Ultra-High-Q Racetrack Resonators on Thick SOI Platform through Hydrogen Annealing Smoothing

Yisbel E. Marin, Arijit Bera, Matteo Cherchi, Timo Aalto

Research output: Contribution to journalArticleScientificpeer-review


We implemented a hydrogen annealing based post-processing technique as a tool to improve the sidewall roughness of 3 μm thick silicon-on-insulator (SOI) waveguides and demonstrated ultra-high- Q factors on racetrack resonators leveraging on the propagation loss reduction achieved through the smoothing process. The designed racetracks are based on a combination of rib waveguides and strip-waveguide-based Euler bends. We measured intrinsic quality factors of 14×10^6 for a racetrack with a footprint of ∼5.5 mm^2 and 10.7×10^6 for a smaller racetrack with footprint of ∼1.48 mm^2 . The estimated propagation loss for the rib waveguides was ∼2.7 dB/m, representing a ×3 reduction respect to the previously measured losses of 3 μm thick SOI rib waveguides treated with thermal oxidation smoothing. Overall, the post-processing technique allowed to significantly reduce the sidewall roughness without altering the geometry of the waveguides, unlike in sub-micron scale SOI platforms, making it an attractive solution for applications demanding ultra-low losses.
Original languageEnglish
Pages (from-to)3642 - 3648
Number of pages7
JournalJournal of Lightwave Technology
Issue number11
Publication statusPublished - 1 Jun 2023
MoE publication typeA1 Journal article-refereed


  • Couplings
  • Hydrogen annealing
  • low-loss waveguides
  • microresonators
  • optical losses
  • Optical waveguides
  • photonic integrated circuits
  • Propagation losses
  • Q-factor
  • resonators
  • Resonators
  • Ribs
  • sidewall roughness
  • silicon photonics
  • Strips


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