JP2014119262A - Optical device, detection device and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical device and a detection device that can obtain a large enhanced strong electric field without using a binding between localized surface plasmon and propagating surface plasmon, and further without depending on dependency of an incidence angle of excitation light.SOLUTION: A detection device 100 has: a light source 130; a condensing lens 131C; and an optical device 10. The optical device 10 has: a substrate 12; a metallic layer 14 that is formed on the substrate; a dielectric layer 16 that is formed on the metallic layer; and a plurality of metal nanoparticles 18 that is formed on the dielectric layer. The substrate has spherical surfaces 10A and 10B with centers P1 and P2 on normal lines L2 and L3 and to be defined by radiuses of curvature R1 and R2 formed on a surface in a region more than areas irradiated with light beams B1 and B2. Let a thickness of the dielectric layer be d, a wavelength of the light beam be λ, a refractive index of the dielectric layer at a wavelength λ be n, and a natural number be m, the thickness d of the dielectric layer is set to m×λ/n.

Description

  The present invention relates to an optical device, a detection apparatus, an electronic apparatus, and the like.

  The demand for medical diagnosis, food inspection, and the like is increasing, and the development of small and high-speed sensing technology is required. Various types of sensors, including electrochemical methods, are being studied, but they can be integrated, low cost, and surface plasmon resonance (SPR) is applied because of the choice of measurement environment. There is growing interest in these sensors. For example, there is known one that detects the presence or absence of substance adsorption, such as the presence or absence of antigen adsorption in an antigen-antibody reaction, using SPR generated on a metal thin film provided on the surface of a total reflection prism.

  Here, in order to realize a highly sensitive surface plasmon resonance sensor using SPR, it is desired that the enhancement of the near electric field is as large as possible (Non-patent Document 1).

  In recent years, SPR sensors using metal nanoparticles or metal nanostructures have been proposed for the purpose of highly sensitive sensing. For example, in the SPR sensor proposed in Patent Document 1, metal nanoparticles are periodically arranged on a metal film via an extremely thin dielectric layer of 2 to 40 nm (see FIG. 1 of Patent Document 1). ). When this sensor is irradiated with light, a bond is created between Localized Surface Plasmon (LSP) and Propagating Surface Plasmon (PSP), and the near electric field appearing on the surface of the metal nanoparticles is greatly enhanced. The When a molecule to be detected is captured by this enhanced near electric field, a strong SERS surface enhanced Raman scattering (SERS) signal is generated, and this signal is acquired and spectroscopically analyzed to identify the molecule to be detected. it can.

Special table 2007-538264 gazette

J. et al. Phys. Soc. Jpn. 52, 3853 (1983)

  However, the metal nanostructure disclosed in Patent Document 1 has a problem that the density (number per unit area) of a place (called a hot site) where a strong near electric field appears is low. For this reason, the sensitivity as a sensor is low, and it has not reached practical use as an SPR sensor. In order to increase the hot site density, the arrangement period of the metal nanoparticles may be shortened. However, if the metal nanoparticles are arranged with a narrow interval, since the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP cannot be used, a dilemma that a sufficiently large enhanced electric field cannot be obtained occurs.

  Some aspects of the present invention provide an optical device, a detection apparatus, an electronic apparatus, and the like that can obtain a sufficiently large enhanced electric field without using coupling between localized surface plasmons and propagating surface plasmons. With the goal.

  Some other aspects of the present invention provide an optical device, a detection apparatus, and an electronic apparatus that can achieve both a large enhanced electric field and a high hot site density and can increase the signal intensity without being influenced by the incident angle dependency of excitation light. The purpose is to provide.

(1) One aspect of the present invention is
A light source that emits light;
A condenser lens for condensing the light;
An optical device for entering the light beam collected by the condenser lens;
An introduction mechanism for introducing a fluid sample into the optical device;
Have
The optical device is
A spherical surface having a normal line of the surface as the center line of the radius of curvature is formed on the surface on which the light beam is incident, and the spherical surface is the same as or wider than the irradiation region of the light beam,
A metal layer formed on the spherical surface;
A dielectric layer formed on the metal layer;
A plurality of metal nanoparticles formed on the dielectric layer;
Have
When the thickness of the dielectric layer is d, the wavelength of the light beam is λ, the refractive index of the dielectric layer at the wavelength λ is n, and the natural number is m, the thickness d of the dielectric layer is m. The present invention relates to a detection device set to xλ / n.

In one embodiment of the present invention, when the thickness d of the dielectric layer is set to m × λ / n, an enhanced electric field can be secured by reflection and interference by the multilayer interference film shown in FIG. That is, a sufficiently large enhanced electric field can be obtained without using the coupling between localized surface plasmons and propagating surface plasmons. In addition, the pitch P (Pb) of the metal nanoparticles of one embodiment of the present invention using the region B of FIG. 2 is the pitch Pa = λ (ε2 + ε1 / ε2) of the metal nanoparticles uniquely determined in the region A of FIG. ) It can be shorter than ^1/2 . Thereby, both a large enhanced electric field and a high hot site density can be achieved, and the detection sensitivity can be improved.

  In one embodiment of the present invention, when a metal layer and a dielectric layer are formed over the above-described substrate on which the spherical surface is formed, a plurality of metal nanoparticles are formed on the spherical surface. For this reason, the incident angle of the light beam collected by the condenser lens is reduced over the entire spherical surface. Therefore, by increasing the numerical aperture NA of the condenser lens, it is possible to enhance the Raman signal intensity according to the theoretical curve shown by the solid line in FIG.

(2) In one aspect of the present invention, the spherical surface has a concave shape in the incident direction of the light beam,
The focal point of the condenser lens can be set upstream of the incident direction of the light beam from the spherical surface.

  As shown in FIG. 19A, by irradiating the concave spherical surface with the light beam that has passed through the focal point of the condenser lens, the incident angle of the light beam is reduced over the entire spherical surface.

  (3) In one aspect of the present invention, the spherical surface has a convex shape in the incident direction of the light beam, and the focal point of the condenser lens is set downstream of the incident direction of the light beam from the spherical surface. Can do.

  As shown in FIG. 19B, by irradiating the convex spherical surface with the light beam before passing through the focal point of the condenser lens, the incident angle of the light beam is reduced over the entire spherical surface.

  (4) In one aspect of the present invention, the center of the radius of curvature of the spherical surface can be set on the optical axis of the light beam.

