Detection device

Abstract

Provided is a detection device for which the degree of freedom of optical design can be increased, while simplifying the entire device.　A detection device 1 that utilizes surface plasmon resonance is provided with: a light source 2; a sensor part 3 including an optical prism 5 and a thin metal film 6, the optical prism 5 having a light incident surface 5a, a bottom surface 5b, and a light emitting surface 5c, and the thin metal film 6 being provided on the bottom surface 5b of the optical prism 5 and reflecting light emitted from the light source 2 and incident on the light incident surface 5a to the light emitting surface 5c side; and a detector 4 that detects the light reflected by the thin metal film 6 of the sensor part 3. The optical prism 5 is formed of a material having a refractive index nd of 1.8-4.0. In the optical prism 5, the angle formed by the light incident surface 5a and the light emitting surface 5c is 5°-170°, an optical axis X1 of the light incident on the light incident surface 5a and the bottom surface 5b of the optical prism 5 are substantially perpendicular to each other, and an optical axis X2 of the light emitted from the light emitting surface 5c and the bottom surface 5b of the optical prism 5 are substantially perpendicular to each other.

Description

Detection device

[0001] The present invention relates to a detection device that utilizes surface plasmon resonance.

[0002] Conventionally, detection devices utilizing surface plasmon resonance have been known. Because the resonance conditions of surface plasmons are sensitive to the presence or absence of a substance near the surface and the refractive index, detection devices utilizing surface plasmon resonance can be used as highly sensitive means for detecting substances. For example, detection devices utilizing surface plasmons can measure minute changes in the refractive index of a measurement object, and are therefore used in fields such as refractive index sensors, biosensors, and chemical sensors.

[0003] The following Patent Document 1 discloses a detection device equipped with a sensor unit having a prism and a flat plate provided below the prism and having a metal film attached to its bottom surface. Patent Document 1 describes that by utilizing surface plasmon resonance generated by total reflection of light incident on the prism at the interface between the flat plate and the metal film, it is possible to measure changes in the refractive index of a measurement object placed on the surface of the metal film, and to measure, for example, protein interactions within cells such as immune reactions.

[0004] Japanese Patent Application Laid-Open No. 2008-191053

[0005] However, a detection device using surface plasmons usually requires a mechanical mechanism for precisely controlling the angle of incidence and the angle of reflection using a rotary stage or the like, and therefore there is a demand for simplification and miniaturization of the entire device. Furthermore, a detection device such as that disclosed in Patent Document 1 has a problem in that it is difficult to increase the degree of freedom in optical design while simplifying the entire device.

[0006] An object of the present invention is to provide a detection device that can simplify the entire device while increasing the degree of freedom in optical design.

[0007] Hereinafter, various aspects of the detection device that solve the above problems will be described.

[0008] A detection device according to a first aspect of the present invention is a detection device that utilizes surface plasmon resonance, and includes: a light source; an optical prism having a light incident surface, a bottom surface, and a light exit surface; a sensor unit provided on the bottom surface of the optical prism and having a metal thin film that reflects light emitted from the light source and incident on the light incident surface toward the light exit surface; and a detector that detects the light reflected by the metal thin film of the sensor unit, wherein the optical prism is made of a material having a refractive index nd of 1.8 or more and 4.0 or less, the angle between the light incident surface and the light exit surface of the optical prism is 5° or more and 170° or less, the optical axis of the incident light that enters the light incident surface and the bottom surface of the optical prism are approximately perpendicular, and the optical axis of the exit light that exits from the light exit surface and the bottom surface of the optical prism are approximately perpendicular. In the optical prism, the light incident surface refers to the surface on which light enters the optical prism from the outside, and the light exit surface refers to the surface on which light exits the optical prism to the outside.

[0009] In the detection device according to Aspect 2, in Aspect 1, it is preferable that the refractive index nd of the glass constituting the optical prism is 1.8 or more and 3.0 or less.

[0010] In the detection device according to Aspect 3, it is preferable that in the optical prism according to Aspect 1 or Aspect 2, the angle formed between the light entrance surface and the light exit surface is less than 90°.

[0011] In the detection device according to aspect 4, in any one of aspects 1 to 3, it is preferable that the cross-sectional shape of the optical prism is trapezoidal, the light incident surface is arranged on one hypotenuse of the trapezoid, and the light exit surface is arranged on the other hypotenuse of the trapezoid.

[0012] In the detection device according to Aspect 5, in any one of Aspects 1 to 4, it is preferable that the wavelength of the light emitted from the light source is not less than 600 nm and not more than 1500 nm.

[0013] In the detection device according to Aspect 6, in any one of Aspects 1 to 5, the refractive index sensitivity is preferably 1000 nm / RIU or more and 30000 nm / RIU or less.

[0014] According to the present invention, it is possible to provide a detection device that can simplify the entire device while increasing the degree of freedom in optical design.

[0015] FIG. 1 is a schematic diagram illustrating a detection device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a detection device according to a second embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a detection device according to a third embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a detection device according to a fourth embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a detection device according to a modified example of the fourth embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a method for determining the apex angle α at which surface plasmon resonance occurs in the detection device according to the second embodiment of the present invention. FIG. 7 is a graph plotting equations (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 1.5. FIG. 8 is a graph plotting equations (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 1.86. FIG. 9 is a graph plotting Equations (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 2.0. FIG. 10 is a graph plotting Equations (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 2.5. FIG. 11 is a graph plotting Equations (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 3.0. FIG. 12 is a graph showing the relationship between the wavelength of incident light and the reflectance when the refractive index nd of the material constituting the optical prism is 2.0 and the apex angle α is 30° in a detection device according to a second embodiment of the present invention. FIG. 13 is a graph showing the relationship between the wavelength of incident light and the reflectance when the refractive index nd of the material constituting the optical prism is 2.0 and the apex angle α is 35° in a detection device according to the second embodiment of the present invention. Fig. 14 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 2.0 in the detection device according to the second embodiment of the present invention. Fig. 15 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 2.0 in the detection device according to the second embodiment of the present invention.FIG. 16 is a graph showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 1.86 in the detection device according to the second embodiment of the present invention. FIG. 17 is a graph showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 1.86 in the detection device according to the second embodiment of the present invention. FIG. 18 is a graph showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 2.5 in the detection device according to the second embodiment of the present invention. FIG. 19 is a graph showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 2.5 in the detection device according to the second embodiment of the present invention. FIG. 20 is a graph showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 3.0 in the detection device according to the second embodiment of the present invention. FIG. 21 is a graph showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 3.0 in the detection device according to the second embodiment of the present invention. FIG. 22 is a graph showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 3.5 in the detection device according to the second embodiment of the present invention. FIG. 23 is a graph showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 3.5 in the detection device according to the second embodiment of the present invention. FIG. 24 is a graph showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 4.0 in the detection device according to the second embodiment of the present invention. FIG. 25 is a graph showing the relationship between the apex angle α and the refractive index of the mixture of water and ethanol in Example 1. FIG. 27 is a graph showing the change in the resonance wavelength versus exposure time (elapsed measurement time) when an aminohexadecanethiol aqueous solution is exposed to the surface of the gold thin film on the bottom surface of the glass prism in Example 2. FIG. 28 is a diagram showing the relationship between the ethanol concentration and the refractive index of a mixed solution of water and ethanol in Example 3.29 is a diagram showing the change in the resonant wavelength versus the exposure time (elapsed measurement time) when an aminohexadecanethiol aqueous solution is exposed to the surface of the gold thin film on the bottom surface of the glass prism in Example 4. FIG. 29 is a diagram showing a schematic configuration of a detection device of a comparative example.

