Subwavelength and quasi-subwavelength diffractive optical elements

Subwavelength diffractive optical elements with characteristic dimensions close to the wavelength can implement interesting optical functions, replacing, advantageously, other structures with dimensional features much smaller than the wavelength. The fabrication process becomes easier and the performance is better controlled. A study of a quasi-subwavelength 3x1 array generator and the design of antireflection structures with use of multilevel subwavelength zero-order gratings will be presented. The diffraction characteristics of these periodic structures are numerically calculated using the rigorous coupled-wave analysis (RCWA).