Generation of Radially Polarized Single Photons with Plasmonic Bullseye Antennas

Abstract

Radially polarized optical beams are desirable in many applications because of their property to generate longitudinally polarized fields when being strongly focused. Singlephoton sources are however normally limited to the generation of linearly polarized photons due to their dipolar nature. Here, we report on emission of radially polarized single photons from a nitrogen-vacancy (NV) center in a nanodiamond (ND) coupled to a bull's-eye plasmonic antenna. Design optimization and characterization of plasmonic bull's-eye antennas consisting of polymer circular nanoridges deterministically fabricated on a silica protected silver film around an NV-ND emitter are reported. We demonstrate with numerical simulations that the collection efficiency for photons emitted at the design wavelength can exceed 80% with optimized bull's-eye structures. Analysis of the emission angular distribution indicates that, even when limiting the detection to the main lobe by using an 0.2 NA objective, the detection efficiency can overreach 55%. A 3-fold enhancement in the total number of detected radially polarized photons is experimentally observed with an NV-ND single-photon emitter being coupled to a bull's-eye antenna. Generation of radially polarized single photons suggests new interesting possibilities for single-photon imaging and sensing.

Molding Photon Emission with Hybrid Plasmon‐Emitter Coupled Metasurfaces

“…For reconstruction, we employ 3D finite difference time domain (FDTD) simulations using the well‐established (theoretically and experimentally) numerical framework. [ 23,24,27,28 ]…”

“…It is seen that for relatively large angles, such as θ = 15°, the doughnut intensity distribution is well reconstructed when using the designed nanoridge pattern ( Figure a), although some distortion is visible (Figure 4b). The latter is believed to be due to relatively stronger forward SPP scattering (with respect to the backward one) by nanoridge arrays, [ 27 ] a circumstance that results in changing the field balance along the RP beam circumference. Importantly, the RP field decomposition into circularly polarized fields reveals opposite orbital angular momenta or topological charges (± 1) in their phases (Figure 4c,d) as expected.…”

“…We would also like to note that the presented approach can further be developed and generalized by using properly designed “anisotropic” (instead of isotropic) nano‐scatterers (Supporting Information, Section 1). This generalization should enable increasing the generation efficiency up to the level of ≈90% [ 27 ] that is expected for the RP generation (when there is a perfect match between in‐plane field components of the reference SPP and signal RP waves).…”

“…[16][17][18][19][20][21][22] Very recently, the design route for optical metasurfaces has been introduced to efficiently mold the single-photon emission from QEs with hybrid plasmon-QE coupled configurations, consisting of dielectric nanoridges surrounding QEs on metal substrates, that appear most attractive from the viewpoint of combining high quantum yield and collection efficiency. [23][24][25][26][27][28] A common feature of these configurations (meta-atoms) is the "efficient" and "nonradiative" coupling of a QE to surface plasmon-polariton (SPP) modes that are subsequently outcoupled by a metasurfaces structure into free propagating waves. [23] Different designs of the outcoupling metasurface resulted in the generation of circularly (with different orbital angular momenta) [23,24] or radially [27] polarized single photons.…”

“…[23][24][25][26][27][28] A common feature of these configurations (meta-atoms) is the "efficient" and "nonradiative" coupling of a QE to surface plasmon-polariton (SPP) modes that are subsequently outcoupled by a metasurfaces structure into free propagating waves. [23] Different designs of the outcoupling metasurface resulted in the generation of circularly (with different orbital angular momenta) [23,24] or radially [27] polarized single photons. Using displaced circular ridges, directional off-normal photon streaming for different, up to 20°, angles has also been experimentally realized.…”