Parametric processes in materials presenting a second- or third-order nonlinearity have been widely used to demonstrate a wide range of all-optical signal processing functionalities, including amplication, wavelength conversion, regeneration, sampling, switching, modulation format conver- sion, optical phase conjugation, etc. The recent evolution of optical ber communication systems towards advanced modulation formats making use of the phase dimension, as well as polarization- and, more recently, space-multiplexing, has created new requirements, as well as new opportunities, for parametric all-optical signal processing. In this presentation, we will review our recent results on the demonstration of all-optical para- metric signal processing using dierent nonlinear platforms, including highly nonlinear optical bers (HNLFs), silicon nanowires, and periodically-poled lithium niobate (PPLN) waveguides. In particu- lar, we will show how phase-sensitive processes can be engineered to demonstrate phase-quadrature separation, which we have recently demonstrated in HNLFs  and PPLN waveguides . Silicon nanowires are particularly attractive for signal processing thanks to their compact size, CMOS- compatible fabrication process, degrees of freedom in dispersion engineering, and high nonlinear coecient. However, the detrimental eect of free-carrier absorption induced by two-photon absorp- tion has so far prevented them from being used for the demonstration of phase-sensitive processing. Thanks to the introduction of p-i-n junctions across silicon waveguides, we have recently been able to demonstrate phase-sensitive extinction ratios as high as 20 dB, allowing the phase regeneration of phase-modulated signals under continuous wave pumping operation . One of the well-known limitations of planar waveguide devices for all-optical signal processing is their inherent polarization- sensitivity. We will show how the introduction of polarization-diversity circuits relying on ecient and wideband polarization splitters and rotators  can overcome this limitation. Finally, we will also discuss the introduction of signal processing functionalities that are compatible with the novel dimension of space multiplexing. More specically, we will show how mode-selective wavelength conversion based on four-wave mixing can be realized in a multimode silicon waveguide .
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35th Progress In Electromagnetics Research Symposium, 2014