Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer

TL;DR

This study investigates how the pump wavelength affects terahertz pulse generation in spintronic thin-film emitters, revealing wavelength insensitivity in efficiency and potential enhancement through dielectric overlayers.

Contribution

It provides systematic analysis of pump-wavelength effects on THz emission in spintronic trilayers and demonstrates enhancement via dielectric overlayers.

Findings

THz generation efficiency is high for pump wavelengths 900-1500 nm.

Spin current generation is largely independent of pump photon energy.

Dielectric overlayers can double the terahertz emission field.

Abstract

We systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic Fe layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially at for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of of up to two in field.