New holographic technique for third-order optical properties measurement

We present a new nonlinear holographic method, which yields the real and imaginary parts of the third-order susceptibility (χ〈3〉) of an optical medium. The method consists in producing a nonlinear interference pattern between two beams of different intensity, where the strong beam induces nonlinear effects in the tested sample. Only three laser shots are required to extract both real and imaginary parts of χ〈3〉 by means of the images recorded on a CCD camera. We apply the method to measure the nonlinear refractive index (n2) of new synthesized organic materials in the pico-second regime (30 ps pulse duration at 1064 nm). The obtained results show that the proposed technique allows the measurement of n2 coefficients in diluted materials with a sensitivity of λ/1500 at 1 GW cm−2 of input intensity.