GaInAsP/InP surface-emitting lasers with current confining structure

In order to reduce the threshold current of GaInAsP/InP surface-emitting (SE) lasers, we search for an effective current confining structure and examined several types; round-low-mesa, round-high-mesa/polyimide-buried, buried-heterostructure (BH), and planar-buried-heterostructure (PBH). The minimum threshold current was reduced down to 18 mA at 77 K and the threshold current density was estimated to be reduced to 3 kA/cm
²
. The operating temperature has been raised to -10°C (263 K). The longitudinal-mode hopping was first observed for GaInAsP/InP SE lasers. The effective refractive index for GaInAsP/InP SE lasers was 4-5, that was almost the same as conventional edge-emitting lasers.