CN209132535U - Polarization independent type orbital angular momentum modulator and orbital angular momentum light-beam generator - Google Patents
Polarization independent type orbital angular momentum modulator and orbital angular momentum light-beam generator Download PDFInfo
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- CN209132535U CN209132535U CN201821991762.2U CN201821991762U CN209132535U CN 209132535 U CN209132535 U CN 209132535U CN 201821991762 U CN201821991762 U CN 201821991762U CN 209132535 U CN209132535 U CN 209132535U
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Abstract
This application involves a kind of polarization independent type orbital angular momentum modulator and orbital angular momentum light-beam generators.The polarization independent type orbital angular momentum modulator includes fiber body.The fiber body has Helical Fiber structure, and the Helical Fiber structure has long-period fiber grating effect.The fiber body axially has periodic spiral refractive index modulation, the spiral refractive index modulation period is located at hundred micron dimensions, the spiral Refractive index modulation distribution generates orbital angular momentum light beam for exciting helical phase in the axial direction, radially and angularly of the fiber body.Above-mentioned polarization independent type orbital angular momentum modulator can excite helical phase in certain bandwidth, not will form to Polarization-Sensitive specific direction, have polarization independence.All optical fibre structure is conducive to integrate in the communications, with good compatibility, assists without other devices, the advantages such as preparation simple with structure, easy.
Description
Technical field
This application involves orbital angular momentum applied technical fields, more particularly to a kind of polarization independent type orbital angular momentum tune
Device processed and orbital angular momentum light-beam generator.
Background technique
Carry orbital angular momentum (orbital angular momentum, OAM) vortex light and traditional plane wave,
There is very big difference in terms of wavefront structure, vortex light shows peculiar around beam center for spherical wave and other polarised lights
Screw type wavefront structure, exist in phase factor and be represented by one of exp (il θ) with mathematical formulae, wherein θ is rotation
Phase angle, l are the topological charge number of optical eddy.
In the related technology, helical phase piece (Spiral phase plates, SPP) can be in the premise of not change pattern
Lower raising transfer efficiency.Helical phase piece is one piece of optical modulating device in uneven thickness, wherein one side is plane, in addition one
Face is spiral camber dielectric disk of the thickness with azimuthal variation.Its helical phase piece slab-thickness presses θ/2 h=l λ with azimuth
π r (n-1) relationship change, wherein n is Refractive Index of Material, and l is the orbital angular momentum light beam topological charge value generated, and θ is azimuth.
When a branch of Gauss light passes through the transmissive medium plate, the thickness passed through at different radii is all different with refraction angle, is obtained
To different optical path differences, and then cause different phase differences.For specific wavelength, if rotating a circle to form the phase difference of 2l π i.e.
Producible topological charge number is l.This method can intuitively generate helical phase, not need other ancillary equipments.But it uses
One helical phase piece cannot generate the orbital angular momentum light beam of multiple and different orders simultaneously, and can only be at particular job wavelength
Generate orbital angular momentum light beam.In addition, the screw pitch of helical phase piece angularly requires strictly, to need very accurate preparation skill
Art.
The computed hologram that can use spatial modulator generation realizes diffraction optical element (Diffractive
Optical Elements, DOEs) function.It can be loaded on the liquid crystal display of spatial light modulator by computer program control
Different voltage changes the form of crystal, to load different holograms on liquid crystal display.It can spirit using different holograms
The topological charge number for the orbital angular momentum light beam that control living generates.But spatial light modulator there are it is expensive, have polarization
The disadvantages of correlation, coupling efficiency are low and can only generate low-power orbital angular momentum light beam.
Long-period fiber grating is combined with pressure plare, rotator or Polarization Controller can inspire helical phase.It is long
Period optical fiber grating implementation pattern is by the coupling of basic mode to higher order mode, and other attachmentes can produce between the higher order mode of coupling
The phase difference of life ± pi/2.Although this method has, coupling efficiency is high, Insertion Loss is low, light weight, at low cost, electromagnetism interference and
With the advantages such as optical fiber telecommunications system is completely compatible.But long-period fiber grating excitation helical phase needs additional attachment with reality
Existing phase-modulation, has polarization correlated.
In conclusion the relevant technologies realize helical phase excitation have wavelength dependency, polarization correlated, structure is complicated with
And the problems such as preparation difficulty.
Utility model content
Based on this, it is necessary to which for the relevant technologies of helical phase are excited, there are wavelength dependencies and polarization correlated, knot
The problem that structure is complicated and preparation is difficult provides a kind of polarization independent type orbital angular momentum modulator and orbital angular momentum light beam hair
Raw device.
A kind of polarization independent type orbital angular momentum modulator, comprising:
Fiber body, has Helical Fiber structure, and the Helical Fiber structure has long-period fiber grating effect；
The fiber body axially has periodic spiral refractive index modulation, and the spiral refractive index modulation period is located at
Hundred micron dimensions, the spiral Refractive index modulation distribution is in the axial direction, radially and angularly of the fiber body, for exciting spiral
Phase generates orbital angular momentum light beam.
