Search results for "quantum dot"

Nonlinear Absorption and Refraction of Picosecond and Femtosecond Pulses in HgTe Quantum Dot Films

2021

We report measurements of the saturated intensities, saturable absorption, and nonlinear refraction in 70-nm thick films containing 4 nm HgTe quantum dots. We demonstrate strong nonlinear refraction and saturable absorption in the thin films using tunable picosecond and femtosecond pulses. Studies were carried out using tunable laser pulses in the range of 400–1100 nm. A significant variation of the nonlinear refraction along this spectral range was demonstrated. The maximal values of the nonlinear absorption coefficients and nonlinear refractive indices determined within the studied wavelength range were −2.4 × 10−5 cm2 W−1 (in the case of 28 ps, 700 nm probe pulses) and −3 × 10−9 cm2 W−1 …

UPTAKE OF SILICA COVERED QUANTUM DOTS ON LIVING CELLS: LONG TERM VITALITY AND MORPHOLOGY STUDY ON HYALURONIC ACID BIOMATERIALS

2015

In this work we prepared colloidal CdSe-CdS core-shell nanocrystal emitting @625 nm and, by a micro-emulsion procedure of water in oil inverse micelle, we encapsulated a single dot inside each silica sphere. In this way the nanoparticles became biocompatible, are simply to prepare and could be used also in a water based environment. Moreover, the silica shield is transparent to the wavelengths of interest.

Optical hybrid nanocomposite sensors for selective explosive detection

2022

Durant l'última dècada, la detecció d'artefactes explosius improvisats (IEDs) tant en l'àmbit militar com civil s'ha convertit en una prioritat estratègica en la seguretat nacional a causa de la creixent amenaça terrorista. Encara que les tècniques convencionals, com la cromatografia de gasos acoblada a espectrometria de masses o la difracció de raigs X mostren notables avantatges degut a la seua elevada sensibilitat i selectivitat, una gran part d’aquestes presenten inconvenients, com per exemple processos de mesura lents, instrumentació cara, complexa i voluminosa, que limiten el mostreig en continu i en temps real. Per aquesta raó, existeix una recerca constant per trobar una plataforma …

Time resolved emission at 1.3 μm of a single InAs quantum dot by using a tunable fibre Bragg grating

2013

Photoluminescence and time resolved photoluminescence from single metamorphic InAs/GaAs quantum dots (QDs) emitting at 1.3 mu m have been measured by means of a novel fibre-based characterization set-up. We demonstrate that the use of a wavelength tunable fibre Bragg grating filter increases the light collection efficiency by more than one order of magnitude as compared to a conventional grating monochromator. We identified single charged exciton and neutral biexciton transitions in the framework of a random population model. The QD recombination dynamics under pulsed excitation can be understood under the weak quantum confinement potential limit and the interaction between carriers at the …

Real-space quantum transport in two-dimensional nanostructures in magnetic fields

2013

Fractal dynamics in chaotic quantum transport

2013

Despite several experiments on chaotic quantum transport in two-dimensional systems such as semiconductor quantum dots, corresponding quantum simulations within a real-space model have been out of reach so far. Here we carry out quantum transport calculations in real space and real time for a two-dimensional stadium cavity that shows chaotic dynamics. By applying a large set of magnetic fields we obtain a complete picture of magnetoconductance that indicates fractal scaling. In the calculations of the fractality we use detrended fluctuation analysis -- a widely used method in time series analysis -- and show its usefulness in the interpretation of the conductance curves. Comparison with a s…

Investigation of Nonlinear Optical Processes in Mercury Sulfide Quantum Dots

2022

European Regional Development Fund (1.1.1.5/19/A/003), State Assignment to Higher Educational Institutions of Russian Federation (FZGU-2020-0035), Russian Foundation for Basic Research (18-29-20062). Institute of Solid State Physics, University of Latvia as the Center of Excellence acknowledges funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.

Vertically Aligned Nanowires and Quantum Dots: Promises and Results in Light Energy Harvesting

2023

The synthesis of crystals with a high surface-to-volume ratio is essential for innovative, high-performance electronic devices and sensors. The easiest way to achieve this in integrated devices with electronic circuits is through the synthesis of high-aspect-ratio nanowires aligned vertically to the substrate surface. Such surface structuring is widely employed for the fabrication of photoanodes for solar cells, either combined with semiconducting quantum dots or metal halide perovskites. In this review, we focus on wet chemistry recipes for the growth of vertically aligned nanowires and technologies for their surface functionalization with quantum dots, highlighting the procedures that yie…