CN108680511B - A reflection-enhanced polarimeter based on circularly polarized light - Google Patents

Abstract

A reflection enhanced polarimeter based on circularly polarized light is characterized in that a semiconductor laser emits partial polarized light, linear polarized light polarized in the Y direction is generated through a polarizing plate, the polarized light is separated into two beams of linear polarized light in the Y direction through a beam splitter, the transmission direction of a transmission beam is kept unchanged, and the direction of the reflection beam is adjusted through a total reflection mirror and is parallel to the transmission beam. The two beams of light respectively pass through a 1/4 wave plate with a fast axis forming an angle of-45 degrees and an angle of 45 degrees with the Y-axis direction to generate right-handed circularly polarized light and left-handed circularly polarized light, and after passing through a solution tank, different additional phases are respectively generated. The invention relies on the combination of wave plates to manually guide the phase change, so that the rotation angles can be accumulated when the light beam is turned back in the optical rotation solution. Meanwhile, linearly polarized light is decomposed into left-handed and right-handed circularly polarized light, the information of the rotation angle is compressed into phase information, the polarization effect of repeated reflection on light is avoided, the rotation angle can be obviously amplified, and higher-precision rotation/concentration measurement and dynamic monitoring are realized.

Description

A reflection-enhanced polarimeter based on circularly polarized light

technical field

The invention belongs to the field of optoelectronics, and in particular relates to a reflection-enhanced polarimeter based on circularly polarized light.

Background technique

In various physical experiments and chemical analysis, the concentration and specific rotation of optically active substance solutions often appear. At present, the instruments used by people are usually optical rotation tubes, which rely on manual, magneto-optical rotation effect or mechanical search methods to measure the optical rotation angle. In recent years, there have been domestically proposed instrument designs that use symmetrical polarizers to convert optical rotation angles into light intensity. However, when the solution concentration is low and the optical rotation angle is small, the accuracy of all the above methods will be affected. The root of this is that, unlike magneto-rotation, when light travels back and forth in natural optically active substances, the angles of optical rotation do not superimpose, but cancel each other out, as shown in Figure 1. However, the optical rotation tube cannot be made too long, so there is a limitation. At the same time, even through some means, the deflection angles of the beams can be superimposed when they are reflected in two groups of mirrors, but because the structure of the parallel plane cavity cannot be used (the composition of the output beams will be more complicated), if the round-trip enhancement is required, each incident It cannot be normal incidence, which will cause the p component and s component of the light wave to correspond to different reflectivities, so that the deflection angle is not only affected by the optical solution, but also affected by the polarization effect of multiple reflections, which directly interferes with the accuracy of the final reading.

And if we can find some ways to make the deflection angles (optical rotation angles) of the optical vibration vector of the light beam reflected between several groups of mirrors superimpose instead of canceling each other, we can repeatedly use the length of the optical rotation tube to improve the measurement accuracy. But there is still a problem, that is: when the light is reflected at the mirror, it will be affected by the polarization effect, and the deflection angle of the light vector cannot be affected by any other factors except the optical solution, so the structure of the parallel plane cavity must be used, so that Every reflection is normal incidence, eliminating polarization effects. But this will make the light never exit, so there must be an angle between the reflective surfaces, but this returns to the problem of "the deflection angle of the light vector cannot be affected by any other factors except the optical solution", and it is caught in a loop.

In summary, we need to make breakthroughs in two aspects: 1. How to make the reflected optical rotation angles accumulate without canceling each other; 2. How to avoid the polarization effect while using mirrors. This is also the two key issues that this patent solves.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a reflection-enhanced polarimeter based on circularly polarized light.

To achieve the above object, the present invention adopts the following technical solutions:

