THz broadband and dual-channel perfect absorbers based on patterned graphene and vanadium dioxide metamaterials

Shanshan Zhuo; Zhimin Liu; Fengqi Zhou; Fengqi Zhou; Yipeng Qin; Xin Luo; Cheng Ji; Guangxin Yang; Ruihan Yang; Yadong Xie

doi:10.1364/OE.476858

1. Introduction

Metamaterials, as an artificially designed electromagnetic medium, exhibit extraordinary physical properties absent from natural materials [1,2], and have attracted widespread attention in recent years. The amplitude, phase, and polarization of light can be controlled in the THz band through a special design, which effectively manipulates electromagnetic waves. The mature development and proven feasibility of metamaterials in the past few decades prompt their application in fields like wave absorbing materials [3–5], biological detection [6,7], stealth technology [8], communication antennas [9], etc. In addition, metamaterials perform excellent optical properties, such as electromagnetic induced transparency (EIT) [10,11], perfect absorption [12,13], negative refractive index [14], etc., among which the perfect absorber is a vital research branch. Landy, N. I, et al. first initiated the perfect absorber in 2008 [15], proposed a metal plasma structure, and achieved perfect absorption at a single frequency point, which grabbed the attention of researchers. Pu, Mingbo, et al. put forward a metal-dielectric-metal structure in 2011, and achieved a multi-band perfect absorption [16]. Pu, Mingbo, et al. further used metal films to broaden the absorption width and achieve broadband absorption in the next year, which was a landmark for communication and sensing research [17]. The traditional absorbers, however, are generally composed of metals, and are difficult to change once the design is completed, limiting further modulation and absorption width. Researchers accordingly found many excellent materials to solve this problem, such as graphene and vanadium dioxide.

Graphene [18] is equipped with a two-dimensional crystalline structure, and is considered a revolutionary material of the future. Thanks to its metal-like properties, it can excite the surface plasma polaritons (SPPs) [19–21]. Compared with metals, the graphene-based SPPs are superior with excellent optical properties, such as dynamic tunability [22–24], strong localization [25], strong dispersion [26], etc., which explains the extensive application of graphene in designing electromagnetic absorbers [27–29] in the THz band. In 2012, R. Alaee et al. proposed a graphene-dielectric-gold metamaterial, and realized a perfect absorption at multi-frequency points by controlling the Fermi level of graphene [30]. Another paper published in the same year also proved 100% absorption in the patterned graphene structure [28]. Benefiting from the excellent optical properties of graphene, these absorbers perform better absorption capacity, and are adjustable. Given the limited current application of narrow-band or fixed frequency range absorption, another noteworthy metamaterial, vanadium dioxide (VO₂), is proposed to achieve perfect broadband absorption. Extensive attention has been paid to VO₂ [31,32], a monoclinic crystal structure with phase change properties [33]. The phase transition temperature is 68 °C, that is, the VO₂ is the insulating phase at T < 68^oC, while the metallic phase at T > 68^oC. Due to this unique property, VO₂ has been widely employed in tunable devices such as optical switches [34], terahertz absorbers [35,36], and sensors [37]. In 2021, Z. Run et al. proposed a VO₂ absorber that achieved a more than 90% absorption with a width of 0.65 THz by varying the temperature [38], which manifested that VO₂ could improve the performance of absorber, and realize broadband absorption. In 2022, Zeng. et al. proposed a graphene and VO₂ hybrid structure to achieve dynamic absorption and multifunctional modulators [39]. Therefore, considering the excellent properties of the two metamaterials mentioned above, this paper attempts to combine graphene and VO₂, which provides a new approach to achieve multiple modulations, and to improve absorption capacity and width [34,40,41].

This paper proposes a hybrid metamaterial based on patterned graphene and VO₂ to achieve a broadband 100% absorption or a high dual-channel absorption, which exhibits excellent performance and prospects in multifunctional modulators. Firstly, the absorption spectrum of the proposed structure in the absence of graphene is investigated, revealing that as VO₂ gradually changes from the insulating phase to the metallic phase, the absorption grows. Most importantly, when the graphene is applied above the structure, the absorption (≈100%) is strengthened from one frequency point to an ultra-wide frequency band. Secondly, when the VO₂ is the insulating phase and graphene is added, two high absorption peaks are observed. The absorption under such situation is greatly enhanced compared with the absence of graphene, which demonstrates the role of graphene in absorption enhancement, and achieving dual-channel absorption. Finally, the Fermi level of graphene and the polarization angle of incident light are controlled to explore the applications of the structure, and an asynchronous optical switch can be realized at f_K₁ = 5.782 THz and f_K₂ = 6.898 THz. Besides, the absorber shows the polarization sensitivity at f₃ = 5.545 THz while the polarization insensitivity at f₄ = 7.684 THz, which is vital for realizing polarizers and other modulators. In summary, this paper presents a new method to improve the performance of the absorber, and realizes an ultra-wide nearly 100% absorption, which guides the multifunctional application.

