Hollow glass waveguides with three-layer dielectric coating fabricated by chemical vapor deposition

Hollow glass waveguides with three dielectric layers are fabricated with a chemical vapor deposition technique. The waveguides have an inner three-layer stack of aluminum oxide and titanium oxide, with the thickness optimized for the 3-μm wavelength of a Er:YAG laser. The measured attenuation spectra of the waveguides in the mid-infrared region show interference peaks that are due to the multiple dielectric layers and also exhibit a low-loss region at the design wavelength of 3 mm. The theoretical evaluation of the waveguide loss, including the inner surface roughness of the guide, shows that the roughness strongly affects the transmission losses of the multilayer-coated waveguides.