Angular dependency of spatial frequency modulation in diffusion media

TL;DR

This paper demonstrates how angular deviation between control and probe beams in EIT-based light storage can modulate the spatial frequency response, transforming diffusion effects from low-pass to tunable band-pass filtering in hot atomic vapors.

Contribution

It introduces a novel method to control spatial frequency filtering in diffusion media using angular deviation, enabling tunable band-pass filtering of optical fields.

Findings

Angular deviation modulates SF response from low-pass to band-pass.

Transverse multimode fields confirm tunable SF filtering.

Potential applications in quantum info and optical imaging.

Abstract

An optical field will undergo coherent diffusion when it is mapped into thermal-motioned atoms, e.g., in a slow or storage light process. As was demonstrated before, such diffusion effect is equivalent to a spatial low-pass filter attenuating the high spatial frequency (SF) components of the optical field. Here, employing electromagnetically induced transparency (EIT) based light storage in hot atomic vapor, we demonstrate that the angular deviation between the control and probe beams could be utilized as a degree of freedom to modulate the SF of the probe beam. The principle is to change the diffusion-induced low-pass filter into a band-pass filter, whose SF response can be tuned by varying the direction and magnitude of the angular deviation. Transverse multimode light fields, such as optical images and Laguerre-Gaussian modes are utilized to study such SF modulation. Our findings could be broadly applied to the fields of quantum information processing, all-optical image manipulation and imaging through diffusive media.