Low-Contrast BIC Metasurfaces with Quality Factors Exceeding 100,000.
basic_science · Level V
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- Record sourced from PubMed, PMID 39916339.
- Also identified by DOI 10.1021/acs.nanolett.4c05880 and PMC identifier 11849022.
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Abstract
Dielectric metasurfaces operating at quasi-bound states in the continuum (qBICs) can achieve exceptionally high radiative quality (<i>Q</i>) factors by introducing small asymmetries into their unit cells. However, fabrication imperfections often impose major limitations on the experimentally observed <i>Q</i> factors. In this study, we experimentally demonstrate BIC metasurfaces with a <i>Q</i> factor of 101,000 under normal excitation of light in the telecom wavelength range achieved by employing low-contrast silicon pairs. Our findings show that such free-space accessible ultrahigh-<i>Q</i> factors can be attained by leveraging both the high radiative <i>Q</i> factors of higher-order qBIC modes and reduced scattering losses in shallow-etched designs. Additionally, we demonstrate stable sub-picometer-level wavelength fluctuations in water, with a limit of detection of 10<sup>-5</sup> for environmental refractive index changes. The proposed approach can be extended to BIC metasurfaces with many other configurations and operating wavelengths for ultrahigh-<i>Q</i> applications in both fundamental physics and advanced devices.