Optical devices and optical systems

Abstract

To provide a novel optical device.SOLUTION: An optical device has at least one magnetic element having a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first and second ferromagnetic layers, a substrate, and a waveguide, and the waveguide and the magnetic element are on or above the substrate and at least part of the light propagating through the waveguide is radiated onto the magnetic element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to optical devices and optical systems. [Background technology]

[0002] In recent years, optical devices using waveguides have been attracting attention. For example, planar lightwave circuits (PLCs) are an example of optical devices and are used in augmented reality (AR) glasses and small projectors. Another example is optical modulators, which are used in optical communications.

[0003] For example, a wavelength division multiplexing circuit, which is an example of an optical device, is described in Patent Document 1. The wavelength division multiplexing circuit described in Patent Document 1 uses a semiconductor photodiode (PD) as a wavelength monitor for a tunable wavelength light source. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-223738 Summary of the Invention [Problem to be solved by the invention]

[0005] Semiconductor photodiodes fabricated as separate components require adjustment of the optical axis relative to the waveguide of the optical device. Furthermore, semiconductor photodiodes fabricated as separate components are large in size. A new breakthrough is needed for further development of optical devices.

[0006] The present invention has been made in view of the above problems, and has an object to provide a novel optical device. [Means for solving the problem]

[0007] In order to solve the above problems, the following means are provided.

[0008] (1) An optical device according to a first aspect 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 substrate, and a waveguide, wherein the waveguide and the magnetic element are located on or above the substrate, and at least a portion of the light propagating through the waveguide is irradiated onto the magnetic element.

[0009] (2) The optical device according to the above aspect may further include an electrode, and an electric field based on an electric signal from the magnetic element may be applied from the electrode to at least a part of the waveguide.

[0010] (3) The optical device according to the above aspect may further include a reflector, and the reflector may reflect at least a portion of the light toward the magnetic element.

[0011] (4) In the optical device according to the above aspect, at least a part of the light may be irradiated onto the magnetic element in a direction intersecting the stacking direction of the magnetic element.

[0012] (5) In the optical device according to the above aspect, at least a part of the light may be irradiated onto the magnetic element from the stacking direction of the magnetic element.

[0013] (6) In the optical device according to the above aspect, the waveguide may further include a monitoring waveguide, and at least a portion of the light may propagate through the monitoring waveguide.

[0014] (7) The optical device according to the above aspect may further include a laser diode and an optical modulation element, wherein the laser diode is optically connected to the waveguide, and the optical modulation element is located between the laser diode and the waveguide and modulates the intensity of light reaching the waveguide.

[0015] (8) In the optical device according to the above aspect, the at least one magnetic element may be a plurality of magnetic elements, and a first magnetic element among the plurality of magnetic elements may be irradiated with at least a portion of the light propagating through the waveguide in a direction from the laser diode toward the waveguide, and a second magnetic element among the plurality of magnetic elements may be irradiated with at least a portion of the light output from the waveguide and reflected by the irradiated body.

[0016] (9) An optical system according to a second aspect includes the optical device according to the above aspect, and an optical system that guides light output from the optical device to an object to be illuminated. [Effects of the Invention]

[0017] The optical device and optical system according to the above aspects can monitor light based on a novel principle. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram of an optical device according to a first embodiment. [Figure 2] FIG. 1 is a plan view of a light modulation element according to a first embodiment. [Figure 3] 1 is a cross-sectional view of a light modulation element according to a first embodiment. [Figure 4] FIG. 2 is a perspective view of the vicinity of a magnetic element of the optical modulation element according to the first embodiment. [Figure 5] FIG. 2 is a cross-sectional view of the magnetic element and its vicinity in the optical modulation element according to the first embodiment. [Figure 6] 3 is an example of a monitoring circuit of the optical modulation element according to the first embodiment. [Figure 7] 4 is another example of a monitoring circuit for the optical modulation element according to the first embodiment. [Figure 8] FIG. 1 is a cross-sectional view of a magnetic element according to a first embodiment. [Figure 9] FIG. 3 is a diagram for explaining a first mechanism of the magnetic element according to the first embodiment. [Figure 10] 5A and 5B are diagrams for explaining a second mechanism of the magnetic element according to the first embodiment. [Figure 11] FIG. 10 is a perspective view of the vicinity of a magnetic element of an optical modulation element according to a second embodiment. [Figure 12] FIG. 10 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to a second embodiment. [Figure 13] FIG. 10 is another cross-sectional view of the vicinity of the magnetic element of the optical modulation element according to the second embodiment. [Figure 14] FIG. 10 is a plan view of a light modulation element according to a third embodiment. [Figure 15] FIG. 11 is a perspective view of a first example of the vicinity of a magnetic element of an optical modulation element according to a third embodiment. [Figure 16] FIG. 11 is a perspective view of a second example of the vicinity of the magnetic element of the optical modulation element according to the third embodiment. [Figure 17] FIG. 10 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to a first modified example. [Figure 18] FIG. 10 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to a second modified example. [Figure 19] FIG. 10 is a plan view of a light modulation element according to a third modified example. [Figure 20] FIG. 10 is a cross-sectional view of a light modulation element according to a third modified example. [Figure 21] FIG. 10 is a cross-sectional view of a light modulation element according to a fourth modified example. [Figure 22] FIG. 11 is a plan view of a light modulation element according to a fifth modified example. [Figure 23] FIG. 11 is a cross-sectional view of a light modulation element according to a fifth modified example. [Figure 24] FIG. 13 is a plan view of an optical device according to a sixth modified example. [Figure 25] FIG. 13 is a cross-sectional view of a light modulation element according to a sixth modified example. [Figure 26] FIG. 13 is a plan view of a light modulation element according to a seventh modified example. [Figure 27] FIG. 13 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to a seventh modified example. [Figure 28] FIG. 13 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to another example of the seventh modified example. [Figure 29] FIG. 13 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to another example of the seventh modified example. [Figure 30] FIG. 13 is a perspective view of the vicinity of a magnetic element of an optical modulation element according to another example of the seventh modified example. [Figure 31] FIG. 13 is a plan view of an optical device according to an eighth modified example. [Figure 32] FIG. 1 is a conceptual diagram of an optical system using an optical device. [Figure 33] FIG. 13 is a conceptual diagram of an optical system according to a ninth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0020] The directions are defined as follows. One direction in the plane in which the substrate 10 (see FIG. 3) extends is the x-direction, and the direction in the plane perpendicular to the x-direction is the y-direction. The direction perpendicular to the substrate 10 (the direction perpendicular to the x-direction and y-direction) is the z-direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction as "down." Up and down do not necessarily coincide with the direction in which gravity is applied.

[0021] "First embodiment" 1 is a block diagram of an optical device 200 according to the first embodiment. The optical device 200 includes an optical modulation element 100 and a control unit 150. The control unit 150 includes, for example, a drive circuit 160, a DC bias application circuit 170, and a control circuit 180. The optical device 200 is, for example, an optical modulator.

[0022] The optical modulation element 100 shown in Fig. 1 converts an electrical signal into an optical signal. in The output light L is modulated according to the modulation signal Sm. outIn this specification, light is not limited to visible light, but also includes infrared light, which has a longer wavelength than visible light, and ultraviolet light, which has a shorter wavelength than visible light. The wavelength of visible light is, for example, 380 nm or more and less than 800 nm. The wavelength of infrared light is, for example, 800 nm or more and 1 mm or less. The wavelength of ultraviolet light is, for example, 200 nm or more and less than 380 nm.

[0023] The drive circuit 160 applies a modulation voltage Vm corresponding to the modulation signal Sm to the electrodes (electrodes 41 and 42 described below) of the light modulation element 100. The DC bias application circuit 170 applies a DC bias voltage Vdc to the electrodes (electrodes 43 and 44 described below) of the light modulation element 100. The control circuit 180 receives an electric signal Sf from the magnetic element 30 of the light modulation element 100, and sends a signal based on the electric signal Sf to the DC bias application circuit 170.

[0024] Fig. 2 is a plan view of the optical modulation element 100 according to the first embodiment. Fig. 3 is a cross-sectional view of the optical modulation element 100 according to the first embodiment, taken along line A-A' in Fig. 2. Fig. 2 also shows power sources 161, 171 and a termination resistor R.

[0025] The optical modulation element 100 comprises a substrate 10, a waveguide 20, a magnetic element 30, and electrodes 41, 42, 43, and 44.

[0026] The first end 41a of the electrode 41 and the first end 42a of the electrode 42 are connected to, for example, a power supply 161. The second end 41b of the electrode 41 and the second end 42b of the electrode 42 are connected to, for example, a termination resistor R. The power supply 161 is part of the drive circuit 160.

[0027] The first end 43a of the electrode 43 and the first end 44a of the electrode 44 are connected to, for example, a power supply 171. The power supply 171 is a part of a DC bias application circuit 170.

[0028] The substrate 10 includes, for example, aluminum oxide. The substrate 10 is, for example, sapphire. The substrate 10 may also be a semiconductor substrate such as silicon.

[0029] The waveguide 20 is formed on a substrate 10. The waveguide 20 includes, for example, a first waveguide 21, a second waveguide 22, an input waveguide 23, an output waveguide 24, a branching portion 25, a coupling portion 26, and a monitoring waveguide 27.

[0030] The input waveguide 23 receives the input light L in The branching portion 25 is located between the input waveguide 23 and the first and second waveguides 21 and 22.

[0031] The first waveguide 21 and the second waveguide 22 extend, for example, in the x direction. The lengths of the first waveguide 21 and the second waveguide 22 in the x direction are, for example, approximately the same.

[0032] The coupling portion 26 is located between the first waveguide 21 and the second waveguide 22 and the output waveguide 24. The output waveguide 24 is connected to the coupling portion 26, and the output light L out and an output terminal from which the signal is output.

[0033] The monitoring waveguide 27 is connected to, for example, the output waveguide 24. At least a portion of the light propagating through the output waveguide 24 propagates through the monitoring waveguide 27. Hereinafter, at least a portion of the light propagating through the waveguide 20 may be referred to as monitoring light. The monitoring waveguide 27 may be connected to a portion of the waveguide 20 other than the output waveguide 24, depending on the portion where the state of light is to be monitored.

[0034] 3, the first waveguide 21 and the second waveguide 22 are composed of a part of a slab 20S and a ridge-shaped portion 20T. The slab 20S extends over the substrate 10. The ridge-shaped portion 20T protrudes from the upper surface of the slab 20S. The slab 20S increases the electric field strength applied to the waveguide 20.

