利用中空光子带隙光纤(HC-PBGF)对光子晶体光纤飞秒激光器输出的激光脉冲进行腔外再压缩。激光器输出的脉冲中心波长为1040 nm,脉冲宽度为475 fs,平均功率为400 mW,单脉冲能量为8 nJ。通过白光干涉法测量了中空光子带隙光纤的色散参数为-48 ps2/km,并利用截断实验得到了所用光纤的最优化长度,压缩后获得的最短脉冲宽度为108 fs,接近变换极限,传输效率为89%。由于该光纤纤芯的非线性系数较低,脉冲在其中传输无非线性效应,压缩后输出光谱保持不变。

The pulse compression for the femtosecond photonic crystal fiber laser is obtained by hollow core photonic bandgap fibers (HC-PBGF). The fiber laser directly outputs 475 fs pulses at a central wavelength of 1040 nm with an average power of 400 mW, corresponding to a pulse energy of 8 nJ. The dispersion of the HC-PBGF is measured with a white light interferometry method, which shows that the fiber has an abnormal dispersion of about -48 ps2/km and can be applied to compensate the positive chirp of femtosecond pulses from the fiber laser. After compression from the fiber with an optimized length, the pulses are compressed to 108 fs, which is close to Fourier transmission limitation. The transmission efficiency is about 89%, which is much better than a grating pair. The spectrum keeps the same as that of the input pulse after passing through the fiber, due to the low nonlinearity and bandgap properties of the HC-PBGF.