Generating an M2 x N2 spot array with a dual-period hybrid Dammann grating fabricated using maskless projection lithography

The Dammann grating (DG), which redistributes a colli-mated laser beam into a spot array with a uniform intensity, is a widely adopted approach for profile measurement. Con-ventional DGs for dense spot projection are binary phase gratings with precisely designed groove structures, which suffer from low efficiency, poor uniformity, and a hard-to -fabricate fine feature size when utilized for a large field of view (FOV). Here, we propose a new, to the best of our knowl-edge, hybrid DG architecture consisting of two different grating periods which effectively generates an engineering M2 x N2 spot array with a non-complex structural design. As a proof-of-concept, a dual-period hybrid DG with a two -scale grating period ratio of 11.88 & mu;m/95.04 & mu;m (-1/8) is designed and fabricated as a means to generate a dense 72 x 72 diffraction spot array with a FOV of 17 & DEG; x 17 & DEG;. In addition, the DG exhibits superior performance, with a high efficiency (> 60%) and a low non-uniformity (< 18%) at a wavelength of 532 nm. This kind of hybrid DG constructed from photoresist patterns with a minimum feature size of-1.2 & mu;m can be perfectly fabricated by maskless projec-tion lithography for large-scale and low-cost production. The proposed dual-period hybrid DG can pave the way for depth -perception-related applications such as face unlocking and motion sensing. & COPY; 2023 Optica Publishing Group

Automated summary

This study proposes a new hybrid Dammann grating structure that can effectively generate an engineering-grade M2 x N2 spot array with a simple structural design. The hybrid Dammann grating exhibits high efficiency and low non-uniformity at a wavelength of 532 nm and can be fabricated through maskless projection lithography for large-scale, low-cost production.