CN202486354U - An annular doped layer optical fiber and a laser comprising the optical fiber - Google Patents

Abstract

The utility model discloses an annular doping layer optical fiber used for an optical fiber laser. The optical fiber is composed of an inner coating layer (101) and an annular doping layer (102), a middle coating layer (103), an outer coating layer (104) and a protecting layer (105) which are outwards coated on the inner coating layer (101) orderly; the inner coating layer (101) is a non-doped fiber core; and a preparation method for the annular doping layer optical fiber and a laser using the annular doping layer optical fiber as a gain medium are also disclosed by the utility model. According to the utility model, traditional fiber core doping is changed into an annular doping layer, so that laser oscillation is actually conducted in annular waveguide; then, the thickness of the annular waveguide is designed reasonably so as to retain single-mode operation; simultaneously, a doping layer has a very larger cross section suitable for high power output; and therefore, output power of the optical fiber laser which uses the optical fiber can be increased.

Description

A kind of annular doping layer optical fiber and comprise the laser instrument of this optical fiber

Technical field

The utility model belongs to the fiber laser technology field, particularly can reach the annular doping layer optical fiber of high power output, and the laser instrument that comprises this optical fiber.

Background technology

Fiber laser is meant with the laser instrument of doped rare earth element glass optical fiber as gain media; Under the effect of pump light, very easily form high power density in the optical fiber; Cause the laser levels " population inversion " of working-laser material, when suitable adding positive feedback loop (formation resonator cavity) just can form laser generation output.

The fiber laser range of application is very extensive; Comprise laser fiber communication, the long distance communication of laser space, industrial shipbuilding, automobile making, laser engraving laser marking cut, printing system roller, metal and nonmetal boring/cutting/welding (brazing, hardening, covering and the degree of depth are welded), military and national defense safety, medicine equipment instrument and equipment, large foundation construction, as the pumping source of other laser instruments etc.

At present, than solid state laser and gas laser, fiber laser is the best laser instrument form of beam quality.Have high-power fiber laser and all very important application prospect will be arranged in industry and military applications field, but the core diameter of the gain media optical fiber of this laser instrument too for a short time be to limit the obstacle that its high power is exported.

Optical fiber is fibre-optic writing a Chinese character in simplified form, and is a kind of total reflection principle and the light conduction instrument reached of light in the fiber that glass or plastics are processed that utilize.In multimode optical fiber, the diameter of fibre core is 15 μ m～50 μ m, and roughly the thickness with people's hair is suitable.And the diameter of single-mode optics fibre core is 8 μ m～10 μ m.

Single cladded-fiber fibre core surrounded the low envelope covering of one deck refractive index ratio fibre core, so that light remains in the fibre core.The outside is the thin plastic wrapper protective seam of one deck again, is used for protecting big envelope.

Because single covering single-mode fiber core diameter is very tiny, generally below 10 μ m, bigger pump light is injected into fiber core and has run into difficulty technically.ESnitzer had proposed doubly clad optical fiber first in 1988; Doubly clad optical fiber is made up of concentric fibre core, inner cladding, surrounding layer and protective seam; The diameter of double clad is much larger than fibre core, and it can keep tiny fibre core yardstick, and pump light is got in the inner cladding of hundreds of micron dimensions.The output power that this technical breakthrough makes optical-fiber laser rises rapidly in surplus ten year, more than the optical-fiber laser power of exporting has continuously at present reached kilowatt.

The gordian technique that improves the fiber laser output power has: resonator cavity technology of preparing, cladding pumping technology and fiber coupling technique.For the cladding pumping technology, proposing effective means at present mainly is the double clad gain fibre that adopts inner cladding structures such as rectangle or D shape.

If the inner cladding cross circular section of doubly clad optical fiber is symmetrical; The light of its internal communication has strict movement locus, can judge, when the single mode doped core drops on the two caustic surfaces zone of a certain light; This light could be absorbed by fibre core; When fibre core was in outside the caustic surface of a certain light, light can not be absorbed, so the absorption efficiency of circle symmetric double cladded-fiber is very low.In order to improve the absorption efficiency of optical fiber, defective inner cladding structure for the symmetrical inner cladding of circle has appearred a lot, like rectangle, hexagon, star, quincunx and D shape etc.After there was defective in inner cladding, two caustic surfaces of light had not just existed yet.Light can not find any rule in the course of inner cladding; After transmission long enough distance; It will arrive any point on the inner cladding xsect; Through can all being absorbed behind the fibre core, so its absorption coefficient is 100% all the time, but the absorption efficiency of optical fiber in unit length is discrepant to final all light because of repeatedly.

