Silicon Nanocrystals in Silica - Novel Active Waveguides for Nanophotonics

Nanophotonic structures combining electronic confinement in nanocrystals with photon confinement in photonic structures are potential building blocks of future Si-based photonic devices. Here, we present a detailed optical investigation of active planar waveguides fabricated by Si+-ion implantation (400 keV, fluences from 3 to 6×1017 cm-2) of fused silica and thermally oxidized Si wafers. Si nanocrystals formed after annealing emit red-IR photoluminescence (PL) (under UV-blue excitation) and define a layer of high refractive index that guides part of the PL emission. Light from external sources can also be coupled into the waveguides (directly to the polished edge facet or from the surface by applying a quartz prism coupler). In both cases the optical emission from the sample facet exhibits narrow polarization-resolved transverse electric and transverse magnetic modes instead of the usual broad spectra characteristic of Si nanocrystals. This effect is explained by a theoretical model which identifies the microcavity-like peaks as leaking modes propagating below the waveguide/substrate boundary. We present also permanent changes induced by intense femtosecond laser exposure, which can be applied to write structures like gratings into the Si-nanocrystalline waveguides. Finally, we discuss the potential for application of these unconventional and relatively simple all-silicon nanostructures in future photonic devices

Waveguide Cores Containing Silicon Nanocrystals as Active Spectral Filters for Silicon-based Photonics

Layers of densely packed luminescent Si nanocrystals embedded in fused silica act as wavelength-specific planar waveguides that filter the wide-band spontaneous emission. The waveguides' light output consists of two spectrally narrow (∼ 10 nm), orthogo

A System for Conducting Surface Science with Attosecond Pulses

We report the development of an apparatus to allow time resolved photoelectron spectroscopy of charge motion on solids and structured surfaces with attosecond resolution in an ultra high vacuum environment. The system, connected to the Attosecond Beamline at Imperial College, allows probing of charge dynamics on surfaces and plasmonic fields on structured surfaces with a few-cycle NIR pulse and attosecond pulse trains. The system incorporates novel methods of vibration isolation to eliminate vibrations coupling to sample and optics from mechanical vibrations. An isolated attosecond pulse can also be used with the addition of a multilayer XUV optic. A two-photon photoemission measure of a hot electron population in gold is presented