Sub-nanometer spatio-temporal phase metrology of LCOS SLMs: calibration efforts towards adaptive coronagraphy

Abstract

Spatial Light Modulators (SLMs) are numerically programmable optical components that modulate the phase of light. We present digital holographic microscope (DHM) metrology results for the calibration of two classical liquid-crystal on-silicon (LCOS) VIS-633 nm SLMs: Meadowlark P1920 and Holoeye ERIS-NIR-153. For both devices, we assessed the phase response in real-time, with sub-nanometer precision along the optical axis, and micrometric lateral resolution. The phase response includes the command-to-phase relation (look-up tables) and the pixels' impulse response. We also characterized the static (wavefront error) and temporal behavior across short timescales to derive stability. We introduce our DHM and the SLM calibration procedures, performance metrics and the simulated practical impact on coronagraphic performance. Particular emphasis is placed on the implications for the SLM-equipped PLACID direct-imaging instrument, which is currently being commissioned on the 4-m DAG telescope.