SEMICONDUCTOR LASER DEVICE

PURPOSE:To realize stable single wavelength oscillation by disposing the convergent lens which outputs the parallel light and the optical waveguide material which has the diffraction grating at the inclined end surface. CONSTITUTION:An output beam of laser 9 is converted to the parallel beam by the convergent lens 11. The parallel beam advances in parallel within the optical waveguide rod 12 and reflected by the diffraction grating 8. Only the light beam which satisfies the wavelength relation determined by the refractive index of rod 12, period of grating 8 and incident angle is reflected in the same direction as the incident beam and then returned to the laser 9. Therefore, when observed from the laser element, the reflectivity is large only for such wavelength and the oscillation threshold level becomes small and thereby single wavelength operation in the vicinity of such wavelength can be realized. Moreover, further excellent efficiency can be obtained by providing the reflection film 15 to the grating 8 while mounting the reflection preventing films 13, 14 to the end of laser 9, lens 11 and rod 12, etc.