210 research outputs found
A Directly-Written Monolithic Waveguide-Laser Incorporating a DFB Waveguide-Bragg Grating
We report the fabrication and performance of the first C-band
directly-written monolithic waveguide-laser. The waveguide-laser device was
created in an Erbium and Ytterbium doped phosphate glass host and consisted of
an optical waveguide that included a distributed feedback Bragg grating
structure. The femtosecond laser direct-write technique was used to create both
the waveguide and the waveguide-Bragg grating simultaneously and in a single
processing step. The waveguide-laser was optically pumped at approximately 980
nm and lased at 1537nm with a bandwidth of less than 4 pm.Comment: 6 pages, 13 references, 4 figure
Generation of heralded single photons beyond 1100 nm by spontaneous four-wave mixing in a side-stressed femtosecond laser-written waveguide
We demonstrate a monolithically integrable heralded photon source in a
femtosecond laser direct written glass waveguide. The generation of photon
pairs with a wide wavelength separation requires a concomitant large
birefringence in the normal dispersion regime. Here, by incorporation of
side-stress tracks, we produce a waveguide with a birefringence of
and propagation loss as low as 0.21 dB/cm near 980~nm. We
measure photon pairs with 300~nm wavelength separation at an internal
generation rate exceeding /s. The second order correlations
indicate that the generated photon pairs are in a strongly non-classical
regime.Comment: 5 pages, 5 figure
A 100 mW monolithic Yb waveguide laser fabricated using the femtosecond laser direct-write technique
A femtosecond laser-written monolithic waveguide laser (WGL) oscillator based
on a distributed feedback (DFB) architecture and fabricated in ytterbium doped
phosphate glass is reported. The device lased at 1033 nm with an output power
of 102 mW and a bandwidth less than 2 pm when bidirectionally pumped at 976 nm.
The WGL device was stable and operated for 50 hours without degradation. This
demonstration of a high performance WGL opens the possibility for creating a
variety of narrow-linewidth laser designs in bulk glasses.Comment: 5 pages, 3 figures, submitted journal manuscrip
Three-dimensional imaging of direct-written photonic structures
Third harmonic generation microscopy has been used to analyze the morphology
of photonic structures created using the femtosecond laser direct-write
technique. Three dimensional waveguide arrays and waveguide-Bragg gratings
written in fused-silica and doped phosphate glass were investigated. A
sensorless adaptive optical system was used to correct the optical aberrations
occurring in the sample and microscope system, which had a lateral resolution
of less than 500 nm. This non-destructive testing method creates volume
reconstructions of photonic devices and reveals details invisible to other
linear microscopy and index profilometry techniques.Comment: 8 pages, 3 color figures, 2 hyper-linked animation
Laser written waveguide photonic quantum circuits
We report photonic quantum circuits created using an ultrafast laser
processing technique that is rapid, requires no lithographic mask and can be
used to create three-dimensional networks of waveguide devices. We have
characterized directional couplers--the key functional elements of photonic
quantum circuits--and found that they perform as well as lithographically
produced waveguide devices. We further demonstrate high-performance
interferometers and an important multi-photon quantum interference phenomenon
for the first time in integrated optics. This direct-write approach will enable
the rapid development of sophisticated quantum optical circuits and their
scaling into three-dimensions.Comment: 4 pages, 4 figures. Submitted to Optics Express 04/04/2009, accepted
for publication 30/06/0
Photonic Technologies for a Pupil Remapping Interferometer
Interest in pupil-remapping interferometry, in which a single telescope pupil
is fragmented and recombined using fiber optic technologies, has been growing
among a number of groups. As a logical extrapolation from several highly
successful aperture masking programs underway worldwide, pupil remapping offers
the advantage of spatial filtering (with single-mode fibers) and in principle
can avoid the penalty of low throughput inherent to an aperture mask. However
in practice, pupil remapping presents a number of difficult technological
challenges including injection into the fibers, pathlength matching of the
device, and stability and reproducibility of the results. Here we present new
approaches based on recently-available photonic technologies in which coherent
three-dimensional waveguide structures can be sculpted into bulk substrate.
