Large near-resonance third-order nonlinearity in an azobenzene-functionalized polymer film

The third-order nonlinear optical response of a thin film containing the azobenzene dye Disperse Red 1 was studied using the z-scan technique with tunable picosecond pulses. A nonlinear refractive index of −5.0 cm2/GW, corresponding to a Re χ(3)=−3.0×10−15 m2/V2 (2.1×10−7 esu), has been measured at 570 nm. The observed nonlinearity is attributed to the change in refractive index induced by the trans-cis transition in the dye molecule.