You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither SPIE nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the SPIE website.
14 July 2003Zero-birefringent polyimide for polymer optical waveguide
A novel zero birefringent and photosensitive polyimide was synthesized. The polymer is soluble in solvents and contains a chalcone group for photo-crosslinking by UV exposure. The glass transition and decomposition temperature of the polymer were 254°C and 430°C before cross-linking. Evolution of the absorption spectra upon UV exposure indicated that the cross-linking reaction is related to the cycloaddition of the double bonds in the chalcone group to form cyclobutane. The photo-crosslinking reaction not only increased the thermal stability, but also induced a refractive index change of the films. The refractive index of the film was reduced upon UV exposure from 1.5862 to 1.5697 for TE mode and from 1.5807 to 1.5697 for TM mode, respectively, resulting in zero birefringence after curing. Loss of p-conjugation in the chalcone group by the crosslinking reaction is supposed to induce the reduction of the refractive indices and orbital change from sp2 to sp3 makes the polymer chain be kinked, resulting in decrease of birefringence. The polymer film showed optical loss of 0.41 dB/cm at 1.3 mm and 0.54 dB/cm at 1.55 mm. Zero birefringence and low optical loss combined with photo-processibility of the material are making it an excellent candidate for the high performance waveguide materials.