Quadratic electro‐absorption (QEA) and quadratic electro‐optic measurements were performed with a guest/host system consisting of 4(4’‐N,N‐Dimethylaminophenyl)‐1,1‐bis(trifluoromethyl sulfonyl)‐1,3‐butadiene doped in poly(ethyl)methacrylate host polymer. The imaginary part of the QEA response was measured over a wavelength range of 450–600 nm. The real and imaginary parts of the electric field induced optical Kerr coefficient were measured at wavelengths near and far from resonance. Under different polarizations of the optical field in the QEA measurement, the two contributing coefficients of the third order susceptibility (&khgr;(3)) were deduced. A distinctive temperature variation of the third order response was observed. Temperature dependence measurements from ambient to well above the glass transition of the guest‐host system were carried out. The same chromophore in a different polymer host, poly(vinyl)chloride, was also investigated. Correct expressions for the real and imaginary parts of the Kerr coefficient are provided. The present results confirm the importance of the electronic contribution to &khgr;(3)at room temperature where molecular reorientation is insignificant. At high temperatures (above the glass transition temperature of the polymer) the ratio of &khgr;(3)3333/&khgr;(3)1133deviates from −2, which is predicted by the elastic model assuming molecular reorientation to be the dominant mechanism. ©1996 American Institute of Physics.