Terahertz radiation

Last updated • 19 min readFrom Wikipedia, The Free Encyclopedia

Tremendously high frequency
Frequency range
0.3 THz to 3 THz
Wavelength range
1 mm to 100 μm
Terahertz waves lie at the far end of the infrared band, just before the start of the microwave band. Spectre Terahertz.svg
Terahertz waves lie at the far end of the infrared band, just before the start of the microwave band.

Terahertz radiation also known as submillimeter radiation, terahertz waves, tremendously high frequency [1] (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the International Telecommunication Union-designated band of frequencies from 0.3 to 3  terahertz (THz), [2] although the upper boundary is somewhat arbitrary and is considered by some sources as 30 THz. [3] One terahertz is 1012  Hz or 1,000 GHz. Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm = 100 μm. Because terahertz radiation begins at a wavelength of around 1 millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy. This band of electromagnetic radiation lies within the transition region between microwave and far infrared, and can be regarded as either.

Contents

Compared to lower radio frequencies, terahertz radiation is strongly absorbed by the gases of the atmosphere, and in air most of the energy is attenuated within a few meters, [4] [5] [6] so it is not practical for long distance terrestrial radio communication. It can penetrate thin layers of materials but is blocked by thicker objects. THz beams transmitted through materials can be used for material characterization, layer inspection, relief measurement, [7] and as a lower-energy alternative to X-rays for producing high resolution images of the interior of solid objects. [8]

Terahertz radiation occupies a middle ground where the ranges of microwaves and infrared light waves overlap, known as the "terahertz gap"; it is called a "gap" because the technology for its generation and manipulation is still in its infancy. The generation and modulation of electromagnetic waves in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques.

Description

In THz-TDS systems, since the time-domain version of the THz signal is available, the distortion effects of the diffraction can be suppressed. Resolution Enhancement.gif
In THz-TDS systems, since the time-domain version of the THz signal is available, the distortion effects of the diffraction can be suppressed.

Terahertz radiation falls in between infrared radiation and microwave radiation in the electromagnetic spectrum, and it shares some properties with each of these. Terahertz radiation travels in a line of sight and is non-ionizing. Like microwaves, terahertz radiation can penetrate a wide variety of non-conducting materials; clothing, paper, cardboard, wood, masonry, plastic and ceramics. The penetration depth is typically less than that of microwave radiation. Like infrared, terahertz radiation has limited penetration through fog and clouds and cannot penetrate liquid water or metal. [10] Terahertz radiation can penetrate some distance through body tissue like x-rays, but unlike them is non-ionizing, so it is of interest as a replacement for medical X-rays. Due to its longer wavelength, images made using terahertz waves have lower resolution than X-rays and need to be enhanced (see figure at right). [9]

The earth's atmosphere is a strong absorber of terahertz radiation, so the range of terahertz radiation in air is limited to tens of meters, making it unsuitable for long-distance communications. However, at distances of ~10 meters the band may still allow many useful applications in imaging and construction of high bandwidth wireless networking systems, especially indoor systems. In addition, producing and detecting coherent terahertz radiation remains technically challenging, though inexpensive commercial sources now exist in the 0.31.0 THz range (the lower part of the spectrum), including gyrotrons, backward wave oscillators, and resonant-tunneling diodes.[ citation needed ] Due to the small energy of THz photons, current THz devices require low temperature during operation to suppress environmental noise. Tremendous efforts thus have been put into THz research to improve the operation temperature, using different strategies such as optomechanical meta-devices. [11] [12]

Sources

Natural

Terahertz radiation is emitted as part of the black-body radiation from anything with a temperature greater than about 2  kelvin. While this thermal emission is very weak, observations at these frequencies are important for characterizing cold 1020  K cosmic dust in interstellar clouds in the Milky Way galaxy, and in distant starburst galaxies.[ citation needed ]

Telescopes operating in this band include the James Clerk Maxwell Telescope, the Caltech Submillimeter Observatory and the Submillimeter Array at the Mauna Kea Observatory in Hawaii, the BLAST balloon borne telescope, the Herschel Space Observatory, the Heinrich Hertz Submillimeter Telescope at the Mount Graham International Observatory in Arizona, and at the recently built Atacama Large Millimeter Array. Due to Earth's atmospheric absorption spectrum, the opacity of the atmosphere to submillimeter radiation restricts these observatories to very high altitude sites, or to space. [13] [14]

Artificial

As of 2012, viable sources of terahertz radiation are the gyrotron, the backward wave oscillator ("BWO"), the molecule gas far-infrared laser, Schottky-diode multipliers, [15] varactor (varicap) multipliers, quantum-cascade laser, [16] [17] [18] [19] the free-electron laser, synchrotron light sources, photomixing sources, single-cycle or pulsed sources used in terahertz time-domain spectroscopy such as photoconductive, surface field, photo-Dember and optical rectification emitters, [20] and electronic oscillators based on resonant tunneling diodes have been shown to operate up to 1.98 THz. [21]

There have also been solid-state sources of millimeter and submillimeter waves for many years. AB Millimeter in Paris, for instance, produces a system that covers the entire range from 8 GHz to 1,000 GHz with solid state sources and detectors. Nowadays, most time-domain work is done via ultrafast lasers.

In mid-2007, scientists at the U.S. Department of Energy's Argonne National Laboratory, along with collaborators in Turkey and Japan, announced the creation of a compact device that could lead to portable, battery-operated terahertz radiation sources. [22] The device uses high-temperature superconducting crystals, grown at the University of Tsukuba in Japan. These crystals comprise stacks of Josephson junctions, which exhibit a property known as the Josephson effect: when external voltage is applied, alternating current flows across the junctions at a frequency proportional to the voltage. This alternating current induces an electromagnetic field. A small voltage (around two millivolts per junction) can induce frequencies in the terahertz range.

In 2008, engineers at Harvard University achieved room temperature emission of several hundred nanowatts of coherent terahertz radiation using a semiconductor source. THz radiation was generated by nonlinear mixing of two modes in a mid-infrared quantum cascade laser. Previous sources had required cryogenic cooling, which greatly limited their use in everyday applications. [23]

In 2009, it was discovered that the act of unpeeling adhesive tape generates non-polarized terahertz radiation, with a narrow peak at 2 THz and a broader peak at 18 THz. The mechanism of its creation is tribocharging of the adhesive tape and subsequent discharge; this was hypothesized to involve bremsstrahlung with absorption or energy density focusing during dielectric breakdown of a gas. [24]

In 2013, researchers at Georgia Institute of Technology's Broadband Wireless Networking Laboratory and the Polytechnic University of Catalonia developed a method to create a graphene antenna: an antenna that would be shaped into graphene strips from 10 to 100 nanometers wide and one micrometer long. Such an antenna could be used to emit radio waves in the terahertz frequency range. [25] [26]

Terahertz gap

In engineering, the terahertz gap is a frequency band in the THz region for which practical technologies for generating and detecting the radiation do not exist. It is defined as 0.1 to 10 THz (wavelengths of 3 mm to 30 μm) although the upper boundary is somewhat arbitrary and is considered by some sources as 30 THz (a wavelength of 10 μm). [27] Currently, at frequencies within this range, useful power generation and receiver technologies are inefficient and unfeasible.

