OPTICAL HEAD.

摘要

The optical head has light emitted from a semiconductor laser (8) input and coupled into a waveguide layer (3C) through a grating coupler (4C). The coupler or spiral rugged periodic structure to form a guided light (12C) that propagates through the layer toward the direction of circumference. The guided light is transferred to a waveguide layer (3B) in the outermost circumferential region of the waveguide layer (3C) to form guided light (12B) which is then emitted through a grating coupler (4B) that has a concentric or spiral periodic structure. The concentrically polarised (or radially polarised) light (13) is converted into linearly polarised light (14) through a polariser (10B) to focus the beam on the reflecting plane of an optical disc. The light reflected by the reflecting surface (16) is converted again into concentrically polarised (or radially polarised) light (17A,17B) through the polariser (10B) and is input and coupled to waveguide layers (3A,3B) through the grating couplers (4A,4B) to form guided lights (18A,18B). The lights propagate through the layers which are then emitted from the ends of the waveguide layers and are received by light detectors (6A,6B) to obtain control signals and reporduced signals.