Chiral Grayscale Imaging with Plasmonic Metasurfaces of Stepped Nanoapertures

Optical chiral imaging, as an important tool in chemical and biological analysis, has recently undergone a revolution with the development of chiral metamaterials and metasurfaces. However, the existing chiral imaging approaches based on metamaterials or metasurfaces can only display binary images with 1 bit pixel depth having either black or white pixels. Here, the unique chiral grayscale imaging based on plasmonic metasurfaces of stepped V-shaped nanoapertures is reported with both high circular dichroism and large polarization linearity in transmission. By interlacing two subarrays of chiral nanoaperture enantiomers into one metasurface, two specific linear polarization profiles are independently generated in transmission under different incident handedness, which can then be converted into two distinct intensity profiles for demonstrating spin-controlled grayscale images with 8 bit pixel depth. The proposed chiral grayscale imaging approach with subwavelength spatial resolution and high data density provides a versatile platform for many future applications in image encryption and decryption, dynamic display, advanced chiroptical sensing, and optical information processing.