“…Semiconductor optical amplifiers (SOAs), 1,2) as well as other devices such as semiconductor optical switches 3,4) and planar lightwave circuits (PLCs), 5) require low reflectivity at both their facets. This low reflectivity is achieved by introducing an antireflection (AR) facet film, 6) a tilted waveguide structure, 7) or a window structure. 8) Of these techniques, the facet film 9) plays an essential role in obtaining high-performance SOAs, optical switches, and PLCs.…”