Modulation Instability in Standing Water Waves

The modulation instability (MI) is responsible for the formation of strong wave localizations on the water surface and in a variety of nonlinear dispersive wave systems. Recent laboratory studies confirmed the validity of breathers to describe several MI scenarios in hydrodynamics, optics, plasma, and Bose-Einstein condensates. We provide experimental evidence of nonlinear and distinct breather focusing in standing water waves, i.e., in two counterpropagating wave trains. The wave measurements are in excellent agreement with the hydrodynamic coupled nonlinear Schrödinger equation and indicate that MI processes are unimpeded during the interplay of two wave systems.