WO1989010647A1 - Device for generating laser pulses of variable duration - Google Patents

Device for generating laser pulses of variable duration Download PDF

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Publication number
WO1989010647A1
WO1989010647A1 PCT/EP1989/000431 EP8900431W WO8910647A1 WO 1989010647 A1 WO1989010647 A1 WO 1989010647A1 EP 8900431 W EP8900431 W EP 8900431W WO 8910647 A1 WO8910647 A1 WO 8910647A1
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Prior art keywords
neodymium
laser
yag
pumped
pulse
Prior art date
Application number
PCT/EP1989/000431
Other languages
German (de)
French (fr)
Inventor
Reinhardt Thyzel
Klaus Irion
Paul Sarkis
Original Assignee
Karl Storz Gmbh & Co.
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 Karl Storz Gmbh & Co. filed Critical Karl Storz Gmbh & Co.
Publication of WO1989010647A1 publication Critical patent/WO1989010647A1/en

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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
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A61B18/22—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
    • A61B18/26—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor for producing a shock wave, e.g. laser lithotripsy

Definitions

  • the invention relates to a device for generating laser pulses of adjustable duration with a neodymium YAG laser according to the preamble of patent claim 1.
  • Lasers in which a neodymium-YAG crystal is used as a laser medium are known in many different designs.
  • Pulsed neodymium-YAG lasers which are operated in the "Q-Switch or Mode-Lock" operating modes, find, among other things, a variety of applications in medicine, for example for the treatment of the front eye media, for crushing concrements in the human body such as kidney stones caused by laser-induced shock waves, etc.
  • Known pulsed neodymium YAG lasers are, for example, the MQL10, OPL3F or OPL4 lasers from Aesculap-Meditec GmbH or the lasers of the SL400 / 800 series from Spectron Laser Systems, LTD.
  • Q-switch neodymium-YAG lasers are used according to the prior art. turns. These lasers are pumped with flash lamps and typically have a pulse width of 5 to 20 ns. With the pulse energies of typically 100 mJ and more required for laser-induced shock wave lithotripsy, such a short pulse duration results in a comparatively high pulse power.
  • dash-neodymium-YAG lasers are now known, i.e. Neodymium YAG lasers pumped continuously, for example, with a noble gas arc lamp, which thereby emit laser light not in the form of pulses but in the form of a "continuous line".
  • Known continuous wave neodymium YAG lasers are, for example, the lasers of the SL500 / 900 series from the already mentioned company Spectron Laser Systems.
  • the invention is based on the object of specifying a neodymium-YAG laser which, in the case of comparatively large pulse energies such as, inter alia, are required for shock wave-induced laser lithotripsy, have pulse widths and thus pulse powers that do not damage an optical fiber even when the coupling in the area of the light entry surface is not optimal.
  • a neodymium YAG laser with a corresponding pulse width can be created by starting from a device for generating laser pulses according to the preamble of claim 1, that is, a so-called continuous wave neodymium YAG laser, in the beam path of which a switchable optical closure serving as a Q switch is arranged.
  • the impulse power which is unsatisfactory in a generic device for generating laser pulses, for example for crushing kidney stones or gallstones, is increased according to the invention in that in the beam path of the continuous wave neodymium YAG laser after the shutter and outside the resonator, a second neodymium YAG crystal is arranged, which is pumped in pulses.
  • This second neodymium-YAG crystal serves as an optical amplifier for the light pulses, which amplifies the light pulses to the desired power.
  • the amplification of the laser light of the actual Nd-YAG laser by a further neodymium-YAG crystal is particularly efficient.
  • the device according to the invention can be switched over to the function of a “normal” continuous wave neodymium YAG laser, ie a continuously operating neodymium YAG laser, on account of this design of the optical amplifier without removing optical components from the beam path: for this purpose it is only necessary that the optical shutter is "permanently opened” and that there is no excitation of the additional neodymium-YAG crystal which is present in the non-excited state for laser light the emission wavelength of Neody-YAG crystals is transparent.
  • the "normal” beam of a continuous wave neodymium YAG laser thus emerges from the device according to the invention (claim 3).
  • the second Nd-YAG crystal is "optically short-circuited" by means of a corresponding arrangement, so the beam of the continuous-wave Nd-YAG laser "is guided around the second crystal” and thus through the second Nd-YAG crystal is not weakened.
  • the pulse duration (defined in the usual way), preferably between 100 ns and 300 ns at typical pulse energies of 60 J to 90 mJ and more (“Claim 6).
  • the pulse duration defined in the usual way
  • typical pulse energies 60 J to 90 mJ and more
  • the neodymium-YAG crystal serving as an optical amplifier is pumped with a flash lamp, the triggering of which is synchronized with the opening of the closure.
