Photonic spin register, information writing method, and information reading method

Abstract

A photonic spin register (100) comprises: a shift register unit (104) having a magnetic material layer (124) of a shape extending in one direction; a light receiver (114) for receiving a serially input, pulse amplitude-modulated optical signal (PL) and converting the optical signal into an optical current (Iph); and a spin Hall element (106) electrically connected to the light receiver (114) and stacked on the magnetic material layer (124) in a partial region thereof, the spin Hall element (106) exhibiting the spin Hall effect when the optical current (Iph) from the light receiver (114) flows therethrough. When the optical current (Iph) flows through the spin Hall element (106), a spin orbit torque acts on the magnetic order of the magnetic domains of the magnetic material layer (124), whereby spin information is written. When a shift current (Is) is flown in one direction through the shift register unit (104), domain walls move in the magnetic material layer (124), whereby the spin information written to the magnetic domains is moved and buffered in the magnetic material layer (124).

Description

[Technical Field]

[0001] The present invention relates to a photonic spin register, a method for writing information, and a method for reading information. [Background technology]

[0002] In recent years, the rapid proliferation of mobile devices and other devices has led to an explosive increase in network traffic, creating a demand for even faster, higher-capacity, and more energy-efficient information technology (IT). The bottleneck in realizing such technologies is the speed gap between optical signals and electrical signals. Currently, optical communication achieves high-speed transmission of 400 Gbps per port, but the clock frequency of Complementary Metal Oxide Semiconductor (CMOS) circuits is only a few GHz, resulting in a two-order-of-magnitude gap between the two.

[0003] Furthermore, conventional optical devices are controlled by voltage and use an amplifier to amplify the photocurrent and convert it into voltage in order to obtain the required output voltage, but this amplifier leads to increased power consumption. On the other hand, there is also a method that replaces the amplifier with a load resistor (see, for example, Non-Patent Document 1), but this requires a large load resistor of about 10kΩ, which increases the RC time constant, and the operating speed remains at several tens of GHz. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] K. Nozaki, S. Matsuo, T. Fujii, K. Takeda, A. Shinya, E. Kuramochi, and M. Notomi, Nature Photonics, volume 13, pages 454-459 (2019) [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] As the speed of optical communication increases, the speed gap between optical signals and electrical signals continues to widen, and this gap is hindering the realization of a high-speed and low-power-consuming optoelectronic interface.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a photonic spin register, an information writing method, and an information reading method capable of realizing a high-speed and low-power-consuming optoelectronic interface.

Means for Solving the Problems

[0007] The photonic spin register according to the first aspect of the present invention includes a shift register section having a magnetic body layer extending in one direction, and information included in a pulse amplitude-modulated optical signal input in series is transferred to a spin state of magnetic domains of the magnetic body layer by a photocurrent corresponding to the optical signal or by irradiation of the optical signal, thereby writing spin information. When a shift current in one direction flows through the shift register section, a magnetic wall moves within the magnetic body layer, so that the spin information moves and is buffered in the magnetic body layer.

[0008] The photonic spin register according to the second aspect of the present invention includes a light receiver that receives a pulse amplitude-modulated optical signal input in series and converts it into a photocurrent, a plurality of shift register sections each having a magnetic body layer extending in one direction and arranged in parallel in a direction orthogonal to the one direction, a writing section that is electrically connected to the light receiver and provided to cross over the plurality of shift register sections, and when a photocurrent from the light receiver flows, transfers information included in the optical signal to a spin state of magnetic domains of each magnetic body layer of the plurality of shift register sections by the spin Hall effect, thereby writing spin information, and a control section that is electrically connected to the plurality of shift register sections and selects one shift register section through which a shift current flows from among the plurality of shift register sections. When a shift current in one direction flows through the one shift register section selected by the control section, a magnetic wall moves within the magnetic body layer of the one shift register section, so that the spin information moves and is buffered in the magnetic body layer.

[0009] A photonic spin register according to a third aspect of the present invention comprises a shift register section having a magnetic layer extending in one direction, a plurality of spin Hall elements that exhibit the spin Hall effect arranged in one direction on the magnetic layer, which write a plurality of spin pieces of information to the magnetic layer by spin orbit torque when a plurality of pulse currents corresponding to input information flow in parallel, a readout element provided adjacent to the plurality of spin Hall elements on the magnetic layer, and an optical modulator electrically connected to the readout element. When a unidirectional shift current flows in the shift register section, a plurality of spin pieces of information move as magnetic domain walls move within the magnetic layer, and the plurality of spin pieces of information are read out in series as electrical signals via the readout element by the magnetoresistance effect. The optical modulator converts the electrical signals read out via the readout element into optical signals and outputs the optical signals.

[0010] A fourth aspect of the present invention provides an information writing method that writes spin information by transferring information contained in a pulse amplitude modulated optical signal input in series to the spin state of magnetic domains of a magnetic material layer that extends in one direction, either by a photocurrent corresponding to the optical signal or by irradiation with the optical signal.

[0011] The fifth aspect of the present invention provides an information readout method in which information contained in a pulse amplitude modulated optical signal input in series is transferred to the spin state of magnetic domains in a magnetic layer extending in one direction by a photocurrent corresponding to the optical signal or by irradiation with the optical signal, thereby writing spin information; a unidirectional shift current causes the magnetic domain walls within the magnetic layer to move, thereby moving the spin information written to the magnetic domains; and by performing the writing and moving of spin information multiple times, multiple spin information is sequentially buffered in the magnetic layer; and the multiple spin information is read out in parallel as multiple electrical signals by the magnetoresistive effect through multiple readout elements arranged in one direction on the magnetic layer.

