Coherent terahertz magnon laser and coherent terahertz communication system

Abstract

A device for generating coherent terahertz radiation is provided. In one example, the device includes one or more multilayer tunable micropillars. Next, the multilayer tunable micropillars may include a substrate, a bottom electrode, a bottom layer of ferromagnetic material, and further include a magnon gain medium (MGM) coupled to the bottom electrode, a tunnel junction coupled to the ferromagnetic material, a spin injector coupled to the tunnel junction, a pinning layer coupled to the spin injector, a reference layer coupled to the pinning layer, and a top electrode. In one example, a housing cavity surrounds at least one of the multilayer tunable micropillars. In one example, a storage cavity surrounds the housing cavity.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Non-Provisional Patent Application Serial No. 16 / 655,472, filed on October 17, 2019, entitled “COHERENT TERAHERTZ MAGNON LASER AND COHERENT TERAHERTZ COMMUNICATION SYSTEM” and U.S. Provisional Patent Application No. 62 / 822,284, filed on March 22, 2019, entitled “COHERENT TERAHERTZ MAGNON LASER AND COHERENT TERAHERTZ COMMUNICATION SYSTEM”. This application is also a continuation-in-part of and claims priority to U.S. Patent Application No. 16 / 245,224, filed on January 10, 2019, entitled “TUNABLE MULTILAYER TERAHERTZ MAGNONGENERATOR”. This application is also a continuation-in-part of and claims priority to U.S. Patent Application No. 16 / 245,247, filed on January 10, 2019, entitled “TERAHERTZ MAGNON GENERATOR COMPRISING PLURALITY OF SINGLE TERAHERTZ MAGNON LASERS”. The entire contents of the above-mentioned applications listed herein are incorporated herein by reference. Technical Field

[0003] The invention relates to the field of magnon lasers for generating terahertz radiation. Background Art

[0004] Terahertz (THz) radiation is a type of electromagnetic radiation with a frequency range of 0.1THz to 30THz, occupying the part of the electromagnetic spectrum between the microwave band and the infrared band.

[0005] The energy of terahertz photons is less than that of optical photons. This is why terahertz waves can penetrate deep into matter where light waves cannot. At terahertz frequencies, molecules vibrate. This is why terahertz waves are useful in molecular research.

[0006] In fact, the unique rotational and vibrational responses of molecules in the terahertz range provide information that is not usually present in optical, X-ray and nuclear magnetic resonance (NMR) images. Terahertz waves can easily penetrate and examine the interior of most dielectric materials, which are opaque to visible light and have low contrast to X-rays, making them a useful complementary imaging source.

[0007] For example, terahertz waves maintain reasonable penetration depths in certain common materials, such as clothing, plastic, wood, sand, and soil. Therefore, terahertz technology has the potential to detect materials wrapped or buried with these explosives, because explosives have unique terahertz spectral characteristics compared to the surrounding materials. The spectral fingerprint of explosive materials can be expected in the terahertz band, and terahertz imaging can be applied to mine detection. However, currently, there is still a lack of efficient and compact solid-state sources in the spectral range of 0.1-30 THz.

[0008] In fact, broadband pulsed terahertz sources are usually based on exciting different materials with ultrashort laser pulses. Several different mechanisms have been developed to generate terahertz radiation, including photocarrier acceleration in photoconductive antennas, second-order nonlinear effects in electro-optical crystals, etc.

[0009] For narrowband terahertz sources, solid-state lasers are usually considered. They are based on inter-band transitions or inter-sub band transitions in narrow-gap semiconductors, i.e. transitions in quantum confined structures (e.g., nanostructures), between confined conductive or valence states. In order to obtain terahertz radiation from direct inter-band transitions, semiconductors with close to zero gap are required. For inter-sub band transitions, conventional wide-gap materials can be used, but precise complex structures are required. Currently, it is feasible to construct multi-quantum well semiconductor structures for laser emission.

[0010] A quantum cascade consists of a repeating structure, in which each repeating unit consists of an injector and an active region. In the active region, there is a population inversion, and electrons transition to lower energy levels, emitting photons of a specific wavelength. Kohler et al. (R. Kohler et al., Nature 417, 156 (2002)) designed a terahertz quantum cascade laser operating at 4.4 THz. The laser consists of a total of more than 700 quantum wells and demonstrates pulsed operation at a temperature of 10K. For comments, see, for example, B Ferguson and X.-C. Zhang, Nat. Matter, 26 (2002).

[0011] Manijeh Razeghi et al. reported recent progress in QCL generators in Photonics Spectra, December 48-51 (2016). The authors used nonlinear mixing of two QCLs. However, the use of nonlinear mixers brings inherent limitations. In fact, nonlinear QCL mixers are very complex devices (each such QCL includes multiple barrier layers and multiple well layers and must be manufactured with an accuracy of up to 0.1 nm), have low output power in the continuous regime (these devices can only reach power outputs of up to 0.5 mW in the pulsed regime); and have very limited tunability in the (2-4.45) THz range.

[0012] Located in City of Industry, California, AdTech Optics has been developing and producing innovative QC lasers since 2005. AdTech's QCLs are designed to cover most of the mid-IR spectral range, from λ = 3.8μm (78THz) to λ = 12.5μm (23.9THz). Almost all of AdTech's QCLs operate continuously at room temperature and can be designed to operate at a single frequency by using distributed feedback waveguide manufacturing. However, AdTech's QCLs are only mechanically tunable, which makes these QCLs impractical for most applications including spectroscopy, communications, to name a few.

[0013] Coherent terahertz magnon lasers can generate coherent radiation in the terahertz spectrum.

[0014] Coherent communication systems in the terahertz spectrum can be used for many unique applications, including but not limited to sending, receiving, and reading received terahertz holographic images.

[0015] Such terahertz holograms can be used to encode secret information, including security codes that cannot be read by any other means except using another terahertz magnon laser that can illuminate such holograms at the receiving end at the same terahertz frequency as was recorded at the transmitting end of such a coherent terahertz communication system. Summary of the invention

[0016] A device for generating coherent terahertz radiation is provided. In one example, the device includes one or more multilayer tunable microcolumns. In turn, the multilayer tunable microcolumns may include a substrate, a bottom electrode, a bottom layer of ferromagnetic material further including a magnon gain medium (MGM) coupled to the bottom electrode, a tunnel junction coupled to the ferromagnetic material, a spin injector coupled to the tunnel junction, a pinning layer coupled to the spin injector, a reference layer coupled to the pinning layer, and a top electrode. In one example, a housing cavity surrounds at least one of the multilayer tunable microcolumns. In one example, a storage cavity surrounds the housing cavity. The present disclosure is provided to introduce a selection of concepts further described in the following specific embodiments. The present disclosure is not intended to identify the key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present technology and, together with the description, explain the following principles:

[0018] Figure 1 A cross-sectional view of a tunable multilayer terahertz magnon laser with a RUDERMAN-KITTEL-KASUYA-YOSIDA (RKKY) pinned layer for purposes of the present technology is depicted, the tunable multilayer terahertz magnon laser comprising a substrate, a bottom electrode, a bottom layer, a tunnel junction, a spin injector, a pinned layer, a reference layer, and a top electrode.

[0019] Figure 2 The dependence of the RUDERMAN-KITTEL-KASUYA-YOSIDA (RKKY) interaction on the thickness of the spacer layer of ruthenium (Ru) is demonstrated for the purpose of the present technique.

[0020] Figure 3 The electronic energy spectrum and generation of non-equilibrium magnons in a half-metal are shown for the purposes of the present technique.

[0021] Figure 4 The design of a tunable terahertz magnon laser with a tunnel junction for the purpose of the present technology is depicted.

[0022] Figure 5 The invention is described as follows: Figure 4 Voltage-based continuous tuning mechanism of tunnel junction tunable terahertz magnon lasers.

[0023] Figure 6An example device according to an aspect of the subject disclosure is described.

[0024] Figure 7 An example method for generating unbalanced magnons in a magnon gain medium is described, resulting in the generation of terahertz radiation.

[0025] Figure 8 and Fig. 9 The equations for magnon generation are stated.

[0026] Fig.10 Another example apparatus according to an aspect of the subject disclosure is described.

[0027] Fig.11 is a front view of a terahertz generator for purposes of the present technology comprising a plurality of single terahertz magnon lasers, each such single terahertz magnon laser further comprising a single multilayer pillar.

[0028] Fig.12 A front view of a terahertz generator for purposes of the present technology comprising a plurality of single terahertz magnon lasers, each such single terahertz magnon laser further comprising a single multilayer pillar, and a terahertz transparent medium separating at least two such single multilayer pillars is illustrated.

[0029] Fig.13 A top view of a terahertz generator for the purpose of the present technology including a plurality of single terahertz magnon lasers is shown, each of which further includes a single multilayer column and a terahertz transparent medium filled between such single multilayer columns.

[0030] Fig.14 A terahertz coherent communication system configured to form, transmit, receive, and read holographic images in the terahertz spectrum is described for purposes of the present technology. DETAILED DESCRIPTION

[0031] Reference will now be made in detail to embodiments of the present technology, examples of which are shown in the accompanying drawings. Although the present technology will be described in conjunction with various embodiments, it should be understood that they are not intended to limit the present technology to these embodiments. On the contrary, the present technology is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the various embodiments defined by the appended claims.

[0032] Furthermore, in the following detailed description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. However, it is apparent to one of ordinary skill in the art that the presented embodiments may be practiced without these specific details. In other instances, well-known methods, processes, components, and circuits are not described in detail to avoid unnecessarily obscuring aspects of the presented embodiments.

[0033] In one embodiment of the present technology, Figure 1 A cross-sectional view of a tunable multilayer terahertz magnon laser 10 is depicted. For purposes of the present technology, the tunable multilayer terahertz magnon laser 10 includes a substrate 12, a bottom electrode 14, a bottom layer 16, a tunnel junction 18, a spin injector 20, a pinned layer 22, a reference layer 24, and a top electrode 28. In one embodiment, the pinned layer 22 may also include a RUDERMAN-KITTEL-KASUYA-YOSIDA (RKKY) pinned layer. A single multilayer column 26 includes a bottom layer 16, a tunnel junction 18, a spin injector 20, a pinned layer 22, a reference layer 24, and a top electrode 28. In one embodiment, the spin injector 20 may be, for example, a top layer. In another embodiment, the bottom electrode 14 may be a ground electrode.

[0034] In an embodiment of the present technology, ( Figure 1 The substrate 12 includes gallium arsenide (GaAs).

[0035] Gallium arsenide (GaAs) is a compound of gallium and arsenic. It is a III-V group direct bandgap semiconductor with a zinc blende crystal structure. GaAs is used in the manufacture of monolithic microwave integrated circuits.

[0036] GaAs is commonly used as a substrate material for epitaxial growth of other III-V semiconductors, including indium gallium arsenide, aluminum gallium arsenide, etc.

[0037] GaAs can be produced using molecular beam epitaxy (MBE). MBE can be performed in, for example, high vacuum or ultra-high vacuum (10 -8 -10 -12 ) is carried out in the care of the patient.

[0038] On the one hand, the deposition rates of MBE (typically less than 3,000 nm / hour) allow for epitaxial growth of films. These deposition rates typically require proportionally better vacuum to achieve the same impurity levels as other deposition techniques. The absence of carrier gases and the ultra-high vacuum environment allow the grown films to achieve the highest purity.

[0039] In solid-source MBE, elements such as gallium and arsenic in ultrapure form are heated in individual quasi-Knudsen effusion cells or electron beam evaporators until they begin to slowly sublime. The gaseous elements then condense on a chip, where they can react with each other. In the case of gallium and arsenic, single-crystalline gallium arsenide is formed. When using evaporation sources such as copper or gold, gaseous elements impinging on the surface may be attracted (e.g., after a time window, the impinging atoms will hop around the surface) or reflected. Atoms on the surface may also desorb.

[0040] Controlling the temperature of the source will control the rate at which material strikes the substrate surface, and the temperature of the substrate affects the rate of hopping or desorption. The term "beam" means that the evaporated atoms do not interact with each other or the chamber gas before reaching the chip because the mean free path of the atoms is long.

[0041] In one embodiment of the present technology, ( Figure 1 The substrate 12 includes aluminum oxide (Al2O3).

[0042] In another embodiment of the present technology, ( Figure 1 The substrate 12 includes aluminum nitride (AlN).

[0043] In another embodiment of the present technology, ( Figure 1 The substrate 12 includes indium tin oxide (InTnO).

