Researchers have built erbium-doped waveguide amplifier (EDWA) based on silicon nitride (Si3N4) photonic integrated circuits of a length up to a half-meter on a millimeter-scale footprint. The device generates a record output power of more than 145 mW. It provides a small-signal net gain above 30 dB, translating to over 1000-fold amplification in the telecommunication band in continuous operation. This performance matches the commercial, high-end erbium-doped fiber amplifiers (EDFAs) and state-of-the-art heterogeneously integrated III-V semiconductor amplifiers in silicon photonics.
The researchers overcame the longstanding challenge by applying ion implantation (a wafer-scale process that benefits from very low cooperative upconversion even at a very high ion concentration) to the ultra low-loss silicon nitride integrated photonic circuits.
The new approach allows the researchers to achieve low loss, high erbium concentration, and a sizeable mode-ion overlap factor in compact waveguides with meter-scale lengths, which have remained unsolved for decades.
The breakthrough signals a renaissance of rare-earth ions as viable gain media in integrated photonics, as erbium-doped waveguide amplifier applications are virtually unlimited, from optical communications and LiDAR for autonomous driving to quantum sensing and memories for large quantum networks. It will trigger follow-up studies that cover even more rare-earth ions, offering optical gain from the visible up to the mid-infrared part of the spectrum and even higher output power.