Postfabrication Phase Error Correction of Silicon Photonic Circuits by Single Femtosecond Laser Pulses

Phase errors caused by fabrication variations in silicon photonic integrated circuits are an important problem, which negatively impacts device yield and performance. This paper reports our recent progress in the development of a method for permanent, postfabrication phase error correction of silicon photonic circuits based on femtosecond laser irradiation. Using beam shaping technique, we achieve a 14-fold enhancement in the phase tuning resolution of the method with a Gaussian-shaped beam compared to a top-hat beam. The large improvement in the tuning resolution makes the femtosecond laser method potentially useful for very fine phase trimming of silicon photonic circuits. We also show that femtosecond laser pulses can directly modify silicon photonic devices through a SiO2 cladding layer, making it the only permanent post-fabrication method that can tune silicon photonic circuits protected by an oxide cladding.