Patent ID: 7949020
Filing Date: 2011-05-24
Classification: B82Y,H01S

Abstract:
1. A tunable distributed feedback (DFB) semiconductor laser comprising: a substrate; an optical waveguide structure disposed on a main surface of the substrate and including an active layer and a diffraction grating that is optically coupled with the active layer, the optical waveguide structure being divided into a first DFB portion, a wavelength-tuning region, and a second DFB portion in that order in an optical axis direction; a first electrode for injecting carriers into the active layer located in the first DFB portion, the first electrode being disposed on the first DFB portion; a second electrode for injecting carriers into the active layer located in the second DFB portion, the second electrode being disposed on the second DFB portion; and a third electrode for supplying a signal for wavelength tuning to the wavelength-tuning region, the third electrode being disposed on the wavelength-tuning region, wherein the diffraction grating is disposed on the active layer in a direction substantially orthogonal to the main surface, and extends over the first DFB portion, the wavelength-tuning region, and the second DFB portion, an optical confinement factor of the wavelength-tuning region in the optical waveguide structure is smaller than an optical confinement factor of each of the first DFB portion and the second DFB portion in the optical waveguide structure, the optical waveguide structure includes an optical confinement layer portion disposed adjacent to the active layer in a direction substantially orthogonal to the main surface and having a refractive index lower than the refractive index of the active layer, the effective refractive index of the wavelength-tuning region in the optical confinement layer portion is lower than the refractive index of each of the first DFB portion and the second DFB portion in the optical confinement layer portion, the optical confinement layer portion in each of the first DFB portion and the second DFB portion is composed of a first optical confinement layer, and the optical confinement layer portion in the wavelength-tuning region is composed of the first optical confinement layer and a second optical confinement laying having a refractive index lower than the refractive index of the first optical confinement layer.