We demonstrate direct three-dimensional (3-D) microfabrication inside a volume of silica glass. The whole fabrication process was carried out in two steps:(i) writing of the preprogrammed 3-D pattern inside silica glass by focused femtosecond (fs) laser pulses and (ii) etching of the written structure in a 5% aqueous solution of HF acid. This technique allows fabrication of 3-D channels as small as 10mum in diameter inside the volume with any angle of interconnection and a high aspect ratio (10mum -diameter channels in a 100mum -thick silica slab).

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The direct electrodeposition of Ag2O films was discovered for the first time using a new strategy termed “oxides synthesis induced by electrogenerated acid”. The Ag2O film with a bandgap energy of 1.46 eV is suited to a light absorption layer in photovoltaic cells.

We used voxels of an intensely modified refractive index generated by multiphoton absorption at the focus of femtosecond laser pulses in Ge-doped silica as photonic atoms to build photonic lattices. The voxels were spatially organized in the same way as atoms arrayed in actual crystals, and a Bragg-like diffraction from the photonic atoms was evidenced by a photonic bandgap (PBG) effect. Postfabrication annealing was found to be essential for reducing random scattering and therefore enhancing PBG. This technique has an intrinsic capability of individually addressing single atoms. Therefore the introduction of defect structures was much facilitated, making the technique quite appealing for photonic research and applications.

To achieve high bit densities (>10 GB/cm3) in optical memory, we accomplished a three-dimensional optical data storage system using vitreous silica as the recording material. We succeeded in high-density optical recording by focusing pulsed laser beams of 532 nm (full width at half maximum [FWHM] 30 ps) and 400 nm (150 fs). A recording density of 72.9 GB/cm3 was achieved, which corresponded to that of 100 compact disks, on a glass plate of (2×2) cm2 and 2.2 mm thickness. We found that the optical damage of silica occurs within 400 ps after irradiation by a single pulse for 30 ps at 532 nm. Three photoluminescence bands were found in the photomodified silica at 283 nm, 468 nm and 558 nm. All the three bands showed similar photoluminescence excitation spectra, i.e. a peak related to oxygen vacancy absorption at 250 nm.

Efficient TiO2 powder and film photocatalysts with the rutile structure were prepared. Their photocatalytic properties were assessed by measuring the photooxidative decomposition of gaseous acetaldehyde. The rutile powder showed much higher photoactivity than Degussa P-25 powder, both in degradation rate and in quantum efficiency. Moreover, the rutile film prepared by sintering the rutile sol at 450 °C also showed rather high photocatalytic activity.

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