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Sample records for intense laser irradiation

  1. Polyatomic molecules under intense femtosecond laser irradiation.

    PubMed

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim V; Jackson, James E; Levine, Benjamin G; Dantus, Marcos

    2014-12-11

    Interaction of intense laser pulses with atoms and molecules is at the forefront of atomic, molecular, and optical physics. It is the gateway to powerful new tools that include above threshold ionization, high harmonic generation, electron diffraction, molecular tomography, and attosecond pulse generation. Intense laser pulses are ideal for probing and manipulating chemical bonding. Though the behavior of atoms in strong fields has been well studied, molecules under intense fields are not as well understood and current models have failed in certain important aspects. Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon excitation. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a "bag of atoms" during field induced ionization. In this article we present a set of experiments and theoretical calculations exploring the behavior of a large collection of aryl alkyl ketones when irradiated with intense femtosecond pulses. Specifically, we consider to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The set of molecules studied is further divided into smaller sets, sorted by type and position of functional groups. The pump-probe time-delay scans show that among positional isomers the variations in relative energies, which amount to only a few hundred millielectronvolts, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). High level ab initio quantum chemical calculations were performed to predict molecular dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose the

  2. Response of graphene to femtosecond high-intensity laser irradiation

    SciTech Connect

    Roberts, Adam; Cormode, Daniel; Reynolds, Collin; Newhouse-Illige, Ty; LeRoy, Brian J.; Sandhu, Arvinder S.

    2011-08-01

    We study the response of graphene to high-intensity, 50-femtosecond laser pulse excitation. We establish that graphene has a high ({approx}3 x 10{sup 12} Wcm{sup -2}) single-shot damage threshold. Above this threshold, a single laser pulse cleanly ablates graphene, leaving microscopically defined edges. Below this threshold, we observe laser-induced defect formation leading to degradation of the lattice over multiple exposures. We identify the lattice modification processes through in-situ Raman microscopy. The effective lifetime of chemical vapor deposition grown graphene under femtosecond near-infrared irradiation and its dependence on laser intensity is determined. These results also define the limits of non-linear applications of graphene in femtosecond high-intensity regime.

  3. Irradiation of myoglobin by intense, ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Chelliah, Juliah J.; Kumar, S. V. K.; Dharmadhikari, Aditya K.; Dharmadhikari, Jayashree A.; Mathur, Deepak

    2016-10-01

    We probe the interaction of myoglobin with intense, femtosecond laser pulses. Significant spectral differences are found between native and the irradiated myoglobin. These arise from the disruption of the heme prosthetic group: geometrical restructuring results in alteration of the oxidation state of Fe (from its initial +3 state) which is found to be reversible on timescales of ~4-6 h. Measurements taken upon addition of OH scavengers establish the key role played by these radicals in the overall dynamics. Myoglobin remains intact upon intense field irradiation, demonstrating the structural robustness of the polypeptide backbone. Experiments utilizing intense, ultrashort laser pulses are expected to open new horizons for following, with high sensitivity, changes in the oxidation state, chemical environment, and electronic state of biomolecules in the aqueous phase.

  4. Irradiation effect of polarization direction and intensity of semiconductor laser on injured peripheral nerve

    NASA Astrophysics Data System (ADS)

    Guo-Xin, Xiong; Lei-lei, Xiong

    2016-08-01

    To investigate the irradiation effect of polarization direction and the intensity of a semiconductor laser on the injured peripheral nerve in rabbits, the model of the injured common peroneal nerve was established, the L5,6 spinal segments of the rabbits were irradiated, a uniform rotating polarizer was placed at the laser output which made the polarization direction and intensity of the output laser change according to the 80 Hz cosine law. The experimental results show that irradiating the spinal segment of injured nerves in rabbits with this changeable semiconductor laser can significantly promote the regeneration of injured peripheral nerves and the function recovery.

  5. Advances in endonasal low intensity laser irradiation therapy

    NASA Astrophysics Data System (ADS)

    Jiao, Jian-Ling; Liu, Timon C.; Liu, Jiang; Cui, Li-Ping; Liu, Song-hao

    2005-07-01

    Endonasal low intensity laser therapy (ELILT) began in China in 1998. Now in China it is widely applied to treat hyperlipidemia and brain diseases such as Alzheimer's disease, Parkinson's disease, insomnia, poststroke depression, intractable headache, ache in head or face, cerebral thrombosis, acute ischemic cerebrovascular disease, migraine, brain lesion and mild cognitive impairment. There are four pathways mediating EILILT, Yangming channel, autonomic nervous systems and blood cells. Two unhealth acupoints of Yangming channal inside nose might mediate the one as is low intensity laser acupuncture. Unbalance autonomic nervous systems might be modulated. Blood cells might mediate the one as is intravascular low intensity laser therapy. These three pathways are integrated in ELILT so that serum amyloid β protein, malformation rate of erythrocyte, CCK-8, the level of viscosity at lower shear rates and hematocrit, or serum lipid might decrease, and melanin production/SOD activity or β endorphin might increase after ELILT treatment. These results indicate ELILT might work, but it need to be verified by randomized placebo-controlled trial.

  6. Spectroscopic study of gold nanoparticle formation through high intensity laser irradiation of solution

    SciTech Connect

    Nakamura, Takahiro Sato, Shunichi; Herbani, Yuliati; Ursescu, Daniel; Banici, Romeo; Dabu, Razvan Victor

    2013-08-15

    A spectroscopic study of the gold nanoparticle (NP) formation by high-intensity femtosecond laser irradiation of a gold ion solution was reported. The effect of varying energy density of the laser on the formation of gold NPs was also investigated. The surface plasmon resonance (SPR) peak of the gold nanocolloid in real-time UV-visible absorption spectra during laser irradiation showed a distinctive progress; the SPR absorption peak intensity increased after a certain irradiation time, reached a maximum and then gradually decreased. During this absorption variation, at the same time, the peak wavelength changed from 530 to 507 nm. According to an empirical equation derived from a large volume of experimental data, the estimated mean size of the gold NPs varied from 43.4 to 3.2 nm during the laser irradiation. The mean size of gold NPs formed at specific irradiation times by transmission electron microscopy showed the similar trend as that obtained in the spectroscopic analysis. From these observations, the formation mechanism of gold NPs during laser irradiation was considered to have two steps. The first is a reduction of gold ions by reactive species produced through a non-linear reaction during high intensity laser irradiation of the solution; the second is the laser fragmentation of produced gold particles into smaller pieces. The gold nanocolloid produced after the fragmentation by excess irradiation showed high stability for at least a week without the addition of any dispersant because of the negative charge on the surface of the nanoparticles probably due to the surface oxidation of gold nanoparticles. A higher laser intensity resulted in a higher efficiency of gold NPs fabrication, which was attributed to a larger effective volume of the reaction.

  7. Magneto-optical imaging of magnetic domain pattern produced by intense femtosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Sinha, Jaivarhan; Mohan, Shyam; Banerjee, S. S.; Kahaly, S.; Kumar, G. Ravindra

    2009-03-01

    An important and intriguing area of research is laser plasma generated giant magnetic field pulses. Interaction of ultrashort high intensity laser pulses with matter involves several mechanisms for generating ultrastrong magnetic fields. By irradiating a magnetic recordable tape constituting of γ-Fe2O3 particles with an intense p-polarized femtosecond laser pulses (˜ 10^16 W cm-2, 100fs), we have found complex magnetic field patterns stored in the tape. We image the local magnetic field distribution around the irradiated region [1] using the high sensitivity magneto-optical imaging technique. We understand the complex magnetic domains patterns recoded on the tape in terms of interesting instabilities [1] generated in the plasma produced during the irradiation of the tape with intense laser pulses. [0pt] [1] Jaivardhan Sinha, Shyam Mohan, S. S Banerjee, S. Kahaly, G. Ravindra Kumar, Phys. Rev. E 77, 046118(2008). *satyajit@iitk.ac.in

  8. Generation of strongly coupled Xe cluster nanoplasmas by low intensive soft x-ray laser irradiation

    SciTech Connect

    Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

    2012-07-11

    A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse ({lambda}=13.9 nm, {approx}7 ps, {<=}5 Multiplication-Sign 10{sup 9} W/cm{sup 2}), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

  9. X-ray enhancement in a nanohole target irradiated by intense ultrashort laser pulses

    SciTech Connect

    Chakravarty, U.; Arora, V.; Chakera, J. A.; Naik, P. A.; Srivastava, H.; Tiwari, P.; Srivastava, A.; Gupta, P. D

    2011-03-01

    In this paper, we present a comparative study of the laser energy absorption, soft x-ray emission (in the water window region: 2.3-4.4 nm) and hard x-ray emission (in the 2-20 keV range) from planar aluminum and nanohole alumina of 40 nm average diameter, when irradiated by Ti:sapphire laser pulses. The laser pulse duration was varied from 45 to 500 fs, and the focused intensity on the target ranged from {approx}3 x 10{sup 16} W/cm{sup 2} to 3x10{sup 17} W/cm{sup 2}. The x-ray yield enhancement from the nanoholes shows an increased coupling of the laser energy to the target. The effect of laser pulse duration on the x-ray emission was also studied, where a resonance like phenomenon was observed. The laser energy absorption measurements in the nanoholes showed a marginal enhancement in absorption as compared to planar Al. The integrated keV x-ray yield, from nanohole alumina and planar Al, at an intensity of 3 x 10{sup 17} W/cm{sup 2}, was 25 and 3.5 {mu}J, respectively. The results can be explained by considering the hydrodynamic expansion of the laser irradiated structure and field enhancement in the nanoholes.

  10. Reaction of cells to local, regional, and general low-intensive laser irradiation

    NASA Astrophysics Data System (ADS)

    Baibekov, Iskander M.; Kasymov, A. S.; Musaev, Erkin S.; Vorojeikin, V. M.; Artikov, S. N.

    1993-07-01

    Local influence of low intensive laser irradiation (LILI) of Helium-Neon (HNL), Copper vapor (CVL), Nitrogen (UVL) and Arsenic Gallium (AGL) lasers cause stimulation of processes of physiological and reparative regeneration in intact skin, and mucous membrane of stomach and duodenum, dermatome wounds and gastroduodenal ulcers. Structural bases of these effects are the acceleration of cell proliferation and differentiation and also the activation of intracellular structures and intensification of cell secretion. Regional influence of the pointed types of LILI on hepar in cirrhosis and hepatitis causes decreasing of the inflammatory and cirrhotic changes. After endo- and exo-vascular laser irradiations of blood the decreasing of the number of pathological forms of erythrocytes and the increasing of their catalase activity, are indicated. General (total) laser irradiation of the organism--laser shower, increases the bone marrow cells proliferation, especially myeloid series. It is accompanied with acceleration of their differentiation and migration in circulation. It was revealed, that HNL to a considerable extent influences the epithelial cells and CVL the connective tissue cells. UVL increases the amount of microorganisms on cell surfaces (membrane bound microorganisms). Regional irradiation of the LILI causes both direct and indirect influence of cells. Structural changes of bone marrow cells and gut mucous membrane cells indicate intersystemic interaction.

  11. Low-intensity laser irradiation use for oral and lip precancer treatment

    NASA Astrophysics Data System (ADS)

    Kunin, Anatoly A.; Podolskaya, Elana E.; Stepanov, Nicolay N.; Petrov, Anatoly; Erina, Stanislava V.; Pankova, Svetlana N.

    1996-09-01

    Precancer and background diseases of the oral mucosa and lips, such as lichen planus, chronic ulcers and fissures, meteorological heilit, lupus erythematosus, after radiation heilit were treated by low-intensity laser irradiation. Laser therapy of the over-mentioned diseases was combined with medicinal treatment. All the patients were selected and treated in the limits of dispensary system. THe choice of diagnostic methods were made according to each concrete nosological form. A great attention was paid to the goal- directly sanitation of the oral cavity and treatment of attended internal diseases. The etiological factors were revealed and statistically analyzed. The results received during our researches demonstrated high effectiveness of laser irradiation combined with medicinal therapy in the treatment of oral mucosa and lips precancer diseases.

  12. Explosive vaporization of a large transparent droplet irradiated by a high intensity laser.

    PubMed

    Zhang, J Z; Lam, J K; Wood, C F; Chu, B T; Chang, R K

    1987-11-15

    Shadowgraph studies of the explosive vaporization of a transparent water droplet after irradiation by a high intensity beam show that dielectric breakdown occurs within the droplet shadow face and generates a dense plasma, which absorbs the laser pulse. The convective forces expel the vapor from the droplet shadow face. We have deduced (1) the vapor propagation velocities, (2) the recoil velocity of the remaining droplet, and (3) the deformation rate of the illuminated face. Droplets are noted to eject fingerlike material from the surface facing the single laser-vaporized droplet when the asymmetrical vapor intercepts the neighboring droplets.

  13. Efficient generation of fusion neutrons from cryogenically cooled heteronuclear clusters irradiated by intense femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Lu, Haiyang; Li, Song; Xu, Yi; Guo, Xiaoyang; Leng, Yuxin; Liu, Jiansheng; Shen, Baifei; Li, Ruxin; Xu, Zhizhan

    2014-02-01

    We present experimental studies on the conversion efficiency of fusion neutrons generated from Coulomb explosion of cryogenically cooled heteronuclear deuterated methane (CD4) clusters irradiated by intense femtosecond laser pulses. A stronger nonlinear relationship between the cluster size and the stagnation temperature for CD4 clusters than that for monoatomic or diatomic clusters is revealed, resulting in marked increases in the average kinetic energy of deuterons and the fusion neutron yield. Finally, a significantly enhanced conversion efficiency of 1.9 × 107 neutrons/J of incident laser energy is achieved by lowering the stagnation temperature to 217 K under a backing pressure of 80 bars.

  14. Photoionization of monocrystalline CVD diamond irradiated with ultrashort intense laser pulse

    NASA Astrophysics Data System (ADS)

    Lagomarsino, Stefano; Sciortino, Silvio; Obreshkov, Boyan; Apostolova, Tzveta; Corsi, Chiara; Bellini, Marco; Berdermann, Eleni; Schmidt, Christian J.

    2016-02-01

    Direct laser writing of conductive paths in synthetic diamond is of interest for implementation in radiation detection and clinical dosimetry. Unraveling the microscopic processes involved in laser irradiation of diamond below and close to the graphitization threshold under the same conditions as the experimental procedure used to produce three-dimensional devices is necessary to tune the laser parameters to optimal results. To this purpose a transient currents technique has been used to measure laser-induced current signals in monocrystalline diamond detectors in a wide range of laser intensities and at different bias voltages. The current transients vs time and the overall charge collected have been compared with theoretical simulations of the carrier dynamics along the duration and after the conclusion of the 30 fs laser pulse. The generated charge has been derived from the collected charge by evaluation of the lifetime of the carriers. The plasma volume has also been evaluated by measuring the modified region. The theoretical simulation has been implemented in the framework of the empirical pseudopotential method extended to include time-dependent couplings of valence electrons to the radiation field. The simulation, in the low-intensity regime, I ˜1 TW /cm2 , predicts substantial deviation from the traditional multiphoton ionization, due to nonperturbative effects involving electrons from degenerate valence bands. For strong field with intensity of about 50 TW /cm2, nonadiabatic effects of electron-hole pair excitation become prominent with high carrier densities eventually causing the optical breakdown of diamond. The comparison of theoretical prediction with experimental data of laser-generated charge vs laser energy density yields a good quantitative agreement over six orders of magnitude. At the highest intensities the change of slope in the trend is explained taking into account the dependence of the optical parameters and the carrier mobility on plasma

  15. Size- and intensity-dependent photoelectron spectra from gas-phase gold nanoparticles irradiated by intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Powell, J.; Robatjazi, S. J.; Makhija, V.; Vajdi, A.; Li, X.; Malakar, Y.; Pearson, W. L.; Rudenko, A.; Sorensen, C.; Stierle, J.; Kling, M. F.

    2016-05-01

    Nanoparticles bridge the gap between atomic/molecular and bulk matter offering unique opportunities to study light interactions with complex systems, in particular, near-field enhancements and excitation of plasmons. Here we report on a systematic study of photoelectron emission from isolated gold nanoparticles irradiated by 800 nm, 25 fs laser pulses at 10-50 TW/ cm2 peak intensities. A combination of an aerodynamic lens nanoparticle injector, high-energy velocity-map imaging spectrometer and a high-speed, single-shot camera is employed to record shot by shot photoelectron emission patterns from individual particles. By sorting the recorded images according to the number of emitted electrons, we select the events from the regions of particular laser intensities within the laser focus, thus, essentially avoiding focal volume averaging. Using this approach, we study the intensity- and size-dependence of photoelectron energy and angular distributions for particle sizes ranging from 5 nm to 400 nm. This work is supported by NSF Award No. IIA-143049. JRML operations and personal are supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of BES, Office of Science, U. S. DOE.

  16. Photochemical mechanisms of biological action of low-intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Klebanov, Gennady I.; Poltanov, Evgeny A.

    2004-08-01

    Low-intensity laser irradiation (LILI) is effectively used in clinical practice but the mechanisms of its stimulating action are still far from being understood completely and considered in the scientific literature only hypothetically. The main effects of LILI proved both in clinics and in experiments are bactericidal effect, vasodilatation, improved microcirculation, formation and growth of new microvessels, acceleration of wound healing, relieving of pain syndrome. We put forward a free radical conception underlying these effects. In this paper the experimental evidences of this conception is considered.

  17. The effects of low-intensity laser irradiation on the fatigue induced by dysfunction of mitochondria

    NASA Astrophysics Data System (ADS)

    Xu, Xiao-Yang; Liu, Timon C.; Duan, Rui; Liu, Xiao-Guang

    2003-12-01

    Exercise-induced fatigue has long been an important field in sports medicine. The electron leak of mitochondrial respiratory chain during the ATP synthesis integrated with proton leak and O-.2 can decrease the efficiency of ATP synthesis in mitochondria. And the exercise-induced fatigue occur followed by the decrease of performance. If the dysfunction of mitochondria can be avoided, the fatigue during the exercise may be delayed and the performance may be enhanced. Indeed there are some kind of materials can partially prevent the decrease of ATP synthesis efficiency in mitochondria. But the side effects and safety of these materials is still needed to be studied. Low intensity laser can improve the mitochondria function. It is reasonable to consider that low intensity laser therapy may become the new and more effective way to delay or elimination the fatigue induced by dysfunction of mitochondria. Because the effect of laser irradiation may not be controlled exactly when study in vivo, we use electrical stimulation of C2C12 muscle cells in culture to define the effect of low intensity laser on the dysfunction of mitochondria, and to define the optimal laser intensity to prevent the decrease of ATP synthesis efficiency. Our study use the C2C12 muscle cells in culture to define some of the mechanisms involved in the contractile-induced changes of mitochondrial function firstly in sports medicine and may suggest a useful study way to other researchers. We also give a new way to delay or eliminating the fatigue induced by dysfunction of mitochondria without side effect.

  18. Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser

    NASA Astrophysics Data System (ADS)

    Borghesani, A. F.; Braggio, C.; Guarise, M.

    2016-06-01

    We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at 1064 nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO3), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.

  19. Properties of metals during the heating by intense laser irradiation using ab initio simulations

    NASA Astrophysics Data System (ADS)

    Holst, Bastian; Recoules, Vanina; Torrent, Marc; Mazevet, Stephane

    2011-10-01

    Ultrashort laser pulses irradiating a target heat the electrons to very high temperatures. In contrast, the ionic lattice is unaffected on the time scale of the laser pulse since the heat capacity of electrons is much smaller than that of the lattice. This non-equilibrium system can be described as a composition of two subsystems: one consisting of hot electrons and the other of an ionic lattice at low temperature. We studied the effect of this intense electronic excitations on the optical properties of gold using ab initio simulations. We additionally use ab initio linear response to compute the phonon spectrum and the electron-phonon coupling constant within Density Functional Theory for several electronic temperatures of few eV. LULI, Ecole Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau, France.

  20. Proton acceleration by irradiation of isolated spheres with an intense laser pulse

    NASA Astrophysics Data System (ADS)

    Ostermayr, T. M.; Haffa, D.; Hilz, P.; Pauw, V.; Allinger, K.; Bamberg, K.-U.; Böhl, P.; Bömer, C.; Bolton, P. R.; Deutschmann, F.; Ditmire, T.; Donovan, M. E.; Dyer, G.; Gaul, E.; Gordon, J.; Hegelich, B. M.; Kiefer, D.; Klier, C.; Kreuzer, C.; Martinez, M.; McCary, E.; Meadows, A. R.; Moschüring, N.; Rösch, T.; Ruhl, H.; Spinks, M.; Wagner, C.; Schreiber, J.

    2016-09-01

    We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2 -3 ×1020Wcm -2 . With a laser focal spot size of 10 μ m full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 μ m . Maximum proton energies of ˜25 MeV are achieved for targets matching the focal spot size of 10 μ m in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.

  1. The hematologic effects of low intensity 650 nm laser irradiation on hypercholesterolemia rabbits

    PubMed Central

    Wang, Hong; Deng, Juan; Tu, Wenjun; Zhang, Lin; Chen, Hongli; Wu, Xiaoguang; Li, Yingxin; Sha, Hong

    2016-01-01

    Purpose: To test the hematologic effects of low intensity 650 nm laser irradiation on hypercholesterolemia rabbits. Methods: Ten male big-eared rabbits were selected from hypercholesterolemia animal model-making and divided into model group and laser treatment groups. Five normal rabbits were selected as control group. Auricle root irradiation of 650 nm laser 100 mW in 30 min were applied on treatment group twice a day, treatment of 6 days in one week, 20 weeks course of treatment. Changes in blood lipid, microcirculation, rheological properties, and aggregation morphology of erythrocytes were observed every two weeks. Histopathological examination were performed in the end of experiments. Results: After 20 weeks’ treatment, triglyceride (TG), cholesterol (CHO), high density lipoprotein (HDL) and low density lipoprotein (LDL) of serum in hypercholesterolemia groups showed less changes in the first 4 weeks, butdifferent decreasing trends were shownin the next 16 weeks’ therapy. Erythrocytes aggregation of model groups showed rouleau state, while red blood cells in control group showed fine homodisperse, erythrocytes in treatment group performed better dispersion than model groups. Erythrocyte deformation index (DI) and blood flow value showed a statistic improvement in treatment group than control and model group (P<0.01). Value of DI in treatment group decreased after 18 weeks than values before therapy (P<0.01). Varying degrees of Aorta plaque formation was observed for individual difference in model and treatment groups, while no plaque was found in control group. Conclusions: Low energy laser improve microcirculation, rheological properties and blood lipid that might be related with erythrocytes aggregation and deformability. PMID:27347336

  2. Optimal ion acceleration from ultrathin foils irradiated by a profiled laser pulse of relativistic intensity

    SciTech Connect

    Andreev, A. A.; Steinke, S.; Sokollik, T.; Schnuerer, M.; Nickles, P. V.; Avetsiyan, S. Ter; Platonov, K. Yu.

    2009-01-15

    Recent investigations of relativistic laser plasmas have shown that the energy transfer from the laser field to the kinetic ion energy and therefore the attainable maximum energy of the ions increases when ultrathin targets are irradiated by laser pulse without prepulse. In this paper, the influence of the target thickness and laser pulse contrast on the energy of the accelerated ions has been studied theoretically as well as experimentally. An optimum target was searched if a real laser pulse with a certain prepulse irradiates the target.

  3. Melt dynamics of aluminum irradiated with ultrafast laser radiation at large intensities

    SciTech Connect

    Mingareev, Ilya; Horn, Alexander

    2009-07-01

    Ablation of bulk aluminum has been investigated in situ using ultrafast laser radiation produced by chirped-pulse amplification technique (t{sub p}=80 fs, lambda=800 nm). Melt dynamics and the contribution of the amplified spontaneous emission (ASE) to the ablation have been studied experimentally and numerically for laser fluences well above ablation threshold (F < or approx. 10{sup 3}xF{sub thr}). Using transient quantitative phase microscopy (TQPm), dimensions and volume of ejected vapor, melt droplets, and liquid jets has been investigated. Computational analysis of the optical phase images has been used to determine the total volume of ejected material. A series of time-resolved phase images of vaporized material and/or melt, which are induced by n=1.8 pulses on an aluminum target, are obtained by means of TQPm up to temporal delay tau=1.65 mus after irradiation. Increase in material ejection rate is observed at delays tauapprox =300 ns and tauapprox =1.1 mus after the incident pulse. For large irradiation intensities a considerable contribution of ASE to ablation dynamics has been detected. Ex situ measurements of the ablated material by means of white-light interferometry and scanning electron microscopy provides corresponding factual removed volumes and highlight the pulse-to-pulse morphology changes.

  4. Profiling of genes central to human mitochondrial energy metabolism following low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Houreld, Nicolette N.; Masha, Roland; Abrahamse, Heidi

    2012-09-01

    Background: Wound healing involves three overlapping phases: inflammation, granulation and tissue remodelling. If this process is disrupted, delayed wound healing ensues, a common complication seen in diabetic patients. Low intensity laser irradiation (LILI) has been found to promote healing in such patients. However, the exact mechanisms of action are poorly understood. Purpose: This study aimed to profile the expression of key genes involved in mitochondrial respiration. Materials and Methods: Diabetic wounded fibroblast cells were exposed to a wavelength of 660 nm and a fluence of 5 J/cm2 and incubated for 30 min. Total RNA was isolated and 1 μg reverse transcribed into cDNA which was used for real-time polymerase chain reaction (PCR) array analysis. The array contained genes important for each of the mitochondrial complexes involved in the electron transport chain (ETC). Adenosine triphosphate (ATP) levels were also determined post-irradiation by ATP luminescence. Results: Genes involved in complex IV (cytochrome c oxidase), COX6B2 and COX6C, and PPA1 which is involved in complex V (ATP synthase) were significantly up-regulated. There was a significant increase in ATP levels in diabetic wounded cells post-irradiation. Discussion and Conclusion: LILI stimulates the ETC at a transcriptional level, resulting in an increase in ATP. This study helps understand the mechanisms of LILI in diabetic wound healing, and gives information on activation of genes in response to LILI.

  5. Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

    DOE PAGES

    Bang, W.

    2015-07-02

    Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

  6. Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

    SciTech Connect

    Bang, W.

    2015-07-02

    Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.

  7. Generation and Transport of Fast Electrons in Laser Irradiated Targets at Relativistic Intensities

    NASA Astrophysics Data System (ADS)

    Amiranoff, F.; Baton, S. D.; Gremillet, L.; Guilbaud, O.; Koenig, M.; Martinolli, E.; Santos, J. J.; Le Gloahec, M. Rabec; Rousseaux, C.; Hall, T.

    2002-10-01

    The transport of relativistic electrons in solid targets irradiated by a short laser pulse at relativistic intensities has been studied both experimentally and numerically. A Monte-Carlo collision code takes into account individual collisions with the ions and electrons in the target. A 3D-hybrid code takes into account these collisions as well as the generation of electric and magnetic fields and the self-consistent motion of the electrons in these fields. It predicts a magnetic guiding of a fraction of the fast electron current over long distances and a localized heating of the material along the propagation axis. In experiments performed at LULI on the 100 TW laser facility, several diagnostics have been implemented to diagnose the geometry of the fast electron transport and the target heating. The typical conditions were: E1 less-than-or-equal 20 J, lambda = 1 mum, tau approximately 300 fs, I approximately 1018-5.1019W/cm2. The results indicate a modest heating of the target (typically 20-40 eV over 20 mum to 50 mum), consistent with an acceleration of the electrons inside a wide aperture cone along the laser axis.

  8. Theory of absorption rate of carriers in fused silica under intense laser irradiation

    SciTech Connect

    Deng, Hongxiang; Xiang, Xia; Zheng, WG; Yuan, XD; Wu, SY; Jiang, XD; Gao, Fei; Zu, Xiaotao T.; Sun, Kai

    2010-11-15

    A quantum non-perturbation theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the Non-perturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on TW / cm2 intensity laser.

  9. Effects of low intensity laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes

    NASA Astrophysics Data System (ADS)

    Xiong, Guoxin; Xiong, Leilei; Li, Xinzhong

    2016-09-01

    To investigate the effects of low intensity semiconductor laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes, a method using a high-fat diet and low-dose intraperitoneal injections of streptozotocin established a type 2 diabetes mellitus rat model. Model rats were randomly divided into a laser acupoint irradiation group, rosiglitazone control group, and placebo group; each group had 10 rats. In addition, 10 normal male rats were selected for the normal control group. The Housanli, Neiting and Yishu acupoints of the rats in the laser acupoint irradiation group were irradiated with a 10 mW semiconductor laser; each point was irradiated for 15 min, once every 2 d over 28 d, for a total of 14 episodes of irradiation. The rosiglitazone group rats were given rosiglitazone (0.2 mg kg-1) intragastrically; the placebo group rats were given 0.9% brine (0.2 mg kg-1) intragastrically, once daily, for four consecutive weeks. The change of fasting blood glucose was determined before and after each treatment. The islet beta-cell apoptosis was determined. The islet beta-cell apoptosis rates of the laser acupoint irradiation group and the rosiglitazone group were significantly lower than the rate of the placebo group. Even though the rate was lower in the laser acupoint irradiation group than in the rosiglitazone group, there was no significant difference between them. It is shown that acupoint irradiation with a semiconductor laser can effectively inhibit islet beta-cell apoptosis in rats with type 2 diabetes.

  10. Effects of low intensity laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes

    NASA Astrophysics Data System (ADS)

    Xiong, Guoxin; Xiong, Leilei; Li, Xinzhong

    2016-09-01

    To investigate the effects of low intensity semiconductor laser acupoint irradiation on inhibiting islet beta-cell apoptosis in rats with type 2 diabetes, a method using a high-fat diet and low-dose intraperitoneal injections of streptozotocin established a type 2 diabetes mellitus rat model. Model rats were randomly divided into a laser acupoint irradiation group, rosiglitazone control group, and placebo group; each group had 10 rats. In addition, 10 normal male rats were selected for the normal control group. The Housanli, Neiting and Yishu acupoints of the rats in the laser acupoint irradiation group were irradiated with a 10 mW semiconductor laser; each point was irradiated for 15 min, once every 2 d over 28 d, for a total of 14 episodes of irradiation. The rosiglitazone group rats were given rosiglitazone (0.2 mg kg‑1) intragastrically; the placebo group rats were given 0.9% brine (0.2 mg kg‑1) intragastrically, once daily, for four consecutive weeks. The change of fasting blood glucose was determined before and after each treatment. The islet beta-cell apoptosis was determined. The islet beta-cell apoptosis rates of the laser acupoint irradiation group and the rosiglitazone group were significantly lower than the rate of the placebo group. Even though the rate was lower in the laser acupoint irradiation group than in the rosiglitazone group, there was no significant difference between them. It is shown that acupoint irradiation with a semiconductor laser can effectively inhibit islet beta-cell apoptosis in rats with type 2 diabetes.

  11. Biochemical responses of isolated lung CSCs after application of low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, Heidi; Crous, Anine

    2016-03-01

    Studies have shown that using high fluences of Low Intensity Laser Irradiation (HF-LILI) produce apoptotic effects on normal and neoplastic cells. This study aimed to determine whether HF-LILI induce cell death in lung CSCs. Lung CSCs were isolated using the stem cell marker CD 133, characterized using flow cytometry, and applied in experiments which included treatment with LILI at wavelengths of 636, 825 and 1060 nm with fluences ranging from 5 J/cm2 to 40 J/cm2. Viability and proliferation studies, using Alamar blue assay and adenosine triphosphate luminescence (ATP), indicated an increase when treating lung CSCs with low fluences of 5 - 20 J/cm2 and a decrease in viability and proliferation as well as an increase in apoptosis when applying a fluence of 40 J/cm2 indicated by flow cytometry using Annexin V and propidium iodide (PI) dyes. Results indicate that LILI, when treating lung CSCs, can induce either a bio-stimulatory or bio-inhibitory effect depending on the wavelength and fluence used. This study indicated successful apoptotic induction of lung CSCs. Future experiments should be able to conclude the exact mechanism behind HF-LILI, which can be used in the targeted treatments of CSC elimination, implementing HF-LILI in the same manner as PDT in the absence of a photosensitizer.

  12. Nonlocal electron transport in the presence of high-intensity laser irradiation

    SciTech Connect

    Epperlein, E.M.; Short, R.W. )

    1994-08-01

    We investigate electron transport in a plasma heated by spatially modulated laser irradiation. When the heating rate is greater than the electron-electron collision rate, the thermal conductivity is reduced by a factor of 3 to 4 from the Spitzer-Haerm [Phys. Rev. 89, 977 (1953)] value for [ital K][lambda][sub [ital e

  13. Ablation and transmission of thin solid targets irradiated by intense extreme ultraviolet laser radiation

    NASA Astrophysics Data System (ADS)

    Aslanyan, V.; Kuznetsov, I.; Bravo, H.; Woolston, M. R.; Rossall, A. K.; Menoni, C. S.; Rocca, J. J.; Tallents, G. J.

    2016-09-01

    The interaction of an extreme ultraviolet (EUV) laser beam with a parylene foil was studied by experiments and simulation. A single EUV laser pulse of nanosecond duration focused to an intensity of 3 × 1010 W cm-2 perforated micrometer thick targets. The same laser pulse was simultaneously used to diagnose the interaction by a transmission measurement. A combination of 2-dimensional radiation-hydrodynamic and diffraction calculations was used to model the ablation, leading to good agreement with experiment. This theoretical approach allows predictive modelling of the interaction with matter of intense EUV beams over a broad range of parameters.

  14. LASER METHODS IN MEDICINE: Light absorption in blood during low-intensity laser irradiation of skin

    NASA Astrophysics Data System (ADS)

    Barun, V. V.; Ivanov, A. P.

    2010-06-01

    An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis.

  15. A first principles study of the lattice stability of diamond-structure semiconductors under intense laser irradiation

    SciTech Connect

    Feng Shiquan; Zhao Jianling; Cheng Xinlu

    2013-01-14

    Using density-functional linear-response theory, we calculated the phonon dispersion curves for the diamond structural elemental semiconductors of Ge, C and zinc-blende structure semiconductors of GaAs, InSb at different electronic temperatures. We found that the transverse-acoustic phonon frequencies of C and Ge become imaginary as the electron temperature is elevated, which means the lattices of C and Ge become unstable under intense laser irradiation. These results are very similar with previous theoretical and experimental results for Si. For GaAs and InSb, not only can be obtained the similar results for their transverse-acoustic modes, but also their LO-TO splitting gradually decreases as the electronic temperature is increased. It means that the electronic excitation weakens the strength of the ionicity of ionic crystal under intense laser irradiation.

  16. Energy absorption of free rare gas clusters irradiated by intense VUV pulses of a free electron laser

    NASA Astrophysics Data System (ADS)

    Schulz, J.; Wabnitz, H.; Laarmann, T.; Gürtler, P.; Laasch, W.; Swiderski, A.; Möller, Th.; de Castro, A. R. B.

    2003-07-01

    As one of the first experiments at the free electron laser of the TESLA Test Facility (TTF) the Coulomb explosion of Xenon clusters irradiated with high intensity pulses at a wavelength of 98 nm has been observed. Classical trajectory calculations have been performed in order to illuminate the energy absorption process. Comparison with typical parameters in the infrared regime shows that above barrier ionization is suppressed due to the fast oscillating field and thermionic ionization prevails.

  17. Terahertz radiation from a wire target irradiated by an ultra-intense laser pulse

    SciTech Connect

    Li Zhichao; Zheng Jian

    2007-05-15

    When an ultra-intense laser pulse impacts the tip of a wire whose other end is grounded, a strong return current can be driven along the wire because some energetic electrons generated in ultra-intense laser matter interaction can escape from the target and an electric field builds up. The wire then behaves like a current-carrying antenna that can emit electromagnetic radiations. If the duration of the driving pulse is several tens of femtoseconds, the radiation spectrum reaches a maximum at terahertz region, and the radiation power per solid angle could be as high as 10{sup 9} W/rad.

  18. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Xun; Ma, Yan-Yun; Zhao, Jun; Yu, Tong-Pu; Yang, Xiao-Hu; Gan, Long-Fei; Zhang, Guo-Bo; Yan, Jian-Feng; Zhuo, Hong-Bin; Liu, Jin-Jin; Zhao, Yuan; Kawata, Shigeo

    2015-10-01

    By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 1023 W/cm2, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ˜15° with an effective temperature of ˜674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (˜13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.

  19. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

    SciTech Connect

    Liu, Jian-Xun; Ma, Yan-Yun; Zhao, Jun; Yu, Tong-Pu Yang, Xiao-Hu; Gan, Long-Fei; Zhang, Guo-Bo; Yan, Jian-Feng; Zhuo, Hong-Bin; Liu, Jin-Jin; Zhao, Yuan; Kawata, Shigeo

    2015-10-15

    By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 10{sup 23 }W/cm{sup 2}, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >10{sup 15} is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ∼15° with an effective temperature of ∼674 MeV. When the laser intensity is doubled, both the positron flux (>10{sup 16}) and temperature (963 MeV) increase, while the divergence angle gets smaller (∼13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.

  20. Observation of neutron spectrum from deuterated plastic irradiated by 100 picosecond and sub-picosecond ultra-intense laser.

    NASA Astrophysics Data System (ADS)

    Izumi, N.; Miyoshi, K.; Takahashi, K.; Habara, H.; Kodama, R.; Sentoku, S.; Fujita, H.; Kitagawa, Y.; Katou, Y.; Mima, K.; Tanaka, K. A.

    1998-11-01

    For understanding of the fundamental physics of the fast ignition, it is crucial to investigate the fast ion production in a high density plasma irradiated by an ultra-intense laser. The energy spectrum of the neutrons produced in the deuterated target reflects the energy spectrum of fast deuterons accelerated in the interacting region. Due to high penetration ability of fast neutron, the neutron spectra directly bring out the information of the hot ions from the high density plasma. We have observed 10^6 of the DD neutrons produced in a deuterated polystyrene (C8D8)x target irradiated by the 500-fs intense laser (up to 10^19 W/cm^2). The fast neutron spectra were measured by multi-channel time-of-flight neutron spectrometer (MANDALA) at the GEKKO XII laser facility of Osaka University. The spectrometer has two sets of 421 channel detector arrays which were located at 90 and 54.7 degrees with respect to the irradiation axis. The observed spectral width of DD neutrons were 1.35 MeV in full width of half maximum. This spectrum result from the fusion reaction created by accelerated ions which have energy about 300 keV. We report the details of the experimental results and the quantitative analysis using particle in cell code.

  1. Enhancement of Efficiency of XUV Generation in Atomic Gases Irradiated by Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Stremoukhov, S. Y.; Shoutova, O. A.

    We present the results of the theoretical study of the high-order harmonic generation (HHG) in atomic gases. It is shown that the photoemission spectra exhibit unusual behavior when the laser field strength approaches near-atomic values. In subatomic field strength the cut-off frequency increases linearly with laser pulse intensity. However, when the field strength approaches near-atomic region firstly cut-off frequency slows down and then saturates. To interpret such kind of photoemission spectrum behavior we have proposed the light-atom interaction theory based on the use of eigenfunctions of boundary value problem for "an atom in the external field" instead of the traditional basis of the "free atom" eigenfunctions.

  2. Spectral analysis of x-ray emission created by intense laser irradiation of copper materials

    SciTech Connect

    Huntington, C. M.; Kuranz, C. C.; Drake, R. P.; Malamud, G.; Park, H.-S.; Maddox, B. R.

    2012-10-15

    We have measured the x-ray emission, primarily from K{sub {alpha}},K{sub {beta}}, and He{sub {alpha}} lines, of elemental copper foil and 'foam' targets irradiated with a mid-10{sup 16} W/cm{sup 2} laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He{sub {alpha}} line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K{sub {alpha}} transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K{sub {beta}} radiation, confirming a lower bulk temperature in the higher volume sample.

  3. Intravascular low-intensity He-Ne laser irradiation therapy on idiopathic edema

    NASA Astrophysics Data System (ADS)

    Gao, Yunqing; Liu, T. C.; Tang, Xiang-Jun

    1998-11-01

    194 patients with psoriasis were treated by intravascular low level laser irradiation combined with Vit C 2.0g iv and O2 inhale to the nose. An hour once a day, for 5-40 times, and 13.06 times in average, ten times with 4-7 days intervals. The results: cured 23 cases, good effected 61 cases, improved 110 cases, relapsed 10 cases. Curative effect was related to treatment times, cured and good effected 5 times 12.5 percent, 10 times 31 percent, 15 times 94 percent. A matched control group in 17 patients was treated by drug. The results: good effected 1 case, improved 13 cases, not effected 3 cases.

  4. Ion acceleration in shell cylinders irradiated by a short intense laser pulse

    SciTech Connect

    Andreev, A.; Platonov, K.; Sharma, A.; Murakami, M.

    2015-09-15

    The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

  5. Ion acceleration in shell cylinders irradiated by a short intense laser pulse

    NASA Astrophysics Data System (ADS)

    Andreev, A.; Platonov, K.; Sharma, A.; Murakami, M.

    2015-09-01

    The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

  6. Effects of laser-plasma interactions on terahertz radiation from solid targets irradiated by ultrashort intense laser pulses

    SciTech Connect

    Li Chun; Zhou Mulin; Ding Wenjun; Du Fei; Liu Feng; Li Yutong; Wang Weimin; Ma Jinglong; Chen Liming; Lu Xin; Dong Quanli; Wang Zhaohua; Wei Zhiyi; Sheng Zhengming; Zhang Jie; Lou Zheng; Shi Shengcai

    2011-09-15

    Interactions of 100-fs laser pulses with solid targets at intensities of 10{sup 18} W/cm{sup 2} and resultant terahertz (THz) radiation are studied under different laser contrast ratio conditions. THz emission is measured in the specular reflection direction, which appears to decrease as the laser contrast ratio varies from 10{sup -8} to 10{sup -6}. Correspondingly, the frequency spectra of the reflected light are observed changing from second harmonic dominant, three-halves harmonic dominant, to vanishing of both harmonics. Two-dimensional particle-in-cell simulation also suggests that this observation is correlated with the plasma density scale length change. The results demonstrate that the THz emission is closely related to the laser-plasma interaction processes. The emission is strong when resonance absorption is a key feature of the interaction, and becomes much weaker when parametric instabilities dominate.

  7. Enhanced electron injection in laser-driven bubble acceleration by ultra-intense laser irradiating foil-gas targets

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Bo; Ma, Yan-Yun; Xu, Han; Hafz, Nasr A. M.; Yang, Xiao-Hu; Chen, Min; Yu, Tong-Pu; Zou, De-Bin; Liu, Jian-Xun; Yan, Jian-Feng; Zhuo, Hong-Bin; Gan, Long-Fei; Tian, Li-Chao; Shao, Fu-Qiu; Yin, Yan; Kawata, S.

    2015-08-01

    A scheme for enhancing the electron injection charge in a laser-driven bubble acceleration is proposed. In this scheme, a thin foil target is placed in front of a gas target. Upon interaction with an ultra-intense laser pulse, the foil emits electrons with large longitudinal momenta, allowing them to be trapped into the transmitted shaped laser-excited bubble in the gaseous plasma target. Two-dimensional particle-in-cell simulation is used to demonstrate this scheme, and an electron beam with a total electron number of 4.21 × 10 8 μ m - 1 can be produced, which is twice the number of electrons produced without the foil. Such scheme may be widely used for applications that require high electron yields such as positron and gamma ray generation from relativistic electron beams interacting with solid targets.

  8. Dynamics and structure of self-generated magnetics fields on solids following high contrast, high intensity laser irradiation

    SciTech Connect

    Albertazzi, B.; Chen, S. N.; Fuchs, J.; Antici, P.; Böker, J.; Swantusch, M.; Willi, O.; Borghesi, M.; Breil, J.; Feugeas, J. L.; Nicolaï, Ph.; Tikhonchuk, V. T.; D'Humières, E.; Dervieux, V.; Nakatsutsumi, M.; Romagnagni, L.; Lancia, L.; Shepherd, R.; Sentoku, Y.; Starodubtsev, M.; and others

    2015-12-15

    The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 10{sup 19 }W cm{sup −2}) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10–20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8–10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.

  9. SPECT study of low intensity He-Ne laser intravascular irradiation therapy for brain infarction

    NASA Astrophysics Data System (ADS)

    Xiao, Xue-Chang; Dong, Jia-Zheng; Chu, Xiao-Fan; Jia, Shao-Wei; Liu, Timon C.; Jiao, Jian-Ling; Zheng, Xi-Yuan; Zhou, Ci-Xiong

    2003-12-01

    We used single photon emission computed tomography (SPECT) in brain perfusion imaging to study the changes of regional cerebral blood flow (rCBF) and cerebral function in brain infarction patients treated with intravascular laser irradiation of blood (ILIB). 17 of 35 patients with brain infarction were admitted to be treated by ILIB on the base of standard drug therapy, and SPECT brain perfusion imaging was performed before and after ILIB therapy with self-comparison. The results were analyzed in quantity with brain blood flow function change rate (BFCR%) model. Effect of ILIB during the therapy process in the other 18 patients were also observed. In the 18 patients, SPECT indicated an improvement of rCBF (both in focus and in total brain) and cerebral function after a 30 min-ILIB therapy. And the 17 patients showed an enhancement of total brain rCBF and cerebral function after ILIB therapy in comparison with that before, especially for the focus side of the brain. The enhancement for focus itself was extremely obvious with a higher significant difference (P<0.0001). The mirror regions had no significant change (P>0.05). BFCR% of foci was prominently higher than that of mirror regions (P<0.0001). In conclusion, the ILIB therapy can improve rCBF and cerebral function and activate brain cells of patients with brain infarction. The results denote new evidence of ILIB therapy for those patients with cerebral ischemia.

  10. Effect of He-Ne laser irradiation and low-intensity millimeter waves on transplanted tumor growth

    NASA Astrophysics Data System (ADS)

    Brill, Gregory E.; Panina, Nadezda P.

    1995-01-01

    In experiments on white rats the influence of He-Ne laser radiation ((lambda) -- 632.8 nm, power density -- 1.5 mW/cm2) and electromagnetic field of extremely high frequency (42.0 - 43.3 GHz, 1 mW/cm2) on transplantability and growth of fibroadenomas of mammary glands, and influence of low power laser irradiation on transplantability and growth of Walker carcinosarcoma were investigated. Skin at the site of future transplantation underwent irradiation. He-Ne laser and EHF-radiation were stated to change properties of tissue accepting tumor cells. A single laser irradiation of the inoculation site of Walker carcinosarcoma cells produced no effect on tumor transplantability, but increased the average life span of animals. Laser and EHF irradiation increase the transplantability of fibroadeonomas but depress growth and rate of multiplication of tumor cells.

  11. Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers.

    PubMed

    Moura-Netto, Cacio; Mello-Moura, Anna Carolina Volpi; Palo, Renato Miotto; Prokopowitsch, Igor; Pameijer, Cornelis H; Marques, Marcia Martins

    2015-03-01

    This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n = 168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz); diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p < 0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p < 0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

  12. Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers

    NASA Astrophysics Data System (ADS)

    Moura-Netto, Cacio; Mello-Moura, Anna Carolina Volpi; Palo, Renato Miotto; Prokopowitsch, Igor; Pameijer, Cornelis H.; Marques, Marcia Martins

    2015-03-01

    This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n=168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p<0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p<0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

  13. Creating astrophysically relevant jets from locally heated targets irradiated by a high-intensity laser

    NASA Astrophysics Data System (ADS)

    Schmitz, Holger; Robinson, Alex

    2014-10-01

    The formation mechanism of jets in the vicinity of young stellar objects has been the subject of investigations for many years. It is thought that jets are formed by the stellar wind interacting with an inhomogeneous plasma. A density gradient from the equator to the poles causes the wind to encounter the inward facing reverse shock at an oblique angle. The wind is focused into a conical flow towards the poles where it emerges as a narrow jet. This mechanism is inaccessible to direct observations due to the small scales on which it operates. Using high intensity lasers to produce comparable jets offers a way to investigate the mechanisms in the laboratory. Previous investigations of jets in the laboratory have directly generated the conical flow, skipping the first part of the formation mechanism. We present simulations of a novel method of generating jets in the laboratory by using magnetic fields generated by resistivity gradients to control the fast electron flow. The return current selectively heats a small region inside the target which drives a blast wave into the low density region behind the target. A conical high density shell focuses the outflow into a narrow jet. We find jets with aspect ratios of over 15 and Mach numbers between 2.5 and 4.3. This work is funded by the European Research Council, Grant STRUCMAGFAST.

  14. Rayleigh scattering correlation spectroscopy on diffusion dynamics of nanoparticles under intense laser irradiation

    NASA Astrophysics Data System (ADS)

    Hee, Ping-Yu; Uwada, Takayuki; Okano, Kazunori; Miura, Atsushi; Masuhara, Hiroshi

    2013-09-01

    Rayleigh scattering correlation microspectroscopy is developed and applied to study diffusion dynamics of some nanospheres in water. It was clearly found that the diffusion constant of gold nanoparticles decreased with increasing excitation laser power at the excitation wavelength of higher absorption cross section. This behavior was explained in terms of a coupling between laser trapping by the scattering excitation laser itself and laser heating of the particle. In the case of non-absorbing nanospheres such as silica and polystyrene, the excitation power dependence can be ascribed only to the laser trapping. Experimental setup is introduced, theoretical formulation is described, and future development of this measurement is considered.

  15. Characteristic x-ray emission from undermines plasmas irradiated by ultra-intense lasers

    SciTech Connect

    Niemann, Christoph

    2012-05-05

    Between FY09 and FY11 we have conducted more than a dozen three-week experimental campaigns at high-power laser facilities around the world to investigate laser-channeling through x-ray and optical imaging and the conversion from laser-energy to xrays. We have performed simultaneous two-wavelength x-ray imaging (K-alpha and He-alpha) to distinguish the hot-plasma region (hot-spot) from the laser-produced electrons (K-alpha). In addition, we have initiated a new collaboration with SNL and have performed first shots on the 100 TW beamlet chamber to commission a fast x-ray streak camera to be used to investigate the temporal evolution of our K-alpha sources. We also collaborated on campaigns at the Rutherford Appleton Laboratory (UK) and the LANL Trident laser to employ laser produced x-ray sources for Thomson scattering off dense matter.

  16. Effective post-acceleration of ion bunches in foils irradiated by ultra-intense laser pulses

    SciTech Connect

    Andreev, A. A.; Nickles, P. V.; Platonov, K. Yu

    2014-08-15

    Two-step laser acceleration of protons with two foils and two laser pulses is modelled and optimized. It is shown that a nearly mono-energetic distribution of proton bunches can be realized by a suitable parameter choice. Two-step acceleration schemes make it possible to obtain both higher efficiency and energy as compared to the acceleration with only one laser pulse of an energy equal to the sum of the energy of the two pulses. With the aid of our analytical model, the optimal distance between the two targets, the delay between the two laser pulses, and the parameters of the laser pulses are determined. Estimates and results of the modelling are proven with 2D PIC simulations of the acceleration of proton bunches moving through the second target.

  17. Hot electron and x-ray production from intense laser irradiation of wavelength-scale polystyrene spheres

    SciTech Connect

    Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Landry, J.; Bansal, G.; Bernstein, A.; Donnelly, T. D.; Karmakar, A.; Pukhov, A.; Ditmire, T.

    2007-06-15

    Hot electron and x-ray production from solid targets coated with polystyrene-spheres which are irradiated with high-contrast, 100 fs, 400 nm light pulses at intensity up to 2x10{sup 17} W/cm{sup 2} have been studied. The peak hard x-ray signal from uncoated fused silica targets is an order of magnitude smaller than the signal from targets coated with submicron sized spheres. The temperature of the x-rays in the case of sphere-coated targets is twice as hot as that of uncoated glass. A sphere-size scan of the x-ray yield and observation of a peak in both the x-ray production and temperature at a sphere diameter of 0.26 {mu}m, indicate that these results are consistent with Mie enhancements of the laser field at the sphere surface and multipass stochastic heating of the hot electrons in the oscillating laser field. These results also match well with particle-in-cell simulations of the interaction.

  18. Hybrid ion acceleration with ultrathin composite foils irradiated by high intensity circularly-polarized laser light

    SciTech Connect

    Andreev, A. A.; Steinke, S.; Schnuerer, M.; Sokollik, T.; Sandner, W.; Henig, A.; Nickles, P. V.; Platonov, K. Y.

    2010-12-15

    A complete analytical description of ion acceleration in the laser radiation-pressure regime is presented. The combined effects of hot electron and light-pressure phenomena are used to qualitatively and quantitatively describe most recent experimental results in this regime. An essential part of the developed model is exhibited in the calculation of nonlinear laser light reflection and transmission properties, as well as in the spectral characterization of the laser light after interaction. The validity of the analytical model is supported by recent experimental results and by particle-in-cell simulations.

  19. Light absorption in blood during low-intensity laser irradiation of skin

    SciTech Connect

    Barun, V V; Ivanov, A P

    2010-06-23

    An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis. (laser methods in medicine)

  20. Temperature changes on the root surfaces of mandibular incisors after an 810-nm high-intensity intracanal diode laser irradiation

    NASA Astrophysics Data System (ADS)

    da Fonseca Alvarez, Andrea; Moura-Netto, Cacio; Daliberto Frugoli, Alexandre; Fernando, Casemiro; Correa Aranha, Ana Cecilia; Davidowicz, Harry

    2012-01-01

    Temperature changes caused by laser irradiation can promote damage to the surrounding dental tissues. In this study, we evaluated the temperature changes of recently extracted human mandibular incisors during intracanal irradiation with an 810-nm diode laser at different settings. Fifty mandibular incisors were enlarged up to an apical size of ISO No. 40 file. After the final rinse with 17% ethylenediaminetetraacetic acid, 0.2% lauryl sodium sulfate biologic detergent, and sterile water, samples were irradiated with circular movements from apex to crown through five different settings of output power (1.5, 2.0, 2.5, 3.0, and 3.5 W) in continuous mode. The temperature changes were measured on both sides of the apical and middle root thirds using two thermopar devices. A temperature increase of 7 °C was considered acceptable as a safe threshold when applying the diode laser. Results: The results showed that only 3.5-W output power increased the outer surface temperature above the critical value. Conclusion: The recommended output power can be stipulated as equal to or less than 3 W to avoid overheating during diode laser irradiation on thin dentin walls.

  1. Specific features of microheterogeneous plasma produced by irradiation of a polymer aerogel target with an intense 500-ps-long laser pulse

    SciTech Connect

    Borisenko, N. G.; Merkul’ev, Yu. A.; Orekhov, A. S.; Chaurasia, S.; Tripathi, S.; Munda, D. S.; Dhareshwar, L. J.; Pimenov, V. G.; Sheveleva, E. E.

    2013-08-15

    The properties of microheterogeneous plasma produced by irradiation of a polymer aerogel target with an intense (10{sup 14} W/cm{sup 3}) short (0.5 ps) 1.064-μm laser pulse were studied. It is found that, even at plasma densities exceeding the critical density, a small fraction of the incident laser radiation penetrates through the plasma in which the processes of density and temperature equalization still take place. The intensification (as compared to plasmas produced from denser foams and solid films) of transport processes in such plasma along and across the laser beam can be caused by the initial microheterogeneity of the solid target. The replacement of a small (10% by mass) part of the polymer with copper nanoparticles leads to a nearly twofold increase in the intensity of the plasma X-ray emission.

  2. Fast ion acceleration from thin foils irradiated by ultra-high intensity, ultra-high contrast laser pulses

    SciTech Connect

    Prasad, R.; Ter-Avetisyan, S.; Doria, D.; Quinn, K. E.; Romagnani, L.; Zepf, M.; Borghesi, M.; Andreev, A. A.; Brenner, C. M.; Gallegos, P.; Carroll, D. C.; McKenna, P.; Tresca, O.; Dover, N. P.; Najmudin, Z.; Palmer, C. A. J.; Neely, D.; Green, J. S.; Foster, P. S.; Schreiber, J.; and others

    2011-09-19

    Ion acceleration resulting from the interaction of ultra-high intensity (2 x 10{sup 20 }W/cm{sup 2}) and ultra-high contrast ({approx}10{sup 10}) laser pulses with 0.05-10 {mu}m thick Al foils at normal (0 deg.) and 35 deg. laser incidence is investigated. When decreasing the target thickness from 10 {mu}m down to 0.05 {mu}m, the accelerated ions become less divergent and the ion flux increases, particularly at normal (0 deg.) laser incidence on the target. A laser energy conversion into protons of {approx}6.5% is estimated at 35 deg. laser incidence. Experimental results are in reasonable agreement with theoretical estimates and can be a benchmark for further theoretical and computational work.

  3. Effect of low intensity helium-neon (HeNe) laser irradiation on experimental paracoccidioidomycotic wound healing dynamics.

