Soliton-effect pulse compression and propagation has been experimentally demonstrated in the temporal domain in fibers [1], fiber Bragg gratings [2], photonic crystal fibers (PhCF) [3][4][5][6], photonic nanowires [7] and in the spectral domain of integrated channel waveguides [8,9].Here we demonstrate the first experimental observations of soliton-effect pulse compression in semiconductor photonic crystal waveguides (PhCWG) in the temporal domain. Pulse compression in the PhCWGs occurs due to the interaction between a strong group-velocity dispersion (GVD) [10] and slow-light enhanced self-phase modulation (SPM) in the periodic dielectric media [11]. Compression of 3 ps input pulses to a minimum pulse duration of 580 fs (~10 pJ) is achieved. The small modal area A eff ~ 10 -13 m 2 combined with a slow-light enhanced optical field allow for ultra-low threshold (~GW/cm 2 ) pulse compression at millimeter length scales. These results open the way for femtosecond and soliton applications on the chip scale.Periodic dielectric structures have long been known to have extremely large dispersion thus enabling observation of soliton effects at centimeter length scales [2,[12][13][14]. The decreased interaction length, however, requires a correspondingly larger intensity-dependent nonlinear effect to match the strength of the dispersion. Increasing the optical intensity inside the waveguide is accomplished through: (a) direct input of larger peak powers; (b) decreasing the effective modal area [7][8][9]; or, most recently, (c) via dispersion-engineered periodic slow-light structures [10,11]. At the so-called slow-light frequencies of PhCWGs, the light experiences a longer effective path length through the lattice via multiple Bragg reflections, leading to an enhanced local field density. The enhanced field scales inversely with the group velocity, thus

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We demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The observations agree well with a coupled-mode model incorporating all relevant nonlinearities. The low switching energy (∼120 fJ), small energy absorption (∼10 fJ), fast on-off response (∼15 ps), limited only by carrier lifetime, and a minimum 10 dB modulation depth suggest practical all-optical switching applications at high repetition rates.

Light transmission measurements and frequency-delay reflectometry maps for GaAs photonic crystal membranes are presented and analyzed, showing the transition from propagation with a well-defined group velocity to a regime completely dominated by disorder-induced coherent scattering. Employing a self-consistent optical scattering theory, with only statistical functions to describe the structural disorder, we obtain excellent agreement with the experiments using no fitting parameters. Our experiments and theory together provide clear physical insight into naturally occurring light localization and multiple coherent-scattering phenomena in slow-light waveguides.

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