Terahertz magnon generator including multiple single terahertz magnon lasers

Abstract

The present invention provides a device for generating adjustable terahertz radiation. The device includes: a plurality of terahertz magnon laser generators, and at least one terahertz magnon laser generator includes a multilayer column and a terahertz transparent medium separating at least two of the terahertz magnon laser generators. At least one of the multilayer columns also includes: a substrate, a bottom electrode coupled to the substrate, a bottom layer coupled to the bottom electrode, a tunneling junction coupled to the bottom layer, a top layer coupled to the tunneling junction, a pinning layer coupled to a spin injector, and a top electrode coupled to the pinning layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional application serial number 16 / 245,247, filed on January 10, 2019, entitled “TERAHERTZ MAGNON GENERATOR COMPRISING PLURALITY OF SINGLE TERAERTZ MAGNON LASERS,” the entire contents of which are incorporated herein. 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, which occupies the part of the electromagnetic spectrum between the microwave band and the infrared band.

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

[0006] In fact, in the terahertz range, the unique rotational and vibrational responses of molecules provide information that is usually not 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 usually opaque to visible light and have low contrast to X-rays, making them a useful complementary imaging source.

[0007] For example, terahertz waves can maintain reasonable penetration depth in some common materials such as clothing, plastic, wood, sand, and soil. Therefore, terahertz technology has the potential to detect explosives wrapped or buried in the above materials because explosives have unique terahertz spectral characteristics compared to the surrounding materials. The spectral fingerprint of explosives can be expected to be obtained in the terahertz band, and terahertz imaging can be used for mine detection. However, 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 THz sources are usually based on exciting different materials with ultrashort laser pulses. Various different mechanisms have been developed to generate THz radiation, including photon carrier acceleration in photoconductive antennas and second-order nonlinear effects in electro-optical crystals.

[0009] For narrowband terahertz sources, solid-state lasers are usually considered. Narrowband terahertz sources are based on inter-band transitions or inter sub band transitions in narrow-gap semiconductors, i.e. transitions between confined conduction states or valence states in quantum confined structures (e.g. nanostructures). 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 and 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, where each repeating unit consists of an injector and an active region. In the active region, there is a population inversion and electrons transition to a lower energy level, emitting photons at 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 more than 700 quantum wells in total and exhibits pulsed operation at a temperature of 10K. For related content, see, for example, B Ferguson and X.-C. Zhang, Nat. Matter, 26 (2002).

[0011] Manijeh Razeghi et al. reported the latest progress of QCL generators in Photonics Spectra, December, 48-51 (2016). They use nonlinear mixing of two QCLs. However, the use of nonlinear mixers brings inherent limitations. In fact, nonlinear QCL mixers are very complex devices (each QCL contains multiple barrier layers and multiple well layers, which are manufactured with a precision of up to 0.1nm), have low output power in the continuous state (these devices can only reach a maximum power output of 0.5 milliwatts in the pulsed state), and have very limited tunability in the region between (2-4.45) THz.

[0012] Ad Tech Optics, located in City of Industry, California, has been developing and producing innovative QC lasers since 2005. Ad Tech'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 Ad Tech's QCLs can be operated continuously at room temperature and can be designed to operate at a single frequency by using distributed feedback waveguide manufacturing. However, Ad Tech's QCLs can only be adjusted mechanically, which makes these QCLs impractical for most applications, including spectroscopy, communications and other use cases. Summary of the invention

[0013] This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify 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.

[0014] The present invention provides a device for generating adjustable terahertz radiation, which comprises: a plurality of terahertz magnon laser generators, at least one of which comprises a multilayer column, and a terahertz transparent medium separating at least two of the terahertz magnon laser generators.

[0015] At least one such multilayer column further includes: a substrate, a bottom electrode coupled to the substrate, a bottom layer coupled to the bottom electrode, a tunneling junction coupled to the bottom layer, a top layer coupled to the tunneling junction, a pinning layer coupled to a spin injector, and a top electrode coupled to the pinning layer. The bottom layer also includes a magnon gain medium. The top layer also includes a spin injector. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 principles described below.

