A complex refractive index measurement system and method based on brewster-transmission combination

Abstract

The application provides a complex refractive index measurement system and method based on Brewster-transmission combination, which comprises a light source, an incident light transmission measurement unit, a reflected light transmission measurement unit, an incident light rotating arm, a reflected light rotating arm, a rotating arm control unit, a sample stage, an incident light signal amplification unit, a reflected light signal amplification unit, a data collector and a data processing controller; the incident light transmission measurement unit is fixedly installed on the upper surface of the incident light rotating arm; and the reflected light transmission measurement unit is fixedly installed on the upper surface of the reflected light rotating arm. The complex refractive index measurement system and method based on Brewster-transmission combination have high measurement precision, can be widely applied to complex refractive index measurement of strong and weak absorption media, are simple and easy to realize, do not need to perform complex K-K conversion solving, are not limited by a wave band range, and can be applied to shorter wave band and monochromatic wave optical parameter measurement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of medium optical constant measurement, and particularly relates to a complex refractive index measurement system and method based on Brewster-transmission combination. BACKGROUND

[0002] Optical constants are the most basic parameters for target radiation transmission numerical calculation, radiation characteristics and remote sensing analysis. Any radiation parameter, such as absorption coefficient and scattering coefficient, can be uniquely determined by optical constants. Studying optical constants can help scholars master and understand the reflection and absorption spectrum distribution characteristics of a medium from the most basic and fundamental level. Complex refractive index is the most important optical constant of an absorbing medium. The complex refractive index is denoted by m, which can be expressed as m = n + iκ. In the formula, the real part n is the refractive index of the absorbing medium, which is determined by the propagation speed of light in the absorbing medium; the imaginary part κ is determined by the attenuation of light in the absorbing medium when propagating in the absorbing medium, which is called the absorption index. i is the imaginary unit. In order to obtain the complete complex refractive index, scholars have developed various methods, such as attenuated total reflection method, transmission method, ellipsometry method, and combination methods of the above methods, such as reflection-transmission combination method and ellipsometry-transmission combination method.

[0003] The principle of the attenuated total reflection method is to solve the complex refractive index according to the attenuation spectrum of the total reflection light of the liquid surface. When light irradiates the liquid container, the absorption of the liquid will cause the total reflectance to decrease, and a correlation between the optical constant and the attenuation ratio of reflectance is established according to this principle. Since the complex refractive index includes the refractive index n and the absorption index κ, at least two related correlation formulas are needed to solve the complete optical constant. Therefore, the Kramers-Kroning (K-K) relationship is needed. First, the initial absorption index is solved according to the reflectance attenuation spectrum, then the initial refractive index is solved according to the K-K relationship, and finally the final complex refractive index is obtained through iteration. If the liquid absorption is weak, the reflectance change is small, which is not conducive to solving the optical constant. Therefore, this method is usually suitable for samples with a large absorption coefficient (μ abs >10 2 –10 3 cm -1 ) and the method needs to use the complex K-K relationship, which is only suitable for measuring the optical constant in a wide waveband.

[0004] The transmission method is one of the most commonly used liquid optical constant measurement methods at present, and the principle is: according to the Beer-Lambert attenuation law of light in a translucent medium, the optical parameters of the sample to be measured are solved by measuring the transmittance. Similarly, only one equation related to the optical constant can be established according to the transmittance, and other relationship equations are needed to form a closed equation set. One solution is to use the K-K relationship, and another method is to measure the transmittance of the same liquid sample with two different liquid layer thicknesses (i.e. optical path), to establish two related equations to solve the refractive index and absorption index by simultaneous equations. The method is called the double optical path method. The transmission method only relies on the measurement data of the transmittance of the sample to solve the optical constant, and the thickness of the liquid to be measured and the absorption strength of the liquid have a great influence on the result. This method is suitable for samples with an absorption coefficient less than 10 2 -10 3 cm -1 .

[0005] The ellipsometry method is a method for solving the optical constant by using the change amount of the polarization amplitude and phase after the light irradiates the surface of the liquid to be measured. The ellipsometry method is suitable for the case of a large absorption coefficient, and when the absorption coefficient is less than 100cm -1 , the method cannot obtain accurate optical constant.

[0006] The traditional total reflection / transmission measurement method is usually only suitable for a small absorption coefficient (μ abs <10 2 -10 3 cm -1 ). And the transmission method and the attenuated total reflection method usually need to be solved by simultaneously solving the complex K-K relationship, and the K-K relationship is an integral of the whole wave band, which will produce a large error when the measurement wave band is narrow. Although the ellipsometry method is suitable for measuring high-absorption liquids, it needs to use high-precision ellipsometry equipment and often needs to design a precise sample container. Therefore, they all have great limitations. SUMMARY

[0007] In view of the defects of the prior art, the present application provides a complex refractive index measurement system and method based on Brewster-transmission combination, which can effectively solve the above problems.

[0008] The technical scheme adopted by the present application is as follows:

[0009] The present application provides a complex refractive index measurement system based on Brewster-transmission combination, which comprises a light source (1), an incident light transmission measurement unit, a reflected light transmission measurement unit, an incident light rotating arm (12-1), a reflected light rotating arm (12-2), a rotating arm control unit, a sample table (9), an incident light signal amplification unit, a reflected light signal amplification unit, a data collector and a data processing controller (19).

[0010] The data processing controller (19) is connected with the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) through the rotating arm control unit, and is used for controlling the rotation of the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) respectively; the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) intersect at the sample table (9);

[0011] The incident light rotating arm (12-1) is fixedly installed with the incident light transmission measurement unit; and the reflected light rotating arm (12-2) is fixedly installed with the reflected light transmission measurement unit.

[0012] The measurement end of the incident light transmission measurement unit is connected to the input end of the data collector through the incident light signal amplification unit; the measurement end of the reflected light transmission measurement unit is connected to the input end of the data collector through the reflected light signal amplification unit; and the output end of the data collector is connected with the data processing controller (19).

[0013] Preferably, the incident light transmission measurement unit comprises a collimator (3), an aperture (4), a first polarizer (5), a beam splitter (6), a second polarizer (7) and a first detector (8).

[0014] The collimator (3), the aperture (4), the first polarizer (5) and the beam splitter (6) are coaxially arranged in sequence in the light incident direction.

[0015] The beam splitter (6) outputs two beams of mutually perpendicular light rays, one of which is coaxial with the light incident direction and is incident on the surface of the sample to be measured; and the other of which is perpendicular to the light incident direction, and the output direction is coaxially arranged in sequence with the second polarizer (7) and the first detector (8).

