Observation of whispering gallery modes in cathode luminescence in TiO2:Eu3+ microspheres

We report cavity enhanced periodic structures in cathode luminescence spectra in TiO2:Eu3+ microspheres ranging from 6.2to12.2μm in diameter. The spectral structures observed at the accelerating voltage below 10kV are attributed to the lower order whispering galley modes, while the additional components appearing at 20kV are to the higher order modes within the microsphere. These observations illustrate that the basic properties of phosphors can be advanced from the point of view of cavity quantum electrodynamics by fabricating a microcavity structure onto a single phosphor crystal.