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M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 BSerabyn, Eugene; Huby, Elsa ; Matthews, Keith et alin Astronomical Journal (The) (2017), 153(1), 43An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational ... [more ▼]An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP79124, which had previously been detected by means of interferometry. With HIP79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L' band versus H band, this new coronagraphic capability will enable high-contrast small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics coronagraphs. [less ▲]Detailed reference viewed: 22 (4 ULg) Characterization of the inner disk around HD 141569 A from Keck/NIRC2 L-band vortex coronagraphyMawet, Dimitri; Choquet, Élodie; Absil, Olivier et alin Astronomical Journal (The) (2017), 153(1), 44HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a ... [more ▼]HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L' band (3.8 micron) during the commissioning of the vector vortex coronagraph recently installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point spread function subtraction, which reveals the innermost disk component from the inner working distance of $\simeq 23$ AU and up to $\simeq 70$ AU. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N and 8.6 micron PAH emission reported earlier. We also see an outward progression in dust location from the L'-band to the H-band (VLT/SPHERE image) to the visible (HST/STIS image), likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST NICMOS in 1999 (respectively at 406 and 245 AU). We fit our new L'-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains, and are consistent with the composition of the outer belts. While our image shows a putative very-faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses. [less ▲]Detailed reference viewed: 21 (2 ULg) End-to-end simulations of the E-ELT/METIS coronagraphsCarlomagno, Brunella ; Absil, Olivier ; Kenworthy, Matthew et alin Marchetti, E.; Close, L.; Véran, J.-P. (Eds.) Adaptive Optics Systems V (2016, July 27)The direct detection of low-mass planets in the habitable zone of nearby stars is an important science case for future E-ELT instruments such as the mid-infrared imager and spectrograph METIS, which ... [more ▼]The direct detection of low-mass planets in the habitable zone of nearby stars is an important science case for future E-ELT instruments such as the mid-infrared imager and spectrograph METIS, which features vortex phase masks and apodizing phase plates (APP) in its baseline design. In this work, we present end-to-end performance simulations, using Fourier propagation, of several METIS coronagraphic modes, including focal-plane vortex phase masks and pupil-plane apodizing phase plates, for the centrally obscured, segmented E-ELT pupil. The atmosphere and the AO contributions are taken into account. Hybrid coronagraphs combining the advantages of vortex phase masks and APPs are considered to improve the METIS coronagraphic performance. [less ▲]Detailed reference viewed: 18 (3 ULg) Controlling the profile of high aspect ratio gratings in diamondVargas Catalan, Ernesto; Forsberg, Pontus; Absil, Olivier et alin Diamond & Related Materials (2016), 63Diamond is an excellent material for infrared optics and for applications in harsh environments. Some of those desirable properties, i.e. hardness and chemical inertness, also make it a challenging ... [more ▼]Diamond is an excellent material for infrared optics and for applications in harsh environments. Some of those desirable properties, i.e. hardness and chemical inertness, also make it a challenging material to machine and etch. In this study we have tested a wide range of etch parameters in an inductively coupled plasma etcher, in order to produce highly controlled, high aspect ratio gratings in diamond. We discuss the effects of pressure, bias power, and some gas mixture variation (pure oxygen and argon-oxygen) on the etch results and how it impacts the etch mask sputtering and redeposition. We also present a method for applying a fresh aluminum mask, in order to etch even deeper optical grating. Gratings with aspect ratios as high as 1:13.5 have been achieved with a 1.42 μm grating period. [less ▲]Detailed reference viewed: 44 (4 ULg) Performance evaluation of mid-IR vortex coronagraphs with centrally obscured segmented pupilsCarlomagno, Brunella ; Absil, Olivier ; Ruane, Garreth J. et alPoster (2015, October)In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L ... [more ▼]In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L band). The AGPM (Annular Groove Phase Mask) is a vortex phase mask with impressive characteristics: small inner working angle, high throughput, achromaticity. A