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 ≈ 100 nm, and electrically tunable from λ = 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.

Droplet deformation and alignment for high-efficiency polarization-dependent holographic polymer-dispersed liquid-crystal reflection gratings.

Droplet deformation and alignment are achieved in holographic polymer-dispersed liquid-crystal reflection gratings by applying an in situ shear during recording. High diffraction efficiency (99%) is obtained for light polarized parallel to the shear, with nearly zero efficiency for perpendicular polarization, and no increase of incoherent scattering. Permanent polarization dependence is related to stress-induced morphology changes of liquid-crystal droplets that are frozen by polymerization. The system is studied by electron microscopy and modeled by anisotropic coupled-wave and scattering theory. The morphology is consistent with the theory of small deformations of liquid droplets in fluid flow. Diffraction efficiency measurements are in agreement with theory incorporating this morphology as well as concomitant orientation and alignment of liquid-crystal molecules.

Volume holographic image storage and electro-optical readout in a polymer-dispersed liquid-crystal film.

We report storage and electrical switching of holographic image data in an economical polymer-dispersed liquidcrystal material. The hologram is recorded in a fast, single-step process and can be reversibly erased and restored repeatedly by the application of fields of approximately 10-15 V/ microm, with a response time of 22 micros and a relaxation time of 42 micros. Simple (quasi-sinusoidal) holographic transmission gratings also are studied with switching fields of <5 V/ microm and with response and relaxation times of 25 and 44 micros, respectively.