对自倍频(SFD)效应在半导体可饱和吸收镜(SESAM)锁模激光器中抑制调Q倾向的机制进行了详细的理论研究和数值模拟。推导了含有自倍频效应的SESAM锁模激光器中非线性损耗的表达式, 建立了描述激光器内脉冲能量变化的方程组。用微扰法分析了锁模激光器的稳定性条件, 证明了适当强度的自倍频效应能够抑制激光器的调Q倾向, 降低稳定锁模的阈值。用计算机仿真模拟了锁模激光器在有无自倍频效应时的特征, 验证了理论推导的结论。

The mechanism which suppresses Q-switched tendency by self-frequency-doubled (SFD) effect in a SFD mode-locked laser with a semiconductor saturable absorbed mirror (SESAM) was theoretically studied and numerically simulated. The expression of nonlinear losses, including the saturable loss of SESAM and the nonlinear loss caused by SFD effect, was deduced. The partial differential equations for intracavity pulse energy were developed. The stable conditions of the mode-locked laser were theoretically studied by the perturbation method. It was proved that suitable SFD effect can suppress Q-switching instabilities and reduce the threshold of stable mode-locking. Numerical simulations of mode-locked laser with and without SFD effect were carried out, which certificated the theoretical analysis.