Intersubband Third-Order Nonlinearities in a GaAs/AIGaAs Step Quantum Well Structure by Phase Conjugation Method

In this letter,we present the observation of phase conjugation at 9.27μm in a GaAs/AlGaAs multiple step quantum well structure.The response is caused by the nearly resonant intersubband transition.The magnitude of X^((3))determined by this phase conjugation method is about 8×10^(-5)esu and the phase conjugate reflectivityηis about 6×10^(-3)uncorrected for Fresnel reflections.