Though adopt the double clad doped fiber laser instrument of inner cladding structures such as rectangle or D shape that the light beam output near diffraction limit can be provided, further improve its output power and still receive the restriction of optical fiber to the high power ability to bear.Promptly reduce optical fiber laser power density in order to increase this ability to bear; Can be through guaranteeing to increase core diameter under the acceptable beam quality situation, design super large mould field that (Large Mode Area, LMA) doubly clad optical fiber waits with the increasing doping content and realizes.

But, increase fibre core and will cause laser work at multistage mould, can reduce beam quality, need select pattern, suppress the vibration of high-order mode in the chamber, obtain the output of fundamental transverse mode laser.For big mould area double-cladding optical fiber such as photonic crystal fiber, because it has bigger core diameter and less fibre core numerical aperture, big core diameter can reduce optical fiber internal power density; Improve the threshold value of fiber nonlinear effect, increased the ability that fibre core bears power, simultaneously; Less numerical aperture makes that transmission ray and fine axle clamp angle are very little in the optical fiber; Electromagnetic field extends farly in covering like this, because the high-order mode loss is very big, therefore has only low-order mode could grow Distance Transmission.But it is further perfect that the preparation technology of super large mould area double-cladding optical fiber also needs.For strengthening doping content, because after strengthening doping content, the pump absorption coefficient of unit length can increase, corresponding gain increases, but also reduces quartzy purity and homogeneity, reduces the laser damage threshold of fiber end face.

The utility model content

One of purpose of the utility model provides a kind of annular doping layer optical fiber; The annular doping layer is changed in traditional fibre core doping, made laser generation in fact in a disc waveguide, carry out, again the thickness of this disc waveguide of appropriate design; Just can keep the single mode running; Doped layer has very big cross-sectional area simultaneously, is fit to high-power output, thereby can improve the output power of the fiber laser that utilizes this optical fiber.

The concrete technical scheme that this purpose adopted that realizes the utility model is:

A kind of annular doping layer optical fiber is used for fiber laser as gain media, and it is by inner cladding and be coated on the annular doping layer on this inner cladding, middle covering, surrounding layer and protective seam from inside to outside successively and form, and wherein said inner cladding is plain fibre core.

As the improvement of the utility model, described annular doping layer is processed by the host material of doped rare earth element.

As the improvement of the utility model, described host material is quartz glass or fluoride glass.

As the improvement of the utility model, the material of described inner cladding and middle covering is all identical with refractive index.

As the improvement of the utility model, the refractive index ratio annular doping layer of the material of described inner cladding and middle covering is little, lateral dimension and numerical aperture are bigger than annular doping layer.

Two of the purpose of the utility model is to propose a kind of fiber laser, and its gain media is above-mentioned annular doping layer optical fiber.

As the improvement of the utility model, this fiber laser also comprises the pumping source of LD array and the resonator cavity that constitutes with total reflective mirror output coupling mirror or fiber grating.

The compared with prior art main following advantage of tool of the utility model:

(1) high power laser light output, middle cladding diameter is big, can bear high pump power, and then obtains high laser power;

(2) big doped layer cross-sectional area, its damage threshold is big like this, provides the foundation for further improving laser output power;

(3) high beam quality is controlled annular doped layer thickness and can be realized single mode output;

(4) technology of preparing is ripe, can be mass-produced.

Description of drawings

Fig. 1 is related annular doping layer optical fiber (is example with cladding structure in the conventional circle) cross sectional representation of the utility model;

Fig. 2 is annular doping layer optical fiber (not comprising a protective seam) refractive index profile;

Fig. 3 is pump light and a Laser Transmission synoptic diagram in the annular doping layer optical fiber cut-open view in the fiber laser;

Fig. 4 is an annular doping layer optical fiber preparation process chart;

Fig. 5 is a Fabry-Perot chamber annular doping layer optical fiber laser structural representation.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the utility model is done further explain.

Annular doping layer optical fiber structure in the present embodiment is as shown in Figure 1, comprises inner cladding (fibre core undopes) 101,annular doping layer 102,middle covering 103, surroundinglayer 104 andprotective seam 105.

