Heating-type light source

Abstract

The present invention provides a heating-type light source (10) capable of emitting a focused light beam using plasmon resonance. The heating-type light source (10) is provided with: a radiation unit (12) that emits, by heating, a light beam that has been enhanced at a specific wavelength that is longer than the visible-light band on the basis of surface plasmon resonance; and a substrate (11) that supports the radiation unit (12). The radiation unit (12) has a metal structure layer (13), a base metal layer (15) that is in contact with the substrate (11), and a dielectric layer (14) that is disposed between the metal structure layer (13) and the base metal layer (15). The metal structure layer (13) is formed by arranging a plurality of nanostructures (16) in which surface plasmons are present, the plurality of nanostructures (16) including two or more types of nanostructures (16) different from each other in at least one of shape and size. The metal structure layer (13) causes the light beam to converge at an arbitrary position by controlling a phase of the light beam with the plurality of nanostructures (16).

Description

heated light source

[0001] This application claims priority from Japanese Patent Application No. 2024-124832, filed on July 31, 2024, the contents of which are incorporated herein by reference.

[0002] For example, the thermal radiation of a blackbody emits light rays in a wide wavelength range. For example, Patent Document 1 discloses an infrared light source that forms a microcavity on the surface and irradiates infrared light by utilizing plasmon resonance.

[0003] Furthermore, Patent Document 2 discloses a heating type light source having a metal structure layer in which openings are periodically arranged two-dimensionally, and which is equipped with a radiation unit that is heated in response to heat transmitted from a heat source and that emits enhanced light rays at a specific wavelength longer than the visible light band based on surface plasmon resonance.

[0004] JP 2014-053088 A International Publication No. 2018-182013

[0005] However, the light sources disclosed in Patent Documents 1 and 2 each emit diffused light that is wider than parallel light, and when used as a light source for various sensors, the amount of light incident on the light receiving element is only a portion of the total amount of emitted light, resulting in low light utilization efficiency.

[0006] The present invention has been proposed in view of the above-mentioned problems, and aims to provide a heating light source that utilizes plasmon resonance and is capable of emitting a focused light beam.

[0007] (1) A heating light source according to aspect 1 of the present invention comprises a radiation unit that, when heated, emits an enhanced light beam at a specific wavelength longer than the visible light band based on surface plasmon resonance, and a substrate that supports the radiation unit. The radiation unit has a metal structure layer, a base metal layer in contact with the substrate, and a dielectric layer disposed between the metal structure layer and the base metal layer. The metal structure layer is formed by arranging a plurality of nanostructures in which surface plasmons exist, and the plurality of nanostructures include two or more types of nanostructures that differ from each other in at least one of their shapes or sizes. The metal structure layer controls the phase of the light beam using the plurality of nanostructures, thereby converging the light beam at any position.

[0008] (2) In the heating light source of aspect 2 of the present invention, in aspect 1, the metal structure layer controls the phase of the light beam using a plurality of the nanostructures, thereby converging the light beam at two or more different positions.

[0009] (3) A heating light source according to aspect 3 of the present invention is the same as that according to aspect 1, wherein the metal structure layer controls the phase of the light beam using a plurality of the nanostructures, thereby converging the light beams of a plurality of wavelengths at two or more different positions.

[0010] (4) A heating light source according to aspect 4 of the present invention is the same as that according to aspect 1, wherein the metal structure layer generates super-spiral light by arranging the plurality of nanostructures in positions twisted at a predetermined angle relative to each other.

[0011] (5) A heating light source according to aspect 5 of the present invention is any one of aspects 1 to 4, in which the nanostructure is cylindrical, and the metal structure layer is formed by arranging a plurality of the nanostructures having different diameters.

[0012] (6) A sixth aspect of the present invention provides a heating light source according to any one of the first to fifth aspects, wherein the nanostructure includes at least one of Au, Ag, Cu, Cr, Al, Fe, Pt, and Pd.

[0013] (7) A seventh aspect of the present invention provides a heating type light source according to any one of the first to sixth aspects, wherein the dielectric layer is made of SiO ２ Includes:

[0014] According to the present invention, it is possible to provide a heating light source that utilizes plasmon resonance and is capable of emitting a focused light beam.

