A terahertz wave emitter and a preparation method and a regulation method thereof

Abstract

This application discloses a terahertz wave transmitter and its fabrication and control methods, relating to the field of terahertz wave transmitter technology. The terahertz wave transmitter includes a stacked flexible substrate layer, a ferromagnetic metal layer, and a heavy metal layer. The ferromagnetic metal layer is pre-magnetized in-plane to possess magnetism. In use, an incident femtosecond laser pulse passes through the flexible substrate layer and irradiates a preset position of the ferromagnetic metal layer, exciting the ferromagnetic metal layer to generate an ultrafast spin current. The spin current diffuses into the heavy metal layer and is converted into a transient charge current, thereby generating a terahertz wave. That is, a terahertz wave can be generated without an external magnetic field. Furthermore, the stacked structure consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer is bent towards the flexible substrate layer or towards the heavy metal layer, so that the preset position of the ferromagnetic metal layer is subjected to stress parallel to the magnetic field direction, changing the magnetic field strength at the preset position of the ferromagnetic metal layer and controlling the intensity of the generated terahertz wave. It is low in cost and easy to apply in practice.

Description

Technical Field

[0001] This application relates to the field of terahertz wave transmitter technology, and in particular to a terahertz wave transmitter and its preparation and control methods. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies ranging from 0.1 THz to 10 THz. This band lies between the infrared and microwave bands and possesses unique electronic energy, giving it many distinctive properties. It has important applications in medicine, biology, materials science, security inspection, and communications. With the increasing use of terahertz waves, the demand for terahertz sources is growing. In recent years, spintronics-based terahertz wave transmitters have emerged as promising technologies. These spintronics terahertz wave transmitters offer advantages such as wide spectral density, flexibility, and low cost, and have been widely studied and developed by researchers.

[0003] To maximize the efficiency of terahertz wave emission, spintronic terahertz wave transmitters typically apply an external magnetic field, usually achieved by a pair of permanent magnets or electromagnets. This compromises the compactness of the device. Current fieldless spintronic terahertz wave transmitters primarily rely on the exchange bias between ferromagnetic / antiferromagnetic structures, but their controllability is relatively limited. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a terahertz wave transmitter and its preparation and control methods, which generate terahertz waves under conditions without an external magnetic field and can effectively control the intensity of the terahertz waves.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0006] A terahertz wave transmitter, comprising:

[0007] Flexible substrate layer;

[0008] A ferromagnetic metal layer located on one side of the flexible substrate layer, the ferromagnetic metal layer being magnetic;

[0009] A heavy metal layer located on the side of the ferromagnetic metal layer opposite to the flexible substrate layer;

[0010] The stack consisting of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer is bent toward either the flexible substrate or the heavy metal layer, such that the ferromagnetic metal layer has tensile and compressive stresses at a predetermined position. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, and the direction of the tensile stress is perpendicular to the direction of the compressive stress. Furthermore, the magnetic field direction at the predetermined position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined position is the location where laser light passes through the flexible substrate and irradiates the ferromagnetic metal layer.

[0011] Optionally, the stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer is symmetrically bent towards the flexible substrate layer or towards the heavy metal layer, and the preset position is the middle position of the ferromagnetic metal layer along the bending direction.

[0012] Optionally, the tensile stress direction at a predetermined position of the ferromagnetic metal layer is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer;

[0013] Alternatively, the compressive stress direction at a predetermined position of the ferromagnetic metal layer is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer.

[0014] Optionally, the material of the flexible substrate layer includes polydimethylsiloxane or polyimide;

[0015] The thickness of the flexible substrate layer ranges from 10 μm to 10 mm, including the endpoint values.

[0016] Optionally, the material of the ferromagnetic metal layer includes Co, Fe, Ni, CoFe, or CoFeB;

[0017] The thickness of the ferromagnetic metal layer ranges from 2nm to 20nm, including the endpoint values.

[0018] Optionally, the material of the heavy metal layer includes Pt, W, Au, Ta, Au, or Ir;

[0019] The thickness of the heavy metal layer ranges from 2nm to 20nm, including the endpoint values.

[0020] A method for fabricating a terahertz wave transmitter includes:

[0021] Provide a flexible substrate layer;

[0022] A ferromagnetic metal layer is formed on one side of the flexible substrate layer;

[0023] A heavy metal layer is formed on the side of the ferromagnetic metal layer opposite to the flexible substrate layer;

[0024] The ferromagnetic metal layer is magnetized in-plane to make it magnetic.

[0025] The entire stack consisting of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer is bent towards the flexible substrate or towards the heavy metal layer, such that the ferromagnetic metal layer has tensile and compressive stresses at a predetermined position. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, the direction of the tensile stress is perpendicular to the direction of the compressive stress, and the magnetic field direction at the predetermined position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined position is the location where laser light passes through the flexible substrate and irradiates the ferromagnetic metal layer.

