Laser

of the titles of this article is ambiguous. For further meanings see laser (term clarifying).
Laser (USAF)
Laser (USAF)

laser [ˈleɪzɚ] is an acronym of Light amplification by Stimulated emission OF radiation (light amplification by stimulated radiation sending). The term became 1957 of Gordon Gould coined/shaped.

Lasers are sources of light, whose community lies in the developing process of the light, i.e. in the so-called stimulated emission. Thus there is a multiplicity of different laser models with the most diverse characteristics. A laser always consists thereby of an optically activeMedium, in which the light is produced, and a resonator, which for the characteristics of the laser beam, as parallelism or jet profile is responsible.

Lasers have fascinating characteristics, them strongly from classical sources of light (like e.g. a lamp) differentiate. Due toihrere high coherency - the Wellennatur of the light z knows characteristics by means of lasers. B. by interference effects to be observed directly. Laser light can be temporally coherent. Thus it is in colored (monochromatically). Because of the high spatial coherency laser light can be bundled, highlyintensively and well focusable, which makes it suitable for applications as gumption and welding tool or also as Laserskalpell in the medicine.

Lasers can be designed also so that they impulses with extremely small duration (~10 telex - range) send, sothat the time-dissolved laser spectroscopy became a standard technique the investigation of fast processes.

Table of contents

history

Albert Einstein described in the thirties 20.Century the stimulated emission as reversal of the absorption. Afterwards it was for a long time puzzled whether the effect could be used for the reinforcement of the light field, since for reaching the reinforcement a population inversion had to occur. This is however in a stable two-level system impossible. Firsta three-level system was considered, and calculations resulted in a stability for radiation within the microwave range. From this the maser followed, the microwave radiation sends. The first laser - a ruby solid laser - was built 1960 by Theodore Maiman and to 26. Mayfinished< ref> Maiman, TO hands (1960) “Stimulated Optical radiation in Ruby”.Nature, 187 4736, pp. 493-494. </ref>.

The further development led then first to gas lasers (nitrogen, CO of 2 - lasers, He-Ne-lasers) and afterwards to coloring material lasers (the laser-active medium is liquid). An advancement of crystal technologiesmade possible a very strong extension of the spectral Nutzbereiches. Tunable lasers for starting a certain wavelength and wide-band lasers like e.g. the titanium sapphire laser rang in the 80's the era of the Ultrakurzpulslaser with impulse lasting from pico and Femtosekunden.

Into thatlate 80ern made possible the semiconductor technology ever more long-lived, highly effective diode laser diodes, those with small achievement in CD and DVD drive assemblies or in glass fiber data networks to be used and in the meantime gradually as pumps with achievements into the KW range the little effective suggestion for lamp ofReplace to solid lasers.

In the 90's new pumping geometry for high laser achievements was carried out, like the disk and the fiber lasers. The latters applied increasing to the turn of the century due to the availability of new production technologies and achievements up to 20 KW during the material processing,where it the types used so far (CO of 2 - lasers, lamp-pumped lp: YAG lasers) to partly replace can.

At the beginning of the third millenium nonlinear effects are used, in order to produce corroding eye customer pulses within the Roentgen range (with it temporal operational sequence can be pursued inside an atom). On the other handreached first blue laser diodes the ready for the market one. In the meantime the laser became an invisible, but irreplaceable instrument of the society.

action principle

Stimulierte Emission: Lasing
stimulated emission: Lasing

by energy input knows an electron of an atom or the Schwingungszustand of a molecule in oneput on condition change. Light results from the fact that an electron or an oscillation mode of such changes for a higher-energy to a energy-poorer condition, whereby the energy difference in form of a light particle (photon) is delivered. The opposite procedure is the absorption,with by the energy of the photon an electron into a higher energy level one lifts.

With conventional sources of light this transition takes place via spontaneous emission, i.e. both the time and the direction, in which the photon is sent, are coincidentally. With the laser however this transition takes place via stimulated emission: A light particle stimulates this transition, and thus develops a second light particle, whose characteristics (frequency, phase, polarization and direction of propagation) are identical to that first: Light amplification.

Those Probability that a photon raises an electron by absorption to a higher level, is just as high in a two-level system as the probability that it releases a stimulated emission. In order to reach a reinforcement from light to, must therefore more conditionsin the higher level are present than in the low, so that due to occupation the probability for the stimulated emission is higher than for the absorption. One calls this condition population inversion.

