A SOLUTION-BASED APPROACH TO THE FABRICATION OF NOVEL CHALCOGENIDE GLASS MATERIALS AND STRUCTURES

Chalcogenide glasses (ChGs) are well known for their large optical nonlinearities and high infrared transparency, and are candidate materials for next-generation thin film-based planar infrared (IR) optical applications. They are also known, however, to possess low thermal and mechanical stability as compared to oxide glasses. Traditional physical vapor deposition (PVD) methods used for the deposition of these materials as thin films often suffer from low deposition rates, deviation from stoichiometry, and cannot coat over complex surfaces. In order to retain the attractive optical properties of ChGs while enabling new fabrication routes and hybrid and composite material systems, we have developed a novel technique for the deposition of ChG-based materials through dissolution of bulk glasses in organic solvents. Utilization of the solution phase allows for new deposition routes such and spin-coating and direct fabrication of ChG optical structures in a single step using micro-stamping techniques. Solution-derived thin films in the As-Ge-Sb-S system are shown to possess similar molecular structure to the parent bulk glass, and vacuum heat treatment allows the preservation of IR transparency through the removal of residual organics. Additionally it is shown that glass-polymer hybrid materials may be created through the incorporation of compatible polymers in the co-solution phase. It was shown that it is possible to tune the optical and mechanical properties of these coatings by tailoring the glass chemistry/polymer content over a broad range, important for applications in IR optical coatings and as interfacial materials where thermal and mechanical property matching is critical. This technique was shown to be a promising route towards the preparation of novel IR optical materials and structures

Engineering of Glasses for Advanced Optical Fiber Applications

Advanced optical applications (such as fiber optics)demand the engineering of innovative materialswhich provide the requisite optical performance in aform with specific functionality necessary for thedesired application. We will report on recent effortsto engineer new non-oxide glasses with tailoredphoto-sensitive response, and multi-component oxideglasses optimized for use in next generation Ramanamplification applications. The ultimate performanceof such glasses relies on control of the formation andstability of defective and/or metastable structuralconfigurations and their impact on physical as well aslinear and nonlinear optical properties. Direct laserwriting has drawn considerable attention since thedevelopment of femtosecond lasers and therecognition that such systems possess the requisiteintensity to modify, reversibly or irreversibly thephysical properties of optical materials. Such“structuring” has emerged as one of several possibleroutes for the fabrication of waveguides and otherphoto-induced structures

Development of novel integrated bio/chemical sensor systems using chalcogenide glass materials

This paper reviews ongoing progress in the design and fabrication of new, on-chip, low loss planar molecular sensors. We report the details of device design, material selection and manufacturing processes used to realise high-index-contrast (HIC), compact micro-disk resonators. These structures have been fabricated in thermally evaporated As- and Ge-based chalcogenide glass films with PDMS (polydimethylsiloxane) micro-fluidic channels using standard UV lithography. Discussed are findings that demonstrate that our novel chalcogenide-based micro-fluidic device can be used as highly sensitive refractive index sensors

Studies on structural, electrical, and optical properties of Cu doped As-Se-Te chalcogenide glasses

Cu doped chalcogenide (ChG) glassy films in the As-Se-Te glass system have been prepared using thermal evaporation techniques. Single-source evaporation from bulk (1-x) As(0.40)Se(0.35)Te(0.25)+x Cu glasses with x=0.05, 0.075, 0.10, 0.125, and 0.15, as well as dual-source coevaporation from As-chalcogenide and Cu-chalcogenide binary glasses as source materials, has been explored. We have shown that it is not possible to deposit high concentration Cu doped ChG glassy films, from the Cu doped bulk samples using single-source evaporation. However, using the dual-source coevaporation technique, we have demonstrated that the films can be doped with high concentrations of Cu. Micro-Raman spectroscopy has been utilized to verify that Cu is introduced into the glass network without disrupting the basic As-chalcogen units. Optical measurements have shown that introduction of Cu decreases the band gap of As-Se-Te glasses. The electrical properties of the investigated films have been measured at different temperatures and it has been shown that Cu incorporation in the As-Se-Te glass system vastly improves electrical conductivity. Moreover, we have shown that the temperature dependence of electrical conductivity can be fitted assuming variable range hopping between states near the Fermi level

Latin America's 19th Century (Mostly Mexico): Formation of State, Subject and Self

This exhibit is a culmination of UT students’ collaborative effort to select, curate, and digitize original documents held in the Nettie Lee Benson Latin American Collection that reveal the region’s tumultuous and transformative 19th-century journeys towards the formation (s) of State, Subject and Self.Department of History & LLILAS Benson Latin American Studies and CollectionsLatin American Studie

Discovery and functional prioritization of Parkinson's disease candidate genes from large-scale whole exome sequencing.

