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

Abstract

The invention provides a packaged optical device, a reception apparatus, a transmission / reception apparatus, a communication system, a terminal apparatus, and an optical system. The optical device includes a waveguide and a magnetic element. The waveguide has a core for light transmission and a cladding covering the core. The core has a diffraction grating on a first surface. The magnetic element is positioned above the first surface in the cladding layer. The magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer.

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. Background Art

[0002] Photoelectric conversion elements are used in various applications.

[0003] For example, Patent Document 1 describes a receiving device that receives an optical signal using a photodiode. A photodiode is, for example, a PN junction diode using a PN junction of a semiconductor, and converts light into an electrical signal.

[0004] Furthermore, a new optical device using a magnetic element is disclosed in, for example, Patent Document 2. When the magnetic element is irradiated with light, its magnetic state changes, and its resistance value changes.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-292107

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2023-47553 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] For example, if laser light from a waveguide is emitted into space and detected using a magnetic element, as described in Patent Document 2, the light utilization efficiency is reduced due to reflection caused by the difference in refractive index between the waveguide and the space. Furthermore, if the waveguide and magnetic element are manufactured as separate components, adjustment of the optical axis is required.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a packaged optical device, a receiving device, a transmitting and receiving device, a communication system, a terminal device, and an optical system.

[0012] Solutions for solving problems

[0013] In order to solve the above problems, the following solutions are provided.

[0014] The optical device of this embodiment includes a waveguide and a magnetic element. The waveguide includes a core for transmitting light and a cladding covering the core. The core includes a diffraction grating on a first surface. The magnetic element is located above the first surface within the cladding. The magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first and second ferromagnetic layers.

[0015] Effects of the Invention

[0016] The optical device of the above solution is packaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a perspective view of the optical device according to the first embodiment.

[0018] Figure 2 This is a cross-sectional view of the optical device according to the first embodiment.

[0019] Figure 3 This is another cross-sectional view of the optical device according to the first embodiment.

[0020] Figure 4 This is an enlarged cross-sectional view of the diffraction grating according to the first embodiment.

[0021] Figure 5 It is a cross-sectional view of the vicinity of the magnetic element of the optical device according to the first embodiment.

[0022] Figure 6 It is a diagram for explaining an operation example of the magnetic element according to the first embodiment.

[0023] Figure 7 It is a diagram for explaining an operation example of the magnetic element according to the first embodiment.

[0024] Figure 8 It is a cross-sectional view of the optical device according to the first modified example.

[0025] Figure 9 It is a perspective view of an optical device according to a second modified example.

[0026] Figure 10 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 second modification.

[0027] Figure 11 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 second modification.

[0028] Figure 12 It is a schematic diagram of the optical element of the first application example.

[0029] Figure 13 This is a conceptual diagram of an optical system using the optical element of the first application example.

[0030] Figure 14 It is a schematic diagram of the transmitting and receiving device of the second application example.

[0031] Figure 15 This is a conceptual diagram of an example of a communication system.

[0032] Figure 16This is a conceptual diagram of another example of a communication system.

[0033] Description of Reference Numerals

[0034] 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 induction layer; 9. Cover layer; 10. Waveguide; 11. Core; 11A. First surface; 12. Cladding layer; 15. Element setting portion; 16. Light transmission portion; 17. Diffraction grating; 17A. Groove; 17B. Protrusion; 20. Magnetic element; 21. Laminated body; 22. First electrode; 23. Second electrode; 30. Terminal unit; 31. First terminal; 32. Second terminal; 33. Third terminal; 34. Fourth terminal; 35. Conductive wiring; 36. Connecting wiring; 40. Substrate; 100, 101, 102. Optical device. DETAILED DESCRIPTION

[0035] 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, and the dimensional ratios of the various components may differ from actual dimensions. The materials, dimensions, and other aspects illustrated in the following description are merely examples, and the present invention is not limited thereto. The present invention can be implemented with appropriate modifications within the scope of achieving the effects of the present invention.

[0036] Define the direction. A direction within the surface of the surface where the substrate extends 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 extends near the magnetic element 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. In the following, 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.

[0037] "First embodiment"

[0038] Figure 1 It is a perspective view of the optical device 100 according to the first embodiment. Figure 2 and Figure 3 It is a cross-sectional view of the optical device 100 according to the first embodiment. Figure 2 is an XZ cross section passing through the center of the core 11 in the Y direction, Figure 3 is the YZ cross section through the center of the magnetic element 20. Figure 1 The cladding 12 and the substrate 40 are omitted.

