Optical chemical sensor device

Abstract

To provide an optical chemical sensor device that is highly accurate and inexpensive and can be reduced in size.SOLUTION: An optical chemical sensor device includes a sensor unit 10, a single color optical laser light source 20, a linear polarizer unit 30, a light-receiving unit 40, and a calculation unit 50. The sensor unit 10 has a substrate 11 and an optical resonator 12 disposed thereon, and has an analysis object adhered thereto. The linear polarizer unit 30 receives the incidence of transmission light that transmits through the sensor unit 10, and forms linear polarized light. The light-receiving unit 40 receives the linear polarized light that transmits through the linear polarizer unit 30, and detects an x-polarization component and a y-polarization component. The calculation unit 50, by using complex amplitudes of the x-polarization component and the y-polarization component received by the light-receiving unit 40, calculates Stokes parameters in a unique polarized state of the optical resonator 12 in the sensor unit 10 in a Jones matrix of a measurement system and measures physical properties of the analysis object by the change in the Stokes parameters by the analysis object that adheres to the sensor unit 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical chemical sensor device, and more particularly to an optical chemical sensor device that measures the physical properties of an analyte by utilizing changes in refractive index. [Background technology]

[0002] Optical chemical sensors are known as devices for non-invasive, highly accurate chemical analysis of analytes. For example, a surface plasmon sensor that utilizes surface plasmon resonance is known. Surface plasmon sensors measure physical properties by irradiating a metal surface with white light at varying angles of incidence and detecting changes in a specific resonance frequency.

[0003] Surface plasmon sensor devices that utilize surface plasmon resonance require spectral analysis using white light, which necessitates a white light source. This can lead to the light source itself being large. Furthermore, the angle of incidence of the white light must be physically changed, which necessitates a mechanical mechanism. Therefore, increasing the size of the device or increasing the accuracy of the angle of incidence inevitably makes it expensive.

[0004] Also known is a measurement device that measures the polarization state of light transmitted through an object to be analyzed, as described in Patent Document 1, for example. The measurement device in Patent Document 1 includes a light source, a modulation unit consisting of a retarder and an analyzer that modulates light emitted from the light source and transmitted through the sample, and a spectrophotometer with a diffraction grating for acquiring light intensity information of the modulated light. The retarder is physically rotated, and optical characteristic elements are calculated based on the theoretical formula for the light intensity of the modulated light modulated by the sample and the light intensity information of the modulated light. Examples of optical characteristic elements include birefringence phase difference, principal axis orientation, optical rotation, Stokes parameters, Mueller matrix elements, and Jones matrix elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-85853 Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned surface plasmon sensor device requires a mechanical mechanism for changing the angle of incidence. Furthermore, in Patent Document 1, a mechanical mechanism for changing the polarization state is required because circularly polarized light is used. This not only makes it difficult to miniaturize these sensor devices, but also makes them expensive because the angle adjustment accuracy directly affects the measurement accuracy, necessitating the use of a highly accurate mechanical mechanism for highly accurate measurements.

[0007] Furthermore, in Patent Document 1, for example, when measuring the Jones matrix, it was necessary to introduce x-polarized light and y-polarized light and measure the polarization states, i.e., amplitude and phase, of the linearly polarized and circularly polarized light that had passed through the object to be analyzed. This required multiple wave plates and a mechanical rotation mechanism. Furthermore, it was necessary to separate the modulated light that had passed through the object to be analyzed into individual wavelengths using a diffraction grating. Furthermore, the transmitted light from the object to be analyzed was measured directly without being amplified.

[0008] Therefore, we aimed to develop a device that does not receive circularly polarized light, does not require splitting, and can be constructed inexpensively.

