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Analog time-reversed ultrasonically encoded (TRUE) optical focusing inside scattering media with high power gain

Ma, Cheng and Xu, Xiao and Wang, Lihong V. (2016) Analog time-reversed ultrasonically encoded (TRUE) optical focusing inside scattering media with high power gain. In: Adaptive Optics and Wavefront Control for Biological Systems II. Proceedings of SPIE. No.9717. Society of Photo-Optical Instrumentation Engineers , Bellingham, WA, Art. No. 97171I. ISBN 9781628419511. http://resolver.caltech.edu/CaltechAUTHORS:20180907-104554019

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Abstract

Focusing light deep inside scattering media plays a key role in such biomedical applications as high resolution optical imaging, control, and therapy. In recent years, wavefront shaping technologies have come a long way in controlling light propagation in complex media. A prominent example is time-reversed ultrasonically encoded (TRUE) focusing, which allows noninvasive introduction of “guide stars” inside biological tissue to guide light focusing. By measuring the optical wavefront emanating from an ultrasound focus created at the target location, TRUE determines the desired wavefront non-iteratively, and achieves focusing at the target position via a subsequent optical time reversal. Compared to digital counterparts that employ slow electronic spatial light modulators and cameras, analog TRUE focusing relies on nonlinear photorefractive crystals that inherently accommodate more spatial modes and eliminate the troublesome alignment and data transfer required by digital approaches. However, analog TRUE focusing suffers from its small gain, defined as the energy or power ratio between the focusing and probing beams in the focal volume. Here, by implementing a modified analog TRUE focusing scheme that squeezes the duration of the time-reversed photon packet below the carrier-recombination-limited hologram decay time of the crystal, we demonstrated a photon flux amplification much greater than unity at a preset focal voxel in between two scattering layers. Although the energy gain was still below unity, the unprecedented power gain will nevertheless benefit new biomedical applications.


Item Type:Book Section
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URLURL TypeDescription
https://doi.org/10.1117/12.2209396DOIArticle
ORCID:
AuthorORCID
Wang, Lihong V.0000-0001-9783-4383
Additional Information:© 2016 Society of Photo-Optical Instrumentation Engineers.
Record Number:CaltechAUTHORS:20180907-104554019
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180907-104554019
Official Citation:Cheng Ma, Cheng Ma, Xiao Xu, Xiao Xu, Lihong V. Wang, Lihong V. Wang, } "Analog time-reversed ultrasonically encoded (TRUE) optical focusing inside scattering media with high power gain (Conference Presentation)", Proc. SPIE 9717, Adaptive Optics and Wavefront Control for Biological Systems II, 97171I (27 April 2016); doi: 10.1117/12.2209396; https://doi.org/10.1117/12.2209396
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89462
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Sep 2018 03:34
Last Modified:08 Sep 2018 03:34

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