    PubMed

    Ferreira, Maria Carolina; Gameiro, Jacy; Nagib, Patrícia Resende Alo; Brito, Vânia Nieto; Vasconcellos, Elza da Costa Cruz; Verinaud, Liana

    2009-01-01

    The effect of HeNe laser on the extracellular matrix deposition, chemokine expression and angiogenesis in experimental paracoccidioidomycotic lesions was investigated. At days 7, 8 and 9 postinfection the wound of each animal was treated with a 632.8 nm HeNe laser at a dose of 3 J cm(-2). At day 10 postinfection, the wounds were examined by using histologic and immunohistochemical methods. Results revealed that laser-treated lesions were lesser extensive than untreated ones, and composed mainly by macrophages and lymphocytes. High IL-1beta expression was shown in the untreated group whereas in laser-treated animals the expression was scarce. On the other hand, the expression of CXCL-10 was found to be reduced in untreated animals and quite intensive and well distributed in the laser-treated ones. Also, untreated lesions presented vascular endothelial growth factor (VEGF) in a small area near the center of the lesion and high immunoreactivity for hypoxia-inducible factor-1 (HIF-1), whereas laser-treated lesions expressed VEGF surrounding blood vessels and little immunoreactivity for HIF-1. Laser-treated lesions presented much more reticular fibers and collagen deposition when compared with the untreated lesion. Our results show that laser was efficient in minimizing the local effects observed in paracoccidioidomycosis and can be an efficient tool in the treatment of this infection, accelerating the healing process. PMID:18764901

  4. Nuclear Fusion In Gases Of Deuterium Clusters And Hot Electron Generation In Droplet Sprays Under Irradiation With An Intense Femtosecond Laser

    SciTech Connect

    T. Ditmire; Zweiback, J; Cowan, T E; Hays, G; Wharton, K B; Crane, J K; Wilks, S C; Smith, R A; Donnelly, T D; Rust, M; Weiner, I; Allen, M

    2001-07-18

    In conclusion, we have observed the production of 2.45 MeV deuterium fusion neutrons when a gas of deuterium clusters is irradiated with a 120 mJ, 35 fs laser pulse. When the focal position is optimized, we have observed as many as 10{sup 4} neutrons per laser shot. This yield is consistent with some simple estimates for the fusion yield. We also find that the fusion yield is a sensitive function of the deuterium cluster size in the target jet, a consequence of the Coulomb explosion origin of the fast deuterons. We also find that the neutron pulse duration is fast, with a characteristic burn time of well under 1 ns. This experiment may represent a means for producing a compact, table-top source of short pulse fusion neutrons for applications. Furthermore, we have measured hard x-ray yield from femtosecond laser interactions with both solid and micron scale droplet targets. Strong hard x-ray production is observed from both targets. However, the inferred electron temperature is somewhat higher in the case of irradiation of the droplets. These data are consistent with PIC simulations. This finding indicates that quite unique hot electron dynamics occur during the irradiation of wavelength scale particles by an intense laser field and likely warrants further study.

  5. L-shell emission from high-Z solid targets by intense 10{sup 19}W/cm{sup 2} irradiation with a 248nm laser

    SciTech Connect

    Nelson, T.R.; Borisov, A.B.; Boyer, K.

    2000-01-05

    Efficient (1.2% yield) multikilovolt x-ray emission from Ba(L) (2.4--2.8{angstrom}) and Gd(L) (1.7--2.1{angstrom}) is produced by ultraviolet (248nm) laser-excited BaF{sub 2} and Gd solids. The high efficiency is attributed to an inner shell-selective collisional electron ejection. Much effort has been expended recently in attempts to develop an efficient coherent x-ray source suitable for high-resolution biological imaging. To this end, many experiments have been performed studying the x-ray emissions from high-Z materials under intense (>10{sup 18}W/cm{sup 2}) irradiation, with the most promising results coming from the irradiation of Xe clusters with a UV (248nm) laser at intensities of 10{sup 18}--10{sup 19}W/cm{sup 2}. In this paper the authors report the production of prompt x-rays with energies in excess of 5keV with efficiencies on the order of 1% as a result of intense irradiation of BaF{sub 2} and Gd targets with a terawatt 248nm laser. The efficiency is attributed to an inner shell-selective collisional electron ejection mechanism in which the previously photoionized electrons are ponderomotively driven into an ion while retaining a portion of their atomic phase and symmetry. This partial coherence of the laser-driven electrons has a pronounced effect on the collisional cross-section for the electron ion interaction.

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

    SciTech Connect

    Kozadaev, K V

    2014-04-28

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

  7. Detection of surface changes of materials caused by intense irradiation with laser-plasma EUV source utilizing scattered or luminescent radiation excited with the EUV pulses

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Rakowski, R.; Szczurek, M.

    2008-04-01

    Extreme ultraviolet (EUV) radiation is absorbed in a thin surface layer of any material. Irradiation of material samples with intense EUV pulses may cause different surface changes. Some of them, especially connected with material desorption, can be clearly visible using an optical or electron microscope. Other changes concerning crystal structure or chemical composition may not be visible under the microscope. They can however be detected using the EUV radiation itself. In this paper a new method of measurement of surface changes by irradiation with a laser-plasma EUV source is presented. The radiation was collected and focused on a material surface using a specially designed multifoil collector. Radiation scattered or excited in the material was detected with the use of a Wolter-type mirror coupled to a back-illuminated CCD camera. Depending on material samples, images with different intensity distributions were registered. For some samples, the intensity distributions of the images obtained before and after irradiation were slightly different. The intensity differences in such cases allowed us to obtain differential images. The appearance of such images was assumed to be evidence of surface changes.

  8. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    PubMed Central

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-01-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017  W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems. PMID:26330230

  9. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    SciTech Connect

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-09-02

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. As a result, femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

  10. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    DOE PAGES

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; et al

    2015-09-02

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in thismore » regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. As a result, femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.« less

  11. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser.

    PubMed

    Faenov, A Ya; Colgan, J; Hansen, S B; Zhidkov, A; Pikuz, T A; Nishiuchi, M; Pikuz, S A; Skobelev, I Yu; Abdallah, J; Sakaki, H; Sagisaka, A; Pirozhkov, A S; Ogura, K; Fukuda, Y; Kanasaki, M; Hasegawa, N; Nishikino, M; Kando, M; Watanabe, Y; Kawachi, T; Masuda, S; Hosokai, T; Kodama, R; Kondo, K

    2015-01-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 10(21)  W/cm(2) is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E(4-5) of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~10(17)  W/cm(2), there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

  12. Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

    NASA Astrophysics Data System (ADS)

    Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

    2015-09-01

    We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4-5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017  W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

  13. Computer simulation of heat and mass transfer in tissue during high-intensity long-range laser irradiation.

    PubMed

    Director, L B; Frid, S E; Mendeleev VYa; Scovorod'Ko, S N

    1998-09-11

    Three-dimensional transient finite difference numerical model of the biological tissue irradiated by powerful laser beam is developed. It is used to simulate the thermal behavior of tissue assuming that radiation wavelength is chosen to give rise for volumetric heat sources. A three-dimensional seven-flow model is used to calculate radiation propagation. Evaporation and burn-out of tissue resulting in a through hole along the axis of the beam are taken into account. Besides the water boiling and corresponding changes of thermal and optical tissue properties the model takes into account one of the heat steam transfer mechanisms. Estimates are carried out for the effects of diffusion transfer and vaporization of water from the tissue surface. Kinetics of protein denaturation process are calculated by Arrenius equation. The problem is solved numerically using discrete grid technique and adaptive time-step control algorithm.

  14. Ionization and acceleration of heavy ions in high-Z solid target irradiated by high intensity laser

    NASA Astrophysics Data System (ADS)

    Kawahito, D.; Kishimoto, Y.

    2016-05-01

    In the interaction between high intensity laser and solid film, an ionization dynamics inside the solid is dominated by fast time scale convective propagation of the internal sheath field and the slow one by impact ionization due to heated high energy electrons coupled with nonlocal heat transport. Furthermore, ionization and acceleration due to the localized external sheath field which co- propagates with Al ions constituting the high energy front in the vacuum region. Through this process, the maximum charge state and then q/A increase in the rear side, so that ions near the front are further accelerated to high energy.

  15. Resonance laser-plasma excitation of coherent terahertz phonons in the bulk of fluorine-bearing crystals under high-intensity femtosecond laser irradiation

    SciTech Connect

    Potemkin, F V; Mareev, E I; Khodakovskii, N G; Mikheev, P M

    2013-08-31

    The dynamics of coherent phonons in fluorine-containing crystals was investigated by pump-probe technique in the plasma production regime. Several phonon modes, whose frequencies are overtones of the 0.38-THz fundamental frequency, were simultaneously observed in a lithium fluoride crystal. Phonons with frequencies of 1 and 0.1 THz were discovered in a calcium fluoride crystal and coherent phonons with frequencies of 1 THz and 67 GHz were observed in a barium fluoride crystal. Furthermore, in the latter case the amplitudes of phonon mode oscillations were found to significantly increase 15 ps after laser irradiation. (interaction of laser radiation with matter)

  16. Intense ion beams accelerated by ultra-intense laser pulses

    NASA Astrophysics Data System (ADS)

    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. .

  17. Photoionization of isooctane and n-octane in intense laser fields. I. Effect of irradiance on ionization rates

    NASA Astrophysics Data System (ADS)

    Healy, Andrew T.; Lipsky, Sanford; Blank, David A.

    2007-12-01

    The population of ejected electrons following multiphoton ionization of neat liquids isooctane and n-octane is investigated over a large range of ionizing irradiance Iex. Transient absorption (TA) at 1200nm in both neat liquids is measured in a 60μm path at time delays of 0.7 and 2.5ps following an intense 400nm (3.1eV) ionizing pulse. As the irradiance of this pulse is varied over the range from 4to410TW/cm2, the dependence of TA on Iex exhibits the periodic structure theoretically predicted for multiphoton channel openings and closings. At low Iex (<9TW/cm2), TA in isooctane is proportional to Iexn where n =3, consistent with nonresonant, near threshold ionization (liquid phase ionization potential=8.6eV). At Iex>9TW/cm2, n declines with increasing Iex up to Iex=13TW/cm2, at which point n abruptly increases to 4. The pattern is repeated at Iex>13TW/cm2, albeit with n declining from 4 and then abruptly increasing to 5 as Iex becomes greater than 100TW/cm2. A similar trend is observed in n-octane. The dependence of the TA on Iex in the regions of channel openings and closings is compared to the nonperturbative, strong field approximation developed by Reiss [Phys. Rev. A 22, 1786 (1980)].

  18. First-principles simulation of the optical response of bulk and thin-film α-quartz irradiated with an ultrashort intense laser pulse

    SciTech Connect

    Lee, Kyung-Min; Min Kim, Chul; Moon Jeong, Tae; Sato, Shunsuke A.; Otobe, Tomohito; Shinohara, Yasushi; Yabana, Kazuhiro

    2014-02-07

    A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 10{sup 10} W/cm{sup 2} to 2 × 10{sup 15} W/cm{sup 2} based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied to investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film, and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials, in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures.

  19. Photoionization of isooctane and n-octane in intense laser fields. I. Effect of irradiance on ionization rates

    SciTech Connect

    Healy, Andrew T.; Lipsky, Sanford; Blank, David A.

    2007-12-07

    The population of ejected electrons following multiphoton ionization of neat liquids isooctane and n-octane is investigated over a large range of ionizing irradiance I{sub ex}. Transient absorption (TA) at 1200 nm in both neat liquids is measured in a 60 {mu}m path at time delays of 0.7 and 2.5 ps following an intense 400 nm (3.1 eV) ionizing pulse. As the irradiance of this pulse is varied over the range from 4 to 410 TW/cm{sup 2}, the dependence of TA on I{sub ex} exhibits the periodic structure theoretically predicted for multiphoton channel openings and closings. At low I{sub ex} (<9 TW/cm{sup 2}), TA in isooctane is proportional to I{sub ex}{sup n} where n=3, consistent with nonresonant, near threshold ionization (liquid phase ionization potential=8.6 eV). At I{sub ex}>9 TW/cm{sup 2}, n declines with increasing I{sub ex} up to I{sub ex}=13 TW/cm{sup 2}, at which point n abruptly increases to 4. The pattern is repeated at I{sub ex}>13 TW/cm{sup 2}, albeit with n declining from 4 and then abruptly increasing to 5 as I{sub ex} becomes greater than 100 TW/cm{sup 2}. A similar trend is observed in n-octane. The dependence of the TA on I{sub ex} in the regions of channel openings and closings is compared to the nonperturbative, strong field approximation developed by Reiss [Phys. Rev. A 22, 1786 (1980)].

  20. Experimental Study on Fast Electrons Transport in Ultra-intense Laser Irradiated Solid Targets by Transition Radiation

    NASA Astrophysics Data System (ADS)

    Zhijian, Zheng; Guangcan, Wang; Yuqiu, Gu

    2008-11-01

    The experiment was performed with SILEX laser facility(Ti-saphhire) at LFRC in China. The SILEX parameter: wavelength 0.8μm, duration 35fs, output power 280TW, contrast 5*105, The focal spot φ10μm(F/1.7), intensity on target surface 1*10^19W/cm^2(F/3). The main diagnostic equipments are the electron spectrometer, OMA spectrometer, optical streak camera. Some experimental results are given: The spectrum of optical emission from rear surface is rather narrow around some particular frequencies(1φ, 2φ, 3φ), We ascribe and confirm that the spike-like spectral line that is coherent transition radiation; The coherent light is also seen on time-integrated image with ring-patter due to Weibel instability of the fast electron transport; Obtained experimental cure of target thickness vs OTR image intensity is relative to mean free path of fast electron; The measuring optical transition radiation(OTR) duration of 171ps much longer than 1ps duration of fast electron transport target, the possible explanation is that the OTR duration to be determined magnetic diffusion time.

  1. Low intensity laser treatment of nerve injuries

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Guang; Liu, Timon Cheng-Yi; Luo, Qing-Ming

    2007-05-01

    The neural regeneration and functional recovery after nerve injuries has long been an important field in neuroscience. Low intensity laser (LIL) irradiation is a novel and useful tool for the treatment of many injuries and disorders. The aim of this study was to assess the role of LIL irradiation in the treatment of peripheral and central nerve injuries. Some animal experiments and clinical investigations have shown beneficial effects of LIL irradiation on neural tissues, but its therapeutic value and efficacy are controversial. Reviewing the data of experimental and clinical studies by using the biological information model of photobiomodulation, we conclude that LIL irradiation in specific parameters can promote the regeneration of injured peripheral and central nerves and LIL therapy is a safe and valuable treatment for superficial peripheral nerve injuries and spinal cord injury. The biological effects of LIL treatment depend largely on laser wavelength, power and dose per site and effective irradiation doses are location-specific.

  2. Interference effects and Stark broadening in XUV intrashell transitions in aluminum under conditions of intense XUV free-electron-laser irradiation

    NASA Astrophysics Data System (ADS)

    Galtier, E.; Rosmej, F. B.; Calisti, A.; Talin, B.; Mossé, C.; Ferri, S.; Lisitsa, V. S.

    2013-03-01

    Quantum mechanical interference effects in the line broadening of intrashell transitions are investigated for dense plasma conditions. Simulations that involved LSJ-split level structure and intermediate coupling discovered unexpected strong line narrowing for intrashell transitions L-L while M-L transitions remained practically unaffected by interference effects. This behavior allows a robust study of line narrowing in dense plasmas. Simulations are carried out for XUV transitions of aluminum that have recently been observed in experiments with the FLASH free-electron laser in Hamburg irradiating solid aluminum samples with intensities greater than 1016 W/cm2. We explore the advantageous case of Al that allows, first, simultaneous observation of M-L transitions and L-L intrashell transitions with high-resolution grating spectrometers and, second, has a convenient threshold to study interference effects at densities much below solid. Finally, we present simulations at near solid density where the line emission transforms into a quasicontinuum.

  3. Time-dependent density functional theory of high-intensity short-pulse laser irradiation on insulators

    NASA Astrophysics Data System (ADS)

    Sato, S. A.; Yabana, K.; Shinohara, Y.; Otobe, T.; Lee, K.-M.; Bertsch, G. F.

    2015-11-01

    We calculate the energy deposition by very short laser pulses in SiO2 (α -quartz) with a view to establishing systematics for predicting damage and nanoparticle production. The theoretical framework is time-dependent density functional theory, implemented by the real-time method in a multiscale representation. For the most realistic simulations we employ a meta-GGA Kohn-Sham potential similar to that of Becke and Johnson. We find that the deposited energy in the medium can be accurately modeled as a function of the local electromagnetic pulse fluence. The energy-deposition function can in turn be quite well fitted to the strong-field Keldysh formula for a range of intensities from below the melting threshold to well beyond the ablation threshold. We find reasonable agreement between the damage threshold and the energy required to melt the substrate. Also, the depth of the ablated crater at higher energies is fairly well reproduced assuming that the material ablated with the energy exceeds that required to convert it to an atomic fluid. However, the calculated ablation threshold is higher than experiment, suggesting a nonthermal mechanism for the surface ablation.

  4. Influence of the fractioned irradiation energy in the phototherapy with low intensity laser on the growth of human dental pulp fibroblasts

    NASA Astrophysics Data System (ADS)

    Meneguzzo, D. T.; Eduardo, C. P.; Ribeiro, M. S.; Marques, M. M.

    2008-03-01

    Laser phototherapy has proven to improve treatment of several pathologies in dentistry. The aim of the present study was to analyze the low power laser phototherapy effects comparing multiple irradiations with the same total energy at once. This in vitro study focuses on the biostimulation of cellular growth of pulp fibroblasts (FP5 cell lineage). The cells were grown in Dulbecco's Modified Eagle's (DME) medium with either 5% (nutritional deficit) or 10% fetal bovine serum (FBS). Laser irradiation was carried out with diode lasers with the following parameters: 685 nm, 40 mW, spot size 0.019 cm2. The groups were: G1(6.3J/cm2, 3 s, 0.12J), G2 (12.6J/cm2, 6 s, 0.24J), G3 (18.9J/cm2, 9 s, 0.36J), G4 (2 irradiations of 6.3J/cm2, 0.24J), G5 (3 irradiations of 6.3J/cm2, 0.36J), G6 (5% SFB, negative control, without irradiation), and G7 (10% SFB, positive control, without irradiation). On groups G4 and G5 the irradiation was performed with 6h-intervals. For growth analysis, the MTT test was used 24 hours after the last irradiation. The data from spectrophotometer were analyzed by ANOVA followed by the Tukey's test. The groups submitted to multiple irradiations presented significantly higher cell growth than the groups with single irradiation. This cell growth was similar to that of positive control group. The laser phototherapy with multiple irradiations is more effective on cellular growth.

  5. Efficient generation of fast ions from surface modulated nanostructure targets irradiated by high intensity short-pulse lasers

    SciTech Connect

    Andreev, Alexander; Kumar, Naveen; Pukhov, Alexander; Platonov, Konstantin

    2011-10-15

    It's shown that the imposition of sub-laser wavelength relief structures on the surface of mass-limited-targets results into several folds higher short-pulse laser absorption, and consequently the efficient generation of fast ions. The optimum relief parameters for enhanced short-pulse laser absorption and higher ion acceleration are estimated numerically by particle-in-cell simulations and then corroborated by analytical scalings. The stability of the pre-imposed surface modulation during the laser pulse foil interaction is also examined.

  6. Ultrafast laser and swift heavy ion irradiation: Response of Gd2O3 and ZrO2 to intense electronic excitation

    NASA Astrophysics Data System (ADS)

    Rittman, Dylan R.; Tracy, Cameron L.; Cusick, Alex B.; Abere, Michael J.; Torralva, Ben; Ewing, Rodney C.; Yalisove, Steven M.

    2015-04-01

    In order to investigate the response of materials to extreme conditions, there are several approaches to depositing extremely high concentrations of energy into very small volumes of material, including ultrafast laser and swift heavy ion (SHI) irradiation. In this study, crystalline-to-crystalline phase transformations in cubic Gd2O3 and monoclinic ZrO2 have been investigated using ultrafast laser irradiation. The phases produced by the extreme conditions of irradiation were characterized by grazing incidence x-ray diffraction (GIXRD) and Raman spectroscopy. Gd2O3 exhibited a cubic-to-monoclinic phase transformation, as evidenced by the appearance of the monoclinic (40 2 ¯ ), (003), (310), and (11 2 ¯ ) peaks in the GIXRD pattern and of four Ag and three Bg Raman modes. ZrO2 underwent a monoclinic-to-tetragonal phase transformation, as evidenced by the emergence of the tetragonal (101) peak in the GIXRD pattern and of Eg and A1g Raman modes. The new phases formed by ultrafast laser irradiation are high temperature polymorphs of the two materials. No evidence of amorphization was seen in the GIXRD data, though Raman spectroscopy indicated point defect accumulation. These results are identical to those produced by irradiation with SHIs, which also deposit energy in materials primarily through electronic excitation. The similarity in damage process and material response between ultrafast laser and SHI irradiation suggests a fundamental relationship between these two techniques.

  7. Genetic expression of adipose derived stem cell and smooth muscle cell markers to monitor differentiation potential following low intensity laser irradiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, Heidi

    2014-02-01

    Mesenchymal stem cells (MSCs) have the capacity to differentiate into a variety of cell types that could potentially be used in tissue engineering and regenerative medicine. Low intensity laser irradiation (LILI) has been shown to induce a significant increase in cell viability and proliferation. Growth factors such as retinoic acid (RA) and transforming growth factor β1 (TGF-β1) play important roles in the differentiation of cells. The aim of this study was to investigate whether LILI in combination with growth factors could induce the differentiation of adipose derived stem cells (ADSCs) cocultured with smooth muscle cells (SMCs). The study used primary and continuous ADSC cell lines and a SMC line (SKUT-1) as control. Cells were co-cultured directly at a ratio of 1:1 using established methods, with and without growth factors and then exposed to LILI at 5 J/cm2 using a 636 nm diode laser. The cellular morphology, viability and proliferation of the co-cultures were assessed over a period of one week. The study also monitored the expression of cell specific markers over the same period of time. Genetic expression of the markers for both adipose derived stem cells (β1 Integrin and Thymidine 1) and smooth muscle cells (Heavy Myosin Chain) was monitored using flow cytometry. Cell viability and proliferation increased significantly in the co-cultured groups that were exposed to laser alone, as well as in combination with growth factors. Furthermore, there was a significant decrease in the expression of stem cell markers in the ADSCs over time. The results indicate that LILI in combination with growth factors not only increases the viability and proliferation of co-cultured cells but also decreases the expression of ADSC stem cell markers. This could indicate the possible differentiation of ADSCs into SMCs.

  8. Energy transport and isochoric heating of a low-Z, reduced-mass target irradiated with a high intensity laser pulse

    SciTech Connect

    Nishimura, H.; Nakamura, H.; Tanabe, M.; Fujiwara, T.; Yamamoto, N.; Fujioka, S.; Mima, K.; Mishra, R.; Sentoku, Y.; Mancini, R.; Hakel, P.; Ohshima, S.; Batani, D.; Veltcheva, M.; Desai, T.; Jafer, R.; Kawamura, T.; Koike, F.

    2011-02-15

    Heat transport in reduced-mass targets irradiated with a high intensity laser pulse was studied. K{alpha} lines from partially ionized chlorine embedded in the middle of a triple-layered plastic target were measured to evaluate bulk electron temperature in the tracer region inside the target. Two groups of K{alpha} lines, one from Cl{sup +}-Cl{sup 6+} (hereby called ''cold K{alpha}''), and the other from Cl{sup 9+} and Cl{sup 10+} (''shifted K{alpha}'') are observed from different regions within the target. Two-dimensional collisional particle-in-cell simulations show two distinct heating mechanisms occurring concurrently: uniform heating by refluxing electrons and local heating by diffusive electrons in the central region. These two heating processes, which made the target temperature distribution nonuniform, are responsible for producing the two groups of K{alpha} lines in the experiment. The blue-shift of cold K{alpha} lines in the experiment is the signature of higher temperatures achieved by the refluxing heating in smaller-mass targets.

  9. Strain and mosaic deformation in laser irradiated silicon

    SciTech Connect

    Gupta, Mukul; Arora, V.; Bagchi, S.; Gupta, Ajay; Chakera, J. A.; Naik, P. A.; Chaddah, P.; Gupta, P. D.

    2012-06-05

    The effect of moderately intense ({approx}GWcm{sup -2} The effect of moderately intense ({approx}GWcm-2), 200 ps laser pulse irradiation on silicon single crystal is reported. The x-ray diffraction measurements performed on the irradiated samples reveal irreversible structural deformations. Raman spectroscopic measurements reveal substantial shift of the peak position as well as an overall broadening, pointing towards the presence of residual strain and formation of micromosaic structures on the laser induced shock recovered samples.

  10. Ultrafast laser and swift heavy ion irradiation: Response of Gd{sub 2}O{sub 3} and ZrO{sub 2} to intense electronic excitation

    SciTech Connect

    Rittman, Dylan R.; Tracy, Cameron L.; Cusick, Alex B.; Abere, Michael J.; Yalisove, Steven M.; Torralva, Ben; Ewing, Rodney C.

    2015-04-27

    In order to investigate the response of materials to extreme conditions, there are several approaches to depositing extremely high concentrations of energy into very small volumes of material, including ultrafast laser and swift heavy ion (SHI) irradiation. In this study, crystalline-to-crystalline phase transformations in cubic Gd{sub 2}O{sub 3} and monoclinic ZrO{sub 2} have been investigated using ultrafast laser irradiation. The phases produced by the extreme conditions of irradiation were characterized by grazing incidence x-ray diffraction (GIXRD) and Raman spectroscopy. Gd{sub 2}O{sub 3} exhibited a cubic-to-monoclinic phase transformation, as evidenced by the appearance of the monoclinic (402{sup ¯}), (003), (310), and (112{sup ¯}) peaks in the GIXRD pattern and of four A{sub g} and three B{sub g} Raman modes. ZrO{sub 2} underwent a monoclinic-to-tetragonal phase transformation, as evidenced by the emergence of the tetragonal (101) peak in the GIXRD pattern and of E{sub g} and A{sub 1g} Raman modes. The new phases formed by ultrafast laser irradiation are high temperature polymorphs of the two materials. No evidence of amorphization was seen in the GIXRD data, though Raman spectroscopy indicated point defect accumulation. These results are identical to those produced by irradiation with SHIs, which also deposit energy in materials primarily through electronic excitation. The similarity in damage process and material response between ultrafast laser and SHI irradiation suggests a fundamental relationship between these two techniques.

  11. Intravascular low-level laser irradiation in the treatment of psoriasis

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Shi, Hong-Min; Zhang, Hui-Guo; Zhang, Mei-Jue; Xu, Jian; Zhou, Min; Hu, Guo-Qiang

    1998-11-01

    Liu TCY et al have put forward the biological information model on low intensity laser irradiation (BIML): low intensity laser irradiation couples with intracellular messenger through the chromophore absorption in the cell membrane: hot-color laser irradiation activates cAMP phosphodiestererase through Gi protein, or activates phosphoinositide phospholipase C through G protein, or activates one of receptor-associated kinases: cAMP; cold- color laser irradiation activates adenylate cyclase through Gs protein: cAMP$ARUP. In this paper, under the guidance of BIML, we applied the intravascular low intensity He-He laser irradiation on blood to a patient of idiopathic edema, and succeeded.

  12. Photoionization of isooctane and n-octane in intense laser fields: The effect of irradiance on ionization rates and electron dynamics

    NASA Astrophysics Data System (ADS)

    Healy, Andrew T.

    Thin path length jets (60 mum) of liquid isooctane and n-octane have been photoionized with 36-70 fs pulses of 3.1 eV photons. The population of electrons ejected post ionization is investigated over a large range of ionizing irradiance, Iex, though transient absorption (TA) measurements at wavelengths in the range 570 nm (2.17 eV) to 1315 nm (0.94 eV). As Iex is varied over a range from 3 TW/cm2 to 410 TW/cm2, the dependence of the TA intensity on Iex at time delays 0.7 ps and 2.5 ps exhibits the periodic structure theoretically predicted to develop as a result of multiphoton channel closings. At low Iex (< 9 TW/cm2), TA intensity in isooctane is proportional to Inex where n = 3, consistent with non-resonant, near threshold ionization (liquid phase ionization potential = 8.6 eV). At I ex > 9 TW/cm2, n declines with increasing Iex up to Iex = 13 TW/cm2, at which point n abruptly increases to 4. The pattern is repeated at Iex > 13 TW/cm 2, albeit with n declining from 4 and then abruptly increasing to 5 as Iex becomes greater than 100 TW/cm2. A similar trend is observed in n-octane. The decay of the TA intensity in both liquids has been measured from 0.50 ps to 180 ps over the same range of irradiance. Via comparison of the two liquids, and electron quenching studies, the TA at wavelengths longer than 800 nm has been assigned to be predominantly due to absorption by the electron. At the lowest irradiances, where n = 3 photons are required for photoionization, the TA decay in isooctane is characteristic of a geminate ion pair decaying via diffusive recombination in a Coulomb field. As the irradiance is increased, an early time, rapid, exponential decay of the TA begins to develop until an irradiance is reached (≅ 13 TW/cm2) at which our studies indicate that the n = 3 channel closes. At this irradiance, the TA decay returns to purely diffusive-like. As the irradiance is further increased, there is a reappearance of the early time exponential decay until the n = 4

  13. Dependence of terahertz power from laser-produced plasma on laser intensity

    NASA Astrophysics Data System (ADS)

    Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.

    2012-07-01

    Power of terahertz radiation from plasma which is generated from air irradiated by coupled (ω, 2ω) femtosecond laser pulses is analyzed for high laser intensities, for which non-linear plasma effects on the pulse propagation become essential, with multidimensional particle-in-cell simulations including the self-consistent plasma kinetics. The growth rate of THz power becomes slower as the laser intensity increases. A reason of such a lowering of efficiency in THz emission is found to be ionization of air by the laser pulse, which results in poor focusing of laser pulses.

  14. Molecules and Clusters in Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Posthumus, Jan

    2001-06-01

    Preface; 1. Ultra-high intensity based on Ti:Sapphire Philip F. Taday and Andrew J. Langley; 2. Diatomic molecules in intense laser fields Jan H. Posthumus and James F. McCann; 3. Small polyatomic molecules in intense laser fields C. Cornaggia; 4. Coherent control in intense laser fields Eric Charron and Brian Sheehy; 5. Experimental studies of laser-heated rare gas clusters M. Lezius and M. Schmidt; 6. Single cluster explosions and high harmonic generation John W. G. Tisch and Emma Springate; 7. Intense laser interaction with extended cluster media Roland A. Smith and Todd Ditmire.

  15. Molecules and Clusters in Intense Laser Fields

    NASA Astrophysics Data System (ADS)

    Posthumus, Jan

    2009-09-01

    Preface; 1. Ultra-high intensity based on Ti:Sapphire Philip F. Taday and Andrew J. Langley; 2. Diatomic molecules in intense laser fields Jan H. Posthumus and James F. McCann; 3. Small polyatomic molecules in intense laser fields C. Cornaggia; 4. Coherent control in intense laser fields Eric Charron and Brian Sheehy; 5. Experimental studies of laser-heated rare gas clusters M. Lezius and M. Schmidt; 6. Single cluster explosions and high harmonic generation John W. G. Tisch and Emma Springate; 7. Intense laser interaction with extended cluster media Roland A. Smith and Todd Ditmire.

  16. Influence of irradiation with {gamma}-ray photons on the photoluminescence of Cd{sub 0.9}Zn{sub 0.1}Te crystals preliminarily subjected to the intense radiation of a neodymium laser

    SciTech Connect

    Glinchuk, K. D.; Medvid', A. P.; Mychko, A. M.; Naseka, Yu. M.; Prokhorovich, A. V.; Strilchuk, O. M.

    2013-04-15

    The effect of the preliminary treatment of Cd{sub 0.9}Zn{sub 0.1}Te crystals with high-power pulses of neodymium laser radiation (the power density is {<=}1.8 MW/cm{sup 2}, at a wavelength of 532 nm) on the low-temperature (5 K) photoluminescence induced by {gamma}-ray radiation (the dose was {Phi}{sub {gamma}} = 5 kGy) is studied. The luminescence bands are related to radiation-stimulated donor-acceptor pairs, which include shallow neutral donors and neutral cadmium vacancies stimulated by {gamma}-ray irradiation, the transition of free electrons to neutral cadmium vacancies formed by radiation, and the annihilation of excitons bound to the above vacancies. It is shown that, in the crystals preliminarily treated with laser radiation, the intensity of the {gamma}-ray-stimulated luminescence bands is significantly lower than in crystals not subjected to laser radiation. This fact is accounted for by a decrease in the concentration of cadmium vacancies generated by the {gamma}-ray radiation as a result of their annihilation during the course of their interaction with laser-stimulated defects, in particular, as a consequence of their recombination at laser-stimulated interstitial cadmium atoms.

  17. Backscattering measuring system for optimization of intravenous laser irradiation dose

    NASA Astrophysics Data System (ADS)

    Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

    1996-11-01

    Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.

  18. Continuous wave laser irradiation of explosives

    SciTech Connect

    McGrane, Shawn D.; Moore, David S.

    2010-12-01

    Quantitative measurements of the levels of continuous wave (CW) laser light that can be safely applied to bare explosives during contact operations were obtained at 532 nm, 785 nm, and 1550 nm wavelengths. A thermal camera was used to record the temperature of explosive pressed pellets and single crystals while they were irradiated using a measured laser power and laser spot size. A visible light image of the sample surface was obtained before and after the laser irradiation. Laser irradiation thresholds were obtained for the onset of any visible change to the explosive sample and for the onset of any visible chemical reaction. Deflagration to detonation transitions were not observed using any of these CW laser wavelengths on single crystals or pressed pellets in the unconfined geometry tested. Except for the photochemistry of DAAF, TATB and PBX 9502, all reactions appeared to be thermal using a 532 nm wavelength laser. For a 1550 nm wavelength laser, no photochemistry was evident, but the laser power thresholds for thermal damage in some of the materials were significantly lower than for the 532 nm laser wavelength. No reactions were observed in any of the studied explosives using the available 300 mW laser at 785 nm wavelength. Tables of laser irradiance damage and reaction thresholds are presented for pressed pellets of PBX9501, PBX9502, Composition B, HMX, TATB, RDX, DAAF, PETN, and TNT and single crystals of RDX, HMX, and PETN for each of the laser wavelengths.

  19. Functional assessment of laser irradiation

    NASA Astrophysics Data System (ADS)

    Robbins, David O.

    1988-03-01

    Exposure of the fovea to intense coherent light can produce either transient or permanent changes in the eye's ability to resolve fine spatial detail. Permanent functional changes can occur in the absence of gross morphological damage and at power densities below the ED50 level. Furthermore, the eye may become increasingly susceptible to damage after repeated low-level exposures which initially produce only transient effects. Independent of any long-term hazards, laser exposures can also disrupt visual/motor behavior for periods of up to 96 hrs

  20. He-Ne laser extravascular irradiation therapy

    NASA Astrophysics Data System (ADS)

    Chen, Rong; Chen, Huifang; Xie, Shusen; Chen, Yanjiao; Zhang, Yanrong

    2000-10-01

    Based on the study of tissue optics related with the laser irradiation blood therapy, a new treatment method, extravascular low-level laser irradiation therapy (ELLLI) is developed. The veins of 30 patients with cerebrovascular disease combined with diabetes, asthma were treated by He-Ne laser (632.8nm, 25mW) which was delivered by an optics fiber. The fiber was outside the patient's skin and the laser irradiated on the blood vessel perpendicularly. The therapy time was 60 minutes each time and about 7-10 times a course of the treatment. The values of blood sugar, blood- fat and hemorrheology were measured as the effective indexes. After the treatment the effective indexes and the symptoms of the patients were all improved. With the advantages of simplicity and safety (no medical infection), laser extravascular irradiation therapy is likely to be a new medical method for heart brain and other diseases.

  1. Intense laser propagation in sapphire

    NASA Astrophysics Data System (ADS)

    Tate, Jennifer L.

    When a sufficiently energetic short laser pulse propagates through a medium it can generate an explosive increase in bandwidth leading to the creation of white light; this is known as supercontinuum generation (SCG). Although it is frequently referred to as a single process, SCG is actually the result of many different parallel and competing processes. In this work we investigate the contribution of the individual physical processes underlying the SCG effect, focusing specifically on Raman processes and plasma formation in sapphire. For our experiments we use an amplified Ti:sapphire laser system producing nearly transform limited 60 fs pulses at 800 nm. Typical pulse energies for the experiments are 1--3 muJ/pulse. Using a new experimental technique, the spectrally resolved interferometric double pump, we study the contribution of non-instantaneous Raman effects. We see two distinct Raman contributions in sapphire which are much stronger than indicated in previous work. One Raman process has a period of approximately 185 fs and is related to an available optical phonon; the second Raman process has a period of 20 fs and is related to defect states caused by an oxygen vacancy in the sapphire crystal. Data from the same experiment show that the SCG light is not phase stable at low excitation energies, but that the phase stability is restored and saturates with increasing laser intensity. In a separate experiment we investigate the dynamics of plasma formation using a pump-probe technique. We observe that in sapphire both the formation and the decay of the plasma occur over time scales much longer than predicted by current theory. The plasma rise time is ˜225 fs, while the decay time is ˜150 ps; we also observe that these values do not depend on input pulse energy. In addition to these experiments, we perform a numerical integration of the extended (3 + 1) dimensional nonlinear Schrodinger equation, which models the propagation of a short laser pulse through a

  2. Study on elucidation of bactericidal effects induced by laser beam irradiation Measurement of dynamic stress on laser irradiated surface

    NASA Astrophysics Data System (ADS)

    Furumoto, Tatsuaki; Kasai, Atsushi; Tachiya, Hiroshi; Hosokawa, Akira; Ueda, Takashi

    2010-09-01

    In dental treatment, many types of laser beams have been used for various surgical treatments, and the influences of laser beam irradiation on bactericidal effect have been investigated. However, most of the work has been performed by irradiating to an agar plate with the colony of bacteria, and very few studies have been reported on the physical mechanism of bactericidal effects induced by laser beam irradiation. This paper deals with the measurement of dynamic stress induced in extracted human enamel by irradiation with Nd:YAG laser beams. Laser beams can be delivered to the enamel surface through a quartz optical fiber. Dynamic stress induced in the specimen using elastic wave propagation in a cylindrical long bar made of aluminum alloy is measured. Laser induced stress intensity is evaluated from dynamic strain measured by small semiconductor strain gauges. Carbon powder and titanium dioxide powder were applied to the human enamel surface as absorbents. Additionally, the phenomenon of laser beam irradiation to the human enamel surface was observed with an ultrahigh speed video camera. Results showed that a plasma was generated on the enamel surface during laser beam irradiation, and the melted tissues were scattered in the vertical direction against the enamel surface with a mushroom-like wave. Averaged scattering velocity of the melted tissues was 25.2 m/s. Induced dynamic stress on the enamel surface increased with increasing laser energy in each absorbent. Induced dynamic stresses with titanium dioxide powder were superior to those with carbon powder. Induced dynamic stress was related to volume of prepared cavity, and induced stress for the removal of unit volume of human enamel was 0.03 Pa/mm 3.

  3. Processing of diamond by laser beam irradiation

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Masanori; Hirata, Atsushi

    1998-10-01

    YAG and ArF excimer laser beams, of which wavelengths are 1.06 micrometers and 193 nm respectively, have been applied to processing of a variety of diamonds. Cutting and smoothing of natural, CVD and sintered diamonds have been performed. CVD diamond films were prepared by arc discharge plasma jet CVD and microwave plasma CVD, and sintered diamonds contain metallic or ceramic binder have been used. Fundamental removal processes of diamond with YAG and ArF excimer laser have been investigated using natural single crystal and CVD diamonds in various atmospheres changing laser irradiation conditions such as average power, energy density and pulse repetition rates. Cutting of natural and CVD diamonds with YAG laser proceeds at higher peal power that occurs at lower pulse repetition rates. Smooth surfaces are obtained by excimer laser irradiation at the incident angle of 80 percent. In the cases of the processing with YAG laser, the effect of local heating by laser beam irradiation mainly assists the diamond processing, and diamond appears to be removed after graphitization and oxidization following vaporization in the atmosphere contains oxygen. The temperature measurement was carried out at backside of irradiation surface, and increase of temperature when YAG laser beam was irradiated was larger than that when excimer laser was irradiated. On the contrary, the detection of C, C2, C+, O2 and CO from the emission at the irradiation area with ArF excimer laser beam suggest that processing partly proceeds by the separation of carbon atoms from the surface of diamond after braking bonds between carbon atoms caused by laser beam. Cutting of sintered diamond with metallic binder was difficult because metallic binder remains in the groove while ceramic binder was easily removed. Processing technique using laser beams has been applied to surface planing, chip preparation and edge formation of CVD diamond and curved surface formation on sintered diamond. Surface planing was

  4. Optimal irradiance for sintering of inkjet-printed Ag electrodes with a 532nm CW laser

    NASA Astrophysics Data System (ADS)

    Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Moon, Seung Jae

    2013-09-01

    Industrial solar cell fabrication generally adopts printing process to deposit the front electrodes, which needs additional heat treatment after printing to enhance electrical conductivity. As a heating method, laser irradiation draws attention not only because of its special selectivity, but also because of its intense heating to achieve high electric conductivity which is essential to reduce ohmic loss of solar cells. In this study, variation of electric conductivity was examined with laser irradiation having various beam intensity. 532 nm continuous wave (CW) laser was irradiated on inkjet-printed silver lines on glass substrate and electrical resistance was measured in situ during the irradiation. The results demonstrate that electric conductivity varies nonlinearly with laser intensity, having minimum specific resistance of 4.1 x 10-8 Ωm at 529 W/cm2 irradiation. The results is interesting because the specific resistance achieved by the present laser irradiation was about 1.8 times lower than the best value obtainable by oven heating, even though it was still higher by 2.5 times than that of bulk silver. It is also demonstrated that the irradiation time, needed to finish sintering process, decreases with laser intensity. The numerical simulation of laser heating showed that the optimal heating temperature could be as high as 300 oC for laser sintering, while it was limited to 250 oC for oven sintering. The nonlinear response of sintering with heating intensity was discussed, based on the results of FESEM images and XRD analysis.

  5. Effect of laser intensity on the characteristic of inkjet-printed silver nanoparticles during continuous laser sintering.

    PubMed

    Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Lee, Jae-Heon; Moon, Seung-Jae

    2014-11-01

    The variation in electric conductivity was examined for laser irradiation with various beam intensities. A 532-nm continuous wave laser was irradiated onto inkjet-printed silver lines on a glass substrate and the electrical resistance was measured in situ during the irradiation. The results demonstrate that electrical conductivity varies nonlinearly with laser intensity, and has a minimum specific resistance of 3.1 x 10(-8) Ωm at 4 kW/cm2 irradiation. These results are interesting because the specific resistance achieved by the present laser irradiation was approximately 1.9 times lower than the best value obtainable by oven heating, even though it was still higher by 1.9 times than that of bulk silver. It is also demonstrated that the irradiation time required to complete the sintering process decreases with laser intensity. The numerical simulation of laser heating shows that the heating temperature could be as high as 250 degrees C for laser sintering, while it is limited to 250 degrees C for oven sintering. The characteristics of sintering with laser intensity based on the results of field emission scanning electron microscope images are discussed. PMID:25958575

  6. Effect of laser intensity on the characteristic of inkjet-printed silver nanoparticles during continuous laser sintering.

    PubMed

    Moon, Yoon Jae; Kang, Heuiseok; Kang, Kyungtae; Hwang, Jun Young; Lee, Jae-Heon; Moon, Seung-Jae

    2014-11-01

    The variation in electric conductivity was examined for laser irradiation with various beam intensities. A 532-nm continuous wave laser was irradiated onto inkjet-printed silver lines on a glass substrate and the electrical resistance was measured in situ during the irradiation. The results demonstrate that electrical conductivity varies nonlinearly with laser intensity, and has a minimum specific resistance of 3.1 x 10(-8) Ωm at 4 kW/cm2 irradiation. These results are interesting because the specific resistance achieved by the present laser irradiation was approximately 1.9 times lower than the best value obtainable by oven heating, even though it was still higher by 1.9 times than that of bulk silver. It is also demonstrated that the irradiation time required to complete the sintering process decreases with laser intensity. The numerical simulation of laser heating shows that the heating temperature could be as high as 250 degrees C for laser sintering, while it is limited to 250 degrees C for oven sintering. The characteristics of sintering with laser intensity based on the results of field emission scanning electron microscope images are discussed.

  7. Effects of Laser Irradiation on Peripheral Nerve

    NASA Astrophysics Data System (ADS)

    Baxter, G. D.; Chow, R.; Armati, P.; Bjordal, J. M.; Laakso, L.

    2009-06-01

    A literature review was undertaken to determine the electrophysiological effects of Laser Irradiation (LI) on peripheral mammalian nerves, as a means of elucidating the potential mechanisms underlying pain relief associated with laser therapy. Relevant computerized databases and reference lists were searched, and experts consulted for further articles. A total of 38 studies, comprising 82 separate experiments were identified. In human studies, all types of LI (red and infrared, pulsed and cw) slowed nerve conduction velocity, and reduced compound action potential of irradiated nerves. In animal studies, infrared LI suppressed conduction velocity, as well as noxious stimulation evoked potential. This review thus indicates the potential of laser irradiation to inhibit activity in peripheral nerves, and highlights one potential mechanism of action for laser-mediated pain relief.

  8. Direct heating of compressed core by ultra-intense laser

    NASA Astrophysics Data System (ADS)

    Sunahara, A.; Johzaki, T.; Sakagami, H.; Nagatomo, H.; Mima, K.; Abe, Y.; Arikawa, Y.; Fujioka, S.; Shiraga, H.; Azechi, H.; Mori, Y.; Sentoku, Y.; Kitagawa, Y.

    2016-05-01

    We propose a new scheme for heating an imploded core in the fast-ignition scheme. In this method, a heating laser irradiates an imploded core plasma directly. The accelerated fast-ions as well as fast-electrons heat the core. Two-dimensional particle in cell (PIC) simulation confirmed that carbon C6+ and deuteron D+ ions were accelerated as well as fast electrons when ultra-intense laser irradiates the CD plasma. In order to estimate the temperature scaling of the heated core in this scheme, we conducted transport simulations in the one-dimensional conical geometry. Our results show that 5 keV of ignition temperature can be achieved at the intensity of 1021 W/cm2, and 1.5 ps pulse for the compressed CD plasma with 10g/cm3 density.

  9. [Wound healing after laser and red light irradiation].

    PubMed

    Hutschenreiter, G; Haina, D; Paulini, K; Schumacher, G

    1980-04-01

    Laser irradiation and red light irradiation, daily 2 respectively 4 J/cm2, do not bring any acceleration of wound healing in rats. No significant effect was evident in the cell pattern of wounds during various phases of healing through the irradiation. The tensile strength of cicatrices increased by laser irradiation, but not by red light irradiation (monochromatic lambda = 633 nm).

  10. Flexible gratings fabricated in polymeric plate using femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Park, Jung-Kyu; Cho, Sung-Hak

    2011-05-01

    Flexible gratings embedded in poly-dimethlysiloxane (PDMS) were fabricated using femtosecond laser pulses. Photo-induced gratings in a flexible PDMS plate were directly written by a high-intensity femtosecond (130 fs) Ti: Sapphire laser ( λp=800 nm). Refractive index modifications with 4 μm diameters were photo-induced after irradiation of the femtosecond pulses with peak intensities of more than 1×10 11 W/cm 2. The graded refractive index profile was fabricated to be symmetric around the center of the focal point. The diffraction efficiency of the grating samples is measured by an He-Ne laser. The maximum value of refractive index change (Δ n) in the laser-modified regions was estimated to be approximately 3.17×10 -3.

  11. [Comparative analysis of application of highly intensive laser irradiation and electrocoagulation during laparoscopic cholecystectomy performed for destructive forms of an acute calculous cholecystitis].

    PubMed

    Nichitayio, M Yu; Bazyak, A M; Klochan, V V; Grusha, P K; Goman, A V

    2015-02-01

    Comparative analysis of results of the laser diode (the wave length 940 nm) and elec- trocoagulation application while performing laparoscopic cholecystectomy was con- ducted. For an acute calculous cholecystitis 52 patients were operated, in whom instead of electrocoagulation the laser was applied, provide for reduction of thermal impact on tissues, the complications absence, reduction of the patients stationary treatment duration postoperatively from (5.2 ± 1.2) to (4.9 ± 0.6) days.

  12. First-principle description for the high-harmonic generation in a diamond by intense short laser pulse

    NASA Astrophysics Data System (ADS)

    Otobe, T.

    2012-05-01

    We present a first-principles description for the electron excitation and the high-harmonic generation (HHG) in a diamond by intense laser pulse irradiation and their laser parameter dependence. Above band gap harmonics are generated after the peak of the incident laser pulse and have duration much shorter than the laser pulse. The intensity of individual harmonic peaks increases as laser intensity increases nonlinearly, and we find the blue shift of the HHG spectrum when the optical breakdown occurs.

  13. Damage thresholds in laser irradiated optical materials

    SciTech Connect

    Guignard, F.; Autric, M.; Baudinaud, V.

    1997-12-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, moulded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KJ pulsed cold cathode electron gun preionized TEA CO{sub 2} laser. Damage mechanisms are controlled by the in-depth absorption of the 10,6 {mu}m radiation according to the Beer-Lambert law. The heating of the interaction area gives rise to thermal or thermo-mechanical damages. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like moulded PMMA at higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  14. Interactions of intense laser radiation with plasma

    NASA Astrophysics Data System (ADS)

    Key, M. H.

    1981-04-01

    The dominant physical processes involved in the interaction of intense laser radiation with plasma are discussed with emphasis on their dependence on the wavelength of the laser radiation. Hydrodynamic pressure resulting from these interactions, acceleration of spherical shell targets, and fluid instability associated with the acceleration are discussed with reference to compression of plasma in laser driven implosions. Experimental data are presented to illustrate the various phenomena.

  15. System for target irradiation in the Iskra-6 high-power laser facility

    SciTech Connect

    Bondarenko, S V; Garanin, Sergey G; Eroshenko, V A; Kochemasov, G G; L'vov, L V; Mochalov, M R

    1999-03-31

    An analysis is made of various systems for direct irradiation of a target enabling achievement of a high degree of the irradiation uniformity. The required departure from uniformity of target irradiation, {delta}I/I {<=} 1% - 2%, may be attained when the number of laser beams is N {>=} 80, the diameter of the waist is approximately equal to the target diameter, and the intensity profile in the waist is Gaussian or super-Gaussian. Various methods of forming the necessary intensity distribution in a transverse cross section of a beam are considered. (interaction of laser radiation with matter. laser plasma)

  16. [Effect of low intensity helium-neon laser and decimeter electromagnetic irradiation on functional indices of immune cells in patients with rheumatoid arthritis].

    PubMed

    Petrov, A V

    2004-03-01

    Clinical, laboratory, and immunoassay of 58 patients with rheumatoid arthritis, first and second degree of activity was carried out. Low-energy helium-neon laser exposure and decimeter electromagnetic radiation (DMEM) of peripheral blood was given along with the use of non-steroidal antiinflammatory drugs and methotrexate. Peculiarities of this magnetic-laser effect on proliferation response and apoptosis of mononuclear leucocytes in vitro and in vivo have been revealed. It was also established that the application of DMEM-therapy brought patients with RA in shorter period of time to clinical improvement evaluated by ACR criteria. PMID:15208869

  17. L-shell emission from high-Z solid targets by intense (10{sup 19}W/cm{sup 2}) irradiation with a 248nm laser

    SciTech Connect

    Nelson, T. R.; Borisov, A. B.; Boyer, K.; Schroeder, W. A.; Santoro, J.; Van Tassle, A. J.; Rhodes, C. K.; Luk, T. S.; Cameron, S.; Longworth, J. W.; McPherson, A.

    1999-11-22

    Efficient (1.2% yield) multikilovolt x-ray emission from Ba(L) (2.4--2.8{angstrom}) and Gd(L) (1.7--2.1{angstrom}) is produced by ultraviolet (248nm) laser-excited BaF{sub 2} and Gd solids. The high efficiency is attributed to an inner shell-selective collisional electron ejection.

  18. Influence of laser irradiation on fiber post retention.

    PubMed

    Nagase, Denis Y; de Freitas, Patricia M; Morimoto, Susana; Oda, Margareth; Vieira, Glauco F

    2011-05-01

    The purpose of this in vitro study was to compare the bond strength between fiber post and laser-treated root canals. Forty single-rooted bovine teeth were endodontically treated and randomly divided into four groups of equal size according to the root canal treatment: group 1 conventional treatment (without laser irradiation); group 2 Nd:YAG laser (1.5 W, 10 Hz, 100 mJ); group 3 Er,Cr:YSGG laser (0.75 W, 20 Hz); and group 4 Nd:YAG + Er,Cr:YSGG lasers. The fiber posts were cemented with an adhesive system + resin cement, in accordance with the manufacturer's instructions. A mini acrylic pipe was fixed on the coronal section of the post using a light-polymerized resin. Specimens were mounted on an acrylic pipe with a self-polymerized resin. Retention forces were determined using a universal testing machine (0.5 mm/min). Data were analyzed using one-way ANOVA and Tukey tests (p <0.05). The post retention force in group 2 was found to be lower than that in the other experimental groups. Fractures were observed at the interface between the dentin and the resin in all groups. High-intensity lasers can be used in conventional endodontic treatment; however, root canal surface irradiation using the Nd:YAG laser was shown to negatively affect the post retention force.

  19. Laser-induced breakdown spectroscopy with laser irradiation on mid-infrared hydride stretch transitions: polystyrene

    NASA Astrophysics Data System (ADS)

    Khachatrian, A.; Dagdigian, P. J.

    2009-09-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of a polymer (polystyrene) with laser irradiation in the mid-infrared (mid-IR) spectral region is presented. A particular goal of this study is to determine whether the LIBS signals are enhanced when the laser wavelength is tuned to that of a vibrational transition of the polymer. Significant enhancements were indeed observed upon irradiation on the C-H stretch fundamental vibrational transitions. In addition, mode-specific effects were observed; the signals were stronger, compared to the relative intensities in the one-photon absorption spectrum, for irradiation on the aromatic (phenyl) C-H stretch transitions, rather than those involving aliphatic (backbone) C-H modes. The applicability of mid-IR resonance enhanced LIBS for detection of residues on surfaces is discussed.

  20. Plasma optical modulators for intense lasers.

    PubMed

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

    2016-01-01

    Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 10(16) W cm(-2) to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations. PMID:27283369

  1. Plasma optical modulators for intense lasers

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. Plasma optical modulators for intense lasers

    PubMed Central

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

    2016-01-01

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

  3. Fourier transform infrared spectroscopy (FTIR) of laser-irradiated cementum

    NASA Astrophysics Data System (ADS)

    Rechmann, Peter; White, Joel M.; Cecchini, Silvia C. M.; Hennig, Thomas

    2003-06-01

    Utilizing Fourier Transform Infrared Spectroscopy (FTIR) in specular reflectance mode chemical changes of root cement surfaces due to laser radiation were investigated. A total of 18 samples of root cement were analyzed, six served as controls. In this study laser energies were set to those known for removal of calculus or for disinfection of periodontal pockets. Major changes in organic as well as inorganic components of the cementum were observed following Nd:YAG laser irradiation (wavelength 1064 nm, pulse duration 250 μs, free running, pulse repetition rate 20 Hz, fiber diameter 320 μm, contact mode; Iskra Twinlight, Fontona, Slovenia). Er:YAG laser irradiation (wavelength 2.94 μm, pulse duration 250 μs, free running, pulse repetition rate 6 Hz, focus diameter 620 μm, air water cooling 30 ml/min; Iskra Twinlight, Fontona, Slovenia) significantly reduced the Amid bands due to changes in the organic components. After irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, q-switched, pulse repetition rate 20 Hz, beam diameter 800 μm, contact mode, water cooling 30 ml/min; laboratory prototype) only minimal reductions in the peak intensity of the Amide-II band were detected.

  4. Strain engineering in graphene by laser irradiation

    SciTech Connect

    Papasimakis, N.; Mailis, S.; Huang, C. C.; Al-Saab, F.; Hewak, D. W.; Luo, Z.; Shen, Z. X.

    2015-02-09

    We demonstrate that the Raman spectrum of graphene on lithium niobate can be controlled locally by continuous exposure to laser irradiation. We interpret our results in terms of changes to doping and mechanical strain and show that our observations are consistent with light-induced gradual strain relaxation in the graphene layer.

  5. [The action of short-range low-intensity infrared laser irradiation on the functional and metabolic parameters of the isolated rat myocardium in hypoxia].

    PubMed

    Luk'ianova, L D; Denisov, I M; Zamula, S V; Meller, S M

    1991-03-01

    It was found that infrared laser radiation (IRL) reduces the sparing action of acute hypoxia on ventricular transport function of low-resistant animals and accelerates the recovery of the function during the post-hypoxia period. The effect was caused by the IRL affecting directly the speed of perfusion through the myocardium and thus the latter's breathing rate. The protective effect of the IRL was practically absent in highly resistant animals, which may be indicative of the existence of basic differences in the regulatory systems which is responsible for local vasodilation and supply of oxygen to cells, and which participates in the formation of resistance of cardiomyocytes to oxygen shortage.

  6. Heat profiles of laser-irradiated nails.

    PubMed

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A; Kendler, Michael; Simon, Jan C; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

  7. Heat profiles of laser-irradiated nails.

    PubMed

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A; Kendler, Michael; Simon, Jan C; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises. PMID:24407504

  8. Heat profiles of laser-irradiated nails

    NASA Astrophysics Data System (ADS)

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A.; Kendler, Michael; Simon, Jan C.; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

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

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Noguchi, Jun; Yan, Jiwang

    2016-10-01

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

  10. Continuous wave laser irradiation of explosives

    NASA Astrophysics Data System (ADS)

    Moore, David; McGrane, Shawn

    2011-06-01

    Quantitative measurements of the levels of continuous wave (CW) laser light that can be safely applied to bare explosives during contact operations were obtained at 532 nm, 785 nm, and 1550 nm wavelengths. A thermal camera was used to record the temperature of explosive pressed pellets and single crystals while they were irradiated using a measured laser power and laser spot size. No deflagration to detonation transitions were observed for the single crystals or pressed pellets in the unconfined geometry tested. Except for the photochemistry of DAAF, TATB and PBX 9502, all reactions appeared to be thermal using a 532 nm wavelength laser. The laser power thresholds for thermal damage in some of the materials at 1550 nm were significantly lower than for the 532 nm laser wavelength. No reactions were observed in any of the studied explosives using the available 300 mW laser at 785 nm wavelength. Laser damage and reaction thresholds are presented for pressed pellets of PBX9501, PBX9502, Composition B, HMX, TATB, RDX, DAAF, PETN, and TNT and single crystals of RDX, HMX, and PETN for each of the laser wavelengths.

  11. Colour changes by laser irradiation of reddish building limestones

    NASA Astrophysics Data System (ADS)

    Grossi, C. M.; Benavente, D.

