Femtosecond dynamics of the nonlinear index near the band edge in AlGaAs waveguides

The transient behavior of the nonresonant nonlinear index is investigated in AlGaAs waveguides with femtosecond time resolution. Both the refractive index and the absorption changes are measured by time division interferometry and pump probe techniques. Different mechanisms which contribute to the nonlinear index are distinguished by examining their dynamics, including the optical Stark effect, resonantly excited carriers, and two‐photon absorption processes. The relative contribution from each mechanism is a strong function of wavelength near the band edge.

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