Studies Of Crystal Growth And Characterization Of Sr:La₂CaB₁₀O₁₉ Crystals

La₂CaB₁₀O₁₉（LCB）crystal is a promising borate nonlinear optical crystal with high nonlinear optical coefficients,high laser damage thresholds,nonhygroscopic and high transparency from ultraviolet to infrared range.The shortest second harmonic generation（SHG）wavelength is 288 nm for type I phase matching,limiting the application of LCB in UV range.By doped with Sr²⁺,it is possible to increase its birefringence to realize shorter SHG output in UV range.This dissertation focuses on the studies of the crystal growth and characterization of Sr²⁺:LCB crystal.High-quality and large-size LCB crystals were obtained by the top seeded solution growth method using CaO-Li₂O-B₂O₃ as flux.The temperature gradient of LCB crystal growth was studied,the growth conditions were optimized to grow the crystal.By comparing,it is found that the alternating bidirectional rotation is more favorable to the solute transport in the melt than the one-way rotation,with significantly increasing thickness of the LCB crystal.In addition,during the growth of Sr:LCB crystal,the crystals grown in[110]direction of the seed are better quality than those in[001]direction.After optimizing the growth parameters,large-size Sr:LCB crystals with nominal ratios of 10%,15%and 30%of Sr²⁺substituted Ca²⁺were grown.The maximum size of the obtained crystals is 30×20×19mm³.The results of inductively coupled plasma-atomic emission spectrometry（ICP-IES）measurements show that real ratios of the grown crystals are 1.17%,2.10%and 4.68%,respectively.X-ray diffraction tests show that the doping of Sr²⁺into LCB crystals do not change the crystal structure,while single-crystal X-ray diffraction tests show minor changes in the cell parameters.Two wafers with（010）facets were oriented,cut and polished from 10%and 30%Sr:LCB crystals,and their transmission spectrum were measured.The transmittance at200 nm is higher than 90%,and the UV cut-off edge of the 30%Sr:LCB crystal is 168nm,which is extended by 5 nm compared with 173 nm for LCB crystal.The thermal expansion and specific heat tests demonstrate that the thermal properties of Sr:LCB crystals are better than that of LCB crystalsThe Sr:LCB crystal with a proportional concentration of 15%was cut to obtain two right-angled prisms with an angle about 30°between the（010）and（001）surfaces.The right-angled and slant surfaces were polished.The refractive indices of these two prisms were tested at different wavelengths,and the Sellmeier equations was calculated.The results shows that the birefringence of Sr:LCB are increased comparing with that of LCB single crystal.The shortest wavelength SHG output of Sr:LCB crystals was calculated to be pushed from the original 288 nm to 270.5 nm in the UV.