Excitation-emission properties of Er^<3+> ions doped in nonlinear optical TeO_2-Nb_2O_5-ZnO glass by 800nm femtosecond laser excitation(<Feature>Glass and Ceramic Materials for Photonics)

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By excitation with 800nm femtosecond laser, we observed the green up-conversion fluorescence at 526nm (^2H_<11/2>-^4I_<15/2>) and 548nm (^4S_<3/2>-^4I_<15/2>) for Er^<3+> ions doped in 76TeO_2・20Nb_2O_5・4ZnO glass. From I_<H,S>〜P^n relationship (I_<H,S>; fluorescence intensity of ^2H_<11/2>-^4I_<15/2> and ^4S_<3/2>-^4I_<15/2>, P: laser power density, n: the number of photons absorbed per visible photon emitted), the n values of 1.4 and 1.3 were obtained at room temperature for I_H and I_S, respectively, and approached "2" at lower temperatures and at lower excitation power densities. This indicates that two photons were involved in the excitation of the up-conversion fluorescence. Considering the up-conversion intensity at various repetition frequencies on fs laser excitation and the emission decay behaviors as well as the results of Judd-Ofelt analysis, we could explain this excitation mechanism in terms of energy transfer (ET: ^4I_<11/2>+^4I_<11/2>→^4F_<7/2>+^4I_<15/2>, and ^4I_<9/2>+^4I_<9/2>→^4S_<3/2>+^4I_<13/2>). We shall also discuss on a back transfer process of the latter ET for the reduction of the n value at room temperature.
社団法人日本セラミックス協会の論文
2008-10-01