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We report on the far field emission profile of pure wurtzite InP nanowires in comparison to InP nanowires with predominantly zincblende crystal structure. The emission profile is measured on individual nanowires using Fourier microscopy. The most intense photoluminescence of wurtzite nanowires is collected at small angles with respect to the nanowire growth axis. In contrast, zincblende nanowires present a minimum of the collected light intensity in the direction of the nanowire growth. Results are explained by the orientation of electric dipoles responsible for the photoluminescence, which is different from wurtzite to zincblende. Wurtzite nanowires have dipoles oriented perpendicular to the nanowire growth direction, whereas zincblende nanowires have dipoles oriented along the nanowire axis. This interpretation is confirmed by both numerical simulations and polarization dependent photoluminescence spectroscopy. Knowledge of the dipole orientation in nanostructures is crucial for developing a wide range of photonic devices such as light-emitting diodes, photodetectors, and solar cells.

A process is described where the position, size, and cladding of an InP nanowire with an embedded InAsP quantum dot are determined by design through lithography, processing, and growth. The vapor-liquid-solid growth mode on a patterned substrate is used to grow the InP core and defines the quantum dot size to better than ±2 nm while selective-area growth is used to define the cladding thickness. The clad nanowires emit efficiently in the range λ=0.95–1.15 μm. Photoluminescence measurements are used to quantify the dependence of the excitonic energy level structure on quantum dot size for diameters 10–40 nm.

Single-mode laser diodes on GaSb substrates were developed using InGaAsSb/AlGaAsSb triple quantum well active regions grown by molecular beam epitaxy. The devices were fabricated using lateral Cr gratings, with a grating pitch designed to coincide with a strong absorption feature of HF gas, deposited adjacent to a dry-etched narrow ridge waveguide. High sidemode suppression was achieved, and in 20 °C continuous-wave operation, devices with a 400 μm long cavity provided 9 mW total output power at the 2396 nm target wavelength. High-resolution direct absorption measurements of HF gas agreed with HiTran calculations, yielding an absorption linewidth of 0.030 nm.

The authors study the quality factor Q of the x-dipole mode in single missing hole defect photonic crystal microcavities in InAs∕InP quantum dot membranes as a function of the structural design parameters. Photoluminescence experiments show an optimized Q in excess of 28 000 for a wavelength close to λ=1550nm. This is to be compared with a Q of 57 000 determined by finite difference time domain calculations. The fabrication tolerances necessary to achieve experimental Q values close to those predicted by theory are identified.

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.