Optical devices and optical systems

Abstract

To provide an optical device and optical system that eliminate the need for high-precision optical axis adjustment and enable appropriate irradiation of a magnetic element with reflected light from an object to be irradiated using a simple configuration. [Solution] The optical device 1A according to the present invention comprises at least one magnetic element 30 having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, laser diodes 11, 12, 13, 14 that emit laser light, and a waveguide 20. The waveguide 20 has at least one light inlet 21i, 22i, 23i, 24i into which the laser light from the laser diodes 11, 12, 13, 14 is incident, and a light outlet 27o that emits the light to the outside, and at least one magnetic element 30 is arranged near the light outlet 27o.

Description

Technical Field

[0001] The present invention relates to an optical device and an optical system.

Background Art

[0002] Laser light is widely used in various fields such as industry, medicine, and communication. In particular, laser diodes that emit laser light are packaged and commercially available, and can packages and butterfly packages are known as typical package forms.

[0003] In recent years, XR glasses such as AR (Augmented Reality) glasses and VR (Virtual Reality) glasses have been expected as small wearable devices. In XR glasses, it is important to miniaturize each component so as to fit into the size of ordinary glasses. Under such circumstances, attention has been increasing on small planar lightwave circuits (PLCs) using laser diodes. In addition, it is expected to use an optical modulator in which an optical waveguide is formed in a material having an electro-optic effect, and in particular, an optical modulator provided with an optical modulation element using a lithium niobate film is expected to be used.

[0004] Patent Document 1 below discloses an optical device comprising an optical modulation element preferably using a lithium niobate film and a plurality of laser diodes. The optical modulation element has a waveguide and a plurality of magnetic elements. The plurality of laser diodes include a near-infrared laser used for eye tracking applications. Near-infrared light emitted by the near-infrared laser is incident on an optical inlet, which is one end of the waveguide, propagates through the waveguide, and is emitted to the outside from an optical outlet, which is the other end of the waveguide, and irradiates the object to be irradiated. A portion of the reflected light reflected by the object to be irradiated returns to the waveguide from the optical outlet and reaches the magnetic elements through a monitoring waveguide connected to the waveguide. The magnetic elements measure the intensity of the reflected light returning through the monitoring waveguide, thereby detecting the state of the eyeball as the object to be irradiated (position of the pupil, point of gaze, etc.). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-155468 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the optical device disclosed in Patent Document 1, it is necessary to adjust the optical axis of the reflected light and the optical axis of the optical output port of the waveguide (waveguide coupling) in order to return the reflected light from the irradiated object back into the waveguide. However, this optical axis adjustment requires high-precision adjustment of the angle and position of the optical axis, and there is a problem that it is not easy to properly return the reflected light back into the waveguide. Furthermore, because propagation loss occurs in the waveguide and monitoring waveguide, the intensity of the reflected light decreases, and there is a problem that a sufficient amount of light is not irradiated onto the magnetic element in order to measure the intensity of the reflected light.

[0007] The present invention has been made in view of the above problems, and aims to provide an optical device and optical system that eliminates the need for high-precision optical axis adjustment and enables appropriate irradiation of a magnetic element with reflected light from an object to be irradiated using a simple configuration. [Means for solving the problem]

[0008] To solve the above problems, the optical device according to the present invention comprises at least one magnetic element having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, a laser diode that emits laser light, and a waveguide, wherein the waveguide has at least one light inlet into which the laser light of the laser diode is incident, and a light outlet that emits the laser light to the outside, and the at least one magnetic element is arranged near the light outlet.

[0009] To solve the above problems, the optical system according to the present invention is characterized by comprising the above-mentioned optical device and an optical system that guides the laser light emitted by the optical device to the object to be irradiated. [Effects of the Invention]

[0010] The present invention provides an optical device and optical system that eliminates the need for high-precision optical axis adjustment and enables appropriate irradiation of a magnetic element with reflected light from an object to be irradiated using a simple configuration. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic plan view of the optical device in the first embodiment of the present invention. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a perspective view showing the vicinity of the magnetic element in Figure 1. [Figure 4] This is a plan view showing the vicinity of the magnetic element in Figure 1. [Figure 5] This is a cross-sectional view along line BB in Figure 1. [Figure 6] It is a cross-sectional view taken along the C-C line of FIG. 1. [Figure 7] It is a view partially enlarging the periphery of the magnetic element of FIG. 5. [Figure 8] It is a cross-sectional view showing the magnetic element of the optical device in the first embodiment of the present invention. [Figure 9] It is a diagram for explaining the first mechanism of the operation regarding the magnetic element of the optical device in the first embodiment of the present invention. [Figure 10] It is a diagram for explaining the second mechanism of the operation regarding the magnetic element of the optical device in the first embodiment of the present invention. [Figure 11] It is a perspective view showing the vicinity of the magnetic element of the optical device in the second embodiment of the present invention. [Figure 12] It is a plan view showing the vicinity of the magnetic element of FIG. 1 \\( 1 \\). [Figure 13] It is a cross-sectional view showing the vicinity of the magnetic element of FIG. 11. [Figure 14] It is a perspective view showing the vicinity of the magnetic element of the optical device in the third embodiment of the present invention. [Figure 15] It is a plan view showing the vicinity of the magnetic element of FIG. 14. [Figure 16] It is a cross-sectional view showing the vicinity of the magnetic element of FIG. 14. [Figure 17] It is a perspective view showing the vicinity of the magnetic element of the optical device in the fourth embodiment of the present invention. [Figure 18] It is a cross-sectional view showing the vicinity of the magnetic element of FIG. 17. [Figure 19] It is a perspective view showing the vicinity of the magnetic element of the optical device in the fifth embodiment of the present invention. [Figure 20] It is a cross-sectional view showing the vicinity of the magnetic element of FIG. 19. [Figure 21] It is a schematic plan view of the optical device in the sixth embodiment of the present invention. [Figure 22] It is a schematic plan view of the optical modulation section of FIG. 21. [Figure 23] It is a conceptual diagram of the optical system according to the present invention. [Figure 24]This is a schematic plan view of an optical device in a derivative example of the present invention. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below, with appropriate reference to the drawings. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features, and the dimensions and proportions of each component may differ from those of the actual components. The materials, dimensions, etc., exemplified in the following description are merely examples. The present invention is not limited to these examples, and can be implemented with appropriate modifications within the scope of achieving the effects of the present invention. Furthermore, the "~" symbol indicating a numerical range means any numerical value within the range that includes the values ​​written before and after it as the lower and upper limits.

[0013] [First Embodiment] The first embodiment of the present invention will be described below.

[0014] First, the configuration of the optical device 1A in the first embodiment of the present invention will be described with reference to Figure 1. Figure 1 is a schematic plan view of the optical device 1A in the first embodiment.

[0015] The optical device 1A shown in Figure 1 comprises a plurality of laser diodes 11, 12, 13, and 14, an optical waveguide element 10A, and a magnetic element 30.

[0016] In this specification, in the xyz Cartesian coordinate system set out in the figure, the direction along one side of the optical waveguide element 10A is defined as the x-direction, the direction perpendicular to the x-direction is defined as the y-direction, and the direction perpendicular to both the x-direction and the y-direction is defined as the z-direction. The x-direction is the longitudinal direction of the optical waveguide element 10A. The y-direction is the width direction of the optical waveguide element 10A. The z-direction is the direction perpendicular to the main surface of the optical waveguide element 10A. Hereafter, we will further consider the orientation and express it as "positive z-direction," "negative z-direction," etc., and in particular, "positive z-direction" may be referred to as the upward direction, and "negative z-direction" as the downward direction. Note that the z-direction, which is the vertical direction, does not necessarily coincide with the direction in which gravity acts.

[0017] The laser diodes 11, 12, 13, and 14 are configured to emit laser light in different wavelength ranges, for example. The laser diodes 11, 12, 13, and 14 may be provided as an integrated light source module. The laser diodes 11, 12, 13, and 14 may be mounted on the top surface of the subcarrier, for example, in a bare chip state. In this case, the laser diodes 11, 12, 13, and 14 can be fixed to the optical waveguide element 10A by bonding the subcarrier and the substrate 28 of the optical waveguide element 10A (see, for example, Figure 2) via a metal junction layer or the like.

[0018] Laser diode 11 is a red laser light source that emits laser light (red light) in the wavelength range of 590 nm to 800 nm, for example. Laser diode 12 is a green laser light source that emits light (green light) in the wavelength range of 490 nm to less than 590 nm, for example. Laser diode 13 is a blue laser light source that emits light (blue light) in the wavelength range of 380 nm to less than 490 nm, for example. Laser diode 14 is a near-infrared laser light source that emits laser light (near-infrared light) in the wavelength range of 780 nm to 2500 nm, for example. The arrangement order and number of laser diodes 11, 12, 13, and 14 that emit light in each wavelength range are not particularly limited.

