Laser Atmospheric Transmitter Receiver-Network (LAnTeRN): A new approach for active measurement of atmospheric greenhouse gases

NASA Astrophysics Data System (ADS)

Dobler, J. T.; Braun, M.; Zaccheo, T.

2012-12-01

The Laser Atmospheric Transmitter Receiver-Network (LAnTeRN) is a new measurement concept that will enable local, regional and continental determination of key greenhouse gases, with unparalleled accuracy and precision. This new approach will offer the ability to make low bias, high precision, quasi-continuous, measurements to the accuracies required for separating anthropogenic and biogenic sources and sinks. In 2004 ITT Exelis developed an airborne demonstration unit, based on an intensity modulated continuous wave (IM-CW) lidar approach, for actively measuring atmospheric CO2 and O2. The multi-functional fiber laser lidar (MFLL) system relies on low peak power, high reliability, and efficient telecom laser components to implement this unique measurement approach. While evaluating methods for discriminating against thin clouds for the MFLL instrument, a new measurement concept was conceived. LAnTeRN has several fundamental characteristics in common with the MFLL instrument, but is a fundamentally different implementation and capability. The key difference is that LAnTeRN operates in transmission rather than in the traditional backscatter lidar configuration, which has several distinct advantages. Operating as a forward scatter, bistatic lidar system, LAnTeRN enables consideration of continuous monitoring from a geostationary orbit to multiple locations on the ground. Having the receivers on the ground significantly lowers cost and risk compared to an all space based mission, and allows the transmitter subsystem to be implemented, near term, as a hosted payload. Furthermore, the LAnTeRN measurement approach is also applicable for ground to ground measurements where high precision measurements over a long open path is required, such as facilities monitoring, or monitoring of passive volcanoes and fault lines. Using narrow linewidth laser sources allows flexibility to select the position on the absorption feature being probed. This feature allows for weighting the absorption toward lower altitudes for the space implementation or to handle large dynamic range measurements as would be required for volcano monitoring. This presentation will discuss results from a detailed instrument performance analyses, retrieval simulations, and from initial testing of a proof of concept demonstration unit being developed by Exelis. Initial analysis indicate that measurements from a transmitter in geostationary orbit to 25 ground receivers in the eastern U.S. can retrieve column integrated CO2 values to a precision of <0.2 ppm on monthly averages and <0.06 ppm on yearly averages, using conservative estimates of cloud cover and aerosol loading. The capability for continuous monitoring over a fixed geometry makes it possible to independently characterize the atmospheric column, using existing capabilities (e.g. aircore, aircraft and in-situ instrumentation), for quantification of bias. Furthermore, the ability to selectively locate the ground receivers can enable focused studies for specific applications.

Effects of continuous wave and fractionated diode laser on human fibroblast cancer and dermal normal cells by zinc phthalocyanine in photodynamic therapy: A comparative study.

PubMed

Navaeipour, Farzaneh; Afsharan, Hadi; Tajalli, Habib; Mollabashi, Mahmood; Ranjbari, Farideh; Montaseri, Azadeh; Rashidi, Mohammad-Reza

2016-08-01

In this experimental study, cancer and normal cells behavior during an in vitro photodynamic therapy (PDT) under exposure of continuous wave (CW) and fractionated mode of laser with different irradiation power and time intervals was compared and investigated. At the first, human fibroblast cancer cell line (SW 872) and human dermal normal (HFFF2) cell line were incubated with different concentrations of zinc phthalocyanine (ZnPc), as a PDT drug. The cells, then, were irradiated with a 675nm diode laser and the cell viability was evaluated using MTT assay. Under optimized conditions, the viability of the cancer cells was eventually reduced to 3.23% and 13.17%, and that of normal cells was decreased to 20.83% and 36.23% using CW and fractionated diode lasers, respectively. In general, the ratio of ZnPc LD50 values for the normal cells to the cancer cells with CW laser was much higher than that of the fractionated laser. Subsequently, cancer cells in comparison with normal ones were found to be more sensitive toward the photodynamic damage induced by ZnPc. In addition, treatment with CW laser was found to be more effective against the cancer cells with a lower toxicity to the normal cells compared with the fractionated diode laser. Copyright © 2016 Elsevier B.V. All rights reserved.

Maximum-Likelihood Estimation for Frequency-Modulated Continuous-Wave Laser Ranging Using Photon-Counting Detectors

DTIC Science & Technology

2013-01-01

are calculated from coherently -detected fields, e.g., coherent Doppler lidar . Our CRB results reveal that the best-case mean-square error scales as 1...1088 (2001). 7. K. Asaka, Y. Hirano, K. Tatsumi, K. Kasahara, and T. Tajime, “A pseudo-random frequency modulation continuous wave coherent lidar using...multiple returns,” IEEE Trans. Pattern Anal. Mach. Intell. 29, 2170–2180 (2007). 11. T. J. Karr, “Atmospheric phase error in coherent laser radar

Preferential flow pathways revealed by field based stable isotope analysis of CO2 by mid-infrared laser spectroscopy

NASA Astrophysics Data System (ADS)

van Geldern, Robert; Nowak, Martin; Zimmer, Martin; Szizybalski, Alexandra; Myrttinen, Anssi; Barth, Johannes A. C.; Jost, Hj

2016-04-01

A newly developed and commercially available isotope ratio laser spectrometer for CO2 analyses has been tested during a 10-day field monitoring campaign at the Ketzin pilot site for CO2 storage in northern Germany. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10-day carbon stable isotope data set with 30 minutes resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within 2σ analytical precision (<0.3 ‰). This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time table isotope data directly in the field. The injected CO2 tracer had a distinct δ13C value that was largely different from the reservoir background value. The laser spectroscopy data revealed a prior to this study unknown, intensive dynamic with fast changing δ13C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The new technique might contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long-term integrity of the reservoir.

Low-Cost Fabrication of Printed Electronics Devices through Continuous Wave Laser-Induced Forward Transfer.

