Substrate effects on surface morphologies and magnetic properties of nanostructured FePt thin films.

The substrate effects on surface morphologies, crystal structures, and magnetic properties of the sputter-deposited FePt thin films on Corning 1737, normal glass, and Si wafer substrates, respectively, were investigated. High in-plane coercivities of 10 kOe were obtained for the air-annealed films on Corning 1737 and Si wafer, where both films similarly have granular-like morphologies. Besides, increasing grain size and surface roughness of all the FePt films with the post-anneal temperature were observed. Moreover, partially separated grains were seen in the film on Si wafer, where the formation of Fe silicides during post-anneal is suspected, in which has enhanced the magnetic ordering.

Energy-Transfer Dye Laser in SolGel Silica.

Coumarin 460 transfers radiative energy to disodium fluorescein when solgel silica is doped with the dyes, producing disodium fluorescein lasing in superradiant mode at a 3.3% peak efficiency under low-energy transverse pumping by a 1.5-mJ N(2) laser, with disodium fluorescein being present at a concentration below its lasing threshold value.

Hot-press molded poly(methyl methacrylate) matrix for solid-state dye lasers.

A hot-press molding method was used to fabricate dye-doped poly(methyl methacrylate) (PMMA) slabs. Three rhodamine dyes, Rh640 (ClO(4)), Rh6G(ClO(4)), and Rh6G (Cl), were impregnated into the PMMA matrix first by dissolving the dye and granular PMMA in a solvent mixture of chloroform and methanol and then heating the mixture in vacuo at 175 degrees C to obtain a spongy preform. The powdered preform was molded into slabs at 175 degrees C and at <1 mbar, to eliminate the formation of bubbles in the slabs. We annealed the slabs for several hours to improve its optical homogeneity and hence its lasing efficiency. When pumped by a 1.5-mJ nitrogen laser, we obtained peak lasing efficiencies of 8% and 7.8%, respectively, for Rh6G (ClO(4)) and Rh640 (ClO(4)) in PMMA matrices. The lasing efficiency of Rh6G (ClO(4))-doped PMMA suffered a reduction rate of 0.012%/shot compared with 0.15%/shot for Rh640 (ClO(4))-doped PMMA. In contrast, Rh6G (Cl) in a hot-press molded PMMA slab suffered thermal bleaching that resulted in a low lasing efficiency of <1%; this can be explained by its absorption and fluorescence characteristics.