non-perfectly circular pupil and non-flat input wavefront result in a starlight leakage, degrading the performance of the vortex coronagraph. In this work, we present end-to-end performance simulations using Fourier optical propagation to determine the quality of the starlight rejection obtained with an infrared vortex coronagraph. We first analyse the performance facing E-ELT pupil variations (segmentations, central obscuration, spiders, missing segments), then pointing jitter and random adaptive optics residual phase screens are introduced to derive more realistic performance. Finally, more advanced concepts of the infrared vortex coronagraph are presented, in order to compensate for performance degradation. [less ▲]Detailed reference viewed: 32 (5 ULg) Realizing the diamond annular groove phase masks for the mid infrared region: five years of successful process development of diamond plasma etchingForsberg, Pontus; Vargas Catalan, Ernesto; Delacroix, Christian et alin Navarro, Ramon; Cunningham, Colin; Barto, Allison (Eds.) Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation (2014, August 07)The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in ... [more ▼]The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in diamond. To improve the AGPM performance, antireflective sub-wavelength gratings are etched on the backside of the components, and such gratings are also discussed. Components for the N-band (around 10 μm) and the L-band (around 3.8 μm) have been successfully fabricated. We are currently developing the process further to improve the precision of the gratings and produce an AGPM for the K-band (around 2.2 μm). © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. [less ▲]Detailed reference viewed: 24 (2 ULg) The VORTEX project: first results and perspectivesAbsil, Olivier ; Mawet, Dimitri; Delacroix, Christian et alin Marchetti, Enrico; Close, Laird; Véran, Jean-Pierre (Eds.) Adaptive Optics Systems IV (2014, July 21)Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the ... [more ▼]Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the diffraction limit of the telescope), a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric sub-wavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about 6e-5 at 2λ/D. Three of them have now been installed on world-leading diffraction-limited infrared cameras, namely VLT/NACO, VLT/VISIR and LBT/LMIRCam. During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit (0.1"). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imager and on future extremely large telescopes (ELTs). In particular, we will briefly describe our current efforts to improve the manufacturing of mid-infrared AGPMs, to push their operation to shorter wavelengths, and to provide deeper starlight extinction by creating new designs for higher topological charge vortices. Within the VORTEX project, we also plan to develop new image processing techniques tailored to coronagraphic images, and to study some pre- and post-coronagraphic concepts adapted to the vortex coronagraph in order to reduce scattered starlight in the final images. [less ▲]Detailed reference viewed: 112 (48 ULg) Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)Delacroix, Christian ; Absil, Olivier ; Carlomagno, Brunella et alin Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal ... [more ▼]One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2pi radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation. [less ▲]Detailed reference viewed: 25 (6 ULg) Mid-IR AGPMs for ELT applicationsCarlomagno, Brunella ; Delacroix, Christian ; Absil, Olivier et alin Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This ... [more ▼]The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument. [less ▲]Detailed reference viewed: 50 (8 ULg) Small-angle, high-contrast exoplanet imaging with the L-band AGPM vector vortex coronagraph now offered at the VLTMawet, Dimitri; Absil, Olivier ; Milli, Julien et alin Shaklan, Stuart (Ed.) Techniques and Instrumentation for Detection of Exoplanets VI (2013, September 26)In November 2012, we installed an L-band annular groove phase mask (AGPM) vector vortex coronagraph (VVC) inside NACO, the adaptive optics camera of ESO's Very Large Telescope. The mask, made out of ... [more ▼]In November 2012, we installed an L-band annular groove phase mask (AGPM) vector vortex coronagraph (VVC) inside NACO, the adaptive optics camera of ESO's Very Large Telescope. The mask, made out of diamond subwavelength gratings has been commissioned, science qualified, and is now offered to the community. Here we report ground-breaking on-sky performance levels in terms of contrast, inner working angle, and discovery space. This new practical demonstration of the VVC, coming a few years after Palomar's and recent