Generalized Heterodyne Interferometry in Kerr Materials

Interferometry has long been used to measure the phase of light signals. Combined with a heterodyne detection scheme, it allows to simultaneously record amplitude and phase variations. In this work, these well‐known techniques are exploited to evaluate the nonlinear phase induced by the optical Kerr effect during the propagation of a laser pulse in a nonlinear medium. It is shown that the nonlinear index can easily be retrieved when the accumulated phase remains small, but counter‐intuitive results can be observed at higher powers. In particular, the combination of pulsed excitation and Kerr nonlinearity results in nonlinear variations of the amplitude of the interference pattern, whose shape depends on the pulse profile and the dispersion of the propagation medium.