Metasurface-based structural coloration is a promising enabling technology for advanced optical encryption with a high-security level. Herein, we propose a paradigm of electrically switchable, polarization-sensitive optical encryption based on designed metasurfaces
Chiral metasurfaces can exhibit a strong circular dichroism, but it is limited by the complicated fabrication procedure and alignment errors. Here, a new type of self‐aligned suspended chiral bilayer metasurface with only one‐step electron beam lithography exposure is demonstrated. A significant optical chirality of 221° µm−1 can be realized using suspended metasurfaces with a thickness of 100 nm. Furthermore, this study experimentally demonstrates that such a structure is capable of label‐free discrimination of the chiral molecules at zeptomole level, exhibiting a much higher sensitivity (orders of magnitude) compared to the conventional circular dichroism spectroscopy. The fundamental principles for chiral sensing using molecules–metasurfaces interactions are explored. Benefiting from the giant chiroptical response, the proposed metadevice may offer promising applications for ultrathin circular polarizers, chiral molecular detectors, and asymmetry information processing.
A lightweight and portable spectrometer is desirable for miniaturization and integration. The unprecedented capability of optical metasurfaces has shown much promise to perform such a task. We propose and experimentally demonstrate a compact high-resolution spectrometer with a multi-foci metalens. The novel metalens is designed based on wavelength and phase multiplexing, which can accurately map the wavelength information into its focal points located on the same plane. The measured wavelengths in the light spectra agree with simulation results upon the illumination of various incident light spectra. The uniqueness of this technique lies in the novel metalens that can simultaneously realize wavelength splitting and light focusing. The compactness and ultrathin nature of the metalens spectrometer render this technology have potential applications in on-chip integrated photonics where spectral analysis and information processing can be performed in a compact platform.
Chirality induction, transfer, and
manipulation have aroused great
interest in achiral nanomaterials. Here, we demonstrate strong upconverted
circularly polarized luminescence from achiral core–shell upconversion
nanoparticles (UCNPs) via a plasmonic chiral metasurface-induced optical
chirality transfer. The Yb3+-sensitized core–shell
UCNPs with good dispersity exhibit intense upconversion luminescence
of Tm3+ and Nd3+ through the energy transfer
process. By spin-coating the core–shell UCNPs on this chiral
metasurface, strong enhancement and circular polarization modulation
of upconversion luminescence can be achieved due to resonant coupling
between surface plasmons and upconversion nanoparticles. In the UCNPs-on-metasurface
composite, a significant upconversion luminescence enhancement can
be achieved with a maximum enhancement factor of 32.63 at 878 nm and
an overall enhancement factor of 11.61. The luminescence dissymmetry
factor of the induced upconverted circularly polarized luminescence
can reach 0.95 at the emission wavelength of 895 nm. The UCNPs-on-metasurface
composite yields efficient modulation for the emission intensity and
polarization of UCNPs, paving new pathways to many potential applications
in imaging, sensing, and anticounterfeiting fields.
Metasurfaces
A self‐aligned suspended chiral bilayer metasurface via single‐step electron‐beam lithography is reported by Tun Cao, Yan Jun Liu, and co‐workers in article number 2203956. A huge optical chirality of 221° μm−1 is achieved by the free‐standing metasurfaces with overall thickness of 100 nm. The bilayer metasurface demonstrates label‐free discrimination of chiral molecules at zeptomole level, with sensitivity orders of magnitude larger than conventional circular dichroism spectroscopy.
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