Underwater optical wireless communication has been merely a theory for a long time because light sources are too weak to use them as emitters for communications. In the past decade, however, underwater optical wireless communications have used laser diodes or light emitting diodes as emitters with visible light in high brightness with low power consumption. Recently, they have become practical. As described in this paper, recent trends of underwater optical wireless communication study, practical modems and prospective uses of underwater optical wireless communication are presented first. Next, optical characteristics of the seawater in various conditions are explained based on the experimental data measured using the profiler for underwater optics produced especially for this study. Then the prototype underwater optical wireless communication modem developed by our team is introduced. It was tested in several sea areas, which confirmed bi-directional communication in the 120m range at 20Mbps and a remote desktop connection between under water vehicles at 100m range. In addition, one modem was set in air; other was set in water. The modems mutually communicated directly through the sea surface.

We developed a new method to improve the efficiency of the PDP (plasma display panel) by the use of a novel protecting film or Gd doped MgO film. In the cells of the PDP, the VUV (vacuum ultraviolet ray) is generated by Xe discharge. The VUV is simply absorbed by the protecting film or MgO film. Therefore, normally the absorbed VUV doesn't contribute to the light conversion efficiency. However, the novel protecting film or MgO:Gd film radiates the ultraviolet ray of which 317 nm wavelength, by the irradiation of the shorter wavelength VUV, and it excites the blue phosphor. Consequently the efficiency of blue emission is improved.