Numerical characterisation of label free optical biosensors

Dar, T. (2015). Numerical characterisation of label free optical biosensors. (Unpublished Doctoral thesis, City University London)

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Abstract

There is a significant need for the development and use of numerical methods to simulate advance and complex optical biosensor structures. Finite Element Method (FEM) has been established as one of the most powerful and versatile numerical method and has been implemented in this thesis to characterize, analyse and optimise label-free optical biosensors for the detection of micron size biological objects like bacteria such as E.coli and nanometre size biomolecules such as antibody, nucleic acids and proteins. These sensors are all suitable for deep-probe sensing as large evanescent field can be excited in the sensing medium with substantial penetration depth achieved by techniques like Surface Plasmon Resonance (SPR) and sensor architectures based on nanowires and slot waveguides.

This thesis presents three different architectures of label-free optical biosensors. First, a fiber optic surface plasmon resonance (SPR) biosensor for the detection of E.Coli is optically modeled by using the finite-element approach in conjunction with the perturbation technique which is computationally more efficient and can be used for waveguides with low or medium loss values. The same sensing architecture is used when surrounding index is varied from 1.30 -1.44 to cover most of the biological elements that are used in the biosensing applications. Second one is based on evanescent-wave guiding properties of nanowire waveguides a theoretical investigation of silica nanowires employing a wire assembled Mach-Zehnder structure to detect the presence of E.Coli is studied second. Finally, a slot-waveguide based micro-ring resonator is investigated for the detection of DNA Hybridization using H-field FEM based full-vector formulation. It is found that all of the numerical methods provide good agreement with the experimental sensitivities and detection limits.

Item Type: Thesis (Doctoral)
Subjects: T Technology > T Technology (General)
T Technology > TA Engineering (General). Civil engineering (General)
Divisions: School of Engineering & Mathematical Sciences
URI: http://openaccess.city.ac.uk/id/eprint/13075

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