[0035] The slab 20S and the ridge-shaped portion 20T contain lithium niobate as a primary component. Therefore, the waveguide 20 contains lithium niobate as a primary component. Some elements in the lithium niobate may be substituted with other elements. The waveguide 20 is covered with, for example, a cladding 28. The cladding 28 may be, for example, SiO2, Al2O3, MgF2, La2O3, ZnO, HfO2, MgO, YO3, CaF2, In2O3, or a mixture thereof. The materials of the slab 20S and the ridge-shaped portion 20T and the cladding 28 are not limited to these examples. For example, the slab 20S and the ridge-shaped portion 20T may be silicon or silicon oxide doped with germanium oxide, and the cladding 28 may be silicon oxide. The input waveguide 23 , the output waveguide 24 , the branching section 25 , the coupling section 26 , and the monitoring waveguide 27 also have the same configuration as the first waveguide 21 and the second waveguide 22 .

[0036] The magnetic element 30 is located at a position where it is irradiated with the monitoring light. The magnetic element 30 is located, for example, at the end of the output end of the monitoring waveguide 27 (in the extension direction of the monitoring waveguide 27). The magnetic element 30 is an example of a first magnetic element.

[0037] Fig. 4 is a perspective view of the vicinity of the magnetic element 30 of the light modulation element 100 according to the first embodiment. Fig. 5 is a cross-sectional view of the vicinity of the magnetic element 30 of the light modulation element 100 according to the first embodiment.

[0038] At least a portion of the light propagating through the waveguide 20 (monitoring light) is irradiated onto the magnetic element 30, for example, from a direction intersecting the stacking direction of the magnetic element 30. The monitoring light is irradiated onto the side surface of the magnetic element 30, for example. The magnetic element 30 is formed on the same substrate 10 on which the waveguide 20 is formed. In other words, the magnetic element 30 and the waveguide 20 are incorporated into a single product. The waveguide 20 and the magnetic element 30 are on or above the substrate 10.

[0039] The magnetic element 30 is electrically connected to, for example, electrodes 51 and 52, via wirings 53 and 54, an input terminal 55, and an output terminal 56.

[0040] The electrode 51 is connected to a first surface of the magnetic element 30. The electrode 52 is connected to a second surface of the magnetic element 30. The first surface and the second surface face each other in the stacking direction of the magnetic element 30.

[0041] The electrodes 51 and 52 include a conductive material. The electrodes 51 and 52 are made of a metal such as Cu, Al, Au, or Ru. Ta or Ti may be laminated above and below these metals. The electrodes 51 and 52 may also be made of a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN. The electrodes 51 and 52 may also be made of TiN or TaN.

[0042] The electrodes 51 and 52 may be transparent to the wavelength range of light irradiated onto the magnetic element 30. For example, the electrodes 51 and 52 may be transparent electrodes containing an oxide transparent electrode material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The electrodes 51 and 52 may also be configured to have a plurality of metal pillars in these transparent electrode materials.

[0043] The via wiring 53 connects the input terminal 55 to the electrode 51 or the electrode 52. There are, for example, two input terminals 55. A current or a voltage is input to one of the input terminals 55, and the other input terminal 55 is connected to a reference potential. The input terminal 55 is exposed, for example, on the upper surface of the clad 28. The via wiring 54 connects the output terminal 56 to the electrode 51 or the electrode 52. There are, for example, two output terminals 56. A signal is output from one of the output terminals 56, and the other output terminal 56 is connected to a reference potential. The output terminal 56 is exposed, for example, on the upper surface of the clad 28. The via wirings 53, 54, the input terminal 55, and the output terminal 56 include a conductive material. The materials of the via wirings 53, 54, the input terminal 55, and the output terminal 56 can be the same as those exemplified for the electrodes 51 and 52.

[0044] 6 and 7 show an example of a light monitoring circuit using the magnetic element 30 of the optical modulation element 100 according to the first embodiment. In FIG. 6 and FIG. 7, the electrode 51 is connected to, for example, the input terminal P in and output terminal P out 6 and 7, the electrode 52 is connected to, for example, the reference potential terminal P G Connected to input terminal P in corresponds to one of the input terminals 55 in Figures 4 and 5. Output terminal P out corresponds to one of the output terminals 56 in Figures 4 and 5. G corresponds to the other of the input terminals 55 and the other of the output terminals 56 in Figures 4 and 5. The reference potential in Figures 6 and 7 is ground G. Ground G may be provided outside the optical modulation element 100. The reference potential may be something other than ground G.

[0045] The magnetic element 30 converts the change in the state of the irradiated light (monitoring light L) into an electrical signal. The output voltage or current from the magnetic element 30 changes depending on the intensity of the irradiated light (monitoring light L).

[0046] Input terminal P in is connected to a current source PS1 or a voltage source PS2. The current source PS1 and the voltage source PS2 are, for example, external to the light modulation element 100. in When connected to the current source PS1, the output terminal P out The input terminal P outputs the resistance value of the magnetic element 30 in the stacking direction as a voltage. in When connected to voltage source PS2, output terminal P out outputs the resistance value in the stacking direction of the magnetic element 30 as a current. When there is no need to apply a current or voltage to the magnetic element 30 from the outside, the input terminal P in And the current source PS1 or the voltage source PS2 may be omitted.

[0047] Fig. 8 is a cross-sectional view of the magnetic element 30 according to the first embodiment. In Fig. 8, electrodes 51 and 52 are shown together, and the direction of magnetization of the ferromagnetic material in the initial state is indicated by an arrow.

[0048] The magnetic element 30 has at least a first ferromagnetic layer 31, a second ferromagnetic layer 32, and a spacer layer 33. The spacer layer 33 is located between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. In addition to these, the magnetic element 30 may have a third ferromagnetic layer 34, a magnetic coupling layer 35, an underlayer 36, a perpendicular magnetization induction layer 37, a cap layer 38, a sidewall insulating layer 39, etc. The magnetic element 30 has a maximum width of, for example, 2000 nm or less in a planar view from the stacking direction. The magnetic element 30 has a maximum width of, for example, 10 nm or more in a planar view from the stacking direction.

[0049] The magnetic element 30 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the spacer layer 33 is made of an insulating material. In this case, the resistance value in the stacking direction of the magnetic element 30 (the resistance value when a current flows in the stacking direction) changes according to a relative change between the state of magnetization M31 of the first ferromagnetic layer 31 and the state of magnetization M32 of the second ferromagnetic layer 32. Such an element is also called a magnetoresistance effect element.

[0050] The first ferromagnetic layer 31 is a light detection layer whose magnetization state changes when irradiated with light from the outside. The first ferromagnetic layer 31 is also called a magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when predetermined external energy is applied. The predetermined external energy is, for example, light (monitoring light L) irradiated from the outside, a current flowing in the stacking direction of the magnetic element 30, or an external magnetic field. The state of the magnetization M31 of the first ferromagnetic layer 31 changes depending on the intensity of the light (monitoring light L) irradiated to the first ferromagnetic layer 31.

[0051] The first ferromagnetic layer 31 includes a ferromagnetic material. The first ferromagnetic layer 31 includes at least one of magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 31 may include a non-magnetic element such as B, Mg, Hf, or Gd in addition to the magnetic elements described above. The first ferromagnetic layer 31 may be, for example, an alloy including a magnetic element and a non-magnetic element. The first ferromagnetic layer 31 may be composed of multiple layers. The first ferromagnetic layer 31 is, for example, a CoFeB alloy, a stacked body in which a CoFeB alloy layer is sandwiched between Fe layers, or a stacked body in which a CoFeB alloy layer is sandwiched between CoFe layers.

[0052] The first ferromagnetic layer 31 may be an in-plane magnetization film having an axis of easy magnetization in the in-plane direction, or a perpendicular magnetization film having an axis of easy magnetization in the direction perpendicular to the film plane (the stacking direction of the magnetic element 30).

[0053] The thickness of the first ferromagnetic layer 31 is, for example, 1 nm or more and 5 nm or less. The thickness of the first ferromagnetic layer 31 is preferably, for example, 1 nm or more and 2 nm or less. When the first ferromagnetic layer 31 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 31 is thin, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 31 is strengthened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 is increased. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 is high, the force that causes the magnetization M31 to return to the direction perpendicular to the film surface (to its original state) is strengthened. On the other hand, if the thickness of the first ferromagnetic layer 31 is thick, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 31 is relatively weakened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 31 is weakened.

[0054] As the thickness of the first ferromagnetic layer 31 decreases, its volume as a ferromagnetic body decreases, and as it increases, its volume as a ferromagnetic body increases. The responsiveness 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 the volume (V) of the first ferromagnetic layer 31. In other words, as the product of the magnetic anisotropy and the volume of the first ferromagnetic layer 31 decreases, the responsiveness to light increases. From this perspective, in order to improve the responsiveness to light, it is preferable to reduce the volume of the first ferromagnetic layer 31 after appropriately designing the magnetic anisotropy of the first ferromagnetic layer 31.

[0055] If the thickness of the first ferromagnetic layer 31 is greater than 2 nm, an insertion layer made of, for example, Mo or W may be provided within the first ferromagnetic layer 31. That is, the first ferromagnetic layer 31 may be a stack of a ferromagnetic layer, an insertion layer, and a ferromagnetic layer stacked in this order. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer enhances the perpendicular magnetic anisotropy of the entire first ferromagnetic layer 31. The thickness of the insertion layer is, for example, 0.1 nm to 0.6 nm.

[0056] The second ferromagnetic layer 32 is a magnetization fixed layer. The magnetization fixed layer is a layer made of a magnetic material whose magnetization state is less likely to change when a predetermined external energy is applied than the magnetization free layer. For example, the magnetization direction of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. Also, for example, the magnitude of the magnetization of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. The coercive force of the second ferromagnetic layer 32 is, for example, greater than the coercive force of the first ferromagnetic layer 31. The second ferromagnetic layer 32 has an easy axis of magnetization in the same direction as the first ferromagnetic layer 31, for example. The second ferromagnetic layer 32 may be an in-plane magnetization film or a perpendicular magnetization film.

[0057] The material constituting the second ferromagnetic layer 32 is, for example, the same as that of the first ferromagnetic layer 31. The second ferromagnetic layer 32 may be, for example, a laminate in which Co is 0.4 nm to 1.0 nm thick, Mo is 0.1 nm to 0.5 nm thick, a CoFeB alloy is 0.3 nm to 1.0 nm thick, and Fe is 0.3 nm to 1.0 nm thick are laminated in this order.

