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 through a unique combination of sparse aperture masking, spatial filtering by single-mode fibers and cross-dispersion in the visible. On-sky commissioning data taken with the instrument installed on the SCExAO platform at the 8-m Subaru telescope show the detection of several stellar companions, including two binary systems with an angular separation of 0.6 λ/D (11mas). Even at such a close separation, FIRST delivers information on the companion spectrum, providing valuable constraints on the stellar parameters, such as the effective temperatures and surface gravity. As a spectro-interferometer fed by a highly effective AO system such as SCExAO, FIRST offers unique capabilities in the context of the spectral characterization of close companions. The discussion concludes with insights into the future of the FIRST instrument, with the move to visible photonic technologies and further advancements in the instrument's capabilities to detect newly formed exoplanets.
A Photonic Lantern (PL) is a novel device that efficiently converts a multi-mode fiber into several single-mode fibers. When coupled with an extreme adaptive optics (ExAO) system and a spectrograph, PLs enable high throughput spectroscopy at high angular resolution. The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system of the Subaru Telescope recently acquired a PL that converts its multi-mode input into 19 single-mode outputs. The single mode outputs feed a R~4,000 spectrograph optimized for the 600 to 760 nm wavelength range. We present here the integration of the PL on SCExAO, and study the device performance in terms of throughput, field of view, and spectral reconstruction. We also present the first on-sky demonstration of a Visible PL coupled with an ExAO system, showing a significant improvement of x12 in throughput compared to the use of a sole single-mode fiber. This work paves the way towards future high throughput photonics instrumentation at small angular resolution.
FIRST is a post Extreme Adaptive-Optics (ExAO) spectro-interferometer operating in the Visible (600-800 nm, R∼400). Its exquisite angular resolution (a sensitivity analysis of on-sky data shows that bright companions can be detected down to 0.25λ/D) combined with its sensitivity to pupil phase discontinuities (from a few nm up to dozens of microns) makes FIRST an ideal self-calibrated solution for enabling exoplanet detection and characterization in the future. We present the latest on-sky results along with recent upgrades, including the integration and on-sky test of a new spectrograph (R∼3,600) optimized for the detection of Hα emission from young exoplanets accreting matter.
Hi-5 is an ERC-funded project hosted at KU Leuven and a proposed visitor instrument for the VLTI. Its primary goal is to image the snow line region around young planetary systems using nulling interferometry in the L’ band, between 3.5 and 4.1 μm, where the contrast between exoplanets and their host stars is very advantageous. The breakthrough is the use of a photonic chip based beam combiner, which only recently allowed the required theoretical raw contrast of 10−3 in this spectral range. The VLTI long baseline interferometry enables to reach high angular resolution (4.2 mas at 3.8 μm wavelength with the Auxiliary Telescopes (ATs)), while high contrast detection is achieved using nulling interferometry. This polarisation requires a high degree of optical symmetry between the four pupils of the VLTI, only possible with precise phase, dispersion and intensity control systems. The instrument is currently in its design phase. In this paper, the warm optics design and the injection system up to the photonic chip are presented. The different properties of the design are presented including the optics used, the characteristics of the four beams and the current drawbacks. Particular attention is devoted to the optical alignment and the tolerance analysis in order to estimate the precision required for the alignment procedure and therefore to choose adapted optical mountings.
Hi-5 is the L’-band (3.5-4.0 μm) high-contrast imager of Asgard, an instrument suite in preparation for the visitor focus of the VLTI. The system is optimized for high-contrast and high-sensitivity imaging within the diffraction limit of a single UT/AT telescope. It is designed as a double-Bracewell nulling instrument producing spectrally-dispersed (R=20, 400, or 2000) complementary nulling outputs and simultaneous photometric outputs for self-calibration purposes. In this paper, we present an update of the project with a particular focus on the overall architecture, opto-mechanical design of the warm and cold optics, injection system, and development of the photonic beam combiner. The key science projects are to survey (i) nearby young planetary systems near the snow line, where most giant planets are expected to be formed, and (2) nearby main sequence stars near the habitable zone where exozodiacal dust that may hinder the detection of Earth-like planets. We present an update of the expected instrumental performance based on full end-to-end simulations using the new GRAVITY+ specifications of the VLTI and the latest planet formation models.
