Stable multicolor periodic-wave arrays
  We study the existence and stability of cnoidal periodic wave arrays propagating in uniform quadratic nonlinear media and discover that they become completely stable above a threshold light intensity. To the best of our knowledge, this is the first example in physics of completely stable periodic wave patterns propagating in conservative uniform media supporting bright solitons. 
Yaroslav V. Kartashov, Alexey A. Egorov, Anna S. Zelenina, Victor A.   Vysloukh, Lluis Torner