Deep ultraviolet spontaneous emission enhanced by layer dependent black phosphorus plasmonics

Casimir interaction with black phosphorus sheets

We calculate the Casimir interaction between isotropic plates (gold or graphene) and black phosphorus (BP) sheets with Lifshitz theory. It is found that the Casimir force with BP sheets is of the order of α times the perfect metal limit, and α is the fine structure constant. Strong anisotropy of the BP conductivity gives rise to a difference in the Casimir force contribution between the two principal axis. Furthermore, increasing the doping concentration both in BP sheets and graphene sheets can enhance the Casimir force. Moreover, introducing substrate and increased temperature can also enhance the Casimir force, by this way we reveal that the Casimir interaction can be doubled. The controllable Casimir force opens a new avenue for designing next generation devices in micro- and nano-electromechanical systems.

Deep ultraviolet spontaneous emission enhanced by layer dependent black phosphorus plasmonics

Although graphene has been the primary material of interest recently for spontaneous emission engineering through the Purcell effect, it features isotropic and thickness-independent optical properties. In contrast, the optical properties of black Phosphorus (BP) are in-plane anisotropic; which supports plasmonic modes and are thickness-dependent, offering an additional degree of freedom for control. Here we investigate how the anisotropy and thickness of BP affect spontaneous emission from a Hydrogenic emitter. We find that the spontaneous emission enhancement rate i.e. Purcell factor (PF) depends on emitter orientation, and PF at a particular frequency and distance can be controlled by BP thickness. At lower frequencies, PF increases with increasing thickness due to infrared (IR) plasmons, which then enhances visible and UV far-field spectra, even at energies greater than 10 eV. By leveraging the thickness and distance-dependent PF, deep UV emission can be switched between 103 nm or 122 nm wavelength from a Hydrogenic emitter. Additionally, we find that doping can significantly tune the PF near BP and this alteration depends on the thickness of the BP. Our work shows that BP is a promising platform for studying strong plasmon-induced light-matter interactions tunable by varying doping levels, emitter orientation, and thickness.