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All-Optical Switching Based on the Plasma Channel Induced by Laser Pulses
摘要： We display a theoretical and experimental study of all-optical switching for signal lasers based on the plasma channel induced by the control laser. Using the plasma channel generated in the carbon disulfide (CS2) solution, the signal light can be modulated as some spatial distributions including unchanging, ring-shaped beam, and other intensity profiles. The modulation on the signal light can be conveniently adjusted by changing the control light’s incident intensity distribution. We can infer the dark spot shape in the modulated signal laser through the intensity profile of control laser beam. These results provide the great potential of plasma channel induced by lasers as an all-optical switching for various optoelectronic applications.
关键词： all-optical switching,plasma channel,spatial modulation,optoelectronic applications,laser pulses
更新于2025-09-12 10:27:22
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Simulation of Self-focusing of Femtosecond Laser Pulses with Normal Dispersion in Air Using the Diffraction-Beam Tube Approach
摘要： Based on numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond Ti:sapphire laser pulses in air is studied. The main features of the filamentation have been determined at various pulse duration, initial beam radii, and peak radiation powers based on the results of numerical solutions of the nonlinear Schr?dinger equation in a Kerr-plasma dissipative dispersion medium and using the diffraction-beam tube approach. Dispersion is detected in the cases where the dispersion length is not a minimum at the scale of the process. It is shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases as the dispersion distortions of the pulse increase, and the filamentation channel length is reduced. For shorter laser pulses (tens of femtoseconds), the filamentation ceases as the laser beam radius increases. The size of the energy-replenishing diffraction-beam tube and the angular divergence of postfilamentation light channels increase for this class of pulses.
关键词： filamentation,self-focusing,femtosecond laser pulses,diffraction-beam tube,normal dispersion
更新于2025-09-12 10:27:22
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High-Repetition-Rate and High-Beam-Quality Laser Pulses with 1.5MW Peak Power Generation from a Two-Stage Nd:YVO <sub/>4</sub> Amplifier <sup>*</sup>
摘要： We develop a two-stage end-pumped Nd:YVO4 amplifier seeded by a passively Q-switched microchip laser. An average output power of 13.5 W with repetition rate up to 7 kHz and pulse duration of ～1.24 ns is obtained, corresponding to a pump extraction efficiency of 16.1% (19.5% for the second stage) and peak power of ～1.5 MW. The beam quality factors at maximum output power are measured to be ?? 2 ?? = 1.56 and ?? 2 ?? = 1.48. We introduce an analytical model to estimate gain and beam quality after amplification. This model focuses on the influence of ratio of seed spot radius to pump spot radius when designing an amplifier. Moreover, our experiments reveal that the re-imaging system in the double-pass configuration can be used to enhance the beam quality.
关键词： peak power,high-beam-quality,Nd:YVO4 amplifier,high-repetition-rate,laser pulses
更新于2025-09-12 10:27:22
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Modeling tomographic measurements of photoelectron vortices in counter-rotating circularly polarized laser pulses
摘要： Recent experiments [D. Pengel, S. Kerbstadt, L. Englert, T. Bayer, and M. Wollenhaupt, Phys. Rev. A 96, 043426 (2017)] have measured the photoelectron momentum distribution for three-photon ionization of potassium by counter-rotating circularly polarized 790-nm laser pulses. The distribution displays spiral vortices, arising from the interference of ionizing wave packets with different magnetic quantum numbers. The high level of multidimensional detail observed in the distribution makes this an ideal case in which to demonstrate the accuracy of emerging theoretical techniques applicable to such problems. We use the R-matrix with time dependence approach to investigate this process. We calculate the full-dimensional photoelectron momentum distribution, and compare against a set of planar projections of this distribution previously measured in experiment.
关键词： multiphoton ionization,potassium,photoelectron vortices,counter-rotating circularly polarized laser pulses,R-matrix with time dependence
更新于2025-09-12 10:27:22
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - THz response of metallic structures to femtosecond laser pulses
摘要： The talk is devoted to the nonlinear effects in metallic structures (like gratings and nanoparticle arrays) irradiated by femtosecond laser pulses. Possible mechanisms of delayed THz response and specific non-quadratic nonlinear regimes of conversion are analyzed. In contrast to previous models, only low-frequency currents inside the metal are considered without involving electron emission and acceleration. Special attention is paid to the role of plasmonic resonances at optical frequency in the enhancement of low-frequency nonlinear response.
