Abstract This thesis is devoted to methods of analyzing optical spectra obtained from turbid liquids, i.e., liquids that are optically very thick and/or scatter light. Data for spectral analysis were obtained with a new, multifunction spectrophotometer developed for industrial liquid samples. One characteristic of the spectrophotometer is that spectral analysis methods can be implemented into the software. Here, the emphasis was on data inversion methods, particularly the Kramers-Kronig analysis and the maximum entropy method, which can be used to gain information on the wavelength-dependent complex refractive index of liquid samples. Relating to such characteristics as density and colour, the complex refractive index also helps to identify the species that form a liquid. The methods were applied to study the internal reflection of light from the prism-liquid interface of the probe and to analyze surface plasmon resonance spectra. This study provided new methods of investigating the optical properties of relatively difficult objects, like offset inks, and of assessing adhesion forces between ink and the substrate system. Another important part of the thesis was the exploration of spectral analysis methods to obtain optical properties of nanoparticles in a liquid matrix. Bounds for the optical properties of multi-component structures in a liquid were considered with the aid of Wiener bounds.

Abstract This thesis describes the application of Low Coherence Interferometry (LCI) and Optical Coherence Tomography (OCT) in paper measurements. The developed measurement system is a combination of a profilometer and a tomographic imaging device, which makes the construction versatile and applicable in several paper measurement applications. The developed system was first used to measure the surface structure of paper. Different grades of paper were selected to provide maximum variation in surface structure. The results show that the developed system is capable of measuring grades of paper from rough base paper to highly coated photo printing paper. To evaluate the developed system in surface characterization, the roughness parameters of five laboratory-made paper samples measured with the developed system and with a commercial optical profilometer were compared. A linear correlation was found with roughness parameters Ra and Rq. Next, the surface quality of paper was evaluated using LCI, a Diffractive Optical Element Based Glossmeter (DOG), and a commercial glossmeter. The results show linear correlation between Ra and gloss measured with the commercial glossmeter. The roughness Ra and averaged gloss measured with the DOG didn't give such a correlation, but a combination of these techniques provided local properties of gloss and surface structure, which can be used to evaluate the local surface properties of paper. In the next study, determination of the filler content of paper using OCT is discussed. The measurement results show clear correspondence of the slope of the averaged logarithmic fringe signal envelope and the filler content. The last studies focus on 2D and 3D imaging of paper using OCT and begin with imaging of a self-made wood fiber network. The visibility of the fibers was clear. Next, several refractive index matcing agents are studied by means of light transmittance and OCT measurements to find the best possible agent for enhancing the imaging depth of OCT in paper. Benzyl alcohol was found to have the best possible combination of optical, evaporation, and sorption characteristics, and it is applied in 2D and 3D visualizations of copy paper.

The development of reliable, affordable, and efficient sensors is a key step forward in providing tools for efficient monitoring of critical environmental parameters. Fiber-optic sensors are already widely used in various industrial sensing fields. They have proven themselves reliable in harsh environments and can measure different physical quantities, such as temperature, pressure, strain, refractive index (RI), and humidity. Fiber-optic Mach-Zehnder Interferometer (MZI) is a well-studied optical fiber interferometer that has proven capacity for sensing ambient refractive index. In this dissertation, we present Fiber Bragg grating (FBG) embedded in a microfiber Mach-Zehnder Interferometer designed for sensing temperature and refractive index. The MZI is constructed by splicing a short length of 40-μm-diameter microfiber between standard single mode fibers. A one-millimeter-long FBG is then written in the microfiber using a direct, point-by-point, ultrafast laser inscription method. The microfiber MZI shows only moderate sensitivity to ambient refractive index and temperature changes. In contrast, the microfiber FBG is insensitive to ambient refractive index change, while it exhibits typical sensitivity to temperature variation. These distinct characteristics of the FBG and MZI sensors enable the simultaneous measurement of refractive index and temperature as well as temperature compensation in ambient refractive index measurement. Further, we report the use of a fiber-optic Mach-Zehnder Interferometer to measure core refractive index changes written by femtosecond laser irradiation. The core-offset interferometer was constructed by splicing a lightly misaligned stub of standard single-mode fiber between the device’s lead-in and lead-out optical fibers. When the core refractive index of an in-fiber interferometer is altered, that process changes the phase of the core light. Since the phase of light propagating in the cladding (reference arm) remains unchanged, the transmission fringe pattern of the interferometer undergoes a spectral shift. In the present research, that spectral shift was used to quantify the effective core refractive index change in a standard single-mode fiber. In addition, we designed and developed a custom flame-based tapering machine that is used to fabricate miniaturized Mach–Zehnder interferometers (MZIs) using sharply tapered photonic crystal fiber (PCF). This technique produces sensors capable of highly sensitive ambient refractive index (RI) measurements. The sensor is fabricated by fusion splicing a small stub of PCF between standard single-mode fibers with fully collapsed air holes of the PCF in a splicing region. Tiny flame geometry enables the sharp tapering of the PCF, resulting in a short fiber length and high RI sensitivity. It appears that sharp tapering has a great impact on RI sensitivity enhancement, when compared with methods that decrease taper waist diameter. The tapering technique is further used to construct the Mach-Zehnder Interferometer-based fiber-optic refractive index (RI) sensor by uniformly tapering standard single mode fibers (SMF) for RI measurement. The fabricated MZI device does not require any splicing of fibers and shows excellent RI sensitivity. / Graduate

