Efficient broadband silicon-on-insulator grating coupler with low backreflection.

We design and fabricate an efficient broadband grating coupler on a 400 nm thick silicon-on-insulator wafer. The measured coupling loss is 3 dB when coupling to a single-mode fiber at 1310 nm wavelength with TE polarization. The spectral FWHM and backreflection are determined to be 58 nm and -27 dB, respectively.

Nonlinear-optical phase modification in dispersion-engineered Si photonic wires.

The strong dispersion and large third-order nonlinearity in Si photonic wires are intimately linked in the optical physics needed for the optical control of phase. By carefully choosing the waveguide dimensions, both linear and nonlinear optical properties of Si wires can be engineered. In this paper we provide a review of the control of phase using nonlinear-optical effects such as self-phase and cross-phase modulation in dispersion-engineered Si wires. The low threshold powers for phase-changing effects in Si-wires make them potential candidates for functional nonlinear optical devices of just a few millimeters in length.

Cross-phase modulation-induced spectral and temporal effects on co-propagating femtosecond pulses in silicon photonic wires.

By performing time-resolved experiments and power-dependent measurements using femtosecond pulses inside submicron cross-section Si photonic-wire waveguides, we demonstrate strong cross-phase modulation (XPM) effects. We find that XPM in Si wires can be significant even for low peak pump powers, i.e., ~15 mW for pi phase shift. Our experimental data closely match numerical simulations using a rigorous coupled-wave theoretical treatment. Our results suggest that XPM is a potentially useful approach for all-optical control of photonic devices in Si wires.

Supercontinuum generation in silicon photonic wires.

We observe spectral broadening of more than 350 nm, i.e., a 3/10-octave span, upon propagation of ultrashort 1.3-mum-wavelength optical pulses in a 4.7-mm-long silicon-photonic-wire waveguide. We measure the wavelength dependence of the spectral features and relate it to waveguide dispersion and input power. The spectral characteristics of the output pulses are shown to be consistent, in part, with higher-order soliton radiative effects.

Ultrafast-pulse self-phase modulation and third-order dispersion in Si photonic wire-waveguides.

By propagating femtosecond pulses inside submicron-crosssection Si photonic-wire waveguides with anomalous dispersion, we demonstrate that the pulse-propagation dynamics is strongly influenced by the combined action of optical nonlinearity and up to third-order dispersion with minimal carrier effects. Because of strong light confinement, a nonlinear phase shift of a few pi due to self-phase modulation is observed at a pulse peak-power of just ~250 mW. We also observe soliton-emitted radiation, fully supported by theoretical analysis, from which we determine directly the third-order dispersion coefficient, beta(3) = -0.73 +/- 0.05 ps(3)/m at 1537 nm.

Conformal dielectric overlayers for engineering dispersion and effective nonlinearity of silicon nanophotonic wires.

We introduce and study numerically a method for dispersion engineering of Si nanophotonic wires using a thin conformal silicon nitride film deposited around the Si core. Simulations show that this approach may be used to achieve the dispersion characteristics required for broadband, phase-matched, four-wave mixing processes, while simultaneously maintaining strong modal confinement within the Si core for high effective nonlinearity.