Light can be coupled into propagating electromagnetic surface waves at a metal-dielectric interface known as surface plasmon polaritons (SPPs). This process has traditionally faced challenges in the polarization sensitivity of the coupling efficiency and in controlling the directionality of the SPPs. We designed and demonstrated plasmonic couplers that overcome these limits using polarization-sensitive apertures in a gold film. Our devices enable polarization-controlled tunable directional coupling with polarization-invariant total conversion efficiency and preserve the incident polarization information. Both bidirectional and unidirectional launching of SPPs are demonstrated. The design is further applied to circular structures that create radially convergent and divergent SPPs, illustrating that this concept can be extended to a broad range of applications.

Optical elements that convert the spin angular momentum (SAM) of light into vortex beams have found applications in classical and quantum optics. These elements-SAM-to-orbital angular momentum (OAM) converters-are based on the geometric phase and only permit the conversion of left- and right-circular polarizations (spin states) into states with opposite OAM. We present a method for converting arbitrary SAM states into total angular momentum states characterized by a superposition of independent OAM. We designed a metasurface that converts left- and right-circular polarizations into states with independent values of OAM and designed another device that performs this operation for elliptically polarized states. These results illustrate a general material-mediated connection between SAM and OAM of light and may find applications in producing complex structured light and in optical communication.

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The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. Because their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces.

We show that the surface plasmon polariton (SPP) radiation patterns of point-dipole emitters in the vicinity of a metal-dielectric interface are generally asymmetric with respect to the location of the emitter. In particular rotating dipoles, which emit elliptically polarized light, produce highly asymmetric SPP radiation fields that include unidirectional emission. Asymmetric SPP radiation patterns also result when a dipole oscillates tilted with respect to the plane of the interface and optical losses or gains are present in the materials.These effects can be used to directionally control SPP emission and absorption, as well as to study emission and scattering processes close to metal-dielectric interfaces. Possible implementations of asymmetrically emitting SPP sources are discussed.Main Text: Surface plasmon polaritons (SPPs) are tightly confined electromagnetic waves that propagate across metal surfaces at the frequencies of infrared or visible light 1 . Their strong interaction with matter close to metal interfaces has led to a variety of applications in modern biological and chemical sensing 2-4 , and to new developments in photovoltaics 5 and quantum optics 6 . Because of their small mode volume and widely controllable properties, SPPs are considered promising candidates to enable on-chip information technology at optical bandwidths 7,8 .The problem of SPP radiation (or, by virtue of time-reversal symmetry, absorption 9 ) by classical point-dipoles is ubiquitous in theoretical plasmonics, as it provides an accurate and efficient model for understanding a broad spectrum of phenomena in light-matter interaction. This includes the interaction with the analyte in plasmonenhanced sensing applications 10,11 , light-SPP coupling 1,12-14 , SPP generation and amplification by gain media [15][16][17] and SPP scattering [18][19][20] . The analysis often distinguishes between a dipole that is oscillating in-plane and a dipole that is oscillating out-of-plane with respect to the metal surface 10,16,21,22 . In these cases the emitted fields have point-symmetry about the location of the dipole in the plane of the interface, which means that the radiated