Working with nanoscale optics requires methods and equipment designed for the purpose. This thesis describes the development of techniques and a system for performing highly localised spectroscopy. The system consists of a nanonics multiview 2000 scanning near-field optical microscope, a grating spectrometer and a photonic crystal fibre supercontinuum light source. Discussion of the microscope includes its modes of operation and development of software to collect and analyse data. In order to demonstrate the setup, an example of localised spectroscopy is presented in the form of an investigation of hollow core photonic crystal fibre. Taking spectra of the components of the cladding of these fibres makes it possible to investigate the origins of bandgap guidance. A core focus of nanoscale optics is the interaction of light with metal structures. This field is called plasmonics. Fabrication of structures is presented and requires special facilities and processes. These processes are both time consuming and expensive, both factors that emphasise the need for prior modelling. Forward difference time domain modelling of a proposed structure comprising of a concentrically arranged ring and disk is explored using home written code and a commercial package called CST Microwave Studio. The investigation of this concentric design through modelling shows a very highly localised field enhancement which can be engineered to have a narrow spectral resonance in the near infrared. The interaction of the two components which govern this resonance is explained using a theory called plasmon hybridization. Once the optical behaviour of small metal objects is understood they can be used in other ways. An example of this is shown in Porous Silicon. As a material it provides an excellent template for formation of metal nano-particles. Embedded in a high surface area network of silicon these particles can be used as very effcient catalysts.

The impact of buoyancy on the development of starting flows in the near field was experimentally investigated using the Digital Particle Image Velocimetry and Planar Laser Induced Flourescence techniques. The experiments were conducted by releasing cylindri-cal columns of fluid into a glass water tank. Two diameters (0.95 and 1.9 cm) and four aspect ratios, ranging from 2 to 8, were examined. The fluid was released by bursting the thin latex membrane that held it in the tube. The buoyant fluid had a density difference of 4.7%. The flow was imaged at 60 Hz up to 7 diameters downstream. For the aspect ratio of 2, the flow developed into a single buoyant vortex ring (BVR), and was compared to a purely momentum driven vortex ring (MVR) generated with the same setup. For the aspect ratios of 4, 6, and 8, the flow was similar to a starting plume, with a vortical cap, followed by a columnar tail. The BVR's diameter grew linearly in space, with a full spreading angle of 18 degrees, while the MVR's diameter remained constant. The BVR started out as an axis touching ring, and transitioned to non-axis touching, opposite of the behavior of the MVR. The total circulation for the BVR was more than twice the amount predicted by the slug flow model, and the impulse grew linearly in time. The impulse of the MVR decayed slightly after the intial growth. The flows began to transition to thermal behavior at down-stream distance proportional to the cube root of the initial fluid volume. For all aspect ratios the impulse grew linearly in time. The growth rate was roportional to the initial buoyant force. The circulation generated by the addition of buoyancy was proportional to the square root of the initial buoyant force. Also the addition of buoyancy suppressed the separation of a starting vortex.

Tip Enhanced Near-field Optical Microscopy (TENOM) is a method for optically imaging at resolutions far below the diffraction limit. This technique requires optical nano-probes with very specialized geometries, in order to obtain large, localized enhancements of the electromagnetic field, which is the driver behind this imaging method. Traditional methods for the fabrication of these nano-probes involve electrochemical etching and subsequent FIB milling. However, this milling process is non-trivial, requiring multiple cuts on each probe. This requires multiple rotations of the probe within the FIB system, which may not be possible in all systems, meaning the sample must be removed from vacuum, rotated by hand and placed back under vacuum. This is time consuming and costly and presents a problem with reproducibility. The method presented here is to replace multiple cuts from a side profile with a small number of cuts from a top down profile. This method uses the inherent imaging characteristics of the FIB, by assigning beam dwell times to specific locations on the sample, through the use of bitmap images. These bitmaps are placed over the sample while imaging and provide a lookup table for the beam while milling. These images are grayscale with the color of each pixel representing the dwell time at that pixel. This technique, combined with grayscale gradients, can provide probes with a symmetric geometry, making the system polarization independent.

