Laser Scanning for Single-Shot Frequency Diverse Photoacoustic Excitation

Photoacoustic and laser-induced ultrasound based imaging systems have been successfully deployed for a range of applications from biomedical imaging to non-destructive testing and remote sensing. Application-specific optimization of the spatial, spectral, and temporal properties of the generated photoacoustic waves requires careful consideration of the optical excitation sub-system. In this work, we study, both analytically and through simulations, the effects of a moving laser source on the generated photoacoustic waves and discuss the additional degrees-of-freedom provided by scanning the laser in a laser-induced ultrasound imaging system. By tuning laser parameters such as the laser scan velocity and modulation frequency, we explore the utility of a moving laser in implementing transmit beam-steering as well as in the generation of angle-dependent, multi-frequency acoustic waves. Finally, as an example application, we demonstrate single-shot, single-sensor imaging.