Monolithically Integrated Erbium-Doped Polycrystalline Al₂O₃ Waveguide Amplifier on Silicon Photonics Platform

We demonstrated the monolithic integration of a polycrystalline Al₂O₃:Er³⁺ waveguide amplifier onto the passive Si₃N₄ TriPleX platform, enabling high-performance on-chip amplification for photonic integrated circuits. The polycrystalline Al₂O₃:Er³⁺ was deposited using reactive magnetron co-sputtering, ensuring compatibility with large-scale fabrication. On-chip wavelength division multiplexers, based on directional couplers, enabled the combining and splitting of the pump and signal powers on-chip. The 30 cm long waveguide amplifier, with a concentration of 1.6 × 10²⁰ ions/cm³, was bidirectionally pumped at 1480 nm. The integrated amplifier demonstrated a small-signal net gain exceeding 16 dB with a noise figure of approximately 3 dB, and a broad gain bandwidth of 80 nm. These results mark a significant step toward fully integrated rare-earth-ion-doped amplifiers for next-generation of active-passive photonic integrated circuits compatible with silicon photonics platforms.