Asymmetric double refraction vortex optical fiber and preparation method thereof
(1) technical field
The present invention relates to a kind of optical fiber and its technology of preparing, and in particular to a kind of asymmetric double refraction vortex optical fiber and its system
Preparation Method, belongs to technical field of optical fiber.
(2) background technology
One of vortex beams be noteworthy characterized by with orbital angular momentum (Physical Review A, 1992,45 (11):
8185-8189), therefore it is widely studied in recent years, and has obtained in communication, optical tweezer, Atomic Manipulation and microtechnique greatly
Using.Generate vortex beams most common process be use spatial light modulator (Optics Express, 2008,16 (21):
16984-16992), however spatial light modulator is typically bulky, it is expensive, and need to realize light in free space
Coupling, thus brings many inconvenience.
And the vortex photoproduction for being based on optical fiber grow up to be a useful person then on remote interaction and system compact have more advantage.Researchers make
With acoustics long-period gratings (Physical Review Letters, 2006,96 (4):43604) or using in multimode fibre
In induced pressure (Applied Optics, 1998,37 (3):469-472) realize vortex optical transmission mode.But in light
Mode Coupling can destroy orbital angular momentum pattern in fibre, so as to cause multipath interference.In most multimode fibres, TE/TM
Pattern and the HE for needing21Pattern coexists, and so they can generate linear polarization pattern (LP through Mode Coupling in outfan
Pattern), LP patterns are not the real eigen mode of optical fiber, and it can not carry orbital angular momentum.Therefore, document (Optics
Letters, 2012,37 (13):2451-2453) report using micro-bend grating to slacken high-order LP11The generation of pattern, and then
Input pattern is converted into required HE21Pattern, ultimately generates highly purified vortex beams.
Preferably standard single-mode fiber has a good geometry circular symmetry, thus the basic mode HE for being transmitted11It is orthogonal mode
The double degenerate mode of formula.But in actual fiber, due to the presence of defect, this double degenerate is destroyed, so as to cause
Mode birefringence, in order to maintain this mode polarization, people to devise polarization maintaining optical fibre in standard single-mode fiber.Polarization maintaining optical fibre makesWithThe effective refractive index of pattern is different, propagation constant β of two orthogonal modesxWith βyDifference increases, two-mode coupling probability
Reduce, so if transmission light being linearly polarized on the parallel direction of one optical axis of optical fiber, then light will be always maintained at this
Plant polarization state to transmit in a fiber.
United States Patent (USP) (US20080101754) and European patent (EP1705503B1) propose a kind of fiber core refractive index only
With the gradient index fibre of azimuthal variation, this optical fiber can regard the space phase plate of longitudinal direction elongation as, using the optical fiber
Vortex beams can be generated.Although the vortex beams maker structure is extremely simple, it is extremely difficult to prepare this optical fiber,
Therefore the present invention is in polarization maintaining optical fibre technical foundation, it is proposed that a kind of Novel asymmetric birefringence vortex optical fiber, this vortex light
Fibre is prepared and is easier, and can produce class vortex beams.
(3) content of the invention
It is an object of the invention to provide it is a kind of generate vortex optical transmission mode asymmetric double refraction vortex optical fiber and
Its preparation method.
What the present invention was realized in:
One of vortex beams is noteworthy characterized by with orbital angular momentum, and in order to obtain orbital angular momentum, optical fiber must be taken
Band higher order pattern, for example, phase shift is two HE of ± pi/221The linear combination of pattern is capable of achieving orbital angular momentum pattern.By
There are single-screw or Double helix stressed zone, and two of Double helix stressed zone in the asymmetric double refraction vortex optical fiber of the present invention
The material adulterated in prestressing force rod is different, therefore the mal-distribution or the difference of stressed zone material of this stressed zone, results in
Asymmetric stress birefringence distribution in fibre core, and this is distributed in optical fiber longitudinal direction in the shape of a spiral, thus when light wave input
To after the optical fiber, can form that radial phase is poor, so that the light field wherein transmitted obtains orbital angular momentum, produce vortex phase and pass
It is defeated, realize class vortex optical transmission mode.
