Preparation And Properties Research Of SrB₄O₇ Optical Materials

The unique application of nonlinear optical crystals in expanding the laser band has attracted widespread attention.At present,a series of nonlinear optical crystals have been successfully developed in the ultraviolet,visible and near-infrared bands,but in the deep ultraviolet band below 200nm there is still a lack of excellent laser frequency-doubling crystals.SrB₄O₇（SBO）crystals have excellent nonlinear optical performance,but its birefringence is too small to achieve angle phase matching,which hinder the application of the crystals in the field of laser frequency doubling.In this thesis,through the research on the growth of lithium ions-doped SBO（Li:SBO）crystals,the effects of process parameters on the quality of the grown crystals are analyzed,and the appropriate growth process parameters are adjusted to grow 57mm×25mm×15mm large single crystal of good quality through the Top Seeded Single Crystal Method.The influence of lithium ions on the structure of SBO crystals are analyzed to realize the frequency-doubled output of Li:SBO crystals under random quasi-phase matching.The transmission spectrum tests of the Li:SBO crystals show that the UV cut-off edge of the Li:SBO crystals are red-shifted to 132nm relative to the pure SBO crystals.The study of second-harmonic generation and crystal defects shows that the derivation of the domain structures is usually accompanied by the appearance of microscopic defects in the crystal structure.The incorporation of lithium ions makes the morphology of the domain structure of the Li:SBO crystals more complicated and the distribution density increased.The frequency-doubled output of the crystals are closely related to the distribution of the domain structures.The transparent wafers on both sides of the core area under the crystal seed crystal have a large number of dislocations and domain structures distribution,and the corresponding wafers in this area have obvious green frequency-doubled light output.While the dislocation distribution of the wafer in the transparent part of the crystal is relatively rare,corresponding to the wafer here has no green frequency-doubled light output.The powders of Sm²⁺single-doped and Li⁺、Sm²⁺co-doped SBO were prepared by solid-phase synthesis method and the luminescence properties of the samples were studied.The XRD results of the samples show that during the solid phase synthesis of the powder,the reaction time can be properly extended to avoid the introduction of the impurity phase.When the content of Sm²⁺reaches 6%,the reaction product appears Sm BO₃ phase,indicating that Sm²⁺is doped at this time,the concentration has been excessive.In the excitation spectrum of the samples,broad excitation peaks due to the4f⁶→4f⁵5d¹ transition of Sm²⁺can be observed.In the emission spectrum,the peaks emission due to the 4f→4f transition of Sm²⁺can be observed in the 600-750nm band.As the concentration of Sm²⁺increases,the emission intensity of the sample increases first and then decreases.Due to the concentration quenching effect,the intensity of the emission peak of the sample decreases.The optimal doping concentration of Sm²⁺is4%.When Li⁺is introduced into the matrix,the incorporation of Li⁺can enhance the luminous intensity of Sm²⁺.