Terahertz smart devices based on phase change material VO2 and metamaterial graphene that combine thermally adjustable absorption and selective transmission

Abstract

In this paper, a classical three-layer structure of proportionate terahertz intelligent device composed of vanadium dioxide and graphene is simulated and designed. The proportionate setting of this intelligent device allows for better control over the size of surface microstructures, thereby enhancing the utilization of materials during the production process. At a temperature of T = 345 K, the device exhibits perfect absorption efficiency of greater than or equal to 90 % in the frequency range of 2.46 THz to 6.85 THz (4.39 THz), spanning almost half of the terahertz band. At a temperature of T = 323 K, the device achieves absorption of over 77.3 % in the frequency range of 3.04 THz to 5.64 THz, with average transmittance rates of 69.61 % and 69.79 % in the frequency ranges of 0.01 THz to 2.32 THz and 6.82 THz to 10.00 THz, respectively. We use vanadium dioxide as the bottom layer to avoid the effect of traditional metal substrates that prevent electromagnetic waves from transmitting and limit the conversion of terahertz device performance. Temperature modulation enables control over absorption and transmission. We first explain the results based on the crystal structure within VO₂ and then analyze the surface electric field of the device at two temperatures using surface plasmons (SPs). By adjusting the structural parameters of the absorber and applying an external bias voltage, the Fermi energy of graphene can be altered, demonstrating the device’s physical coherence, manufacturing tolerance, and dynamic tuning capability. We investigate the influence of different incident angles of external electromagnetic waves on the device performance, showing that it maintains excellent performance over a wide range of angles, which is crucial for practical applications. Finally, we examined the implications of employing the Drude model to characterize silicon dioxide in the terahertz range and its potential impact on device performance. This holds significant implications for communication, detection, sensing, imaging, and provides insights for future terahertz device development.