These advances allow us to miniaturize the photonic processing into a single,
robust, thermally stable element; ideal for demanding observatory or spacecraft
environments. Ultimately, a wide range of optical functionality could be
routinely fabricated into such structures, including beam combiners and
dispersive or wavelength selective elements, bringing us closer to the vision
of an interferometer on a chip.Comment: 9 pages, 6 figures, SPIE 201
Generation of light-producing somatic-transgenic mice using adeno-associated virus vectors
© 2020, The Author(s). We have previously designed a library of lentiviral vectors to generate somatic-transgenic rodents to monitor signalling pathways in diseased organs using whole-body bioluminescence imaging, in conscious, freely moving rodents. We have now expanded this technology to adeno-associated viral vectors. We first explored bio-distribution by assessing GFP expression after neonatal intravenous delivery of AAV8. We observed widespread gene expression in, central and peripheral nervous system, liver, kidney and skeletal muscle. Next, we selected a constitutive SFFV promoter and NFκB binding sequence for bioluminescence and biosensor evaluation. An intravenous injection of AAV8 containing firefly luciferase and eGFP under transcriptional control of either element resulted in strong and persistent widespread luciferase expression. A single dose of LPS-induced a 10-fold increase in luciferase expression in AAV8-NFκB mice and immunohistochemistry revealed GFP expression in cells of astrocytic and neuronal morphology. Importantly, whole-body bioluminescence persisted up to 240 days. We have validated a novel biosensor technology in an AAV system by using an NFκB response element and revealed its potential to monitor signalling pathway in a non-invasive manner in a model of LPS-induced inflammation. This technology complements existing germline-transgenic models and may be applicable to other rodent disease models
Analysing Stratified Medicine Business Models and Value Systems:Innovation-Regulation Interactions
Resolving the ancestry of Austronesian-speaking populations
There are two very different interpretations of the prehistory of Island Southeast Asia (ISEA), with genetic evidence invoked in support of both. The “out-of-Taiwan” model proposes a major Late Holocene expansion of Neolithic Austronesian speakers from Taiwan. An alternative, proposing that Late Glacial/postglacial sea-level rises triggered largely autochthonous dispersals, accounts for some otherwise enigmatic genetic patterns, but fails to explain the Austronesian language dispersal. Combining mitochondrial DNA (mtDNA), Y-chromosome and genome-wide data, we performed the most comprehensive analysis of the region to date, obtaining highly consistent results across all three systems and allowing us to reconcile the models. We infer a primarily common ancestry for Taiwan/ISEA populations established before the Neolithic, but also detected clear signals of two minor Late Holocene migrations, probably representing Neolithic input from both Mainland Southeast Asia and South China, via Taiwan. This latter may therefore have mediated the Austronesian language dispersal, implying small-scale migration and language shift rather than large-scale expansion
Determining Supersymmetric Parameters With Dark Matter Experiments
In this article, we explore the ability of direct and indirect dark matter
experiments to not only detect neutralino dark matter, but to constrain and
measure the parameters of supersymmetry. In particular, we explore the
relationship between the phenomenological quantities relevant to dark matter
experiments, such as the neutralino annihilation and elastic scattering cross
sections, and the underlying characteristics of the supersymmetric model, such
as the values of mu (and the composition of the lightest neutralino), m_A and
tan beta. We explore a broad range of supersymmetric models and then focus on a
smaller set of benchmark models. We find that by combining astrophysical
observations with collider measurements, mu can often be constrained far more
tightly than it can be from LHC data alone. In models in the A-funnel region of
parameter space, we find that dark matter experiments can potentially determine
m_A to roughly +/-100 GeV, even when heavy neutral MSSM Higgs bosons (A, H_1)
cannot be observed at the LHC. The information provided by astrophysical
experiments is often highly complementary to the information most easily
ascertained at colliders.Comment: 46 pages, 76 figure
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