1D photonic crystal nanocavities for optical sensing

Abdul Rahman, Muhammad Ghazali (2017) 1D photonic crystal nanocavities for optical sensing. PhD thesis, University of Glasgow.

Abstract

The ability to detect small refractive index changes in analytes is of uttermost importance since these index changes can be directly correlated to the presence of small amounts of chemicals of interest within analytes. Photonic devices such as 1D PhC nanocavities are one of the interesting structures to be used as optical sensors due to their capability to integrate with CMOS technology. We present in this study, a simple optical technique of detection based on 1D PhC nanocavities that gives good sensitivity for various types of chemicals. The work reported in this thesis concerned with the designed, fabrication, and characterisation of 1D PhC nanocavity devices based on silicon-on-insulator (SOI) material. The objective of this work is to provide an optical wave-guided sensing technology using 1D PhC nanocavity devices in the wavelengths region around 1550 nm. Firstly, the PhC nanocavities were designed and modelled using 2D and 3D Finite-difference time-domain (FDTD) computations to provide insight behaviour of the resonator waveguides. The designated PhC nanocavity devices were carefully fabricated via combination of electron beam lithography (EBL) and the dry and wet etching technology. The nanocavity devices were realised using optimised fabrication process to ensure the sensing chips are reproducible and reliable. This is done by careful control at nanometre scale of fabrication process of the PhC nanocavity devices and the microfluidic chip. Then, the devices were paired with the PDMS based microfluidic channel system. The nanocavity devices were characterised and the sensor system were tested for their optical sensing capabilities. The sensitivity of various Q factor values corresponds to the different cavity lengths are studied. The sensor system sensitivity, S were measured via refractive index sensing experiment varying from 135.78 to 245.72 nmRIU-1 with the detection limit, DL of 8 x 10-6 RIU. The sensing area estimated is 2.35 μm2. In addition, through the non-specific interaction experiment, bio molecular proteins BSA as low as 3.125 μg/ml concentrations were detected. Finally, the sensor system thermal responses were measured.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Johnson, Dr. Nigel
• Date of Award: 2017
• Depositing User: Mr Muhammad Ghazali Abdul Rahman
• Unique ID: glathesis:2017-8288
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 18 Jul 2017 12:43
• Last Modified: 02 Aug 2017 08:27
• URI: https://theses.gla.ac.uk/id/eprint/8288