High-efficiency two-dimensional diffraction grating

Abstract

Higher requirements have been put forward for the performance of two-dimensional (2D) gratings, such as polarization independence, high efficiency, wide broadband and so forth. In this letter, we employ the characteristic of diffraction in the grating and propose a 2×2 2D silver cylindrical array grating under normal incidence with excellent polarization independent high diffraction efficiency (DE) over communication band for beam splitting. The simulation and optimization of the DE are based on rigorous coupled wave analysis (RCWA) and simulated annealing (SA) algorithm, respectively. Under the optimal structural parameters, the highest DE of (±1, 0) orders and (0, ±1) orders can achieve over 24% at 1550nm in both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations. Within moderate manufacture tolerance, the final discrete rotationally symmetric 2D periodic surface pattern has been fabricated by the holographic exposure technology, wet chemical development process and Electron Beam Evaporation. The measurement results of fabricated grating fully verify the correctness and accuracy of the calculation. Therefore, this 2D grating has considerable application potentials in optical communication, displacement measurement and semiconductor manufacturing.