Nanoscale porous silicon waveguide for label-free DNA sensing.

Porous silicon (PSi) is an excellent material for biosensing due to its large surface area and its capability for molecular size selectivity. In this work, we report the experimental demonstration of a label-free nanoscale PSi resonant waveguide biosensor. The PSi waveguide consists of pores with an average diameter of 20nm.

Generation of spin currents via Raman scattering.

We show theoretically that stimulated spin-flip Raman scattering can be used to inject spin currents in doped semiconductors with spin-split bands. A pure spin current, where oppositely oriented spins move in opposite directions, can be injected in zinc blende crystals and structures. The calculated spin current should be detectable by pump-probe optical spectroscopy and anomalous Hall effect measurement.

Pure spin current from one-photon absorption of linearly polarized light in noncentrosymmetric semiconductors.

We show that one-photon absorption of linearly polarized light should produce pure spin currents in noncentrosymmetric semiconductors, including even bulk GaAs. We present 14x14 k.p model calculations of the effect in GaAs, including strain, and pseudopotential calculations of the effect in wurtzite CdSe.

Quantum interference control of ballistic pure spin currents in semiconductors.

We demonstrate all-optical quantum interference injection and control of a ballistic pure spin current (without an accompanying charge current) in GaAs/AlGaAs quantum wells, consisting of spin-up electrons traveling in one direction and spin-down electrons traveling in the opposite direction. This current is generated through quantum interference of one- and two-photon absorption of approximately 100 fs phase-locked pulses that have orthogonal linear polarizations. We use a spatially resolved pump-probe technique to measure carrier movement of approximately 10 nm.