Different mechanisms of extrinsic losses, including aging, in extruded mixed AgClBr fibers are discussed. Additional losses caused by changes in structure of fiber material have been investigated. INTRODUCTION Mechanisms of optical losses in polycrystaffine fibers are still not clear due to theirs complicated dependence on a lot of various parameters of extrusion process and initial characteristics of crystalline preforms [1-4]. Aging effect is also determined by parameters of "fresh" fibers and by influence of environment conditions and way of fiber use. Our last studies were undertaken for better understanding of correlation between structure and optical losses in polycrystalline fibers extruded from crystals of solid solutions AgCI-AgBr. SPIE VoL 1591 Infrared Fiber Optics /11(1991) / 83 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/25/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
New medical applications of IR lasers can be rather wider with flexible cables and catheters for laser power delivery. Optical parameters of fibers for Er; CO-and CO-lasers alongside with design of special optical connectors, efficient coupling units and optics at distal end are reviewed. Applications of cables and catheters for laser therapy and medical diagnostics are analyzed.
Overview of the development in crystalline infrared fibers and is made for the practical use of the last results in applications of the cables based on these fibers. INTRC)DUCTIOLFlexible cables for IR laser power delivery can be based on fluoride or chalcogenide glass fibers, on crystalline fibers. The properties of crystalline fibers and hollow waveguides which are more suitable for power delivery of erbium, CO-and C02-lasers are discussed from the point of view of their application in medicine. CHOICE OF STARTING CRYSIALLThe proper choice of starting crystals is based on the estimation of their minimum of intrinsic optical losses ( Fig.1) along with their fitness to fiber fabrication and a set of other substantial physical parameters (Table 1). Looking for non-fragile, non-toxic and non-hygroscopic material we have to find the AgHal and A12O3 as the best candidates for crystalline fibers. Arid we have to note that the value of absorption in the purest samples is much higher than intrinsic level due to the presence of absorbing impurities. Hence, the technology of more pure crystals needs in further development. The lowest absorption at 10.6 im for AgHal were measured by laser calorimetry for the samples of crystals of solid solutions O.25AgCl : O.75AgBr (KRS-13) and O.5OAgC1 : O.5OAgBr -6-1O cm (26 dB/m). 3. TECHNOLOGY OF FIBER FABRICATIQL There are some known methods of crystalline fiber fabrication: for single-crystalline fibers: -drawing from the melt through the capillar, -'pedestal method, -'travelling zone, and for polycrystalline fibers there are 3 methods of plastic deformation: -extrusion, -rolling, -drawing through the row of dies with reducing orifices. SPIE Vol 1353 Lasers and Medicine (1989) / 189 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/25/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx 3.1 Single crystalline (SC-) fibers, Due to high plasticity of SC-fibers from MeHal their durability to stretch and bending is poor. Besides, there are a problems with a purity of SC-fibers and with a smoothness of their side surface. Up-to-date the best optical losses at 10.6 $trn in SC-fibers are not reproducible at the level less than 1 dB/rn. The most interesting result in fabrication of MeHal SC-fibers was obtained by Dianov, Dmitruk arid others in 1979, when the first core/clad SC-fibers were made [1]. Its much more reasonable to make SC-fibers from the crystal with high hardness and Youngs Modulus. Non-toxic and non-hygroscopic sapphire is a leader in these parameters along with the highest melting temperature (Table 1). A saphire fibers can be made by drawing from the melt through the capillar with rate 1C)±15 mm/mm up to 7÷8 m long [1] or by drawing from laser heated preform, so-called 'pedestal" method [5]. The absorption loss 0.88 dB/m at the Er:YAG line 2.94 .tm was obtained for a Al203 fiber, grown by the last method in an atmosphere of pure oxygen. A damage threshold higher than 1.2 kJ/cm2 was measured for 110 .ts long pulses [2]. The alternative fibers fr...
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