Low-Contrast BIC Metasurfaces with Quality Factors Exceeding 100,000

High Resolution Image Download MS PowerPoint Slide Dielectric metasurfaces operating at quasi-bound states in the continuum (qBICs) can achieve exceptionally high radiative quality ( Q ) factors by introducing small asymmetries into their unit cells. However, fabrication imperfections often impose major limitations on the experimentally observed Q factors. In this study, we experimentally demonstrate BIC metasurfaces with a Q 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- Q factors can be attained by leveraging both the high radiative Q 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 –5 for environmental refractive index changes. The proposed approach can be extended to BIC metasurfaces with many other configurations and operating wavelengths for ultrahigh- Q applications in both fundamental physics and advanced devices.