Phase Change Material Vanadium Dioxide Research Articles

Structural color tunable intelligent mid-infrared thermal control emitter

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of εH = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of εL = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials.

Study of the photothermal response of a multilayer structure doped with VO2@Au nanoshells

In this paper, we demonstrate a theoretical study of a multiphysics problem to solve for the photothermal response of a one-dimensional multilayer structure containing a layer doped with VO2@Au nanoshells. The VO2@Au nanoshell consists of a gold (Au) shell and a core of the phase change material vanadium dioxide (VO2) where the VO2 core transitions from a semiconductor state to a conductor state at the critical temperature of 68 °C. This behaviour results in thermal induced optical tunability through this reversible phase change of the VO2, due to the temperature dependent optical and thermal properties. The presence of the VO2 core, functioning as an ultra-fast and reversible optical phase-change material, leads to the emergence of photothermal induced bistability. The layer doped with the VO2@Au nanoshell is approximated as an effective medium using the Maxwell-Garnett Theory to enable an analytical solution. In this study, the optical response of the multilayer structure is obtained using the Transfer Matrix Method, while the thermal response for both stationary and transient states is solved using the Green’s Function Method and Kirchhoff’s Transformation. These equations are interconnected through the heat source term in the heat diffusion equations, representing the local heat generation induced by the continuous-wave laser applied to the structure. Our findings indicate that at the wavelengths of 658 nm and 747 nm, there are two distinct photothermal responses arising from the phase change of the VO2 core. At these wavelengths, the absorption of light increases and decreases, respectively, because of the VO2 phase change. This analytical method not only offers a thorough exploration of the fundamentals of induced photothermal responses in multilayer structures but also holds considerable potential for various applications, including solar cells, photothermal therapy, and nanothermal sensors.

Tunable terahertz perfect absorber using vanadium dioxide-based metamaterial for sensing applications

We present a design of terahertz (THz) perfect absorber (TPA) based on thermotropic phase change material vanadium dioxide (VO2). The TPA device is composed of a metal-insulator-metal (MIM) structure, and the top metal layer is tailored to form an inner VO2-based disk structure and an outer Au-based connected-ring structure. The electromagnetic responses of TPA device with different geometric parameters operated in the THz band are investigated, and the perfect absorption is achieved at 2.51 THz. Furthermore, by increasing the temperature applied on VO2 from 313 K to 363 K with an interval of 10 K, the disk structure changes from an insulating phase to a metallic phase. There is an extra resonance mode arises, which induces the resonance of TPA device can be switched from single to dual. Additionally, being exposed to an ambient environment with different refraction indices, the TPA device shows a high-efficient sensing capability with a sensitivity of up to 398 GHz per refractive index unit (RIU). These results indicate that the proposed design opens an avenue for tunable absorbers, actively controllable switches, THz logic devices, and high-efficiency sensors.

Photonic thermal switch via metamaterials made of vanadium dioxide-coated nanoparticles.

In this work, a photonic thermal switch is proposed based on the phase-change material vanadium dioxide (VO2) within the framework of near-field radiative heat transfer (NFRHT). The switch consists of two metamaterials filled with core-shell nanoparticles, with the shell made of VO2. Compared to traditional VO2 slabs, the proposed switch exhibits a more than two times increase in the switching ratio, reaching as high as 90.29% with a 100 nm vacuum gap. The improved switching effect is attributed to the capability of the VO2 shell to couple with the core, greatly enhancing heat transfer with the insulating VO2, while blocking the motivation of the core in the metallic state of VO2. The proposed switch opens pathways for active control of NFRHT and holds practical significance for developing thermal photon-based logic circuits.

