Light detection device and transmitting / receiving device

Abstract

The present invention provides a photodetector capable of removing phase-shifted noise signals that occur when light containing an optical signal is irradiated onto a magnetic element. [Solution] The light detection device 100 comprises a first magnetic element 10, a second magnetic element 20, and a differential combining circuit 30. The first magnetic element comprises a first ferromagnetic layer 11, a second ferromagnetic layer 12, and a first spacer layer 13 sandwiched between the first and second ferromagnetic layers. When light containing an optical signal is irradiated onto the first ferromagnetic layer, it generates a first voltage signal corresponding to the optical signal. The second magnetic element comprises a third ferromagnetic layer 21, a fourth ferromagnetic layer 22, and a second spacer layer 23 sandwiched between the third and fourth ferromagnetic layers. When the same light is simultaneously irradiated onto the third ferromagnetic layer, it generates a second voltage signal in the opposite phase to the first voltage signal corresponding to the optical signal. The differential combining circuit differentially combines a first total voltage signal output from the first magnetic element and a second total voltage signal output from the second magnetic element.

Description

[Technical Field]

[0001] The present invention relates to a light detection device and a transmitting / receiving device. [Background technology]

[0002] Photodetectors using photoelectric conversion elements are used in a variety of applications. For example, Patent Document 1 describes a receiving device that receives optical signals using a photodiode. A photodiode is, for example, a pn junction diode using a semiconductor pn junction, which converts light into an electrical signal. For example, Patent Document 2 discloses an optical sensor using a magnetic element that can extract light as an electrical signal, and a receiving device using this optical sensor. For example, Patent Document 3 discloses a laser sensor device that detects laser light as an electrical signal, and describes how to eliminate the effects of stray light using a differential circuit. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2001-292107 [Patent Document 2] Japanese Patent Publication No. 2022-69387 [Patent Document 3] Japanese Patent Application Publication No. 10-221164 [Overview of the project] [Problems that the invention aims to solve]

[0004] FIG. 14 is a diagram showing the configuration of a conventional optical detection device 1000 described in, for example, Patent Document 2 or the like. As shown in FIG. 14, the magnetic element 110 of the conventional optical detection device 1000 includes a first ferromagnetic layer 111 as a magnetization (M1) free layer, a second ferromagnetic layer 112 as a magnetization (M2) fixed layer, and a spacer layer 113. The spacer layer 113 is sandwiched between the first ferromagnetic layer 111 and the second ferromagnetic layer 112, and these form a laminate. The conventional optical detection device 1000 further includes a first electrode 114 and a second electrode 115 so as to sandwich the laminate in the stacking direction (z-axis direction). A bias current I OUT , REAL , NOISE , NOISE , OUT , NOISE , OUT , REAL , NOISE , NOISE , OUT , REAL , REAL , NOISE is caused to flow through the magnetic element 110 by an external constant current source connected to the first electrode 114 and the second electrode 115. An output terminal is connected to the first electrode 114.

[0005] FIG. 15(a) shows the time waveform of an output signal V OUT output from the output terminal when an optical signal Ls having an optical signal is irradiated to the magnetic element 110 in the conventional optical detection device 1000 of FIG. 14, and FIG. 15(b) shows the time waveform of a noise signal V NOISE output from the first electrode 114. The optical signal is assumed to have a light intensity that varies at a predetermined frequency. When an optical signal Ls having an optical signal is irradiated to the conventional optical detection device 1000, an actual (voltage) signal V REAL corresponding to the optical signal is output from the first electrode 114. Also, as shown in FIG. 15(b), a noise signal V NOISE generated by the irradiation of the optical signal Ls having an optical signal is also output from the first electrode 114. That is, the output signal V OUT in FIG. 15(a) output from the output terminal is the sum of the actual signal V REAL and the noise signal V NOISE . V OUT = V REAL + V NOISE . However, it has been found that the noise signal V NOISE has a constant phase difference with respect to the actual signal V REAL . Therefore, the output signal V OUT was distorted. For example, due to the noise signal V NOISE having a phase difference, the actual signal VREAL There was a problem where the peak-to-peak value would change or decrease.

[0006] The present invention has been made in view of the above problems, and aims to provide an optical detection device and a transmitting / receiving device that can remove phase-shifted noise signals that occur when light having an optical signal is irradiated onto a magnetic element. [Means for solving the problem]

[0007] To achieve the above objective, the photodetector according to the present invention comprises a first magnetic element comprising a first ferromagnetic layer, a second ferromagnetic layer, and a first spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, wherein when light containing an optical signal is irradiated onto the first ferromagnetic layer, the first magnetic element generates a first voltage signal corresponding to the optical signal; a second magnetic element comprising a third ferromagnetic layer, a fourth ferromagnetic layer, and a second spacer layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer, wherein when the light is simultaneously irradiated onto the third ferromagnetic layer, the second magnetic element generates a second voltage signal in the opposite phase to the first voltage signal corresponding to the optical signal; and a differential combining circuit that differentially combines a first total voltage signal output from the first magnetic element including the first voltage signal, and a second total voltage signal output from the second magnetic element including the second voltage signal.

[0008] As described above, when light with the same optical signal is simultaneously shone on the first and second magnetic elements, a first voltage signal corresponding to the optical signal is generated from the first magnetic element, and a second voltage signal corresponding to the optical signal and in the opposite phase to the first voltage signal is generated from the second magnetic element. Simultaneously, a first noise signal that is out of phase with respect to the first voltage signal is generated from the first magnetic element, and a second noise signal that is out of phase with respect to the second voltage signal is generated from the second magnetic element. That is, the sum of the first voltage signal and the first noise signal is the first total voltage signal, and this first total voltage signal is input to the differential summing circuit. Similarly, the sum of the second voltage signal and the second noise signal is the second total voltage signal, and this second total voltage signal is input to the differential summing circuit. Here, the first and second voltage signals are out of phase, while the first and second noise signals are in phase. Therefore, the differential summing circuit cancels out the first and second noise signals that are in phase, and the first and second voltage signals that are out of phase are essentially added together. Therefore, with the above configuration, it is possible to remove phase-shifted noise signals that occur when light containing an optical signal is irradiated onto a magnetic element, and to amplify the voltage signal corresponding to the optical signal.

[0009] In the photodetector according to the present invention, the magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer of the first magnetic element may be antiparallel, and the magnetization directions of the third ferromagnetic layer and the fourth ferromagnetic layer of the second magnetic element may be parallel.

[0010] This configuration allows the first voltage signal output from the first magnetic element and the second voltage signal output from the second magnetic element to be in opposite phase. As a result, in the differential summing circuit, the first and second noise signals, which are in phase, cancel each other out, while the first and second voltage signals, which are in opposite phase, are essentially added together. Therefore, with this configuration, it is possible to remove the phase-shifted noise signal that occurs when light containing an optical signal is irradiated onto the magnetic element, and to amplify the voltage signal corresponding to the optical signal.

[0011] The photodetector according to the present invention may be configured such that a first bias current flows from the first ferromagnetic layer toward the second ferromagnetic layer or in the reverse direction, and a second bias current flows from the fourth ferromagnetic layer toward the third ferromagnetic layer or in the reverse direction.

[0012] With this configuration, the photodetector of the present invention can make the first voltage signal output from the first magnetic element and the second voltage signal output from the second magnetic element out of phase. As a result, in the differential summing circuit, the first and second noise signals that are in phase cancel each other out, and the first and second voltage signals that are out of phase are substantially added together. Therefore, with the above configuration, it is possible to remove the phase-shifted noise signal that occurs when light with an optical signal is irradiated onto the magnetic element, and to amplify the voltage signal corresponding to the optical signal.

[0013] In the light detection device according to the present invention, the differential summing circuit may be configured using an operational amplifier.

[0014] This configuration makes it easy to realize a highly accurate differential summing circuit.

[0015] In the photodetector according to the present invention, the differential combining circuit may be configured to include a 180° phase shift circuit that receives the second total voltage signal output from the second magnetic element and shifts the second total voltage signal by 180°, and a power combiner that combines the 180° phase-shifted second total voltage signal and the first total voltage signal output from the first magnetic element.