[0044] Indium tin oxide (ITO) is a ternary composition consisting of indium, tin and oxygen in varying proportions. Depending on the oxygen content, it can be described as a ceramic or an alloy. Indium tin oxide is usually encountered together as an oxygen-saturated composition, with a formula of 74% In, 18% O2 and 8% Sn by weight. The oxygen-saturated composition is so typical that the unsaturated composition is called oxygen-deficient ITO. It is transparent and colorless in thin layers, while in bulk form it is pale yellow to gray. In the infrared region of the spectrum, it acts as a metal-like mirror.

[0045] Indium tin oxide is one of the most widely used transparent conductive oxides because it has two main properties: electrical conductivity and optical transparency, and the ease with which it can be deposited as a thin film. As with all transparent conductive films, a compromise must be made between conductivity and transparency, as increasing thickness and increasing the concentration of charge carriers increases the conductivity of the material but decreases its transparency. Indium tin oxide thin films are most often deposited on a surface by physical vapor deposition. Electron beam evaporation or a range of sputtering deposition techniques are often used.

[0046] In another embodiment of the present technology, ( Figure 1 The substrate 12 includes silicon (Si).

[0047] Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a bluish-grey metallic sheen and is a tetravalent metalloid. It is a member of Group 14 in the periodic table, above carbon and below germanium, tin, lead, and feldspar. It is fairly unreactive, though not as reactive as germanium, but has a strong chemical affinity for oxygen. As a result, it was introduced in 1823 by It was first prepared and characterized in pure form by Jakob Berzelius.

[0048] Silicon is the eighth most common element in the universe by mass, but rarely occurs as a pure element in the Earth's crust. It is most widely distributed in dust, sand, asteroids, and planets as various forms of silicon dioxide (silicon dioxide) or silicates. More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust after oxygen (about 28% by mass). Highly purified silicon is used in integrated circuits.

[0049] In another embodiment of the present technology, ( Figure 1 The substrate 12 includes silicon on sapphire (SoS).

[0050] Silicon-on-sapphire (SOS) is a heteroepitaxial process used in integrated circuit manufacturing, consisting of a thin layer of silicon (typically less than 0.6 μm) grown on a sapphire (Al2O3) chip.

[0051] SOS is part of the Silicon-On-Insulator (SOI) family of CMOS technology. Typically, high-purity artificially grown sapphire crystals are used. Silicon is deposited on a heated sapphire substrate, usually by the decomposition of silane gas (SiH4). The advantage of sapphire is that it is an excellent electrical insulator, preventing radiation-induced stray currents from spreading to nearby circuit elements. SOS faced early challenges in commercial manufacturing due to the difficulty in manufacturing the very small transistors used in modern high-density applications. This is because the SOS process can cause the formation of dislocations, twinning, and stacking faults due to the lattice differences between sapphire and silicon. In addition, there is some substrate contamination from aluminum (a p-type dopant) in the silicon closest to the interface.

[0052] The use of epitaxially grown silicon on sapphire substrates for the manufacture of MOS devices involves a silicon purification process that reduces crystal defects caused by the mismatch between the sapphire and silicon lattices. For example, Peregrine Semiconductor's SP4T switch is formed on an SOS substrate with a final thickness of silicon of approximately 95nm. The silicon is recessed in the area outside the polysilicon gate stack by poly-oxidation and further recessed to a thickness of approximately 78nm by a sidewall spacer formation process.

[0053] In another embodiment of the present technology, ( Figure 1 The substrate 12 includes magnesium oxide (MgO).

[0054] Magnesium oxide (MgO) or magnesium oxide is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium. It has the empirical formula of MgO and consists of a lattice of Mg2 (positive ions) and O2 (negative ions) held together by ionic bonds. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but the reaction can be reversed by heating to separate the water.

[0055] Magnesium oxide was historically known as magnesia alba (literally, a white mineral from magnesium oxide - other sources refer to magnesia alba as MgCO3) to distinguish it from magnesia negra, a black mineral containing what is now known as manganese. Although "magnesium oxide" usually refers to MgO, magnesium peroxide MgO2 is also known as a compound. MgO2 is thermodynamically stable at pressures above 116 GPa (gigaPascals), as predicted by evolved crystal structures, while the entirely new semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa. Due to its stability, MgO is used as a model system for studying the vibrational properties of crystals. Magnesium oxide is produced by calcining magnesium carbonate or magnesium hydroxide.

[0056] In one embodiment of the present technology, still referring to Figure 1 The bottom electrode 14 is selected from the group consisting of the following materials: cobalt-iron alloy (Co 0.5 Fe 0.5 ); silver (Ag); gold (Au); platinum (Pt); cobalt (Co); palladium (Pd); titanium (Ti); and titanium tungsten (TiW).

[0057] Each of these materials can be deposited on a substrate by molecular beam epitaxy (MBE) (see discussion above) or by sputtering deposition.

[0058] Sputtering deposition is a physical vapor deposition (PVD) method of thin film deposition by sputtering. This involves ejecting material from a "target" as a source onto a "substrate", such as a silicon chip. Re-sputtering is the re-emission of deposited material by ion or atomic bombardment during the deposition process. The sputtered atoms ejected from the target have a wide distribution of energies, typically up to tens of eV (100,000K). The sputtered ions (usually only a small fraction of the ejected particles are ionized - about 1%) can fly in a straight trajectory from the target and produce an energetic impact on the substrate or vacuum chamber (causing re-sputtering).

[0059] Alternatively, at higher pressures, ions collide with gas atoms acting as moderators and diffuse, reaching the substrate or vacuum chamber wall and condensing after a random walk. By changing the background pressure, the entire range from high-energy ballistic impact to low-energy thermalization motion can be accessed.

[0060] The sputtering gas is usually an inert gas, such as argon. For efficient momentum transfer, the atomic weight of the sputtering gas should be close to that of the target, so neon is preferred for sputtering light elements, while krypton or xenon are used for sputtering heavy elements. Reactive gases can also be used to sputter the compound. Depending on the process parameters, the compound can form on the target surface, in flight, or on the substrate. The availability of many parameters to control sputtering deposition makes it a complex process, but also allows experts to control the growth and microstructure of the film to a great extent.

[0061] An important advantage of sputtering deposition is that even materials with very high melting points can be easily sputtered, whereas evaporating these materials in a resistance evaporator or Knudsen cell is problematic or impossible. The composition of the sputtering deposited film is close to the composition of the source material. The difference is due to the fact that different elements diffuse differently due to their mass (light elements are more easily deflected by the gas), but this difference is constant.

[0062] Sputtered films generally have better adhesion to the substrate than evaporated films. The targets contain a large amount of material and require no maintenance, making the technique suitable for ultra-high vacuum applications.

[0063] Sputtering sources contain no hot parts (to avoid heating, they are usually water-cooled) and are compatible with reactive gases such as oxygen. Sputtering can be done from the top down, while evaporation must be done from the bottom up. Advanced processes such as epitaxial growth are possible.

[0064] Some disadvantages of the sputtering process are that the process is more difficult to combine with lift-off for film construction. This is because diffusion transport, a characteristic of sputtering, makes a complete shadow impossible. Therefore, it is not possible to completely restrict where the atoms go, which leads to contamination problems. In addition, compared to pulsed laser deposition, active control of layer-by-layer growth is difficult, and the inert sputtering gas enters the growing film as impurities.

[0065] Pulsed laser deposition is a variation of the sputtering deposition technique in which a laser beam is used for sputtering. The role of sputtered and re-sputtered ions as well as background gases is well studied in the pulsed laser deposition process.

[0066] Sputtering sources typically employ magnetrons, which use strong electric and magnetic fields to confine charged plasma particles close to the surface of the sputtering target. In the magnetic field, the electrons follow a spiral path around the magnetic field lines, and more ionizing collisions occur with gaseous neutral particles near the target surface than would otherwise occur. (As the target material is consumed, a "racetrack" erosion profile may appear on the surface of the target.)

[0067] The sputtering gas is usually an inert gas such as argon. The additional argon ions produced due to these collisions lead to a higher deposition rate. The plasma can also be maintained at a lower pressure in this way. The sputtered atoms have a neutral charge and are therefore not affected by the magnetic trap.

[0068] Charge accumulation on insulating targets can be avoided by using RF sputtering, where the sign of the anode-cathode bias changes at a high rate (typically 13.56 MHz). RF sputtering works well to produce highly insulating oxide films, but comes with the added expense of an RF power supply and impedance matching network. Stray magnetic fields leaking from ferromagnetic targets can also interfere with the sputtering process. This usually must be compensated for using specially designed sputtering guns with unusually strong permanent magnets.

[0069] In one embodiment of the present technology, still referring to Figure 1 , the bottom layer 16 is selected from the group consisting of the following materials: chromium dioxide (CrO2); semi-metallic ferromagnetic oxide Sr2FeMoO6; Heusler alloy Co2MnGe; Heusler alloy Co2MnSi (CMS); Heusler alloy Co2FeSi (CFS); Heusler alloy Co2MnSn (CMS); and Heusler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

[0070] For example, in a recent paper published in Nat Commun., 2014 May 30;5:3974. M. Jourdan et al., “Direct observation of half-metallicity in the Heusler compound Co2MnSi”, Co2MnSi samples were grown in a system consisting of a sputtering chamber, a molecular beam epitaxy (MBE) chamber, and a synchrotron radiation ultraviolet emission spectroscopy (SRUPS) chamber equipped with a hemispherical energy analyzer (energy resolution 2.000 Å) with a hemispherical multichannel spin filter. The epitaxial buffer layer of the Heusler compound Co2MnGa (30 nm) was first grown on a MgO(100) substrate by radio frequency (RF) sputtering at room temperature. By an optimized additional annealing process, L21 order was obtained at 550 °C, as shown by high energy electron diffraction (RHEED) and X-ray diffraction (XRD). Co2MnSi (70 nm) was RF sputtered on top at room temperature. Induced by the buffer layer, the Co2MnSi film already exhibited a certain degree of L21 surface order as deposited. By additional annealing, the order was improved, as evidenced by RHEED on the film surface.

[0071] In one embodiment of the present technology, still referring to Figure 1 , the tunnel junction 18 is selected from the group consisting of: magnesium oxide (MgO); aluminum oxide (Al2O3); and spinel MgAl2O4.

[0072] For example, in the paper “Low-temperature atomic layer deposition of MgO thin film on Si” by S Vangelista et al., published in Journal of Physics D: Applied Physics, Vol. 46, No. 48, magnesium oxide (MgO) thin films were grown by atomic layer deposition using bis(cyclopentadienyl)magnesium and H2O precursors in a wide deposition temperature window of 80-350°C. The MgO film was grown at a cycle temperature of ~0.12 nm. -1 The as-synthesized MgO films were deposited on HF-last Si(100) and SiO2 / Si substrates at a constant growth rate of 1.5 Å. The structural, morphological and chemical properties of the synthesized MgO films were investigated by X-ray reflectivity, grazing incidence X-ray diffraction, time-of-flight secondary ion mass spectrometry and atomic force microscopy measurements. Besides good chemical homogeneity and a polycrystalline structure with a thickness of more than 7 nm, the MgO layers are characterized by sharp interfaces with the substrate and limited surface roughness. CV measurements were performed on Al / MgO / Si MOS capacitors with MgO thicknesses in the range of (4.6-11) nm, which allowed the determination of a dielectric constant (κ) of ~11. The Co layer was deposited by chemical vapor deposition in direct contact with the MgO without vacuum break (base pressure 10 -5 -10 -6 The grown Co / MgO stack shows sharp interfaces with no interdiffusion of elements between the layers. CV and IV measurements have been performed on Co / MgO / Si MOS capacitors. The dielectric properties of MgO are not affected by the further Co deposition process.

[0073] In one embodiment of the present technology, still referring to Figure 1 The spin injector 20 is selected from the group consisting of the following materials: chromium dioxide (CrO2); semi-metallic ferromagnetic oxide Sr2FeMoO6; Heusler alloy Co2MnGe; Heusler alloy Co2MnSi (CMS); Heusler alloy Co2FeSi (CFS); Heusler alloy Co2MnSn; and Heusler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

[0074] For example, in the paper “Structural and magnetic properties and tunnel magnetoresistance for Co2(Cr,Fe)Al and Co2FeSi full-Heusler alloys” by K Inomata et al., published in Journal of Physics D: Applied Physics, Vol. 39, No. 5, the Co2(Cr 1_x Structure and magnetization of Co2FeSi all-Heusler alloys. The films were deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultrahigh vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). 75 Fe 25 The magnetic tunnel junction with all-Huesler alloy electrodes was fabricated by stacking a (3nm) / IrMn(15nm) / Ta(60nm) structure and using electron beam lithography and Ar ion etching 10 2 μm 2 The junction area is micro-machined, where Co2YZ represents Co2(Cr 1_x Fex)Al or Co2FeSi. The tunnel barrier is formed by deposition of 1.2nm aluminum followed by plasma oxidation in the chamber. X-ray diffraction reveals A2 or B2 structures, depending on the heat treatment conditions and substrate, but not Co2(Cr 1--_x However, when Co2FeSi thin films were deposited on MgO(001) substrates at high temperatures above 473 K, the L21 structure was obtained. 0.4 Fe 0.6)Al electrode, the maximum tunnel magnetoresistance (TMR) is 52% at room temperature and 83% at 5 K. The junction using Co2FeSi electrode with L21 structure exhibits 41% TMR at room temperature and 60% at 5 K, which can be improved by using a buffer layer to reduce the lattice mismatch between Co2FeSi and MgO(001) substrate.

