All-optical signal reshaping by four-wave mixing in passive micro-ring resonators

A novel approach for realization of all-optical pulse reshaping in an integrated microring resonator is proposed. The concept presented in this study is based on four-wave mixing in a passive GaAs/AlGaAs microring resonator side coupled to a bus waveguide, taking into account all higher order non-linear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), pump depletion and two-photon absorption (TPA), the latter being the dominant process here. We also include in the description changes in absorption and refractive indexes induced by free-carriers generated by TPA. This scheme is investigated for its regenerative characteristics using an optical pump modulation scheme. The application of the modulation bit stream in the pump wave leads in a conjugate wave power being proportional to the square of the pump power, resulting in a corresponding extinction ratio improvement. Because of the strong TPA, enhanced by the resonance effect, the converted signal power saturates as pump power increases, providing noise suppression at high power levels. A detailed study of the static and dynamic reshaping characteristics of the wavelength converter has been carried out. Its performance, evaluated by extinction ratio (ER) and Q factor calculations, showed satisfactory regenerative properties up to 10Gb/s.