Z-scan study on the nonlinear refractive index of copper nanocluster composite silica glass

We used the Z-scan technique for measuring the nonlinear refractive index n2 of a thin composite film formed by copper nanoparticles embedded in silica glass. By varying the number of pulses of the laser shot, we evidenced heating effects induced by the laser during measurements. We were able to estimate the nonthermal refractive-index value, n2=(3.0±0.3)×10−12 cm2/W.