Efficient Terahertz Generation Using Fe/Pt Spintronic Emitters Pumped at Different Wavelengths

TL;DR

This paper demonstrates that Fe/Pt spintronic bilayer emitters can efficiently generate terahertz radiation when excited at both 800 nm and 1550 nm wavelengths, enabling cost-effective THz system integration.

Contribution

The study shows that Fe/Pt spintronic emitters are effective at both 800 nm and 1550 nm excitation wavelengths, expanding their applicability with fiber lasers.

Findings

Efficient THz generation at 800 nm and 1550 nm wavelengths.

Fe/Pt bilayer structure performs comparably at both wavelengths.

Enables integration with low-cost fiber laser systems.

Abstract

Recent studies in spintronics have highlighted ultrathin magnetic metallic multilayers as a novel and very promising class of broadband terahertz radiation sources. Such spintronic multilayers consist of ferromagnetic (FM) and non-magnetic (NM) thin films. When triggered by ultrafast laser pulses, they generate pulsed THz radiation due to the inverse spin-Hall effect, a mechanism that converts optically driven spin currents from the magnetized FM layer into transient transverse charge currents in the NM layer, resulting in THz emission. As THz emitters, FM/NM multilayers have been intensively investigated so far only at 800-nm excitation wavelength using femtosecond Ti:sapphire lasers. In this work, we demonstrate that an optimized spintronic bilayer structure of 2-nm Fe and 3-nm Pt grown on 500 {\mu}m MgO substrate is just as effective as a THz radiation source when excited either at {\lambda} = 800 nm or at {\lambda} = 1550 nm by ultrafast laser pulses from a fs fiber laser (pulse width close to 100 fs, repetition rate around 100 MHz). Even with low incident power levels, the Fe/Pt spintronic emitter exhibits efficient generation of THz radiation at both excitation wavelengths. The efficient THz emitter operation at 1550 nm facilitates the integration of such spintronic emitters in THz systems driven by relatively low cost and compact fs fiber lasers without the need for frequency conversion.