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WO2002066379A2 - Procede pour stabiliser la puissance de depart d'un laser a corps solide et systeme de laser a corps solide - Google Patents

Procede pour stabiliser la puissance de depart d'un laser a corps solide et systeme de laser a corps solide Download PDF

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Publication number
WO2002066379A2
WO2002066379A2 PCT/DE2002/000659 DE0200659W WO02066379A2 WO 2002066379 A2 WO2002066379 A2 WO 2002066379A2 DE 0200659 W DE0200659 W DE 0200659W WO 02066379 A2 WO02066379 A2 WO 02066379A2
Authority
WO
WIPO (PCT)
Prior art keywords
solid
state laser
laser
measured
frequency
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
PCT/DE2002/000659
Other languages
German (de)
English (en)
Other versions
WO2002066379A3 (fr
Inventor
Achim Kittel
Falk Lange
Tobias Letz
Kestutis Pyragas
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.)
Carl Von Ossietzky Universitaet Oldenburg
Max Planck Gesellschaft zur Foerderung der Wissenschaften
Original Assignee
Carl Von Ossietzky Universitaet Oldenburg
Max Planck Gesellschaft zur Foerderung der Wissenschaften
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 Von Ossietzky Universitaet Oldenburg, Max Planck Gesellschaft zur Foerderung der Wissenschaften filed Critical Carl Von Ossietzky Universitaet Oldenburg
Priority to AU2002246022A priority Critical patent/AU2002246022A1/en
Publication of WO2002066379A2 publication Critical patent/WO2002066379A2/fr
Anticipated expiration legal-status Critical
Publication of WO2002066379A3 publication Critical patent/WO2002066379A3/fr
Ceased legal-status Critical Current

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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
    • H01S3/109—Frequency multiplication, e.g. harmonic generation
    • 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
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
    • 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
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/131—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
    • H01S3/1312—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping

