(Color online) Numerical simulations of areal image formation with rectangular (left column) and sinusoidal (right column) grating profiles. Transmission functions of masks with (a) rectangular and (b) sinusoidal grating profiles. (c), (d) Intensity profiles of areal images formed behind the grating illuminated with spatially coherent light of 5% bandwidth. (e), (f) One-dimensional profiles of the areal image obtained at z = 300 μm.
(Color online) Transmission of the one- (a) and two-dimensional hole (d) and pillar (g) masks showing one period and four unit cells of the periodic structures, respectively. In (a) the period and the linewidth are 200 and 100 nm, respectively. In (d) and (g) the period is 100 nm and hole or pillar diameter is 50 nm. (b), (e), (h) Calculated areal images at propagation distance of z = 300 μm (b) and 3000 μm (e), (h). (c), (f), (i) Profiles of the images in (a), (b); (d), (e); and (g), (h) along the black dashed lines, where the dashed and solid lines represent mask transmission and areal image intensity, respectively.
(Color online) Visibility  of the stationary image from the 1D (a) and 2D (b), (c) grating masks as a function of grating duty cycle or feature diameters in two different grating metal thicknesses.
(Color online) Schematic illustration of the mask fabrication process with HSQ (left column) and PMMA (right column) for one- and two-dimensional gratings, respectively. (a) 100 nm Si3N4 membrane with thermally evaporated Cr/Au/Cr (2 nm/5 nm/2 nm) tri-layer and spin-coated resist layer; (b) electron-beam lithography; (c) reactive-ion etching; (d) Au electroplating and resist removal.
SEM images of the fabricated masks. (a) Top-down view and (c) 80°-tilted view of the one-dimensional grating with period p = 200 nm; (b) two-dimensional grating with period p = 100 nm. Scale bars correspond to 100 nm.
SEM images of the experimentally obtained patterns exposed in HSQ resist with low dose (a), (b); medium dose (c)–(f); and high dose (g), (h). Scale bars correspond to 200 nm (a), (c), (e), (g) and 100 nm (b), (d), (f), (h), respectively.
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