Shaping terahertz emission using spintronic emitters

Terahertz (THz) falls in the gap between photonic and electronic in the electromagnetic spectrum. Conventionally, photoconductive antennas and nonlinear crystals, which employ only the electron charge, are used as standard THz sources. An alternative approach utilizes the spin degree of freedom: Exciting magnetic heterostructures with a femtosecond laser pulse results in the generation of an ultrafast spin current, which is then converted into THz transient via the inverse spin Hall effect. Here, we demonstrate the shaping of the THz spectrum from magnetic micropatterned heterostructures fabricated with optical lithography and magnetron sputtering techniques. Our results show that the properties of THz radiation can be controlled by a careful design of micropatterned geometries and dimensions. We demonstrate that the characteristic bandwidth of the THz spectrum can be efficiently controlled using microstructured stripes and the THz polarization can be tuned by forcing the magnetization into curling in chopped microdisks. Our results demonstrate control of THzproperties such as polarization and bandwidth using microfabricated spintronic emitters.