New Methods and Theory for Increasing Transmission of Light through Highly-Scattering Random Media.

Abstract

Scattering hinders the passage of light through random media and consequently limits the usefulness of optical techniques for sensing and imaging. Thus, methods for increasing the transmission of light through such random media are of interest. Against this backdrop, recent theoretical and experimental advances have suggested the existence of a few highly transmitting eigen-wavefronts with transmission coefficients close to one in strongly backscattering random media.

Here, we numerically analyze this phenomenon in 2-D with fully spectrally accurate simulators and provide the first rigorous numerical evidence confirming the existence of these highly transmitting eigen-wavefronts in random media with periodic boundary conditions that is composed of hundreds of thousands of non-absorbing scatterers.

We then develop physically realizable algorithms for increasing the transmission and the focusing intensity through such random media using backscatter analysis. Also, we develop physically realizable iterative algorithms using phase-only modulated wavefronts and non-iterative algorithms for increasing the transmission through such random media using backscatter analysis. We theoretically show that, despite the phase-only modulation constraint, the non-iterative algorithms will achieve at least about 78.5%. We show via numerical simulations that the algorithms converge rapidly, yielding a near-optimum wavefront in just a few iterations.

Finally, we theoretically analyze this phenomenon of perfect transmission and provide the first mathematically, justified random matrix model for such scattering media that can accurately predict the transmission coefficient distribution so that the existence of an eigen-wavefront with transmission coefficient approaching one for random media can be rigorously analyzed.