WO2012086198A1 - Optical-electric-field enhancement device and optical detecting device - Google Patents

Optical-electric-field enhancement device and optical detecting device Download PDF

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Publication number
WO2012086198A1
WO2012086198A1 PCT/JP2011/007153 JP2011007153W WO2012086198A1 WO 2012086198 A1 WO2012086198 A1 WO 2012086198A1 JP 2011007153 W JP2011007153 W JP 2011007153W WO 2012086198 A1 WO2012086198 A1 WO 2012086198A1
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Prior art keywords
photoelectric field
field enhancement
enhancement device
optical
optical waveguide
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PCT/JP2011/007153
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French (fr)
Japanese (ja)
Inventor
納谷　昌之
笠松　直史
達矢 吉弘
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富士フイルム株式会社
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Publication of WO2012086198A1 publication Critical patent/WO2012086198A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons

Definitions

  • the present invention relates to a photoelectric field enhancement device provided with a metal on a fine concavo-convex structure capable of inducing localized plasmons, and a photodetection device provided with the photoelectric field enhancement device.
  • Raman spectroscopy is a method of obtaining a spectrum (Raman spectrum) by dispersing scattered light obtained by irradiating a substance with single wavelength light, and detecting light (Raman scattered light) having a wavelength different from that of the irradiated light. It is used for identification etc.
  • Raman scattered light is greatly enhanced in a structure in which nano-order metal fine particles are distributed and arranged on a surface on which a substance is adsorbed (see, for example, Non-Patent Document 1).
  • the enhancement of Raman scattered light is said to be due to localized plasmon resonance. That is, it is considered that a free electric field in the metal fine particle oscillates in resonance with the electric field of light to generate a strong electric field around the metal fine particle, and the Raman scattered light is enhanced by the influence of this electric field.
  • Patent Document 1 discloses metal fine particles having a size capable of inducing localized plasmon resonance in a plurality of micropores distributed and formed on one surface of a substrate. A method for producing a microstructure using a distributed microstructure and a plating process is disclosed.
  • a plurality of metal fine particles having a size capable of inducing localized plasmon resonance are arranged in fine holes arranged at high density, and the head of the metal fine particles is arranged.
  • the diameter is larger than the diameter of the fine holes.
  • Patent Document 2 discloses an enhanced Raman signal measuring device having a metal layer at the tip of an optical fiber probe and a method of forming a metal layer on the surface of the probe end of the optical fiber probe.
  • Patent Document 3 discloses an optical amplifying element in which a periodic rough surface metal part is provided in a part of an optical fiber as an optical element that utilizes an optical amplification phenomenon using plasmons.
  • the base material of the microstructure is limited to conductive metal.
  • the excitation light intensity and the Raman scattered light intensity are reduced by absorption of the measurement sample and the medium, and the S / N ratio of the measurement signal is reduced.
  • an optical system for detecting the scattered light by making excitation light incident on the photoelectric field enhancement device is separately required, which has a demerit that increases the size of the measuring apparatus.
  • the metal film provided at the tip of the optical fiber does not have an uneven structure, and therefore the amplification of the Raman signal cannot be said to be sufficient.
  • the present invention has been made in view of the above circumstances, and effectively enhances the Raman scattered light and makes it possible to detect the enhanced Raman scattered light with higher sensitivity.
  • the purpose is to provide a device. It is another object of the present invention to provide a measuring apparatus for detecting enhanced light including the photoelectric field enhancing device.
  • the photoelectric field enhancement device of the present invention an optical waveguide member provided with a narrow portion in a part of the optical waveguide, A fine uneven structure provided on the surface of the narrow path portion; A metal film formed on the surface of the fine uneven structure, The fine concavo-convex structure on which the metal film is formed is irradiated with light to produce an electric field enhancement effect by plasmons.
  • the metal film is formed on the surface of the fine uneven structure, and the surface of the metal film has a fine uneven structure corresponding to the transparent fine uneven structure.
  • the fine concavo-convex structure on the surface of the metal film only needs to be capable of inducing localized plasmon when irradiated with light.
  • the fine concavo-convex structure described here is a concavo-convex structure in which the average size and the average pitch of the concavo-convex structure and the concavo-convex structure that can generate localized plasmons are smaller than the wavelength of light irradiated.
  • the average pitch of the projections and depressions and the distance (depth) between the apex of the projection and the bottom of the recess are half or less of the wavelength of light.
  • the average pitch of the unevenness and the distance between the top of the convex part and the bottom of the concave part be 500 nm or less.
  • the average pitch of the unevenness and the distance (depth) between the top of the convex part and the bottom part of the concave part be 200 nm or less.
  • the average pitch of the unevenness is obtained by taking a surface image of the fine unevenness structure with an SEM (scanning electron microscope), binarizing the image, and calculating by statistical processing.
  • the average depth of the unevenness is obtained by measuring the surface shape with an AFM (Atomic Force Microscope) and performing statistical processing.
  • the minimum size of the narrow path portion is 50 times or less of the excitation light wavelength.
  • the narrow path portion may have a tapered shape in which the optical waveguide is gradually narrowed.
  • the optical waveguide member can be configured to have a constriction structure in which the narrow path portion is provided in an intermediate portion of the optical waveguide member.
  • the optical waveguide member may have a tapered structure in which the narrow path portion is provided at one end of the optical waveguide member.
  • the photoelectric field enhancement device of the present invention may include a reflective optical element coupled to one end of the narrow path portion of the optical waveguide member when the optical waveguide member has a tapered structure.
  • the photoelectric field enhancement device of the present invention when the optical waveguide member has a tapered structure, is coupled to one end of the narrow path portion of the optical waveguide member, compared to the reflectance or absorption rate of the irradiated light, You may provide the optical element with a high reflectance or absorptivity with respect to the light of the wavelength range different from this light.
  • Coupled means optical coupling, and the reflective optical element or the optical element may be formed directly on one end of the narrow path portion or via a further optical waveguide member. Alternatively, it may be arranged so as to be separated from one end of the narrow path portion.
  • An optical fiber is suitable as the optical waveguide member.
  • the fine concavo-convex structure can be made of a boehmite layer made of aluminum oxide, aluminum hydroxide, or a hydrate thereof.
  • the metal film may be made of a metal that generates localized plasmons when irradiated with the light, but is selected from the group consisting of Au, Ag, Cu, Al, Pt, and alloys containing these as the main components. It is preferably made of at least one kind of metal. In particular, Au, Ag, or Pt is preferable.
  • the measuring apparatus of the present invention comprises the photoelectric field enhancing device of the present invention, An excitation light source that outputs excitation light guided to the optical waveguide member of the photoelectric field enhancement device, and a light detection unit coupled to the photoelectric field enhancement device are provided.
  • the photoelectric field enhancement device of the present invention includes an optical waveguide member having a narrow path part in an optical waveguide, a fine uneven structure provided on the surface of the narrow path part, and a metal formed on the surface of the fine uneven structure. And a metal fine concavo-convex structure portion formed by forming a metal film in a fine concavo-convex structure. By irradiating light to the metal fine concavo-convex structure portion, the surface of the metal fine concavo-convex structure portion Localized plasmons can be induced effectively, and the photoelectric field enhancement effect by the localized plasmons can be generated.
  • the photoelectric field enhancement device of the present invention is a metal in which a metal film is formed on the surface of a fine concavo-convex structure by utilizing photoelectric field leakage at a narrow path portion provided in a part of an optical waveguide of an optical waveguide member.
  • the fine concavo-convex structure portion can be irradiated with light propagating through the optical waveguide, and there is no need to irradiate excitation light from the outside of the metal fine concavo-convex structure portion. Therefore, in the detection light measurement apparatus using the photoelectric field enhancement device of the present invention, it is possible to suppress a decrease in excitation light intensity or Raman scattered light intensity due to absorption or scattering of the measurement sample or medium. / N It becomes possible to detect the detection light with good frequency. Further, if the device of the present invention is used, excitation light and detection light can be propagated through the optical waveguide member, so that the excitation and detection optical systems can have a very simple configuration.
  • the photoelectric field enhancement device of the present invention can be manufactured by a very simple process, and the cost can be reduced in a short time.
  • Sectional drawing which shows a part of photoelectric field enhancement device which concerns on 1st Embodiment Graph showing the relationship between the minimum taper size and beam divergence angle Sectional drawing which shows the taper formation part in the manufacturing process of the photoelectric field enhancement device which concerns on 1st Embodiment.
  • Sectional drawing which shows Al film formation part in the manufacturing process of the photoelectric field enhancement device which concerns on 1st Embodiment
  • Sectional drawing which shows the boehmite layer formation part in the preparation process of the photoelectric field enhancement device which concerns on 1st Embodiment.
  • Sectional drawing which shows the other example of a taper formation process Sectional drawing which shows a part of photoelectric field enhancement device which concerns on 2nd Embodiment Sectional drawing which shows 2A of design changes of the photoelectric field enhancement device which concerns on 2nd Embodiment Sectional drawing which shows the design modification example 2B of the photoelectric field enhancement device which concerns on 2nd Embodiment Sectional drawing which shows 2C of design changes of the photoelectric field enhancement device which concerns on 2nd Embodiment
  • the perspective view of the photoelectric field enhancement device concerning a 3rd embodiment The schematic diagram showing schematic structure of the surface enhancement Raman detector which concerns on 4th Embodiment
  • FIG. 1 is a cross-sectional view showing a part of a photoelectric field enhancement device 1 according to a first embodiment of the present invention.
  • the photoelectric field enhancement device 1 of the present embodiment has a core diameter that gradually decreases in a part of an optical fiber 20 that is an optical waveguide member including a core part (optical waveguide) 11 and a cladding part 12.
  • a taper portion 13 is provided as a narrow path portion of the optical waveguide, a fine uneven structure 18 made of a boehmite layer is provided on the surface of the taper portion 13, and a metal film 19 is provided on the surface of the fine uneven structure 18.
  • the device 1 is formed by irradiating light (hereinafter referred to as “excitation light”) onto a metal fine concavo-convex structure portion 10 formed by forming a metal film 19 along the fine concavo-convex structure 18. It induces plasmon resonance, and an enhanced photoelectric field is generated on the surface of the metal film 19 by this localized plasmon resonance.
  • the device 1 has a constricted structure in which a tapered portion 13 is formed in an intermediate portion of the optical fiber 20.
  • the fine concavo-convex structure 18 may be provided in the entire circumferential direction of the tapered portion 13 or may be provided only in a part of the circumferential direction.
  • the average size and the average pitch of the concavo-convex convex portions on the surface of the metal fine concavo-convex structure portion 10 configured by forming the metal film 19 on the surface of the fine concavo-convex structure 18 is the excitation light.
  • the concavo-convex structure is fine enough to be shorter than the wavelength, any plasmon that can cause localized plasmons on the surface of the metal fine concavo-convex structure portion 10 may be used.
  • the fine concavo-convex structure 18 has an average depth of 200 nm or less from the top of the convex portion to the bottom of the adjacent concave portion, and an average pitch between the vertices of the most adjacent convex portions separating the concave portions is 200 nm or less.
  • the fine concavo-convex structure 18 is constituted by a boehmite layer, but the fine concavo-convex structure may be provided by polishing the surface of the tapered portion of the optical fiber.
  • corrugation of a preferable pitch and depth can be formed easily, it is preferable to comprise the fine unevenness
  • the metal film 19 may be made of a metal that can generate localized plasmons when irradiated with excitation light.
  • the metal film 19 is made of Au, Ag, Cu, Al, Pt, or an alloy containing these as a main component. It consists of at least one metal selected from the group. In particular, Au, Ag, or Pt is preferable.
  • the metal fine concavo-convex structure portion 10 can maintain a concavo-convex shape capable of generating localized plasmons upon irradiation with excitation light.
  • the thickness is not particularly limited as long as the thickness is about 10 to 1000 nm. In particular, about 50 to 500 nm is preferable.
  • the minimum size (minimum diameter) Dmin of the tapered portion 13 is preferably 50 times or less of the excitation light wavelength.
  • the optical fiber is provided with the tapered portion 13 whose diameter is gradually reduced.
  • the narrow path portion is formed in the optical waveguide, and the optical fiber is not necessarily tapered.
  • the preferred minimum size of the narrow path was determined as follows. Tapered fibers formed by forming tapered portions having different minimum diameters into an optical fiber having a wavelength of 785 nm and an optical fiber having an NA of 0.22 and a core diameter / cladding diameter of 230 nm / 250 nm were guided to the respective tapered fibers. The relationship between the full beam divergence and the core diameter at the taper minimum diameter was measured. FIG. 2 shows the measurement results.
  • the guided light leaks out of the optical fiber when the core diameter is about 37 ⁇ m (about 50 times the pumping light wavelength) and does not satisfy the Etendue conservation law (NA ⁇ core diameter is constant). That is, in the photoelectric field enhancement device of the present invention, if the minimum diameter of the narrow path portion is 50 times or less of the excitation light wavelength, the excitation light leaks to the fine metal uneven structure side in the narrow path portion, and the fine metal uneven structure It is considered that the excitation light can be effectively irradiated to the part.