  In this way, the light beam incident on the spherical surface is incident on the spherical surface with line symmetry with respect to the optical axis, so that the incident angle of the light beam becomes smaller over the entire spherical surface. For this alignment, for example, an in-focus servo mechanism employed in a CD or DVD reader can be used.

  (5) In one aspect of the present invention, the center of the radius of curvature of the spherical surface can coincide with the focal point.

  In this way, the incident angle of the light beam incident on the spherical surface becomes 0 ° irrespective of the incident position on the spherical surface.

  (6) In one aspect of the present invention, the radius of curvature may be on the order of several μm to several tens of μm.

  Since the size of the metal nanoparticles is 1-1000 nm, preferably 100 nm or less, a plurality of metal nanoparticles can be formed on the spherical surface defined by the radius of curvature in the above-described range. In addition, since the beam diameter of the excitation light is about several μm, the light beam can be incident on a plurality of metal nanoparticles present in the spherical portion. In addition, since the irregularities due to the spherical surface formed on the substrate are fine, there is no problem in forming the metal layer and the dielectric layer on the substrate by sputtering or vapor deposition.

  (7) According to another aspect of the present invention, there is provided the detection device according to any one of (1) to (6) described above, a calculation unit that calculates health care information based on detection information from the detection device, The present invention relates to an electronic apparatus including a storage unit that stores medical information and a display unit that displays the health information.

  The electronic device according to another aspect of the present invention is useful for medical diagnosis, food and drink inspection, and the like.

(8) Still another aspect of the present invention provides:
An optical device for entering a light beam,
A spherical surface having a radius of curvature centered on a normal line of the surface is formed on a surface on which the light beam is incident, and the spherical surface is formed to be the same as or wider than the irradiation region of the light beam;
A metal layer formed on the spherical surface;
A dielectric layer formed on the metal layer;
A plurality of metal nanoparticles formed on the dielectric layer and on which the light beam is incident;
Have
When the thickness of the dielectric layer is d, the wavelength of the light beam is λ, the refractive index of the dielectric layer at the wavelength λ is n, and the natural number is m, the thickness d of the dielectric layer is m. X relates to an optical device set to λ / n.

  By using this optical device, the detection apparatus described in (1) can be realized.

FIG. 1A is a cross-sectional view of an optical device according to an embodiment of the present invention, and FIG. 1B is a plan view. It is a characteristic view which shows the dispersion | distribution curve of the optical device structure shown to FIG. 1 (A) (B). It is a figure for demonstrating electric field enhancement by the effect | action of a dipole image (virtual image). It is a figure for demonstrating electric field enhancement by the effect | action of multilayer film interference. FIG. 5A shows a specific example of an optical device, and FIG. 5B is a diagram showing a simulation result of an enhanced electric field obtained with the structure of FIG. 5A. FIG. 6A shows a specific example of the same optical device as FIG. 5A, and FIG. 6B shows the electric field strength E ⁴ obtained by the structure. Figure 7 (A) shows a specific example of an optical device having a different metal layer and FIG. 6 (A), the FIG. 7 (B) shows the electric field intensity E ⁴ obtained by the structure. FIG. 8A shows a specific example of an optical device having two dielectric layers, and FIG. 8B shows the electric field strength E ⁴ obtained by the structure. FIG. 9A to FIG. 9D are diagrams showing a method for manufacturing the optical device shown in FIG. 10A and 10B are diagrams showing examples of the resist pattern shown in FIG. 9C. It is sectional drawing of the optical device which formed the metal nanoparticle formed on a dielectric material in the shape of an island. 12A is a diagram showing signal enhancement obtained by the structure of FIG. 11 which is an embodiment of the present invention, and FIG. 12B is a diagram showing signal enhancement obtained by the conventional structure. It is a figure for demonstrating incident angle (theta) of the excitation light with respect to an optical device. 14A and 14B are characteristic diagrams showing the incident angle dependence of the electric field enhancement for each of S-polarized light and P-polarized light. It is a figure for demonstrating the phase difference (optical path difference) in the dielectric material layer which arises with an incident angle. It is a figure which shows the relationship between the peak deviation | shift amount of a near electric field intensity | strength, and an incident angle. It is a figure which shows a mode that excitation light is condensed with a condensing lens, and injects into a sensor chip. It is a figure which shows the relationship between Raman signal intensity | strength and the numerical aperture NA of a condensing lens. 19A and 19B are diagrams showing the relationship between the concave spherical surface or convex spherical surface of the dielectric layer and the condenser lens. It is a figure which shows the sensor chip in which the some metal nanoparticle was formed on the convex spherical surface of a dielectric material layer. It is a figure which shows the sensor chip by which the metal island was formed on the micro concave lens array of a dielectric material layer. It is a figure which shows the detection apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the dimensions and ratios of the constituent elements are appropriately changed from the actual ones in order to make the constituent elements large enough to be recognized on the drawings.

1. Optical device 1.1. Basic Structure of Optical Device FIG. 1 schematically shows the structure of a surface plasmon resonance sensor chip (optical device) 10 according to this embodiment. 1A is a cross-sectional view and FIG. 1B is a plan view, both of which are part of the structure.

  The sensor chip 10 has a metal layer 14 on a substrate 12 and a dielectric layer 16 having a thickness d on the metal layer 14. The metal nanoparticles 18 are arranged on the metal layer 14 via the dielectric layer 16, for example, in a two-dimensional direction with a period P, for example. The metal layer 14 is thick enough not to transmit excitation light.

  The sensor chip 10 has a feature that is different from the prior art. First, the thickness d of the dielectric layer 16 is sufficiently thicker than the conventional thickness of 2 to 40 nm disclosed in Patent Document 1. It is. Secondly, the enhanced electric field is formed by utilizing the interference between the dipole image and the multilayer film without using the coupling between the localized surface plasmon LSP and the propagating surface plasmon PSP. Third, the period P of the metal nanoparticles 18 is sufficiently smaller than the period (pitch) of the conventional metal nanoparticles.

  Here, the first to third feature points are related to each other. That is, the structure of the first feature point or the second feature point causes the third feature point as a result, and conversely the third feature point causes the third feature point according to the principle of the second feature point. Resulting in the structure of From this, the present invention can be defined in many ways.

