Ideal micro-lenticular lens based on phase modulation of optically isotropic liquid crystal-polymer composite with three terminals

Optical phase modulation in a transparent polymer film composed of nano-sized liquid crystal (LC) droplets embedded within a polymer matrix exhibits a micro-lenticular lensing effect under controlled in-plane field switching (IPS) with interdigitated electrodes. Despite of the lensing effect, the lens profile does not match ideal one and its effective phase modulation is relatively small owing to the weak field strength over the electrodes, which causes an invariant refractive index in these regions. To achieve ideal lens profile and high phase modulation, a vertical electric field is applied between top plane and bottom interdigitated electrodes, while maintaining the in-plane fields between the bottom interdigitated electrodes. The combined effect, referred to as the vertical and in-plane switching (VIS) mode, can achieve larger phase modulation (Δδ) than the IPS mode. Consequently, the proposed micro-lenticular lens has a shorter focal length and a significantly better lens profile, similar to the ideal one. Furthermore, the diffraction efficiency (D_f) is effectively improved by ∼ 6.7%, 4%, and 2% for the zeroth (0^th), ±1^st, and ± 2^nd orders, respectively, compared to those in the IPS mode. The improved phase profile with the proposed micro-lenticular device can be used in a switchable lens from 2-dimensions (2D) to 3-dimension (3D) and tunable diffractors.