为满足合肥先进光源对高品质注入束流的要求，合肥先进光源预研项目研制了一套光阴极微波电子枪系统作为注入器电子源。为降低空间电荷效应引起的束流发射度增长，对驱动激光整形及传输系统进行了理论和实验研究。通过双折射晶体的脉冲时间整形以及采用光阑高斯截断的空间整形，得到了近似均匀分布的激光脉冲。像传递激光传输光路，实现了光阴极表面激光位置的高稳定性。实验结果显示，光阴极表面的激光位置抖动小于4 µm，激光性能满足实验要求。

Brillouin gain spectra (BGS) in an As₂Se₃ photonic crystal fiber (PCF) are investigated numerically. The profiles of the BGS are simulated by calculating the characteristics of different-order optical and acoustic waves in the PCFs with different core diameters. For the small-core PCF, there are two peaks in BGS, but there is only one peak for the large-core PCF. We also reveal that in the small-core PCF, the difference of Brillouin frequency shift between the LP₀₁ and LP₁₁ modes is obvious, while it is not obvious in the large-core PCF. The Brillouin threshold increases with the core diameter increasing.

We propose a switchable multi-wavelength erbium-doped fiber laser based on a four-mode fiber Bragg grating (FBG). The four-mode FBG is fabricated in a hydrogen pre-loaded fiber by the phase mask method, which can support four linearly polarized modes around 1550 nm. The five operation wavelengths are at 1547.5, 1546.8, 1546.0, 1545.1, and 1544.2 nm, respectively. Through adjusting the polarization state and the lateral offset coupling in cavity, the laser can be switched into the operation state of single, dual, or triple wavelengths. The proposed laser has the advantages of simple configuration, stable operation, and easy adjustment.