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Sample records for rate nanosecond laser

  1. All-fiberized SBS-based high repetition rate sub-nanosecond Yb fiber laser for supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Hua, Dacheng; Su, Jianjia; Cui, Wei; Yan, Yaxi; Jiang, Peipei

    2014-12-01

    We report an all-fiberized SBS-based high repetition rate sub-nanosecond Yb fiber laser for supercontinuum generation. The high repetition rate ns laser pulses were produced from a fiber Bragg grating (FBG)-constructed fiber laser cavity consisting of a piece of double cladding Yb fiber as the gain medium and a short piece of Bi/Cr-doped fiber as a saturable absorber (SA). By optimizing the fiber length of the Bi/Cr-doped fiber and the reflectivity of the FBG, the Q-switching state of the fiber laser can be adjusted so that the energy storing condition within the fiber cavity can assure the start of stimulated Brillouin scattering (SBS) and as a result, compress the laser pulse duration. The fiber laser had an average laser power output of 1.2 W at 1064 nm with pulse repetition rate of about 80 kHz, almost four times the reported results. The pulse duration was about 1 ns with peak power of about 15 kW. After one stage of amplification, the laser power was raised to about 3 W and was used to pump a 20 m long photonic crystal fiber (PCF). Supercontiuum (SC) laser output was obtained with average power up to 1.24 W and spectrum spanning from 550 to 2200 nm.

  2. Application of a nanosecond laser pulse to evaluate dynamic hardness under ultra-high strain rate

    NASA Astrophysics Data System (ADS)

    Radziejewska, Joanna

    2016-04-01

    The paper presents results of experimental tests of plastic metals deformation generated by a shock wave induced by laser pulse. Tests were carried out on the Nd:YAG laser with a wavelength of 1064 nm and the laser pulse of 10 ns duration. The shock wave generate by the laser pulse was used to induced local plastic deformation of the material surface. The study examined the possibility of application the process to develop a new method of measuring the dynamic hardness of materials under ultra-high strain rate. It has been shown that the shock wave induced by the laser pulse with an energy of 0.35-1.22 J causes a repeatable plastic deformation of surface of commercially available metals and alloys without thermal effects on the surfaces. Based on the knowledge of an imprint geometry, it is possible to evaluate the dynamic hardness of materials at strain rate in the range of 107 s-1.

  3. Millisecond laser machining of transparent materials assisted by nanosecond laser.

    PubMed

    Pan, Yunxiang; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2015-01-26

    A new form of double pulse composed of a nanosecond laser and a millisecond laser is proposed for laser machining transparent materials. To evaluate its advantages and disadvantages, experimental investigations are carried out and the corresponding results are compared with those of single millisecond laser. The mechanism is discussed from two aspects: material defects and effects of modifications induced by nanosecond laser on thermal stress field during millisecond laser irradiation. It is shown that the modifications of the sample generated by nanosecond laser improves the processing efficiency of subsequent millisecond laser, while limits the eventual size of modified region.

  4. Nanosecond cryogenic Yb:YAG disk laser

    SciTech Connect

    Perevezentsev, E A; Mukhin, I B; Kuznetsov, I I; Vadimova, O L; Palashov, O V

    2014-05-30

    A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ∼10{sup 8}. (lasers)

  5. Nanosecond laser ablation of silver nanoparticle film

    NASA Astrophysics Data System (ADS)

    Chung, Jaewon; Han, Sewoon; Lee, Daeho; Ahn, Sanghoon; Grigoropoulos, Costas P.; Moon, Jooho; Ko, Seung H.

    2013-02-01

    Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.

  6. Nanosecond laser ablation for pulsed laser deposition of yttria

    NASA Astrophysics Data System (ADS)

    Sinha, Sucharita

    2013-09-01

    A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

  7. Texturing of polypropylene (PP) with nanosecond lasers

    NASA Astrophysics Data System (ADS)

    Riveiro, A.; Soto, R.; del Val, J.; Comesaña, R.; Boutinguiza, M.; Quintero, F.; Lusquiños, F.; Pou, J.

    2016-06-01

    Polypropylene (PP) is a biocompatible and biostable polymer, showing good mechanical properties that has been recently introduced in the biomedical field for bone repairing applications; however, its poor surface properties due to its low surface energy limit their use in biomedical applications. In this work, we have studied the topographical modification of polypropylene (PP) laser textured with Nd:YVO4 nanosecond lasers emitting at λ = 1064 nm, 532 nm, and 355 nm. First, optical response of this material under these laser wavelengths was determined. The application of an absorbing coating was also studied. The influence of the laser processing parameters on the surface modification of PP was investigated by means of statistically designed experiments. Processing maps to tailor the roughness, and wettability, the main parameters affecting cell adhesion characteristics of implants, were also determined. Microhardness measurements were performed to discern the impact of laser treatment on the final mechanical properties of PP.

  8. Hydrocarbon level detection with nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Hosseinian S, Raheleh; Nugroho, Waskito; Mohd Marsin, Faridah; Zainal, Jasman

    2013-12-01

    Nanosecond laser induced breakdown in liquid is used as a technique to detect hydrocarbon levels in water. A Q-switched Nd:YAG laser was focused to generate optical breakdown associated with shock wave generation. The shock wave was propagated at the speed of sound in the medium after travelling 1 μs outward from the center of optical breakdown. Different amplitudes of sound were traced with the aid of an ultrasonic probe. The optical properties of the hydrocarbon solution were quantified via fundamental refractive index measurement (the Snell law). A continuous mode diode pumped solid state laser with second harmonic generation was used as the illumination light source. A CCD video camera with Matrox version 4.2 software was utilized to analyze the recording image. Option line analysis was performed to analyze the intensity of optical breakdown at different input energies. Gray level analysis was also conducted on the scattering light after passing through the hydrocarbon solution at different concentrations. The hydrocarbon solution comprised impurities or particles that varied according to the concentration. The average of the gray level is assumed to present the size of the particle. Inherently, as the acoustic wave propagates outward, it transports the mass (particles or impurities) and impacts on the ultrasonic probe. As a result a higher concentration of hydrocarbons reveals a larger amplitude of sound waves. This phenomenon is identified as a finger print for hydrocarbon levels between 100 and 1000 ppm. The transient detection, without complicated sampling preparation and no hazardous chemical involvement, makes laser ablation a promising technique to detect in situ hydrocarbon levels in water.

  9. Time comparison in nanosecond laser synchronization via geostationary satellite

    NASA Astrophysics Data System (ADS)

    Dworak, H. P.

    1980-01-01

    Laser pulse transmission from ground stations to the Sirio 2 satellite will allow intercontinental synchronization of high-precision clocks with an accuracy of several nanoseconds. Time comparison methods currently in use are examined and compared with reference to the increasing user demands. The laser synchronization experiment LASSO is described in detail. Existing operational laser ground facilities are listed and operational aspects are discussed.

  10. Nanosecond-gated laser induced breakdown spectroscopy in hydrocarbon mixtures

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazunobu; Bak, Moon Soo; Tanaka, Hiroki; Do, Hyungrok

    2015-09-01

    Nanosecond-gated laser induced breakdown spectroscopy have been carried out in four different hydrocarbon gas mixtures (CH4/CO2/O2/N2, C2H4/O2/N2, C3H8/CO2/O2/N2 and C4H10/CO2/O2/N2) to investigate the effect of gas species on the laser induced breakdown kinetics and resulting the plasma emission. For this purpose, each mixture that consists of different species has the same atom composition. It is found that the temporal emission spectra and the decay rates of atomic line-intensities are almost identical for the breakdowns in the four different mixtures. This finding may indicate that the breakdown plasmas of these mixtures reach a similar thermodynamic and physiochemical state after its formation, resulting in a similar trend of quenching of excited species.

  11. Multicolor multiphoton microscopy based on a nanosecond supercontinuum laser source.

    PubMed

    Lefort, Claire; O'Connor, Rodney P; Blanquet, Véronique; Magnol, Laetitia; Kano, Hideaki; Tombelaine, Vincent; Lévêque, Philippe; Couderc, Vincent; Leproux, Philippe

    2016-07-01

    Multicolor multiphoton microscopy is experimentally demonstrated for the first time on a spectral bandwidth of excitation of 300 nm (full width half maximum) thanks to the implementation a nanosecond supercontinuum (SC) source compact and simple with a low repetition rate. The interest of such a wide spectral bandwidth, never demonstrated until now, is highlighted in vivo: images of glioma tumor cells stably expressing eGFP grafted on the brain of a mouse and its blood vessels network labelled with Texas Red(®) are obtained. These two fluorophores have a spectral bandwidth covering the whole 300 nm available. In parallel, a similar image quality is obtained on a sample of mouse muscle in vitro when excited with this nanosecond SC source or with a classical high rate, femtosecond and quasi monochromatic laser. This opens the way for (i) a simple and very complete biological characterization never performed to date with multiphoton processes, (ii) multiple means of contrast in nonlinear imaging allowed by the use of numerous fluorophores and (iii) other multiphoton processes like three-photon ones. PMID:26872004

  12. High peak power sub-nanosecond mode-locked pulse characteristics of Nd:GGG laser

    NASA Astrophysics Data System (ADS)

    Zhao, Jia; Zhao, Shengzhi; Li, Tao; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Qiao, Wenchao; Feng, Chuansheng; Wang, Yonggang

    2015-10-01

    Based on the dual-loss modulation, i.e. electro-optic (EO) modulator and GaAs saturable absorber, a sub-nanosecond mode-locked pulsed Nd:GGG laser with kHz repetition rates is presented for the first time. The repetition rate (0.5-10 kHz) of this pulsed laser is controlled by the modulation rate of EO modulator, so high stability can be obtained. The sub-nanosecond pulse width depends on the mode-locked pulse underneath the Q-switched envelope in the Q-switched mode-locked (QML) laser and high peak power can be generated. The condition on the generation of sub-nanosecond pulse and the needed threshold power for different modulation rates of EO are given. The average output power, the pulse width and the peak power versus pump power for different repetition rates are demonstrated. The shortest pulse width is 426 ps and the highest peak power reaches 239.4 kW. The experimental results show that the dual-loss modulation technology with EO and GaAs saturable absorber in QML laser is an efficient method to generate sub-nanosecond mode-locked pulsed laser with kHz repetition rates.

  13. Low charge state heavy ion production with sub-nanosecond laser.

    PubMed

    Kanesue, T; Kumaki, M; Ikeda, S; Okamura, M

    2016-02-01

    We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume. This property might be suitable for low charge state ion production. We used a nanosecond laser and a sub-nanosecond laser for low charge state ion production to investigate the difference of generated plasma using the Zirconium target.

  14. Low charge state heavy ion production with sub-nanosecond laser

    NASA Astrophysics Data System (ADS)

    Kanesue, T.; Kumaki, M.; Ikeda, S.; Okamura, M.

    2016-02-01

    We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume. This property might be suitable for low charge state ion production. We used a nanosecond laser and a sub-nanosecond laser for low charge state ion production to investigate the difference of generated plasma using the Zirconium target.

  15. Nanosecond square pulse generation in fiber lasers with normal dispersion

    NASA Astrophysics Data System (ADS)

    Zhao, L. M.; Tang, D. Y.; Cheng, T. H.; Lu, C.

    2007-04-01

    We report on the generation of nanosecond square pulses in a passively mode-locked fiber ring laser made of purely normal dispersive fibers. Different to the noise-like pulse operation of the laser, the generated square pulses are stable and have no internal structures. We show that the formation of the square pulse is due to the combined action of the pulse peak clamping effect caused by the cavity and the almost linear pulse propagation in the normal dispersive fibers.

  16. Towards acousto-optic tissue imaging with nanosecond laser pulses.

    PubMed

    Resink, S G; Hondebrink, E; Steenbergen, W

    2014-02-10

    We present a way to generate acousto-optical signals in timovssue-like media with nanosecond laser pulses. Our method is based on recording and analyzing speckle patterns formed by interaction of nanosecond laser pulses with tissue, without and with simultaneous application of ultrasound. Stroboscopic application allows visualizing the temporal behavior of speckles while the ultrasound is propagating through the medium. We investigate two ways of quantifying the acousto-optic effect, viz. adding and subtracting speckle patterns obtained at various ultrasound phases. Both methods are compared with the existing speckle contrast method using a 2D scan and are found to perform similarly. Our method gives outlook on overcoming the speckle decorrelation problem in acousto-optics, and therefore brings in-vivo acousto-optic measurements one step closer. Furthermore it enables combining acousto-optics and photoacoustics in one setup with a single laser.

  17. Multipulse nanosecond laser modification of steel surface

    NASA Astrophysics Data System (ADS)

    Chumakov, A. N.; Nikonchuk, I. S.; Gaković, B.; Petrović, S.; Trtica, M.

    2014-09-01

    Results of surface modification are presented for MnNiCrMo-steel samples exposed to a Nd:YAG laser operating in a pulse-periodic mode (10 Hz frequency, 532 nm wavelength and 17 ns pulse duration). The steel samples were irradiated in air by a series of laser pulses at a fluence of 10.7 J cm-2 close to a plasma formation threshold. Surface structures were examined by optical, scanning electron and confocal optical microscopy. The appearance of the detected surface structures strongly depends on the number of laser pulses and power density of laser radiation. Significant differences were found between laser-induced structures in the center of the laser spot, at its edges and in the nearest surrounding of the laser spot. The reasons for such differences are discussed.

  18. Double nanosecond pulses generation in ytterbium fiber laser.

    PubMed

    Veiko, V P; Lednev, V N; Pershin, S M; Samokhvalov, A A; Yakovlev, E B; Zhitenev, I Yu; Kliushin, A N

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode. PMID:27370433

  19. Double nanosecond pulses generation in ytterbium fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Lednev, V. N.; Pershin, S. M.; Samokhvalov, A. A.; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N.

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  20. 100  J-level nanosecond pulsed diode pumped solid state laser.

    PubMed

    Banerjee, Saumyabrata; Mason, Paul D; Ertel, Klaus; Jonathan Phillips, P; De Vido, Mariastefania; Chekhlov, Oleg; Divoky, Martin; Pilar, Jan; Smith, Jodie; Butcher, Thomas; Lintern, Andrew; Tomlinson, Steph; Shaikh, Waseem; Hooker, Chris; Lucianetti, Antonio; Hernandez-Gomez, Cristina; Mocek, Tomas; Edwards, Chris; Collier, John L

    2016-05-01

    We report on the successful demonstration of a 100 J-level, diode pumped solid state laser based on cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier technology. When operated at 175 K, the system delivered a pulse energy of 107 J at a 1 Hz repetition rate and 10 ns pulse duration, pumped by 506 J of diode energy at 940 nm, corresponding to an optical-to-optical efficiency of 21%. To the best of our knowledge, this represents the highest energy obtained from a nanosecond pulsed diode pumped solid state laser. This demonstration confirms the energy scalability of the diode pumped optical laser for experiments laser architecture.

  1. Nanosecond and femtosecond laser spectroscopy of molecules of biological interest

    NASA Astrophysics Data System (ADS)

    Villani, P.; Orlando, S.; Santagata, A.; De Bonis, A.; Veronesi, S.; Giardini, A.

    2007-07-01

    This paper mainly concerns on nanosecond and femtosecond laser spectroscopy of aromatic organic compounds as neurotransmitters, and plume diagnostics of the ablated species, in order to characterize the plasma dynamics, i.e. the temporal and spatial evolution of the plume. Optical emission spectroscopy has been applied to characterize the transient species produced in the femtosecond (fs) and nanosecond (ns) regimes. The laser sources employed for optical emission spectroscopy are a frequency-doubled Nd:YAG Handy ( λ = 532 nm, τ = 5 ns) and a frequency-doubled Nd:glass ( λ = 527 nm, τ = 250 fs). These studies aim to detect and give information on the photoexcitation and photodissociation of these biological molecules and to compare the plasma characteristics in the two ablation regimes.

  2. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum.

    PubMed

    Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A

    2016-04-28

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  3. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum.

    PubMed

    Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A

    2016-04-28

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces. PMID:27131543

  4. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Joly, Alan G.; Tonkyn, Russell G.; Kay, Bruce D.; Kimmel, Greg A.

    2016-04-01

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ˜1010 K/s for temperature increases of ˜100-200 K are obtained. Subsequent rapid cooling (˜5 × 109 K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ˜±2.7% leading to a temperature uncertainty of ˜±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  5. High on/off ratio nanosecond laser pulses for a triggered single-photon source

    NASA Astrophysics Data System (ADS)

    Jin, Gang; Liu, Bei; He, Jun; Wang, Junmin

    2016-07-01

    An 852 nm nanosecond laser pulse chain with a high on/off ratio is generated by chopping a continuous-wave laser beam using a Mach–Zehnder-type electro-optic intensity modulator (MZ-EOIM). The detailed dependence of the MZ-EOIM’s on/off ratio on various parameters is characterized. By optimizing the incident beam polarization and stabilizing the MZ-EOIM temperature, a static on/off ratio of 12600:1 is achieved. The dynamic on/off ratios versus the pulse repetition rate and the pulse duty cycle are measured and discussed. The high-on/off-ratio nanosecond pulsed laser system was used in a triggered single-photon source based on a trapped single cesium atom, which reveals clear antibunching.

  6. High on/off ratio nanosecond laser pulses for a triggered single-photon source

    NASA Astrophysics Data System (ADS)

    Jin, Gang; Liu, Bei; He, Jun; Wang, Junmin

    2016-07-01

    An 852 nm nanosecond laser pulse chain with a high on/off ratio is generated by chopping a continuous-wave laser beam using a Mach-Zehnder-type electro-optic intensity modulator (MZ-EOIM). The detailed dependence of the MZ-EOIM’s on/off ratio on various parameters is characterized. By optimizing the incident beam polarization and stabilizing the MZ-EOIM temperature, a static on/off ratio of 12600:1 is achieved. The dynamic on/off ratios versus the pulse repetition rate and the pulse duty cycle are measured and discussed. The high-on/off-ratio nanosecond pulsed laser system was used in a triggered single-photon source based on a trapped single cesium atom, which reveals clear antibunching.

  7. Picosecond absorption relaxation measured with nanosecond laser photoacoustics

    NASA Astrophysics Data System (ADS)

    Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

    2010-10-01

    Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural—including strongly scattering and nonfluorescent—materials.

  8. Nanosecond laser damage of optical multimode fibers

    NASA Astrophysics Data System (ADS)

    Mann, Guido; Krüger, Jörg

    2016-07-01

    For pulse laser materials processing often optical step index and gradient index multimode fibers with core diameters ranging from 100 to 600 μm are used. The design of a high power fiber transmission system must take into account limitations resulting from both surface and volume damage effects. Especially, breakdown at the fiber end faces and selffocusing in the fiber volume critically influence the fiber performance. At least operation charts are desirable to select the appropriate fiber type for given laser parameters. In industry-relevant studies the influence of fiber core diameter and end face preparation on laser-induced (surface) damage thresholds (LIDT) was investigated for frequently used all-silica fiber types (manufacturer LEONI). Experiments on preform material (initial fiber material) and compact specimens (models of the cladding and coating material) accompanied the tests performed in accordance with the relevant LIDT standards ISO 21254-1 and ISO 21254-2 for 1-on-1 and S-on-1 irradiation conditions, respectively. The relation beam diameter vs. LIDT was investigated for fused silica fibers. Additionally, laser-induced (bulk) damage thresholds of fused silica preform material F300 (manufacturer Heraeus) in dependence on external mechanical stress simulating fiber bending were measured. All experiments were performed with 10-ns laser pulses at 1064 and 532 nm wavelength with a Gaussian beam profile.

  9. Numerical simulation of air-breathing mode laser propulsion by nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Zhao, Shanghong; Chu, Xingchun; Yu, Kanmin; Ma, Lihua; Zhan, Shengbao; Li, Yunxia

    2009-07-01

    Based on Navier-Stokes equations, numerical simulations of air-breathing mode laser propulsion by nanosecond laser pulse are carried out. An analytical model of the thruster's inner flow involving the simple processing of the ignition zone is established. The evolvement of the laser sustained plasma shockwaves is systemic analyzed; also the effects of pulse energy and thruster's structure such as focal length, scale and open angle on propulsion performance are researched. The simulated results show that the focal length dominates among the structural factors of thruster in the propulsion by nanosecond laser pulse. The larger focal length leads to better propulsion performance. It is also evident that for single pulse propulsion, nanosecond laser pulse is better than microsecond laser pulse, the momentum coupling efficient achieved by the former is 2~5 times of the latter's, which is highly agree with the existing experimental results.

  10. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    NASA Astrophysics Data System (ADS)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  11. Nanosecond laser photolysis of opaque heterogeneous photosensitizers

    NASA Astrophysics Data System (ADS)

    Wilkinson, F.

    1988-07-01

    The new technique of diffuse reflectance laser flash photolysis has been used to study the photochemistry of molecules, such as acridine and diphenylpolyenes adsorbed on metal oxide surfaces and electronic energy transfer between benzophenone and methylnaphtalene at interfaces. Triplet-triplet absorption spectra and decay kinetics have been observed from aromatic ketones such as xanthone, butyrophenone and valerophenone included within zeolite channels and from ruthenium (II) tris (2,2' bipyridine) both bound to polymers and within cavities of an ion exchange resin. Photophysical processes within dyed fabrics e.g., aluminum phthalocyanine, eosin and erythrosin on cotton have been investigated directly for the first time. Time resolved spectra following laser excitation of porous doped photoelectrodes e.g., zinc oxide doped with cobalt, have been obtained which show isosbestic points as the transient decays by electron transfer to give back Co2 (+). photochemistry, Interfaces, Surfaces, Kubelka munk theory, Laser flash photolysis, Opaque materials, Photochemistry, Picosecond spectroscopy, Semi conductors, Sensitizers, Silica, Thermal effects, Transient absorption, Transient decay, Triplet states. (MJM)

  12. Low charge state heavy ion production with sub-nanosecond laser.

    PubMed

    Kanesue, T; Kumaki, M; Ikeda, S; Okamura, M

    2016-02-01

    We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume. This property might be suitable for low charge state ion production. We used a nanosecond laser and a sub-nanosecond laser for low charge state ion production to investigate the difference of generated plasma using the Zirconium target. PMID:26931977

  13. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    SciTech Connect

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  14. Biocompatibility Evaluation of Nanosecond Laser Treated Titanium Surfaces

    NASA Astrophysics Data System (ADS)

    Honda, Ryo; Mizutani, Masayoshi; Ohmori, Hitoshi; Komotori, Jun

    We developed surface modification technologies for dental implants in this study. The study contributes to shortening the time required for adhesion between alveolar bone and fixtures which consist of dental implants. A Nd:YVO4 nanosecond laser was used to modify the surfaces of commercially pure titanium (CP Ti) disks, and their biocompatibility was evaluated cytocompatibility and bioactivity. First, rows of 200 µm spaced rectilinear laser treatments were performed on surfaces of CP Ti disks. Osteoblasts derived from rat mesenchymal stem cells were then cultured on the treated surfaces. Cytocompatibility on the laser treated area was evaluated by observing adhesion behavior of cells on these surfaces. The results indicated that the micro-order structure formed by the laser treatment promoted adhesion of osteoblasts and that traces of laser treatment without microstucture didn't affect the adhesion. Second, surfaces of CP Ti disks were completely covered by traces of laser treatment, which created complex microstructures of titania whose crystal structure is rutile and anatase. This phenomenon allowed the creation of hydroxyapatite on the surface of the disks in 1.5-times simulated body fluid (1.5SBF) while no hydroxyapatite was observed on conventional polished surfaces in the same conditions. This result indicates that bioactivity was enabled on CP Ti by the laser treatment. From these two results, laser treatment for CP Ti surfaces is an effective method for enhancing adhesion of osteoblasts and promoting bioactivity, which are highly appreciated properties for dental implants.

  15. Direct modification of silicon surface by nanosecond laser interference lithography

    NASA Astrophysics Data System (ADS)

    Wang, Dapeng; Wang, Zuobin; Zhang, Ziang; Yue, Yong; Li, Dayou; Maple, Carsten

    2013-10-01

    Periodic and quasi-periodic structures on silicon surface have numerous significant applications in photoelectronics and surface engineering. A number of technologies have been developed to fabricate the structures in various research fields. In this work, we take the strategy of direct nanosecond laser interference lithography technology, and focus on the silicon material to create different well-defined surface structures based on theoretical analysis of the formation of laser interference patterns. Two, three and four-beam laser interference systems were set up to fabricate the grating, regular triangle and square structures on silicon surfaces, respectively. From the AFM micrographs, the critical features of structures have a dependence on laser fluences. For a relative low laser fluence, grating and dot structures formed with bumps due to the Marangoni Effect. With the increase of laser fluences, melt and evaporation behaviors can be responsible for the laser modification. By properly selecting the process parameters, well-defined grating and dot structures can been achieved. It can be demonstrated that direct laser interference lithography is a facile and efficient technology with the advantage of a single process procedure over macroscale areas for the fabrication of micro and nano structures.

  16. Over 0.5 MW green laser from sub-nanosecond giant pulsed microchip laser

    NASA Astrophysics Data System (ADS)

    Zheng, Lihe; Taira, Takunori

    2016-03-01

    A sub-nanosecond green laser with laser head sized 35 × 35 × 35 mm3 was developed from a giant pulsed microchip laser for laser processing on organic superconducting transistor with a flexible substrate. A composite monolithic Y3Al5O12 (YAG) /Nd:YAG/Cr4+:YAG/YAG crystal was designed for generating giant pulsed 1064 nm laser. A fibercoupled 30 W laser diode centered at 808 nm was used with pump pulse duration of 245 μs. The 532 nm green laser was obtained from a LiB3O5 (LBO) crystal with output energy of 150 μJ and pulse duration of 268 ps. The sub-nanosecond green laser is interesting for 2-D ablation patterns.

  17. Single-frequency linearly-polarized 1083 nm all fiber nanosecond laser

    NASA Astrophysics Data System (ADS)

    Su, Rongtao; Xu, Jiangmin; Zhou, Pu; Ji, Xiang; Xu, Xiaojun

    2012-12-01

    Single-frequency linearly-polarized 1083 nm all fiber nanosecond master-oscillator power amplifier laser system is demonstrated. A ring laser, whose key components are one saturable absorber and two polarization controllers, delivers a single-frequency continuous wave laser. Using an electro-optic modulator as the modulator, the pulse laser seed is obtained by modulating the CW laser. By amplifying the pulse seed to the average power of 61.6 W in three stages, a single-frequency linearly-polarized laser with pulse duration of 16 ns, repetition rate of 10 MHz and pulse energy of 6.16 μJ is obtained. No nonlinear effect is observed in our experiment. Higher output power can be obtained by increasing LDs of the main amplifier.

  18. Temporal effects of femtosecond-to-nanosecond laser ablation on fresh porcine liver

    NASA Astrophysics Data System (ADS)

    Irwin, Bryan S.; Nguyen, Michael N.; Higbee, Russell G.; Bartels, Kenneth E.; Church, Kenneth H.; Warren, William L.

    2004-07-01

    Using a Ti:Sapphire laser operating at 800nm and a repetition rate of 1 kHz, we investigated the damage induced to fresh cadaveric porcine liver after laser irradiation for pulse widths of 120-fs, 8ps, and 7-ns. The laser was held constant at a focal spot diameter of 100μm yielding a maximum fluence of 9J/cm2. Then, using polarization optics, the energy per pulse was controlled to well below ablation threshold fluences. The tissue samples were translated under the laser via 0.1μm resolution encoded X-Y-Z motorized stages. After irradiation and fixation, we evaluated the tissues using brightfield light microscopy of Hematoxylin and Eosin stained 4 μm thick cross sections, scanning electron microscopy, and transmission electron microscopy. The tissue samples were examined for both removal rates of material, thermal damage to surrounding tissue, and cell disruption for equivalent fluence levels across the temporal range. We found an increase in removal rate along with a decrease in thermal damage as the pulse widths approached the femtosecond regime for a constant fluence. With femtosecond pulses, ablation still occurred below fluences of 2J/cm2. However, for nanosecond pulses, ablation no longer occurred, showing a decrease in ablation threshold as the pulse width decreases. Because of the reduced thermal effects compared to nanosecond pulses, ultrafast lasers may offer a solution to more precise tissue removal with less damage to surrounding cells.

  19. Acceleration of neutrals in a nanosecond laser produced nickel plasma

    SciTech Connect

    Smijesh, N.; Chandrasekharan, K.; Philip, Reji

    2014-12-15

    Time of flight dynamics of slow neutrals, fast neutrals, and ions from a nanosecond laser produced nickel (Ni) plasma are investigated. Species arrival times confirm the hypothesis that fast neutrals are formed by the recombination of fast ions with free electrons. Both neutrals and ions are found to accelerate for a short interval immediately after ablation, which is attributed to internal Coulomb forces which create electrostatic potentials resulting in the charged particle acceleration. This process is further enhanced by laser-plasma energy coupling. Emission from neutrals could be measured for longer axial distances in the plume compared to that of ions confirming that the ions recombine to form neutrals as they move away from the target surface.

  20. Nanosecond-laser plasma-assisted ultradeep microdrilling of optically opaque and transparent solids

    SciTech Connect

    Paul, Stanley; Kudryashov, Sergey I.; Lyon, Kevin; Allen, Susan D.

    2007-02-15

    A mechanism of ultradeep (up to tens of microns per pulse, submillimeter total hole depths) plasma-assisted ablative drilling of optically opaque and transparent materials by high-power nanosecond lasers has been proposed and verified experimentally using optical transmission and contact photoacoustic techniques to measure average drilling rates per laser shot versus laser intensity at constant focusing conditions. The plots of average drilling rates versus laser intensity exhibit slopes which are in good agreement with those predicted by the proposed model and also with other experimental studies. The proposed ultradeep drilling mechanism consists of a number of stages, including ultradeep 'nonthermal' energy delivery into bulk solids by the short-wavelength radiation of the hot ablative plasma, bulk heating and melting, accompanied by subsurface boiling in the melt pool, and resulting melt expulsion from the target.

  1. Laser photoionization of triacetone triperoxide (TATP) by femtosecond and nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Mullen, Christopher; Huestis, David; Coggiola, Michael; Oser, Harald

    2006-05-01

    Laser ionization time-of-flight mass spectrometry has been applied to the study of triacetone triperoxide (TATP), an improvised explosive. Wavelength dependent mass spectra in two time regimes were acquired using nanosecond (5 ns) and femtosecond (130 fs) laser pulses. We find the major difference between the two time regimes to be the detection of the parent molecular ion when femtosecond laser pulses are employed.

  2. Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

    SciTech Connect

    Liu, Chunyang Sui, Xin; Yang, Fang; Ma, Wei; Li, Jishun; Xue, Yujun; Fu, Xing

    2014-03-15

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

  3. Dry and wet laser catapulting and ablation of cells and bacteria by nanosecond CO II laser

    NASA Astrophysics Data System (ADS)

    Shukla, Shishir; Kudryashov, Sergey; Lyon, Kevin; Allen, Susan D.

    2006-02-01

    A lot of work has been done in the area of laser sterilization using UV lasers whereas this area is not much explored using an IR laser. In this study the cells were catapulted from glass or oxidized silicon substrates by a nanosecond IR CO II laser. Removal of cells and bacteria was achieved under the micron thick liquid layer pre-deposited on the substrates and lifted off together with biological species at laser fluences exceeding the corresponding boiling thresholds for the liquids used. Catapulting with front-side laser illumination is studied

  4. Development of selective laser treatment techniques using mid-infrared tunable nanosecond pulsed laser.

    PubMed

    Ishii, Katsunori; Saiki, Masayuki; Hazama, Hisanao; Awazu, Kunio

    2010-01-01

    Mid-infrared (MIR) laser with a specific wavelength can excite the corresponding biomolecular site to regulate chemical, thermal and mechanical interactions to biological molecules and tissues. In laser surgery and medicine, tunable MIR laser irradiation can realize the selective and less-invasive treatments and the special diagnosis by vibrational spectroscopic information. This paper showed a novel selective therapeutic technique for a laser angioplasty of atherosclerotic plaques and a laser dental surgery of a carious dentin using a MIR tunable nanosecond pulsed laser.

  5. Control of optical and electrical properties of ZnO nanocrystals by nanosecond-laser annealing

    NASA Astrophysics Data System (ADS)

    Shimogaki, T.; Ofuji, T.; Tetsuyama, N.; Kawahara, H.; Higashihata, M.; Ikenoue, H.; Nakamura, D.; Okada, T.

    2014-03-01

    Effects of laser annealing on electrical and optical properties of Zinc oxide (ZnO) nanocrystals, which are expected as building blocks for optoelectronic devices, have been investigated in this study. In the case of fabricating p-n junction in single one-dimensional ZnO nanocrystal, phosphorus-ions implanted p-type ZnO nanocrystals were recrystallized and recovered in the optical properties by nanosecond-laser annealing using a KrF excimer laser. Antimony-doped p-type ZnO nanocrystals were synthesized by irradiating laminated structure which antimony thin film were deposited on ZnO nanocrystals with the laser beam. Additionally, it is possible to control the growth rate of ZnO nanowires by using laser annealing. Irradiating with pulsed laser a part of ZnO buffer layer deposited on the a-cut sapphire substrate, then ZnO nanowires were grown on the ZnO buffer layer by the nanoparticle assisted pulsed laser deposition method. As a result, the clear boundary of the laser annealed and non-laser annealed area was appeared. It was observed that ZnO nanowires were grown densely at non-laser annealed area, on the other hand, sparse ones were grown at the laser-annealed region. In this report, the possibility of laser annealing techniques to establish the stable and reliable fabrication process of ZnO nanowires-based LD and LED are discussed on the basis of experimental results.

  6. Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion

    SciTech Connect

    Wu, Jian; Wei, Wenfu; Li, Xingwen; Jia, Shenli; Qiu, Aici

    2013-04-22

    We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm{sup 2} in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag model was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.

  7. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  8. Millisecond laser machining of transparent materials assisted by a nanosecond laser with different delays.

    PubMed

    Pan, Yunxiang; Lv, Xueming; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2016-06-15

    A millisecond laser combined with a nanosecond laser was applied to machining transparent materials. The influences of delay between the two laser pulses on processing efficiencies and modified sizes were studied. In addition, a laser-supported combustion wave (LSCW) was captured during laser irradiation. An optimal delay corresponding to the highest processing efficiency was found for cone-shaped cavities. The modified size as well as the lifetime and intensity of the LSCW increased with the delay decreasing. Thermal cooperation effects of defects, overlapping effects of small modified sites, and thermal radiation from LSCW result in all the phenomena. PMID:27304294

  9. Millisecond laser machining of transparent materials assisted by a nanosecond laser with different delays.

    PubMed

    Pan, Yunxiang; Lv, Xueming; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2016-06-15

    A millisecond laser combined with a nanosecond laser was applied to machining transparent materials. The influences of delay between the two laser pulses on processing efficiencies and modified sizes were studied. In addition, a laser-supported combustion wave (LSCW) was captured during laser irradiation. An optimal delay corresponding to the highest processing efficiency was found for cone-shaped cavities. The modified size as well as the lifetime and intensity of the LSCW increased with the delay decreasing. Thermal cooperation effects of defects, overlapping effects of small modified sites, and thermal radiation from LSCW result in all the phenomena.

  10. Nanosecond laser textured superhydrophobic metallic surfaces and their chemical sensing applications

    NASA Astrophysics Data System (ADS)

    Ta, Duong V.; Dunn, Andrew; Wasley, Thomas J.; Kay, Robert W.; Stringer, Jonathan; Smith, Patrick J.; Connaughton, Colm; Shephard, Jonathan D.

    2015-12-01

    This work demonstrates superhydrophobic behavior on nanosecond laser patterned copper and brass surfaces. Compared with ultrafast laser systems previously used for such texturing, infrared nanosecond fiber lasers offer a lower cost and more robust system combined with potentially much higher processing rates. The wettability of the textured surfaces develops from hydrophilicity to superhydrophobicity over time when exposed to ambient conditions. The change in the wetting property is attributed to the partial deoxidation of oxides on the surface induced during laser texturing. Textures exhibiting steady state contact angles of up to ∼152° with contact angle hysteresis of around 3-4° have been achieved. Interestingly, the superhydrobobic surfaces have the self-cleaning ability and have potential for chemical sensing applications. The principle of these novel chemical sensors is based on the change in contact angle with the concentration of methanol in a solution. To demonstrate the principle of operation of such a sensor, it is found that the contact angle of methanol solution on the superhydrophobic surfaces exponentially decays with increasing concentration. A significant reduction, of 128°, in contact angle on superhydrophobic brass is observed, which is one order of magnitude greater than that for the untreated surface (12°), when percent composition of methanol reaches to 28%.

  11. Retinal threshold studies for nanosecond and picosecond visible laser pulses

    NASA Astrophysics Data System (ADS)

    Roach, William P.; DiCarlo, Cheryl D.; Noojin, Gary D.; Stolarski, David J.; Amnotte, Rodney E.; Smith, Audrey B.; Rogers, Mark E.; Cain, Clarence P.

    1995-05-01

    Threshold measurements for Minimum Visible Lesions (MVL) at the retina are reported for 60 picoseconds (ps) and 4 nanoseconds (ns), single laser pulses in rhesus monkey eyes using a visible wavelength of 532 nanometers (nm) from a doubled Nd:YAG laser. The 50% probability for damage (ED50) dosages are calculated for 1 hour and 24 hour post exposures using 95% fiducial limits. For both pulsewidths, the threshold values calculated by probit analysis decrease between the 1 hour and 24 hour ophthalmoscopic evaluations. The ED50 value determined for the 60 ps pulsewidth was less than half the value at 4 ns (0.43 (mu) J/60 ps vs. 0.90 (mu) J/4 ns at 24 hours) for both readings. Of the 136 exposures for pulse energies ranging from 0.03 to 5.0 (mu) J no hemorrhagic lesions were produced for either pulsewidth studied. However, at 6.6 (mu) J one intraretinal hemorrhagic lesion was observed for 60 ps. The slope of the probit curve was higher for 60 ps when compared with the 4 ns value (3.03 at 60 ps vs. 2.68 at 4 ns). MVL threshold doses calculated are comparable with those reported in the literature. However, the 4 ns MVL values is less than one order of magnitude (a factor 4.7) above the Maximum Permissible Exposure (MPE) level as defined by the 'American National Standard For The Safe Use Of Lasers', ANSI Z136.1-19932. We present the current MVL data as it compares with previous data obtained for picosecond and femtosecond laser pulse thresholds and provide a preliminary assessment of how the ANSI MPE standard might be amended.

  12. Numerical simulation of impurity desorption induced by nanosecond and femtosecond laser pulses

    SciTech Connect

    Chi Yinsheng; Lin Xiaohui; Chen Minhua; Chen Yunfei

    2006-08-01

    A model based on a stochastic process was developed to study the impurity molecule desorption from a substrate induced by nanosecond and femtosecond lasers. The dynamics of adsorbed molecules irradiated by the laser pulses can be considered to be a Brownian motion in the bath of excited energy carriers. A two-step model was used to describe the nonequilibrium heating process induced by the femtosecond laser pulses. The difference between the desorption processes induced by nanosecond and femtosecond lasers was discussed based on the numerical results for the desorption of CO molecules from a Ru surface. Results indicate that the femtosecond laser is a much better tool for desorption than the nanosecond laser.

  13. Thickness dependent self limiting 1-D tin oxide nanowire arrays by nanosecond pulsed laser irradiation

    SciTech Connect

    Shirato, N.; Strader, J.; Kumar, Amit; Vincent, A.; Zhang, P.; Karakoti, Ajay S.; Nachimuthu, Ponnusamy; Cho, H-J.; Seal, Sudipta; Kalyanaraman, R.

    2011-01-23

    Fast, sensitive and discriminating detection of hydrogen at room temperature is crucial for storage, transportation, and distribution of hydrogen as an energy source. One dimensional nanowires of SnO2 are potential candidates for improved H2 sensor performance. The single directional conducting continuous nanowires can decrease electrical noise, and their large active surface area could improve the response and recovery time of the sensor. In this work we discuss synthesis and characterization of nanowire arrays made using nanosecond ultraviolet wavelength (266 nm) laser interference processing of ultrathin SnO2 films on SiO2 substrates. The laser energy was chosen to be above the melting point of the films. The results show that the final nanowire formation is dominated by preferential evaporation as compared to thermocapillary flow. The nanowire height (and hence wire aspect ratio) increased with increasing initial film thickness ho and with increasing laser energy density Eo. Furthermore, a self-limiting effect was observed where-in the wire formation ceased at a specific final remaining thickness of SnO2 that was almost independent of ho for a given Eo. To understand these effects, finite element modeling of the nanoscale laser heating was performed. This showed that the temperature rise under laser heating was a strong non-monotonic function of film thickness. As a result, the preferential evaporation rate varies as wire formation occurs, eventually leading to a shut-off of evaporation at a characteristic thickness. This results in the stoppage of wire formation. This combination of nanosecond pulsed laser experiments and thermal modeling shows that several unique synthesis approaches can be utilized to control the nanowire characteristics.

  14. Decolorization of methylene blue in aqueous suspensions of gold nanoparticles using parallel nanosecond pulsed laser.

    PubMed

    Zong, Yan P; Liu, Xian H; Du, Xi W; Lu, Yi R; Wang, Mei Y; Wang, Guang Y

    2013-01-01

    Using 532 nm parallel nanosecond pulsed laser, the decolorization of methylene blue (MB) in aqueous suspensions of gold nanoparticles (GNPs) was studied. The effects of various experimental parameters, such as irradiation time, laser energy, and initial MB concentration on the decolorization rate were investigated. Experiments using real samples of textile dyeing wastewater were also carried out to examine the effectiveness of the method in more complex samples. From the results, the following conclusions may be drawn: (i) Under the optimum conditions (pH 7.19, 135 mJ laser energy, 4 mg/L MB concentration, and 11.6 mg/L GNP concentration), the rate of MB decolorization could reach 94% in 15 min. The decolorization follows pseudo-first-order kinetics; (ii) The amount of MB decreased rapidly during the decolorization. No intermediates of the decolorization could be detected by high-performance liquid chromatography. These observations indicate that MB was decolorized through a very rapid degradation mechanism; (iii) The rate of MB decolorization increased with the increase in laser energy (at laser energies of 0 to 135 mJ); and, (iv) The efficient decolorization of MB in real samples of textile dyeing wastewater was achieved at a decolorization rate of about 85% in 15 min.

  15. Influence of the reactive atmosphere on the formation of nanoparticles in the plasma plume induced by nanosecond pulsed laser irradiation of metallic targets at atmospheric pressure and high repetition rate

    NASA Astrophysics Data System (ADS)

    Girault, M.; Le Garrec, J.-L.; Mitchell, J. B. A.; Jouvard, J.-M.; Carvou, E.; Menneveux, J.; Yu, J.; Ouf, F.-X.; Carles, S.; Potin, V.; Pillon, G.; Bourgeois, S.; Perez, J.; Marco de Lucas, M. C.; Lavisse, L.

    2016-06-01

    The influence of a reactive atmosphere on the formation of nanoparticles (NPs) in the plasma plume generated by nanosecond pulsed laser irradiation of metal targets (Ti, Al, Ag) was probed in situ using Small Angle X-ray Scattering (SAXS). Air and different O2-N2 gas mixtures were used as reactive gas within atmospheric pressure. SAXS results showed the formation of NPs in the plasma-plume with a mean radius varying in the 2-5 nm range. A decrease of the NPs size with increasing the O2 percentage in the O2-N2 gas mixture was also showed. Ex situ observations by transmission electron microscopy and structural characterizations by X-ray diffraction and Raman spectroscopy were also performed for powders collected in experiments done using air as ambient gas. The stability of the different metal oxides is discussed as being a key parameter influencing the formation of NPs in the plasma-plume.

  16. Soda-lime glass microlens arrays fabricated by laser: Comparison between a nanosecond and a femtosecond IR pulsed laser

    NASA Astrophysics Data System (ADS)

    Delgado, Tamara; Nieto, Daniel; Flores-Arias, María Teresa

    2016-11-01

    We present the manufacturing of microlens arrays on soda-lime glass substrates by using two different IR pulsed lasers: a nanosecond Nd:YVO4 laser (1064 nm) and a femtosecond laser based on Ytterbium crystal technology (1030 nm). In both cases, the fabrication technique consists of the combination of a direct-write laser process, followed by a post-thermal treatment assisted by a CO2 laser. Through the analysis of the morphological characteristics of the generated microlenses, the different physical mechanisms involved in the glass ablation process with a nanosecond and a femtosecond laser are studied. In addition, by analyzing the optical features of the microlenses, a better result in terms of the homogeneity and quality of the spot focuses are observed for those microlenses fabricated with the Nd:YVO4 nanosecond laser. Microlens arrays with a diameter of 80 and 90 μm were fabricated.

  17. Nanosecond laser texturing of aluminium for control of wettability

    NASA Astrophysics Data System (ADS)

    Sharp, Martin C.; Rosowski, Adam P.; French, Paul W.

    2015-07-01

    There is increasing interest in the use of lasers to modify the wettability of surfaces. Here we report on the use of a 20W nS pulsed IR fibre laser to create strong hydrophobicity on the surface of aluminium sheets. This is unexpected, hydrophobicity is usually associated solely with femto- or pico- second laser processing. At a 20W average power level the area coverage rate is too small for many industrial applications. Further trials using a 800W DPSS laser are described and the ability of this system to change surface wettability at a much higher production rate are indicated. There is little reported literature on surface texturing at higher average power levels. Indications of the productivity, or surface coverage rate, are given.

  18. Studies on laser material processing with nanosecond and sub-nanosecond and picosecond and sub-picosecond pulses

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    In this paper, laser ablation of widely used metal (Al, Cu. stainless-steel), semiconductor (Si), transparent material (glass, sapphire), ceramic (Al2O3, AlN) and polymer (PI, PMMA) in industry were systematically studied with pulse width from nanosecond (5-100ns), picosecond (6-10ps) to sub-picosecond (0.8-0.95ps). A critical damage zone (CDZ) of up to 100um with ns laser, <=50um with ps laser, and <=20um with sub-ps laser, respectively was observed as a criteria of selecting the laser pulse width. The effects of laser processing parameters on speed and efficiency were also investigated. This is to explore how to provide industry users the best laser solution for device micro-fabrication with best price. Our studies of cutting and drilling with ns, ps, and sub-ps lasers indicate that it is feasible to achieve user accepted quality and speed with cost-effective and reliable laser by optimizing processing conditions.

  19. Cellular response to high pulse repetition rate nanosecond pulses varies with fluorescent marker identity.

    PubMed

    Steelman, Zachary A; Tolstykh, Gleb P; Beier, Hope T; Ibey, Bennett L

    2016-09-23

    Nanosecond electric pulses (nsEP's) are a well-studied phenomena in biophysics that cause substantial alterations to cellular membrane dynamics, internal biochemistry, and cytoskeletal structure, and induce apoptotic and necrotic cell death. While several studies have attempted to measure the effects of multiple nanosecond pulses, the effect of pulse repetition rate (PRR) has received little attention, especially at frequencies greater than 100 Hz. In this study, uptake of Propidium Iodide, FM 1-43, and YO-PRO-1 fluorescent dyes in CHO-K1 cells was monitored across a wide range of PRRs (5 Hz-500 KHz) using a laser-scanning confocal microscope in order to better understand how high frequency repetition rates impact induced biophysical changes. We show that frequency trends depend on the identity of the dye under study, which could implicate transmembrane protein channels in the uptake response due to their chemical selectivity. Finally, YO-PRO-1 fluorescence was monitored in the presence of Gadolinium (Gd(3+)), Ruthenium Red, and in calcium-free solution to elucidate a mechanism for its unique frequency trend. PMID:27553279

  20. Effect of Pulse Length on Engraving Efficiency in Nanosecond Pulsed Laser Engraving of Stainless Steel

    NASA Astrophysics Data System (ADS)

    Manninen, Matti; Hirvimäki, Marika; Poutiainen, Ilkka; Salminen, Antti

    2015-10-01

    Dependency of laser pulse length on the effectiveness of laser engraving 304 stainless steel with nanosecond pulses was investigated. Ytterbium fiber laser with pulse lengths from 4 to 200 ns was used at a constant average power of 20 W. Measured criteria for effective laser engraving were high material removal rate (MRR), good visual quality of the engraved surface, and low processing temperature. MRR was measured by weighing the samples prior and after the engraving process. Visual quality was evaluated from magnified images. Surface temperature of the samples was measured by two laser spot-welded K-type thermocouples near the laser-processed area. It was noticed that MRR increases significantly with longer pulse lengths, while the quality decreases and processing temperature increases. Some peculiar process behavior was noticed. With short pulses (<20 ns), the process temperature steadily increased as the engraving process continued, whereas with longer pulses the process temperature started to decrease after initially jumping to a specific level. From visually analyzing the samples, it was noticed that the melted and resolidified bottom structure had cracks and pores on the surface when 50 ns or longer pulse lengths were used.

  1. Color center generation in sodium-calcium silicate glass by nanosecond and femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Siiman, Leo A.; Glebov, Leonid B.

    2005-12-01

    It was found that high purity soda lime glass shows a markedly different induced absorption spectra when exposed to different types of ionizing radiation such as UV lamp or femtosecond and nanosecond laser pulses. The following irradiation was used in the experiments: nanosecond pulses at the fundamental and harmonics of a Nd:YAG laser (λ = 1064, 532, 355, and 266 nm), femtosecond pulses of a Ti:sapphire laser operating at λ = 780 nm, ultraviolet rays from a high pressure Xe lamp, X-rays, and Gamma rays. Features of radiation defect generations are discussed.

  2. Nanosecond and femtosecond laser ablation of brass: Particulate and ICPMS measurements

    SciTech Connect

    Liu, C.; Mao, X.L.; Mao, S.; Zeng, X.; Greif, R.; Russo, R.E.

    2003-11-01

    Femtosecond and nanosecond lasers were compared for ablating brass alloys. All operating parameters from both lasers were equal except for the pulse duration. The ablated aerosol vapor was collected on silicon substrates for particle size measurements or sent into an inductively coupled plasma mass spectrometer. The diameters and size distribution of particulates were measured from scanning electron microscope (SEM) images of the collected ablated aerosol. SEM measurements showed that particles ablated using nanosecond pulses were single spherical entities ranging in diameter from several micrometers to several hundred nanometers. Primary particles ablated using femtosecond ablation were {approx}100 nm in diameter but formed large agglomerates. ICPMS showed enhanced signal intensity and stability using femtosecond compared to nanosecond laser ablation.

  3. Micro-processing of NiMnGa shape memory alloy by using a nanosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Biffi, C. A.; Tuissi, A.

    2016-04-01

    The interest on Ferromagnetic Shape Memory Alloys (FSMAs), such as NiMnGa, is growing up, thanks to their functional properties to be employed in a new class of micro-devices. The most evident critical issue, limiting the use of these systems in the production of industrial devices, is the brittleness of the bulk material; its workability by using convectional processing methods is very limited. Thus, alternative processing methods, including laser processing, are encouraged for the manufacture of FSMAs based new devices. In this work, the effect of the nanosecond laser microprocessing on Ni45Mn33Ga22 [at%] has been studied. Linear grooves were realized by a nanosecond 30 W fiber laser; the machined surfaces were analyzed with scanning electron microscopy, coupled with energetic dispersion spectroscopy for the composition analysis. The morphology of the grooves was affected by the laser scanning velocity and the number of laser pulses while the measured material removal rate appeared to be influenced mainly by the number of laser pulses. Compositional modification, associated to the loss of Ga content, was detected only for the lower scanning velocity, because of the high fluence. On the contrary, by increasing the velocity up to 1000 mm/s no Ga loss can be seen, making possible the laser processing of this functional alloy without its chemical modification. The use of short pulses allowed also to reduce the amount of recast material and the compositional change with respect to long pulses. Finally, the calorimetric analysis indicated that laser nanosecond microprocessing could affect the functional properties of this alloy: a larger decrease of the characteristic temperatures of the martensitic transformation was observed in correspondence of the low scanning velocity.

  4. Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

    DOE PAGES

    Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; Moody, Neville R.

    2015-11-14

    Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protectivemore » thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.« less

  5. Catastrophic nanosecond laser induced damage in the bulk of potassium titanyl phosphate crystals

    SciTech Connect

    Wagner, Frank R. Natoli, Jean-Yves; Akhouayri, Hassan; Commandré, Mireille; Duchateau, Guillaume

    2014-06-28

    Due to its high effective nonlinearity and the possibility to produce periodically poled crystals, potassium titanyl phosphate (KTiOPO{sub 4}, KTP) is still one of the economically important nonlinear optical materials. In this overview article, we present a large study on catastrophic nanosecond laser induced damage in this material and the very similar RbTiOPO{sub 4} (RTP). Several different systematic studies are included: multiple pulse laser damage, multi-wavelength laser damage in KTP, damage resistance anisotropy, and variations of the laser damage thresholds for RTP crystals of different qualities. All measurements were carried out in comparable experimental conditions using a 1064 nm Q-switched laser and some were repeated at 532 nm. After summarizing the experimental results, we detail the proposed model for laser damage in this material and discuss the experimental results in this context. According to the model, nanosecond laser damage is caused by light-induced generation of transient laser-damage precursors which subsequently provide free electrons that are heated by the same nanosecond pulse. We also present a stimulated Raman scattering measurement and confront slightly different models to the experimental data. Finally, the physical nature of the transient damage precursors is discussed and similarities and differences to laser damage in other crystals are pointed out.

  6. High Intensity Mirror-Free Nanosecond Ytterbium Fiber Laser System in Master Oscillator Power Amplification

    NASA Astrophysics Data System (ADS)

    Chun-Lin, Louis Chang

    Rare-earth-doped fiber lasers and amplifiers are relatively easy to efficiently produce a stable and high quality laser beam in a compact, robust, and alignment-free configuration. Recently, high power fiber laser systems have facilitated wide spread applications in academics, industries, and militaries in replacement of bulk solid-state laser systems. The master oscillator power amplifier (MOPA) composed of a highly-controlled seed, high-gain preamplifiers, and high-efficiency power amplifiers are typically utilized to scale up the pulse energy, peak power, or average power. Furthermore, a direct-current-modulated nanosecond diode laser in single transverse mode can simply provide a compact and highly-controlled seed to result in the flexible output parameters, such as repetition rate, pulse duration, and even temporal pulse shape. However, when scaling up the peak power for high intensity applications, such a versatile diode-seeded nanosecond MOPA laser system using rare-earth-doped fibers is unable to completely save its own advantages compared to bulk laser systems. Without a strong seeding among the amplifiers, the guided amplified spontaneous amplification is easy to become dominant during the amplification, leading to the harmful self-lasing or pulsing effects, and the difficulty of the quantitative numerical comparison. In this dissertation, we study a high-efficiency and intense nanosecond ytterbium fiber MOPA system with good beam quality and stability for high intensity applications. The all-PM-fiber structure is achieved with the output extinction ratio of >12 dB by optimizing the interconnection of high power optical fibers. The diode-seeded MOPA configuration without parasitic stimulated amplification (PAS) is implemented using the double-pass scheme to extract energy efficiently for scaling peak power. The broadband PAS was studied experimentally, which matches well with our numerical simulation. The 1064-nm nanosecond seed was a direct

  7. Explosive boiling of metals upon irradiation by a nanosecond laser pulse

    SciTech Connect

    Mazhukin, V I; Demin, M M; Shapranov, A V; Samokhin, A A

    2014-04-28

    A repeated effect of explosive boiling has been found in metals exposed to a nanosecond laser pulse in the framework of molecular dynamic simulations combined with a continuum description of a conduction band electrons system. This effect can be used, in particular, as a marker of approaching critical parameters of the region in the irradiated matter. (letters)

  8. Shield gas induced cracks during nanosecond-pulsed laser irradiation of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Noguchi, Jun; Yan, Jiwang

    2016-10-01

    Laser processing techniques have been given increasing attentions in the field of metallic glasses (MGs). In this work, effects of two kinds of shield gases, nitrogen and argon, on nanosecond-pulsed laser irradiation of Zr-based MG were comparatively investigated. Results showed that compared to argon gas, nitrogen gas remarkably promoted the formation of cracks during laser irradiation. Furthermore, crack formation in nitrogen gas was enhanced by increasing the peak laser power intensity or decreasing the laser scanning speed. X-ray diffraction and micro-Raman spectroscopy indicated that the reason for enhanced cracks in nitrogen gas was the formation of ZrN.

  9. Nanosecond laser-induced phase transitions in pulsed laser deposition-deposited GeTe films

    SciTech Connect

    Sun, Xinxing Thelander, Erik; Lorenz, Pierre; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

    2014-10-07

    Phase transformations between amorphous and crystalline states induced by irradiation of pulsed laser deposition grown GeTe thin films with nanosecond laser pulses at 248 nm and pulse duration of 20 ns are studied. Structural and optical properties of the Ge-Te phase-change films were studied by X-ray diffraction and optical reflectivity measurements as a function of the number of laser pulses between 0 and 30 pulses and of the laser fluence up to 195 mJ/cm². A reversible phase transition by using pulse numbers ≥ 5 at a fluence above the threshold fluence between 11 and 14 mJ/cm² for crystallization and single pulses at a fluence between 162 and 182 mJ/cm² for amorphization could be proved. For laser fluences from 36 up to 130 mJ/cm², a high optical contrast of 14.7% between the amorphous and crystalline state is measured. A simple model is used that allows the discussion on the distribution of temperature in dependency on the laser fluence.

  10. High resolution selective multilayer laser processing by nanosecond laser ablation of metal nanoparticle films

    SciTech Connect

    Ko, Seung H.; Pan Heng; Hwang, David J.; Chung, Jaewon; Ryu, Sangil; Grigoropoulos, Costas P.; Poulikakos, Dimos

    2007-11-01

    Ablation of gold nanoparticle films on polymer was explored using a nanosecond pulsed laser, with the goal to achieve feature size reduction and functionality not amenable with inkjet printing. The ablation threshold fluence for the unsintered nanoparticle deposit was at least ten times lower than the reported threshold for the bulk film. This could be explained by the combined effects of melting temperature depression, lower conductive heat transfer loss, strong absorption of the incident laser beam, and the relatively weak bonding between nanoparticles. The ablation physics were verified by the nanoparticle sintering characterization, ablation threshold measurement, time resolved ablation plume shadowgraphs, analysis of ablation ejecta, and the measurement and calculation of optical properties. High resolution and clean feature fabrication with small energy and selective multilayer processing are demonstrated.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Femtosecond ultraviolet laser ablation of silver and comparison with nanosecond ablation

    SciTech Connect

    Toftmann, B.; Schou, J.; Doggett, B.; Budtz-Jorgensen, C.; Lunney, J. G.

    2013-02-28

    The ablation plume dynamics arising from ablation of silver with a 500 fs, 248 nm laser at {approx}2 J cm{sup -2} has been studied using angle-resolved Langmuir ion probe and thin film deposition techniques. For the same laser fluence, the time-of-flight ion signals from femtosecond and nanosecond laser ablation are similar; both show a singly peaked time-of-flight distribution. The angular distribution of ion emission and the deposition are well described by the adiabatic and isentropic model of plume expansion, though distributions for femtosecond ablation are significantly narrower. In this laser fluence regime, the energy efficiency of mass ablation is higher for femtosecond pulses than for nanosecond pulses, but the ion production efficiency is lower.

