Application Of Judd-Ofelt Theory To Optical Transition Of Trivalent Rare Earth Ions

In recent years,rare earth(RE)ions doped luminescent materials have been widely used in the fields such as lighting sources,displays,fiber amplifiers,optical communications,and biomedicine.Therefore,RE doped materials have attracted much attention.Judd-Ofelt(J-O)theory is an effective tool to investigate the optical transition properties for 4f-4f transitions of trivalent RE ions.It is mainly used in transparent materials such as glass and crystals,and has been widely accepted by researchers.However,the traditional J-O theoretical calculation method has some shortcomings in its application.In this paper,the J-O calculation of Eu3+was improved and a method to calculate the J-O parameter of RE3+doped non-transparent materials was proposed.A new route for calculating the J-O parameters of Eu3+was proposed and used in the Eu3+doped borate glasses prepared via a high temperature melt-quenching method.Three sets of J-O parameters were obtained from absorption,emission and excitation spectra,respectively,and the average J-O parameters were used to quantitatively represent the radiative transition properties of Eu3+in the glass.The reliability of the calculated results was verified by comparing the theoretical and experimental values of the fluorescence decay lifetime of the 5D0 level.In addition,the average J-O parameters were used to calculate the radiative transition rates and fluorescence branching ratios of Eu3+in borate glass.A new procedure to obtain the J-O parameters of powdered samples from diffuse-reflection spectrum was proposed and applied to Lu2O3:Er3+phosphors synthesized by a high-temperature solid method.First,the diffuse-reflection spectrum of the powder sample was measured,then the relative absorption spectrum could be obtained by Kubelka-Munk(K-M)equation and the relative J-O parameters were calculated.And then the actual values of the J-O parameters were acquired by using the fluorescence decay data to modify the relative values of the J-O parameters.Finally,the J-O parameters of Er3+calculated by the above method were discussed and evaluated.LnOCl:Er3+(Ln=Y,La,Gd)phosphors with different doping concentrations were successfully prepared by a single displacement reaction at high temperature.The above method was used to calculate the J-O parameters of all samples,and a new approach to verify the reliability of the calculation results was employed.The effects of Er3+concentrations and different Ln3+on the J-O parameters of LnOCl:Er3+(Ln=Y,La,Gd)phosphors were further studied.In the experiment,it was found that in LaOCl:5 mol%Er3+sasmples 2H11/2 and 4S3/2 levels show some splits.The theoretical and experimental values of 2H11/2,4S3/2?4I15/2 transition rate ratios AH/As for Er3+ were obtained by J-O parameters and temperature sensing,respectively.It was found that there was a large gap between the experimental and theoretical values of LaOCl samples.In this connection,we propose to use a sub-level of the 2H11/2 and 4S3/2 levels to perform fluorescence intensity ratio temperature sensing fitting and apply it to LaOCl:5 mol%Er3+samples.