LARGE EXCITONIC NONLINEARITY IN INAS QUANTUM SHEETS

We measure the nonlinearity of the excitonic absorption in isolated InAs planes inserted in a bulk-like GaAs matrix. In cw pump and probe experiments absorption changes as high as 37% are observed at a pumping intensity of 80 W/cm2. The corresponding saturation intensity is 400 W/cm2. The nonlinear absorption cross section is determined to be 1 X 10(-12) cm2, which is in excellent agreement with the theoretical prediction.