[0016] The light input end of the collimator (3) is connected with the light source (1) through an optical fiber (2); and the output end of the first detector (8) is connected to the input end of the incident light signal amplification unit.

[0017] The incident light signal amplification unit comprises a first preamplifier (13) and a first lock-in amplifier (15) arranged in sequence in the light transmission direction.

[0018] Preferably, the reflected light transmission measurement unit comprises a third polarizer (10) and a second detector (11) coaxially arranged in sequence in the light reflection direction; and the output end of the detector C (11) is connected to the input end of the reflected light signal amplification unit.

[0019] The reflected light signal amplification unit comprises a second preamplifier (14) and a second phase-locked amplifier (16) arranged in sequence in the light transmission direction.

[0020] Preferably, the rotating arm control unit comprises a motion controller (18) and a stepping motor (17); the motion controller (18) is connected with the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) respectively through the stepping motor (17).

[0021] The application further provides a method of a complex refractive index measurement system based on the combination of Brewster angle and transmission, comprising the following steps:

[0022] Step 1, obtaining the Brewster angle measurement value θ of the sample to be measured at a set light wavelength λ B ;

[0023] Step 2, obtaining the total transmittance measurement value T of the sample to be measured at a set light wavelength λ exp :

[0024] Step 2.1, respectively measuring the S-polarized state transmitted radiation energy I t,s and the S-polarized state incident radiation energy I i,s , the P-polarized state transmitted radiation energy I t,p and the P-polarized state incident radiation energy I i,p of the sample to be measured by using the transmission method, and calculating the S-polarized state transmittance T s and the P-polarized state transmittance T p by using the following formula:

[0025]

[0026] Step 2.2, calculating the total transmittance measurement value T exp of the sample to be measured by using the following formula:

[0027]

[0028] Step 3, respectively establishing equation (1) about the Brewster angle measurement value θ B and equation (2) about the total transmittance measurement value T exp :

[0029]

[0030] Wherein:

[0031] m1 is the complex refractive index of air;

[0032] n1 is the refractive index of air;

[0033] κ1 is the absorption index of air;

[0034] m2 is the complex refractive index of the sample to be measured;

[0035] n2 is the refractive index of the sample to be measured;

[0036] κ2 is the absorption index of the sample to be measured;

[0037] i is the imaginary unit;

[0038] In equation (1) and equation (2), there are two unknown parameters n2 and κ2;

[0039] Step 4, the absorption index κ2 and the refractive index n2 of the sample to be measured are obtained by solving the equation using the genetic algorithm:

[0040] Step 1.4, the optimization objective function F = min{ (f(n2, κ2) - T exp ) 2} is established;

[0041] Step 4.2, the initial value n 20 of the refractive index and the initial value κ 20 of the absorption index of the sample to be measured are determined respectively:

[0042] Assuming that the absorption index κ2 of the sample to be measured is 0, the refractive index value obtained by solving equation (1) is the initial value n 20 of the refractive index;

[0043] The total transmittance measurement value T exp is substituted into the following formula, and the absorption index obtained by solving is the initial value κ 20 of the absorption index:

[0044]

[0045] Wherein:

[0046] L is the thickness of the sample to be measured;

[0047] ν is the wave number of incident light, λ is the wavelength of incident light;

[0048] Step 4.3, the initial value n 20 of the refractive index and the initial value κ 20 of the absorption index are used as the initial population, and the optimization objective function F established in step 4.1 is solved by using the genetic algorithm, and the termination condition is: F < 10 -15 , the optimal absorption index κ2 and the refractive index n2 of the sample to be measured are obtained;

[0049] Step 5, the complex refractive index m2 of the sample to be measured is obtained according to the formula m2 = n2 + iκ2, and the measurement process of the complex refractive index of the sample to be measured is completed.

[0050] Preferably, step 1 specifically includes:

[0051] Step 1.1, set the incident angle θ of the incident ray. i The rotation range and step size;

[0052] Step 1.2, at the incident angle θ i Within the rotation range, the rotation angles of the incident light arm (12-1) and the reflected light arm (12-2) are controlled according to the step size value, so that the incident angle θ of the incident light is... i The incident rays arrive at each specified angle in sequence, and at each specified angle, the incident angle θ of the incident rays is... i and the reflection angle θ of the reflected light r equal;

[0053] Step 1.3: At each specified angle reached by rotating according to the step size value, the ratio R' of the reflectivity of the P-polarized state to the total reflectivity is obtained. p The method is as follows:

[0054] Step 1.3.1: At each specified angle, the reflectivity R of the S-polarization state is obtained using the following formula. S and the reflectivity R of the P polarization state p :

[0055]

[0056] in:

[0057] I r,s : S-polarized reflected light radiation energy;

[0058] I i,s : S-polarized incident light radiation energy;

[0059] I r,p : P-polarized reflected light radiation energy;

[0060] I i,p : P-polarized incident light radiation energy;

[0061] Step 1.3.2: At each specified angle, the total reflectivity R is obtained using the following formula:

[0062]

[0063] Step 1.3.3: At each specified angle, use the following formula to obtain the ratio R' of the reflectivity of the P-polarized state to the total reflectivity. p :

[0064]

[0065] Step 1.4: Establish the x-axis as each specified angle and the y-axis as the ratio R' of the P-polarized state reflectivity to the total reflectivity. p In the coordinate system, label the ratio R' of the reflectivity of each P polarization state to the total reflectivity obtained in step 1.3. p Thus, multiple discrete points are obtained;

[0066] Curve fitting is performed on multiple discrete points to obtain a parabola;

[0067] In the parabola, find the minimum ratio R' of the reflectivity of the P-polarized state to the total reflectivity. p That is, the Brewster angle measurement value θ of the sample to be tested. B .

[0068] Preferably, at each specified angle, the reflected light radiation energy I in the S-polarized state is... r,s and the incident light radiation energy I in the S polarization state i,s The measurement method is as follows:

[0069] 1) Adjust the orientation of the first polarizer (5), the second polarizer (7), and the third polarizer (10) to the S-polarization state; through the rotating arm control unit, rotate the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) to the specified angle, thereby increasing the incident angle θ of the incident light. i and the reflection angle θ of the reflected light r Equal, both are at a specified angle;

[0070] 2) The light source (1) generates light with a set wavelength λ, which is incident on the collimator (3) through the optical fiber (2) to generate parallel light; after passing through the aperture (4), the parallel light is incident on the first polarizer (5) to generate S-polarized light.

