宽发射面激光二极管作为泵浦源在全固态激光器中得到了广泛的应用, 但由于快慢轴发散角太大和发光面的不对称, 所以需要对其进行光束整形。针对发光面为1 μm(快轴)×200 μm(慢轴)且远场光斑为矩形光斑的宽发射面激光二极管, 分析了输出光束在平行于p-n结方向上光场(侧模)的多光丝分布特性。通过在ZEMAX非序列里, 设置合理的光丝间隔、尺寸和以纵模为间隔的多个波长, 模拟了与实际相符的远场光斑。利用圆柱透镜压缩激光二极管快轴发散角, 再用自聚焦透镜进行聚焦, 最后在离自聚焦透镜后端面1.8 mm处得到快慢轴方向长分别为0.15 mm×0.17 mm的方形光斑, 且快慢轴方向发散角分别为3.3°×2.4°。同时, 通过实验逐步比较了光束通过每一个光学元件后光斑形状的变化和光强分布, 结果表明: 宽发射面激光二极管光束整形中, 通过引入侧模光丝结构的矩形光斑模拟方法是可行的。

The broad-area laser diode is widely used as a pump source in all-solid-state lasers, while the beam of semiconductor laser diode have to be shaped because of large divergence angle and the asymmetry of the narrow rectangular cross section in fast-axis and slow-axis directions. The output laser spot of area-broad diode laser with bright area: 1 μm(fast axis)×200 μm(slow axis) was rectangular and the mode characteristics of multiple filaments in the direction parallel to the p-n junction was analyzed. The far-field optical intensity distributions was simulated based on ZEMAX ray tracing software that operated in a non-sequential mode by setting appropriate filament size, spacing and multi-longitudinal mode. The simulation result was consistent with the real optical intensity distributions. Then a compact optical system of beam shaping was presented which consisted of a cylindrical lens and self-focused lens. The cylindrical lens was responsible for collimating the beam along its fast-axis, while the self-focused lens made the spot size become smaller. Finally, the image size was 0.15 mm×0.17 mm and beam divergence angle was 3.3°×2.4° in fast-axis and slow-axis directions, respectively, at 1.8 mm after self-focused lens. In the end, the comparison between the simulated intensity distribution and the experimental intensity distribution was performed step by step after placing optical element. It is shown that the method of simulating rectangular spots based on the broad area laser diode is feasible by introducing the filament structure.