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

Abstract

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 Ͻ10 ps which are consistent with surface recombination times in the patterned waveguide.

Direct experimental visualization of waves and band structure in 2D photonic crystal slabs

“…Thus any wave with its frequency within the light cone and with a wave vector separated from the light cone by a multiple of the reciprocal lattice vector is 'leaky,' and will eventually scatter away. Leaky modes can be uniquely identified in angle-resolved measurements [45] and have been engineered to enhance the coupling of fluorescent emission for single emitters [46], to improve the extraction efficiency from LEDs [47,48], and to enhance nonlinear interactions [49]. Because the leaky modes decay slowly compared to the subcycle time resolution of our measurement, they are strong features in the experimental dispersion diagrams in figure 3(b).…”