Simple and fast calibration method for phase-only spatial light modulators

Phase-only spatial light modulators (SLMs) are widely used to engineer the phase of light in various applications. However, liquid-crystal-on-silicon SLMs have undesirable spatial variations in phase response and optical flatness across the SLM panel, which must be compensated for accurate phase control. Here, we introduce a simple and fast way to simultaneously extract these two types of SLM nonuniformities at single-pixel resolution using Twyman–Green interferometry without a piezoelectric transducer. By modulating the interference intensity via the SLM gray level, our approach requires N times fewer interferograms than typical N-step phase shift interferometry (PSI), while providing flatness correction as accurate as PSI. In practice, our calibration method works well with as few as 18 interferograms, which can be quickly acquired without concern for phase drift. We detail the calibration procedure and discuss the performance of our calibration.