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Study of moiré grating fabrication on metal samples using nanoimprint lithography.

A moiré grating is a basic optical component used in various moiré methods for deformation measurement. In this study, nanoimprint lithography (NIL) was proposed to produce high frequency moiré gratings on metal samples. A new type of NIL mold and a hot embossing system were developed to overcome the poor flatness and roughness of metal samples. This three-layer mold based on nickel grating was unbreakable, and the self-developed hot embossing system used a bellows cylinder to satisfy the parallelism requirement of grating fabrication on metal samples. In order to generate high quality moiré patterns, the grating profile of the mold was optimized. Then, 1200-3000 lines/mm frequency gratings were successfully fabricated on the different materials such as SiO2, aluminum and stainless steel. In order to evaluate the quality of the replication, the distortion in the fabricated SiO2 grating was analyzed by an inverse moiré method. As an application, the replicated grating on the aluminum sample in combination with the moiré interferometry was used to measure the tensile deformation of the sample. The successful experimental results demonstrate the feasibility and reliability of nanoimprint lithography to produce gratings on metal samples.