Chemistry and Biochemistry / Not available / text

Within recent years, numerous fields of engineering, like mechanics, optics and electronics, have been influenced and revolutionised by the technique of microand nano-structuring. For example, special optical elements for beam shaping, surface structures for the reduction of friction or modern "lab on chip" devices have been produced. Within this thesis a universal system has been developed facilitating the production of such structured surfaces with dimensions down to 500 nm. This system is not only capable of structuring surfaces by means of lithographic processes; it further allows the inspection of surfaces by scanning their topography. To realise such a system, two different technologies have been evaluated: Scanning Near-field Optical Lithography (SNOL), a very sophisticated technique which uses a thin fibre tip to expose a photo resist-covered surface, and confocal scanning technology. Here, the confocal scanning is accomplished using an adapted optical component, the optical pickup unit (OPU), from a gaming console, which turned out to be the most suitable and cost-efficient solution for the realisation of this system. Several test series have been carried out during this work, to verify the performance of the confocal system, both to structure photo resist surfaces and to characterise unknown surfaces. This present work will show the ability of the developed system to produce structures down to the sub-micron range and to characterise unknown surfaces with sub- micron precision. Various patterns have been written into photo resistcoated substrates to structure their surface. Beginning with diffractive optical elements (DOE) for beam shaping, followed by Dammann gratings for twodimensional beam shaping and optical gratings for light guidance as well as producing technical surfaces imitating the properties of sharkskin or simple micromechanical structures, the developed confocal system has shown itself to be flexible and widely-applicable. IV During the development of the confocal system, a strong need for a beam profiling system analysing the light beam diverging from the OPU, was recognised. Due to the fact that no commercially available system was capable of characterising beam sizes within the range of the diffraction limit, a novel method for beam profiling was invented. This method makes use of the fibre tips already applied within the SNOL system, producing tomographical scans of the beam spot.

The microwave near-field detection technique is of interest to many researchers for characterizing materials because of its high sensitivity. It is based on sensing buried objects by producing an evanescent field.The advantage of evanescent fields is their capability to interrogate electrically small objects. In the past, near-field probes have been designed to sense magnetic materials. For dielectric materials, a near-field probe that senses the permittivity of the materials is important. This work presents a novel design of a near-field probe that generates a dominant electric eld. The probe is an electrically small dipole measuring approximately 0.07?? in length operating at 216.3 MHz. The antenna is matched to a 50??? system using two chip inductors distributed symmetrically on the dipole. The numerical and measurement results show that the proposed design is highly sensitive and capable of sensing subsurface object. The proposed design is compact, lightweight and applicable for microwave applications.

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.

This thesis concerns the development of simple, compact scanning optical microscopes which can obtain confocal and interference images. The effects of feeding the reflected signal back into the laser cavity of a confocal microscope are investigated and exploited. Monomode optical fibres are used to perform the spatial filtering required for confocal microscopy and, later, as the source of reference beams for interferometry. The theory describing the basic operation of the microscopes is developed. The optical systems are modelled using scalar diffraction theory and the effects of optical feedback into the laser cavity are described, with the practical implications emphasised. A fully reciprocal arrangement of the microscope is developed, in which a single mode optical fibre both launches the signal towards the object and then collects the reflected signal. The fibre is shown to exhibit the spatial filtering properties required for the source and detector in a confocal microscope. It is shown that a semiconductor laser can be used as a detector of the amplitude of the object signal. This is first demonstrated by directing the microscope signal back into the laser cavity and measuring the variation of the optical intensity in the cavity itself. Comparable results are obtained when the variation of the junction voltage across the cavity is measured. It is also shown that the optical fibre is redundant in this system, since the lasing mode of the cavity itself is sufficiently small to adequately spatially filter the reflected signal. When a Helium-Neon laser is used as the source of illumination the effect of the feedback on the laser is seen to be very different, resulting in interferometry. It is shown that high frequency modulation techniques can be used to obtain both confocal images and surface profiles from the same system. This is first demonstrated using an optical feedback scheme in which the modulation of the optical path length of the object beam is controlled electrooptically. In an alternative scheme the images are obtained by calculation, rather than by using a control loop system. In this case the modulation is achieved mechanically. The theoretical limits for the resolutions of the systems described are discussed. It is shown that the lateral resolution of the surface profile systems is inherently non-linear with feature height. Finally, a semiconductor laser based microscope is developed which can obtain confocal images and surface profiles independently. The dependence of the wavelength on the injection current is exploited as a convenient means of introducing a phase shift into the feedback signal by which profilometry can be achieved. All the systems are described theoretically and demonstrated experimentally.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 41-42). Also available in electronic version.

Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2007. / A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 135-153.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: David A. Vanden Bout. Vita. Includes bibliographical references. Also available from UMI.

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.

No / Near field imaging using microwaves in medical applications has gained much attention recently as various researchers have shown its capability and accuracy in identifying features of interest compared to well-known screening tools. This paper documents microwave imaging experiments for breast cancer detection. A simple phantom consisting of a plastic container with a low dielectric material imitating fatty tissue and a high dielectric constant object emulating tumor is scanned with a UWB microstrip antenna between 4 to 8 GHz. The measured results indicate that the prototype is a good candidate for imaging application.