PubMed

Sopeña, Pol; Arrese, Javier; González-Torres, Sergio; Fernández-Pradas, Juan Marcos; Cirera, Albert; Serra, Pere

2017-09-06

Laser-induced forward transfer (LIFT) is a direct-writing technique that allows printing inks from a liquid film in a similar way to inkjet printing but with fewer limitations concerning ink viscosity and loading particle size. In this work, we prove that liquid inks can be printed through LIFT by using continuous wave (CW) instead of pulsed lasers, which allows a substantial reduction in the cost of the printing system. Through the fabrication of a functional circuit on both rigid and flexible substrates (plastic and paper), we provide a proof-of-concept that demonstrates the versatility of the technique for printed electronics applications.

High-resolution multiphoton microscopy with a low-power continuous wave laser pump.

PubMed

Chen, Xiang-Dong; Li, Shen; Du, Bo; Dong, Yang; Wang, Ze-Hao; Guo, Guang-Can; Sun, Fang-Wen

2018-02-15

Multiphoton microscopy (MPM) has been widely used for three-dimensional biological imaging. Here, based on the photon-induced charge state conversion process, we demonstrated a low-power high-resolution MPM with a nitrogen vacancy (NV) center in diamond. Continuous wave green and orange lasers were used to pump and detect the two-photon charge state conversion, respectively. The power of the laser for multiphoton excitation was 40 μW. Both the axial and lateral resolutions were improved approximately 1.5 times compared with confocal microscopy. The results can be used to improve the resolution of the NV center-based quantum sensing and biological imaging.

Characteristic time scales of coalescence of silver nanocomposite and nanoparticle films induced by continuous wave laser irradiation

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

Paeng, Dongwoo; Grigoropoulos, Costas P., E-mail: cgrigoro@berkeley.edu; Lee, Daeho

2014-08-18

In-situ optical probing has been performed to analyze and compare the characteristic coalescence time scales of silver ion-doped polyvinylalcohol nanocomposite (Ag-PVA NC) and polyvinylpyrrolidone-capped silver nanoparticle (Ag-PVP NP) films subjected to continuous wave laser irradiation. The Ag-PVA NC yielded conductive metallic patterns by photothermal reduction of PVA, formation of nanoparticles from silver ions and their subsequent coalescence. On the other hand, Ag-PVP NP thin films produced conductive patterns through only coalescence of nanoparticles. Upon laser irradiation, Ag-PVA NC and Ag-PVP NP films exhibited different coalescence characteristics.

Laser-diode pumped 40-W Yb:YAG ceramic laser.

PubMed

Hao, Qiang; Li, Wenxue; Pan, Haifeng; Zhang, Xiaoyi; Jiang, Benxue; Pan, Yubai; Zeng, Heping

2009-09-28

We demonstrated a high-power continuous-wave (CW) polycrystalline Yb:YAG ceramic laser pumped by fiber-pigtailed laser diode at 968 nm with 400 mum fiber core. The Yb:YAG ceramic laser performance was compared for different Yb(3+) ion concentrations in the ceramics by using a conventional end-pump laser cavity consisting of two flat mirrors with output couplers of different transmissions. A CW laser output of 40 W average power with M(2) factor of 5.8 was obtained with 5 mol% Yb concentration under 120 W incident pump power. This is to the best of our knowledge the highest output power in end-pumped bulk Yb:YAG ceramic laser.

Le Laser A Argon Ionise : Applications Therapeutiques

NASA Astrophysics Data System (ADS)

Brunetaud, J. M.; Mosquet, L.; Mordon, S.; Rotteleur, G.

1984-03-01

Le laser a argon ionise est un laser a emission continue, reglee en general en multiraies de 487 a 544 nm. Le rayonnement de ce laser est bien absorbe par les tissus vivants, avec une action preferentielle au niveau des pigments rouges (hemoglobine, myoglobine) et noirs (melanine). Le laser a argon est princi-palement utilise en therapeutique pour ses effets thermiques : en fonction du choix des parametres (puissance optique, surface exposee, temps d'exposition) on peut obtenir une coagulation (temperature optimale au niveau des tissus 60° - 80°) ou une volatisation (temperature superieure a 100°). Si la zone volatilisee est tres etroite (inferieure a 0,5 mm) on obtient un effet de coupe. Par rapport aux deux autres lasers egalement utilises pour leurs effets thermiques (CO2 et Nd. YAG) l'argon a des effets intermediaires : la coagulation sera plus superficielle qu'avec le Nd. YAG et la volatisation plus profonde qu'avec le CO2. Lors de la coupe, la necrose sur les berges sera egalement plus importante qu'avec le CO2.

Stabilized Lasers and Precision Measurements.

ERIC Educational Resources Information Center

Hall, J. L.

1978-01-01

Traces the development of stabilized lasers from the Massachusetts Institute of Technology passive-stabilization experiments of the early 1960s up through the current epoch of highly stabilized helium-neon and carbon dioxide and continuous wave dye lasers. (Author/HM)

Broad-gain (Δλ/λ0

PubMed

Fujita, Kazuue; Furuta, Shinichi; Dougakiuchi, Tatsuo; Sugiyama, Atsushi; Edamura, Tadataka; Yamanishi, Masamichi

2011-01-31

Broad-gain operation of λ~8.7 μm quantum cascade lasers based on dual-upper-state to multiple-lower-state transition design is reported. The devices exhibit surprisingly wide (~500 cm(-1)) electroluminescence spectra which are very insensitive to voltage and temperature changes above room temperature. With recourse to the temperature-insensitivity of electroluminescence spectra, the lasers demonstrate an extremely-weak temperature-dependence of laser performances: T0-value of 510 K, associated with a room temperature threshold current density of 2.6 kA/cm2. In addition, despite such wide gain spectra, room temperature, continuous wave operation of the laser with buried hetero structure is achieved.

Additive Manufacturing of Al-12Si Alloy Via Pulsed Selective Laser Melting

NASA Astrophysics Data System (ADS)

Chou, R.; Milligan, J.; Paliwal, M.; Brochu, M.