[0026] A method for controlling a terahertz wave transmitter, applied to any of the terahertz wave transmitters described above, the method comprising:

[0027] The intensity of the terahertz waves emitted by the terahertz wave transmitter can be controlled by adjusting the bending direction and curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer and the heavy metal layer.

[0028] Optionally, adjusting the bending direction of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter includes:

[0029] The stack of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter is bent towards the flexible substrate or towards the heavy metal layer, so that the ferromagnetic metal layer has tensile and compressive stress at a predetermined position. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, the direction of the tensile stress is perpendicular to the direction of the compressive stress, and the magnetic field direction at the predetermined position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined position is the position where the laser passes through the flexible substrate and irradiates the ferromagnetic metal layer.

[0030] Wherein, the tensile stress direction at the preset position of the ferromagnetic metal layer is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer;

[0031] Alternatively, the compressive stress direction at a predetermined position of the ferromagnetic metal layer is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer.

[0032] Optionally, adjusting the curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter includes:

[0033] The curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter is adjusted so that the stress value along the bending direction of the ferromagnetic metal layer in the tensile and compressive stresses at a preset position does not exceed 0.2×d, where d is the thickness of the flexible substrate layer in millimeters.

[0034] Compared with existing technologies, the above technical solution has the following advantages:

[0035] The terahertz wave transmitter provided in this application includes a flexible substrate, a ferromagnetic metal layer located on one side of the flexible substrate, and a heavy metal layer located on the side of the ferromagnetic metal layer facing away from the flexible substrate. The ferromagnetic metal layer is pre-magnetized in-plane to possess magnetism. Thus, when an incident femtosecond laser pulse passes through the flexible substrate and irradiates a predetermined position on the ferromagnetic metal layer, the ferromagnetic metal layer generates an ultrafast spin current under the excitation of the femtosecond laser. This spin current diffuses into the heavy metal layer and, under the action of spin-orbit coupling, is converted into a transient charge current, thereby generating a terahertz wave. Therefore, the terahertz wave transmitter provided in this application does not require an external magnetic field device during use; that is, it can generate terahertz waves without an external magnetic field.

[0036] Furthermore, in the terahertz wave transmitter provided in this application embodiment, the stack composed of a flexible substrate layer, a ferromagnetic metal layer, and a heavy metal layer is bent towards the flexible substrate layer or towards the heavy metal layer, so that the preset position of the ferromagnetic metal layer has tensile stress and compressive stress. The directions of the tensile stress and compressive stress are both tangent to the surface of the ferromagnetic metal layer, and the direction of the tensile stress is perpendicular to the direction of the compressive stress. Moreover, the magnetic field direction at the preset position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The preset position is the position where the laser passes through the flexible substrate layer and irradiates the ferromagnetic metal layer. Thus, the tensile stress and / or compressive stress at the preset position of the ferromagnetic metal layer will necessarily have a component parallel to the magnetic field direction, so that the preset position of the ferromagnetic metal layer is subjected to stress parallel to the magnetic field direction and generates strain, thereby changing the magnetic field strength at the preset position of the ferromagnetic metal layer.

[0037] If the preset position of the ferromagnetic metal layer is subjected to tensile stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer will increase, thereby increasing the intensity of the terahertz waves generated by the terahertz wave transmitter. If the preset position of the ferromagnetic metal layer is subjected to compressive stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer will decrease, thereby decreasing the intensity of the terahertz waves generated by the terahertz wave transmitter. This allows the intensity of the terahertz waves generated by the terahertz wave transmitter to be controlled, so that the intensity of the terahertz waves generated by the terahertz wave transmitter without an external magnetic field can be comparable to the intensity of the terahertz waves generated with an external magnetic field. Therefore, the terahertz wave transmitter can achieve high terahertz wave transmission efficiency without an external magnetic field.

[0038] In summary, the terahertz wave transmitter provided in this application has low production cost, does not require the application of an external magnetic field device, and the intensity of the generated terahertz wave can be flexibly controlled, making it convenient for practical applications. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the structure of a terahertz wave transmitter provided in an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of the structure of a terahertz wave transmitter provided in an embodiment of this application;

[0042] Figure 3 This is a schematic diagram of another terahertz wave transmitter provided in an embodiment of this application;

[0043] Figure 4 This is a schematic diagram of the structure of another terahertz wave transmitter provided in the embodiments of this application;

[0044] Figure 5 This is a schematic diagram of another terahertz wave transmitter provided in the embodiments of this application;

[0045] Figure 6 This is a schematic diagram of a method for fabricating a terahertz wave transmitter provided in an embodiment of this application.

