CN101398511A - Double clad optical fiber for laser unit - Google Patents
Double clad optical fiber for laser unit Download PDFInfo
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- CN101398511A CN101398511A CNA2008101669690A CN200810166969A CN101398511A CN 101398511 A CN101398511 A CN 101398511A CN A2008101669690 A CNA2008101669690 A CN A2008101669690A CN 200810166969 A CN200810166969 A CN 200810166969A CN 101398511 A CN101398511 A CN 101398511A
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Abstract
The invention discloses a dual-clad fiber which is used for high-power laser devices, comprising a fiber core, an internal clad and an external clad; the boundary of the internal clad is an ellipse; the fiber core is arranged on one focus point of the elliptic internal clad and wrapped by the internal clad, the refractive index of which is lower than that of the fiber core; the internal clad is wrapped by the external clad, the refractive index of which is lower than that of the external clad; the dual-clad fiber structure is beneficial for achieving the high-efficiency coupling of pump power, thus providing the gain fiber with high absorption efficiency. When the high-power fiber laser runs, the laser power density of the fiber core part of the end surface of the fiber is reduced, furthermore, without affecting the absorption efficiency of the fiber, the fiber core is closer to the external clad, thus being more beneficial for heat management during the high-power laser output.
Description
Technical field
The present invention relates to the optical fiber technology field, relate in particular to a kind of doubly clad optical fiber that is used for Laser Devices.
Background technology
Fiber laser and amplifier adopt the fibre core pumping usually, initial gain fibre is common single cladding structure, mixing active ions in fibre core is gain media, pump light and signal laser all transmit in fibre core, because fibre core is very little, therefore the several approximately microns of diameter must be coupled to pumping light power in the fibre core of gain fibre effectively, yet the efficient of this coupling in the prior art is very low, thereby makes laser output power also very low.In order to improve the output power of fiber laser, people such as Snitzer have at first proposed the optical fiber of double clad structure, promptly between the fibre core of common single cladding structure optical fiber and covering, introduced an inner cladding, made whole optical fiber comprise three parts: fibre core, circular inner cladding and surrounding layer.The fiber core with single-mold that comprises active ions is refracted the multimode rectangular inner cladding that rate is lower than fibre core and surrounds, this inner cladding is refracted the lower surrounding layer of rate again and surrounds, the pumping laser coupling is injected in the rectangular inner cladding, and limited by the total internal reflection at the interface of interior surrounding layer, when the pump light that transmits in inner cladding passes through fibre core, absorbed by the active ions in the fibre core, thereby realized cladding pumping.When making optical fiber, make the physical dimension of inner cladding big more a lot of than fibre core, make the numerical aperture of inner cladding and cladding refractive index function also big as far as possible simultaneously, can more effectively receive power like this, thereby improve the power of output laser from the multimode pump laser source.
But doubly clad optical fiber structure for this rectangular inner cladding, have only the spot shaping of pumping semiconductor laser output laser in the range of size of the doubly clad optical fiber of required injection, light can be coupled into, light in doubly clad optical fiber range of size outside just can't be coupled in the optical fiber.As shown in Figure 1, circle is a doubly clad optical fiber, and rectangle is the shape after the hot spot compression, and then the light outside the circle just enters less than in the optical fiber, therefore, needs to strengthen the shaping compression to hot spot, could further improve coupling efficiency.
Biography light principle according to optical fiber, there is the light that corkscrews in a large number in circular inner cladding structure, and in whole fiber lengths, propagate but without fibre core, this situation has limited effective absorption of optical fiber, so the optical fiber of rectangular inner cladding structure is quite limited to the utilization of pumping light power.So proposed the inner cladding structure of various special shapes again:, make absorption efficiency improve greatly as eccentric circle, rectangle, D shape, star, polygon etc.The doubly clad optical fiber of eccentric rectangular inner cladding structure as shown in Figure 4, the diode-end-pumped mode will form the spiral light that a part is not passed through the center of circle in rectangular inner cladding, can't be absorbed by the doping active ions of fibre core, therefore, reduce the absorption efficiency of pumping laser.
M.H. Hans Minder is in Chinese patent CN1154764A, the section shape that discloses a kind of inner cladding is the convex polygon doubly clad optical fiber of non-rectangle, as shown in Figure 2, to form a uniform basically radiation field, the various radiation modes that wherein constitute the pumping laser energy isotropically distribute.But for the pumping semiconductor laser of geometric configuration homogeneous semiconductor laser instrument and coupled into optical fibres, the asymmetry of this convex polygon structure is unfavorable for the coupling of pumping light power.
