Enhanced optical performance of multifocal metalens with conic shapes

A multifocal metalens,which focuses incident light at multiple foci,has many applications in imaging systems and optical communications.However,the traditional design strategy of a multifocal metalens combines several lenses that have different focal points into a planar integrated unit,resulting in low imaging quality because of the high background noise.Here we show that the defects of the traditional method can be overcome by designing a metalens with conic shapes(the ellipse and the hyperbola);this approach could improve the imaging performance and substantially decrease the background noise of multifocal metalenses.These benefits arise from the intrinsic properties of the two conic curves,which can focus incident light constructively at all of the foci of the metalens.We further demonstrate that the proposed conicshaped metalens can function well within a broadband operation wavelength that ranges from 600 to 900 nm with the dual polarity actively controlled by the incident circular polarized light.The great agreement between the experimental and simulation results demonstrates that our proposed metalens has significant potential for use in future integrated nanophotonic devices.

Experimental investigation on ice-breaking performance of a novel plasma striker

Aircraft icing has long been a plague to aviation for its serious threat to flight safety.Recently,researches about a newly proposed deicing method based on Plasma Synthetic Jet Actuator(PSJA)have just started.To meet the requirements of in-flight deicing,structure of PSJA needs to be adjusted.This paper completed the detailed design and experimental validation of a novel plasma striker,which was a modified version of PSJA.Influences of mass of the moving part and rod shapes on the ice-breaking performances were also studied.Besides,a“conical-nosed rod configuration”was proposed.Its purpose was to ensure a good ice-breaking performance of the plasma striker on long ice,by generating a splitting failure.Results show that,though mass of the moving part was just several grams,ice-breaking performance was better when the mass was lighter.The rectangular rod could generate an elliptical circumferential crack,whose major axis was parallel to the direction of the long side of the rectangular rod.And the“conical-nosed rod”concept was verified to be able to generate a splitting crack which can spread completely to the far end of long ice,and the crack direction was parallel to edge line of the cone.In general,the plasma striker has the advantages of simple structure,low energy consumption,little harm to the flow field and the aircraft skin.Simulations will be carried out in future works to study in detail the working process of the plasma striker.