[0071] After passing through the beam splitter (6), the S-polarized light is split into beams with an energy ratio of R. a The two mutually perpendicular light rays are the first S-polarized ray and the second S-polarized ray, respectively;

[0072] in:

[0073] The second beam of S-polarized light passes through the second polarizer (7) and is then received by the first detector (8), which detects the radiation energy I of the S-polarized incident light. i,s After being amplified by the incident light signal amplification unit, the signal is collected by the data acquisition unit and then received by the data processing controller (19). The energy received by the data processing controller (19) is multiplied by (1+R). a After that, the radiation energy I of the incident light in the S-polarized state is obtained. i,s ;

[0074] The first S-polarization light is incident on the surface of the sample to be measured, and after being reflected by the surface of the sample to be measured, the reflected light is formed; after the reflected light passes through the third polarizer (10), the S-polarization reflected light is generated, and then the second detector (11) receives it, and the S-polarization reflected light radiation energy I r,s is obtained by the data processing controller (19) after being amplified by the reflected light signal amplification unit, amplified by the data acquisition device, and then received by the data processing controller (19). r,s .

[0075] Preferably, in step 2.1, the S-polarization transmitted radiation energy I t,s of the sample to be measured and the S-polarization incident radiation energy I i,s are measured by the following method:

[0076] 1) Adjust the first polarizer (5), the second polarizer (7) and the third polarizer (10) to be S-polarization; through the rotating arm control unit, the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) are rotated to the horizontal state;

[0077] 2) The light source (1) generates light of a set wavelength λ, and after passing through the collimator (3), the aperture (4) and the first polarizer (5) in turn, S-polarization light is generated;

[0078] After the S-polarization light passes through the beam splitter (6), it is divided into two mutually perpendicular lights with an energy ratio of R a , which are the first S-polarization light and the second S-polarization light, respectively;

[0079] Wherein:

[0080] The second S-polarization light passes through the second polarizer (7), and then the first detector (8) receives it, and after being amplified by the incident light signal amplification unit, it is collected by the data acquisition device, and then received by the data processing controller (19). After the energy received by the data processing controller (19) is multiplied by (1+R a ), the S-polarization incident light radiation energy I i,s is obtained;

[0081] The first S-polarization light is incident on the surface of the sample to be measured, and after being reflected by the surface of the sample to be measured, the reflected light is formed; after the reflected light passes through the third polarizer (10), the S-polarization reflected light is generated, and then the second detector (11) receives it, and the S-polarization reflected light radiation energy I t,s is obtained by the data processing controller (19) after being amplified by the reflected light signal amplification unit, amplified by the data acquisition device, and then received by the data processing controller (19).

[0082] Preferably, if the sample to be measured is a solid medium, the expression of f(n2, κ2) is:

[0083]

[0084] wherein: L is the thickness of the sample under test; and α(n2, κ2) is the absorption coefficient of the sample under test.

[0085] Preferably, if the sample under test is a liquid medium, the liquid medium is placed in a glass container, and a glass-sample-under-test-glass three-layer structure is adopted, i.e.:

[0086] In the direction from left to right, the light is transmitted through the first air layer, the first glass layer, the sample medium layer, and the second glass layer in turn, and then reaches the second air layer;

[0087] The expression of f(n2, κ2) is:

[0088]

[0089] wherein:

[0090] T 01 , T 12 , T 23 , T 30 , T 32 , T 21 are respectively: the interface transmittance when the first air layer is perpendicularly incident on the first glass layer, the interface transmittance when the first glass layer is perpendicularly incident on the sample medium layer, the interface transmittance when the sample medium layer is perpendicularly incident on the second glass layer, the interface transmittance when the second glass layer is perpendicularly incident on the second air layer, the interface transmittance when the second glass layer is perpendicularly incident on the sample medium layer, and the interface transmittance when the sample medium layer is perpendicularly incident on the first glass layer;

[0091] α1, α2, and α3 are respectively: the absorption coefficients of the first glass layer, the sample medium layer, and the second glass layer; wherein, α2 = α2(n2, κ2);

[0092] L1, L2, and L3 are respectively: the thicknesses of the first glass layer, the sample medium layer, and the second glass layer;

[0093] R 10 R 12 R 32 R 30 R 21 are respectively: the interface reflectance when the first glass layer is perpendicularly reflected on the first air layer, the interface reflectance when the first glass layer is perpendicularly reflected on the sample medium layer, the interface reflectance when the second glass layer is perpendicularly reflected on the sample medium layer, the interface reflectance when the second glass layer is perpendicularly reflected on the second air layer, and the interface reflectance when the sample medium layer is perpendicularly reflected on the first glass layer.

[0094] The complex refractive index measurement system and method based on the Brewster-transmission combination provided by the application have the following advantages:

[0095] The complex refractive index measurement system and method based on the combination of Brewster and transmission provided by the application have high measurement accuracy, can be widely applied to the complex refractive index measurement of strong and weak absorption medium, are simple and easy to realize, do not need to perform complex K-K conversion solving, are not limited by the wave band range, and can be applied to the optical parameter measurement of a shorter wave band and monochromatic wave. BRIEF DESCRIPTION OF DRAWINGS

[0096] Figure 1 The complex refractive index measurement system based on the combination of Brewster and transmission provided by the application;

[0097] Figure 2 The Brewster angle measurement schematic diagram provided by the application;

[0098] Figure 3 The schematic diagram of the correlation formula of the Brewster angle and the refractive index provided by the application;

[0099] Figure 4 The measured value of the Brewster angle after the parabolic fitting when the measurement angle interval is 0.01° is θ B ;

[0100] Figure 5 The measured value of the Brewster angle after the parabolic fitting when the measurement angle interval is 0.1° is θ B ;

[0101] Figure 6 The transmission method measurement schematic diagram provided by the application;

[0102] Figure 7 The transmission measurement principle diagram of the liquid medium provided by the application;

[0103] Figure 8 The measurement result comparison diagram of the refractive index of deionized water;

[0104] Figure 9 The measurement result comparison diagram of the absorption index of deionized water;

[0105] Wherein:

[0106] 1 - light source, 2 - optical fiber, 3 - collimator, 4 - aperture, 5 - first polarizer, 6 - beam splitter, 7 - second polarizer, 8 - first detector, 9 - sample stage, 10 - third polarizer, 11 - second detector, 12-1 - incident light rotating arm, 12-2 - reflected light rotating arm, 13 - first preamplifier, 14 - second preamplifier, 15 - first lock-in amplifier, 16 - second lock-in amplifier, 17 - stepper motor, 18 - motion controller, 19 - data processing controller. DETAILED DESCRIPTION

[0107] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0108] The present application provides a new complex refractive index measurement method: Brewster-transmission combination method, which has high measurement accuracy and can be widely used in complex refractive index measurement of strong and weak absorption medium; and is simple and easy to implement, without complex K-K conversion solving, not limited by waveband range, and can be applied to shorter waveband and monochromatic wave optical parameter measurement.

