Opal Based 3D Photonic Crystals
Abstract
In this thesis a self-assembly technique has been used to fabricate Opal Based Photonic Crystals; the three dimensional (3-D) photonic crystals (PhC) are studied in the visible regime. The optical properties of the 3D PhC are modified in various ways such as applying pressure and by the infiltration of other materials. The modified optical properties are investigated experimentally. Crystals are fabricated by capillary growth of mono-dispersed silica and polystyrene spheres with less then 5% standard deviation. For silica spheres the Stober's synthesis method is used, for polystyrene spheres emulsion polymerisation is employed. The self assembled 3D PhCs, also known as synthetic opal, has a partial stop band in the direction. The stop band is tuned permanently towards the shorter wavelength with the application of uni-axial pressure along the direction. As the applied pressure is increased the stop band Full Width Half Maximum (FWHM) also increases. The pressure technique is also used to imprint grating structures on (111) plane of the synthetic opal made of polystyrene spheres. The experimental investigation of the infiltration of a light source such as nano dots inside the opal voids is observed to give modified spontaneous emission of the nano dots. A full photonic band gap in the very near infra-red regime can be achieved by the infiltration of high refractive index material such as Sb2S3 in the opal voids. The opal infiltrated with gold nano-particles shows the superposition of the lattice diffraction and the surface plasmon resonance of the gold particles. Work has also been performed to investigate optical properties of opal based single and double heterostructures. In addition to PhC's, arrays of Split Ring Resonators (SRRs), also periodic structures were fabricated. These subwavelength structures or metamaterials are designed to work in the NIR regime. Three different metals (Au, Ag and Al) are used to fabricate the SRRs on silicon substrates. The optical properties are investigated and compared with the simulation results.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 2007
- Bibcode:
- 2007PhDT.......455K
- Keywords:
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- Electrical engineering;Condensed matter physics