We recently started to investigate how liquid-crystal on silicon (LCOS) spatial light modulator (SLM) would perform as programmable focal-plane phase mask (FPM) coronagraphs. Such “adaptive coronagraphs” could potentially help adapt to observing conditions, but also tackle specific science cases (e.g. binary stars). Active FPMs may play a role in the context of segmented telescope pupils, or to implement synchronous coherent differential imaging (CDI). We present a status update on this work, notably early broadband contrast performance results using our new Swiss Wideband Active Testbed for High-contrast imaging (SWATCHi) facility. Finally, we unveil the upcoming near-infrared PLACID instrument, the Programmable Liquid-crystal Adaptive Coronagraphic Imager for the 4-m DAG observatory in Turkey, with a first light planned for the end of the year 2022.

PLACID optical train design
PLACID NIR SLM coronagraphic performance at H-band, as tested on the SWATCHi tesbed of Fig.1 with a F/60 focal ratio and DAG-shaped entrance pupil and Lyot plane masks (LP in double-pass configuration). (Left) Pupil-plane images in the (a) non-coronagraphic (flat phase on SLM), and coronagraphic (vortex charge n=2) cases (b) without and (c) with the Lyot stop in place; (Right) Focal-plane PSF images in the (d,e) coronagraphic and (f) coronagraphic (vortex charge n=2) cases. In (e), the contrast color scale is stretched at the same level as (f), illustrating how the shot-noise (granularity) at larger angular separation in (e) is suppressed in the coronagraphic image (f), i.e. demonstrating how the dynamic range is improved by being able to integrate longer in the coronagraphic observing mode.
PLACID test bench at the University of Bern

Page last modified on 07 March 2022 à 17h58