[0019] Laser diodes 11, 12, and 13 each emit visible light of the three primary colors (red, green, and blue). By superimposing these emitted lights based on the principle of additive color mixing, a desired color can be expressed. Laser diodes 11, 12, and 13 may also emit light of colors other than the three primary colors.

[0020] Visible light is used, for example, for image display. In order to express a desired color by superimposing light of each color, it is desirable to appropriately adjust the intensity of light of each color. For example, the intensity of the light emitted from laser diodes 11, 12, and 13 may be appropriately controlled. Alternatively, as will be described in the sixth embodiment later, an optical modulation unit may be provided within the optical waveguide element 10A, and optical modulation may be performed within the optical waveguide element 10A.

[0021] The laser diode 14 emits near-infrared light. Near-infrared light is used, for example, in eye-tracking applications.

[0022] An optical waveguide element 10A has a waveguide 20 formed therein for propagating light. As shown in Figure 1, the waveguide 20 is composed of, for example, input waveguides 21, 22, 23, and 24, a first multiplexer 25 and a second multiplexer 26, and an output waveguide 27.

[0023] At the ends of the input waveguides 21, 22, 23, and 24, optical entrance ports 21i, 22i, 23i, and 24i are formed for the laser light emitted by the laser diodes 11, 12, 13, and 14. These optical entrance ports 21i, 22i, 23i, and 24i are optical input ports. Each input waveguide 21, 22, 23, and 24 is optically connected to the laser diodes 11, 12, 13, and 14, respectively. The laser light emitted by the laser diodes 11, 12, 13, and 14 is optically aligned so that it is properly incident on the corresponding optical entrance ports 21i, 22i, 23i, and 24i.

[0024] The input waveguides 21, 22, and 23 merge at the first multiplexer 25 and are connected to the output waveguide 27. Laser light incident at the optical entrance ports 21i, 22i, and 23i propagates through the input waveguides 21, 22, and 23, respectively, and is combined at the first multiplexer 25. Here, the input waveguides 21, 22, and 23 merge at the first multiplexer 25, but the multiplexer may be configured in multiple stages, for example, so that the input waveguide 23 merges after the input waveguides 21 and 22 merge.

[0025] The light combined in the first multiplexing section 25 propagates through the output waveguide 27 and is emitted to the outside as emitted light LE from the light emission port 27o formed at the end of the output waveguide 27. The light emission port 27o is an optical output port. The light emission port 27o is provided on one side of the optical waveguide element 10A. In this specification, the side of the optical waveguide element 10A on which the light emission port 27o is provided is referred to as the light emission surface 10o.

[0026] The input waveguide 24 is connected to the output waveguide 27 through the second multiplexer 26. Laser light incident from the laser diode 14 at the light entry port 24i propagates through the input waveguide 24 and then propagates through the output waveguide 27 via the second multiplexer 26. The light propagating through the output waveguide 27 is emitted to the outside as output light LE from the light exit port 27o formed at the end of the output waveguide 27. Near-infrared light propagating through the input waveguide 24 may be combined with visible light propagating through the input waveguides 21, 22, and 23 in the second multiplexer 26.

[0027] The emitted light LE from the light output port 27o has its optical path controlled by, for example, a MEMS mirror, and reaches the irradiated object E. The irradiated object E is, for example, a human eye. The emitted light LE is reflected by the irradiated object E. The reflected light LR, reflected by the irradiated object E, travels in the opposite direction along the same optical path as the emitted light LE and returns to the vicinity of the light output port 27o. The reflected light LR irradiates the light output surface 10o, including the vicinity of the light output port 27o. Figure 1 schematically illustrates the emitted light LE, the reflected light LR, and the irradiated object E.

[0028] As shown in Figure 1, the magnetic element 30 is positioned near the light output port 27o of the optical waveguide element 10A. The reflected light LR is irradiated onto the magnetic element 30 positioned near the light output port 27o. As a result, the magnetic element 30 can receive the reflected light LR and measure its intensity.

[0029] The magnetic element 30 is used, for example, in eye tracking and functions as an optical sensor that detects the intensity of near-infrared light. The near-infrared light emitted by the laser diode 14 propagates through the waveguide 20 via the light entrance 24i and is emitted as emitted light LE from the light exit 27o. In eye tracking, the direction of the line of sight can be detected by irradiating the human eye with near-infrared light and measuring the intensity of the reflected light LR (corneal reflected light). In addition to the measurement result of the reflected light LR intensity, the direction of the line of sight may be detected with higher accuracy by combining it with measurement results from other sensors, etc.

[0030] Referring to Figure 2, a cross-section of the optical waveguide element 10A of the optical device 1A in the first embodiment will be described. Figure 2 is a cross-sectional view along line AA in Figure 1.

[0031] As shown in Figure 2, the optical waveguide element 10A of the optical device 1A has a waveguide 20 formed on a substrate 28. The waveguide 20 and the upper surface of the substrate 28 may be in contact with each other or separated. The waveguide 20 can be formed, for example, in a layer placed on the substrate 28. Here, the waveguide 20 is provided so as to protrude from the upper surface of the substrate 28 in the positive z direction. However, the shape of the waveguide 20 and the method of forming it are not particularly limited.

[0032] Waveguides 20 are covered with cladding 29. Figure 2 shows cross-sections of input waveguides 21, 22, 23, and 24, but waveguides 20 in other locations are similarly formed on the substrate 28 and covered with cladding 29.

[0033] From the viewpoint of confining light in the waveguide 20 and improving the light propagation efficiency, it is preferable to use a material for the substrate 28 that has a lower refractive index than the material of the waveguide 20. As the material for the substrate 28, for example, a material containing aluminum oxide, particularly sapphire, can be used.

[0034] It is preferable to use a material with a higher refractive index than the substrate 28 for the layer in which the waveguide 20 is formed. Furthermore, a material having an electro-optic effect can be used as the layer material in which the waveguide 20 is formed; for example, a material containing lithium niobate as its main component can be used.

[0035] The material of the cladding 29 can be appropriately selected in accordance with the materials of the waveguide 20 and the substrate 28. It is preferable to use a material for the cladding 29 that has a lower refractive index than the waveguide 20 and is also light-transmitting. Examples of materials that can be used for the cladding 29 include SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, Y2O3, CaF2, In2O3, or mixtures thereof. However, the materials of the waveguide 20, substrate 28, and cladding 29 are not limited to the examples above.

[0036] The magnetic element 30 of the optical device 1A in the first embodiment will be described with reference to Figures 3 to 6. Figure 3 is a perspective view showing the vicinity of the magnetic element 30 in Figure 1. Figure 4 is a plan view showing the vicinity of the magnetic element 30 in Figure 1. Figure 5 is a cross-sectional view along line BB in Figure 1. Figure 5 shows a cross-section of the magnetic element 30 in the zx plane. Figure 6 is a cross-sectional view along line CC in Figure 1. Figure 6 shows a cross-section of the magnetic element 30 in the yz plane.

[0037] As shown in Figures 3 to 6, the magnetic element 30 is positioned near the light output port 27o of the optical waveguide element 10A. The magnetic element 30 is positioned above the substrate 28. Here, it is positioned within the cladding 29 that covers the waveguide 20, so that the magnetic element 30 is integrated with the optical waveguide element 10A and cannot be separated.

[0038] Although not shown in the illustration, the optical device 1A may also be provided with magnetic elements 30 in locations other than near the light output port 27o of the optical waveguide element 10A. That is, the optical device 1A may have multiple magnetic elements, and at least one of the multiple magnetic elements 30 is located near the light output port 27o. The other magnetic elements may be used for other purposes, such as adjusting the white balance of visible light.

[0039] As shown in Figures 3 to 6, the magnetic element 30 is positioned at a offset from the waveguide 20. More specifically, the magnetic element 30 is positioned at a different height or width relative to the waveguide 20 so that light propagating through the waveguide 20 does not irradiate the magnetic element 30. Preferably, the magnetic element 30 is positioned away from the waveguide 20 so that light leaking from the waveguide 20 does not reach the magnetic element 30.

[0040] As shown in Figures 3 to 6, the magnetic element 30 is electrically connected to the upper electrode 41, the lower electrode 42, via wirings 43 and 44, the input terminal 45, and the output terminal 46.

