Control of Optical LOcalized and Rare Structures – COLORS

In this project, we will develop control methods and strategies for the optical localized structures arising in nonlinear passive optical experiments such as shaping the patterns, switching between different coexisting structures, displacing them transversally, or else controlling rare intense events that can occur in spatiotemporal systems and that can have dramatic consequences.
The research will imply to a large extend fundamental studies, both theoretical and experimental, on the nature of the structures under investigation and on the definition of their distinctive features. It will imply as well technological developments on the control of optical structures, such as controlling their dynamics by using convectively traveling regimes, increase or decrease the degree of interaction, shaping a single structure or clusters of them, studying the effects of inherent noise on their dynamics, controlling spatial extreme events. Therefore, we expect that the results of the project will also have an impact on future applications in the field of optical control and optical storage.

We will setup two different types of experiments: optical passive cavity and optical feedback systems. At this purpose we will use nonlinear media that are of large transverse size such as photorefractive crystals, liquid crystal cell or light valves. We will study the conditions for optical bistability or multi-stability in both types of systems. In particular, the cavity configuration is very promising since it will provide a new mechanism for light localization in the presence of optical bistability between different light paths in the cavity. On the other side the feedback configuration presents a simpler configuration for the optical addressing. We will develop novel methods to manipulate the optical structures that arise from the spatial coupling resulting either from the feedback or the cavity configuration. The two main control methods will be based on:

(1) A spatial beam shaping introduced by a spatial light modulator (SLM). By exploiting these performances we can impose specific intensity or phase profiles on the input beam. The optical addressing method by the SLM will permit to test such different experimental schemes as spatial periodic forcing, both one and two-dimensional, phase or intensity gradients, space-time noise. On the other side, the spatial periodic forcing will be used to study front propagation and the behavior of localized structures.

(2) Convective (or drifting) instabilities for achieving transverse motion control. These instabilities can be induced by e.g. a tilt of one mirror. The obtained traveling transverse will allow for motion of optical bits (solitons). Their interplay with noise will be in particular explored in view of studying the behavior of noise-sustained localized patterns.

The characterization of the existence, stability features, dynamical evolution, interaction, and bifurcation diagram of localized complex states will allow us an adequate handling of complex localized states and glimpse novel potential applications.

As mentioned before, we plan to study the statistics and properties of spatial localized intense events in different experimental configurations such as cavity and feedback systems. More specifically, we will explore their localization properties as well as the influence of the convective nature of the system in their statistical properties.