JP2015078904A - Optical element, analyzer, and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element that can confine light propagating in a dielectric layer and a propagated surface plasmon propagated on an interface between the dielectric layer and a metal layer, within an irradiation region of incident light and a nearby region, and can efficiently use energy for enhancing an electric field.SOLUTION: The optical element includes a metal layer, a dielectric layer formed on the metal layer, and a metal particle layer formed on the dielectric layer and receiving incident light, in which a periodical structure is formed in the dielectric layer located in a periphery of the metal particle layer in a plan view.

Description

  The present invention relates to an optical element, an analyzer, and an electronic apparatus.

  In recent years, demand for medical diagnosis, food inspection, and the like has been increasing, and development of a small and high-speed sensing technology has been demanded. Various types of sensors, including electrochemical techniques, have been studied. However, surface plasmon resonance (SPR) is used because it can be integrated, is low-cost, and does not choose the measurement environment. There is growing interest in 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. This technique senses the presence of a molecule to be detected by detecting that the extinction wavelength by SPR shifts before and after the adsorption of the molecule to be detected.

Further, as one of highly sensitive spectroscopic techniques for detecting a low concentration of molecules, attention is focused on surface enhanced Raman scattering (SERS) using SPR. SERS is a phenomenon in which Raman scattered light is enhanced by 10 ² to 10 ¹⁴ times on a metal surface having a nanometer scale uneven structure.

  When a molecule such as a laser is irradiated with excitation light having a single wavelength, light having a wavelength slightly shifted from the wavelength of the excitation light by the vibration energy of the molecule (Raman scattered light) is scattered. When the scattered light is spectrally processed, a spectrum (fingerprint spectrum) unique to the molecular species is obtained. By analyzing the shape of this fingerprint spectrum, it becomes possible to identify the molecule.

  As a structure of such a sensor, for example, in Patent Document 1, a metal nanostructure formed on a conductor via a dielectric layer is formed, and a propagating surface plasmon (PSP) and a localized type are formed. A surface-enhanced Raman sensor chip having a large hot spot density (HSD) using a surface plasmon (LSP) is proposed.

JP 2013-007614 A

  However, in the sensor chip disclosed in Patent Document 1, there is no structural difference between the dielectric layer in the incident light irradiation region on the metal nanostructure and the dielectric layer in the region not irradiated with the incident light. For this reason, the PSP propagating in the plane direction of the substrate propagates to and dissipates in a region other than the irradiation region, resulting in energy loss, and it is difficult to obtain the theoretically expected electric field enhancement.

One of the objects according to some aspects of the present invention is to confine light propagating through the dielectric layer and propagating surface plasmons propagating through the interface between the dielectric layer and the metal layer in the vicinity of the irradiation region of the incident light, It is an object of the present invention to provide an optical element capable of more efficiently using energy for electric field enhancement, and an analysis apparatus and electronic apparatus equipped with the optical element.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

  One aspect of the optical element according to the present invention includes a metal layer, a dielectric layer formed on the metal layer, a metal particle layer formed on the dielectric layer, and incident light is incident thereon, A periodic structure is formed in the dielectric layer located around the metal particle layer in plan view.

  According to such an optical element, when incident light is irradiated on the metal particle layer of the optical element, a periodic structure in which light is not allowed to exist in the surrounding dielectric layer is formed. And propagating surface plasmons propagating through the interface between the dielectric layer and the metal layer can be confined in the vicinity of the incident light irradiation region. Thereby, the loss of energy for enhancing the electric field is reduced, and a high electric field enhancing effect can be obtained.

  In the optical element according to the present invention, the periodic structure has a photonic band gap in which TM polarized light does not propagate in the dielectric layer and at the interface between the metal layer and the dielectric layer at the wavelength of the incident light. May be shown.

  According to such an optical element, a periodic structure having a photonic band gap in which TM polarized light cannot exist is formed in the dielectric layer formed around the metal particle layer. Plasmons cannot exist in the periodic structure. Thereby, the propagation type surface plasmon is reflected by the region of the periodic structure and collected in the region of the metal particle layer. Therefore, the energy for enhancing the electric field can be concentrated more efficiently, so that a higher electric field enhancing effect can be obtained.

  In the optical element according to the present invention, the periodic structure may be arranged so as to reflect TM polarized light generated in the optical element upon incidence of the incident light.

  According to such an optical element, of the propagation surface plasmons that are TM polarized light, the propagation type that is intended to diffuse outward from the periodic structure by the periodic structure of the dielectric layer formed around the metal particle layer. Surface plasmons are reflected back toward the inside of the periodic structure. Thereby, the dissipating energy is recovered and a higher electric field enhancement effect can be obtained.

  In the optical element according to the present invention, in the plan view, the area of the region surrounded by the periodic structure is the area of the region irradiated with the incident light and the outside of the region irradiated with the incident light. The area may be smaller than the sum of the area of the propagation type surface plasmon propagating in the dielectric layer and the interface between the metal layer and the dielectric layer.

  According to such an optical element, of the propagation surface plasmons that are TM polarized light, the propagation type that is intended to diffuse outward from the periodic structure by the periodic structure of the dielectric layer formed around the metal particle layer. Surface plasmons are reflected back toward the inside of the periodic structure. Thereby, the dissipated energy is recovered and a high electric field enhancement effect can be obtained.

  In the optical element according to the present invention, in the plan view, the radius of the region surrounded by the periodic structure is the radius of the region irradiated with the incident light, the inside of the dielectric layer, the metal layer, and the dielectric. It may be smaller than the sum of the distance that the propagation type surface plasmon propagates toward the outside of the region irradiated with the incident light on the interface with the layer.

  According to such an optical element, of the propagation surface plasmons that are TM polarized light, the propagation type that is intended to diffuse outward from the periodic structure by the periodic structure of the dielectric layer formed around the metal particle layer. Surface plasmons are reflected back toward the inside of the periodic structure. Thereby, the dissipated energy is recovered and a high electric field enhancement effect can be obtained.

  One aspect of the analysis apparatus according to the present invention includes the above-described optical element, a light source that irradiates the optical element with the incident light, and a detector that detects light emitted from the optical element.

  According to such an analyzer, since the optical element having a high electric field enhancement effect is provided, the intensity of light based on plasmons is very large, and the substance to be analyzed can be analyzed with extremely high sensitivity.

  One aspect of the electronic device according to the present invention includes the above-described analyzer, a calculation unit that calculates health and medical information based on detection information from the detector, a storage unit that stores the health and medical information, and the health A display unit for displaying medical information.

  According to such an electronic device, an optical element having a large light intensity based on plasmon is provided, and a trace amount substance can be easily detected, and highly accurate medical information can be provided.

  In the electronic device of the present invention, the health care information is selected from at least one biological substance selected from the group consisting of bacteria, viruses, proteins, nucleic acids, and antigens / antibodies, or inorganic molecules and organic molecules. Information on the presence or amount of at least one compound may be included.

  According to such an electronic device, useful health care information can be provided.

