Recent Advances in Terahertz Devices and Applications

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A:Physics".

Deadline for manuscript submissions: closed (31 October 2024) | Viewed by 14318

Special Issue Editors

School of Semiconductors and Physics, North University of China, Taiyuan 030051, China
Interests: metamaterials; terahertz devices; terahertz applications

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Co-Guest Editor
1. Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
2. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
Interests: terahertz imaging; single-pixel cameras; hyperspectral imaging; spatial light modulators

Special Issue Information

Dear Colleagues,

This Special Issue, titled “Recent Advances in Terahertz Devices and Applications”, explores the latest developments in the field of terahertz technology, focusing on innovations in materials,  design, process, measurement, and applications. A terahertz wave is an electromagnetic wave with a frequency ranging from 0.1 THz to 10 THz, which is between an infrared wave and a millimeter wave. Terahertz technology has a higher frequency and a wider bandwidth, and also provides higher capacity compared to 5G technology. Therefore, devices based on terahertz technology have become one of the new research hotspots  and  has great potential in areas such as military radar, medical detection, imaging, communication and sensing, and so on. Central theme of this Special Issue include the multifunctional optimization of . Here are some examples of the key advancements made within this field:

  • Metamaterials, which enable novel properties and functions not found in natural materials, leading to breakthroughs in high-performance terahertz device design;
  • Terahertz lasers, lenses, filter, antennas, and so on, which have the potential to improve terahertz spectrum and imaging  systems, safety inspection, medical devices, and bioinstrumentation;
  • Terahertz actuators, sensors, absorbers, filters, diodes, energy harversters, detectors, and other series of terahertz wave regulation functional devices, which can be used in terahertz communication systems.

Dr. Qiannan Wu
Dr. Rayko Ivanov Stantchev
Guest Editors

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Keywords

  • metamaterials
  • terahertz devices
  • terahertz imaging
  • terahertz communication
  • terahertz biomedicine

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Published Papers (8 papers)

