基于二氧化钒相变实现动态可调的亚波长光学材料和器件(特邀)

Dynamically Tunable Optical Materials and Devices Based on Phase Transition of Vanadium Dioxide(Invited)

亚波长人工微纳结构,诸如超构材料和超构表面等,可以实现很多天然材料所不具备的新颖光学性质,为电磁波的操控提供有效手段。但基于静态结构而研制出的光学材料和器件往往只具有固定的光学功能,难以应对复杂多变的实际应用需求。近年来,人们将二氧化钒等相变材料引入人工微纳结构,实现了一系列可调光学材料和器件,其性能可实时改变和动态控制。本文回顾了二氧化钒的结构、相变机制及其物理特性等研究,展示了热、电、光等激发方式对二氧化钒相变的调控,系统总结了基于二氧化钒相变实现动态可调亚波长光学材料和器件的研究进展,期望推动发展新型亚波长动态可调的光电功能材料和器件。

Artificially subwavelength metastructures,such as metamaterials and metasurfaces,can realize novel optical properties that natural materials do not possess and manipulate electromagnetic waves.However,optical materials and devices based on static structures often only have fixed optical functions,which are challenging to deal with complex and changeable application requirements.In recent years,phase change materials such as vanadium dioxide have been introduced into artificial metastructures,realizing a series of tunable optical materials and devices that can dynamically change the functionalities and gain realtime control.This paper reviews recent advances in dynamically tunable optical materials and devices based on the phase transition of vanadium dioxide as following:Firstly,we introduce the research on vanadium dioxide′s structure,phase transition mechanism,and physical properties.Vanadium dioxide undergoes an insulator-metal phase transition when heated to about68℃,and its crystal structure convert from a monoclinic insulator structure to a rutile metal structure.Based on its crystal structure,the Young’s modulus of vanadium dioxide is about 140 GPa,the strain is about 1%,and its mechanical work output per unit volume is as high as 7 J/cm^(3),so vanadium dioxide is suitable for deformable materials or actuator materials.Since the crystal structure of vanadium dioxide changes after the phase transition,its corresponding energy band structure also changes accordingly.Based on the conversion in the crystal structure and energy band structure of vanadium dioxide before and after the phase transition,people have been working to explore the physical mechanism of its phase transition.Although vanadium dioxide has been studied for more than 60 years,its phase transition mechanism has been controversial for a long time.Two theories have long existed for the phase transition mechanism of vanadium dioxide:the first is the Peierls transition caused by lattice distortion;the second is the Mott transition caused by electron correlation.Recent theoretical treatments tend to bridge the gap between the purely Mott-like and purely Peierls-like pictures.Secondly,the phase transition of vanadium dioxide that can be tuned by external excitations such as heat,electricity,and light have been introduced.The refractive index,dielectric function,and resistance of vanadium dioxide before and after the phase transition and during the phase transition undergo reversible and significant changes.This feature makes it possible to dynamically tune the electromagnetic waves.Various external stimulus has been found to excite the phase transition of vanadium dioxide,such as temperature,optical field,electric field,electrical current,magnetic field,electrochemistry and stress.Among them,thermally,electrically or optically tuning phase transitions of vanadium dioxide are suitable for the design of dynamic optical materials and devices,and have been widely used.Therefore,three excitation methods to make phase transition of vanadium dioxide are introduced here.Thirdly,we summarize recent progress on active materials,structures,and devices based on phase transition of vanadium dioxide,including active metamaterials,metasurfaces,plasmonic nanostructures and waveguides.Integrating vanadium dioxide into optical materials and devices endows those based on static artificial micro-nano structures post-fabrication tunablity.So that dynamically tunable optical materials and devices based on vanadium dioxide phase transition can cope with complex and changeable application scenarios and practical requirements for device versatility.Finally,a brief summary and outlook are given.We expect that this article promotes the development of novel active materials and devices in optoelectronics.