    2016-10-01

    We have used X-ray photoelectron spectroscopy (XPS) as a novel method to investigate the causes of colour changes in a reddish limestone under irradiation by a Q-switched Nd:YAG 1064 nm laser. We irradiated clean dry and wet surfaces of Pidramuelle Roja, a building stone frequently used in the Asturian heritage, at fluences ranging from 0.12 to 1.47 J cm-2. We measured the colour coordinates and undertook XPS analysis of the state of oxidation of iron both before and after irradiation. Visible colour changes and potential aesthetic damage occurred on dry surfaces from a fluence of 0.31 J cm-2, with the stone showing a greening effect and very intense darkening. The colour change on dry surfaces was considerably higher than on wet surfaces, which at the highest fluence (1.47 J cm-2) was also above the human visual detection threshold. The use of XPS demonstrated that the change in colour (chroma and hue) is associated with a reduction in the iron oxidation state on dry surfaces during laser irradiation. This points out to a potential routinary use of XPS to analyse causes of colour changes during laser cleaning in other types of coloured building stones.

  12. Zeeman effect induced by intense laser light.

    PubMed

    Stambulchik, E; Maron, Y

    2014-08-22

    We analyze spectral line shapes of hydrogenlike species subjected to fields of electromagnetic waves. It is shown that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman effect induced by a visible or infrared light can be experimentally observed using present-day powerful lasers. In addition, the effect may be used for diagnostics of focused beam intensities achieved at existing and newly built laser facilities. PMID:25192094

  13. Zeeman effect induced by intense laser light.

    PubMed

    Stambulchik, E; Maron, Y

    2014-08-22

    We analyze spectral line shapes of hydrogenlike species subjected to fields of electromagnetic waves. It is shown that the magnetic component of an electromagnetic wave may significantly influence the spectra. In particular, the Zeeman effect induced by a visible or infrared light can be experimentally observed using present-day powerful lasers. In addition, the effect may be used for diagnostics of focused beam intensities achieved at existing and newly built laser facilities.

  14. Low intensity laser therapy accelerates muscle regeneration in aged rats

    PubMed Central

    Vatansever, Fatma; Rodrigues, Natalia C.; Assis, Livia L.; Peviani, Sabrina S.; Durigan, Joao L.; Moreira, Fernando M.A.; Hamblin, Michael R.; Parizotto, Nivaldo A.

    2013-01-01

    Background Elderly people suffer from skeletal muscle disorders that undermine their daily activity and quality of life; some of these problems can be listed as but not limited to: sarcopenia, changes in central and peripheral nervous system, blood hypoperfusion, regenerative changes contributing to atrophy, and muscle weakness. Determination, proliferation and differentiation of satellite cells in the regenerative process are regulated by specific transcription factors, known as myogenic regulatory factors (MRFs). In the elderly, the activation of MRFs is inefficient which hampers the regenerative process. Recent studies found that low intensity laser therapy (LILT) has a stimulatory effect in the muscle regeneration process. However, the effects of this therapy when associated with aging are still unknown. Objective This study aimed to evaluate the effects of LILT (λ=830 nm) on the tibialis anterior (TA) muscle of aged rats. Subjects and methods The total of 56 male Wistar rats formed two population sets: old and young, with 28 animals in each set. Each of these sets were randomly divided into four groups of young rats (3 months of age) with n=7 per group and four groups of aged rats (10 months of age) with n=7 per group. These groups were submitted to cryoinjury + laser irradiation, cryoinjury only, laser irradiation only and the control group (no cryoinjury/no laser irradiation). The laser treatment was performed for 5 consecutive days. The first laser application was done 24 h after the injury (on day 2) and on the seventh day, the TA muscle was dissected and removed under anesthesia. After this the animals were euthanized. Histological analyses with toluidine blue as well as hematoxylin-eosin staining (for counting the blood capillaries) were performed for the lesion areas. In addition, MyoD and VEGF mRNA was assessed by quantitative polymerase chain reaction. Results The results showed significant elevation (p<0.05) in MyoD and VEGF genes expression levels

  15. Lasers and Intense Pulsed Light Hidradenitis Suppurativa.

    PubMed

    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. PMID:26617364

  16. Lasers and Intense Pulsed Light Hidradenitis Suppurativa.

    PubMed

    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.

  17. Ion acceleration using high-contrast ultra-intense lasers

    NASA Astrophysics Data System (ADS)

    Fuchs, J.; Antici, P.; D'Humières, E.; Lefebvre, E.; Borghesi, M.; Brambrink, E.; Cecchetti, C.; Toncian, T.; Pépin, H.; Audebert, P.

    2006-06-01

    We have compared the acceleration of high-energy ions from the rear-surface of thin foils for various contrast conditions of the ultra-intense laser pulse irradiating the targets. The experiments were performed using the LULI 100 TW facility. We used Al targets of variable thicknesses and the laser pulse contrast ratio ahead of the main pulse was varied using either a fast Pockels cell or a single or double plasma mirror. The latter was installed at an intermediate field position, in between the focusing optics and the target, so that its effect was optimized. By improving with these two methods the laser pulse contrast, we have observed that we could significantly reduce the thickness of the target used for proton acceleration and at the same time increase both the cut-off energy of the accelerated protons and the energy conversion efficiency of the process.

  18. Fundamental Physics Explored with High Intensity Laser

    NASA Astrophysics Data System (ADS)

    Tajima, T.; Homma, K.

    2012-10-01

    Over the last century the method of particle acceleration to high energies has become the prime approach to explore the fundamental nature of matter in laboratory. It appears that the latest search of the contemporary accelerator based on the colliders shows a sign of saturation (or at least a slow-down) in increasing its energy and other necessary parameters to extend this frontier. We suggest two pronged approach enabled by the recent progress in high intensity lasers. First we envision the laser-driven plasma accelerator may be able to extend the reach of the collider. For this approach to bear fruit, we need to develop the technology of high averaged power laser in addition to the high intensity. For this we mention that the latest research effort of ICAN is an encouraging sign. In addition to this, we now introduce the concept of the noncollider paradigm in exploring fundamental physics with high intensity (and large energy) lasers. One of the examples we mention is the laser wakefield acceleration (LWFA) far beyond TeV without large luminosity. If we relax or do not require the large luminosity necessary for colliders, but solely in ultrahigh energy frontier, we are still capable of exploring such a fundamental issue. Given such a high energetic particle source and high-intensity laser fields simultaneously, we expect to be able to access new aspects on the matter and the vacuum structure from fundamental physical point of views. LWFA naturally exploits the nonlinear optical effects in the plasma when it becomes of relativistic intensity. Normally nonlinear optical effects are discussed based upon polarization susceptibility of matter to external fields. We suggest application of this concept even to the vacuum structure as a new kind of order parameter to discuss vacuum-originating phenomena at semimacroscopic scales. This viewpoint unifies the following observables with the unprecedented experimental environment we envision; the dispersion relation of

  19. Nanodot formation induced by femtosecond laser irradiation

    SciTech Connect

    Abere, M. J.; Kang, M.; Goldman, R. S.; Yalisove, S. M.; Chen, C.; Rittman, D. R.; Phillips, J. D.; Torralva, B.

    2014-10-20

    The femtosecond laser generation of ZnSe nanoscale features on ZnSe surfaces was studied. Irradiation with multiple exposures produces 10–100 nm agglomerations of nanocrystalline ZnSe while retaining the original single crystal structure of the underlying material. The structure of these nanodots was verified using a combination of scanning transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The nanodots continue to grow hours after irradiation through a combination of bulk and surface diffusion. We suggest that in nanodot formation the result of ultrafast laser induced point defect formation is more than an order of magnitude below the ZnSe ultrafast melt threshold fluence. This unique mechanism of point defect injection will be discussed.

  20. High-intensity laser-atom interactions

    NASA Astrophysics Data System (ADS)

    Joachain, Charles J.

    2014-11-01

    Following a historical introduction on the nature of light and its interaction with matter, a survey is given of the development of lasers capable of delivering short pulses of very intense radiation. The peak intensities of these laser pulses are so high that the corresponding laser fields can compete with, or even dominate, the Coulomb field in governing the dynamics of atomic systems. As a result, new phenomena, known as multiphoton processes, can occur. An outline is given of the basic properties found in the study of three important multiphoton processes. Firstly, the multiphoton ionization of atoms and the phenomenon of “above-threshold ionization”. Secondly, the emission by atoms of high-order harmonics of the frequency of the driving laser and their use to generate laser pulses having durations in the attosecond range. Thirdly, laser-assisted electron-atom collisions. A review is then given of the main non-perturbative methods which have been used to perform theoretical studies of multiphoton processes.

  1. Intense infrared lasers and laboratory astrophysics

    NASA Astrophysics Data System (ADS)

    Roso, Luis

    2012-02-01

    Electrons accelerate due to the huge electric field of the laser itself, and so they can generate very particular plasmas because the ionization process occurs in a few femtosecond, or even in a fraction of a femtosecond. Lasers can be focused now to intensities beyond 1022W/cm2 and there are projects to arrive up 1026W/cm2. Electric fields of the laser arrive now to 1014V/cm and magnetic fields reach the Megatesla. This is a monster density of electromagnetic energy, so that we are close to obtain light denser than matter. In this respect it is very convenient to observe that the well known Einstein's energy - mass equation, E = mc2, can be rewritten for laser light I = ρc3, I being the laser intensity and ρ the equivalent density. There are several PW lasers around the world, in operation or in construction, and one of them is going to be at Salamanca's CLPU.

  2. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  3. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron–positron pairs can be optimized by a suitable choice of the intensity ratio.

  4. Central nervous system transplantation benefited by low-level laser irradiation

    NASA Astrophysics Data System (ADS)

    Rochkind, S.; Lubart, Rachel; Wollman, Yoram; Simantov, Rabi; Nissan, Moshe; Barr-Nea, Lilian

    1990-06-01

    Effect of low-level laser irradiation on the central nervous system transplantation is reported. Ernbryonal brain allografts were transplanted into the brain of 20 adult rats and peripheral nerve graft transplanted into the severely injured spinal cord of 16 dogs. The operated wound of 10 rats and 8 dogs were exposed daily for 21 days to lowpower laser irradiation CW HeNe laser (35 mW, 632.8 run, energy density of 30 J/cm2 at each point for rats and 70 J/cm2 at each point for dogs). This study shows that (i) the low-level laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between embryonal transplants and host brain; (ii) Dogs made paraplegic by spinal cord injury were able to walk 3-6 months later. Recovery of these dogs was effected by the implantation of a fragment of autologous sciatic nerve at the site of injury and subsequently exposing the dogs to low-level laser irradiation. The effect of laser irradiation on the embryonal nerve cells grown in tissue culture was also observed. We found that low-level laser irradiation induced intensive migration of neurites outward of the aggregates 15-22 The results of the present study and our previous investigations suggest that low-level laser irradiation is a novel tool for treatment of peripheral and central nervous system injuries.

  5. Solar irradiance dictates settlement timing and intensity of marine mussels

    PubMed Central

    Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X. Antón; Fernández-Reiriz, Mª José

    2016-01-01

    Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance. PMID:27384527

  6. Solar irradiance dictates settlement timing and intensity of marine mussels.

    PubMed

    Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X Antón; Fernández-Reiriz, M José

    2016-01-01

    Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance. PMID:27384527

  7. Solar irradiance dictates settlement timing and intensity of marine mussels.

    PubMed

    Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X Antón; Fernández-Reiriz, M José

    2016-07-07

    Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance.

  8. Transverse intensity transformation by laser amplifiers

    NASA Astrophysics Data System (ADS)

    Litvin, Igor A.; King, Gary; Collett, Oliver J. P.; Strauss, Hencharl J.

    2015-03-01

    Lasers beams with a specific intensity profile such as super-Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping. We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.

  9. System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

    DOEpatents

    Skupsky, Stanley; Kessler, Terrance J.; Short, Robert W.; Craxton, Stephen; Letzring, Samuel A.; Soures, John

    1991-01-01

    In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies ("colors") cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers.

  10. Liquid-xenon detector under the intensive pulse irradiation conditions

    NASA Astrophysics Data System (ADS)

    Kirsanov, M. A.

    2016-02-01

    The effect of intense pulsed irradiation on the operation of the liquid xenon spectrometer was studied. The ionization chamber filled with liquid xenon was irradiated by bremsstrahlung pulses of the microtron. The pulse repetition rate was 400 Hz. The absorbed dose ranged from 10-7 to 0.1 Gy per pulse. Stable operation of the liquid xenon spectrometer in the intervals between the pulses of the accelerator was shown for a long time.

  11. Thermal Changes of Maize Seed by Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.

    2015-09-01

    In this research, the thermal evolution in maize seeds ( Zea mays L.) was studied when low-intensity laser irradiation was applied during 60 s. The seeds were irradiated in three different conditions: suspended in air, placed on an aluminum surface, and finally placed on a cardboard; the evolution of the seed temperature was measured by an infrared camera. Photoacoustic spectroscopy and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient (β ) of the seeds. The results indicate that using 650 nm laser light and 27.4 mW, it is possible to produce temperature changes (up to 9.06°C after 1 min) on the seeds. Comparing the mean temperature of the seeds, during and after the incidence of light from a laser, it was found that there were statistically significant differences (P≤ 0.05) from time t1 to time t_{16} (t1 to t_{16}) and t3 to t_{16}, for the laser turned on and off, respectively. The seed condition that had the highest temperature variation, relative to the initial temperature (during the irradiation laser exposure), involved the seeds suspended in air. With regard to the stage of decay of the temperature, it was found that the seed condition that decays more slowly was the seed placed on the cardboard. It was also found that black-dyed maize seeds are optically opaque in the 300 nm to 700 nm range Also, the thermal diffusion length is smaller than the optical penetration length. In the present investigation, it was shown that there is a thermal component associated with the mechanisms of laser biostimulation, which is also a function of the container materials of the seed. In this way, the effects of laser treatment on maize seeds involve at least a temperature effect. It is important to know the temperature changes in the seeds that have been irradiated with a laser beam since they could have substantial practical and theoretical importance.

  12. Generation of Ultra-high Intensity Laser Pulses

    SciTech Connect

    N.J. Fisch; V.M. Malkin

    2003-06-10

    Mainly due to the method of chirped pulse amplification, laser intensities have grown remarkably during recent years. However, the attaining of very much higher powers is limited by the material properties of gratings. These limitations might be overcome through the use of plasma, which is an ideal medium for processing very high power and very high total energy. A plasma can be irradiated by a long pump laser pulse, carrying significant energy, which is then quickly depleted in the plasma by a short counterpropagating pulse. This counterpropagating wave effect has already been employed in Raman amplifiers using gases or plasmas at low laser power. Of particular interest here are the new effects which enter in high power regimes. These new effects can be employed so that one high-energy optical system can be used like a flashlamp in what amounts to pumping the plasma, and a second low-power optical system can be used to extract quickly the energy from the plasma and focus it precisely. The combined system can be very compact. Thus, focused intensities more than 10{sup 25} W/cm{sup 2} can be contemplated using existing optical elements. These intensities are several orders of magnitude higher than what is currently available through chirped pump amplifiers.

  13. Focusing of Intense Laser via Parabolic Plasma Concave Surface

    NASA Astrophysics Data System (ADS)

    Zhou, Weimin; Gu, Yuqiu; Wu, Fengjuan; Zhang, Zhimeng; Shan, Lianqiang; Cao, Leifeng; Zhang, Baohan

    2015-12-01

    Since laser intensity plays an important role in laser plasma interactions, a method of increasing laser intensity - focusing of an intense laser via a parabolic plasma concave surface - is proposed and investigated by three-dimensional particle-in-cell simulations. The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude. Compared with the improvement via laser optics approaches, this scheme is much more economic and appropriate for most femtosecond laser facilities. supported by National Natural Science Foundation of China (Nos. 11174259, 11175165), and the Dual Hundred Foundation of China Academy of Engineering Physics

  14. Pulsed laser irradiation of metal multilayers.

    SciTech Connect

    Adams, David Price; McDonald, Joel Patrick

    2010-11-01

    Vapor-deposited, exothermic metal-metal multilayer foils are an ideal class of materials for detailed investigations of pulsed laser-ignited chemical reactions. Created in a pristine vacuum environment by sputter deposition, these high purity materials have well-defined reactant layer thicknesses between 1 and 1000 nm, minimal void density and intimate contact between layers. Provided that layer thicknesses are made small, some reactive metal-metal multilayer foils can be ignited at a point by laser irradiation and exhibit subsequent high-temperature, self-propagating synthesis. With this presentation, we describe the pulsed laser-induced ignition characteristics of a single multilayer system (equiatomic Al/Pt) that exhibits self-propagating synthesis. We show that the thresholds for ignition are dependent on (i) multilayer design and (ii) laser pulse duration. With regard to multilayer design effects on ignition, there is a large range of multilayer periodicity over which ignition threshold decreases as layer thicknesses are made small. We attribute this trend of decreased ignition threshold to reduced mass transport diffusion lengths required for rapid exothermic mixing. With regard to pulse duration effects, we have determined how ignition threshold of a single Al/Pt multilayer varies with pulse duration from 10{sup -2} to {approx} 10{sup -13} sec (wavelength and spot size are held constant). A higher laser fluence is required for ignition when using a single laser pulse {approx} 100 fs or 1 ps compared with nanosecond or microsecond exposure, and we attribute this, in part, to the effects of reactive material being ablated when using the shorter pulse durations. To further understand these trends and other pulsed laser-based processes, our discussion concludes with an analysis of the heat-affected depths in multilayers as a function of pulse duration.

  15. Laser irradiation in Nd{sup 3+} doped strontium barium niobate glass

    SciTech Connect

    Haro-Gonzalez, P.; Martin, I. R.; Arbelo-Jorge, E.; Gonzalez-Perez, S.; Caceres, J. M.; Nunez, P.

    2008-07-01

    A local nanocrystalline formation in a neodymium doped strontium barium niobate (SBN) glass has been obtained under argon laser irradiation. The intense emission around 880 nm, originated from the {sup 4}F{sub 3/2} ({sup 4}F{sub 5/2}) thermalized level when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam, has been studied. The intensities and lifetimes change from this level inside and outside the irradiated area made by the laser excitation. They have been analyzed and demonstrated that the desvitrification process has been successfully achieved. These results confirm that nanocrystals of SBN have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the emission properties of nanocrystals of the bulk glass ceramic sample. The present study also suggests that the SBN nanocrystal has a potential application as temperature detector.

  16. Interaction of Intense Lasers with Plasmas

    NASA Astrophysics Data System (ADS)

    Shvets, Gennady

    1995-01-01

    This thesis addresses two important topics in nonlinear laser plasma physics: the interaction of intense lasers with a non thermal homogeneous plasma, the excitation of laser wakefields in hollow plasma channels, and the stability of channel guided propagation of laser pulses. In the first half of this thesis a new theoretical approach to the nonlinear interaction of intense laser pulses with underdense plasmas is developed. Unlike previous treatments, this theory is three-dimensional, relativistically covariant, and does not assume that a<<1, where a=eA/mc^2 is a dimensionless vector potential. This formalism borrows the diagrammatic techniques from quantum field theory, yet remains classical. This classical field theory, which treats cold plasma as a relativistic field interacting with the electromagnetic fields, introduces an artificial length scale which is smaller than any physically relevant spatial scale. By adopting a special (Arnowitt -Fickler) gauge, electromagnetic waves in a cold relativistic plasma are separated into "photons" and "plasmons" which are the relativistic extensions of electrostatic and electromagnetic waves in a cold stationary plasma. The field-theoretical formalism is applied to a variety of nonlinear problems including harmonic generation, parametric instabilities, and nonlinear corrections to the index of refraction. For the first time the rate of the second harmonic emission from a homogeneous plasma is calculated and its dependence on the polarization of the incident radiation is studied. An experimental check of this calculation is suggested, based on the predicted non-linear polarization rotation (the second harmonic is emitted polarized perpendicularly to polarization of the incident signal). The concept of renormalization is applied to the plasma and electromagnetic radiation (photons and plasmons). To the lowest order, this corresponds to relativistically correcting the electron mass for its oscillation in an intense EM field

  17. [Classification of laser irradiation and safety measures].

    PubMed

    Takac, S; Stojanović, S

    1998-01-01

    The use of lasers in medicine and especially surgery is rapidly expanding in many disciplines from clinical laboratory to the office practice and operating room. It is essential that users of this powerful tool have knowledge of their potential hazards and the measures to protect patients and personnel against injuries or undesired effects. Below, we have included information about the way lasers are classified; the development of protective standards; the current status of protection standards that apply to lasers, especially those used in medicine/surgery; the specific kinds of hazards associated with medical/surgical applications; and the measures by which hazards have been controlled. Since laser technology is still a young field, it is likely that problems unknown at present will occur and methodologies for controlling hazards will evolve. The American National Standards Committee produced the first consensus standard Z136.1 in 1973. The Standard was revised in 1976 to accommodate differences in biological effects for different wavelengths in the visible spectrum. The ANSI Standard has been revised again in 1980, and currently (1984) there are two additional standards in preparation, Z136.2 and 136.3, which treat the safe use of light-emitting diodes and the safe use of lasers in the health care environment, respectively. Most surgical and medical lasers are Class III or IV. Some lasers have a Class IV therapy level beam plus a Class I or II alignment beam. When using lasers, it is possible to generate incandescence or fluorescence in an irradiated object. This can occur even with protective eyewear, because the correlated radiations are usually of a different wavelength. Generally, this should not be a problem when beams are directed at biological material. However, hazard could be caused by lasers designed to produce fluorescence. Control of correlative radiation in a laser system is required in the federal regulations. Hazards of lasers may be grouped as

  18. Method for mounting laser fusion targets for irradiation

    DOEpatents

    Fries, R. Jay; Farnum, Eugene H.; McCall, Gene H.

    1977-07-26

    Methods for preparing laser fusion targets of the ball-and-disk type are disclosed. Such targets are suitable for irradiation with one or two laser beams to produce the requisite uniform compression of the fuel material.

  19. Laser irradiation of carbon nanotube films: Effects and heat dissipation probed by Raman spectroscopy

    SciTech Connect

    Mialichi, J. R.; Brasil, M. J. S. P.; Iikawa, F.; Verissimo, C.; Moshkalev, S. A.

    2013-07-14

    We investigate the thermal properties of thin films formed by single- and multi-walled carbon nanotubes submitted to laser irradiation using Raman scattering as a probe of both the tube morphology and the local temperature. The nanotubes were submitted to heating/cooling cycles attaining high laser intensities ({approx}1.4 MW/cm{sup 2}) under vacuum and in the presence of an atmosphere, with and without oxygen. We investigate the heat diffusion of the irradiated nanotubes to their surroundings and the effect of laser annealing on their properties. The presence of oxygen during laser irradiation gives rise to an irreversible increase of the Raman efficiency of the carbon nanotubes and to a remarkable increase of the thermal conductivity of multi-walled films. The second effect can be applied to design thermal conductive channels in devices based on carbon nanotube films using laser beams.

  20. Review of Astrophysics Experiments on Intense Lasers

    SciTech Connect

    Remington, B A; Drake, R P; Takabe, H; Arnett, D

    2000-01-19

    Astrophysics has traditionally been pursued at astronomical observatories and on theorists' computers. Observations record images from space, and theoretical models are developed to explain the observations. A component often missing has been the ability to test theories and models in an experimental setting where the initial and final states are well characterized. Intense lasers are now being used to recreate aspects of astrophysical phenomena in the laboratory, allowing the creation of experimental testbeds where theory and modeling can be quantitatively tested against data. We describe here several areas of astrophysics--supernovae, supernova remnants, gamma-ray bursts, and giant planets--where laser experiments are under development to test our understanding of these phenomena.

  1. [The effect of low-intensity red and infrared laser radiation on the rat arterial and deoxygenated blood].

    PubMed

    Timoshenko, T E; Dvoretskiĭ, D P

    2010-10-01

    In vitro experiments the effect of low-intensity red or near-infrared laser irradiation on the blood samples (1.5 ml from abdominal aorta of Wistar rats) were studied. The diode laser light (lambda = 650 nm or 808 nm, power density 15.6 mW/cm2, duration 15 min) were used. In some experiments the deoxygenated blood as object for comparison with arterial blood was chosen. Under red laser irradiation we observed a significant increase of average volume of erythrocytes as well as mean amount of free (disaggregated) leukocytes especially in case of the deoxygenated blood. At the same time the concentration of Ca2+ and Na+ were decreased. The effects of infrared laser irradiation on indices mentioned above were not significant. We believe that red low-intensity laser irradiation on the blood is an important factor for theological properties in the field of microcirculation.

  2. Laser annealing of neutron irradiated boron-10 isotope doped diamond

    SciTech Connect

    Jagannadham, K.; Butler, J. E.

    2011-01-01

    10B isotope doped p-type diamond epilayer grown by chemical vapor deposition on (110) oriented type IIa diamond single crystal substrate was subjected to neutron transmutation at a fluence of 2.4 9 1020 thermal and 2.4 9 1020 fast neutrons. After neutron irradiation, the epilayer and the diamond substrate were laser annealed using Nd YAG laser irradiation with wave length, 266 nm and energy, 150 mJ per pulse. The neutron irradiated diamond epilayer and the substrate were characterized before and after laser annealing using different techniques. The characterization techniques include optical microscopy, secondary ion mass spectrometry, X-ray diffraction, Raman, photoluminescence and Fourier Transform Infrared spectroscopy, and electrical sheet conductance measurement. The results indicate that the structure of the irradiation induced amorphous epilayer changes to disordered graphite upon laser annealing. The irradiated substrate retains the (110) crystalline structure with neutron irradiation induced defects.

  3. Recent numerical results on double-layer simulation in high-intensity laser--plasma interaction

    SciTech Connect

    Szichman, H.

    1988-06-01

    Numerical studies on dynamic electric fields and double layers created inside of plasmas irradiated at laser intensities of 10/sup 17/ and 10/sup 18/ Wcm/sup 2/ were carried out using a macroscopic two-fluid model including nonlinear forces and the complete intensity dependent optical response for heating and dielectric force effects. This was possible only by longer computation times since the temporal and spatial step sizes had to be reduced accordingly. Electrostatic fields as high as 10/sup 9/ and 10/sup 10/ Vcm were, respectively, measured for both laser intensities and the coupling of irradiated electromagnetic waves to generate Langmuir longitudinal waves is shown to be possible for the first time. The development and production of the well-known density minima (cavitons) because of nonlinear forces is also confirmed, their prominent appearance being in direct relation to the stronger effect of the high irradiances applied.

  4. Color changes in CR-39 nuclear track detector by gamma and laser irradiation

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Said, A. F.; Atta, M. R.; El-Melleegy, W. M.; El-Meniawy, S.

    2006-07-01

    A study of the effect of gamma and laser irradiation on the color changes of polyallyl diglycol (CR-39) solid-state nuclear track detector was performed. CR-39 detector samples were classified into two main groups. The first group was irradiated with gamma doses at levels between 20 and 300 kGy, whereas the second group was exposed to infrared laser radiation with energy fluences at levels between 0.71 and 8.53 J/cm(2) . The transmission of these samples in the wavelength range 300-2500 nm, as well as any color changes, was studied. Using the transmission data, both the tristimulus and the coordinate values of the Commission Internationale de l'Eclairage (CIE) LAB were calculated. Also, the color differences between the non-irradiated samples and those irradiated with different gamma or laser doses were calculated. The results indicate that the CR-39 detector acquires color changes under gamma or laser irradiation, but it has more response to color changes by gamma irradiation. In addition, structural property studies using infrared spectroscopy were performed. The results indicate that the irradiation of a CR-39 detector with gamma or laser radiations causes the cleavage of the carbonate linkage that can be attributed to the H abstraction from the backbone of the polymer, associated with the formation of CO 2 and OH with varying intensities.

  5. Suppressed tuberculin reaction in guinea pigs following laser irradiation

    SciTech Connect

    Inoue, K.; Nishioka, J.; Hukuda, S.

    1989-01-01

    Tuberculin reactions were tested at the bilateral sites of the backs of sensitized guinea pigs. Laser irradiation at an energy fluence of 3.6 J at one site of reaction suppressed the reaction not only at the irradiated site but also at the contralateral nonirradiated site. These phenomena were observed when mononuclear cells were dominant in the perivascular cellular infiltration. The results indicate that local irradiation with a low-power laser has systemic inhibitory effects on delayed hypersensitivity reactions.

  6. Effect of laser irradiation of nanoparticles in aqueous uranium salt solutions on nuclide activity

    SciTech Connect

    Simakin, Aleksandr V; Shafeev, Georgii A

    2011-07-31

    This paper presents an experimental study of the effect of laser irradiation of aqueous uranyl chloride solutions containing gold nanoparticles on the activity of the uranium series radionuclides {sup 234}Th, {sup 234m}Pa, and {sup 235}U. The solutions were exposed to femtosecond Ti:sapphire laser pulses and to the second or third harmonic of a Nd:YAG laser (150-ps pulses) at a peak intensity in the medium of {approx}10{sup 12} W cm{sup -2}. The activities of the radionuclides in the irradiated solutions were shown to differ markedly from their equilibrium values. The sign of the deviation depends on the laser wavelength. The measured activity deviations can be interpreted as evidence that laser exposure of nanoparticles accelerates the alpha and beta decays of the radionuclides. The observed effects are accounted for in terms of a mechanism that involves resonant enhancement of optical waves by metallic nanoparticles. (interaction of laser radiation with matter)

  7. The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

    SciTech Connect

    Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.; Adams, David P.

    2015-12-07

    Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.

  8. The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

    NASA Astrophysics Data System (ADS)

    Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.; Adams, David P.

    2015-12-01

    Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.

  9. Effects of speckle-like laser irradiation on growth of bacteria in vitro

    NASA Astrophysics Data System (ADS)

    Popov, A. Yu.; Popova, N. A.; Tyurin, A. V.; Grimblatov, V.

    2013-03-01

    In this work, for the first time, we have demonstrated the biological effects upon in vitro growth of bacteria and human peripheral blood erythrocytes of the irradiation with speckle-like highly-gradient laser light. Measurements of the growth of Staphylococcus aureus with and without antibiotic irradiated with uniform or interference pattern of intensity spatial distribution have shown strong dependence on the spatial frequency of the irradiation. Maximum inhibition of the bacteria growth was achieved at the frequency 1000 fringes/mm. It was also found that human blood erythrocytes exposure to such radiation at the power density typical for laser phototherapy could damage the erythrocytes. A possible explanation of the photo-biological effects of laser speckle irradiation relying on the electron-ion processes similar to those that occur under inhomogeneous illumination in inorganic media and called photo-stimulated diffusion of ions (Dember effect) is proposed and discussed.

  10. Numerical modelling for intense laser physics

    SciTech Connect

    Audit, Edouard; Schurtz, Guy

    2007-04-06

    The recent start-up of large intense laser facilities such as the Ligne d'Integration Laser (LIL) or the LULI2000 and the arrival in the near future of the Laser Megajoule (LMJ) gives a great perspective for laboratory astrophysics, dense matter studies and inertial fusion. To make the most of these opportunities, several teams have set up a program which aims at satisfying simulation needs in the fields of Astrophysics, Hot Dense Matter and Inertial Confinement Fusion. A large part of the scientific production in these fields relies upon simulations of complex unsteady hydro flows, coupled to non equilibrium transport and chemical kinetics. As the characteristic time scales of transport may be much shorter than the fluid time scale, implicit numerical methods are often required. Atomics physics data, and in particular equation of states and opacities, are a key and critical ingredients for the simulations done in stellar physics, laboratory astrophysics and in many other fields of astrophysics. We will show the different codes used in the various fields of the project and the different methods used to capture the desired physics. We will also present ODALISC, a new opacity database aiming at providing the community with spectral opacities and numerical tools to use them efficiently in radiation-hydrodynamics codes.

  11. Fast Electron Generation in Cones with Ultra-Intense Laser Pulses

    SciTech Connect

    Mackinnon, A; VanWoerkom, L; Akli, K; Bartal, T; Beg, F; Chawla, S; Chen, C; Chowdhury, E; Freeman, R; Hey, D; Key, M; King, J; Link, A; MacPhee, A; Offermann, D; Ovchinnikov, V; Patel, P; Schumacher, D; Stephens, R; Tsui, Y; Ma, T

    2007-12-07

    Experimental results from copper cones irradiated with ultra-intense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {micro}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser cone interaction is dominated by preplasma created from the long duration, low energy pre-pulse from the laser.

  12. Energetic electron propagation in solid targets driven by the intense electric fields of femtosecond laser pulses

    SciTech Connect

    Seely, J. F.; Szabo, C. I.; Audebert, P.; Brambrink, E.

    2011-06-15

    An analytical model is used to interpret experimental data on the propagation of energetic electrons perpendicular to and parallel to the propagation direction of intense femtosecond laser pulses that are incident on solid targets. The pulses with {approx_equal}10{sup 20} W/cm{sup 2} intensity are incident normal onto a gadolinium or tungsten wire embedded in an aluminum substrate, and MeV electrons generated in the focal spot propagate along the laser direction into the irradiated wire. Electrons also propagate laterally from the focal spot through the aluminum substrate and into a dysprosium or hafnium spectator wire at a distance up to 1 mm from the irradiated wire. The ratio of the K shell emission from the spectator and irradiated wires is a measure of the numbers and energies of the MeV electrons propagating parallel to and perpendicular to the intense oscillating electric field of the laser pulse. It is found that the angular distribution of electrons from the focal spot is highly non-isotropic, and approximately twice as many electrons are driven by the electric field toward the spectator wire as into the irradiated wire. This quantitative result is consistent with the qualitative experimental observation that the oscillating electric field of an intense femtosecond laser pulse, when interacting with a heavy metal target, preferentially drives energetic electrons in the electric field direction as compared to perpendicular to the field.

  13. Control of light backscattering in blood during intravenous laser irradiation

    NASA Astrophysics Data System (ADS)

    Melnik, Ivan S.; Popov, V. D.; Rusina, Tatyana V.; Dets, Sergiy M.

    1997-02-01

    One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.

  14. Directed fast electron beams in ultraintense picosecond laser irradiated solid targets

    SciTech Connect

    Ge, X. L.; Lin, X. X.; Yuan, X. H. E-mail: ytli@iphy.ac.cn; Sheng, Z. M.; Carroll, D. C.; Neely, D.; Gray, R. J.; Tresca, O.; McKenna, P.; Yu, T. P.; Chen, M.; Liu, F.; Zhuo, H. B.; Zielbauer, B.; and others

    2015-08-31

    We report on fast electron transport and emission patterns from solid targets irradiated by s-polarized, relativistically intense, picosecond laser pulses. A beam of multi-MeV electrons is found to be transported along the target surface in the laser polarization direction. The spatial-intensity and energy distributions of this beam are compared with the beam produced along the laser propagation axis. It is shown that even for peak laser intensities an order of magnitude higher than the relativistic threshold, laser polarization still plays an important role in electron energy transport. Results from 3D particle-in-cell simulations confirm the findings. The characterization of directional beam emission is important for applications requiring efficient energy transfer, including secondary photon and ion source development.

  15. High-power, high-intensity laser propagation and interactions

    SciTech Connect

    Sprangle, Phillip; Hafizi, Bahman

    2014-05-15

    This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.

  16. Influence of He-Ne laser irradiation on giant chromosomes

    NASA Astrophysics Data System (ADS)

    Brill, Gregory E.; Panina, Nadezda P.; Sonin, Vadim K.; Belyanina, Svetlana I.

    1996-01-01

    Influence of He-Ne laser irradiation (lambda - 632.8 nm, power density - 1.5 mW/cm2) on polytene chromosomes of salivary glands cells of Chironomus plumosus in different conditions of exposure was studied. Living larvae or isolated salivary glands were exposed to irradiation. He-Ne laser irradiation was stated to influence the functional activity of polytene chromosomes. The response of the genetic apparatus to the laser light action was shown to depend on the irradiation dose and fractional character of the dose exposure, on the initial functional state of chromosome loci and may be manifested both by activation and inhibition of definite regions of the genome. The phenomenon of adaptation of the genetic system to He- Ne laser irradiation is revealed.

  17. Irradiation Of Prostatic Carcinoma By Neodymium-YAG-Laser

    NASA Astrophysics Data System (ADS)

    Bowering, R.; Hofstetter, A.; Keiditsch, E.; Frank, F.

    1980-05-01

    Human Cadaver prostate tumors and canine prostate glands in vivo were irradiated by Nd:YAG laser with different power levels and pulse durations. Temperature measurements were carried out by an arrangement of micro thermo couple, digital volt meter and computer in different layers of the prostate and the rectum. The temporal and spatial temperature measurements showed a good correlation with the histological findings. Endoscopic laser irradiation of prostatic carcinoma in man was performed after TUR. There was a large penetration depth resulting a deep necrosis, but no perforation and no changes in the rectum were to be found also after high power laser irradiation.

  18. Low intensity laser therapy: the clinical approach

    NASA Astrophysics Data System (ADS)

    Kahn, Fred

    2006-02-01

    Recently, there has been significant improvement in the process of research and application of Low Intensity Laser Therapy (LILT). Despite this positive direction, a wide discrepancy between the research component and clinical understanding of the technology remains. In our efforts to achieve better clinical results and more fully comprehend the mechanisms of interaction between light and cells, further studies are required. The clinical results presented in this paper are extrapolated from a wide range of musculoskeletal problems including degenerative osteoarthritis, repetitive motion injuries, sports injuries, etc. The paper includes three separate clinical studies comprising 151, 286 and 576 consecutive patient discharges at our clinic. Each patient studied received a specific course of treatment that was designed for that individual and was modified on a continuing basis as the healing process advanced. On each visit, clinical status correlation with the duration, dosage and other parameters was carried out. The essentials of the treatment consisted of a three stage approach. This involved a photon stream emanating from a number of specified gallium-aluminum-arsenide diodes; stage one, red light array, stage two consisting of an array of infrared diodes and stage three consisting of the application of an infrared laser diode probe. On average, each of these groups required less than 10 treatments per patient and resulted in a significant improvement / cure rate greater than 90% in all conditions treated. This report clearly demonstrates the benefits of LILT, indicating that it should be more widely adapted in all medical therapeutic settings.

  19. Laser Ion Acceleration from the Interaction of Ultra-Intense laser Pulse with thi foils

    SciTech Connect

    Allen, M

    2004-03-12

    The discovery that ultra-intense laser pulses (I > 10{sup 18} W/cm{sup 2}) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 10{sup 18} W/cm{sup 2}), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by U{sub p} = ([1 + I{lambda}{sup 2}/1.3 x 10{sup 18}]{sup 1/2} - 1) m{sub o}c{sup 2}, where I{lambda}{sup 2} is the irradiance in W{micro}m{sup 2}/cm{sup 2} and m{sub o}c{sup 2} is the electron rest mass.At laser irradiance of I{lambda}{sup 2} {approx} 10{sup 20} W{micro}m{sup 2}/cm{sup 2}, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target.

  20. Morphological analysis of the retrofilled apical dentin surfaces irradiated with CO2 laser

    NASA Astrophysics Data System (ADS)

    Aun, Carlos E.; Lage-Marques, Jose L.; Gavini, Giulio; Clasen, Naya F.; Matsumoto, Koukichi

    1998-04-01

    Countless researches conducted in these last years have compared the sealing capacity of various materials for retrofillings. Besides, the association of laser irradiation to traditional procedures inquires to increase the success of this kind of treatment. The purpose of this study was to evaluate the morphological changes on dentin surface and the junction between retrofilling material and apical cavity, with different materials irradiated or not with CO2 laser, in scanning electron microscopy. The following materials were used: Group A yields Super EBA; group B yields Super EBA and CO2 laser irradiation (Luxar System); group C yields Glass Ionomer Cement; group D yields Glass Ionomer Cement and CO2 laser. In groups B and D the power set was 2 watts, 20 msec, with a CT3105 ceramic point, and the power density for the CO2 laser application was 397,93 w/cm2. The morphological analysis permitted to conclude that the dentin laser irradiation showed different and less intense superficial alteration when compared with retrofilling materials. In most cases, the alterations to the material surfaces showed cavities and craters. Group B presented more irregular and affected surfaces, creating blank spaces in the adjacent areas to the radicular dentinal surfaces after laser application, probably because of the carbonization.

  1. Synthesis of TiO2 nanoscale rods with MHz femtosecond laser irradiation of single crystal surface and characterisation

    NASA Astrophysics Data System (ADS)

    Sivakumar, M.; Tan, Bo; Venkatakrishnan, Krishnan

    2011-06-01

    Growth of nanoscale rods on single crystal rutile TiO2 surface irradiated by MHz pulse repetition rate femtosecond laser in nitrogen environment without a catalyst or template is reported. The rods are of 100 nm in width to 1 micron length. Microraman analysis of the laser irradiated surface shows only a decrease in the intensity of active modes as compared to untreated surface. The growth of TiO2 nanorods can be explained by a method combining nanoparticles formation due to expulsion of molten material from laser irradiated spot and their subsequent growth by vapor-liquid-solid process.

  2. Effect of different laser irradiation on the dysentery bacilli

    NASA Astrophysics Data System (ADS)

    Ou, Lin; Chen, Rong; Chen, Yanjiao; Li, Depin; Wen, Caixia

    1998-08-01

    The S. flexnesi, which have high drug-resistance especially in Cm, Sm, Tc, SD, were irradiated by Ar+ laser at 488 nm and semiconductor laser at 808 nm. The experiment results have shown that both Ar+ laser and semiconductor laser with power density of 1.7 w/cm2 and irradiation dose of 2000 J/cm2 can conduce to the bacterial lethality and increase the mutation rates of the bacterial drug-sensitivity, and 'Colony Count' method have the superiority over the 'Inhibacteria Ring' method. At the mean time it further indicate that the high power semiconductor laser would play an important role in the sciences of laser biological medicine. But the effect of the near infrared semiconductor laser is far lower than that of Ar+ laser of shorter wavelength at the same irradiation dose. It is clear that the output and irradiation dose of near infrared semiconductor laser shall be increased in order to get the same rates of the bacterial lethality and the drug-sensitivity mutation as Ar+ laser's.

  3. [The state of autonomic homeostasis during the use of a low-intensity helium-neon laser as a component of combined anesthesia].

    PubMed

    Avrutskiĭ, M Ia; Musikhin, L V; Finkel'shteĭn, I E; Katkovskiĭ, D G; Guseĭnov, T Iu

    1992-01-01

    The effect of intravenous blood irradiation, using helium-neon laser, on vegetative homeostasis during surgery was studied. It has been established that the introduction of low-intensity laser blood irradiation into a complex of anesthesiologic procedures ensures a more effective protection of patients from the surgical stress. PMID:1524243

  4. Effects of low-intensity laser therapy over mini-implants success rate in pigs.

    PubMed

    Garcez, Aguinaldo S; Suzuki, Selly Sayuri; Martinez, Elisabeth Ferreira; Iemini, Mylene Garcez; Suzuki, Hideo

    2015-02-01

    The success rate of miniscrews when used as temporary orthodontic anchorage is relatively high, but some factors could affect its clinical success such as inflammation around the miniscrew. Low-intensity laser therapy has been widely used for biostimulation of tissue and wound healing specially for its anti-inflammatory effects. The purpose of this study was to evaluate the effect of low-intensity laser therapy over the miniscrew success rate. Five Landrace's pigs received 50 miniscrews on the buccal side of the mandible and on the palate of the maxilla. All the miniscrews were immediately loaded with 250 gf. The laser group were irradiated with a 780-nm diode laser with 70 mWs for 1 min (dose = 34 J/cm(2)); the contralateral side was used as the control group. The miniscrews were photographed and analyzed clinically every week to determine their stability and presence of local inflammation. After 3 weeks, histological analysis and fluorescent microscopy were performed to compare the laser and the control side. Clinical results showed a success rate of 60% for the control group and 80% for the laser-treated group. The histological analysis and fluorescent microscopy demonstrated that the laser group had less inflammatory cells than the control group and the bone neoformation around the miniscrew was more intense. Low-intensity laser therapy increased the success rate of orthodontic miniscrews, probably due to anti-inflammatory effect and bone stimulation. PMID:23929562

  5. Femtosecond and ultraviolet laser irradiation of graphitelike hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Kanaev, Andrei V.; Petitet, Jean-Pierre; Museur, Luc; Marine, Vladimir; Solozhenko, Vladimir L.; Zafiropulos, Vassilis

    2004-10-01

    The effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) on graphitelike hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room temperature using the excimer KrF laser (248nm). In the nanosecond operation mode, the laser-induced fluorescence spectra are found strongly modified depending on the integrated doze, which is attributed to a progressive enrichment of the surface layer by an elemental boron. A slow sample recovery after the laser irradiation has been observed. On the other hand, in the femtosecond mode, the fluorescence spectra depend on the laser fluence, and the changes are reversible: low-energy fluorescence spectra are restored immediately when the laser energy decreases. This effect can be explained by a material bleaching, which favors a bulk centers emission. The ablation threshold has been determined as 78mJ/cm2 in the femtosecond laser operational mode.

  6. Platinum nanostructures formed by femtosecond laser irradiation in water

    SciTech Connect

    Huo Haibin; Shen Mengyan

    2012-11-15

    Platinum nanostructures with various morphologies, such as spike-like, ripple-like and array-like structures, have been fabricated by 400 nm and 800 nm femtosecond laser irradiation in water. Different structures can be formed on the surfaces as a function of the laser wavelength, the fluence and scan methods. The reflectance measurements of these structures show much larger absorption on the irradiated surfaces than untreated platinum surfaces.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  8. Scaling Laws for Proton Acceleration from the Rear Surface of Laser-Irradiated Thin Foils

    NASA Astrophysics Data System (ADS)

    Fuchs, J.; Antici, P.; d'Humières, E.; Lefebvre, E.; Borghesi, M.; Brambrink, E.; Cecchetti, C. A.; Kaluza, M.; Malka, V.; Manclossi, M.; Meyroneinc, S.; Mora, P.; Schreiber, J.; Toncian, T.; Pépin, H.; Audebert, P.

    2006-04-01

    In the last few years, intense research has been conducted on the topic of laser-accelerated ion sources and their applications. Ultra-bright beams of multi-MeV protons are produced by irradiating thin metallic foils with ultra-intense short laser pulses. These sources open new opportunities for ion beam generation and control, and could stimulate development of compact ion accelerators for many applications, in particular proton therapy of deep-seated tumours. Here we show that scaling laws deduced from fluid models reproduce well the acceleration of proton beams for a large range of laser and target parameters. These scaling laws show that, in our regime, there is an optimum in the laser pulse duration of ˜200 fs-1 ps, with a needed laser energy level of 30 to 100 J, in order to achieve e.g. 200 MeV energy protons necessary for proton therapy.

  9. Efficient propagation of ultra-intense laser beam in dense plasma

    SciTech Connect

    Habara, H.; Ivancic, S.; Anderson, K.; Haberberger, D.; Iwawaki, T.; Stoeckl, C.; Tanaka, K. A.; Uematsu, Y.; Theobald, W.

    2015-04-29

    Ultra intense laser propagation in extended, dense plasma is investigated through optical and proton probing. When a >1 kJ, 10 ps laser propagates into a long-density scale length plasma, channel formation was observed up to 0.6 nc from the analysis of optical probe images. The proton track analysis shows the formation of strong electric and magnetic fields along the plasma channel, which may lead to the observed collimated electron beam on the laser axis. These results are promising for the feasibility of the direct irradiation scheme of fast ignition.

  10. Propagation of intense short-pulse laser in homogeneous near-critical density plasmas

    NASA Astrophysics Data System (ADS)

    Habara, H.; Nakaguchi, S.; Uematsu, Y.; Baton, S. D.; Chen, S. N.; Fuchs, J.; Iwawaki, T.; MacDonald, M.; Nazarov, W.; Rousseaux, C.; Tanaka, K. A.

    2016-05-01

    Ultra intense laser light propagation in a homogeneous overdense plasma was investigated using a plastic foam target filling a polyimide tube. Laser propagation into overdense plasma was measured via Doppler red shift of the reflected laser light from the moving plasma at 0.3-0.4 of speed of light. We also observed strongly collimated electron beam possibly caused by the magnetic field surrounding the plasma channel, and high energy X-rays emitted via synchrotron radiation by the oscillating electrons inside the channel. These features imply that UIL propagates inside the overdense plasma as predicted in PIC calculation, and are very important for direct irradiation scheme of fast ignition.

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

    SciTech Connect

    Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun Wang, Kedian; Mei, Xuesong

    2014-03-15

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

  12. High-intensity laser heating in liquids: Multiphoton absorption

    SciTech Connect

    Longtin, J.P.; Tien, C.L.

    1995-12-31

    At high laser intensities, otherwise transparent liquids can absorb strongly by the mechanism of multiphoton absorption, resulting in absorption and heating several orders of magnitude greater than classical, low-intensity mechanisms. The use of multiphoton absorption provides a new mechanism for strong, controlled energy deposition in liquids without bulk plasma formation, shock waves, liquid ejection, etc., which is of interest for many laser-liquid applications, including laser desorption of liquid films, laser particle removal, and laser water removal from microdevices. This work develops a microscopically based model of the heating during multiphoton absorption in liquids. The dependence on pulse duration, intensity, wavelength, repetition rate, and liquid properties is discussed. Pure water exposed to 266 nm laser radiation is investigated, and a novel heating mechanism for water is proposed that uses multiple-wavelength laser pulses.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  14. Large aperture adaptive optics for intense lasers

    NASA Astrophysics Data System (ADS)

    Deneuville, François; Ropert, Laurent; Sauvageot, Paul; Theis, Sébastien

    2015-05-01

    ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.

  15. Homogeneous focusing with a transient soft X-ray laser for irradiation experiments

    NASA Astrophysics Data System (ADS)

    Kazamias, S.; Cassou, K.; Guilbaud, O.; Klisnick, A.; Ros, D.; Plé, F.; Jamelot, G.; Rus, B.; Koslová, M.; Stupka, M.; Mocek, T.; Douillet, D.; Zeitoun, Ph.; Joyeux, D.; Phalippou, D.

    2006-07-01

    We report the work done on a transient soft X-ray laser (SXRL) beam to deliver a proper extreme UV irradiation source for applications. The same optical tool was first demonstrated on a quasi stationnary state (QSS) soft X-Ray laser at the PALS Institute in Prague. The problem set by the transient soft X-Ray laser developed by the LIXAM at the LULI installation in Palaiseau is more crucial, first because the beam spatial profile is more irregular secondly because high repetition rate soft X-ray laser facilities in the future are based on this SXRL type. The spots obtained show a 20 micron average diameter and a rather homogeneous and smooth profile that make them a realistic irradiation source to interact with targets requiring relatively high fluence (near 1 J/cm 2) or intensity (near 10 11 W/cm 2) in the extreme UV domain.

  16. Vacuum aperture isolator for retroreflection from laser-irradiated target

    DOEpatents

    Benjamin, Robert F.; Mitchell, Kenneth B.

    1980-01-01

    The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

  17. Viability of fibroblasts cultured under nutritional stress irradiated with red laser, infrared laser, and red light-emitting diode

    NASA Astrophysics Data System (ADS)

    Volpato, Luiz Evaristo Ricci; de Oliveira, Rodrigo Cardoso; Espinosa, Mariano Martinez; Bagnato, Vanderley Salvador; Machado, Maria A. A. M.

    2011-07-01

    Phototherapy is noninvasive, painless and has no known side effect. However, for its incorporation into clinical practice, more well-designed studies are necessary to define optimal parameters for its application. The viability of fibroblasts cultured under nutritional stress irradiated with either a red laser, an infrared laser, or a red light-emitting diode (LED) was analyzed. Irradiation parameters were: red laser (660 nm, 40 mW, 1 W/cm2), infrared laser (780 nm, 40 mW, 1 W/cm2), and red LED (637 +/- 15 nm, 40 mW, 1 W/cm2). All applications were punctual and performed with a spot with 0.4 mm2 of diameter for 4 or 8 s. The Kruskal-Wallis test and analysis of variance of the general linear model (p <= 0.05) were used for statistical analysis. After 72 h, phototherapy with low-intensity laser and LED showed no toxicity at the cellular level. It even stimulated methylthiazol tetrazolium assay (MTT) conversion and neutral red uptake of fibroblasts cultured under nutritional stress, especially in the group irradiated with infrared laser (p = 0.004 for MTT conversion and p < 0.001 for neutral red uptake). Considering the parameters and protocol of phototherapy used, it can be concluded that phototherapy stimulated the viability of fibroblasts cultured under nutritional deficit resembling those found in traumatized tissue in which cell viability is reduced.

  18. Transient stress evolution and crystallization in laser-irradiated amorphous titania sol-gel films

    SciTech Connect

    Exarhos, G.J.; Hess, N.J.; Wood, S.

    1991-10-01

    Amorphous TiO{sub 2} sol-gel films are irreversibly transformed to a crystalline anatase phase when heated to temperatures in excess of 575 K or subjected to intense pulsed or CW laser irradiation. The laser-induced transformation is initiated as a result of impurity absorption and subsequent heating, and results in densification and relative changes in compressive stress of the film. Isothermally annealed films exhibit a decrease in compressive stress as crystallization proceeds while an increase in compressive stress followed by a decrease in stress is observed when crystallization is laser-induced. Raman spectroscopy has been used to characterize the crystallization ingrowth kinetics and is used in this work as a real time probe of both film temperature and localized stress which can be evaluated from shifts in lattice phonon frequencies measured in real time during laser irradiation. The laser not only induces the phase transformation but excites inelastic Raman scattering from which film stress and temperature can be estimated. A second approach for the determination of these parameters requires incorporation of a thin ruby film between the titania and silica substrate. Here, the wavelength shift of the laser-induced ruby fluorescence can be used to quantify interfacial stress; the fluorescence lifetime measurements are used to determine temperature. The advantages and limitations of these techniques for evaluating transient stress and temperature evolution in thin titania films subjected to CW laser irradiation will be discussed.

  19. Effects of laser irradiation on the morphology of Cu(110)

    SciTech Connect

    Brandstetter, T.; Draxler, M.; Hohage, M.; Zeppenfeld, P.; Stehrer, T.; Heitz, J.; Georgiev, N.; Martinotti, D.; Ernst, H.-J.

    2008-07-15

    The effects of pulsed laser irradiation on the morphology of the Cu(110) surface were investigated by means of reflectance difference spectroscopy (RDS) and spot profile analysis low-energy electron diffraction (SPA-LEED). The laser light induces surface defects (adatoms and islands) as well as subsurface dislocation lines. The high surface mobility leads to efficient annealing of the surface defects even at room temperature, whereas the subsurface dislocation lines persist up to temperatures T>800 K. SPA-LEED profiles of the (00) diffraction spot from the laser irradiated surface suggest an anisotropic distribution of the subsurface line defects related to the geometry of the fcc easy glide system, which is corroborated by STM measurements. Comparative experiments using conventional Ar ion bombardment point out the distinctiveness of the morphological changes induced by laser irradiation.

  20. Effect of low power laser irradiation on macrophage phagocytic capacity

    NASA Astrophysics Data System (ADS)

    Lu, Cuixia; Song, Sheng; Tang, Yu; Zhou, Feifan

    2011-03-01

    Phagocytosis and subsequent degradation of pathogens by macrophages play a pivotal role in host innate immunity in mammals. Laser irradiation has been found to produce photobiological effects with evidence of interference with immunological functions. However, the effects of laser on the immune response have not been extensively characterized. In this study, we focused our attention on the effects of He-Ne laser on the phagocytic activity of macrophages by using flow cytometry (FCM). After irradiating at fluence of 0, 1, 2 J/cm2 with He-Ne laser (632.8 nm, 3mw), the cells were incubated with microsphere and then subjected to FACS analysis. The results showed that Low-power laser irradiation (LPLI) leads to an increase in phagocytosis on both mouse peritoneal macrophages and the murine macrophage-like cell line RAW264.7. In addition, we demonstrated that LPLI increased phagocytosis of microsphere in a dose-dependent manner, reaching a maximum at fluence of 2 J/cm2. Taken together, our results indicated that Low-power laser irradiation with appropriate dosage can enhance the phagocytosis of macrophage, and provided a theoretical base for the clinical use of the He-Ne laser.

  1. Reshaping of intense laser pulse with a capillary

    SciTech Connect

    Cao Lihua; Yu Wei; Yu, M. Y.; Wang Xin; Gu Yuqiu; He, X. T.

    2009-09-15

    The reshaping of intense laser pulse by vacuum capillary is studied by particle-in-cell simulation. It is shown that as an intense laser pulse propagates from free space into a capillary, its profile is reshaped due to laser-plasma interaction near the entrance of capillary. As a result, the free-space mode is self-consistently converted into a capillary mode. Only the relatively low-intensity periphery of the reshaped pulse interacts with the capillary-wall plasma, so that the high-intensity center of the pulse can propagate in the narrow vacuum channel over a distance much larger than the Rayleigh length. The mechanism is then applied to reshape a radially imperfect laser pulse having two wings around the center spot. Most of the output light energy is concentrated in the center spot, and the wings are almost completely removed. That is, the quality of the laser pulse can be greatly improved by a capillary.

  2. Low-fluence CO2 laser irradiation decreases enamel solubility

    NASA Astrophysics Data System (ADS)

    Esteves-Oliveira, M.; Apel, C.; Gutknecht, N.; Velloso, W. F.; Cotrim, M. E. B.; Eduardo, C. P.; Zezell, D. M.

    2008-04-01

    This study investigated whether subablative-pulsed CO2 laser (10.6 μm) irradiation, using fluences lower than 1 J/cm2, was capable of reducing enamel acid solubility. Fifty-one samples of bovine dental enamel were divided into three groups: control group, which was not irradiated (CG); group laser A (LA) irradiated with 0.3 J/cm2; and group laser B (LB) irradiated with 0.7 J/cm2. After irradiation, the samples were subjected to demineralization in an acetate buffer solution and were then analyzed by SEM. A finite-element model was used to calculate the temperature increase. The calcium and phosphorous content in the demineralization solution were measured with an ICP-OES. ANOVA and the t-test pairwise comparison ( p < 0.016) revealed that LB showed significantly lower mean Ca and P content values in the demineralization solution than other groups. A reduction in the enamel solubility can be obtained with pulsed CO2 laser irradiation (0.7 J/cm2, 135 mJ/pulse, 74 Hz, 100 μs) without any surface photomodification and a less than 2°C temperature increase at a 3-mm depth from the surface.