Patented claim CN1542474A discloses a kind of doubly clad optical fiber that adopts asymmetric border inner cladding, as shown in Figure 3, mainly comprise fibre core 301, inner cladding 302 and surrounding layer 303, fibre core 1 places the center of inner cladding 302, and the border of inner cladding 302 is asymmetric border.The optical fiber of this double clad structure makes the communication process of pump light in the inner cladding not have the stable state of local, thereby make more pumping laser can pass through fibre core, improve the coupling efficiency of pumping laser and fibre core in the inner cladding, improved the absorption efficiency of doubly clad optical fiber.But, at high-power fiber laser, during the fiber amplifier operation, the active ions that mix in the fibre core will discharge a large amount of heat energy with the form of nonradiative transition, the temperature at gain fibre fibre core place will reach hundreds of degrees centigrade, therefore in order to realize high-power laser output, must carry out radiating treatment to gain fibre, at present, prior art is to take measures optical fiber is freezed in the outside of surrounding layer, and fibre core is positioned at the structural design at inner cladding center, make as the fibre core of thermal source far with extraneous refrigerating plant distance, radiating efficiency is lower, the thermal management of optical fiber when being unfavorable for the heat radiation of optical fiber and high power laser light output.
Summary of the invention
The technical matters that the present invention solves is, a kind of doubly clad optical fiber that is used for Laser Devices is provided, the thermal management when helping high power laser light output, and make gain fibre have higher absorption efficiency.
The technical solution used in the present invention is, the described doubly clad optical fiber that is used for Laser Devices, comprise fibre core, inner cladding and surrounding layer, the border of inner cladding is oval, fibre core is positioned on the focus of oval inner cladding, and the inner cladding that the rate that is refracted is lower than fibre core surrounds, and inner cladding is refracted the lower surrounding layer of rate again and surrounds.
Adopt technique scheme, the present invention has following advantage at least:
The inner cladding that is used for the doubly clad optical fiber of Laser Devices of the present invention is an ellipsoidal structure, fibre core is positioned on the focus of oval inner cladding, this structure can make the pumping light power coupling be injected on another focus of oval inner cladding structure, utilize oval architectural characteristic, make gain fibre have higher absorption efficiency for the light reflection.When high-capacity optical fiber laser spare moves, the distribution of this fibre core can make feedback be injected into the pumping laser power of the laser of gain fibre and injection respectively on oval-shaped two focuses, near the optical power density of the core segment of fiber end face is reduced, and on the basis that does not influence the optical fiber absorption efficiency, make fibre core more near surrounding layer, thus the thermal management when helping high power laser light output more.
Description of drawings
Fig. 1 is the doubly clad optical fiber and the pumping laser coupling situation synoptic diagram of rectangular inner cladding structure in the prior art;
Fig. 2 is the convex polygon doubly clad optical fiber synoptic diagram that a kind of inner cladding is shaped as non-rectangle;
Fig. 3 is a kind of doubly clad optical fiber synoptic diagram that adopts asymmetric border inner cladding;
Fig. 4 is a kind of doubly clad optical fiber synoptic diagram of eccentric circular configuration;
Fig. 5 is the structural representation of doubly clad optical fiber of the present invention.
Embodiment
Reach technological means and the effect that predetermined purpose is taked for further setting forth the present invention, below in conjunction with drawings and Examples, the described doubly clad optical fiber that is used for Laser Devices to the present invention proposes is described in detail as follows.
The doubly clad optical fiber that the present invention is used for Laser Devices comprises fibre core 1, inner cladding 2, surrounding layer 3 and protective seam 4 as shown in Figure 5.The border of inner cladding 2 is oval, and fibre core 1 is positioned on the focus of inner cladding 2, and another focus of inner cladding is identical with the material of inner cladding 2 other parts.Fibre core 1 is surrounded by inner cladding 2, and inner cladding 2 is surrounded by surrounding layer 3 again.In addition, can also add a protective seam 4 again in surrounding layer 3 outsides of low-refraction as required, protective seam 4 can be selected the optical cement material that shields, and acrylate for example is to protect doubly clad optical fiber more effectively.
