Spatially resolved system-level calibration for high-fidelity complex-amplitude modulation using a phase-only spatial light modulator

We demonstrate a spatially resolved system-level calibration method for high-fidelity complex-amplitude modulation using sequential modulation on a phase-only spatial light modulator (SLM). The spatially varying intensity response of the first SLM region was measured and locally fitted to determine the gray-level pattern required to reproduce a target intensity. The phase distribution was also measured using off-axis interferometry and compensated by the second SLM region. The method therefore compensates for the nonuniform incident-beam profile, the spatially varying nonlinear SLM response, and optical-system alignment errors. Once calibrated, the system can reconstruct various target complex fields without additional calibration. Experimental reconstructions of a diverse range of patterns, including structured beam modes, consistently demonstrated high complex-field fidelity.