[0041] The upper electrode 41 and the lower electrode 42 contain a conductive material. The upper electrode 41 and the lower electrode 42 are composed of plate-shaped members containing, for example, a conductive material, and are arranged facing each other with the magnetic element 30 in between. The upper electrode 41 is connected to the first surface of the magnetic element 30. The lower electrode 42 is connected to the second surface of the magnetic element 30. Hereinafter, the first surface of the magnetic element 30 located on the upper electrode 41 side may be referred to as the upper surface, and the second surface of the magnetic element 30 located on the lower electrode 42 side may be referred to as the lower surface. The upper and lower surfaces of the magnetic element 30 face each other in the stacking direction of the magnetic element 30.

[0042] For example, metals such as Cu, Al, Au, or Ru can be used as the material for the upper electrode 41 and the lower electrode 42. Ta or Ti may be laminated above or below these metals. Alternatively, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN may be used as the upper electrode 41 and the lower electrode 42, or TiN or TaN may be used.

[0043] The upper electrode 41 and the lower electrode 42 may be light-transmitting in the wavelength range of light irradiated onto the magnetic element 30. For example, the upper electrode 41 and the lower electrode 42 may be transparent electrodes containing oxide transparent electrode materials such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO). The upper electrode 41 and the lower electrode 42 may have a configuration in which multiple columnar metals are contained within these transparent electrode materials.

[0044] The via wiring 43 connects the input terminal 45 to the upper electrode 41 or the lower electrode 42. The input terminal 45 is provided corresponding to the via wiring 43. Here, as an example, two via wirings 43 and two input terminals 45 are provided. One end of the input terminal 45 is electrically connected to the upper electrode 41, to which current or voltage is input. The other end of the input terminal 45 is electrically connected to the lower electrode 42 and is connected to a reference potential. The input terminal 45 is exposed, for example, on the upper surface of the cladding 29.

[0045] The via wiring 44 connects the output terminal 46 to the upper electrode 41 or the lower electrode 42. The output terminal 46 is provided corresponding to the via wiring 44. Here, as an example, two via wirings 44 and two output terminals 46 are provided. One of the output terminals 46 is electrically connected to the upper electrode 41 and outputs an electrical signal. The other of the output terminals 46 is electrically connected to the lower electrode 42 and is connected to a reference potential. The output terminals 46 are exposed, for example, on the upper surface of the cladding 29.

[0046] The via wirings 43 and 44, the input terminal 45, and the output terminal 46 include a conductive material. The materials used for the via wirings 43 and 44, the input terminal 45, and the output terminal 46 are the same materials as those used for the upper electrode 41 and lower electrode 42 as exemplified above.

[0047] Referring to Figure 7, the operation of irradiating the magnetic element 30 of the optical device 1A with reflected light LR will be explained. Figure 7 is a partially enlarged view of the area around the magnetic element 30 in Figure 5. Figure 7 schematically shows the operation of irradiating the magnetic element 30 with reflected light LR.

[0048] As shown in Figure 7, the magnetic element 30 is positioned near the light output port 27o. The magnetic element 30 is positioned so as to be embedded within the cladding 29 and is separated from the upper surface of the output waveguide 27.

[0049] The near-infrared light emitted by the laser diode 14 is emitted to the outside as emitted light LE from the light emission port 27o. The emitted light LE is reflected by the human eye, which is the irradiated object E, and travels in the opposite direction along the same optical path as the emitted light LE, irradiating the light emission surface 10o where the light emission port 27o is formed. In Figure 7, the emitted light LE is emitted from the light emission port 27o in the positive x direction, and the reflected light LR is irradiated onto the light emission surface 10o in the negative x direction.

[0050] The reflected light LR irradiated onto the light-emitting surface 10o propagates while diffusing within the cladding 29. At least a portion of the reflected light LR reaches and irradiates the magnetic elements 30 located within the cladding 29. At least a portion of the reflected light LR irradiates the magnetic elements 30 from a direction intersecting the stacking direction of the magnetic elements 30. Specifically, at least a portion of the reflected light LR irradiates the magnetic elements 30 from a direction perpendicular to the stacking direction. The magnetic elements 30 output an electrical signal corresponding to the intensity of the irradiated reflected light LR, thereby allowing the intensity of the reflected light LR to be measured.

[0051] In the conventional technology described above, it is necessary to appropriately adjust the optical axis of the reflected light LR to ensure that a sufficient amount of reflected light LR is incident on the optical outlet 27o of the output waveguide 27. However, there is a problem in that this optical axis adjustment is not easy. Furthermore, in the conventional technology, the reflected light LR needs to propagate through the waveguide 20 (the output waveguide 27 and the monitoring waveguide connected to the output waveguide 27). However, there is a problem in that the magnetic element 30 is not irradiated with reflected light LR of sufficient intensity due to propagation losses in the output waveguide 27 and the monitoring waveguide.

[0052] In contrast, in the optical device 1A of the first embodiment, it is sufficient to irradiate the optical emission surface 10o located around the optical emission port 27o with reflected light LR. The magnetic element 30 is positioned to receive the reflected light LR propagating outside the waveguide 20. The reflected light LR irradiated onto the optical emission surface 10o propagates through the cladding 29 without passing through the output waveguide 27 and irradiates the magnetic element 30. With this configuration, there is no need to perform high-precision optical axis adjustment (waveguide coupling) to cause the reflected light LR to enter the optical emission port 27o, nor is there a need to provide a monitoring waveguide. Furthermore, the reflected light LR reaches the magnetic element 30 located near the optical emission port 27o without propagating through the waveguide 20. As a result, propagation loss in the waveguide 20 does not occur, and a sufficient amount of reflected light LR can be irradiated onto the magnetic element 30.

[0053] The vicinity of the light output port 27o where the magnetic element 30 is located means that the distance between the magnetic element 30 and the light output port 27o is less than or equal to a predetermined distance. The distance between the magnetic element 30 and the light output port 27o should be set so that the magnetic element 30 can sufficiently measure the intensity of the reflected light LR.

[0054] For example, the distance between the magnetic element 30 and the light output port 27o may be set so that it is less than or equal to 10 wavelengths of near-infrared light. Specifically, the wavelength range of near-infrared light is 780 nm to 2500 nm, and for example, the distance between the magnetic element 30 and the light output port 27o may be set to 25 μm or less (less than or equal to 10 wavelengths of 2500 nm). Alternatively, for example, the distance between the magnetic element 30 and the light output port 27o may be set so that 10% or more of the light energy of the reflected light LR irradiated onto the light output surface 10o is irradiated onto the magnetic element 30. By setting it as described above, a sufficient amount of reflected light LR can be irradiated onto the magnetic element 30. Note that these specific values ​​are merely examples. Depending on the near-infrared light transmittance of the cladding 29 and the near-infrared light sensitivity of the magnetic element 30, the distance between the magnetic element 30 and the light output port 27o may be further increased.

[0055] The configuration of the magnetic element 30 will be described with reference to Figure 8. Figure 8 is a cross-sectional view showing the magnetic element 30 of the optical device 1A in the first embodiment. In Figure 8, the magnetizations M31, M32, and M34 in the state (initial state) of the first ferromagnetic layer 31, the second ferromagnetic layer 32, and the third ferromagnetic layer 34 are represented by arrows.

[0056] As shown in Figure 8, the magnetic element 30 has at least a first ferromagnetic layer 31, a second ferromagnetic layer 32, and a spacer layer 33. In Figure 8, the second ferromagnetic layer 32, the spacer layer 33, and the first ferromagnetic layer 31 are stacked in this order in the positive z-direction to form a laminate. The upper surface of the spacer layer 33 is in contact with the lower surface of the first ferromagnetic layer 31. The lower surface of the spacer layer 33 is in contact with the upper surface of the second ferromagnetic layer 32. In this specification, the stacking direction of the magnetic element 30 refers to the stacking direction of the second ferromagnetic layer 32, the spacer layer 33, and the first ferromagnetic layer 31. In Figure 8, the stacking direction of the magnetic element 30 coincides with the z-direction.

[0057] The magnetic element 30 is, for example, an MTJ (Magnetic Tunnel Junction) element. The first ferromagnetic layer 31 and the second ferromagnetic layer 32 are made of ferromagnetic material, and the spacer layer 33 is made of insulating material. In the magnetic element 30, the resistance value when current is passed in the stacking direction changes according to the relative change in the magnetization state M31 of the first ferromagnetic layer 31 and the magnetization state M32 of the second ferromagnetic layer 32. Such an element is also called a magnetoresistive element.

[0058] The laminate constituting the magnetic element 30 includes a third ferromagnetic layer 34, a magnetic coupling layer 35, a base layer 36, a perpendicular magnetization induction layer 37, a cap layer 38, and a sidewall insulating layer 39, and may include other layers as needed. The maximum width of the magnetic element 30 in a plan view from the stacking direction is, for example, 10 nm to 2000 nm.

