Dissertation

Suppressing a Sea of Starlight: Enabling technology for the direct imaging of exoplanets

Promotor: Christoph U. Keller, Co-promotores: Matthew A. Kenworthy, Frans Snik

Author: G.P.P.L. Otten
Date: 29 November 2016
Links: Thesis in Leiden Repository

In this thesis we present multiple techniques to suppress starlight in order to better directly image planets around other stars. We propose a laboratory setup to test a new focal-plane wavefront sensing technique. We also show an optical device that suppresses starlight using liquid crystals (the vector Apodizing Phase Plate or vAPP). A broadband prototype (500-900 nm) is tested in the optical lab and its properties are determined. We suggest an simple but effective adaptation called the grating-vAPP which is insensitive to one of the common manufacturing errors (retardance offset). Two versions are tested on-sky. One narrow-band prototype at the Large Binocular Telescope that shows that the concept of the grating vAPP works. A second at Magellan/Clay that shows that we can produce a single optic with a broadband behaviour from 2 to 5 microns bandwidth that suppresses both sides of the star simultaneously. The on-sky 5 sigma contrast is 8.3 magnitudes at 2 lambda/D and 12.2 magnitudes at 3.5 lambda/D which makes this coronagraph extremely suited for imaging and characterizing planets close to nearby bright stars.