[0015] FIG. 1 is a schematic diagram showing a heating light source according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a heating light source according to a second embodiment of the present invention. FIG. 3 is a graph showing the results of Verification Example 1. FIG. 4 is a schematic diagram showing an experimental apparatus used in Verification Example 2. FIG. 5 is an explanatory diagram showing the experimental conditions for Verification Example 2. FIG. 6 is a graph showing the results of Verification Example 2. FIG. 7 is a radiation pattern diagram showing the results of Verification Example 2. FIG. 8 is an explanatory diagram showing the results of Verification Example 3. FIG. 9 is an explanatory diagram showing the configuration of Verification Example 4. FIG. 10 is a graph specifying the relationship between the size and phase of the nanostructure in Verification Example 4. FIG. 11 is an explanatory diagram showing the nanostructure in Verification Example 4. FIG. 12 is an intensity distribution diagram showing the measurement results of Verification Example 4. FIG. 13 is an explanatory diagram showing the configuration of Verification Example 5. FIG. 14 is an explanatory diagram showing the generation of supercoiled light in Verification Example 5. FIG. 15 is a graph showing the measurement results of Verification Example 5.

[0016] Hereinafter, a heating-type light source according to one embodiment of the present invention will be described with reference to the drawings. Note that the embodiment shown below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show essential parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of the components may not necessarily be the same as those in reality.

[0017] (First embodiment) A heating light source according to a first embodiment of the present invention will be described. Fig. 1 is a schematic diagram showing the configuration of a heating light source according to the first embodiment of the present invention. A heating light source 10 according to this embodiment emits light rays by heating, and includes a substrate 11 and a radiation section 12 made up of a plurality of functional layers that is laminated on one surface 11a of the substrate 11. In order to emit light rays from this heating light source 10, a heating device 19 may be disposed on the other surface 11b of the substrate 11.

[0018] The substrate 11 is a support for supporting the radiation portion 12, and may be made of, for example, a silicon substrate, a sapphire substrate, a glass substrate, etc. In this embodiment, for example, a disk-shaped silicon single crystal wafer is used as the substrate 11.

[0019] The heating device 19 for heating the heating-type light source 10 may be attached as a ceramic heater to the other surface 11b of the substrate 11. Furthermore, such a heating device 19 may be formed on the other surface 11b of the substrate 11 at a distance from the heating-type light source 10.

[0020] The radiating portion 12 of this embodiment has at least a metal structure layer 13 , a base metal layer 15 in contact with the substrate 11 , and a dielectric layer 14 disposed between the metal structure layer 13 and the base metal layer 15 .

[0021] The base metal layer 15 may be a metal film made of an elemental metal or alloy containing at least one of Au (gold), Ag (silver), Cu (copper), Cr (chromium), Al (aluminum), Fe (iron), Pt (platinum), and Pd (palladium). In this embodiment, for example, an Au film with a thickness of 400 nm is used as the base metal layer 15. In some cases, the thickness of the base metal layer 15 may be 200 nm or more.

[0022] Simulations have shown that the light transmittance of the base metal layer 15 decreases exponentially as the thickness of the base metal layer 15 increases. Therefore, if the thickness of the base metal layer 15 is set to 200 nm or more, it is possible to sufficiently block the transmission of light coming from the heating device 19 side.

[0023] Such a base metal layer 15 blocks the transmission of light rays, for example, heat rays, coming from the heating device 19 side. As a result, the light rays emitted from the heating light source 10 are mainly light rays emitted from the radiating section 12, particularly the metal structure layer 13. Note that it is not necessary for all light rays coming from the heating device 19 side to be blocked by the base metal layer 15, and some of the light rays coming from the heating device 19 side are allowed to pass through.

[0024] The distance between the base metal layer 15 and the metal structure layer 13 described later may be, for example, in the range of 10 nm to 100 nm.

[0025] The dielectric layer 14 may be made of an insulating material. In this embodiment, the dielectric layer 14 is made of, for example, SiO 2 having a thickness of 150 nm. ２ In some cases, the thickness of the dielectric layer 14 may be in the range of 10 nm to 200 nm. Intermediate metal films (not shown), for example, Cu films, each having a thickness of about 5 to 10 nm, may be further formed on both sides of the dielectric layer 14 so as to sandwich the dielectric layer 14. Such intermediate metal films may be selected from metals including, for example, Cr, Ti, Ni, etc.

