Optical device, reception apparatus, transmission / reception apparatus, communication system, terminal apparatus, and optical system

Abstract

The invention provides an optical device, a reception apparatus, a transmission / reception apparatus, a communication system, a terminal apparatus, and an optical system. An optical device includes a waveguide, a magnetic element, a first reflector, and a second reflector. The waveguide has a core for light transmission and a cladding covering the core. The first reflector is located forward of a traveling direction of light transmitted within the core. The second reflector is disposed at a position where the second reflector is irradiated with the light reflected by the first reflector and is capable of irradiating the magnetic element with the light. The magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer between the first ferromagnetic layer and the second ferromagnetic layer. The magnetic element is irradiated with light from a side or above.

Description

Technical Field

[0001] The present invention relates to an optical device, a receiving device, a transmitting and receiving device, a communication system, a terminal device and an optical system.

[0002] This application claims priority based on Japanese Patent Application No. 2024-042016 filed in Japan on March 18, 2024, the contents of which are incorporated herein. Background Art

[0003] Photoelectric conversion elements are used in various applications.

[0004] For example, Patent Document 1 describes a receiving device that receives an optical signal using a photodiode. The photodiode is, for example, a pn junction diode using a pn junction of a semiconductor, and converts light into an electrical signal.

[0005] Furthermore, a new optical device using a magnetic element is disclosed in, for example, Patent Document 2. When irradiated with light, the magnetic state of the magnetic element changes, and the resistance value of the magnetic element changes.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-292107

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2022-155468 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] Patent Document 2 discloses irradiating light from below a magnetic element using a reflector. However, in this case, sufficient sensitivity of the optical device may not be achieved.

[0012] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a highly sensitive optical device, a receiving device, a transmitting and receiving device, a communication system, a terminal device, and an optical system.

[0013] Solutions for solving problems

[0014] In order to solve the above problems, the following solutions are provided.

[0015] The optical device involved in this embodiment includes a waveguide, a magnetic element, a first reflector, and a second reflector. The waveguide has a core for transmitting light and a cladding covering the core. The first reflector is located in front of the direction of travel of light transmitted within the core. The second reflector is positioned to be irradiated with light reflected from the first reflector and capable of irradiating light toward the magnetic element. The magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first and second ferromagnetic layers. The magnetic element is irradiated with light from the side or from above.

[0016] Effects of the Invention

[0017] The optical device, receiving device, transmitting / receiving device, communication system, terminal device, and optical system according to the above-described embodiment have high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a perspective view of the optical device according to the first embodiment.

[0019] Figure 2 It is a cross-sectional view of the optical device according to the first embodiment.

[0020] Figure 3 It is a plan view of the optical device according to the first embodiment.

[0021] Figure 4 It is a cross-sectional view of the vicinity of the magnetic element of the optical device according to the first embodiment.

[0022] Figure 5 It is a diagram for explaining an operation example of the magnetic element according to the first embodiment.

[0023] Figure 6 It is a diagram for explaining an operation example of the magnetic element according to the first embodiment.

[0024] Figure 7 It is a cross-sectional view of an optical device according to a first modification.

[0025] Figure 8 It is a cross-sectional view of an optical device according to a second modification.

[0026] Figure 9 It is a cross-sectional view showing a first example of a connection state of a magnetic element in an optical device according to a third modification.

[0027] Figure 10 It is a cross-sectional view showing a second example of the connection state of the magnetic element in the optical device according to the third modification.

[0028] Figure 11Schematic diagram of an optical element according to the first application example.

[0029] Figure 12 This is a conceptual diagram of an optical system using the optical element according to the first application example.

[0030] Figure 13 It is a schematic diagram of a transmitting and receiving device involved in the second application example.

[0031] Figure 14 This is a conceptual diagram of an example of a communication system.

[0032] Figure 15 This is a conceptual diagram of another example of a communication system. DETAILED DESCRIPTION

[0033] The following describes the embodiments in detail with reference to the accompanying drawings as appropriate. The drawings used in the following description may sometimes enlarge characteristic portions for convenience to facilitate understanding of the characteristics, and the dimensional ratios of the various components may differ from actual values. The materials, dimensions, etc. illustrated in the following description are merely examples, and the present invention is not limited to these materials, dimensions, etc., and can be implemented with appropriate modifications within the scope of achieving the effects of the present invention.

[0034] Define the direction. A direction within the surface of the extended surface of the substrate is set as the X direction, and the direction within the surface perpendicular to the X direction is set as the Y direction. For example, the direction in which the core 11 extends near the output end of the core 11 is set as the X direction. In addition, the direction perpendicular to the substrate is set as the Z direction. The Z direction is an example of the stacking direction of the magnetic element 20. Below, the +Z direction is sometimes expressed as "up" and the -Z direction is expressed as "down". The +Z direction is the direction from the core toward the magnetic element. Up and down are not necessarily consistent with the direction in which gravity is applied.

[0035] "First Implementation Method"

[0036] Figure 1 It is a perspective view of the optical device 100 according to the first embodiment. Figure 2 It is a cross-sectional view of the optical device 100 according to the first embodiment. Figure 2 It is an XZ cross section passing through the center of the core 11 in the Y direction. Figure 3 FIG is a top view of the optical device 100 according to the first embodiment. Figure 1 、 Figure 3 In FIG, the cladding 12 and the substrate 50 are omitted.

