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Cavities, waveguides, and metasurfaces: Enhancing Atom-Photon Interactions with Photonic Crystals

Photonic crystals can provide strong confinement and unprecedented control over the flow of photons. When combined with individual atoms or atomic ensembles and quantum optics techniques, these structures can enhance light-matter interactions to regimes of optical
nonlinearities controllable with single photons. Such systems can be utilized in novel photonic devices enabling low-power information processing, as building blocks for scalable quantum information processing applications, and in studies of quantum mechanical phenomena in condensed matter or atomic systems.

Here, I will describe my group’s progress in several experimental efforts in this area. In our newly-built atom cooling and trapping setup, we recently managed to observe loading of cold cesium atoms into a hollow-core photonic-crystal fiber using a magic-wavelength dipole trap guided by the fiber. At the same time, we have been working on integrating high-cooperativity cavities into hollow-core waveguides using laser-written Bragg gratings and photonic-crystal membranes acting as dielectric metasurface mirrors. Such cavities, when loaded with lasercooled mesoscopic atomic ensembles, have the potential to be used as on-chip non-classical light sources, single-photon controlled optical transistors, and photon-number resolving detectors. Lastly, I will present some of our future plans focused on coupling individual laser-cooled atoms to planar photonic-crystal cavities and waveguides.

Photonic-crystal structures : (a) A hollow-core photonic-crystal fibre (HCPCF) with laser-written Bragg grating; (b) photonic-crystal membrane acting as a dielectric metasurface mirror; (c) its simulated reflectivity spectrum; (d) schematic of a fiber-integrated cavity formed by attaching a pair of membranes to a HCPCF; (e) A scanning electron microscope image of an individual planar photonic-crystal nanocavity fabricated in a semiconductor membrane (left inset), a ‘photonic molecule’ consisting of two proximity-coupled nanocavities (right inset) [5], and a schematics of a network of coupled nonlinear cavities implemented with individual lasercooled  atoms (represented by green circles) and an array of proximity-coupled nanocavities.