Abstract: A semiconductor laser apparatus includes a semiconductor substrate, a first cladding layer, an active layer, a second cladding layer, a second electrode, and a pair of resonator mirrors. The semiconductor substrate has a first electrode on one surface. The first cladding layer is formed on the other surface of the semiconductor substrate. The active layer is placed on the cladding layer. The second cladding layer is placed on the active layer. The second electrode is placed on the second cladding layer. The pair of resonator mirrors are placed in a waveguide direction perpendicular to the surfaces of the semiconductor substrate to oppose each other. The active layer is constituted by a quantum well layer having a tensilely strain. The second electrode is separated into portions not less than two portions.

Abstract: A semiconductor laser apparatus includes a semiconductor substrate, a first cladding layer, an active layer, a second cladding layer, a second electrode, and a pair of resonator mirrors. The semiconductor substrate has a first electrode on one surface. The first cladding layer is formed on the other surface of the semiconductor substrate. The active layer is placed on the cladding layer. The second cladding layer is placed on the active layer. The second electrode is placed on the second cladding layer. The pair of resonator mirrors are placed in a waveguide direction perpendicular to the surfaces of the semiconductor substrate to oppose each other. The active layer is constituted by a quantum well layer having a tensilely strain. The second electrode is separated into portions not less than two portions.

Abstract: An encoder includes a semiconductor laser capable of emitting two coherent light beams from two end faces thereof, respectively. The end faces of the semiconductor laser are arranged such that the coherent light beams intersect each other. The two coherent light beams emitted from the end faces of the semiconductor laser are incident on a scale having a plurality of gratings. The two coherent light beams are diffracted by the gratings, resulting in two diffracted light beams. The two diffracted light beams interfere with each other, and the intensity of the resultant interference light beam is detected by a detector. In response to this detection, the detector produces a signal corresponding to the intensity change which is proportional to the relative moving distance between the detector and the scale.