Distribution features of four-port by reflective covered grating

The four-port reflection splitter with 0th order suppressed is proposed. HfO2 was chosen as the material for the grating ridges, achieving a highly-efficient splitting effect. Under normal incidence at 1550 nm wavelength, efficiencies of +/- 1 and +/- 2 orders under TE polarization are 24.45% and 24.56%, respectively, which are 24.10% and 24.08% under TM polarization, respectively. The 0th order of both polarizations is less than 1%. The structure was studied using rigorous coupled-wave analysis and simulated annealing algorithm. In addition, the electric field map of the energy distribution inside the grating during diffraction was depicted by the finite element method.