Generation of 3-dimensional polymer structures in liquid crystalline devices using direct laser writing

Abstract

Direct laser writing is a powerful nonlinear fabrication technique that provides high intensities in the focal plane of a sample to engineer multidimensional structures with submicron feature sizes. Dielectrically and optically anisotropic soft matter is of particular interest when considering a host medium in which exotic topological characteristics may be generated. In this manuscript, we adopt a novel approach for direct laser writing of polymeric structures, whereby the photo-sensitive resin is liquid crystalline (LC) and aligned within electrically addressable LC devices. We show that the laser written polymer structures retain the optical properties of the liquid crystal resin at the point of laser exposure. Thus, birefringent polymer structures can be written, with the orientation of the optic axis tuned during fabrication through switching the liquid crystal with an applied electric field. This gives the potential to create complex spatial variations of the polymer refractive index on a micron scale. Furthermore, we present a range of structures for controlling the liquid crystal alignment in devices, including two-dimensional arrays of polymer pillars, a polymer checkerboard that creates a controllable disclination network, and 3-dimensional helical polymer ribbons and knots. This work introduces a new degree of freedom for the direct laser writing of advanced photonic materials as well as offering significant advances for the control of soft matter.