In a technical laser the light becomes by an arrangementtwo mirrors again and again by the area, in that population inversion (in the active medium z. B. “Lp: YAG - Crystal “or”< math> \ mathrm {CO_2}< /math> - gas ") prevails, led. One calls such an arrangement optical resonator (lat. resonare= back-sing, resound). In the resonator the light becomeswhen running back and forth between the two mirrors ever continues to strengthen, until the performance increase becomes balanced by the reduction of the population inversion and the ever more strongly rising losses within the system. One of the two mirrors is partial (typically: Parts per thousand to 15%,depending upon reinforcement) permeable, in order to be able to uncouple light from the laser. The field strength within the resonator is much higher thereby than the uncoupled achievement. Laser media with very high reinforcement can also with only one mirror or completely without mirrorslasers (superemitters, e.g. Nitrogen laser).

Power outputs of typical laser systems are enough from few micro Watts (µW) with diode lasers up to some Terawatt (powerplant) at pulsed Femto or corroding eye customer lasers with external reinforcement.

The energy, which is needed, around the atoms or molecules inthe put on conditions to shift, must be supplied to the system from the outside. This process is called pumps. It can electrically in form of a gas discharge, by injection of charge carriers with the diode laser or optically by the light of a gas-discharge lamp (Photo-flash lamp or arc lamp) or another laser take place. Also a chemical reaction can serve for pumping. With the free electron laser the pumping energy originates from the electron beam.

characteristics of laser radiation

jet characteristics

the jet characteristics of a laser beam become substantiallyby the kind of the laser resonator determines: the laser emission is made possible by this only in a direction, which is certain by the mirror arrangement and geometry of the active medium. Since lasers send running radiation thereby almost parallel in a direction, can by bundling (focusing) a very much higher power density to be reached than with usual sources of light (e.g. Arc lamps). The behavior of laser beams can be described often well by Gauss jets.

coherency

with a normal lamp light waves become not only alsodifferent wavelength sent, but also temporally easily shifts, thus out of phase. With a laser against it the waves “jump off” nearly in each case at the same time. The waves are thus over more or less long distances nearly (so-called.Coherency length). This makes oneself onealso in the Holografie too use.

polarization

the polarization of laser beams is ideally usually linear due to polarizing optical construction units in the resonator (deflecting mirror, diagonal surfaces (Brewster windows), small height of the resonator with diode lasers).

Frequency, wavelength

the frequency of laser radiation is determined by the active medium. There are materials, which on many wavelengths lasers lively to become to be able - however usually with one particularly well. Therefore lasers are very narrow-band radiation sources. The narrow-bandness is z. B. during the interferometric linear measurement by means of lasers of importance.

continuous line and pulsed lasers

laser light of ungepulsten, continuous line lasers (English: continuous wave of laser, cw-laser) is frequently very narrow-band (mono chrome, in-colored), D. h. it consists of only one wavelength. In particularcontinuous line laser light from sturdy laser resonators is temporal due to the multiple circulation, and/or longitudinal (along its direction of propagation) coherently, which meant that the sent wave trains do not only swing with the same frequency, but also in the phase over a long distance constant it is. Thussuch a light shows particularly pronounced interference features.

Contrary to the continuous line laser a pulsed laser produces radiation with larger an in principle frequency band width. The more briefly the pulse time, is the more broadly the produced spectrum. The smallest attainable impulse lasting lie nowadays in thatOrder of magnitude of Femto and corroding eye customers (see also:Femtosekundenlaser). With such short pulses (length of the radiation package <30 µm, thus a fraction hair width) the sufficient wide-bandness of the intensifying laser medium already plays a role. The repetition frequency, with that the pulses thatLaser abandoned, hangs fashion coupling (English with a form of the instantanen Kerr lenses -. Kerr lens mode locking, a procedure for the production of extremely short, sturdy pulses, from the resonator length: With a resonator with a rotating length from a meter this amounts toabout 300 MHz. From these pulses often individual impulses are cut out and further-strengthened by means of optical switches. With some further cheat succeeds it to produce maximum performances into the Petawatt range which can be focused only in the vacuum transferred and.
The quality modulation (Q-switching) with acustooptical quality switches or Pockels cells is further techniques to production of laser impulses high-energy with small duration.

