Acousto optic tomography (AOT) is a leading approach for deep-tissue imaging based on the combination of light and sound. The Acousto-optic effect is based on the change of the refractive index of a medium due to the presence of sound waves in that medium. Sound waves produce a refractive index grating in the material, which causes a refractive difference between the paths of progression of the sound wave to the rest of the medium. When illuminating the medium with coherent light, the part of the field which passes through the sound wave will be frequency-shifted, or "tagged" with respect to the rest of the field. Next, the "tagged" light can be resolved by using one of a variety of interferometry-based approaches that are sensitive to frequency changes, such as interferometry holography.
The position of the acoustic focus can be controlled inside the sample by an external ultrasound transducer. By scanning the acoustic focus through the sample and detecting the modulated light, we can image optical properties deep inside optically scattering media. This combination of light and sound allows images with optical contrast with the near scatter-free propagation of ultrasound in soft tissues.
Super-resolution at depth
The resolution in AOT is dictated by acoustic diffraction, which is several orders of magnitude inferior to the optical diffraction limit. Thus, optical-resolution microscopy through scattering media is a long-standing challenge with great implications on biomedicine. For pure optical techniques, scattering of light limits the penetration depth of diffraction-limited optical imaging techniques approximately to 1 millimeter.
Our goal is to surpass the acoustic diffraction limit and achieve high-resolution imaging at depths with 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.