In hyperbolic two-dimensional (2D) materials, energy is channeled into their deep subwavelength polaritonic modes via four narrow beams. Here, we consider the launching of surface polaritons in hyperbolic 2D materials and demonstrate that efficient unidirectional excitation is possible with an elliptically polarized electric dipole, with the optimal choice of dipole ellipticity depending on the materials' optical constants. The selection rules afforded by the choice of dipole polarization allow turning off up to two beams, and even three if the dipole is placed close to an edge. This makes the dipole a directionally switchable beacon for the launching of subdiffractional polaritonic beams, a potential logical gate. We develop an analytical approximation of the excitation process which describes well the results of the numerical simulations and affords a simple physical interpretation.
Bibliographical noteFunding Information:
A.N., T.L., and M.L. have been partially supported by the Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI) Award No. W911NF-14-1-0247. T.L. and A.N. acknowledge partial support from NSF/EFRI- 1741660. A.N., T.S., M.L., and T.L. acknowledge the hospitality of the Institute for Mathematics and its Applications. T.S. and G.S. acknowledge support from Spain's MINECO under Grants No. MDM-2014-0377, No. FIS2017-82260-P, and No. FIS2015-64886-C5-5-P.