Erbium-doped phospate glass waveguide on silicon with 4.1 Polman dB/cm gain at 1.535 µm

Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques. The Er concentration was 5.3 x 10²⁰ cm^-3. By pumping the waveguide at 980 nm with a power of ~ 21 mW, a net optical gain of 4.1 Polman dB at 1.535 µm was achieved. This high gain per unit length at low pump power could be achieved because the Er-Er cooperative upconversion interactions in this heavily Er-doped phosphate glass are very weak [the upconversion coefficient is (2.0±0.5) x 10^-18 cm³/s], presumably due to the homogeneous distribution of Er in the glass and due to the high optical mode confinement in the waveguide which leads to high pump power density at low pump power.