WorldWideScience

Sample records for assisted pulsed laser

  1. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Aronne, Antonio [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Bloisi, Francesco, E-mail: bloisi@na.infn.it [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy); Calabria, Raffaela; Califano, Valeria [Istituto Motori – CNR, Naples (Italy); Depero, Laura E. [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Fanelli, Esther [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Federici, Stefania [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Massoli, Patrizio [Istituto Motori – CNR, Naples (Italy); Vicari, Luciano R.M. [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy)

    2015-05-01

    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  2. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    International Nuclear Information System (INIS)

    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence

  3. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    Science.gov (United States)

    Aronne, Antonio; Bloisi, Francesco; Calabria, Raffaela; Califano, Valeria; Depero, Laura E.; Fanelli, Esther; Federici, Stefania; Massoli, Patrizio; Vicari, Luciano R. M.

    2015-05-01

    Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  4. Nanostructured polymer stable glasses via matrix assisted pulsed laser evaporation

    Science.gov (United States)

    Shepard, Kimberly B.

    Amorphous materials, or glasses, which lack a crystalline structure, are technologically ubiquitous with applications including structural components, pharmaceuticals, and electronic devices. Glasses are traditionally formed by rapid cooling from the melt state, where molecules become kinetically trapped into a non-equilibrium configuration. The temperature at which the material transforms from supercooled liquid to glass is the glass transition temperature. The glass transition temperature is the most important property of amorphous materials, as it determines the range of temperatures where they are fabricated, used and stored. Recent technological developments in which glasses are formed by alternative routes, such as physical vapor deposition and matrix assisted pulsed laser evaporation (MAPLE), enable tunability of Tg and related physical properties. High-Tg glasses formed by these techniques are termed "stable glasses" and exhibit a wide range of exceptional properties. This work focuses on the formation and characterization of stable polymer glasses fabricated via MAPLE. Bulk films (>1 microm thick) of glassy polymers fabricated by MAPLE at slow growth rates (polymer glasses. Building on molecular dynamics simulations from the literature on the MAPLE process, we experimentally study the origin of nanostructure in our MAPLE-deposited films. We measure the time-of-flight of MAPLE-deposited material, confirming that the velocity is sufficiently low for intact deposition of polymer nanoglobules. The size distribution of polymer nanoglobules fabricated in short MAPLE depositions provides insight into how nanostructured MAPLE films form. Using our atomic force microscopy-based nanoscale dilatometry technique, we directly probe the nanoscale thermal behavior of individual polymer nanoglobules. We confirm that bulk and nanoscale glasses share many of the same physical behavior: enhanced stability above the glass transition temperature, and ~40% excess volume. We

  5. Surface morphology of thin lysozyme films produced by matrix-assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Purice, Andreea; Schou, Jørgen; Pryds, Nini;

    2007-01-01

    Thin films of the protein, lysozyme, have been deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. Frozen targets of 0.3-1.0 wt.% lysozyme dissolved in ultrapure water were irradiated by laser light at 355 mn with a fluence of 2 J/cm(2). The surface quality of the thin...

  6. Production of active lysozyme films by matrix assisted pulsed laser evaporation at 355 nm

    DEFF Research Database (Denmark)

    Purice, Andreea; Schou, Jørgen; Kingshott, P.;

    2007-01-01

    Thin lysozyme films have been produced in a dry environment by MAPLE (matrix assisted pulsed laser evaporation) from a water ice matrix irradiated by laser light at 355 nm above the absorption threshold of the protein. A significant part of the lysozyme molecules are transferred to the film without...

  7. Processing of C60 thin films by Matrix-Assisted Pulsed Laser Evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Fæster, Søren

    2011-01-01

    Thin films of fullerenes (C60) were deposited onto silicon using matrix-assisted pulsed laser evaporation (MAPLE). The deposition was carried out from a frozen homogeneous dilute solution of C60 in anisole (0.67 wt%), and over a broad range of laser fluences, from 0.15 J/cm2 up to 3.9 J/cm2. MAPL...

  8. Functional polyethylene glycol derivatives nanostructured thin films synthesized by matrix-assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Cristescu, R., E-mail: rodica.cristescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, Bucharest-Magurele (Romania); Popescu, C.; Popescu, A.; Grigorescu, S.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, Bucharest-Magurele (Romania); Mihaiescu, D. [University of Agriculture Sciences and Veterinary Medicine, 59 Marasti, Bucharest (Romania); Gittard, S.D.; Narayan, R.J. [Biomedical Engineering, University of North Carolina, Chapel Hill, NC (United States); Buruiana, T. [Petru Poni Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda, 41A, Iasi (Romania); Stamatin, I. [University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele (Romania); Chrisey, D.B. [Rensselaer Polytechnic Institute, Department of Materials Science and Engineering, Troy, NY (United States)

    2009-09-30

    We report the thin film deposition by matrix-assisted pulsed laser evaporation (MAPLE) of a polymer conjugate with an hydrophilic sequence between metronidazole molecules that was covalently attached to both oligomer ends of carboxylate poly(ethylene glycol) (PEG 1.5-metronidazole). A pulsed KrF* excimer laser was used to deposit the drug-polymer composite films. Fourier transform infrared spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical properties similar to the starting materials. The dependence of the surface morphology on incident laser fluence is given.

  9. Functional polyethylene glycol derivatives nanostructured thin films synthesized by matrix-assisted pulsed laser evaporation

    International Nuclear Information System (INIS)

    We report the thin film deposition by matrix-assisted pulsed laser evaporation (MAPLE) of a polymer conjugate with an hydrophilic sequence between metronidazole molecules that was covalently attached to both oligomer ends of carboxylate poly(ethylene glycol) (PEG 1.5-metronidazole). A pulsed KrF* excimer laser was used to deposit the drug-polymer composite films. Fourier transform infrared spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical properties similar to the starting materials. The dependence of the surface morphology on incident laser fluence is given.

  10. Characterization of lysozyme films produced by matrix assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Purice, Andreea; Schou, Jørgen; Kingshott, Peter;

    2007-01-01

    Thin lysozyme films of thickness up to more than 100 nm have been produced in a dry environment by MAPLE (matrix assisted pulsed laser evaporation) from a water ice matrix. Analysis of the films demonstrates that a significant part of the lysozyme molecules is transferred to the substrate without...... that from a water ice matrix. (C) 2007 Elsevier B.V. All rights reserved....

  11. Long-pulsed dye laser versus long-pulsed dye laser-assisted photodynamic therapy for acne vulgaris: A randomized controlled trial

    DEFF Research Database (Denmark)

    Haedersdal, M.; Togsverd, K.; Wiegell, S.R.;

    2008-01-01

    Background: Long-pulsed dye laser (LPDL)-assisted photodynamic therapy has been suggested to be superior to laser alone for acne vulgaris but no evidence is available. Objective: To evaluate the efficacy and safety of LPDL alone versus LPDL in photodynamic therapy with methylaminolevulinic acid...

  12. Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

    Science.gov (United States)

    György, E.; Pérez del Pino, A.; Sauthier, G.; Figueras, A.

    2009-12-01

    Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ =248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well as target preparation procedure.

  13. UV and RIR matrix assisted pulsed laser deposition of organic MEH-PPV films

    DEFF Research Database (Denmark)

    Christensen, Bo Toftmann; Papantonalis, M.R.; Auyeung, R.C.Y.;

    2004-01-01

    A comparative study of thin film production based on gentle laser-ablation techniques has been carried out with the luminescent polymer poly [2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene]. Using a free-electron laser films were made by resonant infrared pulsed laser deposition (RIR......-PLD). For the first time resonant infrared matrix assisted pulsed laser evaporation (RIR-MAPLE) was successfully demonstrated on a luminescent polymer system. In addition to this, an excimer laser has been used for UV-MAPLE depositions at 193 and 248-nm irradiation. Films deposited onto NaCl and quartz substrates...... were analyzed by Fourier transform infrared spectroscopy, UV-visible absorbance and photoluminescence. Photoluminescent material was deposited by RIR-MAPLE and 248-nm MAPLE, while the RIR-PLD and 193-nm-MAPLE depositions displayed the smoothest surfaces but did not show photoluminescence. (C) 2003...

  14. Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization

    Institute of Scientific and Technical Information of China (English)

    LI Guo-Fu; YU Hai-Jun; DUO Li-Ping; JIN Yu-Qi; WANG Jian; SANG Feng-Ting; FANG Ben-Jie; WANG De-Zhen

    2009-01-01

    The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2-2.9 kPa and single pulse energy is up to 180m J, the corresponding specific output energy is 1.0 J/L.

  15. Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

    Science.gov (United States)

    Greer, James A.

    2011-11-01

    Since the development of the Matrix Assisted Pulsed Laser Evaporation (MAPLE) process by the Naval Research Laboratory (NRL) in the late 1990s, MAPLE has become an active area of research for the deposition of a variety of polymer, biological, and organic thin films. As is often the case with advancements in thin-film deposition techniques new technology sometimes evolves by making minor or major adjustments to existing deposition process equipment and techniques. This is usually the quickest and least expensive way to try out new ideas and to "push the envelope" in order to obtain new and unique scientific results as quickly as possible. This process of "tweaking" current equipment usually works to some degree, but once the new process is further refined overall designs for a new deposition tool based on the critical attributes of the new process typically help capitalize more fully on the all the salient features of the new and improved process. This certainly has been true for the MAPLE process. In fact the first MAPLE experiments the polymer/solvent matrix was mixed and poured into a copper holder held at LN2 temperature on a laboratory counter top. The holder was then quickly placed onto a LN2 cooled reservoir in a vacuum deposition chamber and placed in a vertical position on a LN2 cooled stage and pumped down as quickly as possible. If the sample was not placed into the chamber quickly enough the frozen matrix would melt and drip into the bottom of the chamber onto the chambers main gate valve making a bit of a mess. However, skilled and motivated scientists usually worked quickly enough to make this process work most of the time. The initial results from these experiments were encouraging and led to several publications which sparked considerable interest in this newly developed technique Clearly this approach provided the vision that MAPLE was a viable deposition process, but the equipment was not optimal for conducting MAPLE experiments on a regular basis

  16. Growth of thin fullerene films by matrix assisted pulsed laser evaporation

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Fæster, Søren

    C60 fullerene thin films of average thickness of more than 100 nm on silicon substrates can be produced in vacuum by matrix-assisted pulsed laser evaporation (MAPLE). A 355 nm Nd:YAG laser was directed onto a frozen target of anisole with a concentration of 0.67 wt% C60. At laser fluences below 1.......5 J/cm2 the dominant fraction of the film molecules are C60 transferred to the substrate without any fragmentation. For high fluences high-resolution SEM images of MAPLE deposited films reveal large circular features on the surface with high amount of material concentrated at edges. These features......, observed over a wide range of laser fluences, are caused by ejection of large matrix-fullerene liquid droplets into the gas-phase and subsequent deposition. At similar laser energies, but using an unfocused laser beam, MAPLE favours evaporation of matrix and organic molecules, resulting in films...

  17. Matrix Assisted Pulsed Laser Evaporation for growth of fullerene thin films

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Fæster Nielsen, Søren

    C60 fullerene thin films of average thickness of more than 100 nm can be produced in vacuum by matrix-assisted pulsed laser evaporation (MAPLE). A 355 nm Nd:YAG laser was directed onto a frozen target of anisole with a concentration of 0.67 wt% C60. At laser fluences below 1.5 J/cm2, a dominant...... fraction of the film molecules are C60 transferred to the substrate without any fragmentation. Highresolution SEM images of MAPLE deposited films reveal large circular droplets on the surface with high amount of material concentrated at edges (Fig. 1A). These features, observed over a wide range of laser...... fluences, are caused by ejection of large matrix-fullerene liquid droplets into the gas-phase and subsequent deposition. At similar laser energies, but using an unfocused laser beam, MAPLE favours evaporation of matrix and organic molecules, resulting in production of films with smooth surfaces and minimal...

  18. Growth of thin films of low molecular weight proteins by matrix assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Matei, Andreea; Schou, Jørgen; Constantinescu, C.;

    2011-01-01

    Thin films of lysozyme and myoglobin grown by matrix assisted pulsed laser evaporation (MAPLE) from a water ice matrix have been investigated. The deposition rate of these two low molecular weight proteins (lysozyme: 14307 amu and myoglobin: 17083 amu) exhibits a maximum of about 1–2 ng/cm2 per...... pulse at a fluence of 1–2 J/cm2 and decreases slowly with increasing fluence. This rate is presumably determined by the matrix rather by the proteins. A significant fraction of the proteins are intact in the film as determined by MALDI (Matrix assisted laser desorption ionization) spectrometry....... The results for lysozyme demonstrate that the fragmentation rate of the proteins during the MAPLE process is not influenced by the pH of the water solution prior to freezing....

  19. Matrix-assisted pulsed laser evaporation of polyimide thin films and the XPS study

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Compared with the traditional thin film techniques, the matrix-assisted pulsed laser evaporation (MAPLE) technique has many advantages in the deposition of polymer and organic thin films. It has a wide range of applications in many fields, such as non-linear optics, luminescent devices, electronics, various sensors. We have successfully deposited polyimide thin films by using the MAPLE technique. These films were characterized with XPS. The XPS spectra showed that the single-photon effect is ob-vious at low laser fluence and the chemical bonds will be broken, resulting in decomposition of the films. Contrarily, the single-photon effect will decrease and the multi-photon effect and the photothermal effect will increase at high laser fluence, resulting in the protection of the structure of the polyimide thin films and the obvious decrease in decomposition. High laser fluence is more suitable for the deposition of polymer and organic thin films than low laser fluence.

  20. Radio-frequency assisted pulsed laser deposition of nanostructured WOx films

    International Nuclear Information System (INIS)

    The synthesis of tungsten oxide films with large surface area is promising for gas sensing applications. Thin WOx films were obtained by radio-frequency assisted pulsed laser deposition (RF-PLD). A tungsten target was ablated at 700 and 900 Pa in reactive oxygen, or in a 50% mixed oxygen-helium atmosphere at the same total pressure values. Corning glass was used as substrate, at temperatures including 673, 773 and 873 K. Other deposition parameters such as laser fluence (4.5 J cm-2), laser wavelength (355 nm), radiofrequency power (150 W), target to substrate distance (4 cm), laser spot area (0.7 mm2), and number of laser shots (12,000) were kept fixed. The sensitivity on the deposition conditions of morphology, nanostructure, bond coordination, and roughness of the obtained films were analyzed by scanning and transmission electron microscopy, micro-Raman spectroscopy, and atomic force microscopy.

  1. Gravity-assisted pulsed laser ablation for fabrication of compositional gradient thin film

    International Nuclear Information System (INIS)

    A compositional gradient thin film of Fe/Si was fabricated by gravity-assisted pulsed laser ablation under a gravity field of 5.3 × 104 m/s2. Systematic experiments were conducted by varying the values of several parameters including the gravity, distance between the target and the substrate, and laser fluence. The atomic fraction of Fe was measured by scanning electron microscopy/energy dispersive X-ray spectroscopy. We found that the atomic fraction of Fe increases along the gravity direction, i.e., it exhibits an apparent spatial gradient. We also found the optimal laser fluence at which a thin film having the largest possible spatial compositional gradient is obtained. It is shown that the surface energy density on the substrate surface is the key parameter to control the compositional distribution. The relatively high laser fluence as well as the very narrow space between the target and the substrate are found to be essential to sputter the film material. A plausible model is presented to explain the experimental data. - Highlights: • Gravity-assisted pulsed laser ablation method (GAPLA) is established. • A compositional gradient thin film is fabricated by GAPLA under 5.3 × 104 m/s2 condition. • The surface energy density is an important parameter for GAPLA. • A compositional gradient is generated by selective reevaporation and not diffusion

  2. Development of a high magnetic field assisted pulsed laser deposition system

    Science.gov (United States)

    Zhang, Kejun; Dai, Jianming; Wu, Wenbin; Zhang, Peng; Zuo, Xuzhong; Zhou, Shu; Zhu, Xuebin; Sheng, Zhigao; Liang, Changhao; Sun, Yuping

    2015-09-01

    A high magnetic field assisted pulsed laser deposition (HMF-PLD) system has been developed to in situ grow thin films in a high magnetic field up to 10 T. In this system, a specially designed PLD cylindrical vacuum chamber is horizontally located in the bore configuration of a superconducting magnet with a bore diameter of 200 mm. To adjust the focused pulsed laser into the target in such a narrow PLD vacuum chamber, an ingeniously built-in laser leading-in chamber is employed, including a laser mirror with a reflection angle of 65° and a damage threshold up to 3.4 J/cm2. A laser alignment system consisting of a built-in video-unit leading-in chamber and a low-energy alignment laser is applied to monitor and align the pulsed laser propagation in the PLD vacuum chamber. We have grown La0.7Sr0.3MnO3 (LSMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates by HMF-PLD. The results show that the nanostructures of the LSMO films can be tuned from an epitaxially continuous film structure without field to a vertically aligned nanorod structure with an applied high magnetic field above 5 T, and the dimension size of the nanorods can be tuned by the strength of the magnetic field. The associated magnetic anisotropy is found to be highly dependent on the nanorod structures. We show how the HMF-PLD provides an effective route toward tuning the nanostructures and the physical properties of functional thin films, giving it an important role in development of nanodevices and their application.

  3. Layered double hydroxides/polymer thin films grown by matrix assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Birjega, R.; Matei, A.; Mitu, B.; Ionita, M.D.; Filipescu, M.; Stokker-Cheregi, F.; Luculescu, C.; Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest–Magurele (Romania); Zavoianu, R.; Pavel, O.D. [University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina Elisabeta Bd., Bucharest (Romania); Corobea, M.C. [National R. and S. Institute for Chemistry and Petrochemistry, ICECHIM, 202 Splaiul Independentei Str., CP-35-274, 060021, Bucharest (Romania)

    2013-09-30

    Due to their highly tunable properties, layered double hydroxides (LDHs) are an emerging class of the favorably layered crystals used for the preparation of multifunctional polymer/layered crystal nanocomposites. In contrast to cationic clay materials with negatively charge layers, LDHs are the only host lattices with positively charged layers (brucite-like), with interlayer exchangeable anions and intercalated water. In this work, the deposition of thin films of Mg and Al based LDH/polymers nanocomposites by laser techniques is reported. Matrix assisted pulsed laser evaporation was the method used for thin films deposition. The Mg–Al LDHs capability to act as a host for polymers and to produce hybrid LDH/polymer films has been investigated. Polyethylene glycol with different molecular mass compositions and ethylene glycol were used as polymers. The structure and surface morphology of the deposited LDH/polymers films were examined by X-ray diffraction, Fourier transform infra-red spectroscopy, atomic force microscopy and scanning electron microscopy. - Highlights: • Hybrid composites deposited by matrix assisted pulsed laser evaporation (MAPLE). • Mg–Al layered double hydroxides (LDH) and polyethylene glycol (PEG) are used. • Mixtures of PEG1450 and LDH were deposited by MAPLE. • Deposited thin films preserve the properties of the starting material. • The film wettability can be controlled by the amount of PEG.

  4. High fluence deposition of polyethylene glycol films at 1064 nm by matrix assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Purice, Andreea; Schou, Jørgen; Kingshott, P.;

    2007-01-01

    Matrix assisted pulsed laser evaporation (MAPLE) has been applied for deposition of thin polyethylene glycol (PEG) films with infrared laser light at 1064 nm. We have irradiated frozen targets (of 1 wt.% PEG dissolved in water) and measured the deposition rate in situ with a quartz crystal 2...... microbalance. The laser fluence needed to produce PEG films turned out to be unexpectedly high with a threshold of 9 J/cm(2) and the deposition rate was much lower than that with laser light at 355 nm. Results from matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI...

  5. Functional porphyrin thin films deposited by matrix assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Cristescu, R., E-mail: rodica.cristescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Atomistilor 409, Bucharest-Magurele (Romania); Popescu, C.; Popescu, A.C.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Atomistilor 409, Bucharest-Magurele (Romania); Ciucu, A.A. [Univeristy of Bucharest, Chemistry Department, Bucharest (Romania); Andronie, A.; Iordache, S.; Stamatin, I. [University of Bucharest, 3 Nano-SAE Research Center, P.O. Box MG-38, Bucharest-Magurele (Romania); Fagadar-Cosma, E. [Institute of Chemistry Timisoara of Romanian Academy, Department of Organic Chemistry, 300223 Timisoara (Romania); Chrisey, D.B. [Rensselaer Polytechnic Institute, School of Engineering, Department of Materials Science and Engineering, Troy 12180-3590, NY (United States)

    2010-05-25

    We report the first successful deposition of functionalized and nanostructured Zn(II)- and Co(II)-metalloporphyrin thin films by matrix assisted pulsed laser evaporation onto silicon wafers, quartz plates and screen-printed electrodes. The deposited nanostructures have been characterized by Raman spectrometry and cyclic voltammetry. The novelty of our contribution consists of the evaluation of the sensitivity of the MAPLE-deposited Zn(II)- and Co(II)-metalloporphyrin thin films on screen-printed carbon nanotube electrodes when challenged with dopamine.

  6. Growth of thin fullerene films by Matrix Assisted Pulsed Laser Evaporation

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Fæster, Søren

    of the matrix material, anisole, with a concentration of 0.67 wt% C60. At laser fluences below 1.5 J/cm2, a dominant fraction of the film molecules are C60 transferred to the substrate without any fragmentation. High-resolution SEM images of MAPLE deposited films reveal large circular features on the surface...... bound carbon molecule with a well-defined mass (M = 720 amu) and therefore a good, organic test molecule. C60 fullerene thin films of average thickness of more than 100 nm was produced in vacuum by matrix-assisted pulsed laser evaporation (MAPLE). A 355 nm Nd:YAG laser was di-rected onto a frozen target...... with high amount of material concentrated at edges. These features, observed over a wide range of laser flu-ences, are caused by ejection of large matrix-fullerene liquid droplets into the gas-phase and subsequent deposition. At similar laser energies, but using an unfocused laser beam, MAPLE favours...

  7. Laser-assisted electron scattering in strong-field ionization of dense water vapor by ultrashort laser pulses

    International Nuclear Information System (INIS)

    We report on strong-field ionization of dense water gas in a short infrared laser pulse. By employing a unique combination of photoelectron spectroscopy with a liquid micro-jet technique, we observe how the character of electron emission at high kinetic energies changes with the increase of the medium density. This change is associated with the process of laser-assisted electron scattering (LAES) on neighboring particles, which becomes a dominant mechanism of hot electron emission at higher medium densities. The manifestation of this mechanism is found to require densities that are orders of magnitude lower than those considered for heating the laser-generated plasmas via the LAES process. The experimental results are supported by simulations of the LAES yield with the use of the Kroll–Watson theory. (paper)

  8. Pulsed Chemical Oxygen Iodine Lasers Excited by Pulse Gas Discharge with the Assistance of Surface Sliding Discharge Pre-ionization

    International Nuclear Information System (INIS)

    Continuous-wave chemical oxygen-iodine lasers (COILs) can be operated in a pulsed operation mode to obtain a higher peak power. The key point is to obtain a uniform and stable glow discharge in the mixture of singlet delta oxygen and iodide. We propose using an electrode system with the assistance of surface sliding pre-ionization to solve the problem of the stable glow discharge with a large aperture. The pre-ionization unit is symmetrically fixed on the plane of the cathode surface. A uniform and stable glow discharge is obtained in a mixture of iodide (such as CH3I) and nitrogen at the specific deposition energy of 4.5 J/L, pressure of 1.99–3.32 kPa, aperture size of 11 cm × 10 cm. The electrode system is applied in a pulsed COIL. Laser energy up to 4.4 J is obtained and the specific energy output is 2 J/L. (fundamental areas of phenomenology(including applications))

  9. Protein-resistant polymer coatings obtained by matrix assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Rusen, L. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, 077125, Magurele, Bucharest (Romania); Mustaciosu, C. [Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH, Magurele, Bucharest (Romania); Mitu, B.; Filipescu, M.; Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, 077125, Magurele, Bucharest (Romania); Dinca, V., E-mail: dinali@nipne.ro [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, 077125, Magurele, Bucharest (Romania)

    2013-08-01

    Adsorption of proteins and polysaccharides is known to facilitate microbial attachment and subsequent formation of biofilm on surfaces that ultimately results in its biofouling. Therefore, protein repellent modified surfaces are necessary to block the irreversible attachment of microorganisms. Within this context, the feasibility of using the Poly(ethylene glycol)-block-poly(ε-caprolactone) methyl ether (PEG-block-PCL Me) copolymer as potential protein-resistant coating was explored in this work. The films were deposited using Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique that allows good control of composition, thickness and homogeneity. The chemical and morphological characteristics of the films were examined using Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements and Atomic Force Microscopy (AFM). The FTIR data demonstrates that the functional groups in the MAPLE-deposited films remain intact, especially for fluences below 0.5 J cm{sup −2}. Optical Microscopy and AFM images show that the homogeneity and the roughness of the coatings are related to both laser parameters (fluence, number of pulses) and target composition. Protein adsorption tests were performed on the PEG-block-PCL Me copolymer coated glass and on bare glass surface as a control. The results show that the presence of copolymer as coating significantly reduces the adsorption of proteins.

  10. Nanoparticle Thin Films for Gas Sensors Prepared by Matrix Assisted Pulsed Laser Evaporation

    Directory of Open Access Journals (Sweden)

    Roberto Rella

    2009-04-01

    Full Text Available The matrix assisted pulsed laser evaporation (MAPLE technique has been used for the deposition of metal dioxide (TiO2, SnO2 nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al2O3 substrates. A rather uniform distribution of TiO2 nanoparticles with an average size of about 10 nm and of SnO2 nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit towards ethanol and acetone are presented.

  11. Electrical properties of DLC- (n, p)-Si heterojunctions fabricated by ion-assisted plasma-enhanced deposition and pulsed laser deposition methods

    Science.gov (United States)

    Panosyan, Zhosef R.; Voskanyan, Serjik S.; Yengibaryan, Yerem V.; Avjyan, Karapet E.; Khachatryan, Ashot M.; Matevosyan, Lenrik A.

    2010-10-01

    Electrical characteristics of DLC- (n, p)-Si heterojunctions fabricated by ion-assisted plasma-enhanced deposition and pulsed laser deposition methods were investigated. The mechanisms of carrier flow across the fabricated junctions were analyzed. Keywords: ion-assisted plasma-enhanced deposition, pulsed laser deposition, DLC- (n, p)-Si heterojunctions, currentvoltage & capacitance- voltage characteristics.

  12. Functionalized porphyrin conjugate thin films deposited by matrix assisted pulsed laser evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Iordache, S. [University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele (Romania); Cristescu, R., E-mail: rodica.cristescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele (Romania); Popescu, A.C.; Popescu, C.E.; Dorcioman, G.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele (Romania); Ciucu, A.A. [University of Bucharest, Faculty of Chemistry, Bucharest (Romania); Balan, A.; Stamatin, I. [University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele (Romania); Fagadar-Cosma, E. [Institute of Chemistry Timisoara of Romanian Academy, M. Viteazul Ave. 24, 300223-Timisoara (Romania); Chrisey, D.B. [Tulane University, Departments of Physics and Biomedical Engineering, New Orleans, LA 70118 (United States)

    2013-08-01

    We report on the deposition of nanostructured porphyrin-base, 5(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin thin films by matrix assisted pulsed laser evaporation onto silicon substrates with screen-printed electrodes. AFM investigations have shown that at 400 mJ/cm{sup 2} fluence a topographical transition takes place from the platelet-like stacking porphyrin-based nanostructures in a perpendicular arrangement to a quasi-parallel one both relative to the substrate surface. Raman spectroscopy has shown that the chemical structure of the deposited thin films is preserved for fluences within the range of 200–300 mJ/cm{sup 2}. Cyclic voltammograms have demonstrated that the free porphyrin is appropriate as a single mediator for glucose in a specific case of screen-printed electrodes, suggesting potential for designing a new class of biosensors.

  13. The minimum amount of "matrix " needed for matrix-assisted pulsed laser deposition of biomolecules

    DEFF Research Database (Denmark)

    Tabetah, Marshall; Matei, Andreea; Constantinescu, Catalin;

    2014-01-01

    The ability of matrix-assisted pulsed laser evaporation (MAPLE) technique to transfer and deposit high-quality thin organic, bioorganic, and composite films with minimum chemical modification of the target material has been utilized in numerous applications. One of the outstanding problems in MAPLE...... film deposition, however, is the presence of residual solvent (matrix) codeposited with the polymer material and adversely affecting the quality of the deposited films. In this work, we investigate the possibility of alleviating this problem by reducing the amount of matrix in the target. A series...... of coarse-grained molecular dynamics simulations are performed for a model lysozyme-water system, where the water serves the role of volatile "matrix" that drives the ejection of the biomolecules. The simulations reveal a remarkable ability of a small (5-10 wt %) amount of matrix to cause the ejection...

  14. Study of titania nanorod films deposited by matrix-assisted pulsed laser evaporation as a function of laser fluence

    Science.gov (United States)

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

    2011-11-01

    Chemically synthesized brookite titanium dioxide (TiO2) nanorods with average diameter and length dimensions of 3-4 nm and 35-50 nm, respectively, were deposited by the matrix-assisted pulsed laser evaporation technique. A toluene nanorod solution was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser ( λ=248 nm, τ=20 ns) at the repetition rate of 10 Hz, at different fluences (25 to 350 mJ/cm2). The deposited films were structurally characterized by high-resolution scanning and transmission electron microscopy. single-crystal Si wafers and carbon-coated Cu grids were used as substrates. Structural analyses evidenced the occurrence of brookite-phase crystalline nanospheres coexisting with individually distinguishable TiO2 nanorods in the films deposited at fluences varying from 50 to 350 mJ/cm2. Nanostructured TiO2 films comprising only nanorods were deposited by lowering the laser fluence to 25 mJ/cm2. The observed shape and phase transitions of the nanorods are discussed taking into account the laser-induced heating effects, reduced melting temperature and size-dependent thermodynamic stability of nanoscale TiO2.

  15. Biomimetic nanocrystalline apatite coatings synthesized by Matrix Assisted Pulsed Laser Evaporation for medical applications

    Energy Technology Data Exchange (ETDEWEB)

    Visan, A. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov (Romania); Grossin, D. [CIRIMAT – Carnot Institute, University of Toulouse, ENSIACET, 4 Allée Emile Monso, 31030 Toulouse Cedex 4 (France); Stefan, N.; Duta, L.; Miroiu, F.M. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov (Romania); Stan, G.E. [National Institute of Materials Physics, RO-077125, Magurele-Ilfov (Romania); Sopronyi, M.; Luculescu, C. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov (Romania); Freche, M.; Marsan, O.; Charvilat, C. [CIRIMAT – Carnot Institute, University of Toulouse, ENSIACET, 4 Allée Emile Monso, 31030 Toulouse Cedex 4 (France); Ciuca, S. [Politehnica University of Bucharest, Faculty of Materials Science and Engineering, Bucharest (Romania); Mihailescu, I.N., E-mail: ion.mihailescu@inflpr.ro [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov (Romania)

    2014-02-15

    Highlights: • We report the deposition by MAPLE of biomimetic apatite coatings on Ti substrates. • This is the first report of MAPLE deposition of hydrated biomimetic apatite films. • Biomimetic apatite powder was synthesized by double decomposition process. • Non-apatitic environments, of high surface reactivity, are preserved post-deposition. • We got the MAPLE complete transfer as thin film of a hydrated, delicate material. -- Abstract: We report the deposition by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique of biomimetic nanocrystalline apatite coatings on titanium substrates, with potential application in tissue engineering. The targets were prepared from metastable, nanometric, poorly crystalline apatite powders, analogous to mineral bone, synthesized through a biomimetic approach by double decomposition process. For the deposition of thin films, a KrF* excimer laser source was used (λ = 248 nm, τ{sub FWHM} ≤ 25 ns). The analyses revealed the existence, in synthesized powders, of labile non-apatitic mineral ions, associated with the formation of a hydrated layer at the surface of the nanocrystals. The thin film analyses showed that the structural and chemical nature of the nanocrystalline apatite was prevalently preserved. The perpetuation of the non-apatitic environments was also observed. The study indicated that MAPLE is a suitable technique for the congruent transfer of a delicate material, such as the biomimetic hydrated nanohydroxyapatite.

  16. Matrix assisted pulsed laser evaporation of pullulan tailor-made biomaterial thin films for controlled drug delivery systems

    International Nuclear Information System (INIS)

    We report the first successful deposition of cinnamate-pullulan polysaccharide thin films by Matrix Assisted Pulsed Laser Evaporation (MAPLE). Thin film depositions were performed in vacuum using a KrF* excimer laser source (λ = 248 nm, τ ∼ 20 ns) operated at a repetition rate of 10 Hz. The dependence on incident laser fluence of the induced surface morphology is studied. We demonstrated by Raman spectroscopy that our MAPLE-deposited cinnamate-pullulan thin films are composed of starting materials preserving their chemical structures, with no impurities

  17. Matrix-Assisted Pulsed Laser Thin Film Deposition by Using Nd:YAG Laser

    Directory of Open Access Journals (Sweden)

    Francesco Bloisi

    2012-01-01

    In this paper, the MAPLE technique is described in details, together with a survey of current and possible future applications for both organic and biomaterial deposition taking into account the advantages of using an Nd:YAG laser. Beside other results, we have experimental confirmation that MAPLE applications are not limited to transparent molecules highly soluble in light absorbing solvent, thus allowing deposition of poorly soluble light absorbing molecules suspended in a light transparent liquid.

  18. Combinatorial Matrix Assisted Pulsed Laser Evaporation of a biodegradable polymer and fibronectin for protein immobilization and controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Sima, F., E-mail: felix.sima@inflpr.ro [Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, Măgurele (Romania); Axente, E.; Iordache, I.; Luculescu, C. [Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, Măgurele (Romania); Gallet, O. [ERRMECE, Cergy-Pontoise University, Cergy-Pontoise (France); Anselme, K. [IS2M, CNRS UMR7361, Haute-Alsace University, Mulhouse (France); Mihailescu, I.N. [Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, Măgurele (Romania)

    2014-07-01

    Defined protein quantities were embedded in situ in a biodegradable polymer coating during simultaneous laser vaporization of two targets. Fibronectin (FN) and poly-DL-lactide (PDLLA) were transferred and immobilized concomitantly by Combinatorial Matrix Assisted Pulsed Laser Evaporation onto solid substrates. The film surface with gradient of composition was characterized by optical, scanning electron microscopy and profilometry. Micrometric FN packages were visualized in the polymeric matrix by confocal microscopy. The composition of FN was investigated by FTIR and μFTIR analyses in a polymeric matrix with different thickness.

  19. Combinatorial matrix-assisted pulsed laser evaporation: Single-step synthesis of biopolymer compositional gradient thin film assemblies

    Science.gov (United States)

    Sima, F.; Axente, E.; Sima, L. E.; Tuyel, U.; Eroglu, M. S.; Serban, N.; Ristoscu, C.; Petrescu, S. M.; Toksoy Oner, E.; Mihailescu, I. N.

    2012-12-01

    We introduce a combinatorial approach for the fabrication of organic biopolymer thin films. Structures with compositional gradient are obtained by simultaneous laser vaporization of two distinct targets. Matrix-assisted pulsed laser evaporation deposition method was applied to obtain a compositional library of levan and oxidized levan in form of thin film. The gradient of film composition and structure was demonstrated by infrared spectroscopy while in vitro cell culture assays illustrated characteristic responses of cells to specific surface regions. The method can rapidly generate discrete areas of organic film compositions with improved properties than starting materials.

  20. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers.

    Science.gov (United States)

    González-Rubio, Guillermo; Guerrero-Martínez, Andrés; Liz-Marzán, Luis M

    2016-04-19

    The vast majority of the outstanding applications of metal nanoparticles (NPs) developed during the last two decades have arisen from their unique optical properties. Within this context, rational synthesis and assembly of gold NPs have been the main research focus, aiming at the design of nanoplasmonic devices with tailored optical functionalities. The progress made in this field is thus to be ascribed to the understanding of the origin of the interaction between light and such gold nanostructures, the dynamics of which have been thoroughly investigated with significant contributions from short and ultrashort pulse laser technologies. We focus this Account on the potential of pulse lasers to provide new fundamental insights into the electron dynamics involved in the interaction of light with the free conduction electrons of Au NPs, that is, localized surface plasmon resonances (LSPRs). The excitation of LSPRs with a femtosecond pulse laser is followed by thermalization of the Au NP electrons and the subsequent relaxation of the nanocrystal lattice and the surrounding environment, which generally results in surface melting. By contrast, nanosecond irradiation usually induces AuNP fragmentation and uncontrolled melting due to overlapping excitation and relaxation phenomena. These concepts have been exploited toward the preparation of highly monodisperse gold nanospheres via pulse laser irradiation of polyhedral nanocrystal colloids, or in the fabrication of nanostructures with "written-in" optical properties. The applicability of pulsed coherent light has been extended toward the direct synthesis and manipulation of Au NPs. Through ablation of a gold target in a liquid with pulse lasers, spherical Au NPs can be synthesized with no need of stabilizing ligands, which is a great advantage in terms of reducing toxicity, rendering these NPs particularly suitable for medical applications. In addition, femtosecond laser irradiation has been proven a unique tool for the

  1. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers.

    Science.gov (United States)

    González-Rubio, Guillermo; Guerrero-Martínez, Andrés; Liz-Marzán, Luis M

    2016-04-19

    The vast majority of the outstanding applications of metal nanoparticles (NPs) developed during the last two decades have arisen from their unique optical properties. Within this context, rational synthesis and assembly of gold NPs have been the main research focus, aiming at the design of nanoplasmonic devices with tailored optical functionalities. The progress made in this field is thus to be ascribed to the understanding of the origin of the interaction between light and such gold nanostructures, the dynamics of which have been thoroughly investigated with significant contributions from short and ultrashort pulse laser technologies. We focus this Account on the potential of pulse lasers to provide new fundamental insights into the electron dynamics involved in the interaction of light with the free conduction electrons of Au NPs, that is, localized surface plasmon resonances (LSPRs). The excitation of LSPRs with a femtosecond pulse laser is followed by thermalization of the Au NP electrons and the subsequent relaxation of the nanocrystal lattice and the surrounding environment, which generally results in surface melting. By contrast, nanosecond irradiation usually induces AuNP fragmentation and uncontrolled melting due to overlapping excitation and relaxation phenomena. These concepts have been exploited toward the preparation of highly monodisperse gold nanospheres via pulse laser irradiation of polyhedral nanocrystal colloids, or in the fabrication of nanostructures with "written-in" optical properties. The applicability of pulsed coherent light has been extended toward the direct synthesis and manipulation of Au NPs. Through ablation of a gold target in a liquid with pulse lasers, spherical Au NPs can be synthesized with no need of stabilizing ligands, which is a great advantage in terms of reducing toxicity, rendering these NPs particularly suitable for medical applications. In addition, femtosecond laser irradiation has been proven a unique tool for the

  2. Surface morphology of polyethylene glycol films produced by matrix-assisted pulsed laser evaporation (MAPLE): Dependence on substrate temperature

    DEFF Research Database (Denmark)

    Rodrigo, K.; Czuba, P.; Toftmann, B.;

    2006-01-01

    The dependence of the surface morphology on the substrate temperature during film deposition was investigated for polyethylene glycol (PEG) films by matrix-assisted pulsed laser evaporation (MAPLE). The surface structure was studied with a combined technique of optical imaging and AFM measurements....... There was a clear difference between the films produced below and above the melting point of PEG. For temperatures above the melting point, the polymer material was distributed non-uniformly over the substrate with growths areas, where cluster-like structures merge into large islands of micrometer size...

  3. Deposition of matrix-free fullerene films with improved morphology by matrix-assisted pulsed laser evaporation (MAPLE)

    DEFF Research Database (Denmark)

    Canulescu, Stela; Schou, Jørgen; Fæster, Søren;

    2013-01-01

    Thin films of C60 were deposited by matrix-assisted pulsed laser evaporation (MAPLE) from a frozen target of anisole with 0.67 wt% C60. Above a fluence of 1.5 J/cm2 the C60 films are strongly non-uniform and are resulting from transfer of matrix-droplets containing fullerenes. At low fluence...... the fullerene molecules in the films are intact, the surface morphology is substantially improved and there are no measurable traces of the matrix molecules in the film. This may indicate a regime of dominant evaporation at low fluence which merges into the MAPLE regime of liquid ejection of the host matrix...

  4. Pulsed laser machining apparatus

    International Nuclear Information System (INIS)

    Apparatus and method for directing a controlled number of laser pulses onto a work piece to be machined. More specifically, the laser machining apparatus includes an excitable laser and an excitation lamp for continuously exciting the laser to emit a sequence of laser pulses. The application of the laser pulses to the work piece is controlled by an inner-cavity shutter that is opened to permit a precise number of pulses to be directed onto the work piece. The frequency (REP RATE) and pulse width of the laser pulses are controlled by the excitation lamp and, in turn, are set to create a progressive weld of significant depth and structural integrity. In particular there is provided control means for counting the number of laser pulses applied to a machining site of the work piece, whereby a known controllable quantity of energy is imparted to each site. To this end, the counting of the laser pulses begins after the completion of a laser pulse, whereby the actuation of the inner-cavity shutter is not synchronized to the computer but rather to the laser emission so that only whole laser pulses will be applied to the site

  5. Laser assisted electron dynamics

    CERN Document Server

    Bray, Alexander William

    2016-01-01

    We apply the convergent close-coupling (CCC) formalism to analyse the processes of laser assisted electron impact ionisation of He, and the attosecond time delay in the photodetachment of the H^{-} ion and the photoionisation of He. Such time dependent atomic collision processes are of considerable interest as experimental measurements on the relevant timescale (attoseconds 10^{-18} s) are now possible utilising ultrafast and intense laser pulses. These processes in particular are furthermore of interest as they are strongly influenced by many-electron correlations. In such cases their theoretical description requires a more comprehensive treatment than that offered by first order perturbation theory. We apply such a treatment through the use of the CCC formalism which involves the complete numeric solution of the integral Lippmann-Schwinger equations pertaining to a particular scattering event. For laser assisted electron impact ionisation of He such a treatment is of a considerably greater accuracy than the...

  6. Design and performance of a matrix-assisted laser desorption time-of-flight mass spectrometer utilizing a pulsed nitrogen laser

    International Nuclear Information System (INIS)

    The design considerations and experimental performance of a linear time-of-flight mass spectrometer are reported for performing matrix-assisted laser desorption studies. A simple pulsed gas-discharge nitrogen laser (337.1 nm) is successfully used in contrast to the more widely used frequency-quadrupled (266 nm) or frequency-tripled (355 nm) Nd:YAG solid-state laser. Optical considerations in utilizing the pulsed nitrogen laser are discussed and a simple optical arrangement is described which allows for suitable imaging of the poor spatial beam profile of the pulsed nitrogen laser. Laser spot sizes of 150x450 μm are obtainable. As with the frequency-tripled Nd:YAG laser, sinapic acid is found to be the most useful matrix for producing protonated molecular species from proteins. Appropriate laser power levels are determined, as matrix/sample levels. Adequate response for most small to medium molecular weight proteins is obtained for less than 1 pmol of sample. A simple einsel lens incorporated into the ion source does not appear to provide any significant focusing on the laser-desorbed ions; however, a constant d.c. voltage applied to beam stirring plates enhances the ion signal significantly. Selective, pulsed deflection of the low-mass ions produced from the matrix is also utilized to prevent excessive saturation of the microchannel plate ion detector. High source potentials are found to provide improved resolution and sensitivity in comparison with lower source potentials combined with post-acceleration at the detector. Representative mass spectra of several proteins and peptides are presented. Increased formation of photoinduced adduct ions are observed in comparison with that reported for matrix-assisted laser desorption experiments utilizing a Nd:YAG laser and significant amounts of dimer and trimer ions are produced. Significantly more peak broadening than would normally be expected is observed above 20000 u. This may be due to the post-acceleration design of

  7. Fabrication of nanowires of Al-doped ZnO using nanoparticle assisted pulsed laser deposition (NAPLD) for device applications

    Energy Technology Data Exchange (ETDEWEB)

    Thanka Rajan, S. [ECMS Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 006 (India); Subramanian, B., E-mail: subramanianb3@gmail.com [ECMS Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 006 (India); Nanda Kumar, A.K.; Jayachandran, M. [ECMS Division, CSIR – Central Electrochemical Research Institute, Karaikudi 630 006 (India); Ramachandra Rao, M.S. [Department of Physics, Indian Institute of Technology Madras, Chennai 600 036 (India)

    2014-01-25

    Graphical abstract: -- Highlights: • Novel technique of NP assisted PLD was employed to obtain Al doped ZnO. • AZO nano wires with aspect ratios exceeding 20 were obtained at 500 sccm Ar gas pressure. • AZO films belong to the most stable wurtzite type. • Films show near band edge emission and defect related emission. -- Abstract: Aluminium doped zinc oxide (AZO) nanostructures have been successfully synthesized on sapphire substrates by using nanoparticle assisted pulsed laser deposition (NAPLD) in Ar atmosphere without using any catalyst. The growth of the AZO nanowires has been investigated by varying the argon flow rates. The coatings have been characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), Diffuse Reflectance Spectroscopy (DRS), Laser Raman spectroscopy and Photoluminescence spectroscopy. The results of XRD indicate that the deposited films are crystalline ZnO with hexagonal wurtzite structure with (0 0 2) preferred orientation. FESEM images also clearly reveal the hexagonal structure and the formation of nanowires with aspect ratios between 15 and 20. The surface roughness value of 9.19 nm was observed from AFM analysis. The optical properties of the sample showed that under excitation with λ = 325 nm, an emission band was observed in UV and visible region. The characteristic Raman peaks were detected at 328, 380, 420, 430 cm{sup −1}.

