Study On The Characteristics Of Fluorescence And Laser In The Na⁺-doped Yb³⁺:CaF₂ Crystal

In this thesis, the theoretical and experimental studies on characteristics of the fluorescence spectra, the lower laser thershold and the self-Q-switch operation for a new kind of Na⁺-doped Yb³⁺:CaF₂ crystal are presented. The main contents are as followings.1. The investigative results and developments in Yb³⁺-doped crystals and other ions-doped CaF₂ crystals in recently years are introduced. In particular, the recent advance in the world for developing Yb³⁺:CaF₂ crystal is reviewed.2. For the novel Na⁺ codoped Yb³⁺:CaF₂ crystals, the impact of the codoping concentration of Na⁺ on the fluorescence spectra and the laser thershold is analysed theoretically. By using a novel fluorescence detection way, we measured the fluorescence spectra of crystals with different doping concentration. The experimental results is in consistent with theoretical analyse. Moreover, we also find some emitting peaks of the impurities adulterated rare-earth ions of Er³⁺ and Tm³⁺. According to the contrastively observations and systemic analysis to the crystals with different doping concentration, we proposed, for the first to our knowledge, a new possible transition channel and dynamics process in the crystals with codoped ions of Yb³⁺,Er³⁺ and Tm³⁺.3. The numerical analysis to design a laser cavity was made by means of the ray propagation matrices and the optimized parameter range of the corresponding cavity was obtained. A laser was then built and the laser operation with a lower thershold and a slope efficiency of 20.3% was demonstrated.4. The phenomenon of the Q-switch laser operation at 1050nm of the Na⁺,Yb³⁺:CaF₂ crystals is investigated, and it is presumed that the crystals may be a saturable absorber at 1050nm too. The action of saturable absorption for the Na⁺,Yb³⁺:CaF₂ crystals at 1050nm is experimentally demonstrated by inserting the crystal into a Yb:YAG laser cavity as a saturable absorber and the self-Q-switch operation has been achieved. To compare and analyse the status of self-Q-switch operation in connection with the different ions doping concentration, we find that the best crystal parameters as a saturable absorber at 1050nm is same as that as a laser cryatal at the corresponding wavelength.