Graphene‐Based Terahertz Perfect Absorber with Broadband, Wide‐Angle, and Dynamically Tunable Performance
Pingrui Fu, Zhiquan Chen, Zao Yi, Shubo Cheng, Sohail Ahmad, Bo Li
Abstract
This work introduces a dynamically adjustable terahertz metasurface absorber, utilizing an innovative graphene pattern designed with scalable geometric proportions. The absorber is designed following a scaling principle, wherein the key dimensions of the top‐layer graphene pattern are proportionally scaled, thereby simplifying the design process and optimizing performance. Measured within the frequency range from 1.96 to 5.42 THz, the absorber demonstrates outstanding performance, achieving an average efficiency of 96.13% with values consistently above 90%, which equates to a 3.46 THz bandwidth. Perfect absorption is observed at three specific frequencies: 2.22, 3.27, and 5.06 THz. The broadband absorption are analyzed as follows. First, impedance matching studies indicate that the device's normalized impedance aligns well with that of free space over the target frequency range, leading to strong suppression of reflected waves. Second, pronounced electric field interactions between different structural zones excite coupled localized surface plasmon resonances. Specifically, the low‐frequency peak is attributed to dipole resonance in the central region, the midfrequency peak results from gap plasmon modes in nanoscale separations, and the high‐frequency peak involves hybrid multipolar resonances enabled by coupling among multiple subunits. The spectral overlap and merging of these resonant modes effectively extend the absorption bandwidth. Through careful optimization of structural parameters, the absorber achieves a balanced performance profile and shows considerable robustness against fabrication imperfections. Comprehensive characterization confirms its polarization‐independent behavior. The absorption efficiency can be dynamically tuned by varying the Fermi level of graphene, whereas the response speed is governed by the carrier relaxation time. Combining wide‐angle operational stability with a simple, integrable architecture, this design offers a compelling platform for terahertz stealth and other emerging applications. It is worth noting that the minimum feature size of the proposed design is 4 μm (L3), which is fully compatible with standard ultraviolet (UV) photolithography, ensuring practical fabricability with existing microfabrication processes.