Abstract

We measure the nonlinear index, n₂, and two-photon absorption coefficient, β, for both bulk AlGaAs and AlGaAs/GaAs multiple-quantum-well (MQW) waveguides near half-gap and obtain favorable figures of merit. In addition, using time-resolved pump-probe measurements, we observe for the first time cross-Raman gain at frequencies less than 30 cm⁻¹. A rule of thumb for all-optical switching and quantum optics applications is that a π-phase shift must be obtained with less than 3 dB of absorption, which means that the figure of merit F_m = (2n₂/βλ) must be larger than one.¹ Although we measure an n₂ up to 1.7 times larger in the MQW, we obtain nearly the same value for the figure of merit F_m = 13 in both the bulk material and the MQW because of increased two-photon absorption.

© 1992 Optical Society of America