Asymmetrical photonic spin Hall effect based on dielectric metasurfaces

The photonic spin Hall effect has attracted considerable research interest due to its potential applications in spincontrolled nanophotonic devices.However,realization of the asymmetrical photonic spin Hall effect with a single optical element is still a challenge due to the conjugation of the Pancharatnam-Berry phase,which reduces the flexibility in various applications.Here,we demonstrate an asymmetrical spin-dependent beam splitter based on a single-layer dielectric metasurface exhibiting strong and controllable optical response.The metasurface consists of an array of dielectric nanofins,where both varying rotation angles and feature sizes of the unit cells are utilized to create high-efficiency dielectric metasurfaces,which enables to break the conjugated characteristic of phase gradient.Thanks to the superiority of the phase modulation ability,when the fabricated metasurface is under normal incidence with a wavelength of 1550 nm,the lefthanded circular polarization(LCP)light exhibits an anomalous refraction angle of 28.9°,while the right-handed circular polarization(RCP)light transmits directly.The method we proposed can be used for the flexible manipulation of spin photons and has potentials in high efficiency metasurfaces with versatile functionalities,especially with metasurfaces in a compact space.

Dual-band polarized upconversion photoluminescence enhanced by resonant dielectric metasurfaces

Lanthanide-doped upconversion nanoparticles emerged recently as an attractive material platform underpinning a broad range of innovative applications such as optical cryptography,luminescent probes,and lasing.However,the intricate 4f-associated electronic transition in upconversion nanoparticles leads only to a weak photoluminescence intensity and unpolarized emission,hindering many applications that demand ultrabright and polarized light sources.Here,we present an effective strategy for achieving ultrabright and dual-band polarized upconversion photoluminescence.We employ resonant dielectric metasurfaces supporting high-quality resonant modes at dual upconversion bands enabling two-order-of-magnitude amplification of upconversion emissions.We demonstrate that dual-band resonances can be selectively switched on polarization,endowing cross-polarization controlled upconversion luminescence with ultra-high degrees of polarization,reaching approximately 0.86 and 0.91 at dual emission wavelengths of 540 and 660 nm,respectively.Our strategy offers an effective approach for enhancing photon upconversion processes paving the way towards efficient low-threshold polarization upconversion lasers.

Full-Stokes polarization transformations and time sequence metasurface holographic display

With the development of micro/nano fabrication technology, metasurface holography has emerged as a revolutionary technology for the manipulation of light with excellent performance. However, for applications of full-Stokes polarization encryption and time sequence holographic display, multiplexing strategies of metasurfaces with large bandwidths and simple operations still need to be developed. As one of the most popular schemes of multiplexing, polarization multiplexed metasurfaces have shown flexible recording abilities for both free-space beam and surface waves. Here, by using a dielectric metasurface equipped with double phase holograms, we have achieved flexible polarization multiplexed transformations from one full-Stokes space to another. The vectorial hologram is optimized by a hybrid genetic algorithm and digitalized with subwavelength modulated units. Based on a quantitative map and remarkable information capacity, time sequence holographic display and complex optical encryption are experimentally demonstrated by changing input/output polarization channels in real time. We believe our method will facilitate applications in smart compact devices of dynamic display, dynamic optical manipulation,optical encryption, anticounterfeiting, etc.

Correlated triple hybrid amplitude and phase holographic encryption based on a metasurface

Metasurface holography is becoming a universal platform that has made a considerable impact on nanophotonics and information optics,due to its advantage of large capacity and multiple functionalities.Here,we propose a correlated triple amplitude and phase holographic encryption based on an all-dielectric metasurface.We develop an optimized holographic algorithm to obtain quantitatively correlated triple holograms,which can encrypt information in multiple wavelength and polarization channels.We apply the“static”and“dynamic”pixels in our design,respectively.Two kinds of isotropic square nanofins are selected,one functioning as a transmitter and the other functioning as a blocker counterintuitively at both working wavelengths,while another anisotropic rectangle nanofin can transmit or block light in co-polarization selectively,mimicking“dynamic”amplitude switches.Meanwhile,such“dynamic”nanofins can simultaneously function as a phase modulator in cross-polarization only at the transmission wavelength.That is,through smart design,different dielectric meta-atoms functioning as spectral filters as well as phase contributors can compositely achieve triple hybrid amplitude and phase holograms.Such strategy promises to be applied in compact large-capacity information storage,colorful holographic displays,optical encryption,multifunctional imaging devices,and so on.