| Summary: | The
following thesis is conceded with single mode fibre optic components which
exhibit a
wavelength selective transmission response. The response is achieved by
mechanically polishing the side of a optical fibre in order to asymrnetrically remove a
large proportion of the cladding material, and access the evanescent field of the
propagating lightwave. Resonant interaction between the fibre guided mode and a
multimode
planar waveguide, deposited directly onto the polished interaction region,
impacts a wavelength selective response to the fibre transmission. A theoretical model
is
developed to describe device performance, and the structure is fully investigated as a
function of the
experimentally controllable parameters. A experimental
characterization of device
performance is undertaken and found to be in good agreement
with the theoretical
predictions.
Methods of
depositing organic films directly onto side polished fibres are then
considered, and it is demonstrated that both the dip coating and spin coating of
photoresist films produces solid state devices with 3dB linewidths as narrow as 7.0nm
and insertion losses
consistantly less than O.2dB. The thenno-optic nature of the
overlays is also demonstrated to allow wavelength tunability of the device responses,
exhibiting a linear sensitivity of AÄ3/AT = -0.6mn/°C. This could be exploited as the
basis of a
temperature sensor. The addition of a bulk silver superstrate is then shown to
provide a modulation depth enhancement of 7.6dB for the TM polarization state, with
negligible increase in linewidth.
The
Langmuir-Blodgett (LB) technique is investigated as a means of accurately
fabricating single mode overlays, and in-situ measurements of the deposition of
co-tricosenoic acid films reveals a
strong dependence of transmission response upon lm
thickness
(AÄ0/Ad = 2.4) for this overlay mode order. Through the use of a annular
polishing technique, the repeatability of the LB process can be greatly increased and it is
found that this method allows the
deposition of more complex films. Finally, the
possibility of amplitude modulation is considered through the use of D-rr-A LB lm
forming molecules.
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