Schiff Base Metal Complexes for Second Order Nonlinear Optics

118 Aprile ‘10 N onlinear optics (NLO) is the study of all the phenomena that occur from the interaction of intense light with matter [1, 2]. The interaction with a nonlinear optical material causes a modification of the optical properties of the system, and the next photon that arrives sees a different material. Typically only laser light is sufficiently intense to generate NLO phenomena; therefore the beginning of this research field is often taken to be the discovery of second-harmonic generation by Franken et al. in 1961 [3], the year after the construction of the first laser by Maiman [4]. NLO interactions cause changing in frequency, phase, polarization or path of incident light, and are ‘nonlinear’ because the response of a system to the applied optical field depends in a nonlinear manner upon the strength of the optical field. The chemist’s goal is to develop materials that control this interaction in order to modulate or combine photons (wave mixing), fine tuning both the magnitude and response time of the optical process. The electric field of light, E, interacts with a molecule producing a force that displaces the electron density away from the nucleus, resulting in a charge separation, i.e. an induced polarization p. For small fields the charge displacement from the equilibrium position is proportional to the strength of the applied field through the equation