The material of fibre core 1 can be selected according to different needs among the present invention, mainly constitutes by mixing the laser active ion in the inorganic material such as quartz, and active ions can be rare earth ions, for example: ytterbium, erbium, neodymium, thulium, holmium, terbium etc.The purpose of mixing active ions in fibre core is to realize the gain of signal laser, and the cross section of fibre core is circular, and diameter is generally 5～100 microns.
The border of surrounding layer 3 is circular, and the major semi-axis of the oval inner cladding 2 of its radius ratio is big 30～200 microns.Surrounding layer 3 is selected the material lower than inner cladding refractive index, such as adopting polymeric optical material, so that the numerical aperture of inner cladding 2 reaches more than 0.2.The relation of refractive index and numerical aperture is as follows:
Wherein, NA is a numerical aperture, and the refractive index of inner cladding is n1, and the refractive index of surrounding layer is n2.
The fibre core of doubly clad optical fiber of the present invention is positioned on the focus of oval inner cladding, and this structure can make the coupling of pumping laser power be injected on another focus of oval inner cladding structure.According to the architectural characteristic of ellipse for light reflection: from oval light that focus is sent, through behind the elliptical reflecting, reflection ray all converges on another oval focus.Therefore, make gain fibre have higher absorption efficiency.
Pumping laser can be coupled and be injected in the whole oval inner cladding, this helps improving the coupling efficiency of pumping laser, and on the basis that does not influence the optical fiber absorption efficiency, fibre core is more near surrounding layer, thus the thermal management when helping high power laser light output more.When high-capacity optical fiber laser or amplifier operation, the distribution of this fibre core can make feedback be injected into the pumping laser power of the laser of gain fibre and injection respectively on oval-shaped two focuses, help reducing near the optical power density of the core segment of fiber end face, the heat resistanceheat resistant damage ability of optical fiber when improving high power laser light output.
Inner cladding among the present invention designs for ellipsoidal structure, when using semiconductor laser as pump light source, because the hot spot that semiconductor laser chip sends is for oval, when the major axis of the major axis of the oval inner cladding structure of doubly clad optical fiber and semiconductor laser launch spot during in a direction, again to hot spot carry out a little shaping compression or even need not the shaping compression, just can improve coupling efficiency, thereby reduce the cost of pump laser spot shaping compression.
Though this diode-end-pumped mode will form the spiral light of a part of obstructed overfocus in oval inner cladding, can't be absorbed by the doping active ions of fibre core, but since high-capacity optical fiber laser in order to suppress nonlinear effect etc., usually use the doubly clad optical fiber of big mode field area fibre core, the diameter that is fibre core is bigger, with increasing the coupling efficiency of pumping laser, so the present invention also will have higher absorption efficiency.Usually, the doubly clad optical fiber with big mode field area fibre core can bend to certain radius to gain fibre, and with the bending loss of increase higher order mode, thereby the laser that obtains high light beam quality is exported.Because fibre-optical bending causes the stress in the optical fiber and the change of refractive index, will destroy the transmission of the spiral light in the oval inner cladding.This doubly clad optical fiber with oval inner cladding structure of big mode field area fibre core can suppress the transmission of spiral light equally to a certain extent, thereby obtains absorption efficiency preferably.
By the explanation of embodiment, when can being to reach technological means and the effect that predetermined purpose takes to be able to more deeply and concrete understanding to the present invention, yet appended diagram only provide with reference to the usefulness of explanation, be not to be used for the present invention is limited.
Claims (9)
1, a kind of doubly clad optical fiber that is used for Laser Devices, comprise fibre core, inner cladding and surrounding layer, the border that it is characterized in that inner cladding is for oval, fibre core is positioned on the focus of oval inner cladding, and the inner cladding that the rate that is refracted is lower than fibre core surrounds, and inner cladding is refracted the lower surrounding layer of rate again and surrounds.
2, according to the described doubly clad optical fiber that is used for Laser Devices of claim 1, it is characterized in that, inner cladding greater than the refractive index of surrounding layer so that the numerical aperture of inner cladding reach more than 0.2.
3, according to claim 1 or the 2 described doubly clad optical fibers that are used for Laser Devices, it is characterized in that, the length ratio of the long and short semiaxis of oval inner cladding at 1.1:1 between the 5:1.
According to the described doubly clad optical fiber that is used for Laser Devices of claim 3, it is characterized in that 4, the cross section of fibre core is circular, diameter is 5～100 microns.