Above-mentioned polarization independent type orbital angular momentum modulator, by using fiber body as substrate, the fiber body
Helical Fiber structure with periodic distribution can excite helical phase in certain bandwidth.What the fiber body was formed
Helical Fiber structure has helical symmetry, not will form to Polarization-Sensitive specific direction, has polarization independence.It is described inclined
Vibration independent type orbital angular momentum modulator is all optical fibre structure, is conducive to integrate in communication, has good compatibility, is not necessarily to it
He assists device, the advantages such as preparation simple with structure, easy.Further, the polarization independent type orbital angular momentum modulation
Device coupling efficiency is high, and the OAM of generation can carry random polarization state, and have high-purity.
The fiber body is dual mode optical fiber or four mode fibers in one of the embodiments,.
The fiber body axially has the spiral refractive index of period and uniform depth in one of the embodiments,
Modulation, the range of the spiral refractive index modulated quantity are 2 X 10-4To 2 X 10-3。
The fiber body includes fiber core and covering in one of the embodiments,.
The spiral refractive index modulation in any section of the fiber body has asymmetric in one of the embodiments,
Property, radial along the fiber body, the spiral refractive index modulation reduces with the increase of radius.
The length range of the fiber body is 1 centimetre to 6 centimetres in one of the embodiments,.
A kind of orbital angular momentum light-beam generator, comprising:
Light source；
Polarization Controller, input terminal are connect with the light source；
Polarization independent type orbital angular momentum modulator is connect with the Polarization Controller output end；And
First optical patchcord, with the described one end of polarization independent type orbital angular momentum modulator far from the Polarization Controller
Connection；
Wherein, the polarization independent type orbital angular momentum modulator includes:
Fiber body, has Helical Fiber structure, and the Helical Fiber structure has long-period fiber grating effect；
The fiber body axially has periodic spiral refractive index modulation, and the spiral refractive index modulation period is located at
Hundred micron dimensions, the spiral Refractive index modulation distribution is in the axial direction, radially and angularly of the fiber body, for exciting spiral
Phase generates orbital angular momentum light beam.
In one of the embodiments, further include:
Second optical patchcord, the Polarization Controller input terminal are connect by second optical patchcord with the light source.
In one of the embodiments, further include:
Single mode optical fiber, the polarization independent type orbital angular momentum modulator pass through the single mode optical fiber and the Polarization Control
The connection of device output end.
In one of the embodiments, further include:
Less fundamental mode optical fibre, first optical patchcord pass through the less fundamental mode optical fibre and polarization independent type orbital angular momentum modulator
Connection.
Polarization independent type orbital angular momentum modulator provided by the above embodiment, by using bimodulus or four mode fibers, tool
There are light weight, electromagnetism interference.The orbital angular momentum light-beam generator can generate in certain bandwidth and have spiral shell
The light beam of phase is revolved, the light beam not will form to Polarization-Sensitive specific direction, have polarization independence.
Detailed description of the invention
Fig. 1 is a kind of polarization independent type orbital angular momentum modulator structure schematic diagram provided by the embodiments of the present application；
Fig. 2 is a kind of polarization independent type orbital angular momentum modulator spiral refractive index modulation face provided by the embodiments of the present application
Schematic diagram；
Fig. 3 is a kind of polarization independent type orbital angular momentum modulator preparation method flow chart provided by the embodiments of the present application；
Fig. 4 is another polarization independent type orbital angular momentum modulator preparation method process provided by the embodiments of the present application
Figure；
Fig. 5 is a kind of orbital angular momentum light-beam generator provided by the embodiments of the present application；
Fig. 6 is a kind of polarization independent type orbital angular momentum modulator test device schematic diagram provided by the embodiments of the present application；
Fig. 7 is a kind of polarization independent type orbital angular momentum modulator test spectral result figure provided by the embodiments of the present application；
Fig. 8 is a kind of different polarization state polarization independent type orbital angular momentum modulator test provided by the embodiments of the present application
Result figure.
Drawing reference numeral explanation:
100 polarization independent type orbital angular momentum modulators
110 fiber bodies
400 orbital angular momentum light-beam generators
410 light sources
420 Polarization Controllers
430 first optical patchcords
440 second optical patchcords
450 single mode optical fibers
460 less fundamental mode optical fibres
Specific embodiment
In order to make the above objects, features, and advantages of the present application more apparent, with reference to the accompanying drawing to the application
Specific embodiment be described in detail.Many details are explained in the following description in order to fully understand this Shen
Please.But the application can be implemented with being much different from other way described herein, those skilled in the art can be not
Similar improvement is done in the case where violating the application intension, therefore the application is not limited by following public specific implementation.
