Speaker
Description
Terahertz spectroscopy is a powerful tool to probe numerous low energy excitations. However, there are still challenges regarding broadband, gap-free and efficient sources of terahertz radiation driven by a compact femtosecond oscillator.
In our experiments, we employ laser pulses (duration 10 fs, center wavelength 800 nm, repetition rate 80 MHz, pulse energy 2.5 nJ) from a laser oscillator to launch spin currents in magnetic heterostructures (see Fig. 1). The dynamics of these ultrafast currents are monitored by taking advantage of the inverse spin Hall effect [1] and broadband terahertz emission spectroscopy [2].
In particular, we study THz emission from multilayers consisting of ferromagnetic and nonmagnetic metallic layers. The emission data can be evaluated to give an estimate of the strength of the spin Hall Effect. Spintronic emitters can be developed to provide an efficient and scalable THz electromagnetic pulses that fully cover the range from 1 to 30 THz without gap [3]. This THz source outperforms standard emitters such as zinc telluride in terms of bandwidth while having a comparable conversion efficiency.
The results shown here were obtained in close collaborations with the research groups of L.M. Hayden, M. Kläui, Y. Mokrousov, M. Münzenberg, P.M. Oppeneer, I. Radu and D. Turchinovich.
References
[1] S.A. Wolf et al., Science 294.5546 (2001).
[2] T. Kampfrath et al., Nature Nanotech. 8, 256 (2013).
[3] T. Seifert et al., http://arxiv.org/abs/1510.03729 (2015).
