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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) - Theoretical Investigation of the Optimal Nonlinear Crystal Thickness for THz Generation from two-Color Laser Pulse Ionized Gas under Different Laser Pulse Parameters
摘要： The generation of terahertz (THz) radiation by two-color laser pulse induced gas plasma is an actively researched topic since its exploration. It is a tabletop, powerful spectroscopic tool in the far-infrared spectral regime. It is possible to generate THz radiation by remotely more than 100m from the laser system, the remote sensing of the THz radiation also possible. Furthermore, the THz spectroscopy is capable to identify chemicals in a nondestructive way. By the combination of the former mentioned features, the THz spectroscopy is a powerful tool to identify drugs, poisons and explosives with remotely in a nondestructive way. One of the drawbacks of the THz radiation generated from two-color laser pulse induced gas plasma is the low efficiency. In the last two decades many publications have been published about increasing the efficiency of this method. Spectrally shaped fundamental beam has been proved to be an effective way to control the generated THz field properties. Using a step phase plate is demonstrated to enhance the generated THz intensity with a factor of two. Combining the fundamental, the second harmonic and the third harmonic beams also increase the THz pulse generation efficiency. Increasing the fundamental laser pulse wavelength has proved to be improve the generation efficiency. In this publication, we examined the nonlinear crystal thickness effect on the THz generation from two-color laser pulse induced gas plasma. It was found the at a given fundamental pulse energy and pulse duration there is an optimal thickness for the nonlinear crystal, where the THz generation is the most effective as seen on Fig. 1. In case of a thinner crystal, than the optimal crystal thickness, the second harmonic generation effectivity decrease, which entails the THz generation effectivity also decrease. In case of thicker crystal, than the optimal crystal thickness, the material dispersion decreases both the fundamental and its second harmonic’s peak power, which entails the THz generation effectivity decrease. The optimal nonlinear crystal thickness was examined in the function of the fundamental laser pulse energy, pulse duration, central wavelength and the nonlinear crystal distance from the focal spot. It was found that all the former mentioned parameters have a great impact on the optimal nonlinear crystal thickness. In conclusion, choosing the proper crystal parameters considering the laser and the setup parameters are a crucial point of the THz generation from two-color laser pulse induced gas plasma.
关键词： optimal thickness,two-color laser pulse,gas plasma,nonlinear crystal thickness,THz generation
更新于2025-09-12 10:27:22
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Spin-polarization effects of an ultrarelativistic electron beam in an ultraintense two-color laser pulse
摘要： Spin-polarization effects of an ultrarelativistic electron beam head-on colliding with an ultraintense two-color laser pulse are investigated comprehensively in the quantum radiation-dominated regime. We employ a Monte Carlo method, derived from the recent work of Li et al. [Phys. Rev. Lett. 122, 154801 (2019)], to calculate the spin-resolved electron dynamics and photon emissions in the local constant field approximation. We find that electron radiation probabilities in adjacent half cycles of a two-color laser field are substantially asymmetric due to the asymmetric field strengths and, consequently, after interaction the electron beam can obtain a total polarization of about 11% and a partial polarization of up to about 63% because of radiative spin effects, with currently achievable laser facilities, which may be utilized in high-energy physics and nuclear physics. Moreover, the considered effects are shown to be crucially determined by the relative phase of the two-color laser field and robust with respect to other laser and electron-beam parameters.
关键词： radiative spin effects,Monte Carlo method,quantum radiation-dominated regime,spin-polarization,two-color laser pulse,ultrarelativistic electron beam
更新于2025-09-11 14:15:04
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Semiclassical analysis of photoelectron interference in a synthesized two-color laser pulse
摘要： We measure the photoelectron energy spectra from strong-field ionization of Kr in a two-color laser pulse consisting of a strong 400-nm field and a weak 800-nm field. The intensities of the main above-threshold ionization (ATI) and sideband peaks in the photoelectron energy spectra oscillate roughly oppositely with respect to the relative phase between the two-color components. We study the photoelectron interferometry in the strong-field ATI regime from the view of interference of different electron trajectories in order to extend reconstruction of attosecond harmonic beating by interference of two-photon transitions (RABBITT)-type analysis to the strong-field regime. Based on the strong-field approximation model, we obtain analytical expressions for the oscillations of both ATI and sideband peaks with the relative phase. A phase shift of π/4 with respect to the field maximum of the two-color laser pulse is revealed for the interference maximum in the main ATI peak without including the effect of the atomic potential.
关键词： ATI,RABBITT,photoelectron interference,two-color laser pulse,strong-field ionization,sideband peaks
更新于2025-09-11 14:15:04