CN110231088B - OAM light beam gravity center displacement measuring device and method based on quantum weak measurement - Google Patents
OAM light beam gravity center displacement measuring device and method based on quantum weak measurement Download PDFInfo
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Abstract
The invention discloses a device and a method for measuring orbital angular momentum light beam gravity center displacement based on quantum weak measurement. The amplification effect of quantum weak measurement is utilized, so that the gravity center displacement of the OAM light beam can be directly measured by using a common photoelectric detector, such as a common CCD; the measuring device has simple structure and low cost, and the measuring method is simple and easy to operate; meanwhile, the method is suitable for measuring the vortex rotation with different orders and researching the influence of different incidence angles on the gravity center displacement of the OAM light beam; is expected to obtain important application value in a plurality of technical fields of biomedicine, life science, analytical chemistry, physics, materials science and the like.
Description
Technical Field
The invention relates to the field of optical instruments, in particular to an OAM light beam gravity center displacement measuring device and method based on quantum weak measurement.
Background
The displacement of the center of gravity of an Orbital Angular Momentum (OAM) beam refers to a phenomenon caused by the optical orbital Hall effect. The orbital Hall effect refers to the phenomenon that when a light beam carrying internal orbital angular momentum (such as vortex rotation) is reflected or transmitted through an interface, the gravity center of the light beam is displaced, and the motion of the gravity center of the light beam is related to the orbital-orbital interaction. The research on the tiny displacement of the gravity center of the OAM light beam is helpful for comprehension of the spin and orbital Hall effect of photons, the understanding of the vortex light displacement characteristic can be deepened, and the potential application value of the vortex light displacement characteristic is excavated.
The displacement of the center of gravity of the OAM light beam is extremely small, in the prior art, a very precise and complex optical instrument is required for measuring the displacement, effective and fine displacement measurement cannot be realized through a simple instrument, a related measurement method is complex, the cost of the instrument and time is increased, the operability of research is limited, and the research on the Hall effect of the optical track is not facilitated.
Disclosure of Invention
In order to solve the technical problems, the invention provides an OAM light beam gravity center displacement measuring device and method based on quantum weak measurement, effective OAM light beam gravity center displacement measurement is realized through a simple and common measuring instrument combination, the corresponding weak measurement method can effectively amplify displacement values, and is beneficial to directly using common photoelectric detectors for measurement, such as CCD, position sensors and the like, the measured values can be accurate to hundreds of microns, and fine, convenient and quick measurement is realized.
The technical scheme adopted by the invention is that an OAM light beam gravity center displacement measuring device based on quantum weak measurement comprises: a light emitting device for emitting a light beam to generate a common light beam; an OAM optical beam generator for receiving the optical beam and converting it into an OAM optical beam; the polarization state preparation device is used for receiving the OAM light beam and converting the OAM light beam into linearly polarized light; the displacement generating device is used for receiving the linearly polarized light and reflecting the linearly polarized light, the reflected polarized light has a first polarization state, the polarized light before reflection has an incident polarization state, and the incident polarization state is different from the first polarization state.
The polarization state selector receives the polarized light reflected by the displacement generating device and is provided with a second polarization state, the second polarization state and the first polarization state form a quantum weak measurement light path, and an included angle between the second polarization state and the first polarization state is 90 +/-delta and is less than or equal to 5 degrees; and the photoelectric detector is used for receiving and/or recording the polarized light acted by the polarization state selector.
The light beam emitted by the light-emitting device is changed into vortex rotation carrying orbital angular momentum through the OAM light beam generator and then changed into linear polarization through the polarization state preparation device. Linearly polarized light is reflected by an air-displacement generating device interface, and the reflected polarized light is received by a photoelectric detector after passing through a polarization state selector; a quantum weak measurement light path part is formed between the polarization state of the light beam reflected by the displacement generating device and the polarization state set by the polarization state selector, and the two polarization states are close to be orthogonal, so that a light intensity signal received by the light detector is minimum, and the position change is more visual.
