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arXiv · 2212.12059

High-Q guided-mode resonance of a crossed grating with near-flat dispersion

Reuben Amedalor·Petri Karvinen·Henri Pesonen·Jari Turunen·Tapio Niemi·Subhajit Bej
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Abstract

Guided-mode resonances in diffraction gratings are manifested as peaks (dips) in reflection (transmission) spectra. Smaller resonance line widths (higher Q-factors) ensure stronger light-matter interactions and are beneficial for field-dependent physical processes. However, strong angular and spectral dispersion are inherent to such high-Q resonances. We demonstrate that a class of high-Q resonant modes (Q-factor >1000) exhibiting extraordinarily weak dispersion can be excited in crossed gratings simultaneously with the modes with well-known nearly linear dispersion. Furthermore, we show that the polarization of the incoming light can be adjusted to engineer the dispersion of these modes, and strong to near-flat dispersion or vice-versa can be achieved by switching between two mutually orthogonal linear polarization states. We introduce a semi-analytical model to explain the underlying physics behind these observations and perform full-wave numerical simulations and experiments to support our theoretical conjecture. The results presented here will benefit all applications that rely on resonances in free-space-coupled geometries.

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Reuben Amedalor, Petri Karvinen, Henri Pesonen, Jari Turunen, Tapio Niemi, Subhajit Bej. 2022-12-22. High-Q guided-mode resonance of a crossed grating with near-flat dispersion. https://doi.org/10.1063/5.0138666

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