Two Dimensional Gratings of Connected Holes for High Order Diffraction Suppression

Abstract

The use of two dimensional gratings comprised of connected holes for the high order diffraction suppression will be discussed. An analytical study of the diffraction property of the three kinds of gratings is described, and the dependence of the high order diffraction property on the transmission function is investigated. Notably, theoretical analysis reveals that the 2nd, 3rd and 4th order diffractions adjacent to the 1st order diffraction can be completely suppressed for all three kinds of gratings. The 5th order diffraction is as low as 0.16% of the 1st order diffraction, and thus can be submerged in the background noise for most practical applications. Experimental results are shown to be consistent with the theoretical predictions. Especially, the smallest characteristic size of the grating of the connected zigzag-profiled holes is the half of period \(P_x\), which equals to the traditional 1:1 grating. For the two dimensional phase grating of the connected zigzag-profiled holes, the 1st order diffraction efficiency was 27.72%, which is much higher than 6.25% of the ideal sinusoidal transmission grating. At the same time, the phase grating can suppress completely the 0th order diffraction. These results are of great interest in the wide spectrum unscrambling from the infrared to the x-ray region.