Mass production of devices in this range and operation at room temperature (at which energy kT is equal to the energy of a photon with a frequency of 6.2 THz) are mostly impractical. This leaves a gap between mature microwave technologies in the highest frequencies of the radio spectrum and the well-developed optical engineering of infrared detectors in their lowest frequencies. This radiation is mostly used in small-scale, specialized applications such as submillimetre astronomy. Research that attempts to resolve this issue has been conducted since the late 20th century. [28] [29] [30] [31] [32]

In 2024, an experiment has been published by German researchers [33] where a TDLAS experiment at 4.75 THz has been performed in "infrared quality" with an uncooled pyroelectric receiver while the THz source has been a cw DFB-QC-Laser operated at 43.3 K and laser currents between 480 mA and 600 mA.

Closure of the terahertz gap

Most vacuum electronic devices that are used for microwave generation can be modified to operate at terahertz frequencies, including the magnetron, [34] gyrotron, [35] synchrotron, [36] and free-electron laser. [37] Similarly, microwave detectors such as the tunnel diode have been re-engineered to detect at terahertz [38] and infrared [39] frequencies as well. However, many of these devices are in prototype form, are not compact, or exist at university or government research labs, without the benefit of cost savings due to mass production.

Research

Molecular biology

Terahertz radiation has comparable frequencies to the motion of biomolecular systems in the course of their function (a frequency 1THz is equivalent to a timescale of 1 picosecond, therefore in particular the range of hundreds of GHz up to low numbers of THz is comparable to biomolecular relaxation timescales of a few ps to a few ns). Modulation of biological and also neurological function is therefore possible using radiation in the range hundreds of GHz up to a few THz at relatively low energies (without significant heating or ionisation) achieving either beneficial or harmful effects. [40] [41]

Medical imaging

Unlike X-rays, terahertz radiation is not ionizing radiation and its low photon energies in general do not damage living tissues and DNA. Some frequencies of terahertz radiation can penetrate several millimeters of tissue with low water content (e.g., fatty tissue) and reflect back. Terahertz radiation can also detect differences in water content and density of a tissue. Such methods could allow effective detection of epithelial cancer with an imaging system that is safe, non-invasive, and painless. [42] In response to the demand for COVID-19 screening terahertz spectroscopy and imaging has been proposed as a rapid screening tool. [43] [44]

The first images generated using terahertz radiation date from the 1960s; however, in 1995 images generated using terahertz time-domain spectroscopy generated a great deal of interest.[ citation needed ]

Some frequencies of terahertz radiation can be used for 3D imaging of teeth and may be more accurate than conventional X-ray imaging in dentistry.[ citation needed ]

Security

Terahertz radiation can penetrate fabrics and plastics, so it can be used in surveillance, such as security screening, to uncover concealed weapons on a person, remotely. This is of particular interest because many materials of interest have unique spectral "fingerprints" in the terahertz range. This offers the possibility to combine spectral identification with imaging. In 2002, the European Space Agency (ESA) Star Tiger team, [45] based at the Rutherford Appleton Laboratory (Oxfordshire, UK), produced the first passive terahertz image of a hand. [46] By 2004, ThruVision Ltd, a spin-out from the Council for the Central Laboratory of the Research Councils (CCLRC) Rutherford Appleton Laboratory, had demonstrated the world's first compact THz camera for security screening applications. The prototype system successfully imaged guns and explosives concealed under clothing. [47] Passive detection of terahertz signatures avoid the bodily privacy concerns of other detection by being targeted to a very specific range of materials and objects. [48] [49]

In January 2013, the NYPD announced plans to experiment with the new technology to detect concealed weapons, [50] prompting Miami blogger and privacy activist Jonathan Corbett to file a lawsuit against the department in Manhattan federal court that same month, challenging such use: "For thousands of years, humans have used clothing to protect their modesty and have quite reasonably held the expectation of privacy for anything inside of their clothing, since no human is able to see through them." He sought a court order to prohibit using the technology without reasonable suspicion or probable cause. [51] By early 2017, the department said it had no intention of ever using the sensors given to them by the federal government. [52]

Scientific use and imaging

In addition to its current use in submillimetre astronomy, terahertz radiation spectroscopy could provide new sources of information for chemistry and biochemistry.[ citation needed ]

Recently developed methods of THz time-domain spectroscopy (THz TDS) and THz tomography have been shown to be able to image samples that are opaque in the visible and near-infrared regions of the spectrum. The utility of THz-TDS is limited when the sample is very thin, or has a low absorbance, since it is very difficult to distinguish changes in the THz pulse caused by the sample from those caused by long-term fluctuations in the driving laser source or experiment. However, THz-TDS produces radiation that is both coherent and spectrally broad, so such images can contain far more information than a conventional image formed with a single-frequency source.[ citation needed ]

Submillimeter waves are used in physics to study materials in high magnetic fields, since at high fields (over about 11  tesla), the electron spin Larmor frequencies are in the submillimeter band. Many high-magnetic field laboratories perform these high-frequency EPR experiments, such as the National High Magnetic Field Laboratory (NHMFL) in Florida.[ citation needed ]

Terahertz radiation could let art historians see murals hidden beneath coats of plaster or paint in centuries-old buildings, without harming the artwork. [53]

In additional, THz imaging has been done with lens antennas to capture radio image of the object. [54] [55]

Particle accelerators

New types of particle accelerators that could achieve multi Giga-electron volts per metre (GeV/m) accelerating gradients are of utmost importance to reduce the size and cost of future generations of high energy colliders as well as provide a widespread availability of compact accelerator technology to smaller laboratories around the world. Gradients in the order of 100 MeV/m have been achieved by conventional techniques and are limited by RF-induced plasma breakdown. [56] Beam driven dielectric wakefield accelerators (DWAs) [57] [58] typically operate in the Terahertz frequency range, which pushes the plasma breakdown threshold for surface electric fields into the multi-GV/m range. [59] DWA technique allows to accommodate a significant amount of charge per bunch, and gives an access to conventional fabrication techniques for the accelerating structures. To date 0.3 GeV/m accelerating and 1.3 GeV/m decelerating gradients [60] have been achieved using a dielectric lined waveguide with sub-millimetre transverse aperture.

