Growth And Properties Research Of Cr⁴⁺?Li₂CaGeO₄ Laser Crystals

The crystals of compound oxide doped with transition metal ions as the working medium of solid-state tunable lasers have always been one of the research hotspots in the field of lasers.The tuning range of these crystals covers the entire near-infrared region.Among them,The tuning range of Cr⁴⁺ion-doped crystal is 1-1.6?m,the laser emitted in this range has great application value in the fields of laser medicine,laser imaging and optical communication.In this paper,Cr⁴⁺:Li₂CaGeO₄ polycrystalline materials were synthesized by high-temperature solid-phase method and sol-gel method.The polycrystalline materials prepared by the two synthetic methods were compared for a series of performance characterization.The purpose of preparing polycrystalline materials was to Avoiding the volatilization of GeO₂ during the crystal process,reducing the segregation of components and the generation of other impurity crystals,improving the performance of laser crystals.Cr⁴⁺:Li₂CaGeO₄ laser crystal was successfully grown in China for the first time by self-crystallization method and top seed crystal pulling method with LiCl and Li₂MoO₄ as fluxes,and a series of analyses were performed on the structure and physical properties,spectrum and energy performance of the crystal.Li₂CaGeO₄ crystals with different Cr⁴⁺concentrations were grown by cooling crystallization method and top seed crystal pulling method,and the crystals were processed.The results show that the structure of Cr⁴⁺:Li₂CaGeO₄ crystal is stable.With the increase of Cr⁴⁺ions doping concentration,the lattice constant of Cr⁴⁺:Li₂CaGeO₄ crystal increases,and the density and hardness gradually decrease.The absorption peak of Cr⁴⁺:Li₂CaGeO₄crystal in the range of 600 nm to 750 nm corresponds to the ³A₂?³T₁ energy level transition of Cr⁴⁺ions,and the absorption peak of 750-900 nm corresponds to the³A₂?³T₂ energy level transition of Cr⁴⁺ions;Cr⁴⁺:Li₂CaGeO₄ crystal at Under the excitation of the wavelength of 824 nm or 980 nm,there is a broadband emission in the range of 1000-1500nm,and the highest value is located at 1240 nm or 1200 nm,which is mainly caused by the³T₂?³A₂ transition of Cr⁴⁺ions;The optimal molar doping concentration of Cr⁴⁺ions is 5mol%,and the fluorescence lifetime of Cr⁴⁺:Li₂CaGeO₄ crystal is?s order.XPS analysis shows that Cr ions mainly exist in the form of Cr⁴⁺in Cr⁴⁺:Li₂CaGeO₄ crystals,and no Cr³⁺exists in the crystals.