Mid-IR AGPMs for ELT applications

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.Comment: 8 pages, 5 figures, Proc. of SPIE Vol. 9147 (2014

Mid-IR AGPMs for ELT applications

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

The VORTEX project: first results and perspectives

(abridged) Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations. They feature a very small inner working angle, 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 subwavelength 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 $6\times 10^{-5}$ at $2 \lambda/D$. Three of them have now been installed on world-leading diffraction-limited infrared cameras (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 imagers and on future extremely large telescopes (ELTs).Comment: To appear in SPIE proceedings vol. 914

Three years of harvest with the vector vortex coronagraph in the thermal infrared

For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 {\mu}m). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.Comment: To appear in SPIE proceedings vol. 990

End-to-end simulations of the E-ELT/METIS coronagraphs

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

Design and Manufacturing of a Rotationally Symmetric Cold Gas Nozzle in Silicon

In this master thesis, the goal was to devise design patterns and a fabrication processfor manufacturing a 3-D rotationally symmetric converging-diverging cold gasmicronozzle in silicon.The report explains the theory of etching and the methods involved. The work beginswith calculations and simulations of the etching processes. The chosen etch techniqueutilizes so called microloading and reactive ion etching lag effects, which essentially arephenomena where the etch rate can be adjusted by breaking up mask features intosubpatterns, and the etch depth for a given recipe and time can be made to differlocally. The subpatterns consisted of very small rectangles and triangles withalternating concentration. Five different recipes for the reactive ion etching weretried, where the coil power, platen power, pressure, temperature and time wasvaried.Etch rates could be made to differ locally depending on the concentration ofsubpatterns within the mask feature. The etch rates were also affected by the recipeparameters such as coil power, platen power, and pressure. High coil and platenpower increased the etch rate, while high pressure reduced the etch rate. The platenpower also affected the surface roughness.A solution for reducing misalignment problems in the future for the fusion bondingprocess resulted in the proposed moiré patterns that were made to showmisalignments down to 0.2 μm.Through scanning electron microscopy, the Nozzle 5_4_2 was concluded to have themost rotationally symmetric cross section at both the throat and the outlet. It hasthroat diameter of 31.1 μm with a depth of 34.2 μm and an outlet diameter of146.4 μm with a depth of 113.2 μ

Microfabrication of Optical Components in Synthetic Diamond : Infrared Optics for Applications in Astronomy and Spectroscopy

Infrared optics is a broad general term, relevant to a range of fields. The manufactured diamond optical components utilized within this thesis were applied to both astronomy, in which direct imaging of star system using large ground-based telescopes and diamond coronagraphs was performed, and in absorption spectroscopy probing solvents and proteins using a tuneable quantum cascade laser and diamond waveguides. The optical components presented in this thesis are all made from diamond, as it is one of few materials that is transparent in the infrared regime. Furthermore, diamond has other unique properties that include high thermal conductivity, low thermal expansion and chemically inertness. In this thesis synthetic diamond grown by chemical vapor deposition has been used, using commercially available components and equipment. The focus of this thesis was to produce optical gratings for different applications using plasma etching. The first steps involved understanding the etch process and optimizing the plasma etch parameters to enable the fabrication of new types of nano/micro meter sized structures in diamond. Optimization of the etch masks is also included in the work. With this newfound knowledge, deeper and narrower optical gratings than before could be realized. Optical evaluation of the gratings in special designed optical test benches was used to determine the coronagraphic performance of the manufactured diamond coronagraphs. Most often the designed etch depth could not be reached in the first attempt and therefore a post-fabrication method for tuning the etch depth was developed.  This showed to be vital to realising high performing diamond coronagraphs. Diamond coronagraphs were also installed in several ground based telescopes and discovery of new astronomical objects are presented. With deeper understanding of the etch process more complex coronagraphs in diamond were manufactured opening up for use in the next generation of giant telescopes. In the second part of this thesis, fabrication of diamond waveguides for sensitive analysis of solvents and proteins using infrared spectroscopy is presented.  Different designs of diamond waveguides are demonstrated and initial analysis of organic compounds and glucose using a quantum cascade laser as the light source is presented. This type of biosensor will be used to study the secondary structure of proteins relevant for different diseases

