Semiconductor light source

A semiconductor light source comprising:

• a laser diode for emitting light beams from a front end and from a rear end,
• a photodiode for monitoring the light beams emitted from the rear end of the laser diode,
• a header with an upper surface, a bottom surface and a protrusion on the upper surface for supporting the photodiode on the upper surface and the laser diode on a side of the protrusion,
• leads fitted to the header for supplying driving currents to the laser diode and for extracting photocurrents from the photodiode,
• a cap with a window fixed on the upper surface of the header, and
• a lens fitted in the window,
• wherein the lens, the laser diode chip and the photodiode chip are aligned along a normal of the upper surface of the header,
• wherein the photodiode has a substrate with an upper surface and a bottom surface, epitaxial layers grown on the substrate, a pn-junction produced at a center of the epitaxial layers, an electrode formed on the epitaxial layers above the pn-junction, another electrode formed on the bottom surface of the substrate, an light receiving region defined by the pn-junction, and a peripheral non-receiving region outside the pn-junction.
• wherein the photodiode has a dielectric layer on the non-receiving region for reflecting or absorbing light beams irradiating thereon.

A semiconductor light source comprising:

• a laser diode for emitting light beams from a front end and from a rear end,
• a photodiode for monitoring the light beams emitted from the rear end of the laser diode,
• a header with an upper surface, a bottom surface and a protrusion on the upper surface for supporting the photodiode on the-upper surface and the laser diode on a side of the protrusion,
• leads fitted to the header for supplying driving currents to the laser diode and for extracting photocurrents from the photodiode,
• a cap with a window fixed on the upper surface of the header, and
• a lens fitted in the window,
• wherein the lens, the laser diode chip and the photodiode chip are aligned along a normal of the upper surface of the header,
• wherein the photodiode has an n.sup.+ -type InP substrate with an upper surface and a bottom surface, an undoped InP buffer layer epitaxially grown on the InP substrate, an undoped InGaAs receiving layer epitaxially grown on the InP buffer layer, an undoped InP window layer epitaxially grown on the InGaAs receiving layer, a pn-junction produced by diffusing zinc at a center of the InP window layer and the InGaAs receiving layer, an electrode formed on the InP window layer above the pn-junction, another electrode formed on the bottom surface of the InP substrate, an light receiving region defined by the pn-junction, and a peripheral non-receiving region outside the pn-junction,
• wherein the photodiode has a dielectric layer on the non-receiving region for reflecting or absorbing light beams irradiating thereon.