2. Model design and methods

Figure 1(a) illustrates the schematic diagram of the periodic structure based on a patterned graphene and ring-shaped VO₂ hybrid metamaterial, which enables the interconversion between broadband absorption and dual-channel absorption. Unlike most absorber structures, the proposed structure utilizes the excellent metal-like and the graphene-based SPPs properties of graphene to enhance absorption, exhibiting a broadband perfect absorption. The proposed structure is composed of six layers (Au-VO₂-SiO₂-VO₂-SiO₂-graphene): the bottom layer is a gold layer, which acts as a reflector to reflect most of the light; the 2 μm-thickness VO₂ film, which can also serve as a reflector to reflect most incident light at metal phase VO₂; the first SiO₂ layer; the ring-shaped VO₂ layer with a thickness of 0.1 µm; the second SiO₂ layer, and the top layer, that is, the patterned graphene layer. The graphene layer is deposited with an ionic gel layer, and a metal gate contact is provided on the top graphene structure to connect the gate voltage V_g as shown in the cell structure in Fig. 1(b). The ionic gel, 2.56 in relative permittivity and 1 nm in thickness, connects the graphene together to facilitate the application of gate voltage. Figure 1(c) shows the top view of the graphene layer, which consists of two graphene strips and a graphene square block (referred to as TGSs and GSB for convenience). Figure 1(d) indicates the top view of the ring-shaped VO₂ layer, with R_out and R_in denoting the inner and outer radius of the ring, respectively. In addition, the geometrical parameters of the structure are as follows: t_Au = 2 µm, t_VO2= 2 µm, t_SiO2= 5.2 µm, d_VO2= 0.1 µm, d_SiO2= 0.6 µm, l₁= 4 µm, l₂= 1.5 µm, l₃= 1.75 µm, l₄= 3 µm, p = 10 µm, R_in= 2.5 µm, and R_out= 4 µm.

Fig. 1. (a) Schematic structure based on patterned graphene and VO₂ periodic metamaterials. (b) A cell structure highlighted by the yellow dashed line in Fig. 1(a). (c) Top view of the graphene layer. (d) Top view of the ring-shaped VO₂ layer.

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The x, y, and z directions are set as the periodic boundary, the periodic boundary, and the perfect matching layer (PML), respectively, in simulation. Furthermore, the surface current model of graphene is employed, and the graphene is equivalent to a surface current J, satisfying the differential form of Ohm's law: J = σ_gE, where σ_g and E denote the conductivity of graphene and the electric field, respectively. The graphene conductivity σ_g can be expressed by the Kubo formula [42,43]:

(1)$$\textrm{The total complex conductivity:}{\sigma _g}({\mu _c},\tau ,\omega ,T) = {\sigma _{\textrm{intra}}} + {\sigma _{\textrm{inter}}}, $$

(2)$$\textrm{The intraband contributions:}{\sigma _{^{\textrm{intra}}}} = j\frac{{2{e^2}{k_B}T}}{{\pi {\hbar ^2}(\omega + j{\tau ^{ - 1}})}}\textrm {In}[2\cosh (\frac{{{\mu _c}}}{{2{k_B}T}})], $$

(3)$$\textrm{The interband contributions:}{\sigma _{^{\textrm{inter}}}} = \frac{{j{e^2}(\omega + j{\tau ^{ - 1}})}}{{4\pi {k_B}T}}\int_0^{ + \infty } {\frac{{G(\xi )}}{{{\hbar ^2}{{(\omega + j{\tau ^{ - 1}})}^2}/{{(2{k_B}T)}^2} - {\xi ^2}}}} d\xi, $$

here, µ_c represents the chemical potential, τ represents the electron relaxation time, ħ expresses the Planck constant and k_B expresses the Boltzmann constant. G(Λ)=sinh(Λ)/[cosh(µ_c /k_BT)+cosh(Λ)], in which Λ=ε/k_BT. In the system, the temperature is set as 300 K, and the Fermi level of graphene E_Fis the same as µ_c. Owing to E_F >> k_BT in the THz band, the interband contributions can be ignored. Therefore, the graphene conductivity σ_g can be further shown as:

(4)$${\sigma _g} = \frac{{j{e^2}{E_F}}}{{\pi {\hbar ^2}(\omega + j{\tau ^{ - 1}})}}. $$

In this system, the Fermi level of graphene is set as E_F= 1.0 eV, the mobility is µ = 0.4 m²V^-1s^-1, and the relaxation time is expressed by τ = µE_F/ (ev²_F). Moreover, the Fermi level of graphene can be given by [44]:

(5)$${E_F} = \hbar {\nu _F}\sqrt {\frac{{\pi {\varepsilon _0}{\varepsilon _{Si{O_2}}}{V_g}}}{{et}}}, $$

here, the Fermi velocity v_F= 10^6 m/s and the thickness of the dielectric t = 6.6 µm, respectively. Therefore, the Fermi level E_F can be adjusted by changing the value of V_g to indirectly control the graphene conductivity σ_g. Noteworthily, it has been experimentally demonstrated that the Fermi level of graphene can be regulated in the range of 0-1.2 eV [45,46]. Figures 2(a) and (b) reveal the real and imaginary parts of the single-layer graphene conductivity σ_gas a function of Fermi level E_F and frequency. With the increase of E_F, the real part of graphene conductivity σ_g remains constant, while the imaginary part increases. Thus, graphene gradually exhibits metal-like to achieve the graphene-based SPPs with the increase of E_F.

