CN100490262C - High power dual-cladding fiber laser end-pumped method and device - Google Patents
High power dual-cladding fiber laser end-pumped method and device Download PDFInfo
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- CN100490262C CN100490262C CNB2007100322679A CN200710032267A CN100490262C CN 100490262 C CN100490262 C CN 100490262C CN B2007100322679 A CNB2007100322679 A CN B2007100322679A CN 200710032267 A CN200710032267 A CN 200710032267A CN 100490262 C CN100490262 C CN 100490262C
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Abstract
The invention discloses a high power double-clad fiber laser end face pump method, which is characterized in that: after coating layer and external layer are removed for the double-clad fiber, firstly, an internal clad layer and a fiber core part (naked fiber end face) are arranged at two focal points with a central hole and confocal concave mirror; secondly, pumping light from the laser is focused through the lens coupling system before incident through a central hole of a first concave mirror; focal spot is also arranged on a focal point of the confocal concave mirror; pumping light enters into the fiber from the fiber end face; when the focal spot is bigger than the end face of the internal clad layer in size, initial pump cannot directly enter the fiber but escaped pumping light oscillates and reflects backward and forward between two confocal concave mirrors and continually enters the fiber. The invention has the advantages of not shaping the pumping light, fully using pumping light escaping outside the fiber and enabling the light reenter the fiber, improving stability of the lens coupling system, easily operating and adapting to the coupling for normal multimode fiber or even single mode fiberwith low cost.
Description
Technical field
The invention belongs to the high power fiber laser pump technology, specifically be meant high power dual-cladding fiber laser end-pumped method and device thereof.
Background technology
High-power double-cladding optical fiber laser is owing to itself have good beam quality, efficient height, be easy to heat radiation and be easy to realize characteristics such as high power, development in recent years is rapid, become the important light source in the fields such as high-precision laser processing, laser radar system, high speed optical communication and target indication, more have a wide range of applications in national defense and military fields, therefore, high-capacity optical fiber laser has been subjected to the great attention of national governments, scientific circles and business circles.
Realize the high-power output of double-clad optical fiber laser, pump technology is its key.Method for pumping at present commonly used mainly is divided into two kinds of fiber end face pumping and profile pumps.Representational V-shaped groove pump technology, microprism pump technology and the crotch shape pumped fiber technology of mainly containing in the optical fiber side-pumping technology.The V-shaped groove technology is V-shaped groove of etching on exposed inner cladding, and the surperficial grinding and polishing of groove becomes optical flat, and diode pumping light enters inner cladding through a flank side surface and the total reflection that lenticule focuses on V-shaped groove, implements the pumping to doped core.Though this technology can obtain higher pumping efficiency, can cause certain influence to the mechanical performance of optical fiber, and the V-shaped groove etching technics is comparatively complicated.The microprism technology is to use the optics glue on exposed inner cladding microprism, with lens pump light is focused on then and carries out pumping on the microprism.Though this technology can realize multi-point pump, the size of microprism is too little, and difficulty of processing is bigger, and diode pumping light also wants scioptics or aspherical mirror to focus on the microprism, and whole coupled system is comparatively complicated.Tree-like pumped fiber technology is the patent of IPG company, and this technology is very advanced.But it is very high that the drawing process of tree-like optical fiber requires, though domestic have many scientific research institutions that it is developed, and obtain certain progress, but still fails to draw out desirable tree-like optical fiber.
