Crystalline silver halide fibers with optical losses lower than 50 dB/km in broad IR region and their applications

For the first time crystalline silver halide optical fibers with optical losses lower than 50 dB/km in a broad IR region from 9 to 14 micrometers were fabricated by an extrusion process. The optical loss mechanism essential to the lowest absorption in silver halide materials and fibers, namely intraband absorption by free holes in the valence band is proposed. The crystalline fibers with Rayleigh-type (lambda) (superscript -4) optical scattering were obtained. An IR region near 13 micrometers in AgBrI fibers with optical losses of less than 10 dB/km was discovered. Non-aged, stable IR polycrystalline silver halide optical fiber cables with losses lower than 1 dB/m in the region from 3 to 20 micrometers are demonstrated. Various applications of the developed low- loss silver halide fibers in remote spectroscopic chemical sensing, non-contact temperature monitoring and IR laser power delivery are discussed.