[0058] 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 combination of the second ferromagnetic layer 32, the magnetic coupling layer 35, and the third ferromagnetic layer 34 may be referred to as a magnetization fixed layer.

[0059] The third ferromagnetic layer 34 is magnetically coupled to the second ferromagnetic layer 32, for example. The magnetic coupling is, for example, antiferromagnetic coupling, which occurs due to RKKY interaction. The material constituting the third ferromagnetic layer 34 is, for example, the same as that of the first ferromagnetic layer 31. The magnetic coupling layer 35 is, for example, Ru, Ir, or the like.

[0060] The spacer layer 33 is a non-magnetic layer disposed between the first ferromagnetic layer 31 and the second ferromagnetic layer 32. The spacer layer 33 is a layer made of a conductor, an insulator, or a semiconductor, or a layer containing current-carrying points made of a conductor in an insulator. The thickness of the spacer layer 33 can be adjusted depending on the orientation directions of the magnetization M31 of the first ferromagnetic layer 31 and the magnetization M32 of the second ferromagnetic layer 32 in the initial state, which will be described later.

[0061] For example, when the spacer layer 33 is made of an insulator, the magnetic element 30 has a magnetic tunnel junction (MTJ) consisting of the first ferromagnetic layer 31, the spacer layer 33, and the second ferromagnetic layer 32. Such an element is called an MTJ element. In this case, the magnetic element 30 can exhibit a tunnel magnetoresistance (TMR) effect. When the spacer layer 33 is made of a metal, the magnetic element 30 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The magnetic element 30 may be called an MTJ element, a GMR element, or other names depending on the material of the spacer layer 3, but is also collectively called a magnetoresistance effect element.

[0062] When the spacer layer 33 is made of an insulating material, a material containing aluminum oxide, magnesium oxide, titanium oxide, silicon oxide, or the like can be used. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. A high magnetoresistance ratio can be obtained by adjusting the 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. To efficiently utilize the TMR effect, the thickness of the spacer layer 33 may be approximately 0.5 to 5.0 nm, or approximately 1.0 to 2.5 nm.

[0063] When the spacer layer 33 is made of a nonmagnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. To efficiently utilize the GMR effect, the thickness of the spacer layer 33 may be about 0.5 to 5.0 nm, or about 2.0 to 3.0 nm.

[0064] When the spacer layer 33 is made of a non-magnetic semiconductor material, it can be made of zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, ITO, etc. In this case, the thickness of the spacer layer 33 may be about 1.0 to 4.0 nm.

[0065] When a layer including current-carrying points formed by a conductor in a nonmagnetic insulator is used as the spacer layer 33, the current-carrying points may be formed by a nonmagnetic conductor such as Cu, Au, or Al in a nonmagnetic insulator made of aluminum oxide or magnesium oxide. The conductor may also be formed of a magnetic element such as Co, Fe, or Ni. In this case, the thickness of the spacer layer 33 may be approximately 1.0 to 2.5 nm. The current-carrying points are, for example, columnar bodies with a diameter of 1 nm to 5 nm when viewed perpendicular to the film surface.

[0066] The underlayer 36 is located between the second ferromagnetic layer 32 and the electrode 52. The underlayer 36 is a seed layer or a buffer layer. The seed layer improves the crystallinity of the layer stacked on the seed layer. The seed layer is made of, for example, Pt, Ru, Hf, Zr, or NiFeCr. The seed layer has a thickness of, for example, 1 nm or more and 5 nm or less. The buffer layer is a layer that reduces lattice mismatch between different crystals. The buffer layer is made of, for example, Ta, Ti, W, Zr, Hf, or nitrides of these elements. The buffer layer has a thickness of, for example, 1 nm or more and 5 nm or less.

[0067] The cap layer 38 is located between the first ferromagnetic layer 31 and the electrode 51. The cap layer 38 prevents damage to the lower layer during the process and improves the crystallinity of the lower layer during annealing. The thickness of the cap layer 38 is, for example, 3 nm or less so that the first ferromagnetic layer 31 is irradiated with sufficient light. The cap layer 38 is, for example, made of MgO, W, Mo, Ru, Ta, Cu, Cr, or a laminated film of these materials.

[0068] The perpendicular magnetization induced layer 37 is formed when the first ferromagnetic layer 31 is a perpendicular magnetization film. The perpendicular magnetization induced layer 37 is stacked on the first ferromagnetic layer 31. The perpendicular magnetization induced layer 37 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 31. The perpendicular magnetization induced layer 37 is made of, for example, magnesium oxide, W, Ta, Mo, or the like. When the perpendicular magnetization induced layer 37 is made of magnesium oxide, it is preferable that the magnesium oxide has oxygen deficiency to increase conductivity. The film thickness of the perpendicular magnetization induced layer 37 is, for example, 0.5 nm or more and 2.0 nm or less.

[0069] The sidewall insulating layer 39 covers the periphery of the stack including 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.

[0070] The magnetic element 30 is fabricated through a process of stacking each layer, an annealing process, and a processing process. First, the electrode 52, the underlayer 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 stacked in this order on the substrate 10 (on a portion of the cladding 28). The substrate 10 is the same as the substrate on which the waveguide 20 is formed. Each layer is formed by, for example, sputtering.

[0071] Next, the stacked film is annealed. The annealing temperature is, for example, 250°C to 450°C. The stacked film is then processed into a predetermined columnar shape by photolithography and etching. The columnar shape may be a cylindrical or rectangular columnar shape. For example, the minimum width of the columnar shape as viewed from the stacking direction may be 10 nm to 2000 nm, or 30 nm to 500 nm.

[0072] Next, an insulating layer is formed to cover the side surfaces of the pillars. This insulating layer becomes the sidewall insulating layer 39. The sidewall insulating layer 39 may be laminated multiple times. Next, the upper surface of the cap layer 38 is exposed from the sidewall insulating layer 39 by chemical mechanical polishing (CMP), and an electrode 51 is formed on the cap layer 38. Through the above process, the magnetic element 30 is obtained. The magnetic element 30 can be fabricated regardless of the material constituting the base. Therefore, the magnetic element 30 can be fabricated directly on the substrate 10 on which the waveguide 20 is formed, without an adhesive layer or the like. The magnetic element 30 can be formed together with the waveguide 20 by a process on the same substrate 10. For example, the waveguide 20 and the magnetic element 30 can be formed on the same substrate 10 by a vacuum film deposition process.

[0073] The electrodes 41, 42, 43, and 44 are positioned so that an electric field can be applied to at least a portion of the waveguide 20 (see Figures 2 and 3). An electric field can be applied to the first waveguide 21 from each of the electrodes 41 and 43. The electrodes 41 and 43 are positioned so that they overlap with the first waveguide 21 in a planar view from the z direction, for example. The electrodes 41 and 43 are positioned so that they overlap with the first waveguide 21 in a planar view from the z direction, for example. The electrodes 41 and 43 are positioned so that they overlap with the second waveguide 22 in a planar view from the z direction, for example. The electrodes 42 and 44 are positioned so that they overlap with the second waveguide 22 in a planar view from the z direction, for example. The electrodes 42 and 44 are positioned so that they overlap with the second waveguide 22 in a planar view from the z direction, for example.

[0074] Next, a description will be given of the operation of the optical device 200. The operation of the optical device 200 includes an optical modulation operation for converting an electrical signal into an optical signal, and an adjustment operation for monitoring the optical modulation state and adjusting the optical modulation state.

[0075] First, the optical modulation operation will be described. The optical device 200 converts an electrical signal into an optical signal. The optical modulation element 100 converts input light L in The output light L out modulates to.

[0076] Input light L input from the input waveguide 23 in The light is branched and propagates through the first waveguide 21 and the second waveguide 22. The phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is zero when the light is branched.

[0077] When a voltage is applied between the electrode 41 and the electrode 42, an electric field is applied to the first waveguide 21 and the second waveguide 22, and the refractive indexes of the first waveguide 21 and the second waveguide 22 change due to the electro-optic effect. A modulation voltage Vm corresponding to a modulation signal Sm is applied to the electrodes 41 and 42. The modulation voltage Vm corresponding to the modulation signal Sm is applied by, for example, a power supply 161. For example, the refractive index of the first waveguide 21 changes by +Δn from a reference refractive index n, and the refractive index of the second waveguide 22 changes by −Δn from the reference refractive index n. The voltages applied to the electrodes 41 and 42 are, for example, differential voltages having the same absolute value, opposite signs, and no phase shift.

[0078] When the refractive indexes of the first waveguide 21 and the second waveguide 22 are different, a phase difference occurs between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22. The light propagating through the first waveguide 21 and the second waveguide 22 joins together at the output waveguide 24, and is output as output light L out is output as

[0079] Output light L out is a superposition of the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22. out The intensity of the input light L changes depending on the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22. For example, when the phase difference is an even multiple of π, the lights constructively interact, and when the phase difference is an odd multiple of π, the lights destructively interact. In this manner, the optical modulation element 100 modulates the input light L in response to the electrical signal. in The output light L out modulates to.

[0080] Next, the adjustment operation will be described. In the adjustment operation, for example, the operating point of the optical modulation element 100 is adjusted. The operating point is the voltage at the center of the modulation voltage amplitude. The operating point may fluctuate depending on the temperature of the operating environment, etc. If the operating point fluctuates during use, it is corrected by the DC bias application circuit 170 and the control circuit 180. The control circuit 180 corrects the fluctuation of the operating point according to, for example, the state of the monitoring light. The state of the monitoring light is detected by the magnetic element 30.

[0081] The output voltage or output current from the magnetic element 30 varies depending on the intensity of the light (monitoring light) irradiated onto the first ferromagnetic layer 31. The monitoring light is output light L out A part of the output light L out It is the same situation.

[0082] The exact mechanism by which the output voltage or output current from the magnetic element 30 changes due to irradiation with light is not yet clear, but the following two mechanisms are conceivable, for example.

[0083] 9 is a diagram for explaining a first mechanism of operation of the magnetic element 30 according to the first embodiment. In the upper graph of FIG. 9, the vertical axis represents the intensity of light irradiated to the first ferromagnetic layer 31, and the horizontal axis represents time. In the lower graph of FIG. 9, the vertical axis represents the resistance value in the stacking direction of the magnetic element 30, and the horizontal axis represents time.

