Structural and optical properties of disc-in-wire InGaN/GaN LEDs.

This study examines the role of the microstructure and optical properties of InGaN/GaN nanowire LED structures on Si(111) having different nanowire coverages. Cathodoluminescence (CL) measurements show that all samples exhibit broad emission around the intended energy, 1.95 eV (635 nm).

Time-resolved two-pulse excitation of quantum dots coupled to a photonic crystal cavity in the Purcell regime.

We investigate the nonlinear emission dynamics of quantum dots coupled to photonic crystal cavities in the Purcell regime using luminescence intensity autocorrelation. Two laser pulses with a controlled time delay sequentially excite the coupled system inducing emission that depends on the delay and laser power. We find distinct contrasts between exciton and biexciton emission as a function of time delay which originate from different nonlinearities.

Photoluminescence imaging of focused ion beam induced individual quantum dots.

We report on scanning microphotoluminescence measurements that spectrally and spatially resolve emission from individual InAs quantum dots that were induced by focused ion beam patterning. Multilayers of quantum dots were spaced 2 μm apart, with a minimum single dot emission line width of 160 μeV, indicating good optical quality for dots patterned using this technique. Mapping 16 array sites, at least 65% were occupied by optically active dots and the spectral inhomogeneity was within 30 meV.

Toward Assembly of Non-close-packed Colloidal Structures from Anisotropic Pentamer Particles.

Particles combining multiple anisotropy dimensions offer possibilities for self-assembly that have not been extensively explored to date. The scope for assembly of microparticles in which the anisotropy dimensions of internal bond angle and chemical ordering have been varied is investigated. Colloidal assemblies with interesting open (i.

Filling of hole arrays with InAs quantum dots.

Focused ion beams are used to pattern GaAs(001) surfaces with an array of nanometer-deep holes upon which deposition of InAs results in quantum dot formation at the hole location. Experiments show that the size and quantity of quantum dots formed depend on growth parameters, and ion dose, which affects the size and shape of the resulting holes. Quantum dots fabricated in this fashion have a photoluminescence peak at 1.

Fluidic assembly and packing of microspheres in confined channels.

We study fluidic assembly and packing of spherical particles in rectilinear microchannels that are terminated by a flow constriction. First, we introduce a method for active assembly of particles in the confined microchannels by triggering a local constriction in the fluid channel using a partially closed membrane valve. This microfluidic valve allows active, on-demand particle assembly as opposed to previous passive assembly methods based on terminal channels and weirs.

Programmable fluidic production of microparticles with configurable anisotropy.

We report a technique for continuous production of microparticles of variable size with new forms of anisotropy including alternating bond angles, configurable patchiness, and uniform roughness. The sequence and shape of the anisotropic particles are configured by exploiting a combination of confinement effects and microfluidics to pack precursor colloids with different properties into a narrow, terminal channel. The width and length of the channel relative to the particle size fully specify the configuration of the anisotropic particle that will be produced.