Group of Lange and Ackemann
Nonlinear optics and quantum optics
Institute of Applied Physics
WWU Münster

Single-mirror feedback systems

A conceptually particularly simple scheme which already forms optical patterns consists of a thin slice of a nonlinear medium and a distant plane reflector ( d´Alessandro 1991). During the propagation of the transmitted beam to the mirror and back, different points in the transverse plane are coupled by diffraction. Diffraction also converts phase in amplitude modulation which in turn can change the refractive index of the nonlinear medium and thus close the feedback loop (click here for a more detailed description of the mechanism of the instability). The wavelength of the pattern to emerge scales with the square root of the cell to mirror distance d. This scale can be explained by the Talbot-effect. Current projects in optical pattern formation are

Polarization Patterns

Hexagons, flowers and dynamical phenomena in a quasi-scalar situation

Formation of superlattices and quasiperiodic optical patterns

Dynamics of patterns and spatio-temporal structures

Intrinsic dynamics: spirals and target patterns

Drift Instability/ Locking

Localized Structures

List of publications