Anomalous Purcell decay of strongly driven and disordered emitters coupled to a cavity (Part 1): Experiment

Tailoring the interaction between optical emitters and their electromagnetic environment is of both fundamental interest and practical relevance for applications such as quantum communication and quantum information processing. By tuning the photon density of states, one can drastically modify the emission properties of these emitters, a phenomenon that underpins the thriving research area of cavity quantum electrodynamics. Rare-earth ions embedded in solid-state hosts have naturally long optical lifetimes and are easily integrated with nanoscale optical cavities, and these properties make them ideally suited for optical decay modification experiments. In this work, we explore the experimental modification of the ensemble optical decay of trivalent erbium ions (Er³⁺) coupled to a nanocavity at a temperature of 3 K. The nanocavity consists of an Er³⁺-doped titanium dioxide (TiO₂) layer grown atop silicon-on-insulator wafer, and the small mode volume photonic crystal cavity is defined via etching through both the TiO₂ and Si device layers. The ensemble of Er³⁺ emitters that couples to the cavity exhibit a much broader inhomogeneous linewidth than the cavity. When the optical cavity is tuned through the Er³⁺ inhomogeneous distribution (1520.5 nm), the resultant Purcell factor exhibits an anomalous slowing of the decay when the cavity is resonant with the center of the distribution. We examine the experimental Purcell factor dependence on resonant laser pump power, as well as the spectral dependence of the PLE emission.