  • FIGS. 3A to 3C are cross-sectional views showing the manufacturing process of the photoelectric field enhancing device 1.
  • a multimode quartz fiber having a core diameter of 105 ⁇ m and a cladding diameter of 125 ⁇ m is prepared as the optical fiber 20 including the core portion 11 and the cladding portion 12, and the clad exposed portion from which the coating (not shown) is peeled is heated and stretched.
  • a tapered portion 13 as shown in FIG. 3A is formed.
  • the cladding diameter of the minimum diameter portion Dmin of the tapered portion 13 is set to 30 ⁇ m by heating and stretching.
  • core diameter and the clad diameter and the clad diameter after stretching may be a combination of values different from those of the present embodiment.
  • glass fiber or plastic fiber may be used instead of quartz fiber.
  • Al deposition is performed with the non-tapered portion 16 masked.
  • an Al film 17 having a thickness of 20 nm is formed only on the tapered portion 13.
  • the Al film 17 may be formed over the entire circumference of the taper portion 13 or may be formed only in a part in the circumferential direction.
  • the Al film 17 may be formed not only by metal vapor deposition but also by PVD method or CVD method.
  • a boehmite layer may be formed by hydrothermally treating an aluminum oxide film formed by a sol-gel method.
  • the photoelectric field enhancing device 1 of the present embodiment shown in FIG. 1 can be manufactured.
  • the method for forming the tapered portion 13 is not limited to heating and stretching. As shown in FIG. 4, even if a part of the optical fiber 20 is positioned in the HF solution 15 held between the tweezer tips 14 by the surface tension, and the tapered portion 13 is formed by chemical etching with the HF solution 15. Good. Further, the tapered portion 13 may be formed in advance in a part of the optical fiber by adjusting the drawing speed during the drawing process in the production of the optical fiber.
  • FIG. 5 is a cross-sectional view showing a part of the photoelectric field enhancement device 2 of the present embodiment.
  • symbol is attached
  • the photoelectric field enhancement device 2 is different from the photoelectric field enhancement device 1 of the first embodiment in that it has a tapered structure with a tapered portion 13 at one end of the optical fiber 20.
  • the photoelectric field enhancement device 2 of the present embodiment is produced by the same production method as the photoelectric field enhancement device 1 and is cut at the finest detail (the smallest diameter portion) of the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1. Can be produced.
  • the cutting is not limited to the finest details in the device 1, but may be cut at an arbitrary portion. However, the finest details in the device 2 are preferably 50 times or less of the excitation light wavelength.
  • FIGS. 6 to 8 are cross-sectional views showing a part of devices 2A to 2C of a design change example of the photoelectric field enhancement device 2 of the second embodiment.
  • the photoelectric field enhancing devices 2A to 2C are formed by connecting the tip end 2a of the photoelectric field enhancing device 2 to an optical element that reflects at least the Raman scattered light Lr.
  • the photoelectric field enhancement device 2A shown in FIG. 6 has a reflection optical element 22 made of a metal film or a multilayer film formed at the tip 2a, and reflects light emitted from the tip 2a toward the optical fiber 20 side. Has been.
  • one end of an optical waveguide substrate 23 different from the optical fiber 20 is connected to the tip 2a of the tapered portion of the photoelectric field enhancement device 2, and a reflection optical element is connected to the other end of the optical waveguide substrate 23. 24.
  • the photoelectric field enhancement device 2C shown in FIG. 8 includes a tapered portion tip 2a of the photoelectric field enhancement device 2, a lens 25 provided at a predetermined distance, and a reflective optical element 26 provided behind the lens 25.
  • the lens 25 is arranged and configured to collimate the light emitted from the tapered tip 2a and condense the light reflected by the reflective optical element 26 onto the tapered tip 2a.
  • the amount of light when detecting light from the optical fiber side can be increased.
  • the reflection optical elements provided in the devices 2A to 2C may be simple mirrors, but light to be detected in the measurement apparatus including these devices 2A to 2C (for example, Raman scattered light, fluorescence in the Raman spectroscopic apparatus) It is preferable to efficiently reflect the wavelength of fluorescence in the detection device while absorbing or transmitting the excitation light, because the detection light can be detected with higher accuracy in the measurement device.
  • FIG. 9 is a perspective view showing the photoelectric field enhancement device 3 of the present embodiment.
  • the optical field enhancement device 3 includes an optical waveguide portion 33 having a taper portion 35 at a central portion provided on a part of an LN (LiNbO3) substrate 30 having an optical waveguide (core portion) 31 having a width of 200 ⁇ m.
  • a boehmite layer 18 constituting a fine concavo-convex structure and a metal film 19 provided thereon are formed on the side surface of 35.
  • a method for manufacturing the photoelectric field enhancement device 3 will be briefly described.
  • a portion of the LN substrate 30 is mechanically excavated to form an optical waveguide portion 33 including a core portion 31 having a thickness of 2 mm, a length of 5 mm, and a width of 200 ⁇ m, and a clad portion 32 having a width of 400 ⁇ m.
  • the taper portion 35 is formed by machine excavation so that the core width of the smallest part (the narrowest portion) is 30 ⁇ m.
  • an Al film having a thickness of 20 nm is formed on the side surface of the tapered portion 35, and the boehmite layer 18 is formed by performing hydrothermal treatment.
  • the Au thin film 19 is formed on the surface of the boehmite layer 18, the metal fine uneven structure portion 10 is formed on the side surface of the taper portion 35.
  • the optical waveguide member is not limited to an optical fiber, but may be a substrate.
  • the minimum size of the narrow path portion means the thickness of the thinnest portion, and it is desirable that this thickness is 50 times or more the excitation light wavelength.
  • LN LiNbO3
  • LiTaO3, KN (KNbO3), KTP (KTiOPO4), or LiNb (1-x) TaxO3 (where 0 ⁇ x ⁇ 1) or the like is used as an optical waveguide (core portion).
  • the measurement apparatus of the present embodiment is a surface-enhanced Raman detector 4 that includes the photoelectric field enhancement device 1 described above.
  • FIG. 10 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 4 of the present embodiment.
  • the surface-enhanced Raman detector 4 includes a photoelectric field enhancement device 1 that includes a tapered portion 13 in a part of an optical fiber 20 and a metal fine concavo-convex structure portion 10 formed in the tapered portion.
  • the photoelectric field enhancing device 1 is connected to one end (one end of the optical fiber 20) via the connector 42, and the photodetector 44 is connected to the other end (the other end of the optical fiber 20) of the photoelectric field enhancing device 1.
  • the optical connector 42 has a structure for optically and mechanically coupling the semiconductor laser light source 41 and the optical fiber 20.
  • the optical connector 43 has a structure for optically and mechanically coupling the photodetector 44 and the optical fiber 20.
  • Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown).
  • the excitation light (laser light) L0 propagates through the optical fiber 20 via the optical connector 42, and local plasmons are induced in the metal fine concavo-convex structure portion 10 of the taper portion 13 and are enhanced on the surface of the structure portion 10.
  • a photoelectric field is generated.
  • the Raman scattered light Lr generated from the substance in the sample solution by being excited by the photoelectric field is guided through the optical fiber 20 and detected by the photodetector 44 through the optical connector 43.
  • the photodetector 44 preferably includes an optical element that absorbs or reflects the excitation light and / or an optical element that separates the Raman scattered light. .
  • the measuring apparatus of the present embodiment is a surface-enhanced Raman detector 5 including the above-described photoelectric field enhancing device 1.
  • FIG. 11 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 5 of the present embodiment.
  • the semiconductor laser light source 41 is connected to one end of the photoelectric field enhancing device 1 via an optical connector 42 and an optical fiber coupler (optical directional coupler) 51. It is connected to both ends of the photoelectric field enhancing device via the optical connector 43 and the optical fiber coupler 52.
  • Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown).
  • the excitation light L0 propagates into the photoelectric field enhancement device 1 via the optical connector 42 and the optical fiber coupler 51, and induces localized plasmons in the metal fine concavo-convex structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10.
  • the Raman scattered light Lr generated from the substance in the sample solution under the excitation by the photoelectric field is guided in the photoelectric field enhancement device 1 and partly reaches the optical fiber coupler 52, and another part is light.
  • the optical fiber coupler 52 is reached via the fiber coupler 51, and they are combined and detected by the photodetector 44 via the optical connector 43.
  • the surface-enhanced Raman detector 4 can detect only the Raman scattered light Lr generated in the vicinity of the metal fine concavo-convex structure portion 10 that is guided to the photodetector 44 side, but the surface-enhanced Raman detector 5 of the present embodiment. Then, a part of the light guided to the laser light source 41 side can also be detected via the optical fiber coupler 51, so that detection with higher accuracy is possible.
  • the photodetector 44 since the excitation light L0 propagates to the photodetector 44, the photodetector 44 has an optical element that absorbs or reflects the excitation light inside and / or an optical element that separates the Raman scattered light. It is preferable to provide.
  • the measuring apparatus of the present embodiment is a surface-enhanced Raman detector 6 including the above-described photoelectric field enhancing device 1.
  • FIG. 12 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 6 of the present embodiment.
  • the semiconductor laser light source 41 is connected to one end of the photoelectric field enhancing device 1 via an optical connector 42 and a WDM (wavelength division multiplexing) optical coupler 61, and the photodetector 44 is connected to the optical connector. 43, connected to both ends of the photoelectric field enhancement device 1 through an optical fiber coupler 64 and WDM optical couplers 61 and 62.
  • WDM wavelength division multiplexing
  • the WDM optical coupler 61 demultiplexes the pumping light wavelength and the Raman scattered light wavelength, the port for demultiplexing the pumping light wavelength is connected to the semiconductor laser light source 41, and the port for demultiplexing the Raman scattered light is an optical fiber coupler. 63. Another end of the WDM optical coupler 61 is connected to the photoelectric field enhancement device 1. Similarly to the WDM optical coupler 61, the WDM optical coupler 62 also demultiplexes the pumping light wavelength and the Raman scattered light wavelength, and the port for demultiplexing the pumping light wavelength is connected to the beam diffuser 64 to separate the Raman scattered light wavelength. The wave port is connected to the optical fiber coupler 63.
  • Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown).
  • the excitation light L0 propagates into the photoelectric field enhancement device 1 through the optical connector 42 and the WDM optical coupler 61, and induces localized plasmons in the metal fine uneven structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10.
  • the Raman scattered light Lr generated from the substance in the sample solution under the excitation by the photoelectric field is guided through the photoelectric field enhancing device 1 and partly reaches the optical fiber coupler 63 via the WDM optical coupler 61. Another part reaches the optical fiber coupler 63 via the WDM optical coupler 62.
  • the excitation light that has reached the WDM optical coupler 62 is incident on the beam diffuser 64 and terminated.
  • the Raman scattered light incident on the optical fiber coupler 63 from the WDM optical coupler 61 and the WDM optical coupler 62 is combined and detected by the photodetector 44 through the optical connector 43.
  • the photodetector 44 may include an optical element that absorbs or reflects excitation light or / and an optical element that separates Raman scattered light.
  • the surface-enhanced Raman detector 6 of this embodiment uses the WDM optical couplers 61 and 62 to detect Raman scattered light more efficiently than the surface-enhanced Raman detector 5 according to the fifth embodiment. Can do.
  • the measurement apparatus of the present embodiment is a surface-enhanced Raman detector 7 including the above-described photoelectric field enhancement device 2.
  • FIG. 13 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 7 of the present embodiment.
  • the semiconductor laser light source 41 is connected to the photoelectric field enhancement device 2 via the optical connector 42 and the optical fiber coupler 71, and the photodetector 44 is connected via the optical connector 43 and the optical fiber coupler 71. And connected to the photoelectric field enhancement device 2.
  • Excitation light L0 is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown).
  • the excitation light L0 propagates into the photoelectric field enhancement device 1 through the optical connector 42 and the optical fiber coupler 71, and induces localized plasmons in the metal fine concavo-convex structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10.
  • the Raman scattered light Lr generated from the substance in the sample solution by being excited by the photoelectric field is guided through the photoelectric field enhancing device 1 and reaches the optical connector 43 via the optical fiber coupler 71, and the photodetector 44. Is detected.
  • the photodetector 44 may include an optical element that absorbs or reflects excitation light or / and an optical element that separates Raman scattered light.
  • the optical fiber coupler 71 is a WDM optical coupler that demultiplexes the wavelength of the Raman scattered light toward the optical connector 43 on the photodetector 44 side, it is preferable because the Raman scattered light can be detected more efficiently.
  • the photoelectric field enhancement device 2 instead of the photoelectric field enhancement device 2, a configuration in which the devices 2A to 2C of the design modification example of the second photoelectric field enhancement device 2 are provided may be employed. If a mirror that reflects Raman scattered light is provided on the end face like the photoelectric field enhancing devices 2A to 2C, the amount of Raman scattered light incident on the photodetector 44 can be increased. If a multilayer film that reflects Raman scattered light and acts as a filter that transmits excitation light is provided, the amount of Raman scattered light incident on the photodetector 44 is increased and the excitation incident on the photodetector 44 is increased. The amount of light can be reduced, and detection with a higher S / N is possible.
