A high reflection film coating consisting of an SiO2 /TiO2 multilayer is formed on the facets of the optical resonator of the LD. Further, Cr/Au is evaporated onto the rear surface of the LD chip, and it is then die-bonded onto a heat-sink consisting of a block of such material as Cu or diamond, which have high thermal conductivities, using an AuSn eutectic solder.