Light detecting element

Abstract

The present application provides a light detection element capable of suppressing mutual enhancement caused by light interference between lenses, thereby having excellent S / N, even when multiple lenses are used. The light detection element includes a first magnetic element (101) and a second magnetic element (102), a first lens (201) that irradiates incident light toward the first magnetic element, and a second lens (202) that irradiates incident light toward the second magnetic element. The first lens and the second lens are composed of a superlens having multiple nano structures arranged in two dimensions. The size of the multiple nano structures in the first lens in plan view decreases as the distance from the optical center of the first lens increases in a prescribed region determined based on the distance from the optical center, and the size of the multiple nano structures in the second lens in plan view decreases as the distance from the optical center of the second lens increases in a prescribed region determined based on the distance from the optical center, so that the phases of the focal points of the first lens and the second lens are different, respectively.

Description

Technical Field

[0001] This invention relates to optical detection elements. Background Technology

[0002] Photoelectric conversion elements, such as photodetectors, are used in various applications. For example, Patent Document 1 describes a receiving device that uses a photodiode to receive light signals. The photodiode, for example, is a pn junction diode that uses a semiconductor pn junction, converting light into an electrical signal. Furthermore, for example, Patent Document 2 describes a light sensor using a semiconductor pn junction and an image sensor using that light sensor.

[0003] Moreover, for example, Patent Document 3 discloses a light sensor using a magnetic element and a receiving device using the light sensor, and Patent Document 4 discloses a technique of incorporating a superlens in a light sensor using a magnetic element.

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-292107

[0006] Patent Document 2: U.S. Patent No. 9,842,874

[0007] Patent Document 3: Japanese Patent Application Publication No. 2022-69387

[0008] Patent Document 4: Japanese Patent Application Publication No. 2023-110453 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Photodetectors using PN junctions in semiconductors are widely used, but new photodetectors are needed for further development. Furthermore, improving the signal-to-noise ratio (S / N) in photodetector applications is required. To improve the S / N, the use of multiple photosensitive magnetic elements is considered. For example, one method is to arrange the magnetic elements in an array. To efficiently illuminate each of the multiple magnetic elements individually, it is desirable to use multiple lenses to illuminate them. However, if multiple lenses are used, the light passing through nearby lenses interferes with and reinforces each other, raising concerns that the desired light may not be effectively directed to the magnetic elements.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a light detection element with excellent signal-to-noise ratio (S / N) that can suppress the mutual enhancement of light intensity caused by interference of light passing through adjacent lenses even when multiple lenses are used.

[0012] Solution for solving the problem

[0013] To achieve the above objectives, the photodetector of the present invention comprises: a first magnetic element and a second magnetic element, the first magnetic element and the second magnetic element respectively comprising a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; a first lens comprising a superlens having a plurality of nanostructures arranged in a two-dimensional arrangement, which irradiates incident light toward the first magnetic element; and a second lens comprising a superlens having a plurality of nanostructures arranged in a two-dimensional arrangement, which irradiates incident light toward the second magnetic element, wherein the size of the plurality of nanostructures in the first lens, when viewed from above along the optical axis of the first lens, decreases as the distance from the optical center of the first lens increases in each region defined by the discontinuity point of mathematical formula (1), and the size of the plurality of nanostructures in the second lens, when viewed from above along the optical axis of the second lens, decreases as the distance from the optical center of the second lens increases in each region defined by the discontinuity point of mathematical formula (2).

[0014]

[0015]

[0016] (In the above mathematical formulas (1) and (2), r is the distance from the origin, f is the focal length of the first lens and the second lens, λ is the wavelength of the incident light, φ is the phase, a1 is the distance from the origin to the optical center of the first lens, a2 is the distance from the origin to the optical center of the second lens, Δφ is the phase difference, and floor is the floor function.)

[0017] According to this structure, in the photodetector element of the present invention, the phase at the focal point of the first lens is different from the phase at the focal point of the second lens. The focal points of the first lens and the second lens exist at different points on the same plane (focal plane). Therefore, mutual reinforcement caused by interference of light irradiated from the first and second lenses onto the first and second magnetic elements can be suppressed. Thus, strong light can be irradiated onto the first and second magnetic elements respectively, thereby improving the signal-to-noise ratio (S / N) in the photodetector element. Furthermore, by using superlenses for the first and second lenses, they can be integrally formed using the same process as the first and second magnetic elements, simplifying the manufacturing process.

[0018] In the optical detection element of the present invention, the focal point of the first lens may be configured to overlap with the first magnetic element when viewed from the optical axis direction of the first lens.

[0019] According to this structure, the photodetector of the present invention can irradiate strong light onto the first magnetic element by configuring the focal point of the first lens to overlap with the first magnetic element when viewed from the optical axis direction of the first lens.

[0020] In the optical detection element of the present invention, the focal point of the second lens may be configured such that it does not overlap with the first magnetic element when viewed from the optical axis direction of the second lens.

[0021] According to this structure, the light detection element of the present invention can reduce the effect of light cancellation in the first magnetic element by configuring the focal point of the second lens so that it does not overlap with the first magnetic element when viewed from the optical axis direction of the second lens, thereby irradiating the first magnetic element with strong light.

[0022] In the optical detection element of the present invention, the focal point of the second lens may be disposed in a light spot formed on a plane perpendicular to the optical axis direction of the first lens, where the focal point of the first lens is located.

[0023] According to this structure, the photodetector of the present invention can shorten the distance between the focal points of the first lens and the second lens, and thus shorten the distance between the first magnetic element and the second magnetic element, and can arrange the magnetic elements in a high density.

[0024] In the optical detection element of the present invention, the first lens and the second lens may also be arranged on the same plane.

[0025] According to this structure, the optical detection element of the present invention can make the manufacturing process easier by forming the first lens and the second lens on the same plane.

[0026] In the optical detection element of the present invention, the first lens and the second lens may be configured such that their respective focal points are 180 degrees out of phase.

[0027] According to this structure, the light detection element of the present invention can further suppress the mutual enhancement caused by the interference of light converged by the lenses of the first lens and the second lens by making the phase difference of the focal points of the first lens and the second lens 180 degrees.

[0028] In the optical detection element of the present invention, the first lens and the second lens may also be formed in different regions of a single lens.

[0029] According to this structure, the photodetector of the present invention simplifies the formation process of the first lens and the second lens by forming the first lens and the second lens in different regions of a single lens.

[0030] The photodetector of the present invention comprises: a plurality of magnetic elements, each having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; and a plurality of lenses, each irradiating light onto a corresponding magnetic element among the plurality of magnetic elements. The plurality of lenses are each composed of a superlens having a plurality of nanostructures arranged in two dimensions. The size of the plurality of nanostructures in one of the adjacent lenses, when viewed from above from the optical axis of the lens, decreases as the distance from the optical center of the lens increases in each region defined by the discontinuity point of mathematical formula (1). The size of the plurality of nanostructures in another of the adjacent lenses, when viewed from above from the optical axis of the other lens, decreases as the distance from the optical center of the other lens increases in each region defined by the discontinuity point of mathematical formula (2).

[0031]

[0032]

[0033] (In the above mathematical formulas (1) and (2), r is the distance from the origin, f is the focal length of the adjacent lens, λ is the wavelength of the incident light, φ is the phase, a1 is the distance from the origin to the optical center of one lens, a2 is the distance from the origin to the optical center of the other lens, Δφ is the phase difference, and floor is the floor function.)

[0034] According to this structure, in the photodetector element of the present invention, the phase at the focal point of one lens in adjacent lenses is different from the phase at the focal point of the other lens. The focal points of adjacent lenses exist at different points on the same plane (focal plane). Therefore, mutual reinforcement caused by interference of light irradiated from multiple lenses onto multiple magnetic elements can be suppressed. Thus, strong light can be irradiated onto each of the multiple magnetic elements individually, thereby improving the signal-to-noise ratio (S / N) in the photodetector element. Furthermore, since the multiple lenses are superlenses, they can be integrally formed using the same process as the magnetic elements, simplifying the manufacturing process.

[0035] In the optical detection element of the present invention, the plurality of magnetic elements may also be configured in a lattice shape.

[0036] According to this structure, the photodetector of the present invention can improve the integration of magnetic elements by arranging multiple magnetic elements in a lattice pattern.

[0037] In the optical detection element of the present invention, the plurality of lenses may also be configured in a grid pattern.

[0038] According to this structure, the photodetector of the present invention can improve the integration of lenses by arranging multiple lenses in a grid pattern.

[0039] In the optical detection element of the present invention, the focal point of at least one of the plurality of lenses may be configured to overlap with the magnetic element corresponding to the same lens when viewed from the optical axis direction of the lens.

