WO1989001714A1 - Declencheur (q-switch) passif pour lasers pulses - Google Patents

Declencheur (q-switch) passif pour lasers pulses Download PDF

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Publication number
WO1989001714A1
WO1989001714A1 PCT/DE1988/000490 DE8800490W WO8901714A1 WO 1989001714 A1 WO1989001714 A1 WO 1989001714A1 DE 8800490 W DE8800490 W DE 8800490W WO 8901714 A1 WO8901714 A1 WO 8901714A1
Authority
WO
WIPO (PCT)
Prior art keywords
switch
resonator
switch according
laser
stimulated
Prior art date
Application number
PCT/DE1988/000490
Other languages
German (de)
English (en)
Inventor
Carl Steiner
Alfred Laubereau
Heinrich Graener
Original Assignee
Carl Steiner
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 Carl Steiner filed Critical Carl Steiner
Publication of WO1989001714A1 publication Critical patent/WO1989001714A1/fr

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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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
    • H01S3/1086—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering using scattering effects, e.g. Raman or Brillouin effect
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1123—Q-switching
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10076—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating using optical phase conjugation, e.g. phase conjugate reflection

Definitions

  • the invention relates to a passive Q-switch for pulsed lasers with intensity-dependent resonator losses according to the preamble of claim 1.
  • a light amplification of the radiation by stimulated emission is only possible if there is a population inversion, i.e. if there is an increased number of atoms at a higher energy level.
  • a pump source is always required that converts the laser medium to a higher energy level lifts.
  • One way to supply energy to the system is through the electron impact in a gas discharge. This pumping method is characteristic of the group of gas lasers. With solids and liquids, it is difficult to supply the energy by electron impact. Here the pump energy is usually supplied in the form of light. Solid state and liquid shock lasers work often in pulse mode. In these systems, the inversion is generated by optical pumping, for example using flash lamps.
  • semiconductor lasers In these inverted states are generated directly by the electrical current. Semiconductor lasers can work continuously and in pulse mode.
  • the optical resonator required to operate a laser oscillator consists, for example, of two opposing mirrors. In most cases, interference mirrors are used because of the lower losses, and they are designed either as plane mirrors or as spherical mirrors.
  • the methods for preventing spiking and / or for increasing the laser peak power change the quality of the resonator such that a sufficiently large feedback and thus a time-limited laser operation is possible only for a short time. They are therefore also referred to as Q switching (switching of the quality Q of the resonator).
  • a uniform pulse or - if the quality of the resonator is changed periodically - a sequence of uniform pulses at the output of the laser instead of the irregular pulse sequence, a uniform pulse or - if the quality of the resonator is changed periodically - a sequence of uniform pulses at the output of the laser. Furthermore, due to the initially increased resonator losses during the pumping process, an increased population inversion can be achieved, which leads to a greater peak intensity and a shorter pulse duration of the laser radiation (so-called giant pulses).
  • Q-switches There are basically two types of Q-switches, namely so-called active and so-called passive Q-switches.
  • the resonator quality is changed by influencing a switch from the outside, so that the laser activity starts with significantly higher net amplification per revolution in the resonator than in a pulsed laser without Q-switching.
  • Examples include electronic Q-switches with the aid of an electro-optical or magneto-optical switch (Kerr cell, Pockels cell, etc.) and mechanical Q switches in the form of a rotating mirror or rotating reflection prisms.
  • passive Q-switching changes due to nonlinear, intensity-dependent Effects in the resonator the net gain for the radiation circulating in the laser resonator.
  • the nonlinear increase in the net gain represents the switching stroke of the passive Q-switch.
  • three different physical effects are suitable here:
  • the passive Q-switching by means of dye molecules according to a has proven itself well, since it requires less manufacturing effort in comparison to the active Q-switching and also cheaper emission data of the laser in individual cases - like narrower spectral bandwidths th and shorter pulse duration - enables.
  • the lack of chemical stability of the dye molecules is particularly to be mentioned.
  • this property (especially in the long-wave spectral range) requires technical effort for suitable shielding against interference radiation and further precautions, in order to achieve a suitable lifespan for the Q-switch.
  • suitable dye molecules which meet the technical requirements for the practical use of the Q-switch are generally not available in the long-wave infrared (wavelength lambda greater than 1.1 micrometers).
  • the eye-safe laser is in the spectral range at 1.5 micrometers.
  • Such nonlinear absorbers have not been used commercially so far. So far, only an active Q-switch with a correspondingly high technical outlay has been used for this laser.
  • a fundamental disadvantage of the Q-switch due to nonlinear absorption is its limitation to the wavelength range of the absorption band of the respective dye molecules, which limits the tuning of the laser wavelength.
  • Q-switches according to b) are known in principle, but have been used only to a limited extent, which can be explained by the high intensity requirement and the complicated structure.
  • the invention has for its object to further improve a passive Q-switch for pulsed lasers. This object is achieved by the features of claim 1.
  • suitable dye molecules for the operation of a passive Q-switch due to nonlinear absorption in the long-wave infrared range are often not available, which meet the technical requirements for the practical use of the Q-switch.
  • Such a nonlinear absorber is not commercially available, for example, for the eye-safe laser in the spectral range at 1.5 micrometers.
  • the passive Q-switch due to dye molecules is not suitable for lasers with a large tuning range.
  • the passive Q-switching takes place through the intensity-dependent reflection (backward scattering) in a medium by means of stimulated Brillouin scattering and / or stimulated thermal Brillouin scattering in conjunction with optical components known per se, the resonator end mirror and, for example, other optical components which have suitably set linear optical losses.
  • optical feedback R is achieved of less than 1 by the arrangement, but which is large enough to total in conjunction with the other components (front mirror, laser medium, etc.) a sufficient resonance nator quality and thus not too high a threshold value for laser activity.
  • the nonlinear reflectivity of the Brillouin material increases to a value close to 1. This shortens the effective resonator length and the lossy components between the region of the stimulated backscattering and the end mirror are decoupled, whereby a switching stroke of the Q switch of approximately 1-R is achieved.
  • a suitable value of 1-R for many application examples is, for example, 0.1 to 0.3.
  • the maximum gain coefficient by stimulated scattering is increased and can be set by the absorption coefficient of the medium.
  • the frequency dependence of the gain coefficient is changed.
  • the amplification is broadband, so that the frequency adjustment with the stimulated scattering becomes easier for the adjacent longitudinal resonator modes.
  • the absorption in the Brillouin cuvette reduces the feedback from the resonator mirror. This hinders the competitive process of stimulated anti-Stokes scattering in comparison to the desired process of stimulated Stokes scattering.
  • the quality switching is achieved by consciously accepting side effects previously perceived as disturbing, namely linear transmission and / or reflection losses, in conjunction with the stimulated Brillouin scattering and / or thermal Brillouin scattering.
  • the laser intensity is focused into the Brillouin medium by using imaging elements (for example lenses, concave mirrors).
  • imaging elements for example lenses, concave mirrors.
  • This can also be expediently designed to widen the bundle and thus reduce the radiation load on the end mirror. This results in a reduced effort in the manufacture of mirrors and a reduced risk of radiation damage.

