Polarization vortex for enhanced refractive index sensing.

Area of Science:

• Dielectric photonics
• Metamaterial sensing
• Topological photonics

Background:

• All-dielectric sensors offer high figure of merit (FOM) but low sensitivity.
• Plasmonic sensors provide high sensitivity but suffer from high absorption.
• Bound states in the continuum (BICs) are resonant states with infinite radiative lifetimes, offering a potential solution.

Purpose of the Study:

• To investigate the sensitivity enhancement of dielectric sensors using BICs.
• To explore the relationship between BIC polarization vortices and refractive index changes.
• To demonstrate high angular sensitivity in dielectric sensors.

Main Methods:

• Theoretical computation of BIC polarization vortex dynamics in k-space.
• Analysis of angular and spectral sensitivities of the BIC-based structure.
• Simulation of BIC response to variations in the surrounding medium's refractive index.

Main Results:

• The BIC polarization vortex position in k-space exhibits a square-root dependence on refractive index changes.
• Achieved angular sensitivity comparable to surface plasmon polariton (SPP)-based sensors.
• Observed a blue spectral shift of BICs with increasing refractive index, deviating from conventional responses.
• Identified a BIC regime with significantly higher angular than spectral sensitivity.

Conclusions:

• BICs offer a pathway to high angular sensitivity in all-dielectric sensors.
• The unique k-space vortex dynamics enable enhanced refractive index sensing.
• Findings facilitate the development of advanced dielectric sensors and the study of optical vortex dynamics.