Influence of dopant concentration on thermo-optic properties of PMMA composite

Thermo-optic (TO) coefficient (dT / dn ) as well as thermal expansion coefficients (β) of DR1/PMMA polymer film are measured for both TE (transversal electric) and TM (transversal magnetic) polarizations by using an attenuated total reflection (ATR) configuration at the wavelengths of 650, 832 and 1064 nm. Experimental results indicate that the absolute value of TO coefficient of DR1 (disperse red 1)/PMMA film does not always increase with the increasing wt.% of the dopant. The absolute value of TO coefficient of TE polarization is always larger than that of TM polarization due to the anisotropy of thermal expansion coefficient. Moreover, it is found that the found that the different values of TO coefficient at different wavelengths are mainly caused by the dispersion of the refractive index.