[0109] The complex refractive index measurement system and method based on Brewster-transmission combination provided by the present application mainly include two parts: Brewster angle measurement and transmission measurement, and a complex refractive index and Brewster angle correlation formula and a complex refractive index and transmission correlation formula are respectively established, and the complex refractive index of the sample to be measured is obtained by solving the two formulas.

[0110] As shown in Figure 1 The complex refractive index measurement system based on Brewster-transmission combination provided by the present application includes a light source 1, an incident light transmission measurement unit, a reflected light transmission measurement unit, an incident light rotating arm 12-1, a reflected light rotating arm 12-2, a rotating arm control unit, a sample stage 9, an incident light signal amplification unit, a reflected light signal amplification unit, a data collector and a data processing controller 19.

[0111] The data processing controller 19 is connected with the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 through the rotating arm control unit, and is used for controlling the rotation of the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 respectively; the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 intersect at the sample stage 9; the rotating arm control unit specifically includes a motion controller 18 and a stepping motor 17; the motion controller 18 is connected with the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 through the stepping motor 17.

[0112] The incident light transmission measurement unit is fixedly installed on the upper surface of the incident light rotating arm 12-1; the reflected light transmission measurement unit is fixedly installed on the upper surface of the reflected light rotating arm 12-2.

[0113] The measurement end of the incident light transmission measurement unit is connected to the input end of the data collector through the incident light signal amplification unit; the measurement end of the reflected light transmission measurement unit is connected to the input end of the data collector through the reflected light signal amplification unit; and the output end of the data collector is connected with the data processing controller 19.

[0114] As one specific embodiment, the incident light transmission measurement unit includes: a collimator 3, an aperture 4, a first polarizer 5, a beam splitter 6, a second polarizer 7, and a first detector 8;

[0115] The collimator 3, the aperture 4, the first polarizer 5, and the beam splitter 6 are arranged coaxially in sequence according to the direction of light incidence.

[0116] The beam splitter 6 outputs two mutually perpendicular light beams. One beam is coaxial with the incident light direction and is incident on the surface of the sample to be tested. The other beam is perpendicular to the incident light direction, and its exit direction is coaxially arranged with the second polarizer 7 and the first detector 8.

[0117] The optical input end of the collimator 3 is connected to the light source 1 via optical fiber 2; the output end of the first detector 8 is connected to the input end of the incident light signal amplification unit.

[0118] The incident light signal amplification unit includes a first preamplifier 13 and a first lock-in amplifier 15 arranged sequentially according to the light transmission direction.

[0119] In one specific embodiment, the reflected light transmission measurement unit includes, in sequence, a third polarizer 10 and a second detector 11 arranged coaxially in the direction of light reflection; the output terminal of the detector C11 is connected to the input terminal of the reflected light signal amplification unit.

[0120] The reflected light signal amplification unit includes a second preamplifier 14 and a second lock-in amplifier 16 arranged sequentially according to the light transmission direction.

[0121] Therefore, the complex refractive index measurement device based on Brewster-transmission combination provided by the present invention, such as Figure 1 As shown, it consists of three parts: a light source unit, a mechanical control unit, and a signal acquisition and processing unit.

[0122] The light source section mainly includes light source 1, collimator 3, beam splitter 6, and other devices, primarily used to generate the desired specific light beam. Currently, the experimental setup is equipped with four monochromatic wave light sources: 660.0 nm, 782.2 nm, 1063.4 nm, and 1550.0 nm; and one broadband light source (450–5500 nm), which can achieve monochromatic wave emission by adding filters for the corresponding wavelength bands.

[0123] The motion control unit includes a stepper motor and two rotating arms, which are used to control the rotation of the rotating arms to measure incident or reflected energy at various angles.

[0124] The signal acquisition part comprises two detectors for acquiring incident and reflected energy respectively, preamplifiers, phase-locked amplifiers and a data acquisition computer for acquiring experimental data and post-processing.

[0125] During the experiment, the light is transmitted to the collimator 3 through the optical fiber 2 to generate parallel light, and the specific polarization state of the polarized light is generated after passing through the first polarizer 5, and the light is divided into two mutually perpendicular light beams A and B with an energy ratio of R a After the beam splitter 6. Light A is directly received by the first detector 8, while light B is received by the second detector 11 after being reflected or transmitted by the material surface. The received signal is amplified by the second preamplifier 14 and the second phase-locked amplifier 16 in turn, and finally collected by the data acquisition board. The collimator 3, the first polarizer 5, the beam splitter 6 and the first detector 8 are all installed on the incident light rotating arm 12-1, which can rotate along the axis within the range of -90° to 90° under the control of the stepping motor. The third polarizer 10 and the second detector 11 are installed on the reflected light rotating arm 12-2, which can rotate along the axis within the range of -90° to 90° under the control of the stepping motor. The sample table is composed of a shear lifting table, a high-precision manual lifting table, a manual rotating table and a high-precision manual angular displacement table, which can adjust the sample position and the azimuth angle of the light.

[0126] In order to ensure the measurement accuracy and improve the measurement speed, an automatic control program for the experiment is written by using LabVIEW software. The program can realize full / half-automatic experimental measurement, and automatically complete data processing and output saving.

[0127] The experimental device adopts a horizontal arrangement, and sufficient test space is reserved, which can widely meet the research on the reflection, scattering, internal absorption and transmission characteristics of solid and liquid surfaces with different absorption and different sizes. The experimental table adopts an absolute measurement method, that is, if the two rotating arms are at a certain angle, it is a reflection measurement state, and the energy signals at the incident and reflection ends are collected in real time, and the ratio thereof is the medium reflection data. If the two rotating arms are symmetrically horizontal, it is a transmission measurement state, and the energy signals at the incident and transmission ends are collected in real time, and the ratio thereof is the medium transmission data. In this way, errors caused by unstable light source output can be effectively avoided; and the experimental table is provided with multiple amplification equipment (preamplifiers and phase-locked amplifiers), which can effectively capture weak signals and improve the measurement accuracy.

[0128] The application also provides a method of a complex refractive index measurement system based on Brewster-transmission combination, comprising the following steps:

[0129] Step 1. Obtain the Brewster angle measurement value θ B of the sample to be measured at a set light wavelength λ.

