Recent advances in nanoscience have demonstrated that fundamentally new physical phenomena may be found when the size of samples shrinks. In the area of superconductivity, the reduction of sample size has led to the observation of the paramagnetic Meissner effect in micronsize superconductors (1), the quantization of the Bose condensate in submicron samples (2), and ultimately the suppression of superconductivity in nanometer-scale superconductors (3,4). In this regime, it has also been recognized that the sample topology has particularly strong effects on superconductivity, as reflected in the characteristic features of the phase diagrams for singly-and doubly-connected samples (5,6).A unique feature of doubly-connected superconductors (independent of the sample size) is

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The kinetic energy of superconducting electrons in an ultrathin, doubly connected superconducting cylinder, determined by the applied flux, increases as the cylinder diameter decreases, leading to a destructive regime around half-flux quanta and a superconductor to normal metal quantum phase transition (QPT). Regular steplike features in resistance versus temperature curves taken at fixed flux values were observed near the QPT in ultrathin Al cylinders. It is proposed that these features are most likely resulting from a phase separation near the QPT in which normal regions nucleate in a homogeneous superconducting cylinder.

In this review, we present our recent research progress at the Naval Research Laboratory in the development of highly transparent and rugged ceramic window materials such as MgAl2O4 spinel and β-SiC; high-power solid-state laser gain materials based on sesquioxide such as Yb(3+):Y2O3, Yb(3+):Lu2O3, and Ho(3+):Lu2O3; and composite ceramics in the application for high-energy lasers. Various powder synthesis/purification methods and powder post-process techniques necessary to create high-purity powders are described. Ceramic fabrication processes and chemical, morphological, and optical properties of the ceramics developed at the Naval Research Laboratory (NRL) are highlighted. We also report high-efficiency lasing from a hot-pressed rare-earth sesquioxide single layer and composite ceramics made from coprecipitated powder.