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

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 proo...