44 research outputs found
First starlight spectrum captured using an integrated photonic micro-spectrograph
Photonic technologies have received growing consideration for incorporation
into next-generation astronomical instrumentation, owing to their miniature
footprint and inherent robustness. In this paper we present results from the
first on-telescope demonstration of a miniature photonic spectrograph for
astronomy, by obtaining spectra spanning the entire H-band from several stellar
targets. The prototype was tested on the 3.9 m Anglo-Australian telescope. In
particular, we present a spectrum of the variable star Pi 01 Gru, with observed
CO molecular absorption bands, at a resolving power R = 2500 at 1600 nm.
Furthermore, we successfully demonstrate the simultaneous acquisition of
multiple spectra with a single spectrograph chip by using multiple fibre
inputs.Comment: 5 Pages, 4 Figures; A&A, Volume 544 (2012
Efficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy
Photonic technologies offer numerous advantages for astronomical instruments
such as spectrographs and interferometers owing to their small footprints and
diverse range of functionalities. Operating at the diffraction-limit, it is
notoriously difficult to efficiently couple such devices directly with large
telescopes. We demonstrate that with careful control of both the non-ideal
pupil geometry of a telescope and residual wavefront errors, efficient coupling
with single-mode devices can indeed be realised. A fibre injection was built
within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument.
Light was coupled into a single-mode fibre operating in the near-IR (J-H bands)
which was downstream of the extreme adaptive optics system and the pupil
apodising optics. A coupling efficiency of 86% of the theoretical maximum limit
was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and
was linearly correlated with Strehl ratio. The coupling efficiency was constant
to within <30% in the range 1250-1600 nm. Preliminary on-sky data with a Strehl
ratio of 60% in the H-band produced a coupling efficiency into a single-mode
fibre of ~50%, consistent with expectations. The coupling was >40% for 84% of
the time and >50% for 41% of the time. The laboratory results allow us to
forecast that extreme adaptive optics levels of correction (Strehl ratio >90%
in H-band) would allow coupling of >67% (of the order of coupling to multimode
fibres currently). For Strehl ratios <20%, few-port photonic lanterns become a
superior choice but the signal-to-noise must be considered. These results
illustrate a clear path to efficient on-sky coupling into a single-mode fibre,
which could be used to realise modal-noise-free radial velocity machines,
very-long-baseline optical/near-IR interferometers and/or simply exploit
photonic technologies in future instrument design.Comment: 15 pages, 16 figures, 1 table, published in A&
High-performance 3D waveguide architecture for astronomical pupil-remapping interferometry
The detection and characterisation of extra-solar planets is a major theme
driving modern astronomy, with the vast majority of such measurements being
achieved by Doppler radial-velocity and transit observations. Another technique
-- direct imaging -- can access a parameter space that complements these
methods, and paves the way for future technologies capable of detailed
characterization of exoplanetary atmospheres and surfaces. However achieving
the required levels of performance with direct imaging, particularly from
ground-based telescopes which must contend with the Earth's turbulent
atmosphere, requires considerable sophistication in the instrument and
detection strategy. Here we demonstrate a new generation of photonic
pupil-remapping devices which build upon the interferometric framework
developed for the {\it Dragonfly} instrument: a high contrast waveguide-based
device which recovers robust complex visibility observables. New generation
Dragonfly devices overcome problems caused by interference from unguided light
and low throughput, promising unprecedented on-sky performance. Closure phase
measurement scatter of only has been achieved, with waveguide
throughputs of . This translates to a maximum contrast-ratio
sensitivity (between the host star and its orbiting planet) at
(1 detection) of (when a conventional
adaptive-optics (AO) system is used) or (for typical
`extreme-AO' performance), improving even further when random error is
minimised by averaging over multiple exposures. This is an order of magnitude
beyond conventional pupil-segmenting interferometry techniques (such as
aperture masking), allowing a previously inaccessible part of the star to
planet contrast-separation parameter space to be explored
FIRST, a pupil-remapping fiber interferometer at the Subaru Telescope: on-sky results
FIRST, the Fibered Imager foR a Single Telescope, is a spectro-imager using single-mode fibers for pupil remap- ping, allowing measurements beyond the telescope diffraction limit. Integrated on the Subaru Coronagraphic Extreme Adaptive Optics instrument at the Subaru Telescope, it benefits from a very stable visible light wave- front allowing to acquire long exposure and operate on significantly fainter sources than previously possible. On-sky results demonstrated the ability of the instrument to detect stellar companions separated 43mas in the case of the Capella binary system. A similar approach on an extremely large telescope would offer unique scientific opportunities for companion detection and characterization at very high angular resolution
