Graphene-based tunable hyperbolic metamaterials and enhanced near-field absorption

Area of Science:

• Metamaterials
• Optics
• Condensed Matter Physics

Background:

• Hyperbolic metamaterials (HMs) offer unique electromagnetic properties.
• Graphene's tunable electronic properties make it a promising material for advanced optical devices.

Purpose of the Study:

• To investigate a novel implementation of hyperbolic metamaterial (HM) at far-infrared frequencies using stacked graphene sheets.
• To explore the tunability of infrared iso-frequency wavevector dispersion and reflection/transmission properties.
• To assess the potential of graphene-based HM as a super absorber for near-fields.

Main Methods:

• Derivation of a homogenization formula for a multilayer graphene-dielectric structure using the surface conductivity model of graphene.
• Comparison of homogenization results with a transfer matrix formulation to investigate limits.
• Analysis of dipole radiation enhancement and power scattering near the graphene-based HM surface.

Main Results:

• The infrared iso-frequency wavevector dispersion of the proposed HM is tunable via electrostatic biasing of graphene chemical potential.
• Reflection and transmission properties of the graphene-dielectric multilayer are tunable at terahertz frequencies.
• Graphene-based HM dramatically enhances near-field absorption, increasing dipole emitted power by up to 5 × 10^2 at 2 THz, with most scattered power directed into the HM.
• The homogenized HM model's validity and limits were assessed for both far-field and near-field applications, revealing potential overestimation of dipole radiated power in certain near-field conditions.

Conclusions:

• Stacked graphene sheets form a tunable hyperbolic metamaterial suitable for far-infrared applications.
• Electrostatic biasing allows for dynamic control over the optical properties of graphene-based HMs.
• Graphene-based HMs show significant potential as near-field super absorbers, though model limitations must be considered.