Spin-orbit torque controlled spin-micro-led array device and polarization encryption communication method

Abstract

This invention discloses a spin-orbit moment controlled Spin-Micro-LED array device, comprising an array of flip-chip Spin-Micro-LED pixel units. Each pixel unit includes a flip-chip Micro-LED structure, a spin injection layer deposited thereon, and an electrode group. The electrode group includes a SOT driving electrode group and an LED driving electrode group. The LED driving electrode group is used to drive the flip-chip Micro-LED structure to emit light. The SOT driving electrode group is connected to both ends of the spin injection layer to apply an in-plane SOT driving current to the spin injection layer. The array is an M×N matrix arrangement, where M≥2, N≥2, and M and N are positive integers. A polarization-coded visible light communication system and method are also disclosed. This invention combines spintronics with Micro-LED technology to achieve direct control of the polarization state of light by electrical signals and physical layer hardware encryption, balancing high-speed visible light communication with polarization-coded encryption capabilities.

Description

Technical Field

[0001] This invention relates to a spin-micro-LED array device with spin orbital moment control and a polarization-encrypted communication method, belonging to the field of optical communication technology. Background Technology

[0002] Micro-LED refers to light-emitting diode devices with a chip size of less than 100 micrometers. Benefiting from its miniaturization effect, Micro-LED exhibits excellent modulation bandwidth characteristics and has significant application potential in the field of visible light communication (VLC). In recent years, research on the communication performance of Micro-LED has continued to deepen, and the data transmission rate of a single Micro-LED device has exceeded the Gbps level, fully demonstrating its application value in the field of high-speed optical communication. Spin-LED is a device technology that uses a spin-polarized carrier injection mechanism to control the degree of circular polarization (DOCP) of emitted photons by depositing a ferromagnetic thin layer in the active region or surface of a traditional LED device. Its working principle is based on spin-orbit interaction: when spin-polarized electrons recombine with holes, the conservation of angular momentum determines the polarization state of the emitted photons, thereby achieving active electrical control of the polarization characteristics of light. Spin-Orbit Torque (SOT) is a technique that utilizes the spin Hall effect or interface Rashba effect in heavy metal / ferromagnetic heterostructures. By applying an in-plane current to the heavy metal layer, a spin current is generated at the interface, which in turn applies a torque to the magnetization direction of the ferromagnetic layer, thereby achieving magnetization reversal or control. Introducing the SOT mechanism into the Spin-LED system allows for precise control of the magnitude and direction of the injected current, enabling dynamic control of the magnetization state of the ferromagnetic layer and continuous, reversible adjustment of the circular polarization of the emitted light. This approach achieves direct and rapid control of the polarization state of light by an electrical signal, overcoming the limitations of traditional polarization control that relies on external optical components.

[0003] Since circular polarization, as an intrinsic quantum property of photons, can serve as an independent information carrier for encoding and transmitting information, this characteristic provides the physical basis for encrypted optical communication technology based on polarization state multiplexing. Based on this principle, combining SOT technology with Spin-LED devices can construct a novel optical communication architecture with polarization-encoded encryption capabilities, enabling covert transmission of information along the polarization dimension, preventing unauthorized parties without circular polarization analysis capabilities from obtaining the correct information. This technical approach represents the cross-integration of spintronics and optoelectronics. Building upon this, further combining Spin-LED and Micro-LED technologies to construct SOT-controlled Spin-Micro-LED arrays is expected to simultaneously possess the high-bandwidth communication advantages of Micro-LEDs and the polarization-encoded encryption capabilities of Spin-LEDs, providing a new technical approach for next-generation high-speed encrypted visible light communication systems. Summary of the Invention

[0004] This invention discloses a spin-micro-LED array device with spin orbital moment control.

[0005] The technical solution adopted in this invention is as follows: A spin-orbit moment controlled Spin-Micro-LED array device is characterized by comprising an array of flip-chip Spin-Micro-LED pixel units, each pixel unit comprising a flip-chip Micro-LED structure, a spin injection layer deposited thereon, and an electrode assembly. The spin injection layer includes a spin Hall effect heavy metal layer and a ferromagnetic layer. The electrode group includes an SOT driving electrode group and an LED driving electrode group. The LED driving electrode group is used to drive the flip-chip Micro-LED structure to emit light. The SOT driving electrode group is connected to both ends of the spin injection layer and applies an in-plane SOT driving current to the spin injection layer. The array is arranged in an M×N matrix, where M≥2, N≥2, and M and N are positive integers.

