Overview
This study investigates the conservation of pseudoangular momentum (PAM) in the radiative emission and optical excitation of valley-polarized surface lattice resonances (SLRs). It establishes that the integer pseudoangular momentum of valley-polarized SLRs, specifically those found in parity-broken hexagonal arrays with honeycomb and kagome arrangements, is directly encoded within the phase and polarization characteristics of their emitted electromagnetic fields.
Research Context
Surface lattice resonances (SLRs) are described as collective polaritonic excitations that manifest in nanoparticle arrays. These resonances, particularly their band-edge states, facilitate symmetry-based control over various radiation phenomena. These phenomena include scattering, photoluminescence, conventional and polariton lasing, and condensation.
Approach
The research focuses on valley-polarized SLRs within parity-broken hexagonal arrays, specifically those structured as honeycomb and kagome arrangements. The investigation involved analyzing the effects of parity-symmetry breaking on two distinct angular momentum quantities: the SLR pseudoangular momentum (PAM) and the localized surface plasmon angular momentum associated with the individual nanoparticles that compose the array. A core aspect of the approach was establishing an explicit link between these two quantities.
Leveraging the principle of electromagnetic reciprocity, the study further proposed a structured optical field. This proposed field was designed to possess the same array symmetries and integer PAM as the underlying SLRs. Theoretical and numerical methods were then employed to demonstrate that this structured optical field selectively couples to valley-polarized SLRs that possess a matching quantized PAM.
Findings
- The integer pseudoangular momentum (PAM) of valley-polarized SLRs, when present in parity-broken hexagonal arrays (honeycomb and kagome arrangements), is directly encoded in the phase and polarization structure of their emitted electromagnetic fields.
- The research established an explicit link between the effects of parity-symmetry breaking on SLR PAM and the localized surface plasmon angular momentum associated with individual nanoparticles within the array.
- A structured optical field, possessing array symmetries and integer PAM identical to the underlying SLRs, can selectively couple to valley-polarized SLRs that have matching quantized PAM. This was demonstrated theoretically and numerically.
Why This Matters
The establishment of PAM-resolved light-matter interactions involving lattice resonances offers new avenues. These opportunities include symmetry-selective nanophotonic control, the generation of chiral light, and the engineering of metasurfaces based on angular momentum principles.