Patent ID: 7139235
Filing Date: 2006-11-21
Classification: G11B,H01S

Abstract:
1. An optical semiconductor device comprising: a laser element; an emitted beam dividing portion for dividing an emitted light beam from the laser element into a main beam and two sub beams; a reflected beam dividing portion for dividing a reflected light beam from an information recording medium into light beams in different focused states, the reflected light beam being divided in a direction lateral to the direction in which the emitted beam is divided with the emitted beam dividing portion; servo-signal-detecting photodetector elements for receiving the reflected light beams obtained by the division by the reflected beam dividing portion in a defocused state so as to detect a servo signal using a three-beam method; and a signal-detecting photodetector element for receiving a reflected light beam obtained by diffracting with the emitted beam dividing portion a reflected light beam that has passed through the reflected beam dividing portion, wherein the emitted beam dividing portion includes a first diffraction grating region for generating the main beam, and second and third diffraction grating regions for generating the sub beams, and the signal-detecting photodetector element receives a beam that is obtained by diffracting the reflected light beam of the main beam with the reflected beam dividing portion and then diffracting an obtained zero order diffracted beam with the first diffraction grating region.