An accelerating gradient larger than 1 GeV/m, can potentially be produced by the Cherenkov Smith-Purcell radiative mechanism [61] [62] in a dielectric capillary with a variable inner radius. When an electron bunch propagates through the capillary, its self-field interacts with the dielectric material and produces wakefields that propagate inside the material at the Cherenkov angle. The wakefields are slowed down below the speed of light, as the relative dielectric permittivity of the material is larger than 1. The radiation is then reflected from the capillary's metallic boundary and diffracted back into the vacuum region, producing high accelerating fields on the capillary axis with a distinct frequency signature. In presence of a periodic boundary the Smith-Purcell radiation imposes frequency dispersion.[ citation needed ]

A preliminary study with corrugated capillaries has shown some modification to the spectral content and amplitude of the generated wakefields, [63] but the possibility of using Smith-Purcell effect in DWA is still under consideration.[ citation needed ]

Communication

The high atmospheric absorption of terahertz waves limits the range of communication using existing transmitters and antennas to tens of meters. However, the huge unallocated bandwidth available in the band (ten times the bandwidth of the millimeter wave band, 100 times that of the SHF microwave band) makes it very attractive for future data transmission and networking use. There are tremendous difficulties to extending the range of THz communication through the atmosphere, but the world telecommunications industry is funding much research into overcoming those limitations. [64] One promising application area is the 6G cellphone and wireless standard, which will supersede the current 5G standard around 2030. [64]

For a given antenna aperture, the gain of directive antennas scales with the square of frequency, while for low power transmitters the power efficiency is independent of bandwidth. So the consumption factor theory of communication links indicates that, contrary to conventional engineering wisdom, for a fixed aperture it is more efficient in bits per second per watt to use higher frequencies in the millimeter wave and terahertz range. [64] Small directive antennas a few centimeters in diameter can produce very narrow 'pencil' beams of THz radiation, and phased arrays of multiple antennas could concentrate virtually all the power output on the receiving antenna, allowing communication at longer distances.

In May 2012, a team of researchers from the Tokyo Institute of Technology [65] published in Electronics Letters that it had set a new record for wireless data transmission by using T-rays and proposed they be used as bandwidth for data transmission in the future. [66] The team's proof of concept device used a resonant tunneling diode (RTD) negative resistance oscillator to produce waves in the terahertz band. With this RTD, the researchers sent a signal at 542 GHz, resulting in a data transfer rate of 3 Gigabits per second. [66] It doubled the record for data transmission rate set the previous November. [67] The study suggested that Wi-Fi using the system would be limited to approximately 10 metres (33 ft), but could allow data transmission at up to 100 Gbit/s. [66] [ clarification needed ] In 2011, Japanese electronic parts maker Rohm and a research team at Osaka University produced a chip capable of transmitting 1.5 Gbit/s using terahertz radiation. [68]

Potential uses exist in high-altitude telecommunications, above altitudes where water vapor causes signal absorption: aircraft to satellite, or satellite to satellite.[ citation needed ]

Amateur radio

A number of administrations permit amateur radio experimentation within the 275–3,000 GHz range or at even higher frequencies on a national basis, under license conditions that are usually based on RR5.565 of the ITU Radio Regulations. Amateur radio operators utilizing submillimeter frequencies often attempt to set two-way communication distance records. In the United States, WA1ZMS and W4WWQ set a record of 1.42 kilometres (0.88 mi) on 403 GHz using CW (Morse code) on 21 December 2004. In Australia, at 30 THz a distance of 60 metres (200 ft) was achieved by stations VK3CV and VK3LN on 8 November 2020. [69] [70] [71]

Manufacturing

Many possible uses of terahertz sensing and imaging are proposed in manufacturing, quality control, and process monitoring. These in general exploit the traits of plastics and cardboard being transparent to terahertz radiation, making it possible to inspect packaged goods. The first imaging system based on optoelectronic terahertz time-domain spectroscopy were developed in 1995 by researchers from AT&T Bell Laboratories and was used for producing a transmission image of a packaged electronic chip. [72] This system used pulsed laser beams with duration in range of picoseconds. Since then commonly used commercial/ research terahertz imaging systems have used pulsed lasers to generate terahertz images. The image can be developed based on either the attenuation or phase delay of the transmitted terahertz pulse. [73]

Since the beam is scattered more at the edges and also different materials have different absorption coefficients, the images based on attenuation indicates edges and different materials inside of objects. This approach is similar to X-ray transmission imaging, where images are developed based on attenuation of the transmitted beam. [74]

In the second approach, terahertz images are developed based on the time delay of the received pulse. In this approach, thicker parts of the objects are well recognized as the thicker parts cause more time delay of the pulse. Energy of the laser spots are distributed by a Gaussian function. The geometry and behavior of Gaussian beam in the Fraunhofer region imply that the electromagnetic beams diverge more as the frequencies of the beams decrease and thus the resolution decreases. [75] This implies that terahertz imaging systems have higher resolution than scanning acoustic microscope (SAM) but lower resolution than X-ray imaging systems. Although terahertz can be used for inspection of packaged objects, it suffers from low resolution for fine inspections. X-ray image and terahertz images of an electronic chip are brought in the figure on the right. [76] Obviously the resolution of X-ray is higher than terahertz image, but X-ray is ionizing and can be impose harmful effects on certain objects such as semiconductors and live tissues.[ citation needed ]

To overcome low resolution of the terahertz systems near-field terahertz imaging systems are under development. [77] [78] In nearfield imaging the detector needs to be located very close to the surface of the plane and thus imaging of the thick packaged objects may not be feasible. In another attempt to increase the resolution, laser beams with frequencies higher than terahertz are used to excite the p-n junctions in semiconductor objects, the excited junctions generate terahertz radiation as a result as long as their contacts are unbroken and in this way damaged devices can be detected. [79] In this approach, since the absorption increases exponentially with the frequency, again inspection of the thick packaged semiconductors may not be doable. Consequently, a tradeoff between the achievable resolution and the thickness of the penetration of the beam in the packaging material should be considered.[ citation needed ]

THz gap research

Ongoing investigation has resulted in improved emitters (sources) and detectors, and research in this area has intensified. However, drawbacks remain that include the substantial size of emitters, incompatible frequency ranges, and undesirable operating temperatures, as well as component, device, and detector requirements that are somewhere between solid state electronics and photonic technologies. [80] [81] [82]

Free-electron lasers can generate a wide range of stimulated emission of electromagnetic radiation from microwaves, through terahertz radiation to X-ray. However, they are bulky, expensive and not suitable for applications that require critical timing (such as wireless communications). Other sources of terahertz radiation which are actively being researched include solid state oscillators (through frequency multiplication), backward wave oscillators (BWOs), quantum cascade lasers, and gyrotrons.

Safety

The terahertz region is between the radio frequency region and the laser optical region. Both the IEEE C95.1–2005 RF safety standard [83] and the ANSI Z136.1–2007 Laser safety standard [84] have limits into the terahertz region, but both safety limits are based on extrapolation. It is expected that effects on biological tissues are thermal in nature and, therefore, predictable by conventional thermal models [ citation needed ]. Research is underway to collect data to populate this region of the spectrum and validate safety limits. [ citation needed ]

A theoretical study published in 2010 and conducted by Alexandrov et al at the Center for Nonlinear Studies at Los Alamos National Laboratory in New Mexico [85] created mathematical models predicting how terahertz radiation would interact with double-stranded DNA, showing that, even though involved forces seem to be tiny, nonlinear resonances (although much less likely to form than less-powerful common resonances) could allow terahertz waves to "unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication". [86] Experimental verification of this simulation was not done. Swanson's 2010 theoretical treatment of the Alexandrov study concludes that the DNA bubbles do not occur under reasonable physical assumptions or if the effects of temperature are taken into account. [87] A bibliographical study published in 2003 reported that T-ray intensity drops to less than 1% in the first 500 μm of skin but stressed that "there is currently very little information about the optical properties of human tissue at terahertz frequencies". [88]

See also

Related Research Articles

<span class="mw-page-title-main">Electromagnetic spectrum</span> Range of frequencies or wavelengths of electromagnetic radiation

The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.

