We present a grating imaging scanning lithography system for the fabrication of large-sized gratings. In this technology, +(-)1-order diffractive beams are generated by a phase grating and selected by a spatial filter. Meanwhile, a 4f system enables the +(-)1-order diffractive beams to form a grating image with a clear jagged-edge boundary on the substrate. A high-precision two-dimensional (2D) mobile stage is used for complementary cyclical scanning, thereby effectively eliminating image stitching errors. The absence of such errors results in a seamless and uniform large-sized grating. Characterized by a simple structure, high energy use, and good stability, this lithography system is highly relevant to the high-speed and cost-effective production of large-sized gratings.

A simple modal analysis (MA) method to explain the diffraction process of 0th order nulled phase mask is presented. In MA, multiple reflections of the grating modes at grating interfaces are considered by introducing equivalent Fresnel coefficients. Analytical expressions of the diffraction efficiencies and modal guidelines for the 0th order nulled phase grating design are also presented. The phase mask structure, which comprises a high-index contrast HfO2 grating and a fused-silica substrate, is optimized using rigorous coupled-wave analysis around the 800-nm wavelength, after which the modal guideline for cancellation of the 0th order in a phase mask is verified. The proposed MA method illustrates the inherent physical mechanism of multiple reflections of the grating modes in the diffraction process, which can help to analyze and design both low-contrast and high-contrast gratings.

A simplified modal method to explain the resonance phenomenon in guided mode resonance (GMR) gratings with asymmetric coatings is presented. The resonance observed is due to the interaction of two propagation modes inside the grating. The reflectivity spectra and electric field distributions calculated from the simplified modal method are compared using rigorous coupled-wave analysis (RCWA). The influences of high-order evanescent modes on the resonance peak are analyzed. A matrix Fabry-Perot (FP) resonance condition is developed to evaluate the resonance wavelength. An explanation for the resonance phenomenon observed based on the FP resonance phase condition is also proposed and demonstrated. The simplified method provides clear physical insights into GMR gratings that are useful for the analysis of a variety of other resonance gratings.