  • the amplification ratio of the "optical amplifier” can thus be set within comparatively large limits by appropriately controlling the duration and the power of the flash pulse of the flash lamp.
  • optical closure used as a "quality switch” is designed as an acousto-optical modulator (claim 4).
  • the continuous wave neodymium YAG laser can be designed in a manner known per se.
  • the continuous wave neodymium YAG laser reference is made, for example, to the already mentioned continuous wave laser SL500 / 900 from Spectron Lasers Systems.
  • the continuous wave neodymium YAG laser can be pumped by means of an inert gas high pressure lamp, for example a xenon or krypton lamp (claim 5).
  • an inert gas high pressure lamp for example a xenon or krypton lamp (claim 5).
  • the device according to the invention for generating laser pulses of adjustable duration and variable pulse energy can of course be used for any purpose, for example in material processing, scientific research or measuring and testing technology. Particularly advantageous uses of the devices according to the invention are characterized in claims 7f.
  • FIG. 1 shows an embodiment of a device according to the invention.
  • the device according to the invention has a continuous wave neodymium YAG laser which is known per se and which is generally designated by the reference number 1.
  • the continuous wave laser 1 essentially consists of a neodymium-YAG crystal 2, which is pumped by an inert gas high-pressure lamp 8, for example a xenon or krypton high-pressure lamp.
  • the continuous wave laser 1 also has resonators 3 and 22, within which an acousto-optical modulator 4, which serves as a quality switch, is arranged in the beam path 9 of the laser 1.
  • the acousto-optical modulator 4 opens and closes the beam path 9 of the laser " 1.
  • the flashing of the flash lamp 7 also controls the control unit 5 synchronously with the opening processes of the acousto-optical modulator 4.
  • the neodymium-YAG crystal 6 pumped with a flash lamp 7 thus acts as an optical amplifier for the laser pulses emerging from the "pulsed continuous-wave neodymium-YAG laser" 1, provided that the neodymium-YAG crystal 6 is at the rear passing through the laser pulse is in a sufficiently excited state.
  • the neodymium-YAG crystal 6 is largely transparent to the light from the laser 1 when the neodymium-YAG crystal 6 is “not excited”.
  • the device according to the invention thus has the advantage that, on the one hand, it provides laser pulses of adjustable duration and adjustable pulse energy.
  • the pulse duration (time interval between half the maximum energy on the "rising and falling side") can typically be varied between less than 100 ns and more than 300 ns.
  • the pulse repetition frequency can typically be set between 1 Hz and 100 Hz.
  • the pulse energy is typically variable between less than 50 mJ and more than 500 mJ.
  • a device which emits laser pulses, the pulse duration and pulse energy of which can be set over a wide range at a high pulse repetition frequency.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biomedical Technology (AREA)
  • Otolaryngology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Plasma & Fusion (AREA)
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  • Molecular Biology (AREA)
  • Animal Behavior & Ethology (AREA)
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Abstract

A device for generating laser pulses of a variable duration comprises a resonator in which are arranged a first continuously pumped neodymium-YAG crystal and a switchable optical seal which functions as a Q-switch. To increase the pulse power in the beam path of the continuous-wave neodymium-YAG laser, a second neodymium-YAG crystal, which is pumped in pulses, is arranged after the resonator and outside the seal.

Description

Vorrichtung zur Erzeugung von Laserimpulsen einstellbarer Device for generating laser pulses adjustable
DauerDuration
B e s c h r e i b u n gDescription
Technisches GebietTechnical field
Die Erfindung bezieht sich auf eine Vorrichtung zur Erzeu¬ gung von Laserimpulsen einstellbarer Dauer mit einem Neo¬ dym-YAG-Laser gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to a device for generating laser pulses of adjustable duration with a neodymium YAG laser according to the preamble of patent claim 1.
Stand der TechnikState of the art
Laser, bei denen ein Neodym-YAG-Kristall als Lasermedium verwendet wird, sind in vielfältigen Ausführungen bekannt.Lasers in which a neodymium-YAG crystal is used as a laser medium are known in many different designs.
Gepulste Neodym-YAG-Laser, die in den Betriebsarten "Q- Switch oder Mode-Lock" betrieben werden, finden unter anderem vielfältige Anwendungen in der Medizin, beispiels¬ weise zur Behandlung der vorderen Augenmedien, zur Zer¬ trümmerung von Konkrementen im menschlichen Körper, wie Nierensteinen durch Laser-induzierte Stoßwellen usw.Pulsed neodymium-YAG lasers, which are operated in the "Q-Switch or Mode-Lock" operating modes, find, among other things, a variety of applications in medicine, for example for the treatment of the front eye media, for crushing concrements in the human body such as kidney stones caused by laser-induced shock waves, etc.