  • the measuring device of the present invention can also be applied to a plasmon enhanced fluorescence detector.
  • enhanced fluorescence can be detected in the vicinity of the metal fine concavo-convex structure portion 10 by using the photoelectric field enhancement devices 1 and 2 described above.
  • Raman scattered light and fluorescence not only the measurement of Raman scattered light and fluorescence, but also the above-described enhancement of the photoelectric field not only in measuring devices such as Rayleigh scattered light, Mie scattered light, or second harmonic generated from a subject irradiated with excitation light.
  • an enhanced photoelectric field accompanying local plasmon resonance can be generated in the vicinity of the metal fine concavo-convex structure portion 10, and the enhanced light can be detected.
  • Example 1 A part of the coating of Corning's multimode quartz fiber HI1060 (cladding diameter 125 ⁇ m) was removed, and the exposed clad portion was heated and stretched at 1200 ° C. to form a tapered portion having a thin diameter portion with a cladding diameter of 60 ⁇ m. Evaporation was performed with the coated portion of the optical fiber masked, and a 20 nm Al film was formed on one side of the tapered portion. The Al thin film forming part was hydrothermally treated with hot water at 80 ° C. for 5 minutes to form a boehmite layer. A surface SEM photograph of the formed boehmite layer is shown in FIG. In FIG.
  • the portion observed in white is the convex surface of the fine concavo-convex structure. It was observed that the uneven structure was uniformly formed over the entire area.
  • An Au film having a thickness of 50 nm was formed by vapor deposition on the surface of the fine concavo-convex structure composed of the boehmite layer, and the photoelectric field enhancement device 1 could be produced.
  • An optical fiber (core refractive index 1.45, clad refractive index 1.43) having a core diameter of 230 ⁇ m / cladding diameter of 250 ⁇ m located in water (refractive index of 1.33) is provided with a taper portion having a minimum detail of 40 ⁇ m.
  • a simulation by the beam propagation method was performed for the most detailed case (core diameter 36.8 ⁇ m, clad diameter 40 ⁇ m) and the electric field strength at the clad boundary of the straight portion with the clad diameter 250 ⁇ m.
  • the wavelength of the incident laser light is 785 nm, and is condensed into a Gaussian distribution having a 1 / e width of 0.6 ⁇ m at the simulation start point and coupled to the optical fiber.
  • the straight part is guided over 40 mm from the simulation start point, the electric field strength at the taper part constriction point with a taper length of 10 mm and the smallest diameter of 40 ⁇ m, and the electric field strength when the straight part is guided over 50 mm from the simulation start point. Calculated. The results are shown in FIGS.
  • FIG. 15A shows the electric field strength (solid line) and the refractive index (dashed line) at the taper detail of 40 ⁇ m.
  • FIG. 15B is an enlarged view of the clad boundary portion of FIG.
  • FIG. 16A shows the electric field strength (solid line) and the refractive index (broken line) in the 250 ⁇ m straight optical fiber, and
  • FIG. 16B is an enlarged view of the cladding boundary part of FIG. .
  • the electric field strength is greatly attenuated at the cladding boundary, whereas in the taper detail of 40 ⁇ m as shown in FIG. 15B, at the cladding boundary.
  • the electric field strength was less attenuated, and an electric field stronger by about two orders of magnitude than the electric field strength outside the clad of the straight optical fiber was obtained.
  • a large electric field strength is obtained outside the tapered portion of the optical fiber, and therefore, the photoelectric field strength that induces localized plasmons in the fine metal structure also increases, which is much higher than when the tapered portion is not formed. It is clear that a high photoelectric field enhancement effect can be obtained.
  • Example 2 The Thorlabs semiconductor laser L850P010 is used as the LD light source 41, and the optical connector 42, the photodetector 44, and the photoelectric field enhancement for coupling the LD light source 41 and the photoelectric field enhancement device 1 using the Thorlabs fiber coupled lens pair C230260P-B.
  • An optical connector 43 for coupling the device 1 was configured.
  • a long wave path filter LP02-830RS-25 (Semrock) and a spectroscope C10027-02 (Hamamatsu Photonics) were combined to form a photodetector 44, which was coupled to the output of the optical connector 43.
  • the surface-enhanced Raman detector 4 could be configured using the device exemplified in Example 1 as the photoelectric field enhancing device 1.
  • the semiconductor laser light source 41 is exemplified as the excitation light source according to the present invention, but a solid laser light source, a dye laser light source, or the like may be used as appropriate.

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Abstract

[Problem] To provide an optical-electric-field enhancement device that can detect Raman-scattered light with higher sensitivity. [Solution] In an optical-electric-field enhancement device, localized plasmon is induced on the surface of a metal film by having a fine recessed and projected structure irradiated with light, said recessed and projected structure having the metal film formed thereon. The optical-electric-field enhancement device is configured of: an optical waveguide member (20), which is partly provided with a fine path section (13); a fine recessed and projected structure (18) provided on the surface of the fine path section (13); and a metal film (19) formed on the surface of the fine recessed and projected structure (18).

Description

光電場増強デバイスおよび光検出装置Photoelectric field enhancement device and photodetector
　本発明は、局在プラズモンを誘起しうる微細凹凸構造上に金属を備えた光電場増強デバイスおよびその光電場増強デバイスを備えた光検出装置に関するものである。 The present invention relates to a photoelectric field enhancement device provided with a metal on a fine concavo-convex structure capable of inducing localized plasmons, and a photodetection device provided with the photoelectric field enhancement device.
　金属表面における局在プラズモン共鳴現象による電場増強効果を利用したセンサデバイスやラマン分光用デバイス等の電場増強デバイスが知られている。ラマン分光法は、物質に単波長光を照射して得られる散乱光を分光してスペクトル（ラマンスペクトル）を得、照射光と異なる波長の光（ラマン散乱光）を検出する方法であり、物質の同定等に利用されている。 An electric field enhancement device such as a sensor device or a Raman spectroscopic device using an electric field enhancement effect by a localized plasmon resonance phenomenon on a metal surface is known. Raman spectroscopy is a method of obtaining a spectrum (Raman spectrum) by dispersing scattered light obtained by irradiating a substance with single wavelength light, and detecting light (Raman scattered light) having a wavelength different from that of the irradiated light. It is used for identification etc.
　ラマン散乱光は非常に弱い光であるため一般には検出が難しいが、金属表面に物質を吸着させて光を照射すると、ラマン散乱光の強度が約１０４～１０６倍になることが報告されている。特に、物質を吸着させる面にナノオーダーの金属微粒子が分布配置された構造では、ラマン散乱光が大幅に増強されることが知られている（例えば、非特許文献１参照）。ラマン散乱光の増強は、局在プラズモン共鳴に起因すると言われている。すなわち、金属微粒子内の自由電子が光の電場に共鳴して振動することにより金属微粒子周辺に強い電場が生じ、この電場の影響によりラマン散乱光が増強すると考えられている。 Although it is difficult to detect Raman scattered light in general because it is very weak light, it has been reported that the intensity of Raman scattered light increases about 104 to 106 times when a substance is adsorbed on a metal surface and irradiated with light. . In particular, it is known that Raman scattered light is greatly enhanced in a structure in which nano-order metal fine particles are distributed and arranged on a surface on which a substance is adsorbed (see, for example, Non-Patent Document 1). The enhancement of Raman scattered light is said to be due to localized plasmon resonance. That is, it is considered that a free electric field in the metal fine particle oscillates in resonance with the electric field of light to generate a strong electric field around the metal fine particle, and the Raman scattered light is enhanced by the influence of this electric field.
　ラマン散乱光の増強を実現するデバイスの作製法として、特許文献１には、基体の一表面に分布形成された複数の微細孔内に、局在プラズモン共鳴を誘起し得る大きさの金属微粒子が分布配置された微細構造およびメッキ処理を利用して該微細構造を作製する方法が開示されている。 As a method for manufacturing a device that realizes enhancement of Raman scattered light, Patent Document 1 discloses metal fine particles having a size capable of inducing localized plasmon resonance in a plurality of micropores distributed and formed on one surface of a substrate. A method for producing a microstructure using a distributed microstructure and a plating process is disclosed.
　特許文献１の方法で作製した微細構造体は、高密度に配列された微細孔の中に局在プラズモン共鳴を誘起し得る大きさの複数の金属微粒子が配置され、その金属微粒子の頭部の径が微細孔の孔径よりも大きい構造をしている。この構造によれば、微細構造体表面に物質を吸着させて光を照射した際に、高い増強率でラマン散乱光が増強されるので、精度良くラマン散乱光を検出することができる。 In the fine structure manufactured by the method of Patent Document 1, a plurality of metal fine particles having a size capable of inducing localized plasmon resonance are arranged in fine holes arranged at high density, and the head of the metal fine particles is arranged. The diameter is larger than the diameter of the fine holes. According to this structure, when the substance is adsorbed on the surface of the fine structure and irradiated with light, the Raman scattered light is enhanced at a high enhancement rate, so that the Raman scattered light can be detected with high accuracy.
　特許文献２には、光ファイバ探針の先端部に金属層を備えた増強ラマン信号測定装置および光ファイバ探針の探測端部の表面に金属層を形成する方法が開示されている。 Patent Document 2 discloses an enhanced Raman signal measuring device having a metal layer at the tip of an optical fiber probe and a method of forming a metal layer on the surface of the probe end of the optical fiber probe.
　一方、特許文献３には、プラズモンを利用した光増幅現象を利用する光学素子として、光ファイバの一部に周期的粗面金属部を備えてなる光増幅素子が開示されている。 On the other hand, Patent Document 3 discloses an optical amplifying element in which a periodic rough surface metal part is provided in a part of an optical fiber as an optical element that utilizes an optical amplification phenomenon using plasmons.
特開２００８－３０４３７０号公報JP 2008-304370 A 特開２００８－３２７１６号公報JP 2008-32716 A 特開２００５－３０９２９５号公報JP 2005-309295 A
　しかしながら、特許文献１の方法では陽極酸化およびメッキ処理を利用するため、微細構造体の基材は導電性の金属に限られる。このような励起光波長を透過しない基材で作製したデバイスにより増強されたラマン散乱光を観測するためには、デバイスの微細構造形成面から励起光を入射する必要がある。従って、ラマン散乱光が増強される微細構造部に励起光が到達するまでに、測定試料や媒質の吸収により励起光強度やラマン散乱光強度が減少し、測定信号のＳ／Ｎ比の低下を招く。 However, since the method of Patent Document 1 uses anodization and plating, the base material of the microstructure is limited to conductive metal. In order to observe Raman scattered light enhanced by a device made of such a substrate that does not transmit the excitation light wavelength, it is necessary to make the excitation light incident from the fine structure forming surface of the device. Therefore, before the excitation light reaches the fine structure where the Raman scattered light is enhanced, the excitation light intensity and the Raman scattered light intensity are reduced by absorption of the measurement sample and the medium, and the S / N ratio of the measurement signal is reduced. Invite.
　また、ラマン散乱光を検出するためには、光電場増強デバイスに励起光を入射し、散乱光を検出する光学系が別途必要となり、測定装置の大型化を招くデメリットがある。 Also, in order to detect Raman scattered light, an optical system for detecting the scattered light by making excitation light incident on the photoelectric field enhancement device is separately required, which has a demerit that increases the size of the measuring apparatus.
　特許文献２に記載の光ファイバを備えた増強ラマン信号測定装置においては、光ファイバの先端に設けられている金属膜は凹凸構造を伴わないため、ラマン信号の増幅度が十分とは言えない。 In the enhanced Raman signal measuring apparatus provided with the optical fiber described in Patent Document 2, the metal film provided at the tip of the optical fiber does not have an uneven structure, and therefore the amplification of the Raman signal cannot be said to be sufficient.
　さらに特許文献３に記載のデバイスは、デバイス内部を伝播する光を増幅するものであるため、デバイス外部での電場増強については検討されていない。 Furthermore, since the device described in Patent Document 3 amplifies light propagating inside the device, electric field enhancement outside the device has not been studied.
　本発明は、上記事情に鑑みてなされたものであって、ラマン散乱光を効果的に増強するとともに、その増強されたラマン散乱光をより高い感度で検出することを可能とする、光電場増強デバイスを提供することを目的とする。また、その光電場増強デバイスを備えた増強光を検出するための測定装置を提供することを目的とする。 The present invention has been made in view of the above circumstances, and effectively enhances the Raman scattered light and makes it possible to detect the enhanced Raman scattered light with higher sensitivity. The purpose is to provide a device. It is another object of the present invention to provide a measuring apparatus for detecting enhanced light including the photoelectric field enhancing device.
　本発明の光電場増強デバイスは、光導波路の一部に細路部を備えた光導波路部材と、
　前記細路部の表面に備えられた微細凹凸構造と、
　該微細凹凸構造の表面に形成された金属膜とを備え、
　該金属膜が形成された前記微細凹凸構造に光の照射を受け、プラズモンによる電場増強効果を生じるものであることを特徴とする。 The photoelectric field enhancement device of the present invention, an optical waveguide member provided with a narrow portion in a part of the optical waveguide,
A fine uneven structure provided on the surface of the narrow path portion;
A metal film formed on the surface of the fine uneven structure,
The fine concavo-convex structure on which the metal film is formed is irradiated with light to produce an electric field enhancement effect by plasmons.
