Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x10¹¹ Hz) and 3 terahertz (3x10¹² Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter) and 100 micrometres (ending edge of far-infrared light). Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... The hertz (symbol: Hz) is the SI unit of frequency. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... The hertz (symbol: Hz) is the SI unit of frequency. ... The hertz (symbol: Hz) is the SI unit of frequency. ... The wavelength is the distance between repeating units of a wave pattern. ... A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... This article or section does not cite any references or sources. ...

Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout the range of 1 to 3 THz of the electromagnetic spectrum at a precipitable water vapor level of 0.001 mm. (simulated)

Image File history File links Size of this preview: 750 × 600 pixelsFull resolution (850 × 680 pixel, file size: 6 KB, MIME type: image/png) Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout a range of 1 to 3 THz at a precipitable water vapor level... Image File history File links Size of this preview: 750 × 600 pixelsFull resolution (850 × 680 pixel, file size: 6 KB, MIME type: image/png) Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout a range of 1 to 3 THz at a precipitable water vapor level...

Introduction

Like infrared radiation or [+[microwaves]], these waves usually travel in line of sight. Terahertz radiation is non-ionizing and shares with microwaves the capability to penetrate a wide variety of non-conducting materials. They can pass through clothing, paper, cardboard, wood, masonry, plastic and ceramics. They can also penetrate fog and clouds but cannot penetrate metal or water. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... See also: line of sight in gaming, referring to visibility of units. ... Radiation hazard symbol. ... In science and engineering, conductors are materials that contain movable charges of electricity. ... // Girls wearing formal attire for dancing, an example of one of the many modern forms of clothing. ... A blank sheet of paper Paper is a commodity of thin material produced by the amalgamation of fibers, typically vegetable fibers composed of cellulose, which are subsequently held together by hydrogen bonding. ... Corrugated cardboard. ... Trunks A tree trunk as found at the Veluwe, The Netherlands Wood is a solid material derived from woody plants, notably trees but also shrubs. ... Masonry in action; a Mason at work. ... This article or section does not cite any references or sources. ... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικός (keramikos). ... Evening fog obscures Londons Tower Bridge from passers by. ... Cumulus mediocris clouds, as seen from a plane window. ... Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

The Earth's atmosphere is a strong absorber of terahertz radiation, so the range of terahertz radiation is quite short, limiting its usefulness. In addition, producing and detecting coherent terahertz radiation was technically challenging until the 1990s. Layers of Atmosphere - not to scale (NOAA)[3] Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... For alternative meanings see laser (disambiguation). ... For the band, see 1990s (band). ...

Sources

While terahertz radiation is emitted as part of the black body radiation from anything with temperatures greater than about 10 kelvin, this thermal emission is very weak. As of 2004 the only effective stronger sources of terahertz radiation are the gyrotron, the backward wave oscillator ("BWO"), the far infrared laser ("FIR laser"), quantum cascade laser, the free electron laser (FEL), synchrotron light sources, and single-cycle sources used in Terahertz time domain spectroscopy.The first images generated using terahertz radiation date from the 1960's; however, in 1995, images generated using terahertz time-domain spectroscopy generated a great deal of interest, and sparked a rapid growth in the field of terahertz science and technology. This excitement, along with the associated coining of the term "T-rays," even showed up in a contemporary novel by Tom Clancy. As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. ... A backward wave oscillator is a device that is used to generate terahertz radiation. ... Far infrared laser (FIR laser, terahertz laser) is a laser with output wavelength in far infrared part of the electromagnetic spectrum, between 30-1000 µm (10 THz-300 GHz). ... The quantum cascade laser or QC laser is a unipolar laser which uses electrons as its only charge carrier. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Synchrotron radiation emerging from a beam port. ... In terahertz time domain spectroscopy (THz-TDS), picosecond pulses of terahertz radiation are used to probe different materials. ... 1995 (MCMXCV) was a common year starting on Sunday of the Gregorian calendar. ... In terahertz time domain spectroscopy (THz-TDS), picosecond pulses of terahertz radiation are used to probe different materials. ... Thomas Leo Clancy Jr. ...

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 1000 GHz with solid state sources and detectors. Nowadays, most time-domain work is done via ultrafast lasers.

