基于高掺锗石英光纤的中红外超连续谱产生 = Mid-infrared supercontinuum generation with highly germanium-doped silica fiber

采用波长为2 μm、脉冲宽度为50 ns的掺铥光纤调Q 激光器作为抽运光源，纤芯掺锗浓度为75%的石英光纤为非线性介质，进行了中红外超连续谱产生的研究。实验过程中在掺锗石英光纤的抽运光输入端熔接一截100~200 μm 长的多模光纤以提高光纤的空间耦合效率和损毁阈值，通过优化掺锗石英光纤的长度，最终在1.9 μm(受光谱仪测量范围限制)~2.9 μm 范围内获得了较平坦的超连续谱输出，10 dB 带宽和20 dB 带宽分别达到950 nm 和980 nm，而且其长波限接近目前报道的基于同类光纤的超连续谱的最大长波限。 Mid-infrared supercontinuum generation is demonstrated by using a 75 % germanium-doped silica fiber pumped by a 2 μm Q- switched thulium- doped fiber laser with pulse width of 50 ns. The free space coupling efficiency from the pump laser to the germanium-doped fiber is enhanced by fusion-splicing a 100~200 μm long multimode fiber. Length of germanium-doped fiber is optimized. Broadband supercontinuum generation ranging from 1.9 μm to 2.9 μm with 10 dB and 20 dB bandwidths of 950 nm and 980 nm, respectively. The 2.9 μm long wavelength limit is close to the record reported so far for highly germanium-doped fiber based supercontinuum generation sources.