<span class="mw-page-title-main">Maser</span> Device for producing coherent EM waves in the sub-visible spectrum

A maser is a device that produces coherent electromagnetic waves (microwaves), through amplification by stimulated emission. The term is an acronym for microwave amplification by stimulated emission of radiation. Nikolay Basov, Alexander Prokhorov and Joseph Weber introduced the concept of the maser in 1952, and Charles H. Townes, James P. Gordon, and Herbert J. Zeiger built the first maser at Columbia University in 1953. Townes, Basov and Prokhorov won the 1964 Nobel Prize in Physics for theoretical work leading to the maser. Masers are used as timekeeping devices in atomic clocks, and as extremely low-noise microwave amplifiers in radio telescopes and deep-space spacecraft communication ground-stations.

<span class="mw-page-title-main">Microwave</span> Electromagnetic radiation with wavelengths from 1 m to 1 mm

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, broadly construed. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz, or between 1 and 3000 GHz . The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range; rather, it indicates that microwaves are small, compared to the radio waves used in prior radio technology.

<span class="mw-page-title-main">Rectenna</span> Antenna for receiving power

A rectenna is a special type of receiving antenna that is used for converting electromagnetic energy into direct current (DC) electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with a diode connected across the dipole elements. The diode rectifies the AC induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode. Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching. Large rectennas consist of arrays of many power receiving elements such as dipole antennas.

Extremely high frequency is the International Telecommunication Union designation specifically included in the electromagnetic spectrum classification group with 8 other principal dedicated channel allocation. Extremely high frequency or commonly known as "EHF", is a large broadband that span a radius of about (30 GHz to 300 GHz) for the molecular spectra of radio frequencies. It lies between the super high frequency (3 GHz to 30 GHz) band and the far infrared band (300 GHz to 1015), for which the lower part is the terahertz band. Radio waves in this band have wavelengths from ten to one millimeter, so it is also called the millimeter band and radiation in this band is called millimeter waves, sometimes abbreviated MMW or mmWave. Millimeter-length electromagnetic waves were first investigated by Jagadish Chandra Bose, who generated waves of frequency up to 60 GHz during experiments in 1894–1896.

<span class="mw-page-title-main">Terahertz time-domain spectroscopy</span>

In physics, terahertz time-domain spectroscopy (THz-TDS) is a spectroscopic technique in which the properties of matter are probed with short pulses of terahertz radiation. The generation and detection scheme is sensitive to the sample's effect on both the amplitude and the phase of the terahertz radiation.

<span class="mw-page-title-main">Gyrotron</span> Vacuum tube which generates high-frequency radio waves

A gyrotron is a class of high-power linear-beam vacuum tubes that generates millimeter-wave electromagnetic waves by the cyclotron resonance of electrons in a strong magnetic field. Output frequencies range from about 20 to 527 GHz, covering wavelengths from microwave to the edge of the terahertz gap. Typical output powers range from tens of kilowatts to 1–2 megawatts. Gyrotrons can be designed for pulsed or continuous operation. The gyrotron was invented by Soviet scientists at NIRFI, based in Nizhny Novgorod, Russia.

<span class="mw-page-title-main">Sound amplification by stimulated emission of radiation</span> Device that emites acoustic radiation

Sound amplification by stimulated emission of radiation (SASER) refers to a device that emits acoustic radiation. It focuses sound waves in a way that they can serve as accurate and high-speed carriers of information in many kinds of applications—similar to uses of laser light.

Photomixing is the generation of continuous wave terahertz radiation from two lasers. The beams are mixed together and focused onto a photomixer device which generates the terahertz radiation. It is technologically significant because there are few sources capable of providing radiation in this waveband, others include frequency multiplied electronic/microwave sources, quantum cascade laser and ultrashort pulsed lasers with photoconductive switches as used in terahertz time-domain spectroscopy. The advantages of this technique are that it is continuously tunable over the frequency range from 300 GHz to 3 THz, and spectral resolutions in the order of 1 MHz can be achieved. However, the achievable power is on the order of 10−8 W.

Terahertz tomography is a class of tomography where sectional imaging is done by terahertz radiation. Terahertz radiation is electromagnetic radiation with a frequency between 0.1 and 10 THz; it falls between radio waves and light waves on the spectrum; it encompasses portions of the millimeter waves and infrared wavelengths. Because of its high frequency and short wavelength, terahertz wave has a high signal-to-noise ratio in the time domain spectrum. Tomography using terahertz radiation can image samples that are opaque in the visible and near-infrared regions of the spectrum. Terahertz wave three-dimensional (3D) imaging technology has developed rapidly since its first successful application in 1997, and a series of new 3D imaging technologies have been proposed successively.

<span class="mw-page-title-main">Terahertz metamaterial</span>

A terahertz metamaterial is a class of composite metamaterials designed to interact at terahertz (THz) frequencies. The terahertz frequency range used in materials research is usually defined as 0.1 to 10 THz.

<span class="mw-page-title-main">Tunable metamaterial</span>

A tunable metamaterial is a metamaterial with a variable response to an incident electromagnetic wave. This includes remotely controlling how an incident electromagnetic wave interacts with a metamaterial. This translates into the capability to determine whether the EM wave is transmitted, reflected, or absorbed. In general, the lattice structure of the tunable metamaterial is adjustable in real time, making it possible to reconfigure a metamaterial device during operation. It encompasses developments beyond the bandwidth limitations in left-handed materials by constructing various types of metamaterials. The ongoing research in this domain includes electromagnetic band gap metamaterials (EBG), also known as photonic band gap (PBG), and negative refractive index material (NIM).

<span class="mw-page-title-main">Photonic metamaterial</span> Type of electromagnetic metamaterial

A photonic metamaterial (PM), also known as an optical metamaterial, is a type of electromagnetic metamaterial, that interacts with light, covering terahertz (THz), infrared (IR) or visible wavelengths. The materials employ a periodic, cellular structure.

A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics.

Terahertz nondestructive evaluation pertains to devices, and techniques of analysis occurring in the terahertz domain of electromagnetic radiation. These devices and techniques evaluate the properties of a material, component or system without causing damage.

<span class="mw-page-title-main">TeraView</span>

TeraView Limited, or TeraView, is a company that designs terahertz imaging and spectroscopy instruments and equipment for measurement and evaluation of pharmaceutical tablets, nanomaterials, ceramics and composites, integrated circuit chips and more.