  8. Properties of La and Nb-modified PZT thin films grown by radio frequency assisted pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Verardi, P. [CNR-Istituto di Acustica, Via del Fosso del Cavaliere 100, I-00133 Rome (Italy); Craciun, F. [CNR-Istituto dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133 Rome (Italy); Dinescu, M. [NILPRP, Bucharest, PO Box MG-16, RO-76900 (Romania)]. E-mail: dinescum@ifin.nipne.ro; Scarisoreanu, N. [NILPRP, Bucharest, PO Box MG-16, RO-76900 (Romania); Moldovan, A. [NILPRP, Bucharest, PO Box MG-16, RO-76900 (Romania); Purice, A. [NILPRP, Bucharest, PO Box MG-16, RO-76900 (Romania); Galassi, C. [CNR-ISTEC, Via Granarolo 64, I 48018 Faenza (Italy)

    2005-04-25

    Lead zirconate titanate ferroelectric thin films added with La and Nb has been grown by radio frequency assisted pulsed laser deposition on Pt/Si, starting from sintered targets. The dielectric properties were measured in a large frequency range and their dependence on the a.c. driving field amplitude has been investigated. A linear decreasing of the dielectric permittivity with frequency logarithm increasing has been evidenced. The most important factor for the driving field amplitude influence on the dielectric properties is the type of vacancies introduced by La and Nb substitutions, which indicates that the dynamics involved in a.c. field behavior is controlled by interaction mechanisms between ferroelectric domain or nanodomain walls and pinning (vacancies) centers.

  9. Excimer Laser Pulse Compress With Pulse Feedback

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>To attain a shorter laser pulse, a compressing technique called pulse feedback was developed from the saturation gain switch applied to the amplification in a discharge pumping excimer laser cavity. It can

  10. Laser assisted hair-removal.

    Science.gov (United States)

    Choudhary, S; Elsaie, M L; Nouri, K

    2009-10-01

    A number of lasers and light devices are now available for the treatment of unwanted hair. The goal of laser hair removal is to damage stem cells in the bulge of the hair follicle by targeting melanin, the endogenous chromophore for laser and light devices utilized to remove hair. The competing chromophores in the skin and hair, oxyhemoglobin and water, have a decreased absorption between 690 nm and 1000 nm, thus making this an ideal range for laser and light sources. Laser hair removal is achieved through follicular unit destruction based on selective photothermolysis. The principle of selective photothermolysis predicts that the thermal injury will be restricted to a given target if there is sufficient selective absorption of light and the pulse duration is shorter than the thermal relaxation time of the target. This review will focus on the mechanisms of laser assisted hair removal and provide an update on the newer technologies emerging in the field of lasers assisted hair removal.

  11. Amperometric biosensor based on Laccase immobilized onto a screen-printed electrode by Matrix Assisted Pulsed Laser Evaporation.

    Science.gov (United States)

    Verrastro, Maria; Cicco, Nunzia; Crispo, Fabiana; Morone, Antonio; Dinescu, Maria; Dumitru, Marius; Favati, Fabio; Centonze, Diego

    2016-07-01

    A Laccase-based biosensor for the determination of phenolic compounds was developed by using Matrix Assisted Pulsed Laser Evaporation as an innovative enzyme immobilization technique. and the deriving biosensor was characterized and applied for the first time. Laccase was immobilized onto different substrates including screen printed carbon electrodes and spectroscopic, morphologic and electrochemical characterizations were carried out. A linear range from 1 to 60μM was achieved working at 5.5pH and -0.2V detection potential vs Ag pseudoreference. The limits of detection and quantification were found to be 1 and 5μM, respectively. A good fabrication reproducibility, stability of response and selectivity toward interferents were also found The potential of the developed biosensor was tested in the determination of total polyphenol content in real matrices (tea infusion, ethanolic extract from Muscari comosum bulbs and aqueous solution of a food supplement from black radish root and artichoke leaves) and the results were compared with those obtained by using the Folin-Ciocalteu method.

  12. Deposition of organic dyes for dye-sensitized solar cell by using matrix-assisted pulsed laser evaporation

    Directory of Open Access Journals (Sweden)

    Chih-Ping Yen

    2016-08-01

    Full Text Available The deposition of various distinct organic dyes, including ruthenium complex N3, melanin nanoparticle (MNP, and porphyrin-based donor-π-acceptor dye YD2-o-C8, by using matrix-assisted pulsed laser evaporation (MAPLE for application to dye-sensitized solar cell (DSSC is investigated systematically. It is found that the two covalently-bonded organic molecules, i.e., MNP and YD2-o-C8, can be transferred from the frozen target to the substrate with maintained molecular integrity. In contrast, N3 disintegrates in the process, presumably due to the lower bonding strength of metal complex compared to covalent bond. With the method, DSSC using YD2-o-C8 is fabricated, and an energy conversion efficiency of 1.47% is attained. The issue of the low penetration depth of dyes deposited by MAPLE and the possible resolution to it are studied. This work demonstrates that MAPLE could be an alternative way for deposition of organic dyes for DSSC.

  13. Study of temperature dependence and angular distribution of poly(9,9-dioctylfluorene) polymer films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

    International Nuclear Information System (INIS)

    Poly(9,9-dioctylfluorene) (PFO) polymer films were deposited by matrix-assisted pulsed laser evaporation (MAPLE) technique. The polymer was diluted (0.5 wt%) in tetrahydrofuran and, once cooled to liquid nitrogen temperature, it was irradiated with a KrF excimer laser. 10,000 laser pulses were used to deposit PFO films on Si substrates at different temperatures (-16, 30, 50 and 70 deg. C). One PFO film was deposited with 16,000 laser pulses at a substrate temperature of 50 deg. C. The morphology, optical and structural properties of the films were investigated by SEM, AFM, PL and FTIR spectroscopy. SEM inspection showed different characteristic features on the film surface, like deflated balloons, droplets and entangled polymer filaments. The roughness of the films was, at least partially, controlled by substrate heating, which however had the effect to reduce the deposition rate. The increase of the laser pulse number modified the target composition and increased the surface roughness. The angular distribution of the material ejected from the target confirmed the forward ejection of the target material. PFO films presented negligible modification of the chemical structure respect to the bulk material.

  14. Raman-scattering-assistant broadband noise-like pulse generation in all-normal-dispersion fiber lasers.

    Science.gov (United States)

    Li, Daojing; Shen, Deyuan; Li, Lei; Chen, Hao; Tang, Dingyuan; Zhao, Luming

    2015-10-01

    We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP achieved in all-normal-dispersion fiber lasers. PMID:26480103

  15. Raman-scattering-assistant broadband noise-like pulse generation in all-normal-dispersion fiber lasers

    CERN Document Server

    Li, Daojing; Li, Lei; Chen, Hao; Tang, Dingyuan; Zhao, Luming

    2015-01-01

    We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP achieved in all-normal-dispersion fiber lasers

  16. Raman-scattering-assistant broadband noise-like pulse generation in all-normal-dispersion fiber lasers

    Science.gov (United States)

    Li, Daojing; Shen, Deyuan; Li, Lei; Chen, Hao; Tang, Dingyuan; Zhao, Luming

    2015-10-01

    We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP achieved in all-normal-dispersion fiber lasers

  17. Direct current-dielectrophoresis assisted microscale machining of metal by femtosecond pulsed laser

    Science.gov (United States)

    Park, ChangKyoo; Farson, Dave F.

    2015-07-01

    Accumulation of ablation debris particles interferes with femtosecond laser micromachining of high-aspect ratio grooves in metal. Debris removal from such grooves by an air or inert gas jet requires that the gas jet axis be aligned with the groove. This requirement constrains the motion system design and programming as well as the gas nozzle design for cutting of arbitrary shapes. Gas jet debris removal is also not feasible in vacuum environments. In this study, a novel technique based on DC-dielectrophoresis (DEP) for removing debris from the cut groove was investigated. Femtosecond laser ablation of linear and circular grooves from thick sections of aluminum was performed with no debris removal and with debris removal by air jet or DC-DEP force. Ablation depth and precision were compared for the three experimental conditions. Debris removal by DC-DEP force resulted in the most accurate, consistent, and orientation-independent machining of high-aspect ratio grooves. Moreover, larger electric fields exerted stronger DC-DEP force on debris particles and resulted in better ablation precision and machining rate.

  18. Theory of laser catalysis with pulses

    CERN Document Server

    Vardi, A

    2001-01-01

    The possibility of accelerating molecular reactions by lasers has attracted considerable theoretical and experimental interest. A particular example of laser-modified reaction dynamics is laser catalysis, a process in which the tunneling through a potential barrier is enhanced by transient excitation to a bound electronic state. We have performed detailed calculations of pulsed laser catalysis on one- and two-dimensional potentials, as a function of the reactants' collision energy and the laser's central frequency. In agreement with previous CW results, the reactive lineshapes are Fano-type curves, resulting from interference between nonradiative tunneling and the optically assisted pathway. In contrast to the CW process, the power requirements of pulsed laser catalysis are well within the reach of commonly used pulsed laser sources, making an experimental realization possible. The laser catalysis scenario is shown to be equivalent in the ``dressed'' state picture, to resonant tunneling through a double-barri...

  19. 21 CFR 884.6200 - Assisted reproduction laser system.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Assisted reproduction laser system. 884.6200... Assisted reproduction laser system. (a) Identification. The assisted reproduction laser system is a device that images, targets, and controls the power and pulse duration of a laser beam used to ablate a...

  20. Photo-assisted intersystem crossing: The predominant triplet formation mechanism in some isolated polycyclic aromatic molecules excited with pulsed lasers

    International Nuclear Information System (INIS)

    Naphthalene, anthracene, and phenanthrene are shown to have very long-lived triplet lifetimes when the isolated molecules are excited with nanosecond pulsed lasers resonant with the lowest singlet state. For naphthalene, triplet state populations are created only during the laser pulse, excluding the possibility of normal intersystem crossing at the one photon level, and all molecules have triplet lifetimes greater than hundreds of microseconds, similar to the behavior previously reported for phenylacetylene. Although containing 7-12 thousand cm-1 of vibrational energy, the triplet molecules have ionization thresholds appropriate to vibrationless T1 states. The laser power dependences (slopes of log-log power plots) of the excited singlet and triplet populations are about 0.7 for naphthalene and about 0.5 for anthracene. Kinetic modeling of the power dependences successfully reproduces the experimental results and suggests that the triplet formation mechanism involves an enhanced spin orbit coupling caused by sigma character in states at the 2-photon level. Symmetry Adapted Cluster-Configuration Interaction calculations produced excited state absorption spectra to provide guidance for estimating kinetic rates and the sigma character present in higher electronic states. It is concluded that higher excited state populations are significant when larger molecules are excited with pulsed lasers and need to be taken into account whenever discussing the molecular photodynamics

  1. Raman-scattering-assistant broadband noise-like pulse generation in all-normal-dispersion fiber lasers

    OpenAIRE

    Li, Daojing; Shen, Deyuan; Li, Lei; Chen, Hao; Tang, Dingyuan; Zhao, Luming

    2015-01-01

    We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP...

  2. Quantum interference in laser-assisted photo-ionization excited by a femtosecond x-ray pulse

    Institute of Scientific and Technical Information of China (English)

    Ge Yu-Cheng

    2008-01-01

    The photoelectron energy spectra (PESs) excited by monochromatic femtosecond x-ray pulses in the presence of a femtosecond laser are investigated. APES is composed of a set of separate peaks, showing interesting comb-like structures. These structures result from the quantum interferences between photoelectron wave packets generated at different times. The width and the localization of each peak as well as the number of peaks are determined by all the laser and x-ray parameters. Most of peak heights of the PES are higher than the classical predictions.

  3. Observation of low resistivity and high mobility in Ga doped ZnO thin films grown by buffer assisted pulsed laser deposition

    International Nuclear Information System (INIS)

    Highlights: • Ga doped ZnO thin films were grown using buffer assisted pulsed laser deposition. • Lowest resistivity ∼5.1 × 10−5 Ω cm with a mobility of ∼41.9 cm2/V s was observed. • Buffer assisted growth methodology maintains relatively good crystalline quality. • This plays a key role in decreasing the resistivity of to the aforementioned value. • This resistivity value, to the best of our knowledge is the lowest so far in ZnO. - Abstract: We have grown Ga doped ZnO (GZO) thin films at moderate temperatures with Ga concentrations in the range varying from 0.25 to 3 at.% on sapphire substrates using buffer assisted pulsed laser deposition. Room temperature resistivity measured was ∼5.1 × 10−5 Ω cm with a electron mobility of ∼41.9 cm2/V s for an optimum Ga concentration of ∼0.75 at.% in the GZO films. Buffer assisted growth methodology maintains relatively good crystalline quality of the GZO thin films, thereby improving the electron mobility even at high dopant concentrations. This plays a key role in decreasing the resistivity of GZO films to the aforementioned value, which to the best of our knowledge is the lowest so far. These highly conducting GZO thin films with good mobility are potential candidates for transparent conducting oxide (TCO) applications in various optoelectronic devices

  4. Bringing Pulsed Laser Welding into Production

    DEFF Research Database (Denmark)

    Olsen, Flemmming Ove

    1996-01-01

    production of hermetic weld seams produced on radiator thermostats applying pulsed laser welding. This application has now been running in several years. 2 laser systems are currently welding each serving two welding stations. Another case story is describing a high precision assembly technique of a product......In this paper, some research and develop-ment activities within pulsed laser welding technology at the Tech-nical University of Denmark will be described. The laser group at the Insti-tute for Manufacturing Technology has nearly 20 years of experience in laser materials process-ing. Inter......-nationally the group is mostly known for its contri-butions to the development of the laser cutting process, but further it has been active within laser welding, both in assisting industry in bringing laser welding into production in several cases and in performing fundamental R & D. In this paper some research...

  5. Pulsed laser microtomograph

    Science.gov (United States)

    Antonov, V. B.; Bonch-Bruevich, A. M.; Vasil'Ev, V. I.; Ionov, L. N.; Nikolaev, S. D.; Starobogatov, I. O.

    1994-12-01

    This paper describes a pulsed laser tomographic apparatus that has been implemented in practice and has a spatial resolution of 2-5 microns in the transverse direction and approximately 70 microns in the probe-radiation propagation direction. Experiments have been performed with model objects. Results have been obtained that confirm the possibility of early diagnosis of skin mycoses that cannot be diagnosed by existing methods.

  6. Laser assisted hair-removal.

    Science.gov (United States)

    Choudhary, S; Elsaie, M L; Nouri, K

    2009-10-01

    A number of lasers and light devices are now available for the treatment of unwanted hair. The goal of laser hair removal is to damage stem cells in the bulge of the hair follicle by targeting melanin, the endogenous chromophore for laser and light devices utilized to remove hair. The competing chromophores in the skin and hair, oxyhemoglobin and water, have a decreased absorption between 690 nm and 1000 nm, thus making this an ideal range for laser and light sources. Laser hair removal is achieved through follicular unit destruction based on selective photothermolysis. The principle of selective photothermolysis predicts that the thermal injury will be restricted to a given target if there is sufficient selective absorption of light and the pulse duration is shorter than the thermal relaxation time of the target. This review will focus on the mechanisms of laser assisted hair removal and provide an update on the newer technologies emerging in the field of lasers assisted hair removal. PMID:19834437

  7. Nonlinear optical studies on 4-(ferrocenylmethylimino)-2-hydroxy-benzoic acid thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

    Science.gov (United States)

    Matei, Andreea; Marinescu, Maria; Constantinescu, Catalin; Ion, Valentin; Mitu, Bogdana; Ionita, Iulian; Dinescu, Maria; Emandi, Ana

    2016-06-01

    We present results on a new, laboratory synthesized ferrocene-derivative, i.e. 4-(ferrocenylmethylimino)-2-hydroxy-benzoic acid. Thin films with controlled thickness are deposited by matrix-assisted pulsed laser evaporation (MAPLE), on quartz and silicon substrates, with the aim of evaluating the nonlinear optical properties for potential optoelectronic applications. Dimethyl sulfoxide was used as matrix, with 1% wt. concentration of the guest compound. The frozen target is irradiated by using a Nd:YAG laser (4ω/266 nm, 7 ns pulse duration, 10 Hz repetition rate), at low fluences ranging from 0.1 to 1 J/cm2. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to probe the surface morphology of the films. Fourier transform infrared (FTIR) and Raman spectroscopy reveal similar structure of the thin film material when compared to the starting material. The optical properties of the thin films are investigated by spectroscopic-ellipsometry (SE), and the refractive index dependence with respect to temperature is studied. The second harmonic generation (SHG) potential is assessed by using a femtosecond Ti:sapphire laser (800 nm, 60-100 fs pulse duration, 80 MHz repetition rate), at 200 mW maximum output power, revealing that the SHG signal intensity is strongly influenced by the films' thickness.

  8. CFD assisted simulation of temperature distribution and laser power in pulsed and CW pumped static gas DPALs

    Science.gov (United States)

    Waichman, Karol; Barmashenko, Boris D.; Rosenwaks, Salman

    2015-10-01

    An analysis of radiation, kinetic and fluid dynamic processes in diode pumped alkali lasers (DPALs) is reported. The analysis is based on a three-dimensional, time-dependent computational fluid dynamics (3D CFD) model. The CFD code which solves the gas conservation equations includes effects of natural convection and temperature diffusion of the species in the DPAL mixture. The gas flow conservation equations are coupled to the equations for DPAL kinetics and to the Beer-Lambert equations for pump and laser beams propagation. The DPAL kinetic processes in the Cs/CH4 (K/He) gas mixtures considered involve the three low energy levels, (1) n2S1/2, (2) n2P3/2 and (3) n2P1/2 (where n=4,6 for K and Cs, respectively), three excited alkali states and two alkali ionic states. Using the CFD model, the gas flow pattern and spatial distributions of the pump and laser intensities in the resonator were calculated for end-pumped CW and pulsed Cs and K DPALs. The DPAL power and medium temperature were calculated as a function of pump power and pump pulse duration. The CFD model results were compared to experimental results of Cs and K DPALs.

  9. Vertical La0.7Ca0.3MnO3 nanorods tailored by high magnetic field assisted pulsed laser deposition

    OpenAIRE

    Kejun Zhang; Jianming Dai; Xuebin Zhu; Xiaoguang Zhu; Xuzhong Zuo; Peng Zhang; Ling Hu; Wenjian Lu; Wenhai Song; Zhigao Sheng; Wenbin Wu; Yuping Sun; Youwei Du

    2016-01-01

    La0.7Ca0.3MnO3 (LCMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] single crystal substrates have been prepared by high magnetic field assisted pulsed laser deposition (HMF-PLD) developed by ourselves. Uniformly sized and vertically aligned nanorod structures can be obtained under an applied high magnetic field above 5 T, and the dimension size of the nanorods can be manipulated by varying the applied magnetic field. It is found that the magnetic anisotropy is strongly correlate...

  10. Molecular wakes for ultrashort laser pulses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The molecular wake-assisted interaction between two collinear femotosecond laser pulses is investigated in air,which leads to the generation of a controllable 1.8 mJ super-continuum pulse with an elongated self-guided channel due to the cross-phase modulation of the impulsively aligned diatomic molecules in air. For two parallel launched femtosecond laser pulses with a certain spatial separation,controllable attraction and repulsion of the pulses are observed due to the counter-balance among molecular wakes,Kerr and plasma effects,where the molecular wakes show a longer interaction distance than the others to control the propagation of the intense ultrashort laser pulses.

  11. Training Ultrafast Laser Pulses

    Science.gov (United States)

    Averin, Ruslan; Wells, N.; Todt, M.; Smolnisky, N.; Jastram, N.; Jochim, B.; Gregerson, N.; Wells, E.; Sayler, A.; McKenna, J.; Carnes, K.; Ben-Itzhak, I.; Kling, M. F.

    2009-11-01

    Closed loop control of molecular processes utilizing shaped ultrafast laser pulses has been around for a number of years, yet this type of control has primarily utilized Time of Flight ion yield data for feedback. We present experiments using Velocity Map Imaging (VMI) as the feedback source for the closed loop control. Using VMI allows for pulse optimization not only with respect to the disassociation species but also angular information of the final state. We demonstrate the feasibility of incorporating this kind of feedback into the control loop. Using this technique, we controlled the dissociation branching ratio of CO^+ into C^+ +O or C ^+O^+ and used the VMI information to recover additional information about the control mechanism.

  12. Micro pulse laser radar

    Science.gov (United States)

    Spinhirne, James D. (Inventor)

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  13. Laser-assisted photoelectric effect from surfaces.

    Science.gov (United States)

    Miaja-Avila, L; Lei, C; Aeschlimann, M; Gland, J L; Murnane, M M; Kapteyn, H C; Saathoff, G

    2006-09-15

    We report the first observation of the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 eV and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum. The magnitude of these sidebands as a function of time delay between the laser and extreme ultraviolet pulses represents a cross-correlation measurement of the extreme ultraviolet pulse. This effect promises to be useful to extend extreme ultraviolet pulse duration measurements to higher photon energies, as well as opening up femtosecond-to-attosecond time-scale electron dynamics in solid and surface-adsorbate systems.

  14. Efficient upconversion polymer-inorganic nanocomposite thin film emitters prepared by the double beam matrix assisted pulsed laser evaporation (DB-MAPLE)

    Science.gov (United States)

    Darwish, Abdalla M.; Burkett, Allan; Blackwell, Ashley; Taylor, Keylantra; Walker, Vernell; Sarkisov, Sergey; Koplitz, Brent

    2014-09-01

    We report on fabrication and investigation of optical and morphological properties of highly efficient (a quantum yield of 1%) upconversion polymer-inorganic nanocomposite thin film emitters prepared by the new technique of double beam matrix assisted pulsed laser evaporation (DB-MAPLE). Polymer poly(methyl methacrylate) (PMMA) host was evaporated on a silicon substrate using a 1064-nm pulsed laser beam using a target made of frozen (to the temperature of liquid nitrogen) solution of PMMA in chlorobenzene. Concurrently, the second 532-nm pulsed beam from the same laser was used to impregnate the polymer host with the inorganic nanoparticulate made of the rare earth upconversion compounds NaYF4: Yb3+, Er3+, NaYF4: Yb3+, Ho3+, and NaYF4: Yb3+, Tm3+. The compounds were initially synthesized using the wet process, baked, and compressed in solid pellet targets. The proposed DB-MAPLE method has the advantage of making highly homogeneous nanocomposite films with precise control of the doping rate due to the optimized overlapping of the plumes produced by the ablation of the organic and inorganic target with the infrared and visible laser beams respectively. X-ray diffraction, electron and atomic force microscopy, and optical fluorescence spectroscopy indicated that the inorganic nanoparticulate preserved its crystalline structure and upconversion properties (strong emission in green, red, and blue bands upon illumination with 980-nm laser diode) after being transferred from the target in the polymer nanocomposite film. The produced films can be used in applications varying from the efficiency enhancement of the photovoltaic cells, optical sensors and biomarkers to anti-counterfeit labels.

  15. Films of brookite TiO{sub 2} nanorods/nanoparticles deposited by matrix-assisted pulsed laser evaporation as NO{sub 2} gas-sensing layers

    Energy Technology Data Exchange (ETDEWEB)

    Caricato, A.P.; Cesaria, M.; Luches, A.; Martino, M. [University of Salento, Department of Physics, Lecce (Italy); Buonsanti, R. [Istituto di Nanoscienze del CNR, National Nanotechnology Laboratory (NNL), Lecce (Italy); Catalano, M.; Manera, M.G.; Taurino, A.; Rella, R. [IMM-CNR, Institute for Microelectronics and Microsystems, Lecce (Italy); Cozzoli, P.D. [Istituto di Nanoscienze del CNR, National Nanotechnology Laboratory (NNL), Lecce (Italy); University of Salento, Department of Innovation Engineering, Lecce (Italy)

    2011-09-15

    Titanium dioxide (TiO{sub 2}) nanorods in the brookite phase, with average dimensions of 3-4 nm x 20-50 nm, were synthesized by a wet-chemical aminolysis route and used as precursors for thin films that were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. A nanorod solution in toluene (0.016 wt% TiO{sub 2}) was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser at a fluence of 350 mJ/cm{sup 2} and repetition rate of 10 Hz. Single-crystal Si wafers, silica slides, carbon-coated Cu grids and alumina interdigitated slabs were used as substrates to allow performing different characterizations. Films fabricated with 6000 laser pulses had an average thickness of {proportional_to}150 nm, and a complete coverage of the selected substrate as achieved. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO{sub 2} nanorods and crystalline spherical nanoparticles with an average diameter of {proportional_to}13 nm. Spectrophotometric analysis showed high transparency through the UV-Vis spectral range. Promising resistive sensing responses to 1 ppm of NO{sub 2} mixed in dry air were obtained. (orig.)

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

    Science.gov (United States)

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

    2011-09-01

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

  17. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos; Lozovoy, Vadim V.; Comstock, Matthew

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  18. High-power pulsed lasers

    International Nuclear Information System (INIS)

    The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

  19. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  20. Pulse-Width Jitter Measurement for Laser Diode Pulses

    Institute of Scientific and Technical Information of China (English)

    TANG Jun-Hua; WANG Yun-Cai

    2006-01-01

    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  1. Pulsed laser deposition of liquid crystals

    OpenAIRE

    Gonzalo de los Reyes, José; Dyer, P. E.; Hird, M.

    1997-01-01

    Thin films of 4-cyano-4’-pentylbiphenyl ~5CB! liquid crystal have been fabricated by pulsed laser deposition. The suitability of different lasers ~ArF, KrF and CO2) has been investigated over a range of fluence using visible-UV and infrared absorption and optical microscopy to characterise the films. High performance liquid chromatography ~HPLC! and matrix assisted laser desorption ionization mass spectroscopy ~MALDI-MS! were used to assess the extent of decomposition of the films. The result...

  2. Vertical La0.7Ca0.3MnO3 nanorods tailored by high magnetic field assisted pulsed laser deposition

    Science.gov (United States)

    Zhang, Kejun; Dai, Jianming; Zhu, Xuebin; Zhu, Xiaoguang; Zuo, Xuzhong; Zhang, Peng; Hu, Ling; Lu, Wenjian; Song, Wenhai; Sheng, Zhigao; Wu, Wenbin; Sun, Yuping; Du, Youwei

    2016-01-01

    La0.7Ca0.3MnO3 (LCMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] single crystal substrates have been prepared by high magnetic field assisted pulsed laser deposition (HMF-PLD) developed by ourselves. Uniformly sized and vertically aligned nanorod structures can be obtained under an applied high magnetic field above 5 T, and the dimension size of the nanorods can be manipulated by varying the applied magnetic field. It is found that the magnetic anisotropy is strongly correlated to the dimension size of the nanorods. A significantly enhanced low-field magnetoresistance (LFMR) of -36% under 0.5 T at 100 K can be obtained due to the enhanced carrier scattering at the vertical grain boundaries between the nanorods for the LCMO films. The growth mechanism of the nanorods has been also discussed, which can be attributed to the variation of deposition rate, adatom surface diffusion, and nucleation induced by the application of a high magnetic field in the film processing. The successful achievements of such vertical nanorod structures will provide an instructive route to investigate the physical nature of these nanostructures and achieve nanodevice manipulation.

  3. Ultra-short pulsed laser engineered metal-glass nanocomposites

    CERN Document Server

    Stalmashonak, Andrei; Abdolvand, Amin

    2013-01-01

    Glasses containing metallic nanoparticles exhibit very promising linear and nonlinear optical properties, mainly due to the surface plasmon resonances (SPRs) of the nanoparticles. The spectral position in the visible and near-infrared range and polarization dependence of the SPR are characteristically determined by the nanoparticles’ shapes. The focus of Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites is the interaction of intense ultra-short laser pulses with glass containing silver nanoparticles embedded in soda-lime glass, and nanostructural modifications in metal-glass nanocomposites induced by such laser pulses. In order to provide a comprehensive physical picture of the processes leading to laser-induced persistent shape transformation of the nanoparticles, series of experimental results investigating the dependences of laser assisted shape modifications of nanoparticles with laser pulse intensity, excitation wavelength, temperature are considered. In addition, the resulting local opti...

  4. Ultrashort-pulse laser machining

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D; Rubenchik, A M; Sefcik, J A; Stuart, B C

    1998-09-01

    A new type of material processing is enabled with ultrashort (t < 10 ps) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms that eliminate thermal shock or collateral damage. High-precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  5. Ultrashort-pulse lasers machining

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S; Feit, M D; Nguyen, H T; Perry, M D, Stuart, B C

    1999-01-22

    A new type of material processing is enabled with ultrashort (t < 10 psec) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms which eliminate thermal shock or collateral damage. High precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.

  6. Identification and Removal of High Frequency Temporal Noise in a Nd:YAG Macro-Pulse Laser Assisted with a Diagnostic Streak Camera

    Energy Technology Data Exchange (ETDEWEB)

    Kent Marlett, Bechtel Nevada; Ke-Xun Sun Bechtel Nevada

    2004-09-23

    This paper discusses the use of a reference streak camera (SC) to diagnose laser performance and guide modifications to remove high frequency noise from Bechtel Nevada's long-pulse laser. The upgraded laser exhibits less than 0.1% high frequency noise in cumulative spectra, exceeding National Ignition Facility (NIF) calibration specifications. Inertial Confinement Fusion (ICF) experiments require full characterization of streak cameras over a wide range of sweep speeds (10 ns to 480 ns). This paradigm of metrology poses stringent spectral requirements on the laser source for streak camera calibration. Recently, Bechtel Nevada worked with a laser vendor to develop a high performance, multi-wavelength Nd:YAG laser to meet NIF calibration requirements. For a typical NIF streak camera with a 4096 x 4096 pixel CCD, the flat field calibration at 30 ns requires a smooth laser spectrum over 33 MHz to 68 GHz. Streak cameras are the appropriate instrumentation for measuring laser amplitude noise at these very high frequencies since the upper end spectral content is beyond the frequency response of typical optoelectronic detectors for a single shot pulse. The SC was used to measure a similar laser at its second harmonic wavelength (532 nm), to establish baseline spectra for testing signal analysis algorithms. The SC was then used to measure the new custom calibration laser. In both spatial-temporal measurements and cumulative spectra, 6-8 GHz oscillations were identified. The oscillations were found to be caused by inter-surface reflections between amplifiers. Additional variations in the SC spectral data were found to result from temperature instabilities in the seeding laser. Based on these findings, laser upgrades were made to remove the high frequency noise from the laser output.

  7. Fundamentals of laser-assisted fabrication of inorganic and organic films

    DEFF Research Database (Denmark)

    Schou, Jørgen

    2008-01-01

    The standard method for producing films by laser-assisted methods, Pulsed Laser Deposition (PLD) will be reviewed. The films considered are usually inorganic films, but also films of organic materials have been produced. Also the deposition of organic films by MAPLE (Matrix Assisted Pulsed Laser...

  8. Switching time in laser pulse heat-assisted magnetic recording using L1{sub 0}-FePt nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lyberatos, A., E-mail: lyb@materials.uoc.gr [Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 71003 Heraklion (Greece); Weller, D.; Parker, G. J. [HGST, a Western Digital Company, 3403 Yerba Buena Road, San Jose, California 95135 (United States)

    2015-04-07

    Atomistic spin model simulations using Langevin dynamics are performed to study the factors that determine the thermomagnetic recording time window in FePt media. The onset of thermomagnetic writing occurs at a temperature T{sub o} larger than the Curie temperature T{sub c} as a result of the finite time of relaxation of the magnetization by the linear reversal mode. The Bloch relaxation rate of magnetization growth during cooling below T{sub c} is independent on the write field, provided the field is stronger than some threshold value. Application of a strong write field reduces switching time through better spin alignment in the paramagnetic regime. Finite size effects on the probability distribution of freezing temperatures T{sub f} and the free energy provide insight on the thermomagnetic reversal mechanism. Constraints on the “pulse-mode” of recording when the head field reverses direction during cooling are also considered.

  9. Pulse transformer for GaAs laser

    Science.gov (United States)

    Rutz, E. M.

    1976-01-01

    High-radiance gallium arsenide (GaAs) laser operating at room temperature is utilized in optical navigation system. For efficient transformer-to-laser impedance match, laser should be connected directly to pulse transformer secondary winding.

  10. Investigation of Laser Parameters in Silicon Pulsed Laser Conduction Welding

    Science.gov (United States)

    Shayganmanesh, Mahdi; Khoshnoud, Afsaneh

    2016-03-01

    In this paper, laser welding of silicon in conduction mode is investigated numerically. In this study, the effects of laser beam characteristics on the welding have been studied. In order to model the welding process, heat conduction equation is solved numerically and laser beam energy is considered as a boundary condition. Time depended heat conduction equation is used in our calculations to model pulsed laser welding. Thermo-physical and optical properties of the material are considered to be temperature dependent in our calculations. Effects of spatial and temporal laser beam parameters such as laser beam spot size, laser beam quality, laser beam polarization, laser incident angle, laser pulse energy, laser pulse width, pulse repetition frequency and welding speed on the welding characteristics are assessed. The results show that how the temperature dependent thermo-physical and optical parameters of the material are important in laser welding modeling. Also the results show how the parameters of the laser beam influence the welding characteristics.

  11. Pulse propagation in the laser wakefield accelerator

    International Nuclear Information System (INIS)

    A high-density regime of the laser wakefield accelerator is reviewed in which enhanced acceleration is achieved via resonant self-modulation of the laser pulse. This requires laser power in excess of the critical power for optical guiding and a plasma wavelength short compared to the laser pulse-length. The evolution of the laser pulse is described, including a discussion of self-modulation and laser-hose instabilities. Examples of self-modulated laser wakefield accelerators are presented. copyright 1996 American Institute of Physics

  12. Two-laser infrared and ultraviolet matrix-assisted laser desorption/ionization.

    Science.gov (United States)

    Little, Mark W; Kim, Jae-Kuk; Murray, Kermit K

    2003-07-01

    Matrix-assisted laser desorption/ionization (MALDI) was performed using two pulsed lasers with wavelengths in the IR and UV regions. A 10.6 micro m pulsed CO(2) laser was used to irradiate a MALDI target, followed after an adjustable delay by a 337 nm pulsed nitrogen laser. The sample consisted of a 2,5-dihydroxybenzoic acid matrix and bovine insulin guest molecule. The pulse energy for both of the lasers was adjusted so that the ion of interest, either the matrix or guest ion, was not produced by either of the lasers alone. The delay time for maximum ion yield occurs at 1 micro s for matrix and guest ions and the signal decayed to zero in approximately 400 micro s. A mechanism is presented for enhanced UV MALDI ion yield following the IR laser pulse based on transient heating. PMID:12898657

  13. Progress in time transfer by laser pulses

    Science.gov (United States)

    Li, Xin; Yang, Fu-Min

    2004-03-01

    Time transfer by laser pulses is based on the propagation of light pulses between satellite and ground clocks or between remote clocks on earth. It will realize the synchronization of these clocks with high accuracy and stability. Several experiments of the time transfer by laser pulses had been successfully carried out in some countries. These experiments validate the feasibility of the synchronization of clocks by laser pulses. The paper describes the results of these experiments. The time comparison by laser pulses between atomic clocks on aircraft and ground ones in the United States, and the LASSO and T2L2 projects in France are introduced in detail.

  14. Ultrashort Laser Pulses in Biology and Medicine

    CERN Document Server

    Braun, Markus; Zinth, Wolfgang

    2008-01-01

    Sources of ultrashort laser pulses are nowadays commercially available and have entered many areas of research and development. This book gives an overview of biological and medical applications of these laser pulses. The briefness of these laser pulses permits the tracing of the fastest processes in photo-active bio-systems, which is one focus of the book. The other focus is applications that rely on the high peak intensity of ultrashort laser pulses. Examples covered span non-linear imaging techniques, optical tomography, and laser surgery.

  15. Ion Acceleration by Short Chirped Laser Pulses

    Directory of Open Access Journals (Sweden)

    Jian-Xing Li

    2015-02-01

    Full Text Available Direct laser acceleration of ions by short frequency chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1% can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies in the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e., higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  16. Ion Acceleration by Short Chirped Laser Pulses

    CERN Document Server

    Li, Jian-Xing; Keitel, Christoph H; Harman, Zoltán

    2015-01-01

    Direct laser acceleration of ions by short frequency-chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1 % can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies of the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e. higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

  17. Size-controllable synthesis of Bi/Bi2O3 heterojunction nanoparticles using pulsed Nd:YAG laser deposition and metal-semiconductor-heterojunction-assisted photoluminescence

    Science.gov (United States)

    Patil, Ranjit A.; Wei, Mao-Kuo; Yeh, P.-H.; Liang, Jyun-Bo; Gao, Wan-Ting; Lin, Jin-Han; Liou, Yung; Ma, Yuan-Ron

    2016-02-01

    We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes (LEDs) and laser diodes (LDs).We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes

  18. Dynamic pulsing of a MOPA fiber laser

    Science.gov (United States)

    Romero, Rosa; Guerreiro, Paulo T.; Hendow, Sami T.; Salcedo, José R.

    2011-05-01

    Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.

  19. Laser assisted graffiti paints removing

    Science.gov (United States)

    Novikov, B. Y.; Chikalev, Y. V.; Shakhno, E. A.

    2011-02-01

    It's hard to imagine a modern city view without some drawings and inscriptions, usually called "graffiti". Traditional cleaning methods do not suit modern requirements. Investigation of possibilities of laser assisted paints removing is described in this article. The conditions for removing different paints from different surfaces were defined.

  20. Analysis of Picosecond Pulsed Laser Melted Graphite

    Science.gov (United States)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M. S.; Huang, C. Y.; Malvezzi, A. M.; Bloembergen, N.

    1986-12-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm{sup -1} and the disorder-induced mode at 1360 cm{sup -1}, the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence.

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

    Science.gov (United States)

    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.

  2. Laser-assisted {alpha} decay

    Energy Technology Data Exchange (ETDEWEB)

    Castaneda Cortes, Hector Mauricio; Palffy, Adriana; Keitel, Christoph H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Popruzhenko, Sergey [Moscow State Engineering Physics Institute (Russian Federation)

    2012-07-01

    The spontaneous emission of alpha particles by unstable nuclei was one of the first physical processes to be described by quantum tunneling of a quasistationary state, i.e. a long-lived state. The development of new powerful coherent light sources opens the possibility to study the direct interaction between strong laser fields and atomic nuclei, assisting the tunneling of the {alpha} particle through the nuclear barrier. In this work we investigate for the first time the effect of strong laser fields on the tunneling and {alpha} particle emission of several medium-mass and heavy nuclei. To this end we make use of the formalism we have developed starting from the well-known Strong-Field Approximation and its complex trajectories formulation to describe the laser-assisted decay of quasistationary states [1]. The effect of a static as well as optical and X-ray monochromatic fields on the {alpha} decay lifetimes and {alpha} particle emission spectra is determined. We find that even at strong intensities, the laser-induced acceleration of the {alpha} decay is negligible, and only the spectra are significantly changed by the laser field. In particular, for optical fields, high laser intensities can lead to rescattering of the {alpha} particle off the daughter nucleus.

  3. Ultrashort pulse laser technology laser sources and applications

    CERN Document Server

    Schrempel, Frank; Dausinger, Friedrich

    2016-01-01

    Ultrashort laser pulses with durations in the femtosecond range up to a few picoseconds provide a unique method for precise materials processing or medical applications. Paired with the recent developments in ultrashort pulse lasers, this technology is finding its way into various application fields. The book gives a comprehensive overview of the principles and applications of ultrashort pulse lasers, especially applied to medicine and production technology. Recent advances in laser technology are discussed in detail. This covers the development of reliable and cheap low power laser sources as well as high average power ultrashort pulse lasers for large scale manufacturing. The fundamentals of laser-matter-interaction as well as processing strategies and the required system technology are discussed for these laser sources with respect to precise materials processing. Finally, different applications within medicine, measurement technology or materials processing are highlighted.

  4. Relativistic laser pulse compression in magnetized plasmas

    International Nuclear Information System (INIS)

    The self-compression of a weak relativistic Gaussian laser pulse propagating in a magnetized plasma is investigated. The nonlinear Schrödinger equation, which describes the laser pulse amplitude evolution, is deduced and solved numerically. The pulse compression is observed in the cases of both left- and right-hand circular polarized lasers. It is found that the compressed velocity is increased for the left-hand circular polarized laser fields, while decreased for the right-hand ones, which is reinforced as the enhancement of the external magnetic field. We find a 100 fs left-hand circular polarized laser pulse is compressed in a magnetized (1757 T) plasma medium by more than ten times. The results in this paper indicate the possibility of generating particularly intense and short pulses

  5. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  6. Laser assisted removal of fixed contamination from metallic substrate

    International Nuclear Information System (INIS)

    A single mode pulsed fiber laser was used to remove fixed contamination from stainless steel substrate by ablation. Samples were simulated by electro-deposition technique with 232U as the test contaminant. Laser power, repetition rate, laser beam scanning speed and number of passes were optimised to obtain the desired ablation depth in the substrate. Ablation depth varying between few microns to few hundreds of microns could be achieved through careful control of these processing parameters. The absence of any activity in laser treated samples provided experimental signature of the efficacy of the laser assisted removal of fixed contamination. (author)

  7. Picosecond Pulse Laser Microstructuring of silicon

    Institute of Scientific and Technical Information of China (English)

    赵明; 尹钢; 朱京涛; 赵利

    2003-01-01

    We report the experimental results of picosecond pulse laser microstructuring (pulse duration 35ps, wavelength 1.06μm, repetition rate 10Hz) of silicon using the direct focusing technique. Arrays of sharp conical spikes located below the initial surface have been formed by cumulative picosecond pulsed laser irradiation of silicon in SF6. Irradiation of silicon surface in air, N2, or vacuum creates ripple-like patterns, but does not create the sharp conical spikes.

  8. Classical Dynamics of Free Electromagnetic Laser Pulses

    OpenAIRE

    Goto, S; Tucker, R. W.; Walton, T. J.

    2015-01-01

    We discuss a class of exact finite energy solutions to the vacuum source-free Maxwell field equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged test particles. These solutions are classified in terms of their chiral content based on their influence on particular charge configurations in space. Such solutions offer a computationally efficient parameterization of compact laser pulses used in laser-matter simulations and provide a poten...

  9. Laser-assisted fabrication of materials

    CERN Document Server

    Manna, Indranil

    2013-01-01

    Laser assisted fabrication involves shaping of materials using laser as a source of heat. It can be achieved by removal of materials (laser assisted cutting, drilling, etc.), deformation (bending, extrusion), joining (welding, soldering) and addition of materials (surface cladding or direct laser cladding). This book on ´Laser assisted Fabrication’ is aimed at developing in-depth engineering concepts on various laser assisted macro and micro-fabrication techniques with the focus on application and a review of the engineering background of different micro/macro-fabrication techniques, thermal history of the treated zone and microstructural development and evolution of properties of the treated zone.

  10. High Power Picosecond Laser Pulse Recirculation

    Energy Technology Data Exchange (ETDEWEB)

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  11. Generation of laser pulse trains for tests of multi-pulse laser wakefield acceleration

    Science.gov (United States)

    Shalloo, R. J.; Corner, L.; Arran, C.; Cowley, J.; Cheung, G.; Thornton, C.; Walczak, R.; Hooker, S. M.

    2016-09-01

    In multi-pulse laser wakefield acceleration (MP-LWFA) a plasma wave is driven by a train of low-energy laser pulses separated by the plasma period, an approach which offers a route to driving plasma accelerators with high efficiency and at high pulse repetition rates using emerging technologies such as fibre and thin-disk lasers. Whilst these laser technologies are in development, proof-of-principle tests of MP-LWFA require a pulse train to be generated from a single, high-energy ultrafast pulse. Here we demonstrate the generation of trains of up to 7 pulses with pulse separations in the range 150-170 fs from single 40 fs pulses produced by a Ti:sapphire laser.

