Extrinsic Losses in Silicon Slot Photonic Crystal Waveguides: Influence of the Fabrication Process

We report an experimental study of extrinsic propagation losses of silicon slot photonic crystal waveguides. This specific geometry of hollow core waveguides offers an exceptional platform for the integration of active materials on silicon because of its very strong light/matter overlap. Nevertheless, this approach suffers simultaneously from higher propagation losses than the more conventional geometries of (non-slotted) waveguides. We present in this work an experimental study of the influence of the e-beam and etching fabrication steps of photonic structures on the level of propagation losses in both the fast and slow wave propagation regimes. We have studied the influence of the method and electron dose of irradiation of periodic patterns and extracted from these data the level of propagation losses as a function of the group index of the excited Bloch modes. The collected results reveal a strong influence of the stages of fabrication of the structures and open the way to a possible technological optimization of the propagation losses of slow light slotted waveguides.