Nonlinear optical properties of castor oil

We report on the investigation of the nonlinear optical properties of castor oil using the Z-scan technique. Nonlinear refraction and absorption measurements were performed for two different laser wavelengths, 514 and 810 nm, in the CW regime, and for 810 nm in femtosecond regime. The CW results showed that castor oil has a large negative nonlinear refractive index n2 = -3.2 x 10 cm/W for the laser wavelength at 514 nm, and this value was about one order of magnitude smaller for excitation tuned at 810 nm. The negative sign and the slow response of this nonlinearity indicate the thermal origin of this effect. In the femtosecond regime, it was not possible to observe a typical Z-scan curve for castor oil. The nonlinear absorption was absent for all experimental configurations.