Strong THz and Infrared Optical Forces on a Suspended Single-Layer Graphene Sheet

TL;DR

This paper demonstrates that a suspended single-layer graphene sheet can experience strong, tunable optical forces under terahertz or infrared light, enabling potential applications in nanoscale optomechanics.

Contribution

It reveals that high substrate reflectivity and excitation frequency near graphene's scattering frequency produce significant optical forces on suspended graphene.

Findings

Strong optical forces are achievable with graphene at terahertz/infrared wavelengths.

Optical forces can be tuned in amplitude and direction by adjusting suspension height.

Graphene's Fermi level tuning enables dynamic control of optomechanical interactions.

Abstract

Single-layer graphene exhibits exceptional mechanical properties attractive for optomechanics: it combines low mass density, large tensile modulus, and low bending stiffness. However, at visible wavelengths, graphene absorbs weakly and reflects even less, thereby inadequate to generate large optical forces needed in optomechanics. Here, we numerically show that a single-layer graphene sheet is sufficient to produce strong optical forces under terahertz or infrared illumination. For a system as simple as graphene suspended atop a uniform substrate, high reflectivity from the substrate is crucial in creating a standing-wave pattern, leading to a strong optical force on graphene. This force is readily tunable in amplitude and direction by adjusting the suspension height. In particular, repellent optical forces can levitate graphene to a series of stable equilibrium heights above the substrate. One of the key parameters to maximize the optical force is the excitation frequency: peak forces are found near the scattering frequency of free carriers in graphene. With a dynamically controllable Fermi level, graphene opens up new possibilities of tunable nanoscale optomechanical devices.