Monolithic multifunctional integrated spin terahertz device

Abstract

The application discloses a monolithic multifunctional integrated spin terahertz device, and belongs to the technical field of sensing, and solves the problem of multifunctional modulation of terahertz device integration in the prior art. The technical scheme of the application comprises a spin terahertz antenna unit, the spin terahertz antenna unit comprises a substrate dielectric substrate, a spin film and a waveguide antenna. The waveguide antenna is arranged on the upper surface of the substrate dielectric substrate and is uniformly arranged around the spin film, or the waveguide antenna is located on the upper surface of the spin film and is uniformly arranged around the center of the upper surface of the spin film, thereby realizing the integrated active regulation and control of the spin terahertz unit. By using the amplitude-frequency characteristics of the structure, a spin phased array can be constructed, and an actively tunable spin phased array is realized. The technical scheme of the application constructs a multifunctional device having a modulation effect on terahertz radiation, realizes multifunctional monolithic integration of terahertz wave generation, enhancement and regulation, and has great application potential.

Description

Technical Field

[0001] This invention relates to a monolithic, multifunctional integrated spin terahertz device, and relates to the fields of optics and sensing technology. Background Technology

[0002] Terahertz active phased arrays based on metamaterial antennas are important monolithic, multifunctional integrated spin terahertz devices. Terahertz electromagnetic waves radiated outward from the spin source are processed by the front-end circuitry, transmitted through a waveguide to the antenna, and radiated outward. The metamaterial integrated on the antenna modulates the radiated electromagnetic waves. Information metamaterials are actively programmable, enabling beam control and facilitating the construction of high-power integrated devices.

[0003] Terahertz polarization modulators primarily utilize anisotropic resonant unit structures to create different phase abrupt changes for two polarizations on a metasurface. These include waveplates and chiral (optical rotation) controllers. Broadband waveplates can be fabricated on dielectric materials; sandwiching a broadband waveplate within a metamaterial is a typical polarization modulator structure. The waveplate can be processed according to the modulation function. Polarization modulators can be used to control the polarization of terahertz waves, such as modulating linearly polarized light into circularly polarized light. The main working principle of the modulator is the different phase abrupt changes for two polarizations on the metasurface, which requires the waveplate to have birefringence. Currently, most terahertz waveplates utilize the inherent birefringence of natural materials, such as crystalline quartz and liquid crystals. Induced birefringence can also be achieved by stacking polymers or using grating structures.

[0004] The polarization of terahertz waves emitted from a spin source can be modulated by altering the applied magnetic field. This approach can be further combined with metamaterials for design. A spin terahertz source radiates linearly polarized terahertz waves, and the resulting terahertz electromagnetic waves always have a polarization direction perpendicular to the applied magnetic field. Therefore, by rotating the applied magnetic field and changing its field distribution, the linear polarization direction of the terahertz waves can be modulated. When the applied magnetic field is uniformly distributed, the generated terahertz pulses are always linearly polarized. With careful design of the magnetic field, elliptically polarized terahertz waves can also be generated. When a curved magnetic field passes through a heterostructure, a redistribution of magnetic moments occurs along the magnetic field direction, resulting in local magnetic moment differences. Therefore, the far-field terahertz electromagnetic waves generated by mutually perpendicular electric field components have different phases, enabling the generation of elliptically polarized terahertz electromagnetic waves.

[0005] Existing methods for achieving the control effect mainly include patterned ferromagnetic heterostructures, external magnetic field control of terahertz radiation, terahertz active phased arrays based on metamaterial antennas, and terahertz polarization modulators.

[0006] Patterned ferromagnetic heterostructures (patterned spin thin films) are an important approach for terahertz modulation. Their basic principle involves fabricating striped or block-shaped spin structures using micro / nano fabrication techniques such as etching. These patterned spin thin films offer significant advantages in amplitude and frequency modulation, with characteristic parameter variations stemming from changes in duty cycle and shielding charge effects. Patterned spin thin films can be categorized into stripe and block shapes, and the desired modulation effect can be achieved by adjusting the pattern. However, a drawback is that the fabricated patterns can only achieve specific modulation effects and cannot achieve dynamic modulation. Furthermore, the overall area of ​​the patterned metal thin film is always smaller than that of a complete metal thin film, resulting in a lower intensity terahertz wave compared to electromagnetic waves obtained using a complete metal thin film. This approach sacrifices amplitude for the ability to control other parameters and lacks dynamic adjustment capabilities, limiting its application scenarios.

