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Photonics Dictionary: Q

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Q
The figure of merit of a resonator, defined as (2p) x (average energy stored in the resonator)/(energy dissipated per cycle). The higher the reflectivity of the surfaces of an optical resonator, the...
Q
quality factor (laser resonator)
Q machine
Device in which contact ionization of atomic particles and thermionic electron emission are used to produce magnetically confined plasma that is greatly ionized.
Q-spoiler -> laser Q-spoiler
A fast-action shutter inserted between one end of a laser rod and the end mirror; when inserted to prevent emission and then quickly removed, it causes the laser to discharge suddenly with great...
Q-switch
A device used to rapidly change the Q of an optical resonator. It is used in the optical resonator of a laser to prevent lasing action until a high level of inversion (optical gain and energy...
q-switched operation
Q-switched operation, or q-switching, is a technique used in lasers to produce short and intense pulses of light. The term "Q" in q-switching stands for "quality factor," which is a measure of the...
Q-switched pulse
A laser output that occurs when the cavity resonator Q is first kept very low, using rotating mirrors or saturable absorbers, so that the population inversion achieved is greater than usual. A high...
QA
quality assurance
QAPD
quadrant avalanche photodetector
QC
quality control
QCL
quantum cascade laser
QCW
quasi-continuous wave
QD
quantum dot
QE
quantum efficiency
QED
quantum electrodynamics
qPCR
quantitative polymerase chain reaction system
QPM
quaternary pulse modulation
QPSK
quadrature phase-shift keying
QSR
quick strike reconnaissance
quadratic phase terms
Conceptual formulas that characterize both the transmittance functions of lenses and propagation in the Fresnel zone.
quadratic profile -> parabolic profile
The condition in which the index of refraction in an optical fiber varies as a parabolic function of the radius.
quadrature
Denoting a phase shift of 90°.
quadrupole lens
A device used in electron microscopes and particle accelerators to focus electron beams by the arrangement of four electrodes of alternating signs around the electron beam.
quality area
The region of the cathode-ray tube phosphor screen restricted by the tube and instrument specification.
quality, surface -> surface quality
The specification of allowable flaws in a surface by comparison to reference standards of quality. Two graded sets of surface quality standards are employed. The first denotes defects of a long...
quantitative phase imaging
Quantitative phase imaging (QPI) is an advanced imaging technique used in microscopy to measure and analyze the optical phase information of transparent specimens. Unlike traditional brightfield...
quantizer
A device with a limited number of possible output values (sometimes able to be selected) that can translate an incoming signal into these values or codes for outputting. See pulse code modulation. In...
quantum
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of...
quantum cascade laser
A quantum cascade laser (QCL) is a type of semiconductor laser that operates based on the principles of quantum mechanics. It is a versatile and powerful device used for emitting coherent light in...
quantum confinement
Quantum confinement refers to the phenomenon in quantum mechanics where the motion of charge carriers, such as electrons or holes, is restricted to a region of space that is smaller than their...
quantum detector
A photodetector in which an electrical charge is produced when incident photons change electrons within the detecting material from nonconducting to conducting states. See photoconductive detector;...
quantum dot light-emitting diode
Quantum dot light-emitting diode (QLED) is a display technology that utilizes quantum dots, which are semiconductor nanocrystals, to produce vibrant and high-quality images. QLED displays are...
quantum dots
A quantum dot is a nanoscale semiconductor structure, typically composed of materials like cadmium selenide or indium arsenide, that exhibits unique quantum mechanical properties. These properties...
quantum efficiency
Quantum efficiency (QE) is a measure of the effectiveness with which a device or system, typically in the context of photonics or electronics, converts incoming photons (light) into a useful output...
quantum entanglement
Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become correlated to such an extent that the state of one particle instantly influences the state of the...
quantum key distribution
Quantum key distribution (QKD) is a method of secure communication that utilizes principles from quantum mechanics to establish a shared secret key between two parties, typically referred to as Alice...
quantum mechanics
The science of all complex elements of atomic and molecular spectra, and the interaction of radiation and matter.
quantum noise
Noise generated within an optical communications system link that has both internal (dark current) and external (background noise, or noise in signal) components.
quantum optics
The area of optics in which quantum theory is used to describe light in discrete units or "quanta" of energy known as photons. First observed by Albert Einstein's photoelectric effect, this particle...
quantum photodetector -> photodetector
A photodetector, also known as a photosensor or photodiode, is a device that detects and converts light into an electrical signal. Photodetectors are widely used in various applications, ranging from...
quantum sensing
Quantum sensing refers to a class of sensing technologies that leverage principles from quantum mechanics to enhance the precision and sensitivity of measurements. Traditional sensors operate based...
quantum well
A quantum well is a structure in quantum mechanics that confines particles, such as electrons or holes, in one spatial dimension. This confinement leads to quantized energy levels, creating a...
quantum wire
A narrow channel created by cleaving a crystal made of alternating layers of gallium arsenide and aluminum gallium arsenide, and adding additional layers on the cleaved end face, at right angles to...
quantum-ehanced metrology
Quantum-enhanced metrology refers to the use of quantum mechanics principles and techniques to enhance the precision and sensitivity of measurements in metrology—the science of measurement....
quantum-limited operation
Operation in which the minimum detectable signal is set because of variations in the average signal current; e.g., quantum noise.
quarter-wave plate
A plate made of a double-refracting crystal having such a density that a phase difference of one-quarter cycle is formed between the ordinary and extraordinary elements of light passing through.
quartz
See crystal quartz; fused quartz.
quartz light source
A lamp with a quartz envelope that transmits radiation generally rich in the ultraviolet.
quartz plate
A crystalline-quartz plate designed according to specifications but having its two major faces parallel.
quartz spectrograph
A spectrograph used to detect radiation in the range of the ultraviolet in the electromagnetic spectrum. It is made up of quartz because that material, unlike regular glass, is not opaque to the...

Photonics DictionaryQ

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