[0017] Figure 1 A front view of a terahertz magnon laser is depicted for purposes of the present technology, comprising a substrate, a bottom electrode, and a single multilayer column, the multilayer column also comprising a bottom layer coupled to the bottom electrode, a tunneling junction, a top layer, a pinned layer, and a top electrode.

[0018] Figure 2 A front view of a terahertz generator for purposes of the present technology comprising a plurality of single terahertz magnon lasers, each of which further comprises a single multilayer pillar.

[0019] Figure 3For the purpose of the present technology, a front view of a terahertz generator including a plurality of single terahertz magnon lasers is shown, each of which further includes a single multilayer column and a terahertz transparent medium separating at least two of the single multilayer columns.

[0020] Figure 4 For the purpose of the present technology, a top view of a terahertz generator 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 the single multilayer columns. DETAILED DESCRIPTION

[0021] See for details embodiments of the technology of the present invention, examples of which are shown in the accompanying drawings. Although the technology of the present invention will be described in conjunction with various embodiments, it should be understood that it is not intended to limit the technology of the present invention to the described embodiments. On the contrary, the technology of the present invention 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.

[0022] Furthermore, in the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments presented. However, it will be apparent to those skilled in the art that the embodiments presented herein 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 the embodiments presented.

[0023] In one embodiment of the technology of the present invention, Figure 1 A front view 15 of a single terahertz magnon laser is shown, which includes a substrate 12 , a bottom electrode 14 , and a single multilayer pillar 10 .

[0024] In one embodiment of the technology of the present invention, a single multi-layer column 10 (such as Figure 1 ) also includes a bottom layer 16, a tunneling junction 18, a top layer 20, a pinned layer 22 and a top electrode 24.

[0025] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 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. Gallium arsenide is used in the manufacture of single crystal microwave integrated circuits.

[0026] GaAs is usually used as a substrate material for epitaxial growth of other III-V semiconductors, and the substrate material includes: indium gallium arsenide, aluminum gallium arsenide, etc.

[0027] GaAs can be produced using molecular beam epitaxy (MBE). MBE occurs in a high vacuum or ultra-high vacuum (10 -8 -10 -12 )Torr.

[0028] The most important aspect of MBE is the deposition rate (typically less than 3,000nm per hour) that allows epitaxial growth of thin films. These deposition rates 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 for the highest purity of grown films.

[0029] In solid-source MBE, ultrapure forms of gallium and arsenic are heated in separate quasi-Knudsen effusion cells or electron beam evaporators until they slowly sublime. The gaseous elements then condense on a wafer where they can react with each other. In the case of gallium and arsenic, single crystal gallium arsenide is formed. When using evaporation sources such as copper or gold, gaseous elements impinging on the surface will be adsorbed (after a time window in which the impinging atoms will jump on the surface) or reflected. Atoms on the surface may also be desorbed.

[0030] Controlling the temperature of the source will control the rate at which material strikes the substrate surface, and the temperature of the substrate will affect the rate of hopping or desorption. The term "beam" refers to the fact that the evaporated atoms do not interact with each other or the vacuum chamber gases before reaching the wafer because the mean free path of the atoms is very long.

[0031] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 shown) includes aluminum oxide (Al2O3).

[0032] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 shown) includes aluminum nitride (AlN).

[0033] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 shown) includes indium tin oxide (InTnO).

[0034] Indium tin oxide (ITO) is a ternary composition consisting of indium, tin and oxygen in varying proportions. It can be described as a ceramic or an alloy depending on the oxygen content. Indium tin oxide is commonly encountered as an oxygen-saturated composition, with a formulation of 74% In, 18% O2 and 8% Sn by weight. Oxygen-saturated compositions are so typical that unsaturated compositions are called oxygen-deficient ITO. Oxygen-saturated compositions are transparent and colorless in thin layers, and are yellowish to gray in bulk form. In the infrared region of the spectrum, oxygen-saturated compositions act as mirrors like metals.

