Photorefractive properties of new liquid crystals in the near-infrared range

Abstract

This work focuses on the definition of optical anisotropy of liquid crystals in the near-infrared range. The main goal of this paper was to measure the photorefractive properties of new liquid crystal materials with high refractive index in the near-infrared range such as 1294-1b, which has a relatively high anisotropy of the refractive index in the optical range with Δn having a value of more than 0.35. Optical anisotropy in the near-infrared range of well-known liquid crystals such as 5CB and 6CHBT as described in different papers was used to test the measuring method.

The measured refractive indexes were similar to the refractive indexes published in the literature. Depending on the literature, the data state that the diffraction efficiency is dependent upon the temperature and the polarisation of the read-beam. Interesting applications of liquid crystals in the near-infrared range are also discussed.

In this work the methodology for the measurement of liquid crystals in the near-infrared spectrum is described in some detail. The main aim of the work presented is due to the demand for new materials that will meet the requirements for the telecommunications industry, which uses a third window transmission (with a wavelength of 1.55 μm). There are many indications that materials which may be applicable in these areas may be liquid crystals. The properties of liquid crystalline materials in this band are particularly interesting because of their possible applications. Already, liquid crystals are used for switches and modulators for waves in the near-infrared range.

Keywords:

• liquid crystals
• optical anisotropy
• photorefractivity
• diffraction gratings

Acknowledgements

This work was partially supported by project POIG.01.03.01-14-016/08 ‘New photonic materials and their advanced applications’. The authors would like to thank Professor Dąbrowski's laboratory for providing the LC materials.