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
  • H01S3/02—Constructional details
  • H01S3/03—Constructional details of gas laser discharge tubes
  • H01S3/034—Optical devices within, or forming part of, the tube, e.g. windows, mirrors
  • H01S3/0343—Aerodynamic windows
• • 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
  • H01S3/02—Constructional details
  • H01S3/03—Constructional details of gas laser discharge tubes
  • H01S3/034—Optical devices within, or forming part of, the tube, e.g. windows, mirrors
  • H01S3/0346—Protection of windows or mirrors against deleterious effects

Definitions

• the invention relates to an outcoupling device for laser beams emerging from a laser cavity with an aerodynamic window, comprising a jet nozzle and a diffuser located opposite it for generating a free jet extending from the jet nozzle to the diffuser and covering an outcoupling opening.
• a material window When decoupling laser radiation from a laser cavity, a material window has hitherto been used in gas lasers, which was necessary to shield the laser cavity, which typically has a pressure level of approximately 100 bar, from the ambient atmosphere. Glasses suitable for the respective laser radiation, such as e.g. ZnSe or KC1. used, these windows are arranged either perpendicular to the beam direction or at a Brewster angle inclined to the beam direction.
• thermal runaway Such material windows always absorb a fraction of the irradiated laser power and therefore heat up. At low laser powers, this heating is negligible, but problems occur with high-power lasers for industrial use, especially with C0 2 radiation lasers, since the heating on the one hand results in a change in the absorption behavior of the window material, as a result of which the latter heats up even more and thus leads to a failure of the window material referred to as "thermal runaway".
• the heating results in a deformation of the outcoupling window, which is referred to as "thermal lensing ' r , and in a reduction in the beam quality and a deterioration in the focusability of the outcoupled laser beam, which is disadvantageous especially when lasers are used for material processing.
• the heat load may be so high that the window material is destroyed.
• the object of the invention is to improve a decoupling device of the generic type in such a way that a rational and energy-saving operation of a gas laser is possible.
• this object is achieved in that the decoupling opening on the cavity side can be covered in a pressure-tight manner by a material window and that the material window can be moved away from it after the aerodynamic window has been opened to release the decoupling opening.
• Such a locking device can consist, for example, of a manually operable lock which only prevents the material window from being moved thoughtlessly and for this purpose requires a separate release of the lock.
• a locking device it is far safer if the locking device is effective when the aerodynamic window is not approached, so that it is always ensured that the material window can only be moved away if the aerodynamic window is able to prevent air from entering the laser cavity.
• Various options are conceivable for a query as to when the aerodynamic window approached is fully effective and prevents air from entering the laser cavity.
• pressure sensors can be provided on the aerodynamic window itself, by means of which a perfect function can be ascertained beyond doubt.
• the aerodynamic window when it is fully effective, causes a pressure reduction on the cavity side, which leads to an equilibrium pressure which exactly matches the pressure in the laser cavity, since the aerodynamic Window can only maintain such pressure.
• the aerodynamic window As soon as there is still a different pressure on both sides of the material window, there is still no equilibrium pressure on the side of the aerodynamic window, which would allow the material window to be moved away without disturbing the laser activity and to leave the shielding of the laser cavity from the ambient air to the aerodynamic window.
• the material window can be moved away in a simple manner, it is advantageous if the material window is accommodated in a movable guide.
• the guide prefferably includes the locking device described above. Especially if the intention is not to actuate the material window together with the guide manually, but rather to provide automatic actuation if possible, it is necessary for the guide to have an actuating device.
• the decoupling device according to the invention with automatic actuation provides a control unit for the actuating device which causes the material window to move away from the decoupling opening at approximately the same pressure on both sides of the material window.
• control unit to record the pressures on both sides of the material window is to provide a first pressure measuring device between the aerodynamic window and the material window. This can be used to compare the measured pressure with a known pressure in the laser cavity which is predetermined by the laser conditions, so that the control unit can already work with a pressure measuring device.
• the material window should be arranged relative to the beam direction of the decoupled beam.
