Laser Terms Glossary

Laser Terms Glossary

This is a work in progress. Check back often. The modified date can be found at the end of the document.

A

Ablation

The removal of material by melting, evaporation, or vaporization.  Also see Vaporization. Or, more precisely,  the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave laser beam if the laser intensity is high enough.

Absorbance

The ability of a material to absorb radiant energy. It is expressed as a negative common logarithm of transmittance.

Acrylic

A rigid thermoplastic sign material available in transparent, translucent and opaque appearances. Acrylic sheet can be clear or produced in a variety of color tones. Acrylic that is manufactured by pouring a molten compound into a thin compartment and curing it under heat and pressure is said to be CELL CAST. Acrylic manufactured by casting a liquid compound between moving stainless steel plates that exert heat and pressure is sold to be CONTINUOUS CAST.

Aluminum

A soft, silver colored metal commonly used as an engraving material and for trophy plates and components. ANODIZED ALUMINUM has been electroplated with an aluminum oxide coating which gives it a hard, durable surface. It is available in a variety of colors and is suitable for exterior use. LACQUERED ALUMINUM has been finished on one side and has had a clear of colored coating applied to it. It is commonly used for engraved trophy and plaque plates.

Anode

An electrical element in laser excitation which attracts electrons from a cathode. An anode can be cooled directly by water or by radiation.

Assist Gas

Laser cutting is accomplished by blowing molten metal through the kerf. Oxygen is most commonly used when cutting ferrous metals. Inert gases can be used to produce oxide-free cut edges. Cutting non-metals is usually accomplished with compressed air. See also Gas Jet.

B

Beam Diameter

The distance between diametrically opposed points in the cross section of a circular beam where the intensity is reduced by a factor of 1/e (0.368) of the peak level (for safety standards). The value is normally chosen at 1/e2 (0.135) of the peak level for manufacturing specifications. Beam diameter is NOT the same as spot size.

Beam Divergence

The angle of beam spread measured in radians or milliradians (1 milliradian = 3.4 minutes-of-arc or approximately 1 mil). For small angles where the cord is approximately equal to the arc, the beam divergence can be closely approximated by the ratio of the cord length (beam diameter) divided by the distance (range) from the laser aperture.

Beam Waist

The beam waist (or beam focus) of a laser beam is the location along the propagation direction where the beam radius has a minimum. The waist radius is the beam radius at this location. A small beam waist (more precisely, a beam waist with small waist radius) can be obtained by focusing a laser beam with a lens which has a high numerical aperture, and making sure that the lens aperture is largely filled by the input beam. 
For non-circular beams, the position of the beam waist can be different for different transverse directions. This phenomenon is called astigmatism, and it may be generated or removed e.g. by using cylindrical optics.

Brewster Window

The transmissive end (or both ends) of the laser tube, made of transparent optical material and set at Brewster’s angle in gas lasers to achieve zero reflective loss of vertically polarized light. Non-standard on industrial lasers, but a must if polarization is desired.  See also Brewster's Angle.

C

CAD

Stands for Computer Aided Design. CAD software is the software that you use to make drawings of parts. CAM stands for Computer Aided Manufacturing. CAM software is used to make tool paths. Often CAD and CAM software are included in the same software package for convenience.

Ceramics

Ceramics are hard, high melting point materials, produced by the reaction of metals with elements such as oxygen, nitrogen, and carbon. Common industrial ceramics include alumina (Al2O3), titanium carbide (TiC), titanium nitride (TiN), and tungsten carbide (WC).

CNC

This is an acronym for Computer Numerical Control. In basic terms, a CNC machine has a computer that is controlling the machine's motion. For lasers, CNC is used to control motion tables or for positioning the workpiece beneath the focused laser beam. Also see G-Code.

CO2 Laser

A widely used laser in which the primary lasing medium is carbon dioxide gas. The output wavelength is 10.6 micrometers in the far infrared spectrum. It can be operated in either continuous wave (CW) or pulsed. Beam transmission is via mirrors. Power can be up to 40,000 watts for lasers that are routinely used to cut metals, polymers, wood-based products, and ceramics.

Collimation

Ability of the laser beam to not spread significantly (low divergence) with distance.

Collimator

Optical device consisting of two lenses separated by the sum of their focal length. It is used to provide desired beam diameter to meet specific beam delivery requirements.

