Optical Kerr effect in nematic doped with azo-benzene functionalized POSS nanoparticles

In this work, two novel azo-benzene substituted polyhedral oligomeric silsesquioxanes (POSS) compounds having m =4 and m = 10 in order to check their nonlinear optical properties when dissolved in common nematic mixture E-7 were synthesized. The method of optically induced birefringence of LC or so called Optical Kerr Effect (OKE) was used. The light-induced birefringence in nematic liquid crystals can be treated as a third order nonlinear optical effect because of changes of refractive index of the form: n = n_o + n₂I where nonlinear optical coefficient n₂ is proportional to the cubic optical susceptibility. Excitation within absorption n-π* band of azo-group was able to induce a cycle of trans-cis photoisomerisations leading to inducement of rearrangement of nematic molecules forming a layer in a homogenic LC cell. The results of this work prove that nematic LC doped with POSS based azo-functionalized nanoparticles is a reliable system for dynamic all-optical switching as well as can found application in a real-time holography.