Monolithically integrated optical displacement sensor based on triangulation and optical beam deflection

A monolithically integrated optical displacement sensor based on triangulation and optical beam deflection is reported. This sensor is simple and consists of only a laser diode, a polyimide waveguide, and a split detector (a pair of photodiodes) upon a GaAs substrate. The resultant prototype device is extremely small (750 µm × 800 µm). Experiments have shown that this sensor can measure the displacement of a mirror with resolution of better than 4 nm. Additionally, we have experimentally demonstrated both axial and lateral displacement measurements when we used a cylindrical micromirror (diameter, 125 µm) as a movable external object.