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(1 - 8 of 8)
- Title
- EVALUATION OF THE PHOTO-INDUCED STRUCTURAL MECHANISMS IN CHALCOGENIDE GLASS MATERIALS.
- Creator
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Lopez, Cedric, Richardson, Kathleen, University of Central Florida
- Abstract / Description
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Chalcogenide glasses and their use in a wide range of optical, electronic and memory applications, has created a need for a more thorough understanding of material property variation as a function of composition and in geometries representative of actual devices. This study evaluates compositional dependencies and photo-induced structural mechanisms in As-S-Se chalcogenide glasses. An effective fabrication method for the reproducible processing of bulk chalcogenide materials has been...
Show moreChalcogenide glasses and their use in a wide range of optical, electronic and memory applications, has created a need for a more thorough understanding of material property variation as a function of composition and in geometries representative of actual devices. This study evaluates compositional dependencies and photo-induced structural mechanisms in As-S-Se chalcogenide glasses. An effective fabrication method for the reproducible processing of bulk chalcogenide materials has been demonstrated and an array of tools developed, for the systematic characterization of the resulting material's physical and optical properties. The influence of compositional variation on the physical properties of 13 glasses within the As-S-Se system has been established. Key structural and optical differences have been observed and quantified between bulk glasses and their corresponding as-deposited films. The importance of annealing and aging of the film material and the impact on photosentivity and long term behavior important to subsequent device stability have been evaluated. Photo-induced structures have been created in the thin films using bandgap cw and sub-bandgap femtosecond laser sources and the exposure conditions and their influence on the post-exposure material properties, have been found to have different limitations and driving mechanisms. These mechanisms largely depend on both structural and/or electronic defects, whether initially present in the chalcogenide material or created upon exposure. These defect processes, largely studied previously in individual binary material systems, have now been shown to be consistently present, but varying in extent, across the ternary glass compositions and exposure conditions examined. We thus establish the varying photo-response of these defects as being the major reason for the optical variations observed. Nonlinear optical material properties, as related to the multiphoton processes used in our exposure studies, have been modeled and a tentative explanation for their variation in the context of composition and method of evaluation is presented.
Show less - Date Issued
- 2004
- Identifier
- CFE0000196, ucf:46177
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000196
- Title
- Laser-induced crystallization mechanisms in chalcogenide glass materials for advanced optical functionality.
- Creator
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Sisken, Laura, Richardson, Kathleen, Richardson, Martin, Shah, Lawrence, University of Central Florida
- Abstract / Description
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Glass-ceramics (GC) are promising candidates for gradient refractive index (GRIN) optics. These multi-phase, composite materials also exhibit improved physical properties as compared to the parent base glass resulting from the formation of a secondary crystalline phase(s). Nanocrystal phase formation in a multi-component chalcogenide glass (ChG), (GeSe2-3As2Se3)(1-x)-(PbSe)x glass where x = 0-40 has been investigated, and the role of the starting material morphology has been correlated to the...
Show moreGlass-ceramics (GC) are promising candidates for gradient refractive index (GRIN) optics. These multi-phase, composite materials also exhibit improved physical properties as compared to the parent base glass resulting from the formation of a secondary crystalline phase(s). Nanocrystal phase formation in a multi-component chalcogenide glass (ChG), (GeSe2-3As2Se3)(1-x)-(PbSe)x glass where x = 0-40 has been investigated, and the role of the starting material morphology has been correlated to the resulting composite's optical properties including refractive index, transmission, dispersion, and thermo-optic coefficient. Optical property evolution was related to the type and amount of the crystal phases formed, since through control of the local volume fraction of crystalline phase(s), the effective material properties of the composite can locally be varied. Through computational and experimental studies, tailored nanocomposites exhibiting gradient index properties have been realized. A Raman spectroscopic technique was developed as a means to spatially quantify the extent of conversion from glass to glass ceramic, and to confirm that the scale length of the local refractive index modification can be correlated to the extent of crystallization as validated by X-ray diffraction (XRD). Spatial control of the crystallization was examined by using a laser to locally modify the amount of nucleation and/or growth of crystallites in the glass. A novel technique converse to laser-induced crystallization was also developed and demonstrated that a glass ceramic could be locally re-vitrified back to a fully glassy state, through a laser-induced vitrification (LIV) method. Proof-of-concept demonstrator optics were developed using furnace and laser induced crystallization methods to validate experimental and computational approaches to modify the local volume fraction of nano-crystals. These demonstrators exhibited tailorable optical functionality as focusing optics and diffractive optics. This work paves the way for the design and fabrication of nanocomposite GRIN optics and their use in the mid-wave infrared.