A reflection-enhanced polarimeter based on circularly polarized light, characterized in that it includes: a semiconductor laser, a polarizer one, a beam splitter, a total reflection mirror one, a total reflection mirror two, a total reflection mirror three, and a 1/4 wave plate One, 1/4 wave plate two, solution pool and polarizer two; the semiconductor laser emits a bunch of partially polarized light, the partially polarized light propagates along the horizontal direction, and the direction of its propagation path is the Z direction, and the partially polarized light passes through the polarizer 1. Generate a beam of linearly polarized light polarized in the Y direction. The Y direction is a direction perpendicular to the Z direction on the horizontal plane; the linearly polarized light is separated into two beams of linearly polarized light in the Y direction through a beam splitter, wherein the transmitted beam Keeping the propagation direction unchanged, the direction of the reflected beam is adjusted by total reflection mirror 1 to be parallel to the transmitted beam, and the transmitted beam is adjusted by total reflection mirror 2 and total reflection mirror 3 to make its optical path consistent with the reflected beam; the transmitted beam passes through the fast After the 1/4 wave plate 1 whose axis is -45° to the Y direction, right-handed circularly polarized light is generated, and the reflected beam passes through the 1/4 wave plate 2 whose fast axis is 45° to the Y direction, and left-handed circular polarization is generated Light; the right-handed circularly polarized light and the left-handed circularly polarized light converge on the second polarizer in the Y direction after passing through the solution area.

In order to optimize the above technical solutions, the specific measures taken also include:

The solution pool includes a double glass tube conjoined structure and a magneto-optic component arranged in sequence.

The interior of the double glass tube conjoined structure is filled with solution, including glass tube 1 and glass tube 2 arranged in parallel and connected in the middle;

The incident end and the outgoing end of the glass tube 1 are oppositely provided with a total reflection mirror 4 and a total reflection mirror 6, and the reflection surface of the total reflection mirror 4 is closely connected with a 1 whose fast axis direction is -45° with the Y axis direction. /4 wave plate seven and 1/4 wave plate eight, the reflection surface of the total reflection mirror six is closely connected with 1/4 wave plate nine and 1/4 wave plate ten whose fast axis direction is 45° with the Y axis direction, Right-handed circularly polarized light is incident from the incident end of glass tube one, and passes through 1/4 wave plate ten, total reflection mirror six, 1/4 wave plate nine, 1/4 wave plate eight, total reflection mirror four, and 1/4 After the wave plate seven, it exits from the exit end of the glass tube one;

The incident end and the outgoing end of the glass tube two are oppositely provided with a total reflection mirror five and a total reflection mirror seven, and the reflection surface of the total reflection mirror five is closely connected with a 1/2 angle that the fast axis direction is 45° with the Y axis direction. 4 wave plates five and 1/4 wave plate six, the reflection surface of the total reflection mirror seven is closely connected with 1/4 wave plate three and 1/4 wave plate four whose fast axis direction is -45° with the Y axis direction, Left-handed circularly polarized light is incident from the incident end of glass tube 2, and passes through 1/4 wave plate 3, total reflection mirror 7, 1/4 wave plate 4, 1/4 wave plate 5, total reflection mirror 5, and 1/4 wave After sheet six, it exits from the exit end of glass tube two.

The glass tube one, glass tube two, total reflection mirror four, total reflection mirror five, total reflection mirror six, total reflection mirror seven, 1/4 wave plate three, 1/4 wave plate four, 1/4 wave plate five , 1/4 wave plate 6, 1/4 wave plate 7, 1/4 wave plate 8, 1/4 wave plate 9, 1/4 wave plate 10 are all perpendicular to the light path.

The magneto-optical component includes a magneto-optical glass one and a magneto-optic glass two, the magneto-optic glass one is wound with a coil, the magneto-optic glass two is not wound with a coil, the coil current is controlled by a controllable current source, and the current source and computer connection communication;

The right-handed circularly polarized light emerges from the glass tube 1 and then passes through the magnetic optical rotation glass 2 to form an outgoing beam 1, and the left-handed circularly polarized light exits from the glass tube 2 and passes through the magnetic optical rotation glass 1 to form an outgoing beam 2. The light beam 2 naturally converges on the polarizer 2 after a certain distance.

The second polarizer is installed in the cassette, the second polarizer is lowered and raised by a mechanical structure, and a silicon photocell detector is attached to the back of the polarizer second, and the light intensity data generated by the silicon photocell detector is transmitted to a computer for further processing. deal with.

The beneficial effect of the invention is that the device relies on the combination of wave plates to artificially guide the phase change, so that the optical rotation angle can be accumulated when the light beam returns in the optical rotation solution. At the same time, the linearly polarized light is decomposed into left-handed and right-handed circularly polarized light, and the information of the optical rotation angle is compressed into the phase information, avoiding the polarization effect of multiple reflections on the light. The optical rotation angle can be significantly enlarged to achieve higher-precision optical rotation/concentration measurement and dynamic monitoring.