[0039] The optical device 100 includes, for example, a waveguide 10 , a magnetic element 20 , a terminal unit 30 , and a substrate 40 .

[0040] The waveguide 10, the magnetic element 20, and the terminal unit 30 are formed on a substrate 40. The substrate 40 is, for example, a semiconductor substrate, alumina, sapphire, or the like.

[0041] The waveguide 10 is a structure that forms a path for light transmission. The term "light" in this specification is not limited to visible light but also includes infrared light with longer wavelengths and ultraviolet light with shorter wavelengths. 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 first end of the waveguide 10 is connected to the output end of a laser diode, for example. The light transmitted in the waveguide 10 is, for example, laser light.

[0042] The waveguide 10 includes, for example, a core 11 and a cladding 12. The waveguide 10 totally reflects light using the difference in refractive index between the core 11 and the cladding 12. Light propagates through the core 11. The cladding 12 covers the periphery of the core 11.

[0043] The core 11 contains, for example, lithium niobate as a main component. Some elements of lithium niobate may also 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 made 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.

[0044] The core 11 includes, for example, an element setting portion 15 and a light transmission portion 16. The element setting portion 15 is located in front of the light transmission portion 16 in the direction of travel of light transmitted in the core 11. Light reaches the element setting portion 15 via the light transmission portion 16. The element setting portion 15 is a portion where the magnetic element 20 is set. The width of the element setting portion 15 in the Y direction may be wider than the width of the light transmission portion 16 in the Y direction. Light is irradiated onto the magnetic element 20 at the element setting portion 15. If light expands at the element setting portion 15, the amount of light leakage from the diffraction grating 17 increases, making it easier for light to be irradiated onto the magnetic element 20.

[0045] The core 11 has a diffraction grating 17. The diffraction grating 17 is formed on the first surface 11A of the core 11. The diffraction grating 17 is located in the element installation portion 15, for example.

[0046] Figure 4This is an enlarged cross-sectional view of the diffraction grating 17 of the first embodiment. The diffraction grating 17 includes a plurality of grooves 17A and a plurality of protrusions 17B. The grooves 17A and the protrusions 17B intersect with the propagation direction (e.g., the X direction) of the light L propagating through the element mounting portion 15. The grooves 17A and the protrusions 17B extend, for example, in the Y direction.

[0047] The diffraction grating 17 diffracts the light L propagating in the core 11 according to the following basic formula (1) of the grating coupler. The light L diffracted by the diffraction grating 17 is D It has a component in the Z direction and is output from the core 11 to the upper part.

[0048] sin(θ)=(n eff -mλ / a) / n1···(1)

[0049] like Figure 4 As shown, θ is the light L D The angle between the normal direction of the XY plane and the XY plane. eff is the effective refractive index, expressed as n1×V 17A +n2×V 17B Find V 17A is the volume ratio of the grooves 17A in the diffraction grating 17, V 17B is the volume ratio of convex portions 17B in diffraction grating 17. n1 is the refractive index of the material filling grooves 17A and is the refractive index of cladding 12. n2 is the refractive index of convex portions 17B and is the refractive index of core 11. m is the order. λ is the wavelength of light L propagating through core 11. a is the pitch between convex portions 17B.

[0050] Preferably, the effective refractive index n of the diffraction grating 17 is eff It is larger than the value obtained by dividing the wavelength λ of the light L by the pitch length a of the convex portions 17B. If the diffraction grating 17 satisfies this condition, the light L can be appropriately output from the core 11 to the upper portion.

[0051] The magnetic element 20 is in the cladding 12. The magnetic element 20 is in a different layer from the core 11 and is located above the core 11 in the Z direction. The magnetic element 20 is located above the first surface 11A of the core 11. For example, the magnetic element 20 is located at the same position as the diffraction grating 17 or in front of the diffraction grating 17 in the direction of travel (for example, the X direction) of the light L transmitted in the core 11. Figure 2 In the example shown, the magnetic element 20 is located at the same position in the X direction as the diffraction grating 17. When viewed from the Z direction, the magnetic element 20 is located at a position overlapping the diffraction grating 17. The magnetic element 20 is in contact with the diffraction grating 17 and is located on the diffraction grating 17.

