Detection device

Abstract

The present invention provides a detection device that simplifies the overall apparatus while increasing the degree of freedom in optical design. [Solution] A detection device 1 utilizing surface plasmon resonance, comprising: a light source 2; an optical prism 5 having a light incident surface 5a, a bottom surface 5b, and a light emission surface 5c; a sensor unit 3 having a thin metal film 6 provided on the bottom surface 5b of the optical prism 5 that reflects light emitted from the light source 2 and incident on the light incident surface 5a toward the light emission surface 5c; and a detector 4 that detects the light reflected by the thin metal film 6 of the sensor unit 3, wherein the optical prism 5 is made of a material with a refractive index nd of 1.8 or more and 4.0 or less; in the optical prism 5, the angle between the light incident surface 5a and the light emission surface 5c is 5° or more and 170° or less; the optical axis X1 of the incident light incident on the light incident surface 5a is substantially perpendicular to the bottom surface 5b of the optical prism 5; and the optical axis X2 of the emitted light emitted from the light emission surface 5c is substantially perpendicular to the bottom surface 5b of the optical prism 5.

Description

Technical Field

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

Background Art

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

[0003] The following Patent Document 1 discloses a detection device including a sensor unit having a prism and a flat plate provided below the prism and having a metal film attached to the bottom surface. In Patent Document 1, 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, the change in the refractive index of a measurement target disposed on the surface of the metal film is measured, and for example, it is described that the interaction of proteins within cells such as an immune reaction can be measured.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, detection devices that utilize surface plasmons typically require a mechanical mechanism to precisely control the angle of incidence and the angle of reflection using a rotating stage or the like, so there is a need to simplify and miniaturize the entire device. Furthermore, detection devices like the one described in Patent Document 1 have the problem that it is difficult to simplify the entire device while increasing the degree of freedom in optical design.

[0006] The objective of the present invention is to provide a detection device that simplifies the overall device while increasing the degree of freedom in optical design. [Means for solving the problem]

[0007] The following describes various embodiments of a detection device that solves the above problems.

[0008] A detection device according to embodiment 1 of the present invention is a detection device utilizing surface plasmon resonance, comprising: a light source; an optical prism having a light incident surface, a bottom surface, and a light emission surface; a sensor unit having a metal thin film provided on the bottom surface of the optical prism, which reflects light emitted from the light source and incident on the light incident surface toward the light emission surface; and a detector for detecting 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 incident surface and the light emission surface of the optical prism is 5° or more and 170° or less; the optical axis of the incident light incident on the light incident surface and the bottom surface of the optical prism are substantially perpendicular; and the optical axis of the emitted light emitted from the light emission surface and the bottom surface of the optical prism are substantially perpendicular. In the optical prism, the light incident surface refers to the surface on which light is incident on the optical prism from the outside, and the light emission surface refers to the surface on which light is emitted from the optical prism to the outside.

[0009] In the detection device according to Embodiment 2, 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, as in Embodiment 1.

[0010] In the detection device according to embodiment 3, it is preferable that the angle between the light incident surface and the light output surface in the optical prism of embodiment 1 or embodiment 2 is less than 90°.

[0011] In the detection device according to Embodiment 4, it is preferable that in any one embodiment from Embodiment 1 to Embodiment 3, the cross-sectional shape of the optical prism is trapezoidal, the light incident surface is located on one of the slanted sides of the trapezoid, and the light emission surface is located on the other slanted side of the trapezoid.

[0012] In the detection device according to Embodiment 5, it is preferable that the wavelength of the light emitted from the light source is 600 nm or more and 1500 nm or less in any one embodiment from Embodiment 1 to Embodiment 4.

