High-Gain Er3+:Al2O3 On-Chip Waveguide Amplifiers

High-gain on-chip Er
³⁺
doped Al
₂
O
₃
single-mode ridge waveguide amplifier device is reported. The growth of the active layer is realized using atomic layer deposition (ALD) compatible with Si processing technology. Optimization of the Al
₂
O
₃
and Er
₂
O
₃
growth conditions for fine-tuning the optical properties is systematically investigated. In order to optimize the active ion concentration, heterocycle structures consisting of separately optimized Al
₂
O
₃
and Er
₂
O
₃
are deposited. The structural and optical properties of the active layers were characterized by spectroscopic ellipsometry, X-ray photoelectron spectroscopy, time-resolved photoluminescence, and optical gain measurements. We demonstrated up to 2.74 ± 0.40 dB total gain and 13.71 ± 1.97 dB/cm internal optical net gain per unit length at 1550 ± 12 nm using a 2-mm-long device, pumped using a 980 nm laser diode at 23-mW. This work can be expanded to other rare-earth ion doping processes, paving the way to significant improvements of active on-chip applications.