Complex nonlinear refractive index of DNA

Femtosecond Z-scan technique was used to determine the dispersion of the complex cubic nonlinear susceptibility (related to the nonlinear refractive index n(2) and the two-photon absorption coefficient beta(2)) of deoxyribonucleic acid (DNA) in the range of wavelengths from 530-1300 nm. The nonlinear refractive index of DNA varies from approximate to 2 x 10(-15) to 1 x 10(-14) cm(2)/W at lambda = 1300-530 nm, respectively. Only a weak two-photon absorption is observed below lambda = 600 nm with a nonlinear absorption coefficient beta(2) of about 0.2 cm/GW at lambda = 530 nm. The dispersion is approximated with a simple complex expression. (c) 2006 Published by Elsevier B.V.