Fig. 2. (a) Graphene conductivity σ_g (a) real part and (b) imaginary part as a function of Fermi level E_F and frequency. VO₂ permittivity ε_vo₂ (a) real part and (b) imaginary part as a function of σ_vo₂ and frequency.

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In the THz band, the permittivity of the VO₂ can be expressed by the Drude model, which can be written as [47]:

(6)$${\varepsilon _{V{O_2}}}(\omega ) = {\varepsilon _\infty } - \frac{{{\omega _p}{{({\sigma _{V{O_2}}})}^2}}}{{{\omega ^2} + j\omega \gamma }}, $$

(7)$$\omega _p^2({\sigma _{v{o_2}}}) = \frac{{{\sigma _{v{o_2}}}}}{{{\sigma _0}}}\omega _{p({\sigma _0})}^2, $$

here, ω_p(σ₀) and γ are the plasma frequency and the collision frequency, respectively. The values of relevant parameters are as follows: ε_∞= 12, σ₀= 3 × 10⁵ S/m, ω_p(σ₀) = 1.4 × 10¹⁵rad/s, and γ=5.75 × 10¹³rad/s. Figures 2(c) and (d) show the real and imaginary parts of the permittivity ε_vo₂ as a function of the conductivity σ_vo₂ and frequency, which reveals the decrease of permittivity Real_ε_vo₂, and the increase of Imaginary_ε_vo₂ with the increase of σ_vo₂. But the absolute value of the permittivity |ε_vo2| increases obviously, thus, the increase of permittivity ε_vo₂ prompts the change of VO₂ from insulator to metal when σ_vo₂ climbs from 200 S/m to 20 × 10⁴ S/m. As previous mentioned, the phase change temperature of VO₂ is 68 °C. At 68 °C, the conductivity σ_vo₂ jumps from 2 × 10⁴ S/m to 16 × 10⁴ S/m. Accordingly, σ_vo₂= 200 S/m and 20 × 10⁴ S/m are set as insulator and metal, respectively, in simulation.

During the simulation calculation, we scan the S-parameter, and obtain the reflection coefficient S₁₁ and the transmission coefficient S₂₁. Here, T = |S₂₁|² and R = |S₁₁|². Therefore, the absorption of this system can be expressed as:

(8)$$A = 1 - R - T = 1 - {|{{S_{11}}} |^2} - {|{{S_{21}}} |^2}. $$

3. Results and analysis

Firstly, the absorption property of the proposed structure is analyzed without graphene. Figure 3(a) displays the schematic diagram of the structure and a terahertz light in the x-direction is incident vertically on the surface of the structure. Figure 3(b) displays the absorption spectra of the structure at different conductivities σ_vo₂, where absorption gradually grows with the conductivity σ_vo2 being changed from 0 to 20 × 10⁴ S/m. When the conductivity σ_vo2 reaches 20 × 10⁴ S/m, the absorption is as high as 100% at f = 5.956 THz. In order to investigate the physical mechanism of this process change, we plot the surface electric field distribution at f = 5.956 THz when the temperature changes from 28 °C to 72 °C, as shown in Fig. 3(c). Figure 3(c) reveals that the electric field on the surface of the structure enhances with the increase of the temperature. Specifically, the electric field intensity exhibits no obvious change from 28 °C to 67 °C and from 69 °C to 72 °C, while jumps from 10 V/m to 50 V/m from 67 °C to 69 °C, which comes down to the transition from the insulating to the metallic state of VO₂. At 28 °C-67 °C, the VO₂ is the insulating state, and the conductivity σ_vo₂ is relatively low, so only a small amount of electric field energy is bound inside and outside the ring-shaped VO₂ in the x-direction. At this time, VO₂ is equivalent to a layer of medium, the incident photons cannot resonate between the VO₂ and gold layer, and they are all reflected so that the system represents low absorption, as shown in Fig. 3(b). At 67 °C-69 °C, the conductivity σ_vo₂ grows rapidly and most parts of VO₂ turn into metal, which strengthens the resonance with gold, which explains the climb of absorption. At 69 °C-72 °C, the phase transition of VO₂ is completed and the VO₂ becomes the metallic state, and the energy is mainly bound outside, indicating that the strong resonance of the incident photons between the ring-shaped VO₂ and the VO₂ film causes the absorption peak (see in Fig. 3(b)).

Fig. 3. (a) Schematic diagram of a cell structure without graphene. (b) The absorption spectra of the proposed structure at different conductivities σ_vo₂. (c) The surface electric field distribution at f = 5.956 THz with the temperature being changed from 28 °C to 72 °C. Here, the temperature changes from 28 °C to 72 °C (corresponding conductivity σ_vo₂ from 200 S/m to 20 × 10⁴ S/m).

