百皮秒脉冲放大中自相位调制效应实验研究

Experimental Study on Self-phase Modulation in Hundred-picosecond Pulse Amplification

利用掺镱双包层光纤放大器对百皮秒单脉冲(重复频率1Hz)进行了放大实验,分析了其放大过程中自相位调制对脉冲时域和频域特性的影响.采用小芯径(纤芯直径6.5μm)掺镱双包层光纤作为增益介质,研究了放大器中从小信号增益到增益深度饱和整个变化过程中自相位调制引起的频谱展宽效应,并分析了SPM引起的脉冲波形和频谱光强分布的变化.采用布喇格光纤光栅扫描方法观察了其光谱的变化,解决了单脉冲光谱不易测量的问题.结果表明:区别于无源光纤中的自相位调制效应,随着抽运功率的增加,百皮秒脉冲放大过程中增益饱和效应和自相位调制效应的共同作用,使脉冲频谱分裂成不对称双峰结构,且光强分布先向短波后逐渐向长波集中.

The single hundred-picosecond pulse amplification（the repetition rate is 1 Hz） was studied experimently in the Ytterbium-doped double clad fiber amplifier.The characteristic of time-domain and frequency-domain pulse waveform influenced by the self phase modulation（SPM） effect was presented.In the experiment,the small mode area double clad fiber was adopted with core diameter 6.5 μm as the gain media.As the gain of the amplifier from the small-signal gain to the deeply saturated gain,the evolution of the spectrum broadening,the pulse waveform and intensity distribution because of the SPM effect were observed.Then to overcome the difficulty for measuring the single pulse spectrum,the Bragg fiber grating scanning was introduced to investigate the changing of spectrum broadening.The results indicate that different from the SPM effect in the passive fibers,as the increase of the pump power,due to the competition mechanism of the gain saturation and SPM in the hundred-picosecond pulse amplification,the spectrum exhibits asymmetric double-peak and the pulse intensity is shifting to short wavelength firstly and then to the long wavelength.