The asymmetric double refraction vortex optical fiber of the present invention is from the different of polarization maintaining optical fibre, in the present invention, due to stress
The mal-distribution in area or the difference of stressed zone material, are not in the linear polarization property of polarization maintaining optical fibre, but with spiral
The rotation of stressed zone, the polarization state that light wave is conducted in fibre core is also rotated with, and vortex optical transmission mode occurs.
Compared with prior art, advantages of the present invention is:
1st, the preparation of asymmetric double refraction vortex optical fiber is simple, can directly by the light with single-screw or Double helix stressed zone
Fine prefabricated rods rotation drawing is formed.
2nd, the refractive index Spiral distribution function and stressed zone dopant material of asymmetric double refraction vortex optical fiber is in preparation process
In be controllable, the final control being capable of achieving to generating class vortex beams feature.
3rd, asymmetric double refraction vortex optical fiber space pliability is fabulous, therefore can select in any suitable position and side
Upwards output class vortex beams, are easy in microgranule manipulation and the application for sensing.
(4) illustrate
Fig. 1 is the refraction vortex optical fiber schematic diagram of the asymmetric double with single-screw stressed zone;
Fig. 2 is the cross-sectional view that the asymmetric double with single-screw stressed zone reflects vortex optical fiber;
Fig. 3 is the peacekeeping (b) two of stress birfringence (a) three that the asymmetric double with single-screw stressed zone reflects vortex optical fiber
Dimension schematic diagram;
Fig. 4 is the light intensity transmission schematic diagram of the refraction vortex optical fiber of the asymmetric double with single-screw stressed zone;
Fig. 5 is that the asymmetric double with single-screw stressed zone reflects vortex optical fiber in Z=900 μm of (a), (b) Z=1000 μ
The PHASE DISTRIBUTION figure of m, Z=1100 μm of (c) and (d) Z=1200 μm of cross-section;
Fig. 6 is that the preform with single stress area prepares schematic diagram;
Fig. 7 is that the refraction vortex optical fiber of the asymmetric double with single-screw stressed zone prepares schematic diagram;
Fig. 8 is the refraction vortex optical fiber schematic diagram of the asymmetric double with Double helix stressed zone;
Fig. 9 is the cross-sectional view that the asymmetric double with Double helix stressed zone reflects vortex optical fiber;
Figure 10 is the peacekeeping (b) of stress birfringence (a) three that the asymmetric double with Double helix stressed zone reflects vortex optical fiber
Two-dimensional representation;
Figure 11 is the preform preparation method schematic diagram with double stressed zones;
Figure 12 is the preparation method schematic diagram that the asymmetric double with Double helix stressed zone reflects vortex optical fiber;
Figure 13 is the connection signal that the tail optical fiber with light source and the asymmetric double with single-screw stressed zone reflect vortex optical fiber
Figure.
Figure 14 is the connection signal that the tail optical fiber with light source and the asymmetric double with Double helix stressed zone reflect vortex optical fiber
Figure.
(5) specific embodiment
Illustrate below in conjunction with the accompanying drawings and the present invention is described in more detail:
With reference to Fig. 1-Fig. 5, what the first embodiment of the invention was realized in.
Describe how light wave is producing vortex after the asymmetric double refraction vortex optical fiber that one section of present invention is provided first
The ultimate principle of light field.One section of asymmetric double refraction vortex optical fiber is taken, the optical fiber includes covering 1, fibre core 2 and single-screw stressed zone
3.Due to the presence of single-screw stressed zone 3, stress analysis is carried out to the cross section of optic fibre shown in Fig. 2 and be can be obtained by such as Fig. 3 institutes
(in Fig. 3 (a), column fence area encompassed represents core region, and Z axis represent that stress is double for the stress birfringence distribution shown
Refraction size Ny-Nx, in Fig. 3 (b), gray scale size then represents stress birfringence size), it is this non-right due to existing in fibre core
The stress birfringence distribution of title, so when light source 4 is input into one end of the optical fiber, the optical fiber can generate class vortex optical transport
Pattern, the transmission of its light intensity as shown in figure 4, Z=900 μm, 1000 μm, 1100 μm and 1200 μm cross-section PHASE DISTRIBUTION such as
Shown in Fig. 5, it can be seen that, in the optical fiber, conduction light wave has vortex phase, and it is a species vortex beams.