[0084] First, in a 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 parallel to each other, the resistance value in the stacking direction of the magnetic element 30 indicates a first resistance value R1, and the magnitude of the output voltage or output current from the magnetic element 30 indicates a first value. The first intensity may be the case where the intensity of the light irradiated to the first ferromagnetic layer 31 is zero.

[0085] The resistance value in the stacking direction of the magnetic element 30 can be calculated using Ohm's law from the voltage generated across both ends of the magnetic element 30 in the stacking direction when a sense current is applied in the stacking direction of the magnetic element 30. The output voltage from the magnetic element 30 is generated between the electrodes 51 and 52. In the example shown in FIG. 9, it is preferable to apply the sense current from the first ferromagnetic layer 31 to the second ferromagnetic layer 32. By applying the sense current in this direction, 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 magnetizations M31 and M32 are parallel in the initial state. Furthermore, applying the sense current in this direction can prevent the magnetization M31 of the first ferromagnetic layer 31 from reversing during operation.

[0086] Next, the intensity of the light irradiated to the first ferromagnetic layer 31 changes. The magnetization M31 of the first ferromagnetic layer 31 tilts from its initial state due to external energy caused by the light irradiation. The angle between the direction of the magnetization M31 of the first ferromagnetic layer 31 when the first ferromagnetic layer 31 is not irradiated with light and the direction of the magnetization M31 when the first ferromagnetic layer 31 is irradiated with light is both greater than 0° and smaller than 90°.

[0087] When the magnetization M31 of the first ferromagnetic layer 31 tilts from its initial state, the resistance value in the stacking direction of the magnetoresistive element 30 changes. Consequently, the output voltage or output current from the magnetic element 30 changes. For example, the greater the intensity of the light (monitoring light L) irradiated onto the magnetic element 30, the greater the tilt of the magnetization M31 from its initial state. For example, depending on 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 from a second resistance value R2 to a third resistance value R3 to a fourth resistance value R4, and the output voltage or output current from the magnetic element 30 changes from a second value to a third value to a fourth value. The resistance values ​​increase in the order of the first resistance value R1, the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The output voltage from the magnetic element 30 increases in the order of the first value, the second value, the third value, and the fourth value. When the magnetic element 30 is connected to a constant voltage source, the output current from the magnetic element 30 decreases in the order of the first value, the second value, the third value, and the fourth value.

[0088] When the intensity of the light (monitoring light L) irradiated to the magnetic element 30 changes, the output voltage or output current (resistance value in the stacking direction of the magnetic element 30) from the magnetic element 30 changes. Therefore, the magnetic element 30 can detect the intensity of the monitoring light L as the output voltage or output current from the magnetic element 30 (resistance value of the magnetic element 30).

[0089] Since 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, when the intensity of the light irradiated to the first ferromagnetic layer 31 returns to the first intensity, the magnetization M31, which has been tilted from its initial state, returns to its initial state. When the magnetization M31 returns to its initial state, the resistance value in the stacking direction of the magnetic element 30 returns to the first resistance value R1, and the output voltage or output current from the magnetic element 30 returns to the first value.

[0090] Here, the case where the magnetization M31 and the magnetization M32 are parallel in the initial state has been described as an example, but the magnetization M31 and the magnetization M32 may be antiparallel in the initial state. In this case, the resistance value in the stacking direction of the magnetic element 30 decreases as the magnetization M31 tilts (as the angle of the magnetization M31 from the initial state increases). If the initial state is one in which the magnetization M31 and the magnetization M32 are antiparallel, it is preferable to flow the sense current from the second ferromagnetic layer 32 to the first ferromagnetic layer 31. By flowing the sense current in this direction, a spin transfer torque acts on the magnetization M31 of the first ferromagnetic layer 31 in the opposite direction to the magnetization M32 of the second ferromagnetic layer 32, and the magnetization M31 and the magnetization M32 become antiparallel in the initial state.

[0091] 10 is a diagram for explaining a second mechanism of operation of the magnetic element 30 according to the first embodiment. In the upper graph of FIG. 10, the vertical axis represents the intensity of light irradiated to the first ferromagnetic layer 31, and the horizontal axis represents time. In the lower graph of FIG. 10, the vertical axis represents the resistance value in the stacking direction of the magnetic element 30, and the horizontal axis represents time.

[0092] The initial state shown in Fig. 10 is similar to the initial state shown in Fig. 9. In the example shown in Fig. 10, it is also preferable to flow the sense current from the first ferromagnetic layer 31 toward the second ferromagnetic layer 32. By flowing the sense current in this direction, 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.

[0093] Next, the intensity of the light (monitoring light) irradiated to the first ferromagnetic layer 31 changes. The magnitude of the magnetization M31 of the first ferromagnetic layer 31 decreases from its initial state due to external energy irradiated with light. When the magnetization M31 of the first ferromagnetic layer 31 decreases from its initial state, the resistance value of the magnetoresistive element 30 in the stacking direction changes. The output voltage or current from the magnetic element 30 also changes. For example, the greater the intensity of the light (monitoring light L) irradiated to the magnetic element 30, the smaller the magnitude of the magnetization M31. For example, depending on the magnitude of the magnetization M31 of the first ferromagnetic layer 31, the resistance value of the magnetic element 30 in the stacking direction changes from a second resistance value R2 to a third resistance value R3 to a fourth resistance value R4, and the output voltage or current from the magnetic element 30 changes from a second value to a third value to a fourth value. The resistance values ​​increase in the order of the first resistance value R1, the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The output voltage from the magnetic element 30 increases in the order of the first value, the second value, the third value, and the fourth value. When the magnetic element 30 is connected to a constant voltage source, the output current from the magnetic element 30 decreases in the order of the first value, the second value, the third value, and the fourth value.

[0094] When the intensity of the light irradiated to the first ferromagnetic layer 31 returns to the first intensity, the magnitude of the magnetization M31 of the first ferromagnetic layer 31 returns to its original value, and the magnetic element 30 returns to its initial state. That is, the resistance value in the stacking direction of the magnetic element 30 returns to the first resistance value R1, and the output voltage or output current from the magnetic element 30 returns to the first value.

[0095] 10, the magnetization M31 and the magnetization M32 may be antiparallel in the initial state. In this case, the resistance value in the stacking direction of the magnetic element 30 decreases as the magnitude of the magnetization M31 decreases. When the initial state is one in which the magnetization M31 and the magnetization M32 are antiparallel, it is preferable to flow the sense current from the second ferromagnetic layer 32 to the first ferromagnetic layer 31.

[0096] After going through the above procedure, the output light L out This state can be read as an output voltage or an output current from the magnetic element 30 (the resistance value in the stacking direction of the magnetic element 30).

[0097] The control circuit 180 receives the output voltage or output current (the resistance value of the magnetic element 30 in the stacking direction) from the magnetic element 30, i.e., the electrical signal from the magnetic element 30, and sends a signal based on the result to the DC bias application circuit 170. Based on the signal from the control circuit 180, the DC bias application circuit 170 applies a DC bias voltage Vdc between the electrode 43 and the electrode 44, and applies an electric field to the first waveguide 21 and the second waveguide 22, thereby adjusting the operating point of the optical modulation element 100. The DC bias voltage Vdc is applied by, for example, a power supply 171. In this way, the control unit 150 applies an electric field, the magnitude of which is adjusted based on the electrical signal from the magnetic element 30, from the electrode 43 and the electrode 44 to the first waveguide 21 and the second waveguide 22.

[0098] As described above, in the optical device 200 according to the first embodiment, an electric field based on an electric signal from the magnetic element 30 can be applied to at least a part of the waveguide 20 (the first waveguide 21 and the second waveguide 22) from the electrode 43 and the electrode 44. By the feedback operation described above, the signal (output light L) output from the optical device 200 out ) status can be adjusted.

[0099] Furthermore, the smaller the volume of the first ferromagnetic layer 31, the more easily the magnetization M31 of the first ferromagnetic layer 31 changes in response to light irradiation. In other words, the smaller the volume of the first ferromagnetic layer 31, the more easily the magnetization M31 of the first ferromagnetic layer 31 is tilted or reduced by light irradiation. In other words, by reducing the volume of the first ferromagnetic layer 31, the magnetization M31 can be changed even with a small amount of light. In other words, the magnetic element 30 according to the first embodiment can detect light with high sensitivity.

[0100] More precisely, the changeability of the magnetization M31 is determined by the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 31. The smaller the KuV, the smaller the amount of light required to change the magnetization M31; the larger the KuV, the larger the amount of light required to change the magnetization M31. In other words, the KuV of the first ferromagnetic layer 31 must be designed according to the amount of external light used in the application. When detecting extremely small amounts of light, reducing the KuV of the first ferromagnetic layer 31 makes it possible to detect such small amounts of light. This is a significant advantage, as detecting such small amounts of light becomes difficult with conventional pn junction semiconductors when the element size is reduced. Reducing the volume of the first ferromagnetic layer 31 reduces the KuV.

[0101] "Second embodiment" Fig. 11 is a perspective view of the vicinity of the magnetic element 30 of the light modulation element 101 according to the second embodiment. Fig. 12 is a cross-sectional view of the vicinity of the magnetic element 30 of the light modulation element 101 according to the second embodiment. Fig. 13 is another cross-sectional view of the vicinity of the magnetic element 30 of the light modulation element 101 according to the second embodiment. In the second embodiment, the same components as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0102] The optical modulation element 101 has a reflector 60. The reflector 60 reflects at least a portion of the light propagating through the waveguide 20 toward the magnetic element 30. For example, the reflector 60 reflects the monitoring light output from the monitoring waveguide 27 toward the magnetic element 30. The reflector 60 is located in the traveling direction of the monitoring light from the output end of the monitoring waveguide 27. The reflector 60 has an inclined surface that is inclined with respect to the traveling direction of the monitoring light.

[0103] The reflector 60 reflects light and is, for example, a reflecting mirror.

[0104] The magnetic element 30 is formed in an insulating layer 61 formed on the cladding 28. The insulating layer 61 is, for example, made of the same material as the sidewall insulating layer 39. The magnetic element 30 is located above the substrate 10. The magnetic element 30 is located at a different height from the waveguide 20 and is located farther from the substrate 10 than the waveguide 20. The magnetic element 30 is located above the reflector 60, for example.

