Patent ID: 8615027

Claim:
A laser diode comprising: a laser chip including (a) a first electrode, (b) a substrate, (c) a semiconductor region, and (d) a second electrode, the laser chip including at least one laser stripe which extends in a resonator length direction between a first end surface of the laser chip and a second end surface of the laser chip, the first end surface and the second end surface facing in opposite directions, the laser stripe being a ridge formed in an upper part of the semiconductor region, wherein, an insulating film is formed on both sides of the ridge on the upper part of the semiconductor region, the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, a length of the saturable absorption region is smaller than a length of the gain region, in plan view, a width of the laser stripe linearly increases along the resonator length direction throughout a length defined from the first end surface at the gain region of the laser chip to the second end surface at the saturable absorption region of the laser chip, the second electrode is disposed on the ridge of the laser stripe and is shaped in accordance with a shape of the laser stripe having increased width, the width of the laser stripe in the saturable absorption region is larger than the width of the laser stripe in the gain region, and the first and second end surfaces are coated such that a reflectivity of the first end surface is lower than a reflectivity of the second end surface.