The process of OAM light beam generation, gravity center displacement and gravity center displacement measurement is realized by a small amount of simple instruments, the first polarization state and the second polarization state which are nearly orthogonal form a quantum weak measurement light path, so that the amplification effect in quantum weak measurement is effectively utilized, the light beam passing through the polarization state selector is recorded by a common photoelectric detector, and a very precise instrument is not needed.
The light-emitting device comprises a light source generator, a beam expander arranged on an emergent light path of the light source generator and a light beam direction changing device for changing the direction of light rays; the light source generator is used for emitting light beams; the beam expander is used for expanding the diameter of the parallel input light beam to a larger parallel output light beam, and is beneficial to processing and detecting the light beam; the beam redirector is used to redirect the expanded diameter parallel output beam to facilitate the beam reaching the next component.
Preferably, the light source generator is a laser, a laser diode, a super-radiation light emitting diode, a white light generator or a quantum light source generator, and has strong operability and low cost;
preferably, the beam-redirecting device is a mirror or prism for reflecting the beam, facilitating the beam steering to the OAM beam generator.
The OAM light beam generator is a spatial light modulator or a vortex phase plate, converts a common light beam into a light beam with orbital angular momentum, and provides measurement conditions for a measurement device.
The polarization state preparation device comprises a lens group consisting of more than one lens, a beam energy regulator, a diaphragm and a first polarizer; the lens group is used for imaging, amplifying the light beam and filtering astigmatism;
preferably, the lens group consists of three lenses, including a first lens, a second lens and a third lens; the OAM light beam sequentially passes through the first lens, the light beam energy regulator, the diaphragm, the second lens and the third lens to reach the first polarizer. The first lens is used for being matched with the diaphragm to filter stray light, the beam energy regulator is used for regulating beam energy, the second lens is used for amplifying a beam, and the third lens is used for imaging and imaging a light spot at the reflection point of the displacement generating device on the photoelectric detector. Stray light of the OAM light beam is removed after the OAM light beam passes through the polarization state preparation device, the light beam energy is adjusted through the light beam energy regulator in the preparation device, light beams which are easy to detect and observe are provided, the beneficial effects of light beam amplification and imaging are achieved through the combination of a plurality of lenses, and recording and visual image forming on the photoelectric detector are facilitated. The first polarizer converts the OAM light beam into linearly polarized light, so that the polarization state entering the displacement generating device is purer and single, and subsequent measurement and calculation are facilitated.
Preferably, the beam energy adjuster is a half glass or neutral attenuator. The half wave plate realizes the adjustment of light energy by adjusting the included angle between the direction of the optical axis and the polarization direction of incident light; it is helpful to adjust the light intensity, so as to obtain better imaging.
Preferably, the first polarizer is a glan laser polarizing prism or a polarization beam splitter, and converts the original OAM beam into a linearly polarized light whose vibration direction is determined by the polarization direction of the polarizer.
The displacement generating device is a prism, and the prism has a refractive index n which is greater than the refractive index n of air0The precondition of center of gravity displacement of the OAM light beam is provided, and in addition, the refractive index n can be obtained through data calculation in the light path generation process; the prism may be a triangular prism, a quadrangular prism, a pentagonal prism, or the like.
Preferably, the air-displacement generating device interface of the displacement generating device should be capable of providing a graded index of refraction that provides the external condition for the Hall effect of the optical track.
The polarization state selector comprises a phase compensator and a second polarizer; the phase compensator is used for converting the linearly polarized light reflected by the displacement generating device into elliptically polarized light or circularly polarized light, is favorable for forming the linearly polarized light by combining the polarization state in the second polarizer, then transmits the linearly polarized light to the photoelectric detector and is favorable for the photoelectric detector to record the analysis and calculation of images; the second polarizer is provided with a second polarization state, the second polarization state is approximately orthogonal to the first polarization state, the included angle between the second polarization state and the first polarization state is 90 degrees +/-delta, and delta is less than or equal to 5 degrees, a quantum weak measurement light path is formed, and the amplification effect of a measured light beam is facilitated.
Preferably, the phase compensator is a quarter wave plate;
preferably, the second polarizer is a glan laser polarizer or a polarizing beam splitter.
