Bound states in the continuum enabling ultra-narrowband perfect absorption

Abstract

Resonant dielectric metasurfaces have been demonstrated to hold a great promise for manipulation of light-wave dispersion at the nanoscale due to their resonant photonic environment and high refractive index. However, the efficiency of devices based on dielectric nanostructures is usually limited by the quality (Q) factor of their resonant modes. The physics of the bound sates in the continuum (BICs) provide an elegant solution for control over the Q factor of resonant modes. Here, by engineering the substrate of Si-based metasurfaces, we demonstrate two eigenmodes that exhibit an intrinsic magnetic dipole character and have an infinite radiation lifetime. We reveal that they are characterized by in-plane and out-of-plane magnetic dipole modes and respectively correspond to two groups of BICs, that is, Fabry–Pérot BICs and symmetry-protected BICs. Using temporal coupled-mode theory and numerical simulations, we show that these BIC modes can transform into high-Q quasi-BIC resonances with near-unity absorption under normal incidence through tuning structural parameters. Our work provides a promising route to use BIC-inspired metasurfaces for designing ultra-narrowband absorbers which can be used as absorption filters, photodetectors, and sensors.

Angular‐Dispersive Narrowband Absorption Induced by Quasi‐BIC in SiO2‐Au Metamaterial

“…Accidental BIC in connection with the height of metamaterial has been discussed in literatures, but just the first-order BIC in the Si-SiO 2 -Au configuration. [42,47] The higher-order h-related accidental BIC in absorption system is first discussed in this research. The merging of adjacent orders of accidental BIC, although seems slight, can still improve the magnitude of Q-factors of basic absorptive resonant mode from 10 3 to 10 4 .…”

Fabry–Pérot cavities critically coupled to metal nanodisk arrays for multi-narrowband perfect absorption

“…Various perfect absorbers based on different physical mechanisms, including Fabry–Perot (FP) resonance, 2 , 3 Tamm plasmon polaritons, 4 , 5 localized surface plasmon resonance (LSPR), 6 , 7 guided-mode resonance, 8 , 9 and magnetic resonances, 10 , 11 have been proposed and studied. These absorbers can be generally categorized into two types in terms of their absorption bandwidths: broad-band absorbers 12 , 13 and narrow-band absorbers, 14 , 15 which have different applications. Generally, broad-band absorbers are used in energy harvesting and electromagnetic cloaking, and narrow-band ones are usually applied in fields such as sensing, 16 , 17 thermal detection, 18 surface enhanced Raman scattering, 19 and thermal radiation tailoring 20 .…”

Extreme Nonreciprocity in Metasurfaces Based on Bound States in the Continuum

“…[23] Their useful realization comes in the form of quasi-BICs, which are perturbed BICs that have turned into accessible leaky modes with extreme quality factors (ultralong but finite lifetimes). [24,25] Over recent years, metasurfaces that use these states have been proposed to enhance different effects: circular dichroism, [26][27][28] absorption, [29,30] and more. Furthermore, BICs can be classified into different categories depending on their formation nature.…”