Single-pass tapered semiconductor optical amplifiers and modules for efficient coherent beam combining

We present progress in high power GaAs-based single-pass semiconductor tapered optical amplifiers and modules tailored for coherent beam combining (CBC) in master-oscillator power-amplifier configuration. Amplifier design is first studied, by varying device geometry and epitaxial structure in 976nm devices. Epitaxial structures with large vertical near field and low wave-guiding from the active region enable higher CBC efficiency. However, changes to in-plane geometry did not improve performance. Overall, CBC of tapered amplifiers is stable, reproducible and robust, motivating next the development of 1064nm CBC-ready stand-alone sub-modules. Design, construction and test results from the pilot-series fabrication of these amplifier modules are presented.