Atomic-scale nanophotonics and quantum optics through 2D phonon polaritonics

Recent developments have demonstrated extreme confinement of electromagnetic energy in the mid-infrared via phonon polaritons in polar insulators. Phonon polaritons hold promise for low-loss nanophotonics, as well as realizing extreme interactions with quantum emitters at the single-photon level. To bring these materials to the ultimate limit of optical nano-confinement, it is critical to consider phonon polaritons in low-dimensional polar materials, where the physics of optical phonons is fundamentally different due to the lack of LO-TO splitting. In this talk, we find universal forms for the properties of phonon-polaritons in one- and two-dimensions which result from the unique character of Coulomb interactions in low-dimensional systems. Leveraging first-principles calculations of optical phonons in 2D, we calculate the polaritonic properties of polar insulator monolayers, presenting specific results for hexagonal boron nitride. We find regimes of low-loss and high-confinement of electromagnetic energy, and show how these regimes can be probed with EELS. We then show how nanostructuring can be used to develop ultrafast quantum emitters of phonon polaritons in the mid-IR.