Second harmonic generation in laterally azo-bridged H-shaped ferroelectric dimesogens

Abstract

This contribution describes the analysis of experimental results on second harmonic generation (SHG) in a novel laterally azo-bridged H-shaped ferroelectric liquid crystal (FLC) 2, incorporating a disperse red 1 (DR-1) chromophore along the FLC polar axis, and its two mixtures with a laterally azo-bridged H-shaped FLC host 1, incorporating an azobenzene chromophore. The largest d_ij coefficient at the fundamental wavelength of λ = 1.6 μm is d₂₂ = 4.5 pm/V, the coefficient along the polar axis that is optimized from the viewpoint of the chemical design of NLO FLC molecules. A linear dependence of d₂₂ on the mole fractions of 2 in mixtures has been found, indicating that i) both 1 and 2 have a similar degree of polar order, and ii) dipole–dipole interaction in the DR-1 chromophore of 2 is not strong due to low chromophore density. This work highlights the importance of synthetic tailorability of FLC materials with extra functionality to second-order nonlinear optics applications.