  13. Numerical simulation of regenerative amplification of nanosecond pulses in a CO/sub 2/ laser

    SciTech Connect

    Apollonov, V.V.; Bunkin, F.V.; Sorochenko, V.R.; Firsov, K.N.; Shakir, Y.A.

    1982-04-01

    The results are given of a numerical simulation of regenerative amplification of nanosecond pulses in a high-power electric-discharge CO/sub 2/ laser. The finite contrast of the injected pulse is allowed for in a determination of the ranges of the injection energy and time in which regenerative amplification can be expected. It is shown that the shape of a small-signal pulse has a considerable influence on the energy and contrast of the output pulse. The optimal combinations of the parameters of a regenerative amplification system are determined so as to maximize the energy and contrast of nanosecond pulses.

  14. Investigation of UV Laser Triggered, Nanosecond, Surface Flashover Switches

    SciTech Connect

    Nunnally, W C; Neurath, R; Holmes, C; Sampayan, S; Caporaso, G

    2003-06-03

    Triggered, multi-channel, surface discharges or surface flashover switching have been investigated as a low inductance, low pulse rate switch for conducting large currents. This paper discusses the investigation of UV (355 nm) laser triggered, single channel, low inductance, ns closure and sub-ns jitter switches for applications in switching high dielectric constant, compact pulse forming lines into accelerator loads. The experimental arrangement for evaluating the switch performance and for measuring the high field dielectric constant of the pulse forming lines is presented. Experimental results of delay and jitter measurements versus optical energy on the flashover surface and dc electric field charge.

  15. Nanosecond laser pulse heating of a platinum surface studied by pump-probe X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Shayduk, Roman; Vonk, Vedran; Arndt, Björn; Franz, Dirk; Strempfer, Jörg; Francoual, Sonia; Keller, Thomas F.; Spitzbart, Tobias; Stierle, Andreas

    2016-07-01

    We report on the quantitative determination of the transient surface temperature of Pt(110) upon nanosecond laser pulse heating. We find excellent agreement between heat transport theory and the experimentally determined transient surface temperature as obtained from time-resolved X-ray diffraction on timescales from hundred nanoseconds to milliseconds. Exact knowledge of the surface temperature's temporal evolution after laser excitation is crucial for future pump-probe experiments at synchrotron storage rings and X-ray free electron lasers.

  16. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-01

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2-6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  17. Efficient neutron production from sub-nanosecond laser pulse accelerating deuterons on target front side

    NASA Astrophysics Data System (ADS)

    Klir, D.; Krasa, J.; Cikhardt, J.; Dudzak, R.; Krousky, E.; Pfeifer, M.; Rezac, K.; Sila, O.; Skala, J.; Ullschmied, J.; Velyhan, A.

    2015-09-01

    Neutron-producing experiments have been carried out on the Prague Asterix Laser System. At the fundamental wavelength of 1.315 μm, the laser pulse of a 600 J energy and 300 ps duration was focused on a thick deuterated-polyethylene target. Neutron yields reached (4.1 ± 0.8) × 108 at the peak intensity of ≈3 × 1016 W/cm2. A more detailed analysis of neutron time-of-flight signals showed that a significant fraction of neutron yields was produced both by the 2H(d,n)3He reaction and by other neutron-producing reactions. Neutron energies together with delayed neutron and gamma emission showed that MeV deuterons escaped from a laser-produced plasma and interacted ≈50 ns later with a borosilicate blast-shield glass. In order to increase DD neutron yields and to characterize deuteron beams via nuclear reactions, a secondary deuterated polyethylene target was used in a pitcher-catcher scheme at the target front side. In this experimental arrangement, the neutron yield reached (2.0 ± 0.5) × 109 with the peak neutron fluence of (2.5 ± 0.5) × 108 n/sr. From the neutron yield, it was calculated that the secondary target was bombarded by 2 × 1014 deuterons in the 0.5-2.0 MeV energy range. The neutron yield of 2 × 109 at the laser energy of 600 J implied the production efficiency of 3 × 106 n/J. A very important result is that the efficient neutron production was achieved with the low contrast, sub-nanosecond laser pulse of the intensity of 1016 W/cm2. The latter parameters can be achieved in a rep-rate mode more easily than ultra-high intensities and contrasts.

  18. Dependence of multiply charged ions on the polarization state in nanosecond laser-benzene cluster interaction

    NASA Astrophysics Data System (ADS)

    Wang, Weiguo; Zhao, Wuduo; Hua, Lei; Hou, Keyong; Li, Haiyang

    2016-05-01

    This paper investigated the dependence of multiply charged ions on the laser polarization state when benzene cluster was irradiated with 532 and 1064 nm nanosecond laser. A circle, square and flower distribution for C2+, C3+ and C4+ were observed with 532 nm laser respectively, while flower petals for C2+, C3+ and C4+ were observed at 1064 nm as the laser polarization varied. A theoretical calculation was performed to interpret the polarization state and wavelength dependence of the multiply charged ions. The simulated results agreed well with the experimental observation with considering the contribution from the cluster disintegration.

  19. Selective treatment of atherosclerotic plaques using nanosecond pulsed laser with a wavelength of 5.75 μm for less-invasive laser angioplasty

    NASA Astrophysics Data System (ADS)

    Ishii, K.; Tsukimoto, H.; Hazama, H.; Awazu, K.

    2009-07-01

    XeCl excimer laser coronary angioplasty (ELCA), has gained more attention for the treatment of serious stenosis blocked by plaque. Low degrees of thermal damage after ablation of atherosclerotic plaques have been achieved by ELCA. However, the large number of risks associated with the procedure, for example, dissections or perforations of the coronary arteries limits its application. The laser treatment technique with high ablation efficiency but low arterial wall injury is desirable. Mid-infrared laser with a wavelength of 5.75 μm is selectively well absorbed in C=O stretching vibration mode of ester bonds in cholesteryl ester. We studied the effectiveness of nanosecond pulsed laser at 5.75 μm for novel less-invasive laser angioplasty. In this study, we used a mid-infrared tunable solid-state laser which is operated by difference-frequency generation, at 5.75 μm, a pulse width of 5 ns and a pulse repetition rate of 10 Hz as a treatment light source, and a thoracic aorta of WHHLMI rabbit as an atherosclerosis model. As a result, less-invasive treatment parameters for removing atherosclerotic plaques in a wet condition were confirmed. This study shows that the nanosecond pulsed laser irradiation at 5.75 μm is a powerful tool for selective and less-invasive treatment of atherosclerotic plaques.

  20. Measuring the thickness of protective coatings on historic metal objects using nanosecond and femtosecond laser induced breakdown spectroscopy depth profiling

    NASA Astrophysics Data System (ADS)

    Pouli, P.; Melessanaki, K.; Giakoumaki, A.; Argyropoulos, V.; Anglos, D.

    2005-08-01

    Depth profile analysis by means of laser induced breakdown spectroscopy (LIBS) was investigated with respect to its potential to measure the thickness of different types of thin organic films used as protective coatings on historical and archaeological metal objects. For the materials examined, acrylic varnish and microcrystalline wax, the output from a nanosecond ArF excimer laser at 193 nm was found appropriate for performing a reliable profiling of the coating films leading to accurate determination of the coating thickness on the basis of the number of laser pulses required to penetrate the coating and on the ablation etch rate of the corresponding coating material under the same irradiation conditions. Nanosecond pulses at 248 nm proved inadequate to profile the coatings because of their weak absorption at the laser wavelength. In contrast, femtosecond irradiation at 248 nm yielded well-resolved profiles as a result of efficient ablation achieved through the increased non-linear absorption induced by the high power density of the ultrashort pulses.

  1. Controlled oxide films formation by nanosecond laser pulses for color marking.

    PubMed

    Veiko, Vadim; Odintsova, Galina; Ageev, Eduard; Karlagina, Yulia; Loginov, Anatoliy; Skuratova, Alexandra; Gorbunova, Elena

    2014-10-01

    A technology of laser-induced coloration of metals by surface oxidation is demonstrated. Each color of the oxide film corresponds to a technologic chromacity coefficient, which takes into account the temperature of the sample after exposure by sequence of laser pulses with nanosecond duration and effective time of action. The coefficient can be used for the calculation of laser exposure regimes for the development of a specific color on the metal. A correlation between the composition of the films obtained on the surface of stainless steel AISI 304 and commercial titanium Grade 2 and its color and chromacity coordinates is shown. PMID:25322009

  2. Mono-energetic ions emission by nanosecond laser solid target irradiation

    NASA Astrophysics Data System (ADS)

    Muoio, A.; Tudisco, S.; Altana, C.; Lanzalone, G.; Mascali, D.; Cirrone, G. A. P.; Schillaci, F.; Trifirò, A.

    2016-09-01

    An experimental campaign aiming to investigate the acceleration mechanisms through laser-matter interaction in nanosecond domain has been carried out at the LENS (Laser Energy for Nuclear Science) laboratory of INFN-LNS, Catania. Pure Al targets were irradiated by 6 ns laser pulses at different pumping energies, up to 2 J. Advanced diagnostics tools were used to characterize the plasma plume and ion production. We show the preliminary results of this experimental campaign, and especially the ones showing the production of multicharged ions having very narrow energy spreads.

  3. Production of Picosecond, Kilojoule, and Petawatt Laser Pulses via Raman Amplification of Nanosecond Pulses

    SciTech Connect

    Trines, R. M. G. M.; Bingham, R.; Norreys, P. A.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.

    2011-09-02

    Raman amplification in plasma has been promoted as a means of compressing picosecond optical laser pulses to femtosecond duration to explore the intensity frontier. Here we show for the first time that it can be used, with equal success, to compress laser pulses from nanosecond to picosecond duration. Simulations show up to 60% energy transfer from pump pulse to probe pulse, implying that multikilojoule ultraviolet petawatt laser pulses can be produced using this scheme. This has important consequences for the demonstration of fast-ignition inertial confinement fusion.

  4. Nanosecond pulsed laser generation of holographic structures on metals

    NASA Astrophysics Data System (ADS)

    Wlodarczyk, Krystian L.; Ardron, Marcus; Weston, Nick J.; Hand, Duncan P.

    2016-03-01

    A laser-based process for the generation of phase holographic structures directly onto the surface of metals is presented. This process uses 35ns long laser pulses of wavelength 355nm to generate optically-smooth surface deformations on a metal. The laser-induced surface deformations (LISDs) are produced by either localized laser melting or the combination of melting and evaporation. The geometry (shape and dimension) of the LISDs depends on the laser processing parameters, in particular the pulse energy, as well as on the chemical composition of a metal. In this paper, we explain the mechanism of the LISDs formation on various metals, such as stainless steel, pure nickel and nickel-chromium Inconel® alloys. In addition, we provide information about the design and fabrication process of the phase holographic structures and demonstrate their use as robust markings for the identification and traceability of high value metal goods.

  5. Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes

    SciTech Connect

    Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.

    2012-02-15

    Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

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

    SciTech Connect

    Yu, Ruixuan; Meng, Xuan; Takayanagi, Shinya; Shibayama, Tamaki Yatsu, Shigeo; Ishioka, Junya; Watanabe, Seiichi

    2014-04-14

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

  7. Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing

    NASA Astrophysics Data System (ADS)

    Stankova, N. E.; Atanasov, P. A.; Nikov, Ru. G.; Nikov, R. G.; Nedyalkov, N. N.; Stoyanchov, T. R.; Fukata, N.; Kolev, K. N.; Valova, E. I.; Georgieva, J. S.; Armyanov, St. A.

    2016-06-01

    This article presents experimental investigations of effects of the process parameters on the medical grade polydimethylsiloxane (PDMS) elastomer processed by laser source with irradiation at UV (266 and 355 nm), VIS (532 nm) and NIR (1064 nm). Systematic experiments are done to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the optical properties and the chemical composition in the laser treated areas. Remarkable changes of the optical properties and the chemical composition are observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment is accomplished due to the incubation process occurring below the polymer surface. With increasing of the fluence and the number of the pulses chemical transformations are revealed in the entire laser treated area and hence decreasing of the optical transmittance is observed. The incubation gets saturation after a certain number of pulses and the laser ablation of the material begins efficiently. At the UV and VIS wavelengths the number of the initial pulses, at which the optical transmittance begins to reduce, decreases from 16 up to 8 with increasing of the laser fluence up to 1.0, 2.5 and 10 J cm-2 for 266, 355 and 532 nm, respectively. In the case of 1064 nm the optical transmittance begins to reduce at 11th pulse incident at a fluence of 13 J cm-2 and the number of the pulses decreases to 8 when the fluence reaches value of 16 J cm-2. The threshold laser fluence needed to induce incubation process after certain number of pulses of 8 is different for every wavelength irradiation as the values increase from 1.0 for 266 nm up to 16 J cm-2 for 1064 nm. The incubation and the ablation processes occur in the PDMS elastomer material during its pulsed laser treatment are a complex function of the wavelength, fluence, number of pulses and the material properties as well.

  8. Online monitoring of nanoparticles formed during nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Nováková, Hana; Holá, Markéta; Vojtíšek-Lom, Michal; Ondráček, Jakub; Kanický, Viktor

    2016-11-01

    The particle size distribution of dry aerosol originating from laser ablation of glass material was monitored simultaneously with Laser Ablation - Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis and two aerosol spectrometers - Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer (APS). The unique combination of LA-ICP-MS and FMPS offers the possibility of measuring the particle size distribution every 1 s of the ablation process in the size range of 5.6-560 nm. APS extends the information about particle concentration in the size range 0.54-17 μm. Online monitoring of the dry aerosol was performed for two ablation modes (spot and line with a duration of 80 s) with a 193 nm excimer laser system, using the glass reference material NIST 610 as a sample. Different sizes of laser spot for spot ablation and different scan speeds for line ablation were tested. It was found that the FMPS device is capable of detecting changes in particle size distribution at the first pulses of spot laser ablation and is suitable for laser ablation control simultaneously with LA-ICP-MS analysis. The studied parameters of laser ablation have an influence on the resulting particle size distribution. The line mode of laser ablation produces larger particles during the whole ablation process, while spot ablation produces larger particles only at the beginning, during the ablation of the intact layer of the ablated material. Moreover, spot ablation produces more primary nano-particles (in ultrafine mode size range < 100 nm) than line ablation. This effect is most probably caused by a reduced amount of large particles released from the spot ablation crater. The larger particles scavenge the ultrafine particles during the line ablation mode.

  9. Study on Nonlinear Absorption Effect of Nanosecond Pulse Laser Irradiation for GaAs.

    PubMed

    Sun, Wenjun; Liu, Zhongyang; Zhou, Haijiao

    2016-04-01

    In order to research nonlinear absorption effect of pulse laser irradiation for GaAs, a physical model of Gaussian distribution pulse laser irradiation for semiconductor material was established by software COMSOL Multiphysics. The thermal effects of semiconductor material GaAs was analyzed under irradiation of nanosecond pulse laser with wavelength of 1064 nm. The radial and transverse temperature distribution of semiconductor material GaAs was calculated under irradiation of nanosecond pulse laser with different power density by solving the thermal conduction equations. The contribution of one-photon absorption, two-photon absorption and free carrier absorption to temperature of GaAs material were discussed. The results show that when the pulse laser power density rises to 10(10) W/cm2, free carrier absorption played a leading role and it was more than that of one-photon absorption of material. The temperature contribution of two-photon absorption and free carrier absorption could be ignored at laser power density lower than 10(8) W/cm2. The result is basically consistent with relevant experiments, which shows that physical model constructed is valid. PMID:27451733

  10. Study on Nonlinear Absorption Effect of Nanosecond Pulse Laser Irradiation for GaAs.

    PubMed

    Sun, Wenjun; Liu, Zhongyang; Zhou, Haijiao

    2016-04-01

    In order to research nonlinear absorption effect of pulse laser irradiation for GaAs, a physical model of Gaussian distribution pulse laser irradiation for semiconductor material was established by software COMSOL Multiphysics. The thermal effects of semiconductor material GaAs was analyzed under irradiation of nanosecond pulse laser with wavelength of 1064 nm. The radial and transverse temperature distribution of semiconductor material GaAs was calculated under irradiation of nanosecond pulse laser with different power density by solving the thermal conduction equations. The contribution of one-photon absorption, two-photon absorption and free carrier absorption to temperature of GaAs material were discussed. The results show that when the pulse laser power density rises to 10(10) W/cm2, free carrier absorption played a leading role and it was more than that of one-photon absorption of material. The temperature contribution of two-photon absorption and free carrier absorption could be ignored at laser power density lower than 10(8) W/cm2. The result is basically consistent with relevant experiments, which shows that physical model constructed is valid.

  11. Applications of nanosecond laser annealing to fabricating p-n homo junction on ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Shimogaki, T.; Ofuji, T.; Tetsuyama, N.; Okazaki, K.; Higashihata, M.; Nakamura, D.; Ikenoue, H.; Asano, T.; Okada, T.

    2013-03-01

    Zinc oxide (ZnO) has attracted considerable attension due to its wide applications in particular ultra violet light emitting diode (UV-LED). In addition, the one-dimensional ZnO crystals are quite attractive as building blocks for light emitting devices like laser and LED, because of their high crystallinity and light confinement properties. However, a method for the realization of the stable p-type ZnO has not been well established. In our study, we have investigated the effect of the nanosecond laser irradiation to the ZnO nanorods as an ultrafast melting and recrystallizing process for realization of the p-type ZnO. Fabrication of the p-n homo junction along ZnO nanorods has been demonstrated using phosphorus ion implantation and ns-laser annealing by a KrF excimer laser. Rectifying I-V characteristics attributed to p-n junction were observed from the measurement of electrical properties. In addition, the penetration depth of laser annealed layer was measured by observing cathode luminescence images. Then, it was turned out that high repetition rate laser annealing can anneal ZnO nanorods over the optical-absorption length. In this report, optical, structural, and electrical characteristics of the phosphorus ion-implanted ZnO nanorods annealed by the KrF excimer laser are discussed.

  12. Bimodal velocity distribution of atoms released from nanosecond ultraviolet laser ablation

    SciTech Connect

    Maul, J.; Karpuk, S.; Huber, G.

    2005-01-15

    We have investigated the velocity distributions of atoms released from a metallic gadolinium surface by UV laser ablation. The fluences of the nanosecond laser pulses were chosen for a pure release of neutrals and at a higher fluence level for the release of both neutrals and ions. In both cases a thermal Maxwell-Boltzmann slope has been observed for the low velocities, whereas for high velocities strong deviations from a thermal distribution have been seen. The observed velocity distribution has been explained by a bimodal structure including a thermal phase and a shockwave driven 'blow-off' phase.

  13. Role of suprathermal electrons during nanosecond laser energy deposit in fused silica

    SciTech Connect

    Grua, P.; Hébert, D.; Lamaignère, L.; Rullier, J.-L.

    2014-08-25

    An accurate description of interaction between a nanosecond laser pulse and a wide band gap dielectric, such as fused silica, requires the understanding of energy deposit induced by temperature changes occurring in the material. In order to identify the fundamental processes involved in laser-matter interaction, we have used a 1D computational model that allows us to describe a wide set of physical mechanisms and intended for comparison with specially designed “1D experiments.” We have pointed out that suprathermal electrons are very likely implicated in heat conduction, and this assumption has allowed the model to reproduce the experiments.

  14. Research on the system of energy fluctuation for the nanosecond laser

    NASA Astrophysics Data System (ADS)

    Chang, Cun; Yang, Liu; Song, Yuanpei; Chang, Qing

    2015-10-01

    A detection system of energy fluctuation has been designed using C8051F120 mirco-controller chip as the central processor. The detection system is based on the principle that the current output increases linearly with the growth of the input laser power under the condition of adding anti-biased voltage into PIN photo diode. Real-time monitoring output fluctuation has been achieved by measuring the output voltage of optical-electrical conversion which is related to the peak output of nanosecond laser.

  15. 200 Hz repetition frequency joule-level high beam quality Nd:YAG nanosecond laser

    NASA Astrophysics Data System (ADS)

    Qiu, Jisi; Tang, Xiongxin; Fan, Zhongwei; Wang, Haocheng

    2016-06-01

    A joule-level Nd:YAG nanosecond laser of high repetition frequency and high beam quality is developed out. The laser is designed as a MOPA system mainly including single longitudinal mode seed, pre-amplifier unit an d power amplifier unit. In order to obtain the high-quality laser beam output, phase conjugation is adopted to compensate the laser beam distortion. Under the condition of 200 Hz high repetition frequency and 8.19 μJ single pulse energy injected by the single longitudinal mode seed, 1.53 J output energy is gained. The output laser beam is of 9 mm diameter, 7.41 ns pulse width, the far field beam spot 1.32 times the value of the diffraction limit, 1.2% energy stability (RMS) and less than 13 μrad far field beam spot angle shift.

  16. Effects of nanosecond-duration laser prepulses on solid targets

    SciTech Connect

    Wharton, K.B.; Kim, J.M.; Stuart, B.C.

    2005-05-15

    A critical issue in high-intensity laser-solid interactions is the effect of the laser prepulse on the target, but the experimental details of these lower-intensity interactions are often difficult to measure due to the subsequent high-intensity pulse. We have performed target experiments using a 0.5-ns duration, 800-nm wavelength laser pulse, specifically designed to mimic the typical amplified spontaneous emission (ASE) prepulse from a high-power Ti:Sapphire laser. Using this ''artificial'' ASE prepulse, we find that the threshold for relevant changes to typical solid targets occurs at a fluence of {approx}0.1 J/cm{sup 2}, or {approx}10{sup 8} W/cm{sup 2}, well below the plasma formation threshold. Notably, the results are not consistent with simple surface vaporization, and suggest that the ASE prepulse causes multiatom clusters to be ejected from the target surface. In a full high-intensity experiment, this ablated material would then strongly interact with the subsequent primary laser pulse.

  17. Interaction of nanosecond ultraviolet laser pulses with reactive dusty plasma

    NASA Astrophysics Data System (ADS)

    van de Wetering, F. M. J. H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Gibert, T.; Mikikian, M.; Rabat, H.; Kovačević, E.; Berndt, J.

    2016-05-01

    Even though UV laser pulses that irradiate a gas discharge are small compared to the plasma volume (≲3%) and plasma-on time (≲6 × 10-6%), they are found to dramatically change the discharge characteristics on a global scale. The reactive argon-acetylene plasma allows the growth of nanoparticles with diameters up to 1 μm, which are formed inside the discharge volume due to spontaneous polymerization reactions. It is found that the laser pulses predominantly accelerate and enhance the coagulation phase and are able to suppress the formation of a dust void.

  18. Efficient neutron production from sub-nanosecond laser pulse accelerating deuterons on target front side

    SciTech Connect

    Klir, D.; Krasa, J.; Velyhan, A.; Cikhardt, J.; Rezac, K.; Dudzak, R.; Krousky, E.; Pfeifer, M.; Skala, J.; Ullschmied, J.; Sila, O.

    2015-09-15

    Neutron-producing experiments have been carried out on the Prague Asterix Laser System. At the fundamental wavelength of 1.315 μm, the laser pulse of a 600 J energy and 300 ps duration was focused on a thick deuterated-polyethylene target. Neutron yields reached (4.1 ± 0.8) × 10{sup 8} at the peak intensity of ≈3 × 10{sup 16 }W/cm{sup 2}. A more detailed analysis of neutron time-of-flight signals showed that a significant fraction of neutron yields was produced both by the {sup 2}H(d,n){sup 3}He reaction and by other neutron-producing reactions. Neutron energies together with delayed neutron and gamma emission showed that MeV deuterons escaped from a laser-produced plasma and interacted ≈50 ns later with a borosilicate blast-shield glass. In order to increase DD neutron yields and to characterize deuteron beams via nuclear reactions, a secondary deuterated polyethylene target was used in a pitcher-catcher scheme at the target front side. In this experimental arrangement, the neutron yield reached (2.0 ± 0.5) × 10{sup 9} with the peak neutron fluence of (2.5 ± 0.5) × 10{sup 8 }n/sr. From the neutron yield, it was calculated that the secondary target was bombarded by 2 × 10{sup 14} deuterons in the 0.5–2.0 MeV energy range. The neutron yield of 2 × 10{sup 9} at the laser energy of 600 J implied the production efficiency of 3 × 10{sup 6 }n/J. A very important result is that the efficient neutron production was achieved with the low contrast, sub-nanosecond laser pulse of the intensity of 10{sup 16 }W/cm{sup 2}. The latter parameters can be achieved in a rep-rate mode more easily than ultra-high intensities and contrasts.

  19. Low-order harmonic generation in nanosecond laser ablation plasmas of carbon containing materials

    NASA Astrophysics Data System (ADS)

    Lopez-Quintas, I.; Oujja, M.; Sanz, M.; Martín, M.; Ganeev, R. A.; Castillejo, M.

    2013-08-01

    In this work we report on a systematic study of the spatiotemporal behaviour of low-order harmonics generated in nanosecond laser ablation plasmas of carbon containing materials. Plasmas were generated from targets of graphite and boron carbide ablated with a nanosecond Q-switched Nd:YAG laser at 1064 nm. Low-order harmonics (3rd and 5th) of the fundamental wavelength of a ns Nd:YAG driving laser, propagating perpendicularly to the ablation laser at variable time delays, were observed. The temporal study of the low-order harmonics generated under vacuum and atmospheres of Kr and Xe, revealed the presence of two populations that contribute to the harmonic generation (HG) at different times. It was found that under vacuum only small species contribute to the HG process, whereas under buffer gas, heavier species, such as clusters and nanoparticles, contribute to the HG at longer times. Optical emission spectroscopy, time of flight mass spectrometry and characterization of deposits collected on-line on a nearby substrate provided additional information that complemented the results of the spatiotemporal study of the generated harmonics. This approach to ablation plume analysis allows elucidating the identity of the nonlinear emitters in laser ablation plasmas and facilitates the investigation of efficient, nanoparticle-enhanced, coherent short wavelength generation processes.

  20. Targeted gene transfer into rat facial muscles by nanosecond pulsed laser-induced stress waves

    NASA Astrophysics Data System (ADS)

    Kurita, Akihiro; Matsunobu, Takeshi; Satoh, Yasushi; Ando, Takahiro; Sato, Shunichi; Obara, Minoru; Shiotani, Akihiro

    2011-09-01

    We investigate the feasibility of using nanosecond pulsed laser-induced stress waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis.

  1. Controlling the stimulated Brillouin scattering of self-focusing nanosecond laser pulses in silica glasses

    SciTech Connect

    Mauger, Sarah; Berge, Luc; Skupin, Stefan

    2011-06-15

    We numerically investigate the interplay between Kerr self-focusing (SF) and transient stimulated Brillouin scattering (SBS) for nanosecond pulses in bulk silica. The influences of the input power, phase, or amplitude modulations in the pump pulse together with the incident beam shape on the filamentation dynamics are discussed. We show that appropriate amplitude modulations dividing nanosecond laser pumps into picosecond-long pulse trains inhibit SBS at any power. In contrast, phase-modulated pulses with comparable spectral width undergo multiple filamentation and earlier beam collapse due to modulational instabilities. We demonstrate, however, the existence of a critical pump bandwidth above which SBS can be efficiently suppressed by phase modulations even at high powers. This observation also holds for squared beam shapes with much broader spatial spectra, which decay more easily into multiple filaments over short distances. Intensity profiles of the reflected Stokes waves for such broad pumps are finally discussed.

  2. Spatial and Temporal Dependence of Interspark Interactions in Femtosecond-Nanosecond Dual-Pulse Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Scaffidi, Jon; Pearman, William; Lawrence, Marion; Chance Carter, J.; Colston, Bill W., Jr.; Angel, S. Michael

    2004-09-01

    A femtosecond air spark has recently been combined with a nanosecond ablative pulse in order to map the spatial and temporal interactions of the two plasmas in femtosecond-nanosecond orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Good spatial and temporal correlation was found for reduced atomic emission from atmospheric species (nitrogen and oxygen) and increased atomic emission from ablated species (copper and aluminum) in the femtosecond-nanosecond plasma, suggesting a potential role for atmospheric pressure or nitrogen/oxygen concentration reduction following air spark formation in generating atomic emission enhancements in dual-pulse LIBS.

  3. Anomalous self-generated electrostatic fields in nanosecond laser-plasma interaction

    SciTech Connect

    Lancia, L.; Antici, P.; Grech, M.; Weber, S.; Marques, J.-R.; Romagnani, L.; Bourgeois, N.; Audebert, P.; Fuchs, J.; Nakatsutsumi, M.; Bellue, A.; Feugeas, J.-L.; Nicolaie, Ph.; Tikhonchuk, V. T.; Grismayer, T.; Lin, T.; Nkonga, B.; Kodama, R.

    2011-03-15

    Electrostatic (E) fields associated with the interaction of a well-controlled, high-power, nanosecond laser pulse with an underdense plasma are diagnosed by proton radiography. Using a current three-dimensional wave propagation code equipped with nonlinear and nonlocal hydrodynamics, we can model the measured E-fields that are driven by the laser ponderomotive force in the region where the laser undergoes filamentation. However, strong fields of up to 110 MV/m measured in the first millimeter of propagation cannot be reproduced in the simulations. This could point to the presence of unexpected strong thermal electron pressure gradients possibly linked to ion acoustic turbulence, thus emphasizing the need for the development of full kinetic collisional simulations in order to properly model laser-plasma interaction in these strongly nonlinear conditions.

  4. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  5. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

    PubMed

    Binh, P H; Trong, V D; Renucci, P; Marie, X

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

  6. Bipolar high-repetition-rate high-voltage nanosecond pulser

    SciTech Connect

    Tian Fuqiang; Wang Yi; Shi Hongsheng; Lei Qingquan

    2008-06-15

    The pulser designed is mainly used for producing corona plasma in waste water treatment system. Also its application in study of dielectric electrical properties will be discussed. The pulser consists of a variable dc power source for high-voltage supply, two graded capacitors for energy storage, and the rotating spark gap switch. The key part is the multielectrode rotating spark gap switch (MER-SGS), which can ensure wider range modulation of pulse repetition rate, longer pulse width, shorter pulse rise time, remarkable electrical field distortion, and greatly favors recovery of the gap insulation strength, insulation design, the life of the switch, etc. The voltage of the output pulses switched by the MER-SGS is in the order of 3-50 kV with pulse rise time of less than 10 ns and pulse repetition rate of 1-3 kHz. An energy of 1.25-125 J per pulse and an average power of up to 10-50 kW are attainable. The highest pulse repetition rate is determined by the driver motor revolution and the electrode number of MER-SGS. Even higher voltage and energy can be switched by adjusting the gas pressure or employing N{sub 2} as the insulation gas or enlarging the size of MER-SGS to guarantee enough insulation level.

  7. Cutting and drilling of carbon fiber reinforced plastics (CFRP) by 70W short pulse nanosecond laser

    NASA Astrophysics Data System (ADS)

    Jaeschke, Peter; Stolberg, Klaus; Bastick, Stefan; Ziolkowski, Ewa; Roehner, Markus; Suttmann, Oliver; Overmeyer, Ludger

    2014-02-01

    Continuous carbon fibre reinforced plastics (CFRP) are recognized as having a significant lightweight construction potential for a wide variety of industrial applications. However, a today`s barrier for a comprehensive dissemination of CFRP structures is the lack of economic, quick and reliable manufacture processes, e.g. the cutting and drilling steps. In this paper, the capability of using pulsed disk lasers in CFRP machining is discussed. In CFRP processing with NIR lasers, carbon fibers show excellent optical absorption and heat dissipation, contrary to the plastics matrix. Therefore heat dissipation away from the laser focus into the material is driven by heat conduction of the fibres. The matrix is heated indirectly by heat transfer from the fibres. To cut CFRP, it is required to reach the melting temperature for thermoplastic matrix materials or the disintegration temperature for thermoset systems as well as the sublimation temperature of the reinforcing fibers simultaneously. One solution for this problem is to use short pulse nanosecond lasers. We have investigated CFRP cutting and drilling with such a laser (max. 7 mJ @ 10 kHz, 30 ns). This laser offers the opportunity of wide range parameter tuning for systematic process optimization. By applying drilling and cutting operations based on galvanometer scanning techniques in multi-cycle mode, excellent surface and edge characteristics in terms of delamination-free and intact fiber-matrix interface were achieved. The results indicate that nanosecond disk laser machining could consequently be a suitable tool for the automotive and aircraft industry for cutting and drilling steps.

  8. Selective removal of carious dentin using a nanosecond pulsed laser with a wavelength of 6.02 μm

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Saiki, Masayuki; Yasuo, Kenzo; Yamamoto, Kazuyo; Yoshikawa, Kazushi; Awazu, Kunio

    2010-04-01

    Conventional laser light sources for the treatment of a hard tissue in dental (Er:YAG laser, Er,Cr:YSGG laser and CO2 laser etc.) are good for removal of caries. However these lasers cannot achieve to give a selective treatment effect for caries without a side effect for normal tissue. The objective of this study is to develop the less-invasive treatment technique of carious dentin by selective absorption effect using the laser with a wavelength of 6.02 μm which corresponds to an absorption peak of organic matters called amide 1 band. Mid-infrared nanosecond pulsed laser by difference-frequency generation was used for the experiment of selective treatment. A tunable wavelength range, pulse width and repetition rate is from 5.5 to 10 μm, 5 ns and Hz, respectively. The laser with a wavelength of 6.02 μm and predetermined energy parameters was irradiated to the plate of carious dentin model which is made by soaking in lactic acid solution. After laser irradiation, the surface and cross-sectional surface of samples were observed by a scanning electron microscope (SEM). Average power density about 15 W/cm2 realized to excavate a demineralized region (carious dentin model) selectively in a SEM observation. In the same energy condition, serious side effect was not observed on the surface of normal dentin. A wavelength of 6.02 μm realizes a selective excavation of carious dentin. Using 6.02 μm is a novel and promising technique toward to next-generation dental treatment procedure for realizing MI.

  9. Sub-500-nm patterning of glass by nanosecond KrF excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Bekesi, J.; Meinertz, J.; Simon, P.; Ihlemann, J.

    2013-01-01

    The surface of flint glass of type F2 is patterned by nanosecond KrF excimer laser ablation. Strong UV absorption provides a comparatively low ablation threshold and precise ablation contours. By using a two-grating interferometer, periodic surface patterns with 330 nm period and 100 nm modulation depth are obtained. This method enables the fabrication of 7 mm×13 mm wide grating areas with perfectly aligned grooves without the need of high-precision sample positioning. By double exposure, crossed gratings with adjustable depths in the two orthogonal directions can be generated.

  10. Micro- and nanoparticle generation during nanosecond laser ablation: correlation between mass and optical emissions.

    PubMed

    Palanco, Santiago; Marino, Salvatore; Gabás, M; Bijani, Shanti; Ayala, Luis; Ramos-Barrado, José R

    2014-02-24

    The particulate emission during nanosecond ablation of gold targets was investigated at various fluences (10-100 Jcm(-2)) and vacuum levels (0.05-750 Torr). Atomic emission spectra were acquired during the ablation process and post-mortem characterization of particle spatial distribution was performed using scanning electron microscopy. The discussion of the results in the context of existing theoretical models permitted the identification of four distinct mass removal mechanisms. While the presence, shape and intensity of atomic emission lines is a telltale of the nanoparticle formation process, the fluctuations of the emission signal over a number of laser shots was linked to the production of microscopic debris.

  11. Picosecond and nanosecond laser annealing and simulation of amorphous silicon thin films for solar cell applications

    NASA Astrophysics Data System (ADS)

    Theodorakos, I.; Zergioti, I.; Vamvakas, V.; Tsoukalas, D.; Raptis, Y. S.

    2014-01-01

    In this work, a picosecond diode pumped solid state laser and a nanosecond Nd:YAG laser have been used for the annealing and the partial nano-crystallization of an amorphous silicon layer. These experiments were conducted as an alternative/complementary to plasma-enhanced chemical vapor deposition method for fabrication of micromorph tandem solar cell. The laser experimental work was combined with simulations of the annealing process, in terms of temperature distribution evolution, in order to predetermine the optimum annealing conditions. The annealed material was studied, as a function of several annealing parameters (wavelength, pulse duration, fluence), as far as it concerns its structural properties, by X-ray diffraction, SEM, and micro-Raman techniques.

  12. Evaluation of explosive sublimation as the mechanism of nanosecond laser ablation of tungsten under vacuum conditions

    NASA Astrophysics Data System (ADS)

    Oderji, Hassan Yousefi; Farid, Nazar; Sun, Liying; Fu, Cailong; Ding, Hongbin

    2016-08-01

    A non-equilibrium mechanism for nanosecond laser ablation is suggested herein, and its predictions are compared to the results of W experiments performed under vacuum conditions. A mechanism of particle formation is explained via this model, with partial sublimation of the superheated irradiated zone of the target considered to be the mechanism of laser ablation. In this study, a mixture of vapor and particles was explosively generated and subsequently prevented the rest of a laser pulse from reaching its intended target. This mechanism was found to play an essential role in the ablation of W under vacuum conditions, and it provides a theoretical justification for particle formation. Moreover, special considerations were taken into account for the expansion of plasma into a vacuum. The model was evaluated by measuring the mass of ablated particles using a quartz crystal deposition monitor and time-resolved optical emission spectroscopy. The results of this model were found to be in good agreement with experimental values.

  13. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    SciTech Connect

    Mahdieh, Mohammad Hossein Akbari Jafarabadi, Marzieh

    2015-12-15

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  14. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

    PubMed

    Al-Hadeethi, Y; Al-Jedani, S; Razvi, M A N; Saeed, A; Abdel-Daiem, A M; Ansari, M Shahnawaze; Babkair, Saeed S; Salah, Numan A; Al-Mujtaba, A

    2016-01-01

    Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased. PMID:27228169

  15. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation

    PubMed Central

    Abdel-Daiem, A. M.; Ansari, M. Shahnawaze; Babkair, Saeed S.; Salah, Numan A.; Al-Mujtaba, A.

    2016-01-01

    Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased. PMID:27228169

  16. Nanosecond Laser Lift-Off of a Copper-Indium-Diselenide Thin Film at a Wavelength of 1342 nm

    NASA Astrophysics Data System (ADS)

    Moser, R.; Domke, M.; Marowsky, G.; Huber, H. P.

    Indirectly induced laser lift-off occurs at the interface of a transparent film and an underlying absorbing substrate. Induced laser ablation often referred to as "laser lift-off" is much more energy efficient than direct laser writing. In this paper we report on the selective laser structuring of copper-indium-diselenide (CIS) film on a molybdenum layer at a wavelength of 1342 nm with nanosecond pulses by indirectly induced laser ablation. A wavelength of 1342 nm was chosen, because the CIS layer can act as a transparent film there and this wavelength can be generated with industrial reliability by a laser transition in Nd:Vanadate.

  17. Ultrashort Two-Photon-Absorption Laser-Induced Fluorescence in Nanosecond-Duration, Repetitively Pulsed Discharges

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob Brian

    Absolute number densities of atomic species produced by nanosecond duration, repetitively pulsed electric discharges are measured by two-photon absorption laser-induced fluorescence (TALIF). Relatively high plasma discharge pulse energies (=1 mJ/pulse) are used to generate atomic hydrogen, oxygen, and nitrogen in a variety of discharge conditions and geometries. Unique to this work is the development of femtosecond-laser-based TALIF (fs-TALIF). Fs-TALIF offers a number of advantages compared to more conventional ns-pulse-duration laser systems, including better accuracy of direct quenching measurements in challenging environments, significantly reduced photolytic interference including photo-dissociation and photo-ionization, higher signal and increased laser-pulse bandwidth, the ability to collect two-dimensional images of atomic species number densities with far greater spatial resolution compared with more conventional diagnostics, and much higher laser repetition rates allowing for more efficient and accurate measurements of atomic species number densities. In order to fully characterize the fs-TALIF diagnostic and compare it with conventional ns-TALIF, low pressure (100 Torr) ns-duration pulsed discharges are operated in mixtures of H2, O2, and N2 with different buffer gases including argon, helium, and nitrogen. These discharge conditions are used to demonstrate the capability for two-dimensional imaging measurements. The images produced are the first of their kind and offer quantitative insight into spatially and temporally resolved kinetics and transport in ns-pulsed discharge plasmas. The two-dimensional images make possible comparison with high-fidelity plasma kinetics models of the presented data. The comparison with the quasi-one-dimensional kinetic model show good spatial and temporal agreement. The same diagnostics are used at atmospheric pressure, when atomic oxygen fs-TALIF is performed in an atmospheric-pressure plasma jet (APPJ). Here, the

  18. Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Primo, Gastón A.; Alvarez Igarzabal, Cecilia I.; Pino, Gustavo A.; Ferrero, Juan C.; Rossa, Maximiliano

    2016-04-01

    This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.

  19. Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

    SciTech Connect

    Ren, X. D. Liu, R.; Zheng, L. M.; Ren, Y. P.; Hu, Z. Z.; He, H.

    2015-10-05

    To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

  20. Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

    SciTech Connect

    Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; Moody, Neville R.

    2015-11-14

    Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protective thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.

  1. Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation

    NASA Astrophysics Data System (ADS)

    Ortiz-Morales, M.; Frausto-Reyes, C.; Soto-Bernal, J. J.; Acosta-Ortiz, S. E.; Gonzalez-Mota, R.; Rosales-Candelas, I.

    2014-07-01

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

  2. Nanosecond pulsed laser induced generation of open macro porosity on sintered ZnO pellet surface

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Samanta, Soumen; Sinha, Sucharita

    2015-01-01

    Surface porosity and pore size distribution of sensing material greatly influence performance parameters such as sensitivity, reproducibility and response time of sensors. Various approaches have been employed to generate surface porosity having varying pore size distribution. This paper presents our results on pulsed laser irradiation based surface microstructuring of sintered zinc oxide (ZnO) pellets leading to generation of enhanced surface porosity. ZnO targets have been surface treated using a frequency doubled nanosecond pulsed Nd:YAG laser at laser fluence levels ranging between 2 and 9 J/cm2. Our observations establish that laser irradiation provides an effective technique for generation of surface macro porosity in case of ZnO pellets. Also, extent of surface porosity and the mean pore size could be controlled by appropriately varying the incident laser fluence. Such laser treated ZnO surfaces with enhanced surface porosity and large size pores can serve as potential candidate for humidity sensors with high sensitivity and fast response time, particularly in high humidity range.

  3. One-step fabrication of near superhydrophobic aluminum surface by nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Jagdheesh, R.; García-Ballesteros, J. J.; Ocaña, J. L.

    2016-06-01

    Inspired by the micro and nano structures of biological surface such as lotus leaf, rice leaves, etc. a functional near superhydrophobic surface of pure aluminum has been fabricated using one-step nanosecond laser processing. Thin aluminum sheets are micro-patterned with ultraviolet laser pulses to create near superhydrophobic surface in one-step direct laser writing technique. The impact of number of pulses/microhole with respect to the geometry and static contact angle measurements has been investigated. The microstructure shows the formation of blind microholes along with the micro-wall by laser processing, which improves the composite interface between the three phases such as water, air and solid, thus enhance the wetting property of the surface. The geometrical changes are supported by the chemical changes induced on the surface for improving the degree of hydrophobicity. Laser processed microholes exhibited near superhydrophobic surface with SCA measurement of 148 ± 3°. The static contact angle values are very consistent for repeated measurement at same area and across the laser patterned surface.

  4. Infrared nanosecond pulsed laser irradiation of stainless steel: micro iron-oxide zones generation.

    PubMed

    Ortiz-Morales, M; Frausto-Reyes, C; Soto-Bernal, J J; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2014-07-15

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

  5. Infrared nanosecond pulsed laser irradiation of stainless steel: micro iron-oxide zones generation.

    PubMed

    Ortiz-Morales, M; Frausto-Reyes, C; Soto-Bernal, J J; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2014-07-15

    Nanosecond-pulsed, infrared (1064 nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas. PMID:24699286

  6. Myocardium tissue ablation with hollow-waveguide-delivered near-infrared nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sato, Shunichi; Arai, Tsunenori; Shi, Yi-Wei; Matsuura, Yuji; Miyagi, Mitsunobu; Ashida, Hiroshi

    2001-06-01

    With 1064-nm, nanosecond laser pulses delivered from hollow waveguide, ablation characteristics of porcine myocardium tissue have been investigated in vitro. For the hollow waveguide a vacuum-cored scheme was introduced to suppress the laser-induced air breakdown that limited the available transmitted laser energy/power. The delivered laser pulse beam was focused with a collimation lens and a focusing lens, and it was shown that higher efficiency ablation was obtained when a focusing lens with a shorter focal length was used. Waveguide bending (bending angle 90 degree(s)C, bending radius approximately 50 cm) caused no deteriorating effect on the ablation characteristics for ablation energies up to approximately 60 mJ/pulse. It was demonstrated that deep and sharp ablated holes with aspect ratios > 8 was obtained with the hollow-waveguide-delivered laser pulses. It may be a realistic option to aim at using the present hollow waveguide system for trocar-based applications or replacing articulated mirror-based laser delivery systems. It is an important part of the future works to downsize the waveguide output unit for catheter-based applications.

  7. Investigation of laser induced breakdown in liquid nitromethane using nanosecond shadowgraphy

    NASA Astrophysics Data System (ADS)

    Guo, Wencan; Zheng, Xianxu; Yu, Guoyang; Zhao, Jun; Zeng, Yangyang; Liu, Cangli

    2016-09-01

    A nanosecond time-resolved shadowgraphy is performed to observe a laser-induced breakdown in nitromethane. The digital delays are introduced between a pump beam and an illumination light to achieve a measuring range from 40 ns to 100 ms, which enable us to study the shock wave propagation, bubble dynamics, and other process of the laser-induced breakdown. Compared with distilled water, there are two obvious differences observed in nitromethane: (1) the production of a non-evaporative gas at the final stage, and (2) an absence of the secondary shock wave after the first collapse of the bubble. We also calculated the bubble energy in nitromethane and distilled water under a different incident energy. The results indicate that the bubble energy in nitromethane is more than twice as large as that in water. It is suggested that chemical reactions contribute to the releasing of energy.

  8. Simulation of nanosecond laser-induced thermal dynamics of hollow gold nanoshells for hyperthermia therapy

    SciTech Connect

    Hatef, Ali Fortin-Deschênes, Simon Meunier, Michel

    2014-03-31

    In this report, we investigate numerically the thermodynamics of hollow gold nanoshell (AuNS) irritated by near-infrared (NIR) light. Simulations are performed for the AuNS in aqueous medium. The nanostructure is illuminated by a nanosecond pulsed laser at plasmonic resonance. The spatiotemporal evolution of the temperature profile inside and outside the AuNS is computed using a numerical framework based on the finite element method (FEM). In particular, we show how the temperature varies with the laser fluence and pulse duration. The aim of this study is to provide a description of the physics of heat release of AuNSs and useful insights for the development of these nanostructures for biomedical applications such as drug delivery, photothermal cancer therapy and optoporation of cells.

  9. Frequency-modulation spectroscopy with transform-limited nanosecond laser pulses.

    PubMed

    Eyler, E E; Gangopadhyay, S; Melikechi, N; Bloch, J C; Field, R W

    1996-02-01

    We demonstrate high-quality FM spectra with nanosecond laser pulses. Transform-limited pulses with FM sidebands are produced by pulsed amplification of a phase-modulated cw laser. The pulses can be shifted to the UV by nonlinear mixing. We report both initial experiments on I(2) and what is to our knowledge the first observation of a far-UV transition by FM spectroscopy, at 214.5 nm. Major advantages of this method include (1) spectral resolution of the order of 0.001 cm(-1), (2) better-defined optical phase, and (3) a much smaller and more easily detected modulation frequency, ~500 MHz. The absorption sensitivity is ~10(-4), and considerable further improvement is expected.

  10. Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

    SciTech Connect

    Franta, Benjamin Pastor, David; Gandhi, Hemi H.; Aziz, Michael J.; Mazur, Eric; Rekemeyer, Paul H.; Gradečak, Silvija

    2015-12-14

    Hyperdoped black silicon fabricated with femtosecond laser irradiation has attracted interest for applications in infrared photodetectors and intermediate band photovoltaics due to its sub-bandgap optical absorptance and light-trapping surface. However, hyperdoped black silicon typically has an amorphous and polyphasic polycrystalline surface that can interfere with carrier transport, electrical rectification, and intermediate band formation. Past studies have used thermal annealing to obtain high crystallinity in hyperdoped black silicon, but thermal annealing causes a deactivation of the sub-bandgap optical absorptance. In this study, nanosecond laser annealing is used to obtain high crystallinity and remove pressure-induced phases in hyperdoped black silicon while maintaining high sub-bandgap optical absorptance and a light-trapping surface morphology. Furthermore, it is shown that nanosecond laser annealing reactivates the sub-bandgap optical absorptance of hyperdoped black silicon after deactivation by thermal annealing. Thermal annealing and nanosecond laser annealing can be combined in sequence to fabricate hyperdoped black silicon that simultaneously shows high crystallinity, high above-bandgap and sub-bandgap absorptance, and a rectifying electrical homojunction. Such nanosecond laser annealing could potentially be applied to non-equilibrium material systems beyond hyperdoped black silicon.

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

    PubMed Central

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

    2013-01-01

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

  12. Rapid Laser Induced Crystallization of Amorphous NiTi Films Observed by Nanosecond Dynamic Transmission Electron Microscopy (DTEM)

    SciTech Connect

    LaGrange, T; Campbell, G H; Browning, N D; Reed, B W; Grummon, D S

    2010-03-01

    The crystallization processes of the as-deposited, amorphous NiTi thin films have been studied in detail using techniques such as differential scanning calorimetry and, in-situ TEM. The kinetic data have been analyzed in terms of Johnson-Mehl-Avrami-Kolomogrov (JMAK) semi-empirical formula. The kinetic parameters determined from this analysis have been useful in defining process control parameters for tailoring microstructural features and shape memory properties. Due to the commercial push to shrink thin film-based devices, unique processing techniques have been developed using laser-based annealing to spatially control the microstructure evolution down to sub-micron levels. Nanosecond, pulse laser annealing is particularly attractive since it limits the amount of peripheral heating and unwanted microstructural changes to underlying or surrounding material. However, crystallization under pulsed laser irradiation can differ significantly from conventional thermal annealing, e.g., slow heating in a furnace. This is especially true for amorphous NiTi materials and relevant for shape memory thin film based microelectromechanical systems (MEMS) applications. There is little to no data on the crystallization kinetics of NiTi under pulsed laser irradiation, primarily due to the high crystallization rates intrinsic to high temperature annealing and the spatial and temporal resolution limits of standard techniques. However, with the high time and spatial resolution capabilities of the dynamic transmission electron microscope (DTEM) constructed at Lawrence Livermore National Laboratory, the rapid nucleation events occurring from pulsed laser irradiation can be directly observed and nucleation rates can be quantified. This paper briefly explains the DTEM approach and how it used to investigate the pulsed laser induced crystallization processes in NiTi and to determine kinetic parameters.

  13. Study of laser-plasma interaction using a physics-based model for understanding the physical mechanism of double-pulse effect in nanosecond laser ablation

    SciTech Connect

    Wu Benxin; Zhou Yun; Forsman, Andrew

    2009-12-21

    This paper studies the double-pulse effect in high-intensity ({>=}{approx}GW/cm{sup 2}) nanosecond (ns) laser ablation, which refers to the significant material removal rate enhancement for ablation by two ns laser pulses (often separated by a delay time of {approx}10 to 100 ns). The early-stage interaction of the second laser pulse with the plasma plume created by the first pulse is very important for understanding the physical mechanism of the double pulse effect. However, the plasma properties in the early stage (during a laser pulse or within 20 to 30 ns after the completion of the pulse) are very difficult to measure experimentally. In this letter, a physics-based predictive model is used as the investigation tool, which was previously verified based on experiments on plasma properties in the late stage, which are relatively easy to measure. The study shows that the second laser pulse does not directly strike the target condensed phase. Instead, it mainly interacts with the plasma plume created by the first laser pulse, heats and accelerates the ablated material in the plume lingering above the target surface.

  14. Comparative Study of the Dissociative Ionization of 1,1,1-Trichloroethane Using Nanosecond and Femtosecond Laser Pulses

    PubMed Central

    du Plessis, Anton; Strydom, Christien; Botha, Lourens

    2010-01-01

    Changes in the laser induced molecular dissociation of 1,1,1-trichloroethane (TCE) were studied using a range of intensities and standard laser wavelengths with nanosecond and femtosecond pulse durations. TCE contains C-H, C-C and C-Cl bonds and selective bond breakage of one or more of these bonds is of scientific interest. Using laser ionization time of flight mass spectrometry, it was found that considerable variation of fragment ion peak heights as well as changes in relative peak ratios is possible by varying the laser intensity (by attenuation), wavelength and pulse duration using standard laser sources. The nanosecond laser dissociation seems to occur via C-Cl bond breakage, with significant fragmentation and only a few large mass ion peaks observed. In contrast, femtosecond laser dissociative ionization results in many large mass ion peaks. Evidence is found for various competing dissociation and ionization pathways. Variation of the nanosecond laser intensity does not change the fragmentation pattern, while at high femtosecond intensities large changes are observed in relative ion peak sizes. The total ionization yield and fragmentation ratios are presented for a range of wavelengths and intensities, and compared to the changes observed due to a linear chirp variation. PMID:20480004

  15. Dynamics of femto- and nanosecond laser ablation plumes investigated using optical emission spectroscopy

    SciTech Connect

    Verhoff, B.; Harilal, S. S.; Freeman, J. R.; Diwakar, P. K.; Hassanein, A.

    2012-11-01

    We investigated the spatial and temporal evolution of temperature and electron density associated with femto- and nanosecond laser-produced plasmas (LPP) from brass under similar laser fluence conditions. For producing plasmas, brass targets were ablated in vacuum employing pulses either from a Ti:Sapphire ultrafast laser (40 fs, 800 nm) or from a Nd:YAG laser (6 ns, 1064 nm). Optical emission spectroscopy is used to infer the density and temperature of the plasmas. The electron density (n{sub e}) was estimated using Stark broadened profiles of isolated lines while the excitation temperature (T{sub exc}) was estimated using the Boltzmann plot method. At similar fluence levels, continuum and ion emission are dominant in ns LPP at early times (<50 ns) followed by atomic emission, while the fs LPP provided an atomic plume throughout its visible emission lifetime. Though both ns and fs laser-plasmas showed similar temperatures ({approx}1 eV), the fs LPP is found to be significantly denser at shorter distances from the target surface as well as at early phases of its evolution compared to ns LPP. Moreover, the spatial extension of the plume emission in the visible region along the target normal is larger for fs LPP in comparison with ns LPP.

  16. Nanosecond pulsed laser ablation of Ge investigated by employing photoacoustic deflection technique and SEM analysis

    NASA Astrophysics Data System (ADS)

    Yaseen, Nazish; Bashir, Shazia; Shabbir, Muhammad Kaif; Jalil, Sohail Abdul; Akram, Mahreen; Hayat, Asma; Mahmood, Khaliq; Haq, Faizan-ul; Ahmad, Riaz; Hussain, Tousif

    2016-06-01

    Nanosecond pulsed laser ablation phenomena of single crystal Ge (100) has been investigated by employing photoacoustic deflection as well as SEM analysis techniques. Nd: YAG laser (1064 nm, 10 ns, 1-10 Hz) at various laser fluences ranging from 0.2 to 11 J cm-2 is employed as pump beam to ablate Ge targets. In order to evaluate in-situe ablation threshold fluence of Ge by photoacoustic deflection technique, Continuous Wave (CW) He-Ne laser (632 nm, power 10 mW) is employed as a probe beam. It travels parallel to the target surface at a distance of 3 mm and after passing through Ge plasma it causes deflection due to density gradient of acoustic waves. The deflected signal is detected by photodiode and is recorded by oscilloscope. The threshold fluence of Ge, the velocity of ablated species and the amplitude of the deflected signal are evaluated. The threshold fluence of Ge comes out to be 0.5 J cm-2 and is comparable with the analytical value. In order to compare the estimated value of threshold with ex-situe measurements, the quantitative analysis of laser irradiated Ge is performed by using SEM analysis. For this purpose Ge is exposed to single and multiple shots of 5, 10, 50 and 100 at various laser fluences ranging from 0.2 to 11 J cm-2. The threshold fluence for single and multiple shots as well as incubation coefficients are evaluated. It is observed that the value of incubation co-efficient decreases with increasing number of pulses and is therefore responsible for lowering the threshold fluence of Ge. SEM analysis also reveals the growth of various features such as porous structures, non-uniform ripples and blisters on the laser irradiated Ge. It is observed that both the fluence as well as number of laser shots plays a significant role for the growth of these structures.

  17. A scheme for recording a fast process at nanosecond scale by using digital holographic interferometry with continuous wave laser

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Zhao, Jianlin; Di, Jianglei; Jiang, Biqiang

    2015-04-01

    A scheme for recording fast process at nanosecond scale by using digital holographic interferometry with continuous wave (CW) laser is described and demonstrated experimentally, which employs delayed-time fibers and angular multiplexing technique and can realize the variable temporal resolution at nanosecond scale and different measured depths of object field at certain temporal resolution. The actual delay-time is controlled by two delayed-time fibers with different lengths. The object field information in two different states can be simultaneously recorded in a composite hologram. This scheme is also suitable for recording fast process at picosecond scale, by using an electro-optic modulator.

  18. Observation of nanosecond laser induced fluorescence of in vitro seawater phytoplankton

    SciTech Connect

    Bensky, Thomas J.; Clemo, Lisa; Gilbert, Chris; Neff, Bryan; Moline, Mark A.; Rohan, Dov

    2008-08-01

    Seawater has been irradiated using a train of 70 ns flashes from a 440 nm laser source. This wavelength is on resonance with the blue absorption peak of Chlorophyll pigment associated with the photosystem of in vitro phytoplankton. The resulting fluorescence at 685 nm is instantaneously recorded during each laser pulse using a streak camera. Delayed fluorescence is observed, yielding clues about initiation of the photosynthetic process on a nanosecond time scale. Further data processing allows for determination of the functional absorption cross section, found to be 0.0095 ?{sup 2}, which is the first reporting of this number for in vitro phytoplankton. Unlike other flash-pump studies of Chlorophyll, using a LED or flashlamp-based sources, the short laser pulse used here does not reveal any pulse-to-pulse hysteresis (i.e., variable fluorescence), indicating that the laser pulses used here are not able to drive the photosynthetic process to completion. This is attributed to competition from a back reaction between the photoexcited photosystem II and the intermediate electron acceptor. The significance of this work as a new type of deployable ocean fluorimeter is discussed, and it is believed the apparatus will have applications in thin-layer phytoplankton research.

