Hollow Core Light Cage: Trapping Light behind Bars

Optical waveguides represent the key element of integrated planar photonic circuitry having revolutionized many fields of photonics ranging from telecommunications, medicine, environmental science, and light generation. However, the use of solid cores imposes limitations on applications demanding strong light-matter interaction within low permittivity media such as gases or liquids, which has triggered substantial interest toward hollow core waveguides. Here, we introduce the concept of an on-chip hollow core light cage that consists of free-standing arrays of cylindrical dielectric strands around a central hollow core implemented using 3D nanoprinting. The cage operates by an antiresonant guidance mechanism and exhibits extraordinary properties such as (1) diffractionless propagation in "quasi-air" over more than a centimeter distance within the ultraviolet, visible and near-infrared spectral domains, (2) unique side-wise direct access to the hollow core via open spaces between the strands speeding up gas diffusion times by at least a factor of 10 ⁴ , and (3) an extraordinary high fraction of modal fields in the hollow section (>99.9%). With these properties, the light cage can overcome the limitations of current planar hollow core waveguide technology, allowing unprecedented future on-chip applications within quantum technology, ultrafast spectroscopy, bioanalytics, acousto-optics, optofluidics, and nonlinear optics.