Ultrasound sensing with silicon photonics (invited)

Medical imaging is used to study the interior of a body by imaging its structure and functioning. Ultrasonography is a widely used imaging modality and photoacoustic tomography is an upcoming modality. Both modalities require large matrix of small and sensitive ultrasound sensors for recording the generated ultrasonic wavefield. And while both modalities have recently seen great advances in hardware and algorithms, current high-end system still use piezoelectric ultrasound sensors, which have relatively high noise. Instead, we propose silicon photonic ultrasound sensors. These have the prospect of small and sensitive sensors, wafer-scale fabrication, and matrix read-out via a single optical fibre using photonic multiplexing. In this talk, we first introduce different types of silicon photonic ultrasound sensors. Then, we discuss our latest optomechanical ultrasound sensor with extreme sensitivity that is achieved with a new optomechanical waveguide [Westerveld et al., Nature Photonics 15, 341 (2021)]. Such sensors can enable new applications of clinical and biomedical ultrasonic and photoacoustic imaging.