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8,236 terms
Photonics Dictionary
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power density
In laser welding or heat treating, the instantaneous laser beam power per unit area. This parameter is key in determining the fusion zone profile (area of base metal melted) on a workpiece.
power efficiency
The ratio of emitted power to input power.
power flow equation
Optical fiber channel characterization scheme based on three assumptions; the discrete mode spectrum can be replaced by a continuum; the loss due to coupling between guided and radiation modes...
power modulation
Power modulation refers to the intentional variation of power levels in a signal, often in the context of electronic communication systems. This modulation technique is used to encode information...
power ratio
->
radiant power
The time rate of flow of radiant energy, expressed in watts (W), and carries the units of Joule per second (J/s). The prefix often is dropped and the term "power" used.
power scanning laws
Laws that predict the maximum power output as a function of tube diameter for a hydrogen cyanide laser of a given discharge length and cavity losses, all other parameters being optimized.
power spectrum equalization
A filtering method that restores a blurred image by setting its power spectrum equal to that of the original image.
power supply
Refers to the voltage and current necessary for the operation of circuit devices.
Poynting vector
In remote sensing technology, this represents the intensity of energy flow in the direction of wave propagation.
PP junction
A transition boundary between two regions having different properties in a P-type semiconducting material.
ppb
parts per billion
PPF
polarization-preserving fiber
PPFD
photosynthetic photon flux density
PPKTP
periodically poled potassium titanyl phosphate
PPLN
periodically poled lithium niobate
ppm
pulses per minute; parts per million
PPM
pulse position modulation
pps
pulses per second
PPSLT
periodically poled stoichiometric lithium tantalate
PR
power ratio; photoreflectance
Prandtl number
Ratio of the molecular diffusion coefficients of momentum in terms of heat; used in convection studies.
PRC
photorefractive crystal
precision aperture
An accurately produced hole of any size and shape that is used as a masking device in an optical system. Pinhole apertures of accurate diameters often are produced by laser beam penetration or by...
preform
A glass structure from which an optical fiber waveguide may be drawn.
prefusing
A step before fusion splicing that involves cleaning the fiber end with low-current electricity.
prelasing
When uncontrolled laser energy leaks from a laser cavity prematurely, it causes serious damage to optical components and significant downtime for repair.
Prentice's rule
A method of determining prism power at any point on a lens. Prism power equals the product of the dioptric power and the distance, in centimeters, from the optical center.
presbyopia
A state in which the human eye has very little or no power of accommodation. A common and normal condition in the eyes of those age 50 and older.
pressing
A blank having basic surface curves attained by forming heat-softened glass that is pressed in a mold.
pressure broadening
->
collision broadening
The broadening of spectral lines due to the collision of radiating particles with one another and the resulting interruption of the radiative process.
pressurization
Injecting a gas (usually nitrogen) with a very low moisture content into the body of an optical instrument to create a positive internal pressure. This prevents the entrance of moisture, which could...
PRF
pulse repetition frequency
PRI
pulse repetition interval
primary chromatic aberration
Also referred to as primary color, this is the classic chromatic aberration of a single element caused by the variation of index of refraction as a function of wavelength.
primary coating
In a waveguide, the material in intimate contact with the cladding surface, applied to preserve the integrity of that surface.
primary colors
A set of three colored lights which, when mixed, give the sensation of white light. The set used in color television, for example, is red, green, blue (RGB).
primary fluorescence
Fluorescence produced as a result of the intrinsic property of the material itself or the doping of the material with trace elements.
primary spectrum
The first-order spectrum formed by a diffraction grating.
principal axis
A straight line connecting the curvature centers of the refracting lens surfaces. In a mechanical sense, a line joining the centers of a lens as it is placed in a mount. The principal axis is the...
principal E-plane
The plane in which the axis of maximum radiation and the electric vector are contained.
principal focus
->
focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
principal plane
In a lens or lens system, that surface at which the projections of an entering and exiting ray intersect. Also known as the equivalent refracting surface, the principal plane is most often not...
principal point
The intersection of the principal plane and the optical axis of a lens.
principal point of focus
->
focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
principal ray
The ray of an oblique pencil beam that passes through the center of the pupils. It is the effective axis of the oblique beam. Also called the chief ray.
principal section
A plane passing through a crystal that has the optic axis of the crystal and the light ray under consideration.
principle of least time
->
Fermat's principle
The principle that a light ray extending from one point to another will, after any number of reflections and refractions, follow the path requiring the least transit time. This is also known as the...
printer
A photographic enlarger with a fixed negative plane and a fixed paper plane, often using a roll of paper that is advanced automatically between exposures. The lens is interchangeable to suit a range...
prism apex
The thin edge of a refracting prism; the line of intersection of two refracting surfaces of a prism.
prism base
The thick edge of a refracting prism.
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Photonics Dictionary
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