[0035] 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 it can be easily deposited as a thin film. As with all transparent conductive films, there must be a trade-off between conductivity and transparency, as increasing thickness and increasing the concentration of charge carriers will increase the conductivity of the material, but will reduce its transparency. Indium tin oxide thin films are most commonly deposited on a surface by physical vapor deposition. Electron beam evaporation is often used, or it is deposited using a range of sputtering deposition techniques.

[0036] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 shown) includes silicon (Si).

[0037] Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle, crystalline solid with a blue-grey metallic luster. It is a tetravalent metalloid. Silicon is a member of Group 14 in the periodic table, above carbon and below germanium, tin, lead and feldspar. Silicon is quite inactive, not as active as germanium, but has a strong chemical affinity for oxygen. Therefore, it was introduced in 1823 by It was first prepared and characterized in pure form by Jakob Berzelius.

[0038] Silicon is the eighth most common element in the universe by mass, but is rarely found as a pure element in the Earth's crust. It is most widely distributed in dust, sand, asteroids, or planets as various forms of silicon dioxide (silica) 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). Very highly purified silicon is used in integrated circuits.

[0039] In one embodiment of the technology of the present invention, the substrate 12 (such as Figure 1 ) includes silicon-on-sapphire (SoS).

[0040] 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) wafer.

[0041] SOS is part of the Silicon-On-Insulator (SOI) family of CMOS technologies. High-purity artificially grown sapphire crystals are typically used. Silicon is deposited on a heated sapphire substrate, usually by 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 making the very small transistors used in modern high-density applications. This is because the SOS process causes the formation of dislocations, twinning, and stacking faults due to the lattice differences between sapphire and silicon. In addition, some aluminum (a p-type dopant) contaminates the substrate in the silicon closest to the interface.

[0042] The use of epitaxially grown silicon on sapphire substrates for the manufacture of MOS devices involves a purification process for the silicon that mitigates 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 areas outside the polysilicon gate stack by poly oxidation and further recessed to a thickness of approximately 78nm by a sidewall spacer formation process.

[0043] In one embodiment of the present invention, the substrate 12 (eg Figure 1 shown) includes magnesium oxide (MgO).

[0044] Magnesium oxide (MgO) or magnesia 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 (+ ions) and O2 (- ions) held together by ionic bonding. 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.

[0045] 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 this compound. According to evolutionary crystal structure prediction, MgO2 is thermodynamically stable at pressures above 116 GPa (gigaPascals), while the 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.

[0046] In one embodiment of the technology of the present invention, still refer 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).

[0047] Each of these materials can be deposited on a substrate by molecular beam epitaxy (MBE) (described above) or by sputtering deposition.

[0048] 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 wafer. Re-sputtering is the re-emission of deposited material by bombardment of ions or atoms 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).

[0049] Alternatively, at higher gas pressures, ions collide with gas atoms acting as moderators and diffuse, contact the substrate or the vacuum chamber wall and condense after random walk. By changing the background gas pressure, the entire range from high-energy ballistic impact to low-energy thermalization motion can be accessed.

[0050] 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 material, so neon is preferred for light elements, while krypton or xenon are used for heavy elements. Reactive gases can also be used to sputter the compound. Depending on the process parameters, the compound can be formed 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.

[0051] 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 even impossible. Sputtering deposited films have a composition close to that of the source material. This 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.

[0052] Sputtered films generally have better adhesion to the substrate than evaporated films. The target contains a large amount of material and is maintenance-free, making the technique suitable for ultra-high vacuum applications.

[0053] Sputtering sources contain no hot parts (to avoid overheating, 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.

[0054] The disadvantage of the sputtering process is that it is difficult to combine with lift-off for thin film construction. This is because the diffusion transport, the characteristics of sputtering, make full shadow impossible. Therefore, it is impossible to completely restrict the direction of the atoms, which will lead to contamination problems. In addition, compared with pulsed laser deposition, active control of layer-by-layer growth is difficult, and the inert sputtering gas enters the growing film as an impurity.

[0055] Pulsed laser deposition is a variant of sputtering deposition technology that uses a laser beam for sputtering. The role of sputtered and re-sputtered ions and ambient gases is well studied during pulsed laser deposition.