[0016] In this configuration, the second noise signal is phase-shifted by 180° by the 180° phase-shift circuit and input to the power combiner, while the first noise signal is input to the power combiner as is. That is, the first and second noise signals are in opposite phases and cancel each other out when input to the power combiner. The second voltage signal is phase-shifted by 180° by the 180° phase-shift circuit and input to the power combiner, while the first voltage signal is input to the power combiner as is. That is, the first and second voltage signals are in phase and are input to the power combiner, where the first and second voltage signals are combined. Therefore, with the above configuration, it is possible to remove the phase-shifted noise signal that occurs when light containing an optical signal is irradiated onto a magnetic element, and to amplify the voltage signal corresponding to the optical signal.

[0017] In the photodetector according to the present invention, the differential combining circuit may be configured to include: a +90° phase shift circuit that receives the first total voltage signal output from the first magnetic element and shifts the first total voltage signal by +90°; a -90° phase shift circuit that receives the second total voltage signal output from the second magnetic element and shifts the second total voltage signal by -90°; and a power combiner that combines the first total voltage signal which has been phase shifted by +90° and the second total voltage signal which has been phase shifted by -90°.

[0018] In this configuration, the first noise signal is phase-shifted by +90° by the +90° phase shift circuit and input to the power combiner, and the second noise signal is phase-shifted by -90° by the -90° phase shift circuit and input to the power combiner. That is, the first and second noise signals are in opposite phases and cancel each other out when input to the power combiner. The first voltage signal is phase-shifted by +90° by the +90° phase shift circuit and input to the power combiner, and the second voltage signal is phase-shifted by -90° by the -90° phase shift circuit and input to the power combiner. That is, the first and second voltage signals are in phase and are input to the power combiner and combined. Therefore, with the above configuration, it is possible to remove the phase-shifted noise signal that occurs when light with an optical signal is irradiated onto a magnetic element, and to amplify the voltage signal corresponding to the optical signal.

[0019] In the photodetector according to the present invention, the first magnetic element further comprises a first electrode provided on the side of the first ferromagnetic layer opposite to the first spacer layer and a second electrode provided on the side of the second ferromagnetic layer opposite to the spacer layer, the second magnetic element further comprises a third electrode provided on the side of the third ferromagnetic layer opposite to the second spacer layer and a fourth electrode provided on the side of the fourth ferromagnetic layer opposite to the second spacer layer, and the first electrode and the third electrode may be transparent electrodes.

[0020] This configuration allows the light incident on the first and second magnetic elements to be irradiated onto the first and third ferromagnetic layers with almost no attenuation.

[0021] Furthermore, in order to achieve the above objective, the transmitting and receiving device according to the present invention comprises a transmitting device that includes a light source that emits light with a wavelength of 400 nm to 1500 nm and modulates and outputs the emitted light, and a receiving device that includes any of the above-mentioned light detection devices that detect light with a wavelength of 400 nm to 1500 nm and demodulates the detected light.

[0022] With this configuration, the light detection device of the receiving device can perform photoelectric conversion with high accuracy by receiving light within the above wavelength range. Furthermore, since the light source of the transmitting device emits light within the same wavelength range, a communication system with excellent receiving performance can be efficiently constructed by having each communication device equipped with this transmitting and receiving device. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a photodetector and a transmitting / receiving device that can remove phase-shifted noise signals generated when light having an optical signal is irradiated onto a magnetic element. [Brief explanation of the drawing]

[0024] [Figure 1] This figure shows the basic configuration of a light detection device according to an embodiment of the present invention. [Figure 2] This figure shows a schematic configuration of a light detection device according to the first embodiment of the present invention. [Figure 3] (a) shows the time waveform of the first total voltage signal output from the first magnetic element, (b) shows the time waveform of the second total voltage signal output from the second magnetic element, and (c) shows the time waveform of the output signal output from the differential summing circuit. [Figure 4] This figure shows a schematic configuration of a light detection device according to a second embodiment of the present invention. [Figure 5] (a) shows the time waveform of the first total voltage signal output from the first magnetic element, (b) shows the time waveform of the second total voltage signal output from the second magnetic element, and (c) shows the time waveform of the output signal output from the differential summing circuit. [Figure 6] This figure shows a schematic configuration of a light detection device according to a third embodiment of the present invention. [Figure 7] This figure shows a schematic configuration of a light detection device according to a fourth embodiment of the present invention. [Figure 8] This diagram shows the time waveforms of each signal in a differential summing circuit. [Figure 9]This figure shows a schematic configuration of a light detection device according to a fifth embodiment of the present invention. [Figure 10] This diagram shows the time waveforms of each signal in a differential summing circuit. [Figure 11] This figure shows the configuration of a transmitting and receiving device according to an embodiment of the present invention. [Figure 12] This figure shows the configuration of a communication system according to an embodiment of the present invention. [Figure 13] This figure shows the configuration of a terminal device according to an embodiment of the present invention. [Figure 14] This diagram shows the configuration of a conventional light detection device. [Figure 15] (a) shows the time waveform of the total voltage signal (output signal) output from the magnetic element in the conventional photodetector shown in Figure 14, and (b) shows the time waveform of the noise signal output from the magnetic element. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described in detail below with reference to the drawings. Note that, for ease of understanding, the scale of the parts in the drawings may differ from the actual scale. In the xyz Cartesian coordinate system set in the drawings, the x-axis and y-axis directions are horizontal, and the z-axis direction is vertical. The positive z-axis direction is also called the upward direction, and the negative z-axis direction is also called the downward direction, but this is unrelated to the direction of gravity. A degree of deviation is permissible in directions such as parallel, perpendicular, orthogonal, horizontal, vertical, up and down, and left and right, as long as it does not impair the effects of the embodiment. Furthermore, the "~" indicating a numerical range means that the values ​​written before and after it are included as the lower and upper limits, respectively.

[0026] (Basic configuration) Figure 1 shows the basic configuration of a light detection device 100 according to an embodiment of the present invention. As shown in Figure 1, the light detection device 100 comprises a first magnetic element 10, a second magnetic element 20, and a differential summing circuit 30.

[0027] The first magnetic element 10 comprises a first ferromagnetic layer 11, a second ferromagnetic layer 12, and a first spacer layer 13 sandwiched between the first ferromagnetic layer 11 and the second ferromagnetic layer 12. The first magnetic element 10 further comprises a first electrode 14 provided on the side of the first ferromagnetic layer 11 opposite to the first spacer layer 13, and a second electrode 15 provided on the side of the second ferromagnetic layer 12 opposite to the first spacer layer 13. The first electrode 14 is a transparent electrode that transmits light. This allows light incident on the first magnetic element 10 to be irradiated onto the first ferromagnetic layer 11 with almost no attenuation. When light Ls containing an optical signal is irradiated onto the first ferromagnetic layer 11, the first magnetic element 10 generates a first voltage signal (hereinafter also referred to as the first real signal) V corresponding to the optical signal. REAL_1 This generates the first real signal V REAL_1 A first noise signal V with a phase shift relative to it. NOISE_1 This will result in...

[0028] The second magnetic element 20 comprises a third ferromagnetic layer 21, a fourth ferromagnetic layer 22, and a second spacer layer 23 sandwiched between the third ferromagnetic layer 21 and the fourth ferromagnetic layer 22. Furthermore, the second magnetic element 20 includes a third electrode 24 provided on the side of the third ferromagnetic layer 21 opposite to the second spacer layer 23, and a fourth electrode 25 provided on the side of the fourth ferromagnetic layer 22 opposite to the second spacer layer 23. The third electrode 24 is a transparent electrode that transmits light. This allows light incident on the second magnetic element 20 to be irradiated onto the third ferromagnetic layer 21 with almost no attenuation. When the same light incident on the first ferromagnetic layer 11 is simultaneously irradiated onto the third ferromagnetic layer 21, the second magnetic element 20 generates a second voltage signal (hereinafter also referred to as the second real signal) V, which is in the opposite phase to the first voltage signal, corresponding to the same optical signal. REAL_2 This is generated, along with the second real signal V REAL_2 A second noise signal V with a phase shift relative to it. NOISE_2 This will result in...