　ここで、前記金属膜は微細凹凸構造表面に形成されており、この金属膜表面は透明な微細凹凸構造に応じた微細凹凸構造を有する。金属膜表面の微細凹凸構造が、光の照射を受けて局在プラズモンを誘起しうるものであればよい。なお、ここで述べる微細凹凸構造とは、局在プラズモンを生じうる凹凸構造をなす凸部および凹部の平均的な大きさと平均的なピッチが照射される光の波長よりも小さい凹凸構造である。 Here, the metal film is formed on the surface of the fine uneven structure, and the surface of the metal film has a fine uneven structure corresponding to the transparent fine uneven structure. The fine concavo-convex structure on the surface of the metal film only needs to be capable of inducing localized plasmon when irradiated with light. Note that the fine concavo-convex structure described here is a concavo-convex structure in which the average size and the average pitch of the concavo-convex structure and the concavo-convex structure that can generate localized plasmons are smaller than the wavelength of light irradiated.
　特には、凹凸の平均的なピッチおよび凸部の頂点と凹部の底部間の距離（深さ）が光の波長の半分以下であることが好ましい。例えば１０００ｎｍ以下の可視領域の光を照射する場合には、凹凸の平均的なピッチおよび凸部の頂点と凹部の底部間の距離が５００ｎｍ以下であることが望ましい。さらに、高い電場増強度を得るためには凹凸の平均的なピッチおよび凸部の頂点と凹部の底部間の距離（深さ）が２００ｎｍ以下であることが好ましい。 In particular, it is preferable that the average pitch of the projections and depressions and the distance (depth) between the apex of the projection and the bottom of the recess are half or less of the wavelength of light. For example, when irradiating light in the visible region of 1000 nm or less, it is desirable that the average pitch of the unevenness and the distance between the top of the convex part and the bottom of the concave part be 500 nm or less. Furthermore, in order to obtain a high electric field enhancement strength, it is preferable that the average pitch of the unevenness and the distance (depth) between the top of the convex part and the bottom part of the concave part be 200 nm or less.
　凹凸の平均的なピッチは、ＳＥＭ（走査型電子顕微鏡）で微細凹凸構造の表面画像を撮影し、画像処理をして２値化し、統計的処理によって求めるものとする。 The average pitch of the unevenness is obtained by taking a surface image of the fine unevenness structure with an SEM (scanning electron microscope), binarizing the image, and calculating by statistical processing.
　凹凸の平均的な深さは、ＡＦＭ（原子間力顕微鏡）により表面形状を測定して統計的処理によって求めるものとする。 The average depth of the unevenness is obtained by measuring the surface shape with an AFM (Atomic Force Microscope) and performing statistical processing.
　前記細路部の最小サイズは、励起光波長の５０倍以下であることが望ましい。 It is desirable that the minimum size of the narrow path portion is 50 times or less of the excitation light wavelength.
　前記細路部は、前記光導波路が徐々に細くなるテーパ状とすることができる。 The narrow path portion may have a tapered shape in which the optical waveguide is gradually narrowed.
　前記光導波路部材は、前記細路部を該光導波路部材の中間部に備えてなるくびれ構造を有するように構成することができる。 The optical waveguide member can be configured to have a constriction structure in which the narrow path portion is provided in an intermediate portion of the optical waveguide member.
　また、前記光導波路部材は、前記細路部を該光導波路部材の一端に備えてなる先細構造を有するように構成してもよい。 The optical waveguide member may have a tapered structure in which the narrow path portion is provided at one end of the optical waveguide member.
　本発明の光電場増強デバイスは、前記光導波路部材が先細構造である場合、前記光導波路部材の前記細路部の一端に結合された反射光学素子を備えていてもよい。 The photoelectric field enhancement device of the present invention may include a reflective optical element coupled to one end of the narrow path portion of the optical waveguide member when the optical waveguide member has a tapered structure.
　本発明の光電場増強デバイスは、前記光導波路部材が先細構造である場合、前記光導波路部材の前記細路部の一端に結合された、前記照射される光の反射率または吸収率にくらべ、該光と異なる波長域の光に対する反射率または吸収率が高い光学素子を備えていてもよい。 The photoelectric field enhancement device of the present invention, when the optical waveguide member has a tapered structure, is coupled to one end of the narrow path portion of the optical waveguide member, compared to the reflectance or absorption rate of the irradiated light, You may provide the optical element with a high reflectance or absorptivity with respect to the light of the wavelength range different from this light.
　上記において「結合」とは光学的な結合を意味するものであり、前記反射光学素子あるいは前記光学素子は、前記細路部の一端に直接、あるいはさらなる光導波路部材を介して形成されていてもよいし、細路部の一端とは離間して配置されるものであってもよい。 In the above, “coupling” means optical coupling, and the reflective optical element or the optical element may be formed directly on one end of the narrow path portion or via a further optical waveguide member. Alternatively, it may be arranged so as to be separated from one end of the narrow path portion.
　前記光導波路部材としては、光ファイバが好適である。 An optical fiber is suitable as the optical waveguide member.
　前記微細凹凸構造は、アルミニウム酸化物またはアルミニウム水酸化物またはそれらの水和物からなるベーマイト層からなるものとすることができる。 The fine concavo-convex structure can be made of a boehmite layer made of aluminum oxide, aluminum hydroxide, or a hydrate thereof.
　前記金属膜は、前記光の照射を受けて局在プラズモンを生じる金属からなるものであればよいが、Ａｕ、Ａｇ、Ｃｕ、Ａｌ、Ｐｔ、およびこれらを主成分とする合金からなる群より選択される少なくとも１種の金属からなるものであることが好ましい。特には、Ａｕ、ＡｇあるいはＰｔが好ましい。 The metal film may be made of a metal that generates localized plasmons when irradiated with the light, but is selected from the group consisting of Au, Ag, Cu, Al, Pt, and alloys containing these as the main components. It is preferably made of at least one kind of metal. In particular, Au, Ag, or Pt is preferable.
　本発明の測定装置は、本発明の光電場増強デバイスと、
　該光電場増強デバイスの前記光導波路部材に導光される励起光を出力する励起光源と、　前記光電場増強デバイスに結合された光検出部とを備えたことを特徴とするものである。 The measuring apparatus of the present invention comprises the photoelectric field enhancing device of the present invention,
An excitation light source that outputs excitation light guided to the optical waveguide member of the photoelectric field enhancement device, and a light detection unit coupled to the photoelectric field enhancement device are provided.
　本発明の光電場増強デバイスは、光導波路の一部に細路部を備えた光導波路部材と、細路部の表面に備えられた微細凹凸構造と、微細凹凸構造の表面に形成された金属膜とを備え、金属膜が微細凹凸構造に形成されてなる金属微細凹凸構造部を有しているので、この金属微細凹凸構造部に光が照射されることにより、金属微細凹凸構造部表面に局在プラズモンを効果的に誘起させることができ、この局在プラズモンによる光電場増強効果を生じさせることができる。 The photoelectric field enhancement device of the present invention includes an optical waveguide member having a narrow path part in an optical waveguide, a fine uneven structure provided on the surface of the narrow path part, and a metal formed on the surface of the fine uneven structure. And a metal fine concavo-convex structure portion formed by forming a metal film in a fine concavo-convex structure. By irradiating light to the metal fine concavo-convex structure portion, the surface of the metal fine concavo-convex structure portion Localized plasmons can be induced effectively, and the photoelectric field enhancement effect by the localized plasmons can be generated.
　また、本発明の光電場増強デバイスは、光導波路部材の光導波路の一部に設けられた細路部での光電場漏れを利用して、微細凹凸構造表面に金属膜が形成されてなる金属微細凹凸構造部に、光導波路を伝搬してきた光を照射させることができ、励起光を金属微細凹凸構造部の外部から照射する必要がない。したがって、本発明の光電場増強デバイスを用いた検出光の測定装置においては、測定試料や媒質の吸収や散乱に起因する励起光強度やラマン散乱光強度の減少を抑制することができるので、Ｓ／Ｎよく検出光を検出することが可能となる。また、本発明のデバイスを用いれば、光導波路部材中を励起光や検出光を伝搬させることができるので、励起、検出の光学系を非常に簡単な構成とすることが可能となる。 In addition, the photoelectric field enhancement device of the present invention is a metal in which a metal film is formed on the surface of a fine concavo-convex structure by utilizing photoelectric field leakage at a narrow path portion provided in a part of an optical waveguide of an optical waveguide member. The fine concavo-convex structure portion can be irradiated with light propagating through the optical waveguide, and there is no need to irradiate excitation light from the outside of the metal fine concavo-convex structure portion. Therefore, in the detection light measurement apparatus using the photoelectric field enhancement device of the present invention, it is possible to suppress a decrease in excitation light intensity or Raman scattered light intensity due to absorption or scattering of the measurement sample or medium. / N It becomes possible to detect the detection light with good frequency. Further, if the device of the present invention is used, excitation light and detection light can be propagated through the optical waveguide member, so that the excitation and detection optical systems can have a very simple configuration.
　また、微細凹凸構造を、ベーマイト層により構成する場合には、非常に簡単なプロセスで本発明の光電場増強デバイスを作製することができ、短時間、低コスト化が可能となる。 Further, when the fine concavo-convex structure is constituted by a boehmite layer, the photoelectric field enhancement device of the present invention can be manufactured by a very simple process, and the cost can be reduced in a short time.
第１の実施形態に係る光電場増強デバイスの一部を示す断面図Sectional drawing which shows a part of photoelectric field enhancement device which concerns on 1st Embodiment テーパ部最小サイズとビーム広がり角との関係を示すグラフGraph showing the relationship between the minimum taper size and beam divergence angle 第１の実施形態に係る光電場増強デバイスの作製工程におけるテーパ形成部を示す断面図Sectional drawing which shows the taper formation part in the manufacturing process of the photoelectric field enhancement device which concerns on 1st Embodiment. 第１の実施形態に係る光電場増強デバイスの作製工程におけるＡｌ膜形成部を示す断面図Sectional drawing which shows Al film formation part in the manufacturing process of the photoelectric field enhancement device which concerns on 1st Embodiment 第１の実施形態に係る光電場増強デバイスの作製工程におけるベーマイト層形成部を示す断面図Sectional drawing which shows the boehmite layer formation part in the preparation process of the photoelectric field enhancement device which concerns on 1st Embodiment. テーパ形成工程の他の例を示す断面図Sectional drawing which shows the other example of a taper formation process 第２の実施形態に係る光電場増強デバイスの一部を示す断面図Sectional drawing which shows a part of photoelectric field enhancement device which concerns on 2nd Embodiment 第２の実施形態に係る光電場増強デバイスの設計変更例２Ａを示す断面図Sectional drawing which shows 2A of design changes of the photoelectric field enhancement device which concerns on 2nd Embodiment 第２の実施形態に係る光電場増強デバイスの設計変更例２Ｂを示す断面図Sectional drawing which shows the design modification example 2B of the photoelectric field enhancement device which concerns on 2nd Embodiment 第２の実施形態に係る光電場増強デバイスの設計変更例２Ｃを示す断面図Sectional drawing which shows 2C of design changes of the photoelectric field enhancement device which concerns on 2nd Embodiment 第３の実施形態に係る光電場増強デバイスの斜視図The perspective view of the photoelectric field enhancement device concerning a 3rd embodiment 第４の実施形態に係る表面増強ラマン検出器の概略構成を表す模式図The schematic diagram showing schematic structure of the surface enhancement Raman detector which concerns on 4th Embodiment 第５の実施形態に係る表面増強ラマン検出器の概略構成を表す模式図The schematic diagram showing schematic structure of the surface enhancement Raman detector which concerns on 5th Embodiment 第６の実施形態に係る表面増強ラマン検出器の概略構成を表す模式図The schematic diagram showing schematic structure of the surface enhancement Raman detector which concerns on 6th Embodiment 第７の実施形態に係る表面増強ラマン検出器の概略構成を表す模式図The schematic diagram showing schematic structure of the surface enhancement Raman detector which concerns on 7th Embodiment 実施例で作製した光電場増強デバイスの微細凹凸構造（ベーマイト層）の表面のＳＥＭ画像SEM image of the surface of the fine concavo-convex structure (boehmite layer) of the photoelectric field enhancement device produced in the example テーパ状光ファイバのテーパ部の径方向における電場強度を示すグラフGraph showing the electric field strength in the radial direction of the tapered part of a tapered optical fiber ストレート光ファイバの径方向における電場強度を示すグラフGraph showing the electric field strength in the radial direction of straight optical fiber
　以下、図面を参照して本発明の光電場増強デバイスの実施形態について説明する。なお、視認しやすくするため、図面中の各構成要素の縮尺等は実際のものとは適宜異ならせてある。 Hereinafter, embodiments of the photoelectric field enhancement device of the present invention will be described with reference to the drawings. In addition, for easy visual recognition, the scale of each component in the drawings is appropriately changed from the actual one.
