D.L. Huffaker

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.

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/.

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.

Temperature dependence of lasing characteristics for long-wavelength (1.3-μm) GaAs-based quantum-dot lasers

Data are presented on the temperature dependence of 1.3-/spl mu/m wavelength quantum-dot (QD) lasers. A low-threshold current density of 90 A/cm/sup 2/ is achieved at room temperature using high reflectivity coatings. Despite the low-threshold current density, lasing at the higher temperatures is limited by nonradiative recombination with a rapid increase in threshold current occurring above /spl sim/225 K. Our results suggest that very low threshold current density (/spl les/20 A/cm/sup 2/) can be achieved at room temperature from 1.3-/spl mu/m QD lasers, once nonradiative recombination is eliminated.

Discrete energy level separation and the threshold temperature dependence of quantum dot lasers

Data are presented on one- and two-stack InAs quantum dot lasers that have reduced temperature sensitivity of their lasing threshold. Adjustment of dot size and composition is used to increase the energy separation between the ground and first excited radiative transition energies to 104 meV, with a dot density of ∼3.1×1010 cm−2. The one- and two-stack lasers show broad area as-cleaved room temperature threshold current densities as low as 43 and 35 A/cm2, respectively. The wide energy separation between the ground and first excited radiative transitions leads to significant improvements in the temperature sensitivity of threshold.

Spontaneous emission from planar microstructures

Abstract The alteration of spontaneous emission characteristics in terms of the spontaneous lifetime and spectral emission characteristics are discussed for dipoles in the presence of nearby planar reflecting interfaces and cavities, specifically for the case of semiconductors. For dipoles closely spaced to absorbing metal mirrors, significant lifetime change is possible. Analysis and experimental data are presented for light emitting diodes. For dielectric Fabry-Perot microcavities, the expected lifetime change is small, but significant modification in the radiation pattern of the emitted light occurs. It is shown that the spectral characteristics of emission have a sensitive dependence on the dipole location in the cavity. Comparison is made between a classical against a quantum treatment of the spontaneous emission modification due to the cavity.

Sub-40 μA continuous-wave lasing in an oxidized vertical-cavity surface-emitting laser with dielectric mirrors

Due to two improvements in cavity design, low-threshold lasing is achieved in oxidized vertical-cavity surface-emitting lasers incorporating upper dielectric distributed Bragg reflectors. Intracavity absorption is reduced by removal of a heavily p-type contact layer and the use of a low-loss MgF-ZnSe upper mirror. We report sub-100 /spl mu/A lasing for a 7-/spl mu/m diameter device, and sub-40 /spl mu/A lasing for a 3-/spl mu/m diameter device. The low-loss cavity design also allows for highly multimode operation at a low-bias current of 600 /spl mu/A in a detuned cavity.

Quantum dot vertical-cavity surface-emitting laser with a dielectric aperture

Data are presented on an oxide-confined vertical-cavity surface-emitting laser that uses a quantum dot active region. The laser is grown by molecular beam epitaxy, with the quantum dot active region formed from a five monolayer deposition of In0.50Ga0.35Al0.15As. Lasing occurs at wavelengths corresponding to quantum dot transitions, with a room temperature pulsed threshold as low as 560 μA for a 7 μm diameter oxide aperture.