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Realizing lattices of exciton polariton condensates has been of much interest owing to the potential of such systems to realize analog Hamiltonian simulators and physical computing architectures. Prior work on polariton condensate lattices has primarily been on GaAs-based systems, with the recent advent of organic molecules and perovskite systems allowing room-temperature operation. However, in most of these room temperature systems, the lattices are defined using a bottom-up approach by patterning the bottom mirrors, significantly limiting the types of lattices and refractive index contrast that can be realized. Here, we report a direct write approach that uses a Focused Ion Beam (FIB) to etch 2D lattice into a planar microcavity. Such etching of the cavity allows for realizing high refractive index contrast lattices. We realize the polariton condensate lattice using the highly photostable host-guest Frenkel excitons of an organic dye small molecular ionic lattice (SMILES).1,2 The lattice structures are defined on a planar microcavity embedded with SMILES using FIB, allowing the realization of lattices with different geometries, including defect sites on demand. The band structure of the lattice and the emergence of condensation are imaged using momentum-resolved spectroscopy. The present approach allows us to study periodic, quasi-periodic, and disordered polariton condensate lattices at room temperature using a top-down approach without compromising on the quantum yield of the organic excitonic material embedded in the cavity.

Exciton-polaritons (EP), half-light half-matter quasiparticles that form in optical cavities, are attractive platforms for creating macroscopic coherent states like BECs. EPs based on organic molecules are of particular interest for realizing such states at room temperature while offering the promise of synthetic tunability. However, the demonstrations of such condensates have been limited to a few specific molecular systems1. Here we report a universal platform for realizing molecular polariton condensates using commercial dyes that solves long standing material challenges. This solution is made possible using a new and programable molecular material called small-molecule, ionic isolation lattices (SMILES) with the potential to incorporate a wide array of molecular fluorophores2. We show EP condensation in rhodamine by incorporating it into SMILES lattice placed in a planar microcavity. The SMILES approach overcomes the major drawbacks of organic molecular photophysical systems such as self-quenching, which sets the foundation for realizing practical polaritonic devices operating at ambient temperatures covering wide spectral range.

Single photon sources (SPS), especially those based on solid state quantum emitters, are key elements in future quantum technologies. What is required is the development of broadband, high quantum efficiency, room temperature SPS which can also be tunably coupled to optical cavities which could lead to development of all-optical quantum communication platforms. In this regard deterministic coupling of SPS to plasmonic nanocavity arrays has great advantage due to long propagation length and delocalized nature of surface lattice resonances (SLRs). Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots (CQDs) to localised and delocalised modes in plasmonic nanocavity arrays. Using time-resolved photo-luminescence measurement on isolated CQD, we report significant advantage of SLRs in realizing much higher Purcell effect, despite large dephasing of CQDs, with values of ~22 and ~ 6 for coupling to the lattice and localised modes, respectively. We present measurements on the antibunching of CQDs coupled to these modes with g(2)(0) values in quantum domain providing evidence for an effective cooperative behavior. We present a density matrix treatment of the coupling of CQDs to plasmonic and lattice modes enabling us to model the experimental results on Purcell factors as well as on the antibunching. We also provide experimental evidence of indirect excitation of remote CQDs mediated by the lattice modes and propose a model to explain these observations. Our study demonstrates the possibility of developing nanophotonic platforms for single photon operations and communications with broadband quantum emitters and plasmonic nanocavity arrays since these arrays can generate entanglement between to spatially separated quantum emitters.

Here, we report observations of photonic spin-momentum locking in the form of directional and chiral emission from achiral quantum dots (QDs) evanescently coupled to achiral hyperbolic metamaterials (HMM). Efficient coupling between QDs and the metamaterial leads to emergence of these photonic topological modes which can be detected in the far field. We provide theoretical explanation for the emergence of spin-momentum locking through rigorous modeling based on photon Green's function where pseudo spin of light arises from coupling of QDs to evanescent modes of HMM.