Abstract: 

Optical detection of ultrasound is an emerging technique based on the interaction of strain field and optical field, modulating the optical properties of the resonance cavity for sensitive detection. Such a detection scheme can have several unique advantages, such as broadband response and size-independent sensitivity, compared with conventional piezoelectric transducers. Detector’s high sensitivity is essential for deep penetration depth, especially for high-resolution imaging because of the strong attenuation of high-frequency ultrasound. Besides, small element size has the advantage of realizing wide acceptance angle of ultrasound detection. I will describe highly sensitive and broad band detection of ultrasound by polymer photonic microring resonators, and demonstrate its application for high resolution photoacoustic tomography and photoacoustic microscopy. Similar principle can be applied to THz detection. I will also present thin-film optical transmitters to generate and focus the ultrasound, targeting high-amplitude focused ultrasound for imaging and therapeutic applications. The optoacoustic sources are made of carbon-nanotubes (CNTs) and elastomeric polymers. As the nano-composite works as excellent optical absorbers and efficient heat converters, output pressure with strong amplitudes can be generated and has a corresponding frequency spectrum showing high-frequency characteristics. This approach could provide a versatile tool for cell engineering in terms of harvesting and patterning, and more importantly, non-thermal disruption to facilitate drug delivery and gene therapy for targeted cells. I will discuss recent experiment showing deterministic microbubble generation by highly focused high amplitude ultrasound using the photoacoustic lens.