GB2532294A - Frequency-converted Fiber-MOPA - Google Patents

Frequency-converted Fiber-MOPA Download PDF

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Publication number
GB2532294A
GB2532294A GB1500136.5A GB201500136A GB2532294A GB 2532294 A GB2532294 A GB 2532294A GB 201500136 A GB201500136 A GB 201500136A GB 2532294 A GB2532294 A GB 2532294A
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GB
United Kingdom
Prior art keywords
fiber
radiation
mopa
enclosure
fundamental
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.)
Granted
Application number
GB1500136.5A
Other versions
GB2532294B (en
Inventor
He Fei
Macgillivray Ian
Tauser Florian
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.)
Coherent Scotland Ltd
Original Assignee
Coherent Scotland Ltd
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
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Publication of GB2532294A publication Critical patent/GB2532294A/en
Application granted granted Critical
Publication of GB2532294B publication Critical patent/GB2532294B/en
Active 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
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser 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
    • H01S3/23—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
    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • 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
    • H01S3/10084—Frequency control by seeding
    • 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
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H01S3/1109—Active mode locking
    • 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
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G02B6/3807—Dismountable connectors, i.e. comprising plugs
    • G02B6/3897—Connectors fixed to housings, casing, frames or circuit boards
    • 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
    • G02B6/4251—Sealed packages
    • 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
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • 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
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06704—Housings; Packages
    • 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
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06712—Polarising fibre; Polariser
    • 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
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers

Abstract

Fundamental-wavelength radiation from a fiber MOPA 12 amplified in an active optical fiber 14. The active fiber 14 is terminated at a distal end 14D by an endcap 16 having an exit-face 18 from which fundamental radiation is delivered. The endcap 16 is hermetically sealed to a wall of an enclosure 30 housing frequency conversion elements. Pump-radiation for the active fiber 14 is fiber coupled into the active fiber 14 at a proximal end thereof.

Description

FREQUENCY-CONVERTED FIBER-MOPA
Inventors: Fei He, Ian MacGillivray, and Florian Tauser.
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to frequency-converted fiber master-oscillator power-amplifier (MOPA) systems. The invention relates to frequency-converted fiber-MOPAs, in which MOPA output is frequency-converted by optical I 0 elements in free space in a sealed enclosure.
DISCUSSION OF BACKGROUND ART
In optical apparatus in which the output of a fiber MOPA is frequency-converted by optics in a sealed enclosure, the MOPA output is carried to the enclosure by an active fiber of a final amplification stage of the MOPA. This active fiber is typically terminated by a transparent end-cap having an exit face. The end cap is clamped in to a plug which mates with a socket in a wall of the enclosure. A seal is formed between the plug and the socket such that the exit face of the end cap is effectively within the sealed enclosure.
The active fiber of the final amplifier stage is reverse pumped by diode-laser radiation delivered in free-space. This requires that at least delivery optics for the free-space reverse pumping are included in the enclosure. This greatly complicates the design and construction of the sealed enclosure.
There is a need for a frequency-converted fiber MOPA arrangement in which 25 the exit face of the end cap is protected in the same manner as frequency-conversion optics in the sealed enclosure but wherein pump radiation for the final fiber-amplifier stage is not provided from within the enclosure.
SUMMARY OF THE INVENTION
The invention is defined in the independent claim below to which reference should now be made. Preferred features are set-out in the dependent claims.
In one aspect, the present invention comprises a fiber MOPA generating laser-radiation having a fundamental wavelength. The fiber MOPA has an active optical fiber providing an amplifier stage of the fiber MOPA. The active optical fiber is terminated, at a distal end thereof, by a transparent end-cap having an exit-face. A sealed enclosure is provided having a plurality of optical elements located therein for converting the fundamental-wavelength radiation to output radiation having a frequency-converted wavelength. The end-cap of the active optical fiber is sealed to the enclosure such that the exit-face of the end-cap is effectively within the enclosure. The active optical fiber is forward-pumped by diode-laser radiation fiber-coupled into a proximal end of the active optical fiber.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the specification, schematically illustrate a preferred embodiment of the present invention, and together with the general description given above and the detailed description of the preferred embodiment given below, serve to explain principles of the present invention.
FIG. 1 is a side-elevation view, partly in cross-section schematically illustrating a preferred arrangement of optical apparatus in accordance with the present invention, including a fiber-MOPA having an amplifier-fiber, an enclosure including frequency-conversion elements, the amplifier-fiber terminated by an end-cap, and the end-cap housed in a plug sealably engaging a socket in a wall of the enclosure.
FIG. 2 schematically illustrates details of a preferred architecture of the fiberMOPA of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
Turning now to the drawings, wherein like features are designated by like reference numerals, FIG. 1 schematically illustrates a preferred embodiment 10 of frequency-converted fiber-MOPA apparatus in accordance with the present invention. Apparatus 10 includes a fiber-MOPA 12 delivering laser output pulses having a duration of less than about 500 picoseconds. The pulses are pulses of optical radiation having a fundamental wavelength characteristic of the master oscillator of the MOPA. The pulses are transported by an active optical fiber 14, which can be a final amplifier stage, or the only amplifier stage, of the fiber-MOPA.
Optical fiber 14 is terminated at distal end 14D thereof by an end-cap 16, having an exit face 18. Fiber 14 is pumped by diode-laser radiation fiber-coupled to a proximal end of the optical fiber within MOPA 12. An exemplary pumping arrangement in accordance with the present invention is described in detail further herein below.
An enclosure 30 includes optical elements for frequency-converting output pulses of the fiber-MOPA. Here, the frequency-conversion elements include a focusing lens 32, an optically nonlinear crystal 34, and a collimating lens 36. Frequency-converted output pulses are delivered from the enclosure through a window 38 sealed to the enclosure. This is a simplest frequency-conversion arrangement in which optically nonlinear crystal 34 can be arranged for frequency-doubling or optical parametric conversion (frequency-division). Other frequency conversion arrangements may be included in enclosure 30 without departing from the spirit and scope of the present invention. It is emphasized, here, that enclosure 30 does not include any arrangements for optically pumping active (amplifier) fiber 14.
Optical fiber 14 and end-cap 16 thereon are clamped and sealed to a plug 20 which is inserted into a socket 40 in a wall 42 of enclosure 30. Plug 20 is clamped into socket 40 by screws 22. This clamping compresses an 0-ring seal 46 between plug 20 and an end-wall 44 of socket 40. This completes hermetic sealing of the enclosure and provides that end-face 18 of end-cap 16 is effectively within the sealed enclosure.
It should be noted here that only sufficient detail of the sealing of plug 20 and socket 40 is provided for understanding principles of the present invention. From the description of the invention provided above, persons of ordinary skill in the mechanical engineering art may devise other arrangements, more or less effective, without departing from the scope of the present invention. Such arrangements may include any well-known arrangement for stripping (mode-stripping) residual pump radiation from active fiber 14.
FIG. 2 schematically illustrates a preferred architecture for fiber-MOPA 12 of apparatus 10 FIG. 1. Seed pulses (a seed-signal) from a mode-locked laser are transported by a polarization-maintaining fiber 52. The seed-signal is then transferred into the core of fundamental wavelength transport optical fiber 53 with a fifteen micrometer (15 um) mode-field diameter via a mode-field adapter (MFA) 54. The fundamental wavelength-transport fiber 53 is spliced to a seed-port 56 of a 2+1X1 fiber combiner 70.
Combiner 70 combines the input from the seed-port and two multimode ports (62 and 63) into a proximal end 65P of one double-clad polarization-maintaining output-fiber 65. Fibers 62 and 63 are spliced, respectively to output fibers 60 and 64, of diode-laser packages 58A and 58B, respectively. This provides that radiation (pump-radiation) from the diode-laser packages is fiber-coupled into output fiber 65.
Distal end 65D of output fiber 65 is coupled via a double-clad splice 72 to proximal end 14P of amplifier fiber 14. This provides that pump-radiation is fiber coupled into the amplifier and propagates in the same direction as the seed-signal radiation. This can be referred to as forward-pumping. Preferably, diameters of the core and cladding of fiber 65 and amplifier fiber 14 are closely matched to enable a splice-connection with high transfer-efficiency for both the signal and pump-radiation. In summary, the present invention is described above with reference to a preferred embodiment. The invention, however, is not limited to the embodiment described and depicted herein. Rather, the invention is limited only by the claims appended hereto.