[0040] According to this structure, the light detection element of the present invention can irradiate strong light onto the magnetic element by configuring the focal point of at least one of the multiple lenses to overlap with the magnetic element when viewed from the optical axis direction of the lens.

[0041] In the optical detection element of the present invention, the focal point of at least one of the plurality of lenses may be configured such that it does not overlap with any magnetic element other than the magnetic element irradiated by the lens when viewed from the optical axis direction of the lens.

[0042] According to this structure, in the light detection element of the present invention, the focal point of at least one of the multiple lenses is configured so that it does not overlap with a magnetic element other than the magnetic element irradiated by the lens when viewed from the optical axis direction, thereby suppressing the effect of light cancellation in the magnetic element other than the magnetic element irradiating the light, and thus irradiating strong light.

[0043] In the optical detection element of the present invention, the focal point of at least one of the plurality of lenses may be disposed in a light spot formed on a plane perpendicular to the optical axis direction of the other lenses, where the focal points of the other adjacent lenses are located.

[0044] According to this structure, the optical detection element of the present invention can shorten the distance between the focal points of the two lenses, and thus shorten the distance between the magnetic elements corresponding to the two lenses respectively, and can arrange the magnetic elements at a high density.

[0045] In the optical detection element of the present invention, at least two of the plurality of lenses may be arranged on the same plane.

[0046] According to this structure, the optical detection element of the present invention can facilitate the manufacturing process by arranging at least two of the multiple lenses on the same plane.

[0047] In the optical detection element of the present invention, at least two adjacent lenses among the plurality of lenses may be configured such that their respective focal points are 180 degrees out of phase.

[0048] According to this structure, the optical detection element of the present invention can further suppress mutual enhancement caused by interference of light converged by each other's lenses by making the phase difference of the focal points of at least two adjacent lenses in a plurality of lenses 180 degrees.

[0049] In the optical detection element of the present invention, at least two of the plurality of lenses may be formed in different regions of a single lens.

[0050] According to this structure, the optical detection element of the present invention simplifies the lens formation process by forming at least two of the multiple lenses in different regions of a single lens.

[0051] The effects of the invention

[0052] According to the present invention, it is possible to provide a light detection element that can suppress the mutual enhancement of light intensity caused by interference of light passing through adjacent lenses even when multiple lenses are used, thereby achieving excellent signal-to-noise ratio in light detection. Attached Figure Description

[0053] Figure 1 This is a diagram showing the structure of the light detection element according to the first embodiment of the present invention.

[0054] Figure 2 It means Figure 1 A partially enlarged cross-sectional view of the structure of the magnetic element shown.

[0055] Figure 3 It means in Figure 1 The diagram shows the situation where light is focused by a lens in the light detection element.

[0056] Figure 4 It is a three-dimensional diagram showing the structure of the pillars that make up the superlens.

[0057] Figure 5 It is a graph showing the relationship between the diameter of the column and the phase of the light passing through the column.

[0058] Figure 6 It means Figure 1 The top view of the simulation results of the superlens structure also shows the boundaries, regions, etc.

[0059] Figure 7 (a) is a top view showing the simulation results of the light spot on the focal plane. Figure 7 (b) is a graph representing the simulation results.

[0060] Figure 8 (a) is a top view showing the structure of the lens of the light detection element according to the second embodiment of the present invention. Figure 8 (b) is a top view showing the structure of the magnetic element.

[0061] Figure 9 It means by Figure 8 A top view of the structure of the light spot formed by the lens of the light detection element.

[0062] Figure 10 It means Figure 8 A top view of the simulation results of the superlens structure.

[0063] Figure 11 Is Figure 10 The simulation results show a magnified top view of the boundaries, regions, etc.

[0064] Figure 12 It means Figure 1 A top view of the simulation results of the structure of the deformed example of the superlens.

[0065] Figure 13 This is a diagram showing the first structure of a photodetector element in a related technology.

[0066] Figure 14 It means in Figure 13 The diagram shows the situation where light is focused by a lens in the light detection element.

[0067] Figure 15 It means Figure 13 A top view of the simulation results of the superlens structure.

[0068] Figure 16 (a) means Figure 13 A top view of the simulation results of the light spot on the focal plane of the superlens. Figure 16 (b) is a graph representing the simulation results.

[0069] Figure 17 (a) is a top view showing the structure of the lens of the optical detection element in the related technology. Figure 17 (b) is a top view showing the structure of the magnetic element.

[0070] Figure 18 It means by Figure 17 A top view of the structure of the light spot formed by the lens of the light detection element.

[0071] Explanation of reference numerals in the attached figures

[0072] 1. First ferromagnetic layer; 2. Second ferromagnetic layer; 3. Spacer layer; 4, 13. Covering layer; 10, 101-109. Magnetic element; 11. First electrode; 12. Second electrode; 15. Laminated structure; 16. Insulating layer; 20, 30, 301-309. Lens; 201. First lens; 202. Second lens; 25. Superlens; 26. Nanostructure; 26A. Pillar; 27. Base; 28. Unit structure; 101, 102. Photodetector; 1201. First lens; 1202. Second lens; 1001, 1002. Photodetector; G. Distance between focal points of adjacent lenses; M1, M2. Magnetization; P1, P2, P1-P9. Focal point; S0, S01, S1-S9. Light spot. Detailed Implementation

[0073] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0074] Furthermore, for ease of understanding, the scales of various parts in the accompanying drawings sometimes differ from the actual scales. In the orthogonal xyz coordinate system set in the figures, the x-axis and y-axis directions are horizontal, and the z-axis direction is vertical. The positive z-axis direction is also called the up direction, and the negative z-axis direction is also called the down direction, but this is independent of the direction of gravity. For parallel, right-angled, orthogonal, horizontal, vertical, up-down, left-right, and other directions, deviations are allowed to a degree that does not impair the effect of the implementation method. In addition, the "~" indicating a numerical range means that the values ​​described before and after it are included as the lower limit and upper limit values.

[0075] [First Embodiment]

[0076] First, the first embodiment of the present invention will be described.

[0077] (structure)

[0078] Figure 1 The following figure is a cross-sectional view showing the structure of the light detection element 101 according to the first embodiment. Figure 1 The above figure is a top view showing the schematic structure of the lens system of the light detection element 101. Figure 1 As shown, the photodetector 101 includes a first magnetic element 101, a second magnetic element 102, a first lens 201, and a second lens 202. Hereinafter, the first magnetic element 101 and / or the second magnetic element 102 will also be referred to as "magnetic element 10," and the first lens 201 and / or the second lens 202 will also be referred to as "lens 20." The photodetector 101 can be cylindrical, for example, prismatic, or cylindrical.

[0079] Light passing through lens 20 illuminates magnetic element 10. Magnetic element 10 detects the illuminated light and converts it into an electrical signal. The electrical signal is extracted using a first electrode 11 and a second electrode 12 disposed above and below magnetic element 10.

[0080] The term "light" as used in this specification is not limited to visible light; it can also refer to infrared light with wavelengths longer than visible light, or ultraviolet light with wavelengths shorter than visible light. Visible light has wavelengths of, for example, 380 nm or more and less than 800 nm. Infrared light has wavelengths of, for example, 800 nm or more and less than 1 mm. Ultraviolet light has wavelengths of, for example, 200 nm or more and less than 380 nm.

[0081] The following is an explanation of each component.

[0082] (Magnetic components)

[0083] Figure 2 It means Figure 1 A partially enlarged cross-sectional view of the structure of the magnetic element 10 (first magnetic element 101, second magnetic element 102). Figure 2 As shown, the magnetic element 10 includes at least a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3 sandwiched between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. Figure 2 In the process, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, and a capping layer 4 are sequentially stacked along the positive z-axis to form a stack 15. The stack 15 constituting the magnetic element 10 may also include other layers such as a third ferromagnetic layer, a buffer layer, a seed layer, a magnetic coupling layer, and a vertical magnetization induction layer, as needed.

[0084] like Figure 1 and Figure 2 As shown, a first electrode 11 is formed on the lens 20 side of the laminate 15, and a second electrode 12 is formed on the side of the laminate 15 opposite to the lens 20, separated by a cover layer 13. When referring to the magnetic element 10, it may also include the first electrode 11, the second electrode 12, the cover layer 13, an insulating layer 16, etc., in addition to the laminate 15. The cover layer 4 is located between the first ferromagnetic layer 1 and the first electrode 11, and the cover layer 13 is located between the second ferromagnetic layer 2 and the second electrode 12. The insulating layer 16 is formed between the lens 20 and the cover layer 13 or the second electrode 12, and is configured to cover the area around the laminate 15 and the first electrode 11.