Theoretical and technological uses under development

• Medical imaging:
  • Terahertz radiation is non-ionizing, and thus is not expected to damage DNA, unlike X-rays. Some frequencies of terahertz radiation can penetrate several centimeters of tissue and reflect back. Terahertz radiation can also detect differences in water content and density of a tissue. Terahertz imaging could allow effective detection of epithelial cancer with a safer and less invasive or painful imaging system.
  • Some frequencies of terahertz radiation can be used for 3D imaging of teeth and could be more accurate and safer than conventional X-ray imaging in dentistry.
• Because of terahertz radiation's ability to penetrate fabrics and plastics 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, such as plastic explosives, exhibit unique spectral fingerprints in the terahertz range. This offers the possibility of combining spectral identification with imaging. Some controversy surrounds the use of terahertz scanners for routine security checks due to the potential capability to produce detailed images of a subject's body through clothing.
• Spectroscopy in terahertz radiation could provide novel information in chemistry and biochemistry.
• The recently developed techniques of THz time-domain spectroscopy (THz TDS) and THz tomography have been shown to be capable of performing measurements on, and obtaining images of, samples which 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. On the other hand, the fact that THz-TDS produces radiation that is both coherent and broadband means that such images can contain far more information than a conventional image formed with a single-frequency source.
• There are potential applications to satellite telecommunications, and high-altitude communications (aircraft to satellite or satellite to satellite).
• Many possible applications of terahertz imaging have been proposed in manufacturing, quality control, and process monitoring. These generally exploit the fact that plastics and cardboard are transparent to terahertz radiation, so that it is possible to inspect packaged objects.
• One of the main applications of submillimeter waves in physics is the study of condensed matter in high magnetic fields since at high fields (say above 15 T), the Larmor frequencies are in the submillimeter band. This work is carried out at many high-magnetic field laboratories around the world.
• Another important application is in millimeter/submillimeter wave astronomy

The structure of part of a DNA double helix Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living organisms. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... In zootomy, epithelium is a tissue composed of a layer of cells. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Stereoscopy, stereoscopic imaging or 3-D (three-dimensional) imaging is any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image. ... The visible teeth of a smile. ... A Dentist and Dental Assistant perform surgery on a patient. ... The term plastics covers a range of synthetic or semi-synthetic organic condensation or polymerization products that can be molded or extruded into objects or films or fibers. ... Surveillance cameras An helicopter flying over Lille, France, watching for possible rioting after the 2007 presidential election Surveillance is the monitoring of behavior. ... Baggage is scanned using X-ray machines, passengers walk through metal detectors Baggage sreening monitoring at VTBS Airport security refers to the techniques and methods used in protecting airports and by extension aircraft from crime and terrorism. ... American dollar coin used for concealment Concealment devices, as the term suggests, are used to hide things for the purpose of secrecy. ... The bayonet is used as both knife and spear. ... Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. ... Chemistry - the study of atoms, made of nuclei (conglomeration of center particles) and electrons (outer particles), and the structures they form. ... Biochemistry is the study of the chemical processes and transformations in living organisms. ... In terahertz time domain spectroscopy (THz-TDS), picosecond pulses of terahertz radiation are used to probe different materials. ... Tomography is imaging by sections or sectioning. ... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... In spectroscopy, the absorbance A is defined as , where I is the intensity of light at a specified wavelength λ that has passed through a sample (transmitted light intensity) and is the intensity of the light before it enters the sample (or incident light intensity). ... In physics, a fluctuation is a variation in an extensive or intensive quantity, such as energy, density or voltage, from its spatial or temporal average. ... Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ... In the scientific method, an experiment (Latin: ex-+-periri, of (or from) trying), is a set of actions of going to the bathroom. ... Coherence is from Latin cohaerere = stick together, to be connected with). ... Broadband in telecommunications is a term which refers to a signaling method which includes or handles a relatively wide range of frequencies which may be divided into channels or frequency bins. ... An Earth observation satellite, ERS 2 For other uses, see Satellite (disambiguation). ... Copy of the original phone of Alexander Graham Bell at the Musée des Arts et Métiers in Paris Telecommunication is the transmission of signals over a distance for the purpose of communication. ... In physics, Larmor precession, named after Joseph Larmor refers to the precession of the magnetic moments of electrons, atomic nuclei, and atoms around the direction of an external magnetic field. ... // Overview The National High Magnetic Field Laboratory (NHMFL) develops and operates high magnetic field facilities that scientists use for research in physics, biology, bioengineering, chemistry, geochemistry, biochemistry, materials science, and engineering. ... Alma may refer to: Canada Alma, Ontario, a small village in Ontario, Canada Alma, Quebec, a town in Quebec, Canada Alma, New Brunswick, a fishing village on the Bay of Fundy Crimea Alma (river) and the site of the Battle of Alma (September 20, 1854) Kazakhstan Almaty, until recently the...