Bekannte gepulste Neodym-YAG-Laser sind beispielsweise die Laser MQL10, OPL3F oder OPL4 der Aesculap-Meditec GmbH oder die Laser der Serie SL400/800 der Fa Spectron Laser Systems, LTD.Known pulsed neodymium YAG lasers are, for example, the MQL10, OPL3F or OPL4 lasers from Aesculap-Meditec GmbH or the lasers of the SL400 / 800 series from Spectron Laser Systems, LTD.
Bei verschiedenen Anwendungen derartiger Neodym-YAG-Laser und insbesondere bei der Laser-induzierten Stoßwellen- Lithotripsie tritt nun folgendes Problem auf:The following problem now arises in various applications of such neodymium-YAG lasers and in particular in laser-induced shock wave lithotripsy:
Bei der Laser-induzierten Stoßwellen-Lithotripsie werden nach dem Stand der Technik Q-Switch Neodym-YAG-Laser ver- wendet. Diese Laser werden mit Blitzlampen gepumpt und haben typischerweise eine Impulsbreite von 5 bis 20 ns. Bei den zur Laser-induzierten Stoßwellen-Lithotripsie benötigten Impuls-energien von typischerweise 100 mJ und mehr ergibt sich bei derart kurzen Impulsdauern eine ver¬ gleichsweise hohe Impulsieistung.In laser-induced shock wave lithotripsy, Q-switch neodymium-YAG lasers are used according to the prior art. turns. These lasers are pumped with flash lamps and typically have a pulse width of 5 to 20 ns. With the pulse energies of typically 100 mJ and more required for laser-induced shock wave lithotripsy, such a short pulse duration results in a comparatively high pulse power.
Hohe Impulsleistungen können aber insbesondere dann, wenn zum Führen des Laserstrahls eine vergleichsweise dünne Lichtleitfaser verwendet wird, wie dies beispielsweise in Endoskopen erforderlich ist, zu Problemen führen; insbe¬ sondere kann bei einer "schlechten Einkoppelung" des La¬ serstrahls die Lichtleitfaser in vergleichsweise kurzer Zeit im Bereich der Licht-Eintrittsfläche beschädigt wer¬ den.However, high pulse powers can lead to problems in particular if a comparatively thin optical fiber is used to guide the laser beam, as is required, for example, in endoscopes; in particular, if the laser beam is "poorly coupled", the optical fiber in the area of the light entry surface can be damaged in a comparatively short time.
Es wäre deshalb wünschenswert, Laserimpulse mit einer Energie von 50 mJ und mehr mit einer größeren Impulslänge und damit einer geringeren Impulsleistung als die bekann¬ ten gepulsten Neodym-YAG-Laser zu haben.It would therefore be desirable to have laser pulses with an energy of 50 mJ and more with a larger pulse length and thus a lower pulse power than the known pulsed neodymium YAG lasers.
Es sind nun sogenannte Daüerstrich-Neodym-YAG-Laser be¬ kannt, d.h. kontinuierlich beispielsweise mit einer Edel¬ gas-Bogenlampe gepumpte Neodym-YAG-Laser, die damit Laser¬ licht nicht in Form von Impulsen, sondern in Form eines "DauerStrichs" abgeben. Bekannte Dauerstrich-Neodym-YAG- Laser sind beispielsweise die Laser der SL500/900-Serie der bereits genannten Fa. Spectron Laser Systems.So-called dash-neodymium-YAG lasers are now known, i.e. Neodymium YAG lasers pumped continuously, for example, with a noble gas arc lamp, which thereby emit laser light not in the form of pulses but in the form of a "continuous line". Known continuous wave neodymium YAG lasers are, for example, the lasers of the SL500 / 900 series from the already mentioned company Spectron Laser Systems.
