High performance THz emitters based on ferromagnetic/nonmagnetic heterostructures

摘要

We report a THz emitter with excellent performances based on nonmagnetic (NM)and ferromagnetic (FM) heterostructures. The spin currents are first excited bythe femtosecond laser beam in the NM/FM bilayer, and then transient chargecurrents are generated by inverse spin Hall effect, leading to THz emission outof the structure. The broadband THz waves emitted from our film stacks have apeak intensity exceeding 500 um thick ZnTe crystals (standard THz emitters).Our device is insensitive to the polarization of an incident laser beam whichindicates the noise resistive feature. In contrast, the polarization of THzwaves is fully controllable by an external magnetic field. We have alsofabricated the devices on flexible substrates with a great performance, anddemonstrated that the devices can be driven by low power lasers. Together withthe low cost and mass productive sputtering growth method for the film stacks,the proposed THz emitters can be readily applied to a wide range of THzequipment. Our study also points towards an alternative approach tocharacterize spintronic devices with NM/FM bilayers.