Homogenization studies for optical sensors based on sculptured thin films
In this thesis we investigate theoretically various types of sculptured thin film (STF) envi�sioned as platforms for optical sensing. A STF consists of an array of parallel nanowires which can be grown on a substrate using vapour deposition techniques. Typically, each nanowire has a diameter in th...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2012
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/2547/1/24p%20SITI%20SUHANA%20JAMAIAN.pdf http://eprints.uthm.edu.my/2547/ |
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| Summary: | In this thesis we investigate theoretically various types of sculptured thin film (STF) envi�sioned as platforms for optical sensing. A STF consists of an array of parallel nanowires which
can be grown on a substrate using vapour deposition techniques. Typically, each nanowire
has a diameter in the range from ∼ 10−300 nm while the film thickness is . 1µm. Through
careful control of the fabrication process, both the optical properties and the porosity of
the STF can be tailored to order. These abilities make STFs promising for optical sensing
applications, wherein it is envisaged that the material to be sensed infiltrates the void re�gion in between the parallel nanowires and hence changes the optical properties of the STF.
Various homogenization formalisms can be used to estimate the constitutive parameters of
the infiltrated STFs. In this thesis two different homogenization formalisms were used: the
Bruggeman formalism (extended and non–extended versions) and the strong-permittivity�fluctuation theory (SPFT). These were used in investigations of the following optical–sensing
scenarios: (i) Electromagnetic radiation emitted by a dipole source inside an infiltrated chiral
STF. The effects of using the extended Bruggeman homogenization formalism, which takes
into account the nonzero size of the component particles, were studied. (ii) Surface–plasmon–
polariton waves on a metal–coated, infiltrated columnar thin film. The influences of using
the extended SPFT formalism, which takes into account the nonzero size of the component
particles and their statistical distributions, were explored. (iii) A metal-coated infiltrated
chiral STF which supports both surface-plasmon-polariton waves and the circular Bragg phe�nomenon. The possibility of using in parallel both surface-plasmon-polariton waves and the
circular Bragg phenomenon was investigated using the non–extended Bruggeman formalism.
Our numerical studies revealed that the design performance parameters of the infiltrated STF
are bode well for these optical–sensing scenarios. The use of inverse Bruggeman formalism
was also investigated: this was found to be problematic in certain constitutive parameter
regimes, but not those for optical–sensing scenarios considered in this thesis. |
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