Diana L. Huffaker

Bio: Diana L. Huffaker is an academic researcher from Cardiff University. The author has contributed to research in topics: Quantum dot & Photoluminescence. The author has an hindex of 52, co-authored 393 publications receiving 10025 citations. Previous affiliations of Diana L. Huffaker include University of California & University of Michigan.

1.3 μm room-temperature GaAs-based quantum-dot laser

Abstract: Room-temperature lasing at the wavelength of 1.31 μm is achieved from the ground state of an InGaAs/GaAs quantum-dot ensemble. At 79 K, a very low threshold current density of 11.5 A/cm2 is obtained at a wavelength of 1.23 μm. The room-temperature lasing at 1.31 μm is obtained with a threshold current density of 270 A/cm2 using high-reflectivity facet coatings. The temperature-dependent threshold with and without high-reflectivity end mirrors is studied, and ground-state lasing is obtained up to the highest temperature investigated of 324 K.

Native-Oxide Defined Ring Contact for Low Threshold Vertical-Cavity Lasers

Abstract: Data are presented characterizing a new process for fabrication of vertical‐cavity surface‐emitting lasers based on the selective conversion of high Al composition epitaxial AlGaAs to a stable native oxide using ‘‘wet oxidation.’’ The native oxide is used to form a ring contact to the laser active region. The resulting laser active regions have dimensions of 8, 4, and 2 μm. The lowest threshold laser is achieved with the 8‐μm active region, with a minimum threshold current of 225‐μA continuous wave at room temperature.

Low-threshold oxide-confined 1.3-μm quantum-dot laser

Abstract: Data are presented on low threshold, 1.3-/spl mu/m oxide-confined InGaAs-GaAs quantum dot lasers. A very low continuous-wave threshold current of 1.2 mA with a threshold current density of 28 A/cm/sup 2/ is achieved with p-up mounting at room temperature. For slightly larger devices the continuous-wave threshold current density is as low as 19 A/cm/sup 2/.

Strain relief by periodic misfit arrays for low defect density GaSb on GaAs

Abstract: We demonstrate the growth of a low dislocation density, relaxed GaSb bulk layer on a (001) GaAs substrate. The strain energy generated by the 7.78% lattice mismatch is relieved by a periodic array of 90° misfit dislocations. The misfit array is localized at the GaSb∕GaAs interface and has a period of 5.6nm which is determined by transmission electron microscope images. No threading dislocations are visible. The misfits are identified as 90°, rather than 60°, using Burger’s circuit analysis, and are therefore not associated with generation of threading dislocations. A low dislocation density and planar growth mode is established after only 3 monolayers of GaSb deposition as revealed by reflection high-energy electron diffraction patterns. Calculations corroborate the materials characterization and indicate the strain energy generated by the 7.78% lattice mismatch is almost fully dissipated by the misfit array. The low dislocation density bulk GaSb material on GaAs enabled by this growth mode will lead to new devices, especially in the infrared regime, along with novel integration schemes.

GaAs nanopillar-array solar cells employing in situ surface passivation.

Abstract: Arrays of III–V semiconductor nanopillars are promising photovoltaic materials due to their favourable optical properties, however, they show low power conversion efficiencies. Mariani et al. fabricate a GaAs nanopillar solar cell achieving an efficiency of 6.63% owing to surface passivation.

Optical microcavities

Abstract: Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.

Vacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity

Abstract: Cavity quantum electrodynamics (QED) systems allow the study of a variety of fundamental quantum-optics phenomena, such as entanglement, quantum decoherence and the quantum–classical boundary. Such systems also provide test beds for quantum information science. Nearly all strongly coupled cavity QED experiments have used a single atom in a high-quality-factor (high-Q) cavity. Here we report the experimental realization of a strongly coupled system in the solid state: a single quantum dot embedded in the spacer of a nanocavity, showing vacuum-field Rabi splitting exceeding the decoherence linewidths of both the nanocavity and the quantum dot. This requires a small-volume cavity and an atomic-like two-level system. The photonic crystal slab nanocavity—which traps photons when a defect is introduced inside the two-dimensional photonic bandgap by leaving out one or more holes—has both high Q and small modal volume V, as required for strong light–matter interactions. The quantum dot has two discrete energy levels with a transition dipole moment much larger than that of an atom, and it is fixed in the nanocavity during growth.

The Quantum Theory of Light

Abstract: (b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

Rationale and challenges for optical interconnects to electronic chips

Abstract: The various arguments for introducing optical interconnections to silicon CMOS chips are summarized, and the challenges for optical, optoelectronic, and integration technologies are discussed. Optics could solve many physical problems of interconnects, including precise clock distribution, system synchronization (allowing larger synchronous zones, both on-chip and between chips), bandwidth and density of long interconnections, and reduction of power dissipation. Optics may relieve a broad range of design problems, such as crosstalk, voltage isolation, wave reflection, impedence matching, and pin inductance. It may allow continued scaling of existing architectures and enable novel highly interconnected or high-bandwidth architectures. No physical breakthrough is required to implement dense optical interconnects to silicon chips, though substantial technological work remains. Cost is a significant barrier to practical introduction, though revolutionary approaches exist that might achieve economies of scale. An Appendix analyzes scaling of on-chop global electrical interconnects, including line inductance and the skin effect, both of which impose significant additional constraints on future interconnects.