During more than 20 years the "LEA" Ltd. Co. actively and successfully solves the problems concerning complex material research - from directed search for new effective materials for laser applications and forecasting their structures till technology design of growth of high optical quality crystals related to different classes.
Growth of large perfect single crystals from high-temperature melts and fluxes by Czochralski, Brigeman-Stockbarger, Kuropulos method, TSSG techniques etc. and also from low-temperature aqueous and organic solutions.
Optical quality control of grown crystals.
Evaporation of antireflecting and protective coatings on the element surface.
Integrated scientific designs on search and characterization of crystals with specified properties.
The integrated physical-chemical researchs and technological designs of growing processes of perfect single crystals for laser applications and optoelectronics are concentrated to the following basic directions:
Search for new non-linear materials for UV and mid-IR range and crystal growth of these compounds.
Modifications of the crystals by substitution of lattice atoms and crystal doping by TR cations to obtain new functional properties.
Investigations of new laser single crystals growth processes on the base of ternary halogenide compounds with low phonon energy.
MAIN RESULTS:
Correlation study among growth parameters of non-linear laser crystals, their compositions, structures, defects and functional properties.
Considerable efforts of laboratory research work is directed to the study of crystal physical-chemical characteristics and their structures to define main parameters affecting the variation of single crystals functional properties.
One of the most important parameters is nonstoichiometry of crystal chemical composition.
Close connection was revealed between deviation of stoichiometry in CsLiB6O10, their hydration process and physical-chemical stability of these crystals.
Non-stoichiometry of LiInS(Se)2 was shown to determine the nature of point defects in these crystals and thereby their optical characteristics. In turn, the deviations from stoichiometric composition depends on initial melt composition, growth conditions and annealing rate.
The obtaining of the perfect crystals is more difficult if phase transitions take place in the system. For example, Curie temperature variations in ferroelectrics considerably affect the range of domain-forming. The temperature change of phase transition (ferroelectric -> paraelectric) in non-linear crystals Potassium Titanyl Arsenate (KTA) at substitution of Ti by Zr was studied. The structural transitions of the mixed crystals
KTi1-x Mgx/3 Nb2x/3 P1-y Asy O5 (orthorhombic -> tetragonal) were investigated.
structure
Structural and behavior modifications, analysis of cation and anion sublattices, vacancies and packings.
Doping of the crystals results in new properties. On one hand, successfulness of doping and segregation coefficients between melt and crystal are able to be found experimentally. On the other hand using the theoretical models in the search of a new effective dopants allows to decrease drastically the time of the search. Both directions are successfully realized in the lab.
The anion-packing study by means of Voronoi - Dirichlet method enables to define the location of empty lattice points and their parameters (dimensions). This data are important for analysis of doping elements distribution in the lattice.
The important achievement in laboratory research activity is a design of a new method of chemical bond division in situ. It is possible to obtain a set of ionic radii of all the elements for every crystal depending on packing density.
The newest available software and methods are intensively used in laboratory research activity. The X-ray data analysis is carried out using SHELX, SHELXL (Shedrick, Germany). X-ray powder analysis of different crystals depending on their growth conditions is made by means of software PCW2.4 (Kraus, Nolze, Germany), PowderX (Dong, China). The structure peculiar properties are studied with the help of Ball and Stick software (Kang, Osawa, Japan) and XSHELL (Naumov, Kaznacheeva, Russia).
The results of scientific investigations are published in numerous articles in the foreign and native fundamental journals and in the proceedings of large international conferences. Technological designs and growth methods of a number of single crystals are patented in Russia and awarded by medals and diplomas of the native and international conferences.Since 1993 the laboratory have been maintaining close contacts with the world leading scientific centers such as Lawrence Livenmore National Laboratory, Observatorie de Paris (France), Tohoku University (Japan), Max-Born-Institute (Germany), European Organization on Research and Development (EOARD) etc. Owing to financial support of fundamental research by international scientific foundations: CRDF RC2-129(129100US); CRDF RE2-2222, INCO-COPERNICUS N ERBIC 15CT98 08 14, ISTC 2006 p, RUS 01 223 and another. New promising materials for laser applications and optoelectronics: LiInS2:TR, LiInSe2:TR, AgGaS2:TR, KPb2Cl5:TR, RbPb2Cl5:TR, CsLiB6O10, LiNaCO3, LiKCO3, KTi1-x(MgNb)xAsO5 were created.
Wide assortment of grown single crystal materials provides the getting of coherent radiation in the wavelength range from ultraviolet (0.18 µm) to infrared (18 µm). Monocrystals are element base for modern laser devices, which are effectively used practically in the all fields of medicine, science and technique successfully.
KTP, LBO, AGS, KTA, LB4, AGSe, BBO, LIS, CLBO, LISe, DLAP, GaSe, LiIO3, KPb2Cl5