Crystal

A solid with a regular array of atoms. Sapphire (Ruby Laser) and YAG (Nd:YAG laser) are two crystalline materials used as laser sources.

Cut Initiation

Cut Initiation or Piercing is carefully controlled hole drilling using the laser in its pulsed mode and using air or oxygen as the drilling assist gas.

Cut Quality

A CO2 laser will produce a cut quality similar to a good quality milled edge for mild steels.

Cut Termination

Meeting or crossing a previously cut line usually completes the cut. In the case of all but the thinnest sections, the final millimeter or so of the cut will have a discontinuity of quality. This feature is a result of a change in the material removal mechanism as the top leading edge of the cut zone finishes cutting before the trailing lower edge.

Cut Width

The width of the laser cut in a material. Typically, a cut width will be between 0.1 and 0.4 mm (0.004” - 0.016”). The cut width is dependent upon the properties of the material being cut, the workpiece thickness, the lens focal length, and finally, the type of cutting gas used in the laser. Also see Kerf.

CW

An abbreviation for continuous wave, the continuous-emission mode of a laser as opposed to pulsed operation. See CO2 Laser and Pulsed Laser.

D

Depth Of Field

The working range of the focused beam. It is determined as a function of wavelength, diameter of the unfocused beam, and the focal length of the lens. A shorter focal length produces a smaller depth of the field.

Divergence

The angle at which the laser beam spreads in the far field; the bending of rays away from each other, usually accomplished by a concave lens or convex mirror. The light emitted by a laser is confined to a rather narrow cone. But, when the beam propagates outward, it slowly diverges or fans out. For an electromagnetic beam, beam divergence is the angular measure of the increase in the radius or diameter with distance from the optical aperture as the beam emerges. 


The divergence of a laser beam can be calculated if the beam diameter d1 and d2 at two separate distances are known. Let z1and z2 are the distances along the laser axis, from the end of the laser to points “1” and “2”. Usually, divergence angle is taken as the full angle of opening of the beam. Then, 


Half of the divergence angle can be calculated as


where w1 and w2 are the radii of the beam at z1 and z2.

Like all electromagnetic beams, lasers are subject to divergence, which is measured in milliradians (mrad) or degrees. For many applications, a lower-divergence beam is preferable.

Drift

All undesirable variations in laser output (either amplitude or frequency).

DWG File

An AutoCAD Drawing file. The official specification for this file format is proprietary to AutoDesk Corporation, which makes it difficult for third party vendors to be compatible with it.

DXF File

Drawing Interchange Format (DXF) files or Drawing eXchange Format. Originally developed by AutoDesk to ease the transferring of files between AutoCAD and other software systems, DXF has become a de facto industry standard. Most CAD, drawing, mapping and GIS software packages have some ability to import DXF files.

E

Edge Factor

Laser cut parts exhibit little no edge factor, roll-off, or edge deformation.

Edge Quality

The condition of the cut edge. High edge quality is strongly promoted by good control of the laser beam and by a stable motion system.

Embedded Laser

A laser with an assigned class number higher than the inherent capability of the laser system in which it is incorporated, where the system's lower classification is appropriate to the engineering features limiting accessible emission. Also see Enclosed Laser Device.

Emergency Stop

The Emergency Stop is usually a button that you press to stop the machine in the event of an emergency.

Enclosed Laser Device

Any laser or laser system located within an enclosure which does not permit hazardous optical radiation emission from the enclosure. The laser inside is termed an "embedded laser." Also see Embedded Laser.

Energy

The product of power (watts) and duration (seconds). One watt second = one Joule.

Etch

Marking the material without cutting all the way through. This is typically accomplished by reducing power.

F

F-Number

The focal length of lens divided by its usable diameter. In the case of a laser the usable diameter is the diameter of the laser beam or a smaller aperture that restricts a laser beam.

Failsafe Interlock

An interlock where the failure of a single mechanical or electrical component of the interlock will cause the system to go into, or remain in, a safe mode.

Feed Rate

The speed at which the cutting head moves.

Flame Polishing

A technique for smoothing and polishing the edges of a material using an open flame.

