通过理论推导建立了频率转换过程中强度调制形成的物理模型，认为基频光的强度和相位扰动都将导致三倍频光强度的调制。采用数值模拟方法定量研究了频率转换过程中强度调制的演化规律，研究结果表明通过优化倍频晶体失谐角可以降低基频光强度扰动对三倍频强度调制的影响，而增加频率转换器的接受带宽则可以抑制基频光相位扰动的影响。此外，由于三倍频效率最优和时间调制度最小时对应的混频晶体失谐角略有差别，在优化设计时应综合考虑两个因素的影响。

The physical model of amplitude modulation formation in frequency conversion process is established by theoretical derivation, amplitude modulation of tripling beam can be caused by both amplitude modulation and phase aberration of fundamental beam. The evolution process of amplitude modulation during the third harmonic generation(THG) is researched by numerical simulation, the results show that tripling amplitude modulation caused by fundamental amplitude modulation can be reduced by optimize doubling crystal detuned angle, while the influence of fundamental phase aberration can be depressed by increasing accepting bandwidth of frequency converter. Moreover, because there is a little difference in the optimized tripling detuned angle between optimal THG efficiency and minimal temporal modulation, both factors in an optimal design should be synthesised.