1.2. Period of arrangement direction of metal nanoparticles First, the third feature point will be described. The period (pitch) P in the arrangement direction (one-dimensional direction or two-dimensional direction) of the metal nanoparticles 18 will be described. Note that the period (pitch) P in the arrangement direction of the metal nanoparticles 18 does not need to be constant, and may exhibit non-periodicity. When the island-shaped metal nanoparticles 31 in FIG. 11 described later have an indefinite period or a random arrangement, the following requirements may be satisfied as the maximum pitch P between adjacent metal nanoparticles.

  FIG. 2 is a dispersion curve of the optical device structure shown in FIGS. 1A and 1B. The vertical axis represents the angular frequency ω, and the horizontal axis represents the wave number k. As shown in FIG. 2, there are a dispersion curve of localized surface plasmon LSP excited by the metal nanoparticles 18 and a dispersion curve of propagating surface plasmon PSP excited by the interface between the metal layer 14 and the dielectric layer 16.

  Conventionally, attention has been paid to the region A where the dispersion curve of the localized surface plasmon LSP and the dispersion curve of the propagation surface plasmon PSP intersect. The near electric field on the surface of the metal nanoparticles was enhanced by utilizing the coupling generated between the localized surface plasmon LSP and the propagating surface plasmon PSP. In that case, the intersection of the wave number 2π / Pa given by the metal nanoparticles with the period Pa of the conventional structure and the dispersion curve of the PSP is the resonance wavelength (vertical axis, angular frequency ω0), which is the incident light incident on the sensor chip. It is equal to the excitation wavelength λ.

  That is, the wave number (wave number of the evanescent wave) Ka of the propagation surface plasmon PSP excited when the sensor chip structure is irradiated with light having an angular frequency ω (wavelength λ) is Ka = 2π / Paa. When the period Pa is obtained in relation to the excitation wavelength λ used, when the excitation wavelength λ is 633 nm, the period Pa is as high as 600 nm.

  If the size in plan view is a metal nanoparticle having a diameter of 100 nm, for example, hot sites are generated in the vicinity of the metal nanoparticle, and therefore the density of hot sites is sparse when the period Pa is 600 nm. Further, since the beam diameter of the excitation light is about several μm, the number of hot sites located within the beam diameter is as small as several periods Pa. As described above, when an attempt is made to enhance the near electric field on the surface of the metal nanoparticle by utilizing the bond generated between the LSP and the PSP in the conventional structure, the period Pa of the metal nanoparticle becomes longer, so the density of the hot site is increased. Could not be increased.

  Therefore, in this embodiment, attention is paid to the region B instead of the region A in FIG. The wave number Kb in the region B is larger than the wave number Ka in the region A. Since the wave number is the reciprocal of the period, the arrangement period Pb (P) of the metal nanoparticles 18 of the present embodiment using the region B can be shortened.

Here, the length of the metal nanoparticles 18 in the arrangement direction is 2r. If the metal nanoparticles 18 are circular in plan view, r corresponds to the radius. However, the shape of the metal nanoparticles 18 in plan view is not limited, and may be an ellipse or the like as described later. Further, when λ is an excitation wavelength, ε1 is a complex dielectric constant of the dielectric layer 16, and ε2 is a complex dielectric constant of the metal layer 14, P (Pb) <Pa is satisfied. As an upper limit of the period P, P <Pa = λ (ε2 + ε1 / ε2) ^1/2 is established.

The lower limit of the period P of the metal nanoparticles 13 in the present embodiment is a length at which the two metal nanoparticles 18 adjacent in the arrangement direction do not contact each other. Therefore, the lower limit of the period P is P> 2r. From the above, as the period P of the metal nanoparticles 18 of the present embodiment,
2r <P <λ (ε2 + ε1 / ε2) ^1/2 (1)
Is established.

In order to increase the hot site density by making the period P of the metal nanoparticles 18 of the present embodiment sufficiently smaller than the period Pa of the conventional structure, the coefficient c is set as c>1;
2r <P <λ (ε2 + ε1 / ε2) ^1/2 / c (2)
Can be satisfied. Note that the definition of the upper limit of the coefficient c is not necessary, because if c is excessive, 2r <P is not satisfied and the expression (2) is not satisfied, and therefore the coefficient c naturally has an upper limit. It is.

In consideration of shortening the period P, the length of the metal nanoparticles 18 in the arrangement direction is preferably 2 nm, for example, 30 nm <2r <100 nm. In addition, considering that the excitation wavelength λ is 500 nm <λ <800 nm,
40 nm <P <500 nm (3)
It can be. This numerical range is substantially the same as the range in which the coefficient c in the equation (2) is 1.2 to 15 when the period Pa of the conventional structure is approximately Pa = λ (ε2 + ε1 / ε2) ^1/2 / c = 600 nm.

1.3. Dielectric Layer Thickness The thickness d of the dielectric layer 16 is required to be thicker than 2 to 40 nm, which is the conventional thickness disclosed in Patent Document 1. Therefore,
d> 40 nm, more preferably d> 100 nm (4)
It can be.

  As described above, the thickness of the dielectric layer 16 (first feature point) has a correlation with the second feature point, and the thickness d of the dielectric layer 16 is an absolute value as shown in Expression (4). In addition to the above, it is possible to obtain qualitatively by generating a large enhanced electric field (second feature point) regardless of the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP. This will be described below.

1.4. The formation principle of the enhanced electric field that does not depend on the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP In this embodiment, since the region B in FIG. 2 is used, the period P of the metal nanoparticles 18 is reduced as described above. (Third feature point), and it is necessary to generate a large enhanced electric field only by the localized surface plasmon LSP without using the coupling generated between the localized surface plasmon LSP and the propagating surface plasmon PSP due to the causal relationship. (Second feature point).
For this purpose, it is necessary to increase the electric field acting on the metal nanoparticles 18 so that the metal nanoparticles 18 exhibit a large polarization. In this embodiment, (1) dipole image and (2) multilayer interference are used as the origin of electric field enhancement. From the causal relationship with the utilization principles (1) and (2), as described below, the thickness d of the dielectric layer 16 is thicker than that of the prior art (second feature point).

1.4.1. As shown in FIG. 3, when the polarization induced in the metal nanoparticle 18 by the irradiation of the excitation light is p1, the action of the dipole image (virtual image) of the polarization p2 in the reverse direction that appears in the metal layer 14 The electric field E1 applied to the metal nanoparticles 18 is expressed as follows: the dielectric layer thickness is d, the complex dielectric constant of the dielectric layer 16 is ε1, and the complex dielectric constant of the metal layer 14 is ε2.
E1 = βp1 / (2d) ³ (5)
It becomes. However, the coefficient β = (ε2−ε1) / (ε2 + ε1) giving the size of the dipole image.

