  In this letter, we study a nonlinear interferometric setup based on
diffraction rather than beam combining. It consists of a nonlinear analogue of
Young's double-slit experiment where a nonlinear material is placed exactly
after one of the slits. The presence of nonlinearity breaks the transverse
spatial symmetry of the system and thus modifies the optical path. For moderate
nonlinearities this leads to a self-induced shift of the intensity pattern in
the transverse plane. A simple theoretical model is developed which is
surprisingly accurate in predicting the intensity profile of the main lobes for
a wide range of parameters. We discuss about possible applications of our model
in nonlinear interferometry, for example in measuring the nonlinearities of
optical materials.
