Active coronagraphy and coherence differential imaging in unpolarized light with the Swiss Wideband Active Testbed for Coronagraphic High-contrast imaging (SWATCHi) 2.0

The PLACID instrument installed at the new Turkish 4m-DAG telescope in 2024 will be the first active stellar coronagraph, offering a unique facility to perform innovative high-contrast imaging observing strategies. It is composed of a Spatial Light Modulator (SLM) in reflection in lieu of the usual fixed focal plane mask to digitally set up any phase mask in real time. However, such hardware works with a linearly polarized wave causing the loss of 50% throughput. To retrieve full capacity, PLACID will then be upgraded with polarization-independent solutions to be first tested on the Swiss Wideband Active Testbed for Coronagraphic High-contrast imaging (SWATCHi) 2.0. This testbed is also employed to investigate coherent differential imaging techniques that relies on the fast modulation of the speckle intensity whose signal is recorded with a C-RED ONE camera. This work presents the optical design and first results of SWATCHi 2.0.