We developed a device that is capable of perfectly absorbing any light wavefront into a weakly absorbing material. This project is based on the phenomenon of coherent perfect absorption, which is analogous to operating a laser in reverse by replacing its gain medium with an absorbing medium. Traditionally, coherent perfect absorbers (CPA) could only absorb a single, precisely aligned wavefront, a restriction that confined their application to highly controlled laboratory settings. This project eliminates this limitation, demonstrating the capacity to perfectly absorb complex, random, and dynamic wavefronts into weakly absorbing media, marking a significant step forward in the practical application of coherent perfect absorbers.

Our solution builds on time-reversing a degenerate cavity laser, consisting of a telescopic arrangement of lenses that self-image any light field on the two cavity mirrors onto themselves. Implementing this degenerate cavity design, we demonstrated how complex speckle patterns consisting of more than 1,000 modes, as well as dynamically varying random fields, are absorbed with close to perfect efficiency in a massively parallel interference process.

Previous group works:
Yevgeny Slobodkin, Gil Weinberg, Helmut Hörner, Kevin Pichler, Stefan Rotter, Ori Katz, “Massively degenerate coherent perfect absorber for arbitrary wavefronts”, Science 377 (6609) 995-998 (2022).
Helmut Hörner, Lena Wild, Yevgeny Slobodkin, Gil Weinberg, Ori Katz, Stefan Rotter, “Coherent Perfect Absorption of Arbitrary Wavefronts at an Exceptional Point”, Physical Review Letters 133 (17), 173801 (2024).