Photo-induced trimming of chalcogenide-assisted silicon photonic circuits

We present an innovative and efficient technique for post-fabrication trimming of silicon photonic integrated circuits (PICs). Our approach exploits the high photosensitivity of chalcogenide glasses (ChGs) to induce local and permanent modifications of the optical properties and spectral responses of ChG-assisted silicon devices. We experimentally demonstrate the potential of this technique on ring resonator filters realized on a silicon-on-insulator platform, for which post-fabrication treatments enable to counteract the strong sensitivity to technological tolerances. Photosensitive ChG-assisted silicon waveguides were realized by deposition of a As2S3 chalcogenide layer on top of conventional silicon channel waveguides. A resonant wavelength shift of 6.7 nm was achieved, largely exceeding the random resonance spread due to fabrication tolerances. Neither the ChG layer deposition, nor the trimming process introduces appreciable additional losses with respect to the bare silicon core waveguide. Performances of the trimming technique, such as speed and saturation effects, as well as nonlinear behavior and infrared writing issues are investigated and experimentally characterized.