The perspective view which shows typically the area | region in which the metal particle layer of the optical element of embodiment was formed. The schematic diagram which looked at the area | region in which the metal particle layer of the optical element of embodiment was formed planarly from the thickness direction of the metal layer. The schematic diagram of the cross section perpendicular | vertical to the 1st direction of the area | region in which the metal particle layer of the optical element of embodiment was formed. The schematic diagram of the cross section perpendicular | vertical to the 2nd direction of the area | region in which the metal particle layer of the optical element of embodiment was formed. The schematic diagram which shows an example of a MIM structure. The graph which shows the relationship between the effective refractive index of the insulator at the time of assuming a MIM structure, and the propagation distance of PSP. The perspective view which shows an example of the optical element which concerns on embodiment. The schematic diagram which looked at an example of the periodic structure which concerns on embodiment planarly. The Brillouin zone as an example of the periodic structure according to the embodiment. The photonic band figure of an example of the periodic structure which concerns on embodiment. The perspective view which shows an example of the optical element which concerns on embodiment. The Brillouin zone as an example of the periodic structure according to the embodiment. The schematic diagram which looked at an example of the periodic structure which concerns on embodiment planarly. The Brillouin zone as an example of the periodic structure according to the embodiment. The photonic band figure of an example of the periodic structure which concerns on embodiment. The schematic diagram which shows planarly the relationship of the area | region in which the periodic structure of the metal particle layer, incident light irradiation area | region, and dielectric layer of the optical element which concerns on embodiment was formed. The figure which shows typically the analyzer which concerns on embodiment. 1 is a diagram schematically illustrating an electronic apparatus according to an embodiment.

  Several embodiments of the present invention will be described below. Embodiment described below demonstrates an example of this invention. The present invention is not limited to the following embodiments, and includes various modified embodiments that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

1. Optical Element FIG. 1 is a perspective view schematically showing a region where a metal particle layer 30 of an optical element 100 according to this embodiment which is an example of an optical element according to the present invention is formed. FIG. 2 is a plan view of the region where the metal particle layer 30 of the optical element 100 of this embodiment is formed (viewed from the thickness direction of the metal layer 10). 3 and 4 are schematic views of a cross section of a region where the metal particle layer 30 of the optical element 100 of the present embodiment is formed. The optical element 100 according to this embodiment includes a metal layer 10, a dielectric layer 20, and a metal particle layer 30.

1.1. Metal Layer The optical element 100 according to this embodiment includes a metal layer 10. The metal layer 10 is not particularly limited as long as it provides a metal surface that does not transmit light. For example, the metal layer 10 may have a film, plate, layer, or film shape. The metal layer 10 may be provided on the substrate 1, for example. The substrate 1 in this case is not particularly limited, but a substrate that does not easily affect the propagation surface plasmon excited by the metal layer 10 is preferable. Examples of the substrate 1 include a glass substrate, a silicon substrate, and a resin substrate. The shape of the surface on which the metal layer 10 of the substrate 1 is provided is not particularly limited. When a predetermined structure is formed on the surface of the metal layer 10, it may have a surface corresponding to the structure. When the surface of the metal layer 10 is a flat surface, the surface of the corresponding portion is a flat surface. Also good. In the example of FIGS. 1 to 4, a layered metal layer 10 is provided on the surface (plane) of the substrate 1.

  In this specification, the thickness direction of the metal layer 10 may be referred to as a thickness direction, a height direction, or the like. In the present embodiment, the thickness direction of the metal layer 10 coincides with the thickness directions of a dielectric layer 20 and a metal particle layer 30 described later. When the metal layer 10 is provided on the surface of the substrate 1, the normal direction of the surface of the substrate 1 may be referred to as a thickness direction, a thickness direction, or a height direction. Furthermore, when viewed from the substrate 1, the direction on the metal layer 10 side may be expressed as “up” or “up”, and the opposite direction may be expressed as “down” or “down”. In addition, in this specification, for example, the expression “the member B is provided on the member A” includes the case where the member B is provided on the member A and another member or the member A on the member A. And the case where the member B is disposed through the space.

  The metal layer 10 can be formed, for example, by a technique such as vapor deposition, sputtering, casting, or machining. When the metal layer 10 is provided on the substrate 1 in a thin film shape, it may be provided on the entire upper surface of the substrate 1 or may be provided on a part of the substrate 1. The thickness of the metal layer 10 is not particularly limited as long as propagating surface plasmons can be excited on the metal layer 10. For example, the thickness is 10 nm to 1 mm, preferably 20 nm to 100 μm, more preferably 30 nm to 1 μm. Can do.

The metal layer 10 is a metal that can have an electric field in which the electric field given by the incident light i and the polarization induced by the electric field oscillate in opposite phases, that is, when a specific electric field is given, The real part of the function has a negative value (has a negative dielectric constant) and is composed of a metal that can have a dielectric constant whose imaginary part has a dielectric constant smaller than the absolute value of the dielectric constant of the real part . Examples of metals that can have such a dielectric constant in the visible light region include silver, gold, aluminum, copper, platinum, and alloys thereof. Further, the surface (end surface in the thickness direction) of the metal layer 10 may or may not be a specific crystal plane. Further, the metal layer 10 may be formed to the outside of the dielectric layer 20 in a plan view.

  The metal layer 10 has a function of generating a propagation surface plasmon (PSP) in the optical element 100 of the present embodiment. Under certain conditions, when light enters the metal layer 10, propagation-type surface plasmons are generated in the vicinity of the surface (end surface in the thickness direction) of the metal layer 10. In the present specification, the quantum of vibration in which the vibration of electric charges near the surface of the metal layer 10 and the electromagnetic wave are combined may be referred to as surface plasmon polariton (SPP). Propagation-type surface plasmons generated in the metal layer 10 may interact with localized surface plasmons generated in the metal particle layer 30 described later.

1.2. Dielectric Layer The optical element 100 of the present embodiment includes a dielectric layer 20 that electrically separates the metal layer 10 and the metal particle layer 30 (metal particles 40). The dielectric layer 20 is provided on the metal layer 10 as shown in FIGS. Thereby, the metal layer 10 and the metal particle 40 contained in the metal particle layer 30 can be separated. The dielectric layer 20 can have the shape of a film, layer or film.

The dielectric layer 20 only needs to have a positive dielectric constant, and can be formed of, for example, SiO ₂ , Al ₂ O ₃ , TiO ₂ , polymer, ITO (Indium Tin Oxide), or the like. The dielectric layer 20 may be composed of a plurality of layers made of different materials. Of these, the material of the dielectric layer 20 is more preferably SiO ₂ . In this way, both incident light i and Raman scattered light s can be more easily enhanced when measuring a sample using incident light having a wavelength λ _i of 400 nm or longer.

The dielectric layer 20 has a refractive index n _eff . When the dielectric layer 20 is composed of a plurality of layers or includes a plurality of materials, the effective refractive index of the entire dielectric layer 20 is _defined as a refractive index n _eff . The thickness of the dielectric layer 20 is designed in consideration of the wavelength λ _i of the incident light i irradiated on the optical element 100, the wavelength λ _s of Raman scattered light when the light having the wavelength λ _i is incident, and the like. Details of the incident light i will be described later.

  The dielectric layer 20 can be formed by, for example, techniques such as vapor deposition, sputtering, CVD, and various coatings. The dielectric layer 20 may be provided on the entire surface of the metal layer 10 or may be provided on a part of the surface of the metal layer 10. The dielectric layer 20 is provided at least under the metal particle layer 30 and further provided at a position where the metal particle layer 30 does not exist. That is, the dielectric layer 20 is provided at a position of the metal particle layer 30 and a position outside the metal particle layer 30 when viewed from the thickness direction of the optical element 100. In other words, the dielectric layer 20 is provided so as to include the metal particle layer 30 in a plan view. Alternatively, the dielectric layer 20 is provided up to a region outside the metal particle layer 30 in plan view. In a plan view, a periodic structure is formed at least in the dielectric layer 20 located around the metal particle layer 30. Details of the periodic structure will be described later.

