Multichannel vectorial holographic display and encryption

Since its invention,holography has emerged as a powerful tool to fully reconstruct the wavefronts of light including all the fundamental properties(amplitude,phase,polarization,wave vector,and frequency).For exploring the full capability for information storage/display and enhancing the encryption security of metasurface holograms,smart multiplexing techniques together with suitable metasurface designs are highly demanded.Here,we integrate multiple polarization manipulation channels for various spatial phase profiles into a single birefringent vectorial hologram by completely avoiding unwanted cross-talk.Multiple independent target phase profiles with quantified phase relations that can process significantly different information in different polarization states are realized within a single metasurface.For our metasurface holograms,we demonstrate high fidelity,large efficiency,broadband operation,and a total of twelve polarization channels.Such multichannel polarization multiplexing can be used for dynamic vectorial holographic display and can provide triple protection for optical security.The concept is appealing for applications of arbitrary spin to angular momentum conversion and various phase modulation/beam shaping elements.

Metasurface interferometry toward quantum sensors

Optical metasurfaces open new avenues for the precise wavefront control of light for integrated quantum technology.Here,we demonstrate a hybrid integrated quantum photonic system that is capable of entangling and disentangling two-photon spin states at a dielectric metasurface.Via the interference of single-photon pairs at a nanostructured dielectric metasurface,a path-entangled two-photon NOON state with circular polarization that exhibits a quantum HOM interference visibility of 86±4% is generated.Furthermore,we demonstrate nonclassicality andphase sensitivity in a metasurface-based interferometer with a fringe visibility of 86.8±1.1%in the coincidence counts.This high visibility proves the metasurface-induced path entanglement inside the interferometer.Our findings provide a promising way to develop hybrid-integrated quantum technology operating in the high-dimensional mode space in various applications,such as imaging,sensing,and computing.

Nonlinear optics in all-dielectric nanoantennas and metasurfaces:a review

Free from phase-matching constraints,plasmonic metasurfaces have contributed significantly to the control of optical nonlinearity and enhancement of nonlinear generation efficiency by engineering subwavelength meta-atoms.However,high dissipative losses and inevitable thermal heating limit their applicability in nonlinear nanophotonics.All-dielectric metasurfaces,supporting both electric and magnetic Mie-type resonances in their nanostructures,have appeared as a promising alternative to nonlinear plasmonics.High-index dielectric nanostructures,allowing additional magnetic resonances,can induce magnetic nonlinear effects,which,along with electric nonlinearities,increase the nonlinear conversion efficiency.In addition,low dissipative losses and high damage thresholds provide an extra degree of freedom for operating at high pump intensities,resulting in a considerable enhancement of the nonlinear processes.We discuss the current state of the art in the intensely developing area of all-dielectric nonlinear nanostructures and metasurfaces,including the role of Mie modes,Fano resonances,and anapole moments for harmonic generation,wave mixing,and ultrafast optical switching.Furthermore,we review the recent progress in the nonlinear phase and wavefront control using all-dielectric metasurfaces.We discuss techniques to realize alldielectric metasurfaces for multifunctional applications and generation of second-order nonlinear processes from complementary metal–oxide–semiconductor-compatible materials.

All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers

Dynamic control of compact chip-scale contactless manipulation of particles for bioscience applications remains a challenging endeavor,which is restrained by the balance between trapping efficiency and scalable apparatus.Metasurfaces offer the implementation of feasible optical tweezers on a planar platform for shaping the exerted optical force by a microscale-integrated device.Here we design and experimentally demonstrate a highly efficient silicon-based metalens for two-dimensional optical trapping in the near-infrared.Our metalens concept is based on the Pancharatnam–Berry phase,which enables the device for polarization-sensitive particle manipulation.Our optical trapping setup is capable of adjusting the position of both the metasurface lens and the particle chamber freely in three directions,which offers great freedom for optical trap adjustment and alignment.Two-dimensional(2D)particle manipulation is done with a relatively low-numerical-aperture metalens(NA(ML)=0.6).We experimentally demonstrate both 2D polarization-sensitive drag and drop manipulation of polystyrene particles suspended in water and transfer of angular orbital momentum to these particles with a single tailored beam.Our work may open new possibilities for lab-on-a-chip optical trapping for bioscience applications and microscale to nanoscale optical tweezers.

Metasurfaces help lasers to mode-lock

Metasurface saturable absorbers may result in versatile mode-locking that allows one to obtain stable ultrashort laser pulses with high repetition rates and peak powers,along with broadband operation,within fiber to solid-state laser cavities.

Phase-controlled propagation of surface plasmons

Directional emission of electromagnetic radiation can be achieved using a properly shaped single antenna or a phased array of individual antennas.Control of the individual phases within an array enables scanning or other manipulations of the emission,and it is this property of phased arrays that makes them attractive in modern systems.Likewise,the propagation of surface plasmons at the interface between metal films and dielectric materials can be determined by shaping the individual surface nanostructures or via the phase control of individual elements in an array of such structures.Here,we demonstrate control of the propagation of surface plasmons within a linear array of nanostructures.The generic situation of plasmonic surface propagation that is different on both sides of a metal film provides a unique opportunity for such control:plasmons propagating on the slower side feed into the side with the faster propagation,creating a phased array of interfering antennas and thus controlling the directionality of the wake fields.We further show that by shaping the individual nanoantennas,we can generate an asymmetric propagation geometry.