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Apparent Power/Brightness The intensity of light as it appears to the human eye. The eye is most sensitive to wavelengths (colors) in the center of the visible spectrum. Hence, green light will appear brighter tthan any other color of light of the same power or magnitude. As another example, a 633nm red Helium-Neon laser appears approximately eight times brighter than a red 670nm diode laser of the same output power. See the diagram to the right for relative eye sensitivity versus wavelength.
Beam Diameter The distance between diametrically opposed points in the cross section of a circular beam where the intensity is reduced by a factor of 1/e (0.368) of the peak level (for safety standards). The value is normally chosen at 1/e2 (0.135) of the peak level for manufacturing specifications.
Beam Divergence Angle of beam spread measured in radians or milliradians. For small angles where the cord is approximately equal to the arc, the beam divergence can be closely approximated by the ratio of the cord length (beam diameter) divided by the distance (range) from the laser aperture.
Coherence A term describing light as waves which are in phase in both time and space. Monochrome and low divergence are two properties of coherent light.
CW The output of a laser that is operated in a continuous (pulse duration >0.25s) rather than a pulsed mode
Failsafe Interlock An interlock where the failure of a single mechanical or electrical component of the interlock will cause the system to go into, or remain in, a safe mode.
Frequency The number of light waves passing a fixed point in a given unit of time, or the number of complete vibrations in that period of time.
Heat Sink A substance or device used to dissipate or absorb unwanted heat energy.
KTP Potassium Titanyl Phosphate. A crystal used to change the wavelength of an Nd:YVO4 laser from 1064 nm (infrared) to 532 nm (green).
Laser An acronym for light amplification by stimulated emission of radiation. A laser is a cavity, with mirrors at the ends, filled with material such as crystal, glass, liquid, gas or dye. A device which produces an intense beam of light with the unique properties of coherence, collimation and monochrome.
Longitudinal or Axial Mode Determines the wavelength bandwidth produced by a given laser system controlled by the distance between the two mirrors of the laser cavity. Individual longitudinal modes are produced by standing waves within a laser cavity.
M2 A measurement of laser quality. M2 is a single number that describes the beam's quality in comparison to a theoretically perfect Gaussian beam, and that can be used to predict a real, non-Gaussian beam's behavior in an optics system.
Mode A term used to describe how the power of a laser beam is geometrically distributed across the cross section of the beam. Also used to describe the operating mode of a laser such as continuous or pulsed.
Modulation The ability to superimpose an external signal on the output beam of the laser as a control.
Nd:YVO4 Laser Neodymium:Yttrium Aluminum Garnet. A synthetic crystal used as a laser medium to produce 1064 nm light.
Output Power The energy per second measured in watts emitted from the laser in the form of coherent light.
Polarization Restriction of the vibrations of the electromagnetic field to a single plane, rather than the innumerable planes rotating about the vector axis. Various forms of polarization include random, linear, vertical, horizontal, elliptical, and circular.
Protective Housing A protective housing is a device designed to prevent access to radiant power or energy.
Pumping Addition of energy (thermal, electrical, or optical) into the atomic population of the laser medium, necessary to produce a state of population inversion.
Stability The ability of a laser system to resist changes in its operating characteristics. Temperature, electrical, dimensional, and power stability are included.
TEM00 The lowest order mode possible with a bell-shaped (Gaussian) distribution of light across the laser beam.
Visible Radiation (light) Electromagnetic radiation which can be detected by the human eye. It is commonly used to describe wavelengths which lie in the range between 400 nm and 700-780 nm. The peak of the human spectral response is about 555 nm.
Wavelength The length of the light wave, usually measured from crest to crest, which determines its color. Common units of measurement are the micrometer (micron), the nanometer, and (earlier) the Angstrom unit.
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