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K. Pichler, M. Kühmayer, J. Böhm, A. Brandstötter, P. Ambichl, U. Kuhl, S. Rotter:
"Experimental realization of the random anti-laser";
Talk: Foundations of Nonlinear Optics (FoNLO) 2019, Air Force Institut of Technology, Dayton, Ohio (invited); 2019-08-06 - 2019-08-08.

A very promising phenomenon that was recently discovered in the field of non-Hermitian wave engineering is that of coherent perfect absorption. This effect can be understood as the time-reversed process of lasing at threshold and is therefore commonly referred to as 'anti-lasing'. In this talk, I will present the concept and first experimental realization of random anti-lasing, i.e., the time-reverse of random lasing at the first lasing threshold. While a random laser emits a spatially complex but coherent wave, the random anti-laser absorbs a correspondingly complex incoming field perfectly. We recently implemented such a device in the form of a microwave experiment, where a small absorbing element is embedded in the middle of a disordered medium. Measuring the scattering matrix of the system allows us to determine and then generate an incoming wave field that gets absorbed by about 99.8% inside the disorder. Our approach is scalable in the number of involved modes and could be suitable for numerous applications in which waves need to be perfectly focused, routed, or absorbed.

http://www.fonlo.org/2019/