Effects of structure parameters on high-order diffraction suppression of quasi-periodic gratings

Abstract

We introduce the design and implementation of quasi-periodic gratings for high-order diffraction suppression. The effects of hole shape (circle, rectangle, diamond, and hexagon) and location distribution on the diffraction properties are investigated. We theoretically and experimentally demonstrate that the quasi-triangle array with hexagonal holes is highly advantageous for suppressing high-order diffractions. Additionally, the quasi-periodic location distribution also helps to suppress high-order diffraction. Remarkably, the analytical results show that the 1st, 2nd, 3rd, 4th, 5th, and 6th order diffractions can be completely suppressed for the special structure parameters of the quasi-periodic gratings, and the 7th order diffraction intensity is as low as 2.2×10−5 of the 1st order. The experimental results show there exist only 0th and ±1st order diffraction peaks along the ξ axis, which qualitatively agree with the theoretical and numerical predictions. Compared with the traditional 1∶1 grating, the quasi-triangle array with hexagonal holes can effectively suppress high-order diffractions. We except the quasi-periodic gratings may find significant applications in high-accuracy wide spectral measurement ranging from the far infrared to the x-ray regions.