40,687 research outputs found
Light-sheet microscopy: a tutorial
This paper is intended to give a comprehensive review of light-sheet (LS) microscopy from an optics perspective. As such, emphasis is placed on the advantages that LS microscope configurations present, given the degree of freedom gained by uncoupling the excitation and detection arms. The new imaging properties are first highlighted in terms of optical parameters and how these have enabled several biomedical applications. Then, the basics are presented for understanding how a LS microscope works. This is followed by a presentation of a tutorial for LS microscope designs, each working at different resolutions and for different applications. Then, based on a numerical Fourier analysis and given the multiple possibilities for generating the LS in the microscope (using Gaussian, Bessel, and Airy beams in the linear and nonlinear regimes), a systematic comparison of their optical performance is presented. Finally, based on advances in optics and photonics, the novel optical implementations possible in a LS microscope are highlighted.Peer ReviewedPostprint (published version
Precision near-infrared radial velocity instrumentation II: Non-Circular Core Fiber Scrambler
We have built and commissioned a prototype agitated non-circular core fiber
scrambler for precision spectroscopic radial velocity measurements in the
near-infrared H band. We have collected the first on-sky performance and modal
noise tests of these novel fibers in the near-infrared at H and K bands using
the CSHELL spectrograph at the NASA InfraRed Telescope Facility (IRTF). We
discuss the design behind our novel reverse injection of a red laser for
co-alignment of star-light with the fiber tip via a corner cube and visible
camera. We summarize the practical details involved in the construction of the
fiber scrambler, and the mechanical agitation of the fiber at the telescope. We
present radial velocity measurements of a bright standard star taken with and
without the fiber scrambler to quantify the relative improvement in the
obtainable blaze function stability, the line spread function stability, and
the resulting radial velocity precision. We assess the feasibility of applying
this illumination stabilization technique to the next generation of
near-infrared spectrographs such as iSHELL on IRTF and an upgraded NIRSPEC at
Keck. Our results may also be applied in the visible for smaller core diameter
fibers where fiber modal noise is a significant factor, such as behind an
adaptive optics system or on a small < 1 meter class telescope such as is being
pursued by the MINERVA and LCOGT collaborations.Comment: Proceedings of the SPIE Optics and Photonics Conference "Techniques
and Instrumentation for Detection of Exoplanets VI" held in San Diego, CA,
August 25-29, 201
Characterization of microdot apodizers for imaging exoplanets with next-generation space telescopes
A major science goal of future, large-aperture, optical space telescopes is
to directly image and spectroscopically analyze reflected light from
potentially habitable exoplanets. To accomplish this, the optical system must
suppress diffracted light from the star to reveal point sources approximately
ten orders of magnitude fainter than the host star at small angular separation.
Coronagraphs with microdot apodizers achieve the theoretical performance needed
to image Earth-like planets with a range of possible telescope designs,
including those with obscured and segmented pupils. A test microdot apodizer
with various bulk patterns (step functions, gradients, and sinusoids) and 4
different dot sizes (3, 5, 7, and 10 m) made of small chrome squares on
anti-reflective glass was characterized with microscopy, optical laser
interferometry, as well as transmission and reflectance measurements at
wavelengths of 600 and 800 nm. Microscopy revealed the microdots were
fabricated to high precision. Results from laser interferometry showed that the
phase shifts observed in reflection vary with the local microdot fill factor.
Transmission measurements showed that microdot fill factor and transmission
were linearly related for dot sizes >5 m. However, anomalously high
transmittance was measured when the dot size is <5x the wavelength and the fill
factor is approximately 50%, where the microdot pattern becomes periodic. The
transmission excess is not as prominent in the case of larger dot sizes
suggesting that it is likely to be caused by the interaction between the
incident field and electronic resonances in the surface of the metallic
microdots. We used our empirical models of the microdot apodizers to optimize a
second generation of reflective apodizer designs and confirmed that the
amplitude and phase of the reflected beam closely matches the ideal wavefront.Comment: Space Telescopes and Instrumentation 2018: Optical, Infrared, and
Millimeter Wav
Free-space propagation of high dimensional structured optical fields in an urban environment
Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use
light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical
systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on
these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel
between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal
mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses
on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantumstate
tomography. We present experimental data for the modal degradation in a real urban environment and draw a
comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel
models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured
modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially
through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in
an urban environment
Making SPIFFI SPIFFIER: Upgrade of the SPIFFI instrument for use in ERIS and performance analysis from re-commissioning
SPIFFI is an AO-fed integral field spectrograph operating as part of SINFONI
on the VLT, which will be upgraded and reused as SPIFFIER in the new VLT
instrument ERIS. In January 2016, we used new technology developments to
perform an early upgrade to optical subsystems in the SPIFFI instrument so
ongoing scientific programs can make use of enhanced performance before ERIS
arrives in 2020. We report on the upgraded components and the performance of
SPIFFI after the upgrade, including gains in throughput and spatial and
spectral resolution. We show results from re-commissioning, highlighting the
potential for scientific programs to use the capabilities of the upgraded
SPIFFI. Finally, we discuss the additional upgrades for SPIFFIER which will be
implemented before it is integrated into ERIS.Comment: 20 pages, 12 figures. Proceedings from SPIE Astronomical Telescopes
and Instrumentation 201
Impact of parameter variations on circuits and microarchitecture
Parameter variations, which are increasing along with advances in process technologies, affect both timing and power. Variability must be considered at both the circuit and microarchitectural design levels to keep pace with performance scaling and to keep power consumption within reasonable limits. This article presents an overview of the main sources of variability and surveys variation-tolerant circuit and microarchitectural approaches.Peer ReviewedPostprint (published version
ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory
A new high-order adaptive optics system is now being commissioned at the Lick
Observatory Shane 3-meter telescope in California. This system uses a high
return efficiency sodium beacon and a combination of low and high-order
deformable mirrors to achieve diffraction-limited imaging over a wide spectrum
of infrared science wavelengths covering 0.8 to 2.2 microns. We present the
design performance goals and the first on-sky test results. We discuss several
innovations that make this system a pathfinder for next generation AO systems.
