Studies of long-pulse responses in four-wave mixing using a step-modulated probe

An experimental method for examining temporal responses of nonlinear materials has been studied using four-wave mixing with pulses having widths on the order of 100 ns. By using a special probe pulse modulation technique, fast resonant nonlinear mechanisms can be detected in the presence of dominant thermal mechanisms. In addition, the relative strengths of the fast and slow nonlinearities as they appear in the experiment can be estimated by comparing the experimental results to those of a simple theoretical model. Results for several known materials are presented that demonstrate the method and its sensitivity for detecting fast mechanisms. Methods of increasing the sensitivity are discussed.<
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