[0052] The magnetic element 20 converts the state of the irradiated light or a change in the state into an electrical signal. For example, light having a wavelength of 400 nm to 1500 nm is irradiated to the magnetic element 20.

[0053] 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.

[0054] Figure 5 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 .

[0055] The first electrode 22 is located on the substrate 40 side of the stack 21. The first electrode 22 is conductive. For example, the first electrode 22 is made of a metal such as Cu, Al, or Au. Alternatively, Ta or Ti may be stacked above or below these metals. A stacked film of Cu and Ta, a stacked film of Ta, Cu, and Ti, or a stacked film of Ta, Cu, and TaN may be used for the first electrode 22. Furthermore, the first electrode 22 may be made of TiN or TaN.

[0056] The first electrode 22 may be, for example, a metal containing at least one element selected from the group consisting of ruthenium, molybdenum, and tungsten. The first electrode 22 may be a single-layer film of any of ruthenium, molybdenum, and tungsten, or a laminated film having at least one layer of any of these. Ruthenium, molybdenum, and tungsten have high melting points (above 2000°C) and excellent heat resistance. The first electrode 22 containing these elements is less susceptible to degradation even during heat treatment during crystallization of the laminate 21 or during heat treatment during semiconductor processing.

[0057] In addition, the first electrode 22 may also be a transparent electrode that is transmissive to light in the operating wavelength range. For example, the first electrode 22 preferably transmits more than 80% of the light in the operating wavelength range. The first electrode 22 is, for example, an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode 22 may also be a metal film with a thickness of about 3 nm to 10 nm. If the first electrode 22 is a transparent electrode, light L can be irradiated from below toward the stacked body 21. D , it is possible to efficiently irradiate the stacked body 21 with light.

[0058] The second electrode 23 is opposite to 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, for example, a metal such as Cu, Al, or Au. The second electrode 23 may also be made of Ta or Ti stacked above and below 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 may be used. In addition, as the second electrode 23, TiN or TaN may also be used.

[0059] 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. For example, the laminate 21 may further include a buffer layer 4, a seed layer 5, a third ferromagnetic layer 6, a magnetic coupling layer 7, a perpendicular magnetization induction layer 8, and a cap layer 9.

[0060] 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 has 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 (TMR) effect. If the spacer layer 3 is made of metal, the magnetic element 20 can exhibit the giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The magnetic element 20 is sometimes referred to by different names, such as MTJ element or GMR element, depending on the material of the spacer layer 3, but is also generally referred to as a magnetoresistance element. The z-direction resistance value of the magnetic element 20 (the resistance value when current flows in the z-direction) changes in accordance with the relative changes in the magnetization state of the first ferromagnetic layer 1 and the magnetization state of the second ferromagnetic layer 2.

[0061] The first ferromagnetic layer 1 is a light-detecting layer whose magnetization changes when light is irradiated from the outside. The first ferromagnetic layer 11 is also called a magnetization-free layer. The magnetization-free layer is a layer containing a magnetic body whose magnetization changes when a predetermined energy is applied from the outside. The predetermined energy from the outside is, for example, light irradiated from the outside, a current flowing in the z direction of the magnetic element 20, or an external magnetic field. The magnetization of the first ferromagnetic layer 11 changes in accordance with the intensity of the light irradiated to the first ferromagnetic layer 11 (light irradiated to the magnetic element 20).

[0062] The first ferromagnetic layer 1 contains a ferromagnetic body. For example, the first ferromagnetic layer 1 contains at least one of the magnetic elements such as Co, Fe and Ni. The first ferromagnetic layer 1 may also contain the magnetic elements mentioned above and elements such as B, Mg, Hf, and Gd at the same time. For example, the first ferromagnetic layer 1 may also be an alloy containing magnetic elements and non-magnetic elements. The first ferromagnetic layer 1 may also be composed of multiple layers. For example, the first ferromagnetic layer 1 is a CoFeB alloy, a laminated body composed of Fe layers sandwiching CoFeB alloy layers, or a laminated body composed of CoFe layers sandwiching CoFeB alloy 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 ferromagnetism that is not ferrimagnetism. For example, the CoFeB alloy exhibits ferromagnetism that is not ferrimagnetism.

[0063] The first ferromagnetic layer 1 may be an in-plane magnetization film having an easy magnetization axis in the film plane direction (in either direction in the xy plane) or a perpendicular magnetization film having an easy magnetization axis in the direction perpendicular to the film plane (z direction).