[0013] In the detection device according to Embodiment 6, it is preferable that the refractive index sensitivity is 1000 nm / RIU or more and 30000 nm / RIU or less in any one embodiment from Embodiment 1 to Embodiment 5. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a detection device that simplifies the overall device while increasing the degree of freedom in optical design. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram showing a detection device according to the first embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing a detection device according to a second embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram showing a detection device according to a third embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram showing a detection device according to a fourth embodiment of the present invention. [Figure 5] Figure 5 is a schematic diagram showing a detection device according to a modified example of the fourth embodiment of the present invention. [Figure 6]FIG. 6 is a schematic diagram for explaining how to obtain the apex angle α at which surface plasmon resonance occurs in the detection device according to the second embodiment of the present invention. [Figure 7] 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. [Figure 8] 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. [Figure 9] 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. [Figure 10] 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. [Figure 11] 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. [Figure 12] FIG. 12 is a diagram 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 the detection device according to the second embodiment of the present invention. [Figure 13] FIG. 13 is a diagram 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 the detection device according to the second embodiment of the present invention. [Figure 14] 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. [Figure 15]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. [Figure 16] 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. [Figure 17] 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. [Figure 18] 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. [Figure 19] 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 is 2.5 in the detection device according to the second embodiment of the present invention. [Figure 20] 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. [Figure 21] 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. [Figure 22] 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. [Figure 23] 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. [Figure 24]Figure 24 shows 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 a detection device according to the second embodiment of the present invention. [Figure 25] Figure 25 shows 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 a detection device according to the second embodiment of the present invention. [Figure 26] Figure 26 shows the relationship between the ethanol concentration and the refractive index of the water-ethanol mixture in Example 1. [Figure 27] Figure 27 shows the changes in the exposure time (elapsed measurement time) and resonance wavelength when an aqueous aminohexadecanethiol solution is exposed to the surface of a gold thin film at the bottom of a glass prism in Example 2. [Figure 28] Figure 28 shows the relationship between the ethanol concentration and the refractive index of the water-ethanol mixture in Example 3. [Figure 29] Figure 29 shows the changes in the exposure time (measurement elapsed time) and resonance wavelength when an aqueous aminohexadecanethiol solution is exposed to the surface of a gold thin film on the bottom of a glass prism in Example 4. [Figure 30] This is a schematic diagram showing the detection device of the comparative example. [Modes for carrying out the invention]

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

[0017] [Detection device] (First Embodiment) Figure 1 is a schematic diagram showing a detection device according to the first embodiment of the present invention.

[0018] As shown in Figure 1, the detection device 1 comprises 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 an incident light surface 5a, a base surface 5b, and a light emission 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 triangular. 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 (for example, an isosceles trapezoid). The thin metal film 6 is provided on the base surface 5b of the optical prism 5. In this embodiment, when the cross-sectional shape of the optical prism 5 is an isosceles triangle, the length of the base can be, for example, 5 mm to 20 mm, and the height can be 5 mm to 100 mm. However, the dimensions of the optical prism 5 are not particularly limited and can be appropriately determined according to 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 incident on a polarizing filter (in Figure 1, the optical lens and polarizing filter are not shown). In the polarizing filter, the light is polarized into an s-polarized component and a p-polarized component, and the p-polarized component (hereinafter sometimes simply referred to as light) is emitted towards the optical prism 5. The light that reaches the optical prism 5 is refracted at the light incident surface 5a and propagates toward the bottom surface 5b. The light that reaches the bottom surface 5b is reflected by the metal thin film 6 and propagates toward the light emission surface 5c. The light that reaches the light emission surface 5c is refracted at the light emission surface 5c, focused by an optical lens, and propagates toward the detector 4. In this way, the light reaches the detector 4 in the detection device 1 and is detected.

[0021] The detection device 1 of this embodiment is configured such that light reaching the bottom surface 5b of the optical prism 5 undergoes total internal reflection by the metal thin film 6. In such a 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 object to be detected 10 or the adsorption and desorption of substances to the surface 6a of the metal thin film 6. By measuring or sensing this change, it is possible to track changes in the refractive index nd of the object to be detected 10, or to detect substances contained in the object to be detected 10 and changes in the state of those substances. Therefore, the detection device 1 can be used by placing the object to be detected 10 on the surface 6a of the metal thin film 6, and can be used, for example, 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 with a refractive index nd of 1.8 or more and 4.0 or less. In addition, in the detection device 1, the angle between the light incident surface 5a and the light output surface 5c of the optical prism 5 is 5° or more and 170° or less. As shown in Figure 1, in this embodiment, since the cross-sectional shape of the optical prism 5 is triangular, the angle α between the light incident surface 5a and the light output surface 5c corresponds to the vertex 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. More preferably, the refractive index nC of the glass constituting the optical prism 5 is 1.79 or more and 3.95 or less.

[0024] In the detection device 1, 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. Also, the optical axis X2 of the emitted light emitted from the light emission surface 5c of the optical prism 5 and the bottom surface 5b of the optical prism 5 are approximately perpendicular. In this embodiment, "approximately perpendicular" is used to mean not only perfectly perpendicular but also with an error of ±3.0°. However, it is desirable that the optical axes X1 and X2 and the bottom surface 5b of the optical prism 5 be designed to be perfectly perpendicular.

[0025] Since the detection device 1 of this embodiment has the overall configuration described above, it is possible to 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 at a position opposite the light source 2 and the detector 4. Therefore, the detection device 1 does not require mechanical mechanisms such as a rotating stage to precisely control the angle of incidence and the angle of reflection, thus simplifying and miniaturizing the entire device.

