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Cerium-doped terbium iron garnet (CeTbIG) thin films with varying compositions and thicknesses were deposited to determine a garnet formation region. Both grain size and Faraday rotation (FR) increased in this region as the Ce content increased until 20% of the dodecahedral sites were occupied by Ce. The high Ce content was achieved by lowering the Fe ratio with respect to the total rare earth content. Above 20% Ce, the Faraday rotation was relatively independent of composition at -830o/cm, which is similar in magnitude to positive Faraday rotation garnets, e.g.: + 600o/cm for undoped TbIG. Next, we found that a two-step annealing method, involving a 400°C pre-anneal followed by higher temperatures, effectively reduced the maximum temperature from 900°C to 800°C without decreasing the Faraday rotation. Finally, a Si-integrated interferometer was simulated using the stable (+) and (-) Faraday rotation materials developed in this work. The simulation identified a Si-integrated Mach Zehnder Interferometers (MZI) with “push/pull” nonreciprocal phase shifts (NRPS) of opposite signs that enable mm-scale with zero external magnetic field (field-free).
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Crystallization of high gyrotropy garnets with decreasing thermal processing budgets as analyzed by electron backscatter diffraction
Rare-earth iron garnets with large magnetic gyrotropy, made with reduced thermal budgets, are ideal magneto-optical materials for integrated isolators. However, reduced thermal budgets impact Faraday rotation by limiting crystallization, and characterization of crystallinity is limited by resolution or scannable area. Here, electron backscatter diffraction (EBSD) is used to measure crystallinity in cerium substituted yttrium- and terbium-iron garnets (CeYIG and CeTbIG) grown on planar Si, crystallized using one-step rapid thermal processes, leading to large Faraday rotations > −3500 °/cm at 1550 nm. Varying degrees of crystallinity are observed in planar Si and patterned Si waveguides, and specific dependences of crystallite size are attributed to the nucleation/growth processes of the garnets and the lateral dimensions of the waveguide. On the other hand, a low thermal budget alternative–exfoliated CeTbIG nanosheets–are fully crystalline and maintain high Faraday rotations of −3200 °/cm on par with monolithically integrated thin film garnets.
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- PAR ID:
- 10412679
- Date Published:
- Journal Name:
- Optical Materials Express
- Volume:
- 13
- Issue:
- 2
- ISSN:
- 2159-3930
- Page Range / eLocation ID:
- 357
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1364/OME.476482