• the simplest embodiment provides for the material window to be arranged perpendicular to the beam direction. In order to avoid reflection losses, however, it is favorable to arrange the material window at a Brewster angle to the beam direction.
• the energy consumption and also the noise pollution caused by the aerodynamic window are related to the cross section of the decoupling opening, which must be covered by the free beam, in order to ensure perfect shielding of the laser cavity from the ambient air. For this reason, it is also advantageous to keep the decoupling opening as small as possible.
• optically unstable resonators are generally used, the decoupled laser beam of which has an intensity distribution which is annular around a beam direction, so that an intensity in the middle of the laser beam is close to 0. This has the consequence that the coupling-out opening has to be kept relatively large.
• the coupling-out opening is preceded by a beam-combining optics, so that the entire cross-section of the coupling-out opening is used for coupling out laser intensity if possible.
• the beam-combining optics are telescopic optics, it being favorable for a beam characteristic if a second telescope mirror is arranged coaxially with a first telescope mirror and if the first telescope mirror has a central passage for one that starts from the second telescope mirror Coupling beam has.
• FIG. 3 an enlarged sectional view corresponding to FIG. 2 of a second exemplary embodiment of the decoupling device according to the invention.
• a gas laser designated as a whole by 10 with a decoupling device according to the invention shows in detail a gas channel 12 comprising a bottom part 14, two opposite side parts 16 and 18 and a cover 20.
• This gas channel 12 is excited by molecules 22 in the direction of arrow 22
• Laser gases e.g. C0 2 , flows through.
• a side channel 24 which is' on one side into an opening 26 in the so ⁇ part 16 opens the gas channel 12 and is closed on another side with a rear wall 28th
• a laser cavity Extending transversely to the gas channel 12 and in the longitudinal direction of the side channel 24 is a laser cavity, designated as a whole by 30, with a resonator axis 32, to which a first resonator mirror 34 is concentric on the side part 18 of the gas channel 12 and on the rear wall 28 of the side channel 24 a second resonator mirror 36 are arranged.
• the two resonator mirrors 34 and 36 oriented transversely to the resonator axis 32 form an optically unstable resonator, the first resonator mirror 34 being concave and the second resonator mirror 36 being convex, so that a laser beam reflected back and forth between them is increased ⁇ the number of reflections increasingly away from the resonator axis 32.
• the laser beam incident on the coupling-out mirror 38 to the side of the opening 40 also referred to as the coupling-out beam 42
• the coupling-out beam 42 is in an area around the opening 40 at an angle of 90 °
• Resonator axis 32 is reflected into an outcoupling channel 44 running at an angle of 90 ° to the side channel 24, the outcoupling beam 42 in the outcoupling channel 44 having an annular intensity distribution with respect to a beam direction 46.
• the decoupling channel 44 establishes the connection between the laser cavity 30 and the environment and must therefore be designed in such a way that the ambient air, normally at a pressure of approximately 1000 r ⁇ ar, does not penetrate into the laser cavity, in which a pressure of usually there is about 100 mbar.
• a first side part 48, a second side part 50, a bottom 52 and a cover 54 having a coupling-out channel 44 are provided with an aerodynamic window, designated as a whole by 56, which has an outer jet nozzle 58 which extends over an entire width of the first side part 48 Gas connection 60 and one of these jet nozzle 58 opposite, arranged in the second side part 50 and also extending over its entire width comprises diffuser 62.
• a free jet is generated by the jet nozzle 58, which overlaps a decoupling opening 64 corresponding to a cross section of the decoupling channel 44 and enters the diffuser 62.
• the gas this free jet may end of the diffuser 62, that is on the outside of the second side part 50 again will be contained or flow out freely to the environment.
• a window unit 66 with a material window 68 is connected upstream.
• This material window 68 is accommodated in a window frame 70, which in turn is slidably mounted in a slot-shaped recess 72 which extends from an outer side of the first side part 48 through it, via the coupling channel 44 into the second side part 50.
• the window frame 70 positions the material window 68 approximately concentrically to the beam direction 46, so that the outcoupling beam 42 can pass through it.
• the window frame 70 lies in the. slot-shaped recess 72 next to the outcoupling channel 44, so that the outcoupling beam 42 no longer passes through the material window 68.
• seals 74 are inserted into the window frame 70 in the areas in which the latter contacts the slot-shaped recess 72. which seal the window frame around the decoupling channel 44 with respect to the first side part 48, the second side part 50, the bottom 52 and the cover 54 of the decoupling channel 44.
• the material window 68 is also inserted sealingly into the window frame.