[0105] The light (monitoring light) reflected by the reflector 60 is irradiated onto the magnetic element 30, for example, from the stacking direction of the magnetic element 30. In this case, the electrode 52 is transparent to the wavelength region of the light irradiated onto the magnetic element 30. The electrode 52 transmits part of the monitoring light, so that the monitoring light is irradiated onto the magnetic element 30. Here, an example has been illustrated in which the electrode 52 is arranged closer to the reflector 60 than the electrode 51, but the electrode 51 may also be arranged closer to the reflector 60 than the electrode 52 (the first ferromagnetic layer 31 may also be arranged closer to the reflector 60 than the second ferromagnetic layer 32). In this case, the electrode 51 is transparent to the wavelength region of the light irradiated onto the magnetic element 30. When the electrode 51 is arranged closer to the reflector 60 than the electrode 52, the efficiency of irradiating the monitoring light onto the first ferromagnetic layer 31 is increased.

[0106] The optical device according to the second embodiment has the same effects as the optical device 200. In addition, the reflector 60 allows the direction of irradiation of the monitoring light onto the magnetic element 30 to be freely designed. For example, when the monitoring light is irradiated onto the magnetic element 30 from the stacking direction, the light-receiving area of ​​the magnetic element 30 can be secured to be wide.

[0107] "Third embodiment" Fig. 14 is a plan view of the optical modulation element 102 according to the third embodiment. Fig. 14 also shows power supplies 161, 171 and a termination resistor R. In the third embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and a description thereof will be omitted.

[0108] The waveguide 20A includes, for example, a first waveguide 21, a second waveguide 22, an input waveguide 23, an output waveguide 24, a branching portion 25, and a coupling portion 26. The waveguide 20A does not include a monitoring waveguide 27.

[0109] Fig. 15 is a perspective view of a first example of the vicinity of the magnetic element 30 of the optical modulation element 102 according to the third embodiment. In Fig. 15, the output waveguide 24 has two separate output ends 24t1 and 24t2. The output end 24t1 is located at a different position in the x direction from the output end 24t2.

[0110] The light from the output end 24t1 travels past a reflector 60. The light reflected by the reflector 60 is irradiated onto the magnetic element 30 as monitoring light. That is, a portion of the light output from the output end of the output waveguide 24 is irradiated onto the magnetic element 30 as monitoring light. The output end 24t2 is exposed to the outside. The output light L out will be output.

[0111] Fig. 16 is a perspective view of a second example of the vicinity of the magnetic element 30 of the optical modulation element 102 according to the third embodiment. In Fig. 16, the output waveguide 24 has two separate output ends 24t3 and 24t4. The output end 24t3 is located at a different position in the z direction from the output end 24t4.

[0112] The light from the output end 24t3 travels past a reflector 60. The light reflected by the reflector 60 is irradiated onto the magnetic element 30 as monitoring light. That is, a portion of the light output from the output end of the output waveguide 24 is irradiated onto the magnetic element 30 as monitoring light. The output end 24t4 is exposed to the outside. The output light L out will be output.

[0113] The optical device according to the third embodiment has the same effects as the optical device 200. In addition, the optical modulation element 102 outputs the output light L out Since a portion of the light is directly measured as monitoring light, it is less susceptible to noise and other factors.

[0114] Up to this point, an example of the first to third embodiments has been described in detail with reference to the drawings, but the first embodiment is not limited to this example.

[0115] "First Variation" 17 is a cross-sectional view of the vicinity of the magnetic element of the optical modulation element according to the first modification. As shown in Fig. 17, the stacking direction of the magnetic element 30 may be inclined with respect to the z direction. In this case, the monitoring light is irradiated onto the side surface of the magnetic element 30 and the first surface of the magnetic element 30 on the electrode 51 side.

[0116] "Second Variant" Fig. 18 is a cross-sectional view of the vicinity of a magnetic element of an optical modulation element according to a second modification. For example, as shown in Fig. 18, the input terminal and output terminal for the magnetic element 30 may be common. The magnetic element 30 shown in Fig. 18 is electrically connected to, for example, electrodes 51 and 52, via wiring 58, and input / output terminal 57.

[0117] Via wiring 58 connects input / output terminals 57 to electrodes 51 or 52. There are, for example, two input / output terminals 57. A current or a voltage is input to one of the input / output terminals 57, and a signal is output from the other of the input / output terminals 57. The other of the input / output terminals 57 is connected to a reference potential.

[0118] "Third Variation" Fig. 19 is a plan view of the light modulation element 103 according to the third modified example. Fig. 20 is a cross-sectional view of the light modulation element 103 according to the third modified example. Fig. 20 is a cross-section taken along CC' in Fig. 19. Fig. 19 also shows power supplies 161A, 171A, 161B, 171B, control circuits 181A, 181B, 182A, 182B, and termination resistor R. In the third modified example, the same components as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0119] The optical modulation element 103 includes a substrate 10, a waveguide 20, a magnetic element 30, and electrodes 45, 46, and 47. The waveguide 20 and the magnetic element 30 are on or above the substrate 10. In the optical modulation element 103, similar to the first or second embodiment, the monitoring light propagating through the monitoring waveguide 27 is irradiated onto the magnetic element 30. As shown in FIG. 19 , the shapes and connection relationships of the electrodes 45, 46, and 47 may be different from those of the electrodes 41, 42, 43, and 44 according to the first to third embodiments.

[0120] The waveguide 20 in the optical modulation element 103 is made up of a part of a slab 70 formed on the substrate 10 and a ridge-shaped portion 71 protruding from the slab 70 .

[0121] The electrodes 45 and 46 are positioned so that an electric field can be applied to at least a portion of the waveguide 20. An electric field can be applied to the first waveguide 21 from the electrode 45. An electric field can be applied to the second waveguide 22 from the electrode 46. The electrode 45 is, for example, above the first waveguide 21. The electrode 46 is, for example, above the second waveguide 22. The electrode 47 is, for example, on the side of the electrodes 45 and 46.

[0122] A first end of electrode 45 is connected to, for example, power supplies 161A and 171A, and a second end is connected to termination resistor R. A first end of electrode 46 is connected to, for example, power supplies 161B and 171B, and a second end is connected to termination resistor R. Electrode 47 is connected to the reference potential of power supplies 161A, 171A, 161B, and 171B and termination resistor R. The reference potential is, for example, ground.

[0123] The power supplies 161A and 161B are part of the drive circuit 160. The power supplies 171A and 171B are part of the DC bias application circuit 170. The control circuits 181A, 181B, 182A, and 182B are part of the control circuit 180. In this case, the control circuit 180 shown in FIG. 1 is also connected to the drive circuit 160. Each of the control circuits 181A, 181B, 182A, and 182B can receive an electrical signal from the magnetic element 30.

[0124] Voltages are applied to electrode 45 from power supplies 161A and 171A. Power supply 161A applies a modulated voltage to electrode 45. Power supply 161A is controlled by control circuit 181A. Power supply 171A applies a DC bias voltage to electrode 45. Power supply 171A is controlled by control circuit 182A. Voltages are applied to electrode 46 from power supplies 161B and 171B. Power supply 161B applies a modulated voltage to electrode 46. Power supply 161B is controlled by control circuit 181B. Power supply 171B applies a DC bias voltage to electrode 46. Power supply 171B is controlled by control circuit 182B. In other words, the voltages applied to electrode 45 and electrode 46 can be controlled separately. When a voltage is applied between electrode 45 and electrode 47, an electric field is applied to first waveguide 21, and the refractive index of the first waveguide changes due to the electro-optic effect. When a voltage is applied between the electrodes 46 and 47, an electric field is applied to the second waveguide 22, and the refractive index of the first waveguide changes due to the electro-optic effect.

[0125] The optical device outputs light L out The state of the magnetic element 30 is detected based on the output voltage or output current (resistance value in the stacking direction of the magnetic element 30) from the magnetic element 30, i.e., the electrical signal from the magnetic element 30. The electrical signal from the magnetic element 30 is sent to control circuits 181A, 182A, 181B, and 182B. Each of the control circuits 181A, 182A, 181B, and 182B receives the electrical signal from the magnetic element 30 and sends a signal based on the result to the power supply 161A, power supply 171A, power supply 161B, or power supply 171B.

[0126] Power supply 161A applies a modulated voltage to electrode 45 based on a signal from control circuit 181A. Power supply 161B applies a modulated voltage to electrode 46 based on a signal from control circuit 181B. Power supply 171A applies a DC bias voltage to electrode 45 based on a signal from control circuit 182A. Power supply 171B applies a DC bias voltage to electrode 46 based on a signal from control circuit 182B.

[0127] Control circuits 181A and 181B adjust the modulation voltage applied to electrodes 45 and 46 so that the phase difference between the light propagating through first waveguide 21 and the light propagating through second waveguide 22 becomes π (180°). Control circuits 182A and 182B adjust the DC bias voltage applied to electrodes 45 and 46 so that the phase difference between the light propagating through first waveguide 21 and the light propagating through second waveguide 22 becomes 0 (0°).

[0128] The optical modulation element 103 outputs an output light L when the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is 0 (0°). out becomes maximum, and the output light L is output when the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is π (180°). out is the smallest.

[0129] Under ideal conditions, when no voltage is applied to the electrodes 45 and 46, the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is 0 (0°). out The ideal condition is a condition excluding parameters that affect the refractive indexes of the first waveguide 21 and the second waveguide 22, such as temperature, noise, and DC drift.

[0130] Furthermore, under ideal conditions, for example, when a voltage that changes the phase of the light propagating through the first waveguide 21 by +π / 2 (+90°) is applied to the electrode 45 and a voltage that changes the phase of the light propagating through the second waveguide 22 by −π / 2 (−90°) is applied to the electrode 46, the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is π (180°). out Alternatively, a voltage may be applied to electrode 45 that causes the phase of light propagating through first waveguide 21 to change by −π / 2 (−90°), and a voltage may be applied to electrode 46 that causes the phase of light propagating through second waveguide 22 to change by +π / 2 (+90°).

[0131] Under actual conditions, due to the influence of temperature, noise, DC drift, etc., the phase change of the light propagating through the first waveguide 21 and the second waveguide 22 may not be ideal and may shift.

[0132] For example, when no voltage is applied to electrodes 45 and 46, the phase difference between the light propagating through first waveguide 21 and the light propagating through second waveguide 22 may deviate from 0 (0°). Furthermore, when a voltage is applied to electrodes 45 and 46 so that the phase difference between the light propagating through first waveguide 21 and the light propagating through second waveguide 22 becomes π (180°) under ideal conditions, the phase difference between the light propagating through first waveguide 21 and the light propagating through second waveguide 22 may deviate from π (180°).