[0059] The first ferromagnetic layer 31 is a photodetector layer whose magnetization M31 state changes when light is irradiated from the outside. The first ferromagnetic layer 31 is also called the magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when external energy is applied. External energy applied to the first ferromagnetic layer 31 can be, for example, light irradiated from the outside, a current flowing in the stacking direction of the magnetic element 30, or an external magnetic field. The magnetization M31 state of the first ferromagnetic layer 31 changes according to the intensity of the light irradiated onto the first ferromagnetic layer 31.

[0060] The first ferromagnetic layer 31 contains a ferromagnetic material. The first ferromagnetic layer 31 contains at least one of the magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 31 may also contain non-magnetic elements such as B, Mg, Hf, and Gd along with the magnetic elements mentioned above. The first ferromagnetic layer 31 may be, for example, an alloy containing magnetic and non-magnetic elements. The first ferromagnetic layer 31 may be composed of multiple layers. The first ferromagnetic layer 31 may be, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, or a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers.

[0061] The first ferromagnetic layer 31 may be an in-plane magnetized film having an easy magnetization axis in the direction in the film plane, or a perpendicular magnetized film having an easy magnetization axis perpendicular to the film plane. The direction in the film plane is parallel to the xy plane, and the direction perpendicular to the film plane is the z direction.

[0062] The thickness of the first ferromagnetic layer 31 is, for example, 1.0 nm to 5.0 nm, and preferably 1.0 nm to 2.0 nm. When the first ferromagnetic layer 31 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 31 is thin, the perpendicular magnetic anisotropy becomes stronger due to the interfacial effect between the upper and lower layers of the first ferromagnetic layer 31. As a result, the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 becomes stronger, and the force that causes the magnetization M31 of the first ferromagnetic layer 31 to return to the direction perpendicular to the film surface (initial state) becomes stronger. On the other hand, if the thickness of the first ferromagnetic layer 31 is thick, the interfacial effect between the upper and lower layers of the first ferromagnetic layer 31 becomes relatively weaker. As a result, the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 becomes weaker.

[0063] When the thickness of the first ferromagnetic layer 31 decreases, the volume of the ferromagnetic material decreases, and when it increases in thickness, the volume of the ferromagnetic material increases. The reactivity of the magnetization M31 of the first ferromagnetic layer 31 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 31. That is, when the product of the magnetic anisotropy and volume of the first ferromagnetic layer 31 decreases, the reactivity to light increases. From this viewpoint, in order to increase the reactivity to light, it is preferable to appropriately design the magnetic anisotropy of the first ferromagnetic layer 31 and then reduce the volume of the first ferromagnetic layer 31.

[0064] If the thickness of the first ferromagnetic layer 31 is greater than 2.0 nm, an insertion layer made of, for example, Mo and W may be provided within the first ferromagnetic layer 31. For example, the first ferromagnetic layer 31 may be a laminate in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in that order. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer increases the overall perpendicular magnetic anisotropy of the first ferromagnetic layer 31. The thickness of the insertion layer is, for example, 0.1 nm to 0.6 nm.

[0065] The second ferromagnetic layer 32 is a magnetization-fixed layer. The magnetization-fixed layer is a layer made of a magnetic material in which the state of magnetization M32 changes less easily than that of the magnetization-free layer when external energy is applied.

[0066] When external energy is applied, the direction and strength of the magnetization M32 of the second ferromagnetic layer 32, which is the magnetization fixed layer, are less likely to change than those of the first ferromagnetic layer 31, which is the magnetization free layer. The coercivity of the second ferromagnetic layer 32 is greater than, for example, the coercivity of the first ferromagnetic layer 31. The second ferromagnetic layer 32 has an easy magnetization axis in the same direction as, for example, the first ferromagnetic layer 31. The second ferromagnetic layer 32 may be an in-plane magnetized film or a perpendicular magnetized film.

[0067] The material constituting the second ferromagnetic layer 32 can be, for example, the same material as that used for the first ferromagnetic layer 31. The second ferromagnetic layer 32 may be a laminate in which, for example, Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm are stacked in that order.

[0068] The magnetization M32 of the second ferromagnetic layer 32 may be fixed, for example, by magnetic coupling with the third ferromagnetic layer 34 via the magnetic coupling layer 35. In this case, the second ferromagnetic layer 32, the magnetic coupling layer 35, and the third ferromagnetic layer 34 together may be referred to as the magnetization-fixing layer.

[0069] The third ferromagnetic layer 34 is magnetically coupled to, for example, the second ferromagnetic layer 32. This magnetic coupling is, for example, an antiferromagnetic coupling, and is caused by the RKKY interaction. The material constituting the third ferromagnetic layer 34 can be, for example, the same material as that used for the first ferromagnetic layer 31. The material for the magnetically coupled layer 35 can be, for example, Ru, Ir, etc.

[0070] The spacer layer 33 is a non-magnetic layer placed between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. The spacer layer 33 is sandwiched between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. The spacer layer 33 is composed of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point composed of a conductor within an insulator. The thickness of the spacer layer 33 can be adjusted according to the orientation direction of the magnetization M31 of the first ferromagnetic layer 31 and the magnetization M32 of the second ferromagnetic layer 32 in the initial state described later.

[0071] For example, if the spacer layer 33 is made of an insulator, the magnetic element 30 has a magnetic tunnel junction consisting of a first ferromagnetic layer 31, a spacer layer 33, and a second ferromagnetic layer 32. Such an element is called an MTJ element. In this case, the magnetic element 30 can exhibit the TMR (Tunnel Magnetoresistance) effect. If the spacer layer 33 is made of a non-magnetic conductive material, the magnetic element 30 can exhibit the GMR (Giant Magnetoresistance) effect. Such an element is called a GMR element. The magnetic element 30 may be called an MTJ element, a GMR element, etc., depending on the constituent material of the spacer layer 33, but it is collectively called a magnetoresistive element.

[0072] When the spacer layer 33 is made of an insulating material, the spacer layer 33 can be made of a material containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide. The spacer layer 33 may also contain elements such as Al, B, Si, Mg, or magnetic elements such as Co, Fe, and Ni in addition to these insulating materials. A high magnetoresistance change rate can be obtained by adjusting the film thickness of the spacer layer 33 so that a high TMR effect is exhibited between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. In order to efficiently exhibit the TMR effect, the film thickness of the spacer layer 33 may be around 0.5 nm to 5.0 nm, or even around 1.0 nm to 2.5 nm.

[0073] When the spacer layer 33 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently exhibit the GMR effect, the film thickness of the spacer layer 33 may be approximately 0.5 nm to 5.0 nm, or even 2.0 nm to 3.0 nm.

[0074] When the spacer layer 33 is made of a non-magnetic semiconductor material, metallic materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or ITO can be used for the spacer layer 33. In this case, the film thickness of the spacer layer 33 may be approximately 1.0 nm to 4.0 nm.

[0075] When a layer containing current-carrying points composed of conductors in a non-magnetic insulator is applied as the spacer layer 33, the structure may include current-carrying points composed of non-magnetic conductors such as Cu, Au, and Al in a non-magnetic insulator composed of aluminum oxide or magnesium oxide. Alternatively, the conductors may be composed of magnetic elements such as Co, Fe, and Ni. In this case, the film thickness of the spacer layer 33 may be about 1.0 nm to 2.5 nm. The current-carrying points may be, for example, columnar bodies. The diameter of the columnar bodies when viewed from a direction perpendicular to the film surface can be 1.0 nm to 5.0 nm.

[0076] The base layer 36 is positioned between the third ferromagnetic layer 34 and the lower electrode 42. The base layer 36 is either a seed layer or a buffer layer. A seed layer is a layer that enhances the crystallinity of layers stacked on top of it. Seed layers include, for example, Pt, Ru, Hf, Zr, and NiFeCr. The thickness of the seed layer is, for example, 1.0 nm to 5.0 nm. A buffer layer is a layer that alleviates lattice mismatch between different crystals. Buffer layers include, for example, Ta, Ti, W, Zr, Hf, or nitrides of these elements. The thickness of the buffer layer is, for example, 1.0 nm to 5.0 nm.

[0077] The capping layer 38 is provided between the first ferromagnetic layer 31 and the upper electrode 41. The capping layer 38 prevents damage to the lower layer during the process and enhances the crystallinity of the lower layer during annealing. The thickness of the capping layer 38 is, for example, 3.0 nm or less, so that sufficient light is irradiated onto the first ferromagnetic layer 31. The capping layer 38 is, for example, MgO, W, Mo, Ru, Ta, Cu, Cr, or a multilayer film of these materials.

