Cu/Cul-coated hollow glass waveguides for delivery of infrared radiation

IR-transmissive hollow waveguides have been fabricated by depositing Cu and Cul thin-film coatings inside silica and polycarbonate tubing. These guides, which are similar in design to Ag/Agl-coated ones, have straight losses as low as 0.19 dB/m for a 1000-μm-bore waveguide at 10.6 μm. They also transmit IR wavelengths from 2 to more than 15 μm. This makes them very useful for broadband IR applications, including chemical sensing and radiometry, as well as for use in the delivery of IR laser power for laser surgery and low-power cutting. The thin-film coatings are deposited using a liquid-chemistry technique in which a Cu film is first formed on the inside of the tubing, followed by the deposition of the dielectric Cul layer. The thickness of the Cul layer is adjusted to give low loss at specific IR laser wavelengths or to give a broadband response for the transmission of incoherent light.