[0085] The magnetic element 10 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the spacer layer 3 is made of insulating material. In this case, the magnetic element 10 can exhibit the Tunnel MagnetoResistance (TMR) effect. The resistance value of the magnetic element 10 changes when it is illuminated by light from the outside. The resistance value of the magnetic element 10 in the z-axis direction (the resistance value when current flows in the z-axis direction) changes according to the relative change between the magnetization state M1 of the first ferromagnetic layer 1 and the magnetization state M2 of the second ferromagnetic layer 2. For example, the resistance value of the magnetic element 10 in the z-axis direction changes according to the change in the relative angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 and the direction of the magnetization M2 of the second ferromagnetic layer 2. In addition, for example, the resistance value of the magnetic element 10 in the z-axis direction changes according to the change in the magnitude of the magnetization M1 of the first ferromagnetic layer 1.

[0086] Furthermore, for example, when the spacer layer 3 is made of metal, the magnetic element 10 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. When the magnetic element 10 is a GMR element, the resistance value in the z-axis direction (the resistance value when current flows along the z-axis direction) also changes according to the relative change between the magnetization state M1 of the first ferromagnetic layer 1 and the magnetization state M2 of the second ferromagnetic layer 2. The magnetic element 10 is called an MTJ element, a GMR element, etc., depending on the material of the spacer layer 3; the names are sometimes different, but they are all collectively referred to as a magnetoresistance effect element. The overall thickness of the magnetic element 10 is, for example, 15 nm to 40 nm.

[0087] The magnetic element 10 can be any ferromagnetic material whose magnetization state changes due to light irradiation and whose resistance value changes with the change in magnetization state. As the magnetic element 10, for example, in addition to the MTJ element and GMR element mentioned above, anisotropic magnetoresistance (AMR) effect element, colossal magnetoresistance (CMR) effect element, etc., can also be used.

[0088] The magnetic element 10 is positioned at the focal point of light in the operating frequency band converged by the lens 20. The focal point of the operating frequency band preferably overlaps with, for example, the first ferromagnetic layer 1. For instance, when using visible light, the magnetic element 10 is positioned at the focal point of light in a specific wavelength region within the wavelength range of 380 nm to 800 nm. Similarly, when using infrared light, the magnetic element 10 is positioned at the focal point of light in a specific wavelength region within the wavelength range of 800 nm to 1 mm. Furthermore, when using ultraviolet light, the magnetic element 10 is positioned at the focal point of light in a specific wavelength region within the wavelength range of 200 nm to 380 nm.

[0089] <First Ferromagnetic Layer>

[0090] The first ferromagnetic layer 1 is a light-detecting layer whose magnetization state changes when illuminated by external light. The first ferromagnetic layer 1 is also called a magnetization-free layer. A magnetization-free layer is a layer containing a magnetic material whose magnetization state changes when a specified external energy is applied. The specified external energy can be, for example, externally illuminated light, current flowing along the z-axis of the magnetic element 10, or an external magnetic field. The magnetization M1 of the first ferromagnetic layer 1 changes according to the intensity of the illuminated light.

[0091] The first ferromagnetic layer 1 comprises a ferromagnetic material. For example, the first ferromagnetic layer 1 comprises at least one of magnetic elements such as Co, Fe, and Ni. The first ferromagnetic layer 1 may also comprise elements such as B, Mg, Hf, and Gd in addition to the magnetic elements described above. The first ferromagnetic layer 1 may also be an alloy comprising both magnetic and non-magnetic elements. The first ferromagnetic layer 1 may also consist of multiple layers. For example, the first ferromagnetic layer 1 is a CoFeB alloy, a laminate formed by sandwiching a CoFeB alloy layer with an Fe layer, or a laminate formed by sandwiching a CoFeB alloy layer with a CoFe layer. Generally, "ferromagnetism" includes "ferrimagnetism." The first ferromagnetic layer 1 may also exhibit ferrimagnetism. Alternatively, the first ferromagnetic layer 1 may also exhibit ferromagnetism that is not ferrimagnetic. For example, the CoFeB alloy exhibits ferromagnetism that is not ferrimagnetic.

[0092] The first ferromagnetic layer 1 can be either an in-plane magnetized film with an easy magnetization axis in the direction within the film surface (any direction within the xy plane) or a vertically magnetized film with an easy magnetization axis in the direction perpendicular to the film surface (z-axis direction).

[0093] The thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 5 nm. The thickness of the first ferromagnetic layer 1 is preferably, for example, 1 nm to 2 nm. When the first ferromagnetic layer 1 is a perpendicularly magnetized film, if the thickness of the first ferromagnetic layer 1 is thinner, the effect of perpendicular magnetic anisotropy from the layers above and below the first ferromagnetic layer 1 is enhanced, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is increased. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is higher, the force required for magnetization M1 to return to the z-axis direction is enhanced. On the other hand, if the thickness of the first ferromagnetic layer 1 is thicker, the effect of perpendicular magnetic anisotropy from the layers above and below the first ferromagnetic layer 1 is relatively weakened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is weakened.

[0094] When the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases; conversely, when the thickness of the first ferromagnetic layer 1 increases, its volume as a ferromagnetic material increases. The ease with which the first ferromagnetic layer 1 is magnetized when external energy is applied is inversely proportional to the product of the magnetic anisotropy (Ku) and the volume (V) of the first ferromagnetic layer 1 (KuV). In other words, when the product of the magnetic anisotropy and the volume of the first ferromagnetic layer 1 decreases, its reactivity with light increases. From this perspective, to improve the reactivity with light, it is preferable to reduce the volume of the first ferromagnetic layer 1 while appropriately designing its magnetic anisotropy.

[0095] When the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insert layer composed of Mo or W can be provided within the first ferromagnetic layer 1, for example. That is, the first ferromagnetic layer 1 can also be a laminate formed by sequentially stacking a ferromagnetic layer, an insert layer, and a ferromagnetic layer in the z-axis direction. The overall perpendicular magnetic anisotropy of the first ferromagnetic layer 1 is improved due to the interfacial magnetic anisotropy at the interface between the insert layer and the ferromagnetic layer. The thickness of the insert layer is, for example, 0.1 nm to 1.0 nm.

[0096] <Second Ferromagnetic Layer>

[0097] The second ferromagnetic layer 2 is a magnetization-fixed layer. The magnetization-fixed layer is a layer composed of a magnetic material whose magnetization state is less likely to change compared to a magnetized free layer when a specified external energy is applied. For example, when a specified external energy is applied, the direction of magnetization in the magnetization-fixed layer is less likely to change compared to a magnetized free layer. Furthermore, for example, when a specified external energy is applied, the magnitude of magnetization in the magnetization-fixed layer is less likely to change compared to a magnetized free layer. The coercivity of the second ferromagnetic layer 2 is, for example, greater than that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 has, for example, an easy magnetization axis in the same direction as the first ferromagnetic layer 1. The second ferromagnetic layer 2 can be either an in-plane magnetization film or a perpendicular magnetization film.

[0098] The material constituting the second ferromagnetic layer 2 is, for example, the same as that constituting the first ferromagnetic layer 1. The second ferromagnetic layer 2 can also be, for example, a multilayer film formed by alternating layers of Co with a thickness of 0.4 nm to 1.0 nm and Pt with a thickness of 0.4 nm to 1.0 nm. Alternatively, the second ferromagnetic layer 2 can also be a laminate formed by sequentially layering Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm.

[0099] <Interval Layer>

[0100] Spacer layer 3 is disposed between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. Spacer layer 3 is made of a layer using a conductor, insulator, or semiconductor, or a layer containing current-carrying points made of conductors in an insulator. Spacer layer 3 is, for example, a non-magnetic layer. The film thickness of spacer layer 3 can be adjusted according to the orientation direction of the magnetization of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 in the initial state, as described later.

[0101] When the spacer layer 3 is made of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used as the material for the spacer layer 3. Alternatively, these insulating materials can also contain elements such as Al, B, Si, Mg, and magnetic elements such as Co, Fe, and Ni. By adjusting the thickness of the spacer layer 3, a higher TMR effect can be achieved between the first ferromagnetic layer 1 and the second ferromagnetic layer 2, resulting in a higher magnetoresistance change rate. To efficiently utilize the TMR effect, the thickness of the spacer layer 3 can be set to approximately 0.5 nm to 5.0 nm, or approximately 1.0 nm to 2.5 nm.

[0102] When the spacer layer 3 is composed of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently utilize the GMR effect, the film thickness of the spacer layer 3 can be set to about 0.5 nm to 5.0 nm, or it can be set to about 2.0 nm to 3.0 nm.

[0103] When the spacer layer 3 is made of a non-magnetic semiconductor material, materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or indium tin oxide (ITO) can be used. In this case, the film thickness of the spacer layer 3 can also be set to about 1.0 nm to 4.0 nm.

