Spatiotemporal multimode light waves

Nonlinear propagation of optical pulses in multimode fibers is subject to complex spatio-temporal phenomena. We outline different strategies for the control and optimization of nonlinear mode coupling. The first approach involves transverse wavefront shaping of the input beams, which permits to launch an optimized mode combination, that results in the generation of a stable nonlinear mode alphabet at the fiber output. The second approach involves the longitudinal variation of the core diameter of multimode active and passive tapers, which leads to tailored supercontinuum generation with high spatial beam quality.