[0064] 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 applied by the layers above and below the first ferromagnetic layer 1, 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 applied by the layers above and below the first ferromagnetic layer 1, reducing the perpendicular magnetic anisotropy of the first ferromagnetic layer 1.

[0065] When the thickness of the first ferromagnetic layer 1 decreases, the volume of the ferromagnetic body decreases. When the thickness of the first ferromagnetic layer 1 increases, the volume of the ferromagnetic body increases. The responsiveness of the magnetization intensity of the first ferromagnetic layer 1 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 increases. From this perspective, in order to improve its reactivity to light, it is preferable to reduce the volume of the first ferromagnetic layer 1 while appropriately designing the magnetic anisotropy of the first ferromagnetic layer 1.

[0066] When the thickness of the first ferromagnetic layer 1 is thicker than 2 nm, an insertion layer composed of Mo or W, for example, may be provided within the first ferromagnetic layer 1. In other words, a stacked structure consisting 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 is utilized to increase 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.

[0067] The second ferromagnetic layer 2 is a magnetization-fixed layer. The magnetization-fixed layer is a layer formed of a magnetic material whose magnetization M2 is less likely to change state when a predetermined external energy is applied, compared to the magnetization-free layer. For example, the direction of the magnetization of the magnetization-fixed layer is less likely to change when a predetermined external energy is applied, compared to the magnetization-free layer. Furthermore, for example, the magnitude of the magnetization of the magnetization-fixed layer is less likely to change when a predetermined external energy is applied, 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 an in-plane magnetization film or a perpendicular magnetization film.

[0068] The material constituting the second ferromagnetic layer 2 is, for example, the same as that of the first ferromagnetic layer 1. The second ferromagnetic layer 2 may be, for example, 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) multiple times. Alternatively, the second ferromagnetic layer 2 may be, for example, a laminate formed by sequentially laminating 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).

[0069] The magnetization M2 of the second ferromagnetic layer 2 can be magnetically coupled to the magnetization M6 of the third ferromagnetic layer 6, for example, via the magnetic coupling layer 7. In this case, the layer comprising the second ferromagnetic layer 2, the magnetic coupling layer 7, and the third ferromagnetic layer 6 is sometimes referred to as a magnetization pinned layer. The detailed structures of the magnetic coupling layer 7 and the third ferromagnetic layer 6 will be described later.

[0070] exist Figure 5 The figure shows a bottom pin structure in which the second ferromagnetic layer 2 serving as a magnetization fixing layer is located closer to the substrate 40 than the first ferromagnetic layer 1, but it can also be a top pin structure in which the second ferromagnetic layer 2 serving as a magnetization fixing layer is located farther from the substrate 40 than the first ferromagnetic layer 1.

[0071] 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 their initial state, as described later.

[0072] When spacer layer 3 is composed of an insulating material, materials such as aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used as the material for spacer layer 3. Furthermore, these insulating materials may also contain elements such as aluminum, boron, silicon, and magnesium, or magnetic elements such as cobalt, iron, and nickel. By adjusting the thickness of spacer layer 3 so that a high TMR effect is exhibited between first ferromagnetic layer 1 and second ferromagnetic layer 2, a high magnetoresistance change ratio is 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.

[0073] When the spacer layer 3 is formed 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.

[0074] When the spacer layer 3 is formed 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.

[0075] 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 energization points formed from a non-magnetic conductor such as Cu, Au, or Al are incorporated within a non-magnetic insulator composed of aluminum oxide or magnesium oxide. Alternatively, the conductor can be formed from a magnetic element 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.

[0076] The third ferromagnetic layer 6 is magnetically coupled to the second ferromagnetic layer 2, for example. 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 that of the first ferromagnetic layer 1.

[0077] 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, or the like, for example.

[0078] The buffer layer 4 is a layer that mitigates 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), a 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 suppresses the influence of the crystal structure of the second electrode 23 on the crystal structure of the magnetic element 20.

[0079] The seed layer 5 improves the crystallinity of the layers stacked on the seed layer 5. The seed layer 5 is located, for example, between the buffer layer 4 and the third ferromagnetic layer 6, and on the buffer layer 4. The seed layer 5 is made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of the seed layer 5 is, for example, not less than 1 nm and not more than 5 nm.

[0080] 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 induction layer 8 stacked on and in contact with the first ferromagnetic layer 1. The capping layer 9 prevents damage to the underlying layer during processing and improves the crystallinity of the underlying layer during annealing.

