Thermally stable optical characteristics of sol-gel hybrid material films

Thermo-optic (TO) coefficients for transverse-electric and transverse-magnetic polarized light (dn(TE)/dT and dn(TM)/dT, respectively) were measured for sol-gel-derived, new organic-inorganic hybrid materials. The absolute values of dn(TE)/dT are comparable to those of dn(TM)/dT, indicating low anisotropy (dn(TE)/dT-dn(TM)/dT) in the TO coefficients. The low anisotropy is evidenced by the very small polarization dependence of the refractive index (n(TE)-n(TM)). The high stability of these materials is consistent with a high glass transition temperature (T-g > 150 degrees C), and evidenced by an absence of hysteresis in the refractive index and in film thickness during temperature cycling between 30 and 150 degrees C.