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WO2002027871A1 - Fibre compacte pompee lateralement - Google Patents

Fibre compacte pompee lateralement Download PDF

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Publication number
WO2002027871A1
WO2002027871A1 PCT/US2001/030555 US0130555W WO0227871A1 WO 2002027871 A1 WO2002027871 A1 WO 2002027871A1 US 0130555 W US0130555 W US 0130555W WO 0227871 A1 WO0227871 A1 WO 0227871A1
Authority
WO
WIPO (PCT)
Prior art keywords
grating
fiber
pump
electromagnetic radiation
incident
Prior art date
Application number
PCT/US2001/030555
Other languages
English (en)
Inventor
Monica Minden
Original Assignee
Hrl Laboratories, Llc
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 Hrl Laboratories, Llc filed Critical Hrl Laboratories, Llc
Priority to AU2002211308A priority Critical patent/AU2002211308A1/en
Publication of WO2002027871A1 publication Critical patent/WO2002027871A1/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
    • H01S3/09—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
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre

Definitions

  • the present invention relates to a system for side-pumping an optical fiber. More particularly, the present invention relates to a method for side-pumping a fiber using laser diodes; the fiber is configured as a laser oscillator or amplifier, producing a coherent electromagnetic output signal.
  • Fiber lasers and optical fiber amplifiers have widespread application in a many fields, including telecommunications, environmental sensing, scientific research, medicine, and numerous other areas. As the various fields that utilize fiber systems continue to develop, fiber systems must meet the ever-increasing demands for space-efficiency and high power capabilities. Pumping of fibers from the side instead of the fiber end is one approach to achieving such improvements in fiber system technology.
  • the present invention provides a compact, side pumped fiber system that is easily manufactured and does not require finely dimensioned focusing.
  • the invention further provides a technique for side-pumping a fiber by providing a relief grating on a substantially planar portion of a length of fiber.
  • a relief grating shall be configured, in its period and phase, such that the zeroeth order of the diffracted light is substantially suppressed, and the incident light is coupled via either the +1, the -1, or both the +1 and -1 diffraction orders of the grating into confined cladding modes that are substantially totally internally reflected inside the fiber.
  • the grating itself is both inexpensive and relatively simple to fabricate because the grating technology is essentially analogous to that used for preparing phase masks for the purposes of exposing Bragg gratings into the cores of single mode fibers.
  • One preferred embodiment of the present invention is a cladding-pumped fiber amplifier pumped by a diode laser hereafter referred to as the pump.
  • the pump is focused with the aid of a cylindrical focusing lens.
  • the fiber, into which the electromagnetic radiation from the pump is to be introduced has at least one substantially planar surface, upon which a relief grating is etched.
  • the relief grating can be created using existing technology and techniques for preparing phase masks.
  • the diffraction relief grating is configured, using design rules for diffraction gratings well-known to those skilled in the art, to substantially suppress the zeroeth order of the diffracted incident light. It is also configured to couple the incident light, via the either the +1, the -1 , or both the +1 and -1 orders of the diffraction relief grating, into confined fiber cladding modes that are substantially totally internally reflected.
  • FIG. 1 depicts the side-coupled pumping of a cladding-pumped fiber amplifier via surface relief gratings
  • FIG. 2 depicts the electromagnetic radiation wave-path, showing the suppression of the zeroeth order component and the general path of the +1 order and the -1 order components;
  • FIG. 3 depicts side-coupled pumping of a cladding-pumped fiber amplifier via a surface relief grating wherein the electromagnetic radiation from the pump is incident on the grating at a non-perpendicular angle.
  • the present invention provides a method and an apparatus for side-pumping optical fibers.
  • Side-pumping enables the fibers to be used as amplifiers, with both ends free for splicing to other fibers.
  • This invention allows for fiber optical systems that are more compact and durable, cost less, and are scalable to large parallel arrays of fiber amplifiers. Additionally, the invention may be tailored to a variety of other applications.
  • the following description, in conjunction with the referenced drawings, is presented to enable one of ordinary skill in the art to make and use the invention and to incorporate it in the context of particular applications. Various modifications, as well as a variety of uses in different applications, will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments presented, but is to ;'be accorded the widest scope consistent with the principles and novel features disclosed herein.
  • FIG. 1 A side-coupled, cladding pumped, fiber amplifier, utilizing a surface relief grating according to one embodiment of the present invention, is shown in FIG. 1.