Therefore, at present during the laboratory development high-power double-cladding optical fiber laser, comparatively the Chang Yong end pumping technology that is still utilizes the Lens Coupling system that pump light is focused on the inner cladding of doubly clad optical fiber.This just requires the numerical aperture of set of lenses and focal beam spot size to be complementary with doubly clad optical fiber.Because the pump beam shaping quality is not high, there are reasons such as aberration in lens combination, make under the situation that satisfies the numerical aperture coupling, focal beam spot is often greater than the size of doubly clad optical fiber inner cladding, make quite a few pump light not enter inner cladding and escape to be mapped to outside of fiber, cause pumping efficiency lower.For further improving pumping efficiency, method commonly used is to utilize non-spherical lens that pump beam is carried out shaping, and adopts the Lens Coupling system of accurate design.This just makes process and assemble required precision height, and the price of shaping coupled system is very expensive, is unfavorable for the commercialization of product.On the other hand, existing Lens Coupling mode requires very high to the accuracy of whole optical system, the little deviation of coupled system (making focal spot position change such as vibration) can both directly influence the pumping efficiency of whole system, make system's instability, this just gives the integrated difficulty of bringing of system.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of above-mentioned prior art, a kind of high power dual-cladding fiber laser end-pumped method is proposed, it does not need pump beam is carried out shaping, can make full use of and spill into the outer pump light of optical fiber, make it to reenter optical fiber, can improve the Lens Coupling stability of a system again.
Another object of the present invention is to provide the high power dual-cladding fiber laser end-pumped device of realizing above-mentioned high power dual-cladding fiber laser end-pumped method.
Purpose of the present invention is achieved through the following technical solutions: this high power dual-cladding fiber laser end-pumped method, be meant that the fiber end face that at first makes doubly clad optical fiber remove inner cladding behind coat and the surrounding layer and core segment (being naked fibre) is positioned on the focus of two confocal concave mirrors that have a centre bore, the pump light that sends from laser centre bore incident by preceding concave mirror after the Lens Coupling system focuses on then, and focal spot also is positioned on the focus of confocal concave mirror, pump light enters optical fiber from fiber end face, when focal spot size is bigger than inner cladding face size, first pumping can not directly enter optical fiber and overflow pump light vibration reflection back and forth between two confocal concave mirrors, and constantly entering optical fiber, the focal length big 0.1 of concave mirror is to 0.4mm before the focal distance ratio of back concave surface mirror.
Realize the high power dual-cladding fiber laser end-pumped device of above-mentioned high power dual-cladding fiber laser end-pumped method, comprise laser (adopting the LD pump laser usually), Lens Coupling system, also be disposed with forward and backward two confocal concave mirrors along optical path direction after the described Lens Coupling system, described forward and backward concave mirror surface all is coated with the highly reflecting films to pump light; Forward and backward concave mirror all has centre bore, and the pump light that laser sends is the centre bore incident by preceding concave mirror after the Lens Coupling system focuses on, and focal spot also is positioned on the focus of forward and backward concave mirror; The centre bore of back concave surface mirror is by optical cement and naked fine bonding, and the fiber end face of naked fibre is positioned on the focus of forward and backward concave mirror, and the focal length big 0.1 of concave mirror is to 0.4mm before the focal distance ratio of back concave surface mirror.
For realizing the present invention better, described forward and backward concave mirror is a spherical mirror, also can be paraboloidal mirror or ellipsoidal mirror.
The aperture of the centre bore of described forward and backward concave mirror is respectively r
1And r
2, and r
1=f
1NA, wherein f
1Be the focal length of preceding concave mirror, NA is the numerical aperture of inner cladding; r
2Equal the radius of inner cladding.
Described highly reflecting films reflectivity is greater than 97%.
The refractive index match of described optical cement refractive index and doubly clad optical fiber surrounding layer.
