EP0468986A1 - Laser a gas, notamment laser au co2 - Google Patents

Laser a gas, notamment laser au co2

Info

Publication number
EP0468986A1
EP0468986A1 EP90905496A EP90905496A EP0468986A1 EP 0468986 A1 EP0468986 A1 EP 0468986A1 EP 90905496 A EP90905496 A EP 90905496A EP 90905496 A EP90905496 A EP 90905496A EP 0468986 A1 EP0468986 A1 EP 0468986A1
Authority
EP
European Patent Office
Prior art keywords
gas
laser according
coupling
gas laser
space
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP90905496A
Other languages
German (de)
English (en)
Inventor
Wolfgang Krüger
Hubert Grosse-Wilde
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Siemens Corp
Original Assignee
Siemens AG
Siemens Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG, Siemens Corp filed Critical Siemens AG
Publication of EP0468986A1 publication Critical patent/EP0468986A1/fr
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/097—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser
    • H01S3/0975—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser using inductive or capacitive excitation

Definitions

  • Gas lasers especially C0 2 lasers
  • the laser-active medium is a gas that is excited into a plasma.
  • power must be constantly supplied, which is usually done by applying an electric field that can accelerate the free electrons.
  • the field can be an alternating or alternating field, with the coupling of HF power being particularly suitable.
  • the high-frequency excitation has the advantage that there are no losses at a series resistor or no voltage drops at the cathode.
  • the simple pulsability at the generators is advantageous for use with gas lasers.
  • so-called RF boundary layers occur in the plasma that are laser inactive. A comparatively expensive generator is also required.
  • the frequency of the excitation power can theoretically range up to the radio frequency range and beyond the microwave range.
  • stripline lasers are also known, in which the laser-active gas is located between opposite surfaces of two wall parts, which are equally designed as electrodes for coupling in the energy.
  • DE-OS 37 29 -. 053 - a high-frequency alternating electrical field is coupled into such a stripline laser.
  • the RF power is advantageously coupled in at several points.
  • Band conductor laser to increase the laser output line by increasing the coupled electrical power accordingly. At a constant temperature of the plasma gas, this is possible if the distance between the plasma-delimiting surfaces of the strip conductor laser is reduced, since this improves the diffusion cooling.
  • the object of the invention is therefore to improve the electrical power coupling in a gas laser according to the strip conductor concept in such a way that higher frequencies than previously can be used for uniform excitation and the electrode spacing can also be reduced, since the laser-inactive boundary layers become thinner with increasing frequency. As a result, the laser power can be increased while the dimensions are otherwise the same.
  • a band conductor spacing of about 1/10 mm and less should be achieved, so that the use of optical resonator configurations for gas lasers in the near infrared range after Band conductor concept is possible, which are already known for gas lasers in the far infrared range and for semiconductor lasers.
  • the distance between the wall parts and the opposite surfaces can be varied as desired by the invention. Distances from less than 30 ⁇ m to more than 5 mm are possible.
  • the gas pressure can be between 10 mbar and a few bar.
  • Lasers act, can be kept so low that, for example, regular periodic increases and / or depressions of, for example, 1/4 of the wavelength of the laser radiation can be effective for the formation of a laser resonator.
  • this periodic geometric structure it is also possible to use structures which represent a periodic change in the refractive index for the wavelength of the laser in question.
  • the periodic structure causes the laser radiation to be reflected.
  • Lasers of this type are known in other implementations as “distributed feed-back lasers” (DFB lasers). In such Lasers can be dispensed with the use of mirrors, which is detailed in the specialist literature (D. Marcuse, Hollow Dielectric Waveguide for Distributed Feed ⁇ back Lasers, IEEE Journal of Quantum Electronics, Vol. QE-8, No. 7, July 1972, pages 661 to 669).
  • the plasma space is part of a waveguide structure - hereinafter referred to as the coupling space or coupling waveguide - whose phase wavelength at the operating frequency f of the generator in the longitudinal direction corresponds approximately to the length of the plasma space or exceeds this dimension.
  • the phase wavelength is determined for the selected operating frequency by the cross-sectional geometry of the coupling space in accordance with the design rules for waveguide elements.