These include a unique woofer-tweeter control that provides full dynamic range
correction from tip/tilt to 16 cycles, variable pupil sampling wavefront
sensor, new enhanced silver coatings developed at UC Observatories that improve
science and LGS throughput, and tight mechanical rigidity that enables a
multi-hour diffraction- limited exposure in LGS mode for faint object
spectroscopy science.Comment: 11 pages, 10 figures. Presented at SPIE Astronomical Telescopes +
Instrumentation conference, paper 9148-7
Starlight Demonstration of the Dragonfly Instrument: an Integrated Photonic Pupil Remapping Interferometer for High Contrast Imaging
In the two decades since the first extra-solar planet was discovered, the
detection and characterization of extra-solar planets has become one of the key
endeavors in all of modern science. Recently direct detection techniques such
as interferometry or coronography have received growing attention because they
reveal the population of exoplanets inaccessible to Doppler or transit
techniques, and moreover they allow the faint signal from the planet itself to
be investigated. Next-generation stellar interferometers are increasingly
incorporating photonic technologies due to the increase in fidelity of the data
generated. Here, we report the design, construction and commissioning of a new
high contrast imager; the integrated pupil-remapping interferometer; an
instrument we expect will find application in the detection of young faint
companions in the nearest star-forming regions. The laboratory characterisation
of the instrument demonstrated high visibility fringes on all interferometer
baselines in addition to stable closure phase signals. We also report the first
successful on-sky experiments with the prototype instrument at the 3.9-m
Anglo-Australian Telescope. Performance metrics recovered were consistent with
ideal device behaviour after accounting for expected levels of decoherence and
signal loss from the uncompensated seeing. The prospect of complete
Fourier-coverage coupled with the current performance metrics means that this
photonically-enhanced instrument is well positioned to contribute to the
science of high contrast companions.Comment: 10 pages, 7 figures, accepted to Mon. Not. of Roy. Ast. Soc., 201
Multi-Conjugate Adaptive Optics Simulator for the Thirty Meter Telescope: Design, Implementation, and Results
We present a multi-conjugate adaptive optics (MCAO) system simulator bench,
HeNOS (Herzberg NFIRAOS Optical Simulator). HeNOS is developed to validate the
performance of the MCAO system for the Thirty Meter Telescope, as well as to
demonstrate techniques critical for future AO developments. In this paper, we
focus on describing the derivations of parameters that scale the 30-m telescope
AO system down to a bench experiment and explain how these parameters are
practically implemented on an optical bench. While referring other papers for
details of AO technique developments using HeNOS, we introduce the
functionality of HeNOS, in particular, three different single-conjugate AO
modes that HeNOS currently offers: a laser guide star AO with a Shack-Hartmann
wavefront sensor, a natural guide star AO with a pyramid wavefront sensor, and
a laser guide star AO with a sodium spot elongation on the Shack-Hartmann
corrected by a truth wavefront sensing on a natural guide star. Laser
tomography AO and ultimate MCAO are being prepared to be implemented in the
near future
On-sky single-mode fiber coupling measurements at the Large Binocular Telescope
The demonstration of efficient single-mode fiber (SMF) coupling is a key
requirement for the development of a compact, ultra-precise radial velocity
(RV) spectrograph. iLocater is a next generation instrument for the Large
Binocular Telescope (LBT) that uses adaptive optics (AO) to inject starlight
into a SMF. In preparation for commissioning iLocater, a prototype SMF
injection system was installed and tested at the LBT in the Y-band (0.970-1.065
m). This system was designed to verify the capability of the LBT AO system
as well as characterize on-sky SMF coupling efficiencies. SMF coupling was
measured on stars with variable airmasses, apparent magnitudes, and seeing
conditions for six half-nights using the Large Binocular Telescope
Interferometer. We present the overall optical and mechanical performance of
the SMF injection system, including details of the installation and alignment
procedure. A particular emphasis is placed on analyzing the instrument's
performance as a function of telescope elevation to inform the final design of
the fiber injection system for iLocater.Comment: 11 pages, 7 figure
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