[0046] Figure label:

[0047] Flexible substrate layer-11; ferromagnetic metal layer-12; heavy metal layer-13. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0050] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0051] As described in the background section, spintronic terahertz wave transmitters typically apply an external magnetic field to maximize terahertz wave emission efficiency. This external magnetic field is mainly achieved by a pair of permanent magnets or electromagnets, which is detrimental to the compactness of the device. Current fieldless spintronic terahertz wave transmitters are mainly based on the exchange bias between ferromagnetic / antiferromagnetic structures, but their controllability is relatively limited.

[0052] In view of this, embodiments of this application provide a terahertz wave transmitter. Figure 1 A schematic diagram of a terahertz wave transmitter provided in an embodiment of this application is shown, as follows: Figure 1 As shown, the terahertz wave transmitter includes a flexible substrate layer 11, a ferromagnetic metal layer 12 located on one side of the flexible substrate layer 11, and a heavy metal layer 13 located on the side of the ferromagnetic metal layer 12 away from the flexible substrate layer 11, wherein the ferromagnetic metal layer 12 is pre-magnetized in-plane to have magnetic properties.

[0053] Understandably, the incident femtosecond laser pulse passes through the flexible substrate 11 and irradiates a predetermined position on the ferromagnetic metal layer 12. The photon energy is absorbed by the ferromagnetic metal layer 12, and the electrons in the ferromagnetic metal layer 12 are excited to a state above the Fermi level, forming a non-equilibrium electron distribution. Due to the differences in physical properties such as density, band velocity, lifetime, and mobility of spin-up and spin-down electrons, a spin-polarized current is formed in the ferromagnetic metal layer 12 along the propagation direction (Z direction) of the laser pulse. When the spin current flows into the heavy metal layer 13 (a non-ferromagnetic layer), due to the strong spin-orbit coupling effect of the heavy metal layer 13, the spin-up and spin-down electrons will deflect in opposite directions. This deflection process leads to the generation of in-plane charge flow in the transverse direction, i.e., the anti-spin Hall effect (ISHE). In other words, the ferromagnetic metal layer 12 generates an ultrafast spin current under the excitation of the femtosecond laser. The spin current diffuses into the heavy metal layer 13 and is converted into a transient charge flow under the action of spin-orbit coupling, thereby generating terahertz waves. Therefore, it can be seen that the terahertz wave transmitter provided in this application embodiment does not require the application of an external magnetic field device during use, that is, it can generate terahertz waves without the application of an external magnetic field.

[0054] Furthermore, the flexible substrate layer 11 can be flexibly bent, so that the stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12 and the heavy metal layer 13 can be bent, thereby controlling the magnetism of the ferromagnetic metal layer 12 and controlling the intensity of the generated terahertz wave.

[0055] Optional, such as Figure 1As shown, the stack consisting of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent towards the flexible substrate 11. This allows the ferromagnetic metal layer 12 to have tensile stress at a predetermined position. The predetermined position of the ferromagnetic metal layer 12 is the location where the laser passes through the flexible substrate 11 and irradiates the ferromagnetic metal layer 12. Correspondingly, the predetermined position of the ferromagnetic metal layer 12 also has compressive stress. It can be understood that the directions of both tensile and compressive stress at the predetermined position of the ferromagnetic metal layer 12 are tangent to the surface of the ferromagnetic metal layer 12, and the directions of tensile and compressive stress are perpendicular to each other. It can also be understood that since the ferromagnetic metal layer 12 is pre-magnetized in-plane and thus has magnetism, the predetermined position of the ferromagnetic metal layer 12... The magnetic field direction is also tangent to the surface of the ferromagnetic metal layer 12. With this configuration, the tensile stress direction at the preset position of the ferromagnetic metal layer 12 can be along the X direction, and the compressive stress direction can be along the Y direction. The magnetic field direction at the preset position of the ferromagnetic metal layer 12 can be any direction in the plane formed by the X and Y directions. In other words, no matter which direction in the plane formed by the X and Y directions the magnetic field direction at the preset position of the ferromagnetic metal layer 12 is, the tensile stress and / or compressive stress at the preset position of the ferromagnetic metal layer 12 will necessarily have a component parallel to the magnetic field direction. This causes the preset position of the ferromagnetic metal layer 12 to be subjected to stress parallel to the magnetic field direction and thus produce strain, thereby changing the magnetic field strength at the preset position of the ferromagnetic metal layer 12.

[0056] If the preset position of the ferromagnetic metal layer 12 is subjected to tensile stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 will increase, thereby increasing the intensity of the terahertz wave generated by the terahertz wave transmitter. If the preset position of the ferromagnetic metal layer 12 is subjected to compressive stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 will decrease, thereby decreasing the intensity of the terahertz wave generated by the terahertz wave transmitter. This allows the intensity of the terahertz wave generated by the terahertz wave transmitter to be controlled, so that the intensity of the terahertz wave generated by the terahertz wave transmitter under conditions without an external magnetic field can be comparable to the intensity of the terahertz wave generated under conditions with an external magnetic field. Therefore, the terahertz wave transmitter can achieve high terahertz wave transmission efficiency under conditions without an external magnetic field.

