All-metal flexible large-area multiband waveplate.

We propose and demonstrate an all-metal flexible reflective multiband waveplate based on nano-grating structure using high efficient electroplating growing process, which exhibits quarter waveplate at two wavelengths (λ = 465nm and λ = 921nm) and half waveplate at another wavelength (λ = 656nm). Using Finite Difference Time Domain (FDTD) modeling, the phase shift and reflection efficiency are simulated and designed for a variety of geometrical parameters. A fast and cost-effective technique based on conventional interference lithography and nickel electroplating process is demonstrated to fabricate the all-metal, large-area and flexible waveplate. Experimental results show that the fabricated monolithic all-metal nano structure of the proposed device are in high fidelity with the structure on template and the optical performance of the device are in excellent agreement with the theoretical prediction. The proposed structure and the fabrication method suggests an effective way to realize all-metal, ultrathin, self-supporting and flexible devices for various applications in rugged environment such as high temperature or high pressure environment, and also in the fast growing fields of flexible (wearable) optoelectronics, flexible displays and other curved or nonplanar devices.

All-dielectric metasurface circular dichroism waveplate.

We propose and experimentally demonstrate a high efficient circularly polarizing dichroism waveplate (CPDW) using a Si-based all-dielectric 2Dchiral metasurface. We demonstrate that the CPDW exhibits a unique dichroism in that it functions as a transmissive quarter waveplate for one of either left-or right-handed circularly polarized incident lightand a reflective mirror for the opposite polarization. The circular polarization dichroism (CPD = IRCP - ILCP) in transmission at wavelength ~1.5 µm reaches 97% and the extinction ratio (ER = IRCP/ILCP) is as high as 345:1. Experimental fabrications and measurements of the proposed all-dielectric metasurface are implemented and found to be in excellent agreement with the simulations. The proposed all-dielectric chiral metasurface is of advantages of high-dichroism, easy-fabrication and standard semiconductor fabrication techniques compatible, which could lead to enhanced security in fiber and free-space communications, as well as imaging and sensing applications for circularly polarized light with a highly integrated photonic platform.

Broadband circularly polarizing dichroism with high efficient plasmonic helical surface.

We propose and experimentally demonstrate a broadband and high efficient circularly polarizing dichroism using a simple single-cycle and single-helical plasmonic surface array arranged in square lattice. Two types of helical surface structures (partially or completely covered with a gold film) are investigated. It is shown that the circular polarization dichroism in the mid-IR range (3µm - 5µm) can reach 80% (when the surface is partially covered with gold) or 65% (when the surface is completely covered with gold) with a single-cycle and single-helical surface. Experimental fabrications of the proposed helical plasmonic surface are implemented with direct 3D laser writing followed by electron beam evaporation deposition of gold. The experimental evaluations of the circular polarization dichroism are in excellent agreement with the simulation. The proposed helical surface structure is of advantages of easy-fabrication, high-dichroism and scalable to other frequencies as a high efficient broadband circular polarizer.