Study On Yb CaF₂/SrF₂ Laser Crystals

Nowadays, ultra-intense and ultra-short laser techniques have become the frontier of the development of laser technology. Yb³⁺ ions doped CaF₂/SrF₂ laser crystals were considered as an important laser medium for obtaining high power and ultrafast laser. In this work,effects of doping concentration of La³⁺, Gd³⁺, Sc³⁺, Y³⁺ions on physical properties and spectroscopic properties were discussed. At the same time, the effects of different atmosphere and different annealing processes on the spectral properties were researched.Compared with 3at.%Yb:CaF₂ crystal, the absorption cross section of 3at.%Yb,6at.%La:CaF₂ crystal is increased from 0.57×10-20cm2 to 0.81×10-20cm2, and the emission cross section is increased from 1.91×10-21cm2 to 2.11×10-21cm2 at 1029 nm. The fluorescence lifetime is 2.48 ms, and the fluorescence quantum efficiency is higher.Compared with 3at.%Yb:CaF₂ crystal, the absorption cross section of 3at.%Yb,3at.%Y:Ca_0.5Sr_0.5F₂ and 3at.%Yb,15 at.%Gd:Ca_0.5Sr_0.5F₂ crystals are increased by 62.38% and68.38%, respectively. Compared with 3%Yb:Ca_0.5Sr_0.5F₂ crystal, with decreasing concentration of Y³⁺ions, the absorption cross sections of 3%Yb,x%Y: Ca_0.5Sr_0.5F₂ increase.With increasing concentration of Gd³⁺ ions, the absorption cross sections of3%Yb,x%Gd:Ca_0.5Sr_0.5F₂ increase.The slowly cooling annealing under the vacuum condition can more effectively eliminate the internal stress and improve the optical quality of the crystals. The absorption coefficients of 2.3%Yb:CaF₂, 3%Yb:Ca_0.5Sr_0.5F₂, 5%Yb:Ca_0.5Sr_0.5F₂ crystals are increased by18.79%, 19.04%, 20.53%, and the absorption cross sections of 2.3%Yb:CaF₂,3%Yb:Ca_0.5Sr_0.5F₂ crystals are increased by 16.98%, 23.30% after annealing under the vacuum condition.