Generation of graded index profile in the polymer by dopant-extraction with the aid of compressed carbon dioxide

Abstract

The researches related to the generation of graded index profile(GI-profile) in polymer have been developed from the methods fabricating graded index plastic optical fiber(GI-POF). The GI-POFs fabricated from conventional polymer, such as poly(methyl methacrylate) shows relatively high material dispersion caused by C-H vibration absoption compared with perfluorinated polymer. However, perfluorinated polymer can not apply existing methods for fabrication of GI-profile because the polymer is not polymerized by simple polymerization technique. As a result, dopant-extraction process was proposed as a method fabricating GI-profile in perfluorinated polymer in this thesis. First, a poly(trifluoroethyl methacrylate)(PTFEMA) based polymer rod was polymerized with bromobenzene as dopant whose refractive index was higher than that of PTFEMA itself. This rod would show uniform refractive index throughout the whole rod. Then, the polymerized rod was exposed to the high pressure carbon dioxide. According as time passed, carbon dioxide diffused into the rod from the surface. After some time at arbitrary pressure and temperature, carbon dioxide was released. While carbon dioxide was treated and released, dopant was out-diffused by the difference of concentration and performed parabolic GI-profile because dopant of outer part inside the rod was easier to be out-diffused than that of inner part. The refractive index profile generated by this process was measured by Interference Pattern Analysis(IPA). Second, the simple qualitative simulation related to the result if the process was possible or not, was performed. Consequently, generation of GI-profile by this process was theoretically demonstrated through the simulation.