Optical Kerr Constant of Azo-Dye-Doped Nematic and Polymer-Dispersed Liquid Crystals Determined by Biphotonic Z-Scan Technique

Abstract

We have recently investigated the optical Kerr constant (n₂) of azo-dye-doped nematic liquid crystal (ADDLC) and polymer-dispersed liquid crystal (ADDPDLC) films using the Z-scan technique. The measurements of ADDLC samples are firstly performed with the simultaneous application of two pump beams, which are referred as the biphotonic Z-scan technique. The results show that n₂ for ADDLC films is contributed primarily from the reorientation of liquid crystals induced by the photoisomerization of azo dyes and thermal effect, while that of ADDPDLC films with nano-sized LC droplets results from the thermal effect, and changes markedly with temperature.

Keywords:

• Azo dyes
• nematic liquid crystal
• optical kerr constant
• photoisomerization
• polymer-dispersed liquid crystals
• Z-scan

Acknowledgment

The authors would like to thank the National Science Council of the Republic of China (Taiwan) for financially supporting this research under the Grant No. NSC 98-2112-M-006-011-MY3. Additionally, this work is partially supported by Advanced Optoelectronic Technology Center.