High-efficiency time-reversed ultrasonically encoded optical focusing using a large-area photorefractive polymer

Abstract

Time-reversed ultrasonically encoded (TRUE) optical focusing focuses light beyond one transport mean free path by phase-conjugating the ultrasonically tagged light. However, in previous works, only a small portion of the tagged light was phase-conjugated by using a photorefractive Bi_(12)SiO_(20) crystal, due to its small active area (1x1 cm^2). In this work, we report high-efficiency TRUE focusing using a large-area photorefractive polymer (5x5 cm^2), which demonstrated ~40 times increase in focused energy. Further, we imaged absorbers embedded in a turbid sample of thickness of ~12 transport mean free paths.

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