Patent ID: 6111906
Filing Date: 2000-08-29
Classification: H01S

Abstract:
A distributed-feedback semiconductor laser comprising:an active layer which radiates light as a result of the injection of electrons;a light guide layer which is next to this active layer and guides light emitted from the active layer;a plurality of semiconductor layers between which the active layer and light guide layer are interposed;electrodes which permit electrons to be injected from these semiconductor layers into the active layer;a non-reflective coating which is provided on both ends of the active layer in the direction of oscillation; anda diffraction grating which is provided on the light guide layer for selecting the oscillatory wavelength of the light, the diffraction grating having:a plurality of uniform pitch areas formed with a uniform and equal pitch; anda varying pitch area interposed between the uniform pitch areas and having a plurality of pitches longer and shorter than those of these uniform pitch areas,wherein the absolute value of the sum-total of the amount of phase change in the varying pitch area (cumulative amount of phase change) in relation to the phase in the uniform pitch areas is between 3/2 and 11/2 times the pitch of the diffraction grating of the uniform pitch areas.