  19. NANOSECOND INTERFEROMETRIC STUDIES OF SURFACE DEFORMATIONS OF DIELECTRICS INDUCED BY LASER IRRADIATION

    SciTech Connect

    S. GREENFIELD; ET AL

    2000-05-01

    Transient surface deformations in dielectric materials induced by laser irradiation were investigated with time-resolved interferometry. Deformation images were acquired at various delay times after exposure to single pulses (100 ps at 1.064 {micro}m) on fresh sample regions. Above the ablation threshold, we observe prompt ejection of material and the formation of a single unipolar compressional surface acoustic wave propagating away from the ablation crater. For calcite, no deformation--either transient or permanent--is discernable at laser fluences below the threshold for material ejection. Above and below-threshold behavior was investigated using a phosphate glass sample with substantial near infrared absorption (Schott filter KG3). Below threshold, KG3 exhibits the formation of a small bulge roughly the size of the laser spot that reaches its maximum amplitude by {approx}5 ns. By tens of nanoseconds, the deformations become quite complex and very sensitive to laser fluence. The above-threshold behavior of KG3 combines the ablation-induced surface acoustic wave seen in calcite with the bulge seen below threshold in KG3. A velocity of 2.97 {+-} 0.03 km/s is measured for the KG3 surface acoustic wave, very close to the Rayleigh wave velocity calculated from material elastic parameters. Details of the transient interferometry system will also be given.

  20. Nanosecond multi-pulse laser milling for certain area removal of metal coating on plastics surface

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Jia, Zhenyuan; Ma, Jianwei; Liu, Wei; Wang, Ling

    2014-12-01

    Metal coating with functional pattern on engineering plastics surface plays an important role in industry applications; it can be obtained by adding or removing certain area of metal coating on engineering plastics surface. However, the manufacturing requirements are improved continuously and the plastic substrate presents three-dimensional (3D) structure-many of these parts cannot be fabricated by conventional processing methods, and a new manufacturing method is urgently needed. As the laser-processing technology has many advantages like high machining accuracy and constraints free substrate structure, the machining of the parts is studied through removing certain area of metal coating based on the nanosecond multi-pulse laser milling. To improve the edge quality of the functional pattern, generation mechanism and corresponding avoidance strategy of the processing defects are studied. Additionally, a prediction model for the laser ablation depth is proposed, which can effectively avoid the existence of residual metal coating and reduces the damage of substrate. With the optimal machining parameters, an equiangular spiral pattern on copper-clad polyimide (CCPI) is machined based on the laser milling at last. The experimental results indicate that the edge of the pattern is smooth and consistent, the substrate is flat and without damage. The achievements in this study could be applied in industrial production.

  1. High-adhesion Cu patterns fabricated by nanosecond laser modification and electroless copper plating

    NASA Astrophysics Data System (ADS)

    Lv, Ming; Liu, Jianguo; Zeng, Xiaoyan; Du, Qifeng; Ai, Jun

    2015-10-01

    Adhesion strength is a crucial factor for the performance and reliability of metallic patterns on insulator substrates. In this study, we present an efficient technique for selective metallization of alumina ceramic with high adhesion strength by using nanosecond laser modification and electroless copper plating. Specifically, a 355 nm Nd:YVO4 ultraviolet (UV) laser was employed not only to decompose palladium chloride film locally for catalyzing the electroless reaction, but also to modify the ceramic surface directly using its high fluence. An orthogonal experiment was undertaken to study the effects of processing parameters including laser fluence, scanning speed and scanning line interval on adhesion strength. The adhesion strength was measured by pulling a metallic wire soldered into the copper coating perpendicular to the substrate using a pull tester. The results have shown that a strong adhesion between the copper coating and the alumina ceramic, higher than the tensile strength of tin-lead solder was obtained. Surface and interface characteristics were investigated to understand that, whose results have shown that the high-aspect-ratio microstructures formed by the laser modification is the major reason for the improvement of adhesion.

  2. A mass quadrupole spectrometry investigation on proton emission by nanosecond laser ablation

    SciTech Connect

    Caridi, F.

    2015-02-15

    A nanosecond pulsed Nd:YAG laser operating at the fundamental wavelength of 1064 nm and at an intensity of about 10{sup 10} W/cm{sup 2} was employed to irradiate hydrogenated polymers in vacuum. The produced plasma was characterized in terms of thermal and Coulomb interactions evaluating the equivalent temperature and the acceleration voltage developed in the non-equilibrium plasma core. Particles emission along the normal to the target surface was investigated by measuring, with the Hiden EQP 300 mass quadrupole spectrometer, ion energy distributions and fitting experimental data with the “Coulomb-Boltzmann-shifted” function. Time-of-flight technique was employed in order to measure the proton energy and yield. A comparison between experimental results is presented and discussed, with a special regard to the protons emission.

  3. Damage caused by a nanosecond UV laser on a heated copper surface

    NASA Astrophysics Data System (ADS)

    Henč-Bartolić, V.; Bončina, T.; Jakovljević, S.; Panjan, P.; Zupanič, F.

    2016-08-01

    This work studied the effect of thin copper plate temperature on its surface morphology after irradiation using a pulsed nanosecond UV laser. The surface characteristics were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam and stylus profilometry. When a target was at room temperature, a crater and the radial flow of molten Cu from the crater was observed. When the thin target was warm (about 360 °C ± 20 °C), a crater was smaller, and quasi-semicircular waves with the periodicity of around 3 μm appeared in its vicinity. The origin of the waves is Marangoni effect, causing thermocapillary waves, which in same occasions had a structure of final states of chaos in Rayleigh-Bénard convection.

  4. Study of nanosecond laser-produced plasmas in atmosphere by spatially resolved optical emission spectroscopy

    SciTech Connect

    Wei, Wenfu; Wu, Jian; Li, Xingwen; Jia, Shenli; Qiu, Aici

    2013-09-21

    We investigate the evolution of the species from both the target and the air, and the plasma parameter distribution of the nanosecond laser-produced plasmas in atmospheric air. The technique used is spatially resolved optical emission spectroscopy. It is argued that the N II from the air, which is distributed over a wider region than the target species in the early stages of the discharge, is primarily formed by the shock wave. The ionized species have a larger expansion velocity than the excited atoms in the first ∼100 ns, providing direct evidence for space-charge effects. The electron density decreases with the distance from the target surface in the early stages of the discharge, and both the electron density and the excited temperature variation in the axial direction are found to become insignificant at later stages.

  5. Photo-dissociation quantum yields of mammalian oxyhemoglobin investigated by a nanosecond laser technique

    SciTech Connect

    Yang Ningli; Zhang Shuyi . E-mail: zhangsy@nju.edu.cn; Kuo Paokuang; Qu Min; Fang Jianwen; Li Jiahuang; Hua Zichun

    2007-02-23

    The photo-dissociations of oxyhemoglobin of several mammals, such as human, bovine, pig, horse, and rabbit, have been studied. By means of optical pump-probe technique, the quantum yields for photo-dissociation of these oxyhemoglobin have been determined at pH 7 and 20 {sup o}C. A nanosecond laser at 532 nm is used as the pumping source, and a xenon lamp through a monochrometer provides a probe light at 432 nm. The experimental results show that the quantum yields of these mammalian oxyhemoglobin are different from each other, especially for that of rabbit. By analyzing the amino acid sequences and tetramer structures as well as the flexibility and hydrophobicity of the different hemoglobin, possible explanations for the differences are proposed.

  6. Multiple-frequency injection-seeded nanosecond pulsed laser without parasitic intensity modulation.

    PubMed

    Penninckx, D; Luce, J; Diaz, R; Bonville, O; Courchinoux, R; Lamaignère, L

    2016-07-15

    Thanks to a phase-modulated injection seeder, we report the operation of a nanosecond Nd:YAG Q-switched laser with pulses having both a large spectral bandwidth and a smooth temporal waveform. Because of the smooth temporal waveform, such pulses allow, for instance, reducing the impact of the Kerr effect and, because of the large spectral bandwidth, suppressing stimulated Brillouin scattering. We conducted a parametric study of the features of the generated pulses versus the injection conditions. We show that, as opposed to the central frequency (wavelength) of the seeder, the phase modulation frequency has to be carefully chosen, but it is not a critical parameter and does not require any particular feedback. PMID:27420504

  7. Explosive boiling of a metallic glass superheated by nanosecond pulse laser ablation

    SciTech Connect

    Jiang, M. Q. E-mail: lhdai@lnm.imech.ac.cn; Wei, Y. P.; Wilde, G.; Dai, L. H. E-mail: lhdai@lnm.imech.ac.cn

    2015-01-12

    We report an explosive boiling in a Zr-based (Vitreloy 1) bulk metallic glass irradiated by a nanosecond pulse laser with a single shot. This critical phenomenon is accompanied by the ejection of high-temperature matter from the target and the formation of a liquid-gas spinodal pattern on the irradiated area. An analytical model reveals that the glassy target experiences the normal heating (melting) and significant superheating, eventually culminating in explosive boiling near the spinodal limit. Furthermore, the time lag of nucleation and the critical radius of vapor bubbles are theoretically predicted, which are in agreement with the experimental observations. This study provides the investigation on the instability of a metallic glass liquid near the thermodynamic critical temperature.

  8. Nanosecond laser pulse induced stress waves enhanced magnetofection of human carcinoma cells in vitro

    NASA Astrophysics Data System (ADS)

    Durdík, Š.; Babincová, M.; Bergemann, C.; Babinec, P.

    2012-09-01

    We have developed a novel platform for efficient gene delivery into cells using magnetic force for pre-concentration of gene-magnetic nanoparticle complex on the surface of cells with subsequent nanosecond laser pulse for generation of stress waves in transfection chamber which is able to permeabilize cell membrane for the facilitated delivery of gene into the cell interior. Combination of these two physical factors increased the efficiency of three different human carcinoma cells transfection with plasmid coding green fluorescence protein from 43% to 67%, from 35% to 54%, and from 23% to 39%, for HeLa (cervical carcinoma), MCF-7 (breast carcinoma), and UCI-107 (ovarian carcinoma) cells, respectively, as compared with using only magnetofection. Proposed fast, simple, and efficient method may have far reaching applications for cancer gene therapy.

  9. Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses

    PubMed Central

    Pérez-Gutiérrez, Francisco G.; Camacho-López, Santiago; Evans, Rodger; Guillén, Gabriel; Goldschmidt, Benjamin S.; Viator, John A.

    2010-01-01

    Circulating tumor cells (CTCs) photoacoustic detection systems can aid clinical decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond laser pulses generates photoacoustic waves that make its detection possible. This study aims at: (1) determining melanoma cell survival after laser pulses of 6 ns at λ = 355 and 532 nm; (2) comparing the potential enhancement in the photoacoustic signal using λ = 355 nm in contrast with λ = 532 nm; (3) determining the critical laser fluence at which melanin begins to leak out from melanoma cells; and (4) developing a time-resolved imaging (TRI) system to study the intracellular interactions and their effect on the plasma membrane integrity. Monolayers of melanoma cells were grown on tissue culture-treated clusters and irradiated with up to 1.0 J/cm2. Surviving cells were stained with trypan blue and counted using a hemacytometer. The phosphate buffered saline absorbance was measured with a nanodrop spectrophotometer to detect melanin leakage from the melanoma cells post-laser irradiation. Photoacoustic signal magnitude was studied at both wavelengths using piezoelectric sensors. TRI with 6 ns resolution was used to image plasma membrane damage. Cell survival decreased proportionally with increasing laser fluence for both wavelengths, although the decrease is more pronounced for 355 nm radiation than for 532 nm. It was found that melanin leaks from cells equally for both wavelengths. No significant difference in photoacoustic signal was found between wavelengths. TRI showed clear damage to plasma membrane due to laser-induced bubble formation. PMID:20589533

  10. Observation of repetitively nanosecond pulse-width transverse patterns in microchip self-Q-switched laser

    SciTech Connect

    Dong, Jun; Ueda, Ken-ichi

    2006-05-15

    Repetitively nanosecond pulse-width transverse pattern formation in a plane-parallel microchip Cr,Nd: yttrium-aluminum-garnet (YAG) self-Q-switched laser was investigated. The complex point-symmetric transverse patterns were observed by varying the pump beam diameter incident on the Cr,Nd:YAG crystal. The gain guiding effect and the thermal effect induced by the pump power in microchip Cr,Nd:YAG laser control the oscillating transverse modes. These transverse pattern formations were due to the variation of the saturated inversion population and the thermal induced index profile along radial and longitudinal direction in the Cr,Nd:YAG crystal induced by the pump power incident on the Cr,Nd:YAG crystal. These were intrinsic properties of such a microchip self-Q-switched laser. The longitudinal distribution of the saturated inversion population inside the gain medium plays an important role on the transverse pattern formation. Different sets of the transverse patterns corresponds to the different saturated inversion population distribution inside microchip Cr,Nd:YAG crystal.

  11. Thermal and microstructural effects of nanosecond pulsed Nd:YAG laser irradiation on tooth root surface

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.; Grill, G.; Liaw, Lih-Huei L.; Berns, Michael W.

    1995-05-01

    Plaque, calculus and altered cementum removal by scaling and root planing is a fundamental procedure in periodontal treatment. However, the residual smear layer contains cytotoxic and inflammatory mediators which adversely affect healing. Chemical smear layer removal is also problematic. In previous investigations effective smear layer removal was achieved using long pulsed irradiation at 1.06 (mu) . However, laser irradiation was not adequate as an alternative to scaling and root planing procedures and concurrent temperature rises exceeded thermal thresholds for pulpal and periodontal safety. It was the aim of this study to determine whether nanosecond pulsed irradiation at 1.06 (mu) could be used as an alternative or an adjunct to scaling and root planing. Sixty freshly extracted teeth were divided as follows: 5 control, 5 root planed only, 25 irradiated only, 25 root planed and irradiated. Irradiation was performed at fluences of 0.5 - 2.7 J/cm2, total energy densities of 12 - 300 J/cm2, frequencies of 2 - 10 Hz using the Medlite (Continuum) laser. Irradiation-induced thermal events were recorded using a thermocouple within the root canal and a thermal camera to monitor surface temperatures. SEM demonstrated effective smear layer removal with minimal microstructural effects. Surface temperatures increased minimally (< 3 C) at all parameters, intrapulpal temperature rises remained below 4 C at 2 and 5 Hz, F < 0.5 J/cm2. Without prior scaling and root planing, laser effects did not provide an adequately clean root surface.

  12. A study on the effect of ultrasonic vibration in nanosecond laser machining

    NASA Astrophysics Data System (ADS)

    Kang, Bongchul; Woo Kim, Gun; Yang, Minyang; Cho, Sung-Hak; Park, Jong-Kweon

    2012-12-01

    Laser machining has been used in various industrial manufacturing fields. However the surface finish of a machined surface becomes degraded by the recast layer that is created by the agglomeration of nanoparticles re-deposited on a work surface. In this study, ultrasonic vibration was applied to a nanosecond laser machining process in order to improve the quality of machined surface. A resonance type ultrasonic vibration module was designed to realize a unidirectional motion. To investigate the effects of ultrasonic vibration on the work surface, the morphological change of particles re-deposited on the machined area was observed in various process conditions. The results showed that the surface finish was improved by the near-field surface cooling enhancement induced by ultrasonic vibration. And it was found that such a vibration effect was remarkable in a repetitive machining process. From the chemical composition analysis of a machined surface, it was verified that the vibration can prevent the surface oxidation and the formation of recast layer. As a result, the ultrasonic vibration in ns-laser machining process was effective for improving both the physical and chemical quality of a machined surface.

  13. Nanosecond two-photon excitation fluorescence imaging with a multi color fiber MOPA laser

    NASA Astrophysics Data System (ADS)

    Karpf, Sebastian; Eibl, Matthias; Huber, Robert

    2015-07-01

    A system is presented that uses a fiber based Master Oscillator Power Amplifier (MOPA) with nanosecond-range pulses for two-photon excitation fluorescence (TPEF) imaging. The robust laser in the extended near infrared is based on an actively modulated electro-optical modulator (EOM), enabling free synchronization of the pulses to any other light source or detection unit. Pulses with a freely programmable duration between 0.4 and 10 ns are generated and then amplified to up to kilowatts of peak power with ytterbium doped fiber amplifiers (YDFA). Since we achieve peak power and duty cycles comparable to standard femto- and picosecond setups, the TPEF signal levels are similar, but realized with a robust and inexpensive fiber-based setup. The delivery fiber is further used as an optional, electronically controllable Raman shifter to effectively shift the 1064 nm light to 1122 nm and to 1186 nm. This allows imaging of a manifold of fluorophores, like e.g. TexasRed, mCherry, mRaspberry and many more. We show TPEF imaging of the autofluorescence of plant leaves of moss and algae, acquired in epi-direction. This modular laser unit can be integrated into existing systems as either a fiber-based, alignment free excitation laser or an extension for multi-modal imaging.

  14. Graphene patterning by nanosecond laser ablation: the effect of the substrate interaction with graphene

    NASA Astrophysics Data System (ADS)

    Pérez-Mas, Ana M.; Álvarez, Patricia; Campos, Nuria; Gómez, David; Menéndez, Rosa

    2016-08-01

    This paper focuses on the development of patterned graphene/substrate by means of green nanosecond pulse laser irradiation. Monolayer graphene samples supported on a Si/SiO2 substrate were patterned using 532 nm laser irradiation under fluence conditions ranging from 31 mJ cm‑2 to 4240 mJ cm‑2. Raman spectroscopy was used to investigate the effect of laser irradiation on the graphene. It was found that at 356 mJ cm‑2 selective ablation of the graphene occurs. However, at fluence values above 1030 mJ cm‑2 (when damage to the substrate is observed) no ablation of the graphene takes place. In contrast, its graphenic structure was found to have been modified. Only at fluence values where the ablation of the substrate occurs, is graphene eliminated in an area almost equivalent to that of the ablated substrate. In this case, additional damage to the graphene sheet edges is produced. The increment in the number of oxygenated functional groups in these regions, as measured by x-ray photoelectron spectroscopy (XPS), suggests that this damage is probably caused by thermal phenomena during the ablation of the substrate.

  15. Evidence of water reorientation on model electrocatalytic surfaces from nanosecond-laser-pulsed experiments.

    PubMed

    García-Aráez, Nuria; Climent, Víctor; Feliu, Juan M

    2008-03-26

    The behavior of water at the interface formed between a quasi-perfect Pt(111) single-crystal electrode and an aqueous electrolyte solution is studied by means of the laser-induced temperature jump method. This method is based on the use of nanosecond laser pulses to suddenly increase the temperature at the interface. The measurement of the response of the interface toward the laser heating under coulostatic conditions provides evidence on the net orientation of water at the interface. Especially interesting is the study of the effect on the interfacial water caused by the selective deposition of foreign metal adatoms, because these bimetallic systems usually exhibit appealing electrocatalytic properties. The T-jump methodology shows that the surface composition strongly affects the interaction of water with the surface. The most representative parameter to characterize this interaction is the potential where water reorientation occurs; this potential shifts in different directions, depending on the relative values of the electronegativity of the adatom and the substrate. These results are discussed in the light of available information about the effect of adatom deposition on the work function and the surface potential of the modified surface. Finally, some implications on the enhancement of the electrocatalytic activity are briefly discussed. PMID:18321095

  16. Graphene patterning by nanosecond laser ablation: the effect of the substrate interaction with graphene

    NASA Astrophysics Data System (ADS)

    Pérez-Mas, Ana M.; Álvarez, Patricia; Campos, Nuria; Gómez, David; Menéndez, Rosa

    2016-08-01

    This paper focuses on the development of patterned graphene/substrate by means of green nanosecond pulse laser irradiation. Monolayer graphene samples supported on a Si/SiO2 substrate were patterned using 532 nm laser irradiation under fluence conditions ranging from 31 mJ cm-2 to 4240 mJ cm-2. Raman spectroscopy was used to investigate the effect of laser irradiation on the graphene. It was found that at 356 mJ cm-2 selective ablation of the graphene occurs. However, at fluence values above 1030 mJ cm-2 (when damage to the substrate is observed) no ablation of the graphene takes place. In contrast, its graphenic structure was found to have been modified. Only at fluence values where the ablation of the substrate occurs, is graphene eliminated in an area almost equivalent to that of the ablated substrate. In this case, additional damage to the graphene sheet edges is produced. The increment in the number of oxygenated functional groups in these regions, as measured by x-ray photoelectron spectroscopy (XPS), suggests that this damage is probably caused by thermal phenomena during the ablation of the substrate.

  17. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    SciTech Connect

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.; Shi, Yujun J.; El-Sayed, Hany A.

    2015-05-18

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  18. Enhanced mass removal due to phase explosion during high irradiance nanosecond laser ablation of silicon

    SciTech Connect

    Yoo, Jong Hyun

    2000-05-20

    mechanism for high irradiance laser ablation. Laser processing parameters were also investigated for nanosecond laser ablation of silicon. Longer incident wavelengths and larger laser beam sizes were associated with higher values of a threshold irradiance.

  19. Nanosecond pulse generation in a passively Q-switched Nd:GGG laser at 1331 nm by CVD graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Wang, Yi; Cheng, Yongjie; Yang, Han; Xu, Huiying; Cai, Zhiping

    2015-10-01

    We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:GGG laser at the low-gain transition line of 1331 nm. A three-layer CVD graphene thin film was transferred from Cu foil to a BK7 glass substrate for the use of saturable absorber. A stable Q-switching laser operation was obtained with maximum average output power of 0.69 W and slope efficiency of about 11.0% with respect to the absorbed pump power. The shortest pulse duration and the maximum repetition rate of the pulse trains were registered to be 556 ns and 166.7 kHz with corresponding maximum pulse energy 4.14 μJ and pulse peak power 7.45 W. This is the first demonstration of CVD-graphene-based Q-switched laser operation at 1.3 μm, to the best of our knowledge.

  20. Heat Transfer And Vapor Dynamics Induced By Nanosecond Laser Ablation Of Titanium Target

    SciTech Connect

    Hamadi, F.; Amara, E. H.; Mezaoui, D.

    2008-09-23

    A numerical modelling describing a pulsed nanosecond laser interaction with a titanium target is presented, resulting in the study of the plume expansion in vacuum or in background gas, using the species transport model available in Fluent computational fluid dynamics code. The heat transfers in the solid target and the molten material are modeled using an enthalpy formulation for the solid-liquid phase changing. The effect of laser fluences is investigated, and results are presented as a function of time. Moreover, the plasma or the vapour dynamics is calculated by solving a set of Navier-Stokes equations. The plasma absorption by inverse Bremsstrahlung, the ionization states and the density profiles of the Titanium ions and electrons in the plume are interactively included in the Fluent calculation process by the mean of User Defined Functions (UDFs) used in order to take into account the specificity of our problem. The ionization is computed by solving the Saha-Eggert equation assuming local thermodynamic equilibrium (LTE) conditions.

  1. Breakdown in a bulk of transparent solids under irradiation of a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Rehman, Z. U.; Grigorov, Y. V.; Tran, K. A.; Janulewicz, K. A.

    2014-10-01

    A single pulse of a nanosecond laser was tightly focused in the bulk of transparent materials (soda lime glass, borosilicate glass, fused silica , sapphire and Gorilla Glass) to a beam spot diameter of ~ 2.1μm. A value of the total energy absorbed in the materials was measured with corrections for the transmitted, scattered and reflected components of the incident energy. It was found that 3-11% of the incident radiation was scattered but the total absorption still achieved a very high level of up to 88%. Absorptance dependence on the incident fluence was reasonably approximated by the sigmoidal Hill function. Here we suggest using this analytical description to identify empirical intrinsic laser-induced breakdown threshold (LIBT). Optical damage threshold (ODT) was identified by optical inspection. The results for some materials suggest significantly lower breakdown threshold than that reported earlier for more loosely focused beams. A study of the damage area morphology with a scanning electron microscope (SEM) and a high resolution transmission microscope (HRTEM) revealed existence of the shock waves-affected area with a localized nano-crystallization. Spectroscopic study of the light emission accompanying breakdown showed typical quasi-continuum emission with temperature as high as 8917K (0.8 eV).

  2. Production of picosecond, kilojoule, petawatt laser pulses via Raman amplification of nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Trines, R.; Bingham, R.; Norreys, P.; Fiúza, F.; Fonseca, R. A.; Silva, L. O.; Cairns, R. A.

    2011-10-01

    The demonstration of fast-ignition (FI) inertial confinement fusion (ICF) requires the delivery of 40 kJ - 100 kJ of laser energy to the hot spot within 16 ps. In addition, third harmonic conversion to 351 nm is needed to optimize Iλ2 to obtain the correct hot electron energy. High-energy picosecond petawatt beams at 351 nm are difficult to generate using conventional solid-state laser systems. Previous studies of Raman amplification concentrated on maximizing the intensity and power of femtosecond pulses [Trines et al., Nature Physics (2010)]. Here we present particle-in-cell simulations and analytic theory that confirm that Raman amplification of high-energy nanosecond pulses in plasma can generate petawatt peak power pulses of picosecond duration with high efficiency (up to 60%), even at 351 nm wavelength. This scheme provides a potential new route for the realization of fast ignition ICF in the laboratory, as well as access to wide range of other high energy density physics research applications. This work was supported by STFC's CLF and CfFP, by EPSRC through grant EP/G04239X/1 and by FCT (Portugal) through grants PTDC/FIS/66823/2006 and SFRH/BD/38952/2007.

  3. Production of nanometer-size GaAs nanocristals by nanosecond laser ablation in liquid.

    PubMed

    Abderrafi, Kamal; Jiménez, Ernesto; Ben, Teresa; Molina, Sergio I; Ibáñez, Rafael; Chirvony, Vladimir; Martínez-Pastor, Juan P

    2012-08-01

    This paper reports the formation and characterization of spherical GaAs quantum dots obtained by nanosecond pulsed laser ablation in a liquid (ethanol or methanol). The produced bare GaAs nanoparticles demonstrate rather narrow size distribution which depends on the applied laser power density (from 4.25 to 13.9 J/cm2 in our experiments) and is as low as 2.5 nm for the highest power used. The absolute value of the average diameter also decreases significantly, from 13.7 to 8.7 nm, as the laser power increases in this interval. Due to the narrow nanoparticle size dispersion achieved at the highest laser powers two absorption band edges are clearly distinguishable at about 1.72 and 3.15 eV which are ascribed to E0 and E1 effective optical transitions, respectively. A comparison of the energies with those known for bulk GaAs allows one to conclude that an average diameter of the investigated GaAs nanoparticles is close to 10 nm, i.e., they are quantum dots. High resolution transmission electron microscopy (HRTEM) images show that the bare GaAs nanoparticles are nanocrystalline, but many of them exhibit single/multiple twin boundary defects or even polycrystallinity. The formation of the GaAs crystalline core capped with a SiO2 shell was demonstrated by HRTEM and energy dispersive X-ray (EDX) spectroscopy. Effective band edges can be better distinguished in SiO2 capped nanoparticles than in bare ones, In both cases the band edges are correlated with size quantum confinement effect.

  4. Rhodamine B as an optical thermometer in cells focally exposed to infrared laser light or nanosecond pulsed electric fields

    PubMed Central

    Moreau, David; Lefort, Claire; Burke, Ryan; Leveque, Philippe; O’Connor, Rodney P.

    2015-01-01

    The temperature-dependent fluorescence property of Rhodamine B was used to measure changes in temperature at the cellular level induced by either infrared laser light exposure or high intensity, ultrashort pulsed electric fields. The thermal impact of these stimuli were demonstrated at the cellular level in time and contrasted with the change in temperature observed in the extracellular bath. The method takes advantage of the temperature sensitivity of the fluorescent dye Rhodamine B which has a quantum yield linearly dependent on temperature. The thermal effects of different temporal pulse applications of infrared laser light exposure and of nanosecond pulsed electric fields were investigated. The temperature increase due to the application of nanosecond pulsed electric fields was demonstrated at the cellular level. PMID:26504658

  5. Nonlinear optical absorption of ZnO doped with copper nanoparticles in the picosecond and nanosecond pulse laser field.

    PubMed

    Ryasnyansky, Aleksandr; Palpant, Bruno; Debrus, Solange; Ganeev, Rashid; Stepanov, Andrey; Can, Nurdogan; Buchal, Christoph; Uysal, Sibel

    2005-05-10

    The nonlinear absorption of nanocomposite layers based on ZnO implanted with Cu+ ions with an energy of 160 keV in implantation doses of 10(16) and 10(17) ions/cm2 was investigated. The values of the nonlinear absorption coefficient were measured by the Z-scan method at a wavelength of 532 nm by use of nanosecond and picosecond laser pulses. Possible optical applications of these materials are discussed.

  6. Non-contact acoustic tests based on nanosecond laser ablation: Generation of a pulse sound source with a small amplitude

    NASA Astrophysics Data System (ADS)

    Hosoya, Naoki; Kajiwara, Itsuro; Inoue, Tatsuo; Umenai, Koh

    2014-09-01

    A method to generate a pulse sound source for acoustic tests based on nanosecond laser ablation with a plasma plume is discussed. Irradiating a solid surface with a laser beam expands a high-temperature plasma plume composed of free electrons, ionized atoms, etc. at a high velocity throughout ambient air. The shockwave generated by the plasma plume becomes the pulse sound source. A laser ablation sound source has two features. Because laser ablation is induced when the laser fluence reaches 1012-1014 W/m2, which is less than that for laser-induced breakdown (1015 W/m2), laser ablation can generate a lower sound pressure, and the sound source has a hemispherical radiation pattern on the surface where laser ablation is generated. Additionally, another feature is that laser-induced breakdown sound sources can fluctuate, whereas laser ablation sound sources do not because laser ablation is produced at a laser beam-irradiation point. We validate this laser ablation method for acoustic tests by comparing the measured and theoretical resonant frequencies of an impedance tube.

  7. Temperature dependence of nanosecond laser pulse thresholds of melanosome and microsphere microcavitation

    NASA Astrophysics Data System (ADS)

    Schmidt, Morgan S.; Kennedy, Paul K.; Noojin, Gary D.; Thomas, Robert J.; Rockwell, Benjamin A.

    2016-01-01

    Melanosome microcavitation is the threshold-level retinal pigment epithelium (RPE) damage mechanism for nanosecond (ns) pulse exposures in the visible and near-infrared (NIR). Thresholds for microcavitation of isolated bovine RPE melanosomes were determined as a function of temperature (20 to 85°C) using single ns laser pulses at 532 and 1064 nm. Melanosomes were irradiated using a 1064-nm Q-switched Nd:YAG (doubled for 532-nm irradiation). For comparison to melanosome data, a similar temperature (20 to 65°C) dependence study was also performed for 532 nm, ns pulse exposures of black polystyrene microbeads. Results indicated a decrease in the microcavitation average radiant exposure threshold with increasing sample temperature for both 532- and 1064-nm single pulse exposures of melanosomes and microbeads. Threshold data and extrapolated nucleation temperatures were used to estimate melanosome absorption coefficients in the visible and NIR, and microbead absorption coefficients in the visible, indicating that melanin is a better absorber of visible light than black polystyrene. The NIR melanosome absorption coefficients ranged from 3713 cm-1 at 800 nm to 222 cm-1 at 1319 nm. These data represent the first temperature-dependent melanosome microcavitation study in the NIR and provide additional information for understanding melanosome microcavitation threshold dependence on wavelength and ambient temperature.

  8. Hybrid-modality ocular imaging using a clinical ultrasound system and nanosecond pulsed laser

    PubMed Central

    Lim, Hoong-Ta; Matham, Murukeshan Vadakke

    2015-01-01

    Abstract. Hybrid optical modality imaging is a special type of multimodality imaging significantly used in the recent past in order to harness the strengths of different imaging methods as well as to furnish complementary information beyond that provided by any individual method. We present a hybrid-modality imaging system based on a commercial clinical ultrasound imaging (USI) system using a linear array ultrasound transducer (UST) and a tunable nanosecond pulsed laser as the source. The integrated system uses photoacoustic imaging (PAI) and USI for ocular imaging to provide the complementary absorption and structural information of the eye. In this system, B-mode images from PAI and USI are acquired at 10 Hz and about 40 Hz, respectively. A linear array UST makes the system much faster compared to other ocular imaging systems using a single-element UST to form B-mode images. The results show that the proposed instrumentation is able to incorporate PAI and USI in a single setup. The feasibility and efficiency of this developed probe system was illustrated by using enucleated pig eyes as test samples. It was demonstrated that PAI could successfully capture photoacoustic signals from the iris, anterior lens surface, and posterior pole, while USI could accomplish the mapping of the eye to reveal the structures like the cornea, anterior chamber, lens, iris, and posterior pole. This system and the proposed methodology are expected to enable ocular disease diagnostic applications and can be used as a preclinical imaging system. PMID:26835487

  9. Stoichiometric analysis of ammonium nitrate and ammonium perchlorate with nanosecond laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Sreedhar, S.; Rao, S. Venugopal; Kiran, P. Prem; Tewari, Surya P.; Kumar, G. Manoj

    2010-04-01

    We present our results on the stoichiometric analysis of ammonium nitrate (AN) and ammonium Perchlorate (AP) studied using laser induced breakdown spectroscopy (LIBS) with nanosecond pulses. The LIBS spectra collected for AP and AN, without any gating and using a high resolution spectrometer, exhibited characteristic lines corresponding to O, N, H, C, and K. The Oxygen line at 777.38 nm and three Nitrogen lines (N1, N2, N3) at 742.54 nm, 744.64 nm, 747.12 nm were used for evaluating the Oxygen/Nitrogen ratios. The intensities were calculated using area under the peaks and normalized to their respective transition probabilities and statistical weights. The O/N1 ratios estimated from the LIBS spectra were ~4.94 and ~5.11 for AP and O/N3 ratios were ~1.64 and ~1.47 for AN obtained from two independent measurements. The intensity ratios show good agreement with the actual stoichiometric ratios - four for AP and one for AN.

  10. Laser-assisted vacuum arc extreme ultraviolet source: a comparison of picosecond and nanosecond laser triggering

    NASA Astrophysics Data System (ADS)

    Beyene, Girum A.; Tobin, Isaac; Juschkin, Larissa; Hayden, Patrick; O’Sullivan, Gerry; Sokell, Emma; Zakharov, Vassily S.; Zakharov, Sergey V.; O’Reilly, Fergal

    2016-06-01

    Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable energy from 1 to 100 mJ per pulse. The impact of shortening the laser pulse from 7 ns to 170 ps on the EUV generation has been investigated in detail. The use of ps pulses resulted in an increase in emission of EUV radiation. With a fixed discharge energy of ~4 J, the EUV conversion efficiency tends to plateau at ~2.4  ±  0.25% for the ps laser pulses, while for the ns pulses, it saturates at ~1.7  ±  0.3%. Under similar discharge and laser energy conditions, operating the EUV source with the ps-triggering resulted also in narrower spectral profiles of the emission in comparison to ns-triggering. The results indicate an advantage in using ps-triggering in laser-assisted discharges to produce brighter plasmas required for applications such as metrology.

  11. White-light emission from solid carbon in aqueous solution during hydrogen generation induced by nanosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Akimoto, Ikuko; Yamamoto, Shota; Maeda, Kosuke

    2016-07-01

    We previously discovered a novel method of hydrogen generation from high-grade charcoal in an aqueous solution using nanosecond laser pulse irradiation. In this paper, white-light emission during this reaction is reported: A broad spectrum over the visible range is observed above a threshold excitation energy density. The white-light emission is a simultaneous product of the hydrogen generation reaction and is attributed to blackbody radiation in accordance with Planck's Law at a temperature above 3800 K. Consequently, we propose that hydrogen generation induced by laser irradiation proceeds similarly to classical coal gasification, which features reactions at high pressure and high temperature.

  12. On the formation of nanostructures on a CdTe surface, stimulated by surface acoustic waves under nanosecond laser irradiation

    SciTech Connect

    Vlasenko, A. I.; Baidullaeva, A.; Veleschuk, V. P. Mozol, P. E.; Boiko, N. I.; Litvin, O. S.

    2015-02-15

    The formation of nanoscale structures in the unirradiated part of a p-CdTe crystal surface irradiated by a nanosecond ruby laser is revealed and investigated. It is shown that their formation is caused by the effect of the long-range action of a laser pulse with an intensity of I = 20 MW/cm{sup 2}. Nanoscale-structure formation is explained by the influence of the pressure gradient of the surface acoustic wave, in particular, within the “vacancy-pump” mechanism on the surface.

  13. Gene transfer of human hepatocyte growth factor by the use of nanosecond pulsed laser-induced stress waves

    NASA Astrophysics Data System (ADS)

    Terakawa, Mitsuhiro; Sato, Shunichi; Saitoh, Daizoh; Hasegawa, Makoto; Ashida, Hiroshi; Okano, Hideyuki; Obara, Minoru

    2006-05-01

    We successfully delivered a therapeutic vector construct, which carries hepatocyte growth factor (HGF) gene, to rat skin in vivo. After HGF expression vector had been intradermally injected to rat skin, LISWs were generated by irradiating the laser target put on the rat skin with nanosecond pulses from the second harmonics (532 nm) of a Q-switched Nd:YAG laser. Concentration of HGF protein increased by a factor of four by the application of LISWs when compared with that of control samples without LISW application. We also investigated the effects of LISWs on the integrity of plasmid DNA.

  14. Through nanohole formation in thin metallic film by single nanosecond laser pulses using optical dielectric apertureless probe.

    PubMed

    Kulchin, Y N; Vitrik, O B; Kuchmizhak, A A; Nepomnyashchii, A V; Savchuk, A G; Ionin, A A; Kudryashov, S I; Makarov, S V

    2013-05-01

    Separate nanoholes with the minimum size down to 35 nm (~λ/15) and nanohole arrays with the hole size about 100 nm (~λ/5) were fabricated in a 50 nm optically "thick" Au/Pd film, using single 532 nm pump nanosecond laser pulses focused to diffraction-limited spots by a specially designed apertureless dielectric fiber probe. Nanohole fabrication in the metallic film was found to result from lateral heat diffusion and center-symmetrical lateral expulsion of the melt by its vapor recoil pressure. The optimized apertureless dielectric microprobe was demonstrated to enable laser fabrication of deep through nanoholes.

  15. Fiber grating compression of giant-chirped nanosecond pulses from an ultra-long nanotube mode-locked fiber laser.

    PubMed

    Woodward, R I; Kelleher, E J R; Runcorn, T H; Loranger, S; Popa, D; Wittwer, V J; Ferrari, A C; Popov, S V; Kashyap, R; Taylor, J R

    2015-02-01

    We demonstrate that the giant chirp of coherent, nanosecond pulses generated in an 846 m long, all-normal dispersion, nanotube mode-locked fiber laser can be compensated using a chirped fiber Bragg grating compressor. Linear compression to 11 ps is reported, corresponding to an extreme compression factor of ∼100. Experimental results are supported by numerical modeling, which is also used to probe the limits of this technique. Our results unequivocally conclude that ultra-long cavity fiber lasers can support stable dissipative soliton attractors and highlight the design simplicity for pulse-energy scaling through cavity elongation.

  16. Study of micro/nanostructures formed by a nanosecond laser in gaseous environments for stainless steel surface coloring

    NASA Astrophysics Data System (ADS)

    Luo, Fangfang; Ong, Weili; Guan, Yingchun; Li, Fengping; Sun, Shufeng; Lim, G. C.; Hong, Minghui

    2015-02-01

    Micro/nanostructures are fabricated on the stainless steel surfaces by a nanosecond laser in different gaseous environments, including air, O2, N2 and Ar. Our results indicate that the dimensional feature of the micro/nanostructures is greatly affected by laser scanning speed as well as gaseous environment. The chemical composition of the structures can be flexibly adjusted by laser processing parameters. Oxygen-rich environment is found to boost the growth of the nanostructures. The coloring by the laser processing can be achieved on the laser treated stainless steel surfaces. The multicolor effect on the surfaces is found to be attributed to both feature dimension and chemical composition of the structures. The coloring of the metal surfaces has promising applications in surface marking and code identifying.

  17. Time-resolved analysis of thickness-dependent dewetting and ablation of silver films upon nanosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Qi, Dongfeng; Paeng, Dongwoo; Yeo, Junyeob; Kim, Eunpa; Wang, Letian; Chen, Songyan; Grigoropoulos, Costas P.

    2016-05-01

    Nanosecond pulsed laser dewetting and ablation of thin silver films is investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 5 ns temporal width are irradiated on silver films of different thicknesses (50 nm, 80 nm, and 350 nm). Below the ablation threshold, it is observed that the dewetting process does not conclude until 630 ns after the laser irradiation for all samples, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter at about 700 ns following the laser pulse exposure. In addition to these features, droplet fingers are superposed upon irradiation of 350-nm thick silver films with higher intensity.

  18. Double-pulse machining as a technique for the enhancement of material removal rates in laser machining of metals

    SciTech Connect

    Forsman, A.C.; Banks, P.S.; Perry, M.D.; Campbell, E.M.; Dodell, A.L.; Armas, M.S.

    2005-08-01

    Several nanosecond 0.53-{mu}m laser pulses separated by several tens of nanoseconds have been shown to significantly enhance (three to ten times) material removal rates while minimizing redeposition and heat-affected zones. Economic, high-quality, high-aspect ratio holes (>10:1) in metals are produced as a result. A phenomenological model whereby the second laser pulse interacts with the ejecta produced by the first laser pulse and in close proximity to the material surface is consistent with the observations. Incident laser wavelengths of 1.05 and 0.35 {mu}m also benefit from this pulse format.

  19. Threshold characteristics of ultraviolet and near infrared nanosecond laser induced plasmas

    NASA Astrophysics Data System (ADS)

    Dumitrache, Ciprian; Limbach, Christopher M.; Yalin, Azer P.

    2016-09-01

    The present contribution compares the energy absorption, optical emission, temperature, and fluid dynamics of ultraviolet (UV) λ = 266 nm and near infrared (NIR) λ = 1064 nm nanosecond laser induced plasmas in ambient air. For UV pulses at the conditions studied, energy absorption by the plasmas increases relatively gradually with laser pulse energy starting at delivered energy of E ˜ 8 mJ. Corresponding measurements of plasma luminosity show that the absorption of UV radiation does not necessarily result in visible plasma emission. For the NIR induced plasmas, the energy absorption profile is far more abrupt and begins at ˜55 mJ. In contrast with UV, the absorption of NIR radiation is always accompanied by intense optical emission. The temperatures of both types of plasma have been measured with Rayleigh scattering thermometry (at times after the Thomson signal sufficiently diminishes). The UV plasmas can attain a wider range of temperatures, including lower temperatures, depending on the pulse energy (e.g., T ˜ 400-2000 K for E ˜ 7-35 mJ at Δt = 10 μs after the pulse) while the NIR plasmas show only hotter temperatures (e.g., T ˜ 12 000 K for E = 75 mJ at Δt = 10 μs after the pulse) as is consistent with the literature. Differences in the fluid dynamics for UV versus NIR pulses are shown with Schlieren imaging. The contrast in the UV and NIR plasma threshold behavior is attributed to differing roles of avalanche ionization and multiphoton ionization as is also illustrated by a simple numerical model.

  20. Selective removal of cholesterol ester in atherosclerotic plaque using nanosecond pulsed laser at 5.75 μm

    NASA Astrophysics Data System (ADS)

    Ishii, K.; Tsukimoto, H.; Hazama, H.; Awazu, K.

    2008-02-01

    Laser angioplasty, for example XeCl excimer laser angioplasty, has gained more attention in addition to conventional methods of surgical and interventional treatment of atherosclerotic diseases such as bypass operation and balloon dilatation. Low degrees of thermal damage after ablation of atherosclerotic lesions have been achieved by XeCl excimer laser at 308 nm. However, in most cases, laser ablation is not selective and normal arterial wall is also damaged. To avoid complications such as severe dissections or perforation of the arterial wall in an angioplasty, a laser light source with high ablation efficiency but low arterial wall injury is desirable. At atherosclerotic lesions, cholesterol accumulates on the tunica intima by establishing an ester bond with fatty acids such as oleic acid, and thus cholesterol ester is the main component of atherosclerotic plaques. Mid-infrared pulsed laser at 5.75 μm is selectively well absorbed in C=O stretching vibration mode of ester bonds. The purpose of this study is to determine the effectiveness of nanosecond pulsed laser at 5.75 μm irradiation of cholesterol ester in atherosclerotic plaques. In this study, we used a mid-infrared tunable solid-state laser which is operated by difference frequency generation method, with a wavelength of 5.75 μm, a pulse width of 5 nsec and a pulse duration of 10 Hz. It was confirmed that non-invasive interaction to normal thoracic aortas could be induce by the parameters, the wavelength of 5.75 μm, the average power densities of 35 W/cm2 and the irradiation time under 10 sec. This study shows that nanosecond pulsed laser irradiations at 5.75 μm provide an alternative laser light source as an effectively cutting, less traumatic tool for removal of atherosclerotic plaque.

  1. Permeabilisation de membranes cellulaires a l'aide d'un laser nanoseconde amplifie par nanoparticules plasmoniques

    NASA Astrophysics Data System (ADS)

    St-Louis Lalonde, Bastien

    The plasmic membrane of eukaryot cells provides a selective permeability between the cytoplasm and the external environment. It regulates the passage of ions (O2, N 2, K, etc...) and molecules (H2 O, C2H6 O, etc...) by mechanisms like passive diffusion and active transport. In various fields like molecular biology or drug development, it is sometimes needed to bypass this selective permeability to introduce external molecules that are normally impermeable to cell membrane. Examples of external molecules may be DNA plasmid, RNA segment or drugs. We propose a method based on laser amplification by plasmonic nanoparticles to overcome this biological barrier. This non invasive method increases the membrane permeability of a large number of cells in a short time. Optoporation by laser amplified with plasmonic nanoparticles consists of pulsed laser irradiation on cells that have been previously incubated with gold nanoparticles (AuNPs). The laser-AuNPs interactions will create a cavitation bubble which in turn will decrease the membrane permeability by disrupting the bilipid layer arrangement. Molecules in the external medium may then penetrate inside the cells and under the right experimental conditions, the cells will rapidly reseal their membrane and continue living without nefast effects. The feasibility of high throughput optical perforation amplified by plasmonic nanoparticles have been tested with a nanosecond pulsed laser working at 532 nm and 1064 nm. The plasma membrane of cancerous human fibroblast (melanoma wm278) have been successfully perforated while keeping an excellent viability rate. Up to 30% of cells are perforated in which the Lucifer Yellow fluorophore have been incorporated. The viability 2 h after the treatment was evaluated by PI exclusion and the long term vitality was tested by MTT essay. Under optimal conditions at 532 nm, the 2 h viability is 84% and the vitality start at 64% for 2h and reaches 88% after 72 h. With 1064 nm pusles, the 2 h

  2. Laser Patterning of CIGS thin Films with 1550 nm Nanosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Ehrhardt, Martin; Lorenz, Pierre; Bayer, Lukas; Zagoranskiy, Igor; Zimmer, Klaus

    The results of laser scribing experiments of CIGS thin films deposited on Mo-coated stainless steel sheets, using laser pulses with a wavelength of 1550 nm and a pulse duration of 6 ns, are presented in this study. It is shown that a removal of the CIGS from the Mo film is possible without edge melting of the CIGS or damaging of the Mo. The critical parameter for inducing the delamination lift-off process of the CIGS from the Mo was identified to be the scribing speed of the laser. In dependence on the laser parameters two different material removal processes were found. For a low pulse overlap the laser pulse penetrates the CIGS film and is absorbed in the interface between the CIGS and the Mo causing a lift-off process of the CIGS from the Mo back contact. For a high pulse overlap an ablation process starting from the top side of the CIGS film was found. The composition and morphology of the sample material after the laser patterning were analysed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy.

  3. 1.1 MW peak power in doubly QML composite Nd:YVO4/Nd:YVO4/Nd:YVO4/KTP sub-nanosecond green laser with EO and Bi-GaAs.

    PubMed

    Li, Shixia; Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Li, Xiangyang; Qiao, Hui

    2016-02-22

    By simultaneously employing electro-optic (EO) modulator and Bi-doped GaAs, dual-loss-modulated Q-switched and mode-locked (QML) multi-segment composite Nd:YVO4/Nd:YVO4/Nd:YVO4/KTP sub-nanosecond green laser is demonstrated with low repetition rate and high peak power. When the incident pump power is up to 6.93 W, only one mode-locking pulse underneath a Q-switching envelope is generated with sub-nanosecond pulse duration at one kilohertz repetition rate. An average output power of 445 mW and a pulse duration of 399 ps are obtained with the incident pump power of 11.13 W, corresponding to a peak power of 1.115 MW which is the highest one in doubly QML sub-nanosecond green laser by now. The laser characteristics are better than those obtained with EO and GaAs. The experimental results indicate that Bi-GaAs is a promising saturable absorber for dual-loss-modulated QML laser.

  4. Calcium detection of human hair and nail by the nanosecond time-gated spectroscopy of laser-ablation plume

    NASA Astrophysics Data System (ADS)

    Haruna, Masamitsu; Ohmi, Masato; Nakamura, Mitsuo; Morimoto, Shigeto

    2000-04-01

    We demonstrate the nanosecond time-gated spectroscopy of plume in laser ablation of biological tissue, which allows us to detect calcium (Ca) with high sensitivity by the use of either a UV or a near-IR laser pulse. Clear and sharp peaks of Ca+ appear in the luminescence spectrum of laser-ablation plume although the Ca content is only 0.1 percent in human hair and nail. Luminescence peaks of sodium atom (Na) and ionized carbon are also detectable. This specific spectroscopy is low invasive because a single low-energy laser pulse illuminates the tissue sample, and it does not require any poisonous sensititizers like fluorescence dye. This method, therefore, is a promising candidate for optical biopsy in the near future. In particular, Ca detection of human hair may lead to new diagnosis, including monitor of daily intake of Ca and a screening diagnosis of osteoporosis.

  5. All-fiber-integrated linearly polarized fiber laser delivering 476  μJ, 50  kHz, nanosecond pulses for ultrasonic generation.

    PubMed

    Zhang, Pengfei; Xu, Xiaodong; Yu, Hailong; Su, Rongtao; Wang, Xiaolin; Yang, Lijia

    2016-05-10

    We demonstrate a high-energy linearly polarized pulsed fiber laser for ultrasonic generation based on a master oscillator power amplification (MOPA) scheme, which delivers nanosecond pulses with duration of 4.8 ns and pulse energy of 476 μJ at the repetition rate of 50 kHz. The MOPA is seeded by a gain switch semiconductor laser diode at 1064 nm. In the pre-amplification stages, a double-pass amplification structure is designed and successfully applied to amplify the low-power seed laser for the consideration of suppressing amplified spontaneous emission, decreasing the number of amplification stages, and reducing the nonlinear effects. A highly ytterbium-doped fiber is utilized in the main amplifier to shorten the fiber length and reduce the fiber nonlinearity. The average power is finally boosted to 23.8 W with corresponding optical-to-optical efficiency of 66.9% and a polarization extinction rate of ∼10.5  dB. The corresponding peak power is calculated to be 87.1 kW. Finally, the established laser system is successfully used for ultrasonic generation based on a line excitation configuration and grating excitation configuration, and clear surface acoustic wave signals are detected. Many potential applications in laser ultrasonics can be foreseen. PMID:27168281

  6. Generation of high-power nanosecond pulses from laser diode-pumped Nd:YAG lasers

    NASA Technical Reports Server (NTRS)

    Chan, Kinpui

    1988-01-01

    Simulation results are used to compare the pulse energy levels and pulse energy widths that can be achieved with LD-pumped Nd:YAG lasers for both the pulse-transmission mode (PTM) and pulse-reflection mode (PRM) Q-switching methods for pulse energy levels up to hundreds of microjoules and pulse widths as short as 1 ns. It is shown that high-power pulses with pulse widths as short as 1 ns can be generated with PTM Q-switched in LD-pumped Nd:YAG lasers. With the PRM Q-switching method, pulse widths as short as 2 ns and pulse energy at the level of a few hundred microjoules can also be achieved but require pumping with 8-10-mJ AlGaAs laser diode arrays.

  7. Efficient intracellular delivery of molecules with high cell viability using nanosecond-pulsed laser-activated carbon nanoparticles.

    PubMed

    Sengupta, Aritra; Kelly, Sean C; Dwivedi, Nishant; Thadhani, Naresh; Prausnitz, Mark R

    2014-03-25

    Conventional physical and chemical methods that efficiently deliver molecules into cells are often associated with low cell viability. In this study, we evaluated the cellular effects of carbon nanoparticles believed to emit photoacoustic waves due to nanosecond-pulse laser activation to test the hypothesis that this method could achieve efficient intracellular delivery while maintaining high cell viability. Suspensions of DU145 human prostate carcinoma cells, carbon black (CB) nanoparticles, and calcein were exposed to 5-9 ns long laser pulses of near-infrared (1064 nm wavelength) light and then analyzed by flow cytometry for intracellular uptake of calcein and cell viability by propidium iodide staining. We found that intracellular uptake increased and in some cases saturated at high levels with only small losses in cell viability as a result of increasing laser fluence, laser exposure time, and as a unifying parameter, the total laser energy. Changing interpulse spacing between 0.1 and 10 s intervals showed no significant change in bioeffects, suggesting that the effects of each pulse were independent when spaced by at least 0.1 s intervals. Pretreatment of CB nanoparticles to intense laser exposure followed by mixing with cells also had no significant effect on uptake or viability. Similar uptake and viability were seen when CB nanoparticles were substituted with India ink, when DU145 cells were substituted with H9c2 rat cardiomyoblast cells, and when calcein was substituted with FITC-dextran. The best laser exposure conditions tested led to 88% of cells with intracellular uptake and close to 100% viability, indicating that nanosecond-pulse laser-activated carbon nanoparticles can achieve efficient intracellular delivery while maintaining high cell viability.

  8. Efficient Intracellular Delivery of Molecules with High Cell Viability Using Nanosecond-Pulsed Laser-Activated Carbon Nanoparticles

    PubMed Central

    2015-01-01

    Conventional physical and chemical methods that efficiently deliver molecules into cells are often associated with low cell viability. In this study, we evaluated the cellular effects of carbon nanoparticles believed to emit photoacoustic waves due to nanosecond-pulse laser activation to test the hypothesis that this method could achieve efficient intracellular delivery while maintaining high cell viability. Suspensions of DU145 human prostate carcinoma cells, carbon black (CB) nanoparticles, and calcein were exposed to 5–9 ns long laser pulses of near-infrared (1064 nm wavelength) light and then analyzed by flow cytometry for intracellular uptake of calcein and cell viability by propidium iodide staining. We found that intracellular uptake increased and in some cases saturated at high levels with only small losses in cell viability as a result of increasing laser fluence, laser exposure time, and as a unifying parameter, the total laser energy. Changing interpulse spacing between 0.1 and 10 s intervals showed no significant change in bioeffects, suggesting that the effects of each pulse were independent when spaced by at least 0.1 s intervals. Pretreatment of CB nanoparticles to intense laser exposure followed by mixing with cells also had no significant effect on uptake or viability. Similar uptake and viability were seen when CB nanoparticles were substituted with India ink, when DU145 cells were substituted with H9c2 rat cardiomyoblast cells, and when calcein was substituted with FITC-dextran. The best laser exposure conditions tested led to 88% of cells with intracellular uptake and close to 100% viability, indicating that nanosecond-pulse laser-activated carbon nanoparticles can achieve efficient intracellular delivery while maintaining high cell viability. PMID:24547946

  9. Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2013-11-01

    In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.

  10. Heating and ablation of tokamak graphite by pulsed nanosecond Nd-YAG lasers

    SciTech Connect

    Semerok, A.; Fomichev, S. V.; Weulersse, J.-M.; Brygo, F.; Thro, P.-Y.; Grisolia, C.

    2007-04-15

    The results on laser heating and ablation of graphite tiles of thermonuclear tokamaks are presented. Two pulsed Nd-YAG lasers (20 Hz repetition rate, 5 ns pulse duration and 10 kHz repetition rate, 100 ns pulse duration) were applied for ablation measurements. The ablation thresholds (1.0{+-}0.5 J/cm{sup 2} for 5 ns and 2.5{+-}0.5 J/cm{sup 2} for 100 ns laser pulses) were determined for the Tore Supra tokamak graphite tiles (backside) nonexposed to plasma. The high repetition rate Nd-YAG laser (10 kHz, 100 ns pulse duration) and the developed pyrometer system were applied for graphite heating measurements. Some unexpected features of laser heating of the graphite surface were observed. They were explained by the presence of a thin surface layer with the properties different from those of the bulk graphite. The theoretical models of laser heating and near-threshold ablation of graphite with imperfectly adhered layer were developed to interpret the experimental results.

  11. A unified model to determine the energy partitioning between target and plasma in nanosecond laser ablation of silicon

    SciTech Connect

    Galasso, G.; Kaltenbacher, M.; Tomaselli, A.; Scarpa, D.

    2015-03-28

    In semiconductor industry, pulsed nanosecond lasers are widely applied for the separation of silicon wafers. Here, the high intensities employed activate a cascade of complex multi-physical and multi-phase mechanisms, which finally result in the formation of a laser induced plasma, shielding the target from the incoming laser beam. Such induced plasma plume, by preventing the laser to effectively reach the target, reduces the overall efficiency and controllability of the ablation process. Modelling can be a useful tool in the optimization of industrial laser applications, allowing a deeper understanding of the way the laser energy distributes between target and induced plasma. Nevertheless, the highly multi-physical character of laser ablation poses serious challenges on the implementation of the various mechanisms underlying the process within a common modelling framework. A novel strategy is here proposed in order to simulate in a simplified, yet physically consistent way, a typical industrial application as laser ablation of silicon wafers. Reasonable agreement with experimental findings is obtained. Three fundamental mechanisms have been identified as the main factors influencing the accuracy of the numerical predictions: the transition from evaporative to volumetric mass removal occurring at critical temperature, the collisional and radiative processes underlying the initial plasma formation stage and the increased impact of the liquid ejection mechanism when a sub-millimeter laser footprint is used.

  12. Selective removal of cholesteryl ester in atherosclerotic plaque by nanosecond pulsed laser at 5.75 μm for less-invasive laser angioplasty

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Tsukimoto, Hideki; Hazama, Hisanao; Awazu, Kunio

    2009-02-01

    Laser angioplasty, for example XeCl excimer laser coronary angioplasty (ELCA), has gained more attention for the treatment of serious stenosis blocked by plaque. Low degrees of thermal damage after ablation of atherosclerotic plaques have been achieved by ELCA. However, the large number of risks associated with the procedure, for example, dissections or perforations of the coronary arteries limits its application. A laser treatment technique with high ablation efficiency but low arterial wall injury is desirable. Mid-infrared laser with a wavelength of 5.75 µm is selectively well absorbed in C=O stretching vibration mode of ester bonds in cholesteryl ester. The purpose of this study is to determine the effectiveness of nanosecond pulsed laser at 5.75 µm irradiation for atherosclerotic plaques. We made a study on the irradiation effect to atherosclerotic plaques in tunica intima in a wet condition. In this study, we used a mid-infrared tunable solid-state laser which is operated by difference-frequency generation, with a wavelength of 5.75 µm, a pulse width of 5 ns and a pulse duration of 10 Hz as a treatment light source, and a thoracic aorta of WHHLMI rabbit as an atherosclerosis model. As a result, less-invasive interaction parameters for removing atherosclerotic plaques were confirmed. This study shows that the nanosecond pulsed laser irradiation at 5.75 µm is a powerful tool for selective and less-invasive treatment of atherosclerotic plaques.

