Nondegenerate Two-Photon Absorption in GaAs/AlGaAs Multiple Quantum Well Waveguides

Abstract

We present femtosecond pump-probe measurements of the nondegenerate (1960nm excitation and 1176--1326nm probe) two-photon absorption spectra of 8 nm GaAs/12nm Al${}_{0.32}$Ga${}_{0.68}$As quantum well waveguides. Experiments were performed with light pulses co-polarized normal and tangential to the quantum well plane. The results are compared to perturbative calculations of transition rates between states determined by the $\mathbf{k}\cdot \mathbf{p}$ method with an 8 or 14 band basis. We find excellent agreement between theory and experiment for normal polarization, then use the model to support predictions of orders-of-magnitude enhancement of nondegenerate two-photon absorption as one constituent photon energy nears an intersubband resonance.

13 pages, 8 figures