Electro-optical tuning in Photonic Crystals - Dispersed Liquid Crystalline Metamaterials

Current research efforts on cutting-edge materials, such as Photonic Crystals (PCs), self-organizing nanomaterials, and polymeric and composite materials, are focused on obtaining novel or unique properties enabled by specialized molecular electronic, structural designs or dopants. While most metamaterials developed to date consist of passive material constituents, several studies have emerged where material constituents containing electrooptics, nonlinear optics, or active (gain) material are involved [1]. Control and tuning of the metamaterial electromagnetic response are gaining research interests as a natural research development to attain functionality in metamaterials [2, 3]. In a photonic device application, liquid crystal (LC) is the choice material when a control and tuning is pursued, as evidenced in wide applications to the optical display and photonics switching devices. But, often the geometrical properties of the photonic structures give problems for controlling the alignment of the LC. In this paper we studied a reproducible way to create specific orientational order fields in liquid crystals by means of novel nanostructured aligning surfaces. Two different metamaterial-liquid crystal structures are fabricated with the metamaterials as LC alignment layers. E-beam lithography was used to pattern the electron-sensitive polymer 1D PC structures. The nanostructured aligning surfaces have been characterized by Scanning Electron Microscopy. The Photonic Crystals-Dispersed Liquid Crystalline Metamaterials (PCs-DLCMs) have been investigated through polarized optical microscopy. The threshold voltage for the nematic LCs in a glass cell is also measured as a function of the frequency of the external electric field. [1] D. H. Werner, D.-H. Kwon, I. C. Khoo, A.V. Kildeshev and V.M. Shalaev, "Liquid crystal-clad near-infrared metamaterials with tunable negative-zero-positive refractive indices," Opt. Exp., vol. 15, pp. 3342-3347, 2007. [2] L. Petti, M. Rippa, J. Zhou, L. Manna and P. Mormile, "A Novel hybrid organic/inorganic photonic crystal slab showing a resonance action at the Band Edge", Nanotechnology, vol.22, 285307, 2011. [3] L. Petti, M. Rippa, J. Zhou, L. Manna, M. Zanella and P. Mormile, "Novel hybrid organic/inorganic 2D Quasiperiodic PC: from diffraction pattern to vertical light extraction", Nanoscale Research Letters, vol.6, 371, 2011.