[0130] The accurate acquisition of the Brewster angle is the key to ensure the measurement accuracy. Generally, the Brewster angle is determined according to the intensity change of the reflected light of the sample to be measured. However, this method is susceptible to the output stability of the light source, thereby leading to the decline of the measurement accuracy. The device of the present application adopts the absolute measurement method to effectively overcome the error caused by the instability of the light source. At the same time, the angle accuracy of the rotating motor can reach 0.00125°, which can ensure the accurate measurement of the Brewster angle. The experimental measurement schematic diagram is shown in Figure 2 The sample to be measured is placed on the sample table, and the rotating arm is rotated at an angle interval of 0.1° to measure the reflected P-polarization component and S-polarization component of the sample surface at different angles.

[0131] As shown in Figure 2 , the method specifically comprises the following steps:

[0132] Step 1.1, setting the incident angle θ i of the incident light, the rotating range of the rotating arm and the step value;

[0133] Step 1.2, in the rotating range of the incident angle θ i , the rotating angles of the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 are controlled according to the step value, so that the incident angle θ i of the incident light reaches each specified angle in turn, and at each specified angle, the incident angle θ i of the incident light and the reflection angle θ r of the reflected light are equal;

[0134] Step 1.3, at each specified angle rotated according to the step value, the ratio R' p of the P-polarization state reflectivity and the total reflectivity is obtained, and the method is as follows:

[0135] Step 1.3.1, at each specified angle, the reflectivity R S of the S-polarization state and the reflectivity R p of the P-polarization state are obtained by using the following formula, respectively:

[0136]

[0137] Wherein:

[0138] I r,s : S-polarization state reflected light radiant energy;

[0139] I i,s : S-polarization state incident light radiant energy;

[0140] I r,p : P-polarization state reflected light radiant energy;

[0141] I i,p : P-polarization state incident light radiant energy;

[0142] In this invention, the reflected light energy I in the S-polarized state is... r,s and the incident light radiation energy I in the S polarization state i,s The measurement method, and the radiation energy I of the reflected light in the P-polarized state. r,p and the incident light radiation energy I in the P polarization state i,p The measurement methods are basically the same, with the only difference being that when measuring the energy of each S-polarized state, the first polarizer 5, the second polarizer 7, and the third polarizer 10 in the measurement system need to be adjusted to the S-polarized state; while when measuring the energy of each P-polarized state, the first polarizer 5, the second polarizer 7, and the third polarizer 10 in the measurement system need to be adjusted to the P-polarized state.

[0143] Therefore, the following only considers the radiation energy I of the reflected light in the S-polarized state. r,s and the incident light radiation energy I in the S polarization state i,s The measurement method will be introduced using this example, and the details regarding the radiation energy I of the P-polarized reflected light will not be repeated. r,p and the incident light radiation energy I in the P polarization state i,p The measurement method.

[0144] Specifically, at each specified angle, the reflected light radiation energy I in the S-polarized state r,s and the incident light radiation energy I in the S polarization state i,s The measurement method is as follows:

[0145] 1) Adjust the orientation of the first polarizer 5, the second polarizer 7, and the third polarizer 10 to the S-polarization state; through the rotating arm control unit, rotate the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 to a specified angle, thereby adjusting the incident angle θ of the incident light. i and the reflection angle θ of the reflected light r Equal, both are at a specified angle;

[0146] 2) Light source 1 generates light with a set wavelength λ, which is incident on collimator 3 through optical fiber 2 to generate parallel light; after passing through aperture 4, the parallel light is incident on first polarizer 5 to generate S-polarized light.

[0147] After passing through beam splitter 6, the S-polarized ray is split into beams with an energy ratio of R. a The two mutually perpendicular light rays are the first S-polarized ray and the second S-polarized ray, respectively;

[0148] in:

[0149] The second beam of S-polarized light passes through the second polarizer 7 and is then received by the first detector 8, which detects the radiation energy I of the S-polarized incident light. i,s, after being amplified by the incident light signal amplification unit, is collected by the data collector, and then is received by the data processing controller 19, and after the energy received by the data processing controller 19 is multiplied by (1+R a ), the S-polarization state incident light radiant energy I i,s is obtained.

[0150] The first bundle of S-polarization state light is incident on the surface of the sample to be measured, and after being reflected by the surface of the sample to be measured, the reflected light is formed; after the reflected light passes through the third polarizer 10, the S-polarization state reflected light is generated, and then is received by the second detector 11, and the S-polarization state reflected light radiant energy I r,s is detected, and after being amplified by the reflected light signal amplification unit, is collected by the data collector, and then is received by the data processing controller 19, and thus the S-polarization state reflected light radiant energy I r,s is obtained.

[0151] Step 1.3.2, at each specified angle, the total reflectivity R is obtained by using the following formula:

[0152]

[0153] Step 1.3.3, at each specified angle, the ratio R' p of the P-polarization state reflectivity to the total reflectivity is obtained by using the following formula:

[0154]

[0155] Step 1.4, a coordinate system with the horizontal coordinate being each specified angle and the vertical coordinate being the ratio R' p of the P-polarization state reflectivity to the total reflectivity is established, and each ratio R' p of the P-polarization state reflectivity to the total reflectivity calculated in step 1.3 is marked in the coordinate system, and thus a plurality of discrete points are obtained.

[0156] The plurality of discrete points are subjected to curve fitting, and a parabola is fitted;

[0157] In the parabola, the minimum ratio R' p of the P-polarization state reflectivity to the total reflectivity is found, and thus the measured value θ B of the Brewster angle of the sample to be measured is obtained.

[0158] Specifically, since the R' p component has an angle cosine square correlation, the parabolic fitting is used to improve the measurement accuracy of the Brewster angle, Figure 4 for the measurement angle interval of 0.01°, the measured value θ B of the Brewster angle obtained after the parabolic fitting. Figure 5The measured value of the Brewster angle θ of the sample is obtained by fitting a parabola to the measured values of the angle interval of 0.1° B It can be seen that the accuracy of both can reach 0.01°.

[0159] As shown in Table 1, the Brewster angles of SCHOTT optical glass, standard silicon wafer and distilled water are given, and it can be seen that the accuracy of the Brewster angles of the three samples reaches 0.01°. It shows that the equipment of the application can realize high-precision measurement of the Brewster angle.

[0160] Table 1: Brewster angles of three samples

[0161]

[0162] Step 2: Obtain the total transmittance measurement value T of the sample to be measured at the set light wavelength λ exp :

[0163] Specifically, since the Brewster principle alone cannot give an accurate absorption index, it is necessary to combine the transmission method for measurement. The measurement principle diagram is shown in Figure 6 When measuring, the rotating arm is kept horizontal.