A graphene antenna is a high-frequency antenna based on graphene, a one atom thick two dimensional carbon crystal, designed to enhance radio communications. The unique structure of graphene would enable these enhancements. Ultimately, the choice of graphene for the basis of this nano antenna was due to the behavior of electrons.

Terahertz spectroscopy detects and controls properties of matter with electromagnetic fields that are in the frequency range between a few hundred gigahertz and several terahertz. In many-body systems, several of the relevant states have an energy difference that matches with the energy of a THz photon. Therefore, THz spectroscopy provides a particularly powerful method in resolving and controlling individual transitions between different many-body states. By doing this, one gains new insights about many-body quantum kinetics and how that can be utilized in developing new technologies that are optimized up to the elementary quantum level.

<span class="mw-page-title-main">POlarization Emission of Millimeter Activity at the Sun</span>

The POlarization Emission of Millimeter Activity at the Sun (POEMAS) is a solar patrol system composed of two radio telescopes with superheterodyne circular polarization receivers at 45 and 90 GHz. Since their half power beam width is around 1.4°, they observe the full sun. The acquisition system allows to gather 100 values per second at both frequencies and polarizations, with a sensitivity of around 20 solar flux units (SFU) (1 SFU ≡ 104 Jy). The telescope saw first light in November 2011, and showed excellent performance during two years, when it observed many flares. Since November 2013 is stopped for repairing. The main interest of POEMAS is the observation of solar flares in a frequency range where there are very few detectors and fill the gap between microwaves observed with the Radio Solar Telescope Network (1 to 15.4 GHz) and submillimeter observations of the Solar Submillimeter Telescope (212 and 405 GHz). Moreover, POEMAS is the only current telescope capable of carrying on circular polarization solar flare observations at 90 GHz. (Although, in principle, ALMA band 3 may also observe at 90 GHz with circular polarization).

Kenneth John Button was a solid-state and plasma physicist. He was the editor-in-chief of the International Journal of Infrared and Millimeter Waves from its inception in 1980 until his resignation in 2004.

