Optical-field-induced reorientation of nematic liquid crystal doped with FeTPPCl based on the resonant model

Abstract

Optical-field-induced reorientation of 5CB doped with a 1% volume fraction of FeTPPCl (5,10,15,20–tetraphenylporphineiron(III) chloride) were studied. When excited by Ti:sapphire laser with an 82 MHz repetition rate and a 80 fs pulse duration, the reorientation threshold occurred at an intensity level of 1 mW/mm2 for the resonant absorption region, in contrast to the 115 mW/mm2 value for the transparent region. A guest resonant model is proposed to explain this anomalous phenomenon: when excited by absorbing light, the FeTPPCl molecule produces an intense resonance absorption which induces a very large dielectric anisotropy, and this therefore enhances the reorientation of the doped system. This phenomenon is very useful for using the liquid crystal as a nonlinear optical component.