Terahertz light source, fluid detector, and terahertz wave generating method

Abstract

Provided is a simple and compact configuration for performing optical processing on a terahertz wave. A terahertz light source (1) is provided with a lens (5) formed with a convex surface (6) for passing laser light, and a terahertz radiating layer (2) for radiating a terahertz wave on the basis of laser light. The terahertz radiating layer (2) comprises a non-magnetic layer (3) and a ferromagnetic layer (4) stacked on the non-magnetic layer (3). The terahertz radiating layer (2) is formed on the lens (5).

Description

[Technical Field]

[0001] The present invention relates to a terahertz light source that emits terahertz waves based on laser light, a fluid detector, and a terahertz wave generating method. [Background technology]

[0002] Terahertz waves are electromagnetic waves with a frequency of around 1 THz (wavelength of 300 μm). For example, terahertz waves refer to electromagnetic waves between 0.03 THz and 30 THz in the frequency domain, and between 10 μm and 10 mm in the wavelength domain.

[0003] Terahertz waves are used in security technologies such as checking dangerous goods at airports, and are expected to be a key candidate for an elemental technology in 6G (6th Generation Mobile Communication System), the next generation wireless communication system following 5G (5th Generation Mobile Communication System), or Beyond 5G.

[0004] A terahertz light source having a terahertz radiation layer that includes a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer containing a ferromagnetic metal laminated on the non-magnetic layer, for emitting terahertz waves based on laser light, is known as prior art (Patent Document 1). This terahertz radiation layer is formed on a substrate layer that includes one of glass, quartz crystal, sapphire, polyethylene terephthalate (PET), silicon, etc. This substrate layer can be made of a metal, an insulator, a semiconductor, or other material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 017018 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional terahertz light sources such as those described above, in order to perform optical processing such as converging and diffusing on the emitted terahertz waves, it is necessary to provide separate optical elements such as lenses that perform the optical processing, which results in a problem of complex optical system configuration.

[0007] An object of one aspect of the present invention is to provide a terahertz light source, a fluid detector, and a terahertz wave generating method that have a simple and compact configuration for performing optical processing on terahertz waves. [Means for solving the problem]

[0008] In order to solve the above problems, a terahertz light source according to one aspect of the present invention includes a non-planar optical element having a non-flat surface, and a terahertz radiation layer that emits terahertz waves based on laser light, wherein the terahertz radiation layer has a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal, and the terahertz radiation layer is formed on the non-planar optical element.

[0009] In order to solve the above problems, a fluid detector according to one aspect of the present invention is characterized by comprising a pipeline member for flowing a fluid therethrough, a terahertz light source according to one aspect of the present invention arranged inside the pipeline member, and a terahertz wave detector provided on the inner wall of the pipeline member for detecting terahertz waves emitted from the terahertz radiation layer of the terahertz light source.

[0010] In order to solve the above-mentioned problems, a terahertz wave generating method according to one aspect of the present invention is characterized by including an irradiation step of irradiating a terahertz radiation layer formed on a non-planar optical element, the terahertz radiation layer having a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal, with laser light for generating terahertz waves, and a detection step of detecting the terahertz waves radiated from the terahertz radiation layer based on the laser light.

