We report nonlinear measurements on 80μm silicon photonic crystal waveguides that are designed to support dispersionless slow light with group velocities between c/20 and c/50. By launching picosecond pulses into the waveguides and comparing their output spectral signatures, we show how self phase modulation induced spectral broadening is enhanced due to slow light. Comparison of the measurements and numerical simulations of the pulse propagation elucidates the contribution of the various effects that determine the output pulse shape and the waveguide transfer function. In particular, both experimental and simulated results highlight the significant role of two photon absorption and free carriers in the silicon waveguides and their reinforcement in the slow light regime.

Efficient on-chip molecule and bio-agent detection can be achieved by accessing strong molecular absorption lines in the mid-infrared, but it requires high output power broadband mid-IR sources. Here, we report supercontinuum generation in an air-clad ${\mathrm{Si}}_{0.6}{\mathrm{Ge}}_{0.4}/\mathrm{Si}$ waveguide that emits a broad spectrum spanning from 3.0 μm to 8.5 μm. These waveguides have anomalous dispersion and low propagation loss ($<0.4\mathrm{dB}/\mathrm{cm}$) in the mid-IR, which leads to a supercontinuum output with a high average power of more than 10 mW on-chip. The realization of broadband mid-IR sources with high spectral brightness makes the SiGe-on-Si platform promising for a wide range of applications.

Efficient nonlinear phenomena in integrated waveguides imply the realization in a nonlinear material of tightly confining waveguides sustaining guided modes with a small effective area with ultra-low propagation losses as well as high-power damage thresholds. However, when the waveguide cross-sectional dimensions keep shrinking, propagation losses and the probability of failure events tend to increase dramatically. In this work, we report both the fabrication and testing of high-confinement, ultralow-loss silicon nitride waveguides and resonators showing average attenuation coefficients as low as ∼3 dB/m across the S-, C-, and L bands for 1.6-µm-width × 800-nm-height dimensions, with intrinsic quality factors approaching ∼10⁷ in the C band. The present technology results in very high cross-wafer device performance uniformities, low thermal susceptibility, and high power damage thresholds. In particular, we developed here an optimized fully subtractive process introducing a novel chemical-physical multistep annealing and encapsulation fabrication method, resulting in high quality Si₃N₄-based photonic integrated circuits for energy-efficient nonlinear photonics and quantum optics.

We have optimized the molecular-beam epitaxy growth conditions of self-organized $\mathrm{InAs}∕\mathrm{GaAs}$ quantum dots (QDs) to achieve a low density of dots emitting at 1300 nm at low temperature. We used an ultralow InAs growth rate, lower than $0.002\mathrm{ML}∕\mathrm{s}$ , to reduce the density to $2\text{dots}∕\mu {\mathrm{m}}^2$ and an InGaAs capping layer to achieve longer emission wavelength. Microphotoluminescence spectroscopy at low-temperature reveals emission lines characteristic of exciton-biexciton behavior. We also study the temperature dependence of the photoluminescence, showing clear single QD emission up to 90 K. With these results, $\mathrm{InAs}∕\mathrm{GaAs}$ QDs appear as a very promising system for future applications of single photon sources in fiber-based quantum cryptography.