Show less - Date Issued
- 2017
- Identifier
- CFE0006916, ucf:51684
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006916
- Title
- Distribution of Laser Induced Heating in Multi-Component Chalcogenide Glass and its Associated Effects.
- Creator
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Sisken, Laura, Richardson, Kathleen, Richardson, Martin, Shah, Lawrence, University of Central Florida
- Abstract / Description
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Chalcogenide glasses are well known to have good transparency into the infrared spectrum. These glasses though tend to have low thresholds as compared to oxide glasses for photo-induced changes and thermally-induced changes. Material modification such as photo-induced darkening, bleaching, refractive index change, densification or expansion, ablation of crystallization have been demonstrated, and are typically induced by a thermal furnace-based heat treatment, an optical source such as a...
Show moreChalcogenide glasses are well known to have good transparency into the infrared spectrum. These glasses though tend to have low thresholds as compared to oxide glasses for photo-induced changes and thermally-induced changes. Material modification such as photo-induced darkening, bleaching, refractive index change, densification or expansion, ablation of crystallization have been demonstrated, and are typically induced by a thermal furnace-based heat treatment, an optical source such as a laser, or a combination of photo-thermal interactions. Solely employing laser-based heating has an advantage over a furnace, since one has the potential to be able to spatially modify the materials properties with much greater precision by moving either the beam or the sample.The main properties of ChG glasses investigated in this study were the light-induced and thermally-induced modification of the glass through visible microscopy, white light interferometry, and Raman spectroscopy. Additionally computational models were developed in order to aid in determining what temperature rise should be occurring under the conditions used in experiments.It was seen that ablation, photo-expansion, crystallization, and melting could occur for some of the irradiation conditions that were used. The above bandgap energy simulations appeared to overestimate the maximum temperature that should have been reached in the sample, while the below bandgap energy simulations appeared to underestimate the maximum temperature that should have been reached in the sample. Ultimately, this work produces the ground work to be able to predict and control dose, and therefore heating, to induce localized crystallization and phase change.
Show less - Date Issued
- 2014
- Identifier
- CFE0005261, ucf:50606
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005261
- Title
- Holographic optical elements for visible light applications in photo-thermo-refractive glass.
- Creator
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Kompan, Fedor, Glebov, Leonid, Schulzgen, Axel, Richardson, Kathleen, Rahman, Talat, University of Central Florida
- Abstract / Description
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This dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation...
Show moreThis dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation. The first method involves modification of the original PTR glass rendering it photosensitive to radiation in the visible spectral region and, thus, making possible the recording of holograms in PTR glass with visible radiation. The mechanism of photoionization in this case is based on an excited state absorption upconversion process in the glass when doped with Tb3+. By contrast, the second approach uses the original Ce3+ doped PTR glass and introduces a new modified technique for hologram formation that allows for holographic recording with visible light. Complex HOEs including holographic lenses and holographic curved mirrors were fabricated in PTR glass with visible light using both techniques. The third part of the dissertation takes a step in a different direction and discusses the development of the methods for fabrication of phase masks in PTR glass. A method for relatively straightforward and inexpensive fabrication of phase masks with the aid of a Digital Micromirror Device is presented. This method enabled to produce phase masks containing complex greyscale phase distributions for generation of vortex (helical) beams. A phase mask can be holographically encoded into a transmission Bragg grating where a holographic phase mask (HPM) is formed. HPM has an advantage over a regular phase mask of being capable of multi-wavelength operation. All optical elements recorded in PTR glass preserve the advantages peculiar to VBGs recorded in PTR glass such as stability to heating and illumination with high-power laser beams.
Show less - Date Issued
- 2019
- Identifier
- CFE0007665, ucf:52480
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007665
- Title
- A Study of Crystallization Behavior in Phase Separated Chalcogenide Glasses.
