Intrinsic Negative-Mass from Nonlinearity

Abstract

Scale-free-optics, or diffraction-cancellation is a propagation regime (discovered by DelRe et al. in [1], but first observation can be traced back to [2]) in which the electromagnetic fields is no longer governed by the Helmholtz equation but by a Klein–Gordon-type equation. This is achieved in a disordered out of equilibrium para-electric crystal near the phase transition. In this condition beam propagation is affected by a giant and purely diffusive nonlinearity which has profound implications for wave dynamics. In particular in this regime optical propagation occurs without any limit associated to the optical wavelength [3] (scale-free-optics), where the diffraction is absent, not simply compensated by nonlinear index change or the presence of waveguide (both conditions in which the spatial dimensions scale with $\lambda$). The phenomenon appears also to be intensity and size independent [4], but it is nonetheless nonlinear. Experiments that highlight the nonlinear nature of diffraction cancellation are beam-beam interaction phenomena, which involve beam attraction, crossing, and beam spiraling, three interaction phenomena that are similar to those normally associated to solitons [5]. The unique features of the system allow us to observe anti-diffraction of light and light beams that can be focused to dimensions smaller than the diffraction limit [6, 7].