Development of ultra-low loss glass hollow waveguides transmitting infrared light with several wavelengths simultaneously

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In this research project, we tried to realize infrared glass hollow waveguides with ultra-low losses which can transmit the laser light such as Er : YAG,CO,and CO_2 laser light with several wavelengths simultaneously or independently for medical applications. The main results obtained during the research period are as follows :1.Fabrication of ZnS-coated Ag hollow waveguides by outer deposition technique In order to fabricate dielectric-coated waveguides with a completely circular cross section along the propagation axis, we employed a new mandrel for the outer deposition method. By using a polyimide-coated glass pipe as a mandrel, ZuS-coated Ag hollow waveguides have been fabricated and the maximum energy of 1.6 J of Er : YAG laser light has been successfully transmitted without siginificant degradation of waveguides. This shows that ZuS-coated Ag waveguide can be used for high-energy transmission media and for dental application.2.Fabrication of polymer-coated Ag hollow glass waveguides by liquid phase method After depositing a this silver layr inside a fused silica tube with an ultra-smooth inner surface by using a silver mirror reaction method, polyimide or fluorocarbon polymer has been deposited by using a liquid flow coating method or dipping method. Thin hollow waveguides with inner diameters of 700 mum and 540 mum have been fabricated for transmitting Er : YAG laser light with small losses.3.Studies on mode structures of hollow waveguides Based on the exact characteristic equation, mode structures and mode transitions of circular hollow waveguides with and without inner dielectric layr have been fully clarified. Properties of lower order modes in a uniformly bent circular hollow waveguide are also made clear.