- Creator
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Buff, Andrew, Richardson, Kathleen, Sohn, Yongho, Gaume, Romain, Fargin, Evelyne, University of Central Florida
- Abstract / Description
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Chalcogenide glasses (ChG) are known for their wide transmission ranges in the infrared and for their high refractive indices. However, applications for ChG are often limited by their poor thermal/mechanical properties. Precipitating a secondary crystalline phase in the glass matrix can improve these properties, but too much crystallization and/or large or multiple phase crystallites can lead to a loss in infrared (IR) transmission. Controlled crystallization can be used to tune the...
Show moreChalcogenide glasses (ChG) are known for their wide transmission ranges in the infrared and for their high refractive indices. However, applications for ChG are often limited by their poor thermal/mechanical properties. Precipitating a secondary crystalline phase in the glass matrix can improve these properties, but too much crystallization and/or large or multiple phase crystallites can lead to a loss in infrared (IR) transmission. Controlled crystallization can be used to tune the properties of these glasses. This work examines the crystallization behavior in phase separated chalcogenide glasses in the GeSe2-As2Se3-PbSe glass system.Specifically, the research presented in this thesis work has investigated the crystallization behavior in the 20GeSe2-60As2Se3-20PbSe (20 PbSe) and 15GeSe2-45As2Se3-40PbSe (40 PbSe) glasses for an IR optical system operating in the 3 to 5 (&)#181;m range. While both of these glasses were found to have droplet-matrix phase separation, the morphology differed from each other in two key ways. First, the droplets seen in the 20 PbSe glass (100-130 nm) are roughly twice as big as those in the 40 PbSe glass (35-45 nm). The droplet sizes seen in the base glass directly affect the short wavelength cutoff of the two glasses where the 20 PbSe glass (1.993 (&)#181;m) has a longer wavelength cutoff than the 40 PbSe (1.319 (&)#181;m). Secondly, the 20 PbSe glass has Pb-rich droplets and the 40 PbSe glass has a Pb-rich matrix, impacting where the initial stages of crystallization are initiated. Crystallization occurs in the Pb-rich phase and affects the glass-ceramic properties differently depending on whether the Pb-rich phase is the minority phase (20 PbSe) or the majority phase (40 PbSe). When the crystallization occurs in the majority phase, it greatly affects the hardness, density, and refractive index. When the crystallization occurs in the minority phase, the hardness and density change negligibly while the refractive index still shows significant change. While both glasses show an effective index change and 3-5 (&)#181;m transmission in their base form, only the 40 PbSe maintains the transmission window after the heat-treatments used in this study.The work reported in this thesis has shown how the crystallization process can be used to develop a gradient refractive index (GRIN) component in an IR optical system. While the composition and crystallization protocols are not optimized for further transfer of the technology to commercial products, the basis of this work shows the process of developing a glass-ceramic for the application.
Show less - Date Issued
- 2016
- Identifier
- CFE0006271, ucf:51032
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006271
- Title
- Processing of Advanced Infrared Materials.
- Creator
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Mcgill, Daniel, Richardson, Kathleen, Gaume, Romain, Christodoulides, Demetrios, Rivero Baleine, Clara, University of Central Florida
- Abstract / Description
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Infrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process,...
Show moreInfrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process, which uses a sacrificial pressure-transmitting medium, can be used to fully densify a 70TeO2-20WO3-10La2O3 (TWL) glass powder. The characteristics of the sintered TWL glass is compared to that of a parent glass produced through a conventional melt/quench process to ascertain the impact of process-specific property changes on the resulting material. Additionally, the design, construction and characterization of a custom-made transparent Bridgman crystal growth furnace is undertaken to enable growth of highly birefringent tellurium single crystal. The key obstacles that need to be overcome to scale up the size of the grown crystals are summarized with the end goal of producing commercial grade optical elements.
Show less - Date Issued
- 2019
- Identifier
- CFE0007894, ucf:52761
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007894
- Title
- Fabrication and Characterization of Nonlinear Optical Ceramics for Random Quasi-Phase-Matching.
