A waveguide metasurface based quasi-far-field transverse-electric superlens

The imaging capability of conventional lenses is mainly limited by the diffraction of light,and the so-called superlens has been developed allowing the recovery of evanescent waves in the focal plane.However,the remarkable focusing behavi-or of the superlens is greatly confined in the near-field regime due to the exponential decay of evanescent waves.To tackle this issue,we design a waveguide metasurface-based superlens with an extraordinary quasi-far-field focusing capability beyond the diffraction limit in the present work.Specifically,we analyze the underlying physical mechanism and provide experimental verification of the proposed superlens.The metasurface superlens is formed by an array of gradient nanoslits perforated in a gold slab,and supports transverse-electric(TE)waveguide modes under linearly polar-ized illumination along the long axis of the slits.Numerical results illustrate that exciting such TE waveguide modes can modulate not only optical phase but also evanescent waves.Consequently,some high-spatial-frequency waves can con-tribute to the focusing of the superlens,leading to the quasi-far-field super-resolution focusing of light.Under 405 nm illu-mination and oil immersion,the fabricated superlens shows a focus spot of 98 nm(i.e.λ/4.13)at a focal distance of 1.49μm(i.e.3.68λ)using an oil immersion objective,breaking the diffraction limit ofλ/2.38 in the quasi-far field regime.The developed metasurface optical superlens with such extraordinary capabilities promises exciting avenues to nanolitho-graphy and ultra-small optoelectronic devices.

Transition metal dichalcogenide-based mixed-dimensional heterostructures for visible-light-driven photocatalysis:Dimensionality and interface engineering

Two-dimensional(2D)transition metal dichalcogenides(TMDCs)are emerging as promising building blocks of high-performance photocatalysts for visible-light-driven water splitting because of their unique physical,chemical,electronic,and optical properties.This review focuses on the fundamentals of 2D TMDC-based mixed-dimensional heterostructures and their unique properties as visible-light-driven photocatalysts from the perspective of dimensionality and interface engineering.First,we discuss the approaches and advantages of surface modification and functionalization of 2D TMDCs for photocatalytic water splitting under visible-light illumination.We then classify the strategies for improving the photocatalytic activity of 2D TMDCs via combination with various low-dimensional nanomaterials to form mixed-dimensional heterostructures.Further,we highlight recent advances in the use of these mixed-dimensional heterostructures as high-efficiency visible-light-driven photocatalysts,particularly focusing on synthesis routes,modification approaches,and physiochemical mechanisms for improving their photoactivity.Finally,we provide our perspectives on future opportunities and challenges in promoting real-world photocatalytic applications of 2D TMDC-based heterostructures.

Fine-tune chiroptical activity in discrete chiral Au nanorods

Accurate researches on the surface plasmon resonance(SPR)-based applications of chiral plasmonic metal nanoparticles(NPs)still remain a great challenge.Herein,a series of chiral plasmonic metal NPs,e.g.,chiral Au nanorods(c-Au NRs),c-Au@Ag core–shell,and c-Au@TiO_(2) core–shell NRs,with different chiroptical activities have been produced.Plasmonic circular dichroism(PCD)bands of c-Au NRs can be precisely tailored by tuning the longitudinal SPR(LSPR)and amount of Au NRs as seeds.Besides,a shift of PCD bands within ultraviolet–visible–near infrared ray(UV–vis–NIR)region can also be achieved through the functionalization of a shell of another metal or semiconductor.Interestingly,chirality transfer from c-Au core to Ag shell leads to new PCD bands at the near-UV region.The tuning of PCD bands and chirality transfer are confirmed by our developed theoretical model.Developing chiral Au NRs-based chiral plasmonic nanomaterials with tunable chiroptical activities will be helpful to understand the structure-direct PCD and to extend circularly polarized-based applications.