Microscopic analysis of spin-momentum locking on a geometric phase metasurface

Spin-momentum locking breakdown on plasmonic metasurfaces

“…This simplification allows for a clearer description of the system's physics, as demonstrated in Refs. [15,23]. The effects of field penetration in the metal and associated losses are discussed in Appendixes A, C, and E, showing that the results obtained within the PEC approximation are qualitatively accurate.…”

“…The general derivation of the scattering formalism used in this paper is provided in the Supplemental Material of Ref. [15]. In this section, we present the essential elements required to comprehend the relevant terms of the formalism, along with the article's results.…”

“…1). For this purpose, we employ the coupled-mode method (CMM), which has been extensively used in the study of EM properties in metallic dimple arrays [15,22,23]. The CMM expands the EM fields in plane waves in the free-space regions and waveguide modes inside the dimples and finds the electric-field amplitudes by properly matching the EM fields at the interfaces.…”

“…The first term is the specular reflection, being i 0 the amplitude of the incident plane wave and δ m0 the Kronecker delta. C mm are the geometric couplings [15], which are 2 × 2 matrices operating in polarization space. They couple different Bragg modes (m with m) via scattering with the plasmonic metasurface and encode the geometry of the unit cell through the overlaps between the Bragg and the waveguide modes.…”

“…There have been studies for continuously space-variant structures [13] and for structures with translation and rotation symmetries of the whole lattice under stringent conditions for the direction of the electric field [14]. Recently, we have applied a scattering formalism to study holey plasmonic GPMs that present a chiral arrangement in the unit cell [15].…”