[0037] The optical device 100 includes, for example, a waveguide 10 , a magnetic element 20 , a terminal unit 30 , a first reflector 41 , a second reflector 42 , and a substrate 50 .

[0038] The waveguide 10, the magnetic element 20, the terminal unit 30, the first reflector 41, and the second reflector 42 are formed on a substrate 50. The substrate 50 is, for example, a semiconductor substrate, alumina, sapphire, or the like.

[0039] The waveguide 10 is a structure that forms a path for light transmission. The light herein is not limited to visible light but also includes infrared light with a longer wavelength than visible light and ultraviolet light with a shorter wavelength than visible light. For example, the wavelength of visible light is 380 nm or greater and less than 800 nm. For example, the wavelength of infrared light is 800 nm or greater and less than 1 mm. For example, the wavelength of ultraviolet light is 200 nm or greater and less than 380 nm. The light transmitted through the waveguide 10 is, for example, laser light.

[0040] The waveguide 10 includes, for example, a core 11 and a cladding 12. The waveguide 10 totally reflects light due to the difference in refractive index between the core 11 and the cladding 12. Light propagates within the core 11. Light from, for example, a laser diode is irradiated onto the first end of the core 11. The second end of the core 11 faces the first reflector 41. The cladding 12 surrounds the core 11.

[0041] The core 11 contains, for example, lithium niobate as a main component. Some elements of the lithium niobate may be replaced by other elements. The cladding 12 may be, for example, SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, etc., or a mixture thereof. The material of the core 11 and the material of the cladding 12 are not limited to this example. For example, the core 11 may be obtained by adding germanium oxide to silicon or silicon oxide, and the cladding 12 may be silicon oxide. In addition, for example, the core 11 may be tantalum oxide (Ta2O5), and the cladding 12 may be silicon oxide or aluminum oxide.

[0042] The magnetic element 20 is located within the cladding 12. The magnetic element 20 may be located in the same layer as the core 11 in the Z direction, or in a different layer from the core 11 in the Z direction. The magnetic element 20 is located so that light transmitted through the core 11 and reflected by the second reflector 42 hits the magnetic element 20 from the side or above. For example, the magnetic element 20 is located in front of the first reflector 41 and the second reflector 42 in the direction of travel of the light L transmitted through the core 11 (e.g., the X direction).

[0043] The magnetic element 20 converts the state of the irradiated light or the change in the state into an electrical signal. For example, the magnetic element 20 is irradiated with light having a wavelength of 400 nm to 1500 nm.

[0044] The magnetic element 20 generates a voltage when irradiated with light. As the state of the irradiated light changes, the Z-direction resistance of the magnetic element 20 changes accordingly. As the state of the light irradiating the magnetic element 20 changes, the output voltage from the magnetic element 20 changes accordingly.

[0045] Figure 4 1 is a cross-sectional view of the vicinity of the magnetic element 20 of the optical device 100 according to the first embodiment. The magnetic element 20 includes a laminate 21 , a first electrode 22 , and a second electrode 23 .

[0046] The first electrode 22 is located on the substrate 50 side of the stack 21. The first electrode 22 is conductive. The first electrode 22 is made of, for example, a metal such as Cu, Al, Au, Ta, or Ti. Ta and Ti may also be stacked on and under these metals. The first electrode 22 may also use a stacked film of Cu and Ta, a stacked film of Ta, Cu, and Ti, or a stacked film of Ta, Cu, and TaN. In addition, the first electrode 22 may also be TiN or TaN. If the first electrode 22 contains these materials, the crystallinity of the stack 21 becomes higher. The crystallinity of the stack 21 contributes to the resistance variation amplitude of the stack 21 in the Z direction, thereby affecting the sensitivity of the optical device 100.

[0047] The first electrode 22 preferably contains a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten, for example. The first electrode 22 may be a single-layer film of any one of ruthenium, molybdenum, and tungsten, or a laminated film having at least one layer of any one of ruthenium, molybdenum, and tungsten. Ruthenium, molybdenum, and tungsten have high melting points (above 2000°C) and excellent heat resistance. Even after heat treatment to crystallize the laminate 21 or heat treatment during semiconductor processing, the first electrode 22 containing these elements is less susceptible to degradation.

[0048] The second electrode 23 faces the first electrode 22. The first electrode 22 and the second electrode 23 sandwich the stack 21 in the Z direction. The second electrode 23 is made of a conductive material. The second electrode 23 is made of a metal such as Cu, Al or Au. The second electrode 23 can also be stacked with Ta or Ti on and under these metals. In addition, as the second electrode 23, a stacked film of Cu and Ta, a stacked film of Ta, Cu and Ti, or a stacked film of Ta, Cu and TaN can also be used. In addition, as the second electrode 23, TiN or TaN can also be used. In the case where both the first electrode 22 and the second electrode 23 are not transparent to light in the wavelength range used, light is irradiated from the side of the magnetic element 20.

[0049] Furthermore, the second electrode 23 is preferably a transparent electrode that is transmissive to light within the operating wavelength range. For example, the second electrode 23 preferably transmits at least 80% of light within the operating wavelength range. Examples of the second electrode 23 include oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO). The second electrode 23 may also be a metal film having a thickness of approximately 3 nm to 10 nm. If the second electrode 23 is a transparent electrode, light can be irradiated onto the stack 21 from above, enabling efficient irradiation of the stack 21.