[0057] Further optional, such as Figure 1As shown, the stack composed of flexible substrate 11, ferromagnetic metal layer 12 and heavy metal layer 13 is symmetrically bent towards the flexible substrate 11. The position where the laser shines through the flexible substrate 11 onto the ferromagnetic metal layer 12, which is the preset position, is the middle position of the ferromagnetic metal layer 12 along the bending direction. However, this application does not limit this. Alternatively, the stack composed of flexible substrate 11, ferromagnetic metal layer 12 and heavy metal layer 13 can also be symmetrically bent towards the flexible substrate 11. The position where the laser shines through the flexible substrate 11 onto the ferromagnetic metal layer 12, which is the preset position, can also be any other position of the ferromagnetic metal layer 12 along the bending direction other than the middle position. It depends on the specific situation.

[0058] Based on the fact that the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent towards the flexible substrate layer 11, optionally, as follows: Figure 2 As shown, the direction of tensile stress at the preset position of the ferromagnetic metal layer 12 is parallel to the direction of the magnetic field at the preset position of the ferromagnetic metal layer 12. Thus, the preset position of the ferromagnetic metal layer 12 is subjected to tensile stress parallel to the direction of the magnetic field, which increases the magnetic field strength at the preset position of the ferromagnetic metal layer 12, thereby increasing the intensity of the terahertz wave generated by the terahertz wave transmitter.

[0059] Based on the fact that the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent towards the flexible substrate layer 11, another optional feature is... Figure 3 As shown, the compressive stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12. Thus, the preset position of the ferromagnetic metal layer 12 is subjected to compressive stress parallel to the magnetic field direction, which reduces the magnetic field strength at the preset position of the ferromagnetic metal layer 12, thereby reducing the intensity of the terahertz wave generated by the terahertz wave transmitter.

[0060] Another option, such as Figure 4As shown, the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent towards the heavy metal layer 13. This allows the predetermined position of the ferromagnetic metal layer 12 to have compressive stress. The predetermined position of the ferromagnetic metal layer 12 is the location where the laser passes through the flexible substrate layer 11 and irradiates the ferromagnetic metal layer 12. Correspondingly, the predetermined position of the ferromagnetic metal layer 12 also has tensile stress. It can be understood that the compressive and tensile stress directions at the predetermined position of the ferromagnetic metal layer 12 are both tangent to the surface of the ferromagnetic metal layer 12, and the compressive and tensile stress directions are perpendicular to each other. It can also be understood that since the ferromagnetic metal layer 12 is pre-magnetized in-plane and thus has magnetism, the predetermined position of the ferromagnetic metal layer 12... The magnetic field direction is also tangent to the surface of the ferromagnetic metal layer 12. With this configuration, the compressive stress direction at the preset position of the ferromagnetic metal layer 12 can be along the X direction, and the tensile stress direction can be along the Y direction. The magnetic field direction at the preset position of the ferromagnetic metal layer 12 can be any direction in the plane formed by the X and Y directions. In other words, no matter which direction in the plane formed by the X and Y directions the magnetic field direction at the preset position of the ferromagnetic metal layer 12 is, the compressive stress and / or tensile stress at the preset position of the ferromagnetic metal layer 12 will necessarily have a component parallel to the magnetic field direction. This causes the preset position of the ferromagnetic metal layer 12 to be subjected to stress parallel to the magnetic field direction and thus produce strain, thereby changing the magnetic field strength at the preset position of the ferromagnetic metal layer 12.

[0061] If the preset position of the ferromagnetic metal layer 12 is subjected to compressive stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 will decrease, thereby reducing the intensity of the terahertz waves generated by the terahertz wave transmitter. If the preset position of the ferromagnetic metal layer 12 is subjected to tensile stress parallel to the magnetic field direction, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 will increase, thereby increasing the intensity of the terahertz waves generated by the terahertz wave transmitter. This allows the intensity of the terahertz waves generated by the terahertz wave transmitter to be controlled, so that the intensity of the terahertz waves generated by the terahertz wave transmitter under conditions without an external magnetic field can be comparable to the intensity of the terahertz waves generated under conditions with an external magnetic field. Therefore, the terahertz wave transmitter can achieve high terahertz wave transmission efficiency under conditions without an external magnetic field.