  12. MOPA pulsed fiber laser for silicon scribing

    Science.gov (United States)

    Yang, Limei; Huang, Wei; Deng, Mengmeng; Li, Feng

    2016-06-01

    A 1064 nm master oscillator power amplifier (MOPA) pulsed fiber laser is developed with flexible control over the pulse width, repetition frequency and peak power, and it is used to investigate the dependence of mono-crystalline silicon scribe depth on the laser pulse width, scanning speed and repeat times. Experimental results indicate that long pulses with low peak powers lead to deep ablation depths. We also demonstrate that the ablation depth grows fast with the scanning repeat times at first and progressively tends to be saturated when the repeat times reach a certain level. A thermal model considering the laser pulse overlapping effect that predicts the silicon temperature variation and scribe depth is employed to verify the experimental conclusions with reasonably close agreement. These conclusions are of great benefits to the optimization of the laser material processing with high efficiency.

  13. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2015-01-01

    Full Text Available To understand the performance of laser ranging system under the rain weather condition, we need to know the propagating characteristics of laser pulse in rain. In this paper, the absorption and attenuation coefficients were calculated based on the scattering theories in discrete stochastic media, and the propagating characteristics of laser pulse in rain were simulated and analyzed using Monte-Carlo method. Some simulation results were verified by experiments, and the simulation results are well matched with the experimental data, with the maximal deviation not less than 7.5%. The results indicated that the propagating laser beam would be attenuated and distorted due to the scattering and absorption of raindrops, and the energy attenuation and pulse shape distortion strongly depended on the laser pulse widths.

  14. Injection locked oscillator system for pulsed metal vapor lasers

    Science.gov (United States)

    Warner, Bruce E.; Ault, Earl R.

    1988-01-01

    An injection locked oscillator system for pulsed metal vapor lasers is disclosed. The invention includes the combination of a seeding oscillator with an injection locked oscillator (ILO) for improving the quality, particularly the intensity, of an output laser beam pulse. The present invention includes means for matching the first seeder laser pulses from the seeding oscillator to second laser pulses of a metal vapor laser to improve the quality, and particularly the intensity, of the output laser beam pulse.

  15. Pulse front tilt measurement of femtosecond laser pulses

    Science.gov (United States)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  16. Measurement of pulse lengthening with pulse energy increase in picosecond Nd:YAG laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Cutolo, A.; Zeni, L.; Berardi, V.; Bruzzese, R.; Solimeno, S.; Spinelli, N.

    1989-03-15

    Taking advantage of a new technique, we have monitored the relative variations of time duration and mode size as a function of the pulse energy for 30-ps-long Nd:YAG laser pulses. In particular, by carrying out a statistical analysis, we have observed that the pulse time duration is an increasing function of the pulse energy, according to the theoretical modeling of passively mode-locked lasers. The measurements can be easily extended to the femtosecond regime.

  17. PULSED MODE LASER CUTTING OF SHEETS FOR TAILORED BLANKS

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1999-01-01

    This paper describes how the laser cutting process can be optimised in such a way that the cut sheets can subsequently be used to laser weld tailored blanks. In a number of systematic laboratory experiments the effect of cutting speed, assist gas pressure, average laser power and pulse energy...... was analysed. For quality assessment the squareness, roughness and dross attachment of laser cut blanks were measured. In all tests, the medium strength steel GA 260 with a thickness of 1.8 mm was used. In this work it has been successfully demonstrated that the squareness of a cut can be used as a quality...... item for parameter optimisation of laser cut sheets used for tailored blanks. It was concluded that high quality cut edges with a squareness as small as 0.015 mm may be obtained. Such edges are well suited for subsequent laser welding....

  18. Laser assisted decontamination of nuclear fuel elements

    International Nuclear Information System (INIS)

    Laser assisted removal of loosely bound fuel particulates from the clad surface following the process of pellet loading has decided advantages over conventional methods. It is a dry and noncontact process that generates very little secondary waste and can occur inside a glove box without any manual interference minimizing the possibility of exposure to personnel. The rapid rise of the substrate/ particulate temperature owing to the absorption of energy from the incident laser pulse results in a variety of processes that may lead to the expulsion of the particulates. As a precursor to the cleaning of the fuel elements, initial experiments were carried out on contamination simulated on commonly used clad surfaces to gain a first hand experience on the various laser parameters for which as efficient cleaning can be obtained without altering the properties of the clad surface. The cleaning of a dummy fuel element was subsequently achieved in the laboratory by integrating the laser with a work station that imparted simultaneous rotational and linear motion to the fuel element. (author)

  19. Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

    Energy Technology Data Exchange (ETDEWEB)

    Plateau, Guillaume; Geddes, Cameron; Matlis, Nicholas; Cormier-Michel, Estelle; Mittelberger, Daniel; Nakamura, Kei; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2011-07-19

    Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.

  20. The Dynamics of Compact Laser Pulses

    OpenAIRE

    Goto, S; Tucker, Robin William; Walton, T. J.

    2015-01-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium i...

  1. The dynamics of compact laser pulses

    Science.gov (United States)

    Goto, S.; Tucker, R. W.; Walton, T. J.

    2016-07-01

    We discuss the use of a class of exact finite energy solutions to the vacuum source-free Maxwell equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged point particles. These compact solutions are classified in terms of their chiral content and their influence on particular charge configurations in space. The results of such classical interactions motivate a phenomenological quantum description of a propagating laser pulse in a medium in terms of an effective quantum Hamiltonian.

  2. Short pulse laser train for laser plasma interaction experiments

    International Nuclear Information System (INIS)

    A multiframe, high-time resolution pump-probe diagnostic consisting of a consecutive train of ultrashort laser pulses (∼ps) has been developed for use with a chirped pulse amplification (CPA) system. A system of high quality windows is used to create a series of 1054 nm picosecond-laser pulses which are injected into the CPA system before the pulse stretcher and amplifiers. By adding or removing windows in the pulse train forming optics, the number of pulses can be varied. By varying the distance and thickness of the respective optical elements, the time in between the pulses, i.e., the time in between frames, can be set. In our example application, the CPA pulse train is converted to 527 nm using a KDP crystal and focused into a preformed plasma and the reflected laser light due to stimulated Raman scattering is measured. Each pulse samples different plasma conditions as the plasma evolves in time, producing more data on each laser shot than with a single short pulse probe. This novel technique could potentially be implemented to obtain multiple high-time resolution measurements of the dynamics of physical processes over hundreds of picoseconds or even nanoseconds with picosecond resolution on a single shot

  3. Survey on modern pulsed high power lasers

    International Nuclear Information System (INIS)

    The requirements to be met by lasers for particle acceleration are partially similar to those already known for fusion lasers. The power level wanted in both caes is up to 100 TW or even more. The pulse durations favourable for laser accelerators are in the range from 1 ps to 1000 ps whereas fusion lasers require several ns. The energy range for laser accelerators is thus correspondingly smaller than that for fusion lasers: 1-100 kJ versus several 100 kJ. The design criteria of lasers meeting the requirements are discussed in the following. The CO2, iodine, Nd:glass and excimer lasers are treated in detail. The high repetition rate aspect will not be particularly addressed since for the present generation of lasers the wanted rates of far above 1 Hz are completely out of scope. Moreover, for the demonstration of principle these rates are not needed. (orig./HSI)

  4. Laser-assisted deposition of thin C60 films

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Fæster, Søren

    Metal and metal oxide films with controlled thickness from a fraction of a monolayer up more than 1000 nm and known stoichiometry can be produced by pulsed laser deposition (PLD) relatively easily, and (PLD) is now a standard technique in all major research laboratories within materials science....... However, organic materials are usually not well suited for direct laser irradiation, since the organic molecules may suffer from fragmentation by the laser light. We have, therefore, explored the possible fragmentation of organic molecules by attempting to produce thin films of C60 which is a strongly...... bound carbon molecule with a well-defined mass (M = 720 amu) and therefore a good, organic test molecule. C60 fullerene thin films of average thickness of more than 100 nm was produced in vacuum by matrix-assisted pulsed laser evaporation (MAPLE). A 355 nm Nd:YAG laser was directed onto a frozen target...

  5. Rhabdomyolysis After Cosmetic Laser-Assisted Liposuction.

    Science.gov (United States)

    Shin, Jin-yong; Chang, Hak

    2015-08-01

    A 34-year-old-female patient visited our emergency room for symptoms of disturbance of urination and shortness of breath. She was diagnosed with rhabdomyolysis with acute kidney injury after laser-assisted liposuction and required hemodialysis. Although laser-assisted liposuction is a well-used procedure, it can cause local complications, such as burns and skin irregularities, as well as systemic complications, such as infection, fever, and emboli. However, laser-assisted, liposuction-induced rhabdomyolysis has not been reported. Repetitive exercises, trauma, and crush injury are the major causes of rhabdomyolysis. In this study, a unique case of rhabdomyolysis that developed after laser-assisted liposuction is reported.

  6. Modeling of pulsed lasers for remote sensing

    Science.gov (United States)

    Walsh, Brian M.; Barnes, Norman P.; Petros, Mulugeta; Yu, Jirong; Singh, Upendra N.

    2005-01-01

    Pulsed lasers are useful for remote sensing of wind and greenhouse gases to better understand the atmosphere and its impact on weather patterns and the environment. It is not always practical to develop and optimize new laser systems empirically due to the time and expense associated with such endeavors. A practical option is to use a laser model to predict various performance parameters and compare these with the needs required for a particular remote sensing application. This approach can be very useful in determining the efficacy of potential laser systems, saving both time and money before proceeding with the actual construction of a laser device. As a pedagogical example, the modeling of diode pumped Tm:Ho:YLF and Tm:Ho:LuLF lasers are examined. Tm:Ho lasers operating around 2.0 μm have been used for wind measurements such as clear air turbulence and wake vortices. The model predictions for the laser systems examined here are compared to the actual laser performance, validating the usefulness of the modeling approach. While Tm:Ho fluoride lasers are used as a pedagogical example, the model is applicable to any lanthanide series pulsed laser system. This provides a useful tool for investigating potential laser systems that meet the requirements desired for a variety of remote sensing applications.

  7. Computer control of pulsed tunable dye lasers

    International Nuclear Information System (INIS)

    Pulsed tunable dye lasers are being used extensively for spectroscopic and photo-chemical experiments, and a system for acquisition and spectral analysis of a volume of data generated will be quite useful. The development of a system for wavelength tuning and control of tunable dye lasers and an acquisition system for spectral data generated in experiments with these lasers are described. With this system, it is possible to control the tuning of three lasers, and acquire data in four channels, simultaneously. It is possible to arrive at the desired dye laser wavelength with a reproducibility of ± 0.012 cm-1, which is within the absorption width (atomic interaction) caused by pulsed dye lasers of linewidth 0.08 cm-1. The spectroscopic data generated can be analyzed for spectral identification within absolute accuracy ± 0.012 cm-1. (author). 6 refs., 11 figs

  8. Laser pulse shaping for high gradient accelerators

    Science.gov (United States)

    Villa, F.; Anania, M. P.; Bellaveglia, M.; Bisesto, F.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G.; Moreno, M.; Petrarca, M.; Pompili, R.; Vaccarezza, C.

    2016-09-01

    In many high gradient accelerator schemes, i.e. with plasma or dielectric wakefield induced by particles, many electron pulses are required to drive the acceleration of one of them. Those electron bunches, that generally should have very short duration and low emittance, can be generated in photoinjectors driven by a train of laser pulses coming inside the same RF bucket. We present the system used to shape and characterize the laser pulses used in multibunch operations at Sparc_lab. Our system gives us control over the main parameter useful to produce a train of up to five high brightness bunches with tailored intensity and time distribution.

  9. Laser plasma formation assisted by ultraviolet pre-ionization

    International Nuclear Information System (INIS)

    We present experimental and modeling studies of air pre-ionization using ultraviolet (UV) laser pulses and its effect on laser breakdown of an overlapped near-infrared (NIR) pulse. Experimental studies are conducted with a 266 nm beam (fourth harmonic of Nd:YAG) for UV pre-ionization and an overlapped 1064 nm NIR beam (fundamental of Nd:YAG), both having pulse duration of ∼10 ns. Results show that the UV beam produces a pre-ionized volume which assists in breakdown of the NIR beam, leading to reduction in NIR breakdown threshold by factor of >2. Numerical modeling is performed to examine the ionization and breakdown of both beams. The modeled breakdown threshold of the NIR, including assist by pre-ionization, is in reasonable agreement with the experimental results

  10. Pulsed solid state lasers for medicine

    Science.gov (United States)

    Kertesz, Ivan; Danileiko, A. Y.; Denker, Boris I.; Kroo, Norbert; Osiko, Vyacheslav V.; Prokhorov, Alexander M.

    1994-02-01

    The effect on living tissues of different pulsed solid state lasers: Nd:YAG ((lambda) equals 1.06 micrometers ) Er:glass (1.54 micrometers ), Ho:YAG (2.1 micrometers ) and Er:YAG (2.94 micrometers ) is compared with the continuous wave Nd:YAG- and CO2-lasers used in operating theaters. Portable Er:glass- and Er:YAG-lasers are developed for surgery/cosmetics and HIV-safe blood testing.

  11. Classical Dynamics of Free Electromagnetic Laser Pulses

    CERN Document Server

    Goto, S; Walton, T J

    2015-01-01

    We discuss a class of exact finite energy solutions to the vacuum source-free Maxwell field equations as models for multi- and single cycle laser pulses in classical interaction with relativistic charged test particles. These solutions are classified in terms of their chiral content based on their influence on particular charge configurations in space. Such solutions offer a computationally efficient parameterization of compact laser pulses used in laser-matter simulations and provide a potential means for experimentally bounding the fundamental length scale in the generalized electrodynamics of Bopp, Lande and Podolsky.

  12. Heat accumulation during pulsed laser materials processing.

    Science.gov (United States)

    Weber, Rudolf; Graf, Thomas; Berger, Peter; Onuseit, Volkher; Wiedenmann, Margit; Freitag, Christian; Feuer, Anne

    2014-05-01

    Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived. PMID:24921828

  13. Effect of nitrogen surrounding gas and plasma assistance on nitrogen incorporation in a-C:N films by femtosecond pulsed laser deposition

    Science.gov (United States)

    Bourquard, F.; Maddi, C.; Donnet, C.; Loir, A.-S.; Barnier, V.; Wolski, K.; Garrelie, F.

    2016-06-01

    In the context of nitrogen-rich amorphous carbon thin films ultrafast pulsed laser deposition from graphite targets in inert nitrogen or nitrogen plasma ambient, this study assesses the correlation between the ablation plume composition and dynamics and the thin films contents and structures. The use of both optical emission spectroscopy and spectrally resolved 2D imaging, coupled with intensified CCD temporal resolution, allows to precisely follow such species of the plume as CN and C2 molecules, from their apparition to their deposition on the substrate. The results show that carbon-nitrogen bonding arises at the early time of expansion with little changes in quantity thereafter. The key role of the DC-bias is in lowering the molecular weight of the ambient gas, thus easing molecules way toward the target and interfering with the chemical reaction for CN generation. Depending on the ambient pressure, these processes will have drastically different effects on the thin films properties and contents. This work thus explains the origin of high nitrogen contents in a-C:N thin films obtained using DC-bias, and proposes an easy in situ optical observation-based way to predict and look for the best conditions to maximize those contents in future work.

  14. RF synchronized short pulse laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Okamura, Masahiro [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamazaki, Atsushi [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan)

    2016-02-15

    A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

  15. STATISTICAL ANALYSIS OF FEMTOSECOND PULSES LASER ON HOLE DRILLING OF SILICON WAFER

    OpenAIRE

    Jiao, L; E. Y. K. Ng; Zheng, H.; Wee, L.M.

    2011-01-01

    This study investigated the relationship and parameters interactions between five independent variables in laser percussion drilling of micro-hole. Experiments were conducted on single crystal silicon wafer with material thickness of 725 μm using femtosecond (fs) laser with wavelength of 775 nm and pulse duration of 200 fs. Laser power, focus position, number of pulses, workpiece temperature and assist liquid were selected as independent process variables. Taguchi L18 orthogonal array was app...

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

    Science.gov (United States)

    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.

  17. Laser assisted Breit-Wheeler and Schwinger processes

    CERN Document Server

    Nousch, T; Seipt, D; Kämpfer, B; Titov, A I; Blaschke, D; Panferov, A D; Smolyansky, S A

    2016-01-01

    The assistance of an intense optical laser pulse on electron-positron pair production by the Breit-Wheeler and Schwinger processes in XFEL fields is analyzed. The impact of a laser beam on high-energy photon collisions with XFEL photons consists in a phase space redistribution of the pairs emerging in the Breit-Wheeler sub-process. We provide numerical examples of the differential cross section for parameters related to the European XFEL. Analogously, the Schwinger type pair production in pulsed fields with oscillating components referring to a superposition of optical laser and XFEL frequencies is evaluated. The residual phase space distribution of created pairs is sensitive to the pulse shape and may differ significantly from transiently achieved mode occupations.

  18. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    Science.gov (United States)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  19. Drop shaping by laser-pulse impact

    CERN Document Server

    Klein, Alexander L; Visser, Claas Willem; Lhuissier, Henri; Sun, Chao; Snoeijer, Jacco H; Villermaux, Emmanuel; Lohse, Detlef; Gelderblom, Hanneke

    2015-01-01

    We study the hydrodynamic response of a falling drop hit by a laser pulse. Combining high-speed with stroboscopic imaging we report that a millimeter-sized dyed water drop hit by a milli-Joule nanosecond laser-pulse deforms and propels forward at several meters per second, until it eventually fragments. We show that the drop motion results from the recoil momentum imparted at the drop surface by water vaporization. We measure the propulsion speed and the time-deformation law of the drop, complemented by boundary integral simulations. We explain the drop propulsion and shaping in terms of the laser pulse energy and drop surface tension. These findings are crucial for the generation of extreme ultraviolet (EUV) light in lithography machines.

  20. Pulsed laser illumination of photovoltaic cells

    Science.gov (United States)

    Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

  1. Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

    Science.gov (United States)

    Kojima, Sadaoki; Arikawa, Yasunobu; Morace, Alessio; Hata, Masayasu; Nagatomo, Hideo; Ozaki, Tetsuo; Sakata, Shohei; Lee, Seung Ho; Matsuo, Kazuki; Farley Law, King Fai; Tosaki, Shota; Yogo, Akifumi; Johzaki, Tomoyuki; Sunahara, Atsushi; Sakagami, Hitoshi; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi

    2016-05-01

    The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

  2. Pulsed uv nitrogen laser: dynamical behavior

    International Nuclear Information System (INIS)

    Using the time dependent rate equations, the dynamical behavior of a high power pulsed N2 laser radiating at 337.1 nm is derived. The threshold conditions are given. The output peak power and pulse width as a function of length and initial inversion density are shown. The theoretical results derived are compared with experimental data and are found to be in good agreement

  3. Laser pulse shaping with liquid crystals

    OpenAIRE

    Martín Pereda, José Antonio; Muriel Fernández, Miguel Ángel

    1983-01-01

    A method of unpolarized laser pulses shaping is reported. The basis of the method is the use of an hybrid optical bistable device with nematic liquid-crystals, similar to the one previously reported by us. A sample of the input light constrols, by an asymmetrical electronic comparator, a 1 x 2 electro-optical total switch. The output pulses are reshaped and maintain the same polarization properties as the input light. From triangular input light signals, symmetriacl and asymmetrical output pu...

  4. Short pulse high power fiber laser systems

    OpenAIRE

    Malinowski, A.; Piper, A; Price, J.H.V.; He, F.; Ibsen, M; Nilsson, J.; Richardson, D J

    2005-01-01

    We review the rapid recent progress in the development of short pulse high-power fiber laser and amplifier devices. Use of cladding pump technology now provides a route to compact and efficient laser and amplifier systems with high beam quality and high output powers. A new Yb-fiber CPA system incorporating a CFBG stretcher with both 2nd and 3rd order dispersion is presented for high pulse energy applications. In addition, a simplified Yb-fiber parabolic amplifier system is also shown to be s...

  5. Modeling Pulsed Laser Melting of Embedded Nanoparticles

    Science.gov (United States)

    Sawyer, Carolyn Anne

    A model of pulsed laser melting of embedded nanoparticles is introduced. Pulsed laser melting (PLM) is commonly used to achieve a fast quench rate in nanoparticles; this model enables a better understanding of the influence of PLM on the size distribution of nanoparticles, which is crucial for studying or using their size-dependent properties. The model includes laser absorption according to the Mie theory, a full heat transport model, and rate equations for nucleation, growth, coarsening, and melting and freezing of nanoparticles embedded in a transparent matrix. The effects of varying the laser parameters and sample properties are studied, as well as combining PLM and rapid thermal annealing (RTA) processing steps on the same sample. A general theory for achieving narrow size distributions of nanoparticles is presented, and widths as narrow as 12% are achieved using PLM and RTA.

  6. Polyethylene welding by pulsed visible laser irradiation

    Science.gov (United States)

    Torrisi, L.; Caridi, F.; Visco, A. M.; Campo, N.

    2011-01-01

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  7. Polyethylene welding by pulsed visible laser irradiation

    International Nuclear Information System (INIS)

    Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as 'through transmission visible laser welding'. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part. In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

  8. Short-pulse laser materials processing

    International Nuclear Information System (INIS)

    The goal of this project was to develop, through experiments and modeling, a better understanding of the physics issues and machining techniques related to short-pulse laser materials processing. Although we have successfully demonstrated many types of cuts in a wide range of materials, our general short-pulse machining scientific knowledge and our ability to model the complex physical processes involved are limited. During this past year we made good progress in addressing some of these issues, but there remain many unanswered questions. Section 2 begins with a theoretical look at short-pulse laser ablation of material using a 1-D radiation-hydrodynamic code which includes a self-consistent description of laser absorption and reflection from an expanding plasma. In Section 3 we present measurements of scaling relationships, hole drilling progression, electric field and polarization effects, and a detailed look at the interesting structures formed during hole drilling of metals under various conditions. Section 4 describes the consequences of the presence of a prepulse before the main drilling pulse. In Section 5 we take a brief look at the plasma plume: how it can be useful, and how we can avoid it. Finally, Section 6 contains a couple of examples of machining non-metals. The laser system used for practically all the experimental results presented here was a short-pulse laser based on Ti:sapphire, which produced 150-fs pulses (minimum) centered at 825 nm, of energy up to 5 mJ at 1 kHz, or 5 W average power

  9. Graphene in Ultrafast and Ultrastrong Laser Pulses

    Science.gov (United States)

    Koochakikelardeh, Hamed; Apalkov, Vadym; Stockman, Mark

    2015-03-01

    We have shown that graphene subjected to an ultrafast (near-single-oscillation pulse) and strong (F ~ 1-3 V/Å) pulse exhibits fundamental behavior dramatically different from both insulators and metals. In such an ultrafast and ultrastrong field, the electron dynamics is coherent, in contrast to relatively long pulses (τ>100 fs) where the electron's dephasing becomes important leading to incoherent dynamics. Electron transfer from the valence band (VB) to the conduction band (CB) is deeply irreversible i.e., non-adiabatic, in which the residual CB population (after pulse ends) is close to the maximum one. The residual CB population as a function of wave vector is nonuniform with a few strongly localized spots near the Dirac points, at which the CB population is almost 100%. Furthermore, it is shown the direction of charge transfer depends on the pulse amplitude. Namely, at small pulse amplitude, =1 V/Å, it is in opposite direction of the pulse maximum (negative transferred charge). Consequently, in terms of charge transport, graphene at small pulse intensities behaves as a dielectric while at large intensities acts as a metal. These femtosecond currents and charge transfer in graphene may provide fundamental basis for detection and calibration of ultrashort intense laser pulses and are promising for petahertz information processing. This work was supported by U.S. Office of Naval Research No. N00014-13-1-0649 and NSF Grant No. ECCS-1308473.

  10. Lasers and Intense Pulsed Light Hidradenitis Suppurativa.

    Science.gov (United States)

    Saunte, Ditte M; Lapins, Jan

    2016-01-01

    Lasers and intense pulsed light (IPL) treatment are useful for the treatment of hidradenitis suppurativa (HS). Carbon dioxide lasers are used for cutting or vaporization of the affected area. It is a effective therapy for the management of severe and recalcitrant HS with persistent sinus tract and scarring, and can be performed under local anesthesia. HS has a follicular pathogenesis. Lasers and IPL targeting the hair have been found useful in treating HS by reducing the numbers of hairs in areas with HS. The methods have few side effects, but the studies are preliminary and need to be repeated.

  11. Laser-assisted nuclear photoeffect reexamined

    CERN Document Server

    Kálmán, Péter; Keszthelyi, Tamás

    2013-01-01

    The S-matrix element and the cross section of the laser-assisted nuclear photoeffect are recalculated in a gauge invariant manner taking into account the effect of the Coulomb field of the remainder nucleus. The \\gamma-photon energy dependence of the laser free cross section obtained in the plane wave and long-wavelength Coulomb-Volkov approximations are compared. Numerically the laser-assisted partial cross sections with laser photon energy 2 keV and some different polarization states of \\gamma-photon of energy 3 MeV are investigated.

  12. Pulse solid state lasers in aesthetic surgery

    Science.gov (United States)

    Dobryakov, Boris S.; Greben'kova, Ol'ga B.; Gulev, Valerii S.

    1996-04-01

    The emission of a pulse-periodic laser on alumo-ittrium garnet applied for preventive and medical treatment of a capsule contracture round implanted prostheses in xenoplastics is described in the present paper. The results obtained testify to a high efficiency of suggested method.

  13. Electron photodetachment by short laser pulse

    NARCIS (Netherlands)

    Golovinski, P. A.; Drobyshev, A. A.

    2012-01-01

    Expressions are derived for calculations of the total probabilities and electron spectra for the photodetachment of electrons from negative ions with filled valence s shells by ultrashort laser pulses. Particular calculations have been performed for two negative ions (H- and Li-) and titanium-sapphi

  14. Pulsed laser deposition: Prospects for commercial deposition of epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Muenchausen, R.E.

    1999-03-01

    Pulsed laser deposition (PLD) is a physical vapor deposition (PVD) technique for the deposition of thin films. The vapor source is induced by the flash evaporation that occurs when a laser pulse of sufficient intensity (about 100 MW/cm{sup 2}) is absorbed by a target. In this paper the author briefly defines pulsed laser deposition, current applications, research directed at gaining a better understanding of the pulsed laser deposition process, and suggests some future directions to enable commercial applications.

  15. Cluster-assisted generation of multi-charged ions in nanosecond laser ionization of pulsed hydrogen sulfide beam at 1064 and 532 nm

    Institute of Scientific and Technical Information of China (English)

    Niu Dong-Mei; Li Hai-Yang; Luo Xiao-Lin; Liang Feng; Cheng Shuang; Li An-Lin

    2006-01-01

    The multi-charged sulfur ions of Sq+ (q ≤ 6) have been generated when hydrogen sulfide cluster beams are irradiated by a nanosecond laser of 1064 and 532 nm with an intensity of 1010 ~ 1012W·cm-2. S6+ is the dominant multicharged species at 1064 nm, while S4+, S3+ and S2+ ions are the main multi-charged species at 532 nm. A three-step model (i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing) is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2, λ being the laser wavelength.

  16. Hemifusion of cells using femtosecond laser pulses

    Science.gov (United States)

    Katchinskiy, Nir; Godbout, Roseline; Goez, Helly R.; Elezzabi, Abdulhakem Y.

    2015-03-01

    Attachment of single cells via hemifusion of cellular membranes using femtosecond laser pulses is reported in this manuscript. This is a method to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser is described. A fluorescent dye, Calcein AM, was used to verify that the cell's cytoplasm did not migrate from a dyed cell to a non-dyed cell, in order to ascertain that the cells did not go through cell-fusion process. An optical tweezer was used in order to assess the mechanical integrity of the attached joint membranes. Hemifusion of cellular membranes was successful without initiating full cell fusion. Attachment efficiency of 95% was achieved, while the cells' viability was preserved. The attachment was performed via the delivery of one to two trains of sub-10 femtosecond laser pulses lasting 15 milliseconds each. An ultrafast reversible destabilization of the phospholipid molecules in the cellular membranes was induced due to a laser-induced ionization process. The inner phospholipid cell membrane remained intact during the attachment procedure, and cells' cytoplasm remained isolated from the surrounding medium. The unbounded inner phospholipid molecules bonded to the nearest free phospholipid molecule, forming a joint cellular membrane at the connection point. The cellular membrane hemifusion technique can potentially provide a platform for the creation of engineered tissue and cell cultures.

  17. Dynamics of laser-induced electroconvection pulses.

    Science.gov (United States)

    Giebink, N C; Johnson, E R; Saucedo, S R; Miles, E W; Vardanyan, K K; Spiegel, D R; Allen, C C

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/degrees C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10-20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left (right) side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches approximately 0.3. We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  18. Dynamics of laser-induced electroconvection pulses

    Science.gov (United States)

    Giebink, N. C.; Johnson, E. R.; Saucedo, S. R.; Miles, E. W.; Vardanyan, K. K.; Spiegel, D. R.; Allen, C. C.

    2004-06-01

    We first report that, for planar nematic 4-methoxy-benzilidene-4-butylaniline (MBBA), the electroconvection threshold voltage has a nonmonotonic temperature dependence, with a well-defined minimum, and a slope of about -0.12 V/° C near room temperature at 70 Hz. Motivated by this observation, we have designed an experiment in which a weak continuous-wave absorbed laser beam with a diameter comparable to the pattern wavelength generates a locally supercritical region, or pulse, in dye-doped MBBA. Working 10 20 % below the laser-free threshold voltage, we observe a steady-state pulse shaped as an ellipse with the semimajor axis oriented parallel to the nematic director, with a typical size of several wavelengths. The pulse is robust, persisting even when spatially extended rolls develop in the surrounding region, and displays rolls that counterpropagate along the director at frequencies of tenths of Hz, with the rolls on the left () side of the ellipse moving to the right (left). Systematic measurements of the sample-voltage dependence of the pulse amplitude, spatial extent, and frequency show a saturation or decrease when the control parameter (evaluated at the center of the pulse) approaches ˜0.3 . We propose that the model for these pulses should be based on the theory of control-parameter ramps, supplemented with new terms to account for the advection of heat away from the pulse when the surrounding state becomes linearly unstable. The advection creates a negative feedback between the pulse size and the efficiency of heat transport, which we argue is responsible for the attenuation of the pulse at larger control-parameter values.

  19. Synthesis of high Al content Al{sub x}Ga{sub 1−x}N ternary films by pulsed laser co-ablation of GaAs and Al targets assisted by nitrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Hua; You, Qinghu [Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Hu, Zhigao; Guo, Shuang [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241 (China); Yang, Xu; Sun, Jian; Xu, Ning [Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Wu, Jiada, E-mail: jdwu@fudan.edu.cn [Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China)

    2014-12-15

    Highlights: • Al{sub x}Ga{sub 1−x}N films were synthesized by co-ablation of an Al target and a GaAs target. • Nitrogen plasma was used to assist the synthesis of Al{sub x}Ga{sub 1−x}N ternary films. • The Al{sub x}Ga{sub 1−x}N films are slightly rich in N with an Al content above 0.6. • The Al{sub x}Ga{sub 1−x}N films are hexagonal wurtzite in crystal structure. • The Al{sub x}Ga{sub 1−x}N films have an absorption edge of 260 nm and a band gap of 4.7 eV. - Abstract: We present the synthesis of Al{sub x}Ga{sub 1−x}N ternary films by pulsed laser co-ablation of a polycrystalline GaAs target and a metallic Al target in the environment of nitrogen plasma which provides nitrogen for the films and assists the formation of nitride films. Field emission scanning electron microscopy exposes the smooth surface appearance and dense film structure. X-ray diffraction, Fourier-transform infrared spectroscopy and Raman scattering spectroscopy reveal the hexagonal wurtzite structure. Optical characterization shows high optical transmittance with an absorption edge of about 260 nm and a band gap of 4.7 eV. Compositional analysis gives the Al content of about 0.6. The structure and optical properties of the Al{sub x}Ga{sub 1−x}N films are compared with those of binary GaN and AlN films synthesized by ablating GaAs or Al target with the same nitrogen plasma assistance.

  20. Enhanced subthreshold electron-positron production in short laser pulses

    OpenAIRE

    Titov, A. I.; Takabe, H.; Kampfer, B.; Hosaka, A.

    2012-01-01

    The emission of electron-positron pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g.\\ laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in case of moderate laser pulse intensities.

  1. Enhanced subthreshold e+ e- production in short laser pulses.

    Science.gov (United States)

    Titov, A I; Takabe, H; Kämpfer, B; Hosaka, A

    2012-06-15

    The emission of e+ e- pairs off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g., laser) wave field is analyzed. A significant increase of the total cross section of pair production in the subthreshold region is found for decreasing laser pulse duration even in the case of moderate laser pulse intensities. PMID:23004244

  2. Fundamentals of laser pulse irradiation of silicon

    International Nuclear Information System (INIS)

    A computer model has been developed to describe the space and time evolution of carrier concentration, carrier energy and lattice temperature during nanosecond and picosecond laser pulse irradiation of Si single crystals. In particular the dynamic response has been evaluated for energy density of the ps laser pulse below and above the density threshold for surface melting. The obtained data allow a comparison with time-resolved reflectivity measurements reported in the literature. The available data are fitted by the computer model assuming a relaxation time for the energy transfer from the carriers to the lattice of 1 ps. The validity of the thermal model used to describe laser annealing in the nanosecond regime is assessed. (author)

  3. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim

    2011-07-07

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

  4. Phase Noise Comparision of Short Pulse Laser Systems

    Energy Technology Data Exchange (ETDEWEB)

    S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

    2006-12-01

    This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

  5. Theoretical analysis of pulse modulation of semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Xu Baoxi; Zhan Yushu; Guo Siji

    1987-05-01

    Rate equations of Gaussian shape pulse modulated semiconductor lasers are solved by Runge--Kutta method, and the results are analyzed. The formulae for calculating the delay time, pulse width of laser pulse and maximum bit-rate of Gaussian shape pulse modulation are derived. The experimental results of modulation pattern effects are given.

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

    Science.gov (United States)

    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.

  7. Double nanosecond pulses generation in ytterbium fiber laser

    Science.gov (United States)

    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.

  8. Cluster-assisted generation of multi-charged ions in nanosecond laser ionization of pulsed hydrogen sulfide beam at 1064 and 532 nm

    Science.gov (United States)

    Niu, Dong-Mei; Li, Hai-Yang; Luo, Xiao-Lin; Liang, Feng; Cheng, Shuang; Li, An-Lin

    2006-07-01

    The multi-charged sulfur ions of Sq+ (qlaser of 1064 and 532 nm with an intensity of 1010~ 1012W.cm-2. S6+ is the dominant multi-charged species at 1064 nm, while S4+, S3+ and S2+ ions are the main multi-charged species at 532 nm. A three-step model (i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing) is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2, λ being the laser wavelength.

  9. Pulsed Power for Solid-State Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gagnon, W; Albrecht, G; Trenholme, J; Newton, M

    2007-04-19

    Beginning in the early 1970s, a number of research and development efforts were undertaken at U.S. National Laboratories with a goal of developing high power lasers whose characteristics were suitable for investigating the feasibility of laser-driven fusion. A number of different laser systems were developed and tested at ever larger scale in pursuit of the optimum driver for laser fusion experiments. Each of these systems had associated with it a unique pulsed power option. A considerable amount of original and innovative engineering was carried out in support of these options. Ultimately, the Solid-state Laser approach was selected as the optimum driver for the application. Following this, the Laser Program at the Lawrence Livermore National Laboratory and the University of Rochester undertook aggressive efforts directed at developing the technology. In particular, at Lawrence Livermore National Laboratory, a series of laser systems beginning with the Cyclops laser and culminating in the present with the National Ignition Facility were developed and tested. As a result, a large amount of design information for solid-state laser pulsed power systems has been documented. Some of it is in the form of published papers, but most of it is buried in internal memoranda, engineering reports and LLNL annual reports. One of the goals of this book is to gather this information into a single useable format, such that it is easily accessed and understood by other engineers and physicists for use with future designs. It can also serve as a primer, which when seriously studied, makes the subsequent reading of original work and follow-up references considerably easier. While this book deals only with the solid-state laser pulsed power systems, in the bibliography we have included a representative cross section of papers and references from much of the very fine work carried out at other institutions in support of different laser approaches. Finally, in recent years, there has

  10. Laser assisted Breit-Wheeler and Schwinger processes

    OpenAIRE

    T. Nousch; Otto, A.; Seipt, D.(Helmholtz-Institut Jena, Fröbelstieg 3, Jena, 07743, Germany); Kämpfer, B.; Titov, A. I.; Blaschke, D.; Panferov, A. D.; Smolyansky, S. A.

    2016-01-01

    The assistance of an intense optical laser pulse on electron-positron pair production by the Breit-Wheeler and Schwinger processes in XFEL fields is analyzed. The impact of a laser beam on high-energy photon collisions with XFEL photons consists in a phase space redistribution of the pairs emerging in the Breit-Wheeler sub-process. We provide numerical examples of the differential cross section for parameters related to the European XFEL. Analogously, the Schwinger type pair production in pul...

  11. Photoelectron sidebands induced by a chirped laser field for shot-by-shot temporal characterization of FEL pulses

    Science.gov (United States)

    Liu, Chien-Nan; Morishita, Toru; Fushitani, Mizuho; Hishikawa, Akiyoshi

    2016-02-01

    We theoretically investigate the laser-assisted photoionization of He by an extreme ultra violet (XUV) pulse in the presence of a linearly chirped intense laser pulse by solving the time-dependent Schrödinger equation within the single-active-electron approximation. Analysis based on the time-dependent perturbation theory is also carried out to provide more physical insights. A new scheme is shown to be capable of extracting the arrival time of an XUV free-electron laser (FEL) pulse relative to an external laser pulse as well as the XUV pulse duration from the photoelectron sidebands resulting from XUV ionization in the presence of a chirped laser pulse. This scheme is independent of the energy fluctuation and the timing jittering of the FEL pulse. Therefore it can be implemented in a non-invasive way to characterize FEL pulses on a shot-by-shot basis in time-resolved spectroscopy.

  12. Measurement of electronegativity at different laser wavelengths: accuracy of Langmuir probe assisted laser photo-detachment

    Science.gov (United States)

    Sirse, N.; Oudini, N.; Bendib, A.; Ellingboe, A. R.

    2016-08-01

    Langmuir probe (LP) assisted pulsed laser photo-detachment (LPD) of negative ions is one of the frequently used diagnostic techniques in electronegative plasmas. The technique is based on measuring the rise in electron saturation current following photo-detachment. During the photo-detachment process it is assumed that the background electron parameters (temperature and density) remain unchanged in the laser channel and the photo-detached electrons thermalize instantaneously with the background electrons (same temperature). Therefore, the measured electronegativity should be independent of laser wavelengths. However, our recent simulation results (2015 Phys. Plasmas 22 073509) demonstrates a failure of these assumptions and suggests that the measured rise in electron saturation current has a dependence on the laser wavelength. This letter presents experimental evidence in support of these simulation results. In this work, photo-detachment is performed at two different laser wavelengths in an oxygen inductively coupled plasma discharge. Electronegativity measured by LP assisted LPD is compared with those obtained by the hairpin probe (HPP) assisted LPD which is based on quasi-neutrality assumption. The experimental results reveal that the electronegativities measured by LP assisted LPD are affected by the laser wavelength, whereas, electronegativities measured by HPP assisted LPD are almost independent. The discrepancy between the measurements is higher at high electronegativities. In conclusion, the experimental results validate the weakness of assumptions to estimate electronegativity from LPD combined with LP and therefore emphasizes the need of a more realistic model to analyze raw data or an alternate solution is to utilize HPP.

  13. Evaporation of solids by pulsed laser irradiation

    Science.gov (United States)

    Stafast, H.; Von Przychowski, M.

    The focused beam of a KrF laser (248 nm) has been applied to irradiate targets of Al 2O 3, SiC, graphite, Pb, Ni, Cr, quartz, and NaCl at variable laser energy flux is the range 0-13 J/cm 2. The amount of target material ejected into the vacuum (background pressure about 8 × 10 -4 Torr) was determined from the target weight before and after laser irradiation. The average number of particles (formula weight) evaporated per laser pulse and per unit of irradiated target area is non-linearly dependent on the laser energy flux. The evaporation of Al 2O 3, SiC, and graphite is showing a well-defined flux threshold while the vaporization of Pb, Ni and Cr is rising smoothly with increasing flux. With both groups of materials laser evaporation is monotonically increasing with the laser energy flux. NaCl and quartz, on the other hand, are showing an intermediate maximum in the laser vaporization efficiency.

  14. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Komashko, A

    2003-01-06

    Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for a variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of

  15. Compensation of pulse-distortion in saturated laser amplifiers.

    Science.gov (United States)

    Schimpf, Damian N; Ruchert, Clemens; Nodop, Dirk; Limpert, Jens; Tünnermann, Andreas; Salin, Francois

    2008-10-27

    We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laser-amplifiers. The analytical solution determines the optimum input pulse-shape required to obtain any arbitrary target pulse-shape at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode. The method will prove useful in applications of high power, high energy laser-amplifier systems that need particular pulse-shapes to be efficient, e.g. micromachining and scientific laser-matter-interactions. PMID:18958044

  16. Surface characteristic of stainless steel sheet after pulsed laser forming

    International Nuclear Information System (INIS)

    Laser forming is a non-contact and die-less forming technique of producing bending, spatial forming, modifying and adjusting the curvature of the metallic sheet by using the controlled laser beam energy. One of the problems in laser forming is controlling the characteristic of laser scanned surface. The aim of the investigation is to explore the relation between the surface behaviors of heat affected zone (HAZ) scanned by pulse laser and the pulse parameters of the laser. This paper illustrated the fundamental theory of pulsed laser affected material, and pays attention to the microstructure, micro-hardness and the anticorrosion in the HAZ generated by the laser scanning. Metallographic microscope, scanning electron microscope (SEM), micro-hardness testing system are used to examine the surface characteristics. The work presented in this paper is beneficial to understand the mechanism of pulse laser affect to materials and improve controlling the surface behaviors scanned by pulsed laser.

  17. Laser absorption via QED cascades in counter propagating laser pulses

    CERN Document Server

    Grismayer, Thomas; Martins, Joana L; Fonseca, Ricardo A; Silva, Luis O

    2015-01-01

    A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ($\\sim$ 10 PW) where the laser absorption is negligible, to extreme intensities (> 100 PW) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.

  18. Analysis of laser return pulse from multilayered objects

    Science.gov (United States)

    Hollinger, Jim; Vessey, Alyssa; Close, Ryan; Middleton, Seth; Williams, Kathryn; Rupp, Ronald; Nguyen, Son

    2016-05-01

    Commercial Lidar often focus on reporting the range associated with the strongest laser return pulse, first return pulse, or last return pulse. This technique works well when observing discrete objects separated by a distance greater than the laser pulse length. However, multiple reflections due to more closely layered objects produce overlapping laser return pulses. Resolving the multi-layered object ranges in the resulting complex waveforms is the subject of this paper. A laboratory setup designed to investigate the laser return pulse produced by multi-layered objects is described along with a comparison of a simulated laser return pulse and the corresponding digitized laser return pulse. Variations in the laboratory setup are used to assess different strategies for resolving multi-layered object ranges and how this additional information can be applied to detecting objects partially obscured in vegetation.

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Den Hartog, D J; Ambuel, J R; Borchardt, M T; Falkowski, A F; Harris, W S; Holly, D J; Parke, E; Reusch, J A; Robl, P E; Stephens, H D; Yang, Y M

    2010-10-01

    Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to "pulse-burst" capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned. PMID:21033868

  1. Molecular alignment using circularly polarized laser pulses

    CERN Document Server

    Smeenk, C T L

    2013-01-01

    We show that circularly polarized femtosecond laser pulses produce field-free alignment in linear and planar molecules. We study the rotational wavepacket evolution of O$_2$ and benzene created by circularly polarized light. For benzene, we align the molecular plane to the plane of polarization. For O$_2$, we demonstrate that circular polarization yields a net alignment along the laser propagation axis at certain phases of the evolution. Circular polarization gives us the ability to control alignment of linear molecules outside the plane of polarization, providing new capabilities for molecular imaging.

  2. Nanosecond pulsed laser blackening of copper

    Science.gov (United States)

    Tang, Guang; Hourd, Andrew C.; Abdolvand, Amin

    2012-12-01

    Nanosecond (12 ns) pulsed laser processing of copper at 532 nm resulted in the formation of homogenously distributed, highly organized microstructures. This led to the fabrication of large area black copper substrates with absorbance of over 97% in the spectral range from 250 nm to 750 nm, and a broadband absorbance of over 80% between 750 nm and 2500 nm. Optical and chemical analyses of the fabricated black metal are presented and discussed. The employed laser is an industrially adaptable source and the presented technique for fabrication of black copper could find applications in broadband thermal radiation sources, solar energy absorbers, irradiative heat transfer devices, and thermophotovoltaics.

