Terahertz pulse communication system based on spin orbit moment regulation and control

Abstract

The invention discloses a terahertz pulse communication system based on spin orbit moment regulation and control, and relates to the technical field of spintronics and communication, and the system is characterized in that a regulation and control module regulates and controls the magnetization direction of a spin electron emitter through spin orbit moment; the coding module is in control connection with the regulation and control module and adopts a two-phase coding mode; and the signal transmission module performs data transmission based on signal superposition or time interlaced transmission of the spin electron emitter array. A spin electron emitter is used as a terahertz wave source, and high-speed electric control modulation of the spin electron emitter is realized through a spin orbit moment technology, so that polarization control and high-speed communication of terahertz waves are realized. Ultra-fast magnetization direction switching is realized by using the SOT technology, polarization of terahertz waves is further controlled, and two system structures are designed to improve the communication rate and the integration level. The method has the advantages of high speed, high integration level, low power consumption and the like, and is suitable for a future ultra-high-speed wireless short-range communication system.

Description

Technical Field

[0001] This invention relates to the fields of spintronics and communication technology, and more specifically to a terahertz pulse communication system based on spin orbital moment modulation. Background Technology

[0002] With the rapid development of wireless communication technology, the demand for ultra-high-speed data transmission is increasing. Traditional microwave and optical communication systems are approaching their performance limits and are unable to meet the future single-user Tbps-level transmission requirements. The terahertz band (0.1-30 THz) has attracted much attention due to its ultra-wide bandwidth. Pulse communication systems are considered one of the best ways to utilize the terahertz band because of their advantages of low complexity and small size. However, existing terahertz modulation methods suffer from problems such as slow speed, limited bandwidth, or difficulty in integration. For example, while CMOS-based systems can achieve high data rates, they only cover a portion of the terahertz band; while quantum cascade laser (QCL)-based systems have high modulation speeds, their bandwidth is limited by carrier recombination and thermal effects.

[0003] To achieve higher transmission rates, more novel materials have been developed. 2D materials such as graphene have been widely used in the THz band as representative modulators; secondly, metamaterials based on phase change materials or structures are another typical modulator. In addition, open-ring resonators (SRRs) made of Ge with plasmon-induced transparency (PIT) effect can achieve modulation speeds of 300 GHz.

[0004] While laser-controlled systems can achieve extremely high speeds, their bandwidth is limited. Furthermore, due to their narrow-band response, these systems are primarily based on continuous waves. However, continuous-wave systems require receivers to recover the clock and carrier, which relies on complex circuitry and slow processing. In contrast, pulsed systems are more suitable for high-speed applications because the detector responds only to the presence of a pulse. Therefore, combining electronically controlled pulsed systems with low carrier lifetimes can reduce modulation speeds to picoseconds.

[0005] Spintron emitters hold the potential to build electrically controlled, broadband, highly integrated, and directly modulated systems based on their emission mechanism. Since the emission principle is based on an ultrafast demagnetization process, it can be controlled by a magnetic switch. The speed of the magnetic switch is limited by the half-cycle of ferromagnetic resonance (FMR), and the switching time can reach tens of picoseconds, making it a promising high-speed device. Furthermore, continuous switching of spintronic devices has been achieved. Another advantage of spintron emitters is their good compatibility with fiber-optic coupling systems; the emitter structure is simple, the materials are readily available, and they are easy to implement. In this study, a mask was used to cover a thin film composed of CoFeB / Ta and CoFeB / W strips. When the mask was moved, the strips of the two different materials were alternately exposed to laser light, emitting THz pulses with opposite phases. However, the modulation speed was largely limited by the mechanical movement of the mask.

[0006] Therefore, how to propose a terahertz pulse communication system based on spin orbit moment control to perform high-speed, broadband, and easily integrated terahertz modulation, and overcome the shortcomings of existing technologies, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a terahertz pulse communication system based on spin-orbit moment modulation, which solves the problems of slow modulation speed, limited bandwidth, and difficulty in integration in existing terahertz communication systems, and realizes ultra-high speed, high integration, and low power consumption terahertz communication. To achieve the above objectives, the present invention adopts the following technical solution: A terahertz pulse communication system based on spin orbit moment control includes: a spin electron emitter array, a control module, an encoding module, and a signal transmission module, wherein the spin electron emitter array includes multiple spin electron emitters; The control module regulates the magnetization direction of the spin electron emitter through spin orbital moment; The encoding module is connected to the control module and uses a dual-phase encoding method. The signal transmission module transmits data based on the signal superposition or time-interleaved transmission of the spintron emitter array.

