Loss measurements of ER-doped silicon-on-insulator waveguides

Waveguides optimised at 1.5 μm have been fabricated from erbium-doped Smart Cut® silicon-on-insulator wafers. The wafers were implanted at 1 MeV with a low dose of Er, chosen to minimize structural damage to the layers and reduce the need for prolonged thermal treatment. Single mode rib waveguides were designed using the very thin Si top layer (1.5 μm) of the wafers and the buried silicon dioxide layer of thickness 3 μm. Near field measurements of the lateral and vertical confinement show a single, symmetric, and well-confined optical mode. As predicted in the literature, when the Er is in the waveguiding region itself, the measured waveguide losses increase. This is attributed to the implant-induced damage, which is observed as a broad defect peak in photoluminescence (PL) prior to any annealing. After annealing, sharp luminescence from the erbium appears and the broad PL peak has been removed. Loss measurements reveal that the losses decrease but are still slightly worse than the losses measured for undoped-waveguides.