Erbium-doped slot waveguides containing size-controlled silicon nanocrystals

Silicon based slot waveguides with a slot containing Si nanocrystals (Si-nc) and Erbium ions (Er³⁺) inside a silica matrix were prepared using sputter deposition and low-energy ion implantation. This sequence enabled independent optimization of nanocrystal formation and Er³⁺ incorporation parameters. Using a superlattice approach, the size of the Si-nc inside the slot could be controlled and optimized for maximum Er³⁺ luminescence yield at 1.54 μm. Er³⁺ is found to be efficiently pumped by Si-nc of sizes around 3 to 4 nm. Increasing Er³⁺ photoluminescence at 1.54 μm with increasing post-implantation annealing temperatures up to 1000 °C is attributed to annealing of matrix or Si-nc interface defects mainly. Additionally, a dependence of the Er³⁺ luminescence intensity on both the excitation and emission linear polarization orientation is shown, which demonstrates efficient field enhancement in sputtered slot waveguide structures.