A self-focusing spin terahertz emitter and its application

Abstract

The present invention discloses a self-focusing spin terahertz emitter and its application, specifically relating to the field of spin terahertz emission equipment. The self-focusing spin terahertz emitter comprises a glass substrate, a spin terahertz film, and a magnet pair. The spin terahertz film is composed of a ferromagnetic material and two heavy metal non-magnetic materials with equal and opposite spin Hall angles, alternately arranged on the ferromagnetic material. The self-focusing spin terahertz emitter of the present invention constructs a spin terahertz Fresnel zone plate by specially arranging the two heavy metal non-magnetic materials with equal and opposite spin Hall angles. This enables the generated spin terahertz to have a focusing function, resulting in high terahertz generation efficiency and improved integration of the spin terahertz emitter.

Description

Technical Field

[0001] The present invention relates to the technical field of spin terahertz emission equipment, and more particularly to a self-focusing spin terahertz emitter and its application. Background Art

[0002] The terahertz (THz) frequency band, located between infrared and microwaves (0.1-10 THz), represents a transitional frequency range between macroscopic electronics and microscopic photonics. It possesses numerous advantages, including broadband, low energy, high transparency, and uniqueness. It holds significant scientific value and broad application prospects in fields such as nondestructive testing, satellite communications, medical diagnostics, and satellite communications. Spin THz sources, due to their unique THz generation mechanism, offer advantages such as low cost and high efficiency, making them a key development direction for future THz technology.

[0003] Because existing terahertz devices consist of a series of components, such as terahertz sources and terahertz collimating lenses, to generate, collimate, and focus terahertz waves, their system integration is low and their size is large. Fresnel zone plates can collimate or focus light waves and are characterized by their small size, thinness, and simple manufacturing process. However, existing terahertz Fresnel zone plates can only collimate and focus generated terahertz waves and do not integrate the terahertz source and Fresnel zone plate. Furthermore, only half of the Fresnel zone plate's area can transmit and collimate terahertz waves, resulting in low efficiency. To address these issues, a self-focusing spin terahertz transmitter is proposed. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a self-focusing spin terahertz emitter and its application to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A self-focusing spin terahertz emitter includes a glass substrate, a spin terahertz film, and a magnet pair. The spin terahertz film is composed of a ferromagnetic material layer and heavy metal non-magnetic material layers A and B. The ferromagnetic material layer is arranged on the front surface of the glass substrate, and the heavy metal non-magnetic material layers A and B are arranged on the outer surface of the ferromagnetic material layer.

[0007] In a further embodiment, the spin Hall angles of the heavy metal non-magnetic material layer A and the heavy metal non-magnetic material layer B are equal in size and opposite in direction.

[0008] In a further embodiment, the heavy metal non-magnetic material layer A and the heavy metal non-magnetic material layer B are alternately arranged in a ring shape and distributed on the ferromagnetic material layer.

[0009] In a further embodiment, the radius of the ring formed by the heavy metal non-magnetic material layer A or the heavy metal non-magnetic material layer B is where r n is the radius of the nth ring, n is a positive integer, d is the focal length of the spin terahertz emitter, λ is the central wavelength of the focused spin terahertz, which satisfies λ = c / f, where c is the speed of light and f is the frequency of the corresponding terahertz.

[0010] Further solution, when f = 1 THz and focal length d = 5 cm, the radii of the first 10 rings are:

[0011] r1=0.3876cm, r2=0.5485cm, r3=0.6723cm, r4=0.7769cm, r5=0.8693cm, r6=0.9529cm, r7=1.0301cm, r8=1.1020cm, r9=1.1697cm, r10=1.2339cm.

[0012] In a further embodiment, the magnet pair is fixed on two surfaces of the glass substrate, and the magnetic poles of the magnets on the two surfaces are opposite.

[0013] Another object of the present invention is to provide an application of the self-focusing spin terahertz emitter, which is used for generating and focusing spin terahertz waves.

[0014] Further, the steps of generating and focusing the spin terahertz wave are as follows:

[0015] S1 uses a magnet to magnetize the ferromagnetic material layer of the spin terahertz film.

[0016] S2 irradiates a femtosecond laser onto a spin terahertz film. Based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, ultrafast charge flows are generated at the interface between the ferromagnetic material layer and the heavy metal non-magnetic material layer A, or between the ferromagnetic material layer and the heavy metal non-magnetic material layer B. The directions of adjacent ring-shaped ultrafast charge flows are opposite, thereby generating terahertz radiation with a phase difference of 180° and a polarization direction perpendicular to the magnetic field direction.

