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Journal of Biomedical Optics

Time-reversed ultrasonically encoded optical focusing into tissue-mimicking media with thickness up to 70 mean free paths
Author(s): Honglin Liu; Xiao Xu; Puxiang Lai; Lihong V. Wang
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Paper Abstract

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 long coherence length illuminates a turbid medium, where the incident light undergoes multiple scattering and part of it gets ultrasonically encoded within the ultrasonic focal zone. A conjugated wavefront of the ultrasonically encoded light is then generated by a phase conjugate mirror outside the medium, which traces back the trajectories of the ultrasonically encoded diffused light and converges light to the ultrasonic focal zone. Here, we report the latest experimental improvement in TRUE optical focusing that increases its penetration in tissue-mimicking media from a thickness of 3.75 to 7.00 mm. We also demonstrate that the TRUE focus depends on the focal diameter of the ultrasonic transducer.

Paper Details

Date Published: 1 August 2011
PDF: 7 pages
J. Biomed. Opt. 16(8) 086009 doi: 10.1117/1.3609004
Published in: Journal of Biomedical Optics Volume 16, Issue 8
Show Author Affiliations
Honglin Liu, Washington Univ. in St. Louis (United States)
Xiao Xu, Washington Univ. in St. Louis (United States)
Puxiang Lai, Washington Univ. in St. Louis (United States)
Lihong V. Wang, Washington Univ. in St. Louis (United States)

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