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Demonstration of an electric field conjugation algorithm for improved starlight rejection through a single mode optical fiber

Llop Sayson, Jorge and Ruane, Garreth and Mawet, Dimitri and Jovanovic, Nemanja and Calvin, Benjamin and Levraud, Nicolas and Roberson, Milan and Delorme, Jacques-Robert and Echeverri, Daniel and Klimovich, Nikita and Xin, Yeyuan (2019) Demonstration of an electric field conjugation algorithm for improved starlight rejection through a single mode optical fiber. Journal of Astronomical Telescopes, Instruments, and Systems, 5 (1). Art. No. 019004. ISSN 2329-4124. doi:10.1117/1.jatis.5.1.019004.

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Linking a coronagraph instrument to a spectrograph via a single-mode optical fiber is a pathway toward detailed characterization of exoplanet atmospheres with current and future ground- and space-based telescopes. However, given the extreme brightness ratio and small angular separation between planets and their host stars, the planet signal-to-noise ratio will likely be limited by the unwanted coupling of starlight into the fiber. To address this issue, we utilize a wavefront control loop and a deformable mirror to systematically reject starlight from the fiber by measuring what is transmitted through the fiber. The wavefront control algorithm is based on the formalism of electric field conjugation (EFC), which in our case accounts for the spatial mode selectivity of the fiber. This is achieved by using a control output that is the overlap integral of the electric field with the fundamental mode of a single-mode fiber. This quantity can be estimated by pairwise image plane probes injected using a deformable mirror. We present simulation and laboratory results that demonstrate our approach offers a significant improvement in starlight suppression through the fiber relative to a conventional EFC controller. With our experimental setup, which provides an initial normalized intensity of 3  ×  <sup>10  −  4</sup> in the fiber at an angular separation of 4λ  /  <i>D</i>, we obtain a final normalized intensity of 3  ×  <sup>10  −  6</sup> in monochromatic light at λ  =  635  nm through the fiber (100  ×   suppression factor) and 2  ×  <sup>10  −  5</sup> in Δλ  /  λ  =  8  %   broadband light about λ  =  625  nm (10  ×   suppression factor). The fiber-based approach improves the sensitivity of spectral measurements at high contrast and may serve as an integral part of future space-based exoplanet imaging missions as well as ground-based instruments.

Item Type:Article
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URLURL TypeDescription
Ruane, Garreth0000-0003-4769-1665
Mawet, Dimitri0000-0002-8895-4735
Jovanovic, Nemanja0000-0001-5213-6207
Echeverri, Daniel0000-0002-1583-2040
Additional Information:© 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. Paper 18116 received Nov. 16, 2018; accepted for publication Mar. 7, 2019; published online Mar. 26, 2019.
Group:Astronomy Department
Subject Keywords:exoplanets; high contrast imaging; wavefront control; wavefront sensing; spectroscopy
Issue or Number:1
Record Number:CaltechAUTHORS:20190402-160051415
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Official Citation:Jorge Llop Sayson, Garreth Ruane, Dimitri Mawet, Nemanja Jovanovic, Benjamin Calvin, Nicolas Levraud, Milan Roberson, Jacques-Robert Delorme, Daniel Echeverri, Nikita Klimovich, and Yeyuan Xin "Demonstration of an electric field conjugation algorithm for improved starlight rejection through a single mode optical fiber," Journal of Astronomical Telescopes, Instruments, and Systems 5(1), 019004 (26 March 2019).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94385
Deposited By: George Porter
Deposited On:02 Apr 2019 23:09
Last Modified:16 Nov 2021 17:04

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