| 摘要 |
PURPOSE:To supply a laser driving current and a tuning current to an active waveguide layer and wavelength tuning regions efficiently and reduce an oscillation threshold current and obtain a stable single mode oscillation by a method wherein p-n junctions are formed in an outer waveguide layer in which the active waveguide layer is buried. CONSTITUTION:An outer waveguide layer 4n whose conductivity type is n-type is formed on a protective layer 3 built up on an active waveguide layer 2. Outer waveguide layers 4p whose conductivity type is p-type, opposite to that of the waveguide layer 4n, are formed in wavelength tuning regions of which distributed Bragg reflectors 5 are composed. With this first current constriction structure, p-n junctions formed in boundaries between the region of the outer waveguide layer 4 covering the active waveguide layer 2 and the regions of the outer waveguide layer 4 in the wavelength tuning regions and in neighborhoods of the boundaries isolate both the regions 4p and 4n in the outer waveguide layer 4 electrically from each other. The p-n junction function as barriers against a current applied to the outer waveguide layer 4. Therefore, as oscillation threshold current is reduced and, moreover, the effective refractive index of the outer waveguide layer 4 in the wavelength tuning regions do not fluctuate so that a stable single mode oscillation can be realized. |
