*Article* **Two-Bit Terahertz Encoder Realized by Graphene-Based Metamaterials**

**Shan Yin 1,2, Xintong Shi 1, Wei Huang 1,\*, Wentao Zhang 1,\*, Fangrong Hu 1, Zujun Qin 1 and Xianming Xiong 1**


Received: 5 November 2019; Accepted: 7 December 2019; Published: 12 December 2019

**Abstract:** Terahertz (THz) technologies have achieved grea<sup>t</sup> progress in the past few decades. Developing active devices to control the THz waves is the frontier of THz applications. In this paper, a new scheme of two-bit THz encoder is proposed. Di fferent from the present THz modulators whose spectra at di fferent bands are varied simultaneously, our encoder can realize the individually e fficient modulation of every channel. The encoder comprises the double-sided graphene-based metamaterials, in which the graphene structures on each side are connected to the external electrodes individually. The well-designed metamaterials on the front and back sides determine the resonances at two di fferent bands (0.20 THz and 0.33 THz) separately. Through simulating the performance of this device by changing the conductivities of the graphene on each side independently, we demonstrate two-bit encoding realized by the dual-band modulation of transmission amplitude with electronic control, and the modulation depth can reach as high as 79.6%. Our encoder can promote the development of multifunctional and integrated devices, such as frequency division multiplexers and logical circuitry, which will contribute to THz communications.

**Keywords:** terahertz metamaterials; graphene; encoder; active control
