Investigation and Theoretical Analysis of Low-Loss Three-Dimensional Hollow Waveguides for Widely Tunable Optical Devices

Abstract

A tunable hollow waveguide is a promising candidate for tunable photonic devices in various applications including photonic integrated circuits for dense wavelength division multiplexing networks. We propose two kinds of low-loss three-dimensional (3D) hollow waveguides; one with a simple 3D shape with a rectangular step of 200 nm depth and another with a curved air-core to realize low-loss, temperature-insensitive, and widely tunable photonic devices. Both 3D structures show strong confinement of light in three dimensions. The propagation characteristics of both 3D hollow waveguides have been discussed, and they demonstrate large tunability and low propagation loss. Both waveguides show polarization dependence small enough for use in practical devices and a widely tuned spot size that can be matched with that of a single mode optical fiber.