It should be noted that it can directly on the other element when element is referred to as " being fixed on " another element
Or there may also be elements placed in the middle.When an element is considered as " connection " another element, it, which can be, is directly connected to
To another element or it may be simultaneously present centering elements.
Unless otherwise defined, all technical and scientific terms used herein and the technical field for belonging to the application
The normally understood meaning of technical staff is identical.The term used in the description of the present application is intended merely to description tool herein
The purpose of the embodiment of body, it is not intended that in limitation the application.Term " and or " used herein includes one or more phases
Any and all combinations of the listed item of pass.
Referring to Figure 1, the application provides a kind of polarization independent type orbital angular momentum modulator 100.The polarization independent type
Orbital angular momentum modulator 100 includes fiber body 110.The fiber body 110 has Helical Fiber structure, the spiral light
Fine structure has long-period fiber grating effect.The fiber body 110 is axial to have periodic spiral refractive index modulation, asks
Together referring to fig. 2.The spiral refractive index modulation period is located at hundred micron dimensions, and the spiral Refractive index modulation distribution is in described
The axial direction of fiber body 110, radially and angularly generates orbital angular momentum light beam for exciting helical phase.
The fiber body 110 has periodic spiral refractive index modulation along optical fiber axial direction.In optical fiber axial direction, grating
The period of modulation is in 200 μm of -2000 μ m.On the period of the range, grating resonance peak is generated in C+L wave band, favorably
It is used in being integrated with communication system.The refractive index modulation period is in hundred micron dimensions, so that the Helical Fiber structure has length
Period optical fiber grating effect.The Helical Fiber structure is spiral core structure, can generate helical form to incident light
Refractive index modulation.The refractive index modulation of different tradition long-period fiber grating, the refractive index modulation along optical fiber axial direction, it is radial and
Angularly all have distribution.Thus, in a screen periods, the light being incident in fiber grating, which is removed, is generated height by optical grating reflection
Outside rank mode, an additional helical phase also is generated by being influenced by spiral index distribution.In multiple Grating Modulations
Under the action of period, higher order mode and helical phase are enhanced by resonance, to form the higher order mode with helical phase, i.e. rail
Road angular momentum light beam.It is influenced due to being formed by orbital angular momentum light beam only by spiral refractive index modulation, the electricity with incident light
Field direction of vibration is unrelated, so the orbital angular momentum modulator 100 can be used to excite to polarize unrelated orbital angular momentum mould
Formula.
The polarization independent type orbital angular momentum modulator 100 uses chiral fiber gratings as substrate, can be directly real
The coupling of existing orbital angular momentum, without such as Polarization Controller and stress modulation plate other auxiliary devices.The polarization independent type
Orbital angular momentum modulator 100 has uniform spiral refractive index modulation structure, can periodically be scattered to basic mode light.
Due to the presence of spiral perturbation in the polarization independent type orbital angular momentum modulator 100, the plane phase of basic mode can be made to send out
The variation in raw period.Effect that there are two types of the tools of orbital angular momentum modulator 100, first is that the generation of orbital angular momentum light beam, separately
One is the conversions of orbital angular momentum light beam.Generation for orbital angular momentum light beam uses because of the refractive index modulation of spiral
The generation of helical phase may be implemented in the input light incidence of either polarization state, to generate orbital angular momentum light beam.Meeting
Under conditions of fiber grating phase matched in the polarization independent type orbital angular momentum modulator 100, the energy of basic mode light can
To be coupled on higher order mode by resonance, plane phase is converted to spiral under the action of periodical resonance, thus
It realizes the excitation of helical phase, that is, realizes the generation of orbital angular momentum.
In one embodiment, the fiber body 110 is dual mode optical fiber or four mode fibers.The fiber body can also be with
For one of other less fundamental mode optical fibres.The fiber body 110 may include fiber core and covering.The fibre core diameter
It can be 19 microns, the cladding diameter can be 125 microns.The polarization independent type orbital angular momentum modulator 100 is complete
Optical fibre device, the Helical Fiber structure having can directly excite helical phase, not need other attachmentes auxiliary.Have in the communications
Conducive to integrating, there is good compatibility.
The axial spiral refractive index modulation with period and uniform depth of the fiber body 110, the spiral folding
The range for penetrating rate modulation voltage is 2 X 10-4To 2 X 10-3.The spiral refractive index modulation has period and depth along optical fiber axial direction
Uniform spiral refractive index modulation.In one embodiment, the spiral refractive index tune in any section of the fiber body 110
Fixture has asymmetry, and radial along the fiber body 110, the spiral refractive index modulation reduces with the increase of radius.Institute
It states spiral refractive index modulation depth to be distributed with helicity, the helical phase for excitation beam.Asymmetrical spiral refractive index
Modulation is conducive to the coupling excitation of high-order asymmetric mode.In the section of the axial any position of the fiber body 110, edge
It angularly rotates a circle, corresponding refractive index modulation is uneven and asymmetric, and the integer of 2 π can be realized in a screen periods
Phase-delay quantity again.For the Mode Coupling for realizing high coupling efficiency, filter with low insertion loss, within any period, chiral fiber gratings
2 X 10 of refractive index modulated quantity-4-2ⅹ10-3In range.In one embodiment, the length range of the fiber body 110 is 1
Centimetre to 6 centimetres.In Mode Coupling, which may be implemented high-order core mode according to the variation in period
Excitation.
