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.

In this article, we report on the fabrication of 0.3-lm average grain-sized transparent yttria ceramics using a modified twostep sintering approach. This process yielded full densification of the yttria ceramics with a drastically reduced grain growth. These transparent yttria ceramics exhibited a transparency equivalent to that of single crystals in the near-infrared spectral region. The microhardness and fracture toughness of the 0.3-lm average grain-sized transparent yttria ceramics fabricated by a modified two-step sintering were found to exceed those of B300lm average grain-sized transparent yttria ceramics fabricated by conventional sintering by 25 and 70%, respectively.

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Titanium Alloys Research SummaryAlthough suspension spring materials traditionally have been made of steel, metastable beta-titanium alloys are being considered as possible alternative materials. Among their benefi ts, metastable beta-titanium alloys offer high specifi c strength, low elastic moduli, high corrosion resistance, and manufacturability. However, the cost-effective substitution of metastable beta-titanium for steel will require that titanium suspension springs be manufactured using existing steel suspension fabrication equipment and techniques. These techniques involve coil winding followed by short-time aging and shot peening. This paper describes an evaluation of the effects of the steel suspension fabrication techniques on a prominent metastable beta-titanium alloy.

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