Abstract

Integrated guided wave, all-optical switches are generally designed to operate via an intensity-dependent refractive index resulting from the third order nonlinear susceptibility, χ⁽³⁾ see for example [1], [2]. Recently, De Salvo et al. [3] have shown that nonlinear phase shift and thereby an effective intensity-dependent refractive index and can be obtained from cascading the second order nonlinearity χ⁽²⁾. They demonstrated that the effective intensity-dependent refractive index n_2eff produced by the cascaded second order nonlinearity could be positive or negative depending on the phase matching conditions, and they also measured n_2eff as ±2×10⁻¹⁴ cm² W^-1 for KTP (KTiOPO4), which has a d_eff of 3.1 × 10^-12 m V^-1. The approximate expression they derived for n_2eff was as follows

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