Contents 1. Introduction
All-optical signal processing (e.g. signal regeneration, wavelength conversion and switching) exploiting the nonlinear behaviour of optical devices potentially resolves the communications bottleneck caused by optoelectronic devices and photo-detectors. Generally, the signal processing of broadband signals relies on a nonlinear process that takes place within optical fiber, semiconductor optical amplifier or quasi-phase matched , Optical fiber is favourable for the ultra-fast response of the optical Kerr nonlinearity and its wide bandwidth. However, in contrast with SOA and experiments utilizing centimetre device lengths, fiber-based devices have ordinarily required several kilometre lengths to achieve sufficient nonlinearity, which does not lend well to a compact device or photonic integration. The higher nonlinearity Bismuth oxide glass has been seen as one potential solution [1], though the nonlinearity is not sufficient to enable photonic chip based devices. Chalcogenide glasses appear to resolve these issues and offer a new platform for ultrafast all-optical signal processing in photonic chip based devices. These glasses offer strong third-order nonlinearities over two magnitudes greater than silica, low to moderate nonlinear absorption and strong photosensitivity for inscribing waveguide Bragg gratings [2]. Furthermore, the absence of free carrier effects ensures the virtually instantaneous Kerr response time is maintained, thus permitting near penalty-free processing of high bit rate signals - in stark contrast to many recent SOA based devices.