Definitions

  • the invention relates to a method for stabilizing the output power of a solid-state laser with intracavity frequency multiplication, in which at least two components of the radiation emitted by the solid-state laser are measured and act on a constant value on at least one manipulated variable to regulate the output power of the solid-state laser.
  • the invention further relates to a solid-state laser system with at least one laser diode, a resonator and an internal frequency-multiplying crystal.
  • Solid-state lasers are increasingly being used in technology and science, with lasers that emit radiation in the visible range in particular being in demand. This is achieved in particular by using lasers in which the frequency of the fundamental radiation is increased by doubling or multiplying the frequency of diode-pumped multimode solid-state lasers within the resonator, the frequency of the fundamental radiation being in the infrared range.
  • Frequency doubling emits visible green radiation with 532nm wavelength with a basic radiation of 1064nm.
  • a KTP crystal is used within the optical resonator.
  • Such frequency doubled or multiplied solid-state lasers are compact and have great efficiency.
  • the invention has for its object to provide a particularly reliable method for stabilizing the output power of a solid-state laser. Furthermore, the invention has for its object to provide a corresponding solid-state laser system. This object is achieved with the features of patent claim 1. In terms of the device, the object is achieved with the features of patent claim 11. Advantageous developments of the invention are specified in the subclaims.
  • At least two components of the radiation emitted by the solid-state laser are measured in order to stabilize the output power of a solid-state laser with resonator-internal frequency multiplication, and are given to regulate the output power of the solid-state laser to at least two manipulated variables, so that the behavior of the control is improved by intervention in various parameters becomes.
  • the control bandwidth is comparable to the characteristic frequencies of the fluctuation in the intensity of the solid-state laser, in particular the control bandwidth is of the same order of magnitude as the characteristic frequencies of the fluctuations.
  • the manipulated variables can therefore be regulated in particular in the microsecond range or even in the sub-microsecond range. This achieves dynamic regulation of the solid-state laser, which can react directly to the fluctuation in the intensity of the solid-state laser.
  • Three or more manipulated variables can preferably also be influenced, so that overall a particularly reliable stabilization of the output power has been achieved.
  • a manipulated variable is preferably formed by the pump power of a laser diode, in particular by the current flowing through the laser diode.
  • the pump output of a second laser diode, in particular the current flowing through the laser diode, is preferably used as the second manipulated variable, this laser diode also being used as a pump laser diode the solid-state laser.
  • the laser diodes are part of the solid-state laser system as pump laser diodes.
  • the conversion efficiency from infrared to green of the frequency-multiplying crystal in particular an electric field applied to the frequency-multiplying crystal, can also serve as a manipulated variable.
  • the respective intensity of the different polarization directions of the infrared light is preferably measured and measured in the radiation emitted by the solid-state laser system.
  • it is favorable to measure the intensity of the emitted high-frequency beam in the example mentioned at the beginning, the intensity of the green light.
  • other alternative or additional measurement and control variables can be used, such as the temperatures of individual structural components of the solid-state laser system. Influencing the temperature is helpful to support the process, but not an integral part, since in this way no dynamic regulation, but only a comparatively slow change in the operating point can be achieved.
  • the two different directions of polarization of the infrared light are measured and measured variables, and each of these measured and controlled variables is applied to one of two laser diodes as a manipulated variable.
  • Mixed variables are also possible, so that each of the measurement and control variables is applied to both laser diodes as manipulated variables.
  • this is expressed using a 2x2 matrix.
  • the control is preferably carried out in such a way that the intensities of the different polarization directions of the infrared light are or become approximately the same size, since the conversion efficiency from infrared to green is maximum in this configuration.
  • the control is carried out in a preferred embodiment such that the intensities of the different polarization directions of the infrared light are stabilized, regardless of the mode configuration.
  • 'this can be done so that the intensities of the different Polarisat.ionsraumen be stabilized of the infrared light, without pursuing the goal to reduce the number of modes or the number of the polarization directions.
  • It is particularly preferred to stabilize the intensities of the different polarization directions of the infrared light with the aim that which is known from the literature (for example J. Baer, J. Opt. Soc. At the.
  • the solid-state laser system according to the invention which is used in particular to carry out the method described above, is characterized in that at least two laser diodes are provided, which are aligned in such a way that the polarization directions of the radiation emitted by the laser diodes are different. This enables the resonator operating in multimode to be influenced particularly well. In this way, the output power of the solid-state laser system can be stabilized particularly well.
  • the laser diodes are preferably aligned such that the polarization directions of the radiation emitted by the laser diodes are orthogonal to one another.
  • a beam splitter element or a polarization-maintaining y-fiber is preferably provided for coupling in the radiation from the two laser diodes.
  • a device for generating a controllable electric field is provided as a further manipulated variable, which is arranged in the area of the frequency-multiplying crystal, so that the electric field is generated in the area of the frequency-multiplying crystal.
  • the schematic illustration shows a solid-state laser system according to the invention for carrying out the method according to the invention.
  • 1 shows a solid-state laser system 1 with a first laser diode 10 and a second laser diode 11, which serve as pump laser diodes of the solid-state laser system 1.
  • the beams of the two laser diodes 10 and 11 are aligned coaxially with the aid of a beam splitter 12 and guided into an Nd-YAG crystal 15 with the aid of a collimating lens 13 and a focusing lens 14.
  • a KTP crystal 16 and a coupling-out mirror 17 are arranged behind this. These components 10 to 17 form the actual solid-state laser system 1.
  • the laser diodes 10 and 11 emit polarized radiation of a wavelength of, for example, 808 nm, which is in any case energetically above the fundamental frequency of the Nd-YAG laser 15 with the corresponding wavelength of 1064 nm.
  • the laser diodes 10 and 11 are aligned so that their polarization directions are orthogonal to each other, and their beams are focused into the Nd-YAG crystal 15 via the beam splitter 12 and the collimating lens 13 and the focusing lens 14.
  • the laser diodes are equipped with a Peltier element 21 or a heating and cooling device and a temperature sensor 20, with which the temperature can be measured and influenced.
  • the Nd-YAG crystal 15 which has a cylindrical shape and is mirrored in the left end region in the figure, forms together with the coupling mirror 17, which is concave, the actual resonator of the laser system.
  • another crystal for example an Nd-YLF crystal, can also be used.
  • the Nd-YAG crystal 15 has a temperature sensor 22.
  • the frequency-multiplying crystal, here a frequency-doubling KTP crystal 16 is arranged within the resonator, that is to say between the mirrored end of the Nd-YAG crystal 15 and the coupling-out mirror 17, and converts part of the radiation from the laser system to twice the frequency.
  • a temperature sensor 23 and a device 24, in the form of a capacitor, for applying an electrical field are arranged on the crystal.
  • Behind the decoupling mirror 17 are three measuring devices 25, 26 and 27, of which the measuring device 25 the intensity of the emitted green light, i.e. the light with the short wavelength of 532nm, and the measuring devices 26 and 27 each the intensity of the decoupled infrared light in one of the two orthogonal directions of polarization.
  • the measured variables ⁇ include in particular the temperature of the Nd-YAG crystal measured by the temperature sensor 12, the temperature of the KTP crystal measured by the temperature sensor 23, the temperature of the laser diode 10 measured by the temperature sensor 20 and also the temperature of the laser diode 11 measured by a further temperature sensor as well as the intensities of the laser light measured by the measuring devices 25, 26 and 27.
  • Functions Fj (mi, ..., m n ) are applied to these measured values mi to m n , where j can assume whole values from 1 to 0 ( o > 1).
  • the functions F j act on Pj parameters. It is therefore crucial that the measured variable acts on several, at least two parameters or manipulated variables.
  • this means: p-, F-, (mi, ..., m 0 ).
  • the current flowing through the laser diodes 10, 11 or the temperature of the laser diodes 10, 11 which can be changed with the heating device 21 are considered as parameters.
  • the device 24 it is possible to use the device 24 to influence the electric field applied to the KTP crystal 16 in order to be able to influence its birefringent properties and thus the phase shift.
  • F- j can thus be understood as a two-dimensional matrix of coefficients (oxj).
  • the coefficients can be determined by various optimization algorithms known from the literature, in which the fluctuations in the laser output power are minimized. Optimization algorithms include, for example, the gradient method, simulated anealing, described for example in WH Press et al., "Numerical Recipes in C", Cambridge University Press 1992. Optimization with the aid of genetic algorithms or neural networks is also possible. The optimization process can be carried out before the actual use of the laser or dynamically during the operation of the laser The optimization during laser use has the decisive advantage that also drifting system properties can be corrected.

