双色激光场下太赫兹辐射能量的调控研究

Study on the regulation of terahertz radiation energy in two-color laser field

提升太赫兹(THz)脉冲产生能量一直是近些年超快光学的研究热点之一。基于双色激光在空气中拉丝产生THz波的数值模型,在隧穿电离范围内,详细分析了双色激光场产生THz波的最佳参数组合以及其产生变化的物理机理,用于得到最强的THz波辐射能量。双色激光场组合的电场具有不对称性,其引起的快速振荡有利于电子的加速过程,进而产生更大电子数密度以及在沿拉丝距离形成了更强的累积净电流。当电子密度和净电流增加时,使得单点THz辐射更强,拉丝各点辐射的THz波相干叠加,于是在远场得到了更强的THz波能量。这些研究结果为不同激光产生条件下增强THz波辐射能量提供了详尽的参数分析及理论依据,重点研究了不同寻常波长组合及不同相对相位对激光拉丝产生太赫兹波的影响,对后续大幅增强THz辐射效率具有重要意义。

Increasing the energy of terahertz pulses has been one of the research hotspots of ultrafast optics in recent years. In this paper, based on the numerical model of terahertz wave generated by two-color laser plasma filament in air, in the range of tunneling ionization, we analyze in detail the optimal parameter combination of terahertz wave generated by two-color laser field and the physical mechanism of its change, so as to obtain the strongest terahertz wave radiation energy. We analyze its physical mechanism. The electric field of the combination of two-color laser fields is asymmetric, and the rapid oscillation enhances the acceleration process of electrons,resulting in larger electron number density and stronger cumulative net current along the plasma filament. When the electron density and net current increase, the single point terahertz radiation is stronger, and the terahertz waves radiated at each point of plasma filament are coherently superimposed, so a stronger terahertz wave energy is obtained in the far field. These research results provide a detailed parameter analysis and theoretical basis for enhancing the radiation energy of THz wave under different laser generation conditions, and focus on the influence of unusual wavelength combination and different relative phases on the generation of terahertz wave by laser wire drawing, which is of great significance for greatly enhancing the radiation efficiency of THz in the future.