Ultrafast nonlinear tuning of the reflection properties of AlGaAs photonic crystal waveguides by two-photon absorption

We have studied the power-dependent wavelength shift of photonic coupling resonances of a two-dimensional photonic crystal waveguide by reflection geometry pump-probe measurements. The quadratic response is indicative of two-photon induced carrier creation, which alters the refractive index of the semiconductor core of the photonic lattice. A free-carrier model is used to simulate the phenomenon, giving values of the change in refractive index per unit carrier density that satisfactorily compare to values calculated for bulk AlGaAs under similar conditions. Time-resolved spectra are also presented, showing relaxation times of <10 ps which are consistent with surface recombination times in the patterned waveguide. (C) 2004 American Institute of Physics.