Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 22: Terahertz spintronics

MA 22.4: Talk

Tuesday, April 2, 2019, 14:45–15:00, H52

On-chip generation of unipolar THz current pulses by the inverse spin-Hall effect — •Wolfgang Hoppe¹, Jonathan Weber², Tobias Kampfrath², and Georg Woltersdorf¹ — ¹Martin Luther University Halle-Wittenberg, Physics, Halle, Germany, — ²Free University of Berlin, Physics, Berlin, Germany

We use optical pump pulses to generate current pulses using the spin-dependent Seebeck effect and the inverse spin-Hall effect (ISHE) in heavy metal/ferromagnet bilayers. In our on-chip approach the bilayer structures are used to terminate coplanar waveguides. The optical excitation from an ultrafast amplified laser system injects ultrashort spin current pulses from the ferromagnet into the heavy metal layer via the spin-dependent Seebeck effect [1]. Subsequently, this spin current pulse is converted into a charge current pulse inside the heavy metal layer via the ISHE [2]. The direct measurement of the electric signal using a fast sampling oscilloscope with a bandwidth of 50 GHz provides already picoseconds time resolution but suppresses most of the THz signal. Subpicosecond time resolution is achieved by electro-optic sampling on the chip. Here we measure the change of polarization of linear polarized light induced by the electric pulse and observe a unipolar signal. We determine optical pulse to THz pulse energy conversion efficiency for both methods and compare them.
A. Melnikov. et. al.: arXiv:1606.03614[physics.optics] (2016)
T. Seifert, T. Kampfrath, et. al.: doi:10.1038/nphoton.2016.91