Broad band and low loss mid-IR flexible hollow waveguides

This paper introduces a deposition method to create a multilayered waveguide with alternating layers of high index of refraction contrast. A very thin Ag layer, practically transparent in the mid-IR radiation wavelengths of CO₂ and Er-YAG lasers, was created. This enabled a good contrast of the indices of refraction of silver/silver iodide. Theoretical calculations as well as experiments have shown that transmission was higher at these wavelengths for two pair layers, in comparison to one pair of silver/silver iodide. Windows of transmittance and small sensitivity to bending were demonstrated for those two pair layer waveguides. This method could be extended to an increased number of pairs to configure a true photonic band gap waveguide.