  3. Short-pulse Laser Capability on the Mercury Laser System

    Energy Technology Data Exchange (ETDEWEB)

    Ebbers, C; Armstrong, P; Bayramian, A; Barty, C J; Bibeau, C; Britten, J; Caird, J; Campbell, R; Chai, B; Crane, J; Cross, R; Erlandson, A; Fei, Y; Freitas, B; Jovanovic, I; Liao, Z; Molander, B; Schaffers, K; Stuart, B; Sutton, S; Ladran, T; Telford, S; Thelin, P; Utterback, E

    2006-06-22

    Applications using high energy ''petawatt-class'' laser drivers operating at repetition rates beyond 0.01 Hz are only now being envisioned. The Mercury laser system is designed to operate at 100 J/pulse at 10 Hz. We investigate the potential of configuring the Mercury laser to produce a rep-rated, ''petawatt-class'' source. The Mercury laser is a prototype of a high energy, high repetition rate source (100 J, 10 Hz). The design of the Mercury laser is based on the ability to scale in energy through scaling in aperture. Mercury is one of several 100 J, high repetition rate (10 Hz) lasers sources currently under development (HALNA, LUCIA, POLARIS). We examine the possibility of using Mercury as a pump source for a high irradiance ''petawatt-class'' source: either as a pump laser for an average power Ti:Sapphire laser, or as a pump laser for OPCPA based on YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), ideally producing a source approaching 30 J /30 fs /10 Hz--a high repetition rate petawatt. A comparison of the two systems with nominal configurations and efficiencies is shown in Table 1.

  4. Optical reprogramming with ultrashort femtosecond laser pulses

    Science.gov (United States)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  5. Theory of attosecond delays in laser-assisted photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Dahlström, J.M., E-mail: marcus.dahlstrom@fysik.su.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Atomic Physics, Fysikum, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Guénot, D.; Klünder, K.; Gisselbrecht, M.; Mauritsson, J. [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); L’Huillier, A., E-mail: anne.lhuillier@fysik.lth.se [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Maquet, A. [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France); Taïeb, R., E-mail: richard.taieb@upmc.fr [UPMC Université Paris 6, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); CNRS, UMR 7614, LCPMR, Paris (France)

    2013-03-12

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself.

  6. Theory of attosecond delays in laser-assisted photoionization

    International Nuclear Information System (INIS)

    Highlights: ► We find the phase for laser-assisted XUV ionization transition matrix elements (M). ► The phase of M is simply: the sum of the scattering phase of the intermediate continuum state and an universal phase. ► The universal phase is independent of the initial state and it leads to a delay observed in attosecond time-delay experiments. - Abstract: We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum–continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. The observed time-delay is a sum of two components: a one-photon Wigner-like delay and a universal delay that originates from the probing process itself

  7. Study on pulsed excimer laser deposited films

    CERN Document Server

    Liu Jing Ru; Li Tie Jun; Yao Dong Sheng; Wang Li Ge; Yuan Xiao; Wang Sheng; Ye Xi Sheng

    2002-01-01

    Pulsed lasers of two different durations (30 ns, 500 fs) are used to deposit Hydrogen-free Diamond Like Carbon (DLC) films over large areas. Analysis of DLC films shows remarkable mechanical, optical, electrical, and chemical properties that are close to those of diamond. By optical emission spectroscopy and ion probe, the effects of plasma characteristic on DLC film are on experimentally studied. Amorphous silicon films deposited by PLD are also experimentally studied

  8. Theoretical Studies of the Output Pulse with Variation of the Pumping Pulse for RF Excited CO2 Pulsed Waveguide Laser

    Institute of Scientific and Technical Information of China (English)

    A Rauf; ZHOU Wei; XIN Jian-guo

    2006-01-01

    The behavior of a RF-excited waveguide CO2 laser in the pulse regime is studied theoretically. The output pulse evolution is studied by applying three types of pulses namely the square, sine and the triangular ones as the excitation pulses. The frequency dependence behavior of the output pulse is also presented.

  9. Site-Selective Field Emission Source by Femtosecond Laser Pulses and Its Emission Mechanism

    OpenAIRE

    Yanagisawa, Hirofumi

    2012-01-01

    Recent experimental and theoretical investigations on asymmetric field emission induced by weak femtosecond laser pulses and also its emission mechanisms are briefly reviewed. The emission mechanisms are discussed further for a wider range of DC fields and laser power. It appears that firstly photo-assisted field emission from lower-excitation order grows in the higher DC fields and secondly our simulations can be applied only for lower laser power.

  10. Clinical analysis of eye myopia among 96 primary and middle school students by He-Ne laser acupoint irradiation assisted by electric pulse stimulation%He -Ne激光穴位照射辅助电脉冲刺激治疗中小学生近视眼96例疗效分析

    Institute of Scientific and Technical Information of China (English)

    王东升; 刘保良; 刘怡君; 李云涛; 张建民; 唐伟跃

    2013-01-01

    Objective :To investigate the convenient and effective method of the treatment of juvenile myopia .Methods :Using He-Ne laser acupoint irradiation assisted by electric pulse stimulation .Results :The curative effect of He -Ne laser acupoint irradiation assisted by electric pulse stimulation of juvenile myopia is related to the following factors :naked vision before treatment ,age ,disease duration ,duration of treatment .The treatment efficiency is inversely proportional to eyesight of patients before treatment ,age ,medical history ,and proportional to the duration of He - Ne laser acupoint irradiation assisted by electric pulse stimulation .Conclusion :The curative effect of juvenile myopia using He - Ne laser acupoint irradiation assisted by electric pulse stimulation is worthy of recognition .The prevention of juvenile myopia is very importment and it should accomplish early discovery and treatment .%目的:探索方便有效的治疗青少年近视眼的治疗方法。方法:利用He-Ne激光穴位照射辅助电脉冲刺激。结果:He -Ne激光穴位照射辅助电脉冲刺激治疗青少年近视的疗效与下列因素有关:患者治疗前的裸眼视力、年龄、病程长短、治疗时间长短等。治疗的有效率与患者治疗前视力、年龄、病史成反比,与He-Ne激光穴位照射辅助电脉冲刺激治疗时间成正比。结论:电脉冲刺激穴位治疗青少年近视疗效值得肯定。但青少年近视重在预防,应做到早发现、早治疗。

  11. Statistical Analysis of Femtosecond Pulses Laser on Hole Drilling of Silicon Wafer

    Science.gov (United States)

    Jiao, L.; Ng, E. Y. K.; Zheng, H.; Wee, L. M.

    This study investigated the relationship and parameters interactions between five independent variables in laser percussion drilling of micro-hole. Experiments were conducted on single crystal silicon wafer with material thickness of 725 μm using femtosecond (fs) laser with wavelength of 775 nm and pulse duration of 200 fs. Laser power, focus position, number of pulses, workpiece temperature and assist liquid were selected as independent process variables. Taguchi L18 orthogonal array was applied to design the experiments. The drilling process was evaluated in terms of entrance hole diameter and exit hole diameter. The analysis of the variance (ANOVA) was used to determine the significant parameters that are affecting the entrance hole diameter and exit hole diameter. The result shows that laser power and focus position has highly significant effect on entrance hole diameter. The number of pulses, focus position and assist liquid however has highly significant effect on exit hole diameter.

  12. Heavy ion acceleration using femtosecond laser pulses

    CERN Document Server

    Petrov, G M; Thomas, A G R; Krushelnick, K; Beg, F N

    2015-01-01

    Theoretical study of heavy ion acceleration from ultrathin (<200 nm) gold foils irradiated by a short pulse laser is presented. Using two dimensional particle-in-cell simulations the time history of the laser bullet is examined in order to get insight into the laser energy deposition and ion acceleration process. For laser pulses with intensity , duration 32 fs, focal spot size 5 mkm and energy 27 Joules the calculated reflection, transmission and coupling coefficients from a 20 nm foil are 80 %, 5 % and 15 %, respectively. The conversion efficiency into gold ions is 8 %. Two highly collimated counter-propagating ion beams have been identified. The forward accelerated gold ions have average and maximum charge-to-mass ratio of 0.25 and 0.3, respectively, maximum normalized energy 25 MeV/nucleon and flux . Analytical model was used to determine a range of foil thicknesses suitable for acceleration of gold ions in the Radiation Pressure Acceleration regime and the onset of the Target Normal Sheath Acceleratio...

  13. Pulsed laser deposition of rare earth compounds

    CERN Document Server

    Stone, L A

    2001-01-01

    Magnetostrictive thin films have been deposited using various techniques such as sputtering and evaporation but the use of laser deposition has been limited. This research presents the results from pulsed laser deposition (PLD) of TbFe sub 2 , DyFe sub 2 and Terfenol-D thin films using an infra red Transversely Excited Atmospheric (TEA) CO sub 2 laser at lambda approx 10.6 mu m and an ultra violet Argon-Fluoride (ArF) excimer laser at lambda approx 193 nm. Results have showed that the TEA CO sub 2 laser under the range of conditions studied is not suitable for the production of magnetostrictive films. The problems experienced are a mixture of mostly fracture debris at low fluences (F approx 20 Jcm sup - sup 2) and melt droplets at high fluences (F approx 60 Jcm sup - sup 2). In all cases the destruction of the target is a major problem, with the Terfenol-D targets being the worst affected. Thin films produced were all iron rich. The use of an excimer laser has proved more successful in providing stoichiometri...

  14. Pulsed Nd-YAG laser in endodontics

    Science.gov (United States)

    Ragot-Roy, Brigitte; Severin, Claude; Maquin, Michel

    1994-12-01

    The purpose of this study was to establish an operative method in endodontics. The effect of a pulsed Nd:YAG laser on root canal dentin has been examined with a scanning electron microscope. Our first experimentation was to observe the impacts carried out perpendicularly to root canal surface with a 200 micrometers fiber optic in the presence of dye. Secondarily, the optical fiber was used as an endodontic instrument with black dye. The irradiation was performed after root canal preparation (15/100 file or 40/100 file) or directly into the canal. Adverse effects are observed. The results show that laser irradiation on root canal dentin surfaces induces a nonhomogeneous modified dentin layer, melted and resolidified dentin closed partially dentinal tubules. The removal of debris is not efficient enough. The laser treatment seems to be indicated only for endodontic and periapical spaces sterilization after conventional root canal preparation.

  15. [Effect of pulsed CO2-laser irradiation on bone tissue].

    Science.gov (United States)

    Kholodnov, S E

    1985-01-01

    Different dynamic effects on biological tissue caused by pulsed laser radiation are described. It is shown that the parameters of these effects which take place on the bone tissue affected by pulsed CO2-laser radiation are directly dependent on the parameters of these pulses and may be predicted for any concrete application. PMID:3931698

  16. Twin-Pulse Soliton Operation of a Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    W.; S.; Man; H.; Y.; Tam

    2003-01-01

    We report on the experimental observation of a novel type of twin-pulse soliton in a passively mode-locked fiber ring laser. Twin-pulse soliton interaction in the laser cavity are also experimentally investigated and compared with those of the single pulse soliton.

  17. Drop deformation by laser-pulse impact

    CERN Document Server

    Gelderblom, Hanneke; Klein, Alexander L; Bouwhuis, Wilco; Lohse, Detlef; Villermaux, Emmanuel; Snoeijer, Jacco H

    2015-01-01

    A free-falling absorbing liquid drop hit by a nanosecond laser-pulse experiences a strong recoil-pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the timescale of the pressure pulse, when the drop is still spherical. This yields the kinetic-energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the timescale where surface tension is important the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy-partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependance on the pulse shape: for a given propulsion, a tightly focused pulse results in a...

  18. Wavelength stabilisation during current pulsing of tapered laser

    DEFF Research Database (Denmark)

    Jensen, Ole Bjarlin

    2009-01-01

    The use of external feedback to stabilise the frequency of a tapered laser during current pulsing is reported. Using this technique more than 20 W of peak power in 60 ns pulses from the tapered laser is obtained and owing to the external feedback, the laser is tunable in the 778-808 nm range....... The spectral width of the tapered laser is significantly narrowed compared to the freely running laser....

  19. Pulse width effect on the dissociation probability of CH4+ in the intense femtosecond laser field

    Institute of Scientific and Technical Information of China (English)

    WANG Gao; SONG Di; LIU Yuyan; KONG Fan'ao

    2006-01-01

    The laser pulse width effect on the dissociation probability of CH4+ irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 × 1013 W/cm2 was used. The observed relative yield of the primary fragment ion CH3+ increases with increasing pulse width and tends to saturate when the pulse width is longer than 120 fs. The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCT) calculation were applied to predicting the dissociation probability of CH4+.The calculated probability is corrected with the molecular orientation effect and the spatial distribution of laser intensity. The modified results show that the dissociation requires at least 23 fs and saturates with long pulse widths (≥100 rs). The result is approximately consistent with the experimental observation.

  20. The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    He Feng; Yu Wei; Lu Peixiang; Xu Han; Shen Baifei; Li Ruxin; Xu Zhizhan

    2005-01-01

    In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron,the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude,spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS (laser synchrotron source) is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.

  1. Amplification of Short Pulse High Power UV Laser

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    At recent year, with the development of CPA and other amplification technology, laser intensity achieves great increase and laser power can be high to PW(105) now, this ultrashort pulse lasers offer scientists a route to investigate laser-matter interaction in an absolute new regime.So far the researches on ultrashort pulse laser-matter interaction concentrated on infrared regime, yet ultraviolet laser has the advantage in intense field physics and ICF researches for its short wavelength and less nonlinear effects. KrF excimer is the best medium in UV ultrashort pulse amplification for its small saturation energy and high contrast ratio accessible.

  2. Pulsed laser deposition: the road to hybrid nanocomposites coatings and novel pulsed laser adaptive technique.

    Science.gov (United States)

    Serbezov, Valery

    2013-01-01

    The applications of Pulsed Laser Deposition (PLD) for producing nanoparticles, nanostructures and nanocomposites coatings based on recently developed laser ablating techniques and their convergence are being reviewed. The problems of in situ synthesis of hybrid inorganic-organic nanocomposites coatings by these techniques are being discussed. The novel modification of PLD called Pulsed Laser Adaptive Deposition (PLAD) technique is presented. The in situ synthesized inorganic/organic nanocomposites coatings from Magnesium (Mg) alloy/Rhodamine B and Mg alloy/ Desoximetasone by PLAD are described. The trends, applications and future development of discussed patented methods based on the laser ablating technologies for producing hybrid nanocomposite coatings have also been discussed in this review. PMID:22747717

  3. Dependence of the two-photon photoluminescence yield of gold nanostructures on the laser pulse duration

    DEFF Research Database (Denmark)

    Biagioni, P.; Celebrano, M.; Savoini, M.;

    2009-01-01

    Two-photon photoluminescence (TPPL) from gold nanostructures is becoming one of the most relevant tools for plasmon-assisted biological imaging and photothermal therapy as well as for the investigation of plasmonic devices. Here we study the yield of TPPL as a function of the temporal width δ...... of the excitation laser pulses for a fixed average power. In the δ>1 ps regime, the TPPL yield decreases as δ is increased, while for shorter pulse widths it becomes independent of δ and, consequently, of the laser-pulse peak power. This peculiar dynamics is understood and modeled by considering that two...

  4. Nonparaxial propagation of ultrashort laser pulses in plasma channels

    International Nuclear Information System (INIS)

    The propagation characteristics of an ultrashort laser pulse in a preformed plasma channel are analyzed. The plasma channel is assumed to be parabolic and unperturbed by the laser pulse. Solutions to the wave equation beyond the paraxial approximation are derived that include finite pulse length effects and group velocity dispersion. When the laser pulse is mismatched within the channel, betatron oscillations arise in the laser pulse envelope. A finite pulse length leads to a spread in the laser wave number and consequently a spread in betatron wave number. This results in phase mixing and damping of the betatron oscillation. The damping distance characterizing the phase mixing of the betatron oscillation is derived, as is the dispersion distance characterizing the longitudinal spreading of the pulse. copyright 1999 The American Physical Society

  5. Propagation of λ3 Laser Pulses in Underdense Plasma

    Science.gov (United States)

    Zhidkov, Alexei; Nemoto, Koshichi; Nayuki, Takuya; Oishi, Yuji; Fujii, Takashi

    2008-06-01

    We study the interaction of λ3 laser pulses with underdense plasma by means of real geometry particle-in-cell simulation. Underdense plasma irradiated by even low energy λ3 laser pulses can be an efficient source of multi-MeV electrons, ˜50 nC/J. The electron acceleration driven by low energy λ3 and λ2 laser pulses is monitored by means of fully relativistic 3D particle-in- cell simulation. Strong transverse wave-breaking in the vicinity of the laser focus is found to give rise to an immense electron charge injected to the acceleration phase of laser wake field. While the acceleration by λ2 pulses runs in usual way, strong blowout regime is found for λ3 pulses. Details of laser pulse self-guiding are discussed.

  6. Landau damping of a driven plasma wave from laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Bu Zhigang [Department of Physics, Shanghai University, Shanghai 200444 (China); Ji Peiyong [Department of Physics, Shanghai University, Shanghai 200444 (China); The Shanghai Key Lab of Astrophysics, Shanghai 200234 (China)

    2012-01-15

    The interaction between a laser pulse and a driven plasma wave with a phase velocity approaching the speed of light is studied, and our investigation is focused on the Gaussian laser pulse. It is demonstrated that when the resonance condition between the plasma wave and the laser pulse is satisfied, the Landau damping phenomenon of the plasma wave originated from the laser pulse will emerge. The dispersion relations for the plasma waves in resonance and non-resonance regions are obtained. It is proved that the Landau damping rate for a driven plasma wave is {gamma}>0 in the resonance region, so the laser pulse can produce an inverse damping effect, namely Landau growth effect, which leads an instability for the plasma wave. The Landau growth means that the energy is transmitted from the laser pulse to the plasma wave, which could be an effective process for enhancing the plasma wave.

  7. Optical measurement on quantum cascade lasers using femtosecond pulses

    Science.gov (United States)

    Cai, Hong

    Quantum cascade lasers (QCLs) as the state-of-the-art mid-infrared (mid-IR) coherent sources have been greatly developed in aspects such as output power, energy efficiency and spectral purity. However, there are additional applications of QCLs in high demand, namely mode-locking, mid-IR modulation, etc. The inherent optical properties and ultrafast carrier dynamics can lead to solutions to these challenges. In this dissertation, we further characterize QCLs using mid-IR femtosecond (fs) pulses generated from a laser system consisting of a Ti:sapphire oscillator, a Ti:sapphire regenerative amplifier, an optical parametric amplifier and a difference frequency generator. We study the Kerr nonlinearity of QCLs by coupling resonant and off-resonant mid-IR fs pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-IR pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results. The giant Kerr nonlinearity investigated here may be used to realize ultrafast pulse generation in QCLs. In addition, we temporally resolved the ultrafast mid-infrared transmission modulation of QCLs using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps are used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth

  8. Optodynamic analysis of pulsed-laser processing with a Nd:YAG laser

    OpenAIRE

    Strgar, Simon; Možina, Janez

    2015-01-01

    Laser drilling and laser marking of metals with a pulsed Nd:YAG laser are discussed. Some characteristics of pulsed-laser processing and the possibilities of process optodynamic analysis are presented for the laser-drilling of aluminium. The optodynamic analysis is based on observation of generated shock waves, which propagate in the material as well as in the surrounding air during laser processing. For the detection of laser-induced shock waves in the air and for measurements of their chara...

  9. Preparation of a YBCO superconducting tape by pulsed laser deposition

    International Nuclear Information System (INIS)

    A high current density YBa2Cu3O7-x (YBCO) superconducting thick film on a flexible NiCr alloy substrate tape with ZrO2 + 10%Y2O3 (YSZ) as buffer layer was prepared by pulsed laser deposition (PLD). The buffer layer YSZ of thickness 0.3 microm was formed on the NiCr alloy substrate tape of length 6.0 cm by ion-assisted pulsed laser deposition (ISPLD). The YBCO superconducting thick film with thickness 1.5 microm was deposited on the YSZ/NiCr alloy substrate tape by a KrF Laser. The X-ray diffraction pattern indicates that the YBCO superconducting thick film is with strongly C-axis oriented. The critical current densities versus temperature and magnetic film is with strongly C-axis oriented. The critical current densities versus temperature and magnetic field were measured by standard four-point probe method, the values of critical current density and the critical temperature of the YBCO/YSZ/NiCr alloy superconducting tape are 8.75 x 104 A/cm2 (at 77 K, 0 T) and 88.7 K, respectively

  10. Near threshold laser-assisted nuclear photoeffect

    CERN Document Server

    Kálmán, Péter; Keszthelyi, Tamás

    2013-01-01

    The change of nuclear photoeffect due to an intense coherent (laser) field is discussed near the threshold, where the hindering effect of the Coulomb field of the remainder nucleus is essential. The ratio of laser-assisted and laser free differential cross section is deduced and found to be independent of the polarization state of the \\gamma field and the two types of initial nuclear state considered. The numerical values of this ratio are given at some characteristic parameters of the intense field and the detuning.

  11. Cloning assay thresholds on cells exposed to ultrafast laser pulses

    Science.gov (United States)

    Koenig, Karsten; Riemann, Iris; Fischer, Peter; Becker, Thomas P.; Oehring, Hartmut; Halbhuber, Karl-Juergen

    1999-06-01

    The influence of the peak power, laser wavelength and the pulse duration of near infrared ultrashort laser pulses on the reproduction behavior of Chinese hamster ovary (CHO) cells has been studied. In particular, we determined the cloning efficiency of single cell pairs after exposure to ultrashort laser pulses with an intensity in the range of GW/cm2 and TW/cm2. A total of more than 3500 non- labeled cells were exposed to a highly focused scanning beam of a multiphoton laser microscope with 60 microsecond(s) pixel dwell time per scan. The beam was provided by a tunable argon ion laser pumped mode-locked 76 MHz Titanium:Sapphire laser as well as by a compact solid-state laser based system (Vitesse) at a fixed wavelength of 800 nm. Pulse duration (tau) was varied in the range of 100 fs to 4 ps by out-of- cavity pulse-stretching units consisting of SF14 prisms and blazed gratings. Within an optical (laser power) window CHO cells could be scanned for hours without severe impact on reproduction behavior, morphology and vitality. Ultrastructural studies reveal that mitochondria are the major targets of intense destructive laser pulses. Above certain laser power P thresholds, CHO cells started to delay or failed to undergo cell division and, in part, to develop uncontrolled cell growth (giant cell formation). The damage followed a P2/(tau) relation which is typical for a two- photon excitation process. Therefore, cell damage was found to be more pronounced at shorter pulses. Due to the same P2/(tau) relation for the efficiency of fluorescence excitation, two-photon microscopy of living cells does not require extremely short femtosecond laser pulses nor pulse compression units. Picosecond as well as femtosecond lasers can be used as efficient light sources in safe two photon fluorescence microscopy. Only in three photon fluorescence microscopy, femtosecond laser pulses are advantageous over picosecond pulses.

  12. Development of short pulse laser pumped x-ray lasers

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, J; Osterheld, A L; Hunter, J R; Shlyaptsev, V N

    2000-02-22

    X-ray lasers have been extensively studied around the world since the first laboratory demonstration on the Novette laser at LLNL in 1984. The characteristic properties of short wavelength, high monochromaticity, collimation and coherence make x-ray lasers useful for various applications. These include demonstrations of biological imaging within the water window, interferometry of laser plasmas and radiography of laser-heated surfaces. One of the critical issues has been the high power pump required to produce the inversion. The power scaling as a function of x-ray laser wavelength follows a {approx} {lambda}{sup -4} to {approx} {lambda}{sup -6} law. The shortest x-ray laser wavelength of {approx}35 {angstrom} demonstrated for Ni-like Au was at the limit of Nova laser capabilities. By requiring large, high power lasers such as Nova, the shot rate and total number of shots available have limited the rapid development of x-ray lasers and applications. In fact over the last fifteen years the main thrust has been to develop more efficient, higher repetition rate x-ray lasers that can be readily scaled to shorter wavelengths. The recent state of progress in the field can be found in references. The objective of the project was to develop a soft x-ray laser (XRL) pumped by a short pulse laser of a few joules. In effect to demonstrate a robust, worlung tabletop x-ray laser at LLNL for the first time. The transient collisional scheme as proposed by Shlyaptsev et al. was the candidate x-ray laser for study. The successful endeavor of any scientific investigation is often based upon prudent early decisions and the choice of this scheme was both sound and fruitful. It had been demonstrated very recently for Ne-like Ti at 326 {angstrom} using a small tabletop laser but had not yet reached its full potential. We chose this scheme for several reasons: (a) it was a collisional-type x-ray laser which has been historically the most robust; (b) it had the promise of high efficiency

  13. Extended propagation of powerful laser pulses in focusing Kerr media

    CERN Document Server

    Malkin, V M

    2016-01-01

    Powerful incoherent laser pulses can propagate in focusing Kerr media much longer distances than can coherent pulses, due to the fast phase mixing that prevents transverse filamentation. This distance is limited by 4-wave scattering, which accumulates waves at small transverse wavenumbers, where phase mixing is too slow to retain the incoherence and thus prevent the filamentation. However, we identify how this theoretical limit can be overcome by countering this accumulation through transverse heating of the pulse by random fluctuations of the refractive index. In these new regimes, the laser pulse propagation distances are significantly extended, making feasible a new class of random lasers, in particular, ultra-powerful random lasers in plasmas.

  14. Femtosecond laser ablation of Au film around single pulse threshold

    Institute of Scientific and Technical Information of China (English)

    Xiaochang Ni; Ching-Yue Wang; Yinzhong Wu; Li Yang; Wei Jia; Lu Chai

    2006-01-01

    @@ Ablation process of 1-kHz femtosecond lasers (pulse duration of 148 fs, wavelength of 775 nm) of Au film on silica substrates is studied. The thresholds for single and multi pulses can be obtained directly from the relation between the squared diameter D2 of the ablated craters and the laser fluence φo. From the plot of the accumulated laser fluence Nφth(N) and the number of laser pulses N, incubation coefficient of Au film is obtained to be 0.765. Some experimental data obtained around the single pulse threshold are in good agreement with the theoretical calculation.

  15. Development of short pulse soft x-ray lasers

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, L.B.; MacGowan, B.J.; Koch, J.A.; Mrowka, S.; Matthews, D.L.; Eder, D.; London, R.

    1993-02-01

    X-ray lasers with pulse duration shorter than 20 ps allow the possibility of imaging laser produced plasmas with {mu}m resolution. In addition, the high peak brightness of these new sources will allow us to study nonlinear optics in the xuv region. In this paper we will describe our efforts to produce collisionally pumped short pulse x-ray lasers. Initial results, which have produced {approximately} 45 ps (FWHM) x-ray lasers, using a double pulse irradiation technique are presented along with a discussion of the prospects for reducing the pulse width.

  16. Laser-assisted cleaning: Dominant role of surface

    Indian Academy of Sciences (India)

    J Padma Nilaya; D J Biswas

    2010-12-01

    Pulsed laser-assisted removal of particulates from substrates has decided advantages over the conventional methods of cleaning. Experiments conducted with loose contamination on metal and transparent dielectric surfaces proved conclusively the dominant role played by the absorption of the incident radiation by the surface towards the generation of the cleaning force as against the absorption in the particulates alone. Further, the presence of transparent/semi-transparent particulates on a metal surface was found to result in an increased absorption of the incident radiation by the substrate. This effect, identified as field-enhanced surface absorption was found to increase with reduction in the average particulate size.

  17. Laser grooving of Al2O3 plate by a pulsed Nd:YAG laser: Characteristics and application to the manufacture of gas sensors array heater

    International Nuclear Information System (INIS)

    Laser grooving on a 0.635 mm thick alumina ceramic plate was carried out by a 400 W pulsed Nd:YAG laser. The effects of the laser grooving parameters, such as laser pulse frequency, laser peak pulse energy, assisting gases (oxygen and nitrogen), laser beam diameter and grooving speed on the morphologies of grooves were investigated by using field-emission scanning electron microscopy (FE-SEM) and optical microscopy. Results show that the U-type groove with smooth inner surface was produced at a fixed pulse frequency of 40 Hz, a grooving speed of 4 mm s-1 and an assisting gas pressure of 3 bar. The depth of the U-type groove increased with an increase in laser pulse peak energy. The assisting gas type was found to influence the grooving mechanism, that is, nitrogen gas had a chemical reaction with alumina, and then changed the substrate surface absorptivity to laser beam. So the smaller heat-affected zone (HAZ) was obtained in the substrate than that of the oxygen assisting gas. In addition, the stable and reliable RuO2-buried heater was produced in the U-type groove with smooth inner surface, which reduced sensing element power consumption and improved the thermal response rate in a sensor array

  18. PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

    2006-08-27

    This paper describes phase noise measurements of several different laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on state-of-the-art short pulse lasers, especially drive lasers for photocathode injectors. Phase noise comparison of the FEL drive laser, electron beam and FEL laser output also will be presented.

  19. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

    Haedersdal, M; Beerwerth, F; Nash, J F

    2011-01-01

    Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense...

  20. Generation of Intense THz Pulsed Lasers Pumped Strongly by CO2 Pulsed Lasers

    Institute of Scientific and Technical Information of China (English)

    QI Chun-Chao; CHENG Zu-Hai

    2009-01-01

    A theoretical method dealing with two intense laser fields interacting with a three-level molecular system is proposed.A discussion is presented on the properties of the solutions for time-independent and time-dependent absorption coefficients and gain coemcient on resonance for strong laser fields,based on analytic evaluation of the rate equations for a homogeneously broadened,three-level molecular system.The pump intensity range can be estimated according to the analytic expression of pump saturation intensity.The effects of pulse width,gas pressure and path length on the energy absorbed from pump light are studied theoretically.The results can be applied to the analysis of pulsed,optically pumped terahertz lasers.

  1. Pulsed laser deposition of pepsin thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kecskemeti, G. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary)]. E-mail: kega@physx.u-szeged.hu; Kresz, N. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dom ter 9 (Hungary); Smausz, T. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Hopp, B. [Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dom ter 9 (Hungary); Nogradi, A. [Department of Ophthalmology, University of Szeged, H-6720, Szeged, Koranyi fasor 10-11 (Hungary)

    2005-07-15

    Pulsed laser deposition (PLD) of organic and biological thin films has been extensively studied due to its importance in medical applications among others. Our investigations and results on PLD of a digestion catalyzing enzyme, pepsin, are presented. Targets pressed from pepsin powder were ablated with pulses of an ArF excimer laser ({lambda} = 193 nm, FWHM = 30 ns), the applied fluence was varied between 0.24 and 5.1 J/cm{sup 2}. The pressure in the PLD chamber was 2.7 x 10{sup -3} Pa. The thin layers were deposited onto glass and KBr substrates. Our IR spectroscopic measurements proved that the chemical composition of deposited thin films is similar to that of the target material deposited at 0.5 and 1.3 J/cm{sup 2}. The protein digesting capacity of the transferred pepsin was tested by adapting a modified 'protein cube' method. Dissolution of the ovalbumin sections proved that the deposited layers consisted of catalytically active pepsin.

  2. Microstructuring of silicon with femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Freund, Waldemar; Richters, Jan P.; Voss, Tobias; Gutowski, Juergen [Institute of Solid State Physics, Semiconductor Optics Group, University of Bremen (Germany)

    2011-07-01

    Silicon structured with ultrashort laser pulses which is called ''black silicon'' due to its dark appearance has been a field of intense studies in recent years. It exhibits a nearly uniform absorptivity beyond 90% in the whole visible to near-infrared spectral region. Therefore, it is a promising material for applications in solar cells and photo diodes. In this talk a brief introduction of microstructuring of silicon with ultrashort laser pulses will be given. Structuring is carried out in a sulfurhexafluoride (SF{sub 6}) atmosphere, which simultaneously allows doping of the silicon with sulfur far above the solubility limit. The structuring leads to a specific quasiperiodic surface morphology at which incident light is reflected multiple times. Thus light absorption in the silicon is considerably enhanced. The extremely high doping with sulfur results in the formation of a distinct defect band which is the origin of high absorptance in the near infrared. Furthermore, sulfur acts as a donor in silicon. Hence, microstructuring of p-doped silicon in SF{sub 6} atmosphere leads to the formation of a p-n{sup +} junction. This is an important step towards the fabrication of efficient solar cells and photo diodes with increased infrared sensitivity on base of easy-to-produce black silicon.

  3. Intense laser pulse propagation in capillary discharge plasma channels

    International Nuclear Information System (INIS)

    Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in ∼300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model produce the expected optical guiding, with the laser pulse radius rL exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T3 laser, and preliminary results are reported. copyright 1999 American Institute of Physics

  4. Toward robot-assisted neurosurgical lasers.

    Science.gov (United States)

    Motkoski, Jason W; Yang, Fang Wei; Lwu, Shelly H H; Sutherland, Garnette R

    2013-04-01

    Despite the potential increase in precision and accuracy, laser technology is not widely used in neurological surgery. This in part relates to challenges associated with the early introduction of lasers into neurosurgery. Considerable advances in laser technology have occurred, which together with robotic technology could create an ideal platform for neurosurgical application. In this study, a 980-nm contact diode laser was integrated with neuroArm. Preclinical evaluation involved partial hepatectomy, bilateral nephrectomy, splenectomy, and bilateral submandibular gland excision in a Sprague-Dawley rat model (n = 50). Total surgical time, blood loss as weight of surgical gauze before and after the procedure, and the incidence of thermal, vascular, or lethal injury were recorded and converted to an overall performance score. Thermal damage was evaluated in the liver using tissue samples stained with hematoxylin and eosin. Clinical studies involved step-wise integration of the 980-nm laser system into four neurosurgical cases. Results demonstrate the successful integration of contact laser technology into microsurgery, with and without robotic assistance. In preclinical studies, the laser improved microsurgical performance and reduced thermal damage, while neuroArm decreased intra- and intersurgeon variability. Clinical studies demonstrate dutility in meningioma resection (n = 4). Together, laser and robotic technology offered a more consistent, expedient, and precise tool for microsurgery. PMID:23047855

  5. Generation of Low Jitter Laser Diode Pulse With External Pulse Injection

    Institute of Scientific and Technical Information of China (English)

    Olaf; Reimann; Dieter; Huhse; Dieter; Bimberg

    2003-01-01

    One gain-switched laser diode(LD) was used as external injection seeding source, to reduce the timing jitter of another gain-switched LD, This technique can generate low jitter, frequency-free and wavelength tunable laser pulse.

  6. Solid propellant extinction by laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Novozhilov, B.V. [Russian Academy of Science, Moscow (Russian Federation). Inst. of Chemical Physics; Zanotti, C.; Giuliani, P. [Istituto per la Tecnologia dei Materiali e dei Processi Energetici TeMPE - C.N.R., Milano (Italy)

    2000-12-01

    The possibility to generate a combustion transient of a composite AP.HTPB/86.14 propellant, burning under steady state conditions, was experimentally demonstrated by using a CO{sub 2} laser energy pulse. The experimental results point out that the burning propellant behavior can be defined by the curves separating, for every operating pressure, the continuous burning from the extinction solutions. In this paper, a simplified theoretical approach gives a phenomenological explanation of the energy pulse effect on the combustion process and the consequent burning propellant response after the deradiation transient. In the framework of this study the extinction condition is formulated in terms of the minimum temperature that causes the burning propellant to quench at the Pressure Deflagration Limit. The proposed theoretical work is aimed, first of all, to determine the critical radiant flux values, for different operating pressures, below which the burning propellant extinction is never achieved even if the laser pulse duration tends to infinity. Then, the extinction boundaries are defined choosing two different approximate approaches that take into account the ratio between the condensed phase relaxation time and the radiant energy pulse duration. Two limit cases, defined as slow/fast interaction of the radiant energy with the combustion process, can be used to describe the burning propellant extinction phenomena, and the results of this work indicate that the general trend of the computed boundary limits reproduces the experimental data. (orig.) [German] Mit einem CO{sub 2}-Laser wurde die Moeglichkeit demonstriert, einen Uebergangszustand der Verbrennung eines Komposit-Treibstoffes AP.HTPB/86.14 zu erzeugen, der unter stationaeren Bedingungen brannte. Die experimentellen Ergebnisse zeigen auf, dass das Verbrennungsverhalten durch die Kurven bestimmt werden kann, die fuer jeden Arbeitsdruck die kontinuierlichen Verbrennungsloesungen von den Ausloeschloesung trennen

  7. A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.

    Science.gov (United States)

    Fischer, D; de la Fuente, G F; Jansen, M

    2012-04-01

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C. PMID:22559543

  8. Pulsed laser ablation of solids basics, theory and applications

    CERN Document Server

    Stafe, Mihai; Puscas, Niculae N

    2014-01-01

    The book introduces ‘the state of the art' of pulsed laser ablation and its applications. It is based on recent theoretical and experimental studies. The book reaches from the basics to advanced topics of pulsed laser ablation. Theoretical and experimental fundamental phenomena involved in pulsed laser ablation are discussed with respect to material properties, laser wavelength, fluence and intensity regime of the light absorbed linearly or non-linearly in the target material. The energy absorbed by the electrons leads to atom/molecule excitation, ionization and/or direct chemical bond breaking and is also transferred to the lattice leading to material heating and phase transitions. Experimental  non-invasive optical methods for analyzing these phenomena in real time are described. Theoretical models for pulsed laser ablation and phase transitions induced by laser beams and laser-vapour/plasma interaction during the plume expansion above the target are also presented. Calculations of the ablation speed and...

  9. Generation of ultrashort electron bunches by colliding laser pulses

    International Nuclear Information System (INIS)

    A proposed laser-plasma based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses

  10. Analysis on the characteristics of pulsed laser proximity fuze's echo

    Science.gov (United States)

    Wang, Kun; Chen, Huimin

    2011-06-01

    With the rapid development of semiconductor technology and laser technology, a kind of proximity fuze named pulsed laser proximity fuze has been applied. Compared with other fuzes, pulsed laser proximity fuze has high ranging precision and strong resistance to artificial active interference. It is an important development tendency of proximity fuze. The paper analyze the characteristic of target echo of laser signal, and then make theoretical analysis and calculation on the laser signal transmission in the smog. Firstly, use the pulse width of 10ns semiconductor laser fuze to do typical targets experiment, to get the echo information of target distance is 5m; then to do smog interference experiment, by comparing the pulse width amplitude and backscattering signal amplitude of laser fuze in simulation and experiment, analyzing the effect of anti-clutter, providing the evidence for the subsequent of circuit of signal amplification and processing.

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

    Science.gov (United States)

    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.

  12. Glass drilling by longitudinally excited CO2 laser with short laser pulse

    Science.gov (United States)

    Uno, Kazuyuki; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2015-03-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse and a pulse tail. The energy of the pulse tail was controlled by adjusting medium gas. Using three types of CO2 laser pulse with the same spike-pulse energy and the different pulse-tail energy, the characteristics of the hole drilling of synthetic silica glass was investigated. Higher pulse-tail energy gave deeper ablation depth. In the short laser pulse with the spike-pulse energy of 1.2 mJ, the spike pulse width of 162 ns, the pulse-tail energy of 24.6 mJ, and the pulse-tail length of 29.6 μs, 1000 shots irradiation produced the ablation depth of 988 μm. In the hole drilling of synthetic silica glass by the CO2 laser, a crack-free process was realized.

  13. Solitary Nanostructures Produced by Ultrashort Laser Pulse.

    Science.gov (United States)

    Inogamov, Nail A; Zhakhovsky, Vasily V; Khokhlov, Viktor A; Petrov, Yury V; Migdal, Kirill P

    2016-12-01

    Laser-produced surface nanostructures show considerable promise for many applications while fundamental questions concerning the corresponding mechanisms of structuring are still debated. Here, we present a simple physical model describing those mechanisms happened in a thin metal film on dielectric substrate irradiated by a tightly focused ultrashort laser pulse. The main ingredients included into the model are (i) the film-substrate hydrodynamic interaction, melting and separation of the film from substrate with velocity increasing with increase of absorbed fluence; (ii) the capillary forces decelerating expansion of the expanding flying film; and (iii) rapid freezing into a solid state if the rate of solidification is comparable or larger than hydrodynamic velocities. The developed model and performed simulations explain appearance of microbump inside the focal spot on the film surface. The model follows experimental findings about gradual transformation of the bump from small parabolic to a conical shape and to the bump with a jet on its tip with increasing fluence. Disruption of the bump as a result of thinning down the liquid film to a few interatomic distances or due to mechanical break-off of solid film is described together with the jetting and formation of one or many droplets. Developed theory opens door for optimizing laser parameters for intended nanostructuring in applications. PMID:27044306

  14. Optical gene transfer by femtosecond laser pulses

    Science.gov (United States)

    Konig, Karsten; Riemann, Iris; Tirlapur, Uday K.

    2003-07-01

    Targeted transfection of cells is an important technique for gene therapy and related biomedical applications. We delineate how high-intensity (1012 W/cm2) near-infrared (NIR) 80 MHz nanojoule femtosecond laser pulses can create highly localised membrane perforations within a minute focal volume, enabling non-invasive direct transfection of mammalian cells with DNA. We suspended Chinese hamster ovarian (CHO), rat kangaroo kidney epithelial (PtK2) and rat fibroblast cells in 0.5 ml culture medium in a sterile miniaturized cell chamber (JenLab GmbH, Jena, Germany) containing 0.2 μg plasmid DNA vector pEGFP-N1 (4.7 kb), which codes for green fluorescent protein (GFP). The NIR laser beam was introduced into a femtosecond laser scanning microscope (JenLab GmbH, Jena, Germany; focussed on the edge of the cell membrane of a target cell for 16 ms. The integration and expression efficiency of EGFP were assessed in situ by two-photon fluorescence-lifetime imaging using time-correlated single photon counting. The unique capability to transfer foreign DNA safely and efficiently into specific cell types (including stem cells), circumventing mechanical, electrical or chemical means, will have many applications, such as targeted gene therapy and DNA vaccination.

  15. Laser-induced condensation by ultrashort laser pulses at 248 nm

    OpenAIRE

    Joly, P; Petrarca, M.; Vogel, A.(Physikalisches Institut, University of Bonn, Bonn, Germany); Pohl, T; Nagy, T.; Jusforgues, Q.; Simon, P.; Kasparian, J.; Weber, K.; Wolf, J.-P.

    2013-01-01

    We compare laser-induced condensation by UV laser pulses of femtosecond, sub-picosecond, and nanosecond duration between each other, as well as with respect to near-infrared (NIR) (800 nm) ultrashort laser pulses. Particle nucleation by UV pulses is so efficient that their growth beyond several hundreds of nm is limited by the local concentration of water vapour molecules. Furthermore, we evidence a dual mechanism: While condensation induced by ultrashort UV pulses rely on nitrogen photo-oxid...

  16. Narrow band tuning with small long pulse excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Sze, R.C.; Kurnit, N.; Watkins, D.; Bigio, I.

    1985-12-01

    We discuss frequency narrowing and tuning with simple dispersion elements with small long-pulse excimer lasers. The improved performance over short-pulse lasers is discussed and attributed to the increased number of round trips. A physical model of the dynamics of line narrowing is presented.

  17. Advanced pulsed and CW high-power fiber lasers

    OpenAIRE

    Nilsson, J.; Grudinin, A.B.; Turner, P.W.

    2000-01-01

    We examine design issues for high-energy pulsed as well as for high-power cw fiber lasers. Power handling and pump scalability are primary issues for kilowatt fiber lasers. Special core designs are needed for high-energy pulse generation.

