Quasi-single mode laser output from a terrace structure added on a Nd(3+)-doped tellurite-glass microsphere prepared using localized laser heating.

A Nd(3+)-doped tellurite-glass terrace microsphere was fabricated, and its laser characteristics using free-space pumping were investigated. A localized laser heating technique was used for preparing the 29-µm-diameter microsphere. The uncoated sphere exhibited many laser lines with 1.3-mW threshold. Fewer laser lines were observed after terrace formation. The terrace microsphere's lasing threshold was 0.6-2.4 mW depending on the pumping position in the terrace. These results indicate that the terrace structure can modify the modes of a microsphere laser and decrease the laser threshold due to an increase in the coupling efficiency between the cavity and free-space beam.

Formation of molecular doping patterns in organic-inorganic hybrid films by a capillary electrophoresis doping technique.

A new technique is proposed for the fabrication of fine patterns of molecular doping in organic-inorganic hybrid materials by the combination of capillary electrophoresis doping (CED) and photolithography. The UV-induced polymerization of [Formula: see text] bonds in organic groups yields a fine contrast of structures with the desired pattern in organic-inorganic hybrid films, and CED treatment introduces functional molecules only into unirradiated regions to form the doping patterns of molecules inside the films. The fine patterning of rhodamine-6G doping with from 2 to 4 µm resolution is demonstrated in hybrid films of 10 µm thickness.

Pyramidal assemblies of colloidal particles by micromolding underneath top-gathering pillar arrays.

Assemblies of colloidal particles are known to have special photonic and optical properties. Periodic pyramidal assemblies of SiO2 particles with diameters of 0.5 and 1 microm were fabricated using top-gathering pillar arrays as a new template. These top-gathering pillar arrays consisted of four pillars gathered at the top, and were fabricated by photolithography of an organic-inorganic hybrid material. The top-gathering units were obtained by controlling both the capillary and restoring forces. When a colloidal water suspension was spread on the template and the water was allowed to evaporate, the SiO2 particles were molded under the top-gathering pillars according to particle size, resulting in pyramidal assembly arrays of the particles. From in situ observation during the evaporation of water, it was found that the particles were molded underneath the top-gathering pillars by flux generated by the evaporation and by the capillary force among the particles.

Sol-gel-derived spheres for spherical microcavity.

Encapsulation of light to small spheres ensures the highest quality factor ( Q factor) to enhance the interaction between light and materials. In this Account, we describe the fabrication of micrometer-sized spherical particles of organic-inorganic hybrid materials to study the potential ability as a spherical cavity laser. The spherical particles prepared by the vibrating orifice technique included those of nondoped and doped with organic dyes and rare-earth-metal ions, and some of them were cladded with low-index-coating hybrid materials. Coating of the spheres was carried out by aiming at practical applications: high refractive index spheres from n D = 1.72 to 2.5 prepared by the technique and glass spheres of n D = 1.93. They were pumped by second harmonic pulses of a Q-switched Nd:YAG laser (532 nm wavelength) and CW Ar (+) laser (514 nm wavelength) to investigate as spherical cavity microlasers. The emission from spheres originated from the photoluminescence of dopants and Raman scattering of matrix materials. Lasing or resonant light emission from these spheres were performed by the direct-laser-light-pumping and the light-coupling techniques using an optical waveguide coupler.