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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

L'invention concerne un procédé pour stabiliser la puissance de départ d'un laser à corps solide à multiplication de fréquence à l'intérieur du résonateur. Selon ce procédé, au moins deux éléments du rayonnement émis par le laser à corps solide sont mesurés et servent à régler la puissance de départ du laser sur une valeur constante d'au moins une grandeur de réglage. Afin d'obtenir une très bonne stabilisation, une deuxième grandeur de réglage au moins entre en ligne de compte pour le réglage de la puissance de départ du laser. A cet effet, le système de laser à corps solide comporte un pompage à deux diodes lasers orientées de telle sorte que leurs sens de polarisation diffèrent.
PCT/DE2002/000659 2001-02-22 2002-02-22 Procede pour stabiliser la puissance de depart d'un laser a corps solide et systeme de laser a corps solide Ceased WO2002066379A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002246022A AU2002246022A1 (en) 2001-02-22 2002-02-22 Method for stabilising the output power of a solid-state laser, and a solid-state laser system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10108436.6 2001-02-22
DE2001108436 DE10108436B4 (de) 2001-02-22 2001-02-22 Verfahren zur Stabilisierung der Ausgangsleistung eines Festkörperlasers und Festkörperlasersystem

Publications (2)

Publication Number Publication Date
WO2002066379A2 true WO2002066379A2 (fr) 2002-08-29
WO2002066379A3 WO2002066379A3 (fr) 2003-10-16

Family

ID=7675049

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE2002/000659 Ceased WO2002066379A2 (fr) 2001-02-22 2002-02-22 Procede pour stabiliser la puissance de depart d'un laser a corps solide et systeme de laser a corps solide

Country Status (3)

Country Link
AU (1) AU2002246022A1 (fr)
DE (1) DE10108436B4 (fr)
WO (1) WO2002066379A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7692502B2 (en) 2004-06-11 2010-04-06 Georg-August-Universitat Gottingen Oscillatory system and method for controlling an oscillatory system of this type

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5060233A (en) * 1989-01-13 1991-10-22 International Business Machines Corporation Miniature blue-green laser source using second-harmonic generation
US5175741A (en) * 1989-06-07 1992-12-29 Fuji Photo Film Co., Ltd. Optical wavelength conversion method and laser-diode-pumped solid-state laser
US5249193A (en) * 1991-03-20 1993-09-28 Brother Kogyo Kabushiki Kaisha Solid-state laser system
JP3013121B2 (ja) * 1991-05-10 2000-02-28 富士写真フイルム株式会社 光波長変換装置
DE4205011A1 (de) * 1992-02-19 1993-08-26 Zeiss Carl Fa Frequenzverdoppelter festkoerperlaser
JP3222288B2 (ja) * 1993-11-05 2001-10-22 富士写真フイルム株式会社 光波長変換装置
JPH088480A (ja) * 1994-06-16 1996-01-12 Hitachi Ltd レーザ装置
JPH1070333A (ja) * 1996-08-27 1998-03-10 Shimadzu Corp 波長変換固体レーザ装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7692502B2 (en) 2004-06-11 2010-04-06 Georg-August-Universitat Gottingen Oscillatory system and method for controlling an oscillatory system of this type

Also Published As

Publication number Publication date
AU2002246022A1 (en) 2002-09-04
WO2002066379A3 (fr) 2003-10-16
DE10108436A1 (de) 2002-09-12
DE10108436B4 (de) 2008-08-07

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