  • the fiber amplification system is configured to include a suitable pump 100 that must be coupled into the cladding of the fiber 102.
  • the pump 100 may be a single-emitter pump laser, a multi-element pump laser array, or other suitable laser.
  • Electromagnetic radiation 104 from the pump 100 passes through the cylindrical lens 106 and then impinges on a relief grating 108.
  • the electromagnetic radiation 104 diffracted by the grating 108 substantially follows the path 110 inside the fiber 102.
  • the relief grating 108 is etched on a substantially planar portion of the fiber 102.
  • incident radiation 104 originating with the pump 100 is coupled via the +1 and - 1 order paths 110 of the relief grating 108, into confined modes that are substantially totally internally reflected by the fiber walls 202.
  • the pump 100 is configured to direct substantially collimated electromagnetic radiation 104 onto the relief grating 108, which is etched onto the wall 202 of the fiber 102.
  • the grating 108 is specifically designed to diffract the incident radiation into the +1 and -1 orders 110 at an angle such that the incident radiation 104 is trapped inside the total internal reflection cone of the fiber. To illustrate this, the figure shows the example that after one such internal bounce, the radiation substantially follows the path 204.
  • the relief grating 108 is similar to the type of relief gratings that are fabricated for use in exposing Bragg gratings into fiber cores with excimer lasers.
  • the grating is configured to suppress the zeroeth order components 206 and greater than 95% of the incident radiation 104 is diffracted to the sides 110.
  • a typical design condition for zeroeth order suppression is that the optical thickness of the relief grating 108 be a half wavelength of the incident pump radiation in the fiber medium.
  • the medium will be comprised of fused silica.
  • the thickness is less than 1 micron for a 915 nm- pumped fiber.
  • the pump is configured such that the electromagnetic radiation 104 from the pump 100 impinges onto the relief grating 108 etched into the wall 202 of the fiber 102 at a non-perpendicular angle.
  • the grating 108 is designed to diffract the incident radiation 104 into either the +1 or -1 orders.
  • FIG. 3 depicts the path 302 followed by the incident radiation after diffraction.
  • the radiation 104 from the pump 100 is substantially totally reflected within the fiber 102.
  • the relief gratings 108 of the sort herein described may readily be etched onto the exposed surface 202 of a cladding-pumped fiber 102.
  • Conventional etched-grating fabrication techniques may be applied to the surface 202 of the fiber 102. Specifically, a photo-resist would be applied, and then chemical etching of the fused silica would be performed. Or, conventional electron beam (e-beam) or ion-etching techniques, which are well understood in the art, could be used.
  • Such fabrication techniques may also be applied to an array of a plurality of cladding-pumped fibers by spooling the array such that the desired etching surfaces are exposed.
  • a typical grating period might be 0.7 microns, which would couple light ranging from 0.7 microns through 1.0 micron into angles larger than the total internal reflection angles of the fiber 102.
  • the surface 202 of the cladding-pumped fiber 102 upon which the grating 108 is written is, in the preferred embodiment, substantially planar.
  • Cladding-pumped fibers with rectangular cross-sections are commercially available. The rectangular cross-sectioned fibers are commonly utilized to facilitate mode mixing and overlap of the electromagnetic radiation 104 from the pump 100 with the doped fiber core.
  • side-pumping In contrast to end-pumping, side-pumping enables fibers to be more readily used as amplifiers, since side-pumping leaves both ends of a fiber free for splicing to other fibers; these fibers would be the input and output of the signal radiation for a fiber amplifier, for example. In many systems it is a significant advantage to never have the signal radiation be unconfined by a fiber. In practice, the pump 100, the cylindrical lens 106, and the fiber 102 itself would all be mounted together on the same small structure. Both ends of the fiber 102 would emerge from this structure, and be conveniently available for splicing.
  • the present invention provides an approach to side pumping that is both cost-efficient, and, perhaps more importantly, space-efficient. It provides an approach that is at once compact, inexpensive, and scalable to large parallel arrays of fiber amplifiers. Such an array of pumped fiber amplifiers would allow power scaling of coherent beams, power scaling of a wide variety of temporal waveforms, and beam steering integral to the output aperture of the laser. With increasing component miniaturization, and the costs associated with component size, particularly in the aerospace industry, space efficiency is critical for fiber amplifiers. Other side pumping approaches are designed more for coupling large amounts of power into the fiber, but they do not address the difficulties of manufacturing such couplers for large fiber arrays.
  • Such applications might include avionics, satellite based systems, and other aerospace applications.
  • the invention will also find application where environmental demands are not as great, but where a relatively simple, dependable low cost alternative is desired.

