Mid-infrared quasi-BIC resonances with sub-wavelength slot mode profiles in germanium-based coupled guided-mode resonance structures

Lal Krishna, AS and Menon, S and Prosad, A and Raghunathan, V (2022) Mid-infrared quasi-BIC resonances with sub-wavelength slot mode profiles in germanium-based coupled guided-mode resonance structures. In: Photonics Research, 10 (1). pp. 68-75.

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Abstract

We experimentally demonstrate a novel quasi-bound state in the continuum (BIC) resonance in the mid-infrared wavelength region with the resonant electric field confined as a slot mode within a low-refractive-index medium sandwiched between high-index layers. The structures studied here comprise coupled amorphous germanium guided-mode resonance (GMR) structures with a top one-dimensional grating layer and bottom uniform layer separated by a low-index silicon nitride layer. The slot-mode profile within the silicon nitride layer with mode field confinement >30 is achieved as a solution to the electromagnetic wave propagation through the coupled GMR structure with the dominant field component being perpendicular to the layers. The quasi-BIC resonance in symmetric 1D grating structures can be observed even at normal incidence when considering a realistic excitation beam with finite angular spread. The measured transmission peak is found to redshift (remain almost unchanged) under classical (full-conical) mounting conditions. The highest quality factor of �400 is experimentally extracted at normal incidence under a classical mounting condition with a resonance peak at 3.41 μm wavelength. Such slot-mode GMR structures with appropriately chosen low-index intermediate layers can find applications in resonantly enhanced sensing and active photonic devices. © 2021 Chinese Laser Press

Item Type:	Journal Article
Publication:	Photonics Research
Publisher:	The Optical Society
Additional Information:	The copyright for this article belongs to The Optical Society
Keywords:	Amorphous silicon; Electric fields; Germanium; Guided electromagnetic wave propagation; Infrared devices; Mirrors; Mountings; Photonic devices; Reflection; Refractive index; Resonance; Silicon photonics; Waveguides, Condition; Germaniums (Ge); Guided-mode resonance; Low index; Midinfrared; Mode profiles; Normal incidence; Quasibound state; Resonance structure; Sub-wavelength, Silicon nitride
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	24 Jan 2022 06:10
Last Modified:	24 Jan 2022 06:10
URI:	http://eprints.iisc.ac.in/id/eprint/71022

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