Abstract

Induced focusing in a self-defocusing medium¹ is observed in a GaAs/AlGaAs waveguide. The 1.2-μm guiding region of the 127-μm long waveguide consists of sixty periods of 9.7-nm GaAs/9.9-nm AlGaAs multiple quantum wells. Observation of induced focusing is made using 857-nm 10-ps pulses. The pump pulse leads the orthogonally polarized probe pulse by ~30 ps to allow for complete index-profile buildup while minimizing effects of interference and carrier diffusion. Two induced focusing effects corresponding to two different pump-intensity profiles are observed. In the first effect² 150-pJ Gaussian-profile self-defocusing pump copropagates with a 1.5-pJ probe of the same profile but displaced by 1.2 FWHM diameters. Compared to the guide-exit profile in the absence of the pump, the probe profile in the presence of the pump becomes 45% narrower, is deflected away from the pump, and has a 50% higher peak intensity. In the second effect, induced focusing without deflection is achieved using a twin-peak pump followed by a Gaussian probe. The probe-output profile is ~55% narrower with the peak intensity increased by 60%. These results are consistent with two-transverse-dimension beam-propagation modeling using the plasma theory.

© 1991 Optical Society of America