  13. Optimization of the dynamic wavefront control of a pulsed kilojoule/nanosecond-petawatt laser facility.

    PubMed

    Zou, Ji-Ping; Sautivet, Anne-Marie; Fils, Jérôme; Martin, Luc; Abdeli, Kahina; Sauteret, Christian; Wattellier, Benoit

    2008-02-10

    The wavefront aberrations in a large-scale, flash-lamp-pumped, high-energy, high-power glass laser system can degrade considerably the quality of the final focal spot, and limit severely the repetition rate. The various aberrations induced on the Laboratoire pour l'Utilisation des Lasers Intenses (LULI), laser facility (LULI2000) throughout the amplification are identified and analyzed in detail. Based on these analyses, an optimized procedure for dynamic wavefront control is then designed and implemented. The lower-order Zernike aberrations can be effectively reduced by combining an adaptive-optics setup, comprising a bimorph deformable mirror and a four-wave lateral shearing interferometer, with a precise alignment system. This enables the laser chain to produce a reproducible focal spot close to the diffraction limit (Strehl ratio approximately 0.7). This allows also to increase the repetition rate, initially limited by the recovery time of the laser amplifiers, by a factor of 2 (one shot per hour). The proposed procedure provides an attractive alternative for dynamic correction of the wavefront aberrations of a laser facility as complex as the LULI2000. PMID:18268782

  14. Optimization of the dynamic wavefront control of a pulsed kilojoule/nanosecond-petawatt laser facility

    NASA Astrophysics Data System (ADS)

    Zou, Ji-Ping; Sautivet, Anne-Marie; Fils, Jérôme; Martin, Luc; Abdeli, Kahina; Sauteret, Christian; Wattellier, Benoit

    2008-02-01

    The wavefront aberrations in a large-scale, flash-lamp-pumped, high-energy, high-power glass laser system can degrade considerably the quality of the final focal spot, and limit severely the repetition rate. The various aberrations induced on the Laboratoire pour l'Utilisation des Lasers Intenses (LULI), laser facility (LULI2000) throughout the amplification are identified and analyzed in detail. Based on these analyses, an optimized procedure for dynamic wavefront control is then designed and implemented. The lower-order Zernike aberrations can be effectively reduced by combining an adaptive-optics setup, comprising a bimorph deformable mirror and a four-wave lateral shearing interferometer, with a precise alignment system. This enables the laser chain to produce a reproducible focal spot close to the diffraction limit (Strehl ratio ~0.7). This allows also to increase the repetition rate, initially limited by the recovery time of the laser amplifiers, by a factor of 2 (one shot per hour). The proposed procedure provides an attractive alternative for dynamic correction of the wavefront aberrations of a laser facility as complex as the LULI2000.

  15. Study on the effect of beam propagation through atmospheric turbulence on standoff nanosecond laser induced breakdown spectroscopy measurements.

    PubMed

    Laserna, J J; Reyes, R Fernández; González, R; Tobaria, L; Lucena, P

    2009-06-01

    We report on an experimental study of the effect of atmospheric turbulence on laser induced breakdown spectroscopy (LIBS) measurements. The characteristics of the atmosphere dictate specific performance constraints to this technology. Unlike classical laboratory LIBS systems where the distance to the sample is well known and characterized, LIBS systems working at several tens of meters to the target have specific atmospheric propagation conditions that cause the quality of the LIBS signals to be affected to a significant extent. Using a new LIBS based sensor system fitted with a nanosecond laser emitting at 1064 nm, propagation effects at distances of up to 120 m were investigated. The effects observed include wander and scintillation in the outgoing laser beam and in the return atomic emission signal. Plasmas were formed on aluminium targets. Average signal levels and signal fluctuations are measured so the effect of atmospheric turbulence on LIBS measurements is quantified.

  16. The influence of magnetised electron transport on thermal self-focusing and channelling of nanosecond laser beams

    NASA Astrophysics Data System (ADS)

    Read, Martin; Kingham, Robert; Bissell, John

    2016-05-01

    The propagation of a nanosecond IR laser pulse through an under-dense (0.01 — 0.1ncr) magnetised laser-plasma is considered. The interplay between magnetised transport, B-field evolution and plasma hydrodynamics in the presence of a dynamically evolving beam are investigated by means of a paraxial wave solving module coupled to CTC, a 2D MHD code including Braginskii electron transport and IMPACT, a 2D implicit Vlasov-Fokker-Planck (VFP) code with magnetic fields. Magnetic fields have previously been shown to improve density channel formation for plasma waveguides however fluid simulations presented here indicate that Nernst advection can result in the rapid cavitation of magnetic field in the laser-heated region resulting in beam defocusing. Kinetic simulations indicate that strong non-local transport is present leading to the fluid code overestimating heat-flow and magnetic field advection and resulting in the recovery of beam channelling for the conditions considered.

  17. Characterization of binary silver based alloys by nanosecond-infrared-laser-ablation-inductively coupled plasma-optical emission spectrometer

    NASA Astrophysics Data System (ADS)

    Márquez, Ciro; Sobral, Hugo

    2013-11-01

    A nanosecond infrared laser ablation (LA) system was examined to determine the composition of several silver-copper alloys through an inductively coupled plasma-optical emission spectrometer (ICP-OES). Samples with different concentrations were prepared and analyzed by atomic absorption, and ICP-OES after sample digestion, and compared with an energy-dispersive x-ray spectrometer-scanning electron microscopy (EDX-SEM). Elemental fractionation during the ablation process and within the ICP was investigated for different laser frequencies and fluences. Samples were used for optimizing and calibrating the coupling between LA to the ICP-OES system. Results obtained from the samples analysis were in agreement with those obtained by atomic absorption spectroscopy, ICP-OES and EDX-SEM, showing that fractionation was not significant for laser fluences higher than 55 J cm-2.

  18. Rear surface spallation on single-crystal silicon in nanosecond laser micromachining

    NASA Astrophysics Data System (ADS)

    Ren, Jun; Orlov, Sergei S.; Hesselink, Lambertus

    2005-05-01

    Rear surface spallation of single-crystal silicon under 5-ns laser pulse ablation at intensities of 0.6-60GW/cm2 is studied through postablation examination of the ablated samples. The spallation threshold energy and the spallation depth's dependences on the energy and target thickness are measured. From the linear relation between the spallation threshold energy and the target thickness, an estimation of the material spall strength around 1.4GPa is obtained, in reasonable agreement with the spall strength estimation of 0.8-1.2GPa at a strain rate of 107s-1 using Grady's model for brittle materials. The experiment reveals the internal fracturing process over an extended zone in silicon, which is controlled by the competition between the shock pressure load and the laser ablation rate. The qualities of the laser microstructuring and micromachining results are greatly improved by using an acoustic impedance matching approach.

  19. Widely tunable repetition-rate and pulse-duration nanosecond pulses from two spectral beam combined fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Hu, Man; Zheng, Ye; Yang, Yifeng; Chen, Xiaolong; Zhao, Chun; Liu, Kai; Wang, Jianhua; Qi, Yunfeng; He, Bing; Zhou, Jun

    2016-10-01

    Nanosecond pulses with a widely tunable repetition-rate and pulse-duration at 1 μm wavelength are obtained by spectrally combining two pulse fiber amplifiers using a home-made polarization-independent multilayer dielectric reflective diffraction grating. The width of the combined pulses can be tuned from 4 ns to 800 ns, and the pulse repetition-rate can be ranged from 1 MHz to 200 MHz. Thanks to the spectral beam combining system, the maximum repetition-rate and pulse-duration of the combined pulses are doubled, compared to the single pulse fiber amplifier, by setting a proper temporal delay between the two pulse channels.

  20. Convoluted effect of laser fluence and pulse duration on the property of a nanosecond laser-induced plasma into an argon ambient gas at the atmospheric pressure

    SciTech Connect

    Bai Xueshi; Ma Qianli; Motto-Ros, Vincent; Yu Jin; Sabourdy, David; Nguyen, Luc; Jalocha, Alain

    2013-01-07

    We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between laser fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high fluence of about 160 J/cm{sup 2} where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower fluence of about 65 J/cm{sup 2}, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-ablation interaction between the generated plume and the tailing part of the laser pulse. We demonstrate that the ionization of the layer of ambient gas surrounding the ablation vapor plays an important role in plasma shielding. Such ionization is the consequence of laser-supported absorption wave and directly dependent on the laser fluence and the pulse duration. Further observations of the structure of the generated plume in its early stage of expansion support our explanations.

  1. Surface roughness and electrical resistivity of high-purity zinc irradiated with nanosecond visible laser pulses

    NASA Astrophysics Data System (ADS)

    Butt, M. Z.; Ali, Dilawar; Tanveer, M. Usman; Naseem, S.

    2014-06-01

    Six specimens of 99.995% pure zinc in the form of strips (15 mm × 8 mm × 0.5 mm) were irradiated with Q-switched pulsed Nd:YAG laser (λ = 532 nm, E = 50 mJ, τ = 6 ns, repetition rate = 10 Hz) in vacuum ∼10-3 Torr. The specimens were irradiated with 50, 60, 70, 80, 90 and 100 laser shots; the laser fluence and laser intensity at the irradiation spot were 4.24 J/cm2 and 7.07 × 108 W/cm2, respectively. Surface morphology of laser irradiated specimens was examined by both optical and scanning electron microscopes. Crater area as well as heat affected area were measured by optical microscope using Motic software. Scanning electron microscope (SEM) examination revealed different features, e.g., wavelike structures, ridges, dips, micro cones, cavities, nano and micro size droplets, as well as solid flakes, etc., on the surface. These features are a result of splashing, hydrodynamic and exfoliational sputtering. Average surface roughness was measured from SEM micrographs using Nanotec software WSxM 5.0 develop 1.1. The electrical resistivity was determined by four-point probe technique. It is observed that average surface roughness and electrical resistivity vary with the number of laser shots in an identical manner, and are therefore found to be directly related to each other.

  2. Comparison of nanosecond and picosecond excitation for interference-free two-photon laser-induced fluorescence detection of atomic hydrogen in flames

    SciTech Connect

    Kulatilaka, Waruna D.; Patterson, Brian D.; Frank, Jonathan H.; Settersten, Thomas B

    2008-09-10

    Two-photon laser-induced fluorescence (TP-LIF) line imaging of atomic hydrogen was investigated in a series of premixed CH4/O2/N2, H2/O2, and H2/O2/N2 flames using excitation with either picosecond or nanosecond pulsed lasers operating at 205 nm. Radial TP-LIF profiles were measured for a range of pulse fluences to determine the maximum interference-free signal levels and the corresponding picosecond and nanosecond laser fluences in each of 12 flames. For an interference-free measurement, the shape of the TP-LIF profile is independent of laser fluence. For larger fluences, distortions in the profile are attributed to photodissociation of H2O, CH3, and/or other combustion intermediates, and stimulated emission. In comparison with the nanosecond laser, excitation with the picosecond laser can effectively reduce the photolytic interference and produces approximately an order of magnitude larger interference-free signal in CH4/O2/N2 flames with equivalence ratios in the range of 0.5{<=}{phi}{<=}1.4, and in H{sub 2}/O{sub 2} flames with 0.3{<=}{phi}{<=}1.2. Although photolytic interference limits the nanosecond laser fluence in all flames, stimulated emission, occurring between the laser-excited level, H(n=3), and H(n=2), is the limiting factor for picosecond excitation in the flames with the highest H atom concentration. Nanosecond excitation is advantageous in the richest ({phi}=1.64) CH4/O2/N2 flame and in H2/O2/N2 flames. The optimal excitation pulse width for interference-free H atom detection depends on the relative concentrations of hydrogen atoms and photolytic precursors, the flame temperature, and the laser path length within the flame.

  3. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    NASA Astrophysics Data System (ADS)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  4. Dependence of optimal initial density on laser parameters for multi-keV x-ray radiators generated by nanosecond laser-produced underdense plasma

    NASA Astrophysics Data System (ADS)

    Tu, Shao-yong; Yuan, Yong-teng; Hu, Guang-yue; Miao, Wen-yong; Zhao, Bin; Zheng, Jian; Jiang, Shao-en; Ding, Yong-kun

    2016-01-01

    Efficient multi-keV x-ray sources can be produced using nanosecond laser pulse-heated middle-Z underdense plasmas generated using gas or foam. Previous experimental results show that an optimal initial target density exists for efficient multi-keV x-ray emission at which the laser ionization wave is supersonic. Here we explore the influence of the laser intensity and the pulse duration on this optimal initial target density via a one-dimensional radiation hydrodynamic simulation. The simulation shows that the optimal initial density is sensitive to both the laser intensity and the pulse duration. However, the speed of the supersonic ionization wave at the end of the laser irradiation is always maintained at 1.5 to 1.7 times that of the ion acoustic wave under the optimal initial density conditions.

  5. The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation

    SciTech Connect

    Moscicki, T. Hoffman, J.; Chrzanowska, J.

    2015-10-15

    In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm{sup 2} with a power density of 1 × 10{sup 9 }W/cm{sup 2} (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.

  6. Mouse embryonic fibroblasts accumulate differentially on titanium surfaces treated with nanosecond laser pulses.

    PubMed

    Radmanesh, Mitra; Ektesabi, Amin M; Wyatt, Rachael A; Crawford, Bryan D; Kiani, Amirkianoosh

    2016-01-01

    Biomaterial engineering, specifically in bone implant and osseointegration, is currently facing a critical challenge regarding the response of cells to foreign objects and general biocompatibility of the materials used in the production of these implants. Using the developing technology of the laser surface treatment, this study investigates the effects of the laser repetition rate (frequency) on cell distribution across the surface of the titanium substrates. The main objective of this research is building a fundamental understanding of how cells interact with treated titanium and how different treatments affect cell accumulation. Cells respond differently to surfaces treated with different frequency lasers. The results of this research identify the influence of frequency on surface topography properties and oxidation of titanium, and their subsequent effects on the pattern of cell accumulation on its surface. Despite increased oxidation in laser-treated regions, the authors observe that fibroblast cells prefer untreated titanium to laser-treated regions, except the regions treated with 25 kHz pulses, which become preferentially colonized after 72 h. PMID:27581527

  7. Multiscale analysis: a way to investigate laser damage precursors in materials for high power applications at nanosecond pulse duration

    NASA Astrophysics Data System (ADS)

    Natoli, J. Y.; Wagner, F.; Ciapponi, A.; Capoulade, J.; Gallais, L.; Commandré, M.

    2010-11-01

    The mechanism of laser induced damage in optical materials under high power nanosecond laser irradiation is commonly attributed to the presence of precursor centers. Depending on material and laser source, the precursors could have different origins. Some of them are clearly extrinsic, such as impurities or structural defects linked to the fabrication conditions. In most cases the center size ranging from sub-micrometer to nanometer scale does not permit an easy detection by optical techniques before irradiation. Most often, only a post mortem observation of optics permits to proof the local origin of breakdown. Multi-scale analyzes by changing irradiation beam size have been performed to investigate the density, size and nature of laser damage precursors. Destructive methods such as raster scan, laser damage probability plot and morphology studies permit to deduce the precursor densities. Another experimental way to get information on nature of precursors is to use non destructive methods such as photoluminescence and absorption measurements. The destructive and non destructive multiscale studies are also motivated for practical reasons. Indeed LIDT studies of large optics as those used in LMJ or NIF projects are commonly performed on small samples and with table top lasers whose characteristics change from one to another. In these conditions, it is necessary to know exactly the influence of the different experimental parameters and overall the spot size effect on the final data. In this paper, we present recent developments in multiscale characterization and results obtained on optical coatings (surface case) and KDP crystal (bulk case).

  8. Formation of crownlike and related nanostructures on thin supported gold films irradiated by single diffraction-limited nanosecond laser pulses.

    PubMed

    Kulchin, Yu N; Vitrik, O B; Kuchmizhak, A A; Emel'yanov, V I; Ionin, A A; Kudryashov, S I; Makarov, S V

    2014-08-01

    A type of laser-induced surface relief nanostructure-the nanocrown-on thin metallic films was studied both experimentally and theoretically. The nanocrowns, representing a thin corrugated rim of resolidified melt and resembling well-known impact-induced water-crown splashes, were produced by single diffraction-limited nanosecond laser pulses on thin gold films of variable thickness on low-melting copper and high-melting tungsten substrates, providing different transient melting and adhesion conditions for these films. The proposed model of the nanocrown formation, based on a hydrodynamical (thermocapillary Marangoni) surface instability and described by a Kuramoto-Sivashinsky equation, envisions key steps of the nanocrown appearance and gives qualitative predictions of the acquired nanocrown parameters. PMID:25215830

  9. Formation of crownlike and related nanostructures on thin supported gold films irradiated by single diffraction-limited nanosecond laser pulses.

    PubMed

    Kulchin, Yu N; Vitrik, O B; Kuchmizhak, A A; Emel'yanov, V I; Ionin, A A; Kudryashov, S I; Makarov, S V

    2014-08-01

    A type of laser-induced surface relief nanostructure-the nanocrown-on thin metallic films was studied both experimentally and theoretically. The nanocrowns, representing a thin corrugated rim of resolidified melt and resembling well-known impact-induced water-crown splashes, were produced by single diffraction-limited nanosecond laser pulses on thin gold films of variable thickness on low-melting copper and high-melting tungsten substrates, providing different transient melting and adhesion conditions for these films. The proposed model of the nanocrown formation, based on a hydrodynamical (thermocapillary Marangoni) surface instability and described by a Kuramoto-Sivashinsky equation, envisions key steps of the nanocrown appearance and gives qualitative predictions of the acquired nanocrown parameters.

  10. Possibility of applying a hydrodynamic model to describe the laser erosion of metals irradiated by high-intensity nanosecond pulses

    SciTech Connect

    Kozadaev, K V

    2014-04-28

    We report the results of experimental investigations of the production and development of plasma-vapour plumes upon irradiation of metal targets by nanosecond (10–100 ns) pulses with a high (10{sup 8}–10{sup 10} W cm{sup -2}) power density under atmospheric conditions. The transition from a quasi-stationary thermal mechanism of metal erosion to an explosion hydrodynamic one takes place when the radiation power density increases from 10{sup 8} to 10{sup 9} W cm{sup -2}. The resultant experimental information is extremely important for the laser deposition of metal nanostructures under atmospheric conditions, which is possible only for power densities of 10{sup 8}–10{sup 9} W cm{sup -2}. (interaction of laser radiation with matter)

  11. Measurement of OH, O, and NO densities and their correlations with mouse melanoma cell death rate treated by a nanosecond pulsed streamer discharge

    NASA Astrophysics Data System (ADS)

    Yagi, Ippei; Shirakawa, Yuki; Hirakata, Kenta; Akiyama, Taketoshi; Yonemori, Seiya; Mizuno, Kazue; Ono, Ryo; Oda, Tetsuji

    2015-10-01

    Mouse melanoma cells in a culture medium are treated using a nanosecond pulsed streamer discharge plasma and the correlations between the rate of cell death and the densities of reactive species (OH, O, and NO) in the plasma are measured. The plasma is irradiated onto the culture medium surface with a vertical gas flow of an O2/N2 mixture from a glass tube at various gas flow rates and O2 concentrations. The densities of the reactive species are measured very close to the culture medium surface, where the reactive species interact with the culture medium, using laser-induced fluorescence. In the case of the N2 discharge (O2 = 0%), an increase in gas flow rate decreases OH density because it lowers the water vapor concentration by diluting the vapor, which is required for OH production. The increase in gas flow rate also leads to a decreased cell death rate. In the case of the O2/N2 discharge, on the other hand, an increase in O2 concentration at a fixed flow rate does not affect the rate of cell death, although it considerably changes the O and NO densities. These findings indicate that some reactive species derived from water vapor such as OH are responsible for the melanoma cell death, whereas those from O2, such as O and NO, are less likely responsible. They also indicate the importance of water evaporation from the culture medium surface in cell treatment.

  12. Synthesis of polycaprolactone-titanium oxide multilayer films by nanosecond laser pulses and electrospinning technique for better implant fabrication

    NASA Astrophysics Data System (ADS)

    Naghshine, Babak B.; Cosman, James A.; Kiani, Amirkianoosh

    2016-08-01

    In this study, a combination of electrospinning and laser texturing is introduced as a novel method for increasing the biocompatibility of metal implants. Besides having a rough laser treated surface, the implant benefits from the high porosity and better wettability of an electrospun fibrous structure, which is a more favorable environment for cell proliferation. Titanium samples were patterned using a nanosecond laser beam and were placed as collectors in an electrospinning machine. They were then soaked in simulated body fluid for four weeks. Energy Dispersive X-ray and X-Ray Diffraction results indicate significantly more hydroxyapatite formation on laser treated samples with nanoscale fibers deposited on their surface. This shows that having a laser treated surface underneath the fibrous layer can improve short-term biocompatibility even before degradation of fibers. The thermal conductivity of the electrospun layer, measured using a Hot Disk Transient Plane Source instrument and computer code, was shown to be considerably lower than that of titanium and very close to bone. The presence of this layer can therefore be beneficial in making the implant more compatible to a biological medium. In case of dental implants, it was shown that this layer can act as a thermal barrier while a hot beverage is consumed and it can decrease the temperature rise by about 60%, which avoids any possible damage to newly formed cells during the healing period.

  13. Selective removal of carious human dentin using a nanosecond pulsed laser operating at a wavelength of 5.85 μ m

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-05-01

    Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm. The present study investigated the irradiation effect of the light on carious human dentin classified into "remove," "not remove," and "unclear" categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm2 and irradiation time of 2 s, the ablation depth of "remove" and "not remove," and also the ablation depth of "unclear" and "not remove," were significantly different (p<0.01). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85 μm proved an effective less-invasive caries treatment.

  14. Selective removal of carious human dentin using a nanosecond pulsed laser operating at a wavelength of 5.85 μm.

    PubMed

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-05-01

    Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm . The present study investigated the irradiation effect of the light on carious human dentin classified into "remove," "not remove," and "unclear" categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm² and irradiation time of 2 s, the ablation depth of "remove" and "not remove," and also the ablation depth of "unclear" and "not remove," were significantly different (p<0.01 ). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85  μm proved an effective less-invasive caries treatment.

  15. Laser Cutting of CFRP with a Fibre Guided High Power Nanosecond Laser Source - Influence of the Optical Fibre Diameter on Quality and Efficiency

    NASA Astrophysics Data System (ADS)

    Bluemel, S.; Bastick, S.; Staehr, R.; Jaeschke, P.; Suttmann, O.; Overmeyer, L.

    For the development of a robot based laser cutting process of automotive 3D parts consisting of carbon fibre reinforced plastics (CFRP), investigations with a newly developed fibre guided nanosecond pulsed laser with an average power of PL = 1.5 kW were conducted. In order to investigate the best combination of quality and process time 2 different optical fibres were used, with diameters of df = 400 μm and df = 600 μm. The main differences between the two setups are the resulting focal diameter and the maximum available pulse energy up to EP = 80 mJ. In a first instance, a comparable investigation was performed with both fibres for a constant pulse overlap. For each fibre the minimum required line energy was investigated and cuts were performed, distributed over the complete parameter range of the laser source. The influences of the fibre diameter on the quality and efficiency of the cutting process are summarized and discussed.

  16. Remote imaging laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy using nanosecond pulses from a mobile lidar system.

    PubMed

    Grönlund, Rasmus; Lundqvist, Mats; Svanberg, Sune

    2006-08-01

    A mobile lidar system was used in remote imaging laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) experiments. Also, computer-controlled remote ablation of a chosen area was demonstrated, relevant to cleaning of cultural heritage items. Nanosecond frequency-tripled Nd:YAG laser pulses at 355 nm were employed in experiments with a stand-off distance of 60 meters using pulse energies of up to 170 mJ. By coaxial transmission and common folding of the transmission and reception optical paths using a large computer-controlled mirror, full elemental imaging capability was achieved on composite targets. Different spectral identification algorithms were compared in producing thematic data based on plasma or fluorescence light. PMID:16925920

  17. Identification of the formation phases of filamentary damage induced by nanosecond laser pulses in bulk fused silica

    SciTech Connect

    Shen, Chao; Xu, Zhongjie; Chambonneau, Maxime E-mail: jiangtian198611@163.com; Cheng, Xiang'ai; Jiang, Tian E-mail: jiangtian198611@163.com

    2015-09-14

    Employing a pump-probe polarization-based two-frame shadowgraphy setup, the formation of filamentary damage induced in bulk fused silica by a nanosecond pulse at 1064 nm is investigated with a picosecond probe. Three different phases are exhibited in the damage experiments. The first phase is the formation of a micrometric plasma channel along the laser direction during the beginning of the pulse likely caused by multi-photon ionization. This channel exhibits growth during ∼400 ps, and the newly grown plasma is discrete. Then, during the end of the pulse, this channel evolves into a tadpole-like morphology showing an elliptical head upstream the laser flux followed by a thin tail. This observed asymmetry is attributed to shielding effects caused by both the plasma and hot modified silica. Once the damage shows its almost final morphology, a last phase consists in the launch of a pressure wave enlarging it after the laser pulse. The physical mechanisms that might be involved in the formation of plasma channels are discussed. The experimental data are first confronted to the moving breakdown model which overestimates the filamentary damage length. Finally, taking into account the temporal shape of the laser pulses, the coupling between Kerr-induced self-focusing and stimulated Brillouin scattering is discussed to interpret the observations.

  18. High-repetition-rate laser ignition of fuel-air mixtures.

    PubMed

    Hsu, Paul S; Roy, Sukesh; Zhang, Zhili; Sawyer, Jordan; Slipchenko, Mikhail N; Mance, Jason G; Gord, James R

    2016-04-01

    A laser-ignition (LI) method is presented that utilizes a high-repetition-rate (HRR) nanosecond laser to reduce minimal ignition energies of individual pulses by ∼10 times while maintaining comparable total energies. The most common LI employs a single nanosecond-laser pulse with energies on the order of tens of millijoules to ignite combustible gaseous mixtures. Because of the requirements of high energy per pulse, fiber coupling of traditional LI systems is difficult to implement in real-world systems with limited optical access. The HRR LI method demonstrated here has an order of magnitude lower per-pulse energy requirement than the traditional single-pulse LI technique, potentially allowing delivery through standard commercial optical fibers. Additionally, the HRR LI approach significantly increases the ignition probability of lean combustible mixtures in high-speed flows while maintaining low individual pulse energies. PMID:27192289

  19. Study on the influence of laser pulse duration in the long nanosecond regime on the laser induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Elnasharty, I. Y.

    2016-10-01

    By using a high power pulsed fiber laser, this study reports the experimental investigation of the laser-induced plasma characteristics for the laser pulse duration range extended from 40 ns to 200 ns. The experiments were performed with keeping the laser fluence constant at 64 J/cm2. The measurements show that, for the early phase of plasma formation, the spectral line intensities and the continuum emissions as well as the plasma characteristics decay to a certain extent with the increase of the pulse duration. On the other hand, as the plasma evolves in post laser pulse regime, the electron density and the degree of ionization increase slightly for the longer pulses, while the plume temperature is more or less independent from the pulse duration. Furthermore, the ablation characteristics, such as the ablation rate, coincide with the results of plasma characteristics for the different pulse durations. Eventually, with keeping the laser fluence constant at 64 J/cm2, the analytical performance of Laser-Induced Plasma Spectroscopy (LIPS) for the corresponding pulse duration range is examined by using a temporal gating and non-gating analyses. The measurements show that, in the case of gating analysis, all pulse durations yield almost the same range of limits of detections LODs. On the other hand, for non-gating analysis, the longer pulse durations provide lower LODs (better) than the shorter ones by orders of magnitude. Moreover, the calculated absolute limit of detection (LODAbs) for the longest pulse duration (i.e. 200 ns) is lower by approximately factor 2 than that of the shortest one (i.e. 40 ns).

  20. Theoretical modeling of laser ablation of quaternary bronze alloys: case studies comparing femtosecond and nanosecond LIBS experimental data.

    PubMed

    Fornarini, Lucilla; Fantoni, Roberta; Colao, Francesco; Santagata, Antonio; Teghil, Roberto; Elhassan, Asmaa; Harith, Mohamed A

    2009-12-31

    A model, formerly proposed and utilized to understand the formation of laser induced breakdown spectroscopy (LIBS) plasma upon irradiation with nanosecond laser pulses at different fluences and wavelengths, has been extended to the irradiation with femtosecond laser pulses in order to control the fractionation mechanisms which heavily affect the application of laser-ablation-based microanalytical techniques. The model takes into account the different chemico-physical processes occurring during the interaction of an ultrashort laser pulse with a metallic surface. In particular, a two-temperature description, relevant to the electrons and lattice of the substrate, respectively, has been introduced and applied to different ternary and quaternary copper-based alloys subjected to fs and ns ablation both in the visible (527 nm) and in the UV (248 nm). The model has been found able to reproduce the shorter plasma duration experimentally found upon fs laser ablation. Kinetic decay times of several copper (major element) emission lines have been examined together with those relevant to the main plasma parameters. The plasma experimental temperature, derived assuming a Boltzmann distribution, and the electron density following the Saha equation have been compared with the corresponding theoretical data. A satisfactory description of plasma parameters and main matrix constituent composition has been obtained in the time window where local thermal equilibrium was assumed for LIBS data analysis. Improved analytical capabilities are predicted upon delayed detection of plasma emission in femtosecond LIBS, in relation to the better LOD achieved and to the improved data reproducibility expected. Results support the utilization of ultrafast laser sources for trace detection, despite the residual fractionation occurring in the examined range of fluences which affects the linearity of experimental calibration curves built for tin and lead after internal standardization on copper. The

  1. Nucleation dynamics around single microabsorbers in water heated by nanosecond laser irradiation

    SciTech Connect

    Neumann, Joerg; Brinkmann, Ralf

    2007-06-01

    Suspensions containing micro- and nanoabsorbers, which are irradiated by short laser pulses, are used for a manifold of procedures in medicine, biotechnology, and other fields. Detailed knowledge of the bubble nucleation and dynamics, which is induced by the heat transfer from the absorber to the surrounding transparent water, is essential for understanding the underlying processes occurring on a microscopic scale. We investigated the rapid phase change phenomena including temperature, heating rates, pressure generation, bubble nucleation, and initial bubble growth around absorbing micron-sized melanin particles (retinal pigment epithelial melanosomes) during irradiation with 12 ns (full width at half maximum) laser pulses at a wavelength of 532 nm. The melanosomes were heated at rates in the order of 10{sup 10} K/s. A mean bubble nucleation temperature of 136 deg. C was found. The initial bubble expansion was observed by time-resolved microscopy. The expansion velocities range from 10 m/s at 1.5-fold to 85 m/s at 8.5-fold threshold radiant exposure for bubble formation, respectively. The expansion velocity increases in the investigated range almost linearly with the applied radiant exposure.

  2. Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Guan, Y. C.; Zhou, W.; Zheng, H. Y.; Li, Z. L.

    2013-09-01

    Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200 nm to 1100 nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

  3. Real-time measurement of temperature variation during nanosecond pulsed-laser-induced contamination deposition.

    PubMed

    Kokkinos, Dimitrios; Gailly, Patrick; Georges, Marc P; Tzeremes, Georgios; Rochus, Pierre; Fleury-Frenette, Karl

    2015-12-20

    In this paper, a study of heat generation during UV laser-induced contamination (LIC) and potentially resulting subsequent thermal damage are presented. This becomes increasingly interesting when optics with delicate coatings are involved. During LIC, radiation can interact with outgassing molecules, both in the gas phase and at the surface, thus triggering chemical and photo-fixation reactions. This is a major hazard, in particular for laser units operating under vacuum conditions such as in space applications. The intense photon flux not only affects the contaminant deposition rate but also alters their chemical structure, which can increase their absorption coefficient. Over cumulative irradiation shots, these molecules formed deposits that increasingly absorb photons and produce heat as a by-product of de-excitation, eventually leading to thermal damage. One could better assess the risk of the latter with the knowledge of temperature during the contamination process. For this purpose, a thermoreflectance technique is used here to estimate the temperature variation from pulse to pulse during contamination deposition through the analysis of a temperature-dependent surface reflectance signal.

  4. Spatio-temporal characterization of pulses obtained from a high-energy sub-nanosecond laser system.

    PubMed

    Feng, Chengyong; Xu, Xiaozhen; Diels, Jean-Claude

    2016-03-01

    Spatio-temporal profiles of laser pulses, obtained from each stage of a high-energy sub-nanosecond laser system, are investigated. The laser system is composed of a Q-switched Nd:YAG unstable oscillator, a chain of Nd:YAG amplifiers, a second-harmonic generator, and a high-energy pulse compressor based on stimulated Brillouin scattering (SBS). A curved energy front, i.e., the pulses emerging away from the beam center being gradually delayed from the center pulse, is shown to originate from the unstable oscillator. Our comparative study shows that injection seeding will enlarge the energy front curvature, via reduction of the effective gain. After the laser amplifiers, the energy front curvature is more than doubled due to the gain saturation effect. The latter also modifies the spatial pulse width distribution. While there is a negligible pulse duration spread across the oscillator beam, the amplified pulses are found to have gradually reduced pulse duration away from the beam center. More interestingly, after the SBS pulse compression, not only the pulse width but also the delay is compressed down. This is, to the best of our knowledge, the first study of the spatio-temporal profile of the SBS compressed pulse. To compare with the experiments, two numerical models are developed to simulate the evolution of spatio-temporal profiles within the Nd:YAG laser system and during the SBS pulse compression, respectively. The first model is demonstrated to reproduce the experimental results very well, while the second model predicts part of the features of the SBS compressed pulse. The limitation on the latter is discussed. PMID:26974618

  5. On the applicability of arbitrarily shaped nanosecond laser pulses for high-quality, high-efficiency micromachining

    NASA Astrophysics Data System (ADS)

    Eiselen, Sasia; Riedel, Sebastian; Schmidt, Michael

    2014-05-01

    Progressive developments in temporal shaping of short laser pulses offer entirely new approaches at influence and investigate laser-matter-interactions. Commonly used parameters for describing the behavior of short or ultrashort pulses or pulse trains are fluence and intensity. However, fluence does not imply any information about the temporal behavior of energy input during specific pulse duration τ while using the pulse intensity as describing parameter is more meaningful. Nevertheless it still is an averaging over pulse duration and no change in intensity can be determined if the temporal pulse shape changes within a certain combination of pulse duration and pulse energy. Using a flexible programmable MOPA fiber laser experimental studies on the impact of temporal energy distribution within one single laser pulse in micro machining applications were therefore carried out. With this laser source a direct modulation of the temporal pulse shape in the nanosecond regime can easily be controlled. Experiments were carried out with moved as well as with un-moved beam resulting in areas and dimples respectively drilling holes. The presented results clearly show that any averaging over pulse duration results in missing information about time-dependent interactions but can at the same time lead to significant differences in ablation results. Thus, resulting surface roughness Sa can be decreased up to 25 % when changing the pulse shape at constant parameters of fluence and pulse peak power at a pulse duration of 30 ns. It can be observed that the combination of an intensity peak and a lower edge within one pulse can lead to increasing ablation efficiency as well as higher ablation quality compared to the commonly used Gaussian-like temporal pulse shape.

  6. Coupled photo-thermal and time resolved reflectivity methods to original investigation of laser/material nanosecond interaction

    NASA Astrophysics Data System (ADS)

    Semmar, N.; Martan, J.; Cibulka, O.; Le Menn, E.; Boulmer-Leborgne, C.

    2006-05-01

    A high number of papers were published on the simulation of laser/surface interaction at the level of nanosecond scale. Several assumptions on thermal properties data, laser spot homogeneity, were assumed for describing as well as possible the boundary conditions, the mathematical writing and finally the numerical or the analytical results. A few tentative of surface temperature monitoring during laser processing were proposed for the numerical validation. Also, simulation of the melting kinetics is rarely directly compared to in situ experiments. It is very hard to determine the time duration of a melting pool by in situ experiments. It should be the same for the surface temperature. A new method to plot the thermal history of the surface by using a combination of the Time Resolved Reflectivity (TRR) and the Pulsed Photo-Thermal (PPT) or Infrared Radiometry (IR) methods is proposed in this paper. Surface temperature, melting kinetics, threshold of melting and threshold of plasma formation are determined in the case of KrF laser spot in interaction with several materials. In the first step, the experimental setup including fast detectors (IR, UV, Vis.) and related optical devices is described. In the second step, typical results (TRR and IR spectra) for monocrystaline silicon are presented and discussed. Namely, phase change transitions (melting and resolidification) are detected versus fluence change and number of laser shots change. TRR and IR spectra of metallic surfaces (Cu, Mo, Ni, Stainless steel 15330 and 17246, Sn, Ti), are measured. For each sample the surface temperature during heating, the threshold of melting, melting duration and the threshold of plasma formation are directly deduced.

  7. Formation of micron and submicron structures on a zirconium oxide surface exposed to nanosecond laser radiation

    SciTech Connect

    Ganin, D V; Mikolutskiy, S I; Khomich, V Yu; Yamshchikov, V A; Tokarev, V N; Shmakov, V A

    2014-04-28

    Possibility of forming quasi-periodic structures of micron and submicron dimensions on a surface of zirconium dioxide under the action of eximer ArF laser radiation is shown experimentally and theoretically. (interaction of laser radiation with matter)

  8. A geometry for sub-nanosecond X-ray diffraction from laser-shocked polycrystalline foils

    SciTech Connect

    Wark, Justin; Higginbotham, Andrew; Kimminau, Giles; Murphy, William; Nagler, Bob; Whitcher, Thomas; Hawreliak, James; Kalantar, Dan; Butterfield, Martin; El-Dasher, Bassem; McNaney, James; Milathianaki, Despina; Lorenzana, Hector; Remington, Bruce; Davies, Huw; Thornton, Lee; Park, Nigel; Lukezic, Stan

    2007-12-12

    In situ picosecond X-ray diffraction has proved to be a useful tool in furthering our understanding of the response of shocked crystals at the lattice level. To date the vast majority of this work has used single crystals as the shocked samples, owing to their diffraction efficiency, although the study of the response of polycrystalline samples is clearly of interest for many applications. We present here the results of experiments to develop sub-nanosecond powder/polycrystalline diffraction using a cylindrical pinhole camera. By allowing the incident X-ray beam to impinge on the sample at non-normal angles, the response of grains making a variety of angles to the shock propagation direction can potentially be interrogated.

  9. High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Lu, Jianren; Wang, Yonggang; Chu, Hongwei; Luan, Chao

    2016-08-01

    A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373 mW at a signal wavelength of 1570 nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 µJ, and 1.04 MW, respectively, under a maximum incident pump power of 8.3 W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570 nm with low repetition rates, small pulse widths, and high peak powers.

  10. Selective excavation of human carious dentin using the nanosecond pulsed laser in 5.8-μm wavelength range

    NASA Astrophysics Data System (ADS)

    Kita, Tetsuya; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, 5.8 μm wavelength range was found to be effective for selective excavation of human carious dentin.

  11. Sub-ten nanosecond laser pulse shaping using lithium niobate modulators and a double-passed tapered amplifier

    NASA Astrophysics Data System (ADS)

    Rogers, C. E., III; Gould, P. L.

    2015-05-01

    We present progress on developing a laser pulse shaping system capable of generating pulses shorter than ten nanoseconds and frequency chirps of up to about 5 GHz in 2.5 ns. Shaped control of phase and amplitude on this timescale may prove useful for producing ultracold molecules and controlling atomic hyperfine state populations. The pulses are generated by passing 780 nm light from an external cavity diode laser through a fiber-coupled lithium niobate (LN) phase modulator (PM) in series with an LN intensity modulator (IM). The modulators are driven with a single-channel 8 GS/s arbitrary waveform generator configured with an RF delay line for quasi-two channel pulsed operation. The optical pulses are then amplified in a double-pass tapered amplifier (TA). The TA's intrinsic mode structure leads to an etalon effect that modulates the pulse amplitude during a frequency chirp. To reduce this unwanted effect, a compensating intensity modulation can be programmed onto the seed pulse. This work is supported by DOE.

  12. Micro- and nanosecond laser TiN coating/steel modification: Morphology studies

    NASA Astrophysics Data System (ADS)

    Trtica, M.; Tarasenko, V. F.; Gaković, B.; Panchenko, A. N.; Radak, B.; Stasić, J.

    2009-09-01

    Morphology effects induced during interaction of μs- (Transversely Excited Atmospheric (TEA) CO2 laser) or ns- (HF laser) pulses with titanium nitride (TiN) coating, deposited on austenitic stainless steel AISI 316, were studied. Experiments were carried out in regime of focused laser beam in air at atmospheric pressure. The used laser fluences were found to be sufficient for inducing intensive surface modifications of the target. The energy absorbed from the CO2 as well as HF laser beam is mainly converted into thermal energy, causing different effects like ablation, appearance of hydrodynamic features, etc. Morphology characteristics obtained during ns-pulses irradiation (HF laser) were different to those initiated by μs-pulses (TEA CO2 laser). The changes on the target surface in form of massive resolidifed droplets and crown-like structures were observed only for ns- (HF laser) pulses. It was found that these effects are a consequence of higher temperature and better coupling of the HF laser radiation with the target. Recent investigations of ps-Nd:YAG laser interaction with the same TiN coating showed that morphology picture is quite different including the reduction of thermal effect.

  13. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime.

    PubMed

    Consoli, F; De Angelis, R; Duvillaret, L; Andreoli, P L; Cipriani, M; Cristofari, G; Di Giorgio, G; Ingenito, F; Verona, C

    2016-01-01

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation. PMID:27301704

  14. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

    PubMed Central

    Consoli, F.; De Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Verona, C.

    2016-01-01

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation. PMID:27301704

  15. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

    NASA Astrophysics Data System (ADS)

    Consoli, F.; de Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; di Giorgio, G.; Ingenito, F.; Verona, C.

    2016-06-01

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation.

  16. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime.

    PubMed

    Consoli, F; De Angelis, R; Duvillaret, L; Andreoli, P L; Cipriani, M; Cristofari, G; Di Giorgio, G; Ingenito, F; Verona, C

    2016-06-15

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation.

  17. Predicting laser coating removal rates

    NASA Astrophysics Data System (ADS)

    Liu, Katherine X.; Garmire, Elsa M.; Phipps, Claude R.

    1998-09-01

    Our measurements of laser coating removal rate for 14- micrometer-thick black organic paint coatings on a refractory substrate showed the rather astonishing result that total exposure time (Delta) t required to ablate the coating (for these particular thin organic coatings, in air) is described by (Delta) t equals C X I-3/2 sec where x is the coating thickness, I the incident pulse intensity (W/cm2) and the constant C equals 1.4 X 107 W3/2-s/cm4. This was true for wavelength 350 nm less than (lambda) less than 10.6 micrometer and incident intensity 81 W/cm2 less than I less than 424 MW/cm2, covering a 7-order-of- magnitude. Such a simple result is phenomenal because of the range of different physical processes known to be involved (simple boiling, thermal conduction and differential thermal expansion for the long pulses, but the combined effects of shock spallation, large excursions within the solid equation of state, and acceleration, compression, shocking, thermal conduction, radiation, phase explosion and even some ionization for the shortest pulses). If extensible to other coatings and substrates, it is also very valuable for the design of expensive laser coating removal facilities, which are now receiving strong interest for very large-scale decontamination and aircraft repainting. Our first-order parametric model fits the experimental results to within better than a factor-of-3 in laser intensity throughout the above range.

  18. Direct generation of superhydrophobic microstructures in metals by UV laser sources in the nanosecond regime

    NASA Astrophysics Data System (ADS)

    Ocaña, Jose L.; Jagdheesh, R.; García-Ballesteros, J. J.

    2016-02-01

    The current availability of new advanced fiber and DPSS lasers with characteristic pulse lengths ranging from ns to fs has provided a unique frame in which the development of laser-generated microstructures has been made possible for very diverse kinds of materials and applications. At the same time, the development of the appropriate laser-processing workstations granting the appropriate precision and repeatability of the respective laser interaction processes in line with the characteristic dimension features required in the microstructured samples has definitively consolidated laser surface microstructuring as a reference domain, nowadays, unavoidable for the design and manufacturing of current use microsystem: MEMSs, fluidic devices, advanced sensors, biomedical devices and instruments, etc., are all among the most well-known developments of the micromanufacturing technology. Completing the broad spectrum of applications developed mostly involving the generation of geometrical features on a subtrate with specific functional purposes, a relatively new, emerging class of laser-microstructuring techniques is finding an important niche of application in the generation of physically structured surfaces (particularly of metallic materials) with specific contact, friction, and wear functionalities, for whose generation the concourse of different types of laser sources is being found as an appropriate tool. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is described as an attractive application basis for the generation of self-cleaning properties of extended functional surfaces. Flat aluminum sheets of thickness 100 μm were laser machined with ultraviolet laser pulses of 30 ns with different laser parameters to optimize the process parameters. The samples produced at the optimum conditions with respect to

  19. Nanoscale heat transfer in direct nanopatterning into gold films by a nanosecond laser pulse.

    PubMed

    Lin, Yuanhai; Zhai, Tianrui; Zhang, Xinping

    2014-04-01

    We investigate nanoscale heat transfer and heat-flux overlapping effects in nanopatterning through interactions between interferogram produced by 5-ns laser pulses at 355 nm and gold films. These mechanisms played different roles in direct writing of gold nanolines with different periods. Continuous gold nanolines were produced for large periods, where heat-flux overlapping is too small to effect the laser-metal interactions. Thus, the heat-transfer distance and direct laser-ablation determined the width of resultant gold nanolines. However, gold nanolines consisting of isolated gold nanoparticles were produced for small periods, where the overlapped heat-flux exceeds the threshold for removing or melting gold films.

  20. Nanosecond laser photolysis studies of vitamin K 3 in aqueous solution

    NASA Astrophysics Data System (ADS)

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

    1999-06-01

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

  1. Pulsed hologram recording by nanosecond and subnanosecond small-dimensioned laser system

    NASA Astrophysics Data System (ADS)

    Bespalov, Victor G.; Dikasov, A. B.

    1991-02-01

    The results of the investigation of small-sized laser system on crystals KGd(W04)2 coherence are presented. This laser system generates pulses with durat i on of 3 ns or 0 . 2 ns . The i nvest i gat ion of the rec i pros i ty 1 aw and hologram diffraction efficiency of silver halide holographic materials on these durations are reported. With the help of this hololaser hologram recordings of diffuse objects are produced. 1 .

  2. Broadband supercontinuum generation in a telecommunication fibre pumped by a nanosecond Tm, Ho:YVO4 laser

    NASA Astrophysics Data System (ADS)

    Ren-Lai, Zhou; Jian-Cun, Ren; Shu-Li, Lou; You-Lun, Ju; Yue-Zhu, Wang

    2015-07-01

    Broadband supercontinuum (SC) generation in a telecommunication fibre [8/125-μm single mode fibre (SMF) and 50/125-μm multimode fibre (MMF)] directly pumped by a nanosecond Q-switched Tm, Ho:YVO4 laser is demonstrated. At a 7-kHz pulse repetition frequency (PRF), an output average power of 0.53 W in the 1.95 - 2.5-μm spectral band and 3.51 W in the 1.9 - 2.6-μm spectral band are achieved in SMF and MMF, respectively (the corresponding optic-to-optic conversion efficiencies are 34.6% and 73.7%). The output spectra have extremely high flat segments in the range 2070 - 2390 nm and 2070 - 2475 nm with negligible intensity variation (less than 2%). The SC average power is scalable from 2.1 to 4.2 W by increasing the PRF from 5 to 15 kHz, while maintaining pump power. Compared with the input pump pulse, the output SC pulse width is broadened, and no split is found. The stability of the output SC power has been monitored for a week and the fluctuations being less than 6%.

  3. Synergistic Effect of Superhydrophobicity and Oxidized Layers on Corrosion Resistance of Aluminum Alloy Surface Textured by Nanosecond Laser Treatment.

    PubMed

    Boinovich, Ludmila B; Emelyanenko, Alexandre M; Modestov, Alexander D; Domantovsky, Alexandr G; Emelyanenko, Kirill A

    2015-09-01

    We report a new efficient method for fabricating a superhydrophobic oxidized surface of aluminum alloys with enhanced resistance to pitting corrosion in sodium chloride solutions. The developed coatings are considered very prospective materials for the automotive industry, shipbuilding, aviation, construction, and medicine. The method is based on nanosecond laser treatment of the surface followed by chemisorption of a hydrophobic agent to achieve the superhydrophobic state of the alloy surface. We have shown that the surface texturing used to fabricate multimodal roughness of the surface may be simultaneously used for modifying the physicochemical properties of the thick surface layer of the substrate itself. Electrochemical and wetting experiments demonstrated that the superhydrophobic state of the metal surface inhibits corrosion processes in chloride solutions for a few days. However, during long-term contact of a superhydrophobic coating with a solution, the wetted area of the coating is subjected to corrosion processes due to the formation of defects. In contrast, the combination of an oxide layer with good barrier properties and the superhydrophobic state of the coating provides remarkable corrosion resistance. The mechanisms for enhancing corrosion protective properties are discussed. PMID:26271017

  4. Numerical investigation of heating of a gold nanoparticle and the surrounding microenvironment by nanosecond laser pulses for nanomedicine applications

    NASA Astrophysics Data System (ADS)

    Sassaroli, E.; Li, K. C. P.; O'Neill, B. E.

    2009-09-01

    We have modeled, by finite element analysis, the process of heating of a spherical gold nanoparticle by nanosecond laser pulses and of heat transfer between the particle and the surrounding medium, with no mass transfer. In our analysis, we have included thermal conductivity changes, vapor formation, and changes of the dielectric properties as a function of temperature. We have shown that such changes significantly affect the temperature reached by the particle and surrounding microenvironment and therefore the thermal and dielectric properties of the medium need to be known for a correct determination of the temperature elevation. We have shown that for sufficiently low intensity and long pulses, it is possible to establish a quasi-steady temperature profile in the medium with no vapor formation. As the intensity is increased, a phase-change with vapor formation takes place around the gold nanoparticle. As phase-transition starts, an additional increase in the intensity does not significantly increase the temperature of the gold nanoparticle and surrounding environment. The temperature starts to rise again above a given intensity threshold which is particle and environment dependent. The aim of this study is to provide useful insights for the development of molecular targeting of gold nanoparticles for applications such as remote drug release of therapeutics and photothermal cancer therapy.

  5. Damage threshold and focusability of mid-infrared free-electron laser pulses gated by a plasma mirror with nanosecond switching pulses

    SciTech Connect

    Wang, Xiaolong; Nakajima, Takashi; Zen, Heishun; Kii, Toshiteru; Ohgaki, Hideaki

    2013-11-04

    The presence of a pulse train structure of an oscillator-type free-electron laser (FEL) results in the immediate damage of a solid target upon focusing. We demonstrate that the laser-induced damage threshold can be significantly improved by gating the mid-infrared FEL pulses with a plasma mirror. Although the switching pulses we employ have a nanosecond duration which does not guarantee the clean wavefront of the gated FEL pulses, the high focusability is experimentally confirmed through the observation of spectral broadening by a factor of 2.1 when we tightly focus the gated FEL pulses onto the Ge plate.

  6. Nanosecond x-Ray diffraction from polycrystalline and amorphous materials in a pinhole camera geometry suitable for laser shock compression experiments

    SciTech Connect

    Hawreliak, J.; Lorenzana, H. E.; Remington, B. A.; Lukezic, S.; Wark, J. S.

    2007-08-15

    Nanosecond pulses of quasimonochromatic x-rays emitted from the K shell of ions within a laser-produced plasma are of sufficient spectral brightness to allow single-shot recording of powder diffraction patterns from thin foils of order millimeter diameter. Strong diffraction signals have been observed in a cylindrical pinhole camera arrangement from both polycrystalline and amorphous foils, and the experimental arrangement and foil dimensions are such that they allow for laser shocking or quasi-isentropic loading of the foil during the diffraction process.

  7. Nanosecond x-ray diffraction from polycrystalline and amorphous materials in a pinhole camera geometry suitable for laser shock compression experiments.

    PubMed

    Hawreliak, J; Lorenzana, H E; Remington, B A; Lukezic, S; Wark, J S

    2007-08-01

    Nanosecond pulses of quasimonochromatic x-rays emitted from the K shell of ions within a laser-produced plasma are of sufficient spectral brightness to allow single-shot recording of powder diffraction patterns from thin foils of order millimeter diameter. Strong diffraction signals have been observed in a cylindrical pinhole camera arrangement from both polycrystalline and amorphous foils, and the experimental arrangement and foil dimensions are such that they allow for laser shocking or quasi-isentropic loading of the foil during the diffraction process.

  8. Nanosecond laser micro- and nanotexturing for the design of a superhydrophobic coating robust against long-term contact with water, cavitation, and abrasion

    NASA Astrophysics Data System (ADS)

    Emelyanenko, Alexandre M.; Shagieva, Farida M.; Domantovsky, Alexandr G.; Boinovich, Ludmila B.

    2015-03-01

    Existing and emerging applications of laser-driven methods make an important contribution to advancement in nanotechnological approaches for the design of superhydrophobic surfaces. In this study, we describe a superhydrophobic coating on stainless steel, designed by nanosecond IR laser treatment with subsequent chemisorption of fluorooxysilane for use in heavily loaded hydraulic systems. Coating characterization reveals extreme water repellency, chemical stability on long-term contact with water, and excellent durability of functional properties under prolonged abrasive wear and cavitation loads. The coating also demonstrates self-healing properties after mechanical damage.

  9. Laser Pyro System Standardization and Man Rating

    NASA Technical Reports Server (NTRS)

    Brown, Christopher W.

    2004-01-01

    This viewgraph presentation reviews an X-38 laser pyro system standardization system designed for a new manned rated program. The plans to approve this laser initiation system and preliminary ideas for this system are also provided.

  10. Activity of retinal ganglion cells following intense, nanosecond laser flashes. Final report, 1983-1986

    SciTech Connect

    Glickman, R.D.

    1989-01-01

    The effects of intense, but nonlesion-producing, laser exposures of 20-ns duration were determined on the light responses and spontaneous activity of retinal ganglion cells recorded in situ from the rhesus monkey. (Following a single, 20-ns exposure centered on its receptive field, a ganglion cell produced an 'afterdischarge' of maintained action potentials). The duration of the afterdischarge depended on the diameter of the laser beam on the retina and on the beam's intensity. Laser exposures subtending 0.5 to 2.0 deg, and delivering 45 to 60% of the maximum permissible exposure, elicited afterdischarges that lasted up to 80 s. When the beam diameter was decreased to 0.25 deg, the afterdischarge was reduced to 30 s, and to less than 5 s with the 0.12-deg beam. Light sensitivity after the laser exposure recovered rapidly during the first 10 s and then more slowly, but exponentially, until it reached the preflash level. Color-opponent ganglion cells exhibited a phenomenon called 'response-reversal' after the laser exposure, presumably due to selective adaptation of a mid-wavelength cone-input. Because a 20-ns exposure, regardless of intensity, is likely to photoregenerate more than half of the available visual pigment, the effects of ganglion cell response described here are not likely to be due solely to pigment bleaching.

  11. Nanoscale heat transfer in direct nanopatterning into gold films by a nanosecond laser pulse.

    PubMed

    Lin, Yuanhai; Zhai, Tianrui; Zhang, Xinping

    2014-04-01

    We investigate nanoscale heat transfer and heat-flux overlapping effects in nanopatterning through interactions between interferogram produced by 5-ns laser pulses at 355 nm and gold films. These mechanisms played different roles in direct writing of gold nanolines with different periods. Continuous gold nanolines were produced for large periods, where heat-flux overlapping is too small to effect the laser-metal interactions. Thus, the heat-transfer distance and direct laser-ablation determined the width of resultant gold nanolines. However, gold nanolines consisting of isolated gold nanoparticles were produced for small periods, where the overlapped heat-flux exceeds the threshold for removing or melting gold films. PMID:24718213

  12. Equation of state for simulation of nanosecond laser ablation aluminium in water and air

    NASA Astrophysics Data System (ADS)

    Davydov, R.; Antonov, V.; Kalinin, N.

    2015-11-01

    To analyze the physical processes at high energy densities, when laser is used, an adequate description the thermodynamic property of matter over a broad region of states including the normal conditions and plasma at high pressures and temperatures is required. For describing the thermodynamic properties of metals in nanoparticles production using laser ablation a semi-empirical equation of state model is proposed. To verify this model, an equation of state of aluminum was constructed. Using this equation was calculated ablation depths and crater profile for aluminum and compared with experimental data. Received results are in a good match with experiment.

  13. Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials.

    PubMed

    Holá, Markéta; Mikuska, Pavel; Hanzlíková, Renáta; Kaiser, Jozef; Kanický, Viktor

    2010-03-15

    A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation.

  14. Generation of 7W nanosecond pulses with 670nm ridge-waveguide lasers

    NASA Astrophysics Data System (ADS)

    Klehr, A.; Prziwarka, T.; Liero, A.; Hoffmann, Th.; Pohl, J.; Fricke, J.; Wünsche, H.-J.; Wenzel, H.; Heinrich, W.; Erbert, G.

    2016-03-01

    The aim of this paper is to present detailed experimental and theoretical investigations of the behavior of ridge-waveguide (RW) lasers emitting at 670 nm under injection of sub-ns current pulses with high amplitudes. The RW lasers are based on strained GaInP double quantum wells embedded in an asymmetric AlGaInP/AlInP waveguide structure. The width of the ridge is 15 μm and the cavity length 3 mm. The laser diode is mounted on an in-house developed laser driver with a final stage based on GaN transistors, which generates nearly rectangular shaped current pulses with amplitudes up to 30 A and widths down to 300 ps. The pulse width can be varied electronically between 300 ps and 1.2 ns with a repetition frequency up to 1 MHz, which results in a variation of the pulse width of the emitted optical pulses between 200 ps and 1.2 ns. The maximum pulse power depends on the electrical pulse width and reaches 7.2 W for a ridge width of 15 μm. At high pulse current amplitudes the pulse power saturates. Time-dependent simulations with the drift-diffusion simulator WIAS-TeSCA reveal that accumulation of excess electrons under the ridge is the root cause for the power saturation, limiting the maximum achievable output power.

  15. Characterization Of Nano-Second Laser Induced Plasmas From Al Target In Air At Atmospheric Pressure

    SciTech Connect

    Hegazy, H.; Abdel-Rahim, F. M.; Nossair, A. M. A.; Allam, S. H.; El-Sherbini, Th. M.

    2008-09-23

    In the present work we study the effect of the laser beam energy on the properties of the plasma generated by focusing an intense laser beam on Al solid target in air at atmospheric pressure. Plasma is generated using a Nd:YAG pulsed laser at 1064 nm wavelength, 6 ns pulse duration with a maximum pulse energy of 750mJ. The emission spectrum is collected using an Echelle spectrometer equipped with ICCD camera Andor type. The measurements were performed at several delay times between 0 to 9 {mu}s. Measurements of temperature and electron density of the produced plasmas at different laser energies and at different delay times are described using different emission spectral lines. Based on LTE assumption, excitation temperature is determined from the Boltzmann plot using O I spectral lines at 777.34, 794.93, and 848.65 nm and the electron density is determined from Stark width of Al II at 281.6 and 466.3 nm. The determined density is compared with the density determined from H{sub {alpha}} spectral line.

