This proposal will study phenomena associated with the reflection and transmission of high intensity light at nonlinear interfaces, and the development of optical devices based on the observed effects. Because of its giant nonlinearities, a dye solution will be investigated as the nonlinear medium, using a CW argon laser. This offers a unique opportunity to test existing theories on nonlinear interface effects, such as bistability, beam trapping along the interface, intensity dependent k-vector. To study the more complex dynamics of reflection at saturable absorption interface, the amplitude and phase of reflected and incident ultrashort pulses will be measured, using single shot diagnostic techniques. Femtosecond resolved fluorescence as well as the reflection in amplitude and phase of a probe pulse will be used to monitor the complex susceptibility of the nonlinear medium behind the interface. A new time resolved femtosecond imaging technique will monitor the reflected pattern of intensity dependent k vectors. Direct applications that will be investigated include the nonlinear switch active and passive (important for mode-locking applications), an energy or intensity limiter, and an induced symmetrical waveguide.