  The thickness of the dielectric layer 20 is not particularly limited, and can be, for example, 10 nm to 2000 nm, preferably 20 nm to 500 nm, more preferably 20 nm to 300 nm.

Of the dielectric layer 20, the region sandwiched between the metal layer 10 and the metal particle layer 30 is an MIM (Metal-Insulator-Metal) Insulator (insulating layer) if the metal particle layer 30 is regarded as one layer. (See FIG. 5). And in this case
The dielectric layer 20 can be considered as a waveguide whose boundary is defined by upper and lower metals. Therefore, light can be propagated in the dielectric layer 20 (plane direction: a direction parallel to the dielectric layer 20). Further, the dielectric layer 20 can propagate the propagation type surface plasmon (PSP) generated in the vicinity of the interface between the dielectric layer 20 and the metal layer 10 in the dielectric layer 20 (plane direction).

  Further, when the metal particle layer 30 is regarded as one layer, the metal layer 10 and the metal particle layer 30 can be regarded as a resonator having a structure in which light is reflected at both ends, and the dielectric layer 20 includes the resonator. This corresponds to the optical path. In such a resonator, the incident light i and the reflected light can be superposed. As for the thickness of the dielectric layer 20, the antinodes of the standing wave generated by the superposition of the incident light i and the reflected light are near the center in the thickness direction of the metal particle layer 30 (see the one-dot chain line in FIG. 5). By setting as described above, the strength of the LSP generated in the metal particle layer 30 can be further increased. In consideration of such points, the thickness of the dielectric layer 20 can also be set. The thickness of the dielectric layer 20 may be 230 nm when the wavelength of the incident light i is 633 nm, but is not limited to this, taking such points into consideration.

1.3. Metal Particle Layer The metal particle layer 30 is provided on the dielectric layer 20. In plan view, the metal particle layer 30 is formed in the region where the dielectric layer 20 is formed. Accordingly, the dielectric layer 20 exists outside the metal particle layer 30 in a plan view, and the portion of the outer dielectric layer 20 is disposed so as to surround the metal particle layer 30.

  The metal particle layer 30 includes metal particles 40. The number, size (dimension), shape, arrangement, and the like of the metal particles 40 included in the metal particle layer 30 are not particularly limited. Further, the metal particle layer 30 may include a gas (space), a dielectric, and the like in addition to the metal particles 40.

  The metal particle layer 30 is defined as a portion between an upper surface of the dielectric layer 20 and a surface in contact with the upper end of the metal particle 40 on the side away from the dielectric layer 20 (see FIGS. 3 and 4). For example, the upper and lower surfaces of the metal particle layer 30 are virtual surfaces when the metal particle layer 30 includes the metal particles 40 and a gas (space), and the metal particle layer 30 includes the metal particles 40. The gas arrange | positioned at the side of is also included.

  The planar shape of the metal particle layer 30 is not particularly limited, and may be an arbitrary shape such as a rectangle, a polygon, a circle, an ellipse or the like. Further, when the planar shape of the metal particle layer 30 is similar to the shape of the irradiation region of the incident light i, the energy of the incident light i may be more efficiently used for electric field enhancement. For example, when the shape of the irradiation region of the incident light i is circular, the planar shape of the metal particle layer 30 is a circular shape (concentric circle) sharing the center with the irradiation region of the incident light i. , May be able to increase energy efficiency.

  The number, size (dimension), shape, arrangement, and the like of the metal particles 40 included in the metal particle layer 30 are not particularly limited as long as localized surface plasmons can be generated by irradiation with incident light i.

  1 to 4 show an example of the metal particles 40 included in the metal particle layer 30. In this example, the metal particle layer 30 has a metal particle row 41 in which a plurality of metal particles 40 are arranged at a pitch P1 in the first direction, and the metal particle row 41 is in a second direction intersecting the first direction. , A plurality of lines are arranged at the pitch P2.

Hereinafter, the metal particle layer 30 and the metal particles 40 will be described using this example. As shown in FIGS. 3 and 4, the metal particle layer 30 is a layer including the metal particles 40, but other substances such as dielectrics may be disposed on portions other than the metal particles 40, preferably Gas (space) is arranged.

(Metal particles)
The metal particles 40 are provided away from the metal layer 10 in the thickness direction due to the presence of the dielectric layer 20. The metal particles 40 are disposed on the metal layer 10 via the dielectric layer 20. In the example of FIGS. 1 to 4 of the present embodiment, the dielectric layer 20 is provided on the metal layer 10 and the metal particles 40 are formed thereon, but the dielectric layer 20 may not be layered. The metal layer 10 and the metal particles 40 only need to be spaced apart in the thickness direction.

  The shape of the metal particles 40 is not particularly limited. For example, when projected in the thickness direction of the metal layer 10 or the dielectric layer 20 (in a plan view from the thickness direction), a circle, an ellipse, a polygon, an irregular shape, and the like. The shape may be a fixed shape or a combination thereof, and even when projected in a direction orthogonal to the thickness direction, the shape may be a circle, an ellipse, a polygon, an indefinite shape, or a combination thereof. 1 to 4, the metal particles 40 are all drawn in a cylindrical shape having a central axis in the thickness direction of the dielectric layer 20, but the shape of the metal particles 40 is not limited to this. For example, a prismatic shape, an elliptical columnar shape, a hemispherical shape, a spherical shape, a cone shape, a frustum shape, or the like may be used.

  The size T in the height direction of the metal particles 40 (thickness direction of the dielectric layer 20) refers to the length of a section in which the metal particles 40 can be cut by a plane perpendicular to the height direction. It can be. The size in the first direction orthogonal to the height direction of the metal particles 40 refers to the length of a section in which the metal particles 40 can be cut by a plane perpendicular to the first direction, and is 5 nm or more and 300 nm or less. Can do. For example, when the shape of the metal particles 40 is a cylinder having the height direction as a central axis, the size of the metal particles 40 in the height direction (the height of the cylinder) is 1 nm or more and 300 nm or less, preferably 2 nm or more. The thickness can be 100 nm or less, more preferably 3 nm to 50 nm, and still more preferably 4 nm to 40 nm. When the shape of the metal particle 40 is a cylinder having the height direction as the central axis, the size of the metal particle 40 in the first direction (diameter of the bottom surface of the cylinder) is 10 nm to 300 nm, preferably 20 nm to 200 nm. Hereinafter, more preferably, it may be 25 nm or more and 180 nm or less.

  The shape and material of the metal particles 40 are arbitrary as long as localized surface plasmon (LSP) can be generated by irradiation with incident light i. Examples of materials that can generate localized surface plasmons by light in the vicinity of visible light include gold, silver, aluminum, copper, platinum, and alloys thereof. Among these, the material of the metal particles 40 is more preferably Au or Ag. In this way, a stronger LSP can be obtained and the enhancement of the entire device can be increased.

  The metal particles 40 can be formed by, for example, a patterning method after forming a thin film by sputtering, vapor deposition, or the like, a microcontact printing method, a nanoimprinting method, or the like. The metal particles 40 can be formed by a colloidal chemical technique, and may be disposed on the dielectric layer 20 by an appropriate technique.

The metal particles 40 have a function of generating localized surface plasmons (LSP) in the optical element 100 of the present embodiment. By irradiating the metal particles 40 with incident light i under specific conditions, localized surface plasmons can be generated around the metal particles 40. The wavelength λ _i of the incident light _i , the dielectric layer 20 so that the localized surface plasmon generated in the metal particle 40 can interact with the propagating surface plasmon generated in the vicinity of the interface between the metal layer 10 and the dielectric layer 20. The thickness, the arrangement of the metal particles 40, and the like may be set.