According to the described doubly clad optical fiber that is used for Laser Devices of claim 4, it is characterized in that 5, the border of surrounding layer is circular, the major semi-axis of the oval inner cladding of its radius ratio is big 30～200 microns.
According to the described doubly clad optical fiber that is used for Laser Devices of claim 5, it is characterized in that 6, the material of inner cladding is quartzy or is mixed with the glass material of fluorine, boron, germanium, phosphorus, barium, aluminium.
According to the described doubly clad optical fiber that is used for Laser Devices of claim 5, it is characterized in that 7, inner cladding adopts the material of the photonic crystals optical fiber structure of microstructure to fill.
8,, it is characterized in that fibre core constitutes by mixing active ions in the quartz according to claim 6 or the 7 described doubly clad optical fibers that are used for Laser Devices.
9, the described according to Claim 8 doubly clad optical fiber that is used for Laser Devices is characterized in that, active ions are rare earth ion.
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2008101669690A CN101398511A (en) | 2008-09-28 | 2008-09-28 | Double clad optical fiber for laser unit |
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| CNA2008101669690A CN101398511A (en) | 2008-09-28 | 2008-09-28 | Double clad optical fiber for laser unit |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102298173A (en) * | 2011-08-29 | 2011-12-28 | 武汉安扬激光技术有限责任公司 | Lateral pumped fiber structure and manufacturing method thereof |
| CN107300738A (en) * | 2017-06-27 | 2017-10-27 | 中国电子科技集团公司电子科学研究院 | A kind of optical fiber |
| CN107561635A (en) * | 2017-10-13 | 2018-01-09 | 中国工程物理研究院激光聚变研究中心 | Gradual change absorption coefficient gain fibre and optical system |
| CN108474906A (en) * | 2015-08-13 | 2018-08-31 | 纽弗恩 | Mode mixture optical fiber and use its method and system |
| CN108957626A (en) * | 2018-06-19 | 2018-12-07 | 全球能源互联网研究院有限公司 | A kind of reaction type energy-transmission optic fibre and optical fiber energy transfer system, device |
| CN109642981A (en) * | 2016-02-05 | 2019-04-16 | 纽弗恩 | Mode mixture optical fiber and the method and system for using it |
| CN116885541A (en) * | 2023-08-03 | 2023-10-13 | 上海频准激光科技有限公司 | Spectrum purification system and method based on nonlinear optical fiber amplifier |
-
2008
- 2008-09-28 CN CNA2008101669690A patent/CN101398511A/en active Pending
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102298173A (en) * | 2011-08-29 | 2011-12-28 | 武汉安扬激光技术有限责任公司 | Lateral pumped fiber structure and manufacturing method thereof |
| CN108474906A (en) * | 2015-08-13 | 2018-08-31 | 纽弗恩 | Mode mixture optical fiber and use its method and system |
| CN108474906B (en) * | 2015-08-13 | 2020-09-01 | 纽弗恩 | Mode-mixing optical fiber and method and system using same |
| CN109642981A (en) * | 2016-02-05 | 2019-04-16 | 纽弗恩 | Mode mixture optical fiber and the method and system for using it |
| CN109642981B (en) * | 2016-02-05 | 2021-07-27 | 纽弗恩 | Mode-mixing optical fiber and method and system using same |
| CN107300738A (en) * | 2017-06-27 | 2017-10-27 | 中国电子科技集团公司电子科学研究院 | A kind of optical fiber |
| CN107300738B (en) * | 2017-06-27 | 2024-05-24 | 中国电子科技集团公司电子科学研究院 | Optical fiber |
| CN107561635A (en) * | 2017-10-13 | 2018-01-09 | 中国工程物理研究院激光聚变研究中心 | Gradual change absorption coefficient gain fibre and optical system |
| CN108957626A (en) * | 2018-06-19 | 2018-12-07 | 全球能源互联网研究院有限公司 | A kind of reaction type energy-transmission optic fibre and optical fiber energy transfer system, device |
| CN108957626B (en) * | 2018-06-19 | 2020-09-08 | 全球能源互联网研究院有限公司 | Feedback energy transmission optical fiber and optical fiber energy transmission system and device |
| CN116885541A (en) * | 2023-08-03 | 2023-10-13 | 上海频准激光科技有限公司 | Spectrum purification system and method based on nonlinear optical fiber amplifier |
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Application publication date: 20090401 |