Plasmonic and metamaterial devices incorporating two-dimensional materials such as graphene and transition metal dichalcogenides (TMDCs) have emerged as a transformative platform for advanced optoelectronic applications. The unique electronic and optical properties of these materials enable unprecedented control over light-matter interactions at the nanoscale, facilitating innovations in subwavelength imaging, sensing, and energy harvesting.

Surface plasmon polaritons (SPPs) in 2D materials exhibit strong light confinement and tunability, making them ideal for nanophotonic applications. Graphene, with its gate-tunable conductivity, supports highly confined SPPs in the terahertz to mid-infrared range. The dispersion relation of graphene plasmons can be adjusted via electrostatic gating or chemical doping, allowing dynamic control over resonance frequencies. TMDCs, such as MoS2 and WS2, support exciton-polaritons with strong light-matter coupling, enabling hybrid plasmon-exciton states for enhanced nonlinear optical effects. Engineering SPPs in these materials involves optimizing carrier density, dielectric environment, and nanostructuring to minimize losses while maximizing field confinement.

Hyperbolic metasurfaces, composed of alternating layers of 2D materials and dielectrics, exhibit extreme anisotropy in their optical response. These structures support high-k waveguide modes, enabling subdiffractional light manipulation. For instance, hexagonal boron nitride (hBN) naturally possesses hyperbolic phonon-polaritons in the mid-infrared, allowing for low-loss propagation of deeply confined light. By integrating graphene with hBN, actively tunable hyperbolic dispersion can be achieved, enabling reconfigurable optical devices. The design of such metasurfaces requires precise control over layer thicknesses and interface quality to minimize scattering losses and maintain optical performance.

Tunable absorption in 2D material-based plasmonic systems is critical for applications like photodetection and energy harvesting. Graphene’s broadband absorption, combined with plasmonic nanostructures, can achieve near-unity absorption at selected wavelengths. For example, patterned graphene arrays coupled with metallic resonators enhance light absorption through localized surface plasmons, with absorption peaks adjustable via geometric parameters. TMDCs, with their layer-dependent bandgaps, enable wavelength-selective absorption tuning. By integrating these materials into Fabry-Perot cavities or photonic crystal structures, absorption efficiency can be further enhanced while maintaining spectral selectivity.

Subwavelength imaging leverages the strong near-field enhancement of 2D plasmons to overcome the diffraction limit. Graphene-based superlenses have demonstrated resolution below 50 nm in the mid-infrared range by exploiting the high momentum of SPPs. Challenges include reducing propagation losses and improving fabrication precision to maintain image fidelity. Hyperbolic metamaterials, particularly those using hBN, have also enabled hyperlensing with sub-100 nm resolution, though scalability remains an issue due to the difficulty in assembling large-area, defect-free heterostructures.

Plasmonic sensors utilizing 2D materials offer ultrahigh sensitivity to molecular adsorption and environmental changes. Graphene’s plasmon resonance shifts measurably with adsorbed molecules, enabling label-free detection at the single-molecule level. TMDCs enhance sensitivity through exciton-plasmon coupling, where shifts in exciton peaks indicate binding events. Practical implementations require optimizing the trade-off between sensitivity and stability, as environmental factors like temperature and humidity can influence plasmonic responses.

Energy harvesting applications benefit from the enhanced light-matter interaction in 2D plasmonic systems. Graphene-based hot carrier devices convert plasmon decay into electrical currents with efficiencies influenced by carrier relaxation pathways. TMDCs, with their direct bandgaps, improve photovoltaic performance through exciton harvesting in ultrathin layers. Integrating these materials with metallic nanostructures can further enhance photocurrent generation via plasmon-induced hot electron injection. However, losses due to non-radiative decay and interfacial defects limit overall conversion efficiency, necessitating advances in material quality and device architecture.

Despite their promise, challenges persist in loss mitigation and scalable fabrication. Plasmonic losses in graphene and TMDCs arise from intrinsic carrier scattering and impurity effects. Strategies such as encapsulation in high-quality dielectrics or using alternative 2D materials with lower losses, like hBN, can mitigate these issues. Scalable fabrication of 2D material-based plasmonic devices requires advances in transfer techniques, lithography, and heterostructure assembly to ensure uniformity and reproducibility over large areas.

In summary, plasmonic and metamaterial devices incorporating 2D materials offer unparalleled opportunities for manipulating light at the nanoscale. From tunable SPPs to hyperbolic metasurfaces, these systems enable breakthroughs in imaging, sensing, and energy conversion. Overcoming challenges in loss reduction and scalable manufacturing will be critical for their transition from laboratory prototypes to real-world applications.