Mitigating fabrication variations in silicon ring resonators: theoretical and statistical comparison of all-pass ring and add-drop racetrack designs

Abstract

Ring resonators are pivotal components in silicon photonics, serving as essential building blocks for modulators, demultiplexers, filters, and sensors in high-speed optical communication and integrated photonic systems. Their compact size, wavelength selectivity, and compatibility with CMOS manufacturing make them indispensable for applications like wavelength-division multiplexing and optical interconnects. However, their performance is highly sensitive to process variations, particularly in the coupling region, where even nanometer-scale fabrication imperfections can significantly degrade key metrics like the quality factor, posing a critical bottleneck for reliable, high-volume production. This study proposes a method to mitigate performance variation caused by manufacturing imperfections in coupling regions. Racetrack designs with certain gaps and certain physical coupling lengths are shown prospectively to better manage variations, improving stability compared to standard all-pass rings, as validated by simulations and statistical analysis. The findings offer practical guidelines for designing more reliable photonic devices.