[0078] The perpendicular magnetization induction layer 37 is formed when the first ferromagnetic layer 31 is a perpendicular magnetization film. The perpendicular magnetization induction layer 37 is laminated on top of the first ferromagnetic layer 31. The perpendicular magnetization induction layer 37 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 31. The perpendicular magnetization induction layer 37 can be, for example, magnesium oxide, W, Ta, Mo, etc. When the perpendicular magnetization induction layer 37 is magnesium oxide, it is preferable that the magnesium oxide is oxygen-deficient to enhance conductivity. The thickness of the perpendicular magnetization induction layer 37 is, for example, 0.5 nm to 2.0 nm.

[0079] The sidewall insulating layer 39 surrounds the laminate containing the first ferromagnetic layer 31 and the second ferromagnetic layer 32. The sidewall insulating layer 39 is, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg.

[0080] The following describes the method for manufacturing the magnetic element 30. The magnetic element 30 can be manufactured by lamination steps for each layer, annealing steps, and processing steps.

[0081] A portion of the cladding 29 is laminated onto the substrate 28 on which the waveguide 20 is formed, and the lower electrode 42 is placed on top of it. Then, on top of the lower electrode 42, the base layer 36, the third ferromagnetic layer 34, the magnetic coupling layer 35, the second ferromagnetic layer 32, the spacer layer 33, the first ferromagnetic layer 31, the perpendicular magnetization induction layer 37, and the cap layer 38 are laminated in this order. Each layer is deposited, for example, by sputtering.

[0082] Next, the layered films are annealed as described above. The annealing temperature is, for example, 250°C to 450°C. After that, the layered films are processed into predetermined columnar bodies by photolithography and etching. The columnar bodies may be cylindrical or rectangular. For example, the shortest width of the columnar body when viewed from the layering direction may be 10 nm to 2000 nm, or 30 nm to 500 nm.

[0083] Next, an insulating layer is formed to cover the sides of the columnar body. This insulating layer becomes the sidewall insulating layer 39. The sidewall insulating layer 39 may be laminated multiple times. Then, the upper surface of the cap layer 38 is exposed from the sidewall insulating layer 39 by CMP (chemical mechanical polishing), and the upper electrode 41 is fabricated on the cap layer 38.

[0084] The magnetic element 30 can be manufactured by the above process. Since the magnetic element 30 does not need to be bonded to the substrate material by an adhesive layer or the like, it can be manufactured regardless of the material that makes up the substrate. The magnetic element 30 can be manufactured by the same process as the process of forming the waveguide 20 on the substrate 28. For example, the waveguide 20 and the magnetic element 30 can be formed on the same substrate 28 by a vacuum deposition process or the like. Furthermore, by further laminating the cladding 29 so as to cover the periphery of the side wall insulating layer 39, the magnetic element 30 is positioned so as to be embedded within the cladding 29.

[0085] Figure 8 schematically illustrates the magnetic element 30, the upper electrode 41 that contacts the upper surface of the magnetic element 30, the lower electrode 42 that contacts the lower surface of the magnetic element 30, and the circuits connected to the upper electrode 41 and the lower electrode 42.

[0086] The upper electrode 41 is connected, for example, to an input terminal Pin and an output terminal Pout, and the lower electrode 42 is connected, for example, to a reference potential terminal PG. Input terminal Pin corresponds to one of the input terminals 45 that are electrically connected to the upper electrode 41. Output terminal Pout is electrically connected to the upper electrode 41 and corresponds to one of the output terminals 46. Reference potential terminal PG corresponds to the other input terminal 45 and the other output terminal 46 that are electrically connected to the lower electrode 42. Reference potential terminal PG is connected to a reference potential. The reference potential may be located outside the optical device 1A. The reference potential may be ground G or something other than ground G.

[0087] The magnetic element 30 converts changes in the state of the irradiated light into an electrical signal and outputs it. More specifically, the output voltage or output current of the electrical signal output from the magnetic element 30 changes depending on the intensity of the irradiated light.

[0088] The input terminal Pin is connected to the power supply PS. The power supply PS may be a current source or a voltage source. The power supply PS may be mounted on the optical device 1A or provided outside of the optical device 1A.

[0089] When the input terminal Pin is connected to the power supply PS as a current source, the output terminal Pout outputs the resistance value of the magnetic element 30 in the stacking direction as a voltage. When the input terminal Pin is connected to the power supply PS as a voltage source, the output terminal Pout outputs the resistance value of the magnetic element 30 in the stacking direction as a current. If it is not necessary to apply current or voltage to the magnetic element 30 from an external source, the input terminal Pin and the power supply PS do not need to be provided.

[0090] The mechanism by which the magnetic element 30 operates as a photosensor will be explained with reference to Figures 9 and 10. Figure 9 is a diagram illustrating the first mechanism of operation of the magnetic element 30 of the optical device 1A in the first embodiment. Figure 10 is a diagram illustrating the second mechanism of operation of the magnetic element 30 of the optical device 1A in the first embodiment. In the upper graphs of Figures 9 and 10, the vertical axis represents the intensity of light irradiated onto the first ferromagnetic layer 31, and the horizontal axis represents time. In the middle of Figures 9 and 10, the first ferromagnetic layer 31, the second ferromagnetic layer 32, and the spacer layer 33 are illustrated. In the lower graph of Figure 10, the vertical axis represents the resistance value of the magnetic element 30 in the stacking direction, and the horizontal axis represents time.

[0091] It is known that the output voltage or output current of the electrical signal output from the magnetic element 30 changes depending on the intensity of the irradiated light. The exact mechanism by which the output voltage or output current of the electrical signal output from the magnetic element 30 changes depending on the intensity of the irradiated light is not yet clear, but for example, the following two mechanisms can be considered. The first mechanism is that the direction of magnetization changes according to the intensity of the light irradiated onto the magnetic element 30. The second mechanism is that the magnitude of magnetization changes according to the intensity of the light irradiated onto the magnetic element 30.

[0092] Referring to Figure 9, the first mechanism of operation of the magnetic element 30 of the optical device 1A in the first embodiment will be described.

[0093] In the state where the first ferromagnetic layer 31 is irradiated with light of a first intensity (hereinafter referred to as the initial state), the magnetization M31 of the first ferromagnetic layer 31 and the magnetization M32 of the second ferromagnetic layer 32 are in a parallel relationship. At this time, the resistance value of the magnetic element 30 in the stacking direction is a first resistance value R1, and the magnitude of the output voltage or output current from the magnetic element 30 is a first value. The first intensity may also be the state where the first ferromagnetic layer 31 is not irradiated with light (i.e., the light intensity is zero).

[0094] For example, when a constant current (sense current) is passed through the stacking direction of the magnetic element 30, a voltage is generated across both ends of the magnetic element 30 in the stacking direction. The resistance value of the magnetic element 30 in the stacking direction can be determined from this voltage value using Ohm's law. The output voltage from the magnetic element 30 is generated between the upper electrode 41 and the lower electrode 42.

[0095] In the example shown in Figure 9, it is preferable to flow the sense current from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32. By flowing the sense current from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32, a spin transfer torque acts on the magnetization M31 of the first ferromagnetic layer 31 in the same direction as the magnetization M32 of the second ferromagnetic layer 32. As a result, the magnetization M31 of the first ferromagnetic layer 31 and the magnetization M32 of the second ferromagnetic layer 32 become parallel to each other in the initial state. Furthermore, by flowing the sense current from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32, the magnetization M31 of the first ferromagnetic layer 31 can be prevented from reversing during operation.

[0096] When the intensity of light irradiated onto the magnetic element 30 changes, the external energy applied to the first ferromagnetic layer 31 changes. As a result, the direction of the magnetization M31 of the first ferromagnetic layer 31 tilts relative to its initial state. The angle between the magnetization M31 of the first ferromagnetic layer 31 in the initial state and the magnetization M31 of the first ferromagnetic layer 31 when light is irradiated is greater than 0° and less than 90°.

[0097] When the magnetization M31 of the first ferromagnetic layer 31 tilts from its initial state, the resistance value in the stacking direction of the magnetic element 30 changes, and the output voltage or output current from the magnetic element 30 changes. The greater the intensity of the light irradiated onto the magnetic element 30, the greater the tilt of the magnetization M31 of the first ferromagnetic layer 31 relative to its initial state. As shown in Figure 9, in accordance with the tilt of the magnetization M31 of the first ferromagnetic layer 31, the resistance value in the stacking direction of the magnetic element 30 changes, for example, to a second resistance value R2, a third resistance value R3, and a fourth resistance value R4. Accordingly, the output voltage or output current from the magnetic element 30 changes, for example, to a second value, a third value, and a fourth value.

