Search results for "Quantum dot laser"
showing 10 items of 20 documents
High-efficiency silicon-compatible photodetectors based on Ge quantum dots
2011
We report on high responsivity, broadband metal/insulator/semiconductor photodetectors with amorphous Ge quantum dots (a-Ge QDs) as the active absorbers embedded in a silicon dioxide matrix. Spectral responsivities between 1-4 A/W are achieved in the 500-900 nm wavelength range with internal quantum efficiencies (IQEs) as high as ∼700%. We investigate the role of a-Ge QDs in the photocurrent generation and explain the high IQE as a result of transport mechanisms via photoexcited QDs. These results suggest that a-Ge QDs are promising for high-performance integrated optoelectronic devices that are fully compatible with silicon technology in terms of fabrication and thermal budget. © 2011 Amer…
MBE growth and properties of low-density InAs/GaAs quantum dot structures.
2011
We present the results of a comprehensive study carried out on morphological, structural and optical properties of InAs/GaAs quantum dot structures grown by Molecular Beam Epitaxy. InAs quantum dots were deposited at low growth rate and high growth temperature and were capped with InGaAs upper confining layers. Owing to these particular design and growth parameters, quantum dot densities are in the order of 4-5x109 cm-2 with emission wavelengths ranging from 1.20 to 1.33 µm at 10 K, features that make these structures interesting for single-photon operation at telecom wavelength. High resolution structural techniques show that In content and composition profiles in the structures depend on …
Characterization of quantum dot/conducting polymer hybrid films and their application to light-emitting diodes.
2009
Quantum dot/conducting polymer hybrid films are used to prepare light-emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution-based processes and are also easily micropatterned. The LEDs exhibit a turn-on voltage of 4 V, an external quantum efficiency greater than 1.5%, and almost pure-green quantum-dot electroluminescence.
Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots
2012
We have investigated the temperature dependent recombination dynamics in two bimodally distributed InAs self assembled quantum dots samples. A rate equations model has been implemented to investigate the thermally activated carrier escape mechanism which changes from exciton-like to uncorrelated electron and hole pairs as the quantum dot size varies. For the smaller dots, we find a hot exciton thermal escape process. We evaluated the thermal transfer process between quantum dots by the quantum dot density and carrier escape properties of both samples. © 2012 American Institute of Physics.
Absorption spectroscopy of single InAs self-assembled quantum dots
2004
Abstract Excitonic transitions of single InAs self-assembled quantum dots were directly measured at 4.2 K in an optical transmission experiment. We use the Stark effect in order to tune the exciton energy of a single quantum dot into resonance with a narrow-band laser. With this method, sharp resonances in the transmission spectra are observed. The oscillator strengths as well as the homogeneous line widths of the single-dot optical transitions are obtained. A clear saturation in the absorption is observed at modest laser powers.
Single Photon Emission from Site-Controlled InAs Quantum Dots Grown on GaAs(001) Patterned Substrates
2009
5 páginas, 5 figuras.
Optical properties of exciton confinement in spherical ZnO quantum dots embedded in matrix
2009
Abstract The optical characteristics of ZnO nanoparticles in SiO2 matrix have been determined by UV–visible and photoluminescence (PL) studies. The PL spectrum of the ZnO quantum dots shows two different bands: the first one is a broad green emission band related to deep level emission in the visible range and the second one is situated at 3.48 eV in the ultraviolet region, and is attributed to the recombination of electrons in the conduction band and holes in the valence band. The experimental result that we found was simulated numerically using different methods. Our calculations revealed a good agreement between the matrix element calculation method and the experimental result. We have a…
Multi-gigahertz repetition-rate-selectable passive harmonic mode locking of a fiber laser
2013
We demonstrate a passive harmonically mode-locked erbium-doped fiber laser that operates at selectable harmonics spanning from the 6th to the 928th, which corresponds to repetition rates ranging from 153 MHz to 22.2 GHz. The noteworthy laser output stability is attested by supermode suppression levels as large as 41 dB. The influence of a continuous wave background on harmonics stability is tested.
Ultrafast Gain Recovery in Quantum Dot based Semiconductor Optical Amplifiers
2007
Summary form only given. The limiting factor in ultrahigh bit rate amplification is the ultrafast population recovery in the resonant level, which is mainly limited by carrier capture and relaxation processes in the QD. We use pump-probe measurements resonant to the QDs confined states energies (ground and excited state) to investigate the response to a four fs-pulse train of 1 THz repetition rate. A deep insight about the capture process implied is then obtained, and direct capture from the wetting layer is identified as the dominant mechanism in the high current regime.
Parallel Recording of Single Quantum Dot Optical Emission Using Multicore Fibers
2016
Single Indium Arsenide Quantum Dot emission spectra have been recorded using a four-core, crosstalk-free, multicore fiber placed at the collection arm of a confocal microscope. We developed two different measurement set-ups depending on the relative configuration of the excitation and collection spots. In the single-matched mode, the emission from the excited area is collected by a single core in the multicore fiber, whereas the three remaining cores capture the emission from neighboring, non-excited areas. This procedure allows for the recording of the Quantum Dot emission from carrier diffusion between sample positions separated by more than 6 μm. In the multiple-matched mode, the ex…