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

Er-doped aluminium oxide (Al2O3: Er3+) is known to be a good material for active integrated devices, however, in the past it has produced lower net gain compared to other Er-doped glass materials [1], [2]. One of the issues potentially affecting the gain in Er-doped amplifiers is the choice of pump wavelength, which is typically either ~980 nm or 1480 nm. The main advantages of 1480-nm pumping are higher pumping efficiency due to a higher number of photons per unit power and similar modal properties to the signal. However, 1480-nm pumping can lead to a lower population inversion because of stimulated emission at the pump wavelength from the 4I13/2 manifold. For this reason lower gain has been predicted theoretically in an Al2O3: Er3+ amplifier when pumping at 1480 nm [3]. 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.