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
  • H01S3/09—Processes or apparatus for excitation, e.g. pumping
  • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
  • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
  • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
  • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• • 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
  • H01S3/025—Constructional details of solid state lasers, e.g. housings or mountings
• • 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
  • H01S3/04—Arrangements for thermal management
  • H01S3/042—Arrangements for thermal management for solid state lasers
• • 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
  • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
  • H01S3/06—Construction or shape of active medium
  • H01S3/0602—Crystal lasers or glass lasers
  • H01S3/0604—Crystal lasers or glass lasers in the form of a plate or disc
• • 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
  • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
  • H01S3/16—Solid materials
  • H01S3/1601—Solid materials characterised by an active (lasing) ion
  • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
  • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium
• • 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
  • H01S3/2316—Cascaded amplifiers
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
  • H01S5/0071—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for beam steering, e.g. using a mirror outside the cavity to change the beam direction
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/02—Structural details or components not essential to laser action
  • H01S5/022—Mountings; Housings
  • H01S5/023—Mount members, e.g. sub-mount members
  • H01S5/02325—Mechanically integrated components on mount members or optical micro-benches
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/02—Structural details or components not essential to laser action
  • H01S5/024—Arrangements for thermal management
  • H01S5/02438—Characterized by cooling of elements other than the laser chip, e.g. an optical element being part of an external cavity or a collimating lens
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
  • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
  • H01S5/4031—Edge-emitting structures
• • 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
  • H01S5/00—Semiconductor lasers
  • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
  • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
  • H01S5/4031—Edge-emitting structures
  • H01S5/4056—Edge-emitting structures emitting light in more than one direction

