Laser Glossary

1 Micron
A unit of measure for the core in an optical fiber. 10-6 or one thousandth of a millimeter

To transform radiant energy into a different form, usually with a resultant rise in temperature

The ability of a medium to absorb radiation depending on temperature and wavelength; expressed as the negative common logarithm of the transmittance.

The growth of the radiation field in the laser resonator cavity as the light wave bounces back and forth between the cavity mirrors. It is amp stimulated emission on each pass through it.

AR coatings
Anti-reflection coating, used on the backs of laser output mirrors to suppress unwanted multiple reflections which reduce power.

Average output power
The total energy per pulse times the number of pulses per second. (Joules per second = W).

Axial-flow laser
A gas laser in which the lasing gas mixture is directed through the laser tube in an axial direction. Depending on the design, these can be either the popular fast-axial flow or the less popular slow-axial flow.

Axis, optical axis
The optical center-line for a lens system; the line passing through the centers of curvature of the optical surfaces of a lens.

Beam bender
Hardware assembly or optical device, such as a mirror, capable of changing laser beam direction; used to re-point the beam and in “folded” compact delivery system.

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 location.

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 a diameter as it loves away from the source. It is measured in mill radians (mrads) at specified points.

Beam expander
Optical device increasing beam diameter and reducing divergence. Result: A smaller focused spot for more distance between lens and part.

Beam quality
Ration 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 fiend divergence angles of the real beam and an ideal beam having the same waste diameter. Beam quality is often expressed by M2 or the K. (1/m2)

Beam splitting
the use of an optical deice to split the laser beam into multiple beams, so that more than one location on a work piece can be processed at one time, although at lower power.

The visual sensation of the luminous power of a light beam, as opposed to scientifically measured power of the beam.

Carbon dioxide (CO²) laser
A gas laser that uses a mixture of carbon dioxide, nitrogen (N2), and helium (He) to produce a continuous output of laser light as a wavelength of 10.6 micrometers.

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

The laser resonator, or tube, in which the lasing process occurs.

Circular polarization
Optimal polarization for CO² laser cutting. The laser beam’s two perpendicular components are out of phase, but have the same amplitude providing optimal cutting for CO² laser.

Coherent radiation
Radiation that consists of wave trains traveling in phase with each other.

Collimated light
Divergent light rays rendered parallel by means of a lens or other device, allowing a sharp image of the object to be focused at the focal plane of the lens.

The process by which divergent rays (white, or natural, light) are converted into a parallel rays (coherent light).

Continuous wave (CW)
A laser beam that is product continuously rather than as a series of pulses.

The bending of lights rays toward each other, as by a positive (convex) lens.

A solid material in which the atoms are arrayed in an orderly manner. YAG crystals are used as a laser source, for example.

Depth of field
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.

Diffusion-cooled laser
Typically a CO2 laser design that utilizes gas cooling by diffusion to cool surfaces as opposed to flow through a heat exchanger. This design is simpler and more compact than axis or transverse flow lasers.

Diode laser
Sometimes called semiconductor lasers, the active element is a p-ri semiconductor junction. When current flows across the junction, intense light is emitted from the edge of the chip in the plane of this junction. The majority of the diode lasers have output in the 630 to 1550 nanometer portion of the spectrum.

The angle at which the laser beam spreads in the far field; bending the rays away from each other, as by a concave lens or convex mirror.

Slag or hardened metal material, usually found on the bottom of certain types of laser cuts, such as, when cut with an improper or insufficient nozzle or assist gas flow.

Duty cycle
The length of time the laser beam is actually cutting, drilling, welding or heat-treating, as compared to the entire work cycle time.

Edge Thickness
It is the thickness of the lens or mirror, at its circumference. Determines pressure ranges ratings for a specific optic, and mounting configuration.

Enhanced pulsing
Is an electronic modulation of a laser beam to produce very high peak power at the initial stage of a pulse.

Excimer laser
A family of pulse lasers operating in the ultraviolet region of the spectrum from 193-351 nanometers.

A measure of the total radiant energy incident on the surface per unit area, radiant exposure.

Fiber Laser
A laser in which the active gain medium is an optical fiber doped with rare-earth elements and an applicable range of 1 micron.

Fiber Lens (optics)
Made of Fused Silica (glass) that is ground into specific diameter, edge thickness and focal length with a low absorption coating that is applicable for all 1 micron range application of 1030-1080 nm range.

Fiber Window
A piece of glass (fused Silica) that protects the lens in the laser head. AKA shield, screen, protective glass.

Flash lamp
A tube filled with krypton or xenon used to product stimulated emission in a solid-state laser.

Focal length
The focal length of a lens refers to the distance from the center of midpoint of the lens to the focal point, where the spot size is the smallest.

Focal point
The point at which light rays refracted by a lens meet. The focal point on a focused laser beam is the point of highest energy concentration.

Focus: Noun
The point where rays of light meet which have been converged by a lens, giving rise to a verb: To adjust focal length for the clearest image.

Gas discharge laser
A laser containing a gaseous laser medium in a glass tube in which a constant flow of gas replenishes the molecules depleted by the electricity of chemicals used for excitation. The discharge gas can be filtered and 90% recycled for economy.

Gas jet assist
An assisting coaxial gas, such as oxygen, argon, or nitrogen, which may be used to achieve very high power levels for cutting certain metals.

Heat-Affected Zone, or the area where laser beam and metal (or other) surface are in contact.

Heat sink
A substance or device used to dissipate or absorb unwanted heat, as from a manufacturing process (or, with lasers, from reflected rays).