[0012] The information readout method according to the sixth aspect of the present invention involves writing multiple spin information in parallel to the magnetic layer by spin-orbit torque by passing multiple pulse currents corresponding to input information in parallel to multiple spin Hall elements that exhibit the spin Hall effect, which are arranged in one direction on a magnetic layer having a shape that extends in one direction, and reading out the moving multiple spin information in series as electrical signals by the magnetoresistance effect via a readout element provided on the magnetic layer. The electrical signals are then converted into optical signals using an optical modulator and output as optical signals. [Effects of the Invention]

[0013] According to the present invention, by transferring information contained in an optical signal to the spin state of magnetic domains in a magnetic material layer using a photocurrent or by irradiation with an optical signal, and writing the spin information, a high-speed, low-power photoelectric interface utilizing spintronics can be realized. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view showing a photonic spin register according to a first embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] This is a cross-sectional view taken along the line III-III in Figure 1. [Figure 4A] This is a schematic diagram illustrating an example of the initial magnetic order state of a magnetic layer. [Figure 4B] This is a schematic diagram showing the magnetic order state (spin information) when information contained in an optical signal is written to the magnetic domains of a magnetic material layer by a photocurrent. [Figure 4C] This is a schematic diagram illustrating the movement of magnetic domain walls and the transfer of spin information due to shift current. [Figure 4D] This is a schematic diagram showing the spin information buffered in the magnetic layer. [Figure 5A] This is a schematic diagram illustrating the concept of a conventional photoelectric interface. [Figure 5B] This is a schematic diagram illustrating the concept of a conventional photoelectric interface. [Figure 5C] This is a schematic diagram illustrating the concept of a photoelectric interface according to the first embodiment of the present invention. [Figure 6] This is a functional block diagram showing an example of an on-chip device in which the functionality of a photonic spin register according to the first embodiment is implemented. [Figure 7] This is a schematic diagram showing the configuration of a photonic spin register according to a second embodiment of the present invention. [Figure 8] This is a schematic diagram showing a part of the magnetic layer and the light irradiation section of a photonic spin register according to the third embodiment of the present invention. [Figure 9] This is a perspective view showing a photonic spin register according to a fourth embodiment of the present invention. [Figure 10] This is a cross-sectional view taken along the XX arrow in Figure 9. [Figure 11] This is a cross-sectional view taken along the line XI-XI in Figure 9. [Figure 12A] This is a schematic diagram illustrating the operation of a photonic spin register according to the fourth embodiment. [Figure 12B] This is a schematic diagram illustrating the operation of a photonic spin register according to the fourth embodiment. [Figure 12C] This is a schematic diagram illustrating the operation of a photonic spin register according to the fourth embodiment. [Figure 12D] This is a schematic diagram illustrating the operation of a photonic spin register according to the fourth embodiment. [Figure 13] This is a functional block diagram showing an example of an on-chip device in which the functionality of a photonic spin register according to the fourth embodiment is implemented. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will now be described with reference to the drawings. In the following embodiments, the same or similar components are denoted by the same reference numerals throughout the drawings. The drawings are schematic, and the relationship between planar dimensions and thickness, and the ratio of the thicknesses of each component, differ from those in reality. Furthermore, it goes without saying that there are parts where the dimensional relationships and ratios differ between drawings.

[0016] <First Embodiment> A first embodiment of the present invention will be described with reference to Figures 1 to 5C.

[0017] First, the configuration of the photonic spin register 100 according to the first embodiment will be described. Figure 1 shows a perspective view of the photonic spin register 100, Figure 2 shows a cross-sectional view taken along the line II-II in Figure 1, and Figure 3 shows a cross-sectional view taken along the line III-III in Figure 1.

[0018] The photonic spin register 100 is a serial-to-parallel converter that converts pulse amplitude-modulated optical signals input in series into photoelectric signals and outputs multiple electrical signals in parallel. As shown in Figure 1, the photonic spin register 100 comprises an optical receiver 102, a shift register section 104 with a shape extending in one direction, and a spin Hall element 106 as a writing section provided in a part of the area on the shift register section 104.

[0019] The optical receiver 102 comprises a substrate 110 made of an insulator (for example, SiO2), an optical waveguide 112 provided on the substrate 110, and a photodetector 114 connected to the optical waveguide 112 on the substrate 110. The photodetector 114 comprises a photoelectric conversion element 116 and a metal film 118 sandwiching the photoelectric conversion element 116, forming a plasmon waveguide.

[0020] The photoelectric element 116 is made of a dielectric (semiconductor or insulator) and is continuously connected to the optical waveguide 112. The width w3 of the photoelectric element 116 (see Figure 2) is narrower than the width of the optical waveguide 112, and the optical waveguide 112 has a tapered shape where the connection portion with the photoelectric element 116 narrows towards the photoelectric element 116. The metal films 118 on both sides of the photoelectric element 116 are made of metallic materials such as Au and Ag. The narrower the width w3 of the photoelectric element 116 (for example, w3 = 50 nm), the greater the light confinement effect, making it possible to focus light below the diffraction limit and strengthening the interaction between the photoelectric element 116 and the optical field. As a result, the light absorption rate increases, and a light receiving sensitivity of about 1 A / W can be obtained with an element length of 1 to 2 μm.

[0021] One metal film 118 of the photodetector 114 is connected to one end of the spin Hall element 106. The other metal film 118 also functions as an electrode, and a bias voltage V bias A voltage is applied. An electrode 142 is connected to the other end of the spin Hall element 106. The electrode 142 is grounded. The spin Hall element 106 is made of a heavy metal such as Pt or W that exhibits the spin Hall effect.

[0022] As shown in Figure 3, the shift register section 104 comprises a substrate 120, a spin Hall layer 122 laminated on the substrate 120, and a magnetic layer 124 laminated on the spin Hall layer 122. The spin Hall layer 122 is made of a heavy metal such as Pt or W that exhibits the spin Hall effect. The magnetic layer 124 is made of a topological antiferromagnet (e.g., X is Sn) or a ferrimagnet (e.g., GdFeCo) with the composition formula Mn3X. For example, the thickness ts of the spin Hall layer 122 is 4 nm, and the thickness tm of the magnetic layer 124 is 6 nm.

[0023] The magnetic layer 124 has a first region 124a whose magnetic order direction is fixed in advance by a magnet, and a second region 124b which buffers the magnetic order direction information (spin information) written to the first region 124a by the spin Hall element 106, as described later. The spin Hall element 106 is stacked on the first region 124a at the position closest to the second region 124b.

[0024] As shown in Figure 1, electrodes 126a and 126b are connected to the longitudinal ends of the spin Hall layer 122 and the magnetic layer 124, respectively. Under the control of the control unit, a voltage is applied between these electrodes, causing a DC shift current Is to flow longitudinally through the spin Hall layer 122 and the magnetic layer 124, and the magnetic domain walls of the magnetic layer 124 to move. As a result, spin information moves from the first region 124a to the second region 124b and is buffered within the second region 124b.

[0025] Multiple readout elements 130 are provided on the second region 124b of the magnetic layer 124, arranged longitudinally. Each readout element 130 comprises a barrier layer 132 made of a non-magnetic material (e.g., MgO) laminated on the second region 124b, and a fixed layer 134 laminated on the barrier layer 132, with magnetic order fixed in the direction perpendicular to the plane. A terminal 136 (see Figure 1) for reading electrical signals is connected to the fixed layer 134. The second region 124b functions as a free layer in which the magnetic order can be reversed. Therefore, multiple magnetoresistive elements (e.g., magnetic tunnel junction elements) are formed by the combination of the second region 124b and the multiple readout elements 130. Through the multiple readout elements 130, electrical signals corresponding to the spin information buffered in the magnetic domains of the second region 124b are read out in parallel by the magnetoresistive effect. Note that Figures 1 and 3 show four readout elements 130 for reading 4 bits of data as an example, but the number of readout elements 130 is not limited.