Fluke VR1710 Power Quality Recorder


The Fluke VR1710 Power Quality Recorder is a single-phase, plug-in voltage quality recorder for detecting and recording power quality problems. Power quality parameters including RMS average, transients, flicker, and harmonics up to the 32nd are recorded using a user-selected average period from 1 second to 20 minutes.





Flyback Transformer

A flyback transformer (FBT), also called a line output transformer (LOPT) or high voltage transformer (HVT) is a special type of electrical transformer. It was initially designed to generate high voltage sawtooth signals at a relatively high frequency. In modern applications, it is used extensively in switched-mode power supplies for both low (3 V) and high voltage (over 10 kV) supplies.



Focal Point

That distance from the focusing lens where the laser beam has the smallest diameter. 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.

G

G-Code

G-code is one of a number of computer code languages that are used to instruct CNC machining devices what motions they need to perform such as work coordinates, canned cycles, and multiple repetitive cycles. G-Code is the most popular programming language used for programming CNC machinery. Also eee CNC.

Gain Medium

The active laser medium (also called gain medium or lasing medium) is the source of optical gain within a laser. The gain results from the stimulated emission of electronic or molecular transitions to a lower energy state from a higher energy state previously populated by a pump source.

Gas Jet

Gas which is blown into the cut to clear away molten metals, or other materials in the cutting zone. In some cases, the gas jet can be chosen to react chemically with the workpiece to produce heat and accelerate the cutting speed.

Gas Laser

A type of laser in which the laser action takes place in a gas medium.

Gas Mix

CO2 lasers use a mixture of carbon dioxide, helium, and nitrogen. Most applications can be done using a standard, predetermined ratio of these gases. Some applications require pulses with high peak energy and rapid decay of the pulse tail. Increasing the volume of CO2 gives this result. Increasing the volume of nitrogen allows operation of a laser at lower than its normal minimum CW power level.

Gas Pressure

The pressure of the Assist Gas that is usually measured in pounds per square inch (psi). With oxygen, gas pressure can range from 15 to 50 psi. With inert gases, the gas pressure can range from 30 to 200 psi.

Gaussian Beam

Lasers usually emit beams with a Gaussian profile. A Gaussian beam is a beam of electromagnetic radiation whose transverse electric field and intensity (irradiance) distributions are described by Gaussian functions.

For a Gaussian beam, the  amplitude of the complex electric field is given by

 

 

where,

r       – radial distance from the centre axis of the beam

z       – axial distance from the beam’s narrowest point

i        – imaginary unit (for which i2 = − 1)

k       – wave number (in radians per meter).

w(z)    – radius at which the field amplitude drops to 1/e and field intensity to 1/e2 of their axial values, respectively.

w(0)   – waist size.

E0     =  |E( 0,0) |

R(z)     – radius of curvature of the beam’s wavefronts

ζ(z)   – Gouy phase shift. It is an extra contribution to the phase that is seen in  beams which obey Gaussian profiles.

The corresponding time-averaged intensity (or irradiance) distribution is

 

 

where I0 = I(0,0) is the intensity at the center of the beam at its waist. The constant  is defined as the characteristic impedance of the medium through which the beam is propagating.

For vacuum,



Glass

Most glasses are not laser cut. They have a high absorptivity to CO2 laser light and demonstrate cracking along the edge cut due to the rapid thermal cycle associated with laser cutting. However, a laser can effectively cut quartz and heat resistant glasses.

H

Hard Limit

A hard limit is a stop on the machine that prevents the machine from moving further in a given direction. Typically these are used to prevent the machine from moving beyond its physical limits. Also see Soft Limit.

Hold Tolerance

Term used to describe the variation of a laser cut +/- to a predetermined target, usually measured in thousandths of an inch.

I

Ideal SureTest

The SureTest® Circuit Analyzer takes only seconds to test each outlet and circuit under a full load. This test tool checks for various wiring conditions including: correct wiring, polarity reversal and no ground per UL-1436. A simple menu gives access to measurements of line voltage, voltage drop under a full load condition, ground-neutral voltage and line impedances. The ground fault circuit interrupter (GFCI) test is performed separately in accordance with UL1436 and disrupts the electrical supply if a functional GFCI is present.





Intensity

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

IP Address

An IP address is assigned to every computer on an Ethernet network. Like the street address for your home, an IP address identifies network computers. It helps traffic flow between computers because each one has its own IP address.

