Method and device for measuring solution parameters based on optical spin hall effect rotation

Abstract

The application discloses a solution parameter measurement method and device based on optical spin Hall effect rotation, and through specific setting conditions, optical spin splitting will greatly rotate with slight change of incident polarization, so that the incident polarization change can be greatly amplified. Considering that the polarization change depends on the solution concentration and chirality, the rotation of the spin splitting can also greatly amplify the change of the solution concentration and chirality, so that the application can measure the rotation direction of the optical spin splitting, so as to obtain accurate solution parameters including the solution concentration and the chirality based on a device with low cost and simple structure. The application has the advantages of simple structure, economical cost and high measurement precision.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a method and apparatus for measuring solution parameters based on the optical spin Hall effect. Background Technology

[0002] Solution concentration and chirality are important properties of matter. Chirality reflects the molecular structure of a substance and determines its physical and chemical properties. The measurement of solution concentration and chirality has wide and important applications in materials science, chemical engineering, biology, medicine, and other fields.

[0003] Conventional optical methods for measuring solution concentration and chirality generally rely on the optical rotation of chiral solutions. This means that the solution concentration is proportional to the rotation angle of the polarization plane of linearly polarized light after passing through the solution, and the sign of chirality is determined by the direction of rotation. However, the accuracy of conventional angle measuring instruments is less than 0.01°, resulting in low precision in measuring solution concentration and chirality.

[0004] In recent years, new sensing methods have been proposed to measure solution concentration and chirality, such as using the optical spin Hall effect, which can achieve higher precision (typically 10). -4 (g / ml). However, for solutions with even lower concentrations, there is still a lack of economical and high-precision methods for measurement. Although spectrometers can be used, the equipment is expensive. Therefore, finding a low-cost, high-precision method for measuring solution concentration and chirality remains a worthwhile research problem.

[0005] The optical spin Hall effect is a newly discovered optical phenomenon in recent years, specifically referring to the phenomenon where linearly polarized light, when propagating in a non-homogeneous medium (such as interface reflection and refraction), splits laterally into left- and right-handed circularly polarized light. The manner and magnitude of the optical spin Hall effect reflect the properties of a material, and therefore it has been applied to the measurement and characterization of materials. A common method is to measure the intensity shift caused by the optical spin splitting. However, since the intensity is measured based on the centroid of the light spot, it is prone to errors, and the intensity is easily affected by ambient light; therefore, the accuracy of this method is limited. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method and apparatus for measuring solution parameters based on the optical spin Hall effect. This invention is simple to implement, has low cost, high and adjustable accuracy, and a wide measurable concentration range.

[0007] A method for measuring solution parameters based on the optical spin Hall effect rotation includes the following steps:

[0008] Step 1 involves directing a polarized incident light beam onto a dielectric material, where it is reflected at the dielectric interface, generating an optical spin Hall effect. The polarization direction of the incident light beam at the dielectric interface forms a certain angle with the incident plane.

[0009] Step 2: Use an analyzer to change the polarization direction of the reflected beam, thereby generating two equally sized split beams that can be observed. Record the angle between the polarization direction of the analyzer and the vertical direction, where the vertical direction is perpendicular to the incident plane.

[0010] Step 3: Place the solution to be tested in the optical path of the incident beam to change the polarization direction of the incident beam. Then change the angle between the polarization direction of the analyzer and the vertical direction again until the same split spot as in step 2 is produced. Calculate the angle φ that the analyzer changed at this time compared to step 2.

[0011] Step 4, calculate the concentration parameter c of the solution according to the following formula:

[0012]

[0013] Where d is the optical path length of light through the solution, α is the optical rotation of the solution, and r p It is the reflection coefficient of the polarized portion of the incident beam along the direction of the incident plane, r s It is the reflection coefficient of the polarized portion of the incident beam in the vertical direction.

[0014] The method also includes a process for measuring the chiral parameter of the solution:

[0015] When recording the included angle φ, the chirality of the solution is determined by the sign of φ. A positive φ indicates that the analyzer rotates clockwise, and the solution is right-handed. A negative φ indicates that the analyzer rotates counterclockwise, and the solution is left-handed.

[0016] In the method described above, in step 1, the incident angle of the incident light is close to the Brewster angle, so that φ is greater than the angle of polarization direction of the incident light beam changed by the solution in step 3.

[0017] A solution parameter measurement device based on optical spin Hall effect rotation includes an incident light generating device for generating a polarized incident light beam, a dielectric, a split light spot generating device, a solution container, and a light beam detection device.

