A Fast Interferometric Beam Shaper for Multi-Emitter 3D MINFLUX

Beams of light that feature an intensity zero are essential to a variety of optical microscopy methods. Super-resolution techniques like STED and RESOLFT, together with localization strategies like MINFLUX and MINSTED, rely on accurate and fast displacements of such beams and their zeros. Extending these methods to the third dimension requires axial deflection, which, in contrast to lateral deflection, remains technologically challenging on the microsecond scale. Here, we present a fast general-purpose beam-shaping polarization interferometer that, instead of displacing the entire beam, enables such axial deflections by deforming the beam shape to deflect its zero. Based on this approach, we showcase a four-channel dual-color excitation system for three-dimensional MINFLUX imaging and tracking. We include first demonstrations of improved MINFLUX localization schemes that utilize the combination of distinct beam shapes and three-dimensional multi-emitter tracking. We believe that the presented approach will facilitate the broader adoption of three dimensional MINFLUX and provides a versatile basis for future implementations of advanced single-molecule localization methods.