A Phase Transition Oxide/Graphene Interface for Incident‐Angle‐Agile, Ultrabroadband, and Deep THz Modulation

Abstract

Although plenty of functional materials have been explored to dynamically control the terahertz (THz) transmission, the limits in modulation depth, operation bandwidth, or angle‐agile characteristics hinder their applications in highly active THz devices. Here, a 2D/3D (graphene/phase transition oxide VO2) interface is demonstrated for unprecedented high‐efficiency modulation of THz waves with incident‐angle‐agile and ultrabroadband. An impedance matching state can be met at the graphene/VO2 interface by adjusting the stacked graphene layers, which leads to a minimal terahertz reflection amplitude. Then the interfacial impedance can be changed continuously via the semiconductor–metal phase transition of VO2 and achieve a THz switching. Based on this mechanism, this heterostructure demonstrates giant THz average amplitude modulation of 93%, 94%, and 96% in 0.3–1.5 THz at the incident angle of 35°, 48°, and 53°, respectively. Moreover, the corresponding insertion loss is only −7.4, −4.1, and −6.5, which is much lower than most of the present THz modulation. These coupling phenomena and functions arising from the integration of 2D material and 3D phase transition oxide film broaden the previous materials system for dynamic controlling of THz wave, and would promote advanced THz smart devices for practical applications.

Highly Flexible Ti3C2Tx MXene/Waterborne Polyurethane Membranes for High-Efficiency Terahertz Modulation with Low Insertion Loss

“…However, increasing the content of MXene in MWMs to improve the modulation depth will inevitably lead to a large insertion loss, which is detrimental to THz applications. The insertion loss of MWMs is defined as 20 × log­( E after stretching / E air ), , where E air represents the intensity of the frequency-domain THz signal at 0.37 THz that corresponds to the empty THz beam bath. Figure d shows the insertion loss for MWMs as a function of frequency, and the insertion loss increases with the MXene content.…”

Photothermal conversion of Ti2O3 film for tuning terahertz waves

“…Notably, the resistance change curves during heating and cooling almost coincide, indicating that there is no hysteresis during the metal-insulator transition. Compared with VO 2 , which exhibits the hysteresis loop of the square resistance against temperature (Liang et al, 2019;Zhu et al, 2020), Ti 2 O 3 film is expected to achieve an extensive range of optoelectronic applications. The mid-infrared transmittance properties of the Ti 2 O 3 film on SiO 2 substrate were analyzed.…”