Spintronic Terahertz Emission Spectroscopy Based on Ultrafast Terahertz Scattering Scanning Near-Field Optical Microscope
Spintronic terahertz(THz)emitters offer distinct advantages such as high efficiency,ultrabroadband capability,low cost,and easy integration.These emitters find applications not only in THz time-domain spectrometers driven by high-repetition-rate laser oscillators but also in the generation of intense THz electromagnetic pulses powered by high-energy femtosecond laser amplifiers.They have proven valuable in THz spectroscopy imaging and the exploration of strong-field THz physics.However,previous research on spintronic THz radiation mechanisms and device development relies primarily on far-field THz time-domain spectroscopy.The results of this approach present average THz emission information for the laser-pumped spot areas,which does not provide any insights into ultrafast spin currents and THz emission properties for the materials at micro-and nano-scales.In this study,we employ ultrafast THz scattering scanning near-field optical microscopy,driven by a femtosecond fiber laser oscillator,to investigate the spintronic terahertz emission properties of the ferromagnetic heterojunction material W/CoFeB/Pt at nanoscale.The utilization of this technology enables the detection of high signal-to-noise ratio spintronic THz emission at transverse scales as small as hundreds nanometers.This novel approach explores the generation,detection,and manipulation of ultrafast spin currents at THz frequencies with nano-spatial resolution.This study may inspire innovative ideas for the advancement of ultrafast THz spin optoelectronics.
terahertz radiationelectron spinscattering scanning near-field optical microscopeterahertz spin current
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