Next provides the preparation method that asymmetric double reflects vortex optical fiber.This asymmetric double with single-screw stressed zone
The preparation process of refraction vortex optical fiber can be divided into following step (such as Fig. 6 and Fig. 7):
Step 1:Such as Fig. 6, an eccentric orfice 7 is squeezed in the preform 6 containing core 5, then stressed zone prefabricated rods 8
In insertion eccentric orfice 7, the preform 9 with single stress area is thus obtained;
Step 2:Such as Fig. 7, preform 9 is positioned on wire-drawer-tower, in being total to for vertical distraction power 10 and twisting resistance 11
Torsion wire drawing is carried out under same-action, is prepared into the non-right of single-screw stressed zone after heating and corresponding post processing 12
Claim birefringence vortex optical fiber 13.
With reference to Fig. 8 and Fig. 9, the first embodiment, the asymmetric double refraction of second embodiment of the invention are different from
Vortex optical fiber has two stressed zones 14 and 15, forms Double helix stressed zone structure.For this with Double helix stressed zone
Asymmetric double reflects vortex optical fiber, and Figure 10 is given at the stress birfringence scattergram in fibre core, as can be seen from the figure its stress
Birefringent excursion is greater than the stress birfringence that the asymmetric double with single-screw stressed zone reflects vortex fiber core
Excursion (Fig. 3), thus the ability that this optical fiber produces vortex phase is more projected.
The preparation process of this refraction of the asymmetric double with Double helix stressed zone vortex optical fiber can be divided into following step
Suddenly (such as Figure 11 and Figure 12):
Step 1:Such as Figure 11, two symmetrical eccentric orfices 7 are squeezed in containing core fibre prefabricated rods 6, then two doping
The different stressed zone prefabricated rods 16 and 17 of material are inserted respectively in two symmetrical eccentric orfices 7, thus obtain having double stressed zones
Preform 18;
Step 2:Such as Figure 12, preform 18 is positioned on wire-drawer-tower, in vertical distraction power 10 and twisting resistance 11
Torsion wire drawing is carried out under collective effect, is prepared into the non-of Double helix stressed zone after heating and corresponding post processing 12
Symmetrical birefringence vortex optical fiber 19.
Embodiment 1:
1st, prepared by optical fiber:Method for preparing optical fiber according to the first embodiment is prepared with the non-of single-screw stressed zone
Symmetrical birefringence vortex optical fiber 13;
2nd, light source couples:The refraction vortex of the asymmetric double with the single-screw stressed zone optical fiber 13 for preparing is cut
Cut, be then aligned, weld with the single-mode fiber 20 with light source tail optical fiber, as shown in figure 13;
3rd, vortex beams are generated:Will be in the refraction vortex light of the asymmetric double with single-screw stressed zone after input laser 21
Realize that vortex optical mode is transmitted in fine 13, and can be in optical fiber end output class vortex beams.
Embodiment 2:
1st, prepared by optical fiber:Method for preparing optical fiber according to second embodiment is prepared with the non-of Double helix stressed zone
Symmetrical birefringence vortex optical fiber 19;
2nd, light source couples:The refraction vortex of the asymmetric double with the Double helix stressed zone optical fiber 19 for preparing is cut
Cut, be then aligned, weld with the single-mode fiber 20 with light source tail optical fiber, as shown in figure 14;
3rd, vortex beams are generated:Will be in the refraction vortex light of the asymmetric double with Double helix stressed zone after input laser 21
Realize that vortex optical mode is transmitted in fine 19, and can be in optical fiber end output class vortex beams.