BACKGROUND: Whole-exome sequencing (WES) has been successful in identifying genes that cause familial Parkinson's disease (PD). However, until now this approach has not been deployed to study large cohorts of unrelated participants. To discover rare PD susceptibility variants, we performed WES in 1148 unrelated cases and 503 control participants. Candidate genes were subsequently validated for functions relevant to PD based on parallel RNA-interference (RNAi) screens in human cell culture and Drosophila and C. elegans models. RESULTS: Assuming autosomal recessive inheritance, we identify 27 genes that have homozygous or compound heterozygous loss-of-function variants in PD cases. Definitive replication and confirmation of these findings were hindered by potential heterogeneity and by the rarity of the implicated alleles. We therefore looked for potential genetic interactions with established PD mechanisms. Following RNAi-mediated knockdown, 15 of the genes modulated mitochondrial dynamics in human neuronal cultures and four candidates enhanced α-synuclein-induced neurodegeneration in Drosophila. Based on complementary analyses in independent human datasets, five functionally validated genes-GPATCH2L, UHRF1BP1L, PTPRH, ARSB, and VPS13C-also showed evidence consistent with genetic replication. CONCLUSIONS: By integrating human genetic and functional evidence, we identify several PD susceptibility gene candidates for further investigation. Our approach highlights a powerful experimental strategy with broad applicability for future studies of disorders with complex genetic etiologies

Progress On The Fabrication Of On-Chip, Integrated Chalcogenide Glass (Chg)-Based Sensors

This paper reviews ongoing progress on the material design, fabrication and performance of high-Q chalcogenide glass resonators utilizing cavity-enhancement for high sensitivity MIR chemical sensing. These structures have been fabricated in thermally evaporated As- and Ge-based chalcogenide glass films with PDMS (polydimethylsiloxane) micro-fluidic channels using standard UV lithography. Discussed are findings that demonstrate that our novel chalcogenide-based micro-fluidic device can be used as highly sensitive refractive index sensors. © 2009 Optical Society of America

Progress On The Photoresponse Of Chalcogenide Glasses And Films To Near-Infrared Femtosecond Laser Irradiation: A Review

This paper reviews ongoing progress in exploring the mechanistic origins of photoinduced structural modification in chakogenide glasses (ChGs). These findings, reported by groups at the University of Central Florida, Clemson University, and throughout other research programs within the United States and abroad, have examined the relationship between the network modification and other photoresponse of IR glasses upon exposure to near-infrared (NIR) femtosecond laser exposure. Contained is a review on the principles of femtosecond laser writing in glass, the photoinduced phenomena, and a summary of the main models predicting photoinduced material response. We compare the photoresponse of As- and Ge-based films, taken as example, following NIR femtosecond laser irradiation that results in near-surface photoexpansion and an increase or decrease of the refractive index, respectively. This difference in photoresponse has been related to the layered network of the As-based glass that leads to the breaking and formation of bonds during laser exposure as compared to the 3-D network of Ge-based glass that leads only to a modification of the bond arrangements. Last, an explanation of the need to control the photoresponse of ChGs by aging, changing the glass thermal history, adding modifiers, or replacing the anions forming the network is discussed. © 2008 IEEE

Effect Of Replacement Of As By Ge And Sb On The Photo-Response Under Near Infrared Femtosecond Laser Irradiation In As-Based Sulfide Glasses

Bulk glasses having the compositions As42S58, As36Sb6S58, and As36Ge6S58 have been irradiated at 800 nm using a femtosecond-pulsed laser to determine the relationship between composition and photo-response. Localized variation in the glass volume (photo-expansion) has been determined through interferometric measurements of surface exposures, whereas induced refractive index change (photo-darkening) was determined from the diffraction efficiency of subsurface direct-written phase gratings. To understand the compositional dependence of the photo-response, the linear and nonlinear optical properties and structure of the unexposed glasses have been compared. The ablation threshold is shown to be controlled by variation of the nonlinear absorption, related to shifts of the absorption band gap with exchange of As by Ge or Sb. Changes in the unexposed network structure show that partial replacement of As by Ge or Sb induces an increased number of As-As bonding defects in the glass, particularly in the form of As4S4 molecular units which become polymerized into the network, impacting the photo-modification process. The Ge was found to induce an increase in the ablation threshold, and enhance both photo-darkening and photo-expansion effects, whereas Sb was shown to decrease ablation threshold and inhibit photo-darkening while enhancing photo-expansion. © 2011 The American Ceramic Society and Wiley Periodicals, Inc

Chalcogenide Glasses And Their Photosensitivity: Engineered Materials For Device Applications

Chalcogenide glasses are widely used in device applications which capitalize on their unique linear and nonlinear optical properties, and infrared transparency. The role of the glass\u27 photosensitivity in device fabrication and eventual use, is discussed. © 2010 Optical Society of America