关键词： femtosecond laser pulses,plasmonic resonances,metallic structures,nonlinear effects,THz response
更新于2025-09-12 10:27:22
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Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification || Application of Liquid Laser Ablation: Organic Nanoparticle Formation and Hydrogen Gas Generation
摘要： Laser ablation is induced by a heating process of materials through the absorption of laser light and results in an explosive expansion of materials. For materials located in liquid, in contrast to those in vacuum, laser ablation proceeds under rather mild conditions via a cycle of heating and cooling by mediated solvent; therefore, it is applicable for organic solids to fragment into nanoparticles. Alternatively, for effective light absorbers, the irradiated site becomes the reaction centre of a photochemical reaction even in liquids, resulting in hydrogen gas generation. In this chapter, two topics of laser ablation in the liquid phase are presented: nanoparticle formation of organic materials and hydrogen gas generation from solid carbon in water. Thereby, the extended abilities of liquid laser ablation to transform ordinary materials into functional ones are introduced.
关键词： spectroscopy,carbon-based nanoparticles,hydrogen generation,colloidal solution,nanosecond laser pulses,organic nanoparticles
更新于2025-09-12 10:27:22
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Nonlinear absorption dynamics simulated in internal modification of glass at 532nm and 1064nm by ultrashort laser pulses
摘要： Dynamic ionization process at high pulse repetition rate is analysed based on the model consisting of rate equation for free-electrons, Gaussian beam propagation equation, thermal conduction and thermal ionization, showing the plasma generated near the geometrical focus moves toward the laser source periodically by the contribution of avalanche ionization. The effects of laser wavelength on the ionization process are discussed by comparing the contributions of multiphoton ionization and avalanche ionization. The crack tendency of 532nm and 1064nm is also compared between single pulse and multipulse irradiation.
关键词： thermal conduction model,nonlinear ionization process,glass,internal modificatin,thermal ionization,crack,ultrashort laser pulses
更新于2025-09-12 10:27:22
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Proton acceleration by collisionless shocks using a supersonic H <sub/>2</sub> gas-jet target and high-power infrared laser pulses
摘要： For most laser-driven ion acceleration applications, a well-characterized intense ion beam with a low divergence and a controllable energy spectrum produced at a high repetition rate is needed. Gas-jet targets have given promising results in simulations, and they have several technical advantages for high-repetition-rate lasers. In this work, we report on proton acceleration to energies up to 6 MeV using a supersonic H2 gas-jet target at the LULI PICO2000 laser facility. The experimental results are compared with the plasma hydrodynamics and the particle-in-cell simulations to identify the acceleration mechanisms at play.
关键词： supersonic H2 gas-jet target,collisionless shocks,proton acceleration,high-power infrared laser pulses
更新于2025-09-12 10:27:22
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Plasma formation and relaxation dynamics in fused silica driven by femtosecond short-wavelength infrared laser pulses
摘要： Laser-induced plasma formation and subsequent relaxation in dielectric solids is the precursor to structural modi?cations serving as the basis for direct laser writing of functional optical micro- and nanostructures. Based on an experimental arrangement combining a time-resolved transmission measurement with a cross-phase modulation measurement, we isolate the plasma formation and relaxation dynamics in the bulk of amorphous fused silica excited by femtosecond short-wavelength infrared (k ? 2100 nm) laser pulses. Whereas the relaxation time of the generated subcritical electron-hole plasma was so far assumed to be constant, our ?ndings indicate an intensity-dependent relaxation time. We attribute this intensity dependence to vibrational activation of the medium, leading to detrapping of trapped carriers and a reduced trapping probability.
关键词： plasma formation,femtosecond laser pulses,relaxation dynamics,fused silica,short-wavelength infrared
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photoelectron Circular Dichroism at the Few-Cycle Limit in the Tunnel Ionization Regime
摘要： Photoelectron circular dichroism (PECD) is a process that leads to a forward-backward asymmetry (with respect to the laser propagation direction) in photoelectron distributions created upon interaction of a circularly or elliptically polarized laser with a chiral molecule. The PECD effect has been shown in a broad range of ionization mechanisms from direct photoionization through multi-photon regime, above-threshold ionization to the tunnel ionization [1]. The fact that the effects of chirality can be observed in the tunnel ionization regime opens up the possibility to connect this fundamental effect to strong-field science with prospects for studying and driving sub-laser-cycle and attosecond phenomena connected to PECD [2]. However, a thorough understanding of PECD in the tunneling regime is of yet missing. In this study the effect of trajectory related parameters like electron energy or CEP on the PECD is investigated in order to determine the role of the scattering on the chiral potential.
关键词： few-cycle laser pulses,tunnel ionization,Photoelectron circular dichroism,chiral molecules
更新于2025-09-12 10:27:22