The photoelectric detector is a charge coupled element or a position sensor or a photomultiplier, is used for receiving and recording a polarized light spot image acted by the polarization state selector, and is favorable for further calculating and analyzing the gravity center displacement of the OAM light beam.
An OAM light beam gravity center displacement measurement method based on quantum weak measurement comprises the following steps:
s1, the light-emitting device emits a light beam to the OAM light beam generator, the OAM light beam generator receives the light beam and converts the light beam into an OAM light beam, and then the OAM light beam is emitted to the polarization state preparation device; the OAM light beam is converted into linearly polarized light through a polarization state preparation device to reach a displacement generation device;
s2, the displacement generating device receives the linearly polarized light and reflects the linearly polarized light to the polarization state selector through the displacement generating device-air interface, and the reflected linearly polarized light reaches the photoelectric detector after passing through the polarization state selector;
s3, adjusting the light path generated by the OAM light beam gravity center displacement measuring device in the above steps, so that the light beam polarization state reflected by the displacement generating device and the polarization state set by the polarization state selector form a quantum weak measurement light path part,the angle between the two polarization states is 90 DEG + -Delta, Delta is not more than 5 DEG, and the first polarizer is at the angle
The second polarizer has an angle of
By this step, the first polarizer angle of
The second polarizer has an angle of
The gravity center displacement of the OAM light beam is amplified by 10000 times after passing through the weak measurement light path, and the angle of the first polarizer can be directly measured through a light spot pattern returned by the photoelectric detector
The second polarizer has an angle of
And calculating or simply measuring the center of gravity displacement of the OAM light beam.
S4, fixing the incident angle theta of the displacement generator to a value of 0-90 deg. and fixing the angle of the second polarizer to
And adjusting the first polarizer to an angle of
Obtaining a plurality of by adjusting the angle of the first polarizer a plurality of times
And recording and storing each by a photodetector
The corresponding spot pattern. On the basis of the steps, on the premise that the first polarization state and the second polarization state are approximately orthogonal, the gravity center displacement of the OAM light beam under a plurality of incidence angles is continuously measured; since the change of the incident angle can cause the change of the first polarization state, the accuracy of the measurement of the gravity center displacement of the OAM light beam can be verified by studying the displacement conditions in the plurality of first polarization states on the basis of the above steps, that is, the step includes a verification step. In the step, the gravity center displacement conditions of the OAM light beams in the first polarization states are obtained, and the accuracy of the measuring device is verified through comparison of a plurality of experimental gravity center displacements and a plurality of corresponding theoretical gravity center displacements. In addition, the gravity center displacement of the OAM light beam under a plurality of incidence angles is obtained through the angles of the first polarizers, and the influence of the incidence angles on the gravity center displacement of the OAM light beam is favorably researched. Furthermore, on the basis of the steps, the order of the OAM light beam can be adjusted, so that the OAM light beam gravity center displacement speckle pattern under multiple orders and multiple incidence angles can be obtained. According to the deviation values corresponding to the plurality of light spot patterns, corresponding conditions of experimental gravity center displacement and theoretical gravity center displacement can be obtained, so that corresponding experimental curves and theoretical curves are obtained for comparison, whether the experimental gravity center displacement is close to the theoretical gravity center displacement or not is verified, and the accuracy of the measurement result is verified.
S5, processing a series of spot patterns obtained in the S4 step; to be provided with
The center of gravity of the light spot of the corresponding light spot graph is a zero point,
and the deviation value of the light spot gravity center of the corresponding light spot pattern in the X direction is recorded as X, and the deviation value in the Y direction is recorded as Y, so that the verification of the measurement process of the gravity center displacement of the OAM light beam is realized.
After the polarized light reflected by the displacement generating device in the step S2 reaches the polarization state selector, the polarized light sequentially passes through the phase compensator and the second polarizer, the phase compensator converts the linearly polarized light into circularly polarized light or elliptically polarized light, and the second polarizer is provided with a second polarization state.
Preferably, the phase compensator is a quarter wave plate.