[0017] S3 controls the ring radius of each ring-shaped heavy metal non-magnetic material layer A or heavy metal non-magnetic material layer B to achieve constructive interference of terahertz waves in a specific band, thereby improving the generation efficiency of terahertz waves.

[0018] Compared with the prior art, the technical effects and advantages of the present invention are:

[0019] 1. By preparing two specially arranged heavy metal non-magnetic material layers with equal and opposite spin Hall angles on a ferromagnetic material, a spin terahertz Fresnel zone plate is constructed. This allows the generated spin terahertz to have a convergence function, thereby improving the integration of the spin terahertz emitter.

[0020] 2. Unlike traditional terahertz Fresnel zone plates, where only half of the area is transmissive to terahertz, the present invention uses a magnetron sputtering method to deposit two heavy metal materials with opposite spin Hall angles, so that adjacent zone plate areas can simultaneously generate terahertz waves with a phase difference of 180°. Therefore, the entire area of ​​the sample can generate terahertz waves, and the efficiency is twice that of traditional Fresnel zone plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 The optical field distribution of the terahertz wave with a frequency of f=1 THz is generated for the spin terahertz emitter.

[0023] The accompanying drawings are marked as follows: 101, glass substrate; 102, spin terahertz thin film ferromagnetic material; 103, 104, two heavy metal non-magnetic materials with equal and opposite spin Hall angles; 105, magnet pair. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] As attached Figure 1 In an embodiment, a self-focusing spin terahertz emitter includes a glass substrate 101, a spin terahertz film, and a magnet pair 105, wherein the spin terahertz film is composed of a ferromagnetic material layer 102 and a heavy metal non-magnetic material layer A103 and a heavy metal non-magnetic material layer B104. The ferromagnetic material layer 102 is arranged on the front surface of the glass substrate 101, and the heavy metal non-magnetic material layer A103 and the heavy metal non-magnetic material layer B104 are arranged on the outer surface of the ferromagnetic material layer 102.

[0026] As a preferred technical solution of the present invention, the ferromagnetic material layer in the present invention is deposited on a glass substrate by cobalt iron boron through magnetron sputtering;

[0027] The heavy metal non-magnetic material layer A is formed of platinum using photolithography, mask and other technologies;

[0028] The heavy metal non-magnetic material layer B is formed of tungsten using photolithography, mask and other technologies. The positions of the heavy metal non-magnetic material layer A and the heavy metal non-magnetic material layer B are interchangeable.

[0029] The thickness of the ferromagnetic material layer 102 , the heavy metal non-magnetic material layer A 103 , and the heavy metal non-magnetic material layer B 104 are the same, preferably 2 nm.

[0030] The spin Hall angles of the heavy metal non-magnetic material layer A103 and the heavy metal non-magnetic material layer B104 are equal in size and opposite in direction.

[0031] like Figure 1 The heavy metal non-magnetic material layer A103 and the heavy metal non-magnetic material layer B104 are arranged alternately in a ring shape on the ferromagnetic material layer 102. The radius of each ring is where r n is the radius of the nth ring, n is a positive integer, d is the focal length of the spin terahertz emitter, λ is the central wavelength of the focused spin terahertz, which satisfies λ = c / f, where c is the speed of light and f is the frequency of the corresponding terahertz.

[0032] As a preferred technical solution of the present invention, as shown in the attached Figure 1 As shown, the magnet pair 105 has opposite magnetic poles on two opposite sides, which can generate an in-plane magnetic field parallel to the glass substrate 101 to magnetize the ferromagnetic material layer 102.

[0033] A self-focusing spin terahertz emitter in this embodiment is used for generating, collimating, and focusing spin terahertz waves, which includes the following steps:

[0034] S1: The ferromagnetic material layer of the spin terahertz film is prepared on the front side of the glass substrate by magnetron sputtering;

[0035] S2: Using photolithography, mask and other technologies, a non-magnetic layer is prepared on the ferromagnetic material layer of the spin terahertz film. The non-magnetic layer is composed of heavy metal non-magnetic material layer A103 and heavy metal non-magnetic material layer B104 arranged alternately in a ring. The spin Hall angles of adjacent non-magnetic layer materials are opposite, and the radius of the nth ring is Where d is the focal length of the spin terahertz emitter, λ is the central wavelength of the focused spin terahertz, which satisfies λ = c / f, where c is the speed of light and f is the frequency of the corresponding terahertz;

[0036] S3: Using a magnet to magnetize the ferromagnetic material layer of the spin terahertz film, and based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, when a femtosecond laser is irradiated on the spin terahertz film, an ultrafast charge flow is generated at the interface between the ferromagnetic material layer and the non-magnetic layer of the spin terahertz film, and the directions of adjacent ring-shaped ultrafast charge flows are opposite, thereby generating terahertz radiation with a phase difference of 180° and a polarization direction perpendicular to the magnetic field direction;

[0037] S4: Control the ring radius of each ring-shaped heavy metal non-magnetic material layer A103 or heavy metal non-magnetic material layer B104 to achieve constructive interference of terahertz waves in a specific band, thereby improving the generation efficiency of terahertz waves.

