Iterative, backscatter-analysis algorithms for increasing transmission and focusing light through highly-scattering random media

摘要

Scattering hinders the passage of light through random media and consequentlylimits the usefulness of optical techniques for sensing and imaging. Thus,methods for increasing the transmission of light through such random media areof interest. Against this backdrop, recent theoretical and experimentaladvances have suggested the existence of a few highly transmittingeigen-wavefronts with transmission coefficients close to one in stronglybackscattering random media. Here, we numerically analyze this phenomenon in 2-D with fully spectrallyaccurate simulators and provide rigorous numerical evidence confirming theexistence of these highly transmitting eigen-wavefronts in random media withperiodic boundary conditions that is composed of hundreds of thousands ofnon-absorbing scatterers. Motivated by bio-imaging applications where it is not possible to measure thetransmitted fields, we develop physically realizable algorithms for increasingthe transmission through such random media using backscatter analysis. We showvia numerical simulations that the algorithms converge rapidly, yielding anear-optimum wavefront in just a few iterations. We also develop an algorithmthat combines the knowledge of these highly transmitting eigen-wavefrontsobtained from backscatter analysis, with intensity measurements at a point toproduce a near-optimal focus with significantly fewer measurements than amethod that does not utilize this information.