Future exoplanet direct imaging instruments: Simulating spatial light modulator-based pixelated focal-plane coronagraphy

TL;DR

This paper presents a simulation tool for SLM-based focal-plane coronagraphs, aiding the design and operation of future exoplanet imaging instruments like PLACID on the DAG Telescope.

Contribution

It introduces a Python simulator for pixelated phase masks, analyzing design choices and enabling advanced operation modes for SLM-based coronagraphs.

Findings

Optimal spatial sampling is 10 pixels per λ/D in ideal conditions.

Phase resolution of 8 bits is sufficient for effective FPM performance.

The tool supports real-time instrument optimization and data interpretation.

Abstract

The programmable Liquid-crystal Active Coronagraphic Imager for the DAG Telescope (PLACID) instrument will be installed on the Turkish 4-m Telescope by the fall of 2024 and is expected to be on-sky by the end of the year. PLACID will be the first ''active stellar coronagraph instrument'', equipped with a customized spatial light modulator (SLM), which performs as a dynamically programmable focal-plane phase mask (FPM) from H- to Ks- band. A Python-based numerical simulator of SLM-based focal-plane phase coronagraph is developed to investigate the effects of discrete pixelated FPM patterns in place of classical phase masks. The simulator currently explores the impacts of two design choices, spatial sampling in the coronagraphic focal-plane (number of SLM pixels per $\lambda$/D) and phase resolution (SLM greylevel steps). The preliminary results of the monochromatic simulations show that in ideal conditions (no wavefront errors) it is sufficient to use FPMs with spatial sampling of 10 SLM pixel per $\lambda$/D and phase resolution of 8 bits. The tool is expected to enable detailed simulations of PLACID or similar SLM-based instruments, and to help with real-time operations (optimal choice of FPM for given observing conditions) and interpretation of real data. Additionally, the tool is designed to integrate and simulate advanced operation modes, in particular focal-plane phase diversity for coherent differential imaging (CDI) of exoplanets.