Study On The Spectral Properties Of Two Yb-doped Laser Crystals

Trivalent ytterbium(Yb³⁺)doped materials have demonstrated significant potential for application in ultrafast laser,high-power laser and amplifier system.Yb³⁺ions possess two electronic states of ground state ²F_7/2 and excited state ²F_5/2 that retaining the advantages of low quantum defect,long fluorescence lifetime and high conversion efficiency.So,Yb³⁺doped laser material has become a research hotspot.This paper aims to improve the spectral performance of Yb:Sc₂SiO₅ and Yb:SrF₂ doped Yb3+ion laser crystals by different methods in order to improve the actual laser performance of these two crystals.In this thesis,5 at.%Yb:Sc₂SiO₅,5 at.%Yb,0.3 at.%Nd:Sc₂SiO₅ crystals were successfully grown by the Czochralski method,and 3 at.%Yb,xat.%Gd:SrF₂?x=0,1,3,6,9?crystals was successfully grown by the temperature gradient method.The XRD,Raman spectra,absorption spectra,emission spectra,and fluorescence lifetimes of the related crystals were tested,their laser performance parameters were evaluated,and continuous laser experiments were performed.It was found that the absorption cross section of Yb³⁺,Nd³⁺:Sc₂SiO₅ crystals increased by 28.3%at 980 nm compared with Yb³⁺:Sc₂SiO₅ crystals by doping with Nd³⁺ions.The emission cross section of Yb³⁺,Nd³⁺:Sc₂SiO₅ is 18.9%higher than that of Yb³⁺:Sc₂SiO₅ at 1063 nm.The absorption cross section and emission cross section of 3 at.%Yb:Sr_1-xGd_xF_2+x+x are enhanced by doping with Gd³⁺.3at.%Yb:Sr0.97Gd0.03F2.03 crystal has the best performance.For continuous laser experiments,direct continuous-wave diode pumped Yb³⁺,Nd³⁺:Sc₂SiO₅ laser could generate output power of 6.14 W with slope efficiency of 56.2%.3 at.%Yb³⁺:Sr_0.97Gd_0.03F_2.03 crystals at the output coupler with transmission 3%and a pump power of 8.02 W absorbed,the maximum output power is 3.8 W,which corresponds to an optical-to-optical conversion efficiency of 46.49%and an oblique efficiency of53.5%.This research also analyzes the mechanism of the effect of co-doped ions on the spectrum and laser performance of the Yb³⁺-doped host crystals.When Nd³⁺ions are co-doped in Yb:Sc₂SiO₅,the energy of Nd³⁺ions can be efficiently transmitted to Yb³⁺ions,thus enhancing the luminescence properties;when Yb:SrF₂ is co-doped with Gd³⁺ions,Gd³⁺ions can break the[Yb³⁺-Yb³⁺]clusters,reducing the quenching center,thereby improving the luminous efficiency.