Terahertz versus millimeter and submillimeter waves

One terahertz is 10¹² Hz. Conventionally the microwave band extends to 30 GHz or so while the far-IR is nominally reckoned to start at around 1 THz. So the terahertz band lies between microwaves and the far-IR. On the other hand, in this frequency range the wavelengths of electromagnetic waves (in vacuum) are millimeter or sub-millimeter. So, logically, terahertz waves are the same thing as millimeter or submillimeter waves. However, in practice people who use the term terahertz are generally speaking of signals generated by ultrafast optical techniques or far-IR lasers. Focusing a sub-picosecond pulse on a photoconductive antenna of suitable dimensions will produce EM waves in the THz band. On the other hand, people who use the term millimeter or submillimeter waves are invariably speaking of sources and detectors based on harmonic multiplication of microwave signals.

References

• "Revealing the Invisible". Ian S. Osborne, Science 16 August 2002; 297: 1097.
• Article in Nature 14 November 2002 (local copy from the Jefferson Lab)]
• News and Views in Nature 14 November 2002 (local copy from the Jefferson Lab)
• Instrumentation for millimeter-wave magnetoelectrodynamic investigations... Review of Scientific Instruments, 2000

August 16 is the 228th day of the year (229th in leap years) in the Gregorian calendar. ... For album titles with the same name, see 2002 (album). ... November 14 is the 318th day of the year (319th in leap years) in the Gregorian Calendar, with 47 days remaining. ... For album titles with the same name, see 2002 (album). ... November 14 is the 318th day of the year (319th in leap years) in the Gregorian Calendar, with 47 days remaining. ... For album titles with the same name, see 2002 (album). ...

Books on millimeter and submillimeter waves and RF optics

• Quasioptical systems: Gaussian beam quasioptical propagation and applications, Paul F. Goldsmith, IEEE Press

• Millimeter wave spectroscopy of solids, edited by G. Grüner, Springer

• Detection of light: from the ultraviolet to the submillimeter, George Rieke, Cambridge

• Modern millimeter-wave technologies, Tasuku Teshirogi and Tsukasa Yoneyama, eds, IOS press

• Optoelectronic techniques for microwave and millimeter-wave engineering William Robertson, Artech

See also

• Terahertz
• Terahertz time domain spectroscopy
• Heterojunction bipolar transistor
• HEMT
• Picarin lens

The hertz (symbol: Hz) is the SI unit of frequency. ... In terahertz time domain spectroscopy (THz-TDS), picosecond pulses of terahertz radiation are used to probe different materials. ... The Heterojunction Bipolar Transistor (HBT) is an improvement of the bipolar junction transistor (BJT) that can handle signals of very high frequencies up to several hundred GHz. ... HEMT stands for High Electron Mobility Transistor, and is also called heterostructure FET (HFET). ... Picarin is a plastic used to make optics such as lenses for terahertz radiation (THz radiation). ...

External links

• The Terahertz Science and Technology Network
• SURA Annual Terahertz Applications Symposium
• Terahertz radiation: applications and sources by Eric Mueller
• Blinded By The Light At 20,000 THz
• Shadowy T-rays: Hunting Tumors and Exploring the Universe
• The Center for Terahertz Research at Rensselaer Polytechnic Institute
• The Terahertz Photonics and Electronics research group at the University of Leeds
• The Terahertz Technology group at Chalmers University of Technology
• Handheld T-ray Device
• Ultrafast group at the University of Strathclyde in Glasgow
• Terahertz physics in Freiburg (Germany)