Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
  • B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/20—Bonding
  • B23K26/21—Bonding by welding
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
  • G02B27/0938—Using specific optical elements
  • G02B27/0994—Fibers, light pipes
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
  • G02B6/0288—Multimode fibre, e.g. graded index core for compensating modal dispersion
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/255—Splicing of light guides, e.g. by fusion or bonding
  • G02B6/2552—Splicing of light guides, e.g. by fusion or bonding reshaping or reforming of light guides for coupling using thermal heating, e.g. tapering, forming of a lens on light guide ends
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/36—Mechanical coupling means
  • G02B6/3616—Holders, macro size fixtures for mechanically holding or positioning fibres, e.g. on an optical bench
  • G02B6/3624—Fibre head, e.g. fibre probe termination
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
  • B23K2103/54—Glass

Definitions

• the present invention relates to the field of equipment, processes and processing facilities using power laser radiation, for industrial, medical, artistic or other applications.
• the invention relates to a laser treatment device, a workstation comprising such a device and a processing method using such a device.
• a means known to those skilled in the art for transporting a laser beam to a working area is the optical fiber, which may be provided at its free end with a focusing means of the projected laser beam.
• document EP 2,056,144 discloses an end element for optical fibers in the form of an end-fitting, made of a material identical to that of the core of the fiber and intended to focus the beam. Nevertheless, the mounting of the tip must be extremely precise, which makes it complex and difficult to achieve. In addition, this results in a stiffening of the end of the fiber, limiting its possibilities of orientation of the emitted beam. The resistance to large laser flux is not assured.
• this assembly is difficult to achieve and results in a transmission interface between the core of the fiber and the microsphere, whose properties can not always be precisely determined and which necessarily generates losses.
• the type of fibers used in these two documents does not allow the application of high powers.
• JP 63-98977 discloses, in the field of optical communications, the implementation of optical fibers having a hemispherical end obtained by simple melting of the material of the end of these fibers.
• the purpose of this particular conformation of the end of the fibers is only to limit the return of reflected light and no beam focusing or power application is mentioned.
• the main object of the invention is to provide a functional laser treatment device with a laser head with a simple structure, easy to manufacture, supporting high powers and able to provide a working beam of micrometric size, said device having, in addition, , can optimally exploit this laser head and advantageously allow a concentration of the beam emitted beyond the diffraction limit.
• the invention relates to a laser treatment device comprising, on the one hand, a laser head consisting essentially of an injection module adapted and intended to be powered by a laser source and by an optical fiber formed of a core surrounded by at least one sheath, connected to said injection module and ending with a beam concentrating tip and, secondly, a support system of a part, an article or a material having at least one area to be treated by the laser head, or working area, the concentrating tip and the workpiece, article, or material being positionable and relatively movable relative to each other in a controlled manner ,
• the invention also relates to a workstation and a processing method implementing this device.
• Figure 1 is a symbolic representation of a laser treatment device according to the invention mounted in a work station according to the invention
• FIG. 2 is a partial schematic representation on a different scale of the free end of the optical fiber forming part of the device represented in FIG. 1 (detail A of this figure);
• FIGS. 3A and 3B are graphical representations of two examples of curves that can define the outer shape of the concentrating tip of the fiber shown partially in FIG. 2;
• FIG. 4 is a schematic representation of detail illustrating an optical coupling device between the laser source and the optical fiber, forming part of the device represented in FIG. 1, and,
• FIGS. 1, 4 and 5 illustrate a laser treatment device 1 comprising, on the one hand, a laser head 2 essentially consisting of an injection module 3 adapted and intended to be powered by a laser source 4 and by an optical fiber 5 formed of a core 10 surrounded by at least one sheath 10 ', 10 ", connected to said injection module and ending with a beam concentrating tip 6 and, secondly, a system 7 for supporting the beam.
• a part, an article or a material 8 comprising at least one zone 9 to be treated by the laser head 2, or working zone, the concentrating tip 6 and the part, the article or the material 8 can be positioned and moved relative to one another in a controlled manner.
• this device is characterized in that the concentration tip 6 is formed in one piece with the optical fiber 5, of the type with a solid core, as a shaped portion of the free end portion 5 'of the latter, opposite its end connected to the injection module 3.