Therefore, the polarization p1 is defined as follows: where the polarizability of the metal nanoparticles 18 is α and the electric field of the excitation light is E2.
p1 = [α / (1-αβ / (2d) ³ )] · E2 (6)
It becomes.

As can be seen from the equation (6), the polarization p1 increases or decreases depending on the magnitude of the coefficient 1 / (1-αβ / (2d) ³ ). As long as a general dielectric or metal is used, β> 1 because ε1 is positive and ε2 is negative. Therefore, in order for 1 / (1-αβ / (2d) ³ ), which is the above coefficient, to have a large positive value, α / (2d) ³ ) <1,
d> α ^1/3 / 2 (7)
Is established.

In order to increase the polarization p1 induced in the metal nanoparticle 18 by the action of the dipole image, that is, to enhance the electric field E1 acting on the metal nanoparticle 18, the thickness d of the dielectric layer 16 is set to It means that it is larger than the half value α ^1/3 / 2 of the cube root α ^1/3 of the polarizability α of the particle 18.

Further, in order for the coefficient 1 / (1-αβ / (2d) ³ )) to have a large positive value, the complex dielectric constant ε1 of the dielectric layer 16 and the complex dielectric constant ε2 of the metal layer 14 are: [] Represents the real part of the complex number, and Im [] represents the imaginary part of the complex number,
Re [ε2] ≧ −ε1, Im [ε2] ≈0 (8)
It is desirable that

Examples of the material of the metal nanoparticles 18 that satisfy the formula (8) include Ag and Au. The polarizability α of Ag and Au is approximately 6 × 10 ⁷ (nm ³ ). Substituting this value into Equation (7) results in d> 200 nm, both of which are less than the thickness of the dielectric layer of the prior art of 40 nm. It is necessary to increase the thickness.

  That is, while the period P of the metal nanoparticles 18 is reduced as a structure that does not depend on the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP (third feature point), the bipolar nanoparticles are used to form the metal nanoparticles 18. The acting electric field is increased (second feature point), and for this purpose, the thickness of the dielectric layer 16 needs to be made thicker than before (first feature point). In other words, since the dielectric layer 16 is made thicker than the conventional one (first feature point), the metal is obtained using a bipolar image without depending on the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP. The electric field acting on the nanoparticles 18 can be increased (second characteristic point), and thereby the period P of the metal nanoparticles 18 can be decreased (third characteristic point).

1.4.2. Multilayer Film Interference A layer in which metal nanoparticles 18 shown in FIG. 1 (A (B)) are densely arranged effectively acts as a thin metal layer 18A as shown in FIG. A pair of mirrors are formed with the thick metal layer 14 to form a kind of resonance structure, and light incident on the resonance structures 14, 16, 18A is repeatedly reflected between the upper and lower metal layers 14, 18A. Interference occurs between a large number of reflected waves.

  Therefore, the strength of the electric field acting on the metal nanoparticles 18 depends on the reflectance of the metal layer 18 </ b> A and the thickness of the dielectric layer 16. When a metal material having a high reflectivity with respect to the excitation wavelength λ is used for the metal nanoparticles 18, the strength of the electric field acting on the metal nanoparticles 18 periodically increases or decreases with respect to the thickness d of the dielectric layer 16. Repeat (see FIG. 5B described later). The thickness d of the dielectric layer 16 giving the electric field peak is approximately determined by the following conditions.

d≈mλ / 2√ε1 (9)
That is, when the thickness d of the dielectric layer 16 is substantially equal to mλ / 2√ε1, the electric field peak shown in FIG. 5B can be generated. Where m is a natural number and λ is an excitation wavelength.

  The condition of the following formula (10) may be used instead of the formula (9).

d≈mλ / 2n (10)
Here, m is a natural number, λ is an excitation wavelength, and n is a refractive index of the dielectric layer at the wavelength λ. In this embodiment, it is considered that the principle of giving the electric field peak is multilayer film interference, and the incident angle dependence of the peak deviation of the electric field intensity, which will be described later, is expressed by the equation (10) which is the principle of multilayer film interference. Based on

Examples of the material of the metal nanoparticles 18 having the complex dielectric constant ε2 close to the condition of the equation (8) include Ag and Au. For example, when the excitation wavelength is 633 nm, the dielectric constant of Ag is ε2 = −16. The dielectric constant of 1 + j1.1 and Au is ε2 = −9.4 + j1.1.

When the dielectric layer 16 is made of SiO ₂ (ε1 = 2.1 + j0), the coefficient β that gives the size of the dipole image is β = 1.2 for Ag and β = 1.6 for Au. Therefore, regardless of whether Ag or Au is used for the metal nanoparticles 18, it can be expected that a large polarization p1, that is, a large near electric field appears in the metal nanoparticles 18. At the same time, Ag and Au have high reflectivity at wavelengths in the visible range, so if the thickness of SiO ₂ that is the material of the dielectric layer 16 is set based on the formula (9) or the formula (10), the metal A large electric field can be created at the position of the nanoparticles 18. However, Formula (9) or Formula (10) does not necessarily have to be established with an equal sign, and if the thickness d on the left side is a value close to the formula on the right side, the intensity of the electric field acting on the metal nanoparticles 18 can be increased. Can approach the peak. That is, the thickness d of the dielectric layer 16 may be set based on the formula (9) or (10).

1.5. Correlation Between Thickness of Dielectric Layer or Material of Metal Layer and Strength of Enhanced Electric Field FIG. 5A shows a specific example of the sensor chip structure of FIGS. In this structure, the metal nanoparticles 18 having a cylindrical shape are arranged with a period P of P = 140 nm vertically and horizontally. The metal nanoparticles 18 have a diameter (2r) of 40-110 nm and a height of 20 nm.

In FIG. 5 (B), the time-domain difference: shows the (FDTD Finite Difference Time Domain method) the intensity of the near field obtained by the method ^{E 4.} The reason for focusing on the intensity E ⁴ of the proximity field is as follows.

