Formation of a long-wavelength buried-crescent laser structure on channelled substrates

A laser structure, in which a cresent-shaped GaInAsP active region is isolated within a channel chemically etched in an InP substrate, has been formed in a single stage of liquid-phase epitaxial growth. The growth process was influenced, first, by the magnitude and uniformity of the channel width, cross-section and depth, and, secondly, by melt super-saturation. High strength mask-to-substrate adhesion and low super-saturation were necessary for the reproducible formation of the structure. Lasers with pulsed threshold currents of 30¿40 mA at ¿ 25°C have been obtained, and stable zero-order transverse-mode CW operation was possible up to at least 9 mW. These lasers have operated successfully in experimental optical-fibre transmission systems.