Sub-nanometer address grid in variable shaped e-beam lithography for efficient inscription of high-precision large-area optical gratings

High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several cm 2 . Electron beam lithography with a variable shaped beam (VSB) is well suited but limited by tool-dependent address grid discretization. We adapted address grid interpolation to the VSB method, reducing the effective placement grid to 25 pm, as confirmed by stray light measurements. The technique was further demonstrated on a 0.5 cm ×5 cm phase mask for chirped fiber Bragg gratings (100 pm/mm), achieving excellent spectral broadband reflection quality.