Patent ID: 7745895

Claim:
A semiconductor light emitting device comprising: a semiconductor laser element emitting a laser beam; a semiconductor photodiode including a first conductivity type semiconductor layer disposed on a first surface of a first conductivity type semiconductor substrate, a first conductivity type absorption layer disposed on the first conductivity type semiconductor layer to receive the laser beam, a cap layer disposed on the absorption layer, a second conductivity type region formed in the cap layer and the absorption layer, a second electrode in ohmic contact with the second conductivity type region formed in the cap layer, a transmissive reflection unit disposed on a second surface of the semiconductor substrate, and a first electrode in ohmic contact with the first surface opposite to the second surface of the semiconductor substrate; and a stem on which the semiconductor laser element and the semiconductor photodiode are mounted, wherein the transmissive reflection unit includes a transmissive reflection film having a reflectance of 50% to 90% for light at a wavelength of 1000 nm to 1700 nm, the semiconductor photodiode is mounted with the cap layer side down, and the transmissive reflection unit is irradiated with the laser beam emitted from one end face of the semiconductor laser element so that the laser beam reflected by the transmissive reflection unit is used as output light, and the laser beam transmitted through the transmissive reflection unit is received by the semiconductor photodiode and used for controlling the output of the semiconductor laser element.