The incorporation of optical isolators and related non-reciprocal devices such as circulators within standard optoelectronic wafer platforms is exceptionally challenging. Preferred magneto-optic materials cannot be exploited as waveguide core layers on semiconductor wafers due to a lower refractive index. Our approach to the integration of an optical isolator on semiconductor platforms involves combining a nonreciprocal mode converter with a reciprocal mode converter. We demonstrate that suitably tapered waveguides can be employed to connect the mode converter to other sections thereby avoiding problems caused by mode-matching and reflections from the section interfaces.
The nonreciprocal mode converter is formed from a continuation of the semiconductor waveguide core with a magneto-optic upper cladding so that Faraday rotation occurs through the interaction of the evanescent tail. The phase velocity mismatch due to the waveguide birefringence is overcome using a quasi-phase-matching approach. Lithography is used to pattern the top cladding so that the film immediately on top of the waveguide core alternates between magneto-optic and a non-magneto-optic dielectric of a similar refractive index.
We developed a lift-off process for garnet films in collaboration with Prof. Beth Stadler at the University of Minnesota. This allows annealing of the film in an oxygen atmosphere to facilitate the crystallisation of the garnet phase and realise the potential of the large Verdet coefficiecients available in YIG and related garnets. Our recent work uses substituted Terbium Iron Garnets (TIG) which has the advantage of crystallisation without the requirement for a comprimising garnet seed layer.MRS Webinar on Material for Nonreciprocal Photonics, June 2018
- Prof. David C. Hutchings
- Dr. Barry M. Holmes
- Cui Zhang
- 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, revised ACS Photonics (2019).
- Stadler, B. J.H. and Hutchings, D. (2018) Sputter-deposited magneto-optical garnet thin films for all-mode Faraday rotators. MRS Bulletin, 43(6), pp. 430-435. (doi:10.1557/mrs.2018.121)
- Zhang, C., Dulal, P., Stadler, B. J.H. and Hutchings, D. C. (2017) Monolithically-integrated TE-mode 1D silicon-on-insulator isolators using seedlayer-free garnet. Scientific Reports, 7, 5820. (doi:10.1038/s41598-017-06043-z)
- Dulal, P., Block, A. D., Gage, T. E., Haldren, H. A., Sung, S. Y., Hutchings, D. C. and Stadler, B. J.H. (2016) Optimized magneto-optical isolator designs inspired by seedlayer-free terbium iron garnets with opposite chirality. ACS Photonics, 3(10), pp. 1818-1825.(doi:10.1021/acsphotonics.6b00313)
- D.C. Hutchings, B.M. Holmes, Cui Zhang, P. Dulal, A.D. Block, Sang-Yeob Sung, N.C.A.Seaton, and B.J.H. Stadler (2013) Quasi-phase-matched Faraday rotation in semiconductor waveguides with a magnetooptic cladding for monolithically integrated optical isolators, IEEE Photonics Journal 5 (6), 6602512 DOI: 10.1109/JPHOT.2013.2292339
- Hutchings, D.C. and Holmes, B.M. (2011) A Waveguide Polarisation Toolset Design based on Mode-Beating, IEEE Photonics Journal 3 (3) pp. 450-461 DOI: 10.1109/JPHOT.2011.2146765
- Holmes, BM and Hutchings, DC (2006) Demonstration of quasi-phase-matched nonreciprocal polarization rotation in III-V semiconductor waveguides incorporating magneto-optic upper claddings. Applied Physics Letters 88 pp. 061116.
- Hutchings, DC (2003) Prospects for the implementation of magneto-optic elements in optoelectronic integrated circuits: a personal perspective. Journal Of Physics D-applied Physics 36 pp. 2222-2229.