Influence of the Acceptor Moiety on Nonlinear Optical Properties of Thiophene Derivatives

In this paper we report on the investigation of linear and nonlinear optical properties of six new thiophene derivatives (ThD) with a $\mathrm{D}-\pi-\mathrm{A}$ chemical structure. Chosen compounds contain the same electron-donating moiety and a $\pi$ -conjugated bridge build as covalently bonded benzothiophene and thiophene. As an electron-accepting part we used nitrophenyl and benzonitrile in ortho, meta and para positions. Selected ThDs were prepared as thin films with poly(methyl methacrylate) as a matrix in order to investigate the nonlinear optical properties. For a second and third harmonic generation (SHG/THG) we used Maker fringes method to estimate values of second and third order susceptibility. Photoinduced birefringence measurements were performed with typical Optical Kerr Effect (OKE) experiment.