[0007] Another approach to modulating terahertz radiation is to use an external magnetic field to control the spin source. The basic principle is to alter the electric field distribution in a metallic spin thin film using an external magnetic field, and then control the electron flow using the inverse spin Hall effect, thereby modulating the polarization state of the radiated terahertz electromagnetic waves. This approach modulates terahertz radiation primarily by changing the external magnetic field, thus possessing dynamic modulation capabilities. However, this approach cannot modulate the intensity of terahertz radiation, lacks the ability to enhance terahertz waves, and has limited signal amplitude. Furthermore, the adjustment of the magnetic field is difficult to quantize; achieving precise modulation requires a high level of expertise in magnetic field design.

[0008] In existing spin terahertz modulation device systems, the terahertz antenna modulation system and phased array system are as follows: The terahertz antenna modulation system includes a photoconductive antenna based on subwavelength structure modulation of terahertz radiation (CN109728428A), comprising a GaAs substrate, a thin film, and a metal nanoarray grown on the thin film. Terahertz electromagnetic waves are localized on the GaAs surface by the metal nanoarray, which promotes the absorption of incident light by the photoconductive material, which is beneficial for increasing the number of photogenerated carriers, increasing photocurrent, and improving the radiation power of the terahertz wave. This scheme can achieve the control of electromagnetic waves, but it cannot achieve efficient dynamic tuning. Another similar patent is an electrically controlled terahertz amplitude modulator (CN106094262A), which uses two T-shaped electrodes arranged in a mirror-symmetrical configuration. This patent shortens the distance between the terahertz photoconductive antenna and the periodic metal resonant unit, utilizing the near-field enhancement effect to strengthen the resonance of the electromagnetic wave. At this point, by changing the voltage of the photoconductive antenna, the intensity of the THz wave can be changed accordingly, thus modulating the amplitude of the terahertz electromagnetic wave. This scheme modulates the amplitude of terahertz waves by changing the voltage. However, its modulation performance is poor, and it can only modulate terahertz waves at fixed frequencies. A similar phased array patent is the low-scattering, ultra-wideband, strongly coupled phased antenna based on a novel electromagnetic metamaterial (CN113690628A). This phased array enhances coupling while maintaining the phase difference by altering the properties of the metamaterial, thus improving the antenna's radiation performance. This scheme primarily enhances the transmission and output power of electromagnetic waves, without significant innovation in terahertz wave modulation functionality. Furthermore, most existing technologies have relatively limited functionality and cannot achieve multiple modulation capabilities. Summary of the Invention

[0009] This invention provides a monolithic multifunctional integrated spin terahertz device, which constructs a multifunctional device that modulates terahertz radiation, realizing the multifunctional monolithic integration of terahertz wave generation, enhancement and control, and has great application potential.

[0010] The technical solution adopted in this invention is a monolithic, multifunctional integrated spin terahertz device, comprising a plurality of spin terahertz antenna elements arranged in a spin phased array; the spin terahertz antenna elements include:

[0011] A substrate dielectric substrate and a spin thin film, wherein the spin thin film is a ferromagnetic heterostructure; the spin thin film is constructed on the substrate dielectric substrate.

[0012] Waveguide antennas can be made of metal or metamaterials.

[0013] There is at least one waveguide antenna, which is constructed on a substrate dielectric substrate and arranged around a spin thin film;

[0014] Alternatively, there may be at least one waveguide antenna, which is constructed on a spin thin film and arranged around the center of the upper surface of the spin thin film.

[0015] In the optimized version of the above-mentioned monolithic multifunctional integrated spin terahertz device, the spin thin film is a patterned spin thin film; when there are two waveguide antennas, the two waveguide antennas are constructed on the spin thin film and are arranged relatively spaced on the spin thin film.

