SEMICONDUCTOR LASER DEVICE HAVING A DIFFRACTION GRATING ON ALIGHT REFLECTION SIDE

摘要

A semiconductor device includes an active layer configured to radiate light, a light reflecting facet positioned on a first side of the active layer, a light emitting facet positioned on a second side of the active layer thereby forming a resonant cavity betwe en the light reflecting facet and the light emitting facet, and a partial diffraction grating having a predetermined length and positioned on a light reflecting side of the resonator. The predetermined length of the partial diffraction grating is selected such tha t the semiconductor device emits a light beam having a plurality of longitudinal modes within a predetermined spectral width of an oscillation wavelength spectrum of the semiconductor device. The predetermined length of the partial diffraction grating may be set in relati on to a length of the resonant cavity, or in relation to a coupling coefficient of the diffraction grating. The semiconductor device may also include another partial diffraction grating positioned on the light emitting side of the laser device.