Optical Properties of Graphene and Two-Dimensional Materials

Graphene and its two-dimensional (2D) counterparts exhibit exceptional optical characteristics that arise from their reduced dimensionality, high carrier mobility and strong light–matter interactions. Despite being atomically thin, graphene absorbs a significant fraction of incident light across a broad spectral range, while transition-metal dichalcogenides and other 2D semiconductors host tightly bound excitons with large binding energies. Anisotropy in dielectric response and tunable refractive indices can be achieved through substrate engineering, heterostructuring and electrostatic gating. Plasmon resonances in graphene enable confinement of electromagnetic fields at subwavelength scales, and 2D heterostructures introduce interlayer coupling effects that further enrich optical dispersion and absorption profiles. These features underpin a wide array of applications in photodetectors, modulators, sensors and energy-harvesting devices, and motivate ongoing efforts to characterise and control optical constants with high spatial and spectral resolution.

Research from Nature Portfolio

Recent studies have advanced our understanding of graphene and related 2D crystals by probing their intrinsic optical constants and anisotropic responses. One investigation used imaging spectroscopic ellipsometry to decouple the anisotropic dielectric tensor of hexagonal boron nitride from a graphene monolayer, revealing a nearly 60 percent enhancement in broadband absorption compared with conventional substrates. Another work achieved direct measurement of both in-plane and out-of-plane components of the surface susceptibility tensor by embedding a monolayer crystal within a rigid prism, thereby removing substrate contributions and establishing a definitive theoretical model for 2D optical response. A complementary study of bulk and few-layer molybdenum disulphide combined near-infrared to soft X-ray dielectric and loss-function spectra with temperature-dependent analysis, uncovering unconventional low-loss plasmons and revealing a dimensional crossover between three- and two-dimensional electronic correlations that reshape excitonic features.

Optical Properties of Graphene and Two-Dimensional Materials publication trend

The graph below shows the total number of articles in optical properties of graphene and two-dimensional materials across all publications each year (not limited to Nature Index journals).

Technical terms

Two-dimensional material: A crystal with atomic-scale thickness, exhibiting quantum-confinement effects and strong surface-dominated properties.

Refractive index: A complex quantity describing how light propagates through a medium, with real part indicating phase velocity and imaginary part representing absorption.

Exciton: A bound state of an electron and a hole in a semiconductor, responsible for sharp optical absorption peaks in 2D semiconductors.

Surface plasmon resonance: Collective oscillations of free carriers at a metal or graphene interface that confine light to subwavelength scales and enhance local fields.

Spectroscopic ellipsometry: An optical technique that measures changes in polarisation upon reflection to extract film thickness and complex refractive index.

Susceptibility tensor: A mathematical description of how an anisotropic material polarises in response to electric fields in different directions.

References

1. Anomalous optical response of graphene on hexagonal boron nitride substrates. Communications Physics (2023).
2. Optical detection of the susceptibility tensor in two-dimensional crystals. Communications Physics (2021).
3. Unravelling strong electronic interlayer and intralayer correlations in a transition metal dichalcogenide. Nature Communications (2021).
4. Mapping spectroscopic micro-ellipsometry with sub-5 microns lateral resolution and simultaneous broadband acquisition at multiple angles. Review of Scientific Instruments (2023).
5. Optical Constants of Chemical Vapor Deposited Graphene for Photonic Applications. Nanomaterials (2021).
6. Optical Properties of Graphene Nanoplatelets on Amorphous Germanium Substrates. Molecules (2024).
7. Surface plasmon resonance for characterization of large-area atomic-layer graphene film. Optica (2016).