在色散渐减光子晶体光纤中产生超连续谱的实验研究

本文利用非线性偏振锁模激光器产生的重复频率50 MHz, 脉宽为1.8 ps的脉冲分别抽运外径均匀和色散渐减两种高非线性光子晶体光纤, 在三阶非线性效应 (自相位调制、交叉相位调制、四波混频和受激拉曼散效应等) 和色散共同作用下得到扩展至蓝光部分的超连续谱. 模拟了光谱在色散渐减光纤和均匀光纤中的展宽过程, 通过对比均匀光纤发现色散渐减光纤在调控色散, 加强拉曼孤子和色散波的群速度匹配条件, 产生超带宽光谱方面具有很大优势. 实验利用20 m长的色散渐减光纤, 得到了406.1至671.8 nm的可见光波段增强的较为平坦的超连续谱. 关键词： 超连续谱 色散渐减光子晶体光纤 群速度匹配 非线性效应

Experimental study on supercontinuum generation in zero-dispersion wavelength decreasing photonic crystal fiber

We have carried out experimentally the supercontinuum generation in GeO₂-doped-core uniform photonic crystal fiber and zero-dispersion wavelength-decreasing photonic crystal fiber with pump pulses 1.8 ps operating at 1040 nm. Dispersion and nonlinear effects such as cross-phase modulation, four-wave mixing, modulation instability play a crucial role as they extend the supercontinuum towards short wavelength side. Zero-dispersion wavelength-decreasing photonic crystal fiber can improve group-velocity matching between solitons and dispersive waves deduced from numerical simulation of the evolution of spectra generated in a taper and uniform fiber. We obtained experimentally a spectrum expanding to the blue side and the power variation is indeed of 10 dB over a spectral range of 165.7 nm (between 4061 and 6718 nm) in the taper fiber.
Keywords： supercontinuum taper fiber group-velocity matching nonlinear effects