Terahertz radiation is investigated using nonlinear interaction of a laser beat wave with a density-modulated medium of graphite nanoparticles. A beam-decentering parameter, b, is used to modify the polarizing field’s profile to produce different-shaped laser pulse envelopes, e.g. Gaussian, top head, ring-shaped and cosh-Gaussian. The normal vectors corresponding to the basal planes of graphite nanoparticles are considered to be aligned parallel and perpendicular to the polarization of the propagating laser pulse. The electronic cloud of the graphite nanoparticles acquires a nonlinear oscillatory velocity under the influence of a nonlinear force that produces a strong nonlinear current at the beat-wave frequency . The strong nonlinear current allows the emission of radiation in the terahertz frequency regime. The terahertz radiation intensifies and attains a peak value when the laser beat-wave frequency () equals the plasmon frequency of the nanoparticles. The terahertz radiation’s amplitude is enhanced by up to the fourth order of magnitude in the case of a cosh-Gaussian laser pulse, when the beam-decentering parameter, b, equals 5. The present numerical results reveal that by changing the shape of a laser pulse and the properties of nanoparticles, one can control and tune the THz emission.

使用激光拍波与石墨纳米颗粒的密度调制介质的非线性相互作用研究了太赫兹辐射。光束偏心参数b用于修改偏振场的轮廓，以产生不同形状的激光脉冲包络，例如高斯，顶头，环形和cosh-Gaussian。对应于石墨纳米颗粒基面的法线矢量被认为与传播的激光脉冲的偏振方向平行且垂直。石墨纳米粒子的电子云在非线性力的作用下获得非线性振荡速度，该非线性力在拍波频率下产生强大的非线性电流。强大的非线性电流允许以太赫兹频率范围发射辐射。当激光拍波频率（）等于纳米粒子的等离激元频率时，太赫兹辐射增强并达到峰值。当光束偏心参数b等于5时，在cosh-Gaussian激光脉冲的情况下，太赫兹辐射的幅度增加了多达四个数量级 。目前的数值结果表明，通过改变激光器的形状脉冲和纳米粒子的特性，可以控制和调整THz发射。