[0008] Optionally, the spin electron emitter employs a ferromagnetic metal or non-magnetic metal heterojunction thin film, wherein the heterojunction thin film is a CoFeB / Pt combination. The heterojunction is irradiated by a femtosecond-level laser pulse, which induces an ultrafast demagnetization effect to generate a spin polarization current. This current is converted into a transient charge current through the inverse spin Hall effect of the non-ferromagnetic layer, and the transient charge current oscillates and radiates terahertz pulses.

[0009] Optionally, the control module controls the magnetization direction of the spin electron emitter through spin orbit moment, including: the current in the non-ferromagnetic layer undergoes a spin Hall effect to be converted into a longitudinal pure spin current, the spin current is injected into the ferromagnetic layer and the angular momentum is transferred through exchange interaction, the spin orbit moment torque is applied to drive the magnetization intensity to precess around the effective magnetic field, and overcome the energy barrier to flip to the target easy axis direction.

[0010] Optionally, the spin electron emitter array includes a cumulative amplitude modulation system: A 4×4 transmitter array is used, with each transmitter controlled by an independent current source. Multiple transmitters transmit signals simultaneously and are spatially superimposed to form a composite signal of different amplitudes.

[0011] Optionally, the spin electron emitter array further includes a time-interleaving system: A delay line is set in front of each transmitter. By controlling the laser pulse delay, multiple transmitters emit signals sequentially with a transmission time interval of 5ps. It supports biphase encoding, pulse amplitude modulation, and pulse position modulation.

[0012] Optionally, the biphase encoding method changes the magnetization direction by controlling the current direction, thereby adjusting the polarization state of the terahertz wave, and uses the positive and negative polarization states of the terahertz wave to determine the binary 0 / 1 state.

[0013] Optionally, the amplitude of the synthesized signal satisfies the formula: ; in, For the amplitude of the synthesized signal, Let be the signal amplitude of the i-th transmitter, and n be the number of transmitters.

[0014] Optionally, the delay time of the delay line satisfies the formula: τ=cL; Where τ is the delay time, L is the length of the delay line, and c is the speed of light.

[0015] Optionally, the quantitative description of the transient charge current satisfies the formula: ; in, For electric charge and current, For the spin Hall angle, is the spin current, and m is the magnetization vector.

[0016] Optionally, the flipping satisfies the formula: ; in, The effective magnetic field of the ferromagnetic layer, The Gilbert damping factor. It is the gyromagnetic ratio. For SOT torque, and, , , These are the proportionality coefficients for damping torque and field torque, respectively. It is a spin current.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a terahertz pulse communication system based on spin orbital moment modulation, which has the following beneficial effects: This invention proposes a terahertz pulse communication system based on spin-orbit moment (SOT) modulation, comprising: a spintronic emitter array, a modulation module, an encoding module, and a signal transmission module. The spintronic emitter array includes multiple spintronic emitters. The modulation module controls the magnetization direction of the spintronic emitters through spin-orbit moment modulation. The encoding module is controlled and connected to the modulation module, employing a biphase encoding method. The signal transmission module transmits data based on signal superposition or time-interleaved transmission from the spintronic emitter array. This invention proposes a terahertz pulse communication system and biphase encoding method based on spin-orbit moment (SOT) modulation. This system utilizes a spintronic emitter as a terahertz wave source and achieves high-speed electronic modulation of the spintronic emitter through spin-orbit moment (SOT) technology, thereby realizing terahertz wave polarization control and high-speed communication. This invention utilizes SOT technology to achieve ultrafast magnetization direction switching, thereby controlling the polarization of the terahertz wave, and designs two system structures (cumulative amplitude modulation system and time-interleaved system) to improve communication rate and integration. This method has advantages such as high speed, high integration, and low power consumption, and is suitable for future ultra-high-speed wireless short-range communication systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 The present invention provides a schematic diagram of a terahertz pulse communication system based on spin orbit moment control.