[0029] The first real signal V output from the first magnetic element 10 REAL_1 and the first noise signal V NOISE_1 The sum of these is the first total voltage signal V, which is the sum of the output voltages. TOTAL_1 In other words, the first total voltage signal V TOTAL_1This is a first real signal V that corresponds to the optical signal (e.g., optical modulation signal) contained in the irradiated light. REAL_1 (For example, an electrically modulated signal) and the first real signal V REAL_1 A first noise signal V with a phase shift relative to it. NOISE_1 It consists of the following. Similarly, the second real signal V output from the second magnetic element 20 REAL_2 and the second noise signal V NOISE_2 The sum of these two signals is the second total voltage signal V, which is the sum of the output voltages. TOTAL_2 In other words, the second total voltage signal V TOTAL_2 This is a second real signal V that corresponds to the optical signal (e.g., optical modulation signal) contained in the irradiated light. REAL_2 (For example, an electrically modulated signal) and a second real signal V REAL_2 A second noise signal V with a phase shift relative to it. NOISE_2 It consists of the following: First real signal V REAL_1 and the second real signal V REAL_2 This is in opposite phase, and the first noise signal V NOISE_1 and the second noise signal V NOISE_2 They are in phase.

[0030] The differential summing circuit 30 receives the first real signal V REAL_1 The first total voltage signal V, including the first magnetic element 10, is output from the first magnetic element 10. TOTAL_1 And the second real signal V REAL_2 The second total voltage signal V, including the second magnetic element 20, is output from the second magnetic element 20. TOTAL_2 The differential summing circuit 30 is configured to perform differential summing of the first total voltage signal V TOTAL_1 and the second total voltage signal V TOTAL_2 Output the difference from the above.

[0031] If two identical waveform signals input to the differential summing circuit 30 are in phase, they cancel each other out through differential summing, resulting in an output signal of zero. On the other hand, if two identical waveform signals input to the differential summing circuit 30 are in opposite phase (phase difference of 180°), the output signal becomes twice the single input signal through differential summing.

[0032] The term "light" as used herein is not limited to visible light, but may also include infrared light with a longer wavelength than visible light, or ultraviolet light with a shorter wavelength than visible light. For example, it may include light with a wavelength of 400 nm to 1500 nm. The wavelength of visible light is, for example, 380 nm to less than 800 nm. The wavelength of infrared light is, for example, 800 nm to 1 mm. The wavelength of ultraviolet light is, for example, 200 nm to less than 380 nm.

[0033] The following describes each component.

[0034] (Magnetic element) As shown in Figure 1, the first magnetic element 10 is formed by stacking at least a first electrode 14, a first ferromagnetic layer 11, a first spacer layer 13, a second ferromagnetic layer 12, and a second electrode 15 in this order along the z-axis direction. Similarly, the second magnetic element 20 is formed by stacking at least a third electrode 24, a third ferromagnetic layer 21, a second spacer layer 23, a fourth ferromagnetic layer 22, and a fourth electrode 25 in this order along the z-axis direction. The first magnetic element 10 and the second magnetic element 20 may include layers other than those described above as needed.

[0035] The first magnetic element 10 and the second magnetic element 20 have the same configuration and size, and are arranged side by side in close proximity within the spot of the incident light Ls. The same incident light Ls, which includes an optical signal such as an optical modulation signal, is incident on both the first magnetic element 10 and the second magnetic element 20 simultaneously. Since the first magnetic element 10 and the second magnetic element 20 have the same configuration, only the configuration of the first magnetic element 10 will be described below, but the same applies to the second magnetic element 20.

[0036] The first magnetic element 10 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the first spacer layer 13 is made of an insulating material. In this case, the first magnetic element 10 can exhibit the tunnel magnetoresistance (TMR) effect. The resistance value of the first magnetic element 10 changes when light is irradiated from the outside. The resistance value in the z-axis direction (resistance value when current is passed in the z-axis direction) of the first magnetic element 10 changes in accordance with the relative change between the magnetization M1 state of the first ferromagnetic layer 11 and the magnetization M2 state of the second ferromagnetic layer 12. For example, the resistance value in the z-axis direction of the first magnetic element 10 changes in accordance with the change in the relative angle between the direction of magnetization M1 of the first ferromagnetic layer 11 and the direction of magnetization M2 of the second ferromagnetic layer 12. Also, for example, the resistance value in the z-axis direction of the first magnetic element 10 changes in accordance with the change in the magnitude of magnetization M1 of the first ferromagnetic layer 11.

[0037] Furthermore, for example, if the first spacer layer 13 is made of metal, the first magnetic element 10 can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. When the first magnetic element 10 is a GMR element, the resistance value in the z-axis direction (resistance value when current is passed in the z-axis direction) changes according to the relative change between the magnetization M1 state of the first ferromagnetic layer 11 and the magnetization M2 state of the second ferromagnetic layer 12. The first magnetic element 10 may be called an MTJ element, a GMR element, etc., depending on the constituent material of the first spacer layer 13, but it is collectively called a magnetoresistance effect element. The overall thickness of the first magnetic element 10 is, for example, 15 nm to 40 nm.

[0038] The first magnetic element 10 has a ferromagnetic material whose magnetization state changes upon irradiation with light, and whose resistance value changes in accordance with the change in magnetization state. For example, in addition to the MTJ element and GMR element described above, the first magnetic element 10 can be an anisotropic magnetoresistance (AMR) effect element, a colossal magnetoresistance (CMR) effect element, or the like.

[0039] <First ferromagnetic layer> The first ferromagnetic layer 11 is a photodetector layer whose magnetization M1 state changes when light Ls is irradiated from the outside. The first ferromagnetic layer 11 is also called a magnetization-free layer. A magnetization-free layer is a layer containing a magnetic material whose magnetization M1 state changes when a predetermined external energy is applied. The predetermined external energy can be, for example, light irradiated from the outside, a current flowing in the z-axis direction of the first magnetic element 10, or an external magnetic field. The magnetization M1 of the first ferromagnetic layer 11 changes state according to the intensity of the irradiated light.

[0040] The first ferromagnetic layer 11 contains a ferromagnetic material. The first ferromagnetic layer 11 contains at least one of the magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 11 may also contain elements such as B, Mg, Hf, and Gd along with the magnetic elements mentioned above. The first ferromagnetic layer 11 may be an alloy containing a magnetic element and a non-magnetic element. The first ferromagnetic layer 11 may be composed of multiple layers. The first ferromagnetic layer 11 may be, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, or a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers. Generally, "ferromagnetism" includes "ferrimagnetism". The first ferromagnetic layer 11 may exhibit ferrimagnetism. Alternatively, the first ferromagnetic layer 11 may exhibit ferromagnetism that is not ferrimagnetism. For example, a CoFeB alloy exhibits ferromagnetism that is not ferrimagnetism.

[0041] The first ferromagnetic layer 11 may be an in-plane magnetized film having an easy magnetization axis in the direction within the film plane (any direction in the xy plane), or a perpendicular magnetized film having an easy magnetization axis in the direction perpendicular to the film plane (in the z-axis direction).

[0042] The thickness of the first ferromagnetic layer 11 is, for example, 1 nm to 5 nm. Preferably, the thickness of the first ferromagnetic layer 11 is, for example, 1 nm to 2 nm. When the first ferromagnetic layer 11 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 11 is thin, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 11 is strengthened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 11 increases. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 11 is high, the force that causes the magnetization M1 to return to the z-axis direction is strengthened. On the other hand, if the thickness of the first ferromagnetic layer 11 is thick, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 11 is relatively weakened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 11 is weakened.

[0043] When the thickness of the first ferromagnetic layer 11 decreases, the volume of the ferromagnetic material decreases, and when it increases in thickness, the volume of the ferromagnetic material increases. The reactivity of the magnetization M1 of the first ferromagnetic layer 11 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and volume (V) of the first ferromagnetic layer 11. In other words, when the product of the magnetic anisotropy and volume of the first ferromagnetic layer 11 decreases, the reactivity to light increases. From this viewpoint, in order to increase the reactivity to light, it is preferable to appropriately design the magnetic anisotropy of the first ferromagnetic layer 11 and then reduce the volume of the first ferromagnetic layer 11.

[0044] If the thickness of the first ferromagnetic layer 11 is greater than 2 nm, an insertion layer made of, for example, Mo and W may be provided within the first ferromagnetic layer 11. That is, the first ferromagnetic layer 11 may be a laminate in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in order in the z-axis direction. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer increases the overall perpendicular magnetic anisotropy of the first ferromagnetic layer 11. The thickness of the insertion layer is, for example, 0.1 nm to 1.0 nm.