[0011] In order to solve the above-mentioned problems, another terahertz wave generating method according to one aspect of the present invention is characterized by including a step of providing a terahertz light source including a non-planar optical element and a terahertz radiation layer formed on the non-planar optical element, the terahertz radiation layer emitting terahertz waves based on laser light, and an irradiation step of irradiating the terahertz light source with the laser light. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to realize a terahertz light source, a fluid detector, and a terahertz wave generating method that have a simple and compact configuration for performing optical processing on terahertz waves. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a front view of a terahertz light source according to a first embodiment. [Figure 2] FIG. 2 is a front view of a plano-convex lens provided in the terahertz light source. [Figure 3] FIG. 2 is a perspective view of a terahertz radiation layer provided in the terahertz light source. [Figure 4] 3A to 3C are cross-sectional views showing a method for manufacturing the terahertz light source. [Figure 5] 3A to 3C are diagrams for explaining the operation of the terahertz light source. [Figure 6] 10A and 10B are diagrams for explaining the operation of a terahertz light source according to a comparative example. [Figure 7] FIG. 10 is a front view of a modified example of the terahertz light source. [Figure 8]FIG. 10 is a front view of a terahertz light source according to a second embodiment. [Figure 9] FIG. 2 is a front view of a plano-concave lens provided in the terahertz light source. [Figure 10] 3A to 3C are diagrams for explaining the operation of the terahertz light source. [Figure 11] 10A and 10B are diagrams for explaining the operation of a terahertz light source according to a comparative example. [Figure 12] FIG. 10 is a front view of a modified example of the terahertz light source according to the second embodiment. [Figure 13] FIG. 10 is a perspective view of a terahertz light source according to a third embodiment. [Figure 14] 10 is a perspective view for explaining the operation of a cylinder lens provided in the terahertz light source. FIG. [Figure 15] FIG. 10 is a perspective view for explaining the operation of a spherical lens according to a comparative example. [Figure 16] 10A and 10B are diagrams for explaining the operation of a terahertz light source according to a comparative example. [Figure 17] 10A and 10B are diagrams for explaining another operation of the terahertz light source according to the third embodiment. [Figure 18] 10A and 10B are diagrams for explaining the operation of a terahertz light source according to a comparative example. [Figure 19] FIG. 10 is a front view of a terahertz light source according to a fourth embodiment. [Figure 20] FIG. 10 is a front view of another terahertz light source according to the fourth embodiment. [Figure 21] FIG. 10 is a front view of a terahertz light source according to a comparative example. [Figure 22] FIG. 10 is a perspective view of a fluid detector according to a fifth embodiment. [Figure 23] FIG. 2 is a diagram showing an optical fiber cable of a terahertz light source provided in the fluid detector. [Figure 24] 24 is an enlarged cross-sectional image of part A shown in FIG. 23. [Figure 25] FIG. 2 is a cross-sectional view of the fluid detector. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0015] Fig. 1 is a front view of a terahertz light source 1 according to embodiment 1. Fig. 2 is a front view of a plano-convex lens 5 provided in the terahertz light source 1. Fig. 3 is a perspective view of a terahertz radiation layer 2 provided in the terahertz light source 1.

[0016] As shown in FIGS. 1 and 2, the terahertz light source 1 includes a plano-convex lens 5 (non-planar optical element, lens) onto which laser light is irradiated, and a terahertz radiation layer 2 that radiates terahertz waves based on the laser light.

[0017] The plano-convex lens 5 has one of its two surfaces being a convex surface 6 (non-planar) and the other being a flat surface 7. The convex surface 6 is preferably a spherical surface having a positive focal length. This plano-convex lens 5 is typically used to focus laser light. The plano-convex lens 5 can be made of a transparent material such as glass, quartz, or plastic. This laser light is, for example, visible light, and the plano-convex lens 5 can be a lens for visible light.

[0018] The terahertz radiation layer 2 is then formed on the convex surface 6 of the plano-convex lens 5 .

[0019] As shown in FIG. 3 , the terahertz radiation layer 2 has a non-magnetic layer 3 containing a non-magnetic metal and a ferromagnetic layer 4 containing a ferromagnetic metal and stacked on the non-magnetic layer 3. Alternatively, the terahertz radiation layer 2 may have a ferromagnetic layer 4 and a non-magnetic layer 3 stacked on the ferromagnetic layer 4. The ferromagnetic metal includes at least one of Fe, Co, Ni, CoFeB, GdFe, etc. The non-magnetic metal includes at least one of metals with a large spin-orbit interaction, such as Pt, Au, Ru, Cu, Ta, Pd, W, and Al. In this embodiment, the ferromagnetic layer 4 is made of Fe, and the non-magnetic layer 3 is made of Pt.

[0020] The thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 is, for example, 5 nm, which is extremely thin. From the viewpoint of the intensity of the radiated terahertz waves, the thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 is preferably 2 nm or more and 5 nm or less. The thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 may be 1 nm or more and 20 nm or less.

[0021] When the terahertz radiation layer 2 configured in this manner is irradiated with femtosecond laser light, spin polarization occurs at the interface between the non-magnetic layer 3 and the ferromagnetic layer 4, as shown in FIG. 3, and a spin current j flows from the ferromagnetic layer 4 toward the non-magnetic layer 3. s is a charge current j flowing in a direction parallel to the interface between the non-magnetic layer 3 and the ferromagnetic layer 4. c As a result, the spin-orbit coupling deflects the electrons by the spin-Hall angle γ, and the terahertz waves are emitted from the terahertz emitting layer 2 in a direction that intersects with the interface between the nonmagnetic layer 3 and the ferromagnetic layer 4.

