Gain-assisted critical coupling for enhanced optical absorption in graphene

TL;DR

This paper introduces a gain-assisted approach to achieve critical coupling in graphene, significantly enhancing optical absorption in the near-infrared without altering the device structure, enabling advanced 2D material photonic applications.

Contribution

It presents a novel gain-assisted method to realize critical coupling in graphene, allowing maximum absorption tuning across a broad wavelength range without structural modifications.

Findings

Achieved maximum absorption in graphene at near-infrared wavelengths.

Demonstrated tuning of critical coupling via gain coefficient adjustment.

Enabled wide-wavelength critical coupling in a two-port photonic system.

Abstract

Enhanced optical absorption in two-dimensional (2D) materials has recently moved into the focus of nanophotonics research. In this work, we present a gain-assisted method to achieve critical coupling and demonstrate the maximum absorption in undoped monolayer graphene in the near-infrared. In a two-port system composed of photonic crystal slab loaded with graphene, the gain medium is introduced to adjust the dissipative rate to match the radiation rate for the critical coupling, which is accessible without changing the original structural geometry. The appropriate tuning of the gain coefficient also enables the critical coupling absorption within a wide wavelength regime for different coupling configurations. This work provides a powerful guide to manipulate light-matter interaction in 2D materials and opens up a new path to design ultra-compact and high-performance 2D material optical devices.