Dielectric Mie voids: confining light in air

Manipulating light on the nanoscale has become a central challenge in metadevices,resonant surfaces,nanoscale optical sensors,and many more,and it is largely based on resonant light confinement in dispersive and lossy metals and dielectrics.Here,we experimentally implement a novel strategy for dielectric nanophotonics:Resonant subwavelength localized confinement of light in air.We demonstrate that voids created in high-index dielectric host materials support localized resonant modes with exceptional optical properties.Due to the confinement in air,the modes do not suffer from the loss and dispersion of the dielectric host medium.We experimentally realize these resonant Mie voids by focused ion beam milling into bulk silicon wafers and experimentally demonstrate resonant light confinement down to the UV spectral range at 265 nm(4.68 eV).Furthermore,we utilize the bright,intense,and naturalistic colours for nanoscale colour printing.Mie voids will thus push the operation of functional high-index metasurfaces into the blue and UV spectral range.The combination of resonant dielectric Mie voids with dielectric nanoparticles will more than double the parameter space for the future design of metasurfaces and other micro-and nanoscale optical elements.In particular,this extension will enable novel antenna and structure designs which benefit from the full access to the modal field inside the void as well as the nearly free choice of the high-index material for novel sensing and active manipulation strategies.

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.

Tunable and switchable polarization rotation with non-reciprocal plasmonic thin films at designated wavelengths

We experimentally demonstrate an ultra-thin plasmonic optical rotator in the visible regime that induces a polarization rotation that is continuously tunable and switchable by an external magnetic field.The rotator is a magneto-plasmonic hybrid structure consisting of a magneto-optical EuSe slab and a one-dimensional plasmonic gold grating.At low temperatures,EuSe possesses a large Verdet constant and exhibits Faraday rotation,which does not saturate over a regime of several Tesla.By combining these properties with plasmonic Faraday rotation enhancement,a large tuning range of the polarization rotation of up to 8.4° for a film thickness of 220 nm is achieved.Furthermore,through experiments and simulations,we demonstrate that the unique dispersion properties of the structure enable us to tailor the wavelengths of the tunable polarization rotation to arbitrary spectral positions within the transparency window of the magneto-optical slab.The demonstrated concept might lead to important,highly integrated,non-reciprocal,photonic devices for light modulation,optical isolation,and magnetic field optical sensing.The simple fabrication of EuSe nanostructures by physical vapor deposition opens the way for many potentially interesting magneto-plasmonic systems and three-dimensional magneto-optical metamaterials.

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.