Preferably, the first polarizer and the second polarizer are a glan laser polarizing prism or a polarizing beam splitter.
Preferably, the photodetector is a charge coupled device or a position sensor or a photomultiplier tube, and is used for receiving and recording the polarized light acted by the polarization state selector, so as to provide an image for calculation and analysis.
Compared with the prior art, the invention has the beneficial effects that:
1. the gravity center displacement of the OAM light beam can be directly measured by using the quantum weak measurement amplification effect;
2. the measuring device has simple structure;
3. the precision of the measuring device is up to hundreds of microns;
4. the measuring method is simple and easy to operate;
5. the method is suitable for measuring the influence of vortex rotation with different orders and different incidence angles on the gravity center displacement of the OAM light beam;
6. has strong inhibiting effect on environmental noise and technical noise.
Drawings
Fig. 1 is a structural diagram of an OAM light beam center of gravity displacement measuring apparatus based on quantum weak measurement;
fig. 2 is a comparison graph of a 1, 3 and 5-order OAM beam measurement speckle pattern and a theoretical simulation graph;
fig. 3 is an experimental and theoretical comparison diagram of an offset value X in the X direction and an offset value Y in the Y direction of the OAM beam center of gravity displacement.
In fig. 1: 1. the device comprises a light-emitting device, 2, an OAM light beam generator, 3, a polarization state preparation device, 4, a prism, 5, a polarization state selector, 6, a photoelectric detector, 7, a light source, 8, a beam expander, 9, a reflecting mirror, 10, a lens, 11, an energy adjuster, 12, a diaphragm, 13, a lens, 14, a lens, 15, a polarizer, 16, a phase compensator, 17 and a polarizer.
Detailed Description
The drawings are only for purposes of illustration and are not to be construed as limiting the invention. For a better understanding of the following embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Example 1
As shown in fig. 1, an OAM light beam center of gravity displacement measuring apparatus based on quantum weak measurement includes: a light emitting device 1 for emitting a light beam to generate a general light beam; an OAM optical beam generator 2 for receiving the optical beam and converting it into an OAM optical beam; the polarization state preparation device 3 is used for receiving the OAM light beam and converting the OAM light beam into linearly polarized light; the displacement generating device is a triangular prism 4 and is used for receiving the linearly polarized light and reflecting the linearly polarized light, and the reflected polarized light has a first polarization state; the polarization state selector 5 is used for receiving the polarized light reflected by the prism and is provided with a second polarization state, the second polarization state and the first polarization state form a quantum weak measurement light path, the included angle between the second polarization state and the first polarization state is 90 degrees +/-delta, and delta is less than or equal to 5 degrees; and the photoelectric detector is used for receiving and/or recording the polarized light acted by the polarization state selector.
The light beam emitted by the light emitting device 1 is converted into a vortex optical rotation carrying orbital angular momentum by the OAM light beam generator 2, and then is converted into a linear polarization by the polarization state preparation device 3. Linearly polarized light or circularly polarized light is reflected by an air-prism 4 interface, and the reflected polarized light is received by a photoelectric detector 6 after passing through a polarization state selector 5; a quantum weak measurement light path part is formed between the polarization state of the light beam reflected by the prism 4 and the polarization state set by the polarization state selector 5, and the two polarization states are close to each other, so that a light intensity signal received by the photoelectric detector 6 is minimum, and the position change is more visual.
The light-emitting device comprises a light source generator 7, a beam expander 8 arranged on an emergent light path of the light source generator 7 and a light beam direction changing device 9 for changing the direction of light rays, wherein the light beam phase changing device 9 is a reflector; the light source generator 7 is used for emitting a common light beam to the beam expander 8, and the beam expander 8 expands the diameter of the input light beam to the light beam direction changing device 9 for changing the direction of the light beam, which is helpful for the light beam to reach the OAM light beam generator 2.
The light source generator used in this embodiment is a he-ne laser, the beam direction changing device is a reflector, and the OAM beam generator is a spatial light modulator.
