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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