[0050] The laminate 21 is sandwiched between a first electrode 22 and a second electrode 23. The laminate 21 includes, for example, a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a spacer layer 3. The spacer layer 3 is located between the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The laminate 21 may also include other layers in addition to these layers. For example, the laminate 21 may include a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a perpendicular magnetization inducing layer 8, and a cap layer 9.

[0051] The magnetic element 20 is a magnetic element comprising a ferromagnetic material. For example, if the spacer layer 3 is made of an insulator, the magnetic element 20 comprises a magnetic tunnel junction (MTJ) formed by the first ferromagnetic layer 1, the spacer layer 3, and the second ferromagnetic layer 2. Such an element is called an MTJ element. In this case, the magnetic element 20 can exhibit the tunnel magnetoresistance effect (TMR). If the spacer layer 3 is made of metal, the magnetic element 20 can exhibit the giant magnetoresistance effect (GMR). Such an element is called a GMR element. Depending on the material of the spacer layer 3, the magnetic element 20 is sometimes referred to as an MTJ element, a GMR element, or other term, but is also generally referred to as a magnetoresistance effect element. The Z-direction resistance of the magnetic element 20 (the resistance when current flows in the Z direction) changes according to the relative change between the magnetization states of the first ferromagnetic layer 1 and the second ferromagnetic layer 2.

[0052] The first ferromagnetic layer 1 is a light-detecting layer whose magnetization state changes when exposed to 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 predetermined external energy is applied. Examples of the predetermined external energy include externally irradiated light, a current flowing in the Z direction of the magnetic element 20, and an external magnetic field. The magnetization state of the first ferromagnetic layer 1 changes depending on the intensity of the light irradiating the first ferromagnetic layer 1 (the light irradiating the magnetic element 20).

[0053] The first ferromagnetic layer 1 includes a ferromagnetic material. The first ferromagnetic layer 1 contains, for example, at least one of the magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 1 may also contain elements such as B, Mg, Hf, and Gd in addition to the magnetic elements mentioned above. The first ferromagnetic layer 1 may also be, for example, an alloy containing a magnetic element and a non-magnetic element. The first ferromagnetic layer 1 may also be composed of multiple layers. The first ferromagnetic layer 1 may be, for example, a CoFeB alloy, a laminated body obtained by sandwiching a CoFeB alloy layer with Fe layers, or a laminated body obtained by sandwiching a CoFeB alloy layer with CoFe layers. Generally speaking, "ferromagnetism" includes "ferrimagnetism." The first ferromagnetic layer 1 may also exhibit ferrimagnetism. On the other hand, the first ferromagnetic layer 1 may also exhibit non-ferrimagnetic ferromagnetism. For example, the CoFeB alloy exhibits non-ferrimagnetic ferromagnetism.

[0054] The first ferromagnetic layer 1 may be an in-plane magnetization film having an easy magnetization axis in the film plane direction (in any direction in the XY plane) or a perpendicular magnetization film having an easy magnetization axis in the direction perpendicular to the film plane (in the Z direction).

[0055] The thickness of the first ferromagnetic layer 1 is, for example, not less than 1 nm and not more than 5 nm. The thickness of the first ferromagnetic layer 1 is preferably, for example, not less than 1 nm and not more than 2 nm. If the first ferromagnetic layer 1 is a perpendicular magnetization film, a thinner thickness increases the effect of the perpendicular magnetic anisotropy exerted by the layers above and below the first ferromagnetic layer 1, thereby increasing the perpendicular magnetic anisotropy of the first ferromagnetic layer 1. In other words, a higher perpendicular magnetic anisotropy of the first ferromagnetic layer 1 strengthens the force exerted by the magnetization M1 in the Z direction. On the other hand, a thicker thickness reduces the effect of the perpendicular magnetic anisotropy exerted by the layers above and below the first ferromagnetic layer 1, thereby reducing the perpendicular magnetic anisotropy of the first ferromagnetic layer 1.

[0056] As the thickness of the first ferromagnetic layer 1 decreases, its volume as a ferromagnetic material decreases. As 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 responds to external energy is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 1. In other words, as the product of the magnetic anisotropy and volume of the first ferromagnetic layer 1 decreases, its reactivity to light improves. Based on this perspective, to improve its reactivity to light, it is preferable to reduce the volume of the first ferromagnetic layer 1 while appropriately designing its magnetic anisotropy.

[0057] If the thickness of the first ferromagnetic layer 1 is greater than 2 nm, an insertion layer composed of, for example, Mo or W may be provided within the first ferromagnetic layer 1. Specifically, a stack of a ferromagnetic layer, an insertion layer, and a ferromagnetic layer stacked in this order in the Z direction may be used as the first ferromagnetic layer 1. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer enhances the perpendicular magnetic anisotropy of the entire first ferromagnetic layer 1. The thickness of the insertion layer is, for example, 0.1 nm to 1.0 nm.

[0058] The second ferromagnetic layer 2 is a magnetization-fixed layer. The magnetization-fixed layer is composed of a magnetic material whose magnetization M2 is less likely to change when a predetermined external energy is applied, compared to the magnetization-free layer. For example, when a predetermined external energy is applied, the magnetization direction of the magnetization-fixed layer is less likely to change compared to the magnetization-free layer. Alternatively, when a predetermined external energy is applied, the magnetization magnitude of the magnetization of the magnetization-fixed layer is less likely to change compared to the magnetization-free layer. The coercive force of the second ferromagnetic layer 2 is, for example, greater than that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 has 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.