Description of drawings

Figure 1 is a schematic diagram of the situation where the light beam is reflected once in the optically active solution, and the two optical rotation angles generated during the incident and reflection processes cancel each other out.

Figure 2 is a schematic diagram of the design of the optical system and detection system.

Fig. 3a is a schematic diagram of the connected structure of the double glass tubes of the solution pool.

Figure 3b is a schematic diagram of the solution cell magneto-optical components.

Fig. 4 is a schematic diagram for explaining Fresnel pair optical rotation phenomenon.

Fig. 5 is a schematic diagram of the relation of the relevant coordinate system.

Fig. 6 is a schematic diagram of the relation of the relevant coordinate system.

Fig. 7 is a schematic diagram of the principle of manual guidance at the reflection end to accumulate optical rotation angles.

Fig. 8 is a schematic diagram of the effect of non-normal incidence on the polarization direction.

Fig. 9 is a schematic diagram for explaining the process.

Reference signs are as follows: semiconductor laser 1, polarizer 1 2, beam splitter 3, total reflection mirror 1 4, total reflection mirror 2 5, total reflection mirror 3 6, 1/4 wave plate 1 7, 1/4 wave plate Two 8, polarizer two 9, mechanical structure 10, cassette 11, silicon photocell detector 12, computer 13, total reflection mirror four 14, total reflection mirror five 15, total reflection mirror six 16, total reflection mirror seven 17, 1/ 4 wave plate three 18, 1/4 wave plate four 19, 1/4 wave plate five 20, 1/4 wave plate six 21, 1/4 wave plate seven 22, 1/4 wave plate eight 23, 1/4 wave Sheet nine 24, 1/4 wave plate ten 25, magneto-optical glass one 26, magneto-optical glass two 27, current source 28, glass tube one 29, glass tube two 30;

Partially polarized light L1, linearly polarized light L2, transmitted light beam L3A, reflected light beam L3B, right-handed circularly polarized light L4A, left-handed circularly polarized light L4B, outgoing light beam one L5A, outgoing light beam two L5B.

Detailed ways

The present invention is described in further detail now in conjunction with accompanying drawing.

The present invention mainly comprises the following parts:

1. Optical system and detection system part

As shown in Figure 2, a beam of partially polarized light L1 is emitted by a semiconductor laser 1, and passes through a polarizer 2 to generate a beam of linearly polarized light L2 polarized in the Y direction. This beam of light is separated into two beams of energy by a beam splitter 3 For approximately the same linearly polarized light in the Y direction, the transmission beam L3A keeps the propagation direction unchanged, and the reflected beam L3B adjusts its direction through the total reflection mirror 1 to be parallel to the transmission beam L3A. In order to keep the two beams of light in the same phase, a total reflection mirror 2 5 is used 3. The total reflection mirror 36 adjusts the optical path of the transmitted light beam L3A to make it consistent with the reflected light beam L3B.

The two beams of linearly polarized light L3A and L3B in the Y direction pass through the 1/4 wave plate 17 and 1/4 wave plate 28 whose fast axis is -45° and 45° to the Y axis, respectively, to generate right-handed circularly polarized light L4A and left-handed circularly polarized light L4B. After the two beams of light pass through the solution cell, they each generate different additional phases ΔR and ΔL. For different substances, the size relationship between ΔR and ΔL is different.

After passing through the solution area 14-30, the two outgoing beams are denoted as outgoing light beam one L5A and outgoing light beam two L5B. The outgoing beam 1 L5A and the outgoing beam 2 L5B naturally converge on the polarizer 9 in the Y direction after a certain distance. The polarizer 9 is lowered or raised by the mechanical structure 10, and the stray light of the surrounding environment is shielded by the cassette 11. The silicon photocell detector 12 is close to the back of the polarizing plate 9, and the light intensity data generated is sent to the computer 13 for processing.

Second, the solution pool part

The first part is a double glass tube conjoined structure. As shown in Figure 3a, the double glass tube conjoined structure is filled with solution, including glass tube one 29 and glass tube two 30 which are arranged in parallel and connected in the middle. Total reflection mirrors 14, 15, 16, 17, 1/4 wave plates 18, 19, 22, 23 placed in the direction of -45° between the fast axis direction and the Y axis direction, and placed in a direction of 45° between the fast axis direction and the Y axis direction 1/4 wave plate 20, 21, 24, 25.