[0022] FIG. 4 is a cross-sectional view showing a method for manufacturing the terahertz light source 1.

[0023] 4, the terahertz light source 1 is fabricated as follows: first, Pt is sputtered by magnetron sputtering onto the convex surface 6 of a plano-convex lens 5 placed on a glass substrate 23 and onto the surface of the glass substrate 23 to form a non-magnetic layer 3. Then, Fe is sputtered onto the Pt to form a ferromagnetic layer 4.

[0024] When a large-diameter terahertz light source 1 is fabricated using the above method, variations in the thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 occur depending on the position on the convex surface 6 of the plano-convex lens 5. Therefore, it is important to control and reduce such spatial variations in thickness, and it is preferable to design and fabricate a spatial filter (spatial mask) that takes thickness variations into consideration. Since the intensity of the terahertz waves varies depending on the thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4, controlling the thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 makes it possible to adjust the intensity of the terahertz waves within the plane of the terahertz light source 1. The thickness of the nonmagnetic layer 3 and the ferromagnetic layer 4 can be controlled by controlling the sputtering beam pattern.

[0025] The terahertz light source 1 may be fabricated by other thin film fabrication methods such as MBE (Molecular Beam Epitaxy).

[0026] Fig. 5 is a diagram for explaining the operation of the terahertz light source 1. Fig. 6 is a diagram for explaining the operation of a terahertz light source according to a comparative example.

[0027] When femtosecond laser light is irradiated from the flat surface 7 side of the plano-convex lens 5, the laser light is focused by the plano-convex lens 5 and enters the terahertz emission layer 2 formed on the convex surface 6 of the plano-convex lens 5. The terahertz emission layer 2 emits terahertz waves in the direction opposite to the plano-convex lens 5 based on the laser light incident from the plano-convex lens 5 side. The terahertz waves emitted from the terahertz emission layer 2 are focused at the focal point of the plano-convex lens 5. The structure of the plano-convex lens 5 causes a phase delay in the laser light incident on the plano-convex lens 5, and the terahertz waves emitted from the terahertz emission layer 2 are narrowed.

[0028] In this way, the terahertz light source 1 has the terahertz radiation layer 2 formed on the convex surface 6 of the plano-convex lens 5, and therefore has the built-in function of a focusing lens that focuses the generated terahertz waves.

[0029] 6, the terahertz radiation layer 2 is disposed independently, and therefore a focusing optical element such as a convex lens must be provided separately to focus the generated terahertz waves. Furthermore, lenses for terahertz waves have large chromatic aberrations and are therefore unsuitable for focusing.

[0030] In the terahertz radiation layer 2, the non-magnetic layer 3 is preferably formed on the convex surface 6 of the plano-convex lens 5, and the ferromagnetic layer 4 is preferably formed on the non-magnetic layer 3. However, conversely, the ferromagnetic layer 4 may be formed on the convex surface 6, and the non-magnetic layer 3 may be formed on the ferromagnetic layer 4.

[0031] By configuring the terahertz radiation layer 2 of the terahertz light source 1 to have a large diameter and giving the terahertz waves emitted from the large-diameter terahertz radiation layer 2 a radiation intensity distribution pattern according to the emission position, the radiation intensity distribution pattern of the terahertz waves can be used for computational applications such as optical computing.

[0032] FIG. 7 is a front view of a terahertz light source 1A according to a modified example.

[0033] The terahertz light source 1A includes a plano-convex lens 5 and a terahertz radiation layer 2 formed on the flat surface 7 of the plano-convex lens 5. In this manner, the terahertz radiation layer 2 may be formed on the flat surface 7 of the plano-convex lens 5. In this case, it is preferable to irradiate the femtosecond laser light from the convex surface side of the plano-convex lens 5.

[0034] The terahertz radiation layer 2 may also be formed on one of the convex surfaces of a biconvex lens.

[0035] The femtosecond laser light is preferably irradiated from the side of the plano-convex lens 5 opposite to the side on which the terahertz radiation layer 2 is formed. However, it may also be irradiated from the side on which the terahertz radiation layer 2 is formed.

[0036] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0037] Fig. 8 is a front view of a terahertz light source 1B according to embodiment 2. Fig. 9 is a front view of a plano-concave lens 8 provided in the terahertz light source 1B. Fig. 10 is a diagram for explaining the operation of the terahertz light source 1B. Fig. 11 is a diagram for explaining the operation of a terahertz light source according to a comparative example.

