Optical information storage medium control apparatus

摘要

An optical pickup device includes a laser source for emitting linearly polarized light; an objective lens for focusing source light received from the laser source on an optical information storage medium; a photodetector for receiving signal light reflected from the medium for converting the signal light into an electric signal. The photodetector includes at least a photosensor, a planar optical waveguide formed on the photosensor for propagating the signal light therethrough, diffraction grating for diffracting the signal light propagating through the waveguide, and an incidence coupler provided on the waveguide for reflecting the source light emitted from the laser source and receiving signal light obtained through the objective lens from the medium. A plane of incidence including a normal to a surface of the incidence coupler and the optical axis of the source light is formed at an angle range of 5 to 85 degrees to a plane of polarization of the source light having an electric field vector of the optical axis and the source light. Thus, the direction of polarization of the signal light from the medium is also formed at an angle range of 5 to 85 degrees to the plane of incidence for the signal light to thereby detect the presence/absence of information. This reduces the size of the pickup device.