[0027] Furthermore, in the detection device 1 of this embodiment, since the optical prism 5 is made of a material with a refractive index nd of 1.8 or more and 4.0 or less, it is possible to design the device so that the light reaching the bottom surface 5b of the optical prism 5 is totally reflected by the thin metal film 6, making it easier to generate surface plasmon resonance. Also, 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 output 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 output surface 5c of the optical prism 5 is 5° or more and 170° or less, so the detection device 1 can be designed to increase its refractive index sensitivity. As mentioned 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 output 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 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. Therefore, compared to the case where the optical axis X3 is positioned 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 and the bottom surface 105b of the optical prism 105 are positioned parallel, 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 higher, preferably 1.85 or higher, more preferably 2.0 or higher, and 4.0 or lower, preferably 3.5 or lower, more preferably 3.0 or lower, and even more preferably 2.5 or lower. When the refractive index of the material constituting the optical prism 5 is above the lower limit, the dip wavelength, which will be described later, shifts to the longer wavelength side, so that the loss due to the metal thin film 6 can be reduced, and the refractive index sensitivity of the detection device 1 can be increased. Furthermore, from the viewpoint of broadening the range of material selection, it is preferable that the refractive index of the material constituting the optical prism 5 be below the upper limit. The refractive index nd can be measured using the well-known V-block method. Specifically, a sample is cut to 30 mm × 30 mm × 5 mm, one end is polished at a right angle, the polished surface is mirror-finished, and the refractive index of the d line of a He lamp is measured on the sample using a precision refractive system KPR-2000 (manufactured by Shimadzu Corporation).

[0032] The angle α between the light incident surface 5a and the light output surface 5c of the optical prism 5 is 5° or more, preferably 10° or more, more preferably 30° or more, and 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 output surface 5c of the optical prism 5 is greater than or equal to the lower limit above, the reflection loss of light incident on the light incident surface 5a of the optical prism 5 can be further reduced. In addition, the height of the optical prism 5 can be reduced. When the angle α between the light incident surface 5a and the light output surface 5c of the optical prism 5 is less than or equal to the upper limit above, the range of materials that can be selected to constitute the optical prism 5 can be further broadened.

[0033] The angle α between the light incident surface 5a and the light output 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, when the refractive index nd of the material constituting the optical prism 5 is 1.8 to 2.5. In this case, the refractive index sensitivity of the detection device 1 can be further increased, and the wavelength of the light used can be designed to be within a more desirable range.

[0034] The angle α between the light incident surface 5a and the light output 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, when the refractive index nd of the material constituting the optical prism 5 is 2.5 to 4.0 (nd may be greater than 2.5). In this case, the refractive index sensitivity of the detection device 1 can be further increased, and the wavelength of the light used can be designed to be within a more desirable range.

[0035] In this embodiment, visible light or near-infrared light can be used as the light emitted from the light source 2. Preferably, the wavelength of the light emitted from the light source 2 is between 600 nm and 1500 nm. For example, if the metal thin film 6 is Au, the wavelength of the light emitted from the light source 2 is more preferably between 600 nm and 1200 nm. Furthermore, if the metal thin film 6 is Ag, the wavelength of the light emitted from the light source 2 is more preferably between 400 nm and 1800 nm. The light emitted from the light source 2 may also 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 substantially perpendicular, increasing the degree of freedom in optical design. Therefore, it can be suitably used in detection devices utilizing incoherent light.

[0036] Furthermore, 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 constituting the optical prism 5 is not particularly limited, and 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 can be used. Examples of materials constituting the optical prism 5 include glass, silicon (Si), gallium phosphide (GaP), and diamond. As for the glass, it is preferable that it contains at least one selected from TiO2, Ta2O5, Nb2O5, and La2O3. For example, it is preferable that the glass constituting the optical prism 5 contains 10% to 90% by mass of TiO2 + Ta2O5 + Nb2O5 + La2O3.

[0038] The following explains the preferred range of glass composition when the material constituting the optical prism 5 is glass. Unless otherwise specified, percentages in the description of each component refer to mass percentages.

[0039] TiO2, Ta2O5, Nb2O5, and La2O3 are components that significantly increase the refractive index of glass. The content of TiO2+Ta2O5+Nb2O5+La2O3 (total amount of TiO2, Ta2O5, Nb2O5, and La2O3) is preferably 10% to 90%. More specifically, the lower limit of the TiO2+Ta2O5+Nb2O5+La2O3 content is preferably 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, and especially preferably 60% or more, and the upper limit of the TiO2+Ta2O5+Nb2O5+La2O3 content is preferably 90% or less, and especially preferably 80% or less. The preferred content of each component, TiO2, Ta2O5, Nb2O5, and La2O3, is as follows.

