A quantum cascade laser includes a substrate including first and second regions arranged along a first axis; a stacked semiconductor layer disposed in the second region, the stacked semiconductor layer having an end facet located on a boundary between the first and second regions, the stacked semiconductor layer including a core layer and a cladding layer that are exposed at the end facet thereof; and a distributed Bragg reflection structure disposed in the first region, the distributed Bragg reflection structure including a semiconductor wall and a covering semiconductor wall that covers the end facet of the stacked semiconductor layer. The semiconductor wall and the covering semiconductor wall are made of a single semiconductor material. The semiconductor wall provides first and second side surfaces. The covering semiconductor wall provides an end facet that is located away from the first and second side surfaces of the semiconductor wall.

A method for producing an integrated optical circuit comprising an active device and a passive waveguide circuit includes: applying an active waveguide structure on a source wafer substrate; exposing a portion of the source wafer substrate by selectively removing the active waveguide structure; applying a passive waveguide structure on the exposed portion of the source wafer substrate, wherein an aggregation of the active waveguide structure and the passive waveguide structure forms the active device, the active device having a bottom surface facing the source wafer substrate; removing the source wafer substrate from the active device; and attaching the active device to a target substrate comprising the passive waveguide circuit such that the bottom surface of the active device faces the target substrate.

A semiconductor laser device includes an n-type clad layer, a first p-type clad layer and a ridge stripe. The device also includes an active layer interposed between the n-type clad layer and the first p-type clad layer, and a current-blocking layer formed on side surfaces of the ridge stripe. The ridge stripe of the device includes a second p-type clad layer formed into a ridge stripe shape on the opposite surface of the first p-type clad layer from the n-type clad layer. The ridge stripe is formed such that a first ridge width as the width of a surface of the second p-type clad layer exists on the same side as the first p-type clad layer and a second ridge width as the width of a surface of the second p-type clad layer exists on the opposite side from the first p-type clad layer.