High on-chip gain spiral Al₂O₃:Er³⁺ waveguide amplifiers

We demonstrate reactively sputtered Al₂O₃:Er³⁺ waveguide amplifiers with an erbium concentration of 3.9 × 10²⁰ ions/cm³, capable of achieving over 30 dB small signal net gain at 1532 nm using bidirectional pumping at 1480 nm. We observe on chip output powers of 10.2-13.6 dBm of amplified signal power at 1532 nm for a 12.9 cm waveguide amplifier considering -25.4 dB of lumped coupling losses per facet. Annealing was used to improve the performance of the devices, which were patterned using electron beam lithography and reactive ion etching. This result, to our knowledge, represents record breaking on-chip internal net gain for Al₂O₃:Er³⁺ waveguide amplifiers, which show promise over other technologies due to wafer scalability and promise of easy monolithic integration with other material platforms to support a wide variety of applications.