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After discussing the situation without graphene, the effect of graphene that applied above the structure on the absorption performance is elaborated when x-direction polarized light is irradiated on the structure, as shown in Fig. 4(a). As mentioned before, the graphene is composed of two graphene strips (TGSs) and a graphene square block (GSB). Figure 4 (b) shows the change of absorption spectra with and without graphene when VO₂ is a metal phase, where the red line stands for the results in the presence of graphene, while the blue line in the absence of graphene. The inset in Fig. 4(b) shows an enlarged view of the high broadband absorption from 5.1 THz to 7.3 THz. It’s observed that the absorption is obviously enhanced when graphene is added, and the absorption can reach almost 100% from a frequency point (f = 5.956 THz) to a wide frequency band, where the band width (A≈100%) can be up to 1.683 THz. In order to deepen the understanding of the role of graphene strips and blocks, we also display the absorption spectrum in the presence of TGSs and GSB alone in Fig. 4 (b), in which the pink and green dotted line denote the GSB and TGSs, respectively. Compared to the absence of graphene (the blue line), the absorption is enhanced from 94.2% to 99.7% at f₁ = 5.340 THz when the TGSs exist alone, while the absorption is strengthened from 96.1% to 99.7% at f₂ = 7.023 THz when the GSB exists alone. When GSB and TGSs contribute simultaneously to absorption enhancement, the absorption spectrum exhibits a broadband strong absorption (the red line), which indicates the common participation of GSB and TGSs in the resonate among the ring-shaped VO₂ and the VO₂ film further strengthens the resonate. Therefore, the GSB and TGSs play an important role in the absorption enhancement of this structure, respectively. In addition, we also depict the absorption curve (orange dotted line) in Fig. 4(b) when 2 µm-thickness VO₂ film layer is not present. By comparing the presence (red solid line) and the absence of the VO₂ film layer, it is observed from the inset that the absorption capability is improved significantly when the VO₂ layer is present, bringing the broadband absorption closer to 100%. This is mainly due to fact that the VO₂ layer is in the metal phase under temperature control and forms a resonant cavity with the patterned graphene and the ring-shaped VO₂ layer, and the incident light resonates strongly between them, resulting in a significant increase of absorption.

Fig. 4. (a) Diagram of the cell structure and the top view of the graphene layer, TGSs and GSB. (b) The absorption spectra with and without graphene (solid line) and absorption spectra with the TGSs and GSB (dotted line) existing alone with the VO₂ being the metal state. The electric field distributions of the ring-shaped VO₂ layer, graphene layer, (c) f₁ = 5.340 THz, (d) f₂ = 7.023 THz. Here, the mobility and the fermi level of the graphene are µ = 0.4 m²/Vs and E_F = 1 eV.

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In order to further explore the effect of graphene on the absorption, the electric field distributions of the ring-shaped VO₂ layer and graphene layer are plotted in Figs. 4(c) and (d). According to the previous discussion without graphene (see Fig. .3(c) when σ_vo₂= 20 × 10⁴ S/m), the electric field energy is mainly distributed outside the ring in the x-direction. When the TGSs and GSB are added above the structure, the energy is concentrated outside and inside the ring at the ring-shaped VO₂ layer. At f₁ = 5.340 THz, the field energy is increased outside the ring in the y-direction, indicating that the role of TGSs on the resonance to enhance the absorption from 94.2% to 99.7%. At f₂ = 7.023 THz, the GSB contributes to the resonance between GSB and VO₂ film, so that the most energy is obviously confined inside the ring to strengthen the absorption from 96.1% to 99.7%. The graphene layer in Fig. 4(c) and Fig. 4(d) reveals that the energy is distributed around the TGSs and GSB, respectively, proving that their respective roles in the absorption enhancement at f₁ = 5.340 THz and f₂ = 7.023 THz. All these confirm the prominent role of TGSs and GSB in absorption enhancement at f₁ = 5.340 THz and f₂ = 7.023 THz, respectively.

Figure 5(a) demonstrates the absorption spectra when the VO₂ is the insulating state. Without graphene (the blue curve), the resonance is invalid so that there is no absorption. When the TGSs and GSB are simultaneously added, two absorption resonate peaks appear at f₃ = 5.545 THz and f₄ = 7.684 THz, respectively, where the absorption can reach as high as 100% and 90.7%, respectively. Here, the VO₂ is equal to a layer of medium, and the graphene forms a new resonant cavity with the gold. In addition, when TGSs and GSB respectively exist alone, resonance between the TGSs and gold generates the first absorption peak (the green dotted line), while the GSB produces the second peak (the pink dotted line), as shown in Fig. 5(a). The mutual coupling between TGSs and GSB incurs the dual-channel absorption. Therefore, when VO₂ is the insulating phase, the TGSs and GSB contribute to these two absorption peaks to realize the dual-channel absorption, respectively. Figure 5(b) shows the electric field distribution of the ring-shaped VO₂ layer at f₃ = 5.545 THz and f₄ = 7.684 THz. At the VO₂ insulating state, there is no energy outside the ring-shaped VO₂ in the x-direction, while the most energy is distributed outside the ring in the y-direction at f₃ = 5.545 THz and inside at f₄ = 7.684 THz, which is caused by the TGSs and GSB, respectively. Figure .5(c) reveals the marked effect of the TGSs and GSB at f₃ = 5.545 THz and f₄ = 7.684 THz, respectively, which supports that the two absorption peaks are derived from the TGSs and GSB, respectively. The above verifies the vital role of graphene in this system to enhance resonance, and achieve broadband high absorption and dual-channel absorption.