[0026] The metal structure layer 13 is composed of a plurality of nanostructures 16, 16... in which surface plasmons exist, arranged two-dimensionally on the dielectric layer 14. Each nanostructure 16 is composed of an island-shaped metal film composed of an elemental metal or alloy containing at least one of, for example, Au (gold), Ag (silver), Cu (copper), Cr (chromium), Al (aluminum), Fe (iron), Pt (platinum), and Pd (palladium). In this embodiment, each nanostructure 16 is composed of an Au film. The film thickness of each nanostructure 16 may be, for example, in the range of 10 nm to 100 nm.

[0027] In this embodiment, each nanostructure 16 is formed in a disk shape (disk shape), and multiple nanostructures 16 are arranged two-dimensionally so that the diameter, which is an example of the size of the nanostructure 16, decreases from the center toward the outer edge of the disk-shaped substrate 11. That is, the nanostructure 16 with the largest diameter is arranged at the center of the substrate 11, and multiple nanostructures 16 with diameters that gradually decrease toward the outer edge are arranged regularly around it.

[0028] The nanostructures 16 constituting the metal structure layer 13 can be patterned by a semiconductor process, such as photolithography. For example, an Au film of uniform thickness is formed on the dielectric layer 14, and a resist layer is then formed that resembles the pattern of the nanostructures 16 shown in Figure 1. Then, the Au film exposed from the resist layer is removed by lift-off, thereby forming nanostructures 16 of various sizes in a predetermined arrangement pattern.

[0029] By forming the metal structure layer 13 by arranging nanostructures 16 of a plurality of sizes in such an arrangement pattern, the emitted light beam becomes a focused light beam that converges at a position a certain distance away from the metal structure layer 13. As an example, when forming a heating light source 10 in which the distance between the surface of the metal structure layer 13 and the focusing position of the emitted light beam, i.e., the focal length, is 75 μm and the peak wavelength of the emitted light is 5 μm, the radius of the nanostructures 16 is changed in increments of 0.05 μm in the range of 0.5 μm to 1.5 μm, the formation interval of the nanostructures 16 is 3.0 μm, the thickness of the nanostructures 16 is 50 nm, and the dielectric layer (SiO ２ The thickness of the metal film 14 is set to 150 nm, and the thickness of the base metal layer 15 is set to 200 nm.

[0030] In the heating light source 10 configured as described above, heat is transferred from the heating device 19 to the radiation unit 12, heating the radiation unit 12. That is, the base metal layer 15, dielectric layer 14, and metal structure layer 13 of the radiation unit 12 are heated. In the metal structure layer 13, surface plasmon resonance that enhances radiation of a specific wavelength occurs depending on the shape, size, and formation direction of the nanostructures 16. Then, the light beam with the enhanced peak of the specific wavelength has its phase controlled by the multiple nanostructures 16 whose size changes stepwise from the center to the periphery, and is emitted from the heating light source 10 as convergent light that converges toward a specific focal position (focal point) S.

[0031] Thus, according to the heating light source 10 of this embodiment, by arranging a plurality of nanostructures 16 two-dimensionally, for example, with their sizes gradually changing from the center toward the periphery of the substrate 11, it becomes possible to output the light beam based on plasmon resonance emitted by heating as a converging light beam P that converges toward a specific focusing position (focal point) S.

[0032] Such a heating type light source 10 capable of emitting a converging light beam P by heating can be used in combination with various optical elements, such as lenses, optical filters, polarizing beam splitters, reflecting mirrors, and light receiving elements, so that even a small light receiving element can obtain a sufficient amount of light by converging the light beam, thereby making it possible to realize various small, high-precision sensor devices.

[0033] In the above-described embodiment, each nanostructure 16 is formed in a disk shape protruding from the dielectric layer 14, but the shape of the nanostructure 16 is not limited to this. For example, the metal structure layer can be formed by arranging nanostructures formed in a rectangular plate shape so that the length of one side of the rectangular nanostructure gradually decreases from the center to the periphery of the substrate 11.

[0034] Furthermore, for example, the metal structure layer can be configured by arranging nanostructures formed in an elliptical shape so that the direction of the long side changes stepwise from the center to the periphery of the substrate 11 .

