The status of glasses suitable for use as infrared optical fibers is reviewed. A historical perspective on the technology, and the criteria employed to select appropriate glasses are presented. Heavy metal fluoride and chalcogenide glasses are assessed, with special emphasis on their emerging commercial availability.

Overview of the development in crystalline infrared fibers is made for the practical use of the last results in improvement of fabrication technology and in proper start of crystalline fiber applications.

This paper reviews the current status of research and development of hollow-core waveguides at 10.6 pm wavelength so far reported. Some remarkable features of waveguides are summarized in a table with references.

The main advantage of using infrared fibres in a number of applications is the delivery of radiation to a remote point of application. Fluorozirconate (O.3-5tm) and chalcogenide glass fibres (2-12gm) are receiving most attention, particularly in remote spectroscopy, laser power delivery, fibre lasers and thermal imaging.

Spectral attenuation measurements were obtained on some JR transmitting waveguides to evaluate their applicability for remote sensing and laser power delivery. Since there is such a wide variety of applications for fiber optics in these areas, it is important to evaluate materials with various physical and optical properties. Three categories of waveguides where analyzed: glass, crystalline, and hollow tubes. A fluoroaluminate glass optical fiber was fabricated and the attenuation was considerably higher (102103 times higher) than the more common ZBLAN fluoride optical fibers. A Te-Se-Br glass optical fiber was evaluated and it exhibited an extended JR edge to approximately 14 rim. Attenuation measurements were conducted on single crystal sapphire, silicon, KRS-13, and KBr core/KC1 clad optical fibers. The spectral characteristics of alumina, silica glass, and mullite hollow waveguides were also determined, and all measurements were obtained using a Fourier Transform Infrared Spectrometer.

The Zr - free fluoride glass termed BIZYbT and based on the combination of Baryum, Indium, Zinc, Ytterbium and Thorium fluorides hasbeen optimized in orderto decrease thecriticalcoolingrate and make this glass suitablefor fiberdrawing. The lowest value of 5°C/mn has been obtained and is comparable to the classical ZBLAN fluoride glass.

The Zr - free fluoride glass termed BIZYbT and based on the combination of Baryum, Indium, Zinc, Ytterbium and Thorium fluorides hasbeen optimized in orderto decrease thecriticalcoolingrate and make this glass suitablefor fiberdrawing. The lowest value of 5°C/mn has been obtained and is comparable to the classical ZBLAN fluoride glass.

Chalcogenide glasses of the systems Ge-Sn-Se, Ge-Se-Te and Ge-Sn-Se-Te have been prepared. The region of high IR transparency of Ge-Se-Sn, Ge-Se-Te and Ge-Sn-Se-Te glasses was slightly expanded (1 -2 m) towards longer wavelengths, compared to Ge-Se glasses. The intensity of the impurity absorption peak of Ge-O (at A 12.8 pm) which usually appears in Ge-Se glasses, was reduced or absent in Ge-Sn- Se-Te glasses. The expansion of IR transparency and the reduction of Ge-O absorption peak enable one to employ these glasses for drawing fibers for CO2 laser radiation (10.6 jim) transmission.

Chalcogenide glasses of the systems Ge-Sn-Se, Ge-Se-Te and Ge-Sn-Se-Te have been prepared. The region of high IR transparency of Ge-Se-Sn, Ge-Se-Te and Ge-Sn-Se-Te glasses was slightly expanded (1 -2 m) towards longer wavelengths, compared to Ge-Se glasses. The intensity of the impurity absorption peak of Ge-O (at A 12.8 pm) which usually appears in Ge-Se glasses, was reduced or absent in Ge-Sn- Se-Te glasses. The expansion of IR transparency and the reduction of Ge-O absorption peak enable one to employ these glasses for drawing fibers for CO2 laser radiation (10.6 jim) transmission.

Mechanical properties or As-S, As-Se and Ge-As-Se glass fibers have been investigated. Bending technique has been employed to measare the strength and to study the dynamic ratigue behaviour of these fibers in various environments. The values o the stress corrosion susceptibility parameter are presented. The median bending strengths o:r 856 JPa and 1.19 GPa have been measured for As-S fibers with £luoropolymer P42 coating in the air at room temperature and in liquid nitrogen, respectively.

Tellurium and iodine were added to a base chalcogenide glass composition (Ge33Asl2Se5S) to compare their effects on physical and optical properties. Iodine decreased the glass transition temperature and increased thermal expansion to a greater extent than tellurium. However, density was lowered by the presence of iodine and increased by tellurium. Examination of the multiphonon absorption edge in the 300-900 cm1 range revealed that iodine and tellurium occupy different structural sites which accounts for their varied effect on physical properties. There appears to be no advantage of iodine versus tellurium additions with regard to optical fiber applications based on the results obtained.