Design and Manufacturing of a Rotationally Symmetric Cold Gas Nozzle in Silicon

In this master thesis, the goal was to devise design patterns and a fabrication processfor manufacturing a 3-D rotationally symmetric converging-diverging cold gasmicronozzle in silicon.The report explains the theory of etching and the methods involved. The work beginswith calculations and simulations of the etching processes. The chosen etch techniqueutilizes so called microloading and reactive ion etching lag effects, which essentially arephenomena where the etch rate can be adjusted by breaking up mask features intosubpatterns, and the etch depth for a given recipe and time can be made to differlocally. The subpatterns consisted of very small rectangles and triangles withalternating concentration. Five different recipes for the reactive ion etching weretried, where the coil power, platen power, pressure, temperature and time wasvaried.Etch rates could be made to differ locally depending on the concentration ofsubpatterns within the mask feature. The etch rates were also affected by the recipeparameters such as coil power, platen power, and pressure. High coil and platenpower increased the etch rate, while high pressure reduced the etch rate. The platenpower also affected the surface roughness.A solution for reducing misalignment problems in the future for the fusion bondingprocess resulted in the proposed moiré patterns that were made to showmisalignments down to 0.2 μm.Through scanning electron microscopy, the Nozzle 5_4_2 was concluded to have themost rotationally symmetric cross section at both the throat and the outlet. It hasthroat diameter of 31.1 μm with a depth of 34.2 μm and an outlet diameter of146.4 μm with a depth of 113.2 μ

Microfabrication of Optical Components in Synthetic Diamond : Infrared Optics for Applications in Astronomy and Spectroscopy

Infrared optics is a broad general term, relevant to a range of fields. The manufactured diamond optical components utilized within this thesis were applied to both astronomy, in which direct imaging of star system using large ground-based telescopes and diamond coronagraphs was performed, and in absorption spectroscopy probing solvents and proteins using a tuneable quantum cascade laser and diamond waveguides. The optical components presented in this thesis are all made from diamond, as it is one of few materials that is transparent in the infrared regime. Furthermore, diamond has other unique properties that include high thermal conductivity, low thermal expansion and chemically inertness. In this thesis synthetic diamond grown by chemical vapor deposition has been used, using commercially available components and equipment. The focus of this thesis was to produce optical gratings for different applications using plasma etching. The first steps involved understanding the etch process and optimizing the plasma etch parameters to enable the fabrication of new types of nano/micro meter sized structures in diamond. Optimization of the etch masks is also included in the work. With this newfound knowledge, deeper and narrower optical gratings than before could be realized. Optical evaluation of the gratings in special designed optical test benches was used to determine the coronagraphic performance of the manufactured diamond coronagraphs. Most often the designed etch depth could not be reached in the first attempt and therefore a post-fabrication method for tuning the etch depth was developed.  This showed to be vital to realising high performing diamond coronagraphs. Diamond coronagraphs were also installed in several ground based telescopes and discovery of new astronomical objects are presented. With deeper understanding of the etch process more complex coronagraphs in diamond were manufactured opening up for use in the next generation of giant telescopes. In the second part of this thesis, fabrication of diamond waveguides for sensitive analysis of solvents and proteins using infrared spectroscopy is presented.  Different designs of diamond waveguides are demonstrated and initial analysis of organic compounds and glucose using a quantum cascade laser as the light source is presented. This type of biosensor will be used to study the secondary structure of proteins relevant for different diseases

Microfabrication of Optical Components in Synthetic Diamond : Infrared Optics for Applications in Astronomy and Spectroscopy

Infrared optics is a broad general term, relevant to a range of fields. The manufactured diamond optical components utilized within this thesis were applied to both astronomy, in which direct imaging of star system using large ground-based telescopes and diamond coronagraphs was performed, and in absorption spectroscopy probing solvents and proteins using a tuneable quantum cascade laser and diamond waveguides. The optical components presented in this thesis are all made from diamond, as it is one of few materials that is transparent in the infrared regime. Furthermore, diamond has other unique properties that include high thermal conductivity, low thermal expansion and chemically inertness. In this thesis synthetic diamond grown by chemical vapor deposition has been used, using commercially available components and equipment. The focus of this thesis was to produce optical gratings for different applications using plasma etching. The first steps involved understanding the etch process and optimizing the plasma etch parameters to enable the fabrication of new types of nano/micro meter sized structures in diamond. Optimization of the etch masks is also included in the work. With this newfound knowledge, deeper and narrower optical gratings than before could be realized. Optical evaluation of the gratings in special designed optical test benches was used to determine the coronagraphic performance of the manufactured diamond coronagraphs. Most often the designed etch depth could not be reached in the first attempt and therefore a post-fabrication method for tuning the etch depth was developed.  This showed to be vital to realising high performing diamond coronagraphs. Diamond coronagraphs were also installed in several ground based telescopes and discovery of new astronomical objects are presented. With deeper understanding of the etch process more complex coronagraphs in diamond were manufactured opening up for use in the next generation of giant telescopes. In the second part of this thesis, fabrication of diamond waveguides for sensitive analysis of solvents and proteins using infrared spectroscopy is presented.  Different designs of diamond waveguides are demonstrated and initial analysis of organic compounds and glucose using a quantum cascade laser as the light source is presented. This type of biosensor will be used to study the secondary structure of proteins relevant for different diseases