Delocalized Electric Field Enhancement through Near-Infrared Quasi-BIC Modes in a Hollow Cuboid Metasurface

Area of Science:

• Nanophotonics and Metasurfaces
• Optical Sensing and Spectroscopy

Background:

• Dielectric metasurfaces for sensing face challenges with localized resonances and low experimental Q-factors.
• Existing designs limit electromagnetic field enhancement to the resonator's interior.

Purpose of the Study:

• To propose and theoretically demonstrate a novel dielectric metasurface overcoming limitations in electromagnetic field enhancement for sensing.
• To achieve delocalized modes with ultra-high Q-factors and significant field enhancements.

Main Methods:

• Design of a dielectric metasurface using silicon hollow nanocuboids on a glass substrate.
• Excitation of symmetry-protected quasi-bound states in the continuum (quasi-BICs) by perturbing nanocuboid hole arrangements.
• Unit cell variation with a cluster of four hollow nanocuboids to achieve polarization-insensitive delocalized modes.

Main Results:

• Demonstration of delocalized modes with ultra-high Q-factors.
• Achieved significant electric field enhancements in the range of 10^3-10^4.
• The metasurface exhibits polarization-insensitive resonance characteristics.

Conclusions:

• The proposed dielectric metasurface effectively addresses limitations of localized resonances and low Q-factors in sensing applications.
• This work paves the way for advancements in optical sensing and spectroscopy, including surface-enhanced Raman spectroscopy (SERS).