We employ Random Matrix Theory in order to investigate coherent perfect absorption (CPA) in lossy systems with complex internal dynamics. The loss strength γCPA and energy ECPA, for which a CPA occurs are expressed in terms of the eigenmodes of the isolated cavity -thus carrying over the information about the chaotic nature of the target -and their coupling to a finite number of scattering channels. Our results are tested against numerical calculations using complex networks of resonators and chaotic graphs as CPA cavities.
We employ the Random Matrix Theory framework to calculate the density of zeroes of an M -channel scattering matrix describing a chaotic cavity with a single localized absorber embedded in it. Our approach extends beyond the weakcoupling limit of the cavity with the channels and applies for any absorption strength. Importantly it provides an insight for the optimal amount of loss needed to realize a chaotic coherent perfect absorbing (CPA) trap. Our predictions are tested against simulations for two types of traps: a complex network of resonators and quantum graphs.arXiv:1701.02016v2 [cond-mat.dis-nn]
Coherent perfect absorption is one of the possibilities to get high absorption but typically suffers from being a resonant phenomena, i.e., efficient absorption only in a local frequency range. Additionally, if applied in high power applications, the understanding of the interplay of non-linearities and coherent perfect absorption is crucial. Here we show experimentally and theoretically the formation of non-linear coherent perfect absorption in the proximity of exceptional point degeneracies of the zeros of the scattering function. Using a microwave platform, consisting of a lossy nonlinear resonator coupled to two interrogating antennas, we show that a coherent incident excitation can trigger a self-induced perfect absorption once its intensity exceeds a critical value. Note, that a (near) perfect absorption persists for a broad-band frequency range around the nonlinear coherent perfect absorption condition. Its origin is traced to a quartic behavior that the absorbance spectrum acquires in the proximity of the exceptional points of the nonlinear scattering operator.
We develop a statistical theory of waveform shaping of incident waves that aim to efficiently deliver energy at weakly lossy targets which are embedded inside chaotic enclosures. Our approach utilizes the universal features of chaotic scattering -thus minimizing the use of information related to the exact characteristics of the chaotic enclosure. The proposed theory applies equally well to systems with and without time-reversal symmetry. PACS numbers: Valid PACS appear hereThe prospect of utilizing waveform shaping of incident acoustic or electromagnetic radiation in order to efficiently direct energy to focal points, placed inside chaotic (or disordered) enclosures, has been intensely pursued during the last few years [1]. The excitement for this line of research is twofold: On the fundamental side the interesting question is to identify schemes that will allow us to utilize multiple scattering events in complex media like disordered structures or chaotic reverberation cavities in order to overcome the diffraction limit [2][3][4][5][6][7][8][9]. A successful outcome can revolutionize many applications of wave focusing in complex media, including imaging techniques [10][11][12][13] medical therapies [14], outdoor or indoor wireless communications [15] and electromagnetic warfare [16]. arXiv:1712.00510v2 [cond-mat.dis-nn]
We introduce the concept of multichannel Dynamically Modulated Perfect Absorbers (DM-PAs) which are periodically modulated lossy interferometric traps that completely absorb incident monochromatic waves. The proposed DMPA protocols utilize a Floquet engineering approach which inflicts a variety of emerging phenomena and features: reconfigurability of perfect absorption (PA) for a broad range of frequencies of the incident wave; PA for infinitesimal local losses, and PA via critical coupling with high-Q modes by inducing back-reflection dynamical mirrors.
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