Abstract: A semiconductor laser device has structure including: a semiconductor laser chip having an emission surface and a reflection surface which are opposing end surfaces of a resonator; and a photodiode for detecting light that exits from the reflection surface side, the photodiode being used in a wavelength band where a sensitivity of the photodiode rises as a wavelength lengthens, in which the emission surface has a first dielectric multilayer film formed thereon and the reflection surface has a second dielectric multilayer film formed thereon, and in which, when a wavelength at which a reflectance of the first dielectric multilayer film peaks is given as ?f and a wavelength at which a reflectance of the second dielectric multilayer film peaks is given as ?r, a relation ?f<?r is satisfied.

Abstract: A semiconductor laser device has structure including: a semiconductor laser chip having an emission surface and a reflection surface which are opposing end surfaces of a resonator; and a photodiode for detecting light that exits from the reflection surface side, the photodiode being used in a wavelength band where a sensitivity of the photodiode rises as a wavelength lengthens, in which the emission surface has a first dielectric multilayer film formed thereon and the reflection surface has a second dielectric multilayer film formed thereon, and in which, when a wavelength at which a reflectance of the first dielectric multilayer film peaks is given as ?f and a wavelength at which a reflectance of the second dielectric multilayer film peaks is given as ?r, a relation ?f<?r is satisfied.

Abstract: A semiconductor laser diode comprising a semiconductor substrate having an active layer with a pair of cavity facets opposed to each other on both ends of active layer as well as a first dielectric film of an oxide and a second dielectric film of an oxynitride successively stacked on one cavity facet has sufficient initial characteristics with a film structure having excellent heat radiability for allowing stable high-output lasing over a long period without reducing a catastrophic optical damage level on an emission end.

Abstract: A semiconductor laser diode comprising a semiconductor substrate having an active layer with a pair of cavity facets opposed to each other on both ends of active layer as well as a first dielectric film of an oxide and a second dielectric film of an oxynitride successively stacked on one cavity facet has sufficient initial characteristics with a film structure having excellent heat radiability for allowing stable high-output lasing over a long period without reducing a catastrophic optical damage level on an emission end.