[0038] The terahertz light source 1B includes a plano-concave lens 8 (non-planar optical element, lens) having one of its two surfaces being a concave surface 9 (non-planar) and the other being a flat surface 10, and the terahertz radiation layer 2 is formed on the concave surface 9. The concave surface 9 is preferably a spherical surface with a negative focal length. The plano-concave lens 8 is typically used to expand laser light or increase the focal length in an optical system.

[0039] When femtosecond laser light is irradiated from the flat surface 10 side of the plano-concave lens 8, the laser light passes through the plano-concave lens 8 and is expanded, and then enters the terahertz radiation layer 2 formed on the concave surface 9 of the plano-concave lens 8. The terahertz radiation layer 2 emits terahertz waves in the direction opposite to the plano-concave lens 8 based on the laser light incident from the plano-concave lens 8.

[0040] In this way, the terahertz light source 1B has the terahertz radiation layer 2 formed on the concave surface 9 of the plano-concave lens 8, and therefore has a built-in function as a beam expander that expands the generated terahertz waves.

[0041] 11, the terahertz radiation layer 2 is disposed independently, so that a separate optical element for expansion, such as a concave lens, needs to be provided to expand the generated terahertz waves. Furthermore, lenses for terahertz waves have large chromatic aberrations and are therefore unsuitable for focusing light.

[0042] In the terahertz radiation layer 2, it is preferable that the non-magnetic layer 3 is formed on the concave surface 9 of the plano-concave lens 8, and the ferromagnetic layer 4 is formed on the non-magnetic layer 3. However, conversely, the ferromagnetic layer 4 may be formed on the concave surface 9, and the non-magnetic layer 3 may be formed on the ferromagnetic layer 4.

[0043] FIG. 12 is a front view of a terahertz light source 1C according to a modified example of the second embodiment.

[0044] The terahertz light source 1C includes a plano-concave lens 8 and a terahertz radiation layer 2 formed on a plane 10 of the plano-concave lens 8. In this manner, the terahertz radiation layer 2 may be formed on the plane 10 of the plano-concave lens 8. In this case, it is preferable to irradiate the femtosecond laser light from the concave surface 9 side of the plano-concave lens 8.

[0045] The terahertz radiation layer 2 may also be formed on one concave surface of a biconcave lens.

[0046] The femtosecond laser light is preferably irradiated from the side of the plano-concave lens 8 opposite to the side on which the terahertz radiation layer 2 is formed. However, conversely, the femtosecond laser light may be irradiated from the side on which the terahertz radiation layer 2 is formed.

[0047] [Embodiment 3] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0048] Fig. 13 is a perspective view of a terahertz light source 1D according to embodiment 3. Fig. 14 is a perspective view for explaining the operation of a cylindrical lens 11 provided in the terahertz light source 1D. Fig. 15 is a perspective view for explaining the operation of a spherical lens according to a comparative example. Fig. 16 is a diagram for explaining the operation of a terahertz light source according to a comparative example.

[0049] The terahertz light source 1D includes a cylindrical lens 11 (non-planar optical element, lens) having one of its two side surfaces being a semi-circular surface 12 (non-planar) and the other being a flat surface 13, and the terahertz radiation layer 2 is formed on the flat surface 13. Since refraction occurs only along one plane in the cylindrical lens 11, as shown in Fig. 14, the circular beam spot passing through the cylindrical lens 11 from the semi-circular surface 12 toward the flat surface 13 gradually becomes elliptical and then linear as it approaches its focus.

[0050] In contrast, as shown in Figure 15, the spherical lens of the comparative example has one of its two sides spherical and the other side flat, and refraction occurs uniformly, so the circular beam spot passing through the spherical lens from the spherical surface to the flat surface maintains its circular shape even at the focal position of the spherical lens.

[0051] In the terahertz light source 1D, the terahertz radiation layer 2 is formed on the flat surface 13 of the cylindrical lens 11, and therefore the terahertz wave beam emitted from the terahertz radiation layer 2 based on the femtosecond laser light irradiated from the semicircular surface 12 side of the cylindrical lens 11 is automatically shaped and emitted to the outside of the cylindrical lens 11. If the femtosecond laser light having a circular beam spot is incident on the terahertz radiation layer 2, the beam spot of the terahertz wave emitted from the terahertz radiation layer 2 is shaped into an ellipse at the focal position of the cylindrical lens 11.

