Abstract
Abstract All-dielectric metasurfaces supporting photonic bound states in the continuum (BICs) are an exciting toolkit for achieving resonances with ultranarrow linewidths. However, the transition from theory to experimental realization can significantly reduce the optical performance of BIC-based nanophotonic systems, severely limiting their application potential. Here, we introduce a combined numerical/experimental methodology for predicting how unavoidable tolerances in nanofabrication such as random geometrical variations affect the performance of different BIC metasurface designs. We compare several established all-dielectric BIC unit cell geometries with broken in-plane inversion symmetry including tilted ellipses, asymmetric double rods, and split rings. Significantly, even for low fabrication-induced geometrical changes, both the BIC resonance amplitude and its quality factor (Q-factor) are significantly reduced. We find that the all-dielectric ellipses maintain the highest Q-factors throughout the geometrical variation range, whereas the rod and split ring geometries fall off more quickly. The same behavior is confirmed experimentally, where geometrical variation values are derived from automated processing of sets of scanning electron microscopy (SEM) images. Our methodology provides crucial insights into the performance degradation of BIC metasurfaces when moving from simulations to fabricated samples and will enable the development of robust, high-Q, and easy to manufacture nanophotonic platforms for applications ranging from biomolecular sensing to higher harmonic generation.
Highlights
Nanophotonics has been a vibrant topic of research in the last two decades, focusing on the interactions of subwavelength objects with light and enabling the nanoscale concentration of electromagnetic fields beyond the optical diffraction limit [1, 2]
The transition from theory to experimental realization can significantly reduce the optical performance of BIC-based nanophotonic systems, severely limiting their application potential
We find that the all-dielectric ellipses maintain the highest Q-factors throughout the geometrical variation range, whereas the rod and split ring geometries fall off more quickly
Summary
Nanophotonics has been a vibrant topic of research in the last two decades, focusing on the interactions of subwavelength objects with light and enabling the nanoscale concentration of electromagnetic fields beyond the optical diffraction limit [1, 2]. Photonic bound states in the continuum (BICs) have recently emerged as an exciting toolkit for the design and experimental realization of all-dielectric platforms with sharp resonances and strong near-field enhancements [12,13,14,15,16]. In this context, BIC-based metasurfaces composed of unit cells with broken in-plane inversion symmetry have unlocked precise control over the linewidth and the Q-factor of their resonances [17]. While extremely high Q-factors are straightforward to achieve in numerical simulations [29, 30], the experimental realization of such metasurfaces through nanofabrication invariably introduces geometrical perturbations that can significantly broaden the resonance linewidths and greatly reduce the experimental Q-factors, limiting practical applications
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