[0133] When the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 is shifted from 0 (0°), the control circuits 182A and 182B control the power supplies 171A and 171B based on the electrical signal from the magnetic element 30, so that the power supplies 171A and 171B control the output light L out A DC bias voltage is applied to at least one of the electrodes 45 and 46 so that the potential difference is maximized.

[0134] For example, if the phase of light propagating through first waveguide 21 is shifted to the positive side relative to the phase of light propagating through second waveguide 22, a negative voltage is applied to electrode 45 to change the phase of light propagating through first waveguide 21 to the negative side, and a positive voltage is applied to electrode 46 to change the phase of light propagating through second waveguide 22 to the positive side. Conversely, for example, if the phase of light propagating through first waveguide 21 is shifted to the negative side relative to the phase of light propagating through second waveguide 22, a positive voltage is applied to electrode 45 to change the phase of light propagating through first waveguide 21 to the positive side, and a negative voltage is applied to electrode 46 to change the phase of light propagating through second waveguide 22 to the negative side.

[0135] When the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 deviates from π (180°), the control circuits 181A and 181B control the power supplies 161A and 161B based on the electrical signal from the magnetic element 30, so that the power supplies 161A and 161B control the output light L out A modulation voltage is applied to at least one of the electrodes 45 and 46 so that the voltage V ≠ ...

[0136] In this way, the control unit 150 having the power supplies 161A, 171A, 161B, 171B and the control circuits 181A, 181B, 182A, 182B applies an electric field, the magnitude of which is adjusted based on the electrical signal from the magnetic element 30, from the electrode 45 to the first waveguide 21 and from the electrode 46 to the second waveguide 22.

[0137] By the above operation, the optical device according to the third modification can set the phase difference between the light propagating through the first waveguide 21 and the light propagating through the second waveguide 22 to 0 (0°) or π (180°) under actual conditions, and the output light L out As a result, the optical device according to the third modification can maximize or minimize the output light L out The optical device according to the third modification can compensate for the effects of temperature, noise, DC drift, and the like under actual conditions, thereby improving the signal-to-noise ratio (S / N ratio).

[0138] As described above, in the optical device having the optical modulation element 103 according to the third modification, an electric field based on an electric signal from the magnetic element 30 can be applied to at least a part of the waveguide 20 (the first waveguide 21 or the second waveguide 22) from the electrode 45 or the electrode 46. By the feedback operation as described above, the signal (output light L) output from the optical device having the optical modulation element 103 is out ) status can be adjusted.

[0139] In the third modified example, similarly to the first and second embodiments, the waveguide 20 has a monitoring waveguide 27, and the monitoring light propagating through the monitoring waveguide 27 is irradiated onto the magnetic element 30. The third modified example is not limited to this case, and similarly to the third embodiment, a configuration may be adopted in which part of the light output from the output end of the output waveguide 24 is irradiated onto the magnetic element 30 as the monitoring light.

[0140] "Fourth Variant" 21 is a cross-sectional view of a light modulation element 104 according to the fourth modified example. In the fourth modified example, the same components as those in the third modified example are denoted by the same reference numerals, and the description thereof will be omitted.

[0141] The cross-sectional structure of the optical waveguide may be different from that described above, as shown in Fig. 21. The optical modulation element 104 shown in Fig. 21 is an optical modulation element that utilizes a change in refractive index in a semiconductor quantum well.

[0142] The optical modulation element 104 has a first cladding layer 73, a core 75, a second cladding layer 76, a dielectric 77, and electrodes 45, 46, and 47. The first cladding layer 73 is, for example, an n-type semiconductor such as n-type InP. The first cladding layer 73 has a ridge-shaped portion 74 that protrudes in the z direction.

[0143] The core 75 is located on the ridge-shaped portion 74. The core 75 forms, for example, a semiconductor multiple quantum well. The core 75 is, for example, a multilayer film of InGaAs and InAlAs or a multilayer film of InGaAsP and InP. The core 75 is the waveguide 20.

[0144] The second cladding 76 is on the core 75. The second cladding 76 is, for example, a p-type semiconductor, such as p-type InP. Electrodes 45, 46 are on the second cladding 76. When a voltage is applied to the electrodes 45, 46, the refractive index of the core 75, which has a semiconductor multiple quantum well, changes. The dielectric 77 is, for example, an organic dielectric material, a ceramic dielectric material, or the like. An example of the organic dielectric material is a benzocyclobutene-based resin, or the like. An example of the ceramic dielectric material is silicon oxide, aluminum oxide, or the like.

[0145] As in the third modification, in the optical modulation element 104 according to the fourth modification, the electrode 45 or the electrode 46 is located at a position where an electric field can be applied to at least a part of the waveguide 20 (the first waveguide 21 or the second waveguide 22). An electric field can be applied to the first waveguide 21 from the electrode 45. An electric field can be applied to the second waveguide 22 from the electrode 46. The operation of applying an electric field, the magnitude of which is adjusted based on an electric signal from the magnetic element 30, to the first waveguide 21 from the electrode 45 and to the second waveguide 22 from the electrode 46 is the same as in the third modification.

[0146] The optical modulation element 104 outputs the output light L out This state can be detected based on the output voltage or output current from the magnetic element 30 (the resistance value in the stacking direction of the magnetic element 30), that is, the electrical signal from the magnetic element 30.

[0147] "Fifth Variation" Fig. 22 is a plan view of the light modulation element 105 according to the fifth modified example. Fig. 22 also shows a power supply 161C and a control circuit 181C. Fig. 23 is a cross-sectional view of the light modulation element 105 according to the fifth modified example. Fig. 23 is a cross-section taken along line D-D' in Fig. 22. In the fifth modified example, configurations similar to those in the first and second embodiments are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0148] The optical modulation element 105 shown in Fig. 22 is a ring modulation element that uses a ring resonator 80. As shown in Fig. 22, the configuration of the optical modulation element may be different from the configuration described above.

[0149] The optical modulation element 105 has a ring resonator 80, a waveguide 20B, and a magnetic element 30. The ring resonator 80, the waveguide 20B, and the magnetic element 30 are all located on or above the substrate 10.

[0150] The waveguide 20B has a first waveguide 29 and a monitoring waveguide 27. Light input to a first end of the first waveguide 29 is output from a second end of the first waveguide 29. The monitoring waveguide 27 is connected to the first waveguide 29 at a position between the second end and a position corresponding to the ring resonator 80 of the first waveguide 29. A portion of the light propagating through the first waveguide 29 propagates through the monitoring waveguide 27. As in the first or second embodiment, the monitoring light propagating through the monitoring waveguide 27 is irradiated onto the magnetic element 30. The waveguide 20B is made of, for example, a semiconductor such as silicon, silicon germanium, indium phosphide, or gallium arsenide. The waveguide 20B is covered with a cladding such as SiO2.

[0151] The ring resonator 80 has a ring-shaped waveguide 81 and doped regions 82 and 83 located inside and outside the waveguide 81. The waveguide 81 is a semiconductor, such as silicon, silicon germanium, indium phosphide, or gallium arsenide. The doped regions 82 and 83 are semiconductors doped with carriers. One of the doped regions 82 and 83 is an n-type semiconductor, and the other is a p-type semiconductor. The electrode 48 is connected to the doped region 82, and the electrode 49 is connected to the doped region 83. The waveguide 81, the doped regions 82 and 83, and the electrodes 48 and 49 are covered with a cladding 85 such as SiO2.

[0152] The power supply 161C is connected to the electrode 48 and the electrode 49. The power supply 161C is part of the drive circuit 160. The control circuit 181C is part of the control circuit 180. In this case, the control circuit 180 shown in FIG. 1 is also connected to the drive circuit 160. The control circuit 181C can receive an electrical signal from the magnetic element 30. The control circuit 181C controls the power supply 161C based on the electrical signal from the magnetic element 30.

[0153] When the frequency of the optical signal propagating through the first waveguide 29 matches the resonant frequency of the ring resonator 80, the ring resonator 80 confines the light of the optical signal within the ring resonator 80. Therefore, when the frequency of the optical signal propagating through the first waveguide 29 is close to the resonant frequency, light absorption increases, and the intensity of the output light decreases. The resonant frequency of the ring resonator 80 is determined by the optical path length along the circumference of the waveguide 81. The resonant frequency of the ring resonator 80 can be changed by applying a voltage between the electrodes 48 and 49 to apply an electric field to the waveguide 81, injecting carriers into the waveguide 81, and changing the refractive index of the waveguide 81. For example, in the optical modulator 105, applying a voltage between the electrodes 48 and 49 to make the resonant frequency of the ring resonator 80 different from the frequency of the optical signal propagating through the first waveguide 29 can increase the intensity of the output light. In this way, the optical modulation element 105 can change the intensity of the output light of an optical signal of a specific frequency, and therefore can modulate the light.

[0154] The optical device according to the fifth modification has an output light L out The state can be detected based on the output voltage or output current (resistance value in the stacking direction of the magnetic element 30) from the magnetic element 30, i.e., the electrical signal from the magnetic element 30. The electrical signal from the magnetic element 30 is sent to the control circuit 181C. The control circuit 181C receives the electrical signal from the magnetic element 30 and sends a signal based on the result to the power supply 161C.

[0155] When the resonant frequency of the ring resonator 80 and the frequency of the optical signal propagating through the first waveguide 29 match, the optical modulation element 105 outputs output light L out In the case of a design in which the resonant frequency of the ring resonator 80 when no voltage is applied to the electrodes 48 and 49 matches the frequency of the optical signal propagating through the first waveguide 29, when no voltage is applied to the electrodes 48 and 49 under ideal conditions, the output light L output from the waveguide 20B is out is the smallest.

[0156] However, under actual conditions, due to the influence of temperature, noise, DC drift, etc., even when no voltage is applied to the electrodes 48 and 49, the output light L output from the waveguide 20B may be out may not be the smallest.

[0157] Output light L output from the waveguide 20B out If the output light L is not minimized, the control circuit 181C controls the power supply 161C based on the electrical signal from the magnetic element 30. out A voltage is applied between the electrodes 48 and 49 so that the voltage Vcc is minimized.

[0158] In this way, the control unit 150 having the power supply 161C and the control circuit 181C applies an electric field, the magnitude of which is adjusted based on the electric signal from the magnetic element 30, from the electrodes 48 and 49 to the waveguide 81.