Hi-5 is a proposed L' band high-contrast nulling interferometric instrument for the visitor focus of the Very Large Telescope Interferometer (VLTI). As a part of the ERC consolidator project called SCIFY (Self-Calibrated Interferometry For exoplanet spectroscopY), the instrument aims to achieve sufficient dynamic range and angular resolution to directly image and characterize the snow line of young extra-solar planetary systems. The spectrometer is based on a dispersive grism and is located downstream of an integrated optics beam-combiner. To reach the contrast and sensitivity specifications, the outputs of the I/O chip must be sufficiently separated and properly sampled on the Hawaii-2RG detector. This has many implications for the photonic chip and spectrometer design. We present these technical requirements, trade-off studies, and phase-A of the optical design of the Hi-5 spectrometer in this paper. For both science and contract-driven reasons, the instrument design currently features three different spectroscopic modes (R=20, 400, and 2000). Designs and efficiency estimates for the grisms are also presented as well as the strategy to separate the two polarization states.
Active phase control is a vital component to any interferometry system. On a simple photonic device this can often be achieved using bulk optics before the chip, but for complicated systems active phase control on-chip is a vital component of the photonic design. One method of active phase control is using the thermo-optic effect. Using a chalcogenide waveguides, chromium heaters actively change the refractive index of the glass, this changes the optical path length of the light. This paper shows that chromium deposited above arms of a Mach-Zehnder interferometer will be able to produce multiple pi phase shifts at a rate of approximately 40 mW per π phase shift. Hence a chalcogenide based platform is suitable for a complicated photonic device like a Kernel-Nulling interferometer.
Direct imaging of exoplanets is vital for understanding star system formation and the evolutionary behaviour of exoplanets at large orbits. Typically, imaging a star system to find an exoplanet requires significant attenuation of the host star’s high flux in order to detect the much weaker planetary light. The most common method to do this is coronagraphy, which blocks the starlight with an amplitude mask or a null inducing phase mask [1]. An alternative and attractive method is nulling interferometry where light from multiple telescopes are used to simultaneously form a high resolution image (or its Fourier components) and also to form a null in the vicinity of the host star, thereby attenuating it [2]. This has the advantage over coronagraphy that it is not limited to using a single telescope and is thus able to probe deeper into a star system by virtue of the higher resolution available by an interferometric array.
2D materials, led by graphene, have been widely explored in the last decade as saturable absorber (SA) materials. Most of this work has focussed on fibre compatible designs for use in fibre lasers (e.g. fibre connector sandwich, D-shaped fibre). Realising chip based mode locked lasers is an important challenge, and little work has been carried out on planar waveguide SAs, Here, simulation results for the absorption performance of two types of graphene based TeO2 waveguide SA designs with suitably high absorption and low saturation threshold are presented.
Hybrid integration of different materials will allow for different functionalities such as passive, amplifying, nonlinear, electro-optic, detection etc to build “system on a chip” devices. The vertically stacked layer design commonly proposed significantly increases the difficulty of the lithography process for the bottom-most layer due to the overlying topology. A methodology for significantly improving the fabrication tolerance of planar directional couplers is therefore presented. A parametric design study reveals that significant dimensional sensitivity improvements exist for certain center-to-center spacings for both power and wavelength splitters.
The future of exoplanet detection lies in the mid-infrared (MIR). The MIR region contains the blackbody peak of both hot and habitable zone exoplanets, making the contrast between starlight and planet light less extreme. It is also the region where prominent chemical signatures indicative of life exist, such as ozone at 9.7 μm. At a wavelength of 4 μm the difference in emission between an Earth-like planet and a star like our own is 80 dB. However a jovian planet, at the same separation exhibits 60 dB of contrast, or only 20 dB if it is hot due to its formation energy or being close to its host star. A two dimensional nulling interferometer, made with chalcogenide glass, has been measured to produce a null of 20 dB depth, limited by scattered light. Measures to increase the null depth to the theoretical limit of 60 dB are discussed.
Photonic integrated circuits are established as the technique of choice for a number of astronomical processing functions due to their compactness, high level of integration, low losses, and stability. Temperature control, mechanical vibration and acoustic noise become controllable for such a device enabling much more complex processing than can realistically be considered with bulk optics. To date the benefits have mainly been at wavelengths around 1550 nm but in the important Mid-Infrared region, standard photonic chips absorb light strongly. Chalcogenide glasses are well known for their transparency to beyond 10000 nm, and the first results from coupler devices intended for use in an interferometric nuller for exoplanetary observation in the Mid-Infrared L’ band (3800-4200 nm) are presented here showing that suitable performance can be obtained both theoretically and experimentally for the first fabricated devices operating at 4000 nm.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.