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
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4201—Packages, e.g. shape, construction, internal or external details
  • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
  • G02B6/4228—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements
  • G02B6/423—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements using guiding surfaces for the alignment
  • G02B6/4231—Passive alignment, i.e. without a detection of the degree of coupling or the position of the elements using guiding surfaces for the alignment with intermediate elements, e.g. rods and balls, between the elements
• • 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
  • G02B6/42—Coupling light guides with opto-electronic elements
• • 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
• • 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
  • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
  • G02B6/322—Optical coupling means having lens focusing means positioned between opposed fibre ends and having centering means being part of the lens for the self-positioning of the lightguide at the focal point, e.g. holes, wells, indents, nibs
• • 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
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4292—Coupling light guides with opto-electronic elements the light guide being disconnectable from the opto-electronic element, e.g. mutually self aligning arrangements

Definitions

• the present invention relates to a device for automatically centering a laser beam, in particular in a single-mode optical fiber or in a multimode optical fiber, after a defocusing or a decentering of said beam.
• This device applies more particularly to laser beams whose deflections or offsets are greater than the transverse dimensions of the optical fibers or close to these dimensions.
• the invention also relates to a method of manufacturing this device.
• Static devices mainly use surface light scatterers, more simply called “surface diffusers”, that is to say means whose surface is capable of diffusing (“scatter”) the light from the incident laser beam, but do not provide sufficient uniformity for injections into the fibers, because
• Dynamic devices have the major drawback of requiring a priori knowledge of pointing and off-center variations to correct the positioning of the optical fiber relative to the laser beam.
• Such devices use electronic means which are controlled by a CCD type sensor or a four-quadrant sensor, this sensor being placed on a position which is the image of the core ("core”) of the optical fiber.
• the aim of the present invention is to remedy the above drawbacks.
• a static centering device comprising a volume light diffuser, more simply called a "volume diffuser”, that is to say a means whose volume - and no longer the surface - is suitable to scatter the light of the incident laser beam that we want to center.
• the present invention relates to a device for automatically centering a laser beam in a light guide, this device being characterized in that it comprises a volume diffuser, comprising an entry face of the laser beam and provided for diffusing this laser beam and automatically centering it in the light guide.
• This light guide can be a single mode optical fiber or a multimode optical fiber.
• the thickness of the volume diffuser is at least equal to 100 times the wavelength of the laser beam.
• the volume diffuser can be made of polytetrafluoroethylene.
• the volume diffuser has a cylindrical shape.
• the volume diffuser has a side face and the device further comprises a light reflector which surrounds this side face.
• this device further comprises a lens which is placed on the entry face of the volume diffuser and provided for defocusing the laser beam on this entry face. .
• the volume diffuser has a side face and the device further comprises a light reflector which surrounds this side face, extends beyond the entry face and guides the laser beam to this entry face.
• the device which is the subject of the invention further comprises an auxiliary optical fiber which is optically coupled to the entry face of the volume diffuser and guides the laser beam to this entry face.
• the present invention also relates to a method of manufacturing the device which is the subject of the invention, in which a tubular light guide is produced and the volume diffuser is manufactured from a material capable of diffusing light, using the tubular light guide as a cookie cutter.
• FIG. 2 is a schematic sectional view of a first particular embodiment of the device which is the subject of the invention
• FIG. 3 is a schematic sectional view of a second particular embodiment of the device object of the invention.
• FIG. 4 is a schematic sectional view of a third particular embodiment of the device which is the subject of the invention
• FIG. 5 is a schematic sectional view of a fourth particular embodiment of the device which is the subject of the invention.
• FIG. 6A schematically illustrates a step of manufacturing a device according to
• FIG. 6B is a schematic sectional view of a device according to the invention.
• FIG. 7 schematically illustrates the scattering of light by an elementary volume of diffusing material
• the device which is the subject of the invention overcomes the drawbacks of the prior art, on the one hand, because it is static and, on the other hand, because it uses a volume diffuser. In this case, it is possible to reduce the coherence of the laser beam and therefore the resulting granularity.
• the volume diffuser is made of a suitable material in order to obtain correct uniformities.
• the choice of this material is made in function of the optical scattering coefficient, which must be as large as possible, and the absorption coefficient which must be as low as possible.
• a material such as polytetrafluoroethylene or Teflon (registered trademark) is well suited to laser beams from the visible and near infrared spectra.
• a device according to the invention does not degrade the temporal shape of a pulsed laser beam, as long as the duration of the pulses is not less than 10 11 s, and that the coherence of the beam does not harm not to the uniformity of this beam at the outlet of the diffuser, due to the superposition of decorrelated granularity figures.
• a volume diffuser is used; this means that this diffuser has a length L, or thickness, which is significant with respect to the wavelength of the incident laser beam F which it is desired to center (FIG. 1).
• the thickness of this diffuser is at least equal to 100 times this wavelength.
• This volume diffuser advantageously has the shape of a cylinder whose length is a function of the uniformity and of the desired overall transmission.
• FIG. 1 This is schematically illustrated in Figure 1 where we see a device according to the invention, comprising a volume diffuser 2, of cylindrical shape, in Teflon (registered trademark), length L.
• a volume diffuser 2 of cylindrical shape, in Teflon (registered trademark), length L.
• a laser beam F is focused on one end 4 of the diffuser 2 forming an entry face.
• the laser light is diffused in the form of spherical waves S at the outlet of the diffuser, on the side opposite to the inlet face 4.
• the increase in uniformity at the outlet of the diffuser 2 as well as the increase in the overall transmission are obtained by placing the diffuser in volume in a reflective waveguide.
• FIG. 2 This is schematically illustrated by FIG. 2 where we see the diffuser 2 inserted in a metallic tubular reflector 6 which thus surrounds the lateral face 8 of the diffuser 2.
• This reflector 6, or guide reflects the laser light which reaches this lateral face 8 and thus guides this light in the diffuser 2.
• - A is the section of the metal guide (in m 2 )
• a is the section (in m 2 ) of the optical fiber which is coupled to the diffuser and in which we want to center the laser beam
• - ⁇ is the digital opening angle of the fiber
• - z is the length of the guide (in m)
• scattering cross section (“scattering cross section").
• Auxiliary means can advantageously be added to the reflecting guide in order to increase the flow resistance of the automatic centering device. Indeed, if the laser beam is focused on the entrance face of the diffuser, it risks damaging it.
• a micro-lens is added in front of the diffuser to defocus the laser beam on the entrance face of the diffuser, that is to say so that the laser beam is not focused on this entry face.
• FIG. 3 This is schematically illustrated in FIG. 3 where we see a micro-lens 10 placed against the entry face 4 of the diffuser 2. This micro-lens 10 is able to defocus the incident laser beam 12 on the face 4 of the diffuser , the latter and the microlens 10 being coaxial.
• the diameter of the microlens is equal to the diameter of the diffuser 2.
• FIG. 6A a method of manufacturing the diffuser 2 of FIG. 2 will be explained in a tubular reflector of the same length.
• the diffuser of Figure 4 can be obtained in the same way, in a longer tubular reflector and then pushing the diffuser to the side of the reflector opposite to that by which the diffusing material was introduced.
• a large diameter optical fiber is added in front of the volume diffuser to increase the flow resistance of the automatic centering device.
• a section of optical fiber 16 is added to the device in FIG. 4, the core ("core”) and the cladding ("cladding") of which have the references 18 and 20 respectively.
• the core 18 and the diffuser 2 are coaxial.
• the section 16, the diameter of which is substantially equal to that of the diffuser 2 is housed in the part of the guide 14 which projects beyond the inlet face
• the fiber section 16 thus receives the laser beam 12 before the diffuser, which makes it possible to avoid hot spots in the latter.
• the reflective guide 6 can advantageously serve as a cookie cutter for the development of the diffuser in a flexible diffusing material (if this guide is made of a material of sufficient hardness).
• tubular guide 6 for example made of steel, which is made rigidly integral with a plate 22 of steel and thus forms a projection of this plate 22.
• this plate 22 is fitted, by means of this projection, into a support 24 and made integral with this support by screws symbolized by dashed lines
• the support 24 has a threaded portion 28 onto which an optical fiber connector 30 can be screwed. It is thus able to optically connect the diffuser 2 to the optical fiber 32 with which this connector 30 is provided, the plate 22 and the support 24 being suitably drilled for this purpose.
• the drilling of the plate 22 causes the diffuser 2 to be located in a reflector of the kind 03616
• the device in FIG. 6B allows the laser beam 12 to be centered on the optical fiber 32 thanks to the volume diffuser 2.
• a plate 34 of the flexible diffusing material is used, for example a Teflon plate (registered trademark), and the steel plate 22 is applied against this plate 34 (FIG. 6A).
• the projection formed by the tubular guide 6 of FIG. 6A sinks into the material and part of the latter penetrates into the tubular guide to form the diffuser 2.
• the diffuser is then separated. thus formed from the rest of the material.
• a Teflon diffuser (registered trademark) is used whose length (thickness) is 750 ⁇ m, or nearly 700 times the length d wave of the laser beam, and a metal waveguide of polished steel, which protrudes from the diffuser by 0.3mm on the side from which the laser beam arrives.
• the present invention is not limited to centering a laser beam in an optical fiber (single mode or multimode).
• the variation dL of the luminance L (in / m 2 / sr) through a thickness dz of an elementary volume is such that dL
• Wgest is the albedo of a single particle and d ⁇ the elementary solid angle.
• the reduced incident illumination U r i decreases as a function of exp (-p ⁇ t z) and of the dimension of the laser beam, while the scattered illumination U d increases firstly as a function of z and then decreases thereafter.
• the product p ⁇ t z must be of the order of 10 for U d to be of the order of
• Kl is a constant of proportionality and ⁇ is the aperture angle at l / e 2 of the laser beam in the material, while we can write for 1 scattered illumination, due to the conservation of energy and considering that this illumination is constant on a sphere of radius z:

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Optical Couplings Of Light Guides (AREA)
• Laser Beam Processing (AREA)
• Light Guides In General And Applications Therefor (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=29724941

Family Applications (1)

Country Status (10)

Families Citing this family (6)

Family Cites Families (10)

• 2002
  • 2002-06-27 FR FR0208010A patent/FR2841657B1/fr not_active Expired - Fee Related
• 2003
  • 2003-06-25 JP JP2004516866A patent/JP2005531037A/ja not_active Withdrawn
  • 2003-06-25 RU RU2005101890/28A patent/RU2005101890A/ru not_active Application Discontinuation
  • 2003-06-25 CA CA002490345A patent/CA2490345A1/fr not_active Abandoned
  • 2003-06-25 EP EP03761641A patent/EP1516218A2/de not_active Ceased
  • 2003-06-25 KR KR10-2004-7021287A patent/KR20050013645A/ko not_active Application Discontinuation
  • 2003-06-25 WO PCT/FR2003/001963 patent/WO2004003616A2/fr not_active Application Discontinuation
  • 2003-06-25 US US10/519,015 patent/US20050213881A1/en not_active Abandoned
  • 2003-06-25 AU AU2003260627A patent/AU2003260627A1/en not_active Abandoned
  • 2003-06-25 CN CN03815188XA patent/CN1666127A/zh active Pending

Non-Patent Citations (1)

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