Simultaneous Terahertz Pulse Generation and Manipulation with Spintronic Coding Surface

Abstract

The utilization of spintronic terahertz (THz) emitters has a significant influence on broadband coherent spectroscopy and imaging at THz frequencies. By using femtosecond light to irradiate the spintronic heterostructures, spin currents from the ultrafast demagnetization effect can be transformed into charge currents through the inverse spin Hall effect, leading to the emission of THz waves. In this work, through the incorporation of sequential and inverse deposition of W‐Co20Fe60B20‐Pt heterostructure films, control is gained over the spin currents and THz waveforms, enabling it to achieve a 180° phase difference across a broad frequency spectrum while efficiently radiating THz waves. This, in turn, allows it to control the spatial phase of THz radiation. To test the device's capabilities, lithography‐based devices capable of focusing, producing vortexes, and dividing beams are manufactured. This investigation aims to advance the development of THz pulse sources while providing essential support for cutting‐edge technologies such as THz spectroscopy, high‐resolution imaging, and high‐speed communications.

Holographic THz Beam Generation by Nonlinear Plasmonic Metasurface Emitters

“…For instance, the recently established spintronic emitters show promise in the ongoing endeavor of actively controlling THz radiation. To date, these emitters have exhibited binary phase control and polarization manipulations, enabling polarization switching, beam steering, and lensing. – Another nanoscale approach on the generation of tailored THz emission is based on the utilization of nonlinear metasurfaces (NLMSs). – More precisely, the irradiation of plasmonic metasurfaces with femtosecond laser pulses in close vicinity to their localized surface plasmon resonance induces strong single-cycle THz emission due to optical rectification. , Interestingly, the recent expansion of the Pancharatnam–Berry phase (also called geometric phase) in the THz emission process from metasurfaces has aided in obtaining continuous spatial control over the emission phase . This was shown to demonstrate a variety of functional THz emitters .…”

Generation of a Focused THz Vortex Beam from a Spintronic THz Emitter with a Helical Fresnel Zone Plate

“…Spintronic terahertz emitters (STEs), with the advantages of a low cost and a high performance, are considered as another potential terahertz (THz) source, and they have attracted immense attention in the past decade [ 21 , 22 ]. Recently, Chen et al proved that an STE with an FZP could be produced, and a focused TVB was generated [ 23 ]. Unlike FZPs integrated in nonlinear materials, the π phase difference of the adjacent area of the FZP can be achieved by changing the direction of the deposited sequence of the STE.…”

Inverse design on terahertz multilevel diffractive lens based on 3D printing

“…In the last 20 years, significant attention has been directed into the development of functional devices operating in the THz frequency range, with the aim of generating and manipulating THz waves [5] . Several methods have been proven for the generation of THz pulses, such as photoconductive antennas [6] , nonlinear crystals [7] , air plasma [8] , epsilon-near-zero (ENZ) materials [9] , and spintronics films [10,11] . On the other hand, the manipulation of THz waves has been achieved by the utilization of artificial electromagnetic structures such as metamaterials [12][13][14] and metasurfaces [15][16][17][18] , which have been adapted from different frequency bands.…”