The optical element 100 is irradiated with incident light i from the metal particle layer 30 side. The incident light i interacts with the metal particle layer 30, the dielectric layer 20, and the metal layer 10 in various regions such as diffraction, refraction, and reflection, and in the vicinity of the region irradiated with the incident light i. Plasmon resonance can be generated and a high electric field enhancement effect can be exhibited.

(Arrangement of metal particles)
In the example shown in FIGS. 1 to 4, a plurality of metal particles 40 constitute a metal particle row 41. The metal particles 40 are arranged side by side in a first direction orthogonal to the thickness direction of the metal layer 10 in the metal particle array 41. In other words, the metal particle row 41 has a structure in which a plurality of metal particles 40 are arranged in a first direction orthogonal to the height direction. The number of the metal particles 40 arranged in one metal particle row 41 may be plural, and is preferably 10 or more.

  Here, the distance between the centers of gravity of the metal particles 40 in the first direction in the metal particle array 41 is defined as a pitch P1 (see FIGS. 2 to 4). The distance between the two metal particles 40 in the metal particle array 41 is a length obtained by subtracting the diameter of the cylinder from the pitch P1 when the metal particle 40 is a cylinder having the thickness direction of the metal layer 10 as a central axis. Equal to When the distance between the particles is small, the strength of the localized surface plasmon acting between the particles tends to increase. The interparticle distance is 1 nm or more and 530 nm or less, preferably 5 nm or more and 200 nm or less, more preferably 5 nm or more and 150 nm or less.

  The pitch P1 of the metal particles 40 in the first direction in the metal particle row 41 is, for example, 6 nm to 535 nm, preferably 10 nm to 400 nm, more preferably 20 nm to 350 nm.

  The metal particle array 41 is composed of a plurality of metal particles 40 arranged at a pitch P1 in the first direction. The distribution / strength of localized surface plasmons generated on the metal particles 40 is determined by the arrangement of the metal particles 40. Also depends on. Therefore, the localized surface plasmon that interacts with the propagating surface plasmon generated in the metal layer 10 is not only the localized surface plasmon generated in the single metal particle 40 but also the metal particle 40 in the metal particle array 41. This is a localized surface plasmon considering the arrangement.

  In the example shown in FIGS. 1 to 4, the metal particle rows 41 are arranged side by side with a pitch P <b> 2 in the thickness direction of the metal layer 10 and the second direction intersecting the first direction. The number of the metal particle rows 41 may be a plurality, and is preferably 5 rows or more. Here, the distance between the centroids in the second direction of the adjacent metal particle rows 41 is defined as the pitch P2. When the metal particle row 41 is composed of a plurality of rows, the pitch P2 is the position of the center of gravity in the second direction of the plurality of rows and the center of gravity in the second direction of the plurality of rows of the adjacent metal particle row 41. And the distance between.

  The pitch P2 between the metal particle rows 41 is, for example, 10 nm or more and 10 μm or less, preferably 100 nm or more and 2 μm or less, more preferably 300 nm or more and 1900 nm or less, further preferably 400 nm or more and 1850 nm or less, and particularly preferably 480 nm or more and 1840 nm or less. can do.

  1 to 4 are examples in which the metal particles 40 of the metal particle layer 30 are regularly arranged. In the optical element 100 of the present embodiment, the arrangement of the metal particles 40 is regular. It is not necessary to have, and a random arrangement | positioning may be sufficient and the arrangement | positioning which has regularity partially may be sufficient.

In addition, when the metal particle layer 30 is arranged as shown in FIGS. 1 to 4, the pitch P1 and the pitch P2 are
P1 <P2 ≦ Q + P1
[Where P1 is the first pitch, P2 is the second pitch, Q is the angular frequency of localized surface plasmons excited by the rows of the second metal layer ω, and the metal constituting the metal layer Assuming that the dielectric constant is ε (ω), the dielectric constant around the metal layer is ε, the speed of light in vacuum is c, the incident angle of the incident light i and the inclination angle from the thickness direction of the metal layer is θ, It represents the pitch of the diffraction grating given by the equation. ] (Ω / c) · {ε · ε (ω) / (ε + ε (ω))} ^1/2 = ε ^1/2 · (ω / c) · sin θ + 2 mπ / Q (m = ± 1, ± 2,. )
If the relationship is set so as to satisfy this relationship, a favorable interaction between the localized surface plasmon and the propagating surface plasmon can be generated, and a higher electric field enhancement effect can be obtained.

1.4. Incident light The optical element 100 is irradiated with incident light i from the metal particle layer 30 side. The wavelength λ _i of the incident light i incident on the optical element 100 is not limited as long as a propagation type surface plasmon can be generated in the vicinity of the surface of the metal layer 10 (interface with the dielectric layer 20). , And electromagnetic waves including visible light and infrared light. Further, the incident light i may or may not be polarized light.

The wavelength λ _i of the incident light i can be, for example, 400 nm to 1070 nm, preferably 500 nm to 1070 nm, more preferably 630 nm to 1070 nm.

  Incident light i is incident on the region of the optical element 100 where the metal particle layer 30 is formed. The incident light i may be incident (irradiated) on the entire metal particle layer 30 or may be incident on a part of the metal particle layer 30 in a plan view. Further, the incident light i may be applied to a region wider than the region where the metal particle layer 30 is formed in plan view.

  The irradiation region of the incident light i refers to a region on the upper surface of the metal particle layer 30 and is a region where the incident light i enters the metal particle layer 30. Incident light i may be irradiated by being condensed by a lens or the like. The size of the irradiation area of the incident light i corresponds to a so-called spot size. The incident light i may or may not be collected by a lens or the like. In addition, the irradiation area of the incident light i may be circular or elliptical when viewed in plan, or may have an arbitrary shape using an aperture or the like. Further, when a lens or the like is used, aberration or the like may occur in the incident light i.

When the irradiation area (spot) on the upper surface of the metal particle layer 30 is circular, the aberration is negligible, and the spot radius w ₀ of the light when condensed by a lens with a numerical aperture NA is approximately It is represented by Formula (1).

Here, assuming that the wavelength λ is 633 nm and an objective lens having a numerical aperture NA = 0.25 (a lens that emits light to the metal particle layer 30), w _{0 to} 1.5 μm. Further, when the incident light i and the scattered light s are collected by the same objective lens, the radius of the area where the scattered light s can be collected also follows the formula (1), and therefore the radius is about 1 .5 μm.

  The size of the irradiation region of the incident light i can be adjusted by changing the numerical aperture NA of the lens to be used, the aperture of the lens, the distance from the lens to the metal particle layer 30, and the like.

1.5. Propagation distance of propagation type surface plasmon (PSP) When incident light i enters the optical element 100 from the metal particle layer 30 side, the metal layer 10
Propagation type surface plasmon (PSP) is generated near the interface between the dielectric layer 20 and the dielectric layer 20. Unlike localized surface plasmons, PSP is a plasmon that has a velocity and moves in the plane direction in the vicinity of the upper surface of the metal layer 10, and is a plasmon having an inclination when plotted on a graph of a dispersion relationship.