The incident end and the outgoing end of the glass tube one 29 are oppositely provided with a total reflection mirror four 14 and a total reflection mirror six 16, and the reflection surface of the total reflection mirror four 14 is closely connected with a 1 that the fast axis direction is -45° with the Y axis direction. /4 wave plate seven 22 and 1/4 wave plate eight 23, the reflective surface of the total reflection mirror six 16 is closely connected with 1/4 wave plate nine 24 and 1/4 wave plate that the fast axis direction is 45° with the Y axis direction Ten 25, right-handed circularly polarized light L4A is incident from the incident end of glass tube one 29, and passes through 1/4 wave plate ten 25, total reflection mirror six 16, 1/4 wave plate nine 24, 1/4 wave plate eight 23 , total reflection mirror four 14, 1/4 wave plate seven 22, emerge from the exit end of glass tube one 29.

The incident end and the outgoing end of the glass tube two 30 are oppositely provided with a total reflection mirror five 15 and a total reflection mirror seven 17, and the reflection surface of the total reflection mirror five 15 is closely connected with a 1/2 that the fast axis direction is 45° with the Y axis direction. 4 wave plates five 20 and 1/4 wave plate six 21, the reflective surface side of the total reflection mirror seven 17 is closely connected with 1/4 wave plate three 18 and 1/4 that the fast axis direction is -45° with the Y axis direction 4 wave plate 4 19, left-handed circularly polarized light L4B is incident from the incident end of glass tube 2 30, and passes through 1/4 wave plate 3 18, total reflection mirror 7 17, 1/4 wave plate 4 19, and 1/4 wave plate After five 20, total reflection mirror five 15, 1/4 wave plate six 21, exit from the exit end of glass tube two 30.

All wave plates, mirrors, and glass tubes have a small angle between the exit end surface and the X-axis. The specific value is calculated under the condition that all surfaces are perpendicular to the light path. The schematic diagram here takes three reflections as an example. At the same time, each wave plate is in close contact with the rear total reflection mirror. The figure is only for illustration, and the distance is enlarged.

The second part is the magneto-optical component. As shown in FIG. 3 b , the magneto-optic glass 1 26 is wound with a coil, and the magneto-optic glass 2 27 is not wound with a coil. The coil current is controlled by a controllable current source 28 which is connected to the computer 13 for communication. By scanning the current in the coil, a certain value can be found, so that the light intensity behind the polarizer 9 reaches the maximum value, that is, the effect of the magnetic rotation and the natural rotation are just offset, and the ratio can be calculated according to the specific current reading. Optical rotation and concentration information (see appendix for theoretical derivation).

The core design of the present invention is to use two sets of 1/4 wave plates to artificially intervene in the phase change at the light reflection, so that when the light travels in the reverse direction, the optical rotation angle can continue to be superimposed on the value accumulated during the forward transition. At the same time, according to Fresnel's explanation of the optical rotation phenomenon, the linearly polarized light is converted into circularly polarized light, and the angle information of the optical rotation angle is compressed into the phase, so that every reflection is a total reflection of the s wave, which avoids The polarization problem caused by multiple reflections is opened, which is also conducive to the maintenance of signal strength.

In simple terms, that is: (1) circularly polarized light passes through the solution; (2) the phase of circularly polarized light changes due to the optical rotation of the solution; (3) circularly polarized light is converted into linearly polarized light before reflection and protected, and Introduce artificial phase guidance; (4) p-wave total reflection of linearly polarized light occurs on the mirror; (5) convert linearly polarized light back to circularly polarized light, and introduce artificial phase guidance again; (6) light travels through optical rotation again Solution, at the same time, due to the two phase guides, the phase change produced by the second transition will be superimposed on the previously accumulated value instead of canceling; (7) After repeating the process of 1-6 for several times, the left-handed and right-handed light will converge, All optical rotation information is displayed on the angle between the light vibration direction and the Y axis.

In a specific embodiment, a semiconductor laser with a wavelength around 650 nm is used. The length of the optical rotation tube is 11 cm, the effective length is 10 cm (the distance between the wave plate groups 18, 19 and the wave plate groups 20, 21), and the inner diameter of the tube is 1.5 cm. Each wave plate group is in close contact with the rear reflector. Optically active glass with a Verdet constant of 0.35 min·Oe ^-1 ·cm ^-1 (58.3 degrees·T·cm) was used, the length was 5 cm, and the winding density was 25 turns/cm.

