Nonlinear control of multicolor beams in coupled optical waveguides

Photonic structures with a periodic modulation of the optical refractive index play an important role in the studies of the fundamental aspects of wave dynamics [1, 2]. In particular, photonic crystals, layered media, or closely spaced optical waveguides enable manipulation of the key phenomena governing optical beam propagation: spatial refraction and diffraction. Arrays of coupled optical waveguides are particularly attractive as an experimental testbed due to their easier fabrication and characterization, as well as because of the opportunities they offer for enhanced nonlinear effects as a result of the large propagation distances in such structures. The physics of beam propagation in optical waveguide arrays is governed by the coupling of light between neighboring waveguides and the subsequent interference of the coupled light. Since both the coupling and the interference processes are sensitive to the light wavelength, the output intensity profiles can be drastically different for each spectral component of the input beam. This is a particular concern in many practical cases, including ultra-broad bandwidth optical communications, manipulation of ultra-short pulses or supercontinuum radiation, where the bandwidth of the optical signals can span over a wide frequency range.