The spiral refractive index modulation of the polarization independent type orbital angular momentum modulator 100 is the intrinsic form of grating, therefore
Spiral refractive index modulation function does not change with the external world and is changed, and has not by the external conditions shadow such as temperature, vibration, distortion and bending
Loud advantage.And be appreciated that the rotation of the helical phase that the polarization independent type orbital angular momentum modulator 100 generates only with
The helical modulation for constituting the chiral fiber gratings of the polarization independent type orbital angular momentum modulator 100 itself is related, without with
The polarization state of input light changes and changes.Further, when with helical phase node l but rotation property difference when, the two does not occur
It intercouples.
In one embodiment, the Helical Fiber structure has polarization independence.Helical phase is reflected by the spiral
Rate is modulated, unrelated with incident light polarization state.The rotation direction of helical phase determines by the spiral refractive index rotation direction of grating itself, with
Incident light polarization state is unrelated.The representative mode purity of helical phase determines by the period and intensity of spiral refractive index, and enters
It is unrelated to penetrate polarization state.
The Helical Fiber structure has helical symmetry, to will not be formed to Polarization-Sensitive specific direction.Therefore,
The polarization independent type orbital angular momentum modulator 100 has polarization-independent characteristic.When to the polarization independent type track angular motion
When measuring the basic mode light of the input random polarization state of modulator 100, the height of the coupling of polarization independent type orbital angular momentum modulator 100
Rank mode all has helical phase, therefore the polarization independent type orbital angular momentum modulator 100 has polarization independence, excitation
The OAM of generation can carry random polarization state.The polarization of the input light of the i.e. described polarization independent type orbital angular momentum modulator 100
When state arbitrarily changes, helical phase can be excited by the polarization independent type orbital angular momentum modulator 100.And the height of excitation
The polarization characteristic of rank mode is consistent with the basic mode light of input.In one embodiment, the polarization independent type orbital angular momentum tune
Device 100 processed coupling efficiency with higher, the purity of the helical phase of generation is unrelated with polarization state, while the OAM purity generated
It is high.The polarization independent type orbital angular momentum modulator 110 can produce OAM in certain bandwidth.The bandwidth can be
3dB。
In one embodiment, the rotation direction of the Helical Fiber structure is identical, and the rotation direction is clockwise or counterclockwise.According to
The polarization independent type orbital angular momentum modulator of right hand chiral fiber gratings composition can be divided into according to the difference of the rotation direction
100 and left hand chiral grating fibers constitute the polarization independent type orbital angular momentum modulator 100.The polarization independent type rail
Road angular momentum modulator 100 can produce the orbital angular momentum light beam that topological charge is l=+1 or l=-1.
In one embodiment, the polarization independent type orbital angular momentum modulator 100 further includes protective layer.The protection
Layer is located at outside the fiber body 110, forms mechanical protection to the fiber body 110, extends the polarization independent type rail
The service life of road angular momentum modulator 100.The polarization independent type orbital angular momentum modulator 100 is Full-optical device, side
Just it connect coupling with other optical fibre devices, and there is very high compatibility.It is appreciated that the polarization independent type orbital angular momentum tune
Device 100 processed has the characteristic of light weight, electromagnetism interference.
Please also refer to Fig. 3, the application provides a kind of polarization independent type orbital angular momentum modulator preparation method.It is described inclined
Independent type orbital angular momentum modulator preparation method of shaking includes: S10, heating optical fiber main body 110 to melting state.S20, distortion are melted
The fiber body 110 of molten state.S30, the cooling fiber body 110.Before step S10, by the fiber body
110 both ends are fixed, and one end is fixed on optical fibre rotator, and the other end is fixed in fibre clip.Fiber clamp and optical fibre rotator
It is separately fixed on a displacement platform.In step slo, under the high temperature conditions, the fiber body 110 occurs uniformly to melt
It is molten.The hot conditions are 1800 DEG C or more.The fiber body 110 is less fundamental mode optical fibre, and the less fundamental mode optical fibre is that mode is high-quality
Measure the channel of transmission.The less fundamental mode optical fibre can be the optical fiber such as bimodulus, four moulds.The less fundamental mode optical fibre has light weight, anti-electromagnetism
The advantages that interference.In step S20, equably high speed distorts the fiber body 110 of melting.In step s 30, to described
When fiber body 110 removes heating zone, the fiber body 110 is cooled down rapidly.In the cooling procedure of the fiber body 110
In, freeze portion of residual stress, to form spiral refractive index modulation, has obtained chiral fiber gratings, complete polarization independent type
The preparation of orbital angular momentum modulator 100.
