3.4MW峰值功率皮秒光纤激光系统的光谱特性

Spectral Properties of Picosecond Fiber Laser System with 3.4MW Peak Power

提出了基于主振荡功率放大(MOPA)结构的皮秒光纤激光系统。该系统将重复频率为29.87 MHz的半导体可饱和吸收镜被动锁模光纤激光器作为种子源。采用预放系统并结合声光调制器将种子源的重复频率降至574kHz。MOPA结构基于棒状光子晶体光纤(PCF),利用PCF大模场、高增益的特点直接对脉冲宽度为30ps的脉冲进行放大,有效抑制了自相位调制效应引起的光谱展宽。研究结果表明,所提系统的5dB光谱线宽与光脉冲峰值功率成比例,该系统最终输出了近衍射极限、峰值功率为3.4 MW的皮秒脉冲(输出功率为20 W时,光束质量因子M2=1.01),最高平均输出功率为21.86 W,脉冲宽度为11.1ps,中心波长为1030.74nm,5dB光谱线宽为1.75nm。

A picosecond fiber laser system based on master oscillator power amplifier （MOPA） is proposed. A passive mode-locked fiber laser with a semiconductor saturable absorber mirror （SESAM） which is with repetition rate of 29.87 MHz is used as the seed source. The repetition rate can be reduced to 574 kHz when a pre-amplifier system is combined with an acousto-optic modulator （AOM）. The MOPA structure is based on rod-type photonic crystal fiber （PCF）. The pulse with pulse width of 30 ps can be amplified based on properties of large mode field and high gain of PCF, and the spectral expanding caused by the self-phase modulation is effectively suppressed. Results show that the spectral linewidth of 5 dB is proportional to the peak-power of optical pulse of the proposed system （the beam quality factor M^2 is 1.01 at the output power of 20 W）. The peak-power of the picosecond pulse is 3.4 MW, which is near the diffraction limit. The picosecond pulse with the highest average output power of 21.86 W, pulse width of 11.1 ps, center wavelength of 1030.74 nm and linewidth of 1.75 nm at 5 dB can be obtained.