[0040] The TiO2 content is preferably between 0% and 60%. The lower limit of the TiO2 content is preferably 0%, 1%, 2%, 5%, and especially preferably 10% or more, and the upper limit of the TiO2 content is preferably 60% or less, 50% or less, 40% or less, and especially preferably 30% or less. If the TiO2 content is too high, the glass is likely to become discolored or its resistance to devitrification will decrease.

[0041] The Ta2O5 content is preferably 0% to 60%. The lower limit of the Ta2O5 content is preferably 0%, 1%, 2%, 5%, and especially preferably 10% or more, and the upper limit of the Ta2O5 content is preferably 60% or less, 50% or less, 40% or less, and especially preferably 30% or less. If the Ta2O5 content is too high, the resistance to devitrification tends to decrease.

[0042] The Nb2O5 content is preferably 0% to 60%. The lower limit of the Nb2O5 content is preferably 0%, 1%, 2%, 5%, and especially preferably 10% or more, and the upper limit of the Nb2O5 content is preferably 60% or less, 50% or less, 40% or less, and especially preferably 30% or less. If the Nb2O5 content is too high, the liquid phase temperature tends to rise rapidly, the liquid phase viscosity decreases, and mass production tends to deteriorate. In addition, the internal permeability tends to decrease.

[0043] The La2O3 content is preferably 0% to 60%. The lower limit of the La2O3 content is preferably 0%, 1%, 2%, 5%, and especially preferably 10% or more, and the upper limit of the La2O3 content is preferably 60% or less, 50% or less, 40% or less, and especially preferably 30% or less. If the La2O3 content is too high, the liquid phase viscosity tends to decrease, and mass production efficiency tends to deteriorate.

[0044] For example, Ag, Au, Cu, etc., can be used as the material for the metal thin film 6. The thickness of the metal thin film 6 is preferably 30 nm or more, more preferably 45 nm or more, preferably 70 nm or less, and 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] For the detector 4, for example, a CCD camera, a photodiode, a photomultiplier tube, a spectrometer, and a CCD camera or photodiode array can be used.

[0046] For example, a plastic polarizing film can be used as the polarizing filter. Note that the detection device 1 does not necessarily need to have a polarizing filter.

[0047] As an optical lens, for example, an objective lens can be used. In addition, the detection device 1 does not necessarily have to have an optical lens, and only one of the incident optical lens and the exit optical lens may be provided.

[0048] The refractive index sensitivity of the detection device 1 in this embodiment is preferably 1000 nm / RIU or higher, more preferably 2000 nm / RIU or higher, preferably 30000 nm / RIU or lower, and more preferably 20000 nm / RIU or lower. The refractive index sensitivity (Sn) of the detection device 1 can be determined 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 to be detected 10 (Sn = Δλ / Δn). When the refractive index sensitivity of the detection device 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) Figure 2 is a schematic diagram showing a detection device according to a second embodiment of the present invention.

[0050] As shown in Figure 2, in the detection device 21, the optical prism 25 is a hexahedron with isosceles trapezoids on its sides, and its cross-sectional shape is an isosceles trapezoid. The shape of the optical prism 25 does not have to be a hexahedron with isosceles trapezoids on its sides; it may be a truncated square pyramid. In that case, the shape of the cross-section cut by a plane perpendicular to the base containing the vertex of the pyramid should be an isosceles trapezoid as shown in Figure 2. Note that, as in this embodiment, when the cross-sectional shape of the optical prism 5 is trapezoidal, 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-sectional shape, with the light incident surface 25a located on one of the slanted sides of the trapezoid, and the light emission surface 25c located on the other slanted side of the trapezoid. More specifically, in the hexahedron or truncated square pyramidal shape of the optical prism 25, one of the opposing slanted surfaces is the light incident surface 25a, and the other slanted surface is the light emission surface 25c. In the detection device 21, the angle α between the light incident surface 25a and the light emission surface 25c is the angle between a virtual line in the direction in which the light incident surface 25a extends and a virtual line in the direction in which the light emission surface 25c extends. The angle α between the light incident surface 25a and the light emission surface 25c corresponds to the vertex angle of the triangle formed by connecting the virtual line in the direction in which the light incident surface 25a extends and the virtual line in the direction in which the light emission surface 25c extends. Other aspects are the same as in the first embodiment.

[0052] In the detection device 21 of the second embodiment, the optical prism 25 is made of a material with 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 emission 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 incident on the light incident surface 25a of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Also, the optical axis X2 of the emitted light emitted from the light emission surface 25c of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Therefore, even in the detection device 21 of the second embodiment, the overall device can be simplified while increasing the degree of freedom in optical design.