[0059] 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 may also be a multilayer film formed by alternating layers of Co (0.4 nm to 1.0 nm thick) and Pt (0.4 nm to 1.0 nm thick) several times. The second ferromagnetic layer 2 may also be a laminate formed by sequentially stacking Co (0.4 nm to 1.0 nm thick), Mo (0.1 nm to 0.5 nm thick), a CoFeB alloy (0.3 nm to 1.0 nm thick), and Fe (0.3 nm to 1.0 nm thick).

[0060] The magnetization M2 of the second ferromagnetic layer 2 can also be magnetically coupled to the magnetization M6 of the third ferromagnetic layer 6 via the magnetic coupling layer 7. In this case, the layer formed by the second ferromagnetic layer 2, the magnetic coupling layer 7, and the third ferromagnetic layer 6 may be referred to as a magnetization pinned layer. The details of the magnetic coupling layer 7 and the third ferromagnetic layer 6 will be described later.

[0061] exist Figure 4 , a bottom pin structure is shown in which the second ferromagnetic layer 2 serving as a magnetization fixing layer is located closer to the substrate 50 than the first ferromagnetic layer 1, but the second ferromagnetic layer 2 serving as a magnetization fixing layer may also be a top pin structure located farther from the substrate 50 than the first ferromagnetic layer 1.

[0062] Spacer layer 3 is disposed between first ferromagnetic layer 1 and second ferromagnetic layer 2. Spacer layer 3 is formed from a conductor, an insulator, or a semiconductor, or from an insulator containing a conductive point. Spacer layer 3 is, for example, a nonmagnetic layer. The thickness of spacer layer 3 can be adjusted based on the orientation of the magnetization of first ferromagnetic layer 1 and the magnetization of second ferromagnetic layer 2 in the initial state, as described later.

[0063] When spacer layer 3 is composed of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used as the material for spacer layer 3. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. By adjusting the thickness of spacer layer 3 to achieve a high TMR effect between first ferromagnetic layer 1 and second ferromagnetic layer 2, a high magnetoresistance change rate can be achieved. To effectively utilize the TMR effect, the thickness of spacer layer 3 can be set to approximately 0.5 nm to 5.0 nm, or alternatively, to approximately 1.0 nm to 2.5 nm.

[0064] When the spacer layer 3 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. To effectively utilize the GMR effect, the thickness of the spacer layer 3 can be set to approximately 0.5 nm to 5.0 nm, or approximately 2.0 nm to 3.0 nm.

[0065] 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 ITO can be used. In this case, the thickness of the spacer layer 3 can also be set to about 1.0 nm to 4.0 nm.

[0066] When using a layer containing conductive energization points within a non-magnetic insulator as spacer layer 3, a structure can also be employed in which a non-magnetic insulator composed of aluminum oxide or magnesium oxide contains energization points composed of a non-magnetic conductor such as Cu, Au, or Al. Alternatively, the conductor can be formed using magnetic elements such as Co, Fe, or Ni. In this case, the thickness of spacer layer 3 can be approximately 1.0 nm to 2.5 nm. For example, the energization points are columnar structures with a diameter of at least 1 nm and no more than 5 nm when viewed perpendicular to the film surface.

[0067] The third ferromagnetic layer 6 is magnetically coupled to the second ferromagnetic layer 2 . The magnetic coupling is, for example, antiferromagnetic coupling and occurs through RKKY interaction. The material constituting the third ferromagnetic layer 6 is, for example, the same as the material constituting the first ferromagnetic layer 1 .

[0068] The magnetic coupling layer 7 is located between the second ferromagnetic layer 2 and the third ferromagnetic layer 6. The magnetic coupling layer 7 is made of Ru, Ir, etc., for example.

[0069] The buffer layer 4 is a layer for mitigating the lattice mismatch between different crystals. The buffer layer 4 is, for example, a metal containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cu. More specifically, the buffer layer 4 is, for example, Ta (single element), NiCr alloy, TaN (tantalum nitride), or CuN (copper nitride). The film thickness of the buffer layer 4 is, for example, greater than 1 nm and less than 5 nm. The buffer layer 4 is, for example, amorphous. The buffer layer 4 is, for example, located between the seed layer 5 and the second electrode 23 and in contact with the second electrode 23. The buffer layer 4 is used to suppress the influence of the crystal structure of the second electrode 23 on the crystal structure of the magnetic element 20.

[0070] Seed layer 5 is used to improve the crystallinity of layers stacked on seed layer 5. Seed layer 5 is located, for example, between buffer layer 4 and third ferromagnetic layer 6, and on buffer layer 4. Seed layer 5 can be made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of seed layer 5 is, for example, not less than 1 nm and not more than 5 nm.

[0071] The capping layer 9 is located between the first ferromagnetic layer 1 and the first electrode 22. The capping layer 9 may also include a perpendicular magnetization inducing layer 8 stacked on and in contact with the first ferromagnetic layer 1. The capping layer 9 is used to prevent damage to the underlying layer during the process and to improve the crystallinity of the underlying layer during annealing.

[0072] Perpendicular magnetization inducing layer 8 is used to induce perpendicular magnetic anisotropy in first ferromagnetic layer 1. Perpendicular magnetization inducing layer 8 can be made of, for example, magnesium oxide, W, Ta, or Mo. If magnesium oxide is used, it is preferably oxygen-deficient to improve conductivity. The thickness of perpendicular magnetization inducing layer 8 is, for example, not less than 0.5 nm and not more than 5.0 nm.

