Volume relaxation in polymers and the effect intrinsic to glassy polymers can significantly affect their refractive index over time. Its β rate has been found to be related only to relaxation temperature <i>T</i> and the glass transition temperature of the polymer <i>T</i><sub><i>g</i></sub> and not to the polymeric chemical structure. Universal values of β have been obtained for polymers and were used to predict the minimum index change related to volume in polymers. The index change is in the range from 7.86 × 10<sup>−5</sup> to 5.26 × 10<sup>−4</sup> when the <i>T</i><sub><i>g</i></sub> − <i>T</i> value of polymers is between 90 and 350 °C. These volume-relaxation-induced changes can cause serious deterioration or even failure in corresponding polymer waveguide devices, such as arrayed waveguide gratings and variable optical attenuators, when the <i>T</i><sub><i>g</i></sub> of a polymer is not sufficiently high. A minimum requirement is therefore suggested for the <i>T</i><sub><i>g</i></sub> of polymers used to fabricate waveguide devices.
© 2004 Optical Society of America
(130.3120) Integrated optics : Integrated optics devices
(130.3130) Integrated optics : Integrated optics materials
(160.5470) Materials : Polymers
(230.7390) Optical devices : Waveguides, planar
(250.5300) Optoelectronics : Photonic integrated circuits
Zhiyi Zhang, Gaozhi Xiao, and Chander P. Grover, "Volume Relaxation in Polymers and Its Effect on Waveguide Applications," Appl. Opt. 43, 2325-2331 (2004)