With lasers succeeded controlling light to a high degree (intensity, direction, frequency, polarization, phase, Time).

different one active media of lasers

gas laser

demonstration laser: In the center shining the gas discharge is to be seen, which energizes the laser medium. The laser beam is right as red point on the whiteTo recognize screen.

Laser, with which the active medium is gaseous. Mostly gas lasers are pumped electrically by a gas discharge in the medium.

  • Helium-Neon-Laser (HeNe laser): Most important emission wavelength with 632,8 Nm (red).
  • Carbon dioxide laser (CO of 2 - lasers): about 10.6 μm wavelength (middle infrared),important industrial laser
  • carbon monoxide laser (CO laser): to about 6-8 μm, only cooled nitrogen laser (N of 2 - lasers
  • ) functions to wavelength (middle infrared): 337.1 Nm (ultraviolet)
  • argon ion laser, several lines with 457,9 Nm (8%), 476.5 Nm (12%), 488.0 Nm (20%), 496.5 Nm (12%),501.7 Nm (5%), 514.5 Nm (43%) (blue to green)
  • helium cadmium laser (HeCd laser): most important source of laser for blue (442nm) and close UV (325nm)
  • krypton ion laser, several lines with 350,7nm; 356,4nm; 476,2nm; 482,5nm; 520,6nm; 530,9nm; 586,2nm; 647,1nm (strongest line); 676,4nm; 752,5nm; 799,3nm (blue to low red)
  • Oxygen ion lasers
  • xenon ion laser
  • Dowson gas laser, do not contain pure gases, but a mixture more differently (usually argon and krypton)
  • of Excimerlaser, z. B. KrF (248 Nm), XeF (351-353 Nm), ArF (193 Nm), XeCl (308 Nm), F 2 (157 Nm) (of everything ultraviolet)
  • metal steam laser, z.B.Copper steam laser, with 510,6 and 578,2 Nm. Due to the high reinforcement a copper steam laser can be operated also without resonator mirrors.
  • Metal halide - laser, z. B. Copper bromide laser, with 510,6 and 578,2 Nm. Due to the high reinforcement a copper bromide laser can also without resonator mirrorsare operated.

A special form are the chemically pumped lasers. Here pumping takes place via a chemical reaction in the medium. This medium is used up after the reaction and can be used accordingly only once. Ideally for transportable highs speed's applications, particularly inmilitary range.

  • HCl - laser
  • iodine laser

dye laser

with this type of laser is an organic coloring material in alcoholic solution (often methanol or ethanol) the active medium. The coloring material solution is constantly umgepumpt thereby, in order to avoid a fading (photochemical degeneration).

Examplesfor coloring materials:

dye lasers are pumped generally by other lasers. One accepts a power loss by the finite efficiency of the dye laser, in order to produce other wavelengths. To be pumped can both continuously (briefly cw for English. continuous wave) and pulsed.

solid laser

of the solid lasers was developed the first laser, by Maiman in the year 1960: Ruby laser. A carrier crystal is endowed with ions of a strange material. ThisIons are the actual active medium. The laser transitions of the ions are within the D-Orbitals. This orbital are not involved in chemical connections. The substrate (host crystal, glass) exerts therefore only small influence on the characteristics of the ions. Examples of substratesare:

  • Glass (staff form or fiber laser)
    • advantage: simple production also in large dimensions
    • disadvantage: small heat conductivity, small firmness
  • aluminium 2 O 3 (corundum, sapphire) (e.g. Ruby (chrome doping), titanium: Sapphire laser)
    • advantage: high heat conductivity, high firmness
    • disadvantage:relatively high absorption, expensively
  • YAG (yttrium - aluminum - garnet - laser) doping lp, it, Yb
    • advantage: high heat conductivity, high firmness, small absorption
    • disadvantage: expensively
  • yttrium vanadate (YVO 4), doping lp
  • YLF

of examples of doping materials are:

  • Chrome was thatDoping material of the first laser, ruby laser (694.3 Nm (red)). Due to the small efficiency it is today still used hardly.
  • Neodymium, 1064nm, the most important commercial solid laser: Lp: YAG laser, with 1064 Nm (infrared), and/or frequency-doubles with 532 Nm (green). Also possibleare: Lp: Glass, lp: YLF…
  • Ytterbium, 1030nm, permits in the laser enterprise a high efficiency >to 50%. It requires in addition however narrow-band pumping with laser diodes (940nm). The most important material with this doping is the Yb: YAG laser, e.g. heavily doped as disk lasers with oneWavelength of 1030nm.
  • Titanium an important fashion-coupled solid laser: Titanium: Sapphire laser, 670-1100 Nm (red-infrared), been suitable due to wide-band reinforcement for pulses within the teleprinter range
  • erbium wavelength 3 µm, pumps with 980nm, so-called. “more eye surely” laser, use for laser rangefinders and in the medicine

different one formsthe active medium:

color center laser

as with the solid laser concerns it with the color center laser a laser, with which defects (added ions, lattice defect, charges) are embedded into a carrier crystal. The laser transitions with thatColor center lasers are produced however by the reciprocal effect of the places of malfunction with the lattice. Several single diodes can in a narrow chip (approx. 0.1 x 1 x 10 mm) next to each other integrated its. These so-called ingots supply, onto a heat sink installed, to approx. 50Watt (ingot with several hundred Watts of power output are in the development, conditions Sep.2005). The single diodes are electrically parallel switched thereby. One calls the installed ingot “also submount”.

Examples:

diode laser

with that Diode lasers are used transitions in the semiconductor for the population inversion. Laser diodes are directly electrically pumped lasers. The achievement of laser diodes with good jet quality (M ²< 1.5) amounts to less than a Watt. Multi-mode - diodes reach with worse jet quality (1,5<M ²< 100) achievements to10 W.

Several single diodes can in a narrow chip (approx. 0.1 x 1 x 10 mm) next to each other integrated its. These so-called ingots supply, onto a heat sink installed, to approx. 50 Watts (ingots with several hundred Watts of power output are in thatDevelopment, conditions Sep.2005). The single diodes are electrically parallel switched thereby. One calls the installed ingot “also submount”. By coupling of many such ingot and/or. submounts in a so-called stack (pile) achievements within the KW range are reached with according to bad jet quality (M ²>100). Up to 6 one can add piles by different wavelengths (usual to 3) and polarization directions low-loss without degradation of the jet quality optically. Thus one reaches achievements within the two digit KW range.

For optical pumping of solid lasers by laser diodes the pumping wavelength must accuratelyare met. In addition the diode lasers do not have to be however usually combined into jets with high power density - otherwise only the polarization coupling would be possible.

Further diode lasers are:

free electron laser (FEL)

with free electron lasers functions a high-energy electron beam as active medium. This electron beam becomes by a Undulator, which consists of magnets, lengthwisethe jet direction it is so arranged that the magnetic field changes its direction along the way periodically (it is however constant temporally), guided. Thus the electrons with a certain frequency, while they pass the Undulator, swing and deliver electromagnetic radiation. InForward direction is strongly blue-shifted this electromagnetic radiation by the speed of the electron beam. By mirrors, which are as arranged with other lasers, certain frequencies can interfere constructionally; thus it comes to larger intensities with these frequencies, which again to the stimulated light emissionthe electrons leads. For lasers with larger wavelengths there are electron-transparent mirrors, which consist of a screen, whereby the wire distance is substantially smaller than the laser wavelength; electron-transparent mirrors facilitate the guidance of the electron beam, for that in the Undulator parallel to laser radiationruns. The electron beam, which did not lose much energy after the Undulator, is directed often on an anode and the energy goes as warmth lost. The energy of the electron beam can be also recovered, which increases the efficiency of the system. ThoseLaser wavelength can be continuously changed with free electron lasers, as mirror spacing and electron energy are changed. The efficiency of this type of laser can be relatively high. One hopes to be able to build in the future free electron lasers which emit electromagnetic radiation in the X-raying or even gamma range.

resonators

laser resonators are used with all laser apparatuses, in order to make the jet coherent. Without the resonator the structure would be only one laser. The quality of the resonator affects the jet quality and the coherency characteristics of the laser beam. With the resonatorsone differentiates between in principle two different kinds the different pro and cons possesses.

Unstable resonators

of advantages: Good utilization laser medium, therefore they are usually used in lasers, which point a high reinforcement out per resonator circulation.

Disadvantage: Bad jet quality

sturdy resonators

of advantages: Good one Jet quality by small diffractions within the resonator

disadvantage: Bad utilization of the laser medium


The resonator of the length L consists of two curved mirrors with the radius of curvature r i of the i - ten mirror so this is stable, if applies:

<math> 0 \ le g_1\ g_2 cdot \ le 1 \ quad {\ rm whereby} \ quad g_1 = 1 - \ frac {L} {r_1} \ quad {\ rm and/or} \ quad g_2 = 1 - \ frac {L} {r_2}< /math>

The result is straight 0 or 1 calls one the resonator in such a way borderstably.