2015-03-01

Additive manufacturing (AM) of metallic materials is experiencing a research and commercialization craze in almost all industrial sectors. However, to date, AM has been limited to a small numbers of alloys. With respect to aluminum, two alloys received some attention: Al-12Si and Al-10Si-1Mg. In both cases, fully dense components have been achieved using a continuous-wave selective laser melting system. In this article, a new approach of selective laser melting using a pulsed-laser source as opposed to a continuous-wave laser is proposed. Pulse selective laser melting (P-SLM) would allow for greater control over the heat input and thus further optimization possibilities of the microstructure. P-SLM was demonstrated using the Al-12Si system. Si refinement below 200 nm was achieved throughout the component. Density up to 95% and high hardness of above 135 HV were obtained. The solidification mechanism is also explained.

Simultaneous laser excitation of backward volume and perpendicular standing spin waves in full-Heusler Co2FeAl0.5Si0.5 films

PubMed Central

Chen, Zhifeng; Yan, Yong; Li, Shufa; Xu, Xiaoguang; Jiang, Yong; Lai, Tianshu

2017-01-01

Spin-wave dynamics in full-Heusler Co2FeAl0.5Si0.5 films are studied using all-optical pump-probe magneto-optical polar Kerr spectroscopy. Backward volume magnetostatic spin-wave (BVMSW) mode is observed in films with thickness ranging from 20 to 100 nm besides perpendicular standing spin-wave (PSSW) mode, and found to be excited more efficiently than the PSSW mode. The field dependence of the effective Gilbert damping parameter appears especial extrinsic origin. The relationship between the lifetime and the group velocity of BVMSW mode is revealed. The frequency of BVMSW mode does not obviously depend on the film thickness, but the lifetime and the effective damping appear to do so. The simultaneous excitation of BVMSW and PSSW in Heusler alloy films as well as the characterization of their dynamic behaviors may be of interest for magnonic and spintronic applications. PMID:28195160

Giant enhancement of upconversion in ultra-small Er3+/Yb3+:NaYF4 nanoparticles via laser annealing

NASA Astrophysics Data System (ADS)

Bednarkiewicz, A.; Wawrzynczyk, D.; Gagor, A.; Kepinski, L.; Kurnatowska, M.; Krajczyk, L.; Nyk, M.; Samoc, M.; Strek, W.

2012-04-01

Most of the synthesis routes of lanthanide-doped phosphors involve thermal processing which results in nanocrystallite growth, stabilization of the crystal structure and augmentation of luminescence intensity. It is of great interest to be able to transform the sample in a spatially localized manner, which may lead to many applications like 2D and 3D data storage, anti-counterfeiting protection, novel design bio-sensors and, potentially, to fabrication of metamaterials, 3D photonic crystals or plasmonic devices. Here we demonstrate irreversible spatially confined infrared-laser-induced annealing (LIA) achieved in a thin layer of dried colloidal solution of ultra-small ˜8 nm NaYF4 nanocrystals (NCs) co-doped with 2% Er3+ and 20% Yb3+ ions under a localized tightly focused beam from a continuous wave 976 nm medium power laser diode excitation. The LIA results from self-heating due to non-radiative relaxation accompanying the NIR laser energy upconversion in lanthanide ions. We notice that localized LIA appears at optical power densities as low as 15.5 kW cm-2 (˜354 ± 29 mW) threshold in spots of 54 ± 3 µm diameter obtained with a 10 × microscope objective. In the course of detailed studies, a complete recrystallization to different phases and giant 2-3 order enhancement in luminescence yield is found. Our results are highly encouraging and let us conclude that the upconverting ultra-small lanthanide-doped nanophosphors are particularly promising for direct laser writing applications.

Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

NASA Astrophysics Data System (ADS)

Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

2017-03-01

The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

Microdisk Injection Lasers for the 1.27-μm Spectral Range

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

Kryzhanovskaya, N. V.; Maximov, M. V.; Blokhin, S. A.

2016-03-15

Microdisk injection lasers on GaAs substrates, with a minimum diameter of 15 μm and an active region based on InAs/InGaAs quantum dots, are fabricated. The lasers operate in the continuous-wave mode at room temperature without external cooling. The lasing wavelength is around 1.27 μm at a minimum threshold current of 1.6 mA. The specific thermal resistance is estimated to be 5 × 10–3 °C cm{sup 2}/W.

Control of solid-state lasers using an intra-cavity MEMS micromirror.

PubMed

Lubeigt, Walter; Gomes, Joao; Brown, Gordon; Kelly, Andrew; Savitski, Vasili; Uttamchandani, Deepak; Burns, David

2011-01-31

High reflectivity, electrothermal and electrostatic MEMS (Micro-Electro-Mechanical Systems) micromirrors were used as a control element within a Nd-doped laser cavity. Stable continuous-wave oscillation of a 3-mirror Nd:YLF laser at a maximum output power of 200 mW was limited by thermally-induced surface deformation of the micromirror. An electrostatic micromirror was used to induce Q-switching, resulting in pulse durations of 220 ns - 2 μs over a repetition frequency range of 6 kHz - 40 kHz.

Towards PDT with Genetically Encoded Photosensitizer KillerRed: A Comparison of Continuous and Pulsed Laser Regimens in an Animal Tumor Model.

