Abstract
In this thesis, we investigate the generation of (355nm) light by the fundamental output of the in Q-switched Nd:YAG laser (λ=1064nm) and its second harmonic (λ=532nm) in argon. The emphasis is on the influence of relative phases and intensities of the 2-color light. Based on our simulation of the 3rd harmonic of the Nd:YAG laser, the intensity of the 355nm light will oscillate periodically with the relative phases of the two-frequency driving electric fields. The periodic modulation of the 3rd-order harmonic can be attributed to the interference of third-harmonic signals generated from a direct THG channel (3ω = ω + ω + ω) and four-wave mixing (FWM) channel (3ω = 2ω + 2ω − ω). Our experimental results are in good agreement with the theoretical simulation. In addition, the dependence of the intensity of the 2-color exciting light and the gas pressure dependence of the 3rd-order harmonic signal are also presented. It was found out that the 3rd harmonic output exhibits saturation behavior as the intensity of the second harmonic reaches 7.6×1012 W/cm2. A square-law dependence on gas pressure is also in agreement with the prediction of the theory.