An on-chip atomic layer deposited waveguide amplifier with net gain at C-band

Rare-earth-ion-doped materials provide many opportunities for on-chip amplifiers and light sources, which are important to silicon photonics. Here, we report an erbium-doped waveguide amplifier using atomic layer deposition. Method optimization yields erbium-doped Al2O3 films with excellent optical properties, which are showcased by the high-performance photoresist-erbium-doped Al2O3 hybrid amplifiers. We demonstrate signal enhancements (SE) of 30.4 dB and 16 dB at 1531.6 nm and 1550 nm in a 3.55-cm-long amplifier, respectively, corresponding to net gains of 8.4 dB and 5 dB. Furthermore, SE and gain increase with waveguide length under sufficient pumping, suggesting the potential for achieving greater gains for longer erbium-doped waveguide amplifiers. This work represents an important step towards high-gain rare-earth-ion-doped amplifiers and the integration of active devices on silicon platforms.