[0075] In one embodiment of the present technology, still referring to Figure 1 , the pinning layer 22 is selected from the group consisting of the following materials: iridium manganese chromium (IrMnCr); iridium manganese (IrMn); nickel manganese (NiMn); nickel manganese chromium (NiMnCr); nickel manganese iron (NiMnFe); nickel manganese iridium (NiMnIr); nickel manganese palladium (NiMnPd); nickel manganese platinum (NiMnPt); nickel manganese rhodium (NiMnRh); platinum manganese (PtMn) and nickel manganese ruthenium (NiMnRu).

[0076] For example, in the paper "Magnetic Tunnel Junction Materials for Electronic Applications" by JM Slaughter et al., published in JOM-e, 52(6) (2000), a ferromagnetic film is pinned when in contact with an antiferromagnetic (AF) film due to exchange coupling. For an uncoupled, free ferromagnetic film, the magnetic orientation of the film shows hysteresis behavior pointing in the direction of the last applied saturation field. If a saturation field is applied and then removed, the magnetic orientation of the free film will be in the direction of the field. If the direction of the applied saturation field is reversed and removed again, the magnetic orientation of the film will be reversed. Therefore, in zero applied field, either orientation is possible. A ferromagnetic film pinned by an AF layer exhibits similar behavior, but with an offset. In zero field, the ferromagnetic film will align in one direction. The exchange coupling between the ferromagnetic and AF layers causes the ferromagnetic layers to align preferentially in one direction at their mutual interface. For the memory device in question, this preferential alignment or pinning serves to lock a layer in a fixed direction. Most of the work on AF pinning materials and other aspects of the field has revolved around manganese-based antiferromagnetic materials such as platinum-manganese, iridium-manganese, rhodium-manganese, and iron-manganese. Platinum-manganese is a particularly interesting pinning material because it remains antiferromagnetic at relatively high temperatures. Unlike many commonly used AF alloys, platinum-manganese is not AF as deposited. Instead, this material must be post-annealed, resulting in a phase transition from a face-centered cubic (fcc) to a face-centered tetragonal (fct) crystal structure. The fct phase of platinum-manganese is AF and pins adjacent ferromagnetic films. The pinning strength increases with annealing time. The shift and widening of the nickel-iron hysteresis loop in the annealed material is a characteristic of a pinned ferromagnetic film. Once pinned, the exchange bias causes the film's magnetic orientation to be in one direction at zero applied field.

[0077] In one embodiment of the present technology, still referring to Figure 1 , the pinned layer 22 further includes a RUDERMAN-KITTEL-KASUYA-YOSIDA (RKKY) non-magnetic pinned layer.

[0078] As in Figure 2 As shown in , the RKKY interaction 100 exhibits an antiferromagnetic polarity for a ruthenium spacer having a layer thickness of about 8 angstroms (e.g., at position 102 of the RKKY interaction 100). For references, see SSP Parkin, "Spin Engineering: Direct determination of the Ruderman-Kittel-Kasuya-Yosida far-field function in ruthenium," Phys. Rev. B 44(13), 1991.

[0079] In one embodiment of the present technology, a ruthenium spacer with a thickness of about 8 angstroms is used as the pinning layer ( Figure 1 The magnetization direction of the spin injector 20 can be antiparallel to the magnetization direction of the bottom layer 16 to allow the maximum minority current to be injected into the bottom layer 16 including the magnon gain medium. The injection of the maximum minority current will substantially simplify reaching the magnon lasing point.

[0080] In one embodiment of the present technology, still referring to Figure 1 , reference layer 24 includes a ferromagnetic material for selecting the orientation of bottom layer 16 in a particular direction.

[0081] In an embodiment of the present technology, the reference layer 24 (e.g., free layer) can be implemented by using CFA (B2-orderedCo2FeAl). References: Hiroaki Sukegawa, Zhenchao Wen, Kouta Kondou, Shinya Kasai, Seiji Mitani, Koichiro Inomata; Applied Physics Letters 100, 182403 (2012); "Spin-transfer switching in full-Heusler Co2FeAl-based magnetic tunnel junctions".

[0082] In one embodiment of the present technology, still referring to Figure 1 The top electrode 28 is selected from the group consisting of the following materials: cobalt-iron alloy (Co 0.5 Fe 0.5); silver (Ag); gold (Au); platinum (Pt); cobalt (Co); palladium (Pd); titanium (Ti); and titanium tungsten (TiW). Each of these materials can be deposited by MBE or sputtering.

[0083] In one embodiment of the present technology, still referring to Figure 1 , the spin injector 20 and the pinning layer 22 are replaced by a single layer electron injector. In this embodiment, the electron injector is selected from the group consisting of: metal; metal alloy; ferromagnetic metal; and ferromagnetic alloy.

[0084] In an embodiment of the present technology, the terahertz magnon laser 10 ( Figure 1 ) generates terahertz radiation based on the magnon laser effect. For reference, see US Patents: 7,430,074; 7,508,578; 9,136,665. In one aspect, a voltage bias 74 can be applied to the bottom electrode 14 and the top electrode 28 to promote the generation of terahertz radiation.

[0085] The essence of terahertz radiation based on the magnon laser effect is as follows: A magnon gain medium (MGM) includes a conduction band divided into two subbands separated by an exchange gap, a first subband with spin-up and a second subband with spin-down (not shown).

[0086] In the case of conventional lasing, if an atom is already in an excited state (i.e. there is a population inversion), it may be perturbed by the passage of a photon with a frequency ν21, which corresponds to the energy gap ΔE of the transition from the excited state L2 to the ground state L1 (level 1). In this case, the excited atom relaxes to the ground state and is induced to produce a second photon with a frequency ν21. The original photon is not absorbed by the atom, so the result is two photons of the same frequency. This process is called stimulated emission. In stimulated emission, the induced photon has the same frequency and phase as the incident photon. In other words, the two photons are coherent. Therefore, optical amplification can be provided, as well as production laser systems.

[0087] The magnon lasing process (I. Ya. Korenblit and BG Tankhilevich, High frequency magnongeneration by nonequilibrium electrons and stable of the magnon state, Phys. Lett. A, 64, 307 (1977)) can be realized in ferromagnets with an exchange gap Δ in the electronic spectrum, i.e. in ferromagnetic semiconductors and semimetals.

[0088] Figure 3A system 110 with magnon lasing in a half-metal is shown. In one aspect, by emitting acoustic magnons 114 (at about 10 -12 s), the minority electron 112 injected into the subband with spin down 113 enters the high energy state 116 in the subband with spin up 120 and then reabsorbs the same magnon through the Fermi level 118 (about 10 -13 As a result, the electron strongly reduces its energy δE120 associated with its relaxation on the spin-up electron with Fermi energy and cannot return to the spin-down subband by reabsorbing the magnon.

[0089] The number of nonequilibrium acoustic magnons depends on the magnon-electron damping rate Γ e and the magnon-magnon damping rate Γ m ratio, and at the maximum "birth" rate Γ e and the minimum "death" rate Γ m This corresponds to the maximum number of nonequilibrium magnons. The lasing frequency corresponds to the minimum magnon wave vector Because the magnon-electron damping rate Γ e With q -1 is proportional to; and the magnon-magnon damping Γ m With q 4 is proportional to, so Γ e / Γ m With q -5 The nonequilibrium magnons at the sample boundary relax several times before they scatter onto the equilibrium magnons. But these boundary processes are insignificant because they are elastic and do not change the energy of the magnons, and the change in momentum in an isotropic system is not important. Therefore, for a magnon laser, the minimum magnon wave vector Determines the lasing frequency:

[0090]

[0091] Where D is the magnon stiffness.

[0092] The merging of two magnons of frequency f and almost equal antiparallel wave vectors with directions (q / |q| and (-)q / |q|) generates a photon with frequency 2f. This process is the opposite of the well-known parametric magnon generation by electromagnetic radiation. It is easy to see that the desired pair of magnons is always generated by an electron flow with their momentum vectors oriented (q / |q| and (-)q / |q|). In fact, the Fermi velocity of the electrons in the current is randomly oriented in all directions, since the drift velocity is very small compared to the Fermi velocity. Therefore, among the injected electrons, there are always two electrons with equal but antiparallel momentum. According to the laws of conservation of energy and momentum, such an electron will generate two magnons with equal and antiparallel wave vectors, with the angle between the vector (+)p / |p| and the vector q / |q| being: From this relation, it can be concluded that for a magnon with |q| close to the lasing momentum q1, it is almost antiparallel to the vector p. At the critical pump current density j = 10 4 -10 6 A / cm 2 (The required critical pumping is of the same order of magnitude as in the case of conventional semiconductor lasers), the magnon lasing process begins and the device should generate high-power narrowband terahertz radiation.

[0093] For example, it is estimated that the lasing frequency of THz radiation in Co2MnSi(001) / MgO heterostructures can provide the stiffness (According to Ritchie L. et al., Phys. Rev. B 68, 104430) or (according to Jan Thoene, Stanislav Chadov, Gerhard Fecher, Claudia Felser, Jurgen Kubler) J. Phys. D: Appl. Phys. 42 (2009) 084013)), energy gap Δ = 0.6 eV (Bjorn Hulsen and Matthias Scheffler; Phys. Rev Let. 103, 046802 (2009)), and the effective electron mass m eff =(1.15–1.67)m0 (Steffen Kaltenborn and Hans Christian Schneider, Phys. Rev B 88, 045124 (23013). The energy of terahertz can be twice the minimum frequency of the non-equilibrium magnon (at the magnon lasing point)

[0094] for

[0095] for

[0096] In order for a terahertz magnon laser 10 to work efficiently at room temperature, it is first necessary to have the largest possible polarization, so that the majority electrons with spin up in the spin-up subband are the only electrons present in the semimetal in equilibrium. Researchers at Johannes Gutenberg University of Mainz directly observed 100% spin polarization at room temperature in the Heusler compound Co2MnSi (CMS) with a high Curie temperature of 985K.

[0097] In one aspect, the terahertz magnon laser 10 can be operated at room temperature by (a) injecting spin-down minority electrons into the upper subband of the half-metal, and (b) injecting a threshold critical minority electron current density into the upper subband to achieve the onset of the magnon lasing process.

[0098] In one embodiment of the present technology, Figure 4 The overall design of a voltage-based tunable terahertz magnon laser 140 is depicted, which includes a spin injector 144, a tunnel junction 146, a ferromagnetic material 148, and a terahertz waveguide 150. In one embodiment, the terahertz waveguide can be implemented using one or more 3D printing techniques. In one aspect, the ferromagnetic material 148 can include a magnon gain medium.

[0099] In one embodiment of the present technology, Figure 5 Pictured Figure 4 A mechanism 200 for voltage-based continuous tuning of the magnon laser 140 .

[0100] Typically, the increase in voltage bias 210 increases the spin-down 202 (having a Fermi level E f1 In fact, the minority electron 220 with the largest energy has the highest probability to tunnel through the tunnel junction 214 to propagate to the subband with spin up 204 (with Fermi level E) by flipping its spin. f2 208) and produces a magnon lasing wave vector with the smallest possible The magnon corresponds to the magnon with maximum energy ε max The momentum of the tunneling electron.

[0101] A further increase in the bias after reaching the lasing point leads to a further increase in the maximum energy and momentum of the electron with the highest tunneling probability, which in turn leads to a further decrease in the magnon lasing wave vector and a corresponding further decrease in the terahertz frequency.

[0102] More specifically, tuning in this system can be achieved by changing the bias voltage 210. In one embodiment, the voltage bias 210 may correspond to V bias =(Δ1+ε p ) times dV. This will cause df to change the lasing frequency (tuning):

[0103] (df / f) = -(dV / V)(Δ / ε p ) 1 / 2 (Equation 2)

[0104] Therefore, the tuning of the lasing frequency is parametrically larger than the shift in bias voltage, since a small change in bias leads to a large change in the electron energy and thus to a large change in the lasing frequency. Thus, by using voltage-based tuning, it is possible to cover the entire THz band, at least in the (1–30) THz range.

