We review mechanisms of low-temperature electronic transport through a quantum dot weakly coupled to two conducting leads. Transport in this case is dominated by electron-electron interaction. At temperatures moderately lower than the charging energy of the dot, the linear conductance is suppressed by the Coulomb blockade. Upon further lowering of the temperature, however, the conductance may s...

We report on the first femtosecond vertical external cavity surface emitting laser (VECSEL) exceeding 1 W of average output power. The VECSEL is optically pumped, based on self-assembled InAs quantum dot (QD) gain layers, cooled efficiently using a thin disk geometry and passively modelocked with a fast quantum dot semiconductor saturable absorber mirror (SESAM). We developed a novel gain struc...

In this study graphene oxide (GO) was synthesized by using Hummer’s method. Low dimension graphene quantum dot nanoparticles (GQDs) were synthesized using pulse laser irradiation. Fourier Transform-Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) spectroscopy and photoluminescence (PL) analysis were applied to study the GQDs characteristic. Scanning electron microscopy illustrated the...

Quantum dot structures designed for multi-color infrared detection and high temperature (or room temperature) operation are demonstrated. A novel approach, tunneling quantum dot (T-QD), was successfully demonstrated with a detector that can be operated at room temperature due to the reduction of the dark current by blocking barriers incorporated into the structure. Photoexcited carriers are sel...

We review mechanisms of low-temperature electronic transport through a quantum dot weakly coupled to two conducting leads. Transport in this case is dominated by electron-electron interaction. At temperatures moderately lower than the charging energy of the dot, the linear conductance is suppressed by the Coulomb blockade. Upon further lowering of the temperature, however, the conductance may s...

To discuss the local structure of an atom in the self-organized InAs quantum dot (QD), we perform a site-selective X-ray absorption fine structure (XAFS) measurement, employing the capacitance XAFS method. Since the X-ray-induced photoemission of confined electrons in a QD via inner-shell absorption can be detected by capacitor, the photon energy dependence of the capacitance provides the XAFS ...

We discuss a THz laser device based on a semiconductor quantum dot (QD) gain medium, where the lasing occurs through discrete conduction states. An ensemble of QDs is selectively placed in a high quality cavity, called a microdisk, which is resonant with a terahertz intersublevel QD transition. We simulate the rate equations goveming iasing and discuss a variety of processes affecting lasing in...

We study the Aharonov-Bohm effect in a coupled 2×2 quantum dot array with two-terminals. A striking conductance dip arising from the Fano interference is found as the energy levels of the intermediate dots are mismatched, which is lifted in the presence of a magnetic flux. A novel five peak structure is observed in the conductance for large mismatch. The Aharonov-Bohm evolution of the linear co...

Cathodoluminescence wavelength imaging of InAs/GaAs self-assembled quantum dots ~SAQDs! was performed to study the spatial variation in the spectral line shape of the broadened quantum dot ~QD! ensemble. The line shape was found to vary on a scale of ;mm, revealing attendant variations in the size distribution of SAQD clusters on this spatial scale. Energy variations in clusters of SAQDs are fo...

Being a semiconductor of very tiny size, quantum dots cause the band of energies to change into discrete energy levels. Band gaps and their related energy depend on the relationship between the size of the crystal and the exciton radius. The height and the energy between different energy levels varies inversely with the size of the quantum dot. The smaller the quantum dot, the higher is the ene...