[0052] In contrast, in the terahertz light source according to the comparative example, as shown in FIG. 16, the terahertz radiation layer 2 is disposed alone, and therefore, in order to shape the generated terahertz wave of a circular beam spot into an elliptical beam spot and focus the light, it becomes necessary to separately provide a focusing optical element such as a cylindrical lens.

[0053] The terahertz radiation layer 2 may be formed on the semicircular surface 12 of the cylindrical lens 11. In this case, it is preferable to irradiate the cylindrical lens 11 with femtosecond laser light from the flat surface 13 side.

[0054] The cylindrical lens 11 may have semicircular surfaces 12 on both sides.

[0055] Fig. 17 is a diagram for explaining another operation of the terahertz light source 1D according to embodiment 3. Fig. 18 is a diagram for explaining the operation of a terahertz light source according to a comparative example.

[0056] Since refraction occurs only along one plane in the cylindrical lens 11, as shown in FIG. 17 , when femtosecond laser light having an elliptical beam spot passes through the cylindrical lens 11 from the semicircular surface 12 side toward the plane 13 side and enters the terahertz radiation layer 2, the beam spot of the terahertz wave emitted from the terahertz radiation layer 2 is automatically shaped into a circle at the focal position of the cylindrical lens 11.

[0057] In contrast, in the terahertz light source according to the comparative example, as shown in FIG. 18, the terahertz radiation layer 2 is disposed alone, and therefore, in order to shape the generated terahertz wave of an elliptical beam spot into a circular beam spot and focus the light, it becomes necessary to separately provide a focusing optical element such as a cylindrical lens.

[0058] [Embodiment 4] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0059] 19 is a perspective view of a terahertz light source 1E according to embodiment 3. The terahertz light source 1E includes a parabolic mirror 14 (non-planar optical element), and the terahertz radiation layer 2 is formed on the surface of the parabolic mirror 14.

[0060] When collimated femtosecond laser light is irradiated in the Y-axis direction toward the surface of the parabolic mirror 14, as shown in Figure 19, terahertz waves are emitted from the terahertz radiation layer 2 formed on the surface of the parabolic mirror 14 in the -X-axis direction so as to be focused at the focal position of the parabolic mirror 14.

[0061] In this way, the terahertz light source 1E has the terahertz radiation layer 2 formed on the surface of the parabolic mirror 14, and therefore has a built-in function of collecting collimated light.

[0062] Fig. 20 is a front view of a terahertz light source 1F according to embodiment 4. Fig. 21 is a front view of a terahertz light source according to a comparative example.

[0063] The terahertz light source 1F includes a parabolic mirror 14 and a parabolic mirror 22 disposed opposite to the parabolic mirror 14. The terahertz radiation layer 2 is formed on the surface of the parabolic mirror 14.

[0064] When femtosecond laser light is irradiated toward the surface of parabolic mirror 14 in the −X-axis direction, collimated terahertz waves are emitted along the Y-axis direction toward parabolic mirror 22. The terahertz waves incident on parabolic mirror 22 are then reflected toward the −X-axis direction so as to be collected at the focal position of parabolic mirror 22.

[0065] In this way, the terahertz light source 1F comprises a parabolic mirror 14 and a parabolic mirror 22 arranged opposite the parabolic mirror 14, and the terahertz radiation layer 2 is formed on the surface of the parabolic mirror 14, so that it has a built-in collimator function.

[0066] In contrast to this, in the terahertz light source according to the comparative example, the terahertz radiation layer 2 is disposed alone, and therefore, in order to collimate the generated terahertz waves, it becomes necessary to separately provide the parabolic mirrors 14, 22, and 23.

[0067] The parabolic mirrors 14, 22, and 23 may be any of an ellipsoidal mirror, a hyperbolic mirror, a spherical mirror, and an aspherical mirror.

[0068] [Embodiment 5] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0069] Fig. 22 is a perspective view of a fluid detector 19 according to embodiment 5. Fig. 23 is a diagram showing an optical fiber cable 15 provided in the fluid detector 19. Fig. 24 is an enlarged cross-sectional image of part A shown in Fig. 23. Fig. 25 is a cross-sectional view of the fluid detector 19.

