Spintronic Terahertz Emitter

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This patent describes a spintronic terahertz (THz) emitter that uses a multilayer thin-film structure, comprising a magnetic (ferromagnetic or ferrimagnetic) layer and at least one adjacent second (typically nonmagnetic) layer. When illuminated by an ultrafast (femtosecond) laser pulse, the magnetic layer generates a spin current, which is converted by the second layer into a transverse charge current, emitting linearly polarized terahertz radiation. The invention specifically enables dynamic control (modulation) of the emitted THz polarization by varying the magnetization direction of the magnetic layer at high frequencies, using various methods (magnetic fields, voltage, or optical pulses). This modulation allows precise and rapid tuning of terahertz polarization properties, opening new capabilities for spectroscopy and imaging.

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• High-speed, polarization-modulated THz spectroscopy for material analysis, including studies of anisotropic and complex materials.
• Non-destructive inspection and quality control in manufacturing via polarization-sensitive THz imaging.
• Biomedical imaging and diagnostics that benefit from tunable polarization of THz radiation.
• Wireless high-data-rate communications that use modulated THz signals for data transmission.
• Security screening (e.g., for hidden objects or substances) using controlled-polarization THz sources.
• Fundamental research in spintronics, ultrafast magnetism, and light-matter interaction at nanoscales.

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• Enables fast (kHz to GHz range) electronic and/or optical modulation of terahertz polarization without mechanical moving parts.
• Provides robust and precise control over THz polarization state (direction and polarity), expanding the toolbox for advanced spectroscopy and imaging techniques.
• Improves signal-to-noise in lock-in detection schemes because the modulation can be entirely phase-based (polarity switching) instead of amplitude-based, maximizing efficiency.
• The modular, thin-film device structure permits on-chip integration and scalability for compact and robust THz sources.
• Versatile modulation methods (magnetic field, voltage, or laser-induced switching) enable application tailoring and potentially low-energy operation.
• Can be engineered for ultrafast all-optical control, supporting future developments in ultrafast electronics and optoelectronics.

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Inventors & Applicants

Patent Abstract

The invention regards a spintronic terahertz emitter (1) that comprises: at least one first, magnetic layer (F), at least one second layer (N), and means for producing a magnetization (M) in the first layer (F), wherein the first layer (F) is adapted to drive, upon incidence of a femtosecond laser pulse (2) on the first layer (F) in a direction perpendicular to the plane of the first layer (F), a spin current (js) from the first layer (F) into the second layer (N), wherein the second layer (N) is adapted to convert the spin current (js) into a transverse charge current (jc) in a direction perpendicular to the magnetization (M) of the first layer (F), the transverse charge current (jc) emitting terahertz radiation (3), and wherein the emitted terahertz radiation (3) is linearly polarized. Means are provided for modulating the magnetization (M) in the first layer (F) in the kilohertz, megahertz, or gigahertz range, wherein modulation of the magnetization (M) in the first layer (F) causes modulation of the linear polarization of the terahertz radiation (3). A further aspect of the invention regards a method for modulating the linear polarization of terahertz radiation (3) emitted by a spintronic terahertz emitter.1. Spintronic terahertz emitter (1) comprising:- at least one first, magnetic layer (F),- at least one second layer (N),- means for producing a magnetization (M) in the first layer (F),- wherein the first layer (F) is adapted to drive, upon incidence of a femtosecond laser pulse (2) on the first layer (F) in a direction perpendicular to the plane of the first layer (F), a spin current (js) from the first layer (F) into the second layer (N),- wherein the second layer (N) is adapted to convert the spin current (js) into a transverse charge current (jc) in a direction perpendicular to the magnetization (M) of the first layer (F), the transverse charge current (jc) emitting terahertz radiation (3),- wherein the emitted terahertz radiation (3) is linearly polarized, and wherein the electric field component of the linearly polarized terahertz radiation lies in a plane that is perpendicular to the magnetization (M) of the first layer (F),characterized bymeans (41-44, 51-52, 61-64, 80-84, 90, 100, 12) for modulating the magnetization (M) in the first layer (F) in the kilohertz, megahertz, or gigahertz range, wherein modulation of the magnetization (M) in the first layer (F) causes modulation of the linear polarization of the terahertz radiation (3).2. Terahertz emitter according to claim 1, characterized in that the means (41-44, 51-52, 61-65, 81-85, 90, 100, 12) for modulating the magnetization (M) in the first layer (F) are configured to cause polarity modulation of the linear polarization of the terahertz radiation (3), wherein the magnetization vector of the magnetization (M) is caused to switch between two discrete opposite values.3. Terahertz emitter according to claim 1, characterized in that the means (41-44, 51-52, 61-65, 81-85, 90, 100, 12) for modulating the magnetization (M) in the first layer (F) are configured to cause direction modulation of the linear polarization of the terahertz radiation, wherein the magnetization vector of the magnetization (M) is caused to rotate between two directions (α) or over the full circle of 360°.