Coded Liquid Crystal Metasurface for Achromatic Imaging in the Broadband Wavelength Range

Liquid crystal (LC) metasurfaces have attracted lots of attention recently due to their superior performance, tunability, and relatively simple fabrication. Conventional LC metalenses work either at multiple discrete wavelengths or continuous wavelength band with complicated combinations of multielements. Here, we propose and demonstrate achromatic imaging in the continuous broadband wavelength range with a single coded LC metalens. A cubic coded phase is imposed to the conventional phase profile in the plane of a metalens by manipulating the orientations of LC molecules via photopatterning from which a Pancharatnam-Berry (P-B) phase can be generated. Both theoretical and experimental results show that the phase-coded LC lens exhibits great achromatic imaging behaviors in the broadband wavelength range and wide field of view (FOV) in which a bandwidth of 134 nm and FOV of 24 degrees can be achieved in the visible wavelength range with a phase coding parameter of 30 pi. This work provides a new and practical way of designing liquid crystal metasurfaces for broadband achromatic imaging with advantages of ultrathin, light weight, integrability, and tunability but less fabrication complexity.