[0053] As in the detection device 21 of the second embodiment, the shape of the optical prism 25 is hexahedron or truncated square pyramidal, and the cross-sectional shape of the optical prism 25 is isosceles trapezoidal. In this case, the optical prism 25 can be made low-profile, so the detection device 21 can be made smaller.

[0054] (Third embodiment) Figure 3 is a schematic diagram showing a detection device according to a third embodiment of the present invention.

[0055] As shown in Figure 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. For example, the optical lens described in the first embodiment can be used as the optical lens 37. The slit plate 38 has an incident slit 38a and an exit slit 38b.

[0056] In the detection device 31, light emitted from the light source / detector 40 is made into parallel light by the optical lens 37 and incident on the polarizing filter (in Figure 3, the polarizing filter is not shown). In the polarizing filter, the light is polarized and separated into s-polarized and p-polarized components, and the p-polarized light (hereinafter sometimes simply referred to as light) is emitted towards the slit plate 38. The light that reaches the slit plate 38 passes through the incident slit 38a and is emitted towards the optical prism 25. The light that reaches the optical prism 25 is refracted at the incident surface 25a and propagates towards the bottom surface 25b. The light that reaches the bottom surface 25b is reflected by the thin metal film 6 and propagates towards the light emission surface 25c. The light that reaches the light emission surface 25c is refracted at the light emission surface 25c and is emitted towards the slit plate 38. The light that reaches the slit plate 38 passes through the emission slit 38b and is emitted towards the optical lens 37. Light reaching the optical lens 37 is focused by the optical lens 37 and propagates toward the light source / detector 40. In the detection device 31, the light reaches the detector of the light source / detector 40 in this manner and is detected. Other aspects are the same as in the second embodiment.

[0057] In the detection device 31 of the third embodiment, the optical prism 25 is made of a material with 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 emission 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 incident on the light incident surface 25a of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Also, the optical axis X2 of the emitted light emitted from the light emission surface 25c of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Therefore, even in the detection device 31 of the third embodiment, the overall device can be simplified 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 the light source and detector are integrated. In this case, since the light emitted from the light source / detector 40 returns to the light source / detector 40 and is detected, the entire detection device 31 can be simplified and the detection device 31 can be made smaller. In addition, the detection device 31 may emit a ring-shaped light from the light source / detector 40. Furthermore, the light source / detector 40 may have a structure in which the light source and detector are integrated by a Y-shaped optical fiber. Specifically, the light source may be connected to the first end of the Y-shaped optical fiber and the detector may be connected to the second end. In this case, the light emitted from the light source is emitted from the end (third end, lower end of the Y) to which the light source and detector are not connected. Furthermore, the light reflected by the bottom surface 25b of the optical prism 25 enters from the third end of the Y-shaped optical fiber and travels toward the detector.

[0059] (Fourth embodiment) Figure 4 is a schematic diagram showing a detection device according to a fourth embodiment of the present invention.

[0060] As shown in Figure 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. For example, the optical lens described in the first embodiment can be used as the optical lens 43. In addition, 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 incident on the polarizing filter (in Figure 4, the polarizing filter is not shown). In the polarizing filter, the light is polarized into an s-polarized component and a p-polarized component, and the p-polarized component (hereinafter sometimes simply referred to as light) is emitted towards the optical prism 25. The light that reaches the optical prism 25 is refracted at the light incident surface 25a and propagates toward the bottom surface 25b. The light that reaches the bottom surface 25b is reflected by the thin metal film 6 and propagates toward the light emission surface 25c. The light that reaches the light emission surface 25c is refracted at the light emission surface 25c and emitted toward the mirror 44. The light that reaches the mirror 44 is reflected by the mirror 44, and after the optical axis X2 becomes parallel to the bottom surface 25b, it is emitted toward the optical lens 45. Light reaching the optical lens 45 is focused by the optical lens 45 and propagates toward the detector 4. In the detection device 41, the light reaches the detector 4 in this manner and is detected. Other aspects are the same as in the second embodiment.

[0062] In the detection device 41 of the fourth embodiment, the optical prism 25 is made of a material with 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 emission 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 incident on the light incident surface 25a of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Also, the optical axis X2 of the emitted light emitted from the light emission surface 25c of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Therefore, even in the detection device 41 of the fourth embodiment, the overall device can be simplified while increasing the degree of freedom in optical design.

[0063] (Modification of the fourth embodiment) Figure 5 is a schematic diagram showing a detection device according to a modified example of the fourth embodiment of the present invention.

