Lasers Glossary 2
Rrefraction Index The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.

A 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.


Solid State Laser

A laser in which the active medium is in solid state (usually not including semiconductor lasers).



The ability of a laser system to resist changes in its operating characteristics. Temperature, electrical, dimensional, and power stability are included.


Abbreviation 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 fields.



A Gaussian-curve mode that is the best collimated and produces the smallest spot of high power density for drilling, welding and cutting.


During excitation of the laser medium, this is the point where lasing begins.


Transverse Mode

The geometry of the power distribution in a cross section of a 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 700-780nm. The peak of the human spectral response is about 555nm.


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.


In 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.


An 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- wave retardations.