New Avenues for Phase Imaging: Optical Metasurfaces

Visualizing the phase of an optical field is fundamental to applications ranging from biological microscopy through to material science. Its importance is evidenced by the award of the 1953 Nobel Prize to Frits Zernike for his invention of the phase contrast microscope. Conventional phase imaging techniques, including Zernike phase contrast, differential interference contrast, and interferometry, often rely on bulky optical components and macroscopic propagation distances. These factors hinder the miniaturization and integration into ultracompact imaging systems. Furthermore, computational methods also present challenges due to computational complexity, potentially compromising speed and energy efficiency. The recent emergence of the use of nano-optics, including thin films and metasurfaces, in image processing has opened up possibilities for a new class of compact methods for phase imaging. These nanostructured devices have been shown to permit phase visualization, and we believe that they hold the potential to enable the next generation of imaging systems and photodetectors in a broad range of applications.