Fig. 5. (a) The absorption spectra with and without graphene (solid line) and the absorption spectra with the TGSs and GSB (dotted line) existing alone at the VO₂ insulator. (b) The electric field distributions of the ring-shaped VO₂ layer at f₃ = 5.545 THz and f₄ = 7.684 THz. (c) The electric field distributions of the graphene layer at f₃ = 5.545 THz and f₄ = 7.684 THz. Here, the mobility and the fermi level of the graphene are µ = 0.4 m²/Vs and E_F = 1 eV.

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The impedance matching theory [48] is a classical theory to explain the absorber. At 4.0-9.0 THz, we obtain S-parameters to invert the relative impedance Z of the absorber, where the relative impedance Z can be expressed by:

(9)$$Z = \sqrt {\frac{{{{({1 + {S_{11}}(\omega )} )}^2} - {S_{21}}^2(\omega )}}{{{{({1 - {S_{11}}(\omega )} )}^2} - {S_{21}}^2(\omega )}}}, $$

(10)$$R = \left|{\frac{{Z - {Z_0}}}{{Z + {Z_0}}}} \right|, $$

here, S₁₁ and S₂₁ denote the reflection coefficient and transmission coefficient, respectively. Z₀ is the relative impedance of free space. When the impedance of the absorber and the free space perfectly match (i.e Z = Z₀), the reflection reaches zero (R = 0), so that the absorption peaks. Figures 6(a) and (b) display the real and imaginary parts of the relative impedance Z when the VO₂ are the metal phase and the insulating phase. From f₁ = 5.340 THz to f₂ = 7.023 THz, real part and imaginary part almost equal to 1 and 0, respectively, manifesting the match between the absorber and the free space, thus the broadband high absorption. In Fig. 6(b), only two frequency points (f₃ = 5.545 THz and f₄ = 7.684 THz) match the relative impedance of the free space, which makes the absorber exhibit the dual-channel high absorption.

Fig. 6. (a) The real and imaginary parts of the relative impedance Z, (a) the VO₂ is metal phase, (b) the VO₂ is insulating phase.

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In practical applications, the external conditions are generally controlled to modulate the absorber. Given the favorable dynamic tunability of graphene, the Fermi level E_F can be controlled by an applied gate voltage V_g according to Eq. (5). Figures 7(a) and (b) illustrate the influences of the different E_F on the absorption at different VO₂ phase. Here, The black dotted curve marks 90% absorption. In Fig. 7(a), the absorption spectrum has a blue-shift feature, but the absorption width greater than 90% does not increase significantly, which mainly comes down to the dominant role of the metal phase VO₂ in the absorption resonance, as well as the limited enhancement role of graphene. In Fig. 7(b), the insulating phase VO₂ does not participate in the resonance, the graphene exhibits strong resonance with gold, and is accompanied by a significant blue-shift, where an asynchronous optical switch can be realized at f_K₁ = 5.782 THz and f_K₂ = 6.898 THz. At f_K₁ = 5.782 THz, the optical switch is set as “OFF” state at E_F = 0.8 eV, while as “ON” state at E_F = 1.1 eV. Conversely at f_K₂ = 6.898 THz, the optical switch is set as “ON” state at E_F = 0.8 eV, while as “OFF” state at E_F = 1.1 eV. Therefore, the Fermi level E_F can be adjusted to achieve the optical switch. In addition, the study of the polarization characteristics is vital for the application of the absorber, which can reduce the limitations in practical applications. Figures 7(c) and (d) show the absorption spectra with the increase of polarization angle θ at different VO₂ phase. In Fig. 7 (c), at θ < 45°, it can be observed that the absorption width (A > 90%) has no obvious change, while the width has obviously widened at θ > 45°, which is mainly caused by the rotational asymmetry of the graphene. Thereby, when VO₂ is a metal phase, the broadband absorption shows polarization sensitivity due to the rotational asymmetry of graphene. In addition, Fig. 7(d) reveals that the first absorption peak exhibits polarization sensitivity at f₃ = 5.545 THz, while the second absorption peak shows polarization insensitivity at f₄ = 7.684 THz, which is caused by the rotational symmetry and asymmetry of the GSB and TGSs, respectively. Interestingly, at θ = 45°, while the first absorption peak fades away, a new absorption peak gradually appears near f = 8.896 THz. Here, the new peak is masked by the red dotted line. Therefore, the proposed structure can be applied to multifunctional modulators, such as optical polarizers, switches, and absorbers.

Fig. 7. Absorption spectra at different Fermi levels, (a) the VO₂ is metal phase, (b) the VO₂ is insulating phase. Absorption spectra at different polarization angles, (c) the VO₂ is metal phase, (d) the VO₂ is insulating phase. Here, the black dashed lines indicate that the absorption intensity is greater than 90%.

