Calorimeter

An instrument which measures the heat generated by absorption of the laser beam—another way to measure laser power.

Cathode

The element providing the electrons for the electrical discharge used to excite the lasing medium.

CO2 Laser

A laser largely used in industry in which the primary lasing medium is carbon dioxide.

Coaxial Gas

Most laser welding is done with a shield of inert gas flowing over the work surface to prevent plasma oxidation and absorption, to blow away debris, and to control heat reaction. The gas jet has the same axis as the beam so the two can be aimed together.

Continuous Wave Laser

A laser operating at a continuous output for a period of time equal to or greater than (≥) 0.25 seconds.  Continuous Wave is abbreviated CW.

Controlled (Laser) Area

Any area where the occupancy or activity of those within its confines is subject to access control and/or supervision for the purpose of protection from laser radiation hazards.

Critical Frequency

A pulse repetition frequency above which the laser is considered to operate as a CW laser. [box]Example:  For a short (0.25 s to 10 s) unintentional exposure to nanoseconds (or longer) pulses, the Critical Frequency is 55 kilohertz (kHz) for wavelengths between 400 nanometers (nm) to 1050 nm and 20 kHz for wavelengths between 1050 nm to 1400 nm.[/box]

Current Saturation

Maximum flow of electric force in a conductor; in a laser, the point at which further electrical charge will not increase lasing action.

CW

Abbreviation for Continuous Wave. The continuous-emission mode of a laser, as opposed to pulsed operation.