[0064] As shown in Figure 5, in the detection device 41A, a modified example of the fourth embodiment, the arrangement of the light source 2 and the detector 4 is reversed compared to 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 Figure 5). In the polarizing filter, the light is polarized into an s-polarized component and a p-polarized component, and 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 has its optical axis X1 perpendicular to the bottom surface 25b and travels toward the optical prism 25. The light that reaches the optical prism 25 is refracted at 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 emission surface 25c1. Light that reaches the light-emitting surface 25c1 is refracted at the light-emitting surface 25c1, focused by the optical lens 43, and propagates toward the detector 4. In the detection device 41A, the light reaches the detector 4 in this manner and is detected.

[0066] In the modified detection device 41A of the fourth embodiment, the optical prism 25 is 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 emission 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 incident on the light incident surface 25a1 of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Also, the optical axis X2 of the emitted light emitted from the light emission surface 25c1 of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular.Therefore, even in the modified detection device 41A of the fourth embodiment, the overall device can be simplified while increasing the degree of freedom in optical design.

[0067] The following describes further details of the detection device of the present invention using specific examples. In the following examples, experimental examples based on simulations using the detection device 21 in Figure 2 will be described. In these examples, the angle α between the light incident surface 25a and the light output surface 25c is referred to as the vertex angle α of the triangle formed by connecting a virtual line in the direction in which the light incident surface 25a extends and a virtual line in the direction in which the light output surface 25c extends. In these examples, light was incident at the longitudinal center of the side where the light incident surface 25a is located, within the triangle formed by connecting a virtual line in the direction in which the light incident surface 25a extends and a virtual line in the direction in which the light output surface 25c extends. In addition, an Au film with a thickness of 47 nm was used as the metal thin film 6. In addition, water with a refractive index nd = 1.33 was used as the object to be detected 10.

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

[0069] As shown in Figure 6, in the detection device 21, the optical axis X1 of the incident light incident on the light incident surface 25a of the optical prism 25 and the bottom surface 25b of the optical prism 25 are approximately perpendicular. Therefore, the angle of incidence and angle of refraction of the light incident on the light incident surface 25a of the optical prism 25 can be expressed by Snell's law as shown in equation (1) below.

[0070]

number

[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 light incident on the optical prism 25, the refractive index n of the material constituting the optical prism 25, the thickness of the metal thin film 6, and the refractive index of the object to be detected 10, and can also be expressed as γ(n,λ). Note that this function does not take into account the wavelength dependence 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 as the refractive index nd. From Figure 6, the angle of incidence γ(γ(n,λ)) can be expressed as shown in equation (2) below using the exterior angle theorem.

[0072]

number

[0073] Combining equations 1(1) and 1(2), we get equation (3) below.

[0074]

number

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

[0076]

number

[0077]

number

[0078] Figure 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. Figures 8 to 11 are graphs in Figure 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] Figure 7 shows that when the refractive index nd of the material constituting the optical prism 25 is 1.5, there is no intersection point of equations (4) and (5) where the apex angle α is 0° or greater. On the other hand, Figures 8 to 11 show that when the refractive index nd of the material constituting the optical prism is between 1.86 and 3.0, there is an apex angle α at the intersection of equations (4) and (5) (the apex angle α at which surface plasmon resonance occurs), and it can be seen that the larger the refractive index nd, the larger the apex angle α at the intersection of equations (4) and (5).

[0080] Similarly, the vertex angle α at the intersection of equations (4) and (5) was determined when the wavelength of light incident on the optical prism was 633 nm and the refractive index nd of the materials constituting the optical prism was 3.5 and 4.0. Furthermore, the vertex angle α at the intersection of equations (4) and (5) was determined when the wavelength of light incident on the optical prism was 800 nm and the refractive index nd of the materials 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. Note that 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] [Table 1]

[0082] Next, a specific example of measuring the refractive index sensitivity of the detection device 21 will be described.

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

[0084] Figure 12 shows 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] Figure 13 shows the relationship between the wavelength of incident light and the reflectance in a detection device according to a second embodiment of the present invention, where the refractive index nd of the material constituting the optical prism is 2.0 and the apex angle α is 35°. In Figure 13, the solid line shows the results when an aqueous solution with a refractive index nd = 1.33 is used as the object to be detected 10, and the dashed line shows the results when an aqueous solution with a refractive index nd = 1.34 is used.

[0086] Figure 13 shows 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 (same refractive index nd, but apex angle α is 30°). Also in Figure 13, 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.