• the distance d between the tip 6 'of the concentration of end piece 6 and the working zone 9 is such that 5D c> d> ⁇ 50, the geometry and positioning of the end piece 6 being such that the laser head 2 generates a concentrated and slightly divergent laser beam 11 in the form of a photonic jet, with a diameter D j at the working zone 9 of the order of magnitude of the wavelength ⁇ .
• a fiber 5 with a core 10 of large size allows not only the transport of a stream high power, but also the concentration of this flux to generate a photonic jet 11 at a distance and a limitation of the embrittlement of the free end 5 'of the fiber 5, resulting from the reflow and the structural forming of the end of the heart 10 leading to the concentrating tip 6.
• a working distance d can be ensured such that d> Dc, which guarantees the preservation of the integrity of the tip 6 during the laser treatment process, makes the servo-control of the distance between the tip 6 and the working zone 9 less critical, while allowing a lateral resolution 1 of the order of ⁇ by virtue of the photonic jet generated at the end of nozzle 6.
• b is such that D c / 2 ⁇ b ⁇ 2D c / 3.
• This variant makes it possible to obtain a higher resolution than with the preceding variant (lateral resolution 1 ⁇ ).
• This second variant is advantageous when the laser treatment method is applied to a given material that does not risk to harm the integrity of the tip 6 although the working distance d is such that d ⁇ Dc (example: microgravure of a silicon wafer).
• the fiber 5 is of the monomode or multimode type, preferably with a limited or multimode number of modes with a low number of excited modes and advantageously with a small numerical aperture, preferably a double optical cladding fiber 10 ', surrounded by a mechanical sheath 10 ", or a semitransparent mechanical sheath fiber (not shown),
• the fiber 5 has a cylindrical shape, preferably with a circular section, and / or
• the fiber 5 has a flexible structure allowing bending with a minimum radius of curvature up to at least 20 mm, preferably up to 10 mm.
• the optical fiber 5 has an optical index gradient between the core 10 and the sheath 10 'surrounding the latter, the index varying from a high value in the center of the fiber 5, for example between 1.3 and 3.5, at a low value at the sheath 10 ', for example between 1.2 and 3.
• This index gradient is preferably of the parabolic type and can be obtained by prior doping of the fiber 5 (known technique for the manufacture of index gradient fibers or GRIN index gradient lenses) or during shaping of the tip 6 by thermoforming.
• the optical fiber 5 may have, in the direction of its longitudinal axis AM, a composite structure comprising, on the one hand, a first portion 16 (having the inlet or injection end 5 ") which consists of a fiber with relatively few modes but having a large diameter, preferentially monomode with a small numerical aperture, for example of the broad-modal-mode optical fiber type or LMA fiber (Large Mode Area), and, secondly, a second portion 16 'which is welded to the first portion 16, presents a plus large diameter of the heart and has at its free end the concentrating tip 6 formed integrally and adapted to generate the photonic jet 11.
• a composite structure comprising, on the one hand, a first portion 16 (having the inlet or injection end 5 ") which consists of a fiber with relatively few modes but having a large diameter, preferentially monomode with a small numerical aperture, for example of the broad-modal-mode optical fiber type or LMA fiber (Large Mode Area), and, secondly, a second portion 16 'which is welded
• the first portion 16 allows to excite only the low order modes of the second portion 16 'and thus to further promote the phenomenon of the photonic jet 11 at the output, which allows to concentrate the beam beyond the diffraction limit.
• the injection into the first portion 16 is facilitated (large diameter core).
• the optical fiber 5, or at least the first portion 16 has a small numerical aperture ON (for example 0.05 ⁇ ON ⁇ 0.25), and for a wavelength of 1 ⁇ can by example be of type:
• single-mode LMA fiber with a core diameter of 50 ⁇ , a concentric ring sheath forming a Bragg structure and a numerical aperture of approximately 0.12;
• High power multimode index jump fiber silica core / silica optical cladding / polymer coating: respective dimensions in ⁇ 50/125/250; germanium doped heart; numerical aperture of 0.12.
• the second portion of fiber 16 ', welded with abutment to the first portion 16 may for example be of the type:
• - silica index jump fiber with a core diameter of 50 ⁇ or 100 ⁇ and a numerical aperture 0.22;
• silica core / optical sheath 1 made of silica / optical sheath 2 in TEQS / polymer coating: respective dimensions in ⁇ 200/240/260/400; germanium doped heart; numerical aperture of 0.22.
