SLM-Microscopy: Wavefront Shaping for Microscopy with Spatial Light Modulators

Abstract

The implementation of adjustable diffractive optical elements (DOEs), realized by a spatial light modulator (SLM) in the optical path of a microscope brings an enormous increase in flexibility. We present applications of SLMs placed either in the imaging path or in the illumination path. SLMs can, e.g., be used for quantitative phase contrast imaging by recording common path interferograms, allowing one to measure the optical thickness of phase objects with an accuracy of about 5% of the light wavelength. The modulation of the illumination offers the possibility for flexible adjustment of the coherence of the light source: One can switch between high accuracy measurements with a spatially coherent light source, or higher resolution with an incoherent light source. A combination of two subsequent SLMs provides the option to sculpture wavefronts and to reconstruct 3D field patterns. Complex 3D holograms without speckle can be realized in this way. The complex holograms can be used for sophisticated optical traps, with a specific intensity pattern which simultaneously offer the freedom of independent adjustment of the phase gradient along the “trapping patterns”.