Observation of mutual extinction and transparency in light scattering

TL;DR

This paper experimentally demonstrates how interference of multiple light beams can control extinction and transparency in scattering media, with potential applications in imaging and communication.

Contribution

It introduces the experimental observation of mutual extinction and transparency effects in scattering media, validating theoretical predictions with practical demonstrations.

Findings

Mutual transparency occurs at specific phase relations between incident beams.

Extinction can be tuned from nearly zero to twice the single-beam value.

The effects are demonstrated on human hair and silicon bar samples.

Abstract

Interference of scattered waves is fundamental for modern light-scattering techniques, such as optical wavefront shaping. Recently, a new type of wavefront shaping was introduced where the extinction is manipulated instead of the scattered intensity. The underlying idea is that upon changing the phases or the amplitudes of incident beams, the total extinction will change due to interference described by the cross terms between different incident beams. Here, we experimentally demonstrate the mutual extinction and transparency effects in scattering media, in particular, a human hair and a silicon bar. To this end, we send two light beams with a variable mutual angle on the sample. Depending on the relative phase of the incident beams we observe either nearly zero extinction, mutual transparency, or almost twice the single-beam extinction, mutual extinction, in agreement with theory. We use an analytical approximation for the scattering amplitude, starting from a completely opaque object and we discuss the limitations of our approximation. We discuss the applications of the mutual extinction and transparency effects in various fields such as non-line-of-sight communications, microscopy, and biomedical imaging.