[0164] The specific steps are as follows:

[0165] Step 2.1: The S-polarized state transmittance radiation energy I t,s and the S-polarized state incident radiation energy I i,s , and the P-polarized state transmittance radiation energy I t,p and the P-polarized state incident radiation energy I i,p of the sample to be measured are measured by the transmission method, and the S-polarized state transmittance T s and the P-polarized state transmittance T p are calculated by the following formula:

[0166]

[0167] In this step, the S-polarized state transmittance radiation energy I t,s and the S-polarized state incident radiation energy I i,s of the sample to be measured are measured by the following method:

[0168] 1) Adjust the attitudes of the first polarizer 5, the second polarizer 7 and the third polarizer 10 to be S-polarized state; make the incident light rotating arm 12-1 and the reflected light rotating arm 12-2 both rotate to horizontal state by the rotating arm control unit;

[0169] 2) The light source 1 generates light of a set light wavelength λ, and the S-polarized state light is generated after the light passes through the collimator 3, the aperture 4 and the first polarizer 5 in turn;

[0170] After the S-polarized light passes through the beam splitter 6, it is divided into two beams of mutually perpendicular light with an energy ratio of R a .

[0171] wherein:

[0172] The second S-polarized light is received by the first detector 8 after passing through the second polarizer 7, is amplified by the incident light signal amplification unit, is collected by the data collector, and is then received by the data processing controller 19. After the energy received by the data processing controller 19 is multiplied by (1+R a ), the S-polarized incident light radiant energy I i,s is obtained.

[0173] The first S-polarized light is incident on the surface of the sample to be measured, forms transmitted light after being transmitted by the sample to be measured, and is received by the second detector 11 after passing through the third polarizer 10. After being amplified by the reflected light signal amplification unit, it is collected by the data collector and then received by the data processing controller 19, thereby obtaining the S-polarized transmitted radiant energy I t,s .

[0174] Step 2.2, the total transmittance measurement value T exp of the sample to be measured is calculated using the following formula:

[0175]

[0176] Step 3, equations (1) and (2) are established with respect to the Brewster angle measurement value θ B and the total transmittance measurement value T exp respectively:

[0177]

[0178] wherein:

[0179] m1 is the complex refractive index of air;

[0180] n1 is the refractive index of air;

[0181] κ1 is the absorption index of air;

[0182] m2 is the complex refractive index of the sample to be measured;

[0183] n2 is the refractive index of the sample to be measured;

[0184] κ2 is the absorption index of the sample to be measured;

[0185] i is the imaginary unit;

[0186] In equations (1) and (2), there are two unknown parameters n2 and κ2.

[0187] Specifically, in the measuring system of the application, the Brewster angle measurement value θ of the sample to be measured is measured B and the total transmittance measurement value T exp After that, the complex refractive index can be solved by simultaneously solving equation (1) and equation (2). Since both equations are complex equations containing complex numbers, it is difficult to solve them directly. Therefore, the genetic algorithm inversion method is used to calculate the complex refractive index.

[0188] Where, for equation (1), the principle is as follows: Figure 3 As shown in the figure, it is a schematic diagram of the relationship between the Brewster angle and the refractive index. When natural light is incident on the medium plane, its reflected energy can be represented by two components parallel (P component) and perpendicular (S component) to the incident plane. When the Brewster angle is incident on the medium plane to be measured, the vibration component parallel to the incident plane cannot be reflected at all, and the reflected energy only contains the component perpendicular to the incident plane. According to this characteristic, the relationship between the Brewster angle and the refractive index can be obtained, that is, equation (1).

[0189] Transmittance measurement:

[0190] According to the Beer-Lambert attenuation law of light in a translucent medium, the optical parameters of the sample to be measured are obtained by measuring the transmittance. For a solid medium to be measured, its transmittance can be directly calculated by the Beer-Lambert law. For a liquid medium, a glass-sample-glass three-layer structure is used, and its transmittance is derived by ray tracing method. Specifically as follows:

[0191] As a specific implementation, if the sample to be measured is a solid medium, the expression of f(n2, κ2) is:

[0192]

[0193] Where: L is the thickness of the sample to be measured; α(n2, κ2) is the absorption coefficient of the sample to be measured.

[0194] If the sample to be measured is a liquid medium, the liquid medium is placed in a glass container, and a glass-sample-glass three-layer structure is used. As shown in the figure, it is a schematic diagram of the transmittance measurement principle of the liquid medium, that is: Figure 7

[0195] According to the left-to-right direction, the light is transmitted through the first air layer, the first glass layer, the measured medium layer, and the second glass layer in turn, and then reaches the second air layer;

[0196] The expression of f(n2, κ2) is:

[0197]

[0198] Where:​

[0199] T 01 、T 12 、T 23 、T 30 、T 32 、T 21 , respectively, are: interface transmittance of the first glass layer vertically incident on the first air layer, interface transmittance of the first glass layer vertically incident on the measured medium layer, interface transmittance of the second glass layer vertically incident on the measured medium layer, interface transmittance of the second glass layer vertically incident on the second air layer, interface transmittance of the measured medium layer vertically incident on the first glass layer.

[0200] α1α2α3, respectively, are: absorption coefficients of the first glass layer, the measured medium layer and the second glass layer; wherein, α2 = α2(n2, κ2);

[0201] L1L2L3, respectively, are: thicknesses of the first glass layer, the measured medium layer and the second glass layer;

[0202] R 10 R 12 R 32 R 30 R 21 , respectively, are: interface reflectance of the first glass layer vertically reflecting the first air layer, interface reflectance of the first glass layer vertically reflecting the measured medium layer, interface reflectance of the second glass layer vertically reflecting the measured medium layer, interface reflectance of the second glass layer vertically reflecting the second air layer, interface reflectance of the measured medium layer vertically reflecting the first glass layer.

[0203] Step 4, the absorption index κ2 and the refractive index n2 of the sample to be measured are solved by using genetic algorithm:

[0204] Step 4.1, an optimization objective function F = min{(f(n2, κ2) - T exp ) 2} is established;

[0205] Step 4.2, the initial value n 20 of the refractive index and the initial value κ 20 of the absorption index of the sample to be measured are determined respectively:

[0206] Assuming that the absorption index κ2 of the sample to be measured is 0, the refractive index value obtained by solving equation (1) is the initial value n 20 of the refractive index;

[0207] The total transmittance measurement value T exp is substituted into the following formula, and the absorption index obtained by solving is the initial value κ 20 of the absorption index:

[0208]

[0209] wherein:

[0210] L is the thickness of the sample to be measured;

[0211] ν is the wave number of the incident light, λ is the wavelength of the incident light;

[0212] Step 4.3, the initial value of the refractive index n 20 and the initial value of the absorption index κ 20 As the initial population, the genetic algorithm is used to solve the optimization objective function F established in step 4.1, and the termination condition is: F < 10 -15 , the optimal absorption index κ2 and the refractive index n2 of the sample to be measured are obtained;

[0213] Step 5, according to the formula m2 = n2 + iκ2, the complex refractive index m2 of the sample to be measured is obtained, and the measurement process of the complex refractive index of the sample to be measured is completed.