record-breaking lab experiments in the visible (E. Serabyn et al. 2013, these proceedings), shows once again that this new-generation coronagraph has reached a high level of maturity. [less ▲]Detailed reference viewed: 29 (3 ULg) Laboratory demonstration of a mid-infrared AGPM vector vortex coronagraphDelacroix, Christian ; Absil, Olivier ; Forsberg, Pontus et alin Astronomy and Astrophysics (2013), 553Coronagraphy is a powerful technique to achieve high contrast imaging and hence to image faint companions around bright targets. Various concepts have been used in the visible and near-infrared regimes ... [more ▼]Coronagraphy is a powerful technique to achieve high contrast imaging and hence to image faint companions around bright targets. Various concepts have been used in the visible and near-infrared regimes, while coronagraphic applications in the mid-infrared remain nowadays largely unexplored. Vector vortex phase masks based on concentric subwavelength gratings show great promise for such applications. We aim at producing and validating the first high-performance broadband focal plane phase mask coronagraphs for applications in the mid-infrared regime, and in particular the L band with a fractional bandwidth of ~16% (3.5-4.1 \mu m). Based on rigorous coupled wave analysis, we designed an annular groove phase mask (AGPM) producing a vortex effect in the L band, and etched it onto a series of diamond substrates. The grating parameters were measured by means of scanning electron microscopy. The resulting components were then tested on a mid-infrared coronagraphic test bench. A broadband raw null depth of 2 x 10^{-3} was obtained for our best L-band AGPM after only a few iterations between design and manufacturing. This corresponds to a raw contrast of about 6 x 10^{-5} (10.5 mag) at 2\lambda/D. This result is fully in line with our projections based on rigorous coupled wave analysis modeling, using the measured grating parameters. The sensitivity to tilt and focus has also been evaluated. After years of technological developments, mid-infrared vector vortex coronagraphs finally become a reality and live up to our expectations. Based on their measured performance, our L-band AGPMs are now ready to open a new parameter space in exoplanet imaging at major ground-based observatories. [less ▲]Detailed reference viewed: 64 (22 ULg) Design, manufacturing, and performance analysis of mid-infrared achromatic half-wave plates with diamond subwavelength gratingsDelacroix, Christian ; Forsberg, Pontus; Karlsson, Mikael et alin Applied Optics (2012), 51In this paper, we present an elegant solution for creating robust monolithic achromatic half-wave plates (HWPs) for the infrared, based on the form birefringence of subwavelength gratings (SWGs) made out ... [more ▼]In this paper, we present an elegant solution for creating robust monolithic achromatic half-wave plates (HWPs) for the infrared, based on the form birefringence of subwavelength gratings (SWGs) made out of diamond. We use the rigorous coupled wave analysis to design the gratings. Our analysis shows that diamond, besides its outstanding physical and mechanical properties, is a suitable substrate to manufacture mid-infrared HWPs, thanks to its high refractive index which allows etching SWGs with lower aspect ratio. Based on our optized design, we manufactured a diamond HWP for the 11-13.2 µm region, with an estimated mean retardance ~3.143 ± 0.061 rad (180.08 ± 3.51°). In addition, an antireflective grating was etched on the backside of the wave plate, allowing a total tansmittance between 89 and 95% over the band. [less ▲]Detailed reference viewed: 79 (16 ULg) A diamond AGPM coronagraph for VISIRDelacroix, Christian ; Absil, Olivier ; Mawet, Dimitri et alin McLean, I; Ramsay, S; Takami, H (Eds.) Ground-based and Airborne Instrumentation for Astronomy IV (2012, July 05)In recent years, phase mask coronagraphy has become increasingly efficient in imaging the close environment of stars, enabling the search for exoplanets and circumstellar disks. Coronagraphs are ideally ... [more ▼]In recent years, phase mask coronagraphy has become increasingly efficient in imaging the close environment of stars, enabling the search for exoplanets and circumstellar disks. Coronagraphs are ideally suited instruments, characterized by high dynamic range imaging capabilities, while preserving a small inner working angle. The AGPM (Annular Groove Phase Mask, Mawet et al. 20051) consists of a vector vortex induced by a rotationally symmetric subwavelength grating. This technique constitutes an almost unique solution to the achromatization at longer wavelengths (mid-infrared). For this reason, we have specially conceived a mid-infrared AGPM coronagraph for the forthcoming upgrade of VISIR, the mid-IR imager and