[0105] For example, for Δ / ε p ≈10 2 If dV / V≈1%=>df / f≈10%, then only a 1% change in the tuning voltage is needed to cover f max and 0.9f max The terahertz frequency region between .

[0106] In one embodiment, a micro-synchrotron on a chip may be provided. For example, the parameter is large (Δ / ε p ) 1 / 2 The frequency range (from THz maximum to THz minimum) and high output power can make the THz magnon laser device effectively a microsynchrotron on a chip, since a large range of lasing frequencies can be continuously covered using just one chip-sized device.

[0107] In one embodiment of the present technology, a method for tuning the frequency of terahertz radiation is provided. The method utilizes Figure 4 equipment, Figure 4 The device in includes a spin injector 144, a tunnel junction 146 coupled to the spin injector, and a ferromagnetic material 148 coupled to the tunnel junction 146. The ferromagnetic material 148 includes a magnon gain medium (MGM).

[0108] The method of tuning the terahertz radiation frequency includes the step of applying a bias 142 to shift the Fermi level of the spin injector 144 relative to the Fermi level of the ferromagnetic material 148 to initiate the generation of non-equilibrium magnons by injecting minority electrons into the magnon gain medium of the ferromagnetic material 148 .

[0109] The injected minority electrons enter a high-energy electronic state in a lower subband with the spin of the ferromagnetic material pointing up by flipping their spins in the exchange process. In this process, an unbalanced magnon is generated. The interaction between the generated unbalanced magnons leads to the generation of terahertz electromagnetic radiation.

[0110] The method further comprises the step of tuning the frequency of the generated terahertz radiation by varying the value of the bias voltage 142 .

[0111] Figure 6 An example embodiment of a coherent terahertz magnon laser 600 is illustrated. It includes at least one multilayer tunable micropillar, which includes (from bottom to top): (1) a substrate 602; (2) a bottom electrode 604; (3) a ferromagnetic material, and also includes a magnon gain medium (MGM) 606 coupled to the bottom electrode 604; (4) a tunnel junction 608 coupled to the magnon gain medium 606; (5) a spin injector 610 coupled to the tunnel junction 608; (6) a pinned layer 612 coupled to the spin injector 610; (7) a reference layer 614 coupled to the pinned layer 612; and / or (8) a top electrode 616. The terahertz magnon laser 600 also includes a housing cavity 620 that encloses all the multilayer tunable micropillars in one cavity. In addition, the terahertz magnon laser 600 may additionally or alternatively include a storage cavity 630.

[0112] like Figure 6 As shown, in the example embodiment including the accommodation cavity 620 but not including the storage cavity 630, due to the accommodation cavity 620, the terahertz radiation generated by combining the unbalanced magnons obtains coherent characteristics.

[0113] In fact, the time required to split the generated terahertz photon back into two unbalanced magnons is about 10 -7 seconds (the same time it takes for two unbalanced magnons to merge into a terahertz photon - see above).

[0114] On the other hand, the time it takes for a terahertz photon to escape into free space is approximately

[0115] Τ escape =λ THz / c(speed of light)=c / f THz / c=1 / f Thz. ; (Equation 3)

[0116] So, for example, for a photon with an energy of 10 THz, the escape time is about 10 -13 seconds (for a photon with an energy of 1 terahertz, the escape time is about 10 -12 seconds), much less than 10 -7 seconds (the time it takes for the generated terahertz photon to split back into two non-equilibrium magnons).

[0117] Thus, in some embodiments, absorption of terahertz photons at the surface of the receiving cavity can be ignored (e.g., absorption can be minimized by coating the inner surface of the receiving cavity with gold). A simulated radiation process can be initiated for the generated terahertz photons (e.g., based on the boson property of photons), which will result in the generation of coherent photons that can be output through the outer aperture. The size of d1 satisfies the flow condition:

[0118] λ THz << d1 << L1; (Equation 4)

[0119] where λ THz is the wavelength of the radiated terahertz radiation, and L1 is the size of the receiving cavity 620. Thus, the multi-layer column represents a terahertz antenna, and the radiation surface of the multi-layer column represents a terahertz gain medium.

[0120] However, in an embodiment that only includes the receiving cavity 620, the generation time of this coherent terahertz radiation is about 10 -7 seconds. This means that this terahertz radiation can be modulated up to only 10 MHz at most (it can only be modulated after the radiation is generated). In one embodiment, the storage cavity 630 can have a size of L2 and enclose the receiving cavity 620 with a size of L1:L2 < L1.

[0121] The radiation penetrating from the receiving cavity 620 through the aperture D1 into the storage cavity 630 can be modulated at any modulation frequency f modulation less than the generated terahertz frequency: f THz :f modulation < f THz :

[0122] For practical purposes, if the radiation frequency is 10 THz, the modulation frequency can be as high as 1 THz.

[0123] The radiation from the storage cavity 630 can be output through the outer aperture D2, and the size of the outer aperture D2 satisfies the flow condition: λ THz << D2 << L2.

[0124] As Figure 3 shown, according to embodiments disclosed in the present subject matter, the ferromagnetic material can include a magnon gain medium (MGM). The MGM includes a conduction band that is divided into two sub-bands separated by an exchange energy gap. The first sub-band has spin-up along the magnetization direction of the ferromagnetic material, and the second sub-band has spin-down opposite to the magnetization direction of the ferromagnetic material. The majority of electrons with spin-up are located in the first sub-band with spin-up.

[0125] As Figure 7As shown, when a bias voltage δV is applied between the top electrode 616 and the bottom electrode 604, the at least one multilayer tunable micropillar is configured to shift the Fermi level of the spin injector 610 relative to the Fermi level of the magnon gain medium 606 (for example, relative to the Fermi level of the ferromagnetic material including the magnon gain medium 606). After the Fermi level of the spin injector 610 is shifted relative to the Fermi level of the magnon gain medium 606, the spin injector 610 injects a minority electron with spin down into the magnon gain medium 606 through the tunnel junction 608 by tunneling, and is configured to generate non-equilibrium magnons in the magnon gain medium 606, thereby generating terahertz radiation.

[0126] In one aspect, Figure 3 The physical properties of magnon lasers can be explained.

[0127] An unbalanced electron in the upper subband with spin down rapidly emits a magnon with a large wave vector where m is the effective mass of the electron. According to the law of conservation of energy and momentum, if the energy ε of the electron measured from the bottom of the spin-down subband is p is much smaller than Δ, then the wave vector q of the emitted magnon is in the interval q1≤q≤q2, where p0=(2mΔ) 1 / 2 ,p=(2mε p ) 1 / 2 <<p0. The frequencies of these magnons are in the terahertz region.

[0128] Magnon generation rate and The ratio of their relaxation (when colliding with an equilibrium magnon) is the wave vector Therefore, the nonequilibrium magnon distribution function In a certain wave vector has a maximum value. increases with the electron pump, and due to the simulated emission of magnons, the function exist near When the pump reaches a certain critical value, begins to increase very quickly as the electronic pump increases. Under certain conditions, The generation of magnons becomes like an avalanche, and the magnon system becomes unstable. For details, please see references: I.Ya.Korenblit and BG Tankhilevich, Sov.Phys.-JETP, 46, 1167 (1977); I.Ya.Korenblit and BG Tankhilevich, Sov.Phys.-JETP Lett. 24, 555 (1976); I.Ya.Korenblit and BG Tankhilevich, Phys.Lett. A 64, 307 (1977) and the following equation. As a result, strong terahertz radiation can be obtained.

[0129] In one aspect, generation of magnons can be provided based on a system of equations.

[0130] The equations that govern the behavior of electrons and magnon The distribution function is obtained in the following paper: I. Ya. Korenblit and BG Tankhilevich, Sov. Phys.-JETP, 46, 1167 (1977) in the case of ferromagnetic semiconductors (in the case of semimetals we have very similar basic equations).

[0131] They are in a stable state

[0132]

[0133]

[0134] (Equation 5)

[0135] Figure 8 and 9 Show that these equations apply to the general non-steady-state case.

[0136] here is the relaxation rate when the magnon collides with the electron

[0137]

[0138] where v0 is the unit cell volume.

[0139] γ em is the electron-magnon relaxation rate:

[0140]

[0141] The "smeared" delta function δ(γ|ε) takes into account the finite lifetime of the electron in the final state, which is caused by the interaction with optical phonons, which can be strong in ferromagnetic semiconductors and have an important ionic contribution to chemical bonding.

[0142]

[0143] Due to the emission of longitudinal optical phonons in the case of ferromagnetic semiconductors (or scattering on equilibrium electrons with Fermi energy in the case of semimetals), the rate γ ↑ (p,ε p ) is the known electron damping rate. For energy ε p For electrons approaching Δ, the velocity is estimated to be

[0144] γ8(ε p )=(π / 2)αΩ(Ω / Δ) 1 / 2 ln(4Δ / Ω)<<Δ. (Equation 9)

[0145] Here Ω is the energy of the photon and α is the strength of the electron-phonon interaction.

[0146] The function g(ε) is the generation function of the electron with spin down. We regard it as the delta function

[0147] g(ε p )=g0εδ(ε-ε p ). (Equation 10)

[0148] We assume that the following energy ε is small, ε<<Δ.

[0149] The second term of lhs in the first part of Eq. 5 describes the relaxation of the nonequilibrium magnon when it collides with the equilibrium magnon, assuming Close to its equilibrium value,

[0150]

[0151] is the magnon-magnon relaxation rate. From Equation 5, we can get the following The integral equation of

[0152]

[0153] in

[0154]

[0155] as well as

[0156]

[0157] Equation 12 is reminiscent in form of the expression for the magnon distribution function under parametric pumping conditions. The difference is that here the rate Γ e Itself is function, since the number of emitted magnons depends on the distribution function f of the spin-down electrons ↓ , according to equations 6 and 7, it is not only composed of pump g(ε p ) and also by a certain average value on the magnon distribution function (Equation 14). Therefore, The behavior is different from the case of parametric pumping.

[0158] In one embodiment, Can be associated with a strong pump.

[0159] In another embodiment, the generated unbalanced magnons are isotropic.

[0160] In certain embodiments, the magnon and electron spectra are isotropic. Then Γ e (q) and Γ m (q) does not depend on direction.

[0161] The relaxation rate Γ(q) is usually a power function of q and can be written as

[0162]

[0163] More specifically, if Γ m (q) is determined by magnon-magnon exchange scattering, so for magnons, t = 4, the energy is greater than kT, and

[0164] For the magnon, t = 3, the energy Less than kT.

[0165] When g0 exceeds the critical value G c When , the strong pumping regime comes into play. If the damping of the photon on the electron is less than (εΔ) 1 / 2 , then the critical value is estimated to be

[0166] G c =2g c / (t+1),

[0167] g c =(Δ / ε) 3 / 2 Γ m (q0)[1+N (0) (q0)]. (Equation 16)

[0168] In g0>G cWhen the pumping speed increases, the function N(q) increases exponentially.

[0169] N(q)=[1+N (0) (q0)](p0 / 2p ε (t+1))exp(g0 / G c ), (Equation 17)

[0170] If q falls into the smooth region

[0171]

[0172]

[0173] N(q) with wave vectors outside the above range does not depend on the pump.

[0174] Therefore, under sufficiently strong pumping, the magnon distribution function is There is a peak.

[0175] In one embodiment, the number of electrons pumped per unit cell per second, β, can be defined as:

[0176]

[0177] The pumping estimate is obtained by equation (10)

[0178]

[0179] When g0 = G c In the case of critical pump β c yes

[0180] β c =(v0 q 3 0 / (2(t+1)π 2 ))Γ m (q0)[1+N (0) (q0)]. (Equation 21)

[0181] In embodiments where high frequency magnons are desired, their relaxation is primarily due to the four-magnon exchange interaction. Using the Γ published in the following reference (VG Vaks, AILarkin and SAPIkin, JETP 53 (1967)) m Expression, which can estimate T / T C .0.2, and N (0) (q0)<<1:Γ m .10 8 –10 9 sec -1 .

[0182] Therefore, according to (Equation 21) we estimate β c .10 5 –10 7 sec -1 , we can determine N (0) (q0) is very small.