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Research

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18 pages, 757 KiB  
Article
Preamble Design and Noncoherent ToA Estimation for Pulse-Based Wireless Networks-on-Chip Communications in the Terahertz Band
by Pankaj Singh and Sung-Yoon Jung
Micromachines 2025, 16(1), 70; https://doi.org/10.3390/mi16010070 - 8 Jan 2025
Viewed by 711
Abstract
The growing demand for high-speed data transfer and ultralow latency in wireless networks-on-chips (WiNoC) has spurred exploration into innovative communication paradigms. Recent advancements highlight the potential of the terahertz (THz) band, a largely untapped frequency range, for enabling ultrafast tera-bit-per-second links in chip [...] Read more.
The growing demand for high-speed data transfer and ultralow latency in wireless networks-on-chips (WiNoC) has spurred exploration into innovative communication paradigms. Recent advancements highlight the potential of the terahertz (THz) band, a largely untapped frequency range, for enabling ultrafast tera-bit-per-second links in chip multiprocessors. However, the ultrashort duration of THz pulses, often in the femtosecond range, makes synchronization a critical challenge, as even minor timing errors can cause significant data loss. This study introduces a preamble-aided noncoherent synchronization scheme for time-of-arrival (ToA) estimation in pulse-based WiNoC communication operating in the THz band (0.02–0.8 THz). The scheme transmits the preamble, a known sequence of THz pulses, at the beginning of each symbol, allowing the energy-detection receiver to collect and analyze the energy of the preamble across multiple integrators. The integrator with maximum energy output is then used to estimate the symbol’s ToA. A preamble design based on maximum pulse energy constraints is also presented. Performance evaluations demonstrate a synchronization probability exceeding 0.98 for distances under 10 mm at a signal-to-noise ratio of 20 dB, with a normalized mean squared error below 102. This scheme enhances synchronization reliability, supporting energy-efficient, high-performance WiNoCs for future multicore systems. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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10 pages, 6473 KiB  
Article
Branch Waveguide Couplers with a frequency of 510 GHz for Terahertz Transmit/Receive Isolation Applications
by Hao Li, Dehai Zhang, Jin Meng and Li Wang
Micromachines 2024, 15(9), 1083; https://doi.org/10.3390/mi15091083 - 28 Aug 2024
Viewed by 3449
Abstract
To address the requirement of functioning as a transmit/receive isolation device in terahertz transceiver systems, in this paper, we present two high−isolation multi−branch waveguide directional couplers operating at a center frequency of 510 GHz. One is a high−performance five−branch directional coupler, and the [...] Read more.
To address the requirement of functioning as a transmit/receive isolation device in terahertz transceiver systems, in this paper, we present two high−isolation multi−branch waveguide directional couplers operating at a center frequency of 510 GHz. One is a high−performance five−branch directional coupler, and the other is a new type of three−branch waveguide coupler with lower processing difficulty. Both couplers were fabricated using low−cost CNC milling technologies. The performance of these couplers was verified through measurement results, demonstrating high isolation at the center frequency. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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13 pages, 4556 KiB  
Article
Switchable Vanadium Dioxide Metasurface for Terahertz Ultra-Broadband Absorption and Reflective Polarization Conversion
by Wei Zou, Changqing Zhong, Lujun Hong, Jiangtao Lei, Yun Shen, Xiaohua Deng, Jing Chen and Tianjing Guo
Micromachines 2024, 15(8), 967; https://doi.org/10.3390/mi15080967 - 28 Jul 2024
Cited by 1 | Viewed by 1516
Abstract
Based on the unique insulator-metal phase transition property of vanadium dioxide (VO2), we propose an integrated metasurface with a switchable mechanism between ultra-broadband absorption and polarization conversion, operating in the terahertz (THz) frequency range. The designed metasurface device is constructed using [...] Read more.
Based on the unique insulator-metal phase transition property of vanadium dioxide (VO2), we propose an integrated metasurface with a switchable mechanism between ultra-broadband absorption and polarization conversion, operating in the terahertz (THz) frequency range. The designed metasurface device is constructed using a stacked structure composed of VO2 quadruple rings, a dielectric layer, copper stripes, VO2 film, a dielectric layer, and a copper reflection layer. Our numerical simulations demonstrate that our proposed design, at high temperatures (above 358 K), exhibits an ultra-broadband absorption ranging from 4.95 to 18.39 THz, maintaining an absorptivity greater than 90%, and achieves a relative absorption bandwidth of up to 115%, significantly exceeding previous research records. At room temperature (298 K), leveraging VO2’s insulating state, our proposed structure transitions into an effective polarization converter, without any alteration to its geometry. It enables efficient conversion between orthogonal linear polarizations across 3.51 to 10.26 THz, with cross-polarized reflection exceeding 90% and a polarization conversion ratio over 97%. More importantly, its relative bandwidth reaches up to 98%. These features highlight its wide-angle, extensive bandwidth, and high-efficiency advantages for both switching functionalities. Such an ultra-broadband convertible design offers potential applications in optical switching, temperature dependent optical sensors, and other tunable THz devices in various fields. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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13 pages, 2679 KiB  
Article
Dual Features, Compact Dimensions and X-Band Applications for the Design and Fabrication of Annular Circular Ring-Based Crescent-Moon-Shaped Microstrip Patch Antenna
by Unal Aras, Tahesin Samira Delwar, P. Durgaprasadarao, P. Syam Sundar, Shaik Hasane Ahammad, Mahmoud M. A. Eid, Yangwon Lee, Ahmed Nabih Zaki Rashed and Jee-Youl Ryu
Micromachines 2024, 15(7), 809; https://doi.org/10.3390/mi15070809 - 21 Jun 2024
Cited by 3 | Viewed by 1281
Abstract
This study uses annular circular rings to create multi-band applications using crescent-shaped patch antennas. It is designed to be made up of five circular, annular rings nested inside of each other. Three annular rings are positioned and merged on top of the larger [...] Read more.