PubMed

Shirmanova, Marina; Yuzhakova, Diana; Snopova, Ludmila; Perelman, Gregory; Serebrovskaya, Ekaterina; Lukyanov, Konstantin; Turchin, Ilya; Subochev, Pavel; Lukyanov, Sergey; Kamensky, Vladislav; Zagaynova, Elena

2015-01-01

The strong phototoxicity of the red fluorescent protein KillerRed allows it to be considered as a potential genetically encoded photosensitizer for the photodynamic therapy (PDT) of cancer. The advantages of KillerRed over chemical photosensitizers are its expression in tumor cells transduced with the appropriate gene and direct killing of cells through precise damage to any desired cell compartment. The ability of KillerRed to affect cell division and to induce cell death has already been demonstrated in cancer cell lines in vitro and HeLa tumor xenografts in vivo. However, the further development of this approach for PDT requires optimization of the method of treatment. In this study we tested the continuous wave (593 nm) and pulsed laser (584 nm, 10 Hz, 18 ns) modes to achieve an antitumor effect. The research was implemented on CT26 subcutaneous mouse tumors expressing KillerRed in fusion with histone H2B. The results showed that the pulsed mode provided a higher rate of photobleaching of KillerRed without any temperature increase on the tumor surface. PDT with the continuous wave laser was ineffective against CT26 tumors in mice, whereas the pulsed laser induced pronounced histopathological changes and inhibition of tumor growth. Therefore, we selected an effective regimen for PDT when using the genetically encoded photosensitizer KillerRed and pulsed laser irradiation.

Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

NASA Technical Reports Server (NTRS)

Mcguckin, B. T.; Hemmati, H.; Menzies, R. T.

1992-01-01

Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

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.

Laser Demonstration of Diode-Pumped Nd3+-Doped Fluorapatite Anisotropic Ceramics

NASA Astrophysics Data System (ADS)

Akiyama, Jun; Sato, Yoichi; Taira, Takunori

2011-02-01

We report the first demonstration of a diode-pumped anisotropic ceramic laser that uses microdomain-controlled neodymium-doped hexagonal fluorapatite [Nd3+:Ca10(PO4)6F2, Nd:FAP] polycrystalline ceramics as the gain medium, which were fabricated by the rare-earth-assisted magnetic grain-orientation control method, as a step toward achieving giant micro photonics. The laser delivers 1063.10 and 1063.22 nm output beams when pumped with a central wavelength of 807.5 nm and a 2 nm bandwidth diode laser operating in quasi-continuous-wave (QCW) mode. We obtained a maximum QCW peak power of 255 mW with an uncoated 2 at. % Nd:FAP material.

Five-Channel Infrared Laser Absorption Spectrometer for Combustion Product Monitoring Aboard Manned Spacecraft

NASA Technical Reports Server (NTRS)

Briggs, Ryan M.; Frez, Clifford; Borgentun, Carl E.; Bagheri, Mahmood; Forouhar, Siamak; May, Randy D.

2014-01-01

Continuous combustion product monitoring aboard manned spacecraft can prevent chronic exposure to hazardous compounds and also provides early detection of combustion events. As future missions extend beyond low-Earth orbit, analysis of returned environmental samples becomes impractical and safety monitoring should be performed in situ. Here, we describe initial designs of a five-channel tunable laser absorption spectrometer to continuously monitor combustion products with the goal of minimal maintenance and calibration over long-duration missions. The instrument incorporates dedicated laser channels to simultaneously target strong mid-infrared absorption lines of CO, HCl, HCN, HF, and CO2. The availability of low-power-consumption semiconductor lasers operating in the 2 to 5 micron wavelength range affords the flexibility to select absorption lines for each gas with maximum interaction strength and minimal interference from other gases, which enables the design of a compact and mechanically robust spectrometer with low-level sensitivity. In this paper, we focus primarily on absorption line selection based on the availability of low-power single-mode semiconductor laser sources designed specifically for the target wavelength range.

Near-Simultaneous Measurement of Ground Level Carbon Dioxide and Methane Concentrations with an Open-Path Tunable Diode Laser Sensor at the Bonanza Creek Long Term Ecological Research site near Fairbanks, Alaska

NASA Astrophysics Data System (ADS)

Bailey, D. M.; Miller, J. H. H.

2017-12-01

Beyond anthropogenic carbon emissions, the increase in atmospheric carbon from natural feedbacks such as thawing permafrost poses a risk to the global climate as global temperatures continue to increase. Permafrost is formally defined as soil that is continuously frozen for 24 consecutive months. These soils comprise nearly twenty-five percent of the Earth's terrestrial surface and possess twice the amount of carbon currently in the atmosphere. Continuous collection of carbon dioxide (CO2) and methane (CH4) concentrations is imperative in understanding seasonal and inter-annual variability of carbon feedbacks above thawing permafrost. A multi-year collaborative effort with the University of Alaska - Fairbanks, NASA Goddard Space Flight Center, and our group at George Washington University is underway to monitor these feedbacks near Fairbanks, Alaska. In June 2017, we deployed two open-path tunable diode laser sensors at the Bonanza Long Term Ecological Research Site for measurement of CO2 and CH4 concentrations. The open-path instrument (OPI) is an inexpensive, low-power sensor that collects spatially-integrated measurements of target molecules approximately 1.5 meters above ground level. With a total power burden of 18 W, the sensors ran exclusively on solar power for 15 days in a young thermokarst bog and 3.5 days at a rich fen site. Here we report on initial retrieval of diurnal cycles from each field site and compare our spatially-integrated measurements of CO2 and CH4. For CO2, the magnitude of the diurnal cycles show a strong dependence on daily weather at both field sites. These laser measurements are complemented by point measurements of CO2, temperature, pressure, and humidity made along the laser's optical path by non-dispersive infrared (NDIR) sensors.

Application of NIR Laser Spectroscopy to the Monitoring of Volcanic Plumes: Principles and Practicalities

NASA Astrophysics Data System (ADS)

Hamish, A.; Christenson, B. W.; Mazot, A.