[0087] Figure 14 shows 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. Figure 15 shows 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 change in the resonance wavelength that occurs when the refractive index nd of the surrounding medium changes by 1; a larger value indicates better sensitivity. The resonance wavelength is the wavelength at which the reflectance is smallest when white light is used as the light source, and surface plasmon resonance occurs strongly at this wavelength. Furthermore, the refractive index sensitivity (Sn) was determined, for example, as shown in Figure 12, by dividing the change in the refractive index of the aqueous solution (Δn) by the change in the dip wavelength (resonance wavelength) (Δλ) when the dip wavelength (resonance wavelength) changes with the change in the refractive index of the aqueous solution (Sn = Δλ / Δn).

[0089] As shown in Figures 14 and 15, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 14 and 15 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is set to 2.0, it is desirable, for example, that the apex angle α be 15° or more and 50° or less, more preferably 26° or more and 38° or less.

[0090] Figure 16 shows 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. Figure 17 shows 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] As shown in Figures 16 and 17, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 16 and 17 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is 1.86, it is desirable, for example, that the apex angle α be 5° or more and 40° or less, more preferably 10° or more and 22° or less.

[0092] Figure 18 shows 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. Figure 19 shows 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] As shown in Figures 18 and 19, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 18 and 19 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is 2.5, it is desirable, for example, to set the apex angle α to 30° or more and less than 90°, more preferably 70° or more and 78° or less.

[0094] Figure 20 shows 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. Figure 21 shows 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] As shown in Figures 20 and 21, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 20 and 21 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is set to 3.0, it is desirable, for example, that the apex angle α be 80° or more and 120° or less, more preferably 94° or more and 102° or less.

[0096] Figure 22 shows 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. Figure 23 shows 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, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 22 and 23 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is 3.5, it is desirable, for example, that the apex angle α be 100° or more and 130° or less, more preferably 111° or more and 117° or less.

[0098] Figure 24 shows 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. Figure 25 shows 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, it can be seen that the refractive index sensitivity increases as the apex angle α increases, while the resonance wavelength also increases as the apex angle α increases. Thus, it is desirable to adjust the apex angle α appropriately according to the desired refractive index sensitivity and the wavelength of light used. Considering Figures 24 and 25 and the reasons mentioned above, when the refractive index nd of the material constituting the optical prism 25 is 4.0, it is desirable, for example, that the apex angle α be 110° or more and 140° or less, more preferably 122° or more and 128° or less. [Examples]

[0100] The present invention will be described in more detail below based on specific examples. The present invention is not limited in any way to the following examples, and can be implemented with appropriate modifications without changing its essence.

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

[0102] As the optical prism 25, a hexahedral glass prism with an isosceles trapezoidal side surface, having 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, was used. The glass constituting the glass prism contained at least 10% by mass of TiO2 + Ta2O5 + Nb2O5 + La2O3. A thin gold film 6 was used for the metal thin film 6 on the bottom surface 25b of the glass prism (optical prism 25), with a film thickness of 50 nm. As the light source / detector 40, a light source / detector with a structure in which the light source and detector are integrated by a Y-type optical fiber was used. Specifically, a light source / detector 40 with a structure in which the light source is connected to the first end of the Y-type optical fiber and the detector is connected to the second end was used. 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 that was not connected to the light source and detector (the third end, the lower end of the Y-shape). Light reflected by the bottom surface 25b of the optical prism 25 entered the Y-shaped optical fiber from the third end, traveled towards the detector, and was detected. The object to be detected 10 was a mixture of water and ethanol. Specifically, the refractive index nd of the mixture 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: Chemical Handbook, Basic Edition, 6th Revised Edition, Chapter 14, Table 14.5-3

[0104] Next, the change in resonance wavelength of the water-ethanol mixture was measured using the detection device 31 from Example 1, and the refractive index of the water-ethanol mixture was determined from the change in resonance wavelength that appeared between 650 nm and 780 nm. The results are shown in Figure 26. From Figure 26, it can be seen that in Example 1, the experimental value and the simulated value for the change in resonance wavelength were in good agreement, confirming that the detection device 31 functioned well as a refractive index sensor. The solid line in Figure 26 represents the refractive index value of the mixture, which was interpolated using the refractive index value shown in Reference 1. Since the ethanol concentration in Reference 1 is given in weight percent, it was converted to volume percent using the ethanol density value shown in Reference 2.