In order to realize a highly sensitive surface plasmon resonance sensor applying SPR, it is desirable that the enhancement of the near electric field is as large as possible. As described in Non-Patent Document 1, the enhancement γ is:
γ = (Intensity at excitation wavelength) × (Intensity at Raman scattering wavelength) (11)
Can be defined as

As can be seen from this equation (11), in order to increase the enhancement in Raman scattering, it is necessary to simultaneously increase both the enhancement in the excitation process and the enhancement in the scattering process. Therefore, if the sensor chip has a strong resonance peak in the vicinity of the excitation wavelength and the scattering wavelength, the enhancement effect is dramatically increased by the synergistic effect of both processes. In other words, E ⁴ is a measure of the degree of enhancement.

  As can be seen from FIG. 5B, there is a particle diameter of the metal nanoparticles that maximizes the electric field intensity on the particle surface.

  With respect to the thickness of the dielectric layer 16, as shown in FIG. 5B, the electric field strength has a discrete peak almost periodically. Of these, the maximum peak is not the first peak that occurs when the thickness of the dielectric layer is 40 nm or less as noted in Patent Document 1, but is the second peak that occurs in a thicker dielectric layer. Is clear.

In this example, the intensity of the second peak (E ⁴ ) is approximately twice the intensity of the first peak (E ⁴ ). The reason that the electric field strength depends on the size of the metal nanoparticles 18 is that the particle size determines the resonance wavelength range of the LSP. On the other hand, the reason why the electric field strength periodically changes with respect to the thickness of the dielectric layer 16 is that the external electric field strength at the position of the metal nanoparticles 18 is due to reflection and interference at the upper and lower two interfaces shown in FIG. This is because it is affected.

  From the above, by making the dielectric layer 16 thicker than the conventional one (first feature point), the effect is that the metal nanoparticle 18 does not depend on the coupling between the localized surface plasmon LSP and the propagation surface plasmon PSP. The acting electric field can be enhanced (second feature point). The restriction that the period P of the metal nanoparticles 18 must be increased due to the second feature point is released, and the period P of the metal nanoparticles 18 can be reduced (third feature point). The density can be increased.

FIGS. 6A and 6B and FIGS. 7A and 7B show structures in which the material of the metal layer 14 is different and the electric field strength obtained thereby. 6A shows a structure in which Au is used for the metal layer 14 as in FIG. 5A, and the enhanced electric field obtained in FIG. 6B is shown (the result of FIG. 5B). the same). FIG. 7A shows a structure in which Ag is used for the metal layer 14, and an enhanced electric field obtained in FIG. 7B is shown. Focusing on the second peak in FIG. 6 (B) and FIG. 7 (B), the metal layer 14 is more of Ag than Au, enhancement ^{E 4} of the electric field, it can be seen that approximately 1.2 times greater.

1.6. Lamination of Plural Types of Dielectric Layers FIG. 8 shows a structure in which the dielectric layer is a lamination of a first dielectric layer 16A and a second dielectric layer 16B. The outermost second dielectric layer 16B is made of, for example, SiO ₂ , and the first dielectric layer 16B is made of a different material between the metal layer (Au) 14 and the second dielectric layer 16B. A one-layer dielectric layer 16A was formed. The first dielectric layer 16A is made of, for example, Al ₂ O ₃ and is very thin (≦ 5 nm). Even when the Al ₂ O ₃ layer of the first dielectric layer 16A is 5 nm, the thickness of the _second dielectric layer (SiO ₂ ) 16B giving the electric field peak shown in FIG. Compared with the case where the dielectric layer (Al ₂ O ₃ ) 16A is not provided, the thickness is reduced by about 10 nm. It should be noted that the total thickness of the first and second dielectric layers 16A and 16B satisfies the requirement of the thickness d of the dielectric layer 16 defined by the above formula (9) or (10). That's fine.

The reason for providing the first dielectric layer (Al ₂ O ₃ ) 16A is to prevent the thick SiO ₂ layer from peeling off due to thermal stress when the SiO ₂ layer is formed by sputtering or the like. That is, the first dielectric layer (Al ₂ O ₃ ) 16A is caused to function as an adhesion layer or a peeling prevention layer.

2. Manufacturing method 2.1. Manufacturing Method of Optical Device Having Periodic Metal Nanoparticles FIGS. 9A to 9D show a manufacturing process of the sensor chip shown in FIG. First, as shown in FIG. 9A, a metal layer 14 (for example, Ag or Au) is deposited on the quartz glass substrate 12 by about 150 nm by a vacuum film formation method such as vapor deposition or sputtering. The thickness of the metal layer 14 is a thickness that does not transmit visible light that is excitation light, and ensures the function of the mirror layer described with reference to FIG.

Next, as shown in FIG. 9B, a first dielectric layer (for example, Al ₂ O ₃ ) 16A having excellent thermal conductivity is formed on the surface of the metal layer 14 by sputtering to a thickness of about 5 nm. Subsequently, as shown in FIG. 9C, a second dielectric layer (for example, SiO ₂ ) 16B having a thickness of 230 nm is formed on the surface of the first dielectric layer 16A by sputtering. Further, a resist pattern 20 is formed on a flat surface by imprinting or another method. Here, as the resist pattern 20, FIG. 10A shows an example of a dot pattern, and FIG. 10B shows an example of an elliptic pattern.

  Finally, as shown in FIG. 9D, when a metal is vacuum-deposited from above the resist pattern 20 and then the resist pattern 20 is removed, a two-dimensional periodic array of metal nanoparticles 18 is formed.

2.2. Method for Producing Optical Device Having Metal Nanoislands Instead of the steps of FIGS. 9C and 9D, Ag island 30 is formed on the surface of SiO ₂ layer 16B by vacuum deposition as shown in FIG. It is good also as a random arrangement | sequence where the particle size and pitch of 18 are not constant.

In the example of FIG. 11, the size of the Ag nanoparticles 31 in the Ag island 30 is approximately 40-80 nm, the thickness of the second dielectric layer (for example, SiO ₂ ) 16B is 230 nm, and the first dielectric layer (for example, , Al ₂ O ₃ ) 16A has a thickness of 5 nm.

FIG. 12A shows a Raman spectrum acquired with the structure of FIG. 1.3 × 10 ⁸ is obtained as the signal enhancement corresponding to the count value shown in FIG. For comparison, FIG. 12B shows a Raman spectrum when the thickness of the SiO ₂ layer 16B is 30 nm, which is the prior art. The signal enhancement corresponding to the count value in FIG. 12B is 8.0 × 10 ⁷ . The enhanced electric field under the condition of FIG. 12A corresponds to the second peak, the enhanced electric field under the condition of FIG. 12B corresponds to the first peak, and the signal enhancement in FIG. Which is 1.6 times larger than the signal enhancement in FIG. This value coincides with the tendency of the computer simulation shown in FIG.