[0073] The terminal unit 30 includes, for example, a first terminal 31, a second terminal 32, a third terminal 33, a fourth terminal 34, and a plurality of through-hole wirings 35. The first terminal 31, the second terminal 32, the third terminal 33, and the fourth terminal 34 are exposed on the cladding 12. The first terminal 31 and the fourth terminal 34 are electrically connected to the first electrode 22 via the through-hole wirings 35. The second terminal 32 and the third terminal 33 are electrically connected to the second electrode 23 via the through-hole wirings 35. Current or voltage is input to the first terminal 31, and the second terminal 32 is connected to a reference potential. A signal is output from the third terminal 33, and the fourth terminal 34 is connected to a reference potential. The first terminal 31, the second terminal 32, the third terminal 33, the fourth terminal 34, and the plurality of through-hole wirings 35 are made of a conductive material.

[0074] The first reflector 41 and the second reflector 42 are used to reflect the light output from the core 11 . The first reflector 41 and the second reflector 42 are, for example, mirrors. The first reflector 41 and the second reflector 42 are, for example, located within the cladding 12 .

[0075] The light output from the core 11 is reflected by the first reflector 41 and the second reflector 42 in that order, thereby being irradiated onto the magnetic element 20. It is preferred that the light irradiate the magnetic element 20 from a direction tilted at least 45° relative to the upper surface of the magnetic element 20. In other words, the irradiation angle of the light relative to the magnetic element 20 is preferably a direction tilted at least 45° relative to the XY plane. When the second electrode 23 is a transparent electrode, by satisfying the above conditions, the efficiency of light irradiation onto the stacked body 21 can be improved.

[0076] The first reflector 41 is located in front of the direction of travel of light propagating through the core 11 (for example, the X direction). The height position of the first reflector 41 in the Z direction is the same as the height position of the core 11, or is located above the core 11. When viewed from the X direction, a portion of the reflective surface of the first reflector 41 is located at a position overlapping with the core 11. The height positions of the magnetic element 20 and the first reflector 41 in the Z direction can be the same, or the magnetic element 20 can be located above the first reflector 41.

[0077] The reflective surface 41A of the first reflector 41 is located opposite the light output end of the core 11. The reflective surface 41A is tilted in the +X direction relative to the YZ plane. Light output from the core 11 is reflected by the reflective surface 41A of the first reflector 41 and bent in the Z direction. Light reflected by the first reflector 41 is not limited to light traveling in the Z direction, as long as it has a component in the Z direction.

[0078] The second reflector 42 is located at a position where it can reflect the light reflected by the first reflector 41 and irradiate the magnetic element 20 with the light reflected by the second reflector 42. When viewed in the Z direction, the second reflector 42 can be located at a position overlapping with the first reflector 41 or at a position closer to the first reflector 41 in the +X direction. The height position of the second reflector 42 in the Z direction is, for example, located above the magnetic element 20.

[0079] The reflecting surface 42A of the second reflector 42 is inclined with respect to the YZ plane. Figure 2 , an example is shown in which the reflective surface 42A is tilted in the +X direction relative to the YZ plane. However, the reflective surface 42A may also be tilted in the -X direction relative to the YZ plane depending on the position of the magnetic element 20. In this case, the magnetic element 20 is disposed on the core 11, and the width of the optical device 100 in the X direction can be reduced.

[0080] Next, the operation of the optical device 100 will be described. The output voltage from the optical device 100 changes due to changes in the intensity of light irradiated on the magnetic element 20. The output voltage from the optical device 100 changes due to changes in the resistance value of the magnetic element 20 in the Z direction.

[0081] The magnetic element 20 is irradiated with the light L propagating through the waveguide 10 . The light L propagates in the X direction within the waveguide 10 , is reflected by the first reflector 41 and the second reflector 42 , and is irradiated onto the magnetic element 20 .

[0082] For example, when the intensity of light irradiating the magnetic element 20 changes from a first intensity to a second intensity, the Z-direction resistance value of the magnetic element 20 changes. The first intensity may also be when the intensity of light irradiating the magnetic element 20 is zero. When the Z-direction resistance value of the magnetic element 20 changes, the output voltage from the magnetic element 20 changes.

[0083] Figure 5 and Figure 6 It is a diagram for explaining an operation example of the magnetic element 20 according to the first embodiment. Figure 5 is a diagram for explaining the first mechanism of the operation example, Figure 6 This is a diagram for explaining the second mechanism of the operation example. Figure 5 and Figure 6 In the graph above, the vertical axis is the intensity of light irradiated to the first ferromagnetic layer 1, and the horizontal axis is time. Figure 5 and Figure 6 In the graph below, the vertical axis represents the resistance value of the magnetic element 20 in the Z direction, and the horizontal axis represents time.

[0084] First, in a state where the first ferromagnetic layer 1 is irradiated with light of a first intensity W1 (hereinafter referred to as an initial state), the magnetization M1 of the first ferromagnetic layer 1 and the magnetization M2 of the second ferromagnetic layer 2 are antiparallel, and the Z-direction resistance value of the magnetic element 20 exhibits a second resistance value R2. Here, the state where the intensity of light irradiating the first ferromagnetic layer 1 is zero can also be considered as the state where the first ferromagnetic layer 1 is irradiated with light of the first intensity W1.

[0085] By flowing the sense current Is in the Z direction of the magnetic element 20 , a voltage is generated across both ends of the magnetic element 20 in the Z direction. An output voltage from the magnetic element 20 is generated between the first electrode 22 and the second electrode 23 .