spectrograph on the VLT at ESO (Paranal), in collaboration with members of the VISIR consortium. The implementation phase of the VISIR Upgrade Project is foreseen for May-August 2012, and the AGPM installed will cover the 11-13.2 μm spectral range. In this paper, we present the entire fabrication process of our AGPM imprinted on a diamond substrate. Diamond is an ideal material for mid-infrared wavelengths owing to its high transparency, small dispersion, extremely low thermal expansion and outstanding mechanical and chemical properties. The design process has been performed with an algorithm based on the rigorous coupled wave analysis (RCWA), and the micro-fabrication has been carried out using nano-imprint lithography and reactive ion etching. A precise grating profile metrology has also been conducted using cleaving techniques. Finally, we show the deposit of fiducials (i.e. centering marks) with Aerosol Jet Printing (AJP). We conclude with the ultimate coronagraph expected performances. [less ▲]Detailed reference viewed: 57 (12 ULg) Taking the vector vortex coronagraph to the next level for ground- and space-based exoplanet imaging instruments: review of technology developments in the USA, Japan, and EuropeMawet, Dimitri; Murakami, Naoshi; Delacroix, Christian et alin Shaklan, Stuart (Ed.) Techniques and Instrumentation for Detection of Exoplanets V. (2011, September 01)The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground- and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at ... [more ▼]The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground- and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at Palomar and in the laboratory at JPL, and Hokkaido University. Manufacturing technologies for devices covering wavelength ranges from the optical to the mid-infrared, have been maturing quickly. We will review the current status of technology developments supported by NASA in the USA (Jet Propulsion Laboratory-California Institute of Technology, University of Arizona, JDSU and BEAMCo), Europe (University of Li`ege, Observatoire de Paris- Meudon, University of Uppsala) and Japan (Hokkaido University, and Photonics Lattice Inc.), using liquid crystal polymers, subwavelength gratings, and photonics crystals, respectively. We will then browse concrete perspectives for the use of the VVC on upcoming ground-based facilities with or without (extreme) adaptive optics, extremely large ground-based telescopes, and space-based internal coronagraphs. [less ▲]Detailed reference viewed: 73 (14 ULg) First manufactured diamond AGPM vector vortex for the L- and N-bands: metrology and expected performancesDelacroix, Christian ; Forsberg, Pontus; Karlsson, Mikael et alConference (2010, October 28)The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period ... [more ▼]The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period smaller than λ/n (λ being the observed wavelength and n the refractive index of the grating substrate). Since it is a phase mask, it allows to reach a high contrast with a small working angle. Moreover, its subwavelength structure provides a good achromatization over wide spectral bands. Recently, we have manufactured and measured our first N-band prototypes that allowed us to validate the reproducibility of the microfabrication process. Here, we present newly produced mid-IR diamond AGPMs in the N-band (~10 µm), and in the most wanted L-band (~3.5 µm). We first give an extrapolation of the expected coronagraph performances. We then present the manufacturing and measurement results, using diamond-optimized microfabrication techniques such as nano-imprint lithography (NIL) and reactive ion etching (RIE). Finally, the subwavelength grating profile metrology combines surface metrology (scanning electron microscopy, atomic force microscopy, white light interferometry) with diffractometry on an optical polarimetric bench and cross correlation with theoretical simulations using rigorous coupled wave analysis (RCWA). [less ▲]Detailed reference viewed: 65 (15 ULg) Diamond subwavelength gratings for mid-infrared AGPM coronagraph: manufacturing assessmentDelacroix, Christian ; Habraken, Serge ; Karlsson, Mikael et alConference (2010, October 26)We present the manufacturing and measurement results obtained with a mid-infrared (L-band ~ 3.8 µm) diamond Annular Groove Phase Mask (AGPM) coronagraph (Mawet et al 20051), using subwavelength gratings ... [more ▼]We present the manufacturing and measurement results obtained with a mid-infrared (L-band ~ 3.8 µm) diamond Annular Groove Phase Mask (AGPM) coronagraph (Mawet et al 20051), using subwavelength gratings and diamond-optimized micro-fabrication techniques such as Nano-Imprint Lithography and Reactive Ion Etching. [less ▲]Detailed reference viewed: 65 (12 ULg) 1