An example for this is thatconfocal resonator. With it the radius of curvature of the two mirrors is equal to the resonator length. Thus <math> r_1 = r_2 = L< /math>. The result is thus to zero which border stability confirmed.

uses of lasers

finishing technique

laser leaveuse themselves in all ranges of the finishing technique according to DIN 8580 for different manufacturing methods:

control engineering

  • CAD/CAM lasergesteurte production engineering up to complete production lines
  • Laserguided AGV Spurführung for transport systems without driver


work on []

Medicine

measuring technique

a set of measuring instruments are upLaser basis designs…

  • By interference or the coherency radar precision measurements are possible.
  • With the tunnel construction straight lines a tunnel driving can be achieved by laser beams.
  • In the building industry it is used for levelling.
  • In the Verkehrsüberwachung laser pistols of the police ( executive) become the speed measurement from motor vehicles uses.
  • In bar code readers the lasers are used for scanning bar codes. The jet is linienförmig led evenly across a mirror wheel across the bar code. The reflected jet is evaluated over a photo transistor as light-darkly sequence.
  • In fire alarms (“laser alarm units”)
  • Schwingungsanalyse and molder version by electronic Speckle - sample Interferometrie (ESPI)
  • laser microphone
  • Lidar: Lidar stands for the radar (“radiowave detection and ranging”) for “light detection and ranging” and is relatives method for the telemetering of atmospheric parameters.
  • Laser - Doppler - anemometer and Particle image Velocimetry for the non-contact measurement of the flow rate of gases or liquids.
  • Laser light cut sensor for the measurement of elevator profiles along a line.
  • Position measurement - position determination of the laser beam emphasis with the help of an photo-sensitive receiver on the light emphasis reacts. PSD= photo sensitive sensor.

science

  • measurements of the earth by satellite, measurement of tectonic shifts
  • spectroscopy:
    • Measurement of atomic energy levels (atomic spectroscopy)
    • in chemistry is possible by infrared and Ramanspektroskopie the identification and analysis of molecules.
    • Time-dissolved spectroscopes with ultrakurzenLaser impulses within the spades eye customer range, e.g. temporal operational sequence of chemical reactions
  • nonlinear optics: z. B. Frequency conversion
  • in life sciences: By laser light lively Fluoreszenzfarbstofffe and the use of a confocal microscope or a 2-Photonon-Mikroskops make it, cells and subzelluläre structures possible with more highly temporalto observe and spatial dissolution in the living fabric (in the section of fabric or in vivo).
  • In cell biology as optical tweezers
  • laser cooling and atomic and/or. Ion traps
  • proof of gravitation waves by means of particularly large laser interferometer.
  • Regulation of wind velocities and/or particle concentration in thatGround atmosphere.
  • A new research field is the reciprocal effect of laser light and solids, then is to be made transparent recently succeeded a special crystal lattice material by irradiation of laser light. (Research group Chris Phillips imperially college London). Becomes possible by interference reciprocal effect alsothe crystal structure of the medium. It exists to let the prospect in the future further to arbitrary materials become transparent by laser light.

laser inscription

  • marking and marking: Mark with laser. Paper, pasteboard, wood, glass, leather, plastics, metals. Color erosionof coated articles; Color change on plastics, starter inscription on metal, light engraving on different materials.

holography

  • as art objects
  • for data storage
  • as measuring procedures
  • for Bildspeicherung

data processing technology

micro photolithography

with lasers being able structures in µm - and sub µm range on fotosensitive materials be written. By means of microlithographic systems high-dissolved collecting mains (masks) for most diverse applications become in the direct E-beam slice writing techniqueproduced, then e.g. by means of wide-band high-power lasers in production on the final materials to be umkopiert. Other uses judge the direct letter from structures silicon - Wafern in low numbers of items or the letter of structures on photosensitive films (e.g. Stretch sensors).

u.v.m.