[0104] When using a layer containing a current-carrying point formed by a conductor in a non-magnetic insulator as spacer layer 3, it can also be configured such that a non-magnetic insulator made of alumina or magnesium oxide contains a current-carrying point formed by a non-magnetic conductor such as Cu, Au, or Al. Alternatively, the conductor can be made of magnetic elements such as Co, Fe, or Ni. In this case, the film thickness of spacer layer 3 can be set to approximately 1.0 nm to 2.5 nm. The current-carrying point is, for example, a columnar shape with a diameter of 1 nm to 5 nm when viewed from a direction perpendicular to the film surface.

[0105] <Overlay>

[0106] A capping layer 4 is disposed between the first ferromagnetic layer 1 and the first electrode 11. The capping layer 4 may also include a vertically magnetized induction layer (not shown) stacked on and in contact with the first ferromagnetic layer 1. The capping layer 4 prevents damage to the underlying layer during the manufacturing process and improves the crystallinity of the underlying layer during annealing. To irradiate the first ferromagnetic layer 1 with sufficient light, the thickness of the capping layer 4 is, for example, less than 10 nm.

[0107] <Insulation layer>

[0108] An insulating layer 16 is disposed between the lens 20 (first lens 201, second lens 202) and the second electrode 12 or the cover layer 13, forming a layer around the magnetic element 10 (first magnetic element 101, second magnetic element 102) and the first electrode 11. The insulating layer 16 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. For example, the insulating layer 16 is silicon oxide (SiO₂). x Silicon nitride (SiN) x Silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO2) x The insulating layer 16 allows light of the operating frequency band to pass through. Preferably, the insulating layer 16 allows more than 80% of the light in the operating wavelength region to pass through.

[0109] <Electrode 1>

[0110] The first electrode 11 is disposed, for example, on the lens 20 side of the magnetic element 10. Incident light irradiates the magnetic element 10 from the first electrode 11 side, irradiating at least the first ferromagnetic layer 1. The first electrode 11 is made of a conductive material. The first electrode 11 is, for example, a transparent electrode that is transmissive to light in the wavelength region of use. The first electrode 11 preferably transmits more than 80% of the light in the wavelength region of use. The first electrode 11 is, for example, an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium gallium zinc oxide (IGZO), etc. The first electrode 11 may also be configured to have multiple columnar metals in the transparent electrode material of these oxides.

[0111] The first electrode 11 does not necessarily have to be a transparent electrode material as described above. Light can also reach the first ferromagnetic layer 1 by using a metal material such as Au, Cu, or Al with a relatively thin film thickness. When a metal is used as the material of the first electrode 11, the film thickness of the first electrode 11 is, for example, 3 nm to 10 nm. Furthermore, the first electrode 11 may also have an anti-reflective film on the irradiated surface.

[0112] <Second Electrode>

[0113] The second electrode 12 is made of a conductive material. For example, the second electrode 12 is made of a metal such as Cu, Al, or Au. Ta or Ti may also be stacked on top of these metals. Alternatively, a Cu-Ta laminate, a Ta-Cu-Ti laminate, or a Ta-Cu-TaN laminate may be used. Furthermore, TiN or TaN may also be used as the second electrode 12. The film thickness of the second electrode 12 is, for example, 200 nm to 800 nm.

[0114] The second electrode 12 can also be transmissive to light irradiated onto the magnetic element 10. Similar to the first electrode 11, the material of the second electrode 12 can be a transparent electrode material made of oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). When light is irradiated from the side of the first electrode 11, some light may reach the second electrode 12 depending on the intensity of the light. In this case, by configuring the second electrode 12 as a transparent electrode material containing oxides, light reflection at the interface between the second electrode 12 and the layer adjacent to it can be suppressed compared to the case where the second electrode 12 is made of metal.

[0115] (Lens system)

[0116] like Figure 1 As shown, in the light detection element 101, lenses 20, namely the first lens 201 and the second lens 202, are disposed on the insulating layer 16. The first lens 201 and the second lens 202 are rectangular when viewed from above in the z-axis direction, but they can also be circular, polygonal, etc.

[0117] Figure 3 It means in Figure 1 The diagram illustrates the situation where incident light L incident on the light detection element 101 is focused by lens 20 and illuminates the magnetic element 10. Specifically, the light focused by the first lens 201 illuminates the first magnetic element 101. The light focused by the second lens 202 illuminates the second magnetic element 102.

[0118] In detail, the incident light L incident on the first lens 201 is converged by the first lens 201 to form a light spot centered at the focal point P1 at focal length f (also called the "pre-combination light spot"). The incident light L incident on the second lens 202 is converged by the second lens 202 to form a light spot centered at the focal point P2 at focal length f (also called the "pre-combination light spot"). The focal point P1 of the first lens 201 and the focal point P2 of the second lens 202 are separated by a distance G but close to each other. The pre-combination light spot at focal length f of the first lens 201 and the pre-combination light spot at focal length f of the second lens 202 partially overlap, producing light interference. The distance G is, for example, 1 μm, and the focal length f is, for example, 100 μm.

[0119] The focal points P1 of the first lens 201 and P2 of the second lens 202 exist at different points on the same plane, and the phases at the focal points P1 and P2 of the second lens 202 are different from each other. Therefore, in the overlapping portion of the light irradiated from the first lens 201 to the first magnetic element 101 and from the second lens 202 to the second magnetic element 102, the mutual enhancement of light intensity caused by light interference can be suppressed. Thus, when the light passing through the first lens 201 and the light passing through the second lens 202 are combined, the light spot S1 formed by the first lens 201 and the light spot S2 formed by the second lens 202 are separated, allowing strong light to be irradiated onto both the first magnetic element 101 and the second magnetic element 102. This improves the S / N ratio in the light detection of the photodetector 101.

[0120] In contrast, in the optical detection element 1001 of the related technology, such as Figure 13 and Figure 14 As shown, the light spot formed by the first lens 1201 and the light spot formed by the second lens 1202 partially overlap with each other in phase. The light in the overlapping portion interferes with each other and enhances the light intensity, forming a relatively large light spot S0. The light spot formed by the first lens 1201 and the light spot formed by the second lens 1202 cannot be separated. Therefore, compared with the first embodiment of the present invention, it is not possible to efficiently irradiate strong light onto the first magnetic element 101 and the second magnetic element 102.

[0121] Return to Figure 3 In the first embodiment of the present invention, the focal point P1 of the first lens 201 is configured to overlap with the first magnetic element 101 when viewed from the z-axis direction (plane perpendicular direction). This allows strong light to be irradiated onto the first magnetic element 101. Here, "plane perpendicular direction" refers to the direction perpendicular to the main surface of the lens, or the direction of the optical axis OA1.

[0122] The focal point P2 of the second lens 202 is configured so that it does not overlap with the first magnetic element 101 when viewed from the z-axis direction (the direction perpendicular to the plane or the direction of the optical axis OA2). As a result, the effect of light cancellation in the first magnetic element 101 can be reduced, thereby illuminating the first magnetic element 101 with strong light.

[0123] The focal point P2 of the second lens 202 can also be positioned within the (pre-combination) light spot on the plane (focal plane) where the focal point P1 of the first lens 201 is located. This shortens the distance G between the focal point P1 of the first lens 201 and the focal point P2 of the second lens 202. Consequently, the distance between the first magnetic element 101 and the second magnetic element 102 can be shortened, allowing for a high-density arrangement of the magnetic elements 10.

[0124] The first lens 201 and the second lens 202 can also be arranged on the same plane. This makes the manufacturing process easier.

[0125] The phase at the focal point P1 of the first lens 201 and the phase at the focal point P2 of the second lens 202 can also differ by 180 degrees. This improves the suppression of the mutual enhancement of light intensity caused by interference of light converged by the lenses, or the cancellation effect achieved by light interference.

[0126] At least one of the first lens 201 and the second lens 202 can also be a superlens 25 having a plurality of two-dimensionally arranged nanostructures 26. Therefore, it can be integrally formed with the magnetic element 10 using the same process, simplifying the manufacturing process. In this embodiment, the first lens 201 and the second lens 202 are both superlenses 25 having a plurality of two-dimensionally arranged nanostructures 26.

[0127] <Superlens>

[0128] The superlens 25 is a lens that utilizes a metasurface. The superlens 25 functions as a lens by controlling the phase distribution of light. Metasurfaces utilize planar structures to function as metamaterials. Metamaterials are media with a negative refractive index, or are designed to have a refractive index (dielectric constant, magnetic permeability) not found in nature. The superlens 25 can reduce the focal length, thus enabling the miniaturization of the photodetector element 101.

