A one-way high-efficiency spin terahertz emitter and application

Abstract

The application discloses a one-way high-efficiency spin terahertz emitter and application, and particularly relates to the field of spin terahertz emission equipment. The terahertz emitter comprises a glass substrate, a spin terahertz film, a metal grating and a magnet pair. The spin terahertz film is arranged on the back of the glass substrate, and the metal grating is arranged on the front of the glass substrate. The one-way high-efficiency spin terahertz emitter can make the transmittance of femtosecond pump light higher by using the specially designed metal grating, and can efficiently reflect the back terahertz wave generated by the spin terahertz film, so as to control the emission direction of the terahertz and improve the generation efficiency of the spin terahertz wave.

Description

Technical Field

[0001] This invention relates to the field of spin terahertz emission equipment technology, and more specifically, to a unidirectional high-efficiency spin terahertz transmitter and its application. Background Technology

[0002] Terahertz waves refer to electromagnetic waves with frequencies ranging from 0.1 to 10 THz (wavelengths from 3000 to 30 μm). They overlap with millimeter waves in the long-wavelength band and with infrared light in the short-wavelength band. The terahertz wave band can cover the characteristic spectra of semiconductors, plasmas, organic matter, and biological macromolecules, making it a novel radiation source with many unique advantages. Located between infrared and microwave frequencies, the terahertz band is a transitional band between macroscopic electronics and microscopic optoelectronics, possessing numerous advantages such as wide bandwidth, low energy, high transparency, and uniqueness. It has significant scientific value and broad application prospects in fields such as non-destructive testing, satellite communication, and medical diagnosis. Spin terahertz sources, due to their unique terahertz generation mechanism, offer advantages such as low cost and high efficiency, making them an important future development direction for terahertz technology.

[0003] Since existing spin terahertz transmitters can generate terahertz waves with a direction perpendicular to the spin thin film, and the terahertz waves are composed of forward-propagating terahertz waves and backward-propagating terahertz waves, the efficiency of generating terahertz waves is low and lacks directionality. Therefore, a unidirectional high-efficiency spin terahertz transmitter and its application are proposed. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a unidirectional high-efficiency spin terahertz transmitter to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a unidirectional high-efficiency spin terahertz emitter, comprising a glass substrate, a spin terahertz thin film, a metal grating, and a pair of magnets, wherein the spin terahertz thin film is disposed on the back side of the glass substrate, the metal grating is disposed on the front side of the glass substrate, and the pair of magnets is distributed on both sides of the glass substrate.

[0006] Furthermore, the spin terahertz thin film is composed of a magnetic layer and a non-magnetic layer; wherein the magnetic layer is a cobalt layer and the non-magnetic layer is a platinum layer.

[0007] Furthermore, the metal grating metal layer is composed of periodically distributed metal strips.

[0008] Furthermore, the magnetic poles of the magnets on opposite sides are opposite.

[0009] An application of a unidirectional high-efficiency spin terahertz transmitter for generating spin terahertz waves includes the following steps:

[0010] S1: Spin terahertz thin films are fabricated on the back side of a glass substrate using magnetron sputtering; a metal grating is fabricated on the front side of the glass substrate using photolithography.

[0011] S2: By using a magnet to magnetize the spin terahertz thin film, and based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, when a femtosecond laser irradiates the spin terahertz thin film, the spin terahertz thin film will generate terahertz radiation, and the polarization direction of the terahertz wave will be perpendicular to the direction of the magnetic field.

[0012] S3: The pump light of this unidirectional high-efficiency spin terahertz emitter is pumped from a metal grating on the front side of the glass substrate. The pump beam passing through the metal grating illuminates the spin terahertz film after passing through the glass substrate. The generated terahertz wave has forward emission along the pump light direction and backward emission opposite to the pump light direction. When the backward-emitted terahertz wave reaches the metal grating, since its polarization direction is parallel to the metal grating, the terahertz wave will be reflected by the metal grating and become forward-emitted, and will be superimposed with the forward-emitted terahertz wave.

[0013] A further approach is to achieve constructive interference of terahertz waves in a specific wavelength band by selecting a glass substrate of appropriate thickness, thereby improving the generation efficiency of terahertz waves. Therefore, the thickness of the glass substrate in this application is d = c / (4nf), where c = 3 × 10⁻⁶. 8 m / s is the speed of light in vacuum, n is the refractive index of the glass substrate, which is 1.5; f is the terahertz wave frequency to be enhanced. If f = 1 THz is chosen, the required glass substrate thickness is d = 50 μm.

