Advances in optical detection of ultrasound: towards an acoustic camera-on-a-chip

In the last several decades, ultrasound detection has become almost synonymous with piezoelectric technology. In the field of medical sonography, the piezoelectric array, commercialized in the early 1970s, is still the core technology of contemporary devices. Nonetheless, with the emergence of new ultrasound-based technologies such as optoacoustic tomography and surface-acoustic-wave (SAW) microfluidics, a new need has arisen for novel ultrasound detectors with a level of miniaturization unattainable by piezoelectric technology. While optical detectors of ultrasound have long been considered an alternative to conventional technology, they have mostly remained a niche owing to their susceptibility to mechanical vibrations and the lack of effective schemes for parallel detector read-out

In this talk I will present a new paradigm for optical detection of ultrasound that can overcome the deficiencies of conventional optical techniques. At the heart of the new detection scheme is a sensor interrogation method called pulse interferometry, which achieves the fundamental shot-noise detection limit and is robust against mechanical vibrations. Sensor miniaturization is achieved by the use of light confinement in grating structures in fibers and silicon waveguides. Two applications are demonstrated: an all-optical optoacoustic imaging catheter and a silicon-based SAW detector. Finally, the potential of scaling the new technology to achieve ultra-small detector arrays will be discussed