[0159] By the above operation, the optical device according to the fifth modification produces output light L out As a result, the optical device according to the fifth modification can minimize the output light L out In the modulation of out Furthermore, the optical device according to the fifth modification can compensate for the effects of temperature, noise, DC drift, and the like under actual conditions, and can improve the signal-to-noise ratio (S / N ratio).

[0160] As described above, in the optical device having the optical modulation element 105 according to the fifth modification, an electric field based on the electric signal from the magnetic element 30 can be applied to at least a part of the waveguide 81 from the electrodes 48 and 49. By the feedback operation described above, the signal (output light L) output from the optical device having the optical modulation element 105 is out ) status can be adjusted.

[0161] In the fifth modified example, similarly to the first and second embodiments, a case has been exemplified in which waveguide 20B has monitoring waveguide 27, and monitoring light propagating through monitoring waveguide 27 is irradiated onto magnetic element 30. However, the fifth modified example is not limited to this case, and similarly to the third embodiment, a configuration may be adopted in which part of light output from the output end of first waveguide 29 is irradiated onto magnetic element 30 as monitoring light.

[0162] "Sixth Variation" 24 is a plan view of an optical device 201 according to the sixth modification. In the sixth modification, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0163] The optical device 201 has a plurality of laser diodes 91, 92, and 93, a waveguide 20C, and a magnetic element 30. The optical device 201 is a planar lightwave circuit used in augmented reality (AR) glasses and a small projector. Like the optical device 201 shown in the sixth modified example, the optical device is not limited to an optical modulator.

[0164] Each of the plurality of laser diodes 91, 92, and 93 outputs a laser beam. As an example, the laser diodes 91, 92, and 93 are lasers of three colors: red, green, and blue. The number of laser diodes, the wavelength ranges they output, and the like are not limited to this.

[0165] The waveguide 20C includes, for example, input waveguides 21C, 22C, and 23C, a multiplexing waveguide 24C, an output waveguide 25C, and a monitoring waveguide 27. FIG. 25 is a cross-sectional view of the waveguide 20C of an optical device 201 according to the sixth modification, taken along E-E' in FIG. 24. The input waveguides 21C, 22C, and 23C are located on a substrate 10 and are covered with, for example, a cladding 28. The waveguide 20C and the magnetic element 30 are located on or above the same substrate. The magnetic element 30 is located at a position where it is irradiated with monitoring light. As in the first or second embodiment, the monitoring light propagating through the monitoring waveguide 27 is irradiated onto the magnetic element 30.

[0166] The light beams emitted from the laser diodes 91, 92, and 93 are input to the input waveguides 21C, 22C, and 23C, respectively. The light beams propagating through the input waveguides 21C, 22C, and 23C are combined in the multiplexing path 24C. The light beams combined in the multiplexing path 24C propagate through the output waveguide 25C. The light beams combined in the multiplexing path 24C are output from one end of the output waveguide 25C.

[0167] At least a part of the light propagating through output waveguide 25C is branched into monitoring waveguide 27. The branched light propagates through monitoring waveguide 27 as monitoring light, and is irradiated onto magnetic element 30.

[0168] The output voltage or output current from the magnetic element 30 (the resistance value in the stacking direction of the magnetic element 30) varies depending on the intensity of the monitoring light irradiated onto the first ferromagnetic layer 31. The optical device 201 can read out the intensity of the monitoring light based on the output voltage or output current from the magnetic element 30 (the resistance value of the magnetic element 30), i.e., the electrical signal from the magnetic element 30.

[0169] The optical device 201 can measure the intensity of light output from each of the laser diodes 91, 92, and 93 based on the output voltage or output current from the magnetic element 30 (the resistance value in the stacking direction of the magnetic element 30), that is, the electrical signal from the magnetic element 30.

[0170] The light output from one end of output waveguide 25C is a combination of the light output from each of laser diodes 91, 92, and 93. Optical device 201 can adjust the white balance of the output light by adjusting the intensity of the light output from each of laser diodes 91, 92, and 93. The intensity of the light output from each of laser diodes 91, 92, and 93 can be adjusted by feeding back the measurement result of the output from magnetic element 30 to each of laser diodes 11, 12, and 13.

[0171] In the sixth modified example, similarly to the first and second embodiments, a case has been exemplified in which waveguide 20C has monitoring waveguide 27, and monitoring light propagating through monitoring waveguide 27 is irradiated onto magnetic element 30. However, the sixth modified example is not limited to this case, and similarly to the third embodiment, a configuration may be adopted in which part of the light output from the output end of output waveguide 25C is irradiated onto magnetic element 30 as monitoring light.

[0172] "Seventh Variation" Fig. 26 is a plan view of a light modulation element 110 according to a seventh modified example. Fig. 27 is a cross-sectional view of the vicinity of the magnetic element 30 of the light modulation element 110 according to the seventh modified example. In the seventh modified example, the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0173] The optical modulation element 110 has a support 95 that supports the magnetic element 30. The support 95 is a separate member from the substrate 10 on which the waveguide 20D is formed. The support 95 and the substrate 10 are fixed, for example, on a common support. The magnetic element 30 is located on or above the support 95. Up to this point, examples have been shown in which the waveguide 20 and the magnetic element 30 are formed on or above the same substrate, but in the seventh modification, the waveguide 20D and the magnetic element 30 are formed on different members.

[0174] The support 95 is, for example, made of the same material as the substrate 10. The magnetic element 30 is located within an insulating layer 96 formed on the support 95. The insulating layer 96 is, for example, made of the same material as the sidewall insulating layer 39.

[0175] In the example shown in FIG. 27, the height position of the magnetic element 30 in the z direction is aligned with the height position of the output end of the monitoring waveguide 27 in the z direction.

[0176] 28, the support 95 may be on the substrate 10. The magnetic element 30 is above the upper surface S2 of the substrate 10 and on the support 95. The waveguide 20 (monitoring waveguide 27) is on the upper surface S1 of the substrate 10.

[0177] 29, the traveling direction of the monitoring light from the output end of the monitoring waveguide 27 may coincide with the stacking direction of the magnetic element 30. The support 95 is installed, for example, so that the side surface of the support 95 faces the upper surface S2 of the substrate 10 when the magnetic element 30 is stacked. The monitoring light is irradiated onto the magnetic element 30, for example, from the stacking direction of the magnetic element 30. In this case, the electrode 51 is transparent to the wavelength range of the light irradiated onto the magnetic element 30. The electrode 51 transmits a portion of the monitoring light, and the monitoring light is irradiated onto the magnetic element 30.

[0178] 30 , electrode 51 is connected to input terminal 55A and output terminal 56A. Electrode 52 is connected to input terminal 55A through via wiring 53 and to output terminal 56A through via wiring 54. Input terminal 55A and output terminal 56A are formed on the side surface of support 95.

[0179] Even when the waveguide 20 and the magnetic element 30 are formed on different members, the optical modulation element 110 can monitor at least a part of the light propagating through the waveguide 20D using the magnetic element 30.

[0180] "Eighth Variation" Fig. 31 is a plan view of an optical device 202 according to an eighth modification. In Fig. 31, the same components as those in the optical device 201 shown in Fig. 24 are denoted by the same reference numerals, and the description thereof will be omitted.

[0181] The optical device 202 includes a plurality of laser diodes 91, 92, 93, and 94, a waveguide 20D, a plurality of magnetic elements 30, and an optical modulation element 100.

[0182] The laser diode 94 outputs laser light. The laser diode 94 is optically connected to the waveguide 20D. For example, the laser diode 94 is a near-infrared laser that outputs light (near-infrared light) in a wavelength range of 780 nm or more and 2500 nm or less.

[0183] The shape of waveguide 20D of optical device 202 is different from that of waveguide 20C of optical device 201. The cross-sectional structure of waveguide 20D is similar to that of waveguide 20C. Waveguide 20D has input waveguides 21C, 22C, 23C, and 21D, a multiplexing waveguide 24D, an output waveguide 25C, and multiple monitoring waveguides 27A and 27B.

[0184] The input waveguide 21D is optically connected to the laser diode 94. For example, light output from the laser diode 94 propagates through the input waveguide 21D. The multiplexing path 24D is located between the input waveguides 21C, 22C, 23C, and 21D and the output waveguide 25C. The light propagating through the input waveguides 21C, 22C, 23C, and 21D is combined in the multiplexing path 24D. The output waveguide 25C is connected to the input waveguides 21C, 22C, 23C, and 21D via the multiplexing path 24D, and light from the input waveguides 21C, 22C, 23C, and 21D propagates through the output waveguide 25C.

[0185] Each of the multiple monitoring waveguides 27A, 27B is connected to output waveguide 25C. A plurality of monitoring waveguides 27A may be provided, and each monitoring waveguide 26D may be individually connected to each of input waveguides 21C, 22C, 23C, and 21D. At least a portion of the light propagating through at least one of input waveguides 21C, 22C, 23C, and 21D and output waveguide 25C propagates through monitoring waveguide 27A. At least a portion of the light propagating through output waveguide 25C propagates through monitoring waveguide 27B.

[0186] At the connection portion between first monitoring waveguide 27A and output waveguide 25C, the angle that first monitoring waveguide 27A makes with the +x direction is, for example, smaller than 90°. At the connection portion between second monitoring waveguide 27B and output waveguide 25C, the angle that second monitoring waveguide 27B makes with the +x direction is, for example, larger than 90°. The +x direction is, for example, the direction in output waveguide 25C in which the light output from laser diodes 91, 92, 93, and 94 travels toward the output end of output waveguide 25C.

[0187] Monitoring light propagates through first monitoring waveguide 27A and second monitoring waveguide 27B. At least a portion of the light output from laser diodes 91, 92, 93, and 94 and propagating through at least one of input waveguides 21C, 22C, 23C, and 21D and output waveguide 25C in a direction from laser diodes 91, 92, 93, and 94 toward input waveguides 21C, 22C, 23C, and 21D or output waveguide 25C propagates through first monitoring waveguide 27A. At least a portion of the light output from output waveguide 25C to the outside and reflected by the irradiated object propagates through second monitoring waveguide 27B. Hereinafter, at least a portion of the monitoring light that is output from laser diodes 91, 92, 93, 94 and propagates in the direction from laser diodes 91, 92, 93, 94 to at least one of input waveguides 21C, 22C, 23C, 21D and output waveguide 25C toward input waveguides 21C, 22C, 23C, 21D or output waveguide 25C will be referred to as first monitoring light, and at least a portion of the light that is output to the outside from output waveguide 25C and reflected by the irradiated body will be referred to as second monitoring light.

