Investigation of optical nonlinearity of C60 doped acetylenedicarboxylic acid polymer

The third-order optical nonlinearity of C₆₀ doped acetylenedicarboxylic acid polymer using single-beam Z-scan technique has been investigated. The new acetylenedicarboxylic acid (ADC) polymer was synthesized and characterized using UV-visible, FTIR and NMR measurements. The characterization spectra confirm that the molecular structure of the polymer is consistent with the expectation. The studied samples exhibit absorption and refraction nonlinearities. The negative sign of the nonlinear refractive index n₂ indicates that both materials exhibit self-defocusing optical nonlinearity. The nonlinear refractive index n₂, the nonlinear absorption coefficient β and the third-order optical susceptibility (Re|χ³|,Im|χ³|) were determined and found to be solvent dependent. These values are found to be proportional with the polymer concentration. Reverse saturable absorption is the dominating mechanism for the observed absorption nonlinearities.