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The iterative recovery of quantitative phase information from measurements of the diffracted intensity or flux of a wavefield, has produced entirely new methods in phase imaging. Collectively these approaches may broadly be described as ‘coherent imaging techniques’. Of the numerous types of coherent imaging methods that have emerged ptychography has proved to be one of the most enduringly successful. Not only does ptychography afford high-quality quantitative sample phase data to be obtained it simultaneously reconstructs the incident complex wavefield eliminating artifacts that can be introduced via an imperfect knowledge of the probe or imaging system. Recently we demonstrated that the incorporation of plasmonic nanostructures into optical ptychography results in a significant improvement in both the amplitude and phase contrast. We termed this technique Plasmon Enhanced Ptychography (PE-ptychography). Further, we observed that depending on the incident wavelength the relative values for the individual components of the complex refractive index vary significantly resulting, at certain wavelengths, in a ‘contrast reversal’ relative to the incident probe. Here we discuss the progress and potential of plasmon-mediated phase contrast bioimaging, exploiting the specific near-surface interactions that occur between the sample and plasmon-resonance structure in order to highlight specific sample features. We find that the combination of quantitative phase imaging and plasmonics enables excellent differentiation between sample components that would otherwise be difficult to resolve. The data points to the possibility of significantly enhancing the sensitivity and specificity of label-free bioimaging with the potential to detect the very earliest stages of disease.
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