Background-free quantitative phase imaging with adaptive-optics surface plasmon resonance holographic microscopy

Quantitative phase imaging (QPI) in the near field is a powerful tool for visualizing nanoscale structures in low-dimensional materials, dielectric mixtures and biological cells. Although near-field QPI offers extremely high sensitivity, phase aberrations of the optical system can pose serious limitations. Overcoming these problems, we introduce an adaptive optics approach that takes advantage of the complex amplitude measured by digital holographic microscopy (DHM). By using a spatial light modulator as a beam shaping device, our method allows for in-situ, accurate, fast and flexible aberration correction by quantifying wavefront distortions in terms of Zernike modes, and pre-compensating them with a spatial light modulator. For validation, we demonstrate near-field phase imaging with adaptive-optics surface plasmon resonance holographic microscopy (AO-SPRHM) on microstructured test samples and live cells. With a total correction time below 1 s, background-free time-lapse imaging over many hours becomes feasible. The approach can be easily transferred to other phase imaging techniques, including transmission, reflection and total internal reflection DHM as well as related modalities.