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标题：Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer
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作者：Valynn Katrine Mag-usara ; Mary Clare Escaño ; Christopher E. Petoukhoff 等
期刊名称：iScience
印刷版ISSN：2589-0042
出版年度：2022
卷号：25
期号：7
页码：1-17
DOI：10.1016/j.isci.2022.104615
语种：English
出版社：Elsevier
摘要：SummaryTerahertz emission from ferromagnetic/non-magnetic spintronic heterostructures had been demonstrated as pump wavelength-independent. We report, however, the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. Maximum terahertz generation per total pump power was observed in the 1200- to 1800-nm pump wavelength range, and a marked decrease in the terahertz emission efficiency beyond 2500 nm (pump photon energies <0.5 eV) suggests a ∼0.35-eV threshold pump photon energy for effective spintronic terahertz emission. The inferred threshold is supported by previous theoretical results on the onset energy of significant spin-filtering at the Fe-Pt interface, and confirmed by Fe/Pt electronic structure calculations in this present work. The results of terahertz time-domain emission spectroscopy show the sensitivity of spintronic terahertz emission to both the optical absorptance of the heterostructure and the energy-dependent spin transport, as dictated by the properties of the metallic thin films.Graphical abstractDisplay OmittedHighlights•Excitation wavelength dependence of THz emission from spintronic Fe/Pt bilayer•Maximum THz emission efficiency of Fe/Pt in the 1200 to 1800-nm pump wavelength range•Inferred pump photon energy threshold linked to spin-filtering at the Fe-Pt interface•Effect of pump absorptance and energy-dependent spin transport on Fe/Pt THz emissionPhysics; Photonics; Radiation physics