Exciton–exciton scattering in GaAs/AlAs lateral superlattice

We perform time integrated degenerate four-wave mixing (DFWM) measurements to investigate exciton dephasing in a GaAs/AlAs lateral superlattice (LSL) with a tunable band gap modulation. The excitons are resonantly excited by femtosecond laser pulses. Under optimal conditions of growth layer alignment, the ground state excitons in the LSL are 1D. When the LSL growth is highly tilted, the 1D confining potential vanishes and the LSL effectively becomes a 2D system. The DFWM measurements for the 1D and 2D excitons show that the exciton–exciton scattering strength is significantly reduced in the 1D case. We find that disorder in the LSL cannot fully explain the observed large reduction. It is likely that reduction in dimensionality plays an important role in this.