Achieving enhanced second-harmonic generation in ferroelectric nematics by doping D--A chromophores

The second-order nonlinear optical effect is the foundation of realizing optical wavelength regulation and conversion technology. Improved organic nonlinear optical materials have been shown in recent decades to deliver performances as good as those of inorganic materials, and are hence attracting a revisit by researchers with regards to applying their excellent nonlinear optical properties and processability toward modern flexible devices. Traditional high-performance organic nonlinear optical materials rely on D-& pi;-A chromophores dispersed in apolar polymer systems. A strong electric field has usually been utilized for poling the D-& pi;-A chromophore, which requires complicated processing and faces severe polarization relaxation issues. Here we provided a mechanism for an unprecedented enhancement of nonlinear properties. We employed fluidic ferroelectric nematics as a spontaneous polarization background acting as an internal electric field to polarize doped D-& pi;-A chromophores. We revealed a synergetic effect of polarization enhancement results in a dramatic increase in second-harmonic generation, by about two orders of magnitude, compared to those of the corresponding undoped materials.