A semiconductor device includes a semiconductor layer formed of a III-V group semiconductor crystal containing As as a primary component of a V group. A V group element other than As has been introduced at a concentration of 0.02 to 5% into a V group site of the III-V group semiconductor crystal in the semiconductor layer.

An optical integrated light source includes a plurality of topological ring resonators. Each of the topological ring resonators is defined by an interface between two distinct periodic structures having different topological invariants such that a one-way edge mode may be excited along the interface. A magnetic material is arranged to interact with the plurality of topological ring resonators such that the optical integrated light source is structured and configured to generate plural beams each carrying large orbital angular momentum.

A method for switching a wavelength of a tunable wavelength laser, which is provided with a temperature control device for an etalon and a wavelength detecting section for identifying a wavelength of the laser by a front/back ratio of the etalon, the wavelength of the laser being set in a target wavelength on the basis of a detection result of the wavelength detecting section, and the method comprises: driving the laser at a first wavelength; suppressing output of light of the laser in response to a command indicating an optical output at a second wavelength; starting control of the temperature control device towards a second etalon temperature corresponding to the second wavelength; and before the etalon reaches the second etalon temperature, detecting that the etalon reaches a temperature range corresponding to an allowable wavelength range corresponding to the second wavelength, and cancelling the suppression of light in response thereto.

A wavelength tunable laser device, including: a first reflector; a second reflector; an active layer formed between the first reflector and the second reflector; a quantum well structure layer that exhibits a quantum confined stark effect; and an electrode configured to apply a reverse bias voltage to the quantum well structure layer, wherein the active layer and the second reflector have a gap formed therebetween, the gap having a length to be changed to thereby sweep a resonance wavelength, and wherein the electrode is further configured to change application of the reverse bias voltage to be applied to the quantum well structure layer depending on the length of the gap when the resonance wavelength is swept.

A semiconductor optical device includes a substrate having an optical waveguide, a gain section formed of a compound semiconductor having an optical gain and bonded to an upper surface of the substrate, the gain section having a first mesa, and a first wiring line electrically connected to the gain section. The first mesa of the gain section is optically coupled to the optical waveguide. The substrate includes a first layer, a second layer, and a third layer. The first layer has a higher thermal conductivity than the second layer. The second layer is stacked on the first layer. The third layer is stacked on the second layer. A recess provided in the substrate extends through the third layer to the second layer in the thickness direction. The first wiring line extends from the first mesa of the gain section to the recess.