[0183] To understand these estimates, consider a model in which a spin-down electron is emitted into a 1 cm 2 The active area of ​​the surface area. The lattice constant a of EuO is about 5x10 -8 cm, that is, the unit cell volume is about v0.10 -22 cm 3 . Critical value N e .β c x v0.10 28 -10 29 cm -3 sec -1 This is the number of electrons that should cross the edge in one second to reach 1cm 3 The critical number of magnons emitted within the volume. However, electrons emit magnons very close to the edge and can be estimated as follows.

[0184] Electron-magnon frequency γ em 3x10 12 -10 13 sec -1 . Energy is 10 -2 The speed of an electron of magnitude Δ is 5x10 6 -10 7 cm x sec -1 This gives the mean free path of the electron relative to the magnon emission as: 1.10 -6 cm. Therefore, all electrons that enter the sample (including the magnon gain medium) through the selected side will emit magnons at this distance from that side. Therefore, only the region of width l is active, and we get the current density j = N e xl electrons / second x cm 2 The charge of an electron is 1.6x10 -19 Q. Considering 1 x Q / sec = 1A, we finally get: j = 10 4 -10 5 A / cm 2 In semiconductors (or semimetals), it is easy to reach 10 5 -10 6 A / cm 2 Under the pulse rule, it is possible to obtain current densities as high as: j = 109 The current density is A / cm2.

[0185] Critical Pumping G c The physical meaning of can be understood as follows. The ratio of the generation rate of magnons to their relaxation rate is Γ e / Γ m exist reaches its maximum value at The minimum is reached at , that is, there is excess generation at the left end of the interval compared to the right end. Stimulated emission leads to an increase in this asymmetry. If N (0) >1, then nonlinear generation begins when the difference between the number of unbalanced magnons at the end of the generation interval equals the number of balanced magnons. On the other hand, if the opposite inequality (N (0) <1) holds true, then nonlinear generation starts when the difference between the numbers of unbalanced magnons at the end of the generation interval is equal to 1.

[0186] If the electronic damping caused by photophonon scattering is large, Critical pumping G' c is smaller than gc estimated by (Equation 16)

[0187] G' c =πg c γ ↑ / Δ. (Equation 22)

[0188] The critical region function N(q) changes with g0 2 increases with the increase of , and the wave vector spacing of the generated magnons decreases to 1 / g0:

[0189] N(q)=[1+N (0) (q)](g0 / GΝ c ) 2 . (Equation 23)

[0190] It should be emphasized that only the main generation rules are considered here. More detailed information can be found in the following reference: I. Ya. Korenblit and BG Tankhilevich, Sov. Phys.-JETP, 46, 1167 (1977).

[0191] In one embodiment, the effects of anisotropy and / or instability of a magnon system may be determined.

[0192] If the generation rate and relaxation rate The ratio depends on the wave vector , then in the nonlinear rule, the stimulated emission of magnons leads to a strong anisotropy of the magnon distribution function. For example, we can consider the anisotropy caused by the magnon spectrum The anisotropy of q is close to The magnon spectrum can be written as

[0193] ω q =Dq 2 (1+Λsin 2 θ), (Equation 24)

[0194] in

[0195] Λ=2πgΦ B M s / ω p0 <<1, (Equation 25)

[0196] M s is the magnetization intensity, is a vector and If the inequality If established, The anisotropy means that the generation is maximum at a certain angle θ.

[0197] Consider this situation, when the damping is large, that is, Since the anisotropy is very small (Λ<<1), the anisotropy is only effective under sufficiently strong pumping, greater than the critical pumping, equation (18). In g=G estimated by this equation c At , the number of magnons starts to increase as in the isotropic case. If the basic equation describing the generation of magnons close to equilibrium (Eq. 5) is assumed to be valid also beyond critical pumping, the role of small anisotropy can be revealed.

[0198] As shown in the following reference: I. Ya. Korenblit and BG Tankhilevich, Sov. Phys.-JETP, 46, 1167 (1977), the maximum generation occurs for magnons with θ close to zero and q close to p0. If the pumping reaches a critical value g *

[0199]

[0200] function become

[0201]

[0202] in

[0203] We are At ε q =Δ, we get

[0204]

[0205] When θ = 0, the denominator of this expression becomes zero. Stable solutions of equation (1) exist only for * When the pumping level reaches the critical value g * When , the number of magnons will undergo an avalanche growth, and the wave vectors of these non-equilibrium anisotropic magnons point along the magnetization direction and are equal to p0.

[0206] Note that at sufficiently low temperatures, three-magnon dipole scattering can be more important than the four-magnon exchange scattering discussed above. However, in contrast to the four-magnon exchange scattering probability, the three-magnon scattering probability is highly anisotropic and is related to sin 2 θcos 2 If this were the case, one would expect magnon instabilities for θ = 0 and θ = π / 2.

[0207] In one embodiment, terahertz radiation may be generated.

[0208] The interaction of magnons with electromagnetic radiation is considered in the following reference: MI Kaganov and VMT Sukernik, Sov. Phys.-JETP 37, 587 (1960). Merging two magnons with wave vectors q and q ’ The magnon will generate a photon with a wave vector

[0209]

[0210] And the frequency ν k equal

[0211] ω q +ω q' =v k =ck, (Equation 30)

[0212] where c is the speed of light.

[0213] According to these conservation laws, k is much smaller than q, that is,

[0214] Using the results of the same reference: MI Kaganov and VMT Sukernik, Sov. Phys.-JETP 37, 587 (1960), the rate of change of the photon distribution function n(ν) can be derived as follows:

[0215]

[0216] Here

[0217]

[0218] where Φ is the Bohr magneton. The last term in (Eq. 62) describes the relaxation of the generated photon, while τ ph is the photon relaxation time.

[0219] For EuO, at q0 = 2.6x10 cm -1 , and 4πM S =24x10 3 Gs, you can get W.2x10 7 sec -1 .

[0220] If the magnon distribution function is isotropic, then we can integrate in (Eq. 31) to obtain the following equation:

[0221]

[0222] By analyzing this equation, it is clear that in the initial stage of generation, when n is less than N, the number of photons will increase with N as long as the photon relaxation is small enough. 2 As n increases, the negative term in (Eq. 33) becomes significant and the photons reach a steady state where dn / dt = 0. If this is the case, we have the following expression for the number of photons n in the steady state:

[0223]

[0224] Where w=16W / 15.

[0225] If wτ ph Very big, wτ ph >>1 / N, the number of photons is as follows:

[0226]

[0227] On the other hand, if 1 / N 2 <<wτ ph <<1 / N, then the number of photons is as follows:

[0228] n=wτ ph N 2 ,1<<n<<N. (Equation 36)

[0229] Finally, if the photon relaxes very quickly, wτ ph N 2<<1, the pumping efficiency is low, and

[0230] n≈n (0) . (Equation 37)

[0231] In one embodiment, the frequency of terahertz radiation in a Co2MnSi(001) / MgO heterostructure can be estimated.

[0232] In one aspect, relevant parameters may be estimated.

[0233] For example, stiffness can be estimated according to Ritchie L. et al., Phys. Rev. B 68, 104430 Or according to Jan Thoene, Stanislav Chadov, Gerhard Fecher, Claudia Felser, Jurgen Kubler) J. Phys. D: Appl. Phys. 42 (2009) 084013)

[0234] In another embodiment, the energy gap may be determined according to Bjorn Hulsen and Matthias Scheffler; Phys. Rev Let. 103, 046802 (2009), for example, Δ=0.6 eV.

[0235] In yet another embodiment, the effective electron mass m can be estimated according to Steffen Kaltenborn and Hans Christian Schneider, Phys. Rev B 88, 045124 (23013); DY Smith, B. Segall, Phys. Rev. B 34, 5191 (1986). eff =(1.15–

[0236] 1.67)m0. Therefore, the frequency of terahertz radiation is twice the minimum frequency of the spin wave (at the magnon lasing point)

[0237]

[0238] for

[0239] (5.5 2 -6.2 2 )10 14 cm -2 =2x466(30.25-38.44)

[0240] for

[0241] F = (13.10 - 20.24) THz

[0242] In one embodiment, the time to generate such coherent terahertz radiation can be about 10 -7 seconds. This means that such terahertz radiation can only be modulated up to 10 MHz at most (e.g., it can only be modulated after the radiation is generated). This limitation can be overcome by introducing a storage cavity 630 with size L2 to surround a receiving cavity 620 with size L1: L2 < L1.

[0243] On the one hand, the radiation penetrating from the receiving cavity 620 into the storage cavity 630 through the hole D1 can be modulated at any modulation frequency f THz less than the generated terahertz frequency f modulation : f modulation < f THz .

[0244] For practical purposes, if the radiation frequency is 10 THz, the modulation frequency can be as high as 1 THz.

[0245] The radiation from the storage cavity 630 can be output through an outer hole D2 whose size meets the flow conditions:

[0246] λ THz << D2 << L2. (Equation 38)

[0247] Specific materials can be used for different layers. In one embodiment, the substrate 602 can include: aluminum oxide (Al2O3), indium tin oxide (InTnO); silicon (Si); silicon on sapphire (SoS); or magnesium oxide (MgO).

[0248] In another embodiment, the bottom electrode 604 can include: cobalt iron alloy (Co 0.5 Fe 0.5 ); silver (Ag); gold (Au); platinum (Pt); cobalt (Co); palladium (Pd); titanium (Ti); or titanium tungsten (TiW).

[0249] In another embodiment, the magnon gain medium 606 can include chromium dioxide (CrO2); half - metallic ferromagnetic oxide Sr2FeMoO6; Heusler alloy Co2MnGe; Heusler alloy Co2MnSi (CMS); Heusler alloy Co2FeSi (CFS); Heusler alloy Co2MnSn (CMS); or Heusler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

[0250] For example, Co2MnSi can be used as a material for realizing the magnon gain medium 606. In fact, in a recent paper published in Nat Commun., 2014 May 30; 5:3974. M. Jourdan et al., “Direct observation of half-metallicity in the Heusler compound Co2MnSi”, Co2MnSi samples were obtained in a sputtering chamber, a molecular beam epitaxy (MBE) chamber, and a synchrotron radiation ultraviolet photoelectron spectroscopy (SRUPS) chamber equipped with a hemispherical energy analyzer (energy resolution 1000 nm) with a multi-channel spin filter. The epitaxial buffer layer of the Heusler compound Co2MnGa (30 nm) was first grown on a MgO(100) substrate by radio frequency (RF) sputtering at room temperature. By an optimized additional annealing process, L21 order was obtained at 550 °C, as shown by high energy electron diffraction (RHEED) and X-ray diffraction (XRD). Co2MnSi (70 nm) was RF sputtered on top at room temperature. The Co2MnSi film already exhibited a certain degree of L21 surface order as deposited, induced by the buffer layer. By additional annealing, the order was improved, as evidenced by RHEED on the film surface.

[0251] In another example, the material that can be used as the magnon gain medium 606 can be a Co2+xFe1-xSi Heusler alloy in the L21 phase. See “CoFeSi / MgO(001)Heusler alloys: Influence of off-stoichiometry and lattice distortion on the magnetic properties in bulk andon MgO(001)”, published in the Journal of Applied Physics 109, 07E128 (2011); written by HCHerper et al.

[0252] In another embodiment, the tunnel junction 608 may include magnesium oxide (MgO); aluminum oxide (Al2O3); or spinel MgAl2O4.

[0253] In the paper “MgAlO(001)based magnetic tunnel junctions made by direct sputtering of a sintered spinel target” published in Appl. Phys. Lett. 108, 132404 (2016), Mohamed Belmoubarik, Hiroaki Sukegawa, Tadakatsu Ohkubo, Seiji Mitani and Kazuhiro Hono developed a fabrication process for epitaxial MgAlO barriers for magnetic tunnel junctions (MTJs) by using direct sputtering from a MgAlO spinel sintered target.

[0254] Annealing of the sputter-deposited MgAlO layers sandwiched between Fe electrodes leads to the formation of a (001)-oriented cation-disordered spinel with atomically sharp interfaces and lattice matching with the Fe electrodes. Large tunnel magnetoresistance ratios up to 245% at 297 K (436% at 3 K) and excellent bias voltage dependence are achieved in Fe / MgAlO / Fe(001) MTJs. These results suggest that direct sputtering is an alternative approach to achieve high-performance MTJs with spinel-based tunnel barriers.