[0081] Perpendicular magnetization induction layer 8 senses the perpendicular magnetic anisotropy of first ferromagnetic layer 1. Perpendicular magnetization induction layer 8 can be made of, for example, magnesium oxide, W, Ta, or Mo. When magnesium oxide is used, it is preferable to have a low oxygen content to improve conductivity. The thickness of perpendicular magnetization induction layer 8 is, for example, 0.5 nm to 5.0 nm.

[0082] 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 conductive wirings 35. The first terminal 31, the second terminal 32, the third terminal 33, and the fourth terminal 34 are formed on the cladding layer 12. The first terminal 31 and the fourth terminal 34 are each electrically connected to the first electrode 22 via the conductive wiring 35. The second terminal 32 and the third terminal 33 are each electrically connected to the second electrode 23 via the conductive wiring 35. A 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 conductive wirings 35 are made of a conductive material.

[0083] Next, the operation of the optical device 100 will be described. The output voltage from the optical device 100 changes according to the intensity of light irradiated onto 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.

[0084] 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 diffracted in the Z direction by the diffraction grating 17 , and is irradiated toward the magnetic element 20 .

[0085] 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 output from the magnetic element 20 changes.

[0086] Figure 6 and Figure 7 It is a diagram for explaining an operation example of the magnetic element 20 according to the first embodiment. Figure 6 is a diagram for explaining the first mechanism of the operation example. Figure 7 This is a diagram for explaining the second mechanism of the operation example. Figure 6 and Figure 7 In the graph above, the vertical axis is the intensity of the light irradiated to the first ferromagnetic layer 1, and the horizontal axis is time. Figure 6 and Figure 7 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.

[0087] First, in a state where light of a first intensity W1 is irradiated onto the first ferromagnetic layer 1 (hereinafter 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 are in an antiparallel relationship, and the Z-direction resistance value of the magnetic element 20 is represented by a second resistance value R2. Here, the state where the light of the first intensity W1 is irradiated onto the first ferromagnetic layer 1 can also be assumed to be zero.

[0088] When the sense current Is flows in the Z direction of the magnetic element 20 , a voltage is generated at both ends of the magnetic element 20 in the Z direction. An output voltage output from the magnetic element 20 is generated between the first electrode 22 and the second electrode 23 .

[0089] exist Figure 6In the example shown, it is preferred that the sense current Is flow from the second ferromagnetic layer 2 toward 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 in the initial state, the magnetizations M1 and M2 tend to be antiparallel.

[0090] Next, the intensity of the light irradiating 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 irradiating 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.

[0091] The second intensity W2 is greater than the first intensity W1, causing the magnetization M1 of the first ferromagnetic layer 1 to change 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 magnetization M1 can be determined, for example, by its tilt angle relative to the Z direction and its magnitude.

[0092] For example, in Figure 6 As shown in FIG. 1 , 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 intensity M1 is inclined with respect to the Z direction. Figure 7 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 is tilted relative to the Z direction due to the intensity of the light irradiation, the tilt angle is, for example, greater than 0° and less than 90°.

[0093] When the magnetization M1 of the first ferromagnetic layer 1 changes from its initial state by irradiating the magnetic element 20 with a light pulse, the resistance value of the magnetic element 20 in the Z direction becomes the first resistance value R1, and the magnitude of the output voltage from the magnetic element 20 changes from the first value to the 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 magnetization M1 and magnetization M2 are antiparallel and the resistance value when the magnetization M1 and magnetization M2 are parallel.

[0094] exist Figure 6In 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 tends to return to an antiparallel state with respect to the magnetization M2. When the intensity of the light irradiating the first ferromagnetic layer 1 changes from the second intensity to the first intensity, the magnetization M1 returns to an antiparallel state with respect to the magnetization M2. Figure 7 In the case shown, if the intensity of the light irradiating the first ferromagnetic layer 1 returns to the first intensity W1, the magnetization intensity M1 of the first ferromagnetic layer 1 is restored, 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.

[0095] The output voltage outputted from the optical device 100 changes in accordance with changes in the intensity of the light irradiated onto the magnetic element 20, and changes in the intensity of the irradiated light can be converted into changes in the output voltage outputted 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 outputted from the optical device 100 is above a threshold value, it is processed as a first signal (e.g., "1"), and when the output voltage outputted from the optical device 100 is below the threshold value, it is processed as a second signal (e.g., "0").