[0070] The fluid detector 19 includes a pipeline member 20 for flowing a fluid therein, and a terahertz light source 1G disposed inside the pipeline member 20.

[0071] The terahertz light source 1G has an optical fiber cable 15 (non-planar optical element) onto which femtosecond laser light is irradiated.

[0072] The optical fiber cable 15 has a core 16 into which femtosecond laser light is incident, and a clad 17 formed so as to cover the outer peripheral surface of the core 16. The terahertz radiation layer 2 is formed so as to cover the outer peripheral surface (non-flat surface) of the clad 17.

[0073] The cladding 17 has through grooves 18 for allowing the femtosecond laser light incident on the core 16 to enter the terahertz radiation layer 2. A plurality of through grooves 18 are arranged along the axial direction of the cladding 17 and are formed along the circumferential direction of the cladding 17. The through grooves 18 can be formed by removing the cladding 17 at a constant pitch along the axial direction. The cladding 17 can be made of, for example, acrylic. Alternatively, the cladding 17 may be made of a material that scatters the femtosecond laser light incident on the core 16 at a constant frequency.

[0074] The fluids flowing within the pipeline member 20 include gases and liquids that are to be monitored or analyzed.

[0075] When femtosecond laser light is incident on the core 16 of the optical fiber cable 15 while a fluid is flowing inside the pipeline member 20, the femtosecond laser light incident on the core 16 passes through the through groove 18 formed in the cladding 17 and is incident on the inner surface of the terahertz radiation layer 2 covering the outer surface of the cladding 17.

[0076] When femtosecond laser light is incident on the inner peripheral surface of the terahertz radiation layer 2 , terahertz waves are emitted from the outer peripheral surface of the terahertz radiation layer 2 toward the inner wall of the pipeline member 20 .

[0077] Next, a terahertz wave detector 21 provided on the inner wall of the pipeline member 20 detects the terahertz waves radiated from the outer peripheral surface of the terahertz radiation layer 2. This makes it possible to monitor or analyze the fluid flowing inside the pipeline member 20.

[0078] (summary) In order to solve the above problems, a terahertz light source according to one aspect of the present invention includes a non-planar optical element having a non-flat surface, and a terahertz radiation layer that emits terahertz waves based on laser light, wherein the terahertz radiation layer has a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal, and the terahertz radiation layer is formed on the non-planar optical element.

[0079] According to this feature, a terahertz radiation layer having a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal is formed on a non-planar optical element having a non-planar surface through which laser light passes. Therefore, when the non-planar optical element is irradiated with laser light, the terahertz radiation layer formed on the non-planar optical element emits terahertz waves based on the laser light. When the non-planar optical element is irradiated with laser light from the side opposite the terahertz radiation layer formed on the non-planar optical element, the laser light is optically processed by the non-planar optical element and enters the terahertz radiation layer. Next, the terahertz radiation layer emits terahertz waves based on the incident laser light. Furthermore, when the non-planar optical element is irradiated with laser light from the terahertz radiation layer side, the terahertz radiation layer emits terahertz waves based on the incident laser light. Next, the non-planar optical element on which the terahertz radiation layer is formed optically processes the terahertz waves emitted from the terahertz radiation layer. The terahertz waves that have been optically processed by the non-planar optical element are emitted from the non-planar optical element on the side opposite to the terahertz radiation layer, thereby realizing a terahertz light source that has a simple and compact configuration for optically processing the terahertz waves.

[0080] In the terahertz light source according to one aspect of the present invention, it is preferable that the laser light is incident on the terahertz radiation layer after passing through the non-planar optical element.

[0081] According to the above configuration, the terahertz waves emitted from the terahertz radiation layer are directly emitted to the outside of the terahertz light source without passing through a non-planar optical element, which eliminates the need for the terahertz waves to pass through a non-planar optical element for terahertz waves that has large chromatic aberration.

[0082] In the terahertz light source according to one aspect of the present invention, it is preferable that the non-planar optical element includes a lens, and the terahertz radiation layer is formed on one side surface of the lens.

[0083] According to the above configuration, the lens can perform optical processing on the laser light incident on the terahertz radiation layer or the terahertz wave emitted from the terahertz radiation layer.

[0084] In the terahertz light source according to one aspect of the present invention, it is preferable that the terahertz radiation layer is formed on a side surface opposite to a side surface on which the laser light is incident on the lens.

