Photoluminescence from low temperature grown InAs/GaAs quantum dots

The authors investigated a set of self-assembled InAs/GaAs quantum dots (QDs) formed by mol. beam epitaxy at low temp. (LT, 250 DegC) and postgrowth annealing. A QD photoluminescence (PL) peak around 1.01 eV was obsd. The PL efficiency quickly quenches between 6 and 40 K due to the tunneling out of the QD into traps within the GaAs barrier. The PL efficiency increases by a factor of 45-280 when exciting below the GaAs band gap, directly into the InAs QD layer. This points towards good optical quality QDs, which are embedded in a LT-GaAs barrier with a high trapping efficiency. [on SciFinder (R)

Carrier dynamics of LT InAs/GaAs QDs using time resolved differential reflectivity

We present a Time Resolved Differential Reflectivity (TRDR) study of LT (low temperature grown) Stransky - Krastanov InAs/GaAs Quantum Dots (QDs) grown using molecular beam epitaxy. The photoluminescence (PL) spectrum shows a QD-peak around 1200nm. In the TRDR measurements we observe an initial fast decay (80ps) followed by a much slower decay of about 800ps. The strong temperature dependence of the PL-signal is not observed in the reflectivity signal. This leads us to conclude that the electrons are trapped at a fast rate by As antisite defects while the hole decay dynamics take place at a slower rate, which is also monitored in TRDR

Transmission of pillar-based photonic crystal waveguides in InP technology

Waveguides based on line defects in pillar photonic crystals have been fabricated in InP/InGaAsP/InP technology. Transmission measurements of different line defects are reported. The results can be explained by comparison with two-dimensional band diagram simulations. The losses increase substantially at mode crossings and in the slow light regime. The agreement with the band diagrams implies a good control on the dimensions of the fabricated features, which is an important step in the actual application of these devices in photonic integrated circuit

Single InAs quantum dot arrays and directed self-organization on patterned GaAs (311)B substrates

Formation of laterally ordered single InAs quantum dot (QD) arrays by self-organized anisotropic strain engineering of InGaAs/GaAs superlattice templates on GaAs (311)B by molecular beam epitaxy is achieved through optimization of growth temperature, InAs amount, and annealing. Directed self-organization of these QD arrays is accomplished by coarse substrate patterns providing absolute QD position control over large areas. Due to the absence of one-to-one pattern definition the site-controlled QD arrays exhibit excellent optical properties revealed by resolution limited (80 µeV) linewidth of the low-temperature photoluminescence from individual QDs. © 2009 American Institute of Physics

Quantum dot twin stripe lasers as emitter and receiver in chaotic encrypted communication systems

The complex nonlinear and chaotic regimes observed in laterally coupled diode lasers – or twin stripe lasers– make this device a real contender for the emitter and receiver in chaotic encrypted communication systems, since the chaos is produced on chip and no other elements have to be added to the set-up. The main problem until now was to be able to synchronize two of those devices, due to the difficulty of fabricating a pair similar enough. Our approach is to use Quantum Dots for the active region of the twin stripes, which allows for the use of shallow etching to electrically isolate both stripes due to the zero dimensional confinement of the Quantum Dots. In this paper we present the first time that a pair of twin stripe lasers has been synchronized together with an observation of transitions to chaos such as those found in single-stripe lasers subject to external influences

Quantum dot twin stripe lasers as emitter and receiver in chaotic encrypted communication systems

The complex nonlinear and chaotic regimes observed in laterally coupled diode lasers – or twin stripe lasers– make this device a real contender for the emitter and receiver in chaotic encrypted communication systems, since the chaos is produced on chip and no other elements have to be added to the set-up. The main problem until now was to be able to synchronize two of those devices, due to the difficulty of fabricating a pair similar enough. Our approach is to use Quantum Dots for the active region of the twin stripes, which allows for the use of shallow etching to electrically isolate both stripes due to the zero dimensional confinement of the Quantum Dots. In this paper we present the first time that a pair of twin stripe lasers has been synchronized together with an observation of transitions to chaos such as those found in single-stripe lasers subject to external influences

Electron microscopic and optical investigations of the indium distribution GaAs capped InxGa1-xAs islands

Results from a structural and optical analysis of buried InxGa1-xAs islands carried out after the process of GaAs overgrowth are presented. It is found that during the growth process, the indium concentration profile changes and the thickness of the wetting layer emanating from a Stranski-Krastanow growth mode grows significantly. Quantum dots are formed due to strong gradients in the indium concentration, which is demonstrated by photoluminescence and excitation spectroscopy of the buried InxGa1-xAs islands. (C) 1997 American Institute of Physics