[0016] Preferred embodiments of the present invention will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0017] [Detection Apparatus] (First Embodiment) FIG. 1 is a diagram schematically illustrating the configuration of a detection apparatus according to a first embodiment of the present invention.

[0018] 1, the detection device 1 includes a light source 2, a sensor unit 3, and a detector 4. The sensor unit 3 also includes an optical prism 5 and a metal thin film 6.

[0019] The optical prism 5 has a light incident surface 5a, a bottom surface 5b, and a light exit surface 5c. In this embodiment, the shape of the optical prism 5 is a triangular prism, and the cross-sectional shape of the optical prism 5 is a triangle. In particular, in this embodiment, the cross-sectional shape of the optical prism 5 is an isosceles triangle. However, the shape of the optical prism 5 is not particularly limited, and for example, the cross-sectional shape of the optical prism 5 may be a trapezoid (e.g., an isosceles trapezoid). The metal thin film 6 is provided on the bottom surface 5b of the optical prism 5. When the cross-sectional shape of the optical prism 5 is an isosceles triangle as in this embodiment, the length of the base can be, for example, 5 mm to 20 mm, and the height can be, for example, 5 mm to 100 mm. However, the dimensions of the optical prism 5 are not particularly limited and can be determined appropriately depending on the application of the detection device 1 and the wavelength of light used.

[0020] In the detection device 1, light emitted from the light source 2 is collimated by an optical lens and enters a polarizing filter (the optical lens and polarizing filter are not shown in FIG. 1 ). The polarizing filter separates the light into an s-polarized component and a p-polarized component, of which the p-polarized component (hereinafter sometimes simply referred to as light) exits toward the optical prism 5. The light that reaches the optical prism 5 is refracted at the light entrance surface 5a and travels toward the bottom surface 5b. The light that reaches the bottom surface 5b is reflected by the metal thin film 6 and travels toward the light exit surface 5c. The light that reaches the light exit surface 5c is refracted at the light exit surface 5c, collected by the optical lens, and travels toward the detector 4. In this manner, in the detection device 1, light reaches the detector 4 and is detected.

[0021] The detection device 1 of this embodiment is configured so that light reaching the bottom surface 5b of the optical prism 5 is totally reflected by the metal thin film 6. In this detection device 1, surface plasmon resonance (propagating surface plasmon resonance) occurs at a specific incident resonance angle and wavelength. At this time, the resonance wavelength changes due to changes in the refractive index of the detection target 10 and the adsorption and desorption of substances to and from the surface 6a of the metal thin film 6. By measuring or sensing these changes, it is possible to track changes in the refractive index nd of the detection target 10, or to detect substances contained in the detection target 10 and to track changes in the state of the substances. Therefore, the detection device 1 can be used by placing the detection target 10 on the surface 6a of the metal thin film 6, and can be used in fields such as refractive index sensors, biosensors, and chemical sensors.

[0022] In the detection device 1 of this embodiment, the optical prism 5 is made of a material having a refractive index nd of 1.8 or more and 4.0 or less. In addition, in the detection device 1, the angle formed between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is 5° or more and 170° or less. Note that, as shown in FIG. 1 , in this embodiment, the cross-sectional shape of the optical prism 5 is triangular, and therefore the angle α formed between the light incident surface 5a and the light exit surface 5c corresponds to the apex angle of the triangle.

[0023] In this embodiment, the refractive index nC of the glass constituting the optical prism 5 is preferably 1.78 or more and 3.99 or less, and more preferably 1.79 or more and 3.95 or less.

[0024] In the detection device 1, the optical axis X1 of the incident light entering the light incident surface 5a of the optical prism 5 is approximately perpendicular to the bottom surface 5b of the optical prism 5. Also, the optical axis X2 of the outgoing light exiting the light exit surface 5c of the optical prism 5 is approximately perpendicular to the bottom surface 5b of the optical prism 5. Note that in this embodiment, "approximately perpendicular" is used to mean not only a completely perpendicular state, but also a state with an error of ±3.0°. However, it is desirable to design the optical axis X1, the optical axis X2, and the bottom surface 5b of the optical prism 5 to be completely perpendicular.

[0025] The detection device 1 of this embodiment has the above-described overall configuration, and therefore can simplify the entire device while increasing the degree of freedom in optical design.

[0026] More specifically, in the detection device 1 of this embodiment, sensing using surface plasmon resonance can be performed simply by installing the sensor unit 3 in a position facing the light source 2 and the detector 4. Therefore, the detection device 1 does not require a mechanical mechanism for precisely controlling the angle of incidence or the angle of reflection using, for example, a rotating stage, and the entire device can be simplified and made smaller.

[0027] Furthermore, in the detection device 1 of this embodiment, the optical prism 5 is made of a material with a refractive index nd of 1.8 or more and 4.0 or less, so that the light that reaches the bottom surface 5b of the optical prism 5 can be designed to be totally reflected by the metal thin film 6, making it easier to generate surface plasmon resonance. Furthermore, the larger the refractive index nd of the material that makes up the optical prism 5, the larger the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 can be designed to be.

[0028] Furthermore, in the detection device 1 of this embodiment, the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is 5° or more and 170° or less, so it is possible to design the detection device 1 to have high refractive index sensitivity. As described above, the larger the refractive index nd of the material constituting the optical prism 5, the larger the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 can be.