2014-12-01

The major volatile species in volcanic plume emissions (i.e., H2O, CO2, SO2, HCl, HF) are all strongly infrared (IR)-active, and lend themselves to infrared spectroscopic analysis. However, physical/optical access to plume gases along pathways which include a suitable natural or active IR radiation source is often difficult or impossible to achieve, particularly for timeframes extending beyond short campaign periods. In this study, we present results from preliminary tests conducted on three volcanic CO2 plume emissions using a tunable diode NIR laser system (TDL, Boreal Laser Inc.). The approach is proving itself as a good candidate for continuous monitoring of volcanic plume CO2, and by default all other IR-active constituents for which lasers of appropriate wavelength are available. The CO2 system is configured with a TDL in a transceiver generating laser light which can be tuned to coincide with one of several absorption lines in the CO2 absorption band between 1575 nm and 1585 nm. This beam propagates through the atmosphere (and plume) to a retro-reflector, which returns the beam to a photodiode detector in the transceiver which processes the signal to report real time CO2 column densities. The CO2 absorption line at 1579.1 nm was used to good effect on Mt Ruapehu (NZ) where volcanic gases emanate through a 100 m deep crater lake, resulting in CO2 concentrations of > 78 ppm above background in the mixing zone varying from 4 to 30 m above the lake surface. Subsequent tests on the main plume at White Island, however, generated only poor results with indicated CO2 amounts being less than atmospheric. We concluded that this was the result of interference from a neighboring but comparatively minor H2O absorption band which in the proximal, higher temperature plume (estimated 50-70 °C), had H2O concentrations some 4-5 times greater than ambient. A change to a less sensitive absorption line further removed from potential H2O band interference (1567.9 nm) appears to have solved this problem, and yielded maximum CO2 concentrations along the 730 m pathway in excess of 500 ppm.This approach holds promise for continuous, real-time monitoring of volcanic plume chemistry, and we will now turn our focus to the detection of SO2, HCl and HF plume species.

In vitro histological evaluation of the surgical margins made by different laser wavelengths in tongue tissues

PubMed Central

Azevedo, Ana-Salvaterra; Ferreira, Fernando; Delgado, Maria-Leonor; Garcês, Fernanda; Carreira, Sofia; Martins, Marco; Suarez-Quintanilla, Juan

2016-01-01

Background Lasers have become standard tools for the surgical treatment of oral lesions. The purpose of this study is to determine the surgical margins and histologically evaluate the tissue thermal effects induced by different types of surgical instruments. Material and Methods Cuts were made in pork tongues’ mucosa with different lasers (Er:YAG at 2W with and without air / water spray and at 4W with and without air / water spray; CO2 at 3.5W and 7W in pulsed mode and at 7W in continuous mode; the diode laser at 3.5W and boost 3.5W in pulsed mode; Nd:YAG at 6W, 40Hz and electroscalpel at 5W and conventional scalpel as control. Macroscopic and microscopic morphological changes were evaluated. Results The results of this study showed that the surgical instruments that caused greater tissue damage extension were: the Nd:YAG laser (670.68μm), the diode 3.5W and boost PW (626.82μm), the CO2 7W CW (571.18μm), the CO2 at 7W PW (485.45μm), the diode 3.5W PW (456.15μm), the electroscalpel (409.57μm) and lastly the CO2 laser 3.5W PW (306.19μm) and Er:YAG (74.66μm) laser, regardless of power, mode or air / water spray used. An association between the Tissue Damage Extension and the Degree of Carbonization (r = 0.789; P = 0.01), and an association between the Tissue Damage Extension and Regularity of the Incision were found (r = -, 299; P = 0.01). Conclusions The results of this study suggest that lasers can be used in soft tissues biopsies of the oral cavity, enabling a correct histopathological analysis, as long as the biological effects of each laser type are considered. The Er:YAG laser revealed its potential for biopsies of the oral mucosa ensuring a successful histological evaluation and the CO2 laser at 3,5W in pulsed mode presented itself as the best choice for surgeries with hemostasis. Key words:CO2 laser, diode laser, Er:YAG laser, laser surgery, Nd:YAG laser, oral mucosa, thermal effect. PMID:27703606

Fiber Based Seed Laser for CO 2 Ultrafast Laser Systems

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

Chen, Yuchuan

A compact and effective 10-micron femtosecond laser with pulse duration <500fs and repetition rate of >100Hz or smaller is desirable by DOE for seeding CO 2 ultrafast laser systems to improve the stability, reliability and efficiency in generating 10-micron laser from GW up to 100TW peak power, which is irreplaceable in driving an accelerator for particle beam generation due to the efficiency proportional to the square of the laser wavelength. Agiltron proposes a fiber based ultrafast 10-micron seed laser that can provide the required specifications and high performance. Its success will directly benefit DOE’s compact proton and ion sources. Themore » innovative technology can be used for ultrafast laser generation over the whole mid-IR range, and speed up the development of mid-IR laser applications. Agiltron, Inc. has successfully completed all tasks and demonstrated the feasibility of a fiber based 10-micron ultrafast laser in Phase I of the Program. We built a mode-locked fiber laser that generated < 400fs ultrafast laser pulses and successfully controlled the repetition rate to be the required 100Hz. Using this mode-locked laser, we demonstrated the feasibility of parametric femtosecond laser generation based on frequency down conversion. The experimental results agree with our simulation results. The investigation results of Phase I will be used to optimize the design of the laser system and build a fully functional prototype for delivery to the DOE in the Phase II program. The prototype development in Phase II program will be in the collaboration with Professor Chandrashekhar Joshi, the leader of UCLA Laser-Plasma group. Prof. Joshi discovered a new mechanism for generation of monoenergetic proton/ion beams: Shock Wave Acceleration in a near critical density plasma and demonstrated that high-energy proton beams using CO 2 laser driven collisionless shocks in a gas jet plasma, which opened an opportunity to develop a rather compact high-repetition rate ion source for medical and other applications which could be significantly cheaper than that based on RF acceleration. We propose an output energy >1 μJ, one order of magnitude higher than the DOE original requirement. The performance of the prototype will be tested at UCLA by directly seeding the CO 2 laser system driving an accelerator.« less

Raman spectroscopy differentiates squamous cell carcinoma (SCC) from normal skin following treatment with a high-powered CO2 laser.

