Polarization-Multiplexed Metalens Enables Novel Imaging Techniques

SHANNON, CLARE, IRELAND, October 5, 2026 /CourierPR/ -- Researchers from Opto-Electronic Sciences have introduced a novel liquid-crystal-integrated polarization-multiplexed metalens that enables two distinct bright-field imaging states and one interference-synthesized edge-enhanced state. The metalens, featuring a nominal focal length of 800 micrometers, consists of rectangular hydrogenated amorphous silicon (a-Si:H) nanopillars on a silica (SiO₂) substrate. The two orthogonal polarization channels are designed to be co-focal but have different effective aperture diameters, with D_x = 570 micrometers and D_y = 120 micrometers, corresponding to numerical apertures of approximately 0.336 and 0.075, respectively. These differences in effective aperture result in different spatial-frequency cutoffs for each channel.

The metalens operates by selecting two polarization channels: X-polarized and Y-polarized. Under 45°-polarized illumination followed by a 45° analyzer, the two transmitted fields are projected onto a common polarization basis and interfere coherently. Within the spatial-frequency range transmitted by both channels, a designed relative phase difference of π makes their field contributions interfere destructively. This interference effect enhances the object boundaries, resulting in a distinct edge-enhanced state.

Experiments conducted at 635 nanometers confirmed the metalens's ability to focus, achieve resolution-target imaging, and perform biological imaging. The measured focusing efficiencies for the X-polarized, Y-polarized, and 45°-polarized states were 43%, 36%, and 24%, respectively. The distinct resolution ranges of the two bright-field channels and the paired-edge contours generated by the synthesized state were confirmed through imaging of a USAF 1951 target.

The research was supported by grants from the National Research Foundation (NRF) and the Ministry of Science and ICT (MSIT) of the Korean government, as well as funding from the POSCO-POSTECH-RIST Convergence Research Center. The team's work demonstrates the potential of polarization-multiplexed metasurfaces in achieving compact, electrically selectable, label-free contrast enhancement in optical imaging systems.

The metalens's ability to generate a transfer function beyond those directly encoded in the individual channels through coherent interaction between polarization channels represents a significant advancement in the field of metasurfaces. The device's three voltage-selectable imaging responses, two bright-field states and one edge-enhanced state, can be addressed without moving the optical element or applying digital post-processing. This innovation could have applications in various fields, including medical imaging and biological research, where transparent or weakly absorbing specimens require sophisticated imaging techniques to visualize internal boundaries.