ORCID Profile
0000-0002-3185-0441
Current Organisation
The Hong Kong Polytechnic University
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Publisher: Wiley
Date: 29-01-2023
Abstract: Bound states in the continuum (BICs) offer novel mechanisms to boost the quality factor (Q‐factor) of resonances. Unfortunately, current studies on chiral BICs metasurfaces suffer from a fundamental trade‐off between Q‐factor and circular dichroism (CD), presenting a significant hurdle that severely limits the independent control between CD and Q‐factors. Here, 3D plasmonic metasurfaces are numerically demonstrated that overcome the trade‐off and offer high‐Q quasi‐BIC resonances (Q ≈ 938) with strong CD (≈0.67) in the mid‐infrared. These metasurfaces are made of integrated‐resonance units consisting of a twisted vertical split‐ring resonator (VSRR) and a wall. Importantly, this dissimilar dimer configuration unlocks a new degree of freedom to decouple the Q‐factor and CD, that is, the Q‐factor and CD can be relatively independently manipulated by the height of the wall and the twisted angle of the VSRR, respectively. These results provide novel paradigms to manipulate advanced chiroptical responses, with various applications that require strong CD with enhanced light–matter interaction.
Publisher: Optica Publishing Group
Date: 02-2023
DOI: 10.1364/PRJ.477385
Abstract: Plasmonic resonances empowered by bound states in the continuum (BICs) offer unprecedented opportunities to tailor light–matter interaction. However, excitation of high quality-factor ( Q -factor) quasi-BICs is often limited to collimated light at specific polarization and incident directions, rendering challenges for unpolarized focused light. The major hurdle is the lack of robustness against weak spatial coherence and poor polarization of incident light. Here, addressing this limitation, we demonstrate sharp resonances in symmetric plasmonic metasurfaces by exploiting BICs in the parameter space, offering ultraweak angular dispersion effect and polarization-independent performance. Specifically, a high- Q ( ≈ 71 ) resonance with near-perfect absorption ( 90 % ) is obtained for the input of unpolarized focused light covering wide incident angles (from 0° to 30°). Also, giant electric and magnetic field enhancement simultaneously occurs in quasi-BICs. These results provide a way to achieve efficient near-field enhancement using focused light produced by high numerical aperture objectives.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-11-2018
Publisher: The Optical Society
Date: 09-07-2019
DOI: 10.1364/OE.27.020358
Publisher: Springer Science and Business Media LLC
Date: 21-10-2019
DOI: 10.1038/S41467-019-12637-0
Abstract: Metasurfaces as artificially nanostructured interfaces hold significant potential for multi-functionality, which may play a pivotal role in the next-generation compact nano-devices. The majority of multi-tasked metasurfaces encode or encrypt multi-information either into the carefully tailored metasurfaces or in pre-set complex incident beam arrays. Here, we propose and demonstrate a multi-momentum transformation metasurface (i.e., meta-transformer), by fully synergizing intrinsic properties of light, e.g., orbital angular momentum (OAM) and linear momentum (LM), with a fixed phase profile imparted by a metasurface. The OAM meta-transformer reconstructs different topologically charged beams into on-axis distinct patterns in the same plane. The LM meta-transformer converts red, green and blue illuminations to the on-axis images of “R”, “G” and “B” as well as vivid color holograms, respectively. Thanks to the infinite states of light-metasurface phase combinations, such ultra-compact meta-transformer has potential in information storage, nanophotonics, optical integration and optical encryption.
No related grants have been discovered for Changyuan Yu.