We have developed a compact solar-pumped laser (µSPL) employing an off-axis parabolic mirror with an aperture of 76.2 mm diameter and an yttrium aluminum garnet (YAG) ceramic rod of φ1 mm × 10 mm doped with 1% Nd and 0.1% Cr as a laser medium. The laser oscillation wavelength of 1.06 µm, just below the optical absorption edge of Si cells, is suitable for photoelectric conversion with minimal thermal loss. The concept of laser beam power feeding to an electric vehicle equipped with a photovoltaic panel on the roof was proposed by Ueda in 2010, in which the electricity generated by solar panels over the road is utilized to drive a semiconductor laser located on each traffic signal along the road. By substituting this solar-electricity-driven semiconductor laser with a solar-pumped laser, the energy loss of over 50% in converting the solar electricity to a laser beam can be eliminated. The overall feasibility of this system in an urban area such as Tokyo was investigated.

Interface reactions in $\mathrm{W}{\mathrm{O}}_3∕\text{metal}$ thin-film bilayered structures were examined for applications to optical recording materials. Decreases in the reflectance of the structures caused by temperature elevation were observed and were attributed to (i) coloration of the $\mathrm{W}{\mathrm{O}}_3$ layers, and (ii) decreases in the reflectance of the metal layers resulting from redox reactions between the $\mathrm{W}{\mathrm{O}}_3$ and the metals. The reflectance spectra of the structures before temperature elevation showed moderate wavelength dependence over a wide range, from the visible to the near infrared. Decreases in the reflectance due to temperature elevation occurred over a wide wavelength range. Examination of the $\mathrm{W}{\mathrm{O}}_3∕\mathrm{Al}–\mathrm{Ti}$ bilayered structures as potential optical disk memories revealed that the redox reactions occurred within submicrosecond time periods during irradiation with the recording laser. The results indicate that these structures possess promising properties for applications to optical recording materials that can be used over a wide wavelength range.