微焦耳、百飞秒光子晶体光纤飞秒激光放大器

Photonic Crystal Fiber Femtosecond Laser Amplifier with Millijoules and 100 fs Level Output

实验研究了基于掺Yb3+单偏振大模场面积光子晶体光纤的高单脉冲能量光纤飞秒激光放大器。该放大器为非线性放大,利用自相位调制实现非线性相移得到光谱展宽。由于压缩器提供适当的色散补偿,并优化振荡-放大系统中的增益、非线性、高阶色散参数,使得压缩后脉冲具有较高的峰值功率。同时利用声光调制器降低振荡级的重复频率到1 MHz,最后得到最短脉冲宽度124 fs,单脉冲能量1.56μJ,对应峰值功率12.6 MW的激光输出。

A high pulse energy femtosecond laser amplifier with Yb3＋-doped single polarization large-mode-area photonic crystal fibers（LMA-PCF） is demonstrated.Based on the nonlinear amplifying configuration,amplification of laser pulses in the LMA-PCF is accompanied by spectral broadening and nonlinear phase-shift accumulation due to the self-phase modulation.This configuration can often help to produce high-peak-power ultrashort laser pulses,since the self-phase modulation induced nonlinear phase shift can be compensated by an appropriate negative-dispersion component following the amplification stage.This strategy of ultrashort laser pulse generation requires,however,a precise balance between the gain,nonlinearity,and high-order dispersion in the oscillator-amplifier system.An acousto-optical modulator is applied to reduce the repetition rate to 1 MHz.Laser pulses with 124 fs duration（the shortest pulse） are generated with 1.56 μJ pulse energy,corresponding to 12.6 MW peak power.