[0016] In the optimized, monolithic, multifunctional integrated spin terahertz device, the spin thin film is a patterned spin thin film; when there are two waveguide antennas and they are constructed on a substrate dielectric substrate, the two waveguide antennas are constructed on both sides of the spin thin film.

[0017] The optimized, monolithic, multifunctional integrated spin terahertz device has a spin thin film composed of at least one metal layer and / or an inorganic compound.

[0018] The optimized, monolithic, multifunctional integrated spin terahertz device comprises a Pt layer, a CoFeB layer, and a W layer in its spin thin film; the W layer, CoFeB layer, and Pt layer are stacked sequentially from the bottom to the top of the spin thin film.

[0019] In the optimized version of the aforementioned monolithic multifunctional integrated spin terahertz device, when the waveguide antenna is constructed on a spin thin film, the waveguide antenna is made of a material that is either different from or the same as the top layer material of the spin thin film.

[0020] In the optimized, monolithic, multifunctional integrated spin terahertz device, when the waveguide antenna is constructed on a spin thin film, the waveguide antenna is formed by extending from a portion of the upper surface of the spin thin film in a direction away from the substrate dielectric substrate.

[0021] The beneficial effects of this application are as follows:

[0022] In the technical solution of this application, terahertz waves can be modulated by changing the geometry and material of the metal structure. The main modulation effects include amplitude control, center frequency control, and phase modulation, which can further lead to the control of key parameters such as chirality and polarization state. By changing the structure and position of the metal structure, the emitted beam can be controlled, and the desired electromagnetic wave can be obtained in the terahertz frequency band.

[0023] In the technical solution of this application, modulation of terahertz waves can be achieved by adjusting the metal structure to change the interaction with the terahertz waves. The device of this application can further generate modulation function through an external magnetic field, and the placement of the metal structure can affect the field distribution in space.

[0024] Furthermore, the technical solution of this application, by combining an antiferromagnetic structure, can achieve active control effects in the absence of an external magnetic field.

[0025] In the technical solution of this application, the presence of a metallic structure allows for the coupling of electromagnetic waves with the metal, thereby enhancing terahertz radiation. Therefore, this device can effectively enhance terahertz radiation. Attached Figure Description

[0026] Figure 1 This is a diagram illustrating the principle of terahertz wave modulation.

[0027] Figure 2 This is a schematic diagram of a spin waveguide antenna.

[0028] Figure 3-1 This is a schematic diagram of the structure of one type of spin metasurface antenna. Figure 1 ;

[0029] Figure 3-2 This is a schematic diagram of the structure of one type of spin metasurface antenna. Figure 2 ;

[0030] Figure 4 This is a front view of the spin metasurface antenna of Example 1;

[0031] Figure 5 This is a front view of the spin metasurface antenna of Example 2;

[0032] Figure 6 This is a top view of one type of metal structure spin antenna.

[0033] Figure 7 This is a top view of one type of metal structure spin antenna.

[0034] Figure 8 This is a top view of one type of metal structure spin antenna.

[0035] Figure 9-1 This is one type of spin metasurface array structure. Figure 1 ;

[0036] Figure 9-2 This is one type of spin metasurface array structure. Figure 2 ;

[0037] Figure 10 This is a structural diagram of a spin terahertz phased array device. Detailed Implementation

[0038] The technical features of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] This embodiment is a monolithic multifunctional integrated spin terahertz device, including several spin terahertz antenna elements arranged in a spin phased array; the spin terahertz antenna element includes a substrate dielectric substrate 1, a spin thin film 2, and a waveguide antenna 3.

[0041] The substrate dielectric substrate 1 is a square sheet, and the spin thin film 2 is a ferromagnetic heterostructure that generates a spin source. The spin thin film 2 is attached to the upper surface of the substrate dielectric substrate 1. The waveguide antenna 3 is a metallic structure, and at least two waveguide antennas 3 are required. The waveguide antennas 3 are disposed on the upper surface of the substrate dielectric substrate 1 and are uniformly arranged around the spin thin film 2.

[0042] In this embodiment, there are two waveguide antennas 3, which are disposed on the substrate dielectric substrate 1, and the two waveguide antennas 3 are located on both sides of the spin thin film 2.

