Dual-mode varifocal Moiré metalens for quantitative phase and edge-enhanced imaging.

Abstract

Transport-of-intensity equation (TIE) as a noninterference method for quantitative phase imaging (QPI) has broad applications in micrographic imaging and optical metrology. Previous TIE-based QPI systems require the axial displacement of the detector to capture the axial intensity distributions, thus limiting the systems' response speed, integration, and phase retrieval accuracy. Besides, the TIE-based phase imaging for edge positions with large phase gradients remains challenging. In this work, a compact polarization-multiplexed Moiré metalens is proposed to achieve QPI and edge-enhanced imaging for high-precision and unwrapping phase imaging. This Moiré metalens enables continuous zooming from 58.7 μm to 61.8 μm, allowing flexible selection of the detection positions. Under <i>x</i>-polarization light incidence, the metalens can achieve phase retrieval based on the TIE method, with the Root Mean Square Errors (RMSE) reaching 0.015 rad. Under <i>y</i>-polarization light incidence, the metalens realizes varifocal edge-enhanced imaging for amplitude and phase objects, with a minimum spatial resolution of 1.3 μm. This Moiré metalens opens a new avenue to develop compact, integrated, and multifunctional phase imaging devices and has potential applications in optical detection, microscopy, and biomedical imaging.