高次谐波锁模飞秒掺镱光纤激光器的噪声情况

高重复频率的飞秒激光在高速激光测距和三维成像等领域有着非常重要的作用。其中基于飞秒光纤激光器的高次谐波锁模是获得GHz量级以上高重复频率脉冲的重要手段之一。基于含腔内光栅对色散补偿的非线性偏振旋转（NPR）锁模的掺镱（Yb）光纤激光器，在180 mW泵浦光时获得了稳定的143 MHz基频锁模脉冲序列，当泵浦光功率升至1 W时获得了最高20次谐波（2.86 GHz）锁模脉冲序列输出。系统地对比研究了基频锁模与高次谐锁模状态下，脉冲重复频率精密锁定后的艾伦偏差和相位噪声，7次谐波锁模状态下重复频率锁定精度能够保持在10?13 Hz@1 s的稳定度，为高次谐波锁模飞秒激光脉冲序列用于精密测量提供了实验依据。

Noise of high-order harmonic mode-locked femtosecond Yb fiber laser

Femtosecond lasers with high repetition rates play important roles in advanced manufacturing, such as high-speed laser ranging and three-dimensional imaging. Among them, high-order harmonic mode-locking based on femtosecond fiber lasers is one of the important methods to obtain high repetition rates above GHz. Based on a nonlinear polarization rotation (NPR) mode-locked Ytterbium (Yb) fiber laser with dispersion compensation from intra-cavity grating, a stable 143 MHz fundamental frequency mode-locked pulse sequence was obtained when the pump light was 180 mW. When the pump power was increased to 1 W, the highest 20th harmonic (2.86 GHz) mode-locked pulse train was obtained. The Allen deviation and phase noise of the output pulse repetition rates of the Yb fiber laser were studied systematically when it was running at high harmonic mode-locking and fundamental mode-locking respectively. The repetition frequency locking accuracy can be maintained at a stability of 10?13 Hz@1 s in the 7th harmonic mode locking state. This study provides an experimental basis for high harmonic mode-locked femtosecond laser pulse sequence to be used for precise measurement.