Nanostructured spintronic emitters for polarization-textured and chiral broadband THz fields

Abstract

Spintronic THz emitters (STEs) rely on spin current acceleration or decay, resulting in a burst of broadband THz emission, offering a new route to THz optics. Here, we demonstrate novel metastructures of STEs for molding the vectorial focal distribution of the emitted THz radiations. The metastructures also allow controlling the characteristics of local fields. Performing combined micromagnetic-electromagnetic simulations, we demonstrate the generation of broadband THz fields with designed vectorial, chiral, magnetic, or topological features and discuss the potential of these fields for studying magnetic, multiferroic, and chiral structures. The STEs metastructure is shown to produce higher-order electric and magnetic multipoles as well as localized, longitudinal, broadband magnetoelectric THz pulses. Furthermore, subwavelength features of the near fields at a distance less than 10 μm can be tuned by steering the magnetization of the metastructure. The results point to a new type of engineered STEs for the generation of structured broadband THz fields, with potential applications in the fields of optoelectronics, optics, and ultrafast magnetism.