Zero-Birefringence Silicon Waveguides Based on Tilted Subwavelength Metamaterials

Zero-Birefringence Silicon Waveguides Based on Tilted Subwavelength Metamaterials

Polarization independent silicon-on-insulator nanowires are highly sought after, due the inherent high birefringence of this material platform. State-of-the-art designs of non-birefringent waveguides include ridge waveguides and square nanowires, which either imply large dimensions, multiple etching...

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Bibliographic Details
Main Authors: Alaine Herrero-Bermello, Jose Manuel Luque-Gonzalez, Robert Halir, Pavel Cheben, Alejandro Ortega-Monux, Inigo Molina-Fernandez, Aitor V. Velasco
Format: Article
Language:English
Published: IEEE 2019-01-01
Series:IEEE Photonics Journal
Subjects:
Zero-birefringence waveguides
polarization independence
anisotropy engineering
sub-wavelength grating (SWG)
silicon-on-insulator (SOI).
Online Access:https://ieeexplore.ieee.org/document/8846035/
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Summary:Polarization independent silicon-on-insulator nanowires are highly sought after, due the inherent high birefringence of this material platform. State-of-the-art designs of non-birefringent waveguides include ridge waveguides and square nanowires, which either imply large dimensions, multiple etching steps, low fabrication tolerances or high wavelength dependence. In this work, we overcome all the aforementioned limitations through tilted subwavelength structures which provide anisotropy control of the resulting metamaterial. With a waveguide cross section of only 300&#x00A0;nm &#x00D7; 550&#x00A0;nm (height &#x00D7; width), the zero-birefringence point is obtained for an approximately <inline-formula><tex-math notation="LaTeX">$48^\circ$</tex-math></inline-formula>-tilt of the subwavelength structure. Birefringence of the nominal design deteriorates by only <inline-formula><tex-math notation="LaTeX">$9.10^{-3}$</tex-math></inline-formula> even in the presence of size deviations of <inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>10&#x00A0;nm. Moreover, birefringence is maintained under <inline-formula><tex-math notation="LaTeX">$6.10^{-3}$</tex-math></inline-formula> in a 100-nm bandwidth around the central wavelength of 1550&#x00A0;nm. This innovative approach is readly adaptable to a wide range of waveguide sizes, while maintaining single-etch-step fabrication.
ISSN:1943-0655

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