What is the Brillouin zone of an anisotropic photonic crystal?
Name
PhysRevB.93.054204.pdf
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1.66 MB
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Author(s)
Sivarajah, Prasahnt
Maznev, Alexei
Ofori-Okai, Benjamin Kwasi
Nelson, Keith Adam
Date Issued
February 2016
Journal
Physical Review B
Publisher
American Physical Society
Citation
Sivarajah, P., A. A. Maznev, B. K. Ofori-Okai, and K. A. Nelson. "What is the Brillouin zone of an anisotropic photonic crystal?." Phys. Rev. B 93, 054204 (February 2016). © 2016 American Physical Society
Version
Final published version
Abstract
The concept of the Brillouin zone (BZ) in relation to a photonic crystal fabricated in an optically anisotropic material is explored both experimentally and theoretically. In experiment we used femtosecond laser pulses to excite THz polaritons and image their propagation in lithium niobate and lithium tantalate photonic crystal (PhC) slabs. We directly measured the dispersion relation inside PhCs and observed that the lowest band gap expected to form at the BZ boundary forms inside the BZ in the anisotropic lithium niobate PhC. Our analysis shows that in an anisotropic material the BZ—defined as the Wigner-Seitz cell in the reciprocal lattice—is no longer bounded by Bragg planes and thus does not conform to the original definition of the BZ by Brillouin. We construct an alternative Brillouin zone defined by Bragg planes and show its utility in identifying features of the dispersion bands. We show that for an anisotropic two-dimensional PhC without dispersion, the Bragg plane BZ can be constructed by applying the Wigner-Seitz method to a stretched or compressed reciprocal lattice. We also show that in the presence of the dispersion in the underlying material or in a slab waveguide, the Bragg planes are generally represented by curved surfaces rather than planes. The concept of constructing a BZ with Bragg planes should prove useful in understanding the formation of dispersion bands in anisotropic PhCs and in selectively tailoring their optical properties.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.93.054204