While being locally heated to molten condition to the fiber body 100 using high temperature heat source, to the fiber body
110 carry out translation and distortion, can prepare the chiral fiber gratings with screw type index distribution.The chiral optical fiber light
Grid can be used as the polarization independent type orbital angular momentum modulator 100.The polarization independent type orbital angular momentum modulator 100
Coupling efficiency with higher.The coupling efficiency is the basic mode that will input optically coupling to the ratio in the higher order mode of optical fiber.
The coupling efficiency is related with the mode of spiral optical grating construction and processing.Using above-mentioned polarization independent type orbital angular momentum modulator
Preparation method stability with higher, the chiral optical fiber processed is highly uniform, can be preferably close to the theoretical limit
Value, coupling efficiency with higher.
Please also refer to Fig. 4.In one embodiment, the heating optical fiber main body 110 is used into melting state step
CO2 laser, electric arc continuous discharge, high temperature furnace or any heat source of coil heat the fiber body 100 to melting state.
In one embodiment, in 110 step of the fiber body of the distortion melting state, along instantaneous needle or inverse
The fiber body 110 of clockwise distortion melting state.In one embodiment, in the cooling fiber body
In 110 steps, the fiber body 110 is removed into heating zone, the residual stress generated during distortion is frozen in the light
In fine main body 110.
Please also refer to Fig. 5, the application provides a kind of orbital angular momentum light-beam generator 400.The orbital angular momentum hair
Raw device 400 includes that light source 410, Polarization Controller 420, polarization independent type orbital angular momentum modulator 100 and the first optical fiber are jumped
Line 430.The input terminal of the Polarization Controller 420 is connect with the light source 410.The polarization independent type orbital angular momentum tune
Device 100 processed is connect with the output end of the Polarization Controller 420.First optical patchcord 430 and the polarization independent type rail
Road angular momentum modulator 100 is connected far from one end of the Polarization Controller 420.Wherein, the polarization independent type track angular motion
Measuring modulator 100 includes fiber body 110.The fiber body 110 has Helical Fiber structure, the Helical Fiber structure tool
There is long-period fiber grating effect.110 diameter of fiber body is identical.The fiber body 110 is axial to be had periodically
Spiral refractive index modulation, the spiral refractive index modulation period are located at hundred micron dimensions, the spiral Refractive index modulation distribution in
The axial direction of the fiber body 110, radially and angularly generates orbital angular momentum light beam for exciting helical phase.
The light source 410 can be tunable laser.The tunable laser is adjustable in required wave band.Track angular motion
Amount light-beam generator 400 can generate required OAM light beam in a wider bandwidth.In one embodiment, the band
Width is 3dB.By the input light for adjusting the available required polarization state of the Polarization Controller 420.First optical patchcord
430, for connecting with other instruments, facilitate the orbital angular momentum light-beam generator 400 to be applied in the communications.It can manage
It solves, by corresponding adapter between each type optical fiber, i.e. flange is attached.
The orbital angular momentum light-beam generator 400 further includes the second optical patchcord 440 in one of the embodiments,.
420 input terminal of Polarization Controller is connect by second optical patchcord 440 with the light source 410.Pass through described second
Optical patchcord 440 can guarantee that stablizing for light beam is transmitted.Second optical patchcord 440 can be single mode.
The orbital angular momentum light-beam generator 400 further includes single mode optical fiber 450 in one of the embodiments,.It is described
Polarization independent type orbital angular momentum modulator 100 is connected by the single mode optical fiber 450 with 420 output end of Polarization Controller
It connects.The polarization independent type orbital angular momentum modulator 100 and the Polarization Controller may be implemented in the single mode optical fiber 450
The low-loss transmission of light beam between 420.
The orbital angular momentum light-beam generator 400 further includes less fundamental mode optical fibre 460 in one of the embodiments,.It is described
First optical patchcord 430 is connect by the less fundamental mode optical fibre 460 with the polarization independent type orbital angular momentum modulator 100.Institute
Stating less fundamental mode optical fibre 460 can guarantee that stablizing for the light beam with orbital angular momentum is transmitted.
Please also refer to Fig. 6, the polarization of the polarization independent type orbital angular momentum modulator 100 is tested using test device
Correlation.It builds and a set of detect the polarization independent type orbital angular momentum modulator 100 based on the system of space interference and generate
Orbital angular momentum light beam.Interfered by OAM light beam with spherical wave or plane wave, to detect the phase of OAM.This method
It is to be had what Gaussian beam and the polarization independent type orbital angular momentum modulator 100 based on long period chiral grating generated
The OAM light beam of topological charge l is interfered in space, if two-beam is coaxial in space, spherical wave interference fringe is shown as opening up
Flutter the helical phase pattern that lotus number is l.Interference fringe is counterclockwise or clockwise rotation direction depend on OAM light beam topological charge number l
Symbol.