Auf die vorgenannten bekannten Impuls- bzw. Dauerstrich- Neodym-YAG-Laser sowie die jeweiligen Firmendruckschriften wird im übrigen zur Offenbarung aller hier nicht näher erläuterten Begriffe ausdrücklich Bezug genommen. Es ist zwar möglich, im Strahlengang eines sogenannten Dauerstrich-Neodym-YAG-Laser einen optischen Verschluß anzuordnen, und so den Laserstrahl "zu pulsen". Hierdurch könnte man - je nach Ausbildung des optischen Verschlusses - nahezu beliebige "Impulsbreiten" einstellen. Die er¬ reichbare Impulsleistung bzw. die Impulsenergie ist aber - wenn nicht ein unverhältnismäßiger Aufwand bei der Dauer¬ leistung des kontinuierlich arbeitenden Nedym-YAG-Lasers getrieben wird - vergleichsweise klein. Damit ist der Einsatz von herkömlichen "Dauerstrich-Neodym-YAG-Lasern", deren nach außen tretenden Strahlengang ein Verschluß öffnet und schließt, beispielsweise zur Laser-Lithotrispie unter wirtschaftlichen Gesichtspunkten nicht vertretbar.Reference is expressly made to the aforementioned known pulse or continuous wave neodymium YAG laser and the respective company publications for the disclosure of all terms that are not explained in more detail here. It is indeed possible to arrange an optical shutter in the beam path of a so-called continuous wave neodymium YAG laser, and thus "pulse" the laser beam. This could - depending on the design of the optical shutter - set almost any "pulse widths". The achievable pulse power or the pulse energy is comparatively small - unless a disproportionate effort is made in the continuous power of the continuously operating Nedym-YAG laser. The use of conventional "continuous-wave neodymium-YAG lasers", whose outward beam path opens and closes a shutter, for example for laser lithotrispy, is not economically justifiable.
Darstellung der ErfindungPresentation of the invention
Der Erfindung liegt die Aufgabe zugrunde, einen Neodym- YAG-Laser anzugeben, der bei vergleichsweise großen Im¬ pulsenergien, wie sie u.a. zur Stoßwellen-induzierten Laser-Lithotripsie benötigt werden, Impulsbreiten und damit Impulsleistungen aufweist, die eine Lichtleitfaser auch bei nicht optimaler Ankoppelung im Bereich der Licht- Eintrittsfläche nicht beschädigen.The invention is based on the object of specifying a neodymium-YAG laser which, in the case of comparatively large pulse energies such as, inter alia, are required for shock wave-induced laser lithotripsy, have pulse widths and thus pulse powers that do not damage an optical fiber even when the coupling in the area of the light entry surface is not optimal.
Eine erfindungsgemäße Lösung dieser Aufgabe ist im An¬ spruch 1 angegeben.An inventive solution to this problem is specified in claim 1.
Erfindungsgemäß ist erkannt worden, daß bei Impuisenergien von bis zu 500 J Impulsdauern in der Größenordnung von 50 ns bis 500 ns notwendig sind, damit auch bei einer nicht optimalen "Ankoppelung" des Lasers an die Licht-Eintritts¬ fläche der Lichtleitfaser diese eine hinreichend lange Lebensdauer hat.According to the invention, it has been recognized that with pulse energies of up to 500 J pulse durations of the order of 50 ns to 500 ns are necessary, so that even if the laser is not optimally "coupled" to the light entry surface of the optical fiber, the latter is sufficiently long Has lifespan.
Ein Neodym-YAG-Laser mit einer entsprechenden Impulsbreite kann dadurch geschaffen werden, daß von einer Vorrichtung zur Erzeugung von Laserimpulsen gemäß dem Oberbegriff des Patentanspruchs 1, also von einem sogenannten Dauerstrich- Neodym-YAG-Laser ausgegangen wird, in dessen Strahlengang ein als Güteschalter dienender schaltbarer optischer Ver¬ schluß angeordnet ist.A neodymium YAG laser with a corresponding pulse width can be created by starting from a device for generating laser pulses according to the preamble of claim 1, that is, a so-called continuous wave neodymium YAG laser, in the beam path of which a switchable optical closure serving as a Q switch is arranged.
Die bei einer gattungsgemäßen Vorrichtung zur Erzeugung von Laserimpulsen beispielsweise zur Zertrümmerung von Nierensteinen oder Gallensteinen unbefriedigende Impuls¬ leistung wird erfindungsgemäß dadurch erhöht, daß im Strahlengang des Dauerstrich-Neodym-YAG-Lasers nach dem Verschluß und außerhalb des Resonators ein zweiter Neodym- YAG-Kristall angeordnet ist, der pulsweise gepumpt wird.The impulse power which is unsatisfactory in a generic device for generating laser pulses, for example for crushing kidney stones or gallstones, is increased according to the invention in that in the beam path of the continuous wave neodymium YAG laser after the shutter and outside the resonator, a second neodymium YAG crystal is arranged, which is pumped in pulses.
Dieser zweite Neodym-YAG-Kristall, dem keine Resonator- Spiegel zugeordnet sind, dient als optischer Verstärker für die Lichtimpulse, der die Lichtimpulse auf die ge¬ wünschte Leistung verstärkt. Diese erfindungsgemäße Aus¬ bildung hat eine Reihe von Vorteilen:This second neodymium-YAG crystal, to which no resonator mirrors are assigned, serves as an optical amplifier for the light pulses, which amplifies the light pulses to the desired power. This training according to the invention has a number of advantages:
Zum einen ist die Verstärkung des Laserlichts des eigent¬ lichen Nd-YAG-Lasers durch einen weiteren Neodym-YAG- Kristall besonders effizient.On the one hand, the amplification of the laser light of the actual Nd-YAG laser by a further neodymium-YAG crystal is particularly efficient.
