Melting conditions impact on the properties of copper containing phosphate glasses for high power and high energy amplifiers
Russia has started construction of the 192 channel pulse amplifier facility UFL-2M with an output energy of 2·8 MJ. Large disc active elements (DAE) with a light aperture of 400×400 mm for the UFL-2M are made from a neodymium phosphate glass KNFS3 of the system Na2O–K2O–MgO–CaO–SrO–BaO–B2O3–SiO2–P2O5 with a neodymium concentration of 3·5×10 20 cm–3. One of the rather effective routes that output energy decreases is the so-called parasitic generation in a DAE caused by luminescence quanta propagating along big polished planes of a DAE. The phenomenon of parasitic generation is known to lead to a significant (by tens percents) decrease in the signal gain. To suppress this phenomenon, cladding plates should be pasted to the DAE side edges that are made usually of copper-containing glasses as they have an intense absorption band with a maximum at approximately 880 nm caused by Cu2+ ions. The cladding glass, the photo-resistant glue and the DAE glass must be assembled in such a way that the refractive index, n, meets the following condition nclad>nglue>nDAE. To eliminate thermal strains at the junction of the cladding plates and the DAE, the difference in values of coefficients of thermal expansion |αclad–αDAE| should be close to 0. The decimal coefficient of radiation absorption at the lasing wavelength 1053 nm, a1053, must be in the limits from 1·2 to 2·0 cm–1. The paper shows how such copper-containing glasses were developed that satisfy the requirements on refraction index, coefficient of thermal expansion and absorption coefficient at the lasing wavelength. Their parameters are n e=1·544±0·002, n 1053=1·534±0·002, α20–300=(117±2)×10–7 K–1 as compared with that of the glass KNFS3 n e=1·540±0·002, n1053=1·530±0·002, α=(116±2)×10–7 K–1. The developed copper containing glasses can be used in the production of large disk active elements for the amplifier facility UFL2M.
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Document Type: Research Article
Publication date: 01 April 2015