Mid-infrared Luminescent Properties Of Rare Earth Co-doped Fluorohalide Glass With Energy Transfer

In recent years,the development of middle infrared（MIR）lasers region has attracted great attention.Rare-earth-doped MIR laser are widely used in many fields such as optics,military,medical,biology,materials processing and environmental monitoring.Fiber lasers using rare-earth-doped glass fibers as a gain medium have great advantages,such as good permeability,high rare earth solubility;low phonon energy and wide transmittance region have been widely studied.However,there are still some problems such as the low luminous efficiency of rare earth ions in the glass matrix,the limited emission wavelength,the unclear mechanism of halide emission and the poor tunability.It is expected that a mid-infrared light source with high luminous efficiency and tunable multiple luminous wavelengths can be obtained through matrix optimization and co-doping of rare earth ions.In this work,fluorinated halide glass is used as the main line to conduct rare earth ion co-doping experiments.Luminescence performance is improved by co-doping with rare earth ions and anion substitution.The specific content includes three parts:The Er³⁺/Yb³⁺co-doped Al F₃-based fluorochloride glasses have been prepared.The chloridion doping can significantly increase the infrared emission intensity.The structural stability and absorption and emission cross-section(σ_abs=0.97×10^-20cm²,σ_em=1.06×10^-20cm²)of Er³⁺/Yb³⁺co-doped sample are all larger than that Er³⁺doped sample.Er³⁺:⁴I_13/2→⁴I_15/2and ⁴I_11/2→⁴I_13/2 have longer lifetime during energy level transitions and energy transfer(⁴I_13/2 energy level life is 12.8 ms,⁴I_11/2 energy level life is 5.9 ms).Therefore,Er³⁺/Yb³⁺co-doped Al F₃-based fluorochloride glass is a potential MIR laser material.The Er³⁺/Yb³⁺co-doped ZBLAY fluorochloride glasses have been prepared.The test analyzed XRD spectrum,absorption spectrum,fluorescence spectrum,etc.According to the J-O theory,the spectral parameters of the rare earth ions were calculated.The relationship between luminescence characteristics and doping concentration and co-doped ions was analyzed.The energy transfer mechanism between rare earth ions was analyzed.Er³⁺:⁴I_13/2→⁴I_15/2and ⁴I_11/2→⁴I_13/2 have larger absorption and emission cross-section(σ_abs=9.46×10^-21cm²,σ_em=1.04×10^-20cm²).The Nd³⁺/Yb³⁺co-doped ZBLAN fluorobromide glasses have been prepared.The 3.9μm MIR luminescence of the samples excited at 793 and 980 nm pump excitation were investigated in detail.There is an effective mutual energy transfer process between Nd³⁺and Yb³⁺.It was demonstrated at 793 nm excitation that the luminescence of Nd³⁺:²H_11/2→⁴F_7/2（3.9μm）was reduced by effective energy transfer from the Nd³⁺:²H_11/2→Yb³⁺:²F_5/2level.Meanwhile,it was demonstrated that the effective energy transfer from the Yb³⁺:²F_5/2→Nd³⁺:²H_11/2 level enhanced the luminescence of Nd³⁺:²H_11/2→⁴F_7/2（3.9μm）at 980 nm excitation.The fluorescence decay characteristics of the sample at 3.9μm at the ²H_11/2level were investigated.The Br^-doping reduces the phonon state density of the host matrix.The absorption and emission cross-section(σ_abs=3.87×10^-20 cm²,σ_em=4.25×10^-20 cm²)of the Nd³⁺/Yb³⁺co-doped sample were calculated.In addition,the temperature profile of the sample was studied and analyzed.It is found that the peak intensities of858 and 864 nm are gradually increased and decreased in the temperature range of20K-320K.The change in peak intensity transmission temperature at 1056 nm is almost unchanged.This shows that the sample has good stability against temperature changes.Therefore,Nd³⁺/Yb³⁺co-doped ZBLAN fluorobromide glass is a potential MIR laser material.