Laser

An acronym for light amplification by stimulated emission of radiation. A laser is a cavity, with mirrors at the ends, filled with material such as crystal, glass, liquid, gas or dye. A device which produces an intense beam of light with the unique properties of coherence, collimation and monochrome.

Lenses

A curved piece of optically transparent material which depending on its shape, is used to either converge or diverge light.

Longitudinal Mode

Determines the wavelength bandwidth produced by a given laser system controlled by the distance between the two mirrors of the laser cavity. Individual longitudinal modes are produced by standing waves within a laser cavity.

M2

M2 is a beam quality index that measures the difference between an actual beam and the Gaussian beam.

Mode

A term used to describe how the power of a laser beam is geometrically distributed across the cross section of the beam. Also used to describe the operating mode of a laser such as continuous or pulsed.

Modulation

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

Nd:YVO4 Laser

A solid-state laser of Neodymium: Yttrium Vanadium Oxide, similar to Nd:YAG but with the characteristics of higher gain and shorter upper state lifetime.

Optical Density

Protection factor provided by a filter (such as used in eyewear, viewing windows, etc.) at a specific wavelength. Each unit of OD represents a 10x increase in protection.

Output Power

The energy per second measured in watts emitted from the laser in the form of coherent light.

Polarization

Restriction of the vibrations of the electromagnetic field to a single plane, rather than the innumerable planes rotating about the vector axis. This prevents optical losses at interfaces between the lasing medium and optical elements. Various forms of polarization include random, linear (plane), vertical, horizontal, elliptical, and circular. Of two polarization components (so-called), S and P, the P component has zero losses at Brewster’s angle. ? = wavelength E = electric vector H = magnetic vector.

Prism

A transparent optical element having at least two polished plane faces inclined relative to each other, from which light is reflected or through which light is refracted.

Pumping

The process to raise atoms from lower level to upper level is called pumping. Q: The energy-storing efficiency of a laser resonator. The higher the "Q," the less energy loss.

Rrefraction Index

The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.

Q-Switch

A device that has the effect of a shutter moving rapidly in and out of the beam to "spoil" the resonator’s normal Q, keeping it low to prevent lasing action until a high level of energy is stored. Result: a giant pulse of power when normal Q is restored. It modulates the Q (Quality) of laser cavity to build population inversion first, then release the accumulated energy suddenly, in this way high energy pulses can be created. Q-switch devices are typically electro-optic or acousto-optic.

Solid State Laser

A laser in which the active medium is in solid state (usually not including semiconductor lasers).

Stability

The ability of a laser system to resist changes in its operating characteristics. Temperature, electrical, dimensional, and power stability are included.

TEM

Abbreviation for Transverse Electromagnetic Mode, the cross-sectional shape of the working laser beam. An infinite number of shapes can be produced, but only a relatively small number are needed for industrial applications. In general, "the higher the TEM, the coarser the focusing." Three index are used to indicate the TEM modes. TEMplq, p is the number of radial zero fields, l is the number of angular zero fields, q is the number of longitudinal fields.

TEM00

A Gaussian-curve mode that is the best collimated and produces the smallest spot of high power density for drilling, welding and cutting.

Threshold

During excitation of the laser medium, this is the point where lasing begins.

Transverse Mode

The geometry of the power distribution in a cross section of a laser beam.

Visible Radiation (light)

Electromagnetic radiation which can be detected by the human eye. It is commonly used to describe wavelengths which lie in the range between 400 nm and 700-780nm. The peak of the human spectral response is about 555nm.

Wavelength

The length of the light wave, usually measured from crest to crest, which determines its color. Common units of measurement are the micrometer (micron), the nanometer, and (earlier) the Angstrom unit.

Wavefront

In considering a field of electromagnetic energy emanating from a source, the wavefront is a surface connecting all field points that are equidistant from the source.

Waveplate

An optical element having two principal axes, slow and fast, that resolve an incident polarized beam into two mutually perpendicular polarized beams. The emerging beam recombines to form a particular single polarized beam. Retardation plates produce full-, half- and quarter- wave retardations.