Transmission-matrix-based point-spread-function engineering through a complex medium

Abstract

PSF engineering is of utmost interest, in particular for microscopy, but remains mostly restricted to weakly scattering or transparent samples. We report a method to design at will the spatial profile of transmitted coherent light after propagation through a strongly scattering sample. We compute an operator based on the experimentally measured transmission matrix, obtained by numerically adding an arbitrary mask in the Fourier domain prior to focusing. We demonstrate the strength of the technique through several examples: propagating Bessel beams, thus generating foci smaller than the diffraction-limited speckle grain; donut beams; and helical beams. We characterize the three-dimensional profile of the achieved foci and analyze the fundamental limitations of the technique. Our approach generalizes Fourier optics concepts for random media and opens in particular interesting perspectives for super-resolution imaging through turbid media.