Angle- and position-insensitive electrically tunable absorption in graphene by epsilon-near-zero effect

Area of Science:

• Photonics and Nanotechnology
• Materials Science
• Electrical Engineering

Background:

• Graphene exhibits unique electronic properties, including the epsilon-near-zero (ENZ) effect, which can be exploited for optical applications.
• Nanocavity structures enhance light-matter interactions, crucial for efficient absorption.
• Electrical tunability offers dynamic control over optical device performance.

Purpose of the Study:

• To propose and investigate an electrically tunable optical absorber utilizing the ENZ effect in graphene.
• To achieve high light absorption in an ultrathin graphene monolayer within a nanocavity.
• To demonstrate wide-range tunability of the absorption peak wavelength and explore device applications.

Main Methods:

• Fabrication of a nanocavity structure comprising a metal grating and substrate.
• Embedding an ultrathin graphene monolayer within the nanocavity to leverage the ENZ effect.
• Electrical control of graphene's Fermi-level to tune its optical properties.

Main Results:

• Achieved high light absorption (~80%) in the graphene monolayer due to strong surface-normal electric field confinement.
• Demonstrated wide-range tunability of the absorption peak wavelength by electrically controlling the graphene's Fermi-level.
• Observed incident angle insensitivity due to the ENZ effect and magnetic dipole resonance.

Conclusions:

• The proposed device functions as an effective optical modulator or tunable absorption filter.
• The design exhibits excellent fabrication tolerance due to the dominant and uniform electric field distribution.
• This work presents a promising platform for advanced tunable optical devices based on graphene plasmonics.