Mode-locked ultrashort pulse generation from on-chip normal dispersion microresonators.

We describe generation of stable mode-locked pulse trains from on-chip normal dispersion microresonators. The excitation of hyperparametric oscillation is facilitated by the local dispersion disruptions induced by mode interactions. The system is then driven from hyperparametric oscillation to the mode-locked state with over 200 nm spectral width by controlled pump power and detuning. With the continuous-wave-driven nonlinearity, the pulses sit on a pedestal, akin to a cavity soliton. We identify the importance of pump detuning and wavelength-dependent quality factors in stabilizing and shaping the pulse structure, to achieve a single pulse inside the cavity. We examine the mode-locking dynamics by numerically solving the master equation and provide analytic solutions under appropriate approximations.

Enhanced Raman scattering in slow-light photonic crystals for chip-scale frequency conversion and optical amplification.

We present measurements of enhanced Raman scattering in silicon slow-light photonic crystal waveguides. By utilizing both the Bragg gap edge dispersion of TM-like modes for pump enhancement and the TE-like fundamental mode onset for Stokes enhancement, a six-fold increase in the spontaneous Raman scattering was observed in the double slow-light regime. Both forward and backward Stokes signals are examined, with continuous-wave measurements, in our low-loss photonic crystal membranes. The measured nonlinear enhancement matches well with our numerical model and simulations, and are described in detail in this paper. These observations support the development of chip-scale frequency conversion and optical amplification in silicon nanophotonics.

Observation of zeroth-order band gaps in negative-refraction photonic crystal superlattices at near-infrared frequencies.

We present the first observations of zero-n[over ] band gaps in photonic crystal superlattices consisting of alternating stacks of negative-index photonic crystals and positive-index dielectric materials in the near-infrared range. Guided by ab initio three-dimensional numerical simulations, the fabricated nanostructured superlattices demonstrate the presence of zeroth-order gaps in remarkable agreement with theoretical predictions across a range of different superlattice periods and unit cell variations. These volume-averaged zero-index superlattice structures present a new type of photonic band gap, with the potential for complete wave front control for arbitrary phase delay lines and open cavity resonances.