For substances with low concentration or low optical rotation, use a magneto-optical component to analyze the change in the angle of rotation to measure the concentration or specific rotation.

Taking a substance with a specific optical rotation of 10° g ^-1 ml dm at a room temperature of 25°C for 650nm light as an example, when its concentration is 0.01g/ml, the resulting optical rotation angle is 0.1 degrees, After enhancement, it is expanded to 0.3 degrees. According to the theoretical proof (appendix), the required current (to make the magneto-optical rotation component just offset the natural rotation) is 654.8mA. If the concentration increases by 0.001g/ml, the corresponding current change is 65.48mA, which is within the detectable range.

For substances with high concentration or high optical rotation, the magneto-optical rotation part is removed, and the change of the optical rotation angle is directly analyzed through the intensity of the outgoing light passing through the polarizer 29 to measure the concentration or specific optical rotation.

Taking a substance with a specific optical rotation of 100° g ^-1 ml dm at a room temperature of 25°C for 650nm light as an example, when its concentration is 0.2g/ml, the resulting optical rotation angle is 20 degrees, Enhanced and expanded to 60 degrees. Through theoretical proof (appendix 8), it can be seen that the light intensity received by the light intensity meter is 25% of the maximum value. If the concentration increases by 0.001g/ml, the light intensity is 24.5% of the maximum value, which is within the detectable range.

It can be seen that for substances with high optical rotation at high concentration or substances with low optical rotation at low concentration, the device can perform relatively accurate measurement with high sensitivity. And because the total deflection angle is less than 90 degrees, when using the magnetic optical rotation component, it is possible to find a current with the smallest intensity that can dial back the deflection angle, and judge the optical rotation direction of the substance through the flow direction of the minimum current, and directly detect it , the light intensity corresponds to the rotation angle even more.

At the same time, before use, by adjusting the beam splitter 3, the total reflection mirror 4, 5, 6 and the mechanical structure 10, the two beams of light can be restored to linearly polarized light in the Y direction at the polarizer 2 9, that is, the phase difference is 0 Or an integer multiple of 2π to complete the zeroing work.

appendix

1. Fresnel's explanation of optical rotation effect

According to Fresnel's explanation of the optical rotation effect, the vertical linearly polarized light incident on the optically active solution in the traditional concept of optical rotation can be decomposed into two beams of circularly polarized light with opposite rotation but the same phase. Due to the different speeds of left-handed and right-handed circularly polarized light passing through the optically active material, the two beams of circularly polarized light incident at the same phase have a certain phase difference when they exit. When they are combined again, they are still linearly polarized light, but at this time There is an angle difference between the polarization angle and the vertical direction, that is, the optical rotation angle we observe, as shown in Figure 4.

2. The conversion relationship between the phase difference of left and right circularly polarized light and the optical rotation angle in the traditional concept

As shown in Figure 2, a beam of partially polarized light L1 is emitted by a semiconductor laser 1, and passes through a polarizer 1 to generate a beam of linearly polarized light L2 polarized in the Y direction:

E _Y ＝A ₀ sin(ωt-kz)

This beam of light is split by the beam splitter 3 into two beams of Y-direction linearly polarized light L3A and L3B with approximately the same energy, and they respectively pass through two 1/4 wave plates 7 at 45° and -45° to the Y-axis direction , 8, generating right-handed circularly polarized light L4A and left-handed circularly polarized light L4B. The formula is expressed as follows (where z is the distance traveled by the light beam from the origin, as shown in Figure 5, x and y are the directions of the fast and slow axes of the wave plate, which are different from the uppercase X and Y, which are the directions of the entire instrument system coordinate):

L4A:

E _x ＝A ₁ sin(ωt-kz)

L4B:

E _y =A ₁ sin(ωt-kz)

After passing through the solution pool 14-30, the two beams of light each generate different additional phases ΔR and ΔL, and the relationship between ΔR and ΔL is different for different substances. The two beams of light L5A and L5B after exiting are:

L5A:

E _x ＝A ₂ sin(ωt-kz+ΔR)

L5B:

E _y =A ₂ sin(ωt-kz+ΔL)

