Description
Trivalent Erbium ions in solid state hosts (Er$^{3+}$) are exceptional quantum emitters combining narrow optical transitions within the telecom C-band with long electron and nuclear spin coherence times at cryogenic temperatures. However, the weak point of Er$^{3+}$ sites is their relatively long optical decays exceeding milliseconds and drastically limiting Er$^{3+}$ emission rates in bulk crystals. The integration of single Er$^{3+}$ ions with Si photonic resonators promises to enhance Er$^{3+}$ emission by several orders of magnitude and to enable telecom-compatible single photon sources attractive for quantum information processing and quantum communication. Here, we demonstrate the successful generation of multiple quantum-relevant Er sites in photonic waveguides fabricated in Er-implanted commercial Silicon-On-Insulator (SOI) wafers with 220 nm Czochralski (CZ) and floating zone (FZ) Si device layers. Waveguides were annealed at 500$^o$ or 700$^o$ C after implantation. Si photonic waveguides were packaged with optical fibres using an adiabatic fiber-to-chip interface. Optical and spin properties were investigated using photoluminescence (PL), photoluminescence excitation (PLE), spectral hole burning, and magnetic-field-dependent measurements. Waveguides fabricated in both FZ and CZ Si exhibited multiple Er sites with long spin lifetimes ($>$1 s), narrow homogeneous ($<$100 kHz) and inhomogeneous ($<$1 GHz) broadening. Identical Er optical transitions displayed shorter optical lifetimes at lower post-implantation annealing temperature indicating significant non radiative relaxation processes after low temperature annealing. These results clarify the conditions required for reproducible formation of optically active Er centres in silicon photonic structures and represent an important step toward scalable, CMOS-compatible quantum photonic devices operating at telecom wavelengths.
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