飞秒激光脉冲在高非线性光子晶体光纤中产生超连续谱的实验研究

Experimental research of supercontinuum generationby femtosecond pulse in highly nonlinearphotonic crystal fiber

使用钛宝石激光器抽运一根长1m的高非线性光子晶体光纤,获得的超连续谱波长覆盖范围为420—1700nm,输出功率为170mW,转换效率在20%以上;对实验结果给出了详细的分析,并与理论模拟结果相比较,认为超连续谱产生的主要原因是高阶孤子的分裂和四波混频效应.同时研究了不同抽运功率和不同抽运波长下超连续谱产生的情况,发现对同一根光纤,抽运功率由小到大变化时,可将输出的光谱分为初始展宽,剧烈展宽和饱和展宽三个阶段,当输出的光谱处于初始展宽和饱和展宽阶段时,都会存在一定的抽运残留,当输出的光谱处于剧烈展宽时,转换效率最高;当抽运波长位于光纤的反常色散区时,得到的超连续谱要远宽于位于零色散波长处的情况,但光谱形状却很相似.这些结论对于超连续谱系统的优化设计与控制具有重要意义.

We pumped a 1m long highly nonlinear photonic crystal fiber by a Ti ： sapphire laser and generated a supercontinuum with the wavelength extension form 420-1700 nm, of which the output power was about 170 mW and we conversion efficiency was above 20%. The experiment result was particularly analyzed and compared with calculated result, and we consider the main reasons of supercontinuum generation was fission of high-order solitons and four-wave mixing. We also researched the supercontinuum generation under different pump power and wavelength conditions. With the pump power increased gradually in the same fiber, the output spectrum can be divided into initial broadening stage, dramatic broadening stage and saturation broadening stage. When the output spectrum is in the initial broadening stage or saturation broadening stage, there exists some residual pump, when the output spectrum is in the dramatic broadening stage, the highest conversion efficiency is obtained. When the pump wavelength is in the anomalous dispersion region of the fiber, the spectrum width is far broader than that in the zero dispersion region, but the shapes of the spectra are very similar. These conclusions provide valuable reference for supercontinuum system optimization and control.