Which group velocity of light in a dispersive medium?

The interaction between a light pulse, traveling in air, and a generic linear, non-absorbing and dispersive structure is analyzed. It is shown that energy conservation imposes a constraint between the group velocities of the transmitted and reflected light pulses. It follows that the two fields propagate with group velocities depending on the dispersive properties of the environment (air) and on the transmission properties of the optical structure, and are one faster and the other slower than the incident field. In other words, the group velocity of a light pulse in a dispersive medium is reminiscent of previous interactions. One example is discussed in detail.Comment: To be submitted on PR

Engineering the Photonic Density of States with metamaterials

The photonic density of states (PDOS), like its' electronic coun- terpart, is one of the key physical quantities governing a variety of phenom- ena and hence PDOS manipulation is the route to new photonic devices. The PDOS is conventionally altered by exploiting the resonance within a device such as a microcavity or a bandgap structure like a photonic crystal. Here we show that nanostructured metamaterials with hyperbolic dispersion can dramatically enhance the photonic density of states paving the way for metamaterial based PDOS engineering

Газопроницаемость анодированных оксидно-алюминиевых мембран со слоем палладий-рутениевого сплава

Compositions with a layer of palladium-ruthenium alloy 0.2 μm thick on thermally stable and chemically resistant membranes from polycrystal aluminium gamma-oxide covered by tantalum layer, permeable only for hydrogen, have been prepared. Permeability of hydrogen, nitrogen, argon and helium through initial amorphous and polycrystal membranes, as well as through membranes covered by the layers of tantalum tantalum and palladium-ruthenium alloy has been studied. Membranes permeable solely for hydrogen and applicable for isolation of special-purity hydrogen from hot industrial gases and fit for use in membrane reactors of selective hydrogenation have been obtained. 10 refs., 5 fig

Газопроницаемость анодированных оксидно-алюминиевых мембран со слоем палладий-рутениевого сплава

Compositions with a layer of palladium-ruthenium alloy 0.2 μm thick on thermally stable and chemically resistant membranes from polycrystal aluminium gamma-oxide covered by tantalum layer, permeable only for hydrogen, have been prepared. Permeability of hydrogen, nitrogen, argon and helium through initial amorphous and polycrystal membranes, as well as through membranes covered by the layers of tantalum tantalum and palladium-ruthenium alloy has been studied. Membranes permeable solely for hydrogen and applicable for isolation of special-purity hydrogen from hot industrial gases and fit for use in membrane reactors of selective hydrogenation have been obtained. 10 refs., 5 fig