[0029] Furthermore, in the detection device 1 of this embodiment, the optical axis X1 of the incident light that enters the light incident surface 5a of the optical prism 5 is approximately perpendicular to the bottom surface 5b of the optical prism 5. Therefore, compared to the case where the optical axis X3 is arranged very close to the bottom surface, such as in the detection device 101 of the comparative example in Figure 30, where the optical axis X3 is arranged parallel to the bottom surface 105b of the optical prism 105, the degree of freedom in the optical design of the detection device 1 can be increased, for example, by increasing the beam diameter of the light emitted from the light source 2.

[0030] Therefore, according to the detection device 1 of this embodiment, it is possible to simplify the entire device while increasing the degree of freedom in optical design.

[0031] In this embodiment, the refractive index nd of the material constituting the optical prism 5 is 1.8 or more, preferably 1.85 or more, more preferably 2.0 or more, and 4.0 or less, preferably 3.5 or less, more preferably 3.0 or less, and even more preferably 2.5 or less. If the refractive index of the material constituting the optical prism 5 is equal to or greater than the above-mentioned lower limit, the dip wavelength (described later) shifts to the longer wavelength side, thereby reducing the loss due to the metal thin film 6 and further increasing the refractive index sensitivity of the detection device 1. Furthermore, from the viewpoint of broadening the range of material options, it is preferable that the refractive index of the material constituting the optical prism 5 be equal to or less than the above-mentioned upper limit. The refractive index nd can be measured using the well-known V-block method. Specifically, a sample is cut to a size of 30 mm x 30 mm x 5 mm, one end is polished at a right angle, and the polished surface is mirror-finished. The refractive index of the sample is measured using a precision refraction system KPR-2000 (manufactured by Shimadzu Corporation) for the d-line of a He lamp.

[0032] The angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is 5° or more, preferably 10° or more, more preferably 30° or more, and is 170° or less, preferably 130° or less, more preferably 105° or less, even more preferably less than 90°, and particularly preferably 80° or less. When the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is equal to or greater than the above-mentioned lower limit, the reflection loss of light incident on the light incident surface 5a of the optical prism 5 can be further reduced. Furthermore, the height of the optical prism 5 can be reduced. When the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is equal to or less than the above-mentioned upper limit, the range of materials from which the optical prism 5 can be selected can be further expanded.

[0033] When the refractive index nd of the material constituting the optical prism 5 is 1.8 to 2.5, the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is preferably 5° or more and less than 90°, more preferably 8° or more and 80° or less, and even more preferably 10° or more and 76° or less. In this case, the refractive index sensitivity of the detection device 1 can be further increased, and the wavelength of the light to be used can be designed to be in a more desirable range.

[0034] When the refractive index nd of the material constituting the optical prism 5 is 2.5 to 4.0 (n d may be greater than 2.5), the angle α between the light incident surface 5a and the light exit surface 5c of the optical prism 5 is preferably 70° or more and 170° or less, more preferably 80° or more and 140° or less, and even more preferably 90° or more and 130° or less. In this case, the refractive index sensitivity of the detection device 1 can be further increased, and the wavelength of the light to be used can be designed to be in a more desirable range.

[0035] In this embodiment, the light emitted from the light source 2 may be, for example, visible light or near-infrared light. In particular, the wavelength of the light emitted from the light source 2 is preferably 600 nm or more and 1500 nm or less. For example, if the metal thin film 6 is made of Au, the wavelength of the light emitted from the light source 2 is more preferably 600 nm or more and 1200 nm or less. Furthermore, for example, if the metal thin film 6 is made of Ag, the wavelength of the light emitted from the light source 2 is more preferably 400 nm or more and 1800 nm or less. Furthermore, the light emitted from the light source 2 may be incoherent light. In the detection device 1 of this embodiment, the optical axis X1 of the incident light incident on the light incident surface 5a of the optical prism 5 and the bottom surface 5b of the optical prism 5 are approximately perpendicular, which increases the degree of freedom in optical design and makes the device suitable for use in detection devices that utilize incoherent light.

[0036] The beam diameter of the light emitted from the light source 2 is not particularly limited, but can be, for example, 0.01 mm or more, preferably 1 mm or more, and preferably 10 mm or less.

[0037] The material for forming the optical prism 5 is not particularly limited, and may be, for example, a material having a refractive index nd of 1.8 or more and 4.0 or less, and being transparent to light with a wavelength of 600 nm or more and 1500 nm or less. Examples of the material for forming the optical prism 5 include glass, silicon (Si), gallium phosphide (GaP), diamond, etc. Examples of glass include TiO ２ , Ta ２ O ５ , Nb ２ O ５ and La ２ O ３ The glass constituting the optical prism 5 is preferably a glass containing at least one selected from the following: ２ +Ta ２ O ５ +Nb ２ O ５ +La ２ O ３ It is preferable that the content is 10% to 90%.

[0038] The following describes the reasons for the preferred range of glass composition when the material constituting the optical prism 5 is glass. In the explanation of the range of each component, % refers to mass % unless otherwise specified.

[0039] TiO ２ , Ta ２ O ５ , Nb ２ O ５ and La ２ O ３ is a component that significantly increases the refractive index of glass. ２ +Ta ２ O ５ +Nb ２ O ５ +La ２ O ３ The content of (TiO ２ , Ta ２ O ５ , Nb ２ O ５ and La ２ O ３ The total amount of TiO is preferably 10% to 90%. ２ +Ta ２ O ５ +Nb ２ O ５ +La ２ O ３ The lower limit of the content of TiO is preferably 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, particularly preferably 60% or more. ２ +Ta ２ O ５ +Nb ２ O ５ +La ２ O ３ The upper limit of the content of TiO is preferably 90% or less, particularly preferably 80% or less. ２ , Ta ２ O ５ , Nb ２ O ５ and La ２ O ３ The preferred contents of each component are as follows:

[0040] TiO ２The content of TiO is preferably 0% to 60%. ２ The lower limit of the content of TiO is preferably 0% or more, 1% or more, 2% or more, 5% or more, particularly preferably 10% or more. ２ The upper limit of the content of TiO is preferably 60% or less, 50% or less, 40% or less, and particularly preferably 30% or less. ２ If the content is too high, the glass tends to be colored and the resistance to devitrification tends to decrease.

[0041] Ta ２ O ５ The content of Ta is preferably 0% to 60%. ２ O ５ The lower limit of the content of Ta is preferably 0% or more, 1% or more, 2% or more, 5% or more, particularly preferably 10% or more. ２ O ５ The upper limit of the Ta content is preferably 60% or less, 50% or less, 40% or less, particularly preferably 30% or less. ２ O ５ If the content is too large, the resistance to devitrification tends to decrease.

