Research Of 2.0 ?m Mid-infrared Optical Properties Based On Tm³⁺/Ln(Ho³⁺,Yb³⁺) Co-doped NaYF₄/Na₅Lu₉F₃₂ Single Crystals

The mid-infrared solid-state lasers based on the 2.0?m bands have been noticed by many researchers because of their potential application,such as communications,medicine,military andother fields.The requirement in the marketplace for mid-infrared laser crystals is increasing.Now,the vitalpoint is mainly focused on large-size,high quality and high optical performance lasermaterials.This paper mainly focused on the rare earth doped NaYF₄ and Na₅Lu₉F₃₂ laser crystals for2.0?m mid-infrared bands.Tm³⁺,Ho³⁺,Yb³⁺single doped?-Na YF₄ crystals,Tm³⁺/Yb³⁺,Ho³⁺/Tm³⁺co-doped?-Na YF₄ crystals,Tm³⁺,Ho³⁺single doped?-Na₅Lu₉F₃₂ crystals,Ho³⁺/Tm³⁺co-doped?-Na₅Lu₉F₃₂ crystals were grown by an improved Bridgman method to researchthe luminescence properties of Ho³⁺and Tm³⁺ions at².0?m wavelength,and the sensitization effect of Yb³⁺for Tm³⁺ion.Combined with the energy level structure and ionic interaction for Ho³⁺,Tm³⁺and Yb³⁺ions,we analyzed the optical properties of materials from the crystals structure,infrared transmittance,spectral parameters,fluorescence decay and other aspects.In this paper,the main research contents are as follows:1.We introduced the application and development of laser crystals and the preparation process of fluoridecrystals.We analyzedthe performances and research situation for 2.0?m laser crystals,described thecharacteristics,properties and basic theory of fluoride crystals,including sodium yttrium fluoride and yttriumlithium fluoride laser crystals.2.We respectively analyzed the optical performances of?-Na YF₄ single crystals co-doped with¹.90 mol%Tm³⁺and various Ho³⁺concentrations,and co-doped with¹.9 mol%Ho³⁺and various Tm³⁺concentrations.Research on therelationship between doping concentration and fluorescence intensity for?-Na YF₄ single crystalswith various Tm³⁺concentrations and various Ho³⁺concentrations help us get the best doping concentrations,which are Tm³⁺?1.90mol%?/Ho³⁺?3.89mol%?,Ho³⁺?1.90mol%?/Tm³⁺?1.59 mol%?,respectively.The corresponding maximum emission crosssections are 1.06×10^-20 cm²?2.17×10^-20 cm²,and the corresponding maximum fluorescence lifetimes are 23.23 ms,21.72ms respectively.The results indicate that Na YF₄ has potential application value in the².0?mmid-infrared solid-state lasers.3.The mid-infrared optical performance and fluorescence decay lifetimes for Tm³⁺/Yb³⁺co-doped?-Na YF₄ crystals have been investigated.The calculated maximum value of emission cross section at 1.8 mm is1.63 x 10^-20 cm²,and the obtained energy transfer rate?WET?and energy transfer efficiency???are 1543 s^-1 and 83.8%,respectively.All the results of discussion and calculation show that Na YF₄ has an extensive prospect in the².0?m mid-infrared solid-state lasers.4.The luminescent properties of Ho³⁺/Tm³⁺co-doped Na₅Lu₉F₃₂ single crystals that weregrown by an improved Bridgman method for the first time have been investigated.The DTA/TG and refractive index curves and emission spectra have been analyzed.The J–O intense parameters of Ho³⁺ions were calculated.An intense 2.0 lm emission was achieved with Tm³⁺ions sensitizing Ho³⁺ions by the processing of energy transfer from Tm³⁺ions to Ho³⁺ions under excitation of 800 nm LD.The maximum emissionintensity at 2.0 lm is obtained,and the cross sections of Tm³⁺ions and Ho³⁺ions were calculated.All the results of discussion and calculation show that Na YF₄ has an extensive prospect in the².0?m mid-infrared solid-state lasers.