Reducing the mid-infrared attenuation loss due to absorption of hydroxyl (OH) groups and scattering of metallic Pb species for lead-germanate glass is essential to pave the way for their applications as low-loss mid-infrared fiber optics. In the first part of this study, we report the understanding of the factors that determine dehydration efficiency and metallic Pb formation during the lead-germanate glassmelting process. Combining a dry O 2-rich atmosphere containing ultra-dry N 2 together with the use of chloride dehydration agent and nitrate oxidation agent compound was found to enable efficient dehydration effect and absence of metallic Pb scattering sources in the dehydrated glasses. This glassmelting procedure overcomes previous limitations on the preparation of similar kinds of heavy-metal oxide glasses, where only pure O 2 atmosphere was used and/or use of fluoride dehydration agent deteriorated the glass thermal stability. This work provides guidance for developing other low-loss mid-infrared glasses/fibers containing multivalent heavy-metal ions such as Pb, Bi, Te, Sb, etc K E Y W O R D S dehydration, lead-germanate glass, metallic Pb, mid-infrared fiber optics, scattering loss Note: The sample ID (ie V#-W#-X#-Y#-Z) include glass composition (type and content of chloride dehydration agent), melting conditions and melting atmospheres, and their detailed definitions are as follows: V: S = no NaCl, no PbCl 2 ; P = with PbCl 2 ; N = with NaCl; with #: molar concentration (mol%) of the dehydration agent, PbCl 2 or NaCl. W = Batch-in-temperature: (A) 650°C; (B) 1250°C; (C) 650°C without chlorides, then added PbCl 2 /NaCl at 1250°C; with # = melting time at 1250°C: (1) 40 min; (2) 80 min; (3) 120 min. X = dry gas type: (O) O 2 ; (ON) O 2 + N 2 ; (N) N 2 ; (A) Ar; with # = dry gas flow rate: (2) 1.6 L/min, (4) 4 L/min, (10) 10 L/min, (16) 16 L/min. Y = N * : use of ultra-dry N 2 ; with # = (1) 35 min, (2) 70 min, (3) 105 min GBP time. Z = O * : release of super-dry O 2 in the glass melt via use of NaNO 3 instead of Na 2 CO 3 in glass batch.

Manufacturing optical fibers with a microstructured cross-section relies on the production of a fiber preform in a multiple-stage procedure, and drawing of the preform to fiber. These processes encompass the use of several dedicated and sophisticated equipment, including a fiber drawing tower. Here we demonstrate the use of a commercial table-top low-cost filament extruder to produce optical fibers with complex microstructure in a single step-from the pellets of the optical material directly to the final fiber. The process does not include the use of an optical fiber drawing tower and is time, electrical power, and floor space efficient. Different fiber geometries (hexagonal-lattice solid core, suspended core and hollow core) were successfully fabricated and their geometries evaluated. Air guidance in a wavelength range where the fiber material is opaque was shown in the hollow core fiber.

Fiber optics based on soft glasses have shown their great advantages over silica and silicate-based glasses for generation and transmission of mid-infrared (mid-IR) light, especially in the spectral range of 2.5-5.0 µm, 1 enabling their applications ranging from materials processing, laser medical surgery 2-4 and biomedical diagnostics, 5 to defense, for example, for directional infrared countermeasures, light detection, and ranging (LIDAR) for atmospheric and chemical sensing and monitoring. 6 The rapid progress in emerging novel mid-IR fiber lasers and mid-IR supercontinuum (SC) light sources, eg, the room

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