A low-fabrication-temperature, high-gain chip-scale waveguide amplifier

The increasing prevalence of integrated on-chip optoelectronic devices has identified serious issues regarding inter-device transmission and coupling losses, highlighting an urgent need for on-chip waveguide amplifiers to compensate for these losses. Compared with other Er-based optical materials, erbium silicate is ideally suited to high-efficiency on-chip amplifiers and lasers because of its extremely high Er 3+ concentration (10 22 cm −3 ). Nevertheless, erbium silicate must be annealed above 1000°C to crystallize and activate the Er 3+ , which damages other on-chip optoelectronic components and is not conducive to device integration. Here, we report a low-fabrication-temperature, high-luminescence-efficiency gain material by adding Bi 2 O 3 to an erbium-ytterbium silicate mixed film. Our experiments demonstrate that the proposed film crystallizes at 600° C while the activation of Er 3+ is also achieved, which is the lowest activation temperature of on-chip waveguide amplifier to our knowledge. This material forms the basis for a new chip-scale waveguide amplifier design, with a theoretical multi-energy-level model of Bi-Er-Yb in the mixed thin films used to analyze its signal enhancement properties. We achieve a peak on-chip gain of 23 dB in a 3.3-mm-long waveguide under the pump and signal powers of 300 mW and 1 µW, respectively. These results highlight the potential of the proposed material for realizing on-chip amplifiers and lasers for large-scale nanophotonic integrated circuits.