The propagation distance of the propagation type surface plasmon in the plane direction mainly depends on the material and thickness of the dielectric layer 20. The propagation distance of the propagation type surface plasmon in the plane direction reaches about 5 μm when the thickness of the dielectric layer 20 is 200 nm when SiO ₂ is employed for the dielectric layer 20. That is, when the dielectric layer 20 has a uniform material and structure, the PSP generated in the irradiation region of the incident light i is a region where the incident light i is not irradiated from the end of the irradiation region to the outside. Propagated by about 5 μm.

  When the spot radius is 1.5 μm and the propagation distance of the PSP is 5 μm, the area of the PSP existing region is calculated to be about 19 times the area of the irradiation region of the incident light i. . Therefore, it will be understood that the energy of the incident light i spreads as a PSP in a region outside the incident light i.

  Of the structure of the optical element 100 of the present embodiment, a region where the dielectric layer 20 is sandwiched between the metal layer 10 and the metal particle layer 30 can be regarded as an MIM structure. This structure is schematically shown in FIG. In such a structure, the dielectric is formed so that the antinode of the standing wave obtained by superimposing the incident light i and the reflected wave generated at each interface is present in the vicinity of the center of the metal particle layer 30 (the dashed line portion in FIG. 5). By setting the film thickness of the layer 20, the plasmon resonance wavelength can be set. At this time, equation (2) is approximately given as the relationship between the structural parameter and the plasmon resonance wavelength.

Here, λ is a plasmon resonance wavelength, and m is an integer. Further, n _particle and d _particle are the refractive index and film thickness of the metal particle layer 30 respectively, n _gap and d _gap are the refractive index and film thickness of the dielectric layer 20 respectively, and φ _mirror is the dielectric layer 20 and the metal. This is the amount of phase change [rad] generated when the light is reflected at the interface with the layer 10. When the metal layer 10 is a single-layer metal film, φ _mirror is given by the following equation.

Here, n _mirror and κ _mirror are the refractive index and extinction coefficient of the metal layer 10, respectively. In addition, when the dielectric layer 20 is composed of a plurality of layers, it is preferable that each dielectric layer 20 satisfies the formula (2). At this time, the second term (2n _gap · d _gap ) on the right side of Expression (2) is calculated as the sum of the products of the refractive index and the film thickness of each layer forming the dielectric layer 20.

  Considering a metal-insulator-metal (MIM) waveguide in which a thin dielectric layer 20 is sandwiched between two metals, as shown in FIG. 5, TM polarized light propagating in the dielectric layer 20. In combination, the propagation type surface plasmon is generated at the interface between the metal layer 10 and the dielectric layer 20, and the propagation type surface plasmon propagates in the plane direction.

At this time, the wave number _kgsp of the propagation type surface plasmon is given by the following equation.

Here, k ₀ is the wave number of light in vacuum, and ε _d and ε _m are the dielectric constant of the dielectric layer 20 and the dielectric constant of the metal layer 10 at the wavelength of the incident light i, respectively. The effective refractive index n _{eff of} the waveguide (dielectric layer 20) and the propagation distance L of the propagation surface plasmon are given by the following equations.

Here, when the wavelength is, for example, 633 nm, the real part of the effective refractive index n _eff and the propagation distance L are expressed by the dielectric layer 20 (here, SiO ₂ ) from the equations (5) and (6). When plotted against the thickness t of FIG. Focusing on the propagation distance L of the propagation type surface plasmon (PSP) in FIG. 6, it can be seen that the propagation distance L increases as the thickness of the dielectric layer 20 increases. Further, as already described, it can be seen from FIG. 6 that the propagation distance reaches 5 μm when SiO ₂ is about 200 nm.

  In the optical element 100, the fact that the propagation distance L of the propagation type surface plasmon propagating through the dielectric layer 20 is long, can cause interaction with more metal particles 40 existing in the metal particle layer 30. Show. Thereby, the region where the enhanced electric field is generated can be wide, and SERS can also be generated from a wide range.

  However, in this case, the enhancement per unit area becomes smaller as the propagation distance L becomes longer. In this case, in order to detect the sample (target substance) adsorbed on the metal particle layer 30 (metal particle 40), the SERS light generated from a wide range is collected through a lens and guided to the spectroscopic processing unit. There is a need. Therefore, it is necessary to increase the diameter of the lens used for condensing light.

  On the other hand, in the optical element 100 according to the present embodiment, since the periodic structure is formed in the dielectric layer 20 located around the metal particle layer 30 in a plan view, the optical element 100 propagates through the dielectric layer 20. Even if the propagation distance L of the propagation type surface plasmon is long, the enhancement per unit area can be kept high.

1.6. Periodic Structure In the optical element 100 of the present embodiment, a periodic structure is formed in the dielectric layer 20 located around the metal particle layer 30 when viewed in plan. The periodic structure may be formed of a material constituting the dielectric layer 20 or may be formed of another material. The periodic structure can be formed by patterning using, for example, a photolithography technique, an etching technique or the like widely used in semiconductor manufacturing.

  The periodic structure is formed in such a manner that TM polarized light cannot be present in the structure. Therefore, TM-polarized light such as PSP cannot exist in the periodic structure. The specific structure of the periodic structure is not particularly limited, and may be a structure in which columnar bodies and holes as exemplified below are regularly arranged two-dimensionally or a random structure.

  An example of the periodic structure formed in the dielectric layer 20 will be described with reference to FIGS. 7 and 11 are perspective views showing an example of the optical element 100 of the present embodiment, respectively. FIG. 8 is a schematic view of the periodic structure formed in the dielectric layer in the example of FIG. 9 and 12 show the Brillouin zone of the periodic structure formed in the dielectric layer of the example of FIGS. 7 and 11, respectively. FIG. 10 shows a photonic band diagram of a periodic structure formed in the dielectric layer of the example of FIG. FIG. 13 is a schematic view of another example of the periodic structure formed in the dielectric layer of the optical element 100 of the present embodiment when viewed in plan. FIG. 14 shows a Brillouin zone having a periodic structure formed in the dielectric layer of the example of FIG. FIG. 15 is a photonic band diagram of a periodic structure formed in the dielectric layer of the example of FIG.

  The example shown in FIGS. 7 and 8 is an example in which cylinders made of a dielectric having a square arrangement are arranged around the metal particle layer 30 in a lattice shape. In such an example, the optical element 100 includes a metal layer 10, a dielectric layer 20 formed on the metal layer 10, and a metal particle layer 30 formed on the dielectric layer 20. In plan view, the dielectric layer 20 positioned around the metal particle layer 30 is formed so that a plurality of cylinders 21 remain, and the cylinders 21 are arranged in a square shape when viewed in a plan view, whereby the periodic structure region 23 is formed. Is formed.

  FIG. 8 shows a schematic plan view of the lattice of the cylinders 21 made of dielectrics arranged in a square pattern. In FIG. 8, a is a pitch, r is a radius of the cylinder 21, and an arrow indicates a unit vector. FIG. 9 is a square array Brillouin zone, and the propagation direction is defined as depicted in FIG.

In the periodic structure of such an example, when the internal dielectric constant of the cylinder 21 is 5.9 (assuming TiO ₂ ), the external dielectric constant is 1 (assuming air), and the radius r / a = 0.25, the photonic band diagram Is as shown in FIG.

  FIG. 10 shows that the photonic band is open when ωa / (2πc) = 0.356 to 0.437. Therefore, when ωa / (2πc) = 0.356 to 0.437, light is present in any direction in the periodic structure region 23 (in the dielectric layer 20) where the periodic structure is formed. Is not allowed. Therefore, in plan view, light or PSP existing inside the region surrounded by the periodic structure region 23 of the dielectric layer 20 cannot enter the periodic structure region 23 and is reflected and reflected on the inner dielectric layer. It will be returned to 20.

