B. Appa Rao

Intense upconversion fluorescence in Tm 3+/Yb3+ codoped alumina lead borate glasses

The Tm3+/Yb3+ codoped alumina lead borate glasses were prepared by the conventional melt quenching technique. Optical absorption and FTIR spectra were recorded. The upconversion fluorescence spectra exhibited weak blue (480 nm) and intense red (660 nm) emissions due to 1G4 → 3H6 and 1G4 → 3H4 transitions, respectively. The results concluded that both emissions are due to three photon absorption process. It has been observed that in the upconversion efficiency increases with the increase in the concentration of Yb3+ ions. The strong red upconversion fluorescence indicate that Tm3+/Yb3+ codoped alumina lead borate glasses can be used as potential host material for upconversion lasers.

Luminescence studies of PbO-Bi2O3-Ga2O3-B2O3 glasses doped with Yb3+/Er3+

The effect of Er3+ concentration on red emission in lead bismuth gallium borate glasses codoped with Yb3+ is studied. Optical absorption and luminescence spectra of all the glasses were recorded at room temperature. The results obtained are discussed quantitatively based on the energy transfer between Yb3+ and Er3+.

Spectroscopic Properties and Energy Transfer in Lead Bismuth Gallium Borate Glasses Codoped with Tm3+ and Yb3+

Lead bismuth gallium borate (GTY) glasses codoped with Tm/Yb were prepared by melt quenching technique. The glasses were characterized by X-ray diffraction spectra. Optical absorption, FTIR and photoluminescence spectra of these glasses have been studied. The optical absorption spectra exhibits a band at 980 nm due to transitions from the ground states I15/2 and F7/2 to excited states of Yb . The other absorption bands at 658 nm (H6 → F2), 686 nm (H6 → F3), 792 nm (H6 → H4), 1211 nm (H6 → H5) and 1663 nm (H6 → F4) are attributed to 4f-4f transitions of Tm ions, respectively. Judd-Ofelt theory has been applied to the f  f transitions for evaluating Ω2, Ω4 and Ω6 parameters. Radiative properties like branching ratio r and the radiative life time τR have been determined on the basis Judd–Ofelt theory. Upconversion emissions have been observed under 980nm laser excitation at room temperature. The spectra exhibited two emission bands centered at 468 nm and 654 nm due to G4 → H6 (blue) and G4 → H4 (red) transitions, respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb and Tm. Keywords— Optical absorption, FTIR, Luminescence

Luminescence properties of Tm3+/Yb3+ codoped lead alumina bismuth borate glasses

This paper reports on the spectroscopic properties of Yb3+ and Tm3+ codoped lead alumina bismuth borate glasses. Optical absorption spectra of these Samples were recorded at room temperature in the wavelength range 350-2000 nm. The absorption spectra exhibited the bands at 658 nm (3H6→3F2), 686 nm (3H6→3F3), 792 nm (3H6→3H4), 1211 nm (3H6→3H5) and 1663 nm (3H6→3F4) due to Tm3+ ions. The band at 977 nm (2F7/2→2F5/2) is due to Yb3+ ions. Optical band gap (Eopt) and Urbach energy (ΔE) values were calculated from the spectra. It was observed that the value of optical band gap decreases with increase in the concentration of Tm3+ ions. The upconversion luminescence spectra were measured under excitation of 980 nm laser diode, and the intense blue (470 nm) and green (656 nm) emission were simultaneously observed at room temperature. A proposed upconversion mechanism involving energy transfer from Yb3+ to Tm3+ has been presented.

Upconversion luminescence in Er3+/Yb3+ codoped PbO-Bi2O3-AI2O3-B2O3 glasses

Er3+/Yb3+ co-doped glasses with the composition PbO-Bi2O3-Al2O3-B2O3 were prepared by melt quenching method. Optical absorption (OA) and photoluminescence (PL) and FT-IR spectra of all the glasses were recorded at room temperature. Green and red upconversion emissions centered at 525, 545 and 654 nm corresponding to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions have been obtained under the excitation of 980 nm laser at room temperature. From emission spectra it was observed that the intensity of red emission increases with increasing the concentration of Er3+ ions upto 0.8 mol% and decreases with the further increase in the concentration of Er3+ ions. The spectra have been analyzed in the light of structural modifications in the vicinity of the dopant rare earth ions, due to relative variations in the concentration of Al2O3 and B2O3 in the glass network.

Optical absorption and fluorescence properties of Er3+/Yb3+codoped lead bismuth alumina borate glasses

Lead bismuth alumina borate glasses codoped with Er3+/Yb3+ were prepared by melt quenching technique. Optical absorption, FTIR and photoluminescence spectra of these glasses have been studied. Judd-Ofelt theory has been applied to to the f ↔ f transitions for evaluating Ω2, Ω4 and Ω6 parameters. Radiative properties like branching ratio βr and the radiative life time τR have been determined on the basis of Judd-Ofelt theory. Upconversion emissions have been observed under 980nm laser excitation at room temperature. Green and red up-conversion emissions are centered at 530, 550 and 656 nm corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb3+ and Er3+.

Spectroscopic studies of lead antimony borate glasses doped with erbium ions

Antimony borate glasses of the composition 30PbO–25Sb2O3–(45–x)B2O3–xEr2O3 with x = 0 to 1.0 in steps of 0.2 were prepared by the melt-quenching method. Various physical parameters. radiative parameters, transition probability A, branching ratio β and the radiative life time τ for different emission levels of Er3+ ions, have been evaluated.