Fig. 1: Overview principle of our method to enhance the delivery of light energy deep into the medium.

a Classification of three types of back-scatted photons, ξSS, ξMS1, and ξMS2 photons. b A point-by-point scanning strategy to construct the huge reflection matrix. c The theory of (1) time-reversal operator to separate ξSS, ξMS1, and ξMS2 photons; (2) wavefront shaping to focus light within the medium