  18. Laser-assisted delivery of topical methotrexate - in vitro investigations.

    Science.gov (United States)

    Taudorf, Elisabeth Hjardem

    2016-06-01

    Ablative fractional lasers (AFXL) are increasingly used to treat dermatological disorders and to facilitate laser-assisted topical drug delivery. In this thesis, laser-tissue interactions generated by stacked pulses with a miniaturized low-power 2,940 nm AFXL were characterized (study I). Knowledge of the correlation between laser parameters and tissue effects was used to deliver methotrexate (MTX) topically through microscopic ablation zones (MAZs) of precise dimensions. MTX is a well-known chemotherapeutic and anti-inflammatory drug that may cause systemic adverse effects, and topical delivery is thus of potential benefit. The impact of MAZ depth (study II) and transport kinetics (study III) on MTX deposition in skin as well as transdermal permeation was determined in vitro. Quantitative analyses of dermal and transdermal MTX concentrations were performed by high performance liquid chromatography (HPLC) (study II & III), while qualitative analyses of MTX biodistribution in skin were illustrated and semi-quantified by fluorescence microscopy (study II & III) and desorption electro spray mass spectrometry imaging (DESI-MSI) (study III). Laser-tissue interactions generated by AFXL: AFXL-exposure generated a variety of MAZ-dimensions. MAZ depth increased linearly with the logarithm of total energy delivered by stacked pulses, but was also affected by variations in power, pulse energy, pulse duration, and pulse repetition rate. Coagulation zones lining MAZs increased linearly with the applied total energy, while MAZ width increased linearly with the logarithm of stacked pulses. Results were gathered in a mathematical model estimating relations between laser parameters and specific MAZ dimensions. Impact of MAZ depth on AFXL-assisted topical MTX delivery: Pretreatment by AFXL facilitated topical MTX delivery to all skin layers. Deeper MAZs increased total MTX deposition in skin compared to superficial MAZs and altered the intradermal biodistribution profile towards

  19. Laser Pulse-Stretching Using Multiple Optical Ring-Cavities

    Science.gov (United States)

    Kojima, Jun; Nguyen, Quang-Viet; Lee, Chi-Ming (Technical Monitor)

    2002-01-01

    We describe a simple and passive nanosecond-long (ns-long) laser 'pulse-stretcher' using multiple optical ring-cavities. We present a model of the pulse-stretching process for an arbitrary number of optical ring-cavities. Using the model, we optimize the design of a pulse-stretcher for use in a spontaneous Raman scattering excitation system that avoids laser-induced plasma spark problems. From the optimized design, we then experimentally demonstrate and verify the model with a 3-cavity pulse-stretcher system that converts a 1000 mJ, 8.4 ns-long input laser pulse into an approximately 75 ns-long (FWHM) output laser pulse with a peak power reduction of 0.10X, and an 83% efficiency.

  20. Ultrafast pulse lasers jump to macro applications

    Science.gov (United States)

    Griebel, Martin; Lutze, Walter; Scheller, Torsten

    2016-03-01

    Ultrafast Lasers have been proven for several micro applications, e.g. stent cutting, for many years. Within its development of applications Jenoptik has started to use ultrafast lasers in macro applications in the automotive industry. The JenLas D2.fs-lasers with power output control via AOM is an ideal tool for closed loop controlled material processing. Jenoptik enhanced his well established sensor controlled laser weakening process for airbag covers to a new level. The patented process enables new materials using this kind of technology. One of the most sensitive cover materials is genuine leather. As a natural product it is extremely inhomogeneous and sensitive for any type of thermal load. The combination of femtosecond pulse ablation and closed loop control by multiple sensor array opens the door to a new quality level of defined weakening. Due to the fact, that the beam is directed by scanning equipment the process can be split in multiple cycles additionally reducing the local energy input. The development used the 5W model as well as the latest 10W release of JenLas D2.fs and achieved amazing processing speeds which directly fulfilled the requirements of the automotive industry. Having in mind that the average cycle time of automotive processes is about 60s, trials had been done of processing weakening lines in genuine leather of 1.2mm thickness. Parameters had been about 15 cycles with 300mm/s respectively resulting in an average speed of 20mm/s and a cycle time even below 60s. First samples had already given into functional and aging tests and passed successfully.

  1. POWER RECYCLING OF BURST-MODE LASER PULSES FOR LASER PARTICLE INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun [ORNL

    2016-01-01

    A number of laser-particle interaction experiments such as the laser assisted hydrogen ion beam stripping or X-/ -ray generations via inverse-Compton scattering involve light sources operating in a burst mode to match the tem-poral structure of the particle beam. To mitigate the laser power challenge, it is important to make the interaction inside an optical cavity to recycle the laser power. In many cases, conventional cavity locking techniques will not work since the burst normally has a very small duty factor and low repetition rate and it is impossible to gen-erate an effective control signal. This work reports on the development of a doubly-resonant optical cavity scheme and its locking techniques that enables a simultaneous resonance of two laser beams with different spectra and/or temporal structures. We demonstrate that such a cavity can be used to recycle burst-mode ultra-violet laser pulses with arbitrary burst lengths and repetition rates.

  2. Generation And Measurement Of High Contrast Ultrashort Intense Laser Pulses

    CERN Document Server

    Konoplev, O A

    2000-01-01

    In this thesis, the generation and measurement of high contrast, intense, ultrashort pulses have been studied. Various factors affecting the contrast and pulse shape of ultrashort light pulses from a chirped pulse amplification (CPA) laser system are identified. The level of contrast resulting from influence of these factors is estimated. Methods for improving and controlling the pulse shape and increasing the contrast are discussed. Ultrahigh contrast, 1-ps pulses were generated from a CPA system with no temporal structure up to eleven orders of magnitude. This is eight orders of magnitude higher contrast than the original pulse. This contrast boost was achieved using two techniques. One is the optical pulse cleaning based on the nonlinear birefringence of the chirping fiber and applied to the pulses before amplification. The other is the fast saturable absorber. The fast saturable absorber was placed after amplification and compression of the pulse. The measurements of high-contrast, ultrashort pulse with h...

  3. Towards manipulating relativistic laser pulses with 3D printed materials

    OpenAIRE

    Ji, L. L.; Snyder, J.; Pukhov, A.; Freeman, R. R.; Akli, K. U.

    2015-01-01

    Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser beams irradiating initially flat interfaces with little or no control over the interaction. Here, we propose a novel approach that leverages recent advancements in 3D direct laser writing (DLW) of materials and high contrast lasers to manipulate the laser-matter i...

  4. Additive-pulse modelocking of non-cw neodymium lasers

    Science.gov (United States)

    Heinz, P.; Reuther, A.; Laubereau, A.

    1993-03-01

    Passive modelocking of several flash-lamp pumped neodymium lasers with electro-optic amplitude stabilization is demonstrated using a nonlinear Michelson interferometer. Improved performance is reported for the GSGG- YLF- and glass-laser as compared to the nonlinear absorber, with shorter pulse durations and smaller amplitude fluctuations, e.g. 5 μJ pulses for 460 ± 20 fs for Nd:glass. Evidence is obtained for multi-selfstability of the pulse energy.

  5. Chirp of monolithic colliding pulse mode-locked diode lasers

    DEFF Research Database (Denmark)

    Hofmann, M.; Bischoff, S.; Franck, Thorkild;

    1997-01-01

    Spectrally resolved streak camera measurements of picosecond pulses emitted by hybridly colliding pulse mode-locked (CPM) laser diodes are presented in this letter. Depending on the modulation frequency both blue-chirped (upchirped) and red-chirped (downchirped) pulses can be observed. The two...... different regimes and the transition between them are characterized experimentally and the behavior is explained on the basis of our model for the CPM laser dynamics. (C) 1997 American Institute of Physics....

  6. High energy protons generation by two sequential laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaofeng; Shen, Baifei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn; Zhang, Xiaomei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn; Wang, Wenpeng; Xu, Jiancai; Yi, Longqing; Shi, Yin [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2015-04-15

    The sequential proton acceleration by two laser pulses of relativistic intensity is proposed to produce high energy protons. In the scheme, a relativistic super-Gaussian (SG) laser pulse followed by a Laguerre-Gaussian (LG) pulse irradiates dense plasma attached by underdense plasma. A proton beam is produced from the target and accelerated in the radiation pressure regime by the short SG pulse and then trapped and re-accelerated in a special bubble driven by the LG pulse in the underdense plasma. The advantages of radiation pressure acceleration and LG transverse structure are combined to achieve the effective trapping and acceleration of protons. In a two-dimensional particle-in-cell simulation, protons of 6.7 GeV are obtained from a 2 × 10{sup 22 }W/cm{sup 2} SG laser pulse and a LG pulse at a lower peak intensity.

  7. Propagation of finite length laser pulses in plasma channels

    International Nuclear Information System (INIS)

    Finite pulse length effects are shown to play a major role in the propagation, stability, and guiding of intense laser beams in plasmas. We present the quasiparaxial approximation (QPA) to the wave equation that takes finite pulse length effects into account. The QPA is an extension of the usual paraxial approximation. The laser field is shown to be significantly modified for pulses less than a few tens of wavelengths long. A pair of coupled envelope-power equations having finite pulse length effects, as well as relativistic and atomic electron nonlinearities, is derived and analyzed. Short laser pulses propagating in plasma channels are found to undergo an envelope oscillation in which the front of the pulse is always damped while the back initially grows. The modulation eventually damps due to frequency spread phase mixing. In addition, finite pulse length effects are shown to modify nonlinear focusing processes significantly. thinsp copyright 1999 The American Physical Society

  8. Nonlinear laser pulse response in a crystalline lens.

    Science.gov (United States)

    Sharma, R P; Gupta, Pradeep Kumar; Singh, Ram Kishor; Strickland, D

    2016-04-01

    The propagation characteristics of a spatial Gaussian laser pulse have been studied inside a gradient-index structured crystalline lens with constant-density plasma generated by the laser-tissue interaction. The propagation of the laser pulse is affected by the nonlinearities introduced by the generated plasma inside the crystalline lens. Owing to the movement of plasma species from a higher- to a lower-temperature region, an increase in the refractive index occurs that causes the focusing of the laser pulse. In this study, extended paraxial approximation has been applied to take into account the evolution of the radial profile of the Gaussian laser pulse. To examine the propagation characteristics, variation of the beam width parameter has been observed as a function of the laser power and initial beam radius. The cavitation bubble formation, which plays an important role in the restoration of the elasticity of the crystalline lens, has been investigated. PMID:27192252

  9. Nonlinear laser pulse response in a crystalline lens.

    Science.gov (United States)

    Sharma, R P; Gupta, Pradeep Kumar; Singh, Ram Kishor; Strickland, D

    2016-04-01

    The propagation characteristics of a spatial Gaussian laser pulse have been studied inside a gradient-index structured crystalline lens with constant-density plasma generated by the laser-tissue interaction. The propagation of the laser pulse is affected by the nonlinearities introduced by the generated plasma inside the crystalline lens. Owing to the movement of plasma species from a higher- to a lower-temperature region, an increase in the refractive index occurs that causes the focusing of the laser pulse. In this study, extended paraxial approximation has been applied to take into account the evolution of the radial profile of the Gaussian laser pulse. To examine the propagation characteristics, variation of the beam width parameter has been observed as a function of the laser power and initial beam radius. The cavitation bubble formation, which plays an important role in the restoration of the elasticity of the crystalline lens, has been investigated.

  10. Optodynamic aspect of a pulsed laser ablation process

    Science.gov (United States)

    Hrovatin, Rok; Možina, Janez

    1995-02-01

    A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

  11. Investigation of laser-driven proton acceleration using ultra-short, ultra-intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Fourmaux, S.; Gnedyuk, S.; Lassonde, P.; Payeur, S.; Pepin, H.; Kieffer, J. C. [INRS-EMT, Universite du Quebec, 1650 Lionel Boulet, Varennes, Quebec J3X 1S2 (Canada); Buffechoux, S.; Albertazzi, B. [INRS-EMT, Universite du Quebec, 1650 Lionel Boulet, Varennes, Quebec J3X 1S2 (Canada); LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Capelli, D.; Antici, P. [LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Dipartimento SBAI, Sapienza, Universita di Roma, Via Scarpa 16, 00161 Roma (Italy); Levy, A.; Fuchs, J. [LULI, UMR 7605, CNRS - CEA - Universite Paris 6 - Ecole Polytechnique, 91128 Palaiseau (France); Lecherbourg, L.; Marjoribanks, R. S. [Department of Physics and Institute for Optical Sciences, University of Toronto, Toronto, Ontario M5S 1A7 (Canada)

    2013-01-15

    We report optimization of laser-driven proton acceleration, for a range of experimental parameters available from a single ultrafast Ti:sapphire laser system. We have characterized laser-generated protons produced at the rear and front target surfaces of thin solid targets (15 nm to 90 {mu}m thicknesses) irradiated with an ultra-intense laser pulse (up to 10{sup 20} W Dot-Operator cm{sup -2}, pulse duration 30 to 500 fs, and pulse energy 0.1 to 1.8 J). We find an almost symmetric behaviour for protons accelerated from rear and front sides, and a linear scaling of proton energy cut-off with increasing pulse energy. At constant laser intensity, we observe that the proton cut-off energy increases with increasing laser pulse duration, then roughly constant for pulses longer than 300 fs. Finally, we demonstrate that there is an optimum target thickness and pulse duration.

  12. Theory of attosecond delays in laser-assisted photoionization

    CERN Document Server

    Dahlström, J M; Klünder, K; Gisselbrecht, M; Mauritsson, J; L'Huillier, A; Maquet, A; Taïeb, R

    2011-01-01

    We study the temporal aspects of laser-assisted extreme ultraviolet (XUV) photoionization using attosecond pulses of harmonic radiation. The aim of this paper is to establish the general form of the phase of the relevant transition amplitudes and to make the connection with the time-delays that have been recently measured in experiments. We find that the overall phase contains two distinct types of contributions: one is expressed in terms of the phase-shifts of the photoelectron continuum wavefunction while the other is linked to continuum--continuum transitions induced by the infrared (IR) laser probe. Our formalism applies to both kinds of measurements reported so far, namely the ones using attosecond pulse trains of XUV harmonics and the others based on the use of isolated attosecond pulses (streaking). The connection between the phases and the time-delays is established with the help of finite difference approximations to the energy derivatives of the phases. This makes clear that the observed time-delays...

  13. Antimicrobial nanospheres thin coatings prepared by advanced pulsed laser technique

    Directory of Open Access Journals (Sweden)

    Alina Maria Holban

    2014-06-01

    Full Text Available We report on the fabrication of thin coatings based on polylactic acid-chitosan-magnetite-eugenol (PLA-CS-Fe3O4@EUG nanospheres by matrix assisted pulsed laser evaporation (MAPLE. Transmission electron microscopy (TEM and scanning electron microscopy (SEM investigation proved that the homogenous Fe3O4@EUG nanoparticles have an average diameter of about 7 nm, while the PLA-CS-Fe3O4@EUG nanospheres diameter sizes range between 20 and 80 nm. These MAPLE-deposited coatings acted as bioactive nanosystems and exhibited a great antimicrobial effect by impairing the adherence and biofilm formation of Staphylococcus aureus (S. aureus and Pseudomonas aeruginosa (P. aeruginosa bacteria strains. Moreover, the obtained nano-coatings showed a good biocompatibility and facilitated the normal development of human endothelial cells. These nanosystems may be used as efficient alternatives in treating and preventing bacterial infections.

  14. Interaction of superintense laser pulses with relativistic ions.

    OpenAIRE

    Chirilă, C. C.; Joachain, C. J.; Kylstra, N. J.; Potvliege, R. M.

    2004-01-01

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical resu...

  15. Ultrashort-pulse lasers based on the Sagnac interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Bezrodnyi, V.I.; Prokhorenko, V.I.; Tikhonov, E.A.; Shpak, M.T.; Iatskiv, D.IA.

    1988-01-01

    Results of experimental studies carried out on passively mode-locked and synchronously pumped ultrashort-pulse lasers with cavities based on the Sagnac interferometer are reported. It is shown that the use of the interferometer makes it possible to substantially improve the principal parameters of the ultrashort-pulse laser, such as repeatability, stability, spatial-angular characteristics, and the frequency tuning range. In particular, results are presented for YAG:Nd(3+) and dye lasers with Sagnac interferometers. 10 references.

  16. Development of a compact soft X-ray laser using a pulse-train laser. 4

    International Nuclear Information System (INIS)

    Time behaviour of gain coefficients was studied for the two different pulse train-lasers; one is a normal pulse-train, and the other modified one. The duration time of gain is larger for the modified pulse-train laser compared with the normal one. (author)

  17. The mechanism for SEU simulation by pulsed laser

    Institute of Scientific and Technical Information of China (English)

    HUANG Jianguo; HAN Jianwei

    2004-01-01

    To simulate single event effect (SEE) by pulsed laser is a new approach in ground-based simulation of SEE in recent years. In this paper the way in which picosecond pulsed laser interacts with semiconductor and the mechanism of SEE inducement are analyzed. Additionally, associated calculations are made in the case of Nd:YAG and Ti:Sapphire lasers generally used in experiments and silicon device, with comparisons made between the two lasers. In the meantime, the fundamental principle for determining laser parameters and their typical ranges of values are provided according to the results.

  18. Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

    International Nuclear Information System (INIS)

    Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of few-optical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively. (paper)

  19. Fiber Optic Solutions for Short Pulse Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Beach, R; Dawson, J; Liao, Z; Jovanovic, I; Wattellier, B; Payne, S; Barty, C P

    2003-01-29

    For applications requiring high beam quality radiation from efficient, compact and rugged sources, diffraction limited fiber lasers are ideal, and to date have been demonstrated at average CW power levels exceeding 100 W with near diffraction limited: output. For conventional single-core step-index single-mode fibers, this power level represents the sealing limit because of nonlinear and laser damage considerations. Higher average powers would exceed nonlinear process thresholds such as the Raman and stimulated Brillouin scattering limit, or else damage the fiber due to the high intensity level in the fiber's core. The obvious way to increase the average power capability of fibers is to increase the area of their core. Simply expanding the core dimensions of the fiber allows a straightforward power sealing due to enhanced nonlinear and power handling characteristics that scale directly with the core area. Femtosecond, chirped-pulse, fiber lasers with pulse energies greater than 1mJ have been demonstrated in the literature [2] using this technique. This output energy was still limited by the onset of stimulated Raman scattering. We have pursued an alternative and complimentary approach which is to reduce the intensity of light propagating in the core by distributing it more evenly across the core area via careful design of the refractive index profile [3]. We have also sought to address the primary issue that results from scaling the core. The enhanced power handling capability comes at the expense of beam quality, as increasing the core diameter in standard step index fibers permits multiple transverse modes to lase simultaneously. Although this problem of multimode operation can be mitigated to some extent by appropriately designing the fiber's waveguide structure, limitations such as bend radius loss, sensitivity to thermally induced perturbations of the waveguide structure, and refractive index control, all become more stringent as the core diameter

  20. The Laser-assisted photoelectric effect of He, Ne, Ar and Xe in intense extreme ultraviolet and infrared laser fields

    Science.gov (United States)

    Hayden, P.; Dardis, J.; Hough, P.; Richardson, V.; Kennedy, E. T.; Costello, J. T.; Düsterer, S.; Redlin, H.; Feldhaus, J.; Li, W. B.; Cubaynes, D.; Meyer, M.

    2016-02-01

    In this paper, we report results on two-colour above-threshold ionisation, where extreme ultraviolet pulses of femtosecond duration were synchronised to intense infrared laser pulses of picosecond duration, in order to study the laser-assisted photoelectric effect of atomic helium, neon, krypton and xenon which leads to the appearance of characteristic sidebands in the photoelectron spectra. The observed trends are found to be well described by a simple model based on the soft-photon approximation, at least for the relatively low optical intensities of up to ? employed in these early experiments.

  1. 25 years of pulsed laser deposition

    Science.gov (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    It is our pleasure to introduce this special issue appearing on the occasion of the 25th anniversary of pulsed laser deposition (PLD), which is today one of the most versatile growth techniques for oxide thin films and nanostructures. Ever since its invention, PLD has revolutionized the research on advanced functional oxides due to its ability to yield high-quality thin films, multilayers and heterostructures of a variety of multi-element material systems with rather simple technical means. We appreciate that the use of lasers to deposit films via ablation (now termed PLD) has been known since the 1960s after the invention of the first ruby laser. However, in the first two decades, PLD was something of a 'sleeping beauty' with only a few publications per year, as shown below. This state of hibernation ended abruptly with the advent of high T c superconductor research when scientists needed to grow high-quality thin films of multi-component high T c oxide systems. When most of the conventional growth techniques failed, the invention of PLD by T (Venky) Venkatesan clearly demonstrated that the newly discovered high-T c superconductor, YBa2Cu3O7-δ , could be stoichiometrically deposited as a high-quality nm-thin film with PLD [1]. As a remarkable highlight of this special issue, Venkatesan gives us his very personal reminiscence on these particularly innovative years of PLD beginning in 1986 [2]. After Venky's first paper [1], the importance of this invention was realized worldwide and the number of publications on PLD increased exponentially, as shown in figure 1. Figure 1. Figure 1. Published items per year with title or topic PLD. Data from Thomson Reuters Web of Knowledge in September 2013. After publication of Venky's famous paper in 1987 [1], the story of PLD's success began with a sudden jump in the number of publications, about 25 years ago. A first PLD textbook covering its basic understanding was soon published, in 1994, by Chrisey and Hubler [3]. Within a

  2. Gating attosecond pulse train generation using multicolor laser fields

    International Nuclear Information System (INIS)

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  3. Short-pulse laser interactions with disordered materials and liquids

    Energy Technology Data Exchange (ETDEWEB)

    Phinney, L.M.; Goldman, C.H.; Longtin, J.P.; Tien, C.L. [Univ. of California, Berkeley, CA (United States)

    1995-12-31

    High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regime in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.

  4. Laser pulse spectral shaping based on electro-optic modulation

    Institute of Scientific and Technical Information of China (English)

    Yanhai Wang; Jiangfeng Wang; You'en Jiang; Yan Bao; Xuechun Li; Zunqi Lin

    2008-01-01

    A new spectrum shaping method, based on electro-optic modulation, to alleviate gain narrowing in chirped pulse amplification (CPA) system, is described and numerically simulated. Near-Fourier transform-limited seed laser pulse is chirped linearly through optical stretcher. Then the chirped laser pulse is coupled into integrated waveguide electro-optic modulator driven by an aperture-coupled-stripline (ACSL) electricalwaveform generator, and the pulse shape and amplitude are shaped in time domain. Because of the directrelationship between frequency interval and time interval of the linearly chirped pulse, the laser pulse spectrum is shaped correspondingly. Spectrum-shaping examples are modeled numerically to determine the spectral resolution of this technique. The phase error introduced in this method is also discussed.

  5. Laser assisted modification of poled silver-doped nanocomposite soda-lime glass

    OpenAIRE

    Drevinskas Rokas; Beresna Martynas; Deparis Olivier; Kazansky Peter G.

    2013-01-01

    Thermal poling assisted homogenization of polydisperse Ag nanoparticles embedded in the soda-lime glass is demonstrated. The homogenization leads to the narrowing of the localized surface plasmon resonance. The subsequent irradiation with linearly polarized ultrashort laser pulses induces spectrally defined and four times larger dichroism than in non-poled sample.

  6. Laser assisted modification of poled silver-doped nanocomposite soda-lime glass

    Directory of Open Access Journals (Sweden)

    Drevinskas Rokas

    2013-11-01

    Full Text Available Thermal poling assisted homogenization of polydisperse Ag nanoparticles embedded in the soda-lime glass is demonstrated. The homogenization leads to the narrowing of the localized surface plasmon resonance. The subsequent irradiation with linearly polarized ultrashort laser pulses induces spectrally defined and four times larger dichroism than in non-poled sample.

  7. Airborne bathymetric charting using pulsed blue-green lasers

    Science.gov (United States)

    Kim, H. H.

    1977-01-01

    Laboratory and airborne experiments have proven the feasibility and demonstrated the techniques of an airborne pulsed laser system for rapidly mapping coastal water bathymetry. Water depths of 10 plus or minus 0.25 m were recorded in waters having an effective attenuation coefficient of 0.175 m. A 2-MW peak power Nd:YAG pulsed laser was flown at an altitude of 600 m. An advanced system, incorporating a mirror scanner, a high pulsed rate laser, and a good signal processor, could survey coastal zones at the rate of several square miles per hour.

  8. Laser air-jet engine: the action of shock waves at low laser pulse repetition rates

    International Nuclear Information System (INIS)

    The impact and thermal action of laser sparks on the reflector of a laser engine in which the propulsion is produced by repetitively pulsed radiation is estimated. It is shown that for a low pulse repetition rate, the thermal contact of a plasma with the reflector and strong dynamic resonance loads are inevitable. These difficulties can be surmounted by using the method based on the merging of shock waves at a high pulse repetition rate. (laser applications)

  9. Laser-assisted direct ink writing of planar and 3D metal architectures

    Science.gov (United States)

    Skylar-Scott, Mark A.; Gunasekaran, Suman; Lewis, Jennifer A.

    2016-05-01

    The ability to pattern planar and freestanding 3D metallic architectures at the microscale would enable myriad applications, including flexible electronics, displays, sensors, and electrically small antennas. A 3D printing method is introduced that combines direct ink writing with a focused laser that locally anneals printed metallic features “on-the-fly.” To optimize the nozzle-to-laser separation distance, the heat transfer along the printed silver wire is modeled as a function of printing speed, laser intensity, and pulse duration. Laser-assisted direct ink writing is used to pattern highly conductive, ductile metallic interconnects, springs, and freestanding spiral architectures on flexible and rigid substrates.

  10. Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

    International Nuclear Information System (INIS)

    We investigate a fundamental limitation occurring in vacuum ultraviolet and extreme ultraviolet seeded free electron lasers (FELs). For a given electron beam and undulator configuration, an increase of the FEL output energy at saturation can be obtained via an increase of the seed pulse duration. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect. Numerical studies of the Colson-Bonifacio FEL equations reveal that slippage length and seed laser pulse wings are core ingredients of the dynamics.

  11. Surface plasmon resonance assisted rapid laser joining of glass

    Energy Technology Data Exchange (ETDEWEB)

    Zolotovskaya, Svetlana A.; Tang, Guang; Abdolvand, Amin, E-mail: a.abdolvand@dundee.ac.uk [School of Engineering, Physics and Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom); Wang, Zengbo [School of Electronic Engineering, Bangor University, Bangor LL57 1UT (United Kingdom)

    2014-08-25

    Rapid and strong joining of clear glass to glass containing randomly distributed embedded spherical silver nanoparticles upon nanosecond pulsed laser irradiation (∼40 ns and repetition rate of 100 kHz) at 532 nm is demonstrated. The embedded silver nanoparticles were ∼30–40 nm in diameter, contained in a thin surface layer of ∼10 μm. A joint strength of 12.5 MPa was achieved for a laser fluence of only ∼0.13 J/cm{sup 2} and scanning speed of 10 mm/s. The bonding mechanism is discussed in terms of absorption of the laser energy by nanoparticles and the transfer of the accumulated localised heat to the surrounding glass leading to the local melting and formation of a strong bond. The presented technique is scalable and overcomes a number of serious challenges for a widespread adoption of laser-assisted rapid joining of glass substrates, enabling applications in the manufacture of microelectronic devices, sensors, micro-fluidic, and medical devices.

  12. Generation of elliptically polarized nitrogen ion laser fields using two-color femtosecond laser pulses

    OpenAIRE

    Ziting Li; Bin Zeng; Wei Chu; Hongqiang Xie; Jinping Yao; Guihua Li; Lingling Qiao; Zhanshan Wang; Ya Cheng

    2016-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized...

  13. Micromachining soda-lime glass by femtosecond laser pulses

    Science.gov (United States)

    Jia, Wei; Yu, Jian; Chai, Lu; Wang, Ching-Yue

    2015-08-01

    The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.

  14. Optically pumped terahertz lasers with high pulse repetition frequency: theory and design

    Institute of Scientific and Technical Information of China (English)

    Yude Sun; Shiyou Fu; Jing Wang; Zhenghe Sun; Yanchao Zhang; Zhaoshuo Tian; Qi Wang

    2009-01-01

    Optically pumped terahertz (THz) lasers with high pulse repetition frequency are designed. Such a laser includes two parts: the optically pumping laser and the THz laser. The structures of the laser are described and analyzed. The rate equations for the pulsed THz laser are given. The kinetic process and laser pulse waveform for this kind of laser are numerically calculated based on the theory of rate equations. The theoretical results give a helpful guide to the research of such lasers.

  15. Generation of elliptically polarized nitrogen ion laser fields using two-color femtosecond laser pulses

    Science.gov (United States)

    Li, Ziting; Zeng, Bin; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2016-01-01

    We experimentally investigate generation of nitrogen molecular ion () lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the laser. PMID:26888182

  16. Generation of elliptically polarized nitrogen-ion laser fields using two-color femtosecond laser pulses

    CERN Document Server

    Li, Ziting; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2015-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized molecular nitrogen-ion laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the molecular nitrogen-ion laser.

  17. Stabilizing laser energy density on a target during pulsed laser deposition of thin films

    Science.gov (United States)

    Dowden, Paul C.; Jia, Quanxi

    2016-05-31

    A process for stabilizing laser energy density on a target surface during pulsed laser deposition of thin films controls the focused laser spot on the target. The process involves imaging an image-aperture positioned in the beamline. This eliminates changes in the beam dimensions of the laser. A continuously variable attenuator located in between the output of the laser and the imaged image-aperture adjusts the energy to a desired level by running the laser in a "constant voltage" mode. The process provides reproducibility and controllability for deposition of electronic thin films by pulsed laser deposition.

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

    Science.gov (United States)

    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.

  19. Threshold Determination and Analysis of Laser Pulse Range Finder

    Institute of Scientific and Technical Information of China (English)

    殷聪; 韩绍坤; 刘巽亮; 张化朋; 赵跃进

    2003-01-01

    Under different conditions, the highest detection probability should be acquired while receiving laser echo during laser pulse range finding. The threshold voltage of the signal detection can be set corresponding to different conditions by using resistor network. As a feedback loop, automatic noise threshold circuit could change the threshold voltage following the noise level. The threshold can track the noise closely, rapidly and accurately by adopting this combination. Therefore, the receiving capability of laser echo receiving system will be maximized, and it can detect weaker laser pulse from noise.

  20. LONGITUDINAL DISCH. CO2 LASER WITH PULSED PRE-IONIZATION

    Institute of Scientific and Technical Information of China (English)

    Yu Yanning; Wan Chongyi

    2002-01-01

    A novel pre-ionization scheme of helical transverse-pulsed pre-ionization in a longitudinal discharge CO2 laser is presented. The laser tube is made of glass with inner diameter of 7.5mm and discharge length of 50cm. The laser performance characteristics as functions of parameters, such as pressure, charging capacitance and applied voltage, are investigated. Compared with the same laser structure without pre-ionization, the maximum pulse energy improves by 23%, the optimum electro-optical efficiency increases by 31%, and the specific output energy reaches 26 J/(L·atm).

  1. Laser Assisted Cancer Immunotherapy: Surface Irradiation

    Science.gov (United States)

    Wilson, Joshua; Chen, Hsin-Wei; Bandyopadhyay, Pradip

    2006-03-01

    Experiments in our laboratory incorporate a non-invasive approach to treat superficial tumors in animal models. Based on the concept of Laser Assisted Cancer Immunotherapy, surface irradiation provides good information to compare to invasive alternatives. The procedure involves injecting an immunoadjuvant (Glycated Chitosan) as well as a light absorbing dye (Indocyanine Green) directly into the tumor (5 to 7 mm in diameter). The temperature of the tumor is raised using an infrared diode laser operating at 804 nm, with a silica fiber tip placed a set distance away from the surface of the tumor. We monitor the surface temperature using non-invasive (infrared detector probe) as well as the internal temperature of the tumor using invasive (micro thermocouples) methods. This study aims at the success of the surface irradiation mode to treat solid tumors. * This work is supported by a grant from The National Institute of Health.

  2. Laser-Assisted Photoelectric Effect from Liquids

    Science.gov (United States)

    Arrell, C. A.; Ojeda, J.; Mewes, L.; Grilj, J.; Frassetto, F.; Poletto, L.; van Mourik, F.; Chergui, M.

    2016-09-01

    The laser-assisted photoelectric effect from liquid surfaces is reported for the first time. Photoelectrons generated by 35.6 eV radiation from a liquid microjet of water under vacuum are dressed with a ℏω =1.55 eV laser field. The subsequent redistribution of the photoelectron energies consists in the appearance of sidebands shifted by energies equivalent to ℏω , 2 ℏω , and 3 ℏω . The response has been modeled to the third order and combined with energy-resolved measurements. This result opens the possibility to investigate the dynamics at surfaces of liquid solutions and provide information about the electron emission process from a liquid.

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

    Science.gov (United States)

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

    2013-01-01

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

  4. Parabolic similariton Yb-fiber laser with triangular pulse evolution

    Science.gov (United States)

    Wang, Sijia; Wang, Lei

    2016-04-01

    We propose a novel mode-locked fiber laser design which features a passive nonlinear triangular pulse formation and self-similar parabolic pulse amplification intra cavity. Attribute to the nonlinear reshaping progress in the passive fiber, a triangular-profiled pulse with negative-chirp is generated and paved the way for rapid and efficient self-similar parabolic evolution in a following short-length high-gain fiber. In the meanwhile, the accompanied significantly compressed narrow spectrum from this passive nonlinear reshaping also gives the promise of pulse stabilization and gain-shaping robustness without strong filtering. The resulting short average intra-cavity pulse duration, low amplified spontaneous emission (ASE) and low intra-cavity power loss are essential for the low-noise operation. Simulations predict this modelocked fiber laser allows for high-energy ultra-short transform-limited pulse generation exceeding the gain bandwidth. The output pulse has a de-chirped duration (full-width at half maximum, FWHM) of 27 fs. In addition to the ultrafast laser applications, the proposed fiber laser scheme can support low-noise parabolic and triangular pulse trains at the same time, which are also attractive in optical pulse shaping, all-optical signal processing and high-speed communication applications.

  5. Quantum Electrodynamics Theory of Laser Assisted Recombination

    Institute of Scientific and Technical Information of China (English)

    敖淑艳; 程太旺; 李晓峰; 潘守甫; 傅盘铭

    2003-01-01

    Using a formal scattering theoretical approach, we develop a nonperturbative quantum electrodynamics theory to describe laser assisted recombination (LAR), in which an electron initially in the quantized Volkov state recombines with an ion and emits a high-energy photon with frequency defined by energy conservation laws.The transition probability is expressed as an analytic closed form and the spectrum of LAR reflects mainly the properties of general Bessel functions. For the case of a fast electron the LAR spectrum is confined in a well-defined range, while for a slow electron, the LAR spectrum exhibits a double-plateau structure.

  6. Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

    Institute of Scientific and Technical Information of China (English)

    Hu Qiang-Lin; Liu Shi-Bing

    2006-01-01

    Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target.The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

  7. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    OpenAIRE

    Nakamura, K; Fubiani, G; Geddes, C. G. R.; Michel, P.; van Tilborg, J.; Toth, C; Esarey, E.; Schroeder, C. B.; Leemans, W. P.

    2004-01-01

    An injection scheme for a laser wakefield accelerator that employs a counterpropagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counterpropagating laser intensity a_1 < 0.5 for a drive laser intensity of a_0 = 1.0. Preliminary expe...

  8. Effects of Laser Energy and Wavelength on the Analysis of LiFePO4 Using Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; Martens, Rich; Janssen, Yuri; Kalifah, Peter; Meng, Ying S.

    2015-01-21

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative accuracy of atom probe tomography (APT) examinations of LiFePO4 (LFP) are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted APT of LFP has revealed distinctly different behaviors. With the use of UV laser the major issue was identified as the preferential loss of oxygen (up to 10 at. %) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ increased the observed oxygen concentration to near its correct stoichiometry and was well correlated with systematically higher concentrations of 16O2+ ions. This observation supports the premise that lower laser energies lead to a higher probability of oxygen molecule ionization. Conversely, at higher laser energies the resultant lower effective electric field reduces the probability of oxygen molecule ionization. Green laser assisted field evaporation led to the selective loss of Li (~50% deficiency) and correct ratios of the remaining elements, including the oxygen concentration. The loss of Li is explained by selective dc evaporation of lithium between laser pulses and relatively negligible oxygen loss as neutrals during green-laser pulsing. Lastly, plotting of multihit events on a Saxey plot for the straight-flight path data (green laser only) revealed a surprising dynamic recombination process for some molecular ions mid-flight.

  9. Pulse-shaping mechanism in colliding-pulse mode-locked laser diodes

    DEFF Research Database (Denmark)

    Bischoff, Svend; Sørensen, Mads Peter; Mørk, J.;

    1995-01-01

    The large signal dynamics of passively colliding pulse mode-locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow...... absorber dynamics to achieve mode-locking. Significant chirp is predicted for pulses emitted from long lasers, in agreement with experiment. The pulse width shows a strong dependence on both cavity and saturable absorber length. (C) 1995 American Institute of Physics....

  10. Fundamental studies of pulsed laser ablation

    CERN Document Server

    Claeyssens, F

    2001-01-01

    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  11. Power Enhancement Cavity for Burst-Mode Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun [ORNL

    2015-01-01

    We demonstrate a novel optical cavity scheme and locking method that can realize the power enhancement of picosecond UV laser pulses operating at a burst mode with arbitrary burst (macropulse) lengths and repetition rates.

  12. Double Ionization by Strong Elliptically Polarized Laser Pulses

    OpenAIRE

    Wang, Xu; Eberly, J. H.

    2009-01-01

    We join the tribute to Professor N.B. Delone in this memorial issue by presenting the results of new calculations on the effects of ellipticity on double ionization by short and strong near-optical laser pulses.

  13. Monitor and control of neuronal activities with femtosecond pulse laser

    Institute of Scientific and Technical Information of China (English)

    ZHOU Wei; LIU XiuLi; L(U) XiaoHua; LI JiaSong; LUO QingMing; ZENG ShaoQun

    2008-01-01

    Combined with the fluorescence labeling technique, two-photon microscopy excited with femtosecond pulse laser has become an important tool for neuroscience research. In this research, the calcium signals from neurons in rat cortex slice were monitored by a custom-built two-photon microscopy, and the spontaneous calcium signals and the pharmacological responses as well as the responses to femtosecond pulse laser stimulation were recorded. The results showed that the amplitude of the cal-cium signals increased in direct proportion to the corresponding electrical activities. Glutamate induced a calcium transient, but continuous application resulted in smaller response. Simultaneous monitoring of neuronal populations distinguished the neurons of different microcircuits. The femtosecond pulse laser induced local or global calcium signals in the pyramidal neurons. The approach of interrogation and control of neural activities using femtosecond pulse laser is non-contact, nondestructive, repeatable, and without any additional substrates, which will contribute to the development of neuroscience.

  14. Schwinger Vacuum Pair Production in Chirped Laser Pulses

    CERN Document Server

    Dumlu, Cesim K

    2010-01-01

    The recent developments of high intensity ultra-short laser pulses have raised the hopes of observing Schwinger vacuum pair production which is one of the important non-perturbative phenomena in Quantum electrodynamics (QED). The quantitative analysis of realistic high intensity laser pulses is vital for understanding the effect of the field parameters on the momentum spectrum of the produced particles. In this study, we analyze chirped laser pulses with a sub-cycle structure, and investigate the effects of the chirp parameter on the momentum spectrum of the produced particles. The combined effect of the chirp and carrier phase of the laser pulse is also analyzed. These effects are qualitatively explained by investigating the turning point structure of the potential within the framework of the complex WKB scattering approach to pair production.

  15. 20 W High Efficiency 1550 nm Pulsed Fiber Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High peak power short pulsed lasers have been considered to be an enabling technology to build high power transmitters for future deep space high rate space...

  16. Miniature, Rugged, Pulsed Laser Source for LIDAR Application Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Princeton Optronics proposes to develop a high energy pulsed laser source based on a novel approach. The approach consists of a technique to combine a large number...

  17. Femtosecond laser pulse train interaction with dielectric materials

    Science.gov (United States)

    Dematteo Caulier, O.; Mishchik, K.; Chimier, B.; Skupin, S.; Bourgeade, A.; Javaux Léger, C.; Kling, R.; Hönninger, C.; Lopez, J.; Tikhonchuk, V.; Duchateau, G.

    2015-11-01

    The interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model is investigated. Theoretical predictions are directly confronted with experimental observations in soda-lime glass. It is shown that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in the simulations correspond very well to zones of permanent material modifications observed in the experiments. It turns out that pulse-to-pulse variations of the laser absorption are negligible and of minor influence to permanent material modifications.

  18. Chirped pulse inverse free-electron laser vacuum accelerator

    Science.gov (United States)

    Hartemann, Frederic V.; Baldis, Hector A.; Landahl, Eric C.

    2002-01-01

    A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

  19. Longitudinally excited CO2 laser with short laser pulse for hard tissue drilling

    Science.gov (United States)

    Uno, Kazuyuki; Hayashi, Hiroyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2014-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with a circular beam and a low divergence angle. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse width of 103 ns and a pulse tail length of 32.6 μs. The beam cross-section was circular and the full-angle beam divergence was 1.7 mrad. The laser was used to drill ivory samples without carbonization at fluences of 2.3-7.1 J/cm2. The drilling depth of the dry ivory increased with the fluence. The drilling mechanism of the dry ivory was attributed to absorption of the laser light by the ivory.

  20. Reduction of the pulse duration of the ultrafast laser pulses of the Two-Photon Laser Scanning Microscopy (2PLSM

    Directory of Open Access Journals (Sweden)

    Reshak Ali

    2008-07-01

    Full Text Available Abstract Background We provide an update of our two-photon laser scanning microscope by compressing or reducing the broadening of the pulse width of ultrafast laser pulses for dispersion precompensation, to enable the pulses to penetrate deeply inside the sample. Findings The broadening comes as the pulses pass through the optical elements. We enhanced and modified the quality and the sharpness of images by enhancing the resolution using special polarizer namely Glan Laser polarizer GL10. This polarizer consists of two prisms separated by air space. This air separation between the two prisms uses to delay the red wavelength when the light leaves the first prism to the air then to second prism. We note a considerable enhancing with using the GL polarizer, and we can see the details of the leaf structure in early stages when we trying to get focus through z-stacks of images in comparison to exactly the same measurements without using GL polarizer. Hence, with this modification we able to reduce the time of exposure the sample to the laser radiation thereby we will reduce the probability of photobleaching and phototoxicity. When the pulse width reduced, the average power of the laser pulses maintained at a constant level. Significant enhancement is found between the two kinds of images of the Two-Photon Excitation Fluorescence (TPEF. Conclusion In summary reduction the laser pulse width allowed to collect more diffraction orders which will used to form the images. The more diffraction orders the higher resolution images.

  1. High-energy, short-pulse, carbon-dioxide lasers

    International Nuclear Information System (INIS)

    Lasers for fusion application represent a special class of short-pulse generators; not only must they generate extremely short temporal pulses of high quality, but they must do this at ultra-high powers and satisfy other stringent requirements by this application. This paper presents the status of the research and development of carbon-dioxide laser systems at the Los Alamos Scientific Laboratory, vis-a-vis the fusion requirements

  2. Layer-by-layer pattern propagtion and pulsed laser deposition

    OpenAIRE

    Westerhoff, F.; Brendel, L.; Wolf, D. E.

    2001-01-01

    In this article kinetic Monte Carlo simulations for molecular beam epitaxy (MBE) and pulsed laser depositon (PLD) are compared. It will be shown that an optimal pattern conservation during MBE is achieved for a specific ratio of diffusion to deposition rate. Further on pulsed laser deposition is presented as an alternative way to control layer by layer growth. First results concerning the island density in the submonolayer regime are shown.

  3. Pulsed Laser Centre (CLPU). The Salamanca peta watt laser; Centro de Laseres Pulsados (CLPU). El laser de Petavatio de Salamanca

    Energy Technology Data Exchange (ETDEWEB)

    Franco, L. R.

    2016-08-01

    With pulses lasting 30 photo seconds, the CLPU VEGA laser is capable of generating a peak power level of one peta watt, this making it one of the worlds most powerful lasers. When focussed it can reach extreme intensities. The way in which a pulse of this nature interacts with an atom or what its applications might be are among the questions answered by this article. (Author)

  4. Ultrashort Laser Pulse Heating of Nanoparticles: Comparison of Theoretical Approaches

    Directory of Open Access Journals (Sweden)

    Renat R. Letfullin

    2008-01-01

    Full Text Available The interaction between nanoparticles and ultrashort laser pulses holds great interest in laser nanomedicine, introducing such possibilities as selective cell targeting to create highly localized cell damage. Two models are studied to describe the laser pulse interaction with nanoparticles in the femtosecond, picosecond, and nanosecond regimes. The first is a two-temperature model using two coupled diffusion equations: one describing the heat conduction of electrons, and the other that of the lattice. The second model is a one-temperature model utilizing a heat diffusion equation for the phonon subsystem and applying a uniform heating approximation throughout the particle volume. A comparison of the two modeling strategies shows that the two-temperature model gives a good approximation for the femtosecond mode, but fails to accurately describe the laser heating for longer pulses. On the contrary, the simpler one-temperature model provides an adequate description of the laser heating of nanoparticles in the femtosecond, picosecond, and nanosecond modes.

  5. Experimental verification of physical model of pulsed laser welding

    Energy Technology Data Exchange (ETDEWEB)

    Jellison, J.L.; Keicher, D.M.

    1990-01-01

    Whereas most experimental and theoretical studies of the role of convection in fusion welding have been concerned with continuous heat sources, a pulsed heat source is the focus of this study. This is primarily an experimental study of the pulsed Nd:YAG laser welding of austenitic stainless steels. 12 refs., 9 figs.