[0129] The superlens 25, for example, includes a dielectric that generates surface plasmon excitation. Additionally, the superlens 25 allows light in the operating frequency band to pass through. The superlens 25 may be made of at least one material selected from the group consisting of tantalum oxide, silicon nitride, titanium oxide, gallium oxide, silicon oxide, and aluminum oxide. The film thickness of the superlens 25, i.e., the thickness in the z-axis direction, is, for example, 100 nm to 10 μm.

[0130] The superlens 25 can control the phase distribution of light by adjusting the arrangement of multiple nanostructures 26, the size of each nanostructure 26, and the arrangement period of the multiple nanostructures 26. In addition, by adjusting the size and arrangement period of the nanostructures 26, the focal length of the superlens 25 can be made the same even if the wavelengths of the incident light are different.

[0131] Figure 4 This is a three-dimensional diagram showing the structure of the unit structure 28 that constitutes the superlens 25. For example... Figure 4 As shown, the unit structure 28 constituting the superlens 25 includes a base 27 and pillars 26A as nanostructures 26. The base 27 is a cuboid, with its upper surface being a rectangle of width W1 and depth W2. The width W1 is, for example, 450 nm, and the depth W2 is, for example, 450 nm. Pillars 26A are formed on the upper surface of the base 27 and are cylinders of diameter D and height H. The diameter D of pillars 26A is, for example, 40 nm to 360 nm, and the height H is, for example, 2 μm. The base 27 and pillars 26A are, for example, made of SiO2.

[0132] Figure 5 This is a graph showing the simulation results of the relationship between the diameter D of column 26A and the phase of the light passing through column 26A. The wavelength of the incident light is 520 nm. Figure 5 As shown, the diameter D of column 26A corresponds one-to-one with the phase of light; as the diameter D of column 26A increases, the phase of light decreases. Therefore, by changing the diameter D of column 26A, the phase of light passing through column 26A can be changed.

[0133] Figure 6 It means to Figure 1 A top view showing the results of a simulation of the structure of the superlens 25. (Example) Figure 6 As shown, the superlens 25 has a plurality of nanostructures 26 arranged in two dimensions on the xy plane. The plurality of nanostructures 26 can be arranged in a predetermined pattern on the base 27 within a region R, such as a semicircle, a circle, a ring, or a partially ring. Figure 6 The nanostructure 26 is a cylindrical column 26A, but it can also be a prism, cuboid, etc.

[0134] When the nanostructure 26 is a cylindrical column 26A, the superlens 25 can include various nanostructures 26 with different diameters D of the circular upper surface and cylindrical heights H. When the nanostructure 26 is a cuboid, the superlens 25 can change the arrangement angle of the nanostructures 26 according to their positions within region R. The arrangement angle refers to the angle formed by the long side of the rectangular upper surface of the nanostructure 26 relative to a reference axis (e.g., the x-axis direction). The distribution of the arrangement angles can, for example, exhibit the regularity of Pancharagh Berry geometric phase. The upper surface dimensions of the nanostructure 26 (diameter D of the circular upper surface in the case of a cylinder, length along the long side of the rectangular upper surface in the case of a cuboid, and width along the short side) and the spacing between adjacent nanostructures 26 are below the wavelength of the light used.

[0135] The area of ​​each of the multiple nanostructures 26 enclosed within a region R, such as a semicircle, circle, ring, or partially ring, when viewed from above along the z-axis, can vary, for example, depending on the distance from the center of region R. The area of ​​each of the multiple nanostructures 26 enclosed within region R when viewed from above along the z-axis can, for example, decrease as one moves outward from the center of region R. The center of region R, in the case of a circle or ring, refers to its center; in the case of a semicircle or partially ring, it refers to the center of the complete circle or ring containing them as a part.

[0136] In detail, such as Figure 6 As shown, the size (or diameter or area) of the plurality of nanostructures 26 in the first lens 201 when viewed from above along the z-axis (optical axis) decreases as the distance from the optical center O1 of the first lens 201 increases in each region defined by the discontinuity points of the following mathematical formula (1).

[0137]

[0138] The size (or diameter or area) of the multiple nanostructures 26 in the second lens 202 when viewed from the z-axis direction decreases as the distance from the optical center O2 of the second lens 202 increases in each region defined by the discontinuity points of the following mathematical formula (2).

[0139]

[0140] In the above mathematical formulas (1) and (2), r is the distance from the origin O, f is the focal length of the first lens 201 and the second lens 202, λ is the wavelength of the incident light, φ is the phase of the light, a1 is the distance from the origin O to the optical center O1 of the first lens 201, a2 is the distance from the origin O to the optical center O2 of the second lens 202, Δφ is the phase difference, and floor is the floor function that returns the largest integer below the parameter. The optical center O1 of the first lens 201 refers to the principal point of the first lens 201, which is the intersection of the optical axis passing through the focal point P1 of the first lens 201 and the principal surface of the first lens 201. The optical center O2 of the second lens 202 refers to the principal point of the second lens 202, which is the intersection of the optical axis passing through the focal point P2 of the second lens 202 and the principal surface of the second lens 202. The phase difference Δφ is, for example, π [rad].

[0141] The phase φ(r) of mathematical formula (1) repeats the following behavior: it monotonically decreases from 0 to -2π, and returns to 0 when it reaches -2π. That is, φ(r) becomes a discontinuity at r = B11, B12, B13, B14, ... where φ(r) = -2π. In the first lens 201, the regions R11, R12, R13, R14, ... between adjacent discontinuities are defined by the boundaries of the discontinuities B11, B12, B13, B14, ... Among them, region R11 is the region inside the circle centered on the optical center O1 and passing through the discontinuity B11. If we consider Figure 5 By determining the relationship between the phase and the cylinder diameter, the cylinder diameter at any location in each region can be determined.

[0142] That is, the size (or diameter or area) of the multiple nanostructures 26 (pillars 26A) in the first lens 201 when viewed from above along the z-axis decreases in each region R11, R12, R13, R14, ... defined by the discontinuity points B11, B12, B13, B14, ... of mathematical formula (1) as the distance from the optical center O1 of the first lens 201 increases. A lens that patterns multiple nanostructures 26 based on mathematical formula (1) is also called a "Type I" lens.

[0143] The phase φ(r) of mathematical formula (2) repeats the following behavior: it monotonically decreases from Δφ to Δφ-2π, and returns to Δφ when it reaches Δφ-2π. That is, in the second lens 202, the regions R21, R22, R23, R24, ... between adjacent discontinuities are also defined by the discontinuity points B21, B22, B23, B24, ... . Among them, region R21 is the region inside the circle centered on the optical center O2 and passing through the discontinuity point B21.

[0144] That is, the size (or diameter or area) of the multiple nanostructures 26 (pillars 26A) in the second lens 202 when viewed from the z-axis direction decreases in each region R21, R22, R23, R24, ... defined by the discontinuity points B21, B22, B23, B24, ... of mathematical formula (2) as the distance from the optical center O2 of the second lens 202 increases. A lens that patterns multiple nanostructures 26 based on mathematical formula (2) is also called a "Type II" lens.

[0145] In contrast, in the optical detection element 1001 of the related technology, such as Figure 15 As shown, the structure of the plurality of nanostructures 26 in the second lens 1202 is formed by flipping the plurality of nanostructures 26 in the first lens 1201 left and right. In this structure, the phase at the focal point P1 of the first lens 1201 and the phase at the focal point P2 of the second lens 1202 are the same, and they mutually enhance each other due to interference. Therefore, the light spot S0 of the synthesized light is larger than that of the first embodiment of the present invention.

[0146] Figure 7 (a) is a top view showing the simulation results of the light spot (intensity distribution) on the focal plane in the first embodiment of the present invention. Figure 7 (b) is a graph representing the simulation results. A first magnetic element 101 is positioned at x = -0.5 μm, and a second magnetic element 102 is positioned at x = +0.5 μm. The phase at the focal point P1 of the first lens 201 differs from the phase at the focal point P2 of the second lens 202 by 180 degrees. From... Figure 7 As can be seen from (a), light spots are formed separately for the first magnetic element 101 and the second magnetic element 102. Furthermore, according to... Figure 7 The light intensity at points A and B in (b), and the light intensity (|E|) illuminating each magnetic element. 2 ) is 558 [V 2 / m 2 ] .

[0147] In contrast, in the optical detection element 1001 of the related technology, such as Figure 16 As shown in (a), a light spot is formed for the first magnetic element 101 and the second magnetic element 102. Furthermore, according to... Figure 16 The light intensity at points C and D in (b), and the light intensity (|E|) illuminating the first magnetic element 101 and the second magnetic element 102. 2 ) is 345 [V 2 / m 2 ], it can be known that compared Figure 7 The first embodiment of the present invention shown is low.