[0042] Nb ２ O ５ The content of Nb is preferably 0% to 60%. ２ O ５ The lower limit of the content of Nb is preferably 0% or more, 1% or more, 2% or more, 5% or more, particularly preferably 10% or more. ２ O ５ The upper limit of the Nb content is preferably 60% or less, 50% or less, 40% or less, and particularly preferably 30% or less. ２ O ５ If the content is too high, the liquidus temperature will rise sharply, the liquidus viscosity will decrease, and mass productivity will tend to deteriorate. In addition, the internal transmittance will tend to decrease.

[0043] La ２ O ３ The content of La is preferably 0% to 60%. ２ O ３ The lower limit of the content of La is preferably 0% or more, 1% or more, 2% or more, 5% or more, particularly preferably 10% or more. ２ O ３The upper limit of the content of La is preferably 60% or less, 50% or less, 40% or less, particularly preferably 30% or less. ２ O ３ If the content is too high, the liquidus viscosity decreases, which tends to deteriorate mass productivity.

[0044] Examples of materials that can be used for the metal thin film 6 include Ag, Au, and Cu. The thickness of the metal thin film 6 is preferably 30 nm or more, more preferably 45 nm or more, and is preferably 70 nm or less, more preferably 55 nm or less. When the thickness of the metal thin film 6 is within the above range, surface plasmons can be excited more easily.

[0045] As the detector 4, for example, a CCD camera, a photodiode, a photomultiplier tube, a spectrometer and a CCD camera, a photodiode array, or the like can be used.

[0046] The polarizing filter may be, for example, a plastic polarizing film. Note that the detection device 1 does not necessarily need to be provided with a polarizing filter.

[0047] The optical lens may be, for example, an objective lens. Note that the detection device 1 may not be provided with an optical lens, or may be provided with only one of an optical lens on the incident side and an optical lens on the exit side.

[0048] The refractive index sensitivity of the detector 1 of this embodiment is preferably 1000 nm / RIU or more, more preferably 2000 nm / RIU or more, and preferably 30,000 nm / RIU or less, more preferably 20,000 nm / RIU or less. The refractive index sensitivity (Sn) of the detector 1 can be calculated by dividing the change in dip wavelength (Δλ) by the change in refractive index (Δn) when the dip wavelength changes due to a change in the refractive index of the object 10 to be detected (Sn = Δλ / Δn). When the refractive index sensitivity of the detector 1 is within the above range, it can be suitably used in applications such as refractive index sensors, biosensors, and chemical sensors.

[0049] Second Embodiment FIG. 2 is a schematic diagram showing the configuration of a detection device according to a second embodiment of the present invention.

[0050] As shown in Fig. 2, in the detection device 21, the optical prism 25 has a hexahedron shape with isosceles trapezoidal sides, and its cross-sectional shape is also an isosceles trapezoid. The shape of the optical prism 25 does not have to be a hexahedron with isosceles trapezoidal sides, and it may be a truncated quadrangular pyramid. In this case, the cross-sectional shape of the pyramid taken along a plane perpendicular to the base including the apex is the isosceles trapezoid shown in Fig. 2. Note that when the cross-sectional shape of the optical prism 5 is a trapezoid, as in this embodiment, the length of the base can be, for example, 5 mm to 20 mm, and the height can be 5 mm to 50 mm.

[0051] In the detection device 21, the optical prism 25 has a trapezoidal cross section, with the light incident surface 25a located on one hypotenuse of the trapezoid and the light exit surface 25c located on the other hypotenuse of the trapezoid. More specifically, in the hexahedron or quadrangular pyramid shape of the optical prism 25, one of the opposing slopes is the light incident surface 25a, and the other slope is the light exit surface 25c. In the detection device 21, the angle α between the light incident surface 25a and the light exit surface 25c is the angle between an imaginary line in the extension direction of the light incident surface 25a and an imaginary line in the extension direction of the light exit surface 25c. The angle α between the light incident surface 25a and the light exit surface 25c corresponds to the apex angle of a triangle formed by connecting an imaginary line in the extension direction of the light incident surface 25a and an imaginary line in the extension direction of the light exit surface 25c. Other points are the same as those in the first embodiment.

[0052] In the detection device 21 of the second embodiment, the optical prism 25 is also made of a material having a refractive index nd of 1.8 or more and 4.0 or less. Also in the detection device 21, the angle α between the light incident surface 25a and the light exit surface 25c of the optical prism 25 is 5° or more and 170° or less. Also in the detection device 21, the optical axis X1 of the incident light entering the light incident surface 25a of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Also, the optical axis X2 of the exit light exiting the light exit surface 25c of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Therefore, the detection device 21 of the second embodiment can simplify the entire device while increasing the degree of freedom in optical design.

[0053] As in the detection device 21 of the second embodiment, the optical prism 25 has a hexahedral or quadrangular pyramidal shape, and the cross section of the optical prism 25 is an isosceles trapezoid. In this case, the height of the optical prism 25 can be reduced, and therefore the detection device 21 can be made smaller.

[0054] Third Embodiment FIG. 3 is a schematic diagram showing the configuration of a detection device according to a third embodiment of the present invention.

[0055] 3, the detection device 31 includes a light source / detector 40 in which a light source and a detector are integrated. An optical lens 37 and a slit plate 38 are provided between the light source / detector 40 and the optical prism 25. The optical lens 37 may be the same as that described in the first embodiment. The slit plate 38 has an entrance slit 38a and an exit slit 38b.

[0056] In the detection device 31, light emitted from the light source / detector 40 is collimated by the optical lens 37 and enters the polarizing filter (the polarizing filter is not shown in FIG. 3 ). The polarizing filter separates the light into s-polarized and p-polarized components, of which the p-polarized light (hereinafter sometimes simply referred to as light) exits toward the slit plate 38. The light that reaches the slit plate 38 passes through the incident-side slit 38a and exits toward the optical prism 25. The light that reaches the optical prism 25 is refracted at the light incident surface 25a and travels toward the bottom surface 25b. The light that reaches the bottom surface 25b is reflected by the metal thin film 6 and travels toward the light exit surface 25c. The light that reaches the light exit surface 25c is refracted at the light exit surface 25c and exits toward the slit plate 38. The light that reaches the slit plate 38 passes through the exit-side slit 38b and exits toward the optical lens 37. The light that reaches the optical lens 37 is collected by the optical lens 37 and travels toward the light source / detector 40. In this way, in the detection device 31, the light reaches the detector of the light source / detector 40 and is detected. Other points are the same as those in the second embodiment.