  16. Sub-nanosecond Yb:KLu(WO4)2 microchip laser.

    PubMed

    Loiko, P; Serres, J M; Mateos, X; Yumashev, K; Yasukevich, A; Petrov, V; Griebner, U; Aguiló, M; Díaz, F

    2016-06-01

    A diode-pumped Yb:KLu(WO4)2 microchip laser passively Q-switched by a Cr4+:YAG saturable absorber generated a maximum average output power of 590 mW at 1031 nm with a slope efficiency of 55%. The pulse characteristics were 690 ps/47.6 μJ at a pulse repetition frequency of 12.4 kHz. The output beam had an excellent circular profile with M2<1.05. Yb:KLu(WO4)2 is very promising for ultrathin sub-ns microchip lasers. PMID:27244429

  17. Rapid solidification of polymorphic transition metals induced by nanosecond laser pulses

    NASA Technical Reports Server (NTRS)

    Vitta, Satish

    1991-01-01

    An Nd-YAG laser giving 5 ns, 266 nm pulses was used to melt and subsequently quench thin, pure metallic films on a liquid Al/Al2O3 substrate at 10 to the 10th - 10 to the 12th K/s. Transmission electron microscopy together with electron diffraction was used to study the competitive nucleation and growth behavior of the crystals from the undercooled melt. In the case of Fe and Co, the high-temperature bcc and fcc structures were retained after laser quenching. Ti and Zr in spite of the structural similarities exhibit different preferences for nucleation from the undercooled melt. In all the metals the solid-state transformations were completely suppressed and the crystal growth was found to be limited by the collisional frequency of the atoms onto the growing interface.

  18. Oxidation of silicon nanoparticles produced by nanosecond laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Vaccaro, L.; Camarda, P.; Messina, F.; Buscarino, G.; Agnello, S.; Gelardi, F. M.; Cannas, M.; Boscaino, R.

    2014-10-01

    We investigated nanoparticles produced by laser ablation of silicon in water by the fundamental harmonic (1064 nm) of a ns pulsed Nd:YAG. The silicon oxidation is evidenced by IR absorption features characteristic of amorphous SiO2 (silica). This oxide is highly defective and manifests a luminescence activity under UV excitation: two emission bands at 2.7 eV and 4.4 eV are associated with the twofold coordinated silicon, =SiO••.

  19. FM-to-AM conversion measurement for high power nanosecond lasers

    NASA Astrophysics Data System (ADS)

    PENNINCKX, Denis

    2016-03-01

    Through numerical simulations we show that the spectral content of amplitude modulations induced by a transfer function converting frequency modulations required for high-power lasers may be very broad. Hence, measurement of FM-to-AM conversion should be first done in the spectral domain to remove unwanted transfer functions at low frequency scale and then in the time domain to obtain an accurate value.

  20. High brightness sub-nanosecond Q-switched laser using volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Anderson, Brian M.; Hale, Evan; Venus, George; Ott, Daniel; Divliansky, Ivan; Glebov, Leonid

    2016-03-01

    The design of Q-switched lasers capable of producing pulse widths of 100's of picoseconds necessitates the cavity length be shorter than a few centimeters. Increasing the amount of energy extracted per pulse requires increasing the mode area of the resonator that for the same cavity length causes exciting higher order transverse modes and decreasing the brightness of the output radiation. To suppress the higher order modes of these multimode resonators while maintaining the compact cavity requires the use of intra-cavity angular filters. A novel Q-switched laser design is presented using transmitting Bragg gratings (TBGs) as angular filters to suppress the higher order transverse modes. The laser consists of a 5 mm thick slab of Nd:YAG, a 3 mm thick slab of Cr:YAG with a 20% transmission, one TBG aligned to suppress the higher order modes along the x-axis, and a 40% output coupler. The gratings are recorded in photo-thermo-refractive (PTR) glass, which has a high damage threshold that can withstand both the high peak powers and high average powers present within the resonator. Using a 4.1 mrad TBG in a 10.8 mm long resonator with an 800μm x 400 μm pump beam, a nearly diffraction limited beam quality of M2 = 1.3 is obtained in a 0.76 mJ pulse with a pulse width of 614 ps.

  1. 1D modelling of nanosecond laser ablation of copper samples in argon at P = 1 atm with a wavelength of 532 nm

    NASA Astrophysics Data System (ADS)

    Clair, Guillaume; L'Hermite, Daniel

    2011-10-01

    A one-dimensional model is developed for nanosecond laser ablation of a metal target (Cu) in a background gas (Ar) at any pressure. Simulations are performed with a 6 ns FWHM Gaussian laser pulse at 532 nm with a fluence of 11.3 J.cm-2. Heating, melting, evaporation, and condensation are considered to model the laser-target interaction. Expansion of the plume is investigated solving the Euler equations in a lagrangian formalism. Plasma formation is taken into account by computing the ionic species densities up to the second order of ionization in both the ablated material and the background gas. Such formation implies a strong laser-plasma interaction, assuming that the absorption phenomena are photoionization, electron-atom, and electron-ion inverse Bremsstrahlung. Radiative losses are supposed to be only described by electron-ion Bremsstrahlung. Preliminary results are presented and discussed.

  2. Time evolution of domain-wall motion induced by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Gerasimov, M. V.; Logunov, M. V.; Spirin, A. V.; Nozdrin, Yu. N.; Tokman, I. D.

    2016-07-01

    The time evolution of the magnetization normal component change in a garnet film with a labyrinthine domain structure under the action of circularly and linearly polarized laser pump pulses (the pulse duration is 5 ns; the wavelength is 527 nm) has been studied. The dynamic state of the magnetic film was registered using an induction method with a time resolution of 1 ns. It was found that for the initial state of the magnetic film with an equilibrium domain structure, the form of the photomagnetization pulse reflects the time evolution of a domain-wall motion. The domain-wall motion initiated by the circularly polarized laser pump pulse continues in the same direction for a time more than an order of magnitude exceeding the laser pulse duration. In general, the time evolution of the domain-wall movement occurs in three stages. The separation of the contributions to the photomagnetization from the polarization-dependent and polarization-independent effects was carried out. The photomagnetization pulses that reflect the contributions by the aforementioned effects differ by form, and more than two orders of magnitude by duration. Their form doesn't change under a magnetic bias field change, only the photomagnetization pulse amplitude does: for the polarization-dependent contribution, it's an even function of the field, and for the polarization-independent contribution, it's an odd function. The interconnection between the polarization-dependent and polarization-independent effects, on the one hand, and the domain-wall displacement and the change of the film's saturation magnetization, on the other hand, was identified and described.

  3. Melting of nanocrystals embedded in a crystal matrix heated by nanosecond laser pulses

    SciTech Connect

    Zinoviev, V. A. Dvurechenskii, A. V.; Smagina, Zh. V.; Ivlev, G. D.; Gatskevich, E. I.; Malevich, V. L.

    2012-09-15

    The kinetics of phase transformations of nanocrystals in a crystal matrix is considered upon non-stationary heating by laser pulses. The melting and crystallization kinetics of nanocrystals is described taking into account their size, shape, elemental composition, and elastic deformations appearing due to the mismatch of the lattice constants for nanocrystals and the matrix. The possibility of decreasing the dispersion of nanocrystals over their size in heterostructures with quantum dots is predicted. As an example, melting of Ge nanocrystals in a Si matrix is considered.

  4. Laser-induced damage in dielectrics with nanosecond to subpicosecond pulses. I. Experimental. Part 1

    SciTech Connect

    Stuart, B.C.; Herman, S.; Perry, M.D.

    1994-12-01

    The authors report extensive laser-induced damage threshold measurements on pure and multilayer dielectrics at 1053 and 526 mm for pulse durations, {tau}, ranging from 140 fs to 1 ns. Qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}{sup 1/2} scaling indicate that damage results from plasma formation and ablation for {tau}{le}10 ps and from conventional melting and boiling for {tau}>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with both the pulsewidth and wavelength scaling of experimental results.

  5. Spectral studies of nanosecond laser interaction with magnesium sulfate target in air

    NASA Astrophysics Data System (ADS)

    Salik, Muhammad; Hanif, Muhammad; Wang, Jiasheng; Zhang, Xi-Qing; Zhang

    2014-02-01

    The optical emission characterization of the plasma-assisted pulsed laser ablation of the magnesium sulfate target is discussed in this study. The emission spectrum produced by the magnesium sulfate plasma in the wavelength range 200-700 nm has been carefully investigated for different experimental conditions. The spectra analysis was performed by assuming the local thermodynamic equilibrium (LTE) approximation and calculating the plasma temperature with the Boltzmann plot method using neutral Mg spectral lines. The plasma temperature was obtained for different positions along the expansion axis, which allowed obtaining the electron population distribution as a function of the distance from the target. The plasma temperature along the expansion axis allowed evaluating the evolution of the excited states population when the plume expands. Moreover, the Stark broadening method has been employed for electron number density measurements. In this study, the Stark width of the Mg (I) spectral line at 285.21 nm was used. Besides, we have studied the variation of electron temperature (Te ) and electron number density (Ne ) as a function of laser irradiance.

  6. Self-consistent modeling of jet formation process in the nanosecond laser pulse regime

    SciTech Connect

    Mezel, C.; Hallo, L.; Breil, J.; Souquet, A.; Guillemot, F.; Hebert, D.

    2009-12-15

    Laser induced forward transfer (LIFT) is a direct printing technique. Because of its high application potential, interest continues to increase. LIFT is routinely used in printing, spray generation and thermal-spike sputtering. Biological material such as cells and proteins have already been transferred successfully for the creation of biological microarrays. Recently, modeling has been used to explain parts of the ejection transfer process. No global modeling strategy is currently available. In this paper, a hydrodynamic code is utilized to model the jet formation process and estimate the constraints obeyed by the bioelements during the transfer. A self-consistent model that includes laser energy absorption, plasma formation via ablation, and hydrodynamic processes is proposed and confirmed with experimental results. Fundamental physical mechanisms via one-dimensional modeling are presented. Two-dimensional (2D) simplified solutions of the jet formation model equations are proposed. Predicted results of the model are jet existence and its velocity. The 2D simulation results are in good agreement with a simple model presented by a previous investigator.

  7. Emission features and expansion dynamics of nanosecond laser ablation plumes at different ambient pressures

    SciTech Connect

    Farid, N.; Harilal, S. S. Hassanein, A.; Ding, H.

    2014-01-21

    The influence of ambient pressure on the spectral emission features and expansion dynamics of a plasma plume generated on a metal target has been investigated. The plasma plumes were generated by irradiating Cu targets using 6 ns, 1064 nm pulses from a Q-switched Nd:YAG laser. The emission and expansion dynamics of the plasma plumes were studied by varying air ambient pressure levels ranging from vacuum to atmospheric pressure. The ambient pressure levels were found to affect both the line intensities and broadening along with the signal to background and signal to noise ratios and the optimum pressure conditions for analytical applications were evaluated. The characteristic plume parameters were estimated using emission spectroscopy means and noticed that the excitation temperature peaked ∼300 Torr, while the electron density showed a maximum ∼100 Torr. Fast-gated images showed a complex interaction between the plume and background air leading to changes in the plume geometry with pressure as well as time. Surface morphology of irradiated surface showed that the pressure of the ambient gas affects the laser-target coupling significantly.

  8. Pump-probe imaging of nanosecond laser-induced bubbles in distilled water solutions: Observations of laser-produced-plasma

    SciTech Connect

    Evans, R.; Camacho-Lopez, S.

    2010-11-15

    This article presents the analysis of the laser-produced-plasma (LPP) formed by the focusing of a 9 ns laser pulse, {lambda}=532 nm, with a NA=0.6 aspherical lens using energies between 100-1500 {mu}J, into distilled water with varying solutions of table salt. Observations of the filamentation plasma were made, which are explained by self-focusing of the laser pulse by the LPP through ponderomotive cavitation of the electron plasma in the center of the beam. The filamentation of the beam through a low density plasma wave guide explains why the transmission of the pump laser through the interaction region was notably higher on previous experiments that we performed [R. Evans et al., Opt. Express 16, 7481 (2008)], than a very similar set of experiments performed by Noack and Vogel [IEEE J. Quantum Electron. 35, 1156 (1999)].

  9. Effect of crystal axis in temperature dependence of laser-induced damage thresholds by nanosecond near-infrared laser

    NASA Astrophysics Data System (ADS)

    Mikami, Katsuhiro; Sugita, Tsuyoshi; Azumi, Minako; Jitsuno, Takahisa

    2015-10-01

    Laser-induced damage thresholds in crystalline quartz were evaluated using a single-mode Nd:YAG laser (wavelength 1064 nm, pulse width 4 ns) at temperatures ranging from 123 K to 473 K. In this experiment, three kinds of crystalline quartz different in the cut direction were prepared. The damage morphologies were coincident with the crystal structure. The laser induced damage thresholds in crystalline quartz differed according to the cutting direction. The laser-induced damage thresholds expect in the case of Z-cut sample increased with decreasing temperature. The cutting direction of the Z-cut of crystalline quartz was parallel to the crystal axis. A tendency of the temperature dependence was the same with in the case of the glass materials. In contrast, the laser-induced damage threshold of the Z-cut sample decreased with decreasing temperature. The difference in the temperature-dependent behaviors of crystalline quartz is explained using physical models. The crystal axis influenced strongly to the electron resistivity and the electron avalanche process in laser-induced damage mechanisms was affected in the result.

  10. Spectra of plasmas of Ru, Rh, Pd and Mo produced with nanosecond and picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lokasani, Ragava; Long, Elaine; Sheridan, Paul; Hayden, Patrick; O'Reilly, Fergal; Dunne, Padraig; Endo, Akira; Limpouch, Jiri; O'Sullivan, Gerry

    2015-05-01

    This paper describes the extreme ultraviolet and soft x-ray emission recorded in the 2-12 nm region from Mo, Ru, Rh and Pd ions present in the laser produced plasmas. The spectra were found to be dominated by 3p-3d transitions in the 5-8 nm region, which shift slowly to shorter wavelengths with the increasing atomic number, and by 3d-4p and 3d-4f transitions at shorter wavelengths. These transitions, in a number of neighbouring ion stages, were distinguished by comparison with Cowan code calculations and previously reported data. The experimental results show that strong emission can be observed at the 6.X nm region for Ru, Rh and Pd plasmas.

  11. Numerical simulation of the dynamics of phase transitions in CdTe induced by irradiation with nanosecond pulses of an excimer laser

    SciTech Connect

    Zhvavyi, S. P. Zykov, G. L.

    2006-06-15

    Simulation of the effect of KrF nanosecond pulse excimer laser radiation ({lambda} = 248 nm, {tau} = 20 ns) on phase transitions in cadmium telluride was performed taking into account the diffusion of the melt components and their evaporation from the surface. It is shown that the surface region of the melt is enriched with tellurium due to the evaporation and diffusion of the cadmium telluride components. The obtained value 0.05 J/cm{sup 2} of the threshold energy density for melting is in reasonable agreement with the experimental data.

  12. Estimation of excited-state absorption and photobleaching in Fe²⁺-doped lithium sodium silicate glass under exposure to high-power nanosecond laser pulses.

    PubMed

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

    2015-04-01

    Fe-doped lithium sodium silicate glasses codoped with Sn and C to promote the Fe²⁺ redox state are investigated under simultaneous excitation at the first and third harmonics of a nanosecond Nd:YAG laser. The aim is to evaluate critical parameters associated with the potential use of this material as an optical filter that transmits the third harmonic but blocks the fundamental frequency. Estimations of the excited-state absorption coefficient and photobleaching (reduction of absorption at the fundamental) are provided. The results provide insight on the design and expected operational parameters of this type of Fe-doped materials. PMID:25967187

  13. Ablation of human carious dentin with a nanosecond pulsed laser at a wavelength of 5.85 μm: relationship between hardness and ablation depth

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2014-02-01

    Less invasive treatment and preservation of teeth, referred to as minimal intervention, are strong requirements in dentistry. In our previous study, the fundamental ablation properties of human dentin at wavelengths around 5.8 μm were investigated, and the results indicated that the wavelength of 5.85 μm was optimal for selective removal of carious dentin with less damage to normal dentin. The purpose of this study was to investigate the relationship between the ablation depth and hardness of human dentin including carious lesion. A nanosecond pulsed laser produced by difference-frequency generation was used for irradiations to human carious dentin. It was observed that correlation between ablation depth and Vickers hardness after 2 s laser irradiation at the wavelength of 5.85 μm and the average power density of 30 W/cm2. On the other hand, ablations did not depend on Vickers hardness at the wavelength of 6.00 μm. A nanosecond pulsed laser with the wavelength at 5.85 μm is useful for selective ablation of human carious dentin in accordance with the hardness.

  14. Morphometric comparison of the acute rabbit corneal response to 1540-nm laser light following in-vitro exposure to millisecond or nanosecond pulse widths

    NASA Astrophysics Data System (ADS)

    Eurell, Thomas E.; Johnson, Thomas E.; Roach, William P.

    2002-06-01

    Significant damage to rabbit corneal tissue was produced by a single pulse, in vitro exposure of 1540 m infrared laser light operating in either millisecond or nanosecond pulse widths. Millisecond pulse widths of infrared laser light produced a marked coagulative necrosis of both the corneal epithelium and stroma. We also noted histologic alterations in the stromal matrix within the beam path that we interpreted as matrix remodeling. To test this interpretation, we used an indirect immunohistochemical procedure to detect Matrix Metalloproteinase-2 (MMP-2) activity. Immunohistochemistry revealed that the MMP-2 reaction was mostly limited to the margins of the beam path. In addition, the MMP-2 reaction was less intense than expected given the significant tissue changes observed in the histologic sections. Exposure of rabbit corneal tissue to the nanosecond pulse widths produced a less severe coagulative necrosis of the tissue when compared to the millisecond exposures. However, a markedly stronger immunohistochemical pattern than would have been predicted from the histologic sections was observed, with approximately half of the beam path filled with MMP-2 reaction product. These data suggest an association between infrared laser pulse width and the degree of extracellular matrix remodeling in rabbit corneal tissue.

  15. Angular Distribution of Tungsten Material and Ion Flux during Nanosecond Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Hussain, M. S.; Dogar, A. H.; Qayyum, A.; Abbasi, S. A.

    2016-01-01

    Tungsten thin films were prepared by pulsed laser deposition (PLD) technique on glass substrates placed at the angles of 0∘ to 70∘ with respect to the target surface normal. Rutherford backscattering Spectrometry (RBS) analysis of the films indicated that about 90% of tungsten material flux is distributed in a cone of 40∘ solid angle while about 54% of it lies even in a narrower cone of 10∘ solid angle. Significant diffusion of tungsten in glass substrate has been observed in the films deposited at smaller angles with respect to target surface normal. Time-of-flight (TOF) measurements performed using Langmuir probe indicated that the most probable ion energy decreases from about 600 to 91eV for variation of θ from 0∘ to 70∘. In general ion energy spread is quite large at all angles investigated here. The enhanced tungsten diffusion in glass substrate observed at smaller angles is most probably due to the higher ion energy and ion assisted recoil implantation of already deposited tungsten.

  16. Near-ultraviolet absorption and nanosecond-pulse-laser damage in HfO2 monolayers studied by submicrometer-resolution photothermal heterodyne imaging and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Papernov, S.; Tait, A.; Bittle, W.; Schmid, A. W.; Oliver, J. B.; Kupinski, P.

    2011-06-01

    Localized absorption in hafnium dioxide used as a high-index component in multilayer coatings for near-ultraviolet, nanosecond-pulse-laser applications is directly linked to laser-induced damage. The nature of the absorbing species and their physical properties remains unknown because of their extremely small sizes. Previous experimental evidence provided by the atomic force microscopy mapping of damage morphology points to a few-nanometer scale of these absorbers. This work demonstrates the submicrometer-resolution mapping of 355-nm absorption in HfO2 monolayers using a recently developed photothermal heterodyne imaging technique. The comparison of absorption maps with the atomic force microscopy investigation of pulsed-laser-induced damage morphology allows one to better estimate the spatial distribution of nanoscale absorbing defects in hafnia thin films. Possible defect-formation mechanisms are discussed.

  17. Luminescence in the fluoride-containing phosphate-based glasses: a possible origin of their high resistance to nanosecond pulse laser-induced damage.

    PubMed

    Wang, Pengfei; Lu, Min; Gao, Fei; Guo, Haitao; Xu, Yantao; Hou, Chaoqi; Zhou, Zhiwei; Peng, Bo

    2015-01-01

    Fusion power offers the prospect of an almost inexhaustible source of energy for future generations. It was reported that fusion fuel gains exceeding unity on the National Ignition Facility (NIF) were achieved, but so far great deal of scientific and engineering challenges have to be overcome for realizing fusion power generation. There is a bottleneck for color-separation gratings in NIF and other similar inertial confinement fusion (ICF) lasers. Here we show a series of high performance phosphate-based glasses that can transmit the third harmonic frequency (3ω) laser light with high efficiency meanwhile filter the fundamental (1ω) and the second harmonic frequency (2ω) laser lights through direct absorption, and especially they exhibit excellent damage threshold induced by nanosecond pulse laser compared with that of the fused silica used in NIF. Yellowish-orange fluorescence emits during the laser-material interaction process, and it can be tailored through regulating the glass structure. Study on its structural origin suggests that the fluorescence emission is a key factor that conduces to the high laser-induced damage resistance of these glasses. The results also indicated the feasibility of utilizing these high performance glasses in novel color separation optics, allowing novel design for the final optics assembly in ICF lasers. PMID:25716328

  18. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    NASA Astrophysics Data System (ADS)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J.

    2013-06-01

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 × 10-9 s) at lower energies. Microstructural studies, conducted by X-ray diffraction (θ-2θ and φ techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO⟨111 ⟩||c-YSZ⟨001⟩ and in-plane NiO⟨110⟩||c-YSZ⟨100⟩. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min-1 for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies ease the adsorption of 4-chlorophenol, hydroxyl, and water molecules to the surface. Thus, n

  19. Nanosecond fluorescence spectroscopy

    SciTech Connect

    Leskovar, B.

    1985-03-01

    This article is a summary of a short course lecture given in conjunction with the 1984 Nuclear Science Symposium. Measuring systems for nanosecond fluorescence spectroscopy using single-photon counting techniques are presented. These involve systems based on relaxation-type spark gap light pulser and synchronously pumped mode-locked dye lasers. Furthermore, typical characteristics and optimization of operating conditions of the critical components responsible for the system time resolution are discussed. A short comparison of the most important deconvolution methods for numerical analysis of experimental data is given particularly with respect to the signal-to-noise ratio of the fluorescence signal. 22 refs., 8 figs.

  20. Nanosecond microscopy with spectroscopic resolution

    NASA Astrophysics Data System (ADS)

    Heinrich, Christoph; Bernet, Stefan; Ritsch-Marte, Monika

    2006-03-01

    We demonstrate coherent anti-Stokes Raman scattering (CARS) microscopy in a wide-field setup with nanosecond laser pulse excitation. In contrast to confocal setups, the image of a sample can be recorded with a single pair of excitation pulses. For this purpose, the excitation geometry is specially designed in order to satisfy the phase matching condition over the whole sample area. The spectral, temporal and spatial sensitivity of the method is demonstrated by imaging test samples, i.e. oil vesicles in sunflower seeds, on a nanosecond timescale. The method provides snapshot imaging in 3 ns with a spectral resolution of 25 cm-1.

  1. In vitro study on selective removal of bovine demineralized dentin using nanosecond pulsed laser at wavelengths around 5.8 μm for realizing less invasive treatment of dental caries.

    PubMed

    Kita, Tetsuya; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-04-01

    In the treatment of dental caries, less invasive methods are strongly required. However, conventional dental lasers cannot always achieve selective removal of caries or good bonding with a composite resin. Based on the optical absorption characteristics of dentin, wavelengths around 6 μm are promising in this regard. Our previous study indicated the possibility of selective removal of demineralized dentin using a nanosecond pulsed laser at wavelengths around 6 μm. In the present study, the optimal laser irradiation conditions were investigated for achieving selective removal of demineralized dentin. Bovine dentin was used, and its laser ablation characteristics were evaluated. The results indicated that demineralized dentin could be selectively removed, without causing cracking or damage to sound dentin, at laser wavelengths of 5.75 and 5.80 μm and average power densities of 30-40 W/cm(2). These optimal laser irradiation conditions also realized higher bonding strength with a composite resin than was possible using an Er:YAG laser. The use of nanosecond pulses allowed the thermal confinement condition to be satisfied, leading to a reduction in tissue damage, including degradation of dental pulp vitality. Thus, a nanosecond pulsed laser at 5.8 μm was found to be effective for less invasive caries treatment.

  2. Post-processing of fused silica and its effects on damage resistance to nanosecond pulsed UV lasers.

    PubMed

    Ye, Hui; Li, Yaguo; Zhang, Qinghua; Wang, Wei; Yuan, Zhigang; Wang, Jian; Xu, Qiao

    2016-04-10

    HF-based (hydrofluoric acid) chemical etching has been a widely accepted technique to improve the laser damage performance of fused silica optics and ensure high-power UV laser systems at designed fluence. Etching processes such as acid concentration, composition, material removal amount, and etching state (etching with additional acoustic power or not) may have a great impact on the laser-induced damage threshold (LIDT) of treated sample surfaces. In order to find out the effects of these factors, we utilized the Taguchi method to determine the etching conditions that are helpful in raising the LIDT. Our results show that the most influential factors are concentration of etchants and the material etched away from the viewpoint of damage performance of fused silica optics. In addition, the additional acoustic power (∼0.6  W·cm-2) may not benefit the etching rate and damage performance of fused silica. Moreover, the post-cleaning procedure of etched samples is also important in damage performances of fused silica optics. Different post-cleaning procedures were, thus, experiments on samples treated under the same etching conditions. It is found that the "spraying + rinsing + spraying" cleaning process is favorable to the removal of etching-induced deposits. Residuals on the etched surface are harmful to surface roughness and optical transmission as well as laser damage performance. PMID:27139869

  3. Improved patterning of ITO coated with gold masking layer on glass substrate using nanosecond fiber laser and etching

    NASA Astrophysics Data System (ADS)

    Tan, Nguyen Ngoc; Hung, Duong Thanh; Anh, Vo Tran; BongChul, Kang; HyunChul, Kim

    2015-05-01

    In this paper, an indium-tin oxide (ITO) thin-film patterning method for higher pattern quality and productivity compared to the short-pulsed laser direct writing method is presented. We sputtered a thin ITO layer on a glass substrate, and then, plated a thin gold layer onto the ITO layer. The combined structure of the three layers (glass-ITO-gold) was patterned using laser-induced plasma generated by an ytterbium pulsed fiber laser (λ = 1064 nm). The results showed that the process parameters of 50 mm/s in scanning speed, 14 ns pulse duration, and a repetition rate of 7.5 kHz represented optimum conditions for the fabrication of ITO channels. Under these conditions, a channel 23.4 μm wide and 20 nm deep was obtained. However, built-up spikes (∼15 nm in height) resulted in a decrease in channel quality, and consequently, short circuit occurred at some patterned positions. These built-up spikes were completely removed by dipping the ITO layer into an etchant (18 wt.% HCl). A gold masking layer on the ITO surface was found to increase the channel surface quality without any decrease in ITO thickness. Moreover, the effects of repetition rate, scanning speed, and etching characteristics on surface quality were investigated.

  4. A simple method for experimental determination of electron temperature and electron density in a nanosecond pulsed longitudinal discharge used for excitation of high-power atomic and ionic metal and metal halide vapour lasers

    NASA Astrophysics Data System (ADS)

    Temelkov, K. A.; Vuchkov, N. K.

    2016-05-01

    A simple method based on the time-resolved measurement of electrical discharge parameters, such as tube voltage and discharge current, is developed and applied for determination of electron temperature and electron density in the discharge period of a nanosecond pulsed longitudinal discharge, exciting high-power DUV Cu+ Ne-CuBr, He-Hg+ and He-Sr+ lasers.

  5. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  6. A Simulation of the Effects of Varying Repetition Rate and Pulse Width of Nanosecond Discharges on Premixed Lean Methane-Air Combustion

    DOE PAGES

    Bak, Moon Soo; Cappelli, Mark A.

    2012-01-01

    Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond repetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied from 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger amounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested repetition rates. The shorter pulse width is found to favor the production of species in higher electronicmore » states, but the varying effects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that determines the extent of stabilization over this range of discharge properties studied.« less

  7. Nanosecond laser-induced selective removal of the active layer of CuInGaSe2 solar cells by stress-assisted ablation

    NASA Astrophysics Data System (ADS)

    Buzás, András; Geretovszky, Zsolt

    2012-06-01

    We demonstrate that laser pulses of nanosecond duration (λ=1064 nm, τ=25 ns, PRR =5 kHz) are capable of the clean removal of the CuInGaSe2 (CIGS) and ZnO:Al layers in the layer structure of chalcogenide-based solar cells, leaving the underlying Mo layer undamaged and producing excellent crater morphology. Our results prove that the material removal process is governed by the thermomechanical stress developing in the CIGS layer due to rapid laser heating. In the mechanical ablation of the active layer, three phenomena play a crucial role, namely, delamination, buckling, and fracture. Morphological and compositional analysis of the laser-processed areas is used to identify the experimental parameters where clean mechanical ablation can be achieved. Numerical calculations, performed in the comsol software environment, are also presented to complement the experimental tendencies and verify the proposed model. Our calculation proves the development of a stress distribution that drives the delamination of the CIGS and Mo layers. As the delamination front proceeds radially outward, the separation of the layers ceases in the colder outer regions according to the Griffith's criterion and defines the size of the craters produced afterwards. The free-standing chalcogenide layer continues to deform, and buckling results in a growing tensile stress at the perimeter of the delaminated area, where ultimately fracture will finalize the removal process and facilitate the clean ablation of the laser-irradiated area.

  8. Optimization of graffiti removal on natural stone by means of high repetition rate UV laser

    NASA Astrophysics Data System (ADS)

    Fiorucci, M. P.; López, A. J.; Ramil, A.; Pozo, S.; Rivas, T.

    2013-08-01

    The use of laser for graffiti removal is a promising alternative to conventional cleaning methods, though irradiation parameters must be carefully selected in order to achieve the effective cleaning without damaging the substrate, especially when referring to natural stone. From a practical point of view, once a safe working window is selected, it is necessary to determine the irradiation conditions to remove large paint areas, with minimal time consumption. The aim of this paper is to present a systematic procedure to select the optimum parameters for graffiti removal by means of the 3rd harmonic of a high repetition rate nanosecond Nd:YVO4 laser. Ablation thresholds of four spray paint colors were determined and the effect of pulse repetition frequency, beam diameter and line scan separation was analyzed, obtaining a set of values which optimize the ablation process.

  9. Axial- and radial-resolved electron density and excitation temperature of aluminum plasma induced by nanosecond laser: Effect of the ambient gas composition and pressure

    SciTech Connect

    Dawood, Mahmoud S.; Hamdan, Ahmad E-mail: Joelle.margot@umontreal.ca; Margot, Joëlle E-mail: Joelle.margot@umontreal.ca

    2015-11-15

    The spatial variation of the characteristics of an aluminum plasma induced by a pulsed nanosecond XeCl laser is studied in this paper. The electron density and the excitation temperature are deduced from time- and space- resolved Stark broadening of an ion line and from a Boltzmann diagram, respectively. The influence of the gas pressure (from vacuum up to atmospheric pressure) and compositions (argon, nitrogen and helium) on these characteristics is investigated. It is observed that the highest electron density occurs near the laser spot and decreases by moving away both from the target surface and from the plume center to its edge. The electron density increases with the gas pressure, the highest values being occurred at atmospheric pressure when the ambient gas has the highest mass, i.e. in argon. The excitation temperature is determined from the Boltzmann plot of line intensities of iron impurities present in the aluminum target. The highest temperature is observed close to the laser spot location for argon at atmospheric pressure. It decreases by moving away from the target surface in the axial direction. However, no significant variation of temperature occurs along the radial direction. The differences observed between the axial and radial direction are mainly due to the different plasma kinetics in both directions.

  10. Nanosecond laser switching of surface wettability and epitaxial integration of c-axis ZnO thin films with Si(111) substrates.

    PubMed

    Molaei, R; Bayati, M R; Alipour, H M; Estrich, N A; Narayan, J

    2014-01-01

    We have achieved integration of polar ZnO[0001] epitaxial thin films with Si(111) substrates where cubic yttria-stabilized zirconia (c-YSZ) was used as a template on a Si(111) substrate. Using XRD (θ-2θ and φ scans) and HRTEM techniques, the epitaxial relationship between the ZnO and the c-YSZ layers was shown to be [0001]ZnO || [111]YSZ and [21¯1¯0]ZnO || [1¯01](c-YSZ), where the [21¯1¯0] direction lies in the (0001) plane, and the [1¯01] direction lies in the (111) plane. Similar studies on the c-YSZ/Si interface revealed epitaxy as (111)YSZ || (111)Si and in-plane (110)YSZ || (110)Si. HRTEM micrographs revealed atomically sharp and crystallographically continuous interfaces. The ZnO epilayers were subsequently laser annealed by a single pulse of a nanosecond excimer KrF laser. It was shown that the hydrophobic behavior of the pristine sample became hydrophilic after laser treatment. XPS was employed to study the effect of laser treatment on surface stoichiometry of the ZnO epilayers. The results revealed the formation of oxygen vacancies, which are envisaged to control the observed hydrophilic behavior. Our AFM studies showed surface smoothing due to the coupling of the high energy laser beam with the surface. The importance of integration of c-axis ZnO with Si(111) substrates is emphasized using the paradigm of domain matching epitaxy on the c-YSZ[111] buffer platform along with their out-of-plane orientation, which leads to improvement of the performance of the solid-state devices. The observed ultrafast response and switching in photochemical characteristics provide new opportunities for application of ZnO in smart catalysts, sensors, membranes, DNA self-assembly and multifunctional devices.

  11. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    NASA Astrophysics Data System (ADS)

    Krastelev, E. G.; Sedin, A. A.; Tugushev, V. I.

    2015-12-01

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80-90 ns, and a pulse repetition rate of up to 16 Hz.

  12. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    SciTech Connect

    Krastelev, E. G. Sedin, A. A.; Tugushev, V. I.

    2015-12-15

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.

  13. Nanosecond laser-induced damage at different initial temperatures of Ta{sub 2}O{sub 5} films prepared by dual ion beam sputtering

    SciTech Connect

    Xu, Cheng Jia, Jiaojiao; Fan, Heliang; Qiang, Yinghuai; Liu, Jiongtian; Yang, Di; Hu, Guohang; Li, Dawei

    2014-08-07

    Ta{sub 2}O{sub 5} films were deposited by dual ion beam sputtering method. The nanosecond laser-induced damage threshold (LIDT) at different initial temperatures and time of the films was investigated by an in situ high temperature laser-induced damage testing platform. It was shown that, when the initial temperature increased from 298 K to 383 K, the LIDT at 1064 nm and 12 ns significantly decreased by nearly 14%. Then the LIDT at 1064 nm and 12 ns decreased slower with the same temperature increment. Different damage morphologies were found at different initial temperatures. At low initial temperatures, it was the defects-isolated damage while at high initial temperatures it was the defects-combined damage. The theoretical calculations based on the defect-induced damage model revealed that both the significant increase of the highest temperature and the duration contributed to the different damage morphologies. With the initial temperature being increased, the thermal-stress coupling damage mechanism transformed gradually to the thermal dominant damage mechanism.

  14. Efficient multi-keV x-ray source generated by nanosecond laser pulse irradiated multi-layer thin foils target

    NASA Astrophysics Data System (ADS)

    Tu, Shao-yong; Hu, Guang-yue; Miao, Wen-yong; Zhao, Bin; Zheng, Jian; Yuan, Yong-teng; Zhan, Xia-yu; Hou, Li-fei; Jiang, Shao-en; Ding, Yong-kun

    2014-04-01

    A new target configuration is proposed to generate efficient multi-keV x-ray source using multiple thin foils as x-ray emitters. The target was constructed with several layers of thin foils, which were placed with a specific, optimized spacing. The thin foils are burned though one by one by a nanosecond-long laser pulse, which produced a very large, hot, underdense plasma. One-dimensional radiation hydrodynamic simulations show that the emission region and the multi-keV x-ray flux generated by multi-layer thin foil target are similar to that of the low-density gas or foam target, which is currently a bright multi-keV x-ray source generated by laser heating. Detailed analysis of a range of foil thicknesses showed that a layer-thickness of 0.1 μm is thin enough to generate an efficient multi-keV x-ray source. Additionally, this type of target can be easily manufactured, compared with the complex techniques for fabrication of low-density foam targets. Our preliminary experimental results also verified that the size of multi-keV x-ray emission region could be enhanced significantly by using a multi-layer Ti thin foil target.

  15. Selective excavation of human carious dentin using a nanosecond pulsed laser with a wavelength of 5.85 μm

    NASA Astrophysics Data System (ADS)

    Kita, Tetsuya; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2013-06-01

    Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, the wavelength of 5.85 μm could realize the selective excavation of human carious dentin, but it was necessary to evaluate the stage of caries progression in order to control the ablation property.

  16. Spectra of multiply charged hollow ions in the plasma produced by a short-wavelength nanosecond laser

    SciTech Connect

    Abdallah, J; Skobelev, I Yu; Faenov, A Ya; Magunov, A I; Pikuz, T A; Flora, F; Bollanti, S; DiLazzaro, P; Letardi, T; Burattini, E; Grilli, A; Reale, A; Palladino, L; Tomassetti, G; Scafati, A; Reale, L

    2000-08-31

    Complex spectral structures located between the resonance lines of H- and He-like MgXII and MgXI ions were recorded in experiments on plasma heating by the radiation of a low-power short-wavelength excimer XeCl laser (12-ns pulses with an energy of 2 J). The above spectral structures were shown to arise from transitions in the so-called hollow multicharged ions, i.e., in ions with an empty 1s-shell, which were previously observed in laser produced plasmas only with ultrahigh-power femto- and picosecond laser facilities having extremely high-contrast laser pulses. (interaction of laser radiation with matter. laser plasma)

  17. Two-photon microscopy using fiber-based nanosecond excitation.

    PubMed

    Karpf, Sebastian; Eibl, Matthias; Sauer, Benjamin; Reinholz, Fred; Hüttmann, Gereon; Huber, Robert

    2016-07-01

    Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements.

  18. Two-photon microscopy using fiber-based nanosecond excitation

    PubMed Central

    Karpf, Sebastian; Eibl, Matthias; Sauer, Benjamin; Reinholz, Fred; Hüttmann, Gereon; Huber, Robert

    2016-01-01

    Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements. PMID:27446680

  19. Comparative study of CW, nanosecond- and femtosecond-pulsed laser microcutting of AZ31 magnesium alloy stents.

    PubMed

    Gökhan Demir, Ali; Previtali, Barbara

    2014-06-01

    Magnesium alloys constitute an interesting solution for cardiovascular stents due to their biocompatibility and biodegradability in human body. Laser microcutting is the industrially accepted method for stent manufacturing. However, the laser-material interaction should be well investigated to control the quality characteristics of the microcutting process that concern the surface roughness, chemical composition, and microstructure of the final device. Despite the recent developments in industrial laser systems, a universal laser source that can be manipulated flexibly in terms of process parameters is far from reality. Therefore, comparative studies are required to demonstrate processing capabilities. In particular, the laser pulse duration is a key factor determining the processing regime. This work approaches the laser microcutting of AZ31 Mg alloy from the perspective of a comparative study to evaluate the machining capabilities in continuous wave (CW), ns- and fs-pulsed regimes. Three industrial grade machining systems were compared to reach a benchmark in machining quality, productivity, and ease of postprocessing. The results confirmed that moving toward the ultrashort pulse domain the machining quality increases, but the need for postprocessing remains. The real advantage of ultrashort pulsed machining was the ease in postprocessing and maintaining geometrical integrity of the stent mesh after chemical etching. Resultantly, the overall production cycle time was shortest for fs-pulsed laser system, despite the fact that CW laser system provided highest cutting speed.

  20. Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO{sub 2} ambient gas for spectrochemical application on Mars

    SciTech Connect

    Lie, Zener Sukra; Kurniawan, Koo Hendrik; Tjia, May On; Kagawa, Kiichiro

    2015-08-28

    An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO{sub 2} ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO{sub 2} ambient gas. Meanwhile the considerably weaker carbon emission from the CO{sub 2} gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO{sub 2} gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO{sub 2} ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

  1. Nanosecond Nd-YAG laser induced plasma emission characteristics in low pressure CO2 ambient gas for spectrochemical application on Mars

    NASA Astrophysics Data System (ADS)

    Lie, Zener Sukra; Pardede, Marincan; Tjia, May On; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-08-01

    An experimental study is conducted on the possibility and viability of performing spectrochemical analysis of carbon and other elements in trace amount in Mars, in particular, the clean detection of C, which is indispensible for tracking the sign of life in Mars. For this study, a nanosecond Nd-YAG laser is employed to generate plasma emission from a pure copper target in CO2 ambient gas of reduced pressure simulating the atmospheric condition of Mars. It is shown that the same shock wave excitation mechanism also works this case while exhibiting remarkably long cooling stage. The highest Cu emission intensities induced by 4 mJ laser ablation energy is attained in 600 Pa CO2 ambient gas. Meanwhile the considerably weaker carbon emission from the CO2 gas appears relatively featureless over the entire range of pressure variation, posing a serious problem for sensitive trace analysis of C contained in a solid sample. Our time resolved intensity measurement nevertheless reveals earlier appearance of C emission from the CO2 gas with a limited duration from 50 ns to 400 ns after the laser irradiation, well before the initial appearance of the long lasting C emission from the solid target at about 1 μs, due to the different C-releasing processes from their different host materials. The unwanted C emission from the ambient gas can thus be eliminated from the detected spectrum by a proper time gated detection window. The excellent spectra of carbon, aluminum, calcium, sodium, hydrogen, and oxygen obtained from an agate sample are presented to further demonstrate and verify merit of this special time gated LIBS using CO2 ambient gas and suggesting its viability for broad ranging in-situ applications in Mars.

  2. Wavelength dependence of nanosecond infrared laser-induced breakdown in water: Evidence for multiphoton initiation via an intermediate state

    NASA Astrophysics Data System (ADS)

    Linz, Norbert; Freidank, Sebastian; Liang, Xiao-Xuan; Vogelmann, Hannes; Trickl, Thomas; Vogel, Alfred

    2015-04-01

    Investigation of the wavelength dependence (725-1025 nm) of the threshold for nanosecond optical breakdown in water revealed steps consistent with breakdown initiation by multiphoton ionization, with an initiation energy of about 6.6 eV. This value is considerably smaller than the autoionization threshold of about 9.5 eV, which can be regarded as band gap relevant for avalanche ionization. Breakdown initiation is likely to occur via excitation of a valence band electron into a solvated state, followed by rapid excitation into the conduction band. Theoretical analysis based on these assumptions suggests that the seed electron density required for initiating avalanche ionization amounts to 2.5 ×1015c m-3 at 725 nm and drops to 1.1 ×1012c m-3 at 1025 nm. These results demand changes of future breakdown modeling for water, including the use of a larger band gap than previously employed, the introduction of an intermediate energy level for initiation, and consideration of the wavelength dependence of seed electron density.

  3. Effects of laser acupuncture on blood perfusion rate

    NASA Astrophysics Data System (ADS)

    Wang, Xian-ju; Zeng, Chang-chun; Liu, Han-ping; Liu, Song-hao; Liu, Liang-gang

    2006-09-01

    Based on Pennes equation, the influences of the intensity and the impulse frequency of laser acupuncture on the point tissues' blood flow perfusion rate are discussed. We find that the blood perfusion rate of point tissue increases with the intensity of laser acupuncture increasing. After impulse laser acupuncture the point tissue blood perfusion rate increase little, but after continuum laser acupuncture the point tissues blood perfusion rate increase much.

  4. High-power laser-plasma interaction in nanosecond regimes ‘at a glance’ using proton deflectometry

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Castan, A.; Marquès, J.-R.; Lancia, L.; Gangolf, T.; Fuchs, J.; Masson-Laborde, P.-E.; Teychenné, D.; Debayle, A.; Monteil, M.-C.; Casanova, M.; Rousseaux, C.; Lemaire, S.; Riz, D.

    2016-05-01

    Recent experiments indicate that controlling the propagation of high-power laser beams through millimeter long and low-density plasmas still remains challenging. In such plasma conditions, it is equally important to consider the impact of the plasma on laser propagation and laser properties, and the impact of the laser on plasma conditions. These complex phenomena are still difficult to implement in fluid models owing to the highly non-linear physics at play. Yet, electromagnetic fields prove to be good signatures of most of these low frequency phenomena. In particular, local pressure gradients and electron transport can be inferred from the electric fields. Such in-depth plasma characterization can be achieved through proton deflectometry. For that purpose, we have developed a three-dimensional simulation capability in order to compute protons’ trajectories modified by the local electric fields.

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

    SciTech Connect

    Cahoon, Erica M.; Almirall, Jose R.

    2010-05-01

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

  6. Raman spectroscopic analysis of iron chromium oxide microspheres generated by nanosecond pulsed laser irradiation on stainless steel.

    PubMed

    Ortiz-Morales, M; Soto-Bernal, J J; Frausto-Reyes, C; Acosta-Ortiz, S E; Gonzalez-Mota, R; Rosales-Candelas, I

    2015-06-15

    Iron chromium oxide microspheres were generated by pulsed laser irradiation on the surface of two commercial samples of stainless steel at room temperature. An Ytterbium pulsed fiber laser was used for this purpose. Raman spectroscopy was used for the characterization of the microspheres, whose size was found to be about 0.2-1.7 μm, as revealed by SEM analysis. The laser irradiation on the surface of the stainless steel modified the composition of the microspheres generated, affecting the concentration of the main elemental components when laser power was increased. Furthermore, the peak ratio of the main bands in the Raman spectra has been associated to the concentration percentage of the main components of the samples, as revealed by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. These experiments showed that it is possible to generate iron chromium oxide microspheres on stainless steel by laser irradiation and that the concentration percentage of their main components is associated with the laser power applied.

  7. Nanosecond high-power dense microplasma switch for visible light

    SciTech Connect

    Bataller, A. Koulakis, J.; Pree, S.; Putterman, S.

    2014-12-01

    Spark discharges in high-pressure gas are known to emit a broadband spectrum during the first 10 s of nanoseconds. We present calibrated spectra of high-pressure discharges in xenon and show that the resulting plasma is optically thick. Laser transmission data show that such a body is opaque to visible light, as expected from Kirchoff's law of thermal radiation. Nanosecond framing images of the spark absorbing high-power laser light are presented. The sparks are ideal candidates for nanosecond, high-power laser switches.

  8. Nanosecond high-power dense microplasma switch for visible light

    NASA Astrophysics Data System (ADS)

    Bataller, A.; Koulakis, J.; Pree, S.; Putterman, S.

    2014-12-01

    Spark discharges in high-pressure gas are known to emit a broadband spectrum during the first 10 s of nanoseconds. We present calibrated spectra of high-pressure discharges in xenon and show that the resulting plasma is optically thick. Laser transmission data show that such a body is opaque to visible light, as expected from Kirchoff's law of thermal radiation. Nanosecond framing images of the spark absorbing high-power laser light are presented. The sparks are ideal candidates for nanosecond, high-power laser switches.

  9. Utilizing the transparency of semiconductors via "backside" machining with a nanosecond 2 μm Tm:fiber laser

    NASA Astrophysics Data System (ADS)

    Gehlich, Nils; Bonhoff, Tobias; Sisken, Laura; Ramme, Mark; Gaida, Christian; Gebhardt, Martin; Mingareev, Ilya; Shah, Lawrence; Richardson, Martin C.

    2014-03-01

    Semiconductors such as Si and GaAs are transparent to infrared laser radiation with wavelengths >1.2 μm. Focusing laser light at the back surface of a semiconductor wafer enables a novel processing regime that utilizes this transparency. However, in previous experiments with ultrashort laser pulses we have found that nonlinear absorption makes it impossible to achieve sufficient optical intensity to induce material modification far below the front surface. Using a recently developed Tm:fiber laser system producing pulses as short as 7 ns with peak powers exceeding 100 kW, we have demonstrated it is possible to ablate the "backside" surface of 500-600 μm thick Si and GaAs wafers. We studied laser-induced morphology changes at front and back surfaces of wafers and obtained modification thresholds for multipulse irradiation and surface processing in trenches. A significantly higher back surface modification threshold in Si compared to front surface is possibly attributed to nonlinear absorption and light propagation effects. This unique processing regime has the potential to enable novel applications such as semiconductor welding for microelectronics, photovoltaic, and consumer electronics.

  10. Two dimensional hydrodynamic simulation of high pressures induced by high power nanosecond laser-matter interactions under water

    NASA Astrophysics Data System (ADS)

    Wu, Benxin; Shin, Yung C.

    2007-05-01

    In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the pressure generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the induced pressures near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release wave on pressure spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.

  11. Two dimensional hydrodynamic simulation of high pressures induced by high power nanosecond laser-matter interactions under water

    SciTech Connect

    Wu, Benxin; Shin, Yung C.

    2007-05-15

    In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascals, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. For axisymmetric laser spots with finite size, the pressure generation near the water-coating interface is a two dimensional process in nature. This is in particular the case for microscale LSP performed with very small laser spots, which is a very promising technique to improve the reliability performance of microdevices. However, models capable of predicting two dimensional (2D) spatial distributions of the induced pressures near the coating-water interface in LSP have rarely been reported in literature. In this paper, a predictive 2D axisymmetric model is developed by numerically solving the hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce 2D spatial distributions of material responses near the water-coating interface in LSP, and is verified through comparisons with experimental measurements. The model calculation shows that the effect of radial release wave on pressure spatial distributions becomes more significant as the laser spot size decreases, indicating the importance of a 2D model, particularly for microscale LSP.

  12. Application of External-Cavity Quantum Cascade Infrared Lasers to Nanosecond Time-Resolved Infrared Spectroscopy of Condensed-Phase Samples Following Pulse Radiolysis

    SciTech Connect

    Grills, D.C.; Cook, A.R.; Fujita, E.; George, M.W.; Miller, J.R.; Preses, J.M.; Wishart, J.F.

    2010-06-01

    Pulse radiolysis, utilizing short pulses of high-energy electrons from accelerators, is a powerful method for rapidly generating reduced or oxidized species and other free radicals in solution. Combined with fast time-resolved spectroscopic detection (typically in the ultraviolet/visible/near-infrared), it is invaluable for monitoring the reactivity of species subjected to radiolysis on timescales ranging from picoseconds to seconds. However, it is often difficult to identify the transient intermediates definitively due to a lack of structural information in the spectral bands. Time-resolved vibrational spectroscopy offers the structural specificity necessary for mechanistic investigations but has received only limited application in pulse radiolysis experiments. For example, time-resolved infrared (TRIR) spectroscopy has only been applied to a handful of gas-phase studies, limited mainly by several technical challenges. We have exploited recent developments in commercial external-cavity quantum cascade laser (EC-QCL) technology to construct a nanosecond TRIR apparatus that has allowed, for the first time, TRIR spectra to be recorded following pulse radiolysis of condensed-phase samples. Near single-shot sensitivity of DeltaOD <1 x 10(-3) has been achieved, with a response time of <20 ns. Using two continuous-wave EC-QCLs, the current apparatus covers a probe region from 1890-2084 cm(-1), and TRIR spectra are acquired on a point-by-point basis by recording transient absorption decay traces at specific IR wavelengths and combining these to generate spectral time slices. The utility of the apparatus has been demonstrated by monitoring the formation and decay of the one-electron reduced form of the CO(2) reduction catalyst, [Re(I)(bpy)(CO)(3)(CH(3)CN)](+), in acetonitrile with nanosecond time resolution following pulse radiolysis. Characteristic red-shifting of the nu(CO) IR bands confirmed that one-electron reduction of the complex took place. The availability of

  13. Application of external-cavity quantum cascade infrared lasers to nanosecond time-resolved infrared spectroscopy of condensed-phase samples following pulse radiolysis.

    PubMed

    Grills, David C; Cook, Andrew R; Fujita, Etsuko; George, Michael W; Preses, Jack M; Wishart, James F

    2010-06-01

    Pulse radiolysis, utilizing short pulses of high-energy electrons from accelerators, is a powerful method for rapidly generating reduced or oxidized species and other free radicals in solution. Combined with fast time-resolved spectroscopic detection (typically in the ultraviolet/visible/near-infrared), it is invaluable for monitoring the reactivity of species subjected to radiolysis on timescales ranging from picoseconds to seconds. However, it is often difficult to identify the transient intermediates definitively due to a lack of structural information in the spectral bands. Time-resolved vibrational spectroscopy offers the structural specificity necessary for mechanistic investigations but has received only limited application in pulse radiolysis experiments. For example, time-resolved infrared (TRIR) spectroscopy has only been applied to a handful of gas-phase studies, limited mainly by several technical challenges. We have exploited recent developments in commercial external-cavity quantum cascade laser (EC-QCL) technology to construct a nanosecond TRIR apparatus that has allowed, for the first time, TRIR spectra to be recorded following pulse radiolysis of condensed-phase samples. Near single-shot sensitivity of DeltaOD <1 x 10(-3) has been achieved, with a response time of <20 ns. Using two continuous-wave EC-QCLs, the current apparatus covers a probe region from 1890-2084 cm(-1), and TRIR spectra are acquired on a point-by-point basis by recording transient absorption decay traces at specific IR wavelengths and combining these to generate spectral time slices. The utility of the apparatus has been demonstrated by monitoring the formation and decay of the one-electron reduced form of the CO(2) reduction catalyst, [Re(I)(bpy)(CO)(3)(CH(3)CN)](+), in acetonitrile with nanosecond time resolution following pulse radiolysis. Characteristic red-shifting of the nu(CO) IR bands confirmed that one-electron reduction of the complex took place. The availability of

  14. Nitric oxide density measurements in air and air/fuel nanosecond pulse discharges by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Uddi, M.; Jiang, N.; Adamovich, I. V.; Lempert, W. R.

    2009-04-01

    Laser induced fluorescence is used to measure absolute nitric oxide concentrations in air, methane-air and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single pulse, 20 kV peak voltage, 25 ns pulse duration discharge. A mixture of NO and nitrogen with known composition (4.18 ppm NO) is used for calibration. Peak NO density in air at 60 Torr, after a single pulse, is ~8 × 1012 cm-3 (~4.14 ppm) occurring at ~250 µs after the pulse, with decay time of ~16.5 ms. Peak NO atom mole fraction in a methane-air mixture with equivalence ratio of phiv = 0.5 is found to be approximately equal to that in air, with approximately the same rise and decay rate. In an ethylene-air mixture (also with equivalence ratio of phiv = 0.5), the rise and decay times are comparable to air and methane-air, but the peak NO concentration is reduced by a factor of approximately 2.5. Spontaneous emission measurements show that excited electronic states N2(C 3Π) and NO(A 2Σ) in air at P = 60 Torr decay within ~20 ns and ~1 µs, respectively. Kinetic modelling calculations incorporating air plasma kinetics complemented with the GRI Mech 3.0 hydrocarbon oxidation mechanism are compared with the experimental data using three different NO production mechanisms. It is found that NO concentration rise after the discharge pulse is much faster than predicted by Zel'dovich mechanism reactions, by two orders of magnitude, but much slower compared with reactions of electronically excited nitrogen atoms and molecules, also by two orders of magnitude. It is concluded that processes involving long lifetime (~100 µs) metastable states, such as N2(X 1Σ,v) and O2(b 1Σ), formed by quenching of the metastable N2(A 3Σ) state by ground electronic state O2, may play a dominant role in NO formation. NO decay, in all cases, is found to be dominated by the reverse Zel'dovich reaction, NO + O → N + O2, as well as by conversion into NO2 in a reaction of NO with ozone.

  15. Comparison of 265 nm Femtosecond and 213 nm Nanosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Pb Isotope Ratio Measurements.

    PubMed

    Ohata, Masaki; Nonose, Naoko; Dorta, Ladina; Günther, Detlef

    2015-01-01

    The analytical performance of 265 nm femtosecond laser ablation (fs-LA) and 213 nm nanosecond laser ablation (ns-LA) systems coupled with multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) for Pb isotope ratio measurements of solder were compared. Although the time-resolved signals of Pb measured by fs-LA-MC-ICPMS showed smoother signals compared to those obtained by ns-LA-MC-ICPMS, similar precisions on Pb isotope ratio measurements were obtained between them, even though their operating conditions were slightly different. The mass bias correction of the Pb isotope ratio measurement was carried out by a comparison method using a Pb standard solution prepared from NIST SRM 981 Pb metal isotopic standard, which was introduced into the ICP by a desolvation nebulizer (DSN) via a dual-sample introduction system, and it was successfully demonstrated for Pb isotope ratio measurements for either NIST 981 metal isotopic standard or solder by fs-LA-MC-ICPMS since the analytical results agreed well with the certified value as well as the determined value within their standard deviations obtained and the expanded uncertainty of the certified or determined value. The Pb isotope ratios of solder obtained by ns-LA-MC-ICPMS also showed agreement with respect to the determined value within their standard deviations and expanded uncertainty. From these results, it was evaluated that the mass bias correction applied in the present study was useful and both LA-MC-ICPMS could show similar analytical performance for the Pb isotope ratio microanalysis of metallic samples such as solder.

  16. Comparison of 265 nm Femtosecond and 213 nm Nanosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Pb Isotope Ratio Measurements.

    PubMed

    Ohata, Masaki; Nonose, Naoko; Dorta, Ladina; Günther, Detlef

    2015-01-01

    The analytical performance of 265 nm femtosecond laser ablation (fs-LA) and 213 nm nanosecond laser ablation (ns-LA) systems coupled with multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) for Pb isotope ratio measurements of solder were compared. Although the time-resolved signals of Pb measured by fs-LA-MC-ICPMS showed smoother signals compared to those obtained by ns-LA-MC-ICPMS, similar precisions on Pb isotope ratio measurements were obtained between them, even though their operating conditions were slightly different. The mass bias correction of the Pb isotope ratio measurement was carried out by a comparison method using a Pb standard solution prepared from NIST SRM 981 Pb metal isotopic standard, which was introduced into the ICP by a desolvation nebulizer (DSN) via a dual-sample introduction system, and it was successfully demonstrated for Pb isotope ratio measurements for either NIST 981 metal isotopic standard or solder by fs-LA-MC-ICPMS since the analytical results agreed well with the certified value as well as the determined value within their standard deviations obtained and the expanded uncertainty of the certified or determined value. The Pb isotope ratios of solder obtained by ns-LA-MC-ICPMS also showed agreement with respect to the determined value within their standard deviations and expanded uncertainty. From these results, it was evaluated that the mass bias correction applied in the present study was useful and both LA-MC-ICPMS could show similar analytical performance for the Pb isotope ratio microanalysis of metallic samples such as solder. PMID:26656823

  17. Application of nanosecond-UV laser ablation-inductively coupled plasma mass spectrometry for the isotopic analysis of single submicrometer-size uranium particles.

