Thesis (Ph. D.)--Materials science and engineering, Georgia Institute of Technology, 2005. / Stock, Stuart, Committee Chair ; Sanders, Thomas, Committee Member ; Snyder, Robert, Committee Member ; Johnson, Steven, Committee Member ; Wilkinson, Angus, Committee Member. Vita. Includes bibliographical references.

This thesis proposed and demonstrated a new all-polymer based fabrication process for an all-polymer flexible and parallel optical interconnect cable having a vertical light coupler, which can not only cut down the cost by eliminating metallization process for alignment but also facilitate both in production and application. Throughout the process, polyimide was used as the substrate, coated by Epoclad as claddings, then AP2210B and WPR 5100 were used to fabricate waveguides and 45 degree mirror couplers, respectively. In addition, precisely aligned mirror couplers to waveguides are fabricated by using polymer-based, non-metallic, and transparent alignment marks. Conventional and metallic alignment marks are easy to be detected by camera, when a layer of high reflective material, generally Cr metal, is patterned. However, transparent polymer material is used in this process, as alignment marks made of it which are actually buried phase structures. Therefore, it is hardly to be observed by conventional microscopy system. Hence, to increase the contrast of the alignment marks, I proposed and tested a feature specific alignment camera system for which the shape and depth of the alignment marks are optimized for phase-based imaging, such as phase contrast and Schlieren imaging. The results showed a contrast enhancement of alignment marks image compared to that of a conventional microscopy system. By using the fabrication and alignment process, process for adding waveguides to the structure is identified by using the polymer based alignment marks on the WPR 5100 layer. Mask was made by etch down process using fused silica wafer plate, Cr and AZ 3312 photoresist. At last, the developed and proposed process provides means of all-polymer based fabrication process for a flexible and parallel optical interconnect.

This dissertation presents techniques of three-dimensional microscopy. First, an economical method of microscopic image formation that employs a raster-scanning laser beam focused on a sample, while non-imaging detector receives the scattered light is presented. The images produced by this method are analogous to the scanning electron microscopy with visible effects of shadowing and reflection. Compared to a conventional wide-field imaging system, the system allows for a greater flexibility, as the variety of optical detectors, such as PMT and position-sensitive quadrant photodiode can be used to acquire images. The system demonstrates a simple, low-cost method of achieving the resolution on the order of a micron. A further gain in terms of resolution and the depth of focus by using Bessel rather than Gaussian beams is discussed. Then, a phase-imaging technique to quantitatively study the three-dimensional structure of reflective and transmissive microscopic samples is presented. The method, based on the simultaneous dual-wavelength digital holography, allows for higher axial range at which the unambiguous phase imaging can be performed. The technique is capable of nanometer axial resolution. The noise level, which increases as a result of using two wavelengths, is then reduced to the level of a single wavelength. The method compares favorably to software unwrapping, as the technique does not produce non-existent phase steps. Curvature mismatch between the reference and object beams is numerically compensated. The 3D images of porous coal samples and SKOV-3 ovarian cancer cells are presented.

This dissertation presents a quantitative phase imaging microscopy technique that combines phase-shifting interferometry with multi-wavelength optical phase unwrapping. The technique consists of a Michelson-type interferometer illuminated with any of three types of light sources; light emitting diodes, laser diodes and a ring dye laser. Interference images are obtained by using a 4-frame phase shifting method, and are combined to calculate the phase of the object surface. The 2π ambiguities are removed by repeating the experiment combining two and three different wavelengths, which yields phase images of effective wavelength much longer than the original. The resulting image is a profile of the object surface with a height resolution of several nanometers and range of several microns. To our knowledge, this is the first time that a three wavelength optical phase unwrapping method with no amplified phase noise has been presented for fullframe phase images. The results presented here are divided into three main categories based on the source of illumination; light emitting diodes, laser diodes and a ring dye laser. Results for both two-wavelength optical unwrapping and three-wavelength optical unwrapping techniques are demonstrated. The interferographic images using broadband sources such as light emitting diodes are significantly less affected by coherent noise compared to images obtained using lasers. Our results show that the three wavelength optical phase unwrapping can also be effectively applied to unwrap phase images obtained using coherent light sources such as lasers and laser diodes, without amplifying phase noise in the final phase image. We have successfully shown that our multi-wavelength phase-shifting technique extends the range free of 2π ambiguities in the phase map without using conventional computation intensive phase unwrapping methods. This phase imaging technique can be used to measure physical thickness or height of both biological and other microscopic samples, with nanometer axial resolution. An added advantage of the multi-wavelength optical phase unwrapping technique is that the beat wavelength can be tailored to match height variations of specific samples.

