Spontaneous Pattern Formation with Incoherent White Light

We present the first experimental observation of modulation instability and spontaneous pattern formation with incoherent white light emitted from an incandescent light bulb. We show experimentally that modulation instability of white light propagating in a noninstantaneous self-focusing medium is a collective effect, where the entire temporal spectrum of the light beam becomes unstable at the same threshold value and collectively forms a pattern with a single periodicity. We experimentally demonstrate that the temporal spectrum of the evolving perturbation self-adjusts to match the collective pattern formation phenomenon.

Figure 1

A sketch of the experimental setup. The inset shows the temporal spectrum of the light at the input face of the crystal (left) and the crystal absorption (right).

Figure 2

Total intensity distribution at the output face of the crystal: homogeneous intensity at linear propagation (a) and stable nonlinear propagation below the MI threshold (b); pattern formation above the MI threshold (c),(d).

Figure 3

Visibility as a function of the nonlinearity strength. Different curves correspond to different wavelengths (temporal frequencies).

Figure 4

True color magnified image of a typical filament in white light MI, showing color separation [reddish shade towards the filament edges (shown only in the color version online)] and self-adjustment of the temporal spectrum.