[0086] exist Figure 5In the example shown, the sense current Is preferably flows from the second ferromagnetic layer 2 to the first ferromagnetic layer 1. By flowing the sense current Is in this direction, a spin transfer torque in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1, and magnetizations M1 and M2 tend to be antiparallel in the initial state.

[0087] Next, the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2. For example, when a light pulse is irradiated onto the magnetic element 20, the intensity of the light irradiated onto the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2. The intensity of the light of the second intensity W2 is greater than the intensity of the light of the first intensity W1.

[0088] The second intensity W2 is greater than the first intensity W1, and the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state. The magnetization M1 of the first ferromagnetic layer 1 when not irradiated with light differs from the magnetization M1 of the first ferromagnetic layer 1 when irradiated with light of the second intensity W2. The state of the magnetization M1 can be determined, for example, by its tilt angle and magnitude relative to the Z direction.

[0089] For example, Figure 5 As shown, when the intensity of the light irradiated to the first ferromagnetic layer 1 changes from the first intensity W1 to the second intensity W2, the magnetization M1 tilts with respect to the Z direction. Figure 6 As shown, when the intensity of light irradiating the first ferromagnetic layer 1 changes from a first intensity W1 to a second intensity W2, the magnitude of the magnetization M1 decreases. For example, when the magnetization M1 of the first ferromagnetic layer 1 tilts relative to the Z direction due to the intensity of light irradiation, the tilt angle is, for example, greater than 0° and less than 90°.

[0090] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state due to irradiation of the magnetic element 20 with a light pulse, the Z-direction resistance of the magnetic element 20 assumes a first resistance value R1, and the magnitude of the output voltage from the magnetic element 20 changes from the first value to a second value. As a result, the output from the optical device 100 changes. The first resistance value R1 is smaller than the second resistance value R2. The second value is smaller than the first value. The first resistance value R1 is between the resistance value (second resistance value R2) when the magnetizations M1 and M2 are antiparallel and the resistance value when the magnetizations M1 and M2 are parallel.

[0091] exist Figure 5In the case shown, a spin transfer torque in the opposite direction to the magnetization M2 of the second ferromagnetic layer 2 acts on the magnetization M1 of the first ferromagnetic layer 1. Therefore, the magnetization M1 attempts to return to a state antiparallel to the magnetization M2. When the intensity of the light irradiated on the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the magnetization M1 returns to a state antiparallel to the magnetization M2. Figure 6 In the case shown, when the intensity of the light irradiating the first ferromagnetic layer 1 returns to the first intensity W1, the magnetization M1 of the first ferromagnetic layer 1 returns to its original state, and the magnetic element 20 returns to its initial state. In either case, the Z-direction resistance of the magnetic element 20 returns to the second resistance R2. In other words, when the intensity of the light irradiating the first ferromagnetic layer 1 changes from the second intensity W2 to the first intensity W1, the Z-direction resistance of the magnetic element 20 changes from the first resistance R1 to the second resistance R2.

[0092] The output voltage from the optical device 100 changes in response to changes in the intensity of the light irradiated on the magnetic element 20, and it is possible to convert changes in the intensity of the irradiated light into changes in the output voltage from the magnetic element 20. In other words, the optical device 100 can convert light into an electrical signal. For example, when the output voltage from the optical device 100 is above a threshold value, it is processed as a first signal (e.g., "1"), and when it is below the threshold value, it is processed as a second signal (e.g., "0").

[0093] While the example described here uses the case where magnetization M1 and magnetization M2 are antiparallel in the initial state, magnetization M1 and magnetization M2 can also be parallel in the initial state. In this case, the greater the change in the state of magnetization M1 (for example, the greater the angular change relative to the initial state of magnetization M1), the greater the Z-direction resistance of magnetic element 20. When magnetization M1 and magnetization M2 are parallel as the initial state, sense current Is preferably flows from first ferromagnetic layer 1 to second ferromagnetic layer 2. By flowing sense current Is in this direction, a spin transfer torque in the same direction as magnetization M2 of second ferromagnetic layer 2 acts on magnetization M1 of first ferromagnetic layer 1, causing magnetization M1 and magnetization M2 to be parallel in the initial state.

[0094] In addition, although the light irradiated to the magnetic element 20 is described here as having two levels of intensity, namely, the first intensity and the second intensity, the intensity of the light irradiated to the magnetic element 20 may also be varied in multiple levels or in an analog manner. In this case, the output voltage from the magnetic element 20 is varied in multiple levels or in an analog manner.

[0095] The optical device 100 according to the first embodiment replaces light irradiated by the magnetic element 20 with an output voltage from the magnetic element 20, thereby converting light into an electrical signal. The magnetic element 20 of the optical device 100 according to the first embodiment is located within the cladding 12 and is packaged. Therefore, the waveguide 10 for transmitting light and the magnetic element 20 for detecting light can be treated as a single component, enabling miniaturization of the optical device 100. Furthermore, by packaging the waveguide 10 and the magnetic element 20, adjustments to the optical axes of the waveguide 10 and the magnetic element 20 are no longer necessary.