[0006] The heavy metal layer utilizes the spin Hall effect to convert in-plane charge current into a spin current perpendicular to the current direction, thereby applying a spin orbital moment to the ferromagnetic layer and achieving electrical control over the magnetization direction of the ferromagnetic layer.

[0007] By adjusting the magnitude and direction of the SOT control current applied to the spin injection layer, the magnetization state of the ferromagnetic layer can be continuously and reversibly controlled, thereby adjusting the circular polarization degree of the light emitted by each pixel unit and realizing information encoding based on polarization state. Polarization degree itself, as a quantum property of light, can serve as an independent information carrier, adding an information encoding dimension in addition to the intensity dimension, which can broaden the single-channel transmission rate.

[0008] Preferably, the flip-chip Micro-LED structure includes a buffer layer, a p-type GaN layer, a multi-quantum-well active region, and an n-type GaN layer sequentially grown on a substrate. An insulating layer is disposed on the n-type GaN layer, and an injection window is formed on the insulating layer. The spin injection layer is electrically connected to the n-type GaN layer through the injection window. The spin injection layer also includes a tunneling barrier layer disposed on a ferromagnetic layer, forming a three-layer structure of a tunneling barrier layer, a ferromagnetic layer, and a spin Hall effect heavy metal layer.

[0009] Preferably, the tunneling barrier layer material is selected from at least one of Al2O3 and MgO, and the thickness is 1-4 nm; the ferromagnetic layer material is selected from at least one of CoFeB, Co, and CoPt, and the thickness is 0.8-2 nm; the spin Hall effect heavy metal layer material is selected from at least one of Pt, Ta, and W, and the thickness is 1-5 nm.

[0010] Preferably, the SOT driving electrode group includes a first electrode and a second electrode, which are respectively connected to both ends of the spin injection layer. The LED driving electrode group includes a third electrode and a fourth electrode. The third electrode is a cathode electrode connected to the spin injection layer. All arrayed pixel units share a common substrate layer, a buffer layer, and a portion of the p-type GaN layer. The fourth electrode is a common anode, disposed on the common p-type GaN layer. The SOT control loop (first and second electrodes) and the LED light-emitting driving loop (third and fourth electrodes) are independent of each other and do not interfere with each other, so as to achieve independent control of the circular polarization degree and light emission state of the emitted light of each pixel unit.

[0011] Preferably, the thickness of the n-type GaN layer is 20–80 nm. This thickness range balances the effective injection efficiency of spin-polarized carriers into the active region with the forward voltage characteristics of the device: if the thickness is too small, the ohmic contact quality decreases; if the thickness is too large, the relaxation loss of spin polarization during transmission increases.

[0012] The present invention also discloses a polarization-coded visible light communication system based on a Spin-Micro-LED array device, including a transmitter and a receiver; The transmitting end includes the aforementioned Spin-Micro-LED array device and an SOT control circuit. The SOT control circuit independently controls the DOCP direction of each pixel unit to form a DOCP distribution matrix for encoded transmission data. The receiving end includes a circular polarization analyzer array and a photodetector array. The circular polarization analyzer array and the photodetector array work in parallel to synchronously read the DOCP value and light intensity information of the emitted light of each pixel unit. The receiving end processes the synchronously acquired light intensity information according to the read DOCP distribution matrix to restore the real transmitted data.

[0013] This invention also discloses a polarization-coded visible light communication method, implemented based on the aforementioned Spin-Micro-LED array device. Within a unit transmission time, each pixel unit of the Spin-Micro-LED array device independently transmits binary data, with 1 and 0 represented by an emitting state and an off state, respectively. Simultaneously, the SOT control circuit assigns a predetermined circular polarization direction to each pixel unit. After the unit transmission time ends, the binary values ​​transmitted by each pixel unit are assigned corresponding signs according to their circular polarization direction: positive values ​​are assigned to pixel unit data with positive circular polarization, and negative values ​​are assigned to pixel unit data with negative circular polarization. The algebraic sum of all pixel unit data is then obtained to obtain the final transmitted value. The receiving end verifies and reconstructs the true transmitted value according to the same rules, based on the circular polarization direction read by the circular polarization analyzer array and the pixel unit data read by the photodetector array.