According to Fresnel's explanation, the result of the combination of L5A and L5B should be a linearly polarized light, and the angle between it and the y-axis is the optical rotation angle θ we usually observe, so let's first deduce the relationship between ΔR and ΔL and optical rotation The relationship between the angle θ:

Considering the front surface of polarizer 2 9, z is a certain value at this time. At any time t, the directions of the instantaneous vibration vectors of the two beams of light are (as shown in Figure 6):

According to the induction formula of trigonometric functions, the above two formulas can be transformed into:

θ _L = ωt-kz + ΔL

Synthesize the rotation angle θ in the traditional sense:

so:

Therefore, the two beams of circularly polarized light are recombined into linearly polarized light, but due to the phase difference between them, they form an angle θ with the Y-axis direction after synthesis, which is consistent with the common optical rotation phenomenon from a macroscopic point of view.

3. The principle of artificially guiding the beam back and forth to make the optical rotation angle superimposed and the polarization phenomenon when the light reflects

Because in naturally optically active substances, the direction of rotation of the light polarization vector is only related to the direction of light propagation, as shown in Figure 6, so the rotation angle is reversed during the reverse transition and cannot be accumulated. However, if we conduct some guidance on the reflective surface, as shown in Figure 7, and flip the light polarization vector left and right, the optical rotation angle generated during the reverse transition can be superimposed on the previous optical rotation angle. Repeating this cycle is equivalent to prolonging the distance that light passes through in the solution and increasing the optical rotation angle. In the specific implementation, we replace linearly polarized light with circularly polarized light, so the overall physical expression will be more complicated than this, but the basic physical idea is the same, which is to add artificial intervention at the reflection, so that the deflection angle can be superimposed.

To realize the left and right flip of the optical vibration vector, a wave plate can be used, and a total reflection mirror can be used for reflection. But it is a pity that the linearly polarized light cannot be directly reflected on the mirror surface and then passed through the wave plate to complete the left-right flip, directly realizing Figure 6. The reasons are as follows: First, when the light is incident at a certain angle, the reflectance corresponding to the s-wave and p-wave directions is different, and in our instrument, the s and p components of the light are both quite large values, so the reflected light is different from the incident light Compared with light, it will be unrecoverably disturbed on the light vibration vector (a typical example is Brewster's angle of incidence), and the light vibration direction is the quantity we measure itself, so this effect will have a great impact, As shown in Figure 8. 2. The light cannot be vertically incident, because the vertical incident of the light means that the structure of the parallel plane cavity is used. At this time, the N round-trip and M round-trip lights cannot be separated at the exit end, resulting in the measurement being impossible.

4. Export of the formula

Take L4B-18-17-19-20-15-21-26-L5B as an example, see Figure 9:

Incident left-handed circularly polarized light L4B:

E _y =A ₂ sin(ωt-kz)

After passing through the optically active solution, the front surface of the wave plate 18 becomes:

E _y =A ₃ sin(ωt-kz+ΔL)

ΔL is the effect of the optically active solution with a length of l ₀ on this transition to the phase of the left-handed circularly polarized light. Since the wave plate 18 accelerates the π/2 phase in the y direction, when the wave plate 18 exits, it is:

It should be noted that when passing through the wave plate, the light in the x and y directions will be delayed by phase, but the reduction in the y direction is less, so from a macro perspective, it has caught up with the π/2 phase, that is, strictly written The above formula should be:

where k ₁ is the wave number in the wave plate crystal and d is the thickness of the wave plate crystal. Since writing this way will make the formula lengthy, and we will see later that these k ₁ d will be subtracted from each other when calculating the angle, so keep the simplified way of writing.

Synthesized to:

That is, a beam of linearly polarized light in the Y-axis direction. It can be seen that the modulation information ΔL of the optically active solution to the light has been compressed in the phase. Since the beam of light has only the s component and no p component for the total reflection mirror 17, there will be no other significant effects except slight attenuation in the amplitude. The reflected light is:

It should be noted that z here refers to the scalar distance traveled by the light when it travels all the way here, and does not represent an absolute direction, so there is no need to take a negative sign. When passing through the wave plate 19, the π/2 phase continues to be accelerated in the y direction to complete phase reversal.

