Enhanced Polarisation Control and Extreme Electric Fields: Advances in Terahertz Spectroscopy Applied to Anisotropic Materials and Magnetic Phase Transitions (Springer Theses)

Supervisor’s Foreword
Abstract
Publications
Acknowledgements
Contents
1 Introduction
	1.1 Crystal Optics
		1.1.1 The Dielectric Tensor
		1.1.2 Principal Axes and the Index Ellipsoid
		1.1.3 Plane Wave Propagation Through an Anisotropic Medium
		1.1.4 Effects of an Anisotropic Medium on the Polarisation State of Light
	1.2 Describing the Polarisation State of Electromagnetic Waves
		1.2.1 Ellipticity and Orientation Angle
		1.2.2 Alternative Descriptions of the Polarisation State
	1.3 Electromagnons in Improper Ferroelectrics
		1.3.1 Magnons
		1.3.2 Electromagnons
		1.3.3 Improper Ferroelectricity and Electromagnons in CuO
	1.4 Structure of This Thesis
	References
2 Terahertz Time-Domain Spectroscopy
	2.1 Generation of Broadband Terahertz Radiation
		2.1.1 Photoconductive Emitters
		2.1.2 Optical Rectification
	2.2 Electro-optic Sampling
		2.2.1 Polarisation-Resolved Electro-optic Sampling
	2.3 THz-TDS Experimental Setup
		2.3.1 Performing a THz-TDS Experiment
	2.4 Extracting Sample Properties and Polarisation Information …
		2.4.1 Complex Refractive Index
		2.4.2 Ellipticity and Orientation Angle
	2.5 Summary
	References
3 Rotatable-Polarisation Terahertz Time-Domain Spectroscopy of Anisotropic Media
	3.1 Investigating Anisotropy at Terahertz Frequencies
		3.1.1 Disambiguating Spectral Features Using Polarisation-Resolved Detection Methods
		3.1.2 Terahertz Polarimetry and Ellipsometry
		3.1.3 Methods of Terahertz Polarisation Rotation
	3.2 Rotatable-Polarisation Terahertz Time-Domain Spectrometer
		3.2.1 Rotating the Terahertz Polarisation State
		3.2.2 Polarisation-Resolved Detection Method and Alignment
		3.2.3 Calibration of the Terahertz Emission Strength
		3.2.4 Polarisation State of the Rotated Terahertz Pulses
	3.3 Comparison of Rotatable Polarisation to Projection via Wire-Grid Polarisers
	3.4 Experimental Implementation of RP-THz-TDS
		3.4.1 Sample Details
		3.4.2 Mapping Birefringence and Identifying Polarisation Eigenvectors Using RP-THz-TDS
		3.4.3 Extracting the Full Complex Refractive Index Using RP-THz-TDS
		3.4.4 Anisotropic Absorption and Chromatic Dispersion in CuO
	3.5 Summary
	References
4 Scalable Interdigitated Photoconductive Emitters for the Electrical Modulation of Terahertz Beams with Arbitrary Linear Polarisation
	4.1 Photoconductive Emitter Geometry and Terahertz Polarisation State
		4.1.1 Electric Dipole Radiation from Photoconductive Emitters
		4.1.2 Controlling the Terahertz Polarisation State with the Emitter Geometry
	4.2 Multi-Pixel Interdigitated Photoconductive Emitters
		4.2.1 Emitter Concept and Design
		4.2.2 Device Fabrication
		4.2.3 Simulated Device Performance
	4.3 Experimental Device Performance
		4.3.1 Initial Electrical Biasing Tests
		4.3.2 Generating Arbitrary Linear polarisation States via Electrical Control
	4.4 Rapid Modulation of Circular Polarisation States for Circular …
		4.4.1 Converting from Linear to Circular Polarisation via a Prism
		4.4.2 Stokes Parameters
		4.4.3 Experimental Setup
		4.4.4 Experimental Results
	4.5 Summary
	References
5 High-Field Terahertz Time-Domain Spectroscopy of Single-Walled Carbon Nanotubes and CuO
	5.1 Terahertz Spectroscopy Using Extreme Electric Fields
		5.1.1 Generating High-Field Terahertz Radiation
		5.1.2 Choosing the Right High-Field THz Source for You
	5.2 High-Field Terahertz Time-Domain Spectrometer
		5.2.1 Tilted Pulse-Front Pumping in LiNbO3
		5.2.2 Experimental Setup
		5.2.3 Controlling the Electric Field Strength of Terahertz Pulses
	5.3 A Test Case of Nonlinear THz Transmission: Indium Antimonide
		5.3.1 Experimental Results
	5.4 Nonlinear THz Transmission in Single-Walled Carbon Nanotube Films
		5.4.1 Experimental Results
	5.5 Electric Field-Dependent THz Transmission of CuO
		5.5.1 Electric Field-Dependence of the Electromagnon Response in CuO
	5.6 Summary
	References
6 Conclusions
	6.1 Outlook and Future Work
Appendix  Tracking Disorder Broadening and Hysteresis in First-Order Phase Transitions via the Electromagnon Response in Improper Ferroelectrics