[0057] In the detection device 31 of the third embodiment, the optical prism 25 is also made of a material having a refractive index nd of 1.8 or more and 4.0 or less. Also in the detection device 31, the angle between the light incident surface 25a and the light exit surface 25c of the optical prism 25 is 5° or more and 170° or less. Also in the detection device 31, the optical axis X1 of the incident light entering the light incident surface 25a of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Also, the optical axis X2 of the exit light exiting the light exit surface 25c of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Therefore, the detection device 31 of the third embodiment can simplify the entire device while increasing the degree of freedom in optical design.

[0058] As in the third embodiment, the detection device 31 may include a light source / detector 40 in which a light source and a detector are integrated. In this case, light emitted from the light source / detector 40 returns to the light source / detector 40 and is detected, thereby simplifying the entire detection device 31 and further miniaturizing the detection device 31. In the detection device 31, the light source / detector 40 may emit ring-shaped light. The light source / detector 40 may also have a structure in which the light source and the detector are integrated by a Y-shaped optical fiber. Specifically, the light source may be connected to a first end of the Y-shaped optical fiber, and the detector may be connected to a second end. In this case, the light emitted from the light source is emitted from the end (the third end, the bottom end of the Y) to which the light source and the detector are not connected. Furthermore, light reflected by the bottom surface 25b of the optical prism 25 enters the third end of the Y-shaped optical fiber and travels toward the detector.

[0059] Fourth Embodiment FIG. 4 is a schematic diagram showing the configuration of a detection device according to a fourth embodiment of the present invention.

[0060] 4, the detection device 41 includes a light source 2. An optical lens 43 is provided between the light source 2 and the optical prism 25. The optical lens 43 may be, for example, the optical lens described in the first embodiment. Furthermore, a mirror 44 and an optical lens 45 are provided between the optical prism 25 and the detector 4.

[0061] In the detection device 41, light emitted from the light source 2 is collimated by the optical lens 43 and enters the polarizing filter (the polarizing filter is not shown in FIG. 4 ). The polarizing filter separates the light into an s-polarized component and a p-polarized component, of which the p-polarized component (hereinafter, sometimes simply referred to as light) is emitted toward the optical prism 25. The light that reaches the optical prism 25 is refracted at the light incident surface 25 a and travels toward the bottom surface 25 b. The light that reaches the bottom surface 25 b is reflected by the metal thin film 6 and travels toward the light exit surface 25 c. The light that reaches the light exit surface 25 c is refracted at the light exit surface 25 c and exits toward the mirror 44. The light that reaches the mirror 44 is reflected by the mirror 44, and after its optical axis X2 becomes parallel to the bottom surface 25 b, it is emitted toward the optical lens 45. The light that reaches the optical lens 45 is condensed by the optical lens 45 and travels toward the detector 4. In this way, in the detection device 41, the light reaches the detector 4 and is detected. Other points are the same as those in the second embodiment.

[0062] In the detection device 41 of the fourth embodiment, the optical prism 25 is also made of a material having a refractive index nd of 1.8 or more and 4.0 or less. Also in the detection device 41, the angle between the light incident surface 25a and the light exit surface 25c of the optical prism 25 is 5° or more and 170° or less. Also in the detection device 41, the optical axis X1 of the incident light entering the light incident surface 25a of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Also, the optical axis X2 of the exit light exiting the light exit surface 25c of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Therefore, the detection device 41 of the fourth embodiment can simplify the entire device while increasing the degree of freedom in optical design.

[0063] (Modification of Fourth Embodiment) FIG. 5 is a schematic diagram showing the configuration of a detection device according to a modification of the fourth embodiment of the present invention.

[0064] 5 , in a detection device 41A according to a modification of the fourth embodiment, the arrangement of the light source 2 and the detector 4 is reversed from that of the detection device 41 of the fourth embodiment. Specifically, in the detection device 41A, an optical lens 45 and a mirror 44 are provided between the light source 2 and the optical prism 25. In addition, an optical lens 43 is provided between the optical prism 25 and the detector 4.

[0065] In the detection device 41A, light emitted from the light source 2 travels parallel to the bottom surface 25b of the optical prism 25, is collimated by the optical lens 45, and enters the polarizing filter (the polarizing filter is not shown in FIG. 5 ). The polarizing filter separates the light into an s-polarized component and a p-polarized component, of which the p-polarized component (hereinafter sometimes simply referred to as light) travels parallel to the bottom surface 25b toward the mirror 44 and is reflected by the mirror 44. The light reflected by the mirror 44 travels toward the optical prism 25, with its optical axis X1 perpendicular to the bottom surface 25b. The light that reaches the optical prism 25 is refracted by the light incident surface 25a1 and travels toward the bottom surface 25b. The light that reaches the bottom surface 25b is reflected by the metal thin film 6 and travels toward the light exit surface 25c1. The light that reaches the light exit surface 25c1 is refracted at the light exit surface 25c1, is collected by the optical lens 43, and travels toward the detector 4. In the detection device 41A, the light reaches the detector 4 in this manner and is detected.

[0066] In the detection device 41A of the modified fourth embodiment, the optical prism 25 is also made of a material with a refractive index nd of 1.8 or more and 4.0 or less. Also in the detection device 41A, the angle between the light incident surface 25a1 and the light exit surface 25c1 of the optical prism 25 is 5° or more and 170° or less. Also in the detection device 41A, the optical axis X1 of the incident light entering the light incident surface 25a1 of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Also, the optical axis X2 of the exit light exiting the light exit surface 25c1 of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25. Therefore, the detection device 41A of the modified fourth embodiment can simplify the entire device while increasing the degree of freedom in optical design.

[0067] The detection device of the present invention will be described in further detail below using a specific example. In the following specific example, an experimental example based on a simulation using the detection device 21 of FIG. 2 will be described. In this specific example, the angle α between the light incident surface 25a and the light exit surface 25c is referred to as the apex angle α of a triangle formed by connecting an imaginary line in the extension direction of the light incident surface 25a with an imaginary line in the extension direction of the light exit surface 25c. In this specific example, light was incident on the longitudinal center of the side of the triangle formed by connecting an imaginary line in the extension direction of the light incident surface 25a with an imaginary line in the extension direction of the light exit surface 25c, on which the light incident surface 25a is located. Furthermore, a 47-nm-thick Au film was used as the metal thin film 6. Furthermore, water with a refractive index nd = 1.33 was used as the detection target 10.

[0068] 6 is a schematic diagram illustrating how to determine the apex angle α at which surface plasmon resonance occurs in the detection device according to the second embodiment of the present invention. Note that the light source 2 and the detector 4 shown in FIG. 2 are not shown in FIG.

