Photoreplicated anisotropic liquid-crystalline lenses for aberration control and dual-layer readout of optical discs

This work describes the functional characterization of novel photoreplicated anisotropic lenses obtained from molds with different curvatures. These lenses were prepared by the photopolymerization of mixtures of a reactive liquid-crystalline bisacrylate and non-reactive derivatives of liquid-crystalline cyanobiphenyl. The phase diagrams, the polymerization kinetics as a function of temperature, and the birefringence as a function of temperature for various mixtures were determined. For the fabrication of lenses, the average liquid-crystal (LC) director of the mixtures has to be aligned in a single direction. Photoalignment and rubbing techniques were investigated to create a monodomain of the reactive material. Finally, optimal mixtures were used for the fabrication of anisotropic lenses. Aberrations were below 20 mλ root mean square (rms), which makes these LC lenses interesting for application in light paths, for example, as spherical aberration correction devices for dual- (or multiple-) layer optical storage.