  • FIG. 1 shows the principle of a stripline laser
  • FIGS. 2 to 4 show exemplary embodiments of stripline lasers according to the invention in a perspective view
  • Figure 5 shows another embodiment of an inventive
  • FIG. 6 shows an exemplary embodiment of a transverse contour of the opposing surfaces of the wall parts of the plasma space
  • FIG. 7 shows a corresponding longitudinal contour
  • two plate-shaped wall parts 1 and 2 with associated end parts 3, 4 and 6 enclose a plasma space 5, which characterizes the principle of the stripline gas laser.
  • the wall parts 1 and 2 form electrodes for supplying HF power to a generator 9.
  • the plasma is usually excited with the aid of an electrical high-frequency field, the field strength of which is usually directed perpendicular to these surfaces.
  • the plates are kept at a constant temperature by means of adequately dimensioned water or air cooling.
  • the maximum temperature difference between the hottest point in the plasma, for example the central plane, and the wall is largely determined by the power loss in the plasma and the distance between the plates. If the maximum permissible gas temperature is determined by the laser process in the excitation plasma, for example in the case of the C0 2 and CO laser, the excitation power and consequently the laser output power can be made greater the smaller the distance between the strip conductors.
  • the highest permissible temperature difference between the hottest point in the plasma and the wall surfaces results from the fact that the generation of laser photons rapidly decreases in the plasma at the points where a certain limit temperature is exceeded and that the temperature of the wall surfaces due to the Arrangement of the cooling device and the heat output to be dissipated is specified.
  • the limit for the reduction of the plate spacing and thus also for the increase in laser power is determined by the fact that a boundary layer is always formed along the surfaces, which contributes little or nothing to the generation of the laser radiation.
  • a boundary layer is always formed along the surfaces, which contributes little or nothing to the generation of the laser radiation.
  • the thickness of the boundary layer is about inversely proportional to the frequency of the excitation power decreases.
  • the relative proportion of the usable plasma volume therefore increases at higher excitation frequencies, and the plate spacing can also be reduced to improve the cooling.
  • the laser power can therefore be increased if one goes to higher frequencies.
  • the structure 40 runs the entire length of the plates 10 and 20, while the coupling point 45 is in the middle
  • a distribution space 40 for microwaves is thus created, which is coupled into the structure from the wall parts 10 and 20 via the coupling wall 30.
  • This structure thus forms a coupling space for the microwaves, via which the HF power is transmitted into the plasma located between the surfaces 11 and 21.
  • the coupling wall 30 has coupling openings 31 and 32 which are distributed over the entire longitudinal direction.
  • slots, round or rectangular holes are used as coupling openings or a combination thereof.
  • two rows of slots 31 and 32 can be formed, each of which is spaced along its length.
  • the slots can also be zigzag-shaped or, in combination with round holes, form dumbbell-shaped structures.
  • coupling webs or coupling loops in the coupling wall are also possible.
  • the RF power is thus coupled in uniformly over the entire length of the stripline laser from one of the two sides.
  • the web 27 forms a reflection wall.
  • the HF power is supplied simultaneously from two opposite sides to a stripline laser with the wall parts 10 and 20 and the laser volume enclosed by the surfaces 11 and 21.
  • two distribution spaces 40 and 40 ', each with a horn 45 or 45', are mirrored, which each couple the RF power into the coupling space designed in accordance with FIG. 2 via a coupling wall 30 or 30 '.
  • the first coupling space 40 has, in a known manner, the horn 45 for connecting the HF generator and a coupling wall 30 'with offset coupling openings 33.
  • the HF power is transmitted to the coupling openings 33, which can also have a structure as in FIG second distributor space 40 ′′.
  • the RF power is coupled into the actual stripline laser from there via a second coupling wall 30 ′′ with coupling openings 34.
  • a further equalization of the power over the longitudinal extent of the laser can be achieved by the two adjoining distribution spaces 40 and 40 M , to which in particular the differently designed coupling openings 33 and 34 contribute. It is also possible to influence the waveguide structures by means of webs 41 or 42, which may be movable, in order to realize additional possible variations.
