Patent ID: 8958451
Filing Date: 2015-02-17
Classification: H01S

Abstract:
1. A semiconductor laser comprising: a diffraction grating in which a first diffraction grating region that has a periodic structure with a first pitch, a second diffraction grating region that has a periodic structure with a second pitch different from the first pitch, and a third diffraction grating region that has the periodic structure with the first pitch are arranged sequentially and contiguously side by side along a direction of light propagation beginning from a light-emitting side; an anti-reflection film that is formed on a facet to the light-emitting side; and a reflection film that is formed on a facet that is opposite the end facet to the light-emitting side, wherein the first diffraction grating region is greater, in a length along the direction of light propagation, than the third diffraction grating region, and wherein the second diffraction grating region has the second pitch and the length, which runs along the direction of light propagation, of the second diffraction grating region, in such a manner that a phase of the first diffraction grating region and a phase of the third diffraction grating region are shifted in a range of equal to or more than 0.6 π to equal to or less than 0.9 π, the phase of the first diffraction grating and a phase of the second diffraction grating region are successive on a boundary between the first and second diffraction grating regions and the phase of the second diffraction grating region and the phase of the third diffraction grating region are successive on a boundary between the second and third diffraction grating regions.