Switchable dual-band to broadband terahertz metamaterial absorber incorporating a VO₂ phase transition

Abstract

We design and demonstrate a thermally switchable terahertz metamaterial absorber consisting of an array of orthogonal coupled split-ring metal resonators involving a VO2 phase transition. Numerical results indicate that the active metamaterial always absorbs the TE wave in dual-band regardless of insulating and metallic VO2, while the insulator-to-metal phase transition enables a switchable effect between dual-band and broadband absorption of the TM wave with the resonant frequency tunability of 33%. Especially under the metallic VO2 state, the absorption properties are polarization-dependent and exhibit a switching effect between dual-band and broadband absorption with the increase of the polarization angle. The tunable absorption mechanism can be explained by effective impedance theory and electric energy density distributions. The proposed dual-band to broadband metamaterial switching absorber may have broad applications in sensors, imaging and emitters.

Broadband Polarization‐Insensitive Coherent Rasorber in Terahertz Metamaterial with Enhanced Anapole Response and Coupled Toroidal Dipole Modes

“…Due to the periodicity of the antireflection effect, the identical frequency interval can exist in the spectrum, thus engendering the antireflection phenomenon in a narrow band around f AR . According to Equation (10), by adopting the appropriate dispersion spectrum of n, the sustainable antireflection behavior can appear in a wider band, resulting in great coherent absorption covering the wide frequency band. The investigation of absorption efficiency corresponding to different thicknesses h 1 and refractive index n of the antireflection coating has been performed.…”

“…[ 1,2 ] To meet multispectral stealth requirements in modern electronic warfare, many substructures and compatible multispectral absorbing materials have been adopted to achieve the multiband or broadband electromagnetic energy absorption in the microwave, THz, visible light, and infrared bands. [ 3–7 ] Furthermore, the MMAs with dynamically tunable absorption peaks and the operating band have been proposed in recent years depending on the tunable absorbing materials, e.g., graphene, [ 8 ] crystals, [ 9 ] vanadium dioxide, [ 10 ] etc. However, the high absorption in the entire operation band also traps the electromagnetic wave, thus immensely preventing the equipment from communicating with other systems.…”

Switchable ultra-broadband terahertz wave absorption with VO2-based metasurface

“…For instance, in order to expand the bandwidth, methods such as incorporating multiple resonant modes on a plane or in multiple layers 20 – 25 , and lowering the Q-factor in the resonant system by using high-loss metals 26 – 28 have been extensively studied. On the other hand, tunable MMs based on active materials such as graphene 29 – 33 , or phase-changing materials (PCMs) 34 – 42 have also been widely investigated. In particular, vanadium dioxide (VO 2 )-based MMAs exhibit unique properties thanks to the insulator-to-metal transition (IMT) feature of VO 2 .…”

Optically Transparent Microwave Shielding Hybrid Film Composited by Metal Mesh and Graphene

“…By properly designing and etching the periodic meta-atoms of optically transparent thin film, significant electromagnetic absorption can be achieved at the cost of little optical transmissive insertion loss over a relatively broad frequency spectrum [10]. Different from the absorption-type [11] transparent electromagnetic shielding materials, homogeneous transparent conductive thin films without periodic patterns can achieve reflection-type electromagnetic shielding functionality [12]. Enhanced microwave absorption is also observed in a random disperse system containing conductive (charged) particles [13,14].…”