[0062] Further optional, such as Figure 4As shown, the stack composed of flexible substrate 11, ferromagnetic metal layer 12 and heavy metal layer 13 is symmetrically bent towards the heavy metal layer 13. The position where the laser shines through the flexible substrate 11 onto the ferromagnetic metal layer 12, which is the preset position, is the middle position of the ferromagnetic metal layer 12 along the bending direction. However, this application does not limit this. Alternatively, the stack composed of flexible substrate 11, ferromagnetic metal layer 12 and heavy metal layer 13 can also be symmetrically bent towards the heavy metal layer 13. The position where the laser shines through the flexible substrate 11 onto the ferromagnetic metal layer 12, which is the preset position, can also be any other position of the ferromagnetic metal layer 12 along the bending direction other than the middle position. It depends on the specific situation.

[0063] Based on the fact that the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent towards the heavy metal layer 13, optionally, as follows: Figure 4 As shown, the compressive stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12. Thus, the preset position of the ferromagnetic metal layer 12 is subjected to compressive stress parallel to the magnetic field direction, which reduces the magnetic field strength at the preset position of the ferromagnetic metal layer 12, thereby reducing the intensity of the terahertz wave generated by the terahertz wave transmitter.

[0064] Based on the overall bending of the stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 towards the heavy metal layer 13, another optional feature is... Figure 5 As shown, the direction of tensile stress at the preset position of the ferromagnetic metal layer 12 is parallel to the direction of the magnetic field at the preset position of the ferromagnetic metal layer 12. Thus, the preset position of the ferromagnetic metal layer 12 is subjected to tensile stress parallel to the direction of the magnetic field, which increases the magnetic field strength at the preset position of the ferromagnetic metal layer 12, thereby increasing the intensity of the terahertz wave generated by the terahertz wave transmitter.

[0065] It is understandable that, regardless of whether the stack composed of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 bends towards the flexible substrate 11 or towards the heavy metal layer 13, when the stack composed of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 bends symmetrically, and the laser passes through the flexible substrate 11 to irradiate the ferromagnetic metal layer 12 at the position where the laser is positioned, i.e., the preset position is the middle position of the ferromagnetic metal layer 12 along the bending direction, the tensile and compressive stresses at the middle position of the ferromagnetic metal layer 12 along the bending direction are relatively large. This also makes it easier to control the relationship between the tensile and compressive stress directions at the middle position of the ferromagnetic metal layer 12 along the bending direction and the magnetic field direction, thereby making it easier to control the intensity of the generated terahertz wave.

[0066] It is also understandable that regardless of whether the entire stack composed of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 bends towards the flexible substrate 11 or towards the heavy metal layer 13, when the tensile stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 increases, thereby increasing the intensity of the terahertz waves generated by the terahertz wave transmitter. When the compressive stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 decreases, thereby decreasing the intensity of the terahertz waves generated by the terahertz wave transmitter. In this way, it is convenient to control the relationship between the tensile stress direction and the compressive stress direction at the preset position of the ferromagnetic metal layer 12 and the magnetic field direction, thereby facilitating the control of the intensity of the generated terahertz waves.

[0067] Optionally, the flexible substrate 11 needs to be able to transmit an 800nm ​​laser so that the 800nm ​​laser can pass through the flexible substrate 11 to irradiate the ferromagnetic metal layer 12 and excite the ferromagnetic metal layer 12 to generate a spin current.

[0068] Optionally, the material of the flexible substrate 11 includes, but is not limited to, flexible materials such as polydimethylsiloxane (PDMS) or polyimide (PI).

[0069] Optionally, the thickness of the flexible substrate 11 can range from 10 μm to 10 mm, including the endpoint values. For example, the thickness of the flexible substrate 11 can be 100 μm, 500 μm, or 1 mm.

[0070] Optionally, the material of the ferromagnetic metal layer 12 includes, but is not limited to, magnetic materials such as Co, Fe, Ni, CoFe, or CoFeB.

[0071] Optionally, the thickness of the ferromagnetic metal layer 12 can range from 2nm to 20nm, including the endpoint values. For example, the thickness of the ferromagnetic metal layer 12 can be 2nm, 4nm, or 10nm.

[0072] Optionally, the material of the heavy metal layer 13 includes, but is not limited to, Pt, W, Au, Ta, Au, or Ir.

[0073] Optionally, the thickness of the heavy metal layer 13 can range from 2nm to 20nm, including the endpoint values. For example, the thickness of the heavy metal layer 13 can be 2nm, 4nm, or 10nm.

[0074] In summary, the terahertz wave transmitter provided in this application has low production cost, does not require the application of an external magnetic field device, and the intensity of the generated terahertz wave can be flexibly controlled, making it convenient for practical applications.

[0075] Accordingly, this application also provides a method for fabricating a terahertz wave transmitter. Figure 6 This application provides a schematic flowchart of a method for fabricating a terahertz wave transmitter, as illustrated in an embodiment of the present application. Figure 6 As shown, and in combination Figures 1-5 As shown, the fabrication method of this terahertz wave transmitter includes:

[0076] S10: Provide a flexible substrate layer 11.

