Two-step phase-shifting interferometry for phase-resolved imaging from a spatial light modulator

We demonstrate two-step phase-shifting interferometry (holography) of complex laser modes generated by a spatial light modulator (SLM), in which the amplitude and phase of the signal are determined directly from measurements of phase-shifted interferograms. The reference and signal beams are generated and phase-controlled with a single composite hologram on the SLM and propagated collinearly. This requires no additional optics and leads to measurements that are more accurate and less prone to noise, which we demonstrate with collinearly-referenced measurements of various Laguerre-Gaussian modes and structured images.