Reflective limiters based on self-induced violation of CT symmetry

Abstract

Non-Hermitian bipartite photonic lattices with charge-conjugation symmetry can support resonant defect modes which are resilient to bipartite losses and structural imperfections. When, however, a (self-)induced violation of the -symmetry occurs via tiny permittivity variations, the resonant mode is exposed to the bipartite losses and it is destroyed. Consequently, the transmission peak is suppressed while the reflectance becomes (almost) unity. We propose the use of such photonic systems as power switches, limiters, and sensors. I.

Microwave Limiters Implemented by Coupled Dielectric Resonators Based on a Topological Defect Mode and CT-Symmetry Breaking

“…Consequently the Q-factor of the resonant defect mode will deteriorate leading to its destruction via a transition from an under-damping to an overdamping regime. Such transition is accompanied by a suppression of the transmittance and an increase to (near-)unity values of the reflectance [10]. The orange dashed line shown in fig.…”

“…The additional absorption γ nb introduced on the neighboring sites of the defect will destroy the CT -symmetry of the system itself, but the defect mode is not affected and keeps its structure. In contrast varying the eigenfrequency ν d = ν 0 of the defect resonator will break the CT -symmetry of the mode leading to non vanishing components Ψ n = 0 for n even [10]. Eq.…”

“…We will present here a microwave realization of a reflective limiter based on the CT -symmetry breaking in a bipartite structure which has been proposed in Ref. 10. As opposed to previous proposals, the topological reflective limiter is robust against fabricational errors, while at the same time is resilient to high power incident radiation that might lead to a destruction of existing limiting schemes.…”

Non-Hermitian and topological photonics: optics at an exceptional point

“…On a different front, endowing topological systems with NH symmetries has been used to develop optical devices with new functionalities. These include PT-symmetric resonator arrays in microwave systems (see Figure 6B) [192], optical isolators in waveguide arrays [193], optical limiters [194], and microring laser arrays capable of light steering [195].…”

Non-Hermitian CT-Symmetric Spectral Protection of Nonlinear Defect Modes

“…invention of new topological concepts and classifications. It was, therefore, only natural that the interplay between non-Hermiticity and topological protection attracted recently a lot of theoretical and experimental interest [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Some of the questions that have been raised include the generalization of band-edge correspondence, the emergence of new topological states without any Hermitian counterpart, or the necessity of a new topological phase classification [2,25,29,31].…”