PubMed

Fox, Sara A; Shanblatt, Ashley A; Beckman, Hugh; Strasswimmer, John; Terentis, Andrew C

2014-12-01

The number of cases of non-melanoma skin cancer (NMSC), which include squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), continues to rise as the aging population grows. Mohs micrographic surgery has become the treatment of choice in many cases but is not always necessary or feasible. Ablation with a high-powered CO2 laser offers the advantage of highly precise, hemostatic tissue removal. However, confirmation of complete cancer removal following ablation is difficult. In this study we tested for the first time the feasibility of using Raman spectroscopy as an in situ diagnostic method to differentiate NMSC from normal tissue following partial ablation with a high-powered CO2 laser. Twenty-five tissue samples were obtained from eleven patients undergoing Mohs micrographic surgery to remove NMSC tumors. Laser treatment was performed with a SmartXide DOT Fractional CO2 Laser (DEKA Laser Technologies, Inc.) emitting a wavelength of 10.6 μm. Treatment levels ranged from 20 mJ to 1200 mJ total energy delivered per laser treatment spot (350 μm spot size). Raman spectra were collected from both untreated and CO2 laser-treated samples using a 785 nm diode laser. Principal Component Analysis (PCA) and Binary Logistic Regression (LR) were used to classify spectra as originating from either normal or NMSC tissue, and from treated or untreated tissue. Partial laser ablation did not adversely affect the ability of Raman spectroscopy to differentiate normal from cancerous residual tissue, with the spectral classification model correctly identifying SCC tissue with 95% sensitivity and 100% specificity following partial laser ablation, compared with 92% sensitivity and 60% selectivity for untreated NMSC tissue. The main biochemical difference identified between normal and NMSC tissue was high levels of collagen in the normal tissue, which was lacking in the NMSC tissue. The feasibility of a combined high-powered CO2 laser ablation, Raman diagnostic procedure for the treatment of NMSC is demonstrated since CO2 laser treatment does not hinder the ability of Raman spectroscopy to differentiate normal from diseased tissue. This combined approach could be employed clinically to greatly enhance the speed and effectiveness of NMSC treatment in many cases. © 2014 Wiley Periodicals, Inc.

High-Power Nd:GdVO4 Innoslab Continuous-Wave Laser under Direct 880 nm Pumping

NASA Astrophysics Data System (ADS)

Deng, Bo; Zhang, Heng-Li; Xu, Liu; Mao, Ye-Fei; He, Jing-Liang; Xin, Jian-Guo

2014-11-01

A high-power cw end-pumped laser device is demonstrated with a slab crystal of Nd:GdVO4 operating at 1063 nm. Diode laser stacks at 880 nm are used to pump Nd:GdVO4 into emitting level 4F3/2. The 149 W output power is presented when the absorbed pump power is 390 W and the optical-to-optical conversion efficiency is 38.2%. When the output power is 120 W, the M2 factors are 2.3 in both directions. Additionally, mode overlap inside the resonator is analyzed to explain the beam quality deterioration.

Tensile behavior of laser treated Fe-Si-B metallic glass

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

Joshi, Sameehan S.; Samimi, Peyman; Ghamarian, Iman

2015-10-28

Fe-Si-B metallic glass foils were treated with a linear laser track using a continuous wave Nd-YAG laser and its effect on the overall tensile behavior was investigated. Microstructure and phase evolutions were evaluated using X-ray diffraction, resistivity measurements, and transmission electron microscopy. Crystallization fraction was estimated via the differential scanning calorimetry technique. Metallic glass foils treated with the lower laser fluences (<0.49 J/mm{sup 2}) experienced structural relaxation, whereas higher laser fluences led to crystallization within the laser treated region. The overall tensile behavior was least impacted by structural relaxation, whereas crystallization severely reduced the ultimate tensile strength of the laser treatedmore » metallic glass foils.« less

Laser supported detonation wave source of atomic oxygen for aerospace material testing

NASA Technical Reports Server (NTRS)

Krech, Robert H.; Caledonia, George E.

1990-01-01

A pulsed high-flux source of nearly monoenergetic atomic oxygen was developed to perform accelerated erosion testing of spacecraft materials in a simulated low-earth orbit (LEO) environment. Molecular oxygen is introduced into an evacuated conical expansion nozzle at several atmospheres pressure through a pulsed molecular beam valve. A laser-induced breakdown is generated in the nozzle throat by a pulsed CO2 TEA laser. The resulting plasma is heated by the ensuing laser-supported detonation wave, and then it rapidly expands and cools. An atomic oxygen beam is generated with fluxes above 10 to the 18th atoms per pulse at 8 + or - 1.6 km/s with an ion content below 1 percent for LEO testing. Materials testing yielded the same surface oxygen enrichment in polyethylene samples as observed on the STS mission, and scanning electron micrographs of the irradiated polymer surfaces showed an erosion morphology similar to that obtained on low earth orbit.

FY 1980 Report on Dye Laser Materials

DTIC Science & Technology

1981-02-01

C02H H Rh 19 H C2H 5 CH3 CO9H H i Rh6G H C2H 5 CH3 Co2 C2H5 H RhB C2H5 C2H!5 H CO,H H Rh3B C2A5 C2H5 H CO2CH 5 H Rh 101 RING- RING RING...Dye designations Ring SRh 101 Rh 101 - Diethyl SRh B Rh B Rhb 3B Mono ethyl (methyl) -- Rh 19 (116) Rh 6G Unsubstituted -- Rh 110 Rh 123 Nominal Single...Broadband Lasing Wave-lengths of the Rhodamine Dyes. Lasing Wavelength, n Approximate Dye Conc. x 104 Range Midpoint Rh 110 1.0 567-577 572 2.0 Rh 123

Evaluation of a new laser-resistant fabric and copper foil-wrapped endotracheal tube.

