Wideband reflective quarter-wave plates based on subwavelength mixed metal dielectric gratings

A wideband reflective quarter-wave plate based on the mixed metal dielectric subwavelength grating (SWG) is designed and analyzed. The wideband quarter-wave plate works at wavelengths around 1.55 μm and it can realize high efficiency and uniform phase retardation. The diffraction efficiency is higher than 97% and phase retardation between TE and TM polarizations deviates from ideal value π/2 less than 3° for wavelengths from 1.438 μm to 1.651 μm. The conversion from linearly to circularly polarized waves is simulated by using FDTD algorithm, which shows high performance of the optimized quarter-wave plate. Numerical calculations demonstrate that the optimized quarter-wave sustains large tolerance for fabrication. The wideband mixed metal dielectric reflective quarter-wave plate should be useful in polarized laser systems.