  6. Nonsequential Double Ionization of Atoms in Strong Laser Pulses

    Science.gov (United States)

    Prauzner-Bechcicki, J. S.; Sacha, K.; Eckhardt, B.; Zakrzewski, J.

    2007-10-01

    It is now possible to produce laser pulses with reproducible pulse shape and controlled carrier envelope phase. It is discussed how that can be explored in double ionisation studies. To this end we solve numerically the Schrödinger equation for a limited dimensionality model which nevertheless treats electron repulsion qualitatively correctly and allows to study correlation effects due to the Coulomb repulsion.

  7. Long-pulsed dye laser vs. intense pulsed light for the treatment of facial telangiectasias: a randomized controlled trial

    DEFF Research Database (Denmark)

    Nymann, Peter; Hedelund, Lene; Haedersdal, M

    2010-01-01

    This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias.......This study aims to compare the efficacy and adverse effects of long-pulsed dye laser (LPDL) and intense pulsed light (IPL) in the treatment of facial telangiectasias....

  8. The effect of the laser wavelength on collinear double pulse laser induced breakdown spectroscopy (DP-LIBS)

    Science.gov (United States)

    Wang, Qi; Lin, Yanqing; Liu, Jing; Fan, Shuang; Xu, Zhuopin; Huang, Qing; Wu, Yuejin

    2016-05-01

    The pulsed lasers at wavelengths of 532 nm and 1064 nm were used as two beams of light for collinear double pulse laser induced breakdown spectroscopy (DP-LIBS). By changing the time sequence of two beams of different lasers, we studied the effect of the interval of two pulses of DP-LIBS on spectral signals compared with single pulsed (SP) LIBS.

  9. Pulsed laser ablation of GaAs using nano pulse length

    International Nuclear Information System (INIS)

    Ablation using very short pulses has shown a great promise in facilitating the growth of complex multi-element films with stoichiometries matching those of their parent materials. GaAs is an important material in the electronic and opto-electronic industries and due to its compound structure it is an intriguing candidate for pulsed laser deposition. This work investigates the effect of nanosecond laser pulse lengths on the ablation of GaAs in an inert atmosphere. The number of pulses was varied in order to find the optimal condition for nano particles formation in our setup. The deposited structures were studied by grazing incidence small angle X-ray scattering and atomic force microscopy. It is shown that the GaAs nanoparticle sizes and size distributions can be controlled partly by the number of laser pulses applied in their production.

  10. Synchronization of Sub-Picosecond Electron and Laser Pulses

    International Nuclear Information System (INIS)

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is subpicosecond, with tens of femtosecond synchronization implied for next-generation experiments. Typically, an RF electron accelerator is synchronized to a short pulse laser system by detecting the repetition signal of a laser oscillator, adjusted to an exact subharmonic of the linac RF frequency, and multiplying or phase locking this signal to produce the master RF clock. Pulse-to-pulse jitter characteristic of self-mode-locked laser oscillators represents a direct contribution to the ultimate timing jitter between a high intensity laser focus and electron beam at the interaction point, or a photocathode drive laser in an RF photoinjector. This timing jitter problem has been addressed most seriously in the context of the RF photoinjector, where the electron beam properties are sensitive functions of relative timing jitter. The timing jitter achieved in synchronized photocathode drive laser systems is near, or slightly below one picosecond. The ultimate time of arrival jitter of the beam at the photoinjector exit is typically a bit smaller than the photocathode drive-laser jitter due to velocity compression effects in the first RF cell of the gun. This tendency of the timing of the electron beam arrival at a given spatial point to lock to the RF lock is strongly reinforced by use of magnetic compression

  11. DEVICE FOR INVESTIGATION OF MAGNETRON AND PULSED-LASER PLASMA

    Directory of Open Access Journals (Sweden)

    A. P. Burmakov

    2012-01-01

    Full Text Available Various modifications of complex pulsed laser and magnetron deposition thin-film structures unit are presented. They include joint and separate variants of layer deposition. Unit realizes the plasma parameters control and enhances the possibility of laser-plasma and magnetron methods of coatings deposition.

  12. Theory and simulation of ultra-short pulse laser interactions

    Energy Technology Data Exchange (ETDEWEB)

    More, R.; Walling, R.; Price, D.; Guethlein, G.; Stewart, R.; Libby, S.; Graziani, F.; Levatin, J. [Lawrence Livermore National Lab., Livermore, CA (United States)

    1998-03-01

    This paper describes recent Livermore work aimed at building computational tools to describe ultra-short pulse laser plasmas. We discuss calculations of laser absorption, atomic data for high-charge ions, and a new idea for linear-response treatment of non-equilibrium phenomena near LTE. (author)

  13. Resonant infrared pulsed laser deposition of thin biodegradable polymer films

    DEFF Research Database (Denmark)

    Bubb, D.M.; Toftmann, B.; Haglund Jr., R.F.;

    2002-01-01

    Thin films of the biodegradable polymer poly(DL-lactide-co-glycolide) (PLGA) were deposited using resonant infrared pulsed laser deposition (RIR-PLD). The output of a free-electron laser was focused onto a solid target of the polymer, and the films were deposited using 2.90 (resonant with O...

  14. Precision machining of pig intestine using ultrafast laser pulses

    Science.gov (United States)

    Beck, Rainer J.; Góra, Wojciech S.; Carter, Richard M.; Gunadi, Sonny; Jayne, David; Hand, Duncan P.; Shephard, Jonathan D.

    2015-07-01

    Endoluminal surgery for the treatment of early stage colorectal cancer is typically based on electrocautery tools which imply restrictions on precision and the risk of harm through collateral thermal damage to the healthy tissue. As a potential alternative to mitigate these drawbacks we present laser machining of pig intestine by means of picosecond laser pulses. The high intensities of an ultrafast laser enable nonlinear absorption processes and a predominantly nonthermal ablation regime. Laser ablation results of square cavities with comparable thickness to early stage colorectal cancers are presented for a wavelength of 1030 nm using an industrial picosecond laser. The corresponding histology sections exhibit only minimal collateral damage to the surrounding tissue. The depth of the ablation can be controlled precisely by means of the pulse energy. Overall, the application of ultrafast lasers to ablate pig intestine enables significantly improved precision and reduced thermal damage to the surrounding tissue compared to conventional techniques.

  15. Laser and intense pulsed light hair removal technologies

    DEFF Research Database (Denmark)

    Haedersdal, M; Beerwerth, F; Nash, J F

    2011-01-01

    Light-based hair removal (LHR) is one of the fastest growing, nonsurgical aesthetic cosmetic procedures in the United States and Europe. A variety of light sources including lasers, e.g. alexandrite laser (755 nm), pulsed diode lasers (800, 810 nm), Nd:YAG laser (1064 nm) and broad-spectrum intense...... devices have been sold directly to consumers for treatment in the home. In this review, we outline the principles underlying laser and IPL technologies and undertake an evidence-based assessment of the short- and long-term efficacy of the different devices available to the practising dermatologist...

  16. Ultrashort pulsed fiber laser welding and sealing of transparent materials.

    Science.gov (United States)

    Huang, Huan; Yang, Lih-Mei; Liu, Jian

    2012-05-20

    In this paper, methods of welding and sealing optically transparent materials using an ultrashort pulsed (USP) fiber laser are demonstrated which overcome the limit of small area welding of optical materials. First, the interaction of USP fiber laser radiation inside glass was studied and single line welding results with different laser parameters were investigated. Then multiline scanning was used to obtain successful area bonding. Finally, complete four-edge sealing of fused silica substrates with a USP laser was demonstrated and the hermetic seal was confirmed by water immersion test. This laser microwelding technique can be extended to various applications in the semiconductor industry and precision optic manufacturing. PMID:22614601

  17. Photonic crystal Fano laser: terahertz modulation and ultrashort pulse generation.

    Science.gov (United States)

    Mork, J; Chen, Y; Heuck, M

    2014-10-17

    We suggest and analyze a laser with a mirror realized by Fano interference between a waveguide and a nanocavity. For small-amplitude modulation of the nanocavity resonance, the laser can be modulated at frequencies exceeding 1 THz, not being limited by carrier dynamics as for conventional lasers. For larger modulation, a transition from pure frequency modulation to the generation of ultrashort pulses is observed. The laser dynamics is analyzed by generalizing the field equation for conventional lasers to account for a dynamical mirror, described by coupled mode theory. PMID:25361259

  18. Femtosecond laser pulse train interaction with dielectric materials

    CERN Document Server

    Caulier, O Dematteo; Chimier, B; Skupin, S; Bourgeade, A; Léger, C Javaux; Kling, R; Hönninger, C; Lopez, J; Tikhonchuk, V; Duchateau, G

    2015-01-01

    We investigate the interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model. Our theoretical predictions are directly confronted with experimental observations in soda-lime glass. We show that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in our simulations correspond very well to zones of permanent material modifications observed in the experiments.

  19. Mathematical modelling of multiple pulsed laser percussion drilling

    OpenAIRE

    Suchatawat, Maturose

    2012-01-01

    In laser percussion drilling, a series of laser pulses with specified energies and durations irradiate the workpiece surface to gradually heat, melt, and vaporise material until a hole with required depth and diameter is achieved. Despite being the quickest technique for producing small diameter holes, laser percussion drilling regularly suffers from difficulties in controlling the hole quality such as hole circularity, hole taper and recast layer. Therefore, in order to produce holes to a sp...

  20. Deuterium Clusters Fusion Induced by the Intense Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Jie; CHEN Jia-Bin; WANG Hong-Bin; JIAO Chun-Ye; HE Ying-Ling; WEN Tian-Shu; WEN Xian-Lun; CHEN Ming; ZHENG Zhi-Jian; GU Yu-Qiu; ZHANG Bao-Han; RHEE Yong-Joo; NAM Sung-Mo; HAN Jae-Min; RHEE Yong-Woo; YEA Kwon-Hae

    2007-01-01

    Neutrons (2.45 MeV) from deuterium cluster fusion induced by the intense femtosecond (30 fs) laser pulse are experimentally demonstrated. The average neutron yield 103 per shot is obtained. It is found that the yield slightly increases with the increasing laser spot size. No neutron can be observed when the laser intensity Ⅰ <4.3×1015 W/cm2.

  1. Photodissociation of Cycloketones by Ultraintense Femtosecond Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Photodissociation of cyclopentanone (C5H8O) and cyclohexanone (C6H10O) was studied with 800nm, 50fs laser pulse at intensities of 5.0-13.0×1013 W/cm2. A time of flight mass spectrometer was employed to detect the ion signals. Parent ions dominated at lower laser intensities. Fragmentation of the parent ions increases with increasing laser intensity and molecular size. The fragmentation mechanism was discussed.

  2. Powerful 170-attosecond XUV pulses generated with few-cycle laser pulses and broadband multilayer optics

    Energy Technology Data Exchange (ETDEWEB)

    Schultze, M [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Goulielmakis, E [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Uiberacker, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Hofstetter, M [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany); Kim, J [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, D [Laser Science Laboratory, Department of Physics, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Krausz, F [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermannstrasse 1, D-85748 Garching (Germany); Kleineberg, U [Department fuer Physik, Ludwig-Maximilians-Universitaet, Am Coulombwall 1, D-85748 Garching (Germany)

    2007-07-15

    Single 170-as extreme ultraviolet (XUV) pulses delivering more than 10{sup 6} photons/pulse at {approx}100 eV at a repetition rate of 3 kHz are produced by ionizing neon with waveform-controlled sub-5 fs near-infrared (NIR) laser pulses and spectrally filtering the emerging near-cutoff high-harmonic continuum with a broadband, chirped multilayer molybdenum-silicon (Mo/Si) mirror.

  3. Small rare gas clusters in XUV laser pulses

    CERN Document Server

    Bauer, D

    2003-01-01

    Semi-classical molecular dynamics simulations of small rare gas clusters in short laser pulses of 100 nm wavelength were performed. For comparison, the cluster response to 800 nm laser pulses was investigated as well. The inner ionization dynamics of the multi-electron atoms inside the cluster was treated explicitly. The simulation results underpin that at XUV wavelengths collisions play an important role in the energy absorption and the generation of the surprisingly high charge states of Xe atoms inside clusters, as they were observed in the free-electron laser experiment at DESY, Hamburg, Germany [Wabnitz et al., Nature 420, 482 (2002)].

  4. Transforming graphite to nanoscale diamonds by a femtosecond laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Nueske, R.; Jurgilaitis, A.; Enquist, H.; Harb, M.; Larsson, J. [Atomic Physics Division, Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Fang, Y.; Haakanson, U. [Division of Solid State Physics/Nanometer Structure Consortium at Lund University, P.O. Box 118, S-221 00 Lund (Sweden); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603-146, 100190 Beijing (China)

    2012-01-23

    Formation of cubic diamond from graphite following irradiation by a single, intense, ultra-short laser pulse has been observed. Highly oriented pyrolytic graphite (HOPG) samples were irradiated by a 100 fs pulse with a center wavelength of 800 nm. Following laser exposure, the HOPG samples were studied using Raman spectroscopy of the sample surface. In the laser-irradiated areas, nanoscale cubic diamond crystals have been formed. The exposed areas were also studied using grazing incidence x-ray powder diffraction showing a restacking of planes from hexagonal graphite to rhombohedral graphite.

  5. Propagation of intense laser pulses in strongly magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X. H., E-mail: xhyang@nudt.edu.cn; Ge, Z. Y.; Xu, B. B.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China); Yu, W., E-mail: weiyu@mail.shcnc.ac.cn [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Xu, H. [School of Computer Science, National University of Defense Technology, Changsha 410073 (China); Yu, M. Y., E-mail: myyu@zju.edu.cn [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institut für Theoretische Physik I, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Borghesi, M. [School of Mathematics and Physics, Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom)

    2015-06-01

    Propagation of intense circularly polarized laser pulses in strongly magnetized inhomogeneous plasmas is investigated. It is shown that a left-hand circularly polarized laser pulse propagating up the density gradient of the plasma along the magnetic field is reflected at the left-cutoff density. However, a right-hand circularly polarized laser can penetrate up the density gradient deep into the plasma without cutoff or resonance and turbulently heat the electrons trapped in its wake. Results from particle-in-cell simulations are in good agreement with that from the theory.

  6. Propagation of intense, ultrashort laser pulses through preionized plasma slabs

    International Nuclear Information System (INIS)

    Relativistic self-focusing and channel formation induced by intense, ultrashort laser pulses in preionized targets is modeled for accessible experimental parameters. The stability of channel formation is limited by the nonparaxiality of the laser beam in regions of tight self-focusing. This issue is examined with recently developed nonparaxial theory. Channel formation is also characterized in terms of the transmitted pulse spectrum, the transmitted laser intensity profile, and the radial electron density distribution. Calculations indicate a signature spectral shift in transmission biased toward longer wavelengths, which is attributed to the rapid expulsion of electrons away from the propagation axis

  7. A unified model in the pulsed laser ablation process

    Institute of Scientific and Technical Information of China (English)

    HU De-zhi

    2008-01-01

    In this unified model, we introduce the electron-phonon coupling time (t) and laser pulse width (t). For long pulses, it can substitute for the traditional thermal conduction model; while for ultrashort pulses, it can substitute for the standard two-temperature model. As an example of the gold target, we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain (FDTD) method.It is in good agreement with experimental data. We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nanosecond to femtosecond timescale, which consists well with the experimental data.

  8. The efficiency of photovoltaic cells exposed to pulsed laser light

    Science.gov (United States)

    Lowe, R. A.; Landis, G. A.; Jenkins, P.

    1993-01-01

    Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe2, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current vs bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC 'ringing', and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components.

  9. Ablation of silicon with bursts of femtosecond laser pulses

    Science.gov (United States)

    Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

    2016-03-01

    We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

  10. Laser micro-processing of silicon using nanosecond pulse shaped fibre laser at 1 ?m wavelength

    OpenAIRE

    LI, Kun

    2012-01-01

    Processing of Si in the semiconductor and solar cell industry has been dominated by the Diode Pumped Solid State (DPSS) Ultraviolet (UV) laser. Recent advances in laser source technology have produced fibre lasers with Master Oscillator Power Amplifier (MOPA) architectures that offer high repetition rates, high operational efficiencies, and pulse modulation controls exceeding those of typical Q-switched DPSS lasers. The aim of this research is to investigate 1 ?m fibre laser machining of Si w...

  11. The interaction of intense subpicosecond laser pulses with underdense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Coverdale, C.A.

    1995-05-11

    Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.

  12. Vacuum heating of solid target irradiated by femtosecond laser pulses

    Institute of Scientific and Technical Information of China (English)

    DONG; Quanli(董全力); ZHANG; Jie(张杰)

    2003-01-01

    The interaction of femtosecond laser pulses with solid targets was studied through experiments and particle-in-cell (PIC) simulations. It is proved that the vacuum heating and the inverse bremsstralung process are the main mechanisms of the laser pulse absorption under such conditions. The distribution of hot electrons and that of X-ray are found to have double-temperature structure, which is confirmed by PIC simulations. While the lower temperature is attributed to the resonant absorption, the higher one, however, is caused by the laser-induced electric field in the target normal direction. The time-integrated spectra ofthe reflected laser pulse shows that the mechanism of electron acceleration is determined by the plasma density profile.

  13. Medical applications of ultra-short pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B M; Marion, J E

    1999-06-08

    The medical applications for ultra short pulse lasers (USPLs) and their associated commercial potential are reviewed. Short pulse lasers offer the surgeon the possibility of precision cutting or disruption of tissue with virtually no thermal or mechanical damage to the surrounding areas. Therefore the USPL offers potential improvement to numerous existing medical procedures. Secondly, when USPLs are combined with advanced tissue diagnostics, there are possibilities for tissue-selective precision ablation that may allow for new surgeries that cannot at present be performed. Here we briefly review the advantages of short pulse lasers, examine the potential markets both from an investment community perspective, and from the view. of the technology provider. Finally nominal performance and cost requirements for the lasers, delivery systems and diagnostics and the present state of development will be addressed.

  14. Laser-assisted growth of carbon nanotubes - A review

    NARCIS (Netherlands)

    Burgt, Y. van de

    2014-01-01

    Laser-assisted chemical vapor deposition (LACVD) is an attractive maskless process for growing locally carbon nanotubes at selected places on substrates that may contain temperature-sensitive components. This review gives a comprehensive overview of the reported research with respect to laser assist

  15. Complex Spectra Structure of an Attosecond Pulse Train Driven by Sub-5-fs Laser Pulses

    Institute of Scientific and Technical Information of China (English)

    YUN Chen-Xia; TENG Hao; ZHANG Wei; WANG Li-Feng; ZHAN Min-Jie; HE Xin-Kui; WANG Bing-Bing; WEI Zhi-Yi

    2011-01-01

    We present the observation of the additional spectral components between the odd order harmonics in the harmonic spectrum generated from argon gas driven by sub-5-fs laser pulses.The theoretical analysis shows that the asymmetric laser field in both spatial and temporal domains leads to this complicated spectrum structure of high order harmonics.

  16. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    Directory of Open Access Journals (Sweden)

    Jianqiang Zhu

    2012-01-01

    Full Text Available We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA. The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the KDP crystal as the gain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about 10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments.

  17. Generation of ultrashort electron bunches by colliding laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, C.B.; Lee, P.B.; Wurtele, J.S. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Esarey, E. [Beam Physics Branch, Plasma Physics Division, Navel Research Laboratory, Washington, District of Columbia 20375 (United States); Leemans, W.P. [Center for Beam Physics, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1999-07-01

    A proposed laser-plasma based relativistic electron source [E. Esarey {ital et al.}, Phys. Rev. Lett. {bold 79}, 2682 (1997)] using laser triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counter-propagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses. {copyright} {ital 1999 American Institute of Physics.}

  18. Effects of laser energy and wavelength on the analysis of LiFePO4 using laser assisted atom probe tomography

    International Nuclear Information System (INIS)

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO4 by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygen concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of 16O2+ ions. Green laser assisted field evaporation led to the selective loss of Li (∼33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO4. Plotting of multihit events on Saxey plots also revealed a strong neutral O2 loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency. - Highlights: • Laser wavelength and pulse energy affect accuracy of APT analysis of LiFePO4. • Oxygen deficiency observed for UV laser; stronger at higher laser energies. • Selective loss of Li with green laser due to dc evaporation. • Saxey plots reveal prevalent formation of O2 neutrals. • Quantification of molecular dissociations cannot account for O deficiency

  19. Pulsed Single Frequency MOPA Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Latest advances in semiconductor optoelectronics makes it possible to develop compact light weight robust sources of coherent optical pulses, demanded for numerous...

  20. Self-pinching of pulsed laser beams during filamentary propagation

    International Nuclear Information System (INIS)

    Competing nonlinear optical effects that act on femtosecond laser pulses propagating in a self-generated light filament may give rise to a pronounced radial beam deformation, similar to the z-pinch contraction of pulsed high-current discharges. This self-generated spatial beam contraction is accompanied by a pulse break-up that can be beneficially exploited for on-axis temporal compression of the pulse. The pinching mechanism therefore explains the recently observed self-compression and the complicated spatio-temporal shapes typical for filament propagation experiments. (authors)

  1. Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Bruno Yue [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China); Mao, Xianglei [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Hou, Huaming [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Ocean University of China, Qingdao (China); Zorba, Vassilia; Russo, Richard E. [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Cheung, Nai-Ho, E-mail: nhcheung@hkbu.edu.hk [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China)

    2015-08-01

    For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm{sup −2} orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes. - Highlights: • We devise a two-laser-pulse scheme to analyze the elemental composition of mica as test samples. • We compare the analytical performance of the single 266 nm pulse scheme against the 266 nm – 213 nm two pulse scheme. • The two pulse scheme improves the absolute LODs of the analytes by about a hundred times. • The spectral and temporal properties of the enhanced signal are consistent with the mechanism.

  2. Towards shorter wavelength x-ray lasers using a high power, short pulse pump laser

    International Nuclear Information System (INIS)

    A near-terawatt, KrF* laser system, focussable to power densities >1018 W/cm2 has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs

  3. Laser triggered injection of electrons in a laser wakefield accelerator with the colliding pulse method

    International Nuclear Information System (INIS)

    An injection scheme for a laser wakefield accelerator that employs a counter propagating laser (colliding with the drive laser pulse, used to generate a plasma wake) is discussed. The threshold laser intensity for electron injection into the wakefield was analyzed using a heuristic model based on phase-space island overlap. Analysis shows that the injection can be performed using modest counter propagating laser intensity a1 0 = 1.0. Preliminary experiments were preformed using a drive beam and colliding beam. Charge enhancement by the colliding pulse was observed. Increasing the signal-to-noise ratio by means of a preformed plasma channel is discussed

  4. Pulse-to-pulse interaction analysis and parameter optimization for future-generation ophthalmic laser systems

    Science.gov (United States)

    Tinne, N.; Kaune, B.; Bleeker, S.; Lubatschowski, H.; Krüger, A.; Ripken, T.

    2014-02-01

    The immediate pulse-to-pulse interaction becomes more and more important for future-generation high-repetition rate ophthalmic laser systems. Therefore, we investigated the interaction of two laser pulses with different spatial and temporal separation by time-resolved photography. There are various different characteristic interaction mechanisms which are divided into 11 interaction scenarios. Furthermore, the parameter range has been constricted regarding the medical application; here, the efficiency was optimized to a maximum jet velocity along the scanning axis with minimum applied pulse energy as well as unwanted side effects at the same time. In conclusion, these results are of great interest for the prospective optimization of the ophthalmic surgical process with future-generation fs-lasers.

  5. Timing control of an intense picosecond pulse laser to the SPring-8 synchrotron radiation pulses

    Science.gov (United States)

    Tanaka, Yoshihito; Hara, Toru; Kitamura, Hideo; Ishikawa, Tetsuya

    2000-03-01

    We have developed a control system to synchronize intense picosecond laser pulses to the hard x-ray synchrotron radiation (SR) pulses of SPring-8. A regeneratively amplified mode-locked Ti:sapphire laser is synchronized to 40 ps SR pulses by locking the laser to the radio frequency of the ring. The synchronization of the pulses is monitored by detecting both beams simultaneously on a gold photocathode of a streak camera. This method enabled us to make a precise measurement of the time interval between the beams, even if the trigger of the streak camera drifts. Synchronization between the laser and the SR pulses has been achieved with a precision of ±2 ps for some hours. The stable timing control ensures the possibility of making two-photon excitation and pump-probe experiments with time resolution of a few tens of ps (limited by the pulse duration of the SR). We have used this system to show that closing undulator gaps in the storage ring shifts the arrival time of the SR pulses, in accord with expectations for the increased power loss.

  6. Generation of high harmonics and attosecond pulses with ultrashort laser pulse filaments and conical waves

    Indian Academy of Sciences (India)

    A Couairon; A Lotti; D Faccio; P Di Trapani; D S Steingrube; E Schulz; T Binhammer; U Morgner; M Kovacev; M B Gaarde

    2014-08-01

    Results illustrating the nonlinear dynamics of ultrashort laser pulse filamentation in gases are presented, with particular emphasis on the filament properties useful for developing attosecond light sources. Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes and subcycle pulses generated within the filament. (ii) Simulation results on the spontaneous formation of conical wavepackets during filamentation in gases, which in turn can be used as efficient driving pulses for the generation of high harmonics and isolated attosecond pulses.

  7. Wavelength dependence of soft tissue ablation by using pulsed lasers

    Institute of Scientific and Technical Information of China (English)

    Xianzeng Zhang; Shusen Xie; Qing Ye; Zhenlin Zhan

    2007-01-01

    Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear,sharp cuts following closely the patial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The blation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

  8. Nanosecond pulsed laser generation of holographic structures on metals

    Science.gov (United States)

    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.

  9. COMPLIS: COllinear spectroscopy Measurements using a Pulsed Laser Ion Source

    CERN Multimedia

    2002-01-01

    A Pulsed Laser spectroscopy experiment has been installed for the study of hyperfine structure and isotope shift of refractory and daughter elements from ISOLDE beams. It includes decelerated ion-implantation, element-selective laser ionization, magnetic and time-of-flight mass separation. The laser spectroscopy has been performed on the desorbed atoms in a set-up at ISOLDE-3 but later on high resolution laser collinear spectroscopy with the secondary pulsed ion beam is planned for the Booster ISOLDE set-up. During the first operation time of ISOLDE-3 we restricted our experiments to Doppler-limited resonant ionization laser and $\\gamma$-$\\gamma$ nuclear spectroscopy on neutron deficient platinum isotopes of even mass number down to A~=~186 and A~=~179 respectively. These isotopes have been produced by implantation of radioactive Hg and their subsequent $\\beta$-decay.

  10. Components for monolithic fiber chirped pulse amplification laser systems

    Science.gov (United States)

    Swan, Michael Craig

    The first portion of this work develops techniques for generating femtosecond-pulses from conventional fabry-perot laser diodes using nonlinear-spectral-broadening techniques in Yb-doped positive dispersion fiber ampliers. The approach employed an injection-locked fabry-perot laser diode followed by two stages of nonlinear-spectral-broadening to generate sub-200fs pulses. This thesis demonstrated that a 60ps gain-switched fabry-perot laser-diode can be injection-locked to generate a single-longitudinal-mode pulse and compressed by nonlinear spectral broadening to 4ps. Two problems have been identified that must be resolved before moving forward with this approach. First, gain-switched pulses from a standard diode-laser have a number of characteristics not well suited for producing clean self-phase-modulation-broadened pulses, such as an asymmetric temporal shape, which has a long pulse tail. Second, though parabolic pulse formation occurs for any arbitrary temporal input pulse profile, deviation from the optimum parabolic input results in extensively spectrally modulated self-phase-modulation-broadened pulses. In conclusion, the approach of generating self-phase-modulation-broadened pulses from pulsed laser diodes has to be modified from the initial approach explored in this thesis. The first Yb-doped chirally-coupled-core ber based systems are demonstrated and characterized in the second portion of this work. Robust single-mode performance independent of excitation or any other external mode management techniques have been demonstrated in Yb-doped chirally-coupled-core fibers. Gain and power efficiency characteristics are not compromised in any way in this novel fiber structure up to the 87W maximum power achieved. Both the small signal gain at 1064nm of 30.3dB, and the wavelength dependence of the small signal gain were comparable to currently deployed large-mode-area-fiber technology. The efficiencies of the laser and amplifier were measured to be 75% and 54

  11. Time dynamics of burst-train filamentation assisted femtosecond laser machining in glasses.

    Science.gov (United States)

    Esser, Dagmar; Rezaei, Saeid; Li, Jianzhao; Herman, Peter R; Gottmann, Jens

    2011-12-01

    Bursts of femtosecond laser pulses with a repetition rate of f = 38.5MHz were created using a purpose-built optical resonator. Single Ti:Sapphire laser pulses, trapped inside a resonator and released into controllable burst profiles by computer generated trigger delays to a fast Pockels cell switch, drove filamentation-assisted laser machining of high aspect ratio holes deep into transparent glasses. The time dynamics of the hole formation and ablation plume physics on 2-ns to 400-ms time scales were examined in time-resolved side-view images recorded with an intensified-CCD camera during the laser machining process. Transient effects of photoluminescence and ablation plume emissions confirm the build-up of heat accumulation effects during the burst train, the formation of laser-generated filaments and plume-shielding effects inside the deeply etched vias. The small time interval between the pulses in the present burst train enabled a more gentle modification in the laser interaction volume that mitigated shock-induced microcracks compared with single pulses.

  12. Fuzzy model for Laser Assisted Bending Process

    Directory of Open Access Journals (Sweden)

    Giannini Oliviero

    2016-01-01

    Full Text Available In the present study, a fuzzy model was developed to predict the residual bending in a conventional metal bending process assisted by a high power diode laser. The study was focused on AA6082T6 aluminium thin sheets. In most dynamic sheet metal forming operations, the highly nonlinear deformation processes cause large amounts of elastic strain energy stored in the formed material. The novel hybrid forming process was thus aimed at inducing the local heating of the mechanically bent workpiece in order to decrease or eliminate the related springback phenomena. In particular, the influence on the extent of springback phenomena of laser process parameters such as source power, scan speed and starting elastic deformation of mechanically bent sheets, was experimentally assessed. Consistent trends in experimental response according to operational parameters were found. Accordingly, 3D process maps of the extent of the springback phenomena according to operational parameters were constructed. The effect of the inherent uncertainties on the predicted residual bending caused by the approximation in the model parameters was evaluated. In particular, a fuzzy-logic based approach was used to describe the model uncertainties and the transformation method was applied to propagate their effect on the residual bending.

  13. Temporal pulse cleaning by a self-diffraction process for ultrashort laser pulses

    Science.gov (United States)

    Xie, Na; Zhou, Kainan; Sun, Li; Wang, Xiaodong; Guo, Yi; Li, Qing; Su, Jingqin

    2014-11-01

    Applying the self-diffraction process to clean ultrashort laser pulses temporally is a recently developed effective way to temporal contrast enhancement. In this paper, we attempt to clean ultrashort laser pulses temporally by the self-diffraction process. Experiments were carried out to study the temporal contrast improvement in the front-end system of an ultraintense and ultrashort laser facility, i.e. the super intense laser for experiment on the extremes (SILEX-I). The results show that the maximum conversion efficiency of the first-order self-diffraction (SD1) pulse is 11%. The temporal contrast of the SD1 signal is improved by two orders of magnitude, i.e. to 103, for a 2.4-ns prepulse with initial contrast of ~10. For a 5.5 -ns prepulse with initial contrast of 2×103, the temporal contrast of the SD1 signal is improved by more than three orders of magnitude.

  14. Fractional laser-assisted delivery of methyl aminolevulinate

    DEFF Research Database (Denmark)

    Haak, Christina S; Farinelli, William A; Tam, Joshua;

    2012-01-01

    Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on depth of laser channels and incubation time. This study evaluates whether depth...... of intradermal laser channels and incubation time may affect AFXL-assisted delivery of methyl aminolevulinate (MAL)....

  15. NOTE: Modelling multiple laser pulses for port wine stain treatment

    Science.gov (United States)

    Verkruysse, Wim; van Gemert, Martin J. C.; Smithies, Derek J.; Nelson, J. Stuart

    2000-12-01

    Many port wine stains (PWS) are still resistant to pulsed dye laser treatment. However, anecdotal information suggests that multiple-pulse laser irradiation improves patient outcome. Our aims in this note are to explain the underlying mechanism and estimate the possible thermal effects of multiple pulses in vascular structures typical of PWS. Based on linear response theory, the linear combination of two thermal contributions is responsible for the total increase in temperature in laser irradiated blood vessels: direct light absorption by blood and direct bilateral thermal heat conduction from adjacent blood vessels. The latter contribution to the increase in temperature in the targeted vessel can be significant, particularly if some adjacent vessels are in close proximity, such as in cases of optical shielding of the targeted vessel, or if the vessels are relatively distant but many in number. We present evidence that multiple-pulse laser irradiation targets blood vessels that are optically shielded by other vessels. Therefore, it may be a means of enhancing PWS therapy for lesions that fail to respond to single-pulse dye laser treatment.

  16. Control of giant pulse duration in neodymium mini lasers with controllable cavity length and pulsed pumping

    International Nuclear Information System (INIS)

    In a solid-state laser incident on aLiNdP4O12 crystal, pumped by a short light pulse, giant pulse oscillation without the use of resonator Q switching is realized. Tuning of the oscillation pulse duration from 2 up to 20 ns is achieved by changing the cavity length from 24 to 3 mm, respectively. Our analysis of this mode of laser radiation is made on the basis of the rate equations. The factors influencing oscillation pulse duration a reinvestigated. It is shown that in a limiting case the minimal value of the pulse duration is limited by only the rate of excitation transfer from the pumping band to the metastable level

  17. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Oraevsky, A.A. [Lawrence Livermore National Lab., CA (United States)]|[Rice Univ., Houston, TX (United States). Dept. of Electrical Engineering; DaSilva, L.B.; Feit, M.D. [Lawrence Livermore National Lab., CA (United States)] [and others

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  18. Towards manipulating relativistic laser pulses with 3D printed materials

    CERN Document Server

    Ji, L L; Pukhov, A; Freeman, R R; Akli, K U

    2015-01-01

    Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser beams irradiating initially flat interfaces with little or no control over the interaction. Here, we propose a novel approach that leverages recent advancements in 3D direct laser writing (DLW) of materials and high contrast lasers to manipulate the laser-matter interactions on the micro-scales. We demonstrate, via simulations, that usable intensities >10^23Wcm^(-2) could be achieved with current tabletop lasers coupled to 3D printed plasma lenses. We show that these plasma optical elements act not only as a lens to focus laser light, but also as an electromagnetic guide for secondary particle beams. These results open new paths to engineering light-matter interactions at ultra-relativistic intensities.

  19. Pulsed Mid-infrared Radiation from Spectral Broadening in Laser Wakefield Simulations

    OpenAIRE

    Zhu, W.; Palastro, J. P.; Antonsen, T. M.

    2013-01-01

    Spectral red-shifting of high power laser pulses propagating through underdense plasma can be a source of ultrashort mid-infrared (MIR) radiation. During propagation, a high power laser pulse drives large amplitude plasma waves, depleting the pulse energy. At the same time, the large amplitude plasma wave provides a dynamic dielectric response that leads to spectral shifting. The loss of laser pulse energy and the approximate conservation of laser pulse action imply that spectral red-shifts a...

  20. Diode-Pumped Nanosecond Pulsed Laser with Pulse-Transmission-Mode Q-Switch

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; HUO Yu-Jing; HE Shu-Fang; FENG Li-Chun

    2001-01-01

    Q-switched pulses at 1.064μm with a peak power of 5.02kW and a pulse width of2.8ns were obtained which were pumped by a 1 W laser diode on the Nd:YVO4 microchip at the 1 kHz repetition rate. These values were achieved by combining the techniques of aconsto-optic Q-switching and electro-optic pulse-transmission-mode Q-switching. The temporal characteristics of the pulses were analysed numerically. The experimental results are shown to be in good agreement with theoretical predictions.

  1. Single molecule imaging with longer x-ray laser pulses

    CERN Document Server

    Martin, Andrew V; Caleman, Carl; Quiney, Harry M

    2015-01-01

    In serial femtosecond crystallography, x-ray laser pulses do not need to outrun all radiation damage processes because Bragg diffraction exceeds the damage-induced background scattering for longer pulses ($\\sim$ 50--100 fs). This is due to a "self-gating pulse" effect whereby damage terminates Bragg diffraction prior to the pulse completing its passage through the sample, as if that diffraction were produced by a shorter pulse of equal fluence. We show here that a similar gating effect applies to single molecule diffraction with respect to spatially uncorrelated damage processes like ionization and ion diffusion. The effect is clearly seen in calculations of the diffraction contrast, by calculating the diffraction of average structure separately to the diffraction from statistical fluctuations of the structure due to damage ("damage noise"). Our results suggest that sub-nanometer single molecule imaging with longer pulses, like those produced at currently operating facilities, should not yet be ruled out. The...

  2. Modelling of noise-like pulses generated in fibre lasers

    Science.gov (United States)

    Smirnov, Sergey; Kobtsev, Sergey

    2016-03-01

    The present paper for the first time proposes and studies a relatively simple model of noise-like pulses that matches the experimental data well and suggests that there is a correlation between phases of adjacent spectral components of noiselike pulses. Comparison of a relatively basic model of `random' pulses with the results of noise-like pulse modelling in mode-locked fibre lasers based on coupled non-linear Schrödinger equations demonstrates that it adequately reproduces temporal and spectral properties of noise-like pulses as well as correlation between adjacent modes so that it's possible to use the proposed model for highly efficient simulations of promising applications of noise-like pulses, such as material processing, non-linear frequency conversion, microscopy, and others.

  3. Laser beam deflection monitoring of Nd: YAG laser ablation: pulse shape and repetition rate effects

    Science.gov (United States)

    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.

  4. Pulsed laser deposition of ZnSe N epilayers

    CERN Document Server

    Boo, B H; Xu, N

    2000-01-01

    A high-quality epitaxial film of nitrogen-doped ZsSe has been grown on a GaAs(100) substrate by using pulsed laser deposition assisted by an atomic nitrogen beam produced by a supersonic nozzle beam source. Atomic force microscopy shows that the surface of the ZnSe epilayer grown on GaAs(100) at 2 x 10 sup - sup 3 Torr is flat and dense. It also shows that its roughness is approx = 1.6 nm, less than that of epilayers grown by using metalorganic vapor phase epitaxy. X-ray diffraction results show that this ZnSe epilayer is a single crystalline epitaxial film. X-ray photoelectron spectroscopy (XPS) indicates that the epilayer is composed of 84 % Zn and Se, 10 % N, and 6 % O; other impurities are rare. The XPS spectra involving the Zn(2p sub 3 sub / sub 2) and the N(1s) core levels also indicate that the concentration of doped nitrogen atoms is above 10 sup 2 sup 1 /cm sup 3.

  5. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    International Nuclear Information System (INIS)

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (1012 watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (109 watts) and can be focussed to intensities of /approximately/1016 W/cm2. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs

  6. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    Energy Technology Data Exchange (ETDEWEB)

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.

    1989-04-01

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10/sup 12/ watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10/sup 9/ watts) and can be focussed to intensities of /approximately/10/sup 16/ W/cm/sup 2/. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs.

  7. Theoretical and Experimental studies on CH3OH THz Laser Pumped by Pulse Carbon Dioxide Laser

    Science.gov (United States)

    Fei, Fei; Jing, Wang; Zhaoshuo, Tian; Yanchao, Zhang; Shiyou, Fu; Qi, Wang

    2011-02-01

    In this paper, according to the molecular structure and vibration mode of micro-asymmetric gyroscope CH3OH molecule, dynamic process of optically pumped Terahertz laser is analyzed theoretically. The rate equation models based on three level systems are given according to the theory of typical laser rate equation. The output THz pulsed laser waveform is obtained by solving the rate equation model. An all-metal Terahertz laser pumped by RF waveguide carbon dioxide laser is designed with CH3OH as its working gas. The pulsed Terahertz laser output is obtained. The waveform and repetition frequency of the optically pumped laser are measured in the experiments. The Terahertz laser designed does not need water cooling system. It also has the advantages of simple structure and small size.

  8. Plasma shape control by pulsed solenoid on laser ion source

    International Nuclear Information System (INIS)

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS

  9. Plasma shape control by pulsed solenoid on laser ion source

    Science.gov (United States)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  10. Plasma shape control by pulsed solenoid on laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, M. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Ikeda, S. [Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Romanelli, M. [Cornell University, Ithaca, NY 14850 (United States); Kumaki, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Waseda University, Shinjuku, Tokyo 169-0072 (Japan); Fuwa, Y. [RIKEN, Wako, Saitama 351-0198 (Japan); Kyoto University, Uji, Kyoto 611-0011 (Japan); Kanesue, T. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hayashizaki, N. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); Lambiase, R. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Okamura, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2015-09-21

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  11. Multiple Filamentation of Laser Pulses in a Glass

    Science.gov (United States)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Iglakova, A. N.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.

    2016-03-01

    Results are presented of experiments on investigation of the spatial characteristics of multi-filamentation region of giga- and terawatt pulses of a Ti:sapphire laser in a glass. Dependences are obtained of the coordinate of the beginning of filamentation region, number of filaments, their distribution along the laser beam axis, and length of filaments on the pulse power. It is shown that with increasing radiation power, the number of filaments in the multi-filamentation region decreases, whereas the filament diameter has a quasiconstant value for all powers realized in the experiments. It is shown that as a certain power of the laser pulse with Gauss energy density distribution is reached, the filamentation region acquires the shape of a hollow cone with apex directed toward the radiation source.

  12. Multiphoton ionization with femtosecond laser pulses

    International Nuclear Information System (INIS)

    There are a number of reasons to use subpicosecond pulses in multiphoton ionization experiments. Pulses with shorter risetimes make it possible to study processes with higher rates before one runs into the problem of depletion of target atoms. Furthermore, the momentum of the electron does not change between the point of ionization and the detector if the pulse expires before the electron has time to sample the spatial inhomogeneity of the light intensity. This makes it possible to identify the intensity at which an electron was formed from the energy with which it reaches the detector. Yet another advantage is the fact that the primary ionization products are subject to the ionizing radiation for only a short amount of time, thus reducing the probability of sequential ionization as compared to direct processes. In this paper the experimental results on the multiphoton ionization of xenon with pulses of 100 fs, that were obtained during the preceding year at ENSTA, Palaiseau, will be presented

  13. Real-time single-shot measurement and correction of pulse phase and amplitude for ultrafast lasers

    Science.gov (United States)

    Pestov, Dmitry; Ryabtsev, Anton; Rasskazov, Gennady; Lozovoy, Vadim V.; Dantus, Marcos

    2014-05-01

    The transition of femtosecond lasers from the laboratory to commercial applications requires real-time automated pulse compression, ensuring optimum performance without assistance. Single-shot phase measurements together with closed-loop optimization based on real-time multiphoton intrapulse interference phase scan are demonstrated. On-the-fly correction of amplitude, as well as second- and third-order phase distortions based on the real-time measurements, is accomplished by a pulse shaper.

  14. Long-pulse-width narrow-bandwidth solid state laser

    Science.gov (United States)

    Dane, C.B.; Hackel, L.A.

    1997-11-18

    A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications. 5 figs.

  15. The effect of laser pulse tailored welding of Inconel 718

    Science.gov (United States)

    Mccay, T. Dwayne; Mccay, Mary Helen; Sharp, C. Michael; Womack, Michael G.

    1990-01-01

    Pulse tailored laser welding has been applied to wrought, wrought grain grown, and cast Inconel 718 using a CO2 laser. Prior to welding, the material was characterized metallographically and the solid state transformation regions were identified using Differential Scanning Calorimetry and high temperature x-ray diffraction. Bead on plate welds (restrained and unrestrained) were then produced using a matrix of pulse duty cycles and pulsed average power. Subsequent characterization included heat affected zone width, penetration and underbead width, the presence of cracks, microfissures and porosity, fusion zone curvature, and precipitation and liquated region width. Pedigree welding on three selected processing conditions was shown by microstructural and dye penetrant analysis to produce no microfissures, a result which strongly indicates the viability of pulse tailored welding for microfissure free IN 718.

  16. Long-pulse-width narrow-bandwidth solid state laser

    Science.gov (United States)

    Dane, C. Brent; Hackel, Lloyd A.

    1997-01-01

    A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications.

  17. Laser pulse design for coherent laser control of potassium atoms

    Institute of Scientific and Technical Information of China (English)

    Zhang Xian-Zhou; Jia Guang-Rui; He Hai-Fang

    2007-01-01

    In this paper,the dynamics of coherent laser control of potassium atoms is studied by using the time-dependent multilevel approach (TDMA).The calculation results of population transfer are presented with different laser fields. The results show that the population can be transferred to target state completely by a specially designed laser field.

  18. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.

    Science.gov (United States)

    Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang

    2013-04-01

    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps.