[0045] <Second ferromagnetic layer> The second ferromagnetic layer 12 is a magnetization-fixed (pinned) layer. The magnetization-fixed layer is a layer made of a magnetic material in which the state of magnetization M2 changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. For example, the direction of magnetization M2 in the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. Also, for example, the magnitude of magnetization M2 in the magnetization-fixed layer changes less easily than that of the magnetization-free layer when a predetermined external energy is applied. The coercivity of the second ferromagnetic layer 12 is greater than that of the first ferromagnetic layer 11, for example. The second ferromagnetic layer 12 has an easy magnetization axis in the same direction as the first ferromagnetic layer 11, for example. The second ferromagnetic layer 12 may be an in-plane magnetization film or a perpendicular magnetization film.

[0046] The material constituting the second ferromagnetic layer 12 is, for example, the same as that of the first ferromagnetic layer 11. The second ferromagnetic layer 12 may be a multilayer film in which Co with a thickness of 0.4 nm to 1.0 nm and Pt with a thickness of 0.4 nm to 1.0 nm are alternately stacked several times. The second ferromagnetic layer 12 may also be a laminate in which Co with a thickness of 0.4 nm to 1.0 nm, Mo with a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy with a thickness of 0.3 nm to 1.0 nm, and Fe with a thickness of 0.3 nm to 1.0 nm are stacked in that order.

[0047] <Spacer layer> The first spacer layer 13 is a layer placed between the first ferromagnetic layer 11 and the second ferromagnetic layer 12. The first spacer layer 13 is composed of a conductor, an insulator, or a semiconductor, or a layer containing a current-carrying point composed of a conductor within an insulator. The first spacer layer 13 is, for example, a non-magnetic layer. The thickness of the first spacer layer 13 can be adjusted according to the orientation direction of the magnetization M1 of the first ferromagnetic layer 11 and the magnetization M2 of the second ferromagnetic layer 12 in the initial state, as described later.

[0048] When the first spacer layer 13 is composed of an insulating material, materials containing aluminum oxide, magnesium oxide, titanium oxide, or silicon oxide can be used as the material for the first spacer layer 13. 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 change rate can be obtained by adjusting the film thickness of the first spacer layer 13 so that a high TMR effect is exhibited between the first ferromagnetic layer 11 and the second ferromagnetic layer 12. In order to efficiently utilize the TMR effect, the film thickness of the first spacer layer 13 may be around 0.5 nm to 5.0 nm, or around 1.0 nm to 2.5 nm.

[0049] When the first spacer layer 13 is made of a non-magnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. In order to efficiently utilize the GMR effect, the film thickness of the first spacer layer 13 may be around 0.5 nm to 5.0 nm, or around 2.0 nm to 3.0 nm.

[0050] When the first spacer layer 13 is made of a non-magnetic semiconductor material, materials such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or indium tin oxide (ITO) can be used. In this case, the film thickness of the first spacer layer 13 may be about 1.0 nm to 4.0 nm.

[0051] When a layer containing current-carrying points composed of conductors in a non-magnetic insulator is applied as the first spacer layer 13, the structure may include current-carrying points composed of non-magnetic conductors such as Cu, Au, and Al in a non-magnetic insulator composed of aluminum oxide or magnesium oxide. Alternatively, the conductors may be composed of magnetic elements such as Co, Fe, and Ni. In this case, the film thickness of the first spacer layer 13 may be about 1.0 nm to 2.5 nm. The current-carrying points are, for example, columnar bodies with a diameter of 1.0 nm to 5.0 nm when viewed from a direction perpendicular to the film surface.

[0052] <1st electrode> The first electrode 14 is positioned, for example, on the side of the first ferromagnetic layer 11 opposite to the first spacer layer 13. The incident light Ls is irradiated onto the first magnetic element 10 from the side of the first electrode 14 and irradiates at least the first ferromagnetic layer 11. The first electrode 14 is made of a conductive material. The first electrode 14 is, for example, a transparent electrode that is transparent to light in the wavelength range used. Preferably, the first electrode 14 transmits 80% or more of the light in the wavelength range used. The first electrode 14 is, for example, an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode 14 may have a configuration in which a plurality of columnar metals are contained within the transparent electrode material of these oxides.

[0053] It is not essential to use a transparent electrode material as the first electrode 14; a thin film of a metallic material such as Au, Cu, or Al may be used to allow the irradiated light to reach the first ferromagnetic layer 11. When a metal is used as the material for the first electrode 14, the film thickness of the first electrode 14 is, for example, 3 nm to 10 nm. The first electrode 14 may also have an anti-reflective coating on the irradiated surface to which the light is directed.

[0054] <Second electrode> The second electrode 15 is made of a conductive material. The second electrode 15 is made of a metal such as Cu, Al, or Au. Ta or Ti may be laminated above or below these metals. Alternatively, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN may be used. TiN or TaN may also be used as the second electrode 15. The film thickness of the second electrode 15 is, for example, 200 nm to 800 nm.

[0055] The second electrode 15 may be made transparent to light irradiated onto the first magnetic element 10. As the material of the second electrode 15, similar to the first electrode 14, transparent electrode materials of oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO) may be used. Even when light is irradiated from the first electrode 14, depending on the intensity of the light, the light may reach the second electrode 15. In this case, since the second electrode 15 is made of a transparent electrode material of oxide, the reflection of light at the interface between the second electrode 15 and the layer in contact with it can be suppressed compared to when the second electrode 15 is made of metal.

[0056] The first ferromagnetic layer 11, second ferromagnetic layer 12, first spacer layer 13, first electrode 14, and second electrode 15 of the first magnetic element 10 have been described above, and the same applies to the second magnetic element 20, which has the same structure as the first magnetic element 10. The first ferromagnetic layer 11, second ferromagnetic layer 12, first spacer layer 13, first electrode 14, and second electrode 15 of the first magnetic element 10 correspond to the third ferromagnetic layer 21, fourth ferromagnetic layer 22, second spacer layer 23, third electrode 24, and fourth electrode 25 of the second magnetic element 20, respectively.

[0057] (Manufacturing process) The first magnetic element 10 and the second magnetic element 20 are manufactured, for example, by a lamination process, an annealing process, and a processing process for each layer. Each layer is deposited, for example, by sputtering. Annealing is performed, for example, at a temperature of 250°C to 450°C. Processing of the laminated film is performed, for example, using photolithography and etching. The shortest width of the first magnetic element 10 and the second magnetic element 20 when viewed from the z direction may be, for example, 10 nm to 2000 nm, or 30 nm to 500 nm.

[0058] (Operation instructions) Next, the operation of the light detection device 100 will be described.

[0059] The light Ls incident on the light detection device 100 is focused, for example, by a lens, to form a light spot that simultaneously irradiates the first magnetic element 10 and the second magnetic element 20. Since the first magnetic element 10 and the second magnetic element 20 have the same structure, the operation of the first magnetic element 10 will be described below.

[0060] When the intensity of the light Ls irradiated onto the first ferromagnetic layer 11 changes, the state of the magnetization M1 of the first ferromagnetic layer 11 changes. The state of magnetization M1 refers to, for example, the tilt angle of magnetization M1 with respect to the z-axis direction, the magnitude of magnetization M1, etc.

[0061] For example, when the intensity of the light Ls irradiated onto the first ferromagnetic layer 11 increases, the magnetization M1 of the first ferromagnetic layer 11 tilts from its initial state due to the external energy from the light irradiation. The angle between the direction of the magnetization M1 of the first ferromagnetic layer 11 when it is not irradiated with light Ls (hereinafter referred to as the initial state) and the direction of the magnetization M1 when it is irradiated with light is, for example, greater than 0° and less than 90°. Alternatively, for example, when the intensity of the light irradiated onto the first ferromagnetic layer 11 increases, the magnitude of the magnetization M1 decreases.

[0062] When the magnetization M1 state of the first ferromagnetic layer 11 changes, the resistance value of the first magnetic element 10 in the z-axis direction changes due to the magnetoresistance effect. When a constant current (called sense current or bias current) is passed through the first magnetic element 10 in the positive or negative z-axis direction using the first electrode 14 and the second electrode 15, an output voltage is obtained from the first magnetic element 10. In other words, when the magnetization M1 state of the first ferromagnetic layer 11 changes, the output voltage from the first magnetic element 10 also changes.

[0063] In the initial state of the first ferromagnetic layer 11, the magnetization M1 of the first ferromagnetic layer 11 and the magnetization M2 of the second ferromagnetic layer 12 may be parallel or antiparallel, or the magnetizations M1 and M2 may be orthogonal.

