摘要
超材料具有在亚波长尺度下操控电磁波的能力,近年来,通过对光场、电场、机械或温度场动态调控可以改变其光学特性的主动式超材料受到了广泛的研究。二氧化钒具有在68℃的临界温度下从低温绝缘相转变为高温金属相的特性,其电导率能够实现4~5个数量级的变化,将二氧化钒与超材料相互结合,能够满足可调谐性、高调制深度、多种调谐手段等优点。本文从二氧化钒的相变特性出发,归纳总结了二氧化钒在太赫兹超材料中的不同应用方向,主要包括可调谐太赫兹超材料吸波器、太赫兹调制器、太赫兹波前调控器以及可编程超材料,最后讨论了二氧化钒在太赫兹超材料应用中所面临的挑战和未来的发展方向。
There are many applications for terahertz (THz) waves at different frequencies from 0.1 THz to 10 THz and different wavelengths between millimeter waves and infrared light.THz waves have attracted recent attention due to their extensive applications in detection,imaging,and communication.In terms of the properties of natural materials to THz waves,THz modulation devices have some limitations due to the natural material properties.THz metamaterials,which use periodic structures to modify the phase,amplitude,polarization,and propagation mode of THz waves,can overcome the limitations of natural materials.Compared to passive metamaterials with fixed optical properties,active metamaterials are more capable of reconfiguring and programmability.An active metamaterial can be achieved via combining metamaterial structural units with tunable functional materials.Vanadium dioxide(VO_(2)),undergoing a metal-insulator phase transition,exhibits modulation depths exceeding 85% in electromagnetic wave transmittance from infrared to THz frequencies.Compared with other phase transition materials (i.e.,GeTe),the phase transition temperature is closer to room temperature.VO_(2) has a promising application in active THz metamaterials due to its characteristics.This review represented the design principles and development of reconfigurable THz metamaterials based on VO_(2),emphasizing the structural design and performance of devices for tunable THz modulation.The structure and performance of VO_(2)-based THz metamaterials were described.In the first part of this review,the application of VO_(2) in tunable THz metamaterial absorbers is represented.The phase transition of VO_(2) alters the equivalent resistance,capacitance and inductance of the periodic pattern via replacing the conventional surface metal patterns of absorbers with patterned VO_(2),resulting in tunable resonance absorption frequencies and absorption rates.Moreover,combining VO_(2) with different resonance patterns or other functional materials can further enhance the modulation depth and modulation frequency of THz absorbers.In the second part of this review,we discuss the application of VO_(2) in THz modulator devices based on the electromagnetically induced transparency (EIT) effect.The EIT effect in metamaterials is achieved via coupling"bright modes"and"dark modes"in an external field to generate a transparent window.Integrating VO_(2) into such terahertz metamaterials can improve the instability issue of traditional materials in exciting the EIT effect and further enhance the tunability of metamaterials.This approach also provides a feasible solution for information encryption.In addition,compared to conventional metamaterials for wavefront manipulation,the combination of VO_(2) and metamaterials allows a simultaneous manipulation of the amplitude and phase of THz waves,which significantly improves a holographic imaging quality and offers a design approach for THz imaging,optical encryption,optical communication,and other applications.Note that although the phase transition performance of vanadium dioxide can be adjusted theoretically,the thermal control method is susceptible to the influence of thermal diffusion from neighboring units,resulting in a thermal crosstalk.It is thus essential for future efforts increasing unit density and improving the quality of holographic imaging to integrate low thermal conductivity materials between unit structures.In the final part of this review,we introduce the use of VO_(2) in THz programmable metamaterials.Programmable metamaterials provide some design concepts and directions for metamaterials development.Combining VO_(2) with metamaterials and the hysteresis effect of first-order phase transition,VO_(2) demonstrates as a nonvolatile storage component in programmable metamaterials.In this approach,transition states are stored as"memory",allowing for intelligent THz electromagnetic information processing,and this memory functionality can be also used for adaptive control.Summary and prospects Despite the development of tunable THz metamaterials based on different principles,there are some challenges associated with the difficult etching of VO_(2) as well as the limited precision of the process.In addition,VO_(2) is not the most stable phase of vanadium oxide,which is greatly affected by oxygen during etching,affecting the performance of THz metamaterial devices.For future applications,power consumption and response time must be considered.It is therefore possible to achieve lower power consumption and faster thermal response time via doping vanadium dioxide or tuning the stain by the substrate to lower the phase transition temperature,although this may introduce some challenges such as a decrease in the magnitude of the conductivity change after the phase transition and a reduction in modulation depth.By contrast,it is possible to significantly improve the response time of devices by using pulsed intense laser excitation.Furthermore,machine learning and other methods can be integrated to achieve additional structural optimization.Field-programmable gate array (FPGA) controlled programmable metamaterials,which can switch different functions via changing input encoding sequences in real time,and greatly extend the application of metamaterials by dynamically manipulating electromagnetic waves.Metamaterials application and functionality will be enhanced by adding sensors to detect temperature,humidity,illumination,etc.,facilitating the development of intelligent electromagnetic metamaterials with tunable properties in the future.
作者
高敏
罗毅恒
路畅
林媛
GAO Min;LUO Yiheng;LU Chang;LIN Yuan(School of Materials and Energy,University of Electronic Science and Technology of China,Chengdu 610054,China)
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
2024年第7期2371-2380,共10页
Journal of The Chinese Ceramic Society
基金
国家自然科学基金(52272138,61825102,52021001)
四川省科技计划(2022ZHCG0041)。
关键词
超材料
二氧化钒
相变材料
可调谐
metamaterial
vanadium dioxide
phase change materials
tunable