Vor allem aber ist die e findungsgemäße Vorrichtung auf¬ grund dieser Ausbildung des optischen Verstärkers ohne Entfernung optischer Komponenten aus dem Strahlengang auf die Funktion eines "normalen" Dauerstrich-Neodym-YAG- Lasers, d.h. eines kontinuierlich arbeitenden Neodym-YAG- Lasers umschaltbar: Hierzu ist es lediglich erforderlich, daß der optische Verschluß "dauernd geöffnet" wird, und keine Anregung des zusätzlichen Neodym-YAG-Kristalls er¬ folgt, der im nicht angeregten Zustand für Laserlicht mit der Emissionswellenlänge von Neody -YAG-Kristallen trans¬ parent ist. Damit tritt aus der erfindungsgemäßen Vorrich¬ tung der "normale" Strahl eines Dauerstrich-Neodym-YAG- Lasers aus (Anspruch 3) . Selbstverständlich ist es mög¬ lich, daß mittels einer entsprechenden Anordnung der zwei¬ te Nd-YAG-Kristall "optisch kurz geschlossen wird", so aφ der Strahl des Dauerstrich-Nd-YAG-Lasers "um den zweiten Kristall herumgeleitet" und damit durch den zweiten Nd- YAG-Kristall nicht abgeschwächt wird.Above all, however, the device according to the invention can be switched over to the function of a “normal” continuous wave neodymium YAG laser, ie a continuously operating neodymium YAG laser, on account of this design of the optical amplifier without removing optical components from the beam path: for this purpose it is only necessary that the optical shutter is "permanently opened" and that there is no excitation of the additional neodymium-YAG crystal which is present in the non-excited state for laser light the emission wavelength of Neody-YAG crystals is transparent. The "normal" beam of a continuous wave neodymium YAG laser thus emerges from the device according to the invention (claim 3). Of course, it is possible that the second Nd-YAG crystal is "optically short-circuited" by means of a corresponding arrangement, so the beam of the continuous-wave Nd-YAG laser "is guided around the second crystal" and thus through the second Nd-YAG crystal is not weakened.
Mit der erfindungsgemäßen Vorrichtung ist es ohne weiteres möglich, die Impulsdauer (in üblicher Weise definiert) bevorzugt zwischen 100 ns und 300 ns bei typischen Impul¬ senergien von 60 J bis 90 mJ und mehr zu variieren («An¬ spruch 6) . Selbstverständlich ist es je nach Ausbildung des Dauerstrich-Neodym-YAG-Lasers und des zusätzlichen Neodym-YAG-Kristalls aber auch möglich, wesentlich größere Impulsenergien zu erreichen.With the device according to the invention, it is readily possible to vary the pulse duration (defined in the usual way), preferably between 100 ns and 300 ns at typical pulse energies of 60 J to 90 mJ and more (“Claim 6). Of course, depending on the design of the continuous wave neodymium YAG laser and the additional neodymium YAG crystal, it is also possible to achieve significantly larger pulse energies.
Die Lösung der erfindungsgemäß gestellten Aufgabe mit einer derartigen Anordnung ist insoweit besonders überra¬ schend, da bislang nachgeordnete optische Verstärker ent¬ weder zwischen den Resonatoren des zu verstärkenden Lasers angeordnet worden sind, oder selbst als Laser mit "eige¬ nen" Resonatorspiegeln aufgebaut worden sind. Hierzu wird auf die US-PSen 3 292 102 oder 3 626 318 verwiesen.The solution of the object according to the invention with such an arrangement is particularly surprising in that respect, so far subordinate optical amplifiers have either been arranged between the resonators of the laser to be amplified, or have themselves been constructed as lasers with "own" resonator mirrors . For this purpose, reference is made to US Pat. Nos. 3,292,102 or 3,626,318.
Weiterbildungen der Erfindung sind in den Unteransprüchen angegeben:Further developments of the invention are specified in the subclaims:
Gemäß Anspruch 2 wird der als optischer Verstärker dienen¬ de Neodym-YAG-Kristall mit einer Blitzlampe gepumpt, deren Auslösen mit dem öffnen des Verschlusses synchronisiert ist. Damit läßt sich durch entsprechende Steuerung der Dauer und der Leistung des Blitzimpulses der Blitzlampe das Verstärkungsverhältnis des "optischen Verstärkers" in vergleichsweise großen Grenzen einstellen.According to claim 2, the neodymium-YAG crystal serving as an optical amplifier is pumped with a flash lamp, the triggering of which is synchronized with the opening of the closure. The amplification ratio of the "optical amplifier" can thus be set within comparatively large limits by appropriately controlling the duration and the power of the flash pulse of the flash lamp.
