Third-Harmonic Scattering for Fast and Sensitive Screening of the Second Hyperpolarizability in Solution

Organic materials are promising candidates for integration in optical network components allowing fast communication. Ultimate speeds can be obtained by exploiting third-order nonlinear optical light-matter interactions that ultimately rely on the molecular second hyperpolarizability (y). The exploration of molecular structure-property- relations is crucial to optimize y but requires state of the art measurement techniques which are both sensitive and efficient. Unfortunately, present-day methods for probing the performance of third-order nonlinear optical (NLO) materials fail to meet at least one of those requirements. We have developed third-harmonic scattering (THS) as an alternative method to measure y in solution, featuring a simple experimental setup and straightforward data analysis. Since the signal strength relies on 1242, the method proves to be very sensitive and allows rapid screening of organic molecules in dilute solutions for potential use in third-order NLO applications. In this manuscript, we demonstrate the experimental procedure and calibration of THS and have determined the second hyperpolarizability lyl of commonly used solvents, which can be used as an internal calibration standard. As a proof of concept we determined y of trans-stilbene and found it to be in excellent agreement with values obtained by other techniques.