Pumped double quantum dot with spin-orbit coupling

We study driven by an external electric field quantum orbital and spin dynamics of electron in a one-dimensional double quantum dot with spin-orbit coupling. Two types of external perturbation are considered: a periodic field at the Zeeman frequency and a single half-period pulse. Spin-orbit coupling leads to a nontrivial evolution in the spin and orbital channels and to a strongly spin-dependent probability density distribution. Both the interdot tunneling and the driven motion contribute into the spin evolution. These results can be important for the design of the spin manipulation schemes in semiconductor nanostructures.

External-cavity mode-locked quantum-dot laser diodes for low repetition rate, sub-picosecond pulse generation

This paper presents an investigation of the mode-locking performance of a two-section external-cavity mode-locked InGaAs quantum-dot laser diode, focusing on repetition rate, pulse duration and pulse energy. The lowest repetition rate to-date of any passively mode-locked semiconductor laser diode is demonstrated (310 MHz) and a restriction on the pulse energy (at 0.4 pJ) for the shortest pulse durations is identified. Fundamental mode-locking from 310 MHz to 1.1 GHz was investigated, and harmonic mode-locking was achieved up to a repetition rate of 4.4 GHz. Fourier transform limited subpicosecond pulse generation was realized through implementation of an intra-cavity glass etalon, and pulse durations from 930fs to 8.3ps were demonstrated for a repetition rate of 1 GHz. For all investigations, mode-locking with the shortest pulse durations yielded constant pulse energies of ∼0.4 pJ, revealing an independence of the pulse energy on all the mode-locking parameters investigated (cavity configuration, driving conditions, pulse duration, repetition rate, and output power). © 2011 IEEE.

Optically controlled quantum dot gated transistors with high on/off ratio

We report the design and fabrication of InAs quantum dot gated transistors, which are normally-on, where the channel current can be switched off by laser illumination. Laser light at 650 nm with a power of 850 pW switches the channel current from 5 mu A to 2 pA, resulting in an on/off ratio of more than 60 dB. The switch-off mechanism and carrier dynamics are analyzed with simulated band structure.

Epitaxial Semiconductor Quantum Wires

The investigation on the direct epitaxial quantum wires (QWR) using MBE or MOCVD has been persuited for more than two decades, more lengthy in history as compared with its quantum dot counterpart. Up to now, QWRs with various structural configurations have been produced with different growth methods. This is a reviewing article consisting mainly of two parts. The first part discusses QWRs of various configurations, together with laser devices based on them, in terms of the two growth mechanisms, self-ordering and self-assembling. The second part gives a brief review of the electrical and optical properties of QWRs.