  3. System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

    DOEpatents

    Skupsky, S.; Kessler, T.J.; Short, R.W.; Craxton, S.; Letzring, S.A.; Soures, J.

    1991-09-10

    In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies (''colors'') cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers. 8 figures.

  4. Using laser irradiation for the surgical treatment of periodontal disease

    NASA Astrophysics Data System (ADS)

    Vieru, Rozana D.; Lefter, Agafita; Herman, Sonia

    2002-10-01

    In the marginal pr ogressive profound periodontities, we associated low level laser therapy (LLLT) to the classical surgical treatment with implant of biovitroceramics. From a total of 50 patients, 37 where irradiated with the laser. We used a diode laser, =830 nm, energy density up to 2 J cm2, in Nogier pulsed mode. The laser treatment is used in a complex of therapeutic procedures: odontal, local anti-inflammatory -- as well as in the cabinet and at home --, prosthetic, and for the morphologic and functional rebalancing. The immediate effects where: an evolution without bleeding and without post-surgical complications, as can appear at the patients who didn't benefit of laser irradiation (hematom, pain, functional alteration in the first post-surgical week). Operated tissue is recovering faster. The percentage of recurrences decreases and the success depends less on the biological potential and the immunity of each individual.

  5. Zirconium and titanium nitridation by repeated action of a breakdown plasma induced in nitrogen as a result of microsecond-pulsed TEA CO/sub 2/ laser irradiation

    SciTech Connect

    Ursu, I.; Miha-breveilescu, I.N.; Nistor, L.C.; Teodorescu, V.S.; Prokhorov, A.M.; Konov, V.I.; Uglov, S.A.

    1986-08-15

    New experimental data are reported supporting the conclusion that the formation of surface compound layers by high-intensity multipulse laser irradiation is determined by a critical value of the oxygen impurities concentration in the ambient nitrogen atmosphere.

  6. Cerebrovascular and metabolic effects on the rat brain of focal Nd:YAG laser irradiation

    SciTech Connect

    Kiessling, M.; Herchenhan, E.; Eggert, H.R. )

    1990-12-01

    To investigate the effects of focal neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation (lambda = 1060 nm) on regional cerebral blood flow, cerebral protein synthesis, and blood-brain barrier permeability, the parietal brain surface of 44 rats was irradiated with a focused laser beam at a constant output energy of 30 J. Survival times ranged from 5 minutes to 48 hours. Laser irradiation immediately caused well-defined cortical coagulation necrosis. Within 5 minutes after unilateral irradiation, 14C-iodoantipyrine autoradiographs demonstrated severely reduced blood flow to the irradiation site and perilesional neocortex, but a distinct reactive hyperemia in all other areas of the forebrain. Apart from a persistent ischemic focus in the vicinity of the cortical coagulation necrosis, blood flow alterations in remote areas of the brain subsided within 3 hours after irradiation. Autoradiographic assessment of 3H-tyrosine incorporation into brain proteins revealed rapid onset and prolonged duration of protein synthesis inhibition in perifocal morphologically intact cortical and subcortical structures. Impairment of amino acid incorporation proved to be completely reversible within 48 hours. Immunoautoradiographic visualization of extravasated plasma proteins using 3H-labeled rabbit anti-rat immunoglobulins-showed that, up to 1 hour after irradiation, immunoreactive proteins were confined to the neocortex at the irradiation site. At 4 hours, vasogenic edema was present in the vicinity of the irradiation site and the subcortical white matter, and, at later stages (16 to 36 hours), also extended into the contralateral hemisphere. Although this was followed by a gradual decrease in labeling intensity, resolution of edema was still not complete after 48 hours.

  7. Communication: Mode bifurcation of droplet motion under stationary laser irradiation.

    PubMed

    Takabatake, Fumi; Yoshikawa, Kenichi; Ichikawa, Masatoshi

    2014-08-01

    The self-propelled motion of a mm-sized oil droplet floating on water, induced by a local temperature gradient generated by CW laser irradiation is reported. The circular droplet exhibits two types of regular periodic motion, reciprocal and circular, around the laser spot under suitable laser power. With an increase in laser power, a mode bifurcation from rectilinear reciprocal motion to circular motion is caused. The essential aspects of this mode bifurcation are discussed in terms of spontaneous symmetry-breaking under temperature-induced interfacial instability, and are theoretically reproduced with simple coupled differential equations.

  8. Communication: Mode bifurcation of droplet motion under stationary laser irradiation

    SciTech Connect

    Takabatake, Fumi; Yoshikawa, Kenichi; Ichikawa, Masatoshi

    2014-08-07

    The self-propelled motion of a mm-sized oil droplet floating on water, induced by a local temperature gradient generated by CW laser irradiation is reported. The circular droplet exhibits two types of regular periodic motion, reciprocal and circular, around the laser spot under suitable laser power. With an increase in laser power, a mode bifurcation from rectilinear reciprocal motion to circular motion is caused. The essential aspects of this mode bifurcation are discussed in terms of spontaneous symmetry-breaking under temperature-induced interfacial instability, and are theoretically reproduced with simple coupled differential equations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    PubMed

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

    2014-07-15

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

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

    PubMed

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

    2014-07-15

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

  12. Microengineering Laser Plasma Interactions at Relativistic Intensities

    NASA Astrophysics Data System (ADS)

    Jiang, S.; Ji, L. L.; Audesirk, H.; George, K. M.; Snyder, J.; Krygier, A.; Poole, P.; Willis, C.; Daskalova, R.; Chowdhury, E.; Lewis, N. S.; Schumacher, D. W.; Pukhov, A.; Freeman, R. R.; Akli, K. U.

    2016-02-01

    We report on the first successful proof-of-principle experiment to manipulate laser-matter interactions on microscales using highly ordered Si microwire arrays. The interaction of a high-contrast short-pulse laser with a flat target via periodic Si microwires yields a substantial enhancement in both the total and cutoff energies of the produced electron beam. The self-generated electric and magnetic fields behave as an electromagnetic lens that confines and guides electrons between the microwires as they acquire relativistic energies via direct laser acceleration.

  13. Research of metallic materials irradiation with high energy pulsed laser impact

    NASA Astrophysics Data System (ADS)

    Blesman, A. I.; Postnikov, D. V.; Seropyan, G. M.; Tkachenko, E. A.; Teplouhov, A. A.; Polonyankin, D. A.

    2016-02-01

    In the process of metallic materials treatment by pulsed laser beams with nanosecond duration occurs extremely rapid and intensive heating of their surface. In this case a thin surface layer of material is heated to the boiling point and rapidly evaporates. This leads to arising substantial forces of reactive nature which significantly influence on the shape of the solidified melt and in some cases may cause deformation of the underlying layers. The considered question is relevant in the research of precision treatment of miniature products by laser beams. A metallic powder with microfine material structure was selected as the object of research and was exposed to laser irradiation with nanosecond duration. At the core of reactive forces calculation used the approach similar for laser rocket engines. The paper also presents the model and the results of the forces and the reactive recoil impulse calculation occurring during laser impact to the microfine metallic powder.

  14. Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Liao, G. Q.; Li, Y. T.; Li, C.; Su, L. N.; Zheng, Y.; Liu, M.; Wang, W. M.; Hu, Z. D.; Yan, W. C.; Dunn, J.; Nilsen, J.; Hunter, J.; Liu, Y.; Wang, X.; Chen, L. M.; Ma, J. L.; Lu, X.; Jin, Z.; Kodama, R.; Sheng, Z. M.; Zhang, J.

    2015-06-01

    Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 1 0 0 μ J per steradian in the laser specular direction at an optimal preplasma scale length around 40 - 50 μ m . Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas.

  15. Singlet Oxygen Generation by Laser Irradiation of Gold Nanoparticles

    PubMed Central

    2016-01-01

    The formation of singlet oxygen by irradiation of gold nanoparticles in their plasmon resonance band with continuous or pulsed laser light has been investigated. Citrate-stabilized nanoparticles were found to facilitate the photogeneration of singlet oxygen, albeit with low quantum yield. The reaction caused by pulsed laser irradiation makes use of the equilibrated hot electrons that can reach temperatures of several thousand degrees during the laser pulse. Although less efficient, continuous irradiation, which acts via the short-lived directly excited primary “hot” electrons only, can produce enough singlet oxygen for photodynamic cancer therapy and has significant advantages for practical applications. However, careful design of the nanoparticles is needed, since even a moderately thick capping layer can completely inhibit singlet oxygen formation. Moreover, the efficiency of the process also depends on the nanoparticle size. PMID:27239247

  16. Damage thresholds in laser-irradiated optical materials

    NASA Astrophysics Data System (ADS)

    Guignard, Franck; Autric, Michel L.; Baudinaud, Vincent

    1997-05-01

    An experimental study on the damage induced by laser irradiation on different materials, borosilicate glass, fused silicate, molded and stretched polymethylmethacrylate (PMMA), has been performed. The irradiation source is a 1KL pulsed cold cathode electron gun preionized TEA CO2 laser. Damage mechanisms are controlled by the in-depth absorption of the 10.6 micrometers radiation according to the Beer-Lambert law. PMMA is damaged following a boiling process. Stretched PMMA is fractured first, releasing stresses, then boiled like molded PMMA at a higher energy. BK7 crazed after the irradiation due to thermomechanical stresses, silicate melt and vaporized. Optical damages have been characterized by measuring the contrast transfer function through the irradiated samples.

  17. O2^+ dissociation caused by an ultrashort intense laser pulse

    NASA Astrophysics Data System (ADS)

    Sayler, A. M.

    2005-05-01

    Laser-induced dissociation of O2^+ has been experimentally studied with ultrashort (˜50 fs) intense (10^14 to 10^15 W/cm^2) laser pulses at 790 nm using kinematically complete coincidence 3D momentum imaging. The resulting kinetic energy release (KER) distribution has several distinct peaks, each of which has a unique angular distribution. The lower KER features are peaked around the laser polarization, while at higher KER, dissociation perpendicular to the laser polarization is significant. For comparison, a theoretical study of O2^+ dissociation using the Electron-Nuclear Dynamics (END) approach with a laser pulse included in the time-dependent dynamics is underway. Preliminary results also indicate that ionization, which occurs predominantly at the high end of the intensity range, is strongly peaked along the laser polarization.

  18. Submicro foaming in biopolymers by UV pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Oujja, Mohamed; Rebollar, Esther; Gaspard, Solenne; Abrusci, Concepción; Catalina, Fernando; Lazare, Sylvain; Castillejo, Marta

    2006-05-01

    Microstructuring of polymers and biopolymers is of application in medical technology and biotechnology. Using different fabrication techniques three-dimensionally shaped and micro structured constructs can be developed for drug release and tissue engineering. As an alternative method, laser microstructuring offers a series of advantages including high resolution capability, low heat deposition in the substrate and high level of flexibility. In this work we present evidence of laser microfoam formation in collagen and gelatine by nanosecond pulsed laser irradiation in the UV at 248 and 266 nm. Irradiation at 355 nm produces melting followed by resolidification of the substrate, whereas irradiation at 532 and 1064 nm induces the formation of craters of irregular contours. Single pulse irradiation of a collagen film with an homogenized KrF microbeam yields a 20 μm thick expanded layer, which displays the interesting features of a nanofibrous 3-dimensional network with open cells. In gelatine, irradiation at 248 and 266 nm produces similar morphological modifications. The effect of the structural properties of the substrate on the laser induced microfoam is studied by comparing gelatines differing in gel strength (Bloom values 225 and 75) and in crosslinking degree. While results are discussed on the basis of thermal and photomechanical mechanisms and of the role played by the water content of the substrates, it is thought that such structures could have a biomimic function in future 3D cell culture devices for research.

  19. Recent experiment on fast electron transport in ultra-high intensity laser interaction

    NASA Astrophysics Data System (ADS)

    Batani, D.; Baton, S.; Koenig, M.; Guillou, P.; Loupias, B.; Vinci, T.; Rousseaux, C.; Gremillet, L.; Morace, A.; Redaelli, R.; Nakatsutsumi, M.; Kodama, R.; Ozaki, N.; Norimatsu, T.; Rassuchine, J.; Cowan, T.; Dorchies, F.; Fourment, C.; Santos, J. J.

    2008-05-01

    We performed an experiment with cone targets in planar geometry devoted to the study of fast electron generation, propagation, and target heating. This was done at LULI with the 100 TW laser at intensities up to 1019 W/cm2. Fast electrons penetration, with and without cones, was studied with different diagnostics (Kα imaging, Kα spectroscopy, visible emission) for ω or 2ω irradiation. At ω, the pre-plasma generated by the laser pedestal fills the cone and prevents the beam from reaching the tip.

  20. MeV negative ion generation from ultra-intense laser interaction with a water spray

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Borghesi, M.; Doria, D.; Zepf, M.; Sarri, G.; Ehrentraut, L.; Steinke, S.; Sandner, W.; Schnuerer, M.; Andreev, A.; Nickles, P. V.; Tikhonchuk, V.

    2011-08-01

    MeV negative oxygen ions are obtained from a water spray target irradiated by high intensity (5 x 10{sup 19} W/cm{sup 2}) and ultrashort (50 fs) laser pulses. Generation of negative ions is ascribed to electron-capture processes that the laser-accelerated high-energy positive ion experiences when it interacts with atoms in the spray. This mechanism implies the existence of a large number of MeV neutral oxygen atoms, which is consistent with indirect experimental evidence.

  1. MeV negative ion source from ultra-intense laser-matter interaction

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Doria, D.; Prasad, R.; Borghesi, M.; Andreev, A. A.; Steinke, S.; Schnuerer, M.; Nickles, P. V.; Tikhonchuk, V.

    2012-02-15

    Experimental demonstration of negative ion acceleration to MeV energies from sub-micron size droplets of water spray irradiated by ultra-intense laser pulses is presented. Thanks to the specific target configuration and laser parameters, more than 10{sup 9} negative ions per steradian solid angle in 5% energy bandwidth are accelerated in a stable and reliable manner. To our knowledge, by virtue of the ultra-short duration of the emission, this is by far the brightest negative ion source reported. The data also indicate the existence of beams of neutrals with at least similar numbers and energies.

  2. Distinct photoresponse in graphene induced by laser irradiation

    SciTech Connect

    Wang, Wen Hui; Nan, Hai Yan; Liu, Qi; Ni, Zhen Hua; Liang, Zheng; Yu, Zhi Hao; Liu, Feng Yuan; Wang, Xin Ran; Hu, Wei Da; Zhang, Wei

    2015-01-12

    The graphene-based photodetector with tunable p-p{sup +}-p junctions was fabricated through a simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiated graphene (LIG) junction by scanning photocurrent measurements, and its magnitude can be modulated as a result of a positive correlation between the photocurrent and doping concentration in LIG region. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junctions. Such a simple and low-cost technique offers an alternative way for the fabrication of graphene-based optoelectronic devices.

  3. High-intensity laser therapy during chronic degenerative tenosynovitis experimentally induced in broiler chickens

    NASA Astrophysics Data System (ADS)

    Fortuna, Damiano; Rossi, Giacomo; Bilotta, Teresa W.; Zati, Allesandro; Gazzotti, Valeria; Venturini, Antonio; Pinna, Stefania; Serra, Christian; Masotti, Leonardo

    2002-10-01

    The aims of this study was the safety and the efficacy of High Intensity Laser Therapy (HILT) on chronic degenerative tenosynovitis. We have effectuated the histological evaluation and seroassay (C reactive protein) on 18 chickens affect by chronic degenerative tenosynovitis experimentally induced. We have been employed a Nd:YAG laser pulsed wave; all irradiated subjects received the same total energy (270 Joule) with a fluence of 7,7 J/cm2 and intensity of 10,7 W/cm2. The histological findings revealed a distinct reduction of the mineralization of the choral matrix, the anti-inflammatory effect of the laser, the hyperplasia of the synoviocytes and ectasia of the lymphatic vessels.

  4. LASERS: Laser stand for irradiation of targets by laser pulses from the Iskra-5 facility at a repetition rate of 100 MHz

    NASA Astrophysics Data System (ADS)

    Annenkov, V. I.; Garanin, Sergey G.; Eroshenko, V. A.; Zhidkov, N. V.; Zubkov, A. V.; Kalipanov, S. V.; Kalmykov, N. A.; Kovalenko, V. P.; Krotov, V. A.; Lapin, S. G.; Martynenko, S. P.; Pankratov, V. I.; Faizullin, V. S.; Khrustalev, V. A.; Khudikov, N. M.; Chebotar, V. S.

    2009-08-01

    A train of a few tens of high-power subnanosecond laser pulses with a repetition period of 10 ns is generated in the Iskra-5 facility. The laser pulse train has an energy of up to 300 J and contains up to 40 pulses (by the 0.15 intensity level), the single pulse duration in the train being ~0.5 ns. The results of experiments on conversion of a train of laser pulses to a train of X-ray pulses are presented. Upon irradiation of a tungsten target, a train of X-ray pulses is generated with the shape of an envelope in the spectral band from 0.18 to 0.28 keV similar to that of the envelope of the laser pulse train. The duration of a single X-ray pulse in the train is equal to that of a single laser pulse.

  5. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Marcu, A.; Avotina, L.; Porosnicu, C.; Marin, A.; Grigorescu, C. E. A.; Ursescu, D.; Lungu, M.; Demitri, N.; Lungu, C. P.

    2015-11-01

    A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp3 bonds percentage and possible diamond crystal formation were investigated 'in-depth' and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp3 percent in the low power irradiated areas and similarly 'in the depth' of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an 'in-depth' (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface.

  6. Responses of astrocytes in culture after low dose laser irradiation

    SciTech Connect

    Yew, D.T.; Zheng, D.R.; Au, C.; Li, W.W. )

    1990-03-01

    The effect of Helium-Neon low dose laser on astrocytes was investigated in cultures of isolated astrocytes from albino neonatal rats. The laser appeared to inhibit the growth of astrocytes as exemplified by the smaller sizes of the cells and the decreased leucine uptake in each cell after treatment. Temporary decrease in the number of mitoses was also observed, but this trend was reversed soon after. Electron microscopic studies revealed an increase in buddings from cell bodies and processes (branches) after irradiation.

  7. Hybrid proton acceleration scheme using relativistic intense laser light

    SciTech Connect

    Andreev, A. A.; Platonov, K. Yu.; Schnuerer, M.; Prasad, R.; Ter-Avetisyan, S.

    2013-03-15

    Ion acceleration phenomena at relativistic intense laser interaction with thin foil targets are studied to find an efficient laser-target interaction concept at the conditions, where neither the ponderomotive pressure of the laser light nor the hot electron pressure is negligible. Particle in cell simulations and the analytical model are allowing to predict optimum laser-target parameters and suggesting a significant increase of proton energy if a hybrid proton acceleration scheme is used. In the proposed scenario, the laser polarisation is changed during the acceleration process: First with circularly polarised laser light the target is accelerated as a whole by the ponderamotive pressure, and then with linearly polarised laser light the electrons are heated which additionally increases the accelerating field. The calculations are in good agreement with experimental findings.

  8. Injection locking and saturation intensity of a cadmium iodide laser.

    PubMed

    Greene, D P; Eden, J G

    1985-02-01

    A discharge-pumped cadmium monoiodide (CdI) laser utilizing isotopically pure CdI(2) ((114)CdI(2)) has been injection locked with a flashlamp-pumped dye laser having a linewidth of 0.3 cm(-1). Complete locking of the slave oscillator occurs for wavelengths between 655 and 660 nm and for injection intensities of ~5 W cm(-2). The saturation intensity for the B ? X band of CdI has been directly measured with an excimer-pumped dye laser to be (125 +/- 60) kW cm(-2). PMID:19724345

  9. The effect of low-level laser irradiation on dog spermatozoa motility is dependent on laser output power.

    PubMed

    Corral-Baqués, M I; Rivera, M M; Rigau, T; Rodríguez-Gil, J E; Rigau, J

    2009-09-01

    Biological tissues respond to low-level laser irradiation and so do dog spermatozoa. Among the main parameters to be considered when a biological tissue is irradiated is the output power. We have studied the effects on sperm motility of 655 nm continuous wave diode laser irradiation at different output powers with 3.34 J (5.97 J/cm(2)). The second fraction of fresh dog sperm was divided into five groups: control, and four to be irradiated with an average output power of 6.8 mW, 15.4 mW, 33.1 mW and 49.7 mW, respectively. At 0 min and 45 min after irradiation, pictures were taken and a computer aided sperm analysis (CASA) performed to analyse different motility parameters. The results showed that different output powers affected dog semen motility parameters differently. The highest output power showed the most intense effects. Significant changes in the structure of the motile sperm subpopulation were linked to the different output powers used.

  10. [Effect of intravenous laser irradiation of blood on the homeostasis in patients with hemorrhagic pancreatitis].

    PubMed

    Dedenko, I K

    1989-08-01

    After intravenous blood exposure to low-intensity radiation of Helium-Neon laser patients with haemorrhagic pancreatitis exhibited inhibition of the blood proteolytic activity; enhancement of free-radical oxidation, kallikrein-kinin system activity, blood oxygen transport, correction of endotoxic pancreatogenic syndrome. In addition, the positive shifts were also observed in the immunological status, morphofunctional characteristics of the red blood cells and hemoglobin, hepatic and renal functions. In severe pancreatogenic endotoxicosis the highest response was achieved with combined use of hemosorption and intravenous laser irradiation. PMID:2811243

  11. The collimation of intense relativistic electron beams generated by ultra-intense femtosecond laser in nanometer-scale solid fiber array

    SciTech Connect

    Liao, Leng; Wu, Weidong; Wang, Chaoyang; Zhou, Minjie; Fu, Zhibing; Tang, Yongjian

    2014-02-24

    A scheme to collimate the ultra-intense laser generated MeV electrons by nanometer-scale solid fiber array is proposed. Unlike previous resistivity-structured target schemes, not the magnetic field but the electric field due to the anisotropic resistivity acts to collimate the divergent fast electrons. This concept is well supported by analytical estimation and numerical calculation. The measurements of collimated MeV electron beams at rear of carbon nanotube arrays irradiated by intense femtosecond laser show the viability of this scheme. These results indicate that potential applications include radiography, fast electron beam focusing, and perhaps the electron collimation for fast ignition of inertial confined fusion.

  12. High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

    NASA Astrophysics Data System (ADS)

    Gauthier, M.; Kim, J. B.; Curry, C. B.; Aurand, B.; Gamboa, E. J.; Göde, S.; Goyon, C.; Hazi, A.; Kerr, S.; Pak, A.; Propp, A.; Ramakrishna, B.; Ruby, J.; Willi, O.; Williams, G. J.; Rödel, C.; Glenzer, S. H.

    2016-11-01

    We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetition rate capability, this target is promising for future applications.

  13. Prepulse effects on the interaction of intense femtosecond laser pulses with high-Z solids

    PubMed

    Zhidkov; Sasaki; Utsumi; Fukumoto; Tajima; Saito; Hironaka; Nakamura; Kondo; Yoshida

    2000-11-01

    Kalpha emission of high-Z solid targets irradiated by an intense, short (<100 fs) laser pulse in the 10 keV region is shown to be sensitive to the electron energy cutoff, which is strongly dependent on the density gradient of the plasma corona formed by a long prepulse. The absorption rate of short laser pulses, the hot electron distribution, and x-ray emission from a Cu slab target are studied via a hybrid model, which combines the hydrodynamics, collisional particle-in-cell, and Monte Carlo simulation techniques, and via a direct spectroscopic measurement. An absorption mechanism originating from the interaction of the laser pulse with plasma waves is found to increase the absorption rate by over 30% even for a very short, s-polarized laser pulse. Calculated and measured x-ray spectra are in good agreement, confirming the electron energy cutoff.

  14. Beam intensity reshaping by pump modification in a laser amplifier.

    PubMed

    Litvin, Igor A; Collet, Oliver J P; King, Gary; Strauss, Hencharl

    2015-11-16

    We propose a new technique for laser beam shaping into a desirable beam profile by using a laser amplifier with a pump beam that has a modified intensity profile. We developed the analytical formula, which describes the transformation of the seed beam into the desired beam profile in a four level amplifiers small signal regime. We propose a numerically method to obtain the required pump intensity profile in the case where high pump power saturated the laser crystal or for three level materials. The theory was experimentally verified by one dimensionally shaping a Gaussian shaped seed into a Flat-Top beam in a Ho:YLF amplifier pumped by a Tm:YLF laser with a HG(01) intensity profile. PMID:26698497

  15. Spatial intensity profiling of an industrial laser welding system

    SciTech Connect

    Milewski, J.O.

    1991-12-31

    A investigation was conducted to devise a method to sense the laser beam intensity profile of an industrial laser welding system. The research focuses on monitoring methods and assessing locations within the system where data can be taken which reveal the relationship between the laser beam intensity profile and the input system parameters of the laser beam welding process. Emphasis has been placed on the configuration of a distributed computing environment to acquire, analyze and display the results of the sensed beam profile. Conventional image processing techniques are demonstrated. It was found that a distributed computing environment was useful for processing the large volumes of data generated by this process characterization method, and the distributed computing environment provided the computing power required for computationally intensive analysis and display techniques. The mathematical techniques used to discriminate one data set from another and relate the results to processing conditions are discussed.

  16. Short-pulse, high-intensity lasers at Los Alamos

    SciTech Connect

    Taylor, A.J.; Roberts, J.P.; Rodriguez, G.; Fulton, R.D.; Kyrala, G.A.; Schappert, G.T.

    1994-03-01

    Advances in ultrafast lasers and optical amplifiers have spurred the development of terawatt-class laser systems capable of delivering focal spot intensities approaching 10{sup 20} W/cm{sup 2}. At these extremely high intensities, the optical field strength is more than twenty times larger than the Bohr electric field, permitting investigations of the optical properties of matter in a previously unexplored regime. The authors describe two laser systems for high intensity laser interaction experiments: The first is a terawatt system based on amplification of femtosecond pulses in XeCl which yields 250 mJ in 275 fs and routinely produces intensifies on target in excess of 10{sup 18} W/cm{sup 2}. The second system is based on chirped pulse amplification of 100-fs pulses in Ti:sapphire.

  17. The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation.

    PubMed Central

    Venugopalan, V; Nishioka, N S; Mikić, B B

    1995-01-01

    The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (ArF, lambda = 193 nm) and krypton fluorine (KrF, lambda = 248 nm) excimer laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not cause material removal, the stress transients are consistent with rapid thermal expansion of the tissue. At the threshold radiant exposure for ablation, the peak stress amplitude generated by 248 nm irradiation is more than an order of magnitude larger than that produced by 193 nm irradiation. For radiant exposures where material removal is achieved, the temporal structure of the stress transient indicates that the onset of material removal occurs during irradiation. In this regime, the variation of the peak compressive stress with radiant exposure is consistent with laser-induced rapid surface vaporization. For 193 nm irradiation, ionization of the ablated material occurs at even greater radiant exposures and is accompanied by a change in the variation of peak stress with radiant exposure consistent with a plasma-mediated ablation process. These results suggest that absorption of ultraviolet laser radiation by the extracellular matrix of tissue leads to decomposition of tissue on the time scale of the laser pulse. The difference in volumetric energy density at ablation threshold between the two wavelengths indicates that the larger stresses generated by 248 nm irradiation may facilitate the onset of material removal. However, once material removal is achieved, the stress measurements demonstrate that energy not directly responsible for target decomposition contributes to increasing the specific energy of the plume (and plasma

  18. Probing new physics using high-intensity laser systems

    NASA Astrophysics Data System (ADS)

    Marklund, Mattias; Ilderton, Anton; Lundin, Joakim

    2011-06-01

    Current high-intensity laser sources offer a multitude of research, experiment and application possibilities, ranging from e.g. ionisation studies of atomic and molecular systems to particle acceleration for medical purposes. Planned upgrades of existing laser sources will further increase the deliverable intensities and make certain lowintensity (as compared to the Schwinger field) tests of quantum electrodynamics viable. Moreover, secondary sources of radiation, and planned future facilities, offer several-orders-of-magnitude increases in intensities. Thus, it is highly relevant to ask what kind of physics that may be probed using future light sources.

  19. Segmental irradiation of the bladder with neodymium YAG laser irradiation

    SciTech Connect

    McPhee, M.S.; Mador, D.R.; Tulip, J.; Ritchie, B.; Moore, R.; Lakey, W.H.

    1982-11-01

    The Neodymium YAG laser energy source can be readily adapted for cystoscopic use by some simple modifications of existing urologic equipment. Both the fiberoptic resectoscope and a deflecting cystourethroscope have been adapted for this purpose. Fixation of the fiber tip 1 cm. from the target and use of a divergent beam of 36 degrees allows the delivery of standardized dosage to a relatively large bladder tissue volume. Animal experiments involving 35 mongrel dogs established that repetitive overlapping doses of 200 joules ech can successfully treat a large area of bladder resulting in a full thickness bladder wall injury. This technique has been used in 4 high risk patients with infiltrating bladder cancer without adverse sequelae. The ability to reliably produce a full thickness lesion may give this modality a therapeutic advantage over conventional cautery techniques especially for the treatment of residual infiltrative carcinoma.

  20. In situ observation of structural transformation of gold nanorods under pulsed laser irradiation in an HVEM.

    PubMed

    Sumimoto, Nao; Nakao, Koichiro; Yamamoto, Tomokazu; Yasuda, Kazuhiro; Matsumura, Syo; Niidome, Yasuro

    2014-08-01

    A pulsed laser light illumination system was attached to a high-voltage electron microscope (HVEM) for in situ observation of light-induced behaviors of nano objects. The wavelength λ of emitted laser pulses was 1064, 532 or 266 nm, and the pulse duration was 6-8 ns. Using this combined HVEM system, we observed the deformation behavior of gold nanorods irradiated by a pulsed laser (λ = 1064 nm) at an intensity of 310 J m(-2) pulse or higher. A single shot of pulsed laser reduced the aspect ratio of the gold nanorods from 5 to a much smaller value. The extent of the reduction increased at higher laser intensities. However, at 310 J m(-2) pulse(-1), additional pulsed shots induced limited further deformation. The mean aspect ratio approximated to 2.5 even after irradiation with 7 pulses (total fluence exceeding 2 MJ m(-2)). In situ high resolution transmission electron microscopy (HRTEM) observation revealed that deformation was accompanied by total atomic restructuring of the nanorod interiors.

  1. Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Z. K.; Zheng, H. Y.; Lim, C. P.; Lam, Y. C.

    2009-09-01

    Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm2 produced a hydrophobic surface and 2.1 to 52.7 J/cm2 (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm2 had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness.

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

    SciTech Connect

    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.

  3. Bactericidal effect of Nd:YAG laser irradiation in endodontics

    NASA Astrophysics Data System (ADS)

    Aun, Carlos E.; Barberini, Alexandre F.; Camargo, Selma C. C.; Silva Kfouri, Luciana; Lorenzetti Simionato, Maria R.

    1999-05-01

    The success of endodontic therapy is based on the elimination of bacterial colonization from the endodontic system and periapical tissues. Recent studies have been showing the bactericidal effect of laser in root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canals from upper central incisor. For the experiment 12 teeth were selected, respect at the apical third, sterilized, and 10 μm Streptococcus sanguis liquid culture were inoculated in the root canals. The laser test groups were irradiated with Nd:YAG laser at standard setting of 15Hz, 100mj and 1,5 W for 10, 20 and 30 seconds each in slow helicoidal movements from the apex to the top using a 300 micrometers fiber. After the procedure the specimens were placed in Tryptic Soy Agar, the number of colony forming units was evaluated. The experiment showed a significant reduction on viability of Streptococcus sanguis at the respective time of 20 and 30 seconds.

  4. Tight focusing of ultra-intense laser pulses by innovative plasma optics toward extreme intensity

    NASA Astrophysics Data System (ADS)

    Nakatsutsumi, M.; Kon, A.; Fuchs, J.; Buffechoux, S.; Audebert, P.; Kodama, R.

    2009-11-01

    With rapid advances in laser technology, laser beams are now available that can be routinely focused to intensities approaching >10^21 Wcm-2. Enhancement of laser intensity is achieved by truncating the pulse width, increasing the laser-energy, or reducing the focal spot size. Although the reduction of the spot size is the simplest among those, by using low f-number optics, this method is not frequently employed because of the difficulty in avoiding damage from target debris or complexity of alignment procedure. We developed for the first time very compact (<1 cm^3) extremely low f-number (0.4) plasma-based, confocal ellipsoid focusing systems. Direct measurement of the laser focal spot using low-energy laser indicates 1/5 reduction of spot size compared to standard focusing (using a f/3 optics). Around tenfold enhancement of laser intensity by reduction of the spot size for high power shots is clearly evidenced by remarkable enhancement of proton energy. The experiment was performed at LULI 100TW laser facility.

  5. Treatment of acute pancreatitis with mexidol and low-intensity laser radiation

    NASA Astrophysics Data System (ADS)

    Parzyan, G. R.; Geinits, A. V.

    2001-04-01

    This article presents the results of treatment of 54 patients with acute pancreatitis. The patients were divided into two groups according to the method of treatment. The control group (26 patients) received a conventional therapy, whereas the experimental group (28 patients) received mexidol in combination with the intravenous laser irradiation of blood. Clinical and laboratory tests confirmed a high efficiency of the combined therapy based on the administration of mexidol antioxidant and low-intensity (lambda) equals 0.63 micrometers diode laser irradiation of blood. This therapeutic technique produced an influence on the basic pathogenetic mechanisms of acute pancreatitis. The application of this method of treatment improved the course and prognosis of acute pancreatitis.

  6. Low intensity infrared laser induces filamentation in Escherichia coli cells

    NASA Astrophysics Data System (ADS)

    Fonseca, A. S.; Presta, G. A.; Geller, M.; Paoli, F.

    2011-10-01

    Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the photobiological basis is not well understood. The aim of this wok was to evaluate, using bacterial filamentation assay, effects of laser on Escherichia coli cultures in exponential and stationary growth phase. E. coli cultures, proficient and deficient on DNA repair, in exponential and stationary growth phase, were exposed to low intensity infrared laser, aliquots were spread onto microscopic slides, stained by Gram method, visualized by optical microscopy, photographed and percentage of bacterial filamentation were determined. Low intensity infrared laser with therapeutic fluencies and different emission modes can induce bacterial filamentation in cultures of E. coli wild type, fpg/ mutM, endonuclease III and exonuclease III mutants in exponential and stationary growth phase. This study showed induction of bacterial, filamentation in E. coli cultures expose to low intensity infrared laser and attention to laser therapy protocols, which should take into account fluencies, wavelengths, tissue conditions, and genetic characteristics of cells before beginning treatment.

  7. High-order harmonics from laser-irradiated plasma surfaces

    SciTech Connect

    Teubner, U.; Gibbon, P.

    2009-04-15

    The investigation of high-order harmonic generation (HHG) of femtosecond laser pulses by means of laser-produced plasmas is surveyed. This kind of harmonic generation is an alternative to the HHG in gases and shows significantly higher conversion efficiency. Furthermore, with plasma targets there is no limitation on applicable laser intensity and thus the generated harmonics can be much more intense. In principle, harmonic light may also be generated at relativistic laser intensity, in which case their harmonic intensities may even exceed that of the focused laser pulse by many orders of magnitude. This phenomenon presents new opportunities for applications such as nonlinear optics in the extreme ultraviolet region, photoelectron spectroscopy, and opacity measurements of high-density matter with high temporal and spatial resolution. On the other hand, HHG is strongly influenced by the laser-plasma interaction itself. In particular, recent results show a strong correlation with high-energy electrons generated during the interaction process. The harmonics are a promising tool for obtaining information not only on plasma parameters such as the local electron density, but also on the presence of large electric and magnetic fields, plasma waves, and the (electron) transport inside the target. This paper reviews the theoretical and experimental progress on HHG via laser-plasma interactions and discusses the prospects for applying HHG as a short-wavelength, coherent optical tool.

  8. The shaped critical surface in high intensity laser plasma interactions

    SciTech Connect

    Schumacher, D. W.; Kemp, G. E.; Link, A.; Freeman, R. R.; Van Woerkom, L. D.

    2011-01-15

    This paper describes an investigation of the properties of the relativistic critical surface in a high intensity laser-plasma interaction, specifically the spatial morphology of the surface and its effect upon the divergence of the reflected light. The particle-in-cell code LSP running in two dimensions (2d3v) was used to model the formation of the critical surface and to show that it resides at a varying depth into the material that is dependent on both the intensity radial dependence of the laser focus as well as the shape of the longitudinal vacuum-material interface. The result is a shaped 'mirror' surface that creates a reflected beam with phase and amplitude information informed by the extent of the preplasma present before the intense laser pulse arrived. A robust, highly effective means of experimentally determining the preplasma conditions for any high intensity laser-matter interaction is proposed using this effect. The important physics is elucidated with a simplified model that, within reasonable intensity bounds, recasts the effect of the complex laser-plasma interaction on the reflected beam into a standard Gaussian optics calculation.

  9. Bio-heat transfer simulation of retinal laser irradiation.

    PubMed

    Narasimhan, Arunn; Jha, Kaushal Kumar

    2012-05-01

    Retinopathy is a surgical process in which maladies of the human eye are treated by laser irradiation. A two-dimensional numerical model of the human eye geometry has been developed to investigate transient thermal effects due to laser radiation. In particular, the influence of choroidal pigmentation and that of choroidal blood convection-parameterized as a function of choroidal blood perfusion-are investigated in detail. The Pennes bio-heat transfer equation is invoked as the governing equation, and finite volume formulation is employed in the numerical method. For a 500-μm diameter spot size, laser power of 0.2 W, and 100% absorption of laser radiation in the retinal pigmented epithelium (RPE) region, the peak RPE temperature is observed to be 103 °C at 100 ms of the transient simulation of the laser surgical period. Because of the participation of pigmented layer of choroid in laser absorption, peak temperature is reduced to 94 °C after 100 ms of the laser surgery period. The effect of choroidal blood perfusion on retinal cooling is found to be negligible during transient simulation of retinopathy. A truncated three-dimensional model incorporating multiple laser irradiation of spots is also developed to observe the spatial effect of choroidal blood perfusion and choroidal pigmentation. For a circular array of seven uniformly distributed spots of identical diameter and laser power of 0.2 W, transient temperature evolution using simultaneous and sequential mode of laser surgical process is presented with analysis.

  10. Ablation of dentin by irradiation of violet diode laser

    NASA Astrophysics Data System (ADS)

    Hatayama, H.; Kato, J.; Akashi, G.; Hirai, Y.; Inoue, A.

    2006-02-01

    Several lasers have been used for clinical treatment in dentistry. Among them, diode lasers are attractive because of their compactness compared with other laser sources. Near-infrared diode lasers have been practically used for cutting soft tissues. Because they penetrate deep to soft tissues, they cause sufficiently thick coagulation layer. However, they aren't suitable for removal of carious dentin because absorption by components in dentin is low. Recently, a violet diode laser with a wavelength of 405nm has been developed. It will be effective for cavity preparation because dentin contains about 20% of collagen whose absorption coefficient at a violet wavelength is larger than that at a near-infrared wavelength. In this paper, we examined cutting performance of the violet diode laser for dentin. To our knowledge, there have been no previous reports on application of a violet laser to dentin ablation. Bovine teeth were irradiated by continuous wave violet diode laser with output powers in a range from 0.4W to 2.4W. The beam diameter on the sample was about 270μm and an irradiation time was one second. We obtained the crater ablated at more than an output power of 0.8W. The depth of crater ranged from 20μm at 0.8W to 90μm at 2.4W. Furthermore, the beam spot with an output power of 1.7W was scanned at a speed of 1mm/second corresponding to movement of a dentist's hand in clinical treatment. Grooves with the depth of more than 50μm were also obtained. From these findings, the violet diode laser has good potential for cavity preparation. Therefore, the violet diode laser may become an effective tool for cavity preparation.

  11. Effects of a Low-Intensity Laser on Dental Implant Osseointegration: Removal Torque and Resonance Frequency Analysis in Rabbits.

    PubMed

    Blay, Alberto; Blay, Claudia C; Tunchel, Samy; Gehrke, Sergio Alexandre; Shibli, Jamil Awad; Groth, Eduardo B; Zezell, Denise M

    2016-08-01

    The objective of this study was to investigate how a low-intensity laser affects the stability and reverse torque resistance of dental implants installed in the tibia of rabbits. Thirty rabbits received 60 dental implants with the same design and surface treatment, one in each proximal metaphysis of the tibia. Three groups were prepared (n = 10 animals each): conventional osseointegration without treatment (control group), surgical sites irradiated with a laser beam emitted in the visible range of 680 nm (Lg1 group), surgical sites irradiated with a laser beam with a wavelength in the infrared range of 830 nm (Lg2 group). Ten irradiation sessions were performed 48 hours apart; the first session was during the immediate postoperative period. Irradiation energy density was 4 J/cm(2) per point in 2 points on each side of the tibias. The resonance frequency and removal torque values were measured at 2 time points after the implantations (3 and 6 weeks). Both laser groups (Lg1 and Lg2) presented a significant difference between resonance frequency analysis values at the baseline and the values obtained after 3 and 6 weeks (P > .05). Although the removal torque values of all groups increased after 6 weeks (P < .05), both laser groups presented greater mean values than those of the control group (P < .01). Photobiomodulation using laser irradiation with wavelengths of 680 and 830 nm had a better degree of bone integration than the control group after 6 weeks of observation time.

  12. The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

    SciTech Connect

    Kahn, E. H.; Langford, S. C.; Dickinson, J. T.; Boatner, Lynn A

    2013-01-01

    We report mass-resolved time-of-flight measurements of neutral particles from the surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

  13. Thermodynamic response of soft biological tissues to pulsed infrared-laser irradiation.

    PubMed Central

    Venugopalan, V; Nishioka, N S; Mikić, B B

    1996-01-01

    The physical mechanisms that achieve tissue removal through the delivery of short pulses of high-intensity infrared laser radiation, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed infrared laser irradiation was investigated by measuring and analyzing the stress transients generated by Q-sw Er:YSGG (lambda = 2.79 microns) and TEA CO2 (lambda = 10.6 microns) laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not produce material removal, the stress transients are consistent with thermal expansion of the tissue samples. The temporal structure of the stress transients generated at the threshold radiant exposure for ablation indicates that the onset of material removal is delayed with respect to irradiation. Once material removal is achieved, the magnitude of the peak compressive stress and its variation with radiant exposure are consistent with a model that considers this process as an explosive event occurring after the laser pulse. This mechanism is different from ArF- and KrF-excimer laser ablation where absorption of ultraviolet radiation by the collagenous tissue matrix leads to tissue decomposition during irradiation and results in material removal via rapid surface vaporization. It appears that under the conditions examined in this study, explosive boiling of tissue water is the process that mediates the ablation event. This study provides evidence that the dynamics and mechanism of tissue ablation processes can be altered by targeting tissue water rather than the tissue structural matrix. Images FIGURE 6 PMID:8744336

  14. Intense tera-hertz laser driven proton acceleration in plasmas

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Tibai, Z.; Hebling, J.

    2016-06-01

    We investigate the acceleration of a proton beam driven by intense tera-hertz (THz) laser field from a near critical density hydrogen plasma. Two-dimension-in-space and three-dimension-in-velocity particle-in-cell simulation results show that a relatively long wavelength and an intense THz laser can be employed for proton acceleration to high energies from near critical density plasmas. We adopt here the electromagnetic field in a long wavelength (0.33 THz) regime in contrast to the optical and/or near infrared wavelength regime, which offers distinct advantages due to their long wavelength ( λ = 350 μ m ), such as the λ 2 scaling of the electron ponderomotive energy. Simulation study delineates the evolution of THz laser field in a near critical plasma reflecting the enhancement in the electric field of laser, which can be of high relevance for staged or post ion acceleration.

  15. Thomson scattering in high-intensity chirped laser pulses

    SciTech Connect

    Holkundkar, Amol R.; Harvey, Chris Marklund, Mattias

    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.

  16. Control of a resonant tunneling structure by intense laser fields

    NASA Astrophysics Data System (ADS)

    Aktas, S.; Kes, H.; Boz, F. K.; Okan, S. E.

    2016-10-01

    The intense laser field effects on a resonant tunneling structure were studied using computational methods. The considered structure was a GaAs/InxGa1-xAs/Al0.3Ga0.7As/InyGa1-yAs/AlAs/GaAs well-barrier system. In the presence of intense laser fields, the transmission coefficient and the dwell time of the structure were calculated depending on the depth and the width of InGaAs wells. It was shown that an intense laser field provides full control on the performance of the device as the geometrical restrictions on the resonant tunneling conditions overcome. Also, the choice of the resonant energy value becomes possible depending on the field strength.

  17. Physical and Chemical Changes of Polystyrene Nanospheres Irradiated with Laser

    SciTech Connect

    Mustafa, Mohd Ubaidillah; Juremi, Nor Rashidah Md.; Mohamad, Farizan; Wibawa, Pratama Jujur; Agam, Mohd Arif; Ali, Ahmad Hadi

    2011-05-25

    It has been reported that polymer resist such as PMMA (Poly(methyl methacrylate) which is a well known and commonly used polymer resist for fabrication of electronic devices can show zwitter characteristic due to over exposure to electron beam radiation. Overexposed PMMA tend to changes their molecular structure to either become negative or positive resist corresponded to electron beam irradiation doses. These characteristic was due to crosslinking and scissors of the PMMA molecular structures, but till now the understanding of crosslinking and scissors of the polymer resist molecular structure due to electron beam exposure were still unknown to researchers. Previously we have over exposed polystyrene nanospheres to various radiation sources, such as electron beam, solar radiation and laser, which is another compound that can act as polymer resist. We investigated the physical and chemical structures of the irradiated polystyrene nanospheres with FTIR analysis. It is found that the physical and chemical changes of the irradiated polystyrene were found to be corresponded with the radiation dosages. Later, combining Laser irradiation and Reactive Ion Etching manipulation, created a facile technique that we called as LARIEA NSL (Laser and Reactive Ion Etching Assisted Nanosphere Lithography) which can be a facile technique to fabricate controllable carbonaceous nanoparticles for applications such as lithographic mask, catalysts and heavy metal absorbers.

  18. The Effect of Laser Irradiation on Adipose Derived Stem Cell Proliferation and Differentiation

    NASA Astrophysics Data System (ADS)

    Abrahamse, H.; de Villiers, J.; Mvula, B.

    2009-06-01

    There are two fundamental types of stem cells: Embryonic Stem cells and Adult Stem cells. Adult Stem cells have a more restricted potential and can usually differentiate into a few different cell types. In the body these cells facilitate the replacement or repair of damaged or diseased cells in organs. Low intensity laser irradiation was shown to increase stem cell migration and stimulate proliferation and it is thought that treatment of these cells with laser irradiation may increase the stem cell harvest and have a positive effect on the viability and proliferation. Our research is aimed at determining the effect of laser irradiation on differentiation of Adipose Derived Stem Cells (ADSCs) into different cell types using a diode laser with a wavelength of 636 nm and at 5 J/cm2. Confirmation of stem cell characteristics and well as subsequent differentiation were assessed using Western blot analysis and cellular morphology supported by fluorescent live cell imaging. Functionality of subsequent differentiated cells was confirmed by measuring adenosine triphosphate (ATP) production and cell viability.

  19. Low-intensity infrared laser effects on zymosan-induced articular inflammatory response

    NASA Astrophysics Data System (ADS)

    Januária dos Anjos, Lúcia Mara; da Fonseca, Adenilson d. S.; Gameiro, Jacy; de Paoli, Flávia

    2015-03-01

    Low-level therapy laser is a phototherapy treatment that involves the application of low power light in the red or infrared wavelengths in various diseases such as arthritis. In this work, we investigated whether low-intensity infrared laser therapy could cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosaninduced articular inflammatory process. Inflammatory process was induced in C57BL/6 mouse by intra-articular injection of zymosan into rear tibio-tarsal joints. Thirty animals were divided in five groups: (I) control, (II) laser, (III) zymosan-induced, (IV) zymosan-induced + laser and (V). Laser exposure was performed after zymosan administration with low-intensity infrared laser (830 nm), power 10 mW, fluence 3.0 J/cm2 at continuous mode emission, in five doses. Twenty-four hours after last irradiation, the animals were sacrificed and the right joints fixed and demineralized. Morphological analysis was observed by hematoxylin and eosin stain, pro-apoptotic (caspase-6) was analyzed by immunocytochemistry and DNA fragmentation was performed by TUNEL assay in articular cartilage cells. Inflammatory process was observed in connective tissue near to articular cartilage, in IV and V groups, indicating zymosan effect. This process was decreased in both groups after laser treatment and dexamethasone. Although groups III and IV presented higher caspase-6 and DNA fragmentation percentages, statistical differences were not observed when compared to groups I and II. Our results suggest that therapies based on low-intensity infrared lasers could reduce inflammatory process and could not cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosan-induced articular inflammatory process.

  20. Nanofabrication with ultrafast lasers at critical intensity

    NASA Astrophysics Data System (ADS)

    Ke, Kevin; Hasselbrink, Ernest; Hunt, Alan J.

    2005-03-01

    A principal challenge facing nanotechnology is consistently producing well-defined features much smaller than the wavelength of visible light. We find that the remarkably sharp threshold for femtosecond laser-induced material damage enables nanomachining with unprecedented precision and versatility, allowing highly reproducible machining of structures with nanoscale features. Using this methodology, we demonstrate, in glass, surface trenches that are only tens of nanometers in width but micron in depth, sub-surface channels that are hundreds nanometers in diameter, tens of microns deep, and hundreds microns in length, and 3D microstructures such as cantilevers. Furthermore, we demonstrate reproducible nanometer scale features in mixed and amorphous materials that differ significantly from glass, such as gold and onion cells. This technique is versatile, not material specific, and has potentially broad applications for MEMS construction and design, high density microelectronics, nanofluidics, material science, and optical memory.

  1. Self-organized, gratinglike nanostructures in polymer films with embedded metal nanoparticles induced by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Loeschner, K.; Seifert, G.; Heilmann, A.

    2010-10-01

    The self-organized formation of periodic superstructures in thin plasma polymer films containing noble metal nanoparticles upon femtosecond laser irradiation has been studied in detail. By applying several hundred laser pulses on average per spot, the nanostructure of the metal layer is persistently changed into an approximate line grating with periodical changes in particle size and shape as observed by scanning and transmission electron microscopy. The formation of the structures is only possible within rather narrow ranges of laser intensity and metal content. The orientation of the lines is given by the laser polarization, while their spatial periodicity depends on laser wavelength and incidence angle. These observations give evidence that interference of incident light with light scattered into the film plane is the main mechanism controlling the nanostructure formation. We also discuss the optical spectra of the irradiated regions, in particular the observed dichroism and its relation to the prepared periodic structures.

  2. Generation of a quasi-monoergetic proton beam from laser-irradiated sub-micron droplets

    SciTech Connect

    Ter-Avetisyan, S.; Ramakrishna, B.; Prasad, R.; Borghesi, M.; Nickles, P. V.; Steinke, S.; Schnuerer, M.; Popov, K. I.; Ramunno, L.; Zmitrenko, N. V.; Bychenkov, V. Yu.

    2012-07-15

    Proton bursts with a narrow spectrum at an energy of (2.8 {+-} 0.3 MeV) are accelerated from sub-micron water spray droplets irradiated by high-intensity ({approx}5 Multiplication-Sign 10{sup 19} W/cm{sup 2}), high-contrast ({approx}10{sup 10}), ultra-short (40 fs) laser pulses. The acceleration is preferentially in the laser propagation direction. The explosion dynamics is governed by a residual ps-scale laser pulse pedestal which 'mildly' preheats the droplet and changes its density profile before the arrival of the high intensity laser pulse peak. As a result, the energetic electrons extracted from the modified target by the high-intensity part of the laser pulse establish an anisotropic electrostatic field which results in anisotropic Coulomb explosion and proton acceleration predominantly in the forward direction. Hydrodynamic simulations of the target pre-expansion and 3D particle-in-cell simulations of the measured energy and anisotropy of the proton emission have confirmed the proposed acceleration scenario.

  3. Relativistic intensity laser interactions with low-density plasmas

    NASA Astrophysics Data System (ADS)

    Willingale, L.; Nilson, P. M.; Zulick, C.; Chen, H.; Craxton, R. S.; Cobble, J.; Maksimchuk, A.; Norreys, P. A.; Sangster, T. C.; Scott, R. H. H.; Stoeckl, C.

    2016-03-01

    We perform relativistic-intensity laser experiments using the Omega EP laser to investigate channeling phenomena and particle acceleration in underdense plasmas. A fundamental understanding of these processes is of importance to the hole-boring fast ignition scheme for inertial confinement fusion. Proton probing was used to image the electromagnetic fields formed as the Omega EP laser pulse generated a channel through underdense plasma. Filamentation of the channel was observed, followed by self-correction into a single channel. The channel radius as a function of time was found to be in reasonable agreement with momentum- conserving snowplough models.

  4. Propagation of intense laser pulses in strongly magnetized plasmas

    SciTech Connect

    Yang, X. H. Ge, Z. Y.; Xu, B. B.; Zhuo, H. B.; Ma, Y. Y.; Shao, F. Q.; Yu, W.; Xu, H.; Yu, M. Y.; Borghesi, M.

    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.

  5. Laser versus intense pulsed light: Competing technologies in dermatology.

    PubMed

    Ross, E Victor

    2006-04-01

    Lasers have been competing with non-laser intense pulsed light (IPL) sources in the cosmetic arena over the past 10 years. Initially IPLs were somewhat cumbersome and accepted by a minority of "serious" practitioners. Recently, however, the popularity of full-face visible light skin rejuvenation, enhanced engineering of IPLs, and favorable cost versus many lasers, have lead to a proliferation of IPL devices. No longer a stepchild in the rejuvenation market, IPLs may overtake lasers as the devices of choice among most physicians. We review the pros and cons of lasers and IPLs within the context of design, cost, and other practical concerns for a typical office-based practice. PMID:16596659

  6. Photodynamic therapy with laser scanning mode of tumor irradiation

    NASA Astrophysics Data System (ADS)

    Chepurna, Oksana; Shton, Irina; Kholin, Vladimir; Voytsehovich, Valerii; Popov, Viacheslav; Pavlov, Sergii; Gamaleia, Nikolai; Wójcik, Waldemar; Zhassandykyzy, Maral

    2015-12-01

    In this study we propose a new version of photodynamic therapy performed by laser scanning. The method consists in tumor treatment by a light beam of a small cross section which incrementally moves through the chosen area with a defined delay at each point and repetitively re-scans a zone starting from the initial position. Experimental evaluation of the method in vitro on murine tumor model showed that despite the dose, applied by scanning irradiation mode, was 400 times lower, the tumor inhibition rate conceded to attained with continuous irradiation mode by only 20%.

  7. [Photoablation of the cornea with pulsed 2790 nm ErCr:YSGG laser irradiation. Basic studies].

    PubMed

    Lubatschowski, H; Kermani, O; Asshauer, T

    1993-04-01

    The potential of 3 microns solid-state lasers as an alternative to excimer lasers for photoablative corneal surgery was investigated. A Q-switched ErCr:YSGG laser (2790 nm, 200 ns) was used for irradiation of porcine corneas and agar-agar samples. Mechanical tissue effects (stroma, endothelium) were documented by micromorphology. Laser-induced shock-waves were analyzed by piezo-electric transducers. No sharp ablation threshold, as in excimer laser photoablation, could be determined. Energy fluences < 2 J/cm2 led to dehydration of the irradiated samples. Higher fluences are necessary for the evaporation of tissue water to be so vigorous that the tissue matrix is expelled along with the organic matrix. At high fluences, the ablation rate exceeds the absorption depth of the laser radiation (up to 25 microns/pulse). At fluences between 2.5 and 28 J/cm2 the thermal necrosis zone adjacent to the crater was 7 +/- 3 microns. The intensity of the laser-induced acoustic shock waves can peak to some hundred bar. Small gas bubbles up to 1 mm were found in the surrounding area of the ablation crater. Apparently, they were pressed between the collagen lamellas by the explosive force of the ablative process. In deep excisions (> 75%) endothelial defects underneath the beam axis could be documented. Large-area tissue ablation, with a resolution in the range of 1 micron, as necessary in myopia correction, will not be possible with the present generation of ErCr:YSGG lasers. Its high ablation rate makes this laser suitable as a cutting (astigmatism, keratoplasty, vitreous surgery) and drilling (glaucoma) device.

  8. Investigating the QED vacuum with ultra-intense laser fields

    NASA Astrophysics Data System (ADS)

    King, B.; Di Piazza, A.

    2014-05-01

    In view of the increasingly stronger available laser fields it is becoming feasible to employ them to probe the nonlinear dielectric properties of the vacuum as predicted by quantum electrodynamics (QED) and to test QED in the presence of intense laser beams. First, we discuss vacuum-polarization effects that arise in the collision of a high-energy proton beam with a strong laser field. In addition, we investigate the process of light-by-light diffraction mediated by the virtual electron-positrons of the vacuum. A strong laser beam "diffracts" a probe laser field due to vacuum polarization effects, and changes its polarization. This change of the polarization is shown to be in principle measurable. Also, the possibility of generating harmonics by exploiting vacuum-polarization effects in the collision in vacuum of two ultra-strong laser beams is discussed. Moreover, when two strong parallel laser beams collide with a probe electromagnetic field, each photon of the probe may interact through the "polarized" quantum vacuum with the photons of the other two fields. Analogously to "ordinary" double-slit set-ups involving matter, the vacuum-scattered probe photons produce a diffraction pattern, which is the envisaged observable to measure the quantum interaction between the probe and strong field photons. We have shown that the diffraction pattern becomes visible in a few operating hours, if the strong fields have an intensity exceeding 1024W/cm2.

