Fabrication And Properties Of Dy,Tb:LuAG Transparent Ceramics For Visible Lasers

A yellow laser at 578 nm plays an important role in the treatment of retinal maculopathy and excitation of the Yb lattice clock.However,Dy³⁺-doped fluoride single crystals that can directly generate yellow lasers have low output power.Because the upper and lower laser level of Dy³⁺have a comparable lifetime,which makes it difficult to achieve population inversion.In order to reduce the fluorescence lifetime of the lower energy level of Dy³⁺,Tb³⁺ions were co-doped and LuAG ceramics with high phonon energy were used as the host materials.Therefore,it is promising to realize the yellow laser oscillation in the Dy,Tb:LuAG transparent ceramics.Based on the above background,the main contents of the thesis are as follows:1.3at%Dy,1at%Tb:LuAG（Dy,Tb:LuAG）transparent ceramics were fabricated from co-precipitated nanopowders by vacuum sintering for the first time.The thermal decomposition behavior of the precursor and the microstructures of powders and ceramics were studied.The results showed that the precursor was decomposed completely after calcination at 1100^oC for 4 h,with the total weight loss of 37.2%,and Dy,Tb:LuAG nanopowders with good dispersibility were obtained.However,the Dy,Tb:LuAG ceramics contained the Al₂O₃secondary phase,which resulted in the in-line transmittance of only 14.6%for the ceramics at 578 nm.2.In order to solve the problem of the Al₂O₃secondary phase,we adjusted the composition of the Dy,Tb:LuAG ceramics and tried a new sintering approach.3at%Dy,1at%Tb:Lu_3（1+x）Al₅O₁₂（X=0,0.1%,0.2%,0.3%,0.5%,1.0%）transparent ceramics were prepared by vacuum pre-sintering at different temperatures for 3 h and hot isostatic pressing（HIP）at 1700^oC.The results showed that when the extra Lu content（X）is not less than 0.2at%,the problem of the Al₂O₃secondary phase can be successfully solved.As the extra Lu content is 1.0at%,the in-line transmittance of Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂transparent ceramics reaches 80.1%at 578 nm.3.In order to further improve the optical quality of the Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂ transparent ceramics,we optimized the sintering system of the ceramics,and studied the influences of pre-sintering temperatures and HIP temperatures on the microstructure and optical quality of the ceramics.The results show that the best sintering path for the Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂transparent ceramics is pre-sintering at1600^oC for 3 h under vacuum and HIP post-treatment at 1600^oC.And the in-line transmittance of Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂transparent ceramics prepared by the best sintering path reaches 83.6%at 578 nm.4.In order to study the spectral properties of the Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂ceramics,we prepared Dy:Lu_{3（1+1.0%）}Al₅O₁₂,Tb:Lu_{3（1+1.0%）}Al₅O₁₂and Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂transparent ceramics under the same experimental conditions.The results show that the in-line transmittances of these ceramics are 83.4%,83.2%and 83.6%at 578 nm,respectively.In addition,the absorption cross sections of Dy:Lu_{3（1+1.0%）}Al₅O₁₂and Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂ceramics at 447 nm are 1.2×10^-21cm²and 1.3×10^-21cm²,respectively.However,the absorption cross section of Tb:Lu_{3（1+1.0%）}Al₅O₁₂ceramics at 489 nm is only 2.3×10^-22cm².This suggests Dy,Tb:Lu_{3（1+1.0%）}Al₅O₁₂transparent ceramics have a larger absorption cross section,which is conducive to increase the absorption efficiency for pumping light.