71 research outputs found
Leveraging Nanocavity Harmonics for Control of Optical Processes in 2D Semiconductors
Optical cavities with multiple tunable resonances have the potential to provide unique electromagnetic environments at two or more distinct wavelengths—critical for control of optical processes such as nonlinear generation, entangled photon generation, or photoluminescence (PL) enhancement. Here, we show a plasmonic nanocavity based on a nanopatch antenna design that has two tunable resonant modes in the visible spectrum separated by 350 nm and with line widths of ∼60 nm. The importance of utilizing two resonances simultaneously is demonstrated by integrating monolayer MoS[subscript 2], a two-dimensional semiconductor, into the colloidally synthesized nanocavities. We observe a 2000-fold enhancement in the PL intensity of MoS[subscript 2]—which has intrinsically low absorption and small quantum yield—at room temperature, enabled by the combination of tailored absorption enhancement at the first harmonic and PL quantum-yield enhancement at the fundamental resonance.United States. Dept. of Energy. Center for Excitonics (Award DE-SC0001088)United States. Dept. of Energy. Office of Basic Energy Sciences (Grant DE-SC0001088
Imaging and optical properties of single core-shell GaAs-AlGaAs nanowires
We study the optical properties of a single core-shell GaAs-AlGaAs nanowire
(grown by VLS method) using the technique of micro-photoluminescence and
spatially-resolved photoluminescence imaging. We observe large linear
polarization anisotropy in emission and excitation of nanowires.Comment: IEEE Nano 2006 Proceeding
Temperature dependence of photoluminescence from single core-shell GaAs–AlGaAs nanowires
Temperature-dependent polarized microphotoluminescencemeasurements of single GaAs∕AlGaAs core-shell nanowires are used to probe their electronic states. The low-temperature emission from these wires is strongly enhanced compared with that observed in bare GaAsnanowires and is strongly polarized, reflecting the dielectric mismatch between the nanowire and the surrounding air. The temperature-dependentband gap of the nanowires is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 120K, with an activation energy of 17meV reflecting the presence of nonradiative defects.This work was supported by the University of Cincinnati.
Australian authors gratefully acknowledge the financial
support from the Australian Research Council
A Systematic and Critical Review on the Research Landscape of Finance in Vietnam from 2008 to 2020
This paper endeavors to understand the research landscape of finance research in Vietnam during the period 2008 to 2020 and predict the key defining future research directions. Using the comprehensive database of Vietnam’s international publications in social sciences and humanities, we extract a dataset of 314 papers on finance topics in Vietnam from 2008 to 2020. Then, we apply a systematic approach to analyze four important themes: Structural issues, Banking system, Firm issues, and Financial psychology and behavior. Overall, there have been three noticeable trends within finance research in Vietnam: (1) assessment of financial policies or financial regulation, (2) deciphering the correlates of firms’ financial performances, and (3) opportunities and challenges in adopting innovations and ideas from foreign financial market systems. Our analysis identifies several fertile areas for future research, including financial market analysis in the post-COVID-19 eras, fintech, and green finance
Widely tunable, efficient on-chip single photon sources at telecommunication wavelengths
We demonstrate tunable on-chip single photon sources using the Stark tuning
of single quantum dot (QD) excitonic transitions in short photonic crystal
waveguides (PhC WGs). The emission of single QDs can be tuned in real-time by 9
nm with an applied bias voltage less than 2V. Due to a reshaped density of
optical modes in the PhC WG, a large coupling efficiency \beta>65% to the
waveguide mode is maintained across a wavelength range of 5 nm. When the QD is
resonant with the Fabry-Perot mode of the PhC WG, a strong enhancement of
spontaneous emission is observed leading to a maximum coupling efficiency
\beta=88%. These results represent an important step towards the scalable
integration of single photon sources in quantum photonic integrated circuits.Comment: 15 pages, 5 figue
Ultrafast nonlocal control of spontaneous emission
Solid-state cavity quantum electrodynamics systems will form scalable nodes
of future quantum networks, allowing the storage, processing and retrieval of
quantum bits, where a real-time control of the radiative interaction in the
cavity is required to achieve high efficiency. We demonstrate here the dynamic
molding of the vacuum field in a coupled-cavity system to achieve the ultrafast
nonlocal modulation of spontaneous emission of quantum dots in photonic crystal
cavities, on a timescale of ~200 ps, much faster than their natural radiative
lifetimes. This opens the way to the ultrafast control of semiconductor-based
cavity quantum electrodynamics systems for application in quantum interfaces
and to a new class of ultrafast lasers based on nano-photonic cavities.Comment: 15 pages, 4 figure
Growth, Structural and Optical Properties of High Quality GaAs Nanowires for Optoelectronics
We investigate how growth parameters may be chosen to obtain high quality GaAs nanowires suitable for optoelectronic device applications. Growth temperature and precursor flows have a significant effect on the morphology, crystallographic quality, intrinsic doping and optical properties of the resulting nanowires. Significantly, we find that low growth temperature and high arsine flow rate improve nanowire optical properties, reduce carbon impurity incorporation and drastically reduce planar crystallographic defects. Additionally, cladding the GaAs nanowire cores in an AlGaAs shell enhances emission efficiency. These high quality nanowires should create new opportunities for optoelectronic devices
Foreign Direct Investment in Vietnam: An Overview and Analysis the Determinants of Spatial Distribution Across Provinces
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