[0018] The optical spin Hall effect occurs at the interface of the dielectric.

[0019] The polarization direction of the incident light beam generated by the incident light generating device is at a certain angle to the incident surface.

[0020] The split beam generating device includes a polarizer, which is placed in the optical path of the reflected beam generated at the interface of the medium to be measured, and changes the angle between its own polarization direction and the vertical direction to change the polarization of the reflected beam, so as to generate two split beams of equal size that can be observed, wherein the vertical direction is the direction perpendicular to the incident surface.

[0021] The solution container contains the solution to be tested. After the split beam is generated into two split beams of equal size by the split beam generating device, it is placed into the optical path of the incident beam generated by the incident beam generating device, thereby changing the polarization direction of the incident beam.

[0022] The beam detection device receives and detects the split beam spot so that the analyzer can obtain the same split beam spot by adjusting the angle between its own polarization direction and the vertical direction before and after the solution container is placed, based on the detection result. This allows the analyzer to obtain the angle φ that the analyzer changes before and after the solution container is placed, thereby calculating the concentration parameter of the solution.

[0023] The aforementioned device, the incident polarized light generating device, includes a light source, and an incident lens and a polarizer arranged sequentially along the optical path of the light beam generated by the light source, wherein the polarizer is used to polarize the incident light beam in the direction of the incident surface.

[0024] The aforementioned device, the split beam generating device, includes an analyzer and a reflecting lens arranged sequentially along the optical path of the reflected beam, wherein the analyzer is used to change the polarization direction of the reflected beam in the vertical direction.

[0025] In the aforementioned device, the incident angle of the incident beam is close to the Brewster angle, thereby making φ greater than the angle by which the polarization direction of the incident beam changes due to the placement of the solution.

[0026] The device, after obtaining φ, calculates the concentration parameter c of the solution according to the following formula:

[0027]

[0028] Where d is the optical path length of light through the solution, α is the optical rotation of the solution, and r p It is the reflection coefficient of the polarized portion of the incident beam along the direction of the incident plane, r s It is the reflection coefficient of the polarized portion of the incident beam in the vertical direction.

[0029] The device, after obtaining φ, determines the chirality of the solution based on the sign of φ. A positive φ indicates that the solution is right-handed when the analyzer rotates clockwise, and a negative φ indicates that the solution is left-handed when the analyzer rotates counter-clockwise.

[0030] The technical advantages of this invention are that the solution parameter measurement method is simple and cost-effective. Utilizing the spin Hall effect of reflected light, the device is simple. The core experimental components are a pair of polarizers and analyzers, which are inexpensive. The solution concentration and chirality measurement method of this invention has high accuracy. Within the incident angle range of 50° to 60°, the spin splitting rotation angle φ generated by the optical Hall effect can amplify the change in polarization rotation angle γ caused by chiral solutions by tens of thousands of times, thereby enabling precise measurement of solution concentration and chirality. Clockwise rotation of the spin-splitting light indicates right-handed chirality, while counterclockwise rotation indicates left-handed chirality. The solution concentration and chirality measurement method of this invention can measure a wide concentration range (e.g., 10). -2 ~10 -5 The measurement accuracy is higher (g / ml) and the lower the concentration, the higher the accuracy. For low-concentration solutions, the rotation angle φ is approximately linearly related to the concentration c, thus resulting in higher measurement accuracy. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the optical path structure for measuring solution concentration and chirality based on the optical spin Hall effect, provided in an embodiment of the present invention.

[0033] Figure 2 Cross-polarized light spot diagrams of chiral solutions with different concentrations provided in embodiments of the present invention.

[0034] Figure 3 The graph shows the change of the cross-polarization rotation angle φ with solution concentration c under different concentrations and chiral solutions provided in the embodiments of the present invention.

[0035] Figure reference numerals: 1-Light source, 2-First lens, 3-Polarizer, 4-Cuvette, 5-Glass, 6-Analyzer, 7-Second lens, 8-Laser beam analyzer CCD. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Figure 1This is a schematic diagram of an experimental apparatus for measuring solution concentration and chirality based on the optical spin Hall effect, provided in an embodiment of the present invention. The apparatus includes: 1-light source, 2-first lens, 3-polarizer, 4-cuvette, 5-glass, 6-analyzer, 7-second lens, and 8-CCD laser beam analyzer. The light source is a laser with a wavelength of 589.3 nm. The first lens is a convex lens with a focal length of 50 mm. The second lens has a focal length of 200 mm. The polarizer and analyzer are Glan laser polarizers. The solution to be tested is placed in a cuvette. The dielectric is N-BK7 glass (refractive index equal to 1.515), with a smooth surface, and is placed on a rotating stage.