    PubMed

    Pointurier, Fabien; Pottin, Anne-Claire; Hubert, Amélie

    2011-10-15

    For the first time, laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) was used to carry out isotopic measurement on single submicrometer-size uranium particles. The analytical procedure was applied on two particle-containing samples already analyzed in the same laboratory by established techniques for particle analysis: combination of the fission track technique with thermo-ionization mass spectrometry (FT-TIMS) and secondary ion mass spectrometry (SIMS). Particles were extracted from their initial matrix with ethanol and deposited on a polycarbonate disk where they were fixed in a layer of an organic compound (collodion). Prior to the isotopic analysis, particles were precisely located on the disk's surface by scanning electron microscopy (SEM) for one sample and using the fission track technique for the other sample. Most of the particles were smaller than 1 μm, and their (235)U content was in the femtogram range. (235)U/(238)U ratios were successfully analyzed for all located particles using a nanosecond-UV laser (Cetac LSX 213 nm) coupled to a quadrupole-based ICPMS (Thermo "X-Series II"). LA-ICPMS results, although less precise and accurate (typically 10%) than the ones obtained by FT-TIMS and SIMS due to short (20-40 s), transient, and noisy signals, are in good agreement with the certified values or with the results obtained with other techniques. Thanks to good measurement efficiency (~6 × 10(-4)) and high signal/noise ratio during the analysis, LA-ICPMS can be considered a very promising technique for fast particle analysis, provided that uranium-bearing particles are fixed on the sample holder and located prior to isotope measurement. PMID:21875035

  18. Ablation of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} glass with an ultra-violet nano-second laser

    SciTech Connect

    Knotek, P.; Navesnik, J.; Cernohorsky, T.; Kincl, M.; Vlcek, M.; Tichy, L.

    2015-04-15

    Highlights: • The interaction of (GeS{sub 2}){sub 0.3}(Sb{sub 2}S{sub 3}){sub 0.7} bulk glass and film with UV nanosecond laser. • Ablation process, topography of crater and structure of the material were studied. • Ablation threshold fluencies changed with the spot diameter and number of pulses. • The photo-thermal expansion of the material occurred for low laser fluency. • Laser direct writing process applicable for fabrication of passive optical elements. - Abstract: The results of an experimental study of the laser ablation of bulk and thin films of a GeSbS chalcogenide glass using UV nanosecond pulses are reported. The response of the samples to illumination conditions was studied through the use of atomic force spectroscopy, digital holographic microscopy, Raman scattering and scanning electron microscopy. The multi-pulse ablation thresholds were determined for both the bulk and thin film samples for varying number of pulses and illuminated spot diameter. The possible application of direct laser writing into the bulk and thin films of this material is presented.

  19. Enhanced x-ray emissions from Au-Gd mixture targets ablated by a high-power nanosecond laser

    SciTech Connect

    Dong, Yunsong; Shang, Wanli; Yang, Jiamin Zhang, Lu; Zhang, Wenhai; Li, Zhichao; Guo, Liang; Zhan, Xiayu; Du, Huabing; Deng, Bo; Pu, Yikang

    2014-01-28

    As an important x-ray source, enhancement of x-ray emissions from laser-produced plasmas is imperative for various applications. High-Z Au-Gd mixture targets are proposed to enhance the laser to x-ray conversion efficiency compared to pure Au target. In the experiments, a 1 ns frequency-tripled (351 nm wavelength) laser light was used to obtain an intensity of 3×10{sup 14} W/cm{sup 2} on the targets. The x-ray spectra, total absolute x-ray emissions of all space, M-band fraction and backscattering from pure Au and Au-Gd mixture have been measured, respectively. It is shown that the absolute laser to x-ray conversion efficiency for the Au-Gd mixture containing 60% gold by atom is 47.7%, which has a 15% enhancement compared with that of the pure Au target. The experimental results are consistent with the radiation hydrodynamic simulations.

  20. The Influence of spot size on the expansion dynamics of nanosecond-laser-produced copper plasmas in atmosphere

    SciTech Connect

    Li, Xingwen; Wei, Wenfu; Wu, Jian; Jia, Shenli; Qiu, Aici

    2013-06-28

    Laser produced copper plasmas of different spot sizes in air were investigated using fast photography and optical emission spectroscopy (OES). The laser energy was 33 mJ. There were dramatic changes in the plasma plume expansion into the ambient air when spot sizes changed from {approx}0.1 mm to {approx}0.6 mm. A stream-like structure and a hemispherical structure were, respectively, observed. It appeared that the same spot size resulted in similar expansion dynamics no matter whether the target was located in the front of or behind the focal point, although laser-induced air breakdown sometimes occurred in the latter case. Plasma plume front positions agree well with the classic blast wave model for the large spot-size cases, while an unexpected stagnation of {approx}80 ns occurred after the laser pulse ends for the small spot size cases. This stagnation can be understood in terms of the evolution of enhanced plasma shielding effects near the plasma front. Axial distributions of plasma components by OES revealed a good confinement effect. Electron number densities were estimated and interpreted using the recorded Intensified Charge Coupled Device (ICCD) images.

  1. The Influence of spot size on the expansion dynamics of nanosecond-laser-produced copper plasmas in atmosphere

    NASA Astrophysics Data System (ADS)

    Li, Xingwen; Wei, Wenfu; Wu, Jian; Jia, Shenli; Qiu, Aici

    2013-06-01

    Laser produced copper plasmas of different spot sizes in air were investigated using fast photography and optical emission spectroscopy (OES). The laser energy was 33 mJ. There were dramatic changes in the plasma plume expansion into the ambient air when spot sizes changed from ˜0.1 mm to ˜0.6 mm. A stream-like structure and a hemispherical structure were, respectively, observed. It appeared that the same spot size resulted in similar expansion dynamics no matter whether the target was located in the front of or behind the focal point, although laser-induced air breakdown sometimes occurred in the latter case. Plasma plume front positions agree well with the classic blast wave model for the large spot-size cases, while an unexpected stagnation of ˜80 ns occurred after the laser pulse ends for the small spot size cases. This stagnation can be understood in terms of the evolution of enhanced plasma shielding effects near the plasma front. Axial distributions of plasma components by OES revealed a good confinement effect. Electron number densities were estimated and interpreted using the recorded Intensified Charge Coupled Device (ICCD) images.

  2. Overview of the Lucia laser program: toward 100-Joules, nanosecond-pulse, kW averaged power based on ytterbium diode-pumped solid state laser

    NASA Astrophysics Data System (ADS)

    Chanteloup, J.-C.; Yu, H.; Bourdet, G.; Dambrine, C.; Ferre, S.; Fulop, A.; Le Moal, S.; Pichot, A.; Le Touze, G.; Zhao, Z.

    2005-04-01

    We present the current status of the Lucia laser being built at the LULI laboratory, the national civil facility for intense laser matter interaction in France. This diode pumped laser will deliver a 100 Joules, 10 ns, 10 Hz pulse train from Yb:YAG using 4400 power diode laser bars. We first focus on the amplifier stage by describing the reasons for selecting our extraction architecture. Thermal issues and solutions for both laser and pumping heads are then described. Finally, we emphasize more specifically the need for long-lifetime high-laser-damage-threshold coatings and optics.

  3. Process and application of shock compression by nanosecond pulses of frequency-doubled Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Sano, Yuji; Kimura, Motohiko; Mukai, Naruhiko; Yoda, Masaki; Obata, Minoru; Ogisu, Tatsuki

    2000-02-01

    The authors have developed a new process of laser-induced shock compression to introduce a residual compressive stress on material surface, which is effective for prevention of stress corrosion cracking (SCC) and enhancement of fatigue strength of metal materials. The process developed is unique and beneficial. It requires no pre-conditioning for the surface, whereas the conventional process requires that the so-called sacrificial layer is made to protect the surface from damage. The new process can be freely applied to water- immersed components, since it uses water-penetrable green light of a frequency-doubled Nd:YAG laser. The process developed has the potential to open up new high-power laser applications in manufacturing and maintenance technologies. The laser-induced shock compression process (LSP) can be used to improve a residual stress field from tensile to compressive. In order to understand the physics and optimize the process, the propagation of a shock wave generated by the impulse of laser irradiation and the dynamic response of the material were analyzed by time-dependent elasto-plastic calculations with a finite element program using laser-induced plasma pressure as an external load. The analysis shows that a permanent strain and a residual compressive stress remain after the passage of the shock wave with amplitude exceeding the yield strength of the material. A practical system materializing the LSP was designed, manufactured, and tested to confirm the applicability to core components of light water reactors (LWRs). The system accesses the target component and remotely irradiates laser pulses to the heat affected zone (HAZ) along weld lines. Various functional tests were conducted using a full-scale mockup facility, in which remote maintenance work in a reactor vessel could be simulated. The results showed that the system remotely accessed the target weld lines and successfully introduced a residual compressive stress. After sufficient training

  4. Comparison of plasma temperature and electron density on nanosecond laser ablation of Cu and nano-Cu

    SciTech Connect

    Chen, Anmin; Jiang, Yuanfei; Wang, Tingfeng; Shao, Junfeng; Jin, Mingxing

    2015-03-15

    Laser-induced breakdown spectroscopy is performed through the collection of spectra by spectral detection equipment at different delay times and distances from targets composed of Cu and nano-Cu, which are ablated using a Nd:YAG laser (532 nm, 10 ns, 10 Hz) in our experiments. The measured wavelength range is from 475 nm to 525 nm. Using the local thermodynamic equilibrium model, we analyze the characteristics of the plasma temperature and the electron number density for different distances between the target surface and the lens. The results show that when compared with the nano-Cu plasma case, the temperature of the Cu plasma is higher, while its electron number density is lower.

  5. Space-resolved analysis of trace elements in fresh vegetables using ultraviolet nanosecond laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Juvé, Vincent; Portelli, Richard; Boueri, Myriam; Baudelet, Matthieu; Yu, Jin

    2008-10-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to analyze trace elements contained in fresh vegetables. A quadrupled Nd:YAG laser is used in the experiments for ablation. Analyzed samples come from local markets and represent frequently consumed vegetables. For a typical root vegetable, such as potato, spectral analysis of the plasma emission reveals more than 400 lines emitted by 27 elements and 2 molecules, C 2 and CN. Among these species, one can find trace as well as ultra-trace elements. A space-resolved analysis of several trace elements with strong emissions is then applied to typical root, stem and fruit vegetables. The results from this study demonstrate the potential of an interesting tool for botanical and agricultural studies as well for food quality/safety and environment pollution assessment and control.

  6. Characterization of 1064nm nanosecond laser-induced damage on antireflection coatings grown by atomic layer deposition.

    PubMed

    Liu, Zhichao; Chen, Songlin; Ma, Ping; Wei, Yaowei; Zheng, Yi; Pan, Feng; Liu, Hao; Tang, Gengyu

    2012-01-16

    Damage tests are carried out at 1064nm to measure the laser resistance of TiO(2)/Al(2)O(3) and HfO(2)/Al(2)O(3) antireflection coatings grown by atomic layer deposition (ALD). The damage results are determined by S-on-1 and R-on-1 tests. Interestingly, the damage performance of ALD coatings is similar to those grown by conventional e-beam evaporation process. A decline law of damage resistance under multiple irradiations is revealed. The influence of growth temperature on damage performance has been investigated. Result shows that the crystallization of TiO(2) layer at higher temperature could lead to numerous absorption defects that reduce the laser-induced damage threshold (LIDT). In addition, it has been found that using inorganic compound instead of organic compound as precursors for ALD process maybe effectively prevent carbon impurities in films and will increase the LIDT obviously.

  7. A rapidly-tuned, short-pulse-length, high-repetition-rate CO{sub 2} laser for IR dial

    SciTech Connect

    Zaugg, T.; Thompson, D.; Leland, W.T.; Busch, G.

    1997-08-01

    Analysis of noise sources in Differential Absorption LIDAR (DIAL) in the infrared region of the spectrum indicates that the signal-to-noise ratio for direct detection can be improved if multiple-wavelength, short-pulse-length beams are transmitted and received at high repetition rates. Atmospheric effects can be minimized, albedo can be rapidly scanned, and uncorrelated speckle can be acquired at the maximum possible rate. A compact, rugged, RF-excited waveguide laser can produce 15 nanosecond pulses at a 100 kHz rate with sufficient energy per pulse to reach the speckle limit of the signal-to-noise ratio. A high-repetition-rate laser has been procured and will be used to verify these signal and noise scaling relationships at high repetition rates. Current line-tuning devices are mechanical and are capable of switching lines at a rate up to a few hundred Hertz. Acousto-optic modulators, deflectors or tunable filters can be substituted for these mechanical devices in the resonator of a CO{sub 2} laser and used to rapidly line-tune the laser across the 9 and 10 micron bands at a rate as high as 100 kHz. Several configurations for line tuning using acousto-optic and electro-optic devices with and without gratings are presented. The merits of and constraints on each design are also discussed. A pair of large aperture, acousto-optic deflectors has been purchased and the various line-tuning designs will be evaluated in a conventional, glass tube, CO{sub 2} laser, with a view to incorporation into the high-repetition-rate, waveguide laser. A computer model of the dynamics of an RF-excited, short-pulse-length, high-repetition-rate waveguide laser has been developed. The model will be used to test the consequences of various line-tuning designs.

  8. Study of hydrogen states in a-Si:H films, dehydrogenization treatments and influence of hydrogen on nanosecond pulse laser crystallization of a-Si:H

    NASA Astrophysics Data System (ADS)

    Volodin, V. A.; Galkov, M. S.; Safronova, N. A.; Kamaev, G. N.; Antonenko, A. H.; Kochubey, S. A.

    2014-12-01

    Structures based on hydrogenated amorphous silicon (a-Si:H) films deposited on various substrates (including not refractory ones) are widely applied in giant microelectronics devices, such as flat panel displays based on active matrix thin-film transistors and solar cells. The a-Si:H films produced by plasma enhanced chemical vapor deposition (PECVD) methods, contain up to 40% atoms of hydrogen. The influence of hydrogen on the optical and electrical properties of the films and their degradation is important. Therefore, the development of express and non-destructive methods for control of the hydrogen concentration in thin films continues to be an actual task to date. Previously, from a comparative analysis of infrared (IR) spectroscopy and Raman scattering spectroscopy, the ratios of the integral intensities of Raman peaks due to scattering by vibrations of the Si-H and Si-H2 bonds to the intensity of Raman peak of the Si-Si bonds were experimentally determined. Knowing these ratios, it is possible to measure the hydrogen concentration, moreover, separately in Si-H and Si-H2 states. Proposed quantitative method for determining of the hydrogen concentration from analysis of the Raman spectra is an express, non-destructive method and can be used for "in situ" monitoring of the hydrogen. The aim of this work was to determine the polarization dependence of Raman scattering by stretching vibrations of Si-H bonds and find the form of the corresponding Raman tensors. From analysis of Raman intensities in different polarizations the Raman tensors for Si-H and Si-H2 bonds were determined. The regimes for dehydrogenization of thick (up to 1 micron) a-Si:H films were found. The nanosecond pulse XeCl laser with wavelength of 308 nm and pulse duration of 10 ns was used for pulse crystallization of as-deposited and dehydrogenated films. As it was studied earlier, for a-Si:H films with high hydrogen concentration, the threshold for crystallization is very close to threshold of

  9. A high-energy cladding-pumped 80 nanosecond Q-switched fiber laser using a tapered fiber saturable absorber

    NASA Astrophysics Data System (ADS)

    Moore, Sean W.; Soh, Daniel B. S.; Bisson, Scott E.; Patterson, Brian D.; Hsu, Wen L.

    2013-02-01

    We report a passively Q-switched all-fiber laser using a large mode area (LMA) Yb3+-doped fiber cladding-pumped at 915 nm and an unpumped single-mode Yb3+-doped fiber as the saturable absorber (SA). The saturable absorber and gain fibers were first coupled with a free-space telescope to better study the composite system, and then fusion spliced with fiber tapers to match the mode field diameters. ASE generated in the LMA gain fiber preferentially bleaches the SA fiber before depleting the gain, thereby causing the SA fiber to act as a passive saturable absorber. Using this scheme we first demonstrate a Q-switched oscillator with 40 μJ 79 ns pulses at 1026 nm using a free-space taper, and show that pulses can be generated from 1020 nm to 1040 nm. We scale the pulse energy to 0.40 mJ using an Yb3+-doped cladding pumped fiber amplifier. Experimental studies in which the saturable absorber length, pump times, and wavelengths are independently varied reveal the impact of these parameters on laser performance. Finally, we demonstrate 60 μJ 81 ns pulses at 1030 nm in an all fiber architecture using tapered mode field adaptors to match the mode filed diameters of the gain and SA fibers.

  10. Nanosecond laser-induced ablation and laser-induced shockwave structuring of polymer foils down to sub-μm patterns

    NASA Astrophysics Data System (ADS)

    Lorenz, P.; Bayer, L.; Ehrhardt, M.; Zimmer, K.; Engisch, L.

    2015-03-01

    Micro- and nanostructures exhibit a growing commercial interest where a fast, cost-effective, and large-area production is attainable. Laser methods have a great potential for the easy fabrication of surface structures into flexible polymer foils like polyimide (PI). In this study two different concepts for the structuring of polymer foils using a KrF excimer laser were tested and compared: the laser-induced ablation and the laser-induced shock wave structuring. The direct front side laser irradiation of these polymers allows the fabrication of different surface structures. For example: The low laser fluence treatment of PI results in nano-sized cone structures where the cone density can be controlled by the laser parameters. This allows inter alia the laser fabrication of microscopic QR code and high-resolution grey-tone images. Furthermore, the laser treatment of the front side of the polymer foil allows the rear side structuring due to a laserinduced shock wave. The resultant surface structures were analysed by optical and scanning electron microscopy (SEM) as well as white light interferometry (WLI).

  11. 188 W nanosecond pulsed fiber amplifier at 1064 nm

    NASA Astrophysics Data System (ADS)

    Li, Zebiao; Guo, Chao; Li, Qi; Zhao, Pengfei; Li, Chengyu; Huang, Zhihua; Tang, Xuan; Lin, Honghuan; Xu, Shanhui; Yang, Zhongmin; Wang, Jianjun; Jing, Feng

    2016-07-01

    We report an all-fiber high power nanosecond pulsed laser at a center wavelength of 1064 nm. Optimizing the coiling diameter of the active fiber, 188 W average power is achieved at a repetition rate of 40 kHz. The pulse width is measured as 101 ns, while the peak power can be estimated to 46.5 kW.

  12. Evidence for phase-explosion and generation of large particles during high power nanosecond laser ablation of silicon

    SciTech Connect

    Yoo, J. H.; Jeong, S. H.; Mao, X. L.; Greif, R.; Russo, R. E.

    2000-02-07

    The craters resulting from high-irradiance (1x10{sup 9}-1x10{sup 11} W/cm{sup 2}) single-pulse laser ablation of single-crystal silicon show a dramatic increase in volume at a threshold irradiance of 2.2x10{sup 10} W/CM{sup 2}. Time-resolved shadowgraph images show ejection of large particulates from the sample above this threshold irradiance, with a time delay {approx}300 ns. A numerical model was used to estimate the thickness of a superheated layer near the critical state. Considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency), the calculated thickness of the superheated layer at a delay time of 200-300 ns agreed with the measured crater depths. This agreement suggests that induced transparency promotes the formation of a deep superheated layer, and explosive boiling within this layer leads to particulate ejection from the sample. (c) 2000 American Institute of Physics.

  13. Ultrastructural imaging and molecular modeling of live bacteria using soft x-ray contact microscopy with nanoseconds laser plasma radiation

    SciTech Connect

    Kado, M.; Richardson, M.C.; Gabel, K.; Torres, D.; Rajyaguru, J.; Muszynski, M.J.

    1995-12-31

    Detection for clinical diagnosis and study of microbial cell is performed by a combination of low magnification optical microscopy and direct and indirect labeling techniques. Visual ultrastructural studies on subcellular organelles are possible with variations of electron microscopy (thin section, scanning and freeze fracture), although specimen preparation steps such as fixation, dehydration, resin embedding, ultra-thin sectioning, coating and staining are very specialized, extensive and may introduce artifacts in the original sample. The development of high resolution x-ray microscopy is a new technique well suited to observe the intact structure of a biological specimen at high resolution without any artifacts. Here, x ray images of the various live bacteria, such as Staphylococcus and Streptococcus, and micromolecule such as chromosomal DNA from Escherichia coli, and Lipopolysaccharide from Burkholderia cepacia, are obtained with soft x-ray contact microscopy. A compact tabletop type glass laser system is used to produce x rays from Al, Si, and Au targets. The PMMA photoresists are used to record x-ray images. An AFM (atomic force microscope) is used to reproduce the x-ray images from the developed photoresists. The performance of the 50 nm spatial resolutions are achieved and images are able to be discussed on the biological view.

  14. Spatial characterization of red and white skin potatoes using nano-second laser induced breakdown in air

    NASA Astrophysics Data System (ADS)

    Rehan, Imran; Rehan, Kamran; Sultana, S.; Haq, M. Oun ul; Niazi, Muhammad Zubair Khan; Muhammad, Riaz

    2016-01-01

    We presents spectroscopic study of the plasma generated by a Q-switched Nd:YAG (1064 nm) laser irradiation of the flesh of red and white skin potatoes. From the spectra recorded with spectrometer (LIBS2500+, Ocean Optics, USA) 11 elements were identified in red skin potato, whereas, the white skin potato was found to have nine elements. Their relative concentrations were estimated using CF-LIBS method for the plasma in local thermodynamic equilibrium. The target was placed in ambient air at atmospheric pressure. The electron temperature and number density were calculated from Boltzmann plot and stark broadened line profile methods, respectively using Fe I spectral lines. The spatial distribution of plasma parameters were also studied which show a decreasing trend of 6770 K-4266 K and (3-2.0) × 1016 cm-3. Concentrations of the detected elements were monitored as a function of depth of the potatoes. Our study reveals a decreasing tendency in concentration of iron from top to the centre of potato's flesh, whereas, the concentrations of other elements vary randomly.

  15. High-rate deformation and spall fracture of hadfield steel under action of high-current nanosecond relativistic electron beam

    NASA Astrophysics Data System (ADS)

    Gnyusov, S. F.; Rotshtein, V. P.; Polevin, S. D.; Kitsanov, S. A.

    2010-09-01

    Features of the plastic deformation and dynamic spall fracture of Hadfield steel under conditions of shock wave loading at a straining rate of ˜106 s-1 have been studied. The shock load (˜30 GPa, ˜0.2 μs) was produced by pulses of a SINUS-7 electron accelerator, which generated relativistic electron bunches with an electron energy of up to 1.35 MeV, a duration of 45 ns, and a peak power on the target of 3.4 × 1010 W/cm2. It is established that the spalling proceeds via mixed viscous-brittle intergranular fracture, unlike the cases of quasi-static tensile and impact loading, where viscous transgranular fracture is typical. It is shown that the intergranular character of the spall fracture is caused by the localization of plastic deformation at grain boundaries containing precipitated carbide inclusions.

  16. Nanosecond frame cameras

    SciTech Connect

    Frank, A M; Wilkins, P R

    2001-01-05

    The advent of CCD cameras and computerized data recording has spurred the development of several new cameras and techniques for recording nanosecond images. We have made a side by side comparison of three nanosecond frame cameras, examining them for both performance and operational characteristics. The cameras include; Micro-Channel Plate/CCD, Image Diode/CCD and Image Diode/Film; combinations of gating/data recording. The advantages and disadvantages of each device will be discussed.

  17. Behaviour of metals at ultra-high strain rate by using femtosecond laser shockwaves

    NASA Astrophysics Data System (ADS)

    Cuq-Lelandais, J.-P.; Boustie, M.; Berthe, L.; De Rességuier, T.

    2012-08-01

    The mechanical behavior of materials under extreme conditions can be investigated by using laser driven shocks. Actually, femtosecond (fs) technologies allow to reach strong pressures over a very fast duration. This work is dedicated to characterize metals behavior in this ultra-short mode, (aluminum, tantalum), leading to an extreme dynamic solicitation in the target (>107s-1). The study includes the validation of experimental results obtained on the LULI 100TW facility by comparison with numerical model. Three modeling steps are considered. First, we characterize the pressure loading resulting from the fs laser-matter interaction, different from what happens in the classical nanosecond regime. Then, the shock wave propagation is observed through the target and particularly its pressure decay, strong in this regime. The elastic-plastic influence on the shock attenuation is discussed, particularly for tantalum which has a high elastic limit. Dynamic damage appears with spallation. Experimentally, spallation is characterized by VISAR measurements and post-test observations. Shots with different thicknesses have been carried out to determine the damage properties in function of strain rate. We show in this work that a simple instantaneous rupture criterion is not sufficient to reproduce the damage induced in the sample. Only the Kanel model, which includes damage kinetics, is able to reproduce experimental data (VISAR measurements, spall thickness). A generalization of this model to any strain rate can be performed by confronting these results to other shock generators data (ns laser driven shocks, plate impacts). One remarkable result is that every Kanel parameters follows a power law with strain rate in dynamic regime (105 to 108s-1) for both aluminum and tantalum.

  18. Effect of defocusing distance on the contaminated surface of brass ring with nanosecond laser in a 3D laser scanning system

    NASA Astrophysics Data System (ADS)

    Zhao, Mali; Liu, Tiegen; Jiang, Junfeng; Wang, Meng

    2014-08-01

    Defocusing distance plays a key role in laser cleaning result and can be either positive or negative, depending on the focus position relative to the sample surface. In this paper, we investigate the effect of the defocusing distance on the cleaning efficiency of oxidized brass surface. The oxide layer from the surface of a brass ring was processed with a three dimensional (3-D) dynamically focused laser galvanometer scanning system. The relationship between removal efficiency of the oxide layer and the defocusing distance was analyzed. The sample surface topography, element content before and after the laser cleaning were analyzed by a scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDS), the surface quality after laser cleaning was analyzed by a Atomic Force Microscope (AFM), the chemical constituents of the oxide layer on the sample surface after being processed with different defocusing distances were examined by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The results show that the ratios of Cu/O and Zn/O reach the maximum of 53.2 and 27.78 respectively when the defocusing distance is +0.5 mm. The laser pulses will lose the ability to remove the oxide layer from the substrate surface when the defocusing distance is larger than ±2 mm.

  19. High-energy sub-nanosecond optical pulse generation with a semiconductor laser diode for pulsed TOF laser ranging utilizing the single photon detection approach

    NASA Astrophysics Data System (ADS)

    Huikari, Jaakko; Avrutin, Eugene; Ryvkin, Boris; Kostamovaara, Juha

    2016-06-01

    Bulk and quantum well laser diodes with a large equivalent spot size of d a /Γ a ≈ 3 µm and stripe width/cavity length of 30 µm/3 mm were realized and tested. They achieved a pulse energy and pulse length of the order of ~1 nJ and ~100 ps, respectively, with a peak pulse current of 6-8 A and a current pulse width of 1 ns. The 2D characteristics of the optical output power versus wavelength and time were also analyzed with a monochromator/streak camera set-up. The far-field characteristics were studied with respect to the time-homogeneity and energy distribution. The feasibility of a laser diode with a large equivalent spot size in single photon detection based laser ranging was demonstrated to a non-cooperative target at a distance of a few tens of meters.

  20. Generation of nanosecond and subnanosecond laser pulses by AlGaAs/GaAs laser-thyristor with narrow mesa stripe contact.

    PubMed

    Slipchenko, Sergey O; Podoskin, Aleksandr A; Soboleva, Olga S; Pikhtin, Nikita A; Bagaev, Timur A; Ladugin, Maxim A; Marmalyuk, Aleksandr A; Simakov, Vladimir A; Tarasov, Il'ya S

    2016-07-25

    Lasers-thyristors with a narrow (20 μm) mesa stripe contact have been studied. It was shown that the laser peak power reaches a value of 2.5 W in the long-pulse mode at a pulse width of 13 ns. It was demonstrated that generation of a controlled train of laser pulses with peak power of 1.6 W and width of 90 ps is possible in the short-pulse mode. The maximum value of the pulse repetition frequency was 470 kHz at the following working characteristics of the laser-thyristor: blocking voltage 5.8 V, control current pulse 25 mA. A number of specific features were observed in the short-pulse mode. It was found that the blocking voltage and amplitude of the control current pulse affect the lasing process. We observed that in short pulse mode the lasing spectra have a two-band structure and the lateral near field may degenerate into a single spot with size substantially smaller than the mesa stripe width. It was shown that the main reason for the observed specific features of lasing is the clearly pronounced effect of the spatial localization of the current.

  1. Generation of nanosecond and subnanosecond laser pulses by AlGaAs/GaAs laser-thyristor with narrow mesa stripe contact.

    PubMed

    Slipchenko, Sergey O; Podoskin, Aleksandr A; Soboleva, Olga S; Pikhtin, Nikita A; Bagaev, Timur A; Ladugin, Maxim A; Marmalyuk, Aleksandr A; Simakov, Vladimir A; Tarasov, Il'ya S

    2016-07-25

    Lasers-thyristors with a narrow (20 μm) mesa stripe contact have been studied. It was shown that the laser peak power reaches a value of 2.5 W in the long-pulse mode at a pulse width of 13 ns. It was demonstrated that generation of a controlled train of laser pulses with peak power of 1.6 W and width of 90 ps is possible in the short-pulse mode. The maximum value of the pulse repetition frequency was 470 kHz at the following working characteristics of the laser-thyristor: blocking voltage 5.8 V, control current pulse 25 mA. A number of specific features were observed in the short-pulse mode. It was found that the blocking voltage and amplitude of the control current pulse affect the lasing process. We observed that in short pulse mode the lasing spectra have a two-band structure and the lateral near field may degenerate into a single spot with size substantially smaller than the mesa stripe width. It was shown that the main reason for the observed specific features of lasing is the clearly pronounced effect of the spatial localization of the current. PMID:27464105

  2. High energy pulses generation with giant spectrum bandwidth and submegahertz repetition rate from a passively mode-locked Yb-doped fiber laser in all normal dispersion cavity

    NASA Astrophysics Data System (ADS)

    Lin, J.-H.; Wang, D.; Lin, K.-H.

    2011-01-01

    Robust passively mode-locked pulse generation with low pulse repetition rate and giant spectrum bandwidth in an all-fiber, all-normal-dispersion ytterbium-doped fiber laser has been experimentally demonstrated using nonlinear polarization evolution technique. The highest pulse energy over 20 nJ with spectrum bandwidth over 50 nm can be experimentally obtained at 175 mW pump power. The mode-locked pulses reveal broadened 3-dB pulsewidth about several nanosecond and widened pedestal in time trace that is resulted from enormous dispersion in laser cavity and gain dynamics. At certain mode-locking state, a spectrum gap around 1056 nm are observed between the three and four energy levels of Yb-doped fiber laser. By properly rotating the polarization controller, the gap can be eliminated due to four-wave mixing to produce more flattened spectrum output.

  3. Laser balancing system for high material removal rates

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Georgalas, G.; Ortiz, A. L.

    1984-01-01

    A laser technique to remove material in excess of 10 mg/sec from a spinning rotor is described. This material removal rate is 20 times greater than previously reported for a surface speed of 30 m/sec. Material removal enhancement was achieved by steering a focused laser beam with moving optics to increase the time of laser energy interaction with a particular location on the circumferential surface of a spinning rotor. A neodymium:yttrium aluminum garnet (Nd:YAG) pulse laser was used in this work to evaluate material removal for carbon steel, 347 stainless steel, Inconal 718, and titanium 6-4. This technique is applicable to dynamic laser balancing.

  4. Strain rate dependency of laser sintered polyamide 12

    NASA Astrophysics Data System (ADS)

    Cook, J. E. T.; Goodridge, R. D.; Siviour, C. R.

    2015-09-01

    Parts processed by Additive Manufacturing can now be found across a wide range of applications, such as those in the aerospace and automotive industry in which the mechanical response must be optimised. Many of these applications are subjected to high rate or impact loading, yet it is believed that there is no prior research on the strain rate dependence in these materials. This research investigates the effect of strain rate and laser energy density on laser sintered polyamide 12. In the study presented here, parts produced using four different laser sintered energy densities were exposed to uniaxial compression tests at strain rates ranging from 10-3 to 10+3 s-1 at room temperature, and the dependence on these parameters is presented.

  5. Medium Repetition Rate TEA Laser For Industrial Applications

    NASA Astrophysics Data System (ADS)

    Walter, Bruno

    1987-09-01

    The design and performance of an inexpensive compact repetitively pulsed TEA CO2 laser is described. The device uses a modified corona preionization technique and a fast transverse gas flow to achieve high repetition rates. An output energy of 500 mJ per pulse and an out-put power of 6.2W at 40Hz have been obtained. Due to the small energy needed for preionization, the efficiency of the device is high, whereas the gas dissociation is low when compared with commercial laser systems. This results in the relatively small fresh laser gas exchange of 20 ltr h-1 for long term operation.

  6. Photoinduced laser etching of a diamond surface

    SciTech Connect

    Kononenko, V V; Komlenok, M S; Pimenov, S M; Konov, V I

    2007-11-30

    Nongraphitising ablation of the surface of a natural diamond single crystal irradiated by nanosecond UV laser pulses is studied experimentally. For laser fluences below the diamond graphitisation threshold, extremely low diamond etching rates (less than 1nm/1000 pulses) are obtained and the term nanoablation is used just for this process. The dependence of the nanoablation rate on the laser fluence is studied for samples irradiated both in air and in oxygen-free atmosphere. The effect of external heating on the nanoablation rate is analysed and a photochemical mechanism is proposed for describing it. (interaction of laser radiation with matter. laser plasma)

  7. High removal rate laser-based coating removal system

    DOEpatents

    Matthews, Dennis L.; Celliers, Peter M.; Hackel, Lloyd; Da Silva, Luiz B.; Dane, C. Brent; Mrowka, Stanley

    1999-11-16

    A compact laser system that removes surface coatings (such as paint, dirt, etc.) at a removal rate as high as 1000 ft.sup.2 /hr or more without damaging the surface. A high repetition rate laser with multiple amplification passes propagating through at least one optical amplifier is used, along with a delivery system consisting of a telescoping and articulating tube which also contains an evacuation system for simultaneously sweeping up the debris produced in the process. The amplified beam can be converted to an output beam by passively switching the polarization of at least one amplified beam. The system also has a personal safety system which protects against accidental exposures.

  8. Third-generation megahertz-rate pulse burst laser system.

    PubMed

    Thurow, Brian S; Satija, Aman; Lynch, Kyle

    2009-04-10

    The design and performance of a third-generation megahertz-rate pulse burst laser system is described. The third-generation system incorporates two distinct design changes that distinguish it from earlier-generation systems. The first is that pulse slicing is now achieved by using an economical acousto-optic modulator (AOM), and the second is the use of a variable pulse duration flashlamp driver that provides relatively uniform gain over a ~700 mus window. The use of an AOM for pulse slicing permits flexible operation such as pulse-on-demand operation with variable pulse durations ranging from 10 ns to DC. The laser described here is capable of producing a burst of laser pulses at repetition rates as high as 50 MHz and peak powers of 10 kW. Second-harmonic conversion efficiency using a type II KTP crystal is also demonstrated.

  9. High Rate Laser Pitting Technique for Solar Cell Texturing

    SciTech Connect

    Hans J. Herfurth; Henrikki Pantsar

    2013-01-10

    High rate laser pitting technique for solar cell texturing Efficiency of crystalline silicon solar cells can be improved by creating a texture on the surface to increase optical absorption. Different techniques have been developed for texturing, with the current state-of-the-art (SOA) being wet chemical etching. The process has poor optical performance, produces surfaces that are difficult to passivate or contact and is relatively expensive due to the use of hazardous chemicals. This project shall develop an alternative process for texturing mc-Si using laser micromachining. It will have the following features compared to the current SOA texturing process: -Superior optical surfaces for reduced front-surface reflection and enhanced optical absorption in thin mc-Si substrates -Improved surface passivation -More easily integrated into advanced back-contact cell concepts -Reduced use of hazardous chemicals and waste treatment -Similar or lower cost The process is based on laser pitting. The objective is to develop and demonstrate a high rate laser pitting process which will exceed the rate of former laser texturing processes by a factor of ten. The laser and scanning technologies will be demonstrated on a laboratory scale, but will use inherently technologies that can easily be scaled to production rates. The drastic increase in process velocity is required for the process to be implemented as an in-line process in PV manufacturing. The project includes laser process development, development of advanced optical systems for beam manipulation and cell reflectivity and efficiency testing. An improvement of over 0.5% absolute in efficiency is anticipated after laser-based texturing. The surface textures will be characterized optically, and solar cells will be fabricated with the new laser texturing to ensure that the new process is compatible with high-efficiency cell processing. The result will be demonstration of a prototype process that is suitable for scale-up to a

  10. Dynamics of polymer response to nanosecond shock compression

    NASA Astrophysics Data System (ADS)

    Banishev, Alexandr A.; Shaw, William L.; Curtis, Alexander D.; Dlott, Dana D.

    2014-03-01

    The high strain rate mechanical dynamics of a polymer under shock compression, poly-methyl methacrylate (PMMA, MW = 996 000), were probed in experiments that combined two measurement techniques. The km s-1 impacts with laser-launched flyer plates were characterized by a fast interferometer, and the polymer dynamics were characterized by the nanosecond emission redshifting of Rhodamine 6G dye in PMMA. The thicknesses and velocities of the flyer plates were varied to create shock durations in the 5-22 ns range and pressures in the 2.6-9.2 GPa range. The strain rates were on the order of 107 s-1. With shock durations greater than 10 ns, a two-part rise of the redshift transients was observed, which was interpreted with reference to the well-known viscoelastic shock compression paradigm. However, the initial compression stage, lasting ˜10 ns, was found to be only partially elastic. With an elastic compression, after a shock the density should promptly return to its initial value. But even with the shortest-duration 5 ns shocks, the density relaxation after the shock ended was quite small. The critical shear stress where PMMA loses strength and the viscous compression process begins, appeared to be considerably larger with nanosecond shocks than with microsecond shocks. The loss of strength always took ˜10 ns, and could not be accelerated by increasing the shock pressure, suggesting the rate of strength loss was limited by the need for collective motions of the 30-40 nm polymer chains. The rates and amplitudes of the viscous density relaxation process increased with shock duration and shock pressure.

  11. 1-kHz-repetition-rate femtosecond Raman laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu

    2016-07-01

    A femtosecond Raman laser utilising compressed hydrogen is experimentally investigated under pumping by radiation from a 1-kHz-repetition-rate Ti : sapphire laser. In the regime of double-pulse pumping, the conditions are determined, which correspond to the minimal energy dispersion of Stokes pulses. The optical scheme is realised, which is capable of ensuring the long-term stability of the average power of the first Stokes component with a variation of less than 2%. The Stokes pulses are produced with a pulse duration of 60 fs and energy of 0.26 mJ at a conversion efficiency of 14%.

  12. Analysis of output surface damage resulting from single 351 nm, 3 ns pulses on sub-nanosecond laser conditioned KD2PO4 crystals

    SciTech Connect

    Jarboe, J; Adams, J J; Hackel, R

    2007-10-31

    We observe that by conditioning DKDP using 500 ps laser pulses, the bulk damage threshold becomes essentially equivalent to the surface damage threshold. We report here the findings of our study of laser initiated output surface damage on 500 ps laser conditioned DKDP for test pulses at 351 nm, 3 ns. The relation between surface damage density and damaging fluence (r(f)) is presented for the first time and the morphologies of the surface sites are discussed. The results of this study suggest a surface conditioning effect resulting from exposure to 500 ps laser pulses.

  13. Flexible high-repetition-rate ultrafast fiber laser

    PubMed Central

    Mao, Dong; Liu, Xueming; Sun, Zhipei; Lu, Hua; Han, Dongdong; Wang, Guoxi; Wang, Fengqiu

    2013-01-01

    High-repetition-rate pulses have widespread applications in the fields of fiber communications, frequency comb, and optical sensing. Here, we have demonstrated high-repetition-rate ultrashort pulses in an all-fiber laser by exploiting an intracavity Mach-Zehnder interferometer (MZI) as a comb filter. The repetition rate of the laser can be tuned flexibly from about 7 to 1100 GHz by controlling the optical path difference between the two arms of the MZI. The pulse duration can be reduced continuously from about 10.1 to 0.55 ps with the spectral width tunable from about 0.35 to 5.7 nm by manipulating the intracavity polarization controller. Numerical simulations well confirm the experimental observations and show that filter-driven four-wave mixing effect, induced by the MZI, is the main mechanism that governs the formation of the high-repetition-rate pulses. This all-fiber-based laser is a simple and low-cost source for various applications where high-repetition-rate pulses are necessary. PMID:24226153

  14. The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars

    PubMed Central

    Youssef, G.; Crum, R.; Prikhodko, S. V.; Seif, D.; Po, G.; Ghoniem, N.; Kodambaka, S.; Gupta, V.

    2013-01-01

    An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) and strain rates (>107 s−1), using laser-generated stress waves, are presented. Single-crystalline Cu pillars (∼1.20 μm in tall and ∼0.45 μm in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars. PMID:23526837

  15. The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars

    SciTech Connect

    Youssef, G.; Crum, R.; Seif, D.; Po, G.; Prikhodko, S. V.; Kodambaka, S.; Ghoniem, N.; Gupta, V.

    2013-02-28

    An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) and strain rates (>10{sup 7} s{sup -1}), using laser-generated stress waves, are presented. Single-crystalline Cu pillars ({approx}1.20 {mu}m in tall and {approx}0.45 {mu}m in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars.

  16. Rate-equation approach to atomic-laser light statistics

    SciTech Connect

    Chusseau, Laurent; Arnaud, Jacques; Philippe, Fabrice

    2002-11-01

    We consider three- and four-level atomic lasers that are either incoherently (unidirectionally) or coherently (bidirectionally) pumped, the single-mode cavity being resonant with the laser transition. The intracavity Fano factor and the photocurrent spectral density are evaluated on the basis of rate equations. According to that approach, fluctuations are caused by jumps in active and detecting atoms. The algebra is simple. Whenever a comparison is made, the expressions obtained coincide with the previous results. The conditions under which the output light exhibits sub-Poissonian statistics are considered in detail. Analytical results, based on linearization, are verified by comparison with Monte Carlo simulations. An essentially exhaustive investigation of sub-Poissonian light generation by three- and four-level lasers has been performed. Only special forms were reported earlier.

  17. Plasma heating rate in very intense laser light

    SciTech Connect

    Rashid, S.M.S.

    1982-01-01

    An exact Volkov state solution of the minimally coupled dirac equation is used to calculate the transition rate dR of an electron scattering via a stationary ion in the presence of a very intense laser field. A consistent picture of the scattering is presented in which the electrons' initial and final states are quasi-free states. Accordingly, a modified transition rate dR and a modified Maxwell-Boltzmann distribution are developed. They are used to calculate the heating rate W of a quasi-free plasma in the presence of very intense laser light. In order to simplify the expression for the heating rate W, an important transformation, which changes an infinite sum over Bessel functions into a finite integral, is introdced. It is then shown that the leading term of the heating rate W is similar to the expression of Osborn (with corrections) for intensity I < 10/sup 16/ Watts/cm/sup 2/ Watts/cm/sup 2/ and k/sub B/T < Ike V. A new correction factor is defined to show the effect of very intense laser field when the intensity I > 10/sup 16/ Watts/cm/sup 2/. For k/sub B/T > Ike V, a spin-dependent term of order k/sub B/T/mc/sup 2/ is also discovered. This represents a new term not previously known. It is shown that the effect of this term on the heating rate is substantial and that it is possible to measure its effect with present-day laser systems.

  18. Scaling ablation rates for picosecond lasers using burst micromachining

    NASA Astrophysics Data System (ADS)

    Knappe, Ralf; Haloui, Hatim; Seifert, Albert; Weis, Alexander; Nebel, Achim

    2010-02-01

    High-precision micromachining with picosecond lasers became an established process. Power scaling led to industrial lasers, generating average power levels well above 50 W for applications like structuring turbine blades, micro moulds, and solar cells. In this paper we report, how a smart distribution of energy into groups of pulses can significantly improve ablation rates for some materials, also providing a better surface quality. Machining micro moulds in stainless steel, a net ablation rate of ~1 mm3/min is routinely achieved, e.g. using pulse energy of 200 μJ at a repetition rate of 200 kHz. This is industrial standard, and demonstrates an improvement by two orders of magnitude over the recent years. When the energy was distributed to a burst of 10 pulses (25 μJ), repeated with 200 kHz, the ablation rate of stainless steel was 5 times higher with the same 50 W average power. Bursts of 10 pulses repeated with 1 MHz (5 μJ) even resulted in an ablation rate as high as 12 mm3/min. In addition, optimized pulse delays achieved a reduction of the surface roughness by one order of magnitude, providing Ra values as low as 200 nm. Similar results were performed machining silicon, scaling the ablation rate from 1.2 mm3/min (1 pulse, 250 μJ, 200 kHz) to 15 mm3/min (6 pulses, 8 μJ, 1 MHz). Burst machining of ceramics, copper and glass did not change ablation rates, only improved surface quality. For glass machining, we achieved record-high ablation rates of >50 mm3/min, using a new state-of-the-art laser which could generate >70 W of average power and repetition rates as high as 2 MHz.

  19. Recycle Rate in a Pulsed, Optically Pumped Rubidium Laser

    SciTech Connect

    Miller, Wooddy S.; Sulham, Clifford V.; Holtgrave, Jeremy C.; Perram, Glen P.

    2010-10-08

    A pulsed, optically pumped rubidium laser operating in analogy to the diode pumped alkali laser (DPAL) system at pump intensities as high as 750 kW/cm{sup 2} has been demonstrated with output energies of up to 13 {mu}J/pulse. Output energy is dramatically limited by spin-orbit relaxation rates under these high intensity pump conditions. More than 250 photons are available for every rubidium atom in the pumped volume, requiring a high number of cycles per atom during the 2-8 ns duration of the pump pulse. At 550 Torr of ethane, the spin-orbit relaxation rate is too slow to effectively utilize all the incident pump photons. Indeed, a linear dependence of output energy on pump pulse duration for fixed pump energy is demonstrated.

  20. Nanosecond Pulse Discharges and Fast Ionization Wave Discharges: Fundamental Kinetic Processes and Applications

    NASA Astrophysics Data System (ADS)

    Adamovich, Igor

    2011-10-01

    Over the last two decades, nanosecond pulse discharges and Fast Ionization Wave (FIW) discharges have been studied extensively, both theoretically and experimentally. Current interest in characterization of these discharges is driven mainly by their potential for applications such as plasma chemical fuel reforming, plasma-assisted combustion, high-speed flow control, pumping of electric discharge excited lasers, and generation of high-energy electrons. A unique capability of FIW discharges to generate significant ionization and high concentrations of excited species at high pressures and over large distances, before ionization instabilities have time to develop, is very attractive for these applications. Recent advances in laser optical diagnostics offer an opportunity of making non-intrusive, spatially and time-resolved measurements of electron density and electric field distributions in high-speed ionization wave discharges, on nanosecond time scale. Insight into FIW formation and propagation dynamics also requires development of predictive kinetic models, and their experimental validation. Although numerical kinetic models may incorporate detailed kinetics of charged and neutral species in the propagating ionization wave front (including non-local electron kinetics), analytic models are also attractive due to their capability of elucidating fundamental trends of discharge development. The talk gives an overview of recent progress in experimental characterization and kinetic modeling of nanosecond pulse and fast ionization wave discharges in nitrogen and air over a wide range of pulse repetition rates, 0.1-40 kHz. FIW discharge plasmas sustained at high pulse repetition rates are diffuse and volume filling, with most of the power coupled to the plasma behind the wave, at E/N = 200-300 Td and energy loading of 1-2 meV/molecule/pulse. The results demonstrate significant potential of large volume, diffuse, high pulse repetition rate FIW discharges for novel plasma

  1. Cracks growth behaviors of commercial pure titanium under nanosecond laser irradiation for formation of nanostructure-covered microstructures (with sub-5-μm)

    NASA Astrophysics Data System (ADS)

    Pan, A. F.; Wang, W. J.; Mei, X. S.; Zheng, B. X.; Yan, Z. X.

    2016-11-01

    This study reported on the formation of sub-5-μm microstructures covered on titanium by cracks growth under 10-ns laser radiation at the wavelength of 532 nm and its induced light modification for production of nanostructures. The electric field intensity and laser power density absorbed by commercial pure titanium were computed to investigate the self-trapping introduced by cracks and the effect of surface morphology on laser propagation characteristics. It is found that nanostructures can form at the surface with the curvature radius below 20 μm. Meanwhile, variable laser fluences were applied to explore the evolution of cracks on commercial pure titanium with or without melt as spot overlap number increased. Experimental study was first performed at the peak laser fluence of 1.063 J/cm2 to investigate the microstructures induced only by cracks growth. The results demonstrated that angular microstructures with size between 1.68 μm and 4.74 μm was obtained and no nanostructure covered. Then, at the peak laser fluence of 2.126 J/cm2, there were some nanostructures covered on the melt-induced curved microstructured surface. However, surface molten material submerged in the most of cracks at the spot overlap number of 744, where the old cracks disappeared. The results indicated that there was too much molten material and melting time at the peak laser fluence of 2.126 J/cm2, which was not suitable for obtainment of perfect micro-nano structures. On this basis, peak laser fluence was reduced down to 1.595 J/cm2 and the sharp sub-5 μm microstructures with nanostructures covered was obtained at spot overlap number of 3720.

  2. Wavelength Dependence in the Analysis of Carbon Content in Coal by Nanosecond 266 nm and 1064 nm Laser Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiongwei; Wang, Zhe; Fu, Yangting; Li, Zheng; Ni, Weidou

    2015-08-01

    The wavelength dependence of laser induced breakdown spectroscopy (LIBS) in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square (PLS) model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method. supported by National Natural Science Foundation of China (No. 51276100) and National Basic Research Program of China (973 Program) (No. 2013CB228501)

  3. Vlasov-Fokker-Planck modeling of plasma near hohlraum walls heated with nanosecond laser pulses calculated using the ray tracing equations

    NASA Astrophysics Data System (ADS)

    Joglekar, Archis; Thomas, Alec

    2013-10-01

    Here, we present 2D numerical modeling of near critical density plasma using a fully implicit Vlasov-Fokker-Planck code, IMPACTA, which includes self-consistent magnetic fields as well as anisotropic electron pressure terms in the expansion of the distribution function, as well as an implementation of the Boris CYLRAD algorithm through a ray tracing add-on package. This allows to model inverse brehmsstrahlung heating as a laser travels through a plasma by solving the ray tracing equations. Generated magnetic fields (eg. the Biermann battery effect) as well as field advection through heat fluxes from the laser heating is shown. Additionally, perturbations in the plasma density profile arise as a result of the high pressures and flows in the plasma. These perturbations in the plasma density affect the path of the laser traveling through the plasma and modify the heating profile accordingly. The interplay between these effects is discussed in this study.

  4. High-efficiency and compact semiconductor lasers with monolithically integrated switches for generation of high-power nanosecond pulses in time-of-flight (TOF) systems

    NASA Astrophysics Data System (ADS)

    Slipchenko, Sergey; Podoskin, Aleksandr; Soboleva, Olga; Zakharov, Maxim S.; Bakhvalov, Kirill; Romanovich, Dmitrii; Pikhtin, Nikita; Tarasov, Il`ya; Bagaev, Timur; Ladugin, Maxim; Marmalyuk, Aleksandr; Simakov, Vladimir

    2016-03-01

    We present a new approach based on the integration of the functions of a high-efficiency current switch and a laser emitter into a single heterostructure as elements of time-of-flight (TOF) systems. The approach being developed employs the effect of an electrical bistability, which occurs in the general case in thyristor structures. We report recent results obtained in a study of the dynamic electrical and optical characteristics of the pulsed sources we developed. An effective generation of 2- to 100-ns laser pulses at a wavelength of 905 nm is demonstrated. The possibility of generating laser pulses shorter than 1 ns is considered. The maximum peak power reached values of 7 and 50 W for 10- and 100-ns pulses, respectively.

  5. Fast rate fracture of aluminum using high intensity lasers

    NASA Astrophysics Data System (ADS)

    Dalton, Douglas Allen

    Laser induced shock experiments were performed to study the dynamics of various solid state material processes, including shock-induced melt, fast rate fracture, and elastic to plastic response. Fast rate fracture and dynamic yielding are greatly influenced by microstructural features such as grain boundaries, impurity particles and alloying atoms. Fast fracture experiments using lasers are aimed at studying how material microstructure affects the tensile fracture characteristics at strain rates above 106 s-1. We used the Z-Beamlet Laser at Sandia National Laboratories to drive shocks via ablation and we measured the maximum tensile stress of aluminum targets with various microstructures. Using a velocity interferometer and sample recovery, we are able to measure the maximum tensile stress and determine the source of fracture initiation in these targets. We have explored the role that grain size, impurity particles and alloying in aluminum play in dynamic yielding and spall fracture at tensile strain rates of ˜3x106 s-1. Preliminary results and analysis indicated that material grain size plays a vital role in the fracture morphology and spall strength results. In a study with single crystal aluminum specimens, velocity measurements and fracture analysis revealed that a smaller amplitude tensile stress was initiated by impurity particles; however, these particles served no purpose in dynamic yielding. An aluminum-magnesium alloy with various grain sizes presented the lowest spall strength, but the greatest dynamic yield strength. Fracture mode in this alloy was initiated by both grain boundaries and impurity particles. With respect to dynamic yielding, alloying elements such as magnesium serve to decrease the onset of plastic response. The fracture stress and yield stress showed no evidence of grain size dependence. Hydrodynamic simulations with material strength models are used to compare with our experiments. In order to study the strain rate dependence of spall

  6. High repetition rate laser systems: targets, diagnostics and radiation protection

    SciTech Connect

    Gizzi, Leonida A.; Clark, Eugene; Neely, David; Tolley, Martin; Roso, Luis

    2010-02-02

    Accessing the high repetition regime of ultra intense laser-target interactions at small or moderate laser energies is now possible at a large number of facilities worldwide. New projects such as HiPER and ELI promise to extend this regime to the high energy realm at the multi-kJ level. This opportunity raises several issues on how best to approach this new regime of operation in a safe and efficient way. At the same time, a new class of experiments or a new generation of secondary sources of particles and radiation may become accessible, provided that target fabrication and diagnostics are capable of handling this rep-rated regime. In this paper, we explore this scenario and analyse existing and perspective techniques that promise to address some of the above issues.

  7. Laser-enhanced dynamics in molecular rate processes

    NASA Technical Reports Server (NTRS)

    George, T. F.; Zimmerman, I. H.; Devries, P. L.; Yuan, J.-M.; Lam, K.-S.; Bellum, J. C.; Lee, H.-W.; Slutsky, M. S.

    1978-01-01

    The present discussion deals with some theoretical aspects associated with the description of molecular rate processes in the presence of intense laser radiation, where the radiation actually interacts with the molecular dynamics. Whereas for weak and even moderately intense radiation, the absorption and stimulated emission of photons by a molecular system can be described by perturbative methods, for intense radiation, perturbation theory is usually not adequate. Limiting the analysis to the gas phase, an attempt is made to describe nonperturbative approaches applicable to the description of such processes (in the presence of intense laser radiation) as electronic energy transfer in molecular (in particular atom-atom) collisions; collision-induced ionization and emission; and unimolecular dissociation.

  8. Effects of argon gas flow rate on laser-welding.

    PubMed

    Takayama, Yasuko; Nomoto, Rie; Nakajima, Hiroyuki; Ohkubo, Chikahiro

    2012-01-01

    The purpose of this study was to evaluate the effects of the rate of argon gas flow on joint strength in the laser-welding of cast metal plates and to measure the porosity. Two cast plates (Ti and Co-Cr alloy) of the same metal were abutted and welded together. The rates of argon gas flow were 0, 5 and 10 L/min for the Co-Cr alloy, and 5 and 10 L/min for the Ti. There was a significant difference in the ratio of porosity according to the rate of argon gas flow in the welded area. Argon shielding had no significant effect on the tensile strength of Co-Cr alloy. The 5 L/min specimens showed greater tensile strength than the 10 L/min specimens for Ti. Laser welding of the Co-Cr alloy was influenced very little by argon shielding. When the rate of argon gas flow was high, joint strength decreased for Ti.

  9. Generation of 6.05J nanosecond pulses at a 1Hz repetition rate from a cryogenic cooled diode-pumped Yb:YAG MOPA system

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojin; Wang, Jianlei; Yang, Zhongguo; Liu, Jin; Li, Lei; Shi, Xiangchun; Huang, Wenfa; Wang, Jiangfeng; Chen, Weibiao

    2015-02-01

    Diode-pumped solid state laser system based on cryogenic Yb:YAG active-mirror scheme are presented with recent energy output. With improved optical design, 6.05J/1Hz pulse energy is achieved and a conceptual design with 30J output energy is theoretical simulated. The doubling efficiency of YCa4O (BO3)(YCOB) crystal is also discussed in this paper.

  10. Exact solution to laser rate equations: three-level laser as a Morse-like oscillator

    NASA Astrophysics Data System (ADS)

    León-Montiel, R. de J.; Moya-Cessa, Héctor M.

    2016-08-01

    It is shown how the rate equations that model a three-level laser can be cast into a single second-order differential equation, whose form describes a time-dependent harmonic oscillator. Using this result, we demonstrate that the resulting equation can be identified as a Schrödinger equation for a Morse-like potential, thus allowing us to derive exact closed-form expressions for the dynamics of the number of photons inside the laser cavity, as well as the atomic population inversion.

  11. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity.

    PubMed

    Li, Deyong; Li, Yunliang; Li, Hao; Wu, Xianyou; Yu, Qingxu; Weng, Yuxiang

    2015-05-01

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  12. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity.

    PubMed

    Li, Deyong; Li, Yunliang; Li, Hao; Wu, Xianyou; Yu, Qingxu; Weng, Yuxiang

    2015-05-01

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser. PMID:26026512

  13. A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity

    SciTech Connect

    Li, Deyong; Li, Yunliang; Li, Hao; Weng, Yuxiang; Wu, Xianyou; Yu, Qingxu

    2015-05-15

    Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm{sup −1} as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10{sup −4} ΔOD for a single wavelength detection, and 2 × 10{sup −4} ΔOD for spectral detection in amide I′ region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

  14. Nanosecond pulsed laser damage characteristics of HfO2/SiO2 high reflection coatings irradiated from crystal-film interface.

