1,265 research outputs found
A stable, single-photon emitter in a thin organic crystal for application to quantum-photonic devices
Single organic molecules offer great promise as bright, reliable sources of
identical single photons on demand, capable of integration into solid-state
devices. It has been proposed that such molecules in a crystalline organic
matrix might be placed close to an optical waveguide for this purpose, but so
far there have been no demonstrations of sufficiently thin crystals, with a
controlled concentration of suitable dopant molecules. Here we present a method
for growing very thin anthracene crystals from super-saturated vapour, which
produces crystals of extreme flatness and controlled thickness. We show how
this crystal can be doped with a widely adjustable concentration of
dibenzoterrylene (DBT) molecules and we examine the optical properties of these
molecules to demonstrate their suitability as quantum emitters in nanophotonic
devices. Our measurements show that the molecules are available in the crystal
as single quantum emitters, with a well-defined polarisation relative to the
crystal axes, making them amenable to alignment with optical nanostructures. We
find that the radiative lifetime and saturation intensity vary little within
the crystal and are not in any way compromised by the unusual matrix
environment. We show that a large fraction of these emitters are able to
deliver more than photons without photo-bleaching, making them
suitable for real applications.Comment: 12 pages, 10 figures, comments welcom
Spatially resolved photoluminescence analysis of Se passivation and defect formation in CdSeTe thin films
CdTe is the most commercially successful thin-film photovoltaic technology to
date. The recent development of Se-alloyed CdSeTe layers in CdTe
solar cells has led to higher device efficiencies, due to a lowered bandgap
improving the photocurrent, improved voltage characteristics and longer carrier
lifetimes. Evidence from cross-sectional electron microscopy is widely believed
to indicate that Se passivates defects in CdSeTe solar cells, and
that this is the reason for better lifetimes and voltages in these devices.
Here, we utilise spatially resolved photoluminescence measurements of
CdSeTe thin films on glass to study the effects of Se on carrier
recombination in the material, isolated from the impact of conductive
interfaces and without the need to prepare cross-sections through the samples.
We find further evidence to support Se passivation of grain boundaries, but
also identify an associated increase in below-bandgap photoluminescence that
indicates the presence of Se-enhanced luminescent defects. Our results show
that Se treatment, in tandem with Cl passivation, does increase radiative
efficiencies. However, the simultaneous enhancement of defects within the grain
interiors suggests that although it is overall beneficial, Se incorporation may
still ultimately limit the maximum attainable efficiency of
CdSeTe solar cells
Single-photon-level sub-Doppler pump-probe spectroscopy of rubidium
We propose and demonstrate pump-probe spectroscopy of rubidium absorption
which reveals the sub-Doppler hyperfine structure of the S P (D2) transitions. The counter propagating pump
and probe lasers are independently tunable in frequency, with the probe
operating at the single-photon-level. The two-dimensional spectrum measured as
the laser frequencies are scanned shows fluorescence, Doppler-broadened
absorption dips and sub-Doppler features. The detuning between the pump and
probe lasers allows compensation of the Doppler shift for all atomic velocities
in the room temperature vapor, meaning we observe sub-Doppler features for all
atoms in the beam. We detail a theoretical model of the system which
incorporates fluorescence, saturation effects and optical pumping and compare
this with the measured spectrum, finding a mean absolute percentage error of
4.17\%. In the future this technique could assist in frequency stabilization of
lasers, and the single-photon-level probe could be replaced by a single photon
source.Comment: 5 page paper, 4 page supplemental material. Comments welcom
Efficient excitation of dye molecules for single photon generation
A reliable photon source is required for many aspects of quantum technology.
Organic molecules are attractive for this application because they can have
high quantum yield and can be photostable, even at room temperature. To
generate a photon with high probability, a laser must excite the molecule
efficiently. We develop a simple model for that efficiency and discuss how to
optimise it. We demonstrate the validity of our model through experiments on a
single dibenzoterrylene (DBT) molecule in an anthracene crystal. We show that
the excitation probability cannot exceed 75\% at room temperature, but can
increase to over 99\% if the sample is cooled to liquid nitrogen temperature.
