Electrically Controlled Terahertz Binary Coder Based on Hysteresis of Vanadium Dioxide Embedded Modulator

Abstract

We experimentally demonstrated an electrically controlled terahertz (THz) binary coder based on hysteresis of vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) embedded modulator. The unit cell of the device consists of three horizontal metal lines and one vertical metal bar on a Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -Si composite substrate. When no current is biased, the device has two resonant absorption dips locating at 0.55 and 1.0 THz, respectively. And the transmission of transparent band between two resonant absorption dips can be electrically modulated by the bias current. When the bias current increases to 0.3 A, the maximum modulation depth at 0.8 THz reaches 99%. This electrically tunability is resulted from the insulator-to-metal transition (IMT) of the embedded VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film. Most interestingly, a huge hysteresis is observed, which is important for developing electrically controlled THz binary coders. The high transmission state (I = 0 A) and low transmission state (I = 0.3 A) are defined as “1” and “0”, respectively. And thus, the THz binary code of “1010” can be correspondingly obtained at 0.8 THz. The device can switch and encode the THz wave at selected frequency, which is very useful for THz communication and on-chip integrated THz system in the future.