Previous research on making low-stray-light gratings is mainly focused on process steps after the photoresist mask has been made. We propose to improve the quality of the photoresist mask directly in exposure. We present a broad-beam scanning exposure method along the grating vector (i.e., in the direction perpendicular to the grating grooves), utilizing a reference grating clamped below the substrate on the translation stage for phase and attitude locking. Scanning-exposed gratings with a size of 40 mm×40 mm are successfully made, which have straighter grooves and smoother surfaces, and their stray light levels around the first and second diffraction orders are decreased significantly.
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| http://dx.doi.org/10.1364/OL.40.001346 | DOI Listing |
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