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Refractive Index Control of Polymer Film by Plasma CVD for designing an Optical Waveguide
Author(s) -
Sato Tetsuji,
Moriki Kazunori,
Yumoto Motoshige
Publication year - 2010
Publication title -
ieej transactions on electrical and electronic engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.254
H-Index - 30
eISSN - 1931-4981
pISSN - 1931-4973
DOI - 10.1002/tee.20554
Subject(s) - refractive index , materials science , waveguide , polymer , dangling bond , step index profile , absorption (acoustics) , plasma , analytical chemistry (journal) , optics , optoelectronics , chemistry , organic chemistry , composite material , graded index fiber , physics , quantum mechanics , fiber optic sensor , silicon , fiber
Refractive index control of a polymer film is an important issue in the fabrication of an optical polymer waveguide by using plasma‐enhanced polymerization. In a conventional approach, one attempts to control the same by changing the molecular structure by controlling the plasma conditions, for example, the applied power, pressure, and plasma potential. In another approach, elements other than carbon and hydrogen can be incorporated into the film. However, this approach unfortunately causes an increased optical absorption due to excess radicals, e.g. dangling bonds in the film and the unpredictable and undesirable bases produced during the reaction. We have proposed to control the amount of double bonding by varying the source monomer without changing the plasma conditions, where we used C 6 H 6 and C 6 H 10 as the source monomers. In the present paper, we investigate how the refractive index changes by varying the amount of double bonds by controlling the ratio of C 6 H 6 and C 6 H 10 in a mixture. Moreover, we discuss how the CF 4 plasma atmosphere affects the refractive index and the molecular structure of the film. Consequently, increasing the ratio of C 6 H 6 in the mixture increases the refractive index of the film linearly. The refractive index decreases until the ratio of CF 4 is less than 0.4, and beyond this value the refractive index remains almost constant. Additionally, the deposition rate using CF 4 as the atmosphere is much larger than when using Ar. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.