[0098] As the intensity of light irradiated onto the magnetic element 30 increases, the resistance values ​​increase in the order of first resistance value R1, second resistance value R2, third resistance value R3, and fourth resistance value R4. When the power supply PS is a constant current source, the output voltage from the magnetic element 30 increases in the order of first value, second value, third value, and fourth value. When the power supply PS is a constant voltage source, the output current from the magnetic element 30 decreases in the order of first value, second value, third value, and fourth value.

[0099] Since the magnetization M31 of the first ferromagnetic layer 31 is subjected to a spin transfer torque in the same direction as the magnetization M32 of the second ferromagnetic layer 32, when the intensity of the light irradiated onto the first ferromagnetic layer 31 returns to the first intensity, the magnetization M31 of the first ferromagnetic layer 31 returns to its initial state. At this time, the resistance value of the magnetic element 30 in the stacking direction returns to the first resistance value R1, and the output voltage or output current from the magnetic element 30 returns to the first value.

[0100] Here, as an example, we have described the case where magnetization M31 and magnetization M32 are parallel in the initial state, but magnetization M31 and magnetization M32 may be antiparallel (magnetizations pointing in opposite directions) in the initial state. In this case, the greater the tilt of magnetization M31 relative to the initial state, the smaller the resistance value in the stacking direction of the magnetic element 30 becomes. When magnetization M31 and magnetization M32 are antiparallel in the initial state, it is preferable to flow the sense current from the second ferromagnetic layer 32 toward the first ferromagnetic layer 31. By flowing the sense current from the second ferromagnetic layer 32 toward the first ferromagnetic layer 31, a spin transfer torque in the opposite direction to the magnetization M32 of the second ferromagnetic layer 32 acts on the magnetization M31 of the first ferromagnetic layer 31. As a result, magnetization M31 and magnetization M32 become antiparallel to each other in the initial state.

[0101] Referring to Figure 10, the second mechanism of operation of the magnetic element 30 of the optical device 1A in the first embodiment will be described.

[0102] The initial state shown in Figure 10 is the same as the initial state shown in Figure 9. In the example shown in Figure 10, it is preferable to flow a constant current (sense current) from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32. By flowing a sense current from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32, a spin transfer torque acts on the magnetization M31 of the first ferromagnetic layer 31 in the same direction as the magnetization M32 of the second ferromagnetic layer 32, and the initial state is maintained.

[0103] When the intensity of light irradiated onto the magnetic element 30 changes, the external energy applied to the first ferromagnetic layer 31 changes. As a result, the magnitude of the magnetization M31 of the first ferromagnetic layer 31 becomes smaller than in its initial state.

[0104] As the magnetization M31 of the first ferromagnetic layer 31 decreases from its initial state, the resistance value in the stacking direction of the magnetic element 30 changes, and the output voltage or output current from the magnetic element 30 changes. The greater the intensity of the light irradiated onto the magnetic element 30, the smaller the magnitude of the magnetization M31 of the first ferromagnetic layer 31 becomes compared to the initial state. As shown in Figure 10, the resistance value in the stacking direction of the magnetic element 30 changes according to the magnitude of the magnetization M31 of the first ferromagnetic layer 31, for example, to a second resistance value R2, a third resistance value R3, and a fourth resistance value R4. Accordingly, the output voltage or output current from the magnetic element 30 changes to, for example, a second value, a third value, and a fourth value.

[0105] As the intensity of light irradiated onto the magnetic element 30 increases, the resistance values ​​increase in the order of first resistance value R1, second resistance value R2, third resistance value R3, and fourth resistance value R4. When the power supply PS is a constant current source, the output voltage from the magnetic element 30 increases in the order of first value, second value, third value, and fourth value. When the power supply PS is a constant voltage source, the output current from the magnetic element 30 decreases in the order of first value, second value, third value, and fourth value.

[0106] When the intensity of light irradiated onto the first ferromagnetic layer 31 returns to the first intensity, the magnetization M31 of the first ferromagnetic layer 31 returns to its initial state. At this time, the resistance value of the magnetic element 30 in the stacking direction returns to the first resistance value R1, and the output voltage or output current from the magnetic element 30 returns to the first value.

[0107] In Figure 10, the magnetizations M31 and M32 may be antiparallel in the initial state. In this case, the smaller the magnitude of magnetization M31 is compared to the initial state, the smaller the resistance value of the magnetic element 30 in the stacking direction becomes. When the initial state is one in which magnetizations M31 and M32 are antiparallel, it is preferable to flow the sense current from the second ferromagnetic layer 32 toward the first ferromagnetic layer 31.

[0108] In both the first mechanism shown in Figure 9 and the second mechanism shown in Figure 10, the electrical signal output from the magnetic element 30 changes according to the intensity of the light irradiated onto the magnetic element 30. The magnetic element 30 functions as a light sensor that detects changes in the state of the irradiated light and outputs an electrical signal corresponding to the light intensity.

[0109] [Second Embodiment] A second embodiment of the present invention will now be described. Figure 11 is a perspective view showing the vicinity of the magnetic element 30 of the optical device 1B in the second embodiment. Figure 12 is a plan view showing the vicinity of the magnetic element 30 in Figure 11. Figure 13 is a cross-sectional view showing the vicinity of the magnetic element 30 in Figure 11. The cross-section shown in Figure 13 is a cross-section of the magnetic element 30 in the zx plane and corresponds to the cross-section along the BB line shown in Figure 1. In the second embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted as appropriate.

[0110] As shown in Figures 11 to 13, the optical device 1B in the second embodiment has a plurality of magnetic elements 30. The plurality of magnetic elements 30 are arranged near the light output port 27o. The plurality of magnetic elements 30 are arranged to be embedded, for example, within the cladding 29 of the optical waveguide element 10B. The plurality of magnetic elements 30 are electrically connected to the upper electrode 41 and the lower electrode 42, and each magnetic element 30 functions as an optical sensor for detecting reflected light LR.

[0111] According to the second embodiment, by arranging multiple magnetic elements 30, the irradiation area of ​​reflected light LR can be increased, improving the signal-to-noise ratio (SNR) and thus improving detection accuracy. Furthermore, the arrangement of multiple magnetic elements 30 ensures redundancy, thereby ensuring reliability and availability for the detection of reflected light LR.

[0112] In the examples shown in Figures 11 to 13, the eight magnetic elements 30 are arranged in an array near the light emission port 27o. More specifically, four magnetic elements 30 are arranged in two rows, with the magnetic elements 30 in adjacent rows being staggered. This efficiently increases the area over which the reflected light LR entering the cladding 29 from the light emission surface 10o illuminates multiple magnetic elements 30.

[0113] [Third Embodiment] A third embodiment of the present invention will now be described. Figure 14 is a perspective view showing the vicinity of the magnetic element 30 of the optical device 1C in the third embodiment. Figure 15 is a plan view showing the vicinity of the magnetic element 30 in Figure 14. Figure 16 is a cross-sectional view showing the vicinity of the magnetic element 30 in Figure 14. The cross-section shown in Figure 16 is a cross-section of the magnetic element 30 in the zx plane and corresponds to the cross-section along line BB in Figure 1. In the third embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted as appropriate.

[0114] In the third embodiment, the optical device 1C has a magnetic element 30. The magnetic element 30 is located near the optical output port 27o. The magnetic element 30 is arranged to be embedded, for example, within the cladding 29 of the optical waveguide element 10C.

[0115] As shown in Figures 14 to 16, the magnetic element 30 is electrically connected to the upper electrode 41, the lower electrode 42, the via wiring 47, and the input / output terminal 48. The optical device 1C in the third embodiment differs from the optical device 1A in the first embodiment in that the input terminal 45 and the output terminal 46 are shared as the input / output terminal 48.

[0116] The via wiring 47 connects the input / output terminal 48 to the upper electrode 41 or the lower electrode 42. The input / output terminal 48 is provided corresponding to the via wiring 47. Here, as an example, two via wirings 47 and two input / output terminals 48 are provided. One of the input / output terminals 48 is electrically connected to the upper electrode 41, and current or voltage is input and an electrical signal is output. The other of the input / output terminal 48 is electrically connected to the lower electrode 42 and is connected to a reference potential. The input / output terminal 48 is exposed on the upper surface of the cladding 29, for example.

[0117] According to the third embodiment, the number of terminals can be reduced by performing current or voltage input and electrical signal output through a common input / output terminal 48. This allows for further miniaturization of the optical device 1C and creates space on the substrate 28 for other components, thereby improving design flexibility.

