Research On The Measurement Of Second-order Nonlinear Optical Property Organic Polymer Based Attenuated-total-reflection Technique

In an Attenuated-Total-Internal-Reflection (ATR) multi-layer structure, light reflectivity can be strongly dependent on layer parameters. A tiny variation of the parameters can lead to a large change in the light reflectivity. This characteristic enables us to propose a new method based on the ATR technique for the determination of the second-order optical nonlinear properties of organic polymer.Organic polymer is molecular aggregates, coupled by the weak interaction between molecules. The macroscopic nonlinear optical properties originate from the properties of the molecules. Second-order non-linear optical polymers derive their NLO properties from the first hyperpolarizability of chromophores in them.This article proposes a measurement of the complex first hyperpolarizability of chromophore for electro-optic effect at wavelength of the absorption edge. By employing the information obtained from different wave resonance dips, the values as well as the signs of both parts of the complex second hyperpolarizability are simultaneously obtained without using the Kramers–Kronig transformation. Compared with other techniques for measuring the first hyperpolarizability such as quadratic electroabsorption (QEA) technique, hyper-Rayleigh scattering (HRS) technique, the high-power pulse laser and the lock-in amplifier is no longer needed, which exhibits the benefits of low cost and convenience.