    PubMed

    Cheng, Xinbin; Jiao, Hongfei; Lu, Jiangtao; Ma, Bin; Wang, Zhanshan

    2013-06-17

    The nano-precursors in the subsurface of Nd:YLF crystal were limiting factor that decreased the laser-induced damage threshold (LIDT) of HfO(2)/SiO(2) high reflection (HR) coatings irradiated from crystal-film interface. To investigate the contribution of electric-field (E-field) to laser damage originating from nano-precursors and then to probe the distribution of vulnerable nano-precursors in the direction of subsurface depth, two 1064 nm HfO(2)/SiO(2) HR coatings having different standing-wave (SW) E-field distributions in subsurface of Nd:YLF c5424181043036123rystal were designed and prepared. Artificial gold nano-particles were implanted into the crystal-film interface prior to deposition of HR coatings to study the damage behaviors in a more reliable way. The damage test results revealed that the SW E-field rather than the travelling-wave (TW) E-field contributed to laser damage. By comparing the SW E-field distributions and LIDTs of two HR coating designs, the most vulnerable nano-precursors were determined to be concentrated in a thin redeposition layer that is within 100 nm from the crystal-film interface.

  15. Time-resolved imaging of processes associated with exit-surface damage growth in fused silica following exposure to nanosecond laser pulses.

    PubMed

    Demos, Stavros G; Raman, Rajesh N; Negres, Raluca A

    2013-02-25

    We study the dynamics of energy deposition and subsequent material response associated with exit surface damage growth in fused silica using a time resolved microscope system. This system enables acquisition of two transient images per damage event with temporal resolution of 180 ps and spatial resolution on the order of 1 µm. The experimental results address important issues in laser damage growth that include: a) the specific structural features within a damage site where plasma formation initiates; b) the subsequent growth of the plasma regions; c) the formation and expansion of radial and circumferential cracks; d) the kinetics and duration of material ejection; e) the characteristics of the generated shockwave.

  16. Ultrastructural imaging and molecular modeling of live bacteria using soft x-ray contact microscopy with nanoseconds laser-plasma radiation

    NASA Astrophysics Data System (ADS)

    Kado, Masataka; Richardson, Martin C.; Gaebel, Kai; Torres, David S.; Rajyaguru, Jayshree; Muszynski, Michael J.

    1995-09-01

    X-ray images of the various live bacteria, such as Staphylococcus and Streptococcus, and micromolecule such as chromosomal DNA from Escherichis coli, and Lipopolysacchride from Burkholderia cepacia, are obtained with soft x-ray contact microscopy. A compact tabletop type glass laser system is used to produce x-rays from Al, Si, and Au targets. The PMMA photoresists are used to record x-ray images. An AFM (atomic force microscope) is used to reproduce the x-ray images from the developed photoresists. The performance of the 50nm spatial resolutions are achieved and images are able to be discussed on the biological view.

  17. Influence of nanosecond pulsed laser irradiance on the viability of nanoparticle-loaded cells: implications for safety of contrast-enhanced photoacoustic imaging.

    PubMed

    Bayer, Carolyn L; Kelvekar, Juili; Emelianov, Stanislav Y

    2013-11-22

    Photoacoustic imaging, a promising new diagnostic medical imaging modality, can provide high contrast images of molecular features by introducing highly-absorbing plasmonic nanoparticles. Currently, it is uncertain whether the absorption of low fluence pulsed light by plasmonic nanoparticles could lead to cellular damage. In our studies we have shown that low fluence pulsed laser excitation of accumulated nanoparticles at low concentration does not impact cell growth and viability, while we identify thresholds at which higher nanoparticle concentrations and fluences produce clear evidence of cell death. The results provide insights for improved design of photoacoustic contrast agents and for applications in combined imaging and therapy.

  18. Interaction of nanosecond laser pulse with tetramethyl silane (Si(CH3)4) clusters: Generation of multiply charged silicon and carbon ions

    NASA Astrophysics Data System (ADS)

    Badani, Purav M.; Das, Soumitra; Mundlapati, Venkateswara Rao; Sharma, Pramod; Vatsa, Rajesh K.

    2011-12-01

    Present work reports significantly high levels of ionization, eventually leading to Coulomb explosion of Tetramethyl silane (TMS) clusters, on interaction with laser pulses of intensity ˜109 W/cm2. Tetramethyl silane clusters, prepared by supersonic expansion were photoionized at 266, 355 or 532 nm and the resultant ions were detected using time-of-flight mass spectrometer. It is observed that wavelength of irradiation and the size of the cluster are crucial parameters which drastically affect the nature of charge species generated upon photoionization of cluster. The results show that clusters absorb significantly higher energy from the laser field at longer wavelengths (532 nm) and generate multiply charged silicon and carbon ions which have large kinetic energies. Further, laser-cluster interaction at different wavelengths has been quantified and charge densities at 266, 355 and 532 nm are found to be 4x 1010, 5x 1010 and 5x 1011 charges/cm3 respectively. These unusual results have been rationalized based on dominance of secondary ionization processes at 532 nm ultimately leading to Coulomb explosion of clusters. In another set of experiments, multiply charged ions of Ar (up to +5 state) and Kr (up to +6 state) were observed when TMS doped inert gas clusters were photoionized at 532 and 355 nm. The extent of energy absorption at these two wavelengths is clearly manifested from the charge state of the atomic ions generated upon Coulomb disintegration of the doped cluster. These experiments thus demonstrate a novel method for generation of multiply charged atomic ions of inert gases at laser intensity of ˜ 109 W/cm2. The average size of the cluster exhibiting Coulomb explosion phenomena under giga watt intensity conditions has been estimated to be ˜ 6 nm. Experimental results obtained in the present work agree qualitatively with the model proposed earlier [D. Niu, H. Li, F. Liang, L. Wen, X. Luo, B. Wang, and H. Qu, J. Chem. Phys. 122, 151103(2005)] and point

  19. Tesla coil discharges guided by femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

    2012-04-01

    A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

  20. Comparison of High Rate Laser Ablation and Resulting Structures Using Continuous and Pulsed Single Mode Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Knebel, T.; Streek, A.; Exner, H.

    This paper compares high rate laser ablation and resulting structures of aluminum by using both a continuous wave and a ns-pulsed single mode fiber laser of high average laser power. Two different scan technologies were applied for fast deflection of the laser beams. In this work, 2.5D laser processing was studied by using a high aperture galvanometer scanner with a maximum scan speed of 18 m/s. By contrast, considerably higher scan speeds up to 1,000 m/s were achieved by using the in-house developed polygon scanner system. The ablation rates and the processing rates per unit area were analyzed by means of the depths of line-scan ablation tracks and laser processed cavities. In addition, SEM photograph of the machining samples will be presented in order to evaluate the machining quality. Finally the feasibility of this high rate technology for industrial application is demonstrated by machining examples.

  1. Evaluation of particle size distributions produced during ultra-violet nanosecond laser ablation and their relative contributions to ion densities in the inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Moses, Lance M.; Farnsworth, Paul B.

    2015-11-01

    Relative contributions to ion densities in the inductively coupled plasma (ICP) of particles of various sizes produced by laser ablation (LA) were investigated. Particles generated by 266 nm, ns LA of BaF2, CaF2, and a scandium aluminum alloy, characterized using SEM, consisted of hard and soft agglomerates, spherical particles, and irregularly-shaped particles. Although soft agglomerates and spherical particles were common to aerosols generated by LA in all cases, hard agglomerates appeared to be unique to the scandium aluminum alloy, while irregularly-shaped exfoliated particles were unique to the calcium and barium fluoride windows. The spatial distributions of Ca, Ba, and Sc ions in the ICP were determined from laser-induced fluorescence images taken with filters of pore sizes from 1-8 μm added in-line to the transport tube upstream from the ICP. In all cases, a significant fraction of the ions formed in the ICP originated from micron-sized particles. Differences in the penetration depths of nanometer-sized agglomerates and micron-sized particles were about 2 mm for Ca and 1 mm for Ba. Differences in the penetration depths of nanometer and micron-sized agglomerates observed in the case of aluminum scandium were much less significant. This suggests that micron-sized hard-agglomerates and nanometer-sized soft-agglomerates experience very similar vaporization patterns. Additionally, there was evidence that flow patterns in the transport tube affect the trajectories of particles entering the plasma.

  2. Multiphoton imaging with a nanosecond supercontinuum source

    NASA Astrophysics Data System (ADS)

    Lefort, Claire; O'Connor, Rodney P.; Blanquet, Véronique; Baraige, Fabienne; Tombelaine, Vincent; Lévêque, Philippe; Couderc, Vincent; Leproux, Philippe

    2016-03-01

    Multiphoton microscopy is a well-established technique for biological imaging of several kinds of targets. It is classically based on multiphoton processes allowing two means of contrast simultaneously: two-photon fluorescence (TPF) and second harmonic generation (SHG). Today, the quasi exclusive laser technology used in that aim is femtosecond titanium sapphire (Ti: Sa) laser. We experimentally demonstrate that a nanosecond supercontinuum laser source (STM-250-VIS-IR-custom, Leukos, France; 1 ns, 600-2400 nm, 250 kHz, 1 W) allows to obtain the same kind of image quality in the case of both TPF and SHG, since it is properly filtered. The first set of images concerns the muscle of a mouse. It highlights the simultaneous detection of TPF and SHG. TPF is obtained thanks to the labelling of alpha-actinin with Alexa Fluor® 546 by immunochemistry. SHG is created from the non-centrosymmetric organization of myosin. As expected, discs of actin and myosin are superimposed alternatively. The resulting images are compared with those obtained from a standard femtosecond Ti: Sa source. The physical parameters of the supercontinuum are discussed. Finally, all the interest of using an ultra-broadband source is presented with images obtained in vivo on the brain of a mouse where tumor cells labeled with eGFP are grafted. Texas Red® conjugating Dextran is injected into the blood vessels network. Thus, two fluorophores having absorption wavelengths separated by 80 nm are imaged simultaneously with a single laser source.

  3. Femtosecond laser bone ablation with a high repetition rate fiber laser source

    PubMed Central

    Mortensen, Luke J.; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C.; Xu, Chris; Intini, Giuseppe; Lin, Charles P.

    2014-01-01

    Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process. PMID:25657872

  4. An all-fiber high-energy cladding-pumped 93 nanosecond Q-switched fiber laser using an Y 3+-doped fiber saturable absorber

    NASA Astrophysics Data System (ADS)

    Moore, Sean W.; Patterson, Brian D.; Soh, Daniel B.; Bisson, Scott E.

    2014-03-01

    We report an all-fiber passively Q-switched laser using a large mode area (LMA) Yb3+ -doped fiber claddingpumped at 915 nm and an unpumped single-mode (SM) Yb3+-doped fiber as the saturable absorber (SA). The saturable absorber SM fiber and LMA gain fiber were coupled with a fiber taper designed to match the fundamental spatial mode of the LMA fiber and the expanded LP01 mode of the single mode fiber. The amplified spontaneous (ASE) intensity propagating in the single mode SA saturates the absorption before the onset of gain depletion in the pumped fiber, switching the fiber cavity to a high Q-state and producing a pulse. Using this scheme we demonstrate a Q-switched all-fiber oscillator with 32 μJ 93 ns pulses at 1030 nm. The associated peak power is nearly two orders of magnitude larger than that reported in previous experimental studies using a single Yb+3 saturable absorber fiber. The pulse energy was amplified to 0.230 mJ using an Yb3+-doped cladding pumped fiber amplifier fusion spliced to the fiber oscillator, increasing the energy by eight fold while preserving the all-fiber architecture.

  5. Spectral characteristics of quantum-cascade laser operating at 10.6 μm wavelength for a seed application in laser-produced-plasma extreme UV source.

    PubMed

    Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru; Endo, Akira

    2012-11-15

    In this Letter, we investigate, for the first time to our knowledge, the spectral properties of a quantum-cascade laser (QCL) from a point of view of a new application as a laser seeder for a nanosecond-pulse high-repetition frequency CO(2) laser operating at 10.6 μm wavelength. The motivation for this work is a renewed interest in such a pulse format and wavelength driven by a development of extreme UV (EUV) laser-produced-plasma (LPP) sources. These sources use pulsed multikilowatt CO(2) lasers to drive the EUV-emitting plasmas. Basic spectral performance characteristics of a custom-made QCL chip are measured, such as tuning range and chirp rate. The QCL is shown to have all essential qualities of a robust seed source for a high-repetition nanosecond-pulsed CO(2) laser required by EUV LPP sources.

  6. Spectral characteristics of quantum-cascade laser operating at 10.6 μm wavelength for a seed application in laser-produced-plasma extreme UV source.

    PubMed

    Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru; Endo, Akira

    2012-11-15

    In this Letter, we investigate, for the first time to our knowledge, the spectral properties of a quantum-cascade laser (QCL) from a point of view of a new application as a laser seeder for a nanosecond-pulse high-repetition frequency CO(2) laser operating at 10.6 μm wavelength. The motivation for this work is a renewed interest in such a pulse format and wavelength driven by a development of extreme UV (EUV) laser-produced-plasma (LPP) sources. These sources use pulsed multikilowatt CO(2) lasers to drive the EUV-emitting plasmas. Basic spectral performance characteristics of a custom-made QCL chip are measured, such as tuning range and chirp rate. The QCL is shown to have all essential qualities of a robust seed source for a high-repetition nanosecond-pulsed CO(2) laser required by EUV LPP sources. PMID:23164906

  7. The use of laser diodes for control of uranium vaporization rates

    SciTech Connect

    Hagans, K.; Galkowski, J.

    1993-09-01

    Within the Atomic Vapor Laser Isotope Separation (AVLIS) program we have successfully used the laser absorption spectroscopy technique (LAS) to diagnose process physics performance and control vaporization rate. In the LAS technique, a narrow line-width laser is tuned to an absorption line of the species to be measured. The laser light that is propagated through the sample is and, from this data, the density of the species can be calculated. These laser systems have exclusively consisted of expensive, cumbersome, and difficult to maintain argon-ion-pumped ring dye lasers. While the wavelength flexibility of dye lasers is very useful in a laboratory environment, these laser systems are not well suited for the industrial process control system under development for an AVLIS plant. Diode-lasers offer lower system costs, reduced man power requirements, reduced space requirements, higher system availability, and improved operator safety. We report the. successful deployment and test of a prototype laser diode based uranium vapor rate control system. Diode-laser generated LAS data was used to control the uranium vaporization rate in a hands-off mode for greater than 50 hours. With one minor adjustment the system successfully controlled the vaporization rate for greater than 147 hours. We report excellent agreement with ring dye laser diagnostics and uranium weigh-back measurements.

  8. On mechanism of explosive boiling in nanosecond regime

    NASA Astrophysics Data System (ADS)

    Çelen, Serap

    2016-06-01

    Today laser-based machining is used to manufacture vital parts for biomedical, aviation and aerospace industries. The aim of the paper is to report theoretical, numerical and experimental investigations of explosive boiling under nanosecond pulsed ytterbium fiber laser irradiation. Experiments were performed in an effective peak power density range between 1397 and 1450 MW/cm2 on pure titanium specimens. The threshold laser fluence for phase explosion, the pressure and temperature at the target surface and the velocity of the expulsed material were reported. A narrow transition zone was realized between the normal vaporization and phase explosion fields. The proof of heterogeneous boiling was given with detailed micrographs. A novel thermal model was proposed for laser-induced splashing at high fluences. Packaging factor and scattering arc radius terms were proposed to state the level of the melt ejection process. Results of the present investigation explain the explosive boiling during high-power laser interaction with metal.

  9. High-repetition-rate high-power variable-bandwidth dye laser

    SciTech Connect

    Lavi, S.; Amit, M.; Bialolanker, G.; Miron, E.; Levin, L.A.

    1985-07-01

    An efficient high-repetition-rate dye laser is described which has a bandwidth that can be tailored to match typical atomic inhomogeneous linewidths. The dye laser is pumped by a 4-kHz 2--6 mJ/pulse copper vapor laser. The total efficiency of the dye laser (oscillator and amplifier) is 45% for rhodamine 6G and 30% for rhodamine B.

  10. Cavity-Dumped Communication Laser Design

    NASA Technical Reports Server (NTRS)

    Roberts, W. T.

    2003-01-01

    Cavity-dumped lasers have significant advantages over more conventional Q-switched lasers for high-rate operation with pulse position modulation communications, including the ability to emit laser pulses at 1- to 10-megahertz rates, with pulse widths of 0.5 to 5 nanoseconds. A major advantage of cavity dumping is the potential to vary the cavity output percentage from pulse to pulse, maintaining the remainder of the energy in reserve for the next pulse. This article presents the results of a simplified cavity-dumped laser model, establishing the requirements for cavity efficiency and projecting the ultimate laser efficiency attainable in normal operation. In addition, a method of reducing or eliminating laser dead time is suggested that could significantly enhance communication capacity. The design of a laboratory demonstration laser is presented with estimates of required cavity efficiency and demonstration potential.

  11. A compact nanosecond pulse modulator

    NASA Astrophysics Data System (ADS)

    Sha, Jizhang; Xue, Jianchao; Qiang, Bohan

    Two circuits of nanosecond pulse modulator which generate two different width rectangular pulses respectively are described. The basic configuration of the modulator is the Marx circuit, in which avalanche transistors are used as switching devices. In order to obtain the rectangular pulses a pulse-forming network (PFN) is introduced and fitted into the Marx. A multi-parallel arrangement of the Marx is used to satisfy the broad pulse requirement. Experiments have shown that the two different width rectangular pulses which have 130 V amplitudes and 30 and 200 ns widths respectively can be obtained at a 50 ohms load. The two pulses have steep front edges (3.6 ns and 10 ns respectively) and flat tops with less than + or - 5 percent ripples. Therefore, the modulator can meet the requirements of the nanosecond pulse radar.

  12. Non-contact Laser-based Human Respiration Rate Measurement

    NASA Astrophysics Data System (ADS)

    Scalise, L.; Marchionni, P.; Ercoli, I.

    2011-08-01

    At present the majority of the instrumentation, used in clinical environments, to measure human respiration rate are based on invasive and contact devices. The gold standard instrument is considered the spirometer which is largely used; it needs a direct contact and requires a collaboration by the patient. Laser Doppler Vibrometer (LDVi) is an optical, non-contact measurement system for the assessment of a surface velocity and displacement. LDVi has already been used for the measurement of the cardiac activity and for the measurement of the chest-wall displacements. The aims of this work are to select the best measurement point on the thoracic surface for LDVi monitoring of the respiration rate (RR) and to compare measured data with the RR valued provided by the spirometer. The measurement system is composed by a LDV system and a data acquisition board installed on a PC. Tests were made on 10 different point of the thorax for each patient. Patients population was composed by 33 subjects (17 male and 16 female). The optimal measurement point was chosen considering the maximum peak-to-peak value of the displacement measured by LDV. Before extracting RR we have used a special wavelet decomposition for better selection of the expiration peaks. A standard spirometer was used for the validation of the data. From tests it results that the optimal measurement point, namely is located on the inferior part of the thoracic region (left, front side). From our tests we have obtained a close correlation between the RR values measured by the spirometer and those measured by the proposed method: a difference of 14±211 ms on the RR value is reported for the entire population of 33 subjects. Our method allows a no-contact measurement of lungs activity (respiration period), reducing the electric and biological risks. Moreover it allows to measure in critical environment like in RMN or in burned skin where is difficult or impossible to apply electrodes.

  13. Nanosecond electric pulses trigger actin responses in plant cells

    SciTech Connect

    Berghoefer, Thomas; Eing, Christian; Flickinger, Bianca; Hohenberger, Petra; Wegner, Lars H.; Frey, Wolfgang; Nick, Peter

    2009-09-25

    We have analyzed the cellular effects of nanosecond pulsed electrical fields on plant cells using fluorescently tagged marker lines in the tobacco cell line BY-2 and confocal laser scanning microscopy. We observe a disintegration of the cytoskeleton in the cell cortex, followed by contraction of actin filaments towards the nucleus, and disintegration of the nuclear envelope. These responses are accompanied by irreversible permeabilization of the plasma membrane manifest as uptake of Trypan Blue. By pretreatment with the actin-stabilizing drug phalloidin, the detachment of transvacuolar actin from the cell periphery can be suppressed, and this treatment can also suppress the irreversible perforation of the plasma membrane. We discuss these findings in terms of a model, where nanosecond pulsed electric fields trigger actin responses that are key events in the plant-specific form of programmed cell death.

  14. Comment on "Nanosecond laser textured superhydrophobic metallic surfaces and their chemical sensing applications" by Duong V. Ta, Andrew Dunn, Thomas J. Wasley, Robert W. Kay, Jonathan Stringer, Patrick J. Smith, Colm Connaughton, Jonathan D. Shephard (Appl. Surf. Sci. 357 (2015) 248-254)

    NASA Astrophysics Data System (ADS)

    Boinovich, L. B.; Emelyanenko, A. M.; Emelyanenko, K. A.; Domantovsky, A. G.; Shiryaev, A. A.

    2016-08-01

    Nowadays the problem of design of durable ecologically friendly superhydrophobic surfaces is of great importance for science and technology. A recent paper in Applied Surface Science reports the method of fabricating the superhydrophobic metallic surfaces by infrared nanosecond laser surface texturing without using hydrophobic agents. Since this method of surface texturing can be considered as one of the most suitable for various industrial applications, the nature of superhydrophobic state of surfaces produced by laser texturing in the abovementioned paper deserves to be analyzed in detail. Authors of the commented paper attributed the change in wettability to the partial deoxidation of CuO into Cu2O on the surface during storage in atmosphere. However, such interpretation of the results contradicts to the basic notions in the theory of wetting and to more accurate and detailed data. In our Comment we discuss these contradictions point by point.

  15. Method for generating high-energy and high repetition rate laser pulses from CW amplifiers

    DOEpatents

    Zhang, Shukui

    2013-06-18

    A method for obtaining high-energy, high repetition rate laser pulses simultaneously using continuous wave (CW) amplifiers is described. The method provides for generating micro-joule level energy in pico-second laser pulses at Mega-hertz repetition rates.

  16. Nanosecond pulse pumped, narrow linewidth all-fiber Raman amplifier with stimulated Brillouin scattering suppression

    NASA Astrophysics Data System (ADS)

    Su, Rongtao; Zhou, Pu; Wang, Xiaolin; Lü, Haibin; Xu, Xiaojun

    2014-01-01

    We report on a narrow linewidth nanosecond all-fiber Raman amplifier core pumped by a pulsed laser at approximately 1030 nm. The Raman amplifier was based on a standard single-mode fiber with a length of ∼1 km, and stimulated Brillouin scattering (SBS) was suppressed by employing pulses with a short pulse width. 1083 nm pulses with an average power of 32.6 mW, a repetition rate of 2 MHz, and pulse widths of ∼7.2 ns were achieved. A maximum slope efficiency of 46.1% and a gain of 31 dB were obtained. The output Raman power can be scaled further by using fiber with shorter lengths and pump pulses with a higher power.

  17. Micro-ablation with high power pulsed copper vapor lasers.

    PubMed

    Knowles, M

    2000-07-17

    Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser.

  18. Multi-gigahertz repetition rate passively modelocked fiber lasers using carbon nanotubes.

    PubMed

    Martinez, Amos; Yamashita, Shinji

    2011-03-28

    There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Pérot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1 ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08 nm by launching the laser operating at 9.63 GHz into 30 m of a highly nonlinear dispersion shifted fiber.

  19. Modeling and optimization of single-pass laser amplifiers for high-repetition-rate laser pulses

    SciTech Connect

    Ozawa, Akira; Udem, Thomas; Zeitner, Uwe D.; Haensch, Theodor W.; Hommelhoff, Peter

    2010-09-15

    We propose a model for a continuously pumped single-pass amplifier for continuous and pulsed laser beams. The model takes into account Gaussian shape and focusing geometry of pump and seed beam. As the full-wave simulation is complex we have developed a largely simplified numerical method that can be applied to rotationally symmetric geometries. With the tapered-shell model we treat (focused) propagation and amplification of an initially Gaussian beam in a gain crystal. The implementation can be done with a few lines of code that are given in this paper. With this code, a numerical parameter optimization is straightforward and example results are shown. We compare the results of our simple model with those of a full-wave simulation and show that they agree well. A comparison of model and experimental data also shows good agreement. We investigate in detail different regimes of amplification, namely the unsaturated, the fully saturated, and the intermediate regime. Because the amplification process is affected by spatially varying saturation and exhibits a nonlinear response against pump and seed power, no analytical expression for the expected output is available. For modeling of the amplification we employ a four-level system and show that if the fluorescence lifetime of the gain medium is larger than the inverse repetition rate of the seed beam, continuous-wave amplification can be employed to describe the amplification process of ultrashort pulse trains. We limit ourselves to this regime, which implies that if titanium:sapphire is chosen as gain medium the laser repetition rate has to be larger than a few megahertz. We show detailed simulation results for titanium:sapphire for a large parameter set.

  20. Technological study on reducing blast-hole rate during laser cutting oil pipe

    NASA Astrophysics Data System (ADS)

    Deng, Qiansong; Yang, Weihong; Tang, Xiahui; Peng, Hao; Qin, Yingxiong

    2012-03-01

    In this paper, a laser cutting technology for the oil pipes with the thickness of 10mm, the diameter of 142mm and the material of N80 has been developed, in order to reduce the high hole-blast rate in processing. Experiments are taken on the Rofin DC025 slab CO2 laser cutting system and a set of flexible fixtures. The reasons of forming blast-hole have been analyzed, and the influences of technique parameters on blast-hole rate have been studied, such as laser power, pulse frequency, laser delay, focus position and oxygen pressure. The results show that the blast-hole rate can be controlled lower than 5% at the conditions of laser power 1500W, laser delay 5s, pulse frequency 180Hz, the oxygen pressure 0.6 kg/cm2, focus length 190mm, nozzle diameter 1.5mm.

  1. Technological study on reducing blast-hole rate during laser cutting oil pipe

    NASA Astrophysics Data System (ADS)

    Deng, Qiansong; Yang, Weihong; Tang, Xiahui; Peng, Hao; Qin, Yingxiong

    2011-11-01

    In this paper, a laser cutting technology for the oil pipes with the thickness of 10mm, the diameter of 142mm and the material of N80 has been developed, in order to reduce the high hole-blast rate in processing. Experiments are taken on the Rofin DC025 slab CO2 laser cutting system and a set of flexible fixtures. The reasons of forming blast-hole have been analyzed, and the influences of technique parameters on blast-hole rate have been studied, such as laser power, pulse frequency, laser delay, focus position and oxygen pressure. The results show that the blast-hole rate can be controlled lower than 5% at the conditions of laser power 1500W, laser delay 5s, pulse frequency 180Hz, the oxygen pressure 0.6 kg/cm2, focus length 190mm, nozzle diameter 1.5mm.

  2. Burst-mode-operated, sub-nanosecond fiber MOPA system incorporating direct seed-packet shaping.

    PubMed

    Chen, Tao; Liu, Hao; Kong, Wei; Shu, Rong

    2016-09-01

    We report a novel burst-mode-operated sub-nanosecond fiber Master Oscillator, Power Amplifier (MOPA) system incorporating direct seed-packet shaping without external modulators. A fast digital-to-analog converter with 1 Gsps sampling rate and 16 bit resolution was developed to control the pulse amplitudes and sequences of a distributed feedback semiconductor seed laser to realize packet-shaped burst mode operation. Optical pulses with durations as short as 700 ps and peak power as high as 1 W can be generated from the seed by applying proper reverse voltages after positive electrical pulses to the laser driver to cancel the residual charges at its gate electrode. The average power of the laser can be amplified to nearly 40 W with FWHM spectral linewidth of ~0.12 nm after three stages of polarization maintaining fiber amplifiers. Different packet shapes including ramp-off, Gaussian, square and double rectangle can be produced from the fiber MOPA by finely pre-shaping the seed pulse bursts. It is believed that such a laser has provided a cost-effective solution to the generation of pulse bursts with arbitrary packet shapes for different practical applications including material micromachining and nonlinear frequency conversion. PMID:27607699

  3. Optimized LWIR enhancement of nanosecond and femtosecond LIBS uranium emission

    NASA Astrophysics Data System (ADS)

    Akpovo, Codjo A.; Ford, Alan; Johnson, Lewis

    2016-05-01

    A carbon dioxide (CO2) transverse electrical breakdown in atmosphere (TEA), pulsed laser was used to enhance the laser-induced breakdown spectroscopy (LIBS) spectral signatures of uranium under nanosecond (ns) and femtosecond (fs) ablation. The peak areas of both ionic and neutral species increased by one order of magnitude for ns-ablation and two orders of magnitude for fs-ablation over LIBS when the CO2 TEA laser was used with samples of dried solutions of uranyl nitrate hexahydrate (UO2(NO3)2·6H2O) on silicon wafers. Electron temperature and density measurements show that the spectral emission improvement from using the TEA laser comes from plasma reheating.

  4. The effects of laser repetition rate on femtosecond laser ablation of dry bone: a thermal and LIBS study.

    PubMed

    Gill, Ruby K; Smith, Zachary J; Lee, Changwon; Wachsmann-Hogiu, Sebastian

    2016-01-01

    The aim of this study is to understand the effect of varying laser repetition rate on thermal energy accumulation and dissipation as well as femtosecond Laser Induced Breakdown Spectroscopy (fsLIBS) signals, which may help create the framework for clinical translation of femtosecond lasers for surgical procedures. We study the effect of repetition rates on ablation widths, sample temperature, and LIBS signal of bone. SEM images were acquired to quantify the morphology of the ablated volume and fsLIBS was performed to characterize changes in signal intensity and background. We also report for the first time experimentally measured temperature distributions of bone irradiated with femtosecond lasers at repetition rates below and above carbonization conditions. While high repetition rates would allow for faster cutting, heat accumulation exceeds heat dissipation and results in carbonization of the sample. At repetition rates where carbonization occurs, the sample temperature increases to a level that is well above the threshold for irreversible cellular damage. These results highlight the importance of the need for careful selection of the repetition rate for a femtosecond laser surgery procedure to minimize the extent of thermal damage to surrounding tissues and prevent misclassification of tissue by fsLIBS analysis.

  5. Thermal oxidation rates of Al(x)Ga(1-x)As in H(2)O vapor and oxide-defined vertical cavity surface emitting laser characteristics

    NASA Astrophysics Data System (ADS)

    Ochiai, Mari

    The incorporation of oxides into semiconductor structures formed by the thermal oxidation of Alsb{x}Gasb{1-x}As in water vapor has resulted in a marked improvement in device performance. Vertical cavity surface emitting lasers (VCSEL's), in particular, have benefited from this technology, demonstrating record operating characteristics. This study focuses on the following areas with respect to oxide defined VCSEL's: the establishment of rate laws for the lateral oxidation of AlAs, the fabrication of VCSEL's, and the characterization of VCSEL's designed for high speed operation. An oxidation rate study was conducted on structures with AlAs oxidation layers. At low temperatures and short oxidation times, oxidation was found to be reaction rate limited. Conversely, diffusion across the oxide was determined to be the rate limiting mechanism at high temperature or long oxidation times. The observed rates can be modeled by rate equations by which the two component mechanisms can be separated. An activation energy of 1.6 eV and 0.8 eV was determined for the reaction and diffusion limited mechanism, respectively. A reduction in oxidation rates was observed with decreasing oxidation layer thickness and increasing doping concentration. The thickness dependence can be incorporated into the rate equations by assuming an oxidation reaction rate which is inhibited by the presence of strain in thin layers. The reaction rate can be characterized by a threshold thickness for which a value of 20 nm was determined for Alsb{x}Gasb{1-x}As. Oxide defined GaAs VCSEL's varying in size and oxidation layer composition were fabricated. Threshold currents of 450 muA and external differential quantum efficiencies of 0.5 were obtained. Finally, the large signal modulation characteristics of oxide defined VCSEL's were investigated. A threshold carrier lifetime of 1.6 nanoseconds VCSEL's was determined from laser turn-on delay measurements. The laser turn-on delay was also measured under various

  6. Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

    2009-01-01

    Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

  7. Continuous high-repetition-rate operation of collisional soft-x-ray lasers with solid targets.

    PubMed

    Weith, A; Larotonda, M A; Wang, Y; Luther, B M; Alessi, D; Marconi, M C; Rocca, J J; Dunn, J

    2006-07-01

    We have generated a laser average output power of 2 microW at a wavelength of 13.9 nm by operating a tabletop laser-pumped Ni-like Ag laser at a 5 Hz repetition rate, using a solid helicoidal target that is continuously rotated and advanced to renew the target surface between shots. More than 2 x 10(4) soft-x-ray laser shots were obtained by using a single target. Similar results were obtained at 13.2 nm in Ni-like Cd with a Cd-coated target. This scheme will allow uninterrupted operation of laser-pumped tabletop collisional soft-x-ray lasers at a repetition rate of 10 Hz for a period of hours, enabling the generation of continuous high average soft-x-ray powers for applications. PMID:16770410

  8. CFD Laser-Ignition Predictions and Rate Kinectics Models

    NASA Astrophysics Data System (ADS)

    Beatty, C.; Qin, W.; Chen, Y.-L.; Lewis, J. W. L.

    2000-11-01

    Laser ignition of gas mixtures is a complex phenomenon that includes both plasma and combustion processes. The complexity of the non-equilibrium chemical reactions necessarily restricts the number of reactions, and the selection of the most important of the many reactions is usually challenging. We have studied NH3/O2 laser ignition for several years to elucidate the most important features of this comparatively simple chemical kinetics system. This work will compare various kinetics models for the NH3/O2 ignition and their effects on the CFD* calculated results. Both atmospheric and sub-atmospheric pressures will be discussed. * CFD-ACE, CFD Research Corporation, Huntsville, AL

  9. Theory of absorption rate of carriers in fused silica under intense laser irradiation

    SciTech Connect

    Deng, Hongxiang; Xiang, Xia; Zheng, WG; Yuan, XD; Wu, SY; Jiang, XD; Gao, Fei; Zu, Xiaotao T.; Sun, Kai

    2010-11-15

    A quantum non-perturbation theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the Non-perturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on TW / cm2 intensity laser.

  10. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

    NASA Astrophysics Data System (ADS)

    Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

    1991-11-01

    An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

  11. Noise-like pulses generated at high harmonics in a partially-mode-locked km-long Raman fiber laser

    NASA Astrophysics Data System (ADS)

    Boucon, A.; Barviau, B.; Fatome, J.; Finot, C.; Sylvestre, T.; Lee, M. W.; Grelu, P.; Millot, G.

    2012-02-01

    We present a 5-km-long Raman fiber laser that delivers pulses at high harmonics of the fundamental cavity repetition rate, up to 1 GHz. The observed nanosecond pulses that propagate in an anomalous dispersion regime possess a complex noise-like structure with a coherence time of around 1 picosecond.

  12. Targeted tissue ablation with nanosecond pulses.

    PubMed

    Long, Gary; Shires, Peter K; Plescia, David; Beebe, Stephen J; Kolb, Juergen F; Schoenbach, Karl H

    2011-08-01

    In-vivo porcine studies on the effect of nanosecond high voltage pulses on liver tissue have shown that cell death can be induced in well-defined tissue volumes without damaging collagen-predominant structures. Comparison of the experimental results with the results of a three-dimensional finite element model allowed us to determine the threshold electric field for cell death. For 30, 100 nanosecond long pulses this was found to be in the range from 12 to 15 kV/cm. Modelling of the temperature distribution in the tissue using Pennes' bioheat equation showed that the lethal effect of nanosecond pulses on cells is non-thermal. Muscle contractions, generally caused by high voltage pulses, were significantly reduced for the 100 nanosecond pulses compared to microsecond long pulses. The results of these studies indicate that high voltage nanosecond pulses reliably kill normal liver cells in vivo and therefore may be useful for liver tumor treatments.

  13. Multi-gigahertz repetition rate ultrafast waveguide lasers mode-locked with graphene saturable absorbers

    NASA Astrophysics Data System (ADS)

    Obraztsov, P. A.; Okhrimchuk, A. G.; Rybin, M. G.; Obraztsova, E. D.; Garnov, S. V.

    2016-08-01

    We report the development of an approach to build compact waveguide lasers that operate in the stable fundamental mode-locking regime with multigigahertz repetition rates. The approach is based on the use of depressed cladding multi- or single-mode waveguides fabricated directly in the active laser crystal using the femtosecond laser inscription method and a graphene saturable absorber. Using this approach we achieve the stable self-starting mode-locking operation of a diode-pumped waveguide Nd:YAG laser that delivers picosecond pulses at a repetition rate of up to 11.5 GHz with an average power of 12 mW at a central wavelength of 1064 nm. The saturable absorbers are formed through the chemical vapor deposition of single-layer graphene on the output coupler mirror or directly on the end facet of the laser crystal. The stable self-starting mode-locking operation is achieved by controlling the group delay dispersion in the laser cavity with an intracavity interferometer. The method developed for the creation of compact ultrashort pulse laser generators with gigahertz repetition rates can be extended further and applied for the development of compact high-repetition rate lasers that operate at a wide range of IR wavelengths.

  14. Evaluation of a laser scanning sensor for variable-rate tree sprayer development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate canopy measurement capabilities are prerequisites to automate variable-rate sprayers. A 270° radial range laser scanning sensor was tested for its scanning accuracy to detect tree canopy profiles. Signals from the laser sensor and a ground speed sensor were processed with an embedded comput...

  15. Effects of low-intensity laser therapy over mini-implants success rate in pigs.

    PubMed

    Garcez, Aguinaldo S; Suzuki, Selly Sayuri; Martinez, Elisabeth Ferreira; Iemini, Mylene Garcez; Suzuki, Hideo

    2015-02-01

    The success rate of miniscrews when used as temporary orthodontic anchorage is relatively high, but some factors could affect its clinical success such as inflammation around the miniscrew. Low-intensity laser therapy has been widely used for biostimulation of tissue and wound healing specially for its anti-inflammatory effects. The purpose of this study was to evaluate the effect of low-intensity laser therapy over the miniscrew success rate. Five Landrace's pigs received 50 miniscrews on the buccal side of the mandible and on the palate of the maxilla. All the miniscrews were immediately loaded with 250 gf. The laser group were irradiated with a 780-nm diode laser with 70 mWs for 1 min (dose = 34 J/cm(2)); the contralateral side was used as the control group. The miniscrews were photographed and analyzed clinically every week to determine their stability and presence of local inflammation. After 3 weeks, histological analysis and fluorescent microscopy were performed to compare the laser and the control side. Clinical results showed a success rate of 60% for the control group and 80% for the laser-treated group. The histological analysis and fluorescent microscopy demonstrated that the laser group had less inflammatory cells than the control group and the bone neoformation around the miniscrew was more intense. Low-intensity laser therapy increased the success rate of orthodontic miniscrews, probably due to anti-inflammatory effect and bone stimulation. PMID:23929562

  16. Nanosecond Responses of Proteins to Ultra-High Temperature Pulses

    PubMed Central

    Steel, Bradley C.; McKenzie, David R.; Bilek, Marcela M. M.; Nosworthy, Neil J.; dos Remedios, Cristobal G.

    2006-01-01

    Observations of fast unfolding events in proteins are typically restricted to <100°C. We use a novel apparatus to heat and cool enzymes within tens of nanoseconds to temperatures well in excess of the boiling point. The nanosecond temperature spikes are too fast to allow water to boil but can affect protein function. Spikes of 174°C for catalase and ∼290°C for horseradish peroxidase are required to produce irreversible loss of enzyme activity. Similar temperature spikes have no effect when restricted to 100°C or below. These results indicate that the “speed limit” for the thermal unfolding of large proteins is shorter than 10−8 s. The unfolding rate at high temperature is consistent with extrapolation of low temperature rates over 12 orders of magnitude using the Arrhenius relation. PMID:16844754

  17. Tunable 975 nm nanosecond diode-laser-based master-oscillator power-amplifier system with 16.3 W peak power and narrow spectral linewidth below 10 pm.

    PubMed

    Vu, Thi Nghiem; Klehr, Andreas; Sumpf, Bernd; Wenzel, Hans; Erbert, Götz; Tränkle, Günther

    2014-09-01

    A spectrally tunable, narrow linewidth master oscillator power amplifier system emitting ns pulses with high peak power is presented. The master oscillator is a distributed feedback ridge waveguide (DFB-RW) laser, which is operated in continuous wave (CW) mode and emits at about 975 nm with a spectral line width below 10 pm. The oscillator can be tuned over a range of 0.9 nm by varying the injection current. The tapered amplifier (TA) consists of an RW section and a flared gain-guided section. The RW section of the amplifier acts as an optical gate and converts the CW input beam emitted by the DFB-RW laser into a train of short optical pulses, which are subsequently amplified by the tapered section. The width of the pulses is 8 ns at a repetition rate of 25 kHz. The peak power is 16.3 W. The TA preserves the spectral properties of the emission of the DBR-RW laser. The amplified spontaneous emission is suppressed by about 40 dB. PMID:25166093

  18. Four-wave mixing in nanosecond pulsed fiber amplifiers.

    PubMed

    Fève, Jean-Philippe; Schrader, Paul E; Farrow, Roger L; Kliner, Dahv A V

    2007-04-16

    We present an experimental and theoretical analysis of four-wave mixing in nanosecond pulsed amplifiers based on double-clad ytterbium-doped fibers. This process leads to saturation of the amplified pulse energy at 1064 nm and to distortion of the spectral and temporal profiles. These behaviours are well described by a simple model considering both Raman and four-wave-mixing contributions. The role of seed laser polarization in birefringent fibers is also presented. These results point out the critical parameters and possible tradeoffs for optimization. PMID:19532710

  19. Nanosecond-resolved temperature measurements using magnetic nanoparticles.

    PubMed

    Xu, Wenbiao; Liu, Wenzhong; Zhang, Pu

    2016-05-01

    Instantaneous and noninvasive temperature measurements are important when laser thermotherapy or welding is performed. A noninvasive nanosecond-resolved magnetic nanoparticle (MNP) temperature measurement system is described in which a transient change in temperature causes an instantaneous change in the magnetic susceptibilities of the MNPs. These transient changes in the magnetic susceptibilities are rapidly recorded using a wideband magnetic measurement system with an upper frequency limit of 0.5 GHz. The Langevin function (the thermodynamic model characterizing the MNP magnetization process) is used to obtain the temperature information. Experiments showed that the MNP DC magnetization temperature-measurement system can detect a 14.4 ns laser pulse at least. This method of measuring temperature is likely to be useful for acquiring the internal temperatures of materials irradiated with lasers, as well as in other areas of research. PMID:27250457

  20. Excimer laser ablation of aluminum: influence of spot size on ablation rate

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2016-11-01

    The dependence of ablation rate of an Al alloy on laser beam spot size (10–150 µm) was investigated using an ArF excimer laser operating at a wavelength of 193 nm and pulse width less than 4 ns. Ablation was conducted in air at a fluence of 11 J cm‑2 and at a repetition rate of 20 Hz. Surface morphology and depth of craters produced by a variable number of laser pulses were characterized using optical and scanning electron microscopy. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used as an additional diagnostic technique to estimate the amount of material ablated from craters produced by a laser beam of different diameters. Laser beam spot size and number of laser pulses applied to the same spot were found to influence crater morphology, ablation rate, shape and amount of particles deposited at or around the crater rim. Ablation rate was found to be less dependent on spot size for craters greater than 85 µm. A four-fold increase in ablation rate was observed with decreasing crater size from 150 µm to 10 µm.

  1. A fast CMOS array imager for nanosecond light pulse detection in accumulation mode

    NASA Astrophysics Data System (ADS)

    Zint, Chantal-V.; Uhring, Wilfried; Casadei, Bruno; Le Normand, Jean-P.; Morel, Frederic; Hu, Yann

    2004-09-01

    We designed a camera based on a fast CMOS APS imager for high speed optical detection which produces images simi-larly as a streak camera. This imager produces the intensity information I as function of one spatial dimension and time (I=f(x,t)) from one frame with two spatial dimensions. The time sweeping is obtained by delaying successively the integration phase for each pixel of the same row. For the first FAMOSI (Fast MOs Imager) prototype the start of in-tegration is given by the camera itself. This signal is injected to a laser trigger. This laser emits a 10 nanoseconds light pulse onto the sensor. The temporal evolution of the light pulse is then resolved by the camera with a resolution of 800 ps. In single shot, the maximum dynamic of the camera is estimated to 64 dB and is limited by the readout noise. We decide to work in accumulation mode in order to increase the signal to noise ratio of the camera. But the high laser trigger (about 20 ns rms) does not allow accumulation of several optical events without a large spreading. The camera has been modified in order to be triggered by an external signal delivered by a trigger unit. In this new configuration the laser emit pulses at a repetition rate of 50 Hz. A photodiode detect a part of the laser pulse and generate the trigger signal for FAMOSI. The laser pulse is delayed with an optical fibre before being directed to the camera. The trigger jitter obtained is then less than 100 ps and allows accumulation without significant loss of the temporal resolution. With accumulation the readout noise is attenuated by a √N factor. Then with N = 1000 accumulations, the dynamics approach 93 dB. This allows the camera to work similarly as a synchroscan streak camera and then to observe weak signal.

  2. Fast Laser Excitation and Ultrahigh Strain-Rate Deformation

    SciTech Connect

    Robert Averback

    2007-06-03

    Phase evolution induced by single or repeated excitation with energetic femtosecond laser pulses is examined. Of primary interest is the solidification behavior of pure metals at deep undercoolings and self-organization in simple eutectic alloys. Time resolved measurements using third harmonic generation (THG) of light and ultrafast electron diffraction (UED) are employed to elucidate several issues related to fast laser excitation, including heat transport by ballistic and diffusional electrons through multilayer films, the dependence of crystallization velocities on materials properties, mechanisms controlling the transport of heat away from the crystal-liquid interface, and the possibility for quenching pure metals, such as Cu, Ni, and Fe, into the amorphous state. Special samples designed to maximize the quenching speed are developed. The properties of such pure metallic glasses, such as glass and crystallization temperatures, will be measured, if such samples are successfully produced. The measurements are complemented by molecular dynamics computer simulations of the solidification process. The second interest of this research is mesoscopic, self-organization of materials under repeated laser melting, with diffusional relaxation between pulses. We select binary alloys that are immiscible in the solid state but miscible in the liquid state, such as Ag-Cu. Femtosecond laser irradiation is employed to induce melting and to vary the melting time over a wide range, from a few ps to hundreds of ps. This enables us to perform critical experimental tests of key theoretical predictions self-organization in alloys under external forcing, in particular the existence of a threshold value of the forced mixing length for patterning to take place.

  3. Investigation of defect rate of lap laser welding of stainless steel railway vehicles car body

    NASA Astrophysics Data System (ADS)

    Wang, Hongxiao

    2015-02-01

    In order to resolve the disadvantages such as poor appearance quality, poor tightness, low efficiency of resistance spot welding of stainless steel rail vehicles, partial penetration lap laser welding process was investigated widely. But due to the limitation of processing technology, there will be local incomplete fusion in the lap laser welding seam. Defect rate is the ratio of the local incomplete fusion length to the weld seam length. The tensile shear strength under different defect rate and its effect on the car body static strength are not clear. It is necessary to find the biggest defect rate by numerical analysis of effects of different defect rates on the laser welding stainless steel rail vehicle body structure strength ,and tests of laser welding shear tensile strength.

  4. Nitric Oxide Studies in Low Temperature Plasmas Generated with a Nanosecond Pulse Sphere Gap Electrical Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David Dean

    This dissertation presents studies of NO kinetics in a plasma afterglow using various nanosecond pulse discharges across a sphere gap. The discharge platform is developed to produce a diffuse plasma volume large enough to allow for laser diagnostics in a plasma that is rich in vibrationally-excited molecules. This plasma is characterized by current and voltage traces as well as ICCD and NO PLIF images that are used to monitor the plasma dimensions and uniformity. Temperature and vibrational loading measurements are performed via coherent anti-Stokes Raman spectroscopy (CARS). Absolute NO concentrations are obtained by laser-induce fluorescence (LIF) measurements, and N and O densities are found using two photon absorption laser-induced fluorescence (TALIF). For all dry air conditions studied, the NO behavior is characterized by a rapid rate of formation consistent with an enhanced Zeldovich process involving electronically-excited nitrogen species that are generated within the plasma. After several microseconds, the NO evolution is entirely controlled by the reverse Zeldovich process. These results show that under the chosen range of conditions and even in extreme instances of vibrational loading, there is no formation channel beyond ~2 musec. Both the NO formation and consumption mechanisms are strongly affected by the addition of fuel species, producing much greater NO concentrations in the afterglow.

  5. High-power high-repetition-rate copper-vapor-pumped dye laser

    SciTech Connect

    Singh, S.; Dasgupta, K.; Kumar, S.; Manohar, K.G.; Nair, L.G.; Chatterjee, U.K. . Laser and Plasma Technology Div.)

    1994-06-01

    The design and development of an efficient high average power dye laser oscillator-amplifier system developed at the Laser and Plasma Technology Division, Bhabha Atomic Research Centre, is reported. The dye laser is pumped by a 6.5-kHz repetition rate copper vapor laser. The signal beam to the dye amplifier is obtained from an efficient narrow-band grazing incidence grating (GIG) dye laser oscillator incorporating a multiple prism beam expander. Amplifier extraction efficiency up to 40% was obtained in a single amplifier stage, using rhodamine 6G (Rh6G) in ethanol. The authors have also demonstrated simultaneous amplification of two laser beams at different wavelengths in the same dye amplifier cell.

  6. High Repetition Rate Pulsed 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Uprendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta; Petzar, Paul J.; Trieu, Bo C.; Lee, Hyung

    2009-01-01

    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 at NASA Langley Research Center. Such a laser 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 approximately 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. The measured standard deviation of the laser frequency jitter is about 3 MHz.

  7. Measuring evaporation rates of laser-trapped droplets by use of fluorescent morphology-dependent resonances.

    PubMed

    Pastel, R; Struthers, A

    2001-05-20

    Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2-mum droplets of ethylene glycol. Droplets containing 3 x 10(-5) M Rhodamine-590 laser dye are optically trapped in a 20-mum hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser's intensity within the trap.

  8. High repetition rate sealed CO2 TEA lasers using heterogeneous catalysts

    NASA Technical Reports Server (NTRS)

    Price, H. T.; Shaw, S. R.

    1987-01-01

    The significant operational advantages offered by CO2 lasers, operating in the 10.6 micron region of the spectrum, over current solid state lasers, emitting in the near IR region, have prompted increased interest in the development of compact, reliable, rugged CO2 laser sources. Perhaps the most critical aspect associated with achieving a laser compatible with military use is the development of lasers which require no gas replenishment. Sealed, single shot, CO2 TEA lasers have been available for a number of years. Stark et al were first to demonstrate reliable sealed operation in single shot CO2 TEA lasers in 1975 using gas catalysis. GEC Avionics reported the compact, environmentally qualified, MKIII CO2 TEA laser with a pulse life of greater than 10 to the 6th power pulses in 1980. A sealed laser lifetime of greater than 10 to the 6th power pulses is acceptable for single shot cases, such as direct detection rangefinders for tank laser sights. However, in many other applications, such as tracking of fast moving targets, it is essential that a repetition rate of typically 30Hz to 100Hz is employed. In such cases, a pulse lifetime of 10 to the 6th power pulses is no longer sufficient and a minimum pulse lifetime 10 to the 7th power pulses is essential to ensure a useful service life. In 1983 Stark el al described a sealed, 100Hz CO2 TEA laser, with a life of greater than 2.6 x 10 to the 6th power, which employed heterogeneous catalysis. Following this pioneering work, GEC Avionics has been engaged in the development of sealed high repetition rate lasers with a pulse lifetime of 20 million pulses.

  9. Development of pulsed gas discharge lasers for shock hardening

    NASA Astrophysics Data System (ADS)

    Hintz, Gerd; Tkotz, R.; Keusch, C.; Negendanck, Matthias; Christiansen, Jens; Hoffmann, D. H. H.

    1996-08-01

    Shock hardening of metals (e.g. Ti, stainless steel) by pulsed lasers offers the possibility of large hardening depth (several millimeters) without serious damage to the surface of the workpiece. Previous investigations for shock hardening have mainly been performed with high power solid state lasers. The adaptation of commercial, high power gas discharge lasers to the shock hardening process could make this process relevant for industrial applications, as high repetition rates may be used. Two different laser systems have been investigated: a TEA carbon-dioxide laser and a XeCl laser. Both systems have pulse energies of some joule, a pulse length of several ten nanoseconds, and pulse repetition rates of up to 10 Hertz. The divergence of the beam was minimized to improve focusing properties. Systematic measurements of the laser induced pressure by means of piezo probes have been performed. An enhancement of the hardness of illuminated Ti(RT15) targets has been found and is reported.

  10. Localized pulsed nanosecond discharges in a counterflow nonpremixed flame environment

    NASA Astrophysics Data System (ADS)

    Guerra-Garcia, C.; Martinez-Sanchez, M.; Miles, R. B.; Starikovskiy, A.

    2015-10-01

    A flame is a very unusual environment for the development of a gas discharge, since it presents strong gradients in temperature, composition, and pre-ionization. In this paper we examine how such an environment impacts the development of the plasma when using repetitive pulsed nanosecond discharges, one of the main strategies used in the field of plasma assisted combustion. Experiments were performed in a counterflow nonpremixed burner with parallel electrodes at the nozzle exits and nanosecond-resolved photography of the plasma emission is presented. It was shown that the discharge development in stratified media may take place in the form of a dielectric barrier discharge with a localized energy deposition. In the experiments presented the discharge energy was coupled to the flame front because of the high rate of chemi-ionization and the gas density decrease in the flame.

  11. Diode-pumped passively Q-switched high-repetition-rate Yb microchip laser

    SciTech Connect

    Kisel', V E; Yasukevich, A S; Kondratyuk, N V; Kuleshov, N V

    2009-11-30

    The system of balance equations is modified for quasi-three-level passively Q-switched lasers with a slow saturable absorber. Optimal parameters of a Yb{sup 3+}:YAG microchip laser with a passive Cr{sup 4+}:YAG Q switch are calculated at a pulse repetition rate of {approx}100 kHz. The single-mode operation of the Yb:YAG-Cr:YAG laser with a pulse repetition rate above 100 kHz, the average output power 0.45 W and peak power 1.5 kW is experimentally demonstrated. In the multimode lasing regime, pulses with a peak power of 4.2 kW are obtained at an average output power of 0.8 W and a pulse repetition rate of 10 kHz. (lasers)

  12. Expectation to feel more pain disrupts the habituation of laser-pain rating and laser-evoked potential amplitudes.

    PubMed

    Pazzaglia, Costanza; Testani, Elisa; Giordano, Rocco; Padua, Luca; Valeriani, Massimiliano

    2016-10-01

    Increased pain perception due to the expectation to feel more pain is called nocebo effect. The present study aimed at investigating whether: (1) the mere expectation to feel more pain after the administration of an inert drug can affect the laser-pain rating and the laser-evoked potential (LEP) amplitude, and (2) the learning potentiates the nocebo effect. Eighteen healthy volunteers were told that an inert cream, applied on the right hand, would increase the laser pain and LEP amplitude to right hand stimulation. They were randomly assigned to either "verbal session" or "conditioning session". In the "verbal session", LEPs to both right and left hand stimulation were recorded at the same intensity before (baseline) and after cream application. In the "conditioning session", after an initial cream application the laser stimulus intensity was increased surreptitiously to make the subjects believe that the treatment really increased the pain sensation. Then, the cream was reapplied, and LEPs were recorded at the same stimulus intensity as at the baseline. It was found that the verbal suggestion to feel more pain disrupted the physiological habituation of the laser-pain rating and LEP amplitude to treated (right) hand stimulation. Unlike previously demonstrated for the placebo effect, the learning did not potentiate the nocebo effect. PMID:27461877

  13. Expectation to feel more pain disrupts the habituation of laser-pain rating and laser-evoked potential amplitudes.

    PubMed

    Pazzaglia, Costanza; Testani, Elisa; Giordano, Rocco; Padua, Luca; Valeriani, Massimiliano

    2016-10-01

    Increased pain perception due to the expectation to feel more pain is called nocebo effect. The present study aimed at investigating whether: (1) the mere expectation to feel more pain after the administration of an inert drug can affect the laser-pain rating and the laser-evoked potential (LEP) amplitude, and (2) the learning potentiates the nocebo effect. Eighteen healthy volunteers were told that an inert cream, applied on the right hand, would increase the laser pain and LEP amplitude to right hand stimulation. They were randomly assigned to either "verbal session" or "conditioning session". In the "verbal session", LEPs to both right and left hand stimulation were recorded at the same intensity before (baseline) and after cream application. In the "conditioning session", after an initial cream application the laser stimulus intensity was increased surreptitiously to make the subjects believe that the treatment really increased the pain sensation. Then, the cream was reapplied, and LEPs were recorded at the same stimulus intensity as at the baseline. It was found that the verbal suggestion to feel more pain disrupted the physiological habituation of the laser-pain rating and LEP amplitude to treated (right) hand stimulation. Unlike previously demonstrated for the placebo effect, the learning did not potentiate the nocebo effect.

  14. The HCP To BCC Phase Transformation in Ti Characterized by Nanosecond Electron Microscopy

    SciTech Connect

    Campbell, G; LaGrange, T; King, W; Colvin, J; Ziegler, A; Browning, N; Kleinschmidt, H; Bostanjoglo, O

    2005-06-21

    The general class of martensitic phase transformations occurs by a rapid lattice-distortive mechanism, where kinetics and morphology of the transformation are dominated by the strain energy. Since transformation is diffusionless, phase fronts propagate through a crystal with great speed that can approach the speed of sound. We have observed a particular example of this class of phase transformation, the hexagonal close packed (HCP) to body centered cubic (BCC) transformation in titanium that is driven by a rapid increase in temperature. We have used a novel nanosecond electron microscope (the dynamic transmission electron microscope, DTEM) to acquire diffraction and imaging information on the transformation, which is driven in-situ by nanosecond laser irradiation. Using nanosecond exposure times that are possible in the DTEM, data can be collected about the transient events in these fast transformations. We have identified the phase transformation with diffraction patterns and correlated the time of the phase transformation with calculated conditions in the sample.

  15. The determination of energy transfer rates in the Ho:Tm:Cr:YAG laser material

    NASA Technical Reports Server (NTRS)

    Koker, Edmond B.

    1988-01-01

    Energy transfer processes occurring between atomic, ionic, or molecular systems are very widespread in nature. The applications of such processes range form radiation physics and chemistry to biology. In the field of laser physics, energy transfer processes have been used to extend the lasing range, increase the output efficiency, and influence the spectral and temporal characteristics of the output pulses of energy transfer dye lasers or solid-state laser materials. Thus in the development of solid state lasers, it is important to investigate the basic energy transfer (ET) mechanisms and processes in order to gain detailed knowledge so that successful technical utilization can be achieved. The aim of the present research is to measure the ET rate from a given manifold associated with the chromium sensitizer atom to a given manifold in the holmium activator atom via the thulium transfer atom, in the Ho:Cr:YAG laser material.

  16. Laser beam deflection monitoring of Nd: YAG laser ablation: pulse shape and repetition rate effects

    NASA Astrophysics Data System (ADS)

    Diaci, Janez; Možina, Janez

    1993-05-01

    The laser beam deflection probe has been employed to study blast waves generated during ablation of metallic surfaces by sequences of 1.06 μm Nd:YAG laser pulses separated by less than 1μs. A fluence threshold has been found, below which the effects of individual pulses can be resolved by the laser probe. Above that, the deflection signal has a similar form as if the surface were irradiated with a single pulse. Analysis of the signals in terms of the spherical blast wave theory shows that a pulse sequence generates a weaker blast wave than a single pulse of equal total energy. On the other hand, the sequence yields a higher etch depth than the single pulse.