Research Doctorate - Doctor of Philosophy (PhD) / The photochemistry of poly{p-phenylene[1-(tetrahydrothiophen-1-io)ethylene chloride]} (PPTEC), a water soluble precursor of the semiconducting polymer, poly{p-phenylenevinylene} (PPV), has been studied both under atmospheric conditions and in environments devoid of oxygen. UV-visible spectroscopy and photoluminescence data has been used to provide a picture of the mechanistic pathways involved in UV irradiation of the PPTEC material. A new quantitative model for the effect of UV irradiation upon film morphology is presented. The technique of near-field scanning optical lithography (NSOL) has been used to produce arbitrary structures of the semi-conducting polymer poly{p-phenylenevinylene} at sizes comparable with optical wavelengths. Structures on this scale are of interest for integrated optical devices and organic solar cells. The structures are characterised using AFM and SEM and examined in the context of the electric field distribution at the NSOM tip. The Bethe-Bouwkamp model for electric field distribution at an aperture has been used, in combination with the developed model for precursor solubility dependence on UV energy dose, to predict the characteristics of lithographic features produced by NSOL. Fine structure in the lithographic features that are characteristic of the technique are investigated and their origins explained. Suggestions for the improvement of the technique are made. Presented here for the first time is a device manufactured by the technique of NSOL functioning as an optical device. The technique of NSOL is used to manufacture an optical transmission phase grating (or phase mask) of PPV, this was done as a proof of concept for device manufacture by this method and to demonstrate the potential usefulness of the unique characteristics of the technique. The phase mask was characterised using AFM and SEM and examined in the context of how well a diffraction pattern matches with theoretical calculations.

<p>Mobile Phone, without this we can’t think to pass a day in presence. We have found a rapid increase of mobile phone users from a few years ago till now. Day by day the modern technologies allow the mobile phone to become smaller, cheaper, and more reliable. This also creates new possibilities for applications and integrations of the classical broadcast systems and modern mobile phone technologies. One example is the FM transmitter in mobile phone. The FM transmitter in a mobile phone is a “cool” feature which allows listening to the music content in phone on a car or home radio.</p><p> </p><p>This thesis work deals with the near field characterization of FM transmitters in mobile phone applications. The RF scientists and engineers neglect the near field zone because typical RF links operate at distances of many wavelengths away where near field effects are totally insignificant. But in this work we are interested in the near field properties of the FM transmitter. We measured the field intensity at near field and estimated the field strength at the far field region at 3 meters. To measure the field intensity and the effective radiated power we used HR1 near field scanner. As this is a new measurement approach, we made the validation of this system by measuring a reference dipole antenna at 880MHz and then compare the measured results to the CST simulation results. A basic phone model of FM transmitter has been created by CST simulation and a prototype has been made which was also used as our DUT. After validation of the near field measurement system we measured our DUTs (3 models-one cable fed prototype and two active devices) with the near field system and estimate the effective radiated power and field intensity at 3 meter. Furthermore, we measured our DUTs at 3 meter with a far field measurement system with optical fiber connection. A feasible relation between field strength and measured power was defined in order to correlate the near field scanner results with the far field measurement system.</p><p> </p><p>This paper also provides a short design guide line for built in FM antennas by relating the antenna size and placement to input power and the field strength in mobile phone FM transmitter application</p>

