Observation of phase conjugation at 10.6 μm via intersubband third-order nonlinearities in a GaAs/AlGaAs multi-quantum-well structure

We describe the observation of phase conjugation at 10.6 μm in a GaAs/AlGaAs multi-quantum-well-doped structure. The responsible nonlinear susceptibility χ(3) is due to a nearly resonant intersubband transition. The magnitude of χ(3) is 7×10−5 esu and the phase conjugate reflectivity is a few tenths of a percent.