Thus, for the angular frequency omega _i of wavelength lambda _i of the incident light i, a and r By setting as described above, the inner dielectric region (the periodic structure region 23 is present the metal particle layer 30 in plan view The body layer 20) can confine propagating surface plasmons which are TM polarized light.

  The photonic band diagram is obtained by deriving an eigen equation using the plane wave expansion method and solving it. The photonic band diagram can be obtained by calculation using commercially available software such as BandSOLVE manufactured by Rsoft.

FIG. 11 is an example in which cylindrical holes 22 having a cylindrical shape are provided in a lattice pattern in a square arrangement in the dielectric layer 20 located around the metal particle layer 30 in plan view. In this example, the cylindrical hole 22 corresponds to a space from which the dielectric layer 20 is removed in a cylindrical shape. The internal dielectric constant of the cylindrical hole 22 is 1 (assuming air), the external dielectric constant is 5.9 (assuming TiO ₂ ), a is the pitch, and r is the radius of the inner (inner diameter) of the cylindrical hole 22 (ie, This corresponds to the case where the column 21 is replaced with the column hole 22 in FIG. In this example, the optical element 100 includes a metal layer 10, a dielectric layer 20 formed on the metal layer 10, and a metal particle layer 30 formed on the dielectric layer 20. When viewed, a plurality of cylindrical holes 22 are formed in the dielectric layer 20 located around the metal particle layer 30, and the cylindrical holes 22 are squarely arranged in a plan view, thereby forming the periodic structure region 23. ing.

  In this example, a photonic band diagram in the case of r / a = 0.45 is shown in FIG. As can be seen from FIG. 12, when ωa / (2πc) = 0.327 to 0.354, the photonic band is open. Therefore, when ωa / (2πc) = 0.327 to 0.354, no light is allowed in any direction in the periodic structure region 23 (in the dielectric layer 20). Therefore, similarly to the above-described example, in plan view, the light or PSP existing inside the region surrounded by the periodic structure region 23 cannot enter the periodic structure region 23 and is reflected to be reflected by the inner dielectric. It can be returned to the body layer 20.

Thus, for the angular frequency omega _i of wavelength lambda _i of the incident light i, a and r By setting as described above, the inner dielectric region (the periodic structure region 23 is present the metal particle layer 30 in plan view The body layer 20) can confine propagating surface plasmons which are TM polarized light.

  Moreover, the arrangement | sequence of the cylinder etc. in a periodic structure is not restricted to a square arrangement. FIG. 13 is a plan view schematically showing the case where the circular cylinders 21 made of a dielectric are arranged around the metal particle layer 30 in a triangular lattice pattern. In such an example, the optical element 100 includes a metal layer 10, a dielectric layer 20 formed on the metal layer 10, and a metal particle layer 30 formed on the dielectric layer 20. In plan view, the dielectric layer 20 positioned around the metal particle layer 30 is formed so that a plurality of cylinders 21 remain, and the cylinders 21 are arranged in a triangular pattern when viewed in a plan view, whereby the periodic structure region 23 is formed. Is formed. FIG. 14 shows a triangular array of Brillouin zones, and the propagation direction is defined as depicted in FIG.

The internal dielectric constant of the cylinder 21 is 5.9 (assuming TiO ₂ ), the external dielectric constant is 1 (assuming air), a is the pitch, and r is the radius of the cylinder 21 as shown in FIG. And in this example, the photonic band figure when radius r / a = 0.1 is shown in FIG.

  FIG. 15 shows that the photonic band is open when ωa / (2πc) = 0.537 to 0.575. If the relationship of ωa / (2πc) = 0.537 to 0.575 is satisfied, no light is allowed in any direction in the periodic structure region 23 (in the dielectric layer 20). Therefore, similarly to the above-described example, in plan view, the light or PSP existing inside the region surrounded by the periodic structure region 23 cannot enter the periodic structure region 23 and is reflected to be reflected by the inner dielectric. It can be returned to the body layer 20.

Thus, for the angular frequency omega _i of wavelength lambda _i of the incident light i, a and r By setting as described above, the inner dielectric region (the periodic structure region 23 is present the metal particle layer 30 in plan view The body layer 20) can confine propagating surface plasmons which are TM polarized light.

  Although the periodic structure has been exemplarily described above, the periodic structure is arbitrary as long as the photonic band gap can be formed, and can be designed appropriately. Further, in the above example, the periodic structure exemplifies a uniform arrangement within the periodic structure region, but the period of the periodic structure may change depending on the position. Furthermore, in the above-described example, an example in which the periodic structure region is not formed in the dielectric layer 20 below the metal particle layer 30 is shown. However, if the periodic structure is located around the metal particle layer 30 Since the effect can be obtained, a periodic structure region may be formed in the dielectric layer 20 below the metal particle layer 30.

1.7. Arrangement of Periodic Structure As described above, the periodic structure formed in the dielectric layer 20 has an action of reflecting and confining the PSP which is going to propagate from the inside to the outside. Therefore, when the periodic structure is formed inside the region where the PSP can exist (a region in consideration of the propagation distance L) in plan view, the electric field enhancement in the inner region can be increased.

  FIG. 16 is a schematic view of the optical element 100 according to some examples as seen in a plan view. Hereinafter, the arrangement of the periodic structures in a plan view will be described with reference to FIG. In each example of FIG. 16, the optical element 100 includes a metal layer 10 (not shown), a dielectric layer 20 formed on the metal layer 10, and metal particles formed on the dielectric layer 20. The periodic structure is formed in the dielectric layer 20 located around the metal particle layer 30 in plan view. In FIG. 16, a region where the periodic structure is formed in the dielectric layer 20 is denoted as a periodic structure region 23. In FIG. 16, the irradiation area of the incident light i is denoted as a spot 50. Further, in the example of FIG. 16, the metal particle layer 30, the end of the periodic structure region 23 (20), and the spot 50 of the incident light i are all circular and concentrically drawn. It is as above-mentioned that it is not limited to.

  The example of FIG. 16A shows a mode in which the periodic structure region 23 is formed around the metal particle layer 30 and the irradiation region of the incident light i is not in the entire region of the metal particle layer 30 but in the central portion. Yes. In FIG. 16A, PSP is generated near the interface between the metal layer 10 (not shown) and the dielectric layer 20 at the position of the spot 50. The PSP generated at such a position propagates outside the spot 50 with a propagation distance L corresponding to the material, thickness, etc. of the dielectric layer 20. Then, the PSP that has propagated through the dielectric layer 20 outside the spot 50 or the interface between the dielectric layer 20 and the metal layer 10 is reflected by the inner end (broken line) of the periodic structure region 23, and the metal particle layer 30. Is returned to the dielectric layer 20 in the region where the Thereby, the abundance of PSP in the region where the metal particle layer 30 exists can be increased, and high electric field enhancement can be obtained. In the case of this example, the reflection amount of the PSP increases as the sum of the radius of the spot 50 and the propagation distance L is larger than the radius of the circle forming the inner end of the periodic structure region 23. The effect can be further enhanced. That is, if the periodic structure is arranged so as to reflect TM polarized light (PSP) generated in the optical element 100 by incidence of incident light i, the electric field enhancement effect can be further enhanced.