PubMed

Sosis, M B; Braverman, B; Caldarelli, D D

1996-07-01

The risk of an endotracheal tube's combustion during laser airway surgery necessitates the use of special anesthetic techniques and equipment to prevent this complication. This study was designed to evaluate the Laser-Trach(TM), a new laser-resistant rubber endotracheal tube for use during laser airway surgery. The Laser-Trach endotracheal tubes that were evaluated were size 6.0 mm internal diameter (ID) red rubber endotracheal tubes which had been commercially wrapped by Kendall-Sheridan (Mansfield, Mass.) with copper foil tape and overwrapped with fabric. The fabric layer was saturated with water prior to our tests, as recommended by the manufacturer. The Laser-Trach endotracheal tubes were compared with plain (bare) size 6.0 mm ID Rusch red rubber endotracheal tubes. The tubes under study were positioned horizontally on wet towels in air and had 5 L x min(-1) of oxygen flowing through them. They were subjected to continuous laser radiation at 40 W from either a CO2 or an Nd-YAG laser. The Nd-YAG laser was propagated via a 600-micron fiber bundle. Each laser was directed perpendicularly at the shaft of the endotracheal tube being studied, and its output was continued until a blowtorch fire occurred or 60 seconds had elapsed. Sixty seconds of CO2 laser fire did not ignite any of the eight Laser-Trach endotracheal tubes tested. However, blowtorch ignition of all eight bare rubber tubes tested occurred after 0.87 +/- 0.21 (mean +/- SD) seconds of CO2 laser fire. Nd-YAG laser contact with the Laser-Trach endotracheal tubes caused the perforation and blowtorch ignition of all eight tubes tested after 18.79 +/- 7.83 seconds. This was a significantly (P<.05) longer time than the 5.45 +/- 4.75 seconds required for the blowtorch ignition of all eight plain rubber endotracheal tubes tested with the Nd-YAG laser. Our results show that under the conditions of this study, the shafts of the Kendall-Sheridan Laser-Trach endotracheal tubes were resistant to the C02 laser. However, this endotracheal tube is not recommended for use with the Nd-YAG laser.

Effect of laser processing on physical properties of (Ba0.85Ca0.15Ti0.9Zr0.1O3) lead-free thick films fabricated by the electrophoretic deposition

NASA Astrophysics Data System (ADS)

Ramana, E. Venkata; Ferreira, N. M.; Mahajan, A.; Ferro, Marta C.; Figueiras, F.; Graça, M. P. F.; Valente, M. A.

2018-02-01

In this work, we have fabricated lead-free piezoelectric Ba0.85Ca0.15Ti0.9Zr0.1O3 thick films by the electrophoretic deposition (EPD) followed by a continuous-wave CO2 laser annealing and demonstrated the effect of laser energy on the quality of the final product. Thick films annealed under optimized conditions, 50 W/15 min, show a controlled microstructure/density compared to those derived from higher laser power/annealing time/conventional sintering. The increase in laser power above this limit affects the grain growth kinetics and results in the compositional heterogeneities. From the results of Raman spectra, it was found that the film annealed under optimized conditions has a high degree of crystallinity and tetragonality, while the increase in laser fluence results in the growth of A1g mode. The controlled composition and microstructure, thus has resulted in the improved ferroelectricity with a remanent polarization 12 μC/cm2, on par with the bulk or larger than the films grown by the chemical solution deposition techniques. From the piezoresponse studies, we found that the film annealed at 75 W/5 min has weak ferroelectric nature with no switchable ferroelectric domains compared to those under optimized conditions. Subtle differences in phase transition temperatures and drop in ferroelectric polarization, for films annealed conventionally or at higher laser fluence, are related to porosity or site defects as well as compositional heterogeneities. Our study demonstrates that the combination of EPD and laser annealing is an effective way to achieve high quality piezoelectric thick films with a controlled composition, useful for energy harvesting applications.

Ignition characteristics of the iron-based alloy UNS S66286 in pressurized oxygen

NASA Technical Reports Server (NTRS)

Bransford, James W.; Billard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

1988-01-01

The development of ignition and combustion in pressurized oxygen atmospheres was studied for the iron based alloy UNS S66286. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature to rates greater than what would be expected from increased temperature alone. It is suggested that the source of these endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (25 to 2000 psia).

Catalyst-free growth of ZnO nanowires on ITO seed/glass by thermal evaporation method: Effects of ITO seed layer thickness

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

Alsultany, Forat H., E-mail: foratusm@gmail.com; Ahmed, Naser M.; Hassan, Z.

A seed/catalyst-free growth of ZnO nanowires (ZnO-NWs) on a glass substrate were successfully fabricated using thermal evaporation technique. These nanowires were grown on ITO seed layers of different thicknesses of 25 and 75 nm, which were deposited on glass substrates by radio frequency (RF) magnetron sputtering. Prior to synthesized ITO nanowires, the sputtered ITO seeds were annealed using the continuous wave (CW) CO2 laser at 450 °C in air for 15 min. The effect of seed layer thickness on the morphological, structural, and optical properties of ZnO-NWs were systematically investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM),more » and UV-Vis spectrophotometer.« less

Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy)

PubMed Central

De Rosa, Maurizio; Gagliardi, Gianluca; Rocco, Alessandra; Somma, Renato; De Natale, Paolo; De Natale, Giuseppe

2007-01-01

We report on a continuous-measurement campaign carried out in Vulcano (Aeolian islands, Sicily), devoted to the simultaneous monitoring of CO2 and H2O concentrations. The measurements were performed with an absorption spectrometer based on a semiconductor laser source emitting around a 2-μm wavelength. The emitted radiation was selectively absorbed by two molecular ro-vibrational transitions specific of the investigated species. Data for CO2 and H2O concentrations, and CO2 soil diffusive flux using an accumulation chamber configuration, were collected at several interesting sampling points on the island (Porto Levante beach- PLB, Fossa Grande Crater – FOG- and Valley of Palizzi, PAL). CO2/H2O values, measured on the ground, are very similar (around 0.019 (± 0.006)) and comparable to the previous discrete detected values of 0.213 (Fumarole F5-La Fossa crater rim) and 0.012 (Fumarole VFS – Baia Levante beach) obtaid during the 1977–1993 heating phase of the crater fumaroles. In this work much more homogeneous values are found in different points of the three sites investigated. The field work, although carried out in a limited time window (25th–28th August 2004), pointed out the new apparatus is suitable for continuous gas monitoring of the two species and their ratios, which are important geochemical indicators of volcanic activity, for which other reliable continuous monitoring systems are not yet available. PMID:17448243

Energy modulation of nonrelativistic electrons in an optical near field on a metal microslit

NASA Astrophysics Data System (ADS)

Ishikawa, R.; Bae, J.; Mizuno, K.