[0038] Example

[0039] The concentrations and chirality of solutions containing glucose, sucrose, and fructose were measured. Using... Figure 1 The experimental setup shown is described, and the specific experimental steps are as follows:

[0040] (1) Turn on the light source and adjust the polarization direction of the polarizer to polarize the incident beam horizontally. Focus the beam onto the glass surface through the first lens. Adjust the rotating stage to keep the incident angle within the range of 50° to 60°; here, 56.57° (close to Brewster's angle) is selected. The beam undergoes the optical spin Hall effect at the air-glass interface. The reflected light passes through the analyzer and the second lens and reaches the CCD of the laser beam analyzer. Adjusting the analyzer to be vertical allows observation of two vertically split beam spots.

[0041] (2) Place the glucose solution concentration and chirality into the cuvette to be tested. After the light passes through, the polarization plane rotates, causing the light beam to rotate due to the spin Hall effect when reflected at the glass interface. The reflected light passes through the analyzer and the second lens and reaches the CCD of the laser beam analyzer. Adjust the analyzer until two split light spots can be observed, and record the angle φ between the analyzer and the vertical direction at this time.

[0042] (3) Substitute the value of φ into the formula The value of solution concentration c can then be obtained, and its positive or negative sign represents the chirality of glucose.

[0043] (4) Repeat the above steps with solutions of different concentrations of sucrose and fructose, record the φ value, and substitute it into the formula: The concentration *c* and chirality of the sucrose and fructose solutions can then be obtained. It should be noted that the optical rotation of the three media can be determined using conventional optical rotation experiments, with theoretical values ​​as follows: α... 葡萄糖 =52.5° / (g / ml), α 蔗糖 =66.5° / (g / ml), α 果糖 = -91.9° / (g / ml).

[0044] like Figure 2The intensity diagrams of cross-polarized light spots for glucose and fructose solutions of different concentrations are given. It can be seen that: (1) As the solution concentration c increases, the cross-polarized light spot rotates significantly. Based on this characteristic, the change in concentration can be amplified. (2) For glucose solution, the light spot rotates clockwise, and its molecular structure is right-handed chirality. For fructose solution, the light spot rotates counterclockwise, and its molecules are left-handed chirality. Therefore, this property can be used to identify the chirality of a substance. For this invention, the sign of φ, that is, before and after the solution container is placed into the incident beam path, the analyzer is adjusted clockwise or counterclockwise to produce the same split light spot, which is consistent with the rotation direction of the corresponding split light spot. Therefore, the chirality of the solution can be determined based on the sign of φ. Where φ is positive, it means that the analyzer rotates clockwise, which reflects that the light spot rotates clockwise, and φ is negative, which means that the analyzer rotates counterclockwise, which reflects that the light spot rotates counterclockwise.

[0045] like Figure 3 The diagram shows the solution concentration range of 10. -5 ~10 -4 g / ml, 10 -4 ~10 -3 g / ml, 10 -3 ~10 -2 The curves showing the variation of the cross-polarization angle φ within g / ml are presented. The figure shows the results for three test media: glucose, sucrose, and fructose, according to the formula: The theoretical results show that the magnitude and direction of the rotation angle of the cross-polarized light differ significantly depending on the concentration and chirality of the solution. Therefore, the concentration and chirality of the solution can be determined definitively.

[0046] It is particularly worth noting that the lower the concentration, for example, 10 -5 ~10 -4 For solutions with a concentration of g / ml, the rotation angle φ changes linearly with the concentration c, thus allowing for higher precision in determining solution concentration. In other words, this experimental procedure can measure both solution concentration and chirality, with a minimum concentration of 10. -5 g / ml.

[0047] The solution parameter measurement method provided by this invention is a method for measuring solution concentration and chirality based on the spin Hall effect of light. Unlike previous methods that measure the intensity centroid of optical spin splitting, this invention measures the rotation direction of the optical spin splitting. Under specific conditions, the optical spin splitting will undergo a large rotation with a small change in incident polarization, thus greatly amplifying changes in incident polarization. Considering that polarization changes depend on solution concentration and chirality, the rotation of spin splitting can also greatly amplify changes in solution concentration and chirality. Therefore, we propose to utilize this effect to precisely measure the concentration and chirality of a solution.