FIRST, a pupil-remapping fiber interferometer at the Subaru Telescope: on-sky results
FIRST, the Fibered Imager foR a Single Telescope, is a spectro-imager using single-mode fibers for pupil remap- ping, allowing measurements beyond the telescope diffraction limit. Integrated on the Subaru Coronagraphic Extreme Adaptive Optics instrument at the Subaru Telescope, it benefits from a very stable visible light wave- front allowing to acquire long exposure and operate on significantly fainter sources than previously possible. On-sky results demonstrated the ability of the instrument to detect stellar companions separated 43mas in the case of the Capella binary system. A similar approach on an extremely large telescope would offer unique scientific opportunities for companion detection and characterization at very high angular resolution
Laboratory characterization of FIRSTv2 photonic chip for the study of substellar companions
FIRST (Fibered Imager foR a Single Telescope instrument) is a post-AO instrument that enables high contrast imaging and spectroscopy at spatial scales below the diffraction limit. FIRST achieves sensitivity and accuracy by a unique combination of sparse aperture masking, spatial filtering by single-mode fibers and cross-dispersion in the visible. The telescope pupil is divided into sub-pupils by an array of microlenses, coupling the light into single-mode fibers. The output of the fibers are rearranged in a non redundant configuration, allowing the measurement of the complex visibility for every baseline over the 600-900 nm spectral range. A first version of this instrument is currently integrated to the Subaru Extreme AO bench (SCExAO). This paper focuses on the on-going instrument upgrades and testings, which aim at increasing the instrument’s stability and sensitivity, thus improving the dynamic range. FIRSTv2’s interferometric scheme is based on a photonic chip beam combiner. We report on the laboratory characterization of two different types of 5-input beam combiner with enhanced throughput. The interferometric recombination of each pair of sub-pupils is encoded on a single output. Thus, to sample the fringes we implemented a temporal phase modulation by pistoning the segmented mirrors of a Micro-ElectroMechanical System (MEMS). By coupling high angular resolution and spectral resolution in the visible, FIRST offers unique capabilities in the context of the detection and spectral characterization of close companions, especially on 30m-class telescopes
Modal noise in an integrated photonic lantern fed diffraction-limited spectrograph
In an attempt to develop a streamlined astrophotonic instrument, we demonstrate the
realization of an all-photonic device capable of both multimode to single mode conversion and
spectral dispersion on an 8-m class telescope with efficient coupling. The device was a monolithic photonic spectrograph which combined an integrated photonic lantern and an efficient arrayed waveguide grating device. During on-sky testing, we discovered a previously unreported type of noise that made spectral extraction and calibration extremely difficult. The source of the noise was traced to a wavelength-dependent loss mechanism between the feed fiber’s multimode near-field pattern and the modal acceptance profile of the integrated photonic lantern. Extensive modelling of the photonic components replicates the wavelength-dependent loss, and demonstrates an identical effect on the final spectral output. We outline that this could be mitigated by directly injecting into the integrated photonic lantern.Japan Society for the Promotion of Research (23340051, 26220704, 23103002); Australian
Research Council Centre of Excellence for Ultrahigh bandwidth Devices for Optical Systems
(CE110001018); European Research Council (ERC-STG-639248)
High-angular and high-contrast VLTI observations from Y to M band with the Asgard instrumental suite
This is the final version. Available from SPIE via the DOI in this recordSPIE Astronomical Telescopes + Instrumentation 2022, 17 - 22 July 2022, Montreal, CanadaThe Very Large Telescope Interferometer is one of the most proficient observatories in the world for high angular resolution. Since its first observations, it has hosted several interferometric instruments operating in various bandwidths in the infrared. As a result, the VLTI yields countless discoveries and technological breakthroughs. We introduce to the VLTI the new concept of Asgard: an instrumental suite including four natively collaborating instruments: BIFROST, a stellar interferometer dedicated to the study of the formation of multiple systems; Hi- 5, a nulling interferometer dedicated to imaging young nearby planetary systems in the M band; HEIMDALLR, an all-in-one instrument performing both fringe tracking and stellar interferometry with the same optics; Baldr, a fibre-injection optimiser. These instruments share common goals and technologies. Thus, the idea of this suite is to make the instruments interoperable and complementary to deliver unprecedented sensitivity and accuracy from J to M bands. The interoperability of the Asgard instruments and their integration in the VLTI are the main challenges of this project. In this paper, we introduce the overall optical design of the Asgard suite, the different modules, and the main challenges ahead.European Union Horizon 2020Science and Technology Facilities Council (STFC)European Research Council (ERC