  19. Cooling of rubidium atoms in pulsed diffuse laser light

    Institute of Scientific and Technical Information of China (English)

    Cheng Hua-Dong; Wang Xu-Cheng; Xiao Ling; Zhang Wen-Zhuo; Liu Liang; Wang Yu-Zhu

    2011-01-01

    This paper reports an experiment on laser cooling of 87Rb atoms in pulsed diffuse light, which is the key step towards a compact cold atom clock. It deduces an empirical formula to simulate the pulse cooling process based on the loading of cold atoms in cooling time and the loss in the dead time, which is in agreement with the experimental data. The formula gives a reference to select the parameters for the cold atom clock.

  20. Supercontinuum Emission from Focused Femtosecond Laser Pulses in Air

    Science.gov (United States)

    Sreeja, S.; Rao, S. Venugopal; Bagchi, Suman; Sreedhar, S.; Prashant, T. Shuvan; Radhakrishnan, P.; Tewari, Surya P.; Kiran, P. Prem

    2011-10-01

    We present our experimental results from the measurements of Supercontinuum emission (SCE) from air resulting from propagation of tightly focused femtosecond (40 fs) laser pulses. The effect of linearly polarized (LP) and circularly polarized (CP) light pulses on the SCE in two different external focal geometries (f/6, f/15) is presented. A considerable shift in the minimum wavelength of SCE is observed with external tighter focusing.

  1. Orienting coupled quantum rotors by ultrashort laser pulses

    OpenAIRE

    Shima, Hiroyuki; Nakayama, Tsuneyoshi

    2004-01-01

    We point out that the non-adiabatic orientation of quantum rotors, produced by ultrashort laser pulses, is remarkably enhanced by introducing dipolar interaction between the rotors. This enhanced orientation of quantum rotors is in contrast with the behavior of classical paired rotors, in which dipolar interactions prevent the orientation of the rotors. We demonstrate also that a specially designed sequence of pulses can most efficiently enhances the orientation of quantum paired rotors.

  2. Orienting coupled quantum rotors by ultrashort laser pulses

    OpenAIRE

    Shima, Hiroyuki; Nakayama, Tsuneyoshi

    2004-01-01

    We pointed out that the nonadiabatic orientation of quantum rotors, produced by ultrashort laser pulses, is remarkably enhanced by introducing dipolar interaction between the rotors. This enhanced orientation of quantum rotors is in contrast with the behavior of classical paired rotors, in which dipolar interactions prevent the orientation of the rotors. We demonstrate also that a specially designed sequence of pulses can most efficiently enhance the orientation of quantum paired rotors.

  3. Two-pulse laser control of bond-selective fragmentation

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm

    1996-01-01

    We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we...... be obtained when such a non-stationary vibrating ozone molecule is photodissociated with short laser pulses (similar to 10-15 fs) with a time delay corresponding to half a vibrational period (similar to 17 fs). (C) 1996 American Institute of Physics....

  4. Pulse laser machining and particulate separation from high impact polystyrene

    Energy Technology Data Exchange (ETDEWEB)

    Arif, Saira; Kautek, Wolfgang, E-mail: wolfgang.kautek@univie.ac.at

    2014-01-01

    Opaque high impact polystyrene (HIPS) contaminated with graphite particles and poly(styrene-co-divinyl benzene) spheres can only be removed efficiently with nanosecond-pulsed laser radiation of 532 nm while the substrate is preserved. The destruction thresholds are 1–2 orders of magnitude lower than that of other common technical polymers. The inhomogeneously distributed polybutadiene composite component led to enhanced light scattering in the polystyrene matrix so that increased light absorption and energy density causes a comparatively low ablation threshold. Due to this fact there is advantageous potential for pulse laser machining at comparatively low fluences.

  5. Two-photon Compton process in pulsed intense laser fields

    CERN Document Server

    Seipt, D

    2012-01-01

    Based on strong-field QED in the Furry picture we use the Dirac-Volkov propagator to derive a compact expression for the differential emission probability of the two-photon Compton process in a pulsed intense laser field. The relation of real and virtual intermediate states is discussed, and the natural regularization of the on-shell contributions due to the finite laser pulse is highlighted. The inclusive two-photon spectrum is two orders of magnitude stronger than expected from a perturbative estimate.

  6. Plasma and cavitation dynamics during pulsed laser microsurgery in vivo

    CERN Document Server

    Hutson, M Shane

    2007-01-01

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

  7. Quantum quenching of radiation losses in short laser pulses

    CERN Document Server

    Harvey, Chris; Ilderton, Anton; Marklund, Mattias

    2016-01-01

    Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.

  8. Ultrafast spatiotemporal laser pulse engineering using chromatic dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Li Yuelin; Chemerisov, Sergey [Argonne National Laboratory, Argonne, IL 60439 (United States); Shen Baifei, E-mail: ylli@aps.anl.gov [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, PO Box 800-211, Shanghai 201800 (China)

    2010-12-15

    We discuss a new method for manipulating the optical field distribution in time and space at the focal plane of a chromatic lens. Chromatic dispersion and aberration make it possible to control the photon distribution in both time and space by properly controlling the amplitude and phase of the incident laser pulse, including shortening a laser pulse or generating a specific time-dependent transverse distribution. As an example, we discuss the generation of a quasi-three-dimensional ellipsoidal photon distribution and a proof-of-principle experiment, where favourable agreement between theoretical calculations and the data is observed.

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

    Science.gov (United States)

    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.

  10. Pulsed Yb:KYW laser and UV generation

    OpenAIRE

    Tjörnhammar, Staffan

    2010-01-01

    In this master thesis project, a pulsed UV laser was designed and constructed. Also, the effects of absorption in a volume Bragg grating were investigated. The laser was diode pumped and constructed with Yb:KYW as gain medium. The lasing was at a wavelength of 1029.2 nm with a spectral bandwidth of 0.23 nm, locked by a volume Bragg grating that was used as input coupler for spectral control. Passive Q‑switching was used to generate pulses by placing a Cr:YAG saturable absorber inside the cavi...

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xinxing, E-mail: xinxing.sun@iom-leipzig.de; Thelander, Erik; Lorenz, Pierre; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd [Leibniz Institute of Surface Modification, Permoserstr. 15, D-04318, Leipzig (Germany)

    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.

  12. Cutaneous effects of pulsed nitrogen gas laser irradiation

    International Nuclear Information System (INIS)

    The effects of pulsed nitrogen gas laser emission (337.1 nm wavelength) were studied on human skin. The laser provides high-intensity monochromatic UVA radiation and can elicit delayed erythema in an actual exposure time of about 1 msec (105,000 pulses, each lasting 10 nsec, delivered over 210 sec). The effects of nitrogen laser irradiation were compared clinically and histologically with conventional erythemogenic UVA and UVB exposures from xenon arc or mercury arc lamps and were found to be similar in many respects. The minimal erythema dose is comparable to that obtained using more conventional continuous light sources which have more than 100 times lower intensity. A phototoxicity comparison of oral and topically applied psoralens is presented, indicating that the laser may prove useful in comparing photosensitizing capacity of certain compounds

  13. Interaction of Superintense Laser Pulses with Relativistic Ions

    Science.gov (United States)

    Chirilă, C. C.; Joachain, C. J.; Kylstra, N. J.; Potvliege, R. M.

    2004-12-01

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical results are presented for high-order harmonic emission by a single Ne9+ ion moving with a Lorentz factor γ=15 against a Nd:glass laser beam. The calculations are done within a Coulomb-corrected nondipole strong field approximation. The approximation is tested by comparing with accurate results.

  14. Interaction of superintense laser pulses with relativistic ions.

    Science.gov (United States)

    Chirilă, C C; Joachain, C J; Kylstra, N J; Potvliege, R M

    2004-12-10

    At high intensities, three-step recollision processes driven by low frequency laser pulses, such as high-order harmonic generation and high-order above-threshold ionization, are normally severely suppressed by the magnetic-field component of the laser field. It is shown that this suppression is not severe, even for ponderomotive energies well above 10 keV, for multicharged ions moving at a sufficiently high relativistic velocity against a counterpropagating infrared laser pulse. Numerical results are presented for high-order harmonic emission by a single Ne9+ ion moving with a Lorentz factor gamma=15 against a Nd:glass laser beam. The calculations are done within a Coulomb-corrected nondipole strong field approximation. The approximation is tested by comparing with accurate results. PMID:15697809

  15. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brendel' , V M; Bukin, V V; Garnov, Sergei V; Bagdasarov, V Kh; Denisov, N N; Garanin, Sergey G; Terekhin, V A; Trutnev, Yurii A

    2012-12-31

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation. (laser technologies)

  16. Micro-ablation with high power pulsed copper vapor lasers.

    Science.gov (United States)

    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. PMID:19404369

  17. Curing of Epoxy Resin Induced by Femtosecond Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    LI Yubin; ZHANG Zuoguang

    2005-01-01

    The possibility of curing of epoxy resin induced by femtosecond laser beam was explored through choosing different initiators . Absorption spectroscopy, infrared spectroscopy (IR), stereomicroscopy and scanning electron microscopy (SEM) were applied to analyze the structure of epoxy resin systems after irradiation with a femtosecond laser beam. The experimental results show that the epoxy resin systems containing diaryliodonium salts can be cured by irradiation of Jemtosecond laser pulse, while the systems containing benzoin can not be cured. It is found that diaryliodonium salts decompose under the irradiation of femtosecond laser pulse through multi ( two ) -photon absorption, initiating the ring-opening polymerization of epoxy resin. And the appearance of cured area has a sheet structure consisting of many tiny lamellar structures.

  18. Droplet deformation and fragmentation by ultra-short laser pulses

    CERN Document Server

    Krivokorytov, M S; Sidelnikov, Yu V; Krivtsun, V M; Medvedev, V V; Kompanets, V O; Lash, A A; Koshelev, K N

    2016-01-01

    We report on the experimental studies of the deformation and fragmentation of liquid metal droplets by picosecond and subpicosecond laser pulses. The experiments were performed with laser irradiance varying in 10E13-10E15 W/cm^2 range. The observed evolution of the droplet shape upon the impact dramatically differs from the previously reported for nanosecond laser pulses. Instead of flattening the droplet undergoes rapid asymmetric expansion and transforms into a complex shape which can be interpreted as two conjunct spheroid shells and finally fragments. We explain the described hydrodynamic response to the ultra-short impact as a result of the propagation of the laser-induced convergent shockwave through the volume of droplet.

  19. Ultrafast pulses from a mid-infrared fiber laser.

    Science.gov (United States)

    Hu, Tomonori; Jackson, Stuart D; Hudson, Darren D

    2015-09-15

    Ultrafast laser pulses at mid-infrared wavelengths (2-20 μm) interact strongly with molecules due to the resonance with their vibration modes. This enables their application in frequency comb-based sensing and laser tissue surgery. Fiber lasers are ideal to achieve these pulses, as they are compact, stable, and efficient. We extend the performance of these lasers with the production of 6.4 kW at a wavelength of 2.8 μm with complete electric field retrieval using frequency-resolved optical gating techniques. Contrary to the problems associated with achieving a high average power, fluoride fibers have now shown the capability of operating in the ultrafast, high-peak-power regime. PMID:26371902

  20. Multiple quantum wells for passive ultra short laser pulse generation

    CERN Document Server

    Quintero-Torres, R; Rodriguez-Rodriguez, E; Stintz, Andreas; Diels, Jean-Claude

    2007-01-01

    Solid state lasers are demanding independent control in the gain media and cavity loss to achieve ultra short laser pulses using passive mode-locking. Recently, laser mode-locking is achieved with a MBE structure with multiple quantum wells, designed to achieve two functions; Bragg mirror and changes in absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser proved to be effective to produce femtosecond pulses. The use of saturable absorbers thus far is a trial and error procedure that is changing due to the correlation with more predictive procedures.

  1. Optical trapping of nanoparticles by ultrashort laser pulses.

    Science.gov (United States)

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

    2013-01-01

    Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field. PMID:23738434

  2. High-energy Picosecond Laser Pulse Recirculation for Compton Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, I; Anderson, S G; Betts, S M; Brown, C; Gibson, D J; Hartemann, F V; Hernandez, J E; Johnson, M; McNabb, D P; Messerly, M; Pruet, J; Shverdin, M Y; Siders, C W; Tremaine, A M; Barty, C J

    2007-06-12

    Frequency upconversion of laser-generated photons by inverse Compton scattering for applications such as nuclear spectroscopy and gamma-gamma collider concepts on the future ILC would benefit from an increase of average source brightness. The primary obstacle to higher average brightness is the relatively small Thomson scattering cross section. It has been proposed that this limitation can be partially overcome by use of laser pulse recirculation. The traditional approach to laser recirculation entails resonant coupling of low-energy pulse train to a cavity through a partially reflective mirror. Here we present an alternative, passive approach that is akin to 'burst-mode' operation and does not require interferometric alignment accuracy. Injection of a short and energetic laser pulse is achieved by placing a thin frequency converter, such as a nonlinear optical crystal, into the cavity in the path of the incident laser pulse. This method leads to the increase of x-ray/gamma-ray energy proportional to the increase in photon energy in frequency conversion. Furthermore, frequency tunability can be achieved by utilizing parametric amplifier in place of the frequency converter.

  3. Cooling of relativistic electron beams in chirped laser pulses

    CERN Document Server

    Yoffe, Samuel R; Kravets, Yevgen; Jaroszynski, Dino A

    2015-01-01

    The next few years will see next-generation high-power laser facilities (such as the Extreme Light Infrastructure) become operational, for which it is important to understand how interaction with intense laser pulses affects the bulk properties of a relativistic electron beam. At such high field intensities, we expect both radiation reaction and quantum effects to play a significant role in the beam dynamics. The resulting reduction in relative energy spread (beam cooling) at the expense of mean beam energy predicted by classical theories of radiation reaction depends only on the energy of the laser pulse. Quantum effects suppress this cooling, with the dynamics additionally sensitive to the distribution of energy within the pulse. Since chirps occur in both the production of high-intensity pulses (CPA) and the propagation of pulses in media, the effect of using chirps to modify the pulse shape has been investigated using a semi-classical extension to the Landau--Lifshitz theory. Results indicate that even la...

  4. Demonstration of a self-pulsing photonic crystal Fano laser

    CERN Document Server

    Yu, Yi; Semenova, Elizaveta; Yvind, Kresten; Mork, Jesper

    2016-01-01

    Semiconductor lasers in use today rely on mirrors based on the reflection at a cleaved facet or Bragg reflection from a periodic stack of layers. Here, we demonstrate an ultra-small laser with a mirror based on the Fano resonance between a continuum of waveguide modes and the discrete resonance of a nanocavity. The Fano resonance leads to unique laser characteristics. Since the Fano mirror is very narrow-band compared to conventional lasers, the laser is single-mode and in particular, it can be modulated via the mirror. We show, experimentally and theoretically, that nonlinearities in the mirror may even promote the generation of a self-sustained train of pulses at gigahertz frequencies, an effect that was previously only observed in macroscopic lasers. Such a source is of interest for a number of applications within integrated photonics.

  5. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

    OpenAIRE

    Yao, Jinping; Xie, Hongqiang; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2014-01-01

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, ...

  6. Extensive angiokeratoma circumscriptum - successful treatment with 595-nm variable-pulse pulsed dye laser and 755-nm long-pulse pulsed alexandrite laser.

    Science.gov (United States)

    Baumgartner, Ján; Šimaljaková, Mária; Babál, Pavel

    2016-06-01

    Angiokeratomas are rare vascular mucocutaneous lesions characterized by small-vessel ectasias in the upper dermis with reactive epidermal changes. Angiokeratoma circumscriptum (AC) is the rarest among the five types in the current classification of angiokeratoma. We present a case of an extensive AC in 19-year-old women with Fitzpatrick skin type I of the left lower extremity, characterized by a significant morphological heterogeneity of the lesions, intermittent bleeding, and negative psychological impact. Histopathological examination after deep biopsy was consistent with that of angiokeratoma. The association with metabolic diseases (Fabry disease) was excluded by ophthalmological, biochemical, and genetic examinations. Nuclear magnetic resonance imaging has not detected deep vascular hyperplasia pathognomic for verrucous hemangioma. The combined treatment with 595-nm variable-pulse pulsed dye laser (VPPDL) and 755-nm long-pulse pulsed alexandrite laser (LPPAL) with dynamic cooling device led to significant removal of the pathological vascular tissue of AC. Only a slight degree of secondary reactions (dyspigmentations and texture changes) occurred. No recurrence was observed after postoperative interval of 9 months. We recommend VPPDL and LPPAL for the treatment of extensive AC. PMID:26736060

  7. Polaritonic materials fabricated and tested with ultrashort-pulse lasers

    CERN Document Server

    Ward, D W; Feurer, T; Nelson, K A; Ward, David W.; Statz, Eric R.; Feurer, Thomas; Nelson, Keith A.

    2004-01-01

    Using femtosecond laser machining, we have fabricated photonic bandgap materials that influence propagation of phonon-polaritons in ferroelectric crystals. Broadband polaritons were generated with impulsive stimulated Raman scattering (ISRS) using an ultrashort laser pulse, and the spatial and temporal evolution of the polaritons were imaged as they propagated through the fabricated structures with polariton real-space imaging. These techniques offer a new approach to optical materials design.

  8. Efficient potassium diode pumped alkali laser operating in pulsed mode.

    Science.gov (United States)

    Zhdanov, Boris V; Rotondaro, Matthew D; Shaffer, Michael K; Knize, Randall J

    2014-07-14

    This paper presents the results of our experiments on the development of an efficient hydrocarbon free diode pumped alkali laser based on potassium vapor buffered by He gas at 600 Torr. A slope efficiency of more than 50% was demonstrated with a total optical conversion efficiency of 30%. This result was achieved by using a narrowband diode laser stack as the pump source. The stack was operated in pulsed mode to avoid limiting thermal effects and ionization.

  9. Electrical properties of pulsed UV laser irradiated amorphous carbon

    OpenAIRE

    Y. Miyajima; Adikaari, AADT; Henley, SJ; Shannon, JM; Silva, SRP

    2008-01-01

    Amorphous carbon films containing no hydrogen were irradiated with a pulsed UV laser in vacuum. Raman spectroscopy indicates an increase in the quantity of sp(2) clustering with the highest laser energy density and a commensurate reduction in resistivity. The reduction of resistivity is explained to be associated with thermally induced graphitization of amorphous carbon films. The high field transport is consistent with a Poole-Frenkel type transport mechanism via neutral trapping centers rel...

  10. Characterization of polymer thin films obtained by pulsed laser deposition

    International Nuclear Information System (INIS)

    The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyepichlorhydrin by pulsed laser deposition. Polyepichlorhydrin polymer was deposited on flat substrate (i.e. silicon) using an NdYAG laser (266 nm, 5 ns pulse duration and 10 Hz repetition rate). The obtained thin films have been characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. It was found that for laser fluences up to 1.5 J/cm2 the chemical structure of the deposited polyepichlorhydrin polymer thin layers resembles to the native polymer, whilst by increasing the laser fluence above 1.5 J/cm2 the polyepichlorohydrin films present deviations from the bulk polymer. Morphological investigations (atomic force microscopy and scanning electron microscopy) reveal continuous polyepichlorhydrin thin films for a relatively narrow range of fluences (1-1.5 J/cm2). The wavelength dependence of the refractive index and extinction coefficient was determined by ellipsometry studies which lead to new insights about the material. The obtained results indicate that pulsed laser deposition method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.

  11. Laser grooving of Al{sub 2}O{sub 3} plate by a pulsed Nd:YAG laser: Characteristics and application to the manufacture of gas sensors array heater

    Energy Technology Data Exchange (ETDEWEB)

    Bai Zikui [State Key Laboratory of Plastic Forming Simulation and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Wang Aihua [Nanomaterial and Smart Sensor Research Laboratory, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Xie Changsheng [State Key Laboratory of Plastic Forming Simulation and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China) and Nanomaterial and Smart Sensor Research Laboratory, Department of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: csxie@mail.hust.edu.cn

    2006-11-05

    Laser grooving on a 0.635 mm thick alumina ceramic plate was carried out by a 400 W pulsed Nd:YAG laser. The effects of the laser grooving parameters, such as laser pulse frequency, laser peak pulse energy, assisting gases (oxygen and nitrogen), laser beam diameter and grooving speed on the morphologies of grooves were investigated by using field-emission scanning electron microscopy (FE-SEM) and optical microscopy. Results show that the U-type groove with smooth inner surface was produced at a fixed pulse frequency of 40 Hz, a grooving speed of 4 mm s{sup -1} and an assisting gas pressure of 3 bar. The depth of the U-type groove increased with an increase in laser pulse peak energy. The assisting gas type was found to influence the grooving mechanism, that is, nitrogen gas had a chemical reaction with alumina, and then changed the substrate surface absorptivity to laser beam. So the smaller heat-affected zone (HAZ) was obtained in the substrate than that of the oxygen assisting gas. In addition, the stable and reliable RuO{sub 2}-buried heater was produced in the U-type groove with smooth inner surface, which reduced sensing element power consumption and improved the thermal response rate in a sensor array.

  12. Laser pulses for coherent xuv Raman excitation

    CERN Document Server

    Greenman, Loren; Whaley, K Birgitta

    2014-01-01

    We combine multi-channel electronic structure theory with quantum optimal control to derive Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and phase control facilitated by the pump pulse carrier envelope phase. Our results open a route to creating core-hole excitations in molecules and aggregates that locally address specific atoms and represent the first step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

  13. Temporal laser pulse manipulation using multiple optical ring-cavities

    Science.gov (United States)

    Nguyen, Quang-Viet (Inventor); Kojima, Jun (Inventor)

    2010-01-01

    An optical pulse stretcher and a mathematical algorithm for the detailed calculation of its design and performance is disclosed. The optical pulse stretcher has a plurality of optical cavities, having multiple optical reflectors such that an optical path length in each of the optical cavities is different. The optical pulse stretcher also has a plurality of beam splitters, each of which intercepts a portion of an input optical beam and diverts the portion into one of the plurality of optical cavities. The input optical beam is stretched and a power of an output beam is reduced after passing through the optical pulse stretcher and the placement of the plurality of optical cavities and beam splitters is optimized through a model that takes into account optical beam divergence and alignment in the pluralities of the optical cavities. The optical pulse stretcher system can also function as a high-repetition-rate (MHz) laser pulse generator, making it suitable for use as a stroboscopic light source for high speed ballistic projectile imaging studies, or it can be used for high speed flow diagnostics using a laser light sheet with digital particle imaging velocimetry. The optical pulse stretcher system can also be implemented using fiber optic components to realize a rugged and compact optical system that is alignment free and easy to use.

  14. Symmetric laser-assisted charge transfer: A nonperturbative treatment

    International Nuclear Information System (INIS)

    We present a nonperturbative treatment of laser-assisted charge transfer under conditions of high laser intensity and low collision energy in a specific symmetric charge transfer system: H(1s) + H+ + mhw → H+ + H(n = 1, 2). Previous work in laser-assisted charge transfer has demonstrated that although perturbative treatments are generally valid for lower laser intensities and higher collision energies, nonperturbative treatments are necessary in the present regime where the influence of the laser on the cross sections is more pronounced. The present work is based on the semiclassical impact parameter method, choosing initial conditions appropriate to charge transfer and treating the projectile-target system within a quasimolecular framework. The interaction with the laser is treated semiclassically, in the velocity gauge. We investigate the effect of the laser on both resonant and nonresonant charge transfer processes and provide comparisons with perturbative results. Finally, we shall discuss possibilities for future research

  15. Laser-induced plasma-assisted ablation (LIPAA): fundamental and industrial applications

    Science.gov (United States)

    Hanada, Y.; Sugioka, K.; Midorikawa, K.

    2006-05-01

    The laser-induced plasma-assisted ablation (LIPAA) process developed by our group, in which a single conventional pulsed laser is only used, makes it possible to perform high-quality and high-speed glass microfabrication. Up to the present, this process has been widely applied for micromachining of various transparent hard and soft materials. In this process, the laser beam first passes through the glass substrate since the laser beam has no absorption by the substrate. Then, the transmitted beam is absorbed by a solid target (typically a metal), located behind the substrate so that the target is ablated, resulting in plasma generation. Due to the interaction of the laser beam and the laser-induced plasma, significant ablation takes place at the rear surface of the substrate. Recently, we have developed the proto-type LIPAA system using a second harmonic of diode pumped Q-switched Nd:YAG laser for the practical use. In this paper, we demonstrate micromachining, crack-free marking and color marking of glass materials. Additionally, selective metallization of glass and polyimide by the LIPAA process followed by metal chemical-plating is investigated. A possible mechanism of LIPAA is also discussed based on the results from double pulse irradiation using near-IR fs laser, transient absorption measurement and plasma-conductivity measurement.

  16. An Introduction to Laser Assisted Microfabrication, Current Status and Future Scope of Application

    Science.gov (United States)

    Ostendorf, A.

    From the invention of the laser almost about five decades ago scientists have studied the potential of laser micromachining. Compared to high power laser applications most applications on the microscale require rather moderate average powers in the range of a few watts or below along with good beam qualities and the possibility to use pulsed and/or short wavelength laser systems. Most applications in this field are based on ablation , i.e., material removal for structuring , drilling , or precise cutting of materials. However, current activities are also ongoing in adapting rapid prototyping , i.e., generative processes to the microscale. Finally, a tremendous amount of research activities are carried out to generate nanostructures. Because of the wavelength and the diffraction limit in classical optics new approaches have been taken into account to overcome these limitations and making use of the unique properties of laser radiation also on the nanometer scale. This chapter provides an overview of pulsed laser assisted micromachining with a focus on structuring by laser ablation , laser generative processes, and finally nanomachining.

  17. Polycrystalline ZnTe thin film on silicon synthesized by pulsed laser deposition and subsequent pulsed laser melting

    Science.gov (United States)

    Xu, Menglei; Gao, Kun; Wu, Jiada; Cai, Hua; Yuan, Ye; Prucnal, S.; Hübner, R.; Skorupa, W.; Helm, M.; Zhou, Shengqiang

    2016-03-01

    ZnTe thin films on Si substrates have been prepared by pulsed laser deposition and subsequent pulsed laser melting (PLM) treatment. The crystallization during PLM is confirmed by Raman scattering, x-ray diffraction and room temperature photoluminescence (PL) measurements. The PL results show a broad peak at 574 nm (2.16 eV), which can be assigned to the transitions from the conduction band to the acceptor level located at 0.145 eV above the valence band induced by zinc-vacancy ionization. Our work provides an applicable approach to low temperature preparation of crystalline ZnTe thin films.

  18. Laser fusion neutron source employing compression with short pulse lasers

    Science.gov (United States)

    Sefcik, Joseph A; Wilks, Scott C

    2013-11-05

    A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

  19. In Situ Mitigation of Subsurface and Peripheral Focused Ion Beam Damage via Simultaneous Pulsed Laser Heating.

    Science.gov (United States)

    Stanford, Michael G; Lewis, Brett B; Iberi, Vighter; Fowlkes, Jason D; Tan, Shida; Livengood, Rick; Rack, Philip D

    2016-04-01

    Focused helium and neon ion (He(+)/Ne(+)) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+)/Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposure process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. These results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.

  20. Microstructuring of fused silica by laser-induced backside wet etching using picosecond laser pulses

    International Nuclear Information System (INIS)

    The laser-induced backside wet etching (LIBWE) is an advanced laser processing method used for structuring transparent materials. LIBWE with nanosecond laser pulses has been successfully demonstrated for various materials, e.g. oxides (fused silica, sapphire) or fluorides (CaF2, MgF2), and applied for the fabrication of microstructures. In the present study, LIBWE of fused silica with mode-locked picosecond (tp = 10 ps) lasers at UV wavelengths (λ1 = 355 nm and λ2 = 266 nm) using a (pyrene) toluene solution was demonstrated for the first time. The influence of the experimental parameters, such as laser fluence, pulse number, and absorbing liquid, on the etch rate and the resulting surface morphology were investigated. The etch rate grew linearly with the laser fluence in the low and in the high fluence range with different slopes. Incubation at low pulse numbers as well as a nearly constant etch rate after a specific pulse number for example were observed. Additionally, the etch rate depended on the absorbing liquid used; whereas the higher absorption of the admixture of pyrene in the used toluene enhances the etch rate and decreases the threshold fluence. With a λ1 = 266 nm laser set-up, an exceptionally smooth surface in the etch pits was achieved. For both wavelengths (λ1 = 266 nm and λ2 = 355 nm), LIPSS (laser-induced periodic surface structures) formation was observed, especially at laser fluences near the thresholds of 170 and 120 mJ/cm2, respectively.

  1. Nonlinear 6-fold enhancement of laser drilling efficiency by double pulse mode: prospective in medicine application

    Science.gov (United States)

    Pershina, N. S.; Pershin, S. M.; Cech, M.; Prochazka, I.

    2009-05-01

    The efficiency of laser ablation drilling of metal and dielectric (ceramic, glasses, etc.) samples with single and multiple laser pulses per one laser shot was experimentally studied. The laser is operated on the fundamental (1064 nm) wavelength of Nd:YAG laser with 30 ns pulse length or its second (532 nm) and third (351 nm) harmonics, respectively. The laser shot repletion rate was 1 Hz. The pulses in train were separated by 25-45 μs interval. The crater depth and drilling speed dependence increasing on pulse number in multipulse train was studied. The laser ablation normalized per pulse energy in train dependence is not linear function. The strong ablation enhancement was observed. The optimal (in sense the total pulse energy using) drilling can be obtained with double pulse mode compared with 3 - 5 pulses. Nonlinear more than 6 fold increasing of crater depth produced by the second pulse in train was detected. The mechanism of selective increasing of the second pulse interaction efficiency with the hard target is discussed. Experimental results explained in terms of double pulse mode laser ablation model. Spectroscopy study of laser plasma was observed to confirm discussed model of high efficiency for two laser pulse laser ablation. Efficiency of double pulse mode compared with multipulse mode is discussed to be more perspective for various applications of laser ablation. The medicine (surgery, dentist, ophthalmology and so on) application is the most prospective, for instance, the teeth drilling or glaucoma perforation, can be done with smaller energy value.

  2. A Study of Pulse by Pulse Microscale Patch Transfer Using Picosecond Laser

    Directory of Open Access Journals (Sweden)

    Yung KL

    2016-09-01

    Full Text Available The shape restoring capability of Ti/Ni has potential to overcome the shrinkage of polymer in mould cavity, which has potential of solving the demoulding problems and helps dimension accuracy in micro/nano injection molding. However, the deposition of Ti/Ni film precisely and securely on specific location of the micro mould cavity present difficulties with conventional deposition methods. In this paper, the use of photonic impact forward transfer method to deposit Ti/Ni film patches on specific locations of a substrate is demonstrate using a picosecond laser. Pulse by pulse deposition control parameters affecting position accuracy and spot size were studied in this paper. It was found that although laser power, and distance between donor films and the substrate all influence the spot sizes of pulse by pulse deposited patches, adjusting spot size by changing laser power is better than changing distance due to separated particles being found around the deposited film patches. Results of this study proved the feasibility of depositing Ti/Ni film patches on specific location using pico-second laser with high position accuracy. The potential of using photonic impact forward transfer as a complementing method to laser powder 3D printing of difficult to process material to produce better surface quality microproducts such as micro moulds for micro-injection molding is tremendous.

  3. Application of femtosecond ultrashort pulse laser to photodynamic therapy mediated by indocyanine green

    OpenAIRE

    Sawa, M; Awazu, K; Takahashi, T.; Sakaguchi, H; Horiike, H.; Ohji, M; Tano, Y

    2004-01-01

    Backgrounds/aims: To evaluate treatment with high peak power pulse energy by femtosecond ultrashort pulse laser (titanium sapphire laser) delivered at an 800 nm wavelength for corneal neovascularisation using photodynamic therapy (PDT) mediated by indocyanine green (ICG).

  4. Development of Nanosecond Short Pulse High Power KrF Laser System

    Institute of Scientific and Technical Information of China (English)

    SZATMAR; Sador; BOHUS; Janos

    2011-01-01

    Compression of short pulse laser is demanded by the physical experiments such as EOS for Heaven-I system. A nanosecond short pulse high power discharge pumping excimer laser system was developed under the frame of Science and Technology

  5. CO2 laser pulse switching by optically excited semiconductors

    International Nuclear Information System (INIS)

    The construction and the study of a semi-conductor optical switch used for generating short infrared pulses and to analyse the semiconductor characteristics, are presented. The switch response time depends on semiconductor and control laser characteristics. The results obtained using a Ge switch controlled by N2, NdYag and Dye lasers are presented. The response time was 50 ns limited by Ge recombination time. The reflectivity increased from 7% to 59% using N2 laser to control the switch. A simple model for semiconductor optical properties that explain very well the experimental results, is also presented. (author)

  6. Assisting Gas Optimization in CO2 Laser Welding

    DEFF Research Database (Denmark)

    Gong, Hui; Olsen, Flemming Ove

    1996-01-01

    High quality laser welding is achieved under the condition of optimizing all process parameters. Assisting gas plays an important role for sound welds. In the conventional welding process assisting gas is used as a shielding gas to prevent that the weld seam oxidates. In the laser welding process...... assisting gas is also needed to control the laser induced plasma.Assisting gas is one of the most important parameters in the laser welding process. It is responsible for obtaining a quality weld which is characterized by deep penetration, no interior imperfections, i.e. porosity, no crack, homogeneous seam...... surface, etc. In this work a specially designed flexible off-axis nozzle capable of adjusting the angle of the nozzle, the diameter of the nozzle, and the distance between the nozzle end and the welding zone is tested. In addition to the nozzle parameters three gases, Nitrogen, Argon, and Helium...

  7. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    OpenAIRE

    Poyé, Alexandre; Hulin, Sébastien; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of ...

  8. Direct welding of glass and metal by 1  kHz femtosecond laser pulses.

    Science.gov (United States)

    Zhang, Guodong; Cheng, Guanghua

    2015-10-20

    In the welding process between similar or dissimilar materials, inserting an intermediate layer and pressure assistance are usually thought to be necessary. In this paper, the direct welding between alumina-silicate glass and metal (aluminum, copper, and steel), under exposure from 1 kHz femtosecond laser pulses without any auxiliary processes, is demonstrated. The micron/nanometer-sized metal particles induced by laser ablation were considered to act as the adhesive in the welding process. The welding parameters were optimized by varying the pulse energy and the translation velocity of the sample. The shear joining strength characterized by a shear force testing equipment was as high as 2.34 MPa. This direct bonding technology has potential for applications in medical devices, sensors, and photovoltaic devices. PMID:26560385

  9. Ablation of polymers by ultraviolet pulsed laser

    International Nuclear Information System (INIS)

    The surface modifications of different polymers treated by far UV-Excimer laser (λ = 193mn, 248, 308nm) are analysed by X-Ray Photoelectrons Spectroscopy. The main feature observed depends strongly on the absorption coefficients. For the high absorbing polymers such (PVC, PS, PI,...) the mechanism of the UV-Excimer Laser interaction appears to be governed by an ablative photodecomposition process (APD) with an APD threshold. In the other limit, i.e. low absorbing polymer the interaction leads to a photothermal process. (author). 51 refs, 24 figs, 7 tabs

  10. Pulsed pump: Thermal effects in solid state lasers under super-Gaussian pulses

    Indian Academy of Sciences (India)

    H Nadgaran; M Sabaian

    2006-12-01

    Solid state laser (SSL) powers can be realistically scaled when pumped by a real, efficient and multimode pulse. In this work, a fourth-order super-Gaussian pulse was assumed as a pump for SSL's and a complete analytical expression for the thermal phase shift is given. Moreover, the focal length of thermal lens in paraxial ray approximation regime was studied. The results when applied to a Ti : sapphire crystal show an appreciable correction for abberation compared to a top-hat pulse.

  11. Numeric modeling of synchronous laser pulsing and voltage pulsing field evaporation

    CERN Document Server

    Zhao, L; Houard, J; Blum, I; Delaroche, F; Vurpillot, F

    2016-01-01

    We have recently proposed an atom probe design based on a femtosecond time-resolved pump-probe setup. This setup unlocks the limitation of voltage pulsed mode atom probe thanks to the occurrence of local photoconductive switching effect . In this paper, we have used a numerical model to simulate the field evaporation process triggered by the synchronous two pulses. The model takes into account the local photoconductive effect and the temperature rise caused by the laser application and the voltage pulse distortion due to the RC effect.

  12. RHEED study of titanium dioxide with pulsed laser deposition

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Pryds, Nini; Schou, Jørgen

    2009-01-01

    Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the growth of thin films of titanium dioxide (TiO2) on (1 0 0) magnesium oxide (MgO) substrates by pulsed laser deposition (PLD). The deposition is performed with a synthetic rutile TiO2 target...

  13. Melting of copper surface by ultrashort laser pulses

    NARCIS (Netherlands)

    Oboňa, J.V.; Ocelík, V.; Hosson, J.T.M. de; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to an almost absence of thermal diffusion into bulk material. In this paper

  14. Surface melting of copper by ultrashort laser pulses

    NARCIS (Netherlands)

    Oboňa, J.V.; Ocelík, V.; De Hosson, J.T.M.; Skolski, J.Z.P.; Mitko, V.S.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    The main advantage of ultrashort laser pulses in manufacturing technology is their very high removal rate of material and high quality of microstructures with the smallest dimensions at 1 μm level. The accuracy is mainly due to an almost absence of thermal diffusion into bulk material. In this paper

  15. Intelligent attenuator for laser pulse energy and power stabilization

    Science.gov (United States)

    White, M. S.; Wyatt, R. W.; Brett, A. G.

    1983-06-01

    Encouraging preliminary results are presented from a feed-forward stabilized active optical filter. Its function is to greatly reduce the shot-to-shot and day-to-day pulse energy fluctuations commonly suffered by single shot Q switched lasers and their associated electro-optic gates and switchouts.

  16. Transparent conducting oxides on polymeric substrates by pulsed laser deposition

    NARCIS (Netherlands)

    Dekkers, Jan Matthijn

    2007-01-01

    This thesis describes the research on thin films of transparent conducting oxides (TCOs) on polymeric substrates manufactured by pulsed laser deposition (PLD). TCOs are an indispensable part in optoelectronic applications such as displays, solar cells, light-emitting diodes, etc. At present, in many

  17. Ultra-short pulsed millimeter-wave laser

    Science.gov (United States)

    Wilson, Thomas

    2000-10-01

    High peak power pulses of 1.22-mm wavelength radiation have recently been obtained from a novel cavity-dumped far-infrared optically-pumped laser^1. Smooth reproducible pulses with the following characteristics have been routinely obtained: peak power=25-kW, pulsewidth (FWHM)=5-ns, repetition rate=10 pps. (This compares favorably to typical far-infrared, cavity-dumped output - 11-kW, 30-ns, 1 pps - available from the University of California - Santa Barbara Free Electron Laser). The pumping laser is a grating-tuned, hybrid TEA CO2 laser providing 1J / pulse at the 9P32 transition. The far-infrared gain medium is isotopic (C^13) methyl flouride. Experiments are underway for using the novel source to resonantly excite coherent pulses of 250-GHz longitudinal acoustic phonons in silicon doping superlattices. ^1 Thomas E. Wilson, "Modeling the high-speed switching of far-infrared radiation by photoionization in a semiconductor", Phys. Rev. B 59 (20), 12996 (1999).

  18. Electromagnetic pulses produced by expanding laser-produced Au plasma

    Directory of Open Access Journals (Sweden)

    De Marco Massimo

    2015-06-01

    Full Text Available The interaction of an intense laser pulse with a solid target produces large number of fast free electrons. This emission gives rise to two distinct sources of the electromagnetic pulse (EMP: the pulsed return current through the holder of the target and the outflow of electrons into the vacuum. A relation between the characteristics of laser-produced plasma, the target return current and the EMP emission are presented in the case of a massive Au target irradiated with the intensity of up to 3 × 1016 W/cm2. The emission of the EMP was recorded using a 12 cm diameter Moebius loop antennas, and the target return current was measured using a new type of inductive target probe (T-probe. The simultaneous use of the inductive target probe and the Moebius loop antenna represents a new useful way of diagnosing the laser–matter interaction, which was employed to distinguish between laser-generated ion sources driven by low and high contrast laser pulses.

  19. Magnus expansion for laser-matter interaction: Application to generic few-cycle laser pulses

    DEFF Research Database (Denmark)

    Klaiber, Michael; Dimitrovski, Darko; Briggs, John S.

    2009-01-01

    We treat the interaction of an atom with a short intense few-cycle laser pulse by the use of the Magnus expansion of the time-evolution operator. Terms of the Magnus expansion up to the third order in the pulse duration are evaluated explicitly, and expressions for the transition probability...

  20. Injection of electrons by colliding laser pulses in a laser wakefield accelerator

    Science.gov (United States)

    Hansson, M.; Aurand, B.; Ekerfelt, H.; Persson, A.; Lundh, O.

    2016-09-01

    To improve the stability and reproducibility of laser wakefield accelerators and to allow for future applications, controlling the injection of electrons is of great importance. This allows us to control the amount of charge in the beams of accelerated electrons and final energy of the electrons. Results are presented from a recent experiment on controlled injection using the scheme of colliding pulses and performed using the Lund multi-terawatt laser. Each laser pulse is split into two parts close to the interaction point. The main pulse is focused on a 2 mm diameter gas jet to drive a nonlinear plasma wave below threshold for self-trapping. The second pulse, containing only a fraction of the total laser energy, is focused to collide with the main pulse in the gas jet under an angle of 150°. Beams of accelerated electrons with low divergence and small energy spread are produced using this set-up. Control over the amount of accelerated charge is achieved by rotating the plane of polarization of the second pulse in relation to the main pulse. Furthermore, the peak energy of the electrons in the beams is controlled by moving the collision point along the optical axis of the main pulse, and thereby changing the acceleration length in the plasma.

  1. Effect of laser-assisted bleaching with Nd:YAG and diode lasers on shear bond strength of orthodontic brackets.

    Science.gov (United States)

    Mirhashemi, Amirhossein; Emadian Razavi, Elham Sadat; Behboodi, Sara; Chiniforush, Nasim

    2015-12-01

    The aim of the present study was to assess the effect of laser-assisted bleaching with neodymium:yttrium-aluminum-garnet (Nd:YAG) and diode lasers on shear bond strength (SBS) of orthodontic brackets. One hundred and four extracted human premolars were randomly divided into four groups: group 1: No bleaching applied (control group); group 2: Teeth bleached with 40 % hydrogen peroxide; group 3: Teeth treated with 30 % hydrogen peroxide activated with Nd:YAG laser (1064 nm, 2.5 W, 25 Hz, pulse duration of 100 μs, 6 mm distance); and group 4: Teeth treated with 30 % hydrogen peroxide activated with diode laser (810 nm, 1 W, CW, 6 mm distance). Equal numbers of teeth in groups 2, 3, and 4 were bonded at start, 1 h, 24 h, and 1 week after bleaching. A universal testing machine measured the SBS of the samples 24 h after bonding. After bracket debonding, the amount of residual adhesive on the enamel surface was observed under a stereomicroscope to determine the adhesive remnant index (ARI) scores. The SBS in the unbleached group was significantly higher than that in the bleached groups bonded immediately and 1 h after laser-assisted bleaching (P laser-assisted bleaching, the SBS was found to be significantly lower than that in the control group. Significant differences in the ARI scores existed among groups as well. The SBS of brackets seems to increase quickly within an hour after laser-assisted bleaching and 24 h after conventional bleaching. Thus, this protocol can be recommended if it is necessary to bond the brackets on the same day of bleaching.

  2. Intense ion beams accelerated by ultra-intense laser pulses

    Science.gov (United States)

    Roth, Markus; Cowan, T. E.; Gauthier, J. C.; Vehn, J. Meyer-Ter; Allen, M.; Audebert, P.; Blazevic, A.; Fuchs, J.; Geissel, M.; Hegelich, M.; Karsch, S.; Pukhov, A.; Schlegel, T.

    2002-04-01

    The discovery of intense ion beams off solid targets irradiated by ultra-intense laser pulses has become the subject of extensive international interest. These highly collimated, energetic beams of protons and heavy ions are strongly depending on the laser parameters as well as on the properties of the irradiated targets. Therefore we have studied the influence of the target conditions on laser-accelerated ion beams generated by multi-terawatt lasers. The experiments were performed using the 100 TW laser facility at Laboratoire pour l'Utilisation des Laser Intense (LULI). The targets were irradiated by pulses up to 5×1019 W/cm2 (~300 fs,λ=1.05 μm) at normal incidence. A strong dependence on the surface conditions, conductivity, shape and purity was observed. The plasma density on the front and rear surface was determined by laser interferometry. We characterized the ion beam by means of magnetic spectrometers, radiochromic film, nuclear activation and Thompson parabolas. The strong dependence of the ion beam acceleration on the conditions on the target back surface was confirmed in agreement with predictions based on the target normal sheath acceleration (TNSA) mechanism. Finally shaping of the ion beam has been demonstrated by the appropriate tailoring of the target. .