[0048] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for measuring solution parameters based on the optical spin Hall effect, characterized in that, Includes the following steps: Step 1: A polarized incident light beam is directed toward a dielectric material, and a spin Hall effect is generated when the beam is reflected at the interface of the dielectric material; wherein the polarization direction of the incident light beam at the interface of the dielectric material is at a certain angle to the incident surface. Step 2: Use an analyzer to change the polarization direction of the reflected beam to generate two equally sized split beams that can be observed; record the angle between the polarization direction of the analyzer and the vertical direction at this time, where the vertical direction is the direction perpendicular to the incident surface. Step 3: Place the solution to be tested into the optical path of the incident beam to change the polarization direction of the incident beam. Then, change the angle between the polarization direction of the analyzer and the vertical direction again until the same split beam as in Step 2 is produced. Calculate the angle changed by the analyzer at this point compared to Step 2. ; Step 4, calculate the concentration parameter c of the solution according to the following formula: ； in α is the optical path length of light through the solution, and α is the optical rotation of the solution. It is the reflection coefficient of the polarized portion of the incident beam along the direction of the incident plane. It is the reflection coefficient of the polarized portion of the incident beam in the vertical direction; In step 1, the incident angle of the incident light is close to the Brewster angle, thereby... The angle greater than the change in polarization direction of the incident beam due to the introduction of the solution in step 3.

2. The method according to claim 1, characterized in that, It also includes the measurement process of solution chiral parameters: In the recording angle At that time, according to The sign of the value determines the chirality of the solution, where... A positive value means that if the analyzer is rotated clockwise, the solution is dextrorotatory. A negative value means that if the analyzer is rotated counterclockwise, the solution is left-handed chiral.

3. A solution parameter measuring device based on the optical spin Hall effect, characterized in that, The method for measuring solution parameters based on optical spin Hall effect rotation as described in claim 1 or 2 includes an incident light generating device for generating an incident light beam in a polarized state, a dielectric, a split light spot generating device, a solution container, and a light beam detection device. The optical spin Hall effect occurs at the interface of the dielectric. The polarization direction of the incident light beam generated by the incident light generating device is at a certain angle to the incident surface; The split spot generating device includes a polarizer, which is placed in the optical path of the reflected beam generated at the interface of the medium to be measured, and changes the angle between its own polarization direction and the vertical direction to change the polarization of the reflected beam, so as to generate two split spots of the same size that can be observed, wherein the vertical direction is the direction perpendicular to the incident surface. The solution container contains the solution to be tested. After the split beam is generated into two split beams of equal size by the split beam generating device, it is then placed into the optical path of the incident beam generated by the incident beam generating device, thereby changing the polarization direction of the incident beam. The beam detection device receives and detects the split beam spot, enabling the analyzer to obtain the same split beam spot by adjusting the angle between its polarization direction and the vertical direction before and after the solution container is placed, based on the detection results. This allows the analyzer to determine the angle change of the analyzer before and after the solution container is placed. This allows us to calculate the concentration parameters of the solution.

4. The apparatus according to claim 3, characterized in that, The incident light generating device includes a light source, and an incident lens and a polarizer arranged sequentially along the optical path of the light beam generated by the light source, wherein the polarizer is used to polarize the incident light beam in the direction of the incident surface.

5. The apparatus according to claim 3, characterized in that, The split beam generating device includes an analyzer and a reflecting lens arranged sequentially along the optical path of the reflected beam, wherein the analyzer is used to change the polarization direction of the reflected beam in the vertical direction.

6. The apparatus according to claim 3, characterized in that, The incident angle of the incident beam is close to the Brewster angle, thus... The angle greater than the change in polarization direction of the incident beam due to the placement of the solution container.

7. The apparatus according to claim 3, characterized in that, In obtaining Then, the concentration parameter c of the solution is calculated according to the following formula: ； in α is the optical path length of light through the solution, and α is the optical rotation of the solution. It is the reflection coefficient of the polarized portion of the incident beam along the direction of the incident plane. It is the reflection coefficient of the polarized portion of the incident beam in the vertical direction.

8. The apparatus according to claim 3, characterized in that, In obtaining Afterwards, according to The sign of the value determines the chirality of the solution, where... A positive value means that if the analyzer is rotated clockwise, the solution is dextrorotatory. A negative value means that if the analyzer is rotated counterclockwise, the solution is left-handed chiral.

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