High-Gyrotropy Seedlayer-Free Ce:TbIG for Monolithic Laser-Matched SOI Optical Isolators

Karthik Srinivasan, Cui Zhang, Prabesh Dulal, Cosmin Radu, Thomas E. Gage, David C. Hutchings, Bethanie J.H. Stadler

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Monolithic optical isolators that provide modal (transverse electric, TE) and dimensional (500 nm core) matching to on-chip lasers have been realized with "one step" seedlayer-free garnets. To date, seedlayer-free garnet claddings have required thinner (<340 nm) silicon-on-insulator (SOI) cores because mode-cladding interactions were too weak for laser-matched cores. However, laser matching is important because tapers and mode converters between the laser and the isolator can cause detrimental reflections prior to isolation. This paper reports the use of cerium-doped terbium iron garnet (Ce:TbIG) in a quasi-phase matched nonreciprocal mode conversion (NRMC) isolator that operates on both TE and TM modes without an external field. A key innovation presented here is a repeatable process for foundry-friendly sputter deposition of Ce:TbIG, which enables this high Faraday rotation material (-3200°/cm) to be synthesized in any isolator design that would benefit from one-step lithographical manufacturing. A proof-of-feasibility 500 nm SOI NRMC device is demonstrated with seedlayer-free Ce:TbIG that achieves an isolation ratio of 11 dB. With an optimal length, this NRMC design can provide greater than 30 dB isolation.

Original languageEnglish (US)
Pages (from-to)2455-2461
Number of pages7
JournalACS Photonics
Issue number10
StatePublished - Oct 16 2019

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.


  • Faraday rotation
  • cerium-doped terbium iron garnet
  • isolators
  • magnet-free isolators
  • magneto-optical garnets
  • non-reciprocal mode conversion
  • silicon photonics


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