[0096] While the case where the magnetization M1 and magnetization M2 are antiparallel in the initial state is described here as an example, the magnetization M1 and magnetization M2 can also be parallel in the initial state. In this case, the greater the degree of change in the state of the magnetization M1 (for example, the greater the angular change of the magnetization M1 from the initial state), the greater the Z-direction resistance value of the magnetic element 20. When the magnetization M1 and magnetization M2 are parallel as the initial state, it is preferred that the sense current Is flow from the first ferromagnetic layer 1 toward the second ferromagnetic layer 2. By flowing the sense current Is 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, and the magnetization M1 and magnetization M2 are parallel in the initial state.

[0097] In addition, although the light irradiated to the magnetic element 20 is described here as having two levels of intensity, the first and second levels, 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 output from the magnetic element 20 is varied in multiple levels or in an analog manner.

[0098] The optical device 100 of the first embodiment can convert light into an electrical signal by converting light irradiated onto the magnetic element 20 into an output voltage outputted from the magnetic element 20. In the optical device 100 of the first embodiment, the magnetic element 20 is encapsulated within the cladding 12. Therefore, the waveguide 10 that transmits light and the magnetic element 20 that detects light can be treated as a single component, enabling miniaturization of the optical device 100. Furthermore, since the light transmitted in the waveguide 10 is not outputted to the outside but irradiated onto the magnetic element 20, light loss due to reflection can be reduced. Furthermore, since the waveguide 10 and the magnetic element 20 are encapsulated, there is no need for optical axis adjustment of the waveguide 10 and the magnetic element 20.

[0099] Although an example of the present invention has been described above by taking the first embodiment as an example, the present invention is not limited to this embodiment.

[0100] For example, Figure 8 4 is a cross-sectional view of an optical device 101 according to a first modified example. Figure 8 This is an XZ cross-section passing through the center of the core 11 in the Y direction. Optical device 101 differs from optical device 100 in that magnetic element 20 is located above waveguide 10 and is not in direct contact with waveguide 10. In optical device 101 as well, light diffracted by diffraction grating 17 is directed toward magnetic element 20, thereby converting the light into an electrical signal. Furthermore, because optical device 101 of the first modified example is packaged, it achieves the same effects as optical device 100.

[0101] In addition, for example Figure 9 : is a perspective view of the optical device 102 according to the second modified example. Figure 9 The terminal unit, cladding, and substrate are omitted. The optical device 102 differs from the optical device 100 in that there are multiple magnetic elements 20 (laminates 21), and the magnetic elements 20 (laminates 21) are located so as not to overlap with the diffraction grating 17 when viewed from the Z direction.

[0102] The magnetic element 20 (laminated structure 21) is positioned so as not to overlap the diffraction grating 17 when viewed from the Z direction of the element mounting portion 15. Even when the magnetic element 20 is positioned offset from the diffraction grating 17, leakage light diffracted by the diffraction grating 17 reaches the magnetic element 20, enabling conversion of the light into an electrical signal. The magnetic element 20 formed on a flat surface has high crystallinity in the layers comprising the magnetic element 20, resulting in a large resistance change (magnetoresistance ratio: MR ratio).

[0103] Furthermore, if there are multiple magnetic elements 20, the optical device 102 can combine the outputs from the magnetic elements 20 that behave in the same manner with respect to light. As a result, the optical device 102 can suppress noise in the output signal, thereby increasing the signal-to-noise ratio (SN ratio) of the optical device 102.

[0104] Figure 10 1 is a cross-sectional view showing the first example of the connection state of the magnetic element in the optical device of the second modified example. Figure 10 As shown, the magnetic elements 20 are connected in series. Figure 10 In the embodiment, the magnetic elements 20 are connected in series using the connection wiring 36. Figure 11 2 is a cross-sectional view showing a second example of the connection state of the magnetic element in the optical device of the second modified example. Figure 11 As shown, the magnetic elements 20 are connected in parallel.

[0105] While the second modified example shows an example in which a plurality of magnetic elements 20 (laminated body 21) are provided and the magnetic element 20 (laminated body 21) is located at a position not overlapping with the diffraction grating 17 when viewed in the Z direction, these changes may be made in either direction. That is, there may be a single magnetic element 20 and the magnetic element 20 may be located at a position not overlapping with the diffraction grating 17 when viewed in the Z direction, or there may be a plurality of magnetic elements 20 and the magnetic elements may be located at a position overlapping with the diffraction grating 17 when viewed in the Z direction.

