• Acta Optica Sinica
  • Vol. 45, Issue 9, 0923001 (2025)
Gongli Xiao1, Kai Li1, Hongyan Yang2,*, Linglong Pei1..., Hui Li1, Xingpeng Liu1 and Zanhui Chen1|Show fewer author(s)
Author Affiliations
  • 1Key Laboratory of Microelectronic Devices and Integrated Circuits, School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, Guangxi , China
  • 2School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, Guangxi , China
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    DOI: 10.3788/AOS241949 Cite this Article Set citation alerts
    Gongli Xiao, Kai Li, Hongyan Yang, Linglong Pei, Hui Li, Xingpeng Liu, Zanhui Chen. Switchable Broadband and Narrowband Terahertz Absorber Based on Graphene Interdigital Structure[J]. Acta Optica Sinica, 2025, 45(9): 0923001 Copy Citation Text show less

    Abstract

    Objective

    Terahertz (THz) waves are electromagnetic waves that fall between the infrared and microwave bands. Due to their unique optical and electrical properties, they are valuable in various applications, including radar, remote sensing, communications, and biomedicine. Metamaterials, which are artificial materials characterized by negative refractive indices and negative dielectric constants, have attracted significant attention in recent years. Devices made from metamaterials, such as absorbers, polarizers, and superlenses, have already been successfully implemented in practice. Although there have been numerous studies on broadband, narrowband, and tunable THz absorbers, there remains a notable gap in research regarding broadband and narrowband switchable absorbers. Therefore, investigating tunable THz absorbers that can switch between broadband and narrow band is of great importance.

    Methods

    In this paper, we propose a switchable THz absorber with both broadband and narrowband functionalities based on a graphene interdigital structure. The absorber is modeled and analyzed using the finite difference time domain (FDTD) method and MATLAB simulations. First, we examine the effects of various resonant layer structures on absorption efficiency and the influence of graphene’s Fermi energy levels on conductivity. Structural parameters are optimized to achieve high absorption and a wide operating bandwidth. Second, to investigate the physical mechanisms underlying absorption, we analyze the relative impedance of the device (Z), along with the electric field strengths and vector distributions at four frequency points. We also explore the influences of different structural parameters and polarization angles on absorption performance to further assess the practicality of the absorber. Finally, simulations are conducted to evaluate how changes in graphene’s Fermi energy level affect the absorption rate and bandwidth, thus assessing the device’s tunability.

    Results and Discussions

    The results indicate that the single graphene interdigital structure layer is capable of achieving both broadband and narrowband absorption properties. In broadband mode, it demonstrates a bandwidth of 1.44 THz with absorption exceeding 90%. In narrowband mode, it achieves near-perfect absorption at 1.32 THz and 2.67 THz (Fig. 1). Across the frequency range of 0.5 to 4.3 THz, variations in structural parameters have minimal influences on both absorption bandwidth and absorption rate (Fig. 4). In addition, the structure exhibits significant tunability with changes in the Fermi energy level, which can be adjusted from 0.3 to 1.0 eV, allowing the absorption rate to be dynamically tuned between 60.65% to 99.88% (Fig. 6). The broadband and narrowband switchable absorber developed in this paper demonstrates ultra-broadband and high absorption characteristics. Compared to previously reported results, the switchable functionality is achieved using a single-layer structure (Table 2), significantly reducing fabrication complexity and cost due to its structural simplicity, which enhances integration with the IC process.

    Conclusions

    In this paper, we investigate a tunable THz absorber with broadband and narrowband switching capabilities, based on a three-layer graphene fork-finger structure. The effects of a single-layer graphene interdigital structure on absorption rate and bandwidth are analyzed, revealing that both broadband and narrowband switching can be realized by varying the Fermi energy level (EF) and relaxation time (τ). An analysis of the electric field and current distribution at high absorption frequency points indicates that the absorber achieves strong absorption through the interaction between local plasmon resonance and electric dipole resonance, which are excited by incident THz waves on the graphene. Furthermore, this absorber demonstrates excellent tunability in both physical and chemical aspects, making it promising for applications in THz detection, imaging, and related fields. Its simple structure, broadband absorption, flexible tunability, and compatibility with integrated circuit processes further enhance its practical potential.

    Gongli Xiao, Kai Li, Hongyan Yang, Linglong Pei, Hui Li, Xingpeng Liu, Zanhui Chen. Switchable Broadband and Narrowband Terahertz Absorber Based on Graphene Interdigital Structure[J]. Acta Optica Sinica, 2025, 45(9): 0923001
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