Dual-mode tunable absorber based on quasi-bound states in the continuum

Area of Science:

• Photonics and optical metamaterials.
• All-dielectric nanostructures.
• Light-matter interactions.

Background:

• Bound states in the continuum (BIC) offer high-quality optical resonances.
• Transforming BICs into quasi-BICs (q-BICs) enables practical device applications.
• All-dielectric structures provide low loss and design flexibility.

Purpose of the Study:

• To propose and demonstrate a novel dual-mode tunable absorber.
• To utilize quasi-bound states in the continuum (q-BIC) in an all-dielectric system.
• To explore the tunability and absorption capabilities for optical applications.

Main Methods:

• Designing a silicon cylinders tetramer structure.
• Introducing asymmetry to transform symmetry-protected BICs (SP-BICs) into q-BICs.
• Analyzing the quality factor dependence on asymmetry and applying multipole decomposition and Aleksandra's theory.

Main Results:

• Emergence of dual Fano-like resonant modes (one transmission, one reflection).
• Demonstrated exponential dependence of quality factor on asymmetry parameter (Q ∝ α^-1.75).
• Achieved theoretical maximum absorption for both modes in a graphene-integrated structure.

Conclusions:

• The proposed dual-mode tunable absorber exhibits efficient light absorption and tunability.
• The q-BIC approach in all-dielectric structures is effective for advanced optical devices.
• This work offers insights for optical modulation and graphene-based device development.