（第１の実施形態）
　図１は、本発明の第１の実施形態に係る光電場増強デバイス１の一部を示す断面図である。 (First embodiment)
FIG. 1 is a cross-sectional view showing a part of a photoelectric field enhancement device 1 according to a first embodiment of the present invention.
　図１に示すように、本実施形態の光電場増強デバイス１は、コア部（光導波路）１１およびクラッド部１２からなる光導波部材である光ファイバ２０の一部に徐々にコア径が細くなるテーパ部１３を光導波路の細路部として備え、このテーパ部１３の表面にベーマイト層からなる微細凹凸構造１８を備え、さら微細凹凸構造１８の表面に金属膜１９を備えている。 As shown in FIG. 1, the photoelectric field enhancement device 1 of the present embodiment has a core diameter that gradually decreases in a part of an optical fiber 20 that is an optical waveguide member including a core part (optical waveguide) 11 and a cladding part 12. A taper portion 13 is provided as a narrow path portion of the optical waveguide, a fine uneven structure 18 made of a boehmite layer is provided on the surface of the taper portion 13, and a metal film 19 is provided on the surface of the fine uneven structure 18.
　本デバイス１は、金属膜１９が微細凹凸構造１８に沿って形成されて構成される金属の微細凹凸構造部１０に光（以下において、「励起光」という。）が照射されることにより、局在プラズモン共鳴を誘起するものであり、この局在プラズモン共鳴により金属膜１９の表面に増強された光電場を生じさせるものである。本デバイス１は、光ファイバ２０の中間部にテーパ部１３が形成されてなるくびれ構造を有する。 The device 1 is formed by irradiating light (hereinafter referred to as “excitation light”) onto a metal fine concavo-convex structure portion 10 formed by forming a metal film 19 along the fine concavo-convex structure 18. It induces plasmon resonance, and an enhanced photoelectric field is generated on the surface of the metal film 19 by this localized plasmon resonance. The device 1 has a constricted structure in which a tapered portion 13 is formed in an intermediate portion of the optical fiber 20.
　微細凹凸構造１８は、テーパ部１３の周方向全域に備えられていてもよいし、周方向の一部にのみ備えられていてもよい。 The fine concavo-convex structure 18 may be provided in the entire circumferential direction of the tapered portion 13 or may be provided only in a part of the circumferential direction.
　微細凹凸構造１８は、この微細凹凸構造１８の表面に金属膜１９が形成されて構成される金属微細凹凸構造部１０の表面における凹凸の凸部の平均的な大きさおよび平均ピッチが励起光の波長より短いものとなる程度の微細な凹凸構造であるが、金属微細凹凸構造部１０の表面に局在プラズモンを生じさせうるものであればよい。特には、微細凹凸構造１８は、凸部頂点から隣接する凹部の底部までの平均深さが２００ｎｍ以下、凹部を隔てた最隣接凸部の頂点同士の平均ピッチが２００ｎｍ以下であることが望ましい。 In the fine concavo-convex structure 18, the average size and the average pitch of the concavo-convex convex portions on the surface of the metal fine concavo-convex structure portion 10 configured by forming the metal film 19 on the surface of the fine concavo-convex structure 18 is the excitation light. Although the concavo-convex structure is fine enough to be shorter than the wavelength, any plasmon that can cause localized plasmons on the surface of the metal fine concavo-convex structure portion 10 may be used. In particular, it is desirable that the fine concavo-convex structure 18 has an average depth of 200 nm or less from the top of the convex portion to the bottom of the adjacent concave portion, and an average pitch between the vertices of the most adjacent convex portions separating the concave portions is 200 nm or less.
　本実施形態において、微細凹凸構造１８は、ベーマイト層により構成されるものであるが、微細凹凸構造は光ファイバのテーパ部表面を研磨して設けられたものであってもよい。 In this embodiment, the fine concavo-convex structure 18 is constituted by a boehmite layer, but the fine concavo-convex structure may be provided by polishing the surface of the tapered portion of the optical fiber.
　なお、好ましいピッチおよび深さの凹凸を容易に形成可能であることから微細凹凸構造１８はベーマイトにより構成することが好ましい。 In addition, since the unevenness | corrugation of a preferable pitch and depth can be formed easily, it is preferable to comprise the fine unevenness | corrugation structure 18 with boehmite.
　金属膜１９は、励起光の照射を受けて局在プラズモンを生じうる金属からなるものであればよいが、例えば、Ａｕ、Ａｇ、Ｃｕ、Ａｌ、Ｐｔ、およびこれらを主成分とする合金からなる群より選択される少なくとも１種の金属からなるものである。特には、Ａｕ、ＡｇあるいはＰｔが好ましい。 The metal film 19 may be made of a metal that can generate localized plasmons when irradiated with excitation light. For example, the metal film 19 is made of Au, Ag, Cu, Al, Pt, or an alloy containing these as a main component. It consists of at least one metal selected from the group. In particular, Au, Ag, or Pt is preferable.
　金属膜１９の膜厚は、微細凹凸構造層１８の表面に形成されたときに、金属微細凹凸構造部１０として励起光の照射を受けて局在プラズモンを生じうる凹凸形状を維持することができる程度の厚みであれば特に制限はないが、１０～１０００ｎｍであることが好ましい。特に、５０～５００ｎｍ程度が好ましい。 When the metal film 19 is formed on the surface of the fine concavo-convex structure layer 18, the metal fine concavo-convex structure portion 10 can maintain a concavo-convex shape capable of generating localized plasmons upon irradiation with excitation light. The thickness is not particularly limited as long as the thickness is about 10 to 1000 nm. In particular, about 50 to 500 nm is preferable.
　テーパ部１３の最小サイズ（最小径）Ｄminは、励起光波長の５０倍以下であることが好ましい。 The minimum size (minimum diameter) Dmin of the tapered portion 13 is preferably 50 times or less of the excitation light wavelength.
　本実施形態においては、光ファイバにその径が徐々に小さくなるテーパ部１３を備えるものとしたが、光導波路に細路部が形成されていればよく、必ずしもテーパ状でなくてもよい。 In the present embodiment, the optical fiber is provided with the tapered portion 13 whose diameter is gradually reduced. However, it is only necessary that the narrow path portion is formed in the optical waveguide, and the optical fiber is not necessarily tapered.
　細路部の好適な最小サイズは以下のようにして求めた。波長７８５ｎｍのレーザ光をＮＡ０．２２、コア径／クラッド径が２３０ｎｍ／２５０ｎｍの光ファイバに、異なる最小径を有するテーパ部を形成してなるテーパファイバを作製し、各テーパファイバに導光させたときのビーム広がり全角とテーパ部最小径におけるコア径との関係について測定した。図２はその測定結果を示すものである。 The preferred minimum size of the narrow path was determined as follows. Tapered fibers formed by forming tapered portions having different minimum diameters into an optical fiber having a wavelength of 785 nm and an optical fiber having an NA of 0.22 and a core diameter / cladding diameter of 230 nm / 250 nm were guided to the respective tapered fibers. The relationship between the full beam divergence and the core diameter at the taper minimum diameter was measured. FIG. 2 shows the measurement results.
　図２に示す結果から、コア径が３７μｍ程度（励起光波長の約５０倍）から導波光が光ファイバから漏れ出し、エタンデュ保存則（ＮＡ×コア径が一定）を満たさなくなることがわかる。すなわち、本発明の光電場増強デバイスにおいて、細路部の最小径を励起光波長の５０倍以下とすれば、細路部において励起光が金属微細凹凸構造部側に漏れ出し、金属微細凹凸構造部に励起光を効果的に照射させることができると考えられる。 2. From the results shown in FIG. 2, it can be seen that the guided light leaks out of the optical fiber when the core diameter is about 37 μm (about 50 times the pumping light wavelength) and does not satisfy the Etendue conservation law (NA × core diameter is constant). That is, in the photoelectric field enhancement device of the present invention, if the minimum diameter of the narrow path portion is 50 times or less of the excitation light wavelength, the excitation light leaks to the fine metal uneven structure side in the narrow path portion, and the fine metal uneven structure It is considered that the excitation light can be effectively irradiated to the part.
　次に、本実施形態の光電場増強デバイス１の製造方法について図３Ａ～図３Ｃを参照して説明する。図３Ａ～図３Ｃは光電場増強デバイス１の製造工程を示す断面図である。
　コア部１１およびクラッド部１２からなる光ファイバ２０として、例えば、コア直径１０５μｍ、クラッド直径１２５μｍのマルチモード石英ファイバを用意し、その被覆（図示せず）を剥がしたクラッド露出部分を加熱、延伸し、図３Ａに示すようなテーパ部１３を形成する。このとき、加熱、延伸により、テーパ部１３の最少径部分Ｄminのクラッド直径が３０μｍとなるようにする。 Next, a method for manufacturing the photoelectric field enhancement device 1 of the present embodiment will be described with reference to FIGS. 3A to 3C. 3A to 3C are cross-sectional views showing the manufacturing process of the photoelectric field enhancing device 1. FIG.
For example, a multimode quartz fiber having a core diameter of 105 μm and a cladding diameter of 125 μm is prepared as the optical fiber 20 including the core portion 11 and the cladding portion 12, and the clad exposed portion from which the coating (not shown) is peeled is heated and stretched. A tapered portion 13 as shown in FIG. 3A is formed. At this time, the cladding diameter of the minimum diameter portion Dmin of the tapered portion 13 is set to 30 μm by heating and stretching.
　なお、コア径とクラッド径はおよび延伸後のクラッド直径は、本実施形態と異なる値の組み合わせとしても良い。また、石英ファイバではなくガラスファイバやプラスチックファイバを使用してもよい。 It should be noted that the core diameter and the clad diameter and the clad diameter after stretching may be a combination of values different from those of the present embodiment. Further, glass fiber or plastic fiber may be used instead of quartz fiber.
　次に、非テーパ部１６をマスクしてＡｌ蒸着を行う。これにより、図３Ｂに示すように、テーパ部１３にのみ２０ｎｍのＡｌ膜１７を形成する。Ａｌ膜１７はテーパ部１３の全周にわたって形成してもよいし、周方向の一部のみに形成してもよい。
　なお、Ａｌ膜１７は金属蒸着のみならず、ＰＶＤ法あるいはＣＶＤ法等で形成してもよい。 Next, Al deposition is performed with the non-tapered portion 16 masked. As a result, as shown in FIG. 3B, an Al film 17 having a thickness of 20 nm is formed only on the tapered portion 13. The Al film 17 may be formed over the entire circumference of the taper portion 13 or may be formed only in a part in the circumferential direction.
The Al film 17 may be formed not only by metal vapor deposition but also by PVD method or CVD method.
　次に、Ａｌ膜１７が形成されたテーパ部１３を８０℃の熱水に浸漬させて水熱処理（ベーマイト処理）を施す。これにより、図３Ｃに示すようにＡｌ膜１７は微細凹凸構造１８を形成するベーマイト層となる。微細凹凸構造の他の作製法として、ゾルゲル法により形成したアルミニウム酸化物膜を水熱処理することでベーマイト層を形成してもよい。 Next, the taper portion 13 on which the Al film 17 is formed is immersed in hot water at 80 ° C. and subjected to hydrothermal treatment (boehmite treatment). Thereby, as shown in FIG. 3C, the Al film 17 becomes a boehmite layer that forms the fine relief structure 18. As another method for manufacturing the fine uneven structure, a boehmite layer may be formed by hydrothermally treating an aluminum oxide film formed by a sol-gel method.
　その後、ベーマイト層１８上に、蒸着により、金属膜１９として例えば５０ｎｍ厚みのＡｕ膜を形成することにより、図１に示す本実施形態の光電場増強デバイス１を作製することができる。 Then, by forming an Au film having a thickness of, for example, 50 nm as the metal film 19 on the boehmite layer 18 by vapor deposition, the photoelectric field enhancing device 1 of the present embodiment shown in FIG. 1 can be manufactured.
　なお、テーパ部１３の形成方法は、加熱、延伸に限るものではない。図４に示すように、光ファイバ２０の一部を、ピンセット先端１４間にその表面張力により保持させたＨＦ溶液１５中に位置させ、ＨＦ溶液１５による化学エッチングによりテーパ部１３を形成してもよい。
　また、光ファイバ作製における線引工程時の線引き速度調整により、光ファイバの一部にテーパ部１３を予め作り込むようにしてもよい。 The method for forming the tapered portion 13 is not limited to heating and stretching. As shown in FIG. 4, even if a part of the optical fiber 20 is positioned in the HF solution 15 held between the tweezer tips 14 by the surface tension, and the tapered portion 13 is formed by chemical etching with the HF solution 15. Good.
Further, the tapered portion 13 may be formed in advance in a part of the optical fiber by adjusting the drawing speed during the drawing process in the production of the optical fiber.
（第２の実施形態）
　本発明の第２の実施形態に係る光電場増強デバイス２について説明する。
　図５は、本実施形態の光電場増強デバイス２の一部を示す断面図である。なお、光電場増強デバイス１と同一構成要素には同一符号を付し、その詳細な説明を省略する（以下の実施形態において同様とする。）。 (Second Embodiment)
A photoelectric field enhancement device 2 according to a second embodiment of the present invention will be described.
