All semiconductor low-Δ photonic crystal waveguide for semiconductor optical amplifier

An ultralow group velocity of light in a III-V semiconductor photonic crystal (PC) waveguide is expected to enhance the optical gain per unit length of the waveguide. We discuss the possibility of a compact semiconductor optical amplifier that utilizes a single-line-defect PC waveguide fabricated from an all semiconductor low-Δ slab with deep airholes. From photonic band and traveling-wave rate equation analysis, a gain of larger than 20 dB is expected in a short active PC waveguide of 10 μm length, although the waveguide mode has a large radiation loss. We experimentally demonstrate such a waveguide in the passive wavelength regime. The waveguide is fabricated into a GaInAsP/InP wafer with high-mesa input/output waveguides. We show that the observed transmission characteristics of light correspond well to the photonic band theory