Patent EP-4080178-A1 (EP)
Title: Spintronic terahertz emitter
Inventor: KLÄUI MATHIAS PROF DR
IPC: G01J3/42
Filed: 2021-04-23
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 (j<sub>s</sub>) from the first layer (F) into the second layer (N), wherein the second layer (N) is adapted to convert the spin current (j<sub>s</sub>) into a transverse charge current (j<sub>c</sub>) in a direction perpendicular to the magnetization (M) of the first layer (F), the transverse charge current (j<sub>c</sub>) 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 (j<sub>s</sub>) from the first layer (F) into the second layer (N),- wherein the second layer (N) is adapted to convert the spin current (j<sub>s</sub>) into a transverse charge current (j<sub>c</sub>) in a direction perpendicular to the magnetization (M) of the first layer (F), the transverse charge current (j<sub>c</sub>) 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°.