Narrow ridge GaSb‐based cascade diode lasers fabricated by methane–hydrogen reactive ion etching

GaSb‐based type‐I quantum wells cascade diode lasers with nearly diffraction limited output beam were fabricated using methane–hydrogen dry etching plasma process. Rapid thermal annealing was shown to be a necessary step to reverse the effect of hydrogen plasma on conductivity of AlGaAsSb cladding alloy. Annealed two‐step narrow ridge lasers confined both optical field and current in lateral direction and demonstrated operating voltage, threshold current density and slope efficiency comparable to those of reference wide ridge devices.