Optical Nonlinearities and Molecular Conformations in Thiophene-Based Hydrazone Crystals

Abstract

We have investigated a series of thiophene- and bithiophene-based hydrazone crystals for second-order nonlinear optical applications. The investigated hydrazone crystals exhibit a large nonresonant second-harmonic generation efficiency about 2 orders of magnitude larger than urea. The T-NPH ((thiophene-2-carbaldehyde)-4-nitrophenylhydrazone) crystals having Pn space-group symmetry consist of two T-NPH molecules exhibiting a different conformation influenced by intermolecular interactions, which considerably affects their optical nonlinearities, We have examined the variation of microscopic and macroscopic nonlinearities with different Molecular conformations in the T-NPH crystalline system by finite-field and density functional theory calculations.