FIG. 5 is a cross-sectional view showing a part of the photoelectric field enhancement device 2 of the present embodiment. In addition, the same code | symbol is attached | subjected to the same component as the photoelectric field enhancement device 1, and the detailed description is abbreviate | omitted (it is the same in the following embodiment).
　光電場増強デバイス２は、光ファイバ２０の一端部にテーパ部１３を備えた先細り構造を有するものである点で第１の実施形態の光電場増強デバイス１と異なる。 The photoelectric field enhancement device 2 is different from the photoelectric field enhancement device 1 of the first embodiment in that it has a tapered structure with a tapered portion 13 at one end of the optical fiber 20.
　本実施形態の光電場増強デバイス２は、光電場増強デバイス１と同様の作製方法で作製し、光電場増強デバイス１の金属微細凹凸構造部１０の最細部（最小径の部分）で切断することにより作製することができる。なお、切断するのはデバイス１における最細部に限らず、任意の部分で切断してもよい。ただし、デバイス２における最細部が励起光波長の５０倍以下であることが好ましい。 The photoelectric field enhancement device 2 of the present embodiment is produced by the same production method as the photoelectric field enhancement device 1 and is cut at the finest detail (the smallest diameter portion) of the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1. Can be produced. The cutting is not limited to the finest details in the device 1, but may be cut at an arbitrary portion. However, the finest details in the device 2 are preferably 50 times or less of the excitation light wavelength.
（第２の実施形態の設計変更例）
　図６～８は、第２の実施形態の光電場増強デバイス２の設計変更例のデバイス２Ａ～２Ｃの一部を示す断面図である。
　光電場増強デバイス２Ａ～２Ｃは、光電場増強デバイス２のテーパ部先端２ａが、少なくともラマン散乱光Ｌｒを反射する光学素子に接続されてなる。 (Design change example of the second embodiment)
FIGS. 6 to 8 are cross-sectional views showing a part of devices 2A to 2C of a design change example of the photoelectric field enhancement device 2 of the second embodiment.
The photoelectric field enhancing devices 2A to 2C are formed by connecting the tip end 2a of the photoelectric field enhancing device 2 to an optical element that reflects at least the Raman scattered light Lr.
　図６に示す光電場増強デバイス２Ａは、先端２ａに、金属膜あるは多層膜からなる反射光学素子２２が形成されており、先端２ａから射出される光を光ファイバ２０側に反射するよう構成されている。 The photoelectric field enhancement device 2A shown in FIG. 6 has a reflection optical element 22 made of a metal film or a multilayer film formed at the tip 2a, and reflects light emitted from the tip 2a toward the optical fiber 20 side. Has been.
　図７に示す光電場増強デバイス２Ｂは、光電場増強デバイス２のテーパ部先端２ａに、光ファイバ２０とは異なる光導波路基板２３の一端が接続され、光導波路基板２３の他端に反射光学素子２４を備えてなる。 In the photoelectric field enhancement device 2B shown in FIG. 7, one end of an optical waveguide substrate 23 different from the optical fiber 20 is connected to the tip 2a of the tapered portion of the photoelectric field enhancement device 2, and a reflection optical element is connected to the other end of the optical waveguide substrate 23. 24.
　図８に示す光電場増強デバイス２Ｃは、光電場増強デバイス２のテーパ部先端２ａと所定距離の位置に備えられたレンズ２５とその後方に備えられた反射光学素子２６とを備えている。レンズ２５は、テーパ部先端２ａから射出される光をコリメートするとともに、反射光学素子２６で反射した光をテーパ部先端２ａに集光させるよう配置構成されている。 The photoelectric field enhancement device 2C shown in FIG. 8 includes a tapered portion tip 2a of the photoelectric field enhancement device 2, a lens 25 provided at a predetermined distance, and a reflective optical element 26 provided behind the lens 25. The lens 25 is arranged and configured to collimate the light emitted from the tapered tip 2a and condense the light reflected by the reflective optical element 26 onto the tapered tip 2a.
　デバイス２Ａ～２Ｃのように、テーパ部先端２ａと光学的に接続された反射光学素子を備えてなることにより、光ファイバ側から光を検出する場合の光量を増加させることができる。
　デバイス２Ａ～２Ｃに備えられる反射光学素子は、単なるミラーであってもよいが、これらのデバイス２Ａ～２Ｃを備えた測定装置において検出対象とする光（例えば、ラマン分光装置におけるラマン散乱光、蛍光検出装置における蛍光）の波長を効率よく反射する一方、励起光を吸収あるいは透過するものであれば、測定装置において検出光をより高い精度で検出することができるため、好ましい。 By providing a reflective optical element optically connected to the tapered tip 2a as in the devices 2A to 2C, the amount of light when detecting light from the optical fiber side can be increased.
The reflection optical elements provided in the devices 2A to 2C may be simple mirrors, but light to be detected in the measurement apparatus including these devices 2A to 2C (for example, Raman scattered light, fluorescence in the Raman spectroscopic apparatus) It is preferable to efficiently reflect the wavelength of fluorescence in the detection device while absorbing or transmitting the excitation light, because the detection light can be detected with higher accuracy in the measurement device.
（第３の実施形態）
　本発明の第３の実施形態に係る光電場増強デバイス３について説明する。
　図９は、本実施形態の光電場増強デバイス３を示す斜視図である。 (Third embodiment)
A photoelectric field enhancement device 3 according to a third embodiment of the present invention will be described.
FIG. 9 is a perspective view showing the photoelectric field enhancement device 3 of the present embodiment.
　光電場増強デバイス３は、中央部にテーパ部３５を備えた光導波路部３３が、２００μｍ幅の光導波路（コア部）３１を備えたＬＮ（ＬｉＮｂＯ３）基板３０の一部に設けられ、テーパ部３５の側面に微細凹凸構造を構成するベーマイト層１８およびその上に設けられた金属膜１９が形成されてなるものである。 The optical field enhancement device 3 includes an optical waveguide portion 33 having a taper portion 35 at a central portion provided on a part of an LN (LiNbO3) substrate 30 having an optical waveguide (core portion) 31 having a width of 200 μm. A boehmite layer 18 constituting a fine concavo-convex structure and a metal film 19 provided thereon are formed on the side surface of 35.
　光電場増強デバイス３の製造方法を簡単に説明する。
　ＬＮ基板３０の一部を機械掘削して、厚み２ｍｍ長さ５ｍｍ、２００μｍ幅のコア部３１を含み幅４００μｍクラッド部３２からなる光導波路部３３を形成し、さらに、その長さ方向中央部を機械掘削して最細部（最も幅の薄い部分）のコア幅が３０μｍとなるようにテーパ部３５を形成する。
　そして、テーパ部３５の側面に厚み２０ｎｍのＡｌ膜を形成し、水熱処理を行うことにより、ベーマイト層１８を形成する。さらに、このベーマイト層１８の表面にＡｕ薄膜１９を形成することによりテーパ部３５の側面に金属微細凹凸構造部１０を形成する。 A method for manufacturing the photoelectric field enhancement device 3 will be briefly described.
A portion of the LN substrate 30 is mechanically excavated to form an optical waveguide portion 33 including a core portion 31 having a thickness of 2 mm, a length of 5 mm, and a width of 200 μm, and a clad portion 32 having a width of 400 μm. The taper portion 35 is formed by machine excavation so that the core width of the smallest part (the narrowest portion) is 30 μm.
Then, an Al film having a thickness of 20 nm is formed on the side surface of the tapered portion 35, and the boehmite layer 18 is formed by performing hydrothermal treatment. Further, by forming the Au thin film 19 on the surface of the boehmite layer 18, the metal fine uneven structure portion 10 is formed on the side surface of the taper portion 35.
　本実施形態のように、光導波路部材は光ファイバに限らず、基板状のものであってもよい。基板状の場合、細路部の最小サイズは、厚みの最も薄い箇所の厚みをいうものとし、この厚みが励起光波長の５０倍以上であることが望ましい。 As in this embodiment, the optical waveguide member is not limited to an optical fiber, but may be a substrate. In the case of the substrate shape, the minimum size of the narrow path portion means the thickness of the thinnest portion, and it is desirable that this thickness is 50 times or more the excitation light wavelength.
　なお、基板としては、ＬＮ（ＬｉＮｂＯ３）の他、ＬｉＴａＯ３、ＫＮ（ＫＮｂＯ３）、ＫＴＰ（ＫＴｉＯＰＯ４）、または、ＬｉＮｂ（１－ｘ）ＴａｘＯ３（ただし、０≦ｘ≦１）などに光導波路（コア部）が形成されてなる基板を用いることができる。 As the substrate, in addition to LN (LiNbO3), LiTaO3, KN (KNbO3), KTP (KTiOPO4), or LiNb (1-x) TaxO3 (where 0 ≦ x ≦ 1) or the like is used as an optical waveguide (core portion). ) Can be used.
（第４実施形態）
　次に、本発明の第４実施形態に係る、光電場増強デバイスを備えた測定装置について説明する。本実施形態の測定装置は、上述の光電場増強デバイス１を備えた表面増強ラマン検出器４である。 (Fourth embodiment)
Next, a measurement apparatus including a photoelectric field enhancement device according to a fourth embodiment of the present invention will be described. The measurement apparatus of the present embodiment is a surface-enhanced Raman detector 4 that includes the photoelectric field enhancement device 1 described above.
　図１０は、本実施形態の表面増強ラマン検出器４の概略構成を示す模式図である。
　表面増強ラマン検出器４は、光ファイバ２０の一部にテーパ部１３を備え、該テーパ部に金属微細凹凸構造部１０が形成されてなる光電場増強デバイス１を備え、半導体レーザ光源４１が光コネクタ４２を介して光電場増強デバイス１の一端（光ファイバ２０の一端）に接続されており、光検出器４４が光電場増強デバイス１の他端（光ファイバ２０の他端）に接続されている。光コネクタ４２は半導体レーザ光源４１と光ファイバ２０を光学的に、および機械的に結合する構造を有する。また、光コネクタ４３は光コネクタ４２と同様に、光検出器４４と光ファイバ２０を光学的に、および機械的に結合する構造を有する。 FIG. 10 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 4 of the present embodiment.
The surface-enhanced Raman detector 4 includes a photoelectric field enhancement device 1 that includes a tapered portion 13 in a part of an optical fiber 20 and a metal fine concavo-convex structure portion 10 formed in the tapered portion. The photoelectric field enhancing device 1 is connected to one end (one end of the optical fiber 20) via the connector 42, and the photodetector 44 is connected to the other end (the other end of the optical fiber 20) of the photoelectric field enhancing device 1. Yes. The optical connector 42 has a structure for optically and mechanically coupling the semiconductor laser light source 41 and the optical fiber 20. Similarly to the optical connector 42, the optical connector 43 has a structure for optically and mechanically coupling the photodetector 44 and the optical fiber 20.
　本表面増強ラマン検出器４の作用を説明する。
　図示しない試料溶液中に光電場増強デバイス１の金属微細凹凸構造部１０を挿入した状態で、半導体レーザ光源４１から励起光を射出させる。励起光（レーザ光）Ｌ０は、光コネクタ４２を介して光ファイバ２０中を伝播し、テーパ部１３の金属微細凹凸構造部１０において局在プラズモンが誘起され、構造部１０の表面において増強された光電場が生じる。この光電場による励起を受けて試料溶液中の物質から生じるラマン散乱光Ｌｒは、光ファイバ２０中を導波して光コネクタ４３を介して光検出器４４により検出される。 The operation of the surface-enhanced Raman detector 4 will be described.
Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown). The excitation light (laser light) L0 propagates through the optical fiber 20 via the optical connector 42, and local plasmons are induced in the metal fine concavo-convex structure portion 10 of the taper portion 13 and are enhanced on the surface of the structure portion 10. A photoelectric field is generated. The Raman scattered light Lr generated from the substance in the sample solution by being excited by the photoelectric field is guided through the optical fiber 20 and detected by the photodetector 44 through the optical connector 43.
　なお、励起光Ｌ０も光検出器４４へと伝播するため、光検出器４４は内部に励起光を吸収または反射する光学素子または／およびラマン散乱光を分光する光学素子を備えていることが好ましい。 Since the excitation light L0 also propagates to the photodetector 44, the photodetector 44 preferably includes an optical element that absorbs or reflects the excitation light and / or an optical element that separates the Raman scattered light. .
　（第５実施形態）
　次に、本発明の第５実施形態に係る、光電場増強デバイスを備えた測定装置について説明する。本実施形態の測定装置は、上述の光電場増強デバイス１を備えた表面増強ラマン検出器５である。 (Fifth embodiment)
Next, a measurement apparatus including a photoelectric field enhancement device according to a fifth embodiment of the present invention will be described. The measuring apparatus of the present embodiment is a surface-enhanced Raman detector 5 including the above-described photoelectric field enhancing device 1.
