Massively degenerate coherent perfect absorber for arbitrary wavefronts

TL;DR

This paper introduces a novel degenerate cavity design that enables near-perfect absorption of arbitrary, complex wavefronts, significantly advancing the capabilities of coherent perfect absorbers in photonics.

Contribution

It presents a new cavity-based approach that achieves universal wavefront absorption, overcoming previous mode-specific limitations of CPAs.

Findings

Achieves near-perfect absorption for any wavefront

Enables dynamic tuning of absorption levels

Operates efficiently with complex speckle patterns

Abstract

One of the key insights in the emerging field of non-Hermitian photonics is that well-established concepts like the laser can be operated in reverse to realize a 'coherent perfect absorber' (CPA). While conceptually appealing, such CPAs are limited so far to a single, judiciously shaped wavefront or 'mode'. Here, we demonstrate how this limitation can be overcome by time-reversing a 'degenerate cavity laser', based on a unique cavity that self-images any incident light-field onto itself. Placing a weak, critically-coupled absorber into this cavity, we demonstrate that any incoming wavefront, even a complex and dynamically-varying speckle pattern, is absorbed with close to perfect efficiency in a massively parallel interference process. Moreover, the coherent nature of multi-mode absorption allows us to tune the degree of absorption over a wide range. These characteristics open-up interesting new possibilities for applications in light-harvesting, energy delivery, light control, and imaging.