[0026] Next, with reference to Figures 1 and 4A to 4D, the operation of the photonic spin register 100 from the input of the optical signal PL to the readout of the electrical signal will be explained. In the following, it is assumed that each magnetic domain 128b in the magnetic layer 124 has a perpendicular magnetic order parallel to the direction perpendicular to the plane, and that the magnetic order of the first region 124a is fixed downward beforehand. Also, the four readout elements 130 shown in Figures 4A to 4D will be denoted as 130a, 130b, 130c, and 130d in order of proximity to the spin Hall element 106. Furthermore, it is assumed that the magnetic order of the fixed layer 134 of each readout element is fixed upward, and the data when the magnetic order direction of the magnetic domain 128b directly below the readout element is parallel to the magnetic order direction of the fixed layer 134 is defined as "1", and the data when it is antiparallel is defined as "0".

[0027] When a pulse amplitude-modulated optical signal PL, input in series, is input to the photoelectric conversion element 116 via the optical waveguide 112, the optical signal PL propagates as a surface plasmon polariton at the interface between the photoelectric conversion element 116 and the metal film 118, generating a strong electric field in the surrounding area. At this time, the bias voltage V bias Upon application, the photocurrent I, which is a pulsed current, is transmitted from the photodetector 114 to the spin Hall element 106. ph It flows and enters electrode 142.

[0028] Figure 4A shows an example of the initial magnetic order state of the magnetic layer 124. In this initial state, a photocurrent I is supplied to the spin Hall element 106. ph When a current flows, a spin current is generated in the spin Hall element 106 in a direction perpendicular to the plane, and a spin-orbit torque (SOT) acts on the magnetic order in the first region 124a directly below the spin Hall element 106, making it possible to reverse the magnetic order (see Figure 4B). Figure 4B shows an example in which the magnetic order in the first region 124a is reversed from downward to upward, and spin information corresponding to data "1" is written.

[0029] Here, the photocurrent I phSince the photocurrent I is a pulsed current corresponding to the information contained in the optical signal PL, the magnetic order reverses during the period of pulse width in which a current with a current density above a predetermined value flows, and does not reverse the magnetic order during other periods. In this way, the information contained in the optical signal PL is transmitted to the photocurrent I ph One bit of spin information is written by transferring it to the spin state of the magnetic domain in the first region 124a.

[0030] Then, when a shift current Is flows through the spin Hall layer 122, SOT acts on the magnetic layer 124, causing the magnetic domain wall 128a of the magnetic layer 124 to move in the direction of the shift current Is. As a result, one bit of spin information "1" moves to the position of the readout element 130a, and the magnetic order of the magnetic domains of the first region 124a returns to its initial state (see Figure 4C). In the first embodiment and subsequent embodiments, coherent magnetic domain wall movement is possible.

[0031] The shift current Is also flows through the magnetic layer 124, and the spin transfer torque (STT) can cause the domain wall 128a to move in the direction of electron flow (opposite to the shift current Is). However, the spin Hall layer 122 has a significantly lower resistivity than the magnetic layer 124, and when their respective thicknesses are ts=4nm and tm=6nm as described above, more shift current Is flows through the spin Hall layer 122 than through the magnetic layer 124, and SOT becomes dominant over STT, causing the domain wall 128a to move in the direction of the shift current Is.

[0032] Alternatively, a shift register section 104 without a spin Hall layer 122 may be used. In this case, when a shift current Is is applied to the magnetic layer 124 from electrode 126b (second region 124b side) to electrode 126a (first region 124a side), the magnetic domain wall 128a moves in the opposite direction to the shift current Is due to the STT.

[0033] Photocurrent I phAssume that spin information "1", "0", "0", and "1" are written in order by performing the writing of spin information and the movement of the magnetic domain wall 128a by the shift current Is four times. In this case, in the second region 124b, the first spin information "1" moves to the position of the readout element 130d, the second spin information "0" moves to the position of the readout element 130c, the third spin information "0" moves to the position of the readout element 130b, and the fourth spin information "1" moves to the position of the readout element 130a (see Figure 4D).

[0034] When a predetermined voltage is applied to each magnetoresistive element, which consists of readout elements 130a to 130d and a second region 124b, under the control of the control unit, a readout current flows perpendicular to the surface of each magnetoresistive element and is output via terminal 136. The magnitude of the readout current changes according to the electrical resistance of the magnetoresistive element caused by the magnetoresistive effect, so "1" and "0" can be distinguished by the magnitude of the output readout current (electrical signal). For example, when the magnetic order of the fixed layer 134 and the magnetic order of the magnetic domain 128b directly beneath it are in the same direction (parallel state), the magnetoresistive element is in a low-resistance state, and when they are in opposite directions (antiparallel state), the magnetoresistive element is in a high-resistance state, so the former data can be distinguished as "1" and the latter data as "0".

[0035] When the magnetic domain wall 128a of the magnetic layer 124 moves a distance of 1 bit in 10 ps, ​​4 bits of spin information are sequentially buffered in the second region 124b during 10 ps × 4 = 40 ps. The control unit, as described above, measures time using a clock and controls the four readout elements 130a to 130d to simultaneously read out the four electrical signals corresponding to the 4 bits of spin information 40 ps after the start of the movement of the first spin information. In this way, 4 bits of data ("1001") can be read out in parallel.

[0036] Next, we will explain the energy consumed when writing spin information to the magnetic domains of the magnetic layer 124 and the energy consumed when the magnetic domain walls move.

[0037] Hereinafter, as shown in FIG. 1, the area per bit (bit size) of the shift register unit 104 is defined as w1×w2 from the width w1 of the spin - hole element 106 and the width w2 of the shift register unit 104. The width w1 represents the movement distance for one bit. Also, the photocurrent I ph The thickness of the spin - hole element 106 through which the current flows is set to 10 nm, the thickness ts of the spin - hole layer 122 is set to 4 nm, and the thickness tm of the magnetic layer 124 is set to 6 nm. Further, the longitudinal length of the magnetic layer 124 and the spin - hole layer 122 is denoted as L.