Vor allem aber ist es möglich, vergleichsweise große Im¬ pulsfolgefrequenzen im Bereich zwischen 1 Hz bis 100 Hz auch dann zu erzielen, wenn der als akusto-optischer Modu¬ lator ausgebildete optische Verschluß mit Frequenzen im kHz-Bereich beaufschlagt ist, die für die Betriebsweise des Modulators besonders vorteilhaft sind.Above all, however, it is possible to achieve comparatively large pulse repetition frequencies in the range between 1 Hz to 100 Hz even when the optical shutter, which is designed as an acousto-optical modulator, is acted upon by frequencies in the kHz range which are necessary for the operating mode of the modulator are particularly advantageous.
In jedem Falle ist es besonders vorteilhaft, wenn der als "Güteschalter" eingesetzte optische Verschluß als akusto-optischer Modulator ausgebildet ist (Anspruch 4) .In any case, it is particularly advantageous if the optical closure used as a "quality switch" is designed as an acousto-optical modulator (claim 4).
Im übrigen kann der Dauerstrich-Neodym-YAG-Laser in an sich bekannter Weise ausgebildet sein. Zur Ausbildung des Dauerstrich-Neodym-YAG-Lasers wird beispielsweise auf die bereits erwähnten Dauerstrich-Laser SL500/900 der Fa. Spectron Lasers Systems verwiesen.Otherwise, the continuous wave neodymium YAG laser can be designed in a manner known per se. For the formation of the continuous wave neodymium YAG laser, reference is made, for example, to the already mentioned continuous wave laser SL500 / 900 from Spectron Lasers Systems.
Insbesondere kann der Dauerstrich-Neodym-YAG-Laser mittels einer Edelgas-Hochdrucklampe, beispielsweise einer Xenon¬ oder Krypton-Lampe gepumpt werden (Anspruch 5) .In particular, the continuous wave neodymium YAG laser can be pumped by means of an inert gas high pressure lamp, for example a xenon or krypton lamp (claim 5).
Die erfindungsgemäße Vorrichtung zur Erzeugung von Laser¬ impulsen einstellbarer Dauer und variierbarer Impulsener¬ gie kann selbstverständlich zu beliebigen Zwecken, bei¬ spielsweise in der Materialbearbeitung, der wissenschaft¬ lichen Forschung oder der Meß- und Prüftechnik eingesetzt werden. Besonders vorteilhafte Verwendungen der erfindungsgemäßen Vorrichtungen sind in den Ansprüchen 7f gekennzeichnet.The device according to the invention for generating laser pulses of adjustable duration and variable pulse energy can of course be used for any purpose, for example in material processing, scientific research or measuring and testing technology. Particularly advantageous uses of the devices according to the invention are characterized in claims 7f.
Durch die Verwendung einer erfindungsgemäßen Vorrichtung insbesondere zur Laser-induzierten Stoßwellen-Lithotripsie erhält man einerseits eine besonders effektive Zerstörung beispielsweise von Nieren- oder Gallensteinen, anderer¬ seits aber eine lange Lebensdauer und ein problemloses "Handling" des als "Deliverey"-System eingesetzten Licht¬ wellenleiters mit dem im Anspruch 9 angegebenen Durchmes¬ ser.By using a device according to the invention, in particular for laser-induced shock wave lithotripsy, on the one hand, particularly effective destruction of kidney or gall stones, for example, is obtained, but on the other hand a long service life and problem-free "handling" of the light used as a "deliverey" system ¬ waveguide with the diameter specified in claim 9.
Kurze Beschreibung der ZeichnungBrief description of the drawing
Die Erfindung wird nachstehend anhand der einzigen Figur der Zeichnung näher beschrieben, die schematischThe invention is described below with reference to the single figure of the drawing, which is schematic
ein Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung zeigt.shows an embodiment of a device according to the invention.
Darstellung eines bevorzugten Ausführungsbeispiels Die erfindungsgemäße Vorrichtung weist einen an sich be¬ kannten Dauerstrich-Neodym-YAG-Laser auf, der allgemein mit dem Bezugszeichen 1 bezeichnet ist.Representation of a preferred embodiment The device according to the invention has a continuous wave neodymium YAG laser which is known per se and which is generally designated by the reference number 1.
