The photorefractive properties of SmC* phases are usually studied in samples which are not intrinsically photoconductive and in which light sensitization is achieved by doping. We propose two different approaches: the first one is the use of a liquid crystal which is intrinsically photoconducting and photorefractive without any doping. In this system a PR performance larger than what previously reported for doped systems was measured, as well as the amplitude of the photoinduced space-charge field. A further development of this research is the control of the polarization switching in a bistable surface-stabilized ferroelectric liquid crystal (SSFLC) device via a photorefractive (PR) mechanism. In this case, the space-charge field was generated on the surfaces of the SSFLC device, in two photoconducting layers coated on the sample substrates. The formation of a stable grating was observed.
We present results on the photorefractive performance of cyclometalated complexes in which a central metal atom (Pd or Pt) coordinates two different molecular sub-units in a single species. Depending on the details of their structure, these molecules aggregate in crystals, glasses or liquid crystalline phases. The photorefractive properties of the complexes are discussed by treating separately results obtained in different phases. Crystalline compounds can be dissolved in suitable polymers and we show how phase separation in polymeric composites, which is usually detrimental for sample stability, can be controlled and used to increase photorefractive performance parameters by orders of magnitude. In addition, we present a method for estimating the itensity of the space-charge field in chiral smectic phases without using any of the standard models developed for crystalline or amorphous materials.