• it is intended to use a fiber 5 or a first portion 16 with a large core diameter (advantageously greater than 10 ⁇ , preferably at least 20 ⁇ ) and little modes, preferably substantially monomode, and a low numerical aperture (for example less than 0.20).
• a fiber type LMA is preferred.
• the laser treatment device 1 allows, in connection with a power source 4 laser (that is to say with an effective power P greater than or equal to 100 mW mode continuous or pulsed, preferably at least of the order of 1W) and a solid fiber 5 (in one piece or formed of two portions 16, 16 'connected by welding) capable of transmitting such power, to perform a treatment of a material, in particular a surface treatment (surface etching, surface melting of a material, surface oxidation, marking, surface crystallization, photopolymerization, thin-film drilling, etc.), with a high lateral resolution between ⁇ / 2 and 5 ⁇ .
• a power source 4 laser that is to say with an effective power P greater than or equal to 100 mW mode continuous or pulsed, preferably at least of the order of 1W
• a solid fiber 5 in one piece or formed of two portions 16, 16 'connected by welding
• the resulting laser head 2 is extremely compact at its level. free operational end and reports a great invasive potential for reaching and treating difficult to access areas: action on tissues or organs in an endoscopic application, machining the inside of a metal tube, treatment surface at an undercut or the like.
• the injection module 3 advantageously comprises (see FIG. 4) a means 3 'for quick connection of the end of the device. 5 "input of the optical fiber 5, providing protection of the input section of the latter, and a means 3" of three-dimensional micro-positioning, adapted and intended to have said input section at the focal point of the focusing optics of said module 3.
• the fast connection means 3 ' is preferably a high-power fiber connector that can be cooled.
• the micro-positioning means 3 may, for example, carry a focusing lens 3"'which it ensures the precise positioning with respect to the input end 5 "to achieve an optimized optical coupling.
• the injection module 3 is advantageously configured to be fixed at the output of a power laser or a power laser diode, or to be able to substitute for the optical head of an existing engraving system (replacing by example of a galvano metric head).
• the invention makes it possible to generate a photonic jet by focusing the radiation beyond the diffraction limit.
• control of the injection of the radiation and the privileged use of the light of the modes of weak order can in particular favor this phenomenon.
• the invention can also be implemented for other applications than those mentioned in the introduction while still optimally exploiting the specific laser head proposed.
• Example 4 illustrates a non-limiting practical embodiment corresponding to this variation of the invention.
• the object of the invention is also, as shown schematically and symbolically in FIG. 1, and partially in FIG. 5, a work station 12 for machining parts, articles or materials 8, in particular for the treatment of surface, engraving, cutting, drilling or marking.
• This work station 12 comprises a pulsed or continuous power laser source 4, a control unit 13, connected to sensors (not shown), to actuators (in particular for the relative displacement between head 2 and support 7), to the laser source 4 and possibly to a control and / or programming interface 14, a laser treatment device 1 coupled to the laser source 4 and controlled by the control unit 13 and a structure or a support frame 15.
• This work station 12 is characterized in that the laser processing device 1 corresponds to a device as described above, the relative positioning and displacement between the concentrating tip 6 formed on the end portion 5 'of the fiber optical 5 and the part, the article or the material 8 to be treated being controlled by the control unit 13 by means of sensors and corresponding actuators (not shown - known as such by those skilled in the art ) equipping the laser head 2 and / or the support system 7.
• the relative displacement, continuous or intermittent, between the part, the article or the material 8, on the one hand, and the laser head 2 or the optical fiber 5, on the other hand is controlled by means of the control unit 13 by implementing a control ensuring a control of the distance d between the concentrator tip 6 and the working zone 9, either by keeping an initially set value, or by making one or more adjustments (s) ) of this distance, during such a relative displacement, corresponding to a cycle or an effective phase of treatment.
• the station 12 may also comprise a communication, display and programming interface 14, enabling an operator to parameterize, control and control the operation of said station, in particular as a function of the workpiece, the article or the workpiece. material 8 to be treated and the treatment to be carried out.
• the laser source 4 is a laser source of effective power, with an effective power greater than 100 mW, preferably at least of the order of Watt or ten Watts.
