Erbium Ions Integrated with Silicon Nanophotonic Structures

Abstract

Hybrid quantum systems leverage the complementary strengths of different physical systems to overcome their intrinsic limitations. Rare-earth ion-doped crystals combined with silicon nanophotonic structures provide a particularly versatile platform. Erbium ions offer long optical and spin coherence times together with emission in the telecom C-band, corresponding to the lowest-loss window of optical fibers. At the same time, the solid-state host environment provides tunability and scalable integration. Mature silicon nanofabrication enables high-quality optical and mechanical resonators with strong field confinement.
Two complementary implementations are explored in this thesis. First, silicon photonic crystal cavities are combined with erbium-doped lithium niobate, enabling Purcell-enhanced single-photon emission from individual ions. The optical frequency of the ions is tuned via the linear Stark effect, a key step toward the generation of indistinguishable photons. Second, erbium ions are implanted directly in silicon nanostructures. The optical transition dipole properties are investigated under different magnetic-field regimes, an essential ingredient for optimizing cavity-ion coupling. A general framework is established to determine the transition dipole polarization in spin-1/2 solid-state defects, overcoming limitations of existing approaches. Furthermore, this method enables the determination of the strain-orbital coupling tensor, representing an important step toward coupling erbium spins to mechanical modes supported by our nanostructures.
Overall, this work establishes the experimental foundations for hybrid quantum systems based on erbium ions coupled to silicon nanostructures, providing key building blocks for efficient spin-photon and spin-phonon interfaces and opening new opportunities for nonlinear quantum optomechanics.