Gain bandwidth of 80 nm and 2 dB/cm peak gain in Al_2O_3:Er^3+ optical amplifiers on silicon

TLDR

The authors fabricated Erbium‑doped Al₂O₃ waveguide amplifiers on silicon, optimized the fabrication and waveguide design, pumped at 977 nm, and used a rate‑equation model to predict up to 33 dB internal net gain at 1533 nm and >20 dB across the C‑band for a 24‑cm device. The amplifiers exhibit background losses <0.3 dB/cm at 1320 nm, achieve an 80‑nm bandwidth (1500–1580 nm) with a peak gain of 2.0 dB/cm at 1533 nm, deliver up to 9.3 dB net gain in a 5.4‑cm device, and confirm Al₂O₃:Er³⁺ as a competitive active integrated‑optics platform.

Abstract

Erbium-doped aluminum oxide integrated optical amplifiers were fabricated on silicon substrates, and their characteristics were investigated for Er concentrations ranging from 0.27 to 4.2×1020 cm−3. Background losses below 0.3 dB/cm at 1320 nm were measured. For optimum Er concentrations in the range of 1 to 2×1020 cm−3, an internal net gain was obtained over a wavelength range of 80 nm(1500-1580 nm), and a peak gain of 2.0 dB/cm was measured at 1533 nm. The broadband and high peak gain are attributed to an optimized fabrication process, improved waveguide design, and pumping at 977 nm as opposed to 1480 nm. In a 5.4-cm-long amplifier, a total internal net gain of up to 9.3 dB was measured. By use of a rate-equation model, an internal net gain of 33 dB at the 1533 nm gain peak and more than 20 dB for all wavelengths within the telecom C-band (1525-1565 nm) are predicted for a launched signal power of 1 μW when launching 100 mW of pump power into a 24-cm-long amplifier. The high optical gain demonstrates that Al2O3:Er3+ is a competitive technology for active integrated optics.