Time-reversed optical focusing through scattering media by digital full phase and amplitude recovery using a single phase-only SLM

Qiang Yang,Daxiong Xu,Xinzhu Sang

doi:10.1142/s1793545815500078

Abstract

Focusing light though scattering media beyond the ballistic regime is a challenging task in biomedical optical imaging. This challenge can be overcome by wavefront shaping technique, in which a time-reversed (TR) wavefront of scattered light is generated to suppress the scattering. In previous TR optical focusing experiments, a phase-only spatial light modulator (SLM) has been typically used to control the wavefront of incident light. Unfortunately, although the phase information is reconstructed by the phase-only SLM, the amplitude information is lost, resulting in decreased peak-to-background ratio (PBR) of optical focusing in the TR wavefront reconstruction. A new method of TR optical focusing through scattering media is proposed here, which numerically reconstructs the full phase and amplitude of a simulated scattered light field by using a single phase-only SLM. Simulation results and the proposed optical setup show that the time-reversal of a fully developed speckle field can be digitally implemented with both phase and amplitude recovery, affording a way to improve the performance of light focusing through scattering media.

Highlights

In scattering media, where light is strongly di®used, direct optical focusing beyond one optical transport mean free path ($ 1 mm for human skin) becomes infeasible
According to the proposed optical setup and the simulation results, it is clear that the wavefront reconstruction of a fully scattered opticaleld is entirely possible, using only a single phaseonly spatial light modulator (SLM)
The SLM is divided into two phase-only panels for amplitude reconstruction and phase reconstruction separately, which is feasible for the commercial phase-only SLMs with a length-width ratio up to $ 2

Summary

Introduction

In scattering media, where light is strongly di®used, direct optical focusing beyond one optical transport mean free path ($ 1 mm for human skin) becomes infeasible. Wavefront shaping techniques have been developed to achieve light focusing behind or inside a scattering layer. Three kinds of methods have been developed to shape the optical wavefront: wavefront optimization with feedback signals, transmission matrix characterization, and time-reversal of the light through optical phase conjugation.[1]. This is an Open Access article published by World Scientic Publishing Company. Further distribution of this work is permitted, provided the original work is properly cited

Methods

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Conclusion