Spectrally tunable chiral Bragg reflectors for on-demand beam generation

We demonstrate the generation of spectrally tunable phase-dependent wavefronts, using the 2D Airy as the primary test case, via a polymer-stabilized cholesteric liquid crystal (PSCLC) element. Specifically, we use a novel spatial light modulator (SLM) based projection system to photo-align the initial helix angle landscape of the PSCLC so that it imparts the appropriate cubic phase profile to the reflected beam. This element is spectrally selective, with a reflection bandwidth of &asymp; 100 nm, and electrically tunable from &lambda; = 530 nm to 760 nm. Under both green and red laser illumination, the element is shown to conditionally form an Airy beam depending on the position of the electrically tailored reflection band. We briefly demonstrate the generality of this approach by producing PSCLC elements which form a computer-generated hologram and a higher-order Mathieu beam.</p

Electrically Reconfigurable Liquid Crystalline Mirrors

Reconfigurable optical materials are critical to realizing light control in eyewear or architectural windows. Here, we report on the electrical reconfiguration of the selective reflection of cholesteric liquid crystals (LCs). The distinctive responses detailed here are enabled by the preparation of a structurally chiral polymer stabilizing network that enforces anchoring of a low-molar-mass liquid crystalline media with positive dielectric anisotropy. The pitch of the reflective optical elements is directly regulated by a dc field, resulting in red or blue reflection wavelength tuning or broadening. The use of the positive dielectric LC host in concert with optimization of the material preparation conditions allows for reorientation of the LC molecules to achieve an optically clear state (homeotropic orientation) by the application of an ac field. In this way, the selective reflection of the optical elements can be moved, widened, and turned on and off. The electro-optic characteristics of these materials are another step forward to enabling the use of these materials in optics and photonics