[0009] In view of the above circumstances, the present invention aims to provide an optical chemical sensor device that is highly accurate, inexpensive, and can be made smaller. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object of the present invention, the optical chemical sensor device of the present invention comprises a sensor section having a substrate and an optical resonator arranged on the substrate, which is a coupled system with dipole resonance in the x-axis and y-axis, and to which an analyte is attached; a monochromatic laser light source that irradiates the sensor section with x-polarized and y-polarized monochromatic lasers that are transmissive to the substrate of the sensor section; a linear polarizer section that receives the transmitted light that passes through the sensor section and converts it into linearly polarized light; a light receiving section that receives the linearly polarized light that passes through the linear polarizer section and detects the x-polarized and y-polarized components; and a calculation section that uses the complex amplitudes of the x-polarized and y-polarized components received by the light receiving section to calculate the Stokes parameters of the eigenpolarization state of the optical resonator of the sensor section in the Jones matrix of the measurement system, and measures the physical properties of the analyte from changes in the Stokes parameters due to the analyte attaching to the sensor section.

[0011] Here, the optical resonator of the sensor section may be a coupled plasmonic resonator or a coupled photonic resonator made up of two coupled bodies arranged such that their longitudinal directions are at 90 degrees to each other.

[0012] Furthermore, the optical resonator of the sensor section only needs to adjust the binding amounts of the two binders so that the Jones matrix has an exceptional point when no analyte is attached to the sensor section.

[0013] The optical resonator of the sensor section may be any one that allows the two combined bodies to have different dimensions.

[0014] Furthermore, the optical resonator of the sensor section may be one in which a phase change material is loaded on one of the two combined bodies.

[0015] Furthermore, the linear polarizer section may have four regions with the rotation angle of the transmission axis shifted by 45 degrees, and the light receiving section may consist of four light receiving elements that receive the linearly polarized light transmitted through each of the four regions of the linear polarizer section.

[0016] The calculation unit may be any unit that determines in advance the direction of rotation of the circularly polarized component of the Stokes parameters of the eigenpolarization state, diagonalizes the Jones matrix, and then calculates the Stokes parameters. [Effects of the Invention]

[0017] The optical chemical sensor device of the present invention has the advantages of being highly accurate, inexpensive, and capable of being miniaturized. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic block diagram illustrating an optical chemical sensor device of the present invention. [Figure 2] FIG. 2 is a schematic front view illustrating the linear polarizer portion of the optical chemical sensor device of the present invention. [Figure 3] FIG. 3 is a schematic plan view for explaining the sensor section of the photochemical sensor device of the present invention. [Figure 4] FIG. 4 is a schematic graph of the output of the sensor portion of the optical chemical sensor device of the present invention relative to perturbation of the analyte. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic block diagram illustrating an optical chemical sensor device of the present invention. The optical chemical sensor device measures the physical properties of an analyte by utilizing changes in refractive index. The optical chemical sensor device can be used, for example, as a biosensor device. As shown in the figure, the optical chemical sensor device of the present invention is mainly composed of a sensor unit 10, a monochromatic laser light source 20, a linear polarizer unit 30, a light receiving unit 40, and a calculation unit 50.

[0020] The sensor unit 10 is a device to which an analyte is attached. The sensor unit 10 comprises a substrate 11 and an optical resonator 12. The optical resonator 12 is disposed on the substrate 11. The optical resonator 12 is a coupled system with dipole resonance along the x-axis and y-axis. Specifically, the optical resonator 12 may be, for example, a coupled plasmonic resonator or a coupled photonic resonator of nanostructures. The optical resonator 12 amplifies the interaction between a monochromatic laser beam perpendicularly incident on the sensor unit 10 and the molecules of the nanostructure. In other words, the change in refractive index is enhanced. Any device may be capable of measuring the physical properties of an analyte by attaching the analyte near the optical resonator 12 and utilizing the change in refractive index due to the presence or absence of the analyte. For example, a receptor such as an enzyme, antibody, nucleic acid, or microorganism may be immobilized on the sensor unit 10, and the analyte may be selectively attached to this receptor. The sensor unit 10 amplifies monochromatic light from a monochromatic laser light source 20 (described later) using an optical resonator 12, enabling highly accurate measurement of perturbations in an analyte. In the illustrated example, the optical resonator 12 is disposed on the surface of the substrate 11 facing the monochromatic laser light source 20. However, as described later, the monochromatic light from the monochromatic laser light source 20 is capable of transmitting through the substrate 11. Therefore, the optical resonator 12 may be disposed on the surface of the substrate 11 opposite to the surface facing the monochromatic laser light source 20. Similarly, the surface to which the analyte is attached may be either surface. Details of the sensor unit 10 will be described later. In this way, the sensor unit 10 has reciprocity.

