Component Design And Property Modulation Of Rare Earth Doped?Y,Lu,Gd?₃?Al,Sc?₅O₁₂laser Ceramics

Solid-state lasers pumped by laser diode?LD?are the most common lasers at present,which are widely used in industry,medical treatment,military,scientific research and other fields.The solid-state laser gain media are the core part of the solid-state lasers,which are composed of matrix materials and active ions.Rare earth doped yttrium aluminum garnets?RE:YAG?are laser materials with excellent comprehensive properties,and they have been widely studied and applied.At present,the development trend of solid-state laser is high power laser output,demand of new wave band of laser wavelength,and faster pulse laser generation.In addition,for laser gain medium,it is necessary to have high doping concentration of active ions.However,due to the limitations of inherent physical and chemical properties of the rare earth doped transparent ceramics based on pure YAG matrix,they cannot meet these new requirements.Rare earth doped multi-component garnet based laser ceramics(RE:?Y,Lu,Gd?₃?Al,Sc?₅O₁₂)retain the inherent excellent properties of RE:YAG laser ceramics,and they can improve the performance through matrix design and modification.On the one hand,the substitution of ions can realize the fluctuation of local crystal field,and it can enhance the full width at half maximum?FWHM?of emission peaks of the active ions,which is favor to the generation of mode-locking pulse laser and changes the laser performance such as laser wavelength.On the other hand,the substituted ions also have great influences on the thermal conductivity of the materials and doping concentration of active ions.By selecting appropriate ions for lattice substitution,the RE:?Y,Lu,Gd?₃?Al,Sc?₅O₁₂ transparent ceramics met the above laser development acquirements can be fabricated.Based on the above backgrounds,this dissertation focuses on the component design,controllable fabrication and properties control of RE:?Y,Lu,Gd?₃?Al,Sc?₅O₁₂ laser ceramics.Using the commercial oxide powders as raw materials,RE:?Y,Lu,Gd?₃?Al,Sc?₅O₁₂ transparent ceramics were fabricated by solid-state reaction method and vacuum sintering technology or solid-state reactive sintering combined with hot isostatic pressing?HIP?.The influences of the doping concentration of active ions,kind and content of substitution ions on the microstructure,optical and laser properties of the ceramics were studied.The feasibility on property modulation was explored through the multi-component design.The main contents are as follows:?1?Yb:Y₃Sc Al₄O₁₂ transparent ceramics with different doping concentrations were prepared by solid-state reactive sintering at 1820 ^oC for 30h combined with HIP post-treatment at 1750 ^oC for 3h under 200 MPa Ar.The 10at.%Yb:Y₃Sc Al₄O₁₂ ceramics have the best optical quality,and the in-line transmittance of the 3.2 mm thick sample is 80.9%at 1100 nm.The introduction of Sc³⁺could effectively enhance the full width at half maximum?FWHM?of Yb³⁺absorption and emission peaks.By 929.4 nm LD pumping,the quasi continuous wave?QCW?laser output with the maximum power of11.28 W was achieved for the 10at.%Yb:Y₃Sc Al₄O₁₂ transparent ceramics.?2?10at.%Yb:Y₃Sc_xAl_5-xO₁₂ transparent ceramics with the in-line transmittances higher than 80.0%at 1100 nm were prepared by solid-state reactive sintering at 1820^oC for 30h.With the increase of Sc³⁺content,the FWHM of 1030 nm emission peaks for 10at.%Yb:Y₃Sc_xAl_5-xO₁₂transparent ceramics also increases correspondingly.The FWHM of 1030 nm emission peak for the 10at.%Yb:Y₃Sc_1.5Al_3.5O₁₂ transparent ceramics is 14.53 nm,which is about 1.4 times as large as that of the 10at.%Yb:YAG transparent ceramics.A maximum output power of 11.89 W was obtained for the 10at.%Yb:Y₃Sc_0.5Al_4.5O₁₂ transparent ceramics in QCW regime,which is the largest value ever reported for the Yb:YSAG transparent ceramics.The laser tunable range of the10at.%Yb:Y₃Sc_1.5Al_3.5O₁₂ ceramic laser in QCW operation regime is obviously broader than that of the 10at.%Yb:YAG ceramic laser,reaching 86.2 nm.And it is the largest laser tunable range reported for Yb:YSAG transparent ceramics.?3?4at.%Tm:Y₃Sc Al₄O₁₂ transparent ceramics?3.2 mm thickness?with the in-line transmittance of 79.3%at 2000 nm were prepared by solid-state reactive sintering at1800 ^oC for 30h.The introduction of Sc³⁺causes some absorption and emission peaks of 4at.%Tm:Y₃Sc Al₄O₁₂ transparent ceramics at 1500-2000 nm to disappear and makes double peak structure transfer into single peak structure.Using 790 nm LD pumping,the QCW laser output of 4at.%Tm:Y₃Sc Al₄O₁₂ transparent ceramics was obtained for the first time,and the maximum output power was 0.54 W with the corresponding slope efficiency of 4.8%.?4?Yb:Lu_1.5Y_1.5Al₅O₁₂ transparent ceramics with different doping concentrations and15at.%Yb:Lu_xY_3-xAl₅O₁₂transparent ceramics with different Lu³⁺contents were prepared by solid-state reactive sintering at 1850 ^oC for 30h.For all the ceramics with the thickness of 1.6 mm,the in-line transmittances are higher than 82.0%at 1100 nm which are close to the theoretical values.The Yb³⁺doping concentration mainly influences the microstructure of the Yb:Lu_1.5Y_1.5Al₅O₁₂ceramics,which has little influence on the optical properties,such as optical transmittance,absorption and emission cross sections.With the increase of Lu³⁺content,the FWHM of the main absorption peaks at about 938 nm increases gradually,however,the FWHM of the emission peaks at 1030 nm shows a decrease trend.?5?10at.%Yb:Gd_xY_3-xAl₅O₁₂ transparent ceramics with the in-line transmittances higher than 83.5%?2.5 mm thickness?were prepared by solid-state reactive sintering at 1800 ^oC for 20h combined with HIP post-treatment at 1700 ^oC for 3h under 176 MPa Ar.The absorption coefficients of Yb³⁺at 850-1050 nm for the 10at.%Yb:Gd_xY_3-xAl₅O₁₂ transparent ceramics are similar as that of 10at.%Yb:YAG transparent ceramics.The emission spectra of 10at.%Yb:Gd_xY_3-xAl₅O₁₂ transparent ceramics with different Gd³⁺contents are almost the same.The introduction of Gd³⁺has little influence on the peak position and FWHM for the absorption and emission peaks of Yb³⁺.