SCANNING LASER A laser having a time-varying direction, origin or pattern of
propagation with respect to a stationary frame of reference.
SCINTILLATION This term is used to describe the rapid changes in irradiance
levels in a cross section of a laser beam produced by atmospheric turbulence.
SECURED ENCLOSURE An enclosure. to which casual access is impeded by an appropriate
means (e.g., door secured by lock, magnetically or electrically operated, latch,
or by screws).
SEMICONDUCTOR LASER A type of laser which produces its output from semiconductor
materials such as GaAs.
SERVICE Performance of adjustments, repair or procedures on a non routine basis,
required to return the equipment to its intended state.
SOLID ANGLE The ratio of the area on the surface of a sphere to the square
of the radius of that sphere. It is expressed in steradians (sr).
SOURCE The term source means either laser or laser-illuminated reflecting surface,
i.e., source of light.
SPECTRAL RESPONSE The response of a device or material to monochromatic light
as a function of wavelength.
SPECULAR REFLECTION A mirror-like reflection.
SPONTANEOUS EMISSION Decay of an excited atom to a ground or resting state
by the random emission of one photon. The decay is determined by the lifetime
of the excited state.
SPOT SIZE The mathematical measurement of the diameter of the laser beam.
STABILITY The ability of a laser system to resist changes in its operating
characteristics. Temperature, electrical, dimensional and power stability are
STERADIAN (sr) The unit of measure for a solid angle.
STIMULATED EMISSION When an atom, ion or molecule capable of lasing is excited
to a higher energy level by an electric charge or other means, it will spontaneously
emit a photon as it decays to the normal ground state. If that photon passes near
another atom of the same frequency, the second atom will be stimulated to emit
SUPERPULSE Electronic pulsing of the laser driving circuit to produce a pulsed
output (250-1000 times per second), with peak powers per pulse higher than the
maximum attainable in the continuous wave mode. Average powers of superpulse are
always lower than the maximum in continuous wave. Process often used on CO(2)