摘要
飞秒光学频率梳是当今激光技术领域的重要研究方向。实验基于非线性放大环形镜(NALM)锁模激光器实现了全保偏光纤结构的掺铒光学频率梳。在基于NALM锁模的光纤激光器内部加入非互惠相移器,降低了锁模阈值,实现了超短脉冲激光器的自启动。经过脉冲放大和压缩,脉冲的峰值功率可达61.3 kW。将此高功率超短脉冲注入55 cm的保偏高非线性光纤(PM-HNLF)中,激光器的输出光谱被拓展至一个倍频层(1 030~2 200 nm)。辅以f-2f自参考探测技术,成功探测到了信噪比高达40 dB、线宽为40 kHz的载波包络偏频信号(f_0)。此外,通过使用两套电路反馈系统,将f_0信号与激光器重复频率信号(f_r)的频率抖动量分别降低至521.71 mHz和240μHz,实现了相位稳定的掺铒光学频率梳。
Femtosecond optical frequency comb has been a rich research field in laser optics. We demonstrated an all polarization-maintaining(PM) fiber, Erbium-doped frequency comb based on a nonlinear amplification loop mirror(NALM) mode-locked fiber laser. An integrated nonreciprocal phase shifter was employed in a passively mode-locked NALM-based oscillator to reduce the mode locking threshold and facilitate self-starting. Being amplified and pulse compressed, the peak power of the pulses can achieve as high as 61.3 kW. Injecting the high-power ultrashort pulses into a 55-cm-long PM high nonlinear fiber(HNLF), an octave-spanning supercontinuum from 1 030 nm to 2 200 nm was generated. By using a collinear f-2f interferometer, the carrier-envelop offset signal(f_0)with 40-dB signal-to-noise ratio(SNR) and 40-kHz linewidth was detected. Moreover, with the employment of two feedback locking electronics, the f_0 signal and the repetition rate of the laser(f_r)were phase-locked and it showed the standard deviations of 521.71 mHz and 240 μHz, respectively.
引文
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