[0255] The spin injector 610 can be selected from the group consisting of: chromium dioxide (CrO2); semi-metallic ferromagnetic oxide Sr2FeMoO6; Heusler alloy Co2MnGe; Heusler alloy Co2MnSi (CMS); Heusler alloy Co2FeSi (CFS); Heusler alloy Co2MnSn; and Heusler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

[0256] For example, in the paper “Structural and magnetic properties and tunnel magnetoresistance for Co2(Cr,Fe)Al and Co2FeSi full-Heusler alloys” published by K Inomata et al. in Journal of Physics D: Applied Physics, Volume 39, Number 5, the Co2(Cr 1-The structures and magnetizations of xFex)Al (0≤x≤1) and Co2FeSi full-Heusler alloys were deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultrahigh vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). 75 Fe 25 The magnetic tunnel junction with full Heusler alloy electrodes was fabricated by stacking a 10 nm (3 nm) / IrMn (15 nm) / Ta (60 nm) structure and electron beam lithography and Ar ion etching were used to etch the 10 2 μm 2 The junction area is micromachined, where Co2YZ represents Co2(Cr 1- xFex)Al or Co2FeSi. The tunnel barrier is formed by depositing 1.2nm of aluminum followed by plasma oxidation in the chamber. X-ray diffraction reveals either an A2 or B2 structure, depending on the heat treatment conditions and substrate, but not Co2(Cr 1- However, when Co2FeSi thin films were deposited on MgO(001) substrates at high temperatures above 473 K, the L21 structure was obtained. 0.4 Fe 0.6 )Al electrode, the maximum tunnel magnetoresistance (TMR) is 52% at room temperature (RT) and 83% at 5 K. While the junction using Co2FeSi electrodes with L21 structure exhibits 41% TMR at RT and 60% at 5 K, this can be improved by using a buffer layer to reduce the lattice mismatch between Co2FeSi and MgO(001) substrate.

[0257] The pinning layer 612 can be selected from the group consisting of the following materials: iridium manganese chromium (IrMnCr); iridium manganese (IrMn); nickel manganese (NiMn); nickel manganese chromium (NiMnCr); nickel manganese iron (NiMnFe); nickel manganese iridium (NiMnIr); nickel manganese palladium (NiMnPd); nickel manganese platinum (NiMnPt); nickel manganese rhodium (NiMnRh); platinum manganese (PtMn) and nickel manganese ruthenium (NiMnRu).

[0258] In one embodiment, the pinned layer 612 may also include a Ruderman-Kittel-Kasuya-Yosida non-magnetic pinned layer.

[0259] For example, Figure 2 As shown, the RKKY interaction exhibits an antiferromagnetic polarity for a Ruthenium spacer with a layer thickness of about 8 angstroms (see above).

[0260] In another example of a spacer that utilizes RKKY interaction and exhibits antiferromagnetic polarity, a Cu spacer is used. In one embodiment, the Cu spacer may correspond to the Cu spacer described in "Current-in-Plane Giant Magnetoresistance Sensor Using a Thin Cu Spacer and Dual Nano-Oxide Layers With a DR Greater Than 20 Ohms / sq" by Michael A. Seigler et al., published in IEEE Transactions on Magnetics, Volume: 43 Issue: 2.

[0261] The reference layer 614 may include a ferromagnetic material that is used to select the orientation of the magnon gain medium 606 in a certain direction.

[0262] The reference layer 614 may be, for example, a free layer. The reference layer 614 may be implemented by using CFA (B2-ordered Co2FeAl).

[0263] For example, reference layer 614 may correspond to the reference layer described by Hiroaki Sukegawa, Zhenchao Wen, Kouta Kondou, Shinya Kasai, Seiji Mitani, and Koichiro Inomata, Applied Physics Letters 100, 182403 (2012); “Spin-transfer switching in full-Heusler Co2FeAl-based magnetic tunnel junctions”.

[0264] In another example, the reference layer 614 can be a perpendicularly magnetized [Co / Pd]-based reference layer and an in-plane magnetized CoFeB sensing layer with various thicknesses (tCoFeB). Linear TMR curves for out-of-plane magnetic fields were successfully obtained with a dynamic range of over 600 Oe, corresponding to the coercivity of the [Co / Pd]-based reference layer. The MTJ showed the highest sensitivity of 0.026% / Oe at tCoFeB=1.8nm and the minimum nonlinearity of 0.11% full scale at t=3nm. The sensitivity and nonlinearity of the MTJ are significantly correlated with t, which is attributed to the change in the anisotropic field of the CoFeB sensing layer. See "Magnetic Tunnel Junctions With [Co / Pd]-Based Reference Layer and CoFeB Sensing Layer for Magnetic Sensor" by Takafumi Nakano et al., published in IEEE Transactions on Magnetics (Vol. 52, No. 7, July 2016).

[0265] The top electrode 616 may be selected from the group consisting of: cobalt-iron alloy (Co 0.5 Fe 0.5 ); silver (Ag); gold (Au); platinum (Pt); cobalt (Co); palladium (Pd); titanium (Ti); and titanium tungsten (TiW). Each of these materials can be deposited by MBE or sputtering.

[0266] Therefore, the terahertz magnon laser 600 generates terahertz radiation based on the magnon laser effect. For reference, please refer to US Patents: 7,430,074; 7,508,578; 9,136,665. In one embodiment, the frequency of the generated coherent terahertz radiation can be tuned by changing the bias voltage 618. In another embodiment, a receiving cavity 620 can be used to output the tunable coherent terahertz radiation into the storage cavity 630. In addition or alternatively, the storage cavity 630 can be used to output tunable coherent terahertz radiation. The tunable coherent terahertz radiation can be modulated by modulating the bias voltage 618 with a modulation frequency. In another embodiment, the tunable coherent terahertz radiation can be modulated by modulating the output coherent radiation by external means. In another embodiment, the tunable coherent terahertz radiation can be modulated by using a piezoelectric material to modulate the output coherent radiation to mechanically change the size of the hole D1 and / or the outer hole D2. In yet another embodiment, the tunable coherent terahertz radiation may be modulated by modulating the output coherent radiation using a synthetic ceramic material.The aperture D1 and / or the outer aperture D2 may output coherent terahertz radiation.

[0267] In one embodiment, a coherent terahertz magnon laser may be provided for communication applications. The small divergence of a coherent terahertz laser beam may allow a significant increase in the received power.

[0268] The spot size wz of a coherent laser beam is a function of the position along the Gaussian beam propagation direction z and depends on the aperture size d of the transmitting antenna and the wavelength λ. The coherent terahertz laser beam size w at a distance z = 0 from the aperture wo = d is z Estimated by AE Siegman, Lasers (University Science Books 1986)

[0269] w z =w o √1+(λz / πw o 2 ) 2 (Equation 39)

[0270] Fig.10 1. Device 1000 is illustrated according to one or more embodiments described herein. Device 1000 may include a magnon laser chip 1002 having a cavity 1020. Cavity 1020 may include a window 1024, which may be a hole of cavity 1020. In some embodiments, cavity 1020 may include a height L3. Fig.10 As shown, from the size w o = d = 1 mm window 1024 emits a light with λ(10 THz) = 3x10 -2 mm and the size of the coherent terahertz beam at a distance z = 100 m is: z =10 -3 m√1+(3 10 -5 m 10 2 m / 3.14 10 -6 m 2 ) 2 =1m.

[0271] On the other hand, the divergence of an incoherent terahertz beam at a distance of 100 m will include a sphere with a radius of 100 m. Therefore, by using a coherent beam, the link budget is improved by 40 dB. In fact, (R 2 / w z 2 )=100 2 / 1 2 =10 4= 40dB. Therefore, the receiver can use a small antenna to receive such a signal. Therefore, a secret receiver can receive short-term secret communications on undetectable terahertz frequencies by detecting a 1m-sized terahertz laser beam spot at a distance of 100m from the transmitter. This task can be simplified by transmitting several such coherent laser beams simultaneously.

[0272] In one embodiment, cavity 1020 can be a highly reflective cavity. Cavity 1020 can be made, for example, of a silicon membrane (e.g., see "High-efficiency terahertz-wave generation in Silicon membrane waveguides" published in Proceedings Volume 9199, Terahertz Emitters, Receivers, and Applications V; conference-proceedings-of-SPIE / 9199.toc) 91990D (2014) Event: SPIE Optical Engineering + Applications ( / conference-proceedings-of-spie / browse / SPIE-Optics-Photonics / SPIE-Opti ical-Engineering Applications / 2014), 2014, San Diego, California, USA, published by Hongjun Liu et al.

[0273] In another embodiment, window 1024 can be a high terahertz and far-infrared transparent window (e.g., aperture) made of Ge-Ga-Te far-infrared chalcogenide glass, similar to the Ge-Ga-Te far-infrared chalcogenide glasses described in “Novel NaI improved Ge–Ga–Te far-infrared chalcogenide glasses,” published in Infrared Physics and Technology; Ci Cheng et al., Volume 72, September 2015, Pages 148-152.

[0274] like Fig.10 As shown, the size of the coherent terahertz beam emitted from the window 1024 is: size wo = d = 1 mm, λ(10 THz) = 3x10 -2 mm, at a distance of z = 100 m it will be: w z =10 -3 m√1+(3 10 -5 m 10 2 m / 3.14 10 -6 m 2 ) 2=1m.

[0275] On the other hand, the divergence of an incoherent THz beam at a distance of 100 m will include a sphere with a radius of 100 m. Therefore, by using a coherent beam, the link budget is 40 dB better. In fact (R 2 / w z 2 )=100 2 / 1 2 =10 4 =40dB. Therefore, the receiver can use a small antenna to receive such a signal. Therefore, the secret receiver can receive short-term secret communications on undetectable terahertz frequencies by detecting a 1m-sized terahertz laser beam spot at a distance of 100m from the transmitter. This task can be simplified by transmitting several such coherent laser beams simultaneously. For example, coherent laser beam 1004, coherent laser beam 1006, and coherent laser beam 1008 can be transmitted simultaneously.

[0276] In one embodiment, cavity 1020 can be made of a silicon membrane (see "High-efficiency terahertz-wave generation in Silicon membrane waveguides" published in Proceedings Volume 9199, Terahertz Emitters, Receivers, and Applications V; conference-proceedings-of-SPIE / 9199.toc) 91990D (2014).

[0277] Event: SPIE Optical Engineering + Applications, 2014, San Diego, CA, USA, published by Hongjun Liu et al.

[0278] In one embodiment, window 1024 can be made of Ge-Ga-Te far-infrared chalcogenide glass (see “Novel NaI improved Ge–Ga–Te far-infrared chalcogenide glasses”, published in Infrared Physics and Technology; Vol. 72, September 2015, Ci Cheng et al., pp. 148-152).

[0279] In one embodiment of the present technology, Fig.11 2 is a front view of a terahertz generator including a plurality of single terahertz magnon lasers, each of which further includes a single multilayer column {26,1; 26,2; 26,i; ... 26,k}; wherein i and k are integers. Each of such single multilayer columns 26,i is coupled to a bottom electrode 14, wherein the bottom electrode 14 is coupled to a substrate 12.

[0280] In one embodiment of the present technology, Fig.12 A front view 35 of a terahertz generator is shown, comprising a plurality of single terahertz magnon lasers 10,1; 10,2 ... 10,i, ... 10,k; i and k are integers; each such single terahertz magnon laser further comprises a single multilayer column 80, a bottom electrode 14, a substrate 12, and a terahertz transparent medium 60 separating at least two such single multilayer columns. A bias voltage (not shown) applied to each single terahertz magnon laser 10,i from the top layer of the single multilayer column 80 to the bottom electrode 14 is configured to inject a spin current of a spin injector 610 into the magnon gain medium 606. The injected current enables the spin-down electrons of the spin injector 610 to transition through the tunnel junction 608 to the subband having the spin-down of the magnon gain medium 606, triggering the magnon lasing process by entering the subband having the spin-up of the magnon gain medium 606, which results in the generation of a magnon current from the top surface 45 ( Fig.13 For reference, see U.S. Patents: 7,430,074; 7,508,578; 9,136,665.

[0281] In one embodiment of the present technology, still referring to Fig.12 As shown, the distance L between any two adjacent multilayer columns (eg, the distance 62 between two adjacent multilayer columns 26,1 and 26,2) may be greater than the wavelength λ of the emitted terahertz signal. THz , so that each generated terahertz photon can be born outside the magnon gain medium region.

[0282] D>λ THz (Equation 40)

[0283] In one embodiment of the present technology, reference Fig.12 The terahertz transparent medium 60 is selected from the group consisting of: a crystalline terahertz transparent material; and a polymer terahertz transparent material.

[0284] In one embodiment of the present technology, reference Fig.12The terahertz transparent medium 60 is selected from the group consisting of the following crystalline materials: High Resistivity Float Zone Silicon (HRTZ-Si); crystalline quartz; and sapphire.

[0285] Crystals such as silicon, crystalline quartz and sapphire are very important for the production of terahertz optical devices. For references, see X.-C. Zhang, J. Xu, Introduction to Terahertz Wave Photonics, Springer Science+Business Media, LLC 2010.

