Observation of modulational instability in a quadratically nonlinear optical medium in one and two dimensions

The modulational instability was demonstrated in a 1-cm-long crystal cut for type II phase-matching in the X-Y plane. A detailed investigation of the one-dimensional pattern was achieved by varying the intensity to measure the threshold in the formation of stable solitary wave patterns for beam ellipticities of 5.6:1 and 10.8:1. The dependence of a number of solitary waves present in the modulational instability pattern on the incident intensity is shown for two different ellipticities. As the intensity increases, the number of solitary waves visible at the exit face of the KTP crystal increased