Numerical Study of Coupled Dammann Grating

A Dammann grating coupling method and corresponding coupling condition are proposed. The different diffractive efficiency of the traditional 3x3 Dammann grating are analyzed by using both the scalar diffraction theory and the Fourier Modal Method (FMM). One new 3x3 Dammann grating is designed by using FMM in association with the simulated annealing optimization (SAO), and its diffraction efficiency and uniformity are about 40% and 15%, respectively. The new 3x3 grating and one traditional 64x64 Dammann grating are then coupled and analyzed numerically. The diffractive efficiency and the uniformity of the final 192x192 dense spots array are 30% and 18%, respectively. As the reference object, one 121x121 beam-splitting grating is designed, whose uniformity and overall diffractive efficiency are 50% and 85%, respectively. Numerical results show that the Dammann grating coupling method is more economical and applicable way to generate dense spots array.