Mechanism of nonlinearity in semiconductor doped glasses using Z-scan method

Summary form only given. The third-order nonlinearity in the transparency region (2/spl planck//spl omega/four wave mixing (DFWM) experiments. The discrepancy has been resolved in DFWM experiments, with nonlinear refraction due to carriers generated by two-photon absorption (TPA) being the dominant mechanism. This is a fifth-order effect. The intrinsic third-order electronic nonlinearity in these samples is positive as measured by nondegenerate four wave mixing experiments and is much smaller in magnitude compared to the fifth-order nonlinearity. Picosecond pulses have mainly been used for the Z-scan experiments. For Z-scan, the theoretically simulated data in SDGs with picosecond pulses indicates that it is difficult to distinguish between third and fifth-order nonlinearity. In this paper, we show that by performing the Z-scan with picosecond and femtosecond pulses, one can distinguish between the third and fifth-order processes. We observe the signature of positive third-order nonlinearity in the Z-scan experiments with femtosecond pulses.