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[[Електромагнетни талас]]и познати као '''терахерцно зрачење''', '''терахерцни таласи''', '''T-зраци''', и '''-{THz}-''', покривају спектрално подручје између 300 [[гигахерц]]а (3x10<sup>11</sup> -{[[Херц (јединица)|Hz]]}-) до 3 [[терахерц]]а (3x10<sup>12</sup> -{Hz}-), што одговара таласним дужинама од субмилиметарских (<1 [[милиметар]]) до 100 [[микрон]]ских (крај далеког инфрацрвеног опсега).
 
[[Слика:Atmospheric terahertz transmittance at mauna kea(simulated).gif.gif|мини|десно|400п|Симулација атмосферске пропустљивости терахерцних зрака у опсегу 1 до 3 ТНз-{THz}-, у зениту, на врху Маун аКеа при атмосферском садржају водене паре од 0,001 мм.-{mm}-]]
 
==Увод==
 
<!--Like [[infrared radiation]] or [[microwaves]], these waves usually travel in [[line of sight (telecommunications)|line of sight]]. Terahertz radiation is non-[[ionizing radiation|ionizing]] and shares with microwaves the capability to penetrate a wide variety of non-[[conductor (material)|conducting]] materials. They can pass through [[clothing]], [[paper]], [[cardboard]], [[wood]], [[masonry]], [[plastic]] and [[ceramic]]s. They can also penetrate [[fog]] and [[cloud]]s but cannot penetrate [[metal]] or [[water]].
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 radiation|coherent]] terahertz radiation was technically challenging until the [[1990s]].
 
The Terahertz Photonics and Electronics research group at the Institute of Microwaves and Photonics at the [[University of Leeds]] in the [[United Kingdom]] is one of the main centres of research into uses of Terahertz radiation. [http://www.engineering.leeds.ac.uk/imp/tpae.shtml]-->
 
==Извори==
<!--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]].
 
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.-->
 
==Развој теоријске и технолошке употребе==
<!--
*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 [[centimeter]]s 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]] and replace the [[mammogram]] with a safer and less invasive or painful imaging system.
**Some frequencies of terahertz radiation can be used for [[3D imaging]] of [[tooth|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 [[airport security|security]] screening, to uncover [[concealment device|concealed]] [[weapon]]s 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 [[Terahertz time domain spectroscopy|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 [[infrared|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 [[fluctuation]]s 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]] [[telecommunication]]s, 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 frequency|Larmor]] frequencies are in the submillimeter band. This work is carried out at many [[National High Magnetic Field Laboratory|high-magnetic field laboratories]] around the world.
* Another important application is in [[ALMA|millimeter/submillimeter wave astronomy]]
-->
==Терахерцни наспрам милиметарских и субмилиметарских таласа==
<!--One terahertz is <math>10^{12}</math> 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 micowaves 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.-->
 
==Литература==
* "Revealing the Invisible". Ian S. Osborne, ''Science'' [[16 August]] [[2002]]; 297: 1097.
*[http://www.jlab.org/FEL/terahertz/nature.pdf Article in ''Nature''] [[14 November]] [[2002]] (local copy from the Jefferson Lab)]
*[http://www.jlab.org/FEL/terahertz/nature2.pdf News and Views in ''Nature''] [[14 November]] [[2002]] (local copy from the Jefferson Lab)
*[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=RSINAK000071000001000186000001&idtype=cvips&gifs=Yes Instrumentation for millimeter-wave magnetoelectrodynamic investigations... Review of Scientific Instruments, 2000]
 
==Books on millimeter and submillimeter waves and RF optics==
* [http://www.amazon.com/exec/obidos/tg/detail/-/0780334396?v=glance Quasioptical systems: Gaussian beam quasioptical propagation and applications, Paul F. Goldsmith, IEEE Press]
 
* [http://www.amazon.com/exec/obidos/tg/detail/-/3540628606?v=glance Millimeter wave spectroscopy of solids, edited by G. Gr&uuml;ner, Springer]
* [http://www.amazon.com/exec/obidos/tg/detail/-/0521017106?v=glance Detection of light: from the ultraviolet to the submillimeter, George Rieke, Cambridge]
 
* [http://www.amazon.com/exec/obidos/tg/detail/-/1586030981?v=glance Modern millimeter-wave technologies, Tasuku Teshirogi and Tsukasa Yoneyama, eds, IOS press]
 
* [http://www.amazon.com/exec/obidos/tg/detail/-/0890067112?v=glance Optoelectronic techniques for microwave and millimeter-wave engineering William Robertson, Artech]
 
==Види још==
*[[Терахерц]]
*[[Терахерцна спектроскопија у временском домену]]
<!--*[[Heterojunction bipolar transistor]]
*[[HEMT]]
*[[Picarin lens]]-->
 
== Спољашње везе ==
Линија 67 ⟶ 25:
 
[[Категорија:Електромагнетни спектар]]
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