Spintronic Terahertz Generation Using an Optimized Metallic Bilayer of Epitaxial Grown Fe/Pt on Silicon Substrate

Metallic spintronic heterostructures consisting of ultrathin ferromagnetic (FM) and non-ferromagnetic (NM) layers emit THz radiation through a distinct and efficient THz generation mechanism, which arises from the conversion of spin current generated in the FM layers into transverse charge current in the NM layers [1, 2]. We have previously demonstrated that an optimized bilayer of 2-nm Fe and 3-nm Pt epitaxial grown on 500-μm MgO substrate is a remarkably versatile spintronic THz emitter, as it exhibited fairly the same THz emission efficiency at 780-nm and 1550-nm pulsed excitation wavelengths [2]. In this work, we investigated spintronic THz generation when the Fe/Pt bilayer is epitaxial grown on 500-μm Si substrate. As with the Fe/Pt on MgO, the THz emission properties of the Fe/Pt on Si were probed by standard THz time-domain emission spectroscopy using a mode-locked femtosecond (fs) fiber laser source (pulse duration: ~100-fs; repetition rate: ~100 MHz; central wavelengths: ~780 nm, ~1550 nm).