Segmented waveguide gratings used as optical recording sensors

Abstract

An apparatus and method for detecting focus and tracking error signals and monitoring pointing in an optical device wherein a return beam of light undergoes changes in angle and collimation in response to changes in focus and tracking are provided. A waveguide device includes a substrate having a surface, a waveguide layer on the surface having segments of different thicknesses for adjusting an effective refractive index of each segment, a cladding contacting the waveguide layer with the waveguide layer positioned between the substrate and the cladding, and a linear input coupling grating for input coupling the return beam. The grating includes a processing grating to input couple light to effect a desired change in input coupled intensity with defocus or detracking, an isolation grating for decoupling light scattered within the waveguide, and an interchip grating to couple light already processed to focus and tracking detectors. The grating and detectors are used to generate focus error signals, tracking error signals, and pointing error signals.

Dependencies are inferred from the claim text.