Metamaterials and optical sensing at visible and near infra-red wavelengths

Sharp, Graham James (2015) Metamaterials and optical sensing at visible and near infra-red wavelengths. PhD thesis, University of Glasgow.

Abstract

Developments in the field of optical sensing have seen the creation of a wide variety of new structures and materials. These include metamaterial sensors, which comprise of nanostructures with physical dimensions smaller than the wavelength of light. Two of the most widely researched metamaterial structures are the Split Ring Resonator (SRR) and fishnet. Both of these structures can be physically altered (in terms of geometry, material composition or periodicity) to exhibit plasmonic resonances at frequencies as far as the visible regime. The near-infrared frequency range is of particular interest with regard to optical sensing as many molecular absorption bands can be found here.
This thesis studies the effectiveness of different designs of optical sensors and the fabrication techniques used to produce them. By changing the dimensions and constituent metal of SRRs, their resonance response is analysed and parameters such as the Quality factor (Q-factor) obtained. The sensitivity of a single gap SRR to the presence of a thin film and localised block of Polymethyl methacrylate (PMMA) is experimentally measured. By changing the position of the localised PMMA block, it can be used as a material probe for the sensor, enabling the areas of greatest sensitivity to be determined. The sensitivity of the SRR is found to greatly depend on the polarisation of the incident electric field with respect to the structure, varying between 143 nm/RIU and 612 nm/RIU when PMMA is positioned at the gap in the ring. Complementary simulations offer additional insight into the behaviour of the structure at a range of frequencies. In addition to plasmonic structures, the fabrication and characterisation of a polymer photonic biosensor is also studied. This sensor utilises a distributed Bragg reflector (DBR) cavity adjacent to a rib waveguide to create a narrow stop-band that can potentially be used in the sensing of specifically targeted biological analytes.
For optical sensors to make a transition from research environment to commercial application, the costly fabrication techniques associated with the research and development of nanostructures need to be avoided. Nanoimprint lithography (NIL) offers multiple benefits in terms of cost, fabrication time and the patterning of large areas and is well suited to the commercial sector. NIL has been extensively used throughout the work detailed in this thesis to pattern SRRs, fishnets and polymer sensors.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: optics, photonics, metamaterials, nanoscale, plasmonics
• Subjects: Q Science > QC Physics; T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Johnson, Dr. Nigel P.
• Date of Award: 2015
• Depositing User: Mr Graham James Sharp
• Unique ID: glathesis:2015-6399
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 08 Jun 2015 12:01
• Last Modified: 11 Jun 2015 14:57
• URI: https://theses.gla.ac.uk/id/eprint/6399