Investigation of a Tunable Ultra‐Broadband Terahertz Absorber Based on Composite‐Patterned Monolayer Graphene

This paper proposes an ultra‐broadband terahertz absorber featuring a composite‐patterned monolayer graphene metasurface. By structurally combining a centrally perforated elliptical array with adjacent slotted strips, the absorber achieves a continuous working band from 2.18 to 6.32 THz, with a relative bandwidth of 97.4%. Significantly, the device demonstrates almost perfect absorption properties, reaching 99.9% at 2.5 THz and 99.5% at 5.7 THz. At 4.1 THz, the absorption level remains as high as 97%. The average absorption rate across the entire target frequency band is 95.56%. Further research on the internal electric field distribution reveals the mechanism: rather than acting independently, multiple localized surface plasmon resonance (LSPR) modes strongly couple with each other. This coupling causes the superposition and broadening of the absorption peaks. Furthermore, the proposed metasurface exhibits weak polarization dependence. Despite the complex geometric composition of the unit cell, the absorber maintains broadly comparable absorption profiles under both transverse electric and transverse magnetic incident waves within a moderate incident‐angle range. This angle‐tolerant and polarization‐tolerant response enhances its practical applicability, indicating that the structure has good application potential in terahertz detection and electromagnetic stealth. In addition, the absorber can still maintain effective broadband absorption at oblique incidence angles up to 20°. Under transverse electric (TE) polarization, even at an incident angle of 40°, the absorption rate of the core band remains above 80%. These angle‐tolerant and polarization‐tolerant characteristics enhance the practical applicability of the proposed absorber, indicating its potential for terahertz detection and electromagnetic stealth applications.