  Structured light, particularly in the terahertz frequency range, holds
considerable potential for a diverse range of applications. However, the
generation and control of structured terahertz radiation pose major challenges.
In this work, we demonstrate a novel programmable spintronic emitter that can
flexibly generate a variety of structured terahertz waves. This is achieved
through the precise and high-resolution programming of the magnetization
pattern on the emitter surface, utilizing laser-assisted local field cooling of
an exchange-biased ferromagnetic heterostructure. Moreover, we outline a
generic design strategy for realizing specific complex structured terahertz
fields in the far field. Our device successfully demonstrates the generation of
terahertz waves with diverse structured polarization states, including
spatially separated circular polarizations, azimuthal or radial polarization
states, and a full Poincare beam. This innovation opens a new avenue for
designing and generating structured terahertz radiations, with potential
applications in terahertz microscopy, communication, quantum information, and
light-matter interactions.
