提出采用两个光纤耦合器构成具有复合环的非线性放大环形镜。分析表明,改变构成非线性放大复合环形镜的光纤耦合器的耦合系数可以改变非线性复合光纤环形镜的非线性传输特性,调节非线性光反射和透射率。采用非线性放大复合环形镜与半导体饱和吸收体组成复合腔掺铒光纤激光器,获得了十分稳定的被动锁模脉冲输出,得到了重复频率为248 MHz的谐频锁模脉冲序列。实验表明,采用非线性放大复合环形镜构成复合腔光纤激光器,有可能获得高重复频率的锁模脉冲。

A nonlinear amplifying compound loop mirror (NACLM) constructed by two fiber couplers is presented and analyzed. The analysis shows that the nonlinear reflection characteristics of the NACLM can be adjusted by changing the splitting ratio of the optical fiber couplers. Using the NACLM and a bulk semiconductor saturable absorber, stable passive mode locking in an erbium doped fiber laser can be obtained. Passively mode locked pulses of a repetition rate of 248 MHz has been achieved. It is suggested that using a NACLM as a passive mode locking element, generation of ultrashort pulses of very high repetition rate is promising with a fiber laser.