Resonant optical ultrasound transducer (ROUT) arrays for high resolution photoacoustic imaging

Multi-dimensional, high frequency ultrasound arrays are extremely difficult to fabricate from conventional piezoelectrics. For over a decade, our lab has explored optical detection as an alternate technology for high frequency applications. We have developed several different types of acoustically coupled optical resonators to provide the sensitivity and bandwidth required for biomedical imaging. Waveguide and fiber lasers, thin Fabry-Perot etalons constructed from polymers, and thin microring resonators imprinted into polymers have all been used as ultrasound transducer arrays. Their performance rivals the theoretical conversion efficiency of piezoelectric devices but with bandwidths approaching 100 MHz, array element dimensions approaching 10 um, and no electrical interconnects. In this paper we present results on several resonant optical ultrasound transducer (ROUT) arrays, emphasizing their potential use in photoacoustic imaging. These results strongly suggest that a high resolution photoacoustic microscope can be constructed using a ROUT in a footprint appropriate for endoscopic and minimally invasive applications.