Abstract
The plasmonic responses in the spatially separated phosphorene (single-layer black phosphorus) pairs are investigated, mainly containing the field enhancement, light confinement, and optical force. It is found that the strong anisotropic dispersion of black phosphorus gives rise to the direction-dependent symmetric and anti-symmetric plasmonic modes. Our results demonstrate that the symmetrical modes possess stronger field enhancement, higher light confinement, and larger optical force than the anti-symmetric modes in the nanoscale structures. Especially, the light confinement ratio and optical force for the symmetric mode along the armchair direction of black phosphorus can reach as high as >90% and >3000 pN/mW, respectively. These results may open a new door for the light manipulation at nanoscale and the design of black phosphorus based photonic devices.
Highlights
Surface plasmon polaritons (SPPs) are electromagnetic waves travelling along dielectricconductor interface and coupled to the free electron oscillations in the conductor [1, 2]
The electric field enhancement is a crucial factor for the plasmonic waveguides, which can be defined as the ratio of electric field |Ey| at the Black phosphorus (BP) boundaries (i.e., η = |Ey|(y = 2/g)/|Ey|(y = 2/g + d))
If there exists a ununiformity (e.g., 1 nm) between the BP layers, the relative deviations of field enhancement, light confinement, and optical force we calculated for the symmetric plasmonic modes in armchair direction are less than 6%, 1%, and 10% when g>10 nm, respectively
Summary
Surface plasmon polaritons (SPPs) are electromagnetic waves travelling along dielectricconductor interface and coupled to the free electron oscillations in the conductor [1, 2]. In the single-layer BP (termed ‘phosphorene’), phosphorous atoms covalently bonded with three others form a hexagonal lattice with a puckered honeycomb structure [29]. For the first time to our knowledge, we investigate the characteristics of plasmonic modes in the phosphorene pairs, containing the field enhancement, light confinement, and optical force. Our results reveal that the symmetrical modes exhibit stronger field enhancement, higher light confinement, and larger optical force than the anti-symmetric modes in the phosphorene pairs with nanoscale gap distances. The symmetric plasmonic mode along the armchair direction of phosphorene exhibits the light confinement ratio of >90% and optical force of >3000pN/mW. These results would be helpful for the realization of BP-based nanoscale light manipulation and devices
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