This study uses annular circular rings to create multi-band applications using crescent-shaped patch antennas. It is designed to be made up of five circular, annular rings nested inside of each other. Three annular rings are positioned and merged on top of the larger rings, with two annular rings set along the bottom of the feed line. The factors that set them apart, such as bandwidths, radiation patterns, gain, impedance, and return loss (RL), are analysed. The outcomes show how compact the multi-band annular ring antenna is. The proposed circular annular ring antenna has return losses of −33 dB and operates at two frequencies: 3.1 GHz and 9.3 GHz. This design is modelled and simulated using ANSYS HFSS. The outcomes of the simulation and the tests agree quite well. The X band and WLAN resonant bands have bandwidth capacities of 500 and 4300 MHz, respectively. Additionally, the circular annular ring antenna design is advantageous for most services at these operating bands. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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9 pages, 2864 KiB  
Communication
Terahertz Polarization Isolator Using Two-Dimensional Square Lattice Tellurium Rod Array
by Yong Wang, Yanqing Ai, Lin Gan, Jiao Zhou, Yangyang Wang, Wei Wang, Biaogang Xu, Wenlong He and Shiguo Li
Micromachines 2024, 15(6), 745; https://doi.org/10.3390/mi15060745 - 31 May 2024
Viewed by 1097
Abstract
A novel terahertz polarization isolator using a two-dimensional square lattice tellurium rod array is numerically investigated at the interesting band of 0.22 THz in this short paper. The isolator is designed by inserting six hexagonal tellurium rods into a fully polarized photonic crystals [...] Read more.
A novel terahertz polarization isolator using a two-dimensional square lattice tellurium rod array is numerically investigated at the interesting band of 0.22 THz in this short paper. The isolator is designed by inserting six hexagonal tellurium rods into a fully polarized photonic crystals waveguide with high efficiency of −0.34 dB. The TE and TM photonic band gaps of the 7 × 16 tellurium photonic crystals are computed based on the plane wave expansion method, which happen to coincide at the normalized frequency domain from 0.3859(a/λ) to 0.4033(a/λ), corresponding to the frequency domain from 0.2152 to 0.2249 THz. The operating bandwidth of the tellurium photonic crystals waveguide covers 0.2146 to 0.2247 THz, calculated by the finite element method. The six hexagonal tellurium rods with smaller circumradii of 0.16a serve to isolate transverse electric waves and turn a blind eye to transverse magnetic waves. The polarization isolation function and external characteristic curves of the envisaged structure are numerically simulated, which achieves the highest isolation of −33.49 dB at the central frequency of 0.2104 THz and the maximum reflection efficiency of 98.95 percent at the frequency of 0.2141 THz. The designed isolator with a unique function and high performance provides a promising approach for implementing fully polarized THz devices for future 6G communication systems. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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12 pages, 8499 KiB  
Article
In-Plane Radiation of Surface Plasmon Polaritons Excited by Free Electrons
by Ping Zhang, Yin Dong, Xubo Li, Xinxin Cao, Youfeng Yang, Guohao Yu, Shengpeng Yang, Shaomeng Wang and Yubin Gong
Micromachines 2024, 15(6), 723; https://doi.org/10.3390/mi15060723 - 30 May 2024
Cited by 1 | Viewed by 1137
Abstract
Surface plasmon polaritons (SPPs) have become a research hotspot due to their high intensity and subwavelength localization. Through free-electron excitation, a portion of the momentum of moving electrons can be converted into SPPs. Converting highly localized SPPs into a radiated field is an [...] Read more.
Surface plasmon polaritons (SPPs) have become a research hotspot due to their high intensity and subwavelength localization. Through free-electron excitation, a portion of the momentum of moving electrons can be converted into SPPs. Converting highly localized SPPs into a radiated field is an approach with the potential to aid in the development of a light radiation source. Reducing losses of SPPs is currently a critical challenge that needs to be addressed. The lifetime of SPPs in metal films is longer than that in metal blocks. Traditional optical gratings can transform SPPs into radiation to avoid the decay of SPPs in metal; however, they are created by etching metal films, so they tend to alter the dispersion characteristics of these films and will emit radiation in the direction perpendicular to the metal surface. This paper proposes an approach to converting the SPPs of a metal film excited by free electrons into a radiation field via lateral grating and obtaining in-plane radiation. We investigate the properties of SPP lateral radiation. The study of lateral radiation from metal films holds significant importance for SPP radiation sources and SPP on-chip circuit development. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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13 pages, 12245 KiB  
Article
Design of High-Gain Antenna Arrays for Terahertz Applications
by Xinran Ji, Yu Chen, Jing Li, Dian Wang, Yue Zhao, Qiannan Wu and Mengwei Li
Micromachines 2024, 15(3), 407; https://doi.org/10.3390/mi15030407 - 18 Mar 2024
Cited by 4 | Viewed by 2325
Abstract
A terahertz band (0.1–10 THz) has the characteristics of rich spectrum resources, high transmission speed, strong penetration, and clear directionality. However, the terahertz signal will suffer serious attenuation and absorption during transmission. Therefore, a terahertz antenna with high gain, high efficiency, and wide [...] Read more.
A terahertz band (0.1–10 THz) has the characteristics of rich spectrum resources, high transmission speed, strong penetration, and clear directionality. However, the terahertz signal will suffer serious attenuation and absorption during transmission. Therefore, a terahertz antenna with high gain, high efficiency, and wide bandwidth is an indispensable key component of terahertz wireless systems and has become a research hotspot in the field of antennas. In this paper, a high-gain broadband antenna is presented for terahertz applications. The antenna is a three-layer structure, fed by a grounded coplanar waveguide (GCPW), using polytetrafluoroethylene (PTFE) material as the dielectric substrate, and the metal through-hole of the dielectric substrate forms a substrate-integrated waveguide (SIW) structure. The metal fence structure is introduced to reduce the coupling effect between the radiation patches and increase the radiation bandwidth and gain. The center frequency is 0.6366 THz, the operating bandwidth is 0.61–0.68 THz, the minimum value of the voltage standing wave ratio (VSWR) is 1.00158, and the peak gain is 13.14 dBi. In addition, the performance of the designed antenna with a different isolation structure, the length of the connection line, the height of the substrate, the radius of the through-hole, and the thickness of the patch is also studied. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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Review

