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Photonics Dictionary: A

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atomic force microscope
An atomic force microscope (AFM) is a high-resolution imaging and measurement instrument used in nanotechnology, materials science, and biology. It is a type of scanning probe microscope that...
atomic scattering factor
The efficiency of scattering by an atom in a particular direction, expressed as: where AA is the amplitude of the wave from the atom and AE is the amplitude of the wave from a free electron.
atomic time
Any system of time measurement that is based on atomic resonances. The transition times between the hyperfine levels of cesium-133 have been accepted as the international standard.
ATP
acceptance test plan; Advanced Technology Plan
ATR
attenuated total reflectance; automatic target recognition
attenuated total reflectance spectroscopy
Attenuated total reflectance (ATR) spectroscopy is a technique used in analytical chemistry to obtain IR spectra of samples. It is particularly useful for analyzing solid and liquid samples without...
attenuation
Attenuation refers to the gradual loss or reduction of intensity, force, or magnitude of a particular property as it propagates through a medium or travels over a distance. This concept is prevalent...
attenuation coefficient
The rate of diminution of average optical power and the sum of the scattering and absorption coefficients.
attenuation constant
The real part of the axial propagation constant for a particular mode. The attenuation coefficient for the mode power is twice the attenuation constant.
attenuation meter
A device used to measure power loss in fiber optic connectors, cables or systems.
attenuation-limited power
In fiber optics, the limitation on performance imposed by the amplitude of a received signal rather than distortion.
attenuator
An attenuator is an electronic or optical device used to reduce the power or intensity of a signal without significantly affecting its waveform or other characteristics. Attenuators are commonly used...
attitude -> pitch
In positioning, rotation about an axis normal to the line of sight. Also known as attitude.
atto
In the SI system, prefix meaning 10-18.
attosecond photonics sources
Attosecond photonics sources refer to devices or systems that generate extremely short pulses of light on the order of attoseconds (1 attosecond = 10-18 seconds). These ultrafast light pulses are in...
attosecond-pump attosecond-probe spectroscopy
Attosecond-pump attosecond-probe spectroscopy (APAP) is an advanced technique in ultrafast spectroscopy that allows scientists to study the dynamics of electronic processes occurring on extremely...
ATWL
acoustic traveling wave lens
AU
angstrom unit; astronomical unit
audiovisual
Concerned with the transmission and reception of both sight and sound. An audiovisual system communicates pictorial images and audio signals.
Auger effect
The radiation-free transition that takes place within an ion, in which inner-shell vacancies in neutral atoms are filled by outer-shell electrons, thereby transferring energy to other electrons,...
Auger electron spectroscopy
The energy analysis of electrons released in a secondary step following initial excitation or ionization.
augmented reality
Augmented reality (AR) is a technology that integrates digital information, typically in the form of computer-generated graphics, images, or data, with the real-world environment in real-time. AR...
aureole
The indistinct, less luminous portion lying immediately outside an electric arc whose spectrum often differs from that of the core.
aurora
The strongest light emitted by the Earth's upper atmosphere. It most often can be viewed in the Arctic as the aurora borealis, and in the Antarctic as the aurora australis.
auroral line
The green line, in the spectrum of the aurora borealis, that has a wavelength of 5577 Å; it is caused by a forbidden transition in oxygen.
auto-iris lens
A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.
autocollimating spectrograph
A spectrograph in which the refracted beam returns almost along the path traveled by the incident beam, and is brought to a focus by the lens that collimates the incident beam.
autocollimation
Technique of projecting an illuminated target at infinity and receiving the target image after reflection from a flat mirror surface.
autocollimator
An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a...
autocorrelator
A signal-averaging device that improves signal-to-noise ratio by comparing a sampled signal with a time-delayed form of itself.
autofluorescence
Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...
autofocus system
A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive mechanism to adjust the lens. Active systems generate a light source to...
autoguider
A CCD sensor that provides feedback to the motion control system for a telescope, allowing the telescope to follow a particular object or section of sky automatically.
autoluminescence
The luminescence of a substance that is produced by energy within it (e.g., radioactive material).
automated optical inspection
Automated optical inspection (AOI) is a technology used in manufacturing processes, particularly in electronics, to automatically inspect and detect defects or anomalies in products. AOI systems use...
automatic gain control
A method of producing an essentially constant output signal from an electronic circuit despite variations in the strength of the input signal.
automatic optical inspection
A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...
automatic power control circuit -> monitor current
In a laser diode, the photocurrent produced by a photodiode that detects the emission from the rear facet of the semiconductor chip. It can be used to provide feedback control of the forward current...
automatic profiling
In fiber optics, the use of a detector to study the range of refractive indices achieved at various wavelengths. This information is calculated electronically to establish the divergence between...
automatic recording spectrograph
A direct reading spectrograph having a photomultiplier assembly in place of a photographic plate. The output from the photomultiplier assembly is received by a microammeter or a pen recorder.
autopositive
Any photographic medium that, when chemically developed, produces an exact photographic reproduction of the original.
autoradiography
The photographic recording of the distribution and location of radioactive substances found in a specimen. The record formed is the autoradiograph.
autostigmatic microscope
A microscope to which a beamsplitter and illuminated reticle have been added to measure the radius of curvature of a spherical surface by locating both surface and center and calculating the distance...
aux
auxiliary
auxiliary telescope
A low-power telescope placed at the eyepiece of an optical system to increase overall magnification. Most often used to evaluate image quality.
AV
audiovisual
AVA
Automated Vision Association
avalanche photodiode
A device that utilizes avalanche multiplication of photocurrent by means of hole-electrons created by absorbed photons. When the device's reverse-bias voltage nears breakdown level, the hole-electron...
AVC
active vibration cancellation
AVD
axial vapor deposition

Photonics DictionaryA

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