Nonlinear response from optical bound states in the continuum

Area of Science:

• Nonlinear optics
• Condensed matter physics
• Electromagnetism

Background:

• Optical bound states in the continuum (BICs) offer unique light-matter interaction possibilities.
• Nonlinear effects are crucial for advanced optical devices but complex to model.
• Periodic structures provide a versatile platform for controlling light propagation.

Purpose of the Study:

• To investigate nonlinear effects in light scattering by periodic structures with BICs.
• To understand the mechanism of optical bistability arising from resonant BIC enhancement.
• To develop a simplified analytical model for nonlinear phenomena in such systems.

Main Methods:

• Coupled mode theory to model the resonant mode associated with BICs.
• Derivation of a nonlinear equation for the resonant mode amplitude.
• Comparison of analytical solutions with full-wave solutions of Maxwell's equations.
• Analysis of bistability onset by treating the system as a driven nonlinear oscillator.

Main Results:

• Resonant enhancement of the scattered field near BICs triggers optical bistability.
• The derived nonlinear equation accurately predicts bistable solutions, matching full-wave simulations.
• The coupled mode approach simplifies the analysis of nonlinear Maxwell's equations.
• Bistability can be controlled by varying incident wave parameters.

Conclusions:

• Nonlinear effects in BICs provide a pathway to optical bistability.
• The coupled mode approach offers a powerful and simplified tool for analyzing nonlinear optical phenomena.
• This work facilitates the engineering of optical responses using BICs for novel device applications.