3-D microcavities in on-chip hollow waveguides using cutoff-based mirrors

Hollow-core waveguides are promising candidates for strong interactions between single photons and atoms, owing to their ability to simultaneously confine light and gas-phase media within the same small area, thereby providing long interaction times [1]. Incorporation of mirrors and cavities into hollow-waveguides could further enhance these functionalities, by introducing 3-dimensional (3-D) confinement options. It is challenging to implement conventional axial reflectors (e.g. Bragg gratings, photonic crystals) within hollow-core waveguides [2]. Here, we describe an alternative method that employs mode cut-off sections as axial reflectors; these cut-off sections can be used as mirrors in the formation of 3-D hollow-waveguide-based microcavities. We furthermore show that a thin film buckling process [3] provides a straightforward means to fabricate the proposed structures.