Microcavity exciton-polaritons provide a unique photonic platform that manifests non-equilibrium quantum orders. It combines strong nonlinearity and rich many-body physics of matter with robust coherence and ready accessibility of light, allowing diverse quantum phenomena at high temperature, on a photonic chip. To go beyond 2D condensation physics, it becomes important to control the fundamental properties of polaritons without destroying the quantum orders. I will discuss our effort to incorporate designable slab photonic crystals into the polariton systems, which allow greater freedom to confine, control and couple polaritons in a non-destructive and scalable manner.
For conventional semiconductor quantum wells, we use a subwavelength grating as a high-reflectance mirror to construct the cavity. Strong-coupling was established in the new cavity system. By design of the mirror, we can control fundamental properties of polaritons, including polarization, energy-momentum dispersion, and dimensionality. Coupled polariton systems are readily created. Utilizing the high mode-selectivity of the cavity, we achieve single-mode polariton lasing, which, unlike quasi-2D polariton lasers demonstrated in the past, features Poisson intensity noise expected of a coherent state. Strong condensate interactions manifested in Gaussian line-broadening of the polariton laser. For monolayer van der Waals crystals, we show that sub-wavelength thick slab photonic crystals are naturally suited for achieving strong-coupling, with even greater freedom for mode engineering. These photonic-crystal based polariton structures provide a playground for designing and creating matter-light coupled many-body quantum systems.