  3. Complications from laser-assisted liposuction performed by noncore practitioners.

    Science.gov (United States)

    Blum, Craig A; Sasser, Charles G S; Kaplan, Jonathan L

    2013-10-01

    Liposuction is one of the most commonly performed aesthetic surgery procedures in the United States, and most plastic surgeons perform suction-assisted, ultrasound-assisted, or power-assisted liposuction. The past decade has seen a growing interest in laser-assisted liposuction (LAL) and the proposed advantages of traditional liposuction methods. However, it is performed by a minority of plastic surgeons. In fact, many LAL providers are not trained in aesthetic practice, and many offer LAL as their only body-contouring procedure. When only one method of body contouring is available to a provider, it may lead to inappropriate patient selection with associated poor outcomes. This report discusses the use of laser liposuction in body contouring and the demographics of those performing liposuction, including LAL. Complications from laser-assisted liposuction performed by noncore practitioners are illustrated.

  4. Periodic dark pulse emission induced by delayed feedback in a quantum well semiconductor laser

    Directory of Open Access Journals (Sweden)

    L. Li

    2012-12-01

    Full Text Available We report the experimental observation of periodic dark pulse emission in a quantum-well semiconductor laser with delayed optical feedback. We found that under appropriate operation conditions the laser can also emit a stable train of dark pulses. The repetition frequency of the dark pulse is determined by the external cavity length. Splitting of the dark pulse was also observed. We speculate that the observed dark pulse is a kind of temporal cavity soliton formed in the laser.

  5. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, V V; Pestryakov, E V; Laptev, A V; Petrov, V A; Kuptsov, G V; Trunov, V I; Frolov, S A [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2014-05-30

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ∼1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y{sub 2}O{sub 3} laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 – 0.35 J. (lasers)

  6. Pulse Compression Of An FM Chirped CO2 Laser

    Science.gov (United States)

    Henderson, D. M.; Halmos, M. J.; Duvall, R. L.

    1989-12-01

    FM chirp/pulse compression has long been used in conventional radar systems [1]. The main advantages of such a technique are: 1. Efficient use of the average power available at the transmitter. 2. Increased system accuracy, both in range and velocity measurements. 3. Reduction of jamming vulnerability. We have explored the use of this technique for laser radar systems and in this paper describe an electro-optically FM modulated CO2 waveguide with post detection pulse compression by a surface acoustic wave (SAW) com-pression filter. The CO2 laser has been FM chirp modulated by a CdTe intracavity modulator. A frequency deviation of 95 MHz in 2.1 psec was attained in this fashion. Following heterodyne detection, the chirped pulse was compressed to 15 nsec using a SAW compression filter. This corresponded to a compression factor of 130. The suppression of unwanted sidelobes with a weighting filter was also demonstrated.

  7. Efficient self-sustained pulsed CO laser

    NARCIS (Netherlands)

    Peters, P.J.M.

    1978-01-01

    In this paper a simple sealed-off TEA CO laser is described with a self-sustained discharge without an external UV preionization source. At 77 K this system yields more than 600 mJ from a lasing volume of about 60 cm3 CO-N2-He mixture (45 J/ℓ atm. with 15.6% efficiency).

  8. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P

    2009-08-24

    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  9. Precision resection of intestine using ultrashort laser pulses

    Science.gov (United States)

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

    2016-03-01

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

  10. Diode-pumped solid state laser. (Part V). ; Short pulse laser oscillation. Handotai laser reiki kotai laser. 5. ; Tan pulse hasshin

    Energy Technology Data Exchange (ETDEWEB)

    Kuwabara, M.; Bando, N. (Asahi Glass Co. Ltd., Tokyo (Japan))

    1991-12-25

    A semiconductor laser (LD) excited solid state laser using an LD as an excited light source is under discussion for its practical applications to measurements, processing, communications, office automation, and medical areas. This paper describes the discussions given on the short pulse transmission using AOQ switching elements in the LD excited solid state laser with a long wave length band (1.3{mu}m), which is expected of its application in the communications and measurements area. Based on a possibility of raising a measurements resolution by making the pluses in the LD excited solid state laser, and experiments were performed using Nd:YLF as a laser host. as a results, it was found that the smaller the effective mode volume V {sub eff},the smaller the pulse width, and that the ratio of number of initial inversion distribution (N{sub i}/N{sub t}), an important parameter to determine pulse widths, can be obtained from the ratio of the LD exciting light to the input power (P{sub in}/P{sub t}). 7 refs., 14 figs., 2 tabs.

  11. DISAPPEARANCE OF TWO-PLASMON DECAY INSTABILITY IN PLASMAS PRODUCED BY ULTRASHORT LASER PULSES

    Institute of Scientific and Technical Information of China (English)

    CHEN LI-MING; ZHANG JIE; LIN HAI; LI YU-TONG; ZHAO LI-ZENG; JIANG WEN-MIAN

    2001-01-01

    Harmonic emission was studied from a plasma produced by ultrashort laser pulses. Unlike the harmonics from plasmas created by long (ns) laser pulses, the 3/2 harmonic emission was not observed in the interaction between plasmas and ultrashort laser pulses. A simple model is proposed to explain this phenomenon.

  12. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    Science.gov (United States)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  13. Pulsed laser excitation of phosphate stabilised silver nanoparticles

    Indian Academy of Sciences (India)

    Jyotirmayee Mohanty; Dipak K Palit; Laxminarayan V Shastri; Avinash V Sapre

    2000-02-01

    Laser flash photolysis studies were carried out on two types of silver nanoparticles prepared by -radiolysis of Ag+ solutions in the presence of polyphosphate as the stabiliser. Type I silver nanoparticles displayed a surface plasmon band at 390 nm. Type II silver nanoparticles showed a 390 nm surface plasmon band with a shoulder at 550 nm. On photoexcitation in the surface plasmon band region, using 35 picosecond laser pulses at 355 nm and 532 nm, the type II solutions showed transient bleaching and absorption signals in the 450-900 nm region, which did not decay appreciably up to 5 nanoseconds. These transient changes were found to get annealed in the interval where 5 ns < < 100 ns. Extended photolysis of the nanoparticle solutions with repetitive laser pulses resulted in a decrease in the values of the average particle size which were measured by employing the dynamic light scattering technique.

  14. Laboratory Transferability of Optimally Shaped Laser Pulses for Quantum Control

    CERN Document Server

    Tibbetts, Katharine Moore; Rabitz, Herschel

    2013-01-01

    Optimal control experiments can readily identify effective shaped laser pulses, or "photonic reagents", that achieve a wide variety of objectives. For many practical applications, an important criterion is that a particular photonic reagent prescription still produce a good, if not optimal, target objective yield when transferred to a different system or laboratory, {even if the same shaped pulse profile cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments.} First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found...

  15. Medical and biological applications for ultrafast laser pulses

    Science.gov (United States)

    Lubatschowski, Holger; Heisterkamp, Alexander; Will, Fabian; Singh, Ajoy I.; Serbin, Jesper; Ostendorf, Andreas; Kermani, Omid; Heermann, R.; Welling, Herbert; Ertmer, Wolfgang

    2003-02-01

    Due to the low energy threshold of photodisruption with fs laser pulses, thermal and mechanical side effects are limited to the sub μm range. The neglection of side effects enables the use of ultrashort laser pulses in a broad field of medical applications. Moreover, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue three dimensionally inside the bulk. We demonstrate the feasibility of surgical procedures in different fields of medical interest: In ophthalmology intrastromal cutting and preparing of corneal flaps for refractive surgery in living animals is presented. Besides, the very low mechanical side effects enables the use of fs-laser in otoralyngology to treat ocecular bones. Moreover, the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosclerosis as well as in dentistry to remove caries from dental hard tissue.

  16. PULSE: The Palomar Ultraviolet Laser for the Study of Exoplanets

    CERN Document Server

    Baranec, Christoph; Burruss, Rick S; Bowler, Brendan P; van Dam, Marcos; Riddle, Reed; Shelton, J Christopher; Truong, Tuan; Roberts, Jennifer; Milburn, Jennifer; Tesch, Jonathan

    2014-01-01

    The Palomar Ultraviolet Laser for the Study of Exoplanets (PULSE) will dramatically expand the science reach of PALM-3000, the facility high-contrast extreme adaptive optics system on the 5-meter Hale Telescope. By using an ultraviolet laser to measure the dominant high spatial and temporal order turbulence near the telescope aperture, one can increase the limiting natural guide star magnitude for exquisite correction from mV < 10 to mV < 16. Providing the highest near-infrared Strehl ratios from any large telescope laser adaptive optics system, PULSE uniquely enables spectroscopy of low-mass and more distant young exoplanet systems, essential to formulating a complete picture of exoplanet populations.

  17. Pulsed laser deposition of anatase thin films on textile substrates

    Science.gov (United States)

    Krämer, André; Kunz, Clemens; Gräf, Stephan; Müller, Frank A.

    2015-10-01

    Pulsed laser deposition (PLD) is a highly versatile tool to prepare functional thin film coatings. In our study we utilised a Q-switched CO2 laser with a pulse duration τ ≈ 300 ns, a laser wavelength λ = 10.59 μm, a repetition frequency frep = 800 Hz and a peak power Ppeak = 15 kW to deposit crystalline anatase thin films on carbon fibre fabrics. For this purpose, preparatory experiments were performed on silicon substrates to optimise the anatase deposition conditions including the influence of different substrate temperatures and oxygen partial pressures. Processing parameters were then transferred to deposit anatase on carbon fibres. Scanning electron microscopy, X-ray diffraction analyses, Raman spectroscopy and tactile profilometry were used to characterise the samples and to reveal the formation of phase pure anatase without the occurrence of a secondary rutile phase. Methanol conversion test were used to prove the photocatalytic activity of the coated carbon fibres.

  18. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

    Science.gov (United States)

    Hugenschmidt, Manfred

    1986-10-01

    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  19. Thomson scattering in high-intensity chirped laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Holkundkar, Amol R., E-mail: amol.holkundkar@pilani.bits-pilani.ac.in [Department of Physics, Birla Institute of Technology and Science, Pilani, Rajasthan 333031 (India); Harvey, Chris, E-mail: christopher.harvey@chalmers.se; Marklund, Mattias, E-mail: mattias.marklund@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2015-10-15

    We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.

  20. Fabrication of alkali halide UV photocathodes by pulsed laser deposition

    Science.gov (United States)

    Brendel', V. M.; Bukin, V. V.; Garnov, Sergei V.; Bagdasarov, V. Kh; Denisov, N. N.; Garanin, Sergey G.; Terekhin, V. A.; Trutnev, Yurii A.

    2012-12-01

    A technique has been proposed for the fabrication of atmospheric corrosion resistant alkali halide UV photocathodes by pulsed laser deposition. We produced photocathodes with a highly homogeneous photoemissive layer well-adherent to the substrate. The photocathodes were mounted in a vacuum photodiode, and a tungsten grid was used as an anode. Using pulsed UV lasers, we carried out experiments aimed at evaluating the quantum efficiency of the photocathodes. With a dc voltage applied between the photocathode and anode grid, we measured a shunt signal proportional to the total charge emitted by the cathode exposed to UV laser light. The proposed deposition technique enables one to produce photocathodes with photoemissive layers highly uniform in quantum efficiency, which is its main advantage over thin film growth by resistive evaporation.

  1. Analyses of the short pulse laser pumped transient collisional excited X-ray lasers

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, A.; Utsumi, T.; Moribayashi, K.; Zhidkov, A.; Kado, M.; Tanaka, M.; Hasegawa, N.; Kawachi, T. [Japan Atomic Energy Research Inst., Osaka (Japan). Advanced Photon Research Center

    2001-07-01

    The soft X-ray gain of the transient collisional excited (TCE) Ni-like Ag laser is investigated using the plasma hydrodynamics and atomic kinetics codes. The gain is calculated for a plasma produced from two 100ps laser irradiated solid target to show qualitative agreement with the experiment. The calculation shows significant improvement of the gain using a thin foil target pumped by two short laser pulses, because of a better coupling of the pump laser energy into the gain region of the plasma. The codes will provide performance prediction as well as optimization of the experimental studies of the TCE X-ray lasers. (orig.)

  2. Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR

    Science.gov (United States)

    Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

    Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

  3. Analysis of Thermal Effects in Laser Rod Pumped by Repetitively Pulsed Laser Diode Array

    Institute of Scientific and Technical Information of China (English)

    DAI Qin; LI Xin-zhong; WU Ri-na; WANG Xi-jun

    2007-01-01

    Based on some assumptions, the numerical model of thermal distribution in solid state laser crystal pumped by pulsed laser diode is set up due to the pumped intensity distribution. Taking into account the property of YAG materials that varies with temperature, the transient temperature distribution of the laser crystal is calculated using finite element method on condition that K is a constant and a function of temperature. Then, the influence of the pumping parameters on the thermal effect in laser crystal is also discussed. This study is helpful to optimize the design of the diode side pumped solid state lasers.

  4. Cosmetic and aesthetic skin photosurgery using a computer-assisted CO2 laser-scanning system

    Science.gov (United States)

    Dutu, Doru C. A.; Dumitras, Dan C.; Nedelcu, Ioan; Ghetie, Sergiu D.

    1997-12-01

    Since the first application of CO2 laser in skin photosurgery, various techniques such as laser pulsing, beam scanning and computer-assisted laser pulse generator have been introduced for the purpose of reducing tissue carbonization and thermal necrosis. Using a quite simple XY optical scanner equipped with two galvanometric driven mirrors and an appropriate software to process the scanning data and control the interaction time and energy density in the scanned area, we have obtained a device which can improve CO2 laser application in cosmetic and aesthetic surgery. The opto-mechanical CO2 laser scanner based on two total reflecting flat mirrors placed at 90 degree(s) in respect to the XY scanning directions and independently driven through a magnetic field provides a linear movement of the incident laser beam in the operating field. A DA converter supplied with scanning data by the software enables a scanning with linearity better than 1% for a maximum angular deviation of 20 degree(s). Because the scanning quality of the laser beam in the operating field is given not only by the displacement function of the two mirrors, but also by the beam characteristics in the focal plane and the cross distribution in the laser beam, the surgeon can control through software either the scanning field dimensions or the distance between two consecutive points of the vertically and/or horizontally sweep line. The development of computer-assisted surgical scanning techniques will help control the surgical laser, to create either a reproducible incision with a controlled depth or a controlled incision pattern with minimal incision width, a long desired facility for plastic surgery, neurosurgery, ENT and dentistry.

  5. A study on matrix assisted pulsed evaporation (MAPLE) of organic materials

    DEFF Research Database (Denmark)

    Matei, Andreea; Canulescu, Stela; Constantinescu, Catalin;

    2012-01-01

    Organic films can be produced either by MAPLE or directly by PLD (Pulsed laser deposition). For a reasonable deposition rate of ng/cm2 per pulse for film production by MAPLE a fluence of 1-1.5 J/cm2 is required at the laser wavelength of 355 nm, while the fluence can be considerably lower at 248 ...

  6. Numerical simulation of different pulse width of long pulsed laser on aluminum alloy

    Science.gov (United States)

    Li, Mingxin; Jin, Guangyong; Zhang, Wei; Chen, Guibo; Bi, Juan

    2015-03-01

    Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.

  7. Frequency conversion of high-intensity, femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Banks, P S

    1997-06-01

    Almost since the invention of the laser, frequency conversion of optical pulses via non- linear processes has been an area of active interest. However, third harmonic generation using ~(~1 (THG) in solids is an area that has not received much attention because of ma- terial damage limits. Recently, the short, high-intensity pulses possible with chirped-pulse amplification (CPA) laser systems allow the use of intensities on the order of 1 TW/cm2 in thin solids without damage. As a light source to examine single-crystal THG in solids and other high field inter- actions, the design and construction of a Ti:sapphire-based CPA laser system capable of ultimately producing peak powers of 100 TW is presented. Of special interest is a novel, all-reflective pulse stretcher design which can stretch a pulse temporally by a factor of 20,000. The stretcher design can also compensate for the added material dispersion due to propagation through the amplifier chain and produce transform-limited 45 fs pulses upon compression. A series of laser-pumped amplifiers brings the peak power up to the terawatt level at 10 Hz, and the design calls for additional amplifiers to bring the power level to the 100 TW level for single shot operation. The theory for frequency conversion of these short pulses is presented, focusing on conversion to the third harmonic in single crystals of BBO, KD*P, and d-LAP (deuterated I-arginine phosphate). Conversion efficiencies of up to 6% are obtained with 500 fs pulses at 1053 nm in a 3 mm thick BBO crystal at 200 GW/cm 2. Contributions to this process by unphasematched, cascaded second harmonic generation and sum frequency generation are shown to be very significant. The angular relationship between the two orders is used to measure the tensor elements of C = xt3)/4 with Crs = -1.8 x 1O-23 m2/V2 and .15Cri + .54Crs = 4.0 x 1O-23 m2/V2. Conversion efficiency in d-LAP is about 20% that in BBO and conversion efficiency in KD*P is 1% that of BBO. It is calculated

  8. Fraunhofer-type absorption line splitting and polarization in confocal double-pulse laser induced plasma

    International Nuclear Information System (INIS)

    Strong line splitting and polarization are observed in Fraunhofer-type absorption lines in Pb, Sn, Si, Cd, In, and Zn in confocal double-pulse laser induced plasma (DP-LIP) experiments. This effect is detectable using medium laser power densities: (∼ 1–2) × 1013 W/m2 for the first laser pulse and 1 × 1014 W/m2 for the second laser pulse. Polarization and splitting effects exist only during the second laser pulse (∼ 7 ns). Absorption line polarization and splitting phenomena may be explained by a high overall magnetic field and motional Stark effect caused by the second laser pulse inside the laser plasma created by the first pulse. - Highlights: • Certain Fraunhofer absorption lines in DP LIBS are polarized. • Certain Fraunhofer absorption lines in DP LIBS are split. • Those effects exist during laser pulse. • Effects take place in elements with ns2np2 and ns2 electron ground state

  9. Hard-tissue drilling by short-pulse CO2 laser with controllable pulse-tail energy

    Science.gov (United States)

    Uno, Kazuyuki; Sasaki, Tatsufumi; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with the almost same spike-pulse energy of about 0.8 mJ and the controllable pulse-tail energy of 0-21.26 mJ. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance and a spark-gap switch. In single-shot irradiation using these laser pulses, the dependence of the drilling depth of dry ivory samples on the fluence was investigated. The drilling depth increased with the fluence in the same laser pulse waveform. In this work, the effective short laser pulse for the hard tissue drilling was the laser pulse with the spike pulse energy of 0.87 mJ and the pulse tail energy of 6.33 mJ that produced the drilling depth of 28.1 μm at the fluence of 3.48 J/cm2 and the drilling depth per the fluence of 7.27 μm/J/cm2.

  10. Powerful laser pulse absorption in partly homogenized foam plasma

    International Nuclear Information System (INIS)

    The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented

  11. Pulsed photothermal depth profiling of tattoos undergoing laser removal treatment

    Science.gov (United States)

    Milanic, Matija; Majaron, Boris

    2012-02-01

    Pulsed photothermal radiometry (PPTR) allows noninvasive determination of temperature depth profiles induced by pulsed laser irradiation of strongly scattering biological tissues and organs, including human skin. In present study, we evaluate the potential of this technique for investigational characterization and possibly quantitative evaluation of laser tattoo removal. The study involved 5 healthy volunteers (3 males, 2 females), age 20-30 years, undergoing tattoo removal treatment using a Q-switched Nd:YAG laser. There were four measurement and treatment sessions in total, separated by 2-3 months. Prior to each treatment, PPTR measurements were performed on several tattoo sites and one nearby healthy site in each patient, using a 5 ms Nd:YAG laser at low radiant exposure values and a dedicated radiometric setup. The laser-induced temperature profiles were then reconstructed by applying a custom numerical code. In addition, each tatoo site was documented with a digital camera and measured with a custom colorimetric system (in tristimulus color space), providing an objective evaluation of the therapeutic efficacy to be correlated with our PPTR results. The results show that the laser-induced temperature profile in untreated tattoos is invariably located at a subsurface depth of 300 μm. In tattoo sites that responded well to laser therapy, a significant drop of the temperature peak was observed in the profiles obtained from PPTR record. In several sites that appeared less responsive, as evidenced by colorimetric data, a progressive shift of the temperature profile deeper into the dermis was observed over the course of consecutive laser treatments, indicating that the laser tattoo removal was efficient.

  12. Multiple quasi-monoenergetic electron beams from laser-wakefield acceleration with spatially structured laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.; Li, M. H.; Li, Y. F.; Wang, J. G.; Tao, M. Z.; Han, Y. J.; Zhao, J. R.; Huang, K.; Yan, W. C.; Ma, J. L.; Li, Y. T. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Chen, L. M., E-mail: lmchen@iphy.ac.cn [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100080 (China); Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, D. Z. [Institute of High Energy Physics, CAS, Beijing 100049 (China); Chen, Z. Y. [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621999 (China); Sheng, Z. M. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Zhang, J. [Department of Physics and Astronomy and IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-08-15

    By adjusting the focus geometry of a spatially structured laser pulse, single, double, and treble quasi-monoenergetic electron beams were generated, respectively, in laser-wakefield acceleration. Single electron beam was produced as focusing the laser pulse to a single spot. While focusing the laser pulse to two spots that are approximately equal in energy and size and intense enough to form their own filaments, two electron beams were produced. Moreover, with a proper distance between those two focal spots, three electron beams emerged with a certain probability owing to the superposition of the diffractions of those two spots. The energy spectra of the multiple electron beams are quasi-monoenergetic, which are different from that of the large energy spread beams produced due to the longitudinal multiple-injection in the single bubble.

  13. Performance optimization of water-jet assisted underwater laser cutting of AISI 304 stainless steel sheet

    Science.gov (United States)

    Mullick, Suvradip; Madhukar, Yuvraj K.; Roy, Subhransu; Nath, Ashish K.

    2016-08-01

    Recent development of water-jet assisted underwater laser cutting has shown some advantages over the gas assisted underwater laser cutting, as it produces much less turbulence, gas bubble and aerosols, resulting in a more gentle process. However, this process has relatively low efficiency due to different losses in water. Scattering is reported to be a dominant loss mechanism, which depends on the growth of vapor layer at cut front and its removal by water-jet. Present study reports improvement in process efficiency by reducing the scattering loss using modulated laser power. Judicious control of laser pulse on- and off-time could improve process efficiency through restricting the vapor growth and its effective removal by water-jet within the laser on- and off-time, respectively. Effects of average laser power, duty cycle and modulation frequency on specific energy are studied to get an operating zone for maximum efficiency. Next, the variation in laser cut quality with different process parameters are studied within this operating zone using Design of experiment (DOE). Response surface methodology (RSM) is used by implementing three level Box-Behnken design to optimize the variation in cut quality, and to find out the optimal process parameters for desired quality. Various phenomena and material removal mechanism involved in this process are also discussed.

  14. Electrospray-assisted laser desorption/ionization mass spectrometry for direct ambient analysis of solids.

    Science.gov (United States)

    Shiea, Jentaie; Huang, Min-Zon; Hsu, Hsiu-Jung; Lee, Chi-Yang; Yuan, Cheng-Hui; Beech, Iwona; Sunner, Jan

    2005-01-01

    A new method of electrospray-assisted laser desorption/ionization (ELDI) mass spectrometry, which combines laser desorption with post-ionization by electrospray, was applied to rapid analysis of solid materials under ambient conditions. Analytes were desorbed from solid metallic and insulating substrata using a pulsed nitrogen laser. Post-ionization produced high-quality mass spectra characteristic of electrospray, including protein multiple charging. For the first time, mass spectra of intact proteins were obtained using laser desorption without adding a matrix. Bovine cytochrome c and an illicit drug containing methaqualone were chosen in this study to demonstrate the applicability of ELDI to the analysis of proteins and synthetic organic compounds. PMID:16299699

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

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

    2007-02-01

    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.

  17. Ultrashort pulse laser slicing of semiconductor crystal

    Science.gov (United States)

    Kim, Eunho; Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka

    2016-07-01

    Meanwhile, by the convention wire-saw technique, it is difficult to slice off a thin wafer from bulk SiC crystal without the reserving space for cutting. In this study, we have achieved exfoliation of 4H-SiC single crystal by femtosecond laser induced slicing method. By using this, the exfoliated surface with the root-mean-square roughness of 3 μm and the cutting-loss thickness smaller than 30 μm was successfully demonstrated. We have also observed the nanostructure on the exfoliated surface in SiC crystal.

  18. Pulsed power for angular multiplexed laser fusion drivers

    International Nuclear Information System (INIS)

    The feasibility of using rare gas-halide lasers, in particular the KrF laser, as inertial confinement fusion (ICF) drivers has been assessed. These lasers are scalable to the required high energy (approx. =1-5 MJ) in a short pulse (approx. =10 ns) by optical angular multiplexing, and integration of the output from approx. =100 kJ laser amplifier subsystems. The e-beam current density (approx. =50A/cm2) and voltage (approx. =800 kV) required for these power amplifiers lead to an e-beam impedance of approx. =0.2Ω for approx. =300 ns pump time. This impedance level requires modularization of the large area e-gun, a) to achieve a diode inductance consistent with fast current risetime, b) to circumvent dielectric breakdown constraints in the pulse forming lines, and c) to reduce the requirement for guide magnetic fields. Pulsed power systems requirements, design concepts, scalability, tradeoffs, and performance projections are discussed in this paper

  19. Modification of Cu surface with picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vincenc Oboňa, J. [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Materials innovation institute M2i, Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Ocelík, V., E-mail: v.ocelik@rug.nl [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Rao, J.C. [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Skolski, J.Z.P.; Römer, G.R.B.E. [Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Huis in ‘t Veld, A.J. [Faculty of Engineering Technology, Chair of Applied Laser Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); TNO Technical Sciences, Mechatronics, Mechanics and Materials, De Rondom 1, 5600 HE, Eindhoven (Netherlands); Hosson, J. Th. M. De [Materials innovation institute M2i, Department of Applied Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2014-06-01

    High purity, mirror-polished polycrystalline Cu surface was treated with single picosecond laser pulses at fluence levels close to the single-pulse modification threshold. The induced surface topography and sub-surface changes were examined with scanning and transmission electron microscopy, respectively. The analysis showed an increased absorption of laser energy on the microscopic surface topography inhomogeneities, even at a fluence level below the modification threshold. Many features, like spikes, bubbles, spheres, as well as small periodic ripples at the bottom of scratches, reveal a significant influence of melting and eruptive relaxation of the absorbed laser energy on the final appearance of the surface. Further, it was found that thermal stresses result in twinning to a depth of few tens of nanometers under the surface. Voids at this depth have been observed as well. The results of the observations provide new insights into the early stages of the picosecond laser pulse modification of metals, especially metals with a weak electron–phonon coupling.

  20. Pulsed laser ablation and deposition of ZnS:Cr

    Energy Technology Data Exchange (ETDEWEB)

    Nematollahi, Mohammadreza, E-mail: nematollahim@gmail.com; Yang, Xiaodong; Gibson, Ursula J.; Reenaas, Turid W.

    2015-09-01

    We present a method to deposit films with a range of doping concentrations/dilute alloys, from a single target in pulsed laser deposition (PLD). Cr-doped ZnS films were deposited by ablating a target consisting Cr particles (diameter 20–100 μm) embedded in a ZnS:Cr matrix. The Cr content in the film was varied in the range 2.0–5.0 at.% simply by varying the laser fluence, or by varying the number of pre-ablation pulses. Such a doping/composition range is normally not achieved using a single target in PLD. Details of the target ablation study, which is needed prior to the deposition, are also presented. - Highlights: • ZnS:Cr films (2-5 %) were deposited by pulsed laser deposition using a single target. • Both the laser fluence and target pre-ablation affects the dopant concentration. • The non-stoichiometric transfer was controlled in a reproducible manner.

  1. Respiratory complications after diode-laser-assisted tonsillotomy.

    Science.gov (United States)

    Fischer, Miloš; Horn, Iris-Susanne; Quante, Mirja; Merkenschlager, Andreas; Schnoor, Jörg; Kaisers, Udo X; Dietz, Andreas; Kluba, Karsten

    2014-08-01

    Children with certain risk factors, such as comorbidities or severe obstructive sleep apnea syndrome (OSAS) are known to require extended postoperative monitoring after adenotonsillectomy. However, there are no recommendations available for diode-laser-assisted tonsillotomy. A retrospective chart review of 96 children who underwent diode-laser-assisted tonsillotomy (07/2011-06/2013) was performed. Data for general and sleep apnea history, power of the applied diode-laser (λ = 940 nm), anesthesia parameters, the presence of postoperative respiratory complications and postoperative healing were evaluated. After initially uncomplicated diode-laser-assisted tonsillotomy, an adjustment of post-anesthesia care was necessary in 16 of 96 patients due to respiratory failure. Respiratory complications were more frequent in younger children (3.1 vs. 4.0 years, p = 0.049, 95 % CI -1.7952 to -0.0048) and in children who suffered from nocturnal apneas (OR = 5.00, p diode-laser power higher than 13 W could be identified as a risk factor for the occurrence of a postoperative oropharyngeal edema (OR = 3.45, p diode-laser-assisted tonsillotomy. We recommend a reduced diode-laser power (<13 W) to reduce oropharyngeal edema.

  2. Glass microprocessing by laser-induced plasma-assisted ablation: fundamental to industrial applications

    Science.gov (United States)

    Sugioka, Koji; Midorikawa, Katsumi; Yamaoka, Hiroshi; Gomi, Yutaka; Otsuki, Masayoshi; Hong, Ming Hui; Wu, Dong Jiang; Wong, Lai Lee; Chong, Tow Chong

    2004-07-01

    Laser-induced plasma-assisted ablation (LIPAA), in which a single conventional pulsed laser of small size is employed (typically 2nd harmonic of Nd:YAG laser), enables to process transparent materials like glass with micron order spatial resolution, high speed and low cost. In this process, a laser beam is first directed to a glass substrate placed in vacuum or air. The laser beam passes through the substrate since the wavelength of laser beam must have no absorption by the substrate for the LIPAA process. The transmitted laser beam is absorbed by a solid target (typically metal) located behind the substrate. The target is then ablated, resulting in plasma generation. Due to the interaction of the laser beam and the laser-induced plasma, significant ablation takes place at the rear surface of substrate. This process demonstrates surface microstructuring, crack-free marking, color marking, painting and selective metallization of glass. Based on these achievements, we have developed a prototype of workstation of LIPAA microfabrication system which is now commercially available. The discussion includes mechanism and practical applications in industry of LIPAA process.

  3. Temporal Behavior of the Pump Pulses, Residual Pump Pulses, and THz Pulses for D2O Gas Pumped by a TEA CO2 Laser

    Science.gov (United States)

    Geng, Lijie; Zhang, Zhifeng; Zhai, Yusheng; Su, Yuling; Zhou, Fanghua; Qu, Yanchen; Zhao, Weijiang

    2016-08-01

    Temporal behavior of the pump pulses, residual pump pulses, and THz pulses for optically pumped D2O gas molecules was investigated by using a tunable TEA CO2 laser as the pumping source. The pulse profiles of pump laser pulses, residual pump pulses, and the THz output pulses were measured, simultaneously, at several different gas pressures. For THz pulse, the pulse delay between the THz pulse and the pump pulse was observed and the delay time was observed to increase from 40 to 70 ns with an increase in gas pressure from 500 to 1700 Pa. Both THz pulse broadening and compression were observed, and the pulse broadening effect transformed to the compression effect with increasing the gas pressure. For the residual pump pulse, the full width at half maximum (FWHM) of the main pulse decreased with increasing gas pressure, and the main pulse disappeared at high gas pressures. The secondary pulses were observed at high gas pressure, and the time intervals of about 518 and 435 ns were observed between the THz output pulse and the secondary residual pump pulse at the pressure of 1400 Pa and 1700 Pa, from which the vibrational relaxation time constants of about 5.45 and 5.55 μs Torr were obtained.

  4. Improved pulse contrast on the Texas Petawatt Laser

    Science.gov (United States)

    Gaul, E.; Toncian, T.; Martinez, M.; Gordon, J.; Spinks, M.; Dyer, G.; Truong, N.; Wagner, C.; Tiwari, G.; Donovan, M. E.; Ditmire, T.; Hegelich, B. M.

    2016-05-01

    We have completed a pulse contrast upgrade on the Texas Petawatt Laser. This improvement enables the use of thin and reduced mass targets for ion acceleration, and reduces pre-plasma effects on all experiments. The new design starts with two BBO-based OPCPA stages pumped by an optically synchronized 8-ps laser. These stages amplify slightly chirped few ps pulses by six orders of magnitude. Next there are two LBO-based OPCPA stages that are pumped by 4 ns pulses. With much less gain than before, parametric fluorescence has been reduced by about three orders of magnitude. Prior to the upgrade, lenses caused pencil beam prepulses. Since tilting or wedging lenses was not a viable option, we replaced all lenses in the glass amplifiers with off-axis parabolic mirrors. There are still weak prepulses that we attribute to surface scattering. We eliminated thin transmissive optics to avoid post pulses that would result in prepulses by nonlinear (B-integral) conversion. This required us to reduce from eight to four passes in the 64-mm glass amplifier and to add a two-pass 25-mm “booster amplifier.” As a final upgrade we added an Acousto-Optic Programmable Dispersive-Filter (AOPDF) to improve higher order dispersion and steepen the rising edge of the compressed pulse.

  5. Microencapsulation of silicon cavities using a pulsed excimer laser

    KAUST Repository

    Sedky, Sherif M.

    2012-06-07

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24ns), focused onto an area of 23mm 2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm 2to 800 mJ cm 2, the pulse rate from 1Hz to 50Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible. © 2012 IOP Publishing Ltd.

  6. Ionization of molecular hydrogen in ultrashort intense laser pulses

    International Nuclear Information System (INIS)

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H2 performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H2 and D2 in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  7. Ionization of molecular hydrogen in ultrashort intense laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Vanne, Yulian V.

    2010-03-18

    A novel ab initio numerical approach is developed and applied that solves the time-dependent Schroedinger equation describing two-electron diatomic molecules (e.g. molecular hydrogen) exposed to an intense ultrashort laser pulse. The method is based on the fixed-nuclei and the non-relativistic dipole approximations and aims to accurately describe both correlated electrons in full dimensionality. The method is applicable for a wide range of the laser pulse parameters and is able to describe both few-photon and many-photon single ionization processes, also in a non-perturbative regime. A key advantage of the method is its ability to treat the strong-field response of the molecules with arbitrary orientation of the molecular axis with respect to the linear-polarized laser field. Thus, this work reports on the first successful orientation-dependent analysis of the multiphoton ionization of H{sub 2} performed by means of a full-dimensional numerical treatment. Besides the investigation of few-photon regime, an extensive numerical study of the ionization by ultrashort frequency-doubled Ti:sapphire laser pulses (400 nm) is presented. Performing a series of calculations for different internuclear separations, the total ionization yields of H{sub 2} and D{sub 2} in their ground vibrational states are obtained for both parallel and perpendicular orientations. A series of calculations for 800 nm laser pulses are used to test a popular simple interference model. Besides the discussion of the ab initio numerical method, this work considers different aspects related to the application of the strong-field approximation (SFA) for investigation of a strong-field response of an atomic and molecular system. Thus, a deep analysis of the gauge problem of SFA is performed and the quasistatic limit of the velocity-gauge SFA ionization rates is derived. The applications of the length-gauge SFA are examined and a recently proposed generalized Keldysh theory is criticized. (orig.)

  8. Ion-beam assisted laser fabrication of sensing plasmonic nanostructures

    CERN Document Server

    Kuchmizhak, Aleksandr; Vitrik, Oleg; Kulchin, Yuri; Milichko, Valentin; Makarov, Sergey; Kudryashov, Sergey

    2015-01-01

    Simple high-performance two-stage hybrid technique was developed for fabrication of different plasmonic nanostructures, including nanorods, nanorings, as well as more complex structures on glass substrates. In this technique a thin noble metal film on a dielectric substrate is irradiated by a tightly focused single nanosecond laser pulse and then the modified region is slowly polished by an accelerated argon ion (Ar+) beam. As a result, each nanosecond laser pulse locally modifies the initial metal film through initiation of fast melting and subsequent hydrodynamic processes, while the following Ar+-ion polishing removes the rest of the film, revealing the hidden topography features and fabricating separate plasmonic structures on the glass substrate. We demonstrate that the shape and lateral size of the resulting functional plasmonic nanostructures depends on the laser pulse energy and metal film thickness, while subsequent Ar+-ion polishing enables to vary height of the resulting nanostructures. The plasmon...

  9. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    Science.gov (United States)

    Petrov, V. V.; Pestryakov, E. V.; Laptev, A. V.; Petrov, V. A.; Kuptsov, G. V.; Trunov, V. I.; Frolov, S. A.

    2014-05-01

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ~1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y2O3 laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 - 0.35 J.

  10. Simulation of intense short-pulse laser-plasma interaction

    International Nuclear Information System (INIS)

    We have completed the massive parallelization of a 2-dimensional giga-particle code and have achieved a 530-fold acceleration rate with 512 processing elements (PE's). Using this we have implemented a simulation of the interaction of a solid thin film and a high intensity laser and have discovered a phenomenon in which high quality short pulses from the far ultraviolet to soft X-rays are generated at the back surface of the thin layer. We have also introduced the atomic process database code (Hullac) and have the possibility for high precision simulations of X-ray laser radiation. With respect to laser acceleration we have the possibility to quantitatively evaluate relativistic self-focusing assumed to occur in higher intensity fields. Ion acceleration from a solid target and an underdense plasma irradiated by an intense and an ultra intense laser, respectively, has also been studied by particle-in-cell (PIC) simulations. (author)

  11. Materials processing with a tightly focused femtosecond laser vortex pulse.

    Science.gov (United States)

    Hnatovsky, Cyril; Shvedov, Vladlen G; Krolikowski, Wieslaw; Rode, Andrei V

    2010-10-15

    In this Letter we present the first (to our knowledge) demonstration of material modification using tightly focused single femtosecond laser vortex pulses. Double-charge femtosecond vortices were synthesized with a polarization-singularity beam converter based on light propagation in a uniaxial anisotropic medium and then focused using moderate- and high-NA optics (viz., NA=0.45 and 0.9) to ablate fused silica and soda-lime glass. By controlling the pulse energy, we consistently machine micrometer-size ring-shaped structures with <100nm uniform groove thickness. PMID:20967085

  12. Nanosecond length electron pulses from a laser-excited photocathode

    International Nuclear Information System (INIS)

    A photocathode made from polycrystalline lanthanum hexaboride (LaB6) has produced nanosecond length electron pulses when excited by an excimer laser at 308nm. Peak currents in excess of 1A have been observed, with quantum yields of 4 x 10-5 being measured. A method for extracting the electrons from an emission-limited cathode, plasma extraction, has been demonstrated. This technique uses a low power continuous discharge to provide the electric field needed to extract the photoelectrons. This technique may be useful in producing high repetition rate short pulse ion sources. 10 refs., 4 figs

  13. Nonlinear Theory of Nonparaxial Laser Pulse Propagation in Plasma Channels

    International Nuclear Information System (INIS)

    Nonparaxial propagation of ultrashort, high-power laser pulses in plasma channels is examined. In the adiabatic limit, pulse energy conservation, nonlinear group velocity, damped betatron oscillations, self-steepening, self-phase modulation, and shock formation are analyzed. In the nonadiabatic limit, the coupling of forward Raman scattering (FRS) and the self-modulation instability (SMI) is analyzed and growth rates are derived, including regimes of reduced growth. The SMI is found to dominate FRS in most regimes of interest. (c) 2000 The American Physical Society

  14. Control of charge migration in molecules by ultrashort laser pulses

    CERN Document Server

    Golubev, Nikolay V

    2015-01-01

    Due to electronic many-body effects, the ionization of a molecule can trigger ultrafast electron dynamics appearing as a migration of the created hole charge throughout the system. Here we propose a scheme for control of the charge migration dynamics with a single ultrashort laser pulse. We demonstrate by fully ab initio calculations on a molecule containing a chromophore and an amine moieties that simple pulses can be used for stopping the charge-migration oscillations and localizing the charge on the desired site of the system. We argue that this control may be used to predetermine the follow-up nuclear rearrangement and thus the molecular reactivity.

  15. High power amplification of a tailored-pulse fiber laser

    Science.gov (United States)

    Saby, Julien; Sangla, Damien; Caplette, Stéphane; Boula-Picard, Reynald; Drolet, Mathieu; Reid, Benoit; Salin, François

    2013-02-01

    We demonstrate the amplification of a 1064nm pulse-programmable fiber laser with Large Pitch Rod-Type Fibers of various Mode field diameters from 50 to 70 μm. We have developed a high power fiber amplifier at 1064nm delivering up to 100W/1mJ at 15ns pulses and 30W/300μJ at 2ns with linearly polarized and diffraction limited output beam (M²LBO crystals leading to 50W at 532nm and 25W at 355nm with a diffraction limited output. Similar experiments performed at 1032nm are also reported.

  16. A Novel Femtosecond Laser System for Attosecond Pulse Generation

    OpenAIRE

    Jianqiang Zhu; Xinglong Xie; Meizhi Sun; Qunyu Bi; Jun Kang

    2012-01-01

    We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly stretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric chirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority of the energy gain. At the second stage, a YCOB crystal with the aperture of ~50 mm is used instead of the K...

  17. Laboratory transferability of optimally shaped laser pulses for quantum control

    Energy Technology Data Exchange (ETDEWEB)

    Moore Tibbetts, Katharine; Xing, Xi; Rabitz, Herschel [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    2014-02-21

    Optimal control experiments can readily identify effective shaped laser pulses, or “photonic reagents,” that achieve a wide variety of objectives. An important additional practical desire is for photonic reagent prescriptions to produce good, if not optimal, objective yields when transferred to a different system or laboratory. Building on general experience in chemistry, the hope is that transferred photonic reagent prescriptions may remain functional even though all features of a shaped pulse profile at the sample typically cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments. First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found to still produce near optimal yields on the second laser system. Third, transferring a collection of photonic reagents optimized on the first laser system to the second laser system reproduced systematic trends in photoproduct yields upon interaction with the homologous chemical family. These three transfers of photonic reagents are demonstrated to be successful upon paying reasonable attention to overall laser system characteristics. The ability to transfer photonic reagents from one laser system to another is analogous to well-established utilitarian operating procedures with traditional chemical reagents. The practical implications of the present results for experimental quantum control are discussed.

  18. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

    The semiconductor materials like Si and the transparent dielectric materials like glass and quartz are extensively used in optoelectronics, microelectronics, and microelectromechanical systems (MEMS) industries. The combination of these materials often go hand in hand for applications in MEMS such as in chips for pressure sensors, charge coupled devices (CCD), and photovoltaic (PV) cells for solar energy generation. The transparent negative terminal of the solar cell is made of glass on one surface of the PV cell. The positive terminal (cathode) on the other surface of the solar cell is made of silicon with a glass negative terminal (anode). The digital watches and cell phones, LEDs, micro-lens, optical components, and laser optics are other examples for the application of silicon and or glass. The Si and quartz are materials extensively used in CCD and LED for digital cameras and CD players respectively. Hence, three materials: (1) a semiconductor silicon and transparent dielectrics,- (2) glass, and (3) quartz are chosen for laser micromachining as they have wide spread applications in microelectronics industry. The Q-switched, nanosecond pulsed lasers are most extensively used for micro-machining. The nanosecond type of short pulsed laser is less expensive for the end users than the second type, pico or femto, ultra-short pulsed lasers. The majority of the research work done on these materials (Si, SiO 2, and glass) is based on the ultra-short pulsed lasers. This is because of the cut quality, pin point precision of the drilled holes, formation of the nanometer size microstructures and fine features, and minimally invasive heat affected zone. However, there are many applications such as large surface area dicing, cutting, surface cleaning of Si wafers by ablation, and drilling of relatively large-sized holes where some associated heat affected zone due to melting can be tolerated. In such applications the nanosecond pulsed laser ablation of materials is very

  19. Laser-induced reversion of $\\delta^{'}$ precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe

    CERN Document Server

    Khushaim, Muna; Al-Kassab, Talaat

    2015-01-01

    The influence of tuning the laser energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction and composition of $\\delta^{'}$ precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser energy of 100 pJ was in fairly good agreement with reported range of $\\delta^{'}$ solvus temperature, suggesting a result of reversion upon heating due to laser pulsing.

  20. Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

    CERN Document Server

    Yao, Jinping; Zeng, Bin; Chu, Wei; Li, Guihua; Ni, Jielei; Zhang, Haisu; Jing, Chenrui; Zhang, Chaojin; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2015-01-01

    We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.