| dc.description.abstract | Photoacoustic sensing (PAS) has been used for a number of biomedical applications, which take the advantage of rich optical absorption contrast and deep acoustic penetration depth in tissues. However, current PAS devices are bulky, invasive, and susceptible to interference during excitation. In the thesis, miniaturized PAS probes based on acoustic delay lines (ADLs) are studied. First, a compact two-optical-fiber PAS probe is designed, fabricated, and tested. It consists of one optical fiber for light delivery and the other one for relaying the generated photoacoustic (PA) signal from the target to an outside ultrasound transducer (UTX). With the addition of a suitable time delay, the PA signal can be easily separated from the interference signals. Secondly, to create an even more compact structure, a PAS probe design using a single optical fiber for both light delivery and PA detection is investigated. An optically transparent UTX is developed, which allows the excitation light to pass through and at the same time detect the generated PA signal transmitted through the optical fiber as an ADL. Thirdly, to improve the frequency response of PA detection, a new PAS probe based on silicon acoustic delay lines (SADLs) is explored to replace the fused-silica optical fibers. Compared with fused-silica, single-crystalline silicon has much higher acoustic velocity and lower acoustic attenuation and can therefore support non-dispersive acoustic transmission at much higher frequencies. Lastly, a high-frequency SADL array is demonstrated to enable simultaneous multi-channel PA detection. The multi-channel detection capabilities can also be useful for PA imaging applications. | en |
