Investigating the Terahertz Radiation Emitted from Spintronic Structures

Abstract

In this thesis, a terahertz (THz) time-domain spectrometer with trilayer W/CoFeB/Pt spin-based electronic (spintronic) THz emitters (STEs) was developed and commissioned. The study explored THz emission characteristics of the trilayers and presents an analysis of the pump fluence dependence, revealing attractive performance that surpasses a bilayer CoFeB/Pt STE by a factor of 2.7. Optimal THz emission was achieved with a W layer thickness of approximately 2.25 nm within the W/CoFeB/Pt trilayer. Further exploration focused on W/CoFeB/Pt STEs deposited on different substrates, with notable findings including superior transmission through fused silica (FS) substrate as well as the higher THz emission from the FS-based STE. Measurements on the THz field and the THz pulse energy consistently exhibited the partial damage to the STEs under 5.5-mJ·cm-2 pump laser and the total damage at 8.0 mJ·cm-2 while the total damaged MgO-based STE with higher thermal conductivity demonstrates marginal damage. Specific attention has been given to integrated flip large-area trilayer STEs with an 85-mm diameter, that generate a strong longitudinally polarised THz pulse with a peak electric field of 2 kV·cm-1. The study also incorporates a simulation describing the transverse and longitudinal polarisation profiles of the THz field varying with the propagation of THz radiation, serving as a predictive tool for improving the performance of the THz radiation from such large-aperture STEs.

Date of Award	31 Dec 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Darren Graham (Supervisor), Paul Nutter (Supervisor) & Thomas Thomson (Supervisor)