military equipment

  • marking of goals for self-controlling weapons
  • ranging by means of the laser measure for z. B. Tank
  • first attempts of laser rifles those the opponent z. B. to go blind first
  • high-energy lasers leave ground-based, on airplanes(Boeing AL-1) or ships to the anti-missile defense, there are already so-called laser cannons. They represent simple lasers with high energy. The enterprise is still very complex and expensive, the weapons has a large danger zone, in itself withNo humans operated to stop may.
    see: Tactical High Energy laser · Directed Energy Weapon
  • projected laser satellites to the anti-missile defense by means of high-energy lasers (chemical lasers, Roentgen lasers)

maintenance/media

  • CD player, DVD player
  • laser pointer
  • Disco, Bühnenshows (see Lasershow)
  • RGB - Systems. Advantage: intensive colors by narrow-band laser light, HDTV - color area and very large sharpness depth by high Brillianz of the laser beams (sharpness depth is not infinite, but at best diffraction limited)
    • in the Planetarium ZULIP (frame) of the Jenoptik LDT GmbH
    • in the Planetarium ADLIP (illuminating thatentire dome) likewise of the Jenoptik LDT GmbH. The Planetarium in Peking offers such a complete dome laser system as the first.

laser classes

of laser apparatuses are divided according to the biological effect of laser radiation in classes. Considerably for the national and international laser classesthereby the definition of limit values is, with which no damage is to be expected. Beside the American ANSI - standard publishes those internationally Commission on Non Ionizing radiation Protection of limit values in the spectral region between 400 and 1400nm .

Thereby the thermal line becomes primaryand the border with the not-ionizing radiation pulled. By the optical focusing characteristics of the eye the danger is increased in the visible spectrum. Within the not-visible range there is an adjacent range in that the eye still well focused and transparency is.

the lasers are divided classification

according to DIN EN 60825-1 according to the danger for humans in device classes. The classification according to DIN EN 60825-1 takes place from the manufacturer. (The old classification according to DIN VDI 0837 (see below) may fornew lasers not to be any longer used)

Class description
1 accessible laser radiation is harmless. CD-Player
1M accessible laser radiation is harmless, so long no optical instruments, as magnifying glasses or binoculars are used.
For 2 accessible laser radiation is appropriate only in the visible spectral region(400 Nm to 700 Nm). It is at brief irradiation duration (to 0.25 s) harmless also for the eye. Longer irradiation is prevented by the natural eyelid conclusion reflex. (*)
2M such as class of 2 so long no optical instruments, like magnifying glasses or binocularsare used. (*)
3R accessible laser radiation is dangerous for the eye.
3B accessible laser radiation is dangerous for the eye and in special cases also for the skin.
4 accessible laser radiation is very dangerous for the eye anddangerously for the skin. Also vaguely strewn radiation can be dangerous. Laser radiation can cause fire or danger of explosion.
*) Note to laser class 2 and 2M: By scientific investigations (FH Cologne) it was stated that the eyelid conclusion reflex (this in all other respects stepswithin 0,25 s up; longer irradiation damages the eye) only with <20% of the test persons was given. From the presence of the eyelid conclusion reflex for the protection of the eyes usually may not be proceeded thus. Therefore one should if laser radiationthe class 2 or 2M in the eye meets, consciously the eyes close or turn away immediately. The moreover it is to be noted that the eyelid conclusion reflex takes place only with visible light. Laser radiation within the infrared range e.g. there those does not lead to an eyelid conclusion,Radiation of the eye is not noticed. Therefore particularly careful handling invisible laser radiation is recommended.

the laser classes applied for classification according to

DIN VDI 0837 until March 1997 according to DIN VDI 0837 in Germany. This organization is todaystill in the USA common.

Class description
1 corresponds to the class 1 according to DIN EN 60825-1
2 corresponds to the class of 2 according to DIN EN 60825-1
lasers of this class perhaps today under 1M is classified.
3a accessible laser radiation becomesfor the eye dangerously, if the radiation cross section is made smaller by optical instruments. If this is not the case, sent laser radiation is in the visible spectral region (400 Nm to 700 Nm) at brief irradiation duration (to 0.25 s), in the other spectral regions alsoduring long-term irradiation, harmless.
Depending upon wavelength these lasers are today usually classified under class 2M or 3R.
3b corresponds to the class 3B according to DIN EN of 60825-1
lasers of this class perhaps today under 2M or 3R is classified.
corresponds to 4to the class 4 according to DIN EN 60825-1


see also

literature

of books

  • William T. Silfvast: Laser Fundamentals. Cambridge University press, Cambridge 2004 (2. Aufl.). ISBN of 0-521-83345-0

articles

<of references/>

Web on the left of

Wiktionary: Laser - word origin, synonymsand translations

 

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