Gain Chip: Semiconductor Optical Elements - Inphenix

https://www.inphenix.com/en/gain-chip/

#Gainchips are semiconductor optical elements used as the optical gain medium of external cavity laser diodes. Gain chips are used as a TLS (Tunable Light Source) that can change the oscillation wavelength using a wavelength selection filter such as a diffraction grating.

Gain chips have 2 opposing waveguide end facets, one with high reflectivity or a low reflectivity of several percent.