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

Abstract
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.