Accurate post-fabrication trimming of ultra-compact resonators on silicon

One of the challenges of the high refractive index contrast of silicon photonics platform is the high sensitivity of the resonance wavelength of resonators to dimensional variations caused by fabrication process variations. In this work, we have experimentally demonstrated an accurate post-fabrication trimming technique for optical devices that is robust to process variations. Using this technique, we have reduced the random variation of the resonance wavelength of 4 µm diameter resonators by a factor of 6 to below 50 pm. The level of accuracy achieved in this work is adequate for most of the RF-photonic, interconnect, and optical signal processing applications. We also discuss the throughput of this technique and its viability for wafer-scale post-fabrication trimming of silicon photonic chips.