Third-order nonlinearities in silicon at telecom wavelengths

The two-photon absorption coefficient and Kerr coefficient of bulk crystalline silicon are determined near the telecommunication wavelengths of 1.3 and 1.55 mum using femtosecond pulses and a balanced Z-scan technique. A phase shift sensitivity of the order of 1 mrad is achieved, enabling the accurate measurement of third-order nonlinear coefficients at fluences smaller than 100 muJ/cm(2). From the two-photon absorption coefficient (betasimilar to0.8 cm/GW) and the Kerr coefficient (n(2)similar to4x10(-14) cm(2)/W) at a wavelength lambda=1.54 mum, a value Fsimilar to0.35 for the nonlinear figure of merit for all-optical switching is determined. (C) 2003 American Institute of Physics.