This Master’s dissertation focuses on exploring optical nonlinearities in IIIV semiconductors. This work covers a range of III-V materials and a few devices. To begin with, optical characterization of Aluminium Gallium Arsenide (AlGaAs) waveguides with enhanced nonlinear optical interactions was carried out. We have experimentally demonstrated wide conversion ranges andhigh conversion efficiencies for four-wavemixing inAlGaAswaveguides with three different geometries. In addition to that, both linear and nonlinear losses in each of these geometries were explored. AlGaAs represents only one compound of the large group of III-V semiconductors. To explore the potentials of other semiconductors compounds of this group for nonlinear optics, it is imperative to have information about refractive indices of different III-V compounds. This refractive index information is only available for some binary compounds in isolated spectral windows. In this thesis, we developed a model capable of predicting the values of the refractive indices of binary, ternary and quaternary III-V semiconductor compounds from the values of their band-gap energies. We compared the value predicted by our proposed model with existing experimental data and it was found not only is the predicted values in good agreement with the known values, but also has a lower error margin when compared to previously reported models. Finally, in quest for more suitable material platform for nonlinear photonic integration at different wavelength ranges, a detailed analysis of other potential III-V compounds not previously explored for photonic integration is presented.

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The intensity dependent refractive index change of a medium is frequently described in terms of the product n₂ · I where n₂ is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS₂) however, nuclear motions contribute to n₂. These motions occur on the sub picosecond time scale and thus become especially relevant for ultrashort laser pulses. The neat liquid CS₂ is studied because it exhibits a large nonlinear refractive index in comparison to other liquids. Therefore, it is employed in optical switching, optical limiting, and beam filamentation applications. This thesis presents effective n₂ values for Gaussian shaped linearly polarized pulses with central wavelength at [lambda]= 700nm. A theoretical model describing the time evolution of the material response is applied to distinguish between the instantaneous electronic, the ultrafast nuclear and the slow nuclear origins of the nonlinear refractive index. Moreover, the tensor nature of the material response function is studied by means of circularly polarized light. The relative magnitudes of bound electronic and nuclear contributions to n₂ are experimentally determined. Eventually, the dispersion of the instantaneous electronic response is measured in the spectral range between 390nm and 1064nm.

This study presents results on the use of ellipsometry as a novel probe for thin films of a diblock copolymer. Ellipsometry makes use of the change in polarisation induced upon reflection of light from a film covered substrate to enable calculation of the refractive index and thickness of the film. The infom1ation obtained in these measurements can be compared to differential scanning calorimetry, with the additional advantages that small sample volumes and slow cooling rates can be employed, and expansion coefficients can be determined. The work is presented in two parts; first crystallisation within the phase-separated domains is studied, then a morphological transition in the diblock ordering is characterised. By studying the temperature dependence of the film thickness and refractive index, crystallisation kinetics within very small volumes( 10^-10 L) of a poly (butadiene-b-ethylene oxide) diblock copolymer are measured. Through a comparison of two different PEO block lengths, a reduction in both the crystallisation and melting temperatures is demonstrated as the domain volume is decreased. Upon cooling, an additional transition is observed. We ascribe this to a morphological transition from a layer of ordered spheres to a lamellar layer at the substrate, which is consistent with a comparison between the data and simulated ellipsometry data. The sensitivity of ellipsometry makes it a well suited and versatile technique for probing thin film kinetics in diblock copolymers. / Thesis / Bachelor of Science (BSc)

<p>The chemical and physical properties of nine samples of sodalite have been determined along with the physical properties of an additional thirteen samples. Taken together with selected data from the literature these data indicate that: (1) the cell dimension of sodalite is constant for samples from one deposit within the limits ascribed to experimental error (± 0.0015 A° ) and the variation of a(0) for samples from other deposits is quite limited (i.e. ±0.005 A° ); (2) the specific gravity and refractive index exhibit small but measurable variations which cannot however be related to compositional variation; (3) the variation in chemical composition for sodalite indicated by analyses from the literature appears to be in error; much of the variation is attributed to zeolite impurities which were not removed from the samples before analysis; (4) probably all sodalites are represented to within 5 per cent by 6Na AlSiO(4).2NaCl with less than 0.30 weight per cent H(2)O.</p> <p>A petrographic study of the sodalite deposit at the Princess Quarry, Bancroft, Ontario, indicates that this mineral has formed from the reaction of chlorine-rich solutions with nepheline. The solutions appear to be derived from granite and syenite bodies which are regionally abundant in the vicinity of the Bancroft band of nepheline syenite gneiss. Many facts suggest that the present veins in the quarry have formed by the replacement of a pre-existing nepheline pegmatite.</p> / Thesis / Master of Science (MSc)