  • 10 and 20 mean the wall parts with their opposing surfaces 11 and 21 corresponding to FIG. 2.
  • a distribution space 40 is in turn assigned to the coupling space formed in this way, but in this embodiment is located below the coupling space formed by the wall parts 10 and 20 and adjoins this in the form of a rectangular waveguide 40.
  • a magnetron 46 is arranged directly on the base of the waveguide 40.
  • the RF power is transmitted via cutouts 51 and 52 at the end regions of the boundary wall 14, which are followed by parts 28 and 29 which are dielectric on both sides
  • the effect of the coupling walls 30 and 30 'of FIG. 3 is connected to the cutouts 51 and 52, respectively.
  • a magnetic field can be coupled on both sides from the single distribution space 40 into the coupling space results in largely constant field strength without waste.
  • the laser-active gas plasma can be maintained uniformly between the surfaces 11 and 21 by the predetermined field strength profile over the cross section of the coupling space according to one of FIGS. 2 to 5.
  • the plate spacing can be reduced to 30 ⁇ m, for example, without the boundary layers having a disruptive effect.
  • the gas pressure can vary depending on requirements are between 10 mbar and a few bar.
  • a gas mixture C0 2 : N 2 _He in a ratio of 20:20:60 is provided as the laser gas, for example.
  • FIG. 4 shows an arrangement of the coupling space according to FIG. 2, in which the two wall parts 10 and 20 with their opposing surfaces have a contour 12 and 22 in the transverse direction.
  • This contour can for example each form a circular section.
  • 5 shows a section perpendicular to FIG. 4, in which the wall parts 10 and 20 with their opposite surfaces form a longitudinal contour 12 ′ or 22 ′, which can likewise have a predetermined function.
  • the structures according to FIGS. 8 or 9 combine with the structure according to FIG. 10 in such a way that longitudinal structures are present in the central region of the wall parts 10 and 20 and transverse structures are present in the outer region at least on one of the surfaces.
  • These structures can also be combined at the same time in the case of transverse or longitudinal contours of the opposing surfaces 11 and 21 of the wall parts 10 and 20 which are designed in accordance with FIGS. 6 and 7.
  • HF power in the gigahertz range can be fed into the laser arrangements according to FIGS. 2 to 5 with possible modifications according to FIGS. 6 to 10, since waveguide-like structures for microwaves are formed.
  • the RF power is generated, for example, by means of a coupling pin or a coupling loop of a known coaxial line transition or directly using a coupling pin of a magnetron, for example for
  • Laser arrangements in which new gas is not continuously fed into the plasma are usually provided with a gas supply, the volume of which is, for example, 100 times the volume of gas excited to the plasma state.
  • the coupling space outside the mutually opposing surfaces 11 and 21 and the distributor space 40, which are to be sealed in a vacuum-tight manner, can advantageously be used here as storage space. Additional containers are then unnecessary. 5
  • the coupling walls 30 or 30 'or 30'', which are in the laser gas are located the occurring electric field strength must be sufficiently far below the ignition field strength of the laser gas. This can always be done.
  • Coupling means which emerge from the coupling wall for example webs and / or loops, can be used particularly advantageously here.
  • these devices require a certain temperature to perform their function, they can be heated in the arrangement by a small proportion of the HF power or heated for natural convection of the rising gas heated in the plasma.
  • a certain difficulty which affects many flat discharge paths with a small electrode spacing, lies in the fact that the ignition field strength is substantially higher than the focal field strength. It may therefore be necessary to provide auxiliary devices to ignite the laser plasma.
  • Such an auxiliary device can consist, for example, of a spark gap which is arranged in the vicinity of the two opposing surfaces 11 and 21 and can be ignited from the outside via a vacuum-tight, insulated electrical connection.
  • this UV source can be kept low, in particular if, after the laser plasma has been ignited, the electric field strength in this tube drops below the focal field strength.
  • the overall result is a stripline laser with increased power yield, the excitation power of which is generated and supplied comparatively easily and inexpensively and which is nevertheless designed to be so compact that it can be handled by a robot or other devices in automated production.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

