Yuncheng Zhao

Gbps Terahertz External Modulator Based on a Composite Metamaterial with a Double-Channel Heterostructure

The past few decades have witnessed a substantial increase in terahertz (THz) research. Utilizing THz waves to transmit communication and imaging data has created a high demand for phase and amplitude modulation. However, current active THz devices, including modulators and switches, still cannot meet THz system demands. Double-channel heterostructures, an alternative semiconductor system, can support nanoscale two-dimensional electron gases (2DEGs) with high carrier concentration and mobility and provide a new way to develop active THz devices. In this Letter, we present a composite metamaterial structure that combines an equivalent collective dipolar array with a double-channel heterostructure to obtain an effective, ultrafast, and all-electronic grid-controlled THz modulator. Electrical control allows for resonant mode conversion between two different dipolar resonances in the active device, which significantly improves the modulation speed and depth. This THz modulator is the first to achieve a 1 GHz modulation speed and 85% modulation depth during real-time dynamic tests. Moreover, a 1.19 rad phase shift was realized. A wireless free-space-modulation THz communication system based on this external THz modulator was tested using 0.2 Gbps eye patterns. Therefore, this active composite metamaterial modulator provides a basis for the development of effective and ultrafast dynamic devices for THz wireless communication and imaging systems.

Multiband Frequency-Selective Surface With Five Resonance Peaks in Terahertz Band

We discuss a multiband frequency-selective surface (FSS) device with an irregular electromagnetic structure that has five resonance peaks in the terahertz (THz) regime. The compact asymmetric structure utilizes all components efficiently. Different modes, including LC and quasi-quadrupole resonances, are induced in each unit cell. Simulations indicate that each of the five resonance peaks has independent characteristics with different electric field and surface current distributions. The multiband FSS provides an alternative way to design THz multiband filters, modulators, absorbers, and sensors at small planar dimensions.

Multi-band terahertz active device with complementary metamaterial

We describe a multi-band terahertz-active device using a composite structure made of complementary metamaterial and doped silicon that can be dynamically controlled. This special complementary metamaterial exhibits three resonances that produce three pass-bands. The pass-bands can be uniformly manipulated by exploiting the photoinduced characteristics of the doped silicon. Simulations were performed to analyze the magnetic field and surface current distributions. The simulation results agree well with experimental results obtained from terahertz time-domain spectroscopy. Using an 808-nm-wavelength laser beam, a modulation depth of up to 80% was obtained. In numerical simulations, we used a conductivity mode to characterize photoinduction. The development of multi-band terahertz-active devices has many potential applications, for example, in filters, modulators, switches, and sensors.

Controlling the transparency window in terahertz band using mode coupling metamaterials

Mode-coupling metamaterials are typically composite structures with different resonance modes. Controlling couplings among these modes results in a sharp transparency window within the absorption spectrum of the metamaterials. Here, we present a composite structure of ring and split-ring resonators to constitute a new structure with entirely new mode. Experimental results show that the asymmetric combination of these resonators can result in a variation in transparency strength. The dimensions and relative positions of the split-ring resonator are discussed particularly with a series of experimental results. Simulation results show that the coupling intensity is the main reason for this behavior. Exploiting this aspect, a way to control the transparency window between composite structure metamaterials is proposed.

Mode coupling in terahertz metamaterials using sub-radiative and super-radiative resonators

We theoretically and experimentally explored the electromagnetically induced transparency (EIT) mode-coupling in terahertz (THz) metamaterial resonators, in which a dipole resonator with a super-radiative mode is coupled to an inductance-capacitance resonator with a sub-radiative mode. The interference between these two resonators depends on the relative spacing between them, resulting in a tunable transparency window in the absorption spectrum. Mode coupling was experimentally demonstrated for three spacing dependent EIT metamaterials. Transmittance of the transparency windows could be either enhanced or suppressed, producing different spectral linewidths. These spacing dependent mode-coupling metamaterials provide alternative ways to create THz devices, such as filters, absorbers, modulators, sensors, and slow-light devices.

Fast THz Modulator based on the stagger-netlike GaN HEMT active metamaterial

View Online Fast THz Modulator based on the stagger-netlike GaN HEMT active metamaterial Yuncheng Zhao, Yaxin Zhang,* Shixiong Liang, Zhihong Feng, Ziqiang Yang,* Terahertz Science Cooperative Innovation Center, University of Electronic Science and Technology of China No.4, Section 2, North Jianshe Road, Chengdu, 610054, China 2 National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, Hezuo Road, Shijiazhuang, 050051, China Corresponding Author. Email: Yaxin Zhang, zhangyaxin@uestc.edu.cn; Ziqiang Yang, zqyang@uestc.edu.cn Received: 12 June 2017, Accepted: 18 June 2017, Published Online: 04 October 2017 Citation Information: Yuncheng Zhao, Yaxin Zhang, Shixiong Liang, Zhihong Feng, Ziqiang Yang. Nano-Micro Conference, 2017, 1, 01007 doi: 10.11605/cp.nmc2017.01007 Abstract Terahertz technology promises unique applications in high speed communication, high accuracy imaging and so on [1]. However, one major bottleneck for developing Terahertz application systems is the lack of high-performance dynamic devices for effectively manipulating the Terahertz wave. In recent years, the rapid development of twodimensional electron gas (2DEG) devices provides a promising way to develop dynamic terahertz devices [2]. Here, we combined a stagger-netlike metamaterial array with high-electron-mobility transistor (HEMT) structure to form a electronic grid-controlled THz modulator. By controlling the carrier concentration of 2DEG, the mode conversion between two kinds of dipolar resonances has been realized. Modulation depth of this device can reach up to 94%. More importantly, in the dynamic test, 600 MHz sinusoidal signals was received by a THz detector. It may provide a way to achieve effective active devices in THz wireless communication system.Terahertz technology promises unique applications in high speed communication, high accuracy imaging and so on [1]. However, one major bottleneck for developing Terahertz application systems is the lack of high-performance dynamic devices for effectively manipulating the Terahertz wave. In recent years, the rapid development of twodimensional electron gas (2DEG) devices provides a promising way to develop dynamic terahertz devices [2]. Here, we combined a stagger-netlike metamaterial array with high-electron-mobility transistor (HEMT) structure to form a electronic grid-controlled THz modulator. By controlling the carrier concentration of 2DEG, the mode conversion between two kinds of dipolar resonances has been realized. Modulation depth of this device can reach up to 94%. More importantly, in the dynamic test, 600 MHz sinusoidal signals was received by a THz detector. It may provide a way to achieve effective active devices in THz wireless communication system. Figure 1. (a) 3-D structure of a GaN HEMT metamaterial unit cell. (b) Schematic of the THz modulator. (c)Simulation transmission spectrum results with different carrier density. (d) Image of packaged THz modulator. (e)The received sinusoidal modulating signals. References [1] P. H. Siegel, Terahertz technology. IEEE Transactions on Microwave Theory and Techniques. 50(3), 910-928 (2002). doi:10.1109/22.989974 [2] Yaxin Zhang; Shen Qiao; Shixiong Liang; Zhenhua Wu; Ziqiang Yang; Zhihong Feng; Han Sun; Yucong Zhou; Linlin Sun; Zhi Chen; Xianbing Zou; Bo Zhang; Jianhao Hu; Shaoqian Li; Qin Chen; Ling Li; Gaiqi Xu; Yuncheng Zhao; Shenggang Liu, Gbps Terahertz External Modulator Based on a Composite Metamaterial with a Double-Channel Heterostructure. Nano Letters, 15, 3501-3506 (2015). doi:10.1021/acs.nanolett.5b00869 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License.