Ytterbium-ion-doped double-clad optical fibres were developed, The differential quantum efficiency of a diode-pumped fibre laser, fabricated on the basis of such optical fibres with a fibre Bragg grating, was 90%.

The authors have studied the influence of the extrusion conditions (material, temperature, and heat treatment after extrusion) on the structure and mechanical properties of fibrous light guides made of halides of silver KRS- 13 (AgC 0.25 Br 0.75 ) and cesium (CsI, CsI−Br). They obtained polycrystalline textured fibers with texture axis (110). The lower the extrusion temperature, the finer is the grain and the higher the microhardness of the fibers. In the case of CsI at temperature 0.86 T m the authors obtained a monocrystalline fiber with high plasticity. Polycrystalline fibers of CsI are very brittle, apparently owing to accumulation of point defects, visible against a dark field, on the grain boundaries

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. 1. INTRC)DUCTIOL Flexible 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. 2. CHOICE OF STARTING CRYSIALL The 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

A determination was made of the three main characteristics (coupling-in efficiency, attenuation coefficient, and optical strength) governing the suitability of a KUVI quartz fiber waveguide for transmission of high-power pulse-periodic ultraviolet radiation from excimer lasers emitting at wavelengths λ = 248, 308, and 351 nm. The reasons for serious deterioration in the quality of a fiber (internal damage) as a result of propagation of the λ = 248 nm radiation were analyzed.