Shaping the angular spectrum of a Bessel beam to enhance light transfer through dynamic strongly-scattering media

TL;DR

This study demonstrates that shaping the angular spectrum of a Bessel beam enhances light transmission through dynamic strongly-scattering media, with optimal transmission achieved when the beam's transverse wave vector matches the medium's azimuthal frequencies.

Contribution

The paper introduces a method to optimize Bessel beams for better light transfer through scattering media by matching the wave vector to the medium's frequency components.

Findings

Optimal intensity occurs when $k_\perp$ matches $k_\phi$.

Reasonable enhancement with only 64 segments.

Effective even with moving scatterers if displacement is small.

Abstract

We prepare a quasi-non-diffracting Bessel beam defined within an annular angular spectrum with a spatial light modulator. The beam propagates though a strongly scattering media and the transmitted speckle pattern is measured at one point with a Hadamard Walsh basis that divides the ring into $N$ segments ($N=16,64,256, 1024$). The phase of the transmitted beam is reconstructed with 3 step interferometry and the intensity of the transmitted beam is optimized by projecting the conjugate phase at the SLM. We find that the optimum intensity is attained for the condition that the transverse wave vector $k_\perp$ (of the Bessel beam) matches the spatial azimuthal frequencies of the segmented ring $k_\phi$. Furthermore, compared with beams defined on a 2d grid (i.e. Gaussian) a reasonable enhancement is achieved for all the $k_\perp$ sampled with only 64 elements. Finally, the measurements can be done while the scatterer is moving as long as the total displacement during the measurement is smaller than the speckle correlation distance.