[0056] Sputtering sources typically use 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 target surface.)

[0057] The gas used for sputtering 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 are neutrally charged and are therefore not affected by magnetic traps.

[0058] 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 produces highly insulating oxide films well, but adds expense to the RF power supply and impedance matching network. Stray magnetic fields that leak from ferromagnetic targets can also interfere with the sputtering process. This usually must be compensated for by using specially designed sputtering guns with unusually strong permanent magnets.

[0059] In one embodiment of the technology of the present invention, reference 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).

[0060] Case 1:

[0061] For example, in the paper “Direct observation of half-metallicity in the Heusler compound Co2MnSi” recently published by M. Jourdan et al. in Nat Commun., 2014 May 30;5:3974., Co2MnSi samples were grown in a sputtering chamber, a molecular beam epitaxy (MBE) chamber, and a synchrotron radiation ultraviolet emission spectroscopy (SRUPS) chamber equipped with a He gas discharge lamp (hν = 21.2 eV) and a hemispherical energy analyzer with a multi-channel spin filter ( In situ preparation and complete investigation were carried out in an ultrahigh vacuum cluster consisting of a Sherman function (S=0.42±0.05). First, an epitaxial buffer layer of the Heusler compound Co2MnGa (30nm) was grown on a MgO(100) substrate by radio frequency (RF) sputtering at room temperature. An additional annealing process was optimized to obtain the L21 order at 550°C, as shown by high energy electron diffraction (RHEED) and X-ray diffraction (XRD). Co2MnSi (70nm) was RF sputtered on top at room temperature. Induced by the buffer layer, the Co2MnSi film already showed a certain degree of L21 surface order as deposited. By additional annealing, the order was improved as evidenced by RHEED on the film surface.

[0062] In one embodiment of the technology of the present invention, reference is still made to Figure 1 The tunnel junction 18 is selected from the group consisting of: magnesium oxide (MgO); aluminum oxide (Al2O3); and spinel MgAl2O4.

[0063] Case 2:

[0064] In the paper "Low-temperature atomic layer deposition of MgO thin films on Si" published by S Vangelista et al. in Journal of Physics D: Applied Physics, Vol. 46, No. 48, magnesium oxide (MgO) thin films were grown by atomic layer deposition in a wide deposition temperature window of 80-350°C using bi-(cyclopentadienyl) magnesium and H2O precursors. The MgO film was grown at a cycle temperature of ~0.12 nm. -1The MgO films were deposited at a constant growth rate on HF-last Si (10 0) and SiO2 / Si substrates. The structure, morphology and chemical properties of the synthesized MgO films were studied by X-ray reflectivity, grazing incidence X-ray diffraction, time-of-flight secondary ion mass spectrometry and atomic force microscopy measurements. In addition to good chemical homogeneity and a polycrystalline structure with a thickness of more than 7 nm, the MgO layer is characterized by a sharp interface with the substrate and limited surface roughness. CV measurements were performed on Al / MgO / Si MOS capacitors with a thickness of MgO in the range of (4.6-11) nm, which allowed the determination of a dielectric constant (κ) of ~11. The Co layer was grown by chemical vapor deposition in direct contact with the MgO without vacuum-break (base pressure 10 -5 -10 -6 Pa). 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 process of Co deposition.

[0065] In one embodiment of the technology of the present invention, reference is made 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; Hessler alloy Co2MnGe; Hessler alloy Co2MnSi (CMS); Hessler alloy Co2FeSi (CFS); Hessler alloy Co2MnSn; and Hessler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

[0066] Case 3:

[0067] 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, Vol. 39, No. 5, the structure and magnetization of Co2(Cr1-xFex)Al(0≤x≤1) and Co2FeSi full-Heusler alloys were studied. The films were deposited on thermally oxidized Si(SiO2) and MgO(001) single crystal substrates by ultrahigh vacuum sputtering at different temperatures. After deposition at room temperature (RT), the films were post-annealed. Co2YZ(20nm) / Al(1.2nm)-oxide / Co 75 Fe 25The stacked structure of IrMn(3nm) / IrMn(15nm) / Ta(60nm) was used to fabricate a magnetic tunneling junction with full Hessler alloy electrodes and was microfabricated using electron beam lithography and Ar ion etching. The junction area was 10 2 μm 2 , where Co2YZ represents Co2(Cr 1-x Fe x )Al or Co2FeSi. The tunnel barrier was formed by depositing 1.2nm of aluminum followed by plasma oxidation in the chamber. X-ray diffraction revealed A2 or B2 structures and substrates depending on the heat treatment conditions, but not Co2(Cr 1-x Fe x )Al(0≤x≤1) films. However, when Co2FeSi films were deposited on MgO(001) substrates at high temperatures above 473K, the L21 structure was obtained. 0.4 Fe 0.6 )Al electrode, the maximum tunneling magnetoresistance (TMR) is 52% at RT and 83% at 5K. While the junction using Co2FeSi electrode with L21 structure exhibits 41% TMR at RT and 60% at 5K, this can be improved by using a buffer layer to reduce the lattice misfit between Co2FeSi and MgO(001) substrate.

[0068] In one embodiment of the technology of the present invention, reference is made 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).

[0069] Case 4:

[0070] In the paper by JM Slaughter et al., “Magnetic Tunnel Junction Materials for Electronic Applications”, JOM-e, 52(6) (2000), http: / / www.tms.org / pubs / journals / JOM / 0006 / Slaughter / Slaughter-0006.html, 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 be aligned in one direction. The exchange coupling between the ferromagnetic layer and the AF layer at their mutual interface causes the ferromagnetic layers to align preferentially in one direction. 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 this field revolves around manganese-based antiferromagnetic materials such as Pt-Mn, Ir-Mn, Rh-Mn and Fe-Mn. Pt-Mn is a rather interesting pinning material because it remains antiferromagnetic at relatively high temperatures. Unlike many commonly used AF alloys, as-deposited Pt-Mn is not AF. Instead, this material must be post-annealed, which causes a phase transition from a face-centered cubic (fcc) to a face-centered tetragonal (fct) crystal structure. The fct phase of Pt-Mn is AF and will pin adjacent ferromagnetic films. The pinning strength increases with the annealing time. The shift and broadening of the Ni-Fe hysteresis loop in the annealed material is 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.

[0071] In one embodiment of the technology of the present invention, reference is made to Figure 1 The pinned layer 22 further includes a Ruderman-Kittel-Kasuya-Yosida (RUDERMAN-KITTEL-KASUYA-YOSIDA (RKKY)) non-magnetic pinned layer.

[0072] The thickness of the RKKY interaction layer is about The ruthenium spacer exhibits antiferromagnetic polarity. For reference, see SSP Parkin, "Spin Engineering: Direct determination of the Ruderman-Kitel-Kasuya-Yosida far-field function in ruthenium", Phys. Rev. B 44(13), 1991.

[0073] In one embodiment of the present invention, a Ru spacer is used as a spacer having a thickness of about The pinned layer can make the magnetization direction of the spin injector 20 antiparallel to the magnetization direction of the bottom layer 16, which allows the maximum minority current to be injected into the bottom layer 16 with the magnon gain medium. The injection of the maximum minority current will substantially simplify reaching the magnon laser point.

[0074] In one embodiment of the technology of the present invention, reference is made to Figure 1 The top electrode 24 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.

[0075] In one embodiment of the technology of the present invention, reference is made to Figure 1 , a single layer electron injector is used to replace the spin injector 20 and the pinning layer 22. In this embodiment, the electron injector is selected from the group consisting of: metal; metal alloy; ferromagnetic metal; and ferromagnetic alloy.

[0076] In one embodiment of the technology of the present invention, Figure 2 25 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 {10,1; 10,2; 10,i; ... 10,k}, where i and k are integers. Each single multilayer column 10,i is coupled to a ground electrode 14, and the ground electrode 14 is coupled to a substrate 12.

