13,480 research outputs found
Linear scanning ATR-FTIR for chemical mapping and high-throughput studies of Pseudomonas sp. biofilms in microfluidic channels
A fully automated linear scanning attenuated total reflection (ATR) accessory
is presented for Fourier transform infrared (FTIR) spectroscopy. The approach
is based on the accurate displacement of a multi-bounce ATR crystal relative to
a stationary infrared beam. To ensure accurate positioning and to provide a
second sample characterization mode, a custom-built microscope was integrated
into the system and the computerized work flow. Custom software includes
automated control and measurement routines with a straightforward user
interface for selecting parameters and monitoring experimental progress. This
cost-effective modular system can be implemented on any research-grade
spectrometer with a standard sample compartment for new bioanalytical chemistry
studies. The system was validated and optimized for use with microfluidic flow
cells containing growing Pseudomonas sp. bacterial biofilms. The
complementarity among the scan positioning accuracy, measurement spatial
resolution and the microchannel dimensions paves the way for parallel
biological assays with real-time control over environmental parameters and
minimal manual labor. By rotating the channel orientation relative to the beam
path, the system could also be used for acquisition of linear biochemical maps
and stitched microscope images along the channel length.Comment: 9 pages, 6 figure
Bottom-up Photonic Crystal Lasers
The directed growth of III–V nanopillars is used to demonstrate bottom-up photonic crystal lasers. Simultaneous formation of both the photonic band gap and active gain region is achieved via catalyst-free selective-area metal–organic chemical vapor deposition on masked GaAs substrates. The nanopillars implement a GaAs/InGaAs/GaAs axial double heterostructure for accurate, arbitrary placement of gain within the cavity and lateral InGaP shells to reduce surface recombination. The lasers operate single-mode at room temperature with low threshold peak power density of ~625 W/cm^2. Cavity resonance and lasing wavelength is lithographically defined by controlling pillar pitch and diameter to vary from 960 to 989 nm. We envision this bottom-up approach to pillar-based devices as a new platform for photonic systems integration
Engineering Hybrid Epitaxial InAsSb/Al Nanowire Materials for Stronger Topological Protection
The combination of strong spin-orbit coupling, large -factors, and the
coupling to a superconductor can be used to create a topologically protected
state in a semiconductor nanowire. Here we report on growth and
characterization of hybrid epitaxial InAsSb/Al nanowires, with varying
composition and crystal structure. We find the strongest spin-orbit interaction
at intermediate compositions in zincblende InAsSb nanowires,
exceeding that of both InAs and InSb materials, confirming recent theoretical
studies \cite{winkler2016topological}. We show that the epitaxial InAsSb/Al
interfaces allows for a hard induced superconducting gap and 2 transport in
Coulomb charging experiments, similar to experiments on InAs/Al and InSb/Al
materials, and find measurements consistent with topological phase transitions
at low magnetic fields due to large effective -factors. Finally we present a
method to grow pure wurtzite InAsSb nanowires which are predicted to exhibit
even stronger spin-orbit coupling than the zincblende structure.Comment: 10 pages and 5 figure
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Survey of partitioning techniques in silicon compilation
In the silicon compilation design process, partitioning is usually the first problem to be investigated because partitioning algorithms form the backbone of many algorithms including: system synthesis, processor synthesis, floorplanning, and placement. In this survey, several partitioning techniques will be examined. In addition, this paper will review the partitioning algorithms used by synthesis systems at different design levels
Chalcogenide Glass-on-Graphene Photonics
Two-dimensional (2-D) materials are of tremendous interest to integrated
photonics given their singular optical characteristics spanning light emission,
modulation, saturable absorption, and nonlinear optics. To harness their
optical properties, these atomically thin materials are usually attached onto
prefabricated devices via a transfer process. In this paper, we present a new
route for 2-D material integration with planar photonics. Central to this
approach is the use of chalcogenide glass, a multifunctional material which can
be directly deposited and patterned on a wide variety of 2-D materials and can
simultaneously function as the light guiding medium, a gate dielectric, and a
passivation layer for 2-D materials. Besides claiming improved fabrication
yield and throughput compared to the traditional transfer process, our
technique also enables unconventional multilayer device geometries optimally
designed for enhancing light-matter interactions in the 2-D layers.
Capitalizing on this facile integration method, we demonstrate a series of
high-performance glass-on-graphene devices including ultra-broadband on-chip
polarizers, energy-efficient thermo-optic switches, as well as graphene-based
mid-infrared (mid-IR) waveguide-integrated photodetectors and modulators
Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity
We demonstrate coupling of the zero-phonon line of individual
nitrogen-vacancy centers and the modes of microring resonators fabricated in
single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is
estimated from lifetime measurements at cryogenic temperatures. The devices are
fabricated using standard semiconductor techniques and off-the-shelf materials,
thus enabling integrated diamond photonics.Comment: 5 pages, 4 figure
Internal visual workmanship standard for microelectronic devices /NASA STD XX-2/ and training manual, volume 2
Internal visual workmanship standards for monolithic microelectronic devices - training manua
Vertical-external-cavity surface-emitting lasers and quantum dot lasers
The use of cavity to manipulate photon emission of quantum dots (QDs) has
been opening unprecedented opportunities for realizing quantum functional
nanophotonic devices and also quantum information devices. In particular, in
the field of semiconductor lasers, QDs were introduced as a superior
alternative to quantum wells to suppress the temperature dependence of the
threshold current in vertical-external-cavity surface-emitting lasers
(VECSELs). In this work, a review of properties and development of
semiconductor VECSEL devices and QD laser devices is given. Based on the
features of VECSEL devices, the main emphasis is put on the recent development
of technological approach on semiconductor QD VECSELs. Then, from the viewpoint
of both single QD nanolaser and cavity quantum electrodynamics (QED), a
single-QD-cavity system resulting from the strong coupling of QD cavity is
presented. A difference of this review from the other existing works on
semiconductor VECSEL devices is that we will cover both the fundamental aspects
and technological approaches of QD VECSEL devices. And lastly, the presented
review here has provided a deep insight into useful guideline for the
development of QD VECSEL technology and future quantum functional nanophotonic
devices and monolithic photonic integrated circuits (MPhICs).Comment: 21 pages, 4 figures. arXiv admin note: text overlap with
arXiv:0904.369
The Cleo Rich Detector
We describe the design, construction and performance of a Ring Imaging
Cherenkov Detector (RICH) constructed to identify charged particles in the CLEO
experiment. Cherenkov radiation occurs in LiF crystals, both planar and ones
with a novel ``sawtooth''-shaped exit surface. Photons in the wavelength
interval 135--165 nm are detected using multi-wire chambers filled with a
mixture of methane gas and triethylamine vapor. Excellent pion/kaon separation
is demonstrated.Comment: 75 pages, 57 figures, (updated July 26, 2005 to reflect reviewers
comments), to be published in NIM
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