Nonlinear response from optical bound states in the continuum

TL;DR

This paper investigates how nonlinear effects near optical bound states in the continuum can induce bistability, providing a simplified coupled mode theory approach that aligns well with full Maxwell solutions, aiding optical device design.

Contribution

It introduces a coupled mode framework for analyzing nonlinear optical responses near bound states in the continuum, simplifying complex Maxwell equations.

Findings

Resonant enhancement triggers optical bistability.

Derived a nonlinear equation for the resonant mode amplitude.

Coupled mode approach matches full-wave Maxwell solutions.

Abstract

We consider nonlinear effects in scattering of light by a periodic structure supporting optical bound states in the continuum. In the spectral vicinity of the bound states the scattered electromagnetic field is resonantly enhanced triggering optical bistability. Using coupled mode approach we derive a nonlinear equation for the amplitude of the resonant mode associated with the bound state. We show that such an equation for the isolated resonance can be easily solved yielding bistable solutions which are in quantitative agreement with the full-wave solutions of Maxwell's equations. The coupled mode approach allowed us to cast the the problem into the form of a driven nonlinear oscillator and analyze the onset of bistability under variation of the incident wave. The results presented drastically simplify the analysis nonlinear Maxwell's equations and, thus, can be instrumental in engineering optical response via bound states in the continuum.