  17. Inverse bremsstrahlung heating rate for dense plasmas in laser fields

    NASA Astrophysics Data System (ADS)

    Dey, R.; Roy, A. C.

    2013-07-01

    We report a theoretical analysis of inverse bremsstrahlung heating rate in the eikonal approximation. The present analysis is performed for a dense plasma using the screened electron-ion interaction potential for the ion charge state Zi = 1 and for both the weak and strong plasma screening cases. We have also compared the eikonal results with the first Born approximation (FBA) [M. Moll et al., New J. Phys. 14, 065010 (2012)] calculation. We find that the magnitudes of inverse bremsstrahlung heating rate within the eikonal approximation (EA) are larger than the FBA values in the weak screening case (κ = 0.03 a.u.) in a wide range of field strength for three different initial electron momenta (2, 3, and 4 a.u.). But for strong screening case (κ = 0.3 a.u.), the heating rates predicted by the two approximations do not differ much after reaching their maximum values. Furthermore, the individual contribution of photoemission and photoabsorption processes to heating rate is analysed for both the weak and strong screening cases. We find that the single photoemission and photoabsorption rates are the same throughout the field strength while the multiphoton absorption process dominates over the multiphoton emission process beyond the field strength ≈ 4×108 V/cm. The present study of the dependence of heating rate on the screening parameter ranging from 0.01 to 20 shows that whereas the heating rate predicted by the EA is greater than the FBA up to the screening parameter κ = 0.3 a.u., the two approximation methods yield results which are nearly identical beyond the above value.

  18. Inverse bremsstrahlung heating rate for dense plasmas in laser fields

    SciTech Connect

    Dey, R.; Roy, A. C.

    2013-07-15

    We report a theoretical analysis of inverse bremsstrahlung heating rate in the eikonal approximation. The present analysis is performed for a dense plasma using the screened electron-ion interaction potential for the ion charge state Z{sub i} = 1 and for both the weak and strong plasma screening cases. We have also compared the eikonal results with the first Born approximation (FBA) [M. Moll et al., New J. Phys. 14, 065010 (2012)] calculation. We find that the magnitudes of inverse bremsstrahlung heating rate within the eikonal approximation (EA) are larger than the FBA values in the weak screening case (κ = 0.03 a.u.) in a wide range of field strength for three different initial electron momenta (2, 3, and 4 a.u.). But for strong screening case (κ = 0.3 a.u.), the heating rates predicted by the two approximations do not differ much after reaching their maximum values. Furthermore, the individual contribution of photoemission and photoabsorption processes to heating rate is analysed for both the weak and strong screening cases. We find that the single photoemission and photoabsorption rates are the same throughout the field strength while the multiphoton absorption process dominates over the multiphoton emission process beyond the field strength ≈ 4×10{sup 8} V/cm. The present study of the dependence of heating rate on the screening parameter ranging from 0.01 to 20 shows that whereas the heating rate predicted by the EA is greater than the FBA up to the screening parameter κ = 0.3 a.u., the two approximation methods yield results which are nearly identical beyond the above value.

  19. Dentin ablation-rate measurements in endodontics witj HF and CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Makropoulou, Mersini I.; Serafetinides, Alexander A.; Khabbaz, Marouan; Sykaras, Sotirios; Tsikrikas, G. N.

    1996-01-01

    Recent studies focused on the ability of the laser light to enlarge the root canal during the endodontic therapy. The aim of this research is the experimental and theoretical study of the ablation rate of two infrared laser wavelengths on dentin. Thirty freshly extracted human teeth were longitudinally sectioned at thicknesses ranged from 0.5 to 2 mm, and irradiated on the root canal dentin. The measured ablation rates in dentinal wall of the root canal showed that the HF laser at 2.9 micrometer can more effectively penetrate into the tissue, whereas the carbon dioxide laser at 10.6 micrometer leads to high thermal damage of the ablation crater surroundings.

  20. High-data rate laser communication field experiment in the turbulence channel

    NASA Astrophysics Data System (ADS)

    Sun, Jianfeng; Zhi, Ya'nan; Lu, Wei; Wang, Lijuan; Dai, Enwen; Liu, Liren

    2012-10-01

    At present inter-satellite laser communications have made great success, such as SILEX, TerraSAR-X LCT etc. But satellite to ground laser communications still at the experimental stages because of the atmosphere turbulence channel and the clouds. Once the satellite to ground laser communication technology obtains a breakthrough, the all laser spacebased communication era is coming. In this paper, we suggest a DPSK modulation/self-coherent homodyne reception scheme to overcome the atmosphere turbulence. The key in the scheme lies in the phase error compensation with the external environment change. In our experiment, we use two parallel plates rotating to compensate the phase error. The communication data rate reaches 2.5Gbps in the field experiment. The real time bit error rate was obtained with the variation of the communication channel's turbulence.

  1. Study of nanostructure growth with nanoscale apex induced by femtosecond laser irradiation at megahertz repetition rate

    PubMed Central

    2013-01-01

    Leaf-like nanostructures with nanoscale apex are induced on dielectric target surfaces by high-repetition-rate femtosecond laser irradiation in ambient conditions. We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst. It was found to be possible only in the presence of background nitrogen gas flow. In this synthesis method, the target serves as the source for building material as well as the substrate upon which these nanostructures can grow. In our investigation, it was found that there are three possible kinds of nanotips that can grow on target surfaces. In this report, we have presented the study of the growth mechanisms of such leaf-like nanostructures under various conditions such as different laser pulse widths, pulse repetition rates, dwell times, and laser polarizations. We observed a clear transformation in the kind of nanotips that grew for the given laser conditions. PMID:23607832

  2. Moderate repetition rate ultra-intense laser targets and optics using variable thickness liquid crystal films

    NASA Astrophysics Data System (ADS)

    Poole, P. L.; Willis, C.; Cochran, G. E.; Hanna, R. T.; Andereck, C. D.; Schumacher, D. W.

    2016-10-01

    Liquid crystal films are variable thickness, planar targets for ultra-intense laser matter experiments such as ion acceleration. Their target qualities also make them ideal for high-power laser optics such as plasma mirrors and waveplates. By controlling parameters of film formation, thickness can be varied on-demand from 10 nm to above 50 μm, enabling real-time optimization of laser interactions. Presented here are results using a device that draws films from a bulk liquid crystal source volume with any thickness in the aforementioned range. Films form within 2 μm of the same location each time, well within the Rayleigh range of even tight F / # systems, thus removing the necessity for realignment between shots. The repetition rate of the device exceeds 0.1 Hz for sub-100 nm films, facilitating higher repetition rate operation of modern laser facilities.

  3. Study of nanostructure growth with nanoscale apex induced by femtosecond laser irradiation at megahertz repetition rate

    NASA Astrophysics Data System (ADS)

    Patel, Nikunj B.; Tan, Bo; Venkatakrishnan, Krishnan

    2013-04-01

    Leaf-like nanostructures with nanoscale apex are induced on dielectric target surfaces by high-repetition-rate femtosecond laser irradiation in ambient conditions. We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst. It was found to be possible only in the presence of background nitrogen gas flow. In this synthesis method, the target serves as the source for building material as well as the substrate upon which these nanostructures can grow. In our investigation, it was found that there are three possible kinds of nanotips that can grow on target surfaces. In this report, we have presented the study of the growth mechanisms of such leaf-like nanostructures under various conditions such as different laser pulse widths, pulse repetition rates, dwell times, and laser polarizations. We observed a clear transformation in the kind of nanotips that grew for the given laser conditions.

  4. Study of nanostructure growth with nanoscale apex induced by femtosecond laser irradiation at megahertz repetition rate.

    PubMed

    Patel, Nikunj B; Tan, Bo; Venkatakrishnan, Krishnan

    2013-01-01

    Leaf-like nanostructures with nanoscale apex are induced on dielectric target surfaces by high-repetition-rate femtosecond laser irradiation in ambient conditions. We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst. It was found to be possible only in the presence of background nitrogen gas flow. In this synthesis method, the target serves as the source for building material as well as the substrate upon which these nanostructures can grow. In our investigation, it was found that there are three possible kinds of nanotips that can grow on target surfaces. In this report, we have presented the study of the growth mechanisms of such leaf-like nanostructures under various conditions such as different laser pulse widths, pulse repetition rates, dwell times, and laser polarizations. We observed a clear transformation in the kind of nanotips that grew for the given laser conditions. PMID:23607832

  5. High-repetition rate relativistic electron beam generation from intense laser solid interactions

    NASA Astrophysics Data System (ADS)

    Batson, Thomas; Nees, John; Hou, Bixue; Thomas, A. G. R.; Krushelnick, Karl

    2015-05-01

    Relativistic electron beams have applications spanning materials science, medicine, and home- land security. Recent advances in short pulse laser technology have enabled the production of very high focused intensities at kHz rep rates. Consequently this has led to the generation of high ux sources of relativistic electrons- which is a necessary characteristic of these laser plasma sources for any potential application. In our experiments, through the generation of a plasma with the lambda cubed laser system at the University of Michigan (a 5 × 1018W=cm2, 500 Hz, Ti:Sapphire laser), we have measured electrons ejected from the surface of fused silica nd Cu targets having energies in excess of an MeV. The spectrum of these electrons was measured with respect to incident laser angle, prepulse timing, and focusing conditions. While taken at a high repetition rate, the pulse energy of the lambda cubed system was consistently on the order of 10 mJ. In order to predict scaling of the electron energy with laser pulse energy, simulations are underway which compare the spectrum generated with the lambda cubed system to the predicted spectrum generated on the petawatt scale HERCULES laser system at the University of Michigan.

  6. High repetition rate collisional soft x-ray lasers based on grazing incidence pumping

    SciTech Connect

    Luther, B M; Wang, Y; Larotonda, M A; Alessi, D; Berrill, M; Rocca, J J; Dunn, J; Keenan, R; Shlyaptsev, V N

    2005-11-18

    We discuss the demonstration of gain-saturated high repetition rate table-top soft x-ray lasers producing microwatt average powers at wavelengths ranging from 13.9 to 33 nm. The results were obtained heating a pre-created plasma with a picosecond optical laser pulse impinging at grazing incidence onto a pre-created plasma. This pumping geometry increases the energy deposition efficiency of the pump beam into the gain region, making it possible to saturate soft x-ray lasers in this wavelength range with a short pulse pump energy of only 1 J at 800 nm wavelength. Results corresponding to 5 Hz repetition rate operation of gain-saturated 14.7 nm Ni-like Pd and 32.6 nm line Ne-like Ti lasers pumped by a table-top Ti:sapphire laser are reported. We also discuss results obtained using a 1 {omega} 1054 nm pre-pulse and 2{omega} 527 nm short pulse from a Nd:glass pump laser. This work demonstrates the feasibility of producing compact high average power soft x-ray lasers for applications.

  7. Rotational CARS Temperature Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Zuzeek, Yvette; Takashima, Keisuke; Adamovich, Igor; Lempert, Walter

    2009-10-01

    Time-resolved and spatially resolved temperatures in repetitively pulsed nanosecond discharges in air and ethylene-air mixtures have been measured by purely rotational Coherent Anti-Stokes Raman Specroscopy (CARS). The experiments have been done in a capacitively coupled plane-to-plane discharge and in an atmospheric pressure near-surface Dielectric Barrier Discharge (DBD), both powered by repetitive nanosecond duration voltage pulses. Gated ICCD camera images demonstrated that the capacitively coupled discharge plasma remains diffuse and stable, with no sign of arc filaments. Comparison of the experimental results with plasma chemical kinetic modeling calculations shows good agreement. The results demonstrate that the rate of heating in the fuel-air plasma is significantly more rapid compared to the one in the air plasma. Kinetic model analysis shows that this occurs due to exothermic reactions of fuel with radical species generated in the plasma, such as O atoms. The present results provide additional insight into kinetics of hydrocarbon fuel oxidation in low-temperature plasmas and into the mechanism of localized heating of air flows by nanosecond DBD discharges.

  8. Characteristics of 2-heptanone decomposition using nanosecond pulsed discharge plasma

    NASA Astrophysics Data System (ADS)

    Nakase, Yuki; Fukuchi, Yuichi; Wang, Douyan; Namihira, Takao; Akiyama, Hidenori; Kumamoto University Collaboration

    2015-09-01

    Volatile organic compounds (VOC) evaporate at room temperature. VOCs typically consist of toluene, benzene and ethyl acetate, which are used in cosmetics, dry cleaning products and paints. Exposure to elevated levels of VOCs may cause headaches, dizziness and irritation to the eyes, nose, and throat; they may also cause environmental problems such as air pollution, acid rain and photochemical smog. As such, they require prompt removal. Nanosecond pulsed discharge is a kind of non-thermal plasma consisting of a streamer discharge. Several advantages of nanosecond pulsed discharge plasma have been demonstrated by studies of our research group, including low heat loss, highly energetic electron generation, and the production of highly active radicals. These advantages have shown ns pulsed discharge plasma capable of higher energy efficiency for processes, such as air purification, wastewater treatment and ozone generation. In this research, nanosecond pulsed discharge plasma was employed to treat 2-heptanone, which is a volatile organic compound type and presents several harmful effects. Characteristics of treatment dependent on applied voltage, gas flow rate and input energy density were investigated. Furthermore, byproducts generated by treatment were also investigated.

  9. Influence of laser diode red beams on germination rate of tomato seeds

    NASA Astrophysics Data System (ADS)

    Niculita, P.; Danaila-Guidea, Silvana; Livadariu, Oana; Popa, M.; Ristici, M.; Ristici, Esofina

    2007-08-01

    Laser diodes are lighting devices in which the light is generated by stimulated emission rather than spontaneous emission, with high generation efficiency. A device using 20 red laser diodes is presented. Emission wavelengths are in the 650-670 nm range. Emission power for each laser diode is about 4 mW. This device is used to irradiate the tomato seeds with three different irradiating doses. There were three Petri vessels for each dose having 25 seeds each of them. Results show that the germination rate increases for irradiated seeds. The red light has a positive effect for vegetable cultivated in protected area.

  10. Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate

    NASA Astrophysics Data System (ADS)

    Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang

    2016-01-01

    The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe-Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe-Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.

  11. [INVITED] Laser welding of glasses at high repetition rates - Fundamentals and prospects

    NASA Astrophysics Data System (ADS)

    Richter, Sören; Zimmermann, Felix; Tünnermann, Andreas; Nolte, Stefan

    2016-09-01

    We report on the welding of various glasses with ultrashort laser pulses. Femtosecond laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in multiphoton absorption and heat accumulation from successive pulses. This leads to local melting and subsequent resolidification which can be used to weld the glasses. The fundamental interaction process was studied using an in-situ micro Raman setup to measure the laser induced temperature distribution and its temporal decay. The induced network changes were analyzed by Raman spectrocopy identifying an increase of three and four membered silicon rings within the laser irradiated area. In order to determine the stability of the laser welded samples a three point bending test was used. Thereby, we identified that the maximal achievable breaking strength is limited by laser induced stress surrounding the modified material. To minimize the amount of stress bursts of laser pulses or an post processing annealing step can be applied. Besides fused silica, we welded borosilicate glasses and glasses with a low thermal expansion coefficient. Even the welding of different glass combinations is possible demonstrating the versatility of ultrashort pulse induced laser welding.

  12. High (1 GHz) repetition rate compact femtosecond laser: A powerful multiphoton tool for nanomedicine and nanobiotechnology

    NASA Astrophysics Data System (ADS)

    Ehlers, A.; Riemann, I.; Martin, S.; Le Harzic, R.; Bartels, A.; Janke, C.; König, K.

    2007-07-01

    Multiphoton tomography of human skin and nanosurgery of human chromosomes have been performed with a 1GHz repetition rate laser by the use of the commercially available femtosecond multiphoton laser tomograph DermaInspect as well as a compact galvoscanning microscope. We performed the autofluorescence tomography up to 100μm in the depth of human skin. Submicron cutting lines and hole drillings have been conducted on labeled human chromosomes.

  13. Derivation of heating rate dependent exposure strategies for the selective laser melting of thermoplastic polymers

    NASA Astrophysics Data System (ADS)

    Drummer, Dietmar; Drexler, Maximilian; Wudy, Katrin

    2015-05-01

    The selective laser melting of polymer powder is for rapid prototyping applications an established technology, although a lack in basic process knowledge appears. Considering demands of series production the selective laser melting technique is faced with varies challenges concerning processable material systems, process strategies and part properties. Consequently basic research is necessary to shift from rapid prototyping to rapid manufacturing of small lot sized series. Based on basic research the high potential of selective laser melting for the production of complex parts without any tools can be opened up. For the derivation of part quality increasing process strategies knowledge about interactions between sub-processes of selective laser melting and resulting part properties is necessary. The selective laser melting consists of three major sub-processes: Geometry exposure, tempering and powder feeding. According to the interaction of sub-processes resulting temperature fields during the selective laser melting process determine the part properties by changing micro structural pore number and distribution. Beneath absolute temperatures also the time-dependency of the thermal fields influences the porosity of molten parts. Present process strategies tend to decrease building time by increasing scanning speed and laser power. Although the absolute energy input into the material is constant for increasing scanning speed and laser power in the same ratio, time dependent material effects are neglected. The heating rate is a combined parameter derived from absolute temperature and time. Within the paper the authors analyze the basic interactions between different heating rates and part properties (e.g. porosity, mechanical strengths). Therefore with different heating rates produced specimens are analyzed with imaging technologies as well as mechanical tests. Based on the done basic investigations new heating rate dependent process strategies can be established

  14. Supra-nanosecond dynamics of a red-to-blue photon upconversion system.

    PubMed

    Singh-Rachford, Tanya N; Castellano, Felix N

    2009-03-16

    Blue-green upconverted emission from 2-chloro-bis-phenylethynylanthracene (2CBPEA) sensitized by the red-absorbing platinum(II)tetraphenyltetrabenzoporphyrin (PtTPBP) has been investigated in N,N-dimethylformamide (DMF). The upconverted singlet fluorescence of 2CBPEA resulting from its sensitized triplet-triplet annihilation (TTA) is observed following selective excitation of PtTPBP at 635 +/- 5 nm. Stern-Volmer analysis of the photoluminescence quenching of PtTPBP by 2CBPEA yields a bimolecular quenching constant of 1.62 x 10(9) M(-1) s(-1), slightly below the diffusion limit in DMF at room temperature. The TTA process was confirmed by the quadratic dependence of the integrated upconverted singlet fluorescence emission profile of 2CBPEA measured as a function of 635 nm incident laser power. Time-resolved emission spectra following 630 nm nanosecond laser pulses illustrate the prompt nature of porphyrin phosphorescence quenching and the delayed nature of the upconverted singlet fluorescence from 2CBPEA. Transient absorption decays monitored at the peak of the characteristic 2CBPEA triplet-triplet excited-state absorption (490 nm) measured as a function of incident nanosecond 630 nm pump laser fluence recovered the rate constant for the sensitized TTA process, k(TT) = 5.64 +/- 0.08 x 10(9) M(-1) s(-1). To calculate this rate constant, we determined the triplet-triplet extinction coefficient of 2CBPEA (12,500 M(-1) cm(-1) at 490 nm) utilizing triplet energy transfer from donors with known excited-state extinction coefficients, namely [Ru(bpy)(3)](2+) and 2-acetonaphthone and averaged these values. The current work, to the best of our knowledge, represents the first example of red-to-blue upconversion thus demonstrating another viable sensitized TTA process, as well as providing the first measurements of k(TT) in a photon upconverting scheme. As 2CBPEA is stable under ambient conditions, this chromophore represents an almost ideal candidate for light

  15. High repetition rate (100 Hz), high peak power, high contrast femtosecond laser chain

    NASA Astrophysics Data System (ADS)

    Clady, R.; Tcheremiskine, V.; Azamoum, Y.; Ferré, A.; Charmasson, L.; Utéza, O.; Sentis, M.

    2016-03-01

    High intensity femtosecond laser are now routinely used to produce energetic particles and photons via interaction with solid targets. However, the relatively low conversion efficiency of such processes requires the use of high repetition rate laser to increase the average power of the laser-induced secondary source. Furthermore, for high intensity laser-matter interaction, a high temporal contrast is of primary importance as the presence of a ns ASE pedestal (Amplified Spontaneous Emission) and/or various prepulses may significantly affect the governing interaction processes by creating a pre-plasma on the target surface. We present the characterization of a laser chain based on Ti:Sa technology and CPA technique, which presents unique laser characteristics : a high repetition rate (100 Hz), a high peak power (>5 TW) and a high contrast ratio (ASE<10-10) obtained thanks to a specific design with 3 saturable absorbers inserted in the amplification chain. A deformable mirror placed before the focusing parabolic mirror should allow us to focus the beam almost at the limit of diffraction. In these conditions, peak intensity above 1019W.cm-2 on target could be achieved at 100 Hz, allowing the study of relativistic optics at a high repetition rate.

  16. Video-rate laser Doppler vibrometry by heterodyne holography.

    PubMed

    Samson, Benjamin; Verpillat, Frédéric; Gross, Michel; Atlan, Michael

    2011-04-15

    We report a demonstration video-rate heterodyne holography in off-axis configuration. Reconstruction and display of a one megapixel hologram is achieved at 24 frames per second, with a graphics processing unit. Our claims are validated with real-time screening of steady-state vibration amplitudes in a wide-field, noncontact vibrometry experiment.

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

    PubMed

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

    2016-06-15

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

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

    PubMed

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

    2016-06-15

    We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr3+) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr3+-doped GdLiF4 crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range. PMID:27304265

  19. Control of atomic transition rates via laser-light shaping

    NASA Astrophysics Data System (ADS)

    Jáuregui, R.

    2015-04-01

    A modular systematic analysis of the feasibility of modifying atomic transition rates by tailoring the electromagnetic field of an external coherent light source is presented. The formalism considers both the center of mass and internal degrees of freedom of the atom, and all properties of the field: frequency, angular spectrum, and polarization. General features of recoil effects for internal forbidden transitions are discussed. A comparative analysis of different structured light sources is explicitly worked out. It includes spherical waves, Gaussian beams, Laguerre-Gaussian beams, and propagation invariant beams with closed analytical expressions. It is shown that increments in the order of magnitude of the transition rates for Gaussian and Laguerre-Gaussian beams, with respect to those obtained in the paraxial limit, require waists of the order of the wavelength, while propagation invariant modes may considerably enhance transition rates under more favorable conditions. For transitions that can be naturally described as modifications of the atomic angular momentum, this enhancement is maximal (within propagation invariant beams) for Bessel modes, Mathieu modes can be used to entangle the internal and center-of-mass involved states, and Weber beams suppress this kind of transition unless they have a significant component of odd modes. However, if a recoil effect of the transition with an adequate symmetry is allowed, the global transition rate (center of mass and internal motion) can also be enhanced using Weber modes. The global analysis presented reinforces the idea that a better control of the transitions between internal atomic states requires both a proper control of the available states of the atomic center of mass, and shaping of the background electromagnetic field.

  20. Two-photon polymerization with variable repetition rate bursts of femtosecond laser pulses.

    PubMed

    Baldacchini, Tommaso; Snider, Scott; Zadoyan, Ruben

    2012-12-31

    We describe fabrication of microstructures by two-photon polymerization using bursts of femtosecond laser pulses. With the aid of an acousto-optic modulator driven by a function generator, two-photon polymerization is performed at variable burst repetition rates. We investigate how the time between the bursts of laser pulses influences the ultimate dimensions of lines written in a photosensitive resin. We observe that when using the same laser fluence, polymer lines fabricated at different burst repetition rates have different dimensions. In particular, the widths of two-photon polymerized lines become smaller with decreasing burst repetition rates. Based on the thermal properties of the resin and experimental writing conditions, we attribute this effect to localized heat accumulation. PMID:23388815

  1. High repetition rate laser induced fluorescence applied to Surfatron Induced Plasmas

    NASA Astrophysics Data System (ADS)

    van der Mullen, J. J. A. M.; Palomares, J. M.; Carbone, E. A. D.; Graef, W.; Hübner, S.

    2012-05-01

    The reaction kinetics in the excitation space of Ar and the conversion space of Ar-molecule mixtures are explored using a combination of high rep-rate YAG-Dye laser systems with a well defined and easily controllable Surfatron Induced Plasma set-up. Applying the method of Saturation Time Resolved Laser Induced Fluorescence (SaTiRe-LIF), we could trace excitation and conversion channels and determine rates of electron and heavy particle excitation kinetics. The time resolved density disturbances observed in the Ar excitation space, which are initiated by the laser, reveal the excitation channels and corresponding rates; responses of the molecular radiation in Ar-molecule mixtures corresponds to the presence of conversion processes induced by heavy particle excitation kinetics.

  2. Nanosecond Lipid Dynamics in Membranes Containing Cholesterol

    SciTech Connect

    Armstrong, Clare L; Haeussler, Wolfgang; Seydel, Tilo; Katsaras, John; Rheinstadter, Maikel C

    2014-01-01

    Lipid dynamics in the cholesterol-rich (40 mol%) liquid-ordered (lo) phase of dimyristoylphosphatidylcholine membranes were studied using neutron spin-echo and neutron backscattering. Recent theoretical and experimental evidence supports the notion of the liquid-ordered phase in phospholipid membranes as a locally structured liquid, with small ordered domains of a highly dynamic nature in equilibrium with a disordered matrix [S. Meinhardt, R. L. C. Vink and F. Schmid, Proc. Natl. Acad. Sci. U. S. A., 2013, 110(12), 4476 4481, C. L. Armstrong et al., PLoS One, 2013, 8(6), e66162]. This local structure was found to have a pronounced impact on the membranes' dynamical properties. We found that the long-wavelength dynamics in the liquid-ordered phase, associated with the elastic properties of the membranes, were faster by two orders of magnitude as compared to the liquid disordered phase. At the same time, collective nanoscale diffusion was significantly slower. The presence of a soft-mode (a slowing down) in the longwavelength dispersion relationship suggests an upper size limit for the ordered lipid domain of ~220 A. Moreover, from the relaxation rate of the collective lipid diffusion of lipid lipid distances, the lifetime of these domains was estimated to be about 100 nanoseconds.

  3. Ablation of atheroma by laser energy: a comparative study of the efficacy of different temporal rates of energy deposition

    NASA Astrophysics Data System (ADS)

    Ramsay, Donald J.; Walker, Philip J.; Dadswell, Nicola G.; May, James; Piper, James A.; Wacher, Christine

    1990-06-01

    Laser angioplasty continues to attract interest as a potential method for treating atherosclerotic arterial disease. Current efforts are aimed at finding the most effective combination of laser and delivery system. High energy pulsed ultraviolet or infrared lasers demonstrate good photoablative properties but there remain practical difficulties with the optical fibre delivery. Continuous wave lasers are widely used in conjunction with "hot-tip" fibres for thermal ablation but their direct (optical) ablation efficiency is low, causing significant surrounding thermal damage in soft tissue. While considerable attention has been directed previously at the ablative effects for different laser wavelengths, little systematic study has been made of the efficacy for different temporal rates of energy deposition. We have compared the efficacy for tissue ablation in cadaveric human aorta of three different laser systems with similar wavelengths in the visible (green) but different temporal rates of energy deposition. The laser sources were the continuous wave argon ion laser (514.5 nm), the high pulse energy, frequency doubled Nd:YAG laser (532 nm) and the copper vapour laser. The copper vapour laser is a high repetition rate, high average power, pulsed laser emitting in the green (511 nm) and yellow (578 nm) which has temporal characteristics intermediate between those of the Nd:YAG laser and the argon ion laser, and has the potential to be effective both for direct optical ablation and hot-tip thermal ablation.

  4. Micro-processing of polymers and biological materials using high repetition rate femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ding, Li

    High repetition rate femtosecond laser micro-processing has been applied to ophthalmological hydrogel polymers and ocular tissues to create novel refractive and diffractive structures. Through the optimization of laser irradiation conditions and material properties, this technology has become feasible for future industrial applications and clinical practices. A femtosecond laser micro-processing workstation has been designed and developed. Different experimental parameters of the workstation such as laser pulse duration, focusing lens, and translational stages have been described and discussed. Diffractive gratings and three-dimensional waveguides have been fabricated and characterized in hydrogel polymers, and refractive index modifications as large as + 0.06 have been observed within the laser-irradiated region. Raman spectroscopic studies have shown that our femtosecond laser micro-processing induces significant thermal accumulation, resulting in a densification of the polymer network and increasing the localized refractive index of polymers within the laser irradiated region. Different kinds of dye chromophores have been doped in hydrogel polymers to enhance the two-photon absorption during femtosecond laser micro-processing. As the result, laser scanning speed can be greatly increased while the large refractive index modifications remain. Femtosecond laser wavelength and pulse energy as well as water and dye concentration of the hydrogels are optimized. Lightly fixed ocular tissues such as corneas and lenses have been micro-processed by focused femtosecond laser pulses, and refractive index modifications without any tissue-breakdown are observed within the stromal layer of the corneas and the cortex of the lenses. Living corneas are doped with Sodium Fluorescein to increase the two-photon absorption during the laser micro-processing, and laser scanning speed can be greatly increased while inducing large refractive index modifications. No evidence of cell death

  5. Ignition Rate Measurement of Laser-Ignited Coals

    SciTech Connect

    John C. Chen; Vinayak Kabadi

    1997-10-31

    We established a novel experiment to study the ignition of pulverized coals under conditions relevant to utility boilers. Specifically, we determined the ignition mechanism of pulverized-coal particles under various conditions of particle size, coal type, and freestream oxygen concentration. We also measured the ignition rate constant of a Pittsburgh #8 high-volatile bituminous coal by direct measurement of the particle temperature at ignition, and incorporating this measurement into a mathematical model for the ignition process. The model, called Distributed Activation Energy Model of Ignition, was developed previously by our group to interpret conventional drop-tube ignition experiments, and was modified to accommodate the present study.

  6. Laser ranging system and measurement analysis for space debris with high repetition rate

    NASA Astrophysics Data System (ADS)

    Wu, Zhibo; Zhang, Haifeng; Meng, Wendong; Li, Pu; Deng, Huarong; Tang, Kai; Ding, Renjie; Zhang, Zhongping

    2016-01-01

    Laser measurement technology is inherently high accurate and will play an important role in precise orbit determination, accurate catalog, surveillance to space debris. Shanghai Astronomical Observatory (SHAO) has been developing the technology of laser measurement to space debris for several years. Based on the first successful laser ranging measurement to space debris in country, by applying one new set of high power 532nm wavelength laser system with 200Hz repetition rate, and adopting low dark noise APD detector with high quantum efficiency and high transmissivity of narrow bandwidth spectral filter, SHAO have achieved hundreds of passes of laser data from space debris in 2014, and the measured objects with distance between 500km and 2200km, Radar Cross Section (RCS) of >10m2 to <0.5m2 at the precision of <1m RMS for small RCS targets ,and the success rate of measured passes of up to 80%. The results show that laser ranging technology in China can routinely measure space debris and provide enough measurement data with high accuracy to space debris applications and researches such as surveillance activities in the future.

  7. A contactless microwave-based diagnostic tool for high repetition rate laser systems

    SciTech Connect

    Braggio, C.; Borghesani, A. F.

    2014-02-15

    We report on a novel electro-optic device for the diagnostics of high repetition rate laser systems. It is composed of a microwave receiver and of a second order nonlinear crystal, whose irradiation with a train of short laser pulses produces a time-dependent polarization in the crystal itself as a consequence of optical rectification. This process gives rise to the emission of microwave radiation that is detected by a receiver and is analyzed to infer the repetition rate and intensity of the pulses. We believe that this new method may overcome some of the limitations of photodetection techniques.

  8. Narrow-linewidth megahertz-rate pulse-burst laser for high-speed flow diagnostics.

    PubMed

    Thurow, Brian; Jiang, Naibo; Samimy, Mo; Lempert, Walter

    2004-09-10

    A second-generation pulse-burst laser system for high-speed flow diagnostics is described in detail. The laser can produce a burst of high-energy pulses (of the order of hundreds of millijoules per pulse) with individual pulse durations of less than 10 ns and pulse separations as short as 1 micros. A key improvement is the addition of a phase-conjugate mirror, which effectively isolates the high-intensity, short-duration pulses from the low-intensity, long-duration background illumination. It allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second-harmonic and 40% for third-harmonic generation. Characteristics of the laser system, including gain narrowing, pulse-burst energy distribution, pulse narrowing, and overall pulse-burst energy, are described. In addition, the applicability of the laser for spectroscopic-based flow diagnostics is demonstrated through the presentation of megahertz-rate planar Doppler velocimetry results.

  9. High repetition rate relativistic electron beam generation from intense laser solid interactions

    NASA Astrophysics Data System (ADS)

    Batson, Thomas; Nees, John; Hou, Bixue; Thomas, Alexander; Krushelnick, Karl

    2014-10-01

    Relativistic electron beams have wide-ranging applications in medicine, materials science, and homeland security. Recent advances in short pulse laser technology have enabled the production of very high focused intensities at kHz rep rates. Consequently this has led to the generation of high flux sources of relativistic electrons - which is a necessary characteristic of these laser plasma sources for any potential application. In our experiments, through the generation of a plasma by focusing a 5 × 1018 W/cm2, 500 Hz, Ti:Sapphire laser pulse onto a fused silica target, we have measured electrons ejected from the target surface having energies in excess of an MeV. The spectrum of these electrons, as well as the spatial divergence of the resulting beam, was also measured with respect to incident laser angle, prepulse timing and focusing conditions. The experimental results are compared to particle in cell simulations.

  10. Luminescence of black silicon fabricated by high-repetition rate femtosecond laser pulses

    SciTech Connect

    Chen Tao; Si Jinhai; Hou Xun; Kanehira, Shingo; Miura, Kiyotaka; Hirao, Kazuyuki

    2011-10-01

    We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to ''defect luminescence'' and ''quantum confinement'', respectively.

  11. Design and Development of High-Repetition-Rate Satellite Laser Ranging System

    NASA Astrophysics Data System (ADS)

    Choi, Eun-Jung; Bang, Seong-Cheol; Sung, Ki-Pyoung; Lim, Hyung-Chul; Jung, Chan-Gyu; Kim, In-Yeung; Choi, Jae-Seung

    2015-09-01

    The Accurate Ranging System for Geodetic Observation ? Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station ¡°data validation¡± process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retroreflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

  12. Laser driven nuclear science and applications: The need of high efficiency, high power and high repetition rate Laser beams

    NASA Astrophysics Data System (ADS)

    Gales, S.

    2015-10-01

    Extreme Light Infrastructure (ELI) is a pan European research initiative selected on the European Strategy Forum on Research Infrastructures Roadmap that aims to close the gap between the existing laboratory-based laser driven research and international facility-grade research centre. The ELI-NP facility, one of the three ELI pillars under construction, placed in Romania and to be operational in 2018, has as core elements a couple of new generation 10 PW laser systems and a narrow bandwidth Compton backscattering gamma source with photon energies up to 19 MeV. ELI-NP will address nuclear photonics, nuclear astrophysics and quantum electrodynamics involving extreme photon fields. Prospective applications of high power laser in nuclear astrophysics, accelerator physics, in particular towards future Accelerator Driven System, as well as in nuclear photonics, for detection and characterization of nuclear material, and for nuclear medicine, will be discussed. Key issues in these research areas will be at reach with significant increase of the repetition rates and of the efficiency at the plug of the high power laser systems as proposed by the ICAN collaboration.

  13. Dentin bond strength after ablation using a CO2 laser operating at high pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Hedayatollahnajafi, Saba; Staninec, Michal; Watanabe, Larry; Lee, Chulsung; Fried, Daniel

    2009-02-01

    Pulsed CO2 lasers show great promise for the rapid and efficient ablation of dental hard tissues. Our objective was to demonstrate that CO2 lasers operated at high repetition rates can be used for the rapid removal of dentin without excessive thermal damage and without compromising adhesion to restorative materials. Human dentin samples (3x3mm2) were rapidly ablated with a pulsed CO2 laser operating at a wavelength of 9.3-µm, pulse repetition rate of 300-Hz and an irradiation intensity of 18-J/cm2. The bond strength to composite was determined by the modified single plane shear test. There were 8 test groups each containing 10 blocks: negative control (non-irradiated non-etched), positive control (non-irradiated acid-etched), and six laser treated groups (three etched and three non-etched sets). The first and second etched and non-etched sets were ablated at a speed of 25 mm/sec and 50 mm/sec with water, respectively. The third set was also ablated at 50 mm/sec without application of water during laser irradiation. Minimal thermal damage was observed on the dentin surfaces for which water cooling was applied. Bond strengths exceeded 20 MPa for laser treated surfaces that were acid-etched after ablation (25-mm/sec: 29.9-MPa, 50-mm/sec: 21.3-MPa). The water-cooled etched laser groups all produced significantly stronger bonds than the negative control (p<0.001) and a lower bond strength than the positive control (p<0.05). These measurements demonstrate that dentin surfaces can be rapidly ablated by a CO2 lasers with minimal peripheral thermal damage. Additional studies are needed to determine if a lower bond strength than the acid-etched control samples is clinically significant where durability of these bonded restoration supersedes high bond strength.

  14. Continuous hydroxyl radical planar laser imaging at 50 kHz repetition rate.

    PubMed

    Hammack, Stephen; Carter, Campbell; Wuensche, Clemens; Lee, Tonghun

    2014-08-10

    This study demonstrates high-repetition-rate planar laser-induced fluorescence (PLIF) imaging of hydroxyl radicals (OH) in flames at a continuous framing rate of 50 kHz. A frequency-doubled dye laser is pumped by the second harmonic of an Nd:YAG laser to generate laser radiation near 283 nm with a pulse width of 8 ns and rate of 50 kHz. Fluorescence is recorded by a two-stage image intensifier and complementary metal-oxide-semiconductor camera. The average power of the 283 nm beam reaches 7 W, yielding a pulse energy of 140 μJ. Both a Hencken burner and a DC transient-arc plasmatron are used to produce premixed CH4/air flames to evaluate the OH PLIF system. The average signal-to-noise ratio for the Hencken burner flame is greater than 20 near the flame front and greater than 10 further downstream in a region of the flame near equilibrium. Image sequences of the DC plasmatron discharge clearly illustrate development and evolution of flow features with signal levels comparable to those in the Hencken burner. The results are a demonstration of the ability to make high-fidelity OH PLIF measurements at 50 kHz using a Nd:YAG-pumped, frequency-doubled dye laser. PMID:25320935

  15. Electrode patterning on PEDOT:PSS thin films by pulsed ultraviolet laser for touch panel screens

    NASA Astrophysics Data System (ADS)

    Tseng, Shih-Feng; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Chiang, Donyau

    2013-07-01

    Laser dry etching by a laser driven direct writing apparatus has been extensively used for the micro- and nano-patterning on the solid surface. The purpose of this study is to pattern the PEDOT:PSS thin film coated on the soda-lime glass substrates by a nano-second pulsed ultraviolet laser processing system. The patterned PEDOT:PSS film structure provides the electrical isolation and prevents the electrical contact from each region for capacitive touch screens. The surface morphology, geometric dimension, and edge quality of ablated area after the variety of laser patternings were measured by a 3D confocal laser scanning microscope. After the single pulse laser irradiation, the ablation threshold of the PEDOT:PSS film conducted by the nano-second pulsed UV laser was determined to be 0.135±0.003 J/cm2. The single pulse laser interacted region and the ablated line depth increased with increasing the laser fluence. Moreover, the inner line width of ablated PEDOT:PSS films along the patterned line path increased with increasing the laser fluence but the shoulder width increased with decreasing fluence, respectively. The clean, smooth, and straight ablated edges were accomplished after the electrode patterning with the laser fluence of 1.7 J/cm2 and 90 % overlapping rate.

  16. Programmable picosecond pulse packets for micromachining with multiwatt UV fiber lasers

    NASA Astrophysics Data System (ADS)

    Alekel, Theodore; Foster, David H.; Crist, Jordan

    2009-02-01

    Nanosecond class lasers have been the mainstay of optical machining for decades, delivering pulses with high fluences (>1 J/cm2) that cause many material sets to undergo thermally-induced phase changes to cause removal of matter. While in many cases their delivery of sheer laser power has proved useful, nanosecond lasers have fallen short of addressing current micromachining requirements with respect to decreased feature sizes and more complex substrates. One main issue is the laser pulse width endures throughout the ablation process, depositing energy is deposited into plasma formation and local material heating. Plasma shielding takes place when the laser pulse energy contributes to plasma formation to a greater extent than direct material ablation processes. The result is a crude "plasma cutter" of the substrate, leaving a telltale trail of localized dross and droplet deposition. Nanosecond lasers of sufficient process speeds are typically Q-switched with repetition rates less than 200 kHz. As a result, the scribed lines are made of a sequence of "blast events" that result in a variety of undesired consequences and a limited process speed.

  17. Group velocity locked vector dissipative solitons in a high repetition rate fiber laser.

    PubMed

    Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming

    2016-08-01

    Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the group velocity locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs. PMID:27505834

  18. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

    1998-01-01

    A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

  19. High Repetition Rate and Frequency Stabilized Ho:YLF Laser for CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petros, M.; Petzar, Pau; Trieu, Bo; Lee, Hyung; Singh, U.

    2009-01-01

    High repetition rate operation of an injection seeded Ho:YLF laser has been demonstrated. For 1 kHz operation, the output pulse energy reaches 5.8mJ and the optical-to-optical efficiency is 39% when the pump power is 14.5W.

  20. Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

    2015-12-01

    The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

  1. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

    1998-02-24

    A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

  2. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    NASA Astrophysics Data System (ADS)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-06-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  3. Nanosecond magnetization reversal in nanocrystalline magnetic films

    NASA Astrophysics Data System (ADS)

    Rahman, I. Z.; Gandhi, A. A.; Khaddem-Mousavi, M. V.; Lynch, T. F.; Rahman, M. A.

    2007-03-01

    This paper reports on the investigation of dynamic magnetization reversal process in electrodeposited nanocrystalline Ni and Ni80Fe20 films by employing nanosecond magnetic pulse technique. The surface morphology has been investigated using SEM, EDAX, XRD and AFM analyses and static magnetic properties of the films are characterized by vibrating sample magnetometer (VSM). Two different techniques are designed and employed to study the nanosecond magnetization reversal process in nanocrystalline thin films: Magneto-Optical Kerr Effect (MOKE) and nanosecond pulsed field magnetometer. Results of dynamical behavior as a function of several variables such as magnitude of applied bias magnetic field, amplitude and width of the pulsed magnetic field are analyzed in detail using both techniques. A computer simulation package called Object Oriented Micro-Magnetic Framework (OOMMF) has been used to simulate the magnetic domain patterns of the samples.

  4. Simple rate equation model for hypothetical doubly stimulated emission of both photons and phonons in quantum-well lasers

    SciTech Connect

    Kroemer, H.

    1981-06-15

    The dissipation processes by which electrons and holes lose energy after being trapped in quantum wells might, in a sufficiently heavily pumped quantum well laser, lead to the buildup of such a high phonon population that phonon-assisted laser action by doubly stimulated emission of photons and phonons acquires a higher gain than unassisted laser action. The resulting mode switching exhibits a pronounced hysteresis with pump rate, which should be a characteristic identifying feature of phonon-assisted laser action.

  5. Histopathology of ultrashort-laser-pulse retinal damage

    NASA Astrophysics Data System (ADS)

    Toth, Cynthia A.; Narayan, Drew G.; Osborne, Catherine; Rockwell, Benjamin A.; Stein, Cindy D.; Amnotte, Rodney E.; DiCarlo, Cheryl D.; Roach, William P.; Noojin, Gary D.; Cain, Clarence P.

    1996-05-01

    Recent studies of retinal damage due to ultrashort laser pulses have shown interesting behavior. Laser induced retinal damage for ultrashort (i.e. less than 1 ns) laser pulses is produced at lower energies than in the nanosecond to microsecond laser pulse regime and the energy required for hemorrhagic lesions is much greater times greater for the nanosecond regime. We investigated the tissue effects exhibited in histopathology of retinal tissues exposed to ultrashort laser pulses.

  6. Derivation of effective penetration depth of femtosecond laser pulses in metal from ablation rate dependence on laser fluence, incidence angle, and polarization

    SciTech Connect

    Miyasaka, Yasuhiro; Hashida, Masaki; Nishii, Takaya; Inoue, Shunsuke; Sakabe, Shuji

    2015-01-05

    Ablation rate dependence on laser fluence for copper subjected to oblique femtosecond laser irradiation has been determined experimentally in order to investigate processing induced by oblique irradiation. A difference of ablation rate between p-polarized and s-polarized oblique irradiation is clearly observed. Effective penetration depth is defined to explain the ablation rate dependence instead of using optical penetration depth, which is treated as a key value for determining the ablation rate in conventional theory. The effective penetration depth for copper is presented in simple formulas as a function of laser incidence angle for each polarization.

  7. Diffusively cooled thin-sheath high-repetition-rate TEA and TEMA lasers

    NASA Astrophysics Data System (ADS)

    Yatsiv, Shaul; Gabay, Amnon; Sintov, Yoav

    1993-05-01

    Transverse electric atmospheric (TEA), or multi atmospheric (TEMA) lasers deliver intense short laser pulses of considerable energies. Recurrent high repetition rate pulse trains afford substantial average power levels. In a high rep-rate operation the gas flows across the cavity and is externally cooled to maintain a reasonably low temperature. The gas flow gear and heat exchanger are bulky and costly. In this work we present a repetitively pulsed TEA or TEMA laser that combines energy and peak power features in an individual pulse with the substantial average power levels of a pulse train in a thin layer of gas. Excess heat is disposed of, by conduction through the gas, to cooled enclosing walls. The gas does not flow. The method applies to vibrational transition molecular lasers in the infrared, where elevated temperatures are deleterious to the laser operation. The gist of the method draws on the law that heat conductivity in gases does not depend on their pressure. The fact lends unique operational flexibility and compactness, desirable for industrial and research purposes.

  8. A high repetition rate laser-heavy water based neutron source

    NASA Astrophysics Data System (ADS)

    Hah, Jungmoo; He, Zhaohan; Nees, John; Krushelnick, Karl; Thomas, Alexander; CenterUltrafast Optical Science Team

    2015-11-01

    Neutrons have numerous applications in diverse areas, such as medicine, security, and material science. For example, sources of MeV neutrons may be used for active interrogation for nuclear security applications. Recently, alternative ways to generate neutron flux have been studied. Among them, ultrashort laser pulse interactions with dense plasma have attracted significant attention as compact, pulse sources of neutrons. To generate neutrons using a laser through fusion reactions, thin solid density targets have been used in a pitcher-catcher arrangement, using deuterated plastic for example. However, the use of solid targets is limited for high-repetition rate operation due to the need to refresh the target for every laser shot. Here, we use a free flowing heavy water target with a high repetition rate (500 Hz) laser without a catcher. From the interaction between a 10 micron scale diameter heavy water stream with the Lambda-cubed laser system at the Univ. of Michigan (12mJ, 800nm, 35fs), deuterons collide with each other resulting in D-D fusion reactions generating 2.45 MeV neutrons. Under best conditions a time average of ~ 105 n/s of neutrons are generated.

  9. Laser absorption, mass ablation rate, and shock heating in direct-drive inertial confinement fusiona)

    NASA Astrophysics Data System (ADS)

    Regan, S. P.; Epstein, R.; Goncharov, V. N.; Igumenshchev, I. V.; Li, D.; Radha, P. B.; Sawada, H.; Seka, W.; Boehly, T. R.; Delettrez, J. A.; Gotchev, O. V.; Knauer, J. P.; Marozas, J. A.; Marshall, F. J.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Sangster, T. C.; Shvarts, D.; Skupsky, S.; Smalyuk, V. A.; Yaakobi, B.; Mancini, R. C.

    2007-05-01

    Direct-drive laser absorption, mass ablation rate, and shock heating are experimentally studied on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] to validate hydrodynamics simulations. High-gain, direct-drive inertial confinement fusion target implosions require accurate predictions of the shell adiabat α (entropy), defined as the pressure in the main fuel layer to the Fermi-degenerate pressure, and the implosion velocity of the shell. The laser pulse shape determines the shell adiabat and the hydrodynamic efficiency determines the implosion velocity. A comprehensive set of measurements tracking the flow of energy from the laser to the target was conducted. Time-resolved measurements of laser absorption in the corona are performed on spherical implosion experiments. The mass ablation rate is inferred from time-resolved Ti K-shell spectroscopic measurements of nonaccelerating, solid CH spherical targets with a buried tracer layer of Ti. Shock heating is diagnosed in planar-CH-foil targets using time-resolved x-ray absorption spectroscopy and noncollective spectrally resolved x-ray scattering. The highly reproducible experimental results achieved with a high level of laser drive uniformity [S. P. Regan et al., J. Opt. Soc. Am. B 22, 998 (2005)] constrain the modeling of direct-drive energy coupling. A detailed comparison of the experimental results and the simulations reveals that a single-value flux limiter in the thermal transport model cannot explain all of the experimental observables. Simulations of laser absorption measurements need a time-dependent flux limiter to match the data. Modeling of both resonance absorption and nonlocal effects in the electron thermal conduction from the critical density to the ablation front are underway to resolve the observed discrepancies.

  10. A method for rapid measurement of laser ablation rate of hard dental tissue

    NASA Astrophysics Data System (ADS)

    Perhavec, T.; Gorkič, A.; Bračun, D.; Diaci, J.

    2009-06-01

    The aim of the study reported here is the development of a new method which allows rapid and accurate in-vitro measurements of three-dimensional (3D) shape of laser ablated craters in hard dental tissues and the determination of crater volume, ablation rate and speed. The method is based on the optical triangulation principle. A laser sheet projector illuminates the surface of a tooth, mounted on a linear translation stage. As the tooth is moved by the translation stage a fast digital video camera captures series of images of the illuminated surface. The images are analyzed to determine a 3D model of the surface. Custom software is employed to analyze the 3D model and to determine the volume of the ablated craters. Key characteristics of the method are discussed as well as some practical aspects pertinent to its use. The method has been employed in an in-vitro study to examine the ablation rates and speeds of the two main laser types currently employed in dentistry, Er:YAG and Er,Cr:YSGG. Ten samples of extracted human molar teeth were irradiated with laser pulse energies from 80 mJ to the maximum available energy (970 mJ with the Er:YAG, and 260 mJ with the Er,Cr:YSGG). About 2000 images of each ablated tooth surface have been acquired along a translation range of 10 mm, taking about 10 s and providing close to 1 million surface measurement points. Volumes of 170 ablated craters (half of them in dentine and the other half in enamel) were determined from this data and used to examine the ablated volume per pulse energy and ablation speed. The results show that, under the same conditions, the ablated volume per pulse energy achieved by the Er:YAG laser exceeds that of the Er,Cr:YSGG laser in almost all regimes for dentine and enamel. The maximum Er:YAG laser ablation speeds (1.2 mm 3/s in dentine and 0.7 mm 3/s in enamel) exceed those obtained by the Er,Cr:YSGG laser (0.39 mm 3/s in dentine and 0.12 mm 3/s in enamel). Since the presented method proves to be easy to

  11. Mechanism initiated by nanoabsorber for UV nanosecond-pulse-driven damage of dielectric coatings.

    PubMed

    Wei, Chaoyang; Shao, Jianda; He, Hongbo; Yi, Kui; Fan, Zhengxiu

    2008-03-01

    A model of plasma formation for UV nanosecond pulse-laser interaction with SiO(2) thin film based on nanoabsorber is proposed. The formalism considered the temperature dependence of band gap. The numerical results show that during the process of nanosecond pulsed-laser interaction with SiO(2) films, foreign inclusion absorbing a fraction of incident radiation heats the surrounding host material through heat conduction causing the decrease of the band gap and making the initial transparent matrix into an absorptive medium around the inclusion. During the remainder pulse, the abosorbing volume of the host material is effectively growed and lead to the formation of the damage craters. We investigated the experimental damage craters and compared with theoretical prediction. The pulselength dependence of damage threshold was also investigated. PMID:18542429

  12. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  13. Full-Field Imaging of Acoustic Motion at Nanosecond Time and Micron Length Scales

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Cottle, David Lynn; Larson III, John D.

    2002-10-01

    A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by employing dynamic holography using photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed capable of operation on the nanosecond time and micron length scales. Both acoustic amplitude and phase are recorded allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies at 800-900 MHz illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric to acoustic coupling and performance of these devices. Images of 256x240 pixels are recorded at 18Hz rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

  14. Hydrogen emission under laser exposure of colloidal solutions of nanoparticles

    NASA Astrophysics Data System (ADS)

    Barmina, E. V.; Simakin, A. V.; Shafeev, G. A.

    2016-07-01

    We report the generation of molecular hydrogen from water by laser irradiation, without any electrodes and photocatalysts. A near infrared pulsed nanosecond laser is used for exposure of colloidal solution of Au nanoparticles suspended in water. Laser exposure of the colloidal solution results in formation of breakdown plasma in liquid and emission of H2. The rate of H2 emission depends critically on the energy of laser pulses. There is a certain threshold in laser fluence in liquid (around 50 J/cm2) below which plasma disappears and H2 emission stops. H2 emission from colloidal solution of Au nanoparticles in ethanol is higher than that from similar water colloid. It is found that formation of plasma and emission of H2 or D2 can be induced by laser exposure of pure liquids, either H2O or D2O, respectively. The results are interpreted as water molecules splitting by direct electron impact from breakdown plasma.

  15. Continuous multigram nanoparticle synthesis by high-power, high-repetition-rate ultrafast laser ablation in liquids.

    PubMed

    Streubel, René; Barcikowski, Stephan; Gökce, Bilal

    2016-04-01

    Utilizing a novel laser system consisting of a 500 W, 10 MHz, 3 ps laser source which is fully synchronized with a polygon scanner reaching scanning speeds up to 500 m/s, we explore the possibilities to increase the productivity of nanoparticle synthesis by laser ablation in liquids. By exploiting the high scanning speed, laser-induced cavitation bubbles are spatially bypassed at high repetition rates and continuous multigram ablation rates up to 4 g/h are demonstrated for platinum, gold, silver, aluminum, copper, and titanium. Furthermore, the applicable, ablation-effective repetition rate is increased by two orders of magnitude. The ultrafast ablation mechanisms are investigated for different laser fluences, repetition rates, interpulse distances, and ablation times, while the resulting trends are successfully described by validating a model developed for ultrafast laser ablation in air to hold in liquids as well. PMID:27192268

  16. Low data rate coherent optical link demonstration using frequency stabilized solid state lasers

    NASA Technical Reports Server (NTRS)

    Chen, CHIEN-C.; Win, Moe Z.; Marshall, William K.; Lesh, James R.

    1991-01-01

    A low data rate laboratory heterodyne link demonstration operating at 1.06 micron using frequency stabilized Nd:YAG lasers was implemented. The data was modulated onto the optical carrier at 100 kbps using binary pulse position modulation. Phase coherent reception was achieved by closing the receiver phase tracking loop around the piezo-electric and temperature-tuned local oscillator laser. Initial frequency acquisition was accomplished by linearly scanning the LO frequency over the uncertainty range while a combined frequency and phase tracking loop searches for a lock indicator signal. The link performance was experimentally evaluated and compared to the theoretical predictions.

  17. Temporal compression of pulses from a 100-KHz-repetiton-rate femtosecond ytterbium laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu; Bryukhanov, V. V.

    2016-08-01

    We report the temporal compression a femtosecond ytterbium laser pulse at a pulse repetition rate of 100 kHz using the effect of nonlinear self-phase modulation in a gas-filled capillary. A 260-fs laser pulse is compressed down to 17 fs with an energy efficiency of 40%. An average radiation power at the compressor output is 2 W. At a second compression stage, the time contrast is increased and the pulse duration is reduced in the process of the second harmonic generation in a KDP crystal. The obtained pulses have a duration of 11 fs at an efficiency of 35%.

  18. Experimental observation of contact mode cantilever dynamics with nanosecond resolution

    NASA Astrophysics Data System (ADS)

    Payton, O. D.; Picco, L.; Champneys, A. R.; Homer, M. E.; Miles, M. J.; Raman, A.

    2011-04-01

    We report the use of a laser Doppler vibrometer to measure the motion of an atomic force microscope contact mode cantilever during continuous line scans of a mica surface. With a sufficiently high density of measurement points the dynamics of the entire cantilever beam, from the apex to the base, can be reconstructed. We demonstrate nanosecond resolution of both rectangular and triangular cantilevers. This technique permits visualization and quantitative measurements of both the normal and lateral tip sample interactions for the first and higher order eigenmodes. The ability to derive quantitative lateral force measurements is of interest to the field of microtribology/nanotribology while the comprehensive understanding of the cantilever's dynamics also aids new cantilever designs and simulations.

  19. Variable Thickness Liquid Crystal Films for High Repetition Rate Laser Applications

    NASA Astrophysics Data System (ADS)

    Poole, Patrick; Willis, Christopher; Cochran, Ginevra; Hanna, Randall; Andereck, C. David; Schumacher, Douglass

    2015-05-01

    The presentation of a clean target or target substrate at high repetition rates is of importance to a number of photoelectron spectroscopy and free electron laser applications, often in high vacuum environments. Additionally, high intensity laser facilities are approaching the 10 Hz shot rate at petawatt powers, but are currently unable to insert targets at these rates. We have developed liquid crystal films to address this need for high rep rate targets while preserving the planar geometry advantageous to many applications. The molecular ordering of liquid crystal is variable with temperature and can be manipulated to form a layered thin film. In this way temperature and volume control can be used to vary film thickness in vacuo and on-demand between 10 nm and over 10 μm. These techniques were previously applied to a single-shot ion acceleration experiment in, where target thickness critically determines the physics of the acceleration. Here we present an automatic film formation device that utilizes a linear sliding rail to form liquid crystal films within the aforementioned range at rates up to 0.1 Hz. The design ensures film formation location within 2 μm RMS, well within the Rayleigh range of even short f-number systems. Details of liquid crystal films and this target formation device will be shown as well as recent experimental data from the Scarlet laser facility at OSU. This work was supported by DARPA through a grant from AMRDEC.

  20. 1  J, 0.5  kHz repetition rate picosecond laser.

    PubMed

    Baumgarten, Cory; Pedicone, Michael; Bravo, Herman; Wang, Hanchen; Yin, Liang; Menoni, Carmen S; Rocca, Jorge J; Reagan, Brendan A

    2016-07-15

    We report the demonstration of a diode-pumped chirped pulse amplification Yb:YAG laser that produces λ=1.03  μm pulses of up to 1.5 J energy compressible to sub-5 ps duration at a repetition rate of 500 Hz (750 W average power). Amplification to high energy takes place in cryogenically cooled Yb:YAG active mirrors designed for kilowatt average power laser operation. This compact laser system will enable new advances in high-average-power ultrashort-pulse lasers and high-repetition-rate tabletop soft x-ray lasers. As a first application, the laser was used to pump a 400 Hz λ=18.9  nm laser. PMID:27420530