Multifunctional metamaterial for realizing absorption and polarization conversion on the basis of vanadium dioxide

In this paper, the phase change material vanadium dioxide (VO2) is introduced to propose a tunable multifunctional metamaterial device, which treats the phase change property of VO2 to realize the switching of absorption, linear to linear (LTL) polarization conversion, and linear to circular (LTC) polarization conversion functions. When VO2 is in metal state, the structure can be applied as an absorber to achieve the wide-band and narrow-band absorption. In the broad frequency area of 2.007–2.803 THz, the absorption is above 90%. And the narrow-band absorption near the center frequency 1.0126 THz reaches 95.04%. When VO2 is in the insulator state, the studied device can be treated as a polarization conversion device to achieve LTL and LTC polarization conversion. In the low frequency range, the device achieves LTL with polarization conversion efficiency (PCR) above 90% when the frequency is between 0.439 and 0.907 THz. In the high frequency range, the structure can be treated as the LTC polarization converter to achieve right-hand circular polarization, left-hand circular polarization (LHCP), and LHCP in the ranges of 2.317–2.329 THz, 2.356–2.531 THz and 2.582–2.633 THz, respectively. In addition, the ellipticity is above 0.9. Finally, the effects of geometric parameters, angle of incidence and polarization angle on the absorption and PCR are also discussed. The proposed structure has great potential for advanced technologies such as imaging, sensing, communication, and stealth.

Research on the OAM and reduction of RCS of a dynamically tunable terahertz reconfigurable metasurface

A dynamically tunable reconfigurable metasurface in the terahertz (THz) band combined with the phase-change material vanadium dioxide (VO2) is proposed. Through theoretical and simulation study, the dynamic tunable reconfigurable metasurface designed in this paper works in the wide band of 1.09–2.13 THz frequency, and the polarization conversion ratio of the metasurface can reach more than 95%. Further, the relative bandwidth can reach more than 74%, and it still has good performance after the phase transformation of VO2. A metasurface coded with 3 bits and a special phase arrangement can control the electromagnetic wavefront, generate orbital angular momentum, focus vortices, reflect anomalously, and achieve radar cross section reduction. Therefore, the proposed metasurface has potential applications in secure communication, near-field imaging, wireless transmission, etc.

Tunable smart mid infrared thermal control emitter based on phase change material VO2 thin film

Thermal radiation is one of the three ways of heat transfer, among which the mid-infrared thermal radiation has attracted much attention. At present, static control of thermal emissivity has been unable to meet the practical application, the device of dynamic control of thermal radiation is expected. In this paper, we study an intelligent thermal controlled radiation emitter based on a layered structure formed by phase change material Vanadium Dioxide. The transition denaturation of Vanadium Dioxide can realize the switching process from heat dissipation at high temperature to heat preservation at low temperature. In the mid-infrared wavelength range of 5–13 μm, significant differences in emission characteristics are observed due to variations in the imaginary part of the dielectric constant of Vanadium Dioxide. When it is in the high temperature metallic state, the optimal structural parameters, from top to bottom, are 10 nm, 350 nm, 320 nm, and 200 nm. With these parameters, the structure exhibits an emissivity of 0.78 and a full width at half maximum of 8.03 μm. This configuration achieves effective thermal radiation dissipation, as governed by the Stefan-Boltzmann’s law. On the other hand, when the structure is in the low temperature dielectric state, it exhibits a low absorption effect with an emissivity of 0.10, thus avoiding excessive heat loss. The radiative modulation capability and thermal stability were achieved through the use of thermochromic material Vanadium Dioxide which exhibits temperature switchable behavior. Additionally, the thermal control emitter, utilizing its resonant cavity, enables tunability of peak wavelength and demonstrates a certain degree of independence with respect to polarization and incident angle. The designed emitter structure is simple and easy to fabricate, holding significant prospects for applications in engineering insulation materials, infrared camouflage, and thermal management.

