飞秒激光脉冲在双折射微结构光纤中频率变换的研究

报道了高非线性的双折射微结构光纤(MFs)与纳焦耳量级的飞秒激光脉冲相互作用下，在可见光波段通过相位匹配的四波混频效应获得了波长可调谐的反斯托克斯波的实验结果。由于该光纤的双折射性质，因此在不同偏振方向上具有不同的色散特性，所产生的反斯托克斯超短脉冲的中心波长受到输入脉冲的偏振态的影响。通过旋转输人端的半波片，在相互垂直的两种偏振态的飞秒激光脉冲的作用下，所产生的反斯托克斯波脉冲的中心波长分别为490nm和510nm，在微结构光纤的输出端能分别观察到明亮的蓝光和绿光的基模输出。实验研究了在不同功率飞秒脉冲激光的作用下，在不同长度的双折射微结构光纤中反斯托克斯波的产生情况，并对一系列现象进行了对比分析。

Frequency Conversion in a Birefringent Microstructure Fiber by Femtosecond Pulses

Microstructure fibers (MFs) with a specially designed form birefringence are shown to be ideally suited for the creation of highly efficient frequency-tunable sources of short pulses in the visible range as a result of nonlinear-optical spectral transformation of unamplified femtosecond Ti∶sapphire laser pulses. The modes of doublet polarized along the fast and small axes of the elliptical core of the fiber have different propagation constants. Controlled by a half waveplate, femtosecond pulses of 820 nm pump radiation polarized along the fast and slow axes of the elliptical core of the microstructure fiber can generate intense blue-shifted lines centered at 490 and 510 nm respectively, observed as bright blue and green emission at the output end of the microstructure fiber. The dependence factors, such as length, power, are also compared and analyzed experimentally.