Ferroelectric Fluids for Nonlinear Photonics: Evaluation of Temperature Dependence of Second-Order Susceptibilities

Ferroelectric nematic fluids are promising materials for tunable nonlinear photonics, with applications ranging from second harmonic generation to sources of entangled photons. However, the few reported values of second-order susceptibilities vary widely depending on the molecular architecture. Here, we systematically measure second-order NLO susceptibilities of five different materials that exhibit the ferroelectric nematic phase, as well as the more recently discovered layered smectic A ferroelectric phase. The materials investigated include archetypal molecular architectures as well as mixtures showing room-temperature ferroelectric phases. The measured values, which range from 0.3 to 20 pm/V, are here reasonably predicted by combining calculations of molecular-level hyperpolarizabilities and a simple nematic potential, highlighting the opportunities of modelling-assisted design for enhanced NLO ferroelectric fluids.