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Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and ability of making them into optical fiber. This dissertation summarizes findings on different oxide-based glasses that have been synthesized and characterized for their potential application as Raman gain media. Two main glass families were investigated: phosphate-based glass matrices for broadband Raman gain application and TeO2-based glasses for high Raman gain amplification. A phosphate network was preferred for the broadband application since the phosphate Raman active modes can provide amplification above 1000 cm-1, whilst TeO2-based glasses were selected for the high gain application due to their enhanced nonlinearities and polarizabilities among the other oxide-based network formers. The results summarized in this dissertation show that phosphate-based glasses can provide Raman amplification bandwidths of up to 40 THz, an improvement of almost 5 times the bandwidth of SiO2. On the other hand, tellurite-based glasses appear to be promising candidates for high gain discrete Raman applications, providing peak Raman gain coefficients of up to 50 times higher than SiO2, at 1064 nm. Although, visible spontaneous Raman scattering cross-section measurement is the most frequently used tool for estimating the strength and spectral distribution of Raman gain in materials, especially glasses, there are some issues that one needs to be aware when conducting these measurements near the absorption band edge of the material. This led to the detection of an inherent frequency-dispersion in the Raman susceptibility and a resonant enhancement phenomenon when measurements were conducted near the absorption edge of the material.

Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are still growing analytical and sensing spectroscopic techniques. They significantly reduce the time and labor cost in analysis with simplified instrumentation, and lead to minimal or no sample damage. In this dissertation, fundamental studies to improve LIBS analytical performance were performed and its fusion with Raman into one single sensor was explored. On the fundamental side, Thomson scattering was reported for the first time to simultaneously measure the electron density and temperature of laser plasmas from a solid aluminum target at atmospheric pressure. Comparison between electron and excitation temperatures brought insights into the verification of local thermodynamic equilibrium condition in laser plasmas. To enhance LIBS emission, Microwave-Assisted LIBS (MA-LIBS) was developed and characterized. In MA-LIBS, a microwave field extends the emission lifetime of the plasma and stronger time integrated signal is obtained. Experimental results showed sensitivity improvement (more than 20-fold) and extension of the analytical range (down to a few tens of ppm) for the detection of copper traces in soil samples. Finally, laser spectroscopy systems that can perform both LIBS and Raman analysis were developed. Such systems provide two types of complimentary information – elemental composition from LIBS and structural information from Raman. Two novel approaches were reported for the first time for LIBS-Raman sensor fusion: (i) an Ultra-Violet system which combines Resonant Raman signal enhancement and high ablation efficiency from UV radiation, and (ii) a Ti:Sapphire laser based NIR system which reduces the fluorescence interference in Raman and takes advantage of femtosecond ablation for LIBS.

In recent times, plasmonics has been a hallmark in improving optoelectronic device performance as well as in improving sensing. Confining light in dimensions below the diffraction limit and subsequently converting the incident photons into localized charge-density oscillations called localized surface plasmons, optical enhancements of the local fields by many orders of magnitude is possible. This dissertation explores the use of such surface plasmon resonances in core multishell nanostructures and demonstrates the values of such structures in energy harvesting and sensing. Additionally, it also shows the use of emerging plasmonic materials like metal nitrides (TiN, ZrN) instead of traditional plasmonic materials (Au, Ag) in the nanostructure designs. Utilizing the localized surface plasmon resonance (LSPR) in metallic components of core multishell nanowires, calculations of the local density of states as a measure of emission were made using a Green’s function method, while the absorption and scattering were simulated using the Mie formalism. Combining both the absorption and the emission, the quantum efficiency of white LEDs was calculated and the optimal material/dimensions for maximal performance was determined for different phosphor components in a white LED. Additionally, the use of ZrN as a plasmonic cloak for noise cancellation in Si photodetectors is shown and the performance is compared with an Au cloak. Using the developed methodology, it is proved that ZrN cloaks can outperform Au cloaks in a certain region of the visible spectrum, showing the benefit of using such plasmonic systems in place of traditional materials. The fabrication of the different components of the core multishell nanowires is also presented, and in particular, fabrication of ultra-thin (sub-10 nm) plasmonic TiN is achieved. Utilizing plasmon hybridization, a tunable double resonance feature is observed in Au/SiO2/Au core shell shell (CSS) nanoparticles, which have been then demonstrated to improve the photocatalytic performance in hematite. In particular, the double resonance peak allows absorption of light beyond the band gap of hematite and subsequent conversion into photocurrent through hot electron injection. Comparison has been made with Au nanoparticles, and it has been shown that the CSS nanoparticles outperform Au nanoparticles significantly. These CSS nanoparticles have also been used for bioimaging, in particular for Raman spectroscopy, with strong results at high densities of the nanoparticles. Utilizing stronger scattering SiO2/Au Nanoshells, it has been possible to work towards single particle imaging of molecules and demonstration of this phenomenon has been shown here through the use of coherent Raman scattering spectroscopy.

