Mid-infrared Emission From Rare Earth Doped Zirconate-fluoride Glass Based On Halide Ions Modify And Energy Transfer Methods

Mid-infrared luminescence has broad application prospects in communication,medical treatment and remote sensing.Rare earth doped glass materials are widely concerned in mid-infrared luminescent materials because of the high solubility of rare earth,easy processing and other advantages.Fluorozirconate glass is suitable as a mid-infrared luminescent material because of its high transmission,low loss,low phonon energy,etc.In our work,based on the fluorozirconate glass system,the mid-infrared luminescence properties are improved by anion substitution and sensitizer co-doping.The main research contents are as follows:The transparent Er³⁺/Yb³⁺co-doped fluorochlorozirconate glass was prepared.The results of J-O calculations show that Cl^-ions increase the asymmetry of the local crystal field of rare earth ions and increase the probability of radiation transition.Fourier transform infrared spectroscopy confirmed that the sample had high mid-infrared light transmittance and low hydroxyl content.Raman spectroscopy confirmed the maximum phonon energy of the fluorochlorozirconate glass and indicated that it has a lower phonon density by the Debye model.The fluorescence spectra and energy level lifetimes were obtained by different excitation lights and the energy transfer process was discussed in detail.In the fluorochlorozirconate glass,the increase of the Yb³⁺content not only increases the electron population of the ⁴I_11/2 level,but also affects the relative decrease of the ⁴I_13/2 electron population caused by the excited state absorption,and enhances the mid-infrared luminescence.At the same time,the reduction of ⁴I_11/2 lifetime in the reverse energy transfer process can infer the increase in lifetime during forward transfer.This is advantageous in reducing the pumping threshold and increasing the laser emission power.The combination of anion substitution and sensitizer co-doping increases the mid-infrared luminescence intensity.The transparent Ho³⁺/Yb³⁺co-doped fluorozirconate?Zr-Ba-La-Al-Y,named ZBLAY?glass was prepared.The mid-infrared luminescence properties were studied by adjusting the concentrations of Ho³⁺,Yb³⁺,and BaCl₂.Raman spectroscopy shows that the phonon energy of ZBLAY glass is 588 cm^-1,which is lower than the 600 cm^-1 of ZBLAN,which reduces the probability of non-radiative transition.The calculation results of J-O theory show that Yb³⁺will increase the asymmetry of the crystal field and increase the probability of radiation transition.Infrared fluorescence spectroscopy shows that Yb³⁺can transfer the effective absorbed energy to Ho³⁺to improve the absorption efficiency of Ho³⁺and further improve the infrared luminescence of Ho³⁺.The energy transfer efficiency of Yb³⁺-Ho³⁺is 72.6%.The energy transfer mechanism of Yb³⁺to Ho³⁺in ZBLAY glass is discussed:phonon-assisted energy transfer and cross-relaxation.The Bi³⁺/Ho³⁺co-doped ZBLAY glass was prepared by melt quenching method and the sensitization effect of Bi³⁺on Ho³⁺was investigated.The absorption spectrum indicates that the absorption peak of Ho³⁺near 1200 nm is enhanced by Bi³⁺.The theoretical calculation of J-O shows that Bi³⁺can change the covalentness and asymmetry of glass and increase the probability of transition of Ho³⁺.Fluorescence spectra indicate that Bi³⁺can increase the infrared luminescence of Ho³⁺.Characterization of Er³⁺/Pr³⁺co-doped ZBLAY glass using XRD results in that Pr³⁺co-doping does not result in sample crystallization and the sample still has good visible light transmission.The fluorescence lifetime and fluorescence intensity of all samples were compared.The optimal Er³⁺/Pr³⁺co-doping concentration ratio was 4:0.5.The energy transfer process was discussed with the spectrum and lifetime.The results show that Pr³⁺will cause the ⁴I_13/23/2 energy level to retreat,reducing the lifetime of the ⁴I_13/2 energy level,thus enhancing the 2.7?m luminescence intensity.