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An acousto-optic imaging technique suitable for the local and quantitative determination of subsurface optical properties in turbid media is presented. Acousto-optic signals elicited by ultrasound pulses at two different peak pressures in turbid media are detected by using photorefractive-crystal-based interferometry. The ratio of the measured signals, once(More)
Phase distortions due to scattering in random media restrict optical focusing beyond one transport mean free path. However, scattering can be compensated for by applying a correction to the illumination wavefront using spatial light modulators. One method of obtaining the wavefront correction is by iterative determination using an optimization algorithm. In(More)
Non-invasively focusing light into strongly scattering media, such as biological tissue, is highly desirable but challenging. Recently, ultrasonically guided wavefront shaping technologies have been developed to address this limitation. So far, the focusing resolution of most implementations has been limited by acoustic diffraction. Here, we introduce(More)
Focusing light deep inside living tissue has not been achieved despite its promise to play a central role in biomedical imaging, optical manipulation and therapy. To address this challenge, internal-guide-star-based wavefront engineering techniques--for example, time-reversed ultrasonically encoded (TRUE) optical focusing--were developed. The speeds of(More)
Ultrasound-modulated optical tomography (UOT) has the potential to reveal optical contrast deep inside soft biological tissues at an ultrasonically determined spatial resolution. The optical imaging depth reported so far has, however, been limited, which prevents this technique from broader applications. Our latest experimental exploration has pushed UOT to(More)
Time-reversed ultrasonically encoded (TRUE) optical focusing was recently proposed to deliver light dynamically to a tight region inside a scattering medium. In this letter, we report the first development of a reflection-mode TRUE optical focusing system. A high numerical aperture light guide is used to transmit the diffusely reflected light from a turbid(More)
We report an experimental investigation of time-reversed ultrasonically encoded optical focusing in biological tissue. This technology combines the concepts of optical phase conjugation and ultrasound modulation of diffused coherent light. The ultrasonically encoded (or tagged) diffused light from a tissue sample is collected in reflection mode and(More)
High-intensity focused ultrasound (HIFU) is a promising modality that is used to noninvasively ablate soft tissue tumors. Nevertheless, real-time treatment monitoring with diagnostic ultrasound still poses a significant challenge since tissue necrosis, in the absence of cavitation or boiling, provides little acoustic contrast with normal tissue. In(More)
Scattering dominates light propagation in biological tissue, and therefore restricts both resolution and penetration depth in optical imaging within thick tissue. As photons travel into the diffusive regime-typically 1 mm beneath human skin, their trajectories transition from ballistic to diffusive due to increased number of scattering events, which makes(More)
In turbid media such as biological tissue, multiple scattering hinders direct light focusing at depths beyond one transport mean free path. As a solution to this problem, time-reversed ultrasonically encoded (TRUE) optical focusing is proposed based on ultrasonic encoding of diffused laser light and optical time reversal. In TRUE focusing, a laser beam of(More)