  The example of FIG. 16B shows a mode in which the periodic structure region 23 is formed around the metal particle layer 30 and the irradiation region of the incident light i is wider than the metal particle layer 30. In FIG. 16B, PSP is generated near the interface between the metal layer 10 (not shown) and the dielectric layer 20 at the position of the metal particle layer 30. The generated PSP propagates at a propagation distance L corresponding to the material, thickness, etc. of the dielectric layer 20. In the example of FIG. 16B, the PSP is a dielectric inside the region of the metal particle layer 30. Since it can exist only in the layer 20, the abundance of PSP in the region (dielectric layer 20 inside the periodic structure region 23) can be increased, and high electric field enhancement can be obtained.

In the example of FIG. 16C, the periodic structure region 23 is formed around the metal particle layer 30, and the region inside the metal particle layer 30 (part of the dielectric layer 20 below the metal particle layer 30). Until this, the periodic structure region 23 is formed. And the aspect which has the irradiation area | region (spot 50) of the incident light i in the center part which is not the whole region of the metal particle layer 30 is shown. In FIG. 16C, PSP is generated near the interface between the metal layer 10 (not shown) and the dielectric layer 20 at the position of the spot 50. The PSP generated at such a position propagates outside the spot 50 with a propagation distance L corresponding to the material, thickness, etc. of the dielectric layer 20. Then, the PSP that has propagated through the dielectric layer 20 or the interface between the dielectric layer 20 and the metal layer 10 outside the spot 50 is inside the periodic structure region 23 (in this example, below the metal particle layer 30). Is located (broken line)) and is concentrated in a region of the dielectric layer 20 below the metal particle layer 30 where no periodic structure is formed. Thereby, the abundance of PSP inside the periodic structure region 23 can be increased, and high electric field enhancement can be obtained. In the case of this example, the reflection amount of the PSP increases as the sum of the radius of the spot 50 and the propagation distance L is larger than the radius of the circle forming the inner end of the periodic structure region 23. The effect can be further enhanced. That is, if the periodic structure is arranged so as to reflect TM polarized light (PSP) generated in the optical element 100 by the incidence of the incident light i, the electric field enhancement effect can be further enhanced.

  The example of FIG. 16D is the same as the example of FIG. 16A except that the periodic structure region 23 formed around the metal particle layer 30 is formed in an annular shape. Also in FIG. 16D, PSP is generated in the vicinity of the interface between the metal layer 10 (not shown) and the dielectric layer 20 at the position of the spot 50. The PSP generated at such a position propagates outside the spot 50 with a propagation distance L corresponding to the material, thickness, etc. of the dielectric layer 20. Since the PSP that has propagated through the dielectric layer 20 outside the spot 50 or the interface between the dielectric layer 20 and the metal layer 10 cannot exist in the periodic structure region 23 as described above, Even in the case where the metal particle layer 30 is formed, it is reflected by the inner end portion (inner broken line) of the periodic structure region 23 and returned to the region where the metal particle layer 30 exists. Thereby, the abundance of PSP in the dielectric layer 20 inside the periodic structure region 23 can be increased, and high electric field enhancement can be obtained. Similarly, in the case of this example, the reflection amount of the PSP increases as the sum of the radius of the spot 50 and the propagation distance L is larger than the radius of the circle forming the inner end of the periodic structure region 23. In addition, the electric field enhancing effect can be further enhanced. That is, if the periodic structure is arranged so as to reflect TM polarized light (PSP) generated in the optical element 100 by the incidence of the incident light i, the electric field enhancement effect can be further enhanced.

  Further, regarding the relationship between the areas of the respective regions in plan view, the area of the region surrounded by the periodic structure region 23 (20) is the area of the region (spot 50) irradiated with the incident light i and the outside of the spot 50. The electric field enhancement effect can be further enhanced by making the area smaller than the sum of the areas of the propagation type surface plasmons propagating in the dielectric layer and the interface between the metal layer and the dielectric layer. In addition, when the spot 50 is circular in plan view as in the example of FIG. 16, the radius of the region surrounded by the periodic structure 23 (20) is irradiated with the incident light i as the relationship between the lengths of the regions. By reducing the radius of the region (spot 50) and the propagation distance L of the propagation type surface plasmon toward the outside of the spot 50 in the dielectric layer and the interface between the metal layer and the dielectric layer, The electric field enhancing effect can be further enhanced.

1.8. Operational Effect According to the optical element 100 of the present embodiment, when the incident light i is irradiated on the metal particle layer 30 of the optical element 100, it is allowed that light exists in the surrounding dielectric layer 20 in plan view. Since the periodic structure is not formed, the light that propagates through the dielectric layer 20 and the propagation type surface plasmon that propagates through the interface between the dielectric layer 20 and the metal layer 10 are converted into the dielectric in which the inner periodic structure is not formed. It can be confined in layer 20. Thereby, the loss of energy for enhancing the electric field is reduced, and a high electric field enhancing effect can be obtained. Since the periodic structure exhibits a photonic band gap in which TM polarized light does not propagate at the wavelength λ _i of the incident light i, the propagation surface plasmon that is TM polarized light cannot exist at the position where the periodic structure is formed. . Thereby, the dissipation of energy for enhancing the electric field is reduced, and a high electric field enhancing effect can be obtained.

Further, if the periodic structure is arranged so as to reflect TM polarized light generated in the optical element 100 by incidence of the incident light i, the propagating surface plasmon which is TM polarized light will diffuse outside the periodic structure. Since the propagating surface plasmon is returned toward the inside of the periodic structure, the dissipated energy is recovered and a higher electric field enhancement effect can be obtained.

2. Analysis Device FIG. 17 is a diagram schematically illustrating an analysis device 200 according to the present embodiment. For example, the analysis device 200 is a Raman spectroscopic device, and the analysis device 200 will be described below as a Raman spectroscopic device. As shown in FIG. 17, the analysis device 200 includes a gas sample holding unit 110, a detection unit 120, a control unit 130, and a housing 140 that houses the detection unit 120 and the control unit 130. The gas sample holder 110 includes the optical element according to the present invention. Below, the example containing the above-mentioned optical element 100 is demonstrated.

  The gas sample holding unit 110 includes an optical element 100, a cover 112 that covers the optical element 100, a suction flow path 114, and a discharge flow path 116. The detection unit 120 includes a light source 210, lenses 122a, 122b, 122c, and 122d, a half mirror 124, and a photodetector 220. The control unit 130 includes a detection control unit 132 that processes a signal detected by the photodetector 220 and controls the photodetector 220, and a power control unit 134 that controls power and voltage of the light source 210 and the like. doing. As shown in FIG. 17, the control unit 130 may be electrically connected to a connection unit 136 for connection to the outside.

  In the analyzer 200, when the suction mechanism 117 provided in the discharge flow path 116 is operated, the suction flow path 114 and the discharge flow path 116 become negative pressure, and the target substance to be detected from the suction port 113 is contained. The gas sample is aspirated. The suction port 113 is provided with a dust removal filter 115, which can remove relatively large dust, some water vapor, and the like. The gas sample passes through the suction flow path 114 and the discharge flow path 116 and is discharged from the discharge port 118. The gas sample contacts the metal particle layer 30 of the optical element 100 when passing through such a path.

  The shapes of the suction channel 114 and the discharge channel 116 are such that light from the outside does not enter the optical element 100. Thereby, since the light which becomes noise other than a Raman scattered light does not inject, the S / N ratio of a signal can be improved. The material constituting the channels 114 and 116 is, for example, a material or a color that hardly reflects light.

