Superfluorescence from Erbium-doped crystals

In Superfluorescence process, an initially incoherent ensemble of excited atoms (molecules, etc) gives rise to a macroscopic polarization due to spontaneously synchronization of the atomic dipoles. In this coupled system, every single dipole is correlated with all the others and the atomic transition rate is enhanced by a factor μN, with N the number of correlated atoms and μ a geometrical factor that accounts for the interference effects. The cooperative radiative decay results in the emission of coherent photon bunches whose peak intensity is proportional to μN^2 and the duration scales with (μN)^−1. In this thesis, we present the clear signatures of the Superfluorescence from Erbium-doped Y2SiO5 and YLiF4 crystals at liquid helium temperature. The process is observed for two transitions and involves the remarkable number of 10^12 Erbium ions, accelerating the radiative decay by millions of times. Several aspects of Superfluorescence are deeply investigated and a remarkable agreement with the theoretical expectation is reported.