3. 3. Optical device and detection apparatus for reducing dependence of electric field intensity on incident angle 3.1. Dependence of electric field intensity and Raman signal intensity on light incident angle The performance of the sensor chip 10 described above depends on the incident angle θ of the excitation light with respect to the perpendicular L of the dielectric layer 16, as shown in FIG. FIG 14 (A) (B), FDTD: shows a relationship between the near field strength E ⁴ obtained in (Finite-difference time-domain finite difference time domain) method and the incident angle theta. 14A shows the relationship when the incident linearly polarized light is S-polarized light (the polarization direction is orthogonal to the paper surface), and FIG. 14B shows the relationship when the incident linearly polarized light is P-polarized light (the polarization direction is parallel to the paper surface). Respectively. When the metal nanoparticles 18 are two-dimensionally arranged, the excitation light includes both S-polarized light and P change. As can be seen from the results shown in FIGS. 14A and 14B, when the incident angle θ is 0 °, the near-field strength E ⁴ has a peak at the thickness d = 230 nm of the dielectric layer (SiO ₂ ) 16. The height and position of this peak hardly change when the incident angle θ is in the range of 0 to 10 °. However, the electric field strength E ⁴ decreases from the point when the incident angle θ exceeds 20 °, and when the incident angle θ exceeds 40 °, the electric field can hardly be enhanced.

The reason is 1.4.2. This is because the condition of the thickness d of the dielectric layer (SiO ₂ ) 16 that gives the peak electric field shifts in the direction of increasing thickness as shown in FIGS. 14A and 14B due to the effect of the thin film interference described in the column. .

FIG. 15 is a diagram for explaining the optical path difference (phase difference) δ of the excitation light incident at the incident angle θ. If the refraction angle in the dielectric layer 16 is defined as θ ′ with respect to the incident angle θ, the optical path length d ′ in the dielectric layer 16 is expressed as d ′ = d / cos θ ′. Here, the optical path length in the dielectric layer 16 when the incident angle θ = 0 is equal to the thickness d of the dielectric layer 16. Therefore, the phase difference δ between the optical path length d in the dielectric layer 16 when the incident angle θ = 0 and the optical path length d ′ when the incident angle θ is other than 0 ° is
δ = d′−d = d / cos θ′−d = d (1 / cos θ′−1) (12)
It becomes.

Here, substituting d = λ / 2n when natural number m = 1 in equation (10) into equation (12),
δ = λ (1 / cos θ′−1) / 2n (13)
Is obtained.

Figure 16 shows the incident angle relationship between peak shift amount of the near-field strength E ^4. In FIG. 16, the peak shift amount (nm) at an incident angle of 0 to 40 ° shown in FIG. 14A is plotted. In FIG. 16, the phase difference (optical path difference) expression shown in Expression (13) is further shown by a curve. The peak deviation amount depending on the incident angle θ obtained by the FDTD method in FIG. 14A can be approximated by the curve of the equation (13).

  FIG. 17 illustrates a state in which the excitation light is collected by the condenser lens (objective lens) 131 </ b> C and enters the sensor chip 10. However, in FIG. 17, the illustration of the metal nanoparticles 18 is omitted because of the scale. The numerical aperture NA (numerical aperture) of the condensing lens 131C is represented by NA = sin α, where α is the maximum angle of light incident on the condensing lens 131C. Here, when it is increased from a low NA indicated by a broken line in FIG. 17 to a high NA indicated by a solid line, it is expected that the Raman signal intensity increases as a theoretical curve indicated by a solid line in FIG.

However, in reality, it does not increase monotonously as shown by the broken line in FIG. 18 indicating the analysis result of the FDTD method. When the FIG. 14 (A) near the electric field intensity E ⁴ as shown in (B) has a dependency of the incident angle θ is from around the numerical aperture NA of the condenser lens 131C exceeds 0.3, Raman signal The intensity will be saturated. Therefore, the Raman signal intensity cannot be increased even when the high NA condensing lens 131C is used.

3.2. Sensor chip (optical device) with reduced light incident angle
In order to effectively use the high NA condensing lens 131C shown in FIG. 17 and obtain a large Raman signal intensity, the incident angle of the excitation light to the sensor chip 10 may be made small. 19A and 19B schematically show surfaces (spherical surfaces) 10A and 10B excluding the metal nanoparticles 18 of the optical device 10 with a small incident angle. However, also in FIGS. 19A and 19B, illustration of the metal nanoparticles 18 is omitted due to the scale.

  19A and 19B, the spherical surfaces defined by the radii of curvature R1 and R2 having the centers P1 and P2 on the normal lines L2 and L3 with respect to the surfaces 10A and 10B of the sensor chip 10 are the surfaces 10A and 10B. It is formed in a region larger than the beam area (irradiation area) of the beam diameters D1 and D2. The light irradiation area A on the spherical surfaces 10A and 10B of the sensor chip 10 is given by the following formula from the formula of the surface area of a sphere within a certain height range from one vertex of the spherical surface.

A = 2πR ² (1-cos α) (14)
In FIG. 19A, the spherical surface 10A of the sensor chip 10 is formed in a concave shape. Therefore, the focal point F1 of the condenser lens 131C1 is set on the upstream side of the surface 10A of the sensor chip 10 with respect to the incident direction of the light beam B1. Thus, the light beam B1 having the beam diameter D1 is incident on the surface 10A of the sensor chip 10. On the other hand, in FIG. 19B, the spherical surface 10B of the sensor chip 10 is formed in a concave shape. For this reason, the focal point F2 of the condensing lens 131C2 is set downstream of the surface 10B of the sensor chip 10 with respect to the incident direction of the light beam B2. Thus, the light beam B2 having the beam diameter D2 is incident on the spherical surface 10B of the sensor chip 10.

