Enhanced optical nonlinearity in nematic liquid crystal on doping with CdSe quantum dot

Abstract

Third order nonlinear optical properties of CdSe quantum dot doped liquid crystal was studied in both isotropic and nematic state. CdSe quantum dots were synthesized by kinetic growth method. The optical and morphological analysis provided confirmation of the quantum dot formation. Nonlinear optical properties of the samples were explored by a single beam Z scan technique using Q-switched Nd:YAG laser, delivering pulses at 532 nm and 7 ns pulse width. Nonlinear optical absorption was found to be enhanced significantly on increasing the concentration of quantum dots in the liquid crystal. Janossy effect and charge transfer mechanism play a crucial role in the observed enhancement. The obtained values of the nonlinear refractive index, n2 and the third order optical susceptibility, χ(3) were of the order of 10−10 m2/W and 10−11 esu, respectively. The optical limiting thresholds of the studied systems are found to be 1.57 J/cm2 (isotropic) and 2.1 J/cm2 (nematic). The nonlinear optical characteristics of the CdSe-liquid crystal blend validate its application as an optical limiter.