References

  1. Jones, Graham A.; Layer, David H.; Osenkowsky, Thomas G. (2007). National Association of Broadcasters Engineering Handbook. Taylor and Francis. p. 7. ISBN   978-1-136-03410-7.
  2. "Article 2.1: Frequency and wavelength bands". Radio Regulations (zipped PDF) (2016 ed.). International Telecommunication Union. 2017. Retrieved 9 November 2019.
  3. Dhillon, S.S.; Vitiello, M.S.; Linfield, E.H.; Davies, A.G.; Hoffmann, Matthias C.; Booske, John; et al. (2017). "The 2017 terahertz science and technology roadmap". Journal of Physics D: Applied Physics. 50 (4): 2. Bibcode:2017JPhD...50d3001D. doi: 10.1088/1361-6463/50/4/043001 . hdl: 10044/1/43481 .
  4. Coutaz, Jean-Louis; Garet, Frederic; Wallace, Vincent P. (2018). Principles of Terahertz Time-Domain Spectroscopy: An introductory textbook. CRC Press. p. 18. ISBN   978-1-351-35636-7 via Google Books.
  5. Siegel, Peter (2002). "Studying the Energy of the Universe". NASA. Education materials. U.S. National Aeronautics and Space Administration. Archived from the original on 20 June 2021. Retrieved 19 May 2021.
  6. Gosling, William (2000). Radio Spectrum Conservation: Radio Engineering Fundamentals. Newnes. pp. 11–14. ISBN   9780750637404. Archived from the original on 7 April 2022. Retrieved 25 November 2019.
  7. Petrov, Nikolay V.; Maxim S. Kulya; Anton N. Tsypkin; Victor G. Bespalov; Andrei Gorodetsky (5 April 2016). "Application of Terahertz Pulse Time-Domain Holography for Phase Imaging". IEEE Transactions on Terahertz Science and Technology. 6 (3): 464–472. Bibcode:2016ITTST...6..464P. doi:10.1109/TTHZ.2016.2530938. S2CID   20563289.
  8. Ahi, Kiarash; Anwar, Mehdi F. (26 May 2016). "Advanced terahertz techniques for quality control and counterfeit detection". In Anwar, Mehdi F.; Crowe, Thomas W.; Manzur, Tariq (eds.). Proceedings SPIE Volume 9856, Terahertz Physics, Devices, and Systems X: Advanced Applications in Industry and Defense. SPIE Commercial + Scientific Sensing and Imaging. Baltimore, MD: SPIE: The International Society for Optics and Photonics. Bibcode:2016SPIE.9856E..0GA. doi:10.1117/12.2228684. S2CID   138587594. 98560G. Retrieved 26 May 2016 via researchgate.net.
  9. 1 2 Ahi, Kiarash (2018). "A method and system for enhancing the resolution of terahertz imaging". Measurement. 138: 614–619. doi:10.1016/j.measurement.2018.06.044. S2CID   116418505.
  10. "JLab generates high-power terahertz light". CERN Courier. 1 January 2003.
  11. Liu, Jiawen; Chomet, Baptiste; Beoletto, Paolo; Gacemi, Djamal; Pantzas, Konstantinos; Beaudoin, Grégoire; Sagnes, Isabelle; Vasanelli, Angela; Sirtori, Carlo; Todorov, Yanko (18 May 2022). "Ultrafast Detection of TeraHertz Radiation with Miniaturized Optomechanical Resonator Driven by Dielectric Driving Force". ACS Photonics. 9 (5): 1541–1546. doi:10.1021/acsphotonics.2c00227. S2CID   247959476.
  12. Liu, Jiawen; Gacemi, Djamal; Pantzas, Konstantinos; Beaudoin, Grégoire; Sagnes, Isabelle; Vasanelli, Angela; Sirtori, Carlo; Todorov, Yanko (February 2023). "Nonlinear Oscillation States of Optomechanical Resonator for Reconfigurable Light-Compatible Logic Functions". Advanced Optical Materials. 11 (4): 2202133. doi:10.1002/adom.202202133. S2CID   254776067.
  13. "Atmospheric Absorption & Transmission". Humboldt State Geospatial Online Learning Modules. Humboldt State University. Archived from the original on 7 November 2020. Retrieved 19 May 2021.
  14. "Absorption Bands and Atmospheric Windows". The Earth Observatory. NASA. 17 September 1999. Retrieved 19 May 2021.
  15. "Multipliers". Products. Virginia Diodes. Archived from the original on 15 March 2014.
  16. Köhler, Rüdeger; Tredicucci, Alessandro; Beltram, Fabio; Beere, Harvey E.; Linfield, Edmund H.; Davies, A. Giles; Ritchie, David A.; Iotti, Rita C.; Rossi, Fausto (2002). "Terahertz semiconductor-heterostructure laser". Nature. 417 (6885): 156–159. Bibcode:2002Natur.417..156K. doi:10.1038/417156a. PMID   12000955. S2CID   4422664.
  17. Scalari, G.; Walther, C.; Fischer, M.; Terazzi, R.; Beere, H.; Ritchie, D.; Faist, J. (2009). "THz and sub-THz quantum-cascade lasers". Laser & Photonics Reviews. 3 (1–2): 45–66. Bibcode:2009LPRv....3...45S. doi:10.1002/lpor.200810030. S2CID   121538269.
  18. Lee, Alan W.M.; Qin, Qi; Kumar, Sushil; Williams, Benjamin S.; Hu, Qing; Reno, John L. (2006). "Real-time terahertz imaging over a standoff distance (>25 meters)". Appl. Phys. Lett. 89 (14): 141125. Bibcode:2006ApPhL..89n1125L. doi:10.1063/1.2360210. S2CID   122942520.
  19. Fathololoumi, S.; Dupont, E.; Chan, C.W.I.; Wasilewski, Z.R.; Laframboise, S.R.; Ban, D.; et al. (13 February 2012). "Terahertz quantum-cascade lasers operating up to ~200 K with optimized oscillator strength and improved injection tunneling". Optics Express. 20 (4): 3866–3876. Bibcode:2012OExpr..20.3866F. doi:10.1364/OE.20.003866. hdl: 1721.1/86343 . PMID   22418143. S2CID   9383885.
  20. Ramakrishnan, Gopakumar (2012). Enhanced terahertz emission from thin film semiconductor/metal interfaces. Delft University of Technology, The Netherlands. ISBN   978-94-6191-5641.
  21. Izumi, R.; Suzuki, S.; Asada, M. (2017). "1.98 THZ resonant-tunneling-diode oscillator with reduced conduction loss by thick antenna electrode". 2017 42nd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THZ). pp. 1–2. doi:10.1109/IRMMW-THz.2017.8066877. ISBN   978-1-5090-6050-4.
  22. Science News: New T-ray Source Could Improve Airport Security, Cancer Detection, ScienceDaily (27 November 2007).
  23. Engineers demonstrate first room-temperature semiconductor source of coherent terahertz radiation Physorg.com. 19 May 2008. Retrieved May 2008
  24. Horvat, J.; Lewis, R. A. (2009). "Peeling adhesive tape emits electromagnetic radiation at terahertz frequencies". Optics Letters. 34 (14): 2195–7. Bibcode:2009OptL...34.2195H. doi:10.1364/OL.34.002195. PMID   19823546.
  25. Hewitt, John (25 February 2013). "Samsung funds graphene antenna project for wireless, ultra-fast intra-chip links". ExtremeTech . Retrieved 8 March 2013.
  26. Talbot, David (5 March 2013). "Graphene Antennas Would Enable Terabit Wireless Downloads". MIT Technology Review . Retrieved 8 March 2013.
  27. Dhillon, S S; et al. (2017). "The 2017 terahertz science and technology roadmap". Journal of Physics D: Applied Physics. 50 (4): 2. Bibcode:2017JPhD...50d3001D. doi: 10.1088/1361-6463/50/4/043001 . hdl: 10044/1/43481 .
  28. Gharavi, Sam; Heydari, Babak (25 September 2011). Ultra High-Speed CMOS Circuits: Beyond 100 GHz (1st ed.). New York: Springer Science+Business Media. pp. 1–5 (Introduction) and 100. doi:10.1007/978-1-4614-0305-0. ISBN   978-1-4614-0305-0.
  29. Sirtori, Carlo (2002). "Bridge for the terahertz gap" (Free PDF download). Nature. Applied physics. 417 (6885): 132–133. Bibcode:2002Natur.417..132S. doi: 10.1038/417132b . PMID   12000945. S2CID   4429711.[ permanent dead link ]