Adjuvants can enhance the performance of the pesticide active ingredients in many ways including decreasing surface tension and reducing evaporation. Understanding how adjuvants effect pesticide behavior (e.g., surface persistence) is crucial for developing effective pesticide formulations, as well as facilitating the development of effective approaches to reduce pesticide residues from the surface of fresh produce post-harvest. The objective of this study is to investigate the effect of a non-ionic surfactant, Surf-Ac 910, on the persistence of two model pesticides, thiabendazole and phosmet on apple surfaces. The result shows that the addition of Surf-Ac 910 increased both the maximum wetted area and evaporation rate of thiabendazole, a systemic pesticide, and phosmet, a non-systemic pesticide. Utilizing surface-enhanced Raman spectroscopy to explore the surface and penetrative behaviors of thiabendazole and phosmet revealed that the addition of Surf-Ac 910 influenced the Raman signal of pesticides as well. The addition of Surf-Ac 910 decreased the Raman signal intensity when added to phosmet but did not affect the Raman signal intensity when added to thiabendazole. In terms of penetration, the addition of Surf-Ac 910 did not affect the penetration depth of phosmet but slightly increased the penetration depth of thiabendazole. These findings were true for both short-term, 40 minutes, and long-term, 3 days, exposure. Next, the effects of adjuvants on the removal of pesticide residues were investigated. Common household materials, such as baking soda, were effective at removing surface pesticide residues. After testing a variety of baking soda concentrations and starch granules, 2% baking soda and 2% corn starch were found to be the most effective baking soda concentration and starch granule respectively. 2% corn starch was the most effective removal method overall, with 99% of pesticide with/without adjuvant removed in just 5 minutes of wash time. Overall, this study demonstrated that although adjuvant Surf-Ac 910 could affect the surface persistence of pesticides, washing with common household materials such as 2% corn starch can be used as an effective, safe, and economic way to reduce pesticide exposure through fresh produce.

Raman spectroscopy has been used to characterise both organic and geological samples in order to build a database for the future characterization of biomarker molecules that are of astrobiological relevance. Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA ExoMars mission scheduled for 2018. Several geological features found on the surface of Mars by planetary rovers suggest that a possible extinct biosphere could exist based on similar sources of energy as occurred on Earth. For this reason, analytical instrumental protocols for the detection of isolated biomarkers preserved in suitable geological matrices unequivocally and non-destructively have to be evaluated for future unmanned missions. Raman spectroscopy is currently part of the Pasteur instrumentation suite of the ExoMars mission for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified and the biogeological modifications resulting from extremophilic survival activity have been studied. Here we present the Raman spectral characterization of several examples of organic compounds which have been recorded using 785 nm, 633 nm and 514 nm laser excitation -polycyclic aromatic hydrocarbons (PAHs), organic acids, chlorophyll and carotenoids. Experimental mixtures of ß-carotene in usnic acid, PAHs in usnic acid and PAHs in mineral matrices have also been investigated. Organic compounds and PAHs located under crystalline minerals samples were identified using a 5x objective lens and 785 nm III excitation. The pure compounds and compound mixtures were also analysed using X-ray powder diffraction and scanning electron microscopy (SEM). The results of this study indicate that near infrared laser at 785 nm provided the clearest and the most informative spectra due to the reduction of fluorescence emission. Higher energy lasers operating in the visible region have resulted in the emission of significant background fluorescence. Few samples fluoresce even with the use of 785 nm excitation and FT-Raman spectroscopy remains the instrument of choice for the analysis of these samples.