[0077] S20: A ferromagnetic metal layer 12 is formed on one side of the flexible substrate layer 11.

[0078] Optionally, the ferromagnetic metal layer 12 can be grown using thin film preparation methods such as magnetron sputtering, molecular beam epitaxy, and pulsed laser deposition.

[0079] S30: A heavy metal layer 13 is formed on the side of the ferromagnetic metal layer 12 away from the flexible substrate layer 11.

[0080] Optionally, the heavy metal layer can be grown using thin film preparation methods such as magnetron sputtering, molecular beam epitaxy, and pulsed laser deposition.

[0081] S40: In-plane magnetization of the ferromagnetic metal layer 12 is performed to make the ferromagnetic metal layer 12 magnetic.

[0082] S50: The entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 is bent toward either the flexible substrate layer 11 or the heavy metal layer 13, so that the ferromagnetic metal layer 12 has tensile stress and compressive stress at a predetermined position. The directions of the tensile stress and compressive stress are both tangent to the surface of the ferromagnetic metal layer 12, the direction of the tensile stress is perpendicular to the direction of the compressive stress, and the magnetic field direction at the predetermined position of the ferromagnetic metal layer 12 is tangent to the surface of the ferromagnetic metal layer 12. The predetermined position is the position where the laser passes through the flexible substrate layer 11 and irradiates the ferromagnetic metal layer 12.

[0083] It should be noted that this application does not limit the order of in-plane magnetization of the ferromagnetic metal layer 12 in step S40, and bending the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 towards the flexible substrate layer 11 or towards the heavy metal layer 13 in step S50. That is, step S40, which involves in-plane magnetization of the ferromagnetic metal layer 12, can be performed first to make the ferromagnetic metal layer 12 magnetic, and then step S50, which involves bending the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13, towards the flexible substrate layer 11 or towards the heavy metal layer 13. The bending process can be performed by first bending the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 towards the flexible substrate layer 11 or towards the heavy metal layer 13 in step S50, and then magnetizing the ferromagnetic metal layer 12 in-plane in step S40 to make it magnetic. Finally, the ferromagnetic metal layer 12 is subjected to tensile stress and compressive stress at a predetermined position. The directions of the tensile stress and compressive stress are both tangent to the surface of the ferromagnetic metal layer 12, the direction of the tensile stress is perpendicular to the direction of the compressive stress, and the direction of the magnetic field at the predetermined position of the ferromagnetic metal layer 12 is tangent to the surface of the ferromagnetic metal layer 12.

[0084] It should also be noted that since the ferromagnetic metal layer 12 is a thin film, after in-plane magnetization of the ferromagnetic metal layer 12, the magnetic field direction at each point of the ferromagnetic metal layer 12 is parallel to the surface of the ferromagnetic metal layer 12. Then, when the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12 and the heavy metal layer 13 is bent toward the flexible substrate layer 11 or toward the heavy metal layer 13, the magnetic field direction at the preset position of the ferromagnetic metal layer 12 is tangent to the surface of the ferromagnetic metal layer 12. Furthermore, the magnetic field direction at the preset position of the ferromagnetic metal layer 12 can be controlled during in-plane magnetization of the ferromagnetic metal layer 12, and after the in-plane magnetization of the ferromagnetic metal layer 12 is completed, the magnetic field direction at the preset position of the ferromagnetic metal layer 12 can be fixed.

[0085] This application also provides a method for controlling a terahertz wave transmitter, applied to the terahertz wave transmitter provided in any of the above embodiments. The method for controlling the terahertz wave transmitter includes:

[0086] S100: The bending direction and curvature of the stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12 and the heavy metal layer 13 in the terahertz wave transmitter are adjusted to control the intensity of the terahertz wave emitted by the terahertz wave transmitter.

[0087] Specifically, controlling the bending direction of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter includes:

[0088] S110: The stack of flexible substrate layer 11, ferromagnetic metal layer 12 and heavy metal layer 13 in the terahertz wave transmitter is bent toward the flexible substrate layer 11 or the heavy metal layer 13, so that the preset position of ferromagnetic metal layer 12 has tensile stress and compressive stress. The direction of tensile stress and compressive stress are both tangent to the surface of ferromagnetic metal layer 12. The direction of tensile stress is perpendicular to the direction of compressive stress. The magnetic field direction of the preset position of ferromagnetic metal layer 12 is tangent to the surface of ferromagnetic metal layer 12. The preset position is the position where the laser passes through the flexible substrate layer 11 and irradiates the ferromagnetic metal layer 12.

[0089] The tensile stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12.

[0090] Alternatively, the compressive stress direction at a predetermined position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer 12.

