Reconfigurable liquid crystal diffraction grating based on flexoelectric effect

Abstract

Reconfigurable optical diffraction grating is of great importance for monochromator, spectrometer, optical fiber telecommunication, laser protection, antenna and more. We report a liquid crystal diffraction grating based on flexoelectric effect. When no voltage is applied, the liquid crystal is unidirectionally aligned and does not diffract light. When a DC voltage is applied, the liquid crystal is switched to a 1-dimensional periodic structure due to flexoelectric interaction and becomes diffracting. The periodicity and refractive index undulation of the periodic structure are determined by the elastic energy, due to the spatial variation of the liquid crystal director, and flexoelectric interaction energy. The diffraction angle and efficiency can be controlled by the applied voltage. The liquid crystal diffraction grating has the advantages of low driving voltage, high diffraction efficiency and independency of the polarization of incident light.