Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.     

History of Millimeter and Submillimeter Waves

In this review an attempt is made to identify many of the major events that have occurred in the development of millimeter- and submillimeter-wave technology from its beginnings in the 1890's until the present time. The review is not intended to be the definitive history of the field, but may form the basis for someone to later write a more comprehensive or encyclopedic version. The history conveniently divides into three periods: 1890 through World War II, Post War (1947 to 1965), and Modern Age (after 1965).     

A Review on Thin-film Sensing with Terahertz Waves

In the past two decades, the development and steady improvement of terahertz technology has motivated a wide range of scientific studies designed to discover and develop terahertz applications. Terahertz sensing is one such application, and its continued maturation is virtually guaranteed by the unique properties that materials exhibit in the terahertz frequency range. Thin-film sensing is one branch of this effort that has enjoyed diverse development in the last decade. Deeply subwavelength sample thicknesses impose great difficulties to conventional terahertz spectroscopy, yet sensing those samples is essential for a large number of applications. In this article we review terahertz thin-film sensing, summarizing the motivation, challenges, and state-of-the-art approaches based predominately on terahertz time-domain spectroscopy.     

Millimeter Wave and Terahertz Communications： Feasibility and Challenges

In this paper, the challenges with and motivations for developing millimeter wave and terahertz communications are described. A high-level candidate architecture is presented, and use cases highlighting the potential applicability of high-frequency links are discussed. Mobility challenges at these higher frequencies are also discussed. Difficulties that arise as a result of high carrier frequencies and higher path loss can be overcome by practical, higher-gain antennas that have the added benefit of reducing intercell interference. Simulation methodology and results are given. The results show that millimeter wave coverage is possible in large, outdoor spaces, and only a reasonable number of base stations are needed. Network throughput can exceed 25 Gbit/s, and cell-edge user throughput can reach approximately 100 Mbit/s.     

Multipath Effects on Phase Measurements with Continuous Terahertz Waves

We evaluate the effect of multipath waves on terahertz phase measurements due to multiple reflections between the transmitter antenna and the sample. We show that the phase shift introduced by the sample will be biased by a value which depends on the sample position in the terahertz path. We show how to remove the bias and use the technique in the measurement of the index of refraction of Mylar at 194.4 GHz.     

Terahertz Photonics: Optoelectronic Techniques for Generation and Detection of Terahertz Waves

Optoelectronic techniques for generation and detection of terahertz (THz) signals have been reviewed. The operation principles of THz photomixer sources and THz parametric sources have been studied and recent developments in these areas have been presented. The performances of developed THz optoelectronic sources have been discussed and compared.      

强功率毫米波,亚毫米波辐射源

本文评述了强功率毫米波、亚毫米波辐射源的用途,和相应20种器件的原理及进展。文中指出,回旋管仍然具有很强竞争力,而回旋自谐振脉塞值得优先发展。     

Broadband Orotron Operation at Millimeter and Submillimeter Waves

Due to high selectivity of open cavity, wider electron beams with higher current can be used in orotron as compared with other Cherenkov devices. It provides important advantages at short millimeter and submillimeter waves. Theory and preliminary experiments in the short part of millimeter and long part of submillimeter wavelength range show that orotron with operating voltage of few kV can generate significantly higher output power than existing BWOs. Combined electronic and mechanical frequency tuning in the band of about of octave has been obtained.     

Terahertz Surface Waves Propagating on Metals with Sub-wavelength Structure and Grating Reliefs

Due to their long propagation length at a metal surface in the far infrared, surface plasmons make potentially feasible the design and realization of 2D integrated terahertz systems over a metallic substrate. In this article, we present a review of recent works dedicated to surface plasmon properties on structured metallic surfaces. We study excitation, propagation, diffraction and reflection of terahertz surface plasmon on shallow gratings and of spoof plasmons on deep sub-wavelength structures. The analysis of the experimental data supplied by terahertz time-domain spectroscopy allows us to point out the main parameters that govern this diffraction process and the propagation of a surface plasmon over a flat or corrugated metal surface.