  9. Reflectivity and laser irradiation of plasma sprayed Al coating

    NASA Astrophysics Data System (ADS)

    Gao, Lihong; Ma, Zhuang; Wang, Fuchi; Li, Wenzhi

    2015-05-01

    It's well known that Al has a very high reflectivity in the visible/near-infrared range, which makes it become a promising anti-laser material. But for a plasma sprayed coating, there are usually many defects, such as pores, cracks and interfaces among particles, which lead to properties difference with its bulk material. In this paper, the reflectivity of plasma sprayed Al coating and its laser irradiation effect were investigated. Its reflectivity, surface roughness, porosity, microstructure, and cross-section microstructure were characterized. The results show that a high reflectivity (98.1% at CO2 laser 10.6μm wavelength) of plasma sprayed Al coating, which is comparable with bulk material, could be obtained. Its optical laser damage threshold is 2×104W/cm2 that makes its reflectivity obviously decrease. Its damage mechanism is oxidation.

  10. Target physics results at 248 nm wavelength from the Aurora laser system high-intensity campaign

    SciTech Connect

    Watt, R.G.; Cobble, J.; Gomez, C.; Kephart, J.; Kristal, R.; Turner, T.P.; Oertel, J.; Thomas, S.; Netz, D.; Jones, J.

    1990-10-01

    Au and Si targets have been irradiated using the Aurora KrF laser system, and diagnosed with x-ray and optical diagnostics. The x-ray diagnostics were sensitive to the 0.1--10 keV range. Initial, manually aligned results indicate significant plasma heating and intense x-ray production, with incident peak intensities on target of 1 {minus} 2 {times} 10{sup 14} W/cm{sup 2} in a focal spot of order 500 {mu}m diameter. Total energy delivered to the target in 36 of the available 48 target beams was approximately 1200 J in pulses with FWHM in the 3--5 ns range. M-band radiation was observed from Au foil targets. Initial bandwidth measurements on the laser indicate {approx}20 cm{sup {minus}1} without bandwidth enhancement efforts.

  11. Is there a stimulation of blood microcirculation at low level laser irradiation

    NASA Astrophysics Data System (ADS)

    Rogatkin, Dmitry; Dunaev, Andrey

    2014-05-01

    In 1980-2000 besides the laser surgery an intensive evolution of Low Level Laser Therapy (LLLT) had started in medicine, especially in Russia as well as in several other East-European countries. At the same time the biophysical mechanisms of LLLT are still the subject of disputes. One of the most popular clinical effects at Low Level Laser Irradiation (LLLI) being mentioned in medical publications for justification of the LLLT healing outcome is a stimulation of blood microcirculation in irradiated area. It was declared a priori at a dawn of LLLT and is now a basis of medical interpretation of healing mechanisms of LLLT at least in Russia. But in past 20 years a lot of investigation was carried out on optical registration of microhaemodynamic parameters in vivo as well as a number of noninvasive diagnostic tools was created for that. So, today it is possible to experimentally check the blood microcirculation stimulation hypothesis. Our study was aimed on that during the past 10 years. The most precision and accurate experiments we have carried out recently using simultaneously three different noninvasive diagnostic techniques: Laser Doppler Flowmetry, Tissue Reflectance Oximetry and Infrared Thermography. All these methods didn't confirm the effect on the blood microcirculation stimulation in skin or mucosa at irradiation with the power density below 50 mW/cm2 and irradiation time up to 5-6 minutes. Above this threshold the heating on 0,8…1 °C of tissue in the field of irradiation and the corresponding synchronous increase of all parameters of microhemodynamics were observed.

  12. Study of fast electron jet produced from interaction of intense laser beam with solid target at oblique incidence

    SciTech Connect

    Sanyasi Rao, Bobbili; Arora, Vipul; Anant Naik, Prasad; Dass Gupta, Parshotam

    2012-11-15

    Fast electrons generated along target normal direction from the interaction of intense ultrashort Ti:sapphire laser pulses ({lambda}{sub 0} = 800 nm) with planar copper target at 45 Degree-Sign incidence angle have been experimentally studied under different interaction conditions. Angular spread and energy spectrum of the fast electrons was measured for both p- and s-polarized laser irradiation at intensities in the range 4 Multiplication-Sign 10{sup 16}- 4 Multiplication-Sign 10{sup 17} W/cm{sup 2} (for a fixed pulse duration of 45 fs) and for pulse duration in the range 45 fs-1.2 ps (for a fixed laser fluence of 1.8 Multiplication-Sign 10{sup 4} J/cm{sup 2}). The fast electrons were observed consistently along the target normal direction over the entire range of interaction conditions in the form of a collimated jet, within a half cone angle of 20 Degree-Sign . The fast electrons have continuous energy spectrum with effective temperature 290 keV and 160 keV, respectively, for p- and s-polarized 45 fs laser pulse irradiation at intensity 4 Multiplication-Sign 10{sup 17} W/cm{sup 2}. Scaling laws for temperature of fast electrons with laser intensity and pulse duration were obtained. The experimental results have been explained on the basis of laser absorption and fast electron generation through the resonance absorption mechanism.

  13. Electrodynamics of electron in a superintense laser field: New principles of diagnostics of relativistic laser intensity

    SciTech Connect

    Galkin, A. L.; Klinkov, V. K.; Korobkin, V. V.; Romanovsky, M. Yu.; Shiryaev, O. B.; Kalashnikov, M. P.

    2010-05-15

    The dynamics and energy spectra of electrons driven by a relativistically intense laser pulse are analyzed. The description is based on the numerical solution of the relativistic Newton's equation with the Lorentz force generated by a strong focused optical field. After the interaction with it, electrons retain a considerable fraction of the energy of their oscillations during the interaction. The electron postinteraction energy spectrum is calculated. The energies in the spectrum high-energy tail are determined by the laser pulse intensity at the focal spot. An approach to estimating absolute values of the laser pulse intensity based on the measurement of the energy spectra of the electrons is proposed.

  14. Bragg cell laser intensity modulation: effect on laser Doppler velocimetry measurements

    SciTech Connect

    Mychkovsky, Alexander G.; Chang, Natasha A.; Ceccio, Steven L.

    2009-06-20

    In most laser Doppler velocimetry (LDV) systems, the frequency of one of the two laser beams that intersect to create the probe volume is shifted with an acousto-optic element. It is shown here that Bragg shifting can impose a problematic fluctuation in intensity on the frequency-shifted beam, producing spurious velocity measurements. This fluctuation occurs at twice the Bragg cell frequency, and its relative amplitude to the time average intensity is a function of the ratio of the laser beam diameter to the Bragg cell acoustic wavelength. A physical model and a configuration procedure to minimize adverse effects of the intensity modulations are presented.

  15. Atomic electron correlations in intense laser fields

    SciTech Connect

    DiMauro, L.F.; Sheehy, B.; Walker, B.; Agostini, P.A.; Kulander, K.C.

    1998-11-01

    This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although their ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear.

  16. Atomic electron correlations in intense laser fields

    SciTech Connect

    Agostini, P A; DiMauro, L F; Kulander, K; Sheehy, B; Walker, B

    1998-09-03

    Abstract. This talk examines two distinct cases in strong opbical fields where electron correlation plays an important role in the dynamic.s. In the first. example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two- level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although our ability to describe the one- electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unc

  17. Study of the laser cleaning on plaster sculptures. The effect of laser irradiation on the surfaces

    NASA Astrophysics Data System (ADS)

    Pelosi, C.; Fodaro, D.; Sforzini, L.; Rubino, A. R.; Falqui, A.

    2013-06-01

    The focus of this paper is to study the effects caused by the laser irradiation on nineteenth and twentieth century plaster sculptures. Before applying the laser cleaning on the sculptures, it was tested on samples prepared in laboratory according to the results of the scientific investigation carried out on the selected works of art. The characterization of the surface finishing materials of the sculptures was performed by Fourier Transform Infrared spectrometry (FTIR), X-ray Fluorescence spectroscopy (XRF), UV fluorescence photography, and internal micro stratigraphic analysis. Regarding the finishing materials, shellac, zinc white, siccative oil and proteins were found on the surfaces. The results of the scientific investigation, together with the examination of the ancient technical manuals, were used to create the laboratory samples to carry out the irradiation tests with laser. The laser irradiation and cleaning tests were carried out with a Q-switched Nd:YAG system. The irradiated surfaces were analyzed before and after the laser tests with the aid of a video microscope and a reflectance spectrophotometer, in order to evaluate the color changes of the surfaces. The possible morphological modifications caused by laser irradiation were also investigated by Scanning Electron Microscopy (SEM) together with ancillary Energy Dispersive Spectroscopy (EDS) elemental analysis. Concerning the laser cleaning test on the samples, in general little color changes were observed both with the 532 and 1064 nm wavelength. Total color changes, expressed as Δ E*, are always small apart from the samples made of shellac and zinc white in linseed oil, as finishing layer. As regards these samples the surface irradiated with the laser greyed lightly, corresponding to a decrease of L* parameter (lightness). SEM imaging of the treated and not-treated samples, both at low and high magnification, does not show evidence of significant morphological differences due to the laser beam

  18. Spectrum line intensity as a surrogate for solar irradiance variations.

    PubMed

    Livingston, W C; Wallace, L; White, O R

    1988-06-24

    Active Cavity Radiometer Irradiance Monitor (ACRIM) solar constant measurements from 1980 to 1986 are compared with ground-based, irradiance spectrophotometry of selected Fraunhofer lines. Both data sets were identically sampled and smoothed with an 85-day running mean, and the ACRIM total solar irradiance (S) values were corrected for sunspot blocking (S(c)). The strength of the mid-photospheric manganese 539.4-nanometer line tracks almost perfectly with ACRIM S(e), Other spectral features formed high in the photosphere and chromosphere also track well. These comparisons independently confirm the variability in the ACRIM S(e), signal, indicate that the source of irradiance is faculae, and indicate that ACRIM S(e), follows the 11-year activity cycle. PMID:17842428

  19. Laser irradiation for central-type lung cancer

    NASA Astrophysics Data System (ADS)

    Sun, Kai

    1993-03-01

    Based on laser irradiation experiments on isolated lung specimens of animals done in 1989, 8 patients with central type lung cancer were treated with Nd:YAG laser irradiation via fiberoptic bronchoscope from January 1990 to August 1991 in our hospital. The patients recruited were all diagnosed by fiberoptic bronchoscopy and histology as having central type bronchopulmonary cancer without distal metastasis. All patients were male with a mean age of 64 (range 57 - 72). Of 8 patients, 4 had squamous cell carcinoma, 3 adenocarcinoma, and 1 undifferentiated small cell carcinoma, all being stage TUM 3. After laser treatment, 6 cases had a result of significant response and 2 had minor response. Among 6 cases of atelectasis, 4 were completely cured or partially improved and 4 recovered from their hemoptysis. The subjective symptoms in all cases remitted. A combined chemotherapy was carried out accompanying laser therapy for all, 6 of whom had a shrink of focus over 25%. Six cases were re-examined with fiberoptic bronchoscopy, showing a distinct reduction of the tumor. Four cases expectorated black charring tissues and residual tumorous tissues persistently as an outcome. Two typical cases are reported, the characteristics, indications, techniques, and side effects of laser therapy are analyzed and factors affecting efficacy discussed, indicating that the technique has such advantages as easy operation, accurate orientation, and safe outcome. The procedure is really an effective one for treating central type lung cancer in intermediate or late stage.

  20. Control of the local devitrification on oxyfluoride glass doped with Er{sup 3+} ions under diode laser irradiation

    SciTech Connect

    Gonzalez-Perez, S.; Martin, I. R.; Jaque, D.; Haro-Gonzalez, P.; Capuj, N.

    2010-11-15

    Temperature control of the devitrification process in an erbium doped oxyfluoride glass under laser irradiation is reported. The green upconversion emissions around 525 and 545 nm originated from the thermalized {sup 2}H{sub 11/2} and {sup 4}S{sub 3/2} levels were studied when the glass structure changes to glass ceramic during irradiation with a laser beam. Power dependence of the fluorescence intensity ratio was used to determine the temperature of the irradiated zone. The transition from glass to glass ceramic takes place under 2300 mW of laser power with an estimated temperature around 783 K. This result agrees with the one obtained in the samples devitrified under conventional furnace treatment. Therefore, the estimation of the temperature of the irradiated zone through the fluorescence intensity ratio method allows a controlled devitrification. Moreover, an irradiated line has been written in the glass showing an important diffusion of the Pb{sup 2+} and F{sup -} ions. These results confirm that nanocrystals have been created due to the laser action.

  1. Laser irradiation effects: A functional assessment

    NASA Astrophysics Data System (ADS)

    Robbins, David O.

    1994-08-01

    Specification of damage criteria and establishment of morphological data resulting from laser exposure has been an important mission for biomedical researchers and strategic planners. Equally important, however, from a military standpoint is the impact that this alteration, whether temporary or permanent, has on the ability of a soldier to complete a visually guided mission. Furthermore, while permanent visual loss associated with distinct morphological damage is of course serious it must also be recognized that temporary shifts in visual acuity or contrast sensitivity can occur at energy densities below those associated with distinct tissue damage. These temporary visual performance shifts could themselves be life threatening and may be the result of reversible or minute physical changes that are undetectable using current damage criteria. Our result suggests that significant shifts in visual sensitivity does occur at or below the ED50 level and that these shifts can be long lasting. Using a behavioral technique to measure on-going visual acuity, we have exposed awake, task-oriented rhesus monkeys to a variety of laser exposures which vary in energy density and temporal and spatial distribution on the retina. Our preliminary results in this project are consistent with the results of our previous studies and have extended the various exposure and performance criteria already established.

  2. Effect of free electron laser (FEL) irradiation on tooth dentine

    NASA Astrophysics Data System (ADS)

    Ogino, Seiji; Awazu, Kunio; Tomimasu, Takio

    1996-12-01

    Free electron laser (FEL) gives high efficiency for the photo-induced effects when the laser is tuned to the absorption maximum of target materials. The effect on dentine was investigated using the FEL tuned to 9.4 micrometers , which is an absorption maximum of phosphoric acid in infrared region. As a result, irradiated dentine surface which was amorphous had changed to the recrystalized structure by the spectroscopic analysis of IR absorption and x-ray diffraction. Furthermore, the atomic ratio of P/Ca had reduced from 0.65 to 0.60. These results indicated that 9.4micrometers -FEL irradiation caused the selective ablation of phosphoric acid ion and the reconstruction of disordered atoms.

  3. Influence Of Low Intensity Laser Therapy On Diabetic Polyneuropathy

    NASA Astrophysics Data System (ADS)

    Abdel-Raoof, N. A.; Elnhas, N. G.; Elsayed, I. M.

    2011-09-01

    Diabetic peripheral neuropathy is a consequence of diabetes-mediated impairment of blood flow, and resultant hypoxia of nerves that may develop within 10 years of the onset of diabetes in 40-50% of people with type 1 or type 2 diabetes. Low Intensity Laser Therapy (LILT) has been advocated for the treatment of chronic pain disorders as blood flow is an important determinant for pain relief. Comparing the effect of Helium-Neon Laser therapy versus Infrared laser therapy on blood vessels diameter and flow as well as level of sensation for neuropathy. Twenty diabetic patients suffering from neuropathy were enrolled in the study with age 45-55 years. They were assigned randomly into two equal groups in number; Group A underwent an application of He-Neon laser while Group B underwent an application of Infrared laser. Both groups received laser for 2 months. Blood flow velocity, and blood vessel diameter were investigated by using duplex Doppler ultrasound and peripheral neuropathy parameters were investigated by Semmes-Weinstein monofilament assessment. The results revealed that He-Neon laser as well as Infrared laser groups showed significant improvement in blood flow velocity, blood vessel diameter & neuropathy tested parameters after treatment but there was no significance difference between the two types of LILT. LILT is a safe, non-invasive and drug free method for improving blood flow & sensation in patients suffering from diabetic polyneuropathy in addition to preventing one of the most threatening microvascular complications of diabetes.

  4. Experimental measurements of multiphoton enhanced air breakdown by a subthreshold intensity excimer laser

    SciTech Connect

    Way, Jesse; Hummelt, Jason; Scharer, John

    2009-10-15

    This work presents density, spectroscopic temperature, and shockwave measurements of laser induced breakdown plasma in atmospheric air by subthreshold intensity (5.5x10{sup 9} W/cm{sup 2}) 193 nm laser radiation. Using molecular spectroscopy and two-wavelength interferometry, it is shown that substantial ionization (>10{sup 16} cm{sup -3}) occurs that is not predicted by collisional cascade (CC) breakdown theory. While the focused laser irradiance is three orders of magnitude below the theoretical collisional breakdown threshold, the substantial photon energy at 193 nm (6.42 eV/photon) compared with the ionization potential of air (15.6 eV) significantly increases the probability of multiphoton ionization effects. By spectroscopically monitoring the intensity of the N{sub 2}{sup +} first negative system (B {sup 2}SIGMA{sub u}{sup +}-X {sup 2}SIGMA{sub g}{sup +}) vibrational bandhead (v{sup '}=0,v{sup ''}=0) at low pressure (20 Torr) where multiphoton effects are dominant, it is shown that two photon excitation, resonant enhanced multiphoton ionization is the primary mechanism for quantized ionization of N{sub 2} to the N{sub 2}{sup +}(B {sup 2}SIGMA{sub u}{sup +}) state. This multiphoton effect then serves to amplify the collisional breakdown process at higher pressures by electron seeding, thereby reducing the threshold intensity from that required via CC processes for breakdown and producing high density laser formed plasmas.

  5. Intense laser field effects on p-d exchange interaction in single manganese doped GaAs

    SciTech Connect

    Vieira Moura, Fabio; Qu Fanyao; Gargano, Ricardo

    2011-11-01

    We have developed a comprehensive theory about optical control of p - d exchange interaction between spins of hole and Mn{sup 2+} in single-manganese doped GaAs material irradiated by a monochromatic, linearly polarized, intense pulsed laser field (PLF) under nonresonant conditions. The p - d exchange interaction leads to formation of magnetic polaron. While the PLF induces a dressed acceptor Coulomb potential, which transforms single center problem into the one with two virtual positively charged centers, resembling hydrogen molecule ion (H{sub 2}{sup +}). The dichotomy of hole wave functions, determined by the laser-intensity, affects strongly the p - d exchange interaction as well as binding energy of magnetic polaron. Increasing the laser intensity reduces the magnetic polaron binding energy. At larger excitation intensity, the magnetic polaron can be completely dissolved.

  6. Nonlinear broadband photoluminescence of graphene induced by femtosecond laser irradiation

    SciTech Connect

    Liu, Wei-Tao; Wu, S.W.; Schuck, P.J.; Salmeron, Miquel; Shen, Y.R.; Wang, F.

    2010-07-01

    Upon femtosecond laser irradiation, a bright, broadband photoluminescence is observed from graphene at frequencies well above the excitation frequency. Analyses show that it arises from radiative recombination of a broad distribution of nonequilibrium electrons and holes, generated by rapid scattering between photoexcited carriers within tens of femtoseconds after the optical excitation. Its highly unusual characteristics come from the unique electronic and structural properties of graphene.

  7. Dichotomy of the exciton wave function in semiconductors under intense laser fields

    SciTech Connect

    Lima, F. M. S.; Nunes, O. A. C.; Amato, M. A.; Fonseca, A. L. A.; Silva, E. F. Jr. da

    2008-06-01

    We study the behavior of excitons in a semiconductor irradiated by a monochromatic, linearly polarized, intense laser field. By taking the finiteness of the hole effective mass into account and including the radiation field in a semiclassical manner, we solved the two-body quantum problem in the framework of a nonperturbative theory based upon the Kramers-Henneberger translation transformation for the Schroedinger equation. In the Kramers frame, the rapidly oscillating potential is expanded in a Fourier-Floquet series and, for laser frequencies high enough, only the zeroth-order term survives, the so-called 'laser-dressed' potential. By applying the Ehlotzky's approximation, this potential simplifies to a two-center potential that resembles that for the electronic motion in the H{sub 2}{sup +} molecule ion. The binding energy for an exciton in bulk GaAs under a nonresonant laser field is then computed by following a variational scheme we recently adapted from the linear combination of atomic orbitals-molecular orbitals method for the H{sub 2}{sup +} system. Similarly to the binding energy in H{sub 2}{sup +} in the separated-atoms limit, we found that, instead of vanishing, the exciton binding energy tends to a quarter of the excitonic Rydberg energy with the increase of the laser intensity. We also trace a correlation between this residual binding and the dichotomy of the excitonic wave function in the large dressing parameter limit, which indicates the possibility of excitons becoming stable against ionization.

  8. Effect of low level laser therapy and high intensity laser therapy on endothelial cell proliferation in vitro: preliminary communication

    NASA Astrophysics Data System (ADS)

    Lukowicz, Malgorzata; Szymanska, Justyna; Goralczyk, Krzysztof; Zajac, Andrzej; Rość, Danuta

    2013-01-01

    Background: The main purpose of this study was to analyze the influence of power intensity and wavelength of Low Level Laser Therapy (LLLT) and HILT (High Intensity Laser Therapy) on endothelial cell proliferation. Material and methods: The tests were done on human umbilical vein endothelial cells (HUVEC). Cultures were exposed to laser irradiation of 660 nm and 670 nm at different dosages, power output was 10 - 40 mW as well as 820 nm with power 100 mW and 808 nm with power 1500 mW. Energy density was from 0.28 to 11,43 J/cm2. Cell proliferation of a control and tested culture was evaluated with a colorimetric device to detect live cells. The tests were repeated 8 times. Results: We observed good effects of LLLT on live isolated ECs and no effects in experiments on previous deep-frozen cultures. Also HILT stimulated the proliferation of HUVEC. Conclusion: Endothelial cells play a key role in vascular homeostasis in humans. We observed the stimulatory effect of LLLT and HILT on proliferation of HUVEC. Many factors influence the proliferation of EC, so is it necessary to continue the experiment with different doses, intensity and cell concentration.

  9. Chirped-Standing-Wave Acceleration of Ions with Intense Lasers.

    PubMed

    Mackenroth, F; Gonoskov, A; Marklund, M

    2016-09-01

    We propose a novel mechanism for ion acceleration based on the guided motion of electrons from a thin layer. The electron motion is locked to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the layer. This provides a stable longitudinal field of charge separation, thus giving rise to chirped-standing-wave acceleration of the residual ions of the layer. We demonstrate, both analytically and numerically, that stable proton beams, with energy spectra peaked around 100 MeV, are feasible for pulse energies at the level of 10 J. Moreover, a scaling law for higher laser intensities and layer densities is presented, indicating stable GeV-level energy gains of dense ion bunches, for soon-to-be-available laser intensities. PMID:27636480

  10. Deflection of a Reflected Intense Vortex Laser Beam.

    PubMed

    Zhang, Lingang; Shen, Baifei; Zhang, Xiaomei; Huang, Shan; Shi, Yin; Liu, Chen; Wang, Wenpeng; Xu, Jiancai; Pei, Zhikun; Xu, Zhizhan

    2016-09-01

    An interesting deflection effect deviating the optical reflection law is revealed in the relativistic regime of intense vortex laser plasma interaction. When an intense vortex laser obliquely impinges onto an overdense plasma target, the reflected beam deflects out of the plane of incidence with an experimentally observable deflection angle. The mechanism is demonstrated by full three-dimensional particle-in-cell simulation as well as analytical modeling using the Maxwell stress tensor. The deflection results from the rotational symmetry breaking of the foil driven by the unsymmetrical shear stress of the vortex beam. The l-dependent shear stress, where l is the topological charge, as an intrinsic characteristic to the vortex beam, plays an important role as the ponderomotive force in relativistic vortex laser matter interaction. PMID:27661689

  11. Chirped-Standing-Wave Acceleration of Ions with Intense Lasers.

    PubMed

    Mackenroth, F; Gonoskov, A; Marklund, M

    2016-09-01

    We propose a novel mechanism for ion acceleration based on the guided motion of electrons from a thin layer. The electron motion is locked to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the layer. This provides a stable longitudinal field of charge separation, thus giving rise to chirped-standing-wave acceleration of the residual ions of the layer. We demonstrate, both analytically and numerically, that stable proton beams, with energy spectra peaked around 100 MeV, are feasible for pulse energies at the level of 10 J. Moreover, a scaling law for higher laser intensities and layer densities is presented, indicating stable GeV-level energy gains of dense ion bunches, for soon-to-be-available laser intensities.

  12. Chirped-Standing-Wave Acceleration of Ions with Intense Lasers

    NASA Astrophysics Data System (ADS)

    Mackenroth, F.; Gonoskov, A.; Marklund, M.

    2016-09-01

    We propose a novel mechanism for ion acceleration based on the guided motion of electrons from a thin layer. The electron motion is locked to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the layer. This provides a stable longitudinal field of charge separation, thus giving rise to chirped-standing-wave acceleration of the residual ions of the layer. We demonstrate, both analytically and numerically, that stable proton beams, with energy spectra peaked around 100 MeV, are feasible for pulse energies at the level of 10 J. Moreover, a scaling law for higher laser intensities and layer densities is presented, indicating stable GeV-level energy gains of dense ion bunches, for soon-to-be-available laser intensities.

  13. The TEA CO2-Lasers with High Output Emission Intensity

    NASA Astrophysics Data System (ADS)

    Panchenko, Yu. N.; Losev, V. F.; Puchikin, А. V.; Jun, Yao

    2014-03-01

    TEA CO2-lasers generating short pulse radiation and operating in a pulse-periodic mode with the repetition rate up to 10 Hz have been developed. It is shown that the addition of nitrogen up to 8% in the mixture of molecular gases СО2:H2 = 500:50 at a total pressure of P = 0.6 bar enhances the peak emission power maintaining the temporary pulse shape. An output beam intensity of 12.3 MW/cm2 was obtained for the 30 ns pulse at a laser efficiency of 2.8%. In a compact TEA СО2-laser with an active medium volume of 6 cm3, a beam with an output intensity of 24 MW/cm2 at pulse duration of 70 ns was obtained.

  14. Electron emission and fragmentation of molecules in intense laser fields

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Prümper, G.; Hatamoto, T.; Okunishi, M.; Mathur, D.

    2007-06-01

    We have constructed an apparatus for high-resolution electron spectroscopy and electron-ion coincidence experiments on gas-phase molecules in intense laser fields. The apparatus comprises an electron time-of-flight (TOF) spectrometer and an ion TOF spectrometer with a position detector, placed on either side of an effusive molecular beam. The ionizing radiation is either the fundamental (800 nm wavelength) of a Ti:sapphire laser or frequency doubled 400-nm light, with pulse durations of ~ 150 fs and the repetition rate of 1 kHz. We have investigated the electron emission and fragmentation of linear alcohol molecules, methanol, ethanol and 1-propanol, in laser fields with peak intensities up to ~ 1×10 14 W/cm2. Details of our apparatus are described along with an overview of some recent results.

  15. Highly efficient terahertz radiation from a thin foil irradiated by a high-contrast laser pulse

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Zhuo, H. B.; Nakazawa, T.; Shin, J. H.; Wakamatsu, S.; Yugami, N.; Hosokai, T.; Zou, D. B.; Yu, M. Y.; Sheng, Z. M.; Kodama, R.

    2016-09-01

    Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ˜10.5 mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7 % . The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.

  16. Structural and optical properties of laser irradiated nano structured cadmium oxide thin film synthesized by sol-gel spin coating method

    NASA Astrophysics Data System (ADS)

    Farooq, W. A.; Al Saud, M.; Alahmed, Z. A.

    2016-05-01

    Cadmium oxide CdO nanostructured thin films are synthesized using sol-gel spin coating method. The prepared samples of CdO thin films are irradiated with 10 mJ laser from pulsed Q-Switched Nd:YAG laser at 1064 and 532 nm wavelength. The samples were exposed to 45 pulses of 7 ns pulse duration. Morphology and structural analysis were carried out with scanning electron microscope (SEM) micrographs and X-ray diffraction (XRD) patterns. Optical investigations were obtained with spectrometer and fluorospectrometer from Shimadzu. SEM micrographs confirm the nanostructure of the CdO film and indicate agglomeration of nanoparticles with laser irradiation. XRD patterns show decrease in the intensity of orientation peaks after laser irradiation. Variation in band gap energy, absorption peaks, and photoluminescence spectra with laser irradiation are observed.

  17. Toxicity of laser irradiated photoactive fluoride PrF3 nanoparticles toward bacteria

    NASA Astrophysics Data System (ADS)

    Pudovkin, M. S.; Korableva, S. L.; Krasheninnicova, A. O.; Nizamutdinov, A. S.; Semashko, V. V.; Zelenihin, P. V.; Alakshin, E. M.; Nevzorova, T. A.

    2014-11-01

    The article is devoted to exploration of biological effects of crystalline PrF3 nanoparticles toward Salmonella typhimurium TA 98 bacteria under the laser irradiation. Obtained results show bactericidal activity of PrF3 nanoparticles and optimal parameters of laser irradiation (power of laser irradiation, wavelength, diameter of the laser spoil, and exposure time) have been found under which the effects of bactericidal activity become the most significant. Survival of bacterial cells under laser irradiation with wavelength 532 nm in colloidal solution of PrF3 nanoparticles was 39%, 34%, 20% for exposure times 5 minutes, 15 minutes and 30 minutes, correspondingly.

  18. Emittance of positron beams produced in intense laser plasma interaction

    SciTech Connect

    Chen Hui; Hazi, A.; Link, A.; Anderson, S.; Gronberg, J.; Izumi, N.; Tommasini, R.; Wilks, S.; Sheppard, J. C.; Meyerhofer, D. D.; Baldis, H. A.; Marley, E.; Park, J.; Williams, G. J.; Fedosejev, R.; Kerr, S.

    2013-01-15

    The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be useful as an alternative positron source for future accelerators.

  19. Effect of He-Ne laser irradiation on erythrocyte and lymphocyte membranes of children in vitro as studied by the intrinsic and extrinsic fluorescence techniques

    NASA Astrophysics Data System (ADS)

    Volotovskaya, Anna V.; Kozlova, Nataly M.; Slobozhanina, Ekaterina I.; Ulaschik, Vladimir S.; Mostovnikov, Vasili A.

    2000-11-01

    In recent years the treatment of blood with low intensity laser irradiation has become popular in a variety of clinical applications due to its anti-inflammatory, biostimulative and immune-stimulatory effects etc. Despite of wide using of laser blood irradiation in the pediatric practice there is lack of information concerning the sensitivity of children blood cells to laser irradiation. At present study the influence of the He-Ne laser irradiation on the lipid physico-chemical state in lymphocytes and isolated erythrocyte membranes of 8-16 years old children using lipophilic fluorescence probe pyrene was investigated in vitro. It was shown that fluorescence parameters of pyrene incorporated into erythrocyte and lymphocyte membranes after laser irradiation ((lambda) equals 630nm) at dose of 24 J/cm2 at t equals 18 +/- 2 (degree)C were unchanged. The intensity of intrinsic protein UV-fluorescence ((lambda)ex equals 297 nm, (lambda)em equals 332 nm) of lymphocytes exposed to the same irradiation was decreased insignificantly. The obtained data indicate that He-Ne laser irradiation at the above dose does not affect the lipid microviscosity of erythrocyte and lymphocyte membranes.

  20. Ion acceleration in a solitary wave by an intense picosecond laser pulse.

    PubMed

    Zhidkov, A; Uesaka, M; Sasaki, A; Daido, H

    2002-11-18

    Acceleration of ions in a solitary wave produced by shock-wave decay in a plasma slab irradiated by an intense picosecond laser pulse is studied via particle-in-cell simulation. Instead of exponential distribution as in known mechanisms of ion acceleration from the target surface, these ions accelerated forwardly form a bunch with relatively low energy spread. The bunch is shown to be a solitary wave moving over expanding plasma; its velocity can exceed the maximal velocity of ions accelerated forward from the rear side of the target.

  1. Ablation dynamics of Co/ZnS targets under double pulse femtosecond laser irradiation.

    PubMed

    Lopez-Quintas, Ignacio; Loriot, Vincent; Ávila, David; Izquierdo, Jesus G; Rebollar, Esther; Bañares, Luis; Castillejo, Marta; de Nalda, Rebeca; Martin, Margarita

    2016-02-01

    Femtosecond lasers, used as tools to investigate the ablation dynamics of solids, can help to develop strategies to control the deposition of nanomaterials by pulsed laser ablation. In this work, Co/ZnS targets, potential candidates for the synthesis of diluted magnetic semiconductor materials, are irradiated by sequences of two femtosecond laser pulses delayed in the picosecond time scale. The ionic composition of the ablation plasma and the dependence of the ion signals on the interpulse delay and relative fluence are determined by time-of-flight mass spectrometry. The results show that, when pulses of different fluence are used, highly asymmetric ion yields are obtained, with more intense ion signals detected when the lower fluence pulse is temporally ahead. The comparison between asymmetric and equal fluence double pulse ablation dynamics provides some understanding of the different processes that modify the properties of the layer irradiated by the first pulse and of the mechanisms affecting the coupling of the delayed pulse into the material. The final outcome of the double pulse irradiation is characterized through the analysis of the deposits produced upon ablation. PMID:26751831

  2. Calculations of population transfer during intense laser pulses

    SciTech Connect

    Schafer, K.J.; Kulander, K.C.

    1993-08-01

    Recent experiments by several groups have examined the question of population transfer to resonantly excited states during intense short laser pulses, in particular the amount of population that remains ``trapped`` in excited states at the end of a laser pulse. In this chapter we present calculations of population transfer and resonant ionization in xenon at both 660 and 620 nm. At the longer wavelength, the seven photon channel closes at 2.5{times}10{sup 13} W/cm{sup 2}. Pulses with peak intensities higher than this result in ``Rydberg trapping``, the resonant transfer of population to a broad range of high-lying states. The amount of population transferred depends on both the peak intensity and pulse duration. At 620 mm there are numerous possible six photon resonances to states with p or f angular momentum. We have done a large number of calculations for 40 fs pulses at different peak intensities and have examined the population transferred to these low-lying resonant states as a function of the peak laser intensity. We do not have room to comment upon the resonantly enhanced ionized electron energy spectra that we also determine in the same calculations. Our calculations involve the direct numerical integration of the time-dependent Schroedinger equation for an atom interacting with a strong laser field. The time-dependent wave function of a given valence electron is calculated on a spatial grid using a one-electron pseudo potential. This single active electron approximation (SAE) has been shown to be a good approximation for the rare gases at the intensities and wavelengths that we will consider. The SAE potential we use has an explicit angular momentum dependence which allows us to reproduce all of the excited state energies for xenon quite well.

  3. Modification of Atomic Collision Dynamics by Intense Ultrashort Laser Pulses.

    NASA Astrophysics Data System (ADS)

    Sizer, Theodore, II

    During the past decade there has been a great deal of effort put toward demonstrating that the dynamics of atomic collisions can be modified by the presence of intense laser fields. The term "modified collision dynamics" means here that the potential energy surfaces which govern the collision dynamics are actually distorted by the ac -Stark effect induced by the intense laser field. This results in altered probabilities for the scatterers to end up in certain outgoing channels. The attractiveness of the idea of modified collisions, of course, lies in the possibility of selectively controlling physical or chemical processes by judicious choice of laser frequency and intensity. If one uses laser pulses whose duration is less than an individual collision then the experimenter can actively change the shape of the potentials during the collision. In principle, if one can open and close reactive channels at appropriate times during the collision, one can strongly influence its outcome. In this thesis the first experimental observation of the modification of atomic collision dynamics by ultrashort laser pulses is reported. In order to more fully understand the interaction of the ultrashort laser field with the colliding atomic system, a theoretical model was developed using a solution to Schroedinger's equation in Bloch equation form. The numerical solution was then averaged over various uncontrollable parameters present in the experiment when using a thermally random distribution of atoms. Averaging over these parameters as well as using a realistic temporal pulse shape and spatial beam profile has proven to be extremely important in modeling the experimental outcome. The output of a dye oscillator-amplifier combination was used to study the collision process Na(3s) + Ar + (H/2PI)(omega) (--->) Na(3P(, 1/2)) + Ar. It has been found that at fixed laser intensity the efficiency of exciting the Na(3P(, 1/2)) state is higher for pulses shorter than a collision duration than

  4. Investigation on Soft X-Ray Lasers with a Picosecond-Laser-Irradiated Gas Puff Target

    SciTech Connect

    Fiedorowiez, H; Bartnik, A; Jarocki, R; Rakowski, R; Dunn, J; Smith, R F; Hunter, J; Hilsen, J; Shlyaptsev, V N

    2002-10-09

    We present results of experimental studies on transient gain soft x-ray lasers with a picosecond-laser-irradiated gas puff target. The target in a form of an elongated gas sheet is formed by pulsed injection of gas through a slit nozzle using a high-pressure electromagnetic valve developed and characterized at the Institute of Optoelectronics. The x-ray laser experiments were performed at the Lawrence Livermore National Laboratory using the tabletop Compact Multipulse Terawatt (COMET) laser to irradiate argon, krypton or xenon gas puff targets. Soft x-ray lasing in neon-like argon on the 3p-3s transition at 46.9 nm and the 3d-3p transition at 45.1 nm have been demonstrated, however, no amplification for nickel-like krypton or xenon was observed. Results of the experiments are presented and discussed.

  5. Evaluation of the Morphological Characteristics of Laser-Irradiated Dentin

    PubMed Central

    Lilaj, Bledar; Franz, Alexander; Degendorfer, Daniela; Moritz, Andreas

    2015-01-01

    Abstract Objective: The aim of this study was to investigate the effect of different energy settings of Er:YAG laser irradiation on dentin surface morphology with respect to the number of opened dentinal tubules. Background data: An ideally prepared dentin surface with opened dentinal tubules is a prerequisite for adhesive fixation. No study, however, has yet compared the numbers of opened dentinal tubules with regard to statistical differences. Methods: Conventional preparations using a bur with or without additional acid etching acted as control groups. Dentin specimens were prepared from human third molars and randomly divided into eight groups according to the energy settings of the laser (1, 1.5, 4, 6, 7.5, and 8 W) and two controls (bur and bur plus acid etching). After surface preparation, dentin surfaces were analyzed with a scanning electron microscope, and the number of opened dentinal tubules in a defined area was counted. Results: The control groups showed smooth surfaces with (bur plus acid etching) and without opened dentinal tubules (bur), whereas all laser-irradiated surfaces showed rough surfaces. Using the energy setting of 4 W resulted in significantly more opened dentinal tubules than the conventional preparation technique using the bur with additional acid etching. In contrast, the energy setting of 8 W showed significantly fewer opened dentinal tubules, and also exhibited signs of thermal damage. Conclusions: The Er:YAG laser with an energy setting of 4 W generates a dentin surface with opened dentinal tubules, a prerequisite for adhesive fixation. PMID:26389986

  6. Absorption of ultra-intense intense laser pulse in self-generated pair plasma

    NASA Astrophysics Data System (ADS)

    Grismayer, Thomas; Vranic, Marija; Fonseca, Ricardo; Silva, Luis

    2014-10-01

    Plasma physics in extreme fields requires taking into account Quantum Electrodynamics effects such as non-linear Compton scattering and Breit-Wheeler pair production. Such effects intervene in laser-plasma interactions at ultra high intensities (I >1023 W/cm2). The self-consistent modeling of these scenarios is challenging since some localized regions of ultra-intense field will produce a vast number of pairs that may cause memory overflow during the simulation. To overcome this issue, we have developed a merging algorithm that allows merging a large number of particles into fewer particles with higher particle weights while conserving local particle distributions. This algorithm is crucial to investigate the laser absorption in self-generated pair plasmas. During the interaction, the laser energy is converted into pairs and photons and the absorption become significant when the plasma density reaches the critical density. We present the results of 3D PIC-QED simulations (Osiris 2.0) showing the respective fraction of laser energy transferred into pairs and photons. The dependence of the laser absorption on the laser parameters for various configurations is also discussed.

  7. The Effect of Intense Laser Radiation on Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Young, Stephen Michael Radley

    1991-02-01

    Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used

  8. Direct synthesis of nanodiamonds by femtosecond laser irradiation of ethanol

    PubMed Central

    Nee, Chen-Hon; Yap, Seong-Ling; Tou, Teck-Yong; Chang, Huan-Cheng; Yap, Seong- Shan

    2016-01-01

    Carbon nanomaterials exhibit novel characteristics including enhanced thermal, electrical, mechanical, and biological properties. Nanodiamonds; first discovered in meteorites are found to be biocompatible, non-toxic and have distinct optical properties. Here we show that nanodiamonds with the size of <5 nm are formed directly from ethanol via 1025 nm femtosecond laser irradiation. The absorption of laser energy by ethanol increased non-linearly above 100 μJ accompanied by a white light continuum arises from fs laser filamentation. At laser energy higher than 300 μJ, emission spectra of C, O and H in the plasma were detected, indicating the dissociation of C2H5OH. Nucleation of the carbon species in the confined plasma within the laser filaments leads to the formation of nanodiamonds. The energy dependence and the roles of the nonlinear phenomenon to the formation of homogeneous nanodiamonds are discussed. This work brings new possibility for bottom-up nanomaterials synthesis based on nano and ultrafast laser physics. PMID:27659184

  9. Target Material Irradiation Studies for High-Intensity Accelerator Beams

    SciTech Connect

    Simos, N.; Kirk, H.; Ludewig, H.; Thieberger, P.; Weng, W.T.; McDonald, K.; Sheppard, J.; Evangelakis, G.; Yoshimura, K.; /KEK, Tsukuba

    2005-08-16

    This paper presents results of recent experimental studies focusing on the behavior of special materials and composites under irradiation conditions and their potential use as accelerator targets. The paper also discusses the approach and goals of on-going investigations on an expanded material matrix geared toward the neutrino superbeam and muon collider initiatives.

  10. Cellular immunological effects of laser irradiation and immunoadjuvant application

    NASA Astrophysics Data System (ADS)

    Chen, Wei R.; Mohamed, Abdiwahab; Naylor, Mark F.; Bartels, Kenneth E.; Ritchey, Jerry W.; Liu, Hong; Nordquist, Robert E.

    2007-02-01

    Immune system is critical in the fight against cancer. Particular important is the responses through immune cells that regulate immunological functions. Certain cytokines enhance cancer immunity (such as IL12 and interferon gamma) and others interfere or impede cancer immunity (such as IL10). The clinical outcome can be linked to the balance of these cytokines, such as IL10 to IL12 ratio. Effective treatments often reduce the IL10:IL12 ratio, indicating higher levels of the cancer fighting IL12. To enhance immune responses, a combination of laser irradiation and concurrent use of immunostimulants has been applied for the treatment of tumors. In a recent study, an 805-nm laser in conjunction with indocyanine green (ICG) has been used to treat EMT6 mammary tumors in mice. An immunoadjuvant, glycated chitosan (GC), was intratumoral injected after the laser irradiation. Our preliminary results showed that tumor-bearing mice treated either with the immunoadjuvant alone or with the combination of laser and immunoadjuvant had lower IL10:IL12 ratios than animals that received no treatment. This may play an important in the treatment to decrease tumor size and to increase survival times of mice. Cellular activities after laser-ICG-GC treatment of DBMA-4 mammary tumors in rats also showed infiltration of immune cells to the treatment sites, indicating a possible induced immunity. The combination of laser treatment and immunotherapy has been used to treat late-stage melanoma patients; the responses, both treated primary tumors and the metastases, to the treatment have been promising. The histology of two patients, before and after treatment, is presented to show the effects of this novel treatment method.

  11. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    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.

  12. Electron spectra of xenon clusters irradiated with a laser-driven plasma soft-x-ray laser pulse

    SciTech Connect

    Namba, S.; Takiyama, K.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

    2011-11-15

    Xenon clusters were irradiated with plasma soft-x-ray laser pulses (having a wavelength of 13.9 nm, time duration of 7 ps, and intensities of up to 10 GW/cm{sup 2}). The laser photon energy was high enough to photoionize 4d core electrons. The cross section is large due to a giant resonance. The interaction was investigated by measuring the electron energy spectra. The photoelectron spectra for small clusters indicate that the spectral width due to the 4d hole significantly broadens with increasing cluster size. For larger clusters, the electron energy spectra evolve into a Maxwell-Boltzmann distribution, as a strongly coupled cluster nanoplasma is generated.

  13. Plasmas and Short-Pulse, High-Intensity Lasers

    NASA Astrophysics Data System (ADS)

    Clark, Thomas

    1999-11-01

    Many of the applications of short-pulse, high-intensity laser systems, including coherent UV and X-ray generation, compact particle accelerators, and non-perturbative nonlinear optics as well as the study of laser-matter interaction physics, require large intensity-interaction length products. In recent years, plasma structures resulting from the hydrodynamic evolution of laser-produced plasma filaments have proven to be attractive media for guiding pulses with peak powers approaching the terawatt level over lengths many times the vacuum Rayleigh range. The hydrodynamics of plasma waveguides have been characterized using time- and space-resolved interferometry measurements of electron density profiles. The laser-driven ionization and heating phase of the plasma filament creation is followed by hot electron driven plasma expansion. Density profiles suitable for optical guiding develop within the first few hundred picoseconds after plasma creation, during which rapid cooling occurs. At longer times the plasma expansion closely follows that of a cylindrical blast wave, with further cooling due to expansion work. The observed guided intensity profiles of end-coupled and tunnel-coupled pulses compare favorably with calculations of the quasi-bound waveguide modes based on the measured electron density profiles. Time- and space-resolved electron density measurements of a laser-driven concentric implosion were also performed. The implosion is the result of the interaction of a second laser pulse with an existing plasma waveguide. The two-pulse absorption and ionization significantly exceed that due to a single pulse of the same total energy. The author would like to acknowledge the significant contributions of Prof. Howard M. Milchberg to the work being presented.

  14. Different photodynamic effect between continuous wave and pulsed laser irradiation modes in k562 cells in vitro

    NASA Astrophysics Data System (ADS)

    Klimenko, V. V.; Bogdanov, A. A.; Knyazev, N. A.; Rusanov, A. A.; Dubina, M. V.

    2014-10-01

    Photodynamic therapy is a cancer treatment method is used primarily continuous mode laser radiation. At high power density irradiation occurs intense consumption of molecular oxygen and this caused hypoxic tumor tissue, which leads to inefficiency PDT. In this paper, pulsed and continuous irradiation modes during PDT photosensitizer Radachlorin were compared. A mathematical model for the generation of singlet oxygen 1O2 in tumor cells during photodynamic therapy with tissue oxygenation was developed. Our study theoretically and experimentally demonstrates the increased singlet oxygen generation efficiency in a pulsed irradiation mode compared to continuous wave mode with the same power density 20mW/cm2. Experimental in vitro showed that pulsed irradiation mode mostly induces apoptosis k562 tumor cells at irradiation doses of k562 1.25 - 2.5J/cm2 while the continuous mode induced necrosis.

  15. Testing Unruh Radiation with Ultra-Intense Lasers

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Tajima, Toshiki

    1997-04-01

    We point of that using the state-of-the-art (or soon to be) intense ultrafast laser technology, violent acceleration of electrons that may be suitable for testing general relativistic effects can be realized in the laboratory settings. In particular we demonstrate that the Unruh radiation is detectable, in principle, beyond the conventional radiation (most notably the Larmor radiation) background noise, by taking the advantages of their specific dependences on the laser power, their different characters in spectral-angular distributions, and the time structure of the signals.

  16. Acceleration of electrons by a tightly focused intense laser beam.

    PubMed

    Li, Jian-Xing; Zang, Wei-Ping; Li, Ya-Dong; Tian, Jian-Guo

    2009-07-01

    The recent proposal to use Weinger transformation field (WTF) [Opt. Express 17, 4959-4969 (2009)] for describing tightly focused laser beams is investigated here in detail. In order to validate the accuracy of WTF, we derive the numerical field (NF) from the plane wave spectrum method. WTF is compared with NF and Lax series field (LSF). Results show that LSF is accurate close to the beam axis and divergent far from the beam axis, and WTF is always accurate. Moreover, electron dynamics in a tightly focused intense laser beam are simulated by LSF, WTF and NF, respectively. The results obtained by WTF are shown to be accurate.

  17. Two-photon Compton process in pulsed intense laser fields

    NASA Astrophysics Data System (ADS)

    Seipt, Daniel; Kämpfer, Burkhard

    2012-05-01

    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 2 orders of magnitude stronger than expected from a perturbative estimate.

  18. Acceleration of electrons by a tightly focused intense laser beam.

    PubMed

    Li, Jian-Xing; Zang, Wei-Ping; Li, Ya-Dong; Tian, Jian-Guo

    2009-07-01

    The recent proposal to use Weinger transformation field (WTF) [Opt. Express 17, 4959-4969 (2009)] for describing tightly focused laser beams is investigated here in detail. In order to validate the accuracy of WTF, we derive the numerical field (NF) from the plane wave spectrum method. WTF is compared with NF and Lax series field (LSF). Results show that LSF is accurate close to the beam axis and divergent far from the beam axis, and WTF is always accurate. Moreover, electron dynamics in a tightly focused intense laser beam are simulated by LSF, WTF and NF, respectively. The results obtained by WTF are shown to be accurate. PMID:19582099

  19. Plasma heating rate in very intense laser light

    SciTech Connect

    Rashid, S.M.S.

    1982-01-01

    An exact Volkov state solution of the minimally coupled dirac equation is used to calculate the transition rate dR of an electron scattering via a stationary ion in the presence of a very intense laser field. A consistent picture of the scattering is presented in which the electrons' initial and final states are quasi-free states. Accordingly, a modified transition rate dR and a modified Maxwell-Boltzmann distribution are developed. They are used to calculate the heating rate W of a quasi-free plasma in the presence of very intense laser light. In order to simplify the expression for the heating rate W, an important transformation, which changes an infinite sum over Bessel functions into a finite integral, is introdced. It is then shown that the leading term of the heating rate W is similar to the expression of Osborn (with corrections) for intensity I < 10/sup 16/ Watts/cm/sup 2/ Watts/cm/sup 2/ and k/sub B/T < Ike V. A new correction factor is defined to show the effect of very intense laser field when the intensity I > 10/sup 16/ Watts/cm/sup 2/. For k/sub B/T > Ike V, a spin-dependent term of order k/sub B/T/mc/sup 2/ is also discovered. This represents a new term not previously known. It is shown that the effect of this term on the heating rate is substantial and that it is possible to measure its effect with present-day laser systems.

  20. Production of proton beams with narrow-band energy spectra from laser-irradiated ultrathin foils

    SciTech Connect

    Robinson, A. P. L; Gibbon, P.

    2007-01-15

    Three-dimensional gridless particle simulations of proton acceleration via irradiation of a very thin foil by a short-pulse, high-intensity laser have been performed to evaluate recently proposed microstructured target configurations. It is found that a pure proton microdot target does not by itself result in a quasimonoenergetic proton beam. Such a beam can only be produced with a very lightly doped target, in qualitative agreement with one-dimensional theory. The simulations suggest that beam quality in current experiments could be dramatically improved by choosing microdot compositions with a 5-10 times lower proton fraction.

  1. The Irradiation Effect of a Simultaneous Laser and Electron Dual-beam on Void Formation

    PubMed Central

    Yang, Zhanbing; Watanabe, Seiichi; Kato, Takahiko

    2013-01-01

    Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids. PMID:23383371

  2. The irradiation effect of a simultaneous laser and electron dual-beam on void formation.

    PubMed

    Yang, Zhanbing; Watanabe, Seiichi; Kato, Takahiko

    2013-01-01

    Randomly distributed lattice point defects such as supersaturated vacancies (SVs) and Frenkel-pairs (FPs, an interstitial and a vacancy) can be simultaneously introduced into the crystal by energetic beam irradiation in outer space and/or nuclear reactors, but their behavior has not been fully understood. Using a high-voltage electron microscope equipped with a laser (laser-HVEM), we show the striking effects of simultaneous laser-electron (photon-electron) dual-beam irradiation on void formation. Our results reveal that during laser-electron sequential irradiation, pre-laser irradiation enhanced void nucleation and subsequent electron irradiation enhanced void growth. However, the laser-electron dual-beam irradiation was analyzed to depress void swelling remarkably because the recombination of SVs and interstitials was enhanced. The results provide insight into the mechanism underlying the dual-beam radiation-induced depression of void swelling in solids.

  3. A Method for Monitoring Enamel Erosion Using Laser Irradiated Surfaces and Optical Coherence Tomography

    PubMed Central

    Chan, Kenneth H.; Tom, Henry; Darling, Cynthia L.; Fried, Daniel

    2015-01-01

    Introduction Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the non-ablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Methods Thirteen bovine enamel blocks were used in this in vitro study. Each 10 mm × 2 mm block was partitioned into five regions, the central region was unprotected, the adjacent windows were irradiated by a CO2 laser operating at 9.3 μm with a fluence of 2.4J/cm2, and the outermost windows were coated with acid resistant varnish. The samples were exposed to a pH cycling regimen that caused both erosion and subsurface demineralization for 2, 4 and 6 days. The surfaces were scanned using a time-domain polarization sensitive optical coherence tomography (PS-OCT) system and the degree of surface loss (erosion) and the integrated reflectivity with lesion depth was calculated for each window. Results There was a large and significant reduction in the depth of surface loss (erosion) and the severity of demineralization in the areas irradiated by the laser. Conclusion Irradiation of the enamel surface with a pulsed carbon dioxide laser at sub-ablative intensities results in significant inhibition of erosion and demineralization under the acid challenge employed in this study. In addition, these results suggest that it may be feasible to modify regions of the enamel surface using the laser to serve as reference marks to monitor the rate of erosion in vivo. PMID:25147133

  4. Optimum laser intensity for the production of energetic deuterium ions from laser-cluster interaction

    SciTech Connect

    Bang, W.; Dyer, G.; Quevedo, H. J.; Bernstein, A. C.; Gaul, E.; Rougk, J.; Aymond, F.; Donovan, M. E.; Ditmire, T.

    2013-09-15

    We measured, using Petawatt-level pulses, the average ion energy and neutron yield in high-intensity laser interactions with molecular clusters as a function of laser intensity. The interaction volume over which fusion occurred (1–10 mm{sup 3}) was larger than previous investigations, owing to the high laser power. Possible effects of prepulses were examined by implementing a pair of plasma mirrors. Our results show an optimum laser intensity for the production of energetic deuterium ions both with and without the use of the plasma mirrors. We measured deuterium plasmas with 14 keV average ion energies, which produced 7.2 × 10{sup 6} and 1.6 × 10{sup 7} neutrons in a single shot with and without plasma mirrors, respectively. The measured neutron yields qualitatively matched the expected yields calculated using a cylindrical plasma model.

  5. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    NASA Astrophysics Data System (ADS)

    Yan, Wei; He, Hao; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-01

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca2+ release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  6. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    SciTech Connect

    Yan, Wei; He, Hao Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue

    2014-02-24

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  7. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

    SciTech Connect

    Shepherd, R; Chen, H; Ping, Y; Dyer, G; Wilks, S; Chung, H; Kemp, A; Hanson, S; Widmann, K; Fournier, K; Faenov, A; Pikuz, T; Niles, A; Beiersdorfer, P

    2007-02-27

    We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.

  8. The study towards high intensity high charge state laser ion sources.

    PubMed

    Zhao, H Y; Jin, Q Y; Sha, S; Zhang, J J; Li, Z M; Liu, W; Sun, L T; Zhang, X Z; Zhao, H W

    2014-02-01

    As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible.

  9. Characterization of material ablation driven by laser generated intense extreme ultraviolet light

    SciTech Connect

    Tanaka, Nozomi Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki; Sunahara, Atsushi

    2015-09-14

    We present a comparative study on the hydrodynamic behaviour of plasmas generated by material ablation by the irradiation of nanosecond extreme ultraviolet (EUV or XUV) or infrared laser pulses on solid samples. It was clarified that the difference in the photon energy deposition and following material heating mechanism between these two lights result in the difference in the plasma parameters and plasma expansion characteristics. Silicon plate was ablated by either focused intense EUV pulse (λ = 9–25 nm, 10 ns) or laser pulse (λ = 1064 nm, 10 ns), both with an intensity of ∼10{sup 9 }W/cm{sup 2}. Both the angular distributions and energy spectra of the expanding ions revealed that the photoionized plasma generated by the EUV light differs significantly from that produced by the laser. The laser-generated plasma undergoes spherical expansion, whereas the EUV-generated plasma undergoes planar expansion in a comparatively narrow angular range. It is presumed that the EUV radiation is transmitted through the expanding plasma and directly photoionizes the samples in the solid phase, consequently forming a high-density and high-pressure plasma. Due to a steep pressure gradient along the direction of the target normal, the EUV plasma expands straightforward resulting in the narrower angular distribution observed.

  10. The study towards high intensity high charge state laser ion sources.

    PubMed

    Zhao, H Y; Jin, Q Y; Sha, S; Zhang, J J; Li, Z M; Liu, W; Sun, L T; Zhang, X Z; Zhao, H W

    2014-02-01

    As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible. PMID:24593615

  11. Model experiment of cosmic ray acceleration due to an incoherent wakefield induced by an intense laser pulse

    SciTech Connect

    Kuramitsu, Y.; Sakawa, Y.; Takeda, K.; Tampo, M.; Takabe, H.; Nakanii, N.; Kondo, K.; Tsuji, K.; Kimura, K.; Fukumochi, S.; Kashihara, M.; Tanimoto, T.; Nakamura, H.; Ishikura, T.; Kodama, R.; Mima, K.; Tanaka, K. A.; Mori, Y.; Miura, E.; Kitagawa, Y.

    2011-01-15

    The first report on a model experiment of cosmic ray acceleration by using intense laser pulses is presented. Large amplitude light waves are considered to be excited in the upstream regions of relativistic astrophysical shocks and the wakefield acceleration of cosmic rays can take place. By substituting an intense laser pulse for the large amplitude light waves, such shock environments were modeled in a laboratory plasma. A plasma tube, which is created by imploding a hollow polystyrene cylinder, was irradiated by an intense laser pulse. Nonthermal electrons were generated by the wakefield acceleration and the energy distribution functions of the electrons have a power-law component with an index of {approx}2. The maximum attainable energy of the electrons in the experiment is discussed by a simple analytic model. In the incoherent wakefield the maximum energy can be much larger than one in the coherent field due to the momentum space diffusion or the energy diffusion of electrons.

