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.

A curved piece of optically transparent material which depending on its shape, is used to either converge or diverge light.

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 is a beam quality index that measures the difference between an actual beam and the Gaussian beam.

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.

The ability to superimpose an external signal on the output beam of the laser as a control.

A solid-state laser of Neodymium: Yttrium Vanadium Oxide, similar to Nd:YAG but with the characteristics of higher gain and shorter upper state lifetime.

Protection factor provided by a filter (such as used in eyewear, viewing windows, etc.) at a specific wavelength. Each unit of OD represents a 10x increase in protection.

The energy per second measured in watts emitted from the laser in the form of coherent light.

Restriction of the vibrations of the electromagnetic field to a single plane, rather than the innumerable planes rotating about the vector axis. This prevents optical losses at interfaces between the lasing medium and optical elements. Various forms of polarization include random, linear (plane), vertical, horizontal, elliptical, and circular. Of two polarization components (so-called), S and P, the P component has zero losses at Brewster’s angle. λ = wavelength E = electric vector H = magnetic vector.

A transparent optical element having at least two polished plane faces inclined relative to each other, from which light is reflected or through which light is refracted.

The process to raise atoms from lower level to upper level is called pumping. 
Q: The energy-storing efficiency of a laser resonator. The higher the "Q," the less energy loss.