[0035] Furthermore, a metal structure layer can be formed by arranging circular concave nanostructures in a metal layer formed to a predetermined thickness, with the radius gradually decreasing from the center to the periphery of the substrate 11.

[0036] (Second embodiment) A heating light source according to a second embodiment of the present invention will be described. Fig. 2 is a schematic diagram showing the configuration of a heating light source according to a second embodiment of the present invention. Note that the same components as those in the first embodiment are given the same reference numerals, and redundant explanations will be omitted. A heating light source 20 according to the second embodiment includes a plurality of nanostructures 26 as the metal structure layer 23. Each nanostructure 26 is a laminated film, and in this embodiment, for example, SiO ２and a metal film 26b made of Au deposited on top of the dielectric film 26a.

[0037] The nanostructure 26 is composed of two types of nanostructures 26A and 26B having different heights (thicknesses). The metal structure layer 23 is formed by alternately arranging the two types of nanostructures 26A and 26B in a two-dimensional pattern.

[0038] The heights (thicknesses) of the nanostructures 26A and 26B are changed by varying the thickness of the dielectric films 26a. By forming two types of nanostructures 26A and 26B with different heights, the wavelength of the light emitted by heating can be controlled. For example, the nanostructure 26A emits a light ray P1 with a wavelength of 4 μm, and the nanostructure 26B emits a light ray P2 with a wavelength of 6 μm.

[0039] When the heating-type light source 20 of the second embodiment is used, CO ２ gas and NO that reacts to light P2 with a wavelength of 6 μm ２ The light beams can be converged at two focal positions toward the light receiving elements S1 and S2 that detect the CO gas, respectively. By measuring the light intensity of the light beam P1 with a wavelength of 4 μm and the light beam P2 with a wavelength of 6 μm that are incident on the light receiving elements S1 and S2, respectively, the CO gas in the atmosphere through which the light beam from the heating light source 20 passes can be determined. ２ Gas concentration and NO ２ The gas concentration can be detected.

[0040] In this embodiment, the height of the nanostructure is set to two levels, thereby enabling convergent light of two different wavelengths to be emitted toward two focal points, respectively. However, it is also possible to configure the nanostructure to have a height of four levels, for example, enabling convergent light of four different wavelengths to be emitted toward four focal points, respectively.

[0041] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0042] The heating light source of the present invention is an array of nanostructured light scatterers (conductive or dielectric: metasurface) arranged at subwavelength intervals at an interface, which can locally shift the phase of incident light and shape its wavefront according to the spatial distribution of the scatterers. By spatially adjusting the geometric parameters (size, shape, overall surface orientation, etc.) of the metal structural layer, i.e., metasurface building block (MBB), it is possible to freely control the reflected or transmitted wavefront.

[0043] While conceptually related to the reflective and transmitting arrays demonstrated in millimeter-wave and microwave applications, metasurfaces offer a distinct advantage: subwavelength placement of MBBs. This allows for the control of fundamental properties of light (phase, amplitude, and polarization) with high spatial resolution. Furthermore, the subwavelength placement of metasurfaces avoids the formation of spurious diffraction orders that occur in conventional diffractive devices with wavelength-scale spacing. These spurious orders not only reduce the efficiency of diffractive devices but also cause undesirable effects such as virtual foci, halos, and ghost images. These improvements enable a wide range of unprecedented designs.

[0044] A metasurface with MBBs designed to focus light is also called a metalens. Such a metalens is designed according to the phase profile shown in Equation (1) below to convert an incident plane wavefront into a spherical wavefront.

[0045] In equation (1), x and y are spatial coordinates based on the center of the metalens (x = y = 0), φ is the phase, λ is the wavelength, and f is the focal length.

[0046] By applying a phase difference to the metasurface according to equation (1), the incident plane waves become in phase at the focal point, allowing the emitted light to be converged. It is also known that metalenses can be designed with a high numerical aperture. The resolution of optical imaging systems such as lenses is limited by the refraction of light, and this resolution is expressed by the following equation (2).

[0047] In equation (2), U represents the distance between adjacent metasurfaces, λ represents the wavelength of light, and NA represents the numerical aperture.

[0048] Equation (2) shows that the minimum resolution depends on the phase difference between adjacent structures. Therefore, a metalens with a large phase difference between adjacent metasurfaces due to the strong light confinement by the subwavelength structure can achieve a high numerical aperture.

