Beam instabilities in second harmonic generation

In this paper we discuss modulational instability experiments which were performed in bulk KTP doubling crystal and their supporting theoretical calculations. Furthermore, we also show that solitonic beams can break up due to the well-known parametric instability into multiple quadratic solitons. Finally, we demonstrate that when two soliton beams interact (in a slab waveguide), they fuse, repulse one another or exchange energy on propagation, depending on the relative phase between the solitons.