  12. Biophysics behavior of acupuncture points irradiated with low energy lasers.

    PubMed

    Moldovan, C

    2007-01-01

    This work describes the Low Energy Laser (LEL) coherent light interaction with the skin cover on acupuncture loci for the purpose of detecting and measuring the spatial and temporal alteration of the thermal, electric and optical properties of the LI4 (HEGU) acupoint, irradiated with a 685 nm, 30 mW, III.B Laser. Novel electrostatic imaging technique, an original Acupuncture 3-D Thermal and Electric Mapping Technique and an original Method for Laser-Skin Reflectance, were used in the study. The results indicate that the visible laser light, with low frequency and low power, specifically modify the 3-D pattern of the temperature, electric potential and electric impedance outline of an acupuncture point, meanwhile with a significant decrease of the laser reflectance index, all measured on a 27 apparently healthy subject lot (48 years mean age, 54% male), when comparing with a non-active, non-acupunctural skin area, placed on the volar side of the same hand. The biophysical method presented, combines in a complex way and reproducible the electro stasis exploration (bioelectric homeostasis), with cutaneous thermodynamic exploration and photo-optical exploration of the derma and provides information that can be appreciated in dynamics and compared depending on the exploration target.

  13. Generation of shock waves and formation of craters in a solid material irradiated by a short laser pulse

    SciTech Connect

    Gus'kov, Sergei Yu; Borodziuk, S; Kasperczuk, A; Pisarczyk, T; Kalal, M; Limpouch, J; Kralikova, B; Krousky, E; Masek, K; Pfeifer, M; Rohlena, K; Skala, J; Ullschmied, J; Pisarczyk, P

    2004-11-30

    The results of investigations are presented which are concerned with laser radiation absorption in a target, the plasma state of its ablated material, the energy transfer to the solid target material, the characteristics of the shock wave and craters on the target surface. The investigation involved irradiation of a planar target by a subnanosecond plasma-producing laser pulse. The experiments were carried out with massive aluminium targets using the PALS iodine laser, whose pulse duration (0.4 ns) was much shorter than the shock wave attenuation and on-target crater formation times (50-200 ns). The investigations were conducted for a laser radiation energy of 100 J at two wavelengths of 0.438 and 1.315 {mu}m. For a given pulse energy, the irradiation intensity was varied in a broad range (10{sup 13}-10{sup 16} W cm{sup -2}) by varying the radius of the laser beam. The efficiency of laser radiation-to-shock energy transfer was determined as a function of the intensity and wavelength of laser radiation; also determined were the characteristics of the plasma plume and the shock wave propagating in the solid target, including the experimental conditions under which two-dimensional effects are highly significant. (invited paper)

  14. Histology of porcine nasal cartilage grafts following Nd:YAG (1320 nm) laser-mediated reshaping: effects of sequential irradiation

    NASA Astrophysics Data System (ADS)

    Kim, Hong K.; Wong, Brian J.; Benton, Hilary P.; Liaw, Lih-Huei L.; Nelson, J. Stuart; Milner, Thomas E.

    2001-07-01

    Mechanically deformed morphologic cartilage grafts undergo temperature dependent stress relaxation during sustained laser irradiation resulting in stable shape changes. In this study, the porcine nasal septal cartilage specimens were evaluated histologically following laser mediated reshaping using H&E. Cartilage specimens were irradiated with light emitted from a Nd:YAG laser (25 W/cm2, 1 = 1.32 mm) while recording simultaneously radiometric surface temperature, internal stress, and backscattered light intensity from a probe laser. Each specimen received one, two, or three sequential laser exposures. The duration of each exposure was determined from real-time measurements of characteristic changes in backscattered light intensity that correlate with accelerated stress relaxation. A five minute time interval between each laser exposures allowed the cartilage specimen to return to thermal equilibrium. Specimens were then fixed in formalin, serially dehydrated in ethanol, embedded in paraffin, and sectioned with a microtome for histologic examination using light microscopy. Large variation in native tissue histology was observed among individual tissue samples, and vascular were identified in several specimens. Large lacunae with shrunken chondrocytes were identified along with cells with pyknotic nuclei, although these histologic observations did not correlate with the degree of laser exposure. These observations are discussed.

  15. A Review of Astrophysics Experiments on Intense Lasers

    SciTech Connect

    Remington, B.A.; Arnett, D.; Drake, R.P.; Takabe, H.

    1999-03-03

    Astrophysics traditionally has been the domain of large astronomical observatories and theorists' computers, the former producing images from deep space, and the latter constructing intricate models to explain the observations. A component often missing has been the ability to quantitatively test the theories and models in an experimental setting where the initial and final states are well characterized. In a new development, intense lasers are being used to recreate aspects of astrophysical phenomena in the laboratory, allowing the creation of experimental testbeds where theory and modeling can be quantitatively compared with data. We summarize here several areas of astrophysics: supernovae, supernova remnants, gamma-ray bursts, and giant planets. In each of these areas, experiments are under development at intense laser facilities to test and refine our understanding of these phenomena.

  16. Electron Dynamics in Intense Laser Fields: A Bohmian Mechanics Study

    NASA Astrophysics Data System (ADS)

    Jooya, Hossein Z.; Telnov, Dmitry A.; Chu, Shih-I.

    2016-05-01

    We study the electron quantum dynamics of atomic hydrogen under intense near infrared laser fields by means of the De Broglie-Bohm's framework of Bohmian mechanics. This method is used to study the mechanism of the multiple plateau generation and the cut-off extension, as the main characteristic features of high order harmonic generation spectrum. Electron multiple recollision dynamics under intense mid-infrared laser fields is also investigated. In this case, the resulting patterns in the high-order harmonic generation and the above-threshold ionization spectra are analyzed by comprehensive picture provided by Bohmian mechanics. The time evolution of individual trajectories is closely studied to address some of the major structural features of the photoelectron angular distributions. This work is partially supported by DOE.

  17. [Modalities of breast cancer irradiation in 2016: Aims and indications of intensity modulated radiation therapy].

    PubMed

    Bourgier, C; Fenoglietto, P; Lemanski, C; Ducteil, A; Charissoux, M; Draghici, R; Azria, D

    2016-10-01

    Irradiation techniques for breast cancer (arctherapy, tomotherapy) are evolving and intensity-modulated radiation therapy is being increasingly considered for the management of these tumours. Here, we propose a review of intensity-modulated radiation therapy planning issues, clinical toxicities and indications for breast cancer. PMID:27614497

  18. Reactive effect of low intensity He-Ne laser upon damaged ultrastructure of human erythrocyte membrane in Fenton system by atomic force microscopy.

    PubMed

    Cui, Yanhong; Guo, Zhouyi; Zhao, Yanping; Zheng, Ying; Qiao, Yanfang; Cai, Jiye; Liu, Songhao

    2007-07-01

    To find out the mechanism of modulating the deformability of erythrocytes with low intensity He-Ne laser action, we studied the effect of low intensity He-Ne laser on the ultrastructure of human erythrocyte membrane. Erythrocytes were treated with free radicals from a Fenton reaction system before exposing them to low intensity He-Ne laser. The ultrastructure of damaged erythrocyte membrane was examined by atomic force microscopy. The results showed that the erythrocyte membrane became very rough and the molecules on the surface of the membrane congregated into particles of different magnitudes sizes after treating with free radicals. Comparing the degree of congregation of the molecular particles in the non-irradiated group and the He-Ne laser irradiated (9 mW and 18 mW) group, we found the average size of molecular particles in the laser irradiated group was smaller than that in the non-irradiated group, indicating that the low intensity laser had repairing function to the damage of erythrocyte membrane produced by the free radicals.

  19. Reactive effect of low intensity He-Ne laser upon damaged ultrastructure of human erythrocyte membrane in Fenton system by atomic force microscopy.

    PubMed

    Cui, Yanhong; Guo, Zhouyi; Zhao, Yanping; Zheng, Ying; Qiao, Yanfang; Cai, Jiye; Liu, Songhao

    2007-07-01

    To find out the mechanism of modulating the deformability of erythrocytes with low intensity He-Ne laser action, we studied the effect of low intensity He-Ne laser on the ultrastructure of human erythrocyte membrane. Erythrocytes were treated with free radicals from a Fenton reaction system before exposing them to low intensity He-Ne laser. The ultrastructure of damaged erythrocyte membrane was examined by atomic force microscopy. The results showed that the erythrocyte membrane became very rough and the molecules on the surface of the membrane congregated into particles of different magnitudes sizes after treating with free radicals. Comparing the degree of congregation of the molecular particles in the non-irradiated group and the He-Ne laser irradiated (9 mW and 18 mW) group, we found the average size of molecular particles in the laser irradiated group was smaller than that in the non-irradiated group, indicating that the low intensity laser had repairing function to the damage of erythrocyte membrane produced by the free radicals. PMID:17622467

  20. Sudden perturbation of hydrogen atoms by intense ultrashort laser pulses

    SciTech Connect

    Lugovskoy, A. V.; Bray, I.

    2005-12-15

    We study theoretically how hydrogen atoms respond to intense ultrashort laser pulses of duration {tau} shorter than the inverse of the initial-state energy {epsilon}{sub i}{sup -1}. An analytical expression for the evolution operator S is derived up to the first order of the sudden perturbation approximation. This approximation treats the laser-atom interaction beyond the dipole approximation and yields S as a series in the small parameter {epsilon}{sub i}{tau}. It is shown that the effect of realistic laser pulses on atoms begins at the first order of {epsilon}{sub i}{tau}. Transitions between atomic (nlm) states of different m become possible due to the action of the pulse's magnetic field. Transitions between states of same m and arbitrary l become possible if the static Coulomb potential is taken into account during the pulse.

  1. Experimental results to study astrophysical plasma jets using Intense Lasers

    NASA Astrophysics Data System (ADS)

    Loupias, B.; Gregory, C. D.; Falize, E.; Waugh, J.; Seiichi, D.; Pikuz, S.; Kuramitsu, Y.; Ravasio, A.; Bouquet, S.; Michaut, C.; Barroso, P.; Rabec Le Gloahec, M.; Nazarov, W.; Takabe, H.; Sakawa, Y.; Woolsey, N.; Koenig, M.

    2009-08-01

    We present experimental results of plasma jet, interacted with an ambient medium, using intense lasers to investigate the complex features of astrophysical jets. This experiment was performed in France at the LULI facility, Ecole Polytechnique, using one long pulse laser to generate the jet and a short pulse laser to probe it by proton radiography. A foam filled cone target was used to generate high velocity plasma jet, and a gas jet nozzle produced the well known ambient medium. Using visible pyrometry and interferometry, we were able to measure the jet velocity and electronic density. We get a panel of measurements at various gas density and time delay. From these measurements, we could underline the growth of a perturbed shape of the jet interaction with the ambient medium. The reason of this last observation is still in debate and will be presented in the article.

  2. Reduction of time-averaged irradiation speckle nonuniformity in laser-driven plasmas due to target ablation

    NASA Astrophysics Data System (ADS)

    Epstein, R.

    1997-09-01

    In inertial confinement fusion (ICF) experiments, irradiation uniformity is improved by passing laser beams through distributed phase plates (DPPs), which produce focused intensity profiles with well-controlled, reproducible envelopes modulated by fine random speckle. [C. B. Burckhardt, Appl. Opt. 9, 695 (1970); Y. Kato and K. Mima, Appl. Phys. B 29, 186 (1982); Y. Kato et al., Phys. Rev. Lett. 53, 1057 (1984); Laboratory for Laser Energetics LLE Review 33, NTIS Document No. DOE/DP/40200-65, 1987 (unpublished), p. 1; Laboratory for Laser Energetics LLE Review 63, NTIS Document No. DOE/SF/19460-91, 1995 (unpublished), p. 1.] A uniformly ablating plasma atmosphere acts to reduce the contribution of the speckle to the time-averaged irradiation nonuniformity by causing the intensity distribution to move relative to the absorption layer of the plasma. This occurs most directly as the absorption layer in the plasma moves with the ablation-driven flow, but it is shown that the effect of the accumulating ablated plasma on the phase of the laser light also makes a quantitatively significant contribution. Analytical results are obtained using the paraxial approximation applied to the beam propagation, and a simple statistical model is assumed for the properties of DPPs. The reduction in the time-averaged spatial spectrum of the speckle due to these effects is shown to be quantitatively significant within time intervals characteristic of atmospheric hydrodynamics under typical ICF irradiation intensities.

  3. Three-body fragmentation of CO{sub 2} driven by intense laser pulses

    SciTech Connect

    Wu, Chengyin Liu, Yunquan; Gong, Qihuang; Wu, Cong; Fan, Yameng; Xie, Xiguo; Wang, Peng; Deng, Yongkai

    2015-03-28

    Dissociative ionization dynamics were studied experimentally for CO{sub 2} driven by intense laser pulses. Three-dimensional momentum vectors of correlated atomic ions were obtained for each three-body fragmentation event using triple ion coincidence measurement. Newton diagram demonstrated that three-body fragmentation of CO{sub 2}{sup n+} (n = 3-6) can occur through Coulomb explosion process and sequential fragmentation process depending on the fragmentation channels. The experimental data from these two processes were disentangled by using correlation diagram of correlated ions. Based on the accurate Coulomb explosion data, we reconstructed the bond angle distributions of CO{sub 2}{sup n+} at the moment of fragmentation, which are close to that of neutral CO{sub 2} before laser irradiation.

  4. Heating of thin foils with a relativistic-intensity short-pulse laser.

    PubMed

    Audebert, P; Shepherd, R; Fournier, K B; Peyrusse, O; Price, D; Lee, R; Springer, P; Gauthier, J-C; Klein, L

    2002-12-23

    K-shell x-ray spectroscopy of sub-100 nm Al foils irradiated by high contrast, spatially uniform, 150 fs, Ilambda (2)=2 x 10(18) W microm(2)/cm(2), laser pulses is obtained with 500 fs time resolution. Two distinct phases occur: At /=500 fs the resonance transitions dominate. Initial satellites arise from a large area, high density, low temperature (approximately 100 eV) plasma created by fast electrons. Thus, contrary to predictions, a short, high intensity laser incident on a thin foil does not create a uniform, hot dense plasma. PMID:12484827

  5. Proton shock acceleration using a high contrast high intensity laser

    NASA Astrophysics Data System (ADS)

    Gauthier, Maxence; Roedel, Christian; Kim, Jongjin; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Propp, Adrienne; Goyon, Clement; Pak, Art; Kerr, Shaun; Ramakrishna, Bhuvanesh; Ruby, John; William, Jackson; Glenzer, Siegfried

    2015-11-01

    Laser-driven proton acceleration is a field of intense research due to the interesting characteristics of this novel particle source including high brightness, high maximum energy, high laminarity, and short duration. Although the ion beam characteristics are promising for many future applications, such as in the medical field or hybrid accelerators, the ion beam generated using TNSA, the acceleration mechanism commonly achieved, still need to be significantly improved. Several new alternative mechanisms have been proposed such as collisionless shock acceleration (CSA) in order to produce a mono-energetic ion beam favorable for those applications. We report the first results of an experiment performed with the TITAN laser system (JLF, LLNL) dedicated to the study of CSA using a high intensity (5x1019W/cm2) high contrast ps laser pulse focused on 55 μm thick CH and CD targets. We show that the proton spectrum generated during the interaction exhibits high-energy mono-energetic features along the laser axis, characteristic of a shock mechanism.

  6. Laser-induced breakdown spectroscopy with laser irradiation resonant with vibrational transitions

    SciTech Connect

    Khachatrian, Ani; Dagdigian, Paul J.

    2010-05-01

    An investigation of laser-induced breakdown spectroscopy (LIBS) of polymers, both in bulk form and spin coated on Si wafers, with laser irradiation in the mid-infrared spectral region is presented. Of particular interest is whether the LIBS signals are enhanced when the laser wavelength is resonant with a fundamental vibrational transition of the polymer. Significant increases in the LIBS signals were observed for irradiation on hydride stretch fundamental transitions, and the magnitude of the enhancement showed a strong dependence on the mode excited. The role of the substrate was investigated by comparison of results for bulk and spin-coated samples. The polymers investigated were Nylon 12 and poly(vinyl alcohol-co-ethylene).

  7. Modification of structural and optical properties of polyvinyl alcohol/polyethylene glycol thin film by laser irradiation

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Benthami, K.; Abutalib, M. M.

    2016-02-01

    The effect of infrared laser irradiation on the structural and the optical properties of polyvinyl alcohol/polyethylene glycol (PVA/PEG) co-polymer has been investigated. Thin films of PVA/PEG (nearly 50 µm thickness) were irradiated up to 15 J/cm2 of Ga-As laser pulses of 904 nm, 5 W power, and 200-ns pulse duration. The resultant effect of laser irradiation on the structural properties of PVA/PEG has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Further, the refractive index and the color difference between the exposed samples and the pristine have been studied. FTIR spectroscopy showed that the PVA/PEG samples exhibited degradation under the effect of laser irradiation up to 9 J/cm2, where crosslinking started and continued until 15 J/cm2. The refractive index had a minimum value of 1.5020 at 9 J/cm2, accompanied by a high degree of ordering and maximum value of 1.5640 at 15 J/cm2, with an increase in disordering character due to the degradation and crosslinking formation inside the sample, respectively. Moreover, the color intensity ΔE was greatly increased with increasing the laser fluence, accompanied by a significant increase in the yellow color component.

  8. Au-C allotrope nano-composite films at extreme conditions generated by intense ultra-short laser

    NASA Astrophysics Data System (ADS)

    Khan, Saif A.; Saravanan, K.; Tayyab, M.; Bagchi, S.; Avasthi, D. K.

    2016-07-01

    Structural evolution of gold-carbon allotrope nano-composite films under relativistically intense, ultra-short laser pulse irradiation is studied in this work. Au-C nano-composite films, having 4 and 10 at.% of Au, were deposited by co-sputtering technique on silicon substrates. Au-C60 NC films with 2.5 at.% Au were deposited on 12 μm thick Al foil using co-evaporation technique. These samples were radiated with single pulse from 45 fs, 10 TW Ti:Sapphire Laser at RRCAT at an intensity of 3 × 1018 W cm-2. The morphological and compositional changes were investigated using scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS) techniques. Laser pulse created three morphologically distinct zones around the point of impact on samples with silicon substrates. The gold content in 600 μm circular region around a point of impact is found to reduce by a factor of five. Annular rings of ∼70 nm in diameter were observed in case of Au-C NC film after irradiation. Laser pulse created a hole of about 400 μm in the sample with Al foil as substrate and wavy structures of 6 μm wavelength are found to be created around this hole. The study shows radial variation in nano-structure formation with varying local intensity of laser pulse.

  9. Low-fluence carbon dioxide laser irradiation of lentigines

    SciTech Connect

    Dover, J.S.; Smoller, B.R.; Stern, R.S.; Rosen, S.; Arndt, K.A.

    1988-08-01

    Low-fluence carbon dioxide (CO2) laser irradiation of skin has previously been shown to induce damage limited primarily to the epidermis. To evaluate whether this technique was therapeutically effective for pigmented epidermal lesions, ten lentigines caused by methoxsalen and ultraviolet light therapy were treated in one patient using the CO2 laser at fluences ranging from 3.0 to 7.7 J/cm2 for 0.1-s exposures with 4.5-mm spot size. Based on substantial clearing in seven of ten lesions treated, 146 solar lentigines were treated in five patients at fluences of 3.0, 3.7, or 4.4 J/cm2. Biopsies were performed on a total of 30 lesions immediately and 24 hours, seven days, and six weeks after irradiation. Of 125 lesions followed up clinically for six weeks, 12 cleared completely, 81 lightened substantially, and 28 remained unchanged. Only two demonstrated atrophic change. Hyperpigmentation or hypopigmentation did not occur. All lesions that improved had been treated at 3.7 or 4.4 J/cm2. Immediate histologic injury consisted of vacuolar and spindly change and subsequent vesiculation limited to the basilar epidermis. Twenty-four hours later there was epidermal necrosis with regeneration, 0.1 mm of dermal basophilia and stromal condensation, and a mild inflammatory infiltrate. These alterations were dose-dependent, with near complete epidermal necrosis and superficial dermal involvement at the highest fluence, and only focal epidermal necrosis at the lowest. At seven days, epidermal regeneration was complete with traces of melanin remaining in keratinocytes. Melanophages first appeared at seven days and persisted at six weeks, by which time the inflammatory infiltrate had cleared. No lentiginous proliferation was evident and epidermal pigmentation had become normal. Low-fluence CO2 laser irradiation is an effective means of damaging the epidermis with only minimal dermal change.

  10. Materials Modification with Intense Extreme Ultraviolet Pulses from a Compact Laser

    NASA Astrophysics Data System (ADS)

    Grisham, M. E.; Vaschenko, G.; Menoni, C. S.; Juha, L.; Bittner, M.; Pershyn, Yu. P.; Kondratenko, V. V.; Zubarev, E. N.; Vinogradov, A. V.; Artioukov, I. A.; Rocca, J. J.

    In summary, we have realized a series of experiments with a compact 46.9 nm wavelength laser that produces intense pulses of nanosecond duration to study the ablation behavior of metals, common polymers, and Sc/Si multilayers. The key ablation process in polymers is likely to be a radiolysis of the polymer chains by EUV photons, resulting in the formation of numerous small molecular fragments that are subsequently removed from the surface of the samples. The EUV ablation rates for different polymers were found to be almost material independent, ˜ 50 - 400 nm/pulse. In each material EUV irradiation was observed to leave smooth craters with well defined edges and without signs of thermal damage. No threshold behavior was detected in the EUV ablation of the polymers in the range of fluences used in the experiment. In contrast to polymers the irradiation damage in metals and in Sc/Si multilayers is thermal in nature. A damage threshold of 0.08 J/cm2 was measured in the multilayer mirror coatings deposited on Si or borosilicate glass substrates, compared with a measured value of 0.7 J/cm2 for bare Si substrates. These results are relevant to the use of these mirrors with newly developed high-power EUV laser sources and provide a benchmark for their further improvement. In combination, the experiments demonstrate that compact extreme ultraviolet lasers are new tools available for surface modification studies and patterning.

  11. Optimal proton acceleration from lateral limited foil sections and different laser pulse durations at relativistic intensity

    SciTech Connect

    Toncian, T.; Swantusch, M.; Toncian, M.; Willi, O.; Andreev, A. A.; Platonov, K. Y.

    2011-04-15

    The proton acceleration from a thin foil irradiated by a laser pulse at relativistic intensities is a process highly dependent on the electron dynamic at the rear side of the foil. By reducing the lateral size of the laser irradiated foil the hot electrons are confined in a small volume leading to an enhancement of both the maximum proton energy and the conversion efficiency in the target normal sheath acceleration regime. In this paper we demonstrate that an optimal lateral size of the target can be found. While a smaller target surface leads to a better hot electron confinement and enhances the Debye sheath accelerating the protons, it also leads to an increase of preplasma formation due to limited laser contrast available experimentally and hence to a decrease of the proton acceleration. The experimentally found optimum is in good agreement with analytic theory and 2D particle in cell simulations. In addition, the maximum proton energy as a function of pulse duration has been investigated. The experimental results fit to an analytical model.

  12. Design and testing of low intensity laser biostimulator

    PubMed Central

    Valchinov, Emil S; Pallikarakis, Nicolas E

    2005-01-01

    -wave retardation plate. The proposed method for testing the device efficiency employs a biofeedback from the subject by recording the biopotentials evoked by the laser stimulus at related distant SLB sites. Therefore measuring of SLB biopotentials caused by the stimulus would indicate that a biopotential has been evoked at the irradiated site and has propagated to the measurement sites, rather than being caused by local changes of the electrical skin conductivity. Results A prototype device was built according to the proposed design using relatively inexpensive and commercially available components. The laser output can be pulse modulated from 0.1 to 1000 Hz with a duty factor from 10 to 90 %. The average output power density can be adjusted in the range 24 – 480 mW/cm2, where the total irradiation is limited to 2 Joule per stimulation session. The device is controlled by an 8-bit RISC Flash microcontroller with internal RAM and EEPROM memory, which allows for a wide range of different stimulation protocols to be implemented and memorized. The integrated laser diode driver with its onboard light power control loop provides safe and consistent laser modulation. The prototype was tested on the right Tri-Heater (TH) acupuncture meridian according to the proposed method. Laser evoked potentials were recorded from most of the easily accessible SLB along the meridian under study. They appear like periodical spikes with a repetition rate from 0.05 to 10 Hz and amplitude range 0.1 – 1 mV. Conclusion The prototype's specifications were found to be better or comparable to those of other existing devices. It features low component count, small size and low power consumption. Because of the low power levels used the possibility of sensory nerve stimulation via the phenomenon of shock or heat is excluded. Thus senseless optical stimulation is achieved. The optical system presented offers simple and cost effective way for beam collimation and polarization change. The novel method proposed

  13. Improving the intensity of the HELEN Laser at AWE

    NASA Astrophysics Data System (ADS)

    Hopps, Nicholas; Nolan, Jonathan; Girling, Mark; Kopec, Maria; Harvey, Ewan

    2005-04-01

    The HELEN laser is a three-beam, large aperture Nd:glass laser, used for plasma physics studies at the Atomic Weapons Establishment in the UK. Two of the beams nominally deliver 500 J each in 1 ns at the second harmonic (527 nm). The third beam, the "backlighter", has recently been upgraded to operate as a chirped pulse amplification system and it now routinely delivers 70 J to target in 500 fs. Optimal focal spot performance is achieved using a closed-loop adaptive optics system, which ensures good wavefront characteristics, irrespective of whether previous firing of the amplifiers has induced refractive index variations in the laser glass. The system uses a 32 element bimorph mirror with 98 mm aperture, roughly half way through the laser chain. A Shack-Hartman wavefront sensor, positioned at the output of the laser is the diagnostic used to provide feedback to the deformable mirror. Correction of the static and slowly varying aberrations on the beam has been demonstrated. The fast aberrations induced during the flashlamp discharge have been evaluated. The improved focal spot characteristics result in an intensity on target of significantly greater than 1019 Wcm-2.

  14. Anomalous transport of Sb in laser irradiated Ge

    SciTech Connect

    Bruno, E.; Scapellato, G. G.; Boninelli, S.; Priolo, F.; Privitera, V.; La Magna, A.; Cuscuna, M.; Fortunato, G.; Napolitani, E.

    2012-10-22

    Excimer laser annealing is shown to be very promising to promote Sb incorporation in Ge up to concentrations as high as 1 Multiplication-Sign 10{sup 21} at./cm{sup 3}. However, we demonstrate that when Ge is melted by laser irradiation, a high excess of vacancies is generated in the molten region. These vacancies induce Sb electrical deactivation at the melt depth through the formation of Sb{sub m}-V{sub n} complexes that act as a sink for further Sb atoms, even leading Sb to back-diffuse towards the surface, against the concentration gradient. These results are fundamental for the realization of new generation Ge-based micro and optoelectronic devices.

  15. Reducing wall plasma expansion with gold foam irradiated by laser

    SciTech Connect

    Zhang, Lu; Ding, Yongkun Jiang, Shaoen Yang, Jiamin; Li, Hang; Kuang, Longyu; Lin, Zhiwei; Jing, Longfei; Li, Liling; Deng, Bo; Yuan, Zheng; Chen, Tao; Yuan, Guanghui; Tan, Xiulan; Li, Ping

    2015-11-15

    The experimental study on the expanding plasma movement of low-density gold foam (∼1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum.

  16. Heating model for metals irradiated by a subpicosecond laser pulse

    SciTech Connect

    Chimier, B.; Tikhonchuk, V. T.; Hallo, L.

    2007-05-15

    We propose a model describing the heating and ablation of a metallic target irradiated by a subpicosecond laser pulse. It takes into account the temperature equilibration between the electrons and ions and the density variation of the target material during the heating process. A simple analytical equation of state is developed, which allows one to calculate the total pressure in the heated layer for different electron and ion temperatures. The thermodynamic behavior of a nonequilibrium system is discussed, and nonequilibrium spinodals and cohesion limits are introduced. The model is applied for a description of the thermal ablation process driven by a sub-ps laser pulse. Aluminum and copper targets are considered, and it is shown that the dominant ablation process is due to breaking the nonequilibrium cohesion limit. The numerical results are in good agreement with recent experimental data.

  17. Intense Laser Ionization and Acceleration of Electrons in Highly-Charged Ions Using Vortex Laser Beams

    NASA Astrophysics Data System (ADS)

    Pi, Liang-Wen; Vikartofsky, Andrew; Starace, Anthony F.

    2016-05-01

    Recent advances in laser technology have led to the development of high-power petawatt lasers, making possible laser intensities of the order of 1022 W /cm2 . An electron in a highly-charged ion can be ionized in a laser field at its peak intensity and swiftly accelerated to GeV energies. Our prior investigation of laser acceleration of electrons using linearly-polarized Gaussian beams (with zero orbital angular momentum) has revealed that the final-state energies and ejection angles of the electrons depend on the initial target ion positions relative to the laser focus. We report here recent simulations of laser ionization and acceleration of electrons using linearly-polarized vortex laser beams (i.e., Laguerre-Gaussian beams), which carry orbital angular momentum and can spin microscopic objects. These simulations show that the inherent spiral phase structure of the vortex beams leads to improved final-state energy and ejection angle distributions of the electrons. This work is supported in part by DOE, Office of Science, Division of Chemical Sciences, Geosciences, and Biosciences, under Grant No. DE-FG02-96ER14646.

  18. Laser irradiation of centrosomes in newt eosinophils: evidence of centriole role in motility

    SciTech Connect

    Koonce, M.P.; Cloney, R.A.; Berns, M.W.

    1984-06-01

    Newt eosinophils are motile granulated leukocytes that uniquely display a highly visible centrosomal area. Electron microscope and tubulin antibody fluorescence confirms the presence of centrioles, pericentriolar material, and radiating microtubules within this visible area. Actin antibodies intensely stain the advancing cell edges and tail but only weakly stain pseudopods being withdrawn into the cell. Randomly activated eosinophils follow a roughly consistent direction with an average rate of 22.5 ..mu..m/min. The position of the centrosome is always located between the trailing cell nucleus and advancing cell edge. If the cell extends more than one pseudopod, the one closest to or containing the centrosome is always the one in which motility continues. Laser irradiation of the visible centrosomal area resulted in rapid cell rounding. After several minutes following irradiation, most cells flattened and movement continued. However, postirradiation motility was uncoordinated and directionless, and the rate decreased to an average of 14.5 ..mu..m/min. Electron microscopy and tubulin immunofluorescence indicated that an initial disorganization of microtubules resulted from the laser microirradiations. After several minutes, organized microtubules reappeared, but the centrioles appeared increasingly damaged. The irregularities in motility due to irradiation are probably related to the damaged centrioles. The results presented in this paper suggest that the centrosome is an important structure in controlling the rate and direction of newt eosinophil motility.

  19. Acceleration of highly charged GeV Fe ions from a low-Z substrate by intense femtosecond laser

    SciTech Connect

    Nishiuchi, M. Sakaki, H.; Esirkepov, T. Zh.; Pirozhkov, A. S.; Sagisaka, A.; Ogura, K.; Kiriyama, H.; Fukuda, Y.; Kando, M.; Bulanov, S. V.; Kondo, K.; Nishio, K.; Orlandi, R.; Koura, H.; Imai, K.; Pikuz, T. A.; Faenov, A. Ya.; Skobelev, I. Yu.; Sako, H.; Matsukawa, K.; and others

    2015-03-15

    Almost fully stripped Fe ions accelerated up to 0.9 GeV are demonstrated with a 200 TW femtosecond high-intensity laser irradiating a micron-thick Al foil with Fe impurity on the surface. An energetic low-emittance high-density beam of heavy ions with a large charge-to-mass ratio can be obtained, which is useful for many applications, such as a compact radio isotope source in combination with conventional technology.

  20. Fragmentation dynamics of fullerenes in intense femtosecond-laser fields: Loss of small neutral fragments on a picosecond time scale

    SciTech Connect

    Boyle, M.; Laarmann, T.; Shchatsinin, I.; Schulz, C.P.; Hertel, I.V.

    2005-05-08

    The fragmentation dynamics of C{sub 60} irradiated with intense femtosecond laser pulses is studied with one-color pump-probe spectroscopy. Small neutral fragments (C, C{sub 2}, and C{sub 3}) are formed by an 800-nm pump pulse which are then postionized by a delayed probe pulse. The respective ion signals detected by the time-of-flight mass spectrometry dramatically increase on a time scale of 10-20 ps.

  1. What is the surface temperature of a solid irradiated by a Petawatt laser?

    NASA Astrophysics Data System (ADS)

    Kemp, A. J.; Divol, L.

    2016-09-01

    When a solid target is irradiated by a Petawatt laser pulse, its surface is heated to tens of millions of degrees within a few femtoseconds, facilitating a diffusive heat wave and the acceleration of electrons to MeV energies into the target. Using numerically converged collisional particle-in-cell simulations, we observe a competition between two surface heating mechanisms-inverse bremsstrahlung in solid density on the one hand and electron scattering on turbulent electric fields on the other. Collisionless heating effectively dominates above the relativistic intensity threshold. Our numerical results show that a high-contrast 40 fs, f/5 laser pulse with 1 J energy will heat the skin layer to 5 keV, and the inside of the target over several microns deep to bulk temperatures in the range of 10-100 eV at solid density.

  2. Modeling laser irradiation conditions for mucosal tissues in antimicrobial photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Zalesskaya, G. A.; Astaf'eva, L. G.; Plavskii, V. Yu.

    2012-05-01

    We use computer modeling to analzye empirically selected conditions for antimicrobial photodynamic therapy of mucosal tissues. We calculate the optical and thermal fields for experimental conditions for low-intensity (cold) laser irradiation used in treatment of lesions in mucosal tissues stained by methylene blue: λ = 670 nm, power density 150-300 mW/cm2, doses 9-18 J/cm2; λ = 632.8 nm, 15 mW/cm2, dose 4.5 J/cm2. For numerical estimates, we used the optical characteristics of methylene blue and three layers of mucosal tissues at the laser radiation wavelengths, and also the thermal characteristics of the tissues. The experimental conditions were optimized using the ratio of the tissue penetration depth for the absorbed optical energy and the penetration depth of methylene blue into the lesion, while maintaining safe tissue heating temperatures.

  3. The intravenous laser blood irradiation in chronic pain and fibromyalgia.

    PubMed

    Momenzadeh, Sirous; Abbasi, Mohammadzaki; Ebadifar, Asghar; Aryani, Mohammadreza; Bayrami, Jafar; Nematollahi, Fatemeh

    2015-01-01

    Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karu at the same time. An abstract is to be found in her work "The Science of Low-Power Laser-Therapy" PMID:25699161

  4. The Intravenous Laser Blood Irradiation in Chronic Pain and Fibromyalgia

    PubMed Central

    Momenzadeh, Sirous; Abbasi, Mohammadzaki; Ebadifar, Asghar; Aryani, Mohammadreza; Bayrami, Jafar; Nematollahi, Fatemeh

    2015-01-01

    Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karu at the same time. An abstract is to be found in her work "The Science of Low-Power Laser-Therapy" PMID:25699161

  5. Short-pulse high intensity laser thin foil interaction

    NASA Astrophysics Data System (ADS)

    Audebert, Patrick

    2003-10-01

    The technology of ultrashort pulse laser generation has progressed to the point that optical pulses larger than 10 J, 300 fs duration or shorter are routinely produced. Such pulses can be focused to intensities exceeding 10^18 W/cm^2. With high contrast pulses, these focused intensities can be used to heat solid matter to high temperatures with minimal hydrodynamic expansion, producing an extremely high energy-density state of matter for a short period of time. This high density, high temperature plasma can be studied by x-ray spectroscopy. We have performed experiments on thin foils of different elements under well controlled conditions at the 100 Terawatt laser at LULI to study the characteristics X-ray emission of laser heated solids. To suppress the ASE effect, the laser was frequency doubled. S-polarized light with a peak intensity of 10^19W/cm^2 was used to minimize resonance absorption. To decrease the effect of longitudinal temperature gradients very thin (800 μ) aluminum foil targets were used. We have also studied the effect of radial gradient by limiting the measured x-ray emission zone using 50μ or 100μ pinhole on target. The spectra, in the range 7-8Å, were recorded using a conical crystal spectrometer coupled to a 800 fs resolution streak camera. A Fourier Domain Interferometry (FDI) of the back of the foil was also performed providing a measurement of the hydrodynamic expansion as function of time for each shot. To simulate the experiment, we used the 1D hydrodynamic code FILM with a given set of plasma parameter (ρ, Te) as initial conditions. The X-ray emission was calculated by post processing hydrodynamic results with a collisional-radiative model which uses super-configuration average atomic data. The simulation reproduces the main features of the experimental time resolved spectrum.

  6. Wound healing after irradiation of bone tissues by Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Watanabe, Hisashi; Yoshino, Toshiaki; Aoki, Akira; Ishikawa, Isao

    1997-05-01

    Clinical applications of Er:YAG laser are now developing in periodontics and restorative dentistry. To date, there have been few studies indicating safety criteria for intraoral usage of the Er:YAG laser. The present study examined the effects of the Er:YAG laser on bone tissues, supposing mis- irradiation in the oral cavity during dental application, especially periodontal surgery. The experiments were performed using the newly-developed Er:YAG laser apparatus equipped with a contact probe. In experiment 1, 10 pulses of laser irradiation were administered to the parietal bone of a rat at 50, 150 and 300 mJ/pulse with and without water irrigation, changing the irradiation distance to 0, 5, 10 and 20 mm, respectively. As a control, electric knife was employed. Macroscopic and SEM observations of the wound surface were performed. In experiment 2, laser irradiation in a straight line was performed at 150 mJ/pulse, 1- pps and 0,5, 10 mm irradiation distance without water irrigation. Wound healing was observed histologically at 0, 3, 7, 14 and 28 days after laser irradiation and compared with that of the control. Non-contact irradiation by Er:YAG laser did not cause severe damage to the parietal bone tissue under water irrigation. Contact irradiation induced a limited wound, however, new bone formation was observed 28 days after laser irradiation, while osseous defect with thermal degenerative tissue remained at the control site. In conclusion, irradiation with an Er:YAG laser would not cause severe damage to surrounding bone tissues in the oral cavity when used within the usual power settings for dental treatment. Furthermore, this laser may be applicable for osseous surgery because of its high ablation efficiency and good wound healing after irradiation.

  7. Explosive Boiling In Carbon Target Irradiated By Third Harmonic Of Nd :YAG Laser

    SciTech Connect

    Yahiaoui, K.; Kerdja, T.; Malek, S.

    2008-09-23

    In order to identify the physical phenomena responsible to the formation of droplets onto thin films grown during laser ablation, and to correlate between the appearance of those droplets versus the laser flux, we have measured the amount of ejected matter for carbon target irradiated by a third harmonic of Nd:YAG laser by changing laser flux. The measurement was achieved by a quartz microbalance placed in front of the target. The obtained results show at first a linear increase of the ejected material followed by a saturation behavior, and then an abrupt increase of the ablated mass beyond a laser Intensity of 3,64x10{sup 10} W/cm{sup 2}. This increasing is assigned to the homogeneous nucleation of bubbles in a layer of the molten material, also called phase explosion, the surface temperature of the target will approaches the critical thermodynamic temperature (T{sub tc}). We have also measured time-of-flight (TOF) distributions of positives ions of carbons in the plasma using a charge collector. The TOF signals have been fitted with a shifted Maxwellian distribution function. This has allowed us to estimate the critical temperature T{sub tc} of the material.

  8. Raman and electron microscopy analysis of carbon nanotubes exposed to high power laser irradiance

    SciTech Connect

    Ramadurai, Krishna; Cromer, Christopher L.; Lehman, John H.; Dillon, Anne C.; Mahajan, Roop L.

    2009-05-01

    High power laser radiometry requires efficient and damage-resistant detectors. The current study explores the evolving nature of carbon nanotube coatings for such detectors upon their exposure to incrementally increasing laser power levels. Electron microscopy images along with the D-band to G-band intensity ratios from the Raman spectra from eight irradiance levels are used to evaluate changes before and after the exposure. Electron microscopy images of the exposed multiwalled carbon nanotubes revealed the formation of intermittent pockets of moundlike structures at high power densities exceeding 11 kW/cm{sup 2}. Raman spectroscopy measurements also demonstrated higher values for the ratio of the D-band intensity to that of the G-band, suggesting the possible transformation of nanotubes into structurally different forms of carbon. Exposure to a sample of single-walled nanotubes did not demonstrate the evolution of structural changes, which could be due in part to the higher irradiance levels relative to the damage threshold, employed in the experiment.

  9. Recent High-Intensity Experiments at the Trident Laser

    NASA Astrophysics Data System (ADS)

    Cobble, James; Palaniyappan, Sasikumar; Gautier, Cort; Kim, Yongho; Huang, Chengkun

    2014-10-01

    With near-diffraction-limited irradiance of 2 × 1020 W/cm2 on target and prelase contrast better than 10-8, we have accessed the regime of relativistic transparency (RT) at the Trident Laser. The goal was to assess electron debris emitted from the target rear surface with phase-contrast imaging (PCI) and current density measurements (hence, the total electron current). Companion diagnostics show whether the experiments are in the target-normal-sheath-acceleration mode or in the RT regime. The superb laser contrast allows us to shoot targets as thin as 50 nm. PCI at 527 nm is temporally resolved to 600 fs. It has shown the evolution of electron behavior over tens of ps, including thermal electrons accompanying the ion jet, accelerated to many tens of MeV earlier in time. Faraday-cup measurements indicate the transfer of many microC of charge during the laser drive. As a ride-along experiment using a gas Cherenkov detector (GCD), we have detected gamma rays of energy >5 MeV. This radiation has a prompt component and a lesser source, driven by accelerated ions, that is time resolved by the GCD. The ion time of flight is compared to Thomson parabola data. Electron energy spectra are also collected. This work is supported by US DOE/NNSA, performed at LANL, operated by LANS LLC under Contract DE-AC52-06NA25396.

  10. The effect of low-intensity laser therapy on wound healing in Streptozotocin-induced diabetic rats

    NASA Astrophysics Data System (ADS)

    Rabelo, Sylvia B.; Villaverde, Antonio G. J. B.; Salgado, Miguel A. C.; Melo, Milene d. S.; Nicolau, Renata A.; Pacheco, Marcos T. T.

    2004-10-01

    Diabetes Mellitus is a condition that results in a delay of the wound healing process, that is associated with an insufficient production of collagen, a decrease of the amount of collagen fibrils and deficient blood flow in the wound area. It is sugested that Low Intensity Laser Therapy acts by improving wound healing in normal organisms, accelerating tissue regeneration. The aim of this work was to investigate the biostimulatory effect of the HeNe laser irradiation, at 632.8 nm, on wound healing in 15 male rats suffering from diabetes induced by Streptozotocin, compared to 15 control diabetic animals. Irradiation parameters were: laser power of 15mW, exposition time of 17 s., irradiated area of 0.025 cm2 and laser energy density of 10 J/cm2. Full-thickness skin squared samples, with 5 mm of non-injured tissue around the wound, were obtained at 4, 7 and 15 days after wounding procedure (5 treated and 5 control animals each time). The histopathologic analysis performed by haematoxylin-cosin staining. Results suggested that the irradiation of diabetic rats was efficient for wound healing. Treated group presented better quality of the wound tissues by the macroscopic observation than control group and the microscopic analysis demonstrated that treated animals had better histopathologic evaluation than non treated.

  11. Resonant absorption effects induced by polarized laser light irradiating thin foils in the TNSA regime of ion acceleration

    NASA Astrophysics Data System (ADS)

    Torrisi, L.; Badziak, J.; Rosinski, M.; Zaras-Szydlowska, A.; Pfeifer, M.; Torrisi, A.

    2016-04-01

    Thin foils were irradiated by short pulsed lasers at intensities of 1016-19W/cm2 in order to produce non-equilibrium plasmas and ion acceleration from the target-normal-sheath-acceleration (TNSA) regime. Ion acceleration in forward direction was measured by SiC detectors and ion collectors used in the time-of-flight configuration. Laser irradiations were employed using p-polarized light at different incidence angles with respect to the target surface and at different focal distances from the target surface. Measurements demonstrate that resonant absorption effects, due to the plasma wave excitations, enhance the plasma temperature and the ion acceleration with respect to those performed without to use of p-polarized light. Dependences of the ion flux characteristics on the laser energy, wavelength, focal distance and incidence angle will be reported and discussed.

  12. Observation of photoexcited emission clusters in the bulk of KDP and laser conditioning under 355-nm irradiation

    SciTech Connect

    De Yoreo, J. J.; Demos, S. G.; Radousky, H. B.; Staggs, M.; Yan, M.

    1998-12-15

    Defect clusters in the bulk of large KDP crystals are revealed using a microscopic fluorescence imaging system and CW laser illumination. Exposure of the crystal to high power 355-nm, 3-ns laser irradiation leads to a significant reduction of the number of observed optically active centers. The initially observed defect cluster concentration is approximately 104-106 per mm3 depending on the crystal growth method and sector of the crystal. The number of defect clusters can be reduced by a factor of 102 or more under exposure to 355-nm laser irradiation while their average intensities also decreases. Spectroscopic measurements provide information on the electronic structure of the defects.

  13. Surface and bulk effects in silica fibers caused by 405 nm CW diode laser irradiation and means for mitigation

    NASA Astrophysics Data System (ADS)

    Gonschior, C. P.; Klein, K.-F.; Sun, T.; Grattan, K. T. V.

    2012-11-01

    Surface and bulk effects in silica optics due to high intensity laser light are well known using short pulse and high power laser systems. Surfaces are quickly destroyed mechanically if not properly prepared and thoroughly cleaned. Linear and non-linear absorption of high intensity laser light in the bulk of the optics causes material modifications, like voids, cracks and UV defects. In ablation experiments with very short pulses on wide band-gap dielectrics, periodic surface structures in the form of ripples were found. Surprisingly, we found similar structures on fiber end-faces after long-term irradiation with 405 nm CW laser light. Power densities on the end-face are in the range of 1 MW/cm2, three magnitudes of order below the power threshold at which the described damages occur. Nevertheless a ripple structure perpendicular to the polarization direction of the laser was formed and grows with irradiation time. An increased absorption band at 214 nm (E' center) along the fiber was discovered by spectral absorption measurements. E' centers can be generated by 405 nm laser light in the bulk, therefore defects on the surface are possible as well. The generation of defect centers on the silica surface can enhance the formation of an unstable surface layer.

  14. Resonant high-order harmonic generation from plasma ablation: Laser intensity dependence of the harmonic intensity and phase

    SciTech Connect

    Milosevic, D. B.

    2010-02-15

    Experimentally observed strong enhancement of a single high-order harmonic in harmonic generation from low-ionized laser plasma ablation is explained as resonant harmonic generation. The resonant harmonic intensity increases regularly with the increase of the laser intensity, while the phase of the resonant harmonic is almost independent of the laser intensity. This is in sharp contrast with the usual plateau and cutoff harmonics, the intensity of which exhibits wild oscillations while its phase changes rapidly with the laser intensity. The temporal profile of a group of harmonics, which includes the resonant harmonic, has the form of a broad peak in each laser-field half cycle. These characteristics of resonant harmonics can have an important application in attoscience. We illustrate our results using examples of Sn and Sb plasmas.

  15. Simulation of the thermal effect of laser irradiation to optimize laser epilation

    NASA Astrophysics Data System (ADS)

    Russ, Detlef; Kienle, Alwin; Falkenstein, Werner; Steiner, Rudolf W.

    2000-11-01

    For hair removal commonly lasers are used with wavelengths being selectively absorbed by melanin .As a consequence, laser radiation leads to an increase of the temperature not only in melanin containing structures of the hair but also in the epidermis. Therefore, we simulated and studied the laser induced temperature development in tissue for various laser wavelengths and various pulse profiles. Modifying the beam parameters can improve the selectivity of the method. Monte- Carlo-Simulations were used to calculate light absorption in dermal structures, considering the tissue specific optical properties. The thermal diffusion in tissue was calculated by a finite difference method. The biological reaction due to the temperature rise was determined by an Arrhenius formalism and depends on temperature and time of laser-tissue interaction. The simulation program allows to calculate the temperature distribution and thermal damage for various temporal pulse profiles, fluence rates and irradiation geometries. Superficial cooling has an important influence and has been considered in the calculations. The results of our simulations for various laser types show differences in the thermal reaction which can be used to optimize the treatment modalities. The potential and limits of laser epilation can be estimated from these results. For example, a series of laser pulses has some advantages compared to a longer single pulse.

  16. 3D nanotube-based composites produced by laser irradiation

    SciTech Connect

    Ageeva, S A; Bobrinetskii, I I; Nevolin, Vladimir K; Podgaetskii, Vitalii M; Selishchev, S V; Simunin, M M; Konov, Vitalii I; Savranskii, V V; Ponomareva, O V

    2009-04-30

    3D nanocomposites have been fabricated through self-assembly under near-IR cw laser irradiation, using four types of multiwalled and single-walled carbon nanotubes produced by chemical vapour deposition, disproportionation on Fe clusters and cathode sputtering in an inert gas. The composites were prepared by laser irradiation of aqueous solutions of bovine serum albumin until the solvent was evaporated off and a homogeneous black material was obtained: modified albumin reinforced with nanotubes. The consistency of the composites ranged from paste-like to glass-like. Atomic force microscopy was used to study the surface morphology of the nanomaterials. The nanocomposites had a 3D quasi-periodic structure formed by almost spherical or toroidal particles 200-500 nm in diameter and 30-40 nm in visible height. Their inner, quasi-periodic structure was occasionally seen through surface microfractures. The density and hardness of the nanocomposites exceed those of microcrystalline albumin powder by 20% and by a factor of 3-5, respectively. (nanostructures)

  17. Nonlinear Compton scattering of ultrashort intense laser pulses

    SciTech Connect

    Seipt, D.; Kaempfer, B.

    2011-02-15

    The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

  18. Nonlinear Compton scattering of ultrashort intense laser pulses

    NASA Astrophysics Data System (ADS)

    Seipt, D.; Kämpfer, B.

    2011-02-01

    The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

  19. Ion acceleration from the interaction of ultra-intense lasers with solid foils

    NASA Astrophysics Data System (ADS)

    Allen, Matthew Mark

    The discovery that ultra-intense laser pulses (I > 10 18 W/cm2) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. In this thesis we present several experiments that study the accelerated ions by affecting the contamination layer from which they originate. Radiative heating was employed as a method of removing contamination from palladium targets doped with deuterium. We present evidence that ions heavier than protons can be accelerated if hydrogenous contaminants that cover the laser target can be removed. We show that deuterons can be accelerated from the deuterated-palladium target, which has been radiatively heating to remove contaminants. Impinging a deuteron beam onto a tritiated-titanium catcher could lead to the development of a table-top source of short-pulse, 14-MeV fusion neutrons. We also show that by using an argon-ion sputter gun, contaminants from one side of the laser target can be selectively removed without affecting the other side. We show that irradiating a thin metallic foil with an ultra-intense laser pulse produces a proton beam with a yield of 1.5--2.5 10 11 and temperature, kT = 1.5 MeV with a maximum proton energy >9 MeV. Removing contaminants from the front surface of the laser target with an argon-ion sputter gun, had no observable effect on the proton beam. However, removing contaminants from the back surface of the laser target reduced the proton beam by two orders of magnitude to, at most, a yield of ˜10 9 and a maximum proton energy <4 MeV. Based on these observations, we conclude that the majority (>99%) of high energy protons (E > 5 MeV) from the interaction of an ultra-intense laser pulse with a thin foil originate on the back surface of the foil---as predicted by the TNSA model. Our experimental results are in agreement with PIC simulations showing back surface protons reach energies up to 13 MeV, while front

  20. Effects of surface ligands and solvents on quantum dot photostability under pulsed UV laser irradiation

    NASA Astrophysics Data System (ADS)

    Krivenkov, Victor A.; Samokhvalov, Pavel S.; Linkov, Pavel A.; Prokhorov, Sergey D.; Martynov, Igor L.; Chistyakov, Alexander A.; Nabiev, Igor

    2015-05-01

    The organic ligands passivating the surface of semiconductor quantum dots (QDs) and the solvents used strongly determine the photostability of QD solutions. Highly purified QD solutions in chloroform have been shown to photodegrade upon pulsed ultraviolet (UV) irradiation, irrespectively of the type of surface ligand. However, the photostability of QDs dissolved in n-octane, a more photochemically inert solvent, strongly depends on the ligands passivating their surface. In n-octane, hexadecylamine-coated QDs are completely stable and display no photochemical response to pulsed UV laser irradiation. In solutions of octanethiol-capped QDs, the photoluminescence intensity slightly decreases under irradiation. QDs coated with trioctylphosphine oxide exhibit a more complex pattern of photobleaching, which depends on the initial value of fluorescence quantum yield of QDs. This complex pattern may be accounted for by two competing processes: (1) ligand photodesorption accompanied by photobleaching due to specific alignment of the band levels of QDs and highest occupied molecular orbital of the ligand and (2) photoinduced decrease in the population of trapping states. Furthermore, practically no thermodynamic degradation of QD solutions has been observed for the micromolar QD concentration used in the study, in contrast to lower concentrations, thus confirming the photoinduced origin of the changes caused by UV irradiation. Obtained results show that the photostability of QDs may be strongly increased by careful selection of the ligands passivating their surface and the solvents used in the experiments.

  1. A laser speckle contrast analysis (LSCA) study of the effect of curing irradiance on composite polymerization kinetics

    NASA Astrophysics Data System (ADS)

    Wells-Gray, Elaine M.; Kirkpatrick, Sean J.; Duncan, Don D.

    2011-03-01

    The kinetics of resin composite polymerization plays an important, though not well understood, role it the development of shrinkage stress and the resultant integrity of the final restoration. In this report we investigate the effect of curing irradiance on the polymerization kinetics using a dynamic light scattering technique known as laser speckle contrast analysis (LSCA). Thin layer samples are considered with focus given to the effect of sample thickness on the rate results obtained with this method. We present results for the intensity fluctuation rate as a function of irradiance for two statistical models of intensity decorrelation: Lorentzian and Gaussian. Results indicate that the rate of scatterer motion varies approximately with the square root of irradiance, which agrees well with theory and previous results in the literature. Our results suggest that dynamic light scattering techniques, and LSCA in particular, provide an effective, non-contact means of assessing polymerization kinetics.

  2. Controlled intensity emission from patterned porous silicon using focused proton beam irradiation

    SciTech Connect

    Teo, E.J.; Mangaiyarkarasi, D.; Breese, M.B.H.; Bettiol, A.A.; Blackwood, D.J.

    2004-11-08

    We have fabricated light emitting porous silicon micropatterns with controlled emission intensity. This has been achieved by direct write irradiation in heavily doped p-type silicon (0.02 {omega} cm) using a 2 MeV proton beam, focused to a spot size of 200 nm. After electrochemical etching in hydrofluoric acid, enhanced photoluminescence is observed from the irradiated regions. The intensity of light emission is proportional to the dose of the proton beam, so the PL intensity of the micropattern can be tuned and varied between adjacent regions on a single substrate. This behavior is in contrast to previous ion beam patterning of p-type silicon, as light is preferentially created as opposed to quenched at the irradiated regions.

  3. Ho:YAG laser irradiation in blood vessel as a vasodilator: ex vivo study

    NASA Astrophysics Data System (ADS)

    Nakatani, E.; Iwasaki, T.; Kaneko, K.; Shimazaki, N.; Arai, T.

    2007-02-01

    We studied Ho:YAG laser irradiation in blood vessel as a vasodilator ex vivo. We thought that the Ho:YAG laser-induced bubble expansion might be able to dilate the vessel because we found the vessel wall expansion after the Ho:YAG laser irradiation, that is steady deformation, in the vessel ex vivo. There have been many reports regarding to the Ho:YAG laser irradiation in the vessel. Most of studies concentrated on the interaction between Ho:YAG laser irradiation and vessel wall to investigate side effect on Ho:YAG laser angioplasty. We proposed to use the Ho:YAG laser-induced bubble expansion as a vasodilator. We studied vasodilation effect of the Ho:YAG laser-induced bubble ex vivo. The flash lamp excited Ho:YAG laser surgical unit (IH102, NIIC, Japan) (λ=2.1μm) was used. The laser energy was delivered by a silica glass fiber (outer diameter: 1000μm, core diameter: 600μm). The laser-induced bubble was generated in the extracted fresh porcine carotid artery with the warmed saline perfusion. The laser energy at the fiber tip was ranging from 170-1300mJ per pulse. Number of the laser irradiation was ranged from 20pulses to 100pulses. The outer diameter of the vessel was observed. To examine the change in mechanical properties of the vessel wall, the stress-strain curve of the laser-irradiated vessel was measured. Birefringence observation and microscopic observation of staining specimen were performed. When the laser energy was set to 1300mJ per pulse, the outer diameter of the vessel after the laser irradiation was expanded by 1.4 times comparing with that of before the laser irradiation and the dilatation effect was kept even at 10minutes after the irradiation. The elasticity modulus of the artery by collagen was changed by the laser irradiation. In the polarized microscopic observation, the brightness of the intimal side of the vessel is increased comparing with that of the normal. We think this brightness increasing may be attributed to birefringence change

  4. Densification of silica glass induced by 0.8 and 1.5 {mu}m intense femtosecond laser pulses

    SciTech Connect

    Saliminia, A.; Nguyen, N.T.; Chin, S.L.; Vallee, R.

    2006-05-01

    We investigate the physical mechanisms responsible for waveguide formation in silica glass induced by 1 kHz intense femtosecond laser pulses from a Ti-sapphire laser at 0.8 {mu}m as well as from a femtosecond optical parametric amplifier at 1.5 {mu}m. It is demonstrated that the densification taking place at the irradiated region is the principal cause for refractive index change in the waveguides written with both 0.8 and 1.5 {mu}m pulses. The birefringence induced by the stress arising from such densification and its behavior against thermal annealing are also studied.

