9320308 Stegeman A broad research program is proposed. 1) Establish experimentally and theoretically the basic physics of cascading; 2) Fabricate waveguides suitable for implementing cascading effects; 3) Investigate all-optical features needed for an optical transistor such as modulation, gain etc. in waveguides; 4) Investigate all- optical switching using cascading in waveguides. The experimental program will be implemented in both bulk media and waveguides. Cascading interactions will first be studied in bulk crystals using Gaussian beams to establish the basic science. Standard second order crystals will be used and will require high power lasers (which we have). In parallel our poled polymer waveguide technology will be developed towards phase-matched SHG. Then, using such waveguides we will investigate low power cascading operations, working towards an optical transistor. The PI's expect that after three years they should be able to assess whether the cascading approach is useful for signal processing in general, and an optical transistor in particular. ***