[0049] Thus, metalenses can achieve diffraction-limited focusing with low wavefront error by having a 2π phase range with the same scattering amplitude for all phases, and have high-efficiency performance at high numerical apertures compared to conventional refractive lenses. Therefore, metalenses have the potential to exceed the performance achievable with conventional diffractive optics due to their design flexibility and versatility.

[0050] The heating light source of the present invention applies the above-mentioned principle. By adjusting the structure of the gold nanostructures in the metal structure layer, it is possible to create a phase difference of approximately 2π for reflected light in the mid-infrared region. Therefore, by placing nanostructures of appropriate size in appropriate positions, it is possible to control the phase of the emitted light and emit focused light.

[0051] (Verification Example 1) A heating-type light source according to the first embodiment shown in Fig. 1 was created. Then, the phase of the emitted light was analyzed by the finite-difference time-domain method (FDTD) when the radius of the disk-shaped nanostructure was changed. The results are shown in Fig. 3.

[0052] According to the results shown in FIG. 3, a phase difference of approximately 2π was obtained in the range of 0.5 μm to 1.1 μm by changing the radius of the nanostructure.

[0053] (Verification Example 2) The experimental apparatus shown in Figure 4 was assembled. The experimental conditions are shown in Figure 5. Two types of devices were used: a light-collecting structure (example of the present invention) in which nanostructures with varying radii were arranged, as shown in Figure 1, and a uniform structure (comparison example) in which nanostructures with a uniform radius were arranged.

[0054] As a result of this verification example 2, a graph showing the relationship between wavelength and intensity is shown in FIG. 6, and an example of a radiation pattern is shown in FIG.

[0055] 6, the example of the present invention exhibits a large peak at a wavelength of approximately 6.8 μm, demonstrating a high light intensity. Furthermore, the results shown in FIG. 7 indicate that the example of the present invention exhibits a maximum intensity of 153.2, which is approximately 2.35 times stronger than the comparative example.

[0056] (Verification Example 3) A heated light source according to the second embodiment shown in Figure 2 was created. It is known that a black body (perfect radiator) emits a black body radiation spectrum that follows Planck's law depending on its temperature. However, ordinary materials do not follow Planck's law and exhibit radiation that is smaller than black body radiation. In this case, the ratio of the radiance of a radiator to the black body radiation at the same temperature is called the emissivity ε. According to Kirchhoff's law, the emissivity ε of a material is equal to its absorptance A (ε = A).

[0057] Therefore, the radiation characteristics of a material can be estimated from its absorption spectrum, and vice versa. The radiation of a material is determined by the product of its blackbody spectrum and emissivity, so the radiation of a material with higher absorption approaches blackbody radiation, enabling more efficient radiation. Therefore, if a device with perfect absorption at any wavelength can be realized, a light source that efficiently emits any wavelength can be obtained.

[0058] The heating-type light source of the present invention allows selection of the resonance wavelength depending on the material, shape, and size due to the properties of localized surface plasmon resonance, and therefore it is possible to design various absorption characteristics such as single wavelength or dual band, etc. Therefore, the heating-type light source of the present invention functions as a radiator that emits only the designed specific wavelength with high efficiency.

[0059] When infrared light is incident on a material, the energy can be absorbed by the material, reducing the intensity of the transmitted light. This phenomenon is called infrared absorption, and the infrared spectrum displays a vibrational spectrum specific to the material. This is mainly because the molecules that make up the material absorb the light energy as quantized vibrational and rotational state changes. The relationship shown in equation (3) below holds between the frequency (wave number ν) of the absorbed infrared light and the vibrational energy level of the molecule when the vibrational state changes from state i to state j.

[0060] In equation (3), h is Planck's constant and c is the speed of light.

[0061] One infrared sensor that utilizes this phenomenon is the non-dispersive infrared (NDIR) method. The infrared ray corresponding to the characteristic frequency of the target gas molecules is irradiated, and the irradiation intensity I ０ By measuring the transmittance T, which is the ratio of the transmitted light intensity I at the light receiving element to the transmitted light intensity I at the light receiving element, the concentration c of the target gas molecules can be obtained according to the Beer-Lambert law shown in equation (4).

