Efficient ultrabroad terahertz emission from nanometer-thick spintronic heterostructures

Optically excited THz spintronic emitters have become promising THz sources, permitting a gapless broadband spectrum. We experimentally investigate THz spintronic emission based on the spin Hall effect in ferromagnetic/metal heterostructures with different femtosecond pulse excitations. We demonstrate the combination of high efficiencies (>10-5) and ultrabroad emission with a 23 fs high power Ytterbium laser.