Acousto-optic tomography (AOT) is a leading approach for deep-tissue imaging that combines light and sound. The acousto-optic effect is based on the change in the refractive index of a medium due to the presence of sound waves within it. Sound waves create a refractive index grating in the material, causing a difference in refractive index between the paths of the sound wave and the rest of the medium. When the medium is illuminated with coherent light, the portion of the field that passes through the sound wave will be frequency-shifted or "tagged" relative to the rest of the field. The "tagged" light can then be resolved using various interferometry-based approaches sensitive to frequency changes, such as holographic interferometry.
The position of the acoustic focus can be controlled within the sample by an external ultrasound transducer. Scanning the acoustic focus through the sample and detecting the modulated light allows us to image optical properties deep within optically scattering media. This combination of light and sound enables images with optical contrast, along with the near scatter-free propagation of ultrasound in soft tissues.
Super-resolution at depth
AOT resolution is determined by acoustic diffraction, which is significantly inferior to the optical diffraction limit. As a result, achieving optical-resolution microscopy through scattering media remains a long-standing challenge with significant implications for biomedicine. For purely optical techniques, light scattering limits the penetration depth of diffraction-limited optical imaging techniques to approximately 1 millimeter.
Our goal is to surpass the acoustic diffraction limit and achieve high-resolution imaging at depth using standard AOT systems.
Previous group works:
Rosenfeld, Moriya Gil Weinberg, Daniel Doktofsky, Yunzhe Li, Lei Tian, and Ori Katz, "Acousto-optic ptychography," Optica 8, 936-943 (2021)
Doktofsky, Daniel, Moriya Rosenfeld, and Ori Katz. “Acousto optic imaging beyond the acoustic diffraction limit using speckle decorrelation”. Communications Physics 31 (2020): , 3, 1, 1-8.
Katz, Ori, et al. “Controlling light in complex media beyond the acoustic diffraction-limit using the acousto-optic transmission matrix”. Nature communications 10.1 (2019): , 10, 1, 717.