Helium-neon laser (HeNe)
Laser in which the active medium is a mixture of helium and neon, which is in the visible range. Used widely in the industry for alignment, recording, printing and measuring. It is also valuable as a pointer or aligner of invisible CO2 laser light.

Hertz (Hz)
Cycles per second used to measure the repetition rate of a laser pulse.

The magnitude of radiant energy (light) per unit, such as time or reflecting surface.

Internal mirror
Cavity optics or mirrors for internal use in laser oscillators also called folding mirrors.

Joule (J)
A measurement of energy per pulse in pulsed lasers. The rate, at which, energy is generated in a measure of output power; with one watt equal to a rate of one joule per second.

The physical path of the cut, where the material is removed.


Laser hardening
Laser beam traversal of metal to harden quenching process producing the maximum hardness.

Laser oscillation
The buildup of the coherent wave between laser cavity end mirrors. In CW mode, the wave bounding back and forth between mirrors transmits a fraction of its energy on each trip, in pulsed operation, emission happens instantaneously.

Laser rod
The solid material in rich a lasing medium is embedded for the lasing process in a solid-state laser. Generally, a crystal material.

An acronym of Light Amplification by Stimulated Emission of Radiation. The laser cavity has mirrors at the ends and is filled with lasable material such as crystal, glass, liquid, gas or dye. These materials must have atoms, ions, or molecules capable of being excited to a metastable state of light, electric discharge, or other stimulus. The transition from this metastable state back to the normal ground state is accompanied by the emission of photons which form a coherent beam.

Lens Protector
A piece of glass with a diameter and edge thickness that is specified by the OEM and protects the fiber laser optics.

Meniscus lens
This lens has one side convex, the other concave. It enables a smaller beam diameter and spot size creating more power in a smaller area.

A description of the cross sectional shape of the laser beam.

The ability to superimpose an external signal on the output beam of the laser as a control.

A light that consists of only one wavelength. An industrial laser beam consists of a very narrow band of wavelengths around a central wavelength.

90º Phase Retarder
Usually installed as the last mirror in the beam delivery system. These mirrors have a special reflective coating which ensures that the delivered beam is circularly polarized, in order to eliminate the slightly ragged, uneven cut associated with laser cutting.

Nd: YAG laser
A solid-state laser that uses a crystal of yttrium aluminum garnet (YAG) doped with neodymium (Nd) as the lasing medium.

Optical pumping
The use of a flash lamp arc lamp or other light source to excite the lasing medium.

Another word to describe a laser cavity, which is electromagnetic oscillator.

Output Coupler
The resonator mirror which transmits light: the one at the opposite end is totally reflective.

Output power
The measurement of the energy per unit time produced by the laser, measured in watts.

Oxygen Assist
In certain cutting operations, coaxial oxygen initiates an exothermic reaction to enhance the cutting rate for thick metals: in other words, oxygen actually does the cutting, with the reaction being maintained by the laser beam.

A particle of light that has energy but no mass or charge. A photon has properties of both a particle and a wave.

Plano Convex
Has one flat surface and on convex surface (flat surface faces cutting surface). This provides a greater width of cut for general purpose cutting applications.

In laser welding, a metal vapor that forms above the spot where the beam reacts with the metal.

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. Polarized light consists of two perpendicular linear polarized components. Polarized light will affect cutting dynamics, since the beam had different characteristics in the x and y cutting axis, depending on the phase and amplitude of each component.

Popular inversion
A state in which more atoms or molecules of a lasing medium are at a high energy level than some lower energy levels, so that photons can be released for the lasing process to occur.

Power density
Laser output per unit area, such as watts per square centimeter (W/cm2)

Power meter
An accessory used to monitor laser beam power at the rear reflector, tune the beam for optimum power, or monitor power delivered to the work station.

Power ramping
A controlled change in the power level of a laser beam, either linearly, as up a ramp, across and down again or in several discrete steps. Useful for smooth completion of circular welds and for preventing fractures from rapid cooling.

Pulse energy
The power of a single, brief emission from a laser programmed for pulsed behavior rather than continuous operation. Pulse energy can be several times greater than CW emission.

A single burst of energy from a laser.

Pulsed laser
A laser that emits light in a series of pulses rather than continuously.

Pulse width
Also known as pulse length, this is the time or duration of the pulse emitted by a pulsed laser, in seconds.

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. Q-switching is often provided as an option on continuous wave lasers.

Radiant energy
Energy traveling as wave motion: specifically, the energy of electromagnetic waves (light, x-rays, radio, gamma rays).

The return of radiant energy (incident light) by a surface, with no change in wavelength.

The change in direction of propagation of any wave, such as, an electromagnetic wave, when it passes from one medium to another in which the wave velocity is different. Simply put the bending of incident rays as they pass from one medium to another, such as air to water.

Repetition rate
The number of pulses per second produced by a pulsed laser.

the laser cavity, lasing medium and rod, and the two reflecting mirrors. The mirrors reflect protons of light back and forth (i.e. cause them to resonate), and the laser beam is amplified.

Slab laser
A solid-state laser concept in which the beam is amplified through a series of reflections along the walls of the cavity to produce high output powers in a compact laser design.

Solid-state laser
A laser that uses a glass or crystal as a host to an impurity such as neodymium, which produces the lasing action.

The side of microns, of the focal point of a lens, determined by beam divergence, lens imperfections or spherical aberrations.

The ability of a laser system to maintain a beam with constant output characteristics.