Optical phase microscopy provides a view of objects that have minimal to no effect on the detected intensity of light that are unobservable by standard microscopy techniques. Since its inception just over 60 years ago that gave us a vision to an unseen world and earned Frits Zernike the Nobel prize in physics in 1953, phase microscopy has evolved to find various applications in biological cell imaging, crystallography, semiconductor failure analysis, and more. Two common and commercially available techniques are phase contrast and differential interference contrast (DIC). In phase contrast method, a large portion of the unscattered light that accounts for the majority of the light passing unaffected through a transparent medium is blocked to allow the scattered light due to the object to be observed with higher contrast. DIC is a self-referenced interferometer that transduces phase variation to intensity variation. While being established as fundamental tools in many scientific and engineering disciplines, the traditional implementation of these techniques lacks the ability to provide the means for quantitative and repeatable measurement without an extensive and cumbersome calibration. The rapidly growing fields in modern biology meteorology and nano-technology have emphasized the demand for a more robust and convenient quantitative phase microscopy. The recent emergence of modern optical devices such as high resolution programmable spatial light modulators (SLM) has enabled a multitude of research activities over the past decade to reinvent phase microscopy in unconventional ways. This work is concerned with an implementation of a DIC microscope containing a 4-f system at its core with a programmable SLM placed at the frequency plane of the imaging system that allows for employing Fourier pair transforms for wavefront manipulation. This configuration of microscope provides a convenient way to perform both wavefront shearing with quantifiable arbitrary shear amount and direction as well as phase stepping interferometry by programming the SLM with a series of numerically generated patterns and digitally capturing interferograms for each step which are then used to calculate the objects phase gradient map. Wavefront shearing is performed by generating a pattern for the SLM where two phase ramp patterns with opposite slopes are interleaved through a random selection process with uniform distribution in order to mimic the simultaneous presence of the ramps on the same plane. The theoretical treatment accompanied by simulations and experimental results and discussion are presented in this work.

The objective of this research project was to evaluate the mechanical, morphological, and permeability properties of electrospun blends of polydioxanone and poly(lactic acid) for application as vascular grafts. Mechanical analysis was performed by uniaxial tensile testing to examine the peak load, peak stress, elastic modulus, and strain at break of the fibrous materials. The morphological characteristics of the polymer blends were analyzed using phase contrast microscopy, scanning electron microscopy, and image analysis software. Scanning electron microscopy and image analysis software were used to assess fiber diameter and pore size of electrospun scaffolds. Scaffold permeability measurements were also used to calculate fiber diameter and pore size, and the values were compared to those obtained using image analysis. The material property results acquired from the research suggest that the electrospun polymer blends have potential for use in vascular graft applications.

In this dissertation, improved techniques in digital holography, that have produced high-resolution, high-fidelity images, are discussed. In particular, the angular spectrum method of calculating holographic optical field is noted to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. It is observed that spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. In the angular spectrum method, the reconstruction distance does not have a lower limit, and the off-axis angle between the object and reference waves can be lower than that of the Fresnel requirement, while still allowing the zero-order background to be cleanly separated. Holographic phase images are largely immune from the coherent noise commonly found in amplitude images. With the use of a miniature pulsed laser, the resulting images have 0.5um diffraction-limited lateral resolution and the phase profile is accurate to about several nanometers of optical path length. Samples such as ovarian cancer cells (SKOV-3) and mouse-embryo fibroblast cells have been imaged. These images display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. This technique clearly exceeds currently available methods in phase-contrast opticalmicroscopy in both resolution and detail and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available. Furthermore, we also demonstrate that phase imaging digital holographic movies provide a novel method of non-invasive quantitative viewing of living cells and other objects. This technique is shown to have significant advantages over conventional microscopy.