The polarization state preparation device 3 comprises a first lens 10, a second lens 13, a third lens 14, a beam energy regulator 11, a diaphragm 12 and a first polarizer 15; the OAM light beam generator receives the common light beam and emits an OAM light beam to the polarization state preparation device 3, and the OAM light beam sequentially passes through the first lens 10, the light beam energy regulator 11, the diaphragm 12, the second lens 13 and the third lens 14 to reach the first polarizer 15. The first lens 10 is matched with the diaphragm 12 to filter stray light of the OAM light beam, the light beam energy regulator 13 regulates energy of the light beam, the second lens 13 amplifies the light beam passing through the diaphragm, and the third lens 14 images the light beam passing through the second lens 13 to form a light spot and reflects the light spot to the photoelectric detector 6 through the prism 4 to realize image recording of the photoelectric detector 6. The OAM beam is also converted into linearly polarized light by the first polarizer 15 before it reaches the prism 4.
The beam energy adjuster used in this embodiment is a half glass slide, and the first polarizer is a glan laser polarizing prism.
The prism 4 receives linearly polarized light emitted by the first polarizer 15 and reflects the polarized light through a prism-air interface, and the reflected polarized light reaches the polarization state selector 5.
The prism 4 in this embodiment is a prism having a refractive index n larger than that of air, and has a triangular shape0。
The polarization state selector 5 comprises a phase compensator 16, a second polarizer 17; the phase compensator 16 receives the linearly polarized light reflected by the prism 4, converts the linearly polarized light reflected by the prism 4 into elliptically polarized light or circularly polarized light, combines the elliptically polarized light or the circularly polarized light with a second polarization state set by the second polarizer 17 to form linearly polarized light, and projects the linearly polarized light to the photoelectric detector 6; and the second polarization state is approximately orthogonal to the first polarization state, the included angle between the second polarization state and the first polarization state is 90 +/-delta, and delta is less than or equal to 5 degrees, so that a quantum weak measurement light path is formed, and the amplification effect of the measured light beam is facilitated.
The phase compensator used in this embodiment is a quarter-wave plate and the second polarizer is a glan laser polarizer.
The photodetector 6 receives the polarized light acted on by the second polarizer 17 and records the pattern of spots formed by said polarized light.
The photodetector 6 in this embodiment is a charge coupled device CCD.
The specific implementation principle is as follows: the he-ne laser 7 emits laser, and after the laser passes through the beam expander 8 and the reflector 9, light spots are distributed on the modulation element of the whole spatial light modulator 2, so that high-quality vortex optical rotation is generated. After passing through the first lens 10, the vortex light has its focus on the stop 12, which removes stray light and then adjusts the appropriate light intensity through one half of the glass slide 11. The displacement of the center of gravity of the light beam at the reflection point of the prism 4 is then imaged by the second lens 13 and the third lens 14 at the CCD6, and the image is recorded by the CCD 6. The light beam is transformed into linearly polarized light when passing through the first polarizer 15, which is reflected at the air-prism interface, the polarization state of the reflected linearly polarized light being the pre-selected state psi for the weak measurementiDue to the effect of a gradient index of refraction, the light beam here experiences the optical orbital hall effect and the center of gravity of the OAM light beam is slightly shifted (as an observable value)
). The reflected linearly polarized light becomes circularly polarized light after passing through the phase compensator 16. The second polarizer 17 is set to have a polarization state (post-selection state ψ f as a weak measurement) such that the polarization state of the light beam reflected from the prism and the polarization state set by the polarizer constitute a quantum weak measurement optical path portion, and the angle between the two polarization states is 90 ° ± Δ, and Δ is not more than 5 °. Then the final weak value Aw(i.e., directly observable displacement values) can be represented by equation (i):
when the included angle between the two polarization states is 90 +/-delta and delta is not more than 5 degrees, namely the front and back selection states are nearly orthogonal, an infinitely amplified displacement value can be obtained, and the actual amplification factor is about 10000 times. According to the above theory, it is easy to calculate and obtain the gravity center displacement value of the OAM beam.