[0020] Among them, 1-laser irradiation, 2-ferromagnetic layer, 3-nonferromagnetic layer, 4-terahertz wave, 5-magnetization direction, 6-spin current, and 7-induced current. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention discloses a terahertz pulse communication system based on spin-orbit moment modulation, such as... Figure 1 As shown, it includes: a spintronic emitter array, a control module, an encoding module, and a signal transmission module, wherein the spintronic emitter array includes multiple spintronic emitters; The control module controls the magnetization direction 5 of the spin electron emitter through the spin orbital moment; The encoding module is connected to the control module and uses a dual-phase encoding method. The signal transmission module transmits data based on the signal superposition or time-interleaved transmission of the spintron emitter array.

[0023] Furthermore, the spin electron emitter employs a ferromagnetic metal or non-magnetic metal heterojunction thin film, wherein the heterojunction thin film is a CoFeB / Pt combination. The heterojunction is irradiated by a femtosecond-level laser pulse, which induces an ultrafast demagnetization effect to generate a spin polarization current. This current is converted into a transient charge current through the inverse spin Hall effect of the non-ferromagnetic layer 3. The transient charge current oscillates and radiates terahertz pulses.

[0024] Furthermore, the control module controls the magnetization direction 5 of the spin electron emitter through spin orbit moment, including: the current in the non-ferromagnetic layer 3 undergoes a spin Hall effect to be converted into a longitudinal pure spin current, the spin current is injected into the ferromagnetic layer 2 and the angular momentum is transferred through exchange interaction, the spin orbit moment torque is applied to drive the magnetization intensity to precess around the effective magnetic field, overcome the energy barrier and flip to the target easy axis direction.

[0025] Furthermore, the spin electron emitter array includes a cumulative amplitude modulation system: A 4×4 transmitter array is used, with each transmitter controlled by an independent current source. Multiple transmitters transmit signals simultaneously and are spatially superimposed to form a composite signal of different amplitudes.

[0026] Furthermore, the spin electron emitter array also includes a time-interleaving system: A delay line is set in front of each transmitter. By controlling the laser pulse delay, multiple transmitters emit signals sequentially with a transmission time interval of 5ps. It supports biphase encoding, pulse amplitude modulation, and pulse position modulation.

[0027] Furthermore, the biphase encoding method changes the magnetization direction 5 by controlling the current direction, thereby adjusting the polarization state of the terahertz wave 4, and uses the positive and negative polarization states of the terahertz wave 4 to determine the binary 0 / 1 state.

[0028] Furthermore, the amplitude of the synthesized signal satisfies the formula: ; in, For the amplitude of the synthesized signal, Let be the signal amplitude of the i-th transmitter, and n be the number of transmitters.

[0029] Furthermore, the delay time of the delay line satisfies the formula: τ=cL; Where τ is the delay time, L is the length of the delay line, and c is the speed of light.

[0030] Furthermore, the quantitative description of the transient charge current satisfies the formula: ; in, For electric charge and current, For the spin Hall angle, is the spin current, and m is the magnetization vector.

[0031] Furthermore, the flipping satisfies the formula: ; in, The effective magnetic field of the ferromagnetic layer, The Gilbert damping factor. It is the gyromagnetic ratio. For SOT torque, and, , , These are the proportionality coefficients for damping torque and field torque, respectively. It is a spin current.

[0032] In a specific implementation, a terahertz pulse communication system based on spin orbital moment modulation (SOT) technology is provided to achieve high-speed electronically controlled modulation of a spin electron emitter. Through the SOT effect, the magnetization direction 5 can be switched within a 50 ps period, thereby controlling the polarization of the terahertz wave 4. Specifically, it includes two communication system structures based on spin electron emitters: A. Cumulative Amplitude Modulation System: Amplitude modulation is achieved by constructing a spintronic transmitter array. This system utilizes multiple transmitters to simultaneously emit signals, and the signals of different amplitudes are spatially superimposed to increase the data transmission rate.

[0033] B. Time-Interleaved System: This system achieves time-interleaved emission by constructing a spintronic emitter array and introducing delay lines. By controlling the delay of laser pulses, multiple emitters sequentially transmit signals, thereby increasing the modulation speed.

[0034] A biphase encoding method is adopted: the polarization of terahertz wave 4 is controlled by the magnetization direction 5, and the binary 0 / 1 state is determined by the positive or negative sign of terahertz wave 4 to achieve biphase encoding. This method has high noise immunity and data transmission efficiency.

