Massively degenerate coherent perfect absorber for arbitrary wavefronts

One of the key insights of non-Hermitian photonics is that well-established concepts such as the laser can be operated in reverse to realize a coherent perfect absorber (CPA). Although 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, any incoming wavefront, even a complex and dynamically varying speckle pattern, is absorbed with close to perfect efficiency in a massively parallel interference process. These characteristics open up interesting new possibilities for applications in light harvesting, energy delivery, light control, and imaging.

Automated summary

One of the key insights of non-Hermitian photonics is the concept of coherent perfect absorber (CPA), which can be achieved by reversing the operation of well-established concepts like lasers. This study demonstrates the possibility of overcoming the limitation of CPA by time-reversing a degenerate cavity laser based on a unique cavity that self-images any incident light field onto itself. The results show that placing a weak, critically coupled absorber into this cavity allows for nearly perfect absorption of any incoming wavefront, even complex and dynamically varying speckle patterns. This opens up new possibilities for applications in light harvesting, energy delivery, light control, and imaging.