Active Terahertz Shielding and Absorption Based on Graphene Foam Modulated by Electric and Optical Field Excitation

Abstract Ultralight materials for broadband terahertz (THz) shielding and absorption are promising in practical THz applications. Here, active THz shielding and absorption properties of 3D graphene foam (GF) controlled by both laser pumping and biased electric field are investigated. The GF can be tuned from OFF‐shielding state to ON‐shielding state when the external field excitations are applied, and 10 dB shielding bandwidth expands from 0 to a broad band of 0.2–1.6 THz. Further researches show that the GF always keeps very low THz reflection either with or without external fields, but its absorption characteristics can be remarkably controlled from 13% to 95.4% at 0.3 THz by the power of the external excitations, and its specific average terahertz absorption performance increases from 3.9 × 10³ to 1.95 × 10⁴ dB cm³ g⁻¹. This modulation mechanism reveals that the carrier density in GF increases one order of magnitude from 2.6 × 10¹⁴ cm⁻³ to 3.15 × 10¹⁵ cm⁻³. Finally, the tunable THz shielding and absorption characteristics of this GF device are demonstrated by THz transmission imaging, which shows its great potential applications in active THz imaging, radar, and electromagnetic compatibility.