The light of tunable single long wavelength laser output is exported through optical patchcord enters adjustable point after 10 times of object lens collimate again
Light is divided into two optical paths, i.e. reference path and test light than polarization beam apparatus (Polarization Beam Splitter, PBS)
Road.The input light of the reference path is after 1/2 wave plate, into bundling device.The input light sequence of the optical system for testing is passed through
The polarizer, quarter wave plate, 10 times of object lens, 100 sample of polarization independent type orbital angular momentum modulator, 40 times of object lens and analyzing
Enter bundling device after device.Two-way light meets on the bundling device and then generates interference, finally utilizes infrared CCD (Charge
Coupled Device) real-time recording interference fringe.
Further, the light that the tunable laser issues first passes around 10 times of object lens and carries out collimation amplification.One
In a embodiment, using model VA5-1550, the amplified light beam of PBS collimation of Thorlabs is split.The PBS
Splitting ratio it is adjustable and the two-beam that separates is p-polarization light and s polarised light respectively.The input light of the optical system for testing is through reflecting mirror
After changing optical path direction, the input light of different polarization states is successively generated after the polarizer and the quarter wave plate.The input
Light includes linear polarization (linear polarization, LP), Left-hand circular polarization (left-handed circular
Polarization, CP-) and right-hand circular polarization (left-handed circular polarization, CP+).The test
After the input light of optical path then passes through 10 times of object lens, the polarization independent type orbital angular momentum modulator 100 and 40 times of object lens,
Into the analyzer.The analyzer analyzes the polarization state of the OAM light beam of generation.The input light of the reference path
Through 1/2 wave plate by the direction of vibration of linear polarization input light be adjusted to from the analyzer come out optical system for testing light vibration side
To identical, it is ensured that reference light and test light two-beam interfere.Finally collected using bundling device (Beam Combiner, BS)
Two-way light is interfered.In one embodiment, BS the model VC5-1550, Thorlabs.
After completion optical path is built, it is added without reference light first, only with the distribution of optical system for testing measurement mould field.Simultaneously
It is cut, and guaranteed using both ends of the precision cutting devices to 100 sample of polarization independent type orbital angular momentum modulator
The end face flatness of sample.Then its sample fiber end face will be fixed on using fibre holder 220 and is placed between object lens
On platform.In one embodiment, the fibre holder 220 can be both arms fiber clamp.
After completing preparation, firstly, removing the polarizer, the quarter wave plate and the inspection from the optical system for testing
Inclined device, and the wavelength of the tunable single long wavelength laser is set in the polarization independent type orbital angular momentum modulator 100
Resonance wave strong point.The three-D displacement platform at 100 both ends of polarization independent type orbital angular momentum modulator described in fine adjustment.So that institute
It states 100 former and later two object lens of polarization independent type orbital angular momentum modulator and gathers the polarization independent type orbital angular momentum respectively
The end face of left and right two of 100 sample of modulator.During debugging, spot intensity is detected by the infrared CCD in real time,
Until the hot spot brightness maximum position observed on the screen from the infrared CCD, at this time slave object lens to it is described polarization it is unrelated
The coupling efficiency highest of type orbital angular momentum modulator 100.
Secondly, being put into the polarizer, the quarter wave plate and the analyzer in the optical system for testing.Institute is tested first
The case where input light for stating 100 sample of polarization independent type orbital angular momentum modulator is linearly polarized light.For ease of description, it is specified that
The direction for being parallel to paper is 0 degree.Since the output light of the tunable laser is linearly polarized light, by the light passing of the polarizer
The fast axis direction of axis direction and the quarter wave plate is all placed in 0 degree of position, and the input light of linear polarization can be obtained.The linear polarization
Light is after 100 sample of polarization independent type orbital angular momentum modulator, using the analyzer.Utilize the CCD points
Ji Lu be located at four different angles when the analyzer light transmission shaft: 0 degree, 90 degree, 180 degree and 270 degree of whens individual mould field are believed
Breath.
Again, the reference path is added, interferes the reference path with the light in the optical system for testing.It utilizes
CCD record analyzer is located at described: 0 degree, 90 degree, interference information when 180 degree and 270 degree of four angles passes through interference
The available orbital angular momentum of mode phase information.
Finally, by the fast axle angle of the light transmission shaft and quarter wave plate that adjust the polarizer, available Left-hand circular polarization and the right side
Rounding polarization.When inputting the input light of different polarization states every time, all repeatedly aforesaid operations be can be completed unrelated to the polarization
The test process of type orbital angular momentum modulator 100.
