Subwavelength antennas, drivers, and systems
Embodiments generally relate to subwavelength antennas and, more particularly, extreme subwavelength antennas with high radiation efficiency. One embodiment and its derivatives achieve the objective of an extreme subwavelength dual acoustic and electromagnetic antenna by using spin-orbit torque in an array of nanomagnets.
1. A subwavelength electromagnetic antenna, comprising
a piezoelectric substrate;
an array of magnetostrictive nanomagnets in elastic contact with the piezoelectric substrate; and
a driver configured to actuate the array by causing magnetization oscillations in the magnetostrictive nanomagnets using surface acoustic waves (SAWs) launched in the piezoelectric substrate, wherein the driver is configured to change SAW frequencies to cause the array to radiate electromagnetic waves at multiple frequencies that match the SAW frequencies up to a predetermined limit,
wherein the array of magnetostrictive nanomagnets is configured to (i) convert phonons of the SAWs to magnons via phonon-magnon coupling and (ii) convert the magnons to photons of the electromagnetic waves via magnon-photon coupling.
2. The subwavelength electromagnetic antenna of claim 1 , wherein the driver is configured to launch the surface acoustic wave (SAW) in the substrate with an alternating electrical voltage.
3. The subwavelength electromagnetic antenna of claim 1 , wherein the array of nanomagnets define an emitting area (A) and, when driven, radiate an electromagnetic wave of a wavelength (λ), wherein the ratio A/λ 2 is on the order of 10 −9 .
4. The subwavelength electromagnetic antenna of claim 1 , wherein the magnetostrictive nanomagnets are each 100-500 nm in length and/or 100-500 nm in width.
5. The subwavelength electromagnetic antenna of claim 1 , wherein a greater number of magnetostrictive nanomagnets in the array corresponds with a greater emitted signal strength.