[0038] In the case of ferrimagnetic materials, it has been reported that magnetic order reversal occurs by applying a pulse current of 7×10 12 A / m 2 for about 10 ps (Y. Yang et al., Science Advances, Vol.3, e1603117 (2017)). Also, in the case of the topological antiferromagnet Mn3Sn, it is expected that magnetic order reversal occurs within several ps by a current on the order of 10 12 A / m 2 . Here, the current density required for magnetic order reversal hardly changes with a pulse width on the order of the reversal time (damping rate).

[0039] When the magnetic layer 124 is made of a ferrimagnetic material (for example, GdFeCo), for a spin - hole element 106 with a bit size of 50 nm×50 nm and a bit resistance R of 50 Ω, when a photocurrent I of 7×10 12 A / m 2 (3.5 mA) is applied for 9 ps, the energy consumption per bit I ph Rt (t is time) is (3.5×10 ph 2 ) -3 ) 2 A 2 ×50 Ω×9 ps = 5.5 fJ.

[0040] When the magnetic layer 124 is made of a topological antiferromagnet (for example, Mn3Sn), for a spin - hole element 106 with a bit size of 100 nm×50 nm and a bit resistance R of 25 Ω, when a photocurrent of 7×1012 A / m 2 (7mA) photocurrent I ph When 2 ps is applied, the energy consumption per bit is I ph 2 Rt is (7 × 10 -3 ) 2 A 2 ×25Ω×2ps = 2.5fJ.

[0041] Thus, both ferrimagnetic materials and topological antiferromagnetic materials can use ultrashort pulse currents with a pulse width of 10 ps or less to reduce the energy consumption per bit during writing to less than 10 fJ.

[0042] Regarding magnetic domain wall movement, in ferrimagnetic materials, 10 11 A / m 2 It has been reported that a magnetic domain wall velocity of 4 km / s can be reached with a current of the order of magnitude (K. Cai et al., Nature Electronics, Vol.3, pages 37-42 (2020)). Also, in Mn3Sn, 1 × 10⁻¹⁶ 12 A / m 2 It is expected that a magnetic domain wall velocity of 10 km / s will be reached with the following current: the photocurrent I, which is the writing current. ph A shift current Is with a current density an order of magnitude smaller than that can be expected to cause magnetic domain wall movement at magnetic domain wall velocities of several km / s or more.

[0043] When the magnetic layer 124 is made of ferrimagnet, the spin Hall layer 122 is made of Pt, the bit size is 50 nm × 50 nm, and the longitudinal length L is 1000 nm (= 1 μm). In this case, the resistance R of the shift register section 104 is approximately 900 Ω. Also, if the magnetic domain wall velocity is 5 km / s, the magnetic domain wall moves the distance w1 (= 50 nm) of one bit in 10 ps. 5 × 10 11 A / m 2 When a shift current Is of (0.25mA) is applied longitudinally for 10ps, the energy consumption per bit is Is 2 Rt is (2.5 × 10 -4 ) 2 A2 ×900Ω × 10ps = 0.5fJ.

[0044] When the magnetic layer 124 is made of a topological antiferromagnet, the spin Hall layer 122 is made of Pt, the bit size is 100 nm × 50 nm, and the longitudinal length L is 2000 nm (= 2 μm). In this case, the resistance R of the shift register section 104 is approximately 1800 Ω. Also, if the magnetic domain wall velocity is 10 km / s, the magnetic domain wall moves a distance of 1 bit w1 (= 100 nm) in 10 ps. 1 × 10⁻¹⁰ 12 A / m 2 When a shift current Is of (0.5mA) is applied longitudinally for 10ps, the energy consumption per bit is Is 2 Rt is (5 × 10 -4 ) 2 A 2 × 1800Ω × 10ps = 4.5fJ.

[0045] Thus, both ferrimagnetic materials and topological antiferromagnetic materials can reduce the energy consumption per bit due to current-driven magnetic domain wall movement to approximately a few fJ.

[0046] In the first embodiment described above, the photodetector 114 is shown as a plasmon waveguide photodetector, but the input optical signal PL is converted into a photocurrent I ph Other photoelectric conversion devices that convert to this may be used.

[0047] Furthermore, although an example where the shift current Is is DC has been shown, the shift current Is may also be a pulsed current generated from the optical signal PL. In this case, the optical signal PL can be split into two by an optical splitter, one optical signal PL can be input to the optical receiver 102, and the other optical signal PL can be input to a photoelectric conversion device such as a photodiode to generate a pulsed current, and the generated pulsed current can be applied to the shift register unit 104 as the shift current Is.

[0048] Next, with reference to Figures 5A to 5C, the differences between a conventional photoelectric interface and the photoelectric interface according to the first embodiment will be explained.

[0049] As shown in Figure 5A, a photodetector such as a photodiode absorbs the optical signal and generates a photocurrent I ph It outputs a signal, but in order to process the signal with a large-scale integrated circuit (LSI), the photocurrent I ph It is necessary to convert the photocurrent I ph The signal is amplified and converted into a voltage, and the resulting voltage V out It outputs [this]. However, TIA has performance issues such as operating speed, power consumption, and sensitivity (noise).

[0050] On the other hand, as shown in Figure 5B, the TIA is the load resistor (resistance value R load There is a method that replaces it with ). In this method, the photocurrent I from the photodetector ph The current flows through the load resistor, and the voltage drop across the load resistor causes a voltage V out (=R load I ph ) can be read. However, the 1V voltage V used in LSIs out To obtain this, a large load resistance of about 10kΩ is required, but there is a problem that the operating speed, which is determined by the RC time constant, slows down as the load resistance increases. For high-speed operation, the parasitic capacitance of the photodetector needs to be 1fF or less. For example, Non-Patent Literature 1 discloses that an extremely small parasitic capacitance of about 1fF can be realized by using a photodetector that utilizes a photonic crystal structure. However, current-to-voltage conversion is required, and a high load resistance of 24kΩ is needed, so the operating speed is limited to several tens of GHz.

[0051] In the photonic spin register 100 according to the first embodiment, as shown in Figure 5C, current-to-voltage conversion is not required, and the photocurrent I from the photodetector is not required. ph This directly reverses the magnetic order of the magnetic layer and transfers the information contained in the optical signal to the spin state. Therefore, the effective resistance value R of the load resistor MThis allows the load to be reduced to less than 100Ω, which can lead to a significant improvement in operating speed. For example, using a photodetector with a parasitic capacitance of approximately 1fF and a load resistor of approximately 100Ω, the operating speed determined by the RC time constant will be close to 1THz.

[0052] Although Figures 1 to 3 show an example where the substrate 120 for the shift register unit 104 and the substrate 110 for the optical receiver 102 are provided separately, both the functions of the shift register unit 104 and the optical receiver 102 may be mounted on a single substrate.

