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Title: THz on-chip waveguides for ultrafast magnetic measurements
Author: Peters, Nicolas Aaron
ISNI:       0000 0004 7431 8185
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2018
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This thesis describes the development of on-chip terahertz (THz) waveguides for use in ultrafast magnetic measurements. An epitaxial transfer method is used to bond photoconductive switch material to quartz substrates. This, combined with optical lithography methods, allows on-chip generation and detection of THz pulses. Normally, the metal in a waveguide has a high conductivity (eg. gold or copper) in order to reduce ohmic loss. However, if this metal is instead a magnetic multilayer, then the THz pulse interaction with the metal can be used to measure ultrafast magnetic effects. This was performed using Cobalt/Copper multilayers, and a THz GMR was seen in a transmitted pulse. Additionally, an ’inverse’ GMR was noted in input pulses and in the pulse tail of transmitted pulses. It is believed that this is the first time such behaviour has been documented. Lateral spin valves offer the ability to separate charge and spin effects; however, the dimensions of these devices is in the hundreds of nanometers range. Coplanar waveguides were used to confine and concentrate THz pulses into this spatial regime. Curved waveguides were fabricated to prove confinement, and magnetoresistance properties were used to demonstrate field concentration. Devices were then designed to allow picosecond current injection into a lateral spin valve geometry. Initial results are obscured due to interference from the excitation pulse, but improvements to the design and fabrication could pave the way for this technology in the future.
Supervisor: Cunningham, John ; Hickey, Bryan Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available