[0043] In the technical solution of this application, the spin thin film 2 can be made of a single material or a combination of different materials. When the spin thin film 2 is made of a combination of different materials, it can be constructed by stacking multiple layers of different materials or by combining different materials in other ways. The spin thin film 2 can be made of materials such as metals and inorganic compounds.

[0044] In this embodiment, the spin thin film 2 adopts a three-layer structure, which includes a Pt layer 21, a CoFeB layer 22, and a W layer 23. The CoFeB layer 22 is a cobalt-iron-boron layer, the Pt layer 21 is a platinum metal layer, and the W layer 23 is a tungsten metal layer. The W layer 23, the CoFeB layer 22, and the Pt layer 21 are stacked sequentially from the bottom end to the top end of the spin thin film 2.

[0045] like Figure 1 As shown, Figure 1 This is a typical spin terahertz emission source, in which a metal modulation structure is coated on a thin film generated by the spin source.

[0046] In this application, terahertz waves can be modulated by changing the geometry and material of the metal structure. The main modulation effects include amplitude control, center frequency control, and phase modulation, which can further lead to the control of key parameters such as chirality and polarization state. The shape of the metal structure can be freely designed according to the modulation requirements. Waveguide antenna 3 is a geometrically shaped metal structure.

[0047] In this application, the metallic structure encompasses a variety of possible materials and geometries. A typical structure is a spin metasurface antenna, which can be categorized into waveguide antenna structures and metasurface antenna structures based on its termination structure, as shown below. Figure 2As shown in Figure 3, when a femtosecond pulse excites a ferromagnetic heterostructure, the generated terahertz waves are coupled not only to free space in the form of far-field radiation but also to the metal structure. Since there is a coupling effect between the metal structure and the spin terahertz waves, adjusting the metal structure to change the interaction with the terahertz waves can achieve modulation of the terahertz waves.

[0048] In this embodiment, the waveguide antenna 3 is a metal structure or metamaterial structure of any shape, and there is at least one waveguide antenna 3. The number of waveguide antennas 3 can be multiple. It can be any one of the following: a cubic metal block, a strip metal strip, a metal block with a trapezoidal cross section, a C-shaped metal strip, a cubic metamaterial block, a strip metamaterial strip, a metamaterial block with a trapezoidal cross section, or a C-shaped metamaterial strip. The geometric structure of the waveguide antenna 3 is not limited to the above-mentioned shapes, and its shape can be set according to actual needs.

[0049] Figure 4 This is a typical front view of a spin metasurface antenna, where a metal structure is placed on both sides of the spin thin film.

[0050] In this embodiment, modulation can be further achieved by applying an external magnetic field, and the placement of the metal structure can influence the field distribution in space. The spin terahertz source is primarily generated through the inverse spin Hall effect, and the distribution of the electromagnetic field can affect the parameters of the terahertz radiation. The terahertz radiation can be controlled by designing the magnetic field. Due to the presence of the metal structure, the coupling between the electromagnetic wave and the metal can enhance the terahertz radiation. Therefore, this device can enhance terahertz radiation. Unlike traditional methods that use a designed magnetic field to control the polarization state of terahertz radiation, this device utilizes the coupling between the metal structure and the terahertz wave to enhance terahertz radiation. In addition to enhancing radiation, at the system level, this device can employ metasurfaces and waveguides to construct various modulation systems integrated on ferromagnetic heterostructures. By changing the geometry or position of the radiated terahertz wave, frequency and phase modulation, as well as chiral modulation, can be achieved.

[0051] Figure 6 Figure 7 Figure 8 These are top views of several typical spin antennas, the main feature of which is the difference in the geometry of the metal modulation structures on both sides. Figure 8 The diagram shows the arrays for two different structures. Figure 2The structure allows for the control of the active antenna through rotation of the azimuth angle or magnetic field direction. The antenna width and length are actively tunable parameters. Figure 3 compares a spin structure similar to a slot antenna with an externally coupled spin-resonator (SRR) based on the slot antenna, where the SRR is a spin metasurface structure with an open-loop resonator. Based on the implementation of the slot antenna, a bandpass and bandstop tunable spin transmitter structure was realized. This scheme has extremely high application value for miniaturized and integrated tunable spin transmitters.