[0053] Alternatively, the photonic spin register 100 and the functions of other devices may be implemented on a single substrate. For example, as shown in Figure 6, an on-chip device 1000 can be realized on a single substrate 160, which implements the functions of the photonic spin register 100 and an application-specific integrated circuit (ASIC) 162. In the on-chip device 1000, an optical signal PL is input in series to the photonic spin register 100, and multiple electrical signals ES are output in parallel from the photonic spin register 100 to the ASIC 162.

[0054] <Second Embodiment> Next, a second embodiment of the present invention will be described with reference to Figure 7. The second embodiment deals with a photonic spin register in which a plurality of the shift register sections of the first embodiment are provided.

[0055] As shown in Figure 7, the photonic spin register 200 according to the second embodiment comprises an optical receiver 202, a first shift register section 204_1 to a seventh shift register section 204_7, a writing section 240, and a control unit 250.

[0056] The optical receiver 202 has the same configuration as the optical receiver 102 of the first embodiment. The first shift register section 204_1 to the seventh shift register section 204_7 are arranged parallel to each other in a direction perpendicular to the longitudinal direction. Figure 7 shows an example in which seven shift register sections are provided, but the number of shift register sections is not limited. Each shift register section has the same configuration as the shift register section 104 of the first embodiment (Figure 3), and consists of a substrate 120, a spin Hall layer 122, and a magnetic layer 124 stacked on top of each other.

[0057] Multiple read elements 130 are provided on the second region 124b of the magnetic layer 124 of each shift register section, arranged in the longitudinal direction. Figure 7 shows an example in which 16 read elements 130 are provided, but the number of read elements 130 is not limited.

[0058] A spin Hall element 106 is stacked on the first region 124a of the magnetic layer 124 at the position closest to the second region 124b. The spin Hall elements 106 of adjacent shift register sections are electrically connected to each other, thereby forming the writing section 240. In this way, the writing section 240 is provided intersectingly on the first shift register section 204_1 to the seventh shift register section 204_7. The optical receiver 202 is directly connected to the spin Hall element 106 of the first shift register section 204_1, and the photocurrent I from the optical receiver 202 ph The current flows throughout the entire writing section 240 and into the electrodes connected to the spin Hall element 106 on the seventh shift register section 204_7.

[0059] The control unit 250 is electrically connected to the first shift register section 204_1 to the seventh shift register section 204_7 and selects the shift register section through which the shift current Is flows. The control unit 250 also controls the timing of reading out multiple electrical signals via the multiple readout elements 130.

[0060] Next, we will explain the operation of the photonic spin register 200, from the input of the optical signal PL to the readout of the electrical signal.

[0061] When a pulse amplitude modulated optical signal PL, input in series, is input to the optical receiver 202, the photodetector of the optical receiver 202 generates a photocurrent I ph A photocurrent I is generated and flows to the writing unit 240. ph When the current flows, a spin current is generated in the spin Hall element 106 in the direction perpendicular to the plane, and the SOT acts on the magnetic order in the first region 124a directly below the spin Hall element 106, so that 1 bit of spin information is written to the magnetic domain. At this time, the control unit 250 flows the shift current Is only to the first shift register section 204_1, and the spin information written to the magnetic domain moves due to the movement of the magnetic domain wall caused by the shift current Is.

[0062] Here, the current density of the shift current Is is set so that the magnetic domain wall of the magnetic layer 124 moves a distance of 1 bit in 10 ps, ​​as described in the first embodiment. Photocurrent I ph By performing spin information writing and magnetic domain wall movement by shift current Is 16 times, 16 bits of spin information are sequentially buffered in the second region 124b within 10 ps × 16 = 160 ps. The control unit 250 measures time using a clock and controls the 16 readout elements 130 to read out 16 electrical signals corresponding to the 16 bits of spin information in parallel 160 ps after the start of the initial spin information movement.

[0063] Once the writing of 16 bits of spin information to the first shift register section 204_1 is complete, the control unit 250 stops supplying the shift current Is to the first shift register section 204_1 and supplies the shift current Is to the second shift register section 204_2. Similarly, once the writing of 16 bits of spin information to the second shift register section 204_2 is complete, the control unit 250 stops supplying the shift current Is to the second shift register section 204_2 and supplies the shift current Is to the third shift register section 204_3. Similarly, spin information is written to the third shift register section 204_3 through the seventh shift register section 204_7. Once the writing of 16 bits of spin information to the seventh shift register section 204_7 is complete, the overwriting of spin information to the first shift register section 204_1 begins.

[0064] Here, it takes 160 ps × 6 (~1 ns) from the completion of writing 16 bits of spin information to the first shift register section 204_1 until the completion of writing 16 bits of spin information to the seventh shift register section 204_7. During this approximately 1 ns, 16 bits of electrical signals are read out in parallel via the 16 readout elements 130 on the first shift register section 204_1. In other words, while spin information is being written to the second shift register section 204_2 through the seventh shift register section 204_7 (for approximately 1 ns), 16 bits of electrical signals are read out in parallel from the first shift register section 204_1.

[0065] Each shift register transmits 1 bit of data in 10 ps, ​​resulting in a transfer rate of 100 Gbps. In contrast, the transfer rate in the CMOS circuit is only 1 / 100th of that, at 1 Gbps (1 ns per bit). Therefore, when outputting an electrical signal to the CMOS circuit, the 16 bits of electrical signal are read in parallel from the first shift register 204_1 over a period of approximately 1 ns, in accordance with the CMOS circuit's transfer rate. The approximately 1 ns during which the electrical signal is read from the first shift register 204_1 is used as time to write spin information to the other six shift registers (second shift register 204_2 to seventh shift register 204_7). Similarly, while the 16 bits of electrical signal are read in parallel from the second shift register 204_2, spin information is written to the other six shift registers (third shift register 204_3 to seventh shift register 204_7 and first shift register 204_1). The same applies when reading 16-bit electrical signals from each of the third shift register section 204_3 to the seventh shift register section 204_7.

[0066] Thus, the photonic spin register 200 according to the second embodiment can efficiently write spin information and read electrical signals by utilizing the difference in transfer rates between each shift register section and the CMOS circuit.

[0067] <Third Embodiment> Next, a third embodiment of the present invention will be described with reference to Figure 8. The third embodiment deals with a photonic spin register that utilizes all-optical magnetization switching (AOS), which reverses the magnetization (magnetic order) by directly irradiating a magnetic layer with an input optical signal.

