A Fluorescence-Based Determination of Quantum Efficiency

Abstract : This work attempts to apply the method of determining quantum efficiency described by de Mello et al. in order to verify that it is accurate and can be used to measure unknown samples in the future. This method takes direct spectra of the fluorescence of a sample excited by an incoming excitation laser beam in an integrating sphere. Three scenarios are considered: a sphere with no sample inside such that only the laser light is scattered, a sphere with the sample inside but not in the direct path of the laser, and a sample inside and in the direct path of the laser. Samples of 1% ceramic neodymium (Nd): yttrium aluminum garnet (YAG) and 10% crystal ytterbium (Yb):YAG (chosen after the poor result achieved for Nd:YAG) were tested, since both are thought to have high quantum efficiencies of close to 1. In this experiment, the quantum efficiency values determined were 0.54 and 0.99, respectively. These results forced a consideration of all possible sources of error in this method; future work will be needed to determine if the technique is still viable.