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

Abstract

Un déclencheur (Q-switch) passif pour laser pulsés à pertes de résonance variables avec l'intensité permet d'obtenir un déclenchement pour réflexion non-linéaire au moyen d'une diffusion stimulé de Brillouin et/ou d'une diffusion thermique stimulé de Brillouin avec un coefficient d'absorption alpha égal/supérieur à 0.05 cm, la longueur de la course de déclenchement étant réglable au moyen des pertes linéaires du résonateur laser.
PCT/DE1988/000490 1987-08-10 1988-08-08 Declencheur (q-switch) passif pour lasers pulses WO1989001714A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEP3726896.1 1987-08-10
DE19873726896 DE3726896A1 (de) 1987-08-10 1987-08-10 Passiver gueteschalter fuer gepulsten laser

Publications (1)

Publication Number Publication Date
WO1989001714A1 true WO1989001714A1 (fr) 1989-02-23

Family

ID=6333612

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1988/000490 WO1989001714A1 (fr) 1987-08-10 1988-08-08 Declencheur (q-switch) passif pour lasers pulses

Country Status (3)

Country Link
AU (1) AU2255588A (fr)
DE (1) DE3726896A1 (fr)
WO (1) WO1989001714A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4102409C2 (de) * 1991-01-28 1995-08-17 Eichler Hans Joachim Prof Dr Laser mit frequenzangepaßtem Schallwellenspiegel
WO2003007438A1 (fr) * 2001-07-12 2003-01-23 Agency For Science, Technology And Research Laser declenche

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1614325A1 (de) * 1967-01-31 1970-08-20 Pohl Dipl Phys Dieter Einrichtung zur Steuerung des Guetefaktors Q eines Resonators eines optischen Senders fuer kohaerente elektromagnetische Strahlung zum Zwecke der Erzeugung von Riesenimpulsen(Q-Schaltung)
US4538274A (en) * 1983-01-04 1985-08-27 The United States Of America As Represented By The United States Department Of Energy Q-Switched Raman laser system

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Optics Letters, Band 6, nr. 7, Juli 1981, Optical society of America, (New York, US), M.M. Denariez-Roberge et al.: "Highpower single-mode laser operation using stimulated Rayleigh scattering", Seiten 339-341 *
Soviet Journal of Quantum Electronics, Band 10, Nr. 3, Marz 1980, American Institute of Physics, (New York, US), V.I. Bezrodnyi et al.: "Mechanism of laser Q switching by intracavity stimulated scattering", Seiten 382-383 *
Soviet Journal of Quantum Electronics, Band 12, Nr. 9, September 1982, American Institute of Physics, (New York, US), N.N. II'ichev et al.: "Laser with diffraction-limited divergence and Q switching by stimulated Brillouin scattering", Seiten 1161-1164 *
Soviet Physics Technical Physics, Band 27, Nr. 2, Februar 1982, American Institute of Physics, (New York, US), M.V. Vasil'ev et al.: "Q-switching of an optical resonator by a stimulated Brillouin scattering mirror", seiten 205-208 *

Also Published As

Publication number Publication date
DE3726896A1 (de) 1989-02-23
AU2255588A (en) 1989-03-09

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