Active planar optical waveguide made from luminescent silicon nanocrystals

We show experimentally that a layer of silicon nanocrystals, prepared by the Si-ion implantation (with the energy of 400 keV) into a synthetic silica slab and exhibiting room-temperature red photoluminescence, can serve simultaneously as a single-mode planar optical waveguide. The waveguide is shown to self-select guided transverse electric and transverse magnetic modes from the broad photoluminescence emission of the nanocrystals resulting in a substantially narrower emission spectrum for these modes. We further report on an investigation of optical gain in a sample implanted to a dose of 4×1017 cm−2. Despite the occurrence of strong waveguiding, results of the variable stripe length method turned out not to be able to give unambiguous evidence for optical gai

Analysis of trap spectra in LEC and epitaxial GaAs

Different methods of trap parameter measurement are analysed. Transient photoconductivity and thermally stimulated effects were used to investigate the influence of traps in LEC SI-GaAs and high resistivity epitaxial GaAs. The peculiarities of the TSC were analysed and shown to be related to the influence of crystal micro-inhomogeneities.Comment: Invited talk, 6-th Workshop on Gallium Arsenide and Related Compounds June 22-26, 1998 Praha-Pruhonice, Czech Republi

Light amplification due to free and localized exciton states in ZnCdSe GRINSCH structures

International audienceIn this paper we present measurements of light amplification in optically pumped ZnCdSe GRINSCH (graded refraction index separate confinement heterostructures), In several differently designed samples we observe the presence of two gain mechanisms, which involve localized excitons and exciton-exciton inelastic scattering processes, respectively. The influence of the GRINSCH sample structure on gain is discussed in terms of their improved light-guiding properties

Micrometer and sub micrometer-size structures fabricated by direct writing using femtosecond light pulses

In this report we present the results of the sub micrometer-size hillocks and bits recording on the surface and in the volume of dielectric materials using a direct femtosecond laser writing (DFLW) method. Lateral and axial dimensions of fabricated defects were measured (170 ±50) and (440 ±100) nm, respectively. 2D and 3D matrixes with the corresponding densities of 1 Gbit/cm2 and 6 Tbit/cm3 as well as waveguides were recorded using DFLW method

Stimulated emission of optically excited MOVPE grown ZnCdSe-ZnSe GRINSCH quantum well

International audienc

Ultrafast decay of femtosecond laser-induced grating in silicon-quantum-dot-based optical waveguides

Femtosecond transient laser-induced grating (LIG) experiments were performed in planar optical waveguides made of luminescent silicon quantum dots. The LIG was created by interference of two pulses from the frequency-doubled output of a Ti-sapphire lase

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