The second order hyperpolarizability of cis azobenzene isomer

The second order hyperpolarizability of cis azobenzene isomer (γc) was obtained by measuring the third harmonic generation (THG) variation of an azobenzene doped polymer film when the film was optically pumped to create a large amount of cis isomers via photoisomerization. A steady state theory was developed to treat the THG intensity variation by considering the optical pump induced redistribution and reorientation of azobenzene in the polymer film and the contribution of cis isomer to the THG signal. The ratio of γ of cis and trans molecule, (γc/γt), was found to be 0.51. After the γt was obtained from the time-resolved optical Kerr effect (OKE) measurement, γc was deduced to be 5.6 × 10−33 esu. The result shows that the optical nonlinearity of cis isomer is clearly not negligible.