Mid-Infrared Off-Axis Resonant Mode Hybridization in Amorphous Silicon Sub-Wavelength Grating Structures

Krishna AS, L and Biswas, R and Raghunathan, V (2023) Mid-Infrared Off-Axis Resonant Mode Hybridization in Amorphous Silicon Sub-Wavelength Grating Structures. In: Advanced Optical Materials .

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Abstract

In this study, the off-axis excited guided-mode resonance (GMR) hybridization is experimentally investigated in one dimensional (1D) partially etched amorphous silicon (a-Si) subwavelength grating structures operating in the mid-infrared wavelength range. The 1D dielectric photonic lattice is a promising platform for studying resonance hybridization effects owing to its simple working principle and ease of electromagnetic design, fabrication, and experimental characterization. It is observed that with increasing duty-cycle of the gratings, the avoided crossing between the coupled GMR branches underwent band-closure and subsequent band-flip, resulting in the Friedrich–Wintgen type bound-states-in-the-continuum (FW-BICs) transitioning from the upper to the lower GMR branch. On either side of the band closure, the transmission spectra show an interesting electromagnetically induced transparency (EIT)-like resonance, which manifests as a transmission peak within a broad transmission dip with increased electric field concentration near the peak. As a conceptual application of coupled GMRs, differential enhancement of infrared absorption from a polymethyl methacrylate (PMMA) layer coated on the grating structure with one of the optical resonances aligned to the absorption feature and the other acting as a built-in reference is demonstrated. The differential transmission contrast is enhanced by more than two orders of magnitude when compared to that of the native PMMA layer.

Item Type:	Journal Article
Publication:	Advanced Optical Materials
Publisher:	John Wiley and Sons Inc
Additional Information:	The copyright for this article belongs to John Wiley and Sons Inc
Keywords:	Amorphous silicon; Diffraction gratings; Electric fields; Infrared absorption; Infrared devices; Optical lattices; Quantum optics; Transparency, Bound-state-in-continuum; Bound-states; Electromagnetically-induced transparency; Grating structures; Guided-mode resonance; Hybridisation; Mode hybridization; Off-axis; Resonantly enhanced infrared absorption; Sub-wave length grating, Light absorption
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	15 Jun 2023 09:31
Last Modified:	15 Jun 2023 09:31
URI:	https://eprints.iisc.ac.in/id/eprint/82042

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