[0077] In one embodiment of the technology of the present invention, Figure 3A front view 35 of a terahertz generator including a plurality of single terahertz magnon lasers 10,1; 10,2 ... 10,i, ... 10,k; (i and k are integers) is shown; each such single terahertz magnon laser further includes a single multilayer column 80, a bottom electrode 14 and a substrate 12, and a terahertz transparent medium 60 separating at least two single multilayer columns. A bias voltage (not shown) applied to each single terahertz magnon laser 10,i, i.e., from the top layer to the bottom electrode 14, is configured to inject the spin current of the spin injector into the bottom layer having the magnon gain medium. The injected current enables the spin-down electrons of the spin injector to transition through the tunneling junction into the spin-down subband of the bottom layer having the magnon gain medium, triggering the magnon lasing process by entering the spin-up subband of the bottom layer having the magnon gain medium, which results in the generation of a spin current from the top surface 45 ( Figure 4 For reference, see U.S. Patents: 7,430,074; 7,508,578; 9,136,665.

[0078] In one embodiment of the technology of the present invention, reference is made to Figure 3 The distance D between any two adjacent multilayer columns (for example, the distance 62 between two adjacent multilayer columns 10,1 and 10,2) should be greater than the wavelength λ of the emitted terahertz signal. THz , so that each generated terahertz photon can be generated outside the region of the magnon gain medium.

[0079] D>λ THz

[0080] (Eq.1)

[0081] In one embodiment of the technology of the present invention, reference is made to Figure 3 The terahertz transparent medium 60 is selected from the group consisting of: a crystalline terahertz transparent material; and a polymer terahertz transparent material.

[0082] In one embodiment of the technology of the present invention, see Figure 3 The terahertz transparent medium 60 is selected from the group consisting of the following crystalline materials: High Resistivity Float Zone Silicon (HRTZ-Si); crystal quartz; and sapphire.

[0083] Crystals such as silicon, quartz crystal and sapphire are very important for the production of terahertz optical products. For related references, see X.-C. Zhang, J. Xu, Introduction to Terahertz Wave Photonics, Springer Science+Business Media, LLC 2010.

[0084] Apart from artificial 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). Compared to diamond, its production and processing costs are lower. In addition, silicon can have a relatively large size, allowing the manufacturing of rapidly developing terahertz electronic components on this basis.

[0085] One of the best materials for wavelengths above 50 μm is z-cut crystalline quartz. Importantly, the windows of z-cut crystalline quartz are transparent in the visible range and can therefore be easily tuned 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.

[0086] Sapphire-like crystalline quartz is transparent in the terahertz region as well as 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 manufacture terahertz photoconductive antennas due to its similar refractive index values ​​to terahertz.

[0087] In one embodiment of the technology of the present invention, reference is made to Figure 3 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).

[0088] Among the wide variety of available polymers, there are some excellent terahertz transparent materials with relatively low reflectivity. The best materials in this sense are TPX (polymethylpentene), polyethylene (PE), polypropylene (PP) and polytetrafluoroethylene (PTFE or Teflon). At longer wavelengths, the transmission structure of these polymers is less 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.

[0089] Polymethylpentene (TPX) is the lightest of all known polymers. It is optically transparent in the UV, visible and THz range, allowing, for example, alignment with HeNe laser beams. The refractive index is ~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, TPX is used in particular for CO2 laser-pumped molecular lasers as output windows, since it is transparent in the entire THz range and completely suppresses ~10 μm pump radiation. Furthermore, TPX windows are used as "cold" windows in cryostats. The THz transparency of TPX does not change with temperature. The temperature coefficient of the refractive index is 3.0*10 -4 K -1 (Applicable in the range of 8-120K). TPX shows excellent optical properties compared to other materials for working in the terahertz range, for example it is a good replacement for Picarin (Tsurupica) lenses. Moreover, compared to Picarin, TPX is cheaper and commercially available.

[0090] 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 the same over a wide wavelength range. Usually high-density polyethylene (HDPE) is used for the production of components. In addition to relatively 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 is independent of 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).

[0091] Polytetrafluoroethylene (PTFE) is a white solid at room temperature with a density of about 2.2g / cm 3 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 ~1.43 over a wide wavelength range.

