G

Gain

Another term for amplification.

Gas discharge laser

A laser containing a gaseous lasing medium in a glass tube in which a constant flow of gas replenishes the molecules depleted by the electricity or chemicals used for excitation.

Gas laser

A type of laser in which the laser action takes place in a gas medium.

Gated pulse

A discontinuous burst of laser light, made by timing (gating) a continuous wave output, usually in fractions of a second.

Gaussian beam

A beam of light that has most of its energy in the center. The irradiance of the beam is symmetric about the beam axis and varies with radial distance r from the axis as

where r₁ is the radial extent of the beam where the irradiance has dropped to 1/e² of its value on the beam axis, I₀.

Gaussian curve

Statistical curve showing a peak with normal, even distribution on either side. May either be a sharp peak with steep sides or a blunt peak with shallower sides. Used to show power distribution in a beam. The concept is important in controlling the geometry of the laser impact.

Ground state

Lowest energy level of an atom.