Flexible Terahertz Metamaterials Absorber based on VO2

Terahertz (THz) metamaterials have attracted great attention due to their widely application potential in smart THz devices; however, most of them are fabricated on rigid substrate and thus limit the exploration of flexible THz electronics. In this paper, a flexible THz metamaterial absorber (MMA) incorporated with phase change material vanadium dioxide (VO2) is proposed. The simulation results indicate that two absorption peaks at around 0.24 THz (marked as A) and 0.46 THz (marked as B) can be observed by designing a I-shaped metamaterial combined with split ring structure. The strong absorption over 92% at 0.24 THz is bending-insensitive, but the absorption at 0.46 THz is bending-sensitive, across the bending angle in the range of 0–50 degrees. Moreover, dynamic modulation of the absorption can be achieved across the insulator-metal phase transition of VO2. Particularly, the absorption of the A-peak can be tuned from 99.4% to 46.9%, while the absorption of the B-peak can be tuned from 39.6% to 99.3%. This work would provide significance for the design of flexible THz smart devices.

Interconversion between dual-peak electromagnetically induced transparency and dual-peak electromagnetically induced absorption utilizing metasurface

Utilizing metasurface (MS), the transition between dual-peak electromagnetically induced transparency (EIT) and dual-peak electromagnetically induced absorption (EIA) in four states has been proposed in the terahertz (THz) band with the incidence of a circularly polarized (CP) wave. Additionally, the phase-change material vanadium dioxide (VO2) and photosensitive material silicon (Si) have been adopted. The four state transitions can be achieved by adjusting the pump light and the temperature which is not affected by incident CP waves. With the incidence of the pump light, Si can transform from the insulating state to the metallic state. Similarly, when the temperature exceeds 68 °C, VO2 enters the metallic state. Two different dual-peak EIT (State 1 and State 2) accompanied by slow light effect can be observed by modulating the state of VO2 without the action of Si. However, once Si is in metallic state, two different states of dual-peak EIA (State 3 and State 4) are achieved by changing the state of VO2. Notably, the MS has the property of polarization insensitivity. The theoretical oscillator model and equivalent RLC-circuit model verify the feasibility of dual-peak EIT and EIA.

Adjustable strong circular dichroism based on a tricircular arc metasurface.

Circular dichroism has promising applications in biology, molecular chemistry, and other fields. The key to obtaining strong circular dichroism is to introduce symmetry breaking into the structure, which leads to a great difference in the response to different circularly polarized waves. Here, we propose a metasurface structure based on three circular arcs, which produces strong circular dichroism. The metasurface structure combines the split ring with the three circular arcs and increases the structural asymmetry by changing the relative torsional angle. The causes of the strong circular dichroism are analyzed in this paper, and the influence of metasurface parameters on it is discussed. According to the simulation data, the response of the proposed metasurface to different circularly polarized waves varies greatly, with absorption of up to 0.99 at 5.095THz for a left-handed circularly polarized wave and a maximum circular dichroism of over 0.93. In addition, the incorporation of the phase change material vanadium dioxide on the structure allows flexible modulation of circular dichroism and modulation depths of up to 98.6%. The change of angle within a certain range has little effect on the structural performance. We believe that this flexible and angle robust chiral metasurface structure is suitable for complex reality, and large modulation depth is more practical.

Switchable Wideband Terahertz Absorber Based on Refractory and Vanadium Dioxide Metamaterials

Achieving actively tunable metamaterial absorption is a significant development direction. Phase-transition materials have attracted growing interest for the use in nanophotonics owing to their flexibility. In this work, we firstly demonstrate a wideband terahertz refractory absorber that achieves more than 90% absorptance in the range of 1.71--3.31 THz. The metal composing the structure is refractory metal, which could function in high-temperature conditions and complex electromagnetic environment. Then, we incorporate phase-change material vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) film to this refractory absorber, realizing high reflection of more than 93% in the metallic state, while the wideband perfect absorption peak over 98% is obtained in the insulating state. Calculated results show that metamaterial absorber obtains switchable functions. Furthermore, the tunable absorber has polarization-insensitive behavior. So, our designed absorber with dynamic tunable characteristics provides flexibility to adjust the absorption performance and has significant value in application. The proposed architecture offers a novel method for creating dynamic and multi-functional photonic devices in phase-change materials.

