High-performance polarizer based on the double-layer metallic gratings with air-gaps

A high-performance polarizer based on the double-layer metallic gratings with air-gaps is theoretically investigated. It is observed that the transmission of the TM polarized light greatly exceeds the double-layer metallic gratings without air-gaps. The electric field distributions are plotted to interpret the physical mechanism. The improvement is attributed to the enhanced coupling between the two metal layers. The transmission efficiency and extinction ratio of the proposed polarizer in terms of different structure parameters and the incident angles are discussed. At the period of 100 nm, the optimized structure can reach an extinction ratio higher than 30 dB and the TM transmission efficiency over 80% until the incident angle is 30
^o
. The study presented here is of great importance in designing and fabricating metallic grating polarizer with better performance.