  30. Borak, A. (2005). "Toward bridging the terahertz gap with silicon-based lasers" (Free PDF download). Science. Applied physics. 308 (5722): 638–639. doi:10.1126/science.1109831. PMID   15860612. S2CID   38628024.[ permanent dead link ]
  31. Karpowicz, Nicholas; Dai, Jianming; Lu, Xiaofei; Chen, Yunqing; Yamaguchi, Masashi; Zhao, Hongwei; et al. (2008). "Coherent heterodyne time-domain spectrometry covering the entire terahertz gap". Applied Physics Letters (Abstract). 92 (1): 011131. Bibcode:2008ApPhL..92a1131K. doi: 10.1063/1.2828709 .
  32. Kleiner, R. (2007). "Filling the terahertz gap". Science (Abstract). 318 (5854): 1254–1255. doi:10.1126/science.1151373. PMID   18033873. S2CID   137020083.
  33. Wubs, Jente R.; Macherius, Uwe; Lü, Xiang; Schrottke, Lutz; Budden, Matthias; Kunsch, Johannes; Weltmann, Klaus-Dieter; van Helden, Jean-Pierre H. (January 2024). "Performance of a High-Speed Pyroelectric Receiver as Cryogen-Free Detector for Terahertz Absorption Spectroscopy Measurements". Applied Sciences. 14 (10): 3967. doi: 10.3390/app14103967 . ISSN   2076-3417.
  34. Larraza, Andres; Wolfe, David M.; Catterlin, Jeffrey K. (21 May 2013). "Terahertz (THZ) reverse magnetron". Dudley Knox Library. Monterey, California: Naval Postgraduate School. US Patent 8,446,096 B1.[ full citation needed ]
  35. Glyavin, Mikhail; Denisov, Grigory; Zapevalov, V.E.; Kuftin, A.N. (August 2014). "Terahertz gyrotrons: State of the art and prospects". Journal of Communications Technology and Electronics. 59 (8): 792–797. doi:10.1134/S1064226914080075. S2CID   110854631 . Retrieved 18 March 2020 via researchgate.net.
  36. Evain, C.; Szwaj, C.; Roussel, E.; Rodriguez, J.; Le Parquier, M.; Tordeux, M.-A.; Ribeiro, F.; Labat, M.; Hubert, N.; Brubach, J.-B.; Roy, P.; Bielawski, S. (8 April 2019). "Stable coherent terahertz synchrotron radiation from controlled relativistic electron bunches". Nature Physics. 15 (7): 635–639. arXiv: 1810.11805 . Bibcode:2019NatPh..15..635E. doi:10.1038/s41567-019-0488-6. S2CID   53606555.
  37. "UCSB free-electron laser source". www.mrl.ucsb.edu. Terahertz facility. University of California – Santa Barbara.[ full citation needed ]
  38. Sensale-Rodríguez, B.; Fay, P.; Liu, L.; Jena, D.; Xing, H. G. (2012). "Enhanced Terahertz Detection in Resonant Tunnel Diode-Gated HEMTs". ECS Transactions. 49 (1): 93–102. Bibcode:2012ECSTr..49a..93S. doi:10.1149/04901.0093ecst.
  39. Davids, Paul (1 July 2016). Tunneling rectification in an infrared nanoantenna coupled MOS diode. Office of Scientific and Technical Information. Meta 16. osti.gov. Malaga, Spain: U.S. Department of Energy.[ full citation needed ]
  40. Liu, Xi; Qiao, Zhi; Chai, Yuming; Zhu, Zhi; Wu, Kaijie; Ji, Wenliang; Daguang, Li; Xiao, Yujie; Mao, Lanqun; Chang, Chao; Wen, Quan; Song, Bo; Shu, Yousheng (2021). "Nonthermal and reversible control of neuronal signaling and behavior by midinfrared stimulation". Proceedings of the National Academy of Sciences (U.S.A.). 118 (10). doi: 10.1073/pnas.2015685118 . PMC   7958416 . PMID   33649213.
  41. Zhang, Jun; Song, Li; Li, Weidong. "Advances of terahertz technology in neuroscience: Current status and a future perspective". iScience. doi: 10.1016/j.isci.2021.103548 . PMC   8683584 . PMID   34977497.
  42. Sun, Q.; He, Y.; Liu, K.; Fan, S.; Parrott, E. P. J.; Pickwell-MacPherson, E. (2017). "Recent advances in terahertz technology for biomedical applications". Quantitative Imaging in Medicine and Surgery. 7 (3): 345–355. doi: 10.21037/qims.2017.06.02 . PMC   5537133 . PMID   28812001.
  43. "Terahertz spectroscopy opens options in COVID-19 screening". LabPulse.com. 22 June 2020. Retrieved 14 June 2021.
  44. US 2021038111,Ahi, Kiarash,"Method and System for Enhancing Resolution of Terahertz Imaging and Detection of Symptoms of COVID-19",published 2021-02-11
  45. "Space in Images – 2002 – 06 – Meeting the team". European Space Agency. June 2002.
  46. Space camera blazes new terahertz trails. timeshighereducation.co.uk. 14 February 2003.
  47. Winner of the 2003/04 Research Councils' Business Plan Competition – 24 February 2004. epsrc.ac.uk. 27 February 2004
  48. "Camera 'looks' through clothing". BBC News 24. 10 March 2008. Retrieved 10 March 2008.
  49. "ThruVision T5000 T-Ray Camera sees through Clothes". I4u.com. Retrieved 17 May 2012.
  50. Parascandola, Bruno (23 January 2013). "NYPD Commissioner says department will begin testing a new high-tech device that scans for concealed weapons". NYDailyNews.com. Retrieved 10 April 2013.
  51. Golding, Bruce & Conley, Kirsten (28 January 2013). "Blogger sues NYPD over gun detecting 'terahertz' scanners". NYpost.com. Retrieved 10 April 2013.
  52. Parascandola, Rocco (22 February 2017). "NYPD's pricey, controversial 'T-Ray' gun sensors sit idle, but that's OK with cops". New York Daily News. Retrieved 22 February 2017.
  53. Hidden Art Could be Revealed by New Terahertz Device Newswise, Retrieved 21 September 2008.
  54. Hillger, Philipp; Grzyb, Janusz; Jain, Ritesh; Pfeiffer, Ullrich R. (January 2019). "Terahertz Imaging and Sensing Applications With Silicon-Based Technologies". IEEE Transactions on Terahertz Science and Technology. 9 (1): 1–19. Bibcode:2019ITTST...9....1H. doi: 10.1109/TTHZ.2018.2884852 . S2CID   57764017.
  55. Ghavidel, Ali; Myllymäki, Sami; Kokkonen, Mikko; Tervo, Nuutti; Nelo, Mikko; Jantunen, Heli (2021). "A Sensing Demonstration of a Sub THz Radio Link Incorporating a Lens Antenna". Progress in Electromagnetics Research Letters. 99: 119–126. doi: 10.2528/PIERL21070903 . S2CID   237351452.
  56. Dolgashev, Valery; Tantawi, Sami; Higashi, Yasuo; Spataro, Bruno (25 October 2010). "Geometric dependence of radio-frequency breakdown in normal conducting accelerating structures". Applied Physics Letters. 97 (17): 171501. Bibcode:2010ApPhL..97q1501D. doi:10.1063/1.3505339.
  57. Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X. (6 October 2015). "Terahertz-driven linear electron acceleration". Nature Communications. 6 (1): 8486. arXiv: 1411.4709 . Bibcode:2015NatCo...6.8486N. doi: 10.1038/ncomms9486 . PMC   4600735 . PMID   26439410.
  58. Jing, Chunguang (2016). "Dielectric Wakefield Accelerators". Reviews of Accelerator Science and Technology. 09 (6): 127–149. Bibcode:2016RvAST...9..127J. doi:10.1142/s1793626816300061.
  59. Thompson, M.C.; Badakov, H.; Cook, A.M.; Rosenzweig, J.B.; Tikhoplav, R.; Travish, G.; et al. (27 May 2008). "Breakdown limits on gigavolt-per-meter electron-beam-driven wakefields in dielectric structures". Physical Review Letters. 100 (21): 214801. Bibcode:2008PhRvL.100u4801T. doi:10.1103/physrevlett.100.214801. OSTI   933022. PMID   18518609. S2CID   6728675.
  60. O'Shea, B.D.; Andonian, G.; Barber, S.K.; Fitzmorris, K.L.; Hakimi, S.; Harrison, J.; et al. (14 September 2016). "Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators". Nature Communications. 7 (1): 12763. Bibcode:2016NatCo...712763O. doi: 10.1038/ncomms12763 . PMC   5027279 . PMID   27624348.
