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]

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

The working range of the beam, a function of wavelength, diameter of the unfocused beam, and focal length of the lens. To achieve a small diameter spot size, and thus a high power density, a short depth of field must be accepted.

A change in the spatial distribution of the laser beam by virtue of its reflective interaction in many directions by a non-specular (non-mirror like) surface or other reflecting medium.