[0091] As previously known, regardless of whether the entire stack composed of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 bends towards the flexible substrate 11 or towards the heavy metal layer 13, when the tensile stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 increases, thereby increasing the intensity of the terahertz waves generated by the terahertz wave transmitter. When the compressive stress direction at the preset position of the ferromagnetic metal layer 12 is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer 12, the magnetic field strength at the preset position of the ferromagnetic metal layer 12 decreases, thereby decreasing the intensity of the terahertz waves generated by the terahertz wave transmitter. Thus, it is convenient to control the relationship between the tensile and compressive stress directions at the preset position of the ferromagnetic metal layer 12 and the magnetic field direction, thereby facilitating the control of the intensity of the generated terahertz waves.

[0092] Furthermore, adjusting the curvature of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter includes:

[0093] S120: Adjust the curvature of the stack consisting of flexible substrate layer 11, ferromagnetic metal layer 12 and heavy metal layer 13 in the terahertz wave transmitter, so that the stress value along the bending direction of ferromagnetic metal layer 12 in the tensile stress and compressive stress at the preset position of ferromagnetic metal layer 12 does not exceed 0.2×d, where d is the thickness of flexible substrate layer 11 in millimeters.

[0094] Understandably, to a certain extent, the greater the curvature of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter—that is, the greater the curvature and the smaller the radius of curvature—the greater the tensile and compressive stresses at the preset positions of the ferromagnetic metal layer 12, and the easier it is to control the intensity of the generated terahertz waves. However, when the curvature of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter becomes large enough, that is, when the radius of curvature becomes small enough, the ability of the tensile and compressive stresses at the preset positions of the ferromagnetic metal layer 12 to control the intensity of the generated terahertz waves will tend to saturate.

[0095] It is also understandable that when the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter bends towards the flexible substrate layer 11, as... Figure 2 and Figure 3 As shown, among the tensile stress and compressive stress at the preset position of the ferromagnetic metal layer 12, the tensile stress is the stress along the bending direction of the ferromagnetic metal layer 12. At this time, if the tensile stress is parallel to the magnetic field direction, the intensity of the generated terahertz wave can be increased; if the tensile stress is perpendicular to the magnetic field direction, the intensity of the generated terahertz wave can be decreased.

[0096] Similarly, when the entire stack consisting of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter bends towards the heavy metal layer 13, as... Figure 4 and Figure 5 As shown, among the tensile stress and compressive stress at the preset position of the ferromagnetic metal layer 12, the compressive stress is the stress along the bending direction of the ferromagnetic metal layer 12. At this time, if the compressive stress is parallel to the magnetic field direction, the intensity of the generated terahertz wave can be reduced; if the compressive stress is perpendicular to the magnetic field direction, the intensity of the generated terahertz wave can be increased.

[0097] Furthermore, the tensile and compressive stresses at the predetermined positions of the ferromagnetic metal layer 12, with the stress along the bending direction of the ferromagnetic metal layer 12, can be expressed as ε = T / 2R, where T is the total thickness of the stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13, and R is the bending radius of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13. The thickness of the flexible substrate layer 11, expressed in millimeters, is denoted as d.

[0098] Through experimental research, the inventors discovered that by adjusting the curvature of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter, so that the value of the stress ε along the bending direction of the ferromagnetic metal layer 12 in the tensile and compressive stresses at the preset position of the ferromagnetic metal layer 12 exceeds 0.2×d, the ability of the stress along the bending direction of the ferromagnetic metal layer 12 in the tensile and compressive stresses at the preset position of the ferromagnetic metal layer 12 to control the intensity of the generated terahertz waves tends to saturate. Therefore, by adjusting the curvature of the entire stack composed of the flexible substrate layer 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter, so that the value of the stress ε along the bending direction of the ferromagnetic metal layer 12 in the tensile and compressive stresses at the preset position of the ferromagnetic metal layer 12 does not exceed 0.2×d, the intensity of the generated terahertz waves can be better controlled.

[0099] For example, the flexible substrate 11 has a thickness of 25 μm, and the thickness d (in millimeters) of the flexible substrate 11 is 0.025. By adjusting the curvature of the entire stack composed of the flexible substrate 11, the ferromagnetic metal layer 12, and the heavy metal layer 13 in the terahertz wave transmitter, the stress value along the bending direction of the ferromagnetic metal layer 12 at a predetermined position is kept below 0.2 × d = 0.005, so as to better control the intensity of the generated terahertz wave. It can be understood that the greater the thickness of the flexible substrate 11, the greater the stress value corresponding to 0.2 × d will be.

[0100] The various parts of this manual are described in a combination of parallel and progressive methods. Each part focuses on the differences between the other parts, and the same or similar parts can be referred to each other.

