Determination of nonlinear refractive index of paprika oil and pepper oil under cw visible laser illumination

We report the observation of multiple diffraction rings patterns in paprika and pepper oils using continuous wave laser beams .The patterns occur at relatively low intensities . The number of rings together with outermost ring diameter of each pattern increases monotonically with increasing input power . The total changes in refractive index , ∆n ,and nonlinear refractive index,n2 ,are determined using the number of rings observed in both samples and 473 nm and 532 nm laser beams . We obtained good values of ∆n = 0.01 and n2 = 10-6 cm2/w . These large values are  attributed  to  thermal effects .