Reflection z-scan for measuring the nonlinear refractive index of porous silicon

An experimental investigation on the nonlinear refractive index of nanoporous silicon at wavelengths of 532 nm and 1064 nm is reported by the reflection z-scan(RZ-scan) method with picosecond pulses.The porous silicon(PS) does not need to be peeled from silicon substrate.The method uses a p-polarized beam with oblique incidence.The modification of the reflected beam intensity gives the information of the surface nonlinear refractive index.The index of porous silicon at 1064 nm is at the same order of magnitude as that obtained by the conventional transmission z-scan technique,and the measured absolute value of nonlinear refractive index n2 at 532 nm is two orders of magnitude higher than that at 1064 nm.