Direct phase modulation is one of the most urgent and difficult issues in the terahertz research area. Here, we propose a new method employing a two-dimensional electron gas (2DEG) perturbation ...microstructure unit coupled to a transmission line to realize high-precision digital terahertz phase manipulation. We induce local perturbation resonances to manipulate the phase of guided terahertz waves. By controlling the electronic transport characteristics of the 2DEG using an external voltage, the strength of the perturbation can be manipulated, which affects the phase of the guided waves. This external control permits electronic manipulation of the phase of terahertz waves with high precision, as high as 2−5° in the frequency range 0.26–0.27 THz, with an average phase error of only 0.36°, corresponding to a timing error of only 4 fs. Critically, the average insertion loss is as low as 6.14 dB at 0.265 THz, with a low amplitude fluctuation of 0.5 dB, so the device offers near-ideal phase-only modulation.A terahertz phase modulator based on the switchable perturbation resonance in two-dimensional electron gas is demonstrated. Phase manipulation with precision ranging from 2° to 5° is obtained at frequencies in the range from 0.26 to 0.27 THz.
Terahertz (THz) science and technology promise unique applications in high-speed communications, high-accuracy imaging, and so on. To keep up with the demand for THz systems, THz dynamic devices ...should feature large phase shift modulation and high speed. To date, however, only a few devices can efficiently manipulate the phase of THz waves. In this paper, we demonstrate that efficient phase modulation of THz waves can be addressed by an active and enhanced resonant metamaterial embedded with a nanostructured 2D electron gas (2DEG) layer of a GaN high electron mobility transistor (HEMT). The enhanced resonant metaunit couples the traditional dipolar and inductance-capacitance resonances together to realize a coupling mode with enhanced resonance. Embedded with the nanostructured 2DEG layer of GaN HEMT, the resonance intensity and surface current circuit of the enhanced resonant mode in the metamaterial unit can be dynamically manipulated by the electrical control of the carrier distribution and depletion of the 3 nm 2DEG, leading to a phase shift greater than 150° in simulation. In the dynamic experiments, a 137° phase shift was achieved with an external controlling voltage of only several volts in the THz transmission mode. This work represents the first realization of a phase shift greater than 100° in a dynamic experiment in transmission mode using an active metamaterial structure with only a single layer. In addition, given the high-speed modulation ability of the HEMT, this concept provides a promising approach for the development of a fast and effective phase modulator in THz application systems.
Terahertz (THz) technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems. One of the key challenges facing the ...field is the need for tools to enable agile engineering of THz wave fronts. Here, we describe a reconfigurable metasurface based on GaN technology with an array-of-subarrays architecture. This subwavelength-spaced array, under the control of a 1-bit digital coding sequence, can switch between an enormous range of possible configurations, providing facile access to nearly arbitrary wave front control for signals near 0.34 THz. We demonstrate wide-angle beam scanning with 1° of angular precision over 70 GHz of bandwidth, as well as the generation of multi-beam and diffuse wave fronts, with a switching speed up to 100 MHz. This device, offering the ability to rapidly reconfigure a propagating wave front for beam-forming or diffusively scattered wide-angle coverage of a scene, will open new realms of possibilities in sensing, imaging, and networking.
The special position of terahertz wave in the electromagnetic spectrum makes it possess the characteristics of orientation, broadband, penetration and low energy, which promotes the extensive ...research of terahertz wave in the fields of communication, radar, imaging, sensing, security inspection and so on. The solid‐state terahertz sources based on semiconductor devices have attracted extensive attention in the field of terahertz information technology due to their characteristics such as being able to work at room temperature, being small in size, being easy to integrate and having good frequency stability. Terahertz planar Schottky diode is a kind of low parasitic semiconductor device. Its high cutoff frequency makes it work well in the terahertz range. The frequency multiplier based on planar Schottky diode is an important part of terahertz solid state source. In this review, the development of Schottky diodes technology in recent years have been introduced, including the structures and preparation of Schottky diodes. In addition, the current situation and performance of different types of terahertz sources based on Schottky diodes are further introduced, and the future development trend is discussed.
In the past ten years, terahertz technology has developed rapidly in wireless communications, spectroscopy, and imaging. Various functional devices have been developed, such as filters, absorbers, ...polarizers, mixers, and modulators. Among these, the terahertz phase modulation is a current research hotspot. It is the core technology to realize flexible control of the terahertz wavefront, beam scanning, focusing deflection. It is indispensable in terahertz wireless communication, high-resolution imaging, and radar systems. This review summarizes the research progress of terahertz phase modulators from the two major types: free space and guided wave integration. Among these, the free space terahertz phase modulator is realized by combining the tunable materials and artificial metasurfaces. Based on different types of tunable materials, the terahertz free space phase modulator combining the semiconductor, liquid crystal, phase change materials, graphene, and other two-dimensional materials are introduced, and the influence of different materials on the phase modulation performance is discussed and analyzed. The monolithic integration and waveguide embedding methods are introduced separately, and the characteristics of different forms of terahertz-guided wave phase modulation are also discussed. Finally, the development trends of terahertz phase modulators, possible new methods, and future application requirements are discussed.
Isogeometric analysis (IGA), due to its high efficiency and accuracy, can be replaced by the conventional finite element method in the topology optimizations (TOs). In this paper, we present an ...efficient isogeometric TO method based on the scheme of bi-directional evolutionary structural optimization (BESO). The structural response analysis is implemented by the IGA, and the detailed derivation is introduced. Based on the local support property of the non-uniform rational B-spline (NURBS), a NURBS filter is proposed to smooth the sensitivity numbers, of which NURBS space is different from that used in the IGA as long as the element spans keep consistency. Three benchmark numerical examples with different filters and mesh sizes are presented to validate the stability and mesh-dependency of the proposed isogeometric TO method.
In this paper, the enhanced terahertz (THz) electromagnetically induced transparency (EIT) resonance is achieved based on the coupled electric field dropping effect within the undulated meta-surface. ...It is found that the height difference between the inner ring and the outer split ring could lead to a significant coupled mode with electric field dropping distribution. When the height of the inner ring increases, the electric field of the inner ring gradually cascades to the outer ring just as a waterfall so that the coupling between the two rings in a unit cell and two adjacent units is enhanced. Both the simulation and experimental results show that a nearly 95% transparency window which is twice that of traditional EIT can be observed by applying such coupled electric field dropping effect, which may provide a promising way to develop the high resonance intensity meta-surface in the THz region.
Terahertz communication technology can provide abundant frequency resources, strong confidentiality, antijamming capability, communication tracking capability and the ability to achieve highspeed ...data transmissions and can serve as an important technical method for high-speed communications in the future. Among these terahertz communication technologies, terahertz direct modulation technology is a key means to achieve low system complexity and power consumption. In this paper, a review and outlook of terahertz direct modulation technology are proposed from the aspects of high-electron-mobility-transistor-based terahertz direct modulation, parallelswitch terahertz direct modulation, diode-based terahertz direct modulation, quantum cascade laser-based terahertz direct modulation and new-material-based terahertz direct modulation. We hope through this paper that more readers can gain knowledge about the development and challenges of terahertz direct modulation technology for high-speed communication systems, thus promoting the development of high-speed terahertz communication technology based on direct modulation.
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