[0021] The monochromatic laser light source 20 irradiates the sensor unit 10 with a monochromatic laser. The monochromatic laser may be any laser that is transmissive to the substrate 11 of the sensor unit 10. The monochromatic laser light source 20 may be any laser that is capable of irradiating the sensor unit 10 with x-polarized and y-polarized monochromatic lasers. The monochromatic laser light source 20 may be, for example, a semiconductor laser light source, and any existing or future developed light source may be used.

[0022] The transmitted light that passes through the sensor unit 10 is incident on the linear polarizer unit 30. The linear polarizer unit 30 may be any unit that converts the incident light into linearly polarized light. Specifically, the linear polarizer unit 30 may be any unit that obtains linearly polarized light with a rotation angle shifted by 45 degrees from the incident light. The type of polarizer used in the linear polarizer unit 30 is not particularly limited, and any existing or future developed polarizers, such as a wire grid type or a crystalline type, may be used.

[0023] The linear polarizer unit 30 will be described in detail with reference to FIG. 2. FIG. 2 is a schematic front view illustrating the linear polarizer unit of the photochemical sensor device of the present invention. As shown in the figure, the linear polarizer unit 30 may be configured to have four regions, each with a transmission axis rotation angle shifted by 45 degrees. More specifically, the linear polarizer unit 30 has four regions with transmission axes of 0 degrees, 45 degrees, -45 degrees, and 90 degrees. This makes it possible to convert incident light into linearly polarized light with rotation angles shifted by 45 degrees without using a mechanical mechanism for physically rotating the linear polarizer. When using such a linear polarizer unit 30, the monochromatic laser light source 20 may be a monochromatic laser light source that has a constant radiant intensity for a predetermined region, such as a flat-top beam, so that the monochromatic laser light can be incident on all four regions. Note that if miniaturization of the photochemical sensor device is not particularly required, the linear polarizer unit 30 may of course be configured using a mechanical mechanism for physically rotating the linear polarizer by 45 degrees.

[0024] The light receiving unit 40 receives the linearly polarized light that passes through the linear polarizer unit 30. The light receiving unit 40 detects the x-polarized component and the y-polarized component from the linearly polarized light. The light receiving unit 40 may be any element that includes a photoelectric conversion element capable of converting light into an electrical signal, such as a photodiode. As described above, if the linear polarizer unit 30 has, for example, four regions, the light receiving unit 40 may be any element that includes four light receiving elements that respectively receive the linearly polarized light that passes through each of the four regions of the linear polarizer unit 30. Alternatively, the light receiving unit 40 may be an area sensor, such as a CCD sensor or CMOS sensor, in which photodiodes are arranged in an array and light in a predetermined range covering the four regions is converted into an electrical signal.

