High-contrast phase imaging based on nonlinear holographic hot image model

Imaging for weak-phase objects is a challenging issue in the linear imaging process. Here, we demonstrate a high-contrast phase imaging method based on a nonlinear holographic hot image model. Due to the nonlinear Kerr effect, the holographic hot image can transform a weak phase into strong amplitude as a signal amplifier. The phase information is iteratively obtained from the light field distribution of the holographic hot image. The strong signal-to-noise ratio helps improve the imaging contrast. Using a tunable photorefractive crystal, we numerically and experimentally demonstrate the advantage of this method for imaging weak-phase objects. For the determined sample, our method doubles the imaging contrast. As far as we know, this is the first report using the nonlinear holographic hot image for imaging technology. This study can provide a potential strategy to achieve high-contrast imaging for various weak-phase objects applied in biomedical imaging, semiconductor metrology, and photolithography.