8,019 research outputs found
MYSTIC: Michigan Young STar Imager at CHARA
We present the design for MYSTIC, the Michigan Young STar Imager at CHARA.
MYSTIC will be a K-band, cryogenic, 6-beam combiner for the Georgia State
University CHARA telescope array. The design follows the image-plane
combination scheme of the MIRC instrument where single-mode fibers bring
starlight into a non-redundant fringe pattern to feed a spectrograph. Beams
will be injected in polarization-maintaining fibers outside the cryogenic dewar
and then be transported through a vacuum feedthrough into the ~220K cold volume
where combination is achieved and the light is dispersed. We will use a C-RED
One camera (First Light Imaging) based on the eAPD SAPHIRA detector to allow
for near-photon-counting performance. We also intend to support a 4-telescope
mode using a leftover integrated optics component designed for the VLTI-GRAVITY
experiment, allowing better sensitivity for the faintest targets. Our primary
science driver motivation is to image disks around young stars in order to
better understand planet formation and how forming planets might influence disk
structures.Comment: Presented at the 2018 SPIE Astronomical Telescopes + Instrumentation,
Austin, Texas, US
Simultaneous interrogation of multiple fiber bragg grating sensors using an arrayed waveguide grating filter fabricated in SOI platform
A novel fiber Bragg grating (FBG) interrogator is demonstrated based on an optimized arrayed waveguide grating (AWG) filter. The AWG response is optimized to achieve large crosstalk between the output channels, which allows simultaneous detection of multiple FBG peaks, using centroid signal processing techniques, without constraints on the minimum FBG peak spectral width. The measured interrogator resolution is 2.5 pm, and the total measurement range is 50 nm. The device is fabricated in a silicon-on-insulator platform and has a footprint of only 2.2 x 1.5 mm. A novel approach to minimize the polarization dependence of the device is proposed and experimentally demonstrated
Astronomical photonics in the context of infrared interferometry and high-resolution spectroscopy
We review the potential of Astrophotonics, a relatively young field at the
interface between photonics and astronomical instrumentation, for
spectro-interferometry. We review some fundamental aspects of photonic science
that drove the emer- gence of astrophotonics, and highlight the achievements in
observational astrophysics. We analyze the prospects for further technological
development also considering the potential synergies with other fields of
physics (e.g. non-linear optics in condensed matter physics). We also stress
the central role of fiber optics in routing and transporting light, delivering
complex filters, or interfacing instruments and telescopes, more specifically
in the context of a growing usage of adaptive optics.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June
2016, 21 pages, 10 Figure
Development of ultrafast laser inscribed astrophotonic components
The rapid development of astronomical instrumentation has been aided by many
innovative new photonic designs, which offer improvements in stability, precision, size
and cost, scalability, etc. ─ the field of astrophotonics. A powerful technique enabling
many of these astrophotonic devices, ultrafast laser inscription (ULI), creates highly
localised and controlled refractive index modification, which guides the path of light in
a very efficient manner. This thesis discusses three separate astrophotonic devices, each
with a specific application, to demonstrate the versatility of ULI.
Firstly, a reformatting device based on a photonic lantern and 3D ULI waveguide
reformatting component, transforms a multimode telescope PSF to a diffraction-limited
pseudo-slit. When used to feed a spectrograph, a significant reduction in modal noise ─
a limiting factor in high-resolution multimode fibre-fed spectrographs ─ is
demonstrated, with the potential for improved near-infrared radial velocity observations.
Secondly, a similar ULI reformatting device for an integral field unit, based on
multicore fibre with affixed microlenses, may enable the direct imaging of exoplanets
and characterisation of their atmospheres. Thirdly, a two-telescope K-band beam
combiner based on ULI directional couplers with an achromatic 3dB splitting ratio is
presented. Such a device will upgrade the stellar interferometry capabilities of the
CHARA array
Multiband processing of multimode light: combining 3D photonic lanterns with waveguide Bragg gratings
The first demonstration of narrowband spectral filtering of multimode light
on a 3D integrated photonic chip using photonic lanterns and waveguide Bragg
gratings is reported. The photonic lanterns with multi-notch waveguide Bragg
gratings were fabricated using the femtosecond direct-write technique in
boro-aluminosilicate glass (Corning, Eagle 2000). Transmission dips of up to 5
dB were measured in both photonic lanterns and reference single-mode waveguides
with 10.4-mm-long gratings. The result demonstrates efficient and symmetrical
performance of each of the gratings in the photonic lantern. Such devices will
be beneficial to space-division multiplexed communication systems as well as
for units for astronomical instrumentation for suppression of the atmospheric
telluric emission from OH lines.Comment: 5 pages, 4 figures, accepted to Laser & Photonics Review
The Subaru Coronagraphic Extreme Adaptive Optics system: enabling high-contrast imaging on solar-system scales
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is a
multipurpose high-contrast imaging platform designed for the discovery and
detailed characterization of exoplanetary systems and serves as a testbed for
high-contrast imaging technologies for ELTs. It is a multi-band instrument
which makes use of light from 600 to 2500nm allowing for coronagraphic direct
exoplanet imaging of the inner 3 lambda/D from the stellar host. Wavefront
sensing and control are key to the operation of SCExAO. A partial correction of
low-order modes is provided by Subaru's facility adaptive optics system with
the final correction, including high-order modes, implemented downstream by a
combination of a visible pyramid wavefront sensor and a 2000-element deformable
mirror. The well corrected NIR (y-K bands) wavefronts can then be injected into
any of the available coronagraphs, including but not limited to the phase
induced amplitude apodization and the vector vortex coronagraphs, both of which
offer an inner working angle as low as 1 lambda/D. Non-common path, low-order
aberrations are sensed with a coronagraphic low-order wavefront sensor in the
infrared (IR). Low noise, high frame rate, NIR detectors allow for active
speckle nulling and coherent differential imaging, while the HAWAII 2RG
detector in the HiCIAO imager and/or the CHARIS integral field spectrograph
(from mid 2016) can take deeper exposures and/or perform angular, spectral and
polarimetric differential imaging. Science in the visible is provided by two
interferometric modules: VAMPIRES and FIRST, which enable sub-diffraction
limited imaging in the visible region with polarimetric and spectroscopic
capabilities respectively. We describe the instrument in detail and present
preliminary results both on-sky and in the laboratory.Comment: Accepted for publication, 20 pages, 10 figure
SPIFI: a Direct-Detection Imaging Spectrometer for Submillimeter Wavelengths
The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind -a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI ’s focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 μm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI’s sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument ’s large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope
Integrated photonic building blocks for next-generation astronomical instrumentation II: the multimode to single mode transition
There are numerous advantages to exploiting diffraction-limited
instrumentation at astronomical observatories, which include smaller
footprints, less mechanical and thermal instabilities and high levels of
performance. To realize such instrumentation it is imperative to convert the
atmospheric seeing-limited signal that is captured by the telescope into a
diffraction-limited signal. This process can be achieved photonically by using
a mode reformatting device known as a photonic lantern that performs a
multimode to single-mode transition. With the aim of developing an optimized
integrated photonic lantern, we undertook a systematic parameter scan of
devices fabricated by the femtosecond laser direct-write technique. The devices
were designed for operation around 1.55 {\mu}m. The devices showed (coupling
and transition) losses of less than 5% for F/# 12 injection and the
total device throughput (including substrate absorption) as high as 75-80%.
Such devices show great promise for future use in astronomy.Comment: 12 pages, 9 figure
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