Landscapes

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

Abstract

L'invention concerne un amplificateur de fibres compactes pompées latéralement pouvant être fabriqué facilement et ne nécessitant pas de mise au point de fines dimensions. L'invention concerne également une technique de pompage latéral d'une fibre (102) par utilisation d'un réseau de diffraction (108) en relief sur une partie latérale sensiblement plane d'une longueur de la fibre (102). Un tel réseau de diffraction (108) est configuré de manière que l'ordre zéro (206) de la lumière incidente soit sensiblement supprimé, et la lumière incidente (104) est couplée via les ordres +1 et -1 (110) en quasi confinement via une réflexion interne totale. Le réseau lui-même est à la fois peu coûteux et relativement simple à créer.
PCT/US2001/030555 2000-09-27 2001-09-27 Fibre compacte pompee lateralement WO2002027871A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002211308A AU2002211308A1 (en) 2000-09-27 2001-09-27 Compact side-pumped fiber

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US67073100A 2000-09-27 2000-09-27
US09/670,731 2000-09-27

Publications (1)

Publication Number Publication Date
WO2002027871A1 true WO2002027871A1 (fr) 2002-04-04

Family

ID=24691630

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2001/030555 WO2002027871A1 (fr) 2000-09-27 2001-09-27 Fibre compacte pompee lateralement

Country Status (2)

Country Link
AU (1) AU2002211308A1 (fr)
WO (1) WO2002027871A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5854865A (en) * 1995-12-07 1998-12-29 The United States Of America As Represented By The Secretary Of The Navy Method and apparatus for side pumping an optical fiber
WO2000054377A1 (fr) * 1999-03-08 2000-09-14 Optigain, Inc. Laser a fibre a pompage lateral
EP1059707A2 (fr) * 1999-06-03 2000-12-13 TRW Inc. Laser et amplificateur de haute puissance à fibre optique en forme de ruban
EP1065764A2 (fr) * 1999-06-18 2001-01-03 TRW Inc. Appareil de pompage optique latéral d'une fibre optique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5854865A (en) * 1995-12-07 1998-12-29 The United States Of America As Represented By The Secretary Of The Navy Method and apparatus for side pumping an optical fiber
WO2000054377A1 (fr) * 1999-03-08 2000-09-14 Optigain, Inc. Laser a fibre a pompage lateral
EP1059707A2 (fr) * 1999-06-03 2000-12-13 TRW Inc. Laser et amplificateur de haute puissance à fibre optique en forme de ruban
EP1065764A2 (fr) * 1999-06-18 2001-01-03 TRW Inc. Appareil de pompage optique latéral d'une fibre optique

Also Published As

Publication number Publication date
AU2002211308A1 (en) 2002-04-08

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