D. G. Deppe

Vacuum Rabi Splitting with a Single Quantum Dot in a Photonic Crystal Nanocavity

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.

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

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

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.

Atom diffusion and impurity .. induced layer disordering In quantum well III ... V semiconductor heterostructures

The process of impurity‐induced layer disordering (IILD) or layer intermixing, in AlxGa1−xAs‐GaAs quantum well heterostructures (QWHs) and superlattices (SLs), and in related III‐V quantum well heterostructures, has developed extensively and is reviewed. A large variety of experimental data on IILD are discussed and provide newer information and further perspective on crystal self‐diffusion, impurity diffusion, and also the important defect mechanisms that control diffusion in AlxGa1−xAs‐GaAs, and in related III‐V semiconductors. Based on the behavior of Column III vacancies and Column III interstitials, models for the crystal self‐diffusion and impurity diffusion that describe IILD are reviewed and discussed. Because impurity‐induced layer disordering has proved to be an important method for III‐V quantum well heterostructure device fabrication, we also review the application of IILD to several different laser diode structures, as well as to passive waveguides. We mention that it may be possible to reali...

1.3 μm InAs quantum dot laser with To=161 K from 0 to 80 °C

Data are presented on the influence of p-type modulation doping on the gain characteristics of 1.3 μm InAs quantum dot lasers. The improvement in optical gain leads to very high characteristic temperatures for the lasing threshold that reach 161 K in the temperature range between 0 and 80 °C. 1.3 μm ground state lasing is obtained up to a temperature of 167 °C.

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

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/.

Stripe‐geometry quantum well heterostructure AlxGa1−xAs‐GaAs lasers defined by defect diffusion

Impurity‐free selective layer disordering, utilizing Si3N4 masking stripes and SiO2 defect (vacancy) sources, is used to realize room‐temperature continuous AlxGa1−xAs‐GaAs quantum well heterostructure lasers.

Room-temperature continuous-wave operation of a single-layered 1.3 μm quantum dot laser

Room-temperature continuous-wave operation of a 1.3 μm quantum dot laser is reported. The threshold current for a single layer active region with p–up mounting is only 4.1 mA with a threshold current density of 45 A/cm2. The minimum room temperature threshold current density is 25 A/cm2 for pulsed operation. Cryogenic and temperature dependent measurements are performed on broad-area lasers fabricated from the same active material. At 4 K the broad-area threshold current density for uncoated facets is 6 A/cm2.

Electroluminescence efficiency of 1.3 μm wavelength InGaAs/GaAs quantum dots

Data are presented characterizing the spectral emission and the electroluminescence efficiency dependence on growth conditions of 1.3 μm wavelength InGaAs/GaAs quantum dots. We show that highly efficient 1.3 μm room temperature electroluminescence can be achieved with only ten total deposited monolayers with an averaged In content of 50%. Atomic force microscopy shows that the 1.3 μm wavelength quantum dots form with a density of ∼1.3×1010 cm−2.

Scanning a photonic crystal slab nanocavity by condensation of xenon

Allowing xenon or nitrogen gas to condense onto a photonic crystal slab nanocavity maintained at 10–20 K results in shifts of the nanocavity mode wavelength by as much as 5 nm (~=4 meV). This occurs in spite of the fact that the mode defect is achieved by omitting three holes to form the spacer. This technique should be useful in changing the detuning between a single quantum dot transition and the nanocavity mode for cavity quantum electrodynamics experiments, such as mapping out a strong coupling anticrossing curve. Compared with temperature scanning, it has a much larger scan range and avoids phonon broadening.