July 2020
Spotlight Summary by Guangyuan Li
Improved refractive-index sensing performance in medium contrast gratings by asymmetry engineering
Vyas and Hegde predicted ultra-sharp spectral features in asymmetry-engineered medium contrast gratings (MCGs), based on CMOS compatible silicon nitride and the excitation of quasi-bound states in continuum (QBIC) resonances. BICs are waves that remain perfectly confined without any radiation even though they coexist with a continuous spectrum of radiating waves that can carry energy away. At BIC resonances, extremely sharp spectral profiles with ultrahigh quality factors and strong field enhancement can be obtained, enabling potential applications in low-threshold lasing, highly sensitive biochemical sensing, and narrow-linewidth filtering. Most studies of QBICs are focused on silicon-based gratings or metasurfaces.
In this study, the authors investigated asymmetry-engineered silicon nitride MCGs, aiming to achieve ultra-sharp spectral features based on QBICs that are excited under normal incidence. They systematically studied the general class of period-doubling asymmetries which combine width and displacement perturbations. The dual resonances with sharp spectral features obtained under normal incidence of either polarization, and the simulated bulk and surface sensing performance in both spectral-shift and intensity-shift modalities suggest that the proposed structure is appealing for on-chip label-free biosensing. Their exciting results can be further extended to 2D structures and to a wider range of applications such as lasing and nonlinear optics.
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In this study, the authors investigated asymmetry-engineered silicon nitride MCGs, aiming to achieve ultra-sharp spectral features based on QBICs that are excited under normal incidence. They systematically studied the general class of period-doubling asymmetries which combine width and displacement perturbations. The dual resonances with sharp spectral features obtained under normal incidence of either polarization, and the simulated bulk and surface sensing performance in both spectral-shift and intensity-shift modalities suggest that the proposed structure is appealing for on-chip label-free biosensing. Their exciting results can be further extended to 2D structures and to a wider range of applications such as lasing and nonlinear optics.
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Article Information
Improved refractive-index sensing performance in medium contrast gratings by asymmetry engineering
Hardik Vyas and Ravi S. Hegde
Opt. Mater. Express 10(7) 1616-1629 (2020) View: Abstract | HTML | PDF