[0014] Preferably, a receiver that does not have circular polarization resolution capability can only obtain the raw light intensity data of each pixel unit and cannot determine the positive or negative direction of the circular polarization degree of each pixel unit. Therefore, it cannot correctly apply the operation symbols, and the resulting algebraic sum does not match the actual transmitted value, and cannot restore the actual transmitted information.

[0015] The beneficial effects of this invention are as follows: (1) Direct and rapid control of the circular polarization state of light by electrical signals is realized. By using the SOT effect to adjust the magnetization state of the ferromagnetic layer by controlling the magnitude and direction of the current, the circular polarization degree of the emitted light can be continuously adjusted. It does not rely on any external optical components, has a compact structure, and a fast response speed.

[0016] (2) It combines high-speed communication and physical layer encryption. The inherent high modulation bandwidth of Micro-LED (up to Gbps level for a single device) ensures the high-speed data transmission capability of the system, while the circular polarization degree, as an independent information carrier, realizes the encryption encoding of the polarization dimension. The two are organically integrated into the same device platform.

[0017] (3) The array design supports matrix addressing, and the polarization state and emission state of each pixel unit can be independently and synchronously controlled, providing a technical foundation for multi-channel polarization multiplexing communication and image-level polarization coding. The array design enables each pixel unit to transmit data independently and participate in algebraic sum operations. The larger the array size, the more the number of symbol combinations that the attacker needs to guess increases exponentially, and the encryption strength increases significantly with the expansion of the array size. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view of a single flip-chip Spin-Micro-LED pixel unit of the present invention.

[0019] Figure 2This is a three-dimensional schematic diagram of the 3×3 Spin-Micro-LED array of the present invention, showing the distribution and connection relationship of the four electrodes.

[0020] Figure 3 This is a schematic diagram of the overall framework of the polarization-coded visible light communication system of the present invention, showing the composition of the transmitter SOT control circuit and the Spin-Micro-LED array, as well as the structural relationship of the parallel operation of the receiver circular polarization analyzer array and the photodetector array.

[0021] Figure 4 This is a schematic diagram of the polarization coding algebra and calculation process of the present invention, showing the DOCP direction and transmission value of each pixel unit at the transmitting end, as well as the process by which a legitimate receiver calculates the algebra and restores the true transmission value according to the DOCP symbol, and compares it with the erroneous result obtained by a receiver that does not have circular polarization resolution capability. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as “up,” “down,” “front,” “back,” “left,” “right,” etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the scope of protection of this invention.

[0024] Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources.

[0025] Example 1: A SOT-controlled Spin-Micro-LED array device Combination Figure 1 and Figure 2 The device structure of Example 1 will be described.

[0026] Overall device structure: In this embodiment, the array consists of 9 flip-chip Spin-Micro-LED pixel units of 3×3, each pixel unit is 60µm in size and the pixel pitch is 100µm.

[0027] (1) See Figure 1A single flip-chip Spin-Micro-LED pixel unit comprises the following layers from the substrate upwards: Sapphire substrate 1; Buffer layer 2; p-type GaN layer 3; Multi-quantum-well active region 4; The n-type GaN layer 5 has a thickness of 30 nm. This thickness ensures effective injection of spin-polarized carriers while keeping spin relaxation losses within an acceptable range. Insulation layer 6; The spin injection layer 7 is composed of a heterostructure of MgO (2nm) / CoFeB (2nm) / Ta (5nm). The Ta layer generates spin current using the spin Hall effect. The CoFeB layer and the interface with the underlying MgO form a vertical magnetic anisotropy, which stabilizes the magnetization direction in two states, upward or downward, corresponding to the positive and negative values ​​of the circular polarization degree of the emitted light of the device, respectively. Metal electrode layer 8, the material is Ti / Au.

[0028] (2) See Figure 2 Each pixel unit is configured with four electrodes. Electrodes 81 and 82 are located at opposite ends of the spin injection layer and are used to apply in-plane SOT driving current. Electrode 83 is connected to the spin injection layer and works with electrode 84 to drive the LED light emission; electrode 84 is a common p-polar electrode, which makes ohmic contact with the p-type GaN layer and serves as a common anode. The SOT control circuit (electrodes 81 and 82) and the LED light emission driving circuit (electrodes 83 and 84) are independent of each other.

