Optimizing microring resonator performance via femtosecond laser: post-fabrication trimming of resonance wavelength and coupling regimes

Integrated silicon photonic devices, especially microring resonators, are susceptible to fabrication variations, with even nanoscale errors potentially leading to suboptimal performance, thereby hindering their large-scale production and commercialization. This study demonstrates femtosecond-laser-based post-fabrication trimming of microring resonators, achieving controllable and permanent adjustments to the resonance wavelengths and coupling regimes. Micro-Raman spectroscopy revealed the trimming mechanism, whereas systematic analysis highlighted performance variations among the on-chip devices. The experimental results showed directional resonance wavelength shifts with long-term stability and minimal reduction in the quality factor. The overcoupling devices were tuned to near-critical coupling to improve the extinction ratio exceeding 22 dB. This approach promises to accelerate the industrialization of high-performance, cost-effective photonic devices.