Bright-Field and Edge-Enhanced Imaging Using an Electrically Tunable Dual-Mode Metalens

The imaging of microscopic biological samples faces numerousdifficultiesdue to their small feature sizes and low-amplitude contrast. Metalenseshave shown great promise in bioimaging as they have access to thecomplete complex information, which, alongside their extremely smalland compact footprint and potential to integrate multiple functionalitiesinto a single device, allow for miniaturized microscopy with exceptionalfeatures. Here, we design and experimentally realize a dual-mode metalensintegrated with a liquid crystal cell that can be electrically switchedbetween bright-field and edge-enhanced imaging on the millisecondscale. We combine the concepts of geometric and propagation phase to design the dual-mode metalens and physically encode the requiredphase profiles using hydrogenated amorphous silicon for operationat visible wavelengths. The two distinct metalens phase profiles include(1) a conventional hyperbolic metalens for bright-field imaging and(2) a spiral metalens with a topological charge of +1 for edge-enhancedimaging. We demonstrate the focusing and vortex generation abilityof the metalens under different states of circular polarization andprove its use for biological imaging. This work proves a method for in vivo observation and monitoring of the cell responseand drug screening within a compact form factor.

Automated summary

In this paper, a dual-mode metalens integrated with a liquid crystal cell capable of electrically switching between bright-field and edge-enhanced imaging on the millisecond scale is designed and experimentally realized. The metalens, designed using the concepts of geometric and propagation phase and physically encoded with hydrogenated amorphous silicon, demonstrates the ability to focus and generate vortex under different states of circular polarization, proving its use for biological imaging. This work provides a compact form factor for in vivo observation and monitoring of cell response and drug screening.