[0068] As shown in Figure 8, the photonic spin register according to the third embodiment includes a light irradiation unit 340 as a writing unit, which directly irradiates a series-input pulse amplitude modulated optical signal PL onto a magnetic material layer 324 made of ferrimagnetic material. This eliminates the need for a photodetector as in the first and second embodiments. The photonic spin register according to the third embodiment has a structure in which the optical receiver 102 and spin Hall element 106 of the photonic spin register 100 according to the first embodiment are replaced with the light irradiation unit 340 shown in Figure 8.

[0069] The light irradiation unit 340 comprises a light emission unit 342 and a lens 344. The light emission unit 342 emits an optical signal PL, which is an ultrashort pulse light with a pulse width of about 100 fs. The optical signal PL emitted from the light emission unit 342 is focused into the magnetic material layer 324 by the lens 344. Here, since the optical signal PL is pulsed light, when light with an intensity above a threshold is irradiated, the magnetic order of the magnetic domains of the magnetic material layer 324 is reversed, and when light with an intensity below the threshold is irradiated, no magnetic order reversal occurs. In this way, 1 bit of spin information is written by transferring the information contained in the optical signal PL to the spin state of the magnetic domains of the magnetic material layer 324.

[0070] According to the photonic spin register of the third embodiment, there is no need to convert the optical signal PL into a photocurrent, and the magnetic order direction of the magnetic layer 324 can be controlled directly with light. Therefore, power consumption due to the photocurrent can be completely suppressed.

[0071] The magnetic layer 324 may also be a composite film in which a ferrimagnetic material is laminated on a topological antiferromagnetic material.

[0072] <Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to Figures 9 to 12D. The fourth embodiment deals with a photonic spin resistor that converts multiple electrical signals input in parallel into a series optical signal.

[0073] First, the configuration of the photonic spin register 400 according to the fourth embodiment will be described. Figure 9 shows a perspective view of the photonic spin register 400, Figure 10 shows a cross-sectional view taken along the XX arrow in Figure 9, and Figure 11 shows a cross-sectional view taken along the XI-XI arrow in Figure 9.

[0074] As shown in Figure 9, the photonic spin register 400 comprises an optical signal output section 402 and a first shift register section 404a and a second shift register section 404b, both having a shape that extends in one direction. Each shift register section includes a plurality of spin Hall elements 440 arranged longitudinally as a writing section, and a single readout element 430 provided adjacent to the plurality of spin Hall elements 440. In Figure 9, an example is shown in which 10 spin Hall elements 440 for writing 10 bits of data are arranged in each of the first shift register section 404a and the second shift register section 404b, but the number of spin Hall elements 440 is not limited.

[0075] The optical signal output unit 402 comprises a substrate 410, an optical modulator 414 provided on the substrate 410, and an input waveguide 412a and an output waveguide 412b connected to the optical modulator 414 on the substrate 410. The optical modulator 414 comprises an electro-optic element 416 and a metal film 418 sandwiching the electro-optic element 416, forming a plasmon waveguide.

[0076] The electro-optic element 416 is made of an electro-optic (EO) polymer, and the metal films 418 on both sides of the electro-optic element 416 are made of metallic materials such as Au and Ag. An input waveguide 412a is continuously connected to one end of the electro-optic element 416, and an output waveguide 412b is continuously connected to the other end of the electro-optic element 416. The width w4 of the electro-optic element 416 (see Figure 10) is narrower than the widths of the input waveguide 412a and the output waveguide 412b. The input waveguide 412a has a tapered shape where the connection portion with the electro-optic element 416 narrows toward the electro-optic element 416, and the output waveguide 412b also has a tapered shape where the connection portion with the electro-optic element 416 narrows toward the electro-optic element 416. The narrower the width w4 of the electro-optic element 416, the greater the light confinement effect, making it possible to focus light below the diffraction limit, and the stronger the interaction between the electro-optic element 416 and the optical field. This increases the Pockels effect, which will be discussed later, enabling highly efficient optical modulation.

[0077] Since the first shift register section 404a and the second shift register section 404b have the same size and configuration, only the configuration of the first shift register section 404a will be described below. As shown in Figure 11, the first shift register section 404a comprises a substrate 420, a spin Hall layer 422 laminated on the substrate 420, and a magnetic layer 424 laminated on the spin Hall layer 422. The spin Hall layer 422 and the magnetic layer 424 are made of the same material and have the same thickness as the spin Hall layer 122 and magnetic layer 124 shown in Figure 3, respectively. The magnetic order direction of the magnetic layer 424 is fixed in advance by a magnet.

[0078] Multiple spin Hall elements 440 are arranged longitudinally on the magnetic layer 424. Each spin Hall element 440 is made of the same material and has the same bit size as the spin Hall element 106 shown in Figures 1 and 3. Each spin Hall element 440 is sandwiched between electrodes 442a and 442b, and a writing current Iw flows from electrode 442a to electrode 442b under the control of the control unit. When the writing current Iw flows through the spin Hall element 440, the SOT acts on the magnetic order of the magnetic layer 424 directly beneath it, and spin information is written as information about the direction of the magnetic order.

[0079] Here, the writing current Iw is a pulsed current corresponding to the information ("1" or "0") input from a CMOS circuit or the like. Therefore, during the period when a current with a current density above a predetermined value flows, the magnetic order of the magnetic domains of the magnetic material layer 424 is reversed, and during other periods, magnetic order reversal does not occur. In this way, 1 bit of spin information is written by transferring the input information to the spin state of the magnetic domains of the magnetic material layer 424 using the writing current Iw.

[0080] Similar to the shift register section 104 in Figure 1, electrodes are connected to both longitudinal ends of the spin Hall layer 422 and the magnetic layer 424. Under the control of the control unit, a voltage is applied between these electrodes, causing a shift current Is to flow longitudinally through the spin Hall layer 422 and the magnetic layer 424, and the magnetic domain walls of the magnetic layer 424 to move. As a result, multiple spin pieces of information written in parallel to the magnetic layer 424 by multiple spin Hall elements 440 are simultaneously moved.

[0081] The readout element 430 comprises a barrier layer 432 made of a non-magnetic material laminated on the magnetic layer 424, and a fixed layer 434 laminated on the barrier layer 432, with magnetic order fixed in the direction perpendicular to the plane. The magnetic layer 424 functions as a free layer in which the magnetic order can be reversed, and the combination of the magnetic layer 424 and the readout element 430 constitutes a magnetoresistive element (e.g., a magnetic tunnel junction element). When a predetermined voltage is applied to this magnetoresistive element under the control of the control unit, multiple spin information moving within the magnetic layer 424 is sequentially read out as electrical signals due to the magnetoresistive effect. The readout element 430 is connected to one metal film 418 of the optical modulator 414 via a conductor 438.

