Sub-Nyquist sampling boosts targeted light transport through opaque scattering media

TL;DR

This paper demonstrates that sub-Nyquist sampling in optical time-reversal techniques can produce brighter focus and improved efficiency through opaque media, challenging traditional sampling requirements.

Contribution

It introduces and experimentally validates the use of sub-Nyquist sampling in optical time reversal, showing it enhances focus brightness and efficiency.

Findings

Under-sampling can still produce effective light focusing.

Sub-Nyquist sampling yields about ten times brighter focus.

Improves signal-to-noise ratio and collection efficiency.

Abstract

Optical time-reversal techniques are being actively developed to focus light through or inside opaque scattering media. When applied to biological tissue, these techniques promise to revolutionize biophotonics by enabling deep-tissue non-invasive optical imaging, optogenetics, optical tweezers and photodynamic therapy. In all previous optical time-reversal experiments, the scattered light field was well-sampled during wavefront measurement and wavefront reconstruction, following the Nyquist sampling criterion. Here, we overturn this conventional practice by demonstrating that even when the scattered field is under-sampled, light can still be focused through or inside opaque media. Even more surprisingly, we show both theoretically and experimentally that the focus achieved by under-sampling is usually about one order of magnitude brighter than that achieved by conventional well-sampling conditions. Moreover, sub-Nyquist sampling improves the signal-to-noise ratio and the collection efficiency of the scattered light. We anticipate that this newly explored under-sampling scheme will transform the understanding of optical time reversal and boost the performance of optical imaging, manipulation, and communication through opaque scattering media.