[0118] [Fourth Embodiment] A fourth embodiment of the present invention will now be described. Figure 17 is a perspective view showing the vicinity of the magnetic element 30 of the optical device 1D in the fourth embodiment. Figure 18 is a cross-sectional view showing the vicinity of the magnetic element 30 in Figure 17. The cross-section shown in Figure 18 is a cross-section of the magnetic element 30 in the zx plane and corresponds to the cross-section along the BB line in Figure 1. In the fourth embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted as appropriate.

[0119] As shown in Figures 17 and 18, the optical device 1D in the fourth embodiment differs from the optical device 1A in the first embodiment in that the stacking direction of the magnetic element 30 is inclined with respect to the z direction.

[0120] In the fourth embodiment, the optical device 1D has a magnetic element 30. The magnetic element 30 is located near the light output port 27o and is positioned to be embedded within the cladding 29 of the optical waveguide element 10D.

[0121] The stacking direction of the magnetic elements 30 may be inclined with respect to the z-direction. At least a portion of the reflected light LR is irradiated onto the magnetic elements 30 from a direction intersecting the stacking direction of the magnetic elements 30. However, in the first embodiment described above, at least a portion of the reflected light LR is irradiated onto the magnetic elements 30 from a direction perpendicular to the stacking direction, whereas in the fourth embodiment, it is irradiated onto the magnetic elements 30 from a direction oblique to the stacking direction (not perpendicular). The angle between the stacking direction of the magnetic elements 30 and the z-direction is not particularly limited, but can be set to, for example, 45°.

[0122] In Figures 17 and 18, the upper surface of the magnetic element 30 is positioned to face the light-emitting surface 10o, which is the direction from which the reflected light LR arrives. In this case, it is preferable to use a material that is light-transmitting in the wavelength range of the reflected light LR as the material for the upper electrode 41. The lower surface of the magnetic element 30 may also be positioned to face the light-emitting surface 10o. In this case, it is preferable to use a material that is light-transmitting in the wavelength range of the reflected light LR as the material for the lower electrode 42.

[0123] According to the fourth embodiment, by arranging the magnetic element 30 at an angle, the light-receiving area of ​​the reflected light LR on the magnetic element 30 can be increased. This increases the interaction between the magnetic element 30 and the reflected light LR, thereby improving the detection accuracy of the reflected light LR.

[0124] [Fifth Embodiment] A fifth embodiment of the present invention will now be described. Figure 19 is a perspective view showing the vicinity of the magnetic element 30 of the optical device 1E in the fifth embodiment. Figure 20 is a cross-sectional view showing the vicinity of the magnetic element 30 in Figure 19. The cross-section shown in Figure 20 is a cross-section of the magnetic element 30 in the zx plane and corresponds to the cross-section along line BB in Figure 1. In the fifth embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted as appropriate.

[0125] As shown in Figures 19 and 20, the optical device 1E in the fifth embodiment differs from the optical device 1A in the first embodiment in that it includes a reflector 50.

[0126] The optical device 1E in the fifth embodiment has a magnetic element 30. The magnetic element 30 is located near the optical output port 27o. The magnetic element 30 is arranged to be embedded, for example, within the cladding 29 of the optical waveguide element 10E.

[0127] The reflector 50 is positioned near the light emission port 27o so as to be embedded within the cladding 29. Reflected light LR irradiated onto the light emission surface 10o propagates within the cladding 29 while diffusing. The reflector 50 reflects a portion of the reflected light LR, changing its direction of propagation. For example, a mirror can be used as the reflector 50. The mirror has an inclined surface 51 that reflects light. In the example shown in Figures 19 and 20, the reflector 50 changes (reflects) the direction of propagation of reflected light LR propagating within the cladding 29 in the negative x direction to the positive z direction. The normal to the inclined surface 51 is, for example, at an angle of 45° with respect to the x and z directions.

[0128] The magnetic element 30 is positioned where it is illuminated by light from the reflector 50. In the examples shown in Figures 19 and 20, the magnetic element 30 is positioned above the reflector 50. At least a portion of the reflected light LR has its direction of travel changed by the reflector 50 and is illuminated onto the magnetic element 30 from the stacking direction of the magnetic element 30.

[0129] In Figures 19 and 20, the lower surface of the magnetic element 30 is positioned facing the reflector 50. In this case, it is preferable to use a material that transmits light in the wavelength range of reflected light LR as the material for the lower electrode 42. The upper surface of the magnetic element 30 may also be positioned facing the reflector 50. In this case, it is preferable to use a material that transmits light in the wavelength range of reflected light LR as the material for the lower electrode 42. The stacking direction of the magnetic element 30 may be inclined with respect to the z direction, and the side surface of the magnetic element 30 may be positioned facing the reflector 50.

[0130] According to the fifth embodiment, the irradiation efficiency of the reflected light LR onto the magnetic element 30 can be improved by changing the direction of propagation of the reflected light LR propagating within the cladding 29 using the reflector 50. Furthermore, the placement position of the magnetic element 30 can be flexibly set, improving the degree of design freedom.

[0131] [Sixth Embodiment] A sixth embodiment of the present invention will now be described. Figure 21 is a schematic plan view of the optical device 1F in the sixth embodiment. Figure 22 is a schematic plan view of the optical modulation unit 60 in Figure 21. In the sixth embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and their descriptions are omitted as appropriate.

[0132] As shown in Figure 21, the optical waveguide element 10F of the optical device 1F includes an optical modulation unit 60 that modulates the intensity of visible light of each color emitted by the laser diodes 11, 12, and 13. Laser diodes 11, 12, and 13 can be those that emit laser light of a constant intensity. The optical modulation unit 60 can be provided, for example, in each of the input waveguides 21, 22, and 23, and can independently modulate the visible light of each color.

[0133] In the optical modulation section 60, a Mach-Zehnder type waveguide 70 having the structure of a Mach-Zehnder interferometer is formed as the waveguide 20. It is preferable to use a material that exhibits electro-optic effects for the Mach-Zehnder type waveguide 70, for example, a material containing lithium niobate as its main component.

[0134] The optical modulation unit 60 shown in Figure 22 will now be described. Although Figure 22 shows an optical modulation unit 60 installed in a part of the input waveguide 21, optical modulation units 60 installed in input waveguides 22 and 23 have a similar configuration. The optical modulation unit 60 shown in Figure 22 is just one example and is not limited to this configuration.

[0135] The optical modulation 60 shown in Figure 22 comprises an upstream waveguide 71, a demultiplexer 72, a first waveguide 73 and a second waveguide 74, a multiplexer 75, and a downstream waveguide 76. The upstream waveguide 71 constitutes the portion of the input waveguide 21 closest to the optical entrance 21i. The downstream waveguide 76 constitutes the portion of the input waveguide 21 closest to the first multiplexer 25.

[0136] The upstream waveguide 71 branches into a first waveguide 73 and a second waveguide 74 at the demultiplexing section 72. The first waveguide 73 and the second waveguide 74 extend parallel to each other and merge into the downstream waveguide 76 at the joining section 75.

[0137] The optical modulation unit 60 further comprises electrodes 81, 82, 83, and 84 for applying an electric field to the Mach-Zehnder waveguide 70, power supplies 85 and 86, and a termination resistor 87. Power supply 85 applies a modulation voltage to the Mach-Zehnder waveguide 70 through electrodes 81 and 82. Power supply 86 applies a DC bias voltage to the Mach-Zehnder waveguide 70 through electrodes 83 and 84.

[0138] When performing optical modulation, a voltage is applied between electrodes 81 and 82. This applies an electric field to the first waveguide 73 and the second waveguide 74, and the refractive index of the first waveguide 73 and the second waveguide 74 changes due to the electro-optic effect. The visible light emitted from the laser diode 11 propagates through the upstream waveguide 71, is demultiplexed in the demultiplexer 72, and then propagates through the first waveguide 73 and the second waveguide 74. When a refractive index difference is generated between the first waveguide 73 and the second waveguide 74, a phase difference is created between the light propagating through the first waveguide 73 and the light propagating through the second waveguide 74. By controlling this phase difference, the intensity of the light combined in the combiner 75 can be controlled to a desired value.

[0139] According to the sixth embodiment, optical modulation can be performed by the optical modulation unit 60 mounted on the optical waveguide element 10F, and compared to the case where the intensity of the emitted light from the laser diodes 11, 12, and 13 is controlled, it is possible to reduce power consumption while achieving excellent responsiveness.

