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Published March 2010 | Published
Journal Article Open

Turbidity suppression from the ballistic to the diffusive regime in biological tissues using optical phase conjugation

Abstract

We describe the amplitude and resolution trends of the signals acquired by turbidity suppression through optical phase conjugation (TSOPC) with samples that span the ballistic and diffusive scattering regimes. In these experiments, the light field scattered through a turbid material is written into a hologram, and a time-reversed copy of the light field is played back through the sample. In this manner, the wavefront originally incident on the sample is reconstructed. We examine a range of scattering samples including chicken breast tissue sections of increasing thickness and polyacrylamide tissue-mimicking phantoms with increasing scattering coefficients. Our results indicate that only a small portion of the scattered wavefront (<0.02%) must be collected to reconstruct a TSOPC signal. Provided the sample is highly scattering, all essential angular information is contained within such small portions of the scattered wavefront due to randomization by scattering. A model is fitted to our results, describing the dependence of the TSOPC signal on other measurable values within the system and shedding light on the efficiency of the phase conjugation process. Our results describe the highest level of scattering that has been phase conjugated in biological tissues to date.

Additional Information

© 2010 Society of Photo-Optical Instrumentation Engineers. Paper 09539R; Received 3 December 2009; revised 16 February 2010; accepted 19 February 2010; published 29 April 2010. The authors gratefully acknowledge Christopher Kovalchick and Guruswami Ravichandran for sharing their expertise on polyacrylamide. The authors also thank Shuo Pang for making scanning electron microscope (SEM) particle size measurements. This work was supported by a National Science Foundation (NSF) Career Award, Grant No. BES-0547657, as well as National Institutes of Health (NIH) Grant No. R21 EB008866-01. E. McDowell acknowledges support from a NSF graduate research fellowship.

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