Analysis of Effect of Aberrations on the Quality of Beams in Third Harmonic Generation

A theoretical analysis is presented for the beam quality of the third-harmonic generation.A split-step algorithm based on the Fast Fourier Transform and a Runge-Kutta integrator is used.Taking into account the affects of the second-order nonlinear,the third-order nonlinear,transverse walk-off and diffraction,mostly the effects of aberrations of the input fundamental wave on the harmonic beam's quality are discussed.The result shows that the aberrations,including the amplitude modulation and phase modulation,of the input fundamental wave will decreases the quality of the beams, and the latter's effects is more severe.While if the phase modulation of the input fundamental wave is smaller enough,it will not affect the quality of the third-harmonic wave.