Normalized-lifetime thermal-lens method for the determination of luminescence quantum efficiency and thermo-optical coefficients: Application to Nd 3+ -doped glasses

We present a new method based on thermal lens (TL) technique to determine the fluorescence quantum efficiency, $\ensuremath{\eta}$, and thermo-optical coefficients of fluorescent materials. These parameters can be obtained from the linear dependence of the TL signal with the experimental lifetimes of a set of samples with different luminescent ion concentrations. The method was applied in ${\mathrm{Nd}}^{3+}$-doped materials (Q-98 Phosphate, fluorozirconate, and fluoroindate). The obtained values are in agreement with those determined by other approaches based on TL methods and the ratio between experimental and radiative lifetime values (Judd-Ofelt theory). The method hereafter presented is very simple and does not require comparison with a reference sample or the use of multiple excitation wavelengths. In addition, the nature of concentration quenching taking into account the achieved $\ensuremath{\eta}$ and $\ensuremath{\tau}$ values and respective energy transfer microparameters, is discussed.