In the optical path of coaxial interference testing helical phase test device, increase the polarizer and the wave plate etc., it is real
The input light of existing random polarization state, polarization measurement is combined with helical phase, can test polarization independent type track angle
The characteristic of momentum modulator 100.The angle for adjusting the analyzer light transmission shaft and the quarter wave plate fast axle, it is inclined to can produce line
The light of the random polarization states such as vibration and rotatory polarization, it is possible thereby to input the light of different polarization states.The analyzer of rear end can simultaneously
To be used to analyze polarization state possessed by output light.It can test out and mode is swashed in this way in different polarization states
Hair influences.
Please also refer to Fig. 7, the dextrorotation of the polarization independent type orbital angular momentum modulator 100 and left-handed spectrum such as Fig. 7
(a) and shown in Fig. 7 (b).Two 100 sample cycles of polarization independent type orbital angular momentum modulator are all 1192um, dextrorotation
The position of the resonance peak of polarization independent type orbital angular momentum modulator 100 is in 1554.5nm, coupling depth -24.6dB.It is left-handed inclined
The position of the resonance peak of vibration independent type orbital angular momentum modulator 100 is in 1550.9nm, coupling depth -22.5dB.The result shows that
The coupling efficiency of the polarization independent type orbital angular momentum modulator 100 is up to 86%.Two polarization independent type track angles
The small variations of the resonance peak of 100 sample of momentum modulator are that the polarization independent type orbital angular momentum modulator 100 makes
Extraneous shake in the process causes the structure partial of grating unevenly caused.It is appreciated that the position period of the resonance peak determines
It is fixed.The coupling depth and screen periods number, i.e. spiral number are related to the uniformity of process.
Please also refer to Fig. 8,100 sample test of polarization independent type orbital angular momentum modulator described in the right hand is not first
With the excitation situation of polarization state lower railway angular momentum, shown in result such as Fig. 8 (a).When input light is linearly polarized light, ginseng is not added
Shown in the mould field such as Fig. 8 (a11) for examining optical path.When light is after the polarization independent type orbital angular momentum modulator 100, basic mode quilt
It is energized into the orbital angular momentum of high-order.It can see hollow annulus from figure, and work as the analyzer and rotate a circle, can go out
The variation of existing light and shade illustrates that the light beam generated has the characteristics that linear polarization.In order to observe helical phase information, the reference is added
Optical path, and interfered with the optical system for testing, its phase information is determined by interference technique.It is from Fig. 8 (a12) it can be found that inverse
The spiral optical field distribution of hour hands rotation, i.e. topological charge l=+1.By above-mentioned experiment it is known that when input light is linear polarization
Light time can inspire the orbital angular momentum with linear polarization.Similarly when input light is right-hand circular polarization (CP+), from Fig. 8
(a21) it can see hollow annulus, and when the analyzer rotates a circle, no change has taken place for the intensity of hot spot, this
The polarization state for illustrating the light beam is circular polarization.Furthermore it can be observed that the interference fringe for rotation of taking advantage of a situation, illustrates to produce topological electricity
Lotus is the orbital angular momentum of l=+1.Also there is the phenomenon as CP+ when the polarization state of input light is Left-hand circular polarization (CP-).
Show that the polarization independent type orbital angular momentum modulator 100 can excite l=+ in different polarization states by above-mentioned experiment
1 orbital angular momentum has and polarizes incoherent characteristic.Furthermore we utilize the polarization independent type track angle of left hand helix
Momentum modulator 100 can also inspire the orbital angular momentum of l=-1 under different polarization states.Experiment shows to pass through high temperature
The polarization independent type orbital angular momentum modulator 100 prepared by heat source local heating and the method for translating distortion has polarization nothing
The characteristics of pass, the device are expected to play a great role in the communications field.
The herein described 100 uncorrelated spy of polarization based on chiral fiber gratings of polarization independent type orbital angular momentum modulator
Property, the orbital angular momentum light beam of ± 1 rank of l=, and the l=-1 or l excited can be excited under conditions of random polarization state
=+1 is only dependent upon the rotation of the 100 Helical Fiber grating of polarization independent type orbital angular momentum modulator.Its period is micro- hundred
Rice magnitude, helical modulation is uniform, and spectral quality is high, and Mode Coupling is clear.The polarization independent type orbital angular momentum modulation simultaneously
Device 100 is based on less fundamental mode optical fibre, is a kind of modulator of full fiber type, has small in size, at low cost, coupling efficiency height, easy of integration
Etc. advantages, in fiber optic communication, there is important application in optical tweezer, the fields such as particle manipulation.
Each technical characteristic of embodiment described above can be combined arbitrarily, for simplicity of description, not to above-mentioned reality
It applies all possible combination of each technical characteristic in example to be all described, as long as however, the combination of these technical characteristics is not deposited
In contradiction, all should be considered as described in this specification.