2001-04-01

Energy modulation of nonrelativistic electrons with a laser beam using a metal microslit as an interaction circuit has been investigated. An optical near field is induced in the proximity of the microslit by illumination of the laser beam. The electrons passing close to the slit are accelerated or decelerated by an evanescent wave contained in the near field whose phase velocity is equal to the velocity of the electrons. The electron-evanescent wave interaction in the microslit has been analyzed theoretically and experimentally. The theory has predicted that electron energy can be modulated at optical frequencies. Experiments performed in the infrared region have verified theoretical predictions. The electron-energy changes of more than ±5 eV with a 10 kW CO2 laser pulse at the wavelength of 10.6 μm has been successfully observed for an electron beam with an energy of less than 80 keV.

Comparative study on morphologic changes and cell attachment of periodontitis-affected root surfaces following conditioning with CO2 and Er:YAG laser irradiations.

PubMed

Belal, Mahmoud Helmy; Watanabe, Hisashi

2014-10-01

Clinical application of lasers in periodontal therapy has continued to expand in last decades; however there are still some controversies. The present study aimed to compare the conditioning effects of the carbon dioxide (CO2) or erbium-doped: yttrium, aluminum and garnet (Er:YAG) laser on periodontally diseased root surfaces following scaling and root planing (SRP) in terms of the alteration of morphologies as well as the attachment of periodontal ligament cells. Forty-five periodontally affected root specimens were prepared and randomly assigned into three groups: I control (untreated diseased), II. SRP+CO2 laser (pulsed, noncontact mode), and III. SRP+Er:YAG laser (slight contact mode). After treatment, five specimens in each group were used for surface topographic examination. The remaining 10 specimens in each group were incubated with human periodontal ligament cell suspension. All the specimens were finally evaluated by scanning electron microscopy. The control specimens showed the lowest number of cultured cells, mostly in oval shape, with no tightly attached cells. The CO2 lased specimens showed a significant increase in the number of attached cells compared with controls, but demonstrated some major thermal alterations on the surfaces. The Er:YAG lased specimens showed the significantly highest number of attached cells, mostly in flat form, and did not show distinct thermal damage. The present study suggests that compared with the CO2 laser, the Er:YAG laser may constitute a more useful conditioning tool for enhancing periodontal cell attachment to periodontally diseased root surfaces, with fewer undesirable thermal side effects.

Thermal effects of λ = 808 nm GaAlAs diode laser irradiation on different titanium surfaces.

PubMed

Giannelli, Marco; Lasagni, Massimo; Bani, Daniele

2015-12-01

Diode lasers are widely used in dental laser treatment, but little is known about their thermal effects on different titanium implant surfaces. This is a key issue because already a 10 °C increase over the normal body temperature can induce bone injury and compromise osseo-integration. The present study aimed at evaluating the temperature changes and surface alterations experienced by different titanium surfaces upon irradiation with a λ = 808 nm diode laser with different settings and modalities. Titanium discs with surfaces mimicking different dental implant surfaces including TiUnite and anodized, machined surfaces were laser-irradiated in contact and non-contact mode, and with and without airflow cooling. Settings were 0.5-2.0 W for the continuous wave mode and 10-45 μJ, 20 kHz, 5-20 μs for the pulsed wave mode. The results show that the surface characteristics have a marked influence on temperature changes in response to irradiation. The TiUnite surface, corresponding to the osseous interface of dental implants, was the most susceptible to thermal rise, while the machined surfaces, corresponding to the implant collar, were less affected. In non-contact mode and upon continuous wave emission, the temperature rose above the 50 °C tissue damage threshold. Scanning electron microscopy investigation of surface alterations revealed that laser treatment in contact mode resulted in surface scratches even when no irradiation was performed. These findings indicate that the effects of diode laser irradiation on implant surfaces depend on physical features of the titanium coating and that in order to avoid thermal or physical damage to implant surface the irradiation treatment has to be carefully selected.

Ripplon laser through stimulated emission mediated by water waves

NASA Astrophysics Data System (ADS)

Kaminski, Samuel; Martin, Leopoldo L.; Maayani, Shai; Carmon, Tal

2016-12-01

Lasers rely on stimulated electronic transition, a quantum phenomenon in the form of population inversion. In contrast, phonon masers depend on stimulated Raman scattering and are entirely classical. Here we extend Raman lasers to rely on capillary waves, which are unique to the liquid phase of matter and relate to the attraction between intimate fluid particles. We fabricate resonators that co-host capillary and optical modes, control them to operate at their non-resolved sideband and observe stimulated capillary scattering and the coherent excitation of capillary resonances at kilohertz rates (which can be heard in audio files recorded by us). By exchanging energy between electromagnetic and capillary waves, we bridge the interfacial tension phenomena at the liquid phase boundary to optics. This approach may impact optofluidics by allowing optical control, interrogation and cooling of water waves.

Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.

PubMed

Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert

2013-01-01

Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.

Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers

NASA Astrophysics Data System (ADS)

Eigenwillig, Christoph M.; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R.; Klein, Thomas; Jirauschek, Christian; Huber, Robert

2013-05-01

Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.

Diode-side-pumped continuous wave Nd³⁺ : YVO₄ self-Raman laser at 1176 nm.

PubMed

Kores, Cristine Calil; Jakutis-Neto, Jonas; Geskus, Dimitri; Pask, Helen M; Wetter, Niklaus U

2015-08-01

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.