[0025] The calculation unit 50 measures the physical properties of the analyte using the complex amplitudes of the x-polarized and y-polarized components received by the light receiving unit 40. Specifically, the calculation unit 50 uses the complex amplitudes of the x-polarized and y-polarized components obtained from the x-polarized and y-polarized monochromatic lasers emitted by the monochromatic laser light source 20. These complex amplitudes are then used to complete the Jones matrix and calculate the Stokes parameters of the eigenpolarization states. Conventional photochemical sensors measure the physical properties of the analyte using changes in resonance frequency from the spectrum. In contrast, the photochemical sensor device of the present invention measures the physical properties of the analyte by measuring changes in the complex amplitudes of the x-polarized and y-polarized components as changes in the Stokes parameters. The photochemical sensor device of the present invention assumes a relationship, i.e., symmetry, that the eigenpolarization states of the measurement system must satisfy. This makes it possible to use the Jones matrix even when using a linear polarizer unit 30 that generates only linearly polarized light. Therefore, by reconstructing the Jones matrix using only the linear polarizer unit 30 and calculating the Stokes parameters for each eigenpolarization state from the Jones matrix, it is possible to measure the physical properties of the analyte at a single wavelength.

[0026] The calculation unit 50 measures the physical properties of the analyte based on the changes in the Stokes parameters thus obtained. In other words, perturbations of the analyte adhering to the sensor unit 10 are directly reflected in changes in the Stokes parameters, and measuring these changes reveals the physical properties of the analyte. For example, when the photochemical sensor device of the present invention is used as a biosensor, quantum interactions with a biological substance as the analyte can be detected as an optical signal. For example, a receptor such as an enzyme, antibody, nucleic acid, or microorganism can be immobilized on the sensor unit 10 in advance, and the Stokes parameters can be measured. Using this as the initial state, changes in the Stokes parameters can be measured when the analyte is adhering to the receptor on the sensor unit 10, and the physical properties of the analyte can be measured by comparing the results with the initial state. It is also possible to measure changes in the analyte in real time by measuring changes in the Stokes parameters with the analyte adhering. The calculation method used by the calculation unit 50 will be described in detail below. The calculation unit 50 may be, for example, an electronic computer such as a microcomputer or a personal computer.

[0027] The optical chemical sensor device of the present invention configured as described above can be realized using only semiconductor elements such as a monochromatic laser light source and a photodiode, making it possible to reduce the size of the device. Furthermore, since only a linear polarizer is used, there is no need for angular resolution, and the measurement system is stably maintained under the same conditions, making it possible to measure physical properties inexpensively and with high accuracy. Furthermore, if no mechanical mechanism is used, the device can be further reduced in size.

[0028] Next, the sensor unit 10 will be described in detail using FIG. 3. FIG. 3 is a schematic plan view illustrating the sensor unit of the optical chemical sensor device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. As shown in the figure, the sensor unit 10 comprises a substrate 11 and an optical resonator 12. The optical resonator 12 may be a coupled system with dipole resonance along the x-axis and y-axis, specifically, two coupled bodies 12a and 12b. The coupled bodies 12a and 12b are arranged so that their longitudinal directions are at a 90-degree angle. That is, the coupled bodies 12a and 12b are arranged so that their longitudinal directions are oriented in the x-axis and y-axis directions, respectively. More specifically, as shown in the figure, the two coupled bodies 12a and 12b are arranged in a T-shape. In this way, the optical resonator 12 may be a coupled system with dipole resonance along the x-axis and y-axis. Such an optical resonator 12, which is a coupled system with dipole resonance, can obtain two eigenvalues ​​and eigenstates.

[0029] The two coupled bodies 12a and 12b of the optical resonator 12 may be, for example, metal bodies. When the two coupled bodies 12a and 12b are made of metal bodies, the optical resonator 12 becomes a coupled plasmonic resonator. Furthermore, the two coupled bodies 12a and 12b may be made of a dielectric material. When the two coupled bodies 12a and 12b are made of a dielectric material, the optical resonator 12 becomes a coupled photonic resonator.