Example 2
As shown in fig. 1, a method for measuring OAM light beam center of gravity displacement based on quantum weak measurement includes:
s1, converting the OAM light beam into a common light beam by a spatial light modulator, wherein the OAM light beam is l-order eddy optical rotation, reaches the first polarizer 15 through the first lens 10, the light beam energy adjuster 11, the diaphragm 12, the second lens 13 and the third lens 14, and is converted into linearly polarized light by the first polarizer 15, and at the moment, the angle of the first polarizer 15 is equal to that of the linearly polarized light
S2, the prism 4 receives the linearly polarized light and reflects the polarized light to the second polarizer 17 at the prism-air interface, the incident angle of the linearly polarized light-prism is theta, the reflected polarized light has a first polarization state, the reflected polarized light reaches the second polarizer through the phase compensator 16, the phase compensator is a quarter glass sheet, the angle is 45 degrees, the light beam reaches the second polarizer 17 after passing through the phase polarizer, and the angle of the second polarizer is theta
The second polarization state set by the second polarizer 17 acts on the elliptically polarized light or the circularly polarized light, converts the elliptically polarized light or the circularly polarized light into linearly polarized light and transmits the linearly polarized light to the photoelectric detector 6; when the second polarizer angle is
The second polarizer is set with a second polarization state, a quantum weak measurement light path is formed by the second polarization state and the first polarization state, and an included angle between the second polarization state and the first polarization state is 90 +/-delta, and delta is less than or equal to 5 degrees;
s3, based on the above steps, the spatial light modulator is fixed by generating one 1 st order vortex light to be incidentThe prism incident angle theta is 45 deg., and then the second polarizer angle is fixed
And adjusting the first polarizer
In the range 161 deg. -165 deg. (in which case an angle of 90 deg. + -. DELTA., DELTA. not more than 5 deg. between the two polarization states has been satisfied). The corresponding spot pattern at this time is recorded at regular intervals of degrees within the range. Furthermore, on the basis of the above steps, the order l can be adjusted to 3 and 5, and the difference of the order is recorded
The corresponding spot pattern. Thereby recording a plurality of at each order
And acquiring the gravity center offset condition of the OAM light beam under different orders and different angles by corresponding light spot patterns.
As shown in FIG. 2, the first row and the second row respectively correspond to the first row and the second row respectively representing the vortex rotation order of 1
The following theory and experiment barycenter comparison graph; the third line and the fourth line respectively correspond to the third line and the fourth line respectively and represent the vortex rotation order of 3
The following theory and experiment barycenter comparison graph; the fourth line and the fifth line respectively represent the vortex rotation order of 5
The following theory and experiment barycenter comparison graph; and analyzing and calculating the light spot pattern after obtaining the light spot pattern.
(1) The gravity center displacement of the experimental images recorded under various conditions is calculated and obtained, taking the spot pattern with the image name of 'image 4' as an example,
the corresponding MATLAB calculation program is as follows:
clear；
n＝4；
fileName＝strcat(′image_′，num2str(n)，′.jpg′)；
[Ff]＝imread(fileName)；
Ff＝double(Ff)；
F0＝squeeze(Ff(：，：，1)+Ff(：，：，2)+Ff(：，：，3))；
X＝-640：639；
Y＝-512：511；
[x，y]＝meshgrid(X，Y)；
F1＝F0；
F_thrh＝15；
F1(F1＜F_thrh)＝0；
F＝F1；
AveX＝sum(sum(x.*F))/sum(sum(F))；
AveY＝sum(sum(y.*F))/sum(sum(F))；
figure；pcolor(x，y，F)；shading flat；hold on；
plot(AveX，AveY，′r+′)；
above AveX is the offset value X of the center of gravity in the X-direction, and AveY is the offset value Y of the center of gravity in the Y-direction.
