Frequency comb generation for wave transmission through the nonlinear dimer

TL;DR

This paper investigates how a nonlinear dimer responds to monochromatic waves, revealing a frequency comb effect due to instabilities linked to a symmetry-protected bound state in the continuum.

Contribution

It demonstrates the emergence of frequency combs in a nonlinear dimer caused by instabilities related to a symmetry-protected bound state.

Findings

Existence of a domain with unstable stationary solutions

Generation of multiple harmonics forming a frequency comb

Instability linked to a singular response of a bound state in the continuum

Abstract

We study dynamical response of a nonlinear dimer to a symmetrically injected monochromatic wave. We find a domain in the space of frequency and amplitude of the injected wave where all stationary solutions are unstable. In this domain scattered waves carry multiple harmonics with equidistantly spaced frequencies (frequency comb effect). The instability is related to a symmetry protected bound state in the continuum whose response is singular as the amplitude of the injected wave tends to zero.