Αμίαντος (asbestos) θεωρείται μια ομάδα ινωδών ορυκτών τα οποία παρουσιάζουν μια σειρά ιδιοτήτων που τον έχουν καταστήσει ιδανική λύση ως κατασκευαστικό και μονωτικό υλικό εδώ και δεκαετίες. Αμιαντούχα υλικά σήμερα βρίσκονται σχεδόν παντού. Εξαιτίας της σύνδεσής του με βλάβες στην ανθρώπινη υγεία (αμιάντωση, μεσοθηλίωμα, καρκίνος πνεύμονα) έχει απαγορευθεί η εμπορία και η χρήση του στην Ελλάδα από 1-1-2005. Οι κίνδυνοι περιορίζονται πλέον κατά την εργασία αφαίρεσης αμιάντου και στις συντηρήσεις και ανακαινίσεις κτιρίων, πλοίων και τρένων. Η νομοθεσία που σχετίζεται με τον αμίαντο και την προστασία εργαζομένων, καταναλωτικού κοινού και περιβάλλοντος εξελίσσεται, επακόλουθο των εξελίξεων στην ιατρική και στην τεχνολογία. Η μέθοδος μικροσκοπίας αντίθεσης φάσης χρησιμοποιήθηκε για τον υπολογισμό της συγκέντρωσης ινών στο χώρο εργασίας λατομείου. Τα αποτελέσματα των αναλύσεων μπορούν μελλοντικά να αξιοποιηθούν κατάλληλα, όπως γενικά και η χρήση της μεθόδου σε ανάλογες περιπτώσεις. / -

Treatment of cancers has been improved and new findings in research communities areconstantly found, but there are still many questions about how to treat these complex diseases.One way to treat cancer is to expose cancer cells to drugs that kill the cancer cells to a largerextent than the normal cell from the same as well as other tissue types. Different drugcompounds have diverse molecular effects on the cancer cells and to evaluate them, studies ondifferent cell lines were performed.Experiments were performed to study morphological and metabolic changes on treatedcells. Morphological changes in growing populations of MCF-7 cells and MCF-10A cellswere studied by using a phase contrast video microscopy (IncuCyte) image analysis. Changesin levels of metabolites and proteins were analyzed using two different mass spectrometricmethods. Hierarchical clustering was used to study the relationship between the collectedspectra and the most outstanding subgroup (cluster) was a set of compounds related toestrogens.There were apparent morphological differences between the two different cell lines, bothwhen untreated and after induction of apoptosis. This study shows that, when examining themetabolic patterns, there are tendencies among the substances studied to form clustersaccording their pharmacological classes. Although more studies have to be performed in thisarea it has been showed that there are possibilities to determine which pharmacological class asubstance belongs to by examining the morphological and metabolic patterns.