[0069] As shown in FIG. 6, in the detection device 21, the optical axis X1 of the incident light entering the light incident surface 25a of the optical prism 25 is approximately perpendicular to the bottom surface 25b of the optical prism 25, and therefore the angle of incidence and the angle of refraction of the light entering the light incident surface 25a of the optical prism 25 are expressed by the following formula (1) according to Snell's law.

[0070]

[0071] Furthermore, the angle of incidence γ of light onto the metal thin film 6 (the angle of incidence γ at which surface plasmon resonance occurs) is a function of the wavelength λ of the light incident on the optical prism 25, the refractive index n of the material constituting the optical prism 25, the film thickness of the metal thin film 6, the refractive index of the detection target 10, etc., and is also expressed as γ(n, λ). Note that this function does not take into account the wavelength dependency of the refractive index of the material constituting the optical prism. Therefore, it is assumed that the refractive index at wavelengths other than the d-line is the same value as the refractive index nd. From FIG. 6, the angle of incidence γ (γ(n, λ)) can be expressed as the following equation (2) using the exterior angle theorem.

[0072]

[0073] Equation 1(1) and equation (2) can be summarized as equation (3) below.

[0074]

[0075] From equation (3), it can be seen that in order to find the apex angle α at which surface plasmon resonance occurs, it is sufficient to plot the following equations (4) and (5) and find the intersection point.

[0076]

[0077]

[0078] Fig. 7 is a graph plotting formulas (4) and (5) when the wavelength λ of light incident on the optical prism is 633 nm and the refractive index nd of the material constituting the optical prism is 1.5. Figs. 8 to 11 are graphs plotting the same formulas as in Fig. 7 when the refractive index nd of the material constituting the optical prism is 1.86, 2.0, 2.5, and 3.0, respectively.

[0079] 7 shows that when the refractive index nd of the material constituting the optical prism 25 is 1.5, there is no intersection of equations (4) and (5) where the apex angle α is 0° or greater. On the other hand, from Figures 8 to 11, it can be seen that when the refractive index nd of the material constituting the optical prism is 1.86 to 3.0, there is an intersection angle α of equations (4) and (5) (the apex angle α at which surface plasmon resonance occurs), and the larger the refractive index nd, the larger the intersection angle α of equations (4) and (5).

[0080] Similarly, the apex angle α at the intersection of equations (4) and (5) was calculated when the wavelength of light incident on the optical prism was 633 nm and the refractive index nd of the material constituting the optical prism was 3.5 and 4.0. Furthermore, the apex angle α at the intersection of equations (4) and (5) was calculated when the wavelength of light incident on the optical prism was 800 nm and the refractive index nd of the material constituting the optical prism was 1.86, 2.0, 2.5, 3.0, 3.5, and 4.0. The results are shown in Table 1 below. In Table 1, the detection target 10 is an aqueous solution (refractive index nd is 1.33), and the incident angle γ at which surface plasmon resonance occurs is also shown.

[0081]

[0082] Next, a specific example of refractive index sensitivity measurement by the detector 21 will be described.

[0083] 12 is a diagram showing the relationship between the wavelength of incident light and reflectance when the refractive index nd of the material constituting the optical prism is set to 2.0 and the apex angle α is set to 30° in the detection device according to the second embodiment of the present invention. In Fig. 12, the solid line shows the results when an aqueous solution with a refractive index nd = 1.33 is used as the detection object 10, and the dashed line shows the results when an aqueous solution with a refractive index nd = 1.34 is used.

[0084] From Figure 12, it can be seen that when the refractive index nd of the aqueous solution used as the detection target 10 is 1.34, the dip wavelength (resonance wavelength) at which surface plasmon resonance occurs is shifted to the longer wavelength side compared to when the refractive index nd of the aqueous solution is 1.33.

[0085] 13 is a diagram showing the relationship between the wavelength of incident light and reflectance when the refractive index nd of the material constituting the optical prism is set to 2.0 and the apex angle α is set to 35° in the detection device according to the second embodiment of the present invention. In Fig. 13, the solid line shows the results when an aqueous solution with a refractive index nd = 1.33 is used as the detection object 10, and the dashed line shows the results when an aqueous solution with a refractive index nd = 1.34 is used.

[0086] From Figure 13, it can be seen that by setting the apex angle α to 35°, the dip wavelength (resonance wavelength) at which surface plasmon resonance occurs is shifted to the longer wavelength side compared to the graph in Figure 12 (where the refractive index nd is the same and the apex angle α is 30°). Also from Figure 13, it can be seen that when the refractive index nd of the aqueous solution used as the detection object 10 is 1.34, the dip wavelength (resonance wavelength) at which surface plasmon resonance occurs is shifted to the longer wavelength side compared to when the refractive index nd of the aqueous solution is 1.33.

[0087] Fig. 14 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 2.0 in the detection device according to the second embodiment of the present invention. Also, Fig. 15 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 2.0 in the detection device according to the second embodiment of the present invention.

[0088] The refractive index sensitivity is the amount of change in the resonant wavelength that occurs when the refractive index nd of the surrounding medium changes by 1; the greater the sensitivity, the better. The resonant wavelength is the wavelength at which the reflectance is smallest when white light is used as the light source, and at this wavelength, surface plasmon resonance is strong. The refractive index sensitivity (Sn) was calculated by dividing the change in the refractive index of the aqueous solution (Δn) by the change in the dip wavelength (resonant wavelength) (Δλ) as shown in Figure 12, for example.

[0089] 14 and 15 , it can be seen that the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account the above-mentioned reasons and the like, when the refractive index nd of the material constituting the optical prism 25 is 2.0, it is desirable to set the apex angle α to, for example, 15° or more and 50° or less, more preferably 26° or more and 38° or less.

[0090] Fig. 16 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 1.86 in the detection device according to the second embodiment of the present invention. Also, Fig. 17 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 1.86 in the detection device according to the second embodiment of the present invention.

[0091] 16 and 17 , it can be seen that the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account the above-mentioned reasons and the like, when the refractive index nd of the material constituting the optical prism 25 is 1.86, it is desirable to set the apex angle α, for example, to 5° or more and 40° or less, more preferably 10° or more and 22° or less.

[0092] Fig. 18 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 2.5 in the detection device according to the second embodiment of the present invention. Also, Fig. 19 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism 25 is 2.5 in the detection device according to the second embodiment of the present invention.

[0093] 18 and 19 , it can be seen that the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account Figures 18 and 19 and the reasons described above, when the refractive index nd of the material constituting the optical prism 25 is set to 2.5, it is desirable to set the apex angle α to, for example, 30° or more and less than 90°, more preferably 70° or more and 78° or less.

