The requirements for coherent combination of high power GaAs-based single-pass tapered amplifiers are studied. Changes to the epitaxial layer structure are shown to bring higher beam quality and hence improved combining efficiency for one fixed device geometry. Specifically, structures with large vertical near field and low wave-guiding from the active region show 10% higher beam quality and coherent combining efficiency than reference devices. As a result, coherent combining efficiency is shown to be limited by beam quality, being directly proportional to the power content in the central lobe across a wide range of devices with different construction. In contrast, changes to the in-plane structure did not improve beam quality or combining efficiency. Although poor beam quality does correlate with increased optical intensities near the input aperture, locating monolithically-integrated absorption regions in these areas did not lead to any performance improvement. However, large area devices with subsequently improved cooling do achieve higher output powers. Phase noise can limit coherent combining, but this is shown to be small and independent of device design. Overall, tapered amplifiers are well suited for high power coherent combining applications.

中文翻译：

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用于高效相干光束组合的低指数量子势垒单通锥形半导体光放大器

研究了高功率GaAs基单通锥形放大器相干组合的要求。外延层结构的变化显示出更高的光束质量，从而提高了一种固定器件几何形状的组合效率。具体而言，具有大垂直近场和来自有源区的低波导的结构显示出比参考器件高 10% 的光束质量和相干组合效率。因此，相干组合效率受光束质量的限制，与具有不同结构的各种设备的中心瓣中的功率含量成正比。相比之下，面内结构的改变并没有提高光束质量或组合效率。尽管较差的光束质量确实与输入孔径附近增加的光学强度相关，但在这些区域定位单片集成吸收区域并没有导致任何性能改进。然而，随后改进冷却的大面积设备确实实现了更高的输出功率。相位噪声会限制相干组合，但这被证明是很小的并且与设备设计无关。总的来说，锥形放大器非常适合高功率相干组合应用。