[0188] Each of the multiple magnetic elements 30 is the magnetic element 30 described above. One of the magnetic elements 30 is referred to as the first magnetic element 30A, and the other is referred to as the second magnetic element 30B. The first magnetic element 30A is located at a position where it is irradiated with the first monitoring light. The first magnetic element 30A is located at the end of the output end of the first monitoring waveguide 27A. The second magnetic element 30B is located at a position where it is irradiated with the second monitoring light. The second magnetic element 30B is located at the end of the output end of the second monitoring waveguide 27B. The first magnetic element 30A is irradiated with the first monitoring light, and the second magnetic element 30B is irradiated with the second monitoring light.

[0189] The optical modulation element 100 is optically connected to, for example, each of the input waveguides 21C, 22C, and 23C. The optical modulation element 100 is, for example, the optical modulation element shown in FIG. 2. The optical modulation element 100 can be replaced with another optical modulation element. Furthermore, the magnetic element 30 and the monitoring waveguide 27 may be omitted from the optical modulation element 100.

[0190] The optical modulation element 100 can adjust the intensity of each light beam reaching the multiplexing path 24D while maintaining constant the output of the laser diodes 91, 92, and 93. A configuration that adjusts the intensity of light using the optical modulation element 100 can reduce power consumption compared to a configuration that directly adjusts the output of the laser diodes 91, 92, and 93.

[0191] The optical device 202 can measure the change in state of the irradiated object by measuring the intensity of the light reflected from the irradiated object using the second magnetic element 30B.

[0192] 32 is a conceptual diagram of an optical system 300 using the optical device 202. The optical system 300 can be implemented in glasses 1000, for example.

[0193] The optical system 300 includes an optical device 202, an optical system 210, drivers 220 and 221, and a controller 230. The optical system 210 includes, for example, a collimator lens 211, a slit 212, an ND filter 213, and an optical scanning mirror 214. The optical system 210 guides light output from the optical device 202 to an object to be illuminated (the eye in this example). The optical scanning mirror 214 is, for example, a two-axis MEMS mirror that changes the reflection direction of laser light in the horizontal and vertical directions. The optical system 210 is an example and is not limited to this example. The driver 220 controls the output of each of the laser diodes 91, 92, 93, and 94. The driver 221 is a control system that drives the optical scanning mirror 214. The controller 230 controls the drivers 220 and 221.

[0194] Light L output from laser diodes 91, 92, 93, and 94 of the optical device 202 GThe light propagates through the optical system 210, is reflected by the lenses of the glasses 1000, and enters the eye. Here, an example is shown in which the light is reflected by the lenses of the glasses 1000, but the light may be irradiated directly onto the eye.

[0195] Red, green, and blue light L emitted from laser diodes 91, 92, and 93, respectively. G displays an image. The image can be freely controlled by adjusting the output intensity of each of the laser diodes 91, 92, and 93 with the light modulation element 100. The output intensity of each of the laser diodes 91, 92, and 93 can be adjusted based on the measurement results of the output from the first magnetic element 30A that is irradiated with the visible light output from each of the laser diodes 91, 92, and 93. Note that the output of the laser diodes 91, 92, and 93 may be adjusted directly without using the light modulation element 100.

[0196] The near-infrared light emitted from the laser diode 94 of the optical device 202 is reflected by the pupil of the eye. R Is, Light L G The reflected light L , which is near-infrared light, passes through the same optical axis as the reflected light L , and reaches the optical device 202. R At least a part of the reflected light L propagates from the output end of the output waveguide 25C through the second monitoring waveguide 27B and is irradiated onto the second magnetic element 30B. R The optical system 300 measures the intensity of the near-infrared light irradiated at the position adjusted by the optical scanning mirror 214 and the reflected light L R The movement of the gaze point (point of gaze) can be identified from the intensity of the reflected light L R is not limited to light reflected from the pupil of the eye, but may be light reflected from the cornea of ​​the eye or light reflected from the sclera of the eye.

[0197] Here, a system capable of both image display and eye tracking has been exemplified as an example of an optical system, but the present invention is not limited to this example.

[0198] For example, the eye-tracking laser diode 94 may be removed from the optical system described above. In this case, the optical system becomes a system for image display. In this case, the laser diode 94, input waveguide 21D, second monitoring waveguide 27B, and second magnetic element 30B can be removed from optical device 202.

[0199] "Ninth Variation" 33 is a conceptual diagram of an optical system 500 according to a ninth modification. The optical system 500 includes a transmitting device 510 and a receiving device 520. The transmitting device 510 and the receiving device 520 are connected by, for example, an optical fiber FB, and transmit and receive signals via the optical fiber FB. The optical system 500 is, for example, an optical communication system.

[0200] The transmitting device 510 has a plurality of drivers 511, a plurality of optical modulation elements 103, a plurality of filters 512, and a multiplexer 513. To the multiplexer 513, for example, two units each consisting of a driver 511, an optical modulation element 103, and a filter 512 are connected.

[0201] The optical modulation element 103 is an example, and the optical modulation element 103 may be replaced with other optical modulation elements 100 to 102, 104, 105, and 110. The driver 511 is connected to, for example, power supplies 161A and 161B of the optical modulation element 103, and changes the potential of the electrodes 45, 46, and 47. The filters 512 are, for example, bandpass filters or band-eliminate filters. The frequency bands of optical signals that can pass through each filter 512 are different. The multiplexer 513 multiplexes the light that has passed through each filter 512. The multiplexed light propagates to the receiving device 520 via the optical fiber FB.

[0202] The receiving device 520 has a duplexer 521, a plurality of filters 522, and a plurality of receivers 523. To the duplexer 521, for example, two units each consisting of a filter 522 and a receiver 523 are connected.

[0203] The demultiplexer 521 separates the optical signal propagated through the optical fiber FB into frequency bands. The demultiplexer 521 separates the optical signal into frequency bands that have passed through each of the filters 512, for example. The optical signals separated by the demultiplexer 521 are demodulated by each of the receivers 523 via the filter 522. The filter 522 may be the same as the filter 512.

[0204] The optical system 500 according to the ninth modification is a frequency multiplexing optical communication system, and is capable of transmitting a large amount of information at once.

[0205] As described above, the present invention is not limited to the above-described embodiment and modifications, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. For example, the characteristic features of the above-described embodiment and modifications may be combined. [Explanation of symbols]

[0206] 10...substrate, 20, 20A, 20B, 20C, 20D, 20E...waveguide, 27...monitoring waveguide, 30...magnetic element, 30A...first magnetic element, 30B...second magnetic element, 41, 42, 43, 44, 45, 46, 47, 48, 49...electrodes, 60...reflector, 100, 101, 102, 103, 104, 105, 110...optical modulation element, 150...control unit, 200, 201, 202...optical device, 210...optical system, 300, 500...optical system

Claims

1. 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 substrate; a waveguide; the waveguide and the magnetic element are on or above the substrate; the magnetic element and the waveguide are integrated into one article; A portion of the light propagating through the waveguide is irradiated onto the magnetic element, the first ferromagnetic layer is a light detection layer whose magnetization state changes when irradiated with light, the second ferromagnetic layer is a magnetization fixed layer whose magnetization state is less likely to change than the first ferromagnetic layer; the spacer layer is a nonmagnetic layer, The magnetic element is an optical device that outputs a voltage or a current according to the intensity of the irradiated light when the first ferromagnetic layer is irradiated with the light.

2. Further comprising an electrode, The optical device according to claim 1 , wherein an electric field based on an electric signal from the magnetic element can be applied from the electrode to at least a part of the waveguide.

3. Further comprising a reflector; The optical device according to claim 1 , wherein the reflector reflects at least a portion of the light toward the magnetic element.

4. 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 substrate; a waveguide; the waveguide and the magnetic element are on or above the substrate; the magnetic element and the waveguide are integrated into one article; A portion of the light propagating through the waveguide is irradiated onto the magnetic element, the first ferromagnetic layer is a light detection layer whose magnetization state changes when irradiated with light, the second ferromagnetic layer is a magnetization fixed layer whose magnetization state is less likely to change than the first ferromagnetic layer; the spacer layer is a nonmagnetic layer, the magnetic element outputs a voltage or a current according to the intensity of the irradiated light when the first ferromagnetic layer is irradiated with the light; An optical device, wherein at least a portion of the light is irradiated onto the magnetic element from a direction intersecting a stacking direction of the magnetic element.

5. the magnetic element further includes a first electrode connected to a first surface of the magnetic element and a second electrode connected to a second surface of the magnetic element opposite to the first surface; At least one of the first electrode and the second electrode is transparent to a wavelength range of light irradiated onto the magnetic element, 4. The optical device according to claim 1, wherein at least a portion of the light is irradiated onto the magnetic element from the stacking direction of the magnetic element.

6. the waveguide further comprises a monitoring waveguide; 6. The optical device according to claim 1, wherein a portion of the light propagating through the waveguide propagates through the monitoring waveguide.

7. further comprising a laser diode and an optical modulation element; the laser diode is optically coupled to the waveguide; 7. The optical device according to claim 1, wherein the optical modulation element is located between the laser diode and the waveguide and modulates the intensity of light reaching the waveguide.

8. 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 substrate; A waveguide; A laser diode; a light modulation element; the waveguide and the magnetic element are on or above the substrate; the magnetic element and the waveguide are integrated into one article; A portion of the light propagating through the waveguide is irradiated onto the magnetic element, the first ferromagnetic layer is a light detection layer whose magnetization state changes when irradiated with light, the second ferromagnetic layer is a magnetization fixed layer whose magnetization state is less likely to change than the first ferromagnetic layer; the spacer layer is a nonmagnetic layer, the magnetic element outputs a voltage or a current according to the intensity of the irradiated light when the first ferromagnetic layer is irradiated with the light; the laser diode is optically coupled to the waveguide; the optical modulation element is located between the laser diode and the waveguide and modulates the intensity of light reaching the waveguide; the at least one magnetic element is a plurality of magnetic elements; a first magnetic element among the plurality of magnetic elements is irradiated with a portion of light propagating through the waveguide in a direction from the laser diode toward the waveguide; an optical device, wherein a second magnetic element of the plurality of magnetic elements is irradiated with at least a portion of light output from the waveguide and reflected by an irradiated object;

9. 9. An optical system comprising: the optical device according to claim 7; and an optical system that guides light output from the optical device to an object to be illuminated.

Images