  As is apparent from FIGS. 19A and 19B, the light beam B1 incident on the spherical surfaces 10A and 10B of the sensor chip 10 is compared with that in which the surface of the sensor chip 10 is flat as shown in FIG. , B2 has a significantly smaller incident angle. In particular, if the center P1 of the radius of curvature R1 coincides with the focal point F1 in FIG. 19A and the center P2 of the radius of curvature R2 coincides with the focal point F2 in FIG. 19B, the spherical surface 10A of the sensor chip 10 is obtained. , 10B, the incident angles of the light beams B1, B2 are 0 ° without depending on the incident positions on the spherical surfaces 10A, 10B. Since the curvature radii R1 and R2 are several μm to several tens of μm, respectively, P1 = F1 or P2 = by appropriately setting the distance between the condenser lenses 131C1 and 131C2 and the sensor chips 10A and 10B. It can be set to F2. As described above, when the incident angle is always small, the Raman signal intensity can be increased as the numerical aperture NA of the condenser lenses 131C1 and 131C2 is increased along the theoretical curve shown by the solid line in FIG.

  FIG. 20 schematically shows a state where a plurality of spherical surfaces 10B shown in FIG. A plurality of metal nanoparticles 18 are formed on each of the plurality of spherical surfaces 10B. FIG. 21 shows a state in which the spherical surface 10B shown in FIG. 19A is formed in an array shape as a micro concave lens, and the metal nanoparticles 18 are formed in an island shape on the spherical surface 10A.

  As shown in FIGS. 19B and 20, it is preferable that the optical axis L1 of the condenser lens 131C2 coincides with the normal line L3 on the center line with respect to one spherical surface 10B of the sensor chip 10. Similarly, as shown in FIG. 19A, the optical axis L1 of the condensing lens 131C1 is normal L2 on the center line with respect to one spherical surface 10A on the sensor chip 10 (one micro concave lens shown in FIG. 21). It is preferable to match. As a result, the centers P1 and P2 of the radii of curvature R1 and R2 exist on the optical axis L1, and the spherical surfaces 10A and 10B of the sensor chip 10 are axisymmetric with respect to the optical axis L1. Thereby, the light beams B1 and B2 can be incident as designed at a small incident angle.

  In order to make the optical axis L1 coincide with the normal lines L2 and L3, the condenser lenses 131C1 and 131C2 and the sensor chip 10 are relatively aligned. For this alignment, for example, an in-focus servo mechanism employed in a CD or DVD reader can be used. For example, the reflected light from the sensor chip 10 is monitored, and the positions of the condenser lenses 131C1 and C2 can be precisely controlled by a servo motor using a focus error signal, a tracking error signal, and the like.

  When the metal nanoparticles 18 are formed on each of the fine irregularities having the spherical surfaces 10A and 10B on the surface of the sensor chip 10 as in the present embodiment, the incident angle of the light beam as excitation light is reduced, and the condensing lens 131C By increasing the numerical aperture NA, the Raman signal intensity can be enhanced according to the theoretical curve shown by the solid line in FIG. Thereby, the measurement time is shortened and the SN ratio is improved. If the variation range of the incident angle of the light beam incident on the sensor chip 10 is large, the incident angle dependence of the enhanced electric field is the same between the S-polarized light and the P-polarized light as shown in FIGS. In other words, dependence on incident polarization occurs. When the variation range of the incident angle of the light beam is small as in the present embodiment, the polarization distribution in the light irradiation region on the sensor chip 10 becomes small. For this reason, it is possible to acquire a stable signal without being influenced by the incident polarization dependency inherent to the sensor chip 10, and to perform quantitative analysis in addition to qualitative analysis.

3.3. Manufacturing Method The sensor chip 10 shown in FIGS. 19A, 19B, 20 and 21 is different from the manufacturing process of the sensor chip 10 shown in FIG. This is the point where fine irregularities having a curvature are provided. Here, typical radii of curvature R1 and R2 shown in FIGS. 19A and 19B are several μm to several tens of μm. Therefore, for example, even if a film of a metal layer 14 and a dielectric layer 16 of nm order is attached to the substrate 12 on which the fine irregularities shown in FIG. A film is formed with a uniform thickness.

In the example shown in FIG. 21, a metal layer (Au layer) 14, a dielectric layer (SiO ₂ ) layer 16 and metal nanoparticles (Ag island) are formed on the surface of the substrate 12 on which a micro concave lens array having a curvature radius of about 10 μm is formed. ) 18 is formed. The metal nanoparticles (Ag island) 18 can be formed by vacuum deposition, and the metal layer 14 and the dielectric layer 16 can be formed by sputtering. The thickness of the metal layer (Au layer) 14 is 150 nm, the thickness of the dielectric layer (SiO ₂ ) 16 is 230 nm, and the size of the metal nanoparticles (Ag island) 18 is about 40 to 80 nm. The micro concave lens array on the surface of the substrate 12 can be manufactured by a method such as glass molding.

4). Next, the entire configuration of the detection device will be described. FIG. 22 shows a specific configuration example of the detection apparatus of the present embodiment. 22 includes a sample supply channel 101 having a suction port 101A and a dust removal filter 101B, a sample discharge channel 102 having a discharge port 102A, FIGS. 19 (A), (B), FIG. 20, or FIG. An optical device unit 110 including an optical device (sensor chip) 103 having the structure shown in FIG. Light is incident on the optical device 103. The casing 120 of the detection apparatus 100 includes a sensor cover 122 that can be opened and closed by a hinge part 121. The optical device unit 110 is detachably arranged with respect to the housing 120 in the sensor cover 122. Whether the optical device unit 110 is mounted / not mounted can be detected by the sensor detector 123.

  The sample supply channel 101 and the sample discharge channel 102 are formed so as to be detoured, and have a structure in which external light is difficult to enter.

  Note that the shape of the path for sucking and discharging the fluid sample is considered so that the light resistance from the fluid sample becomes small in addition to the fact that light from the outside does not enter the sensor. By preventing external light from entering the optical device 103, light that becomes noise other than Raman scattered light does not enter, and the S / N ratio of the signal is improved. In addition to the shape of the flow path, it is necessary to select the material, color, and surface shape of the material that forms the flow path so that it is difficult to reflect light. Further, by reducing the fluid resistance with respect to the fluid sample, a large amount of fluid sample in the vicinity of this apparatus can be collected, and highly sensitive detection becomes possible. The shape of the flow path is made smooth by eliminating the corners as much as possible, so that the stay at the corners is eliminated. In addition, as the negative pressure generating unit 104 provided in the fluid discharge channel 102, it is necessary to select a fan or a pump having a static pressure and an air volume corresponding to the channel resistance.

