Photonic spin-multiplexing metasurface for switchable spiral phase contrast imaging
Pengcheng Huo, Cheng Zhang, Wenqi Zhu, Mingze Liu, Song Zhang, Si Zhang, Lu Chen, Henri J. Lezec, Amit K. Agrawal, Yanqing Lu, Ting Xu
As the two most representative operation modes in an optical imaging system, bright-field imaging and phase contrast imaging can address different dimensionalities of an object. Developing a miniature and low-cost system capable of switching between these two imaging modes is thus very attractive for a series of applications, such as biomedical imaging and surface defect detection. Here, we propose and demonstrate that a Fourier transform setup incorporating an all-dielectric metasurface filter can be dynamically switched between the bright-field imaging mode and spiral phase contrast imaging mode. The metasurface spatial filter is formed by an array of subwavelength nanopillars and able to provide two spin-dependent, uncorrelated phase profiles for the visible light. As a result, based on the spin-state of incident light, the system can be used for diffraction-limited bright-field imaging or isotropic edge-enhanced phase contrast imaging. Combined with the advantages of planar architecture, ultrathin thickness and high pixel density of the metasurface, we envision this approach may open new vistas in the very interdisciplinary field of imaging and microscopy.