Temporal modulation of the control parameter in electroconvection in the nematic liquid crystal I52

I report on the effects of a periodic modulation of the control parameter o n electroconvection in the nematic liquid crystal I52. Without modulation, the primary bifurcation from the uniform state is a direct transition to a state of spatiotemporal chaos. This state is the result of the interaction of four degenerate traveling modes: right and left zig and zag rolls. Perio dic modulations of the driving voltage at approximately twice the traveling frequency are used. For a large enough modulation amplitude, standing wave s that consist of only zig or zag rolls are stabilized. The standing waves exhibit regular behavior in space and time. Therefore, modulation pf the co ntrol parameter represents a method of eliminating spatiotemporal chaos. As the modulation frequency is varied away from twice the traveling frequency , standing waves that are a superposition of zig and zag rolls, i.e., stand ing rectangles, are observed. These results are compared with existing pred ictions based on coupled complex Ginzbug-Landau equations.