[0064] In the photodetector 100 shown in Figure 1, a first magnetic element 10 and a second magnetic element 20 having the same physical structure are connected to a differential summing circuit 30. In this configuration, when the first magnetic element 10 and the second magnetic element 20 are simultaneously irradiated with light Ls having the same optical signal, a first noise signal V NOISE_1 and the second noise signal V NOISE_2 Since the phase and amplitude are the same, they cancel each other out in the differential summing circuit 30, becoming zero, and the influence of the noise signal can be suppressed. Also, the first real signal V REAL_1 and the second real signal V REAL_2 Regarding this, by setting the phase difference between the first magnetic element 10 and the second magnetic element 20 to 180°, the peak-to-peak value of the output voltage can be increased in the differential summing circuit 30.

[0065] For details, see Figure 1, where the first total voltage signal V TOTAL_1 and the second total voltage signal V TOTAL_2 It can be expressed as follows: V TOTAL_1 =V REAL_1 +V NOISE_1 V TOTAL_2 =V REAL_2 +V NOISE_2 Also, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 teeth, V NOISE_1 =V NOISE_2 Therefore, the output signal V OUT teeth, V OUT =V TOTAL_1 -V TOTAL_2 =(V REAL_1 +V NOISE_1 )-(V REAL_2 +V NOISE_2 ) =V REAL_1 -V REAL_2 This is the result.

[0066] [First Embodiment] A first embodiment of the present invention will now be described. Figure 2 is a diagram showing a schematic configuration of a light detection device 101 according to the first embodiment of the present invention. The first embodiment differs from the basic configuration in that the magnetization states of the first magnetic element 10 and the second magnetic element 20 are specified. The other configurations are the same as the basic configuration, and the same reference numerals are used for the same components, and their descriptions are omitted as appropriate.

[0067] (composition) As shown in Figure 2, in the photodetector 101, the magnetization directions of the first ferromagnetic layer 11 and the second ferromagnetic layer 12 of the first magnetic element 10 are antiparallel (AP), and the magnetization directions of the third ferromagnetic layer 21 and the fourth ferromagnetic layer 22 of the second magnetic element 20 are parallel (parallel (P)). In other words, the first magnetic element 10 is set to an antiparallel magnetization state, and the second magnetic element 20 is set to a parallel magnetization state.

[0068] A bias current (also called a sense current) I is applied externally to the first magnetic element 10. B1 The bias current I flows from the second electrode 15 to the first electrode 14 via the second ferromagnetic layer 12, the first spacer layer 13, and the first ferromagnetic layer 11 in the positive z-axis direction. That is, in the first magnetic element 10, the bias current I flows from the pin layer (second ferromagnetic layer 12) to the free layer (first ferromagnetic layer 11). B1 A bias current I is applied externally to the second magnetic element 20. B2 The current flows from the fourth electrode 25 through the fourth ferromagnetic layer 22, the second spacer layer 23, and the third ferromagnetic layer 21 to the third electrode 24. That is, in the second magnetic element 20, similar to the first magnetic element 10, the bias current I flows from the pin layer (fourth ferromagnetic layer 22) to the free layer (third ferromagnetic layer 21). B2 It is being swept away. Alternatively, in the first magnetic element 10, a bias current I is applied in the direction from the free layer (first ferromagnetic layer 11) to the pinned layer (second ferromagnetic layer 12). B1 A bias current I flows through the second magnetic element 20, and in the same way as the first magnetic element 10, a bias current I flows from the free layer (third ferromagnetic layer 21) to the pinned layer (fourth ferromagnetic layer 22). B2 It may be allowed to flow away.

[0069] With this configuration, the first real signal V output from the first magnetic element 10 REAL_AP and the second real signal V output from the second magnetic element 20 REAL_P can be made to have opposite phases (a phase difference of 180°).

[0070] (Operation Explanation) In the differential synthesis circuit 30, the first noise signal V with the same phase NOISE_AP and the second noise signal V NOISE_P cancel each other out, and the first real signal V with the opposite phase REAL_AP and the second real signal V REAL_P are substantially added. The second real signal V output from the second magnetic element 20 in the parallel magnetization state REAL_P is almost zero, and most of the second total voltage signal V TOTAL_P is the second noise signal V NOISE_P .

[0071] Specifically, in FIG. 2, the first total voltage signal V TOTAL_AP and the second total voltage signal V TOTAL_P are expressed as follows. V TOTAL_AP =V REAL_AP +V NOISE_AP V TOTAL_P =V REAL_P +V NOISE_P Also, the first noise signal V NOISE_AP [[ID= fifty - one]]and the second noise signal V NOISE_P are V NOISE_AP =V NOISE_P Therefore, the output signal V OUT is V OUT =V TOTAL_AP -V​​​​​​​​​​​​​​​​​​​​​​​​REAL_P ≒V REAL_AP (∵V REAL_P ≒0) This is the result.

[0072] Figure 3(a) shows the first total voltage signal V output from the first magnetic element 10. TOTAL_AP The time waveform is shown, and Figure 3(b) shows the second total voltage signal V output from the second magnetic element 20. TOTAL_P The time waveform is shown, and Figure 3(c) shows the output signal V output from the differential summing circuit 30. OUT This figure shows the time waveform. As can be seen from Figure 3, the second total voltage signal V is output from the second magnetic element 20 in the parallel magnetization state. TOTAL_P This is the first total voltage signal V output from the first magnetic element 10 in an antiparallel magnetization state. TOTAL_AP The amplitude is smaller and the phase is reversed. Output signal V from differential summing circuit 30 OUT This is the first real signal V REAL_AP The first total voltage signal V, whose main component is TOTAL_AP Alternatively, the first real signal V REAL_AP It can be seen that this is a time waveform with amplitude amplified.

[0073] As described above, the photodetector 101 of the first embodiment can remove phase-shifted noise signals that occur when light with an optical signal is irradiated onto a magnetic element, and can also amplify the voltage signal corresponding to the optical signal.

[0074] [Second Embodiment] Next, a second embodiment of the present invention will be described. Figure 4 is a diagram showing a schematic configuration of a photodetector 102 according to the second embodiment of the present invention. The second embodiment differs from the basic configuration in that the direction of the bias current flowing through the first magnetic element 10 and the second magnetic element 20 is specified. The other configurations are the same as the basic configuration, and the same reference numerals are used for the same components, and their descriptions are omitted as appropriate.

[0075] (composition) As shown in Figure 4, in the photodetector 102, the magnetization directions of the first ferromagnetic layer 11 and the second ferromagnetic layer 12 of the first magnetic element 10 are antiparallel, and the magnetization directions of the third ferromagnetic layer 21 and the fourth ferromagnetic layer 22 of the second magnetic element 20 are antiparallel. In other words, both the first magnetic element 10 and the second magnetic element 20 are set to an antiparallel magnetization state.

[0076] Regarding the bias current, a first bias current I is applied from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I flows from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 A current is flowed. Alternatively, a first bias current I is flowed from the second ferromagnetic layer 12 of the pin layer toward the first ferromagnetic layer 11 of the free layer. B1 A second bias current I flows from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 It may be allowed to flow away.

[0077] With this configuration, the first real signal V output from the first magnetic element 10 REAL_I+ Then, the second real signal V is output from the second magnetic element 20. REAL_I- It is possible to make them out of phase (with a phase difference of 180°).

[0078] (Operation instructions) In the differential summing circuit 30, the first noise signal V has the same phase. NOISE_I+ and the second noise signal V NOISE_I- These cancel each other out. The first real signal V is in opposite phase. REAL_I+ and the second real signal V REAL_I- These are effectively added together. As a result, the output signal V OUT Alternatively, the peak-to-peak value is amplified.

[0079] For details, see Figure 4, where the first total voltage signal V TOTAL_I+ and the second total voltage signal V TOTAL_I- It can be expressed as follows: V TOTAL_I+ =V REAL_I+ +V NOISE_I+ V TOTAL_I- =VREAL_I- +V NOISE_I- Also, the first noise signal V NOISE_I+ and the second noise signal V NOISE_I- teeth, V NOISE_I+ =V NOISE_I- Therefore, the output signal V OUT teeth, V OUT =V TOTAL_I+ -V TOTAL_I- =(V REAL_I+ +V NOISE_I+ )-(V REAL_I- +V NOISE_I- ) =V REAL_I+ -V REAL_I- This is the result.

