Efficient generation of third harmonic radiation of air filament induced by plasma grating

Abstract

In this paper, the dependences of the third harmonic generation (THG) of a probe filament on the relative position of the probe filament interacting with the plasma grating and the position of the plasma grating interacting with the probe filament are investigated. The phase matching between the third harmonic of the probe filament and the fundamental wave of the plasma grating is earlier to achieve when the head of the probe filament interacts with the plasma grating, inducing the enhancement of the third harmonic generation, while the phase mismatching happens when the trail of the probe filament interacts with the plasma grating. The distribution of the clamping laser intensity inside the plasma grating results in the dependence of the THG on the positions of the plasma grating interacting with the probe filaments. It is an effective method of promoting the THG by setting the crossing angle between the probe filament and the plasma grating to be very small.