Synthesis and characterization of cross-linkable fluorinated polyimide for optical waveguide

摘要

Fluorinated polyimides (FPI) including cross-linkable (CLFPI) and non-cross-linked (NCFPI) have been synthesized by the polycondensation of 1,3-bis-(4-amino-2-trifluoromethylphenoxy) benzene (BATB), 4,4'-(4,4'-isopropylidene -diphenoxy) bis (phthalic anhydride) (BPADA), and 2,2-bis[4-(4-aminophenoxy) phenyl]-hexa-fluoropropane (6FBAPP). These polymers exhibit excellent thermal stability with a glass transition temperature (T_g) of 198 ℃, and the weight loss is only 5 % even when the temperature is above 500 ℃. The spin-coated polymer films are highly transparent in both visible and near-infrared regions, with a good film-forming characteristic. Inverted ridge optical waveguides were fabricated using the fluorinated polyimide. The near-field mode patterns of the waveguides were recorded and analyzed. Results showed that the overall propagation loss of the inverted ridge optical waveguides was 0.2 dB/cm at 1,310 nm and 0.36 dB/cm at 1,550 nm evaluated by the cutback method, indicating the promise of these FPI materials for passive optical waveguide device applications.