Polarization-insensitive high-efficiency two-dimensional metal-dielectric grating by nanodisks arrays

Abstract

In this paper, a two-dimensional (2D) reflective grating with nanodisks arrays (NDA) is described, which is capable of achieving high-efficiency and polarization-insensitive output of (−1, 0) order. The proposed grating has been optimized by the finite element method (FEM) at a central wavelength of 780 nm under Littrow mounting, where the grating achieves diffraction efficiencies of 98.01% and 97.54% at the (−1, 0) order for transverse electric (TE) and transverse magnetic (TM) polarizations, respectively. In addition, the extinction ratios of TE and TM polarizations are 33.01 dB and 35.74 dB, respectively. The electric field distribution, wavelength bandwidth, angular bandwidth and fabrication tolerance of the 2D grating are analyzed in detail. The analysis shows that the proposed grating offers a significant improvement in wavelength (bandwidth of 14 nm) and angular (bandwidth of 6.4°) bandwidths compared to previously reported 2D gratings. At the same time, the tolerance analyses demonstrate the feasibility and advantages of NDA grating in practical manufacturing processes. The results are very helpful in understanding and designing 2D gratings, and the proposed grating has great application potential in 2D grating measurement system (GMS).