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The above discussion validates that the proposed structure further improves the absorption performance of the absorber, and exhibits excellent modulation means. On the one hand, the band width of the almost 100% absorption can reach as high as 1.631 THz; on the other hand, the interconversion between broadband absorption and two-channel absorption can be controlled by the temperature. Some recent literatures on broadband absorption are shown in Table 1.

Table 1. Comparison of broadband absorption based on graphene and VO₂ recently.

View Table

4. Conclusions

This paper proposes an absorber based on patterned graphene and VO₂ hybrid metamaterials, which realizes the conversion between broadband high absorption and dual-channel absorption. The physical property of VO₂ can be adjusted by temperature, so that VO₂ can be regulated between the metal phase and the insulating phase. The introduction of patterned graphene can greatly enhance the resonance reaction of incident photons in the system, achieving a broadband ≈100% absorption and a two-channel absorption. The vital effect of GSB and TGSs on absorption at different VO₂ phases is also proved, not only to enhance resonance and achieve broadband high absorption, but also to achieve a dual-channel absorption. In addition, the absorber can be controlled by changing external conditions, which enables multifunctional applications such as optical switches, polarizers, and broadband absorption. So, the proposed absorber provides guidance for absorber regulation and multifunctional modulator

Funding

National Natural Science Foundation of China (11804093, 11847026, 12164018, 61764005); Natural Science Foundation of Jiangxi Province (20192BAB212003, 20202ACBL212005, 20202BABL201019, 20224ACB201008); Science and technology project of Jiangxi Provincial Department of Education (GJJ210603).

Disclosures

The authors declare no conflicts of interest.

Data availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

References

1. N.I. Zheludev and Y.S. Kivshar, “From metamaterials to metadevices,” Nat. Mater. 11(11), 917–924 (2012). [CrossRef]

2. Y. Liu and X. Zhang, “Metamaterials: a new frontier of science and technology,” Chem. Soc. Rev. 40(5), 2494–2507 (2011). [CrossRef]

3. Z. Jia, K. Lin, G. Wu, H. Xing, and H. Wu, “Recent progresses of high-temperature microwave-absorbing materials,” Nano 13(06), 1830005 (2018). [CrossRef]

4. H. Pang, Y. Duan, L. Huang, L. Song, J. Liu, T. Zhang, X. Yang, J. Liu, X. Ma, and J. Di, “Research advances in composition, structure and mechanisms of microwave absorbing materials,” Composites, Part B 224, 109173 (2021). [CrossRef]

5. S. X. Xia, X. Zhai, L. L. Wang, and S. C. Wen, “Polarization-independent plasmonic absorption in stacked anisotropic 2D material nanostructures,” Opt. Lett. 45(1), 93–96 (2020). [CrossRef]

6. T. Chen, S. Li, and H. Sun, “Metamaterials application in sensing,” Sensors 12(3), 2742–2765 (2012). [CrossRef]

7. X. Yan, M. Yang, Z. Zhang, L. Liang, D. Wei, M. Wang, M. Zhang, T. Wang, L. Liu, and J. Xie, “The terahertz electromagnetically induced transparency-like metamaterials for sensitive biosensors in the detection of cancer cells,” Biosens. Bioelectron. 126, 485–492 (2019). [CrossRef]

8. J. Kim, K. Han, and J.W. Hahn, “Selective dual-band metamaterial perfect absorber for infrared stealth technology,” Sci. Rep. 7(1), 6740 (2017). [CrossRef]

9. X. Liu, K. Li, Z. Meng, Z. Zhang, and Z. Wei, “Hybrid metamaterials perfect absorber and sensitive sensor in optical communication band,” Front. Phys. 9, 637602 (2021). [CrossRef]

10. J.P. Marangos, “Electromagnetically induced transparency,” J. Mod. Opt. 45(3), 471–503 (1998). [CrossRef]

11. Z. Liu, X. Zhang, F. Zhou, X. Luo, Z. Zhang, Y. Qin, S. Zhuo, E. Gao, H. Li, and Z. Yi, “Triple plasmon-induced transparency and optical switch desensitized to polarized light based on a mono-layer metamaterial,” Opt. Express 29(9), 13949–13959 (2021). [CrossRef]

12. H. Feng, Z. Xu, K. Li, M. Wang, W. Xie, Q. Luo, B. Chen, W. Kong, and M. Yun, “Tunable polarization-independent and angle-insensitive broadband terahertz absorber with graphene metamaterials,” Opt. Express 29(5), 7158–7167 (2021). [CrossRef]

13. Y. Li, J. Lin, H. Guo, W. Sun, S. Xiao, and L. Zhou, “A tunable metasurface with switchable functionalities: from perfect transparency to perfect absorption,” Adv. Opt. Mater. 8(6), 1901548 (2020). [CrossRef]

14. D.R. Smith, J.B. Pendry, and M.C. Wiltshire, “Metamaterials and negative refractive index,” Science 305(5685), 788–792 (2004). [CrossRef]

15. N.I. Landy, S. Sajuyigbe, J.J. Mock, D.R. Smith, and W.J. Padilla, “Perfect metamaterial absorber,” Phys. Rev. Lett. 100(20), 207402 (2008). [CrossRef]

