Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals

A polarization-independent and high-diffraction-efficiency Fresnel lens is developed based on blue phase liquid crystals (BPLCs). The optically isotropic characteristic of BPLCs is used to produce a polarization-independent Fresnel lens. The small optical phase shift of BPLCs that is induced by the Kerr effect is sufficient for the BPLC Fresnel lens to have high theoretical and experimental diffraction efficiencies of 41% and ～34%, respectively. An electrically erasable memory effect in the focusing diffraction at an electric field E>4.44?V/μm is observed. The electro-optical properties of the BPLC Fresnel lens are analyzed and discussed.