[0052] The combination of the metal structure and the spin source can take many forms. In this embodiment, the metal waveguide structure of the waveguide antenna 3 is connected to the spin emission source, i.e., both sides of the spin thin film 2. In some other cases, the metal structure of the waveguide antenna 3 can be uniformly arranged along the periphery of the spin thin film 2, either in a ring or in other forms.

[0053] The technical solution of this embodiment can be combined with other terahertz modulation schemes. While using the metal structure in this embodiment to modulate the terahertz wave, an electromagnet can be placed on the outside to modulate the electric field distribution. The combination of both modulates the terahertz wave. Figure 6 , Figure 7 , Figure 8 As shown.

[0054] Based on the above structure, by adjusting the orientation of the SRRs and finding a structure with a fixed phase difference, we can construct a spin phased array for the terahertz band, such as... Figure 10 As shown.

[0055] The structures of adjacent columns have similar amplitudes at the same frequency and a phase difference of 180°. When this array is excited by a femtosecond laser, due to the fixed phase gradient, a beam control effect occurs at the output, thus realizing an integrated spin terahertz phased array.

[0056] The self-selected terahertz device of this application can realize multiple functions such as enhancement, frequency modulation, amplitude modulation, phase modulation, and chiral control, which improves the single-function defect of traditional monolithic multi-functional integrated spin terahertz devices; the metal structure can also be dynamically designed according to modulation requirements, with a wide range of application scenarios and great application potential.

[0057] Example 2

[0058] The difference between this embodiment and Embodiment 1 is that: Figure 5 In contrast to the metal structure placement method of Embodiment 1, in this embodiment, the waveguide antenna 3 is located on the upper surface of the spin film 2 and arranged around the center of the upper surface of the spin film 2.

[0059] Taking one embodiment as an example, the waveguide antenna 3 can be selected as two, with the two waveguide antennas 3 located on the upper surface of the spin film 2 and arranged at a relative interval on the upper surface of the spin film 2.

[0060] Meanwhile, the two waveguide antennas 3 are Au metal blocks, and the two waveguide antennas 3 are located at both ends of the upper surface of the spin thin film 2.

[0061] Example 3

[0062] The difference between this embodiment and the above embodiment is that when the two waveguide antennas 3 are located on the upper surface of the spin thin film 2, the two waveguide antennas 3 are formed by extending and thickening from both ends of the upper surface of the spin thin film 2 in a direction away from the substrate dielectric substrate 1.

[0063] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A monolithic, multifunctional integrated spin terahertz device, comprising a plurality of spin terahertz antenna elements arranged in a spin phased array; the spin terahertz antenna elements comprising: A substrate dielectric substrate (1) and a spin thin film (2), wherein the spin thin film (2) is a ferromagnetic heterostructure; the spin thin film (2) is constructed on the substrate dielectric substrate (1); Waveguide antenna (3), which is a metal structure or a metamaterial structure; Its features are: The spin film (2) is formed by stacking at least one metal layer and / or an inorganic compound; The spin film (2) includes a Pt layer (21), a CoFeB layer (22), and a W layer (23); the W layer (23), the CoFeB layer (22), and the Pt layer (21) are stacked sequentially from the lower end to the upper end of the spin film (2); The spin film (2) is a patterned spin film; When there are two waveguide antennas (3), the two waveguide antennas (3) are constructed on the spin thin film (2) and the two waveguide antennas (3) are arranged relatively spaced on the spin thin film (2); or, when there are two waveguide antennas (3) and they are constructed on the substrate dielectric substrate (1), the two waveguide antennas (3) are constructed on both sides of the spin thin film (2).

2. The monolithic multifunctional integrated spin terahertz device according to claim 1, characterized in that: When the waveguide antenna (3) is constructed on the spin film (2), the material of the waveguide antenna (3) is either different from or the same as the top layer material of the spin film (2).

3. The monolithic multifunctional integrated spin terahertz device according to claim 1, characterized in that: When the waveguide antenna (3) is constructed on the spin thin film (2), the waveguide antenna (3) is formed by extending from a portion of the upper surface of the spin thin film (2) in a direction away from the substrate dielectric substrate (1).

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