[0101] The features described above regarding the disclosed embodiments can be substituted or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application 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 wave transmitter, characterized in that, include: Flexible substrate layer; A ferromagnetic metal layer located on one side of the flexible substrate layer, the ferromagnetic metal layer being magnetic; A heavy metal layer located on the side of the ferromagnetic metal layer opposite to the flexible substrate layer; The stack consisting of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer is bent towards either the flexible substrate or the heavy metal layer, causing the ferromagnetic metal layer to have tensile and compressive stresses at a predetermined location. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, and the direction of the tensile stress is perpendicular to the direction of the compressive stress. Furthermore, the magnetic field direction at the predetermined location of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined location is where the laser passes through the flexible substrate and irradiates the ferromagnetic metal layer, causing the ferromagnetic metal layer to generate an ultrafast spin current under the excitation of the femtosecond laser. The spin current diffuses into the heavy metal layer and is converted into a transient charge current under the action of spin-orbit coupling, thereby generating terahertz waves.

2. The terahertz wave transmitter according to claim 1, characterized in that, The stack consisting of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer is symmetrically bent toward either the flexible substrate or the heavy metal layer, with the preset position being the middle position of the ferromagnetic metal layer along the bending direction.

3. The terahertz wave transmitter according to claim 1, characterized in that, The direction of tensile stress at a predetermined position of the ferromagnetic metal layer is parallel to the direction of magnetic field at the predetermined position of the ferromagnetic metal layer; Alternatively, the compressive stress direction at a predetermined position of the ferromagnetic metal layer is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer.

4. The terahertz wave transmitter according to any one of claims 1-3, characterized in that, The material of the flexible substrate layer includes polydimethylsiloxane or polyimide; The thickness of the flexible substrate layer ranges from 10 μm to 10 mm, including the endpoint values.

5. The terahertz wave transmitter according to any one of claims 1-3, characterized in that, The material of the ferromagnetic metal layer includes Co, Fe, Ni, CoFe, or CoFeB; The thickness of the ferromagnetic metal layer ranges from 2nm to 20nm, including the endpoint values.

6. The terahertz wave transmitter according to any one of claims 1-3, characterized in that, The material of the heavy metal layer includes Pt, W, Au, Ta, Au, or Ir; The thickness of the heavy metal layer ranges from 2nm to 20nm, including the endpoint values.

7. A method for fabricating a terahertz wave transmitter, characterized in that, include: Provide a flexible substrate layer; A ferromagnetic metal layer is formed on one side of the flexible substrate layer; A heavy metal layer is formed on the side of the ferromagnetic metal layer opposite to the flexible substrate layer; The ferromagnetic metal layer is magnetized in-plane to make it magnetic. The entire stack consisting of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer is bent towards either the flexible substrate or the heavy metal layer, so that a predetermined position of the ferromagnetic metal layer has tensile and compressive stresses. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, and the direction of the tensile stress is perpendicular to the direction of the compressive stress. The magnetic field direction at the predetermined position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined position is the location where the laser passes through the flexible substrate and irradiates the ferromagnetic metal layer, so that the ferromagnetic metal layer generates an ultrafast spin current under the excitation of the femtosecond laser. The spin current diffuses into the heavy metal layer and is converted into a transient charge current under the action of spin-orbit coupling, thereby generating terahertz waves.

8. A method for controlling a terahertz wave transmitter, characterized in that, The method for controlling the terahertz wave transmitter, applicable to any one of claims 1-6, comprises: The intensity of the terahertz waves emitted by the terahertz wave transmitter can be controlled by adjusting the bending direction and curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer and the heavy metal layer.

9. The method for controlling a terahertz wave transmitter according to claim 8, characterized in that, Adjusting the bending direction of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter includes: The stack of the flexible substrate, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter is bent towards the flexible substrate or towards the heavy metal layer, so that the ferromagnetic metal layer has tensile and compressive stress at a predetermined position. The directions of the tensile and compressive stresses are both tangent to the surface of the ferromagnetic metal layer, the direction of the tensile stress is perpendicular to the direction of the compressive stress, and the magnetic field direction at the predetermined position of the ferromagnetic metal layer is tangent to the surface of the ferromagnetic metal layer. The predetermined position is the position where the laser passes through the flexible substrate and irradiates the ferromagnetic metal layer. Wherein, the tensile stress direction at the preset position of the ferromagnetic metal layer is parallel to the magnetic field direction at the preset position of the ferromagnetic metal layer; Alternatively, the compressive stress direction at a predetermined position of the ferromagnetic metal layer is parallel to the magnetic field direction at the predetermined position of the ferromagnetic metal layer.

10. The method for controlling a terahertz wave transmitter according to claim 9, characterized in that, Adjusting the curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter includes: The curvature of the entire stack consisting of the flexible substrate layer, the ferromagnetic metal layer, and the heavy metal layer in the terahertz wave transmitter is adjusted so that the stress value along the bending direction of the ferromagnetic metal layer in the tensile and compressive stresses at a preset position does not exceed 0.2×d, where d is the thickness of the flexible substrate layer in millimeters.

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