　図１１は、本実施形態の表面増強ラマン検出器５の概略構成を示す模式図である。
　表面増強ラマン検出器５は、半導体レーザ光源４１が光コネクタ４２と光ファイバカプラ（光方向性結合器）５１を介して光電場増強デバイス１の一端に接続されており、光検出器４４が、光コネクタ４３と光ファイバカプラ５２を介して光電場増強デバイスの両端に接続されてなる。 FIG. 11 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 5 of the present embodiment.
In the surface-enhanced Raman detector 5, the semiconductor laser light source 41 is connected to one end of the photoelectric field enhancing device 1 via an optical connector 42 and an optical fiber coupler (optical directional coupler) 51. It is connected to both ends of the photoelectric field enhancing device via the optical connector 43 and the optical fiber coupler 52.
　本表面増強ラマン検出器５の作用を説明する。
　図示しない試料溶液中に光電場増強デバイス１の金属微細凹凸構造部１０を挿入した状態で、半導体レーザ光源４１から励起光を射出させる。励起光Ｌ０は、光コネクタ４２および光ファイバカプラ５１を介し光電場増強デバイス１中に伝播し、テーパ部１３の金属微細凹凸構造部１０において局在プラズモンを誘起する。これにより、金属微細凹凸構造部１０の表面において増強された光電場が生じる。この光電場による励起を受けて試料溶液中の物質から生じるラマン散乱光Ｌｒは、光電場増強デバイス１中を導波して一部は光ファイバカプラ５２に直接到達し、別の一部は光ファイバカプラ５１を経由して光ファイバカプラ５２に到達し、それぞれが合波され、光コネクタ４３を介して光検出器４４で検出される。 The operation of the surface enhanced Raman detector 5 will be described.
Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown). The excitation light L0 propagates into the photoelectric field enhancement device 1 via the optical connector 42 and the optical fiber coupler 51, and induces localized plasmons in the metal fine concavo-convex structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10. The Raman scattered light Lr generated from the substance in the sample solution under the excitation by the photoelectric field is guided in the photoelectric field enhancement device 1 and partly reaches the optical fiber coupler 52, and another part is light. The optical fiber coupler 52 is reached via the fiber coupler 51, and they are combined and detected by the photodetector 44 via the optical connector 43.
　表面増強ラマン検出器４では、金属微細凹凸構造部１０近傍で生じたラマン散乱光Ｌｒのうち、光検出器４４側に導波したものしか検出できないが、本実施形態の表面増強ラマン検出器５では、レーザ光源４１側に導波したものの一部も光ファイバカプラ５１を介して検出することができるため、より高い精度の検出が可能となる。 The surface-enhanced Raman detector 4 can detect only the Raman scattered light Lr generated in the vicinity of the metal fine concavo-convex structure portion 10 that is guided to the photodetector 44 side, but the surface-enhanced Raman detector 5 of the present embodiment. Then, a part of the light guided to the laser light source 41 side can also be detected via the optical fiber coupler 51, so that detection with higher accuracy is possible.
　なお、本実施形態においても、励起光Ｌ０が光検出器４４へと伝播するため、光検出器４４は内部に励起光を吸収または反射する光学素子または／およびラマン散乱光を分光する光学素子を備えていることが好ましい。 Also in this embodiment, since the excitation light L0 propagates to the photodetector 44, the photodetector 44 has an optical element that absorbs or reflects the excitation light inside and / or an optical element that separates the Raman scattered light. It is preferable to provide.
　（第６実施形態）
　次に、本発明の第６実施形態に係る、光電場増強デバイスを備えた測定装置について説明する。本実施形態の測定装置は、上述の光電場増強デバイス１を備えた表面増強ラマン検出器６である。 (Sixth embodiment)
Next, a measurement apparatus including a photoelectric field enhancement device according to a sixth embodiment of the present invention will be described. The measuring apparatus of the present embodiment is a surface-enhanced Raman detector 6 including the above-described photoelectric field enhancing device 1.
　図１２は、本実施形態の表面増強ラマン検出器６の概略構成を示す模式図である。
　表面増強ラマン検出器６は、半導体レーザ光源４１が光コネクタ４２とＷＤＭ（波長分割多重）光カプラ６１を介して光電場増強デバイス１の一端に接続されており、光検出器４４が、光コネクタ４３、光ファイバカプラ６４およびＷＤＭ光カプラ６１，６２を介して光電場増強デバイス１の両端に接続されてなる。
　ＷＤＭ光カプラ６１は励起光波長とラマン散乱光波長を分波するものであり、励起光波長を分波するポートが半導体レーザ光源４１に接続され、ラマン散乱光を分波するポートが光ファイバカプラ６３に接続されている。ＷＤＭ光カプラ６１の別の一端は光電場増強デバイス１に接続される。ＷＤＭ光カプラ６２もＷＤＭ光カプラ６１と同様に励起光波長とラマン散乱光波長を分波するものであり、励起光波長を分波するポートはビームディフューザ６４に接続され、ラマン散乱光波長を分波するポートは光ファイバカプラ６３に接続されている。 FIG. 12 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 6 of the present embodiment.
In the surface-enhanced Raman detector 6, the semiconductor laser light source 41 is connected to one end of the photoelectric field enhancing device 1 via an optical connector 42 and a WDM (wavelength division multiplexing) optical coupler 61, and the photodetector 44 is connected to the optical connector. 43, connected to both ends of the photoelectric field enhancement device 1 through an optical fiber coupler 64 and WDM optical couplers 61 and 62.
The WDM optical coupler 61 demultiplexes the pumping light wavelength and the Raman scattered light wavelength, the port for demultiplexing the pumping light wavelength is connected to the semiconductor laser light source 41, and the port for demultiplexing the Raman scattered light is an optical fiber coupler. 63. Another end of the WDM optical coupler 61 is connected to the photoelectric field enhancement device 1. Similarly to the WDM optical coupler 61, the WDM optical coupler 62 also demultiplexes the pumping light wavelength and the Raman scattered light wavelength, and the port for demultiplexing the pumping light wavelength is connected to the beam diffuser 64 to separate the Raman scattered light wavelength. The wave port is connected to the optical fiber coupler 63.
　本表面増強ラマン検出器６の作用を説明する。
　図示しない試料溶液中に光電場増強デバイス１の金属微細凹凸構造部１０を挿入した状態で、半導体レーザ光源４１から励起光を射出させる。励起光Ｌ０は、光コネクタ４２およびＷＤＭ光カプラ６１を介して光電場増強デバイス１中に伝播し、テーパ部１３の金属微細凹凸構造部１０において局在プラズモンを誘起する。これにより、金属微細凹凸構造部１０の表面において増強された光電場が生じる。この光電場による励起を受けて試料溶液中の物質から生じるラマン散乱光Ｌｒは、光電場増強デバイス１中を導波して一部はＷＤＭ光カプラ６１を介して光ファイバカプラ６３に到達する。別の一部はＷＤＭ光カプラ６２を介して光ファイバカプラ６３に到達する。ＷＤＭ光カプラ６２に到達した励起光はビームディフューザ６４に入射され、終端される。ＷＤＭ光カプラ６１とＷＤＭ光カプラ６２から光ファイバカプラ６３に入射したラマン散乱光は合波され、光コネクタ４３を介して光検出器４４で検出される。 The operation of the surface enhanced Raman detector 6 will be described.
Excitation light is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown). The excitation light L0 propagates into the photoelectric field enhancement device 1 through the optical connector 42 and the WDM optical coupler 61, and induces localized plasmons in the metal fine uneven structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10. The Raman scattered light Lr generated from the substance in the sample solution under the excitation by the photoelectric field is guided through the photoelectric field enhancing device 1 and partly reaches the optical fiber coupler 63 via the WDM optical coupler 61. Another part reaches the optical fiber coupler 63 via the WDM optical coupler 62. The excitation light that has reached the WDM optical coupler 62 is incident on the beam diffuser 64 and terminated. The Raman scattered light incident on the optical fiber coupler 63 from the WDM optical coupler 61 and the WDM optical coupler 62 is combined and detected by the photodetector 44 through the optical connector 43.
　光検出器４４は内部に励起光を吸収または反射する光学素子または／およびラマン散乱光を分光する光学素子を備えていても良い。 The photodetector 44 may include an optical element that absorbs or reflects excitation light or / and an optical element that separates Raman scattered light.
　本実施形態の表面増強ラマン検出器６は、ＷＤＭ光カプラ６１、６２を使用することで、第５実施形態に係る表面増強ラマン検出器５よりも、さらにラマン散乱光を高効率に検出することができる。 The surface-enhanced Raman detector 6 of this embodiment uses the WDM optical couplers 61 and 62 to detect Raman scattered light more efficiently than the surface-enhanced Raman detector 5 according to the fifth embodiment. Can do.
　（第７実施形態）
　次に、本発明の第７実施形態に係る、光電場増強デバイスを備えた測定装置について説明する。本実施形態の測定装置は、上述の光電場増強デバイス２を備えた表面増強ラマン検出器７である。 (Seventh embodiment)
Next, a measurement apparatus including a photoelectric field enhancement device according to a seventh embodiment of the present invention will be described. The measurement apparatus of the present embodiment is a surface-enhanced Raman detector 7 including the above-described photoelectric field enhancement device 2.
　図１３は、本実施形態の表面増強ラマン検出器７の概略構成を示す模式図である。
　表面増強ラマン検出器７は、半導体レーザ光源４１が光コネクタ４２と光ファイバカプラ７１を介して光電場増強デバイス２に接続されており、光検出器４４が光コネクタ４３と光ファイバカプラ７１を介して光電場増強デバイス２に接続されてなる。 FIG. 13 is a schematic diagram showing a schematic configuration of the surface-enhanced Raman detector 7 of the present embodiment.
In the surface-enhanced Raman detector 7, the semiconductor laser light source 41 is connected to the photoelectric field enhancement device 2 via the optical connector 42 and the optical fiber coupler 71, and the photodetector 44 is connected via the optical connector 43 and the optical fiber coupler 71. And connected to the photoelectric field enhancement device 2.
　本表面増強ラマン検出器７の作用を説明する。
　図示しない試料溶液中に光電場増強デバイス１の金属微細凹凸構造部１０を挿入した状態で、半導体レーザ光源４１から励起光Ｌ０を射出させる。励起光Ｌ０は、光コネクタ４２および光ファイバカプラ７１を介し光電場増強デバイス１中に伝播し、テーパ部１３の金属微細凹凸構造部１０において局在プラズモンを誘起する。これにより、金属微細凹凸構造部１０の表面において増強された光電場が生じる。この光電場による励起を受けて試料溶液中の物質から生じるラマン散乱光Ｌｒは、光電場増強デバイス１中を導波して光ファイバカプラ７１を介して光コネクタ４３に到達し、光検出器４４で検出される。 The operation of the surface-enhanced Raman detector 7 will be described.
Excitation light L0 is emitted from the semiconductor laser light source 41 in a state where the metal fine concavo-convex structure portion 10 of the photoelectric field enhancement device 1 is inserted into a sample solution (not shown). The excitation light L0 propagates into the photoelectric field enhancement device 1 through the optical connector 42 and the optical fiber coupler 71, and induces localized plasmons in the metal fine concavo-convex structure portion 10 of the taper portion 13. Thereby, an enhanced photoelectric field is generated on the surface of the metal fine concavo-convex structure portion 10. The Raman scattered light Lr generated from the substance in the sample solution by being excited by the photoelectric field is guided through the photoelectric field enhancing device 1 and reaches the optical connector 43 via the optical fiber coupler 71, and the photodetector 44. Is detected.
　光検出器４４は内部に励起光を吸収または反射する光学素子または／およびラマン散乱光を分光する光学素子を備えていても良い。 The photodetector 44 may include an optical element that absorbs or reflects excitation light or / and an optical element that separates Raman scattered light.
　光ファイバカプラ７１が、ラマン散乱光波長を光検出器４４側の光コネクタ４３に向けて分波するＷＤＭ光カプラであれば、より効率的にラマン散乱光を検出することができ好ましい。 If the optical fiber coupler 71 is a WDM optical coupler that demultiplexes the wavelength of the Raman scattered light toward the optical connector 43 on the photodetector 44 side, it is preferable because the Raman scattered light can be detected more efficiently.
　また、光電場増強デバイス２の代わりに、第２の光電場増強デバイス２の設計変更例のデバイス２Ａ～２Ｃを備えた構成としてもよい。
　光電場増強デバイス２Ａ～２Ｃのように、端面にラマン散乱光を反射するミラーを備えていれば、光検出器４４に入射するラマン散乱光量を増加させることができる。また、ラマン散乱光を反射させると共に、励起光を透過するフィルタとして作用する多層膜を備えていれば、光検出器４４に入射するラマン散乱光量を増加させると共に、光検出器４４に入射する励起光量を低減することができ、よりＳ／Ｎの高い検出が可能となる。 Further, instead of the photoelectric field enhancement device 2, a configuration in which the devices 2A to 2C of the design modification example of the second photoelectric field enhancement device 2 are provided may be employed.
If a mirror that reflects Raman scattered light is provided on the end face like the photoelectric field enhancing devices 2A to 2C, the amount of Raman scattered light incident on the photodetector 44 can be increased. If a multilayer film that reflects Raman scattered light and acts as a filter that transmits excitation light is provided, the amount of Raman scattered light incident on the photodetector 44 is increased and the excitation incident on the photodetector 44 is increased. The amount of light can be reduced, and detection with a higher S / N is possible.