[0096] Furthermore, the light transmitted in the waveguide 10 is reflected by the first reflector 41 and the second reflector 42 and irradiates the magnetic element 20 from the side or above the magnetic element 20. The layers constituting the magnetic element 20 are very thin, and the crystallinity of each layer is easily affected by the substrate. In the case of irradiating light from below the magnetic element 20, the material of the first electrode 22 is limited, and the crystallinity of the magnetic element 20 cannot be fully improved. In contrast, since the optical device 100 involved in this embodiment is irradiated with light from the side or above the magnetic element 20, there is no restriction on the material of the first electrode 22. When the crystallinity of the magnetic element 20 is improved, the resistance change amplitude (MR ratio) of the magnetic element 20 becomes larger, and the sensitivity of the optical device 100 is improved.

[0097] Although the first embodiment has been used as an example to describe the present invention, the present invention is not limited to this embodiment.

[0098] For example, Figure 7 It is a cross-sectional view of an optical device 101 according to a first modification. Figure 7 It is an XZ cross section passing through the center of the core 11 in the Y direction. Figure 7 The optical device 101 shown includes a waveguide 10, a magnetic element 20, a terminal unit 30, a first reflector 41, a second reflector 43, and a substrate 50. The shape of the second reflector 43 is different from that of the second reflector 42 described above. The reflective surface 43A of the second reflector 43 is curved. Light reflected by the reflective surface 43A converges and irradiates the magnetic element 20.

[0099] The optical device 101 according to the first modification example exhibits the same effects as the aforementioned optical device 100. In addition, the optical device 101 can improve the efficiency of irradiating the magnetic element 20 with light by converging the light using the reflection surface 43A.

[0100] For example, Figure 8 It is a cross-sectional view of an optical device 102 according to a second modification. Figure 8 It is an XZ cross section passing through the center of the core 11 in the Y direction. Figure 8The optical device 102 shown includes a waveguide 10, a magnetic element 20, a terminal unit 30, a first reflector 41, a second reflector 44, and a substrate 50. The shape of the second reflector 44 is different from that of the second reflector 42 described above.

[0101] The second reflector 44 is a super-reflective mirror having a meta-diffraction grating. A meta-diffraction grating is a metamaterial. A meta-diffraction grating is composed of multiple unit cells, each containing multiple meta-atoms. A meta-diffraction grating can change the refractive index distribution depending on the shape of the unit cell. A meta-reflective mirror exhibits high reflectivity when irradiated with light of a specified wavelength. The specified wavelength can be controlled by changing the structure of the meta-diffraction grating.

[0102] The optical device 102 according to the second modification example exhibits the same effects as the aforementioned optical device 100. The optical device 102 includes the second reflector 44 formed of a super reflector, thereby being able to control the wavelength of light irradiated to the magnetic element 20.

[0103] Furthermore, although the example in which the magnetic element 20 is one has been disclosed so far, the magnetic element 20 may be multiple.

[0104] Furthermore, when there are multiple magnetic elements 20, the outputs from the respective magnetic elements 20 that behave similarly with respect to light can be combined and output from the optical device. This can suppress noise in the output signal to the optical device and increase the SN ratio of the optical device 102.

[0105] Figure 9 1 is a cross-sectional view showing a first example of a connection state of a magnetic element in an optical device according to a third modified example. Figure 9 As shown, the individual magnetic elements 20 can be connected in series. Figure 9 In the embodiment, the magnetic elements 20 are connected in series via the connection wiring 36. Figure 10 1 is a cross-sectional view showing a second example of a connection state of a magnetic element in an optical device according to a third modification. Figure 10 As shown, the individual magnetic elements 20 may be connected in parallel.

[0106] In addition, although the example in which two reflectors (the first reflector 41 and the second reflector 42) are provided between the core 11 and the magnetic element 20 in the light path has been shown so far, the number of reflectors between the core 11 and the magnetic element 20 may be three or more.

[0107] The optical devices according to the above-described embodiment and modifications can be used in various applications.

[0108] Figure 112 is a schematic diagram of an optical element 200 according to a first application example. Figure 11 The illustrated optical element 200 includes a waveguide element 110 and a light source 120. The waveguide element 110 includes the aforementioned optical device 100 and a waveguide 111. The waveguide 111 includes an output waveguide 112 and a monitor waveguide 113. The output waveguide 112 is a waveguide for outputting light from the light source 120 to the outside. The monitor waveguide 113 is a waveguide for branching a portion of the light propagating in the output waveguide 112 toward the optical device 100. The monitor waveguide 113 is connected to the core 11 of the optical device 100.

[0109] Light source 120 is, for example, a laser light source. Light source 120 includes, for example, a red laser 121, a green laser 122, and a blue laser 123. Light output from light source 120 is transmitted through output waveguide 112 and output to the outside. A portion of the light output from light source 120 is transmitted through monitoring waveguide 113 and reaches optical device 100.

[0110] Optical element 200 outputs laser light to the outside while monitoring the output from light source 120 using optical device 100. Optical element 200 can adjust the white balance of light output from output waveguide 112 by adjusting the intensity of light output from each laser.

[0111] Figure 12 2 is a conceptual diagram of an optical system 300 using the optical element 200. The optical system 300 can be attached to the glasses 1000, for example.

[0112] The optical system 300 includes the above-mentioned optical element 200, an optical system 310, drivers 320 and 321, and a controller 330. The optical system 310 includes, for example, a collimating lens 301, a slit 302, an ND filter 303, and an optical scanning mirror 304. The optical system 310 guides the light output from the optical element 200 to the irradiated object (the eye in this example). The optical scanning mirror 304 is, for example, a biaxial MEMS mirror that changes the reflection direction of the laser into the horizontal direction and the vertical direction. The optical system 310 is an example and is not limited to this example. The driver 320 controls the output of the light source 120 from the optical element 200. The driver 321 is a control system that moves the optical scanning mirror 304. The controller 330 controls the drivers 320 and 321.

