Moiré microstructure generated binary amplitude gratings for suppression of high diffraction orders

Abstract

We propose 2D gratings with 2D sinusoidal-like transmittance for spectral analysis in a wide wavelength range. Our design deploys the concept of the multiplicative superimposition of two mutually inclined or orthogonally crossed 1D binary amplitude gratings with appropriately selected opening numbers. In result the trapezoidal transmittance function without the 3rd and even harmonics is obtained in two perpendicular directions corresponding to the so-called subtractive and additive moiré patterns. The distance between main diffraction orders, i.e., -1, 0 and +1 in both directions is easily controlled by adjusting the angle between component grating lines. The moiré microstructure acting as 2D diffraction grating comprises 4 sided parallelogram holes up to the angle of 90 degrees for which they become rectangles. Diffraction efficiencies and free-standing parameters of our grating and the solutions reported in the literature, i.e., the inclined rectangular aperture grating (IRAG) and the grating with hexagonal holes are calculated and compared. Additionally, the methods of design for the literature reported gratings which start from square or rectangular shape apertures are introduced for the sake of comprehensive treatment of gratings with suppressed high diffraction orders. Design considerations are corroborated by the moiré Fourier spectra numerical simulations, their visualizations and experimental works.