A Displacement Sensor Based on Directional Resonant Photodetector

We describe a micro-optical displacement encoder based on resonant photodetector with directional sensitivity for the specific incident angle. A layered silicon photodetector thinner than the incident wavelength is designed to confine the light beam for the effective encoder signal detection by guided resonant effect. Fabricated device shows the highly enhanced sensitivity at the angle illuminated from scale grating of encoder. The displacement signal with submicron resolution was achieved by the proposed resonant photodetector and simple optical configuration.