Abstract

At the molecular level, the second-order nonlinear optical (NLO) response of the molecular materials is related with the first-order hyperpolarizability of their constituent molecules. For this reason, there has been a great effort to obtain molecules with remarkable first-order hyperpolarizability and, in this context, the organic molecules have presented great possibilities due to their flexibility on terms of structural engineering, allowing the development of molecules with tunable nonlinear optical properties in accord with the targeted applications. Inside of this class of materials, the design and synthesis of polymeric systems for NLO applications (such as frequency doublers, high speed modulators) have received considerable interest over the past years. Polybinaphthalenes show particularly interesting properties for applications in this field and chiral donorembedded polybinaphthalenes can benefit from contributions, inherently to chirality, which can increase the NLO response [1-4]. In this context, we report the giant first-order hyperpolarizability of four chiral donorembedded polybinaphthalenes. In order to obtain this effect, we used Hyper-Rayleigh scattering technique with picoseconds pulse trains. Figure 1(a) shows the normalized absorption spectra of all four chiral polymers. It is possible to see that all samples are transparent for 1064nm (ω), the 532nm (2ω) (scattered photon) is inside of absorption band. In Figure 1 (b), it is possible to see that the intensity of the first-order hyperpolarizability signal (I(2ω)/I²(ω)) increases as the concentration increases for each chiral polymer, depicting a linear tendency which is in accordance with Hyper-Rayleigh signal as function of the concentration.

© 2015 IEEE