Molecular beam epitaxy of III-V and III-nitride semiconductors, cavity quantum electrodynamics and strong coupling phenomena, low-dimensional quantum confined systems, quantum dot lasers and detectors, optoelectronic integrated circuits, spintronic devices, visible LEDs and lasers.
Quantum Dot and Quantum Dash Lasers: The work involves both narrow- and broad-band 1.55µm QD lasers grown by MBE on InP substrates. The growth conditions for quantum dots and dashes and their relation with optical properties are investigated. The focus of the project is on the dynamic properties of the lasers, including small-signal modulation bandwidth, chirp, and α-factor.
InAs Quantum Dot Rolled-Up Microtube Optoelectronic Devices: Strained bi-layers can be released from their parent substrate to form a microcavity. With the insertion of active gain media, such as quantum dots, it is possible to realize microcavity lasers. In addition, we have demonstrated the use of rolled-up microtubes for the realization of directional couplers, phototransceivers and sensors.
Epitaxy of InGaN/GaN Quantum Dot Heterostructures and their Application to Visible Lasers and LEDs: We were the first group to demonstrate visible LEDs and lasers with InGaN/GaN self-organized quantum dots. The QD and device heterostructures are grown by MBE. The objectives of the projects on this subject are to understand QD growth, optimization of their optical properties and to demonstrate visible (green and red-emitting) LEDs with high efficiency and lasers with high output power and low threshold.
GaN-Based Nanowires on Silicon: The nanowires are grown on silicon with or without Ga self-catalyst. They grow with a radial relaxation of strain and are relatively defect free. InGaN/GaN nanowire heterostructures and QDs are used for fundamental studies and for the realization of LEDs, single photon sources and polariton lasers.
Strong Coupling Phenomena and Polariton Lasers: We investigate the properties of exciton-polaritons in a variety of GaAs – and GaN-based microcavities with quantum wells and nanowires. We have demonstrated Bose-Einstein Condensation (BEC) of polaritons at room temperature. We have also demonstrated the first electrically injected polariton laser.