1,720,975 research outputs found
The fabrication and characterization of infra-red optical fibre, ultra-thin fibre and large diameter chalcogenide glass
No full textThe development of speciality infra-red glasses has produced a number of alternative compositions which have become well established for many applications, both for industrial use and academic research. Among them, gallium lanthanum sulphide glass (GLS) is a particularly suitable competitor. This glass possesses a tunable and uniquely located transmission window among chalcogenides, ranging from 500 nm to 15 µm in bulk glass. In addition to its mechanical strength and high transition temperatures, the combination of visible and infra-red transmission makes this glass an exceptional candidate for a variety of applications, such as thermal imaging and chemical sensing. The thermal properties of GLS make shaping it to conform to a particular application delicate and challenging work. In particular, its crystallization temperature lies near its softening temperature, making any process involving softened or molten glass highly time constrained. In this work, previously established techniques have been revisited and improved upon, and a set of novel methods have been developed and employed, in order to enable gallium lanthanum sulphide to fulfil new applications. In particular, oxygen-free GLS fibre has been fabricated, significantly increasing the breadth of its transmission window in fibre form. Optimization through design of experiments (DOE) has allowed to fabricate crucible-drawn GLS fibre for the first time. Further refinements of GLS processing developed herein include the fabrication of ultra-thin fibre (less than 10 µm in diameter), casting and cutting into fibre drawing preforms and the fabrication of large diameter (>90mm) windows. Its glass formation range has also been expanded by increasing the quenching rate, new characterization methods have been implemented, and in-house polishing techniques for cylindrical sections of glass have been developed. Overall, this work has advanced the use of chalcogenides based on GLS for a number of applications which include infra-red optical fibre fabrication, multi spectral windows, chemical sensing and imaging fibre bundles
Laser-aided manufacturing of ultra-high-aspect ratio optical fibers
No full textThe current landscape of optical fiber technology is dominated by fibers with a circular cross-section with axial symmetry and a centrally positioned waveguiding core. This typical layout is dictated by traditional manufacturing routes that often utilize furnaces, gas burners, and glass lathes. Contrastingly, in our work, we utilize laser-based glass additive-manufacturing to melt, weld, and reshape glass powders and prefabricates to create fiber preforms. Additionally, through a combination of mid-IR CO2 laser melting and oxide nano-powder jets aimed into laser-induced hot-zone, high quality glass features can be 3D-printed onto the fiber preform. In our work we focus on high-aspect ratio preforms that can be then drawn in traditional draw towers into over 100 m long ultra-thin fibers. Here, flat fibers as thin as 35 µm and aspect-ratio of up to 27:1 with sub-µm surface flatness were made. Furthermore, by utilizing this novel print-stack-draw approach, microstructure and chemically doped features for e.g., waveguiding and optical gain can be spatially tailored, both laterally and along the direction of draw. Compatibility of these fibers with standard counterparts such as commercial single-mode-fibers was demonstrated through e.g., laser-based splicing. The new manufacturing approach utilized in this work unlocks highly flexible, novel photonic designs with large disruptive potential for areas including lab-in-fiber, physical sensors and fiber lasers.</p
Chalcogenide optical fibres based on gallium lanthanum sulphide-Se for passive and active applications
No full textChalcogenide optical fibres contain mixtures of chalcogen elements (i.e. S, Se and Te) bonded covalently to other metallic elements that facilitate a stable glass formation. Our work in particular focuses on chalcogenide glasses containing a high proportion of lanthanum, that is gallium lanthanum sulphide glasses (GLS). These glasses due to their nature are characterized by a range of desirable properties such as chemical durability, host for rare-earth (RE) ions, low thermal expansion, high laser damage threshold, density and refractive index and a good transparency in the infrared (IR) region. Characteristics that are beneficial for active and passive applications such as sensors or high-energy IR laser power delivery, as examples. To increase the IR transmission window of GLS glasses a new family of chalcogenides have been developed, incremental additions of Se to the GLS glasses have proved their value to improve the transmission spectrum from visible to Long Wavelength Infrared (LWIR) range up to 15μm, depending on the composition. The strong thermal and mechanical characteristics of GLS-Se glasses compared to GLS have also shown that they can suit the production of optical elements, such as optical fibres that require certain thermal and mechanical stability for fibre drawing to avoid crystallization and breakages. [1-5] Theoretical minimum loss predictions in GLS based optical fibres have shown up to 0.5 dB km-1 at 3.5 μm, used in thermal imaging, unfortunately we are still far from that value but big efforts are being made to improve the production of optical fibres as shown in Fig. 1 by obtaining novel processes and more pure raw materials. [6] Chalcogenide RE doped glasses have demonstrated laser action, showing that they are suitable for active applications such as optical amplifiers and lasers [7]. The aim of this research is to join the well-known properties of chalcogenides glasses for the IR region with the development of a novel process to obtain functional passive and active optical fibres and prove the reliability as a host for RE ions, future work will include laser demonstration