Operation principle of the present invention is: the pumping laser bundle through the Lens Coupling system be focused into be mapped to fiber end face after, even focal spot size is bigger than inner cladding size, because fiber end face just is positioned on the focus of confocal concave mirror, the pump light of overflowing will become intimate parallel light beam after the back concave surface mirroring, penetrate then on preceding concave mirror, these collimated light beams converge on the fiber end face once more.If effusion is arranged again, will carry out the convergence of second leg according to said process.Like this, after repeatedly vibration is reflected into fibre, just can improve greatly into fine coupling efficiency.And, because the focal length of concave mirror is bigger before the focal distance ratio of back concave surface mirror, so the size of collimated light beam can be increasing in oscillatory process, its will more and more littler by the focal spot size that preceding concave mirror focus forms (this be by the conversion characteristics decision of Gaussian beam), this obviously helps being coupled.On the other hand,, make partial parallel light beam (especially from optical axis part far away) may not focus on fiber end face after reflection just, and often penetrate on the close side of fiber end face owing to reasons such as the small aberrations of concave mirror.This part pump light is after passing through naked fine inner cladding and fibre core, from the opposite side ejaculation of naked fibre.Because incidence point very near the focus of bi-concave mirror, so transmitted light beam relies on the vibration reflection of confocal bi-concave mirror, still can be doped fibre core and constantly absorb when repeatedly passing through optical fiber.Like this, pump beam just can obtain to make full use of, thereby effectively improves coupling efficiency.
The present invention compared with prior art has following advantage and beneficial effect:
(1) utilizes two confocal concave mirrors, make those pump lights that can not enter optical fiber reflect focalization that between concave mirror, vibrates back and forth, and constantly enter inner cladding, improve pumping efficiency naturally thereby can make things convenient for through first pumpings.
(2) fiber end face method for pumping provided by the invention does not need pump beam is carried out special shaping, do not need the numerical aperture and the focal beam spot size of set of lenses to mate fully with doubly clad optical fiber yet, can directly transform the Lens Coupling system, help reducing cost, and method is simple, and experimental condition is had adaptability more widely.
(3) even the Lens Coupling system is because external factor (as vibration) makes focal spot slightly depart from the inner cladding of doubly clad optical fiber, utilize the end-pumped method that is reflected into fibre based on confocal bi-concave mirror vibration provided by the invention, also external factor can be reduced to bottom line to the influence of pumping efficiency, this helps improving the stability of Lens Coupling system, thereby helps realizing the commercialization of the integrated and product of Lens Coupling system.
(4) based on end-pumped method of the present invention, be not only applicable to doubly clad optical fiber, also be applicable to the coupling of common multimode fiber even monomode fiber.
Description of drawings
Fig. 1 is a doubly clad optical fiber structural representation of the present invention;
Fig. 2 a, 2b are respectively confocal concave mirror vertical view of the present invention and end view;
Fig. 3 is the structural representation of the high power dual-cladding fiber laser end-pumped device of the present invention;
Fig. 4 is that laser beam vibrates between confocal bi-concave mirror of the present invention and is reflected into fine schematic diagram.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment
As shown in Figure 1, doubly clad optical fiber of the present invention is made up of fibre core 1, inner cladding 2, surrounding layer 3, coat 4 from the inside to the outside, and the parameter of the doubly clad optical fiber in the present embodiment is: fibre core 1 diameter: 20 ± 2 μ m; Inner cladding 2 diameters: 130 ± 15 μ m; Surrounding layer 3 diameters: 300 ± 20 μ m; Fibre core numerical aperture NA.1:0.06 ± 0.01; Inner cladding 2 numerical aperture NA.2:0.45 ± 0.01.
As shown in Figure 2, concave mirror schematic diagram of the present invention, forward and backward concave mirror are spherical mirror, also can be paraboloidal mirror or ellipsoidal mirror.Concave mirror mirror body 5 materials are SiO2, and its centre bore 6 can be got with the high power femtosecond pulse laser.The femtosecond pulse laser wavelength that adopts in the present embodiment is 810 ± 2nm, and pulse duration is 80fs, and peak power is 1000kw, and spot diameter is adjustable between 100 μ m～7mm.The centre bore radius of preceding concave mirror 9 and back concave surface mirror 10 is respectively r
1And r
2, and r
1≈ f
1(NA.2), f wherein
1Be the focal length of concave mirror 9, NA.2 is the numerical aperture of inner cladding; r
2Approximate optical fiber and remove last naked fine 11 radius behind coat and the surrounding layer.Afterwards, plate highly reflecting films (reflectivity is greater than 97%) on concave mirror 9 and 10 surfaces to pump light.Two confocal placements of concave mirror, the bigger 0.1～0.4mm of focal length of the focal distance ratio concave mirror 9 of concave mirror 10 wherein, in this example, big approximately 0.2mm.
