Optical characteristics of graphene oxide film and its application in planar waveguide devices / Lim Weng Hong
Investigation of the optical characteristics of Graphene Oxide (GO) film was carried out. The GO film was fabricated by drop-casting of GO solution onto a planar substrate. The GO solution was prepared using improved Hummer’s method. The optical conductivity of GO film for TE-polarised light (per...
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| Format: | Thesis |
| Published: |
2016
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| Online Access: | http://studentsrepo.um.edu.my/6321/1/weng_hong.pdf http://studentsrepo.um.edu.my/6321/ |
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| Summary: | Investigation of the optical characteristics of Graphene Oxide (GO) film was carried
out. The GO film was fabricated by drop-casting of GO solution onto a planar substrate.
The GO solution was prepared using improved Hummer’s method. The optical
conductivity of GO film for TE-polarised light (perpendicular to the stacking axis of GO
layers) is in the magnitude of ~103 Sm-1, which results in very high optical absorption.
On the other hand, TM-polarised light will encounter relatively smaller absorption due to
a much lower optical conductivity. It was also observed that the conductivity of the GO
film is affected by the amount of water molecule present in the film. Water molecules are
able to permeate in and out of the GO film freely due to the film natural properties. The
permeated water molecules readily interact with the functional groups of each individual
GO layer and this interaction reduces the film conductivity by further widening its
bandgap. This process was reversible when the water content in the film was reduced. In
addition, photothermal reduction through optical phonon relaxation of GO film using near
infrared light source was studied. A numerical model of wave propagation in GO film
was then developed followed by experimental verification of the model.
The GO film was then coated onto a planar optical waveguide. Strong polarisation
effect was observed due to the large anisotropy complex dielectric function of GO film.
The GO film functionalized waveguide polariser showed a broad band response over the
visible and near infrared wavelength range with a maximum polarisation extinction ratio
of more than 40 dB in the 1550 nm optical fibre communication window. The response
of GO film to changing water content has also been applied in optical water detection and
humidity sensing. Finally, by exploring the reversible photothermal reduction
characteristics of GO film, an all-optical GO-based waveguide modulator with a
modulation depth of 72% and response time of <100 ms was demonstrated. |
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