arXiv subjects

Dimitri P. Mawet

Publications and source records attributed to Dimitri P. Mawet.

4 recordsLinked to original sources

arXiv2026

CATKit2-HCI: a collaborative framework for advancing high-contrast coronagraph testbeds

High-contrast exoplanet imaging requires dedicated laboratory testbeds for the development and validation of coronagraph architectures, wavefront sensing and control methods, calibration strategies, and system-level observing concepts. These testbeds often share similar software needs, yet many tools are developed independently at each institution. The CATKit2-High-Contrast-Imaging collaboration, or CATKit2-HCI, addresses this gap by providing a shared software framework for reusable HCI infrastructure. Built on top of CATKit2, an open-source hardware control and synchronization framework originally developed for the High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed at the Space Telescope Science Institute, CATKit2-HCI provides the collaborative layer for HCI-specific algorithms, calibration tools, diagnostics, visualization, and performance metrics. The collaboration currently includes multiple coronagraph testbeds in the United States and Europe. Its goals are to reduce duplicated software development, improve code quality through shared review, enable more direct comparison of results across facilities, and facilitate the movement of students, postdoctoral researchers, and collaborators between laboratories. We describe the motivation, architecture, collaboration model, shared technical capabilities, and early cross-testbed examples of CATKit2-HCI as a framework for accelerating coronagraph technology development.

astro-ph.IM↗

arXiv2024

Thermal control of long delay lines in a high-resolution astrophotonic spectrograph

High-resolution astronomical spectroscopy carried out with a photonic Fourier transform spectrograph (FTS) requires long asymmetrical optical delay lines that can be dynamically tuned. For example, to achieve a spectral resolution of R = 30,000, a delay line as long as 1.5 cm would be required. Such delays are inherently prone to phase errors caused by temperature fluctuations. This is due to the relatively large thermo-optic coefficient and long lengths of the waveguides, in this case composed of SiN, resulting in thermally dependent changes to the optical path length. To minimize phase error to the order of 0.05 radians, thermal stability of the order of 0.05° C is necessary. A thermal control system capable of stability such as this would require a fast thermal response and minimal overshoot/undershoot. With a PID temperature control loop driven by a Peltier cooler and thermistor, we minimized interference fringe phase error to +/- 0.025 radians and achieved temperature stability on the order of 0.05° C. We present a practical system for precision temperature control of a foundry-fabricated and packaged FTS device on a SiN platform with delay lines ranging from 0.5 to 1.5 cm in length using inexpensive off-the-shelf components, including design details, control loop optimization, and considerations for thermal control of integrated photonics.

astro-ph.IM↗

arXiv2024

Laboratory demonstration of the wrapped staircase scalar vortex coronagraph

Of the over 5000 exoplanets that have been detected, only about a dozen have ever been directly imaged. Earth-like exoplanets are on the order of 10 billion times fainter than their host star in visible and near-infrared, requiring a coronagraph instrument to block primary starlight and allow for the imaging of nearby orbiting planets. In the pursuit of direct imaging of exoplanets, scalar vortex coronagraphs (SVCs) are an attractive alternative to vector vortex coronagraphs (VVCs). VVCs have demonstrated 2e-9 raw contrast in broadband light but have several limitations due to their polarization properties. SVCs imprint the same phase ramp as VVCs on the incoming light and do not require polarization splitting, but they are inherently chromatic. Discretized phase ramp patterns such as a wrapped staircase help reduce SVC chromaticity and simulations show it outperforms a chromatic classical vortex in broadband light. We designed, fabricated, and tested a wrapped staircase SVC, and here we present the broadband characterization on the high contrast spectroscopy testbed. We also performed wavefront correction on the in-air coronagraph testbed at NASA's Jet Propulsion Laboratory and achieved an average raw contrasts of 3.2e-8 in monochromatic light and 2.2e-7 across a 10% bandwidth.

astro-ph.IM↗

arXiv2021

A Layered Debris Disk around M Star TWA 7 in Scattered Light

We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the STIS instrument in visible light. Together with archival observations including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at $H$-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey--Greenstein phase functions, we report new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ${\approx}150$ au$^2$ elliptical clump. The most extended ring peaks at $28$ au, and the other components are on its outskirts. Our point source detection limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body and local Keplerian; we also observe underdensity regions for the secondary ring that might result from mean motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, STIS-SPHERE radial distribution peak difference for the tertiary ring, and high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.

astro-ph.EP↗