Nonlinear optical studies of newly synthesized polythiophenes containing pyridine and 1,3,4-oxadiazole units

Abstract

We report measurements of the third-order nonlinear optical properties of a newly synthesized thiophene- based copolymer. The nonlinear transmission measurements were performed on the copolymer dissolved in tetrahydrofuran by employing the single beam Z-scan technique. Q-switched laser output at 532-nm wavelength was used for this purpose. The nonlinear absorption coefficient, β, nonlinear refractive index, n<inf>2</inf>, and the real and imaginary parts of third-order susceptibility, x(3), were, 18.93 cm/GW, 3.037 x 10 -17 m2/W (1.022 x 10-10 esu), 1.512 x 10-20 m2/V2(-1.080 x 10 -12 esu) and 0.399 x 10-20 2m/V2 (0.285 x 10 -12 esu), respectively. The excited state absorption crosssection σ<inf>exc</inf>, was found to be larger than the ground state absorption crosssection σg, indicating reverse saturable absorption (RSA) in the copolymer sample. The co- polymer exhibits an optical power limiting threshold of about 120 μJ and saturated output of less than 80 μJ. Hence, the copolymer seems to be a promising material for photonic device applications. © 2008 Society of Plastics Engineers.