[0286] Apart from synthetic diamond, high-resistivity silicon is the only isotropic crystalline material suitable for an extremely wide range of wavelengths from NIR (1.2 μm) to millimeter (1000 μm) waves. It is cheaper to grow and process than diamond. In addition, it can be of considerable size, allowing the rapidly developing terahertz electronic components to be manufactured on its basis.

[0287] One of the best materials for wavelengths above 50 μm is z-cut crystalline quartz. Importantly, z-cut crystalline quartz windows are transparent in the visible range, thus allowing easy adjustment with HeNe lasers, without changing the light polarization state, and can be cooled below the lambda point of liquid helium. Crystalline quartz is a birefringent material, and care should be taken if the polarization of the radiation is important.

[0288] Like crystalline quartz, sapphire is transparent both in the terahertz region and in the visible region. For measured samples with a thickness of 1 to 5 mm, the transmittance below 600 μm depends strongly on the sample thickness. Like HRFZ-Silicon, sapphire can also be used to make terahertz photoconductive antennas, as the refractive index values ​​for terahertz are similar.

[0289] In one embodiment of the present technology, reference Fig.12 The terahertz transparent medium 60 is selected from the group consisting of the following polymer materials: high-density polyethylene (HDPE); polymethylpentene (TPX); polyethylene (PE); and polytetrafluoroethylene (PTFE).

[0290] Among the wide variety of available polymers, there are some excellent terahertz transparent materials with relatively low reflectivity. In this sense, the best materials are TPX (polymethylpentene), polyethylene (PE), polypropylene (PP) and polytetrafluoroethylene (PTFE or Teflon). At longer wavelengths, the transmission of these polymers is less structured and flat. Going into shorter wavelengths, mainly below 200 μm, characteristic bands of intrinsic vibrations appear and scattering increases due to inhomogeneities. Polymers generally become increasingly opaque at shorter wavelengths.

[0291] Polymethylpentene (TPX) is the lightest of all known polymers. It is optically transparent in the UV, visible and terahertz ranges, allowing, for example, alignment with HeNe laser beams. The refractive index is about 1.46 and is relatively independent of the wavelength. Losses are very low, down to millimeter wavelengths. TPX has excellent thermal resistance and is highly resistant to most organic and inorganic commercial chemicals. TPX is a hard, solid material that can be mechanically formed into various optical components such as lenses and windows. In addition, in particular TPX is used in CO2 laser-pumped molecular lasers as output windows, since it is transparent in the entire terahertz range and completely suppresses pump radiation around 10 μm. In addition, TPX windows are used as "cold" windows in cryostats. The terahertz transparency of TPX does not change with temperature. The temperature coefficient of the refractive index is 3.0*10 -4 K -1 (8-120K range). TPX shows excellent optical properties compared to other materials used for working in the terahertz range and can be a good replacement for Picarin (Tsurupica) lenses, for example. Moreover, compared to Picarin, TPX is cheaper and commercially available.

[0292] Polyethylene (PE) is a light elastic crystalline material. Depending on the grade, it can be heated to 110 ° C and cooled to -45÷-120 ° C. PE has good dielectric properties, chemical resistance and radiation resistance. On the contrary, it is unstable to UV radiation, fats and oils. PE is biologically inert and easy to process. The density (23 ° C) is 0.91-0.925 g / cm3. The tensile flow limit (23 ° C) is 8-13 MPa. The elastic modulus (23 ° C) is 118-350 MPa. The refractive index is about 1.54 and is fairly equal over a wide wavelength range. Usually high-density polyethylene (HDPE) is used for the production of components. In addition to rather thick lenses and windows, thin HDPE films are used for terahertz polarizers. In addition, HDPE is used as a window for Golay cells. The terahertz transmission of HDPE does not depend on the temperature, which allows the use of HDPE windows in cryostats. The temperature coefficient of the refractive index is 6.2*10 -4 K -1 (8-120K range).

[0293] Polytetrafluoroethylene (PTFE) is a white solid at room temperature with a density of about 2.2 g / cm3. Its melting point is 327°C, but its properties remain at useful levels over a wide temperature range of -73°C to 204°C. The refractive index is about 1.43 over a wide wavelength range.

[0294] In one embodiment of the present technology, Fig.13A top view of a terahertz generator including a plurality of single terahertz magnon lasers is shown, each of which includes a single multilayer column 80 and a terahertz transparent medium 60 filled between such single multilayer columns 80 .

[0295] In one embodiment of the present technology, at least one single terahertz magnon laser 10,i( Fig.12 ) generates terahertz radiation based on the magnon laser effect. For reference, please refer to US Patents: 7,430,074; 7,508,578; 9,136,665.

[0296] In one embodiment of the present technology, there is provided a method of Fig.11 The device 25 generates a terahertz signal, the device comprising a plurality of terahertz magnon laser generators (10, 1-10, k) and a terahertz transparent medium ( Fig.12 of 60). Figure 1 At least one such terahertz magnon laser generator 15 includes: a substrate 12; a bottom electrode 14 coupled to the substrate 12; and a multilayer column 26 coupled to the bottom electrode 14. The multilayer column also includes a bottom layer 16, which also includes a magnon gain medium; a tunnel junction 18 coupled to the bottom layer 16; a spin injector 20 coupled to the tunnel junction 18; a pinned layer 22 coupled to the spin injector 20; and a top electrode 28 coupled to the pinned layer 22. In one embodiment, the spin injector 20 can be a top layer including the spin injector.

[0297] In one embodiment of the present technology, by using Fig.11 The method of generating a terahertz signal by the device 25 further includes: (A) fixing the magnetization of the spin injector 20 in an antiparallel direction relative to the magnetization of the bottom layer 16 including the magnon gain medium; (B) applying a voltage to at least one such multilayer pillar 26 between the top electrode 28 and the bottom electrode 14, wherein the terahertz radiation signal is configured to pass through the terahertz transparent medium ( Fig.12 of 60) spread.

[0298] In one embodiment of the present technology, by using Fig.11 The method for generating a terahertz signal by the device 25 further includes: (A1) using the RKKY pinning layer 22 ( Figure 1 ); (A2) The thickness of the RKKY pinning layer is selected to fix the magnetization of the spin injector in an antiparallel orientation relative to the magnetization of the bottom layer 16 comprising the magnon gain medium.

[0299] In one embodiment of the present technology, by using Fig.11The method for generating a terahertz signal by the device 25 further comprises the step (C) of placing each pair of such multilayer columns at a distance L ( Fig.12 In another embodiment of the present technology, reference Fig.14 , a terahertz coherent communication system 1400 may be provided. In some embodiments, a coherent terahertz illumination beam may be provided to an object 1402. In some embodiments, a coherent terahertz reference beam may be provided to an atmosphere 1404 for use in a terahertz holographic detection and processing system 1406. In one embodiment, the coherent terahertz reference beam may be generated by a split terahertz total reflection mirror (THz mirror). In another embodiment, the coherent terahertz reference beam may be a second terahertz beam. The terahertz holographic detection and processing system 1406 may include, for example, a terahertz detector, a terahertz beam illuminator, a processing unit, and / or a display. In some embodiments, a coherent terahertz illumination beam may be generated and / or received. The coherent terahertz illumination beam may illuminate the object 1402. In addition, a coherent terahertz reference beam may be generated and / or received. Two received terahertz coherent beams (e.g., a coherent terahertz illumination beam and a coherent terahertz reference beam) may be combined to form a holographic image of the object 1402. The holographic image of the object 1402 may be illuminated, for example, by a terahertz reading beam configured to read the holographic image of the object 1402. Additionally, the holographic image of the object 1402 may be displayed on a computer-readable display of the terahertz holographic detection and processing system 1406. In some embodiments, the frequency of the coherent terahertz magnon laser may be tuned to enable the coherent terahertz laser beam to propagate through the propagation window of the atmosphere 1404. In some embodiments, the terahertz holographic image may be recorded on a terahertz multilayer material.

[0300] (The following discussion is taken from Wikipedia):

[0301] "Temporal coherence is a measure of the average correlation between the value of a wave at any time for a delay τ and itself. Temporal coherence tells us how monochromatic a source is. In other words, it characterizes how much the wave interferes with itself at different times. The delay at which the phase or amplitude drifts by a significant amount (and hence the correlation decreases significantly) is defined as the coherence time τ. c At a delay of τ = 0, the coherence is perfect, but as the delay exceeds τ = τ c , it will drop significantly. The coherence length L c Defined as the wave in time τ c The distance it travels.”

[0302] Care should be taken not to confuse the coherence time with the duration of the signal, and not to confuse the coherence length with the coherence area.

[0303] The terahertz magnon laser system using the temporal coherence characteristic comprises a single terahertz magnon laser, a terahertz receiver, and a processing unit.

[0304] It can be shown that the larger the frequency range Δf covered by the wave, the faster the wave will decorrelate (thus τ c Therefore, there is a trade-off:

[0305] τ c Δf≤1 (Equation 41)

[0306] Formally, this follows from the convolution theorem in mathematics, which relates the Fourier transform of the power spectrum (the intensity of each frequency) to its autocorrelation

[0307] Examples of temporal coherence. We consider four examples of temporal coherence.

[0308] According to the above relationship, a wave containing only a single frequency (monochromatic) is perfectly correlated with itself at all time delays. In contrast, a wave whose phase drifts rapidly will have a short coherence time.

[0309] Similarly, pulses (wave packets) of waves naturally have a wide frequency range and, because the amplitude of the waves changes rapidly, have a short coherence time.

[0310] Finally, white light has a wide range of frequencies and is a wave with rapidly varying amplitude and phase. Since it therefore has a very short coherence time (only 10 cycles or so), it is often referred to as incoherent.

[0311] Monochromatic sources are usually lasers; such high monochromaticity means long coherence lengths (up to hundreds of meters). For example, a stable single-mode helium-neon laser can easily produce light with a coherence length of 300m.

[0312] However, not all lasers are monochromatic (e.g., for a mode-locked titanium sapphire laser, Δλ≈2nm–70nm). Light-emitting diodes are characterized by Δλ≈50nm, while tungsten filament lamps exhibit Δλ≈600nm, so these sources have shorter coherence times than most monochromatic lasers. Holography requires light with long coherence times.

[0313] In contrast, the classic version of optical coherence tomography uses light with a shorter coherence time.

[0314] In optics, temporal coherence is measured in interferometers such as a Michelson interferometer or a Mach-Zehnder interferometer. In these devices, a wave combines with a copy of itself delayed by a time τ. A detector measures the time-averaged intensity of the light leaving the interferometer. The resulting visibility of the interference gives the temporal coherence for a delay of τ. Since for most natural light sources the coherence time is much shorter than the temporal resolution of any detector, the detector itself performs the temporal averaging.

[0315] Spatial coherence

[0316] The coherent terahertz magnon laser system using spatial coherence includes at least two coherent terahertz magnon lasers generating two terahertz coherent laser beams, which are received by a receiving terahertz laser, which combines the two beams to obtain a holographic image.

[0317] In some systems, such as water waves or optical systems, the wave-like state can be extended to one or two dimensions. Spatial coherence describes the ability of two points x1 and x2 in space to interfere with each other over the range of the wave, when averaged over time. More precisely, spatial coherence is the cross-correlation between two points in the wave at all times. A wave is perfectly spatially coherent if it has only 1 amplitude value over an infinite length. The range of separation between two points where there is significant interference defines the diameter A of the coherent region. c (The coherence length, usually a characteristic of a source, is an industry term usually related to the coherence time of the source, rather than the coherent area in the medium.) A c A related type of coherence in Young's double-slit interferometer. It is also used in optical imaging systems, especially various types of astronomical telescopes. Sometimes people also use "spatial coherence" to refer to the visibility of a wave-like state when it is combined with copies of itself moving in space.

[0318] Consider the filament of a tungsten light bulb. Different points in the filament emit light independently and without a fixed phase relationship. In detail, at any point in time, the profile of the emitted light will be distorted. The profile will vary randomly over the coherence time. Since white light sources such as light bulbs are small, filaments are considered to be spatially incoherent sources. In contrast, a radio antenna array has great spatial coherence because the antennas at either end of the array emit with a fixed phase relationship. The light waves produced by lasers typically have high temporal and spatial coherence (although the degree of coherence depends greatly on the exact characteristics of the laser). Spatial coherence of a laser beam also manifests itself as the speckle pattern and diffraction fringes seen at the edges of a shadow.

[0319] Holography requires temporally and spatially coherent light. Its inventor, Dennis Gabor, successfully produced holograms more than a decade before the invention of the laser. To produce coherent light, he passed monochromatic light from the emission line of a mercury vapor lamp through a pinhole spatial filter.

