Exploration Of Novel Deep-ultraviolet Silicates Nonlinear Optical Crystal Materials And Growth Of The K₃Ba₃Li₂Al₄B₆O₂₀F Crystal

As an important component of all-solid-state laser,ultraviolet(UV)and deep ultraviolet(deep-UV)nonlinear optical(NLO)crystals with excellent performance can be widely used in photochemistry,microfabrication,biomedical and other fields,by converting the fixed laser wavelength to UV and deep-UV coherent light sources.Therefore,it is of great scientific value and academic significance to explore and study new deep-UV NLO crystals.In this paper,we have done a lot of experiments in exploring the synthesis and properties of deep-UV silicate NLO crystals.Meanwhile,we have further studied the large-size single crystal growth and properties of deep-UV NLO crystal K3Ba3Li2Al4B6O20F,the contents are as follows:(1)Exploration on novel deep-UV silicate NLO crystalA new deep-UV silicate NLO crystal material Rb2ZnSi3O8 was successfully obtained by high temperature solid state method and flux method.This compound exhibits a three-dimensional framework structure formed by SiO4 tetrahedra and ZnO4 tetrahedra alternately connect with each other.In terms of NLO properties,it exhibits a second harmonic generation(SHG)approximately 0.5 times that of KDP;remarkably,Rb2ZnSi3O8 is phase matchable and exhibits a larger SHG than that of?-SiO2 which is well known to be non-phase-matchable.The UV-visualnear-infrared diffuse reflectance spectrum shows that Rb2ZnSi3O8 has a wide transparency window down to 190nm,meanwhile,differential thermal analysis indicating that Rb2ZnSi3O8 exhibits high thermal stability and water resistance test demonstrated that Rb2ZnSi3O8 is nonhygroscopic.Furthermore,the first-principles calculations and a real-space atom-cutting technique analyses the contributions of individual groups to the largest SHG coefficient and the results reveal that ZnO4 and SiO4 tetrahedra determine the optical properties in the crystal Rb2ZnSi3O8.(2)Growth,optical and thermal properties of the deep-UV NLO crystal K3Ba3Li2Al4B6O20FA K3Ba3Li2A14B6O20F crystal with sizes of 18 × 13 × 8 mm3 was successfully grown from the LiOH-H3BO3-BaF2 flux by the top-seeded solution growth method.We have optimized the growth technics by changing the flux ratio,adjusting the crystal growth rates and the temperature gradient of the crystal furnace,analyzing and calculating the volatilization of the raw materials.The UV transmittance spectrum and refractive indices were accurately measured,and the Sellmeier equations and type-1,type-II phase-matchable curves constructed.In addition,we have systematically investigated the thermophysical properties including specific heat,thermal expansion and thermal conductivity.