[0082] Next, referring to Figures 12A to 12D, the operation of the photonic spin register 400 from parallel input of electrical signals to series output of optical signals will be explained. In the following, an example is given in which 10 bits of information are written in parallel at once to each of the first shift register section 404a and the second shift register section 404b, but this is not the only example.

[0083] First, as shown in Figure 12A, a write current Iw corresponding to the input information flows simultaneously to each spin Hall element 440 of the first shift register 404a. As a result, SOT acts on the magnetic order of the magnetic layer 424 from each spin Hall element 440, and 10 bits of spin information are written to the magnetic layer 424. The time required to write the spin information to the magnetic layer 424 is, for example, 100 ps.

[0084] Next, as shown in Figure 12B, when a shift current Is is applied to the spin Hall layer 422 and magnetic layer 424 of the first shift register section 404a, the magnetic domain walls of the magnetic layer 424 move in the longitudinal direction, and the spin information written to the magnetic layer 424 moves. When the magnetic domain walls of the magnetic layer 424 move a distance of 1 bit in 10 ps, ​​10 bits of spin information are moved in a period of 100 ps, ​​and electrical signals are sequentially read out from the readout element 430. That is, the electrical signals from the readout element 430 are transmitted to the optical modulator 414 at a transfer rate of 100 Gbps.

[0085] When a voltage corresponding to the electrical signal from the readout element 430 is applied to the optical modulator 414, the incident light Lb from the input waveguide 412a is phase-modulated by the Pockels effect, and the modulated light ML is output to the output waveguide 412b.

[0086] While the shift current Is is flowing through the first shift register section 404a, the write current Iw is flowing through the spin Hall element 440 of the second shift register section 404b. As a result, 10 bits of spin information are simultaneously written to the magnetic layer 424 by the SOT.

[0087] Next, as shown in Figure 12C, when a write current Iw is applied to the spin Hall element 440 of the first shift register section 404a, 10 bits of spin information are simultaneously written to the magnetic layer 424 by the SOT. While the spin information is being written to the first shift register section 404a, a shift current Is is applied to the second shift register section 404b. As a result, the 10 bits of spin information are sequentially read out as electrical signals from the readout element 430 of the second shift register section 404b and transmitted to the optical modulator 414. In the optical modulator 414, the electrical signals are converted into optical signals, and the modulated light ML is output.

[0088] Next, as shown in Figure 12D, a shift current Is is applied to the first shift register section 404a. As a result, 10 bits of spin information are sequentially read out as electrical signals from the readout element 430 of the first shift register section 404a and transmitted to the optical modulator 414. In the optical modulator 414, the electrical signals are converted into optical signals, and modulated light ML is output. At this time, a write current Iw is applied to the spin Hall element 440 of the second shift register section 404b, and 10 bits of spin information are simultaneously written to the magnetic layer 424 by the SOT.

[0089] In this manner, while an electrical signal is being read from the second shift register section 404b, spin information is written to the first shift register section 404a, and while an electrical signal is being read from the first shift register section 404a, spin information is written to the second shift register section 404b.

[0090] According to the photonic spin register 400 of the fourth embodiment, similar to the photonic spin register 100 of the first embodiment, the energy consumption per bit when writing spin information to the magnetic domains of the magnetic material layer 424 and the energy consumption per bit during magnetic domain wall movement can be reduced to the order of a few fJ. Furthermore, as described above, a high-speed transfer rate of 100 Gbps can be achieved.

[0091] In Figures 9 to 11, an example is shown in which the substrate 420 for the first shift register section 404a, the substrate 420 for the second shift register section 404b, and the substrate 410 for the optical signal output section 402 are provided separately. However, the functions of each shift register section and the optical signal output section 402 may be mounted on a single substrate.

[0092] Alternatively, the photonic spin register 400 and the functions of other devices may be implemented on a single substrate. For example, as shown in Figure 13, an on-chip device 4000 can be realized on a single substrate 460, which implements the functions of the photonic spin register 400, the ASIC 462, and the light source 464. In the on-chip device 4000, multiple electrical signals ES output from the ASIC 462 are input in parallel to the photonic spin register 400, as well as incident light Lb from the light source 464, and modulated light ML is output in series from the photonic spin register 400.

[0093] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0094] For example, the photonic spin registers of each embodiment described above can be used in various applications, such as being mounted in on-chip devices as shown in Figures 6 and 13, as well as in information processing devices and magnetic memories that require photoelectric or electro-optical conversion. [Explanation of Symbols]

[0095] 100 Photonic Spin Registers 102 Optical Receiver 104 Shift register section 106 Spin Hall element (writing section) 110 circuit boards 112 Optical waveguide 114 Receiver 116 Photoelectric conversion element 118 Metal film 120 circuit boards 122 Spin Hall Layer 124 Magnetic layer 124a 1st area 124b 2nd area 130 Readout element 132 Barrier layer 134 Fixed layer 160 circuit boards 162 ASIC 200 Photonic Spin Registers 202 Optical Receiver 204_1 First Shift Register Section 204_2 Second Shift Register Section 204_3 Third Shift Register Section 204_4 4th Shift Register Section 204_5 Fifth Shift Register Section 204_6 6th Shift Register Section 204_7 7th Shift Register Section 240 writing section 250 Control Unit 324 Magnetic layer 340 Light-emitting section (writing section) 342 Light-emitting section 344 Lens 400 Photonic Spin Register 402 Optical signal output section 404a First Shift Register Section 404b Second Shift Register Section 410 circuit boards 412a Input waveguide 412b Output waveguide 414 Optical modulator 416 Electro-optic elements 418 Metal film 420 circuit boards 422 Spin Hall Layer 424 Magnetic layer 430 Readout elements 432 Barrier layer 434 Fixed layer 440 Spin Hall Elements 460 circuit boards 462 ASIC 464 Light source 1000, 4000 on-chip devices

Claims

1. A shift register section having a magnetic layer with a shape extending in one direction, A writing unit that writes spin information by transferring information contained in a pulse amplitude modulated optical signal input in series in a time series to the spin state of the magnetic domains of the magnetic material layer by a photocurrent corresponding to the optical signal or by irradiation with the optical signal, Equipped with, A photonic spin register in which, when the unidirectional shift current flows through the shift register section, the magnetic domain walls move within the magnetic layer, causing the spin information to move and be buffered in the magnetic layer while maintaining the time-series order.

2. The photonic spin register according to claim 1, wherein the magnetic layer is made of a topological antiferromagnet or a ferrimagnet.