This counterpropagating left-handed circularly polarized light passes through the solution again and becomes:

After the functions of 20, 15, and 21, it becomes:

Complete the last crossing:

On the surface of polarizer 2 9, the instantaneous vibration direction of the light vector is:

Right now

After considering the work of the magneto-optical rotation device, it becomes:

V is the Verdet constant, n is the number of coil windings per unit length, I is the magnitude of the current, L is the length of the optical glass, and μ is the magnetic permeability of the medium. When another beam of dextrorotatory light meets with it, the light vector vibrates along the direction:

That is the final synthesis: ·

As we know from part 2

ΔR-ΔL=2θ=2[a]cl ₀

therefore:

When adjusting the current so that θ is compensated back to 0 degrees:

or:

It should be noted that l ₀ should be the distance that light passes through the solution when it travels in one direction, but in fact the lengths of the three transits are slightly different, and their specific values are definitely not the effective length defined here as 10cm. However, since the effective length is 10cm and the tube diameter is 1.5cm, the difference between the actual optical path distance and six times the effective length is about 1mm, which is one hundredth of the value of 10cm, so the calculation can be simplified.

When we decompose linearly polarized light into circularly polarized light, we will explain the principle of direct reflection causing the rotation angle to return: for left-handed light, the phase increases by ΔL after one transition, but after direct reflection, due to the phase relationship of the x and y direction components remains unchanged, x is still leading, so the original left-handed circularly polarized light becomes right-handed circularly polarized light in the new propagation direction, and the transition phase increases by ΔR again. The same is true for right-handed light, and the right-handed light phase first increases by ΔR , increase ΔL after reflection, so there is no phase difference between the left-handed and right-handed lights when they emerge, that is, the synthesized linearly polarized light is still the linearly polarized light in the Y direction, that is, the deflection angle is restored. Here, since the influence of the 1/4 wave plate on light has nothing to do with the direction of light propagation, one reflection accelerates the phase in the y direction twice consecutively (different from the intuitive "reversible"), surpassing the x direction, so the The incident light becomes left-handed circularly polarized light in the new propagation direction, and still enjoys the phase increase of ΔL, so it continues to expand the phase difference between the left-handed circularly polarized light instead of restoring it. The final effect is to prevent the recovery of the deflection angle .

5. For substances with high concentration or high optical rotation

Let the light intensity received by the front surface of polarizer 29 be I ₀ , and the light intensity received by the detector after passing through the polarizer be I, according to Marius’ law:

I＝I ₀ (cosθ) ²

Right now

Therefore, by measuring the light intensity received by the front surface of the polarizer 29 as I ₀ , and the light intensity after passing through the polarizer as I, the deflection angle can be calculated, and the specific rotation and concentration can be further obtained:

and

It should be noted that terms such as "upper", "lower", "left", "right", "front", and "rear" quoted in the invention are only for clarity of description, not for Limiting the practicable scope of the present invention, and the change or adjustment of the relative relationship shall also be regarded as the practicable scope of the present invention without substantive changes in the technical content.

The above are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (4)

1. A circularly polarized light-based reflection enhanced polarimeter comprising: the device comprises a semiconductor laser (1), a first polaroid (2), a beam splitter (3), a first total reflection mirror (4), a second total reflection mirror (5), a third total reflection mirror (6), a first 1/4 wave plate (7), a second 1/4 wave plate (8), a solution tank and a second polaroid (9); the semiconductor laser (1) emits a beam of partial polarized light (L1), the partial polarized light (L1) propagates horizontally, the propagation path direction of the partial polarized light (L1) is in the Z direction, the partial polarized light (L1) passes through the first polarizer (2) to generate a beam of linearly polarized light (L2) polarized in the Y direction, and the Y direction is a direction perpendicular to the Z direction on a horizontal plane; the linearly polarized light (L2) is separated into two linearly polarized light beams in the Y direction through a beam splitter (3), wherein the transmission direction of a transmitted light beam (L3A) is kept unchanged, a reflected light beam (L3B) is adjusted in direction through a first total reflection mirror (4) and is parallel to the transmitted light beam (L3A), and the transmitted light beam (L3A) is adjusted through a second total reflection mirror (5) and a third total reflection mirror (6) so that the optical path of the transmitted light beam (L3A) is consistent with that of the reflected light beam (L3B); the transmission light beam (L3A) passes through a 1/4 wave plate I (7) with a fast axis forming an angle of-45 degrees with the Y direction to generate right-handed circularly polarized light (L4A), and the reflection light beam (L3B) passes through a 1/4 wave plate II (8) with a fast axis forming an angle of 45 degrees with the Y direction to generate left-handed circularly polarized light (L4B); after passing through the solution area, the right-handed circularly polarized light (L4A) and the left-handed circularly polarized light (L4B) are converged on a second polaroid (9) in the Y direction, and the second polaroid (9) is arranged in the cassette (11); the solution tank comprises a double glass tube connected structure and a magneto-optical rotation component which are sequentially arranged; the inside of the double-glass-tube connected structure is filled with a solution, and the double-glass-tube connected structure comprises a first glass tube (29) and a second glass tube (30) which are arranged in parallel and communicated with each other at the middle part;

