Polarization-independent absorption enhancement in a graphene square array with a cascaded grating structure

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Graphene exhibits unique optical properties, making it a candidate for advanced optical devices.
• Achieving high and polarization-independent absorption in graphene remains a challenge for near-infrared applications.

Purpose of the Study:

• To investigate a polarization-independent enhanced absorption effect in graphene within the near-infrared spectrum.
• To explore the underlying physical mechanisms responsible for this absorption enhancement.

Main Methods:

• Fabrication of a structure comprising a graphene square array on a dielectric square array, backed by a two-dimensional multilayer grating.
• Analysis of electromagnetic field distributions to understand the physical origin of the absorption phenomenon for both polarizations.

Main Results:

• Demonstrated near-unity, polarization-independent absorption in graphene at resonance with an ultra-narrow spectrum.
• Attributed total optical absorption to critical coupling via guided-mode resonance and photonic band gap effects.
• Showcased tunability of polarization-independent absorption by altering geometric parameters.

Conclusions:

• The designed graphene absorber effectively achieves polarization-independent, enhanced absorption in the near-infrared range.
• The combined effects of guided-mode resonance and photonic band gap are crucial for critical coupling and absorption.
• This work holds significant potential for developing novel graphene-based optoelectronic devices.