Quantum State Engineering of Multiphoton Systems Using Plasmonic Nano-antennae

Surface-plasmon polaritons (SPPs) are charge oscillations that arise from the coupling of photons to the electromagnetic field along the surface of a metal. SPPs can couple back to free-space light, and the quantum coherence properties of this light strongly depend on the geometry of the metal's surface. With recent advancements in nanofabrication, plasmonic metasurfaces present a novel opportunity to engineer the quantum properties of light. Here, we investigate the light-matter interactions of plasmonic nano-structures as they change the quantum coherence properties of multi-photon systems in free space propagation. Specifically, we design and fabricate an array of nano-antennae that exploit the metal's surface geometry to control the coherence properties of light. We use plasmonic waveguides to couple two independent sources of psuedothermal light to SPPs. The nano-antennae manipulate these sources, producing a single output with varying degrees of second-order coherence along the output's optical axis which we quantify using the second-order correlation function. We believe the fine control of multiphoton coherence properties using plasmonic nanostructures will enable the use of compact, versatile light sources in advanced experiments and emerging quantum technologies.