Ultra-thin (<20µm) zero-waste lithium ion conducting glass fibre fabrication using crucible drawing for solid-state battery applications
No full textCrucible drawing was employed to demonstrate the feasibility of zero-waste fabrication of Lithium Zirconia Silicate (LZS) glass fibres with diameters between 20 to 9 µm (±1 µm), used as an electrolyte in solid-state batteries
GLS-Se optical fibre from extruded glass structured preforms and rods for the IR region
No full textDepending on composition, chalcogenide glasses have been proven as a reliable medium to transmit light in the range from the visible to the long-wave infrared (LWIR), specialty glasses based on gallium lanthanum sulfide (GLS) with a selenium (Se) addition. This family of glasses offers a broad transparency window depending on the composition. Their optical, mechanical, and thermal properties have been exploited in their bulk form. In this paper, we demonstrate the fabrication of optical fibres from extruded structured (core-clad) preforms and rods, with an emphasis on maintaining the intrinsic characteristics of the glass and exploiting the optical fibre geometry for light delivery
Compact high-resolution FBG strain interrogator based on laser-written 3D scattering structure in flat optical fiber
No full textWe demonstrate a fiber Bragg grating (FBG) strain interrogator based on a scattering medium to generate stable and deterministic speckle patterns, calibrated with applied strain, which are highly dependent on the FBG back-reflection spectral components. The strong wavelength-dependency of speckle patterns was previously used for high resolution wavemeters where scattering effectively folds the optical path, but instability makes practical realization of such devices difficult. Here, a new approach is demonstrated by utilizing femtosecond laser-written scatterers inside flat optical fiber, to enhance mechanical stability. By inscribing 15 planes of pseudo-randomized nanovoids (714 × 500 voids per plane) as a 3D array in a 1 × 0.7 × 0.16 mm volume, the intrinsic stability and compactness of the device was improved. Operating as a wavemeter, it remained stable for at least 60 h with 45 pm resolution over the wavelength range of 1040–1056 nm. As a reflection mode FBG interrogator, after calibrating speckle patterns by applying tensile strain to the FBG, the device is capable of detecting microstrain changes in the range of 0–200 μϵ with a standard error of 4 μϵ , limited by the translation stage step size. All these characteristics make it an interesting technology for filling the niche of low-cost, high-resolution wavemeters and interrogators which offer the best available trade-off between resolution, compactness, price and stability.</p
Manufacturing of GLS-Se glass rods and structured preforms by extrusion for optical fiber drawing for the IR region
No full textChalcogenide glasses are amorphous solid materials formed from chalcogen elements bonding with metals to form typically in binary or tertiary compounds. One family of chalcogenide glasses, based on gallium and lanthanum sulphides, possesses properties important for the infrared (IR) window transmissions and IR applications; these include thermal stability, high solubility of rare earth ions, low phonon energy and high laser damage threshold. Efforts have been made to produce new chalcogenide glasses that can extend the IR transmission window further into the IR. Work has led to the successful melting of a selenium-modified gallium lanthanum sulphide (GLS-Se) glass that can transmit up to 15 μm, however these glasses have, to date, only been demonstrated in bulk glass form. We aim to develop processes for the fabrication of chalcogenide optical fiber to exploit the properties of chalcogenide glasses. Several potential applications include sensing for the civil, medical, and military areas, as these materials offer transmission over much of the molecular fingerprint region (2 to 25 μm). The aim of our work is to understand and control the thermal properties and stability of GLS-Se glasses without compromising their optical properties, in order to produce transparent glass rods and demonstrate the feasibility in fabrication for structured optical preforms by extrusion, as the first step to achieve optical fiber from GLS-Se glass.</p
Fabrication of structured GLS-Se glass preforms by extrusion for fibre drawing
No full textChalcogenide glasses due to their low phonon energy and high ion solubility, make them an ideal candidate for active and passive fibres for infrared applications. Co-extrusion process for structured preform fabrication is explored
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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