Suppression of the Zeroth Order by a Mixed Metal Dielectric Grating

A mixed metal dielectric grating is designed and analyzed to suppress the zeroth order in the reflection region instead of the transmission structure. There are no +/- 2nd orders for the grating period in this paper, which leads to high efficiencies in the +/- 1st orders. Efficiencies of 48.36% for TE polarization and 48.34% for TM polarization can be diffracted into the +/- 1st orders at the incident wavelength of 1550 nm, respectively. While in the zeroth order, there are only efficiencies of 0.21% for TE polarization and 0.23% for TM polarization. For the transmission grating, efficiencies are usually modulated cosinoidally based on a modal method. It is difficult to achieve wide fabrication tolerance for the etching depth. For the reflective grating in this paper, the wide etching depth range is tolerated, particularly for TM polarization. The low-contrast structure and good performance can make the reflective grating useful, with the zeroth order suppressed.