Research and development on silver halide fibers at Tel Aviv University

Abstract

This paper presents a survey of current work at Tel Aviv University on properties and applications of silver halide infrared transmitting fibers. Various infrared spectral features of core-only fibers, extruded from pure mixed halide crystals of composition AgClBr1(O < x < 1), are presented and discussed. In the best fibers, total loss is as low as 0.15 dB per meter at a wavelength of 10.6 jim. The fibers can be repetitively bent on a 5 cm radius without degrading the transmission, up to thousands of bends. Fibers with a smooth core-clad structure have also been fabricated, but the optical losses are still relatively high. Novel applications of these fibers in spectrophotometry and radiometry are described.

Infrared fibers

“…Stepindex fibers have been co-extruded into fiber in this fashion [118,159], but they usually have a highly irregular core region and poor core-cladding interface quality, resulting in higher losses than unclad fibers. There has been much progress in reducing the loss in clad polycrystalline IR fibers through careful adjustment of the core and cladding compositions and the extrusion parameters.…”

“…IR fibers may also be fabricated by the hot-extrusion technique, which enables "drawing" polycrystalline halides [118,119,124,159] into fibers with diameters in the range 500-900 μm with no buffer jacket. In this method, a single-crystal billet is placed in a heated chamber and a piston forces it through a die.…”

Mid-Infrared Fiber-Coupled Photoacoustic Sensor for Biomedical Applications

“…The transmission of silver halide fibers covers a broad wavelength range (3–30 μ m) but it is not entirely flat due to impurity bands near 2.9, 6.28 and 7.15 μ m and scattering losses [26]. Unlike in silica fibers, where the scattering losses vary with 1/ λ 4 (Rayleigh scattering), the scattering in silver halide fibers decreases for longer wavelength with 1/ λ 2 [27].…”

Sensor Systems Based on Mid‐Infrared Transparent Fibers

“…Considering their temperature stability (up to 350°C), their flexibility due to their polycrystalline structure and their transparency to the entire MIR spectral range, these fibers are very attractive for spectroscopic applications. 61,62 With appropriate protection of the fibers by polymer jacketing the gradual increase of transmission losses due to their sensitivity to UV radiation can be prevented to a large extent. 63 Direct sensing applications of silver halide fibers have been demonstrated mainly for fiberoptic thermometric applications in the low temperature range (<200°C), where the usually preferred quartz fibers are limited by their opacity above 2 µm.…”