Unitary control of partially coherent waves. I. Absorption

TL;DR

This paper develops a systematic theory for controlling the absorption of partially coherent waves using unitary transformations, enabling tailored absorption levels for applications in energy, imaging, and sensing.

Contribution

It introduces analytical expressions and algorithms for achieving desired absorption levels of partially coherent waves through unitary control, including new phenomena like partial perfect absorption.

Findings

Derived conditions for partially coherent perfect absorption.

Established the relationship between coherence and absorption intervals.

Provided algorithms for constructing unitary control schemes.

Abstract

The coherent control of wave absorption has important applications in areas such as energy harvesting, imaging, and sensing. However, most practical scenarios involve the absorption of partially coherent rather than fully coherent waves. Here we present a systematic theory of unitary control over the absorption of partially coherent waves by linear systems. Given an absorbing system and incident partially coherent wave, we provide analytical expressions for the range of attainable absorptivity under arbitrary unitary transformations of the incident field. We also present an explicit algorithm to construct the unitary control scheme that achieves any desired absorptivity within that attainable range. As applications of our theory, we derive the conditions required for achieving two new phenomena - partially coherent perfect absorption and partially coherent zero absorption. Furthermore, we prove a theorem relating the coherence properties of the incident field, as quantified by majorization, to the resulting absorption intervals. Our results provide both fundamental insights and practical prescriptions for exploiting unitary control to shape the absorption of partially coherent waves. The theory applies across the electromagnetic spectrum as well as to other classical wave systems such as acoustic waves.