理论分析了波长为2 µm的掺铥光纤放大器中受激布里渊散射（SBS）对激光输出性能的影响，研究了双包层掺铥光纤在793 nm的泵浦波长和1.9~2.1 µm的激光工作波段的光模分布、有效折射率、有效模场面积和归一化频率，数值计算了在1.9~2.1µm的激光工作波段双包层掺铥光纤中的布里渊频移和布里渊增益谱等SBS特性。利用增益光纤中的受激布里渊散射理论模型，研究了受激布里渊散射对掺铥光纤放大器激光输出性能的影响。在DTDF-10/130双包层掺铥光纤中，使用功率为100 W、波长为793 nm的连续光作为泵浦，可对波长为2 μm、功率为0.01 W的连续信号光进行放大。当泵浦光功率填充因子为0.01、0.02和0.03时，信号光的最大输出功率分别为25.27 W、31.08 W和34.06 W。对应的最佳双包层光纤长度为2.66 m、2.02 m和1.75 m，由受激布里渊散射产生的斯托克斯光功率分别为1.68 W、1.39 W和1.14 W。结果表明，在掺铥光纤放大器中使用泵浦光功率填充因子大的双包层光纤可以降低光纤长度，从而减小受激布里渊散射对信号激光输出功率的影响。本文的数值模型可以对光纤放大器的光纤长度进行优化，对提高实验效率、降低实验成本具有重要价值。

The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was 40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.