[0029] (3) Working process: When an in-plane current is applied to electrodes 81 and 82, and the current density exceeds the critical value, the Ta layer generates a sufficient spin current, which applies a spin orbital moment to the CoFeB ferromagnetic layer, causing its magnetization direction to reverse. By changing the current flow direction (electrode 81->82 or electrode 82->81), the magnetization state can be switched to upward or downward respectively. When magnetized upward, the circular polarization coefficient (DOCP) of the emitted light is positive, approximately +15%; when magnetized downward, the DOCP is negative, approximately -15%. At the same time, a forward bias voltage of 4V is applied to electrodes 83 and 84 to drive the light emission of the multi-quantum-well active region.

[0030] Examples 2-6

[0031] In this set of embodiments, the device structure and working process are basically the same as those in Embodiment 1, the difference being the different spin injection layer material system.

[0032] The spin-injected layer adopts one of the following heterostructures: Example 2: MgO / CoFeB / Pt; Example 3: MgO / CoFeB / W; Example 4: MgO / Co / Ta; Example 5: MgO / CoPt / Ta; Example 6: Al2O3 / CoPt / Ta; The tunneling barrier layer has a thickness of 1-2 nm, the ferromagnetic layer has a thickness of 3 nm, and the spin Hall layer has a thickness of 5 nm. Correspondingly, the n-type GaN layer has a thickness of 20 nm. The remaining structure, electrode configuration, and operating parameters are the same as in Example 1. It has been verified that changing the current direction of the SOT driving electrode group can reverse the magnetization state of the ferromagnetic layer.

[0033] Based on Example 2, the MgO layer thickness was extended to 4 nm, the CoFeB thickness was adjusted to 0.8 nm, and the Pt layer thickness was adjusted to 1 nm, which can also achieve DOCP deflection.

[0034] Example 7: A polarization-encrypted communication method based on the above array Combination Figure 3 and Figure 4 A specific implementation of the encrypted communication method of the present invention will be described.

[0035] (1) See Figure 3 The transmitting end adopts the 3×3 Spin-Micro-LED array described in Example 1, and independently drives the DOCP direction of each pixel unit with the SOT control circuit; the receiving end is equipped with a circular polarization analyzer array and a photodetector array, which work in parallel to synchronously read the DOCP value and light intensity information of each pixel unit.

[0036] (2) See Figure 4 Within a certain unit transmission time, the SOT control circuit will switch each pixel unit to the predetermined DOCP direction. The number of bits of binary data transmitted by a single pixel unit in a single transmission can be flexibly defined according to actual needs and is not limited to a specific number of bits.

[0037] This example uses 3 bits of binary (000~111, corresponding to decimal 0~7): ch1(+) transmits data: 100 (decimal value 4) ch2(+) transmits data: 011 (decimal value 3) ch3(-) transmits data: 011 (decimal value 3) ch4(+) transmits data: 010 (decimal value 2) ch5(-) transmits data: 001 (decimal value 1) ch6(+) transmits data: 110 (decimal value 6) ch7(-) transmits data: 101 (decimal value 5) ch8(+) transmits data: 010 (decimal value 2) ch9(+) transmits data: 100 (decimal value 4) After each unit transmission time, apply operators in the DOCP direction for each pixel and calculate the algebraic sum of all data: (+4)+(+3)+(-3)+(+2)+(-1)+(+6)+(-5)+(+2)+(-4)= 10 (00001010) The final transmitted value is 10 (00001010). The receiving end reads the DOCP direction of each pixel through a circular polarization analyzer, reads the data of each pixel through a photodetector, and verifies it according to the same rules, obtaining the same result.

[0038] Since the data that can be transmitted on a single channel is 000 to 111 (0 to 7), the final transmitted value can be 11000001 to 00111111 (-63 to 63).

[0039] (3) Eavesdroppers lacking circular polarization resolution can only read the light intensity data of each pixel and obtain the original values ​​of each channel, but cannot determine the positive or negative direction of the DOCP of each pixel, and therefore cannot correctly apply the operation. Taking this embodiment as an example, each of the 9 data pixels has two possibilities, positive and negative, with a total of 2 9 There are 512 possible symbol combinations. The probability that an eavesdropper will guess the correct combination is 1 / 512. This probability decreases further as the array size increases.

[0040] Additional notes: This embodiment uses a 3×3 array as an example for illustration. The array structure of this invention is also applicable to M×N matrix arrangements of other sizes. The larger the array size, the more pixel units participate in the calculation, the wider the range of the final transmitted values, and the more symbol combinations the attacker needs to guess. M×N The encryption strength increases exponentially with the increase of array size.