[0038] In one embodiment, the femtosecond laser pumps the spin terahertz emitter with self-focusing function from the back of the glass substrate 101. If f=1 THz and the focal length f=5 cm, the radii of the first 10 rings are

[0039] r1=0.3876cm, r2=0.5485cm, r3=0.6723cm, r4=0.7769cm, r5=0.8693cm, r6=0.9529cm, r7=1.0301cm, r8=1.1020cm, r9=1.1697cm, r10=1.2339cm.

[0040] Attachment Figure 2 The self-focusing spin terahertz emitter generates a 1 THz terahertz wave distribution, where the z direction is the propagation direction of the terahertz. It can be seen that the terahertz wave in this frequency band is focused, and its focal length is 5 cm.

[0041] Among them, the most common magnetron sputtering method involves, for example, filling a high vacuum chamber with an appropriate amount of argon gas, applying a DC voltage of several hundred kilovolts between the cathode (cylindrical or planar target) and the anode (coating chamber wall), and generating a magnetron-type abnormal glow discharge in the coating chamber, ionizing the argon gas. The argon ions are accelerated by the cathode and bombard the cathode target surface, sputtering atoms from the target material, such as cobalt iron boron, platinum, and tungsten, which are deposited on the substrate surface to form cobalt iron boron, platinum, and tungsten thin films.

[0042] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0043] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A self-focusing spin terahertz emitter, comprising a glass substrate (101), a spin terahertz film, and a magnet pair (105), characterized in that: The spin terahertz film is composed of a ferromagnetic material layer (102), a heavy metal non-magnetic material layer A (103), and a heavy metal non-magnetic material layer B (104), wherein the ferromagnetic material layer (102) is arranged on the front surface of the glass substrate (101), and the heavy metal non-magnetic material layer A (103) and the heavy metal non-magnetic material layer B (104) are arranged on the outer surface of the ferromagnetic material layer (102); The spin Hall angles of the materials in the heavy metal non-magnetic material layer A (103) and the heavy metal non-magnetic material layer B (104) are equal in size and opposite in direction, and are alternately arranged in a ring shape and distributed on the ferromagnetic material layer (102).

2. The self-focusing spin terahertz emitter according to claim 1, characterized in that: The radius of the ring formed by the heavy metal non-magnetic material layer A (103) or the heavy metal non-magnetic material layer B (104) , where r n is the radius of the nth ring, n is a positive integer, d is the focal length of the spin terahertz emitter, λ is the central wavelength of the focused spin terahertz, which satisfies λ = c / f ,in c is the speed of light, f is the frequency corresponding to terahertz.

3. The self-focusing spin terahertz emitter according to claim 2, characterized in that: when f =1THz, focal length d =5cm, the radii of the first 10 rings are: r1=0.3876cm, r2=0.5485cm, r3=0.6723cm, r4=0.7769cm, r5=0.8693cm, r6=0.9529cm, r7=1.0301cm, r8=1.1020cm, r9=1.1697cm, r10=1.2339cm.

4. The self-focusing spin terahertz emitter according to claim 1, characterized in that: The magnet pair (105) is fixed on two sides of the glass substrate (101), and the magnetic poles of the two opposite sides are opposite.

5. The use of a self-focusing spin terahertz emitter according to any one of claims 1 to 4, characterized in that: It is used for the generation and focusing of spin terahertz waves.

6. The use according to claim 5, characterized in that: The steps for generating and focusing spin terahertz waves are as follows: S1 magnetizes the ferromagnetic material layer (102) of the spin terahertz film using a magnet pair (105). S2 irradiates a femtosecond laser onto a spin terahertz film, and based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, generates ultrafast charge flows at the interface between the ferromagnetic material layer (102) and the heavy metal non-magnetic material layer A (103), or the ferromagnetic material layer (102) and the heavy metal non-magnetic material layer B (104), and the directions of the adjacent ring-shaped ultrafast charge flows are opposite, thereby generating terahertz radiation with a phase difference of 180 degrees and a polarization direction perpendicular to the magnetic field direction; S3 controls the ring radius of each ring-shaped heavy metal non-magnetic material layer A (103) or heavy metal non-magnetic material layer B (104) to achieve constructive interference of terahertz waves in a specific band, thereby improving the generation efficiency of terahertz waves.

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