Improved photon upconversion photoluminescence and intrinsic optical bistability from a rare earth co-doped lanthanum oxide phosphor via Bi3+ doping

In this paper, an Er3+, Yb3+ co-doped La2O3 phosphor has been synthesized through a solid state reaction method. Structural analysis reveals the strong crystalline nature of samples. EDS measurements confirm the presence of La, O, Er, Yb and Bi elements in the sample. FTIR measurements of samples show bands due to La-O stretching vibrations. UV-vis-NIR spectra of samples show a large number of absorption bands due to different transitions of Bi3+, Er3+ and Yb3+ ions. The intensities of the absorption bands increase over the entire region due to Bi3+ doping. The phosphor sample emits intense green and weak red upconverted photoluminescence centered at 523 and 671 nm, respectively, upon excitation at 976 nm. The emission intensity of the phosphor is optimum for a 0.7 mol% Er3+ ion concentrations. Pump power versus emission intensity studies shows the absorption of two photons for this upconverted emission and color tunability. The emission intensity of the Er3+, Yb3+ co-doped La2O3 phosphor is enhanced up to similar to 65 times as a result of Bi3+ doping. The enhancement in emission intensity is observed due to an increase in crystallinity and the intensity of the absorption bands. The Er3+, Yb3+ co-doped La2O3 phosphor also shows intrinsic optical bistability (IOB) and the area of the IOB curves increases significantly following Bi3+ doping. Thus, the Er3+, Yb3+, Bi3+ co-doped La2O3 phosphor may be used in photonic and optically bistable devices.