[0062] In equation (4), ε is the absorbance of the target gas molecules, and d is the optical path length, and these values ​​are constants.

[0063] Currently, LEDs and quantum cascade lasers (QCLs) are the mainstream light sources for the mid-infrared region, but each faces challenges in terms of increasing output power, miniaturization, and cost reduction. Therefore, the heating-type light source of this embodiment, which can efficiently emit light of a specific wavelength by heating, can be suitably used as a small, high-output infrared light source for this NDIR gas sensor. Furthermore, by using the same metasurface in the detection section, it can have an absorption spectrum similar to the emission spectrum, making it applicable as a filter-free, highly efficient detector.

[0064] In the heating type light source of the second embodiment shown in FIG. 2, a dielectric film (SiO ２ By alternately arranging multiple types of nanostructures with different thicknesses, it becomes possible to simultaneously emit light of different wavelengths. Furthermore, by designing according to equation (5), which expands the focal positions (x0 and y0 in equation (1)) as parameters, it is possible to focus light of two wavelengths at each specified focal point.

[0065] The positions and intensities of two light beams with different focal points (convergence points) emitted from the heating-type light source of the second embodiment were obtained by FDTD diffraction. The results are shown in Figure 8. The results shown in Figure 8 confirm that the first light beam with a wavelength of 5 μm was focused at the x, y, and z coordinates (-5.09, 1.79, 21.7), and the second light beam with a wavelength of 6 μm was focused at the x, y, and z coordinates (8.51, 1.79, 21.7).

[0066] (Verification Example 4) As a modification of the heating type light source of the first embodiment, a heating type light source having the configuration shown in Fig. 9 was created. This heating type light source 50 emits light at four mutually different wavelengths λ １ , λ ２ , λ ３ , λ ４ In contrast, the nanostructure is formed such that two of the nanostructure elements 51a, 51b, 51c, and 51d that converge light at four different focal positions cross each other in a cross shape.

[0067] Specifically, the nanostructure 52A has a wavelength of λ １and the nanostructure element 51a corresponding to λ ２ Similarly, the nanostructure 52B is formed by crossing the nanostructure element 51b corresponding to λ ３ and the nanostructure element 51c corresponding to λ ４ The nanostructure element 51d is crossed in a cross shape with the nanostructure element 51a corresponding to the nanostructure element 51b.

[0068] Two of these nanostructures 52A and two of these nanostructures 52B are arranged in a rectangular shape to form one nanostructure unit 53, and a large number of these nanostructure units 53 are arranged on a radiation section 12 formed on one surface of a substrate 11 to form a four-wavelength divided radiation focusing type heating light source 50.

[0069] First, the relationship between the size and phase of the cross-shaped nanostructure described above at wavelengths of 5.0 μm, 5.5 μm, 6.0 μm, and 6.5 μm was determined, and the results are shown in FIG.

[0070] Based on the above results, a heating-type light source 50 was designed in which nanostructure units 53, each of which has two nanostructures 52A and two nanostructures 52B arranged in a rectangular shape, each 6.0 μm on a side, are arranged in a circular area with a diameter of 78 μm, as shown in Fig. 11. Such nanostructure units 53 focus 5.0 μm and 6.5 μm light for x-polarized light, and 5.5 μm and 6.0 μm light for y-polarized light.

[0071] 12 shows the results of a simulation of the electric field intensity distribution when light with wavelengths of 5.0 μm, 5.5 μm, 6.0 μm, and 6.5 μm was focused using this heating-type light source 50. The focal length was set to 30 μm, and the focal coordinates were set to (X: ±12 μm, Y: ±12 μm). The simulation was performed using photonic simulation software "Ansys Lumerical FDTD."

[0072] According to the results shown in FIG. 12, λ １ and the nanostructure element 51a corresponding to λ ２ and a nanostructure 52A in which a nanostructure element 51b corresponding to λ is crossed in a cross shape. ３ and the nanostructure element 51c corresponding to λ ４It was confirmed that by regularly arranging the nanostructure elements 51d corresponding to the wavelengths 1 and 2 and the nanostructures 52B crossed in a cross shape, it becomes possible to focus light at different positions for each wavelength. Therefore, it was confirmed that a four-wavelength division radiation focusing type heating light source can be realized.