L’imagerie de polarisation est une technique permettant de révéler des contrastes qui n’apparaissent pas dans les images d’intensité classiques. En d’autres termes, elle permet de transformer une différence de propriétés polarimétriques en différence de niveau de gris. Elle trouve des applications en décamouflage, télédétection, microscopie, etc. Les imageurs polarimétriques utilisent souvent des modulateurs de polarisation basés sur des matrices de cristaux liquides rapides et fiables. Cependant, les LCVR contrôlent l’état de polarisation de la lumière à seulement une longueur d’onde donnée, et si le système est utilisé à d’autres longueurs d’ondes, il a des performances réduites. Si la lumière qui illumine la scène à un spectre large, il est donc nécessaire d’insérer un filtre spectral de bande étroite dans la voie d’imagerie, ce qui a pour effet de réduire la quantité de lumière entrant dans le système et donc le rapport signal à bruit des images.Un moyen de résoudre ce problème est d’utiliser des modulateurs de polarisation achromatiques, mais cela induit un coût et une complexité accrus qui peuvent ne pas être nécessaires si l’objectif est d’améliorer la performance de détection de cible en augmentant le contraste entre l’objet d’intérêt et le fond. Dans cette thèse, j’étudie l’impact d’un élargissement du spectre d’illumination sur la performance de détection de cible par des systèmes d’imagerie polarimétriques utilisant des composants chromatiques. A travers des simulations, je montre tout d’abord qu’élargir le spectre d’illumination peut augmenter le contraste car l’augmentation du flux de lumière compense la perte de précision polarimétrique. De plus, en prenant en compte les caractéristiques polarimétriques chromatiques des composants, on peut accroître encore l’augmentation du contraste. Ces résultats sont ensuite validés à travers des expériences réelles d’imagerie polarimétrique active. Ils démontrent que la largeur du spectre d’éclairement peut être considérée comme un paramètre additionnel pour optimiser ces systèmes d’imagerie.Afin de mettre en pratique l’expertise acquise en imagerie polarimétrique active à un autre domaine, j’ai collaboré avec un partenaire industriel (Carl Zeiss, Germany) pour doter un microscope optique d’une capacité polarimétrique. L’imagerie d’un échantillon fin et transparent est un problème difficile. Par exemple, la coloration de l’échantillon peut ajouter des détails parasites et n’est pas applicable à l’imagerie du vivant. Une technique prometteuse est le contraste de phase différentiel (DPC) qui consiste à extraire le gradient de phase de l’objet à partir de deux images illuminées de manière asymétrique et acquises selon des angles complémentaires. La source de lumière est une matrice de LED programmables qui peut générer différents motifs d’illumination. Cependant, cette méthode d’imagerie prend du temps et les flashs intermittents émis par la source peuvent rendre l’observation inconfortable.J’ai donc proposé une solution alternative consistant à installer deux polariseurs avec des axes orthogonaux devant la source de lumière et une caméra sensible à la polarisation qui peut détecter simultanément des polarisations orthogonales. La lumière polarisée atteint la caméra sensible à la polarisation après avoir traversé l’échantillon transparent. Les composantes orthogonales sont extraites de l’image acquise par un procédé de débayerisation. A travers différentes expériences, je compare les performances de cette méthode innovante avec la méthode de DPC classique. Je montre qu’elles fournissent des qualités d’images similaires dans la plupart des cas alors que la nouvelle méthode permet de diviser le temps d’acquisition par deux, tout en supprimant les flashs intermittents. / Polarization imaging is a technique which reveals contrasts that do not appear in classical intensity images. It transforms the difference in polarimetric properties of a scene into difference in gray level of an image. This technique has found applications in decamouflaging, remote sensing, microscopy etc. Polarimetric imagers often use polarization modulation devices based on liquid crystal variable retarders (LCVR), which are fast and reliable. However, LCVR control the polarization state of light only at one given nominal wavelength, and performance loss might be observed if imaging is performed at other wavelengths, due to the wavelength dependence of the LCVR. If the light source that illuminates the scene has a broad spectrum, it is thus necessary to insert a narrowband spectral filter in the imaging path. However, spectral filtering significantly decreases the amount of light entering the system and thus the signal-to-noise ratio of polarimetric images.A way to circumvent this issue is to achromatize the polarization modulators. However, this comes at the price of higher complexity and cost, and this may not be needed if the objective is to improve target detection performance by increasing the target/background discriminability (or contrast). In the thesis, we present the investigation of the impact of broadening the spectrum of the light entering the system on the discriminability performance of active polarimetric systems. Through simulations, we show that broadening the bandwidth of the illumination can increase the contrast between two regions, as the increase of light flux compensates for the loss of polarimetric precision. Moreover, we show that taking into account the chromatic characteristics of the components of the imaging system, it is possible to further enhance the contrast. We validate these findings through experiments in active polarimetric imaging configuration, and demonstrate that the spectral bandwidth can be considered as an additional parameter to optimize polarimetric imaging set-ups.We collaborated with an industrial partner (Carl Zeiss, Germany) to implement polarization imaging in optical microscopy. Imaging thin and transparent specimen in microscopy is a challenging task. Staining the sample is a solution but it adds false/spurious details to the image, thus not suitable for live imaging. Recently, differential phase contrast (DPC) imaging by asymmetric illumination is proved to be a desirable choice. This works on the principle that the phase gradient of a transparent specimen can be extracted from two images, illuminated and recorded at complementary angles. Then, DPC is computed as normalized difference between two images. Here the light source is programmable LED array and different pattern of illumination can be generated. This imaging method consumes more time and intermittent flash of light from light source makes sample observation inconvenient for the observer.A practical solution we propose is to install two polarization foils with orthogonal polarization axes below the light source side by side and a polarization sensitive camera which can detect orthogonal eigen polarization states at a time in the existing setup. The polarization foils separate light waves from complementary angles since orthogonally polarized light waves do not interact with each other. The polarized light reaches polarization sensitive camera after passing through transparent sample. The pixels sensitive to horizontal and vertical polarization detect horizontal and vertical polarized light respectively. Then horizontal and vertical polarized light information are separated from the recorded image and reconstructed the missing information using debayering process. Through experiments, we show that polarization based DPC and standard DPC images have similar quality in most cases and the new technique reduces time consumption by half.