Claims (6)

  1. CLAIMS1. Optical apparatus, comprising: a fiber-MOPA generating laser-radiation having a fundamental wavelength, the fiber-MOPA having an active optical fiber providing an amplifier stage of the fiber-MOPA, and the active optical fiber being terminated at a distal end thereof by a transparent end-cap having an exit-face; a sealed enclosure having a plurality of optical elements located therein, the plurality of optical elements for converting the fundamental-wavelength radiation to output radiation having a frequency-converted wavelength, the end cap of the active optical fiber being sealed to the enclosure such that the exit-face of the end-cap is effectively within the enclosure; and wherein the active optical fiber is forward-pumped by diode-laser radiation fiber-coupled into a proximal end of the active optical fiber.
  2. 2. The apparatus of claim 1, wherein the diode laser radiation is provided by a plurality N of diode-lasers.
  3. 3. The apparatus of claim 2, wherein the diode-lasers are fiber coupled into a proximal end of a double-clad fundamental-wavelength radiation transport fiber via N transport fibers using a N+ I X I fiber-combiner and the distal end of the fundamental-wavelength transport fiber is double-clad spliced to the proximal end of the active optical fiber.
  4. 4. The apparatus of claim 2 or claim 3, where Nis 2.
  5. 5. The apparatus of any preceding claim, wherein the plurality of optical elements for converting the fundamental-wavelength radiation includes an optically nonlinear crystal.
  6. 6. An optical apparatus as herein described with reference to, and as illustrated by, the accompanying drawings.
GB1500136.5A 2014-11-14 2015-01-06 Frequency-converted Fiber-MOPA Active GB2532294B (en)

Applications Claiming Priority (1)

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US201462080018P 2014-11-14 2014-11-14

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GB2532294B GB2532294B (en) 2017-11-08

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2303467A (en) * 1995-07-21 1997-02-19 Northern Telecom Ltd Hermetic metallised optical fibre feed-through
EP0978745A1 (en) * 1998-08-04 2000-02-09 Pouyet S.A. Entrypiece for an optical cable
WO2011037749A2 (en) * 2009-09-23 2011-03-31 Coherent, Inc. Fiber mopa with amplifying transport fiber

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2303467A (en) * 1995-07-21 1997-02-19 Northern Telecom Ltd Hermetic metallised optical fibre feed-through
EP0978745A1 (en) * 1998-08-04 2000-02-09 Pouyet S.A. Entrypiece for an optical cable
WO2011037749A2 (en) * 2009-09-23 2011-03-31 Coherent, Inc. Fiber mopa with amplifying transport fiber

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Publication number Publication date
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