As shown in Figure 3, this high power dual-cladding fiber laser end-pumped device, comprise LD pump laser 7, Lens Coupling system 8, Lens Coupling system 8 backs also are disposed with forward and backward two confocal concave mirrors 9,10 along optical path direction, and forward and backward concave mirror 9,10 surfaces all are coated with the highly reflecting films to pump light; Forward and backward concave mirror 9,10 all has centre bore 6, doubly clad optical fiber is removed behind coat 4 and the surrounding layer 3 only remaining naked fine 11, and naked fine length equals the focal length of concave mirror 10.Coat optical cement (refractive index match of its refractive index and doubly clad optical fiber surrounding layer) respectively at the central small hole inwall of naked fine 11 end profile and concave mirror 10, then naked fine 11 central small hole from concave mirror 10 are stretched into, and fiber end face just is positioned on the focus of confocal concave mirror 9,10, after treating that optical cement solidifies, optical fiber promptly links together securely with concave mirror 10.Laser 7 emitted laser bundles after centre bore 6 incidents of concave mirror 9, and also are positioned on the focus of confocal concave mirror 9,10 focal spot through Lens Coupling system 8 packs.Since be subjected to the restriction of centre bore 6, numerical aperture NA.3 ≈ sin (arctan the NA.2)＜NA.2 of incident pump beam, thus satisfy the numerical aperture matching condition, and leave certain leeway, for being reflected into fibre, ensuing bi-concave mirror vibration creates conditions.
This high power dual-cladding fiber laser end-pumped device is to realize the end pumping process like this:
The fiber end face of naked fine 11 (inner cladding 2 and fibre core 1 parts) of doubly clad optical fiber is positioned on the focus of two confocal concave mirrors 9,10 that have a centre bore 6, the pump light that sends from laser 7 centre bore 6 incidents by preceding concave mirror 9 after Lens Coupling system 8 focuses on then, and focal spot also is positioned on the focus of confocal concave mirror 9,10, thereby pump light enters optical fiber from fiber end face;
The pumping laser bundle through Lens Coupling system 8 be focused into be mapped to fiber end face after, even focal spot size is bigger than inner cladding 2 sizes, because fiber end face just is positioned on the focus of confocal concave mirror 9,10, the pump light of overflowing will become intimate parallel light beam after 10 reflections of back concave surface mirror, penetrate then on preceding concave mirror 9, these collimated light beams converge on the fiber end face once more.If effusion is arranged again, will carry out the convergence of second leg according to said process.Like this, after repeatedly vibration is reflected into fibre, just can improve greatly into fine coupling efficiency.And, because the focal length of concave mirror 9 is bigger before the focal distance ratio of back concave surface mirror 10, so the size of collimated light beam can be increasing in oscillatory process, to focus on the focal spot size that forms will more and more littler (this be by the conversion characteristics decision of Gaussian beam) by preceding concave mirror 9 for it, and this obviously helps being coupled.On the other hand,, make partial parallel light beam (especially from optical axis part far away) may not focus on fiber end face after reflection just, and often penetrate on the close side of fiber end face owing to reasons such as the small aberrations of concave mirror.This part pump light penetrates from naked fine 11 opposite side after passing through naked fine 11 inner claddings 2 and fibre core 1.Because incidence point very near the focus of bi-concave mirror 9,10, so transmitted light beam relies on the vibration reflection of confocal bi-concave mirror 9,10, still can be doped fibre core 1 and constantly absorb when repeatedly passing through optical fiber.Like this, pump beam just can obtain to make full use of, thereby effectively improves coupling efficiency.
