Abstract

Ultrafast photoacoustics can be used to “look through” opaque thin layers, by both exciting an acoustic pulse and detecting its echo optically at the top surface [1]. Because the acoustically induced reflectivity changes are typically very small, rapid scanning with high signal-to-noise ratio is challenging. A common alternative to using a mechanical delay stage to scan the pump-probe delay is asynchronous optical sampling (ASOPS) [2]. This scheme consists of two separate pulsed lasers with a fixed repetition rate offset for fast scanning. Here, we show that adding frequency modulation to ASOPS can significantly improve the measurement noise floor.

© 2023 IEEE