(2) And calculating and obtaining the theoretical light spot gravity center displacement condition under each condition. In order of 1 (corresponding to 1 for m in the program), the angle of incidence θ is 45,
for example, the corresponding Matlab calculation program is as follows:
clear all；
lambda＝0.6328；k0＝2*pi/lambda；
mu1＝1；mu_o＝1；mu_e＝1；
eps1＝1；eps_o＝1.515^2；eps_e＝eps_o；
m＝1；
w0＝lambda*120；
th0＝45；
ph1＝162.66；
ph2＝45；
Xi＝-2*ph2/180*pi；
a＝cos(ph1./180*pi)；
b＝sin(ph1./180*pi)；
th1＝th0/180*pi；
n1＝sqrt(eps1*mu1)；k1＝k0*n1；
[rs，rp，drs，drp]＝cal_rf_fc(eps1，eps_o，eps_e，mul，mu_o，mu_e，k0，th1)；
kw＝(k1.*w0).^2；
g＝-1；
M＝(rp-g.*rs).*cot(th1)；
N＝(rs-g.*rp).*cot(th1)；
NN＝600；
kw＝(k1.*w0).^2；
kkx＝linspace(-300/w0./k1，300/w0./k1，NN)；
[kx，ky]＝meshgrid(kkx*k1，kkx*k1)；
A＝(w0/sqrt(2))^(abs(m)+1)/sqrt(pi*factorial(abs(m)))；
u0＝A*exp(-(kx.^2+ky.^2).*w0.^2./4).*(-li.*kx+sign(m).*ky).^(abs(m))；
u＝(a.*(rp+g.*kx./k1.*drp)+b.*ky./k1.*M).*u0 -li*exp(li*Xi).*(b.*(rs+
g.*kx./k1.*drs)-a.*ky./k1.*N).*u0；
xx＝(-NN/2：NN/2-1)/NN/(kx(2，2)-kx(2，1))*2*pi；
[x，y]＝meshgrid(xx，xx)；
E＝ifftshift(ifit2(u))；
I＝abs(E).^2；
AveX＝sum(sum(x.*I))/sum(sum(I))；
AveY＝sum(sum(y.*I))/sum(sum(I))；
figure；pcolor(x，y，I)；shading fiat；hold on；
plot(AveX，AveY，′b+′)；
above AveX is the offset value X of the center of gravity in the X-direction, and AveY is the offset value Y of the center of gravity in the Y-direction.
As shown in fig. 2, a theoretical diagram of behaviors 1, 3 and 5 and an experimental diagram of behaviors 2, 4 and 6. The "+" mark is the center of gravity position. The graph comparing the curves of the offset value X of the gravity center of the theoretical and experimental light spots in the X direction and the offset value Y in the Y direction is shown in fig. 3, and it can be known from the graph that the gravity center displacement of the experimental OAM light beam is compared with the theory and accords with the related intrinsic rule.
The accuracy of the measuring device is verified through comparison of experiments and theoretical OAM gravity center displacement under multiple orders and multiple angles, as shown in fig. 3, the difference between an experimental graph curve and a theoretical graph curve is small, and the device has high accuracy.
The theoretical and experimental spot diagrams at 162.66-162.98 degrees are analyzed after being calculated, and as shown in fig. 3, experiments show that when l is 5, the displacement of the gravity center of the OAM light beam in the x direction is about 50 microns, and the displacement in the y direction is about 100 microns, so that the device effectively measures the displacement of the gravity center of the OAM light beam.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention claims should be included in the protection scope of the present invention claims.
Claims (8)
1. An orbital angular momentum light beam center of gravity displacement measuring device based on quantum weak measurement, comprising:
a light emitting device for emitting a light beam;
an orbital angular momentum beam generator for receiving the light beam and converting it into an orbital angular momentum beam;
the polarization state preparation device is used for receiving the orbital angular momentum light beam and converting the orbital angular momentum light beam into linearly polarized light; the polarization state maker comprises a first polarizer;
the displacement generating device is used for receiving the linearly polarized light and reflecting the linearly polarized light, and the reflected polarized light has a first polarization state;
the polarization state selector is provided with a second polarization state; the polarization state selector comprises a second polarizer; the polarization state selector is used for receiving the polarized light reflected by the displacement generating device, the second polarization state and the first polarization state form a quantum weak measurement optical path, the included angle between the second polarization state and the first polarization state is 90 degrees +/-Delta, and the Delta is less than or equal to 5 degrees;
and the photoelectric detector is used for receiving and/or recording the polarized light acted by the polarization state selector.
