Optically induced holographic gratings in a ferroelectric nematic liquid crystal activated by an electric field

One of the fundamental components in modern optics and advanced photonics is diffraction grating, crucial for designing compact and highly tunable advanced optical devices. We demonstrate formation of a dynamic diffraction grating induced by two wave-mixing in a ferroelectric nematic liquid crystal (N_FLC) with the assistance of a weak electric field. A grating with a first-order diffraction efficiency of ∼3.8% was recorded with a recording intensity of 64 mW/cm². The corresponding effective nonlinear refractive index <i>n</i>₂ was around 2.6 × 10^-2 cm²/W, which is notably higher than that of pure nematic liquid crystals. The underlying mechanism is attributed to the reorientation of the director field caused by the synergic effect of combined torques originating from the optical and electric fields. The observed high nonlinearity offers a pathway for designing novel versatile liquid crystal-based devices, to our knowledge, expanding potential applications of ferroelectric nematics in various nonlinear and electro-optical processes.