16. M. Pu, C. Hu, M. Wang, C. Huang, Z. Zhao, C. Wang, Q. Feng, and X. Luo, “Design principles for infrared wide-angle perfect absorber based on plasmonic structure,” Opt. Express 19(18), 17413–17420 (2011). [CrossRef]

17. M. Pu, Q. Feng, M. Wang, C. Hu, C. Huang, X. Ma, Z. Zhao, C. Wang, and X. Luo, “Ultrathin broadband nearly perfect absorber with symmetrical coherent illumination,” Opt. Express 20(3), 2246–2254 (2012). [CrossRef]

18. A.K. Geim, “Graphene: status and prospects,” Science 324(5934), 1530–1534 (2009). [CrossRef]

19. Y.V. Bludov, A. Ferreira, N.M. Peres, and M.I. Vasilevskiy, “A primer on surface plasmon-polaritons in graphene,” Int. J. Mod. Phys. B 27(10), 1341001 (2013). [CrossRef]

20. X. Zhang, F. Zhou, Z. Liu, Z. Zhang, Y. Qin, S. Zhuo, X. Luo, E. Gao, and H. Li, “Quadruple plasmon-induced transparency of polarization desensitization caused by the Boltzmann function,” Opt. Express 29(18), 29387–29401 (2021). [CrossRef]

21. S. Xia, X. Zhai, L. Wang, Y. Xiang, and S. Wen, “Plasmonically induced transparency in phase-coupled graphene nanoribbons,” Phys. Rev. B 106(7), 075401 (2022). [CrossRef]

22. Z. Liu, Z. Zhang, F. Zhou, X. Zhang, E. Gao, and X. Luo, “Dynamically tunable electro-optic switch and multimode filter based on twisted bilayer graphene strips,” J. Opt. 23(2), 025104 (2021). [CrossRef]

23. H. Cheng, S. Chen, P. Yu, X. Duan, B. Xie, and J. Tian, “Dynamically tunable plasmonically induced transparency in periodically patterned graphene nanostrips,” Appl. Phys. Lett. 103(20), 203112 (2013). [CrossRef]

24. F. Zhou, Y. Wang, X. Zhang, J. Wang, Z. Liu, X. Luo, Z. Zhang, and E. Gao, “Dynamically adjustable plasmon-induced transparency and switching application based on bilayer graphene metamaterials,” J. Phys. D: Appl. Phys. 54(5), 054002 (2021). [CrossRef]

25. A. Lherbier, B. Biel, Y.-M. Niquet, and S. Roche, “Transport length scales in disordered graphene-based materials: strong localization regimes and dimensionality effects,” Phys. Rev. Lett. 100(3), 036803 (2008). [CrossRef]

26. D.W. Johnson, B.P. Dobson, and K.S. Coleman, “A manufacturing perspective on graphene dispersions,” Curr. Opin. Colloid Interface Sci. 20(5-6), 367–382 (2015). [CrossRef]

27. E. Gao, Z. Liu, H. Li, H. Xu, Z. Zhang, X. Luo, C. Xiong, C. Liu, B. Zhang, and F. Zhou, “Dynamically tunable dual plasmon-induced transparency and absorption based on a single-layer patterned graphene metamaterial,” Opt. Express 27(10), 13884–13894 (2019). [CrossRef]

28. S. Thongrattanasiri, F.H. Koppens, and F.J.G. De Abajo, “Complete optical absorption in periodically patterned graphene,” Phys. Rev. Lett. 108(4), 047401 (2012). [CrossRef]

29. S. X. Xia, X. Zhai, Y. Huang, J. Q. Liu, L. L. Wang, and S.-C. Wen, “Multi-band perfect plasmonic absorptions using rectangular graphene gratings,” Opt. Lett. 42(15), 3052–3055 (2017). [CrossRef]

30. R. Alaee, M. Farhat, C. Rockstuhl, and F. Lederer, “A perfect absorber made of a graphene micro-ribbon metamaterial,” Opt. Express 20(27), 28017–28024 (2012). [CrossRef]

31. Y. Ke, S. Wang, G. Liu, M. Li, T.J. White, and Y. Long, “Vanadium dioxide: The multistimuli responsive material and its applications,” Small 14(39), 1802025 (2018). [CrossRef]

32. M. Qazilbash, K. Burch, D. Whisler, D. Shrekenhamer, B. Chae, H. Kim, and D. Basov, “Correlated metallic state of vanadium dioxide,” Phys. Rev. B 74(20), 205118 (2006). [CrossRef]

33. T.-C. Chang, X. Cao, S.-H. Bao, S.-D. Ji, H.-J. Luo, and P. Jin, “Review on thermochromic vanadium dioxide based smart coatings: from lab to commercial application,” Adv. Manuf. 6(1), 1–19 (2018). [CrossRef]

34. Y. Liu, R. Huang, and Z. Ouyang, “Terahertz absorber with dynamically switchable dual-broadband based on a hybrid metamaterial with vanadium dioxide and graphene,” Opt. Express 29(13), 20839–20850 (2021). [CrossRef]