- Creator
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Chen, Xuan, Gaume, Romain, Richardson, Kathleen, Challapalli, Suryanarayana, Sohn, Yongho, Kuebler, Stephen, University of Central Florida
- Abstract / Description
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A number of technologies rely on the conversion of short laser pulses from one spectral domain to another. Efficient frequency conversion is currently obtained in ordered nonlinear optical materials and requires a periodic spatial modulation of their nonlinear coefficient which results in a narrow bandwidth. One can trade off efficiency for more spectral bandwidth by relaxing the strict phase-matching conditions and achieve nonlinear interaction in carefully engineered disordered crystalline...
Show moreA number of technologies rely on the conversion of short laser pulses from one spectral domain to another. Efficient frequency conversion is currently obtained in ordered nonlinear optical materials and requires a periodic spatial modulation of their nonlinear coefficient which results in a narrow bandwidth. One can trade off efficiency for more spectral bandwidth by relaxing the strict phase-matching conditions and achieve nonlinear interaction in carefully engineered disordered crystalline aggregates, in a so-called random quasi-phase-matching (rQPM) process. In this dissertation, we examine appropriate fabrication pathways for (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) and ZnSe transparent ceramics for applications in the mid-IR. The main challenge associated with the fabrication of high transparency PMN-PT ceramics is to avoid the parasitic pyrochlore phase. The most effective method to suppress the formation of this undesired phase is to use magnesium niobate (MgNb2O6) as the starting material. We have found that, contrary to commercially available lead oxide powders, nanopowders synthesized in our lab by the combustion method help improve the densification of ceramics and their overall optical quality. The effects of dopants on the microstructure evolution and phase-purity control in PMN-PT ceramics are also investigated and show that La3+ helps control grain-growth and get a pure perovskite phase, thereby improving the samples transparency. With large second order susceptibility coefficients and wide transmission window from 0.45 to 21 (&)#181;m, polycrystalline zinc selenide is also an ideal candidate material for accessing the MWIR spectrum through rQPM nonlinear interaction. We have investigated non-stoichiometric heat-treatment conditions necessary to develop adequate microstructure for rQPM from commercial CVD-grown ZnSe ceramics. We have been able to demonstrate the world's first optical parametric oscillation (OPO) based on rQPM in ZnSe transparent ceramic, enabling broadband frequency combs spanning 3-7.5 (&)#181;m.
Show less - Date Issued
- 2018
- Identifier
- CFE0007748, ucf:52403
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007748
- Title
- Design of surface chemical reactivity and optical properties in glasses.
- Creator
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Lepicard, Antoine, Richardson, Kathleen, Seal, Sudipta, Gaume, Romain, Dussauze, Marc, Kuebler, Stephen, University of Central Florida
- Abstract / Description
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Thermal poling is a technique which involves the application of a strong DC electric field to a glass substrate heated below its glass transition temperature (Tg). Following the treatment, a static electric field is frozen inside the glass matrix, effectively breaking its centrosymmetry. Historically, this treatment has been used as a way to gain access to second order non-linear optical properties in glasses. However, recent efforts have shown that the treatment was responsible for...
Show moreThermal poling is a technique which involves the application of a strong DC electric field to a glass substrate heated below its glass transition temperature (Tg). Following the treatment, a static electric field is frozen inside the glass matrix, effectively breaking its centrosymmetry. Historically, this treatment has been used as a way to gain access to second order non-linear optical properties in glasses. However, recent efforts have shown that the treatment was responsible for structural changes as well as surface property modifications. Our study was focused on using this technique to tailor surface properties in oxide (borosilicate and niobium borophosphate) and chalcogenide glasses. A strong emphasis was put on trying to control all changes at the micrometric scale. After poling, property changes were assessed using a set of characterization tools: the Maker fringes technique (a Second Harmonic Generation ellipsometry technique), micro-Second Harmonic Generation ((&)#181;-SHG), vibrational spectroscopy and Secondary Ion Mass Spectroscopy (SIMS). Surface reactivity in borosilicate glasses was effectively changed while in niobium borophosphate and chalcogenide glasses, the optical properties were controlled linearly and nonlinearly. Finally, property changes were effectively controlled at the micrometric scale. This opens up new applications of thermal poling as a mean to design glass substrate for integrated photonics and lab-on-a-chip devices.
Show less - Date Issued
- 2016
- Identifier
- CFE0006471, ucf:51435
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006471