Definitions

• the present invention relates to the field of devices for longitudinal pumping of a laser amplifier medium.
• It relates more particularly to a device for longitudinal pumping of a laser amplifying medium comprising at least one laser diode capable of emitting at least one laser beam, means for collimating said laser beam, and means for focusing said collimated laser beam on said medium. laser amplifier.
• Such devices are for example known from the German application DE 10235713 disclosing a device comprising a plurality of laser diodes each emitting a laser beam. These diodes are positioned axially around the direction of propagation of the laser beam, and emit radiation which is collimated by a lens array which directs the beam to a laser medium at a relatively small angle to the direction of propagation of the laser beam. .
• a first of the present invention is therefore to provide a longitudinal pumping device whose compactness is improved.
• Another object of the present invention is to provide a longitudinal pumping device that can operate at high energies.
• Another object of the present invention is to provide a longitudinal pumping device that can operate in the presence of a large number of pump laser diodes.
• Another object of the present invention is to provide a longitudinal pumping device for which the pumped area is moved away from the contours of the pumped bar, and this to avoid the effects of diffraction.
• Another object of the present invention is to allow a substantially homogeneous pumping of the laser amplifying medium.
• a longitudinal pumping device of a laser amplifier medium comprising at least one laser diode capable of emitting at least one laser beam, means for collimating said laser beam capable of generating a collimated laser beam, means for focusing said collimated laser beam on said laser amplifying medium, characterized in that said focusing means comprise at least one mirror, said mirror being arranged such that said collimated beam is reflected towards said amplifying medium.
• said axis of rotation of said cylinder being positioned along a longitudinal emission axis of said laser medium and said device comprises a plurality of diodes surrounding said laser medium . In this way, the device according to the invention is compact since the mirrors allow the reflection of the beams towards the amplifying medium.
• said plurality of diodes is formed by a plurality of diode arrays oriented along a longitudinal transmission axis of said amplifying medium, said device comprising a plurality of mirrors, each of said mirrors being associated with one of said bar.
• said bars are spaced angularly around said amplifying medium, each of said strips defining an angle formed by the axis defined by the line between said strip and the center of said mirror associated with said strip and the axis of emission of said laser medium, said mirror being inclined with respect to the line connecting said bar and the center of said mirror associated with said bar and the axis of emission of said laser medium according to said angle.
• the device comprises means for cooling said compensating medium, said cooling means being positioned between said at least one diode and said amplifying medium, an undoped material positioned between said at least one mirror and said amplifying medium in the path of said reflected beam. In this way, the power of the thermal lens created by said cooling means is reduced.
• said device comprises a first laser diode able to emit a first laser beam, and a second laser diode capable of emitting a second laser beam, said device comprising a first mirror associated with said first diode, and a second mirror associated with said second diode, said amplifying medium comprising a first longitudinal face and a second longitudinal face, said first mirror being arranged so as to reflect said first laser beam towards said first face of said amplifying medium, said second mirror being arranged with so as to reflect said second laser beam towards said second face of said amplifying medium.
• said at least one mirror is a parabolic mirror.
• FIG. 1 represents a longitudinal pumping device according to a first embodiment of the invention
• FIG. 2 represents a longitudinal pumping device according to a second embodiment of the invention
• FIG. 3 shows the use of an undoped portion between the mirror and the amplifying medium according to the present invention
• FIG. 4 represents a longitudinal pumping device adapted for low energies
• FIG. 5 represents a longitudinal pumping device adapted for medium energies
• FIG. 6 is a view from above of FIG.
• longitudinal pumping will be used to designate a pumping mode according to which a beam (or a plurality of pumping beams) is inserted into the amplifying medium by the same optical faces as the input faces. or output of the amplified laser beam.
• a longitudinal pumping device 1 according to the invention comprises a laser amplifier medium 2 in the form of a laser bar, a diode array 3, and one or more deflection mirrors 4. It also comprises beam collimation means emitted by the diodes, for example in the form of a lens assembly 5. It also comprises a cooling device 6 of the diodes 3 and the bar 2, for example positioned between the diodes 3 and the bar 2.
• the laser diode strips 3 form a ring which surrounds the solid amplifying medium 2 of cylindrical shape, the axis of revolution of the cylinder corresponding to the direction of emission of the laser beam ⁇ .
• the beams emitted by the bars 3 are collimated by the lens assembly 5 and taken up by a concave mirror 4.
• the concave mirror is then arranged to focus the beams on one end of the laser bar 2.
• the multiple collimated beams from the diodes are superimposed at the end of the laser bar to form a substantially homogeneous spot whose intensity is stronger in the center.
• a laser bar 2 comprising a first end 2a and a second end 2b, a first ring of diode strips 3A and a second ring of diode bars 3B. These two rings surround the bar 2.
• the first ring 3A emits a collimated light beam to a first mirror 4A on the side of the end 2a. This beam is then reflected towards the first end 2a.
• a light beam emitted by the bars 3B is reflected by a mirror 4B towards the end 2b.
• a thermal lens of revolution is created around the axis of revolution of the system.
• One way to reduce the power of the thermal lens is to cool the bar by its ends so as to give a longitudinal component to the thermal gradient. To do this, illustrated FIG. 3, undoped tips 7 are welded, so not thermally charged at one end of the bar, which allows to effectively cool the bar at the location where the thermal deposition is the most important. In this way, the optical distortions due to thermal deposits in the amplifying medium 2 are maintained at a relatively low level.
• FIG. 4 For low energy pumping devices, and thus with a small number of diodes, an arrangement as illustrated in FIG. 4 in which a strip 3A, or a stack of a small number of diode strips emits a collimated beam to a mirror 4A.
• the mirror 4A then reflects the beam to the laser medium 2.
• a second bar 3B is positioned substantially symmetrically to the first bar relative to the focal point of the first beam.
• a second mirror 4B is also positioned to reflect the collimated beams coming from the second strip 3B towards the middle 2.
• the gain volume thus created is suitable for amplifying a laser beam of diameter 1 mm in a YAG plate. doped.
• the configuration is dimensioned on the basis of the knowledge of various parameters, such as, for example, the section of the pumped volume, for example defined by its diameter d, evaluated from the output energy. and characteristics of the laser material employed, and the energy contained in the pump pulse or pumping power. From this last energy, it is possible to deduce the number N of laser bars necessary.
• the diameter D of the ring of diode strips 3 is adjusted so that the strips are contiguous to each other.
• the preferred form of the mirror 4, 4A, 4B is a parabolic form of focal length f.
• the diode 3 is collimated along a single axis, said axis "fast" with a cylindrical lens.
• the mirror 4 thus forms two images of the diode.
• the first image is the image of the junction collimated by the cylindrical lens and located at the main focus of the mirror 4, and the second image is the direct image of the bar on the mirror.
• the beam has the smallest dimension, and it is this dimension that should coincide with the diameter d of the pumped volume.
• this image is not on the axis of the mirror and therefore the images given by the different bars of the crown are not confused.
• the mirror 4 can be divided into a plurality of identical sub-mirrors according to the number of diode bars
• each sub-mirror is then inclined with respect to the axis of the system by an angle a if 2a is the angle supported by the axis ⁇ bar-center of the mirror ⁇ and the axis of the system ⁇ .
• Arctan [D / (2 * (x + f))], where x is the distance along the axis of the bar to the focus of the mirror, D is the diameter of the ring of bars and f is the focal length of the mirror.
• Yb YAG according to the configuration of FIG. 4 so as to pump a section volume of about 1 mm by 1.8 mm corresponding to a laser beam of diameter 1 mm which circulates at the incidence of Brewster in the blade.
• a focal length of 15 mm is chosen, the pumping laser strips having a standard length of 10 mm.
• the magnification of the mirror is therefore 0.18.
• the Newton formula giving the magnification g f / x if x is the distance along the axis of the bar to the focus of the mirror then provides a distance x of 83 mm.
• the previously defined diode has a total divergence of 10 °.
• the diameter of the mirror must then have a diameter of at least 34 mm to intercept the entire beam.
• a metal mirror of this diameter is quite feasible by diamond machining.
• the gap between the diodes being 1.4 mm, the images of the diodes in the blade will be spaced 0.25 mm.
• the mirrors By adjusting the mirrors so that the images are staggered, it is then substantially the desired section taking into account the thickness of the images in the plane.
• FIGS. 5 and 6 An average energy configuration is now described with reference to FIGS. 5 and 6.
• forty laser diode arrays 3 are used. These 40 arrays are divided into eight stacks. five bars arranged head to tail and pumping two bars 2A and 2B, which has the advantage of distributing the thermal load.
• Four sub-mirrors are provided on each side of the device, only two of which are shown in FIG. 5. The dimension of the diagonal of the stack determines the pumped diameter. With a spacing of the bars of 1, 2 mm, the magnification given by the mirror must be 0.36.
• the distance x from the bar to the focus of the mirror is 83 mm and the distance x 'from the second image to the focal plane is 11 mm.
• the angle of inclination ⁇ of a sub-mirror with respect to the axis of the system is about 5 ° for a crown diameter of 40 mm.
• the diameter of the crown is calculated so that the trace of the beams is entirely contained in each sub-mirror.

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

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• 2006
  • 2006-01-31 FR FR0650339A patent/FR2896921B1/fr not_active Expired - Fee Related
• 2007
  • 2007-01-25 JP JP2008551824A patent/JP2009525592A/ja active Pending
  • 2007-01-25 US US12/223,229 patent/US20100014547A1/en not_active Abandoned
  • 2007-01-25 EP EP07730861A patent/EP1979998A1/fr not_active Ceased
  • 2007-01-25 WO PCT/FR2007/000143 patent/WO2007088263A1/fr active Application Filing

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