[0148] As described above, in the optical detection element 1001 of the related art, the focal points P1 and P2 of adjacent lenses 1201 and 1202 have the same phase, making it impossible to separate the light spots for each magnetic element 10. That is, the light spots converged by the two lenses 1201 and 1202 are combined into a single light spot S0. In contrast, in the first embodiment of the present invention, the focal points P1 and P2 of adjacent lenses 201 and 202 have different phases, thus enabling the separation of light spots S1 and S2 for each magnetic element 101 and 102.

[0149] Furthermore, in the first embodiment, the light incident on the lens 20 may also be light that has passed through a polarizing filter. The light detection element 101 may also have a polarizing filter on the side of the lens 20 opposite to the magnetic element 10. If the light incident on the light detection element 101 is polarized light such as laser light, a polarizing filter may not be required.

[0150] <Variation Example>

[0151] Figure 12 It means Figure 1 A top view of the simulation results for a deformed example of the superlens 25. Figure 12 In the illustrated variation, the first lens 201 and the second lens 202 are formed in different regions of a single lens 20. Specifically, the first lens 201 and the second lens 202 are integrally formed, with multiple nanostructures 26 of the first lens 201 disposed in a region to the left of the center, and multiple nanostructures 26 of the second lens 202 disposed in a region to the right of the center. Thus, by integrally forming the lenses rather than forming them separately, the fabrication process of the first lens 201 and the second lens 202 becomes easier.

[0152] (Manufacturing process)

[0153] The photodetector 101 is obtained by sequentially fabricating the second electrode 12, the magnetic element 10, the first electrode 11, the insulating layer 16, and the lens 20.

[0154] The magnetic elements 10 (first magnetic element 101 and second magnetic element 102) are fabricated using layer stacking, annealing, and processing steps. First, a capping layer 13, a second ferromagnetic layer 2, a spacer layer 3, a first ferromagnetic layer 1, and a capping layer 4 are sequentially stacked on the second electrode 12. Each layer is formed into a film, for example, by sputtering.

[0155] Next, the laminated film is annealed. The annealing temperature is, for example, 250°C to 400°C. Afterward, the laminated film is processed into a stack 15 as a columnar body, for example, by photolithography and etching. In this embodiment, two stacks 15 are formed. The entire stack 15 or each layer can be mesa-shaped, cylindrical, prism-shaped, frustum-shaped, or truncated cone-shaped, etc. The shortest width of the stack 15 when viewed from the z-axis direction is, for example, 10 nm to 1000 nm.

[0156] Next, an insulating layer 16 is formed covering the sides of the laminate 15. The insulating layer 16 can also be laminated in multiple layers. Next, for example, by chemical mechanical polishing, the upper surface of the capping layer 4 is exposed from the insulating layer 16, and a first electrode layer is formed on the capping layer 4 and the insulating layer 16 by sputtering. For example, the first electrode layer is processed into a columnar or plate-shaped first electrode 11, such as a cylindrical shape, prism shape, frustum shape, or pyramidal shape, by photolithography and etching. Next, the insulating layer 16 is filled around the first electrode 11. Next, as needed, for example, by chemical mechanical polishing, the upper surface of the first electrode 11 is exposed from the insulating layer 16. Next, the insulating layer 16 is formed on the first electrode 11 and the insulating layer 16. The insulating layer 16 can also be laminated in multiple layers.

[0157] Next, lenses 20 (first lens 201 and second lens 202) are disposed on the insulating layer 16. Specifically, a substrate 27 is formed on the upper surface of the insulating layer 16, and a resist with a predetermined pattern formed by photolithography is formed on the upper surface of the substrate 27, followed by dry etching. By dry etching, a plurality of nanostructures 26 with a predetermined pattern are formed on the upper surface of the substrate 27, thereby forming a superlens 25. Through the above process, the photodetector element 101 is obtained. In this way, in the fabrication of the photodetector element 101, the magnetic element 10 and the superlens 25 can be continuously formed by a vacuum film deposition process.

[0158] Furthermore, the first lens 201 and the second lens 202 are superlenses, but they could also be microlenses, for example. When the lens 20 is a superlens, the first lens 201 and the second lens 202 can be integrally formed with it using the same process as the magnetic element 10, which simplifies the manufacturing process.

[0159] (Action description)

[0160] Next, the operation of the light detection element 101 in the first embodiment will be described.

[0161] like Figure 3As shown, incident light L incident on the light detection element 101 is focused by the lens 20 and irradiates the magnetic element 10, particularly the first ferromagnetic layer 1. When the intensity of the light irradiating the first ferromagnetic layer 1 changes, the magnetization M1 state of the first ferromagnetic layer 1 changes. The magnetization M1 state refers to, for example, the tilt angle of magnetization M1 relative to the z-axis direction, the magnitude of magnetization M1, etc.

[0162] For example, when the intensity of light illuminating the first ferromagnetic layer 1 increases, the magnetization M1 of the first ferromagnetic layer 1 tilts from its initial state due to the external energy generated by the light irradiation. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 1 in the state without light irradiation and the direction of the magnetization M1 in the state with light irradiation is, for example, greater than 0° and less than 90°. Alternatively, for example, when the intensity of light illuminating the first ferromagnetic layer 1 increases, the magnitude of the magnetization M1 decreases.

[0163] When the magnetization M1 of the first ferromagnetic layer 1 changes, the resistance value of the magnetic element 10 in the z-axis direction changes due to the magnetoresistance effect. When a certain current (sensing current) flows along the positive or negative z-axis of the magnetic element 10 using the first electrode 11 and the second electrode 12, an output voltage is obtained from the magnetic element 10. That is, when the magnetization M1 of the first ferromagnetic layer 1 changes, the output voltage from the magnetic element 10 also changes.

[0164] The intensity of light illuminating the first ferromagnetic layer 1 can take two values, for example: a first intensity and a second intensity. The first intensity can also be the case where the intensity of light illuminating the first ferromagnetic layer 1 is zero. Furthermore, the intensity of light illuminating the first ferromagnetic layer 1 can take multiple values ​​and can be simulated to change. When the intensity of the incident light takes multiple values, the output voltage of the magnetic element 10 also takes multiple values; when the light intensity is simulated to change, the output voltage of the magnetic element 10 can also be simulated to change. The differences in these output voltages (resistance values) can be read from the light detection element 101 as two values, multiple values, or simulated data.

[0165] In the state where the first ferromagnetic layer 1 is irradiated with light of the first intensity (referred to as the "initial state"), the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 can be in a parallel or antiparallel relationship, and the magnetization M1 and magnetization M2 can also be orthogonal.

[0166] With magnetization M1 and magnetization M2 initially parallel, a sensing current flows from the first ferromagnetic layer 1 toward the second ferromagnetic layer 2. By directing the sensing current in this direction, a spin-transfer torque in the same direction as the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, making magnetization M1 and magnetization M2 parallel in the initial state. Furthermore, by directing the sensing current in this direction, it is possible to prevent the magnetization M1 of the first ferromagnetic layer 1 from reversing during operation.

[0167] In the initial state, when magnetization M1 and magnetization M2 are antiparallel, the sensing current preferably flows from the second ferromagnetic layer 2 toward the first ferromagnetic layer 1. By directing the sensing current in this direction, a spin-transfer torque opposite to that of magnetization M2 in the second ferromagnetic layer 2 acts on magnetization M1 in the first ferromagnetic layer 1, so that magnetization M1 and magnetization M2 are antiparallel in the initial state.

[0168] When the intensity of the light irradiating the first ferromagnetic layer 1 returns to the first intensity, the spin-transfer torque is generated by sensing the current, or under the action of magnetic anisotropy, the magnetization M1 state of the first ferromagnetic layer 1 is restored, and the magnetic element 10 returns to the initial state.

[0169] Thus, the light detection element 101 of the first embodiment can convert changes in the intensity of the irradiated light into changes in the output voltage from the magnetic element 10. That is, the light detection element 101 can convert light into an electrical signal.

[0170] As described above, in the first embodiment of the present invention, in order to improve the sensitivity of the magnetic element 10, a plurality of magnetic elements 10 (a first magnetic element 101 and a second magnetic element 102) are arranged, and a plurality of lenses 20 are arranged to irradiate light onto the plurality of magnetic elements 10 respectively. Furthermore, the mutual enhancement of light intensity caused by light interference at the overlapping portions of light passing through, for example, adjacent lenses 20 (a first lens 201 and a second lens 202) is suppressed, or the light intensity is mutually weakened or mutually canceled by light interference. For this purpose, the phase at the focal point of each adjacent lens 20 differs from each other by, for example, 180 degrees. Thus, the light spots formed by the adjacent lenses 20 can be separated to irradiate the plurality of magnetic elements 10 with strong light, thereby improving the S / N ratio in the light detection of the light detection element 101.