[0080] Figure 5(a) shows the first total voltage signal V output from the first magnetic element 10. TOTAL_I+ The time waveform is shown, and Figure 5(b) shows the second total voltage signal V output from the second magnetic element 20. TOTAL_I- The time waveform is shown, and Figure 5(c) shows the output signal V output from the differential summing circuit 30. OUT This figure shows the time waveform. As can be seen from Figure 5, a bias current I flows from the pin layer to the free layer. B2 The second total voltage signal V is output from the second magnetic element 20 in an antiparallel magnetization state through which the current flows. TOTAL_I- This is the first total voltage signal V output from the first magnetic element 10, which is in an antiparallel magnetization state where a bias current flows from the free layer to the pin layer. TOTAL_I+ The amplitude is smaller and the phase is reversed. Output signal V from differential summing circuit 30 OUT This is the first real signal V REAL_I+ The first total voltage signal V, whose main component is TOTAL_I+ Alternatively, the first real signal V REAL_I+ It can be seen that this is a time waveform with amplitude amplified.

[0081] As described above, the photodetector 102 of the second embodiment, like the first embodiment, can remove phase-shifted noise signals that occur when light with an optical signal is irradiated onto a magnetic element, and can also amplify the voltage signal corresponding to the optical signal.

[0082] [Third Embodiment] A third embodiment of the present invention will now be described. Figure 6 is a diagram showing the schematic configuration of a light detection device 103 according to the third embodiment of the present invention. The third embodiment differs from the basic configuration in that the configuration of the differential summing circuit 30A is specified. The other configurations are the same as those of the basic configuration, and the same reference numerals are used for the same components, and their descriptions are omitted as appropriate.

[0083] (composition) As shown in Figure 6, in the photodetector 103, the differential summing circuit 30A is configured using an operational amplifier 35. Specifically, the first electrode 14 of the first magnetic element 10 is connected to the non-inverting input terminal of the operational amplifier 35 via a resistor 33 (R3). The third electrode 24 of the second magnetic element 20 is connected to the inverting input terminal of the operational amplifier 35 via a resistor 31 (R1). The output terminal of the operational amplifier 35 is connected to the inverting input terminal via a resistor 32 (R2). The non-inverting input terminal is grounded via a resistor 34 (R4).

[0084] In the photodetector 103, the direction of magnetization M1 of the first ferromagnetic layer 11 and the direction of magnetization M2 of the second ferromagnetic layer 12 are antiparallel in the first magnetic element 10, and the direction of magnetization M3 of the third ferromagnetic layer 21 and the direction of magnetization M4 of the fourth ferromagnetic layer 22 are antiparallel in the second magnetic element 20. In other words, both the first magnetic element 10 and the second magnetic element 20 are set to an antiparallel magnetization state.

[0085] Regarding the bias current, a first bias current I is applied from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I flows from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2A current is flowed. Alternatively, a first bias current I is flowed from the second ferromagnetic layer 12 of the pin layer toward the first ferromagnetic layer 11 of the free layer. B1 A second bias current I flows from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 It may be allowed to flow away.

[0086] Alternatively, the first magnetic element 10 may be set to an antiparallel magnetization state, and the second magnetic element 20 may be set to a parallel magnetization state. In this case, the first bias current I is applied from the second ferromagnetic layer 12 of the pinned layer to the first ferromagnetic layer 11 of the free layer. B1 A second bias current I is applied from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 To allow the current to flow, or to flow the first bias current I from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I is applied from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 You can also run it.

[0087] With this configuration, the first real signal V output from the first magnetic element 10 REAL_1 Then, the second real signal V is output from the second magnetic element 20. REAL_2 The two can be made out of phase (phase difference of 180°). On the other hand, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 They are in phase.

[0088] (Operation instructions) In the differential summing circuit 30A, the first noise signal V is in phase. NOISE_1 and the second noise signal V NOISE_2 These cancel each other out. The first real signal V is in opposite phase. REAL_1 and the second real signal V REAL_2 This is essentially added together. As a result, the output signal V OUT Alternatively, the peak-to-peak value is amplified.

[0089] For details, see Figure 6, where the first total voltage signal V TOTAL_1 and the second total voltage signal V TOTAL_2It can be expressed as follows: If R1=R2=R3=R4, V TOTAL_1 =V REAL_1 +V NOISE_1 V TOTAL_2 =V REAL_2 +V NOISE_2 Also, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 teeth, V NOISE_1 =V NOISE_2 Therefore, the output signal V OUT teeth, V OUT ={(R1+R2) / R1}·{R1 / (R3+R4)}V TOTAL_1 -(R2 / R1)V TOTAL_2 =V TOTAL_1 -V TOTAL_2 =(V REAL_1 +V NOISE_1 )-(V REAL_2 +V NOISE_2 ) =V REAL_1 -V REAL_2 This is the result.

[0090] As described above, the photodetector 103 of the third embodiment can easily realize a highly accurate differential summing circuit 30A, in addition to the effects obtained with the basic configuration described above.

[0091] [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. Figure 7 is a diagram showing the schematic configuration of a light detection device 104 according to the fourth embodiment of the present invention. The fourth embodiment differs from the basic configuration in that the configuration of the differential summing circuit 30B is specified. The other configurations are the same as those of the basic configuration, and the same reference numerals are used for the same components, and their descriptions are omitted as appropriate.

[0092] (composition) As shown in Figure 7, in the photodetector 104, the differential summing circuit 30B receives the second total voltage signal V output from the second magnetic element 20. TOTAL_2 Input the second full voltage signal V TOTAL_2 A 180° phase shift circuit 36 ​​that shifts the phase of the first signal by 180°, and a second full voltage signal V that has been phase-shifted by 180°. TOTAL_2 And the first total voltage signal V output from the first magnetic element 10 TOTAL_1 It includes a power combiner 37 that combines and .

[0093] In the photodetector 104, the magnetization directions of the first ferromagnetic layer 11 and the second ferromagnetic layer 12 are antiparallel in the first magnetic element 10, and the magnetization directions of the third ferromagnetic layer 21 and the fourth ferromagnetic layer 22 are antiparallel in the second magnetic element 20. In other words, both the first magnetic element 10 and the second magnetic element 20 are set to an antiparallel magnetization state.

[0094] Regarding the bias current, a first bias current I is applied from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I flows from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 A current is flowed. Alternatively, a first bias current I is flowed from the second ferromagnetic layer 12 of the pin layer toward the first ferromagnetic layer 11 of the free layer. B1 A second bias current I flows from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 It may be allowed to flow away.

[0095] Alternatively, the first magnetic element 10 may be set to an antiparallel magnetization state, and the second magnetic element 20 may be set to a parallel magnetization state. In this case, the first bias current I is applied from the second ferromagnetic layer 12 of the pinned layer to the first ferromagnetic layer 11 of the free layer. B1 A second bias current I is applied from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 To allow the current to flow, or to flow the first bias current I from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1A second bias current I is applied from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 You can also run it.

[0096] With this configuration, the first real signal V output from the first magnetic element 10 REAL_1 Then, the second real signal V is output from the second magnetic element 20. REAL_2 The two can be made out of phase (phase difference of 180°). On the other hand, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 They are in phase.

[0097] (Operation instructions) Second noise signal V NOISE_2 The signal is phase-shifted by 180° by the 180° phase-shift circuit 36 ​​and input to the power combiner 37, and the first noise signal V NOISE_1 This is directly input to the power combiner 37. That is, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 This is in opposite phase and is input to power combiner 37, where it cancels out.

[0098] Second actual signal V REAL_2 The signal is phase-shifted by 180° by the 180° phase-shift circuit 36 ​​and input to the power combiner 37, and the first real signal V REAL_1 This is directly input to the power combiner 37. That is, the first real signal V REAL_1 and the second real signal V REAL_2 These signals are in phase and are input to the power combiner 37, which then receives the first real signal V REAL_1 and the second real signal V REAL_2 These are combined to produce the output signal V OUT Alternatively, the peak-to-peak value is amplified.

