Optical Nonlinearities in Chalcogenide Glasses and their Applications Photonics which uses photons for information and image processing has been labeled the technology of the 21st century for which non linear optical processes provide the key functions of frequency conversion and optical switching. Chalcogenide glass fiber is one of the most promising candidates for use as a non linear optical medium because of its high optical nonlinearity and long interaction length. Since the chalcogenide glass fibers transmit into the IR there are numerous potential applications in the civil medical and military areas. One of the most exciting developments in the future is going to be in the area of rare earth ion doping of chalcogenide fibers for IR fluorescence emission. The IR light sources lasers and amplifiers developed using this phenomena will be very useful in civil medical and military applications. Remote IR spectroscopy and imaging using flexible fibers will be realized for applications. Other future research areas which will inevitably be explored includes non linear optical properties of these IR glasses. High speed optical communication requires ultra fast all optical processing and switching capabilities. The Kerr non linearity an ultrafast optical non linearity is often used as the basic switching mechanism. A practical small device that can be switched ~ 1 pJ energies requires a large Kerr effect with minimal losses (both linear and non linear). Chalcogenides have a Kerr non linearity hundred of times larger that silica making them excellent and unique for ultrafast all optical devices. Results of non linearity of chalcogenide glasses indicate the great potential of some of these glasses for all optical switching and all optical processing devices. Keywords: All Optical Switching Amorphous Semiconductors Chalcogenide Glasses Glasses for Integrated Optics