Broadband electrically tunable VO₂‑Metamaterial terahertz switch with suppressed reflection

Abstract

Devices designed to dynamically control the transmission, reflection, and absorption of terahertz (THz) radiation are essential for the development of a broad range of THz technologies. A viable approach utilizes materials which undergo an insulator‐to‐metal transition (IMT), switching from transmissive to reflective upon becoming metallic. However, for many applications, it is undesirable to have spurious reflections that can scatter incident light and induce noise to the system. We present an electrically actuated, broadband THz switch which transitions from a transparent state with low reflectivity, to an absorptive state for which both the reflectivity and transmission are strongly suppressed. Our device consists of a patterned high‐resistivity silicon metamaterial layer that provides broadband reflection suppression by matching the impedance of free space. This is integrated with a VO2 ground plane, which undergoes an IMT by means of a DC bias applied to an interdigitated electrode. THz time domain spectroscopy measurements reveal an active bandwidth of 700 GHz with suppressed reflection and more than 90% transmission amplitude modulation with a low insertion loss. We utilize finite‐difference time domain (FDTD) simulations in order to examine the loss mechanisms of the device, as well as the sensitivity to polarization and incident angle. This device validates a general approach toward suppressing unwanted reflections in THz modulators and switches which can be easily adapted to a broad array of applications through straightforward modifications of the structural parameters.

Electrical and optical properties of highly crystalline W-VO2 nano-films prepared by thermal oxidation of V-WO3 precursors

“…The metal-insulator transition (MIT) of vanadium dioxide (VO 2 ) can lead to significant changes in its electric, thermal, and optical properties, [1][2][3][4] which had been studied in many applications, such as smart glazes, [5][6][7] optical and electrical switching devices, [8][9][10] thermal sensors, 11) and memory devices. 12) The critical transition temperature (T c ) and thermal hysteresis of the MIT of the VO 2 must be adjusted for different applications.…”

A review of the preparation, properties and applications of VO2 thin films with the reversible phase transition

“…In fact, there have been a lot of reports on the application of VO 2 in the direction of smart windows. However, there are still several difficulties in the application of vanadium dioxide in the direction of smart windows: 1) The phase change temperature is adjusted to near room temperature; 2) The environmental stability of VO 2 thin film coatings is altered; and 3) Improve visible light transmittance; 4) Improve the ability to regulate solar energy (Zhang et al, 2020). This necessitates the modification of the smart window to improve its performance by improving the visible light transmittance and solar energy modulation amplitude.…”

A Review: The Functional Materials-Assisted Terahertz Metamaterial Absorbers and Polarization Converters

“…When VO2 film is in metal state, the ellipticity of the LTC converter is close to -1, while the axis ratio is lower than 3 dB in the range of 1.07-1.67 THz. Due to the dielectric properties of the VO 2 with insulating state, transmission function combined with other functions can also be realized [119,[157][158][159]. In Figure 15a, L. L. Chen et al introduced VO 2 film into a multi-layer design to achieve the dual-function of absorption and high transmission [157].…”

“…When VO 2 is in insulator state, the proposed structure can be used as a transparent conducting metal. In 2020, J. S. Schalch et al designed an electrically actuated, broad-band terahertz switch, which can be transformed from the transparent state with low reflection to the absorption state suppressing the reflection and transmission [158]. The structure is integrated with a nonstructured VO 2 film performing the insulator-metal-transition.…”