[0092] In one embodiment of the present technology, Figure 4A top view 100 of a terahertz generator including a plurality of single terahertz magnon lasers 102 is shown, each of which further includes a single multilayer column (not shown) and a terahertz transparent medium 110 filling between each of the single multilayer columns.

[0093] In one embodiment of the present technology, at least one single terahertz magnon laser 10, i (such as Figure 3 (shown in FIG. 1 ) generates terahertz radiation based on the magnon laser effect. For reference, please refer to U.S. Patents: 7,430,074; 7,508,578; 9,136,665.

[0094] In one embodiment of the technology of the present invention, a method is provided using Figure 2 A method for generating a terahertz signal by using a device 25, wherein the device 25 comprises a plurality of terahertz magnon lasers (10,1-10,k) and a terahertz transparent medium (such as Figure 3 of 60). Figure 1 At least one terahertz magnon laser generator 15 includes: a substrate 12; a bottom electrode 14 coupled to the substrate 12; and a multilayer column 10 coupled to the bottom electrode 14, the multilayer column also including a bottom layer 16, the bottom layer 16 also including a magnon gain medium; a tunneling junction 18 coupled to the bottom layer 16; a top layer 20 coupled to the tunneling junction 18; the top layer 20 including a spin injector; a pinned layer 22 coupled to the spin injector 20; and a top electrode 24 coupled to the pinned layer 22.

[0095] In one embodiment of the present invention, by using Figure 2 The method of generating a terahertz signal in a device 25 includes: (A) fixing the magnetization of the spin injector 20 to an antiparallel orientation relative to the magnetization of the bottom layer 16 including the magnon gain medium; (B) applying a voltage to at least one multilayer column 10 between the top electrode 24 and the bottom electrode 14; wherein the terahertz radiation signal is configured to pass through the terahertz transparent medium (such as Figure 3 of 60) spread.

[0096] In one embodiment of the present invention, the Figure 2 The method for generating a terahertz signal by the device 25 further includes: (A1) using a RKKY pinning layer 22 (such as 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.

[0097] In one embodiment of the present invention, by using Figure 2The method of generating a terahertz signal by the device 25 further comprises the step (C) of separating each pair of such multilayer pillars by a distance D ( Figure 3 of 62).

[0098] The above discussion has described various exemplary integrated device operations, as well as various embodiments related to exemplary methods of operating these integrated devices. In various embodiments, one or more steps of implementing the method (e.g., calculating the 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.

[0099] In one embodiment, computer readable and computer executable instructions may reside on a computer usable / readable medium.

[0100] Thus, computer executable instructions such as program modules executed by a computer may be used to control or implement one or more operations of various embodiments. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In addition, the techniques of the present invention may 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 may be located in storage media of local and remote computers, including memory storage devices.

[0101] Although specific steps of the exemplary implementation method are disclosed herein, these steps are examples of steps that may 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 may be performed in an order different from that presented, and not all steps need to be performed in a particular embodiment.

[0102] 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 technology of the present invention. Such systems should not be interpreted as having any dependency or correlation with any one or combination of components or functions shown in the disclosed examples.

[0103] 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 tunable terahertz radiation, comprising: Multiple terahertz magnon laser generators; At least one of the terahertz magnon laser generators comprises: substrate; a bottom electrode coupled to the substrate; and a multilayer column coupled to the bottom electrode, the multilayer column comprising: a bottom layer coupled to the bottom electrode; the bottom layer comprising a magnon gain medium; a tunneling junction coupled to the bottom layer; a top layer coupled to the tunneling junction; the top layer comprising a spin injector; a pinned layer coupled to the spin injector, the pinned layer comprising a Ruderman–Kittel–Kasuya–Yosida (RKKY) nonmagnetic pinned layer; and a top electrode coupled to the pinned layer; and A terahertz transparent medium is used to separate at least two of the terahertz magnon laser generators. Wherein, at least one of the terahertz magnon laser generators is configured to generate a terahertz radiation signal; wherein each pair of multilayer columns is separated by a distance greater than the wavelength of the generated terahertz signal, wherein each generated terahertz photon is generated outside the region of the magnon gain medium; and wherein the device is configured to emit the terahertz radiation signal, and the terahertz radiation signal is configured to propagate through the terahertz transparent medium.

