Active Tuning of Midinfrared Surface Plasmon Resonance and Its Hybridization in Black Phosphorus Sheet Array

Abstract

The behaviors of anisotropic plasmons in black phosphorus have been fully exploited across a complete variety of system including individual nanoribbon, vertically offset paired ones, and nanoribbon/sheet hybrid system. Benefiting from its twodimensional nature, plasmons can be actively controlled by either geometrical parameters or the carrier doping in black phosphorus, which allows for the emerging phenomenon of strong light−matter interaction at mid-infrared region. Remarkably, Rabi splitting over 17.3 meV is observed in the plasmonic spectra of the nanoribbon/ sheet hybrid structure as harnessed by the strong interaction of coupled plasmons. We also propose a scheme that supports plasmon on a continuous monolayer black phosphorus by using a diffraction grating. By adjusting the geometrical parameters of the grating and the Fermi level of the black phosphorus slightly, the resonance wavelength can be changed notably. The results appealing open up possibilities of devising black phosphorusbased plasmons in the application of optical detection and sensing within the deep subwavelength regime at mid-infrared region.

Nanoimaging of the Edge-Dependent Optical Polarization Anisotropy of Black Phosphorus

“…In BP nanoribbons, predicted to support anisotropic plasmons and surface plasmon polaritons, edge effects could readily dominate the system’s behavior. 24 − 27 Edge reconstructions of BP occur readily due to the corrugated orthorhombic lattice and are associated with unique in-gap edge electronic states and phonon modes; 14 , 28 metallic edge states of BP have been predicted theoretically. 29 , 30 However, distinguishing the critical interplay of edge and interior electronic behaviors and their effect on the direction-dependent dielectric function and optical properties of BP is not accessible with the limited spatial resolution of near-IR and visible optical microscopies, and is currently unknown.…”

“…Morphological features have been observed or predicted to modify the electronic and phononic properties of BP on the nanoscale. − Like other 2D materials prepared via mechanical exfoliation from polycrystalline bulk, few-layer BP can have uncontrolled structural morphology such as grain boundaries, variations in layer thickness, edges, defects, and strain that varies over 10–100s of nanometers, which interrupt the properties predicted for defect-free lattices of BP. − While some structural morphology can be mitigated by “bottom-up” preparation methods, morphological features such as edges are omnipresent in many functional applications. In BP nanoribbons, predicted to support anisotropic plasmons and surface plasmon polaritons, edge effects could readily dominate the system’s behavior. − Edge reconstructions of BP occur readily due to the corrugated orthorhombic lattice and are associated with unique in-gap edge electronic states and phonon modes; , metallic edge states of BP have been predicted theoretically. , However, distinguishing the critical interplay of edge and interior electronic behaviors and their effect on the direction-dependent dielectric function and optical properties of BP is not accessible with the limited spatial resolution of near-IR and visible optical microscopies, and is currently unknown.…”

Artificial Metaphotonics Born Naturally in Two Dimensions

“…Furthermore, a waveguide platform can be introduced to graphene by turning on/off the interband transition to design an optical modulator in the near-IR frequency range . This electrical control or chemical doping can also be applied to bandgap materials such as BP or TMDs. , The basic physics of this procedure is to modify the electron/hole carrier density and the Fermi level in the system. In this way, polaritonic modes such as SPs or exciton polaritons can be tuned.…”

Infrared Plasmonic Sensing with Anisotropic Two-Dimensional Material Borophene

“…For example, the Nanomaterials 2021, 11, 1165 2 of 11 plasmon resonances of nanostructured graphene can be actively tuned by an external voltage to probe molecules selectively in mid-infrared [24,25]. BP possesses anisotropic plasmons in the plane, which offer richer physics to the sensing design [26,27]. However, low carrier densities (~10 17 m −2 ) of those 2D materials limit their plasmonic sensing to midinfrared and THz regimes.…”