Infrared transmissive, hollow plastic waveguides with inner Ag-AgI coatings

Hollow polycarbonate waveguides with thin-film coatings of Ag-AgI were fabricated by liquidphase chemistry methods. These hollow waveguides, which have bore sizes ranging from 500 to 2000 (mu)m and lengths as long as 2 m, are transmissive from 2 to more than 20 (mu)m. The lowest loss of 0.02 dB/m was obtained for a straight 2000 (mu)m bore guide at 10.6 (mu)m. This is to our knowledge the lowest loss measured for any IR fiber at CO2 laser wavelengths. The bending losses were found to increase as 1/R, where R is the radius of the bend. These waveguides were able to withstand 18 W of CO2 laser input power for bore sizes greater than 1000 (mu)m.