Generation and manipulation of chiral broadband terahertz waves from cascade spintronic terahertz emitters

TLDR

Polarization‑shaped terahertz sources are critical for wireless communications, sensing, imaging, and coherent control, and while spintronic emitters promise high‑performance broadband output, systematic control of circular polarization has yet to be achieved. This study demonstrates generation of circularly polarized terahertz waves in cascade spintronic emitters by engineering amplitudes, magnetic field directions, and phase differences in two‑stage beams, and further manipulates chirality, azimuthal angle, and ellipticity. The authors achieve this by delicately tuning the amplitudes, applied magnetic field orientations, and phase offsets between two terahertz beams in a cascade spintronic emitter configuration. The results advance understanding of ultrafast optical‑magnetic physics and pave the way for improved terahertz sources and optospintronic devices.

Abstract

Polarization shaped terahertz sources play a key factor in terahertz wireless communications, biological sensing, imaging, coherent control in fundamental sciences, and so on. Recently developed spintronic terahertz emitters have been considered as one of the next-generation promising high performance broadband terahertz sources. However, until now, polarization control, especially for twisting the circularly polarized terahertz waves at the spintronic terahertz source, has not yet been systematically explored and experimentally achieved. In this work, we not only demonstrate the generation of circularly polarized terahertz waves in cascade spintronic terahertz emitters via delicately engineering the amplitudes, applied magnetic field directions, and phase differences in two-stage terahertz beams but also implement the manipulation of the chirality, azimuthal angle, and ellipticity of the radiated broadband terahertz waves. We believe our work can help with further understanding of the ultrafast optical magnetic physics and may have valuable contributions for developing advance terahertz sources and optospintronic devices.