China
Africa
Explore chapters and articles related to this topic
Introduction to Optical, Infrared, and Terahertz Frequency Bands
Published in Song Sun, Wei Tan, Su-Huai Wei, Emergent Micro- and Nanomaterials for Optical, Infrared, and Terahertz Applications, 2023
Song Sun, Wei Tan, Su-Huai Wei
At the long wavelength end of FIR regime, there exists a special electromagnetic wave band called terahertz (also called T-ray, T-wave or T-light) with frequencies from 0.3 THz to 10 THz, or equivalently from 1 mm to ˜30 μm in wavelength (sometimes it also refers to the frequency range from 0.1 THz to 10 THz). Falling at the transition region between infrared and microwave domains, terahertz wave shares some properties from each of them. Similar to microwaves, terahertz radiation can penetrate many non-conducting materials including clothing, paper, wood, plastic, and ceramics. Although the penetration depth is smaller than that of microwave, terahertz radiation could generate images with higher resolution due to its shorter wavelength, which makes it potentially suitable for non-destructive testing. Similar to infrared wave, terahertz radiation is strongly absorbed by certain gas and liquid molecules, which makes it capable for spectroscopic analyzing. In particular, terahertz wave could penetrate some distance into human tissue in a non-ionizing manner, which makes it a potential replacement for medical X-rays. These unique properties of terahertz band have driven the development of novel technologies in many applications. Note that some communities such as astronomy also name terahertz wave as submillimeter wave. These two concepts are essentially identical.
Special Topic
Published in Anna M. Doro-on, Handbook of Systems Engineering and Risk Management in Control Systems, Communication, Space Technology, Missile, Security and Defense Operations, 2023
According to Reddy (2009), quantum cascade lasers (QCLs) are a new class of semiconductor lasers that are unipolar and can work effectively in mid-infrared and terahertz spectral regions, even at room temperatures. QCLs are thus ideal light sources for probing the strong fundamental vibration-rotational absorption bands of most gaseous molecules in nature, which have tell-tale spectral finger prints in these spectral regions (Reddy 2009). Combined with sensitive laser spectroscopic techniques like cavity ringdown spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), QCLs provide ultra-sensitive detection capability to meet the challenge of standoff detection of lower concentration of IEDs and other hazardous chemicals in the field environment (Reddy 2009). Because of its low interference and non-ionizing characteristics, terahertz imaging is expected to be a powerful technique for safe, in vivo medical imaging, where the use of a longer wavelength allows for deeper penetration in the investigated material (Reddy 2009). QCLs in the mid-infrared to far-infrared, including at THz region, are going to play a pivotal role in the investigation of new science and revisiting the most viable technologies (Reddy 2009).
Electric Transport Properties in PEDOT Thin Films
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
Nara Kim, Ioannis Petsagkourakis, Shangzhi Chen, Magnus Berggren, Xavier Crispin, Magnus P. Jonsson, Igor Zozoulenko
Terahertz radiation is conventionally defined as light in the frequency range from 0.1 THz to 10 THz. It is an interesting range since it is at the boundary between electronics (microwaves) and photonics (infrared light).146 Because free charge carriers are sensitive to low energy excitation, low-energy THz radiation (1 THz corresponds to 0.00414 eV) can be used to probe their transport mechanisms in materials, including conducting polymers like PEDOT.147 Among THz characterization tools developed for the study of material properties, terahertz time-domain spectroscopy (THz-TDS) is currently the prevailing method.148 THz-TDS offers non-contact measurements of optical conductivity and permittivity of materials in the THz range, providing information about both free and localized charge carriers. The method has been widely used to characterize conducting polymers, including polyaniline, polypyrrole, polythiophene, and PEDOT.149–153
Terahertz generation and detection of 1550-nm-excited LT-GaAs photoconductive antennas
Published in Journal of Modern Optics, 2021
Zhi-Chen Bai, Xin Liu, Jing Ding, Hai-Lin Cui, Bo Su, Cun-Lin Zhang
Terahertz (THz) usually refers to an electromagnetic wave with a wavelength of 30–3000 μm and a frequency of 0.1–10 THz [1,2]. At the beginning of the twentieth century, there was a lot of interest in THz waves. However, due to technical limitations, THz band research has been stagnant for an extended period of time. In recent years, with the development of semiconductors, advanced electronic technology, and ultrafast optics, THz generation and detection technology have become increasingly mature. Accordingly, THz spectroscopy technology is now widely used in many fields, such as biology, physics, chemistry, security inspection, and imaging [3,4].
A vision of 6G – 5G's successor
Published in Journal of Management Analytics, 2020
Terahertz refers to electromagnetic waves with a frequency between 0.1 and 10 THz. It has extremely rich spectrum resources. The available spectrum resources can even reach tens of GHz, which can meet the spectrum requirements for extremely high transmission rates from 100 Gbit/s to Tbit/s. It is a wireless communication technology with great potential for future mobile communication. Currently, the United States, the European Union, China, and several other countries are accelerating the development of 6G-oriented terahertz communication technology (Giordani et al., 2020; Han et al., 2019; Yan, Han, & Yuan, 2020).
THz wavefront manipulation based on metal waveguides
Published in Journal of Modern Optics, 2018
Mengru Wu, Tingting Lang, Changyu Shen, Guohua Shi, Zhanghua Han
Terahertz radiation with the frequency ranging from 0.1 to 10 THz is a general term for electromagnetic radiation in a specific band, which is located between the microwave and the infrared radiation in the electromagnetic spectrum. Similar to optical frequencies, in the terahertz regime it is also important to use free space optical elements to control the phase of the optical field to realize any desired functions. However, full control of the phase is difficult to reach at the micro-scale owing to rather limited variations in the permittivity and permeability of conventional materials (1). Conventional optical elements typically rely on the three-dimensional (3D) shaping of shifts accumulated during light propagation (2). As a result, the thickness of the transparent materials, so that phase modulation of them is caused by gradual phase designed diffractive optical elements is substantially larger than the wavelength of the incident optical wave. Due to the large wavelength of terahertz radiation, these optical components are often bulky, which is not conducive for system integration (3). Therefore, the latest phase modulation structures in the terahertz region, mould light flow using two-dimensional artificial materials, the so-called metasurfaces. These complex structures, in the form of nanoholes (4, 5), nanofins (6), nanorod (7),V-shaped antennas (3, 8, 9), C-shaped split ring resonators (10, 11), achieving their functions according to different phases of the scattered light from individual elements, normally either need large scale computations to design or are challenging to fabricate. A simple mechanism combining the advantages of simple design from conventional optical elements and of compact structures from metasurfaces will benefit the design of wavefront manipulation in the THz regime.