GeO2-ZnO-K2O glass as the cladding material of 940-cm−1 CO2 laser-light transmitting hollow-core waveguide

A hollow-core optical waveguide for 940-cm−1 CO2 laser light was fabricated with 80 mol % GeO2-10 mol % ZnO-10 mol % K2O glass functioning as the cladding, of which the refractive index nr is about 0.6 at 940 cm−1. The waveguide transmission loss is minimized at 940 cm−1 using the glass and is on the order of 0.1 dB/m for a 1-mm-i.d. hollow-core waveguide. Preliminary experiments of CO2 laser-light transmission for 0.6-mm-diam waveguides are also given. Measured loss, normalized to 1-mm-i.d. standard waveguide, is obtained to be 2 dB/m. The transmission mode observed is of the HE11-type only.