[0094] Fig. 20 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 3.0 in the detection device according to the second embodiment of the present invention. Also, Fig. 21 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 3.0 in the detection device according to the second embodiment of the present invention.

[0095] 20 and 21 , it can be seen that the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account the above-mentioned reasons and the like, when the refractive index nd of the material constituting the optical prism 25 is set to 3.0, it is desirable to set the apex angle α to, for example, 80° or more and 120° or less, more preferably 94° or more and 102° or less.

[0096] Fig. 22 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 3.5 in the detection device according to the second embodiment of the present invention. Also, Fig. 23 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 3.5 in the detection device according to the second embodiment of the present invention.

[0097] As shown in Figures 22 and 23, the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account Figures 22 and 23 and the reasons described above, when the refractive index nd of the material constituting the optical prism 25 is set to 3.5, it is desirable to set the apex angle α, for example, to 100° or more and 130° or less, more preferably 111° or more and 117° or less.

[0098] Fig. 24 is a diagram showing the relationship between the apex angle α and the refractive index sensitivity when the refractive index nd of the material constituting the optical prism is 4.0 in the detection device according to the second embodiment of the present invention. Also, Fig. 25 is a diagram showing the relationship between the apex angle α and the resonance wavelength when the refractive index nd of the material constituting the optical prism is 4.0 in the detection device according to the second embodiment of the present invention.

[0099] As shown in Figures 24 and 25, the larger the apex angle α, the greater the refractive index sensitivity, while the larger the apex angle α, the longer the resonance wavelength. Thus, it is desirable to appropriately adjust the apex angle α depending on the desired refractive index sensitivity and the wavelength of the light being used. Taking into account Figures 24 and 25 and the reasons described above, when the refractive index nd of the material constituting the optical prism 25 is 4.0, it is desirable to set the apex angle α to, for example, 110° or more and 140° or less, more preferably 122° or more and 128° or less.

[0100] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0101] Example 1 In Example 1, a refractive index sensor for measuring a resonance wavelength was fabricated as a detection device. The sensor configuration was the same as that of the detection device 31 of the third embodiment shown in FIG. 3 . In this detection device 31, light emitted from a light source / detector 40 is collimated by an optical lens 37 and enters a polarizing filter (the polarizing filter is not shown in FIG. 3 ). The polarizing filter separates the light into an s-polarized component and a p-polarized component, of which the p-polarized component (hereinafter sometimes simply referred to as light) exits toward the slit plate 38. The light that reaches the slit plate 38 passes through the entrance slit 38a and exits toward the optical prism 25. The light that reaches the optical prism 25 is refracted at the light entrance surface 25a and travels toward the bottom surface 25b. The light that reaches the bottom surface 25b is reflected by the metal thin film 6 and travels toward the light exit surface 25c. The light that reaches the light exit surface 25c is refracted at the light exit surface 25c and exits toward the slit plate 38. The light that reaches the slit plate 38 passes through the exit-side slit 38b and exits toward the optical lens 37. The light that reaches the optical lens 37 is collected by the optical lens 37 and travels toward the light source / detector 40. In this way, in the detection device 31, the light reaches the detector of the light source / detector 40 and is detected.

[0102] The optical prism 25 used was a hexahedral glass prism having an isosceles trapezoidal side with a refractive index nd of 2.0, an apex angle α of 30°, a height of 11.2 mm, and a base length of 14.6 mm. The glass constituting the glass prism contained, in mass %, TiO ２ +Ta ２ O ５ +Nb ２ O ５ +La ２ O ３ Glass containing 10% or more of fluorine was used. The metal thin film 6 on the bottom surface 25b of the glass prism (optical prism 25) was a gold thin film with a film thickness of 50 nm. The light source / detector 40 used had a structure in which the light source and detector were integrated by a Y-shaped optical fiber. Specifically, the light source was connected to the first end of the Y-shaped optical fiber, and the detector was connected to the second end. A halogen lamp (manufactured by Ocean Optics) was used as the white light source. An optical spectrometer (USB-2000, manufactured by Ocean Optics) was used as the detector. Light emitted from the light source was emitted from the end of the Y-shaped optical fiber to which the light source and detector were not connected (the third end, the bottom end of the Y). Furthermore, light reflected from the bottom surface 25b of the optical prism 25 entered the third end of the Y-shaped optical fiber, traveled toward the detector, and was detected. The detection target 10 was a mixture of water and ethanol. Specifically, the refractive index (nd) of the mixed solution was controlled by changing the mixing ratio of water and ethanol. According to Reference 1, the refractive index (nd) of water at 15°C is 1.33345, and the refractive index (nd) of ethanol is 1.36332.

[0103] Reference 1: Chemistry Handbook, Basic Edition, 6th Revised Edition, Chapter 14, Table 14.5-3

[0104] Next, the resonant wavelength change of a water and ethanol mixture was measured using the detector 31 of Example 1, and the refractive index of the water and ethanol mixture was calculated from the change in the resonant wavelength appearing at wavelengths from 650 nm to 780 nm. The results are shown in FIG. 26 . As shown in FIG. 26 , the experimental and simulated values ​​for the resonant wavelength change in Example 1 generally agreed, confirming that the detector 31 performed well as a refractive index sensor. The solid line in FIG. 26 represents the refractive index of the mixture obtained by interpolating the refractive index value given in Reference 1. Since the ethanol concentration in Reference 1 is expressed in weight percent, it was converted to volume percent using the ethanol density value given in Reference 2.

[0105] Reference 2: Science Chronology 2025 Edition, Physics / Chemistry Department, Density of Various Substances

[0106] Example 2 In Example 2, a chemical sensor for detecting a substance was fabricated as a detection device. The sensor configuration was the same as in Example 1. The detection target was a 0.05 mM aqueous solution of aminohexadecanethiol. When aminohexadecanethiol comes into contact with a thin gold film, a self-assembled monolayer grows on the surface of the gold film. This self-assembled monolayer optically behaves as a dielectric thin film. In Example 2, an aqueous solution of aminohexadecanethiol was exposed to the surface of the thin gold film on the bottom surface of a glass prism, and the thickness of the dielectric thin film was calculated from the change in the resonance wavelength. The calculated thickness of the dielectric thin film was also compared with the theoretical thickness of the dielectric thin film (the length of the aminohexadecanethiol molecule calculated from the molecular structure and bond length).

