A new high-frequency photoacoustic sensing probe using silicon acoustic delay lines

In this paper, we report a high-frequency photoacoustic sensing (PAS) probe design consisting of an optical fiber for light delivery and two silicon acoustic delay lines (SADLs) for detecting/relaying the PA signals. A beveled tip is formed at the distal end of the optical fiber to overlap the illumination region with the detection zone of the SADLs. Detected PA signals are transmitted through the SADLs with low loss at frequencies up to 17 MHz. For demonstration, a prototype PAS probe using SADLs is designed, fabricated, and tested. Testing results show that the PAS probe provides superior sensitivity with considerable high-frequency improvement.