NIR to visible upconversion emission from Dy3+: ZBLYAN glasses

This paper reports on the near infrared (730–783 nm) to the visible upconversion emissions at 482 nm (4F9/2→6H15/2), 576 nm (4F9/2→6H13/2) and 662 nm (4F9/2→6H11/2) from the Dy3+doped 53ZrF4–20BaF2–2LaF3–2YF3–3AlF3–19NaF–1DyF3 glasses. We have also carried out a systematic study on the normal emission properties of these glasses in order to understand their performance both as a NIR upconverted visible luminescent and as normal visible fluorescent optical systems of technical importance. With an increase in Dy3+ concentration beyond a particular value (1 mol%), activator–activator interaction becomes a significant cause of concentration quenching in the luminescence properties. The dependence of the emission spectra on the excitation wavelengths has also been examined and 451 nm was found to be the ideal excitation wavelength in the measurement of normal fluorescence spectra. In the case of NIR upconverted visible emission, we have observed that the NIR excitation at 783 nm as the suitable pump wavelength in demonstrating prominent visible emission colours from these glasses. The relevance in undertaking these optical materials lies in their potential for upconversion laser application in the visible wavelength region. The NIR upconversion phenomenon has been explained in terms of energy level schemes due to excited state absorption (ESA) and energy transfer upconversion (ETU) processes.