The present invention is not only applicable to doubly clad optical fiber, is applicable to the coupling of common multimode fiber even monomode fiber yet.
As mentioned above, just can realize the present invention preferably, the foregoing description is preferred embodiment of the present invention only, is not to be used for limiting practical range of the present invention; Be that all equalizations of doing according to content of the present invention change and modification, all contained by claim of the present invention scope required for protection.
Claims (6)
1, high power dual-cladding fiber laser end-pumped method, it is characterized in that: doubly clad optical fiber is removed on the focus that fiber end face that inner cladding behind coat and the surrounding layer and core segment be naked fibre is positioned at two confocal concave mirrors that have a centre bore, the pump light that sends from laser centre bore incident by preceding concave mirror after the Lens Coupling system focuses on then, and focal spot also is positioned on the focus of confocal concave mirror, pump light enters optical fiber from fiber end face, when focal spot size is bigger than inner cladding face size, first pumping can not directly enter optical fiber and overflow pump light vibration reflection back and forth between two confocal concave mirrors, and constantly entering optical fiber, the focal length big 0.1 of concave mirror is to 0.4mm before the focal distance ratio of back concave surface mirror.
2, realize the high power dual-cladding fiber laser end-pumped device of the described high power dual-cladding fiber laser end-pumped method of claim 1, comprise laser, Lens Coupling system, it is characterized in that: also be disposed with forward and backward two confocal concave mirrors along optical path direction after the described Lens Coupling system, described forward and backward concave mirror surface all is coated with the highly reflecting films to pump light; Forward and backward concave mirror all has centre bore, and the pump light that laser sends is the centre bore incident by preceding concave mirror after the Lens Coupling system focuses on, and focal spot also is positioned on the focus of forward and backward concave mirror; The centre bore of back concave surface mirror is by optical cement and naked fine bonding, and the fiber end face of naked fibre is positioned on the focus of forward and backward concave mirror, and the focal length big 0.1 of concave mirror is to 0.4mm before the focal distance ratio of back concave surface mirror.
3, according to the described high power dual-cladding fiber laser end-pumped device of claim 2, it is characterized in that: described forward and backward concave mirror is spherical mirror, paraboloidal mirror or ellipsoidal mirror.
4, according to the described high power dual-cladding fiber laser end-pumped device of claim 2, it is characterized in that: the aperture of the centre bore of described forward and backward concave mirror is respectively r
1And r
2, and r
1=f
1NA, wherein f
1Be the focal length of preceding concave mirror, NA is the numerical aperture of inner cladding; r
2Equal the radius of inner cladding.
5, according to the described high power dual-cladding fiber laser end-pumped device of claim 2, it is characterized in that: described highly reflecting films reflectivity is greater than 97%.
6, according to the described high power dual-cladding fiber laser end-pumped device of claim 2, it is characterized in that: the refractive index match of described optical cement refractive index and doubly clad optical fiber surrounding layer.
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|---|---|---|---|
| CNB2007100322679A CN100490262C (en) | 2007-12-07 | 2007-12-07 | High power dual-cladding fiber laser end-pumped method and device |
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|---|---|---|---|
| CNB2007100322679A CN100490262C (en) | 2007-12-07 | 2007-12-07 | High power dual-cladding fiber laser end-pumped method and device |
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| CN101183771A CN101183771A (en) | 2008-05-21 |
| CN100490262C true CN100490262C (en) | 2009-05-20 |
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| CN103900796B (en) * | 2014-03-21 | 2016-11-02 | 上海大学 | Application cascade doubly clad optical fiber measures nonlinear fiber specific refractivity device |
| CN106998031A (en) * | 2017-05-17 | 2017-08-01 | 中国兵器装备研究院 | A kind of manufacture method of the quartzy end cap of high power |
| CN112909727B (en) * | 2020-12-14 | 2022-05-13 | 太原理工大学 | High-power chaotic semiconductor laser generating device |
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