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Photonics-based quantum information technologies require efficient, high emission rate sources of single photons. Position-controlled quantum dots embedded within a broadband nanowire waveguide provide a fully scalable route to fabricating highly efficient single-photon sources. However, emission rates for single-photon devices are limited by radiative recombination lifetimes. Here, we demonstrate a multiplexed single-photon source based on a multidot nanowire. Using epitaxially grown nanowires, we incorporate multiple energy-tuned dots, each optimally positioned within the nanowire waveguide, providing single photons with high efficiency. This linear scaling of the single-photon emission rate with number of emitters is demonstrated using a five-dot nanowire with an average multiphoton emission probability of

We demonstrate the selective optical excitation and detection of subsets of quantum dots (QDs) within an InAs/InP ensemble using a SiO2/Ta 2O5-based optical microcavity. The low variance of the exciton transition energy and dipole moment tied to the narrow linewidth of the microcavity mode is expected to facilitate effective qubit encoding and manipulation in a quantum dot ensemble with ease of quantum state readout relative to qubits encoded in single quantum dots. © 2013 AIP Publishing LLC.

Planar InAs/InP quantum-dot microcavities using multilayer SiO2/Ta2O5 Bragg reflectors have been studied in emission. For an eight-pair mirror design, the stop band extends from 700 to 900 meV and the cavity linewidth is ∼500 μeV for emission at 850 meV. Measurements as a function of incident power show quantum-dot saturation behavior, with the emission intensity going to the wetting layer outside the cavity stop band. Saturation behavior at fixed pump power is also observed as a function of decreasing temperature. Dispersion measurements as a function of emission angle show polarization splitting in reasonable agreement with theory.

This chapter contains sections titled: Introduction Directed self-assembly Spectroscopic signatures Application of electric fields Optical cavities Conclusions

We demonstrate precise control of electron charging within a single deterministically positioned InAs/InP quantum dot emitting in the telecommunications band around 1500 nm. Photolumine-scence emission as a function of vertical electric field is used to monitor the electron number within the dot. From Stark shift spectroscopy, we extract strength and orientation for the built-in dipole moment that suggests a uniform InAs dot composition and a configuration in which the electron lies above the hole at zero electric field. The scalable gating technology we employ to electrically contact individual prepositioned quantum dots promises arrays of initialized single spins that can be used for fiber-based quantum information applications.

Summary form only given.Significant advances have been made in recent years in the fabrication of high power diode lasers utilizing the aluminum free InGaAsP-GaAs material system, which has some advantages over the more commonly used AlGaAs system. Although numerous and detailed studies have been performed on the growth, fabrication and characterization of InGaAsP based lasers, very little has been reported on fundamental material properties, such as the index of refraction. From the perspective of designing optoelectronic devices such as diode lasers, a detailed knowledge of the optical constants of the materials at the relevant wavelengths is required. In this paper, the optical constants of InGaAsP, ranging in composition from GaAs to InGaP, are presented.

We perform an experimental and computational study of the effects of external stress and intermixing on single site-selected InAs/InP quantum dots in a highly scalable stress-sensitive environment. While such effects are well known for their ability to tune emission spectra, little is known on how they influence emission shell spacing, electron-hole effective mass renormalization, and the physical size of the embedded quantum dot, which are all important parameters affecting the intended functionality. We show excellent agreement between experiment and finite-element solutions of the coupled Navier and Schrödinger equations, including recent atomistic pseudopotential calculations in the literature. These results indicate that using single self-assembled quantum dots in highly scalable, stress-sensitive settings as active elements in future bottom-up nanosystems offers greater versatility to not only quantum information systems where they serve as scalable single-photon sources but also to ultra-sensing capabilities in future nano-electro-mechanical architectures.

We have studied the tuning behavior of an external cavity laser in Littrow configuration using antireflection/high-reflection coated InAs∕InGaAsP∕InP quantum dot laser diodes as the amplifying element. Adding the coatings improves the performance of the setup, and the tunability of the external cavity laser output has been increased up to 166nm. Detailed investigations have revealed that laser diode length and width influence the magnitude of the tuning range. Furthermore, the external differential quantum efficiency is systematically increasing as the external cavity laser wavelength is decreasing. These characteristics are discussed in terms of energy levels available in the inhomogeneous broadening of the self-assembled quantum dots.