Drug trafficking and smuggling is an ongoing challenge for law enforcement agencies. Cocaine smuggling is a high-value pursuit for smugglers and has been attempted using a variety of concealment methods including the use of bottled liquids, canned milk, wax and suspensions in cans of beer. In particular, traffickers have used clothing impregnated with cocaine for smuggling. Handling, transportation or re-packaging of drugs of abuse and explosives will inevitably leave residual material on the clothing and other possessions of the involved persons. The nails and skin of the person may also be contaminated through the handling of these substances. This research study describes the development of Raman spectroscopic techniques for the detection of drugs of abuse and explosives on biomaterials of forensic relevance including undyed natural and synthetic fibres and dyed textile specimens, nail and skin. Confocal Raman microscopy has been developed and evaluated for the detection and identification of particulates of several drugs of abuse and explosives on different substrates. The results show that excellent spectroscopic discrimination can be achieved between single particles and substrate materials, giving a ubiquitous non-destructive approach to the analysis of pico-gram quantities of the drugs and explosives in-situ. Isolating the particle in this way corresponds with an analytical sensitivity comparable with the most sensitive analytical techniques currently available e.g. the highly sensitive, yet destructive ionization desorption mass spectrometry. With the confocal Raman approach, this work demonstrates that definitive molecular-specific information can be achieved within seconds without significant interference from the substrate. The potential for the application of this technique as a rapid preliminary, forensic screening procedure is obvious and attractive to non-specialist operators as it does not involve prior chemical pretreatment ii or detachment of the analyte from the substrate. As a result, evidential materials can be analysed without compromising their integrity for future investigation. Also, the applications of benchtop and portable Raman spectroscopy for the in-situ detection of drugs of abuse in clothing impregnated with the drugs have been demonstrated. Raman spectra were obtained from a set of undyed natural and synthetic fibres and dyed textiles impregnated with these drugs. The spectra were collected using three Raman spectrometers; one benchtop dispersive spectrometer coupled to a fibre-optic probe and two portable spectrometers. High quality spectra of the drugs could be acquired in-situ within seconds and without any sample preparation or alteration of the evidential material. A field-portable Raman spectrometer is a reliable instrument that can be used by emergency response teams to rapidly identify unknown samples. This method lends itself well to further development for the in-situ examination by law enforcement officers of items associated with users, handlers and suppliers of drugs of abuse in the forensics arena. In the last section of this study, a portable prototype Raman spectrometer ( DeltaNu Advantage 1064) equipped with 1064 nm laser excitation has been evaluated for the analysis of drugs of abuse and explosives. The feasibility of the instrument for the analysis of the samples both as neat materials and whilst contained in plastic and glass containers has been investigated. The advantages, disadvantages and the analytical potential in the forensics arena of this instrument have been discussed. / Egyptian Government and Sohag University

Compound semiconductors are the foundation of many electronic and optoelectronic devices. As a result semiconductor epitaxy can be viewed as the first significant step in device engineering. Accurate and reliable characterization methods are needed to measure semiconductor properties including optical, electrical, vibrational and crystal structure. In this thesis, the epitaxy of ZnTe thin films on sapphire substrate by Pulsed Laser Deposition system at different growth temperatures is studied. The texture analysis is inspected by Two Dimensional X-Ray Diffraction. The lattice constant of the films and strain studies are investigated by High Resolution X-Ray Diffraction. UV-Vis spectroscopy is applied to find absorption edge in ZnTe thin film in order to estimate optical bandgap. These common characterization methods reveal the great effect of growth temperature on crystalline and optical properties of ZnTe thin films. In addition, Raman spectroscopy is used for the first time in the Preston's group to examine vibrational modes in ZnTe thin films. This new characterization method, which is the main focus of this thesis, uncovers some new features of ZnTe thin films not accessible through other techniques. In this thesis, optimum experimental conditions, instrumentation and data analysis of Raman observations in thin films are studied in detail. The final results are in good agreement with other characterization methods and they can justify crystalline and optical observations. These results demonstrate that Raman spectroscopy is a non-destructive characterization method applicable to thin film analysis. / Thesis / Master of Applied Science (MASc)