  The shape of the suction channel 114 and the discharge channel 116 is such that the fluid resistance to the gas sample is reduced. Thereby, highly sensitive detection becomes possible. For example, retention of the gas sample at the corners can be eliminated by making the shapes of the channels 114 and 116 as smooth as possible by eliminating the corners. As the suction mechanism 117, for example, a fan motor or a pump having a static pressure and an air volume corresponding to the flow path resistance is used.

  In the analyzer 200, the light source 210 irradiates the optical element 100 with light (for example, laser light having a wavelength of 633 nm, incident light i). As the light source 210, for example, a semiconductor laser or a gas laser can be used. The light emitted from the light source 210 is collected by the lens 122a and then enters the optical element 100 via the half mirror 124 and the lens 122b. SERS light is emitted from the optical element 100, and the light reaches the photodetector 220 via the lens 122b, the half mirror 124, and the lenses 122c and 122d. That is, the light detector 220 detects light emitted from the optical element 100. Since the SERS light includes Rayleigh scattered light having the same wavelength as the incident wavelength from the light source 210, the Rayleigh scattered light may be removed by the filter 126 of the photodetector 220. The light from which the Rayleigh scattered light has been removed is received by the light receiving element 128 through the spectroscope 127 of the photodetector 220 as Raman scattered light. For example, a photodiode is used as the light receiving element 128.

The spectroscope 127 of the photodetector 220 is formed of, for example, an etalon using Fabry-Perot resonance, and the pass wavelength band can be made variable. The light receiving element 128 of the light detector 220 obtains a Raman spectrum peculiar to the target substance. For example, the signal intensity of the target substance can be detected by collating the obtained Raman spectrum with data stored in advance. it can.

  The analyzer 200 includes the optical element 100, the light source 210, and the photodetector 220, and is not limited to the above example as long as the target substance can be adsorbed on the optical element 100 and the Raman scattered light can be acquired.

  Further, in the case of detecting Rayleigh scattered light as in the Raman spectroscopy according to the present embodiment described above, the analysis apparatus 200 does not have the filter 126, and the Rayleigh scattered light and the Raman scattered light are detected by the spectrometer. Spectroscopy may be performed.

  The analysis apparatus 200 includes the optical element 100 that can reduce the loss of energy for the electric field enhancement described above and can obtain a high electric field enhancement effect. Therefore, the intensity of Raman scattered light can be increased. Therefore, the analyzer 200 can have high detection sensitivity.

3. Next, an electronic device 300 according to the present embodiment will be described with reference to the drawings. FIG. 18 is a diagram schematically illustrating the electronic apparatus 300 according to the present embodiment. The electronic device 300 can include a Raman spectroscopic device according to the present invention. Hereinafter, an example including the analysis apparatus 200 as a Raman spectroscopic apparatus according to the present invention will be described.

  As shown in FIG. 18, the electronic device 300 includes an analysis device 200, a calculation unit 310 that calculates health and medical information based on detection information from the photodetector 220, a storage unit 320 that stores health and medical information, And a display unit 330 that displays health care information.

  The calculation unit 310 is, for example, a personal computer or a personal digital assistant (PDA) and receives detection information (signals or the like) sent from the photodetector 220. The calculation unit 310 calculates health and medical information based on detection information from the photodetector 220. The calculated health and medical information is stored in the storage unit 320.

  The storage unit 320 is, for example, a semiconductor memory, a hard disk drive, or the like, and may be configured integrally with the calculation unit 310. The health care information stored in the storage unit 320 is sent to the display unit 330.

  The display unit 330 includes, for example, a display board (liquid crystal monitor or the like), a printer, a light emitter, a speaker, and the like. The display unit 330 displays or issues information based on the health and medical information calculated by the calculation unit 310 so that the user can recognize the contents.

  The health care information includes at least one biological substance selected from the group consisting of bacteria, viruses, proteins, nucleic acids, and antigens / antibodies, or at least one compound selected from inorganic molecules and organic molecules. Information about presence or absence or quantity can be included.

  The electronic apparatus 300 includes an analyzer 200 that can easily cope with a change in plasmon resonance wavelength. Therefore, the electronic device 300 can easily detect a trace amount substance, and can provide highly accurate health care information.

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, it is possible to appropriately combine each embodiment and each modification.

  For example, the optical element according to the present invention can also be used as an affinity sensor that detects the presence or absence of substance adsorption, such as the presence or absence of antigen adsorption in an antigen-antibody reaction. The affinity sensor makes white light incident on the sensor, measures the wavelength spectrum with a spectroscope, and detects the amount of shift of the surface plasmon resonance wavelength due to adsorption, thereby making the absorption of the detection substance to the sensor chip highly sensitive. Can be detected.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Substrate, 10 ... Metal layer, 20 ... Dielectric layer, 21 ... Cylinder, 22 ... Cylindrical hole, 23 ... Periodic structure area, 30 ... Metal particle layer, 40 ... Metal particle, 41 ... Metal particle row, 50 ... Spot DESCRIPTION OF SYMBOLS 100 ... Optical element 110 ... Gas sample holding part, 112 ... Cover, 113 ... Suction port, 114 ... Suction channel, 115 ... Dust filter, 116 ... Drain channel, 117 ... Suction mechanism, 118 ... Suction port, 120 Detecting unit, 122a, 122b, 122c, 122d ... lens, 124 ... half mirror, 126 ... filter, 127 ... spectroscope, 128 ... light receiving element, 130 ... control unit, 132 ... detection control unit, 134 ... power control unit, DESCRIPTION OF SYMBOLS 136 ... Connection part, 140 ... Housing | casing, 200 ... Raman spectroscopy apparatus, 210 ... Light source, 220 ... Photodetector, 300 ... Electronic device, 310 ... Calculation part, 320 ... Memory | storage part, 330 ... Display

Claims (8)

A metal layer,
A dielectric layer formed on the metal layer;
A metal particle layer formed on the dielectric layer and receiving incident light;
Including
An optical element in which a periodic structure is formed in the dielectric layer located around the metal particle layer in plan view. In claim 1,
The optical element in which the periodic structure exhibits a photonic band gap in which TM polarized light does not propagate in the dielectric layer and the interface between the metal layer and the dielectric layer at the wavelength of the incident light. In claim 1 or claim 2,
The said periodic structure is an optical element arrange | positioned so that the TM polarized light which arises in the said optical element by incidence of the said incident light may be reflected. In any one of Claims 1 thru | or 3,
In the plan view, the area of the region surrounded by the periodic structure is such that the area of the region irradiated with the incident light and the outside of the region irradiated with the incident light are within the dielectric layer and the metal layer. And an area of a region where a propagation type surface plasmon propagating through the interface between the dielectric layer and the dielectric layer propagates is smaller than the sum of the areas. In any one of Claims 1 thru | or 4,
In the plan view, the radius of the region surrounded by the periodic structure is such that the radius of the region irradiated with the incident light and the interface between the metal layer and the dielectric layer in the dielectric layer and the incident light. An optical element that is smaller than the sum of the distance that the propagation type surface plasmon propagates toward the outside of the region irradiated with. An optical element according to any one of claims 1 to 5,
A light source for irradiating the optical element with the incident light;
A detector for detecting light emitted from the optical element;
Analytical device equipped with.   7. The analyzer according to claim 6, a calculation unit that calculates health and medical information based on detection information from the detector, a storage unit that stores the health and medical information, and a display unit that displays the health and medical information. And electronic equipment.   8. The health care information according to claim 7, wherein the health care information is at least one selected from the group consisting of bacteria, viruses, proteins, nucleic acids, and antigens / antibodies, or at least selected from inorganic molecules and organic molecules. Electronic equipment containing information on the presence or amount of one compound.