Hollow Core Waveguides Made of Polycrystalline Materials

Based on our knowledge of material properties and fabrication technology of polycrystalline materials, we propose three types of hollow core waveguides which allow for a low loss radiation transmission in the mid IR spectral range with low loss in a low-mode regime. This fabrication technology is known to be based on extrusion process which creates preforms only with relatively simple structure. We discuss three of them, namely, the singular capillary, the square waveguide and the Bragg waveguide and demonstrate that the optimal structure of the waveguide is the square one. It has the minimal loss in all transmission bands and is also resistant to bending.