A polarization-selective cavity inside a hollow-core optical fiber*

We fabricate and characterize a polarization-selective cavity inside a hollow-core optical fiber by attaching photonic-crystal (PC) membranes acting as metasurface mirrors to the end faces of a segment of such fiber. These slabs are comprised of a thin film of a dielectric material (silicon nitride) perforated with a pattern of holes where the reflective properties are dictated by the type and dimensions of the hole pattern. By breaking the x-y symmetry of the photonic crystal pattern using a rectangular lattice of elliptical holes, the mirrors become polarization-selective, i.e., the mirrors are highly reflective for one linear polarization and almost fully transparent for the orthogonal polarization. The holes of the PC slab allow injection of gasses into the hollow core of the fiber, which would not be possible if the fiber was capped with a dielectric stack mirror. The polarization selectivity is also a unique feature not possible with conventional mirrors.

This novel type of polarization dependent fiber-integrated cavity can enhance quantum optics schemes with atomic ensembles relying on cavity field and single-pass field with the ensemble by choosing the appropriate polarizations of the fields.