Optimization of high performance spintronic terahertz sources

TL;DR

This paper presents a novel method for optimizing spintronic terahertz sources using remnant magnetization, achieving high efficiency and broadband emission comparable to traditional nonlinear crystals, with potential for cost-effective ultrabroadband applications.

Contribution

It introduces a remnant magnetization technique for stable terahertz emission from magnetic nanofilms and optimizes laser parameters to enhance efficiency, demonstrating performance comparable to established methods.

Findings

Optimized wavelength and incidence angle improve emission efficiency.

Achieved broadband terahertz spectra comparable to ZnTe crystals.

Demonstrated stable, continuous terahertz pulses without external magnets.

Abstract

To achieve high efficiency and good performance of spintronic terahertz sources, we propose and corroborate a remnant magnetization method to radiate continuously and stably terahertz pulses from W/CoFeB/Pt magnetic nanofilms without carrying magnets on the transmitters driven by femtosecond laser pulses. We systematically investigate the influences of the pumping central wavelength and find out the optimal wavelength for a fixed sample thickness. We also optimize the incidence angle of the pumping laser and find the emission efficiency is enhanced under oblique incidence. Combing the aforementioned optimizations, we finally obtain comparable radiation efficiency and broadband spectra in W/CoFeB/Pt heterostructures compared with that from 1 mm thick ZnTe nonlinear crystals via optical rectification under the same pumping conditions of 100 fs pulse duration from a Ti:sapphire laser oscillator, which was not previously demonstrated under such pulse duration. We believe our observations not only benefit for a deep insight into the physics of femtosecond spin dynamics, but also help develop novel and cost-effective ultrabroadband spintronic terahertz emitters.