3. The shift register further comprises a spin Hall layer that exhibits the spin Hall effect when the shift current flows through it. The photonic spin register according to claim 1 or 2, wherein the magnetic layer is laminated on the spin Hall layer, and the magnetic domain wall moves due to the spin orbit torque from the spin Hall layer.

4. The photonic spin register according to claim 1 or 2, wherein the magnetic domain wall moves due to the spin transfer torque as the shift current flows through the magnetic layer.

5. The magnetic layer comprises a first region in which the magnetic order direction is fixed in advance, and a second region that buffers information on the magnetic order direction as spin information. The writing unit writes the spin information to the magnetic domains of the first region. The photonic spin register according to any one of claims 1 to 4, wherein in the magnetic layer, the spin information moves from the first region to the second region due to the movement of the magnetic domain wall by the shift current.

6. The magnetic layer further comprises a plurality of readout elements arranged in one direction on the second region of the magnetic layer, By performing the writing and moving of the spin information multiple times, multiple spin information is sequentially buffered in the second region. The photonic spin register according to claim 5, wherein the plurality of spin information is read out in parallel as a plurality of electrical signals by the magnetoresistive effect through the plurality of readout elements.

7. The device further comprises a photodetector that receives the aforementioned optical signal and converts it into the aforementioned photocurrent, The writing unit is electrically connected to the photodetector, is laminated on a portion of the magnetic layer, and includes a spin Hall element that exhibits the spin Hall effect when the photocurrent from the photodetector flows through it. A photonic spin register according to any one of claims 1 to 6, wherein when the photocurrent flows through the spin Hall element, the spin-orbit torque acts on the magnetic order of the magnetic domains, thereby enabling the reversal of the magnetic order.

8. The photonic spin register according to claim 7, comprising a photodetector and a plasmon waveguide.

9. The photonic spin register according to claim 7 or 8, wherein the photodetector generates an ultrashort pulse current with a pulse width of 10 ps or less as the photocurrent.

10. The writing unit includes a light irradiation unit that directly irradiates a portion of the magnetic layer with the optical signal. The photonic spin register according to any one of claims 1 to 6, wherein the magnetic order of the magnetic domains can be reversed by irradiation with the aforementioned optical signal.

11. A photodetector that receives pulse amplitude modulated optical signals input in series in time and converts them into a photocurrent, Each has a magnetic layer that extends in one direction, and a plurality of shift register sections are arranged parallel to a direction perpendicular to the said one direction, A writing unit is electrically connected to the photodetector and is provided intersectingly on the plurality of shift register sections. When the photocurrent flows from the photodetector, the writing unit writes spin information by transferring the information contained in the optical signal to the spin state of the magnetic domains of each of the magnetic material layers of the plurality of shift register sections through the spin Hall effect. A control unit is electrically connected to the plurality of shift register units and selects one shift register unit from among the plurality of shift register units to supply shift current, Equipped with, A photonic spin register in which, when the unidirectional shift current flows through the shift register selected by the control unit, the magnetic domain walls move within the magnetic layer of the shift register, causing the spin information to move and be buffered in the magnetic layer while maintaining the time-series order.

12. Each of the multiple shift register sections further comprises a plurality of readout elements arranged in one direction on the magnetic layer, By performing the writing and transfer of the spin information multiple times, multiple pieces of spin information are sequentially buffered in the magnetic layer. The photonic spin register according to claim 11, wherein the plurality of spin information is read out in parallel as a plurality of electrical signals by the magnetoresistive effect through the plurality of readout elements.

13. The photonic spin register according to claim 12, wherein the control unit flows the unidirectional shift current to one of the multiple shift registers while the multiple electrical signals are being read out in parallel from one shift register via the multiple readout elements.

14. A shift register section having a magnetic layer with a shape extending in one direction, A plurality of spin Hall elements that exhibit the spin Hall effect, arranged in one direction on the magnetic layer, wherein when a plurality of pulse currents corresponding to input information flow in parallel, the plurality of spin Hall elements write a plurality of spin pieces of information to the magnetic layer by spin-orbit torque, A readout element provided adjacent to the plurality of spin Hall elements on the magnetic layer, An optical modulator electrically connected to the readout element, Equipped with, When the unidirectional shift current flows through the shift register, the magnetic domain walls move within the magnetic layer, causing the multiple spin information to move. Due to the magnetoresistance effect, the multiple spin information is read out in series as an electrical signal via the readout element. The optical modulator is a photonic spin register that converts the electrical signal read out via the readout element into an optical signal and outputs the optical signal.

15. A method for writing information, comprising writing spin information by transferring information contained in a pulse amplitude modulated optical signal input in series in a time series to the spin state of a magnetic domain of a magnetic material layer having a shape extending in one direction, using a photocurrent corresponding to the optical signal or by irradiation with the optical signal.

16. The optical signal is received using a photodetector and converted into a photocurrent, The information writing method according to claim 15, wherein the photocurrent is passed through a spin Hall element capable of exhibiting the spin Hall effect, which is provided on the magnetic layer, and the spin orbit torque acts on the magnetic order of the magnetic domains, thereby reversing the magnetic order.

17. The information writing method according to claim 15, wherein the optical signal is directly irradiated onto the magnetic material layer by the light irradiation unit to reverse the magnetic order of the magnetic domains.

18. Spin information is written by transferring the information contained in a pulse amplitude modulated optical signal input in series in a time series to the spin state of a magnetic domain of a magnetic material layer that extends in one direction, using a photocurrent corresponding to the optical signal or by irradiation with the optical signal. The unidirectional shift current causes the magnetic domain walls to move within the magnetic layer, thereby moving the spin information written in the magnetic domains. By performing the writing and transfer of the spin information multiple times, multiple spin pieces of information are sequentially buffered in the magnetic layer while maintaining the chronological order. An information readout method comprising reading out the plurality of spin information as a plurality of electrical signals in parallel by the magnetoresistive effect through a plurality of readout elements arranged in one direction on the magnetic layer.

19. By passing multiple pulse currents corresponding to input information in parallel to multiple spin Hall elements that exhibit the spin Hall effect, which are arranged in one direction on a magnetic layer having a shape extending in one direction, multiple spin pieces of information are written to the magnetic layer in parallel by spin-orbit torque. As the magnetic wall moves within the magnetic layer due to the unidirectional shift current, the plurality of spin information moves, and the moving plurality of spin information is read out in series as an electrical signal via a readout element provided on the magnetic layer due to the magnetoresistance effect. An information readout method that converts the electrical signal into an optical signal using an optical modulator and outputs the optical signal.

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