　本発明の測定装置の実施形態として、上記においては表面増強ラマン検出器について説明したが、本発明の測定装置は、プラズモン増強蛍光検出置に適用することもできる。蛍光検出装置において、上述の光電場増強デバイス１、２を用いることにより、金属微細凹凸構造部１０近傍において、増強された蛍光を検出することができる。 Although the surface-enhanced Raman detector has been described above as an embodiment of the measuring device of the present invention, the measuring device of the present invention can also be applied to a plasmon enhanced fluorescence detector. In the fluorescence detection apparatus, enhanced fluorescence can be detected in the vicinity of the metal fine concavo-convex structure portion 10 by using the photoelectric field enhancement devices 1 and 2 described above.
　さらには、ラマン散乱光、蛍光の測定のみならず、励起光の照射を受けた被検体から生じるレーリー散乱光、ミー散乱光、あるいは第２高調波などの測定装置においても、上述の光電場増強デバイス１、２を用いることにより、金属微細凹凸構造部１０近傍において、局在プラズモン共鳴に伴う増強された光電場を生じさせることができ、増強された光を検出することができる。 Furthermore, not only the measurement of Raman scattered light and fluorescence, but also the above-described enhancement of the photoelectric field not only in measuring devices such as Rayleigh scattered light, Mie scattered light, or second harmonic generated from a subject irradiated with excitation light. By using the devices 1 and 2, an enhanced photoelectric field accompanying local plasmon resonance can be generated in the vicinity of the metal fine concavo-convex structure portion 10, and the enhanced light can be detected.
　（実施例１）
　Corning社のマルチモード石英ファイバHI1060（クラッド直径１２５μｍ）の一部の被覆を除去し、クラッド露出部分を１２００℃で加熱、延伸し、クラッド直径６０μｍの細径部を有するテーパ部を形成した。光ファイバの被覆部分をマスクして蒸着を行い、２０ｎｍのＡｌ膜をテーパ部の片面に形成した。Ａｌ薄膜形成部を８０℃の熱水で５分間水熱処理を行い、ベーマイト層を形成した。形成したベーマイト層の表面ＳＥＭ写真を図９に示す。図１４において、白く観察される箇所が微細凹凸構造の凸部表面である。全域に亘って一様に凹凸構造が形成されている様子が観察された。このベーマイト層からなる微細凹凸構造表面に蒸着によりＡｕ膜を５０ｎｍの厚さで形成し、光電場増強デバイス１を作製することができた。 Example 1
A part of the coating of Corning's multimode quartz fiber HI1060 (cladding diameter 125 μm) was removed, and the exposed clad portion was heated and stretched at 1200 ° C. to form a tapered portion having a thin diameter portion with a cladding diameter of 60 μm. Evaporation was performed with the coated portion of the optical fiber masked, and a 20 nm Al film was formed on one side of the tapered portion. The Al thin film forming part was hydrothermally treated with hot water at 80 ° C. for 5 minutes to form a boehmite layer. A surface SEM photograph of the formed boehmite layer is shown in FIG. In FIG. 14, the portion observed in white is the convex surface of the fine concavo-convex structure. It was observed that the uneven structure was uniformly formed over the entire area. An Au film having a thickness of 50 nm was formed by vapor deposition on the surface of the fine concavo-convex structure composed of the boehmite layer, and the photoelectric field enhancement device 1 could be produced.
　（電場強度シミュレーション）
　水中（屈折率１．３３）に位置するコア径２３０μｍ／クラッド径２５０μｍの光ファイバ（コア屈折率１．４５、クラッド屈折率１．４３）について、一部に最細部４０μｍとなるテーパ部を設けた場合の最細部（コア径３６．８μｍ、クラッド径４０μｍ）と、クラッド径２５０μｍのストレート部のクラッド境界における電場強度についてビーム伝播法によるシミュレーションを行った。ここで、入射レーザ光の波長は７８５ｎｍ、シミュレーション開始点で１／ｅ幅０．６μｍのガウス分布に集光されて光ファイバと結合されている。シミュレーション開始点から４０ｍｍにわたりストレート部を導波させ、テーパ長１０ｍｍ、最細部直径４０μｍのテーパ部くびれ点の電場強度と、シミュレーション開始点から５０ｍｍにわたりストレート部を導波させたときの電場強度についてそれぞれ計算した。この結果を図１５、図１６に示す。 (Electric field strength simulation)
An optical fiber (core refractive index 1.45, clad refractive index 1.43) having a core diameter of 230 μm / cladding diameter of 250 μm located in water (refractive index of 1.33) is provided with a taper portion having a minimum detail of 40 μm. A simulation by the beam propagation method was performed for the most detailed case (core diameter 36.8 μm, clad diameter 40 μm) and the electric field strength at the clad boundary of the straight portion with the clad diameter 250 μm. Here, the wavelength of the incident laser light is 785 nm, and is condensed into a Gaussian distribution having a 1 / e width of 0.6 μm at the simulation start point and coupled to the optical fiber. The straight part is guided over 40 mm from the simulation start point, the electric field strength at the taper part constriction point with a taper length of 10 mm and the smallest diameter of 40 μm, and the electric field strength when the straight part is guided over 50 mm from the simulation start point. Calculated. The results are shown in FIGS.
　図１５（Ａ）は、４０μｍのテーパ最細部における電場強度（実線）および屈折率（破線）を示したものである。図１５（Ｂ）は同図（Ａ）のクラッド境界部の拡大図である。
　図１６（Ａ）は、２５０μｍストレート光ファイバにおける電場強度（実線）および屈折率（破線）を示したものであり、図１６（Ｂ）は同図（Ａ）のクラッド境界部の拡大図である。 FIG. 15A shows the electric field strength (solid line) and the refractive index (dashed line) at the taper detail of 40 μm. FIG. 15B is an enlarged view of the clad boundary portion of FIG.
FIG. 16A shows the electric field strength (solid line) and the refractive index (broken line) in the 250 μm straight optical fiber, and FIG. 16B is an enlarged view of the cladding boundary part of FIG. .
　図１６（Ｂ）に示すように、２５０μｍストレート光ファイバにおいては、クラッド境界で大きく電場強度が減衰するのに対し、図１５（Ｂ）に示すように、４０μｍのテーパ最細部では、クラッド境界での電場強度の減衰が小さく、ストレート光ファイバのクラッド外側の電場強度よりも２桁程度強い電場が得られるという結果が得られた。
　このように、光ファイバのテーパ部の外部では、大きな電場強度が得られ、従って微細金属構造において局在プラズモンを誘起する光電場強度も増加し、テーパ部を形成しない場合と比較して非常に高い光電場増強効果を得ることができることが明らかである。 As shown in FIG. 16B, in the 250 μm straight optical fiber, the electric field strength is greatly attenuated at the cladding boundary, whereas in the taper detail of 40 μm as shown in FIG. 15B, at the cladding boundary. As a result, the electric field strength was less attenuated, and an electric field stronger by about two orders of magnitude than the electric field strength outside the clad of the straight optical fiber was obtained.
In this way, a large electric field strength is obtained outside the tapered portion of the optical fiber, and therefore, the photoelectric field strength that induces localized plasmons in the fine metal structure also increases, which is much higher than when the tapered portion is not formed. It is clear that a high photoelectric field enhancement effect can be obtained.
　（実施例２）
　Thorlabs社の半導体レーザL850P010をＬＤ光源４１とし、Thorlabs社のファイバ結合レンズペアC230260P-Bを使用してＬＤ光源４１と光電場増強デバイス１を結合させる光コネクタ４２および光検出器４４と光電場増強デバイス１を結合する光コネクタ４３を構成した。Semrock社のロングウェーブパスフィルタLP02-830RS-25と浜松ホトニクス社分光器C10027-02を組み合わせて光検出器４４とし、光コネクタ４３の出力と結合させた。光電場増強デバイス１として実施例１に例示したデバイスを使用し、表面増強ラマン検出器４を構成することができた。 (Example 2)
The Thorlabs semiconductor laser L850P010 is used as the LD light source 41, and the optical connector 42, the photodetector 44, and the photoelectric field enhancement for coupling the LD light source 41 and the photoelectric field enhancement device 1 using the Thorlabs fiber coupled lens pair C230260P-B. An optical connector 43 for coupling the device 1 was configured. A long wave path filter LP02-830RS-25 (Semrock) and a spectroscope C10027-02 (Hamamatsu Photonics) were combined to form a photodetector 44, which was coupled to the output of the optical connector 43. The surface-enhanced Raman detector 4 could be configured using the device exemplified in Example 1 as the photoelectric field enhancing device 1.
　なお、本発明は上記実施例に限定されず、特許請求の範囲に記載された技術的思想を逸脱しない範囲で各種の変更や修正が可能である。例えば、本発明に係る励起光源として、本実施形態では、半導体レーザ光源４１を例示したが、適宜固体レーザ光源や色素レーザ光源などを用いても構わない。

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the technical idea described in the claims. For example, in the present embodiment, the semiconductor laser light source 41 is exemplified as the excitation light source according to the present invention, but a solid laser light source, a dye laser light source, or the like may be used as appropriate.

Claims (10)

  1. 　光導波路の一部に細路部を備えた光導波路部材と、
    　前記細路部の表面に備えられた微細凹凸構造と、
    　該微細凹凸構造の表面に形成された金属膜とを備え、
    　該金属膜が形成された前記微細凹凸構造に光の照射を受け、プラズモンによる電場増強効果を生じるものであることを特徴とする光電場増強デバイス。     An optical waveguide member having a narrow path portion in a part of the optical waveguide; and
    A fine uneven structure provided on the surface of the narrow path portion;
    A metal film formed on the surface of the fine uneven structure,
    A photoelectric field enhancement device, wherein the fine concavo-convex structure on which the metal film is formed is irradiated with light to produce an electric field enhancement effect by plasmons.
  2. 　前記細路部の最小サイズが励起光波長の５０倍以下であることを特徴とする請求項１記載の光電場増強デバイス。 2. The photoelectric field enhancement device according to claim 1, wherein the minimum size of the narrow path portion is 50 times or less of the excitation light wavelength.
  3. 　前記細路部が、前記光導波路が徐々に細くなるテーパ状であることを特徴とする請求項１または２記載の光電場増強デバイス。 3. The photoelectric field enhancement device according to claim 1, wherein the narrow path portion has a tapered shape in which the optical waveguide is gradually narrowed.
  4. 　前記光導波路部材が、前記細路部を該光導波路部材の中間部に備えてなるくびれ構造を有していることを特徴とする請求項１から３いずれか１項記載の光電場増強デバイス。 The photoelectric field enhancement device according to any one of claims 1 to 3, wherein the optical waveguide member has a constriction structure in which the narrow path portion is provided in an intermediate portion of the optical waveguide member.
  5. 　前記光導波路部材が、前記細路部を該光導波路部材の一端に備えてなる先細構造を有していることを特徴とする請求項１から３いずれか１項記載の光電場増強デバイス。 The photoelectric field enhancing device according to any one of claims 1 to 3, wherein the optical waveguide member has a tapered structure in which the narrow path portion is provided at one end of the optical waveguide member.
  6. 　前記光導波路部材の前記細路部の一端に結合された反射光学素子を備えていることを特徴とする請求項５記載の光電場増強デバイス。 6. The photoelectric field enhancement device according to claim 5, further comprising a reflective optical element coupled to one end of the narrow path portion of the optical waveguide member.
  7. 　前記光導波路部材の前記細路部の一端に結合された、前記照射される光の反射率または吸収率にくらべ、該光と異なる波長域の光に対する反射率または吸収率が高い光学素子を備えていることを特徴とする請求項５載の光電場増強デバイス。 An optical element coupled to one end of the narrow path portion of the optical waveguide member and having a higher reflectance or absorptance with respect to light in a wavelength region different from the reflectance or absorptance of the irradiated light. The photoelectric field enhancing device according to claim 5, wherein
  8. 　前記光導波路部材が光ファイバであることを特徴とする請求項１から７いずれか１項記載の光電場増強デバイス。 The photoelectric field enhancing device according to any one of claims 1 to 7, wherein the optical waveguide member is an optical fiber.
  9. 　前記微細凹凸構造が、アルミニウム酸化物を含む化合物を主成分とすることを特徴とする請求項１から８いずれか１項記載の光電場増強デバイス。 The photoelectric field enhancement device according to any one of claims 1 to 8, wherein the fine concavo-convex structure contains a compound containing an aluminum oxide as a main component.
  10. 　請求項１から９いずれか１項記載の光電場増強デバイスと、
    　該光電場増強デバイスの前記光導波路部材に導光される励起光を出力する励起光源と、　前記光電場増強デバイスに結合された光検出部とを備えたことを特徴とする測定装置。     The photoelectric field enhancement device according to any one of claims 1 to 9,
    A measurement apparatus comprising: an excitation light source that outputs excitation light guided to the optical waveguide member of the photoelectric field enhancement device; and a light detection unit coupled to the photoelectric field enhancement device.
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