Colloidal quantum dots for guided wave photonics : from optical gain to ultrafast modulation

Silicium is gekend bij het grote publiek als de bouwsteen voor micro-elektronische circuits op 'chips'. Maar het materiaal is ook uitstekend geschikt voor het bouwen van 'fotonische' chips, waar licht in plaats van elektriciteit wordt gebruikt om informatie over te dragen. Door hetzelfde materiaal te gebruiken, kan de 'fotonica' zo reuzensprongen maken naar commercialisatie. Silicium is prima om licht geleiden en te filteren, maar schiet tekort op vlak van modulatie en versterking. In dit doctoraat worden de mogelijkheden bekeken om die tekortkomingen op te lossen met behulp van een nieuw soort materiaal: 'quantum dots' of nano-kristallen, een duizendste van een micrometer groot. Door hun waanzinnig kleine afmetingen vertonen deze bouwblokjes interessante optische eigenschappen die de limieten van silicium en de silicium-fotonica kunnen remediëren

Are the new and old EU countries financially integrated?

During the last four years, the eight Eastern European countries that joined the EU in 2004 have made significant strides toward financial integration with the EU. Several pieces of evidence support this finding. First, yields on long-term sovereign bonds in accession countries have converged towards EU levels. This is true for both bonds denominated in local currency and bonds denominated in euro. Second, while the issuance of euro-denominated corporate bonds from accession countries is limited, yields on existing corporate bonds are in line with those in the old EU countries. Third, margins in the banking sector have narrowed, which is consistent with the integration of banking markets. Finally, we note that the current stock market rally is consistent with equity market integration.financial integration, Eastern Europe, EU enlargement

Optical properties of SOI waveguides functionalized with close-packed quantum dot films

It is shown that dipolar coupling between neighboring quantum dots enhances the absorption of light in close packed monolayers of colloidal quantum dots. Based on this concept, the experimentally determined losses in planarized waveguides coated by a quantum dot monolayer can be successfully simulated. These simulations rely on replacing the quantum dot layer by an effective medium with a dielectric function determined by dipolar coupling and use the dielectric constant of the quantum dot host medium as the only adjustable parameter. This leads to a generic approach for the simulation of optical materials including close packed quantum dot layers

Absorption enhancement in 2D nanocrystal superlattices through near-field dipolar coupling: a novel optical phenomenon at the nanoscale

We demonstrate giant and broadband enhancement of the nanocrystal absorption cross section in close packed nanocrystal superlattices, which is the first report on a collective optical phenomenon in this type of self-assembled metamaterials to date

Nearly Blinking-Free, High-Purity Single-Photon Emission by Colloidal InP/ZnSe Quantum Dots

Colloidal core/shell InP/ZnSe quantum dots (QDs), recently produced using an improved synthesis method, have a great potential in life-science applications as well as in integrated quantum photonics and quantum information processing as single-photon emitters. Single-particle spectroscopy of 10-nm QDs with 3.2-nm cores reveals strong photon antibunching attributed to fast (70-ps) Auger recombination of multiple excitons. The QDs exhibit very good photostability under strong optical excitation. We demonstrate that the antibunching is preserved when the QDs are excited above the saturation intensity of the fundamental-exciton transition. This result paves the way towards their usage as high-purity on-demand single-photon emitters at room temperature. Unconventionally, despite the strong Auger blockade mechanism, InP/ZnSe QDs also display very little luminescence intermittency ("blinking"), with a simple on/off blinking pattern. The analysis of single-particle luminescence statistics places these InP/ZnSe QDs in the class of nearly blinking-free QDs, with emission stability comparable to state-of-the-art thick-shell and alloyed-interface CdSe/CdS, but with improved single-photon purity.Comment: 15 pages, 5 figure