Micromanipulation of InP lasers with optoelectronic tweezers for integration on a photonic platform.

The integration of light sources on a photonic platform is a key aspect of the fabrication of self-contained photonic circuits with a small footprint that does not have a definitive solution yet. Several approaches are being actively researched for this purpose. In this work we propose optoelectronic tweezers for the manipulation and integration of light sources on a photonic platform and report the positional and angular accuracy of the micromanipulation of standard Fabry-Pérot InP semiconductor laser die.

Two-photon absorption and all-optical modulation in germanium-on-silicon waveguides for the mid-infrared.

The nonlinear absorption properties of a germanium-on-silicon waveguide have been characterized across the two-photon absorption (TPA) transmission window. The results show that the TPA parameters in germanium waveguides are much stronger than the peak values in silicon, in good agreement with selected measurements conducted in bulk materials. Exploiting the large nonlinear absorption near the bandedge, efficient all-optical modulation is achieved with a modulation depth of ∼8  dB and a response time <5  ps.

Mid-infrared all-optical modulation in low-loss germanium-on-silicon waveguides.

All-optical modulation has been demonstrated in a germanium-on-silicon rib waveguide over the mid-infrared wavelength range of 2-3 μm using a free-carrier absorption scheme. Transmission measurements have shown the waveguides to have low propagation losses that are relatively independent of wavelength out to 3.8 μm, indicating that the modulation could be extended further into the mid-infrared region for applications in sensing and spectroscopy.

Functional properties of human ferroportin, a cellular iron exporter reactive also with cobalt and zinc.

Iron homeostasis is achieved by regulating the intestinal absorption of the metal and its recycling by macrophages. Iron export from enterocytes or macrophages to blood plasma is thought to be mediated by ferroportin under the control of hepcidin. Although ferroportin was identified over a decade ago, little is understood about how it works.

Observations of ejecta clouds produced by impacts onto Saturn's rings.

We report observations of dusty clouds in Saturn's rings, which we interpret as resulting from impacts onto the rings that occurred between 1 and 50 hours before the clouds were observed. The largest of these clouds was observed twice; its brightness and cant angle evolved in a manner consistent with this hypothesis. Several arguments suggest that these clouds cannot be due to the primary impact of one solid meteoroid onto the rings, but rather are due to the impact of a compact stream of Saturn-orbiting material derived from previous breakup of a meteoroid.