The possibility of high photon generation efficiency with only modest cooling
is a significant step towards a reliable photon source that is simple and
practical.Comment: Main article (8 pages), Supplementary material (4 pages). Comments
welcom
Protein proximity networks and functional evaluation of the casein kinase 1 gamma family reveal unique roles for CK1γ3 in WNT signaling
Aberrant activation or suppression of WNT/β-catenin signaling contributes to cancer initiation and progression, neurodegeneration, and bone disease. However, despite great need and more than 40 years of research, targeted therapies for the WNT pathway have yet to be fully realized. Kinases are considered exceptionally druggable and occupy key nodes within the WNT signaling network, but several pathway-relevant kinases remain understudied and dark. Here, we studied the function of the casein kinase 1γ (CSNK1γ) subfamily of human kinases and their roles in WNT signaling. miniTurbo-based proximity biotinylation and mass spectrometry analysis of CSNK1γ1, CSNK1γ2, and CSNK1γ3 revealed numerous components of the β-catenin-dependent and β-catenin-independent WNT pathways. In gain-of-function experiments, we found that CSNK1γ3 but not CSNK1γ1 or CSNK1γ2 activated β-catenin-dependent WNT signaling, with minimal effect on other signaling pathways. We also show that within the family, CSNK1γ3 expression uniquely induced low-density lipoprotein receptor-related protein 6 phosphorylation, which mediates downstream WNT signaling transduction. Conversely, siRNA-mediated silencing of CSNK1γ3 alone had no impact on WNT signaling, though cosilencing of all three family members decreased WNT pathway activity. Finally, we characterized two moderately selective and potent small-molecule inhibitors of the CSNK1γ family. We show that these inhibitors and a CSNK1γ3 kinase-dead mutant suppressed but did not eliminate WNT-driven low-density lipoprotein receptor-related protein 6 phosphorylation and β-catenin stabilization. Our data suggest that while CSNK1γ3 expression uniquely drives pathway activity, potential functional redundancy within the family necessitates loss of all three family members to suppress the WNT signaling pathway
African linguistics on the prairie: Selected papers from the 45th Annual Conference on African Linguistics
African Linguistics on the Prairie features select revised peer-reviewed papers from the 45th Annual Conference on African Linguistics, held at the University of Kansas. The articles in this volume reflect the enormous diversity of African languages, as they focus on languages from all of the major African language phyla. The articles here also reflect the many different research perspectives that frame the work of linguists in the Association for Contemporary African Linguistics. The diversity of views presented in this volume are thus indicative of the vitality of current African linguistics research. The work presented in this volume represents both descriptive and theoretical methodologies and covers fields ranging from phonetics, phonology, morphology, typology, syntax, and semantics to sociolinguistics, discourse analysis, language acquisition, computational linguistics and beyond. This broad scope and the quality of the articles contained within holds out the promise of continued advancement in linguistic research on African languages
African linguistics on the prairie: Selected papers from the 45th Annual Conference on African Linguistics
African Linguistics on the Prairie features select revised peer-reviewed papers from the 45th Annual Conference on African Linguistics, held at the University of Kansas. The articles in this volume reflect the enormous diversity of African languages, as they focus on languages from all of the major African language phyla. The articles here also reflect the many different research perspectives that frame the work of linguists in the Association for Contemporary African Linguistics. The diversity of views presented in this volume are thus indicative of the vitality of current African linguistics research. The work presented in this volume represents both descriptive and theoretical methodologies and covers fields ranging from phonetics, phonology, morphology, typology, syntax, and semantics to sociolinguistics, discourse analysis, language acquisition, computational linguistics and beyond. This broad scope and the quality of the articles contained within holds out the promise of continued advancement in linguistic research on African languages
African linguistics on the prairie: Selected papers from the 45th Annual Conference on African Linguistics
African Linguistics on the Prairie features select revised peer-reviewed papers from the 45th Annual Conference on African Linguistics, held at the University of Kansas. The articles in this volume reflect the enormous diversity of African languages, as they focus on languages from all of the major African language phyla. The articles here also reflect the many different research perspectives that frame the work of linguists in the Association for Contemporary African Linguistics. The diversity of views presented in this volume are thus indicative of the vitality of current African linguistics research. The work presented in this volume represents both descriptive and theoretical methodologies and covers fields ranging from phonetics, phonology, morphology, typology, syntax, and semantics to sociolinguistics, discourse analysis, language acquisition, computational linguistics and beyond. This broad scope and the quality of the articles contained within holds out the promise of continued advancement in linguistic research on African languages
African linguistics on the prairie: Selected papers from the 45th Annual Conference on African Linguistics
African Linguistics on the Prairie features select revised peer-reviewed papers from the 45th Annual Conference on African Linguistics, held at the University of Kansas. The articles in this volume reflect the enormous diversity of African languages, as they focus on languages from all of the major African language phyla. The articles here also reflect the many different research perspectives that frame the work of linguists in the Association for Contemporary African Linguistics. The diversity of views presented in this volume are thus indicative of the vitality of current African linguistics research. The work presented in this volume represents both descriptive and theoretical methodologies and covers fields ranging from phonetics, phonology, morphology, typology, syntax, and semantics to sociolinguistics, discourse analysis, language acquisition, computational linguistics and beyond. This broad scope and the quality of the articles contained within holds out the promise of continued advancement in linguistic research on African languages
African linguistics on the prairie: Selected papers from the 45th Annual Conference on African Linguistics
African Linguistics on the Prairie features select revised peer-reviewed papers from the 45th Annual Conference on African Linguistics, held at the University of Kansas. The articles in this volume reflect the enormous diversity of African languages, as they focus on languages from all of the major African language phyla. The articles here also reflect the many different research perspectives that frame the work of linguists in the Association for Contemporary African Linguistics. The diversity of views presented in this volume are thus indicative of the vitality of current African linguistics research. The work presented in this volume represents both descriptive and theoretical methodologies and covers fields ranging from phonetics, phonology, morphology, typology, syntax, and semantics to sociolinguistics, discourse analysis, language acquisition, computational linguistics and beyond. This broad scope and the quality of the articles contained within holds out the promise of continued advancement in linguistic research on African languages
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