Fabrication And Optical Properties Of The Nd:LuAG Laser Transparent Ceramics

Since the Nd:YAG ceramics were fabricated by Ikesue et al,the YAG have been widely applied for the solid-state lasers as a host material for its excellent physical and chemical properties.In recent years,Lu₃Al₅O₁₂（LuAG）which has the same structure with the YAG has attracted great attention,due to its superior properties than YAG,such as stable thermal conductivity,higher melting point.In addition,when Nd doped in LuAG,Nd:LuAG possess smaller splitting of ⁴F_3/2 state(67cm^-1)and larger stark energy splitting of ⁴I_9/2 than that of Nd:YAG.At present,Nd³⁺ceramic laser materials have been widely investigated with the advancement of ceramic growth techniques.However,Nd³⁺ceramic lasers operating at the important¹.4μm eye-safe spectral region are very limited.Though Zhang et al.reported the first Nd:YAG ceramic laser at 1442.8 nm in2013,there is few research about the Nd:LuAG applied in this area.In this work,the Nd:LuAG transparent ceramics were prepared by two kinds of sintering process.One is the vacuum sintering method,and the other is the vacuum sintering combined with HIP sintering method.Specific studies are as follows:Nd:LuAG ceramics were fabricated by the solid-state reaction under vacuum sintering using SiO₂ and MgO as sintering aids,commercial Lu₂O₃,Al₂O₃ and Nd₂O₃ as raw materials.The microstructure of the Nd:LuAG ceramics sintered from 1620 ^oC to 1800^oC for 12 h were analyzed by SEM.The phase evolution of LuAG ceramics were also described in detail.On the basis of this,the microstructure and spectral properties of LuAG with different doping concentrations of Nd were studied.When the samples were sintered at 1800 ^oC,the 0.4at%Nd:LuAG had clean gain boundary,full dense as well as highly transmittance which can reach 83.91%at 1064 nm（3 mm thickness）.So,we reported on continuous-wave laser operation of a diode-pumped Nd:LuAG ceramic in eye-safe spectral region,for the first time to our knowledge.A simultaneous dual-wavelength laser at 1418 nm and 1442 nm was achieved with maximum output power of 1.37 W and slope efficiency of 13.5%using a plane-concave laser cavity configuration.The M2 factor of the dual-wavelength laser was measured to be about2.93 and 3.16 in x and y directions.Laser generation at another emission line of 1432nm is also realized with a maximum output power of 0.82 W with the help of an intracavity etalon,and obtained better power stability.To improve the laser beam quality,a parallel plane laser cavity operating still at 1418 nm and1442 nm is adopted in free-running mode In addition,the HIP sintering method was also investigated with the effects of densification and transmittance.