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29 pages, 8732 KiB  
Review
Microfabrication Technologies for Interaction Circuits of THz Vacuum Electronic Devices
by Xinghui Li and Jinjun Feng
Micromachines 2024, 15(11), 1357; https://doi.org/10.3390/mi15111357 - 8 Nov 2024
Viewed by 2031
Abstract
Advances in manufacturing technology are allowing for the realization of interaction circuit with microstructures. The capability to produce small circuit structures is allowing new opportunities for vacuum electronic devices producing terahertz (THz) frequency radiation, which is impractical with traditional machining technology. This publication [...] Read more.
Advances in manufacturing technology are allowing for the realization of interaction circuit with microstructures. The capability to produce small circuit structures is allowing new opportunities for vacuum electronic devices producing terahertz (THz) frequency radiation, which is impractical with traditional machining technology. This publication reviews recent progress on advanced microfabrication technologies applicable to interaction circuits of THz vacuum electronic devices, including LIGA/UV-LIGA (Ultraviolet Lithographic, Galvonoformung and Abformung), deep reactive ion etching (DRIE), micro/nano computer numerical control (CNC) milling, three-dimension (3D) printing, etc., and describes the current State-of-the-Art of their applications. Full article
(This article belongs to the Special Issue Recent Advances in Terahertz Devices and Applications)
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