Active tuning hBN phonon polaritons and spontaneous emission rates based on VO&lt;sub&gt;2&lt;/sub&gt; and graphene

&lt;sec&gt;Active tunability of phonon dispersion and spontaneous emission (SE) are still open problems due to their exciting potential applications. In view of the fact that polaritons are very sensitive to the dielectric environment, in this study, with the help of the differences in optical property between the phase change material vanadium dioxide (VO&lt;sub&gt;2&lt;/sub&gt;) during the phase transition from the insulating state to metallic state and the tunable surface plasmon polaritons (SPPs) in graphene, a heterostructure composed of hyperbolic material hexagonal boron nitride (hBN) and graphene and VO&lt;sub&gt;2&lt;/sub&gt; is proposed to investigate the active tunability of hBN phonon polaritons (PhPs). In order to illustrate the underlying physical mechanism of the above heterostructures, the dispersion distributions of the above heterostructures are calculated and represented by the imaginary part of the p-polarized Fresnel reflection coefficient of the heterostructure, meanwhile the dispersion relation of the hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure in hyperbolic region is verified by the quasi-static approximation method.&lt;/sec&gt;&lt;sec&gt;Results indicate that the active tunability of hBN PhPs inside type-I and type-II hyperbolic bands can be achieved by controlling VO&lt;sub&gt;2&lt;/sub&gt; phase transition in hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure. The PhP dispersion change of the hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure is mainly caused by the change of the VO&lt;sub&gt;2&lt;/sub&gt; dielectric function when VO&lt;sub&gt;2&lt;/sub&gt; substrate changes from the insulating state into metallic state, which affects the total Fresnel reflection coefficient of the heterostructure, finally resulting in the PhP dispersion change of hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure. When graphene is introduced into the hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure, coupled hyperbolic plasmon-phonon polaritons (HPPPs) are obtained within type-I and type-II hyperbolic band of hBN, while the surface plasmon-phonon polaritons (SPPPs) are generated outside its hyperbolic bands. Moreover, comparative analysis of SE rates is presented for a quantum emitter positioned with the hBN/VO&lt;sub&gt;2&lt;/sub&gt; and graphene/hBN/VO&lt;sub&gt;2&lt;/sub&gt; heterostructure, revealing that the SE rates of these heterostructures can be modulated by the passive means including changing the hBN thickness and distance between the dipole emitter and the proposed heterostructure, and also by the active means including tuning VO&lt;sub&gt;2&lt;/sub&gt; phase states and graphene chemical potential without changing structural configurations. This study provides a theoretical guidance in realizing active tunability of both phonon dispersion and SE rate of the natural or artificial anisotropic optical materials by using functional materials including phase change materials and graphene.&lt;/sec&gt;

Transition from electromagnetically induced transparency to Electromagnetically Induced Absorption Utilizing Phase-Change Material Vanadium Dioxide Based on Circularly Polarized Waves

A circular-polarization metastructure (MS) with switchable functions connected to the transition from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) is theoretically proposed under the action of circularly polarized (CP) waves in the terahertz (THz) band. Additionally, we use the phase-change material vanadium dioxide (VO 2 ) to achieve functional transformation. The MS is mainly composed of two metal bright modes and a VO 2 resonator. When the VO 2 is insulating, the EIT with a high and wide transmission window is realized between 0.460 THz and 0.911 THz due to the coupling between two bright modes. Once VO 2 reaches the metal state, the original high transmission window is transformed into the high absorption window and the phenomena from EIT to EIA (vice versa) are successfully achieved from 0.460 THz to 0.911 THz. The group delays and group index of EIT are 161 ps and 1126, respectively. The simulation results of EIT and EIA are verified by fitting the theoretical two-oscillator model. • The proposed MS provides a new idea to manipulate the transition between EIT and EIA. • Multiple parameters can be adjusted to manipulate the transmission amplitude and frequency. • The presented structure is great transparency or absorption for the EM wave. • The thickness of the proposed MS is subwavelength. • The proposed MS can be applied to antenna fields and wave plates.