[0041] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A spin-micro-LED array device with spin orbital moment control, characterized in that, It includes arrayed flip-chip Spin-Micro-LED pixel units, each pixel unit including a flip-chip Micro-LED structure, a spin-injection layer deposited thereon, and an electrode assembly; The spin injection layer includes a spin Hall effect heavy metal layer and a ferromagnetic layer. The electrode group includes an SOT driving electrode group and an LED driving electrode group. The LED driving electrode group is used to drive the flip-chip Micro-LED structure to emit light. The SOT driving electrode group is connected to both ends of the spin injection layer and applies an in-plane SOT driving current to the spin injection layer. The array is arranged in an M×N matrix, where M≥2, N≥2, and M and N are positive integers.

2. The Spin-Micro-LED array device according to claim 1, characterized in that: The flip-chip Micro-LED structure includes a buffer layer, a p-type GaN layer, a multi-quantum-well active region, and an n-type GaN layer grown sequentially on a substrate. An insulating layer is disposed on the n-type GaN layer, and an injection window is formed on the insulating layer. The spin injection layer is electrically connected to the n-type GaN layer through the injection window. The spin injection layer also includes a tunneling barrier layer disposed on a ferromagnetic layer, forming a three-layer structure of a tunneling barrier layer, a ferromagnetic layer, and a spin Hall effect heavy metal layer.

3. The Spin-Micro-LED array device according to claim 2, characterized in that: The tunneling barrier layer material is selected from at least one of Al2O3 and MgO, with a thickness of 1 to 4 nm; the ferromagnetic layer material is selected from at least one of CoFeB, Co, and CoPt, with a thickness of 0.8 to 2 nm; the spin Hall effect heavy metal layer material is selected from at least one of Pt, Ta, and W, with a thickness of 1 to 5 nm.

4. The Spin-Micro-LED array device according to claim 3, characterized in that: The SOT driving electrode group includes a first electrode and a second electrode, which are respectively connected to the two ends of the spin injection layer. The LED driving electrode group includes a third electrode and a fourth electrode. The third electrode is a cathode electrode connected to the spin injection layer. All array-type pixel units share a common substrate layer, a buffer layer, and a portion of the p-type GaN layer. The fourth electrode is a common anode and is disposed on the common p-type GaN layer.

5. The Spin-Micro-LED array device according to claim 4, characterized in that: The thickness of the n-type GaN layer is 20–80 nm.

6. A polarization-coded visible light communication system based on a Spin-Micro-LED array device, comprising a transmitter and a receiver; The transmitting end includes the Spin-Micro-LED array device according to any one of claims 1-5, and the SOT control circuit, wherein the SOT control circuit independently controls the DOCP direction of each pixel unit to form a DOCP distribution matrix for encoding and transmitting data; The receiving end includes a circular polarization analyzer array and a photodetector array. The circular polarization analyzer array and the photodetector array work in parallel to synchronously read the DOCP value and light intensity information of the emitted light of each pixel unit. The receiving end processes the synchronously acquired DOCP value and light intensity information according to the read DOCP distribution matrix to restore the real transmitted data.

7. A method for polarization-coded visible light communication, implemented based on the Spin-Micro-LED array device according to any one of claims 1-5, characterized in that: During a unit transmission time, each pixel unit of the Spin-Micro-LED array independently transmits binary data, with 1 and 0 represented by the light-emitting state and the off state, respectively. At the same time, the SOT control circuit assigns a predetermined circular polarization direction to each pixel unit. After the unit transmission time ends, the binary values ​​transmitted by each pixel unit are assigned corresponding signs according to their circular polarization direction: the data of the pixel unit with positive circular polarization is assigned a positive value, and the data of the pixel unit with negative circular polarization is assigned a negative value. The algebraic sum of all pixel unit data is obtained to obtain the final transmitted value. The receiving end verifies and restores the true transmitted value according to the same rules based on the circular polarization direction of each pixel unit read by the circular polarization analyzer array and the data of each pixel unit read by the photodetector array.

8. The polarization-coded visible light communication method according to claim 7, characterized in that: Receivers lacking circular polarization resolution can only acquire the raw light intensity data of each pixel unit, and cannot determine the positive or negative direction of the circular polarization degree of each pixel unit. Therefore, they cannot correctly apply the operation symbols, and the resulting algebraic sum does not match the actual transmitted value, making it impossible to restore the actual transmitted information.

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