All-optical multiplexing of femtosecond signals using an AlGaAs nonlinear directional coupler

One of the most powerful applications of integrated all optical switching devices is the multi/demultiplexing of high repetition rate signals. All-optical demultiplexing using nonlinear directional couplers (NLDC) has been successfully demonstrated in recent years[1]. All-optical multiplexing has also been demonstrated using fibers[2]. However, because of the weak nonlinearity in the fiber, fiber lengths on the order of kilometers are required. Thus, such devices suffer from long transit times which can be unacceptable. The passive means of multiplexing, using 3 dB couplers, Y-junctions and such, suffer from a 3 dB loss. Using strong pump pulses to control a signal pulse train through cross-phase modulation, we demonstrate an efficient and compact method of multiplexing femtosecond signals using a NLDC.