POLARIZATION AND FIELD-DEPENDENT 2-PHOTON ABSORPTION IN GAAS/ALGAAS MULTIQUANTUM WELL WAVE-GUIDES IN THE HALF-BAND GAP SPECTRAL REGION

We report the observation of two photon absorption which is strongly dependent on the applied electric field and the optical polarization. At 1.55-mu-m wavelength, the two-photon absorption coefficient of the GaAs/AlGaAs multiquantum well (MQW) waveguides for transverse-magnetic light is about seven times lower than for transverse-electric polarized light and changes by a factor of approximately 4 for a change in applied direct-current electric field of approximately 140 kV/cm. Ultrafast nonlinear refraction causing phase changes of over pi-radians without appreciable excess loss is observed. These measurements demonstrate that GaAs/AlGaAs MQW waveguides could be successfully used for subpicosecond all-optical switching near half-band gap, at wavelengths corresponding to the 1.55-mu-m optical communications band.