ratio of the velocity of light in a vacuum to the velocity
of light in a refractive material for a given wavelength.
device that has the effect of a shutter moving rapidly
in and out of the beam to "spoil" the resonator¡¯s
normal Q, keeping it low to prevent lasing action until
a high level of energy is stored. Result: a giant pulse
of power when normal Q is restored. It modulates the
Q (Quality) of laser cavity to build population inversion
first, then release the accumulated energy suddenly,
in this way high energy pulses can be created. Q-switch
devices are typically electro-optic or acousto-optic.
laser in which the active medium is in solid state (usually
not including semiconductor lasers).
ability of a laser system to resist changes in its operating
characteristics. Temperature, electrical, dimensional,
and power stability are included.
for Transverse Electromagnetic Mode, the cross-sectional
shape of the working laser beam. An infinite number
of shapes can be produced, but only a relatively small
number are needed for industrial applications. In general,
"the higher the TEM, the coarser the focusing."
Three index are used to indicate the TEM modes. TEMplq,
p is the number of radial zero fields, l is the number
of angular zero fields, q is the number of longitudinal
Gaussian-curve mode that is the best collimated and
produces the smallest spot of high power density for
drilling, welding and cutting.
excitation of the laser medium, this is the point where
geometry of the power distribution in a cross section
of a laser beam.
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 700-780nm. The peak of
the human spectral response is about 555nm.
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.
considering a field of electromagnetic energy emanating
from a source, the wavefront is a surface connecting
all field points that are equidistant from the source.
optical element having two principal axes, slow and
fast, that resolve an incident polarized beam into two
mutually perpendicular polarized beams. The emerging
beam recombines to form a particular single polarized
beam. Retardation plates produce full-, half- and quarter-