[0085] According to the above configuration, the terahertz waves emitted from the terahertz radiation layer are emitted directly to the outside of the terahertz light source without passing through a lens, which eliminates the need for the terahertz waves to pass through a lens for terahertz waves that has large chromatic aberration.

[0086] In the terahertz light source according to one aspect of the present invention, it is preferable that the lens includes a plano-convex lens in which one of both sides of the lens is convex and the other of the both sides is flat.

[0087] According to the above configuration, the terahertz waves emitted from the terahertz radiation layer can be collected by the plano-convex lens.

[0088] In the terahertz light source according to one aspect of the present invention, it is preferable that the lens includes a plano-concave lens in which one of both side surfaces of the lens is concave and the other of both side surfaces is flat.

[0089] According to the above configuration, the terahertz waves radiated from the terahertz radiation layer can be expanded by the plano-concave lens.

[0090] In the terahertz light source according to one aspect of the present invention, it is preferable that the lens includes a cylindrical lens in which one of both side surfaces of the lens is a semicircular surface and the other of the both side surfaces is a flat surface.

[0091] According to the above configuration, the terahertz waves radiated from the terahertz radiation layer can be shaped by the cylindrical lens.

[0092] In the terahertz light source according to one aspect of the present invention, it is preferable that the lens includes a biconvex lens having convex sides, or a biconcave lens having concave sides.

[0093] According to the above configuration, the terahertz waves emitted from the terahertz radiation layer can be focused or expanded by the biconvex lens or the biconcave lens.

[0094] In the terahertz light source according to one aspect of the present invention, it is preferable that the non-planar optical element includes a mirror, the terahertz radiation layer is formed on a surface of the mirror, and the mirror includes at least one of a parabolic mirror, an ellipsoidal mirror, a hyperbolic mirror, a spherical mirror, and an aspherical mirror.

[0095] According to the above configuration, the terahertz wave beam emitted from the terahertz radiation layer can be transformed by focusing, collimating, or the like using the mirror.

[0096] In a terahertz light source according to one aspect of the present invention, it is preferable that the non-planar optical element includes an optical fiber cable, the optical fiber cable having a core into which the laser light is incident and a cladding formed to cover the outer surface of the core, the terahertz radiation layer being formed to cover the outer surface of the cladding, and the cladding having a through groove for allowing the laser light incident on the core to enter the terahertz radiation layer.

[0097] According to the above configuration, terahertz waves can be emitted from the outer surface of the terahertz radiation layer based on laser light that is incident on the core of the optical fiber cable, passes through a through groove formed in the cladding that covers the outer surface of the core, and is incident on the inner surface of the terahertz radiation layer that covers the outer surface of the cladding.

[0098] In order to solve the above problems, a fluid detector according to one aspect of the present invention is characterized by comprising a pipeline member for flowing a fluid therethrough, a terahertz light source according to one aspect of the present invention arranged inside the pipeline member, and a terahertz wave detector provided on the inner wall of the pipeline member for detecting terahertz waves emitted from the terahertz radiation layer of the terahertz light source.

[0099] In order to solve the above-mentioned problems, a terahertz wave generating method according to one aspect of the present invention is characterized by including an irradiation step of irradiating a terahertz radiation layer formed on a non-planar optical element, the terahertz radiation layer having a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal, with laser light for generating terahertz waves, and a detection step of detecting the terahertz waves radiated from the terahertz radiation layer based on the laser light.

[0100] In order to solve the above-mentioned problems, another terahertz wave generating method according to one aspect of the present invention is characterized by including a step of providing a terahertz light source including a non-planar optical element and a terahertz radiation layer formed on the non-planar optical element, the terahertz radiation layer emitting terahertz waves based on laser light, and an irradiation step of irradiating the terahertz light source with the laser light.

[0101] In another terahertz wave generating method according to one aspect of the present invention, it is preferable that the non-planar optical element includes a lens, and in the irradiation step, the laser light is irradiated from the side of the lens opposite to the side on which the terahertz radiation layer is formed.

[0102] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0103] 1. Terahertz light source 2 Terahertz radiation layer 3 Non-magnetic layer 4 Ferromagnetic layer 5 Plano-convex lenses (non-planar optical elements, lenses) 6 Convex (non-planar) 7 plane 8 Plano-concave lenses (non-planar optical elements, lenses) 9 Concave (non-planar) 10 planes 11 Cylinder lens (non-planar optical element, lens) 12 Half circumferential surface (non-plane) 13 plane 14 Parabolic mirror (non-planar optical element) 15 Fiber optic cable (non-planar optical element) 16 cores 17 Clad 18 Through groove 19 Fluid detector 20 Pipeline components 21 Terahertz wave detector

Claims

1. a non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; A terahertz light source, wherein the laser light is incident on the terahertz radiation layer after passing through the non-planar optical element.