[0106] The optical devices according to the above-described embodiments and modifications can be used in various applications.

[0107] Figure 12 Schematic diagram of an optical element 200 according to a first application example. The optical element 200 can be used as a part of an optical system, for example. Figure 12 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 that branches 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.

[0108] Light source 120 is, for example, a laser light source. Light source 120 includes, for example, red laser light 121, green laser light 122, and blue laser light 123. Light output from light source 120 propagates through output waveguide 112 and is output externally. A portion of the light output from light source 120 propagates through monitoring waveguide 113 and reaches optical device 100.

[0109] The optical element 200 outputs laser light to the outside while monitoring the output from the light source 120 by the optical device 100. The optical element 200 can adjust the white balance of the light output from the output waveguide 112 by adjusting the intensity of the light output from each laser.

[0110] Figure 13 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.

[0111] 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, an aperture 302, a neutral density filter 303, and a light 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 light scanning mirror 304 is, for example, a two-axis MEMS mirror that changes the reflection direction of the laser light 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 light scanning mirror 304. The controller 330 controls the drivers 320 and 321.

[0112] 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 be directly directed to the eye.

[0113] The red, green, and blue lights L emitted from the light source 120 G The image can be freely controlled. The output intensity of each of the red laser 121, the green laser 122, and the 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, the green laser 122, and the blue laser 123, respectively.

[0114] By using the optical system 300, an image can be projected onto the glasses 1000. Furthermore, the intensity of the projected light is monitored by the optical device 100, thereby adjusting the color tone of the image.

[0115] Figure 14 1 is a block diagram of a transceiver 400 according to a 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.

[0116] The 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 the receiving device 410, the optical device of the light detection device 411 is irradiated with, for example, a light pulse. The optical signal L1 is composed of the light pulse. The light detection device 411 converts the light signal L1 into an electrical signal. The signal processing unit 412 processes the electrical signal converted by the light detection device 411. By processing the electrical signal generated by the light detection device 411, the signal processing unit 412 receives the signal included in the light signal L1. The receiving device 410 receives the signal included in the light signal L1 based on the output signal output by the light detection device 411.

[0117] 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 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.

[0118] Figure 15 This is a conceptual diagram of an example of a communication system. Figure 13 The communication system shown has two terminal devices 500. The terminal devices 500 are, for example, smartphones, tablet computers, personal computers, and the like.

[0119] 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 detecting device 411.

[0120] also, Figure 16 This is a conceptual diagram of an example of a communication system. Figure 15 , the terminal devices 500 are all smartphones, but the terminal devices 500 may be different in the transmitting side and the receiving side. Figure 16 The terminal device 500 shown is a smartphone, and the terminal device 501 is a personal computer.

Claims

1. An optical device, wherein: The optical device has a waveguide and a magnetic element. The waveguide has a core for transmitting light and a cladding covering the core. The core has a diffraction grating on the first surface, The magnetic element is located above the first surface in the cladding. The magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer located between the first ferromagnetic layer and the second ferromagnetic layer.

2. The optical device according to claim 1, wherein The magnetic element is located at the same position as the diffraction grating or in front of the diffraction grating in the traveling direction of light propagating in the core.

3. The optical device according to claim 1, wherein The magnetic element is located at a position overlapping with the diffraction grating when viewed from the stacking direction. The optical device according to claim 1 , wherein: The magnetic element is located at a position not overlapping with the diffraction grating when viewed from the stacking direction. The optical device according to claim 1 , wherein: The magnetic element is in contact with the diffraction grating. The optical device according to claim 1 , wherein: The core has an element-setting portion and a light-transmitting portion reaching the element-setting portion, The width of the core in the element-disposing portion is wider than the width of the core in the light-transmitting portion.

7. The optical device according to claim 1, wherein The optical device has a plurality of the magnetic elements.

8. A receiving device, wherein: The receiving device includes the optical device according to claim 1.

9. A transmitting and receiving device, wherein: The transmitting and receiving device includes the receiving device according to claim 8.

10. A communication system, wherein: This communication system includes the receiving device according to claim 8.

11. A terminal device, wherein: The terminal device includes the receiving device according to claim 8.

12. An optical system, wherein: This optical system includes the optical device according to claim 1 .

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