[0073] Verification Example 5 As a modification of the heating light source of the first embodiment, a heating light source having the configuration shown in Fig. 13 was created. This heating light source 60 is capable of generating super-spiral light, and comprises a radiation unit 12 formed on one surface of a substrate 11 and a large number of nanostructures 61 each consisting of rectangular parallelepiped nanostructure elements 61a, 61b formed in different layers in the thickness direction, arranged on the radiation unit 12.

[0074] The nanostructure elements 61a and 61b that respectively constitute the nanostructure 61 are formed so that their longitudinal directions are inclined at an arbitrary angle to each other when viewed in a plan view from above.

[0075] A heating light source 60 having an array of nanostructures 61 of this configuration can emit superhelical light, a beam mode that combines the properties of both circularly polarized light, in which the polarization state circulates as it propagates, and a light beam called a Laguerre-Gaussian beam, in which light travels in a spiral pattern, by manipulating nanoparticles to accelerate and modulate particles trapped by interparticle photoinduced forces, as shown in the schematic diagram of Figure 14.

[0076] Such superhelical light is observed as if the particle itself is rotating and revolving around itself. Particles trapped in the superhelical light can be accelerated or decelerated depending on the direction of the circular polarization.

[0077] In this verification example, circular dichroism absorbance (CD) was used to evaluate performance. Circular dichroism is a method of analyzing the three-dimensional structure of an object (optically active material) by irradiating it with circularly polarized light of right-handed circular rotation (RCP) and left-handed circular rotation (LCP) and measuring the difference in absorption. CD is an index of this circular dichroism. The closer this CD is to 1, the more complete the circular dichroism is.

[0078] 15 is a graph showing the measured absorptance of RCP, LCP, and CD at each wavelength. According to these experimental results, the peak absorptance of RCP is about 0.96, and the peak absorptance of CD is about 0.71.

[0079] Figure 16 is a graph showing the experimental results of emissivity and circular dichroism evaluation for this verification example. According to these experimental results, the absorptance was less than 0.5 in all modes. This is presumably due to a performance degradation caused by the array configuration, and it is considered necessary to mitigate the degradation by adjusting the film thickness, etc.

[0080] As described above, it was confirmed that the heating-type light source 60 in which the nanostructures 61 of this verification example are arranged can generate high-purity super-spiral light by optimizing the design of the nanostructure elements 61a and 61b. Such a heating-type light source 60 is expected to be used to further advance optical particle manipulation technology and to apply it to weight reduction.

[0081] REFERENCE SIGNS LIST 10: Heating light source 11: Substrate 12: Radiation portion 13: Metal structure layer 14: Dielectric layer 15: Base metal layer 19: Heating device

Claims

1. A heated light source comprising: a radiation unit that, when heated, emits light rays that are enhanced at a specific wavelength longer than the visible light band based on surface plasmon resonance; and a substrate that supports the radiation unit; wherein the radiation unit has a metal structure layer, a base metal layer in contact with the substrate, and a dielectric layer arranged between the metal structure layer and the base metal layer; the metal structure layer is formed by arranging a plurality of nanostructures in which surface plasmons exist; the plurality of nanostructures include two or more types of nanostructures that differ from each other in at least one of their shapes or sizes; and the metal structure layer controls the phase of the light rays using the plurality of nanostructures, thereby focusing the light rays at any position.

2. The heated light source according to claim 1, wherein the metal structure layer controls the phase of the light beam using a plurality of the nanostructures, thereby converging the light beam at two or more positions different from each other.

3. The heated light source according to claim 1, wherein the metal structure layer controls the phase of the light beam using a plurality of the nanostructures, thereby converging the light beams of multiple wavelengths at two or more different positions.

4. The heated light source according to claim 1, wherein the metal structure layer generates super-spiral light by arranging the nanostructures in positions twisted at a predetermined angle relative to each other.

5. A heating light source according to any one of claims 1 to 4, wherein the nanostructure is cylindrical, and the metal structure layer is formed by arranging a plurality of the nanostructures having different diameters.

6. The heating light source according to any one of claims 1 to 4, wherein the nanostructure contains at least one of Au, Ag, Cu, Cr, Al, Fe, Pt, and Pd.

7. The dielectric layer is made of SiO ２ The heated light source according to claim 1 , comprising:

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