[0014] The technical effects and advantages of this invention are as follows:

[0015] 1. Compared with existing technologies, by preparing spin terahertz thin films and specially designed metal gratings on both sides of a glass substrate, it can simultaneously achieve high pump light transmittance and high terahertz wave reflectivity, realize the reflection transmission of back-emitted terahertz waves, and superimpose them with forward-emitted terahertz waves to achieve constructive interference of terahertz waves in a special band, thereby controlling the emission direction of terahertz waves and improving the generation efficiency of spin terahertz waves.

[0016] 2. Compared with ordinary spin terahertz transmitters, this spin terahertz transmitter can not only achieve unidirectional forward transmission of terahertz waves, but also generate terahertz wave power more than 4 times due to the constructive interference between the reflected backward-emitted terahertz waves and the forward-emitted terahertz waves.

[0017] 3. This application selects periodically distributed metal strips, which have high reflection of terahertz waves in the range of 0.1-5THz. Furthermore, by selecting a glass substrate of appropriate thickness, constructive interference of terahertz waves in a specific band can be achieved, thereby improving the generation efficiency of terahertz waves. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 The reflectivity of the metal grating to terahertz waves;

[0020] Figure 3 To generate a three-dimensional far-field distribution of terahertz wave power;

[0021] Figure 4 Two-dimensional far-field distribution for generating terahertz wave power.

[0022] The reference numerals in the figures are: 101, glass substrate; 102, spin terahertz thin film; 103, metal grating; 104, magnet pair; 1031, metal strip. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0024] As attached Figure 1 Appendix Figure 2 Appendix Figure 3 and attached Figure 4 As shown, an embodiment of a unidirectional high-efficiency spin terahertz emitter includes a glass substrate 101, a spin terahertz thin film 102, a metal grating 103, and a pair of magnets 104. The spin terahertz thin film 102 is disposed on the back side of the glass substrate 101, the metal grating 103 is disposed on the front side of the glass substrate 101, and the pair of magnets 104 are distributed on both sides of the glass substrate 101.

[0025] As a preferred embodiment of the present invention, the spin terahertz thin film 102 is composed of a magnetic layer and a non-magnetic layer; wherein the magnetic layer is a cobalt layer and the non-magnetic layer is a platinum layer, and the cobalt layer and the platinum layer have the same thickness, preferably 4 nm.

[0026] As a preferred technical solution of the present invention, as shown in the appendix Figure 1 As shown, the metal grating 103 is composed of periodically distributed metal strips 1031; preferably, the metal strips 1031 are made of gold, aluminum, copper, etc.; preferably, there are multiple sets of metal gratings 103 evenly distributed, wherein the width of one set of metal gratings 103 is 10μm, the width of the metal strips 1031 is 200nm, the thickness is 100nm, each metal strip 1031 in the same set is spaced 300nm apart, and each set of metal gratings 103 is spaced 5μm apart.

[0027] As a preferred technical solution of the present invention, as shown in the appendix Figure 1 As shown, the magnetic poles of the magnet pair 104 are opposite on opposite sides, which can generate an in-plane magnetic field that is perpendicular to the direction of the metal grating 103 and parallel to the glass substrate 101, so as to facilitate the magnetization of the spin terahertz thin film 102.

[0028] An application of a unidirectional high-efficiency spin terahertz transmitter in the embodiment, used for spin terahertz wave generation, includes the following steps:

[0029] S1: A spin terahertz thin film 102 is fabricated on the back side of a glass substrate 101 by magnetron sputtering; a metal grating 103 is fabricated on the front side of the glass substrate 101 by photolithography.

[0030] S2: By using the magnet to magnetize the spin terahertz thin film 102, and based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, when the femtosecond laser irradiates the spin terahertz thin film 102, the spin terahertz thin film 102 will generate terahertz radiation, and the polarization direction of the generated terahertz wave is perpendicular to the direction of the magnetic field.

[0031] S3: The pump light of this unidirectional high-efficiency spin terahertz emitter is pumped from the metal grating 103 on the front side of the glass substrate 101. The pump beam passing through the metal grating 103 passes through the glass substrate 101 and then irradiates the spin terahertz film 102. The generated terahertz wave has forward emission along the pump light direction and backward emission opposite to the pump light direction. When the backward-emitted terahertz wave reaches the metal grating 103, since its polarization direction is parallel to the metal grating 103, the terahertz wave will be reflected by the metal grating 103 and become forward-emitted, and will be superimposed with the forward-emitted terahertz wave.