2. the non-planar optical element comprises a lens; The terahertz light source according to claim 1 , wherein the terahertz radiation layer is formed on one side of the lens.

3. The terahertz light source according to claim 2 , wherein the lens includes a plano-convex lens having one of its two surfaces convex and the other of its two surfaces flat.

4. A non-planar optical element having a non-planar surface; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a lens; the terahertz radiation layer is formed on one side of the lens; The terahertz radiation layer is formed on a side surface opposite to the side surface on which the laser light enters the lens.

5. A non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a lens; the terahertz radiation layer is formed on one side of the lens; The terahertz light source includes a plano-concave lens in which one of the two side surfaces of the lens is concave and the other of the two side surfaces is flat.

6. A non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a lens; the terahertz radiation layer is formed on one side of the lens; The terahertz light source includes a cylindrical lens in which one of both side surfaces of the lens is a semicircular surface and the other of the both side surfaces is a flat surface.

7. A non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a lens; the terahertz radiation layer is formed on one side of the lens; The terahertz light source includes a biconvex lens having convex sides on both sides thereof, or a biconcave lens having concave sides on both sides thereof.

8. A non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a mirror; the terahertz radiation layer is formed on a surface of the mirror; The terahertz light source, wherein the mirror includes at least one of a parabolic mirror, an ellipsoidal mirror, a hyperbolic mirror, a spherical mirror, and an aspherical mirror.

9. A non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a fiber optic cable; the optical fiber cable has a core into which the laser light is incident; a cladding formed to cover an outer peripheral surface of the core, the terahertz radiation layer is formed to cover an outer peripheral surface of the cladding, A terahertz light source, wherein the cladding has a through groove for allowing laser light incident on the core to enter the terahertz radiation layer.

10. a pipeline member for allowing a fluid to flow therethrough; a terahertz light source disposed inside the pipeline member; a terahertz wave detector provided on an inner wall of the pipeline member to detect terahertz waves radiated from the terahertz radiation layer of the terahertz light source; Terahertz light sources are a non-planar optical element having a non-planar surface formed thereon; a terahertz radiation layer that radiates terahertz waves based on the laser light, the terahertz radiation layer comprises a non-magnetic layer containing a non-magnetic metal; a ferromagnetic layer including a ferromagnetic metal and laminated on the nonmagnetic layer, the terahertz radiation layer is formed on the non-planar optical element; the non-planar optical element comprises a fiber optic cable; the optical fiber cable has a core into which the laser light is incident; a cladding formed to cover an outer peripheral surface of the core, the terahertz radiation layer is formed to cover an outer peripheral surface of the cladding, A fluid detector, wherein the cladding has a through groove for allowing laser light incident on the core to enter the terahertz radiation layer.

11. an irradiation step of irradiating a terahertz radiation layer formed on a non-planar optical element, the terahertz radiation layer having a non-magnetic layer containing a non-magnetic metal and a ferromagnetic layer stacked on the non-magnetic layer and containing a ferromagnetic metal, with laser light for generating terahertz waves; and detecting terahertz waves emitted from the terahertz radiation layer based on the laser light, a terahertz wave generating method, wherein the laser light is transmitted through the non-planar optical element and then incident on the terahertz radiation layer;

12. providing a terahertz light source including a non-planar optical element and a terahertz radiation layer formed on the non-planar optical element, the terahertz radiation layer emitting terahertz waves based on laser light; an irradiation step of irradiating the laser light to the terahertz light source, a terahertz wave generating method, wherein the laser light is transmitted through the non-planar optical element and then incident on the terahertz radiation layer;

13. A method of providing a terahertz light source including a non-planar optical element and a terahertz radiation layer formed on the non-planar optical element, the terahertz radiation layer radiating terahertz waves based on laser light; an irradiation step of irradiating the laser light to the terahertz light source, the non-planar optical element comprises a lens; In the irradiating step, the laser light is irradiated from the side of the lens opposite to the side on which the terahertz radiation layer is formed.

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