Reflectometry based on two-photon absorption of a silicon avalanche photodiode

Proposed and demonstrated a novel reflectometry system based on two-photon absorption process in a silicon photodetector. This method can measure the optical path difference of several millimeters to several meters with a simple system configuration. The study on improving the accuracy and resolution is currently under investigation. We also plan to apply the same method to measuring the surface shape of objects using the two-photon absorption of silicon image sensors.