The type Ⅰ/Ⅱ angle-detuning scheme for third harmonics generation has been taken as an example,and then the influence of low-frequency phase perturbation on the focal characterization of the tripling field has been discussed in details.

Using type I/II angle-detuning schemes for third harmonics generation,the effect of third-order nonlinear interaction of KDP crystal on the tripling efficiency and beam quality under high power condition has been studied.

The influence of third harmonics generation on the focal spot of the tripling field has been discussed.

Inverse problem of monochromatic third-harmonic generation;

Based on the nonlinear coupling equations,the relation between group-velocities of 1ω,2ω and 3ω waves in the mixing process of broadband third-harmonic generation(THG)is investigated theoretically.

A theoretical analysis is presented for third harmonic conversion in KDP (KH_2PO_4) for type Ⅰ/ type Ⅱ angle-detuning scheme of high-intensity laser.

Using type Ⅰ/type Ⅱ angle-detuning scheme for third harmonic generation,the effect of phase ripple on the characteristic of third harmonic conversion is considered and calculated when the input fundamental field is super-Gaussian beam.