Spatio-temporal coherent molding and retrieval of pulsed signals in optical waveguides.

Optical waveguides are key elements for high-fidelity, long-distance optical communications. Coupled waveguide arrays allow for higher information density, steering the propagation direction, and encoding information. However, due to the mixing of relative phases for short pulses containing multiple waveguide-mode frequencies, a process for retrieving an encoded input state once these signals undergo coherent propagation remains elusive. A concept is presented to extract with high fidelity the phase-encrypted input signal from spatio-temporally propagated states. As a realization, an array of coupled waveguides is suggested, with the retrieval mechanism being realized by local phase shifts that comply with the identified retrieval concept. Three-dimensional full-wave electromagnetic simulations for broadband optical signals in coupled dielectric waveguides confirm the validity of the scheme and the high fidelity of information retrieval, pointing to potential applications, for instance, in ultrafast coherent coding and decoding of information imprinted on pulse sequences.