2. The apparatus for measuring the displacement of the center of gravity of an orbital angular momentum beam based on quantum weak measurement as claimed in claim 1, wherein the polarization state preparation device further comprises a lens group consisting of more than one lens, a beam energy regulator, and a diaphragm, wherein the beam energy regulator is a half glass slide; the first polarizer is a Glan laser polarizing prism or a polarizing beam splitter.
3. The apparatus for measuring the displacement of the center of gravity of an orbital angular momentum beam based on quantum weak measurement as claimed in claim 1, wherein the polarization state selector further comprises a phase compensator, the phase compensator is a quarter wave plate; the second polarizer is a Glan laser polarizer or a polarizing beam splitter.
4. The device for measuring the orbital angular momentum beam gravity center displacement based on the quantum weak measurement as claimed in claim 1, wherein the light emitting device comprises a light source generator, a beam expander arranged on an emergent light path of the light source generator and a beam direction changing device for changing the direction of a light beam; the light source generator is a laser, a super-radiation light emitting diode, a white light generator or a quantum light source generator; the beam direction changing device is a reflector or a prism and is used for changing the direction of the beam.
5. The device for measuring the orbital angular momentum beam gravity center displacement based on quantum weak measurement as claimed in claim 1, wherein the photodetector is a charge coupled device or a position sensor or a photomultiplier tube.
6. The device for measuring the displacement of the center of gravity of an orbital angular momentum beam based on quantum weak measurement as claimed in claim 1, wherein the displacement generator is a prism, the prism has a refractive index n, and the refractive index n is greater than the refractive index n of air0。
7. A method for measuring the displacement of the center of gravity of an orbital angular momentum beam based on quantum weak measurement, which is implemented by the device of any one of claims 1 to 6, and which comprises:
s1, the light emitting device emits light beams to the orbital angular momentum light beam generator, the orbital angular momentum light beam generator receives the light beams and converts the light beams into orbital angular momentum light beams, and then the orbital angular momentum light beams are emitted to the polarization state preparation device; the orbital angular momentum light beam is converted into linearly polarized light through a polarization state preparation device and reaches a displacement generation device;
s2, the displacement generating device receives the linearly polarized light and reflects the linearly polarized light to the polarization state selector through the displacement generating device-air interface, and the reflected linearly polarized light reaches the photoelectric detector after passing through the polarization state selector;
s3, adjusting the light path generated by the orbital angular momentum light beam gravity center displacement measuring device in the above steps, so that the light beam polarization state reflected by the displacement generating device and the polarization state set by the polarization state selector form a quantum weak measurement light path part, the included angle between the two polarization states is 90 degrees +/-Delta, the Delta is not more than 5 degrees, and the first polarizer is positioned at the angle
The second polarizer has an angle of
S4, returning a light spot pattern by the photoelectric detector, analyzing and calculating the light spot pattern to obtain a first polarizer with an angle of
The second polarizer has an angle of
The displacement value of the center of gravity of the orbital angular momentum light beam.
8. The method for measuring the displacement of the center of gravity of an orbital angular momentum beam based on quantum infinitesimal measurement as claimed in claim 7, wherein the incident angle θ of the displacement generator is fixed to a value of 0 to 90 ° and then the angle of the second polarizer is fixed to a value of 0 to 90 ° based on the step of S4
And adjusting the first polarizer to an angle of
Obtaining a plurality of by adjusting the angle of the first polarizer a plurality of times
And recording and storing each by a photodetector
Obtaining a series of light spot patterns according to the corresponding light spot patterns; processing a series of patterns of spots to
The center of gravity of the light spot of the corresponding light spot graph is a zero point,
and (3) marking the deviation value of the light spot gravity center of the corresponding light spot pattern in the X direction as X and the deviation value in the Y direction as Y, and further verifying the measurement process of the gravity center displacement of the orbital angular momentum light beam.
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