[0107] Figure 27 shows the relationship between measurement time and resonance wavelength when an aminohexadecanethiol aqueous solution was exposed to the surface 6a of the gold thin film (metal thin film 6) on the bottom surface 25b of the glass prism. As shown in Figure 27, exposure to the aminohexadecanethiol aqueous solution began 200 seconds after the start of measurement. 3,200 seconds after the start of measurement (3,000 seconds after the start of exposure), the change in resonance wavelength nearly stopped, and the formation of the dielectric thin film was determined to be complete. At this time, the resonance wavelength changed from 674 nm to 682 nm, resulting in a change of 8 nm in resonance wavelength. Based on a simulation value showing a 3.4 nm change in resonance wavelength per 1 nm of dielectric thin film thickness on the gold thin film, the thickness of the dielectric thin film was calculated to be approximately 2.35 nm. This thickness was approximately consistent with the length of the aminohexadecanethiol molecule (2.3 nm) calculated from the molecular structure and bond length. 4,000 seconds after the start of measurement (3,800 seconds after the start of exposure), the surface was rinsed with water to terminate the reaction. In addition, in Example 2, the thickness of the dielectric thin film calculated from the experimental values ​​was roughly consistent with the theoretical thickness of the dielectric thin film, and it was confirmed that the chemical sensor functioned well.

[0108] Example 3 In Example 3, a refractive index sensor for measuring a resonance wavelength according to another embodiment was fabricated as a detection device. The sensor configuration was the same as that of the detection device 41 of the fourth embodiment shown in FIG. 4. In this detection device 41, light emitted from the light source 2 passes through an optical lens 43 and a polarizing plate (polarizing filter, not shown) and enters the glass prism 25 such that the optical axis X1 of the incident light is perpendicular to the bottom surface 25b of the glass prism. The light emitted from the glass prism then travels such that the optical axis X2 of the emitted light is perpendicular to the bottom surface 25b, is reflected by a mirror 44, passes through an objective lens (optical lens 45), and then enters the detector 4.

[0109] The optical prism 25 used was the same glass prism as in Example 1. As in Example 1, a gold thin film was used as the metal thin film on the bottom surface 25b of the glass prism, and the film thickness was 50 nm. A halogen lamp (manufactured by Ocean Optics) was used as the white light source 2. An optical spectrometer (USB-2000, manufactured by Ocean Optics) was used as the detector 4. The detection target 10 was the same as in Example 1.

[0110] Next, the resonant wavelength change of a water and ethanol mixed solution was measured using the detector 41 of Example 3, and the refractive index of the water and ethanol mixed solution was calculated from the change in the resonant wavelength appearing at wavelengths from 650 nm to 780 nm. The results are shown in FIG. 28. As shown in FIG. 28, in Example 3, the experimental and simulated values ​​for the change in the resonant wavelength generally agreed, confirming that the device performed well as a refractive index sensor. The solid line in FIG. 28 represents the refractive index of the mixed solution, interpolated from the literature values ​​for the refractive index given in Reference 1, as in FIG. 26.

[0111] Example 4 In Example 4, a chemical sensor for detecting a substance was fabricated as a detection device. The sensor configuration was the same as in Example 3. The detection target was a 0.5 mM aqueous ethanol solution of aminohexadecanethiol. The thickness of the dielectric thin film was calculated using the same method as in Example 2. The calculated thickness of the dielectric thin film was compared with the theoretical thickness of the dielectric thin film (the length of the aminohexadecanethiol molecule calculated from the molecular structure and bond length).

[0112] Figure 29 shows the relationship between measurement time and resonance wavelength when an aminohexadecanethiol aqueous solution (0.5 mM) was exposed to the surface 6a of the gold thin film on the bottom surface 25b of the glass prism. As shown in Figure 29, exposure to the aminohexadecanethiol aqueous solution began 500 seconds after the start of measurement. The change in resonance wavelength nearly stopped 1500 seconds after the start of measurement (1000 seconds after the start of exposure), indicating the completion of dielectric thin film formation. At this time, the resonance wavelength changed from 625 nm to 634 nm, resulting in a change of 9 nm in resonance wavelength. Based on a simulation result showing that the resonance wavelength changes by 3.4 nm per 1 nm of dielectric thin film thickness on the gold thin film, the thickness of the dielectric thin film was calculated to be approximately 2.6 nm. This thickness was approximately consistent with the length of the aminohexadecanethiol molecule (2.3 nm) calculated from the molecular structure and bond length. The reaction was terminated by rinsing the surface with water 5900 seconds after the start of measurement (5400 seconds after the start of exposure). As described above, in Example 4, the thickness of the dielectric thin film calculated from the experimental values ​​was roughly consistent with the theoretical thickness of the dielectric thin film, and it was confirmed that the chemical sensor functioned well.

[0113] DESCRIPTION OF SYMBOLS 1, 21, 31, 41, 41A...Detection device 2...Light source 3...Sensor unit 4...Detector 5, 25...Optical prism 5a, 25a, 25a1...Light incident surface 5b, 25b...Bottom surface 5c, 25c, 25c1...Light exit surface 6...Metal thin film 6a...Surface 10...Detection target 37, 43, 45...Optical lens 38...Slit plate 38a...Incoming slit 38b...Outgoing slit 40...Light source / detector 44...Mirror

Claims

1. A detection device that utilizes surface plasmon resonance, comprising: a light source; an optical prism having a light entrance surface, a bottom surface, and a light exit surface; a sensor unit provided on the bottom surface of the optical prism and having a metal thin film that reflects light emitted from the light source and incident on the light entrance surface toward the light exit surface; and a detector that detects the light reflected by the metal thin film of the sensor unit; wherein the optical prism is made of a material with a refractive index nd of 1.8 or more and 4.0 or less; the angle between the light entrance surface and the light exit surface of the optical prism is 5° or more and 170° or less; the optical axis of the incident light that enters the light entrance surface and the bottom surface of the optical prism are approximately perpendicular; and the optical axis of the exiting light that exits from the light exit surface and the bottom surface of the optical prism are approximately perpendicular.

2. A detection device according to claim 1, wherein the refractive index nd of the glass constituting the optical prism is 1.8 or more and 3.0 or less.

3. A detection device according to claim 1 or 2, wherein the angle formed between the light entrance surface and the light exit surface of the optical prism is less than 90°.

4. A detection device according to claim 1 or 2, wherein the cross-sectional shape of the optical prism is trapezoidal, the light incident surface is arranged on one oblique side of the trapezoid, and the light exit surface is arranged on the other oblique side of the trapezoid.

5. A detection device according to claim 1 or 2, wherein the wavelength of the light emitted from the light source is 600 nm or more and 1500 nm or less.

6. The detection device according to claim 1 or 2, wherein the refractive index sensitivity is 1000 nm / RIU or more and 30000 nm / RIU or less.

Images