The Granular Laser

In the last chapter, we have seen how to analytically treat the interplay between nonlinearity and disorder in the framework of the spin glass theory. The emerging results show how the increasing degree of disorder can drastically change the underlying thermodynamics by switching the optical device from a standard laser to a random one while controlling the furnished energy permits to observe the nonlinear emerging phenomena, like the mode-locked transition. By an experimental point of view, the latter mechanism is much simpler to control and hence the related literature is much wider than the former one. Here, we want to visually demonstrate through a set of experiments that the random laser emission depends not only on the furnished energy, the nonlinear processes, but primarily on the structural informations, that is the degree of disorder inside. In order to study how random laser features are affected and controlled by the state of the motion of the sample, and then on the disordered considered configuration, we have to choose the more appropriate physical system. Here, we use shaken granular materials.