• the work station 12 may comprise, on the one hand, a sensor 17 for measuring the light reflected back by the working zone 9 in the optical fiber 5 through the tip 6 and, secondly, a coupler (not shown) mounted at the input end 5 "of the optical fiber 5 and adapted to recover and transmit to said sensor 17 the retroreflected light having passed through said fiber 5 from the tip 6, these measured values being exploited, preferably in real time, by the control unit 13 to control the distance d between the tip 6 and the working zone 9.
• the workstation 12 may comprise a measurement sensor 17 in the form of a camera with a macro lens which observes the region of the tip 6 and the working zone 9, illuminated by a or a plurality of dedicated light source (s) (not shown), the images provided by said camera 17 being exploited, preferably in real time, by the control unit 13 to control the distance d between the tip 6 and the work area 9.
• a measurement sensor 17 in the form of a camera with a macro lens which observes the region of the tip 6 and the working zone 9, illuminated by a or a plurality of dedicated light source (s) (not shown), the images provided by said camera 17 being exploited, preferably in real time, by the control unit 13 to control the distance d between the tip 6 and the work area 9.
• One of the dedicated light sources may possibly correspond to a laser pointer associated with the power laser source 4 and illuminating the working zone 9.
• the invention also relates to a process for treating an article, a part or a material 8 implementing a laser treatment device 1 as described above, preferably forming part of a workstation. 12 as mentioned above.
• This method is characterized in that it consists, prior to a cycle or an effective treatment phase, in fixing an optical fiber 5 having a concentration tip 6, shaped in one piece and suitable and intended to produce a jet 11, on the part, the article or the material 8 in the working zone 9, to adjust the relative positioning of the input section of the fiber 5 to optimize the injection (of the laser beam from the source 4 ), possibly to conform the fiber 5 according to the shape of the part, the article or the material 8 to be treated, the location of the working zone 9, the path to be traveled to perform the treatment cycle or similar geometrical and / or topological considerations, in particular to adjust the power of the laser source 4, the optimum distance d between the tip 6 and the workpiece, the article or the material 8 and the relative speed of movement, as a function of the less of the nature of ladi the workpiece, said article or said material 8 or its surface and, finally, start the treatment under the control of the control unit 13, preferably following a path or a preprogrammed treatment cycle.
• the method of melt-molding the tip 6 of the optical fiber 5 may, for example, be similar to that used for the production of SNOM microscopy probes (near-field optical microscope) and proposed by the Lovalite companies and Laseoptics.
• SNOM microscopy probes near-field optical microscope
• Laseoptics proposed by the Lovalite companies and Laseoptics.
• the working zone 9 is located at a distance d of 150 ⁇ from the tip and the etching resolution is 1 ⁇ 3 ⁇ .
• a work station 12 is produced with a nanosecond pulsed laser in the near infrared having an effective power P ⁇ 5 W and ⁇ ⁇ 1 ⁇ (for example Nd: YAG or Ytterbium doped fiber laser), a pulse duration of 20 ns and a repetition frequency of 20 kHz and with a silica fiber 5:
• a nanosecond pulsed laser in the near infrared having an effective power P ⁇ 5 W and ⁇ ⁇ 1 ⁇ (for example Nd: YAG or Ytterbium doped fiber laser), a pulse duration of 20 ns and a repetition frequency of 20 kHz and with a silica fiber 5:
• glass can also be etched on the surface.
• a work station 12 is produced with a pulsed or continuous laser diode 4 in the near infrared having an effective power P ⁇ 100 mW, ⁇ ⁇ 1 ⁇ .
• the working area 9 is located at a distance d of 800 ⁇ from the tip and the etching resolution is 1 - 5-10 ⁇ .

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Laser Beam Processing (AREA)
• Laser Surgery Devices (AREA)

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• 2015
  • 2015-05-13 FR FR1554317A patent/FR3036050B1/fr not_active Expired - Fee Related
• 2016
  • 2016-05-13 JP JP2018511526A patent/JP2018521859A/ja active Pending
  • 2016-05-13 EP EP16730450.0A patent/EP3295229A2/de not_active Withdrawn
  • 2016-05-13 WO PCT/FR2016/051141 patent/WO2016181088A2/fr active Application Filing
  • 2016-05-13 US US15/573,044 patent/US20180120506A1/en not_active Abandoned
  • 2016-05-13 CN CN201680027547.8A patent/CN107864672A/zh active Pending

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