Pattern formation

We are interested in the role of noise and fluctuations in spatially extended dynamical systems and we have been studying this using an experimental arrangement composed of a liquid crystal light valve in an optical feedback loop. This system offers very large space bandwidth product and can be used with relatively low power lasers. Other advantages are that it is quite easy to limit the range of spatial frequencies and you can introduce external perturbations. We have carried out experiments both here at Cal Poly and at the Istituto Nazionale di Ottica Applicata (INOA), Florence.

We have studied stochastic resonance and shown how the local coupling of oscillators can enhance the SR response (PRE 62, 1413, 2000, PRE, 67, 056222, 2003)

San Luis Obispo system

Florence system

In collaboration with P. L. Ramazza in Florence, we were the first to show experimentally the constructive effects of parameter modulation in a two-dimensional optical system. (PRL, 96, 094101, 2006)

The pictures show, reading L-R, the effects of light modulation at frequencies of 6, 14, 20 and 200 Hz. The clearest hexagonal patterning occurs at 14 Hz, a frequency comparable to the inverse relaxation time of the LCLV.

We were able to explain the formation of these patterns using a combination of computer simulation and weakly nonlinear theory.

Collaborators

P. L. Ramazza, INOA, Florence

K. Saunders, Physics, Cal Poly