The optical properties of metamaterials

Khan, Saima Ishfaque (2016) The optical properties of metamaterials. PhD thesis, University of Glasgow.

Abstract

This thesis studies the parametric investigation, polarisation dependence and characterization of fishnet structure at near infrared wavelengths. Detailed simulations are performed to understand the behaviour of the structure at near infrared and optical wavelengths. Simulations are performed to obtain negative refractive index of the fishnet structure formed from nanoimprint lithography (NIL) by taking into account the effect of substrate and polymethyl methacrylate (PMMA) beneath it. Two different structures have been designed and fabricated of varying dimensions using NIL and their resonant wavelength measured in the near infrared at 1.45 µm and 1.88 µm. Simulations suggest that a negative refractive index real part with the magnitude -0.24 is found at 1.53 µm and this decrease to a maximum magnitude of -0.57 at 1.9 µm. The PMMA and suppressed pillars are here responsible for the increasing material losses and limiting the value of negative refractive index.
An analytical approach has been suggested to characterise fishnet structures at oblique incidence. The expressions for an absorbing medium are rewritten for an alternative definition of refractive index. The expressions are initially validated for a dielectric slab and a metal film. These results provide the possibility that this proposal may yield a general algorithm for obtaining the complex reflection and transmission coefficients for artificial structures. FDTD simulations have been extensively used in this thesis to understand the optical metamaterials and their characterization.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Characterization of metamaterials
• Subjects: T Technology > TA Engineering (General). Civil engineering (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Johnson, Dr. Nigel and De La Rue, Prof. Richard
• Date of Award: 2016
• Depositing User: Mrs Saima Khan
• Unique ID: glathesis:2016-7781
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 09 Nov 2016 16:02
• Last Modified: 05 Dec 2016 11:54
• URI: https://theses.gla.ac.uk/id/eprint/7781