Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 microm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO(2) precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Long lengths (250 meters) of a flexible 150 microm diameter glass-clad optical fiber containing a 15 microm diameter crystalline and phase-pure germanium core was fabricated using conventional optical fiber draw techniques. X-ray diffraction and spontaneous Raman scattering measurements showed the core to be very highly crystalline germanium with no observed secondary phases. Elemental analysis confirmed a very well-defined core-clad interface with a step-profile in composition and nominally 4 weight-percent oxygen having diffused into the germanium core from the glass cladding. For this proof-of-concept fiber, polycrystalline n-type germanium of unknown dopant concentration was used. The measured infrared transparency of the starting material was poor and, as a likely outcome, the attenuation of the resultant fiber was too high to be measured. However, the larger Raman cross-section, infrared and terahertz transparency of germanium over silicon should make these fibers of significant value for fiber-based mid- to long-wave infrared and terahertz waveguides and Raman-shifted infrared light sources once high-purity, high-resistivity germanium is employed.

The preparation and photophysical properties of two heavier main group element analogues of boron-dipyrromethene (BODIPY) chromophores are described. Specifically, we have prepared dipyrrin complexes of dichlorogallate (GADIPY) or phenylphosphenium (PHODIPY) units. Whereas cationic PHODIPY is labile, decomposing to a phosphine over time, GADIPY is readily prepared in good yield as a crystalline solid having moderate air- and water-stability. Crystallographically characterized GADIPY displays intense green photoluminescence (λem = 505 nm, Φem = 0.91 in toluene). These inaugural heavier main group element analogues of BODIPY offer a glimpse into the potential for elaboration to a panoply of chromophores with diverse photophysical properties.

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Nature provides a rich panoply of structural motifs comprised of composites whose mechanical properties exceed those of their individual components. The human endeavor to likewise craft value‐added structural materials from underappreciated, sustainably sourced feedstocks remains a formidable challenge. Herein, efforts are made to achieve durable composites by synergistic combination of sulfur and cellulose. Composites are achieved in which bulk sulfur is reinforced by a network of 1–20% by mass cellulose cross‐linked with polysulfide chains. Composites described herein are remeltable and have flexural strength exceeding that of Portland cement. A thorough analysis of these materials has been undertaken through nuclear magnetic resonance, infrared spectroscopy, Raman spectroscopy, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. These analyses of both as‐prepared composites and fractionated materials unequivocally validate the formulation of these composites and the separability of the bulk sulfur from the reinforcing polysulfide‐cross‐linked cellulose network. The thermomechanical properties of these recyclable composites portend their tantalizing potential to supplant inherently unsustainable structural elements in numerous commercial applications. Further applications to improve the environmental resistance and flexural strength of Portland cement by treatment with the sulfur–cellulose composites are also discussed.