Apertureless near-field scanning infrared microscopy is a technique in which an impinging infrared beam is scattered by a sharp atomic force microscopy (AFM) tip oscillating at the resonant frequency of the cantilever in close proximity to a sample. Several advantages offered by near-field imaging include nanoscale imaging with high spatial resolution (near-field imaging is not restricted by the diffraction limit of light) and the ability to differentiate between chemical properties of distinct compounds present in the sample under study due to differences in the scattered field. An overview of the assembly, tuning, and implementation of the near-field instrumentation is provided, as well as detailed descriptions about the samples probed and other instrumentation used. A description of the near-field phenomena, a comparison between aperture and apertureless-type near-field microscopy, and the coupled dipoles model explaining the origin of the chemical contrast present in near-field infrared imaging was discussed. Simultaneous topographic and chemical contrast images were collected at different wavelengths for the block copolymer thin film, polystyrene-b-poly(methyl ethacrylate) (PS-b-PMMA) and for amyloid fibrils synthesized from the #21-31 peptide of β2-microglobulin. In both cases it was observed that the experimental scattered field spectrum correlates strongly with that calculated using the far-field absorption spectrum, and using near-field microscopy, nanoscale structural and/or compositional variations were observed, which would not have been possible using ensemble FTIR measurements. Lastly, tip-enhanced Raman spectra of the #21-31 and #16-22 peptide fragments from the β2-microglobulin and Aβ(1-40) peptide were collected, examined, and an outline of the optimization conditions described.

Mobile Phone, without this we can’t think to pass a day in presence. We have found a rapid increase of mobile phone users from a few years ago till now. Day by day the modern technologies allow the mobile phone to become smaller, cheaper, and more reliable. This also creates new possibilities for applications and integrations of the classical broadcast systems and modern mobile phone technologies. One example is the FM transmitter in mobile phone. The FM transmitter in a mobile phone is a “cool” feature which allows listening to the music content in phone on a car or home radio.   This thesis work deals with the near field characterization of FM transmitters in mobile phone applications. The RF scientists and engineers neglect the near field zone because typical RF links operate at distances of many wavelengths away where near field effects are totally insignificant. But in this work we are interested in the near field properties of the FM transmitter. We measured the field intensity at near field and estimated the field strength at the far field region at 3 meters. To measure the field intensity and the effective radiated power we used HR1 near field scanner. As this is a new measurement approach, we made the validation of this system by measuring a reference dipole antenna at 880MHz and then compare the measured results to the CST simulation results. A basic phone model of FM transmitter has been created by CST simulation and a prototype has been made which was also used as our DUT. After validation of the near field measurement system we measured our DUTs (3 models-one cable fed prototype and two active devices) with the near field system and estimate the effective radiated power and field intensity at 3 meter. Furthermore, we measured our DUTs at 3 meter with a far field measurement system with optical fiber connection. A feasible relation between field strength and measured power was defined in order to correlate the near field scanner results with the far field measurement system.   This paper also provides a short design guide line for built in FM antennas by relating the antenna size and placement to input power and the field strength in mobile phone FM transmitter application

