Broadband circular polarizer based on high-contrast gratings

A circular polarizer, which is composed of periodic and two-dimensional dielectric high-contrast gratings, is designed theoretically such that a unity conversion efficiency is achieved at lambda(0) = 1.55 mu m. The operation is obtained by the achievement of the simultaneous unity transmission of transverse magnetic and transverse electric waves with a phase difference of pi/2, meaning that an optimized geometrical anisotropy is accomplished. By the utilization of the rigorous coupled-wave analysis and finite-difference time-domain methods, it is shown that a percent bandwidth of similar to 50% can be achieved when the operation bandwidth is defined as the wavelengths for which the conversion efficiency exceeds 0.9. (c) 2012 Optical Society of America