An IP address is formatted as a series of four values separated by periods:

192.168.0.1

Each value ranges from 0 through 255.

Each period is just a period.
For your home or office network, the IP address is most likely assigned by the router, using something called DHCP. The router keeps track of every computer’s NIC and maps an IP address to the NIC every time the computer joins the network. In the end, all computers have a unique IP address, and the world is safe for local networking.
  • The IP address assigned to your PC on a network is a local address. Similar IP addresses are used on the Internet to identify domains and other resources. Those are Internet IP addresses, separate from your local address.

  • The router is assigned an IP address by your Internet service provider (ISP). That IP address is an Internet IP address. It’s shared by all PCs on your network.

  • Local IP addresses start with 192.168 and 10.0.

  • The IP addresses discussed here are IPv4 addresses. Because the number of unique IP addresses is limited, a second standard, IPv6, has been established. The IPv6 standard allows for many more addresses, which will help accommodate future growth of the Internet.

  • If the router doesn’t assign an IP address, one must be configured manually.

  • No two computers on the network can have the same IP address.

  • IP is often prefixed by the acronym TCP, as in TCP/IP. The TCP part stands for Transfer Control Protocol: It’s simply a set of rules for transmitting information on a network. Technically, TCP/IP refers to the methods and engineering as opposed to a specific address or value.

J


K

Kerf

A groove, slit, or notch made by a cutting tool, such as a laser cutter or the width of a groove made by a laser cutting tool. The kerf is dependent upon the properties of the material being cut, the workpiece thickness, the lens focal length, and finally, the type of cutting gas used in the laser. Also see Cut Width.

L

Laser

Is 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. It is a device that produces an intense beam of light with the unique properties of coherence, collimation and monochromaticity.

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 Power Supply Unit

A laser power supply contains a flyback transformer to provide high voltage to excite glass laser tubes. Some have integral low voltage DC power outputs and some do not. Also see Power Supply (PSU).

Laser Pumping

Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited state, population inversion is achieved. In this condition, the mechanism of stimulated emission can take place and the medium can act as a laser or an optical amplifier. The pump power must be higher than the lasing threshold of the laser.

The pump energy is usually provided in the form of light or electric current, but more exotic sources have been used, such as chemical or nuclear reactions.

Lens

An optic (either reflective or refractive) that causes rays of light to converge to a point. A lens is the optic used to focus a laser beam on the workpiece. Short focal length lenses provide narrow beam convergence angles, necessary to penetrate thick metal sections. Beam diameter is an important consideration in lens selection. Power density and depth of focus can change with differing beam diameters.

M

Master Oscillator Fiber Amplifier

The term master oscillator fiber amplifier (MOFA, MOPFA, or fiber MOPA) is a variation of the term master oscillator power amplifier (MOPA), meaning a system where the power amplifier is a fiber amplifier. The latter is usually a cladding-pumped high-power amplifier, often based on an ytterbium-doped fiber. The main attractions of such fiber-based power amplifiers are:
  1. A high output power can be achieved with a high power efficiency.
  2. The cooling system can be relatively simple.
  3. The beam quality can be high; it is often close to diffraction-limited.
  4. The gain can easily be as high as tens of decibels. For comparison, most bulk amplifiers, particularly those with high average output power, have a much lower gain.
  5. master oscillator fiber amplifier (fiber MOPA)
However, the use of fibers also has disadvantages:

  1. Various kinds of fiber nonlinearities can make it difficult to reach very high peak powers and pulse energies in pulsed systems. For example, a few millijoules of pulse energy in a nanosecond pulse system are already considered high for a fiber device, whereas bulk lasers can provide much higher energies. In single-frequency systems, stimulated Brillouin scattering (SBS) can severely limit the output power.
  2. Due to the high gain, fiber amplifiers are relatively sensitive to back-reflections e.g. from a workpiece. At high power levels, it is not easy to use a Faraday isolator for solving this problem.
  3. The polarization state is often undefined and unstable, unless polarization-maintaining fibers are used.
  4. It can be attractive to use a gain-switched laser diode as seed laser for a fiber MOPA. Such devices compete with Q-switched lasers, e.g. for application in laser marking. Their advantages partly lie in their flexibility concerning output formats: it is easy to modify not only the pulse repetition rate but also the pulse duration and shape, and of the course the pulse energy.
  5. A special aspect of MOFAs is that the saturation power even of a large mode area double-clad fiber is low compared with the typical output power. Therefore, the power extraction can be as efficient as in a fiber laser, even for relatively low seed powers.

