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. See Brewster Windows. λ = wavelength E = electric vector H = magnetic vector.

When more molecules (atoms, ions) in a laser are in a metastable state than in the ground state (a situation needed for sustaining a high rate of stimulated emissions), a “population inversion” is said to exist. Without a population inversion, there can be no lasing action.

The amount of radiant energy concentrated on a surface.

An accessory used to monitor laser beam power at the rear reflector, tune the beam for optimum power, or monitor power delivered to the work station.

A controlled change in the power level of a laser beam, either linearly, as up a ramp, across, and down again—or in several discrete steps. Useful for smooth completion of circular welds and for preventing fractures from rapid cooling.