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实验研究了掺镱大模场面积光子晶体光纤(LMA PCF)飞秒激光二级放大系统。振荡级和预放基于双包层保偏大模场面积光子晶体光纤,主放大级基于7芯大模场面积光子晶体光纤。7个纤芯六角排布,总的模场面积高达5000μm2,有效降低了光纤中的非线性。而且各个纤芯之间离散分布,热应力等问题也得到了缓解。当抽运功率较小时,输出的模式为多个超模的叠加。在高功率抽运下,获得了平坦的同相位超模输出,对应远场具有很好的高斯分布。获得了重复频率1 MHz,平均功率24 W的激光放大输出。经光栅对压缩后,脉冲宽度为110 fs,对应的峰值功率达到150 MW。
Experimental study of Ytterbium-doped large-mode-area photonic crystal fiber (LMA PCF) femtosecond laser amplification system. Oscillating stage and pre-release Based on double-clad PM PMF fiber, the main amplifier stage is based on a 7-core large mode field photonic crystal fiber. Seven core hexagonal arrangement, the total mode field area up to 5000μm2, effectively reducing the nonlinear fiber. And discrete distribution between the various cores, thermal stress and other issues have been eased. When pumping power is small, the output mode is the superposition of multiple supermodes. Under the condition of high power pumping, a flat output with the same phase is obtained, which has a good Gaussian distribution corresponding to the far field. A laser amplification output with a repetition rate of 1 MHz and an average power of 24 W was obtained. After grating pair compression, the pulse width is 110 fs and the corresponding peak power is 150 MW.