[0320] Holography

[0321] The coherent superposition of light wave fields comprises holography. Holographic objects are often used in everyday life in banknotes and credit cards.

[0322] Non-optical wave field

[0323] Further applications involve the coherent superposition of non-optical wave fields. For example, in quantum mechanics we consider a probability field, which is related to the wave function (explanation: the density of probability amplitudes). Applications here involve, for example, future technologies of quantum computing and already available techniques of quantum cryptography.

[0324] Quantum cryptography is the science of exploiting the properties of quantum mechanics to perform cryptographic tasks. The most famous example of quantum cryptography is quantum key distribution, which provides an information-theoretically secure solution to the key exchange problem. The advantage of quantum cryptography is that it allows a variety of cryptographic tasks that are proven or speculated to be impossible to accomplish using only classical (i.e. non-quantum) bated objects.

[0325] In one embodiment of the present technology, a terahertz holographic image of an object may be recorded on a terahertz multilayer material.

[0326] Example 9. Layered tungsten disulfide crystals can be used to record terahertz holographic images. See “Terahertz surface emission of d-band electrons from a layered tungsten disulfide crystal by the surface field”, Longhui Zhang, Yuanyuan Huang, Qiyi Zhao, Lipen Zhu, Zehan Yao, Yixuan Zhou, Wanyi Du, and Xinlong Xu; Phys. Rev. B 96, 155202–published on October 6, 2017.

[0327] The above discussion has described the operation of various exemplary systems and devices, as well as various embodiments related to exemplary methods of operating these systems and devices. In various embodiments, one or more steps of an implementation method (e.g., calculating an optimal voltage bias) are performed by a processor under the control of computer-readable and computer-executable instructions. Therefore, in some embodiments, these methods are implemented by a computer.

[0328] In one embodiment, computer readable and computer executable instructions may reside on a computer usable / readable medium.

[0329] Therefore, one or more operations of various embodiments can be controlled or implemented using computer-executable instructions such as program modules executed by a computer. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In addition, the present technology can also be practiced in a distributed computing environment, where tasks are performed by remote processing devices linked through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media, including memory storage devices.

[0330] Although specific steps of an exemplary implementation method are disclosed herein, these steps are examples of steps that can be performed according to various exemplary embodiments. That is, the embodiments disclosed herein are well suited to performing various other steps or variations of the steps. In addition, the steps disclosed herein can be performed in an order different from that presented, and not all steps must be performed in a particular embodiment.

[0331] Although various electronic and software-based systems are discussed herein, these systems are merely examples of environments that may be utilized and are not intended to imply any limitation on the scope of use or functionality of the present technology. Such systems should also not be interpreted as having any dependency or association with any one or combination of components or functions shown in the disclosed examples.

[0332] Although the subject matter has been described in language specific to structural features and / or methodological acts, the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A device for generating coherent terahertz radiation, comprising: One or more multi-layered adjustable micro-columns, each of which further comprises: substrate; bottom electrode; a bottom layer of ferromagnetic material, further comprising a magnon gain medium coupled to the bottom electrode; a tunnel junction coupled to the ferromagnetic material; a spin injector coupled to the tunnel junction; a pinning layer coupled to the spin injector; a reference layer coupled to the pinned layer; and Top electrode; as well as The receiving cavity surrounds at least one of the multi-layer adjustable micro-pillars. The magnon gain medium is configured to carry unbalanced magnons generated by unbalanced electrons, wherein the unbalanced electrons with spin down are injected from the spin injector into the magnon gain medium via the tunnel junction.

2. The device according to claim 1, wherein: The receiving cavity includes a first aperture configured to output the coherent terahertz radiation.

3. The device according to claim 2, further comprising: A storage cavity surrounds the accommodating cavity.

4. The device according to claim 3, wherein: The size of the storage cavity is larger than the corresponding size of the accommodating cavity.

5. The device according to claim 3, wherein: The storage cavity includes a second aperture configured to output coherent terahertz radiation.

6. The device according to claim 1, wherein: A bias voltage is applied to at least one of the multi-layer tunable micropillars between the top electrode and the bottom electrode, and the bias voltage is configured to shift the Fermi level of the spin injector relative to the Fermi level of the ferromagnetic material.

7. The device according to claim 6, wherein: The ferromagnetic material also includes a conduction band split into two sub-bands, the two sub-bands including a first sub-band with spin up and a second sub-band with spin down separated by an exchange energy gap, and wherein the first sub-band includes electrons polarized with spin up in the magnetization direction of the ferromagnetic material, and wherein the second sub-band includes electrons polarized with spin down in a direction opposite to the magnetization direction of the ferromagnetic material.

8. The device according to claim 1, wherein: The magnon gain medium is configured to generate terahertz radiation using the unbalanced magnons.

9. The device according to claim 1, wherein: The substrate is made of a material selected from the group consisting of: aluminum oxide (Al2O3); indium tin oxide (InTnO); silicon (Si); silicon on sapphire (SoS); and magnesium oxide (MgO).

10. The device according to claim 1, wherein: The bottom electrode is made of a material selected from the group consisting of: cobalt-iron alloy (Co 0.5 Fe 0.5 ); silver (Ag); gold (Au); platinum (Pt); cobalt (Co); palladium (Pd); titanium (Ti); and titanium tungsten (TiW).

11. The device according to claim 1, wherein: The magnon gain medium is made of a material selected from the group consisting of: chromium dioxide (CrO2); semi-metallic ferromagnetic oxide Sr2FeMoO6; Heusler alloy Co2MnGe; Heusler alloy Co2MnSi (CMS); Heusler alloy Co2FeSi (CFS); Heusler alloy Co2MnSn; and Heusler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

12. The device according to claim 1, wherein: The tunnel junction is made of a material selected from the group consisting of: magnesium oxide (MgO); aluminum oxide (Al2O3); and spinel MgAl2O4.

13. A method for tuning the frequency of terahertz radiation by using a coherent terahertz magnon laser, wherein: The coherent terahertz magnon laser comprises: one or more multi-layer tunable micro-pillars, each of which further comprises: a substrate; a bottom electrode; a bottom layer of a ferromagnetic material, and further comprises a magnon gain medium coupled to the bottom electrode; a tunnel junction coupled to the ferromagnetic material; a spin injector coupled to the tunnel junction; a pinned layer coupled to the spin injector; a reference layer coupled to the pinned layer; and a top electrode; and a receiving cavity surrounding at least one of the multi-layer tunable micro-pillars, the method comprising: Applying a bias voltage to the at least one multilayer tunable microcolumn to shift the Fermi level of the spin injector relative to the Fermi level of the magnon gain medium to initiate generation of unbalanced magnons; wherein interaction between the unbalanced magnons results in generation of terahertz radiation; tuning the frequency of the generated coherent terahertz radiation by varying the bias voltage; and The cavity is used to output tunable coherent terahertz radiation. The magnon gain medium is configured to carry unbalanced magnons generated by unbalanced electrons, wherein the unbalanced electrons with spin down are injected from the spin injector into the magnon gain medium via the tunnel junction.

14. The method according to claim 13, further comprising: The step of modulating the tunable coherent terahertz radiation by modulating the bias voltage with a modulation frequency.

15. A method for tuning the frequency of terahertz radiation by using a coherent terahertz magnon laser, wherein: The coherent terahertz magnon laser comprises: one or more multi-layer tunable micro-pillars, each of which further comprises: a substrate; a bottom electrode; a bottom layer of a ferromagnetic material, and a magnon gain medium coupled to the bottom electrode; a tunnel junction coupled to the ferromagnetic material; a spin injector coupled to the tunnel junction; a pinning layer coupled to the spin injector; a reference layer coupled to the pinning layer; and a top electrode; and a receiving cavity surrounding at least one of the multi-layer tunable micro-pillars, and Wherein, the accommodating cavity is enclosed in the storage cavity, and the method comprises: Applying a bias voltage to the at least one multilayer tunable microcolumn to shift the Fermi level of the spin injector relative to the Fermi level of the magnon gain medium to initiate generation of unbalanced magnons; wherein interaction between the unbalanced magnons results in generation of terahertz radiation; tuning the frequency of the generated coherent terahertz radiation by varying the bias voltage; Outputting adjustable coherent terahertz radiation to the storage cavity using the accommodation cavity; and The storage cavity is used to output tunable coherent terahertz radiation. The magnon gain medium is configured to carry unbalanced magnons generated by unbalanced electrons, wherein the unbalanced electrons with spin down are injected from the spin injector into the magnon gain medium via the tunnel junction.

16. The method according to claim 15, further comprising: The step of modulating the tunable coherent terahertz radiation by modulating the bias voltage with a modulation frequency.

17. The method according to claim 15, further comprising: The step of modulating the tunable coherent terahertz radiation by modulating the output coherent radiation by external means.

18. The method according to claim 15, further comprising: The step of modulating the output coherent radiation by using a piezoelectric material to mechanically vary the size of the output aperture.

19. The method according to claim 15, further comprising: The step of modulating the tunable coherent terahertz radiation by modulating the output coherent radiation using a synthetic ceramic material.

20. A coherent terahertz communication system, comprising: At least one coherent terahertz magnon laser; each of the coherent terahertz magnon lasers is configured to generate a coherent terahertz laser beam, wherein the coherent terahertz magnon laser comprises: one or more multi-layer tunable micro-pillars, each of the multi-layer tunable micro-pillars further comprises: a substrate; a bottom electrode; a bottom layer of ferromagnetic material, and also comprises a magnon gain medium coupled to the bottom electrode; a tunnel junction coupled to the ferromagnetic material; a spin injector coupled to the tunnel junction; a pinned layer coupled to the spin injector; a reference layer coupled to the pinned layer; and a top electrode; and a receiving cavity surrounding at least one of the multi-layer tunable micro-pillars; and A terahertz coherent detection system configured to receive at least one of the coherent terahertz laser beams, and configured to combine each of the received coherent terahertz laser beams into a combined terahertz beam; the combined terahertz beam is selected from the group consisting of: 3D terahertz image; terahertz spatial coherence image; terahertz temporal coherence image; terahertz spatiotemporal coherence image; terahertz holographic image; and quantum cryptography image The magnon gain medium is configured to carry unbalanced magnons generated by unbalanced electrons, wherein the unbalanced electrons with spin down are injected from the spin injector into the magnon gain medium via the tunnel junction.

21. The coherent terahertz communication system according to claim 20, wherein: The receiving cavity includes a first aperture configured to output the coherent terahertz radiation.

22. The coherent terahertz communication system according to claim 21, further comprising: A storage cavity surrounds the accommodating cavity.

23. The coherent terahertz communication system according to claim 22, wherein: The size of the storage cavity is larger than the corresponding size of the accommodating cavity.

24. The coherent terahertz communication system according to claim 22, wherein: The storage cavity includes a second aperture configured to output coherent terahertz radiation.

25. A method of coherent terahertz communication using at least one coherent terahertz magnon laser and a terahertz coherent detection system, wherein: The coherent terahertz magnon laser comprises: one or more multi-layer tunable micro-pillars, each of which further comprises: a substrate; a bottom electrode; a bottom layer of a ferromagnetic material, and further comprises a magnon gain medium coupled to the bottom electrode; a tunnel junction coupled to the ferromagnetic material; a spin injector coupled to the tunnel junction; a pinned layer coupled to the spin injector; a reference layer coupled to the pinned layer; and a top electrode; and a receiving cavity surrounding at least one of the multi-layer tunable micro-pillars, the method comprising: generating a coherent terahertz illumination beam; illuminating an object with the coherent terahertz illumination beam; generating a coherent terahertz reference beam; receiving the coherent terahertz illumination beam illuminating the object; receiving the coherent terahertz reference beam; combining the coherent terahertz illumination beam and the coherent terahertz reference beam to form a holographic image of the object; illuminating the holographic image of the object with a terahertz reading beam configured to read the holographic image of the object; as well as displaying the holographic image of the object on a computer readable display, The magnon gain medium is configured to carry unbalanced magnons generated by unbalanced electrons, wherein the unbalanced electrons with spin down are injected from the spin injector into the magnon gain medium via the tunnel junction.

26. The method according to claim 25, wherein: Generating the coherent terahertz reference beam further comprises the following steps: The frequency of the coherent terahertz magnon laser is tuned to enable the coherent terahertz laser beam to propagate through a propagation window of the atmosphere.

27. The method according to claim 25, wherein: Displaying the holographic image of the object on a computer readable display further comprises the steps of: The terahertz holographic image is recorded on the terahertz multilayer material.

Images