Electric and magnetic dipole emission of Eu3+: Effect of proximity to a thin aluminum film

Abstract

A nearby presence of a metal surface can significantly modify luminescent properties of a fluorophore. This study shows experimental results of emission spectrum changes of CaF2 doped with Eu3+ ions in the vicinity of an aluminum surface. The effect of metal presence can be both positive and negative, depending on, among other things, whether the transition has an electric-dipole or magnetic-dipole nature. The optimal distance between the metal surface and the fluorophore was found for both types of transition. Significantly lower quenching was observed for magnetic-dipole transition. Measurements were made for the distance between aluminum and fluorescent layer of 2.2 nm, 7.3 nm, 12.8 nm, 17.2 nm, and 25.2 nm. The fluorescence was excited both directly by laser light with a wavelength of 403 nm and by the surface plasmon resonance of an aluminum layer in the Kretschmann configuration. The difference between each type of excitation is studied for all the distances.