35. Z. Zheng, Y. Luo, H. Yang, Z. Yi, J. Zhang, Q. Song, W. Yang, C. Liu, X. Wu, and P. Wu, “Thermal tuning of terahertz metamaterial absorber properties based on VO 2,” Phys. Chem. Chem. Phys. 24(15), 8846–8853 (2022). [CrossRef]

36. Y. Zhao, Q. Huang, H. Cai, X. Lin, and Y. Lu, “A broadband and switchable VO2-based perfect absorber at the THz frequency,” Opt. Commun. 426, 443–449 (2018). [CrossRef]

37. B. Hu, Y. Ding, W. Chen, D. Kulkarni, Y. Shen, V.V. Tsukruk, and Z.L. Wang, “External-strain induced insulating phase transition in VO2 nanobeam and its application as flexible strain sensor,” Adv. Mater. 22(45), 5134–5139 (2010). [CrossRef]

38. R. Zhou, T. Jiang, Z. Peng, Z. Li, M. Zhang, S. Wang, L. Li, H. Liang, S. Ruan, and H. Su, “Tunable broadband terahertz absorber based on graphene metamaterials and VO2,” Opt. Mater. 114, 110915 (2021). [CrossRef]

39. D. Zeng, S. Zong, G. Liu, W. Yuan, X. Liu, and Z. Liu, “Dynamically electrical/thermal-tunable perfect absorber for a high-performance terahertz modulation,” Opt. Express 30(22), 39736–39746 (2022). [CrossRef]

40. Z. Xu and Z. Song, “VO 2-Based Switchable Metasurface With Broadband Photonic Spin Hall Effect and Absorption,” IEEE Photonics J. 13(4), 1–5 (2021).

41. H. Zhu, Y. Zhang, L. Ye, Y. Li, Y. Xu, and R. Xu, “Switchable and tunable terahertz metamaterial absorber with broadband and multi-band absorption,” Opt. Express 28(26), 38626–38637 (2020). [CrossRef]

42. Z. Liu, E. Gao, Z. Zhang, H. Li, H. Xu, X. Zhang, X. Luo, and F. Zhou, “Dual-mode on-to-off modulation of plasmon-induced transparency and coupling effect in patterned graphene-based terahertz metasurface,” Nanoscale Res. Lett. 15(1), 1–9 (2020). [CrossRef]

43. Z. Liu, E. Gao, X. Zhang, H. Li, H. Xu, Z. Zhang, X. Luo, and F. Zhou, “Terahertz electro-optical multi-functional modulator and its coupling mechanisms based on upper-layer double graphene ribbons and lower-layer a graphene strip,” New J. Phys. 22(5), 053039 (2020). [CrossRef]

44. Y. Qin, F. Zhou, Z. Liu, X. Zhang, S. Zhuo, X. Luo, C. Ji, G. Yang, Z. Zhou, and L. Sun, “Triple plasmon-induced transparency and dynamically tunable electro-optics switch based on a multilayer patterned graphene metamaterial,” J. Opt. Soc. Am. A 39(3), 377–382 (2022). [CrossRef]

45. D.K. Efetov and P. Kim, “Controlling electron-phonon interactions in graphene at ultrahigh carrier densities,” Phys. Rev. Lett. 105(25), 256805 (2010). [CrossRef]

46. S. Balci, O. Balci, N. Kakenov, F.B. Atar, and C. Kocabas, “Dynamic tuning of plasmon resonance in the visible using graphene,” Opt. Lett. 41(6), 1241–1244 (2016). [CrossRef]

47. H. Liu, J. Lu, and X.R. Wang, “Metamaterials based on the phase transition of VO2,” Nanotechnology 29(2), 024002 (2018). [CrossRef]

48. C. Cen, Z. Chen, D. Xu, L. Jiang, X. Chen, Z. Yi, P. Wu, G. Li, and Y. Yi, “High quality factor, high sensitivity metamaterial graphene—perfect absorber based on critical coupling theory and impedance matching,” Nanomaterials 10(1), 95 (2020). [CrossRef]

49. L.N. Deekonda, S.K. Sahu, and A.K. Panda, A Graphene-Based Broadband Metamaterial Absorber. (IEEE, 2021).

50. W. Liu, J. Xu, and Z. Song, “Bifunctional terahertz modulator for beam steering and broadband absorption based on a hybrid structure of graphene and vanadium dioxide,” Opt. Express 29(15), 23331–23340 (2021). [CrossRef]

Ref.	Absorber bandwidth (THz)	Absorptivity	Materials	Years
[49]	0.91	>99%	Graphene	2021
[50]	0.45	>99%	Graphene, VO₂	2021
[12]	0.45	>99%	Graphene, VO₂	2021
[39]	1.321	>99%	Graphene, VO₂	2022
This paper	1.683	>99%	Graphene, VO₂

THz broadband and dual-channel perfect absorbers based on patterned graphene and vanadium dioxide metamaterials

Abstract

1. Introduction

2. Model design and methods

3. Results and analysis

4. Conclusions

Funding

Disclosures

Data availability

References

Data availability

Cited By

Figures (7)

Tables (1)

Equations (10)

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