Toroidal Dipole BIC-Driven Highly Robust Perfect Absorption with a Graphene-Loaded Metasurface

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Perfect absorption in few-layer 2D materials is vital for optoelectronics and sensing.
• Existing methods exhibit strong dependence of central wavelength on structural parameters.

Purpose of the Study:

• To propose a structure-parameter-deviation immune method for perfect absorption at desired wavelengths.
• To demonstrate a versatile design using toroidal dipole-bound states in the continuum (TD BIC).

Main Methods:

• Experimental demonstration using a monolayer-graphene-loaded compound grating structure.
• Harnessing the TE31 mode for TD BIC to enable transition from bound states in the continuum (BIC) to quasi-BIC.
• Tailoring quality factors by varying the gap distance without breaking structural symmetry.

Main Results:

• Achieved perfect absorption with high robustness and wavelength stability ratio of >15.
• Demonstrated stable resonance wavelength independent of structural parameter deviations.
• Showcased the versatility of the TD BIC approach for tunable absorption.

Conclusions:

• The proposed TD BIC method offers a robust and versatile approach for perfect absorption in 2D materials.
• This method overcomes the limitations of structural parameter dependence seen in traditional techniques.
• The approach is readily applicable to other 2D materials, broadening its impact.