Annular doping layer 102 is processed by host material such as the quartz glass or the fluoride glass etc. of doped rare earth element;

The material ofinner cladding 101 and middle covering 103 is identical with refractive index; That material can select is little by refractive index ratio annular doping layer, lateral dimension and numerical aperture host material such as the preparations such as quartz glass or fluoride glass bigger than annular doping layer; Surroundinglayer 104 is processed by refractive index ratioinner cladding 101 little polymkeric substance, and outermostprotective seam 105 is by material preparations such as duroplastss.

Pump light is transmission in middle covering 103 in this annular doping layer optical fiber in the annular doping layer optical fiber laser; Repeatedly dopedlayer 102 is passed in total reflection inmiddle covering 103; Be doped ionic absorption, to last energy level, transition produced laser after accumulation formed population inversion with the dopant ion pumping.Because dopedlayer 102 is annulars, pump light can evenly pass dopedlayer 102 at an easy rate.

The thickness ofannular doping layer 102 is reference with the single-mode fiber core diameter, is generally 8 μ m～10 μ m.Inner cladding 101 diameter spans are extensive, middle covering 103, surroundinglayer 104 and common double cladded-fiber inner cladding, surrounding layer consistency of thickness.

As get the annular overall diameter be 200 μ m, thickness is 10 μ m, then the cross-sectional area of its doped layer is equivalent to the doubly clad optical fiber fibre core area that diameter is 87 μ m; As get the annular overall diameter be 300 μ m, thickness is 10 μ m, then the cross-sectional area of its doped layer is equivalent to the double clad fibre core area that diameter is 107 μ m.With present mature fiber laser technology, such annular doping layer optical fiber provides possibility for the output of structure 100kW single-mode laser.

The preparation method of above-mentioned annular doping layer optical fiber is as shown in Figure 4, comprises the steps:

(1) makes the restraining barrier and the loose sandwich layer of preform with chemical vapour deposition technique (MCVD) technology.

1. at first pure quartz pushrod is inserted in the crystal reaction tube, fixing behind maintenance and the reaction tube coaxial cable, by high purity oxygen gas (O₂) carry silicon tetrachloride (SiCl₄), phosphorus oxychloride (POCl₄), CFC (CCl₂F₂) wait raw material to get in the rotating annular high purity quartz substrate reaction pipe, below with oxyhydrogen flame heat reaction tube, make raw material at high temperature oxidation reaction take place and be deposited on equably in the quartz ampoule, form and contain SiO₂-P₂O₅The optical fiber restraining barrier of-F.

The effect on restraining barrier is to stop diffusion of contaminants to core, so the deposition number of plies on restraining barrier is preferably 20～40 layers so that institute's fibre loss of doing is as far as possible little of purpose.Simultaneously the restraining barrier also will with reaction tube together as the inner cladding of optical fiber, so will control its refractive index and reaction tube is complementary.

2. reduce flame temperature to optimum range (1300-1500 ℃) then, according to same process by high purity oxygen gas (O₂) carry silicon tetrachloride (SiCl₄), phosphorus oxychloride (POCl₄), germanium tetrachloride (GeCl₄) wait raw material to get in the rotating annular high purity quartz substrate reaction pipe, below with oxyhydrogen flame heat reaction tube, making raw material at high temperature oxidation reaction take place and be deposited on equably in the quartz ampoule, the formation component is SiO₂-GeO₂-P₂O₅The loose sandwich layer of deposition.The depositing temperature of loose sandwich layer is looked test situation and is decided, because the change of different quartz ampoules and some other factors all can influence depositing temperature.The thickness of weaker zone and porousness do not occur coming off being advisable evenly to reach.

(2) solute doping.

Adopt the punching injection method with rare earth ion doped in prefabricated rods, under big traffic protection gas, with the oxyhydrogen flame rifle at the aperture of opening a diameter 5mm near the tail gas end, with syringe with the prior YbCl that prepare₃And AlCl₃Injection ring shaped reaction pipe guarantees the lathe uniform rotation simultaneously in the solution, is equivalent to solution is at the uniform velocity stirred.

