The Light Cage: an on-chip hollow-core waveguide implemented by 3D nanoprinting

GARGIULO, JULIÁN; JANG, BUMJOON; LI, GUANGRUI; MAIER, STEFAN A.; SCHMIDT, MARKUS A.

Munich

Conferencia; CLEO/EUROPE; 2019

European Physical Society

Strong light-matter interaction is essential for various applications in biochemical sensing, quantum information processing and magnetometry. Along with recent developments of integrated photonic devices on silicon chips, integrated on-chip waveguides have become an attractive platform for light-matter interaction. The solid-core nature of the many planar waveguides limits the degree of overlap between electromagnetic field and matter. To tackle this boundary, different solutions have been proposed, such as slot waveguides and anti-resonant reflecting optical waveguides (ARROWs). They exploit either evanescent fields outside the core or strong mode concentration in the slot. However, slot modes are usually on the nanometer range thus limiting the light-matter interaction volume. On the other hand, analyte access to the core of ARROWs is through their open ends, leading to long diffusion times.Here, we present an on-chip hollow-core waveguide ? the light cage ? fabricated by 3D nanoprinting using two-photon polymerization, which allows propagating light in ?quasi-air? over centimeter distances. Inspired by hollow core fibers, the waveguide consists of either six or twelve feely suspended micrometer-size rods arranged in a hexagonal lattice surrounding a hollow core. The distribution of dielectric rods essentially forms a cage for the light, which support leaky modes along the axis of the waveguide across centimeter distances. The guided mode is mainly located in the core, with the fraction of guided field in the hollow section reaching values as high as >99.9%. A unique feature of the light cage is the open space between rods that allows for atoms or molecules to side-wise diffuse into the waveguide and interact with light. This feature makes the light cage concept a promising platform for real-time gas sensing or nano-object tracking. During the presentation, we will discuss all relevant details including fabrication, optical characterization, physics of light guidance and application in gas sensing experiments.