[0035] In a specific embodiment, the spin electron emitter specifically includes: A ferromagnetic / non-magnetic metal (e.g., CoFeB / Pt) heterojunction thin film is used as a spin electron emitter. An ultrashort (femtosecond-level) laser pulse is focused onto the heterojunction of the emitter (typically a ferromagnetic / non-magnetic metal, such as CoFeB / Pt). The laser energy is rapidly absorbed by electrons in the ferromagnetic (FM) layer, inducing an ultrafast demagnetization effect. This causes spin-up and spin-down electrons to relax at different rates, generating a net spin-polarized current (spin current) within the FM layer. This spin current is perpendicular to the film plane. The generated spin current diffuses from the FM layer into the adjacent non-ferromagnetic (NM) layer. Due to the strong spin-orbit coupling effect of the NM layer material (e.g., the inverse spin Hall effect, ISHE), the flowing spin is subjected to a force perpendicular to its direction. This force effectively converts the angular momentum of the spin current into the directional motion of charge, thereby inducing a picosecond-level transient charge current in the NM layer.

[0036] Specifically, induced current The quantitative description is given by the following formula: ; in, For electric charge and current, For the spin Hall angle, is the spin current, and m is the magnetization vector.

[0037] This transient charge current oscillates violently in the nanoscale thin film structure, with a rate of change reaching the terahertz frequency band (10⁻¹⁰). 12 According to Maxwell's equations, any accelerating electric charge radiates electromagnetic waves. Therefore, this ultrafast current oscillation efficiently radiates broadband terahertz pulses outward.

[0038] In a specific implementation, the spin orbital moment (SOT) controls the magnetization direction 5, specifically including: In the non-ferromagnetic layer 3, the current undergoes a spin Hall effect (SHE), where flowing electrons are scattered to different sides due to their different spin directions, resulting in the spatial separation of spin-up and spin-down electrons. That is, a transverse charge current is successfully converted into a longitudinal pure spin current, perpendicular to the current direction. This spin current is injected into the adjacent ferromagnetic layer 2. Through exchange interactions at the interface, these spin-polarized electrons transfer their angular momentum to the local magnetic moment of the ferromagnetic layer 2. To align their own spin direction with the local magnetization direction 5, these electrons exert a torque on the magnetic moment, known as the spin orbital moment (SOT). This torque effectively exerts a force on the magnetization M, attempting to push it away from its current equilibrium direction. Driven by the SOT torque, the magnetization M begins damped precession, precessing around the effective magnetic field direction, and its precession angle gradually increases due to Gilbert damping. Ultimately, the magnetization vector M will overcome the energy barrier and stably flip to another easy axis direction (from the +x direction to the -x direction), completing one flip operation.

[0039] Specifically, the process of reversing the magnetization direction 5 can be described by the following formula: ; Where m is the magnetization vector of the ferromagnetic layer, and t is the time variable. It is the effective magnetic field of the ferromagnetic layer. It is the Gilbert damping factor. It is the gyromagnetic ratio. It is a torque caused by current, consisting of damping-like torque (DL) and field-like torque (FL).

[0040] It is derived from the following formula: ; in, and This refers to the proportionality coefficient between DL and FL torques and the current. It is a spin current. The spin Hall angle is proportional to the current value, therefore materials with a large spin Hall angle perform better in high-speed systems.

[0041] In a specific implementation, the communication system setup includes: (1) Cumulative amplitude modulation system Multiple spin electron emitters are arranged in a 4×4 array. Each emitter is controlled by an independent current source, enabling different magnetization directions, thus generating terahertz waves with different polarizations. When multiple emitters transmit signals simultaneously, the terahertz waves superimpose in space, forming a composite signal of varying amplitudes. The specific amplitude calculation formula is as follows: ; in, The amplitude of the synthesized signal, Let be the signal amplitude generated by the i-th transmitter, and n be the number of transmitters. This system can achieve 16 different amplitude states (16-PAM) and a data rate of up to 0.08 Tbit / s. Compared to a single transmitter, its maximum transmit power is increased by 16 times, making it suitable for operation in high signal-to-noise ratio (SNR) environments.

