Local-field effect on the spontaneous radiative emission rate

The effect of the dielectric medium upon the spontaneous emission rate was investigated using lead borate glass of various compositions lightly doped with the Eu(3+) lanthanide ion. A dual approach used the variation of (i) electric dipole/magnetic dipole (ED/MD) emission rates from spectral integrations and (ii) absolute ED emission rates from lifetime measurements for comparison with the variation of the refractive index of the glass medium. Contrary to a previous study [Phys. Rev. Lett. 91, 203903 (2003)], the results show the relevance of the virtual-cavity model in this case. The MD emission rates were taken to follow the n(3) increase in density of photon states in the medium. The justifications for employing Eu(3+) for identifying the appropriate model are given.