锁模光纤激光的倍频及波长调谐实验研究

利用周期性极化铌酸锂（Periodically Poled Lithium Niobate, PPLN）晶体实现了对掺镱锁模光纤激光器输出单横模激光的倍频，产生了532nm波长附近的倍频脉冲光。基于准相位匹配（Quasi Phase Matching, QPM）技术，通过改变基频光到PPLN晶体的入射角，使不同中心波长的基频光达到准相位匹配条件，实现倍频光波长的调谐。对带宽60 nm的锁模激光倍频得到带宽1.5 nm、中心波长532nm的脉冲激光输出。以掺Yb锁模光纤激光作为基频光，调节PPLN晶体角度，获得了中心波长连续变化的倍频激光，入射角度调节范围0°~25°，对应的倍频光波长调谐范围531.8nm~535.6nm。波长变化趋势与理论分析一致。

Experimental study on frequency doubling and wavelength tuning of a mode-locked fiber laser

Frequency doubling pulse laser around 532nm has been obtained through irradiating PPLN crystal with a single mode laser beam, which emitting from a Yb-doped mode-locked fiber laser. Based on Quasi Phase Matching technology, the SHG (Second Harmonic Generation) wavelength tuning can be realized by changing incident angel of fundamental wave that irradiating the PPLN. Pumped by a mode-locked fiber laser which has a bandwidth of 60 nm, the pulse laser SHG (Second Harmonic Generation) is obtained from the PPLN, and the output laser has a bandwidth of 1.5 nm and center wavelength of 532 nm. The SHG wavelength was continuously detuned by adjusting the angle of PPLN crystal. It worked out an angle tuning range of 0° to 25°, corresponding to the SHG wavelength tuning from 531.8nm to 535.6nm. The wavelength detuning is in good agreement with the theory.