Master Oscillator Power Amplifier

The term master oscillator power amplifier (MOPA) refers to a configuration consisting of a master laser (or seed laser) and an optical amplifier to boost the output power. A special case is the master oscillator fiber amplifier (MOFA), where the power amplifier is a fiber device. In other cases, a MOPA may consist of a solid-state bulk laser and a bulk amplifier, or of a tunable external-cavity diode laser and semiconductor optical amplifier.

Although a MOPA configuration is in principle more complex than a laser which directly produces the required output power, the MOPA concept can have certain advantages:
  1. With a MOPA instead of a laser, it can be easier to reach the required performance e.g. in terms of linewidth, wavelength tuning range, beam quality or pulse duration if the required power is very high. This is because various performance aspects are decoupled from the generation of high powers. This gives extra flexibility, e.g. when a gain-switched laser diode is used as a seed laser. Note also that it can be advantageous to avoid the presence of additional optical components such as wavelength tuning elements in a high-power laser resonator; with a MOPA architecture, one can place these in the oscillator, where they do not have to withstand high optical intensities, do not spoil the power efficiency, etc.
  2. The same aspects apply to other kinds of modulation, e.g. intensity or phase modulation: it may be advantageous to modulate the low-power seed laser, or to use an optical modulator between seed laser and power amplifier, rather than to modulate a high-power device directly. Slower power modulation may be done by adjusting the amplifier’s pump power, without significantly affecting e.g. the obtained pulse duration or wavelength.
  3. The combination of an existing laser with an existing amplifier (or an amplifier chain) may be simpler than developing a new laser with higher output power.
  4. The optical intensities are lower in an amplifier, compared with the intracavity intensities in a laser.
However, the MOPA approach can also have disadvantages:
  1. The complexity of the setup is higher.
  2. The wall-plug efficiency is often lower. However, it may also be higher, e.g. if that approach allows to remove lossy optical elements from the high-power stage.
  3. The resulting laser noise tends to be higher, since an amplified source can not reach the shot noise level (→ amplifier noise). Effects of drifts of the seed power may be suppressed, however, if the amplifier is operated in a strongly saturated regime.
  4. A MOPA can be sensitive to back-reflections, which are amplified again before entering the master laser. This feedback sensitivity can often be cured only by placing a Faraday isolator behind the amplifier. Particularly for high-power pulsed devices, this can introduce serious limitations.
MOPA architectures are also used for pulsed laser sources. In that case, the amplifier may be used as a reservoir of energy. If a pulse from the seed laser extracts a significant fraction of the stored energy, the effect of gain saturation is relevant: the amplifier gain drops during the pulse. This can lead to a deformation of the temporal pulse shape. In some cases, the pulse shape from the seed source is tailored so as to obtain the desired pulse shape after amplification.

N

Nanometer (nm)

A unit of wavelength, normally used to describe visble and ultraviolet light. One nanometer (nm) equals 1 x 10-9 meters. One nanometer also equals 0.001 micrometers.

Nd:Glass Laser

A solid-state laser of Neodymium glass offering high power or short pulses, or both, for specific industrial applications.

Nd:YAG Laser

solid-state laser of Neodymium:Yttrium-Aluminum Garnet, similar to the Nd:glass laser. Both are pumped by flashlamp. Beam transmission is via fiber optics. Power is up to 4,000 watts. The wavelength is 1.06 micrometers. Nd:YAG laser light can perform finer detail work and is better suited for work on highly reflective materials than CO2 laser light. Also see CO2 Laser and Nd:Glass Laser.

Nesting

Part-on-part nesting capabilities optimizes material use, reducing material waste, and increasing cost-effectiveness. Stacking or nesting optimizes material and can significantly reduce cutting times.

Nozzle

An element of Gas Jet used for cutting. The nozzle is used to constrict and direct the assist gas to produce a columnar flow. The flow of gas serves to push the molten metal through the kerf. Nozzles vary in shape and exit orifice. (Common orifice diameters are 0.040" and 0.060".)