[0099] The upper left diagram in Figure 8 shows the first real signal V before it is input to the differential summing circuit 30B. REAL_1 and the second real signal V REAL_2 This figure shows the time waveform. The upper right figure of Figure 8 shows the first real signal V before it is input to the power combiner 37 of the differential summing circuit 30B. REAL_1 and the second real signal VREAL_2 This figure shows the time waveform of the first real signal V before it is input to the differential summing circuit 30B. REAL_1 and the second real signal V REAL_2 It has a phase difference of 180°. Second real signal V REAL_2 The first real signal V before it is input to the power combiner 37 is shifted by 180° due to the 180° phase shift circuit 36. REAL_1 and the second real signal V REAL_2 The phase difference is 0° (i.e., they are in phase). Therefore, the first real signal V REAL_1 and the second real signal V REAL_2 It is synthesized by the power combiner 37.

[0100] On the other hand, the lower left diagram of Figure 8 shows the first noise signal V before it is input to the differential summing circuit 30B. NOISE_1 and the second noise signal V NOISE_2 This figure shows the time waveform. The lower right figure of Figure 8 shows the first noise signal V before it is input to the power combiner 37 of the differential summing circuit 30B. NOISE_1 and the second noise signal V NOISE_2 This figure shows the time waveform of the first noise signal V before it is input to the differential summing circuit 30B. NOISE_1 and the second noise signal V NOISE_2 The phase difference is 0° (i.e., in phase). Second noise signal V NOISE_2 The first noise signal V before it is input to the power combiner 37 is shifted by 180° due to the 180° phase shift circuit 36. NOISE_1 and the second noise signal V NOISE_2 The phase difference is 180° (i.e., opposite phase). Therefore, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 This is canceled out by the power combiner 37.

[0101] As described above, the photodetector 104 of the fourth embodiment can easily realize a highly accurate differential summing circuit 30B in addition to the effects obtained with the basic configuration described above.

[0102] [Fifth Embodiment] Next, a fifth embodiment of the present invention will be described. Figure 9 is a diagram showing the schematic configuration of a light detection device 105 according to the fifth embodiment of the present invention. The fifth embodiment differs from the basic configuration in that the configuration of the differential summing circuit 30C is specified. The other configurations are the same as those of the basic configuration, and the same reference numerals are used for the same components, and their descriptions are omitted as appropriate.

[0103] (composition) As shown in Figure 9, in the photodetector 105, the differential summing circuit 30C receives the first total voltage signal V output from the first magnetic element 10. TOTAL_1 Input the first total voltage signal V TOTAL_1 A +90° phase shift circuit 38 that shifts the phase of the signal by +90°, and a second total voltage signal V output from the second magnetic element 20. TOTAL_2 Input the second full voltage signal V TOTAL_2 A -90° phase shift circuit 39 shifts the voltage signal by -90°, and the first total voltage signal V is phase shifted by +90°. TOTAL_1 And the second full voltage signal V, which is phase-shifted by -90°. TOTAL_2 It includes a power combiner 37 that combines and .

[0104] In the light detection device 105, the magnetization directions of the first ferromagnetic layer 11 and the second ferromagnetic layer 12 are antiparallel in the first magnetic element 10, and the magnetization directions of the third ferromagnetic layer 21 and the fourth ferromagnetic layer 22 are antiparallel in the second magnetic element 20. In other words, both the first magnetic element 10 and the second magnetic element 20 are set to an antiparallel magnetization state.

[0105] Regarding the bias current, a first bias current I is applied from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I flows from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 A current is flowed. Alternatively, a first bias current I is flowed from the second ferromagnetic layer 12 of the pin layer toward the first ferromagnetic layer 11 of the free layer. B1 A second bias current I flows from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 It may be allowed to flow away.

[0106] Alternatively, the first magnetic element 10 may be set to an antiparallel magnetization state, and the second magnetic element 20 may be set to a parallel magnetization state. In this case, the first bias current I is applied from the second ferromagnetic layer 12 of the pinned layer to the first ferromagnetic layer 11 of the free layer. B1 A second bias current I is applied from the fourth ferromagnetic layer 22 of the pinned layer towards the third ferromagnetic layer 21 of the free layer. B2 To allow the current to flow, or to flow the first bias current I from the first ferromagnetic layer 11 of the free layer to the second ferromagnetic layer 12 of the pinned layer. B1 A second bias current I is applied from the third ferromagnetic layer 21 of the free layer to the fourth ferromagnetic layer 22 of the pinned layer. B2 You can also run it.

[0107] With this configuration, the first real signal V output from the first magnetic element 10 REAL_1 Then, the second real signal V is output from the second magnetic element 20. REAL_2 The two can be made out of phase (phase difference of 180°). On the other hand, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 They are in phase.

[0108] (Operation instructions) First noise signal V NOISE_1 The signal is phase-shifted by +90° by the +90° phase shift circuit 38 and input to the power combiner 37, and the second noise signal V NOISE_2 The first noise signal V is phase-shifted by -90° by the -90° phase shift circuit 39 and input to the power combiner 37. NOISE_1 and the second noise signal V NOISE_2 This is in opposite phase and is input to power combiner 37, where it cancels out.

[0109] First actual signal V REAL_1 This signal is phase-shifted by +90° by the +90° phase shift circuit 38 and input to the power combiner 37, and the second real signal V REAL_2 The signal is phase-shifted by -90° by the -90° phase shift circuit 39 and input to the power combiner 37. That is, the first real signal V REAL_1 and the second real signal VREAL_2 This is in phase and is input to the power combiner 37, which then receives the first real signal V REAL_1 and the second real signal V REAL_2 These are combined to produce the output signal V OUT Alternatively, the peak-to-peak value is amplified.

[0110] The upper left diagram of Figure 10 shows the first real signal V before it is input to the differential summing circuit 30C. REAL_1 and the second real signal V REAL_2 This is a diagram showing the time waveform. The upper right diagram of Figure 10 shows the first real signal V before it is input to the power combiner 37 of the differential summing circuit 30C. REAL_1 and the second real signal V REAL_2 This figure shows the time waveform of the first real signal V before it is input to the differential summing circuit 30C. REAL_1 and the second real signal V REAL_2 The first real signal V has a phase difference of 180°. REAL_1 The second real signal V is shifted by +90° by the +90° phase shift circuit 38. REAL_2 The first real signal V before it is input to the power combiner 37 is shifted by -90° by the -90° phase shift circuit 39. REAL_1 and the second real signal V REAL_2 The phase difference is 0° (i.e., they are in phase). Therefore, the first real signal V REAL_1 and the second real signal V REAL_2 It is synthesized by the power combiner 37.

[0111] On the other hand, the lower left diagram of Figure 10 shows the first noise signal V before it is input to the differential summing circuit 30C. NOISE_1 and the second noise signal V NOISE_2 This figure shows the time waveform. The lower right figure of Figure 10 shows the first noise signal V before it is input to the power combiner 37 of the differential summing circuit 30C. NOISE_1 and the second noise signal V NOISE_2 This figure shows the time waveform of the first noise signal V before it is input to the differential summing circuit 30C. NOISE_1 and the second noise signal V NOISE_2 The phase difference is 0° (i.e., in phase). First noise signal V NOISE_1The second noise signal V is shifted by +90° by the +90° phase shift circuit 38. NOISE_2 The first noise signal V before it is input to the power combiner 37 is shifted by -90° by the -90° phase shift circuit 39. NOISE_1 and the second noise signal V NOISE_2 The phase difference is 180° (i.e., opposite phase). Therefore, the first noise signal V NOISE_1 and the second noise signal V NOISE_2 This is canceled out by the power combiner 37.

[0112] As described above, the photodetector 105 of the fifth embodiment can easily realize a highly accurate differential summing circuit 30C in addition to the effects obtained with the basic configuration described above.

[0113] [Examples of application] The light detection devices 100 to 105 according to the above embodiment can be applied, for example, to a transceiver 400 in a communication system.

[0114] Figure 11 shows the configuration of a transceiver 400 as an example of its application. As shown in Figure 11, the transceiver 400 comprises a receiving device 200 and a transmitting device 300. The receiving device 200 receives an optical signal L1, and the transmitting device 300 transmits an optical signal L2.

[0115] The receiving device 200 includes, for example, a photodetector 201 and a signal processing unit 202. The photodetector 201 is one of the photodetectors 100 to 105 according to the above embodiment. The following describes the case in which the photodetector 100 is used as the photodetector 201. The photodetector 201 converts the optical signal L1 into an electrical signal. The photodetector 201 is irradiated with light containing the optical signal L1, whose light intensity changes. Specifically, the first ferromagnetic layer 11 of the first magnetic element 10 and the third ferromagnetic layer 21 of the second magnetic element 20 are simultaneously irradiated with the same light containing the optical signal L1. The light containing the optical signal L1 may be, for example, light with a wavelength of 400 nm to 1500 nm.

