Synthetic Reflectionless Mode Exceptional Degeneracies via Emergent Local Symmetries

TL;DR

This paper introduces a new type of exceptional point degeneracies called synthetic reflectionless modes (SRM) that arise from local PT-symmetry in Floquet-driven systems, enabling reflectionless wave control and frequency conversion.

Contribution

It presents a novel class of physically realizable EPDs based on synthetic frequency dimensions and local PT-symmetry, expanding the understanding of wave degeneracies in driven systems.

Findings

Simulation validation with RF resonators confirms the theory.

SRM-EPDs enable flat transmission spectra and targeted frequency conversion.

The approach leverages Floquet driving to induce local PT-symmetry.

Abstract

We propose a new kind of physically realizable exceptional point degeneracies (EPDs) corresponding to synthetic reflectionless modes (SRM). These are solutions of an auxiliary wave operator that is defined in synthetic frequency dimensions and describe incoming reflectionless waves onto a Floquet-driven cavity. The SRM-EPD emerges as a consequence of a spontaneous local PT-symmetry imposed on the auxiliary operator via appropriate Floquet driving. Its presence signifies the possibility to design wavefronts and time-modulated schemes with up/down targeted frequency conversion and flat transmission spectra. The theory is validated via simulations with driven RF resonators.