High-performance Al₂O₃:Er³⁺ integrated optical amplifiers

Al2O3:Er3+ amplifiers with different Er concentrations have been investigated. Up to 2.0 dB/cm net gain has been demonstrated at 1533 nm for an Er concentration of 2 x 10^20 cm^-3 when pumping at 977 nm. Peak total gain of 9.3 dB was also demonstrated in a 5.4-cm amplifier and positive gain was achieved over an 80-nm bandwidth. Using a rate-equation model, up to 33 dB at the peak and >20 dB between 1525-1565 nm is predicted in a 24-cm-long amplifier for a pump power of 100 mW. In Er-doped fiber amplifiers, the long excited-state lifetime means transmission at bit rates around 40 Gbit/s is possible. We recently showed open-eye diagrams and only a small power penalty of 1 dB in bit-error-rate measurements for on-chip 40 Gbit/s signal transmission in an integrated Al2O3:Er3+ amplifier. This result, coupled with the high and broad gain demonstrates that such amplifiers are well-suited to compensating for on-chip losses incurred in high-bit-rate signals. The high gain also indicates that a laser source is possible in a material which can be integrated with passive optical materials such as silicon, providing high functionality on a single chip.