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Title: Design of a photonic enabled lab-on-chip for spectroscopy and sensing in the terahertz domain
Author: Seddon, James
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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The research in this thesis is concerned with the design of a lab on chip operating in the sub millimetre - Terahertz (THz) region of the spectrum. The lab on chip design utilises Uni-Travelling Carrier (UTC) photodiodes for Continuous Wave generation of THz and optoelectronic downconversion of THz. The system forms an integral part of a THz Frequency domain spectrometer with high spectral resolution. The use of UTC photodiodes enables the use of commercial 1550 nm laser sources and fibre optic components which add a great deal of flexibility to the operation of the spectrometer. In this work we review the on-chip waveguide options in the literature for THz waveguiding and select an appropriate waveguide based on initial design considerations. The waveguide chosen was a metamaterial waveguide in the form of a Spoof Plasmon waveguide which allows for field enhancement at the metamaterial surface. Following this the impedances of both the emitter UTC photodiode and receiver UTC photodiode are evaluated under their optimum operating conditions to maximise the power transfer across the spectrometer sample pathway. Using the Impedance information, a transition is designed to convert from guided co-planar waveguide modes to surface wave modes supported by the metamaterial waveguide. In addition, a resonator is also designed and coupled to the waveguide for refractive index sensing applications. Finally, the optical sub-system is designed to create a tuneable frequency domain spectrometer that down-converts the received sub-millimetre wave signals to the MHz range which can be easily extracted through the device bias circuit. The system is used to demonstrate a proof of concept free space spectroscopy system for remote sensing of Glucose concentrations in the 50-65 GHz spectral range.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available