[0171] [Second Embodiment]

[0172] Next, the second embodiment of the present invention will be described.

[0173] The second embodiment differs from the first embodiment in that it includes three or more magnetic elements and three or more lenses. Other structures are the same as in the first embodiment; the same reference numerals are used to label the same components, and descriptions are omitted where appropriate.

[0174] Figure 8 (a) is a top view showing the structure of the lens 30 of the light detection element 102 in the second embodiment. Figure 8 (b) is a top view showing the structure of magnetic element 10. For example... Figure 8 As shown, the photodetector 102 includes nine magnetic elements 101, 102, 103, 104, 105, 106, 107, 108, and 109, and nine lenses 301, 302, 303, 304, 305, 306, 307, 308, and 309. The number of magnetic elements 10 and the number of lenses 10 are both 9, but are not limited to this, and can be any integer greater than 3.

[0175] like Figure 3 As shown, magnetic elements 101, 102, 103, 104, 105, 106, 107, 108, and 109 each have a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3 sandwiched between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. Each lens 30 illuminates light onto its corresponding magnetic element 10. Specifically, lenses 301, 302, 303, 304, 305, 306, 307, 308, and 309 illuminate light onto magnetic elements 101, 102, 103, 104, 105, 106, 107, 108, and 109, respectively. Each lens 10 is rectangular, but can also be any shape such as circular or polygonal.

[0176] Magnetic elements 101, 102, 103, 104, 105, 106, 107, 108, and 109 are arranged in a lattice pattern, for example, but the arrangement pattern is not limited to this and can be arbitrarily selected. The spacing G between adjacent magnetic elements 10 is, for example, 1 μm. By arranging multiple magnetic elements 10 in a lattice pattern, the integration density of the magnetic elements 10 can be improved.

[0177] Lenses 301, 302, 303, 304, 305, 306, 307, 308, and 309 are also arranged in a grid pattern, but the arrangement pattern can be changed according to the arrangement pattern of the magnetic element 10. By arranging multiple lenses 30 in a grid pattern, the integration density of the lenses 30 can be improved.

[0178] At least one of the multiple lenses 30 n The focus P n When configured to be viewed from the z-axis direction (perpendicular to the plane), the same lens 30 n Corresponding magnetic element 10n Overlap (n is an integer where 1 ≤ n ≤ 9). Therefore, it is possible to... (The sentence is incomplete and requires more context to translate accurately.) n Irradiate with strong light.

[0179] In this embodiment, such as Figure 8 As shown in (b), when viewed from the z-axis direction, the focal point P1 of lens 301 overlaps with magnetic element 101, the focal point P2 of lens 302 overlaps with magnetic element 102, the focal point P3 of lens 303 overlaps with magnetic element 103, the focal point P4 of lens 304 overlaps with magnetic element 104, the focal point P5 of lens 305 overlaps with magnetic element 105, the focal point P6 of lens 306 overlaps with magnetic element 106, the focal point P7 of lens 307 overlaps with magnetic element 107, the focal point P8 of lens 308 overlaps with magnetic element 108, and the focal point P9 of lens 309 overlaps with magnetic element 109.

[0180] Figure 9 It means by Figure 8 A top view of the structure of the light spot formed by the lens 30 of the light detection element 102. (See attached image.) Figure 9 As shown, in the focal plane perpendicular to the z-axis, lens 301 forms a light spot S1 centered on focal point P1. Lens 302 forms a light spot S2 centered on focal point P2. Lens 303 forms a light spot S3 centered on focal point P3. Lens 304 forms a light spot S4 centered on focal point P4. Lens 305 forms a light spot S5 centered on focal point P5. Lens 306 forms a light spot S6 centered on focal point P6. Lens 307 forms a light spot S7 centered on focal point P7. Lens 308 forms a light spot S8 centered on focal point P8. Lens 309 forms a light spot S9 centered on focal point P9. Light spots S1 to S9 do not overlap with adjacent light spots.

[0181] As described above, the focal points of the multiple lenses 30 are located at different points on the same plane. The phase at the focal point of each of the multiple lenses 30 is different from the phase at the focal point of the adjacent lens. Therefore, the mutual enhancement of light intensity caused by interference of light irradiated from the multiple lenses 30 to the multiple magnetic elements 10 can be suppressed. Strong light can be efficiently irradiated onto each of the multiple magnetic elements 10. Therefore, the signal-to-noise ratio (S / N) in the light detection of the photodetector 102 can be improved.

[0182] In contrast, in the optical detection element 1002 of the related technology, such as Figure 17 and Figure 18As shown, the phase at the focal point of the plurality of lenses 1301, 1302, 1303, 1304, 1305, 1306, 1307, 1308, and 1309 is the same as the phase at the focal point of the adjacent lens 130. This results in mutual enhancement of light intensity caused by interference of light irradiated from the plurality of lenses 130 to the plurality of magnetic elements 10, forming a large light spot S01 as a whole. It is impossible to separate the light spot formed by each lens 130 from the light spot formed by its adjacent lens 130. Therefore, in the light detection element 1002, compared to the second embodiment of the present invention, it is not possible to efficiently irradiate the plurality of magnetic elements 10 with strong light individually.

[0183] In a second embodiment of the present invention, at least one of the plurality of lenses 30 n The focus P n It can also be configured so that the magnetic element 10 does not interact with the irradiated light when viewed from the z-axis direction (perpendicular to the plane). n The magnetic elements 10 are overlapped (n is an integer between 1 and 9). Therefore, the magnetic elements 10 can be reduced in the presence of irradiated light. n The light in the magnetic element 10 is canceled out, thereby irradiating the magnetic element 10 with strong light.

[0184] At least one of the multiple lenses 30 n The focus P n It can also be arranged in the light spot formed on the plane where the focal points of the other adjacent lenses 30 are located (n is an integer between 1 and 9). As a result, the distance G between the focal points of the two adjacent lenses 30 can be shortened. As a result, the distance between the magnetic elements 10 corresponding to the two lenses 30 can be shortened, and thus the magnetic elements 10 can be arranged at a high density.

[0185] At least two of the multiple lenses 30 are arranged on the same plane. This makes the manufacturing process easier.

[0186] The focal points of at least two adjacent lenses 30 are, for example, 180 degrees out of phase. This allows for the suppression of mutual reinforcement caused by interference of light converged by adjacent lenses 30.

[0187] At least two of the multiple lenses 30 can also be formed in different regions of a single lens. This makes the fabrication process of at least these two lenses 30 easier.

[0188] At least one of the multiple lenses 30 is a superlens having a plurality of nanostructures 26 arranged in two dimensions. Therefore, it can be integrally formed with the magnetic element 10 using the same process, simplifying the manufacturing process. In this embodiment, lenses 301, 302, 303, 304, 305, 306, 307, 308, and 309 are each a superlens having a plurality of nanostructures 26 arranged in two dimensions.

[0189] <Superlens>

[0190] Figure 10 It means Figure 8 (a) is a top view of the simulation results of the structure of lens 30, which is composed of a superlens. Figure 11 yes Figure 10 A magnified top view of a portion of the view.

[0191] Lenses 30 are classified into Group 1 and Group 2 by grouping adjacent lenses into different groups. Specifically, lenses 301, 303, 305, 307, and 309 belong to Group 1, while lenses 302, 304, 306, and 308 belong to Group 2.

[0192] like Figure 11 As shown, the size (or diameter or area) of multiple nanostructures 26 in one of the lenses (the lenses of the first group) in an adjacent lens 30, when viewed from above in the z-axis direction (optical axis direction), decreases as the distance from the optical center of the lens increases in each region defined by the discontinuity points of the following mathematical formula (1).

[0193]

[0194] The size (or diameter or area) of multiple nanostructures 26 (pillars 26A) in another lens (the second group of lenses) in adjacent lenses 30, when viewed from above along the z-axis, decreases as the distance from the optical center of the lens increases in each region defined by the discontinuity points of the following mathematical formula (2).

[0195]

[0196] In the above mathematical formulas (1) and (2), r is the distance from the origin O, f is the focal length of the lens, λ is the wavelength of the incident light, φ is the phase, a1 is the distance from the origin O to the optical center of one lens, a2 is the distance from the origin to the optical center of another lens, Δφ is the phase difference, and floor is the floor function that returns the largest integer below the parameter. Lens 30 n Optical center O n This refers to lens 30. n The main point is through lens 30 nThe focus P n Optical axis and lens 30 n The intersection points between the principal planes (n is an integer greater than 1 and less than 9). The phase difference Δφ is, for example, π [rad].

