Control of spatio-temporal complexity in nonlinear optics

Spatio-temporal complexity is a common phenomenon in nonlinear optics. The coupling of diffraction with optical nonlinearities often leads to regular or irregular spatial structures either stationary, oscillatory or temporally erratic. In order to utilise the large flexibility of spatially extended optical systems, control is necessary. Here we provide evidence of successful control techniques developed for models of nonlinear optical devices. Application of standard methods for the control of chaos lead to stabilisation of multi-transverse mode lasers at low pump values. Phase masks are used to control the position of Optical Bullet Holes (localised structures in the plane perpendicular to the direction of light propagation). Stabilisation, selection and tracking of unstable patterns is achieved by control techniques using instantaneous feedback appropriately filtered in Fourier space. Finally, elimination of spatio-temporal disorder is demonstrated in a wide variety of nonlinear optical systems by generalising the Fourier method devised for the control of unstable spatio-temporal structures.