Kerr and free carrier ultrafast all-optical switching of GaAs/As nanostructures near the three photon edge of GaAs

We performed nondegenerate pump-probe experiments on a GaAs/AlAs photonic cavity structure. We switched the photonic properties using the optical Kerr effect and free carriers excited by three photon absorption. The structure was probed at 1150–1640 nm, in the telecom spectral range below the stop gap. In the measurements we observe surprisingly large nondegenerate electronic Kerr coefficients over a broad wavelength range. We also extracted the three photon absorption coefficient for GaAs at three wavelengths in the near infrared. We conclude that the electronic Kerr effect is so large that the resonance of a moderate Q (Q>1000) photonic cavity could be successfully switched instantaneous.