The several embodiments of the application above described embodiment only expresses, the description thereof is more specific and detailed, but simultaneously
The limitation to claim therefore cannot be interpreted as.It should be pointed out that coming for those of ordinary skill in the art
It says, without departing from the concept of this application, various modifications and improvements can be made, these belong to the protection of the application
Range.Therefore, the scope of protection shall be subject to the appended claims for the application patent.
Claims (10)
1. a kind of polarization independent type orbital angular momentum modulator (100) characterized by comprising
Fiber body (110), has Helical Fiber structure, and the Helical Fiber structure has long-period fiber grating effect；
The fiber body (110) axially has periodic spiral refractive index modulation, the spiral refractive index modulation period position
In hundred micron dimensions, the spiral Refractive index modulation distribution is used in the axial direction, radially and angularly of the fiber body (110)
Helical phase is excited, orbital angular momentum light beam is generated.
2. polarization independent type orbital angular momentum modulator (100) according to claim 1, which is characterized in that the optical fiber
Main body (110) is dual mode optical fiber or four mode fibers.
3. polarization independent type orbital angular momentum modulator (100) according to claim 1, which is characterized in that the optical fiber
Main body (110) axially has the spiral refractive index modulation in period and uniform depth, the model of the spiral refractive index modulated quantity
It encloses for 2 X 10-4To 2 X 10-3。
4. polarization independent type orbital angular momentum modulator (100) according to claim 1, which is characterized in that the optical fiber
Main body (110) includes fiber core and covering.
5. polarization independent type orbital angular momentum modulator (100) according to claim 1, which is characterized in that the optical fiber
The spiral refractive index modulation in main body (110) any section has asymmetry, radial along the fiber body (110), institute
Spiral refractive index modulation is stated to reduce with the increase of radius.
6. polarization independent type orbital angular momentum modulator (100) according to claim 1, which is characterized in that the optical fiber
The length range of main body (110) is 1 centimetre to 6 centimetres.
7. a kind of orbital angular momentum light-beam generator (400) characterized by comprising
Light source (410)；
Polarization Controller (420), input terminal are connect with the light source (410)；
Polarization independent type orbital angular momentum modulator (100) is connect with the Polarization Controller (420) output end；And
First optical patchcord (430), with the polarization independent type orbital angular momentum modulator (100) far from the Polarization Controller
(420) one end connection；
Wherein, the polarization independent type orbital angular momentum modulator (100) includes:
Fiber body (110), has Helical Fiber structure, and the Helical Fiber structure has long-period fiber grating effect；
The fiber body (110) axially has periodic spiral refractive index modulation, the spiral refractive index modulation period position
In hundred micron dimensions, the spiral Refractive index modulation distribution is used in the axial direction, radially and angularly of the fiber body (110)
Helical phase is excited, orbital angular momentum light beam is generated.
8. orbital angular momentum light-beam generator (400) according to claim 7, which is characterized in that further include:
Second optical patchcord (440), Polarization Controller (420) input terminal pass through second optical patchcord (440) and institute
State light source (410) connection.
9. orbital angular momentum light-beam generator (400) according to claim 7, which is characterized in that further include:
Single mode optical fiber (450), the polarization independent type orbital angular momentum modulator (100) by the single mode optical fiber (450) with
Polarization Controller (420) the output end connection.
10. orbital angular momentum light-beam generator (400) according to claim 7, which is characterized in that further include:
Less fundamental mode optical fibre (460), first optical patchcord (430) pass through the less fundamental mode optical fibre (460) and polarization independent type track
Angular momentum modulator (100) connection.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109407353A (en) * | 2018-11-28 | 2019-03-01 | 深圳大学 | Polarization independent type orbital angular momentum modulator and preparation method thereof |
| CN111323903A (en) * | 2020-02-17 | 2020-06-23 | 南京师范大学 | Optical fiber orbital angular momentum mode separation method based on spiral structure |
| CN112305673A (en) * | 2020-08-07 | 2021-02-02 | 上海大学 | All-fiber mode conversion device and method and detection device |
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2018
- 2018-11-28 CN CN201821991762.2U patent/CN209132535U/en active Active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109407353A (en) * | 2018-11-28 | 2019-03-01 | 深圳大学 | Polarization independent type orbital angular momentum modulator and preparation method thereof |
| CN109407353B (en) * | 2018-11-28 | 2024-05-14 | 深圳大学 | Polarization independent orbital angular momentum modulator and preparation method thereof |
| CN111323903A (en) * | 2020-02-17 | 2020-06-23 | 南京师范大学 | Optical fiber orbital angular momentum mode separation method based on spiral structure |
| CN111323903B (en) * | 2020-02-17 | 2021-09-28 | 南京师范大学 | Optical fiber orbital angular momentum mode separation method based on spiral structure |
| CN112305673A (en) * | 2020-08-07 | 2021-02-02 | 上海大学 | All-fiber mode conversion device and method and detection device |
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