[0197] The phase φ(r) of mathematical formula (1) repeats the following behavior: it monotonically decreases from 0 to -2π, and returns to 0 when it reaches -2π. That is, φ(r) becomes a discontinuity at r = B51, B52, B53... where φ(r) = -2π. In lens 305, the regions R51, R52, ... between adjacent discontinuities are defined by the boundaries of the discontinuities B51, B52, ... Among them, region R51 is the region inside the circle centered on the optical center O5 and passing through the discontinuity B51. If we consider Figure 5 By determining the relationship between the phase and the cylinder diameter, the cylinder diameter at any location in each region can be determined.

[0198] That is, for example, the size (or diameter or area) of the multiple nanostructures 26 (pillars 26A) in lens 305 when viewed from above along the z-axis decreases in each region R51, R52, ... defined by the discontinuity points B51, B52, ... of mathematical formula (1) as the distance from the optical center O5 of lens 305 increases. The same applies to the other lenses 301, 303, 307, 309 in Group 1. Lenses that pattern multiple nanostructures 26 based on mathematical formula (1) are also called "Type I" lenses.

[0199] The phase φ(r) of mathematical formula (2) repeats the following behavior: it monotonically decreases from Δφ to Δφ-2π, and returns to Δφ when it reaches Δφ-2π. That is, for example, for lens 306, the regions R61, R62, R63, ... between adjacent discontinuities are also defined by the discontinuity points B61, B62, B63, ... . Among them, region R61 is the region inside the circle centered on the optical center O6 and passing through the discontinuity point B61.

[0200] That is, the size (or diameter or area) of the multiple nanostructures 26 (pillars 26A) in lens 306 when viewed from the z-axis direction decreases in each region R61, R62, R63, ... defined by the discontinuity points B61, B62, B63, ... of mathematical formula (2) as the distance from the optical center O6 of lens 306 increases. The other lenses 302, 304, and 308 in the second group are the same. Lenses that pattern multiple nanostructures 26 based on mathematical formula (2) are also called "Type II" lenses.

[0201] In addition, such as Figure 11As shown, the optical centers of lenses 301, 302, 303, 304, 305, 306, 307, 308, and 309 are O1, O2, O3, O4, O5, O6, O7, O8, and O9, respectively, and are set corresponding to focal points P1, P2, P3, P4, P5, P6, P7, P8, and P9.

[0202] The manufacturing process of the photodetector 102 is the same as that in the first embodiment.

[0203] As described above, in the second embodiment of the present invention, in order to improve the sensitivity of the magnetic element 10, three or more magnetic elements 10 (magnetic elements 101 to 109) and the same number of lenses 30 (lenses 301 to 309) are arranged in a high-density lattice pattern. Furthermore, the mutual enhancement of light intensity caused by light interference at the overlapping portions of light passing through, for example, adjacent lenses 30 is suppressed, or the light intensity is mutually weakened or mutually canceled by light interference. For this purpose, the phase at the focal point of each adjacent lens 30 differs from each other by, for example, 180 degrees. Thus, the light spots formed by adjacent lenses 30 can be separated to irradiate the multiple magnetic elements 10 with strong light, thereby improving the signal-to-noise ratio (S / N) in the light detection of the light detection element 102.

[0204] [Application Example]

[0205] The light detection elements 101 and 102 in the first and second embodiments can be applied, for example, to light sensors such as image sensors that have multiple light detection elements arranged in one or two dimensions. Such light sensors can be used in information terminal devices such as smartphones, tablets, personal computers, and digital cameras.

[0206] Furthermore, the optical detection elements 101 and 102 of the first and second embodiments can be applied, for example, to the photoelectric conversion elements of the receiving devices in transceivers that transmit and receive optical signals such as lasers in a communication system where multiple transceivers are connected by optical fibers. The aforementioned communication system can also be, for example, a communication system for short- and medium-distance communication within and between data centers, or long-distance communication between cities. The transceivers are, for example, installed within a data center.

[0207] Alternatively, the aforementioned communication system can also be a wireless communication system for transmitting and receiving optical signals, such as near-infrared light, between portable terminals such as smartphones and tablets. Furthermore, the aforementioned communication system can also be a wireless communication system for transmitting and receiving optical signals, such as near-infrared light, between a portable terminal and an information processing device such as a personal computer.

[0208] This invention is not limited to the embodiments described above, and various modifications and alterations can be made within the scope of the spirit of the invention as described in the claims.

[0209] As described above, the present invention has the effect of suppressing the mutual enhancement of light intensity caused by the interference of light passing through adjacent lenses even when multiple lenses are used, thereby achieving excellent signal-to-noise ratio in optical detection, which is useful for the optical detection element as a whole.

Claims

1. A photodetector element, wherein, This optical detection element has the following features: The first magnetic element and the second magnetic element respectively have a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; The first lens, which is composed of a superlens having multiple nanostructures arranged in a two-dimensional pattern, irradiates incident light toward the first magnetic element; and The second lens, which is composed of a superlens with multiple nanostructures arranged in a two-dimensional pattern, irradiates the incident light toward the second magnetic element. The size of the plurality of nanostructures in the first lens, viewed from above along the optical axis of the first lens, decreases as the distance from the optical center of the first lens increases in each region defined by the discontinuity points of mathematical formula (1). The size of the plurality of nanostructures in the second lens, viewed from the optical axis of the second lens, decreases as the distance from the optical center of the second lens increases in each region defined by the discontinuity point of mathematical formula (2). In the above mathematical formulas (1) and (2), r is the distance from the origin, f is the focal length of the first lens and the second lens, λ is the wavelength of the incident light, φ is the phase, a1 is the distance from the origin to the optical center of the first lens, a2 is the distance from the origin to the optical center of the second lens, Δφ is the phase difference, and floor is the floor function.

2. The optical detection element according to claim 1, wherein, The focal point of the first lens is configured to overlap with the first magnetic element when viewed from the optical axis direction of the first lens.

3. The optical detection element according to claim 1, wherein, The focal point of the second lens is configured so that it does not overlap with the first magnetic element when viewed from the optical axis direction of the second lens.

4. The optical detection element according to claim 1, wherein, The focal point of the second lens is positioned in a light spot formed on a plane perpendicular to the optical axis of the first lens, where the focal point of the first lens is located.

5. The optical detection element according to claim 1, wherein, The first lens and the second lens are arranged on the same plane.

6. The optical detection element according to claim 1, wherein, The focal points of the first lens and the second lens are 180 degrees out of phase.

7. The optical detection element according to claim 1, wherein, The first lens and the second lens are formed in different regions of a single lens.

8. A photodetector element, wherein, This optical detection element has the following features: Multiple magnetic elements, each having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; as well as Multiple lenses, each illuminating a corresponding magnetic element among the multiple magnetic elements, The multiple lenses are each composed of a superlens having multiple nanostructures arranged in a two-dimensional pattern. The size of the plurality of nanostructures in one of the adjacent lenses, viewed from the optical axis of the lens, decreases as the distance from the optical center of the lens increases in each region defined by the discontinuity point of mathematical formula (1). The size of the plurality of nanostructures in one of the adjacent lenses, viewed from the optical axis of the other lens, decreases as the distance from the optical center of the other lens increases in each region defined by the discontinuity point of mathematical formula (2). In the above mathematical formulas (1) and (2), r is the distance from the origin, f is the focal length of the adjacent lens, λ is the wavelength of the incident light, φ is the phase, a1 is the distance from the origin to the optical center of one lens, a2 is the distance from the origin to the optical center of the other lens, Δφ is the phase difference, and floor is the floor function.

9. The optical detection element according to claim 8, wherein, The plurality of magnetic elements are arranged in a lattice pattern.

10. The optical detection element according to claim 8, wherein, The multiple lenses are arranged in a grid pattern.

11. The optical detection element according to claim 8, wherein, The focal point of at least one of the plurality of lenses is configured to overlap with the magnetic element corresponding to the lens when viewed from the optical axis direction of the lens.

12. The optical detection element according to claim 8, wherein, The focal point of at least one of the plurality of lenses is configured such that, when viewed from the optical axis of the lens, it does not overlap with any magnetic element other than the magnetic element illuminated by the lens.

13. The optical detection element according to claim 8, wherein, The focal point of at least one of the plurality of lenses is disposed in a light spot formed on a plane perpendicular to the optical axis of the adjacent other lenses, where the focal points of the other lenses are located.

14. The optical detection element according to claim 8, wherein, At least two of the plurality of lenses are arranged on the same plane.

15. The optical detection element according to claim 8, wherein, The focal points of at least two adjacent lenses in the plurality of lenses are 180 degrees out of phase.

16. The optical detection element according to claim 8, wherein, At least two of the plurality of lenses are formed in different regions of a single lens.

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