# Coherent perfect absorbers: linear control of light with light

## TL;DR

This paper reviews the concept of coherent perfect absorbers, devices that achieve complete electromagnetic energy absorption through wave interference control, highlighting design principles, structures, and potential applications in nanophotonics.

## Contribution

It provides a comprehensive overview of the theoretical foundations, various photonic structures, and future prospects of coherent perfect absorbers, integrating recent advances in the field.

## Key findings

- Complete absorption achieved via wave interference control.
- Various structures enable coherent perfect absorption, including graphene and 3D systems.
- Potential applications in nanophotonics and sensing.

## Abstract

Absorption of electromagnetic energy by a material is a phenomenon that underlies many applied problems, including molecular sensing, photocurrent generation and photodetection. Commonly, the incident energy is delivered to the system through a single channel, for example by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity- and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics and, finally, we survey the perspectives for the future of this field.