Semi-Ellipsoid Nanoarray for Angle-Independent Plasmonic Color Printing

Employing a silver nano semi-ellipsoid nanoarray with high symmetry into applications in plasmonic color printing,we fulfill printing images with colors independent of observing angles.Also,by decreasing the period of a nano semi-ellipsoid array into deep-subwavelength scales,we obtain high reflectivity over 50%,promising high efficiency for imaging generations.A facile technique based on the transfer of anodized aluminum oxide template is developed to fabricate the silver nano semi-ellipsoid nanoarray,realizing plasmonic color printing with features of low cost,scalable,full color and high flexibility.Our approach provides a feasible way to address the angledependent issue in the previous practice of plasmonic color printing,and boosts this field on its way to real-world commercial applications.

Multiplexed manipulation of orbital angular momentum and wavelength in metasurfaces based on arbitrary complex-amplitude control

Due to its unbounded and orthogonal modes,the orbital angular momentum(OAM)is regarded as a key optical degree of freedom(DoF)for future information processing with ultra-high capacity and speed.Although the manipulation of OAM based on metasurfaces has brought about great achievements in various fields,such manipulation currently remains at single-DoF level,which means the multiplexed manipulation of OAM with other optical DoFs is still lacking,greatly hampering the application of OAM beams and advancement of metasurfaces.In order to overcome this challenge,we propose the idea of multiplexed coherent pixel(MCP)for metasurfaces.This approach enables the manipulation of arbitrary complex-amplitude under incident lights of both plane and OAM waves,on the basis of which we have realized the multiplexed DoF control of OAM and wavelength.As a result,the MCP method expands the types of incident lights which can be simultaneously responded by metasurfaces,enriches the information processing capability of metasurfaces,and creates applications of information encryption and OAM demultiplexer.Our findings not only provide means for the design of high-security and high-capacity metasurfaces,but also raise the control and application level of OAM,offering great potential for multifunctional nanophotonic devices in the future.

Strong light–matter interactions based on excitons and the abnormal all-dielectric anapole mode with both large field enhancement and low loss

The room temperature strong coupling between the photonic modes of micro/nanocavities and quantum emitters(QEs) can bring about promising advantages for fundamental and applied physics.Improving the electric fields(EFs) by using plasmonic modes and reducing their losses by applying dielectric nanocavities are widely employed approaches to achieve room temperature strong coupling.However,ideal photonic modes with both large EFs and low loss have been lacking.Herein,we propose the abnormal anapole mode (AAM),showing both a strong EF enhancement of~70-fold (comparable to plasmonic modes) and a low loss of 34 meV,which is much smaller than previous records of isolated all-dielectric nanocavities.Besides realizing strong coupling,we further show that by replacing the normal anapole mode with the AAM,the lasing threshold of the AAM-coupled QEs can be reduced by one order of magnitude,implying a vital step toward on-chip integration of nanophotonic devices.

Full-colour nanoprint-hologram synchronous metasurface with arbitrary hue-saturationbrightness control

The colour gamut,a two-dimensional(2D)colour space primarily comprising hue and saturation(HS),lays the most important foundation for the colour display and printing industries.Recently,the metasurface has been considered a promising paradigm for nanoprinting and holographic imaging,demonstrating a subwavelength image resolution,a flat profile,high durability,and multi-functionalities.Much effort has been devoted to broaden the 2D HS plane,also known as the CIE map.However,the brightness(B),as the carrier of chiaroscuro information,has long been neglected in metasurface-based nanoprinting or holograms due to the challenge in realising arbitrary and simultaneous control of full-colour HSB tuning in a passive device.Here,we report a dielectric metasurface made of crystal silicon nanoblocks,which achieves not only tailorable coverage of the primary colours red,green and blue(RGB)but also intensity control of the individual colours.The colour gamut is hence extruded from the 2D CIE to a complete 3D HSB space.Moreover,thanks to the independent control of the RGB intensity and phase,we further show that a singlelayer silicon metasurface could simultaneously exhibit arbitrary HSB colour nanoprinting and a full-colour hologram image.Our findings open up possibilities for high-resolution and high-fidelity optical security devices as well as advanced cryptographic approaches.

Perturbative countersurveillance metaoptics with compound nanosieves

The progress of metaoptics relies on identifying photonic materials and geometries,the combination of which represents a promising approach to complex and desired optical functionalities.Material candidate options are primarily limited by natural availability.Thus,the search for meta-atom geometries,by either forward or inverse means,plays a pivotal role in achieving more sophisticated phenomena.Past efforts mainly focused on building the geometric library of individual meta-atoms and synthesizing various ones into a design.However,those efforts neglected the powerfulness of perturbative metaoptics due to the perception that perturbations are usually regarded as adverse and in need of being suppressed.Here,we report a perturbation-induced countersurveillance strategy using compound nanosieves mediated by structural and thermal perturbations.Private information can be almost perfectly concealed and camouflaged by the induced thermal-spectral drifts,enabling information storage and exchange in a covert way.This perturbative metaoptics can self-indicate whether the hidden information has been attacked during delivery.Our results establish a perturbative paradigm of securing a safer world of information and internet of things.

Color-selective three-dimensional polarization structures

Polarization as an important degree of freedom for light plays a key role in optics.Structured beams with controlled polarization profles have diverse applications,such as information encoding,display,medical and biological imaging,and manipulation of microparticles.However,conventional polarization optics can only realize two-dimensional polarization structures in a transverse plane.The emergent ultrathin optical devices consisting of planar nanostructures,so-called metasurfaces,have shown much promise for polarization manipulation.Here we propose and experimentally demonstrate color-selective three-dimensional(3D)polarization structures with a single metasurface.The geometric metasurfaces are designed based on color and phase multiplexing and polarization rotation,creating various 3D polarization knots.Remarkably,different 3D polarization knots in the same observation region can be achieved by controlling the incident wavelengths,providing unprecedented polarization control with color information in 3D space.Our research findings may be of interest to many practical applications such as vector beam generation,virtual reality,volumetric displays,security,and anti-counterfeiting.

Integrating lattice and gap plasmonic modes to construct dual-mode metasurfaces for enhancing light–matter interaction

Photonic structures with optical resonances beyond a single controllable mode are strongly desired for enhancing light±matter interactions and bringing about advanced photonic devices. However, the realization of effective multimodal photonic structures has been restricted by the limited tunable range of mode manipulation, the spatial dispersions of electric fields or the polarization-dependent excitations. To overcome these limitations, we create a dualmode metasurface by integrating the plasmonic surface lattice resonance and the gap plasmonic modes;this metasurface offers a widely tunable spectral range, good overlap in the spatial distribution of electric fields, and polarization independence of excitation light. To show that such dual-mode metasurfaces are versatile platforms for enhancing light±matter interactions, we experimentally demonstrate a significant enhancement of second-harmonic generation using our design, with a conversion efficiency of 1±3 orders of magnitude larger than those previously obtained in plasmonic systems. These results may inspire new designs for functional multimodal photonic structures.