Les lasers à gaz dans lesquels le gaz laser est excité par l'apport d'une énergie de haute fréquence sont connus. Le laser à gaz décrit présente les caractéristiques suivantes: il s'agit d'un laser à conducteur allongé, dans lequel la chambre (5) de plasma actif est agencée entre des faces (11, 21) mutuellement opposées de deux parties de paroi (10, 20) et présente une hauteur réduite; les parties de paroi (10, 20) forment des éléments d'une chambre de couplage ayant au moins une paroi de couplage (30) reliée à au moins une chambre de distribution (40, 50). L'énergie de haute fréquence est apportée à travers la paroi de couplage (30) et active de manière voulue le plasma gazeux sur toute sa longueur. L'énergie de haute fréquence d'excitation du plasma se situe dans le domaine des gigahertz; on peut utiliser à cet effet par exemple un magnétron.
EP90905496A 1989-04-17 1990-04-10 Laser a gas, notamment laser au co2 Ceased EP0468986A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3912568 1989-04-17
DE3912568A DE3912568A1 (de) 1989-04-17 1989-04-17 Gas-laser, insbesondere co(pfeil abwaerts)2(pfeil abwaerts)-laser

Publications (1)

Publication Number Publication Date
EP0468986A1 true EP0468986A1 (fr) 1992-02-05

Family

ID=6378846

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90905496A Ceased EP0468986A1 (fr) 1989-04-17 1990-04-10 Laser a gas, notamment laser au co2

Country Status (5)

Country Link
US (1) US5224117A (fr)
EP (1) EP0468986A1 (fr)
JP (1) JPH04504782A (fr)
DE (1) DE3912568A1 (fr)
WO (1) WO1990013160A1 (fr)

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US5379317A (en) * 1993-05-28 1995-01-03 California Institute Of Technology Microwave-excited slab waveguide laser with all metal sealed cavity
US5661746A (en) * 1995-10-17 1997-08-26 Universal Laser Syatems, Inc. Free-space gas slab laser
JPH09205241A (ja) * 1996-01-25 1997-08-05 Matsushita Electric Ind Co Ltd マイクロ波励起ガスレーザ発振器
US6331994B1 (en) * 1996-07-19 2001-12-18 Canon Kabushiki Kaisha Excimer laser oscillation apparatus and method, excimer laser exposure apparatus, and laser tube
US5881087A (en) * 1997-04-30 1999-03-09 Universal Laser Systems, Inc. Gas laser tube design
US5901167A (en) * 1997-04-30 1999-05-04 Universal Laser Systems, Inc. Air cooled gas laser
US5867517A (en) * 1997-04-30 1999-02-02 Universal Laser Systems, Inc. Integrated gas laser RF feed and fill apparatus and method
US6804285B2 (en) 1998-10-29 2004-10-12 Canon Kabushiki Kaisha Gas supply path structure for a gas laser
EP1026796B1 (fr) * 1999-02-01 2005-11-16 Tadahiro Ohmi Dispositif laser, appareil d'exposition l'utilisant et méthode de fabrication
JP4256520B2 (ja) * 1999-02-26 2009-04-22 忠弘 大見 レーザ発振装置、露光装置及びデバイスの製造方法
JP2000312045A (ja) * 1999-02-26 2000-11-07 Tadahiro Omi レーザ発振装置、露光装置及びデバイスの製造方法
JP4303350B2 (ja) * 1999-03-26 2009-07-29 忠弘 大見 レーザ発振装置、露光装置及びデバイスの製造方法
WO2002075870A2 (fr) * 2001-03-17 2002-09-26 Peter Vitruk Guide d'ondes a nervure tronquee pour excitation de laser a gaz entierement metallique
EP1361437A1 (fr) * 2002-05-07 2003-11-12 Centre National De La Recherche Scientifique (Cnrs) Un nouveau marqueur biologique pour des tumeurs et des méthodes pour la détection de phénotype cancéreux ou non-cancéreux de cellules
US7497922B2 (en) * 2002-05-08 2009-03-03 Btu International, Inc. Plasma-assisted gas production
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US7498066B2 (en) * 2002-05-08 2009-03-03 Btu International Inc. Plasma-assisted enhanced coating
US7445817B2 (en) * 2002-05-08 2008-11-04 Btu International Inc. Plasma-assisted formation of carbon structures
US7504061B2 (en) * 2002-05-08 2009-03-17 Leonhard Kurz Gmbh & Co., Kg Method of decorating large plastic 3D objects
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US20060062930A1 (en) * 2002-05-08 2006-03-23 Devendra Kumar Plasma-assisted carburizing
US7494904B2 (en) * 2002-05-08 2009-02-24 Btu International, Inc. Plasma-assisted doping
US20060057016A1 (en) * 2002-05-08 2006-03-16 Devendra Kumar Plasma-assisted sintering
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US7465362B2 (en) * 2002-05-08 2008-12-16 Btu International, Inc. Plasma-assisted nitrogen surface-treatment
US7560657B2 (en) * 2002-05-08 2009-07-14 Btu International Inc. Plasma-assisted processing in a manufacturing line
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JP2007295003A (ja) * 2007-07-23 2007-11-08 Tadahiro Omi エキシマレーザ発振装置及び発振方法、露光装置ならびにレーザ管

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Also Published As

Publication number Publication date
JPH04504782A (ja) 1992-08-20
WO1990013160A1 (fr) 1990-11-01
DE3912568A1 (de) 1990-10-18
US5224117A (en) 1993-06-29

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