[0032] In one embodiment, a femtosecond laser with a center wavelength of 800 nm pumps the unidirectional high-efficiency spin terahertz emitter from one side of the metal grating 103. The selected metal strip 1031 is made of gold, and the thickness of the glass substrate 101 is d = c / (4nf), where c = 3 × 10^8 m / s is the speed of light in vacuum, n is the refractive index of the glass substrate 101 with a value of 1.5, and f is the frequency of the terahertz wave to be enhanced. When f = 1 THz is selected, the required thickness of the glass substrate 101 is d = 50 μm.

[0033] Appendix Figure 1 In the metal grating 103, the metal part is composed of periodically distributed metal strips 1031. When the polarization direction of the pump light with a wavelength of 800nm ​​is perpendicular to the direction of the metal strips 1031, its transmittance is about 97%.

[0034] Appendix Figure 2The reflectivity of the metal grating for terahertz waves is shown, indicating that it exhibits high reflectivity for terahertz waves in the 0.1-5 THz range. By selecting a glass substrate 101 of appropriate thickness, constructive interference of terahertz waves in a specific wavelength band can be achieved, thereby improving the generation efficiency of terahertz waves.

[0035] Figure 3 The diagram shows the three-dimensional far-field terahertz power distribution of this unidirectional high-efficiency spin terahertz emitter at f = 1 THz, where the z-direction is the pump light direction. Figure 3 It can be seen that the transmitter can achieve unidirectional terahertz wave output.

[0036] Figure 4 The solid line represents the two-dimensional far-field distribution of the terahertz wave power generated by the normalized unidirectional high-efficiency spin terahertz transmitter, while the dashed line represents the far-field distribution of the terahertz wave power generated by the ordinary spin terahertz transmitter under the same pump light. It can be seen that there are forward and backward terahertz waves of the same magnitude.

[0037] One common method is magnetron sputtering. For example, a suitable amount of argon gas is filled into a high vacuum, and a DC voltage of several hundred kilovolts is applied between the cathode (cylindrical or planar target) and the anode (coating chamber wall). This generates a magnetron-controlled abnormal glow discharge within the coating chamber, ionizing the argon gas. The argon ions are accelerated by the cathode and bombard the cathode target surface, sputtering the target surface atoms and depositing them onto the substrate surface to form a cobalt-platinum thin film.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for generating spin terahertz waves using a unidirectional high-efficiency spin terahertz emitter, characterized by, The unidirectional high-efficiency spin terahertz emitter comprises a glass substrate (101), a spin terahertz film (102), a metal grating (103) and a magnet pair (104), the spin terahertz film (102) is arranged on the back of the glass substrate (101), the metal grating (103) is arranged on the front of the glass substrate (101), and the magnet pair (104) is distributed on both sides of the glass substrate (101); the metal layer of the metal grating (103) is composed of periodically distributed metal strips (1031); The method comprises the following steps: S1: The spin terahertz film (102) is prepared on the back of the glass substrate (101) by a magnetron sputtering method; and the front of the glass substrate (101) is provided with the metal grating (103) by a photolithography technology; S2: The spin terahertz film (102) is magnetized by the magnet pair (104), and based on the inverse Hall effect between the magnetic layer and the non-magnetic layer, when the femtosecond laser irradiates on the spin terahertz film (102), the spin terahertz film (102) generates terahertz radiation, and the polarization direction of the terahertz wave is perpendicular to the magnetic field direction; S3: The pump light of the unidirectional high-efficiency spin terahertz emitter is pumped from the metal grating (103) on the front of the glass substrate (101), the pump light beam passing through the metal grating (103) irradiates on the spin terahertz film (102) after passing through the glass substrate (101), and the terahertz wave generated thereby exists forward emission along the pump light direction and back emission opposite to the pump light direction; when the back emission terahertz wave reaches the metal grating (103), because the polarization direction is parallel to the metal grating (103), the terahertz wave is reflected by the metal grating (103) to become forward emission, and is superimposed with the forward emission terahertz wave, so that interference of the terahertz wave of a specific wave band is lengthened, and the generation efficiency of the terahertz wave is improved.

2. The method of claim 1, wherein the method comprises: The thickness of the glass substrate (101) is d = c / (4nf), where c = 3 x 10 8 m / s is the speed of light in vacuum, n is the refractive index of the glass substrate, which is 1.5; f is the frequency of the terahertz wave to be enhanced.

3. A unidirectional high-efficiency spin terahertz emitter comprising the method of any one of claims 1-2, characterized by: The spin terahertz film (102) is composed of a magnetic layer and a non-magnetic layer; The magnetic layer is a cobalt layer, and the non-magnetic layer is a platinum layer.

4. The unidirectional high-efficiency spin terahertz emitter of claim 3, wherein: The magnetic poles of the magnet pair (104) on opposite sides are opposite.

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