Abstract: A semiconductor light source system includes a laser diode that is operated in a variable temperature environment and a driver circuit, wherein the driver circuit sets a magnitude of a signal current supplied to the laser diode below an upper limit level that corresponds to a maximum operational temperature of the laser diode. The driver circuit simultaneously sets a relative magnitude of the signal current with respect to a bias current such that a sufficient extinction ratio is achieved in an output optical beam and further sets a relative magnitude of the signal current with respect to the bias current such that a sufficiently small oscillation delay is achieved in the laser diode.

Abstract: An optical processing device for converting a wavelength of an optical signal comprises an optical processing unit supplied with an input optical beam carrying thereon one or more optical signals with respective wavelengths that are different from each other, the optical processing means being further supplied with a control optical beam having a stabilized reference wavelength and selecting the optical signal that has a first wavelength and outputting the same with a second wavelength that is specified by the reference wavelength; and a control unit for controlling the optical processing unit by specifying the first wavelength of the optical beam to be selected.

Abstract: An optical processing device for converting a wavelength of an optical signal comprises an optical processing unit supplied with an input optical beam carrying thereon one or more optical signals with respective wavelengths that are different from each other, the optical processing means being further supplied with a control optical beam having a stabilized reference wavelength and selecting the optical signal that has a first wavelength and outputting the same with a second wavelength that is specified by the reference wavelength; and a control Unit for controlling the optical processing unit by specifying the first wavelength of the optical beam to be selected.

Abstract: A semiconductor optical waveguide comprises a substrate of a semiconductor material doped to a first conductivity type, a multiple quantum well layer provided on the substrate for guiding an optical beam, a clad layer doped to a second conductivity type and provided on the multiple quantum well layer for confining the optical beam, a first electrode provided on the upper major surface of the clad layer for injecting carriers of a first type into the quantum well layer, and a second electrode provided on the lower major surface of the substrate for injecting carriers of a second type into the quantum well layer, wherein multiple quantum well layer comprises an alternate stacking of: a quantum well layer having a composition set to provide a smallest band gap that is possible under a constraint that the quantum well layer maintains a lattice constant with the substrate and a thickness set with respect to the optical energy of the optical beam such that a discrete quantum level of carriers is formed in the quant

Abstract: A semiconductor laser including a stripe-shaped active layer, a clad region, and a diffraction grating. The stripe-shaped active layer has a thickness in a first direction, has a first energy gap, and extends in a second direction orthogonal to the first direction. The clad region surrounds the stripe-shaped active layer, and has a second energy band gap greater than the first energy band gap. The diffraction grating is provided in parallel with and adjacent to, the stripe-shaped active layer. The stripe-shaped active layer has a first portion with a first light propagation constant and with a first dimension in a third direction orthogonal to the first and second directions, and has a second portion with a second light propagation constant and with a second dimension in the third direction. The first dimension and the second dimension are different from each other. The second portion has a length L in the second direction. The stripe-shaped active layer satisfies the condition that a product of .DELTA..beta.