THz spintronic emitters with magnetoelectric control of the polarization and applications to polarimetry.

We present a scheme to achieve coherent polarization rotation without multipolar or rotating external magnetic bias nor complex cascaded emitters, by exploiting artificially engineered strong uniaxial anisotropy in intermetallic heterostructures of rare-earth and transition metals. By replacing the FM layer of the spintronic emitter with a carefully designed FeCo/TbCo2/FeCo heterostructure, we demonstrated Stoner-Wolfarth-like coherent rotation of the THz polarization only by a unipolar variation of the strength of the hard axis field. In a second step we demonstrated the magnetoelectric control of the polarization direction. These results improve greatly the feasibility of fast polarization switchable integrated THz sources impacting practical applications such as ultrabroadband THz spectroscopic ellipsometry without rotating elements, or polarization modulated high speed wireless data communications, but also fundamental physical studies into ultrafast terahertz optospintronics.