Terahertz technology

A backward wave oscillator (BWO), also called carcinotron or backward wave tube, is a device that is used to generate microwaves and terahertz radiation. It consists of a vacuum tube that provides 1 mW to 50 mW of power. Some types can produce frequencies in a range of 200 GHz to 1.1 THz. It sustains the oscillations by reflecting the traveling wave backwards against the beam. It is derived from the traveling wave tube. It has two main subtypes, the M-type (M-BWO) and O-type (O-BWO). Carcinotrons are used as powerful and stable microwave sources. Due to the good quality wavefront they produce, they find use as illuminators in terahertz imaging. ...more on Wikipedia about "Backward wave oscillator"

Cadmium zinc telluride, (CdZnTe) or CZT, is (as the name indicates) a compound of cadmium, zinc and tellurium or more strictly speaking, an alloy of cadmium telluride and zinc telluride. A wide, direct bandgap semiconductor, it is used in a variety of applications, including radiation detectors, photorefractive gratings, electro-optic modulators and terahertz generation and detection. ...more on Wikipedia about "Cadmium zinc telluride"

A comb generator is a signal generator that produces multiple harmonics of its input signal. The appearance of the output at the spectrum analyzer screen, resembling teeth of a comb, gave the device its name. ...more on Wikipedia about "Comb generator"

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). It is one of the possible sources of terahertz radiation. ...more on Wikipedia about "Far infrared laser"

A free electron laser, or FEL, generates tunable, coherent, high power radiation, currently ranging in wavelength from millimeters to the visible. While an FEL laser beam shares the same optical properties as conventional lasers such as coherent radiation, the operation of an FEL is quite different. Unlike gas or diode lasers which rely on bound atomic or molecular states, FELs use a relativistic electron beam as the lasing medium, hence the term free-electron. Free electron lasers can be used to generate terahertz radiation. ...more on Wikipedia about "Free electron laser"

A Gunn diode, also known as a transferred electron device (TED) is a form of diode used in high-frequency electronics. It is somewhat unusual in that it consists only of N-doped semiconductor material, whereas ordinary diodes consist of both P and N-doped regions. In the Gunn diode, three regions exist: two of them are heavily N-doped on each terminal, with a thin layer of lightly doped material in between. When a voltage is applied to the device, the electrical gradient will be largest across the thin middle layer. Eventually, this layer starts to conduct, reducing the gradient across it, preventing further conduction. In practice, this means a Gunn diode has a region of negative differential resistance. ...more on Wikipedia about "Gunn diode"

Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. Typical output powers range from 10s of kilowatts to 1-2 megawatts. Output frequencies range from about 20 to 250 GHz. Gyrotrons can be designed for pulsed or continuous operation. Gyrotron manufacturers include CPI (USA), Gycom (Russia), Thales Group (EU), and Toshiba (Japan). A prevalent application of gyrotrons is as a source of plasma heating in nuclear fusion research experiments. ...more on Wikipedia about "Gyrotron"

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HEMT stands for High Electron Mobility Transistor, and is also called heterostructure FET (HFET). A HEMT is a Field effect transistor with a junction between two materials with different band gaps (i.e. a heterojunction) as the channel instead of an n-doped region. A commonly used combination is GaAs with AlGaAs. The effect of this junction is to create a very thin layer where the Fermi energy is above the conduction band, giving the channel very low resistance (or to put it another way, "high electron mobility"). This layer is sometimes called a two-dimensional electron gas. As with all the other types of FETs, a voltage applied to the gate alters the conductivity of this layer. ...more on Wikipedia about "HEMT"

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. It is common nowadays in ultrafast circuits, mostly radio-frequency (RF) systems. ...more on Wikipedia about "Heterojunction bipolar transistor"

The quantum cascade laser or QC laser is a unipolar solid state laser which uses electrons as its only charge carrier. The " cascade" is a series of equal energy steps built into the material matrix while the crystal is being grown. When the electrons are transmitted through the laser crystal, they emit one photon at each of these cascade steps, unlike diode lasers which only emit one photon per electron transmitted. ...more on Wikipedia about "Quantum cascade laser"

Radio waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, T-rays, T-light, T-lux and THz, are in the region of the light 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). ...more on Wikipedia about "Terahertz radiation"

In terahertz time domain spectroscopy (THz-TDS), picosecond pulses of terahertz radiation are used to probe different materials. The radiation has several distinct advantages over other forms of spectroscopy: it is nonpolar, most materials are transparent to THz, works safely on biological tissues, is non-ionizing, and has relatively good resolution. ...more on Wikipedia about "Terahertz time domain spectroscopy"

Zinc telluride ( ) is an intrinsic semiconductor material with band gap of 2.23-2.25 eV. It is usually a p-type semiconductor. Its crystal structure is cubic, of sphalerite. Its lattice constant is 0.61034 nm, allowing it to be grown with or on aluminium antimonide, gallium antimonide, indium arsenide, and lead selenide. ** Its CAS number is . Its melting point is 1238.5 °C. It has the appearance of grey or brownish-red powder, or ruby-red crystals when refined by sublimation. ...more on Wikipedia about "Zinc telluride"

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