Radiation frequency switching in quadratically nonlinear tunnel-coupled optical waveguides

Analytical and numerical investigations are reported of all-optical switching of radiation from frequency 2ω to frequency ω (and conversely) in quadratically nonlinear tunnel-coupled optical waveguides under conditions of phase matching of the coupled modes. The solutions are found and analysed for fields at both frequencies in different waveguides. Simple formulas are derived for describing such switching, including a formula for the differential intensity gain of a signal.