  5. Gigagauss Magnetic Field Generation from High Intensity Laser Solid Interactions

    NASA Astrophysics Data System (ADS)

    Sefcik, J.; Perry, M. D.; Lasinski, B. F.; Langdon, A. B.; Cowan, T.; Hammer, J.; Hatchett, S.; Hunt, A.; Key, M. H.; Moran, M.; Pennington, D.; Snavely, R.; Trebes, J.; Wilks, S. C.

    2004-11-01

    Intense laser (>1021 W/cm2) sources using pulse compression techniques in the sub-picosecond time frame have been used to create dynamic electric field strengths in excess of 100 Megavolts/micron with associated magnetic field strengths in the gigagauss regime. We have begun a series of experiments using the Petawatt Laser system at LLNL to determine the potential of these sources for a variety of applications. Hot electron spectra from laser-target interactions in Au have been measured with energies up to 100 MeV. Hot x-ray production has been measured using filtered thermoluminescent dosimeters and threshold nuclear activation (γ,n) from giant resonance interactions. High-resolution radiographs through ρr ≥ 165 gm/cm2 have been obtained. Dose levels in the x-ray band from 2-8 MeV have been measured at the level of several rads at one meter from the target for a single pulse. The physics of these sources and the scaling relationships and laser technology required to provide high magnetic fields are discussed. Results of preliminary magnetic field calculations are presented along with potential applications of this technology and estimates of the fundamental scaling limits for future development.

  6. Self-Steepening of intense laser pulses in plasmas

    NASA Astrophysics Data System (ADS)

    Vieira, Jorge; Fiúza, Frederico; Silva, Luis

    2007-11-01

    In state-of-the-art Laser Wake Field Acceleration (LWFA) experiments [1], the self-modulations of the laser pulse (both transverse and longitudinal) play an important role in the enhancement of the plasma wave, which can trap, accelerate and lead to quasi-mono-energetic electron beams. In this work, the self-steepening of intense laser pulses is studied analytically resorting to the photon-kinetic theory [2]. Rates for the growth of self-steepening in the early laser propagation are provided in the long and short pulse limits, and in the weakly and ultra relativistic regimes. Thresholds for the on-set, maximum and minimum growth of self-steepening are determined. We find very good agreement between the analytical model and one-dimensional PIC simulations with OSIRIS [3]. Implications of our results to state-of-the-art LWFA experiments are discussed. [1] W.P. Leemans et al Nat. Phys., 2 (10), 696-699 (2006) [2] L.O. Silva et al, IEEE TPS 28 (4) 1128-1134 (2000) [3] R. A. Fonseca et al, LNCS 2331, 342-351, (Springer, Heidelberg, 2002).

  7. Double ionization of H2 by intense attosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-08-01

    We present calculations of the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV using the time-dependent close-coupling method within the fixed nuclei approximation. We focus on two-photon absorption processes and examine how the response of the ejected electrons, in particular the single- and the double-energy differential probabilities, is affected by linear and circular polarizations at laser-field intensities ranging from 10^{15}\\; \\rm W\\,cm^{-2} to 10^{16}\\; \\rm W\\,cm^{-2} . In general, we find that for both linearly and circularly polarized pulses, sequential peaks and non-sequential wells that appear in both the single- and double-energy differential probabilities are akin to the analogous two-electron photoemission processes in the helium atom driven by intense attosecond pulses. In addition, for the case of a linearly polarized pulse, a clear signature of the sequential double-electron above the threshold ionization process can be seen in these spectra.

  8. Double Ionization of Hydrogen Molecule by Intense Attosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Pindzola, M. S.; Robicheaux, F.

    2010-03-01

    Time-dependent close-coupling calculations within the fixed nuclei approximation are carried out for the double ionization of H2 induced by an intense attosecond laser pulse at a photon energy of 40 eV. We consider here the two-photon absorption processes and examine the response of the ejected electrons, particularly the single- and the double-electron energy distributions, to linearly and circularly polarized pulse at laser intensities between 10^15 W/cm^2 and 10^16 W/cm^2. We find that, for both the linearly and circularly polarized pulses, sequential peaks and non-sequential wells appear in both the single- and double-electron energy distributions that are generally akin to the analogous two electrons photoemission processes in He atom driven by a linearly polarized intense attosecond pulse [1,2]. Furthermore, a clear signature of the sequential double-electron above threshold ionization process can be seen in the single- and double-electron energy distributions when a linearly polarized pulse is being used.[4pt] [1] I. F. Barna, J. Wang, and J. Burgdorfer, Phys. Rev. A. 73, 023402 (2006) [0pt] [2] T-G Lee, M. S. Pindzola and F. Robicheaux, Phys. Rev. A. 79, 053420 (2009)

  9. Optical properties of carbon nanostructures produced by laser irradiation on chemically modified multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Santiago, Enrique Vigueras; López, Susana Hernández; Camacho López, Marco A.; Contreras, Delfino Reyes; Farías-Mancilla, Rurik; Flores-Gallardo, Sergio G.; Hernández-Escobar, Claudia A.; Zaragoza-Contreras, E. Armando

    2016-10-01

    This research focused on the nanosecond (Nd: YAG-1064 nm) laser pulse effect on the optical and morphological properties of chemically modified multi-walled carbon nanotubes (MWCNT). Two suspensions of MWCNT in tetrahydrofuran (THF) were prepared, one was submitted to laser pulses for 10 min while the other (blank) was only mechanically homogenized during the same time. Following the laser irradiation, the suspension acquired a yellow-amber color, in contrast to the black translucent appearance of the blank. UV-vis spectroscopy confirmed this observation, showing the blank a higher absorption. Additionally, photoluminescence measurements exhibited a broad blue-green emission band both in the blank and irradiated suspension when excited at 369 nm, showing the blank a lower intensity. However, a modification in the excitation wavelength produced a violet to green tuning in the irradiated suspension, which did not occur in the blank. Lastly, the electron microscopy analysis of the treated nanotubes showed the abundant formation of amorphous carbon, nanocages, and nanotube unzipping, exhibiting the intense surface modification produced by the laser pulse. Nanotube surface modification and the coexistence with the new carbon nanostructures were considered as the conductive conditions for optical properties modification.

  10. Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

    2014-10-01

    We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

  11. Hyperspectral and gated ICCD imagery for laser irradiated carbon materials

    NASA Astrophysics Data System (ADS)

    Roberts, Charles D.; Acosta, Roberto A.; Marciniak, Michael A.; Perram, Glen P.

    2013-02-01

    New optical diagnostics for studying laser ablation and induced combustion for carbon materials are key to monitoring the evolving, spatial distribution of the gas plume. We are developing high speed imaging FTIR and gated ICCD imagery for materials processing, manufacture process control, and high energy laser applications. The results from two projects will be discussed. First, an imaging Fourier Transform Spectrometer with a 320 x 256 InSb focal plane array frames at 1.9 kHz with a spatial resolution of 1 mm and spectral resolution of up to 0.25 cm-1. Gas phase plumes above the surface of laser-irradiated black plexiglass, fiberglass and painted thin metals have been spectrally resolved. Molecular emission from CO, CO2, H2O, and hydrocarbons is readily identified. A line-by-line radiative transfer model is used to derive movies for specie concentrations and temperatures. Second, excimer laser pulsed ablation of bulk graphite into low-pressure (0.05 - 1 Torr) argon generates highly ionized, high speed (M>40) plumes. A gated, intensified CCD camera with band pass filtering has been used to generate plume imagery with temporal resolution of 10ns. The Sedov-Taylor shock model characterizes the propagation of the shock front if the dimensionality of the plume is allowed to deviate from ideal spherical expansion. A drag model is more appropriate when the plume approaches extinction (~10 μs) and extends the characterization into the far field. Conversion of laser pulse energy to the shock is efficient.

  12. Beneficial Effects of Synchronous Laser Irradiation on the Characteristics of Cold-Sprayed Copper Coatings

    NASA Astrophysics Data System (ADS)

    Li, Bo; Yang, Lijing; Li, Zhihong; Yao, Jianhua; Zhang, Qunli; Chen, Zhijun; Dong, Gang; Wang, Liang

    2015-06-01

    Cold spray (CS) is an emerging materials deposition technique in which metallic particles are accelerated to a high velocity in a supersonic gas flow and then impinged onto a substrate to form a coating at a temperature well below the melting point of sprayed materials. The coating microstructure and properties are greatly influenced by particle preheating and substrate softening. This article presents a study of CS process of copper powder, with assistance of synchronous laser irradiation. The influence of synchronous laser irradiation on the Cu coating characteristics was investigated. The results show that the coating surface with laser irradiation is smoother than that without laser irradiation. The peak coating thickness is increased by about 70% as synchronous laser irradiation is employed, indicating an improvement in deposition efficiency. It is also found that with synchronous laser irradiation the coating is denser and the coating-substrate interfacial bonding is better as compared with that without laser irradiation. Moreover, the EDS and XRD analyses find Cu oxidation occurrence in the SLD coating, but the oxide is trivial. The aforementioned improvements on the coating largely arise from particle preheating and substrate softening by synchronous laser irradiation in the CS process.

  13. Large amplitude electromagnetic solitons in intense laser plasma interaction

    NASA Astrophysics Data System (ADS)

    Li, Bai-Wen; S, Ishiguro; M, Skoric M.

    2006-09-01

    This paper shows that the standing, backward- and forward-accelerated large amplitude relativistic electromagnetic solitons induced by intense laser pulse in long underdense collisionless homogeneous plasmas can be observed by particle simulations. In addition to the inhomogeneity of the plasma density, the acceleration of the solitons also depends upon not only the laser amplitude but also the plasma length. The electromagnetic frequency of the solitons is between about half and one of the unperturbed electron plasma frequency. The electrostatic field inside the soliton has a one-cycle structure in space, while the transverse electric and magnetic fields have half-cycle and one-cycle structure respectively. Analytical estimates for the existence of the solitons and their electromagnetic frequencies qualitatively coincide with our simulation results.

  14. [Use of the thermal laser effect of laser irradiation for cardiovascular applications exemplified by the Nd:YAG laser].

    PubMed

    Ischinger, T; Coppenrath, K; Weber, H; Enders, S; Unsöld, E; Hessel, S

    1989-11-01

    Techniques of percutaneous transluminal application of laser energy for vessel recanalization have been used clinically since 1983. The commonly used Nd:YAG and argon lasers achieve ablation of atherosclerotic plaques by thermal action (vaporization). In order to reduce undesirable thermal damage in the neighborhood of the target tissue and to avoid vessel perforation, optimal irradiation parameters, modified (atraumatic) fiber tips (hot tips, sapphires), and steerable catheter systems needed to be implemented. Favorable results from peripheral application have encouraged use in the coronary circulation. More recently, coagulative tissue effects of circumferential irradiation of the vessel wall during balloon dilatation have been used for stabilization of acute and late results after mechanical balloon angioplasty. Enhancement of the differential light absorption of atherosclerotic plaque by use of biological dyes may further improve selective intravascular laser application. Intraoperative ECG-guided laser coagulation of arrhythmogenic areas of myocardium is a method for treatment of malignant arrhythmias. Transluminal non-operative application of myocardial laser photocoagulation has now been tested experimentally and shown to be safe and effective. There was no arrhythmogenicity or thermal damage of coronary arteries associated with this method. Innovative techniques such as nanosecond pulsed excimer lasers (athermal action) and development of "intelligent" lasers--which are equipped with spectroscopy-guided feedback systems for plaque recognition--have opened new perspectives and will further improve safety and efficacy of clinical laser application. However, according to current experience, the thermally acting Nd:YAG laser is an effective and versatile mode of laser therapy for selected cardiovascular indications. PMID:2532812

  15. [Use of the thermal laser effect of laser irradiation for cardiovascular applications exemplified by the Nd:YAG laser].

    PubMed

    Ischinger, T; Coppenrath, K; Weber, H; Enders, S; Unsöld, E; Hessel, S

    1989-11-01

    Techniques of percutaneous transluminal application of laser energy for vessel recanalization have been used clinically since 1983. The commonly used Nd:YAG and argon lasers achieve ablation of atherosclerotic plaques by thermal action (vaporization). In order to reduce undesirable thermal damage in the neighborhood of the target tissue and to avoid vessel perforation, optimal irradiation parameters, modified (atraumatic) fiber tips (hot tips, sapphires), and steerable catheter systems needed to be implemented. Favorable results from peripheral application have encouraged use in the coronary circulation. More recently, coagulative tissue effects of circumferential irradiation of the vessel wall during balloon dilatation have been used for stabilization of acute and late results after mechanical balloon angioplasty. Enhancement of the differential light absorption of atherosclerotic plaque by use of biological dyes may further improve selective intravascular laser application. Intraoperative ECG-guided laser coagulation of arrhythmogenic areas of myocardium is a method for treatment of malignant arrhythmias. Transluminal non-operative application of myocardial laser photocoagulation has now been tested experimentally and shown to be safe and effective. There was no arrhythmogenicity or thermal damage of coronary arteries associated with this method. Innovative techniques such as nanosecond pulsed excimer lasers (athermal action) and development of "intelligent" lasers--which are equipped with spectroscopy-guided feedback systems for plaque recognition--have opened new perspectives and will further improve safety and efficacy of clinical laser application. However, according to current experience, the thermally acting Nd:YAG laser is an effective and versatile mode of laser therapy for selected cardiovascular indications.

  16. Low- and high-intensity lasers in the treatment of herpes simplex virus 1 infection.

    PubMed

    Bello-Silva, Marina Stella; de Freitas, Patricia Moreira; Aranha, Ana Cecília Corrêa; Lage-Marques, José Luiz; Simões, Alyne; de Paula Eduardo, Carlos

    2010-02-01

    Herpes simplex virus (HSV) is one of the most common viral infections of the human being. Although most of the seropositive persons do not manifest symptoms, infected individuals may present recurrent infections, characterized by cold sores. HSV-1 infection can result in potentially harmful complications in some patients, especially in those with compromised immunity. We report a clinical case of a patient with severe oral HSV-1 infection in the lower lip. The treatment of the lesions with the association of high-intensity (erbium-doped yttrium aluminum garnet, 2.94 mum, 80 mJ/pulse, 2-4 Hz) and low-intensity (indium gallium aluminum phosphide, 660 nm, 3.8 J/cm(2), 10 mW) lasers has not been reported in the literature. During treatment, no systemic or topical medication was used. Pain sensitivity was completely gone after the first irradiation with the low-intensity laser. During the healing process, lesions were traumatized twice, on the days 4 and 7. Even though the lesions were completely healed within 10 days. PMID:19712025

  17. Frequency conversion of high-intensity, femtosecond laser pulses

    SciTech Connect

    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

  18. Coherent combs in ionization by intense and short laser pulses

    NASA Astrophysics Data System (ADS)

    Krajewska, K.; Kamiński, J. Z.

    2016-03-01

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented.

  19. Counterintuitive alignment of H2(+) in intense femtosecond laser fields.

    PubMed

    Frasinski, L J; Plumridge, J; Posthumus, J H; Codling, K; Taday, P F; Divall, E J; Langley, A J

    2001-03-19

    The multiphoton ionization of H2 has been studied using laser pulses of 266 nm wavelength, 250 fs duration, and 5x10(13) W/cm(2) peak intensity. Dissociation of H2(+) via one-photon absorption proceeds through two channels with markedly different proton angular distributions. The lower-energy channel (2.6 eV kinetic energy release) is produced in the bond softening mechanism, which generates parallel alignment. The higher-energy channel (3.5 eV) originates from population trapping in a light-induced bound state, where bond hardening generates orthogonal, counterintuitive alignment.

  20. Measurement of the relaxation time of hot electrons in laser-solid interaction at relativistic laser intensities

    SciTech Connect

    Chen, H; Shepherd, R; Chung, H K; Dyer, G; Faenov, A; Fournier, K B; Hansen, S B; Hunter, J; Kemp, A; Pikuz, T; Ping, Y; Widmann, K; Wilks, S C; Beiersdorfer, P

    2006-08-22

    The authors have measured the relaxation time of hot electrons in short pulse laser-solid interactions using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. Employing laser intensities of 10{sup 17}, 10{sup 18}, and 10{sup 19} W/cm{sup 2}, they find increased laser coupling to hot electrons as the laser intensity becomes relativistic and thermalization of hot electrons at timescales on the order of 10 ps at all laser intensities. They propose a simple model based on collisional coupling and plasma expansion to describe the rapid relaxation of hot electrons. The agreement between the resulting K{sub {alpha}} time-history from this model with the experiments is best at highest laser intensity and less satisfactory at the two lower laser intensities.

  1. Ultrastructural changes in liver after the test exposition of laser irradiation

    SciTech Connect

    Dubrzynski, A.; Roszkiewicz, A.; Bautembach, S.

    1986-12-01

    The aim of this research was to verify characteristic morphological changes in the liver with regard to survival time after laser irradiation. The duration of irradiation was constant. For the purpose of irradiation we used a helium-neon laser. The value of the energy absorbed during the exposition amounted to about 2.5 J. Segments from the irradiated liver field of rats were taken directly after decapitation following different times of survival, and the changes were estimated in an ultrastructural microscope. Our results showed dependence of certain morphological changes (perceptible only by ultrastructural examination) on the time of survival after irradiation.

  2. Ultlra-intense laser-matter interactions at extreme parameters

    SciTech Connect

    Hegellich, Bjorn M

    2010-11-24

    thinnest of these at less than 3nm, i.e. 1/300 of the laser wavelength, are even thinner than the plasma skin depth. This drastically changes the laser-matter interaction physics leading to the emergence of new particle acceleration mechanisms, like Break-Out Afterburner (BOA) Acceleration, driven by a relativistic, kinetic plasma instability or Radiation Pressure Acceleration (RPA), driven by stabilized charge separation. Furthermore, these interactions also produce relativistic high harmonics in forward direction as well as mono-en,ergetic electron pulses which might lend itself as a source for fully coherent Thomson scattering in the mulit-keV regime. In this talk I will present an overview over the laser developments leading to this paradigm change as well as over the theoretical and experimental results following from it. Specifically we were able for the first time to demonstrate BOA acceleration of Carbon ions to up to 0.5 GeV using a laser pulse with {approx}10{sup 20} W/cm{sup 2} intensity and showing the scalability of this mechanism into regimes relevant for Hadron Therapy. We were further able to demonstrate mono-energetic electron break-out from ultrathin targets, as a first step towards a flying mirror.

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

    SciTech Connect

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

    2015-02-15

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

  4. A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: the problem of Coulomb explosion

    NASA Astrophysics Data System (ADS)

    Bulgakova, Nadezhda M.; Stoian, Razvan; Rosenfeld, Arkadi; Marine, Wladimir; Campbell, Eleanor E.

    2004-09-01

    We present a continuum model, based on a drift-diffusion approach, aimed to describe the dynamics of electronic excitation, heating and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, under near-infrared femtosecond irradiation regimes, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, simulations of UV nanosecond pulsed laser interaction with bulk silicon have pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.

  5. A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: The problem of Coulomb explosion

    NASA Astrophysics Data System (ADS)

    Bulgakova, N. M.; Stoian, R.; Rosenfeld, A.; Hertel, I. V.; Marine, W.; Campbell, E. E. B.

    2005-07-01

    We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.

  6. Hydrodynamic study of the behavior of chondroitin sulphate under nondestructive laser irradiation of cartilage

    NASA Astrophysics Data System (ADS)

    Sobol, Emil N.; Omelchenko, Alexander I.; Sviridov, Alexander P.; Harding, Stephen E.; Jumel, Kornelia; Jones, Nicholas

    2000-06-01

    The effects of laser irradiation on molecular mass and conformation of pure chondroitin sulphate dissolved in phosphate buffered saline were investigated using size exclusion chromatography/multi-angle light scattering (SEC/MALS) and sedimentation velocity in the analytical ultracentrifuge. In addition, cartilage pieces immersed in buffer were irradiated with a laser in order to study whether cartilage components may diffuse away from the matrix and into the surrounding aqueous medium as a result of laser treatment. Size exclusion chromatography/multi-angle light scattering and sedimentation velocity measurements showed that (a) laser irradiation decreases the molecular mass of chondroitin sulphate and (b) laser irradiation of cartilage induces diffusion of macromolecules into the medium. The results obtained allow us to understand the mechanism of stress relaxation and structural alterations in cartilage under non- destructive laser radiation.

  7. On the formation of Na nanoparticles in femtosecond-laser irradiated glasses

    SciTech Connect

    Jiang Nan; Su Dong; Spence, John C. H.; Qiu Jianrong

    2010-03-15

    This work discusses the response of Na to both high-energy electrons and femtosecond-laser (fs-laser) pulses in the soda-lime glass. The evidence for different responses of Na to high-energy electron irradiation between glasses with and without fs-laser irradiation suggests that the chemical and/or physical states of Na in the fs-laser irradiated glass are different from those in the original glass. Fs-laser pulses in the glass may be able to neutralize Na, which may form clusters. These results suggest that close attention should be paid to the defects associated with Na when optical or physical data are interpreted in fs-laser irradiated Na glasses.

  8. Generation of high-quality mega-electron volt proton beams with intense-laser-driven nanotube accelerator

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Tanaka, M.

    2013-04-01

    An ion acceleration scheme using carbon nanotubes (CNTs) is proposed, in which embedded fragments of low-Z materials are irradiated by an ultrashort intense laser to eject substantial numbers of electrons. Due to the resultant characteristic electrostatic field, the nanotube and embedded materials play the roles of the barrel and bullets of a gun, respectively, to produce highly collimated and quasimonoenergetic ion beams. Three-dimensional particle simulations, that take all the two-body Coulomb interactions into account, demonstrate generation of quasimonoenergetic MeV-order proton beams using nanometer-size CNT under a super-intense electrostatic field ˜1014 V m-1.

  9. Melanosomes are a primary target of Q-switched ruby laser irradiation in guinea pig skin

    SciTech Connect

    Polla, L.L.; Margolis, R.J.; Dover, J.S.; Whitaker, D.; Murphy, G.F.; Jacques, S.L.; Anderson, R.R.

    1987-09-01

    The specific targeting of melanosomes may allow for laser therapy of pigmented cutaneous lesions. The mechanism of selective destruction of pigmented cells by various lasers, however, has not been fully clarified. Black, brown, and albino guinea pigs were exposed to optical pulses at various radiant exposure doses from a Q-switched, 40 nsec, 694 nm ruby laser. Biopsies were analyzed by light and electron microscopy (EM). Albino animals failed to develop clinical or microscopic evidence of cutaneous injury after irradiation. In both black and brown animals, the clinical threshold for gross change was 0.4 J/cm2, which produced an ash-white spot. By light microscopy, alterations appeared at 0.3 J/cm2 and included separation at the dermoepidermal junction, and the formation of vacuolated epidermal cells with a peripheral cytoplasmic condensation of pigment. By EM, enlarged melanosomes with a central lucent zone were observed within affected epidermal cells at 0.3 J/cm2. At 0.8 and 1.2 J/cm2, individual melanosomes were more intensely damaged and disruption of melanosomes deep in the hair papillae was observed. Dermal-epidermal blisters were formed precisely at the lamina lucida, leaving basal cell membranes and hemidesmosomes intact. Possible mechanisms for melanosomal injury are discussed. These observations show that the effects of the Q-switched ruby laser are melanin-specific and melanin-dependent, and may be useful in the selective destruction of pigmented as well as superficial cutaneous lesions.

  10. Nanostructure evolution in joining of Al and Fe nanoparticles with femtosecond laser irradiation

    SciTech Connect

    Jiao, Z.; Huang, H.; Zhou, Y. E-mail: nzhou@uwaterloo.ca; Liu, L.; Hu, A.; Duley, W.; He, P. E-mail: nzhou@uwaterloo.ca

    2014-04-07

    The joining of Al-Fe nanoparticles (NPs) by femtosecond (fs) laser irradiation is reported in this paper. Fe and Al NPs were deposited on a carbon film in vacuum via fs laser ablation. Particles were then exposed to multiple fs laser pulses at fluences between 0.5 and 1.3 mJ/cm{sup 2}. Transmission Electron Microscopy (TEM) and Electron Diffraction X-ray observations indicate that Al and Fe NPs bond to each other under these conditions. For comparison, bonding of Al to Al and Fe to Fe NPs was also investigated. The nanostructure, as observed using TEM, showed that individual Al NPs were monocrystalline while individual Fe NPs were polycrystalline prior to joining and that these structures are retained after the formation of Al-Al and Fe-Fe NPs. Al-Fe NPs produced by fs laser joining exhibited a mixed amorphous and crystalline phase at the interface. Bonding is suggested to originate from intermixing within a region of high field intensity between particles.

  11. Radiation reaction and resulting photon emission from laser-irradiated solid targets

    NASA Astrophysics Data System (ADS)

    Stark, David; Arefiev, Alexey; Hegelich, Manuel

    2014-10-01

    Once completed, an ongoing upgrade of the Texas-PW laser system would allow us to achieve on-target laser intensities of up to 5 ×1022 W/cm2. As experimental confirmation of the radiation reaction force and the variety of models describing it remains a challenge, here we present a scenario that would enable us to observe the effect by detecting the resulting photon emission. A laser with our planned intensity could accelerate an electron to hundreds of MeV, but the radiation reaction and thus the photon emission would be relatively weak if the electron co-propagates with the wave. We consider a solid density target irradiated by a laser beam so that strong fields are generated due to charge separation. These fields can alter the electron trajectories, leading to strong radiation reaction and photon emission in the focal spot. Simulating this interaction using the particle-in-cell code EPOCH, we perform a target density scan that allows us to optimize the fraction of the laser energy converted into photons and to determine the photon spectrum. Knowing the spectrum and the angular emission is critical for measurements in the lab, since these photons must be distinguished from those from other processes. We use HPC resources from the Texas Advanced Computing Center. This work is supported by DOD-Air Force Contract No. FA9550-14-1-0045, US DOE Contract No. DE-FG02-04ER54742, and DOE SCGF by ORISE-ORAU under Contract No. DE-AC05-06OR23100.

  12. Simulations of controlled spectral emission of Al plasmas generated by temporally tailored laser irradiation

    SciTech Connect

    Colombier, J. P.; Guillermin, M.; Garrelie, F.; Audouard, E.; Stoian, R.

    2010-10-08

    Hydrodynamics simulations and irradiation experiments were performed to correlate ul-trashort intensity envelopes of the laser fields and thermodynamical states reached by the emerging plasma phase in ablation regimes. We discuss the efficiency of energy coupling as a function of different intensity envelopes and the resulting temperature, density and ionization states since the energy delivery rate is an essential factor that predetermines the material thermodynamic evolution. Subsequently, we examine the plasma composition in calculating the proportion of neutral/ion species typical of LIBS signals and comparing it with neutral/ion ratios given by experimental results. Moreover, the calculations allow to investigate the efficiency of nanoparticles generation from materials subjected to different heating rates. These can be related to hydrodynamic ejection of nanosized liquid layers upon the action of mechanic waves. With support from numerical simulations of the hydrodynamic advance of the excited matter, experiments revealed that mastering intensity envelopes of ultrashort laser pulse leads to further control on the ablation products. Emerging plasma phase in a hot state generates specific spectral emission patterns that can serve as indicators for its controlled formation and kinetic evolution.

  13. Laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) by single-mode fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kawaguchi, Yoshizo; Sato, Tadatake; Narazaki, Aiko; Kurosaki, Ryozo; Muramatsu, Mayu; Harada, Yoshihisa; Anzai, Kenji; Aoyama, Mitsuaki; Matsushita, Masafumi; Furukawa, Koichi; Nishino, Michiteru; Fujisaki, Akira; Miyato, Taizo; Kayahara, Takashi

    2014-03-01

    We report on the laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) with a cw IR fiber laser (single-mode fiber laser, average power: 350 W). CFRTP is a high strength composite material with a lightweight, and is increasingly being used various applications. A well-defined cutting of CFRTP which were free of debris and thermal-damages around the grooves, were performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scanpass method.

  14. Investigations of ultrafast charge dynamics in laser-irradiated targets by a self probing technique employing laser driven protons

    NASA Astrophysics Data System (ADS)

    Ahmed, H.; Kar, S.; Cantono, G.; Nersisyan, G.; Brauckmann, S.; Doria, D.; Gwynne, D.; Macchi, A.; Naughton, K.; Willi, O.; Lewis, C. L. S.; Borghesi, M.

    2016-09-01

    The divergent and broadband proton beams produced by the target normal sheath acceleration mechanism provide the unique opportunity to probe, in a point-projection imaging scheme, the dynamics of the transient electric and magnetic fields produced during laser-plasma interactions. Commonly such experimental setup entails two intense laser beams, where the interaction produced by one beam is probed with the protons produced by the second. We present here experimental studies of the ultra-fast charge dynamics along a wire connected to laser irradiated target carried out by employing a 'self' proton probing arrangement - i.e. by connecting the wire to the target generating the probe protons. The experimental data shows that an electromagnetic pulse carrying a significant amount of charge is launched along the wire, which travels as a unified pulse of 10s of ps duration with a velocity close to speed of light. The experimental capabilities and the analysis procedure of this specific type of proton probing technique are discussed.

  15. Low power laser irradiation does not affect the generation of signals in a sensory receptor

    SciTech Connect

    Lundeberg, T.; Zhou, J.

    1989-01-01

    The effect of low power Helium-Neon (He-Ne) and Gallium-Arsenide (Ga-As) laser on the slowly adapting crustacean stretch receptor was studied. The results showed that low power laser irradiation did not affect the membrane potential of the stretch receptor. These results are discussed in relation to the use of low power laser irradiation on the skin overlaying acupuncture points in treatment of pain syndrome.

  16. Low-power laser irradiation enhance macrophage phagocytic capacity through Src activation

    NASA Astrophysics Data System (ADS)

    Wu, Shengnan; Zhou, Feifan; Xing, Da

    2012-03-01

    Phagocytosis and subsequent degradation of pathogens by macrophages play a pivotal role in host innate immunity in mammals. Laser irradiation has been found to produce photobiological effects with evidence of interference with organic functions. In this study, we focused our attention on the effects of He-Ne laser on the phagocytic activity of macrophages, the regulation mechanism of phagocytosis was also discussed. Our results indicated that Low-power laser irradiation can enhance the phagocytosis of macrophage through activation of Src.

  17. Paramount Deuteron Acceleration Using High-Intensity Short Laser Pulses

    NASA Astrophysics Data System (ADS)

    Yu, F.; Raymond, A.; Zulick, C.; Willingale, L.; Krushelnick, K.; Maksimchuk, A.; Petrov, G.; Davis, J.

    2012-10-01

    It has long been a challenge to efficiently generate laser-driven ion beams having none-proton ions as the dominant species since protons are generally present as contamination layers on the target surface. During recent experiments at the University of Michigan, ion beams composed mainly of deuterons were produced with only a small relative number of protons and oxygen ions. The experiments were performed with the 400 fs, 20 TW T-cubed laser which has focused intensity up to 4*10^19 W/cm^2 at 1053 nm and ASE intensity contrast of 10-7. The accelerated deuterons originate from liquid deuterium oxide deposited on both the front and rear surfaces of a cryogenically cooled Cu target (normally at -160C) by spraying ˜50 microliters of heavy water from 2 nozzles in the vicinity of the target's front and rear. The ion beams had a Maxwellian spectrum with maximum energy of 8 MeV for deuterons and 10 MeV for protons. Using a Thomson parabola ion spectrometer system combined with CR39 indicated that the forward-propagating deuteron beam had about 10^12 ions per steradian (integrated over spectrum). The FWHM of the beam was 20 degrees, ideal for applications involving neutron generation and isotope activation.

  18. First demonstration of a free-electron laser driven by electrons from a laser irradiated photocathode

    NASA Astrophysics Data System (ADS)

    Curtin, Mark; Bennett, Glenn; Burke, Robert; Benson, Stephen; Madey, J. M. J.

    Results are reported from the first observation of a free-electron laser (FEL) driven by an electron beam from a laser-irradiated photocathode. The Rocketdyne/Stanford FEL achieved sustained oscillations lasting over three hours and driven by photoelectrons accelerated by the Stanford Mark III radio-frequency linac. A LaB6 cathode, irradiated by a tripled Nd:YAG mode-locked drive laser, is the source of the photoelectrons. The drive laser, operating at 95.2 MHz, is phase-locked to the 30th subharmonic of the S-band linac. Peak currents in excess of 125 amps are observed and delivered to the Rocketdyne two-meter undulator, which is operated as a stand-alone oscillator. The electron beam has an energy spread of 0.8 percent (FWHM) at 38.5 MeV and an emittance, at the undulator, comparable to that observed for thermionic operation of the electron source. Small signal gain in excess of 150 percent is observed. Preliminary estimates of the electron beam brightness deliverable to the undulator range from 3.5 to 5.0 x 10 to the 11 amps/sq m.

  19. Influence of periodic compressible vortices on laser beam intensity

    NASA Astrophysics Data System (ADS)

    Weston, C. P.

    1982-12-01

    This study explored the effect of narrow-band, vortex-induced density fluctuations on the beam quality of a laser propagated through the fluctuating flow. The research was a dual investigation. First, the ability to create and characterize 'tailored', fluctuating flows was explored. Second, the degradation of the laser beam due to these various flows was assessed. The flows of periodic vortices were created by cylindrical rods placed at the exit plane of a 1 cm by 10 cm rectangular free jet issuing air at M = .6. Reynolds number based on rod diameter varied from 4,600 to 110,000. Mean and fluctuating mass flux, total pressure and static pressure time histories of the flows were measured in order to derive fluid eddy passage frequency, eddy length and periodic density fluctuation data. Schlieren photographs were obtained for further assessment of the flow fields. A nominal 1 mW laser beam was propagated at two wavelengths transversely through the periodic portion of each flow. The far field beam cross-section was analyzed to determine beam intensity degradation. A Strehl ratio for each flow field was deduced from pseudo-quantitative data.

  20. Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components.

    PubMed

    Benetti, Carolina; Ana, Patricia Aparecida; Bachmann, Luciano; Zezell, Denise Maria

    2015-12-01

    The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

  1. Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components.

    PubMed

    Benetti, Carolina; Ana, Patricia Aparecida; Bachmann, Luciano; Zezell, Denise Maria

    2015-12-01

    The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures. PMID:26555304

  2. Optothermal response of plasmonic nanofocusing lens under picosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Du, Z.; Chen, C.; Traverso, L.; Xu, X.; Pan, L.; Chao, I.-H.; Lavine, A. S.

    2014-03-01

    This work studied the optothermal response of plasmonic nanofocusing structures under picosecond pulsed laser irradiation. The surface plasmon polariton is simulated to calculate the optical energy dissipation as the Joule heating source and the thermal transport process is studied using a two temperature model (TTM). At the picosecond time scale that we are interested in, the Fourier heat equation is used to study the electron thermal transport and the hyperbolic heat equation is used to study the lattice thermal transport. For comparison, the single temperature model (STM) is also studied. The difference between TTM and STM indicates that TTM provides more accurate estimates in the picosecond time scale and the STM results are only reliable when the local electron and lattice temperature difference is negligible.

  3. Enhancement of hydrogen gas sensing of nanocrystalline nickel oxide by pulsed-laser irradiation.

    PubMed

    Soleimanpour, A M; Khare, Sanjay V; Jayatissa, Ahalapitiya H

    2012-09-26

    This paper reports the effect of post-laser irradiation on the gas-sensing behavior of nickel oxide (NiO) thin films. Nanocrystalline NiO semiconductor thin films were fabricated by a sol-gel method on a nonalkaline glass substrate. The NiO samples were irradiated with a pulsed 532-nm wavelength, using a Nd:YVO(4) laser beam. The effect of laser irradiation on the microstructure, electrical conductivity, and gas-sensing properties was investigated as a function of laser power levels. It was found that the crystallinity and surface morphology were modified by the pulsed-laser irradiation. Hydrogen gas sensors were fabricated using both as-deposited and laser-irradiated NiO films. It was observed that the performance of gas-sensing characteristics could be changed by the change of laser power levels. By optimizing the magnitude of the laser power, the gas-sensing property of NiO thin film was improved, compared to that of as-deposited NiO films. At the optimal laser irradiation conditions, a high response of NiO sensors to hydrogen molecule exposure of as little as 2.5% of the lower explosion threshold of hydrogen gas (40,000 ppm) was observed at 175 °C.

  4. Microstructures and properties of materials under repeated laser irradiation

    SciTech Connect

    Averback, Robert; Bellon, Pascal

    2007-02-12

    This research program has explored the stability of alloys under pulsed laser irradiation. Two primary directions were investigated: (i) phase transitions during a single laser pulse, and (ii) phase stability under repeated laser irradiation. The first theme was primarily concerned with both the crystalline to amorphous phase transition and the transition of liquids and glasses to crystalline matter. The second project examined the phase evolution during laser pulsing in situations where plastic deformation was prevalent (high-energy laser pulses). Both computer simulation and experimental programs were undertaken. Our work using computer simulations had several notable successes. For the work connected with multiple pulsing, we used molecular dynamics (MD) to simulate the behavior of alloys under severe plastic deformation. We found that during high strain-rate deformation atomic mixing of chemical species is random, independent of the detailed thermochemical properties of the system. This result contrasts with recent reports. In this work, we also developed two new methods of analyzing atomic mixing, one is based on relative mean square displacements (RMSD) of atoms and the other, Burgers vector analysis (BVA), on nearest neighbor displacements. The RMSD analysis is valuable in that it specifies the length scales over which deformation processes take place, and we applied it to understand deformation in nanocrystalline, amorphous and large-grained systems. The BVA analysis, on the other hand, reveals if the damage is homogeneous. Finally we showed that at elevated temperatures, the phase stability is not determined from a simple competition between shearing events and vacancy diffusion, which has long been assumed, but rather atomic mixing in the shearing events is temperature dependent. This work is significant in that it elucidates the fundamental mechanisms that underlie high strain rate deformation, and it provides computational tools for other researchers to

  5. Ultraviolet pulsed laser irradiation of multi-walled carbon nanotubes in nitrogen atmosphere

    SciTech Connect

    Pérez del Pino, Ángel Cabana, Laura; Tobias, Gerard; György, Enikö; Ballesteros, Belén

    2014-03-07

    Laser irradiation of randomly oriented multi-walled carbon nanotube (MWCNT) networks has been carried out using a pulsed Nd:YAG UV laser in nitrogen gas environment. The evolution of the MWCNT morphology and structure as a function of laser fluence and number of accumulated laser pulses has been studied using electron microscopies and Raman spectroscopy. The observed changes are discussed and correlated with thermal simulations. The obtained results indicate that laser irradiation induces very fast, high temperature thermal cycles in MWCNTs which produce the formation of different nanocarbon forms, such as nanodiamonds. Premelting processes have been observed in localized sites by irradiation at low number of laser pulses and low fluence values. The accumulation of laser pulses and the increase in the fluence cause the full melting and amorphization of MWCNTs. The observed structural changes differ from that of conventional high temperature annealing treatments of MWCNTs.

  6. Ultraviolet pulsed laser irradiation of multi-walled carbon nanotubes in nitrogen atmosphere

    NASA Astrophysics Data System (ADS)

    Pérez del Pino, Ángel; György, Enikö; Cabana, Laura; Ballesteros, Belén; Tobias, Gerard

    2014-03-01

    Laser irradiation of randomly oriented multi-walled carbon nanotube (MWCNT) networks has been carried out using a pulsed Nd:YAG UV laser in nitrogen gas environment. The evolution of the MWCNT morphology and structure as a function of laser fluence and number of accumulated laser pulses has been studied using electron microscopies and Raman spectroscopy. The observed changes are discussed and correlated with thermal simulations. The obtained results indicate that laser irradiation induces very fast, high temperature thermal cycles in MWCNTs which produce the formation of different nanocarbon forms, such as nanodiamonds. Premelting processes have been observed in localized sites by irradiation at low number of laser pulses and low fluence values. The accumulation of laser pulses and the increase in the fluence cause the full melting and amorphization of MWCNTs. The observed structural changes differ from that of conventional high temperature annealing treatments of MWCNTs.

  7. Role of laser fluence in protein synthesis of cultured DRG neurons following low-level laser irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Liqin; Qiu, Caimin; Wang, Yuhua; Zeng, Yixiu; Yang, Hongqin; Zhang, Yanding; Xie, Shusen

    2014-11-01

    Low-level lasers have been used to relieve pain in clinical for many years. But the mechanism is not fully clear. In animal models, nitric oxide (NO) has been reported involving in the transmission and modulation of nociceptive signals. So the objective of this study was to establish whether low-level laser with different fluence could stimulate the production of nitric oxide synthese (NOS), which produces NO in cultured primary dorsal root ganglion neurons (DRG neurons). The primary DRG neurons were isolated from healthy Sprague Dawley rats (8-12 weeks of age) and spread on 35 mm culture dishes specially used for confocal microscopy. 24 hours after spreading, cells were irradiated with 658 nm laser for two consecutive days at the energy density of 20, 40, 60 and 80 mJ·cm-2 respectively. Control groups were not exposed to the laser, but were kept under the same conditions as the irradiated ones. The synthesis of NOS after laser irradiation was detected by immunofluorescence assay, and the changes of NOS were evaluated using confocal microscopy and Image J software. The results showed that all the laser fluence could promote the production of NOS in DRG neurons, especially the 60 mJ·cm-2 . These results demonstrated that low-level laser irradiation could modify protein synthesis in a dose- or fluence- dependent manner, and indicated that low-level laser irradiation might achieve the analgesic effect through modulation of NO production.

  8. Microsized structures assisted nanostructure formation on ZnSe wafer by femtosecond laser irradiation

    SciTech Connect

    Wang, Shutong; Feng, Guoying E-mail: zhoush@scu.edu.cn

    2014-12-22

    Micro/nano patterning of ZnSe wafer is demonstrated by femtosecond laser irradiation through a diffracting pinhole. The irradiation results obtained at fluences above the ablation threshold are characterized by scanning electron microscopy. The microsized structure with low spatial frequency has a good agreement with Fresnel diffraction theory. Laser induced periodic surface structures and laser-induced periodic curvelet surface structures with high spatial frequency have been found on the surfaces of microsized structures, such as spikes and valleys. We interpret its formation in terms of the interference between the reflected laser field on the surface of the valley and the incident laser pulse.

  9. Analytical model for interaction of short intense laser pulse with solid target

    SciTech Connect

    Luan, S. X.; Ma, G. J.; Yu, Wei; Yu, M. Y.; Zhang, Q. J.; Sheng, Z. M.; Murakami, M.

    2011-04-15

    A simple but comprehensive two-dimensional analytical model for the interaction of a normally incident short intense laser pulse with a solid-density plasma is proposed. Electron cavitation near the target surface by the laser ponderomotive force induces a strong local electrostatic charge-separation field. The cavitation makes possible mode conversion of the laser light into longitudinal electron oscillation at laser frequency, even for initial normal incidence of laser pulse. The intense charge-separation field in the cavity can significantly enhance the laser induced uxB electron oscillation at twice laser frequency to density levels even higher than that of the initial target.

  10. Bactericidal Effects of Diode Laser Irradiation on Enterococcus faecalis Using Periapical Lesion Defect Model

    PubMed Central

    Nagayoshi, Masato; Nishihara, Tatsuji; Nakashima, Keisuke; Iwaki, Shigetsugu; Chen, Ker-Kong; Terashita, Masamichi; Kitamura, Chiaki

    2011-01-01

    Objective. Photodynamic therapy has been expanded for use in endodontic treatment. The aim of this study was to investigate the antimicrobial effects of diode laser irradiation on endodontic pathogens in periapical lesions using an in vitro apical lesion model. Study Design. Enterococcus faecalis in 0.5% semisolid agar with a photosensitizer was injected into apical lesion area of in vitro apical lesion model. The direct effects of irradiation with a diode laser as well as heat produced by irradiation on the viability of microorganisms in the lesions were analyzed. Results. The viability of E. faecalis was significantly reduced by the combination of a photosensitizer and laser irradiation. The temperature caused by irradiation rose, however, there were no cytotoxic effects of heat on the viability of E. faecalis. Conclusion. Our results suggest that utilization of a diode laser in combination with a photosensitizer may be useful for clinical treatment of periapical lesions. PMID:21991489

  11. Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy

    SciTech Connect

    Zielony, E.; Placzek-Popko, E.; Henrykowski, A.; Gumienny, Z.; Kamyczek, P.; Jacak, J.; Nowakowski, P.; Karczewski, G.

    2012-09-15

    Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm{sup -1}. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm{sup -1}. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium-related peaks appearing at wavenumbers around 120 cm{sup -1} and 140 cm{sup -1}. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.

  12. Molecules in intense laser fields: Beyond the dipole approximation

    SciTech Connect

    Bandrauk, A. D.; Lu, H. Z.

    2006-01-15

    The time-dependent Schroedinger equation is solved for a Born-Oppenheimer (static nuclei) three-dimensional H{sub 2}{sup +} in super intense laser fields (I=4x10{sup 18}, 10{sup 19}, and 4x10{sup 19} W/cm{sup 2}) at wavelength {lambda}{sub L}=45 nm and 25 nm to assess the influence of nondipolar (magnetic) effects on high order harmonic generation spectra in molecules. It is found that even harmonics appear due to the magnetic field component direction perpendicular to the electric field polarization with intensities about two orders of magnitude less than the odd harmonics emitted along the electric field polarization. The even harmonics exhibit plateaus with cutoffs which exceed in intensity the odd harmonic plateaus and maximum energies predicted by semiclassical electron recollision models. Although the spectra are weak, the wavelength of the recollision electron in the maximum energy regions correspond to subatomic dimensions and the corresponding emitted photons have subnanometer wavelengths.

  13. Ultrafast x-ray diffraction of laser-irradiated crystals

    NASA Astrophysics Data System (ADS)

    Heimann, P. A.; Larsson, J.; Chang, Z.; Lindenberg, A.; Schuck, P. J.; Judd, E.; Padmore, H. A.; Bucksbaum, P. H.; Lee, R. W.; Murnane, M.; Kapteyn, H.; Wark, J. S.; Falcone, R. W.

    1997-07-01

    An apparatus has been developed for measuring time-dependent x-ray diffraction. X-ray pulses from an Advanced Light Source bend magnet are diffracted by a sagittally-focusing Si (111) crystal and then by a sample crystal, presently InSb (111). Laser pulses with 100 fs duration and a repetition rate of 1 KHz irradiate the sample inducing a phase transition. Two types of detectors are being employed: an x-ray streak camera and an avalanche photodiode. The streak camera is driven by a photoconductive switch and has a 2 ps temporal resolution determined by trigger jitter. The avalanche photodiode has high quantum efficiency and sufficient time resolution to detect single x-ray pulses in ALS two bunch or `camshaft' operation. A beamline is under construction dedicated for time resolved and micro-diffraction experiments. In the new beamline a toroidal mirror collects 3 mrad horizontally and makes a 1:1 image of the bend magnet source in the x-ray hutch. A laser induced phase transition has been observed in InSb occurring within 70 ps.

  14. Effect of low intensity laser therapy in an experimental model of cranio-encephalic trauma in rats

    NASA Astrophysics Data System (ADS)

    Meneguzzo, Daiane T.; Okada, Cristina Y.; Koike, Márcia K.; Silva, Bomfim A., Jr.; Moreira, Maria S.; Eduardo, Carlos d. P.; Martins Marques, Marcia

    2007-02-01

    The aim of this study was to analyze the effects of phototherapy with low intensity laser on the inflammatory reaction after rat brain injury. Cryogenic injury was performed at the brain of 16 male Wistar rats (250-300g) using a cooper probe at -80º C. Immediately, 24 h and 48 h later, the rats received laser irradiation using a GaAlAs laser (830 nm, 100 mW). The samples were randomly divided into four groups (n= 4 per group): A: control (non- irradiated); B: energy density of 14.28 J/cm2; C: 28.57 J/cm2; D: 42.85 J/cm2. Three days later, the cerebral vascular permeability and the inflammatory cells at the trauma site were evaluated. For vascular permeability analysis, 2 h prior sacrifice an intra vascular injection of Evans blue stain was done in the rats. For inflammatory cells counting, frozen samples were sectioned and the histological slides were stained with Giemsa. The data were compared by either ANOVA or Kruskall-Wallis complemented by the Dunn's test. The irradiated groups presented higher cerebral vascular permeability than controls (A: 2.6 +/- 0.8; B:12.0 +/- 2.0; C: 13.1 +/- 4.1, and D: 12.4 +/- 1.8; p=0.016). The inflammatory cell numbers of irradiated samples were similar to controls (A: 65 +/- 6; B:85 +/- 9; C: 84 +/-14, and D: 83 +/- 3; p=0.443). The data showed that phototherapy with low intensity laser modulates the inflammatory reaction in the brain by increasing the cerebral vascular permeability after a cryogenic trauma.

  15. Coherence effects in the ultra-intense laser-induced ultrafast response of complex atoms

    NASA Astrophysics Data System (ADS)

    Li, Yongqiang; Yuan, Jianmin

    2016-05-01

    Both coherent pumping and energy relaxation play important roles in understanding physical processes of ultra-intense coherent light-matter interactions. Here, using a large-scale quantum master equation approach, we describe dynamical processes of practical open quantum systems driven by both coherent and stochastic interactions. As examples, two typical cases of light-matter interactions are studied. First, we investigate coherent dynamics of inner-shell electrons of a neon gas irradiated by a high intensity X-ray laser along with vast number of decaying channels. In these single-photon dominated processes, we find that, due to coherence-induced Rabi oscillations and power broadening effects, the photon absorptions of a neon gas can be suppressed resulting in differences in ionization processes and final ion-stage distributions. Second, we take helium as an example of multi-photon and multichannel interference dominated electron dynamics, by investigating the transient absorption of an isolated atto-second pulse in the presence of a femto-second infrared laser pulse.

  16. Dominant deuteron acceleration with a high-intensity laser for isotope production and neutron generation

    SciTech Connect

    Maksimchuk, A.; Raymond, A.; Yu, F.; Dollar, F.; Willingale, L.; Zulick, C.; Krushelnick, K.; Petrov, G. M.; Davis, J.

    2013-05-13

    Experiments on the interaction of an ultra-short pulse laser with heavy-water, ice-covered copper targets, at an intensity of 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, were performed demonstrating the generation of a 'pure' deuteron beam with a divergence of 20 Degree-Sign , maximum energy of 8 MeV, and a total of 3 Multiplication-Sign 10{sup 11} deuterons with energy above 1 MeV-equivalent to a conversion efficiency of 1.5%{+-} 0.2%. Subsequent experiments on irradiation of a {sup 10}B sample with deuterons and neutron generation from d-d reactions in a pitcher-catcher geometry, resulted in the production of {approx}10{sup 6} atoms of the positron emitter {sup 11}C and a neutron flux of (4{+-}1) Multiplication-Sign 10{sup 5} neutrons/sterad, respectively.

  17. Investigation on the Influence of Different Laser Beam Intensity Distributions on Keyhole Geometry During Laser Welding

    NASA Astrophysics Data System (ADS)

    Volpp, J.

    An analytical quasi-static model of the keyhole during laser deep penetration welding is introduced. This model is used to calculate the keyhole geometry depending on spatial laser beam intensity. Keyhole shapes can be found solving the energy and pressure equations. All necessary physical effects like Fresnel and plasma absorption, heat conduction and vaporization are implemented in the model. For evaluation a Gaussian and a top hat beam profile were used. Experimental measurements of the keyhole shape using copper inlays in aluminum base material show good agreement with the results of the modeling.

  18. Apraclonidine effects on ocular responses to YAG laser irradiation to the rabbit iris

    SciTech Connect

    Sugiyama, K.; Kitazawa, Y.; Kawai, K. )

    1990-04-01

    Apraclonidine (p-aminoclonidine) ophthalmic solution effectively reduces the rise in intraocular pressure (IOP) following anterior segment laser surgery. We tested the effect of topical 0.5% apraclonidine on intraocular pressure and on protein and prostaglandin (PG) E2 concentrations in aqueous humor following Q-switched Nd:YAG laser irradiation to the iris of albino rabbits, at an energy level of 2 to 200 mJ. IOP was measured prior to and for 24 hr after irradiation. Aqueous humor was withdrawn before and 1 hr after laser irradiation for determining protein (Lowry method) and PGE2 (radioimmunoassay). Four to seven rabbits were used for each experiment. The increase in IOP and protein concentration following laser irradiation was demonstrated to be dependent on the amount of laser energy. Apraclonidine completely abolished the IOP rise, and significantly reduced the elevation of protein content. Apraclonidine failed to affect the increase in PGE2.

  19. Reduction of Sm(3+) to Sm(2+) by an intense femtosecond laser pulse in solution.

    PubMed

    Nishida, Daisuke; Yamade, Eriko; Kusaba, Mitsuhiro; Yatsuhashi, Tomoyuki; Nakashima, Nobuaki

    2010-05-13

    Samarium 3+ ions in methanol were found to be reduced to the corresponding 2+ ions upon irradiation with intense femtosecond laser pulses. The reduction was observed at both pulses with central wavelengths of 403 nm converted from an 800 fs fundamental pulse and 800 nm with a duration of 43 fs. When the laser wavelength was tuned to the 4f-4f absorption at 403 nm corresponding to the (6)P(3/2) <-- (6)H(5/2) transition, the reduction occurred by multiphoton absorption, presumably due to reaching the deep charge transfer state. In the case of excitation by 800 nm pulses of the fundamental wavelength of the Ti:sapphire laser, the reduction is considered to occur via solvent ionization followed by electron capture by Sm(3+). The product Sm(2+) was detected by its fluorescence, which was observed for the first time in solution and showed a broad spectrum peak around 750 nm with a quantum yield of 0.050 in methanol in the presence of 15-crown-5-ether. PMID:20405937

  20. Ultra-Intense Laser Pulse Propagation in Gas and Plasma

    SciTech Connect

    Antonsen, T. M.

    2004-10-26

    It is proposed here to continue their program in the development of theories and models capable of describing the varied phenomena expected to influence the propagation of ultra-intense, ultra-short laser pulses with particular emphasis on guided propagation. This program builds upon expertise already developed over the years through collaborations with the NSF funded experimental effort lead by Professor Howard Milchberg here at Maryland, and in addition the research group at the Ecole Polytechnique in France. As in the past, close coupling between theory and experiment will continue. The main effort of the proposed research will center on the development of computational models and analytic theories of intense laser pulse propagation and guiding structures. In particular, they will use their simulation code WAKE to study propagation in plasma channels, in dielectric capillaries and in gases where self focusing is important. At present this code simulates the two-dimensional propagation (radial coordinate, axial coordinate and time) of short pulses in gas/plasma media. The plasma is treated either as an ensemble of particles which respond to the ponderomotive force of the laser and the self consistent electric and magnetic fields created in the wake of pulse or as a fluid. the plasma particle motion is treated kinetically and relativistically allowing for study of intense pulses that result in complete cavitation of the plasma. The gas is treated as a nonlinear medium with rate equations describing the various stages of ionization. A number of important physics issues will be addressed during the program. These include (1) studies of propagation in plasma channels, (2) investigation of plasma channel nonuniformities caused by parametric excitation of channel modes, (3) propagation in dielectric capillaries including harmonic generation and ionization scattering, (4) self guided propagation in gas, (5) studies of the ionization scattering instability recently

  1. Ion Acceleration from the Interaction of Ultra-Intense Lasers with Solid Foils

    SciTech Connect

    Allen, Matthew M.

    2004-01-01

    The discovery that ultra-intense laser pulses (I > 1018 W/cm2) can produce short pulse, high energy proton beams has renewed interest in the fundamental mechanisms that govern particle acceleration from laser-solid interactions. Experiments have shown that protons present as hydrocarbon contaminants on laser targets can be accelerated up to energies > 50 MeV. Different theoretical models that explain the observed results have been proposed. One model describes a front-surface acceleration mechanism based on the ponderomotive potential of the laser pulse. At high intensities (I > 1018 W/cm2), the quiver energy of an electron oscillating in the electric field of the laser pulse exceeds the electron rest mass, requiring the consideration of relativistic effects. The relativistically correct ponderomotive potential is given by Up = ([1 + Iλ2/1.3 x 1018]1/2 - 1) m{sub o}c2, where Iλ2 is the irradiance in W μm2/cm2 and moc2 is the electron rest mass. At laser irradiance of Iλ2 ~ 1020 W μm2/cm2, the ponderomotive potential can be of order several MeV. A few recent experiments--discussed in Chapter 3 of this thesis--consider this ponderomotive potential sufficiently strong to accelerate protons from the front surface of the target to energies up to tens of MeV. Another model, known as Target Normal Sheath Acceleration (TNSA), describes the mechanism as an electrostatic sheath on the back surface of the laser target. According to the TNSA model, relativistic hot electrons created at the laser-solid interaction penetrate the foil where a few escape to infinity. The remaining hot electrons are retained by the target potential and establish an electrostatic sheath on the back surface of the target. In this thesis we present several experiments that study the accelerated ions by

  2. Time-dependent intensity and phase measurements of ultrashort laser pulses as short as 10 fs

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.; Taft, G.; Rundquist, A.; Murnane, M.M.; Kapteyn, H.C.; Christov, I.P.

    1995-05-01

    Frequency-Resolved Optical Gating (FROG) measures the time-dependent intensity and phase of an ultrashort laser pulse. Using FROG, we have tested theories for the operation of sub{minus}10 fs laser oscillators.

  3. Spectroscopic Analysis of High Intensity Laser Beam Jets Interaction Experiments on the Leopard Laser at UNR

    NASA Astrophysics Data System (ADS)

    Petkov, E. E.; Weller, M. E.; Kantsyrev, V. L.; Safronova, A. S.; Moschella, J. J.; Shrestha, I.; Shlyapsteva, V. V.; Stafford, A.; Keim, S. F.; University of Nevada Reno Team

    2013-10-01

    Results of Ar gas-puff experiments performed on the high power Leopard laser at UNR are presented. Flux density of laser radiation in focal spot was up to 2 × 1016 W/cm2 (pulse duration was 0.8 ns and laser wavelength was 1.057 μm). Specifically, spectroscopic analysis of K-shell Ar spectra are investigated and compared as functions of the orientation of the laser beam to linear gas jet. The laser beam axis was positioned either along the jet plane or orthogonal to it at a distance of 1 mm from the nozzle output. The diagnostics used included a time-integrated x-ray spectrometer along with a set of filtered Si diodes with various cutoff energies. In order to identify lines, a non-local thermodynamic equilibrium (non-LTE) kinetic model was utilized and was also used to determine plasma parameters such as electron temperature and density. The importance of the spectroscopic study of high intensity laser beam-jets interaction experiments is discussed. This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-13-1-0033, to University of Nevada, Reno, and in part by the DOE/NNSA Cooperative agreements DE-NA0001984 and DE-FC52-06NA27616.

