Dr. Alex Krasnok


          Absorption of light is directly associated with dissipative processes in a material. In suitably
tailored resonators, a specific level of dissipation can support coherent perfect absorption, the
time-reversed analogue of lasing, which enables total absorption and zero scattering in open
cavities. On the contrary, the scattering zeros of lossless objects strictly occur at complex frequencies. While usually considered non-physical due to their divergent response in time, these
zeros play a crucial role in the overall scattering dispersion. Here, we introduce the concept of coherent virtual absorption, accessing these modes by temporally shaping the incident waveform.
We show that engaging these complex zeros enables storing and releasing the electromagnetic
energy at will within a lossless structure for arbitrary amounts of time, under the control of the
impinging field. We demonstrate that the observed effect may have important implications for
flexible control of light propagation and storage, low-energy memory, and optical modulation.

Coherent Photonics