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

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

[0107] Figure 27 shows the relationship between the measurement elapsed time and the resonance wavelength when an aminohexadecanethiol aqueous solution was exposed to the surface 6a of a gold thin film (metal thin film 6) on the bottom surface 25b of a glass prism. As shown in Figure 27, exposure to the aminohexadecanethiol aqueous solution began 200 seconds after the start of measurement, and the change in the resonance wavelength almost stopped 3200 seconds after the start of measurement (3000 seconds after the start of exposure), indicating that the formation of the dielectric thin film was complete. At this time, the resonance wavelength changed from 674 nm to 682 nm, so the change in resonance wavelength was 8 nm. From the simulation value that the resonance wavelength changes by 3.4 nm for every 1 nm thickness of the dielectric thin film on the gold thin film, the thickness of the dielectric thin film was calculated to be approximately 2.35 nm. This thickness was in close agreement with the length of the aminohexadecanethiol molecule (2.3 nm) determined from the molecular structure and bond length. The reaction was terminated by rinsing the surface with water 4000 seconds after the start of measurement (3800 seconds after the start of exposure). In this way, in Example 2, the thickness of the dielectric thin film calculated from experimental values ​​and the theoretical thickness of the dielectric thin film were in good agreement, confirming that it functioned well as a chemical sensor.

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

[0109] As the optical prism 25, a glass prism similar to that used in Example 1 was used. Similar to Example 1, a gold thin film was used for the metal thin film on the bottom surface 25b of the glass prism, with a film thickness of 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 object to be detected 10 was the same as in Example 1.

[0110] Next, the change in resonance wavelength of a mixed solution of water and ethanol was measured using the detection device 41 from Example 3, and the refractive index of the water-ethanol mixture was determined from the change in resonance wavelength that appeared between 650 nm and 780 nm. The results are shown in Figure 28. From Figure 28, it can be seen that in Example 3, the experimental value and the simulated value for the change in resonance wavelength were in good agreement, confirming that the refractive index sensor functioned well. The solid line shown in Figure 28 represents the refractive index of the mixture with the literature value for refractive index shown in Reference 1 interpolated, similar to Figure 26.

[0111] (Example 4) In Example 4, a chemical sensor for detecting substances was fabricated as a detection device. The sensor configuration was the same as in Example 3. The substance to be detected 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 (length of the aminohexadecanethiol molecule determined from the molecular structure and bond length).

[0112] Figure 29 shows the relationship between the measurement elapsed time and the resonance wavelength when an aqueous aminohexadecanethiol solution (0.5 mM) was exposed to the surface 6a of a gold thin film on the bottom surface 25b of a glass prism. As shown in Figure 29, exposure to the aqueous aminohexadecanethiol solution began 500 seconds after the start of measurement, and the change in the resonance wavelength almost stopped 1500 seconds after the start of measurement (1000 seconds after the start of exposure), indicating that the formation of the dielectric thin film was complete. At this time, the resonance wavelength changed from 625 nm to 634 nm, so the change in resonance wavelength was 9 nm. From the simulation value that the resonance wavelength changes by 3.4 nm for every 1 nm thickness of the dielectric thin film on the gold thin film, the thickness of the dielectric thin film was calculated to be approximately 2.6 nm. This thickness was in close agreement with the length of the aminohexadecanethiol molecule (2.3 nm) determined 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). Thus, in Example 4, the thickness of the dielectric thin film calculated from experimental values ​​and the theoretical thickness of the dielectric thin film were in good agreement, confirming that it functioned well as a chemical sensor. [Explanation of symbols]

[0113] 1, 21, 31, 41, 41A... Detection devices 2...Light source 3...Sensor unit 4… Detector 5.25...Optical prism 5a, 25a, 25a1...Light incidence surface 5b, 25b...bottom 5c, 25c, 25c1...Light exit surface 6…Metal thin film 6a…Surface 10...Detected object 37, 43, 45… Optical lenses 38…Slit plate 38a...Induction side slit 38b... Exit side slit 40…Light source / detector 44...Mirror

Claims

1. A detection device that utilizes surface plasmon resonance, Light source and A sensor unit comprising an optical prism having a light incident surface, a bottom surface, and a light emission surface, and a metal thin film provided on the bottom surface of the optical prism, which reflects light emitted from the light source and incident on the light incident surface toward the light emission surface, A detector that detects light reflected by the metal thin film of the sensor unit, Equipped with, The optical prism is made of a material with a refractive index nd of 1.8 or more and 4.0 or less. In the optical prism, the angle between the light incident surface and the light emission surface is 5° or more and 170° or less. The optical axis of the incident light incident on the light incident surface and the bottom surface of the optical prism are substantially perpendicular. A detection device in which the optical axis of the emitted light emitted from the light-emitting surface and the bottom surface of the optical prism are substantially perpendicular.

2. The 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. The detection device according to claim 1 or 2, wherein the angle between the light incident surface and the light emission surface in the optical prism is less than 90°.

4. The cross-sectional shape of the optical prism is trapezoidal. The light incident surface is positioned on one of the slanted sides of the trapezoid, The detection device according to claim 1 or 2, wherein the light emitting surface is arranged on the other slanted side of the trapezoid.

5. The 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 1,000 nm / RIU or more and 30,000 nm / RIU or less.

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