the incident end and the emergent end of the glass tube I (29) are oppositely provided with a total reflection mirror IV (14) and a total reflection mirror VI (16), a reflection surface of the total reflection mirror IV (14) is closely connected with a 1/4 wave plate seven (22) and a 1/4 wave plate eight (23) which form an angle of-45 DEG with the Y axis direction, a reflection surface of the total reflection mirror VI (16) is closely connected with a 1/4 wave plate nine (24) and a 1/4 wave plate ten (25) which form an angle of 45 DEG with the Y axis direction, and right-handed circularly polarized light (L4A) enters from the incident end of the glass tube I (29) and sequentially passes through the 1/4 wave plate ten (25), the total reflection mirror IV (16), the 1/4 wave plate nine (24), the 1/4 wave plate eight (23), the total reflection mirror IV (14) and the 1/4 wave plate seven (22) and then exits from the emergent end of the glass tube I (29);

the incident end and the emergent end of the glass tube II (30) are oppositely provided with a total reflection mirror five (15) and a total reflection mirror seven (17), the reflection surface of the total reflection mirror five (15) is closely connected with a 1/4 wave plate five (20) and a 1/4 wave plate six (21) which are both 45 degrees in the fast axis direction and the Y axis direction, the reflection surface of the total reflection mirror seven (17) is closely connected with a 1/4 wave plate three (18) and a 1/4 wave plate four (19) which are both-45 degrees in the fast axis direction and the Y axis direction, left-handed circularly polarized light (L4B) is incident from the incident end of the glass tube II (30) and sequentially passes through the 1/4 wave plate three (18), the total reflection mirror five (17), the 1/4 wave plate four (19), the total reflection mirror five (15) and the 1/4 wave plate six (21) and then exits from the emergent end of the glass tube II (30).

2. A circularly polarized light-based reflection-enhanced polarimeter as recited in claim 1, wherein: the emergent end surfaces of the first glass tube (29), the second glass tube (30), the fourth full-reflecting mirror (14), the fifth full-reflecting mirror (15), the sixth full-reflecting mirror (16), the seventh full-reflecting mirror (17), the third 1/4 wave plate (18), the fourth 1/4 wave plate (19), the fifth 1/4 wave plate (20), the sixth 1/4 wave plate (21), the seventh 1/4 wave plate (22), the eighth 1/4 wave plate (23), the ninth 1/4 wave plate (24) and the tenth 1/4 wave plate (25) are perpendicular to the light path.

3. A circularly polarized light-based reflection-enhanced polarimeter as recited in claim 1, wherein: the magneto-optical rotation component comprises a magneto-optical rotation glass I (26) and a magneto-optical rotation glass II (27), wherein the magneto-optical rotation glass I (26) is wound with a coil, the magneto-optical rotation glass II (27) is not wound with a coil, the coil current is controlled by a controllable current source (28), and the current source (28) is connected and communicated with a computer (13);

the right-handed circularly polarized light (L4A) is emitted from the first glass tube (29) and then passes through the second magnetic rotating glass (27) to form an emergent light beam I (L5A), the left-handed circularly polarized light (L4B) is emitted from the second glass tube (30) and then passes through the first magnetic rotating glass (26) to form an emergent light beam II (L5B), and the emergent light beam I (L5A) and the emergent light beam II (L5B) are naturally converged on the second polarizer (9) after passing a distance.

4. A circularly polarized light-based reflection-enhanced polarimeter as recited in claim 1, wherein: the second polaroid (9) is put down and lifted up through a mechanical structure (10), a silicon photocell detector (12) is closely attached to the rear face of the second polaroid (9), and light intensity data generated by the silicon photocell detector (12) are transmitted into a computer (13) for processing.