Der Dauerstrich-Laser 1 besteht im wesentlichen aus einem Neodym-YAG-Kristall 2, den eine Edelgas-Hochdrucklampe 8, beispielsweise eine Xenon- oder Krypton-Hochdrucklampe pumpt. Der Dauerstrich-Laser 1 weist ferner Resonatoren 3- und 22 auf, innerhalb derer ein akusto-optischer Modulator 4, der als Güteschalter dient, im Strahlengang 9 des La¬ sers 1 angeordnet ist.The continuous wave laser 1 essentially consists of a neodymium-YAG crystal 2, which is pumped by an inert gas high-pressure lamp 8, for example a xenon or krypton high-pressure lamp. The continuous wave laser 1 also has resonators 3 and 22, within which an acousto-optical modulator 4, which serves as a quality switch, is arranged in the beam path 9 of the laser 1.
Der akusto-optische Modulator 4 öffnet und schließt den Strahlengang 9 des Lasers" 1. Eine Steuereinheit 5, die in an sich bekannter Weise aufgebaut ist, betätigt den Modu- lator 4 und ermöglicht ein Einstellen der Öffnungszeiten und der Folgefrequenz der Durchlaßperioden des Modulators 4.The acousto-optical modulator 4 opens and closes the beam path 9 of the laser " 1. A control unit 5, which is constructed in a manner known per se, actuates the module. 4 and enables the opening times and the repetition frequency of the pass periods of the modulator 4 to be set.
Außerhalb der Resonatorspiegel 3- und 3- ist im Strahlen¬ gang 9' des Dauerstrich-Lasers 1 ein weiterer Neodym-YAG- Kristall 6 angeordnet, den eine Blitzlampe 7 pumpt. Das Aufleuchten der Blitzlampe 7 steuert ebenfalls die Steu¬ ereinheit 5 synchron zu den Öffnungsvorgängen des akusto- optischen Modulators 4.A further neodymium YAG crystal 6, which a flash lamp 7 pumps, is arranged outside the resonator mirrors 3 and 3 in the beam path 9 'of the continuous wave laser 1. The flashing of the flash lamp 7 also controls the control unit 5 synchronously with the opening processes of the acousto-optical modulator 4.
Der mit einer Blitzlampe 7 gepumpte Neodym-YAG-Kristall 6 wirkt damit als optischer Verstärker der aus dem "gepul¬ sten Dauerstrich-Neodym-YAG-Lasers" 1 austretenden Laser¬ impulse, sofern der Neodym-YAG-Kristall 6 sich beim Hin¬ durchtreten des Laserimpulses in einem ausreichend ange¬ regten Zustand befindet.The neodymium-YAG crystal 6 pumped with a flash lamp 7 thus acts as an optical amplifier for the laser pulses emerging from the "pulsed continuous-wave neodymium-YAG laser" 1, provided that the neodymium-YAG crystal 6 is at the rear passing through the laser pulse is in a sufficiently excited state.
Andererseits ist der Neodym-YAG-Kristall 6 für das Licht des Lasers 1 weitgehend transparent, wenn der Neodym-YAG- Kristall 6 "nicht angeregt" ist.On the other hand, the neodymium-YAG crystal 6 is largely transparent to the light from the laser 1 when the neodymium-YAG crystal 6 is “not excited”.
Die erfindungsgemäße Vorrichtung hat damit den Vorteil, daß sie zum einen Laserimpulse einstellbarer Dauer und einstellbarer Impulsenergie bereitstellt. Die Impulsdauer (Zeitabstand zwischen der halben Maximalenergie auf der "Anstiegs- und Abfallseite) kann dabei typischerweise zwischen weniger als 100 ns und mehr als 300 ns variiert werden. Die Impuls-Folgefrequenz kann typischerweise zwi¬ schen 1 Hz und 100 Hz eingestellt werden.The device according to the invention thus has the advantage that, on the one hand, it provides laser pulses of adjustable duration and adjustable pulse energy. The pulse duration (time interval between half the maximum energy on the "rising and falling side") can typically be varied between less than 100 ns and more than 300 ns. The pulse repetition frequency can typically be set between 1 Hz and 100 Hz.
Bei Verwendung eines "Dauerstrich-Neodym-YAG-Lasers", der entsprechend der bereits erwähnten SL500/900 Serie der Fa. Spectron Lasers Systems aufgebaut ist, und bei Einsatz eines entsprechend angepaßten Neodym-YAG-Kristalls 6 ist die Impulsenergie typischerweise zwischen weniger als 50 mJ und mehr als 500 mJ variierbar. Selbstverständlich ist es aber auch möglich, Laserimpulse oder "Dauerstrich- Laserlicht" ohne optische Verstärkung dadurch abzugeben, daß der Neodym-YAG-Kristall 6 nicht gepumpt wird.When using a "continuous wave neodymium YAG laser", which is constructed in accordance with the already mentioned SL500 / 900 series from Spectron Lasers Systems, and when in use a correspondingly adapted neodymium-YAG crystal 6, the pulse energy is typically variable between less than 50 mJ and more than 500 mJ. Of course, it is also possible to emit laser pulses or "continuous wave laser light" without optical amplification in that the neodymium-YAG crystal 6 is not pumped.
