The attenuation of incoherent infrared radiation for wavelengths from 6 to 20 μm was investigated for hollow sapphire and silica waveguides suitable for applications in spectroscopy and thermometry. A low-attenuation region was exhibited between 9.6 and 17.2 μm for hollow sapphire fibers and between 7.25 and 9.5 μm for hollow silica fibers as a result of the cladding index of refraction dipping below that of the air core (n ≈ 1). Losses have been characterized as a function of fiber diameter, launch conditions, and waveguide bend radius for cladding regions of both n > 1 and n < 1. In addition, the remote infrared sensing capability of the hollow waveguides was demonstrated by the detection of CO2 in N2 by utilizing hollow sapphire fibers capped with ZnSe windows.
© 1991 Optical Society of America
Original Manuscript: August 21, 1990
Revised Manuscript: November 1, 1990
Manuscript Accepted: October 10, 1990
Published: January 1, 1991
Steven J. Saggese, James A. Harrington, and George H. Sigel, "Attenuation of incoherent infrared radiation in hollow sapphire and silica waveguides," Opt. Lett. 16, 27-29 (1991)