Dual-function terahertz ultra-broadband modulator based on the vanadium dioxide and gold

In this paper, we introduce a dual-functional terahertz metasurface based on vanadium dioxide (VO
2
). Within the same frequency range, it seamlessly transitions between functioning as a wideband absorber and a reflective wideband linear-to-cross (LTX) polarization converter. This metasurface design offers numerous advantages, including functional versatility, a substantial relative bandwidth, and an expanded operational range for incident angles and polarization orientations. In its metallic phase, VO
2
enables the multifunctional metasurface to achieve absorption rates exceeding 90% within the 1.11-3.36 THz frequency range. The bandwidth and relative bandwidth are 2.25 THz and 100.7%, respectively. We analyze the underlying principles of the absorption effect using surface current images and impedance matching theory. In its insulating phase, a polarization conversion efficiency exceeding 90% within the 0.86-2.25 THz frequency range is facilitated by VO2, with a relative bandwidth of 89.4%. Moreover, it functions as a half-wave plate. In its insulating phase, a polarization conversion efficiency exceeding 90% within the 0.86-2.25 THz frequency range is facilitated by VO2, with a relative bandwidth of 89.4%. Moreover, it functions as a half-wave plate. This research has expanded its operational bandwidth and endowed it with additional functionalities. The proposed dual-functional terahertz modulator has the characteristics of a large relative bandwidth, simple structure, and high process feasibility, which makes it potentially useful in terahertz detection, modulation, and switching fields.