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)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Lasers (AREA)
• Laser Surgery Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (4)

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Citations (3)

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• 1988
  • 1988-04-21 DE DE19883813482 patent/DE3813482A1/de not_active Ceased
• 1989
  • 1989-04-21 WO PCT/EP1989/000431 patent/WO1989010647A1/de not_active Application Discontinuation
  • 1989-04-21 EP EP19890905093 patent/EP0366751A1/de not_active Withdrawn
  • 1989-04-21 JP JP50449489A patent/JPH04501342A/ja active Pending

Patent Citations (3)

Non-Patent Citations (2)

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