  4. Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

    SciTech Connect

    Pan, A.; Dias, A.; Gomez-Aranzadi, M.; Olaizola, S. M.; Rodriguez, A.

    2014-05-07

    The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observed with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.

  5. Influence of He-Ne laser blood irradiation on morphofunctional state of monocytes in asthmatic patients

    NASA Astrophysics Data System (ADS)

    Paleev, N. R.; Slinchenko, O. I.; Ilchenko, V. A.; Vasilenko, Irina A.; Konradov, Alexander A.; Tychinsky, Vladimir P.

    1996-01-01

    In recent years we have been working out a new method of treatment of steroid-resistant asthma -- extracorporeal He-Ne-laser blood irradiation. The procedures gave good clinical effect and allowed reduction of steroid dose in a majority of patients. The monocytes were investigated by luminol-dependent chemiluminescence and the method of living cell microcopy. Extracorporeal He-Ne laser blood irradiation normalized both monocytes chemiluminescence and cell oscillation in asthmatic patients significantly earlier than in cases of ordinary treatment, although the mechanisms of action of He-Ne-laser irradiation upon blood steroid-resistant asthmatics were not fully determined.

  6. Increase in RNA and protein synthesis by mitochondria irradiated with helium-neon laser

    SciTech Connect

    Greco, M.; Guida, G.; Perlino, E.; Marra, E.; Quagliariello, E. )

    1989-09-29

    To gain further insight into the mechanism of cell photostimulation by laser light, both RNA and protein synthesis were measured in mitochondria irradiated with the low power continuous wave He-Ne laser (Energy dose: 5 Joules/cm{sup 2}). Following mitochondrial irradiation, both the rate and amount of incorporation of alpha-({sup 32}P)UTP and L-({sup 35}S)methionine, used to monitor RNA and protein synthesis respectively, proved to increase. Electrophoretic analysis made of the synthesis products clearly shows that He-Ne laser irradiation stimulates the synthesis of all mitochondrial transcription and translation products.

  7. Interstitial Laser Irradiation of Solid Tumors in Laser Assisted Cancer Immunotherapy

    NASA Astrophysics Data System (ADS)

    Evans, Lindsay; Bandyopadhyay, Pradip

    2006-03-01

    Laser Assisted Cancer Immunotherapy (LACI) is an experimental therapeutic approach in cancer treatment. Current experiments in our laboratory begin with growing superficial tumors 5 to 7 mm in diameter in BALB/C mice using the CRL-2539 cell line. Tumor sizes were measured with a vernier caliper prior to injection of light absorbing dye (Indocyanine Green, ICG) and immunoadjuvant (Glycated Chitosan, GC). These measurements were continued during the post-therapy period. After injection with the ICG and GC, the mice underwent interstitial irradiation of the tumor with a diode laser operating at 804 nm. Microthermocouples were inserted into the tumor and the laser power was varied in order to monitor the temperature and keep it within in the desired range. Tumors were irradiated at 55^o C, 65^oC, and 75^oC to find out at which temperature the maximum amount of tumor necrosis and strong immune response could be elicited. The growth of the tumors after the LACI treatment will be plotted to show the affect of the therapy at different temperatures. The data suggest that the growth rate of the tumors is slowed down considerably using this approach. * This work is supported by a grant from The National Institutes of Health.

  8. Basic studies on intravascular low-intensity laser therapy

    NASA Astrophysics Data System (ADS)

    Liu, Timon Cheng-Yi; Duan, Rui; Wang, Shuang-Xi; Liu, Jiang; Cui, Li-Ping; Jin, Hua; Liu, Song-Hao

    2006-09-01

    Intravascular low intensity laser therapy (ILILT) was originally put forward in USA in 1982, but popularized in Russia in 1980s and in China in 1990s, respectively. A randomized placebo-controlled study has shown ILILT clinical efficacy in patients suffering from rheumatoid arthritis. As Chinese therapeutic applications of ILILT were the most widely in the world, its basic research, such as intracellular signal transduction research, blood research in vitro, animal blood research in vivo, human blood research in vivo and traditional Chinese medicine research, was also very progressive in China. Its basic studies will be reviewed in terms of the biological information model of photobiomodulation in this paper. ILILT might work in view of its basic studies, but the further randomized placebo-controlled trial and the further safety research should be done.

  9. Possibilities for Nuclear Photo-Science with Intense Lasers

    SciTech Connect

    Barty, C J; Hartemann, F V; McNabb, D P; Messerly, M; Siders, C; Anderson, S; Barnes, P; Betts, S; Gibson, D; Hagmann, C; Hernandez, J; Johnson, M; Jovanovic, I; Norman, R; Pruet, J; Rosenswieg, J; Shverdin, M; Tremaine, A

    2006-06-26

    The interaction of intense laser light with relativistic electrons can produce unique sources of high-energy x rays and gamma rays via Thomson scattering. ''Thomson-Radiated Extreme X-ray'' (T-REX) sources with peak photon brightness (photons per unit time per unit bandwidth per unit solid angle per unit area) that exceed that available from world's largest synchrotrons by more than 15 orders of magnitude are possible from optimally designed systems. Such sources offer the potential for development of ''nuclear photo-science'' applications in which the primary photon-atom interaction is with the nucleons and not the valence electrons. Applications include isotope-specific detection and imaging of materials, inverse density radiography, transmutation of nuclear waste and fundamental studies of nuclear structure. Because Thomson scattering cross sections are small, < 1 barn, the output from a T-REX source is optimized when the laser spot size and the electron spot size are minimized and when the electron and laser pulse durations are similar and short compared to the transit time through the focal region. The principle limitation to increased x-ray or gamma-ray brightness is ability to focus the electron beam. The effects of space charge on electron beam focus decrease approximately linearly with electron beam energy. For this reason, T-REX brightness increases rapidly as a function of the electron beam energy. As illustrated in Figure 1, above 100 keV these sources are unique in their ability to produce bright, narrow-beam, tunable, narrow-band gamma rays. New, intense, short-pulse, laser technologies for advanced T-REX sources are currently being developed at LLNL. The construction of a {approx}1 MeV-class machine with this technology is underway and will be used to excite nuclear resonance fluorescence in variety of materials. Nuclear resonance fluorescent spectra are unique signatures of each isotope and provide an ideal mechanism for identification of nuclear

  10. Mapping of laser diode radiation intensity by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  11. Biodegradability of poly(lactic-co-glycolic acid) after femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Shibata, Akimichi; Yada, Shuhei; Terakawa, Mitsuhiro

    2016-06-01

    Biodegradation is a key property for biodegradable polymer-based tissue scaffolds because it can provide suitable space for cell growth as well as tailored sustainability depending on their role. Ultrashort pulsed lasers have been widely used for the precise processing of optically transparent materials, including biodegradable polymers. Here, we demonstrated the change in the biodegradation of a poly(lactic-co-glycolic acid) (PLGA) following irradiation with femtosecond laser pulses at different wavelengths. Microscopic observation as well as water absorption and mass change measurement revealed that the biodegradation of the PLGA varied significantly depending on the laser wavelength. There was a significant acceleration of the degradation rate upon 400 nm-laser irradiation, whereas 800 nm-laser irradiation did not induce a comparable degree of change. The X-ray photoelectron spectroscopy analysis indicated that laser pulses at the shorter wavelength dissociated the chemical bonds effectively, resulting in a higher degradation rate at an early stage of degradation.

  12. Low Intensity Laser Therapy Applied in the Healing of Wounds

    NASA Astrophysics Data System (ADS)

    Kahn, Fred; Matthews, Jeffrey

    2009-06-01

    Objective: The aim of this study was to determine the outcomes of Low Intensity Laser Therapy (LILT) on wound healing for patients presenting with pain, compromised neurological and physical function and tissue damage associated with vascular/diabetic ulcerations of the lower extremity. Methods: A retrospective case review of six patients treated with LILT (GaAlAs SLD, 660 nm, 750 mW, 3.6 J/cm2; GaAlAs SLD, 840 nm, 1,500 mW, 6.48 J/cm2; GaAlAs laser, 830 nm, 75 mW, 270 J/cm2) was conducted of clinical features including pain, measured by visual analogue scale (VAS), motor function, measured by range of motion (ROM) and visual outcome, measured by wound dimensions for six patients (n = 6; 5 males, 1 female; age = 67.83 years). Results: Significant progress with regard to alleviation of pain (ΔVAS = -5), improvements in motor function (ΔROM = +40%), epithelialization (wound closure rate = 3%/week) and complete wound closure was achieved. No recurrence of pathology at least one month post cessation of therapy was evident (x¯% reduction in wound area = 100%). Conclusions: LILT achieved consistent, effective and clear endpoints, was cost effective, created no adverse effects and ultimately led to the salvage of extremities.

  13. Appearance of Density Cavitations in the Laser Wake in Simulations of High Intensity Laser-Plasma Interactions

    SciTech Connect

    Wang, T.-L.

    2009-01-22

    Nonlinear interactions of high intensity, ultrashort laser pulses with underdense plasmas produce many interesting features that may appear in computer simulations. One of these features commonly observed in Particle-In-Cell (PIC) simulations is the spontaneous appearance of long-lived density cavitations in the plasma wake region behind the laser pulse. To study these cavitations, several small 2D PIC simulations are run in which plasma density, density ramps, total simulation time, laser pulsewidth, laser intensity, and laser polarization parameters have been varied. Based on the simulation results, some possible aspects of an experiment designed to directly detect these structures are discussed.

  14. Integrated analysis of millisecond laser irradiation of steel by comprehensive optical diagnostics and numerical simulation

    NASA Astrophysics Data System (ADS)

    Doubenskaia, M.; Smurov, I.; Nagulin, K. Yu.

    2016-04-01

    Complimentary optical diagnostic tools are applied to provide comprehensive analysis of thermal phenomena in millisecond Nd:YAG laser irradiation of steel substrates. The following optical devices are employed: (a) infrared camera FLIR Phoenix RDASTM equipped by InSb sensor with 3 to 5 µm band pass arranged on 320 × 256 pixels array, (b) ultra-rapid camera Phantom V7.1 with SR-CMOS monochrome sensor in the visible spectral range, up to 105 frames per second for 64 × 88 pixels array, (c) original multi-wavelength pyrometer in the near-infrared range (1.370-1.531 µm). The following laser radiation parameters are applied: variation of energy per pulse in the range 15-30 J at a constant pulse duration of 10 ms with and without application of protective gas (Ar). The evolution of true temperature is restored based on the method of multi-colour pyrometry; by this way, melting/solidification dynamics is analysed. Emissivity variation with temperature is studied, and hysteresis type functional dependence is found. Variation of intensity of surface evaporation visualised by the camera Phantom V7.1 is registered and linked with the surface temperature evolution, different surface roughness and influence of protective gas atmosphere. Determination of the vapour plume temperature based on relatively intensities of spectral lines is done. The numerical simulation is carried out applying the thermal model with phase transitions taken into account.

  15. Void-nanograting transition by ultrashort laser pulse irradiation in silica glass.

    PubMed

    Dai, Ye; Patel, Aabid; Song, Juan; Beresna, Martynas; Kazansky, Peter G

    2016-08-22

    The structural evolution from void modification to self-assembled nanogratings in fused silica is observed for moderate (NA > 0.4) focusing conditions. Void formation, appears before the geometrical focus after the initial few pulses and after subsequent irradiation, nanogratings gradually occur at the top of the induced structures. Nonlinear Schrödinger equation based simulations are conducted to simulate the laser fluence, intensity and electron density in the regions of modification. Comparing the experiment with simulations, the voids form due to cavitation in the regions where electron density exceeds 1020 cm-3 but is below critical. In this scenario, the energy absorption is insufficient to reach the critical electron density that was once assumed to occur in the regime of void formation and nanogratings, shedding light on the potential formation mechanism of nanogratings. PMID:27557213

  16. In-depth Plasma-Wave Heating of Dense Plasma Irradiated by Short Laser Pulses

    NASA Astrophysics Data System (ADS)

    Sherlock, M.; Hill, E. G.; Evans, R. G.; Rose, S. J.; Rozmus, W.

    2014-12-01

    We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described.

  17. Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

    SciTech Connect

    Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T.

    2013-12-15

    Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

  18. Er:YAG laser irradiation to control the progression of enamel erosion: an in situ study.

    PubMed

    Scatolin, R S; Colucci, V; Lepri, T P; Alexandria, A K; Maia, L C; Galo, R; Borsatto, M C; Corona, S A M

    2015-07-01

    This in situ study evaluated the effect of Er:YAG laser irradiation in controlling the progression of enamel erosion-like lesions. Fifty-six enamel slabs (330 KHN ± 10 %) with one fourth of the surface covered with resin composite (control area) were submitted to initial erosion-like lesion formation with citric acid. The slabs were divided into two groups: irradiated with Er:YAG laser and non-irradiated. Fourteen volunteers used an intraoral palatal appliance containing two slabs, in two phases of 5 days each. During the intraoral phase, in a crossed-over design, half of the volunteers immersed the appliance in citric acid while the other half used deionized water, both for 5 min, three times per day. Enamel wear was determined by an optical 3D profilometer. ANOVA revealed that when deionized water was used as immersion solution during the intraoral phase, lower values of wear were showed when compared with the groups that were eroded with citric acid, whether irradiated or non-irradiated with Er:YAG laser. When erosion with citric acid was performed, Er:YAG laser was not able to reduce enamel wear. Small changes on enamel surface were observed when it was irradiated with Er:YAG laser. It may be concluded that Er:YAG laser irradiation did not reduce the progression of erosive lesions on enamel submitted to in situ erosion with citric acid.

  19. Effect of semiconductor GaAs laser irradiation on pain perception in mice

    SciTech Connect

    Zarkovic, N.; Manev, H.; Pericic, D.; Skala, K.; Jurin, M.; Persin, A.; Kubovic, M.

    1989-01-01

    The influence of subacute exposure (11 exposures within 16 days) of mice to the low power (GaAs) semiconductive laser-stimulated irradiation on pain perception was investigated. The pain perception was determined by the latency of foot-licking or jumping from the surface of a 53 degrees C hot plate. Repeated hot-plate testing resulted in shortening of latencies in both sham- and laser-irradiated mice. Laser treatment (wavelength, 905 nm; frequency, 256 Hz; irradiation time, 50 sec; pulse duration, 100 nsec; distance, 3 cm; peak irradiance, 50 W/cm2 in irradiated area; and total exposure, 0.41 mJ/cm2) induced further shortening of latencies, suggesting its stimulatory influence on pain perception. Administration of morphine (20 mg/kg) prolonged the latency of response to the hot plate in both sham- and laser-irradiated mice. This prolongation tended to be lesser in laser-irradiated animals. Further investigations are required to elucidate the mechanism of the observed effect of laser.

  20. Control of plasma parameters and spectral analysis sensitivity under bichromatic laser irradiation of materials in gases

    NASA Astrophysics Data System (ADS)

    Chumakov, A. N.; Bosak, N. A.; Panina, A. V.

    2016-01-01

    Double-pulse nanosecond bichromatic laser irradiation of carbon and brass targets is implemented. The dependence of temperature and density of electrons, as well as the specific recoil momentum of an outflowing plasma jet, on the ordering of laser pulses and the interpulse time delay is found. The results obtained can be used for the development of laser- plasma spacecraft microengines and the enhancement of laser spectral analysis’ sensitivity.

  1. Fusion neutron yield from a laser-irradiated heavy-water spray

    SciTech Connect

    Ter-Avetisyan, S.; Schnuerer, M.; Hilscher, D.; Jahnke, U.; Busch, S.; Nickles, P.V.; Sandner, W.

    2005-01-01

    The fusion neutron yield from a laser-irradiated heavy-water (D{sub 2}O) spray target was studied. Heavy-water droplets of about 150 nm diameter in the spray were exposed to 35 fs laser pulses at an intensity of 1x10{sup 19} W/cm{sup 2}. Due to the 10-50 times bigger size of the spray droplets compared to usual cluster sizes, deuterons are accelerated to considerably higher kinetic energies of up to 1 MeV. Neutrons are generated by the deuterons escaping from the plasma and initiating a fusion reaction within the surrounding cold plume of the spray jet. For each 0.6 J of laser pulse energy, 6x10{sup 3} neutrons are produced by about 10{sup 11} accelerated deuterons. This corresponds to a D(d,n) reaction probability of about 6x10{sup -8}. Compared to cluster targets, the reaction probability in the spray target is found to be two orders of magnitude larger. This finding apparently is due to both the considerably higher deuteron energies and the larger effective target thickness in the spray target. The measured neutron yield per accelerated deuteron [i.e., the D(d,n) reaction probability], is employed to compare and extrapolate the neutron emission characteristics from different target arrangements.

  2. Low-level Ga-Al-As laser irradiation enhances osteoblast proliferation through activation of Hedgehog signaling pathway

    NASA Astrophysics Data System (ADS)

    Li, Qiushi; Qu, Zhou; Chen, Yingxin; Liu, Shujie; Zhou, Yanmin

    2014-12-01

    Low-level laser irradiation has been reported to promote bone formation, but the molecular mechanism is still unclear. Hedgehog signaling pathway has been reported to play an important role in promoting bone formation. The aim of the present study was to examine whether low-level Ga-Al-As laser (808 nm) irradiation could have an effect on Hedgehog signaling pathway during osteoblast proliferation in vitro. Mouse osteoblastic cell line MC3T3-E1 was cultured in vitro. The cultures after laser irradiation (3.75J/cm2) were treated with recombinant N-terminals Sonic Hedgehog (N-Shh)or Hedgehog inhibitor cyclopamine (cy). The experiment was divided into 4 group, group 1:laser irradiation, group 2: laser irradiation and N-Shh, group 3: laser irradiation and cy, group 4:control with no laser irradiation. On day 1,2 and 3,cell proliferation was determined by cell counting, Cell Counting Kit-8.On 12 h and 24 h, cell cycle was detected by flow cytometry. Proliferation activity of laser irradiation and N-Shh group was remarkably increased compared with those of laser irradiation group. Proliferation activity of laser irradiation and cy group was remarkably decreased compared with those of laser irradiation group, however proliferation activity of laser irradiation and cy group was remarkably increased compared with those of control group. These results suggest that low-level Ga-Al-As laser irradiation activate Hedgehog signaling pathway during osteoblast proliferation in vitro. Hedgehog signaling pathway is one of the signaling pathways by which low-level Ga-Al-As laser irradiation regulates osteoblast proliferation.

  3. Effect of XeCl laser irradiation on the defect structure of Nd:YAG crystals

    NASA Astrophysics Data System (ADS)

    Panahibakhsh, S.; Jelvani, S.; Maleki, M. H.; Mollabashi, M.; Abolhosseini, S.

    2014-09-01

    This paper presents the effect of XeCl laser irradiation on Nd:YAG single crystal samples with various number of pulses at different repetition rates and laser fluences. Effects of the irradiation on the optical and structural properties of the crystal are analyzed by UV-vis-NIR spectroscopy. Annihilation of some point defects of the crystal structure is observed following laser irradiation at a fluence of 100 mJ cm-2 with 100 and 500 pulses. Increasing the laser fluence and pulse numbers leads to saturation and new defects are found to be formed in the crystal. Additional absorption spectra of the irradiated samples show that oxygen vacancies in the Nd:YAG crystals are removed during the low-dose irradiation. The laser irradiation is compared to the thermal annealing process for Nd:YAG crystal modification. Additional absorption spectrum of an annealed sample reveals that induced negative absorption band at 236 nm is correlated with the annihilation of the oxygen vacancy center. Our results also demonstrate that XeCl laser treatment has several advantages upon annealing at high temperatures in the Nd:YAG crystal quality improvement. Thus, the present work can give a new approach to modify Nd:YAG crystals to be used in a wide variety of solid-state laser engineering.

  4. The irradiation of rabbit sperm cells with He-Ne laser prevents their in vitro liquid storage dependent damage.

    PubMed

    Iaffaldano, Nicolaia; Rosato, Maria Pina; Paventi, Gianluca; Pizzuto, Roberto; Gambacorta, Mario; Manchisi, Angelo; Passarella, Salvatore

    2010-05-01

    The aim of the study was to investigate the effects of different energy doses of helium-neon (He-Ne) laser irradiation on both mitochondrial bioenergetics functions and functional quality of rabbit spermatozoa during 48 h of in vitro liquid storage at 15 degrees C. 11 rabbit semen pools were each divided into four aliquots: three of them were irradiated with He-Ne laser with different energy doses (3.96, 6.12 and 9.00 J/cm(2)) being the last control kept under the same experimental conditions without irradiation. Sperm motility, viability and acrosome integrity were monitored together with cytochrome c oxidase (COX) activity and the cell energy charge (EC) at 0, 24 and 48 h of storage. Irradiated samples stored for 24 and 48 h better maintained motility (P < 0.01), acrosome integrity (P < 0.01) and viability (P < 0.05) with respect to the control, particularly with the energy dose of 6.12 J/cm(2) that showed the most intense biostimulative effect. COX activity and EC were immediately increased by irradiation particularly in the treatments 6.12 and 9.00 J/cm(2) (P < 0.05), that maintained their levels higher with respect to the control after 48 h of storage (P < 0.01). COX activity of rabbit sperm cells was positively correlated with EC (P < 0.05), viability (P < 0.01) and acrosome integrity (P < 0.05) parameters. These results indicate that the effects of He-Ne laser irradiation on sperm cells are mediated through the stimulation of the sperm mitochondrial respiratory chain and that this effect plays a significant role in the augmentation of the rabbit sperm cells' capability to survive during liquid storage conditions. PMID:19932573

  5. Strong visible light emission from well-aligned multiwalled carbon nanotube films under infrared laser irradiation

    SciTech Connect

    Zhang Yong; Gong Tao; Liu Wenjin; Zhang Xianfeng; Chang Jianguo; Wang Kunlin; Wu Dehai

    2005-10-24

    We report strong and brilliant visible light emission from well-aligned multiwalled carbon nanotube (AMWNT) films under infrared (IR) laser irradiation with wavelength at 1.06 and 10.6 {mu}m, respectively. The AMWNT film shows a high durability against laser irradiation and achieved a conversion from IR laser to visible light. It is a good candidate for optical converter. Light emission spectra versus different wavelengths and various powers were found to have similar line shapes. It could be explained as combination of laser-induced photoluminescence and resistive heating.

  6. Steplike Intensity Threshold Behavior of Extreme Ionization in Laser-Driven Xenon Clusters

    SciTech Connect

    Doeppner, T.; Mueller, J. P.; Przystawik, A.; Goede, S.; Tiggesbaeumker, J.; Meiwes-Broer, K.-H.; Varin, C.; Ramunno, L.; Brabec, T.; Fennel, T.

    2010-07-30

    The generation of highly charged Xe{sup q+} ions up to q=24 is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses ({lambda}=800 nm). Laser intensity resolved measurements show that the high-q ion generation starts at an unexpectedly low threshold intensity of about 10{sup 14} W/cm{sup 2}. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.

  7. Femtosecond laser-induced size reduction of carbon nanodots in solution: Effect of laser fluence, spot size, and irradiation time

    SciTech Connect

    Nguyen, Vanthan; Yan, Lihe Si, Jinhai; Hou, Xun

    2015-02-28

    Photoluminescent carbon nanodots (C-dots) with size tunability and uniformity were fabricated in polyethylene glycol (PEG{sub 200N}) solution using femtosecond laser ablation method. The size distributions and photoluminescence (PL) properties of C-dots are well controlled by adjusting the combined parameters of laser fluence, spot size, and irradiation time. The size reduction efficiency of the C-dots progressively increases with decreasing laser fluence and spot size. The optimal PL spectra are red-shifted and the quantum yields decrease with the increase in C-dots size, which could be attributed to the more complex surface functional groups attached on C-dots induced at higher laser fluence and larger spot size. Moreover, an increase in irradiation time leads to a decrease in size of C-dots, but long-time irradiation will result in the generation of complex functional groups on C-dots, subsequently the PL spectra are red-shifted.

  8. Intensity noise properties of Nd:YVO 4 microchip lasers pumped with an amplitude squeezed diode laser

    NASA Astrophysics Data System (ADS)

    Becher, C.; Boller, K.-J.

    1998-02-01

    We report on intensity noise measurements of single-frequency Nd:YVO 4 microchip lasers optically pumped with amplitude squeezed light from an injection-locked diode laser. Calibrated homodyne measurements show a minimum intensity noise of 10.1 dB above the SQL at a frequency of 100 kHz. The measured intensity noise spectra are described with high accuracy by a theoretical model based on the quantum mechanical Langevin rate equations, including classical and quantum noise sources.

  9. An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets.

    PubMed

    Price, C J; Donnelly, T D; Giltrap, S; Stuart, N H; Parker, S; Patankar, S; Lowe, H F; Drew, D; Gumbrell, E T; Smith, R A

    2015-03-01

    We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10(17) W cm(-2)) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies. PMID:25832224

  10. An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets.

    PubMed

    Price, C J; Donnelly, T D; Giltrap, S; Stuart, N H; Parker, S; Patankar, S; Lowe, H F; Drew, D; Gumbrell, E T; Smith, R A

    2015-03-01

    We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10(17) W cm(-2)) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

  11. An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

    SciTech Connect

    Price, C. J. Giltrap, S.; Stuart, N. H.; Parker, S.; Patankar, S.; Lowe, H. F.; Smith, R. A.; Donnelly, T. D.; Drew, D.; Gumbrell, E. T.

    2015-03-15

    We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10{sup 17} W cm{sup −2}) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

  12. Increase of bulk optical damage threshold fluences of KDP crystals by laser irradiation and heat treatment

    DOEpatents

    Swain, J.E.; Stokowski, S.E.; Milam, D.; Kennedy, G.C.; Rainer, F.

    1982-07-07

    The bulk optical damage threshold fluence of potassium dihydrogen phosphate (KDP) crystals is increased by irradiating the crystals with laser pulses of duration 1 to 20 nanoseconds of increasing fluence, below the optical damage threshold fluence for untreated crystals, or by baking the crystals for times of the order of 24 hours at temperatures of 110 to 165/sup 0/C, or by a combination of laser irradiation and baking.

  13. Controversial effects of low level laser irradiation on the proliferation of human osteoblasts

    NASA Astrophysics Data System (ADS)

    Bölükbaşı Ateş, Gamze; Ak, Ayşe.; Garipcan, Bora; Yüksel, Šahru; Gülsoy, Murat

    2015-03-01

    Low level laser irradiation (LLLI) is the application of red or near infrared lasers irradiating between 600-1100 nm with an output power of 1-500 mW. Several researches indicate that LLLI modulates cellular mechanisms and leads to enhance proliferation. Although the biological mechanisms are not fully understood, it is known that the effects depend on several parameters such as wavelength, irradiation duration, energy level, beam type and energy density. The aim of this study is to investigate the effect of low level laser irradiation at varying energy densities with two different wavelengths (635 nm and 809 nm) on the proliferation of human osteoblasts in vitro. The cells are seeded on 96 well plates (105cells/well) and after 24 h incubation cells are irradiated at energy densities 0.5 J/cm2, 1 J/cm2 and 2 J/cm2. Cell viability test is applied after 24 h, 48 h and 72 h in order to examine effects of laser irradiation on osteoblast proliferation. 635 nm light irradiation did not appear to have significant effect on the proliferation of osteoblasts as compared to the control. On the other hand, 809 nm laser irradiation caused significant (p ≤ 0.01) biostimulation effect on the osteoblast cell cultures at 48 h and 72 h. In conclusion, irradiation of both wavelengths did not cause any cytotoxic effects. 809 nm light irradiation can promote proliferation of human osteoblasts in vitro. On the other hand, 635 nm light irradiation has no positive effect on osteoblast proliferation. As a result, LLLI applied using different wavelengths on the same cell type may lead to different biological effects.

  14. Overview of inertial fusion and high-intensity laser plasma research in Europe

    NASA Astrophysics Data System (ADS)

    Tassart, J.

    2004-12-01

    Inertial fusion science is driven by 'the quest for ignition'. For many years, a 'conventional' route towards inertial fusion has been investigated using two different approaches: ignition by an inertial central hot spot could be obtained either through the direct or the indirect drive scheme. Both imply the use of a very large facility to operate the driver, which is a powerful laser in the current projects (LMJ in France as well as NIF in the US). The LMJ construction being on the way, a large amount of experimental and computational work is currently being done to deepen the understanding of ignition requirements. On the other hand, the so-called 'fast ignition' approach has led to an increasingly important amount of scientific work since it was proposed at the beginning of the 1990s. During the last several years (from the previous IFSA held in Kyoto in 2001), several PW-class high-intensity laser facilities have been built in Europe. In the meantime, a large number of interesting results related to fast electron and proton production have been obtained with the existing facilities. Observation of laser-irradiated solid targets has provided the first evidence of electron bunches separated by half the period of light. Nevertheless, target heating remains modest. On the other hand, multi-megaelectronvolt highly collimated electron beams have been produced by table-top lasers interacting with the low-density plasmas. They open the feasibility of a lot of applications: x-ray probe beams in plasma physics, biology, chemistry, injector for conventional accelerators, etc). Laser-produced proton beams is also a growing field, with a lot of promising applications: proton therapy, radio-isotope production, diagnostic for transient phenomena in laser-plasma interaction, etc. Inertial fusion research is fostered by a sustained effort of organization and coordination at the national level (the creation of an Institute for Lasers and Plasmas in France) as well as at the

  15. Surface nano-texturing of silicon by picosecond laser irradiation through TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Babu, K. E. Sarath Raghavendra; Duraiselvam, Muthukannan

    2015-10-01

    This article presents, nano-texturing of crystalline silicon by irradiating picosecond laser with variable spatial intensity, caused by optically non-linear TiO2 nanotube arrays (TNTA). Along with micro-scale surface structure, highly ordered laser-induced periodic surface structures (LIPSS) was observed at nano-scale. The periodicity (Λ) of the LIPSS generated was near to the laser wavelength (532 nm). Surface morphology at micro-level was characterized by optical microscopy (OM) and white light interferometer (WLI) and at the nano-scale by scanning electron microscope (SEM) and atomic force microscope (AFM). The results highlight the potential use of TNTA as a single step process to produce micro/nanostructures without any gas/liquid medium under ambient condition.

  16. Laser-based irradiation apparatus and method to measure the functional dose-rate response of semiconductor devices

    DOEpatents

    Horn, Kevin M.

    2008-05-20

    A broad-beam laser irradiation apparatus can measure the parametric or functional response of a semiconductor device to exposure to dose-rate equivalent infrared laser light. Comparisons of dose-rate response from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems can determine if aging has affected the device's overall functionality. The dependence of these changes on equivalent dose-rate pulse intensity and/or duration can be measured with the apparatus. The synchronized introduction of external electrical transients into the device under test can be used to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure while exposing the device to dose-rate equivalent infrared laser light.

  17. Morphology adjustments of multi-walled carbon nanotubes by laser irradiation

    NASA Astrophysics Data System (ADS)

    Yuan, Yanping; Chen, Jimin

    2016-06-01

    In this study, nanoscale welding quality and morphology changes of multi-walled carbon nanotubes are investigated by changing laser wavelengths and the irradiation time. Lasers with 1064 nm and 355 nm are used in our experiments. The 1064 nm laser can lead to nanowelding with good quality, while the 355 nm laser changes the curvature. The experiments demonstrate that the morphology, structures and the welding quality can be adjusted by changing laser wavelengths. In this letter, the dynamic process of nanostructures changing is studied by changing the irradiation time. The experimental results show that the morphology and structures can be controlled by adjusting the irradiation time. The detailed dynamic process of nanostructures changing confirms the formation mechanism of nano-welding and the thermal effects during the process.

  18. Bonding of lithium niobate to silicon in ambient air using laser irradiation

    NASA Astrophysics Data System (ADS)

    Kawano, Hiroki; Takigawa, Ryo; Ikenoue, Hiroshi; Asano, Tanemasa

    2016-08-01

    In this paper, we introduce a bonding method in ambient air using laser irradiation to the face-to-face interface of dissimilar materials. This method is performed while keeping whole wafers of the materials at room temperature. We demonstrate the bonding of LiNbO3 to Si using pulsed nanosecond green laser irradiation. Laser use can minimize thermal stress owing to a large thermal expansion mismatch. The bonding characteristic obtained by an irradiation laser up to 2.5 J/cm2 in fluence is investigated. It is found that a LiNbO3 chip is strongly bonded to a Si chip by setting the laser fluence at the optimum range. A bond strength of over 2 MPa, which may be enough for the device applications, can be obtained.

  19. Low-Energy Laser Irradiation And The Nervous System: Method And Results

    NASA Astrophysics Data System (ADS)

    Rochkind, S.; Lubart, R.; Nissan, M.; Barr-Nea, L.

    1988-06-01

    The present study introduces a novel method for assessing the efficacy of so-called soft tissue lasers on the peripheral and central nervous systems. In any readily available method relying on low energy laser irradiation, one of the most critical factors is obviously the wavelength of the laser, for this will determine how much of the energy applied to the skin or muscle actually reaches the target nerve. The present findings reaffirm our conclusion that low energy laser irradiation is bene-ficial in the treatment of injured peripheral or central nervous system, the beneficial effect diminishing with decreasing wavelength from 632nm down to 465nm. Our results pave the way for a new approach to the treatment of traumatic paraplegia and argue in favor of a combination of laser irradiation and PNS or CNS transplantation for the treatment of spinal cord injury.

  20. Characterization of high temperature conductive graphite surfaces irradiated with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sivakumar, M.; Tan, B.; Venkatakrishnan, K.

    2011-09-01

    In this study high temperature conductive graphite surfaces irradiated with megahertz pulse repetition rate femtosecond laser pulses under ambient condition were characterized using electron microscopy and spectroscopy techniques. Scanning electron microscopy analysis of the treated surface shows formation of self assembled weblike nanofibrous structure in and around the laser irradiated spots. Further transmission electron microscopy investigation revealed that this structure was formed due to aggregation of graphite nanoparticles. In addition the broadening of microraman peaks at 1340 and 1580 cm-1 of the laser irradiated sample was due to confinement of optical phonons in graphite nanoparticles. X-ray photoelectron spectroscopy analysis shows a marginal increase of sp2 and sp3 species with laser treated samples as compared to that of untreated samples. The results show that femtosecond laser treatment is rather a simple technique for the direct synthesis graphite nanostructures without significant changes in their chemistry as compared to the bulk.

  1. Lack of dentin acid resistance following 9.3 um CO2 laser irradiation

    NASA Astrophysics Data System (ADS)

    Le, Charles Q.; Fried, Daniel; Featherstone, John D. B.

    2008-02-01

    Previous studies have shown that laser irradiation of dental enamel by specific carbon dioxide laser conditions can inhibit subsequent acid dissolution of the dental enamel surface. The purpose of this study was to determine whether similar carbon dioxide laser conditions would have a protective effect on dentin. Blocks of human dentin roots (3x3 mm2) were irradiated at 9.3 µm wavelength with a 15-18 µs pulse duration laser and fluences of 0.50-1.50 J/cm2. A motion controller system was used to ensure uniform irradiation of the entire dentin surface. Surface acid dissolution profiles following irradiation were acquired for the five study groups, control group (Non-irradiated) and four laser-treated groups. Dissolution profiles of low fluence groups (0.50 and 0.75 J/cm2) exhibited similar profiles to the control group. Dissolution profiles of higher fluence groups (1.0 and 1.5 J/cm2) showed an increased dissolution rate over the control group, but these differences were not statistically significant (p>0.05). This study demonstrated that the application of carbon dioxide laser irradiation significantly alters the surface of dentin but did not decrease the acid dissolution rate.

  2. Effects of laser irradiation on immature olfactory neuroepithelial explants from the rat

    SciTech Connect

    Mester, A.F.; Snow, J.B. Jr.

    1988-07-01

    The photobiological effect of low-output laser irradiation on the maturation and regeneration of immature olfactory bipolar receptor cells of the rat was studied. The maturation and regeneration of the receptor cells of rat fetuses were quantified in neuroepithelial explants with morphometric analysis. The number of explants with outgrowth and the number and length of neuritic outgrowths were determined on a regular basis for 12 days. Explants in the experimental group were irradiated with a helium-neon laser using different incident energy densities (IED). Explants in the fluorescent light control group were exposed to fluorescent light for the same periods of time as those in the experimental group were exposed to laser irradiation. Explants in another control group were not exposed to laser or fluorescent light irradiation. The IED of 0.5 J/cm2 laser irradiation has been found to increase significantly the number of explants with outgrowth and the number and length of the outgrowths. Other laser IEDs or fluorescent light irradiation did not influence maturation or regeneration.

  3. Intense laser beams; Proceedings of the Meeting, Los Angeles, CA, Jan. 23, 24, 1992

    NASA Technical Reports Server (NTRS)

    Wade, Richard C. (Editor); Ulrich, Peter B. (Editor)

    1992-01-01

    Various papers on intense laser beams are presented. Individual topics addressed include: novel methods of copper vapor laser excitation, UCLA IR FEL, lasing characteristics of a large-bore copper vapor laser (CVL), copper density measurement of a large-bore CVL, high-power XeCl excimer laser, solid state direct-drive circuit for pumping gas lasers, united energy model for FELs, intensity and frequency instabilities in double-mode CO2 lasers, comparison of output power stabilities of CO and CO2 lasers, increasing efficiency of sealed-off CO lasers, thermal effects in singlet delta oxygen generation, optical extraction from the chemical oxygen-iodine laser medium, generation and laser diagnostic analysis of bismuth fluoride. Also discussed are: high-Q resonator design for an HF overtone chemical lasers, improved coatings for HF overtone lasers, scaled atmospheric blooming experiment, simulation on producing conjugate field using deformable mirrors, paraxial theory of amplitude correction, potential capabilities of adaptive optical systems in the atmosphere, power beaming research at NASA, system evaluations of laser power beaming options, performance projections for laser beam power to space, independent assessment of laser power beaming options, removal of atmospheric CFCs by lasers, efficiency of vaporization cutting by CVL.

  4. Low-energy helium-neon laser irradiation increases the motility of cultured human keratinocytes

    SciTech Connect

    Haas, A.F.; Isseroff, R.R.; Wheeland, R.G.; Rood, P.A.; Graves, P.J. )

    1990-06-01

    Helium-neon (HeNe) laser irradiation is known to stimulate wound healing. We investigated whether the biostimulatory effects of HeNe irradiation result from enhancement of keratinocyte proliferation or motility. HeNe effects on keratinocyte motility were evaluated by irradiating a wounded culture with 0.8 J/cm2 3 times over a 20-h period. At 20 h post-irradiation, videocinemicroscopy and sequential quantitative measurements of the leading edge were taken over a 6-h period. There was a significant difference in migration of the leading edge in irradiated wounds compared to non-irradiated wounded controls (12.0 microns/h vs 4.0 microns/h, p less than 0.0001). To determine if the increase in migration observed in irradiated cultures resulted from a proliferative effect of HeNe irradiation, subconfluent human keratinocyte cultures were irradiated with single or multiple doses of different fluences of HeNe irradiation (0.4 to 7.2 J/cm2) and evaluated 72 h post-irradiation. Irradiated and non-irradiated keratinocyte cultures grown on a microporous membrane surface were co-cultured with irradiated and non-irradiated fibroblasts to determine if HeNe irradiation induced a paracrine effect on keratinocyte proliferation. No significant increase in keratinocyte proliferation was demonstrated in any of these treatments. The biostimulatory effects of HeNe irradiation may now be extended to include enhancement of keratinocyte motility in vitro; this may contribute to the efficacy of HeNe irradiation in wound healing.

  5. Efficiency and threshold pump intensity of CW solar-pumped solid-state lasers

    SciTech Connect

    Hwang, I.H. . Dept. of Physics); Lee, J.H. . Langley Research Center)

    1991-09-01

    This paper reports on the efficiencies and threshold pump intensities of various solid-state laser materials that have been estimated to compare their performance characteristics as direct solar-pumped CW lasers. Among the laser materials evaluated in this research, alexandrite has the highest slope efficiency of about 12.6%; however, it does not seem to be practical for solar-pumped laser application because of its high threshold pump intensity. Cr:Nd:GSGG is the most promising for solar-pumped lasing. Its threshold pump intensity is about 100 air-mass-zero (AMO) solar constants and its slope efficiency is about 12% when thermal deformation is completely prevented.

  6. The effect of diode laser irradiation on dentin as a preventive measure against dental erosion: an in vitro study.

    PubMed

    de-Melo, Mary A S; Passos, Vanara F; Alves, Jose J; Barros, Eduardo B; Santiago, Sérgio L; Rodrigues, Lidiany K A

    2011-09-01

    Increasing rates of non-carious cervical lesions due to dental erosion, exposure of dentinal tubules, and hypersensitivity to environmental stimuli have led to the development of new prevention strategies. This study evaluated the effects of a low-intensity diode laser (λ = 808 nm) on the dentinal chemical composition and prevention of demineralization. In addition, the study monitored temperature changes during the course of irradiation. Forty dentin specimens were randomly allocated into four groups (n = 10): G1 - No treatment (control), G2 - irradiated with 15 J/cm(2), G3 - irradiated with 30 J/cm(2), and G4 - irradiated with 60 J/cm(2). Each specimen was partially covered with nail varnish, treated according to the group irradiation levels, and exposed to an erosive challenge (1.0 M hydrochloric acid) for 5 min. Afterwards, dentin loss was profilometrically analyzed and examined by scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX). Intrapulpal temperatures were measured during the dentin irradiation. One-way ANOVA and Tukey tests (p < 0.05) were performed to assess differences. For all irradiated groups, intrapulpal temperature changes were less than 3°C. The G2 group showed statistically significant differences when compared to the other groups, representing the lowest temperature increase. A quantitative element analysis via EDX did not significantly differ (p < 0.05) for Ca, P, F, O, or C between the four groups when measured after irradiation/erosion. The mean wear rates (± SD, μm) were 35.66 ± 7.28; 40.70 ± 5.03; 38.17 ± 10.81 and 25.25 ± 6.87 for G1-G4, respectively. The G4 group statistically differed from all other groups representing the lowest wear rate. These results suggest that dentin irradiation, using a diode laser with levels set at 60 J/cm(2), may induce inhibitory effects on root dentin demineralization without causing any harmful thermal effects. However, the exact mechanism of the action of the laser

  7. Four-color laser irradiation system for laser-plasma interaction experiments

    SciTech Connect

    Pennington, D.M.; Henesian, M.A.; Wilcox, R.B.

    1996-06-01

    Since 1986, optical smoothing of the laser irradiance on targets for Inertial Confinement Fusion (ICF) has gained increasing attention. Optical smoothing can significantly reduce wavefront aberrations that produce nonuniformities in the energy distribution of the focal spot. Hot spots in the laser irradiance can induce local self focusing of the light, producing filamentation of the plasma. Filamentation can have detrimental consequences on the hydrodynamics of an ICF plasma, and can affect the growth of parametric instabilities, as well as add to the complexity of the study of such instabilities as stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). As experiments approach and exceed breakeven (i.e., where driver energy = fusion yield), the likelihood of significant excitation of these processes increases. As a result, the authors are including a scheme for implementing optical-beam smoothing for target experiments in the baseline design for the proposed next-generation ICF facility--the National Ignition Facility (NIF). To verify the efficacy of this design for the suppression of parametric instabilites in NIF-like indirect-drive targets, the authors successfully modified a Nova beamline to simulate the proposed NIF conditions. In this article, they discuss the laser science associated with a four-color target campaign on Nova to test the effect of f-number (ratio of focal length to beam diameter) and temporal smoothing on the scaling of SBS with a four-segment interaction beam using NIF-like parameters. The results of the target series associated with the four-color configuration are discussed elsewhere.

  8. Effect of Nd: YAG laser irradiation on surface properties and bond strength of zirconia ceramics.

    PubMed

    Liu, Li; Liu, Suogang; Song, Xiaomeng; Zhu, Qingping; Zhang, Wei

    2015-02-01

    This study investigated the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser irradiation on surface properties and bond strength of zirconia ceramics. Specimens of zirconia ceramic pieces were divided into 11 groups according to surface treatments as follows: one control group (no treatment), one air abrasion group, and nine laser groups (Nd: YAG irradiation). The laser groups were divided by applying with different output power (1, 2, or 3 W) and irradiation time (30, 60, or 90 s). Following surface treatments, the morphological characteristics of ceramic pieces was observed, and the surface roughness was measured. All specimens were bonded to resin cement. After, stored in water for 24 h and additionally aged by thermocycling, the shear bond strength was measured. Dunnett's t test and one-way ANOVA were performed as the statistical analyses for the surface roughness and the shear bond strength, respectively, with α = .05. Rougher surface of the ceramics could be obtained by laser irradiation with higher output power (2 and 3 W). However, cracks and defects were also found on material surface. The shear bond strength of laser groups was not obviously increased, and it was significantly lower than that of air abrasion group. No significant differences of the shear bond strength were found among laser groups treated with different output power or irradiation time. Nd: YAG laser irradiation cannot improve the surface properties of zirconia ceramics and cannot increase the bond strength of the ceramics. Enhancing irradiation power and extending irradiation time cannot induce higher bond strength of the ceramics and may cause material defect.

  9. Thermal effects in tissues induced by interstitial irradiation of near infrared laser with a cylindrical diffuser

    NASA Astrophysics Data System (ADS)

    Le, Kelvin; Johsi, Chet; Figueroa, Daniel; Goddard, Jessica; Li, Xiaosong; Towner, Rheal A.; Saunders, Debra; Smith, Nataliya; Liu, Hong; Hode, Tomas; Nordquist, Robert E.; Chen, Wei R.

    2011-03-01

    Laser immunotherapy (LIT), using non-invasive laser irradiation, has resulted in promising outcomes in the treatment of late-stage cancer patients. However, the tissue absorption of laser light limits the clinical applications of LIT in patients with dark skin, or with deep tumors. The present study is designed to investigate the thermal effects of interstitial irradiation using an 805-nm laser with a cylindrical diffuser, in order to overcome the limitations of the non-invasive mode of treatment. Cow liver and rat tumors were irradiated using interstitial fiber. The temperature increase was monitored by thermocouples that were inserted into the tissue at different sites around the cylinder fiber. Three-dimensional temperature distribution in target tissues during and after interstitial laser irradiation was also determined by Proton Resonance Frequency. The preliminary results showed that the output power of laser and the optical parameters of the target tissue determined the light distribution in the tissue. The temperature distributions varied in the tissue according to the locations relative to the active tip of the cylindrical diffuser. The temperature increase is strongly related to the laser power and irradiation time. Our results using thermocouples and optical sensors indicated that the PRF method is reliable and accurate for temperature determination. Although the inhomogeneous biological tissues could result in temperature fluctuation, the temperature trend still can be reliable enough for the guidance of interstitial irradiation. While this study provides temperature profiles in tumor tissue during interstitial irradiation, the biological effects of the irradiation remain unclear. Future studies will be needed, particularly in combination with the application of immunostimulant for inducing tumor-specific immune responses in the treatment of metastatic tumors.

  10. Effective observation of treatment of chronic pharyngitis with semiconductor laser irradiation at acupuncture points

    NASA Astrophysics Data System (ADS)

    Li, Suxian; Wang, Xiaoyan; Wang, Yanrong

    1993-03-01

    The treatment of this disease with laser such as He-Ne laser, Nd:YAG laser, and CO2 laser, etc., has been applied in our country, but application of the semiconductor laser therapy has received few reports. It has many advantages, such as ting volume, steady function, simple operation (the patient can operate it by himself), no side effects, remarkable results, and it is very convenient. So the semiconductor laser can be used to treat the chronic pharyngitis with irradiation on acupunctural points. One-hundred-twenty chronic pharyngitis patients were divided into 2 groups, a laser group and a medicine group, 60 cases for each. The effective rate is 91.6% and 66.6%, respectively. Obviously the treatment of chronic pharyngitis with semiconductor laser is valuable for widespread use. The principle of the laser therapy is discussed in the last part of this paper.

  11. Bond strength of an adhesive system irradiated with Nd:YAG laser in dentin treated with Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Malta, D. A. M. P.; Costa, M. M.; Pelino, J. E. P.; de Andrade, M. F.; Lizarelli, R. F. Z.

    2008-02-01

    The purpose of this in vitro study was to verify through micro tensile bond test the bond strength of an adhesive system irradiated with Nd:YAG laser in dentine previously treated with Er:YAG laser. Twenty caries free extracted human third molars were used. The teeth were divided in four experimental groups (n = 5): (G1) control group; (G2) irradiation of the adhesive system with the Nd:YAG laser; (G3) dentin treatment with Er:YAG laser; (G4) dentin treatment with Er:YAG laser followed by the irradiation of the adhesive system with Nd:YAG laser. The Er:YAG laser fluency parameter for the dentin treatment was of 60 J/cm2. The adhesive system was irradiated with the Nd:YAG laser with fluency of 100 J/cm2. Dental restorations were performed with Adper Single Bond 2/Z250. One tooth from each group was prepared for the evaluation of the adhesive interface under SEM and bond failure tests were also performed and evaluated. The statistical analysis showed statistical significant difference between the groups G1 and G3, G1 and G4, G2 and G3, and G2 and G4; and similarity between the groups G1 and G2, and G3 and G4. The adhesive failures were predominant in all the experimental groups. The SEM analysis showed an adhesive interface with features confirming the results of the mechanical tests. The Nd:YAG laser on the adhesive system did not influence the bond strength in dentin treated or not with the Er:YAG laser.

  12. Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

    PubMed

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2016-09-01

    Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM.

  13. Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

    PubMed

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2016-09-01

    Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM. PMID:27607281

  14. Interstitial laser irradiation of metastatic mammary tumors in combination with intratumoral injection of immunoadjuvant

    NASA Astrophysics Data System (ADS)

    Joshi, Chet; Jose, Jessnie; Figueroa, Daniel; Goddard, Jessica; Li, Xiaosong; Liu, Hong; Nordquist, Robert E.; Hode, Tomas; Chen, Wei R.

    2012-03-01

    Laser immunotherapy (LIT) was developed to treat metastatic cancers using a combination of laser irradiation and immunological stimulation. The original design of LIT employs a non-invasive, selective laser photothermal interaction, using an in situ light-absorbing dye. However, this non-invasive treatment mode faces challenges in treating deep, large tumors. Furthermore, it has difficulties in the cases of highly pigmented skin overlying target tumors. To overcome these limitations, interstitial laser immunotherapy (ILIT) was proposed. In ILIT, a cylindrical, side-fire fiber diffuser is placed inside the target tumor to induce thermal damage. To enhance the interstitial irradiation induced photothermal interaction, an immunological modifier, glycated chitosan (GC), is injected into the tumor after the laser treatment. In this study, a cylindrical diffuser with an active length of 1 cm was used to treat tumors of 1 to 1.5 cm in size. Different laser powers (1 to 3 watts) and different irradiation durations (10 to 30 minutes) were used to test the thermal effects of ILIT. Different doses of the GC (1.0%, 0.1 to 0.6 ml per rat) were used to determine the immunological effects of ILIT. Our results show that the animal survival depends on both laser dose and GC dose. A dose of 0.2 ml per tumor appeared to result in the highest survival rate under interstitial laser irradiation with 2.5 watts and 20 minutes. While the results in this study are not conclusive, they indicate that interstitial laser irradiation can be combined with immunotherapy to treat metastatic cancers. Furthermore, our results suggest that an optimal combination of laser dose and GC dose could be obtained for future clinical protocols using interstitial laser immunotherapy.

  15. Elevation of plasma membrane permeability upon laser irradiation of extracellular microbubbles.

    PubMed

    Zhou, Yu; Zhou, Xi-Yuan; Wang, Zhi-Gang; Zhu, Ye-Feng; Li, Pan

    2010-07-01

    Laser-mediated gene transfection has received much attention as a new method for targeted gene therapy because of the high controllability of laser energy and direction. In this report, we describe a combination laser-microbubble system that enables membrane-impermeable molecules to penetrate cell membranes. The main theories we apply are optical breakdown and photoacoustic generation, which are induced by laser irradiation. Firstly, different types of laser light (Ar-green, Novus Varia poly-wavelength and Nd:YAG laser) were adopted to blast liposome microbubble contrast medium; subsequently, the Nd:YAG laser (1064 nm, 4 ns), which could successfully blast microbubbles, and ultrasound were used in combination to irradiate a mixture of liposome microbubbles and retinoblastoma (Rb) cells. After irradiation, membrane permeability was evaluated by flow cytometric assay using propidium iodide (PI) and fluorescein diacetate (FDA). The proportion of permeabilized resealed cells was affected by changes in the light energy. All of the Nd:YAG laser, Nd:YAG combination laser-microbubble and combination ultrasound-microbubble systems were able to permeabilize the Rb cells. These results suggest that this combination laser-microbubble system is a new means of delivering exogenous materials into living cells.

  16. Investigation of laser ion acceleration inside irradiated solid targets by neutron spectroscopy

    SciTech Connect

    Youssef, A.; Kodama, R.; Tampo, M.

    2006-03-15

    Origins and acceleration directions of accelerated ions inside solid LiF, CH-LiF, and LiF-CH targets irradiated by a 450 fs, 20 J, 1053 nm laser at an intensity of 3x10{sup 18} W/cm{sup 2} have been investigated by neutron spectroscopy. The irradiated targets generate neutrons through the reaction {sup 7}Li (p,n){sup 7}Be between accelerated protons and background {sup 7}Li ions inside the target. The produced neutron spectra observed from two different observation angles 20 deg. and 120 deg. to the target rear-side normal. From the measured and calculated spectra, by three-dimensional Monte Carlo code, the maximum energy, the total number, and the slope temperature of the accelerated ions are investigated. The results indicate that ions are not only accelerated from the front surface toward the rear surface, but also from the rear surface toward the front surface with comparable maximum energy and higher number.

  17. Space–time characterization of ultra-intense femtosecond laser beams

    NASA Astrophysics Data System (ADS)

    Pariente, G.; Gallet, V.; Borot, A.; Gobert, O.; Quéré, F.

    2016-08-01

    Femtosecond lasers can now deliver ultrahigh intensities at focus, making it possible to induce relativistic motion of charged particles with light and opening the way to new generations of compact particle accelerators and X-ray sources. With diameters of up to tens of centimetres, ultra-intense laser beams tend to suffer from spatiotemporal distortions, that is, a spatial dependence of their temporal properties that can dramatically reduce their peak intensities. At present, however, these intense electromagnetic fields are characterized and optimized in space and time separately. Here, we present the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100 TW peak-power laser, and reveal the spatiotemporal distortions that can affect such beams. This new measurement capability opens the way to in-depth characterization and optimization of ultra-intense lasers and ultimately to the advanced control of relativistic motion of matter with femtosecond laser beams structured in space–time.

  18. Space-time characterization of ultra-intense femtosecond laser beams

    NASA Astrophysics Data System (ADS)

    Pariente, G.; Gallet, V.; Borot, A.; Gobert, O.; Quéré, F.

    2016-08-01

    Femtosecond lasers can now deliver ultrahigh intensities at focus, making it possible to induce relativistic motion of charged particles with light and opening the way to new generations of compact particle accelerators and X-ray sources. With diameters of up to tens of centimetres, ultra-intense laser beams tend to suffer from spatiotemporal distortions, that is, a spatial dependence of their temporal properties that can dramatically reduce their peak intensities. At present, however, these intense electromagnetic fields are characterized and optimized in space and time separately. Here, we present the first complete spatiotemporal experimental reconstruction of the field E(t,r) for a 100 TW peak-power laser, and reveal the spatiotemporal distortions that can affect such beams. This new measurement capability opens the way to in-depth characterization and optimization of ultra-intense lasers and ultimately to the advanced control of relativistic motion of matter with femtosecond laser beams structured in space-time.

  19. Laser safety evaluation and output measurements for the VITAL -2 Variable Intensity Tactical Aiming Light (laser) used with the Proforce M-4 system in force-on-force exercises.

    SciTech Connect

    Augustoni, Arnold L.

    2004-02-01

    A laser safety hazard evaluation and pertinent output measurements were performed (June 2003 through August 2003) on several VITAL-2 Variable Intensity Tactical Aiming Light--infrared laser, associated with the Proforce M-4 system used in force-on-force exercises. The VITAL-2 contains two diode lasers presenting 'Extended Source' viewing out to a range on the order of 1.3 meters before reverting to a 'Small Source' viewing hazard. Laser hazard evaluation was performed in concert with the ANSI Std. Z136.1-2000 for the safe use of lasers and the ANSI Std. Z136.6-2000 for the safe use of lasers outdoors. The results of the laser hazard analysis for the VITAL-2, indicates that this Tactical Aiming IR laser presents a Class 1 laser hazard to personnel in the area of use. Field measurements performed on 71 units confirmed that the radiant outputs were at all times below the Allowable Emission Limit and that the irradiance of the laser spot was at all locations below the Maximum Exposure Limit. This system is eye-safe and it may be used under current SNL policy in force-on-force exercises. The VITAL-2 Variable Intensity Tactical Aiming Light does not present a laser hazard greater than Class 1, to aided viewing with binoculars.

  20. High Intensity Laser Therapy (HILT) versus TENS and NSAIDs in low back pain: clinical study

    NASA Astrophysics Data System (ADS)

    Zati, Allesandro; Fortuna, Damiano; Valent, A.; Filippi, M. V.; Bilotta, Teresa W.

    2004-09-01

    Low back pain, caused by lumbar disc herniation, is prevalently treated with a conservative approach. In this study we valued the efficacy of High Intensity Laser Therapy (HILT), compared with accepted therapies such as TENS and NSAIDs. Laser therapy obtained similar results in the short term, but better clinical effect over time than TENS and NSAIDs. In conclusion high intensity laser therapy appears to be a interesting new treatment, worthy of further research.