In the literatures of investigating the coupling mechanism between laser diodes and fibers, Gaussian beam profile was used to describe the propagation of laser beams. But the real laser diode beams exist astigmatism. In order to understand the distributions of real laser diode beams, we used single-mode fiber interferometer to measure the near-field intensity and phase distributions of laser diodes. The nanometer aperture of taper fiber was used to scan through the horizontal and vertical directions across the maximal intensity point of the planes which were perpendicular to propagation axis to measure the intensity and phase distributions of laser diodes. In the measurement of phase distributions, these two single-mode fibers produced interference fringes through accepting laser beams. When the taper fiber scanned the optical field and the reference fiber kept a fixed distance from a laser diode for a stationary phase, the interference fringes shifted because of the phase difference of laser diodes change. In the measurement, in order to improve the stability of interference fringes and consider the aperture of taper fiber, we altered some experiment frameworks. There were four types of experimental framework. According to the experiment results of the near-field measurements, the measured beam widths along the horizontal and vertical directions at the laser diode facet were 4.11 £gm and 1.57 £gm respectively. The measured wavefront radius curvature were 6.59 £gm and 2.96 £gm in horizontal axis and vertical axis respectively. After Gaussian beam fitting, the beam widths along the horizontal and vertical directions at the laser diode facet were 4.04 £gm and 0.83 £gm respectively. The difference in beam widths between measured values and Gaussian fitting were 0.07 £gm and 0.74 £gm. The measured beam widths and the Gaussian beam curve fitting had similar results. We could see that the beam spread tendency in the z-axis for the laser beam which propagated in the z direction. In the phase distribution measurement, the measured wavefront radius curvatures and the theoretically calculated Gaussian beam values had a slight difference. The calculated wavefront radius curvatures at the laser diode facet were 11921.51 £gm and 3.48 £gm in horizontal axis and vertical axis respectively. They were 1809 times and 1.2 times of the measured values. The aperture of taper fiber was expanded because of the energy of laser beams, which also caused the spatial resolution degeneration. Moreover, the wavefront radius curvature in horizontal direction was biggish so the measurement framework also limited the ability of the phase distribution measurement. The above points were the reasons to cause the error of the phase distribution measurement. Furthermore, the measurement of the laser diode facet is under investigation.

This thesis presents a computational analysis of the magnetic field of low-frequency power transmission lines, and the approaches to its suppression. First, according to the structure of Taiwan's three-phase A.C. transmission network, this research calculated the distribution of conducting wires' magnetic field under specific configuration by applying the theories of Near-field effect, Biot Savart's law, and double complex number. Second, this research explored the features of various approaches to magnetic field suppression with magnetic-field vector analyses and Matlab simulations. Finally, two magnetic-field cancellation methods, the ¡§circuit space arrangement¡¨ and ¡§time phase permutations¡¨ were adopted to investigate their magnetic effects under various structures and combinations of transmission lines. This study reveals that the magnetic field can be effectively suppressed by using appropriate configuration of transmission lines in space and phase. By applying the result to the design and construction of transmission lines, we can meet not only the requirements of magnetic field reduction, but also the needs of the least cost.

Near-field light confinement on scanning probe is the backbone technology for near-field imaging with subwavelength resolution that overcomes the diffraction limit by exploiting the properties of evanescent waves. The fusion of the photonics and the latest nanofabrication technology creates emerging frontier for near-field light confinement research with new design approach. The propagation of light can now be controlled by periodical structure at subwavelength scale with low loss in the artificially synthesized dielectric material. New light propagation patterns can now be implemented in subwavelength structure, such as directional free space light focus grating coupler, photonic bandgap material like photonic crystal by permitting light propagation at certain wavelength while prohibiting light outside of bandgap, and nano-slot light resonator for increased light-matter interaction at nanometer scale. Advances in this research area will have tremendous impact on electromagnetic modeling and biomedical technology for probe based subwavelength optical detection. My doctoral research focused on investigating highly efficient, nanofabrication compatible directional light coupling structure and near-field subwavelength light focus through photonic crystal material. The distinct significance of this research was placed on exploitation of the embedded metallic grating coupler of high free space directivity and subwavelength light processing circuit of enhanced near-field transmission rate, the two most dominating basic elements of the scanning optical imaging system. First, I designed a compact elliptical grating coupler based on embedded noble metal such as gold or silver that efficiently interconnects free space with dielectric rectangular waveguide. The dense system integration capability shows the application potential for on-chip interfacing subwavelength light processing circuits and near-field fluorescent biosensors with far-field detection of superb radiation directivity and coupling efficiency. Second, a novel all-dielectric light confinement probe designed by slotted photonic crystal waveguide provides a light confinement mechanism on the lateral plane. The resonating nano-cavities and the λ/4 nano-slot are used to enlarge the light throughput while as the nano-slot waveguide provides single subwavelength center lobe. The impetus of this research is the growing interests by near-field imaging researchers to obtain a low loss visible light confinement probe designs through mass production. / text