[0030] Below, we will explain in detail the Jones matrix of the measurement system using such a sensor unit 10. First, the relationship between the light incident on the linear polarizer unit 30 and the light transmitted through the linear polarizer unit 30 is defined as follows.

number

[0031] Furthermore, since the measurement system between the monochromatic laser light source 20 and the light receiving unit 40 has reciprocity, the following relationship holds for the individual elements of the Jones matrix.

number

[0032] Here, when the light incident on the linear polarizer section 30 is light that has passed through the sensor section 10 configured as a coupled system having dipole resonance as shown in FIG. 3, the following relationship holds.

number

[0033] From this, the following relationship can be derived:

number

[0034] In the case of the sensor section 10 configured as a coupled system having dipole resonance, the following relationship holds:

number

[0035] Therefore, the Jones matrix finally has the following relationship:

number

[0036] Next, the Stokes parameters of the measurement system, which are the eigenpolarization state, can be expressed only by the light intensity as shown in the following equation (7). xx ,t yy is expressed as a Stokes parameter.

number

[0037] Here, the rotation direction of the circular polarization component S3 of the Stokes parameters of the eigenpolarization state can be determined in advance. That is, whether the circular polarization component S3 of the Stokes parameters of the eigenpolarization state is clockwise or counterclockwise depends on the measurement system used, and therefore can be determined in advance by simulation. Specifically, it can be determined by simulation whether the right side of the circular polarization component S3 is positive or negative.

[0038] Then, when the Stokes parameters of the eigenpolarization state are expressed by complex amplitude, the following equation 8 is obtained: That is, equation 8 expresses the eigenvectors of the Jones matrix in terms of Stokes parameters.

number

[0039] The calculation unit 50 calculates the Stokes parameters of the eigenpolarization state of the optical resonator 12 of the sensor unit 10 in the Jones matrix of the measurement system using the complex amplitudes of the x-polarized component and the y-polarized component received by the light receiving unit 40. Specifically, first, x-polarized light is incident from the monochromatic laser light source 20. Then, the intensities of four types of light, 0 degrees, 45 degrees, -45 degrees, and 90 degrees, are obtained, which are transmitted through the sensor unit 10 and the linear polarizer unit 30 and received by the light receiving unit 40. Then, using Equation 7, t xx ,t yxNext, y-polarized light is incident from the monochromatic laser light source 20. Then, the light passes through the sensor unit 10 and the linear polarizer unit 30, and is received by the light receiving unit 40, and four types of light intensity at 0 degrees, 45 degrees, -45 degrees, and 90 degrees are obtained. Then, using Equation 7, t xy ,t yy At this time, by using the relationship in equation 2, the four elements t xx ,t xy ,t yx ,t yy The phase relationship between these two is determined. This completes the Jones matrix T. The completed Jones matrix T is then diagonalized to determine two eigenpolarization states. That is, two eigenvectors are obtained, which are expressed as complex amplitudes. Each eigenvector is then used as a Stokes parameter using equation 8. Using the Stokes parameters thus determined, the calculation unit 50 can measure the physical properties of the analyte from changes in the Stokes parameters due to the analyte adhering to the sensor unit 10.

[0040] Next, we will explain how to further improve the accuracy of the optical chemical sensor device of the present invention. In order to improve the accuracy of the optical chemical sensor device of the present invention, the optical resonator 12 of the sensor unit 10 can be configured so that the Jones matrix has an exceptional point. Note that an exceptional point refers to a unique situation in which two eigenvalues ​​and eigenstates are obtained in the optical resonator 12, but these are unique.

[0041] First, the change in the resonant frequency in the eigenpolarization state is expressed by the following equation.

number

number

[0042] If the two coupled bodies 12a and 12b of the optical resonator 12 are configured so that Δ in the number 10 is 0, the Jones matrix will have an exceptional point. That is, the coupling amount of the two coupled bodies 12a and 12b of the optical resonator 12 in the sensor unit 10 can be adjusted so that Δ is 0. The two coupled bodies 12a and 12b are configured as a non-Hermitian coupled system with space-time reversal symmetry (PT symmetry) and have an exceptional point. Here, PT symmetry is a symmetry in which the system is invariant when a spatially inverting operation P and a temporally inverting operation T are performed simultaneously.

