Energy absorbed from double quantum dot-metal nanoparticle hybrid system.

This work proposes the double quantum dot (DQD)-metal nanoparticle (MNP) hybrid system for a high energy absorption rate. The structure is modeled using density matrix equations that consider the interaction between excitons and surface plasmons. The wetting layer (WL)-DQD transitions are considered, and the orthogonalized plane wave (OPW) between these transitions is considered. The DQD energy states and momentum calculations with OPW are the figure of merit recognizing this DQD-MNP work. The results show that at the high pump and probe application, the total absorption rate [Formula: see text] of the DQD-MNP hybrid system is increased by reducing the distance between DQD-MNP. The high [Formula: see text] obtained may relate to two reasons: first, the WL washes out modes other than the condensated main mode. Second, the high flexibility of manipulating DQD states compared to QD states results in more optical properties for DQD. The [Formula: see text] is increased at a small MNP radius on the contrary to the [Formula: see text] which is increased at a wider MNP radius. Under high tunneling, a broader blue shift in the [Formula: see text] due to the destructive interference between fields is seen and the synchronization between [Formula: see text] and [Formula: see text] is destroyed. [Formula: see text] for the DQD-MNP is increased by six orders while [Formula: see text] is by eight orders compared to the single QD-MNP hybrid system. The high absorption rate of the DQD-MNP hybrid system comes from the transition possibilities and flexibility of choosing the transitions in the DQD system, which strengthens the transitions and increases the linear and nonlinear optical properties. This will make the DQD-MNP hybrid systems preferable to QD-MNP systems.

Second-order nonlinearity in ladder-plus-Y configuration in double quantum dot structure.

Second-order nonlinear susceptibility (SONS) in a ladder-plus-Y double quantum dot structure was modeled and then studied numerically under the application of an electric field. The density matrix theory was used to formulate the system while the orthogonalized plane waves for wetting layer-quantum dot (WL-QD) were considered to state the momentum matrix elements for this system. It is found that the momenta follow the smallest energy difference between states with an obvious overlap of the mediated states. Since WL-QD momenta are small, neglecting WL gives high SONS. Millimeter waves are predicted, and a huge SONS can be obtained by the application of more optical fields, which is important in medical and biological applications. The possibility of changing light speed between subluminal and superluminal was predicted here. This opens the way for many applications like multichannel waveguide-multichannel quantum information processing, real quality imaging, and temporal clock.

All-optical processes in double quantum dot structure.

The ladder-plus-Y double quantum dot structure was modeled for all-optical processing by combining the density matrix theory with the pulse width description of the applied pulse. The momentum matrix elements are calculated including the wetting layer. The ladder-plus-Y structure exhibits pattern-free output with high bit rate (50 Tbps), which is critical in optical communication applications. It is shown that very high ground-state occupation with periodic shape for state occupations is critical in obtaining a pattern-free eye diagram.

Two-window InSbBi quantum-dot photodetector.

Quantum efficiency (QE) was modeled for an n-type doping InSb1-xBix quantum-dot (QD) photodetector with a p-type doping AlGaAs bulk region. First, the relations of the electron and hole contributions to the current were stated. The absorption coefficient was calculated for the structure, and two windows were predicted in the quantum efficiency spectrum, which is important in the detection applications. High quantum efficiency was obtained due to the Bi inclusion in the structure of the photodetector.

Terahertz emission in ladder plus Y-configurations in double quantum dot structure.

The ladder plus Y-double quantum dot (QD) structure has been proposed to improve the second-order nonlinear susceptibility (SONS) under applied electric field. For this purpose, the wetting layer (WL) and QD inhomogeneity contribution in SONS has been considered. In addition, the structure size effect, energy level separation, momentum matrix elements, and pump detuning have been examined, and show that the SONS is increased by using the WL, a low momentum matrix element of WL-QD transition in comparison with interdot transition while QD inhomogeneity reduces SONS to half. This work is predicted to play a key role in terahertz applications, since the frequency emissions obtained are in the range of 75.5-600 µm.

Quantum efficiency of InSbBi quantum dot photodetector.

An InSb(1-x)Bi(x) quantum dot (QD) photodetector was studied in this work. First, the quantum efficiency (QE) was modeled for this structure where the relations of electron and hole densities and their contribution to current density are derived. The absorption of p-, n- and depletion regions were calculated before specifying their contribution to QE. It is shown that adding Bi to Sb-based QD structures increases their absorption and QE. High Bi content extended the cutoff detection wavelength of these detectors.

Four-wave mixing in quantum dot semiconductor optical amplifiers.

The theory of four-wave mixing (FWM) in the quantum dot (QD) semiconductor optical amplifiers (SOAs) is discussed by combining the QD rate equations system, the quantum-mechanical density-matrix theory, and the pulse propagation in QD SOAs including the three region of QD structure ground state (GS), excited state (ES), and wetting layer. Also, relations for differential gain, gain integral, and nonlinear susceptibility of both pump, probe, and signal pulses were discussed. Gain and differential gain have been calculated for QD structure. FWM efficiency and its components [spectral hole burning (SHB), carrier heating, and carrier density pulsation] are calculated. It is found that inclusion of ES in the formulas and in the calculations is essential since it works as a carrier reservoir for GS. It is found that QD SOA with enough capture time from ES to GS will reduce the SHB component, and so it is suitable for telecommunication applications that require symmetric conversion and independent detuning.