Research shows Yb in sandwich layer middle rare earth ion concentration and the solution³⁺Ion concentration, solution temperature and soak time have relation, and the suitable soak time of confirming through experiment is about 1.5 hours, makes Yb³⁺Be adsorbed on uniformly on the loose sandwich layer.

(3) the dehydration excellent sleeve pipe that contracts.

Solution is extracted out from reaction tube, under suitable temperature, fed high-purity Cl₂, O₂Mixed gas reaction tube carried out drying and dehydrating handle, dewatering time is about 40 minutes.

(4) prefabricated rods processed.

To through the reaction tube that dehydrating at high temperature burning shrinkage become the transparent Yb of mixing that has³⁺The prefabricated rods of sandwich layer.Carry out sleeve pipe to suitable dimensions than needing to prefabricated rods according to the size of doing optical fiber preform core and the core diameter that is drawn into optical fiber.

(5) drawing process.

Acid treatment is carried out on surface to the preform after the processing, and cleans, dries, and it is clamped on the wire-drawer-tower bar feeding mechanism sends in the graphite resistor furnace then, under 2000 ℃ high temperature, rod is heated to molten condition, is drawn into the satisfactory optical fiber of diameter.The diameter of optical fiber is measured by silk footpath measurement and control instrument, guarantees that through the adjustment to molten excellent temperature, delivery speed and haulage speed the fluctuation in silk footpath is no more than the deviation of regulation.The ultraviolet-curing paint of online coating low-refraction is as the surrounding layer of optical fiber.

As shown in Figure 5; Annular doping layer optical fiber laser in the present embodiment, with annular doping layeroptical fiber 504 as gain media, withLD array 501 as pumping source, constitute the annular doping layer optical fiber laser that resonator cavitys are built with totalreflective mirror 503output coupling mirrors 505.

The pump light thatLD array 501 sends gets into annular doping layeroptical fiber 504 through collimationfocus lens system 502 it is carried out pumping; Twodichroic mirrors 503 and 505 pairs of laser are high anti-, thoroughly high to pump light; Common formation resonator cavity, output laser obtains desired light beam through optical shaping system.

Claims (6)

Translated fromChinese

1. 一种环形掺杂层光纤，作为增益介质用于光纤激光器中，其特征在于，该光纤由内包层（101）和由内而外依次包覆在该内包层（101）上的环形掺杂层（102）、中包层（103）、外包层（104）和保护层（105）组成，其中所述内包层（101）为不掺杂的纤芯。1. A ring-shaped doped fiber, which is used as a gain medium in fiber lasers, is characterized in that the fiber is composed of an inner cladding (101) and a ring-shaped doped fiber that is sequentially coated on the inner cladding (101) from inside to outside. The mixed layer (102), the middle cladding (103), the outer cladding (104) and the protective layer (105), wherein the inner cladding (101) is an undoped fiber core.2.根据权利要求1所述的环形掺杂层光纤，其特征在于，所述的环形掺杂层（102）由掺稀土元素的基质材料制成。2. The annular doped layer optical fiber according to claim 1, characterized in that, the annular doped layer (102) is made of a matrix material doped with rare earth elements.3.根据权利要求2所述的环形掺杂层光纤，其特征在于，所述的基质材料为石英玻璃或氟化物玻璃。3. The annular doped layer optical fiber according to claim 2, characterized in that, said matrix material is quartz glass or fluoride glass.4.根据权利要求1-3之一所述的环形掺杂层光纤，其特征在于，所述的内包层（101）和中包层（103）的材料和折射率均相同。4. The annular doped layer optical fiber according to any one of claims 1-3, characterized in that the material and refractive index of the inner cladding (101) and the middle cladding (103) are the same.5.根据权利要求4所述的环形掺杂层光纤，其特征在于，所述的内包层（101）和中包层（103）的材料为折射率比环形掺杂层小、横向尺寸和数值孔径比环形掺杂层大的基质材料。5. The annular doped layer optical fiber according to claim 4, characterized in that, the material of the inner cladding (101) and the middle cladding (103) has a refractive index smaller than that of the annular doped layer, and the lateral size and value are A matrix material with pores larger than the annular doped layer.6.一种光纤激光器，其特征在于，该光纤激光器的增益介质为上述权利要求1-5之一所述的环形掺杂层光纤。6. A fiber laser, characterized in that the gain medium of the fiber laser is the ring-shaped doped layer fiber according to any one of claims 1-5.

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