[0214] The inventors measured and calculated the refractive index and absorption index of deionized water at five wavelengths in the visible-near infrared band, and compared the results with the measurement results of Wang et al. and Segelstein. As shown in Figure 8 , it is a comparison chart of the measurement results of the refractive index of deionized water; as shown in Figure 9 , it is a comparison chart of the measurement results of the absorption index of deionized water.

[0215] From Figure 8 and Figure 9 It can be seen that at five wavelengths, the refractive index and absorption index obtained by the present application can be well consistent with the research results of Wang and Segelstein, the error of the refractive index compared with the results of Wang et al. is less than 0.23%, and the error compared with the results of Segelstein is less than 0.22%; the error of the absorption index compared with the research results of Wang et al. is less than 10.0%, and the error compared with the results of Segelstein is less than 5.5%. Water has weak absorption in the visible light band, and strong internal absorption in the near infrared band. It shows that the Brewster-transmission combined method proposed in the present application has high measurement accuracy for weak absorption and strong absorption media.

[0216] The complex refractive index measurement system and method based on the combination of Brewster transmission has the following advantages: first, by combining the Brewster angle measurement and transmission measurement, the deficiency of the traditional transmission method that cannot measure strong absorption medium can be overcome to a certain extent, and the medium absorption range is relatively wider; second, the method can be applied to different types of media, and the liquid or solid with clean and smooth plane can adopt the method; in addition, the method principle is simple and easy to realize, without processing complex sample container and without complex K-K conversion.

[0217] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method of a complex refractive index measurement system based on Brewster-transmission combination, the complex refractive index measurement system based on Brewster-transmission combination comprising a light source (1), an incident light transmission measurement unit, a reflected light transmission measurement unit, an incident light swing arm (12-1), a reflected light swing arm (12-2), a swing arm control unit, a sample stage (9), an incident light signal amplification unit, a reflected light signal amplification unit, a data collector and a data processing controller (19); the data processing controller (19) is connected with the incident light swing arm (12-1) and the reflected light swing arm (12-2) through the swing arm control unit, and is used for controlling the rotation of the incident light swing arm (12-1) and the reflected light swing arm (12-2) respectively; the incident light swing arm (12-1) and the reflected light swing arm (12-2) intersect at the sample stage (9); the incident light transmission measurement unit is fixedly installed on the incident light swing arm (12-1); and the reflected light transmission measurement unit is fixedly installed on the reflected light swing arm (12-2); a measurement end of the incident light transmission measurement unit is connected to an input end of the data collector through the incident light signal amplification unit; a measurement end of the reflected light transmission measurement unit is connected to an input end of the data collector through the reflected light signal amplification unit; and an output end of the data collector is connected with the data processing controller (19); the incident light transmission measurement unit comprises: a collimator (3), an aperture (4), a first polarizer (5), a beam splitter (6), a second polarizer (7) and a first detector (8); the collimator (3), the aperture (4), the first polarizer (5) and the beam splitter (6) are coaxially arranged in sequence in the light incident direction; the beam splitter (6) outputs two mutually perpendicular light beams, one of which is coaxial with the light incident direction and is incident on the surface of the sample to be measured; and the other of which is perpendicular to the light incident direction, and the exit direction of which is coaxially arranged in sequence with the second polarizer (7) and the first detector (8); a light input end of the collimator (3) is connected with the light source (1) through an optical fiber (2); and an output end of the first detector (8) is connected to an input end of the incident light signal amplification unit; wherein the incident light signal amplification unit comprises a first preamplifier (13) and a first lock-in amplifier (15) arranged in sequence in the light transmission direction; the reflected light transmission measurement unit comprises a third polarizer (10) and a second detector (11) coaxially arranged in sequence in the light reflection direction; and an output end of the second detector (11) is connected to an input end of the reflected light signal amplification unit; wherein the reflected light signal amplification unit comprises a second preamplifier (14) and a second lock-in amplifier (16) arranged in sequence in the light transmission direction. The rotating arm control unit comprises a motion controller (18) and a stepping motor (17); the motion controller (18) is connected with the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) respectively through the stepping motor (17); The method comprises the following steps: Step 1, setting the light wavelength Next, the Brewster angle measurement value of the sample to be measured is obtained ; Step 2, set the wavelength of light Next, the total transmittance measurement of the sample under test is obtained : Step 2.

1. The polarized state of the transmitted radiant energy is measured for the sample under test using the transmission method Polarized state of the transmitted radiant energy and Polarized state of the incident radiant energy and Polarized state of the transmitted radiant energy and Polarized state of the incident radiant energy The polarized state of the transmitted radiant energy is calculated using the following formula Polarized state of the transmitted radiant energy and Polarized state of the transmitted radiant energy : ； Step 2.

2. Calculate the total transmittance measurement of the sample under test from the measurements of the reference sample and the sample under test using the following formula : ； Step 3, equations (1) and (2) are established for the measured values of the Brewster angle and the total transmittance respectively: ； Wherein: Refractive index of air; The refractive index of air; Absorption index for air; n2is the complex refractive index of the sample to be measured; n is the refractive index of the sample to be measured; Absorbance index of the sample to be measured; is the imaginary unit; In equations (1) and (2), there are two unknown parameters and ; Step 4, the absorption index of the sample to be tested is solved by using genetic algorithm and refractive index : Step 4.1, Establishing the optimization objective function ; Step 4.2, determining the initial value of the refractive index and the initial value of the absorption index of the sample to be measured, respectively and the absorption index : Assuming the absorbance index of the sample to be tested Given a value of 0, solve equation (1) to obtain the initial refractive index value. ; The total transmittance measurements Substituting into the following equation, the absorption index obtained by solving is the absorption index initial value : ； Wherein: t is the thickness of the sample to be measured; for the incident light wave number, , for the incident light wavelength; Step 4.3, initial value of refractive index and initial value of absorption index As the initial population, genetic algorithm is used to solve the optimization objective function established in step 4.1 , and the termination condition is: F < 10 -15 , to obtain the optimal absorption index of the sample to be tested and refractive index ; Step 5, obtaining the complex refractive index of the sample under test according to the formula The measurement process of the complex refractive index of the sample under test is completed.​ 2. The method of the complex refractive index measurement system based on the combination of Brewster's transmission and reflection according to claim 1, characterized in that, Step 1 is specifically: Step 1.1, setting the incident angle of the incident light ray the range of rotation and the step value; Step 1.2, in the rotation range of the incident angle , the rotation angle of the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) is controlled respectively by the step value, so that the incident angle of the incident light reaches each designated angle in turn, and at each designated angle, the incident angle of the incident light and the reflection angle of the reflected light are equal; Step 1.3, at each specified angle of rotation by a step value, a value of Ratio of polarized state reflectivity to total reflectivity The method comprises the steps of: Step 1.3.1, at each specified angle, using the following formula, respectively, to obtain Reflectivity of the polarization state and Reflectivity of the polarization state : ； Wherein: : polarization state of the reflected light radiation energy; : polarization state of the incident light radiation energy; : polarization state of the reflected light radiation energy; : polarization state of the incident light radiation energy; Step 1.3.2, at each specified angle, the total reflectance is obtained using the following formula : ； Step 1.3.3, at each specified angle, using the following formula, gives Ratio of polarized state reflectivity to total reflectivity : ； Step 1.

