Reprogrammable optical metasurfaces by electromechanical reconfiguration

Broadband and high-efficiency polarization conversion with a nano-kirigami based metasurface

Nano-kirigami metasurfaces have attracted increasing attention due to their ease of three-dimension (3D) nanofabrication, versatile shape transformations, appealing manipulation capabilities and rich potential applications in nanophotonic devices. Through adding an out-of-plane degree of freedom to the double split-ring resonators (DSRR) by using nano-kirigami method, in this work we demonstrate the broadband and high-efficiency linear polarization conversion in the near-infrared wavelength band. Specifically, when the two-dimensional DSRR precursors are transformed into 3D counterparts, a polarization conversion ratio (PCR) of more than 90% is realized in wide spectral range from 1160 to 2030 nm. Furthermore, we demonstrate that the high-performance and broadband PCR can be readily tailored by deliberately deforming the vertical displacement or adjusting the structural parameters. Finally, as a proof-of-concept demonstration, the proposal is successfully verified by adopting the nano-kirigami fabrication method. The studied nano-kirigami based polymorphic DSRR mimic a sequence of discrete bulk optical components with multifunction, thereby eliminating the need for their mutual alignment and opening new possibilities.

Nano-kirigami enabled chiral nano-cilia with enhanced circular dichroism at visible wavelengths

Nano-kirigami method enables rich diversity of structural geometries that significantly broaden the functionalities of optical micro/nano-devices. However, the methodologies of various nano-kirigami are still limited and as a result, the chiral nano-kirigami structure has yet been pushed to the limit for operation at visible wavelength region. Here, the merits of the various nano-kirigami strategies are comprehensively explored and bio-inspired nano-cilia metasurface with enhanced circular dichroism at visible wavelengths is demonstrated. The stereo chiral nano-cilia metasurface is designed with three-fold rotational symmetry, which exhibits tuneable chiroptical responses when the nano-cilia are deformed to form strong chiral light-matter interactions. By employing electron-beam lithography (EBL) and focused ion beam (FIB) lithography, on-chip nano-cilia metasurfaces are experimentally realized in near-infrared wavelengths region and at visible wavelengths, respectively, successfully validating the giant circular dichroism revealed in simulations. Our work is useful to broaden the existing platform of micro/nano-scale manufacturing and could provide an effective method for the realization of versatile bioinspired nanostructures with profound chiroptical responses.