[0116] Lenses may be placed on the first electrode 14 side and the third electrode 24 side of the photodetector 201 in the stacking direction, respectively, so that the light that passes through the lenses and is focused irradiates the first ferromagnetic layer 11 and the third ferromagnetic layer 21 simultaneously. The lenses may be formed during the wafer manufacturing process in which the photodetector 201 is formed.

[0117] Alternatively, the light passing through the waveguide may be simultaneously irradiated onto the first ferromagnetic layer 11 of the first magnetic element 10 and the third ferromagnetic layer 21 of the second magnetic element 20 in the photodetector 201. The light irradiated onto the first ferromagnetic layer 11 of the first magnetic element 10 and the third ferromagnetic layer 21 of the second magnetic element 20 in the photodetector 201 is, for example, laser light. The signal processing unit 202 processes the electrical signal converted by the photodetector 201. The signal processing unit 202 demodulates the modulated signal included in the optical signal L1 by processing the electrical signal generated from the photodetector 201.

[0118] The transmitting device 300 includes, for example, a light source 301, an electrical signal generation unit 302, and an optical modulation unit 303. The light source 301 is, for example, a laser element. The light source 301 may be located outside the transmitting device 300. The electrical signal generation unit 302 generates an electrical signal based on the transmission information. The electrical signal generation unit 302 may be integrated with the signal conversion element of the signal processing unit 202. The optical modulation unit 303 modulates the light output from the light source 301 based on the electrical signal generated by the electrical signal generation unit 302 and outputs an optical signal L2. The light output from the light source 301 may be, for example, light with a wavelength of 400 nm to 1500 nm.

[0119] Figure 12 is a conceptual diagram of an example of a communication system. The communication system shown in Figure 12 has two terminal devices 500. The terminal devices 500 are, for example, smartphones, tablets, personal computers, etc.

[0120] Each terminal device 500 is equipped with a transceiver 400 having a receiving device 200 and a transmitting device 300. An optical signal transmitted from the transmitting device 300 of one terminal device 500 is received by the receiving device 200 of the other terminal device 500. The light used for transmission and reception between terminal devices 500 may be, for example, visible light, or light with a wavelength of 400 nm to 1500 nm. The receiving device 200 has one of the above-described optical detection devices 100 to 105 as an optical detection unit 201.

[0121] Furthermore, the above communication system may be, for example, a communication system that wirelessly transmits and receives optical signals, such as near-infrared light, between mobile terminals such as smartphones and tablets. Alternatively, the above communication system may be, for example, a communication system that wirelessly transmits and receives optical signals, such as near-infrared light, between a mobile terminal and an information processing device such as a personal computer.

[0122] The above communication system may be a communication system that performs short- and medium-distance communication, such as within and between data centers, or long-distance communication, such as between cities. The transceiver 400 is installed, for example, within a data center.

[0123] Furthermore, the light detection devices 100 to 105 of the above embodiment can be applied, for example, to the light detection unit 201 of a receiving device 200 of a transmitting / receiving device 400 that transmits and receives optical signals such as laser light in a communication system in which multiple transmitting / receiving devices are connected by optical fibers.

[0124] Furthermore, the light detection devices 100 to 105 of the above embodiment can be applied to an optical sensor device 700, such as an image sensor, in which a plurality of light detection devices 100 are arranged in one or two dimensions. Such an optical sensor device 700 can be used in terminal devices such as smartphones, tablets, personal computers, and digital cameras.

[0125] Figure 13 is a schematic diagram of an example of a terminal device 600. The left side of Figure 13 shows the front surface of the terminal device 600, and the right side shows the back surface of the terminal device 600. The terminal device 600 has a camera CA. The above-mentioned optical sensor device 700 can be used as the image sensor of this camera CA. In Figure 13, a smartphone is used as an example of a terminal device 600, but it is not limited to this case. In addition to smartphones, the terminal device 600 can be, for example, a tablet, a personal computer, a digital camera, etc.

[0126] The present invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

[0127] As described above, the present invention has the effect of being able to remove phase-shifted noise signals that occur when light having an optical signal is irradiated onto a magnetic element, and is useful for light detection devices and transmitting / receiving devices in general. [Explanation of Symbols]

[0128] 10 First magnetic element 11, 111 First ferromagnetic layer 12, 112 second ferromagnetic layer 13. First Spacer Layer 14, 114 1st electrode 15, 115 2nd electrode 20 Second magnetic related 21 Third ferromagnetic layer 22 4th ferromagnetic layer 23 Second Spacer Layer 24 3rd electrode 25 4th electrode 30, 30A, 30B, 30C differential synthesis circuit 31, 32, 33, 34 resistor 35 Op-amps 36. 180° Phase Shift Circuit 37 Power Combiner 38 +90° Phase Shift Circuit 39 -90° Phase Shift Circuit 100, 101, 102, 103, 104, 105 Light detection device 110 Magnetic elements 113 Spacer layer 200 Receiver 201 Light detection unit 202 Signal Processing Unit 300 Transmitter 301 Light source 302 Electrical signal generation unit 303 Optical Modulation Section 400 Transceiver 500, 600 terminal devices 700 Optical sensor device 1000 Conventional light detection devices M1, M2, M3, M4 magnetization

Claims

1. A first magnetic element comprising a first ferromagnetic layer, a second ferromagnetic layer, and a first spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, wherein when light containing an optical signal is irradiated onto the first ferromagnetic layer, a first voltage signal is generated in accordance with the optical signal. A second magnetic element comprising a third ferromagnetic layer, a fourth ferromagnetic layer, and a second spacer layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer, wherein when the third ferromagnetic layer is simultaneously irradiated with the light, it generates a second voltage signal that is in opposite phase to the first voltage signal in correspondence with the light signal, A differential summing circuit that differentially sums a first total voltage signal output from the first magnetic element, including the first voltage signal, and a second total voltage signal output from the second magnetic element, including the second voltage signal. A light detection device equipped with the following features.

2. The magnetization directions of the first ferromagnetic layer and the second ferromagnetic layer of the first magnetic element are antiparallel, The photodetector according to claim 1, wherein the magnetization directions of the third ferromagnetic layer and the fourth ferromagnetic layer of the second magnetic element are parallel.

3. The photodetector according to claim 1, wherein a first bias current is passed from the first ferromagnetic layer toward the second ferromagnetic layer or in the reverse direction, and a second bias current is passed from the fourth ferromagnetic layer toward the third ferromagnetic layer or in the reverse direction.

4. The light detection device according to claim 1, wherein the differential summing circuit is configured using an operational amplifier.

5. The differential summing circuit is A 180° phase shift circuit that receives the second full voltage signal output from the second magnetic element and shifts the second full voltage signal by 180°, A power combiner that combines the 180° phase-shifted second total voltage signal and the first total voltage signal output from the first magnetic element, The light detection device according to claim 1, comprising:

6. The differential summing circuit is A +90° phase shift circuit that receives the first total voltage signal output from the first magnetic element and shifts the first total voltage signal by +90°, A -90° phase shift circuit that receives the second full voltage signal output from the second magnetic element and shifts the second full voltage signal by -90°, A power combiner that combines the first total voltage signal which has been phase-shifted by +90° and the second total voltage signal which has been phase-shifted by -90°, The light detection device according to claim 1, comprising:

7. The first magnetic element further comprises a first electrode provided on the side of the first ferromagnetic layer opposite to the first spacer layer, and a second electrode provided on the side of the second ferromagnetic layer opposite to the first spacer layer. The second magnetic element further comprises a third electrode provided on the side of the third ferromagnetic layer opposite to the second spacer layer, and a fourth electrode provided on the side of the fourth ferromagnetic layer opposite to the second spacer layer. The photodetector according to claim 1, wherein the first electrode and the third electrode are transparent electrodes.

8. A light source that emits light with a wavelength of 400 nm to 1500 nm, and a transmitting device that modulates and outputs the emitted light, A light detection device according to any one of claims 1 to 7, which detects light with a wavelength of 400 nm or more and 1500 nm or less, and a receiving device that demodulates the detected light, A transmitter and receiver equipped with a transmitter and receiver.

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