O

Oxygen Assist

In certain laser cutting operations, coaxial oxygen is used to initiate an exothermic reaction to improve the cutting rate for thick metals. This means the oxygen actually does the cutting, with the reaction being maintained by the laser beam. See Gas Jet Assist.

P

Peak Power

The maximum power delivered in a laser pulse. Peak power is an important metric in laser safety as the higher the peak power of a pulsed laser, the more damage it can cause to a safety filter. Consider a laser that generates pulses with an energy of 100mJ (1 x 10-1 J). If the pulse duration is 200µs (2 x 10-4 S), the peak power is 1 x 10-1 / 2 x 10-4 equals 500 Watts. If the pulse duration were to reduce to 10ns (1 x 10-8 S), the peak power would rise to 1 x 10-1 / 1 x 10-8 equals 10MW (1 x 107 Watts).

Ply

An individual layer of a laminated material.

Polymers

Polymers, or plastics, are divided up into two main groups, thermoplastics and thermosets. See Thermoplastics and Thermosets.

Positioning Tolerance

The ability to position a part to be laser cut within a degree of inches for the x, y, and z-axis. The positioning tolerance specifies how closely a component has to be placed relative to its ideal placement. The positioning tolerance measures the position of uncertainty between where a part is supposed to be placed or a cut to be made and where it actually occurs. See Repeatability Tolerance.

Power

The rate of energy delivery. Power (or more correctly, radiant flux) is used to express the output of continuous (CW) lasers and is measured in Watts (W). One Watt is a Joule per second. The average power from a pulsed laser is the product of energy per pulse (in Joules) and pulse repetition frequency (in Hertz). For example, if a giant pulsed laser produces 10 pulses per second (i.e. 10Hz) and the energy of each pulse is 100mJ (1 x 10-1 J), the average power is 10 * 1 x 10-1 equals 1 Watt.

Power Density

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

Power Supply Unit

A power supply unit (or PSU) converts mains AC to various AC and/or DC voltages for the internal components of a device. Most use switched-mode power supplies. Some power supplies have a manual switch for selecting input voltage, while others automatically adapt to the mains voltage.  See also Laser Power Supply (LPSU).

Pulse

A discontinuous burst of laser, light or energy, as opposed to a continuous beam. A single burst of energy from a laser. A true pulse achieves higher peak powers than that attainable in a CW output. See CW.

Pulse Frequency

The rate at which pulses are generated. Pulse frequency is expressed in pulses per second (Hz).

Pulse Length

Time, expressed in fractions of seconds, in which energy is delivered. Application Report shows the electrical input pulse length, which corresponds to the half height of the leading and trailing edges of the optical pulse.

Pulsed Laser

Laser which delivers energy in the form of a single or train of pulses. This provides higher power at shorter intervals and is most often associated with the burr-free cutting of stainless steel and other high-strength, hard-to-cut materials. See CW.

Pulsing

  1. Electrical modulation of a laser power supply to produce discreet pulses of energy at a given pulse length and pulse period (pulse repetition rate).
  2. Mechanical interruption of the laser beam by a rotating chopper, which alternately blocks or passes the laser beam.
  3. Acousto-optical modulation of the beam within the laser resonator, caused by a device generically called a Q-switch. See Q-Switch.

Q

Q-Switch

A device that has the effect of a shutter to control the laser resonator's ability to oscillate. Control allows one to spoil the resonator's "Q-factor," keeping it low to prevent lasing action. When a high level of energy is stored, the laser can emit a very high-peak-power pulse. See Pulsing.

R

Ramp Test

The ramp test is a method for determining the optimum focal distance between your focusing lens and the material you're cutting.  You can place a block of wood that has been cut at an angle (the ramp) on the bed then engrave a straight line up the ramp.  The point where the burn size is the smallest is the focal point for your laser. Generally speaking, when engraving you will want the surface of the material to be at that height and when cutting you will usually want the center of the material to be at that height.

Reflection

The return of light waves from a surface (mirror). See Reflectivity.

Reflectivity

The measure of a materials' reflection of laser light. Highly reflective materials like copper and aluminum alloys are difficult to cut requiring reduced work speeds. See Reflection.

Refraction

Deflection from a straight path, undergone by a light ray or energy wave, in passing obliquely from one medium (like air) into another (like glass) in which its velocity is different.