Vorstehend ist die Erfindung anhand eines Ausführungsbei- spiels ohne Beschränkung des allgemeinen Erfindungsgedan¬ kens, wie er sich insbesondere aus den Ansprüchen ergibt, beschrieben worden. Insbesondere ist es selbstverständ¬ lich, daß anstelle der nur beispielhaft erwähnten Laser- Bauteile auch Bauteile bzw. Laserkomponenten anderer Fir¬ men eingesetzt werden können. Ferner kann die Ausbildung der Pumpquellen und/oder die Koppelung zwischen Modulator und Pumpquelle des zusätzlichen Kristalls 6 anders reali¬ siert sein.The invention has been described above on the basis of an exemplary embodiment without restricting the general inventive concept, as is evident in particular from the claims. In particular, it goes without saying that instead of the laser components mentioned only by way of example, it is also possible to use components or laser components from other companies. Furthermore, the formation of the pump sources and / or the coupling between the modulator and the pump source of the additional crystal 6 can be realized differently.
In jedem Falle erhält man jedoch eine Vorrichtung, die Laserimpulse abgibt, deren Impulsdauer und Impulsenergie in einem großen Bereich bei hoher Impuls-Folgefrequenz einstellbar sind. In any case, however, a device is obtained which emits laser pulses, the pulse duration and pulse energy of which can be set over a wide range at a high pulse repetition frequency.

Claims

P a t e n t a n s p r ü c h e Patent claims
1. Vorrichtung zur Erzeugung von Laserimpulsen einstell¬ barer Dauer mit einem ersten kontinuierlich gepumpten Neodym-YAG-Kristall, der in einem Resonator angeordnet ist, in dem ein als Güteschalter dienender schalbarer optischer Verschluß angeordnet ist, dadurch gekennzeichnet, daß zur Erhöhung der Lichtimpuls- Leistung im Strahlengang (9) des Dauerstrich-Neodym-YAG- Lasers (1) nach dem Verschluß (4) und außerhalb des Reso¬ nators (3-,3,) ein zweiter Neodym-YAG-Kristall (6,7) angeordnet ist, der pulsweise gepumpt wird.1. Device for generating laser pulses adjustable duration with a first continuously pumped neodymium-YAG crystal, which is arranged in a resonator in which a switchable optical shutter serving as a Q-switch is arranged, characterized in that to increase the light pulse Power in the beam path (9) of the continuous wave neodymium YAG laser (1) after the shutter (4) and outside the resonator (3, 3,), a second neodymium YAG crystal (6,7) is arranged , which is pumped in pulses.
2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der zweite Neodym-YAG-Kristall2. Device according to claim 1, characterized in that the second neodymium-YAG crystal
(6) mit einer Blitzlampe (7) gepumpt wird, und daß die Blitzlampe mit dem Verschluß (4) synchronisiert ist.(6) with a flash lamp (7) is pumped, and that the flash lamp is synchronized with the shutter (4).
3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß zum Umschalten auf kontinuier¬ lichen Laserbetrieb der optische Verschluß dauernd offen sein kann.3. Apparatus according to claim 1 or 2, characterized in that the optical shutter can be continuously open to switch to continuous laser operation.
4. Vorrichtung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der optische Verschluß ein akusto-optischer Modulator (4) ist.4. Device according to one of claims 1 to 3, characterized in that the optical closure is an acousto-optical modulator (4).
5. Vorrichtung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der erste Neodym-YAG-Kristall (2) von einer Edelgas-Hochdrucklampe (8) gepumpt ist. 5. Device according to one of claims 1 to 4, characterized in that the first neodymium-YAG crystal (2) is pumped by an inert gas high-pressure lamp (8).
PCT/EP1989/000431 1988-04-21 1989-04-21 Device for generating laser pulses of variable duration WO1989010647A1 (en)

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DE19883813482 DE3813482A1 (en) 1988-04-21 1988-04-21 DEVICE FOR GENERATING LASER IMPULSES OF ADJUSTABLE DURATION

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WO1992003977A2 (en) * 1990-09-06 1992-03-19 Massachusetts Institute Of Technology A pulsed laser system for the surgical removal of tissue
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CN110350392A (en) * 2019-08-02 2019-10-18 华中科技大学鄂州工业技术研究院 The changeable device of continuous and pulse based on stimulated Brillouin scattering, method
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