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The all-dielectric metasurface supporting BIC based on dimer structures is proposed with the rectangular holes etched in amorphous silicon thin films. By introducing perturbations of the rotation angle of the rectangular hole as well as the difference in length and width, quasi-BIC modes in the near-infrared band can be created. Meanwhile, the research found that two different perturbations display different tuning abilities on the Fano resonance induced by the quasi-BIC. This paper reveals that the formation of the BIC mode originates from the interference between competing multipole moments, which ultimately leads to the emergence of a pair of reverse parallel electric dipoles. It explains the mismatch between the macroscopic response of the structure under the influence of competing multipole moments and the results of the multipole expansion. From the perspective of the influence of asymmetry on multipole moments, we explain the resulting radiation sources. The study demonstrates that the proposed dimer metasurface can support optical sensing under both x-polarization and circular polarization excitation, and it is observed that different perturbations have different abilities to modulate the sensitivity, which has great potential for device performance optimization and precise modulation. more...

In this study, based on the single-layer metasurface structure, a dual-wavelength polarization multiplexing metalens is designed at the communication wavelengths of 1310 nm and 1550 nm, respectively. Using the dual-phase modulation method, a single-wavelength polarization multiplexing metalens is proposed, which can simultaneously control left-handed circularly polarized light (LCP) and right-handed circularly polarized light (RCP). Furthermore, the cross superposition method is used to combine them to achieve the dual-wavelength polarization multiplexing metalens. The results show that the system can achieve polarization multiplexing at the two wavelengths of 1310 nm and 1550 nm, which is consistent with the expected results, and the focusing efficiency reached 61%. With the increase of the numerical aperture, the focusing intensity of the left and right focal points gradually approaches, and the difference between the full width at half maximum of the two focal points also decreases accordingly. It provides a new way for the optical imaging, information detection and the realization of multifunctional ultra-surface devices. more...

We construct a numerical model for a liquid microlens formed by filling a microwell with two immiscible liquids, namely oil and water. The water–oil interface can be actuated as a tunable liquid lens because its curvature is well controlled by applying an external electric field. The contact angle of the oil droplet has the opposite tendency to that of a traditional water-filled microwell because of the repulsion force from the water phase. We study the dynamic interface deformation as functions of time and applied voltage, which typically within 10 ms is good enough as an imaging system for human eyes. In addition, using two different filling liquids provides more possibilities for tuning the focal length. more...