Switchable dual-function metasurfaces with electromagnetic induction transparency-like and absorption

Two terahertz switchable metasurfaces with dual-function are proposed in this paper. Both metasurfaces contain a periodically arranged pattern layer made of silver, which is mounted on the stacking layer of polyimide and phase change material vanadium dioxide (VO2). The simulation results show that the designed metasurfaces can be converted from multi-band absorbers to electromagnetically induced transparency-like (EIT-like) analogs. When VO2 is in conductive state, the above metasurfaces work as dual-band absorber and tri-band absorber respectively, with absorptivities over 90 %; while VO2 is in insulating state, both structures are EIT-like. The physical mechanism of absorption and EIT-like effect is explained by the surface current distribution. In addition, by adjusting the structural parameters, the peak frequency of the absorbers and the window bandwidth of the EIT-like changes. Meanwhile, the dual-function of the metasurfaces can be maintained within a certain range of incidence and polarization angles. These results show that the switchable metasurfaces can achieve potential applications of modulators, optical buffers, and sensors at terahertz frequencies in the infrared light range.

Design of Thermal-Switchable Absorbing Metasurface Based on Vanadium Dioxide

This letter presents a thermal-switchable absorbing metasurface (TSAM) based on the phase-change material vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). A thin film of VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> was deposited on a sapphire substrate by a magnetron sputtering and then sliced into tiny chips, which can be regarded as thermal-switchable resistors. The surface structure of the TSAM element is realized by loading four VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> chips into a square metallic loop. Polytetrafluoroethylene is used as the substrate due to its high thermal conductivity compared with foam. The TSAM is on the “absorbing” mode when it is heated underneath and is switched into the “reflecting” mode at room temperature. The absorbing mode is characterized by a wideband absorption (8–22 GHz). A TSAM prototype was fabricated and measured to verify this design.

Active optical modulation of quasi-BICs in Si-VO2 hybrid metasurfaces.

Active optical modulation breaks the limitation of a passive device, providing a new, to the best of our knowledge, alternative to achieve high-performance optical devices. The phase-change material vanadium dioxide (VO2) plays an important role in the active device due to its unique reversible phase transition. In this work, we numerically investigate the optical modulation in resonant Si-VO2 hybrid metasurfaces. The optical bound states in the continuum (BICs) in an Si dimer nanobar metasurface are studied. The quasi-BICs resonator with high quality factor (Q-factor) can be excited by rotating one of the dimer nanobars. The multipole response and near-field distribution confirm that magnetic dipoles dominate this resonance. Moreover, a dynamically tunable optical resonance is achieved by integrating a VO2 thin film to this quasi-BICs Si nanostructure. With the increase of temperature, VO2 gradually changes from the dielectric state to metal state, and the optical response exhibits a significant change. Then, the modulation of the transmission spectrum is calculated. Situations where VO2 is located in different positions are also discussed. A relative transmission modulation of 180% is achieved. These results fully confirm that the VO2 film shows an excellent ability to modulate the quasi-BICs resonator. Our work provides a route for the active modulation of resonant optical devices.

Tunable anisotropic metasurface by utilizing phase change material in terahertz range

Due to the capability of achieving versatile control of differently polarized electromagnetic waves, anisotropic metasurfaces have attracted extensive attentions. To manipulate terahertz waves flexibly, we propose a tunable anisotropic metasurface based on phase change material vanadium dioxide (VO2). It is composed of a gold bottom layer deposited on the back of polyimide dielectric layer and a gold patch located on the front of the polyimide dielectric substrate. When VO2 is in the insulating state, the predesigned metasurface produces diversified functions, including terahertz beam splitting, deviation focusing, and multivortex beam under different polarization terahertz wave incidence. When VO2 becomes a metallic state, the proposed metasurface changes the number of terahertz beams, the shape of vortex beams, and the focusing effect. This scheme provides an innovative idea for the dynamic regulation of the terahertz wave in future terahertz technology systems.