Repeatability Tolerance

Measures the ability of a CNC controlled machine, like a laser cutter, to repeat the exact part positioning or cutting pattern within the stated amount of variance for each part placement or cut. The smaller the repeatability tolerance, the more uniform the cut parts will be. Often measured in ten-thousandths of an inch or even in microns — hundred-thousandths of an inch. See Positioning Tolerance.

Ruida DSP Controller

The Ruida series controllers are popular in many 50 watt and up Chinese laser engravers. They offer PWM laser power control and are quite advanced. These can be retrofitted into most lasers, even the K40, but require a higher level of technical aptitude to install as the connections will have to be configured manually and the control head will have to be flush mounted into the chassis.

The Ruida DSP ships with RDWorks which is also based off of CorelDRAW. LightBurn Software is the only other software known to work with the Ruida and it offers vast improvements over the shipped software. The cost of this controller is in the $300-$500 range. Some popular model numbers are RDC6442G, RDC6442GS, RDC6332G, RDLC-320A, and the R5-DSP (Rebranded for Lightobject).

S

Scalable Vector Graphics (SVG) File

SVG is an XML-based vector image format for two-dimensional graphics with support for interactivity and animation. The SVG specification is an open standard developed by the World Wide Web Consortium (W3C) since 1999.

SVG images and their behaviors are defined in XML text files. This means that they can be searched, indexed, scripted, and compressed. As XML files, SVG images can be created and edited with any text editor, as well as with drawing software.

All major modern web browsers—including Mozilla Firefox, Internet Explorer, Google Chrome, Opera, Safari, and Microsoft Edge—have SVG rendering support.

Soft Limit

Software limit. A means of defining an area or boundary of motion for which the laser cutting machine cannot exceed. Typically these are used to define the cutting envelope in which the head can move without crashing into something. This is done in software, instead of hardware, so that it can be changed when you change your fixturing or setup, and so that the machine can warn you ahead of time before you attempt to do an impossible move. See Hard Limit.

Spot Size

Spot size is nothing but the radius of the beam itself and is technically not the same as the beam diameter. The irradiance of the beam decreases gradually at the edges. The distance across the center of the beam for which the irradiance (intensity) equals 1/e 2 of the maximum irradiance (1/e 2 = 0.135) is defined as the beam diameter.

The spot size (w) of the beam is defined as the radial distance (radius) from the center point of maximum irradiance to the 1/e2 point.

Gaussian laser beams are said to be diffraction limited when their radial beam divergence  is close to the minimum possible value, which is given by

 

 

where  λ is the wavelength of the given laser and w0 is the radius of the beam at the narrowest point, which is termed as the beam waist.

Stability

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

T

Taper

Taper is the difference between the top profile of the laser cut verses the bottom profile of the laser cut. Typically, the laser cut width is narrower at the bottom than at the top.

TEA Laser

An acronym for transversely excited atmospheric laser. This CO2 gas laser uses a transverse flow of gas and operates at higher pressures than other gas lasers, generally near atmospheric pressure. The result is a higher energy beam.

TEM

TEM is an abbreviation for Transverse ElectroMagnetic modes. This term is used to designate the cross-sectional shape of the beam.

Thermal Conductivity

A measure of a materials ability to move heat from one place to another. During laser cutting, the cut zone should be heated without wasting energy heating up surrounding workpiece material. Materials with high thermal conductivity, such as copper and aluminum, cutting is slowed down as heat escapes from the cut zone.

Thermoplastics

Polymers that can be repeatedly melted down and cast into new shapes. Thermoplastics include polypropylene, polystyrene, polyethylene, polyamide (nylon) and others.

Thermosets

Materials that cannot be remelted once they have been made into their initial shape. Epoxies, phenolic resins, and most natural rubber products are included in this category.

Traverse

A traverse is normal machine movement without laser cutting. For example, a laser is traversing when moving the cutting head into position to cut.

U

Ultraviolet (UV) Radiation

Electromagnetic radiation with wavelengths from 180-400 nm

Ultraviolet Lasers

Excimer lasers and frequently tripled and quadrupled Nd:YAG lasers that are very precise and well suited for micromachining of polymer materials. See Polymers and Nd:YAG Lasers.

V

Vaporization

Conversion of a solid or liquid into a vapor. Lasers vaporize the metal or material they are cutting.

W


X


Y


Z





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