[0043] Specifically, by differentiating the dimensions of the two coupled bodies 12a and 12b, for example, and thereby creating a difference in loss, it is possible to effectively achieve PT symmetry. Furthermore, by loading one of the two coupled bodies 12a and 12b with a phase-change material, it is possible to similarly create a difference in loss and effectively achieve PT symmetry. Furthermore, by adjusting the shift amount in the x-axis direction of one coupled body 12b of the two coupled bodies 12a and 12b arranged in a T-shape, it is possible to configure the device so that it has an exceptional point at a specific frequency. In other words, the frequency of the exceptional point can be adjusted by the shift amount.

[0044] Figure 4 shows a schematic graph of the output of the sensor section of the optical chemical sensor device of the present invention in response to perturbations in the analyte. That is, it is a graph of wavelength change versus refractive index change. As shown by the dotted line in the figure, if the Jones matrix does not have an exceptional point, the wavelength change is proportional to the refractive index change. However, if the Jones matrix is ​​configured to have an exceptional point, as shown by the solid line, the wavelength change is proportional to the square root of the refractive index change near the exceptional point due to square root dependence. In other words, the sensitivity is improved by a factor of two. Because the exceptional point state is immediately destroyed by even a slight perturbation of the analyte, it is clear that a highly sensitive sensor can be constructed by using such a small perturbation region.

[0045] The optical chemical sensor device of the present invention is not limited to the above-described illustrated example, and various modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0046] 10 Sensor section 11 Circuit Board 12 Optical resonator 12a,12b conjugate 20 Monochromatic laser light source 30 Linear polarizer section 40 Light receiving part 50 Arithmetic section

Claims

1. An optical chemical sensor device for measuring a physical property of an object to be analyzed by utilizing a change in refractive index, the optical chemical sensor device comprising: a sensor unit having a substrate and an optical resonator, which is a coupled system having dipole resonance in the x-axis and y-axis, disposed thereon, to which an analyte is attached; a monochromatic laser light source that irradiates the sensor unit with x-polarized and y-polarized monochromatic laser light that can be transmitted through the substrate of the sensor unit; a linear polarizer unit that receives transmitted light passing through the sensor unit and converts the transmitted light into linearly polarized light; a light receiving unit that receives the linearly polarized light transmitted through the linear polarizer unit and detects the x-polarized component and the y-polarized component; a calculation unit that calculates Stokes parameters of the eigenpolarization state of the optical resonator of the sensor unit in the Jones matrix of the measurement system using the complex amplitudes of the x-polarized component and the y-polarized component received by the light receiving unit, and measures the physical properties of the analyte from changes in the Stokes parameters due to the analyte adhering to the sensor unit; An optical chemical sensor device comprising:

2. 2. The optical chemical sensor device according to claim 1, wherein the optical resonator of the sensor unit is a coupled plasmonic resonator or a coupled photonic resonator consisting of two coupled bodies arranged so that their longitudinal directions are at 90 degrees to each other.

3. 3. The optical chemical sensor device according to claim 2, wherein the optical resonator of the sensor unit adjusts the amount of binding of the two binding entities so that the Jones matrix has an exceptional point when no analyte is attached to the sensor unit.

4. 4. The optical chemical sensor device according to claim 3, wherein the optical resonator of said sensor section has two combined bodies with different sizes.

5. 4. The optical chemical sensor device according to claim 3, wherein the optical resonator of said sensor section is configured such that a phase change material is loaded on one of two combined bodies.

6. The optical chemical sensor device according to claim 1, the linear polarizer portion has four regions whose transmission axes are rotated by 45 degrees, the light receiving section includes four light receiving elements that receive linearly polarized light transmitted through each of the four regions of the linear polarizer section, An optical chemical sensor device characterized by:

7. 2. The photochemical sensor device according to claim 1, wherein the calculation unit predetermines the direction of rotation of the circularly polarized component of the Stokes parameters of the eigenpolarization state, diagonalizes the Jones matrix, and then calculates the Stokes parameters.

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