  61. Ponomarenko, A.A.; Ryazanov, M.I.; Strikhanov, M.N.; Tishchenko, A.A. (2013). "Terahertz radiation from electrons moving through a waveguide with variable radius, based on Smith–Purcell and Cherenkov mechanisms". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 309: 223–225. Bibcode:2013NIMPB.309..223P. doi:10.1016/j.nimb.2013.01.074.
  62. Lekomtsev, K.; Aryshev, A.; Tishchenko, A.A.; Shevelev, M.; Ponomarenko, A.A.; Karataev, P.; et al. (2017). "Sub-THz radiation from dielectric capillaries with reflectors". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 402: 148–152. arXiv: 1706.03054 . Bibcode:2017NIMPB.402..148L. doi:10.1016/j.nimb.2017.02.058. S2CID   119444425.
  63. Lekomtsev, K.; Aryshev, A.; Tishchenko, A.A.; Shevelev, M.; Lyapin, A.; Boogert, S.; et al. (10 May 2018). "Driver-witness electron beam acceleration in dielectric mm-scale capillaries". Physical Review Accelerators and Beams. 21 (5): 051301. Bibcode:2018PhRvS..21e1301L. doi: 10.1103/physrevaccelbeams.21.051301 .
  64. 1 2 3 Rappaport, Theodore S.; Xing, Yunchou; Kanhere, Ojas; Ju, Shihao; Madanayake, Arjuna; Mandal, Soumyajit; Alkhateeb, Ahmed; Trichopoulos, Georgios C. (2019). "Wireless Communications and Applications Above 100 GHz: Opportunities and Challenges for 6G and Beyond". IEEE Access. 7: 78729–78757. Bibcode:2019IEEEA...778729R. doi: 10.1109/ACCESS.2019.2921522 . ISSN   2169-3536.
  65. Ishigaki, K.; Shiraishi, M.; Suzuki, S.; Asada, M.; Nishiyama, N.; Arai, S. (2012). "Direct intensity modulation and wireless data transmission characteristics of terahertz-oscillating resonant tunnelling diodes". Electronics Letters. 48 (10): 582. Bibcode:2012ElL....48..582I. doi:10.1049/el.2012.0849.
  66. 1 2 3 "Milestone for Wi-Fi with 'T-rays'". BBC News. 16 May 2012. Retrieved 16 May 2012.
  67. Chacksfield, Marc (16 May 2012). "Scientists show off the future of Wi-Fi – smash through 3Gbps barrier". Tech Radar. Retrieved 16 May 2012.
  68. "New chip enables record-breaking wireless data transmission speed". techcrunch.com. 22 November 2011. Retrieved 30 November 2011.
  69. Clausell, A. (11 September 2020). Distance records (PDF). ARRL.org (Report). World above 50 MHz standings. American Radio Relay League . Retrieved 19 November 2020.
  70. Day, Peter; Qaurmby, John (9 May 2019). Microwave distance records (Report). UK Microwave Group. Retrieved 2 August 2019.
  71. Australian VHF-UHF records (PDF) (Report). Wireless Institute of Australia. 5 January 2021. Retrieved 5 January 2021.
  72. Hu, B.B.; Nuss, M.C. (15 August 1995). "Imaging with terahertz waves". Optics Letters. 20 (16): 1716. Bibcode:1995OptL...20.1716H. doi:10.1364/OL.20.001716. PMID   19862134. S2CID   11593500.
  73. Chan, Wai Lam; Deibel, Jason; Mittleman, Daniel M. (1 August 2007). "Imaging with terahertz radiation". Reports on Progress in Physics. 70 (8): 1325–1379. Bibcode:2007RPPh...70.1325C. doi:10.1088/0034-4885/70/8/R02. S2CID   17397271.
  74. Prince, Jerry L. Jr.; Links, Jonathan M. (2006). Medical imaging signals and systems. Upper Saddle River, N.J.: Pearson Prentice Hall. ISBN   978-0-13-065353-6.
  75. Marshall, Gerald F.; Stutz, Glenn E., eds. (2012). Handbook of optical and laser scanning (2nd ed.). Boca Raton, FL: CRC Press. ISBN   978-1-4398-0879-5.
  76. Ahi, Kiarash; Shahbazmohamadi, Sina; Tehranipoor, Mark; Anwar, Mehdi (13 May 2015). "Terahertz characterization of electronic components and comparison of terahertz imaging with X-ray imaging techniques". In Anwar, Mehdi F.; Crowe, Thomas W.; Manzur, Tariq (eds.). Proceedings Volume 9483, Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense. SPIE Sensing Technology + Applications. Baltimore, MD. Bibcode:2015SPIE.9483E..0KA. doi:10.1117/12.2183128. S2CID   118178651. 94830K.
  77. Mueckstein, Raimund; Mitrofanov, Oleg (3 February 2011). "Imaging of terahertz surface plasmon waves excited on a gold surface by a focused beam". Optics Express. 19 (4): 3212–3217. Bibcode:2011OExpr..19.3212M. doi: 10.1364/OE.19.003212 . PMID   21369143. S2CID   21438398.
  78. Adam, Aurele; Brok, Janne; Seo, Min Ah; Ahn, Kwang Jun; Kim, Dai Sik; Kang, Ji-Hun; Park, Q-Han; Nagel, M.; Nagel, Paul C.M. (19 May 2008). "Advanced terahertz electric near-field measurements at sub-wavelength diameter metallic apertures: erratum". Optics Express. 16 (11): 8054. Bibcode:2008OExpr..16.8054A. doi: 10.1364/OE.16.008054 .
  79. Kiwa, Toshihiko; Tonouchi, Masayoshi; Yamashita, Masatsugu; Kawase, Kodo (1 November 2003). "Laser terahertz-emission microscope for inspecting electrical faults in integrated circuits". Optics Letters. 28 (21): 2058–60. Bibcode:2003OptL...28.2058K. doi:10.1364/OL.28.002058. PMID   14587814.
  80. Ferguson, Bradley; Zhang, Xi-Cheng (2002). "Materials for terahertz science and technology" (free PDF download). Nature Materials. 1 (1): 26–33. Bibcode:2002NatMa...1...26F. doi:10.1038/nmat708. PMID   12618844. S2CID   24003436.
  81. Tonouchi, Masayoshi (2007). "Cutting-edge terahertz technology" (free PDF download). Nature Photonics. 1 (2): 97–105. Bibcode:2007NaPho...1...97T. doi:10.1038/nphoton.2007.3. 200902219783121992.
  82. Chen, Hou-Tong; Padilla, Willie J.; Cich, Michael J.; Azad, Abul K.; Averitt, Richard D.; Taylor, Antoinette J. (2009). "A metamaterial solid-state terahertz phase modulator" (PDF). Nature Photonics. 3 (3): 148. Bibcode:2009NaPho...3..148C. CiteSeerX   10.1.1.423.5531 . doi:10.1038/nphoton.2009.3. OSTI   960853. Archived from the original (free PDF download) on 29 June 2010. Retrieved 25 August 2022.
  83. IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz (Report). Institute of Electrical and Electronics Engineers. 2005. IEEE C95.1–2005.
  84. American National Standard for Safe Use of Lasers (Report). American National Standards Institute. 2007. ANSI Z136.1–2007.
  85. 1 2 Alexandrov, B.S.; Gelev, V.; Bishop, A. R.; Usheva, A.; Rasmussen, K.O. (2010). "DNA breathing dynamics in the presence of a terahertz field". Physics Letters A . 374 (10): 1214–1217. arXiv: 0910.5294 . Bibcode:2010PhLA..374.1214A. doi:10.1016/j.physleta.2009.12.077. PMC   2822276 . PMID   20174451.
  86. "How terahertz waves tear apart DNA". MIT Technology Review . Emerging Technology from the arXiv. 30 October 2010. Retrieved 5 June 2021;
    MIT Tech. Rev. article cites Alexandrov et al. (2010) [85] as source.
  87. Swanson, Eric S. (2010). "Modelling DNA Response to THz Radiation". Physical Review E. 83 (4): 040901. arXiv: 1012.4153 . Bibcode:2011PhRvE..83d0901S. doi:10.1103/PhysRevE.83.040901. PMID   21599106. S2CID   23117276.
  88. Fitzgerald, A.J.; Berry, E.; Zinov'Ev, N.N.; Homer-Vanniasinkam, S.; Miles, R.E.; Chamberlain, J.M.; Smith, M.A. (2003). "Catalogue of human tissue optical properties at terahertz frequencies". Journal of Biological Physics. 29 (2–3): 123–128. doi:10.1023/A:1024428406218. PMC   3456431 . PMID   23345827.

Further reading