New IR glasses transmitting from 1 to 20 im and having low loss potentiality in the 8- 12 pm region have been obtained in the Te-Br-Se and Te-I-Se systems. Single index fibers have been drawn from rods and the attenuation measuredin normal atmospheric conditions. The influence ofthe band gap absorption mechanism appears to be very critical as well as the addition ofelements such as Bi which seems to improve the mechnical properties.

Short-lived intrinsic defects in AgCl, AgBr, KRS-13 crystals have been investigated. The observed primary Frenkel defects in . . . 0 2+- cationic sublattice are assumed to be Ag. and Ag V • These primary defects are created with similar efficiency in both AgC1 and KRS-13. The deviation from the Vegard's law (linear dependence of a lattice parameter on a component concentration containing in the solid solution), especially well pronounced in the vicinity of KRS-13 compound, has been observed. An attempt of the vacuum purification of KRS-13 samples from oxygen containing impurities has been undertaken. An analysis of the thermally stimulated depol.arization current measurements has showed that carrier redistribution between traps had taken place.

The results of the investigation of structural, electrical, luminiscent and mechanical properties of KRS-13 fibers produced under various extrusion conditions are discussed below.

The paper deals with a number o abrioated by an extrusion cladded crystalline fibers. Low-mode fibers have been rabricated after appropriate initial fiber materials and extrusion process parameters were experimentally found. Dierent optical characteristics o such crystalline fibers have been investigated at 10,6 Lm. We discuss the significance o material coatings Lor considerable improvement or optical and. mechanical properties o crystalline core-clad ribers. Fabricated clacided fibers have been coated with dierent protective materials: polymeric and metallic. The erect o such coatings on mechanical properties o core-clad fibers are studied. The et'rect of metal coatings on thelaser damage threshold was estimated ror the continuous regime. We have considered conditions or the ericient second---hainonic generation in core-clad crystalline fibers. At fist time we observed the SHG ot' CO and YAG: Nd lasers in the core-clad crystalline fiber with the cuprous halide core.

We present here a comparison between the calculated propagation parameters, the power threshold, the root mean square (RMS) output pulse width and pulse shape for 10.6 itm laser propagation through hollow circular metallic waveguides and infrared (JR) optical fibers. Initially reported experimental results indicate that hollow metallic waveguides exhibit 10 times smaller loss than optical fibers at 10.6 sn and this is in good agreement with the calculated results. On the other hand, compared to common communication fibers at 1.5m, hollow waveguides have an attenuation coefficient 10 210Lf larger and therefore are not suitable for infrared communications.

An articulated arm containing hollow-alumina waveguides has been developed for use with surgical, carbon-dioxide lasers. It has been demonstrated that this arm has excellent pointing ability and it can be used with micromanipulators, handpieces, and endoscopic-waveguides. This arm incorporates lower cost materials and much shorter assembly and alignment times than conventional articulated arms. A separate system has been developed for the combining of a carbon-dioxide laser beam delivered by an articulated arm with a Nd:YAG laser beam delivered by a fiber and the launching of the combined beams into an endoscopic alumina waveguide. This system can deliver more then 85% of the CO2 and over 40% of the Nd:YAG radiation to tissue.

Development of hollow metal waveguides (1-1MW) with rectangular cross-section for delivery of high-power O and CO2laser light is described. We propose a loss calculation model for hollow waveguides that takes into account contribution of non-coherent light scattering on rougbnesses of reflecting surfaces, which allowed to define a wavelength dependence of HMW bending 1osses. Additional twisting losses in HMW are indenpendent of the quality of waveguide reflecting walls and they are practically indentical for JO and JO21aser wavelengths.

A power delivery system capable of delivering high energy densities of infrared radiation at 2.94 tm is required for the application of the Erbium-YAG laser in the medical industry. Conventional silica fibers have high intrinsic absorption coefficients in this spectral region, making them unsuitable for this application. Several alternative fibers were evaluated as candidates for delivering laser radiation at this wavelength, including single crystal fibers of sapphire and silicon, polycrystalline fibers of KRS-13, and glass fibers of fluorozirconate and fluoroaluminate compositions. For each of these, damage thresholds, fiber attenuation coefficients and maximum deliverable energies were determined. Commercially available fluorozirconate fibers proved to be the most promising candidates for this application, with a loss of under 40 dB/km and a damage threshold of over 1000 J/ cm2.

