Optical frequency combs based on a perioddoubling mode-locked Er-doped fiber laser

The phase locking mechanism and results of frequency comb based on double period mode locked (PD-ML) fiber laser are studied. Mode locked fiber lasers are designed to switch from basic period mode locking (FML) to PD-ML with similar output pulses by simply changing the pump. The experimental results show that the new comb generated in PD-ML has a strong correlation with the original teeth, and has a consistent carrier envelope offset (CEO) frequency. Therefore, the carrier envelope offset frequency and repetition frequency of the PD-ML laser can be locked by controlling the pump and cavity length. In the same f-2f heterodyne system and locking circuit, the phase locking of optical combs of PD-ML and FML with two repetition rates and the switching between them can be realized only by changing the pump.

本研究针对基于双周期锁模（PD-ML）光纤激光器的频率梳锁相机制与效果展开探究。通过仅调整泵浦参数，即可实现锁模光纤激光器从基频周期锁模（FML）到双周期锁模的切换，且二者输出脉冲特性相近。实验结果表明，双周期锁模模式下产生的新型频率梳与原始梳齿具有强相关性，且载波包络偏移（CEO）频率保持一致。因此，可通过调控泵浦参数与腔长，实现双周期锁模激光器的载波包络偏移频率与重复频率的锁相。在同一套f-2f外差系统与锁相电路中，仅通过调整泵浦参数，即可实现两种重复频率下双周期锁模与基频周期锁模光纤频率梳的锁相，以及二者之间的模式切换。