Spectra Narrowing of a 976 nm High Power External-Cavity Semiconductor Laser Based on a Transmission Grating

Broad-area 976 nm semiconductor lasers have garnered widespread attention for their applications in generating high-power 488 nm blue laser light and as pump sources for solid-state and ytterbium-doped fiber lasers. Nevertheless, these lasers exhibit a wide gain bandwidth, short cavity length, and usually use the natural cleavage surface as the output window, resulting in a broad emitting spectrum in free-running state. We investigated a high-power narrow-linewidth 976 nm edge emitting broad area semiconductor laser (EEL) through external cavity feedback technology by employing a transmission grating as the dispersive element. This configuration achieved a high output power of 11 W and a spectral linewidth of 0.36 nm at 976 nm, corresponding to an intracavity power of 15.7 W. It provided a more flexible cavity structure for direct frequency doubling of the semiconductor laser to generate a high power of 488 nm blue laser.