GeSeTe and GeAsSe glass fibers with core-cladding structure were prepared by a crucible drawing method. The transmission losses at 10.6 im were 1.8 - 2.2 dB/m cor GeSeTe fibers and 5.2 - 5.5 dB/m for GeAsSe fibers. The power transmission characteristics of C02 laser(1O.6 jim) through these fibers were investigated. The power up to 4.6 W(2.9 kW/cm2) could be transmitted through the GeSeTe fiber of 100 cm long. The output power through the GeAsSe fiber(100 cm) was less than 2.2 W(1.4 kW/cm2 ). In each case, the core area was apt to be fused when the output power exceeded these values. Cooling of fiber was effective to suppress such damage. The power of 20 W could be launched into the GeSeTe fiber cooled by water and the output power of 6.5 W(4.1 kW/cm2 ) was obtained. The transmission efficiency was considerably improved by the antireflection coating of PbF2 onto the fiber ends. The output power of 10.7 W(6.7 kW/cm2) was attained when the GeSeTe fiber with PbF2 coating was cooled by water.

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 witha 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 fiber radiometry for remote monitoring of surface temperature is demonstrated with fluoride glass, sapphire single crystal, silver halide polycrystalline and chalcogenide glass fibers. Analytical and experimental characteristics for various radiometer designs are described. Temperature measurement capability from subambient at 253 degrees Kelvin to 823 degrees Kelvin has been demonstrated along with minimum resolvable temperature difference of 0.1 degrees.

Infrared transmitting heavy metal fluoride optical fiber has been used to separate an FTIR analyzer from a remote measurement point. Several types of remote sensors have been developed for species concentration measurements. Remote transmission cells connected to fiber cables have been used for the measurement of spectra of liquids and gases. Evanescent wave probes have been developed to obtain spectra in highly absorbing and highly scattering media. Remote spectra taken with an FTIR fiber-optic analyzer in the 8000 - 2000 cm1 spectral region are presented. A calculation of detectability limits for these species based on the measured data will be presented. A discussion of sensor multiplexing applied to remote fiber optic FTIR spectroscopy will be given.

A novel approach for the problem of in-situ and real time monitoring processes in thin film photoresists is presented. The approach is based on the fact that all the essential processing steps, such as softbaking, exposure, hardbaking, and development, can be monitored by the induced spectral modifications in the infrared spectrum of the resist film. The technique of fiber-optic-based evanescent field spectroscopy, is proposed as the method for measuring these spectral changes. The technique is demonstrated using a silver halide infrared transmitting optical fiber coated with thin photoresist film, as the sensing element, and a tunable lead salt diode laser, as the infrared monochromatic source. As an example, immense changes in the resist IR spectrum, induced by thermolysis, are measured. The advantages of using all-fiber technology for remote real time sensing is further discussed, and the possibility to monitor the resist film temperature and thickness, using the same silver halide fibers, is emphasized.

One of the modern achievements of fiber optic technology is the development of JR (2-20 mm) optical fibers. Several types of such fibers are available now in the General Physics Jnstitute due to the works of groups, headed by V.G.Artjushenko and V.G.Plotnichenko . For JR fibers fabrication several materials such as chalcogenide and fluoride glasses, as well as thallium, silver and alkali-metal halide crystals are used. These are 0.3-1 mm diameter fibers with optical losses about 0.1-1 dB/m. Although this parameter is far from ideal it is possible now to use such fibers in diode laser spectroscopy having in mind the rapid technological progress. The main reason for this work was to make the first, experimental iteration to JR diode laser fiber optic spectrometer, to receive concrete experience in manufacturing and exploitation of this device. The present paper is the first short report about this work. The development of this device was based on previous experiments on coupling JR diode lasers and fibers1'2.

The short duration repeat pulse laser has advantage prevent of carbonize and sharp cut for biotissue. We considered the medical applications of higher power pulse CO2laser. We have investigated IR beam guide by hollow tube for COlaser. The hollow tube with compound the metal and polymer is effectively system for CW CO2 higher power laser beam transmission. We have tried to transmit the high peak power pulse C02 laser beam with hollow tube guide. Using the C02 laser have high peak power(22MW max.),short pulse duration(8Ons) and repeat pulse(under lOpps). In this experiments, the laser beam transmittance was obtained ca.90% per meter in straight state hollow tube. The delivery peak power was 1.5MW,energy per pulse was l2OmJ and average power was 1.2W.

We have developed an Improved spectrometer using the acousto-optic tunable filter (AOTF) to obtain high speed spectroscopic data. The fIlter has been used with infrared transmitting fluoride glass fibers for remote spectroscopy. The AOTF Is made from tellurium dioxide, and can be configured to operate anywhere from 360 nm to 5 microns. Potential applications Include medical diagnostIcs, chemical process control, and spectral imaging.

Plastic hollow fibers were used for non-contact temperature measurement. Using these fibers we performed temperature measurements between room temperature and 120°C. The output signal of the infrared detector, amplified by a lock-in-amplifier, was measured compared to the controlled thermal source temperature. Several inner diameters (ID) of the hollow fibers were employed to investigate the energy transmission. Spatial resolution was approximately equal to the fiber inner diameter.

ABSTRACT Investigations o! heterophase impurity inclusions and their influence on optical losses in As-S and As-Se chalcogenide glasses and fibers are presented.