Computations of the acoustically induced phase shifts of optical paths in acoustophotonic imaging with photorefractive-based detection.

Acoustophotonic imaging uses ultrasound-modulated scattered light to improve the quality of optical imaging in diffusive media. Experiments that use photorefractive-crystal-based detection have shown that there is a large dc shift in the acoustically modulated or ac optical signal, which could be utilized to further improve optical imaging resolution. We report that photon paths in a diffusive medium were generated by a Monte Carlo simulation, and the optical phase shifts of the various photons induced by the presence of a realistic focused ultrasound beam were calculated. Quantities that characterize the ac and dc signal components were evaluated by use of the calculated phase shifts. It was confirmed that the dc component dominates owing to coherent summation of the contributions from all the photons.