2. The device according to claim 1, wherein: The bottom layer also includes a ferromagnetic material selected from the group consisting of: Ferromagnetic semiconductors; diluted magnetic semiconductors (DMS); half-metallic ferromagnets (HMF); and ferromagnetic conductors in which there is a gap in the density of states of minority electrons around the Fermi level of the ferromagnetic material.

3. The device of claim 2, wherein: The half-metallic ferromagnet (HMF) is selected from the group consisting of: Spin-polarized Hessler alloys; spin-polarized giant magnetoresistive materials; and CrO2.

4. The device of claim 3, wherein: The spin-polarized Hessler alloy is selected from the group consisting of: Semi-metallic ferromagnetic oxide Sr2FeMoO6; Hessler alloy Co2MnGe; Hessler alloy Co2MnSi (CMS); Hessler alloy Co2FeSi (CFS); Hessler alloy Co2MnSn; and Hessler alloy Co2FeAl 0.5 Si 0.5 (CFAS).

5. The device of claim 1, wherein: The tunnel junction is selected from the group consisting of: Magnesium oxide (MgO); aluminum oxide (Al2O3); and spinel MgAl2O4.

6. The device of claim 1, wherein: The spin injector is selected from the group consisting of: semimetals; and ferromagnetic alloys.

7. The device of claim 1, wherein: The pinning layer also includes: An antiferromagnetic pinning layer selected from the group consisting of: 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).

8. The device of claim 1, wherein: The substrate is selected from the group consisting of: Gallium arsenide (GaAs); aluminum oxide (Al2O3); aluminum nitride (AlN); indium tin oxide (InTnO); silicon (Si); silicon on sapphire (SoS); and magnesium oxide (MgO).

9. The device of claim 1, wherein: The bottom electrode is 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).

10. The device of claim 1, wherein: The terahertz transparent medium is selected from the group consisting of: Crystalline terahertz transparent media; and polymer terahertz transparent media.

11. The device of claim 10, wherein: The crystalline terahertz transparent medium is selected from the group consisting of the following crystalline materials: High resistance floating zone silicon (HRTZ-Si); crystal quartz; and sapphire.

12. The device of claim 10, wherein: The polymer terahertz transparent medium is selected from the group consisting of the following polymer materials: High-density polyethylene (HDPE); polyethylene (TPX); polyethylene (PE); and polytetrafluoroethylene (PTFE).

13. A method for generating a terahertz signal by using an apparatus including a plurality of terahertz magnon laser generators; At least one of the terahertz magnon laser generators includes: a substrate; a bottom electrode coupled to the substrate; and a multilayer column coupled to the bottom electrode; and a terahertz transparent medium for separating at least two of the terahertz magnon laser generators; the multilayer column also includes a bottom layer, the bottom layer also includes a magnon gain medium; a tunneling junction coupled to the bottom layer; a top layer coupled to the tunneling junction; the top layer includes a spin injector; a pinned layer coupled to the spin injector, the pinned layer includes a Ruderman–Kittel–Kasuya–Yosida (RKKY) non-magnetic pinned layer; and a top electrode coupled to the pinned layer; the method includes: (A) fixing the magnetization of the spin injector in an antiparallel direction relative to the magnetization of the underlying layer comprising the magnon gain medium; (B) applying a voltage to at least one of the multi-layer pillars between the top electrode and the bottom electrode; and (C) separating each pair of multilayer pillars by a distance greater than a wavelength of a generated terahertz signal, wherein each generated terahertz photon is generated outside a region of the magnon gain medium; The device is configured to emit a terahertz radiation signal, and the terahertz radiation signal is configured to propagate through the terahertz transparent medium.

14. The method of claim 13, wherein: The step (A) further comprises: (A2) The thickness of the RKKY pinning layer is selected to pin the magnetization of the spin injector in an antiparallel direction relative to the magnetization of the underlying layer comprising the magnon gain medium.

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