4. Establish a coordinate system with the horizontal axis as the specified angles and the vertical axis as the ratio of the reflectivity of the polarization state to the total reflectivity the coordinate system, and mark the calculated reflectivity of each polarization state in step 1.3 on the coordinate system the ratio of the reflectivity of the polarization state to the total reflectivity , thus obtaining a plurality of discrete points; The multiple discrete points are subjected to curve fitting, and a parabola is fitted; In a parabola, the minimum is found at The ratio of the reflectivity of the polarization state and the total reflectivity The measured value of the Brewster angle of the sample under test is obtained .

3. The method of the complex refractive index measurement system based on the combination of Brewster's transmission and reflection according to claim 2, characterized in that, At each specified angle, Polarization state of reflected light radiant energy And Polarization state of incident light radiant energy The measurement method is: 1) Adjust the attitude of the first polarizer (5), the second polarizer (7) and the third polarizer (10) to S polarization state; through the rotating arm control unit, make the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) rotate to the specified angle, so that the incident angle of the incident light and the reflection angle of the reflected light are equal, both are the specified angle; 2) The light source (1) generates a set light wavelength The light rays pass through the optical fiber (2) and are incident on the collimator (3), producing parallel light rays; after passing through the aperture (4), the parallel light rays are incident on the first polarizer (5), producing S-polarized light rays; After passing through the beam splitter (6), the S-polarized ray is split into two beams with an energy ratio of... The two mutually perpendicular light rays are the first S-polarized ray and the second S-polarized ray, respectively; Wherein: The second beam of S-polarization state light is received by the first detector (8) after passing through the second polarizer (7), and the detection is obtained Polarization state incident light radiation energy , amplified by the incident light signal amplification unit, collected by the data collector, and then received by the data processing controller (19). After the energy received by the data processing controller (19) is multiplied by (1+ ), the following is obtained Polarization state incident light radiation energy ; The first beam of S-polarized light is incident on the surface of the sample to be measured, and after being reflected by the surface of the sample to be measured, the reflected light is formed; after the reflected light passes through the third polarizer (10), the S-polarized reflected light is generated, and then the second detector (11) receives it, and the detection is obtained The energy of the polarized reflected light radiation After being amplified by the reflected light signal amplification unit, it is collected by the data collector, and then received by the data processing controller (19), thereby obtaining The energy of the polarized reflected light radiation .

4. The method of the Brewster-transmission combination-based complex refractive index measurement system according to claim 1, characterized by, In step 2.1, the polarization state of the transmitted radiant energy of the sample under test polarization state of the transmitted radiant energy and polarization state of the incident radiant energy is measured by the following method: 1) Adjust the first polarizer (5), the second polarizer (7) and the third polarizer (10) to be in a S polarization state; through the rotating arm control unit, the incident light rotating arm (12-1) and the reflected light rotating arm (12-2) are rotated to a horizontal state; 2) The light source (1) generates a set light wavelength The light rays pass through the collimator (3), aperture (4) and first polarizer (5) in sequence to produce S-polarized light rays; After passing through the beam splitter (6), the S-polarized ray is split into two beams with an energy ratio of... The two mutually perpendicular light rays are the first S-polarized ray and the second S-polarized ray, respectively; Wherein: The second beam of S polarization state light passes through the second polarizer (7) and is received by the first detector (8). After being amplified by the incident light signal amplification unit, it is collected by the data collector and then received by the data processing controller (19). After the energy received by the data processing controller (19) is multiplied by (1+ ), the polarization state incident light radiation energy is obtained. ; The first beam of S-polarized light is incident on the surface of the sample to be measured, and after being transmitted through the sample to be measured, the transmitted light is formed; the transmitted light passes through the third polarizer (10) and is received by the second detector (11), is amplified by the reflected light signal amplification unit, is collected by the data collector, and then is received by the data processing controller (19), thereby obtaining Polarization state of the transmitted radiation energy .

5. The method of the Brewster-transmission combination-based complex refractive index measurement system according to claim 1, characterized by, If the sample to be measured is a solid medium, then The expression is: ； wherein: is the thickness of the sample to be measured; is the absorption coefficient of the sample to be measured.

6. The method of the Brewster-transmission combination-based complex refractive index measurement system according to claim 1, wherein, If the sample to be measured is a liquid medium, the liquid medium is placed in a glass container, and a glass-sample-glass three-layer structure is adopted, that is: In the direction from left to right, the light is transmitted through the first air layer, the first glass layer, the measured medium layer and the second glass layer in sequence, and then reaches the second air layer; Then The expression is: ； Wherein: , , , , , , respectively: the interface transmittance when the first air layer is normally incident on the first glass layer, the interface transmittance when the first glass layer is normally incident on the measured medium layer, the interface transmittance when the measured medium layer is normally incident on the second glass layer, the interface transmittance when the second glass layer is normally incident on the second air layer, the interface transmittance when the second glass layer is normally incident on the measured medium layer, and the interface transmittance when the measured medium layer is normally incident on the first glass layer. , respectively: absorption coefficients of the 1st glass layer, the measured medium layer and the 2nd glass layer; wherein, ; , respectively: thickness of the 1st glass layer, the measured medium layer and the 2nd glass layer; R1, R2, R3, and R4 are the interface reflectivities of the first glass layer vertically reflecting the first air layer, the first glass layer vertically reflecting the measured medium layer, the second glass layer vertically reflecting the measured medium layer, the second glass layer vertically reflecting the second air layer, and the measured medium layer vertically reflecting the first glass layer, respectively.

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