Deposition and characterization of metal sulfide dielectric coatings for hollow glass waveguides.

Metal sulfide dielectric thin films have been deposited using dynamic wet chemistry processing on silver coated hollow glass waveguides (HGWs). The sulfides used were cadmium sulfide (CdS) and lead sulfide (PbS); both films have excellent infrared transparency and high refractive index contrast. The thickness of these thin films can be tailored to minimize the attenuation of the HGW over specific infrared wavelengths. We have made both single and multiple dielectric (2 and 3 layer) metal coated HGWs using CdS and PbS deposited over an inner Ag layer. The straight lowest loss measured at 1.55 microm for a 1,000-microm bore Ag/CdS/PbS/CdS HGW was 0.06 dB/m. This loss is three times less than that measured for a single layer Ag/CdS coated HGW at 1.55 microm.