[0140] [Optical System] The optical system according to the present invention will now be described. Figure 23 is a conceptual diagram of the optical system 100 according to the present invention. Figure 23 illustrates the optical system 100 equipped with the optical device 1A in the first embodiment, but optical devices 1B to 1F in the second to sixth embodiments may also be used.

[0141] The present invention can provide an optical system 100 comprising optical devices 1A to 1F according to the first to sixth embodiments described above. The optical system 100 constitutes an image display device that displays information that can be visually recognized as images (still images and moving images). The optical system 100 can be implemented in, for example, glasses-type terminals such as XR glasses 200.

[0142] The XR glasses 200 shown in Figure 23 include a light source module 110, an optical system 120, a laser driver 130, an optical scanning mirror driver 140, and a video controller 150 that controls these drivers.

[0143] The XR glasses 200 can be equipped with the optical devices 1A to 1F described in the first to sixth embodiments above as a light source module 110. The light source module 110 is installed, for example, on the frame 201 of the XR glasses 200.

[0144] The optical system 120 optically processes the emitted light LE from the light source module 110. For example, it includes a collimator lens 121, a slit 122, an ND filter 123, and a light scanning mirror 124. The optical system 120 shown in Figure 23 is an example, and other configurations are possible.

[0145] For example, a MEMS mirror can be used as the optical scanning mirror 124. To project a two-dimensional image, it is preferable to use a two-axis MEMS mirror as the optical scanning mirror 124, which vibrates to reflect laser light by changing angles in the horizontal and vertical directions.

[0146] In the XR glasses 200 shown in Figure 23, a light source module 110 attached to the frame 201 emits light LE. The emitted light LE is reflected by the optical scanning mirror 124 and then reflected again by the lens 202 of the XR glasses 200. The light reflected by the lens 202 enters the human eye (eyeball) and is formed on the retina M, allowing it to be visually recognized as an image.

[0147] The XR glasses 200 shown in Figure 23 have an eye-tracking function. Near-infrared light emitted by the laser diode 14 is used for eye tracking. The near-infrared light emitted by the laser diode 14 is reflected by the human eyeball. Examples of parts of the eyeball that reflect the light include the cornea, pupil, iris, retina, and sclera. The reflected light LR, reflected by the eyeball, travels in the reverse direction along the same optical path as the emitted light LE and reaches the light source module 110.

[0148] The reflected light LR is irradiated onto the light-emitting surfaces 10o of the optical devices 1A to 1F that constitute the light source module 110. A portion of the reflected light LR irradiated onto the light-emitting surfaces 10o propagates through the cladding 29 and irradiates the magnetic element 30. The magnetic element 30 outputs an electrical signal corresponding to the intensity of the reflected light LR. The XR glasses 200 can determine the movement of the line of sight (point of gaze) based on the irradiation position of the near-infrared light adjusted by the optical scanning mirror 124 and the intensity of the reflected light LR.

[0149] [Derivative examples] Figure 24 is a schematic plan view of optical device 1G in a derivative example of the present invention. While optical devices 1A to 1F described above are configured to emit both visible light and near-infrared light, optical device 1G is configured to emit only near-infrared light.

[0150] The optical device 1G shown in Figure 24 includes a laser diode 14, an optical waveguide element 10G, and a magnetic element 30. A waveguide 90 for propagating light is formed in the optical waveguide element 10G. An optical entrance port 90i is formed at one end of the waveguide 90. An optical exit port 90o is formed at the other end of the waveguide 90. Waveguide 90 corresponds to the waveguide 20 described above. The optical entrance port 90i and the optical exit port 90o correspond to the optical entrance port 24i and the optical exit port 27o described above, respectively.

[0151] The laser diode 14 emits near-infrared light. The laser light emitted by the laser diode 14 is incident on the optical input port 90i of the waveguide 90 and is emitted as output light LE from the optical output port 90o. The output light LE irradiates the object to be irradiated E. The reflected light LR reflected by the object to be irradiated E travels in the opposite direction along the same optical path as the output light LE and irradiates the optical output surface 10o of the optical waveguide element 10G.

[0152] In the optical device 1G, the magnetic element 30 is located near the light output port 90o. The magnetic element 30 is positioned, for example, so as to be embedded within the cladding 29 of the optical waveguide element 10G.

[0153] In the optical device 1G shown in Figure 24, the configuration of the magnetic element 30 and its vicinity is the same as that of the optical device 1A in the first embodiment described above. However, the same configuration as that of the second to fifth embodiments described above may also be used.

[0154] The reflected light LR irradiated onto the light-emitting surface 10o propagates through the cladding 29 and irradiates the magnetic element 30. The magnetic element 30 outputs an electrical signal corresponding to the intensity of the irradiated reflected light LR, thereby allowing the intensity of the reflected light LR to be measured.

[0155] Thus, according to a derivative example of the present invention, an optical device 1G for eye-tracking applications can be provided that emits near-infrared light as emitted light LE and measures the intensity of the reflected light LR. Furthermore, according to a derivative example of the present invention, an optical system for eye-tracking applications equipped with the optical device 1G can also be provided.

[0156] Although various embodiments of the present invention have been described, the present invention is not limited to these embodiments. Various modifications and changes are possible without departing from the spirit of the present invention, and the embodiments can be combined as appropriate.

[0157] As described above, the present invention has the effect of eliminating the need for high-precision optical axis adjustment and allowing reflected light from the object to be irradiated to be appropriately irradiated to the magnetic element with a simple configuration, making it useful for light detection technology in general. In particular, the present invention has the effect of allowing reflected light from the human eyeball to be appropriately irradiated to the magnetic element, making it useful for eye tracking technology in general. [Explanation of Symbols]

[0158] 1A, 1B, 1C, 1D, 1E, 1F, 1G Optical Devices 10A, 10B, 10C, 10D, 10E, 10F, 10G optical waveguide device 10o light exit surface 11, 12, 13, 14 Laser diodes 20, 90 waveguides 21, 22, 23, 24 Input waveguides 21i, 22i, 23i, 24i, 90i light entrance 25. First wave section 26. Second Wave Intersection 27 Output waveguide 27°, 90° light output port 28 circuit boards 29 Clad 30 Magnetic elements 31 First ferromagnetic layer 32 Second ferromagnetic layer 33 Spacer layer 34 Third ferromagnetic layer 35 Magnetic coupling layer 36 Base layer 37. Perpendicular magnetization-induced layer 38 Cap Layer 39. Sidewall insulation layer 41 Upper electrode 42 Lower electrode Via wiring 43, 44, 47 45. Pin Input Terminal 46. ​​Pout output terminal 48 Input / output terminal 50 Reflectors 51 Slope 60 Optical Modulation Section 70. Mach-Zehnder Waveguide 71 Upstream Waveguide 72 Demultiplexer 73 Waveguide 1 74 Waveguide 2 75 Wave section 76 Downstream waveguide 81, 82, 83, 84, PS electrode 85, 86 Power supply 87 Termination resistor 100 Optical Systems 110 Light Source Modules 120 Optical system 121 Collimator lens 122 slits 123 ND filter 124 Optical scanning mirrors 130 Laser Drivers 140 Optical Scanning Mirror Driver 150 Video Controllers 200 XR Glasses 201 frames 202 Lens E Irradiated object G Ground LE output light LR reflected light M31, M32, M34 magnetization PG reference potential terminal

Claims

1. A magnetic element comprising a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first and second ferromagnetic layers, A laser diode that emits laser light, A waveguide and, The waveguide has at least one light inlet into which the laser light of the laser diode is incident, and a light outlet for which the laser light is emitted to the outside. An optical device characterized in that the at least one magnetic element is arranged near the light emission port.

2. The optical device according to claim 1, characterized in that at least a portion of the reflected light of the laser light emitted from the light emission port is irradiated onto the at least one magnetic element.

3. The optical device according to claim 2, characterized in that the at least one magnetic element is positioned to receive the reflected light propagating outside the waveguide.

4. The optical device according to claim 1 or 2, further comprising a substrate, wherein the waveguide is formed on the substrate.

5. The optical device according to claim 4, characterized in that the substrate is composed of aluminum oxide.

6. The optical device according to claim 4, characterized in that the waveguide is formed in a layer containing lithium niobate disposed on the substrate.

7. The optical device according to claim 4, further comprising a cladding covering the waveguide.

8. The optical device according to claim 7, characterized in that the at least one magnetic element is disposed within the cladding.

9. The optical device according to claim 1 or 2, further comprising a reflector disposed near the light emission port.

10. The optical device according to claim 1 or 2, characterized in that the laser diode emits near-infrared light as the laser light.

11. An optical system comprising an optical device according to claim 1 or 2, and an optical system for guiding the laser light emitted by the optical device to an object to be irradiated.

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