Tunable plasmonics with Au nanoparticles coupled to thin film vanadium dioxide

The development of active devices featuring dynamic tunable plasmonic resonances is vital for wide implementation in many optoelectronic devices. By coupling plasmonic nanoparticles to an underlying thin film of phase change material vanadium dioxide (VO2), dynamic tuning of the plasmon resonance can be achieved within the visible and near IR spectral regions. It is shown through selection of single nanoparticle or dimer structures, the plasmon resonances can be tuned over a large spectral range, the scattering cross-section can be increased, and the E-field enhancement and spatial profile can be controlled via the VO2 phase transition. Hybrid Au nanocuboid–VO­2 structures exhibit larger reversible wavelength shifts than rounded nanoparticles, such as rods and discs, of similar dimensions. A plasmon resonance shift of over 600 nm is observed in the near-IR after the semiconducting to metallic VO2 phase transition. The largest increases in the scattering cross-section are achieved with a VO2 thin film thickness of 30–50 nm. Disc, rod, bowtie and cuboid dimers show larger increases of the scattering cross-section at lower wavelengths, even extending into the visible spectral range. On VO2 phase transition the bowtie dimers can provide an increase in the scattering cross-section of over 70% and 3.6-fold increase in the E-field intensity within the dimer gap. Additionally, the near-field enhancement spreads over the entire height of the dimer gap, and in particular, there is a large enhancement at the surface of the dimers. The increased scattering cross-section and modification of the spatial profile of the E-field enhancement provides mechanisms for tunable metasurfaces.

Dynamic bifunctional THz metasurface via dual-mode decoupling

Metasurfaces have powerful light field manipulation capabilities and have been researched and developed extensively in various fields. With an increasing demand for diverse functionalities, terahertz (THz) metasurfaces are also expanding their domain. In particular, integrating different functionalities into a single device is a compelling domain in metasurfaces. In this work, we demonstrate a functionally decoupled THz metasurface that can incorporate any two functions into one metasurface and switch dynamically through external excitation. This proposed metasurface is formed by the combination of split-ring resonators and phase change material vanadium dioxide ( VO 2 ). It operates in the single-ring resonant mode and double-ring resonant mode with varying VO 2 in insulating and metallic states, respectively. More importantly, the phase modulation is independent in two operating modes, and both cover a 360° cross-polarized phase with efficient polarization conversion. This characteristic makes it obtain arbitrary independent phase information on the metasurface with different modes to switch dual functions dynamically. Here, we experimentally demonstrate the functions of a tunable focal length and large-angle focus deflection of a THz off-axis parabolic mirror to verify the dual-function switching characteristics of the functionally decoupled metasurface. The functionally decoupled metasurface developed in this work broadens the way for the research and application of multifunctional modulation devices in the THz band.

State Switching of Terahertz Reflection and Orbital Angular Momentum in Phase Change Metasurfaces

Metasurfaces with dynamically switchable functions have received extensive attention, and are in high demand in various applications. In this work, dynamically switchable metasurfaces are proposed based on phase change material-vanadium dioxide. They consist of vanadium dioxide blocks, silicon dioxide spacer, and gold film. By changing the size of vanadium dioxide block, vanadium dioxide in the metallic state forms a gradient metasurface. A specially arranged gradient metasurface is designed to achieve a 360° phase modulation capability. Normally incident plane wave is reflected to the right side at the angle of 36.9° at 2.5 THz. When vanadium dioxide switches from the metallic state to the insulating state, the switching of anomalous reflection and specular reflection is realized. In addition, when vanadium dioxide is metal, a vortex beam generator is implemented to generate orbital angular momentum beams with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 1 and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 2. The number of orbital angular momentum mode can be switched from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 0 to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 1 or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 2 by changing the state of vanadium dioxide. Since the structure of meta-atom is a square block, the design is simple and easy to integrate. At the same time, the switchable function is accurately implemented without side lobe. The proposed design has potential applications in terahertz switching and communication.