[0113] The light L output from the light source 120 of the optical element 200 G The light propagates through the optical system 310, is reflected by the lenses of the glasses 1000, and enters the eye. Here, an example in which the light is reflected by the lenses of the glasses 1000 is shown, but the light may also be directly irradiated to the eye.

[0114] The red, green, and blue lights L emitted from the light source 120 G The image is displayed. The image can be freely controlled. The output intensities of the red laser 121, green laser 122, and blue laser 123 can be adjusted based on the measurement results of the output of the optical device 100 irradiated with visible light emitted from the red laser 121, green laser 122, and blue laser 123, respectively.

[0115] When the optical system 300 is used, an image can be projected onto the glasses 1000. In addition, by monitoring the intensity of the projected light using the optical device 100, the color tone of the image can be adjusted.

[0116] Figure 13 1 is a block diagram of a transceiver 400 according to the second application example. The transceiver 400 includes a receiver 410 and a transmitter 420. The receiver 410 receives an optical signal L1, and the transmitter 420 transmits an optical signal L2.

[0117] Receiving device 410 includes, for example, a light detection device 411 and a signal processing unit 412. The light detection device 411 can use the aforementioned optical device. In receiving device 410, the optical device of light detection device 411 is irradiated with, for example, a light pulse. Light signal L1 is composed of light pulses. Light detection device 411 converts light signal L1 into an electrical signal. Signal processing unit 412 processes the electrical signal converted by light detection device 411. By processing the electrical signal generated by light detection device 411, signal processing unit 412 receives the signal contained in light signal L1. Receiving device 410 receives the signal contained in light signal L1 based on the output signal from light detection device 411.

[0118] Transmitting device 420 includes, for example, a light source 421, an electrical signal generating element 422, and an optical modulator 423. Light source 421 is, for example, a laser element. Light source 421 may also be located external to transmitting device 420. Electrical signal generating element 422 generates an electrical signal based on transmission information. Electrical signal generating element 422 may also be integrated with the signal conversion element of signal processing unit 412. Optical modulator 423 modulates the light output from light source 421 based on the electrical signal generated by electrical signal generating element 422, and outputs optical signal L2.

[0119] Figure 14 This is a conceptual diagram of an example of a communication system. Figure 14 The communication system shown has two terminal devices 500. The terminal devices 500 are, for example, smartphones, tablet computers, personal computers, and the like.

[0120] Each terminal device 500 includes a receiving device 410 and a transmitting device 420. An optical signal transmitted from the transmitting device 420 of one terminal device 500 is received by the receiving device 410 of another terminal device 500. The light used for transmission and reception between the terminal devices 500 is, for example, visible light. The receiving device 410 includes a light detection device 411.

[0121] in addition, Figure 15 This is a conceptual diagram of an example of a communication system. Figure 14 , the terminal devices 500 are all smartphones, but the terminal devices 500 may be different on the sending side and the receiving side. Figure 15 The terminal device 500 shown is a smartphone, and the terminal device 501 is a personal computer.

[0122] Description of Reference Numerals

[0123] 1: First ferromagnetic layer; 2: Second ferromagnetic layer; 3: Spacer layer; 4: Buffer layer; 5: Seed layer; 6: Third ferromagnetic layer; 7: Magnetic coupling layer; 8: Perpendicular magnetization inducing layer; 9: Cover layer; 10: Waveguide; 11: Core; 12: Cladding; 20: Magnetic element; 21: Stacked body; 22: First electrode; 23: Second electrode; 30: Terminal unit; 31: First terminal; 32: Second terminal; 33: Third terminal; 34: Fourth terminal; 35: Path wiring; 36: Connection wiring; 41: First reflector; 42: Second reflector; 50: Substrate; 100, 101, 102: Optical device.

Claims

1. An optical device, wherein: It includes a waveguide, a magnetic element, a first reflector and a second reflector, The waveguide has a core for light transmission and a cladding covering the core. The first reflector is located in front of the traveling direction of the light transmitted in the core. The second reflector is arranged at a position where it is irradiated with the light reflected by the first reflector and can irradiate the light toward the magnetic element. The magnetic element comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer. The magnetic element is illuminated with light from the side or from above.

2. The optical device according to claim 1, wherein The magnetic element is irradiated with light from a direction inclined at 45° or more with respect to the upper surface of the magnetic element.

3. The optical device according to claim 1, wherein The reflecting surface of the second reflector is curved, The light reflected and converged by the reflecting surface is irradiated onto the magnetic element. The optical device according to claim 1 , wherein: The magnetic element has a first electrode and a second electrode, The second electrode is located above the first electrode. The first electrode is made of a metal containing at least one element selected from the group consisting of copper, aluminum, gold, tantalum, titanium, ruthenium, molybdenum, and tungsten. The optical device according to claim 1 , wherein: There are multiple magnetic elements.

6. A receiving device, The optical device according to claim 1 is provided.

7. A transmitting and receiving device, A receiving device according to claim 6 is provided.

8. A communication system, A receiving device according to claim 6 is provided.

9. A terminal device, A receiving device according to claim 6 is provided.

10. An optical system, The optical device according to claim 1 is provided.

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