  In the housing 120, a light source 130, an optical system 131, a light detection unit 132, a signal processing / control unit 133, and a power supply unit 134 are provided.

  In FIG. 22, the light source 130 is, for example, a laser, and a vertical cavity surface emitting laser can be preferably used from the viewpoint of miniaturization, but is not limited thereto.

  The light from the light source 130 is collimated by the collimator lens 131 </ b> A constituting the optical system 131. A polarization control element may be provided downstream of the collimator lens 131A and converted to linearly polarized light. However, if, for example, a surface emitting laser is used as the light source 130 and light having linearly polarized light can be emitted, the polarization control element can be omitted.

  The light collimated by the collimator lens 131A is guided in the direction of the optical device 103 by the half mirror (dichroic mirror) 131B, is condensed by the objective lens (condensing lens) 131C, and enters the optical device 103. Rayleigh scattered light and Raman scattered light from the optical device 103 pass through the objective lens 131C and are guided toward the light detection unit 100 by the half mirror 131B. As described above, the objective lens (condensing lens) 131C monitors the reflected light from the sensor chip 10, for example, and precisely controls the position by a servo motor using a focus error signal and a tracking error signal. Can do.

  Rayleigh scattered light and Raman scattered light from the optical device 103 are collected by the condenser lens 131 </ b> D and input to the light detection unit 132. First, the light detection unit 132 reaches the optical filter 132A. Raman scattered light is extracted by the optical filter 32A (for example, a notch filter). This Raman scattered light is further received by the light receiving element 132C via the spectroscope 132B. The spectroscope 132B is formed of, for example, an etalon using Fabry-Perot resonance, and the pass wavelength band can be made variable. The wavelength of the light passing through the spectroscope 132B can be controlled (selected) by the signal processing / control circuit 133. A Raman spectrum peculiar to the target molecule 1 is obtained by the light receiving element 132C, and the target molecule 1 can be specified by collating the obtained Raman spectrum with data held in advance.

  The power supply unit 134 supplies power from the power supply connection unit 135 to the light source 130, the light detection unit 132, the signal processing / control unit 133, the fan 104, and the like. The power supply unit 134 can be configured by, for example, a secondary battery, and may be configured by a primary battery, an AC adapter, or the like. The communication connection unit 136 is connected to the signal processing / control unit 133 and mediates data, control signals, and the like to the signal processing / control unit 133.

  In the example of FIG. 22, the signal processing / control unit 133 can send commands to the light detection unit 132, the fan 104, and the like other than the light source 130 shown in FIG. Furthermore, the signal processing / control unit 1330 can execute spectroscopic analysis using a Raman spectrum, and the signal processing / control unit 133 can specify the target molecule 1. The signal processing / control unit 133 can transmit the detection result by Raman scattered light, the spectroscopic analysis result by Raman spectrum, and the like to an external device (not shown) connected to the communication connection unit 136, for example.

  A calculation unit (not shown) for calculating information on health or medical care based on a detection result from the detection device, a display unit (not shown) for displaying these, and a storage unit (not shown) for storing them. The provided electronic device is useful for medical diagnosis, inspection of food and drink, and the like. For example, it is possible to use this electronic device to detect the trace amount of acetone contained in human breath, display the amount of fat burning, and grasp the relationship with the amount of exercise, etc., which can be useful for prevention of adult diseases etc. it can.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Further, the configurations and operations of the optical device, the detection apparatus, and the like are not limited to those described in this embodiment, and various modifications can be made.

  DESCRIPTION OF SYMBOLS 10 Optical device (sensor chip), 10A, 10B Spherical surface (surface), 12 board | substrate, 14 metal layer, 16 dielectric layer, 16A 1st layer dielectric layer, 16B 2nd layer dielectric layer, 18, 31 Metal nanoparticle , 20 resist pattern, 30 metal island, 100 detector, 130 light source, 131C, 131C1, 131C2 condenser lens, 132 photodetector, B1, B2 light beam, d dielectric layer thickness, F1, F2 focus, L1 Optical axis, L2, L3 normal, P Metal nanoparticle pitch (period), P1, P2 radius of curvature center, R1, R2 radius of curvature

Claims (8)

A light source that emits light;
A condenser lens for condensing the light;
An optical device for entering the light beam collected by the condenser lens;
An introduction mechanism for introducing a fluid sample into the optical device;
Have
The optical device is
A spherical surface having a normal line of the surface as the center line of the radius of curvature is formed on the surface on which the light beam is incident, and the spherical surface is the same as or wider than the irradiation region of the light beam,
A metal layer formed on the spherical surface;
A dielectric layer formed on the metal layer;
A plurality of metal nanoparticles formed on the dielectric layer;
Have
When the thickness of the dielectric layer is d, the wavelength of the light beam is λ, the refractive index of the dielectric layer at the wavelength λ is n, and the natural number is m, the thickness d of the dielectric layer is m. A detection device set to xλ / n. In claim 1,
The spherical surface has a concave shape in the incident direction of the light beam,
The focus of the said condensing lens is set to the upstream of the incident direction of the said light beam rather than the said spherical surface, The detection apparatus characterized by the above-mentioned. In claim 1,
The spherical surface is shaped to be convex in the incident direction of the light beam,
The focus of the condensing lens is set downstream of the spherical surface in the incident direction of the light beam. In claim 2 or 3,
The center of the radius of curvature of the spherical surface is set on the optical axis of the light beam. In claim 4,
The center of the radius of curvature of the spherical surface coincides with the focal point. In any one of Claims 1 thru | or 5,
The detecting device according to claim 1, wherein the radius of curvature is on the order of several μm to several tens of μm.   The detection device according to any one of claims 1 to 6, a calculation unit that calculates health care information based on detection information from the detection device, a storage unit that stores health care information, and the health care An electronic device comprising: a display unit that displays information. An optical device for entering a light beam,
A spherical surface having a radius of curvature centered on a normal line of the surface is formed on a surface on which the light beam is incident, and the spherical surface is formed to be the same as or wider than the irradiation region of the light beam;
A metal layer formed on the spherical surface;
A dielectric layer formed on the metal layer;
A plurality of metal nanoparticles formed on the dielectric layer and on which the light beam is incident;
Have
When the thickness of the dielectric layer is d, the wavelength of the light beam is λ, the refractive index of the dielectric layer at the wavelength λ is n, and the natural number is m, the thickness d of the dielectric layer is m. An optical device characterized by being set to xλ / n.