Wavefront control experiments with a single mode fiber at the High-Contrast Spectroscopy Testbed for Segmented Telescopes (HCST)

Llop-Sayson, Jorge; Jovanović, Nemanja; Morrissey, Grady; Echeverri, Daniel; Mawet, Dimitri

doi:10.1117/12.2562973

Cited by 6 publications

(7 citation statements)

References 11 publications

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“…Specifically, the SMF has a small solid angle on sky minimizing thermal background leaking into the spectrograph, which is critical in K and L bands. They can also help filter out unwanted speckle (star light), 32 and they make future wavefront control relatively simple in that only a few spatial frequencies need to be addressed, 33 which allows the bandwidth to be increased with these algorithms. 34 Finally, they allow the use of compact fiber-fed spectrographs that can be located of the telescope in a more stable environment.…”

Section: Fiu Phase I Goals and Requirementsmentioning

confidence: 99%

Keck Planet Imager and Characterizer: a dedicated single-mode fiber injection unit for high-resolution exoplanet spectroscopy

Delorme

Jovanović

Echeverri

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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The Keck Planet Imager and Characterizer (KPIC) is a purpose-built instrument to demonstrate technological and instrumental concepts initially developed for the exoplanet direct imaging field. Located downstream of the current Keck II adaptive optic (AO) system, KPIC contains a fiber injection unit (FIU) capable of combining the high-contrast imaging capability of the AOs system with the high dispersion spectroscopy capability of the current Keck high resolution infrared spectrograph (NIRSPEC). Deployed at Keck in September 2018, this instrument has already been used to acquire high-resolution spectra (R > 30;000) of multiple targets of interest. In the near term, it will be used to spectrally characterize known directly imaged exoplanets and low-mass brown dwarf companions visible in the northern hemisphere with a spectral resolution high enough to enable spin and planetary radial velocity measurements as well as Doppler imaging of atmospheric weather phenomena. Here, we present the design of the FIU, the unique calibration procedures needed to operate a single-mode fiber instrument and the system performance. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Fiu Phase I Goals and Requirementsmentioning

confidence: 99%

Keck Planet Imager and Characterizer: a dedicated single-mode fiber injection unit for high-resolution exoplanet spectroscopy

Delorme

Jovanović

Echeverri

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…In Ref. 21, we presented the first results of this algorithm (abbreviated here to EFC-SMF) at HCST with monochromatic light, where we achieved SMF raw contrast levels of better than 1 × 10 −8 . The EFC-SMF runs were negatively affected by T/T issues; the fluctuating shape of the contrast versus iteration curves shown in figure 2 of Ref.…”

Section: Previous Results: Monochromatic Experimentsmentioning

confidence: 99%

“…Therefore, the DM requires significantly less stroke to achieve a high-contrast solution through the SMF with respect to digging a DH. 19,21 Furthermore, with EFC-SMF, the broadband solution is easier to obtain over broader bandwidths for the same reasons. 15 The implementation of EFC-SMF to work with broadband light follows the exact same approach as in conventional image-based EFC 20 ; sub-bandpass channels are added to the control matrix, and the solution is the optimal DM solution, in the least-squares sense.…”

Section: Wavefront Sensing and Control Algorithmmentioning

confidence: 99%

Laboratory demonstration of wavefront control through a single-mode fiber over a 20% bandwidth for the characterization of exoplanet atmospheres

Llop-Sayson

Coker

Jovanović

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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To address the fundamental questions of exoplanetary science, future space-based observatories will have to obtain quality spectra of a large enough set of Earth-like planets around main-sequence stars. Although coronagraph instruments provide the necessary observational efficiency to probe many systems with respect to a starshade observation, they typically suffer from a limited achievable bandwidth at the necessary contrast and relatively poor throughput to off-axis sources. This is mainly due to the fact that the starlight is suppressed within the optical system, so the quasi-static aberrations from optical imperfections are the dominant term and need to be dealt with deformable mirrors (DMs). The DMs have limited capabilities to achieve large bandwidths, and their high stroke after corrections is highly detrimental to the Strehl ratio of off-axis sources. A technological path to overcome these issues is the use of single-mode fibers (SMFs). Coupling the planet light into an SMF to feed a high-resolution spectrograph has been shown to improve the final signal-to-noise ratio. Furthermore, it has been shown that it is more favorable to do broadband wavefront control with SMFs when exploiting their modal selectivity; the DMs have to work less so the bandwidth is improved and the off-axis throughput is better. Here, we demonstrate the potential of this technology by performing wavefront control through an SMF in a two-step process: first, by digging a small dark hole around the position of the SMF, and second, performing an innovative version of the electric field conjugation algorithm modified for SMFs. We perform these experiments with 20% bandwidth light at the high-contrast spectroscopy testbed achieving 2.5 × 10 −8 raw contrast.

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“…Lastly, we presented narrowband results for a modified EFC algorithm for single mode fibers, reaching 1×10 −8 normalized intensity. 22 In Fig. 2 we show the current layout of HCST, and we refer to Ref.…”

Section: Laboratory Setup: the High Contrast Spectroscopy Testbed (Hcst)mentioning

confidence: 99%

New method to achieve the proper polarization state for a vector vortex coronagraph

Llop-Sayson,

Kappel,

Jovanovic

et al. 2021

Preprint

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The vector vortex coronagraph (VVC) performance in the laboratory and in ground-based observatories has earned it a spot on the NASA mission concepts HabEx and LUVOIR. The VVC induces a phase ramp through the manipulation of the polarization state. Left-and right-circular polarizations get imprinted a phase ramp of opposite signs, which prevents model-based focal plane wavefront sensing and control strategies in natural light. We thus have to work with a polarization state than ensures circularly polarized light at the VVC mask. However, achieving this polarization state can be non trivial if there are optics that add phase retardance of any kind between the circular polarizer and the focal plane mask. Here we present the method currently used at the Caltech high contrast spectroscopy testbed (HCST) to achieve the proper circular polarization state for a VVC, which only uses the deformable mirror and appropriate rotation of the circular polarizer and analyzer optics. At HCST we achieve raw contrast levels of 10 −8 for broadband light with a VVC.

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Wavefront control experiments with a single mode fiber at the High-Contrast Spectroscopy Testbed for Segmented Telescopes (HCST)

Cited by 6 publications

References 11 publications

Keck Planet Imager and Characterizer: a dedicated single-mode fiber injection unit for high-resolution exoplanet spectroscopy

Keck Planet Imager and Characterizer: a dedicated single-mode fiber injection unit for high-resolution exoplanet spectroscopy

Laboratory demonstration of wavefront control through a single-mode fiber over a 20% bandwidth for the characterization of exoplanet atmospheres

New method to achieve the proper polarization state for a vector vortex coronagraph

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