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This paper reports theoretical and experimental studies that explain how the size-dependent shape and elemental composition of PbS quantum dots (QDs) affect the arrangement and density of adsorbed ligands by QDs surfaces, and their related susceptibility to oxidation. By considering the differences of Pb:S ratios of the particles, we predict a size-dependent Pb:S ratio that is consistent with our...
Hyperspectroscopy consists of spatially-resolved collection of spectra. In order to characterize the performance of electron emitters, in particular thermionic emitters, the thermal characteristics must be known. In this work, we use hyperspectroscopy to map out the blackbody temperature distribution on the surface of an optically-excited source comprised of a carbon nanotube (CNT) forest — a promising...
We describe a planar photonic circuit in silicon-on-insulator that efficiently generates pairs of non-degenerate photons in a single mode output channel through spontaneous four-wave mixing when pumped with 10's of µW of continuous-wave radiation at wavelengths near 1.5 µm. The structure is based on a set of three coupled photonic crystal microcavities, each of which is judiciously coupled to single...
Size and shape sensitive trapping of Au nanoparticles in silicon-on-insulator photonic crystal slot microcavjties at sub-mW power is demonstrated. Coupling to the microcavity via slot waveguides is shown to significantly enhance the transmission signal of the devices.
Relaxation dynamics is universal in science and engineering; its study serves to parameterize a system's response and to help identify a microscopic model of the processes involved. When measured data for a phenomenon cannot be fitted using one exponential, the choice of an alternative function to describe the decay becomes nontrivial. Here, we contrast two different, but fundamentally related approaches...
We report optical trapping of 60 nm Au nanoparticles using photonic crystal slot-cavities with Q's of ∼7200 and 0.3mW of guided power at 1.6µm. Histograms of the cavity transmission are used to quantitatively analyze the trapping dynamics by modeling the back-action of the nanoparticles in the trap.
We report on simulation results that shows optimum photon absorption by superconducting nanowires can happen at a fill-factor that is much less than 100%. We also present experimental results on high performance of our superconducting nanowire single photon detectors realized using NbTiN on oxidized silicon.
We propose a Y-branch coupler to efficiently transfer light from a silicon nanowire waveguide to a slot waveguide. The coupler is 500 nm long and functions with greater than 90 % efficiency over a 200 nm bandwidth when operated either in air or solvent. Its versatility makes it a good candidate for photonic circuits with applications including sensing, nonlinear optics and information processing.
We demonstrate the lithography simulation for the fabrication of silicon photonic devices using deep-ultraviolet lithography. Once the distortions arising from the fabrication process are accounted for, the comparison between predicted and measured results is excellent.
We demonstrate that guided mode resonances enhanced second- and third-harmonic generation (SHG and THG) in an azo-polymer resonant waveguide grating (RWG). The enhancement factor for SHG emission is at least 1000 compared to that of a sample without RWG e ffect.
Modelling results are described that deal with the coupling of excitons in colloidal nanocrystals to silicon-based photonic crystal microcavities, and to the design of structures that couple the microcavities to ridge waveguides and input/output gratings that are realized on 200 mm diameter silicon-on-insulator wafers.
We demonstrate the saturation of non-resonantly pumped, cavity-coupled exciton emission from 5 nm PbSe nanocrystals on silicon photonic crystal microcavities at microwatt excitation powers at room temperature, in agreement with simulations.
A high Q mode in a silicon planar photonic crystal microcavity is dynamically perturbed by injection of free carriers, and modelled by a damped harmonic oscillator which undergoes an instantaneous frequency and lifetime shift.
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