[0042] (2) Time-interlaced system

[0043] A delay line is placed in front of each transmitter; the delay line can be implemented using optical fiber or a dielectric substrate of varying lengths. The formula for calculating the delay time (τ) is as follows: τ=cL; Where L is the length of the delay line and c is the speed of light. By controlling the delay of the laser pulses, multiple transmitters emit signals sequentially. The emission time interval between each transmitter is 5 ps, thus achieving time-staggered emission and improving the modulation speed. This system can achieve a data rate of 0.2 Tbit / s, making it suitable for applications requiring high modulation speeds. Furthermore, the system supports multiple encoding methods, including bi-phase coding, pulse amplitude modulation (PAM), and pulse position modulation (PPM).

[0044] In a specific implementation, the biphase coding method specifically includes: In communication systems, the polarization state of terahertz wave 4 is altered by controlling the direction of the current to change the magnetization direction 5, thus achieving biphase coding: when the current direction changes, the magnetization direction 5 also changes, thereby changing the polarization state of terahertz wave 4. Biphase coding utilizes the positive and negative polarization states of terahertz wave 4 to determine data for data transmission. Biphase coding has high noise immunity because its decision threshold is 0, making it less sensitive to noise.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A terahertz pulse communication system based on spin-orbit torque regulation, characterized in that, The application relates to a spin electron emitter array, a regulation module, a coding module and a signal transmission module. The regulation module regulates the magnetization direction of the spin electron emitter through spin-orbit torque. The coding module is connected with the regulation module and adopts a two-phase coding mode. The signal transmission module transmits data based on the signal superposition or time-interleaved emission of the spin electron emitter array. The spin electron emitter adopts a ferromagnetic metal or non-magnetic metal heterojunction film, the heterojunction film is a CoFeB / Pt combination, a femtosecond laser pulse is focused and irradiated on the heterojunction to generate a spin-polarized current through an ultrafast demagnetization effect, the spin-polarized current is converted into a transient charge current through the inverse spin Hall effect of a non-ferromagnetic layer, and the transient charge current oscillates to radiate a terahertz pulse. 2.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 1, wherein The regulation module regulates the magnetization direction of the spin electron emitter through spin-orbit torque, including that a current in the non-ferromagnetic layer generates a spin Hall effect to convert into a longitudinal pure spin current, the spin current is injected into a ferromagnetic layer and transfers angular momentum through exchange interaction, a spin-orbit torque is applied to drive the magnetization intensity to precess around an effective magnetic field, and the magnetization intensity is flipped to a target easy axis direction by overcoming an energy barrier. 3.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 1, wherein, The spin electron emitter array comprises an accumulated amplitude modulation system. 4.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 1, wherein, A 4*4 emitter array is adopted, each emitter is controlled by an independent current source, multiple emitters emit signals simultaneously and the signals are superposed in space to form a synthesized signal with different amplitudes. The spin electron emitter array further comprises a time-interleaved system.

5. The terahertz pulse communication system based on spin-orbit torque modulation according to claim 4, wherein, A delay line is arranged in front of each emitter, multiple emitters emit signals in sequence by controlling the delay of laser pulses, the emission time interval is 5ps, and the two-phase coding, pulse amplitude modulation and pulse position modulation are supported. The two-phase coding mode changes the magnetization direction by controlling the current direction, and then adjusts the polarization state of the terahertz wave, and the positive and negative polarization states of the terahertz wave are used to determine binary 0 / 1 states.

6. The terahertz pulse communication system based on spin-orbit torque modulation according to claim 1, wherein, The amplitude of the synthesized signal satisfies the formula:

7. The terahertz pulse communication system based on spin-orbit torque modulation according to claim 4, wherein, The delay time of the delay line satisfies the formula: ； in, For the amplitude of the synthesized signal, Let be the signal amplitude of the i-th transmitter, and n be the number of transmitters. 8.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 5, wherein, tau=cL; Wherein, tau is the delay time, L is the length of the delay line, and c is the speed of light. The quantitative description of the transient charge current satisfies the formula: 9.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 2, wherein, The flipping satisfies the formula: ； wherein, is the charge current, is the spin Hall angle, is the spin current, m is the magnetization vector. 10.The terahertz pulse communication system based on spin-orbit torque modulation according to claim 3, wherein, ​ ； wherein, Heffis the effective magnetic field for the ferromagnetic layer, G is the Gilbert damping factor, γ is the gyromagnetic ratio, TSOTis the SOT torque, and, , , are the proportionality coefficients for the damping-like torque and the field-like torque, respectively, is the spin current.

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