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Glossary of laser terms


Frequently asked questions

Average output power: The total energy per pulse times the number of pulses per second. (Joules per second = W).
Beam delivery system: The use of optics, such as mirrors, lenses, and optical fibers, arranged in such a way that a laser beam can be precisely directed to a specific locations.
Beam diameter: The diameter of the portion of the laser beam that contains 86% of the total energy of the beam.
Beam divergence: The tendency of a laser beam to expand in diameter as it moves away from the source, measured in milliradians (mrad) at specified points.
Beam quality: Ratio between a real beam focus-spot diameter and the focus-spot diameter that would be produced by a theoretically perfect beam. Equivalently, it is the ratio of the far field divergence angles of the real beam and an ideal beam having the same waist diameter.
Brightness: A measure of the energy density achievable by a laser, directly related to the focussability of a particular wavelength of laser light.
Cavity: The laser resonator, or tube, in which the lasing process occurs.
Coherent radiation: Radiation that consists of wave trains travelling in phase with each other.
Collimate: Modifying the output of a laser to correct the natural divergence of the beam being produced.
Continuous wave (CW): A laser beam that is produced continuously rather than as a series of pulses.
Crystal: A solid material in which the atoms are arrayed in an orderly manner. Yttrium Aluminium Garnet (YAG) crystals are used as a laser source, for example.
Enhanced Pulsing: Electronic modulation of a laser beam to produce very high peak Power at the initial stage of the pulse.
Fibre: Optical fibres consist of a central glass core surrounded by a glass 'optical cladding'. The core has a higher refractive index than the cladding, causing light propagating in the core to be totally internally reflected at the core/clad interface. Thus, the light pulses down the fibre with hardly any attenuation.
Flashlamp: A tube filled with krypton or xenon used to stimulate emission in a solid-state laser.
Foaming: Surface modification by localised expansion of a material, usually a polymer. Used as a mechanism for marking.
Focal point: The point at which light rays refracted (or reflected) by a lens meet. The focal point of a focused laser beam is the point of highest energy concentration.
Gaussian: The bell-shaped curve that represents the normal distribution of a large number of possible events.
Ground state: The rest or neutral energy level of a lasing medium. A molecule returns to its ground state when discharged.
Hertz (Hz): Cycles per second used to express the repetition rate of a pulsed laser.
Joule (J): A measurement of energy per pulse in pulsed lasers. The rate at which energy is generated is a measure of output power, with one watt equal to a rate of one joule per second.
Laser rod: The solid material in which a lasing medium is embedded for the lasing process in a solid-state laser. Generally a crystal material.
Mode: A description of the cross sectional shape of the laser beam. See also TEM.
Monochromatic: Light that consists of only one wave-length. An industrial laser beam consists of a very narrow band of wavelengths around a central wavelength.
Optical pumping: The use of a flash-lamp, arc lamp, or other light source to excite the lasing medium.
Oscillator: Another word to describe a laser cavity, which is an electromagnetic oscillator.
Output power: The measurement of the energy per unit time produced by the laser, measured in watts (W).
Photon: A particle of light that has energy but no mass or charge. A photon has properties of both a particle and a wave.
Polarization: A means of restricting the vibrations of the electromagnetic field to a single plane. In a laser, this prevents optical loss and produces a higher-quality beam.
Population inversion: A state in which more atoms or molecules of a lasing medium are at a high energy level than at some lower energy level, so that photons can be released for the lasing process to occur.
Power density: Laser output per unit area, such as watts per square centimetre (W/cm 2).
Pulse: A single burst of energy from a laser.
Pulsewidth: Also known as pulse length, this is the time or duration of the pulse emitted by a pulsed laser, in seconds.
Pulsed laser: A laser that emits light in a series of pulses rather than continuously.
Q-switch: A device that acts as a shutter to move in and out of the beam path at regular intervals so that a large amount of energy is stored and then released in a burst of energy.
Repetition rate: The number of pulses per second produced by a pulsed laser.
Resonator: The laser cavity, lasing medium and rod, and the two reflecting mirrors. The mirrors reflect photons of light back and forth (i.e., cause them to resonate), and the laser beam is amplified.
Stability: The ability of a laser system to maintain a beam with constant out-put characteristics, such as power levels.
TEM: The transverse electromagnetic mode is a means of describing the cross sectional shape of a laser beam. Typical TEM modes for industrial lasers include a Gaussian-shaped beam energy distribution, a bimodal-shaped beam, and a ring-shaped distribution.
Wavelength: The length of the light wave, measured from crest to crest. The wavelength determines the colour of the light, and also has an impact on the way in which electromagnetic radiation will interact with materials.
Wallplug efficiency: The efficiency of a laser installation. Expressed in percentage terms of energy consumed versus laser energy output.

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