Higher gain in 977-nm-pumped Al₂O₃:Er³⁺ integrated optical amplifiers

In this paper we experimentally compare pumping at 977 nm and 1480 nm and the influence on gain in an Al2O3:Er3+ amplifier. We show that significantly higher gain can be achieved when pumping at 977 nm, and a record-high peak gain and gain bandwidth obtains compared to previous results in this material. Al2O3:Er3+ straight channel waveguide amplifiers were fabricated on thermally-oxidized silicon substrates by reactive co-sputtering, standard lithography and reactive ion etching. The amplifiers were ~6-cm-long with a waveguide cross section of 1 um x 4 um and an etch depth of ~70 nm. The waveguide dimensions were selected for single-mode propagation at wavelengths of 977 nm and above, good overlap of pump and signal mode profiles (for both 977-nm and 1480-nm pumping) and strong confinement of the propagating pump and signal within the active region.