• the window frame 70 In order for the window frame 70 to be automatically displaceable between its inserted and its pulled-out position, it is connected to an actuating device 78 via a push rod 76 which extends from the outside into the slot-shaped recess 72 and which is, for example, on a. on. the first side part 48 held support plate 80 is mounted.
• a first pressure sensor 82 is provided in the second side part 50 between the material window 68 and the aerodynamic window 56, this pressure sensor 82 in a recess 84 opening into the coupling channel 44 is held. Furthermore, a second pressure sensor 86 is provided on the cavity side in front of the material window 68, for example in the side channel 24j.
• the two pressure sensors 84 and 86 are connected via two lines 88 and 90 to a control unit 92 which controls the actuating device 78 as a function of the pressures measured by the pressure sensors 82 and 86.
• the decoupling device according to the invention works as follows:
• the window mount 70 is first moved into its inserted position by the actuating device 78, in which it seals the laser cavity 30 in a pressure-tight manner with respect to the surroundings.
• the laser cavity can thus now be brought to the required pressure of approximately 100 rabar, so that when the gas channel 12 is flowed through accordingly with excited laser gas, the laser activity in the laser cavity 30 begins, the laser, for example, for performing Adjustment work is not carried out at full power. Under these conditions, the intensity in the outcoupling beam 42 is not so great, so that no problems occur when the outcoupling beam 42 passes through the material window 68.
• the aerodynamic becomes before an increase in laser power Moved to window 56 so that the free jet covers the decoupling opening 64 and leads to a reduction in the pressure on the cavity side in a region of the decoupling channel 44 lying between the decoupling opening 64 and the material window 68.
• the aerodynamic window 56 must be designed such that the pressure generated by this cavity side corresponds to the pressure desired in the laser cavity 30.
• the pressures on both sides of the material window 68 are measured by the pressure sensors 82 and 86 and compared with one another in the control unit 92. As soon as the aerodynamic window 56 has caused a decrease in the pressure in the laser cavity 30 in the area of the pressure sensor 82, the control unit 92 recognizes that the material window 68 can now be pulled out and issues a corresponding command to it Actuator 78.
• the laser cavity 30 is only shielded from the ambient pressure by the aerodynamic window 56.
• the laser can thus be operated at full power without the difficulties caused by the material window 68 occurring.
• the window unit 66 is modified in that it has a socket body 100 which, in its inserted position, has a recess 102 which extends coaxially to the beam direction 46 and has at least the same cross section as the outcoupling channel 44.
• a first Brewster window 104 and a second Brewster window 106 are inserted, which are inclined opposite to each other by a Brewster angle with respect to the beam direction, so that a through the first Brewster window 104 resulting offset of the coupling beam 42 through the second Brewster window 106 can be compensated.
• the two Brewster windows 104 and 106 are sealingly inserted into the socket body 100 and the latter is also sealed around the coupling channel 44 by the seals 74.
• a telescope optical system which comprises a concavely curved first telescope mirror 108 arranged in the outcoupling channel 44 in front of the window unit 66.
• This first telescope mirror 108 reflects the outcoupling beam 42 back in the direction of the outcoupling mirror 38, which according to the invention is provided with a second opening 110 arranged perpendicular to the first opening 40, so that the reflected back outcoupling beam 42 enters the second opening 110 and strikes a second telescopic mirror 112, which is held in this or on the side channel 24 and which is adjustable in such a convex manner that it generates an outcoupling beam 42 *, which also has an annular intensity distribution around the beam direction 46, the However, the diameter is smaller compared to the outcoupling beam 42.
• the cross section of the region 44 'of the coupling channel 44 which adjoins the first telescope mirror 108 in the beam direction can thus be selected to be smaller, so that the coupling opening 64' also. ⁇ one. has a smaller cross section than in the first embodiment.
• the aerodynamic window 56 can be dimensioned smaller overall, so that at least a lower gas consumption results in the generation of the free jet and, as a rule, the aerodynamic window 56 is also more tight and less susceptible to interference.

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

Applications Claiming Priority (2)

Publications (1)

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ID=6314375

Family Applications (1)

Country Status (2)

Citations (5)

Family Cites Families (3)

• 1986
  • 1986-11-20 DE DE19863639671 patent/DE3639671A1/de active Granted
• 1987
  • 1987-11-15 WO PCT/EP1987/000712 patent/WO1988004110A1/de unknown

Patent Citations (5)

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